Pressure-induced transformations of multiferroic relaxor PbFe0.5Nb0.5O3

NASA Astrophysics Data System (ADS)

Basu, Abhisek; Ahart, Muhtar; Holtgrewe, Nicholas; Lin, Chuanlong; Hemley, Russell J.

2018-02-01

The effects of hydrostatic pressure at ambient temperature on the structural and dielectric properties of PbFe0.5Nb0.5O3 (PFN) were investigated using second harmonic generation (SHG) and powder x-ray diffraction measurements to 31 GPa. The results demonstrate that PFN undergoes a pressure-induced structural transition from the R3m ferroelectric to the R 3 ¯ m paraelectric phase. SHG measurements showed a continuous decrease in the signal with pressure and complete disappearance at 7.1 GPa. Effective nonlinear optical coefficients were determined from the SHG data, and their pressure behavior was used to infer the nature of the transition. The loss of the SHG signal is accompanied by drastic changes in line widths of Bragg reflections, but no discontinuous change in volume was observed. The pressure-volume data were fit to various equations of state, and a bulk modulus K0 = 136 (±2) GPa, bulk modulus pressure derivative K0' = 4.0 (±0.2), and initial volume V0 = 64.5 (±0.1) Å3 were obtained.

Comparative in situ X-ray Diffraction Study of San Carlos Olivine: Influence of Water on the 410 km Seismic Velocity Jump in Earth’s Mantle

DOE Office of Scientific and Technical Information (OSTI.GOV)

J Chen; H Liu; J Girard

2011-12-31

A comparative study of the equation of states of hydrous (0.4 wt% H{sub 2}O) and anhydrous San Carlos olivine (<30 ppm H2O) was conducted using synchrotron X-rays up to 11 GPa in a diamond anvil cell (DAC) at ambient temperature. Both samples were loaded in the same high-pressure chamber of the DAC to eliminate the possible pressure difference in different experiments. The obtained compression data were fitted to the third-order Birch-Murnaghan equation of state, yielding a bulk modulus K{sub 0} = 123(3) GPa for hydrous olivine and K{sub 0} = 130(4) GPa for anhydrous olivine as K{sub 0}' is fixedmore » at 4.6. Therefore, 0.4 wt% H{sub 2}2O in olivine results in a 5% reduction in bulk modulus. Previous studies reported bulk modulus reduction by water in olivine's high-pressure polymorph (wadsleyite), to which the transformation from olivine gives rise to the seismic discontinuity at 410 km depth. The new data results in a reduction in the magnitude of the discontinuity by 50% in v{sub P} and 30% in v{sub S} (for 1:5 water partitioning between olivine and wadsleyite) with respect to anhydrous mantle. Previous knowledge of the influence of water on this phase transition has been in opposition to a large amount of water [e.g., 200 ppm by Wood (1995)] existing at 410 km depth. Calculation of the seismic velocities based on newly available elasticity data of the hydrous phases indicates that the presence of water is favorable for the mineral composition model (pyrolite) and seismic observations in terms of the magnitude of the 410 km discontinuity.« less

Lattice dynamics and thermomechanical properties of zirconium(IV) chloride: Evidence for low-temperature negative thermal expansion

NASA Astrophysics Data System (ADS)

Kim, Eunja; Weck, Philippe F.; Borjas, Rosendo; Poineau, Frederic

2018-01-01

The crystal structure, lattice dynamics and themomechanical properties of bulk monoclinic zirconium tetrachloride (ZrCl4) have been investigated using zero-damping dispersion-corrected density functional theory [DFT-D3(zero)]. Phonon analysis reveals that ZrCl4 (cr) undergoes negative thermal expansion (NTE) near T ≈ 10 K, with a coefficient of thermal expansion of α = - 1.2 ppm K-1 and a Grüneisen parameter of γ = - 1.1 . The bulk modulus is predicted to vary from K0 = 8.7 to 7.0 GPa in the temperature range 0-550 K. The isobaric molar heat capacity derived from phonon calculations within the quasi-harmonic approximation is in fair agreement with existing calorimetric data.

Compression behavior of WC and WC-6%Co up to 50 GPa determined by synchrotron x-ray diffraction and ultrasonic techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amulele, George M.; Manghnani, Murli H.; Marriappan, Sekar

2008-07-23

The equations of state (pressure-volume relations) for WC and WC-6%Co have been determined by synchrotron x-ray diffraction measurements on polycrystalline powder samples loaded in a diamond anvil cell as well as by ultrasonic measurements on hot-pressed polycrystalline, cylindrical samples loaded in a multianvil high-pressure apparatus. The third-order Birch-Murnaghan equation of state fitted to the x-ray diffraction pressure-density sets of data, collected up to 50 GPa, yields ambient pressure isothermal bulk moduli of K{sub oT} = 411.8{+-}12.1 GPa and K{sub oT} = 402.4{+-}14.1 GPa, with pressure derivatives of K{sub oT}' = 5.45{+-}0.73 and K{sub oT}' = 7.50{+-}0.86 for WC and WC-6%Co,more » respectively. The ultrasonic measurements, conducted up to 14 GPa, enabled the determination of the pressure dependences of both bulk and shear moduli. Using Eulerian finite strain equations to fit the ultrasonic data, we obtain for WC an ambient pressure adiabatic bulk modulus of K{sub os} = 383.8{+-}0.8 GPa, and K{sub os}' = 2.61{+-}0.07 for its pressure derivative, while values of G{sub os} = 304.0{+-}0.3 GPa and G{sub os}' = 1.50{+-}0.09 were determined for the shear modulus and its pressure derivative, respectively. Meanwhile, for WC-6%Co, we obtain K{sub os} = 357.5{+-}1.0 GPa, K{sub os}' = 5.18{+-}0.14, G{sub os} = 253.5{+-}0.3 GPa, and G{sub os}' = 1.09{+-}0.09. The equations of state derived from the ultrasonic data are in good agreement with extrapolated results reported previously by Day and Ruoff [J. Appl. Phys. 44, 2447 (1973)] and Gerlich and Kennedy [J. Appl. Phys. 50, 3331 (1978)] who carried out measurements up to 0.2 and 1.0 GPa, respectively.« less

Thermal equation of state of NaMg0.5Si2.5O6 and new data on the compressibility of clinopyroxenes

NASA Astrophysics Data System (ADS)

Dymshits, A. M.; Sharygin, I. S.; Podborodnikov, I. V.; Litasov, K. D.; Shatskiy, A. F.; Otani, E.; Pushcharovskii, D. Yu.

2015-03-01

The results of studies of the P-V-T equations of state (EOS) of Na-pyroxene using the multi-anvil technique and synchrotron radiation at pressures up to 15.3 GPa and temperatures up to 1673 K are presented. By fitting the Birch-Murnaghan EOS, the following parameters were determined: V 0 = 407.2 (5) Å3, the space group P2/ n, K T0 = 103 (2) GPa, K T0 = 6.2 (7), ∂ K T /∂ T = -0.018 (7), α = 3.38(13) + 0.65(62) T. Thus, despite the small volume of the cell, Na-pyroxene has a sufficiently high bulk modulus. This can be caused by the appearance of antipathetic bonds in Na-polyhedron, Si-tetrahedra rotation, and the ordering of Mg and Si cations in the M1 position. Thus, it is substantiated that the phase transformations in the minerals accompanied by the presence of Si in octahedral coordination are characterized by a significant change in the physical characteristics, such as density (ρ) and bulk modulus ( K T ). Such transformations occurring in the minerals and deep Earth can lead to significant jumps in the seismic wave velocities. Therefore, the presence of phases with silicon in sixfold coordination, such as Na-Ca majoritic garnet is of fundamental importance for understanding the Earth's upper mantle.

Stress Wave Interactions with Tunnels Buried in Well-Characterized Jointed Media.

DTIC Science & Technology

1980-06-01

27 14 Particle Velocity and Principal Stress Fields at 62 jisec for the Elastic- Plastic Media Model (Case 1, 0.8 kbar...is used; the basic formulation is similar to the HEMP code (Ref. 3) . Tn numerical solutions and material properties are luscriben in Section 3. 3...media is 16A rock simulant. The elastic- plastic properties are modeled with the following parameters: Bulk Modulus K = .131 Mbar Shear Modulus G

Thermoelectric Materials

NASA Astrophysics Data System (ADS)

Gao, Peng; Berkun, Isil; Schmidt, Robert D.; Luzenski, Matthew F.; Lu, Xu; Bordon Sarac, Patricia; Case, Eldon D.; Hogan, Timothy P.

2014-06-01

Mg2(Si,Sn) compounds are promising candidate low-cost, lightweight, nontoxic thermoelectric materials made from abundant elements and are suited for power generation applications in the intermediate temperature range of 600 K to 800 K. Knowledge on the transport and mechanical properties of Mg2(Si,Sn) compounds is essential to the design of Mg2(Si,Sn)-based thermoelectric devices. In this work, such materials were synthesized using the molten-salt sealing method and were powder processed, followed by pulsed electric sintering densification. A set of Mg2.08Si0.4- x Sn0.6Sb x (0 ≤ x ≤ 0.072) compounds were investigated, and a peak ZT of 1.50 was obtained at 716 K in Mg2.08Si0.364Sn0.6Sb0.036. The high ZT is attributed to a high electrical conductivity in these samples, possibly caused by a magnesium deficiency in the final product. The mechanical response of the material to stresses is a function of the elastic moduli. The temperature-dependent Young's modulus, shear modulus, bulk modulus, Poisson's ratio, acoustic wave speeds, and acoustic Debye temperature of the undoped Mg2(Si,Sn) compounds were measured using resonant ultrasound spectroscopy from 295 K to 603 K. In addition, the hardness and fracture toughness were measured at room temperature.

Lattice dynamics and thermomechanical properties of zirconium(IV) chloride: Evidence for low-temperature negative thermal expansion

DOE PAGES

Kim, Eunja; Weck, Philippe F.; Borjas, Rosendo; ...

2017-11-01

For this research, the crystal structure, lattice dynamics and themomechanical properties of bulk monoclinic zirconium tetrachloride (ZrCl 4) have been investigated using zero-damping dispersion-corrected density functional theory [DFT-D3(zero)]. Phonon analysis reveals that ZrCl 4(cr) undergoes negative thermal expansion (NTE) near T≈10 K, with a coefficient of thermal expansion of α=-1.2 ppm K -1 and a Grüneisen parameter of γ=-1.1. The bulk modulus is predicted to vary from K 0=8.7 to 7.0 GPa in the temperature range 0–550 K. Lastly, the isobaric molar heat capacity derived from phonon calculations within the quasi-harmonic approximation is in fair agreement with existing calorimetric data.

Lattice dynamics and thermomechanical properties of zirconium(IV) chloride: Evidence for low-temperature negative thermal expansion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Eunja; Weck, Philippe F.; Borjas, Rosendo

For this research, the crystal structure, lattice dynamics and themomechanical properties of bulk monoclinic zirconium tetrachloride (ZrCl 4) have been investigated using zero-damping dispersion-corrected density functional theory [DFT-D3(zero)]. Phonon analysis reveals that ZrCl 4(cr) undergoes negative thermal expansion (NTE) near T≈10 K, with a coefficient of thermal expansion of α=-1.2 ppm K -1 and a Grüneisen parameter of γ=-1.1. The bulk modulus is predicted to vary from K 0=8.7 to 7.0 GPa in the temperature range 0–550 K. Lastly, the isobaric molar heat capacity derived from phonon calculations within the quasi-harmonic approximation is in fair agreement with existing calorimetric data.

Path-integral simulation of ice Ih: The effect of pressure

NASA Astrophysics Data System (ADS)

Herrero, Carlos P.; Ramírez, Rafael

2011-12-01

The effect of pressure on structural and thermodynamic properties of ice Ih has been studied by means of path-integral molecular dynamics simulations at temperatures between 50 and 300 K. Interatomic interactions were modeled by using the effective q-TIP4P/F potential for flexible water. Positive (compression) and negative (tension) pressures have been considered, which allowed us to approach the limits for the mechanical stability of this solid water phase. We have studied the pressure dependence of the crystal volume, bulk modulus, interatomic distances, atomic delocalization, and kinetic energy. The spinodal point at both negative and positive pressures is derived from the vanishing of the bulk modulus. For P<0, the spinodal pressure changes from -1.38 to - 0.73 GPa in the range from 50 to 300 K. At positive pressure the spinodal is associated with ice amorphization, and at low temperatures it is found to be between 1.1 and 1.3 GPa. Quantum nuclear effects cause a reduction of the metastability region of ice Ih.

Relaxation of the bulk modulus in partially molten dunite?

NASA Astrophysics Data System (ADS)

Cline, C. J.; Jackson, I.

2016-11-01

To address the possibility of melt-related bulk modulus relaxation, a forced oscillation experiment was conducted at seismic frequencies on a partially molten synthetic dunite specimen (melt fraction = 0.026) utilizing the enhanced capacity of the Australian National University attenuation apparatus to operate in both torsional and flexural oscillation modes. Shear modulus and dissipation data are consistent with those for melt-bearing olivine specimens previously tested in torsion, with a pronounced dissipation peak superimposed on high-temperature background. Flexural data exhibit a monotonic decrease in complex Young's modulus with increasing temperature under transsolidus temperatures. The observed variation of Young's modulus is well described by the relationship 1/E 1/3G, without requiring relaxation of the bulk modulus. At high homologous temperatures, when shear modulus is low, extensional and flexural oscillation measurements have little resolution of bulk modulus, and thus, only pressure oscillation measurements can definitively constrain bulk properties at these conditions.

The elastic constants of San Carlos olivine to 17 GPa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abramson, E.H.; Brown, J.M.; Slutsky, L.J.

1997-06-01

All elastic constants, the average bulk and shear moduli, and the lattice parameters of San Carlos olivine (Fo{sub 90}) (initial density 3.355gm/cm{sup 3}) have been determined to a pressure of 12 GPa at room temperature. Measurements of c{sub 11}, c{sub 33}, c{sub 13}, and c{sub 55} have been extended to 17 GPa. The pressure dependence of the adiabatic, isotropic (Hashin-Shtrikman bounds) bulk modulus, and shear modulus may be expressed as K{sub HS}=129.4+4.29P and by G{sub HS}=78+1.71P{minus}0.027P{sup 2}, where both the pressure and the moduli are in gigapascals. The isothermal compression of olivine is described by a bulk modulus given asmore » K{sub T}=126.3+4.28P. Elastic constants other than c{sub 55} can be adequately represented by a linear relationship in pressure. In the order (c{sub 11},c{sub 12},c{sub 13},c{sub 22},c{sub 23},c{sub 33},c{sub 44},c{sub 55},c{sub 66}) the 1 bar intercepts (gigapascal units) are (320.5, 68.1, 71.6, 196.5, 76.8, 233.5, 64.0, 77.0, 78.7). The first derivatives are (6.54, 3.86, 3.57, 5.38, 3.37, 5.51, 1.67, 1.81, 1.93). The second derivative for c{sub 55} is {minus}0.070GPa{sup {minus}1}. Incompressibilities for the three axes may also be expressed as linear relationships with pressure. In the order of {bold a, b}, and {bold c} axes the intercepts in gigapascals are (547.8, 285.8, 381.8) and the first derivatives are (20.1, 12.3, 14.0).{copyright} 1997 American Geophysical Union« less

High Temperature Elastic Properties of Reduced Activation Ferritic-Martensitic (RAFM) Steel Using Impulse Excitation Technique

NASA Astrophysics Data System (ADS)

Tripathy, Haraprasanna; Raju, Subramanian; Hajra, Raj Narayan; Saibaba, Saroja

2018-03-01

The polycrystalline elastic constants of an indigenous variant of 9Cr-1W-based reduced activation ferritic-martensitic (RAFM) steel have been determined as a function of temperature from 298 K to 1323 K (25 °C to 1000 °C), using impulse excitation technique (IET). The three elastic constants namely, Young's modulus E, shear modulus G, and bulk modulus B, exhibited significant softening with increasing temperature, in a pronounced non-linear fashion. In addition, clearly marked discontinuities in their temperature variations are noticed in the region, where ferrite + carbides → austenite phase transformation occurred upon heating. Further, the incidence of austenite → martensite transformation upon cooling has also been marked by a step-like jump in both elastic E and shear moduli G. The martensite start M s and M f finish temperatures estimated from this study are, M s = 652 K (379 °C) and M f =580 K (307 °C). Similarly, the measured ferrite + carbide → austenite transformation onset ( Ac 1) and completion ( Ac 3) temperatures are found to be 1126 K and 1143 K (853 °C and 870 °C), respectively. The Poisson ratio μ exhibited distinct discontinuities at phase transformation temperatures; but however, is found to vary in the range 0.27 to 0.29. The room temperature estimates of E, G, and μ for normalized and tempered microstructure are found to be 219 GPa, 86.65 GPa, and 0.27, respectively. For the metastable austenite phase, the corresponding values are: 197 GPa, 76.5 GPa, and 0.29, respectively. The measured elastic properties as well as their temperature dependencies are found to be in good accord with reported estimates for other 9Cr-based ferritic-martensitic steel grades. Estimates of θ D el , the elastic Debye temperature and γ G, the thermal Grüneisen parameter obtained from measured bulk elastic properties are found to be θ D el = 465 K (192 °C) and γ G = 1.57.

Pressure derivatives of elastic moduli of fused quartz to 10 kb

USGS Publications Warehouse

Peselnick, L.; Meister, R.; Wilson, W.H.

1967-01-01

Measurements of the longitudinal and shear moduli were made on fused quartz to 10 kb at 24??5??C. The anomalous behavior of the bulk modulus K at low pressure, ???K ???P 0, at higher pressures. The pressure derivative of the rigidity modulus ???G ???P remains constant and negative for the pressure range covered. A 15-kb hydrostatic pressure vessel is described for use with ultrasonic pulse instrumentation for precise measurements of elastic moduli and density changes with pressure. The placing of the transducer outside the pressure medium, and the use of C-ring pressure seals result in ease of operation and simplicity of design. ?? 1967.

The velocity, refractive index, and equation of state of liquid ammonia at high temperatures and high pressures.

PubMed

Li, Fangfei; Li, Min; Cui, Qiliang; Cui, Tian; He, Zhi; Zhou, Qiang; Zou, Guangtian

2009-10-07

The high temperature and high pressure Brillouin scattering studies of liquid ammonia have been performed in a diamond anvil cell. Acoustic velocity, refractive index, adiabatic bulk modulus, and the equation of state of liquid ammonia were determined at temperatures up to 410 K and at pressures up to the solidification point. Velocity and refractive index increase smoothly with increasing pressure along isothermals but decrease slightly with the temperature increase. The bulk modulus increases linearly with pressure and its slope dB/dP decreases slightly with increasing temperature from 6.67 at 297 K to 5.94 at 410 K.

Equation of state of rhenium and application for ultra high pressure calibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anzellini, Simone; Dewaele, Agnès; Occelli, Florent

2014-01-28

The isothermal equation of state of rhenium has been measured by powder X-ray diffraction experiments up to 144 GPa at room temperature in a diamond anvil cell. A helium pressure transmitting medium was used to minimize the non-hydrostatic stress on the sample. The fit of pressure-volume data yields a bulk modulus K{sub 0} = 352.6 GPa and a pressure derivative of the bulk modulus K′{sub 0}=4.56. This equation of state differs significantly from a recent determination [Dubrovinsky et al., Nat. Commun. 3, 1163 (2012)], giving here a lower pressure at a given volume. The possibility of using rhenium gasket X-ray diffraction signal, with themore » present equation of state, to evaluate multi-Mbar pressures in the chamber of diamond anvil cells is discussed.« less

Effects of temperature and pressure on thermodynamic properties of Cd0.50 Zn0.50 Se alloy

NASA Astrophysics Data System (ADS)

Aarifeen, Najm ul; Afaq, A.

2017-09-01

Thermodynamic properties of \\text{C}{{\\text{d}}0.50} \\text{Z}{{\\text{n}}0.50} Se alloy are studied using quasi harmonic model for pressure range 0-10 GPa and temperature range 0-1000 K. The structural optimization is obtained by self consistent field calculations and full-potential linear muffin-tin orbital method with GGA+U as an exchange correlation functional where U=2.3427 eV is the hubbard potential. The effects of temperature and pressure on the bulk modulus, Helmholtz free energy, internal energy, entropy, Debye temperature, Grüneisen parameter, thermal expansion coefficient and heat capacities of the material are observed and discussed. The bulk modulus, Helmholtz free energy and Debye temperature are found to decrease with increasing temperature while there is an increasing behavior when the pressure rises. Whereas internal energy has increasing trend with rises in temperature and it almost remains insensitive to pressure. The entropy of the system increases (decreases) with a rise of pressure (temperature).

Resonant Ultrasound Spectroscopy studies of Berea sandstone at high temperature

DOE PAGES

Davis, Eric S.; Sturtevant, Blake T.; Sinha, Dipen N.; ...

2016-09-04

Resonant Ultrasound Spectroscopy was used in this paper to determine the elastic moduli of Berea sandstone from room temperature to 478 K. Sandstone is a common component of oil reservoirs, and the temperature range was chosen to be representative of typical downhole conditions, down to about 8 km. In agreement with previous works, Berea sandstone was found to be relatively soft with a bulk modulus of approximately 6 GPa as compared to 37.5 GPa for α-quartz at room temperature and pressure. Finally, it was found that Berea sandstone undergoes a ~17% softening in bulk modulus between room temperature and 385more » K, followed by an abnormal behavior of similar stiffening between 385 K and 478 K.« less

Resonant Ultrasound Spectroscopy studies of Berea sandstone at high temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Eric S.; Sturtevant, Blake T.; Sinha, Dipen N.

Resonant Ultrasound Spectroscopy was used in this paper to determine the elastic moduli of Berea sandstone from room temperature to 478 K. Sandstone is a common component of oil reservoirs, and the temperature range was chosen to be representative of typical downhole conditions, down to about 8 km. In agreement with previous works, Berea sandstone was found to be relatively soft with a bulk modulus of approximately 6 GPa as compared to 37.5 GPa for α-quartz at room temperature and pressure. Finally, it was found that Berea sandstone undergoes a ~17% softening in bulk modulus between room temperature and 385more » K, followed by an abnormal behavior of similar stiffening between 385 K and 478 K.« less

Correlation between physical properties and ultrasonic relaxation parameters in transition metal tellurite glasses

NASA Astrophysics Data System (ADS)

Abd El-Moneim, A.

2003-07-01

The correlation between activation energy of ultrasonic relaxation process through the temperature range from 140 to 300 K and some physical properties has been investigated in pure TeO 2 and transition metal TeO 2-V 2O 5 and TeO 2-MoO 3 glasses according to Bridge and Patel's theory. The oxygen density (loss centers), number of two-well systems, hopping distance and mechanical relaxation time have been calculated in these glasses from the data of density, bulk modulus and stretching force constant of the glass. It has been found that the acoustic activation energy increased linearly with both the oxygen density and the number of two-well systems. The correlation between the acoustic activation energy and bulk modulus was achieved through the stretching force constant of the network and other structural parameters. Moreover, the experimental values of activation energy (V) agree well with those calculated from an empirical equation presented in this study in the form V=2.9×10 -7 F( F/ K) 3.37, where F is the stretching force constant of the glass and K is the experimental bulk modulus.

The Compressibility of a Natural Kyanite at 300 K

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, X.; Shieh, S; Fleet, M

2009-01-01

The compressional behaviour of a natural kyanite, (Al{sub 1.99}Fe{sub 0.01})SiO{sub 5}, has been investigated to about 17.5 GPa at 300 K using a diamond-anvil cell and synchrotron X-ray diffraction. The pressure-volume data fitted to the third-order Birch-Murnaghan equation of state (EoS) yield an isothermal bulk modulus (K{sub 0T}) of 192 {+-} 6 GPa and pressure derivative (K'{sub 0T}) of 6 {+-} 1. When K'{sub 0T} is fixed as 4, the derived K{sub 0T} is 201 {+-} 2 GPa. These values are in excellent agreement with most experimental determinations in the literature. Consequently, it can be concluded that the compressibility ofmore » kyanite under high pressures has been accurately constrained.« less

Bulk Modulus Relaxation in Partially Molten Dunite?

NASA Astrophysics Data System (ADS)

Jackson, I.; Cline, C. J., II

2016-12-01

Synthetic solgel-derived Fo90 olivine was mixed with 3.5 wt % basaltic glass and hot-pressed within Ni/Fe foil to produce a dense aggregate expected to contain a small melt fraction at temperatures ≥ 1100°C. This specimen was precision ground and tested in both torsional and flexural forced oscillation to determine the relaxation behavior of both shear (G) and bulk (K) moduli at seismic frequencies. A recent upgrade of our experimental facility allows such measurements to be made without alteration of the driver/detector geometry, and uses an oscillating bending force rather than a bending moment, as previously described. The torsional and flexural tests were conducted in a gas apparatus at 200 MPa confining pressure, with oscillation periods ranging between 1 and 1000 s, during slow staged-cooling from 1300 to 25°C. Shear modulus and associated dissipation data are consistent with those for melt-bearing olivine specimens previously tested in torsion, with a pronounced dissipation peak superimposed on high-temperature background within the 1-1000 s observational window at temperatures of 1100-1200°C. A filament elongation model relates the observed flexural measurements to the variations along the experimental assembly of the complex Young's modulus (E*), bending moment and diametral moment of inertia. With E* given by 1/E*=1/(3G*) + 1/(9K*), and the complex shear modulus (G*) derived from torsional oscillation, any relaxation of K can be identified. Preliminary modeling shows that the viscoelastic properties in flexure are broadly consistent with those expected from the shear-mode viscoelasticity with anharmonic (real) values of K. However, some discrepancies between modeled results and flexure data at super-solidus temperatures require further investigation of possible differences in shear modulus relaxation between the torsional and flexural modes, and of potential relaxation of the bulk modulus through stress-induced changes in melt redistribution and/or proportions of coexisting crystalline and melt phases.

Single crystal growth, crystalline structure investigation and high-pressure behavior of impurity-free siderite (FeCO3)

NASA Astrophysics Data System (ADS)

Liang, Wen; Yin, Yuan; Li, Zeming; Li, Rui; Li, Lin; He, Yu; Dong, Haini; Li, Zengsheng; Yan, Shuai; Zhai, Shuangmeng; Li, Heping

2018-03-01

Single crystals of impurity-free siderite were grown successfully using high-temperature-pressure annealing. The size of crystals ranged up to 100 µm, and they exhibited a rhomboid shape upon cleavage along the (101) plane. The composition of Fe0.9988±0.0011CO3 was quantified using electron probe analysis. Accurate crystalline structural data were investigated by means of single crystal X-ray diffraction (XRD) and the unit cell dimensions obtained in the rhombohedral symmetry of the R\\bar {3}c space group were a = 4.6861(3) and c = 15.362(2), and the final R = 0.0499. Using in situ synchrotron XRD, the high-pressure behavior of impurity-free siderite was investigated up to 20 GPa at ambient temperature. The pressure-volume (P-V) EoS was fitted by a third-order Birch-Murnaghan equation, and the isothermal bulk modulus was K 0 = 97.5(11) GPa for K 0' = 4. High-pressure Raman spectroscopy was performed at up to 30 GPa at ambient temperature, and the Raman bands shifted as the increase of pressure ({{d/ν _i}}{{{d}P}} ) was determined. In combination with the high-pressure Raman results and the bulk modulus K 0, the mode Grüneisen parameters of each vibration were calculated. Meanwhile, high-temperature Raman spectroscopy was carried out at up to 300 °C and the Raman band shift ({{d/ν _i}}{{{d}t}} ) was also quantified.

Polycrystalline gamma plutonium's elastic moduli versus temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Migliori, Albert; Betts, J; Trugman, A

2009-01-01

Resonant ultrasound spectroscopy was used to measure the elastic properties of pure polycrystalline {sup 239}Pu in the {gamma} phase. Shear and longitudinal elastic moduli were measured simultaneously and the bulk modulus was computed from them. A smooth, linear, and large decrease of all elastic moduli with increasing temperature was observed. They calculated the Poisson ratio and found that it increases from 0.242 at 519 K to 0.252 at 571 K. These measurements on extremely well characterized pure Pu are in agreement with other reported results where overlap occurs.

High Pressure Properties of a Ba-Cu-Zn-P Clathrate-I

DOE PAGES

Dolyniuk, Juli -Anna; Kovnir, Kirill

2016-08-12

Here, the high pressure properties of the novel tetrel-free clathrate, Ba 8Cu 13.1Zn 3.3P 29.6, were investigated using synchrotron powder X-ray diffraction. The pressure was applied using a diamond anvil cell. No structural transitions or decomposition were detected in the studied pressure range of 0.1–7 GPa. The calculated bulk modulus for Ba 8Cu 13.1Zn 3.3P 29.6 using a third-order Birch-Murnaghan equation of state is 65(6) GPa at 300 K. This bulk modulus is comparable to the bulk moduli of Ge- and Sn-based clathrates, like A 8Ga 16Ge 30 (A = Sr, Ba) and Sn 19.3Cu 4.7P 22I 8, but lowermore » than those for the transition metal-containing silicon-based clathrates, Ba 8 T xSi46–x, T = Ni, Cu; 3 ≤ x ≤ 5.« less

Structural, vibrational and thermophysical properties of pyrophyllite by semi-empirical density functional modelling

NASA Astrophysics Data System (ADS)

Ulian, Gianfranco; Valdrè, Giovanni

2015-07-01

Pyrophyllite has a significant role in both geophysics as a hydrous phase, which can recycle water into the Earth's mantle, and many industrial applications, such as petroleum and civil engineering. However, very few works have been proposed to fully characterize the thermodynamic properties of this mineral, especially at atomic scale. In the present work, we report structural, vibrational, thermochemical and thermophysical properties of pyrophyllite, calculated at the density functional theory level with the hybrid B3LYP functional, all-electron Gaussian-type orbitals and taking into account a correction to include dispersive forces. V( P, T) data at 300 K fit with isothermal third-order Birch-Murnaghan equations of state and yield K T 0 = 46.57 GPa, K' = 10.51 and V 0 = 213.67 Å3, where K T 0 is the thermal bulk modulus at 0 GPa, K' is the first derivative and V 0 is the volume at zero pressure, in very good agreement with recent experimental results obtained by in situ single-crystal synchrotron XRD. The compressional behaviour is highly anisotropic, with axial compressibility in ratio β( a):β( b):β( c) = 1.218:1.000:4.188. Pyrophyllite bulk modulus, thermal expansion coefficients and heat capacity at different P- T conditions are provided. The results of this kind of analysis can be useful in both geophysical and technological applications of the mineral and expand the high-temperature and high-pressure knowledge of this phase at physical conditions that are still difficult to obtain by experimental means. The simulated vibrational spectrum can also be used as a guideline by other authors in their experimental investigation of pyrophyllite.

Single-crystal X-ray diffraction study of Fe 2SiO 4 fayalite up to 31 GPa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jin S.; Hu, Yi; Shelton, Hannah

2016-10-03

Olivine is widely believed to be the most abundant mineral in the Earth’s upper mantle. Here, we report structural refinement results for the Fe-end-member olivine, Fe 2SiO 4 fayalite, up to 31 GPa in diamond-anvil cell, using single-crystal synchrotron X-ray diffraction. Unit-cell parameters a, b, c and V, average Si–O Fe–O bond lengths, as well as Si–O Fe–O polyhedral volumes continuously decrease with increasing pressure. The pressure derivative of isothermal bulk modulus K' T0 is determined to be 4.0 (2) using third-order Birch–Murnaghan equation of state with ambient isothermal bulk modulus fixed to 135 GPa on the basis of previousmore » Brillouin measurements. The Si–O tetrahedron is stiffer than the Fe–O octahedra, and the compression mechanism is dominated by Fe–O bond and Fe–O octahedral compression. Densities of olivine along 1600 and 900 K adiabats are calculated based on this study. The existence of metastable olivine inside the cold subduction slab could cause large positive buoyancy force against subduction, slow down the subduction and possibly affect the slab geometry.« less

Ab-initio study of C15-type Laves phase superconductor LaRu2

NASA Astrophysics Data System (ADS)

Kholil, Md. Ibrahim; Islam, Md. Shahinur; Rahman, Md. Atikur

2017-01-01

Structural, elastic, electronic, optical, thermodynamic, and superconducting properties of the Laves phase superconductor LaRu2 with Tc 1.63 K were investigated using the first-principles calculations for the first time. The corresponding evaluated structural parameters are in good agreement with the available theoretical values. The different elastic properties like as, elastic constants, bulk modulus B, shear modulus G, Young's modulus E, and Poisson ratio ν were calculated using the Voigt-Reuss-Hill approximation. The ductility nature appears in both values of Cauchy pressure and Pugh's ratio. The band structure and Cauchy pressure shows that the material behaves metallic nature. The calculated total density of state is 6.80 (electrons/eV) of LaRu2. The optical properties such as reflectivity, absorption spectrum, refractive index, dielectric function, conductivity, and energy loss spectrum are also calculated. The photoconductivity reveals the metallic nature of LaRu2 and absorption coefficient is good in the infrared region. The evaluated density and Debye temperature are 9.55 gm/cm3 and 110.51 K, respectively. In addition, the study of thermodynamic properties like as minimum thermal conductivity, melting temperature, and Dulong-Petit limit are 0.26 (Wm-1 K-1), 1,471.65 K, and 74.80 (J/mole K), respectively. Finally, the investigated electron-phonon coupling constant is 0.66 of LaRu2 superconductor.

Friction of sodium alginate hydrogel scaffold fabricated by 3-D printing.

PubMed

Yang, Qian; Li, Jian; Xu, Heng; Long, Shijun; Li, Xuefeng

2017-04-01

A rapid prototyping technology, formed by three-dimensional (3-D) printing and then crosslinked by spraying Ca 2+ solution, is developed to fabricate a sodium alginate (SA) hydrogel scaffold. The porosity, swelling ratio, and compression modulus of the scaffold are investigated. A friction mechanism is developed by studying the reproducible friction behavior. Our results show that the scaffold can have 3-D structure with a porosity of 52%. The degree of swelling of the SA hydrogel scaffold is 8.5, which is nearly the same as bulk SA hydrogel. SA hydrogel exhibits better compressive resilience than bulk hydrogel despite its lower compressive modulus compared to bulk hydrogel. The SA hydrogel scaffold exhibits a higher frictional force at low sliding velocity (10 -6 to 10 -3  m/s) compared to bulk SA hydrogel, and they are equal at high sliding velocity (10 -2 to 1 m/s). For a small pressure (0.3 kPa), the SA hydrogel scaffold shows good friction reproducibility. In contrast, bulk SA hydrogel shows poor reproducibility with respect to friction behavior. The differences in friction behaviors between the SA hydrogel scaffold and bulk SA hydrogel are related to the structure of the scaffold, which can keep a stable hydrated lubrication layer.

Alloying effects on structural and thermal behavior of Ti{sub 1-x}Zr{sub x}C: A first principles study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chauhan, Mamta, E-mail: mamta-physics@yahoo.co.in; Gupta, Dinesh C., E-mail: sosfizix@gmail.com

2016-05-06

The formation energy, equilibrium lattice parameter, bulk modulus, Debye temperature and heat capacity at constant volume have been calculated for TiC, ZrC, and their intermediate alloys (Ti{sub 1-x}Zr{sub x}C, x = 0,0.25.0.5,0.75,1) using first principles approach. The calculated values of lattice parameter and bulk modulus agree well with the available experimental and earlier theoretical reports. The variation of lattice parameter and bulk modulus with the change in concentration of Zr atom in Ti{sub 1-x}Zr{sub x}C has also been reported. The heat capacities of TiC, ZrC, and their intermediate alloys have been calculated by considering both vibrational and electronic contributions.

Worms under Pressure: Bulk Mechanical Properties of C. elegans Are Independent of the Cuticle

PubMed Central

Gilpin, William; Uppaluri, Sravanti; Brangwynne, Clifford P.

2015-01-01

The mechanical properties of cells and tissues play a well-known role in physiology and disease. The model organism Caenorhabditis elegans exhibits mechanical properties that are still poorly understood, but are thought to be dominated by its collagen-rich outer cuticle. To our knowledge, we use a novel microfluidic technique to reveal that the worm responds linearly to low applied hydrostatic stress, exhibiting a volumetric compression with a bulk modulus, κ = 140 ± 20 kPa; applying negative pressures leads to volumetric expansion of the worm, with a similar bulk modulus. Surprisingly, however, we find that a variety of collagen mutants and pharmacological perturbations targeting the cuticle do not impact the bulk modulus. Moreover, the worm exhibits dramatic stiffening at higher stresses—behavior that is also independent of the cuticle. The stress-strain curves for all conditions can be scaled onto a master equation, suggesting that C. elegans exhibits a universal elastic response dominated by the mechanics of pressurized internal organs. PMID:25902429

A First-Principles Theoretical Study on the Thermoelectric Properties of the Compound Cu5AlSn2S8

NASA Astrophysics Data System (ADS)

Li, Weijian; Zhou, Chenyi; Li, Liangliang

2016-03-01

A new compound of Cu5AlSn2S8, which contained earth-abundant and environment-friendly elements and had a diamond-like crystal structure, was designed, and its electronic structure and thermoelectric transport properties from 300 K to 700 K were investigated by first-principles calculations, Boltzmann transport equations, and a modified Slack's model. The largest power factors of Cu5AlSn2S8 at 700 K were 47.5 × 1010 W m-1 K-2 s-1 and 14.7 × 1010 W m-1 K-2 s-1 for p- and n-type semiconductors, respectively. The lattice thermal conductivity of Cu5AlSn2S8 was calculated with its shear modulus and isothermal bulk modulus, which were also obtained by first-principles calculations. The lattice thermal conductivity was 0.9-2.2 W m-1 K-1 from 300 K to 700 K, relatively low among thermoelectric compounds. This theoretical study showed that Cu5AlSn2S8 could be a potential thermoelectric material.

Impedance Spectroscopy and AC Conductivity Studies of Bulk 3-Amino-7-(dimethylamino)-2-methyl-hydrochloride

NASA Astrophysics Data System (ADS)

El-Shabaan, M. M.

2018-02-01

Impedance spectroscopy and alternating-current (AC) conductivity (σ AC) studies of bulk 3-amino-7-(dimethylamino)-2-methyl-hydrochloride (neutral red, NR) have been carried out over the temperature (T) range from 303 K to 383 K and frequency (f) range from 0.5 kHz to 5 MHz. Dielectric data were analyzed using the complex impedance (Z *) and complex electric modulus (M *) for bulk NR at various temperatures. The impedance loss peaks were found to shift towards high frequencies, indicating an increase in the relaxation time (τ 0) and loss in the material, with increasing temperature. For each temperature, a single depressed semicircle was observed at high frequencies, originating from the bulk transport, and a spike in the low-frequency region, resulting from the electrode effect. Fitting of these curves yielded an equivalent circuit containing a parallel combination of a resistance R and constant-phase element (CPE) Q. The carrier transport in bulk NR is governed by the correlated barrier hopping (CBH) mechanism, some parameters of which, such as the maximum barrier height (W M), charge density (N), and hopping distance (r), were determined as functions of both temperature and frequency. The frequency dependence of σ AC at different temperatures indicated that the conduction in bulk NR is a thermally activated process. The σ AC value at different frequencies increased linearly with temperature.

Static and vibrational properties of equiatomic Na-based binary alloys

NASA Astrophysics Data System (ADS)

Vora, Aditya M.

2007-09-01

The computations of the static and vibrational properties of four equiatomic Na-based binary alloys viz. Na0.5Li0.5, Na0.5K0.5, Na0.5Rb0.5 and Na0.5Cs0.5, to second order in local model potential is discussed in terms of real-space sum of Born von Karman central force constants. The local field correlation functions due to Hartree (H), Ichimaru Utsumi (IU) and Sarkar et al. (S) are used to investigate the influence of the screening effects on the aforesaid properties. Results for the lattice constants C11, C12, C44, C12 C44, C12/C44 and bulk modulus B obtained using the H-local field correction function have higher values in comparison with the results obtained for the same properties using IU- and S-local field correction functions. The results for the Shear modulus (C‧), deviation from Cauchy's relation, Poisson's ratio σ, Young modulus Y, propagation velocity of elastic waves, phonon dispersion curves and degree of anisotropy A are highly appreciable for the four equiatomic Na-based binary alloys.

Temperature and pressure correlation for volume of gas hydrates with crystal structures sI and sII

NASA Astrophysics Data System (ADS)

Vinš, Václav; Jäger, Andreas; Hielscher, Sebastian; Span, Roland; Hrubý, Jan; Breitkopf, Cornelia

The temperature and pressure correlations for the volume of gas hydrates forming crystal structures sI and sII developed in previous study [Fluid Phase Equilib. 427 (2016) 268-281], focused on the modeling of pure gas hydrates relevant in CCS (carbon capture and storage), were revised and modified for the modeling of mixed hydrates in this study. A universal reference state at temperature of 273.15 K and pressure of 1 Pa is used in the new correlation. Coefficients for the thermal expansion together with the reference lattice parameter were simultaneously correlated to both the temperature data and the pressure data for the lattice parameter. A two-stage Levenberg Marquardt algorithm was employed for the parameter optimization. The pressure dependence described in terms of the bulk modulus remained unchanged compared to the original study. A constant value for the bulk modulus B0 = 10 GPa was employed for all selected hydrate formers. The new correlation is in good agreement with the experimental data over wide temperature and pressure ranges from 0 K to 293 K and from 0 to 2000 MPa, respectively. Compared to the original correlation used for the modeling of pure gas hydrates the new correlation provides significantly better agreement with the experimental data for sI hydrates. The results of the new correlation are comparable to the results of the old correlation in case of sII hydrates. In addition, the new correlation is suitable for modeling of mixed hydrates.

Thermoelastic properties of liquid Fe-C revealed by sound velocity and density measurements at high pressure

NASA Astrophysics Data System (ADS)

Shimoyama, Yuta; Terasaki, Hidenori; Urakawa, Satoru; Takubo, Yusaku; Kuwabara, Soma; Kishimoto, Shunpachi; Watanuki, Tetsu; Machida, Akihiko; Katayama, Yoshinori; Kondo, Tadashi

2016-11-01

Carbon is one of the possible light elements in the cores of the terrestrial planets. The P wave velocity (VP) and density (ρ) are important factors for estimating the chemical composition and physical properties of the core. We simultaneously measured the VP and ρ of Fe-3.5 wt % C up to 3.4 GPa and 1850 K by using ultrasonic pulse-echo method and X-ray absorption methods. The VP of liquid Fe-3.5 wt % C decreased linearly with increasing temperature at constant pressure. The addition of carbon decreased the VP of liquid Fe by about 2% at 3 GPa and 1700 K and decreased the Fe density by about 2% at 2 GPa and 1700 K. The bulk modulus of liquid Fe-C and its pressure (P) and temperature (T) effects were precisely determined from directly measured ρ and VP data to be K0,1700 K = 83.9 GPa, dKT/dP = 5.9(2), and dKT/dT = -0.063 GPa/K. The addition of carbon did not affect the isothermal bulk modulus (KT) of liquid Fe, but it decreased the dK/dT of liquid Fe. In the ρ-VP relationship, VP increases linearly with ρ and can be approximated as VP (m/s) = -6786(506) + 1537(71) × ρ (g/cm3), suggesting that Birch's law is valid for liquid Fe-C at the present P-T conditions. Our results imply that at the conditions of the lunar core, the elastic properties of an Fe-C core are more affected by temperature than those of Fe-S core.

Dynamic analysis of bulk-fill composites: Effect of food-simulating liquids.

PubMed

Eweis, Ahmed Hesham; Yap, Adrian U-Jin; Yahya, Noor Azlin

2017-10-01

This study investigated the effect of food simulating liquids on visco-elastic properties of bulk-fill restoratives using dynamic mechanical analysis. One conventional composite (Filtek Z350 [FZ]), two bulk-fill composites (Filtek Bulk-fill [FB] and Tetric N Ceram [TN]) and a bulk-fill giomer (Beautifil-Bulk Restorative [BB]) were evaluated. Specimens (12 × 2 × 2mm) were fabricated using customized stainless steel molds. The specimens were light-cured, removed from their molds, finished, measured and randomly divided into six groups. The groups (n = 10) were conditioned in the following mediums for 7 days at 37°C: air (control), artificial saliva (SAGF), distilled water, 0.02N citric acid, heptane, 50% ethanol-water solution. Specimens were assessed using dynamic mechanical testing in flexural three-point bending mode and their respective mediums at 37°C and a frequency range of 0.1-10Hz. The distance between the supports were fixed at 10mm and an axial load of 5N was employed. Data for elastic modulus, viscous modulus and loss tangent were subjected to ANOVA/Tukey's tests at significance level p < 0.05. Significant differences in visco-elastic properties were observed between materials and mediums. Apart from bulk-fill giomer, elastic modulus was the highest after conditioning in heptane. No apparent trends were noted for viscous modulus. Generally, loss tangent was the highest after conditioning in ethanol. The effect of food-simulating liquids on the visco-elastic properties of bulk-fill composites was material and medium dependent. Copyright © 2017 Elsevier Ltd. All rights reserved.

High Pressure Elastic Behavior of Synthetic Mg 3 Y 2 (SiO 4 ) 3 Garnet up to 9 GPa

DOE PAGES

Fan, Dawei; Ma, Maining; Wei, Shuyi; ...

2013-01-01

Tmore » he compression behavior of synthetic magnesium- (Mg-) yttrium (Y) garnet Mg 3 Y 2 (SiO 4 ) 3 has been investigated upto about 8.79 GPa at 300 K using in situ angle-dispersive X-ray diffraction and a diamond anvil cell at the beamline X17C, National Synchrotron Light Source, Brookhaven National Laboratory. No phase transition has been observed within the pressure range investigated. he unit-cell parameters and volume decreased systematically with increasing pressure, and a reliable isothermal bulk modulus ( K 0 ) and its pressure derivative ( K 0 ′ ) were obtained in this study. he values of zero-pressure volume V 0 , K 0 , and K 0 ′ refined with a third-order Birch-Murnaghan equation of state are V 0 = 1727.9 ± 0.2  Å 3 , K 0 = 145 ± 3  GPa, and K 0 ′ = 8.5 ± 0.9 . If K 0 ′ is fixed at 4, K 0 is obtained as 158 ± 2  GPa.« less

High Pressure Elastic Behavior of Synthetic Mg 3 Y 2 (SiO 4 ) 3 Garnet up to 9 GPa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Dawei; Ma, Maining; Wei, Shuyi

Tmore » he compression behavior of synthetic magnesium- (Mg-) yttrium (Y) garnet Mg 3 Y 2 (SiO 4 ) 3 has been investigated upto about 8.79 GPa at 300 K using in situ angle-dispersive X-ray diffraction and a diamond anvil cell at the beamline X17C, National Synchrotron Light Source, Brookhaven National Laboratory. No phase transition has been observed within the pressure range investigated. he unit-cell parameters and volume decreased systematically with increasing pressure, and a reliable isothermal bulk modulus ( K 0 ) and its pressure derivative ( K 0 ′ ) were obtained in this study. he values of zero-pressure volume V 0 , K 0 , and K 0 ′ refined with a third-order Birch-Murnaghan equation of state are V 0 = 1727.9 ± 0.2  Å 3 , K 0 = 145 ± 3  GPa, and K 0 ′ = 8.5 ± 0.9 . If K 0 ′ is fixed at 4, K 0 is obtained as 158 ± 2  GPa.« less

High-pressure X-ray diffraction and Raman spectroscopy of CaFe2O4-type β-CaCr2O4

NASA Astrophysics Data System (ADS)

Zhai, Shuangmeng; Yin, Yuan; Shieh, Sean R.; Shan, Shuangming; Xue, Weihong; Wang, Ching-Pao; Yang, Ke; Higo, Yuji

2016-04-01

In situ high-pressure synchrotron X-ray diffraction and Raman spectroscopic studies of orthorhombic CaFe2O4-type β-CaCr2O4 chromite were carried out up to 16.2 and 32.0 GPa at room temperature using multi-anvil apparatus and diamond anvil cell, respectively. No phase transition was observed in this study. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields a zero-pressure volume of V 0 = 286.8(1) Å3, an isothermal bulk modulus of K 0 = 183(5) GPa and the first pressure derivative of isothermal bulk modulus K 0' = 4.1(8). Analyses of axial compressibilities show anisotropic elasticity for β-CaCr2O4 since the a-axis is more compressible than the b- and c-axis. Based on the obtained and previous results, the compressibility of several CaFe2O4-type phases was compared. The high-pressure Raman spectra of β-CaCr2O4 were analyzed to determine the pressure dependences and mode Grüneisen parameters of Raman-active bands. The thermal Grüneisen parameter of β-CaCr2O4 is determined to be 0.93(2), which is smaller than those of CaFe2O4-type CaAl2O4 and MgAl2O4.

Thermodynamic properties of α-uranium

NASA Astrophysics Data System (ADS)

Ren, Zhiyong; Wu, Jun; Ma, Rong; Hu, Guichao; Luo, Chao

2016-11-01

The lattice constants and equilibrium atomic volume of α-uranium were calculated by Density Functional Theory (DFT). The first principles calculation results of the lattice for α-uranium are in agreement with the experimental results well. The thermodynamic properties of α-uranium from 0 to 900 K and 0-100 GPa were calculated with the quasi-harmonic Debye model. Volume, bulk modulus, entropy, Debye temperature, thermal expansion coefficient and the heat capacity of α-uranium were calculated. The calculated results show that the bulk modulus and Debye temperature increase with the increasing pressure at a given temperature while decreasing with the increasing temperature at a given pressure. Volume, entropy, thermal expansion coefficient and the heat capacity decrease with the increasing pressure while increasing with the increasing temperature. The theoretical results of entropy, Debye temperature, thermal expansion coefficient and the heat capacity show good agreement with the general trends of the experimental values. The constant-volume heat capacity shows typical Debye T3 power-law behavior at low temperature limit and approaches to the classical asymptotic Dulong-Petit limit at high temperature limit.

Impact of Reservoir Fluid Saturation on Seismic Parameters: Endrod Gas Field, Hungary

NASA Astrophysics Data System (ADS)

El Sayed, Abdel Moktader A.; El Sayed, Nahla A.

2017-12-01

Outlining the reservoir fluid types and saturation is the main object of the present research work. 37 core samples were collected from three different gas bearing zones in the Endrod gas field in Hungary. These samples are belonging to the Miocene and the Upper - Lower Pliocene. These samples were prepared and laboratory measurements were conducted. Compression and shear wave velocity were measured using the Sonic Viewer-170-OYO. The sonic velocities were measured at the frequencies of 63 and 33 kHz for compressional and shear wave respectively. All samples were subjected to complete petrophysical investigations. Sonic velocities and mechanical parameters such as young’s modulus, rigidity, and bulk modulus were measured when samples were saturated by 100%-75%-0% brine water. Several plots have been performed to show the relationship between seismic parameters and saturation percentages. Robust relationships were obtained, showing the impact of fluid saturation on seismic parameters. Seismic velocity, Poisson’s ratio, bulk modulus and rigidity prove to be applicable during hydrocarbon exploration or production stages. Relationships among the measured seismic parameters in gas/water fully and partially saturated samples are useful to outline the fluid type and saturation percentage especially in gas/water transitional zones.

Effects of water on P-V-T equation of state of pyrope

NASA Astrophysics Data System (ADS)

Fan, Dawei; Lu, Chang; Xu, Jingui; Yan, Bingmin; Yang, Bin; Chen, Jiuhua

2017-06-01

High-pressure single-crystal/powder synchrotron X-ray diffraction was carried out on a hydrous pure magnesium pyrope (Mg3Al2Si3O12) containing 900 ppmw H2O, synthesized at 4.0 GPa and 1300 K. The pressure-volume (P-V) single-crystal data from room pressure to 9.81 GPa at ambient temperature were fitted by a third-order Birch-Murnaghan equation of state (BM-EoS) yielding a unit-cell volume of V0 = 1505.14 ± 0.38 Å3, an isothermal bulk modulus of K0 = 160 ± 3 GPa and its pressure derivative K‧0 = 5.2 ± 0.4. When fixing K'0 = 4.0, the data yielded V0 = 1504.58 ± 0.32 Å3 and K0 = 166 ± 2 GPa. The pressure-volume-temperature (P-V-T) EoS of the synthetic hydrous pyrope was also measured at temperatures up to 900 K and pressures up to 16.75 GPa, using a diamond anvil cell in conjunction with in situ synchrotron angle-dispersive powder X-ray diffraction. The P-V data at room temperature and in a pressure range of 0.0001-14.81 GPa were then analyzed by a third-order BM-EoS and yielded V0 = 1505.35 ± 0.25 Å3, K0 = 161 ± 2 GPa, K‧0 = 5.0 ± 0.3. With K'0 fixed to 4.0, we also obtained V0 = 1505.04 ± 0.29 Å3 and K0 = 167 ± 1 GPa. Consequently, we fitted the P-V-T data with the high-temperature third-order BM-EoS approach and obtained the thermoelastic parameters of V0 = 1505.4 ± 0.3 Å3, K0 = 162 ± 1 GPa, K‧0 = 4.9 ± 0.2, the temperature derivative of the bulk modulus (∂K0/∂T)P = -0.018 ± 0.004 GPa K-1, and the thermal expansion coefficient at ambient conditions α0 = (3.2 ± 0.1) × 10-5 K-1. These properties were consistent with the thermal pressure EoS analysis. These new results on hydrous pyrope were also compared with previous studies of anhydrous pyrope. The main effect of hydration on pyrope is to decrease K0 and increase K'0 by increasing the vacancies or unoccupied volume in the structure. The entire dataset enabled us to examine the thermoelastic properties of important mantle garnets and this data has further applications for modeling the P-T conditions in the upper mantle of the Earth's interior using deep mineral assemblages.

Investigation to determine the vulnerability of reclaimed land to building collapse using near surface geophysical method

NASA Astrophysics Data System (ADS)

Adewoyin, O. O.; Joshua, E. O.; Akinyemi, M. L.; Omeje, M.; Joel, E. S.

2017-05-01

Adequate knowledge of the geology and the structures of the subsurface would assist engineers in the best way to carry out constructions to avoid building collapse. In this study, near surface seismic refraction method was used to determine the geotechnical parameters of the subsurface, the results obtained were correlated with the result of borehole data drilled in the study area. The results of seismic refraction method delineated mostly two distinct layers with the first layer having the lower geotechnical parameters. It was observed that in the first layer, the Young’s modulus ranged from 0.168 to 0.458 GPa, shear modulus ranged between 0.068 and 0.185 GPa, the bulk modulus ranged between 0.106 and 0.287 GPa while the bearing capacity ranged from 0.083 to 0.139 MPa. On the other hand, in the second layer, the Young’s modulus ranged between 3.717 and 7.018 GPa, shear modulus ranged from 1.500 to 2.830 GPa while the bulk modulus ranged from 2.383 to 4.449 GPa. Significantly, the formation of the second layer appeared to be more competent than the first layer, therefore engineering construction in this geological setting is recommended to be founded on the second layer at depth ranging between 7 and 16 m.

Elasticity of Pargasite Amphibole: A Hydrous Phase at Mid Lithospheric Discontinuity

NASA Astrophysics Data System (ADS)

Peng, Y.; Mookherjee, M.

2017-12-01

Mid Lithospheric Discontinuity (MLD) is characterized by a low shear wave velocity ( 3 to 10 %). In cratons, the depth of MLD varies between 80 and 100 km. The reduction of the shear wave velocity at MLD is similar to what is observed in the lithosphere-asthenosphere boundary (LAB). Such low velocity at MLD could be caused by partial melting, temperature induced grain boundary sliding, changes in the elastic anisotropy, and/or metasomatism which may lead to the formation of hydrous phases including mica and amphibole. Thus, it is clear that in order to assess the role of metasomatism at MLD, we need better constraints on the elasticity of hydrous phases. However, such elasticity data are scarce. In this study, we explore elasticity of pargasite amphibole [NaCa2(Mg4Al)(Si6Al2)O22(OH)2] using density functional theory (DFT) with local density approximation (LDA) and generalized gradient approximation (GGA). We find that the pressure-volume results can be adequately described by a finite strain equation with the bulk modulus, K0 being 102 and 85 GPa for LDA and GGA respectively. We also determined the full elastic constant tensor (Cij) using the finite difference method. The bulk modulus, K0 determined from the full elastic constant tensor is 104 GPa for LDA and 87 GPa for GGA. The shear modulus, G0 determined from the full elastic constant tensor is 64 GPa for LDA and 58 GPa for GGA. The bulk and shear moduli predicted with LDA are 5 and 1 % stiffer than the recent results [1]. In contrast, the bulk and shear moduli predicted with GGA are 12 and 10 % softer compared to the recent results [1]. The full elastic constant tensor for pargasite shows significant anisotropy. For instance, LDA predicts compressional (AVP) and shear (AVS) wave anisotropy of 22 and 20 % respectively. At higher pressure, elastic moduli stiffen. However, temperature is likely to have an opposite effect on the elasticity and this remains largely unknown for pargasite. Compared to the major mantle minerals, pargasite has softer elastic constants and significant anisotropy and may explain the reduction in shear wave velocity at MLD. Reference: [1] Brown, J. M., Abramson, E. H.,2016, Phys. Earth Planet. Int., 261, 161-171. Acknowledgement: This work is supported by US NSF award EAR 1639552.

Experimental and theoretical investigation of a mesoporous KxWO3 material having superior mechanical strength

NASA Astrophysics Data System (ADS)

Dey, Sonal; Anderson, Sean T.; Mayanovic, Robert A.; Sakidja, Ridwan; Landskron, Kai; Kokoszka, Berenika; Mandal, Manik; Wang, Zhongwu

2016-01-01

Mesoporous materials with tailored properties hold great promise for energy harvesting and industrial applications. We have synthesized a novel tungsten bronze mesoporous material (KxWO3; x ~ 0.07) having inverse FDU-12 type pore symmetry and a crystalline framework. In situ small angle X-ray scattering (SAXS) measurements of the mesoporous K0.07WO3 show persistence of a highly ordered meso-scale pore structure to high pressure conditions (~18.5 GPa) and a material with remarkable mechanical strength despite having ~35% porosity. Pressure dependent in situ SAXS measurements reveal a bulk modulus κ = 44 +/- 4 GPa for the mesoporous KxWO3 which is comparable to the corresponding value for the bulk monoclinic WO3 (γ-WO3). Evidence from middle angle (MAXS) and wide angle X-ray scattering (WAXS), high-resolution transmission electron microscopy (HR-TEM) and Raman spectroscopy shows that the presence of potassium leads to the formation of a K-bearing orthorhombic tungsten bronze (OTB) phase within a monoclinic WO3 host structure. Our ab initio molecular dynamics calculations show that the formation of the OTB phase provides superior strength to the mesoporous K0.07WO3.Mesoporous materials with tailored properties hold great promise for energy harvesting and industrial applications. We have synthesized a novel tungsten bronze mesoporous material (KxWO3; x ~ 0.07) having inverse FDU-12 type pore symmetry and a crystalline framework. In situ small angle X-ray scattering (SAXS) measurements of the mesoporous K0.07WO3 show persistence of a highly ordered meso-scale pore structure to high pressure conditions (~18.5 GPa) and a material with remarkable mechanical strength despite having ~35% porosity. Pressure dependent in situ SAXS measurements reveal a bulk modulus κ = 44 +/- 4 GPa for the mesoporous KxWO3 which is comparable to the corresponding value for the bulk monoclinic WO3 (γ-WO3). Evidence from middle angle (MAXS) and wide angle X-ray scattering (WAXS), high-resolution transmission electron microscopy (HR-TEM) and Raman spectroscopy shows that the presence of potassium leads to the formation of a K-bearing orthorhombic tungsten bronze (OTB) phase within a monoclinic WO3 host structure. Our ab initio molecular dynamics calculations show that the formation of the OTB phase provides superior strength to the mesoporous K0.07WO3. Electronic supplementary information (ESI) available: Experimental details of SEM and TEM measurements, SAXS data analysis, the procedure for Rietveld refinement, peak fitting for the Raman results, the modelling approach, UV-Vis and N2 sorption measurements. See DOI: 10.1039/c5nr07941a

Pressure effect on the structural, phonon, elastic and thermodynamic properties of L12 phase RH3TA: First-principles calculations

NASA Astrophysics Data System (ADS)

Wang, Leini; Jian, Zhang; Ning, Wei

2018-06-01

The phonon, elastic and thermodynamic properties of L12 phase Rh3Ta have been investigated by the density functional theory (DFT) approach combined with the quasi-harmonic approximation model. The results of the phonon band structure show that L12 phase Rh3Ta possesses dynamical stability in the pressure range from 0-80 GPa due to the absence of imaginary frequencies. The pressure dependences with the elastic constants Cij, shear modulus G, bulk modulus B, Young’s modulus Y, Poisson’s ratio and B/G ratio have been analyzed. The results of the elastic properties studies show that L12 phase Rh3Ta compound is mechanically stable and possesses a higher hardness, improved ductility and plasticity under higher pressures. The pressure and temperature relationship of the thermodynamic properties, such as the Debye temperature ΘD, heat capacity Cp, thermal expansion coefficient α and the Grüneisen parameter γ are predicted by the quasi-harmonic Debye model in a wide pressure (0-80 GPa) and temperature (0-750 K) ranges.

First-principles investigation for some physical properties of some fluoroperovskites compounds ABF3 (A = K, Na; B = Mg, Zn)

NASA Astrophysics Data System (ADS)

Bakri, Badis; Driss, Zied; Berri, Saadi; Khenata, Rabah

2017-12-01

In this work, the structural, electronic and optical properties of fluoroperovskite ABF3 (A = K, Na; B = Mg, Zn) were studied using two different approaches: the full-potential linearized augmented plane wave method and the pseudo-potential plane wave scheme in the frame of generalized gradient approximation features such as the lattice constant, bulk modulus and its pressure derivative are reported. The ground state properties of these compounds such as the equilibrium lattice constant and the bulk modulus are in good agreement with the experimental results. The first principles calculations were performed to study the electronic structures of ABF3(A = K, Na; B = Mg, Zn) compounds and the results indicated that these four compounds are indirect band gap insulators. The optical properties are analysed and the source of some peaks in the spectra is discussed. Besides, the dielectric function, refractive index and extinction coefficient for radiation up to 25 eV have also been reported and discussed.

The acoustic velocity, refractive index, and equation of state of liquid ammonia dihydrate under high pressure and high temperature.

PubMed

Ma, Chunli; Wu, Xiaoxin; Huang, Fengxian; Zhou, Qiang; Li, Fangfei; Cui, Qiliang

2012-09-14

High-pressure and high-temperature Brillouin scattering studies have been performed on liquid of composition corresponding to the ammonia dihydrate stoichiometry (NH(3)·2H(2)O) in a diamond anvil cell. Using the measured Brillouin frequency shifts from 180° back- and 60° platelet-scattering geometries, the acoustic velocity, refractive index, density, and adiabatic bulk modulus have been determined under pressure up to freezing point along the 296, 338, 376, and 407 K isotherms. Along these four isotherms, the acoustic velocities increase smoothly with increasing pressure but decrease with the increased temperature. However, the pressure dependence of the refractive indexes on the four isotherms exhibits a change in slope around 1.5 GPa. The bulk modulus increases linearly with pressure and its slope, dB/dP, decreases from 6.83 at 296 K to 4.41 at 407 K. These new datasets improve our understanding of the pressure- and temperature-induced molecular structure changes in the ammonia-water binary system.

Elastic properties of Sr- and Mg-doped lanthanum gallate at elevated temperature

NASA Astrophysics Data System (ADS)

Okamura, T.; Shimizu, S.; Mogi, M.; Tanimura, M.; Furuya, K.; Munakata, F.

The elastic moduli, i.e., Young's modulus, shear modulus and Poisson's ratio, of a sintered La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ bulk have been experimentally determined in the temperature range from room temperature to 1373 K using a resonance technique. Anomalous elastic properties were observed over a wide temperature range from 473 to 1173 K. In the results for internal friction and in X-ray diffraction measurements at elevated temperature, two varieties of structural changes were seen in La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ in the examined temperature range. The results agreed with the findings of a previous crystallographic study of the same composition system by Slater et al. In addition, the temperature range in which a successive structural change occurred in La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ was the same as that exhibiting the anomalous elastic properties. Taking all the results together, it can be inferred that the successive structural change in the significant temperature range is responsible for the elastic property anomaly of La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ.

Printable Single-Crystal Silicon Micro/Nanoscale Ribbons, Platelets and Bars Generated from Bulk Wafers

DTIC Science & Technology

2007-08-28

enables high yield integration onto wafers, glass plates, plastic sheets, rubber slabs or other surfaces. As one application example, bottom gate thin... EPDMS 1m2Si ESi 1m2PDMS 23 is the critical strain for buck- ling, epre is the degree of prestrain, k0 and A0 are...Young’s modulus of Si and PDMS. The following values were used to yield the calcualted value of it (i.e., 84 lm): ESi = 160 GPa, EPDMS = 2 MPa, mPDMS

Compressibility of Cs2SnBr6 by X-ray diffraction and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Yuan, Guan; Huang, Shengxuan; Niu, Jingjing; Qin, Shan; Wu, Xiang; Ding, Hongrui; Lu, Anhuai

2018-07-01

Cs2SnBr6, one promising material applied in perovskite solar cells, has been investigated up to 20 GPa by synchrotron X-ray diffraction and Raman spectroscopy. Both experimental data demonstrate that no phase transition occurs up to 20 GPa. By fitting the third-order Birch-Murnaghan equation of state, we have obtained V0 = 1288 (14) Å3, K0 = 11 (1) GPa and K0‧ = 7 (1). The ultralow value of bulk modulus K0 demonstrates the soft nature of Cs2SnBr6. Combining calculated values with experimental results, we find that x coordinate of Sn (x,0,0) atoms increases and Snsbnd Br bond lengths get shortened on compression. We have assigned vibrational peaks of Cs2SnBr6 in Raman measurements, and all the three Raman bands present nonlinear correlations with pressure.

Elastic properties of crystalline and liquid gallium at high pressures

NASA Astrophysics Data System (ADS)

Lyapin, A. G.; Gromnitskaya, E. L.; Yagafarov, O. F.; Stal'Gorova, O. V.; Brazhkin, V. V.

2008-11-01

The elastic properties of gallium, such as the bulk modulus B, the shear modulus G, and the Poisson’s ratio σ, are investigated and the relative change in the volume is determined in the stability regions of the Ga I, Ga II, and liquid phases at pressures of up to 1.7 GPa. The observed lines of the Ga I-Ga II phase transition and the melting curves of the Ga I and Ga II phases are in good agreement with the known phase diagram of gallium; in this case, the coordinates of the Ga I-Ga II-melt triple point are determined to be 1.24 ± 0.40 GPa and 277 ± 2 K. It is shown that the Ga I-Ga II phase transition is accompanied by a considerable decrease in the moduli B (by 30%) and G (by 55%) and an increase in the density by 5.7%. The Poisson’s ratio exhibits a jump from typically covalent values of approximately 0.22-0.25 to values of approximately 0.32-0.33, which are characteristic of metals. The observed behavior of the elastic characteristics is described in the framework of the model of the phase transition from a “quasi-molecular” (partially covalent) metal state to a “normal” metal state. An increase in the Poisson’s ratio in the Ga I phase from 0.22 to 0.25 with an increase in the pressure can be interpreted as a decrease in the degree of covalence, i.e., the degree of spatial anisotropy of the electron density along the bonds, whereas the large value of the pressure derivative of the bulk modulus (equal to approximately 8) observed up to the transition to the Ga II phase or the melt is associated not only with the quasicovalent nature of the Ga I phase but also with the structural features. In view of the presence of seven neighbors for each gallium atom in the Ga I phase, the gallium lattice can be treated as a structure intermediate between typical open-packed and close-packed structures. Premelting effects, such as a flattening of the isothermal dependence of the shear modulus G( p) with increasing pressure and an increase in the slope of the isobaric dependences G( T) with increasing temperature, are revealed in the vicinity of the melting curve. The bulk modulus of liquid gallium near the melting curve proves to be rather close to the corresponding values for the normal metal Ga II.

Density of jadeite melts under high pressure and high temperature conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

SAKAMAKI, Tatsuya

2017-01-01

The density of the jadeite (NaAlSi2O6) melt has been measured up to 6.5 GPa and 2273 K using the X–ray absorption technique at beamline 13–BM–D of the Advanced Photon Source. A fit of the pressure–density–temperature data to the high temperature Birch–Murnaghan equation of state yielded the following thermoelastic parameters: density, ρ0 = 2.36 g/cm3, isothermal bulk modulus, KT0 = 21.5 ± 0.8 GPa, its pressure derivative, K0' = 8.9 ± 1.2, and the temperature derivative (∂KT/∂T)P = -0.0021 ± 0.0011 GPa/K at a reference temperature T0 = 1473 K. The densification of jadeite melt at low pressures is primarily dominatedmore » by topological changes in the structure, including a decrease in T–O–T angle and breaking and reforming of the T–O bond (T = Si4+, Al3+). Compressibilities of jadeite, albite, diopside, phonolite and peridotite melts display a systematic trend: the K0–K0' plot of these silicate melts exhibits an inverse linear relation.« less

Challenging the Standard Model: Equation of State of Natural Peridotite at Lower-Mantle Conditions

NASA Astrophysics Data System (ADS)

Jeanloz, R.; Lee, K. K.; Shim, S.

2002-12-01

High-resolution x-ray diffraction of natural peridotite, before and after (subsolidus) laser heating at pressures as high as 107 GPa, yields results challenging the paradigm that the Earth's mantle is a homogeneously mixed layer having the bulk composition of pyrolite. The starting material for the experiments is representative of fertile upper mantle, and is indistinguishable from Ringwood's pyrolite compositions. It transforms to an assemblage of 76 (2)% (Mg0.88Fe0.06Al0.12Si0.94)O3 orthorhombic perovskite (opv) by volume at zero pressure, 17 (2)% (Mg0.80Fe0.20)O magnesiow\\x81stite (mw) and 7 (1)% CaSiO3 perovskite (cpv), and room-temperature isotherms for each phase within the assemblage are in good agreement with past results on the individual mineral phases. Different measurement techniques yield reproducible results, with the observed scatter being well explained by the (small) compositional variations within the mineral phases of the natural starting material. We find values of the opv/mw Fe/Mg partition coefficient consistent with prior results, 0.20 (0.10) with no evidence of any pressure dependence, and recent work on CaSiO3 perovskite shows that its structure exhibits slight tetragonal distortion at lower-mantle pressures. The thermal equation of state of the high-pressure assemblage, described in terms of the Debye temperature, Gruneisen parameter and its volume dependence, is well determined if past measurements at high pressures and temperatures are reanalysed in terms of internally-consistent calibration standards. In particular, one model for the thermal equation of state of gold that has been used to calibrate several key experiments is faulty and yields biased results. Our re-analysis shows that all experiments point to relatively high values for the thermal expansion of opv (hence of the entire high-pressure assemblage), compatible with earlier rather than more recent analyses. The resulting high-pressure, high-temperature bulk modulus of the high-pressure assemblage is constrained to about 5% at lower-mantle conditions, and is expected to be relatively insensitive to Fe abundance. Minimum temperatures of about 2000 K at 700 km depth rising to about 3000 K at 2500 km depth are required for the bulk modulus of the high-pressure assemblage to match the seismologically observed bulk modulus of the lower mantle. These values of temperature are in good accord with current estimates. The density of the pyrolite-composition high-pressure assemblage is then found to be at least 2 (1)%, (and plausibly 4 (2)%) lower than the seismologically determined density at corresponding depths. The density mismatch is partly attributable to the effect of Al on the volume of opv, as also found by others. Uncertainties in the measurements and analysis appear to be well constrained, and rule out pyrolite as a viable bulk composition for the preponderance of the mantle.

Radiation-damage-induced transitions in zircon: Percolation theory applied to hardness and elastic moduli as a function of density

NASA Astrophysics Data System (ADS)

Beirau, Tobias; Nix, William D.; Ewing, Rodney C.; Pöllmann, Herbert; Salje, Ekhard K. H.

2018-05-01

Two in literature predicted percolation transitions in radiation-damaged zircon (ZrSiO4) were observed experimentally by measurement of the indentation hardness as a function of density and their correlation with the elastic moduli. Percolations occur near 30% and 70% amorphous fractions, where hardness deviates from its linear correlation with the elastic modulus (E), the shear modulus (G) and the bulk modulus (K). The first percolation point pc1 generates a cusp in the hardness versus density evolution, while the second percolation point is seen as a change of slope.

NASA Astrophysics Data System (ADS)

Knight, Kevin S.; Marshall, William G.; Hawkins, Philip M.

2014-06-01

The fluoroperovskite phase RbCaF3 has been investigated using high-pressure neutron powder diffraction in the pressure range ~0-7.9 GPa at room temperature. It has been found to undergo a first-order high-pressure structural phase transition at ~2.8 GPa from the cubic aristotype phase to a hettotype phase in the tetragonal space group I4/ mcm. This transition, which also occurs at ~200 K at ambient pressure, is characterised by a linear phase boundary and a Clapeyron slope of 2.96 × 10-5 GPa K-1, which is in excellent agreement with earlier, low-pressure EPR investigations. The bulk modulus of the high-pressure phase (49.1 GPa) is very close to that determined for the low-pressure phase (50.0 GPa), and both are comparable with those determined for the aristotype phases of CsCdF3, TlCdF3, RbCdF3, and KCaF3. The evolution of the order parameter with pressure is consistent with recent modifications to Landau theory and, in conjunction with polynomial approximations to the pressure dependence of the lattice parameters, permits the pressure variation of the bond lengths and angles to be predicted. On entering the high-pressure phase, the Rb-F bond lengths decrease from their extrapolated values based on a third-order Birch-Murnaghan fit to the aristotype equation of state. By contrast, the Ca-F bond lengths behave atypically by exhibiting an increase from their extrapolated magnitudes, resulting in the volume and the effective bulk modulus of the CaF6 octahedron being larger than the cubic phase. The bulk moduli for the two component polyhedra in the tetragonal phase are comparable with those determined for the constituent binary fluorides, RbF and CaF2.

Compressibility and expansivity of anglesite (PbSO4) using in situ synchrotron X-ray diffraction at high-pressure and high-temperature conditions

NASA Astrophysics Data System (ADS)

Li, Bo; Xu, Jingui; Chen, Wei; Ye, Zhilin; Huang, Shijie; Fan, Dawei; Zhou, Wenge; Xie, Hongsen

2018-04-01

The compressibility and expansivity of anglesite (PbSO4) have been measured at high pressure up to 21.6 GPa and high temperature up to 700 K using in situ angle-dispersive X-ray diffraction and diamond anvil cell. The third-order Birch-Murnaghan equation of state (III-BM-EoS) was used to analyze the pressure-volume (P-V) data of PbSO4. We obtained the bulk modulus K 0 = 59(1) GPa, and its pressure derivative K0' = 5.3(4), respectively. Using Holland-Powell thermal EoS to fit the temperature-volume (T-V) data, the thermal expansion coefficient α 0 = 4.59(2) × 10- 5 K- 1 for PbSO4 was also derived. Simultaneously, the ambient-pressure axial compressibilities (β a0 = 1.79(4) × 10- 3 GPa- 1, β b0 = 1.75(5) × 10- 3 GPa- 1, β c0 = 2.12(4) × 10- 3 GPa- 1) and axial thermal expansivities (α a0 = 1.23(4) × 10- 5 K- 1, α b0 = 1.93(2) × 10- 5 K- 1, and α c0 = 1.43(1) × 10- 5 K- 1) along a-axis, b-axis and c-axis were derived at 300 K, respectively. Furthermore, the potential influencing factors (e.g., the effective size of M2+ cation, polarizability and electronegativity) on the bulk moduli of barite-type (belonging to Pbnm space group) sulfates (anglesite, barite, and celestine) were discussed. We found that the polarizability might be the most important factor. Finally, the anisotropic linear compressibility and thermal expansivity in barite-type sulfates were also discussed, respectively.

Primate lens capsule elasticity assessed using Atomic Force Microscopy

PubMed Central

Ziebarth, Noël M.; Arrieta, Esdras; Feuer, William J.; Moy, Vincent T.; Manns, Fabrice; Parel, Jean-Marie

2011-01-01

The purpose of this project is to measure the elasticity of the human and non-human primate lens capsule at the microscopic scale using Atomic Force Microscopy (AFM). Elasticity measurements were performed using AFM on the excised anterior lens capsule from 9 cynomolgus monkey (5.9–8.0 years), 8 hamadryas baboon (2.8–10.1 years), and 18 human lenses (33–79 years). Anterior capsule specimens were obtained by performing a 5mm continuous curvilinear capsulorhexis and collecting the resulting disk of capsular tissue. To remove the lens epithelial cells the specimen was soaked in 0.1% trypsin and 0.02% EDTA for five minutes, washed, and placed on a Petri dish and immersed in DMEM. Elasticity measurements of the capsule were performed with a laboratory-built AFM system custom designed for force measurements of ophthalmic tissues. The capsular specimens were probed with an AFM cantilever tip to produce force-indentation curves for each specimen. Young’s modulus was calculated from the force-indentation curves using the model of Sneddon for a conical indenter. Young’s modulus of elasticity was 20.1–131kPa for the human lens capsule, 9.19–117kPa for the cynomolgus lens capsule, and 13.1–62.4kPa for the baboon lens capsule. Young’s modulus increased significantly with age in humans (p=0.03). The age range of the monkey and baboon samples was not sufficient to justify an analysis of age dependence. The capsule elasticity of young humans (<45 years) was not statistically different from that of the monkey and baboon. In humans, there is an increase in lens capsule stiffness at the microscale that could be responsible for an increase in lens capsule bulk stiffness. PMID:21420953

Structural stability and phase transition of Bi 2 Te 3 under high pressure and low temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, J. L.; Zhang, S. J.; Zhu, J. L.

2017-09-01

Structural stability and phase transition of topological insulator Bi2Te3 were studied via angle-dispersive synchrotron radiation X-ray diffraction under high pressure and low temperature condition. The results manifest that the R-3m phase (phase I) is stable at 8 K over the pressure range up to 10 GPa and phase transition occurs between 8 K and 45 K at 8 GPa. According to the Birch-Murnaghan equation of state, the bulk modulus at ambient pressure B0 was estimated to be 45 ± 3 GPa with the assumption of B0' = 4. The structural robustness of phase I at 8 K suggests that themore » superconductivity below 10 GPa is related to phase I. Topological properties of superconducting Bi2Te3 phase under pressure were discussed.« less

Effect of aluminium on the compressibility of silicate perovskite

NASA Astrophysics Data System (ADS)

Daniel, Isabelle; Bass, Jay D.; Fiquet, Guillaume; Cardon, Hervé; Zhang, Jianzhong; Hanfland, Michael

2004-08-01

Volume measurements for aluminous MgSiO3 perovskite containing 5 mol% Al2O3 were carried out up to pressures of 40 GPa at ambient temperature, using monochromatic synchrotron X-ray diffraction. A least-squares refinement of the data to the Birch-Murnaghan equation of state yields the following parameters V0 = 163.234(8) Å3, KT0 = 251.5(13) GPa, K'0 = 4. Within uncertainties, the presence of 5 mol% Al2O3 in MgSiO3 perovskite induces a decrease of the bulk modulus in the range of 0% to 1.8%. Thus, KT of perovskite is affected little if at all by the presence of Al3+. This result is in excellent agreement with the values deduced from sound velocity measurements on the same sample [Jackson et al., 2004]. We discuss the possible origin of discrepancies among the different bulk moduli reported to date for aluminous perovskite. In light of recent calculations, our results are consistent with aluminium being dissolved in MgSiO3 perovskite through a coupled substitution mechanism involving the replacement of both Mg2+ and Si4+ in the dodecahedral and octahedral sites by 2 Al3+. Moreover, any slight reduction in the bulk modulus of MgSiO3 perovskite induced by the dissolution of 5 mol% Al2O3, indicates that the relative proportions of the minerals characteristic of the lower mantle, as inferred from seismological models, should not be significantly altered by the introduction of Al in the system.

Synthesis of Hf 8O 7, a new binary hafnium oxide, at high pressures and high temperatures

DOE PAGES

Bayarjargal, L.; Morgenroth, W.; Schrodt, N.; ...

2017-01-23

In this paper, two binary phases in the system Hf-O have been synthesized at pressures between 12 and 34 GPa and at temperatures up to 3000 K by reacting Hf with HfO 2 using a laser-heated diamond anvil cell. In situ X-ray diffraction in conjunction with density functional theory calculations has been employed to characterize a previously unreported tetragonal Hf 8O 7 phase. This phase has a structure which is based on an fcc Hf packing with oxygen atoms occupying octahedral interstitial positions. Its predicted bulk modulus is 223(1) GPa. The second phase has a composition close to Hf 6O,more » where oxygen atoms occupy octahedral interstitial sites in an hcp Hf packing. Its experimentally determined bulk modulus is 128(30) GPa. Finally, the phase diagram of Hf metal was further constrained at high pressures and temperatures, where we show that α-Hf transforms to β-Hf around 2160(150) K and 18.2 GPa and β-Hf remains stable up to at least 2800 K at this pressure.« less

Mechanical properties of Fe rich Fe-Si alloys: ab initio local bulk-modulus viewpoint

NASA Astrophysics Data System (ADS)

Bhattacharya, Somesh Kr; Kohyama, Masanori; Tanaka, Shingo; Shiihara, Yoshinori; Saengdeejing, Arkapol; Chen, Ying; Mohri, Tetsuo

2017-11-01

Fe-rich Fe-Si alloys show peculiar bulk-modulus changes depending on the Si concentration in the range of 0-15 at.%Si. In order to clarify the origin of this phenomenon, we have performed density-functional theory calculations of supercells of Fe-Si alloy models with various Si concentrations. We have applied our recent techniques of ab initio local energy and local stress, by which we can obtain a local bulk modulus of each atom or atomic group as a local constituent of the cell-averaged bulk modulus. A2-phase alloy models are constructed by introducing Si substitution into bcc Fe as uniformly as possible so as to prevent mutual neighboring, while higher Si concentrations over 6.25 at.%Si lead to contacts between SiFe8 cubic clusters via sharing corner Fe atoms. For 12.5 at.%Si, in addition to an A2 model, we deal with partial D03 models containing local D03-like layers consisting of edge-shared SiFe8 cubic clusters. For the cell-averaged bulk modulus, we have successfully reproduced the Si-concentration dependence as a monotonic decrease until 11.11 at.%Si and a recovery at 12.5 at.%Si. The analysis of local bulk moduli of SiFe8 cubic clusters and Fe regions is effective to understand the variations of the cell-averaged bulk modulus. The local bulk moduli of Fe regions become lower for increasing Si concentration, due to the suppression of bulk-like d-d bonding states in narrow Fe regions. For higher Si concentrations till 11.11 at.%Si, corner-shared contacts or 1D chains of SiFe8 clusters lead to remarkable reduction of local bulk moduli of the clusters. At 12 at.%Si, on the other hand, two- or three-dimensional arrangements of corner- or edge-shared SiFe8 cubic clusters show greatly enhanced local bulk moduli, due to quite different bonding nature with much stronger p-d hybridization. The relation among the local bulk moduli, local electronic and magnetic structures, and local configurations such as connectivity of SiFe8 clusters and Fe-region sizes has been analyzed. The ab initio local stress has opened the way for obtaining accurate local elastic properties reflecting local valence-electron behaviors.

Theoretical study of phonon dispersion, elastic, mechanical and thermodynamic properties of barium chalcogenides

NASA Astrophysics Data System (ADS)

Musari, A. A.; Orukombo, S. A.

2018-03-01

Barium chalcogenides are known for their high-technological importance and great scientific interest. Detailed studies of their elastic, mechanical, dynamical and thermodynamic properties were carried out using density functional theory and plane-wave pseudo potential method within the generalized gradient approximation. The optimized lattice constants were in good agreement when compared with experimental data. The independent elastic constants, calculated from a linear fit of the computed stress-strain function, were used to determine the Young’s modulus (E), bulk modulus (B), shear modulus (G), Poisson’s ratio (σ) and Zener’s anisotropy factor (A). Also, the Debye temperature and sound velocities for barium chalcogenides were estimated from the three independent elastic constants. The calculations of phonon dispersion showed that there are no negative frequencies throughout the Brillouin zone. Hence barium chalcogenides have dynamically stable NaCl-type crystal structure. Finally, their thermodynamic properties were calculated in the temperature range of 0-1000 K and their constant-volume specific heat capacities at room-temperature were reported.

Electronic structure, mechanical and thermodynamic properties of BaPaO3 under pressure.

PubMed

Khandy, Shakeel Ahmad; Islam, Ishtihadah; Gupta, Dinesh C; Laref, Amel

2018-05-07

Density functional theory (DFT)-based investigations have been put forward on the elastic, mechanical, and thermo-dynamical properties of BaPaO 3 . The pressure dependence of electronic band structure and other physical properties has been carefully analyzed. The increase in Bulk modulus and decrease in lattice constant is seen on going from 0 to 30 GPa. The predicted lattice constants describe this material as anisotropic and ductile in nature at ambient conditions. Post-DFT calculations using quasi-harmonic Debye model are employed to envisage the pressure-dependent thermodynamic properties like Debye temperature, specific heat capacity, Grüneisen parameter, thermal expansion, etc. Also, the computed Debye temperature and melting temperature of BaPaO 3 at 0 K are 523 K and 1764.75 K, respectively.

X-ray Diffraction Study of Aluminum Carbide Powder to 50 GPa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, C.; Ma, Y; Chyu, M

2009-01-01

The crystal structure and equation of state (EOS) of aluminum carbide (Al{sub 4}C{sub 3}) have been determined directly up to 50.1 GPa at room temperature by the synchrotron x-ray diffraction techniques. The results indicate that Al{sub 4}C{sub 3} remained in rhombohedral structure under all tested pressure-temperature conditions and exhibited anisotropic compressibility, with the c-axis more compressible than the a-axis. Fitting the experimental data to third order Birch-Murnaghan EOS yields a bulk modulus of K{sub OT} = 233 {+-} 6 GPa with its pressure derivative K{sub OT}{prime} = 3.4 {+-} 0.4, while the second-order EOS yields K{sub OT} = 223 {+-}more » 2 GPa.« less

First-principles study of the structural, electronic and thermal properties of CaLiF3

NASA Astrophysics Data System (ADS)

Chouit, N.; Amara Korba, S.; Slimani, M.; Meradji, H.; Ghemid, S.; Khenata, R.

2013-09-01

Density functional theory calculations have been performed to study the structural, electronic and optical properties of CaLiF3 cubic fluoroperovskite. Our calculations were carried out by means of the full-potential linearized augmented plane-wave method. The exchange-correlation potential is treated by the local density approximation and the generalized gradient approximation (GGA) (Perdew, Burke and Ernzerhof). Moreover, the alternative form of GGA proposed by Engel and Vosko is also used for band structure calculations. The calculated total energy versus volume allows us to obtain structural properties such as the lattice constant (a0), bulk modulus (B0) and pressure derivative of the bulk modulus (B'0 ). Band structure, density of states and band gap pressure coefficients are also given. Our calculations show that CaLiF3 has an indirect band gap (R-Γ). Following the quasi-harmonic Debye model, in which the phononic effects are considered, the temperature and pressure effects on the lattice constant, bulk modulus, thermal expansion coefficient, Debye temperature and heat capacities are calculated.

Bulk modulus and its pressure derivative of YBa2Cu3O7-x

NASA Astrophysics Data System (ADS)

Cankurtaran, M.; Saunders, G. A.; Willis, J. R.; Al-Kheffaji, A.; Almond, D. P.

1989-02-01

Pressure dependences of the ultrasonic wave velocities in polycrystalline YBa2Cu3O7-x are reported. Porosity effects are taken into account using wave-scattering theory in a porous medium. The bulk modulus B0 at atmospheric pressure for the nonporous matrix is 65 GPa, much smaller than B(P) obtained at high pressures from lattice-parameter measurements. This discrepancy accrues from the large value of (∂B/∂P). The comparatively small B0 and large (∂B/∂P) are due to vacant anion sites in this defect perovskite.

Ab-initio thermodynamic and elastic properties of AlNi and AlNi3 intermetallic compounds

NASA Astrophysics Data System (ADS)

Yalameha, Shahram; Vaez, Aminollah

2018-04-01

In this paper, thermodynamic and elastic properties of the AlNi and AlNi3 were investigated using density functional theory (DFT). The full-potential linearized augmented plane-wave (APW) in the framework of the generalized gradient approximation as used as implemented in the Wien2k package. The temperature dependence of thermal expansion coefficient, bulk modulus and heat capacity in a wide range of temperature (0-1600 K) were investigated. The calculated elastic properties of the compounds show that both intermetallic compounds of AlNi and AlNi3 have surprisingly negative Poisson’s ratio (NPR). The results were compared with other experimental and computational data.

Biocompatible Zr-Al-Fe bulk metallic glasses with large plasticity

NASA Astrophysics Data System (ADS)

Hua, NengBin; Li, Ran; Wang, JianFeng; Zhang, Tao

2012-09-01

In the present study, high-zirconium ternary Zr-Al-Fe bulk metallic glasses (BMGs) with low Young's modulus and good plasticity were developed. Zr75Al7.5Fe17.5 BMG exhibits a low Young's modulus of 70 GPa and high Poisson's ratio of 0.403. Pronounced plasticity was demonstrated under both compression and bending conditions for the BMGs. Furthermore, the alloys show high corrosion resistance in phosphate buffered solution. The combination of desirable mechanical and chemical properties implies potential for biomedical applications.

Density of Fe-3.5 wt% C liquid at high pressure and temperature and the effect of carbon on the density of the molten iron

NASA Astrophysics Data System (ADS)

Shimoyama, Yuta; Terasaki, Hidenori; Ohtani, Eiji; Urakawa, Satoru; Takubo, Yusaku; Nishida, Keisuke; Suzuki, Akio; Katayama, Yoshinori

2013-11-01

Carbon is a plausible light element candidate in the Earth’s outer core. We measured the density of liquid Fe-3.5 wt% C up to 6.8 GPa and 2200 K using an X-ray absorption method. The compression curve of liquid Fe-C was fitted using the third-order Birch-Murnaghan equation of state. The bulk modulus and its pressure derivative are K0,1500K = 55.3 ± 2.5 GPa and (dK0/dP)T = 5.2 ± 1.5, and the thermal expansion coefficient is α = 0.86 ± 0.04 × 10-4 K-1. The Fe-C density abruptly increases at pressures between 4.3 and 5.5 GPa in the range of present temperatures. Compared with the results of previous density measurements of liquid Fe-C, the effect of carbon on the density of liquid Fe shows a nonideal mixing behavior. The abrupt density increase and nonideal mixing behavior are important factors in determining the light element content in the Earth’s core.

Modeling and Experimental Evaluation of Bending Behavior of Soft Pneumatic Actuators Made of Discrete Actuation Chambers.

PubMed

Alici, Gursel; Canty, Taylor; Mutlu, Rahim; Hu, Weiping; Sencadas, Vitor

2018-02-01

In this article, we have established an analytical model to estimate the quasi-static bending displacement (i.e., angle) of the pneumatic actuators made of two different elastomeric silicones (Elastosil M4601 with a bulk modulus of elasticity of 262 kPa and Translucent Soft silicone with a bulk modulus of elasticity of 48 kPa-both experimentally determined) and of discrete chambers, partially separated from each other with a gap in between the chambers to increase the magnitude of their bending angle. The numerical bending angle results from the proposed gray-box model, and the corresponding experimental results match well that the model is accurate enough to predict the bending behavior of this class of pneumatic soft actuators. Further, by using the experimental bending angle results and blocking force results, the effective modulus of elasticity of the actuators is estimated from a blocking force model. The numerical and experimental results presented show that the bending angle and blocking force models are valid for this class of pneumatic actuators. Another contribution of this study is to incorporate a bistable flexible thin metal typified by a tape measure into the topology of the actuators to prevent the deflection of the actuators under their own weight when operating in the vertical plane.

The effect of Ca doping on specific heat of YCoO{sub 3} cobaltate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thakur, Rasna, E-mail: rasnathakur@yahoo.com; Thakur, Rajesh K., E-mail: thakur.rajesh2009@gmail.com; Gaur, N. K., E-mail: srl-nkgaur@yahoo.co.in

2016-05-06

We have investigated the thermodynamic properties of Y{sub 1-x}Ca{sub x}CoO{sub 3} (0.0≤x≤0.1) perovskites by means of a modified rigid ion model (MRIM). The variations of specific heat at wide temperatures 1 K ≤ T ≤ 1000 K are reported. Also, the effect of lattice distortions on the elastic and thermal properties of pure and Ca doped cobaltates has been studied by an atomistic approach. Besides, we have reported bulk modulus (B), cohesive energy (ϕ), molecular force constant (f), Reststrahlen frequency (υ), Debye temperature (θ{sub D}), Gruneisen parameter (γ) and specific heat (C). It is found that the present model has a promisemore » to predict the thermodynamic properties of other perovskites as well.« less

Temperature and pressure dependent thermodynamic behavior of 2H-CuInO2

NASA Astrophysics Data System (ADS)

Bhamu, K. C.

2018-05-01

Density functional theory and quasi-harmonic Debye model has been used to study the thermodynamic properties of 2H-CuInO2. At the optimized structural parameters, pressure (0 to 80 GPa) dependent variation in the various thermodynamic properties, i.e. unit cell volume (V), bulk modulus (B), specific heat (Cv), Debye temperature (θD), Grüneisen parameter (γ) and thermal expansion coefficient (α) are calculated for various temperature values. The results predict that the pressure has significant effect on unit cell volume and bulk modulus while the temperature shows negligible effect on both parameters. With increasing temperature thermal expansion coefficient increase while with increasing pressure it decreases. The specific heat remains close to zero for ambient pressure and temperature values and it increases with increasing temperature. It is observed that the pressure has high impact on Debye temperature and Grüneisen parameter instead of temperature. Debye temperature and Grüneisen parameter both remains almost constant for the temperature range (0-300K) while Grüneisen parameter decrease with increasing pressure at constant temperature and Debye temperature increases rapidly with increasing pressure. An increase in Debye temperature with respect to pressure shows that the thermal vibration frequency changes rapidly.

First-principles studies of electronic, transport and bulk properties of pyrite FeS2

NASA Astrophysics Data System (ADS)

Banjara, Dipendra; Malozovsky, Yuriy; Franklin, LaShounda; Bagayoko, Diola

2018-02-01

We present results from first principle, local density approximation (LDA) calculations of electronic, transport, and bulk properties of iron pyrite (FeS2). Our non-relativistic computations employed the Ceperley and Alder LDA potential and the linear combination of atomic orbitals (LCAO) formalism. The implementation of the LCAO formalism followed the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). We discuss the electronic energy bands, total and partial densities of states, electron effective masses, and the bulk modulus. Our calculated indirect band gap of 0.959 eV (0.96), using an experimental lattice constant of 5.4166 Å, at room temperature, is in agreement with the measured indirect values, for bulk samples, ranging from 0.84 eV to 1.03 ± 0.05 eV. Our calculated bulk modulus of 147 GPa is practically in agreement with the experimental value of 145 GPa. The calculated, partial densities of states reproduced the splitting of the Fe d bands to constitute the dominant upper most valence and lower most conduction bands, separated by the generally accepted, indirect, experimental band gap of 0.95 eV.

Mechanical and Thermal Properties of Praseodymium Monopnictides: AN Ultrasonic Study

NASA Astrophysics Data System (ADS)

Bhalla, Vyoma; Kumar, Raj; Tripathy, Chinmayee; Singh, Devraj

2013-09-01

We have computed ultrasonic attenuation, acoustic coupling constants and ultrasonic velocities of praseodymium monopnictides PrX(X: N, P, As, Sb and Bi) along the <100>, <110>, <111> in the temperature range 100-500 K using higher order elastic constants. The higher order elastic constants are evaluated using Coulomb and Born-Mayer potential with two basic parameters viz. nearest-neighbor distance and hardness parameter in the temperature range of 0-500 K. Several other mechanical and thermal parameters like bulk modulus, shear modulus, Young's modulus, Poisson ratio, anisotropic ratio, tetragonal moduli, Breazeale's nonlinearity parameter and Debye temperature are also calculated. In the present study, the fracture/toughness (B/G) ratio is less than 1.75 which implies that PrX compounds are brittle in nature at room temperature. The chosen material fulfilled Born criterion of mechanical stability. We also found the deviation of Cauchy's relation at higher temperatures. PrN is most stable material as it has highest valued higher order elastic constants as well as the ultrasonic velocity. Further, the lattice thermal conductivity using modified approach of Slack and Berman is determined at room temperature. The ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation mechanisms have been computed using modified Mason's approach. The results with other well-known physical properties are useful for industrial applications.

Short-range correlations control the G/K and Poisson ratios of amorphous solids and metallic glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaccone, Alessio; Terentjev, Eugene M.

2014-01-21

The bulk modulus of many amorphous materials, such as metallic glasses, behaves nearly in agreement with the assumption of affine deformation, namely that the atoms are displaced just by the amount prescribed by the applied strain. In contrast, the shear modulus behaves as for nonaffine deformations, with additional displacements due to the structural disorder which induce a marked material softening to shear. The consequence is an anomalously large ratio of the bulk modulus to the shear modulus for disordered materials characterized by dense atomic packing, but not for random networks with point atoms. We explain this phenomenon with a microscopicmore » derivation of the elastic moduli of amorphous solids accounting for the interplay of nonaffinity and short-range particle correlations due to excluded volume. Short-range order is responsible for a reduction of the nonaffinity which is much stronger under compression, where the geometric coupling between nonaffinity and the deformation field is strong, whilst under shear this coupling is weak. Predictions of the Poisson ratio based on this model allow us to rationalize the trends as a function of coordination and atomic packing observed with many amorphous materials.« less

Correlation between structure and physical properties of chalcogenide glasses in the AsxSe1-x system

NASA Astrophysics Data System (ADS)

Yang, Guang; Bureau, Bruno; Rouxel, Tanguy; Gueguen, Yann; Gulbiten, Ozgur; Roiland, Claire; Soignard, Emmanuel; Yarger, Jeffery L.; Troles, Johann; Sangleboeuf, Jean-Christophe; Lucas, Pierre

2010-11-01

Physical properties of chalcogenide glasses in the AsxSe1-x system have been measured as a function of composition including the Young’s modulus E , shear modulus G , bulk modulus K , Poisson’s ratio ν , the density ρ , and the glass transition Tg . All these properties exhibit a relatively sharp extremum at the average coordination number ⟨r⟩=2.4 . The structural origin of this trend is investigated by Raman spectroscopy and nuclear magnetic resonance. It is shown that the reticulation of the glass structure increases continuously until x=0.4 following the “chain crossing model” and then undergoes a transition toward a lower dimension pyramidal network containing an increasing number of molecular inclusions at x>0.4 . Simple theoretical estimates of the network bonding energy confirm a mismatch between the values of mechanical properties measured experimentally and the values predicted from a continuously reticulated structure, therefore corroborating the formation of a lower dimension network at high As content. The evolution of a wide range of physical properties is consistent with this sharp structural transition and suggests that there is no intermediate phase in these glasses at room temperature.

Thermal equation of state of (Mg 0.9Fe 0.1) 2SiO 4 olivine

NASA Astrophysics Data System (ADS)

Liu, Wei; Li, Baosheng

2006-08-01

In situ synchrotron X-ray diffraction measurements have been carried out on San Carlos olivine (Mg 0.9Fe 0.1) 2SiO 4 up to 8 GPa and 1073 K. Data analysis using the high-temperature Birch-Murnaghan (HTBM) equation of state (EoS) yields the temperature derivative of the bulk modulus (∂ KT/∂ T) P = -0.019 ± 0.002 GPa K -1. The thermal pressure (TH) approach gives αKT = 4.08 ± 0.10 × 10 -3 GPa K -1, from which (∂ KT/∂ T) P = -0.019 ± 0.001 GPa K -1 is derived. Fitting the present data to the Mie-Grüneisen-Debye (MGD) formalism, the Grüneisen parameter at ambient conditions γ0 is constrained to be 1.14 ± 0.02 with fixed volume dependence q = 1. Combining the present data with previous results on iron-bearing olivine and fitting to MGD EoS, we obtain γ0 = 1.11 ± 0.01 and q = 0.54 ± 0.36. In this study the thermoelastic parameters obtained from various approaches are in good agreement with one another and previous results.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Lei; Wang, Shanmin; Zhu, Jinlong

Here, we report high-pressure synthesis of chromium monoboride (CrB) at 6 GPa and 1400 K. The elastic and plastic behaviors have been investigated by hydrostatic compression experiment and micro-indentation measurement. CrB is elastically incompressible with a high bulk modulus of 269.0 (5.9) GPa and exhibits a high Vickers hardness of 19.6 (0.7) GPa under the load of 1 kg force. Based on first principles calculations, the observed mechanical properties are attributed to the polar covalent Cr-B bonds interconnected with strong zigzag B-B covalent bonding network. The presence of metallic Cr bilayers is presumably responsible for the weakest paths in shearmore » deformation.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Lei; College of Construction Engineering, Jilin University, Changchun, Jilin 130061; Wang, Shanmin

We report high-pressure synthesis of chromium monoboride (CrB) at 6 GPa and 1400 K. The elastic and plastic behaviors have been investigated by hydrostatic compression experiment and micro-indentation measurement. CrB is elastically incompressible with a high bulk modulus of 269.0 (5.9) GPa and exhibits a high Vickers hardness of 19.6 (0.7) GPa under the load of 1 kg force. Based on first principles calculations, the observed mechanical properties are attributed to the polar covalent Cr-B bonds interconnected with strong zigzag B-B covalent bonding network. The presence of metallic Cr bilayers is presumably responsible for the weakest paths in shear deformation.

NRL Plasma Formulary. Revision

DTIC Science & Technology

1990-01-01

Description SI Gaussian 9B 1l0B Faraday’s law V x E -- V x E =-- at c Ot c9D 10D 4wr Ampere’s law V x H + J V x H =- + -J at c Ot c Poisson equation V - D = p...Froude Fr V/(g L) 1/ 2 t(Inertial force/gravitational or V/NL buoyancy force) 1 /2 Gay- Lussac Ga 1/fOAT Inverse of relative change in volume during... law heat coefficient, k = crAT0ax Volumetric expansion coefficient, dV/V = )3dT Bulk modulus (units kg m 1 s - 2) 6R, AV, Ap, AT Imposed difference in

Elastic-plastic and phase transition of zinc oxide single crystal under shock compression

NASA Astrophysics Data System (ADS)

Liu, Xun; Mashimo, Tsutomu; Li, Wei; Zhou, Xianming; Sekine, Toshimori

2015-03-01

The Hugoniot data for zinc oxide (ZnO) single crystals were measured up to 80 GPa along both the ⟨ 11 2 ¯ 0 ⟩ (a-axis) and ⟨0001⟩ (c-axis) directions using a velocity interferometer system for any reflector and inclined-mirror method combined with a powder gun and two-stage light gas gun. The Hugoniot-elastic limits of ZnO were determined to be 10.5 and 11.5 GPa along the a- and c-axes, respectively. The wurtzite (B4) to rocksalt (B1) phase transition pressures along the a- and c-axes are 12.3 and 14.4 GPa, respectively. Shock velocity (Us) versus particle velocity (Up) relation of the final phase is given by the following relationship: Us (km/s) = 2.76 + 1.51Up (km/s). Based on the Debye-Grüneisen model and Birch-Murnaghan equation of state (EOS), we discuss the EOS of the B1 phase ZnO. The bulk modulus (K0) and its pressure derivative (K0') are estimated to be K0 = 174 GPa and K0' = 3.9, respectively.

The bonding, charge distribution, spin ordering, optical, and elastic properties of four MAX phases Cr2AX (A = Al or Ge, X = C or N): From density functional theory study

NASA Astrophysics Data System (ADS)

Li, Neng; Mo, Yuxiang; Ching, Wai-Yim

2013-11-01

In this work, we assess a full spectrum of properties (chemical bonding, charge distribution, spin ordering, optical, and elastic properties) of Cr2AC (A = Al, Ge) and their hypothetical nitride counterparts Cr2AN (A = Al, Ge) based on density functional theory calculations. The calculated total energy values indicate that a variety of spin ordering of these four compounds depending on interlayer-interactions between M-A and M-X within the sublattice, which is supported by bonding analysis. MAX phase materials are discovered to possess exotic magnetic properties which indicates that these materials could serve as promising candidates for novel layered magnetic materials for various electronic and spintronic applications. Further analysis of optical properties for two polarization vectors of Cr2AX shows that the reflectivity is high in the visible-ultraviolet region up to ˜15 eV suggesting Cr2AX as a promising candidate for use as a coating material. The elastic coefficients (Cij) and bulk mechanical properties [bulk modulus (K), shear modulus (G), Young's modulus (E), Poisson's ratio (η), and Pugh ratio (G/K)] of these four Cr2AX compounds are also calculated and analyzed, which pave the way to predict or design new MAX phases that are less brittle or tougher by having a lower G/K value or higher η.

Collapsed tetragonal phase transition in LaRu 2 P 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drachuck, Gil; Sapkota, Aashish; Jayasekara, Wageesha T.

Here, the structural properties of LaRu 2P 2 under external pressure have been studied up to 14 GPa, employing high-energy x-ray diffraction in a diamond-anvil pressure cell. At ambient conditions, LaRu 2P 2 (I4/ mmm) has a tetragonal structure with a bulk modulus of B = 105(2) GPa and exhibits superconductivity at T c = 4.1 K. With the application of pressure, LaRu 2P 2 undergoes a phase transition to a collapsed tetragonal (cT) state with a bulk modulus of B = 175(5) GPa. At the transition, the c-lattice parameter exhibits a sharp decrease with a concurrent increase of themore » a-lattice parameter. The cT phase transition in LaRu 2P 2 is consistent with a second-order transition, and was found to be temperature dependent, increasing from P = 3.9(3) GPa at 160 K to P = 4.6(3) GPa at 300 K. In total, our data are consistent with the cT transition being near, but slightly above 2 GPa at 5 K where superconductivity is suppressed. Finally, we compare the effect of physical and chemical pressure in the RRu 2P 2 ( R = Y, La–Er, Yb) isostructural series of compounds and find them to be analogous.« less

Collapsed tetragonal phase transition in LaRu2P2

NASA Astrophysics Data System (ADS)

Drachuck, Gil; Sapkota, Aashish; Jayasekara, Wageesha T.; Kothapalli, Karunakar; Bud'ko, Sergey L.; Goldman, Alan I.; Kreyssig, Andreas; Canfield, Paul C.

2017-11-01

The structural properties of LaRu2P2 under external pressure have been studied up to 14 GPa, employing high-energy x-ray diffraction in a diamond-anvil pressure cell. At ambient conditions, LaRu2P2 (I4/mmm) has a tetragonal structure with a bulk modulus of B =105 (2 ) GPa and exhibits superconductivity at Tc=4.1 K. With the application of pressure, LaRu2P2 undergoes a phase transition to a collapsed tetragonal (cT) state with a bulk modulus of B =175 (5 ) GPa. At the transition, the c -lattice parameter exhibits a sharp decrease with a concurrent increase of the a -lattice parameter. The cT phase transition in LaRu2P2 is consistent with a second-order transition, and was found to be temperature dependent, increasing from P =3.9 (3 ) GPa at 160 K to P =4.6 (3 ) GPa at 300 K. In total, our data are consistent with the cT transition being near, but slightly above 2 GPa at 5 K where superconductivity is suppressed. Finally, we compare the effect of physical and chemical pressure in the RRu2P2 (R = Y, La -Er , Yb) isostructural series of compounds and find them to be analogous.

Collapsed tetragonal phase transition in LaRu 2 P 2

DOE PAGES

Drachuck, Gil; Sapkota, Aashish; Jayasekara, Wageesha T.; ...

2017-11-10

Here, the structural properties of LaRu 2P 2 under external pressure have been studied up to 14 GPa, employing high-energy x-ray diffraction in a diamond-anvil pressure cell. At ambient conditions, LaRu 2P 2 (I4/ mmm) has a tetragonal structure with a bulk modulus of B = 105(2) GPa and exhibits superconductivity at T c = 4.1 K. With the application of pressure, LaRu 2P 2 undergoes a phase transition to a collapsed tetragonal (cT) state with a bulk modulus of B = 175(5) GPa. At the transition, the c-lattice parameter exhibits a sharp decrease with a concurrent increase of themore » a-lattice parameter. The cT phase transition in LaRu 2P 2 is consistent with a second-order transition, and was found to be temperature dependent, increasing from P = 3.9(3) GPa at 160 K to P = 4.6(3) GPa at 300 K. In total, our data are consistent with the cT transition being near, but slightly above 2 GPa at 5 K where superconductivity is suppressed. Finally, we compare the effect of physical and chemical pressure in the RRu 2P 2 ( R = Y, La–Er, Yb) isostructural series of compounds and find them to be analogous.« less

High-pressure behavior of intermediate scapolite: compressibility, structure deformation and phase transition

NASA Astrophysics Data System (ADS)

Lotti, Paolo; Comboni, Davide; Merlini, Marco; Hanfland, Michael

2018-05-01

Scapolites are common volatile-bearing minerals in metamorphic rocks. In this study, the high-pressure behavior of an intermediate member of the scapolite solid solution series (Me47), chemical formula (Na1.86Ca1.86K0.23Fe0.01)(Al4.36Si7.64)O24[Cl0.48(CO3)0.48(SO4)0.01], has been investigated up to 17.79 GPa, by means of in situ single-crystal synchrotron X-ray diffraction. The isothermal elastic behavior of the studied scapolite has been described by a III-order Birch-Murnaghan equation of state, which provided the following refined parameters: V 0 = 1110.6(7) Å3, {K_{{V_0}}} = 70(2) GPa ({β _{{V_0}}} = 0.0143(4) GPa-1) and {K_{{V}}^' = 4.8(7). The refined bulk modulus is intermediate between those previously reported for Me17 and Me68 scapolite samples, confirming that the bulk compressibility among the solid solution increases with the Na content. A discussion on the P-induced structure deformation mechanisms of tetragonal scapolite at the atomic scale is provided, along with the implications of the reported results for the modeling of scapolite stability. In addition, a single-crystal to single-crystal phase transition, which is displacive in character, has been observed toward a triclinic polymorph at 9.87 GPa. The high-pressure triclinic polymorph was found to be stable up to the highest pressure investigated.

Effect of pore geometry on the compressibility of a confined simple fluid

NASA Astrophysics Data System (ADS)

Dobrzanski, Christopher D.; Maximov, Max A.; Gor, Gennady Y.

2018-02-01

Fluids confined in nanopores exhibit properties different from the properties of the same fluids in bulk; among these properties is the isothermal compressibility or elastic modulus. The modulus of a fluid in nanopores can be extracted from ultrasonic experiments or calculated from molecular simulations. Using Monte Carlo simulations in the grand canonical ensemble, we calculated the modulus for liquid argon at its normal boiling point (87.3 K) adsorbed in model silica pores of two different morphologies and various sizes. For spherical pores, for all the pore sizes (diameters) exceeding 2 nm, we obtained a logarithmic dependence of fluid modulus on the vapor pressure. Calculation of the modulus at saturation showed that the modulus of the fluid in spherical pores is a linear function of the reciprocal pore size. The calculation of the modulus of the fluid in cylindrical pores appeared too scattered to make quantitative conclusions. We performed additional simulations at higher temperature (119.6 K), at which Monte Carlo insertions and removals become more efficient. The results of the simulations at higher temperature confirmed both regularities for cylindrical pores and showed quantitative difference between the fluid moduli in pores of different geometries. Both of the observed regularities for the modulus stem from the Tait-Murnaghan equation applied to the confined fluid. Our results, along with the development of the effective medium theories for nanoporous media, set the groundwork for analysis of the experimentally measured elastic properties of fluid-saturated nanoporous materials.

Structure and bulk modulus of Ln-doped UO2 (Ln = La, Nd) at high pressure

NASA Astrophysics Data System (ADS)

Rittman, Dylan R.; Park, Sulgiye; Tracy, Cameron L.; Zhang, Lei; Palomares, Raul I.; Lang, Maik; Navrotsky, Alexandra; Mao, Wendy L.; Ewing, Rodney C.

2017-07-01

The structure of lanthanide-doped uranium dioxide, LnxU1-xO2-0.5x+y (Ln = La, Nd), was investigated at pressures up to ∼50-55 GPa. Samples were synthesized with different lanthanides at different concentrations (x ∼ 0.2 and 0.5), and all were slightly hyperstoichiometric (y ∼ 0.25-0.4). In situ high-pressure synchrotron X-ray diffraction was used to investigate their high-pressure phase behavior and determine their bulk moduli. All samples underwent a fluorite-to-cotunnite phase transformation with increasing pressure. The pressure of the phase transformation increased with increasing hyperstoichiometry, which is consistent with results from previous computational simulations. Bulk moduli are inversely proportional to both the ionic radius of the lanthanide and its concentration, as quantified using a weighted cationic radius ratio. This trend was found to be consistent with the behavior of other elastic properties measured for Ln-doped UO2, such as Young's modulus.

Structure and bulk modulus of Ln-doped UO 2 (Ln = La, Nd) at high pressure

DOE PAGES

Rittman, Dylan R.; Park, Sulgiye; Tracy, Cameron L.; ...

2017-04-10

The structure of lanthanide-doped uranium dioxide, Ln xU 1-xO 2-0.5x+y (Ln = La, Nd), was investigated at pressures up to ~50–55 GPa. Samples were synthesized with different lanthanides at different concentrations (x ~ 0.2 and 0.5), and all were slightly hyperstoichiometric (y ~ 0.25–0.4). In situ high-pressure synchrotron X-ray diffraction was used to investigate their high-pressure phase behavior and determine their bulk moduli. All samples underwent a fluorite-to-cotunnite phase transformation with increasing pressure. The pressure of the phase transformation increased with increasing hyperstoichiometry, which is consistent with results from previous computational simulations. Bulk moduli are inversely proportional to both themore » ionic radius of the lanthanide and its concentration, as quantified using a weighted cationic radius ratio. As a result, this trend was found to be consistent with the behavior of other elastic properties measured for Ln-doped UO 2, such as Young's modulus.« less

Increased Upper Trapezius Muscle Stiffness in Overhead Athletes with Rotator Cuff Tendinopathy

PubMed Central

Leong, Hio Teng; Hug, François; Fu, Siu Ngor

2016-01-01

Although excessive tension of the upper trapezius (UT) is thought to contribute to rotator cuff tendinopathy, no study examined UT tension in athletes with and without rotator cuff tendinopathy. Here we used UT shear modulus measured using ultrasound shear wave elastography as an index of muscle stiffness/tension. The aims of this study were twofold: 1) to determine whether the UT muscle shear modulus is altered in athletes with rotator cuff tendinopathy compared to asymptomatic athletes, and 2) to detect optimal cut-off points of UT shear modulus in identifying athletes with rotator cuff tendinopathy. Forty-three male volleyball players (17 asymptomatic and 26 with rotator cuff tendinopathy, mean age = 22.9±3.5 years) participated in the study. UT shear modulus was quantified during active arm holding at 30° and 60° of shoulder abduction and passive arm positioning at 0°, 30° and 60° of shoulder abduction. During the active tasks, the UT shear modulus was higher in athletes with rotator cuff tendinopathy than the asymptomatic athletes (p = 0.002), regardless the arm position. During the passive tasks, athletes with rotator cuff tendinopathy exhibited a higher UT shear modulus than asymptomatic athletes only at 0° of shoulder abduction (13.0±2.5 kPa vs 10.2±1.8 kPa, p = 0.001). When considering the active task, an optimal cut-off shear modulus of 12.0 kPa at 30° of shoulder abduction (sensitivity = 0.84, specificity = 0.57, AUC = 0.757, p = 0.008) and 9.5 kPa at 60° of shoulder abduction (sensitivity = 0.88, specificity = 0.67, AUC = 0.816, p = 0.002) was detected. When considering the passive task at 0° of shoulder abduction, a cut-off of 12.2 kPa was found (sensitivity = 0.73, AUC = 0.817, p = 0.001). Findings from the present study show that monitoring passive and active UT muscle shear modulus may provide important information for the prevention/rehabilitation of rotator cuff tendinopathy. PMID:27159276

Increased Upper Trapezius Muscle Stiffness in Overhead Athletes with Rotator Cuff Tendinopathy.

PubMed

Leong, Hio Teng; Hug, François; Fu, Siu Ngor

2016-01-01

Although excessive tension of the upper trapezius (UT) is thought to contribute to rotator cuff tendinopathy, no study examined UT tension in athletes with and without rotator cuff tendinopathy. Here we used UT shear modulus measured using ultrasound shear wave elastography as an index of muscle stiffness/tension. The aims of this study were twofold: 1) to determine whether the UT muscle shear modulus is altered in athletes with rotator cuff tendinopathy compared to asymptomatic athletes, and 2) to detect optimal cut-off points of UT shear modulus in identifying athletes with rotator cuff tendinopathy. Forty-three male volleyball players (17 asymptomatic and 26 with rotator cuff tendinopathy, mean age = 22.9±3.5 years) participated in the study. UT shear modulus was quantified during active arm holding at 30° and 60° of shoulder abduction and passive arm positioning at 0°, 30° and 60° of shoulder abduction. During the active tasks, the UT shear modulus was higher in athletes with rotator cuff tendinopathy than the asymptomatic athletes (p = 0.002), regardless the arm position. During the passive tasks, athletes with rotator cuff tendinopathy exhibited a higher UT shear modulus than asymptomatic athletes only at 0° of shoulder abduction (13.0±2.5 kPa vs 10.2±1.8 kPa, p = 0.001). When considering the active task, an optimal cut-off shear modulus of 12.0 kPa at 30° of shoulder abduction (sensitivity = 0.84, specificity = 0.57, AUC = 0.757, p = 0.008) and 9.5 kPa at 60° of shoulder abduction (sensitivity = 0.88, specificity = 0.67, AUC = 0.816, p = 0.002) was detected. When considering the passive task at 0° of shoulder abduction, a cut-off of 12.2 kPa was found (sensitivity = 0.73, AUC = 0.817, p = 0.001). Findings from the present study show that monitoring passive and active UT muscle shear modulus may provide important information for the prevention/rehabilitation of rotator cuff tendinopathy.

The thermodynamic properties of the earth's lower mantle

NASA Astrophysics Data System (ADS)

Anderson, Orson L.; Sumino, Yoshio

1980-12-01

The thermodynamic properties of the lower mantle are determined from the seismic profile, where the primary thermodynamic variables are the bulk modulus K and density ρ. It is shown that the Bullen law ( K ∝ P) holds in the lower mantle with a high correlation coefficient for the seismic parametric Earth model (PEM). Using this law produces no ambiguity or trade-off between ρ0 and K0, since both K0 and K' 0 are exactly determined by applying a linear K- ρ relationship to the data. On the other hand, extrapolating the velocity data to zero pressure using a Birch-Murnaghan equation of state (EOS) results in an ambiguous answer because there are three unknown adjustable parameters ( ρ0, K0, K' 0) in the EOS. From the PEM data, K = 232.4 + 3.19 P (GPa). The PEM yields a hot uncompressed density of 3.999 ± 0.0026 g cm -3 for material decompressed from all parts of the lower mantle. Even if the hot uncompressed density were uniform for all depths in the lower mantle, the cold uncompressed mantle would be inhomogeneous because the decompression given by the Bullen law crosses isotherms; for example, the temperature is different at different depths. To calculate the density distribution correctly, an isothermal EOS must be used along an isotherm, and temperature corrections must be placed in the thermal pressure PTH. The thermodynamic parameters of the lower mantle are found by iteration. Values of the three uncompressed anharmonic parameters are first arbitrarily selected: α0 (hot), the coefficient of thermal expansion; γ0, the Grüneisen parameter; and δ, the second Grüneisen parameter. Using γ0 and the measured ρ0 (hot) and K0 (hot), the values of θ0 (Debye temperature) and q = dln γ/dln ρ are found from the measured seismic velocities. Then from ( αKT) 0 and q the thermal pressure PTH at all high temperatures is found. Correlating PTH against T to the geotherm for the lower mantle, PTH is found at all depths Z. The isothermal pressure, along the 0 K isotherm, at every Z is found by subtracting PTH from the measured P given by the seismic model. Using the isothermal pressure at depth Z, the solution for the cold uncompressed density ρ0C and the cold uncompressed bulk modulus, KT0 is found as a trace in the KT0 - ρ0C plane. A narrow band of solutions is then found for ρ0C and KT0 at all depths. The thermal expansion at all T is found from [ ρ0C - ρ0 (hot)/ ρ0C. From Suzuki's formula, the best fit to the thermal expansion determines γ0 and α0 (hot). When the values of these two parameters do not agree with the original assumptions, the calculation is repeated until they do agree. In this way all the important thermodynamic parameters are found as a self-consistent set subject only to the assumptions behind the equations used.

Elastic, magnetic and electronic properties of iridium phosphide Ir 2P

DOE PAGES

Wang, Pei; Wang, Yonggang; Wang, Liping; ...

2016-02-24

Cubic (space group: Fm3¯m) iridium phosphide, Ir 2P, has been synthesized at high pressure and high temperature. Angle-dispersive synchrotron X-ray diffraction measurements on Ir 2P powder using a diamond-anvil cell at room temperature and high pressures (up to 40.6 GPa) yielded a bulk modulus of B 0 = 306(6) GPa and its pressure derivative B 0'= 6.4(5). Such a high bulk modulus attributed to the short and strongly covalent Ir-P bonds as revealed by first – principles calculations and three-dimensionally distributed [IrP 4] tetrahedron network. Indentation testing on a well–sintered polycrystalline sample yielded the hardness of 11.8(4) GPa. Relatively lowmore » shear modulus of ~64 GPa from theoretical calculations suggests a complicated overall bonding in Ir 2P with metallic, ionic, and covalent characteristics. Additionally, a spin glass behavior is indicated by magnetic susceptibility measurements.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Pei; Wang, Yonggang; Wang, Liping

Cubic (space group: Fm3¯m) iridium phosphide, Ir 2P, has been synthesized at high pressure and high temperature. Angle-dispersive synchrotron X-ray diffraction measurements on Ir 2P powder using a diamond-anvil cell at room temperature and high pressures (up to 40.6 GPa) yielded a bulk modulus of B 0 = 306(6) GPa and its pressure derivative B 0'= 6.4(5). Such a high bulk modulus attributed to the short and strongly covalent Ir-P bonds as revealed by first – principles calculations and three-dimensionally distributed [IrP 4] tetrahedron network. Indentation testing on a well–sintered polycrystalline sample yielded the hardness of 11.8(4) GPa. Relatively lowmore » shear modulus of ~64 GPa from theoretical calculations suggests a complicated overall bonding in Ir 2P with metallic, ionic, and covalent characteristics. Additionally, a spin glass behavior is indicated by magnetic susceptibility measurements.« less

Mapping of elasticity and damping in an α + β titanium alloy through atomic force acoustic microscopy

PubMed Central

Phani, M Kalyan; Kumar, Anish; Jayakumar, T; Samwer, Konrad

2015-01-01

Summary The distribution of elastic stiffness and damping of individual phases in an α + β titanium alloy (Ti-6Al-4V) measured by using atomic force acoustic microscopy (AFAM) is reported in the present study. The real and imaginary parts of the contact stiffness k * are obtained from the contact-resonance spectra and by using these two quantities, the maps of local elastic stiffness and the damping factor are derived. The evaluation of the data is based on the mass distribution of the cantilever with damped flexural modes. The cantilever dynamics model considering damping, which was proposed recently, has been used for mapping of indentation modulus and damping of different phases in a metallic structural material. The study indicated that in a Ti-6Al-4V alloy the metastable β phase has the minimum modulus and the maximum damping followed by α′- and α-phases. Volume fractions of the individual phases were determined by using a commercial material property evaluation software and were validated by using X-ray diffraction (XRD) and electron back-scatter diffraction (EBSD) studies on one of the heat-treated samples. The volume fractions of the phases and the modulus measured through AFAM are used to derive average modulus of the bulk sample which is correlated with the bulk elastic properties obtained by ultrasonic velocity measurements. The average modulus of the specimens estimated by AFAM technique is found to be within 5% of that obtained by ultrasonic velocity measurements. The effect of heat treatments on the ultrasonic attenuation in the bulk sample could also be understood based on the damping measurements on individual phases using AFAM. PMID:25977847

Mapping of elasticity and damping in an α + β titanium alloy through atomic force acoustic microscopy.

PubMed

Phani, M Kalyan; Kumar, Anish; Jayakumar, T; Arnold, Walter; Samwer, Konrad

2015-01-01

The distribution of elastic stiffness and damping of individual phases in an α + β titanium alloy (Ti-6Al-4V) measured by using atomic force acoustic microscopy (AFAM) is reported in the present study. The real and imaginary parts of the contact stiffness k (*) are obtained from the contact-resonance spectra and by using these two quantities, the maps of local elastic stiffness and the damping factor are derived. The evaluation of the data is based on the mass distribution of the cantilever with damped flexural modes. The cantilever dynamics model considering damping, which was proposed recently, has been used for mapping of indentation modulus and damping of different phases in a metallic structural material. The study indicated that in a Ti-6Al-4V alloy the metastable β phase has the minimum modulus and the maximum damping followed by α'- and α-phases. Volume fractions of the individual phases were determined by using a commercial material property evaluation software and were validated by using X-ray diffraction (XRD) and electron back-scatter diffraction (EBSD) studies on one of the heat-treated samples. The volume fractions of the phases and the modulus measured through AFAM are used to derive average modulus of the bulk sample which is correlated with the bulk elastic properties obtained by ultrasonic velocity measurements. The average modulus of the specimens estimated by AFAM technique is found to be within 5% of that obtained by ultrasonic velocity measurements. The effect of heat treatments on the ultrasonic attenuation in the bulk sample could also be understood based on the damping measurements on individual phases using AFAM.

Crystal structures and compressibility of novel iron borides Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50} synthesized at high pressure and high temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bykova, E., E-mail: elena.bykova@uni-bayreuth.de; Laboratory of Crystallography, University of Bayreuth, D-95440 Bayreuth; Gou, H.

2015-10-15

We present here a detailed description of the crystal structures of novel iron borides, Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50} with various iron content (x=1.01(1), 1.04(1), 1.32(1)), synthesized at high pressures and high temperatures. As revealed by high-pressure single-crystal X-ray diffraction, the structure of Fe{sub 2}B{sub 7} possesses short incompressible B–B bonds, which make it as stiff as diamond in one crystallographic direction. The volume compressibility of Fe{sub 2}B{sub 7} (the bulk modulus K{sub 0}= 259(1.8) GPa, K{sub 0}′= 4 (fixed)) is even lower than that of FeB{sub 4} and comparable with that of MnB{sub 4}, known for highmore » bulk moduli among 3d metal borides. Fe{sub x}B{sub 50} adopts the structure of the tetragonal δ-B, in which Fe atoms occupy an interstitial position. Fe{sub x}B{sub 50} does not show considerable anisotropy in the elastic behavior. - Graphical abstract: Crystal structures of novel iron borides, Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50} (x=1.01(1), 1.04(1), 1.32(1)). - Highlights: • Novel iron borides, Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50}, were synthesized under HPHT conditions. • Fe{sub 2}B{sub 7} has a unique orthorhombic structure (space group Pbam). • Fe{sub 2}B{sub 7} possesses short incompressible B–B bonds that results in high bulk modulus. • Fe{sub x}B{sub 50} adopts the structure of the tetragonal δ-B composed of B{sub 12} icosahedra. • In Fe{sub x}B{sub 50} intraicosahedral bonds are stiffer than intericosahedral ones.« less

Pressure-volume relations and bulk modulus under pressure of tetrahedral compounds

NASA Astrophysics Data System (ADS)

Soma, T.; Takahashi, Y.; Kagaya, H.-M.

1985-03-01

The pressure-volume relation and the compression effect on the bulk modulus of tetrahedral compounds such as GaP, InP, ZnS, ZnSe, ZnTe and CdTe are investigated from the electronic theory of solids by using a recently presented binding force, which includes mainly covalent interactions in the pseudopotential formalism and partially ionic interactions. The calculated results of the pressure-volume relations involving the pressure-induced phase transition are useful when comparing with the experimental data under high pressure. The calculated bulk modulus of these compounds increases as the crystal volume decreases. Further, the pressure derivative of bulk modulus is not constant and decreases with the reduction of the crystal volume.

The compression behavior of blödite at low and high temperature up to ~10GPa: Implications for the stability of hydrous sulfates on icy planetary bodies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Comodi, Paola; Stagno, Vincenzo; Zucchini, Azzurra

Recent satellite inferences of hydrous sulfates as recurrent minerals on the surface of icy planetary bodies link with the potential mineral composition of their interior. Blödite, a mixed Mg-Na sulfate, is here taken as representative mineral of icy satellites surface to investigate its crystal structure and stability at conditions of the interior of icy bodies. To this aim we performed in situ synchrotron angle-dispersive X-ray powder diffraction experiments on natural blödite at pressures up to ~10.4 GPa and temperatures from ~118.8 K to ~490.0 K using diamond anvil cell technique to investigate the compression behavior and establish a low-to-high temperaturemore » equation of state that can be used as reference when modeling the interior of sulfate-rich icy satellites such as Ganymede. The experimentally determined volume expansivity, α, varies from 7.6 (7) 10 -5 K -1 at 0.0001 GPa (from 118.8 to 413.15 K) to 2.6 (3) 10 -5 K -1 at 10 GPa (from 313.0 to 453.0 K) with a δα/δ P coefficient = -5.6(9)10 -6 GPa -1 K -1. The bulk modulus calculated from the least squares fitting of P-V data on the isotherm at 413 K using a second-order Birch - Murnaghan equation of state is 38(5) GPa, which gives the value of δK/δ T equal to 0.01(5) GPa K -1. The thermo-baric behavior of blödite appears strongly anisotropic with c lattice parameter being more deformed with respect to a and b. Thermogravimetric analyses performed at ambient pressure showed three endotherms at 413 K, 533 K and 973 K with weight losses of approximately 11%, 11% and 43% caused by partial dehydration, full dehydration and sulfate decomposition respectively. Interestingly, no clear evidence of dehydration was observed up to ~453 K and ~10.4 GPa, suggesting that pressure acts to stabilize the crystalline structure of blödite. The data collected allow to write the following equation of state, V(P, T) = V 0[1 + 7.6(7)10 - 5ΔT - 0.026(3)P - 5.6(9)10 - 6PΔT-6.6(9)10 - 6PΔT)] from which the density of blödite can be determined at conditions of the mantle of the large icy satellites of Jupiter. Blödite has higher density, bulk modulus and thermal stability than similar hydrous sulfates (e.g. mirabilite and epsomite) implying, therefore, a different contribution of these minerals to the extent of deep oceans in icy planets and their distribution over the local geotherms.« less

The compression behavior of blödite at low and high temperature up to ∼10 GPa: Implications for the stability of hydrous sulfates on icy planetary bodies

NASA Astrophysics Data System (ADS)

Comodi, Paola; Stagno, Vincenzo; Zucchini, Azzurra; Fei, Yingwei; Prakapenka, Vitali

2017-03-01

Recent satellite inferences of hydrous sulfates as recurrent minerals on the surface of icy planetary bodies link with the potential mineral composition of their interior. Blödite, a mixed Mg-Na sulfate, is here taken as representative mineral of icy satellites surface to investigate its crystal structure and stability at conditions of the interior of icy bodies. To this aim we performed in situ synchrotron angle-dispersive X-ray powder diffraction experiments on natural blödite at pressures up to ∼10.4 GPa and temperatures from ∼118.8 K to ∼490.0 K using diamond anvil cell technique to investigate the compression behavior and establish a low-to-high temperature equation of state that can be used as reference when modeling the interior of sulfate-rich icy satellites such as Ganymede. The experimentally determined volume expansivity, α, varies from 7.6 (7) 10-5 K-1 at 0.0001 GPa (from 118.8 to 413.15 K) to 2.6 (3) 10-5 K-1 at 10 GPa (from 313.0 to 453.0 K) with a δα/δP coefficient = -5.6(9)10-6 GPa-1 K-1. The bulk modulus calculated from the least squares fitting of P-V data on the isotherm at 413 K using a second-order Birch - Murnaghan equation of state is 38(5) GPa, which gives the value of δK/δT equal to 0.01(5) GPa K-1. The thermo-baric behavior of blödite appears strongly anisotropic with c lattice parameter being more deformed with respect to a and b. Thermogravimetric analyses performed at ambient pressure showed three endotherms at 413 K, 533 K and 973 K with weight losses of approximately 11%, 11% and 43% caused by partial dehydration, full dehydration and sulfate decomposition respectively. Interestingly, no clear evidence of dehydration was observed up to ∼453 K and ∼10.4 GPa, suggesting that pressure acts to stabilize the crystalline structure of blödite. The data collected allow to write the following equation of state, V(P, T) = V0[1 + 7.6(7)10- 5ΔT - 0.026(3)P - 5.6(9)10- 6PΔT-6.6(9)10- 6PΔT)] from which the density of blödite can be determined at conditions of the mantle of the large icy satellites of Jupiter. Blödite has higher density, bulk modulus and thermal stability than similar hydrous sulfates (e.g. mirabilite and epsomite) implying, therefore, a different contribution of these minerals to the extent of deep oceans in icy planets and their distribution over the local geotherms.

Scaling Problems for Wave Propagation in Layered Systems. Volume 2

DTIC Science & Technology

1989-09-01

PROPERTIES OF ALUMINIUM , LEXAN AND CONCRETE ^lumiunui Lexan Concrete* Bulk Modulus (Gpa) 80 3.47 13.1 Shear Modulus (Gpa) 30 0.90 9.4 Density (kg/’m3...783 TXXii3. TZZW=O. SzX11=0. EhiO. S 0J . zDKiEi=xD (LVABI5) YDliki!D WLAF.4) F T 3. 1 8011 = 0. 1ASSSD. L 3= LVIRS C-PI1, THE COOBD. OF CELLS AROUND

Measuring anisotropic muscle stiffness properties using elastography.

PubMed

Green, M A; Geng, G; Qin, E; Sinkus, R; Gandevia, S C; Bilston, L E

2013-11-01

Physiological and pathological changes to the anisotropic mechanical properties of skeletal muscle are still largely unknown, with only a few studies quantifying changes in vivo. This study used the noninvasive MR elastography (MRE) technique, in combination with diffusion tensor imaging (DTI), to measure shear modulus anisotropy in the human skeletal muscle in the lower leg. Shear modulus measurements parallel and perpendicular to the fibre direction were made in 10 healthy subjects in the medial gastrocnemius, soleus and tibialis anterior muscles. The results showed significant differences in the medial gastrocnemius (μ‖ = 0.86 ± 0.15 kPa; μ⊥ = 0.66 ± 0.19 kPa, P < 0.001), soleus (μ‖ = 0.83 ± 0.22 kPa; μ⊥ = 0.65 ± 0.13 kPa, P < 0.001) and the tibialis anterior (μ‖ = 0.78 ± 0.24 kPa; μ⊥ = 0.66 ± 0.16 kPa, P = 0.03) muscles, where the shear modulus measured in the direction parallel is greater than that measured in the direction perpendicular to the muscle fibres. No significant differences were measured across muscle groups. This study provides the first direct estimates of the anisotropic shear modulus in the triceps surae muscle group, and shows that the technique may be useful for the probing of mechanical anisotropy changes caused by disease, aging and injury. Copyright © 2013 John Wiley & Sons, Ltd.

The bonding, charge distribution, spin ordering, optical, and elastic properties of four MAX phases Cr{sub 2}AX (A = Al or Ge, X = C or N): From density functional theory study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Neng, E-mail: lineng@umkc.edu; Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, Missouri 64110; Mo, Yuxiang

2013-11-14

In this work, we assess a full spectrum of properties (chemical bonding, charge distribution, spin ordering, optical, and elastic properties) of Cr{sub 2}AC (A = Al, Ge) and their hypothetical nitride counterparts Cr{sub 2}AN (A = Al, Ge) based on density functional theory calculations. The calculated total energy values indicate that a variety of spin ordering of these four compounds depending on interlayer-interactions between M-A and M-X within the sublattice, which is supported by bonding analysis. MAX phase materials are discovered to possess exotic magnetic properties which indicates that these materials could serve as promising candidates for novel layered magnetic materials for various electronicmore » and spintronic applications. Further analysis of optical properties for two polarization vectors of Cr{sub 2}AX shows that the reflectivity is high in the visible-ultraviolet region up to ∼15 eV suggesting Cr{sub 2}AX as a promising candidate for use as a coating material. The elastic coefficients (C{sub ij}) and bulk mechanical properties [bulk modulus (K), shear modulus (G), Young's modulus (E), Poisson's ratio (η), and Pugh ratio (G/K)] of these four Cr{sub 2}AX compounds are also calculated and analyzed, which pave the way to predict or design new MAX phases that are less brittle or tougher by having a lower G/K value or higher η.« less

Structural, electronic, and elastic properties of CuFeS2: first-principles study

NASA Astrophysics Data System (ADS)

Zhou, Meng; Gao, Xiang; Cheng, Yan; Chen, Xiangrong; Cai, Lingcang

2015-03-01

The structural, electronic, and elastic properties of CuFeS2 have been investigated by using the generalized gradient approximation (GGA), GGA + U (on-site Coulomb repulsion energy), the local density approximation (LDA), and the LDA + U approach in the frame of density functional theory. It is shown that when the GGA + U formalism is selected with a U value of 3 eV for the 3d state of Fe, the calculated lattice constants agree well with the available experimental and other theoretical data. Our GGA + U calculations indicate that CuFeS2 is a semiconductor with a band gap of 0.552 eV and with a magnetic moment of 3.64 µB per Fe atom, which are well consistent with the experimental results. Combined with the density of states, the band structure characteristics of CuFeS2 have been analyzed and their origins have been specified, which reveals a hybridization existing between Fe-3d, Cu-3s, and S-3p, respectively. The charge and Mulliken population analyses indicate that CuFeS2 is a covalent crystal. Moreover, the calculated elastic constants prove that CuFeS2 is mechanically stable but anisotropic. The bulk modulus obtained from elastic constants is 87.1 GPa, which agrees well with the experimental value of 91 ± 15 GPa and better than the theoretical bulk modulus 74 GPa obtained from GGA method by Lazewski et al. The obtained shear modulus and Debye temperature are 21.0 GPa and 287 K, respectively, and the latter accords well with the available experimental value. It is expected that our work can provide useful information to further investigate CuFeS2 from both the experimental and theoretical sides.

Hardness, elastic, and electronic properties of chromium monoboride

DOE PAGES

Han, Lei; Wang, Shanmin; Zhu, Jinlong; ...

2015-06-03

Here, we report high-pressure synthesis of chromium monoboride (CrB) at 6 GPa and 1400 K. The elastic and plastic behaviors have been investigated by hydrostatic compression experiment and micro-indentation measurement. CrB is elastically incompressible with a high bulk modulus of 269.0 (5.9) GPa and exhibits a high Vickers hardness of 19.6 (0.7) GPa under the load of 1 kg force. Based on first principles calculations, the observed mechanical properties are attributed to the polar covalent Cr-B bonds interconnected with strong zigzag B-B covalent bonding network. The presence of metallic Cr bilayers is presumably responsible for the weakest paths in shearmore » deformation.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stan, Camelia V.; Dutta, Rajkrishna; White, Claire E.

Lead fluoride, PbF 2, was investigated experimentally in the laser-heated diamond anvil cell by x-ray diffraction to pressures of 75 GPa at room temperature and to 64.5 GPa and 2430 K, as well as through first-principles density functional theory calculations up to 70 GPa. During room temperature compression, no discontinuous changes in the x-ray diffraction pattern or volume were observed, but the lattice parameters displayed highly anomalous trends between 10-22 GPa with enhanced compressibility along the a direction and reduced or even negative compressibility along b and c. Theoretical calculations of valence electron densities at 22 GPa showed that α-PbFmore » 2 underwent a pressure-induced isosymmetric phase transition to a postcotunnite Co 2Si structure and also revealed the detailed atomic rearrangements associated with the development of an extra Pb-F bond in the high-pressure phase. Our x-ray results and theoretical calculations are consistent with an isosymmetric phase transition smoothly occurring over 10-22 GPa rather than abruptly as previously suggested. The characteristic values for the cell constants a/c and (a+c)/b, which are used to distinguish among cotunnite-, Co 2Si-, and Ni 2In-type phases, require modification based on our results. An equation of state fit yields a bulk modulus, K 0, of 72(3) GPa for the cotunnite-type, and an ambient-pressure volume, V 0, of 182(2)Å 3, and K 0=81(4)GPa for the Co 2Si-type phase when fixing the pressure derivative of the bulk modulus, K 0'=4. Upon heating above 1200 K at pressures at or above 25.9 GPa, PbF 2 partially transformed to the hexagonal Ni 2In-type phase but wholly or partially reverted back to Co 2Si-type phase upon temperature quench. From 43-65 GPa, nearly complete transformation to the Ni 2In-type PbF 2 was observed at high temperature, but the material partially transformed back to the orthorhombic phase upon temperature quench. Our results show that high-pressure behavior of PbF 2 is distinct from that of the alkaline earth fluorides with similar ionic radii. These results also have relevance to understanding the behavior of lanthanide and actinide dioxides, which have been predicted theoretically to exhibit similar isosymmetric transitions at Mbar pressures.« less

High-pressure polymorphism of Pb F 2 to 75 GPa

DOE PAGES

Stan, Camelia V.; Dutta, Rajkrishna; White, Claire E.; ...

2016-07-06

Lead fluoride, PbF 2, was investigated experimentally in the laser-heated diamond anvil cell by x-ray diffraction to pressures of 75 GPa at room temperature and to 64.5 GPa and 2430 K, as well as through first-principles density functional theory calculations up to 70 GPa. During room temperature compression, no discontinuous changes in the x-ray diffraction pattern or volume were observed, but the lattice parameters displayed highly anomalous trends between 10-22 GPa with enhanced compressibility along the a direction and reduced or even negative compressibility along b and c. Theoretical calculations of valence electron densities at 22 GPa showed that α-PbFmore » 2 underwent a pressure-induced isosymmetric phase transition to a postcotunnite Co 2Si structure and also revealed the detailed atomic rearrangements associated with the development of an extra Pb-F bond in the high-pressure phase. Our x-ray results and theoretical calculations are consistent with an isosymmetric phase transition smoothly occurring over 10-22 GPa rather than abruptly as previously suggested. The characteristic values for the cell constants a/c and (a+c)/b, which are used to distinguish among cotunnite-, Co 2Si-, and Ni 2In-type phases, require modification based on our results. An equation of state fit yields a bulk modulus, K 0, of 72(3) GPa for the cotunnite-type, and an ambient-pressure volume, V 0, of 182(2)Å 3, and K 0=81(4)GPa for the Co 2Si-type phase when fixing the pressure derivative of the bulk modulus, K 0'=4. Upon heating above 1200 K at pressures at or above 25.9 GPa, PbF 2 partially transformed to the hexagonal Ni 2In-type phase but wholly or partially reverted back to Co 2Si-type phase upon temperature quench. From 43-65 GPa, nearly complete transformation to the Ni 2In-type PbF 2 was observed at high temperature, but the material partially transformed back to the orthorhombic phase upon temperature quench. Our results show that high-pressure behavior of PbF 2 is distinct from that of the alkaline earth fluorides with similar ionic radii. These results also have relevance to understanding the behavior of lanthanide and actinide dioxides, which have been predicted theoretically to exhibit similar isosymmetric transitions at Mbar pressures.« less

High-pressure polymorphism of Pb F2 to 75 GPa

NASA Astrophysics Data System (ADS)

Stan, Camelia V.; Dutta, Rajkrishna; White, Claire E.; Prakapenka, Vitali; Duffy, Thomas S.

2016-07-01

Lead fluoride, Pb F2 , was investigated experimentally in the laser-heated diamond anvil cell by x-ray diffraction to pressures of 75 GPa at room temperature and to 64.5 GPa and 2430 K, as well as through first-principles density functional theory calculations up to 70 GPa. During room temperature compression, no discontinuous changes in the x-ray diffraction pattern or volume were observed, but the lattice parameters displayed highly anomalous trends between 10-22 GPa with enhanced compressibility along the a direction and reduced or even negative compressibility along b and c . Theoretical calculations of valence electron densities at 22 GPa showed that α -Pb F2 underwent a pressure-induced isosymmetric phase transition to a postcotunnite C o2Si structure and also revealed the detailed atomic rearrangements associated with the development of an extra Pb-F bond in the high-pressure phase. Our x-ray results and theoretical calculations are consistent with an isosymmetric phase transition smoothly occurring over 10-22 GPa rather than abruptly as previously suggested. The characteristic values for the cell constants a /c and (a +c )/b , which are used to distinguish among cotunnite-, C o2Si -, and N i2In -type phases, require modification based on our results. An equation of state fit yields a bulk modulus, K0, of 72(3) GPa for the cotunnite-type, and an ambient-pressure volume, V0, of 182 (2 ) Å3 , and K0=81 (4 ) GPa for the C o2Si -type phase when fixing the pressure derivative of the bulk modulus, K0 '=4 . Upon heating above 1200 K at pressures at or above 25.9 GPa, Pb F2 partially transformed to the hexagonal N i2In -type phase but wholly or partially reverted back to C o2Si -type phase upon temperature quench. From 43-65 GPa, nearly complete transformation to the N i2In -type Pb F2 was observed at high temperature, but the material partially transformed back to the orthorhombic phase upon temperature quench. Our results show that high-pressure behavior of Pb F2 is distinct from that of the alkaline earth fluorides with similar ionic radii. Our results also have relevance to understanding the behavior of lanthanide and actinide dioxides, which have been predicted theoretically to exhibit similar isosymmetric transitions at Mbar pressures.

Ab initio predictions of structural and elastic properties of struvite: contribution to urinary stone research.

PubMed

Piechota, Jacek; Prywer, Jolanta; Torzewska, Agnieszka

2012-01-01

In the present work, we carried out density functional calculations of struvite--the main component of the so-called infectious urinary stones--to study its structural and elastic properties. Using a local density approximation and a generalised gradient approximation, we calculated the equilibrium structural parameters and elastic constants C(ijkl). At present, there is no experimental data for these elastic constants C (ijkl) for comparison. Besides the elastic constants, we also present the calculated macroscopic mechanical parameters, namely the bulk modulus (K), the shear modulus (G) and Young's modulus (E). The values of these moduli are found to be in good agreement with available experimental data. Our results imply that the mechanical stability of struvite is limited by the shear modulus, G. The study also explores the energy-band structure to understand the obtained values of the elastic constants.

Apparent elastic modulus and hysteresis of skeletal muscle cells throughout differentiation

NASA Technical Reports Server (NTRS)

Collinsworth, Amy M.; Zhang, Sarah; Kraus, William E.; Truskey, George A.

2002-01-01

The effect of differentiation on the transverse mechanical properties of mammalian myocytes was determined by using atomic force microscopy. The apparent elastic modulus increased from 11.5 +/- 1.3 kPa for undifferentiated myoblasts to 45.3 +/- 4.0 kPa after 8 days of differentiation (P < 0.05). The relative contribution of viscosity, as determined from the normalized hysteresis area, ranged from 0.13 +/- 0.02 to 0.21 +/- 0.03 and did not change throughout differentiation. Myosin expression correlated with the apparent elastic modulus, but neither myosin nor beta-tubulin were associated with hysteresis. Microtubules did not affect mechanical properties because treatment with colchicine did not alter the apparent elastic modulus or hysteresis. Treatment with cytochalasin D or 2,3-butanedione 2-monoxime led to a significant reduction in the apparent elastic modulus but no change in hysteresis. In summary, skeletal muscle cells exhibited viscoelastic behavior that changed during differentiation, yielding an increase in the transverse elastic modulus. Major contributors to changes in the transverse elastic modulus during differentiation were actin and myosin.

Mechanical properties of nano and bulk Fe pillars using molecular dynamics and dislocation dynamics simulation

NASA Astrophysics Data System (ADS)

Nath, S. K. Deb

2017-10-01

Using molecular dynamics simulation, tension and bending tests of a Fe nanopillar are carried out to obtain its Young's modulus and yield strength. Then the comparative study of Young's modulus and yield strength of a Fe nanopillar under bending and tension are carried out varying its diameter in the range of diameter 1-15nm. We find out the reasons why bending Young's modulus and yield strength of a Fe nanopillar are higher than those of tension Young's modulus and yield strength of a Fe nanopillar. Using the mobility parameters of bulk Fe from the experimental study [N. Urabe and J. Weertman, Materials Science and Engineering 18, 41 (1975)], its temperature dependent stress-strain relationship, yield strength and strain hardening modulus are obtained from the dislocation dynamics simulations. Strain rate dependent yield strength and strain hardening modulus of bulk Fe pillars under tension are studied. Temperature dependent creep behaviors of bulk Fe pillars under tension are also studied. To verify the soundness of the present dislocation dynamics studies of the mechanical properties of bulk Fe pillars under tension, the stress vs. strain relationship and dislocation density vs. strain of bulk Fe pillars obtained by us are compared with the published results obtained by S. Queyreau, G. Monnet, and B. Devincre, International Journal of Plasticity 25, 361 (2009).

Cohesive Energy-Lattice Constant and Bulk Modulus-Lattice Constant Relationships: Alkali Halides, Ag Halides, Tl Halides

NASA Technical Reports Server (NTRS)

Schlosser, Herbert

1992-01-01

In this note we present two expressions relating the cohesive energy, E(sub coh), and the zero pressure isothermal bulk modulus, B(sub 0), of the alkali halides. Ag halides and TI halides, with the nearest neighbor distances, d(sub nn). First, we show that the product E(sub coh)d(sub 0) within families of halide crystals with common crystal structure is to a good approximation constant, with maximum rms deviation of plus or minus 2%. Secondly, we demonstrate that within families of halide crystals with a common cation and common crystal structure the product B(sub 0)d(sup 3.5)(sub nn) is a good approximation constant, with maximum rms deviation of plus or minus 1.36%.

Characteristics of low polymerization shrinkage flowable resin composites in newly-developed cavity base materials for bulk filling technique.

PubMed

Nitta, Keiko; Nomoto, Rie; Tsubota, Yuji; Tsuchikawa, Masuji; Hayakawa, Tohru

2017-11-29

The purpose of this study was to evaluate polymerization shrinkage and other physical properties of newly-developed cavity base materials for bulk filling technique, with the brand name BULK BASE (BBS). Polymerization shrinkage was measured according to ISO/FDIS 17304. BBS showed the significantly lowest polymerization shrinkage and significantly higher depth of cure than conventional flowable resin composites (p<0.05). The Knoop hardness, flexural strength and elastic modulus of that were significantly lower than conventional flowable resin composites (p<0.05). BBS had the significantly greatest filler content (p<0.05). SEM images of the surface showed failure of fillers. The lowest polymerization shrinkage was due to the incorporation of a new type of low shrinkage monomer, which has urethane moieties. There were no clear correlations between inorganic filler contents and polymerization shrinkage, flexural strength and elastic modulus. In conclusion, the low polymerization shrinkage of BBS will be useful for cavity treatment in dental clinics.

Structural and thermomechanical properties of the zinc-blende AlX (X = P, As, Sb) compounds

NASA Astrophysics Data System (ADS)

Ha, Vu Thi Thanh; Hung, Vu Van; Hanh, Pham Thi Minh; Nguyen, Viet Tuyen; Hieu, Ho Khac

2017-08-01

The structural and thermomechanical properties of zinc-blende aluminum class of III-V compounds have been studied based on the statistical moment method (SMM) in quantum statistical mechanics. Within the SMM scheme, we derived the analytical expressions of the nearest-neighbor distance, thermal expansion coefficient, atomic mean-square displacement and elastic moduli (Young’s modulus, bulk modulus and shear modulus). Numerical calculations have been performed for zinc-blende AlX (X = As, P, Sb) at ambient conditions up to the temperature of 1000 K. Our results are in good and reasonable agreements with earlier measurements and can provide useful references for future experimental and theoretical works. This research presents a systematic approach to investigate the thermodynamic and mechanical properties of materials.

Insight into the structural, electronic, elastic and optical properties of the alkali hydride compounds, XH (X = Rb and Cs)

NASA Astrophysics Data System (ADS)

Jaradat, Raed; Abu-Jafar, Mohammed; Abdelraziq, Issam; Mousa, Ahmad; Ouahrani, Tarik; Khenata, Rabah

2018-04-01

The equilibrium structural parameters, electronic and optical properties of the alkali hydrides RbH and CsH compounds in rock-salt (RS) and cesium chloride (CsCl) structures have been studied using the full-potential linearized augmented plane-wave (FP-LAPW) method. Wu and Cohen generalized gradient approximation (WC-GGA) was used for the exchange-correlation potential to compute the equilibrium structural parameters, such as the lattice constant (a0), the bulk modulus (B) and bulk modulus first order pressure derivative (B'). In addition to the WC-GGA, the modified Becke Johnson (mBJ) scheme has been also used to overcome the underestimation of the band gap energies. RbH and CsH compounds are found to be semiconductors (wide energy-band gap) using the WC-GGA method, while they are insulators using the mBJ-GGA method. Elastic constants, mechanical and thermodynamic properties were obtained by using the IRelast package. RbH and CsH compounds at ambient pressure are mechanically stable in RS and CsCl structures; they satisfy the Born mechanical stability criteria. Elastic constants (Cij), bulk modulus (B), shear modulus (S) and Debye temperatures (θD) of RbH and CsH compounds decrease as the alkali radius increases. The RS structure of these compounds at ambient conditions is mechanically stronger than CsCl structure. RbH and CsH in RS and CsCl structures are suitable as dielectric compounds. The wide direct energy band gap for these compounds make them promising compounds for optoelectronic UV device applications. Both RbH and CsH have a wide absorption region, on the other hand RbH absorption is very huge compared to the CsH absorption, RbH is an excellent absorbent material, maximum absorption regions are located in the middle ultraviolet (MUV) region and far ultraviolet (FUV) region. The absorption coefficient α (w), imaginary part of the dielectric constant ɛ2(w) and the extinction coefficient k(w) vary in the same way. The present calculated results are in good agreement with the experimental data, indicating the high accuracy of the performed calculations and reliability of the obtained results.

High-Pressure Study of Perovskites and Postperovskites in the (Mg,Fe)GeO 3 System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stan, Camelia V.; Dutta, Rajkrishna; Cava, Robert J.

2017-06-22

The effect of incorporation of Fe 2+ on the perovskite (Pbnm) and postperovskite (Cmcm) structures was investigated in the (Mg,Fe)GeO 3 system at high pressures and temperatures using laser-heated diamond anvil cell and synchrotron X-ray diffraction. Samples with compositions of Mg# ≥ 48 were shown to transform to the perovskite (~30 GPa and ~1500 K) and postperovskite (>55 GPa, ~1600–1800 K) structures. Compositions with Mg# ≥ 78 formed single-phase perovskite and postperovskite, whereas those with Mg# < 78 showed evidence for partial decomposition. The incorporation of Fe into the perovskite structure causes a decrease in octahedral distortion as well asmore » a modest decrease in bulk modulus (K 0) and a modest increase in zero-pressure volume (V 0). It also leads to a decrease in the perovskite-to-postperovskite phase transition pressure by ~9.5 GPa over compositions from Mg#78 to Mg#100.« less

Influence of interface point defect on the dielectric properties of Y doped CaCu3Ti4O12 ceramics

NASA Astrophysics Data System (ADS)

Deng, Jianming; Sun, Xiaojun; Liu, Saisai; Liu, Laijun; Yan, Tianxiang; Fang, Liang; Elouadi, Brahim

2016-04-01

CaCu3Ti4-xYxO12 (0≤x≤0.12) ceramics were fabricated with conventional solid-state reaction method. Phase structure and microstructure of prepared ceramics were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The impedance and modulus tests both suggested the existence of two different relaxation behavior, which were attributed to bulk and grain boundary response. In addition, the conductivity and dielectric permittivity showed a step-like behavior under 405K. Meanwhile, frequency independence of dc conduction became dominant when above 405K. In CCTO ceramic, rare earth element Y3+ ions as an acceptor were used to substitute Ti sites, decreasing the concentration of oxygen vacancy around grain-electrode and grain boundary. The reason to the reduction of dielectric behavior in low frequencies range was associated with the Y doping in CCTO ceramic.

Thermal equation of state of hcp-iron: Constraint on the density deficit of Earth's solid inner core: THERMAL EQUATION OF STATE OF HCP-IRON

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fei, Yingwei; Murphy, Caitlin; Shibazaki, Yuki

We conducted high-pressure experiments on hexagonal close packed iron (hcp-Fe) in MgO, NaCl, and Ne pressure-transmitting media and found general agreement among the experimental data at 300 K that yield the best fitted values of the bulk modulus K 0 = 172.7(±1.4) GPa and its pressure derivative K 0'= 4.79(±0.05) for hcp-Fe, using the third-order Birch-Murnaghan equation of state. Using the derived thermal pressures for hcp-Fe up to 100 GPa and 1800 K and previous shockwave Hugoniot data, we developed a thermal equation of state of hcp-Fe. The thermal equation of state of hcp-Fe is further used to calculate themore » densities of iron along adiabatic geotherms to define the density deficit of the inner core, which serves as the basis for developing quantitative composition models of the Earth's inner core. We determine the density deficit at the inner core boundary to be 3.6%, assuming an inner core boundary temperature of 6000 K.« less

Cell wall elasticity: I. A critique of the bulk elastic modulus approach and an analysis using polymer elastic principles

NASA Technical Reports Server (NTRS)

Wu, H. I.; Spence, R. D.; Sharpe, P. J.; Goeschl, J. D.

1985-01-01

The traditional bulk elastic modulus approach to plant cell pressure-volume relations is inconsistent with its definition. The relationship between the bulk modulus and Young's modulus that forms the basis of their usual application to cell pressure-volume properties is demonstrated to be physically meaningless. The bulk modulus describes stress/strain relations of solid, homogeneous bodies undergoing small deformations, whereas the plant cell is best described as a thin-shelled, fluid-filled structure with a polymer base. Because cell walls possess a polymer structure, an alternative method of mechanical analysis is presented using polymer elasticity principles. This initial study presents the groundwork of polymer mechanics as would be applied to cell walls and discusses how the matrix and microfibrillar network induce nonlinear stress/strain relationships in the cell wall in response to turgor pressure. In subsequent studies, these concepts will be expanded to include anisotropic expansion as regulated by the microfibrillar network.

Anticorrelated seismic velocity anomalies from post-perovskite in the lowermost mantle

USGS Publications Warehouse

Hutko, Alexander R.; Lay, T.; Revenaugh, Justin; Garnero, E.J.

2008-01-01

Earth's lowermost mantle has thermal, chemical, and mineralogical complexities that require precise seismological characterization. Stacking, migration, and modeling of over 10,000 P and S waves that traverse the deep mantle under the Cocos plate resolve structures above the core-mantle boundary. A small -0.07 ?? 0.15% decrease of P wave velocity (Vp) is accompanied by a 1.5 ?? 0.5% increase in S wave velocity (Vs) near a depth of 2570 km. Bulk-sound velocity [Vb = (V p2 - 4/3Vs2)1/2] decreases by -1.0 ?? 0.5% at this depth. Transition of the primary lower-mantle mineral, (Mg1-x-y FexAly)(Si,Al) O3 perovskite, to denser post-perovskite is expected to have a negligible effect on the bulk modulus while increasing the shear modulus by ???6%, resulting in local anticorrelation of Vb and Vs anomalies; this behavior explains the data well.

Pressure-induced stiffness of Au nanoparticles to 71 GPa under quasi-hydrostatic loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Xinguo; Duffy, Thomas S.; Ehm, Lars

2015-11-16

The compressibility of nanocrystalline gold (n-Au, 20 nm) has been studied by x-ray total scattering using high-energy monochromatic x-rays in the diamond anvil cell under quasi-hydrostatic conditions up to 71 GPa. The bulk modulus, K 0, of the n-Au obtained from fitting to a Vinet equation of state is ~196(3) GPa, which is about 17% higher than for the corresponding bulk materials (K 0: 167 GPa). At low pressures (<7 GPa), the compression behavior of n-Au shows little difference from that of bulk Au. With increasing pressure, the compressive behavior of n-Au gradually deviates from the equation of state (EOS)more » of bulk gold. Analysis of the pair distribution function, peak broadening and Rietveld refinement reveals that the microstructure of n-Au is nearly a single-grain/domain at ambient conditions, but undergoes substantial pressure-induced reduction in grain size until 10 GPa. The results indicate that the nature of the internal microstructure in n-Au is associated with the observed EOS difference from bulk Au at high pressure. Full-pattern analysis confirms that significant changes in grain size, stacking faults, grain orientation and texture occur in n-Au at high pressure. We have observed direct experimental evidence of a transition in compressional mechanism for n-Au at ~20 GPa, i.e. from a deformation dominated by nucleation and motion of lattice dislocations (dislocation-mediated) to a prominent grain boundary mediated response to external pressure. In conclusion, the internal microstructure inside the nanoparticle (nanocrystallinity) plays a critical role for the macro-mechanical properties of nano-Au.« less

Pressure-induced stiffness of Au nanoparticles to 71 GPa under quasi-hydrostatic loading.

PubMed

Hong, Xinguo; Duffy, Thomas S; Ehm, Lars; Weidner, Donald J

2015-12-09

The compressibility of nanocrystalline gold (n-Au, 20 nm) has been studied by x-ray total scattering using high-energy monochromatic x-rays in the diamond anvil cell under quasi-hydrostatic conditions up to 71 GPa. The bulk modulus, K0, of the n-Au obtained from fitting to a Vinet equation of state is ~196(3) GPa, which is about 17% higher than for the corresponding bulk materials (K0: 167 GPa). At low pressures (<7 GPa), the compression behavior of n-Au shows little difference from that of bulk Au. With increasing pressure, the compressive behavior of n-Au gradually deviates from the equation of state (EOS) of bulk gold. Analysis of the pair distribution function, peak broadening and Rietveld refinement reveals that the microstructure of n-Au is nearly a single-grain/domain at ambient conditions, but undergoes substantial pressure-induced reduction in grain size until 10 GPa. The results indicate that the nature of the internal microstructure in n-Au is associated with the observed EOS difference from bulk Au at high pressure. Full-pattern analysis confirms that significant changes in grain size, stacking faults, grain orientation and texture occur in n-Au at high pressure. We have observed direct experimental evidence of a transition in compressional mechanism for n-Au at ~20 GPa, i.e. from a deformation dominated by nucleation and motion of lattice dislocations (dislocation-mediated) to a prominent grain boundary mediated response to external pressure. The internal microstructure inside the nanoparticle (nanocrystallinity) plays a critical role for the macro-mechanical properties of nano-Au.

Increasing Elasticity through Changes in the Secondary Structure of Gelatin by Gelation in a Microsized Lipid Space.

PubMed

Sakai, Atsushi; Murayama, Yoshihiro; Fujiwara, Kei; Fujisawa, Takahiro; Sasaki, Saori; Kidoaki, Satoru; Yanagisawa, Miho

2018-04-25

Even though microgels are used in a wide variety of applications, determining their mechanical properties has been elusive because of the difficulties in analysis. In this study, we investigated the surface elasticity of a spherical microgel of gelatin prepared inside a lipid droplet by using micropipet aspiration. We found that gelation inside a microdroplet covered with lipid membranes increased Young's modulus E toward a plateau value E * along with a decrease in gel size. In the case of 5.0 wt % gelatin gelled inside a microsized lipid space, the E * for small microgels with R ≤ 50 μm was 10-fold higher (35-39 kPa) than that for the bulk gel (∼3 kPa). Structural analysis using circular dichroism spectroscopy and a fluorescence indicator for ordered beta sheets demonstrated that the smaller microgels contained more beta sheets in the structure than the bulk gel. Our finding indicates that the confinement size of gelling polymers becomes a factor in the variation of elasticity of protein-based microgels via secondary structure changes.

Increasing Elasticity through Changes in the Secondary Structure of Gelatin by Gelation in a Microsized Lipid Space

PubMed Central

2018-01-01

Even though microgels are used in a wide variety of applications, determining their mechanical properties has been elusive because of the difficulties in analysis. In this study, we investigated the surface elasticity of a spherical microgel of gelatin prepared inside a lipid droplet by using micropipet aspiration. We found that gelation inside a microdroplet covered with lipid membranes increased Young’s modulus E toward a plateau value E* along with a decrease in gel size. In the case of 5.0 wt % gelatin gelled inside a microsized lipid space, the E* for small microgels with R ≤ 50 μm was 10-fold higher (35–39 kPa) than that for the bulk gel (∼3 kPa). Structural analysis using circular dichroism spectroscopy and a fluorescence indicator for ordered beta sheets demonstrated that the smaller microgels contained more beta sheets in the structure than the bulk gel. Our finding indicates that the confinement size of gelling polymers becomes a factor in the variation of elasticity of protein-based microgels via secondary structure changes. PMID:29721530

High-pressure single-crystal synchrotron X-ray diffraction of kainite (KMg(SO4) Cl 3H2O)

NASA Astrophysics Data System (ADS)

Nazzareni, S.; Comodi, P.; Hanfland, M.

2018-03-01

Kainite (KMg(SO4) Cl 3H2O) is a "mixed-salt" sulfate from the group of evaporitic minerals more soluble than Ca-sulfate hydrate and NaCl. The compressibility and structural modifications of monoclinic (sp. gr. C2/m) kainite up to a pressure of 14 GPa were studied by high-pressure single-crystal synchrotron X-ray diffraction. Kainite remains stable over the investigated pressure range and no phase transition was recognised. The bulk modulus is K 0 = 31.6 (1) GPa, with K' fixed to 4, as obtained by fitting the P-volume data with a second-order Birch-Murnaghan EoS (BM2); instead of using a BM3 EoS, we obtained K 0 = 32.2(5) GPa, K' =3.8 (1). The linear moduli calculated for the lattice parameters fitting the data with a BM3 EoS are for a-axis M 0a = 117(4) GPa, Mpa = 11(1), for b-axis M 0b = 113(2) GPa, Mpc = 8.6(5), and c-axis M 0c = 68.2(3) GPa, Mpc = 14(1). Structure refinements showed a strong compression of the K polyhedra and in particular K(1) and K(3) polyhedra have similar polyhedral bulk moduli: K 0K(1) = 20.8(7) GPa, K'=4.8(3); K 0K(2) = 29(1) GPa, K'=8.1(6); K 0K(3) = 26(1) GPa, K'=4.2(4). The most compressible bond distances are K(1)-Cl(2) with a shortening of about 13%, K(1)-Cl(1) with a shortening of about 10%, K(3)-Ow(6) and K(3)-O8(B) both with a shortening of 9%. S-tetrahedra are almost incompressible and Mg-octahedra bulk moduli are K 0Mg(2) = 102(4) GPa, and K 0Mg(4) = 72(1) GPa, K 0Mg(1) = 41(4) GPa K'= 8.9(1.7), and K 0Mg(3) = 65(5) GPa K'= 10(2). The strain tensor analysis indicates that the most compressible direction of the kainite monoclinic structure is oriented 29.7(2)° from the c-axis in the (0 1 0) plane. The shortening of the K(1)-K(2) distance (from 4.219(4) Å at ambient P to 3.521(7) Å at 11.9 GPa) and the different compressibilities of the octahedra/tetrahedra may explain why the stiffer direction of kainite is in the a-c plane approximatively along the direction where K(1)-K(2) and Mg(4)-Mg(3)-Mg(4) polyhedra align. This may explain the anisotropic compressional behaviour of the crystallographic axes, where c is more compressible (by tetrahedral tilting mechanism) than a and b, where cation-cation repulsion and a more rigid configuration make these directions stiffer. Following the structure modification increasing pressure a new sets of hydrogens bonds could form as oxygens and chlorine atoms get at less than 3 Å distance from the Ow.

Dielectric Relaxation Study of Multiferroic BiFe0.95(Ni0.5Ti0.5)0.05O3

NASA Astrophysics Data System (ADS)

Abdelkafi, Z.; Khasskhoussi, G.; Abdelmoula, N.

2018-03-01

The doping of BiFeO3 (BFO) with 5% of Ni and Ti to form the composition BiFe0.95(Ni0.5Ti0.5)0.05O3 (BFNT05) was prepared via a solid state reaction technique. X-ray diffraction (XRD) shows that the prepared ceramic has a pure-phase perovskite structure with rhombohedral symmetry. Thermal evolution of the permittivity reveals a large value of permittivity accompanied by a strong dispersion. This evolution indicates a dielectric anomaly at around 520 K near the Néel temperature ( T N), which supports a strong magneto-dielectric coupling. The dielectric dispersion in BFNT05 was studied by the measurement of the permittivity over a wide frequency range from 20 Hz to 1 MHz at different temperatures 300-700 K. The experimental dielectric data was described by the Cole-Cole relaxation equation modified by introducing the conductivity. Modified impedance and modulus expressions were used successfully as tools to separate the contribution from grains and grain boundaries of BFNT05. The calculated bulk grain conductivity indicated an anomalous behavior near the temperature related to the antiferro-paramagnetic phase transition of the corresponding BFNT05 ceramic. In contrast, this ceramic exhibited a predominant grain boundaries behavior at the studied temperature and frequency range. In this case, they were the elements responsible for dielectric dispersion, and also they played an important role in the improvement of the dielectric behavior of this ceramic. The ac conductivity study confirmed the modified impedance and modulus expressions.

Dielectric Relaxation Study of Multiferroic BiFe0.95(Ni0.5Ti0.5)0.05O3

NASA Astrophysics Data System (ADS)

Abdelkafi, Z.; Khasskhoussi, G.; Abdelmoula, N.

2017-12-01

The doping of BiFeO3 (BFO) with 5% of Ni and Ti to form the composition BiFe0.95(Ni0.5Ti0.5)0.05O3 (BFNT05) was prepared via a solid state reaction technique. X-ray diffraction (XRD) shows that the prepared ceramic has a pure-phase perovskite structure with rhombohedral symmetry. Thermal evolution of the permittivity reveals a large value of permittivity accompanied by a strong dispersion. This evolution indicates a dielectric anomaly at around 520 K near the Néel temperature (T N), which supports a strong magneto-dielectric coupling. The dielectric dispersion in BFNT05 was studied by the measurement of the permittivity over a wide frequency range from 20 Hz to 1 MHz at different temperatures 300-700 K. The experimental dielectric data was described by the Cole-Cole relaxation equation modified by introducing the conductivity. Modified impedance and modulus expressions were used successfully as tools to separate the contribution from grains and grain boundaries of BFNT05. The calculated bulk grain conductivity indicated an anomalous behavior near the temperature related to the antiferro-paramagnetic phase transition of the corresponding BFNT05 ceramic. In contrast, this ceramic exhibited a predominant grain boundaries behavior at the studied temperature and frequency range. In this case, they were the elements responsible for dielectric dispersion, and also they played an important role in the improvement of the dielectric behavior of this ceramic. The ac conductivity study confirmed the modified impedance and modulus expressions.

Ultrasonic velocimetry studies on different salts of chitosan: Effect of ion size.

PubMed

Mohan, C Raja; Sathya, R; Nithiananthi, P; Jayakumar, K

2017-11-01

In the present investigation, the effect of ion size on the thermodynamical properties such as ultrasonic velocity (U), adiabatic compressibility (β), acoustic impedance (Z), adiabatic bulk modulus (K s ), relaxation strength (r s ) have been obtained for the different salts of chitosan viz., formate (3.5Å), acetate (4.5Å), Succinate (5Å) and Adipate (6Å). To find the effect of ion size, the effect due to water has been removed by calculating the change in ultrasonic velocity (dU), change in adiabatic compressibility (dβ), in acoustic impedance (dZ), in adiabatic bulk modulus (dK s ), and in relaxation strength (dr s ). Space filling factor and polarizability has been obtained from the refractive index data through Lorentz-Lorentz relation. FTIR studies confirm the formation of different quaternary salts of chitosan and their size (mass) effects which has been verified with Hooke's law. All the said properties vary both with ion size and concentration of different salts of chitosan. This investigation may throw some light on better usage of chitosan in biomedical applications. The detailed results are presented and discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Ab-initio study of electronic structure and elastic properties of ZrC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mund, H. S., E-mail: hmoond@gmail.com; Ahuja, B. L.

2016-05-23

The electronic and elastic properties of ZrC have been investigated using the linear combination of atomic orbitals method within the framework of density functional theory. Different exchange-correlation functionals are taken into account within generalized gradient approximation. We have computed energy bands, density of states, elastic constants, bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, lattice parameters and pressure derivative of the bulk modulus by calculating ground state energy of the rock salt structure type ZrC.

Passive stiffness of monoarticular lower leg muscles is influenced by knee joint angle.

PubMed

Ateş, Filiz; Andrade, Ricardo J; Freitas, Sandro R; Hug, François; Lacourpaille, Lilian; Gross, Raphael; Yucesoy, Can A; Nordez, Antoine

2018-03-01

While several studies demonstrated the occurrence of intermuscular mechanical interactions, the physiological significance of these interactions remains a matter of debate. The purpose of this study was to quantify the localized changes in the shear modulus of the gastrocnemius lateralis (GL), monoarticular dorsi- and plantar-flexor muscles induced by a change in knee angle. Participants underwent slow passive ankle rotations at the following two knee positions: knee flexed at 90° and knee fully extended. Ultrasound shear wave elastography was used to assess the muscle shear modulus of the GL, soleus [both proximally (SOL-proximal) and distally (SOL distal)], peroneus longus (PERL), and tibialis anterior (TA). This was performed during two experimental sessions (experiment I: n = 11; experiment II: n = 10). The shear modulus of each muscle was compared between the two knee positions. The shear modulus was significantly higher when the knee was fully extended than when the knee was flexed (P < 0.001) for the GL (averaged increase on the whole range of motion: + 5.8 ± 1.3 kPa), SOL distal (+ 4.5 ± 1.5 kPa), PERL (+ 1.1 ± 0.7 kPa), and TA (+ 1.6 ± 1.0 kPa). In contrast, a lower SOL-proximal shear modulus (P < 0.001, - 5.9 ± 1.0 kPa) was observed. As the muscle shear modulus is linearly related to passive muscle force, these results provide evidence of a non-negligible intermuscular mechanical interaction between the human lower leg muscles during passive ankle rotations. The role of these interactions in the production of coordinated movements requires further investigation.

Experimental and first-principles studies on the elastic properties of α-hafnium metal under pressure

DOE PAGES

Qi, Xintong; Wang, Xuebing; Chen, Ting; ...

2016-03-30

Compressional and shear wave velocities of the α phase of hafnium have been measured up to 10.4 GPa at room temperature using ultrasonic interferometry in a multi-anvil apparatus. A finite strain equation of state analysis yielded K s0 = 110.4 (5) GPa, G 0 = 54.7(5) GPa,K s0' = 3.7 and G 0' = 0.6 for the elastic bulk and shear moduli and their pressure derivatives at ambient conditions. Complementary to the experimental data, the single crystal elastic constants, elastic anisotropy and the unit cell axial ratio c/a of α-hafnium at high pressures were investigated by Density Functional Theory (DFT)more » based first principles calculations. A c/a value of 1.605 is predicted for α-Hf at 40 GPa, which is in excellent agreement with previous experimental results. The low-pressure derivative of the shear modulus observed in our experimental data up to 10 GPa was found to originate from the elastic constant C44 which exhibits negligible pressure dependence within the current experimental pressure range. At higher pressures (>10 GPa), C 44 was predicted to soften and the shear wave velocity ν S trended to decrease with pressure, which can be interpreted as a precursor to the α-ω transition similar to that observed in other group IV elements (titanium and zirconium). Here, the acoustic velocities, bulk and shear moduli, and the acoustic Debye temperature (θ D = 240.1 K) determined from the current experiments were all compared well with those predicted by our theoretical DFT calculations.« less

Effect of bulk modulus on deformation of the brain under rotational accelerations

NASA Astrophysics Data System (ADS)

Ganpule, S.; Daphalapurkar, N. P.; Cetingul, M. P.; Ramesh, K. T.

2018-01-01

Traumatic brain injury such as that developed as a consequence of blast is a complex injury with a broad range of symptoms and disabilities. Computational models of brain biomechanics hold promise for illuminating the mechanics of traumatic brain injury and for developing preventive devices. However, reliable material parameters are needed for models to be predictive. Unfortunately, the properties of human brain tissue are difficult to measure, and the bulk modulus of brain tissue in particular is not well characterized. Thus, a wide range of bulk modulus values are used in computational models of brain biomechanics, spanning up to three orders of magnitude in the differences between values. However, the sensitivity of these variations on computational predictions is not known. In this work, we study the sensitivity of a 3D computational human head model to various bulk modulus values. A subject-specific human head model was constructed from T1-weighted MRI images at 2-mm3 voxel resolution. Diffusion tensor imaging provided data on spatial distribution and orientation of axonal fiber bundles for modeling white matter anisotropy. Non-injurious, full-field brain deformations in a human volunteer were used to assess the simulated predictions. The comparison suggests that a bulk modulus value on the order of GPa gives the best agreement with experimentally measured in vivo deformations in the human brain. Further, simulations of injurious loading suggest that bulk modulus values on the order of GPa provide the closest match with the clinical findings in terms of predicated injured regions and extent of injury.

FP-LAPW study of structural, electronic, elastic, mechanical and thermal properties of AlFe intermetallic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jain, Ekta, E-mail: jainekta05@gmail.com; Pagare, Gitanjali, E-mail: gita-pagare@yahoo.co.in; Sanyal, S. P., E-mail: sps.physicsbu@gmail.com

2016-05-06

The structural, electronic, elastic, mechanical and thermal properties of AlFe intermetallic compound in B{sub 2}-type (CsCl) structure have been investigated using first-principles calculations. The exchange-correlation term was treated within generalized gradient approximation. Ground state properties i.e. lattice constants (a{sub 0}), bulk modulus (B) and first-order pressure derivative of bulk modulus (B’) are presented. The density of states are derived which show the metallic character of present compound. Our results for C{sub 11}, C{sub 12} and C{sub 44} agree well with previous theoretical data. Using Pugh’s criteria (B/G{sub H} < 1.75), brittle character of AlFe is satisfied. In addition shear modulusmore » (G{sub H}), Young’s modulus (E), sound wave velocities and Debye temperature (θ{sub D}) have also been estimated.« less

From chemistry to mechanics: bulk modulus evolution of Li-Si and Li-Sn alloys via the metallic electronegativity scale.

PubMed

Li, Keyan; Xie, Hui; Liu, Jun; Ma, Zengsheng; Zhou, Yichun; Xue, Dongfeng

2013-10-28

Toward engineering high performance anode alloys for Li-ion batteries, we proposed a useful method to quantitatively estimate the bulk modulus of binary alloys in terms of metallic electronegativity (EN), alloy composition and formula volume. On the basis of our proposed potential viewpoint, EN as a fundamental chemistry concept can be extended to be an important physical parameter to characterize the mechanical performance of Li-Si and Li-Sn alloys as anode materials for Li-ion batteries. The bulk modulus of binary alloys is linearly proportional to the combination of average metallic EN and atomic density of alloys. We calculated the bulk moduli of Li-Si and Li-Sn alloys with different Li concentrations, which can agree well with the reported data. The bulk modulus of Li-Si and Li-Sn alloys decreases with increasing Li concentration, leading to the elastic softening of the alloys, which is essentially caused by the decreased strength of constituent chemical bonds in alloys from the viewpoint of EN. This work provides a deep understanding of mechanical failure of Si and Sn anodes for Li-ion batteries, and permits the prediction of the composition dependent bulk modulus of various lithiated alloys on the basis of chemical formula, metallic EN and cell volume (or alloy density), with no structural details required.

Control of thermal expansion in a low-density framework modification of silicon

NASA Astrophysics Data System (ADS)

Beekman, Matt; Kaduk, James A.; Wong-Ng, Winnie; Troesch, Michael; Lee, Glenn S.; Nolas, George S.

2018-04-01

The low-density clathrate-II modification of silicon, Si136, contains two distinct cage-like voids large enough to accommodate various types of guest atoms which influence both the host structure and its properties. Although the linear coefficient of thermal expansion of Si136 (293 K < T < 423 K) is only about 20% larger than that of the ground state α-Si (diamond structure), the coefficient of thermal expansion monotonically increases by more than 150% upon filling the framework cages with Na atoms in NaxSi136 (0 < x < 24), ranging from α = 2.6 × 10-6 K-1 (x = 0) to 6.8 × 10-6 K-1 (extrapolated to x = 24) by only varying the Na content, x. Taken together with the available heat capacity and bulk modulus data, the dramatic increase in thermal expansion can be attributed to an increase in the mode-averaged Grüneisen parameter by a factor of nearly 3 from x = 0 to x = 24. These results highlight a potential mechanism for tuning thermal expansion, whereby guest atoms are incorporated into the voids of rigid, covalently bonded inorganic frameworks to influence the lattice dynamics.

Compression-sensitive magnetic resonance elastography

NASA Astrophysics Data System (ADS)

Hirsch, Sebastian; Beyer, Frauke; Guo, Jing; Papazoglou, Sebastian; Tzschaetzsch, Heiko; Braun, Juergen; Sack, Ingolf

2013-08-01

Magnetic resonance elastography (MRE) quantifies the shear modulus of biological tissue to detect disease. Complementary to the shear elastic properties of tissue, the compression modulus may be a clinically useful biomarker because it is sensitive to tissue pressure and poromechanical interactions. In this work, we analyze the capability of MRE to measure volumetric strain and the dynamic bulk modulus (P-wave modulus) at a harmonic drive frequency commonly used in shear-wave-based MRE. Gel phantoms with various densities were created by introducing CO2-filled cavities to establish a compressible effective medium. The dependence of the effective medium's bulk modulus on phantom density was investigated via static compression tests, which confirmed theoretical predictions. The P-wave modulus of three compressible phantoms was calculated from volumetric strain measured by 3D wave-field MRE at 50 Hz drive frequency. The results demonstrate the MRE-derived volumetric strain and P-wave modulus to be sensitive to the compression properties of effective media. Since the reconstruction of the P-wave modulus requires third-order derivatives, noise remains critical, and P-wave moduli are systematically underestimated. Focusing on relative changes in the effective bulk modulus of tissue, compression-sensitive MRE may be useful for the noninvasive detection of diseases involving pathological pressure alterations such as hepatic hypertension or hydrocephalus.

Effect of AlF3 on the Density and Elastic Properties of Zinc Tellurite Glass Systems

PubMed Central

Sidek, Haji Abdul Aziz; Rosmawati, Shaharuddin; Halimah, Mohamed Kamari; Matori, Khamirul Amin; Talib, Zainal Abidin

2012-01-01

This paper presents the results of the physical and elastic properties of the ternary zinc oxyfluoro tellurite glass system. Systematic series of glasses (AlF3)x(ZnO)y(TeO2)z with x = 0–19, y = 0–20 and z = 80, 85, 90 mol% were synthesized by the conventional rapid melt quenching technique. The composition dependence of the physical, mainly density and molar volume, and elastic properties is discussed in term of the AlF3 modifiers addition that are expected to produce quite substantial changes in their physical properties. The absence of any crystalline peaks in the X-ray diffraction (XRD) patterns of the present glass samples indicates the amorphous nature. The addition of AlF3 lowered the values of the densities in ternary oxyfluorotellurite glass systems. The longitudinal and transverse ultrasonic waves propagated in each glass sample were measured using a MBS8020 ultrasonic data acquisition system. All the velocity data were taken at 5 MHz frequency and room temperature. The longitudinal modulus (L), shear modulus (G), Young’s modulus (E), bulk modulus (K) and Poisson’s ratio (σ) are obtained from both velocities data and their respective density. Experimental data shows the density and elastic moduli of each AlF3-ZnO-TeO2 series are found strongly depend upon the glass composition. The addition of AlF3 modifiers into the zinc tellurite causes substantial changes in their density, molar volume as well as their elastic properties.

Influence of isotopic disorder on solid state amorphization and polyamorphism in solid H2O -D2O solutions

NASA Astrophysics Data System (ADS)

Gromnitskaya, E. L.; Danilov, I. V.; Lyapin, A. G.; Brazhkin, V. V.

2015-10-01

We present a low-temperature and high-pressure ultrasonic study of elastic properties of isotopic H2O-D2O solid solutions, comparing their properties with those of the isotopically pure H2O and D2O ices. Measurements were carried out for solid state amorphization (SSA) from 1h to high-density amorphous (HDA) ice upon compression up to 1.8 GPa at 77 K and for the temperature-induced (77 -190 K ) u-HDA (unrelaxed HDA) → e-HDA (expanded HDA) → low-density amorphous (LDA )→1 c cascade of ice transformations near room pressure. There are many similarities in the elasticity behaviour of H2O ,D2O , and H2O-D2O solid solutions, including the softening of the shear elastic modulus as a precursor of SSA and the HDA →LDA transition. We have found significant isotopic effects during H/D substitution, including elastic softening of H2O -D2O solid solutions with respect to the isotopically pure ices in the case of the bulk moduli of ices 1c and 1h and for both bulk and shear elastic moduli of HDA ice at high pressures (>1 GPa ) . This softening is related to the configurational isotopic disorder in the solid solutions. At low pressures, the isotope concentration dependence of the elastic moduli of u-HDA ice changes remarkably and becomes monotonic with pronounced change of the bulk modulus (≈20 %) .

Electronegativity calculation of bulk modulus and band gap of ternary ZnO-based alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Keyan; Kang, Congying; Xue, Dongfeng, E-mail: dongfeng@ciac.jl.cn

2012-10-15

In this work, the bulk moduli and band gaps of M{sub x}Zn{sub 1−x}O (M = Be, Mg, Ca, Cd) alloys in the whole composition range were quantitatively calculated by using the electronegativity-related models for bulk modulus and band gap, respectively. We found that the change trends of bulk modulus and band gap with an increase of M concentration x are same for Be{sub x}Zn{sub 1−x}O and Cd{sub x}Zn{sub 1−x}O, while the change trends are reverse for Mg{sub x}Zn{sub 1−x}O and Ca{sub x}Zn{sub 1−x}O. It was revealed that the bulk modulus is related to the valence electron density of atoms whereasmore » the band gap is strongly influenced by the detailed chemical bonding behaviors of constituent atoms. The current work provides us a useful guide to compositionally design advanced alloy materials with both good mechanical and optoelectronic properties.« less

Sound velocity of liquid Fe-Ni-S at high pressure

NASA Astrophysics Data System (ADS)

Kawaguchi, Saori I.; Nakajima, Yoichi; Hirose, Kei; Komabayashi, Tetsuya; Ozawa, Haruka; Tateno, Shigehiko; Kuwayama, Yasuhiro; Tsutsui, Satoshi; Baron, Alfred Q. R.

2017-05-01

The sound velocity of liquid Fe47Ni28S25 and Fe63Ni12S25 was measured up to 52 GPa/2480 K in externally resistance-heated and laser-heated diamond-anvil cells using high-resolution inelastic X-ray scattering. From these experimental data, we obtained the elastic parameters of liquid Fe47Ni28S25, KS0 = 96.1 ± 2.7 GPa and KS0' = 4.00 ± 0.13, where KS0 and KS0' are the adiabatic bulk modulus and its pressure derivative at 1 bar, when the density is fixed at ρ0 = 5.62 ± 0.09 g/cm3 for 1 bar and 2000 K. With these parameters, the sound velocity and density of liquid Fe47Ni28S25 were calculated to be 8.41 ± 0.17 km/s and 8.93 ± 0.19 to 9.10 ± 0.18 g/cm3, respectively, at the core mantle boundary conditions of 135 GPa and 3600-4300 K. These values are 9.4% higher and 17-18% lower than those of pure Fe, respectively. Extrapolation of measurements and comparison with seismological models suggest the presence of 5.8-7.5 wt % sulfur in the Earth's outer core if it is the only light element.

Stabilisation of Ce-Cu-Fe amorphous alloys by addition of Al

NASA Astrophysics Data System (ADS)

Kelhar, Luka; Ferčič, Jana; Boulet, Pascal; Maček-Kržmanc, Marjeta; Šturm, Sašo; Lamut, Martin; Markoli, Boštjan; Kobe, Spomenka; Dubois, Jean-Marie

2016-10-01

The present work describes the formation of amorphous alloys in the (Al1-xCex)62Cu25Fe13 quaternary system (0 ≤ x ≤ 1). When the amount of Ce falls in the range 0.67 ≤ x ≤ 0.83, the alloys obtained exhibit a completely amorphous structure confirmed by powder X-ray diffraction. Otherwise, at compositions x = 0.5, 0.58, 0.92 and 1, a primary crystalline phase forms together with an amorphous matrix. The crystallisation temperature (Tx) decreases with increasing Ce content, varying from 593 K for x = 0.5-383 K for x = 1. Composition x = 0.75 is considered as the best glass former, exhibiting a large supercooled liquid region of 40 K width that precedes crystallisation. In order to form bulk amorphous alloys, ribbons with this later composition were consolidated into few millimetre thick discs using pulsed electric current sintering at different temperatures, yet preserving the amorphous structure. Meanwhile, increasing temperature above 483 K triggers crystallisation of a primary phase isostructural to AlCe3. Further increase in the temperature up to 573 K yields a higher fraction of the crystalline phase. Testing mechanical properties, using nanoindentation, revealed that both elastic modulus (E) and hardness (H) depend on the Al content, ranging from E = 85.6 ± 3.7 GPa and H = 6.2 ± 0.7 GPa for x = 0.5 down to E = 39.8 ± 1.0 GPa and H = 3.1 ± 0.2 GPa for x = 0.92.

AC conductivity and dielectric behavior of bulk Furfurylidenemalononitrile

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Ali, H. A. M.

2012-06-01

AC conductivity and dielectric behavior for bulk Furfurylidenemalononitrile have been studied over a temperature range (293-333 K) and frequency range (50-5×106 Hz). The frequency dependence of ac conductivity, σac, has been investigated by the universal power law, σac(ω)=Aωs. The variation of the frequency exponent (s) with temperature was analyzed in terms of different conduction mechanisms, and it was found that the correlated barrier hopping (CBH) model is the predominant conduction mechanism. The temperature dependence of σac(ω) showed a linear increase with the increase in temperature at different frequencies. The ac activation energy was determined at different frequencies. Dielectric data were analyzed using complex permittivity and complex electric modulus for bulk Furfurylidenemalononitrile at various temperatures.

Pressure-induced transition in the grain boundary of diamond

NASA Astrophysics Data System (ADS)

Chen, J.; Tang, L.; Ma, C.; Fan, D.; Yang, B.; Chu, Q.; Yang, W.

2017-12-01

Equation of state of diamond powder with different average grain sizes was investigated using in situ synchrotron x-ray diffraction and a diamond anvil cell (DAC). Comparison of compression curves was made for two samples with average grain size of 50nm and 100nm. The two specimens were pre-pressed into pellets and loaded in the sample pressure chamber of the DAC separately to minimized differences of possible systematic errors for the two samples. Neon gas was used as pressure medium and ruby spheres as pressure calibrant. Experiments were conducted at room temperature and high pressures up to 50 GPa. Fitting the compression data in the full pressure range into the third order Birch-Murnaghan equation of state yields bulk modulus (K) and its pressure derivative (K') of 392 GPa and 5.3 for 50nm sample and 398GPa and 4.5 for 100nm sample respectively. Using a simplified core-shell grain model, this result indicates that the grain boundary has an effective bulk modulus of 54 GPa. This value is similar to that observed for carbon nanotube[1] validating the recent theoretical diamond surface modeling[2]. Differential analysis of the compression cures demonstrates clear relative compressibility change at the pressure about 20 GPa. When fit the compression data below and above this pressure separately, the effect of grain size on bulk modulus reverses in the pressure range above 20 GPa. This observation indicates a possible transition of grain boundary structure, likely from sp2 hybridization at the surface[2] towards sp3like orbital structure which behaves alike the inner crystal. [1] Jie Tang, Lu-Chang Qin, Taizo Sasaki, Masako Yudasaka, Akiyuki Matsushita, and Sumio Iijima, Compressibility and Polygonization of Single-Walled Carbon Nanotubes under Hydrostatic Pressure, Physical Review Letters, 85(9), 1187-1198, 2000. [2] Shaohua Lu, Yanchao Wang, Hanyu Liu, Mao-sheng Miao, and Yanming Ma, Self-assembled ultrathin nanotubes on diamond (100) surface, Nature Communications, DOI: 10.1038/ncomms4666, 2014

Crystal structure of the Chevrel phase Sn Mo6 S8 at high pressure

NASA Astrophysics Data System (ADS)

Ehm, L.; Dera, P.; Knorr, K.; Winkler, B.; Krimmel, A.; Bouvier, P.

2005-07-01

The high-pressure behavior of the Chevrel phase SnMo6S8 was investigated by angular dispersive synchrotron powder diffraction. The experiments were accompanied by first principles calculations at the density functional theory level. The fit of a Birch-Murnaghan equation-of-state gave the volume at zero pressure V0=277(1)Å3 , the bulk modulus at zero pressure B0=84(3)GPa , and the pressure derivative of the bulk modulus B'=3.0(4) for the experimental data and V0=281.6(3)Å3 , B0=76(1)GPa , and B'=4.7(1) for the calculated data. The analysis of the bond distances and the bond population reveals the formation of new bonds and changes of the bond characteristics in the structure under pressure. The compression mechanism is analysed by means of the distortion of the Mo6S8 cluster and the rotation of the cluster with respect to the unit cell edges.

Characterization of ultraviolet light cured polydimethylsiloxane films for low-voltage, dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

Töpper, Tino; Wohlfender, Fabian; Weiss, Florian; Osmani, Bekim; Müller, Bert

2016-04-01

The reduction the operation voltage has been the key challenge to realize of dielectric elastomer actuators (DEA) for many years - especially for the application fields of robotics, lens systems, haptics and future medical implants. Contrary to the approach of manipulating the dielectric properties of the electrically activated polymer (EAP), we intend to realize low-voltage operation by reducing the polymer thickness to the range of a few hundred nanometers. A study recently published presents molecular beam deposition to reliably grow nanometer-thick polydimethylsiloxane (PDMS) films. The curing of PDMS is realized using ultraviolet (UV) radiation with wavelengths from 180 to 400 nm radicalizing the functional side and end groups. The understanding of the mechanical properties of sub-micrometer-thin PDMS films is crucial to optimize DEAs actuation efficiency. The elastic modulus of UV-cured spin-coated films is measured by nano-indentation using an atomic force microscope (AFM) according to the Hertzian contact mechanics model. These investigations show a reduced elastic modulus with increased indentation depth. A model with a skin-like SiO2 surface with corresponding elastic modulus of (2.29 +/- 0.31) MPa and a bulk modulus of cross-linked PDMS with corresponding elastic modulus of (87 +/- 7) kPa is proposed. The surface morphology is observed with AFM and 3D laser microscopy. Wrinkled surface microstructures on UV-cured PDMS films occur for film thicknesses above (510 +/- 30) nm with an UV-irradiation density of 7.2 10-4 J cm-2 nm-1 at a wavelength of 190 nm.

Uncloaking the thermodynamics of the studtite to metastudtite shear-induced transformation

DOE PAGES

Weck, Philippe F.; Kim, Eunja

2016-07-11

The interplay between thermodynamics and mechanical properties in the transformation of studtite, (UO 2)(O 2)(H 2O) 2·2H 2O, into metastudtite, (UO 2)(O 2)(H 2O) 2, two important corrosion phases observed on the surface of uranium dioxide exposed to water, is revealed using density functional perturbation theory. Phonon calculations within the quasi-harmonic approximation predict that the standard entropy change for the (UO 2)(O 2)(H 2O) 2·2H 2O → (UO 2)(O 2)(H 2O) 2 + 2H 2O reaction is ΔS 0 = +80 J·mol –1·K –1 for the production of water in the liquid state and +389 J·mol–1·K–1 for water vapor. Similarmore » to bulk H 2O(l), the bulk modulus of (UO 2)(O 2)(H 2O) 2·2H 2O increases with temperature, contrasting with (UO 2)(O 2)(H 2O) 2 which features the typical Anderson–Gruneisen temperature dependence of oxide solids. Upon removal of interstitial H 2O in studtite, the most important changes in the shear modulus, the parameter limiting the mechanical stability, arise in the planes normal to chain propagation directions. Lastly, the present findings have important implications for the dehydration of other hygroscopic materials.« less

Uncloaking the thermodynamics of the studtite to metastudtite shear-induced transformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weck, Philippe F.; Kim, Eunja

The interplay between thermodynamics and mechanical properties in the transformation of studtite, (UO 2)(O 2)(H 2O) 2·2H 2O, into metastudtite, (UO 2)(O 2)(H 2O) 2, two important corrosion phases observed on the surface of uranium dioxide exposed to water, is revealed using density functional perturbation theory. Phonon calculations within the quasi-harmonic approximation predict that the standard entropy change for the (UO 2)(O 2)(H 2O) 2·2H 2O → (UO 2)(O 2)(H 2O) 2 + 2H 2O reaction is ΔS 0 = +80 J·mol –1·K –1 for the production of water in the liquid state and +389 J·mol–1·K–1 for water vapor. Similarmore » to bulk H 2O(l), the bulk modulus of (UO 2)(O 2)(H 2O) 2·2H 2O increases with temperature, contrasting with (UO 2)(O 2)(H 2O) 2 which features the typical Anderson–Gruneisen temperature dependence of oxide solids. Upon removal of interstitial H 2O in studtite, the most important changes in the shear modulus, the parameter limiting the mechanical stability, arise in the planes normal to chain propagation directions. Lastly, the present findings have important implications for the dehydration of other hygroscopic materials.« less

Elastic modulus and internal friction of SOFC electrolytes at high temperatures under controlled atmospheres

NASA Astrophysics Data System (ADS)

Kushi, Takuto; Sato, Kazuhisa; Unemoto, Atsushi; Hashimoto, Shinichi; Amezawa, Koji; Kawada, Tatsuya

2011-10-01

Mechanical properties such as Young's modulus, shear modulus, Poisson's ratio and internal friction of conventional electrolyte materials for solid oxide fuel cells, Zr0.85Y0.15 O1.93 (YSZ), Zr0.82Sc0.18O1.91 (ScSZ), Zr0.81Sc0.18Ce0.01O2-δ (ScCeSZ), Ce0.9Gd0.1O2-δ (GDC), La0.8Sr0.2Ga0.8Mg0.15Co0.05O3-δ (LSGMC), La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM), were evaluated by a resonance method at temperatures from room temperature to 1273 K in various oxygen partial pressures. The Young's modulus of GDC gradually decreased with increasing temperature in oxidizing conditions. The Young's moduli of the series of zirconia and lanthanum gallate based materials drastically decreased in an intermediate temperature range and increased slightly with increasing temperature at higher temperatures. The Young's modulus of GDC considerably decreased above 823 K in reducing atmospheres in response to the change of oxygen nonstoichiometry. However, temperature dependences of the Young's moduli of ScCeSZ and LSGMC in reducing atmospheres did not show any significant differences with those in oxidizing atmospheres.

First measurement of the K-n →Λπ- non-resonant transition amplitude below threshold

NASA Astrophysics Data System (ADS)

Piscicchia, K.; Wycech, S.; Fabbietti, L.; Cargnelli, M.; Curceanu, C.; Del Grande, R.; Marton, J.; Moskal, P.; Scordo, A.; Silarski, M.; Sirghi, D.; Skurzok, M.; Tucakovic, I.; Vázquez Doce, O.; Zmeskal, J.; Branchini, P.; Czerwinski, E.; De Leo, V.; De Lucia, E.; Di Cicco, A.; Fermani, P.; Fiore, S.; Krzemien, W.; Mandaglio, G.; Martini, M.; Perez del Rio, E.; Selce, A.

2018-07-01

We present the analysis of K- absorption processes on 4He leading to Λπ- final states, measured with the KLOE spectrometer at the DAΦNE e+e- collider and extract, for the first time, the modulus of the non-resonant K-n → Λπ- direct production amplitude about 33 MeV below the K ‾N threshold. This analysis also allows to disentangle the K- nuclear absorption at-rest from the in-flight capture, for K- momenta of about 120 MeV. The data are interpreted with the help of a phenomenological model, and the modulus of the non-resonant K-n → Λπ- amplitude for K- absorption at-rest is found to be |A K- n → Λπ- | = (0.334 ± 0.018 stat-0.058+0.034 syst)fm.

Low temperature and high pressure thermoelastic and crystallographic properties of SrZrO3 perovskite in the Pbnm phase

NASA Astrophysics Data System (ADS)

Knight, Kevin S.; Bull, Craig L.

2016-12-01

The thermoelastic and structural properties of SrZrO3 perovskite in the Pnma (Pbnm) phase have been studied using neutron powder diffraction at 82 temperatures between 11 K and 406 K at ambient pressure, and at sixteen pressures between 0.07 and 6.7 GPa at ambient temperature. The bulk modulus, derived by fitting the equation of state to a second order Birch-Murnaghan equation-of-state, 157(5) GPa, is in excellent agreement with that deduced in a recent resonant ultrasound investigation. Experimental axial compressional moduli are in agreement with those calculated from the elastic stiffness coefficients derived by ab-initio calculation, although the experimental bulk modulus is significantly softer than that calculated. Following low temperature saturation for temperatures less than 40 K, the unit cell monotonically increases with a predicted high temperature limit in the volume expansivity of ∼2.65 × 10-5 K-1. Axial linear thermal expansion coefficients are found to be in the order αb < αc < αa for all temperatures greater than 20 K with the b axis indicating a weak, low temperature negative expansion coefficient at low temperatures. The thermoelastic properties of SrZrO3 can be approximated by a two-term Debye model for the phonon density of states with Debye temperatures of 238(4) K and 713(6) K derived in a self-consistent manner by simultaneously fitting the isochoric heat capacity and the unit cell volume. Atomic displacement parameters have been fitted to a modified Debye model in which the zero-point term is an additional refinable variable and shows the cations and anions have well separated Debye temperatures, mirroring the need for two Debye-like distributions in the vibrational density of states. The temperature dependence of the crystal structure is presented in terms of the amplitudes of the seven symmetry-adapted basis vectors of the aristotype phase that are consistent with space group Pbnm, thus permitting a direct measure of the order parameter evolution in SrZrO3. The temperature variation of the in-phase tilt, which is lost at the phase transition at 973 K, is consistent with tricritical behaviour, in agreement with published results based on high temperature crystallographic data.

High-Temperature and High-Pressure Study of Electronic and Thermal Properties of PbTaO3 and SnAlO3 Metal Perovskites by Density Functional Theory Calculations

NASA Astrophysics Data System (ADS)

Khandy, Shakeel Ahmad; Islam, Ishtihadah; Ganai, Zahid Saleem; Gupta, Dinesh C.; Parrey, Khursheed Ahmad

2018-01-01

First principles calculations on the thermodynamic properties of PbTaO3 and SnAlO3 in a temperature range from 0 K to 800 K and pressure range from 0 GPa to 30 GPa have been carried out within the framework of density functional theory (DFT). The band structures of these oxides at different pressures display an increase in metallic character with a concomitant decrease in lattice constants, while the bulk modulus increases with increasing pressure. The thermal concert of these materials has been analyzed in terms of the temperature and pressure variation in Debye temperature, thermal expansion, entropy, and the Grüneisen parameter. Debye temperatures have been calculated from the elastic parameters as well as the quasi-harmonic Debye model, which are 339.07 GPa for PbTaO3 and 714.36 GPa for SnAlO3.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winterrose, M.; Lucas, M; Yue, A

Synchrotron x-ray diffraction (XRD) measurements, nuclear forward scattering (NFS) measurements, and density functional theory (DFT) calculations were performed on L12-ordered Pd3Fe. Measurements were performed at 300 K at pressures up to 33 GPa, and at 7 GPa at temperatures up to 650 K. The NFS revealed a collapse of the 57Fe magnetic moment between 8.9 and 12.3 GPa at 300 K, coinciding with a transition in bulk modulus found by XRD. Heating the sample under a pressure of 7 GPa showed negligible thermal expansion from 300 to 523 K, demonstrating Invar behavior. Zero-temperature DFT calculations identified a ferromagnetic ground statemore » and showed several antiferromagnetic states had comparable energies at pressures above 20 GPa.« less

Depth-Dependent Transverse Shear Properties of the Human Corneal Stroma

PubMed Central

Petsche, Steven J.; Chernyak, Dimitri; Martiz, Jaime; Levenston, Marc E.

2012-01-01

Purpose. To measure the transverse shear modulus of the human corneal stroma and its profile through the depth by mechanical testing, and to assess the validity of the hypothesis that the shear modulus will be greater in the anterior third due to increased interweaving of lamellae. Methods. Torsional rheometry was used to measure the transverse shear properties of 6 mm diameter buttons of matched human cadaver cornea pairs. One cornea from each pair was cut into thirds through the thickness with a femtosecond laser and each stromal third was tested individually. The remaining intact corneas were tested to measure full stroma shear modulus. The shear modulus from a 1% shear strain oscillatory test was measured at various levels of axial compression for all samples. Results. After controlling for axial compression, the transverse shear moduli of isolated anterior layers were significantly higher than central and posterior layers. Mean modulus values at 0% axial strain were 7.71 ± 6.34 kPa in the anterior, 1.99 ± 0.45 kPa in the center, 1.31 ± 1.01 kPa in the posterior, and 9.48 ± 2.92 kPa for full thickness samples. A mean equilibrium compressive modulus of 38.7 ± 8.6 kPa at 0% axial strain was calculated from axial compression measured during the shear tests. Conclusions. Transverse shear moduli are two to three orders of magnitude lower than tensile moduli reported in the literature. The profile of shear moduli through the depth displayed a significant increase from posterior to anterior. This gradient supports the hypothesis and corresponds to the gradient of interwoven lamellae seen in imaging of stromal cross-sections. PMID:22205608

Modified Silicone-Rubber Tooling For Molding Composite Parts

NASA Technical Reports Server (NTRS)

Baucom, Robert M.; Snoha, John J.; Weiser, Erik S.

1995-01-01

Reduced-thermal-expansion, reduced-bulk-modulus silicone rubber for use in mold tooling made by incorporating silica powder into silicone rubber. Pressure exerted by thermal expansion reduced even further by allowing air bubbles to remain in silicone rubber instead of deaerating it. Bubbles reduce bulk modulus of material.

Three-body interactions and the elastic constants of hcp solid 4He

NASA Astrophysics Data System (ADS)

Barnes, Ashleigh L.; Hinde, Robert J.

2017-09-01

The effect of three-body interactions on the elastic properties of hexagonal close packed solid 4He is investigated using variational path integral (VPI) Monte Carlo simulations. The solid's nonzero elastic constants are calculated, at T = 0 K and for a range of molar volumes from 7.88 cm3/mol to 20.78 cm3/mol, from the bulk modulus and the three pure shear constants C0, C66, and C44. Three-body interactions are accounted for using our recently reported perturbative treatment based on the nonadditive three-body potential of Cencek et al. Previous studies have attempted to account for the effect of three-body interactions on the elastic properties of solid 4He; however, these calculations have treated zero point motions using either the Einstein or Debye approximations, which are insufficient in the molar volume range where solid 4He is characterized as a quantum solid. Our VPI calculations allow for a more accurate treatment of the zero point motions which include atomic correlation. From these calculations, we find that agreement with the experimental bulk modulus is significantly improved when three-body interactions are considered. In addition, three-body interactions result in non-negligible differences in the calculated pure shear constants and nonzero elastic constants, particularly at higher densities, where differences of up to 26.5% are observed when three-body interactions are included. We compare to the available experimental data and find that our results are generally in as good or better agreement with experiment as previous theoretical investigations.

Concentration Dependent Physical Properties of Ge1-xSnx Solid Solution

NASA Astrophysics Data System (ADS)

Jivani, A. R.; Jani, A. R.

2011-12-01

Our own proposed potential is used to investigate few physical properties like total energy, bulk modulus, pressure derivative of bulk modulus, elastic constants, pressure derivative of elastic constants, Poisson's ratio and Young's modulus of Ge1-xSnx solid solution with x is atomic concentration of α-Sn. The potential combines linear plus quadratic types of electron-ion interaction. First time screening function proposed by Sarkar et al is used to investigate the properties of the Ge-Sn solid solution system.

Exploration of phase transition in Th2C under pressure: An Ab-initio investigation

NASA Astrophysics Data System (ADS)

Sahoo, B. D.; Joshi, K. D.; Kaushik, T. C.

2018-05-01

With the motivation of searching for new compounds in the Th-C system, we have performed ab initio evolutionary searches for all the stable compounds in this binary system in the pressure range of 0-100 GPa. We have found previously unknown, thermodynamically stable, composition Th2C along with experimentally known ThC, ThC2 and Th2C3 phases at 0 GPa. Interestingly at pressure of 13 GPa the predicted ground state orthorhombic (SG no. 59, Pmmn) phase of Th2C transforms to trigonal (SG no. 164, P-3m1) phase. We also find the mechanical and dynamical stability of both the phases. Further, the theoretically determined equation of state has been utilized to derive various physical quantities such as zero pressure equilibrium volume, bulk modulus, and pressure derivative of bulk modulus of Pmmn phase at ambient conditions.

Development of a Test Rig for Measuring Isentropic Bulk Modulus

DTIC Science & Technology

2013-01-01

Figure 4, was fabricated from 17 - 4PH heat-treated steel. The cell is a three-part design consisting of a top and bottom with a thermowell sandwiched in...Bulk Modulus, Speed-of-Sound, Fuel 16. SECURITY CLASSIFICATION OF: 17 . LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE

Estimation of elasticity map of soft biological tissue mimicking phantom using laser speckle contrast analysis

NASA Astrophysics Data System (ADS)

Suheshkumar Singh, M.; Rajan, K.; Vasu, R. M.

2011-05-01

Scattering of coherent light from scattering particles causes phase shift to the scattered light. The interference of unscattered and scattered light causes the formation of speckles. When the scattering particles, under the influence of an ultrasound (US) pressure wave, vibrate, the phase shift fluctuates, thereby causing fluctuation in speckle intensity. We use the laser speckle contrast analysis (LSCA) to reconstruct a map of the elastic property (Young's modulus) of soft tissue-mimicking phantom. The displacement of the scatters is inversely related to the Young's modulus of the medium. The elastic properties of soft biological tissues vary, many fold with malignancy. The experimental results show that laser speckle contrast (LSC) is very sensitive to the pathological changes in a soft tissue medium. The experiments are carried out on a phantom with two cylindrical inclusions of sizes 6mm in diameter, separated by 8mm between them. Three samples are made. One inclusion has Young's modulus E of 40kPa. The second inclusion has either a Young's modulus E of 20kPa, or scattering coefficient of μs'=3.00mm-1 or absorption coefficient of μa=0.03mm-1. The optical absorption (μa), reduced scattering (μs') coefficient, and the Young's modulus of the background are μa=0.01mm-1, μs'=1.00mm-1 and 12kPa, respectively. The experiments are carried out on all three phantoms. On a phantom with two inclusions of Young's modulus of 20 and 40kPa, the measured relative speckle image contrasts are 36.55% and 63.72%, respectively. Experiments are repeated on phantoms with inclusions of μa=0.03mm-1, E =40kPa and μs'=3.00mm-1. The results show that it is possible to detect inclusions with contrasts in optical absorption, optical scattering, and Young's modulus. Studies of the variation of laser speckle contrast with ultrasound driving force for various values of μa, μs', and Young's modulus of the tissue mimicking medium are also carried out.

Measurements of unjacketed moduli of porous rock

NASA Astrophysics Data System (ADS)

Tarokh, A.; Makhnenko, R. Y.; Labuz, J.

2017-12-01

Coupling of stress and pore pressure appears in a number of applications dealing with subsurface (sedimentary) rock, including petroleum exploration and waste storage. Poroelastic analyses consider the compressibility of the solid constituents forming the rock, and often times solid bulk modulus Ks is assumed to be the same as the dominant mineral bulk modulus. In fact, there are two different parameters describing solid compressibility of a porous rock: the unjacketed bulk modulus Ks' and the unjacketed pore modulus Ks". Experimental techniques are developed to measure the two poroelastic parameters of fluid-saturated porous rock under the unjacketed condition. In an unjacketed experiment, the rock without a membrane is loaded by the fluid in a pressure vessel. The confining fluid permeates the connected pore space throughout the interior of the rock. Therefore, changes in mean stress P will produce equal changes in pore pressure p, i.e. ΔP = Δp. The test can also be performed with a jacketed rock specimen by applying equal increments of mean stress and pore pressure. The unjacketed bulk modulus, Ks', is obtained by measuring the bulk strain with resistive strain gages. The unjacketed pore modulus, Ks", the pore volume counterpart to Ks', is a measure of the change in pore pressure per unit pore volume strain under the unjacketed condition. Several indirect estimates of Ks" have been reported but limitations of these approaches do not provide an accurate value. We present direct measurements of Ks" with detailed calibration on the system volumetric response. The results indicate that for Dunnville sandstone Ks' and Ks" are equal while for Berea sandstone, a difference between the two moduli exists, which is explained by the presence of non-connected pores. The experiments also strongly suggest that both Ks' and Ks" are independent of effective stress.

A Comparative Study of Structural Stability and Mechanical and Optical Properties of Fluorapatite (Ca5(PO4)3F) and Lithium Disilicate (Li2Si2O5) Components Forming Dental Glass-Ceramics: First Principles Study

NASA Astrophysics Data System (ADS)

Biskri, Z. E.; Rached, H.; Bouchear, M.; Rached, D.; Aida, M. S.

2016-10-01

The aim of this paper is a comparative study of structural stability and mechanical and optical properties of fluorapatite (FA) (Ca5(PO4)3F) and lithium disilicate (LD) (Li2Si2O5), using the first principles pseudopotential method based on density functional theory (DFT) within the generalized gradient approximation (GGA). The stability of fluorapatite and lithium disilicate compounds has been evaluated on the basis of their formation enthalpies. The results show that fluorapatite is more energetically stable than lithium disilicate. The independent elastic constants and related mechanical properties, including bulk modulus ( B), shear modulus ( G), Young's modulus ( E) and Poisson's ratio ( ν) as well as the Vickers hardness ( H v), have been calculated for fluorapatite compound and compared with other theoretical and experimental results. The obtained values of the shear modulus, Young's modulus and Vickers hardness are smaller in comparison with those of lithium disilicate compound, implying that lithium disilicate is more rigid than fluorapatite. The brittle and ductile properties were also discussed using B/ G ratio and Poisson's ratio. Optical properties such as refractive index n( ω), extinction coefficient k( ω), absorption coefficient α( ω) and optical reflectivity R( ω) have been determined from the calculations of the complex dielectric function ɛ( ω), and interpreted on the basis of the electronic structures of both compounds. The calculated values of static dielectric constant ɛ 1(0) and static refractive index n(0) show that the Li2Si2O5 compound has larger values compared to those of the Ca5(PO4)3F compound. The results of the extinction coefficient show that Li2Si2O5 compound exhibits a much stronger ultraviolet absorption. According to the absorption and reflectivity spectra, we inferred that both compounds are theoretically the best visible and infrared transparent materials.

Physical properties of a new sonically placed composite resin restorative material.

PubMed

Ibarra, Emily T; Lien, Wen; Casey, Jeffery; Dixon, Sara A; Vandewalle, Kraig S

2015-01-01

A new nanohybrid composite activated by sonic energy has been recently introduced as a single-step, bulk-fill restorative material. The purpose of this study was to compare the physical properties of this new composite to various other composite restorative materials marketed for posterior or bulk-fill placement. The following physical properties were examined: depth of cure, volumetric shrinkage, flexural strength, flexural modulus, fracture toughness, and percent porosity. A mean and standard deviation were determined per group. One-way ANOVA and Tukey's post hoc tests were performed per property (α = 0.05). Percent porosity was evaluated with a Kruskal-Wallis/Mann-Whitney test (α = 0.005). Significant differences were found between groups (P < 0.001) per test type. Compared to the other composite restorative materials, the new nanohybrid composite showed low shrinkage and percent porosity, moderate fracture toughness and flexural modulus, and high flexural strength. However, it also demonstrated a relatively reduced depth of cure compared to the other composites.

A study of the influence of micro and nano phase morphology on the mechanical properties of a rubber-modified epoxy resin

NASA Astrophysics Data System (ADS)

Russell, Bobby Glenn

Epoxy resins are thermosets with extraordinary adhesion; high strength; good resistance to creep, heat, and chemicals; and they have low shrinkage. Conversely, these polymers are brittle, they are sensitive to moisture, and they exhibit poor toughness. To improve their toughness, they are often modified by introducing dispersed rubber particles in the primary phase. In this study, the epoxy resin was modified with carboxyl-terminated butadiene acrylonitrile (CTBN), liquid-reactive rubbers. The initiator concentration, percent acrylonitrile in the CTBN rubber, and cure temperatures were altered to give varying materials properties. Statistical analysis of the morphology data showed that the percentage of rubber acrylonitrile had an effect on both the rubber particle size and volume fraction. The cure temperature had an effect on the rubber particle volume and modulus. Plots of the rubber particle size, volume fraction, and modulus versus bulk elastic storage modulus and fracture toughness revealed that rubber particle size had no effect on bulk properties, volume fraction and rubber particle modulus had an effect on both the bulk storage elastic modulus and fracture toughness.

Structural relaxation driven increase in elastic modulus for a bulk metallic glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arora, Harpreet Singh; Aditya, Ayyagari V.; Mukherjee, Sundeep, E-mail: sundeep.mukherjee@unt.edu

2015-01-07

The change in elastic modulus as a function of temperature was investigated for a zirconium-based bulk metallic glass. High temperature nano-indentation was done over a wide temperature range from room temperature to the glass-transition. At higher temperature, there was a transition from inhomogeneous to homogeneous deformation, with a decrease in serrated flow and an increase in creep displacement. Hardness was found to decrease, whereas elastic modulus was found to increase with temperature. The increase in elastic modulus for metallic glass at higher temperature was explained by diffusive rearrangement of atoms resulting in free volume annihilation. This is in contrast tomore » elastic modulus increase with temperature for silicate glasses due to compaction of its open three dimensional coordinated structure without any atomic diffusion.« less

Theoretical investigation on thermoelectric properties of (Ca,Sr,Ba)Fe2(As/Bi)2 compounds under temperature

NASA Astrophysics Data System (ADS)

Jayalakshmi, D. S.; Sundareswari, M.; Viswanathan, E.; Das, Abhijeet

2018-04-01

The electrical conductivity, resistivity and Seebeck coefficient, Pauli magnetic susceptibility and power factor are computed under temperature (100 K - 800 K) in steps of 100 K for the theoretically designed compounds namely (Ca,Sr,Ba)Fe2Bi2 and their parent compounds namely (Ca,Sr,Ba)Fe2As2 by using Boltzmann transport theory interfaced to the Wien2k program. The Bulk modulus, electron phonon coupling constant, thermoelectric figure of merit (ZT) and transition temperature are calculated for the optimized anti ferromagnetic phase of the proposed compounds. The results are discussed for the novel compounds in view of their superconductivity existence and compared with their parent unconventional superconducting compounds.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winterrose, M.L.; Lucas, M.S.; Yue, A.F.

Synchrotron x-ray diffraction (XRD) measurements, nuclear forward scattering (NFS) measurements, and density functional theory (DFT) calculations were performed on L1{sub 2}-ordered Pd{sub 3}Fe. Measurements were performed at 300 K at pressures up to 33 GPa, and at 7 GPa at temperatures up to 650 K. The NFS revealed a collapse of the Fe57 magnetic moment between 8.9 and 12.3 GPa at 300 K, coinciding with a transition in bulk modulus found by XRD. Heating the sample under a pressure of 7 GPa showed negligible thermal expansion from 300 to 523 K, demonstrating Invar behavior. Zero-temperature DFT calculations identified a ferromagneticmore » ground state and showed several antiferromagnetic states had comparable energies at pressures above 20 GPa.« less

Carbon fiber polymer-matrix structural composites tailored for multifunctionality by filler incorporation

NASA Astrophysics Data System (ADS)

Han, Seungjin

This dissertation provides multifunctional carbon fiber polymer-matrix structural composites for vibration damping, thermal conduction and thermoelectricity. Specifically, (i) it has strengthened and stiffened carbon fiber polymer-matrix structural composites by the incorporation of halloysite nanotubes, carbon nanotubes and silicon carbide whiskers, (ii) it has improved mechanical energy dissipation using carbon fiber polymer-matrix structural composites with filler incorporation, (iii) it has increased the through-thickness thermal conductivity of carbon fiber polymer-matrix composite by curing pressure increase and filler incorporation, and (iv) it has enhanced the thermoelectric behavior of carbon fiber polymer-matrix structural composites. Low-cost natural halloysite nanotubes (0.1 microm diameter) were effective for strengthening and stiffening continuous fiber polymer-matrix composites, as shown for crossply carbon fiber (5 microm diameter, ˜59 vol.%) epoxy-matrix composites under flexure, giving 17% increase in strength, 11% increase in modulus and 21% decrease in ductility. They were less effective than expensive multiwalled carbon nanotubes (0.02 microm diameter), which gave 25% increase in strength, 11% increase in modulus and 14% decrease in ductility. However, they were more effective than expensive silicon carbide whiskers (1 microm diameter), which gave 15% increase in strength, 9% increase in modulus and 20% decrease in ductility. Each filler, at ˜2 vol.%, was incorporated in the composite at every interlaminar interface by fiber prepreg surface modification. The flexural strength increase due to halloysite nanotubes incorporation related to the interlaminar shear strength increase. The measured values of the composite modulus agreed roughly with the calculated values based on the Rule of Mixtures. Continuous carbon fiber composites with enhanced vibration damping under flexure are provided by incorporation of fillers between the laminae. Exfoliated graphite (EG) as a sole filler is more effective than carbon nanotube (SWCNT/MWCNT), halloysite nanotube (HNT) or nanoclay as sole fillers in enhancing the loss tangent, if the curing pressure is 2.0 (not 0.5) MPa. The MWCNT, SiC whisker and halloysite nanotube as sole fillers are effective for increasing the storage modulus. The combined use of a storage-modulus-enhancing filler (CNT, SiC whisker or HNT) and a loss-tangent-enhancing filler (EG or nanoclay) gives the best performance. With EG, HNT and 2.0-MPa curing, the loss modulus is increased by 110%, while the flexural strength is decreased by 14% and the flexural modulus is not affected. With nanoclay, HNT and 0.5-MPa curing, the loss modulus is increased by 96%, while the flexural strength and modulus are essentially not affected. The low through-thickness thermal conductivity limits heat dissipation from continuous carbon fiber polymer-matrix composites. This conductivity is increased by up to 60% by raising the curing pressure from 0.1 to 2.0 MPa and up to 33% by incorporation of a filler (61.5 vol.%) at the interlaminar interface. The thermal resistivity is dominated by the lamina resistivity (which is contributed substantially by the intralaminar fiber--fiber interfacial resistivity), with the interlaminar interface thermal resistivity being unexpectedly negligible. The lamina resistivity and intralaminar fiber-fiber interfacial resistivity are decreased by up to 56% by raising the curing pressure and up to 36% by filler incorporation. Thermoelectric structural materials are potentially attractive for large-scale energy harvesting. Through filler incorporation and unprecedented decoupling of the bulk (laminae) and interfacial (interlaminar interfaces) contributions to the Seebeck voltage (through-thickness Seebeck voltage of a crossply continuous carbon fiber/epoxy composite laminate), this work provides thermoelectric power magnitudes at ˜70°C up to 110, 1670 and 11000 microV/K for the laminate, a lamina and an interlaminar interface respectively. The interface provides an apparent thermoelectric effect due to carrier backflow. The interfacial voltage is opposite in sign from the laminate and lamina voltages and is slightly lower in magnitude than the lamina voltage. The through-thickness thermoelectric behavior of continuous carbon fiber epoxy-matrix structural composites has been greatly improved by the use of tellurium particles (13 vol.% of composite), bismuth telluride particles (2 vol.%) and carbon black (2 vol.%) at the interlaminar interface. The thermoelectric power is increased from 8 to 163 microV/K, while the electrical resistivity is decreased from 0.17 to 0.02 O.cm, the thermal conductivity is decreased from 1.31 to 0.51 W/m.K, and the dimensionless thermoelectric figure of merit ZT at 70°C is increased from 9 x 10-6 to 9 x 10-2. Decrease in the curing pressure from 4.0 to 0.5 MPa decreases ZT slightly, mainly due to the increase in electrical resistivity.

Electrical conductivity of Gd doped BiFeO3-PbZrO3 composite

NASA Astrophysics Data System (ADS)

Satpathy, Santosh Kumar; Mohanty, Nilaya Kumar; Behera, Ajay Kumar; Behera, Banarji; Nayak, Pratibindhya

2013-09-01

The composite, 0.5(BiGd0.15Fe0.85O3)-0.5(PbZrO3), was synthesized using the solid-state reaction technique. The formation of the compound was confirmed by XRD with an orthorhombic structure at room temperature. The impedance parameters were studied using an impedance analyzer in a wide range of frequency (102-106 Hz) at different temperatures. The Nyquist plot suggests the contribution of bulk effect and a slight indication of grain boundary effect and the bulk resistance decreases with a rise in temperature. The presence of temperature-dependent relaxation process occurs in the material. Electrical modulus reveals the presence of the hopping mechanism in the materials. The value of exponent n, pre-factor A and σ dc were obtained by fitting ac conductivity data with Jonscher's universal power law. The activation energies calculated from the ac conductivity were found to be 0.50, 0.46, 0.44, 0.43, 0.42 and 0.38 eV at 1, 10, 50, 100, 500 kHz and 1 MHz respectively in the temperature region of 110°C-350°C. The dc conductivity was found to increase with the rise in temperature. The activation energy calculated from complex impedance plot and from the fitted Jonscher's power law are very close, which results similar type of charge carrier exist in conduction mechanism of the material.

Structural and transport properties of double perovskite Dy{sub 2}NiMnO{sub 6}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chanda, Sadhan, E-mail: sadhan.physics@gmail.com; Saha, Sujoy; Dutta, Alo

2015-02-15

Highlights: • Sol–gel citrate method is used to prepare the double perovskite Dy{sub 2}NiMnO{sub 6}. • Structure and dielectric relaxation of the sample are studied for nano and bulk phases. • The relaxation mechanism of the sample is modeled by Cole–Cole equation. • With increasing sintering temperature conductivity increases. • Electronic structures and magnetic properties have been studied by DFT calculations. - Abstract: The double perovskite oxide Dy{sub 2}NiMnO{sub 6} (DNMO) is synthesized in nano and bulk phase by the sol–gel citrate method. The Rietveld refinement of X-ray diffraction pattern of the sample at room temperature shows the monoclinic P2{submore » 1}/n phase. Dielectric relaxation of the sample is investigated in the impedance and electric modulus formalisms in the frequency range from 50 Hz to 1 MHz and in the temperature range from 253 to 415 K. The Cole–Cole model is used to explain the relaxation mechanism in DNMO. The frequency-dependent maxima in the imaginary part of impedance are found to obey an Arrhenius law with activation energy of 0.346 and 0.344 eV for nano and bulk DNMO, respectively. A significant increase in conductivity of bulk DNMO has been observed than that of the nanoceramic. Electronic structures and magnetic properties of DNMO have been studied by performing first principles calculation based on density functional theory.« less

Model for the alpha and beta shear-mechanical properties of supercooled liquids and its comparison to squalane data

NASA Astrophysics Data System (ADS)

Hecksher, Tina; Olsen, Niels Boye; Dyre, Jeppe C.

2017-04-01

This paper presents data for supercooled squalane's frequency-dependent shear modulus covering frequencies from 10 mHz to 30 kHz and temperatures from 168 K to 190 K; measurements are also reported for the glass phase down to 146 K. The data reveal a strong mechanical beta process. A model is proposed for the shear response of the metastable equilibrium liquid phase of supercooled liquids. The model is an electrical equivalent-circuit characterized by additivity of the dynamic shear compliances of the alpha and beta processes. The nontrivial parts of the alpha and beta processes are each represented by a "Cole-Cole retardation element" defined as a series connection of a capacitor and a constant-phase element, resulting in the Cole-Cole compliance function well-known from dielectrics. The model, which assumes that the high-frequency decay of the alpha shear compliance loss varies with the angular frequency as ω-1 /2, has seven parameters. Assuming time-temperature superposition for the alpha and beta processes separately, the number of parameters varying with temperature is reduced to four. The model provides a better fit to the data than an equally parametrized Havriliak-Negami type model. From the temperature dependence of the best-fit model parameters, the following conclusions are drawn: (1) the alpha relaxation time conforms to the shoving model; (2) the beta relaxation loss-peak frequency is almost temperature independent; (3) the alpha compliance magnitude, which in the model equals the inverse of the instantaneous shear modulus, is only weakly temperature dependent; (4) the beta compliance magnitude decreases by a factor of three upon cooling in the temperature range studied. The final part of the paper briefly presents measurements of the dynamic adiabatic bulk modulus covering frequencies from 10 mHz to 10 kHz in the temperature range from 172 K to 200 K. The data are qualitatively similar to the shear modulus data by having a significant beta process. A single-order-parameter framework is suggested to rationalize these similarities.

Model for the alpha and beta shear-mechanical properties of supercooled liquids and its comparison to squalane data.

PubMed

Hecksher, Tina; Olsen, Niels Boye; Dyre, Jeppe C

2017-04-21

This paper presents data for supercooled squalane's frequency-dependent shear modulus covering frequencies from 10 mHz to 30 kHz and temperatures from 168 K to 190 K; measurements are also reported for the glass phase down to 146 K. The data reveal a strong mechanical beta process. A model is proposed for the shear response of the metastable equilibrium liquid phase of supercooled liquids. The model is an electrical equivalent-circuit characterized by additivity of the dynamic shear compliances of the alpha and beta processes. The nontrivial parts of the alpha and beta processes are each represented by a "Cole-Cole retardation element" defined as a series connection of a capacitor and a constant-phase element, resulting in the Cole-Cole compliance function well-known from dielectrics. The model, which assumes that the high-frequency decay of the alpha shear compliance loss varies with the angular frequency as ω -1/2 , has seven parameters. Assuming time-temperature superposition for the alpha and beta processes separately, the number of parameters varying with temperature is reduced to four. The model provides a better fit to the data than an equally parametrized Havriliak-Negami type model. From the temperature dependence of the best-fit model parameters, the following conclusions are drawn: (1) the alpha relaxation time conforms to the shoving model; (2) the beta relaxation loss-peak frequency is almost temperature independent; (3) the alpha compliance magnitude, which in the model equals the inverse of the instantaneous shear modulus, is only weakly temperature dependent; (4) the beta compliance magnitude decreases by a factor of three upon cooling in the temperature range studied. The final part of the paper briefly presents measurements of the dynamic adiabatic bulk modulus covering frequencies from 10 mHz to 10 kHz in the temperature range from 172 K to 200 K. The data are qualitatively similar to the shear modulus data by having a significant beta process. A single-order-parameter framework is suggested to rationalize these similarities.

Temperature effects on the universal equation of state of solids

NASA Technical Reports Server (NTRS)

Vinet, P.; Ferrante, J.; Smith, J. R.; Rose, J. H.

1986-01-01

Recently it has been argued based on theoretical calculations and experimental data that there is a universal form for the equation of state of solids. This observation was restricted to the range of temperatures and pressures such that there are no phase transitions. The use of this universal relation to estimate pressure-volume relations (i.e., isotherms) required three input parameters at each fixed temperature. It is shown that for many solids the input data needed to predict high temperature thermodynamical properties can be dramatically reduced. In particular, only four numbers are needed: (1) the zero pressure (P=0) isothermal bulk modulus; (2)it P=0 pressure derivative; (3) the P=0 volume; and (4) the P=0 thermal expansion; all evaluated at a single (reference) temperature. Explicit predictions are made for the high temperature isotherms, the thermal expansion as a function of temperature, and the temperature variation of the isothermal bulk modulus and its pressure derivative. These predictions are tested using experimental data for three representative solids: gold, sodium chloride, and xenon. Good agreement between theory and experiment is found.

Temperature effects on the universal equation of state of solids

NASA Technical Reports Server (NTRS)

Vinet, Pascal; Ferrante, John; Smith, John R.; Rose, James H.

1987-01-01

Recently it has been argued based on theoretical calculations and experimental data that there is a universal form for the equation of state of solids. This observation was restricted to the range of temperatures and pressures such that there are no phase transitions. The use of this universal relation to estimate pressure-volume relations (i.e., isotherms) required three input parameters at each fixed temperature. It is shown that for many solids the input data needed to predict high temperature thermodynamical properties can be dramatically reduced. In particular, only four numbers are needed: (1) the zero pressure (P = 0) isothermal bulk modulus; (2) its P = 0 pressure derivative; (3) the P = 0 volume; and (4) the P = 0 thermal expansion; all evaluated at a single (reference) temperature. Explicit predictions are made for the high temperature isotherms, the thermal expansion as a function of temperature, and the temperature variation of the isothermal bulk modulus and its pressure derivative. These predictions are tested using experimental data for three representative solids: gold, sodium chloride, and xenon. Good agreement between theory and experiment is found.

Component-Based Reduced Basis for Eigenproblems

DTIC Science & Technology

2013-07-17

σ),Mi(µ, σ) ∈ RKi×Ki for component i, which have entries Aik′,k(µ, σ) = ai(ψi,k + bi,k(µ, σ), ψi,k′ + bi,k′(µ, σ);µ), Mik ′,k(µ, σ) = mi(ψi,k + bi,k...to the beam width in the following, we nondimensionalize the Young’s modulus E with respect to a reference value E0, and we nondimensionalize time...in which case the coefficents Cijkl(µ) are functions of only two parameters: Poisson’s ratio ν and Young’s modulus E . In the following we always fix

Nanomechanical properties of dental resin-composites.

PubMed

El-Safty, S; Akhtar, R; Silikas, N; Watts, D C

2012-12-01

To determine by nanoindentation the hardness and elastic modulus of resin-composites, including a series with systematically varied filler loading, plus other representative materials that fall into the categories of flowable, bulk-fill and conventional nano-hybrid types. Ten dental resin-composites: three flowable, three bulk-fill and four conventional were investigated using nanoindentation. Disc specimens (15mm×2mm) were prepared from each material using a metallic mold. Specimens were irradiated in the mold at top and bottom surfaces in multiple overlapping points (40s each) with light curing unit at 650mW/cm(2). Specimens were then mounted in 3cm diameter phenolic ring forms and embedded in a self-curing polystyrene resin. After grinding and polishing, specimens were stored in distilled water at 37°C for 7 days. Specimens were investigated using an Agilent Technologies XP nanoindenter equipped with a Berkovich diamond tip (100nm radius). Each specimen was loaded at one loading rate and three different unloading rates (at room temperature) with thirty indentations, per unloading rate. The maximum load applied by the nanoindenter to examine the specimens was 10mN. Dependent on the type of the resin-composite material, the mean values ranged from 0.73GPa to 1.60GPa for nanohardness and from 14.44GPa to 24.07GPa for elastic modulus. There was a significant positive non-linear correlation between elastic modulus and nanohardness (r(2)=0.88). Nonlinear regression revealed a significant positive correlation (r(2)=0.62) between elastic moduli and filler loading and a non-significant correlation (r(2)=0.50) between nanohardness and filler loading of the studied materials. Varying the unloading rates showed no consistent effect on the elastic modulus and nanohardness of the studied materials. For a specific resin matrix, both elastic moduli and nanohardness correlated positively with filler loading. For the resin-composites investigated, the group-average elastic moduli and nanohardnesses for bulk-fill and flowable materials were lower than those for conventional nano-hybrid composites. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Physical property measurements of doped cesium iodide crystals

NASA Technical Reports Server (NTRS)

Synder, R. S.; Clotfelter, W. N.

1974-01-01

Mechanical and thermal property values are reported for crystalline cesium iodide doped with sodium and thallium. Young's modulus, bulk modulus, shear modulus, and Poisson's ratio were obtained from ultrasonic measurements. Young's modulus and the samples' elastic and plastic behavior were also measured under tension and compression. Thermal expansion and thermal conductivity were the temperature dependent measurements that were made.

Real time studies of Elastic Moduli Pu Aging using Resonant Ultrasound Spectroscopy

NASA Astrophysics Data System (ADS)

Maiorov, Boris

Elastic moduli are fundamental thermodynamic susceptibilities that connect directly to thermodynamics, electronic structure and give important information about mechanical properties. To determine the time evolution of the elastic properties in 239Pu and it Ga alloys, is imperative to study its phase stability and self-irradiation damage process. The most-likely sources of these changes include a) ingrowth of radioactive decay products like He and U, b) the introduction of radiation damage, c) δ-phase instabilities towards α-Pu or to Pu3Ga. The measurement of mechanical resonance frequencies can be made with extreme precision and used to compute the elastic moduli without corrections giving important insight in this problem. Using Resonant Ultrasound Spectroscopy, we measured the time dependence of the mechanical resonance frequencies of fine-grained polycrystalline δ-phase 239Pu, from 300K up to 480K. At room temperature, the shear modulus shows an increase in time (stiffening), but the bulk modulus decreases (softening). These are the first real-time measurements of room temperature aging of the elastic moduli, and the changes are consistent with elastic moduli measurements performed on 44 year old δ-Pu. As the temperature is increased, the rate of change increases exponentially, with both moduli becoming stiffer with time. For T>420K an abrupt change in the time dependence is observed indicating that the bulk and shear moduli have opposite rates of change. Our measurements provide a basis for ruling out the decomposition of δ-Pu towards α-Pu or Pu3Ga, and indicate a complex defect-related scenario from which we are gathering important clues.

High pressure experimental studies on Na3Fe(PO4)(CO3) and Na3Mn(PO4)(CO3): Extensive pressure behaviors of carbonophosphates family

NASA Astrophysics Data System (ADS)

Gao, Jing; Huang, Weifeng; Wu, Xiang; Qin, Shan

2018-04-01

Carbon-bearing phases in the Earth's interior have profound implications for the long-term Earth carbon cycle. Here we investigate high-pressure behaviors of carbonophosphates bonshtedtite Na3Fe(PO4)(CO3) and sidorenkite Na3Mn(PO4)(CO3) in diamond anvil cells up to ∼12 GPa at room temperature. Modifications in in situ synchrotron X-ray diffraction patterns and Raman spectra confirm the structural stability of carbonophosphates within the pressure region. Fitting the third-order Birch-Murnaghan equation of state to the volume compression curve, the isothermal bulk modulus parameters are obtained to be K0 = 56(1) GPa, K0' = 3.3(1), V0 = 303.3(3) Å3 for Na3Fe(PO4)(CO3) and K0 = 54(1) GPa, K0' = 3.4(1), V0 = 313.4(2) Å3 for Na3Mn(PO4)(CO3). Crystallographic axes exhibit an elastic anisotropy with a more compressible c-axis relative to the ab-plane. An inverse linear correlation between the K0 value and the ionic radius of M2+ (M = Mg, Fe, Mn) is well determined for carbonophosphates. The pressure-dependence responsiveness of [PO4] and [CO3] in carbonophosphates show a negative relationship to the M2+ radius. We also discussed the effect of [PO4] group on the structural variations and high-pressure behaviors of carbonates. Furthermore, the geochemical properties of carbonophosphates hold implications to diamond genesis.

Elastic Nonlinear Response in Granular Media Under Resonance Conditions

NASA Astrophysics Data System (ADS)

Jia, X.; Johnson, P. A.

2004-12-01

We are studying the elastic linear and nonlinear behavior of granular media using dynamic wave methods. In the work presented here, our goal is to quantify the elastic nonlinear response by applying wave resonance. Resonance studies are desirable because they provide the means to easily study amplitude dependencies of elastic nonlinear behavior and thus to characterize the physical nature of the elastic nonlinearity. This work has implications for a variety of topics, in particular, the in situ nonlinear response of surface sediments. For this work we constructed an experimental cell in which high sensitivity dynamic resonance studies were conducted using granular media under controlled effective pressure. We limit our studies here to bulk modes but have the capability to employ shear waves as well. The granular media are composed of glass beads held under pressure by a piston, while applying resonance waves from transducers as both the excitation and the material probe. The container is closed with two fitted pistons and a normal load is applied to the granular sample across the top piston. Force and displacement are measured directly. Resonant frequency sweeps with frequencies corresponding to the fundamental bulk mode are applied to the longitudinal source transducer. The pore pressure in the system is 1 atm. The glass beads used in our experiments are of diameter 0.5 mm, randomly deposited in a duralumin cylinder of diameter 30 mm and height of 15 mm. This corresponds to a granular skeleton acoustic wave velocity of v ª 750m/s under 50 N of force [0.07 Mpa]. The loaded system gives fundamental mode resonances in the audio frequency band at half a wavelength where resonance frequency is effective-pressure dependent. The volume fraction of glass beads thus obtained is found to be 0.63 ± 0.01. Plane-wave generating and detecting transducers of diameter 30 mm are placed on axis at the top and bottom of the cylindrical container in direct contact with the glass beads. The wave signals are detected using a lock-in amplifier, and frequency and amplitude are recorded on computer. Drive frequency is swept from below to above the resonance mode. A typical frequency sweep is 3 kHz in width with a frequency sampling of 6 Hz. Frequency sweeps are applied at progressively increasing drive voltages to test for nonlinear-dynamical induced modulus softening. The resonance frequency at peak amplitude corresponds directly to modulus. We find significant elastic nonlinearity at all effective pressures, manifest by the fundamental-mode resonance curves decreasing progressively, at progressively increasing drive level. This is equivalent to progressive material softening with wave amplitude, meaning the wavespeed and modulus diminish. The wave dissipation simultaneously increases (Johnson and Sutin 2004). For example, at 0.11 Mpa effective pressure the observed change in resonance frequency of about 2.6% corresponds to a material bulk modulus decrease of about 5.2%. Strain amplitudes are 10-7-10-6. Thus, we would predict that surface sediments should have significant elastic nonlinear response beginning at about 10-6 strain amplitude. reference: Johnson, P. and A. Sutin, Slow dynamics in diverse solids, J. Acoust. Soc Am., in press (2004).

Combining AFM and Acoustic Probes to Reveal Changes in the Elastic Stiffness Tensor of Living Cells

PubMed Central

Nijenhuis, Nadja; Zhao, Xuegen; Carisey, Alex; Ballestrem, Christoph; Derby, Brian

2014-01-01

Knowledge of how the elastic stiffness of a cell affects its communication with its environment is of fundamental importance for the understanding of tissue integrity in health and disease. For stiffness measurements, it has been customary to quote a single parameter quantity, e.g., Young’s modulus, rather than the minimum of two terms of the stiffness tensor required by elasticity theory. In this study, we use two independent methods (acoustic microscopy and atomic force microscopy nanoindentation) to characterize the elastic properties of a cell and thus determine two independent elastic constants. This allows us to explore in detail how the mechanical properties of cells change in response to signaling pathways that are known to regulate the cell’s cytoskeleton. In particular, we demonstrate that altering the tensioning of actin filaments in NIH3T3 cells has a strong influence on the cell's shear modulus but leaves its bulk modulus unchanged. In contrast, altering the polymerization state of actin filaments influences bulk and shear modulus in a similar manner. In addition, we can use the data to directly determine the Poisson ratio of a cell and show that in all cases studied, it is less than, but very close to, 0.5 in value. PMID:25296302

A first principle calculation of anisotropic elastic, mechanical and electronic properties of TiB

NASA Astrophysics Data System (ADS)

Zhang, Junqin; Zhao, Bin; Ma, Huihui; Wei, Qun; Yang, Yintang

2018-04-01

The structural, mechanical and electronic properties of the NaCl-type structure TiB are theoretically calculated based on the first principles. The density of states of TiB shows obvious density peaks at -0.70eV. Furthermore, there exists a pseudogap at 0.71eV to the right of the Fermi level. The calculated structural and mechanical parameters (i.e., bulk modulus, shear modulus, Young's modulus, Poisson's ratio and universal elastic anisotropy index) were in good agreement both with the previously reported experimental values and theoretical results at zero pressure. The mechanical stability criterion proves that TiB at zero pressure is mechanistically stable and exhibits ductility. The universal anisotropic index and the 3D graphics of Young's modulus are also given in this paper, which indicates that TiB is anisotropy under zero pressure. Moreover, the effects of applied pressures on the structural, mechanical and anisotropic elastic of TiB were studied in the range from 0 to 100GPa. It was found that ductility and anisotropy of TiB were enhanced with the increase of pressure.

Liquid Between Macromolecules in Protein Crystals: Static Versus Dynamics

NASA Technical Reports Server (NTRS)

Chernov, A. A.

2005-01-01

Protein crystals are so fragile that they often can not be handled by tweezers. Indeed, measurements of the Young modulus, E, of lysozyme crystals resulted in E approx. equals 0.1 - 1 GPa, the lower figures, 0.1 - 0.5 GPa, being obtained from triple point bending of as-grown and not cross-linked crystals sitting in solution. The bending strength was found to be approx.10(exp -2) E. On the other hand, ultrasound speed and Mandelstam-Raman-Brilloin light scattering experiments led to much higher figures, E approx. equals 2.7 GPa. The lower figures for E were found from static or low frequency crystal deformations measurements, while the higher moduli are based on high frequency lattice vibrations, 10(exp 7) - 10(exp 10) 1/s. The physical reason for the about an order of magnitude discrepancy is in different behavior of water filling space between protein molecules. At slow lattice deformation, the not-bound intermolecular water has enough time to flow from the compressed to expanded regions of the deformed crystal. At high deformation frequencies in the ultra- and hypersound waves, the water is confined in the intermolecular space and, on that scale, behaves like a solid, thus contributing to the elastic crystal moduli. In this case, the reciprocal crystal modulus is expected to be an average of the water protein and water compressibilities (reciprocal compressibilities): the bulk modulus for lysozyme is 26 GPa, for water it is 7 GPa. Anisotropy of the crystal moduli comes from intermolecular contacts within the lattice while the high frequency hardness comes from the bulk of protein molecules and water bulk moduli. These conclusions are based on the analysis of liquid flow in porous medium to be presented.

Mechanical properties of novel forms of graphyne under strain: A density functional theory study

NASA Astrophysics Data System (ADS)

Majidi, Roya

2017-06-01

The mechanical properties of two forms of graphyne sheets named α-graphyne and α2-graphyne under uniaxial and biaxial strains were studied. In-plane stiffness, bulk modulus, and shear modulus were calculated based on density functional theory. The in-plane stiffness, bulk modulus, and shear modulus of α2-graphyne were found to be larger than that of α-graphyne. The maximum values of supported uniaxial and biaxial strains before failure were determined. The α-graphyne was entered into the plastic region with the higher magnitude of tension in comparison to α2-graphyne. The mechanical properties of α-graphyne family revealed that these forms of graphyne are proper materials for use in nanomechanical applications.

Specific heat of new perovskite-type cobaltates Pr{sub 1-x}Nd{sub x}CoO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thakur, Rasna, E-mail: rasnarishu@gmail.com; Thakur, Rajesh K.; Gaur, N. K.

2016-05-23

Specific heat and Bulk modulus (B) of new perovskite-type cobaltates Pr{sub 1-x}Nd{sub x}CoO{sub 3} has been studied by means of a Modified Rigid Ion Model (MRIM) and Atoms in Molecules (AIM) theory in a wide temperature range (1 K ≤ T ≤1000 K). The effect of Nd doping on the elastic, cohesive and thermal properties of PrCoO{sub 3} have been studied probably for the first time by an atomistic approach. The computed results are in good agreement with the available experimental data.

The mechanical, optoelectronic and thermoelectric properties of NiYSn (Y = Zr and Hf) alloys

NASA Astrophysics Data System (ADS)

Hamioud, Farida; Mubarak, A. A.

2017-09-01

First-principle calculations are performed using DFT as implemented in Wien2k code to compute the mechanical, electronic, optical and thermoelectric properties of NiYSn (Y = Zr and Hf) alloys. The computed lattice constants, bulk modulus and cohesive energy of these alloys at 0 K and 0 GPa are performed. NiZrSn and NiHfSn are found to be anisotropic and elastically stable. Furthermore, both alloys are confirmed to be thermodynamically stable by the calculated values of the standard enthalpy of formation. The Young’s and shear moduli values show that NiZrSn seems to be stiffer than NiHfSn. The optical properties are performed using the dielectric function. Some beneficial optoelectronic applications are found as exposed in the optical spectra. Moreover, the alloys are classified as good insulators for solar heating. The thermoelectric properties as a function of temperature are computed utilizing BoltzTrap code. The major charge carriers are found to be electrons and the alloys are classified as p-type doping alloys.

The compression mechanism of garnets based on in situ observations

NASA Astrophysics Data System (ADS)

Dymshits, Anna; Sharygin, Igor; Litasov, Konstantin; Shatskiy, Anton

2014-05-01

Previously it was showed that the bulk modulus of garnet is strongly affected by the bulk modulus of the dodecahedra, while compressibility of other individual polyhedra displays no correlation with the compressibility of the structure as a whole (Milman et al., 2001). If so, Na-majorite (Na-maj) would have the smallest bulk modulus of all silicate garnets, as a phase with a predicted dodecahedral bulk modulus of approximately 70 GPa (Hazen et al., 1994). In fact Na-maj has the largest bulk modulus among the silicate garnets. This behavior must reflect the all-mineral framework of Na-maj with very small cell volume and silicon in the octahedral position. Thus, we conclude that not only the dodecahedral sites, but also the behavior of the garnet framework and relative sizes of the 8- and 6-coordinated cations, control garnet compression. The octahedral site in Na-maj is quite small (1.79 Å) and contains only silicon in comparison to the pyrope (1.85 Å) or majorite (1.88 Å). The small and highly charged octahedra shares four edges with the dodecahedra and thus restrict the volume of the large and low charged dodecahedra. In spite Na-maj has a large average X-cation radius (RNa = 1.07 Å) its dodecahedral volume is relatively small (V = 21.23 and 21.26 Å3). Pacalo et al. (1992) suggested that XO8 polyhedra act as braces and controls the amount of rotation between tetrahedra and octahedra within the corner-linked chains. In case of pyrope XO8 cite is not filled up and polyhedra within the corner-linked chains can rotate freely to accommodate applied stress. In case of Na-maj the dodecahedral site is filled up and rotational freedom is minimized. The dodecahedral site in knorringite (Knr) contains cation with a small radius (Mg-O = 2.22 and 2.34 Å), so XO8 polyhedra is not filled up and can rotate freely to accommodate applied stress. In case of uvarovite not only octahedral but the dodecahedral site is also large (Ca-O = 2.35 and 2.51 Å), so the rotational freedom is minimized and such relations between the XO8 and YO6 sites provide evidence for comparatively more rigid structure. In case of uvarovite the bulk modulus is 162 GPa (Leger et al., 1990), while for Knr we obtain 154 GPa. Such relations between the XO8 and YO6 sites provide evidence for comparatively more rigid structure. As a result, Na-maj with all octahedral sites occupied by silicon has the largest value of the bulk modulus among garnets. It would be interesting to study compressibility of Li-majorite expressed by Yang et al. (2009). That phase has smaller cell volume (1430 Å3) and X-O distance (2.26 Å) but the same YO6 polyhedra fully occupied by silicon. The study was supported by Ministry of Education and Science of Russian Federation, project Nos 14.B25.31.0032, MK-265.2014.5, Russian Foundation for Basic Research No 14-05-00957-a. Hazen, R.M., Downs, R.T., Conrad, P.G., Finger, L.W., Gasparik, T. Comparative compressibilities of majorite-type garnets // Physics and Chemistry of Minerals, 1994, v.21, p.344-349. Leger, J., Redon, A., Chateau, C. Compressions of synthetic pyrope, spessartine and uvarovite garnets up to 25 GPa // Physics and Chemistry of Minerals, 1990, v.17, p.161-167. Milman, V., Akhmatskaya, E., Nobes, R., Winkler, B., Pickard, C., White, J. Systematic ab initio study of the compressibility of silicate garnets // Acta Crystallographica Section B: Structural Science, 2001, v.57, p.163-177. Yang, H., Konzett, J., Frost, D.J., Downs, R.T. X-ray diffraction and Raman spectroscopic study of clinopyroxenes with six-coordinated Si in the Na(Mg0.5Si0.5)Si2O6-NaAlSi2O6 system // American Mineralogist, 2009, v.94, p.942-949.

Frequency-dependent complex modulus of the uterus: preliminary results

NASA Astrophysics Data System (ADS)

Kiss, Miklos Z.; Hobson, Maritza A.; Varghese, Tomy; Harter, Josephine; Kliewer, Mark A.; Hartenbach, Ellen M.; Zagzebski, James A.

2006-08-01

The frequency-dependent complex moduli of human uterine tissue have been characterized. Quantification of the modulus is required for developing uterine ultrasound elastography as a viable imaging modality for diagnosing and monitoring causes for abnormal uterine bleeding and enlargement, as well assessing the integrity of uterine and cervical tissue. The complex modulus was measured in samples from hysterectomies of 24 patients ranging in age from 31 to 79 years. Measurements were done under small compressions of either 1 or 2%, at low pre-compression values (either 1 or 2%), and over a frequency range of 0.1-100 Hz. Modulus values of cervical tissue monotonically increased from approximately 30-90 kPa over the frequency range. Normal uterine tissue possessed modulus values over the same range, while leiomyomas, or uterine fibroids, exhibited values ranging from approximately 60-220 kPa.

Relevance of Kondo physics for the temperature dependence of the bulk modulus in plutonium

DOE PAGES

Janoschek, Marc; Lander, Gerry; Lawrence, Jon M.; ...

2017-01-10

The recent PNAS paper by Migliori et al. (1) attempts to explain the unusually strong temperature dependence of the bulk modulus of fcc plutonium (δ-Pu) by use of the disordered local moment (DLM) model. It is our opinion that this approach does not correctly incorporate the dynamic magnetism of δ-Pu. We provide the following note as commentary.

Elastic, thermodynamic and optical behavior of V2AC (A = Al, Ga) MAX phases

NASA Astrophysics Data System (ADS)

Khatun, M. R.; Ali, M. A.; Parvin, F.; Islam, A. K. M. A.

This article reports the first-principles calculations of yet unexplored Mulliken bond population, Vickers hardness, thermodynamic and optical properties of MAX phases V2AC (A = Al, Ga). We have also revisited the structural and elastic properties of these phases in order to assess the reliability of our calculations. The temperature and pressure dependence of bulk modulus, Debye temperature, specific heats, and thermal expansion coefficient have been successfully estimated through the quasi-harmonic Debye model in the temperature range from 0 to 1000 K and the pressure range from 0 to 50 GPa. The optical properties such as the dielectric function, refractive index, photoconductivity, absorption coefficients, reflectivity and loss function are also evaluated for the first time. The reflectivity is found to be high which indicates that V2AC (A = Al, Ga) having the same characteristics could be good candidate materials to reduce solar heating up to ∼15 eV.

Mechanical, electronic and thermodynamic properties of full Heusler compounds Fe2VX(X = Al, Ga)

NASA Astrophysics Data System (ADS)

Khalfa, M.; Khachai, H.; Chiker, F.; Baki, N.; Bougherara, K.; Yakoubi, A.; Murtaza, G.; Harmel, M.; Abu-Jafar, M. S.; Omran, S. Bin; Khenata, R.

2015-11-01

The electronic structure, mechanical and thermodynamic properties of Fe2VX, (with X = Al and Ga), have been studied self consistently by employing state-of-the-art full-potential linearized approach of augmented plane wave plus local orbitals (FP-LAPW + lo) method. The exchange-correlation potential is treated with the local density and generalized gradient approximations (LDA and GGA). Our predicted ground state properties such as lattice constants, bulk modulus and elastic constants appear more accurate when we employed the GGA rather than the LDA, and these results are in very good agreement with the available experimental and theoretical data. Further, thermodynamic properties of Fe2VAl and Fe2VGa are predicted with pressure and temperature in the ranges of 0-40 GPa and 0-1500 K using the quasi-harmonic Debye model. We have obtained successfully the variations of the heat capacities, primitive cell volume and volume expansion coefficient.

First-principles calculations on thermodynamic properties of BaTiO3 rhombohedral phase.

PubMed

Bandura, Andrei V; Evarestov, Robert A

2012-07-05

The calculations based on the linear combination of atomic orbitals have been performed for the low-temperature phase of BaTiO(3) crystal. Structural and electronic properties, as well as phonon frequencies were obtained using hybrid PBE0 exchange-correlation functional. The calculated frequencies and total energies at different volumes have been used to determine the equation of state and thermal contribution to the Helmholtz free energy within the quasiharmonic approximation. For the first time, the bulk modulus, volume thermal expansion coefficient, heat capacity, and Grüneisen parameters in BaTiO(3) rhombohedral phase have been estimated at zero pressure and temperatures form 0 to 200 K, based on the results of first-principles calculations. Empirical equation has been proposed to reproduce the temperature dependence of the calculated quantities. The agreement between the theoretical and experimental thermodynamic properties was found to be satisfactory. Copyright © 2012 Wiley Periodicals, Inc.

Orientation and size dependence of the elastic properties of zinc oxide nanobelts

NASA Astrophysics Data System (ADS)

Kulkarni, A. J.; Zhou, M.; Ke, F. J.

2005-12-01

Molecular dynamics simulations are performed to characterize the response of zinc oxide (ZnO) nanobelts to tensile loading. The ultimate tensile strength (UTS) and Young's modulus are obtained as functions of size and growth orientation. Nanobelts in three growth orientations are generated by assembling the unit wurtzite cell along the [0001], [01\\bar {1} 0] , and [2\\bar {1} \\bar {1}0] crystalline axes. Following the geometric construction, dynamic relaxation is carried out to yield free-standing nanobelts at 300 K. Two distinct configurations are observed in the [0001] and [01\\bar {1} 0] orientations. When the lateral dimensions are above 10 Å, nanobelts with rectangular cross-sections are seen. Below this critical size, tubular structures involving two concentric shells similar to double-walled carbon nanotubes are obtained. Quasi-static deformations of belts with [2\\bar {1} \\bar {1} 0] and [01\\bar {1} 0] orientations consist of three stages, including initial elastic stretching, wurtzite-ZnO to graphitic-ZnO structural transformation, and cleavage fracture. On the other hand, [0001] belts do not undergo any structural transformation and fail through cleavage along (0001) planes. Calculations show that the UTS and Young's modulus of the belts are size dependent and are higher than the corresponding values for bulk ZnO. Specifically, as the lateral dimensions increase from 10 to 40 Å, decreases between 38-76% and 24-63% are observed for the UTS and Young's modulus, respectively. This effect is attributed to the size-dependent compressive stress induced by tensile surface stress in the nanobelts. [01\\bar {1} 0] and [2\\bar {1} \\bar {1} 0] nanobelts with multi-walled tubular structures are seen to have higher values of elastic moduli (~340 GPa) and UTS (~36 GPa) compared to their wurtzite counterparts, echoing a similar trend in multi-walled carbon nanotubes.

A network model of correlated growth of tissue stiffening in pulmonary fibrosis

NASA Astrophysics Data System (ADS)

Oliveira, Cláudio L. N.; Bates, Jason H. T.; Suki, Béla

2014-06-01

During the progression of pulmonary fibrosis, initially isolated regions of high stiffness form and grow in the lung tissue due to collagen deposition by fibroblast cells. We have previously shown that ongoing collagen deposition may not lead to significant increases in the bulk modulus of the lung until these local remodeled regions have become sufficiently numerous and extensive to percolate in a continuous path across the entire tissue (Bates et al 2007 Am. J. Respir. Crit. Care Med. 176 617). This model, however, did not include the possibility of spatially correlated deposition of collagen. In the present study, we investigate whether spatial correlations influence the bulk modulus in a two-dimensional elastic network model of lung tissue. Random collagen deposition at a single site is modeled by increasing the elastic constant of the spring at that site by a factor of 100. By contrast, correlated collagen deposition is represented by stiffening the springs encountered along a random walk starting from some initial spring, the rationale being that excess collagen deposition is more likely in the vicinity of an already stiff region. A combination of random and correlated deposition is modeled by performing random walks of length N from randomly selected initial sites, the balance between the two processes being determined by N. We found that the dependence of bulk modulus, B(N,c), on both N and the fraction of stiff springs, c, can be described by a strikingly simple set of empirical equations. For c<0.3, B(N,c) exhibits exponential growth from its initial value according to B(N,c)\\approx {{B}_{0}}exp (2c)\\left[ 1+{{c}^{\\beta }}ln \\left( {{N}^{{{a}_{I}}}} \\right) \\right], where \\beta =0.994+/- 0.024 and {{a}_{I}}=0.54+/- 0.026. For intermediate concentrations of stiffening, 0.3\\leqslant c\\leqslant 0.8, another exponential rule describes the bulk modulus as B(N,c)=4{{B}_{0}}exp \\left[ {{a}_{II}}\\left( c-{{c}_{c}} \\right) \\right], where {{a}_{II}} and {{c}_{c}} are parameters that depend on N. For c>0.8, B(N,c) is linear in c and independent of N, such that B(N,c)=100\\;{{B}_{0}}-100{{a}_{III}}(1-c){{B}_{0}}, where {{a}_{III}}=2.857. For small concentrations, the physiologically most relevant regime, the forces in the network springs are distributed according to a power law. When c = 0.3, the exponent of this power law increases from -4.5, when N = 1, and saturates to about -2, as N increases above 40. These results suggest that the spatial correlation of collagen deposition in the fibrotic lung has a strong effect on the rate of lung function decline and on the mechanical environment in which the cells responsible for remodeling find themselves.

Study of phonon modes and elastic properties of Sc36Al24Co20Y20 and Gd36Al24Co20Y20 rare-earth bulk metallic glasses

NASA Astrophysics Data System (ADS)

Suthar, P. H.; Gajjar, P. N.; Thakore, B. Y.; Jani, A. R.

2013-04-01

A phonon modes and elastic properties of two different rare-earth based bulk metallic glasses Sc36Al24Co20Y20 and Gd36Al24Co20Y20 are computed using Hubbard-Beeby approach and our well established model potential. The local field correlation functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar Sen et al (S) are employed to investigate the influence of the screening effects on the vibrational dynamics of Sc36Al24Co20Y20 and Gd36Al24Co20Y20 bulk metallic glasses. The results for bulk modulus BT, modulus of rigidity G, Poisson's ratio ξ, Young's modulus Y, Debye temperature ΘD, propagation velocity of elastic waves and dispersion curves are reported. The computed elastic properties are found to be in good agreement with experimental and other available data.

Static analysis of a sonar dome rubber window

NASA Technical Reports Server (NTRS)

Lai, J. L.

1978-01-01

The application of NASTRAN (level 16.0.1) to the static analysis of a sonar dome rubber window (SDRW) was demonstrated. The assessment of the conventional model (neglecting the enclosed fluid) for the stress analysis of the SDRW was made by comparing its results to those based on a sophisticated model (including the enclosed fluid). The fluid was modeled with isoparametric linear hexahedron elements with approximate material properties whose shear modulus was much smaller than its bulk modulus. The effect of the chosen material property for the fluid is discussed.

Strain amplitude-dependent anelasticity in Cu-Ni solid solution due to thermally activated and athermal dislocation-point obstacle interactions

NASA Astrophysics Data System (ADS)

Kustov, S.; Gremaud, G.; Benoit, W.; Golyandin, S.; Sapozhnikov, K.; Nishino, Y.; Asano, S.

1999-02-01

Experimental investigations of the internal friction and the Young's modulus defect in single crystals of Cu-(1.3-7.6) at. % Ni have been performed for 7-300 K over a wide range of oscillatory strain amplitudes. Extensive data have been obtained at a frequency of vibrations around 100 kHz and compared with the results obtained for the same crystals at a frequency of ˜1 kHz. The strain amplitude dependence of the anelastic strain amplitude and the average friction stress acting on a dislocation due to solute atoms are also analyzed. Several stages in the strain amplitude dependence of the internal friction and the Young's modulus defect are revealed for all of the alloy compositions, at different temperatures and in different frequency ranges. For the 100 kHz frequency, low temperatures and low strain amplitudes (˜10-7-10-5), the amplitude-dependent internal friction and the Young's modulus defect are essentially temperature independent, and are ascribed to a purely hysteretic internal friction component. At higher strain amplitudes, a transition stage and a steep strain amplitude dependence of the internal friction and the Young's modulus defect are observed, followed by saturation at the highest strain amplitudes employed. These stages are temperature and frequency dependent and are assumed to be due to thermally activated motion of dislocations. We suggest that the observed regularities in the entire strain amplitude, temperature and frequency ranges correspond to a motion of dislocations in a two-component system of obstacles: weak but long-range ones, due to the elastic interaction of dislocations with solute atoms distributed in the bulk of the crystal; and strong short-range ones, due to the interaction of dislocations with solute atoms distributed close to dislocation glide planes. Based on these assumptions, a qualitative explanation is given for the variety of experimental observations.

Measurement at low strain rates of the elastic properties of dental polymeric materials.

PubMed

Chabrier, F; Lloyd, C H; Scrimgeour, S N

1999-01-01

To evaluate a simple static test (i.e. a slow strain rate test) designed to measure Young's modulus and the bulk modulus of polymeric materials (The NOL Test). Though it is a 'mature' test as yet it has never been applied to dental materials. A small cylindrical specimen is contained in a close-fitting steel constraining ring and compressive force applied to the ends by steel pistons. The initial (unconstrained) deformation is controlled by Young's modulus. Lateral spreading leads to constraint from the ring and subsequent deformation is controlled by the bulk modulus. A range of dental materials and reference polymers were selected and both moduli measured. From these data Poisson's ratios were calculated. The test proved be a simple reliable method for obtaining values for these properties. For composite the value of Young's modulus was lower, bulk modulus relatively similar and Poisson's ratio higher than that obtained from high strain rate techniques (as expected for a strain rate sensitive material). This test does fulfil a requirement for a simple test to define fully the elastic properties of dental polymeric materials. Measurements are made at the strain rates used in conventional static tests and values reflect this test condition. The higher values obtained for Poisson's ratio at this slow strain rate has implications for FEA, in that analysis is concerned with static or slow rate loading situations.

Compressibility determination by electrical resistance measurement: a universal method for both crystalline and amorphous solids

NASA Astrophysics Data System (ADS)

Yan, Xiaozhi; He, Duanwei; Xu, Chao; Ren, Xiangting; Zhou, Xiaoling; Liu, Shenzuo

2012-12-01

A new method is introduced for investigating the compressibility of solids under high pressure by in situ electrical resistance measurement of a manganin wire, which is wrapped around the sample. This method does not rely on the lattice parameters measurement, and the continuous volume change of the sample versus pressure can be obtained. Therefore, it is convenient to look at the compressibility of solids, especially for the X-ray diffraction amorphous materials. The I-II and II-III phase transition of Bi accompanying with volume change of 4.5% and 3.5% has been detected using the method, respectively, while the volume change for the phase transition of Tl occurring at 3.67 GPa is determined as 0.5%. The fit of the third-order Birch-Murnaghan equation of state to our data yields a zero-pressure bulk modulus K 0=28.98±0.03 GPa for NaCl and 6.97±0.02 GPa for amorphous red phosphorus.

Formulation and characterization of a porous, elastomeric biomaterial for vocal fold tissue engineering research

PubMed Central

Gaston, Joel; Bartlett, Rebecca S.; Klemuk, Sarah A.

2014-01-01

Objectives Biomaterials able to mimic the mechanical properties of vocal fold tissue may be particularly useful for furnishing three dimensional microenvironment allowing for in vitro investigation of cell and molecular responses to vibration. Motivated by the dearth of biomaterials available to be used in an in vitro model for vocal fold tissue, we investigated polyether polyurethane (PEU) matrices which are porous, mechanically tuneable biomaterials that are inexpensive and require only standard laboratory equipment for fabrication. Methods Rheology, dynamic mechanical analysis and scanning electron microscopy were performed on PEU matrices at 5%, 10% and 20% w/v mass concentrations. Results For 5%, 10%, and 20% w/v concentrations, shear storage modulus were 2 kPa, 3.4 kPa, and 6 kPa, respectively with shear loss modulus being 0.2 kPa, 0.38 kPa and 0.62 kPa, respectively. Storage modulus responded to applied frequency as a linear function. Mercury intrusion porosimetry revealed that all three mass concentrations of PEU have similar overall percent porosity, but differ in pore architecture. Conclusions 20 µm diameter pores are ideal for cell seeding, and range of mechanical properties indicates that the higher mass concentration PEU formulations are best suited for mimicking the viscoelastic properties of vocal fold tissue for in vitro research. PMID:24944281

Compressibility behaviour of conducting ceramic TiB2

NASA Astrophysics Data System (ADS)

Arpita Aparajita, A. N.; Kumar, N. R. Sanjay; Shekar, N. V. Chandra; Kalavathi, S.

2017-09-01

To address the large spread in the bulk modulus value of TiB2 reported in literature, high pressure compressibility study of a phase pure polycrystalline sample has been carried out using in situ high pressure x-ray diffraction technique (HPXRD) in angle dispersive mode. The study has been done up to 23 GPa at ambient temperature with methanol-ethanol-water (MEW) as pressure transmitting medium. The hexagonal lattice has been found to be stable in the pressure range studied. The isothermal bulk modulus is estimated to be 333(6) GPa by employing 3rd order Birch-Murnaghan equation of state. The obtained high value of bulk modulus is understood in terms of band filling effect, and the nature of bonding between B-B and Ti-B in TiB2. Compressibility along ‘a’ and ‘c’ axis is found to be anisotropic with compressibility values of 0.93(2) TPa-1 and 1.14(2) TPa-1 respectively. From the estimated bond lengths for Ti-B and B-B it is found that B-B bonds are less compressible compared to Ti-B bonds which is in accordance with the respective nature of Ti-B and B-B bonds. A change in the rate of bond contraction was seen around 12 GPa which is due to the bond hardening for both Ti-B and B-B bonds with pressure.

Adiabatic bulk modulus of elasticity for 2D liquid dusty plasmas

NASA Astrophysics Data System (ADS)

Feng, Yan; Huang, Dong; Li, Wei

2018-05-01

From the recently obtained equation of state (EOS) for two-dimensional (2D) liquid dusty plasmas, their various physical quantities have been derived analytically, such as the specific heat CV, the Grüneisen parameter, the bulk modulus of elasticity, and the isothermal compressibility. Here, the coefficient of volumetric thermal expansion αV and the relative pressure coefficient αP of 2D liquid dusty plasmas are derived from their EOS. Using the obtained CV, αV, and αP, the analytical expression of their heat capacity under constant-pressure conditions CP is obtained. Thus, the heat capacity ratio, expressed as CP/CV , is analytically achieved. Then the adiabatic bulk modulus of elasticity is derived, so that the adiabatic sound speeds are obtained. These obtained results are compared with previous findings using a different approach.

Investigation of the bulk modulus of silica aerogel using molecular dynamics simulations of a coarse-grained model.

PubMed

Ferreiro-Rangel, Carlos A; Gelb, Lev D

2013-06-13

Structural and mechanical properties of silica aerogels are studied using a flexible coarse-grained model and a variety of simulation techniques. The model, introduced in a previous study (J. Phys. Chem. C 2007, 111, 15792-15802), consists of spherical "primary" gel particles that interact through weak nonbonded forces and through microscopically motivated interparticle bonds that may break and form during the simulations. Aerogel models are prepared using a three-stage protocol consisting of separate simulations of gelation, aging, and a final relaxation during which no further bond formation is permitted. Models of varying particle size, density, and size dispersity are considered. These are characterized in terms of fractal dimensions and pore size distributions, and generally good agreement with experimental data is obtained for these metrics. The bulk moduli of these materials are studied in detail. Two different techniques for obtaining the bulk modulus are considered, fluctuation analysis and direct compression/expansion simulations. We find that the fluctuation result can be subject to systematic error due to coupling with the simulation barostat but, if performed carefully, yields results equivalent with those of compression/expansion experiments. The dependence of the bulk modulus on density follows a power law with an exponent between 3.00 and 3.15, in agreement with reported experimental results. The best correlate for the bulk modulus appears to be the volumetric bond density, on which there is also a power law dependence. Polydisperse models exhibit lower bulk moduli than comparable monodisperse models, which is due to lower bond densities in the polydisperse materials.

Correlation between macro- and nano-scopic measurements of carbon nanostructured paper elastic modulus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Omar, Yamila M.; Al Ghaferi, Amal, E-mail: aalghaferi@masdar.ac.ae, E-mail: mchiesa@masdar.ac.ae; Chiesa, Matteo, E-mail: aalghaferi@masdar.ac.ae, E-mail: mchiesa@masdar.ac.ae

2015-07-20

Extensive work has been done in order to determine the bulk elastic modulus of isotropic samples from force curves acquired with atomic force microscopy. However, new challenges are encountered given the development of new materials constructed of one-dimensional anisotropic building blocks, such as carbon nanostructured paper. In the present work, we establish a reliable framework to correlate the elastic modulus values obtained by amplitude modulation atomic force microscope force curves, a nanoscopic technique, with that determined by traditional macroscopic tensile testing. In order to do so, several techniques involving image processing, statistical analysis, and simulations are used to find themore » appropriate path to understand how macroscopic properties arise from anisotropic nanoscale components, and ultimately, being able to calculate the value of bulk elastic modulus.« less

Stability, Elastic Properties, and Deformation of LiBN2: A Potential High-Energy Material.

PubMed

Zhu, Chunye; Zhu, Wenjun; Yang, Yanqiang

2018-05-15

Searching for high-energy-density materials is of great interest in scientific research and for industrial applications. Using an unbiased structure prediction method and first-principles calculations, we investigated the phase stability of LiBN 2 from 0 to100 GPa. Two new structures with space groups P4̅2 1 m and Pnma were discovered. The theoretical calculations revealed that Pnma LiBN 2 is stable with respect to a mixture of 1 / 3 Li 3 N, BN, and 1 / 3 N 2 above 22 GPa. The electronic band structure revealed that Pnma LiBN 2 has an indirect band gap of 2.3 eV, which shows a nonmetallic feature. The Pnma phase has a high calculated bulk modulus and shear modulus, indicating its incompressible nature. The microscopic mechanism of the structural deformation was demonstrated by ideal tensile shear strength calculations. It is worth mentioning that Pnma LiBN 2 is dynamically stable under ambient conditions. The decomposition of this phase is exothermic, releasing an energy of approximately 1.23 kJ/g at the PBE level. The results provide new thoughts for designing and synthesizing novel high-energy compounds in ternary systems.

Deduced elasticity of sp3-bonded amorphous diamond

NASA Astrophysics Data System (ADS)

Ballato, J.; Ballato, A.

2017-11-01

Amorphous diamond was recently synthesized using high temperature and pressure techniques [Z. Zeng, L. Yang, Q. Zeng, H. Lou, H. Sheng, J. Wen, D. J. Miller, Y. Meng, W. Yang, W. L. Mao, and H. K. Mao, Nat. Commun. 8, 322 (2017)]. Here, selected physical properties of this new phase of carbon are deduced using an extension of the Voigt-Reuss-Hill (VRHx) methodology whereby single crystal values are averaged over all orientations to yield values for the amorphous analog. Specifically, the elastic constants were deduced to be c11 = 1156.5 GPa, c12 = 87.6 GPa, and c44 = 534.5 GPa, whereas the Young's modulus, bulk modulus, and Poisson's ratio were also estimated to be 1144.2 GPa, 443.9 GPa, and 0.0704, respectively. These numbers are compared with experimental and theoretical literature values for other allotropic forms, specifically, Lonsdaleite, and two forms each of graphite and amorphous carbon. It is unknown at this time how the high temperature and pressure synthesis approach employed influences the structure, hence properties, of amorphous diamond at room temperature. However, the values provided herein constitute a baseline against which future structure/property/processing analyses can be compared.

Semiconducting cubic titanium nitride in the Th 3 P 4 structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhadram, Venkata S.; Liu, Hanyu; Xu, Enshi

We report the discovery of a long-sought-after phase of titanium nitride with stoichiometry Ti 3 N 4 using diamond anvil cell experiments combined with in situ high-resolution x-ray diffraction and Raman spectroscopy techniques, supported by ab initio calculations. Ti 3 N 4 crystallizes in the cubic Th 3 P 4 structure [space group I ¯ 4 3 d (220)] from a mixture of TiN and N 2 above ≈ 75 GPa and ≈ 2400 K. The density ( ≈ 5.22 g/cc) and bulk modulus ( K 0 = 290 GPa) of cubic- Ti 3 N 4 ( c - Timore » 3 N 4 ) at 1 atm, estimated from the pressure-volume equation of state, are comparable to rocksalt TiN. Ab initio calculations based on the GW approximation and using hybrid functionals indicate that c - Ti 3 N 4 is a semiconductor with a direct band gap between 0.8 and 0.9 eV, which is larger than the previously predicted values. The c - Ti 3 N 4 phase is not recoverable to ambient pressure due to dynamic instabilities, but recovery of Ti 3 N 4 in the defect rocksalt (or related) structure may be feasible.« less

The kinetics of crystallization of molten binary and ternary oxide systems and their application to the origination of high modulus glass fibers

NASA Technical Reports Server (NTRS)

Bacon, J. F.

1971-01-01

Emphasis on the consideration of glass formation on a kinetic process made it possible to think of glass compositions different from those normally employed in the manufacture of glass fibers. Approximately 450 new glass compositions were prepared and three dozen of these compositions have values for Young's modulus measured on bulk specimens greater than nineteen million pounds per square inch. Of the new glasses about a hundred could be drawn into fibers by mechanical methods at high speeds. The fiber which has a Young's modulus measured on the fiber of 18.6 million pounds per square inch and has been prepared in quantity as a monofilament (to date more than 150 million lineal feet of 0.2 to 0.4 mil fiber have been produced). This fiber has also been successfully incorporated both in epoxy and polyimide matrices. The epoxy resin composite has shown a modulus forty percent better than that achievable using the most common grade of competitive glass fiber, and twenty percent better than that obtainable with the best available grade of competitive glass fiber. Other glass fibers of even higher modulus have been developed.

Axionic D3-D7 inflation

NASA Astrophysics Data System (ADS)

Burgess, C. P.; Cline, J. M.; Postma, M.

2009-03-01

We study the motion of a D3 brane moving within a Type IIB string vacuum compactified to 4D on K3 × T2/Z2 in the presence of D7 and O7 planes. We work within the effective 4D supergravity describing how the mobile D3 interacts with the lightest bulk moduli of the compactification, including the effects of modulus-stabilizing fluxes. We seek inflationary solutions to the resulting equations, performing our search numerically in order to avoid resorting to approximate parameterizations of the low-energy potential. We consider uplifting from D-terms and from the supersymmetry-breaking effects of anti-D3 branes. We find examples of slow-roll inflation (with anti-brane uplifting) with the mobile D3 moving along the toroidal directions, falling towards a D7-O7 stack starting from the antipodal point. The inflaton turns out to be a linear combination of the brane position and the axionic partner of the K3 volume modulus, and the similarity of the potential along the inflaton direction with that of racetrack inflation leads to the prediction ns <= 0.95 for the spectral index. The slow roll is insensitive to most of the features of the effective superpotential, and requires a one-in-104 tuning to ensure that the torus is close to square in shape. We also consider D-term inflation with the D3 close to the attractive D7, but find that for a broad (but not exhaustive) class of parameters the conditions for slow roll tend to destabilize the bulk moduli. In contrast to the axionic case, the best inflationary example of this kind requires the delicate adjustment of potential parameters (much more than the part-per-mille level), and gives inflation only at an inflection point of the potential (and so suffers from additional fine-tuning of initial conditions to avoid an overshoot problem).

First-Principles Study of Structural, Electronic, Optical, and Thermal Properties of BeSiSb2 and MgSiSb2

NASA Astrophysics Data System (ADS)

Benlamari, S.; Boukhtouta, M.; Taïri, L.; Meradji, H.; Amirouche, L.; Ghemid, S.

2018-03-01

Structural, electronic, optical, and thermal properties of ternary II-IV-V2 (BeSiSb2 and MgSiSb2) chalcopyrite semiconductors have been calculated using the full-potential linearized augmented plane wave scheme␣in the generalized gradient approximation. The optimized equilibrium structural parameters ( a, c, and u) are in good agreement with theoretical results obtained using other methods. The band structure and density of states reveal that BeSiSb2 has an indirect (Γ-Z) bandgap of about 0.61 eV, whereas MgSiSb2 has a direct (Γ-Γ) bandgap of 0.80 eV. The dielectric function, refractive index, and extinction coefficient were calculated to investigate the optical properties, revealing that BeSiSb2 and MgSiSb2 present very weak birefringence. The temperature dependence of the volume, bulk modulus, Debye temperature, and heat capacities ( C v and C p) was predicted using the quasiharmonic Debye model at different pressures. Significant differences in properties are observed at high pressure and high temperature. We predict that, at 300 K and 0 GPa, the heat capacity at constant volume C v, heat capacity at constant pressure C P, Debye temperature θ D, and Grüneisen parameter γ will be about 94.91 J/mol K, 98.52 J/mol K, 301.30 K, and 2.11 for BeSiSb2 and about 96.08 J/mol K, 100.47 J/mol K, 261.38 K, and 2.20 for MgSiSb2, respectively.

Estimation of Dry Fracture Weakness, Porosity, and Fluid Modulus Using Observable Seismic Reflection Data in a Gas-Bearing Reservoir

NASA Astrophysics Data System (ADS)

Chen, Huaizhen; Zhang, Guangzhi

2017-05-01

Fracture detection and fluid identification are important tasks for a fractured reservoir characterization. Our goal is to demonstrate a direct approach to utilize azimuthal seismic data to estimate fluid bulk modulus, porosity, and dry fracture weaknesses, which decreases the uncertainty of fluid identification. Combining Gassmann's (Vier. der Natur. Gesellschaft Zürich 96:1-23, 1951) equations and linear-slip model, we first establish new simplified expressions of stiffness parameters for a gas-bearing saturated fractured rock with low porosity and small fracture density, and then we derive a novel PP-wave reflection coefficient in terms of dry background rock properties (P-wave and S-wave moduli, and density), fracture (dry fracture weaknesses), porosity, and fluid (fluid bulk modulus). A Bayesian Markov chain Monte Carlo nonlinear inversion method is proposed to estimate fluid bulk modulus, porosity, and fracture weaknesses directly from azimuthal seismic data. The inversion method yields reasonable estimates in the case of synthetic data containing a moderate noise and stable results on real data.

Soft resonator of omnidirectional resonance for acoustic metamaterials with a negative bulk modulus

PubMed Central

Jing, Xiaodong; Meng, Yang; Sun, Xiaofeng

2015-01-01

Monopolar resonance is of fundamental importance in the acoustic field. Here, we present the realization of a monopolar resonance that goes beyond the concept of Helmholtz resonators. The balloon-like soft resonator (SR) oscillates omnidirectionally and radiates from all parts of its spherical surface, eliminating the need for a hard wall for the cavity and baffle effects. For airborne sound, such a low-modulus resonator can be made extremely lightweight. Deep subwavelength resonance is achieved when the SR is tuned by adjusting the shell thickness, benefiting from the large density contrast between the shell material and the encapsulated gas. The SR resonates with near-perfect monopole symmetry, as demonstrated by the theoretical and experimental results, which are in excellent agreement. For a lattice of SRs, a band gap occurs and blocks near-total transmission, and the effective bulk modulus exhibits a prominent negative band, while the effective mass density remains unchanged. Our study shows that the SR is suitable for building 3D acoustic metamaterials and provides a basis for constructing left-handed materials as a new means of creating a negative bulk modulus. PMID:26538085

First-principles investigation of mechanical and electronic properties of tetragonal NbAl3 under tension

NASA Astrophysics Data System (ADS)

Jiao, Zhen; Liu, Qi-Jun; Liu, Fu-Sheng; Tang, Bin

2018-06-01

Using the density functional theory calculations, the mechanical and electronic properties of NbAl3 under different tensile loads were investigated. The calculated lattice parameters, elastic constants and mechanical properties (bulk modulus, shear modulus, Young's modulus, Poisson's ratio, Pugh's criterion and Cauchy's pressure) indicated that our results were in agreement with the published experimental and theoretical data at zero tension. With respect to NbAl3 under tension in this paper, the crystal structure was changed from tetragonal to orthorhombic under tension along the [100] and [101] directions. The NbAl3 crystal has been classified as brittle material under tension from 0 to 20 GPa. The obtained Young's modulus and Debye temperature monotonically decreased with increasing tension stress. Combining with mechanical and electronic properties in detail, the decreased mechanical properties were mainly due to the weakening of covalency.

First-principles investigations on structural, elastic, electronic properties and Debye temperature of orthorhombic Ni3Ta under pressure

NASA Astrophysics Data System (ADS)

Li, Pan; Zhang, Jianxin; Ma, Shiyu; Jin, Huixin; Zhang, Youjian; Zhang, Wenyang

2018-06-01

The structural, elastic, electronic properties and Debye temperature of Ni3Ta under different pressures are investigated using the first-principles method based on density functional theory. Our calculated equilibrium lattice parameters at 0 GPa well agree with the experimental and previous theoretical results. The calculated negative formation enthalpies and elastic constants both indicate that Ni3Ta is stable under different pressures. The bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν are calculated by the Voigt-Reuss-Hill method. The bigger ratio of B/G indicates Ni3Ta is ductile and the pressure can improve the ductility of Ni3Ta. In addition, the results of density of states and the charge density difference show that the stability of Ni3Ta is improved by the increasing pressure. The Debye temperature ΘD calculated from elastic modulus increases along with the pressure.

The geochemical and petrological characteristics of prenatal caldera volcano: a case of the newly formed small dacitic caldera, Hijiori, Northeast Japan

NASA Astrophysics Data System (ADS)

Miyagi, Isoji; Kita, Noriko; Morishita, Yuichi

2017-09-01

Evaluating the magma depth and its physical properties is critical to conduct a better geophysical assessment of magma chambers of caldera volcanoes that may potentially cause future volcanic hazards. To understand pre-eruptive conditions of a magma chamber before its first appearance at the surface, this paper describes the case of Hijiori caldera volcano in northeastern Japan, which emerged approximately 12,000 years ago at a place where no volcano ever existed. We estimated the depth, density, bulk modulus, vesicularity, crystal content, and bulk H_2O content of the magma chamber using petrographic interpretations, bulk and microchemical compositions, and thermodynamic calculations. The chemical mass balance calculations and thermodynamic modeling of the erupted magmas indicate that the upper portion of the Hijiori magmatic plumbing system was located at depths between 2 and 4 km, and had the following characteristics: (1) pre-eruptive temperature: about 780 °C; (2) bulk magma composition: 66 ± 1.5 wt% SiO2; (3) bulk magmatic H_2O: approximately 2.5 wt%, and variable characteristics that depend on depth; (4) crystal content: ≤57 vol%; (5) bulk modulus of magma: 0.1-0.8 GPa; (6) magma density: 1.8-2.3 g/cm3; and (7) amount of excess magmatic H_2O: 11-32 vol% or 48-81 mol%. The range of melt water contents found in quartz-hosted melt inclusions (2-9 wt%) suggests the range of depth phenocrysts growth to be wide (2˜13 km). Our data suggest the presence of a vertically elongated magma chamber whose top is nearly solidified but highly vesiculated; this chamber has probably grown and re-mobilized by repeated injections of a small amount of hot dacitic magma originated from the depth.

Effective Biot theory and its generalization to poroviscoelastic models

NASA Astrophysics Data System (ADS)

Liu, Xu; Greenhalgh, Stewart; Zhou, Bing; Greenhalgh, Mark

2018-02-01

A method is suggested to express the effective bulk modulus of the solid frame of a poroelastic material as a function of the saturated bulk modulus. This method enables effective Biot theory to be described through the use of seismic dispersion measurements or other models developed for the effective saturated bulk modulus. The effective Biot theory is generalized to a poroviscoelastic model of which the moduli are represented by the relaxation functions of the generalized fractional Zener model. The latter covers the general Zener and the Cole-Cole models as special cases. A global search method is described to determine the parameters of the relaxation functions, and a simple deterministic method is also developed to find the defining parameters of the single Cole-Cole model. These methods enable poroviscoelastic models to be constructed, which are based on measured seismic attenuation functions, and ensure that the model dispersion characteristics match the observations.

Electronic, elastic and optical properties of divalent (R+2X) and trivalent (R+3X) rare earth monochalcogenides

NASA Astrophysics Data System (ADS)

Kumar, V.; Chandra, S.; Singh, J. K.

2017-08-01

Based on plasma oscillations theory of solids, simple relations have been proposed for the calculation of bond length, specific gravity, homopolar energy gap, heteropolar energy gap, average energy gap, crystal ionicity, bulk modulus, electronic polarizability and dielectric constant of rare earth divalent R+2X and trivalent R+3X monochalcogenides. The specific gravity of nine R+2X, twenty R+3X, and bulk modulus of twenty R+3X monochalcogenides have been calculated for the first time. The calculated values of all parameters are compared with the available experimental and the reported values. A fairly good agreement has been obtained between them. The average percentage deviation of two parameters: bulk modulus and electronic polarizability for which experimental data are known, have also been calculated and found to be better than the earlier correlations.

Spinel and post-spinel phase assemblages in Zn 2TiO 4: an experimental and theoretical study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yanyao; Liu, Xi; Shieh, Sean R.

Zn2TiO4 spinel (Zn2TiO4-Sp) was synthesized by a solid-state reaction method (1573 K, room P and 72 h) and quasi-hydrostatically compressed to ~24 GPa using a DAC coupled with a synchrotron X-ray radiation (ambient T). We found that the Zn2TiO4-Sp was stable up to ~21 GPa and transformed to another phase at higher P. With some theoretical simulations, we revealed that this high-P phase adopted the CaTi2O4-type structure (Zn2TiO4-CT). Additionally, the isothermal bulk modulus (KT) of the Zn2TiO4-Sp was experimentally obtained as 156.0(44) GPa and theoretically obtained as 159.1(4) GPa, with its first pressure derivative K'TKT' as 3.8(6) and 4.37(4), respectively.more » The volumetric and axial isothermal bulk moduli of the Zn2TiO4-CT were theoretically obtained as KT = 150(2) GPa (K'TKT' = 5.4(2); for the volume), KT-a = 173(2) GPa (K'T-aKT-a' = 3.9(1); for the a-axis), KT-b = 74(2) GPa (K'T-bKT-b' = 7.0(2); for the b-axis), and KT-c = 365(8) GPa (K'T-cKT-c' = 1.5(4); for the c-axis), indicating a strong elastic anisotropy. The Zn2TiO4-CT was found as ~10.0 % denser than the Zn2TiO4-Sp at ambient conditions. The spinel and post-spinel phase assemblages for the Zn2TiO4 composition at high T have been deduced as Zn2TiO4-Sp, ZnTiO3-ilmenite + ZnO-wurtzite, ZnTiO3-ilmenite + ZnO-rock salt, ZnTiO3-perovskite + ZnO-rock salt, and Zn2TiO4-CT as P increases, which presumably implies a potential stability field for a CT-type Mg2SiO4 at very high P.« less

Noninvasive Assessment of Collagen Gel Microstructure and Mechanics Using Multiphoton Microscopy

PubMed Central

Raub, Christopher B.; Suresh, Vinod; Krasieva, Tatiana; Lyubovitsky, Julia; Mih, Justin D.; Putnam, Andrew J.; Tromberg, Bruce J.; George, Steven C.

2007-01-01

Multiphoton microscopy of collagen hydrogels produces second harmonic generation (SHG) and two-photon fluorescence (TPF) images, which can be used to noninvasively study gel microstructure at depth (∼1 mm). The microstructure is also a primary determinate of the mechanical properties of the gel; thus, we hypothesized that bulk optical properties (i.e., SHG and TPF) could be used to predict bulk mechanical properties of collagen hydrogels. We utilized polymerization temperature (4–37°C) and glutaraldehyde to manipulate collagen hydrogel fiber diameter, space-filling properties, and cross-link density. Multiphoton microscopy and scanning electron microscopy reveal that as polymerization temperature decreases (37–4°C) fiber diameter and pore size increase, whereas hydrogel storage modulus (G′, from 23 ± 3 Pa to 0.28 ± 0.16 Pa, respectively, mean ± SE) and mean SHG decrease (minimal change in TPF). In contrast, glutaraldehyde significantly increases the mean TPF signal (without impacting the SHG signal) and the storage modulus (16 ± 3.5 Pa before to 138 ± 40 Pa after cross-linking, mean ± SD). We conclude that SHG and TPF can characterize differential microscopic features of the collagen hydrogel that are strongly correlated with bulk mechanical properties. Thus, optical imaging may be a useful noninvasive tool to assess tissue mechanics. PMID:17172303

Synthetic lead bromapatite: X-ray structure at ambient pressure and compressibility up to about 20 GPa

NASA Astrophysics Data System (ADS)

Liu, Xi; Fleet, Michael E.; Shieh, Sean R.; He, Qiang

2011-05-01

Lead bromapatite [Pb10(PO4)6Br2] has been synthesized via solid-state reaction at pressures up to 1.0 GPa, and its structure determined by single-crystal X-ray diffraction at ambient temperature and pressure. The large bromide anion is accommodated in the c-axis channel by lateral displacements of structural elements, particularly of Pb2 cations and PO4 tetrahedra. The compressibility of bromapatite was also investigated up to about 20.7 GPa at ambient temperature, using a diamond-anvil cell and synchrotron X-ray radiation. The compressibility of lead bromapatite is significantly different from that of lead fluorapatite. The pressure-volume data of lead bromapatite ( P < 10 GPa) fitted to the third-order Birch-Murnaghan equation yield an isothermal bulk modulus ( K T ) of 49.8(16) GPa and first pressure derivative ( KT^' } ) of 10.1(10). If KT^' } is fixed at 4, the derived K T is 60.8(11) GPa. The relative difference of the bulk moduli of these two lead apatites is thus about 12%, which is about two times the relative difference of the bulk moduli (~5%) of the calcium apatites fluorapatite [Ca10(PO4)6F2], chlorapatite [Ca10(PO4)6Cl2] and hydroxylapatite [Ca10(PO4)6(OH)2]. Another interesting feature apparently related to the replacement of F by Br in lead apatite is the switch in the principle axes of the strain ellipsoid: the c-axis is less compressible than the a-axis in lead bromapatite but more compressible in lead fluorapatite.

Measurement of mechanical properties of metallic glass at elevated temperature using sonic resonance method

NASA Astrophysics Data System (ADS)

Kaluvan, Suresh; Zhang, Haifeng; Mridha, Sanghita; Mukherjee, Sundeep

2017-04-01

Bulk metallic glasses are fully amorphous multi-component alloys with homogeneous and isotropic structure down to the atomic scale. Some attractive attributes of bulk metallic glasses include high strength and hardness as well as excellent corrosion and wear resistance. However, there are few reports and limited understanding of their mechanical properties at elevated temperatures. We used a nondestructive sonic resonance method to measure the Young's modulus and Shear modulus of a bulk metallic glass, Zr41.2Ti13.8Cu12.5Ni10Be22.5, at elevated temperatures. The measurement system was designed using a laser displacement sensor to detect the sonic vibration produced by a speaker on the specimen in high-temperature furnace. The OMICRON Bode-100 Vector Network Analyzer was used to sweep the frequency and its output was connected to the speaker which vibrated the material in its flexural mode and torsional modes. A Polytec OFV-505 laser vibrometer sensor was used to capture the vibration of the material at various frequencies. The flexural and torsional mode frequency shift due to the temperature variation was used to determine the Young's modulus and Shear modulus. The temperature range of measurement was from 50°C to 350°C. The Young's modulus was found to reduce from 100GPa to 94GPa for the 300°C temperature span. Similarly, the Shear modulus decreased from 38.5GPa at 50°C to 36GPa at 350°C.

Thermoelastic properties of chromium oxide Cr2O3 (eskolaite) at high pressures and temperatures

NASA Astrophysics Data System (ADS)

Dymshits, Anna M.; Dorogokupets, Peter I.; Sharygin, Igor S.; Litasov, Konstantin D.; Shatskiy, Anton; Rashchenko, Sergey V.; Ohtani, Eiji; Suzuki, Akio; Higo, Yuji

2016-06-01

A new synchrotron X-ray diffraction study of chromium oxide Cr2O3 (eskolaite) with the corundum-type structure has been carried out in a Kawai-type multi-anvil apparatus to pressure of 15 GPa and temperatures of 1873 K. Fitting the Birch-Murnaghan equation of state (EoS) with the present data up to 15 GPa yielded: bulk modulus ( K 0, T0), 206 ± 4 GPa; its pressure derivative K'0 ,T , 4.4 ± 0.8; (∂ K 0 ,T /∂ T) = ‒0.037 ± 0.006 GPa K‒1; a = 2.98 ± 0.14 × 10-5 K-1 and b = 0.47 ± 0.28 × 10‒8 K‒2, where α 0, T = a + bT is the volumetric thermal expansion coefficient. The thermal expansion of Cr2O3 was additionally measured at the high-temperature powder diffraction experiment at ambient pressure and α 0, T0 was determined to be 2.95 × 10-5 K-1. The results indicate that coefficient of the thermal expansion calculated from the EoS appeared to be high-precision because it is consistent with the data obtained at 1 atm. However, our results contradict α 0 value suggested by Rigby et al. (Brit Ceram Trans J 45:137-148, 1946) widely used in many physical and geological databases. Fitting the Mie-Grüneisen-Debye EoS with the present ambient and high-pressure data yielded the following parameters: K 0, T0 = 205 ± 3 GPa, K'0, T = 4.0, Grüneisen parameter ( γ 0) = 1.42 ± 0.80, q = 1.82 ± 0.56. The thermoelastic parameters indicate that Cr2O3 undergoes near isotropic compression at room and high temperatures up to 15 GPa. Cr2O3 is shown to be stable in this pressure range and adopts the corundum-type structure. Using obtained thermoelastic parameters, we calculated the reaction boundary of knorringite formation from enstatite and eskolaite. The Clapeyron slope (with {{d}}P/{{d}}T = - 0.014 GPa/K) was found to be consistent with experimental data.

Material model measurements and predictions for a random pore poly(epsilon-caprolactone) scaffold.

PubMed

Quinn, T P; Oreskovic, T L; Landis, F A; Washburn, N R

2007-07-01

We investigated material models for a polymeric scaffold used for bone. The material was made by co-extruding poly(epsilon-caprolactone) (PCL), a biodegradable polyester, and poly(ethylene oxide) (PEO). The water soluble PEO was removed resulting in a porous scaffold. The stress-strain curve in compression was fit with a phenomenological model in hyperbolic form. This material model will be useful for designers for quasi-static analysis as it provides a simple form that can easily be used in finite element models. The ASTM D-1621 standard recommends using a secant modulus based on 10% strain. The resulting modulus has a smaller scatter in its value compared with the coefficients of the hyperbolic model, and it is therefore easier to compare differences in material processing and ensure quality of the scaffold. A prediction of the small-strain elastic modulus was constructed from images of the microstructure. Each pixel of the micrographs was represented with a brick finite element and assigned the Young's modulus of bulk PCL or a value of 0 for a pore. A compressive strain was imposed on the model and the resulting stresses were calculated. The elastic constants of the scaffold were then computed with Hooke's law for a linear-elastic isotropic material. The model was able to predict the small-strain elastic modulus measured in the experiments to within one standard deviation. Thus, by knowing the microstructure of the scaffold, its bulk properties can be predicted from the material properties of the constituents. Copyright 2006 Wiley Periodicals, Inc.

First-principles calculations of the structural, elastic and thermodynamic properties of mackinawite (FeS) and pyrite (FeS2)

NASA Astrophysics Data System (ADS)

Wen, Xiangli; Liang, Yuxuan; Bai, Pengpeng; Luo, Bingwei; Fang, Teng; Yue, Luo; An, Teng; Song, Weiyu; Zheng, Shuqi

2017-11-01

The thermodynamic properties of Fe-S compounds with different crystal structure are very different. In this study, the structural, elastic and thermodynamic properties of mackinawite (FeS) and pyrite (FeS2) were investigated by first-principles calculations. Examination of the electronic density of states shows that mackinawite (FeS) is metallic and that pyrite (FeS2) is a semiconductor with a band gap of Eg = 1.02 eV. Using the stress-strain method, the elastic properties including the bulk modulus and shear modulus were derived from the elastic Cij data. Density functional perturbation theory (DFPT) calculations within the quasi-harmonic approximation (QHA) were used to calculate the thermodynamic properties, and the two Fe-S compounds are found to be dynamically stable. The isothermal bulk modulus, thermal expansion coefficient, heat capacities, Gibbs free energy and entropy of the Fe-S compounds are obtained by first-principles phonon calculations. Furthermore, the temperature of the mackinawite (FeS) ⟶ pyrite (FeS2) phase transition at 0 GPa was predicted. Based on the calculation results, the model for prediction of Fe-S compounds in the Fe-H2S-H2O system was improved.

Metal-Organic-Inorganic Nanocomposite Thermal Interface Materials with Ultralow Thermal Resistances.

PubMed

Yegin, Cengiz; Nagabandi, Nirup; Feng, Xuhui; King, Charles; Catalano, Massimo; Oh, Jun Kyun; Talib, Ansam J; Scholar, Ethan A; Verkhoturov, Stanislav V; Cagin, Tahir; Sokolov, Alexei V; Kim, Moon J; Matin, Kaiser; Narumanchi, Sreekant; Akbulut, Mustafa

2017-03-22

As electronic devices get smaller and more powerful, energy density of energy storage devices increases continuously, and moving components of machinery operate at higher speeds, the need for better thermal management strategies is becoming increasingly important. The removal of heat dissipated during the operation of electronic, electrochemical, and mechanical devices is facilitated by high-performance thermal interface materials (TIMs) which are utilized to couple devices to heat sinks. Herein, we report a new class of TIMs involving the chemical integration of boron nitride nanosheets (BNNS), soft organic linkers, and a copper matrix-which are prepared by the chemisorption-coupled electrodeposition approach. These hybrid nanocomposites demonstrate bulk thermal conductivities ranging from 211 to 277 W/(m K), which are very high considering their relatively low elastic modulus values on the order of 21.2-28.5 GPa. The synergistic combination of these properties led to the ultralow total thermal resistivity values in the range of 0.38-0.56 mm 2 K/W for a typical bond-line thickness of 30-50 μm, advancing the current state-of-art transformatively. Moreover, its coefficient of thermal expansion (CTE) is 11 ppm/K, forming a mediation zone with a low thermally induced axial stress due to its close proximity to the CTE of most coupling surfaces needing thermal management.

Structural, elastic and electronic properties of transition metal carbides ZnC, NbC and their ternary alloys ZnxNb1-xC

NASA Astrophysics Data System (ADS)

Zidi, Y.; Méçabih, S.; Abbar, B.; Amari, S.

2018-02-01

We have investigated the structural, electronic and elastic properties of transition-metal carbides ZnxNb1-xC alloys in the range of 0 ≤ x ≤ 1 using the density functional theory (DFT). The full potential linearized augmented plane wave (FP-LAPW) method within a framework of the generalized gradient approximation (GGA) and GGA + U (where U is the Hubbard correlation terms) approach is used to perform the calculations presented here. The lattice parameters, the bulk modulus, its pressure derivative and the elastic constants were determined. We have obtained Young's modulus, shear modulus, Poisson's ratio, anisotropy factor by the aid of the calculated elastic constants. We discuss the total and partial densities of states and charge densities.

Equations of state and anisotropy of Fe-Ni-Si alloys

NASA Astrophysics Data System (ADS)

Morrison, R. A.; Jackson, J. M.; Sturhahn, W.; Zhang, D.; Greenberg, E.

2017-12-01

Seismic observations provide constraints on the density, bulk sound speed, and bulk modulus of Earth's inner core, and x-ray diffraction (XRD) experiments can experimentally constrain such properties of iron alloys. The deviation of these seismically-inferred values from the properties of iron suggests the presence of light elements (e.g. Si, O, S, C, H) inside the core. While cosmochemical studies suggest Earth's core is composed primarily of iron alloyed with 5 wt% nickel, existing experimental XRD studies constraining pressure-density relations have predominantly focused on iron and iron alloyed with light elements, while neglecting the effect of nickel. In this study, we present high-precision equations of state for bcc- and hcp-structured Fe0.91Ni0.09 and Fe0.80Ni0.10Si0.10 using powder XRD at room temperature up to 167 GPa and 175 GPa, respectively. By using tungsten powder as a pressure calibrant and helium as a pressure transmitting medium, we minimize error due to pressure calibration and non-hydrostatic stresses. The results are high fidelity equations of state (EOS). By systematically comparing our findings to an established EOS of hcp-Fe [Dewaele et al. 2006], we constrain the effect of nickel and silicon on the density, bulk sound speed, and bulk modulus of iron alloys, which is a critical step towards constraining the inner core's composition. We find that for iron alloys, high quality ambient temperature EOSs can dramatically improve the extrapolated high temperature equations of state to inner core conditions. By combining seismic observations and their associated uncertainties with our data and existing Fe light-element-alloy EOSs, we estimate their densities, bulk moduli, and bulk sound speeds at inner core conditions and propose an experimentally and seismologically consistent range of inner core compositions. Additionally, we obtain an unprecedented constraint on the effect of nickel and silicon on the axial ratio of iron alloys. Nickel has a measurably distinct effect on the c/a axial ratio of iron, as does alloying iron-nickel with silicon. We investigate the relationship between the c/a axial ratio and elastic anisotropy of iron alloys and discuss the implications for inner core seismic anisotropy.

Evidence for Jahn-Teller distortions at the antiferromagnetic transition in LaTiO3.

PubMed

Hemberger, J; Krug von Nidda, H-A; Fritsch, V; Deisenhofer, J; Lobina, S; Rudolf, T; Lunkenheimer, P; Lichtenberg, F; Loidl, A; Bruns, D; Büchner, B

2003-08-08

LaTiO3 is known as a Mott insulator which orders antiferromagnetically at T(N)=146 K. We report on results of thermal expansion and temperature dependent x-ray diffraction together with measurements of the heat capacity, electrical transport measurements, and optical spectroscopy in untwinned single crystals. At T(N) significant structural changes appear, which are volume conserving. Concomitant anomalies are also observed in the dc resistivity, in bulk modulus, and optical reflectivity spectra. We interpret these experimental observations as evidence of orbital order.

Properties of Desert Sand and CMAS Glass

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Choi, Sung R.

2014-01-01

As-received desert sand from a Middle East country has been characterized for its phase composition and thermal stability. X-ray diffraction analysis showed the presence of quartz (SiO2), calcite (CaCO3), gypsum (CaSO4.2H2O), and NaAlSi3O8 phases in as-received desert sand and showed weight loss of approx. 35 percent due to decomposition of CaCO3 and CaSO4.2H2O when heated to 1400 C. A batch of as-received desert sand was melted into calcium magnesium aluminosilicate (CMAS) glass at approx. 1500 C. From inductively coupled plasma-atomic emission spectrometry, chemical composition of the CMAS glass was analyzed to be 27.8CaO-4MgO-5Al2O3-61.6SiO2-0.6Fe2O3-1K2O (mole percent). Various physical, thermal and mechanical properties of the glass have been evaluated. Bulk density of CMAS glass was 2.69 g/cc, Young's modulus 92 GPa, Shear modulus 36 GPa, Poisson's ratio 0.28, dilatometric glass transition temperature (T (sub g)) 706 C, softening point (T (sub d)) 764 C, Vickers microhardness 6.3 +/- 0.4 GPa, indentation fracture toughness 0.75 +/- 0.15 MPa.m (sup 1/2), and coefficient of thermal expansion (CTE) 9.8 x 10 (exp -6)/degC in the temperature range 25 to 700 C. Temperature dependence of viscosity has also been estimated from various reference points of the CMAS glass using the Vogel-Fulcher-Tamman (VFT) equation. The glass remained amorphous after heat treating at 850 C for 10 hr but crystallized into CaSiO3 and Ca-Mg-Al silicate phases at 900 C or higher temperatures. Crystallization kinetics of the CMAS glass has also been investigated by differential thermal analysis (DTA). Activation energies for the crystallization of two different phases in the glass were calculated to be 403 and 483 kJ/mol, respectively.

Dynamic mechanical properties of a Ti-based metallic glass matrix composite

NASA Astrophysics Data System (ADS)

Li, Jinshan; Cui, Jing; Qiao, Jichao; Bai, Jie; Kou, Hongchao; Wang, Jun

2015-04-01

Dynamic mechanical behavior of a Ti50Zr20Nb12Cu5Be13 bulk metallic glass composite was investigated using mechanical spectroscopy in both temperature and frequency domains. Storage modulus G' and loss modulus G″ are determined by temperature, and three distinct regions corresponding to different states in the bulk metallic glass composite are characterized. Physical parameters, such as atomic mobility and correlation factor χ, are introduced to analyze dynamic mechanical behavior of the bulk metallic glass composite in the framework of quasi-point defects (QPD) model. The experimental results are in good agreement with the prediction of QPD model.

Dynamic mechanical properties of a Ti-based metallic glass matrix composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jinshan, E-mail: ljsh@nwpu.edu.cn; Cui, Jing; Bai, Jie

2015-04-21

Dynamic mechanical behavior of a Ti{sub 50}Zr{sub 20}Nb{sub 12}Cu{sub 5}Be{sub 13} bulk metallic glass composite was investigated using mechanical spectroscopy in both temperature and frequency domains. Storage modulus G′ and loss modulus G″ are determined by temperature, and three distinct regions corresponding to different states in the bulk metallic glass composite are characterized. Physical parameters, such as atomic mobility and correlation factor χ, are introduced to analyze dynamic mechanical behavior of the bulk metallic glass composite in the framework of quasi-point defects (QPD) model. The experimental results are in good agreement with the prediction of QPD model.

Predicting burst pressure of radiofrequency-induced colorectal anastomosis by bio-impedance measurement.

PubMed

Zhao, Lingxi; Zhou, Yu; Song, Chengli; Wang, Zhigang; Cuschieri, Alfred

2017-03-01

The present study investigates the relationship between bio-impedance and burst pressure of colorectal anastomosis created by radiofrequency (RF)-induced tissue fusion. Colorectal anastomosis were created with ex vivo porcine colorectal segments, during which 5 levels of compression pressure were applied by a custom-made bipolar prototype, with 5 replicate experiments at each compression pressure. Instant anastomotic tensile strength was assessed by burst pressure. Bio-impedance of fused tissue was measured by Impedance Analyzer across frequency that 100 Hz to 3 MHz. Statistical analysis shows only a weak correlation between bio-impedance modulus and burst pressures at frequency of 445 kHz ([Formula: see text]  =  -0.426, P  =  0.099  >  0.05). In contrast, results demonstrated a highly significant negative correlation between reactance modulus and burst pressures ([Formula: see text]  =  -0.812, P  =  0.000  <  0.05). The decrease in mean reactance modulus with increasing burst pressures was highly significant (P  =  0.019  <  0.05). The observed strong negative correlation between reactance modulus and burst pressures at frequency of 445 kHz indicates that reactance is likely to be a good index for tensile strength of RF-induced colorectal anastomosis, and should be considered for inclusion in a feedback loops in devices design.

Development of low modulus material for use in ceramic gas path seal applications

NASA Technical Reports Server (NTRS)

Eaton, H. E.; Novak, R. C.

1981-01-01

Three candidate materials were examined: Brunsbond (R) Pad; plasma sprayed porous NiCrAlY; and plasma sprayed low modulus microcracked zirconia. Evaluation consisted of mechanical, thermophysical, and oxidation resistance testing along with optical microscopy and a feasibility demonstration of attaching the material to a suitable substrate. The goals of the program were the following: feasibility of fastening or depositing the low modulus system onto a broad range of substrate alloys; feasibility of depositing or forming the low modulus system to a thickness of 0.19 cm to 0.38 cm; potential to attain a modulus of elasticity in the range of 3.4 to 6.9 GPa (0.5 to 1.0 MSI), and an ultimate strength of 17.2 MPa (2.5 ksi); suitable thermal conductivity; and static oxidation life of at least 1000 hours at 1311 K. The results of the program indicate that all three systems offer attractive properties as a strain isolator material.

Equation of state and thermodynamic Gruneisen parameter of monoclinic 1,1-diamino-2,2-dinitroethylene

DOE PAGES

Zhang, Jianzhong; Velisavljevic, Nenad; Zhu, Jinlong; ...

2016-08-05

In situ synchrotron x-ray diffraction experiments were conducted on 1,1-diamino-2,2 dinitroethylene (FOX-7) at pressures up to 6.8 GPa and temperatures up to 485 K. Within th resolution of the present diffraction data, our results do not reveal evidence for a pressureinduce structural phase transition near 2 GPa, previously observed in several vibrationa spectroscopy experiments. Based on unit-cell volume measurements, the least-squares fi using the third-order Birch–Murnaghan equation of state (EOS) yields K 0 = 12.6 ± 1.4 GP and K 0 = 11.3 ± 2.1 for the α-phase of FOX-7, which are in good agreement with recentl reported values formore » the deuterated sample, indicating that the effect of hydrogen–deuteriu substitution on the compressibility of FOX-7 is negligibly small. A thermal EOS is als obtained for the α-phase of FOX-7, including pressure dependence of thermal expansivity (∂α/∂P) T = -7.0 ± 2.0 × 10 -5 K -1 GPa -1, and temperature derivative of the bulk modulus (∂K T/∂T) P = -1.1 × 10 -2 GPa K -1. From these EOS parameters, we calculate heat capacit at constant volume (C V) and thermodynamic Grüneisen parameter (γ TH) as a function o temperature. At ambient conditions, the calculated γTH is 1.055, which is in good agreemen with the value (1.09) previously obtained from density functional theory (DFT). The obtaine C V, however, is 13% larger than that calculated from the first-principles calculations indicating that the dispersion correction in the DFT calculations may need to be furthe improved for describing intermolecular interactions of molecular crystals.« less

Equation of state and thermodynamic Gruneisen parameter of monoclinic 1,1-diamino-2,2-dinitroethylene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jianzhong; Velisavljevic, Nenad; Zhu, Jinlong

In situ synchrotron x-ray diffraction experiments were conducted on 1,1-diamino-2,2 dinitroethylene (FOX-7) at pressures up to 6.8 GPa and temperatures up to 485 K. Within th resolution of the present diffraction data, our results do not reveal evidence for a pressureinduce structural phase transition near 2 GPa, previously observed in several vibrationa spectroscopy experiments. Based on unit-cell volume measurements, the least-squares fi using the third-order Birch–Murnaghan equation of state (EOS) yields K 0 = 12.6 ± 1.4 GP and K 0 = 11.3 ± 2.1 for the α-phase of FOX-7, which are in good agreement with recentl reported values formore » the deuterated sample, indicating that the effect of hydrogen–deuteriu substitution on the compressibility of FOX-7 is negligibly small. A thermal EOS is als obtained for the α-phase of FOX-7, including pressure dependence of thermal expansivity (∂α/∂P) T = -7.0 ± 2.0 × 10 -5 K -1 GPa -1, and temperature derivative of the bulk modulus (∂K T/∂T) P = -1.1 × 10 -2 GPa K -1. From these EOS parameters, we calculate heat capacit at constant volume (C V) and thermodynamic Grüneisen parameter (γ TH) as a function o temperature. At ambient conditions, the calculated γTH is 1.055, which is in good agreemen with the value (1.09) previously obtained from density functional theory (DFT). The obtaine C V, however, is 13% larger than that calculated from the first-principles calculations indicating that the dispersion correction in the DFT calculations may need to be furthe improved for describing intermolecular interactions of molecular crystals.« less

Linking microscopic and macroscopic response in disordered solids

NASA Astrophysics Data System (ADS)

Hexner, Daniel; Liu, Andrea J.; Nagel, Sidney R.

2018-06-01

The modulus of a rigid network of harmonic springs depends on the sum of the energies in each of the bonds due to an applied distortion such as compression in the case of the bulk modulus or shear in the case of the shear modulus. However, the distortion need not be global. Here we introduce a local modulus, Li, associated with changing the equilibrium length of a single bond, i , in the network. We show that Li is useful for understanding many aspects of the mechanical response of the entire system. It allows an efficient computation of how the removal of any bond changes the global properties such as the bulk and shear moduli. Furthermore, it allows a prediction of the distribution of these changes and clarifies why the changes of these two moduli due to removal of a bond are uncorrelated; these are the essential ingredients necessary for the efficient manipulation of network properties by bond removal.

[Effects of Geometrical Dimensions and Material Properties on the Rotation Characteristics of Head].

PubMed

Chen, Yue; Cui, Shihai; Li, Haiyan; Ruan, Shijie

2016-08-01

The validated finite element head model(FEHM)of a 3-year-old child,a 6-year-old child and a 50 th percentile adult were used to investigate the effects of head dimension and material parameters of brain tissues on the head rotational responses based on experimental design.Results showed that the effects of head dimension and directions of rotation on the head rotational responses were not significant under the same rotational loading condition,and the same results appeared in the viscoelastic material parameters of brain tissues.However,the head rotational responses were most sensitive to the shear modulus(G)of brain tissues relative to decay constant(β)and bulk modulus(K).Therefore,the selection of material parameters of brain tissues is most important to the accuracy of simulation results,especially in the study of brain injury criterion under the rotational loading conditions.

Temperature-dependent elasticity of Pb [(Mg0.33Nb0.67 ) 1 -xT ix ] O3

NASA Astrophysics Data System (ADS)

Tennakoon, Sumudu; Gladden, Joseph; Mookherjee, Mainak; Besara, Tiglet; Siegrist, Theo

2017-10-01

Relaxor ferroelectric materials, such as Pb [(Mg0.33Nb0.67 ) 1 -xT ix ] O3 (PMN-PT) with generic stoichiometry, undergo a ferroelectric-to-paraelectric phase transition as a function of temperature. The exact transition characterized by Curie temperature (Tc) varies as a function of chemistry (x ), i.e., the concentration of Ti. In this study, we investigated the structural phase transition by exploring the temperature dependence of the single-crystal elastic properties of Pb [(Mg0.33Nb0.67 ) 0.7T i0.3 ] O3 , i.e., x ≈0.3 . We used resonant ultrasound spectroscopy to determine the elasticity at elevated temperatures, from which Tc=398 ±5 K for PMN-PT (x ≈0.3 ) was determined. We report the full elastic constant tensor (Ci j={ C11,C12,C44 }), acoustic attenuation (Q-1), longitudinal (VP) and shear (VS) sound velocities, and elastic anisotropy of PMN-PT as a function of temperature for 400 Tc the material first stiffens and reaches maxima in the vicinity of the Burns temperature (Tb˜673 K ), followed by a more typical gradual softening of the elastic constants. Similar temperature-dependent anomalies are also observed with anisotropy and Q-1, with minima in the vicinity of Tb. We used the temperature dependence of Ci j, Q-1, VP,VS , and anisotropy to infer the evolution of polar nanoregions as the material evolved from T >Tc .

Mechanical heterogeneity in ionic liquids

NASA Astrophysics Data System (ADS)

Veldhorst, Arno A.; Ribeiro, Mauro C. C.

2018-05-01

Molecular dynamics (MD) simulations of five ionic liquids based on 1-alkyl-3-methylimidazolium cations, [CnC1im]+, have been performed in order to calculate high-frequency elastic moduli and to evaluate heterogeneity of local elastic moduli. The MD simulations of [CnC1im][NO3], n = 2, 4, 6, and 8, assessed the effect of domain segregation when the alkyl chain length increases, and [C8C1im][PF6] assessed the effect of strength of anion-cation interaction. Dispersion curves of excitation energies of longitudinal and transverse acoustic, LA and TA, modes were obtained from time correlation functions of mass currents at different wavevectors. High-frequency sound velocity of LA modes depends on the alkyl chain length, but sound velocity for TA modes does not. High-frequency bulk and shear moduli, K∞ and G∞, depend on the alkyl chain length because of a density effect. Both K∞ and G∞ are strongly dependent on the anion. The calculation of local bulk and shear moduli was accomplished by performing bulk and shear deformations of the systems cooled to 0 K. The simulations showed a clear connection between structural and elastic modulus heterogeneities. The development of nano-heterogeneous structure with increasing length of the alkyl chain in [CnC1im][NO3] implies lower values for local bulk and shear moduli in the non-polar domains. The mean value and the standard deviations of distributions of local elastic moduli decrease when [NO3]- is replaced by the less coordinating [PF6]- anion.

P-V-T equation of state of CaCO3 aragonite to 29 GPa and 1673 K: In situ X-ray diffraction study

NASA Astrophysics Data System (ADS)

Litasov, Konstantin D.; Shatskiy, Anton; Gavryushkin, Pavel N.; Bekhtenova, Altyna E.; Dorogokupets, Peter I.; Danilov, Boris S.; Higo, Yuji; Akilbekov, Abdirash T.; Inerbaev, Talgat M.

2017-04-01

Pressure-volume-temperature relations have been measured to 29 GPa and 1673 K for CaCO3 aragonite using synchrotron X-ray diffraction with a multianvil apparatus at the 'SPring-8' facility. A least-squares fit of the room-temperature compression data to the Vinet-Rydberg equation of state (EOS) yielded KT0 = 65.7 ± 0.8 GPa and KT' = 5.1 ± 0.1, with fixed V0 = 227.11 Å3. Further analysis of the high-temperature compression data led to the temperature derivative of the bulk modulus (∂KT/∂T)P = -0.016 ± 0.001 GPa/K and zero-pressure thermal expansion α = a0 + a1T with a0 = 4.98 (22) × 10-5 K-1 and a1 = 2.81(38) × 10-8 K-2. The Mie-Gruneisen-Debye approach revealed the Gruneisen parameter γ0 = 1.39 at a fixed Debye temperature θ0 = 516 K and the parameter q = 1. Analysis of axial compressibility and thermal expansion indicates that the c-axis is two times more compressible than the b-axis and four times more compressible than the a-axis, whereas zero-pressure thermal expansion of the a-axis (a0a = 2.6 × 10-5 K-1 and a1a = 2.3 × 10-8 K-2) is weaker than that of the b-axis axis (a0b = 6.3 × 10-5 K-1 and a1b = 0.1 × 10-8 K-2) and c-axis axis (a0c = 5.2 × 10-5 K-1 and a1c = 9.5 × 10-8 K-2). A full set of thermodynamic parameters (including heat capacity, enthalpy and free energy) for aragonite and updated equations of state for magnesite and siderite was obtained using the Kunc-Einstein approach. The new EOS parameters were used for thermodynamic calculations for aragonite decarbonation reactions. The present thermal EOS provides accurate calculations of aragonite density to deep mantle. Decarbonation of subducting oceanic crust containing 2 wt% aragonite would result in a 0.5% density reduction at 30 GPa and 1273 K. Aragonite becomes denser than magnesite at pressures about 16 GPa along the 1500 K isotherm and at 9 GPa along the 298 K isotherm.

Maximum of the modulus of kernels in Gauss-Turan quadratures

NASA Astrophysics Data System (ADS)

Milovanovic, Gradimir V.; Spalevic, Miodrag M.; Pranic, Miroslav S.

2008-06-01

We study the kernels K_{n,s}(z) in the remainder terms R_{n,s}(f) of the Gauss-Turan quadrature formulae for analytic functions on elliptical contours with foci at pm 1 , when the weight omega is a generalized Chebyshev weight function. For the generalized Chebyshev weight of the first (third) kind, it is shown that the modulus of the kernel \\vert K_{n,s}(z)\\vert attains its maximum on the real axis (positive real semi-axis) for each ngeq n_0, n_0Dn_0(rho,s) . It was stated as a conjecture in [Mathematics of Computation 72 (2003), 1855-1872]. For the generalized Chebyshev weight of the second kind, in the case when the number of the nodes n in the corresponding Gauss-Turan quadrature formula is even, it is shown that the modulus of the kernel attains its maximum on the imaginary axis for each ngeq n_0, n_0Dn_0(rho,s) . Numerical examples are included. Retrieve articles in all Journals with MSC (1991): [41]41A55, [42]65D30, [43]65D32

Relaxation processes and conduction mechanism in bismuth ferrite lead titanate composites

NASA Astrophysics Data System (ADS)

Sahu, Truptimayee; Behera, Banarji

2018-02-01

In this study, samarium (Sm)-doped multiferroic composites of 0.8BiSmxFe1-xO3-0.2PbTiO3 where x = 0.05, 0.10, 0.15, and 0.20 were prepared via the conventional solid state reaction route. The electrical properties of these composites were analyzed using an impedance analyzer over a wide range of temperatures and frequencies (102-106 Hz). The impedance and modulus analyses confirmed the presence of both bulk and grain boundary effects in the materials. The temperature dependence of impedance and modulus spectrum indicated the negative temperature coefficient of resistance behavior. The dielectric relaxation exhibited non-Debye type behavior and it was temperature dependent. The relaxation time (τ) and DC conductivity followed an Arrhenius type behavior. The frequency-dependent AC conductivity obeyed Jonscher's power law. The correlated barrier hopping model was appropriate to understand the conduction mechanism in the composites considered.

Real-time contrast ultrasound muscle perfusion imaging with intermediate-power imaging coupled with acoustically durable microbubbles.

PubMed

Seol, Sang-Hoon; Davidson, Brian P; Belcik, J Todd; Mott, Brian H; Goodman, Reid M; Ammi, Azzdine; Lindner, Jonathan R

2015-06-01

There is growing interest in limb contrast-enhanced ultrasound (CEU) perfusion imaging for the evaluation of peripheral artery disease. Because of low resting microvascular blood flow in skeletal muscle, signal enhancement during limb CEU is prohibitively low for real-time imaging. The aim of this study was to test the hypothesis that this obstacle can be overcome by intermediate- rather than low-power CEU when performed with an acoustically resilient microbubble agent. Viscoelastic properties of Definity and Sonazoid were assessed by measuring bulk modulus during incremental increases in ambient pressure to 200 mm Hg. Comparison of in vivo microbubble destruction and signal enhancement at a mechanical index (MI) of 0.1 to 0.4 was performed by sequential reduction in pulsing interval from 10 to 0.05 sec during limb CEU at 7 MHz in mice and 1.8 MHz in dogs. Destruction was also assessed by broadband signal generation during passive cavitation detection. Real-time CEU perfusion imaging with destruction-replenishment was then performed at 1.8 MHz in dogs using an MI of 0.1, 0.2, or 0.3. Sonazoid had a higher bulk modulus than Definity (66 ± 12 vs 29 ± 2 kPa, P = .02) and exhibited less inertial cavitation (destruction) at MIs ≥ 0.2. On in vivo CEU, maximal signal intensity increased incrementally with MI for both agents and was equivalent between agents except at an MI of 0.1 (60% and 85% lower for Sonazoid at 7 and 1.8 MHz, respectively, P < .05). However, on progressive shortening of the pulsing interval, Definity was nearly completely destroyed at MIs ≥ 0.2 at 1.8 and 7 MHz, whereas Sonazoid was destroyed only at 1.8 MHz at MIs ≥ 0.3. As a result, real-time CEU perfusion imaging demonstrated approximately fourfold greater enhancement for Sonazoid at an MI of 0.3 to 0.4. Robust signal enhancement during real-time CEU perfusion imaging of the limb is possible when using intermediate-power imaging coupled with a durable microbubble contrast agent. Copyright © 2015 American Society of Echocardiography. All rights reserved.

Depth of cure, flexural properties and volumetric shrinkage of low and high viscosity bulk-fill giomers and resin composites.

PubMed

Tsujimoto, Akimasa; Barkmeier, Wayne W; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

2017-03-31

The purpose of this study was to investigate the depth of cure, flexural properties and volumetric shrinkage of low and high viscosity bulk-fill giomers and resin composites. Depth of cure and flexural properties were determined according to ISO 4049, and volumetric shrinkage was measured using a dilatometer. The depths of cure of giomers were significantly lower than those of resin composites, regardless of photo polymerization times. No difference in flexural strength and modulus was found among either high or low viscosity bulk fill materials. Volumetric shrinkage of low and high viscosity bulk-fill resin composites was significantly less than low and high viscosity giomers. Depth of cure of both low and high viscosity bulk-fill materials is time dependent. Flexural strength and modulus of high viscosity or low viscosity bulk-fill giomer or resin composite materials are not different for their respective category. Resin composites exhibited less polymerization shrinkage than giomers.

Exploring phase stability, electronic and mechanical properties of Ce–Pb intermetallic compounds using first-principles calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, Xiaoma; Computational Alloy Design Group, IMDEA Materials Institute, Getafe, Madrid 28906; Wang, Ziru

2016-05-15

The phase stability, electronic and mechanical properties of Ce–Pb intermetallics have been investigated by using first-principles calculations. Five stable and four metastable phases of Ce–Pb intermetallics were verified. Among them, CePb{sub 2} has been confirmed as HfGa{sub 2}-type structure. For Ce{sub 5}Pb{sub 3}, the high pressure phase transformation from D8{sub m} to D8{sub 8} with trivalent Ce has been predicted to occur at P=1.2 GPa and a high temperature phase transformation has been predicted from D8{sub m} to D8{sub 8} with tetravalent Ce at 531.5 K. The calculated lattice constants of the five stable phases are in good agreement withmore » experimental values. The electronic density of states, charge density and electron localization function of Ce{sub 3}Pb have been calculated, which indicated that the Ce and Pb show ionic behavior. The polycrystalline bulk modulus, shear modulus, Young's modulus, and Poisson's ratio are also estimated from the calculated single crystalline elastic constants. All of the calculated elastic constants satisfy mechanical stability criteria. The microhardness and mechanical anisotropy are predicted. The anisotropic nature of the Ce–Pb intermetallic compounds are demonstrated by the three-dimensional orientation dependent surfaces of Young's moduli and linear compressibility are also demonstrated. The longitudinal, transverse and average sound velocities and the Debye temperatures are also obtained in this work. The Ce{sub 3}Pb has the largest Debye temperature of 192.6 K, which means the Ce{sub 3}Pb has a highest melting point and high thermal conductivity than other compounds. - Graphical abstract: The convex hull plots of the enthalpies of formation for Ce–Pb binary systems calculated at 0 K. - Highlights: • The five stable and four metastable phases in the Ce–Pb binary system were predicted. • The crystal structure of CePb{sub 2} has been confirmed as HfGa{sub 2}-type.« less

Fatigue stipulation of bulk-fill composites: An in vitro appraisal.

PubMed

Vidhawan, Shruti A; Yap, Adrian U; Ornaghi, Barbara P; Banas, Agnieszka; Banas, Krzysztof; Neo, Jennifer C; Pfeifer, Carmem S; Rosa, Vinicius

2015-09-01

The aim of this study was to determine the Weibull and slow crack growth (SCG) parameters of bulk-fill resin based composites. The strength degradation over time of the materials was also assessed by strength-probability-time (SPT) analysis. Three bulk-fill [Tetric EvoCeram Bulk Fill (TBF); X-tra fil (XTR); Filtek Bulk-fill flowable (BFL)] and a conventional one [Filtek Z250 (Z250)] were studied. Seventy five disk-shaped specimens (12mm in diameter and 1mm thick) were prepared by inserting the uncured composites in a stainless steel split mold followed by photoactivation (1200mW/cm(2)/20s) and storage in distilled water (37°C/24h). Degree of conversion was evaluated in five specimens by analysis of FT-IR spectra obtained in the mid-IR region. The SCG parameters n (stress corrosion susceptibility coefficient) and σf0 (scaling parameter) were obtained by testing ten specimens in each of the five stress rates: 10(-2), 10(-1), 10(0), 10(1) and 10(2)MPa/s using a piston-on-three-balls device. Weibull parameter m (Weibull modulus) and σf0 (characteristic strength) were obtained by testing additional 20 specimens at 1MPa/s. Strength-probability-time (SPT) diagrams were constructed by merging SCG and Weibull parameters. BFL and TBF presented higher n values, respectively (40.1 and 25.5). Z250 showed the highest (157.02MPa) and TBF the lowest (110.90MPa) σf0 value. Weibull analysis showed m (Weibull modulus) of 9.7, 8.6, 9.7 and 8.9 for TBF, BFL, XTR and Z250, respectively. SPT diagram for 5% probability of failure showed strength decrease of 18% for BFL, 25% for TBF, 32% for XTR and 36% for Z250, respectively, after 5 years as compared to 1 year. The reliability and decadence of strength over time for bulk-fill resin composites studied are, at least, comparable to conventional composites. BFL shows the highest fatigue resistance under all simulations followed by TBF, while XTR was at par with Z250. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Ab initio study of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L10 FeNi (tetrataenite)

NASA Astrophysics Data System (ADS)

Werwiński, Mirosław; Marciniak, Wojciech

2017-12-01

We present results of ab initio calculations of several L10 FeNi characteristics, such as the summary of the magnetocrystalline anisotropy energies (MAEs), the full potential calculations of the anisotropy constant K 3, and the combined analysis of the Fermi surface and 3D {k} -resolved MAE. Other calculated parameters are the spin and orbital magnetic moments, the magnetostrictive coefficient λ0 0 1 , the bulk modulus B 0, and the lattice parameters. The MAEs summary shows rather big discrepancies among the experimental MAEs from the literature and also among the calculated MAE’s. The MAEs calculated in this work with the full potential and generalized gradient approximation (GGA) are equal to 0.47 MJ m-3 from WIEN2k, 0.34 MJ m-3 from FPLO, and 0.23 MJ m-3 from FP-SPR-KKR code. These results suggest that the MAE in GGA is below 0.5 MJ m-3 . It is expected that due to the limitations of the GGA, this value is underestimated. The L10 FeNi has further potential to improve its MAE by modifications, like e.g. tetragonal strain or alloying. The presented 3D {k} -resolved map of the MAE combined with the Fermi surface gives a complete picture of the MAE contributions in the Brillouin zone. The obtained, from the full potential FP-SPR-KKR method, magnetocrystalline anisotropy constants K 2 and K 3 are several orders of magnitude smaller than the MAE/K 1 and equal to -2.0 kJ m-3 and 110 J m-3 , respectively. The calculated spin and orbital magnetic moments of the L10 FeNi are equal to 2.72 and 0.054 μB for Fe and 0.53 and 0.039 μB for Ni atoms, respectively. The calculations of geometry optimization lead to a c/a ratio equal to 1.0036, B 0 equal to 194 GPa, and λ0 0 1 equal to 9.4  ×  10-6.

First-Principles Calculations of Structural, Electronic and Optical Properties of Ternary Semiconductor Alloys ZAs x Sb1- x ( Z = B, Al, Ga, In)

NASA Astrophysics Data System (ADS)

Bounab, S.; Bentabet, A.; Bouhadda, Y.; Belgoumri, Gh.; Fenineche, N.

2017-08-01

We have investigated the structural and electronic properties of the BAs x Sb 1- x , AlAs x Sb 1- x , GaAs x Sb 1- x and InAs x Sb 1- x semiconductor alloys using first-principles calculations under the virtual crystal approximation within both the density functional perturbation theory and the pseudopotential approach. In addition the optical properties have been calculated by using empirical methods. The ground state properties such as lattice constants, both bulk modulus and derivative of bulk modulus, energy gap, refractive index and optical dielectric constant have been calculated and discussed. The obtained results are in reasonable agreement with numerous experimental and theoretical data. The compositional dependence of the lattice constant, bulk modulus, energy gap and effective mass of electrons for ternary alloys show deviations from Vegard's law where our results are in agreement with the available data in the literature.

Size dependent compressibility of nano-ceria: Minimum near 33 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodenbough, Philip P.; Chemistry Department, Columbia University, New York, New York 10027; Song, Junhua

2015-04-20

We report the crystallite-size-dependency of the compressibility of nanoceria under hydrostatic pressure for a wide variety of crystallite diameters and comment on the size-based trends indicating an extremum near 33 nm. Uniform nano-crystals of ceria were synthesized by basic precipitation from cerium (III) nitrate. Size-control was achieved by adjusting mixing time and, for larger particles, a subsequent annealing temperature. The nano-crystals were characterized by transmission electron microscopy and standard ambient x-ray diffraction (XRD). Compressibility, or its reciprocal, bulk modulus, was measured with high-pressure XRD at LBL-ALS, using helium, neon, or argon as the pressure-transmitting medium for all samples. As crystallite sizemore » decreased below 100 nm, the bulk modulus first increased, and then decreased, achieving a maximum near a crystallite diameter of 33 nm. We review earlier work and examine several possible explanations for the peaking of bulk modulus at an intermediate crystallite size.« less

Prediction of Material Properties of Nanostructured Polymer Composites Using Atomistic Simulations

NASA Technical Reports Server (NTRS)

Hinkley, J.A.; Clancy, T.C.; Frankland, S.J.V.

2009-01-01

Atomistic models of epoxy polymers were built in order to assess the effect of structure at the nanometer scale on the resulting bulk properties such as elastic modulus and thermal conductivity. Atomistic models of both bulk polymer and carbon nanotube polymer composites were built. For the bulk models, the effect of moisture content and temperature on the resulting elastic constants was calculated. A relatively consistent decrease in modulus was seen with increasing temperature. The dependence of modulus on moisture content was less consistent. This behavior was seen for two different epoxy systems, one containing a difunctional epoxy molecule and the other a tetrafunctional epoxy molecule. Both epoxy structures were crosslinked with diamine curing agents. Multifunctional properties were calculated with the nanocomposite models. Molecular dynamics simulation was used to estimate the interfacial thermal (Kapitza) resistance between the carbon nanotube and the surrounding epoxy matrix. These estimated values were used in a multiscale model in order to predict the thermal conductivity of a nanocomposite as a function of the nanometer scaled molecular structure.

Constitutive models for a poly(e-caprolactone) scaffold.

PubMed

Quinn, T P; Oreskovic, T L; McCowan, C N; Washburn, N R

2004-01-01

We investigate material models for a porous, polymeric scaffold used for bone. The material was made by co-extruding poly(e-caprolactone) (PCL), a biodegradable polyester, and poly(ethylene oxide) (PEO). The water soluble PEO was removed resulting in a porous scaffold. The stress-strain curve in compression was fit with a phenomenological model in hyperbolic form. This material model will be useful for designers for quasi-static analysis as it provides a simple form that can easily be used in finite element models. The ASTM D-1621 standard recommends using a secant modulus based on 10% strain. The resulting modulus has a smaller scatter in its value compared to the coefficients of the hyperbolic model, and it is therefore easier to compare material processing differences and ensure quality of the scaffold. A third material model was constructed from images of the microstructure. Each pixel of the micrographs was represented with a brick finite element and assigned the Young's modulus of bulk PCL or a value of 0 for a pore. A compressive strain was imposed on the model and the resulting stresses were calculated. The elastic constants of the scaffold were then computed using Hooke's law for a linear-elastic isotropic material. The model was able to predict the small strain Young's modulus measured in the experiments to within one standard deviation. Thus, by knowing the microstructure of the scaffold, its bulk properties can be predicted from the material properties of the constituents.

Thermodynamics and Equations of State of Iron to 350 GPa and 6000 K

NASA Astrophysics Data System (ADS)

Dorogokupets, P. I.; Dymshits, A. M.; Litasov, K. D.; Sokolova, T. S.

2017-03-01

The equations of state for solid (with bcc, fcc, and hcp structures) and liquid phases of Fe were defined via simultaneous optimization of the heat capacity, bulk moduli, thermal expansion, and volume at room and higher temperatures. The calculated triple points at the phase diagram have the following parameters: bcc-fcc-hcp is located at 7.3 GPa and 820 K, bcc-fcc-liquid at 5.2 GPa and 1998 K, and fcc-hcp-liquid at 106.5 GPa and 3787 K. At conditions near the fcc-hcp-liquid triple point, the Clapeyron slope of the fcc-liquid curve is dT/dP = 12.8 K/GPa while the slope of the hcp-liquid curve is higher (dT/dP = 13.7 K/GPa). Therefore, the hcp-liquid curve overlaps the metastable fcc-liquid curve at pressures of about 160 GPa. At high-pressure conditions, the metastable bcc-hcp curve is located inside the fcc-Fe or liquid stability field. The density, adiabatic bulk modulus and P-wave velocity of liquid Fe calculated up to 328.9 GPa at adiabatic temperature conditions started from 5882 K (outer/inner core boundary) were compared to the PREM seismological model. We determined the density deficit of hcp-Fe at the inner core boundary (T = 5882 K and P = 328.9 GPa) to be 4.4%.

Thermodynamics and Equations of State of Iron to 350 GPa and 6000 K.

PubMed

Dorogokupets, P I; Dymshits, A M; Litasov, K D; Sokolova, T S

2017-03-06

The equations of state for solid (with bcc, fcc, and hcp structures) and liquid phases of Fe were defined via simultaneous optimization of the heat capacity, bulk moduli, thermal expansion, and volume at room and higher temperatures. The calculated triple points at the phase diagram have the following parameters: bcc-fcc-hcp is located at 7.3 GPa and 820 K, bcc-fcc-liquid at 5.2 GPa and 1998 K, and fcc-hcp-liquid at 106.5 GPa and 3787 K. At conditions near the fcc-hcp-liquid triple point, the Clapeyron slope of the fcc-liquid curve is dT/dP = 12.8 K/GPa while the slope of the hcp-liquid curve is higher (dT/dP = 13.7 K/GPa). Therefore, the hcp-liquid curve overlaps the metastable fcc-liquid curve at pressures of about 160 GPa. At high-pressure conditions, the metastable bcc-hcp curve is located inside the fcc-Fe or liquid stability field. The density, adiabatic bulk modulus and P-wave velocity of liquid Fe calculated up to 328.9 GPa at adiabatic temperature conditions started from 5882 K (outer/inner core boundary) were compared to the PREM seismological model. We determined the density deficit of hcp-Fe at the inner core boundary (T = 5882 K and P = 328.9 GPa) to be 4.4%.

Thermodynamics and Equations of State of Iron to 350 GPa and 6000 K

PubMed Central

Dorogokupets, P. I.; Dymshits, A. M.; Litasov, K. D.; Sokolova, T. S.

2017-01-01

The equations of state for solid (with bcc, fcc, and hcp structures) and liquid phases of Fe were defined via simultaneous optimization of the heat capacity, bulk moduli, thermal expansion, and volume at room and higher temperatures. The calculated triple points at the phase diagram have the following parameters: bcc–fcc–hcp is located at 7.3 GPa and 820 K, bcc–fcc–liquid at 5.2 GPa and 1998 K, and fcc–hcp–liquid at 106.5 GPa and 3787 K. At conditions near the fcc–hcp–liquid triple point, the Clapeyron slope of the fcc–liquid curve is dT/dP = 12.8 K/GPa while the slope of the hcp–liquid curve is higher (dT/dP = 13.7 K/GPa). Therefore, the hcp–liquid curve overlaps the metastable fcc–liquid curve at pressures of about 160 GPa. At high-pressure conditions, the metastable bcc–hcp curve is located inside the fcc-Fe or liquid stability field. The density, adiabatic bulk modulus and P-wave velocity of liquid Fe calculated up to 328.9 GPa at adiabatic temperature conditions started from 5882 K (outer/inner core boundary) were compared to the PREM seismological model. We determined the density deficit of hcp-Fe at the inner core boundary (T = 5882 K and P = 328.9 GPa) to be 4.4%. PMID:28262683

Stress-strain behavior under static loading in Gd123 high-temperature superconductors at 77 K

NASA Astrophysics Data System (ADS)

Fujimoto, Hiroyuki; Murakami, Akira; Teshima, Hidekazu; Morita, Mitsuru

2013-10-01

Mechanical properties of melt-growth GdBa2Cu3Ox (Gd123) superconducting samples with 10 wt.% Ag2O and 0.5 wt.% Pt were evaluated at 77 K through flexural tests for specimens cut from the samples in order to estimate the mechanical properties of the Gd123 material without metal substrates, buffer layers or stabilization layers. We discuss the mechanical properties; the Young's modulus and flexural strength with stress-strain behavior at 77 K. The results show that the flexural strength and fracture strain of Gd123 at 77 K are approximately 100 MPa and 0.1%, respectively, and that the origin of the fracture is defects such as pores, impurities and non-superconducting compounds. We also show that the Young's modulus of Gd123 is estimated to be 160-165 GPa.

Mechanical, Anisotropic, and Electronic Properties of XN (X = C, Si, Ge): Theoretical Investigations.

PubMed

Ma, Zhenyang; Liu, Xuhong; Yu, Xinhai; Shi, Chunlei; Wang, Dayun

2017-08-08

The structural, mechanical, elastic anisotropic, and electronic properties of Pbca -XN (X = C, Si, Ge) are investigated in this work using the Perdew-Burke-Ernzerhof (PBE) functional, Perdew-Burke-Ernzerhof for solids (PBEsol) functional, and Ceperly and Alder, parameterized by Perdew and Zunger (CA-PZ) functional in the framework of density functional theory. The achieved results for the lattice parameters and band gap of Pbca -CN with the PBE functional in this research are in good accordance with other theoretical results. The band structures of Pbca -XN (X = C, Si, Ge) show that Pbca -SiN and Pbca -GeN are both direct band gap semiconductor materials with a band gap of 3.39 eV and 2.22 eV, respectively. Pbca -XN (X = C, Si, Ge) exhibits varying degrees of mechanical anisotropic properties with respect to the Poisson's ratio, bulk modulus, shear modulus, Young's modulus, and universal anisotropic index. The (001) plane and (010) plane of Pbca -CN/SiN/GeN both exhibit greater elastic anisotropy in the bulk modulus and Young's modulus than the (100) plane.

Mechanical, Anisotropic, and Electronic Properties of XN (X = C, Si, Ge): Theoretical Investigations

PubMed Central

Ma, Zhenyang; Liu, Xuhong; Yu, Xinhai; Shi, Chunlei; Wang, Dayun

2017-01-01

The structural, mechanical, elastic anisotropic, and electronic properties of Pbca-XN (X = C, Si, Ge) are investigated in this work using the Perdew–Burke–Ernzerhof (PBE) functional, Perdew–Burke–Ernzerhof for solids (PBEsol) functional, and Ceperly and Alder, parameterized by Perdew and Zunger (CA–PZ) functional in the framework of density functional theory. The achieved results for the lattice parameters and band gap of Pbca-CN with the PBE functional in this research are in good accordance with other theoretical results. The band structures of Pbca-XN (X = C, Si, Ge) show that Pbca-SiN and Pbca-GeN are both direct band gap semiconductor materials with a band gap of 3.39 eV and 2.22 eV, respectively. Pbca-XN (X = C, Si, Ge) exhibits varying degrees of mechanical anisotropic properties with respect to the Poisson’s ratio, bulk modulus, shear modulus, Young’s modulus, and universal anisotropic index. The (001) plane and (010) plane of Pbca-CN/SiN/GeN both exhibit greater elastic anisotropy in the bulk modulus and Young’s modulus than the (100) plane. PMID:28786960

Determination of Young's modulus of individual electrospun nanofibers by microcantilever vibration method

NASA Astrophysics Data System (ADS)

Yuya, Philip A.; Wen, Yongkui; Turner, Joseph A.; Dzenis, Yuris A.; Li, Zheng

2007-03-01

The authors report a technique for measuring Young's modulus of a single electrospun nanofiber using the vibrations of two microcantilevers coupled with the nanofiber. The modulus is calculated from the resonant frequency shift resulting from the nanofiber. Polyacrylonitrile nanofibers (200nm diameter) were collected during electrospinning and wrapped on two similar microcantilevers causing a shift in first resonance from 10.0to19.4kHz. Finite element analysis was used to analyze the frequency shift using images from a scanning electron microscope giving a modulus of the as-spun polyacrylonitrile nanofiber of 26.8GPa.

Reliable protocol for shear wave elastography of lower limb muscles at rest and during passive stretching.

PubMed

Dubois, Guillaume; Kheireddine, Walid; Vergari, Claudio; Bonneau, Dominique; Thoreux, Patricia; Rouch, Philippe; Tanter, Mickael; Gennisson, Jean-Luc; Skalli, Wafa

2015-09-01

Development of shear wave elastography gave access to non-invasive muscle stiffness assessment in vivo. The aim of the present study was to define a measurement protocol to be used in clinical routine for quantifying the shear modulus of lower limb muscles. Four positions were defined to evaluate shear modulus in 10 healthy subjects: parallel to the fibers, in the anterior and posterior aspects of the lower limb, at rest and during passive stretching. Reliability was first evaluated on two muscles by three operators; these measurements were repeated six times. Then, measurement reliability was compared in 11 muscles by two operators; these measurements were repeated three times. Reproducibility of shear modulus was 0.48 kPa and repeatability was 0.41 kPa, with all muscles pooled. Position did not significantly influence reliability. Shear wave elastography appeared to be an appropriate and reliable tool to evaluate the shear modulus of lower limb muscles with the proposed protocol. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Hydrostatic pressure effects on the structural, elastic and thermodynamic properties of the complex transition metal hydrides A2OsH6 (A = Mg, Ca, Sr and Ba)

NASA Astrophysics Data System (ADS)

Souadia, Z.; Bouhemadou, A.; Boudrifa, O.; Bin-Omran, S.; Khenata, R.; Al-Douri, Y.

2017-10-01

We report a systematic first-principles density functional theory study on the pressure dependence of the structural parameters, elastic constants and related properties and thermodynamic properties of the complex transition metal hydrides Mg2OsH6, Ca2OsH6, Sr2OsH6 and Ba2OsH6. The calculated structural parameters are in excellent agreement with the existing data in the scientific literature. The single-crystal elastic constants and related properties were predicted using the stress-strain method. The elastic moduli of the polycrystalline aggregates were evaluated via the Voigt-Reuss-Hill approach. The dependences of the lattice parameter, bulk modulus, volume thermal expansion coefficient, isobaric and isochoric heat capacity and Debye temperature on the pressure and temperature, ranging from 0 to 15 GPa and from 0 to 1000 K, respectively, were investigated using the quasi-harmonic Debye model in combination with first-principles calculations.

Quantum Monte Carlo Simulation of condensed van der Waals Systems

NASA Astrophysics Data System (ADS)

Benali, Anouar; Shulenburger, Luke; Romero, Nichols A.; Kim, Jeongnim; Anatole von Lilienfeld, O.

2012-02-01

Van der Waals forces are as ubiquitous as infamous. While post-Hartree-Fock methods enable accurate estimates of these forces in molecules and clusters, they remain elusive for dealing with many-electron condensed phase systems. We present Quantum Monte Carlo [1,2] results for condensed van der Waals systems. Interatomic many-body contributions to cohesive energies and bulk modulus will be discussed. Numerical evidence is presented for crystals of rare gas atoms, and compared to experiments and methods [3]. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DoE's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000.[4pt] [1] J. Kim, K. Esler, J. McMinis and D. Ceperley, SciDAC 2010, J. of Physics: Conference series, Chattanooga, Tennessee, July 11 2011 [0pt] [2] QMCPACK simulation suite, http://qmcpack.cmscc.org (unpublished)[0pt] [3] O. A. von Lillienfeld and A. Tkatchenko, J. Chem. Phys. 132 234109 (2010)

Full potential study of the elastic, electronic, and optical properties of spinels MgIn{sub 2}S{sub 4} and CdIn{sub 2}S{sub 4} under pressure effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Semari, F.; Khenata, R.; Depatment of Physics and Astronomy, King Saud University, PO Box 2455, Riyadh 11451

2010-12-15

The structural, elastic, electronic, and optical properties of cubic spinel MgIn{sub 2}S{sub 4} and CdIn{sub 2}S{sub 4} compounds have been calculated using a full relativistic version of the full-potential linearized-augmented plane wave with the mixed basis FP/APW+lo method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA). Moreover, the Engel-Vosko GGA formalism is also applied to optimize the corresponding potential for band structure calculations. The ground state properties, including the lattice constants, the internal parameter, the bulk modulus, and the pressure derivative of the bulk modulus are in reasonable agreement with the available data. Using the totalmore » energy-strain technique, we have determined the full set of first-order elastic constants C{sub ij} and their pressure dependence, which have not been calculated or measured yet. The shear modulus, Young's modulus, and Poisson's ratio are calculated for polycrystalline XIn{sub 2}S{sub 4} aggregates. The Debye temperature is estimated from the average sound velocity. Electronic band structures show a direct band gap ({Gamma}-{Gamma}) for MgIn{sub 2}S{sub 4} and an indirect band gap (K-{Gamma}) for CdIn{sub 2}S{sub 4}. The calculated band gaps with EVGGA show a significant improvement over the GGA. The optical constants, including the dielectric function {epsilon}({omega}), the refractive index n({omega}), the reflectivity R({omega}), and the energy loss function L({omega}) were calculated for radiation up to 30 eV. -- Graphical abstract: Calculated total and partial densities of states for MgIn{sub 2}S{sub 4} and CdIn{sub 2}S{sub 4}« less

Endothelial, cardiac muscle and skeletal muscle exhibit different viscous and elastic properties as determined by atomic force microscopy

NASA Technical Reports Server (NTRS)

Mathur, A. B.; Collinsworth, A. M.; Reichert, W. M.; Kraus, W. E.; Truskey, G. A.

2001-01-01

This study evaluated the hypothesis that, due to functional and structural differences, the apparent elastic modulus and viscous behavior of cardiac and skeletal muscle and vascular endothelium would differ. To accurately determine the elastic modulus, the contribution of probe velocity, indentation depth, and the assumed shape of the probe were examined. Hysteresis was observed at high indentation velocities arising from viscous effects. Irreversible deformation was not observed for endothelial cells and hysteresis was negligible below 1 microm/s. For skeletal muscle and cardiac muscle cells, hysteresis was negligible below 0.25 microm/s. Viscous dissipation for endothelial and cardiac muscle cells was higher than for skeletal muscle cells. The calculated elastic modulus was most sensitive to the assumed probe geometry for the first 60 nm of indentation for the three cell types. Modeling the probe as a blunt cone-spherical cap resulted in variation in elastic modulus with indentation depth that was less than that calculated by treating the probe as a conical tip. Substrate contributions were negligible since the elastic modulus reached a steady value for indentations above 60 nm and the probe never indented more than 10% of the cell thickness. Cardiac cells were the stiffest (100.3+/-10.7 kPa), the skeletal muscle cells were intermediate (24.7+/-3.5 kPa), and the endothelial cells were the softest with a range of elastic moduli (1.4+/-0.1 to 6.8+/-0.4 kPa) depending on the location of the cell surface tested. Cardiac and skeletal muscle exhibited nonlinear elastic behavior. These passive mechanical properties are generally consistent with the function of these different cell types.

Single phase Pb0.7Bi0.3Fe0.65Nb0.35O3 multiferroic: Neutron diffraction, impedance and modulus studies

NASA Astrophysics Data System (ADS)

Dadami, Sunanda T.; Matteppanvar, Shidaling; Shivaraja, I.; Rayaprol, Sudhindra; Deshpande, S. K.; Angadi, Basavaraj

2018-04-01

The Pb0.7Bi0.3Fe0.65Nb0.35O3 (PBFNO) multiferroic solid solution was synthesized by using single step solid state reaction method. Single phase formation was confirmed through room temperature (RT) X Ray Diffraction (XRD) and Neutron Diffraction (ND). Rietveld refinement was used to perform the structural analysis using FullProf Suite program. RT XRD and ND patterns well fitted with monoclinic structure (Cm space group) and cell parameters from the ND data are found to be a = 5.6474(4) Å, b = 5.6415(3) Å, c = 3.9992(3) Å and β = 89.95(2)°. ND data at RT exhibits G-type antiferromagnetic structure. The electrical properties (impedance and modulus) of PBFNO were studied as a function of frequency (100 Hz - 5 MHz) and temperature (133 K - 293 K) by Impedance spectroscopy technique. Impedance and modulus spectroscopy studies confirm the contribution to the conductivity is from grains only and the relaxation is of non-Debye type. The PBFNO sample exhibits negative temperature coefficient of resistance (NTCR) behaviour. PBFNO is found be a potential candidate for RT applications.

Physical properties and depth of cure of a new short fiber reinforced composite.

PubMed

Garoushi, Sufyan; Säilynoja, Eija; Vallittu, Pekka K; Lassila, Lippo

2013-08-01

To determine the physical properties and curing depth of a new short fiber composite intended for posterior large restorations (everX Posterior) in comparison to different commercial posterior composites (Alert, TetricEvoCeram Bulk Fill, Voco X-tra base, SDR, Venus Bulk Fill, SonicFill, Filtek Bulk Fill, Filtek Superme, and Filtek Z250). In addition, length of fiber fillers of composite XENIUS base compared to the previously introduced composite Alert has been measured. The following properties were examined according to ISO standard 4049: flexural strength, flexural modulus, fracture toughness, polymerization shrinkage and depth of cure. The mean and standard deviation were determined and all results were statistically analyzed with analysis of variance ANOVA (a=0.05). XENIUS base composite exhibited the highest fracture toughness (4.6MPam(1/2)) and flexural strength (124.3MPa) values and the lower shrinkage strain (0.17%) among the materials tested. Alert composite revealed the highest flexural modulus value (9.9GPa), which was not significantly different from XENIUS base composite (9.5GPa). Depth of cure of XENIUS base (4.6mm) was similar than those of bulk fill composites and higher than other hybrid composites. The length of fiber fillers in XENIUS base was longer (1.3-2mm) than in Alert (20-60μm). The new short fiber composite differed significantly in its physical properties compared to other materials tested. This suggests that the latter could be used in high-stress bearing areas. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The Earth's core composition from high pressure density measurements of liquid iron alloys

NASA Astrophysics Data System (ADS)

Morard, G.; Siebert, J.; Andrault, D.; Guignot, N.; Garbarino, G.; Guyot, F.; Antonangeli, D.

2013-07-01

High-pressure, high-temperature in situ X-ray diffraction has been measured in liquid iron alloys (Fe-5 wt% Ni-12 wt% S and Fe-5 wt% Ni-15 wt% Si) up to 94 GPa and 3200 K in laser-heated diamond anvil cells. From the analysis of the X-ray diffuse scattering signal of the metallic liquids, we determined density and bulk modulus of the two liquid alloys. Comparison with a reference Earth model indicates that a core composition containing 6% of sulfur and 2% of silicon by weight would best match the geophysical data. Models with 2.5% of sulfur and 4-5% of silicon are still consistent with geophysical constraints whereas silicon only compositions are not. These results suggest only moderate depletion of sulfur in the bulk Earth.

In-situ high-pressure powder X-ray diffraction study of α-zirconium phosphate.

PubMed

Readman, Jennifer E; Lennie, Alistair; Hriljac, Joseph A

2014-06-01

The high-pressure structural chemistry of α-zirconium phosphate, α-Zr(HPO4)2·H2O, was studied using in-situ high-pressure diffraction and synchrotron radiation. The layered phosphate was studied under both hydrostatic and non-hydrostatic conditions and Rietveld refinement carried out on the resulting diffraction patterns. It was found that under hydrostatic conditions no uptake of additional water molecules from the pressure-transmitting medium occurred, contrary to what had previously been observed with some zeolite materials and a layered titanium phosphate. Under hydrostatic conditions the sample remained crystalline up to 10 GPa, but under non-hydrostatic conditions the sample amorphized between 7.3 and 9.5 GPa. The calculated bulk modulus, K0 = 15.2 GPa, showed the material to be very compressible with the weak linkages in the structure of the type Zr-O-P.

DFT-BASED AB INITIO STUDY OF THE ELECTRONIC AND OPTICAL PROPERTIES OF CESIUM BASED FLUORO-PEROVSKITE CsMF3 (M = Ca AND Sr)

NASA Astrophysics Data System (ADS)

Harmel, M.; Khachai, H.; Ameri, M.; Khenata, R.; Baki, N.; Haddou, A.; Abbar, B.; UǦUR, Ş.; Omran, S. Bin; Soyalp, F.

2012-12-01

Density functional theory (DFT) is performed to study the structural, electronic and optical properties of cubic fluoroperovskite AMF3 (A = Cs; M = Ca and Sr) compounds. The calculations are based on the total-energy calculations within the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential is treated by local density approximation (LDA) and generalized gradient approximation (GGA). The structural properties, including lattice constants, bulk modulus and their pressure derivatives are in very good agreement with the available experimental and theoretical data. The calculations of the electronic band structure, density of states and charge density reveal that compounds are both ionic insulators. The optical properties (namely: the real and the imaginary parts of the dielectric function ɛ(ω), the refractive index n(ω) and the extinction coefficient k(ω)) were calculated for radiation up to 40.0 eV.

Surface and bulk effects of K in Cu 1-xK xIn 1-yGa ySe 2 solar cells

DOE PAGES

Muzzillo, Christopher P.; Anderson, Timothy J.

2017-12-29

Two strategies for enhancing photovoltaic (PV) performance in chalcopyrite solar cells were investigated: Cu 1-xK xIn 1-yGa ySe 2 absorbers with low K content (K/(K+Cu), or x ~ 0.07) distributed throughout the bulk, and CuIn 1-yGa ySe 2 absorbers with KIn 1-yGa ySe 2 grown on their surfaces. Distributing K throughout the bulk absorbers improved power conversion efficiency, open-circuit voltage (VOC) and fill factor (FF) for Ga/(Ga+In) of 0, 0.3 and 0.5. Surface KIn 1-yGa ySe 2 and bulk x ~ 0.07 Cu 1-xK xIn 1-yGa ySe 2 films with Ga/(Ga+In), or y of 0.3 and 0.5 also had improvedmore » efficiency, VOC, and FF, relative to CuIn 1-yGa ySe 2 baselines. On the other hand, y ~ 1 absorbers did not benefit from K introduction. Similar to Cu 1-xK xInSe 2, the formation of Cu 1-xK xGaSe 2 alloys was favored at low temperatures and high Na supply by the substrate, relative to the formation of mixed-phase CuGaSe 2 + KGaSe 2. KIn 1-yGa ySe 2 alloys were grown for the first time, as evidenced by X-ray diffraction and ultraviolet/visible spectroscopy. For all Ga/(Ga+In) compositions, the surface KIn 1-yGa ySe 2 absorbers had superior PV performance in buffered and buffer-free devices. However, the bulk x ~ 0.07 absorbers only outperformed the baselines in buffered devices. The data demonstrate that KIn 1-yGa ySe 2 passivates the surface of CuIn 1-yGa ySe 2 to increase efficiency, VOC, and FF, while bulk Cu 1-xK xIn 1-yGa ySe 2 absorbers with x ~ 0.07 enhance efficiency, VOC, and FF by some other mechanism.« less

Surface and bulk effects of K in Cu 1-xK xIn 1-yGa ySe 2 solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muzzillo, Christopher P.; Anderson, Timothy J.

Two strategies for enhancing photovoltaic (PV) performance in chalcopyrite solar cells were investigated: Cu 1-xK xIn 1-yGa ySe 2 absorbers with low K content (K/(K+Cu), or x ~ 0.07) distributed throughout the bulk, and CuIn 1-yGa ySe 2 absorbers with KIn 1-yGa ySe 2 grown on their surfaces. Distributing K throughout the bulk absorbers improved power conversion efficiency, open-circuit voltage (VOC) and fill factor (FF) for Ga/(Ga+In) of 0, 0.3 and 0.5. Surface KIn 1-yGa ySe 2 and bulk x ~ 0.07 Cu 1-xK xIn 1-yGa ySe 2 films with Ga/(Ga+In), or y of 0.3 and 0.5 also had improvedmore » efficiency, VOC, and FF, relative to CuIn 1-yGa ySe 2 baselines. On the other hand, y ~ 1 absorbers did not benefit from K introduction. Similar to Cu 1-xK xInSe 2, the formation of Cu 1-xK xGaSe 2 alloys was favored at low temperatures and high Na supply by the substrate, relative to the formation of mixed-phase CuGaSe 2 + KGaSe 2. KIn 1-yGa ySe 2 alloys were grown for the first time, as evidenced by X-ray diffraction and ultraviolet/visible spectroscopy. For all Ga/(Ga+In) compositions, the surface KIn 1-yGa ySe 2 absorbers had superior PV performance in buffered and buffer-free devices. However, the bulk x ~ 0.07 absorbers only outperformed the baselines in buffered devices. The data demonstrate that KIn 1-yGa ySe 2 passivates the surface of CuIn 1-yGa ySe 2 to increase efficiency, VOC, and FF, while bulk Cu 1-xK xIn 1-yGa ySe 2 absorbers with x ~ 0.07 enhance efficiency, VOC, and FF by some other mechanism.« less

Polymerization Behavior and Mechanical Properties of High-Viscosity Bulk Fill and Low Shrinkage Resin Composites.

PubMed

Shibasaki, S; Takamizawa, T; Nojiri, K; Imai, A; Tsujimoto, A; Endo, H; Suzuki, S; Suda, S; Barkmeier, W W; Latta, M A; Miyazaki, M

The present study determined the mechanical properties and volumetric polymerization shrinkage of different categories of resin composite. Three high viscosity bulk fill resin composites were tested: Tetric EvoCeram Bulk Fill (TB, Ivoclar Vivadent), Filtek Bulk Fill posterior restorative (FB, 3M ESPE), and Sonic Fill (SF, Kerr Corp). Two low-shrinkage resin composites, Kalore (KL, GC Corp) and Filtek LS Posterior (LS, 3M ESPE), were used. Three conventional resin composites, Herculite Ultra (HU, Kerr Corp), Estelite ∑ Quick (EQ, Tokuyama Dental), and Filtek Supreme Ultra (SU, 3M ESPE), were used as comparison materials. Following ISO Specification 4049, six specimens for each resin composite were used to determine flexural strength, elastic modulus, and resilience. Volumetric polymerization shrinkage was determined using a water-filled dilatometer. Data were evaluated using analysis of variance followed by Tukey's honestly significant difference test (α=0.05). The flexural strength of the resin composites ranged from 115.4 to 148.1 MPa, the elastic modulus ranged from 5.6 to 13.4 GPa, and the resilience ranged from 0.70 to 1.0 MJ/m 3 . There were significant differences in flexural properties between the materials but no clear outliers. Volumetric changes as a function of time over a duration of 180 seconds depended on the type of resin composite. However, for all the resin composites, apart from LS, volumetric shrinkage began soon after the start of light irradiation, and a rapid decrease in volume during light irradiation followed by a slower decrease was observed. The low shrinkage resin composites KL and LS showed significantly lower volumetric shrinkage than the other tested materials at the measuring point of 180 seconds. In contrast, the three bulk fill resin composites showed higher volumetric change than the other resin composites. The findings from this study provide clinicians with valuable information regarding the mechanical properties and polymerization kinetics of these categories of current resin composite.

Casimir effect in rugby-ball type flux compactifications

NASA Astrophysics Data System (ADS)

Elizalde, Emilio; Minamitsuji, Masato; Naylor, Wade

2007-03-01

As a continuation of the work by Minamitsuji, Naylor, and Sasaki [J. High Energy Phys.JHEPFG1029-8479 12 (2006) 07910.1088/1126-6708/2006/12/079], we discuss the Casimir effect for a massless bulk scalar field in a 4D toy model of a 6D warped flux compactification model, to stabilize the volume modulus. The one-loop effective potential for the volume modulus has a form similar to the Coleman-Weinberg potential. The stability of the volume modulus against quantum corrections is related to an appropriate heat kernel coefficient. However, to make any physical predictions after volume stabilization, knowledge of the derivative of the zeta function, ζ'(0) (in a conformally related spacetime) is also required. By adding up the exact mass spectrum using zeta-function regularization, we present a revised analysis of the effective potential. Finally, we discuss some physical implications, especially concerning the degree of the hierarchy between the fundamental energy scales on the branes. For a larger degree of warping our new results are very similar to the ones given by Minamitsuji, Naylor, and Sasaki [J. High Energy Phys.JHEPFG1029-8479 12 (2006) 07910.1088/1126-6708/2006/12/079] and imply a larger hierarchy. In the nonwarped (rugby ball) limit the ratio tends to converge to the same value, independently of the bulk dilaton coupling.

Equation of state of pyrite to 80 GPa and 2400 K

DOE PAGES

Thompson, Elizabeth C.; Chidester, Bethany A.; Fischer, Rebecca A.; ...

2016-05-02

The high-cosmic abundance of sulfur is not reflected in the terrestrial crust, implying it is either sequestered in the Earth’s interior or was volatilized during accretion. As it has widely been suggested that sulfur could be one of the contributing light elements leading to the density deficit of Earth’s core, a robust thermal equation of state of iron sulfide is useful for understanding the evolution and properties of Earth’s interior. We performed X-ray diffraction measurements on FeS 2 achieving pressures from 15 to 80 GPa and temperatures up to 2400 K using laser-heated diamond-anvil cells. No phase transitions were observedmore » in the pyrite structure over the pressure and temperature ranges investigated. Combining our new P-V-T data with previously published room-temperature compression and thermochemical data, we fit a Debye temperature of 624(14) K and determined a Mie-Grüneisen equation of state for pyrite having bulk modulus K T = 141.2(18) GPa, pressure derivative K' T = 5.56(24), Grüneisen parameter γ 0 = 1.41, anharmonic coefficient A 2 = 2.53(27) × 10 –3 J/(K 2·mol), and q = 2.06(27). These findings are compared to previously published equation of state parameters for pyrite from static compression, shock compression, and ab initio studies. This revised equation of state for pyrite is consistent with an outer core density deficit satisfied by 11.4(10) wt% sulfur, yet matching the bulk sound speed of PREM requires an outer core composition of 4.8(19) wt% S. Here, this discrepancy suggests that sulfur alone cannot satisfy both seismological constraints simultaneously and cannot be the only light element within Earth’s core, and so the sulfur content needed to satisfy density constraints using our FeS 2 equation of state should be considered an upper bound for sulfur in the Earth’s core.« less

Elastic and transport properties of topological semimetal ZrTe

NASA Astrophysics Data System (ADS)

Guo, San-Dong; Wang, Yue-Hua; Lu, Wan-Li

2017-11-01

Topological semimetals may have substantial applications in electronics, spintronics, and quantum computation. Recently, ZrTe was predicted as a new type of topological semimetal due to the coexistence of Weyl fermions and massless triply degenerate nodal points. In this work, the elastic and transport properties of ZrTe are investigated by combining the first-principles calculations and semiclassical Boltzmann transport theory. Calculated elastic constants prove the mechanical stability of ZrTe, and the bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio also are calculated. It is found that spin-orbit coupling (SOC) has slightly enhanced effects on the Seebeck coefficient, which along the a(b) and c directions for pristine ZrTe at 300 K is 46.26 μVK-1 and 80.20 μVK-1, respectively. By comparing the experimental electrical conductivity of ZrTe (300 K) with the calculated value, the scattering time is determined as 1.59 × 10-14 s. The predicted room-temperature electronic thermal conductivity along the a(b) and c directions is 2.37 {{Wm}}-1{{{K}}}-1 and 2.90 {{Wm}}-1{{{K}}}-1, respectively. The room-temperature lattice thermal conductivity is predicted as 17.56 {{Wm}}-1{{{K}}}-1 and 43.08 {{Wm}}-1{{{K}}}-1 along the a(b) and c directions, showing very strong anisotropy. Calculated results show that isotope scattering produces an observable effect on lattice thermal conductivity. To observably reduce lattice thermal conductivity by nanostructures, the characteristic length should be smaller than 70 nm, based on cumulative lattice thermal conductivity with respect to the phonon mean free path (MFP) at 300 K. It is noted that the average room-temperature lattice thermal conductivity of ZrTe is slightly higher than that of isostructural MoP, which is due to larger phonon lifetimes and smaller Grüneisen parameters. Finally, the total thermal conductivity as a function of temperature is predicted for pristine ZrTe. Our works provide valuable information for ZrTe-based nano-electronics devices, and motivate further experimental works to study elastic and transport properties of ZrTe.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heffernan, Karina M.; Ross, Nancy L., E-mail: nross@vt.edu; Spencer, Elinor C.

Accurate elastic constants for gadolinium phosphate (GdPO{sub 4}) have been measured by single-crystal high-pressure diffraction methods. The bulk modulus of GdPO{sub 4} determined under hydrostatic conditions, 128.1(8) GPa (K′=5.8(2)), is markedly different from that obtained with GdPO{sub 4} under non-hydrostatic conditions (160(2) GPa), which indicates the importance of shear stresses on the elastic response of this phosphate. High pressure Raman and diffraction analysis indicate that the PO{sub 4} tetrahedra behave as rigid units in response to pressure and that contraction of the GdPO{sub 4} structure is facilitated by bending/twisting of the Gd–O–P links that result in increased distortion in themore » GdO{sub 9} polyhedra. - Graphical abstract: A high-pressure single crystal diffraction study of GdPO{sub 4} with the monazite structure is presented. The elastic behaviour of rare-earth phosphates are believed to be sensitive to shear forces. The bulk modulus of GdPO{sub 4} measured under hydrostatic conditions is 128.1(8) GPa. Compression of the structure is facilitated by bending/twisting of the Gd−O−P links that result in increased distortion in the GdO{sub 9} polyhedra. Display Omitted - Highlights: • The elastic responses of rare-earth phosphates are sensitive to shear forces. • The bulk modulus of GdPO{sub 4} measured under hydrostatic conditions is 128.1(8) GPa. • Twisting of the inter-polyhedral links allows compression of the GdPO{sub 4} structure. • Changes to the GdO{sub 9} polyhedra occur in response to pressure (<7.0 GPa).« less

Effective Elastic and Neutron Capture Cross Section Calculations Corresponding to Simulated Fluid Properties from CO2 Push-Pull Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chugunov, Nikita; Altundas, Bilgin

The submission contains a .xls files consisting of 10 excel sheets, which contain combined list of pressure, saturation, salinity, temperature profiles from the simulation of CO2 push-pull using Brady reservoir model and the corresponding effective compressional and shear velocity, bulk density, and fluid and time-lapse neutron capture cross section profiles of rock at times 0 day (baseline) through 14 days. First 9 sheets (each named after the corresponding CO2 push-pull simulation time) contains simulated pressure, saturation, temperature, salinity profiles and the corresponding effective elastic and neutron capture cross section profiles of rock matrix at the time of CO2 injection. Eachmore » sheet contains two sets of effective compressional velocity profiles of the rock, one based on Gassmann and the other based on Patchy saturation model. Effective neutron capture cross section calculations are done using a proprietary neutron cross-section simulator (SNUPAR) whereas for the thermodynamic properties of CO2 and bulk density of rock matrix filled with fluid, a standalone fluid substitution tool by Schlumberger is used. Last sheet in the file contains the bulk modulus of solid rock, which is inverted from the rock properties (porosity, sound speed etc) based on Gassmann model. Bulk modulus of solid rock in turn is used in the fluid substitution.« less

Evaluation of a high response electrohydraulic digital control valve

NASA Technical Reports Server (NTRS)

Anderson, R. L.

1973-01-01

The application is described of a digital control valve on an electrohydraulic servo actuator. The digital control problem is discussed in general as well as the design and evaluation of a breadboard actuator. The evaluation revealed a number of problems associated with matching the valve to a hydraulic load. The problems were related to lost motion resulting from bulk modulus and leakage. These problems were effectively minimized in the breadboard actuator by maintaining a 1000 psi back pressure on the valve circuit and thereby improving the effective bulk modulus.

Elasticity of fluorite at high temperatures

NASA Astrophysics Data System (ADS)

Eke, J.; Tennakoon, S.; Mookherjee, M.

2017-12-01

Fluorite (CaF2) is a simple halide with cubic space group symmetry (Fm-3m) and is often used as an internal pressure calibrant in moderate high-pressure/high-temperature experiments [1]. In order to gain insight into the elastic behavior of fluorite, we have conducted Resonant Ultrasound Spectroscopy (RUS) on a single crystal of fluorite with rectangular parallelepiped geometry. Using single crystal X-ray diffraction, we aligned the edges of the rectangular parallelepiped with [-1 1 1], [-1 1 -2], and [-1 -1 0] crystallographic directions. We conducted the RUS measurements up to 620 K. RUS spectra are influenced by the geometry, density, and the full elastic moduli tensor of the material. In our high-temperature RUS experiments, the geometry and density were constrained using thermal expansion from previous studies [2]. We determined the elasticity by minimizing the difference between observed resonance and calculated Eigen frequency using Rayleigh-Ritz method [3]. We found that at room temperature, the single crystal elastic moduli for fluorite are 170, 49, and 33 GPa for C11, C12, and C44 respectively. At room temperatures, the aggregate bulk modulus (K) is 90 GPa and the shear modulus (G) is 43 GPa. We note that the elastic moduli and sound wave velocities decrease linearly as a function of temperature with dVP /dT and dVS /dT being -9.6 ×10-4 and -5.0 ×10-4 km/s/K respectively. Our high-temperature RUS results are in good agreement with previous studies on fluorite using both Ultrasonic methods and Brillouin scattering [4,5]. Acknowledgement: This study is supported by US NSF awards EAR-1639552 and EAR-1634422. References: [1] Speziale, S., Duffy, T. S. 2002, Phys. Chem. Miner., 29, 465-472; [2] Roberts, R. B., White, G. K., 1986, J. Phys. C: Solid State Phys., 19, 7167-7172. [3] Migliori, A., Maynard, J. D., 2005, Rev. Sci. Instrum., 76, 121301. [4] Catlow, C. R. A., Comins, J. D., Germano, F. A., Harley, R. T., Hayes, W., 1978, J. Phys. C Solid State Phys., 11, 3197; [5] Jones, L. E. A., 1977, Phys. Earth Planet. Inter., 15(1), 77-89.

3D Modeling Effect of Spherical Inclusions on the Magnetostriction of Bulk Superconductors

NASA Astrophysics Data System (ADS)

Zhao, Yufeng; Pan, Baocai

2018-02-01

In this paper, the dependence of the effective magnetostriction of bulk superconductors on the elastic parameters including the volume fraction and elastic modulus ratio is studied by a three-dimensional model consisting of a spherical inclusion-superconducting matrix system. The effect of the elastic modulus and volume fraction on the magnetostriction is also obtained through the magnetostriction loop. The results indicate that the elastic modulus and volume fraction have obvious effects on the effective magnetostriction of the superconducting composite, which gives an explanation about the differences between the experimental and the theoretical results. Furthermore, it is worth pointing out that the linear field dependence of magnetostriction is unique to the Bean model by comparing the curve shapes of the magnetostriction loop with and without inclusion.

Surface and Bulk Effects of K in Highly Efficient Cu1-xKxInSe2 Solar Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muzzillo, Christopher; Mansfield, Lorelle M; Ramanathan, Kannan

To advance knowledge of the beneficial effects of K in Cu(In,Ga)(Se,S)2 (CIGS) photovoltaic (PV) absorbers, recent Cu-K-In-Se phase growth studies have been extended to PV performance. First, the effect of distributing K throughout bulk Cu1-xKxInSe2 absorbers at low K/(K+Cu) compositions (0 = x = 0.30) was studied. Efficiency, open-circuit voltage (VOC), and fill factor (FF) were greatly enhanced for x ~ 0.07, resulting in an officially-measured 15.0%-efficient solar cell, matching the world record CuInSe2 efficiency. The improvements were a result of reduced interface and bulk recombination, relative to CuInSe2 (x ~ 0). However, higher x compositions had reduced efficiency, short-circuitmore » current density (JSC), and FF due to greatly increased interface recombination, relative to the x ~ 0 baseline. Next, the effect of confining K at the absorber/buffer interface at high K/(K+Cu) compositions (0.30 = x = 0.92) was researched. Previous work showed that these surface layer growth conditions produced CuInSe2 with a large phase fraction of KInSe2. After optimization (75 nm surface layer with x ~ 0.41), these KInSe2 surface samples exhibited increased efficiency (officially 14.9%), VOC, and FF as a result of decreased interface recombination. The KInSe2 surfaces had features similar to previous reports for KF post-deposition treatments (PDTs) used in world record CIGS solar cells - taken as indirect evidence that KInSe2 can form during these PDTs. Both the bulk and surface growth processes greatly reduced interface recombination. However, the KInSe2 surface had higher K levels near the surface, greater lifetimes, and increased inversion near the buffer interface, relative to the champion bulk Cu1-xKxInSe2 absorber. These characteristics demonstrate that K may benefit PV performance by different mechanisms at the surface and in the absorber bulk.« less

An isothermal equation of state for solids

NASA Astrophysics Data System (ADS)

Bose Roy, Papiya; Bose Roy, Sushil

2004-07-01

An isothermal equation of state (EOS) for solids, recently suggested by the authors in the realistic form, V/ V0= f( P), with relative volume as the dependent and the pressure as the independent variable, was shown to have an advantage for some close-packed materials in that it allows B‧ ∞=(∂ Bs/∂ P) s( P→∞) to be fitted, and this is where the usual standard equations fail. In the present study, our EOS is applied to a number of inorganic as well as organic solids, including alloys, glasses, rubbers and plastics; varying widely in their bonding and structural characteristics, as well as in their bulk modulus values. A very good agreement is observed between the data and fits. The results obtained are compared with those from two well-known equations, expressible in the realistic form, proposed by Murnaghan and Luban. Further, the results are also compared with those from the widely used two- and three-parameter EOSs, expressible in the unrealistic form only, P= f( V/ V0), proposed by Birch-and also with those from the EOS model of Keane in which B‧ ∞ is explicitly expressed as an equation of state parameter. The results obtained from our model compare well to these EOSs. Our EOS, in general, yields the smallest mean-squared deviations between data and fits. The values of B‧ ∞calculated from our EOS are compared with those from Keane's model. Further, we have studied the variation of B‧ ∞with temperature using the experimental isotherms of Mo and W at 10 different temperatures ranging from 100 to 1000 K, and observed that the values of B‧ ∞ yielded by our model and that of Keane vary, as expected, within a narrow range. Furthermore, our EOS is applied to study the stability of the fit parameters with variation in the pressure ranges with reference to the isothermal compression data on Mo and W-and also to study the variation of isothermal bulk modulus with pressure, with reference to the ultrasonic data on NaCl and noted a very good agreement with experiment. In addition, our model is applied, with B0 and B‧ 0 constrained to the theoretical values, to the five theoretical isotherms of MgO at 300, 500, 1000, 1500 and 2000 K obtained on the basis of a first principles approach-a good agreement is observed with the predictions, and the values of B‧ ∞ inferred at different temperatures tend to converge to a constant value.

Light transmittance and micro-mechanical properties of bulk fill vs. conventional resin based composites.

PubMed

Bucuta, Stefan; Ilie, Nicoleta

2014-11-01

The aim of this study was to quantify the blue light that passes through different incremental thicknesses of bulk fill in comparison to conventional resin-based composites (RBCs) and to relate it to the induced mechanical properties. Seven bulk fill, five nanohybrid and two flowable RBCs were analysed. Specimens (n = 5) of three incremental thicknesses (2, 4 and 6 mm) were cured from the top for 20 s, while at the bottom, a spectrometer monitored in real time the transmitted irradiance. Micro-mechanical properties (Vickers hardness, HV, and indentation modulus, E) were measured at the top and bottom after 24 h of storage in distilled water at 37 °C. Electron microscope images were taken for assessing the filler distribution and size. Bulk fill RBCs (except SonicFill) were more translucent than conventional RBCs. Low-viscosity bulk fill materials showed the lowest mechanical properties. HV depends highly on the following parameters: material (ηp (2) = 0.952), incremental thickness (0.826), filler volume (0.747), filler weight (0.746) and transmitted irradiance (0.491). The bottom-to-top HV ratio (HVbt) was higher than 80 % in all materials in 2- and 4-mm increments (except for Premise), whereas in 6-mm increments, this is valid only in four bulk fill materials (Venus Bulk Fill, SDR, x-tra fil, Tetric EvoCeram Bulk Fill). The depth of cure is dependent on the RBC's translucency. Low-viscosity bulk fill RBCs have lower mechanical properties than all other types of analysed materials. All bulk fill RBCs (except SonicFill) are more translucent for blue light than conventional RBCs. Although bulk fill RBCs are generally more translucent, the practitioner has to follow the manufacturer's recommendations on curing technique and maximum incremental thickness.

Physical and mechanical characterisation of 3D-printed porous titanium for biomedical applications.

PubMed

El-Hajje, Aouni; Kolos, Elizabeth C; Wang, Jun Kit; Maleksaeedi, Saeed; He, Zeming; Wiria, Florencia Edith; Choong, Cleo; Ruys, Andrew J

2014-11-01

The elastic modulus of metallic orthopaedic implants is typically 6-12 times greater than cortical bone, causing stress shielding: over time, bone atrophies through decreased mechanical strain, which can lead to fracture at the implantation site. Introducing pores into an implant will lower the modulus significantly. Three dimensional printing (3DP) is capable of producing parts with dual porosity features: micropores by process (residual pores from binder burnout) and macropores by design via a computer aided design model. Titanium was chosen due to its excellent biocompatibility, superior corrosion resistance, durability, osteointegration capability, relatively low elastic modulus, and high strength to weight ratio. The mechanical and physical properties of 3DP titanium were studied and compared to the properties of bone. The mechanical and physical properties were tailored by varying the binder (polyvinyl alcohol) content and the sintering temperature of the titanium samples. The fabricated titanium samples had a porosity of 32.2-53.4% and a compressive modulus of 0.86-2.48 GPa, within the range of cancellous bone modulus. Other physical and mechanical properties were investigated including fracture strength, density, fracture toughness, hardness and surface roughness. The correlation between the porous 3DP titanium-bulk modulus ratio and porosity was also quantified.

Structural, electronic, mechanical, thermal and optical properties of B(P,As)1-xNx; (x = 0, 0.25, 0.5, 0.75, 1) alloys and hardness of B(P,As) under compression using DFT calculations

NASA Astrophysics Data System (ADS)

Viswanathan, E.; Sundareswari, M.; Jayalakshmi, D. S.; Manjula, M.; Krishnaveni, S.

2017-09-01

First principles calculations are carried out in order to analyze the structural, electronic, mechanical, thermal and optical properties of BP and BAs compounds by ternary alloying with nitrogen namely B(P,As)1-xNx (x = 0.25, 0.5, 0.75) alloys at ambient condition. Thereby we report the mechanical and thermal properties of B(P,As)1-xNx (x = 0.25, 0.5, 0.75) alloys namely bulk modulus, shear modulus, Young's modulus, hardness, ductile-brittle nature, elastic wave velocity, Debye temperature, melting point, etc.; optical properties of B(P)1-xNx (x = 0.25, 0.5, 0.75) and B(As)1-xNx (x = 0.25, 0.75) alloys namely the dielectric function of real and imaginary part, refractive index, extinction coefficient and reflectivity and the hardness profile of the parent compounds BP and BAs under compression. The charge density plot, density of states histograms and band structures are plotted and discussed for all the ternary alloys of the present study. The calculated results agree very well with the available literature. Analysis of the present study reveals that the ternary alloy combinations namely BP.25N.75 and BAs.25N.75 could be superhard materials; hardness of BP and BAs increases with compression.

Correlated Time-Variation of Asphalt Rheology and Bulk Microstructure

NASA Astrophysics Data System (ADS)

Ramm, Adam; Nazmus, Sakib; Bhasin, Amit; Downer, Michael

We use noncontact optical microscopy and optical scattering in the visible and near-infrared spectrum on Performance Grade (PG) asphalt binder to confirm the existence of microstructures in the bulk. The number of visible microstructures increases linearly as penetration depth of the incident radiation increases, which verifies a uniform volume distribution of microstructures. We use dark field optical scatter in the near-infrared to measure the temperature dependent behavior of the bulk microstructures and compare this behavior with Dynamic Shear Rheometer (DSR) measurements of the bulk complex shear modulus | G* (T) | . The main findings are: (1) After reaching thermal equilibrium, both temperature dependent optical scatter intensity (I (T)) and bulk shear modulus (| G* (T) |) continue to change appreciably for times much greater than thermal equilibration times. (2) The hysteresis behavior during a complete temperature cycle seen in previous work derives from a larger time dependence in the cooling step compared with the heating step. (3) Different binder aging conditions show different thermal time-variations for both I (T) and | G* (T) | .

First-principles investigation of thermodynamic, elastic and electronic properties of Al{sub 3}V and Al{sub 3}Nb intermetallics under pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zhe; Zhang, Peng; Chen, Dong

2015-02-28

The thermodynamic, elastic, and electronic properties of D0{sub 22}-type Al{sub 3}V and Al{sub 3}Nb intermetallics were studied using the first-principle method. The results showed the pressure has profound effects on the structural, mechanical and electronic properties in both Al{sub 3}V and Al{sub 3}Nb. Thermodynamically, the formation enthalpies for Al{sub 3}V and Al{sub 3}Nb were derived, which agreed well with available experimental and theoretical values. Comparably, Al{sub 3}Nb was a more stable phase with the more negative H{sub f} than Al{sub 3}V. Mechanically, the calculated elastic constants showed linearly increasing tendencies, and satisfied the Born's criteria from 0–20 GPa, indicating the mechanicallymore » stability of Al{sub 3}V and Al{sub 3}Nb under this pressure range. Further, the mechanical parameters (i.e., bulk modulus (B), shear modulus (G), and Young's modulus (E)) were derived using the Voigt-Reuss-Hill (VRH) method, and in good agreement with available experimental results at the ground state. All these parameters presented the linearly increasing dependences on the external pressure. The B/G ratios and Poisson's ratio indicated that the Al{sub 3}V and Al{sub 3}Nb crystals should exhibit brittle behavior at 0–20 GPa. Additionally, the bulk modulus can be obtained through fitting the Birch-Murnaghan equation (B{sub 0}), computing by VRH method (B{sub H}), and deriving from the elastic theory (B{sub relax}) in both intermetallics. The uniformity of these calculated bulk moduli in each compound exhibited the excellent reliability and self-consistency. In addition, Debye temperature was estimated from the average sound velocity. The Debye temperature showed an increasing dependence on the pressures. Finally, through density of states analysis, Al{sub 3}V and Al{sub 3}Nb were suggested to possess naturally metallic behavior. Under pressures, it was noted that the shapes of peaks and pseudogaps exhibited relative few changes, suggesting Al{sub 3}V and Al{sub 3}Nb has kept structurally stable up to 20 GPa. At zero pressure, Al{sub 3}Nb was considered as a more structurally stable phase with the more number of bonding electrons per atom than Al{sub 3}V. This conclusion was in consistent with the one drawn from the thermodynamic analysis.« less

Metal–Organic–Inorganic Nanocomposite Thermal Interface Materials with Ultralow Thermal Resistances

DOE PAGES

Yegin, Cengiz; Nagabandi, Nirup; Feng, Xuhui; ...

2017-02-27

As electronic devices get smaller and more powerful, energy density of energy storage devices increases continuously, and moving components of machinery operate at higher speeds, the need for better thermal management strategies is becoming increasingly important. The removal of heat dissipated during the operation of electronic, electrochemical, and mechanical devices is facilitated by high-performance thermal interface materials (TIMs) which are utilized to couple devices to heat sinks. Here in this paper, we report a new class of TIMs involving the chemical integration of boron nitride nanosheets (BNNS), soft organic linkers, and a copper matrix -- which are prepared by chemisorption-coupledmore » electrodeposition approach. These hybrid nanocomposites demonstrate bulk thermal conductivities ranging from 211 to 277 W/(m.K), which are very high considering their relatively low elastic modulus values on the order of 21.2 to 28.5 GPa. The synergistic combination of these properties lead to the ultra-low total thermal resistivity values in the range of 0.38 to 0.56 mm 2.K/W for a typical bondline thickness of 30-50 um, advancing the current state-of-art transformatively. Moreover, its coefficient of thermal expansion (CTE) is 11 ppm/K, forming a mediation zone with a low thermally-induced axial stress due to its close proximity to the CTE of most coupling surfaces needing thermal management.« less

Metal–Organic–Inorganic Nanocomposite Thermal Interface Materials with Ultralow Thermal Resistances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yegin, Cengiz; Nagabandi, Nirup; Feng, Xuhui

As electronic devices get smaller and more powerful, energy density of energy storage devices increases continuously, and moving components of machinery operate at higher speeds, the need for better thermal management strategies is becoming increasingly important. The removal of heat dissipated during the operation of electronic, electrochemical, and mechanical devices is facilitated by high-performance thermal interface materials (TIMs) which are utilized to couple devices to heat sinks. Here in this paper, we report a new class of TIMs involving the chemical integration of boron nitride nanosheets (BNNS), soft organic linkers, and a copper matrix -- which are prepared by chemisorption-coupledmore » electrodeposition approach. These hybrid nanocomposites demonstrate bulk thermal conductivities ranging from 211 to 277 W/(m.K), which are very high considering their relatively low elastic modulus values on the order of 21.2 to 28.5 GPa. The synergistic combination of these properties lead to the ultra-low total thermal resistivity values in the range of 0.38 to 0.56 mm 2.K/W for a typical bondline thickness of 30-50 um, advancing the current state-of-art transformatively. Moreover, its coefficient of thermal expansion (CTE) is 11 ppm/K, forming a mediation zone with a low thermally-induced axial stress due to its close proximity to the CTE of most coupling surfaces needing thermal management.« less

Comparison of glutaraldehyde and carbodiimides to crosslink tissue engineering scaffolds fabricated by decellularized porcine menisci.

PubMed

Gao, Shuang; Yuan, Zhiguo; Guo, Weimin; Chen, Mingxue; Liu, Shuyun; Xi, Tingfei; Guo, Quanyi

2017-02-01

The objectives of this study were to fabricate porous scaffolds using decellularized meniscus, and to explore a preferable crosslinking condition to enhance mechanical properties of scaffolds. Moreover, the microstructure, porosity, biodegradation and cytotoxicity were also evaluated. EDAC or GTA in different concentration was used to crosslink scaffolds. FTIR demonstrated functional groups change in crosslinking process. SEM photography showed that crosslinked scaffolds had blurry edges, which resulted scaffolds crosslinked by 1.2mol/l EDAC had smaller porosity than other groups. The structure change enhanced antidegradation property. After immersing in enzyme solution for 96h, scaffolds crosslinked by GTA and EDAC could maintain their mass >70% and 80%. Most importantly, mechanical properties of crosslinked scaffolds were also improved. Uncrosslinked Scaffolds had only 0.49kPa in compression modulus and 12.81kPa in tensile modulus. The compression and tensile modulus of scaffolds crosslinked by 1.0% GTA were 1.42 and 567.44kPa respectively. The same value of scaffolds crosslinked by 1.2mol/l EDAC were 1.49 and 532.50kPa. Scaffolds crosslinked by 1.0% and 2.5% GTA were toxic to cells, while EDAC groups showed no cytotoxicity. Chondrocytes could proliferate and infiltrate within scaffolds after seeding. Overall, 1.2mol/l EDAC was a preferable crosslinking condition. Copyright © 2016 Elsevier B.V. All rights reserved.

A novel pressure variation study on electronic structure, mechanical stability and thermodynamic properties of potassium based fluoroperovskite

NASA Astrophysics Data System (ADS)

Erum, Nazia; Azhar Iqbal, Muhammad

2017-09-01

The effect of pressure variation on stability, structural parameters, elastic constants, mechanical, electronic and thermodynamic properties of cubic SrKF3 fluoroperovskite have been investigated by using the full-potential linearized augmented plane wave (FP-LAPW) method combined with Quasi-harmonic Debye model in which the phonon effects are considered. The calculated lattice parameters show a prominent decrease in lattice constant and bonds length with the increase in pressure. The application of pressure from 0 to 25 GPa reveals a predominant characteristic associated with widening of bandgap with GGA and GGA plus Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. The influence of pressure on elastic constants and their related mechanical parameters have been discussed in detail. Apart of linear dependence of elastic coefficients, transition from brittle to ductile behavior is also observed at elevated pressure ranges. We have successfully computed variation of lattice constant, volume expansion, bulk modulus, Debye temperature and specific heat capacities at pressure and temperature in the range of 0-25 GPa and 0-600 K.

High pressure effects on U L 3 x-ray absorption in partial fluorescence yield mode and single crystal x-ray diffraction in the heavy fermion compound UCd 11

DOE PAGES

Nasreen, Farzana; Antonio, Daniel; VanGennep, Derrick; ...

2016-02-15

© 2016 IOP Publishing Ltd. We report a study of high pressure x-ray absorption (XAS) performed in the partial fluorescence yield mode (PFY) at the U L 3 edge (0-28.2 GPa) and single crystal x-ray diffraction (SXD) (0-20 GPa) on the UCd 11 heavy fermion compound at room temperature. Under compression, the PFY-XAS results show that the white line is shifted by +4.1(3) eV at the highest applied pressure of 28.2 GPa indicating delocalization of the 5f electrons. The increase in full width at half maxima and decrease in relative amplitude of the white line with respect to the edgemore » jump point towards 6d band broadening under high pressure. A bulk modulus of K 0 = 62(1) GPa and its pressure derivative, = 4.9(2) was determined from high pressure SXD results. Both the PFY-XAS and diffraction results do not show any sign of a structural phase transition in the applied pressure range.« less

X-ray-diffraction study of californium metal to 16 GPa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peterson, J.R.; Benedict, U.; Dufour, C.

1983-01-01

The first series of measurements to determine the structural behavior of californium (Cf) metal under pressure has been carried out. The initial dhcp structure transformed sluggishly with increasing pressure to a fcc structure. A bulk modulus of 50(5) GPa was derived for dhcp Cf metal from the relative volume (V/V/sub 0/) data to 10 GPa.

Stability and Elastic, Electronic, and Thermodynamic Properties of Fe2TiSi1- x Sn x Compounds

NASA Astrophysics Data System (ADS)

Jong, Ju-Yong; Yan, Jihong; Zhu, Jingchuan; Kim, Chol-Jin

2017-10-01

We have systematically studied the structural, phase, and mechanical stability and elastic, electronic, and thermodynamic properties of Fe2TiSi1- x Sn x ( x = 0, 0.25, 0.5, 0.75, 1) compounds using first-principles calculations. The structural and phase stability and elastic properties of Fe2TiSi1- x Sn x ( x = 0, 0.25, 0.5, 0.75, 1) indicated that all of the compounds are thermodynamically and mechanically stable. The shear modulus, bulk modulus, Young's modulus, Poisson's ratio, electronic band structure, density of states, Debye temperature, and Grüneisen parameter of all the substituted compounds were studied. The results show that Sn substitution in Fe2TiSi enhances its stability and mechanical and thermoelectric properties. The Fe2TiSi1- x Sn x compounds have narrow bandgap from 0.144 eV and 0.472 eV for Sn substitution from 0 to 1. The calculated band structure and density of states (DOS) of Fe2TiSi1- x Sn x show that the thermoelectric properties can be improved at substituent concentration x of 0.75. The lattice thermal conductivity was significantly decreased in the Sn-substituted compounds, and all the results indicate that Fe2TiSi0.25Sn0.75 could be a new candidate high-performance thermoelectric material.

Structural and thermodynamic properties of WB at high pressure and high temperature

NASA Astrophysics Data System (ADS)

Chen, Hai-Hua; Bi, Yan; Cheng, Yan; Ji, Guangfu; Peng, Fang; Hu, Yan-Fei

2012-12-01

The structure parameters and electronic structures of tungsten boride (WB) have been investigated by using the density functional theory (DFT). Our calculating results display the bulk modulus of WB are 352±2 GPa (K‧0=4.29) and 322±3 GPa (K‧0=4.21) by LDA and GGA methods, respectively. We have analyzed the probable reason of the discrepancy from the bulk modulus between theoretical and experimental results. The compression behavior of the unit cell axes is anisotropic, with the c-axis being more compressible than the a-axis. By analyzing the bond lengths information, it also demonstrated that WB has a lower compressibility at high pressure. From the partial densities of states (PDOS) of WB, we found that the Fermi lever is mostly contributed by the d states of W atom and p states of B atom and that the contributions from the s, p states of W atom and s states of B atom are small. Moreover, using the Gibbs 2 program, the thermodynamic properties of WB are obtained in a wide temperature range at high pressure for the first time in this work.

Shape, size and temperature dependency of thermal expansion, lattice parameter and bulk modulus in nanomaterials

NASA Astrophysics Data System (ADS)

Goyal, M.; Gupta, B. R. K.

2018-06-01

A theoretical model is described here for studying the effect of temperature on nanomaterials. The thermodynamic equation of state (EoS) proposed by Goyal and Gupta in High Temp.-High Press. 45, 163 (2016); Oriental J. Chem. 32( 4), 2193 (2016), is extended in the present study using Qi and Wang model [ Mater. Chem. Phys. 88, 280 (2004)]. The thermal expansion coefficient is expressed in terms of shape and size and used to obtain the isobaric EoS of nanomaterials for the change in volume V/{V_0}. The variation in V/{V_0} with temperature is estimated for spherical nanoparticles, nanowires and nanofilms. It is found that the volume thermal expansivity decreases as size of the nanomaterial increases, whereas V/{V_0} increases with temperature across nanomaterials of different sizes. The lattice parameter variation with temperature is studied in Zn nanowires, Se and Ag nanoparticles. It is found that lattice constant increases with increase in temperature. Also, bulk modulus is found to increase with temperature in nanomaterials. The results obtained from the present model are compared with the available experimental data. A good consistency between the compared results confirms the suitability of the present model for studying thermal properties of the nanomaterials.

Temperature dependent behavior of thermal conductivity of sub-5 nm Ir film: Defect-electron scattering quantified by residual thermal resistivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Zhe; Xu, Zaoli; Xu, Shen

2015-01-14

By studying the temperature-dependent behavior (300 K down to 43 K) of electron thermal conductivity (κ) in a 3.2 nm-thin Ir film, we quantify the extremely confined defect-electron scatterings and isolate the intrinsic phonon-electron scattering that is shared by the bulk Ir. At low temperatures below 50 K, κ of the film has almost two orders of magnitude reduction from that of bulk Ir. The film has ∂κ/∂T > 0, while the bulk Ir has ∂κ/∂T < 0. We introduce a unified thermal resistivity (Θ = T/κ) to interpret these completely different κ ∼ T relations. It is found that the film and the bulk Ir share a very similar Θ ∼ T trend,more » while they have a different residual part (Θ{sub 0}) at 0 K limit: Θ{sub 0} ∼ 0 for the bulk Ir, and Θ{sub 0} = 5.5 m·K{sup 2}/W for the film. The Ir film and the bulk Ir have very close ∂Θ/∂T (75–290 K): 6.33 × 10{sup −3} m K/W for the film and 7.62 × 10{sup −3} m K/W for the bulk Ir. This strongly confirms the similar phonon-electron scattering in them. Therefore, the residual thermal resistivity provides an unprecedented way to quantitatively evaluating defect-electron scattering (Θ{sub 0}) in heat conduction. Moreover, the interfacial thermal conductance across the grain boundaries is found larger than that of Al/Cu interface, and its value is proportional to temperature, largely due to the electron's specific heat. A unified interfacial thermal conductance is also defined and firmly proves this relation. Additionally, the electron reflection coefficient is found to be large (88%) and almost temperature independent.« less

A Novel Quantitative 500-MHz Acoustic-microscopy System for Ophthalmologic Tissues

PubMed Central

Rohrbach, Daniel; Jakob, Anette; Lloyd, Harriet O.; Tretbar, Steffen H.; Silverman, Ronald H.; Mamou, Jonathan

2017-01-01

Objective This paper describes development of a novel 500-MHz scanning acoustic microscope (SAM) for assessing the mechanical properties of ocular tissues at fine resolution. The mechanical properties of some ocular tissues, such as lamina cribrosa (LC) in the optic nerve head, are believed to play a pivotal role in eye pathogenesis. Methods A novel etching technology was used to fabricate silicon-based lens for a 500-MHz transducer. The transducer was tested in a custom designed scanning system on human eyes. Two-dimensional (2D) maps of bulk modulus (K), mass density (ρ) were derived using improved versions of current state-of-the-art signal processing approaches. Results The transducer employed a lens radius of 125 μm and had a center frequency of 479 MHz with a −6-dB bandwidth of 264 MHz and a lateral resolution of 4 μm. The LC, Bruch’s membrane (BM) at the interface of the retina and choroid, and Bowman’s layer (BL) at the interface of the corneal epithelium and stroma, were successfully imaged and resolved. Analysis of the 2D parameter maps revealed average values of LC, BM and BL with KLC = 2.81 ± 0.17; GPa, KBM = 2.89 ± 0.18; GPa, K BL = 2.6 ± 0.09; GPa, ρ LC = 0.96 ± 0.03 g/cm3; ρ BM = 0.97 ± 0.04 g/cm3; ρ BL = 0.98 ± 0.04g/cm3; Significance This novel SAM was shown to be capable of measuring mechanical properties of soft biological tissues at microscopic resolution; it currently is the only system that allows Simultaneous measurement of K, ρ, and attenuation in large lateral scales (field area > 9 mm2) and at fine resolutions. PMID:27249824

Mechanical Properties of β-Ti-35Nb-2.5Sn Alloy Synthesized by Mechanical Alloying and Pulsed Current Activated Sintering

NASA Astrophysics Data System (ADS)

Omran, Abdel-Nasser; Woo, Kee-Do; Lee, Hyun Bom

2012-12-01

A developed Ti-35 pct Nb-2.5 pct Sn (wt pct) alloy was synthesized by mechanical alloying using high-energy ball-milled powders, and the powder consolidation was done by pulsed current activated sintering (PCAS). The starting powder materials were mixed for 24 hours and then milled by high-energy ball milling (HEBM) for 1, 4, and 12 hours. The bulk solid samples were fabricated by PCAS at 1073 K to 1373 K (800 °C to 1100 °C) for a short time, followed by rapid cooling to 773 K (500 °C). The relative density of the sintered samples was about 93 pct. The Ti was completely transformed from α to β-Ti phase after milling for 12 hours in powder state, and the specimen sintered at 1546 K (1273 °C) was almost transformed to β-Ti phase. The homogeneity of the sintered specimen increased with increasing milling time and sintering temperature, as did its hardness, reaching 400 HV after 12 hours of milling. The Young's modulus was almost constant for all sintered Ti-35 pct Nb-2.5 pct Sn specimens at different milling times. The Young's modulus was low (63.55 to 65.3 GPa) compared to that of the standard alloy of Ti-6Al-4V (100 GPa). The wear resistance of the sintered specimen increased with increasing milling time. The 12-hour milled powder exhibited the best wear resistance.

Ab initio investigation of Ti2Al(C,N) solid solutions

NASA Astrophysics Data System (ADS)

Arróyave, Raymundo; Radovic, Miladin

2011-10-01

Mn+1AXn phases (M: early transition metal, A: IIIA- or IVA-group element, X: carbon or nitrogen) are layered ternary compounds that possess both metal- and ceramic-like properties with numerous potential applications in bulk and thin film forms, particularly under high-temperature conditions. In this work, we use the cluster expansion formalism to investigate the energetics of C-N interactions across the entire Ti2AlC-Ti2AlN composition range. It is shown that there is a definite tendency for ordering in the C,N sublattice. However, the molar volume and bulk modulus of the ordered structures found along the Ti2AlC-Ti2AlN composition range show small deviations from the (linear) rule of mixing, indicating that despite the ordering tendencies, the C-N interactions are not strong and the solution becomes disordered at relatively low temperatures. Random solid solutions of Ti2AlC1-xNx are simulated using special quasirandom structures (SQS) with x=0.25, 0.50, and 0.75. The thermodynamic properties of these structures are compared to those of the structures found to belong to the ground state through the cluster expansion approach. It is found that the structural properties of these approximations to random alloys do not deviate significantly from Vegard's law. The trend in the structural parameters of these SQS are found to agree well with available experimental data and the predictions of the bulk modulus suggest a very weak alloying effect—with respect to Vegard's law—on the elastic properties of Ti2AlC1-xNx.

Low Young's modulus Ti-based porous bulk glassy alloy without cytotoxic elements.

PubMed

Nicoara, M; Raduta, A; Parthiban, R; Locovei, C; Eckert, J; Stoica, M

2016-05-01

A new a biocompatible Ti42Zr40Ta3Si15 (atomic %) porous bulk glassy alloy was produced by combination of rapid solidification and powder metallurgy techniques. Amorphous alloy ribbons were fabricated by melt spinning, i.e. extremely fast quenching the molten alloy with 10(6)K/s from T=1973K down to room temperature. The ribbons were then cryo-milled at liquid nitrogen temperature in order to produce powder, which was subsequently hot pressed. The resulting thick pellets have a porosity of about 14vol%, a high compression strength of 337MPa and a Young's modulus of about E=52GPa, values very close to those characteristic of cortical bone. Moreover, the morphology of the samples is very similar to that of cortical bone. The biocompatibility, which is due to the absence of any toxic element in the chemical composition, together with the suitable mechanical behavior, make these samples promising for orthopedic and dentistry applications. Ti-based alloys are nowadays the standard solution for biomedical implants. However, both the conventional crystalline and amorphous alloys have higher rigidity as the human bone, leading to the damage of the bone at the interface, and contains harmful elements like vanadium, aluminum, nickel or beryllium. The hierarchical porous structures based on glassy alloys with biocompatible elements is a much better alternative. This work presents for the first time the manufacturing of such porous bodies starting from Ti-based amorphous alloy ribbons, which contains only non-harmful elements. The morphology and the compressive mechanical properties of these new products are analyzed in regard with those characteristic to the cortical bone. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

MRI-based morphological modeling, synthesis and characterization of cardiac tissue-mimicking materials.

PubMed

Kossivas, Fotis; Angeli, S; Kafouris, D; Patrickios, C S; Tzagarakis, V; Constantinides, C

2012-06-01

This study uses standard synthetic methodologies to produce tissue-mimicking materials that match the morphology and emulate the in vivo murine and human cardiac mechanical and imaging characteristics, with dynamic mechanical analysis, atomic force microscopy (AFM), scanning electron microscopy (SEM) and magnetic resonance imaging. In accordance with such aims, poly(glycerol sebacate) (PGS) elastomeric materials were synthesized (at two different glycerol (G)-sebacic (S) acid molar ratios; the first was synthesized using a G:S molar ratio of 2:2, while the second from a 2:5 G:S molar ratio, resulting in PGS2:2 and PGS2:5 elastomers, respectively). Unlike the synthesized PGS2:2 elastomers, the PGS2:5 materials were characterized by an overall mechanical instability in their loading behavior under the three successive loading conditions tested. An oscillatory response in the mechanical properties of the synthesized elastomers was observed throughout the loading cycles, with measured increased storage modulus values at the first loading cycle, stabilizing to lower values at subsequent cycles. These elastomers were characterized at 4 °C and were found to have storage modulus values of 850 and 1430 kPa at the third loading cycle, respectively, in agreement with previously reported values of the rat and human myocardium. SEM of surface topology indicated minor degradation of synthesized materials at 10 and 20 d post-immersion in the PBS buffer solution, with a noted cluster formation on the PGS2:5 elastomers. AFM nanoindentation experiments were also conducted for the measurement of the Young modulus of the sample surface (no bulk contribution). Correspondingly, the PGS2:2 elastomer indicated significantly decreased surface Young's modulus values 20 d post-PBS immersion, compared to dry conditions (Young's modulus = 1160 ± 290 kPa (dry) and 200 ± 120 kPa (20 d)). In addition to the two-dimensional (2D) elastomers, an integrative platform for accurate construction of three-dimensional tissue-mimicking models of cardiac anatomy from 2D MR images using rapid prototyping manufacturing processes was developed. For synthesized elastomers, doping strategies with two different concentrations of the MRI contrast agent Dotarem allowed independent and concurrent control of the imaging characteristics (contrast and relaxivity) during the synthetic process for increased contrast agent absorption, with tremendous potential for non-destructive in vivo use and applications to cardiovascular and cerebrovascular diseases.

The bulk, surface and corner free energies of the square lattice Ising model

NASA Astrophysics Data System (ADS)

Baxter, R. J.

2017-01-01

We use Kaufman’s spinor method to calculate the bulk, surface and corner free energies {f}{{b}},{f}{{s}},{f}{{s}}\\prime ,{f}{{c}} of the anisotropic square lattice zero-field Ising model for the ordered ferromagnetic case. For {f}{{b}},{f}{{s}},{f}{{s}}\\prime our results of course agree with the early work of Onsager, McCoy and Wu. We also find agreement with the conjectures made by Vernier and Jacobsen (VJ) for the isotropic case. We note that the corner free energy f c depends only on the elliptic modulus k that enters the working, and not on the argument v, which means that VJ’s conjecture applies for the full anisotropic model. The only aspect of this paper that is new is the actual derivation of f c, but by reporting all four free energies together we can see interesting structures linking them.

Evidence for Electromagnetic Granularity in the Polycrystalline Iron-Based Superconductor LaO(0.89)F(0.11)FeAs

DTIC Science & Technology

2008-01-01

oriented grain-boundaries. In this work we show considerable evidence for such weak-coupling by study of the dependence of magnetization in bulk and...powdered samples. Bulk sample magnetization curves show very little hysteresis while remanent magnetization shows almost no sample size dependence...K Fig. 2 (Color online) Magnetization hysteresis loops at 5 and 20 K for the bulk LaO0.89F0.11FeAs. Inset shows the temperature dependence of

Optical fiber pressure sensor based on fiber Bragg grating

NASA Astrophysics Data System (ADS)

Song, Dongcao

In oil field, it is important to measure the high pressure and temperature for down-hole oil exploration and well-logging, the available traditional electronic sensor is challenged due to the harsh, flammable environment. Recently, applications based on fiber Bragg grating (FBG) sensor in the oil industry have become a popular research because of its distinguishing advantages such as electrically passive operation, immunity to electromagnetic interference, high resolution, insensitivity to optical power fluctuation etc. This thesis is divided into two main sections. In the first section, the design of high pressure sensor based on FBG is described. Several sensing elements based on FBG for high pressure measurements have been proposed, for example bulk-modulus or free elastic modulus. But the structure of bulk-modulus and free elastic modulus is relatively complex and not easy to fabricate. In addition, the pressure sensitivity is not high and the repeatability of the structure has not been investigated. In this thesis, a novel host material of carbon fiber laminated composite (CFLC) for high pressure sensing is proposed. The mechanical characteristics including principal moduli in three directions and the shape repeatability are investigated. Because of it's Young's modulus in one direction and anisotropic characteristics, the pressure sensor made by CFLC has excellent sensitivity. This said structure can be used in very high pressure measurement due to carbon fiber composite's excellent shape repetition even under high pressure. The experimental results show high pressure sensitivity of 0.101nm/MPa and high pressure measurement up to 70MPa. A pressure sensor based on CFLC and FBG with temperature compensation has been designed. In the second section, the design of low pressure sensor based on FBG is demonstrated. Due to the trade off between measurement range and sensitivity, a sensor for lower pressure range needs more sensitivity. A novel material of carbon fiber ribbon-wound composite cylindrical shell is proposed. The mechanical characteristics are analyzed. Due to the smaller longitudinal Young's modulus of this novel material, the sensitivity is improved to 0.452nm/MPa and the measurement range can reach 8MPa. The experimental results indicated excellent repeatability of the material and a good linearity between Bragg wavelength shift and the applied pressure. The sensor has the potential to find many industrial low pressure applications.

A new Ca3MgSi2O8 compound and some of its thermodynamic properties

NASA Astrophysics Data System (ADS)

Bao, Xinjian; Zhang, Yanyao; Zhang, Zhigang; Zhang, Lifei; Liu, Xiaoyang; Dong, Jianjun; Liu, Xi

2017-11-01

A new calcium magnesium orthosilicate with the composition Ca3MgSi2O8 was synthesized by a solid-state reaction process at 1.2 GPa and 1373 K for 7 days. We refined the crystallographic structure of this new compound using single-crystal X-ray data, and obtained some of its thermodynamic properties by performing some first-principles simulations. Our single-crystal X-ray analysis has shown that this new compound is monoclinic with the space group C2/c, and its unit-cell parameters are a = 9.344(4) Å, b = 5.3308(3) Å, c = 13.290(6) Å, α = 90°, β = 92.072(7)°, γ = 90°, and V = 658.7(6) Å3. The compressibility of this new compound was studied with the CASTEP code using density functional theory and planewave pseudopotential technique, which led to an isothermal bulk modulus B0 of 99(2) GPa with a pressure derivative B0‧ of 3.5(5). The phonon dispersions and vibrational density of the states (VDoS) of this new compound were calculated by using density functional perturbation theory. Subsequently, the VDoS was combined with a quasi-harmonic approximation to compute the isobaric heat capacity (Cp) and standard vibrational entropy (S298SUP>0), yielding Cp = 3.927(2) × 102 - 1.159(6) × 103T-0.5 - 1.054(4) × 107T-2 + 1.362(8) × 109T-3 J mol-1 K-1 for the T range of 298-1000 K and S2980 = 270.5(60) J mol-1 K-1.

Bibliography of Ice Properties and Forecasting Related to Transportation in Ice-Covered Waters.

DTIC Science & Technology

1980-09-01

bulk modulus mobility exponent m were calculated from the strain and a shear mode that obeys a Maxwell model. A rate sensitivity of flow stress. The...were conducted with a mobile microwave A study of airborne microwave brightness tempera- laboratory containing a number of microwave radi. ture...highest brightness temperatures, averaging -3.0"C a mobile platform has been a goal of researchers and and -0.5"C, respectively. organizations, such

Ab initio calculations of the structural, electronic, thermodynamic and thermal properties of BaSe1-x Te x alloys

NASA Astrophysics Data System (ADS)

Drablia, S.; Boukhris, N.; Boulechfar, R.; Meradji, H.; Ghemid, S.; Ahmed, R.; Omran, S. Bin; El Haj Hassan, F.; Khenata, R.

2017-10-01

The alkaline earth metal chalcogenides are being intensively investigated because of their advanced technological applications, for example in photoluminescent devices. In this study, the structural, electronic, thermodynamic and thermal properties of the BaSe1-x Te x alloys at alloying composition x = 0, 0.25, 0.50, 0.75 and 1 are investigated. The full potential linearized augmented plane wave plus local orbital method designed within the density functional theory was used to perform the total energy calculations. In this research work the effect of the composition on the results of the parameters and bulk modulus as well as on the band gap energy is analyzed. From our results, we found a deviation of the obtained results for the lattice constants from Vegard’s law as well as a deviation of the value of the bulk modulus from the linear concentration dependence. We also carried out a microscopic analysis of the origin of the band gap energy bowing parameter. Furthermore, the thermodynamic stability of the considered alloys was explored through the measurement of the miscibility critical temperature. The quasi-harmonic Debye model, as implemented in the Gibbs code, was used to predict the thermal properties of the BaSe1-x Te x alloys, and these investigations comprise our first theoretical predictions concerning the BaSe1-x Te x alloys.

High-temperature Brillouin scattering study of haplogranitic glasses and liquids: Effects of F, K, Na and Li on Tg and elastic properties

NASA Astrophysics Data System (ADS)

Manghnani, M. H.; Hushur, A.; Williams, Q. C.; Dingwell, D. B.

2010-12-01

The density, compressibility and viscosity of silicate melts are important in understanding the thermodynamic and fluid dynamic properties of magmatic systems. Knowledge of the compressibility of silicate melts at 1 bar is an important component in the construction of accurate pressure-volume-temperature equations of state. In light of this, the velocity (nVp, Vp, Vs) and refractive index n of four anhydrous haplogranitic glasses and liquids with similar alkali abundances, but different cations, are measured at high temperature by Brillouin scattering spectroscopy through the glass transition temperature (Tg) in both platelet and back scattering geometry. The compositions of four haplogranites are 5 wt% of the components Li2O, Na2O, K2O and F each added to a base of haplogranitic (HPG8) composition. The glass transition temperature Tg of different haplogranite samples at the GHz frequency of the Brillouin probe are determined from the change in slope of the temperature-dependent longitudinal or transverse sound velocity. HPG8-Li5 has the lowest glass transition temperature (466°C), while HPG8-K5 has the highest glass transition temperature (575°C). Our Brillouin results, when compared with DSC measurements, show lower Tg values. This raises the possibility of a role of either heating rates or a frequency dependence of the glass transition in explaining the discrepancies in Tg values derived from the two methods. The sound velocity (nVp, Vp, Vs) shows markedly different temperature dependences (including differences in sign) below Tg depending on their different alkali contents. The unrelaxed elastic moduli of three haplogranitic glasses with added Li2O, Na2O and F components have been obtained as a function of temperature. The unrelaxed bulk modulus, shear modulus and Poisson’s ratio show strong compositional dependences at ambient temperature. On heating, The K initially decreases with increasing temperature up to ~ 135°C, then increases up to Tg, and then shows negative temperature dependences for HPG8-Na5. The slope changes from -0.0043(18) GPa/°C below 135°C to 0.0040(5) GPa/°C between 135°C and Tg. In the case of HPG8-Li5, both K and G decrease with increasing temperature.. For HPG8-F5, the K shows a markedly positive temperature dependence below Tg, and a very small temperature dependence above Tg. The shear modulus G shows a slight positive temperature dependence below Tg, and a larger negative temperature dependence above Tg. The Poisson’s ratios of HPG8-Li5 and HPG8-F5 glasses increase monotonically in the measured temperature range, while the Poisson’s ratio of HPG8-Na5 shows a distinct minimum at 135°C. Our results thus provide constraints on the visco-elastic properties of model granitic systems at a range of temperatures above and below their glass transition temperature.

Polyurethane Foams for Thermal Insulation Uses Produced from Castor Oil and Crude Glycerol Biopolyols.

PubMed

Carriço, Camila S; Fraga, Thaís; Carvalho, Vagner E; Pasa, Vânya M D

2017-07-02

Rigid polyurethane foams were synthesized using a renewable polyol from the simple physical mixture of castor oil and crude glycerol. The effect of the catalyst (DBTDL) content and blowing agents in the foams' properties were evaluated. The use of physical blowing agents (cyclopentane and n-pentane) allowed foams with smaller cells to be obtained in comparison with the foams produced with a chemical blowing agent (water). The increase of the water content caused a decrease in density, thermal conductivity, compressive strength, and Young's modulus, which indicates that the increment of CO₂ production contributes to the formation of larger cells. Higher amounts of catalyst in the foam formulations caused a slight density decrease and a small increase of thermal conductivity, compressive strength, and Young's modulus values. These green foams presented properties that indicate a great potential to be used as thermal insulation: density (23-41 kg·m -3 ), thermal conductivity (0.0128-0.0207 W·m -1 ·K -1 ), compressive strength (45-188 kPa), and Young's modulus (3-28 kPa). These biofoams are also environmentally friendly polymers and can aggregate revenue to the biodiesel industry, contributing to a reduction in fuel prices.

Crystal-to-glass-transition induced elastic anomaly of cerium-iron multilayer films and texture-related mechanical properties after hydrogenation

NASA Astrophysics Data System (ADS)

Hassdorf, R.; Arend, M.; Felsch, W.

1995-04-01

The flexural modulus EF of pure and hydrided cerium-iron multilayer films has been measured at 300 K as a function of the modulation wavelength Λ using a vibrating-reed technique. EF is strongly correlated to the structure of the layered systems. In the pure Ce/Fe multilayers, the Fe sublayers show a structural transition from an amorphous to the bcc crystalline phase for a thickness near 20 Å. At this transition, the modulus EF is reduced by ~70%. The elastic softening occurs already, as a precursor to the structural change, for the crystalline Fe sublayers somewhat above the thickness for amorphous growth. This behavior reveals close similarities to the crystal-to-glass transition in bulk metallic alloys and compounds which seems to be driven by a shear instability of the crystal lattice. Hydrogenation leads to multilayers built of CeH~2/Fe. The Fe sublayers grow in the bcc structure above 10 Å, with a pronounced (110) or (111) texture for low- or room-temperature deposition. The flexural moduli are larger as compared to the nonhydrided multilayers and distinctly different for the two Fe textures. A simple calculation shows that the texture-related differences mainly result from the bulk properties of the Fe layers, but a contribution of interfacial effects cannot be excluded.

Non-free gas of dipoles of non-singular screw dislocations and the shear modulus near the melting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malyshev, Cyril, E-mail: malyshev@pdmi.ras.ru

2014-12-15

The behavior of the shear modulus caused by proliferation of dipoles of non-singular screw dislocations with finite-sized core is considered. The representation of two-dimensional Coulomb gas with smoothed-out coupling is used, and the stress–stress correlation function is calculated. A convolution integral expressed in terms of the modified Bessel function K{sub 0} is derived in order to obtain the shear modulus in approximation of interacting dipoles. Implications are demonstrated for the shear modulus near the melting transition which are due to the singularityless character of the dislocations. - Highlights: • Thermodynamics of dipoles of non-singular screw dislocations is studied below themore » melting. • The renormalization of the shear modulus is obtained for interacting dipoles. • Dependence of the shear modulus on the system scales is presented near the melting.« less

Dispersion and Attenuation Due to Scattering from Heterogeneities of the Frame Bulk Modulus of a Poroelastic Medium

DTIC Science & Technology

2010-02-19

attenuation is a function of the Hurst exponent which characterizes the fractal het- erogeneity. Muller and Gurevich15,16 used statistical smoothing of...modified Bessel function of the third kind, Γ denotes the gamma function, and ν is the Hurst coefficient which is assumed to be 0 < ν ≤ 1. The three...The Hurst coefficient, ν, is ν = 0.1 (long-dashed line), ν = 0.5 (short-dashed line), and ν = 0.9 (long-short dashed line). In (a) the sound speed

Using a gel/plastic surrogate to study the biomechanical response of the head under air shock loading: a combined experimental and numerical investigation.

PubMed

Zhu, Feng; Wagner, Christina; Dal Cengio Leonardi, Alessandra; Jin, Xin; Vandevord, Pamela; Chou, Clifford; Yang, King H; King, Albert I

2012-03-01

A combined experimental and numerical study was conducted to determine a method to elucidate the biomechanical response of a head surrogate physical model under air shock loading. In the physical experiments, a gel-filled egg-shaped skull/brain surrogate was exposed to blast overpressure in a shock tube environment, and static pressures within the shock tube and the surrogate were recorded throughout the event. A numerical model of the shock tube was developed using the Eulerian approach and validated against experimental data. An arbitrary Lagrangian-Eulerian (ALE) fluid-structure coupling algorithm was then utilized to simulate the interaction of the shock wave and the head surrogate. After model validation, a comprehensive series of parametric studies was carried out on the egg-shaped surrogate FE model to assess the effect of several key factors, such as the elastic modulus of the shell, bulk modulus of the core, head orientation, and internal sensor location, on pressure and strain responses. Results indicate that increasing the elastic modulus of the shell within the range simulated in this study led to considerable rise of the overpressures. Varying the bulk modulus of the core from 0.5 to 2.0 GPa, the overpressure had an increase of 7.2%. The curvature of the surface facing the shock wave significantly affected both the peak positive and negative pressures. Simulations of the head surrogate with the blunt end facing the advancing shock front had a higher pressure compared to the simulations with the pointed end facing the shock front. The influence of an opening (possibly mimicking anatomical apertures) on the peak pressures was evaluated using a surrogate head with a hole on the shell of the blunt end. It was revealed that the presence of the opening had little influence on the positive pressures but could affect the negative pressure evidently.

Solid solubility, phase transitions, thermal expansion, and compressibility in Sc{sub 1−x}Al{sub x}F{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morelock, Cody R.; Gallington, Leighanne C.; Wilkinson, Angus P., E-mail: angus.wilkinson@chemistry.gatech.edu

2015-02-15

With the goal of thermal expansion control, the synthesis and properties of Sc{sub 1−x}Al{sub x}F{sub 3} were investigated. The solubility limit of AlF{sub 3} in ScF{sub 3} at ∼1340 K is ∼50%. Solid solutions (x≤0.50) were characterized by synchrotron powder diffraction at ambient pressure between 100 and 900 K and at pressures <0.414 GPa while heating from 298 to 523 K. A phase transition from cubic to rhombohedral is observed. The transition temperature increases smoothly with Al{sup 3+} content, approaching 500 K at the solid solubility limit, and also upon compression at fixed Al{sup 3+} content. The slope of themore » pressure–temperature phase boundary is ∼0.5 K MPa{sup −1}, which is steep relative to that for most symmetry-lowering phase transitions in perovskites. The volume coefficient of thermal expansion (CTE) for the rhombohedral phase is strongly positive, but the cubic-phase CTE varies from negative (x<0.15) to near-zero (x=0.15) to positive (x>0.20) between ∼600 and 800 K. The cubic solid solutions elastically stiffen on heating, while Al{sup 3+} substitution causes softening at a given temperature. - Graphical abstract: The cubic-phase coefficient of thermal expansion for Sc{sub 1−x}Al{sub x}F{sub 3}(solubility limit ∼50% at ∼1340 K) becomes more positive with increased Al{sup 3+} substitution, but the average isothermal bulk modulus decreases (elastic softening). - Highlights: • The solubility limit of AlF{sub 3} in ScF{sub 3} at ∼1340 K is ∼50%. • The phase transition temperature of Sc{sub 1−x}Al{sub x}F{sub 3} increases smoothly with x. • The cubic-phase volume CTE varies from negative to positive with increasing x. • The cubic solid solutions elastically stiffen on heating. • Al{sup 3+} substitution causes softening at a given temperature.« less

Experimental determination of the bulk Rashba parameters in BiTeBr

NASA Astrophysics Data System (ADS)

Martin, C.; Suslov, A. V.; Buvaev, S.; Hebard, A. F.; Bugnon, P.; Berger, H.; Magrez, A.; Tanner, D. B.

2016-12-01

Shubnikov-de Haas (SdH) oscillations, Hall effect, and optical reflectance (R(ω)) measurements have been performed on single crystals of BiTeBr. Under magnetic fields up to 32 tesla and at temperatures as low as 0.4 K, the SdH data shows a single oscillation frequency F = 102 +/- 5 \\text{tesla} . The combined transport and optical studies establish that the SdH effect originates from the Rashba spin-split bulk conduction band, with the chemical potential situated about 13 meV below the crossing (Dirac) point. The bulk carrier concentration was ne≈5×1018 \\text{cm}-3 and the effective mass m1*= 0.16m0 . Combining SdH and optical data, we reliably determine the Rashba parameters for the bulk conduction band of BiTeBr: the Rashba energy ER = 28 \\text{meV} and the momentum spin-split kR = 0.033 \\unicode{8491}-1 . Hence, the bulk Rashba coupling strength αR = 2ER/kR is found to be 1.7 eVÅ.

Numerical modelling of iron-pnictide bulk superconductor magnetization

NASA Astrophysics Data System (ADS)

Ainslie, Mark D.; Yamamoto, Akiyasu; Fujishiro, Hiroyuki; Weiss, Jeremy D.; Hellstrom, Eric E.

2017-10-01

Iron-based superconductors exhibit a number of properties attractive for applications, including low anisotropy, high upper critical magnetic fields (H c2) in excess of 90 T and intrinsic critical current densities above 1 MA cm-2 (0 T, 4.2 K). It was shown recently that bulk iron-pnictide superconducting magnets capable of trapping over 1 T (5 K) and 0.5 T (20 K) can be fabricated with fine-grain polycrystalline Ba0.6K0.4Fe2As2 (Ba122). These Ba122 magnets were processed by a scalable, versatile and low-cost method using common industrial ceramic processing techniques. In this paper, a standard numerical modelling technique, based on a 2D axisymmetric finite-element model implementing the H -formulation, is used to investigate the magnetisation properties of such iron-pnictide bulk superconductors. Using the measured J c(B, T) characteristics of a small specimen taken from a bulk Ba122 sample, experimentally measured trapped fields are reproduced well for a single bulk, as well as a stack of bulks. Additionally, the influence of the geometric dimensions (thickness and diameter) on the trapped field is analysed, with a view of fabricating larger samples to increase the magnetic field available from such trapped field magnets. It is shown that, with current state-of-the-art superconducting properties, surface trapped fields >2 T could readily be achieved at 5 K (and >1 T at 20 K) with a sample of diameter 50 mm. Finally, an aspect ratio of between 1 and 1.5 for R/H (radius/thickness) would be an appropriate compromise between the accessible, surface trapped field and volume of superconducting material for bulk Ba122 magnets.

Temperature dependence of structure, bending rigidity, and bilayer interactions of dioleoylphosphatidylcholine bilayers.

PubMed

Pan, Jianjun; Tristram-Nagle, Stephanie; Kucerka, Norbert; Nagle, John F

2008-01-01

X-ray diffuse scattering was measured from oriented stacks and unilamellar vesicles of dioleoylphosphatidylcholine lipid bilayers to obtain the temperature dependence of the structure and of the material properties. The area/molecule, A, was 75.5 A(2) at 45 degrees C, 72.4 A(2) at 30 degrees C, and 69.1 A(2) at 15 degrees C, which gives the area expansivity alpha(A) = 0.0029/deg at 30 degrees C, and we show that this value is in excellent agreement with the polymer brush theory. The bilayer becomes thinner with increasing temperature; the contractivity of the hydrocarbon portion was alpha(Dc) = 0.0019/deg; the difference between alpha(A) and alpha(Dc) is consistent with the previously measured volume expansivity alpha(Vc) = 0.0010/deg. The bending modulus K(C) decreased as exp(455/T) with increasing T (K). Our area compressibility modulus K(A) decreased with increasing temperature by 5%, the same as the surface tension of dodecane/water, in agreement again with the polymer brush theory. Regarding interactions between bilayers, the compression modulus B as a function of interbilayer water spacing D'(W) was found to be nearly independent of temperature. The repulsive fluctuation pressure calculated from B and K(C) increased with temperature, and the Hamaker parameter for the van der Waals interaction was nearly independent of temperature; this explains why the fully hydrated water spacing, D'(W), that we obtain from our structural results increases with temperature.

In vivo quantification of the shear modulus of the human Achilles tendon during passive loading using shear wave dispersion analysis.

PubMed

Helfenstein-Didier, C; Andrade, R J; Brum, J; Hug, F; Tanter, M; Nordez, A; Gennisson, J-L

2016-03-21

The shear wave velocity dispersion was analyzed in the Achilles tendon (AT) during passive dorsiflexion using a phase velocity method in order to obtain the tendon shear modulus (C 55). Based on this analysis, the aims of the present study were (i) to assess the reproducibility of the shear modulus for different ankle angles, (ii) to assess the effect of the probe locations, and (iii) to compare results with elasticity values obtained with the supersonic shear imaging (SSI) technique. The AT shear modulus (C 55) consistently increased with the ankle dorsiflexion (N = 10, p < 0.05). Furthermore, the technique showed a very good reproducibility (all standard error of the mean values <10.7 kPa and all coefficient of variation (CV) values ⩽ 0.05%). In addition, independently from the ankle dorsiflexion, the shear modulus was significantly higher in the proximal location compared to the more distal one. The shear modulus provided by SSI was always lower than C55 and the difference increased with the ankle dorsiflexion. However, shear modulus values provided by both methods were highly correlated (R = 0.84), indicating that the conventional shear wave elastography technique (SSI technique) can be used to compare tendon mechanical properties across populations. Future studies should determine the clinical relevance of the shear wave dispersion analysis, for instance in the case of tendinopathy or tendon tear.

Structure and elasticity of serpentine at high-pressure

NASA Astrophysics Data System (ADS)

Mookherjee, Mainak; Stixrude, Lars

2009-03-01

Serpentines occur in the subduction zone settings, both along the slab and within the mantle wedge, they are candidates for transporting water in to the deep earth. Their presence is manifested by serpentine mud volcanoes, high electrical conductivities, magnetic and seismic anomalies. Using theoretical methods, we predict a pressure induced structural transformations in serpentine. The transformations are related to the behavior of the silicate framework and misfit between octahedral and tetrahedral layers. As the structure is compressed, the octahedral layer and tetrahedral layers are compressed at different rates. At 7 GPa, the misfit between the layers vanishes. This causes non-linear pressure dependence of tetrahedral rotational angle. This is also manifested by the onset of anomalous pressure dependence of the elastic constants c11, c33, c12, c13. Beyond 7 GPa, the misfit between the layers grows again reaching extremum at 22 GPa. This is also manifested by discontinuity in average Si-O bond length, volume of tetrahedron and re-orientation of hydroxyl vector. The symmetry of the crystal-structure however, remains unaffected. Evidence of pressure-induced hydrogen bonding is absent in serpentine, as evident from reduction of O-H bond length upon compression. Results of compression for the low-pressure regime ( P < 7 GPa) is well represented by a fourth order Birch-Murnaghan finite strain expression with K0 = 79 GPa, K0' = 12 and K0″ = - 2, where K is the bulk modulus, prime indicates pressure derivatives, and O refers to zero pressure. Our best estimates of K0, K0' and the Grüneisen parameter, γ at 300 K and zero pressure based on our results are: 61 GPa, 17, and 0.77, respectively. At low pressures, serpentine structure is anisotropic with c11 ~ 2.4 × c33. The pressure derivative of elastic constants ( ∂cij/ ∂P) are such, that around 22 GPa c11~ c33. An elastic instability ( c66 < 0) at somewhat higher pressures (> 50 GPa) is also noted. The elastic constant tensor reveals large acoustic anisotropy (41% in VP) and seismic wave velocities that are significantly higher than those inferred from experiments on serpentinites.

Theoretical Investigation of the Thermodynamic Properties of η'-(Cu, Co)6Sn5 Alloys

NASA Astrophysics Data System (ADS)

Wu, Heng; Zhang, Xuechao; Zheng, Bing; Zhao, Xiuchen; Liu, Ying; Li, Hong; Cheng, Jingwei

2018-02-01

We perform theoretical investigations on the structures of η'-Cu6Sn5-based intermetallic compounds (IMCs) with different Co doping concentration (0-12.2 wt.%) based on density functional theory (DFT). The variations of the structural, elastic and thermodynamic properties of (Cu, Co)6Sn5 IMCs with pressure (0-18 GPa) and temperature (0-500 K) are obtained with the application of quasi-harmonic Debye model for the non-equilibrium Gibbs free energy. It is found that the volume of (Cu, Co)6Sn5 shrinks with Co concentration increasing in the range of imposed pressure and temperature. At the same time, the bulk modulus of Cu4Co2Sn5 is the largest among those of Cu6Sn5, Cu5Co1Sn5 and Cu4Co2Sn5. By calculating the Debye temperature of Cu6Sn5, we find that it is higher than that of Cu5Co1Sn5 and Cu4Co2Sn5 when the pressure is higher than 2 GPa. Meanwhile, heat capacities of all three Cu6Sn5, Cu5Co1Sn5, and Cu4Co2Sn5 converge to a near-constant value at about 1090 J/mol K in the range of the imposed pressures.

NRL (Naval Research Laboratory) Plasma Formulary. Revised.

DTIC Science & Technology

1983-01-01

EQUATIONS Name Rationalized inks Gaussian Faday’s law V xE -- !-s VxE--l1p .aD -l3D 4i" Ampere’slta xH-VxH -- +J VxH -- .- +- J at C at C Poison’s eqution...energy density Froude Fr t V (gL ) 1/2 (Inertial forces/gravitational or VINL buoyancy forces) t/2 Gay- Lussac Ga I/PA T (Relative volume change...112 Alfvin speed a Newton’s- law heat coefficient, k x " aA T aix Volumetric expansion coefficient, dV/ V - )dT r Bulk modulus (units m/it 2 ) AR, A

Charge-regularized swelling kinetics of polyelectrolyte gels

NASA Astrophysics Data System (ADS)

Sen, Swati; Kundagrami, Arindam

The swelling kinetics of polyelectrolyte gels with fixed and variable degrees of ionization in salt-free solvent is studied by solving the constitutive equation of motion of the spatially and temporally varying displacement variable. Two methods for the swelling kinetics - the Bulk Modulus Method (BMM), which uses a linear stress-strain relationship (and, hence a bulk modulus), and the Stress Relaxation Method (SRM), which uses a phenomenological expression of osmotic stress, are explored to provide the spatio-temporal profiles for polymer density, osmotic stress, and degree of ionization, along with the time evolution of the gel size. Further, we obtain an analytical expression for the elastic modulus for linearized stress in the limit of small deformations. We match our theoretical profiles with the experiments of swelling of PNIPAM (uncharged) and Imidazolium-based (charged) minigels available in the literature. Ministry of Human Resource Development (MHRD), Government of India.

Equation of state and thermodynamic Grüneisen parameter of monoclinic 1,1-diamino-2,2-dinitroethylene

NASA Astrophysics Data System (ADS)

Zhang, Jianzhong; Velisavljevic, Nenad; Zhu, Jinlong; Wang, Liping

2016-10-01

In situ synchrotron x-ray diffraction experiments were conducted on 1,1-diamino-2,2-dinitroethylene (FOX-7) at pressures up to 6.8 GPa and temperatures up to 485 K. Within the resolution of the present diffraction data, our results do not reveal evidence for a pressure-induced structural phase transition near 2 GPa, previously observed in several vibrational spectroscopy experiments. Based on unit-cell volume measurements, the least-squares fit using the third-order Birch-Murnaghan equation of state (EOS) yields K 0  =  12.6  ±  1.4 GPa and K0\\prime   =  11.3  ±  2.1 for the α-phase of FOX-7, which are in good agreement with recently reported values for the deuterated sample, indicating that the effect of hydrogen-deuterium substitution on the compressibility of FOX-7 is negligibly small. A thermal EOS is also obtained for the α-phase of FOX-7, including pressure dependence of thermal expansivity, (∂α/∂P)T  =  -7.0  ±  2.0  ×  10-5 K-1 GPa-1, and temperature derivative of the bulk modulus, (∂K T/∂T)P  =  -1.1  ×  10-2 GPa K-1. From these EOS parameters, we calculate heat capacity at constant volume (C V) and thermodynamic Grüneisen parameter (γ TH) as a function of temperature. At ambient conditions, the calculated γ TH is 1.055, which is in good agreement with the value (1.09) previously obtained from density functional theory (DFT). The obtained C V, however, is 13% larger than that calculated from the first-principles calculations, indicating that the dispersion correction in the DFT calculations may need to be further improved for describing intermolecular interactions of molecular crystals.

Temperature dependence of elastic and strength properties of T300/5208 graphite-epoxy

NASA Technical Reports Server (NTRS)

Milkovich, S. M.; Herakovich, C. T.

1984-01-01

Experimental results are presented for the elastic and strength properties of T300/5208 graphite-epoxy at room temperature, 116K (-250 F), and 394K (+250 F). Results are presented for unidirectional 0, 90, and 45 degree laminates, and + or - 30, + or - 45, and + or - 60 degree angle-ply laminates. The stress-strain behavior of the 0 and 90 degree laminates is essentially linear for all three temperatures and that the stress-strain behavior of all other laminates is linear at 116K. A second-order curve provides the best fit for the temperature is linear at 116K. A second-order curve provides the best fit for the temperature dependence of the elastic modulus of all laminates and for the principal shear modulus. Poisson's ratio appears to vary linearly with temperature. all moduli decrease with increasing temperature except for E (sub 1) which exhibits a small increase. The strength temperature dependence is also quadratic for all laminates except the 0 degree - laminate which exhibits linear temperature dependence. In many cases the temperature dependence of properties is nearly linear.

Comparison of shear wave velocity measurements assessed with two different ultrasound systems in an ex-vivo tendon strain phantom.

PubMed

Rosskopf, Andrea B; Bachmann, Elias; Snedeker, Jess G; Pfirrmann, Christian W A; Buck, Florian M

2016-11-01

The purpose of this study is to compare the reliability of SW velocity measurements of two different ultrasound systems and their correlation with the tangent traction modulus in a non-static tendon strain model. A bovine tendon was fixed in a custom-made stretching device. Force was applied increasing from 0 up to 18 Newton. During each strain state the tangent traction modulus was determined by the stretcher device, and SW velocity (m/s) measurements using a Siemens S3000 and a Supersonic Aixplorer US machine were done for shear modulus (kPa) calculation. A strong significant positive correlation was found between SW velocity assessed by the two ultrasound systems and the tangent traction modulus (r = 0.827-0.954, p < 0.001), yet all SW velocity-based calculations underestimated the reference tissue tangent modulus. Mean difference of SW velocities with the S3000 was 0.44 ± 0.3 m/s (p = 0.002) and with the Aixplorer 0.25 ± 0.3 m/s (p = 0.034). Mean difference of SW velocity between the two US-systems was 0.37 ± 0.3 m/s (p = 0.012). In conclusion, SW velocities are highly dependent on mechanical forces in the tendon tissue, but for controlled mechanical loads appear to yield reproducible and comparable measurements using different US systems.

Multiple caloric effects in (Ba0.865Ca0.135Zr0.1089Ti0.8811Fe0.01)O3 ferroelectric ceramic

NASA Astrophysics Data System (ADS)

Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

2015-07-01

Multiple caloric effects have been investigated for Fe-doped bulk (Ba0.865Ca0.135Zr0.1089Ti0.8811Fe0.01)O3 (BCZTO-Fe) ferroelectric ceramic. Indirect predictions were made using Maxwell's relations in conjunction with data from experimental observations. It was revealed that bulk BCZTO-Fe has huge untapped potential for solid-state refrigeration. A peak electrocaloric effect of 0.45 K (347 K) was predicted for 0-3 kV.mm-1 electric field, significantly higher than other BCZTO based materials. A maximum elastocaloric cooling of 1.4 K (298 K) was achieved for applied stress of 0-200 MPa. Finally, an unforeseen component of electric field driven caloric effect has been reported as inverse piezocaloric effect, with a maximum temperature change of 0.28 K (298 K).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chuvashova, Irina, E-mail: irina.chuvashova@gmail.com; Bayerisches Geoinstitut, University of Bayreuth, D-95440 Bayreuth; Bykova, Elena

In the present study single crystals of rhombohedral α-B were investigated under pressure to 60 GPa by means of single-crystal X-ray diffraction. The bulk modulus of α-B was found to be K=224(7) GPa (K′=3.0(3)). Measurements of interatomic distances as a function of pressure revealed that the intericosahedral two-center two-electron (2c–2e) bonds are almost as stiff as some of intraicosahedral ones. The three-center two-electron (3c–2e) intericosahedral bonds show much higher compliance compared to other bonds in α-B. The vibrational properties of α-B under pressure were investigated by Raman spectroscopy at pressures up to 160 GPa and IR spectroscopy at pressures upmore » to 53 GPa. - Graphical abstract: The rhombohedral α-B is highly incompressible and extremely stable: it maintains its crystal structure up to 160 GPa and its intericosahedral 2e2c bonds are almost as stiff as some of intraicosahedral ones. - Highlights: • Structural stability of α-B has been investigated up to 160 GPa on single crystals. • Single-crystal x-ray diffraction reveals that α-B is highly incompressible. • Compressibility of B{sub 12} icosahedra is considerably lower than that of the bulk material. • Intericosahedral 2e2c bonds are almost as stiff as some of intraicosahedral ones.« less

Charge-regularized swelling kinetics of polyelectrolyte gels: Elasticity and diffusion

NASA Astrophysics Data System (ADS)

Sen, Swati; Kundagrami, Arindam

2017-11-01

We apply a recently developed method [S. Sen and A. Kundagrami, J. Chem. Phys. 143, 224904 (2015)], using a phenomenological expression of osmotic stress, as a function of polymer and charge densities, hydrophobicity, and network elasticity for the swelling of spherical polyelectrolyte (PE) gels with fixed and variable charges in a salt-free solvent. This expression of stress is used in the equation of motion of swelling kinetics of spherical PE gels to numerically calculate the spatial profiles for the polymer and free ion densities at different time steps and the time evolution of the size of the gel. We compare the profiles of the same variables obtained from the classical linear theory of elasticity and quantitatively estimate the bulk modulus of the PE gel. Further, we obtain an analytical expression of the elastic modulus from the linearized expression of stress (in the small deformation limit). We find that the estimated bulk modulus of the PE gel decreases with the increase of its effective charge for a fixed degree of deformation during swelling. Finally, we match the gel-front locations with the experimental data, taken from the measurements of charged reversible addition-fragmentation chain transfer gels to show an increase in gel-size with charge and also match the same for PNIPAM (uncharged) and imidazolium-based (charged) minigels, which specifically confirms the decrease of the gel modulus value with the increase of the charge. The agreement between experimental and theoretical results confirms general diffusive behaviour for swelling of PE gels with a decreasing bulk modulus with increasing degree of ionization (charge). The new formalism captures large deformations as well with a significant variation of charge content of the gel. It is found that PE gels with large deformation but same initial size swell faster with a higher charge.

Effect of ripples on the finite temperature elastic properties of hexagonal boron nitride using strain-fluctuation method

NASA Astrophysics Data System (ADS)

Thomas, Siby; Ajith, K. M.; Valsakumar, M. C.

2017-11-01

This work intents to put forth the results of a classical molecular dynamics study to investigate the temperature dependent elastic constants of monolayer hexagonal boron nitride (h-BN) between 100 and 1000 K for the first time using strain fluctuation method. The temperature dependence of out-of-plane fluctuations (ripples) is quantified and is explained using continuum theory of membranes. At low temperatures, negative in-plane thermal expansion is observed and at high temperatures, a transition to positive thermal expansion has been observed due to the presence of thermally excited ripples. The decrease of Young's modulus, bulk modulus, shear modulus and Poisson's ratio with increase in temperature has been analyzed. The thermal rippling in h-BN leads to strong anharmonic behaviour that causes large deviation from the isotropic elasticity. A detailed study shows that the strong thermal rippling in large systems is also responsible for the softening of elastic constants in h-BN. From the determined values of elastic constants and elastic moduli, it has been elucidated that 2D h-BN sheets meet the Born's mechanical stability criterion in the investigated temperature range. The variation of longitudinal and shear velocities with temperature is also calculated from the computed values of elastic constants and elastic moduli.

AFM nanoscale indentation in air of polymeric and hybrid materials with highly different stiffness

NASA Astrophysics Data System (ADS)

Suriano, Raffaella; Credi, Caterina; Levi, Marinella; Turri, Stefano

2014-08-01

In this study, nanomechanical properties of a variety of polymeric materials was investigated by means of AFM. In particular, selecting different AFM probes, poly(methyl methacrylate) (PMMA), polydimethylsiloxane (PDMS) bulk samples, sol-gel hybrid thin films and hydrated hyaluronic acid hydrogels were indented in air to determine the elastic modulus. The force-distance curves and the indentation data were found to be greatly affected by the cantilever stiffness and by tip geometry. AFM indentation tests show that the choice of the cantilever spring constant and of tip shape is crucially influenced by elastic properties of samples. When adhesion-dominated interactions occur between the tip and the surface of samples, force-displacement curves reveal that a suitable functionalization of AFM probes allows the control of such interactions and the extraction of Young' modulus from AFM curves that would be otherwise unfeasible. By applying different mathematical models depending on AFM probes and materials under investigation, the values of Young's modulus were obtained and compared to those measured by rheological and dynamic mechanical analysis or to literature data. Our results show that a wide range of elastic moduli (10 kPa-10 GPa) can be determined by AFM in good agreement with those measured by conventional macroscopic measurements.

Thermal Conductivity and Elastic Modulus Evolution of Thermal Barrier Coatings under High Heat Flux Conditions

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

1999-01-01

Laser high heat flux test approaches have been established to obtain critical properties of ceramic thermal barrier coatings (TBCs) under near-realistic temperature and thermal gradients that may he encountered in advanced engine systems. Thermal conductivity change kinetics of a thin ceramic coating were continuously monitored in real time at various test temperatures. A significant thermal conductivity increase was observed during the laser simulated engine heat flux tests. For a 0.25 mm thick ZrO2-8%Y2O3 coating system, the overall thermal conductivity increased from the initial value of 1.0 W/m-K to 1. 15 W/m-K, 1. 19 W/m-K and 1.5 W/m-K after 30 hour testing at surface temperatures of 990C, 1100C, and 1320C. respectively. Hardness and modulus gradients across a 1.5 mm thick TBC system were also determined as a function of laser testing time using the laser sintering/creep and micro-indentation techniques. The coating Knoop hardness values increased from the initial hardness value of 4 GPa to 5 GPa near the ceramic/bond coat interface, and to 7.5 GPa at the ceramic coating surface after 120 hour testing. The ceramic surface modulus increased from an initial value of about 70 GPa to a final value of 125 GPa. The increase in thermal conductivity and the evolution of significant hardness and modulus gradients in the TBC systems are attributed to sintering-induced micro-porosity gradients under the laser-imposed high thermal gradient conditions. The test techniques provide a viable means for obtaining coating data for use in design, development, stress modeling, and life prediction for various thermal barrier coating applications.

Mechanical relaxation in a Zr-based bulk metallic glass: Analysis based on physical models

NASA Astrophysics Data System (ADS)

Qiao, J. C.; Pelletier, J. M.

2012-08-01

The mechanical relaxation behavior in a Zr55Cu30Ni5Al10 bulk metallic glass is investigated by dynamic mechanical analysis in both temperature and frequency domains. Master curves can be obtained for the storage modulus G' and for the loss modulus G'', confirming the validity of the time-temperature superposition principle. Different models are discussed to describe the main (α) relaxation, e.g., Debye model, Havriliak-Negami (HN) model, Kohlrausch-Williams-Watt (KWW) model, and quasi-point defects (QPDs) model. The main relaxation in bulk metallic glass cannot be described using a single relaxation time. The HN model, the KWW model, and the QPD theory can be used to fit the data of mechanical spectroscopy experiments. However, unlike the HN model and the KWW model, some physical parameters are introduced in QPD model, i.e., atomic mobility and correlation factor, giving, therefore, a new physical approach to understand the mechanical relaxation in bulk metallic glasses.

Hinge-like structure induced unusual properties of black phosphorus and new strategies to improve the thermoelectric performance

PubMed Central

Qin, Guangzhao; Yan, Qing-Bo; Qin, Zhenzhen; Yue, Sheng-Ying; Cui, Hui-Juan; Zheng, Qing-Rong; Su, Gang

2014-01-01

We systematically investigated the geometric, electronic and thermoelectric (TE) properties of bulk black phosphorus (BP) under strain. The hinge-like structure of BP brings unusual mechanical responses such as anisotropic Young's modulus and negative Poisson's ratio. A sensitive electronic structure of BP makes it transform among metal, direct and indirect semiconductors under strain. The maximal figure of merit ZT of BP is found to be 0.72 at 800 K that could be enhanced to 0.87 by exerting an appropriate strain, revealing BP could be a potential medium-high temperature TE material. Such strain-induced enhancements of TE performance are often observed to occur at the boundary of the direct-indirect band gap transition, which can be attributed to the increase of degeneracy of energy valleys at the transition point. By comparing the structure of BP with SnSe, a family of potential TE materials with hinge-like structure are suggested. This study not only exposes various novel properties of BP under strain, but also proposes effective strategies to seek for better TE materials. PMID:25374306

Physical and chemical properties of some new perfluoropolyalkylether lubricants prepared by direct fluorination

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.; Bierschenk, T. R.; Juhlke, T. J.; Kawa, H.; Lagow, R. J.

1993-01-01

A series of perfluoropolyalkylether (PFPAE) fluids was synthesized by direct fluorination. Viscosity-temperature properties, oxidation stabilities, oxidation-corrosion properties, bulk modulus, lubricity, surface tension and density were measured. It was shown that as the carbon to oxygen ratio in the polymer repeating unit decreases, the viscometric properties improve, the fluids may become poorer boundary lubricants, the bulk modulus increases, the surface tension increases and the fluid density increases. The presence of difluoromethylene oxide units in the polymer does not significantly lower the oxidation and oxidation-corrosion stabilities as long as the difluoromethylene oxide units are separated by other units.

Density-velocity equations with bulk modulus for computational hydro-acoustics

NASA Astrophysics Data System (ADS)

Lin, Po-Hsien; Chen, Yung-Yu; John Yu, S.-T.

2014-02-01

This paper reports a new set of model equations for Computational Hydro Acoustics (CHA). The governing equations include the continuity and the momentum equations. The definition of bulk modulus is used to relate density with pressure. For 3D flow fields, there are four equations with density and velocity components as the unknowns. The inviscid equations are proved to be hyperbolic because an arbitrary linear combination of the three Jacobian matrices is diagonalizable and has a real spectrum. The left and right eigenvector matrices are explicitly derived. Moreover, an analytical form of the Riemann invariants are derived. The model equations are indeed suitable for modeling wave propagation in low-speed, nearly incompressible air and water flows. To demonstrate the capability of the new formulation, we use the CESE method to solve the 2D equations for aeolian tones generated by air flows passing a circular cylinder at Re = 89,000, 46,000, and 22,000. Numerical results compare well with previously published data. By simply changing the value of the bulk modulus, the same code is then used to calculate three cases of water flows passing a cylinder at Re = 89,000, 67,000, and 44,000.

Hybrid functional study of α-uranium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaur, Gurpreet, E-mail: gurpreet@igcar.gov.in; Chinnappan, Ravi; Panigrahi, B. K.

2016-05-23

We have used the hybrid density functionals to study the structural and electronic properties of alpha-U. The fraction of exact Hartree Folk exchange used is varied from 0.0 to 0.6. The equilibrium volume is found to be underestimated and bulk modulus overestimated with HSE as compared to both calculated by PBE and the experimental values. Electronic bands below the Fermi level are found to shift to lower energy with respect to PBE electronic bands which itself gives the bands shifted to lower energies as compared to UPS experiments.

Robust high pressure stability and negative thermal expansion in sodium-rich antiperovskites Na 3OBr and Na 4OI 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yonggang; Wen, Ting; Park, Changyong

2016-01-14

The structure stability under high pressure and thermal expansion behavior of Na 3OBr and Na 4OI 2, two prototypes of alkali-metal-rich antiperovskites, were investigated by in situ synchrotron X-ray diffraction techniques under high pressure and low temp. Both are soft materials with bulk modulus of 58.6 GPa and 52.0 GPa for Na 3OBr and Na 4OI 2, resp. The cubic Na 3OBr structure and tetragonal Na 4OI 2 with intergrowth K 2NiF 4 structure are stable under high pressure up to 23 GPa. Although being a characteristic layered structure, Na 4OI 2 exhibits nearly isotropic compressibility. Neg. thermal expansion wasmore » obsd. at low temp. range (20-80 K) in both transition-metal-free antiperovskites for the first time. The robust high pressure structure stability was examined. and confirmed by first-principles calculations. among various possible polymorphisms qualitatively. The results provide in-depth understanding of the neg. thermal expansion and robust crystal structure stability of these antiperovskite systems and their potential applications.« less

Linking lipid architecture to bilayer structure and mechanics using self-consistent field modelling.

PubMed

Pera, H; Kleijn, J M; Leermakers, F A M

2014-02-14

To understand how lipid architecture determines the lipid bilayer structure and its mechanics, we implement a molecularly detailed model that uses the self-consistent field theory. This numerical model accurately predicts parameters such as Helfrichs mean and Gaussian bending modulus kc and k̄ and the preferred monolayer curvature J(0)(m), and also delivers structural membrane properties like the core thickness, and head group position and orientation. We studied how these mechanical parameters vary with system variations, such as lipid tail length, membrane composition, and those parameters that control the lipid tail and head group solvent quality. For the membrane composition, negatively charged phosphatidylglycerol (PG) or zwitterionic, phosphatidylcholine (PC), and -ethanolamine (PE) lipids were used. In line with experimental findings, we find that the values of kc and the area compression modulus kA are always positive. They respond similarly to parameters that affect the core thickness, but differently to parameters that affect the head group properties. We found that the trends for k̄ and J(0)(m) can be rationalised by the concept of Israelachivili's surfactant packing parameter, and that both k̄ and J(0)(m) change sign with relevant parameter changes. Although typically k̄ < 0, membranes can form stable cubic phases when the Gaussian bending modulus becomes positive, which occurs with membranes composed of PC lipids with long tails. Similarly, negative monolayer curvatures appear when a small head group such as PE is combined with long lipid tails, which hints towards the stability of inverse hexagonal phases at the cost of the bilayer topology. To prevent the destabilisation of bilayers, PG lipids can be mixed into these PC or PE lipid membranes. Progressive loading of bilayers with PG lipids lead to highly charged membranes, resulting in J(0)(m) > 0, especially at low ionic strengths. We anticipate that these changes lead to unstable membranes as these become vulnerable to pore formation or disintegration into lipid disks.

The equation of state of n-pentane in the atomistic model TraPPE-EH

NASA Astrophysics Data System (ADS)

Valeev, B. U.; Pisarev, V. V.

2018-01-01

In this work, we study the vapor-liquid equilibrium in n-pentane. We use the TraPPE-EH (transferable potentials for phase equilibria-explicit hydrogen) forcefield, where each hydrogen and carbon atom is considered as independent center of force. The fluid behavior was investigated with different values of density and temperature by molecular dynamics method. The n-pentane evaporation curve was calculated in the temperature range of 290 to 390 K. The densities of the coexisting phases are also calculated. The compression curve at 370 K was calculated and isothermal bulk modulus was found. The simulated properties of n-pentane are in good agreement with data from a database of the National Institute of Standards and Technology, so the TraPPE-EH model can be recommended for simulations of hydrocarbons.

Glassy selenium at high pressure: Le Chatelier's principle still works

NASA Astrophysics Data System (ADS)

Brazhkin, V. V.; Tsiok, O. B.

2017-10-01

Selenium is the only easily vitrified elementary substance. Numerous experimental studies of glassy Se (g -Se) at high pressures show a large spread in the data on the compressibility and electrical resistivity of g -Se. Furthermore, H. Liu et al. [Proc. Natl. Acad. Sci. USA 105, 13229 (2008), 10.1073/pnas.0806857105] have arrived at the surprising conclusion that the volume of glass increases during pressure-induced crystallization. We have performed high-precision measurements of the specific volume and electrical resistivity of glassy selenium (g -Se) at high hydrostatic pressures up to 9 GPa. The measured bulk modulus at normal pressure is B =(9.0 5 ±0.15 ) GPa and its pressure derivative is BP'=6.4 ±0.2 . In the pressure range P <3 GPa, glassy selenium has an anomalously large negative second derivative of the bulk modulus. The electrical resistivity of g -Se decreases almost exponentially with increasing pressure and reaches 20 Ω cm at a pressure of 8.75 GPa. The inelastic behavior and weak relaxation of the volume for g -Se begin at pressures above 3.5 GPa; the volume and logarithm of the electrical resistivity relax significantly (logarithmically with the time) at pressures above 8 GPa. Bulk measurements certainly indicate that the volume of g -Se glass in the crystallization pressure range is larger than the volumes of both appearing crystalline phases (by 2% and 4%). Therefore, the "volume expansion phenomenon" suggested in [H. Liu et al., Proc. Natl. Acad. Sci. USA 105, 13229 (2008), 10.1073/pnas.0806857105] is not observed, and the pressure-induced crystallization of glassy selenium is consistent with the laws of thermodynamics.

Fatigue and nanomechanical properties of K3XF nickel-titanium instruments.

PubMed

Shen, Y; Zhou, H; Campbell, L; Wang, Z; Wang, R; Du, T; Haapasalo, M

2014-12-01

To examine the fatigue behaviour of heat-treated NiTi instruments when immersed in aqueous media and to determine the effect of cyclic fatigue on the hardness and elastic modulus of NiTi instruments using a nanoindentation technique. K3XF and K3 NiTi instruments, both in sizes 25, 0.04 taper and 40, 0.04 taper, were subjected to rotational bending at a curvature of 42° either in air or under deionized water, and the number of revolutions to fracture (Nf ) was recorded. The fracture surface of all fragments was examined with a scanning electron microscope. The hardness and elastic modulus of the fracture surface of instruments sized 25, 0.04 taper were then measured using a nanoindentation test. The K3XF instruments had a fatigue resistance superior to K3 instruments under dry and aqueous environments (P < 0.05). The fatigue life of K3 instruments was similar under both conditions, whereas the Nf of K3XF was greater under water than in air, especially at the size 40, 0.04 taper (P < 0.05). The values for the fraction of the area occupied by the dimple region were significantly smaller in K3XF instruments than in K3 instruments, especially under water (P < 0.05). There was no difference in hardness on K3XF instruments between new files and instruments subjected to the fatigue process. The hardness of instruments subjected to the fatigue process was significantly lower in K3XF than in K3 instruments (P < 0.05). The fatigue life of K3XF instruments under water is longer than it is for K3XF instruments in air. There was no work-hardening effect on K3XF instruments subjected to the fatigue process. © 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Characterization of human passive muscles for impact loads using genetic algorithm and inverse finite element methods.

PubMed

Chawla, A; Mukherjee, S; Karthikeyan, B

2009-02-01

The objective of this study is to identify the dynamic material properties of human passive muscle tissues for the strain rates relevant to automobile crashes. A novel methodology involving genetic algorithm (GA) and finite element method is implemented to estimate the material parameters by inverse mapping the impact test data. Isolated unconfined impact tests for average strain rates ranging from 136 s(-1) to 262 s(-1) are performed on muscle tissues. Passive muscle tissues are modelled as isotropic, linear and viscoelastic material using three-element Zener model available in PAMCRASH(TM) explicit finite element software. In the GA based identification process, fitness values are calculated by comparing the estimated finite element forces with the measured experimental forces. Linear viscoelastic material parameters (bulk modulus, short term shear modulus and long term shear modulus) are thus identified at strain rates 136 s(-1), 183 s(-1) and 262 s(-1) for modelling muscles. Extracted optimal parameters from this study are comparable with reported parameters in literature. Bulk modulus and short term shear modulus are found to be more influential in predicting the stress-strain response than long term shear modulus for the considered strain rates. Variations within the set of parameters identified at different strain rates indicate the need for new or improved material model, which is capable of capturing the strain rate dependency of passive muscle response with single set of material parameters for wide range of strain rates.

Effects of ionizing radiation on extracellular matrix

NASA Astrophysics Data System (ADS)

Mohamed, F.; Bradley, D. A.; Winlove, C. P.

2007-09-01

The extracellular matrix is a ubiquitous and important component of tissues. We investigated the effects of ionizing radiation on the physical properties of its principal macromolecular components, pericardial collagen, ligament elastin and hyaluronan, a representative glycosaminoglycan. Samples were exposed to X-rays from an electron linear accelerator in the range of 10-100 Gy to cover the range of irradiation exposure during radiotherapy. A uniaxial mechanical testing protocol was used to characterize the fibrous proteins. For pericardial tissue the major change was an increase in the elastic modulus in the toe region of the curve (⩽20% strain), from 23±18 kPa for controls to 57±22 kPa at a dose of 10 Gy ( p=0.01, α=0.05). At larger strain (⩾20% strain), the elastic modulus in the linear region decreased from 1.92±0.70 MPa for control pericardium tissue to 1.31±0.56 MPa ( p=0.01, α=0.05) for 10 Gy X-irradiated sample. Similar observations have been made previously on tendon collagen at larger strains. For elastin, the stress-strain relationship was linear up to 30% strain, but the elastic modulus decreased significantly with irradiation (controls 626±65 kPa, irradiated 474±121 kPa ( p=0.02, α=0.05), at 10 Gy X-irradiation). The results suggest that for collagen the primary effect of irradiation is generation of additional cross-links, while for elastin chain scissions are important. The viscosity of HA (at 1.25% w/v and 0.125% w/v) was measured by both cone and plate and capillary viscometry, the former providing measurement at uniform shear rate and the latter providing a more sensitive indication of changes at low viscosity. Both techniques revealed a dose-dependent reduction in viscosity (from 3400±194 cP for controls to 1500±88 cP at a shear rate of 2 s -1 and dose of 75 Gy), again suggesting depolymerization.

Comparative study of magnetic ordering in bulk and nanoparticles of Sm0.65Ca0.35MnO3: Magnetization and electron magnetic resonance measurements

NASA Astrophysics Data System (ADS)

Goveas, Lora Rita; Anuradha, K. N.; Bhagyashree, K. S.; Bhat, S. V.

2015-05-01

To explore the effect of size reduction to nanoscale on the hole doped Sm0.65Ca0.35MnO3 compound, dc magnetic measurements and electron magnetic resonance (EMR) were done on bulk and nanoparticle samples in the temperature range 10 ≤ T ≤ 300 K. Magnetization measurement showed that the bulk sample undergoes a charge ordering transition at 240 K and shows a mixed magnetic phase at low temperature. However, the nanosample underwent a ferromagnetic transition at 75 K, and the charge ordered state was destabilized on size reduction down to nanoscale. The low-temperature ferromagnetic component is found to be enhanced in nanoparticles as compared to their bulk counterpart. Interestingly around room temperature, bulk particles show higher magnetization where as at low temperature nanoparticles show higher magnetization. Ferromagnetism in the bulk is due to super exchange where as ferromagnetism in nanoparticles is due to uncompensated spins of the surface layer. Temperature variation of EMR parameters correlates well with the results of magnetic measurements. The magnetic behaviour of the nanoparticles is understood in terms of the core shell scenario.

Reactive Ball Milling to Fabricate Nanocrystalline Titanium Nitride Powders and Their Subsequent Consolidation Using SPS

NASA Astrophysics Data System (ADS)

El-Eskandarany, M. Sherif

2017-05-01

The room-temperature reactive ball milling (RBM) approach was employed to synthesize nanostructured fcc-titanium nitride (TiN) powders, starting from milling hcp-titanium (Ti) powders under 10 bar of a nitrogen gas atmosphere, using a roller mill. During the first and intermediate stage of milling, the agglomerated Ti powders were continuously disintegrated into smaller particles with fresh surfaces. Increasing the RBM time led to an increase in the active-fresh surfaces of Ti, resulting increasing of the mole fraction of TiN against unreacted hcp-Ti. Toward the end of the RBM time (20 h), ultrafine spherical powder (with particles 0.5 μm in diameter) of the fcc-TiN phase was obtained, composed of nanocrystalline grains with an average diameter of 8 nm. The samples obtained after different stages of RBM time were consolidated under vacuum at 1600 °C into cylindrical bulk compacts of 20 mm diameter, using spark plasma sintering technique. These compacts that maintained their nanocrystalline characteristics with an average grain size of 56 nm in diameter, possessed high relative density (above 99% of the theoretical density). The Vickers hardness of the as-consolidated TiN was measured and found to be 22.9 GPa. The modulus of elasticity and shear modulus of bulk TiN were measured by a nondestructive test and found to be 384 and 189 GPa, respectively. In addition, the coefficient of friction of the end-product TiN bulk sample was measured and found to be 0.35.

Tensile testing method for rare earth based bulk superconductors at liquid nitrogen temperature

NASA Astrophysics Data System (ADS)

Kasaba, K.; Katagiri, K.; Murakami, A.; Sato, G.; Sato, T.; Murakami, M.; Sakai, N.; Teshima, H.; Sawamura, M.

2005-10-01

Bending tests have been commonly carried out to investigate the mechanical properties of melt-processed rare earth based bulk superconductors. Tensile tests by using small specimen, however, are preferable to evaluate the detailed distribution of the mechanical properties and the intrinsic elastic modulus because no stress distributions exist in the cross-section. In this study, the tensile test method at low temperature by using specimens with the dimensions of 3 × 3 × 4 mm from Y123 and Gd123 bulks was examined. They were glued to Al alloy rods at 400 K by using epoxy resin. Tests were carried out at liquid nitrogen temperature (LNT) by using the immersion type jig. Although the bending strength in the direction perpendicular to the c-axis of the bulks at LNT is higher than that at room temperature (RT), the tensile strength at LNT was lower than that at RT. Many of specimens fractured near the interface between the specimen and the Al alloy rod at LNT. According to the finite element method analysis, it was shown that there was a peak thermal stress in the loading direction near the interface and it was significantly higher at LNT than that at RT. It was also shown that the replacement of the Al alloy rod to Ti rod of which the coefficient of thermal expansion is close to that of bulks significantly increased the tensile strength.

Quantum size effects on the (0001) surface of double hexagonal close packed americium

NASA Astrophysics Data System (ADS)

Gao, D.; Ray, A. K.

2007-01-01

Electronic structures of double hexagonal close-packed americium and the (0001) surface have been studied via full-potential all-electron density-functional calculations with a mixed APW+lo/LAPW basis. The electronic and geometric properties of bulk dhcp Am as well as quantum size effects in the surface energies and the work functions of the dhcp Am (0001) ultra thin films up to seven layers have been examined at nonmagnetic, ferromagnetic, and antiferromagnetic configurations with and without spin orbit coupling. The anti-ferromagnetic state including spin-orbit coupling is found to be the ground state of dhcp Am with the 5f electrons primarily localized. Our results show that both magnetic configurations and spin-orbit coupling play important roles in determining the equilibrium lattice constant, the bulk modulus as well as the localized feature of 5f electrons for dhcp Am. Our calculated equilibrium lattice constant and bulk modulus at the ground state are in good agreement with the experimental values respectively. The work function of dhcp Am (0001) 7-layer surface at the ground state is predicted to be 2.90 eV. The surface energy for dhcp Am (0001) semi-infinite surface energy at the ground state is predicted to be 0.84 J/m2. Quantum size effects are found to be more pronounced in work functions than in surface energies.

MnNiO3 revisited with modern theoretical and experimental methods

NASA Astrophysics Data System (ADS)

Dzubak, Allison L.; Mitra, Chandrima; Chance, Michael; Kuhn, Stephen; Jellison, Gerald E.; Sefat, Athena S.; Krogel, Jaron T.; Reboredo, Fernando A.

2017-11-01

MnNiO3 is a strongly correlated transition metal oxide that has recently been investigated theoretically for its potential application as an oxygen-evolution photocatalyst. However, there is no experimental report on critical quantities such as the band gap or bulk modulus. Recent theoretical predictions with standard functionals such as LDA+U and HSE show large discrepancies in the band gaps (about 1.23 eV), depending on the nature of the functional used. Hence there is clearly a need for an accurate quantitative prediction of the band gap to gauge its utility as a photocatalyst. In this work, we present a diffusion quantum Monte Carlo study of the bulk properties of MnNiO3 and revisit the synthesis and experimental properties of the compound. We predict quasiparticle band gaps of 2.0(5) eV and 3.8(6) eV for the majority and minority spin channels, respectively, and an equilibrium volume of 92.8 Å3, which compares well to the experimental value of 94.4 Å3. A bulk modulus of 217 GPa is predicted for MnNiO3. We rationalize the difficulty for the formation of ordered ilmenite-type structure with specific sites for Ni and Mn to be potentially due to the formation of antisite defects that form during synthesis, which ultimately affects the physical properties of MnNiO3.

Low Thermal Conductivity of Bulk Amorphous Si1- x Ge x Containing Nano-Sized Crystalline Particles Synthesized by Ball-Milling Process

NASA Astrophysics Data System (ADS)

Muthusamy, Omprakash; Nishino, Shunsuke; Ghodke, Swapnil; Inukai, Manabu; Sobota, Robert; Adachi, Masahiro; Kiyama, Makato; Yamamoto, Yoshiyuki; Takeuchi, Tsunehiro; Santhanakrishnan, Harish; Ikeda, Hiroya; Hayakawa, Yasuhiro

2018-06-01

Amorphous Si0.65Ge0.35 powder containing a small amount of nano-sized crystalline particles was synthesized by means of the mechanical alloying process. Hot pressing for 24 h under the pressure of 400 MPa at 823 K, which is below the crystallization temperature, allowed us to obtain bulk amorphous Si-Ge alloy containing a small amount of nanocrystals. The thermal conductivity of the prepared bulk amorphous Si-Ge alloy was extremely low, showing a magnitude of less than 1.35 Wm-1 K-1 over the entire temperature range from 300 K to 700 K. The sound velocity of longitudinal and transverse waves for the bulk amorphous Si0.65Ge0.35 were measured, and the resulting values were 5841 m/s and 2840 m/s, respectively. The estimated mean free path of phonons was kept at the very small value of ˜ 4.2 nm, which was mainly due to the strong scattering limit of phonons in association with the amorphous structure.

Analysis of Hansen's Inferior and Superior Partial Anomalies and the Division of the Elliptic Orbit into Two Segments

NASA Astrophysics Data System (ADS)

Sharaf, M. A.; Saad, A. S.

2017-10-01

In this paper, a novel analysis was established to prove how Hansen's inferior and superior partial anomalies k and k_1 can divide the elliptic orbit into two segments. The analysis depends on the departures of r (for k) and 1/r (for k1) from their minima. By these departures, we can find: (i) Transformations relating the eccentric anomaly to k and the true anomaly to k1. (ii) Expressions for k and k_1 in terms of the orbital elements. (iii) The interpretation and the intervals of definition of two moduli (X, S) related to k and k_1. (iv) The extreme values of r and the elliptic equations in terms of k and k1. (v) For r' and r'', the modulus X as a measure of the asymmetry of r' (or r'') from r'' (or r'), and the modulus S12 as a measure of the asymmetry of r' and r'' from the minimum value of r. (vi) A description of the segments represented by k and k1. (vii) The relative position of the radius vector at k0° and k1=180°.

Equation of state, phase stability, and phase transformations of uranium-6 wt. % niobium under high pressure and temperature

NASA Astrophysics Data System (ADS)

Zhang, Jianzhong; Vogel, Sven; Brown, Donald; Clausen, Bjorn; Hackenberg, Robert

2018-05-01

In-situ time-of-flight neutron diffraction experiments were conducted on the uranium-niobium alloy with 6 wt. % Nb (U-6Nb) at pressures up to 4.7 GPa and temperatures up to 1073 K. Upon static compression at room temperature, the monoclinic structure of U-6Nb (α″ U-6Nb) remains stable up to the highest experimental pressure. Based on the pressure-volume measurements at room temperature, the least-squares fit using the finite-strain equation of state (EOS) yields an isothermal bulk modulus of B0 = 127 ± 2 GPa for the α″-phase of U-6Nb. The calculated zero-pressure bulk sound speed from this EOS is 2.706 ± 0.022 km/s, which is in good agreement with the linear extrapolation of the previous Hugoniot data above 12 GPa for α″ U-6Nb, indicating that the dynamic response under those shock-loading conditions is consistent with the stabilization of the initial monoclinic phase of U-6Nb. Upon heating at ambient and high pressures, the metastable α″ U-6Nb exhibits complex transformation paths leading to the diffusional phase decomposition, which are sensitive to applied pressure, stress state, and temperature-time path. These findings provide new insight into the behavior of atypical systems such as U-Nb and suggest that the different U-Nb phases are separated by rather small energies and hence highly sensitive to compositional, thermal, and mechanical perturbations.

Correlation of the mechanical and structural properties of cortical rachis keratin of rectrices of the Toco Toucan (Ramphastos toco).

PubMed

Bodde, S G; Meyers, M A; McKittrick, J

2011-07-01

Mechanical characterization of the cortex of rectrices (tail feathers) of the Toco Toucan (Ramphastos toco) has been carried out by tensile testing of the rachis cortex in order to systematically determine Young's modulus and maximum tensile strength gradients on the surfaces and along the length of the feather. Of over seventy-five samples tested, the average Young's modulus was found to be 2.56±0.09 GPa, and maximum tensile strength was found to be 78±6 MPa. The Weibull modulus for all sets is greater than one and less than four, indicating that measured strength is highly variable. The highest Weibull moduli were reported for dorsal samplings. Dorsal and ventral surfaces of the cortex are both significantly stiffer and stronger than lateral rachis cortex. On the dorsal surface, cortex sampled from the distal end of the feather was found to be least stiff and weakest compared to that sampled from proximal and middle regions along the length of the feather. Distinctive fracture patterns correspond to failure in the superficial cuticle layer and the bulk of the rachis cortex. In the cuticle, where supramolecular keratinous fibers are oriented tangentially, evidence of ductile tearing was observed. In the bulk cortex, where the fibers are bundled and oriented longitudinally, patterns suggestive of near-periodic aggregation and brittle failure were observed. Copyright © 2011 Elsevier Ltd. All rights reserved.

Elastic Properties across the y→α Volume Collapse in Cerium versus Pressure and Temperature

DOE PAGES

Lipp, M. J.; Jenei, Zs.; Cynn, H.; ...

2017-10-31

Here, the longitudinal and transverse sound speeds, c L and c T, of polycrystalline cerium were measured isothermally vs pressure up to the critical temperature across the iso-structural γ-α volume collapse (VC) phase transition. We deduce values for the adiabatic bulk modulus BS, the shear modulus G = ρc T 2, the Poisson’s ratio ν and the Debye temperature, θ D(p). We find that the elastic constant C 12 is solely responsible for the decrease of B S with pressure towards the VC at RT. With increasing temperature, the lattice contribution ΔS vib(γ→α) to the total entropy change across themore » VC decreases more rapidly to zero than the total entropy itself suggesting that another mechanism, possibly disorder, assists in stabilizing the γ-phase entropically against the α-phase. Also, with increasing temperature, the Poisson’s ratio becomes negative near the VC transition, meaning that cerium metal takes on auxetic characteristics over a small pressure range. At the critical point the Poisson’s ratio ought to be -1, since the isothermal bulk modulus vanishes and the shear modulus remains nonzero.« less

Elastic Properties across the y→α Volume Collapse in Cerium versus Pressure and Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lipp, M. J.; Jenei, Zs.; Cynn, H.

Here, the longitudinal and transverse sound speeds, c L and c T, of polycrystalline cerium were measured isothermally vs pressure up to the critical temperature across the iso-structural γ-α volume collapse (VC) phase transition. We deduce values for the adiabatic bulk modulus BS, the shear modulus G = ρc T 2, the Poisson’s ratio ν and the Debye temperature, θ D(p). We find that the elastic constant C 12 is solely responsible for the decrease of B S with pressure towards the VC at RT. With increasing temperature, the lattice contribution ΔS vib(γ→α) to the total entropy change across themore » VC decreases more rapidly to zero than the total entropy itself suggesting that another mechanism, possibly disorder, assists in stabilizing the γ-phase entropically against the α-phase. Also, with increasing temperature, the Poisson’s ratio becomes negative near the VC transition, meaning that cerium metal takes on auxetic characteristics over a small pressure range. At the critical point the Poisson’s ratio ought to be -1, since the isothermal bulk modulus vanishes and the shear modulus remains nonzero.« less

First-principles calculations of the electronic, vibrational, and elastic properties of the magnetic laminate Mn₂GaC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thore, A., E-mail: andth@ifm.liu.se; Dahlqvist, M., E-mail: madah@ifm.liu.se, E-mail: bjoal@ifm.liu.se, E-mail: johro@ifm.liu.se; Alling, B., E-mail: madah@ifm.liu.se, E-mail: bjoal@ifm.liu.se, E-mail: johro@ifm.liu.se

2014-09-14

In this paper, we report the by first-principles predicted properties of the recently discovered magnetic MAX phase Mn₂GaC. The electronic band structure and vibrational dispersion relation, as well as the electronic and vibrational density of states, have been calculated. The band structure close to the Fermi level indicates anisotropy with respect to electrical conductivity, while the distribution of the electronic and vibrational states for both Mn and Ga depend on the chosen relative orientation of the Mn spins across the Ga sheets in the Mn–Ga–Mn trilayers. In addition, the elastic properties have been calculated, and from the five elastic constants,more » the Voigt bulk modulus is determined to be 157 GPa, the Voigt shear modulus 93 GPa, and the Young's modulus 233 GPa. Furthermore, Mn₂GaC is found relatively elastically isotropic, with a compression anisotropy factor of 0.97, and shear anisotropy factors of 0.9 and 1, respectively. The Poisson's ratio is 0.25. Evaluated elastic properties are compared to theoretical and experimental results for M₂AC phases where M = Ti, V, Cr, Zr, Nb, Ta, and A = Al, S, Ge, In, Sn.« less

Engineering an in vitro model of a functional ligament from bone to bone.

PubMed

Paxton, Jennifer Z; Grover, Liam M; Baar, Keith

2010-11-01

For musculoskeletal tissues that transmit loads during movement, the interfaces between tissues are essential to minimizing injury. Therefore, the reproduction of functional interfaces within engineered musculoskeletal tissues is critical to the successful transfer of the technology to the clinic. The goal of this work was to rapidly engineer ligament equivalents in vitro that contained both the soft tissue sinew and a hard tissue bone mimetic. This goal was achieved using cast brushite (CaHPO(4)·2H(2)O) anchors to mimic bone and a fibrin gel embedded with fibroblasts to create the sinew. The constructs formed within 7 days. Fourteen days after seeding, the interface between the brushite and sinew could withstand a stress of 9.51 ± 1.7  kPa before failure and the sinew reached a Young's modulus value of 0.16 ± 0.03  MPa. Treatment with ascorbic acid and proline increased the collagen content of the sinew (from 1.34% ± 0.2% to 8.34% ± 0.37%), strength of the interface (29.24 ± 6  kPa), and modulus of the sinew (2.69 ± 0.25  MPa). Adding transforming growth factor-β resulted in a further increase in collagen (11.25% ± 0.39%), interface strength (42 ± 8  kPa), and sinew modulus (5.46 ± 0.68  MPa). Both scanning electron and Raman microscopy suggested that the interface between the brushite and sinew mimics the in vivo tidemark at the enthesis. This work describes a major step toward the development of tissue-engineered ligaments for the repair of ligament ruptures in humans.

A model for the influence of pressure on the bulk modulus and the influence of temperature on the solidification pressure for liquid lubricants

NASA Technical Reports Server (NTRS)

Jacobson, B. O.; Vinet, P.

1986-01-01

Two pressure chambers, for compression experiments with liquids from zero to 2.2 GPa pressure, are described. The experimentally measured compressions are then compared to theoretical values given by an isothermal model of equation of state recently introduced for solids. The model describes the pressure and bulk modulus as a function of compression for different types of lubricants with a very high accuracy up to the pressure limit of the high pressure chamber used (2.2 GPa). In addition the influence of temperature on static solidification pressure was found to be a simple function of the thermal expansion of the fluid.

Scattering theory derivation of a 3D acoustic cloaking shell.

PubMed

Cummer, Steven A; Popa, Bogdan-Ioan; Schurig, David; Smith, David R; Pendry, John; Rahm, Marco; Starr, Anthony

2008-01-18

Through acoustic scattering theory we derive the mass density and bulk modulus of a spherical shell that can eliminate scattering from an arbitrary object in the interior of the shell--in other words, a 3D acoustic cloaking shell. Calculations confirm that the pressure and velocity fields are smoothly bent and excluded from the central region as for previously reported electromagnetic cloaking shells. The shell requires an anisotropic mass density with principal axes in the spherical coordinate directions and a radially dependent bulk modulus. The existence of this 3D cloaking shell indicates that such reflectionless solutions may also exist for other wave systems that are not isomorphic with electromagnetics.

Higher Order Multipole Potentials and Electrostatic Screening Effects on Cohesive Energy and Bulk Modulus of Metallic Nanoparticles

NASA Astrophysics Data System (ADS)

Barakat, T.

2011-12-01

Higher order multipole potentials and electrostatic screening effects are introduced to incorporate the dangling bonds on the surface of a metallic nanopaticle and to modify the coulomb like potential energy terms, respectively. The total interaction energy function for any metallic nanoparticle is represented in terms of two- and three-body potentials. The two-body part is described by dipole-dipole interaction potential, and in the three-body part, triple-dipole (DDD) and dipole-dipole-quadrupole (DDQ) terms are included. The size-dependent cohesive energy and bulk modulus are observed to decrease with decreasing sizes, a result which is in good agreement with the experimental values of Mo and W nanoparticles.

Correlations between the resonant frequency shifts and the thermodynamic quantities for the α-β transition in quartz

NASA Astrophysics Data System (ADS)

Lider, M. C.; Yurtseven, H.

2018-05-01

The resonant frequency shifts are related to the thermodynamic quantities (compressibility, order parameter and susceptibility) for the α-β transition in quartz. The experimental data for the resonant frequencies and the bulk modulus from the literature are used for those correlations. By calculating the order parameter from the mean field theory, correlation between the resonant frequencies of various modes and the order parameter is examined according to the quasi-harmonic phonon theory for the α-β transition in quartz. Also, correlation between the bulk modulus in relation to the resonant frequency shifts and the order parameter susceptibility is constructed for the α-β transition in this crystalline system.

Bulk and nanocrystalline electron doped Gd0.15Ca0.85MnO3: Synthesis and magnetic characterization

NASA Astrophysics Data System (ADS)

Dhal, Lakshman; Chattarpal; Nirmala, R.; Santhosh, P. N.; Kumary, T. Geetha; Nigam, A. K.

2014-09-01

Polycrystalline Gd0.15Ca0.85MnO3 sample was prepared by solid state reaction method and nanocrystalline samples of different grain sizes of the same were prepared by sol-gel method. Phase purity and composition were verified by room temperature X-ray diffraction and SEM-EDAX analysis. Magnetization data of bulk Gd0.15Ca0.85MnO3 in 5 kOe field shows a peak at 119 K (TN) suggesting an antiferromagnetic transition. Nanocrystalline Gd0.15Ca0.85MnO3 sample ( 54 nm size) also shows a cusp at 107 K and a broad thermal hysteresis between field cooled cooling (FCC) and field cooled warming (FCW) data around this temperature. This thermal hysteresis suggests possible crystal structural transition. Field variation of magnetization of bulk Gd0.15Ca0.85MnO3 at 5 K shows a tendency to saturate, but yields a magnetic moment value of only 1.12 μB/f.u. in 70 kOe. The value of magnetization of nanocrystalline sample at 5 K in 70 kOe field is slightly larger and is 1.38 μB/f.u. which is probably due to the surface moments of the nanoparticle samples. Both the samples show Curie-Weiss-like behaviour in their paramagnetic state.

Equation of state of liquid Indium under high pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Huaming, E-mail: huamingli@gatech.edu, E-mail: mo.li@gatech.edu; Li, Mo, E-mail: huamingli@gatech.edu, E-mail: mo.li@gatech.edu; School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332

2015-09-15

We apply an equation of state of a power law form to liquid Indium to study its thermodynamic properties under high temperature and high pressure. Molar volume of molten indium is calculated along the isothermal line at 710K within good precision as compared with the experimental data in an externally heated diamond anvil cell. Bulk modulus, thermal expansion and internal pressure are obtained for isothermal compression. Other thermodynamic properties are also calculated along the fitted high pressure melting line. While our results suggest that the power law form may be a better choice for the equation of state of liquids,more » these detailed predictions are yet to be confirmed by further experiment.« less

Nanoindentation study of bulk zirconium hydrides at elevated temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cinbiz, Mahmut Nedim; Balooch, Mehdi; Hu, Xunxiang

Here, the mechanical properties of zirconium hydrides was studied using nano-indentation technique at a temperature range of 25 – 400 °C. Temperature dependency of reduced elastic modulus and hardness of δ- and ε-zirconium hydrides were obtained by conducting nanoindentation experiments on the bulk hydride samples with independently heating capability of indenter and heating stage. The reduced elastic modulus of δ-zirconium hydride (H/Zr ratio =1.61) decreased from ~113 GPa to ~109 GPa while temperature increased from room temperature to 400°C. For ε-zirconium hydrides (H/Zr ratio=1.79), the reduced elastic modulus decreased from 61 GPa to 54 GPa as temperature increased from roommore » temperature to 300 °C. Whereas, hardness of δ-zirconium hydride significantly decreased from 4.1 GPa to 2.41 GPa when temperature increased from room temperature to 400 °C. Similarly, hardness of ε-zirconium hydride decreased from 3.06 GPa to 2.19 GPa with temperature increase from room temperature to 300°C.« less

Nanoindentation study of bulk zirconium hydrides at elevated temperatures

DOE PAGES

Cinbiz, Mahmut Nedim; Balooch, Mehdi; Hu, Xunxiang; ...

2017-08-02

Here, the mechanical properties of zirconium hydrides was studied using nano-indentation technique at a temperature range of 25 – 400 °C. Temperature dependency of reduced elastic modulus and hardness of δ- and ε-zirconium hydrides were obtained by conducting nanoindentation experiments on the bulk hydride samples with independently heating capability of indenter and heating stage. The reduced elastic modulus of δ-zirconium hydride (H/Zr ratio =1.61) decreased from ~113 GPa to ~109 GPa while temperature increased from room temperature to 400°C. For ε-zirconium hydrides (H/Zr ratio=1.79), the reduced elastic modulus decreased from 61 GPa to 54 GPa as temperature increased from roommore » temperature to 300 °C. Whereas, hardness of δ-zirconium hydride significantly decreased from 4.1 GPa to 2.41 GPa when temperature increased from room temperature to 400 °C. Similarly, hardness of ε-zirconium hydride decreased from 3.06 GPa to 2.19 GPa with temperature increase from room temperature to 300°C.« less

High pressure phase transformation in uranium carbide: A first principle study

NASA Astrophysics Data System (ADS)

Sahoo, B. D.; Joshi, K. D.; Gupta, Satish C.

2013-02-01

First principles calculations have been carried out to analyze structural, elastic and dynamic stability, of UC under hydrostatic compression. The comparison of enthalpies of rocksalt type (B1) and body centered orthorhombic (bco) structures as a function of pressure suggests the B1 →bco transition at ˜ 23 GPa, in good agreement with experimental value of 27 GPa. From the lattice dynamic calculations we have determined the phonon dispersion relations for B1 phase at various compressions. It is found that TA phonon branch along Γ-X direction becomes imaginary around the transition pressure. Further, the phonon instability so caused is of long wavelength nature as it occurs near the Brillouin zone centre. This long wavelength phonon instability at the transition point indicates that the B1 →bco transition is driven by elastic failure (the vanishing of C44 modulus). Various physical quantities such as equilibrium volume, bulk modulus, pressure derivative of bulk modulus and elastic constants have been determined at zero pressure and compared with data available in literature.

Modulating surface rheology by electrostatic protein/polysaccharide interactions.

PubMed

Ganzevles, Renate A; Zinoviadou, Kyriaki; van Vliet, Ton; Cohen, Martien A; de Jongh, Harmen H

2006-11-21

There is a large interest in mixed protein/polysaccharide layers at air-water and oil-water interfaces because of their ability to stabilize foams and emulsions. Mixed protein/polysaccharide adsorbed layers at air-water interfaces can be prepared either by adsorption of soluble protein/polysaccharide complexes or by sequential adsorption of complexes or polysaccharides to a previously formed protein layer. Even though the final protein and polysaccharide bulk concentrations are the same, the behavior of the adsorbed layers can be very different, depending on the method of preparation. The surface shear modulus of a sequentially formed beta-lactoglobulin/pectin layer can be up to a factor of 6 higher than that of a layer made by simultaneous adsorption. Furthermore, the surface dilatational modulus and surface shear modulus strongly (up to factors of 2 and 7, respectively) depend on the bulk -lactoglobulin/pectin mixing ratio. On the basis of the surface rheological behavior, a mechanistic understanding of how the structure of the adsorbed layers depends on the protein/polysaccharide interaction in bulk solution, mixing ratio, ionic strength, and order of adsorption to the interface (simultaneous or sequential) is derived. Insight into the effect of protein/polysaccharide interactions on the properties of adsorbed layers provides a solid basis to modulate surface rheological behavior.

High pressure stability of lithium metatitanate and metazirconate: Insight from experiments & ab-initio calculations

NASA Astrophysics Data System (ADS)

Chitnis, Abhishek; Chakraborty, B.; Tripathi, B. M.; Tyagi, A. K.; Garg, Nandini

2018-02-01

Lithium metatitanate (LTO) and lithium metazirconate (LZO) are lithium rich ceramics which can be used as tritium breeder materials for thermonuclear reactors. In-situ x-ray diffraction and ab-initio studies at high pressure show that LTO has a higher bulk modulus than that of LZO. In fact these studies indicate that they are the least compressible of the known lithium rich ceramics like Li2O or Li4SiO4, which are potential candidates for blanket materials. These studies show that the TiO6 octahedra are responsible for the higher bulk modulus of LTO when compared to that of LZO. It has also been shown that the compressibility and distortion of the softer LiO6 octahedra can be controlled by altering the stacking sequence of the more rigid covalently bonded octahedra. This knowledge can be used by chemists to design new lithium based ceramics with higher bulk modulus. It was observed that LTO was stable upto 34 GPa. Ab initio DFT calculations helped to understand the anisotropy in compressibility of both LZO and LTO. This study also shows, that even though the empirical potentials developed by Vijaykumar et al. successfully determine the ambient pressure structure of lithium metatitanate, they cannot be used at non ambient conditions like high pressure [1].

Prediction of trabecular bone qualitative properties using scanning quantitative ultrasound

PubMed Central

Qin, Yi-Xian; Lin, Wei; Mittra, Erik; Xia, Yi; Cheng, Jiqi; Judex, Stefan; Rubin, Clint; Müller, Ralph

2012-01-01

Microgravity induced bone loss represents a critical health problem in astronauts, particularly occurred in weight-supporting skeleton, which leads to osteopenia and increase of fracture risk. Lack of suitable evaluation modality makes it difficult for monitoring skeletal status in long term space mission and increases potential risk of complication. Such disuse osteopenia and osteoporosis compromise trabecular bone density, and architectural and mechanical properties. While X-ray based imaging would not be practical in space, quantitative ultrasound may provide advantages to characterize bone density and strength through wave propagation in complex trabecular structure. This study used a scanning confocal acoustic diagnostic and navigation system (SCAN) to evaluate trabecular bone quality in 60 cubic trabecular samples harvested from adult sheep. Ultrasound image based SCAN measurements in structural and strength properties were validated by μCT and compressive mechanical testing. This result indicated a moderately strong negative correlations observed between broadband ultrasonic attenuation (BUA) and μCT-determined bone volume fraction (BV/TV, R2=0.53). Strong correlations were observed between ultrasound velocity (UV) and bone’s mechanical strength and structural parameters, i.e., bulk Young’s modulus (R2=0.67) and BV/TV (R2=0.85). The predictions for bone density and mechanical strength were significantly improved by using a linear combination of both BUA and UV, yielding R2=0.92 for BV/TV and R2=0.71 for bulk Young’s modulus. These results imply that quantitative ultrasound can characterize trabecular structural and mechanical properties through measurements of particular ultrasound parameters, and potentially provide an excellent estimation for bone’s structural integrity. PMID:23976803

Prediction of trabecular bone qualitative properties using scanning quantitative ultrasound

NASA Astrophysics Data System (ADS)

Qin, Yi-Xian; Lin, Wei; Mittra, Erik; Xia, Yi; Cheng, Jiqi; Judex, Stefan; Rubin, Clint; Müller, Ralph

2013-11-01

Microgravity induced bone loss represents a critical health problem in astronauts, particularly occurred in weight-supporting skeleton, which leads to osteopenia and increase of fracture risk. Lack of suitable evaluation modality makes it difficult for monitoring skeletal status in long term space mission and increases potential risk of complication. Such disuse osteopenia and osteoporosis compromise trabecular bone density, and architectural and mechanical properties. While X-ray based imaging would not be practical in space, quantitative ultrasound may provide advantages to characterize bone density and strength through wave propagation in complex trabecular structure. This study used a scanning confocal acoustic diagnostic and navigation system (SCAN) to evaluate trabecular bone quality in 60 cubic trabecular samples harvested from adult sheep. Ultrasound image based SCAN measurements in structural and strength properties were validated by μCT and compressive mechanical testing. This result indicated a moderately strong negative correlations observed between broadband ultrasonic attenuation (BUA) and μCT-determined bone volume fraction (BV/TV, R2=0.53). Strong correlations were observed between ultrasound velocity (UV) and bone's mechanical strength and structural parameters, i.e., bulk Young's modulus (R2=0.67) and BV/TV (R2=0.85). The predictions for bone density and mechanical strength were significantly improved by using a linear combination of both BUA and UV, yielding R2=0.92 for BV/TV and R2=0.71 for bulk Young's modulus. These results imply that quantitative ultrasound can characterize trabecular structural and mechanical properties through measurements of particular ultrasound parameters, and potentially provide an excellent estimation for bone's structural integrity.

Polymerization shrinkage kinetics and shrinkage-stress in dental resin-composites.

PubMed

Al Sunbul, Hanan; Silikas, Nick; Watts, David C

2016-08-01

To investigate a set of resin-composites and the effect of their composition on polymerization shrinkage strain and strain kinetics, shrinkage stress and the apparent elastic modulus. Eighteen commercially available resin-composites were investigated. Three specimens (n=3) were made per material and light-cured with an LED unit (1200mW/cm(2)) for 20s. The bonded-disk method was used to measure the shrinkage strain and Bioman shrinkage stress instrument was used to measure shrinkage stress. The shrinkage strain kinetics at 23°C was monitored for 60min. Maximum strain and stress was evaluated at 60min. The shrinkage strain rate was calculated using numerical differentiation. The shrinkage strain values ranged from 1.83 (0.09) % for Tetric Evoceram (TEC) to 4.68 (0.04) % for Beautifil flow plus (BFP). The shrinkage strain rate ranged from 0.11 (0.01%s(-1)) for Gaenial posterior (GA-P) to 0.59 (0.07) %s(-1) for BFP. Shrinkage stress values ranged from 3.94 (0.40)MPa for TET to 10.45 (0.41)MPa for BFP. The apparent elastic modulus ranged from 153.56 (18.7)MPa for Ever X posterior (EVX) to 277.34 (25.5) MPa for Grandio SO heavy flow (GSO). The nature of the monomer system determines the amount of the bulk contraction that occurs during polymerization and the resultant stress. Higher values of shrinkage strain and stress were demonstrated by the investigated flowable materials. The bulk-fill materials showed comparable result when compared to the traditional resin-composites. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Acoustic attenuation due to transformation twins in CaCl2: Analogue behaviour for stishovite

NASA Astrophysics Data System (ADS)

Zhang, Zhiying; Schranz, Wilfried; Carpenter, Michael A.

2012-09-01

CaCl2 undergoes a tetragonal (P42/mnm) to orthorhombic (Pnnm) transition as a function of temperature which is essentially the same as occurs in stishovite at high pressures. It can therefore be used as a convenient analogue material for experimental studies. In order to investigate variations in elastic properties associated with the transition and possible anelastic loss behaviour related to the mobility of ferroelastic twin walls in the orthorhombic phase, the transition in polycrystalline CaCl2 has been examined using resonant ultrasound spectroscopy (RUS) at high frequencies (0.1-1.5 MHz) in the temperature interval 7-626 K, and dynamic mechanical analysis (DMA) at low frequencies (0.1-50 Hz) in the temperature interval 378-771 K. RUS data show steep softening of the shear modulus as the transition temperature is approached from above and substantial acoustic dissipation in the stability field of the orthorhombic structure. DMA data show softening of the storage modulus, which continues through to a minimum ˜20 K below the transition point and is followed by stiffening with further lowering of temperature. There is no obvious acoustic dissipation associated with the transition, as measured by tan δ, however. The elastic softening and stiffening matches the pattern expected for a pseudoproper ferroelastic transition as predicted elsewhere. Acoustic loss behaviour at high frequencies fits with the pattern of behaviour expected for a twin wall loss mechanism but with relaxation times in the vicinity of ˜10-6 s. With such short relaxation times, the shear modulus of CaCl2 at frequencies corresponding to seismic frequencies would include relaxations of the twin walls and is therefore likely to be significantly lower than the intrinsic shear modulus. If these characteristics apply also to twin wall mobility in stishovite, the seismic signature of the orthorhombic phase should be an unusually soft shear modulus but with no increase in attenuation.

Transport characteristics and colossal dielectric response of cadmium sulfide nanoparticles

NASA Astrophysics Data System (ADS)

Ahmad, Mushtaq; Rafiq, M. A.; Hasan, M. M.

2013-10-01

We report here the synthesis of ˜20 nm sized cadmium sulfide (CdS) nanoparticles via conventional solid state reaction at low temperature ˜200 °C and ambient pressure. X-ray diffraction and high resolution transmission electron microscopy analysis confirmed the synthesis of hexagonal phased nanoparticles. Impedance and electrical modulus investigations were carried out in the frequency range 20 Hz to 2 MHz and at temperature from 300 K to 400 K, which show the presence of bulk, grain boundary, and sub-grain boundary phases in CdS nanoparticles. Overlapped large polaron tunneling was the observed mechanism of charge carriers in used temperature range. The presence of colossal dielectric constant in the system is attributed to the Maxwell-Wagner type polarization. High and temperature dependent dielectric constants make the CdS nanoparticles efficient material to be used in capacitive energy storage devices.

Characterization of the Properties of Photopatterned Hydrogels for Use in Regenerative Medicine

NASA Astrophysics Data System (ADS)

Fiedler, Callie Irene

The goal of this thesis was to locally photopattern cytocompatible hydrogels to exhibit a wide range of mechanical properties and to probe the fundamental parameters governing these materials printed via stereolithography (SLA). Fabricating cell-laden structures with locally defined mechanical properties is non-trivial because the use of multiple precursor materials is wasteful, slow, and can lead to cell-death. To investigate the range of mechanical properties a single precursor solution can produce, I initially formed a single-network hydrogel and cyclically in- swelled fresh precursor solution followed by photo-exposure of the swollen gel ("swelling + exposure" or SE cycle). Because transport (i.e., diffusion and swelling) can occur on the same time scale as photopolymerization reaction kinetics, I first characterized the variable modulus hydrogels in bulk to isolate the reaction kinetics. In these experiments, I demonstrated the ability modify the mechanical and chemical (i.e., compressive modulus, toughness, crosslink density, swelling ratio) properties by up to 10-fold using only 2-4 SE cycles. I then used the understanding gained via these bulk experiments to locally photopattern the elastic modulus of a cytocompatible hydrogel with pixel-limited resolution (˜10s mum) employing a custom SLA system. Here I demonstrated the ability to fabricate hydrogels with a 500% elastic moduli increase with respect to the unpatterned hydrogel using atomic force microscopy. I monitored monomer attachment to the existing matrix as a function of SE cycle using confocal fluorescence microscopy to characterize the shape and size of printed features. I validated that the dependence of these features on material and processing conditions could be explained by a first-order reaction/diffusion model. With this understanding, I fabricated SLA 3D printed, soft, cytocompatible hydrogels (˜10s kPa) with ˜250 mum channels in addition to fabricating 3D printed stiff, cytocompatible hydrogels (39 MPa) both with ˜10 mum resolution.

Equation of state of molten fayalite (Fe2SiO4)

NASA Astrophysics Data System (ADS)

Waller, C.; Liu, Q.; Agee, C. B.; Asimow, P. D.; Lange, R. A.

2010-12-01

We have conducted new equation of state measurements on liquid fayalite (Fe2SiO4) in a collaborative, multi-technique study. Using a shared bulk starting material, we have measured the liquid density, the bulk modulus (K), and its pressure derivative (K’) from 1 atm to 163 GPa using 1-atm double-bob Archimedean and ultrasonic, sink/float, and shock wave techniques to form a coherent, internally consistent equation of state. Previous shock studies of liquid fayalite were conducted up to pressures of 40 GPa1; we extended this data set with two additional pre-heated, molten (1573 K) fayalite shock compression experiments at 121 and 163 GPa. Linear fitting of this data in shock velocity (US)-particle velocity (up) space defines a Hugoniot with an unconstrained zero-pressure intercept that crosses within error at the bulk sound speed (Co) determined by ultrasonic techniques. Fixing the intercept at this ultrasonic value reduces the error on the linear fit and yields the relation: US =1.65(0.02)up+ 2.4377(0.006) km/s. This relationship indicates that the behavior of the liquid is relaxed during shock compression and demonstrates consistency across experimental methods. Likewise, results from new static compression sink/float experiments conducted in piston-cylinder and multi-anvil devices are in agreement with shock wave and ultrasonic data, consistent with an isothermal K=19.4 and K’=5.57 at 1500°C. In solid materials, the Grüneisen parameter (γ) generally decreases upon compression. However, preliminary calculations for γ of this liquid using additional initially solid shock data from Chen et al.(2002) indicate that γ increases upon compression. Using the functional form γ = γo(ρo/ρ)q at a density of 7.65 Mg/m3 yields a q value of -1.77 (γo = 0.41 is known from low-pressure data), which is similar to the reported q values of forsterite2, enstatite3, and anorthite-diopside liquids4. This result shows that iron-bearing mafic to ultramafic silicate liquids follow the same general behavior as iron-free liquids such that -2.0 ≤ q ≤ -1.5 for the compression range 1 ≥ ρo/ρ ≥ 0.50. We will be performing an additional shock wave experiment on initially solid (300 K) fayalite to confirm this result. We will be continuing collaborative equation of state measurements on additional iron-bearing silicate liquids, working to further clarify the properties of melts and their importance to understanding the dynamics of the early magma ocean and of melt migration within the mantle. In particular, understanding the properties of iron-rich silicates and their melts will constrain hypotheses of melting and of iron enrichment for explaining the occurrence and characteristics of ultra-low velocity zones near the CMB.

Ultrasonic Sound Velocity of Diopside Liquid Under High Pressure and High Temperature Conditions

NASA Astrophysics Data System (ADS)

Xu, M.; Jing, Z.; Chantel, J.; Yu, T.; Wang, Y.; Jiang, P.

2017-12-01

The equation of state (EOS) of silicate liquids is of great significance to the understanding of the dynamics and differentiation of the magmatic systems in Earth and other terrestrial planets. Sound velocity of silicate liquids measured at high pressure can provide direct information on the bulk modulus and its pressure derivative and hence tightly constrain the EOS of silicate liquids. In addition, the sound velocity data can be directly compared to seismic observations to infer the presence of melts in the mantle. While the sound velocity for silicate liquids at ambient pressure has been well established, the high-pressure sound velocity data are still lacking due to experimental challenges. In this study, we successfully determined the sound velocities of diopside (CaMgSi2O6) liquid in a multi-anvil apparatus under high pressure-high temperature conditions from 1 to 4 GPa and 1973 to 2473 K by the ultrasonic interferometry in conjunction with synchrotron X-ray techniques. Diopside was chosen to study because it is not only one of the most important phases in the Earth's upper mantle, but also an end-member composition of model basalt. It is thus an ideal simplified melt composition in the upper mantle. Besides, diopside liquid has been studied by ambient-pressure ultrasonic measurements (e.g., Ai and Lange, 2008) and shock-wave experiments at much higher pressure (e.g., Asimow and Ahrens, 2010), which allows comparison with our results over a large pressure range. Our high-pressure results on the sound velocity of Di liquid are consistent with the ambient-pressure data and show an increase of velocity with pressure (from 3039 m/s at 0.1 GPa to 4215 m/s at 3.5 GPa). Fitting to the Murnaghan EOS gives an isentropic bulk modulus (Ks) of 24.8 GPa and its pressure dependence (K'S) of 7.8. These are consistent with the results from shock-wave experiments on Di liquid (Asimow and Ahrens, 2010), indicating that the technique used in this study is capable to accurately determine the sound velocity of silicate liquids at high pressures. We will use these results to better constrain the hard sphere EOS model for silicate liquids (Jing and Karato, 2011), with implications to the stability of melt layers in the deep mantle under gravity and the presence of partial melts in low velocity zones in the mantle.

Gassmann Theory Applies to Nanoporous Media

NASA Astrophysics Data System (ADS)

Gor, Gennady Y.; Gurevich, Boris

2018-01-01

Recent progress in extraction of unconventional hydrocarbon resources has ignited the interest in the studies of nanoporous media. Since many thermodynamic and mechanical properties of nanoscale solids and fluids differ from the analogous bulk materials, it is not obvious whether wave propagation in nanoporous media can be described using the same framework as in macroporous media. Here we test the validity of Gassmann equation using two published sets of ultrasonic measurements for a model nanoporous medium, Vycor glass, saturated with two different fluids, argon, and n-hexane. Predictions of the Gassmann theory depend on the bulk and shear moduli of the dry samples, which are known from ultrasonic measurements and the bulk moduli of the solid and fluid constituents. The solid bulk modulus can be estimated from adsorption-induced deformation or from elastic effective medium theory. The fluid modulus can be calculated according to the Tait-Murnaghan equation at the solvation pressure in the pore. Substitution of these parameters into the Gassmann equation provides predictions consistent with measured data. Our findings set up a theoretical framework for investigation of fluid-saturated nanoporous media using ultrasonic elastic wave propagation.

The high-pressure behavior of spherocobaltite (CoCO3): a single crystal Raman spectroscopy and XRD study

NASA Astrophysics Data System (ADS)

Chariton, Stella; Cerantola, Valerio; Ismailova, Leyla; Bykova, Elena; Bykov, Maxim; Kupenko, Ilya; McCammon, Catherine; Dubrovinsky, Leonid

2018-01-01

Magnesite (MgCO3), calcite (CaCO3), dolomite [(Ca, Mg)CO3], and siderite (FeCO3) are among the best-studied carbonate minerals at high pressures and temperatures. Although they all exhibit the calcite-type structure ({R}\\bar{3}{c}) at ambient conditions, they display very different behavior at mantle pressures. To broaden the knowledge of the high-pressure crystal chemistry of carbonates, we studied spherocobaltite (CoCO3), which contains Co2+ with cation radius in between those of Ca2+ and Mg2+ in calcite and magnesite, respectively. We synthesized single crystals of pure spherocobaltite and studied them using Raman spectroscopy and X-ray diffraction in diamond anvil cells at pressures to over 55 GPa. Based on single crystal diffraction data, we found that the bulk modulus of spherocobaltite is 128 (2) GPa and K' = 4.28 (17). CoCO3 is stable in the calcite-type structure up to at least 56 GPa and 1200 K. At 57 GPa and after laser heating above 2000 K, CoCO3 partially decomposes and forms CoO. In comparison to previously studied carbonates, our results suggest that at lower mantle conditions carbonates can be stable in the calcite-type structure if the radius of the incorporated cation(s) is equal or smaller than that of Co2+ (i.e., 0.745 Å).

Shear-wave elastography for breast masses: local shear wave speed (m/sec) versus Young modulus (kPa).

PubMed

Youk, Ji Hyun; Son, Eun Ju; Park, Ah Young; Kim, Jeong-Ah

2014-01-01

To evaluate and compare the performance of shear-wave elastography (SWE) for breast masses using the local shear wave speed (m/sec) vs. Young modulus (kPa). A total of 130 breast lesions in 123 women who underwent SWE before ultrasound- guided core needle biopsy or surgical excision were included. With the region-of-interest placed over the stiffest areas of the lesion on SWE, the quantitative mean, maximum, and standard deviation (SD) of the elasticity values were measured in kPa and m/sec for each lesion. The SD was also measured with the region-of-interest including the whole breast lesion (wSD). The area under the receiver operating characteristic curve (AUC), sensitivity, and specificity of each elasticity value measured in kPa and m/sec were compared. Of the 130 lesions, 49 (37.7%) were malignant and 81 (62.3%) were benign. The AUCs for the mean, maximum, and SD of the elasticity values using kPa and m/sec did not differ significantly: mean, 0.974 vs. 0.974; maximum, 0.960 vs. 0.976; SD, 0.916 vs. 0.916. However, the AUC for wSD showed a significant difference: 0.964 (kPa) vs. 0.960 (m/sec) (P=0.036). There was no significant difference in the sensitivity and specificity of the mean, maximum, and wSD of the elasticity values. However, the specificity of the SD was significantly different between the two different measurements: 95.1% (kPa) vs. 87.7% (m/sec) (P=0.031). The quantitative elasticity values measured in kPa and m/sec on SWE showed good diagnostic performance. The specificity of the SD and AUC of the wSD measured in kPa were significantly higher than those measured in m/sec.

Performances and impedance spectroscopy of Small-molecule bulk heterojunction solar cells based on PtOEP: PCBM

NASA Astrophysics Data System (ADS)

Abuelwafa, A. A.; Dongol, M.; El-Nahass, M. M.; Soga, T.

2018-03-01

Small-molecule bulk heterojunction (SBHJ) solar cells based on platinum octaethylporphyrin (PtOEP) as donor material and phenyl-C61-butyric acid methyl ester (PCBM) as the acceptor were fabricated using spin coating techniques with weight ratios from 1:0.1 to 1:9. The formation of charge transfer complex CTC in the PtOEP: PCBM blend was specified from the redshift of the PtOEP absorption peak after blending with PCBM. The photovoltaic performance for PtOEP: PCBM blends were investigated using the external quantum efficiency (EQE) besides the current density-voltage (J-V) characteristics under illumination100 mW/cm2 (AM1.5G). The BHJ solar cell with PtOEP: PCBM ratio of 1:9 exhibited the best performance. The impedance spectroscopy (IS) was examined in the frequency range from 25 Hz to 1 MHz. The equivalent circuit model was evaluated in details to evaluate the impedance spectroscopy parameters. Dielectric constant {ɛ ^' }, dielectric loss {ɛ ^' ' }} and dielectric modulus were included and discussed in terms of dielectric polarization processes. Dielectric modulus displays the non-Debye relaxation in PtOEP: PCBM BHJ solar cells.

Synthesis and Equation of State of Perovskites and Post-Perovskites in the (Mg,Fe)GeO3 System

NASA Astrophysics Data System (ADS)

Stan, C. V.; Dutta, R.; Krizan, J. W.; Cava, R. J.; Prakapenka, V.; Duffy, T. S.

2016-12-01

Knowledge of the effect of Fe on the physical and chemical properties of bridgmanite (perovskite, pv) and post-perovskite (ppv) is essential for interpreting seismic and geodynamic studies of the deep Earth. Silicate ppv is especially challenging to study due to the high pressure and temperature required for its synthesis ( 125 GPa and 2500 K in MgSiO3). This restricts the range of experiments possible and makes it very difficult to achieve well-characterized pressure-temperature conditions. Germanates have often been used as analogues because they undergo a similar sequence of phase transitions, but at lower pressures than their silicate counterparts. For example, MgGeO3 ppv can be synthesized at 63 GPa and 1800 K. In this study, polycrystalline pyroxenes (px) with compositions of (MgxFe1-x)2Ge2O6 (x = 1, 0.92, 0.78, 0.61, 0.52, 0) were synthesized and characterized using x-ray diffraction, Raman, Mössbauer, and microprobe analysis at ambient conditions. The px samples were found to exhibit a linear increase in lattice parameters and Raman mode shift with iron content. High-pressure x-ray diffraction experiments in the laser-heated diamond anvil cell were performed at beamline 13-ID-D of the Advanced Photon Source. All compositions were shown to transform to the pv ( 30 GPa and 1500 K) and ppv (> 55 GPa, 1600-1800 K) structures. Compositions with Mg# > 78 formed single-phase pv and ppv. Incorporation of Fe into the pv structure causes a decrease in octahedral distortion relative to the ideal cubic pv. Additionally, it leads to a modest decrease in bulk modulus (K0) and a modest increase in zero pressure volume (V0), and lowers the pv to ppv phase transition pressure by 10 GPa in the case of Mg#78 versus Mg#100. These novel high-pressure and -temperature analog phases can be of use for further investigation of the effect of Fe on the behavior of pv and ppv, including studies of site occupancies, spin state, and partitioning behavior.

Ab Initio Study of the Electronic Structure, Elastic Properties, Magnetic Feature and Thermodynamic Properties of the Ba2NiMoO6 Material

NASA Astrophysics Data System (ADS)

Deluque Toro, C. E.; Mosquera Polo, A. S.; Gil Rebaza, A. V.; Landínez Téllez, D. A.; Roa-Rojas, J.

2018-04-01

We report first-principles calculations of the elastic properties, electronic structure and magnetic behavior performed over the Ba2NiMoO6 double perovskite. Calculations are carried out through the full-potential linear augmented plane-wave method within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient and Local Density Approximations, including spin polarization. The elastic properties calculated are bulk modulus (B), the elastic constants (C 11, C 12 and C 44), the Zener anisotropy factor (A), the isotropic shear modulus (G), the Young modulus (Y) and the Poisson ratio (υ). Structural parameters, total energies and cohesive properties of the perovskite are studied by means of minimization of internal parameters with the Murnaghan equation, where the structural parameters are in good agreement with experimental data. Furthermore, we have explored different antiferromagnetic configurations in order to describe the magnetic ground state of this compound. The pressure and temperature dependence of specific heat, thermal expansion coefficient, Debye temperature and Grüneisen parameter were calculated by DFT from the state equation using the quasi-harmonic model of Debye. A specific heat behavior C V ≈ C P was found at temperatures below T = 400 K, with Dulong-Petit limit values, which is higher than those, reported for simple perovskites.

Influence of ZnO doping on the properties of single domain YBCO bulks fabricated by RE+011 TSIG process

NASA Astrophysics Data System (ADS)

Yang, W. M.; Yuan, X. C.; Guo, Y. X.

2017-10-01

Single domain YBCO bulk superconductors with different additions of ZnO have been successfully fabricated by RE+011 TSIG process with a new solid phase of [(100-x)(Y2O3 + 1.2BaCuO2)+xZnO] and a new liquid phase of (Y2O3+6CuO+10BaCuO2). The effects of ZnO additions on the growth morphology, microstructure, critical temperature (Tc), the levitation force and trapped field of the YBCO bulks have been investigated. It is found that within the range of ZnO additions x=0-1.0 wt.%, all the samples are of the typical characteristic of single-domain YBCO bulk; the Tc of the samples decreases from 92 K to 80 K when the ZnO addition x increases from x=0 wt.% to x=1.0 wt.%; the levitation force and trapped field of the samples firstly increase and then decrease with increase of ZnO additions after going through a maximum, which is closely related with the ZnO addition and the resulting flux pinning force caused by lattice distortion due to the substitution of Zn2+ for Cu2+ site in the YBCO crystal; the largest levitation force 36.8 N (77 K, 0.5 T) and trapped field 0.416 T (77 K, 0.5 T) of the samples are obtained when x=0.1 wt.%, respectively. This result is significantly important and helpful for us to improve the properties of YBCO bulk superconductors.

Mechanical characterization of human brain tumors from patients and comparison to potential surgical phantoms.

PubMed

Stewart, Daniel C; Rubiano, Andrés; Dyson, Kyle; Simmons, Chelsey S

2017-01-01

While mechanical properties of the brain have been investigated thoroughly, the mechanical properties of human brain tumors rarely have been directly quantified due to the complexities of acquiring human tissue. Quantifying the mechanical properties of brain tumors is a necessary prerequisite, though, to identify appropriate materials for surgical tool testing and to define target parameters for cell biology and tissue engineering applications. Since characterization methods vary widely for soft biological and synthetic materials, here, we have developed a characterization method compatible with abnormally shaped human brain tumors, mouse tumors, animal tissue and common hydrogels, which enables direct comparison among samples. Samples were tested using a custom-built millimeter-scale indenter, and resulting force-displacement data is analyzed to quantify the steady-state modulus of each sample. We have directly quantified the quasi-static mechanical properties of human brain tumors with effective moduli ranging from 0.17-16.06 kPa for various pathologies. Of the readily available and inexpensive animal tissues tested, chicken liver (steady-state modulus 0.44 ± 0.13 kPa) has similar mechanical properties to normal human brain tissue while chicken crassus gizzard muscle (steady-state modulus 3.00 ± 0.65 kPa) has similar mechanical properties to human brain tumors. Other materials frequently used to mimic brain tissue in mechanical tests, like ballistic gel and chicken breast, were found to be significantly stiffer than both normal and diseased brain tissue. We have directly compared quasi-static properties of brain tissue, brain tumors, and common mechanical surrogates, though additional tests would be required to determine more complex constitutive models.

High thermal conductivity in soft elastomers with elongated liquid metal inclusions.

PubMed

Bartlett, Michael D; Kazem, Navid; Powell-Palm, Matthew J; Huang, Xiaonan; Sun, Wenhuan; Malen, Jonathan A; Majidi, Carmel

2017-02-28

Soft dielectric materials typically exhibit poor heat transfer properties due to the dynamics of phonon transport, which constrain thermal conductivity ( k ) to decrease monotonically with decreasing elastic modulus ( E ). This thermal-mechanical trade-off is limiting for wearable computing, soft robotics, and other emerging applications that require materials with both high thermal conductivity and low mechanical stiffness. Here, we overcome this constraint with an electrically insulating composite that exhibits an unprecedented combination of metal-like thermal conductivity, an elastic compliance similar to soft biological tissue (Young's modulus < 100 kPa), and the capability to undergo extreme deformations (>600% strain). By incorporating liquid metal (LM) microdroplets into a soft elastomer, we achieve a ∼25× increase in thermal conductivity (4.7 ± 0.2 W⋅m -1 ⋅K -1 ) over the base polymer (0.20 ± 0.01 W⋅m -1 ·K -1 ) under stress-free conditions and a ∼50× increase (9.8 ± 0.8 W⋅m -1 ·K -1 ) when strained. This exceptional combination of thermal and mechanical properties is enabled by a unique thermal-mechanical coupling that exploits the deformability of the LM inclusions to create thermally conductive pathways in situ. Moreover, these materials offer possibilities for passive heat exchange in stretchable electronics and bioinspired robotics, which we demonstrate through the rapid heat dissipation of an elastomer-mounted extreme high-power LED lamp and a swimming soft robot.

Magnetic, Optical and Magneto-optical Properties of Ni2MnGe Alloy Films

NASA Astrophysics Data System (ADS)

Kim, R. J.; Kudryavtsev, Y. V.; Kim, K. W.

2005-03-01

The influence of atomic ordering on the magnetic, the optical and the magneto-optical (MO) properties of Ni2MnGe Heusler alloy (HA) films was investigated. The bulk Ni2MnGe HA was prepared by arc melting, and the films were deposited by flash evaporation onto glass substrates at several substrate temperatures from 150 to 730 K. The bulk Ni2MnGe HA exhibits the cubic L21 structure with a = b = c = 0.5761 nm, and the annealed (at 573 K) bulk alloy is in the tetragonal structure with a = b = 0.5720 nm and c = 0.5865 nm. While the films deposited at 720 K show a well-ordered L21 structure, the deposition at 150 K < T < 710 K results in the formation of a nanocrystalline or an amorphous microstructure. It was found the structural disorder in Ni2MnGe films induces lack of the ferromagnetic order and noticeable changes in the optical and MO response.

Thermodynamic data of lawsonite and zoisite in the system CaO-Al2O3-SiO2-H2O based on experimental phase equilibria and calorimetric work

NASA Astrophysics Data System (ADS)

Grevel, Klaus-Dieter; Schoenitz, Mirko; Skrok, Volker; Navrotsky, Alexandra; Schreyer, Werner

2001-08-01

The enthalpy of drop-solution in molten 2PbO.B2O3 of synthetic and natural lawsonite, CaAl2(Si2O7)(OH)2.H2O, was measured by high-temperature oxide melt calorimetry. The enthalpy of formation determined for the synthetic material is ΔfHOxides=-168.7+/-3.4 kJ mol-1, or ΔfH0298=-4,872.5+/-4.0 kJ mol-1. These values are in reasonable agreement with previously published data, although previous calorimetric work yielded slightly more exothermic data and optimisation methods resulted in slightly less exothermic values. The equilibrium conditions for the dehydration of lawsonite to zoisite, kyanite and quartz/coesite at pressures and temperatures up to 5 GPa and 850 °C were determined by piston cylinder experiments. These results, other recent phase equilibrium data, and new calorimetric and thermophysical data for lawsonite and zoisite, Ca2Al3(SiO4)(Si2O7)O(OH), were used to constrain a mathematical programming analysis of the thermodynamic data for these two minerals in the chemical system CaO-Al2O3-SiO2-H2O (CASH). The following data for lawsonite and zoisite were obtained: ΔfH0298 (lawsonite)=-4,865.68 kJ mol-1 , S0298 (lawsonite)=229.27 J K-1 mol-1 , ΔfH0298 (zoisite)=-6,888.99 kJ mol-1 , S0298 (zoisite)=297.71 J K-1 mol-1 . Additionally, a recalculation of the bulk modulus of lawsonite yielded K=120.7 GPa, which is in good agreement with recent experimental work.

Visualising elastic anisotropy: theoretical background and computational implementation

NASA Astrophysics Data System (ADS)

Nordmann, J.; Aßmus, M.; Altenbach, H.

2018-02-01

In this article, we present the technical realisation for visualisations of characteristic parameters of the fourth-order elasticity tensor, which is classified by three-dimensional symmetry groups. Hereby, expressions for spatial representations of uc(Young)'s modulus and bulk modulus as well as plane representations of shear modulus and uc(Poisson)'s ratio are derived and transferred into a comprehensible form to computer algebra systems. Additionally, we present approaches for spatial representations of both latter parameters. These three- and two-dimensional representations are implemented into the software MATrix LABoratory. Exemplary representations of characteristic materials complete the present treatise.

Test of parameter-free local pseudopotential for the study of dynamical elastic constants - Cu as a prototype

NASA Astrophysics Data System (ADS)

Bhatia, K. G.; Vyas, S. M.; Patel, A. B.; Bhatt, N. K.; Vyas, P. R.; Gohel, V. B.

2018-05-01

Using parameter-free (first principles local) pseudopotential, in the present communication we have calculated dynamical elastic constants (C11, C12 and C44), bulk modulus (B), shear modulus (µp), Young's modulus (Y) and Poisson's ratio (σ) in long wavelength limit. Our computed results are well agreed for C44 and B with experiment and with other theoretical results obtained within framework of second order perturbation pseudopotential theory. From the present study we conclude that pseudopotential used contain s-p hybridization and no extra term is required to account core-core repulsion.

Equation of state and thermodynamic Grüneisen parameter of monoclinic 1,1-diamino-2,2-dinitroethylene.

PubMed

Zhang, Jianzhong; Velisavljevic, Nenad; Zhu, Jinlong; Wang, Liping

2016-10-05

In situ synchrotron x-ray diffraction experiments were conducted on 1,1-diamino-2,2-dinitroethylene (FOX-7) at pressures up to 6.8 GPa and temperatures up to 485 K. Within the resolution of the present diffraction data, our results do not reveal evidence for a pressure-induced structural phase transition near 2 GPa, previously observed in several vibrational spectroscopy experiments. Based on unit-cell volume measurements, the least-squares fit using the third-order Birch-Murnaghan equation of state (EOS) yields K 0  =  12.6  ±  1.4 GPa and [Formula: see text]  =  11.3  ±  2.1 for the α-phase of FOX-7, which are in good agreement with recently reported values for the deuterated sample, indicating that the effect of hydrogen-deuterium substitution on the compressibility of FOX-7 is negligibly small. A thermal EOS is also obtained for the α-phase of FOX-7, including pressure dependence of thermal expansivity, (∂α/∂P)T  =  -7.0  ±  2.0  ×  10(-5) K(-1) GPa(-1), and temperature derivative of the bulk modulus, (∂K T/∂T)P  =  -1.1  ×  10(-2) GPa K(-1). From these EOS parameters, we calculate heat capacity at constant volume (C V) and thermodynamic Grüneisen parameter (γ TH) as a function of temperature. At ambient conditions, the calculated γ TH is 1.055, which is in good agreement with the value (1.09) previously obtained from density functional theory (DFT). The obtained C V, however, is 13% larger than that calculated from the first-principles calculations, indicating that the dispersion correction in the DFT calculations may need to be further improved for describing intermolecular interactions of molecular crystals.

Update on Breast Cancer Detection Using Comb-push Ultrasound Shear Elastography

PubMed Central

Denis, Max; Bayat, Mahdi; Mehrmohammadi, Mohammad; Gregory, Adriana; Song, Pengfei; Whaley, Dana H.; Pruthi, Sandhya; Chen, Shigao; Fatemi, Mostafa; Alizad, Azra

2015-01-01

In this work, tissue stiffness estimates are used to differentiate between benign and malignant breast masses in a group of pre-biopsy patients. The rationale being that breast masses are often stiffer than healthy tissue; furthermore, malignant masses are stiffer than benign masses. The comb-push ultrasound shear elastography (CUSE) method is used to noninvasively assess a tissue’s mechanical properties. CUSE utilizes a simultaneous multiple laterally spaced radiation force (ARF) excitations and detection sequence to reconstruct the region of interest (ROI) shear wave speed map, from which a tissue stiffness property is quantified by Young’s modulus. In this study, the tissue stiffness of 73 breast masses is interrogated. The mean shear wave speeds for malignant masses (3.42 ± 1.32 m/s) were higher than benign breast masses (6.04 ± 1.25 m/s). These speed values correspond to higher stiffness in malignant breast masses (114.9 ± 40.6 kPa) than benign masses (39.4 ± 28.1 kPa and p < 0.001), when tissue elasticity is quantified by Young’s modulus. A Young’s modulus > 83 kPa is established as a cut-off value for differentiating between malignant and benign suspicious breast masses, with receiver operating characteristic curve (ROC) of 89.19% sensitivity, 88.69% specificity, and 0.911 for the area under the curve (AUC). PMID:26688871

High P-T phase transitions and P-V-T equation of state of hafnium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hrubiak, Rostislav; Drozd, Vadym; Karbasi, Ali

2016-07-29

We measured the volume of hafnium at several pressures up to 67 GPa and at temperatures between 300 to 780 K using a resistively heated diamond anvil cell with synchrotron x-ray diffraction at the Advanced Photon Source. The measured data allows us to determine the P-V-T equation of state of hafnium. The previously described [Xia et al., Phys. Rev. B 42, 6736-6738 (1990)] phase transition from hcp ({alpha}) to simple hexagonal ({omega}) phase at 38 GPa at room temperature was not observed even up to 51 GPa. The {omega} phase was only observed at elevated temperatures. Our measurements have alsomore » improved the experimental constraint on the high P-T phase boundary between the {omega} phase and high pressure bcc ({beta}) phase of hafnium. Isothermal room temperature bulk modulus and its pressure derivative for the {alpha}-phase of hafnium were measured to be B{sub 0} = 112.9{+-}0.5 GPa and B{sub 0}'=3.29{+-}0.05, respectively. P-V-T data for the {alpha}-phase of hafnium was used to obtain a fit to a thermodynamic P-V-T equation of state based on model by Brosh et al. [CALPHAD 31, 173-185 (2007)].« less

High magnetic field processing of liquid crystalline polymers

DOEpatents

Smith, M.E.; Benicewicz, B.C.; Douglas, E.P.

1998-11-24

A process of forming bulk articles of oriented liquid crystalline thermoset material, the material characterized as having an enhanced tensile modulus parallel to orientation of an applied magnetic field of at least 25 percent greater than said material processed in the absence of a magnetic field, by curing a liquid crystalline thermoset precursor within a high strength magnetic field of greater than about 2 Tesla, is provided, together with a resultant bulk article of a liquid crystalline thermoset material, said material processed in a high strength magnetic field whereby said material is characterized as having a tensile modulus parallel to orientation of said field of at least 25 percent greater than said material processed in the absence of a magnetic field.

High magnetic field processing of liquid crystalline polymers

DOEpatents

Smith, Mark E.; Benicewicz, Brian C.; Douglas, Elliot P.

1998-01-01

A process of forming bulk articles of oriented liquid crystalline thermoset material, the material characterized as having an enhanced tensile modulus parallel to orientation of an applied magnetic field of at least 25 percent greater than said material processed in the absence of a magnetic field, by curing a liquid crystalline thermoset precursor within a high strength magnetic field of greater than about 2 Tesla, is provided, together with a resultant bulk article of a liquid crystalline thermoset material, said material processed in a high strength magnetic field whereby said material is characterized as having a tensile modulus parallel to orientation of said field of at least 25 percent greater than said material processed in the absence of a magnetic field.

Thermal Characterization of Dynamic Silicon Cantilever Array Sensors by Digital Holographic Microscopy

PubMed Central

Zakerin, Marjan; Novak, Antonin; Toda, Masaya; Emery, Yves; Natalio, Filipe; Butt, Hans-Jürgen; Berger, Rüdiger

2017-01-01

In this paper, we apply a digital holographic microscope (DHM) in conjunction with stroboscopic acquisition synchronization. Here, the temperature-dependent decrease of the first resonance frequency (S1(T)) and Young’s elastic modulus (E1(T)) of silicon micromechanical cantilever sensors (MCSs) are measured. To perform these measurements, the MCSs are uniformly heated from T0 = 298 K to T = 450 K while being externally actuated with a piezo-actuator in a certain frequency range close to their first resonance frequencies. At each temperature, the DHM records the time-sequence of the 3D topographies for the given frequency range. Such holographic data allow for the extracting of the out-of-plane vibrations at any relevant area of the MCSs. Next, the Bode and Nyquist diagrams are used to determine the resonant frequencies with a precision of 0.1 Hz. Our results show that the decrease of resonance frequency is a direct consequence of the reduction of the silicon elastic modulus upon heating. The measured temperature dependence of the Young’s modulus is in very good accordance with the previously-reported values, validating the reliability and applicability of this method for micromechanical sensing applications. PMID:28545236

MnNiO 3 revisited with modern theoretical and experimental methods

DOE PAGES

Dzubak, Allison L.; Mitra, Chandrima; Chance, Michael; ...

2017-11-03

MnNiO 3 is a strongly correlated transition metal oxide that has recently been investigated theoretically for its potential application as an oxygen-evolution photocatalyst. However, there is no experimental report on critical quantities such as the band gap or bulk modulus. Recent theoretical predictions with standard functionals such as LDA+U and HSE show large discrepancies in the band gaps (about 1.23 eV), depending on the nature of the functional used. Hence there is clearly a need for an accurate quantitative prediction of the band gap to gauge its utility as a photocatalyst. In this work, we present a diffusion quantum Montemore » Carlo study of the bulk properties of MnNiO 3 and revisit the synthesis and experimental properties of the compound. We predict quasiparticle band gaps of 2.0(5) eV and 3.8(6) eV for the majority and minority spin channels, respectively, and an equilibrium volume of 92.8 Å 3, which compares well to the experimental value of 94.4 Å 3. A bulk modulus of 217 GPa is predicted for MnNiO 3. As a result, we rationalize the difficulty for the formation of ordered ilmenite-type structure with specific sites for Ni and Mn to be potentially due to the formation of antisite defects that form during synthesis, which ultimately affects the physical properties of MnNiO 3.« less

MnNiO 3 revisited with modern theoretical and experimental methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dzubak, Allison L.; Mitra, Chandrima; Chance, Michael

MnNiO 3 is a strongly correlated transition metal oxide that has recently been investigated theoretically for its potential application as an oxygen-evolution photocatalyst. However, there is no experimental report on critical quantities such as the band gap or bulk modulus. Recent theoretical predictions with standard functionals such as LDA+U and HSE show large discrepancies in the band gaps (about 1.23 eV), depending on the nature of the functional used. Hence there is clearly a need for an accurate quantitative prediction of the band gap to gauge its utility as a photocatalyst. In this work, we present a diffusion quantum Montemore » Carlo study of the bulk properties of MnNiO 3 and revisit the synthesis and experimental properties of the compound. We predict quasiparticle band gaps of 2.0(5) eV and 3.8(6) eV for the majority and minority spin channels, respectively, and an equilibrium volume of 92.8 Å 3, which compares well to the experimental value of 94.4 Å 3. A bulk modulus of 217 GPa is predicted for MnNiO 3. As a result, we rationalize the difficulty for the formation of ordered ilmenite-type structure with specific sites for Ni and Mn to be potentially due to the formation of antisite defects that form during synthesis, which ultimately affects the physical properties of MnNiO 3.« less

Temperature dependence of the elastic moduli and damping for polycrystalline LiF-22 pct CaF2 eutectic salt

NASA Technical Reports Server (NTRS)

Wolfenden, A.; Lastrapes, G.; Duggan, M. B.; Raj, S. V.

1991-01-01

Young's and shear moduli and damping were measured for as-cast polycrystalline LiF-(22 mol pct)CaF2 eutectic specimens as a function of temperature using the piezoelectric ultrasonic composite oscillator technique. The shear modulus decreased with increasing temperature from about 40 GPa at 295 K to about 30 GPa at 1000 K, while the Young modulus decreased from about 115 GPa at 295 K to about 35 GPa at 900 K. These values are compared with those derived from the rule of mixtures using elastic moduli data for LiF and CaF2 single crystals. It is shown that, while the shear modulus data agree reasonably well with the predicted trend, there is a large discrepancy between the theoretical calculations and the Young modulus values, where this disagreement increases with increasing temperature.

Molecular modeling of polymers 16. Gaseous diffusion in polymers: a quantitative structure-property relationship (QSPR) analysis.

PubMed

Patel, H C; Tokarski, J S; Hopfinger, A J

1997-10-01

The purpose of this study was to identify the key physicochemical molecular properties of polymeric materials responsible for gaseous diffusion in the polymers. Quantitative structure-property relationships, QSPRs were constructed using a genetic algorithm on a training set of 16 polymers for which CO2, N2, O2 diffusion constants were measured. Nine physicochemical properties of each of the polymers were used in the trial basis set for QSPR model construction. The linear cross-correlation matrices were constructed and investigated for colinearity among the members of the training sets. Common water diffusion measures for a limited training set of six polymers was used to construct a "semi-QSPR" model. The bulk modulus of the polymer was overwhelmingly found to be the dominant physicochemical polymer property that governs CO2, N2 and O2 diffusion. Some secondary physicochemical properties controlling diffusion, including conformational entropy, were also identified as correlation descriptors. Very significant QSPR diffusion models were constructed for all three gases. Cohesive energy was identified as the main correlation physicochemical property with aqueous diffusion measures. The dominant role of polymer bulk modulus on gaseous diffusion makes it difficult to develop criteria for selective transport of gases through polymers. Moreover, high bulk moduli are predicted to be necessary for effective gas barrier materials. This property requirement may limit the processing and packaging features of the material. Aqueous diffusion in polymers may occur by a different mechanism than gaseous diffusion since bulk modulus does not correlate with aqueous diffusion, but rather cohesive energy of the polymer.

Bulk Properties of Ni3Al(gamma') With Cu and Au Additions

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John

1995-01-01

The BFS method for alloys is applied to the study of 200 alloys obtained from adding Cu and Au impurities to a Ni3Al matrix. We analyze the trends in the bulk properties of these alloys (heat of formation, lattice parameter, and bulk modulus) and detect specific alloy compositions for which these quantities have particular values. A detailed analysis of the atomic interactions that lead to the preferred ordering patterns is presented.

Preparation and characterization of starch-based loose-fill packaging foams

NASA Astrophysics Data System (ADS)

Fang, Qi

Regular and waxy corn starches were blended in various ratios with biodegradable polymers including polylactic acid (PLA), Eastar Bio Copolyester 14766 (EBC) and Mater-Bi ZF03U (MBI) and extruded with a C. W. Brabender laboratory twin screw extruder using a 3-mm die nozzle at 150°C and 150 rev/min. Physical characteristics including radial expansion, unit density and bulk density and water solubility index, water absorption characteristics, mechanical properties including compressibility, Young's modulus, spring index, bulk compressibility and bulk spring index and abrasion resistance were investigated as affected by the ingredient formulations, i.e. type of polymers, type of starches, polymer to starch ratio and starch moisture content. A completely randomized factorial blocking experimental design was used. Fifty-four treatments resulted. Each treatment was replicated three times. SAS statistical software package was used to analyze the data. Foams made of waxy starch had better radial expansion, lower unit density and bulk density than did foams made of regular starch. Regular starch foams had significantly lower water solubility index than did the waxy starch foams. PLA-starch foams had the lowest compressibility and Young's modulus. MBI-starch foams were the most rigid. All foams had excellent spring indices and bulk spring indices which were comparable to the spring index of commercial expanded polystyrene foam. Correlations were established between the foam mechanical properties and the physical characteristics. Foam compressibility and Young's modulus decreased as increases in radial expansion and decreases in unit and bulk densities. Their relationships were modeled with power law equations. No correlation was observed between spring index and bulk spring index and foam physical characteristics. MBI-starch foams had the highest equilibrium moisture content. EBC-starch and PLA-starch foams had similar water absorption characteristics. No significant difference existed in water absorption characteristics between foams made of regular and waxy starches. Empirical models were developed to correlate foam water absorption characteristics with relative humidity and polymer content. The developed models fit the data well with relatively small standard errors and uniformly scattered residual plots. Foams with higher polymer content had better abrasion resistance than did foams with lower polymer content.

Effect of sintering temperatures on the in vitro bioactivity, molecular structure and mechanical properties of titanium/carbonated hydroxyapatite nanobiocomposites

NASA Astrophysics Data System (ADS)

Youness, Rasha A.; Taha, Mohammed A.; Ibrahim, Medhat A.

2017-12-01

Titanium-containing carbonated hydroxyapatite (Ti-CHA) nanocomposite powders, with different CHA contents, have been prepared using high-energy ball milling method. The effect of sintering temperatures, 900, 1100 and 1300 °C on molecular structure and microstructure of these samples were examined by XRD; Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), respectively. Furthermore, their mechanical properties including hardness, longitudinal modulus, Young's modulus, shear modulus, bulk modulus and Poisson's ratio were measured by ultrasonic non-destructive technique. Moreover, bioactivity of sintered samples at different firing temperatures was assessed by immersing them in simulated body fluid at 37 ± 0.5 °C for 7 days and then, analyzed by FTIR spectroscopy. The results pointed out that increasing sintering temperature up to 1100 °C caused significant increases in densities and mechanical properties of these nanocomposite samples. However, further increase of firing temperature to 1300 °C was responsible for complete CHA decomposition and the resultant α-tricalcium (α-TCP) phase greatly affected these properties. On the contrary, better bioactivity was observed for sintered samples at 900 °C only. However, increase of sintering temperature of these samples up to 1300 °C led to severe decrease in their bioactivity due to the formation of highly soluble α-TCP phase.

Frequency dependent electrical characteristics of ferroelectric Pb{4.0}K{1.0}Li{1.0}Nb{10}O{30} ceramics

NASA Astrophysics Data System (ADS)

Rao, K. S.; Krishna, P. M.; Prasad, D. M.; Latha, T. S.; Hussain, M.

2007-09-01

Dielectric, impedance, modulus and conductivity studies were performed over temperature 35 °C 600 °C and frequency 45 Hz 5 MHz range on the Lead Potassium Lithium Niobate (Pb{4.0}K{1.0}Li{1.0}Nb{10}O{30}, PKLN) ceramics. These studies established the conduction ion motion and polarization mechanism in the material. The dispersive dielectric loss at high temperature reveals the ionic conductivity. From frequency variation of \\varepsilonl response the pre-factor A(T) and critical exponent n(T) are evaluated, and are used in Jonscher's dielectric dispersion relation for \\varepsilon ' to fit with the experimental data. Complex impedance plots showed a non Debye type relaxation, are used to evaluate the grain and grain boundary conduction and relaxation activation energies. DC and ac conduction activation energies are estimated from Arrhenius plots. Occupancy of Li+ for C-sites gave a completely filled structure and enhanced the phase transition temperature to 520 °C compared to PKN. This is supported by the conduction activation energy in ferro region is more than the para region. Also, the dc conductivity characterized from bulk resistance and M^ll peak frequency. Polaron hoping mechanism at room temperature has been confirmed via the linear variation of the plot log (σ ac-σ dc) as a function of log ω 2. Stretched exponential parameter, β (0 < β ≤slant 1) has been evaluated from impedance plots, interpreted as a result of correlated motions between the Li+ ions and distribution of dielectric relaxation. Compared the results from different techniques, and discussed the conduction mechanism in the material.

Fabrication of Bi2223 bulks with high critical current properties sintered in Ag tubes

NASA Astrophysics Data System (ADS)

Takeda, Yasuaki; Shimoyama, Jun-ichi; Motoki, Takanori; Kishio, Kohji; Nakashima, Takayoshi; Kagiyama, Tomohiro; Kobayashi, Shin-ichi; Hayashi, Kazuhiko

2017-03-01

Randomly grain oriented Bi2223 sintered bulks are one of the representative superconducting materials having weak-link problem due to very short coherence length particularly along the c-axis, resulting in poor intergrain Jc properties. In our previous studies, sintering and/or post-annealing under moderately reducing atmospheres were found to be effective for improving grain coupling in Bi2223 sintered bulks. Further optimizations of the synthesis process for Bi2223 sintered bulks were attempted in the present study to enhance their intergrain Jc. Effects of applied pressure of uniaxial pressing and sintering conditions on microstructure and superconducting properties have been systematically investigated. The best sample showed intergrain Jc of 2.0 kA cm-2 at 77 K and 8.2 kA cm-2 at 20 K, while its relative density was low ∼65%. These values are quite high as for a randomly oriented sintered bulk of cuprate superconductors.

Elastic collapse in disordered isostatic networks

NASA Astrophysics Data System (ADS)

Moukarzel, C. F.

2012-02-01

Isostatic networks are minimally rigid and therefore have, generically, nonzero elastic moduli. Regular isostatic networks have finite moduli in the limit of large sizes. However, numerical simulations show that all elastic moduli of geometrically disordered isostatic networks go to zero with system size. This holds true for positional as well as for topological disorder. In most cases, elastic moduli decrease as inverse power laws of system size. On directed isostatic networks, however, of which the square and cubic lattices are particular cases, the decrease of the moduli is exponential with size. For these, the observed elastic weakening can be quantitatively described in terms of the multiplicative growth of stresses with system size, giving rise to bulk and shear moduli of order e-bL. The case of sphere packings, which only accept compressive contact forces, is considered separately. It is argued that these have a finite bulk modulus because of specific correlations in contact disorder, introduced by the constraint of compressivity. We discuss why their shear modulus, nevertheless, is again zero for large sizes. A quantitative model is proposed that describes the numerically measured shear modulus, both as a function of the loading angle and system size. In all cases, if a density p>0 of overconstraints is present, as when a packing is deformed by compression or when a glass is outside its isostatic composition window, all asymptotic moduli become finite. For square networks with periodic boundary conditions, these are of order \\sqrt{p} . For directed networks, elastic moduli are of order e-c/p, indicating the existence of an "isostatic length scale" of order 1/p.

Robust high pressure stability and negative thermal expansion in sodium-rich antiperovskites Na{sub 3}OBr and Na{sub 4}OI{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yonggang, E-mail: yyggwang@gmail.com, E-mail: yangwg@hpstar.ac.cn, E-mail: yusheng.zhao@unlv.edu; Institute of Nanostructured Functional Materials, Huanghe Science and Technology College, Zhengzhou, Henan 450006; High Pressure Synergetic Consortium

2016-01-14

The structure stability under high pressure and thermal expansion behavior of Na{sub 3}OBr and Na{sub 4}OI{sub 2}, two prototypes of alkali-metal-rich antiperovskites, were investigated by in situ synchrotron X-ray diffraction techniques under high pressure and low temperature. Both are soft materials with bulk modulus of 58.6 GPa and 52.0 GPa for Na{sub 3}OBr and Na{sub 4}OI{sub 2}, respectively. The cubic Na{sub 3}OBr structure and tetragonal Na{sub 4}OI{sub 2} with intergrowth K{sub 2}NiF{sub 4} structure are stable under high pressure up to 23 GPa. Although being a characteristic layered structure, Na{sub 4}OI{sub 2} exhibits nearly isotropic compressibility. Negative thermal expansion was observed at lowmore » temperature range (20–80 K) in both transition-metal-free antiperovskites for the first time. The robust high pressure structure stability was examined and confirmed by first-principles calculations among various possible polymorphisms qualitatively. The results provide in-depth understanding of the negative thermal expansion and robust crystal structure stability of these antiperovskite systems and their potential applications.« less

Structural, magnetic, elastic, dielectric and electrical properties of hot-press sintered Co1-xZnxFe2O4 (x = 0.0, 0.5) spinel ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Singh Yadav, Raghvendra; Kuřitka, Ivo; Havlica, Jaromir; Hnatko, Miroslav; Alexander, Cigáň; Masilko, Jiri; Kalina, Lukas; Hajdúchová, Miroslava; Rusnak, Jaroslav; Enev, Vojtěch

2018-02-01

In this article, Co1-xZnxFe2O4 (x = 0.0 and 0.5) disc-shaped pellets were formed by hot-press sintering of nanoparticles at temperature 925 °C for 10 min in vacuum atmosphere under 30 MPa mechanical pressure. X-ray diffraction study confirmed the formation of spinel cubic ferrite structure of hot-press sintered spinel ferrite Co1-xZnxFe2O4 (x = 0.0 and 0.5) samples. The scanning electron microscopy image indicated that the growth and densification of smaller ferrite nanoparticles were higher than larger ferrite nanoparticles. Magnetic properties of sintered samples were investigated by the superconducting quantum interface device (SQUID) magnetometer at room temperature. The hot press sintered Co1-xZnxFe2O4 (x = 0.0 and 0.5) pellet samples exhibited magnetic properties dependent on the grain size of spinel ferrite particles. The maximum saturation magnetization 82.47 emu/g was obtained for Co0.5Zn0.5Fe2O4 hot press sintered sample of ball-milled ferrite particles. Further, the impact of grain size and density of sample on hardness, dielectric property and ac conductivity of hot-press sintered samples was investigated. In addition, the longitudinal wave velocity (Vl), transverse wave velocity (Vt), mean elastic wave velocity (Vm), bulk modulus (B), rigidity modulus (G), Young's modulus (E), Poisson ratio (σ) and Debye temperature (θD) were calculated. The elastic moduli of hot press sintered ferrite samples were corrected to zero porosity using Hosselman and Fulrath model.

Experimental and Theoretical Equation of State of GeO2 to 1.2 Mbars

NASA Astrophysics Data System (ADS)

Dutta, R.; White, C.; Greenberg, E.; Prakapenka, V. B.; Duffy, T. S.

2017-12-01

Germanium dioxide, GeO2, has been used widely as an analog in structural studies of crystalline, amorphous, and liquid SiO2 at high pressures (Micoulaut et al. 2006). Crystalline GeO2 follows a similar sequence of phase transitions as crystalline SiO2 but at substantially lower pressures making it useful as an analog for the behavior of silica in deep interiors of terrestrial and extra-solar planets. However, much of the existing work on GeO2 is fragmentary, and there is limited experimental data above 50 GPa. In this study, we report detailed equation of state (EOS) data for four phases (rutile, CaCl2, α-PbO2 and pyrite-type) of GeO2 using both laser-heated diamond anvil cell experiments and theoretical density functional theory (DFT) calculations. Experiments were conducted at sector 13 of the Advanced Photon Source. The rutile phase was synthesized from α-quartz starting material by laser heating at 4.7 GPa. The pressure-volume data for this phase can be fit using a 3rd order Birch-Murnaghan equation of state (EOS) with V0 = 55.33 Å3 (fixed), K0 = 225(10) GPa, K0' = 5(1), where V0, K0, K0' are the zero-pressure volume, bulk modulus and its pressure derivative respectively. In a separate run, the CaCl2-type phase was synthesized at 35.9 GPa and the sample remained in this structure up to 68.3 GPa. The EOS parameters in this case are V0 = 55.9 (1) Å3, K0 = 238 (4) GPa and K0' = 4 (fixed). The α-PbO2-type phase was examined between 51 and 90 GPa, yielding the following EOS parameters: V0 = 107.6 (2) Å3, K0 = 291 (5) GPa and K0' = 4 (fixed). The pyrite-type phase was then synthesized and examined up to the peak pressure of 119.5 GPa. The best fit to the data is obtained using V0 = 100.7 (1) Å3, K0 = 339 (4) GPa and K0' = 4 (fixed). These values will be compared with the results of theoretical calculations using different exchange correlation functionals. Our results will also be compared with shock wave data for GeO2 to better understand the behavior of this material under dynamic compression. In addition, detailed comparison between GeO2 crystals and glass as well as with SiO2 crystals and glass will provide insights into how structural changes and densification of germanate and silicate glasses at high pressure compare with the corresponding crystalline phases. ReferencesMicoulaut M, Cormier L, Henderson GS (2006) J Phys-Condens Matter 18: R753-R784.

Finite element analysis for transverse carpal ligament tensile strain and carpal arch area.

PubMed

Yao, Yifei; Erdemir, Ahmet; Li, Zong-Ming

2018-05-17

Mechanics of carpal tunnel soft tissue, such as fat, muscle and transverse carpal ligament (TCL), around the median nerve may render the median nerve vulnerable to compression neuropathy. The purpose of this study was to understand the roles of carpal tunnel soft tissue mechanical properties and intratunnel pressure on the TCL tensile strain and carpal arch area (CAA) using finite element analysis (FEA). Manual segmentation of the thenar muscles, skin, fat, TCL, hamate bone, and trapezium bone in the transverse plane at distal carpal tunnel were obtained from B-mode ultrasound images of one cadaveric hand. Sensitivity analyses were conducted to examine the dependence of TCL tensile strain and CAA on TCL elastic modulus (0.125-10 MPa volar-dorsally; 1.375-110 MPa transversely), skin-fat and thenar muscle initial shear modulus (1.6-160 kPa for skin-fat; 0.425-42.5 kPa for muscle), and intratunnel pressure (60-480 mmHg). Predictions of TCL tensile strain under different intratunnel pressures were validated with the experimental data obtained on the same cadaveric hand. Results showed that skin, fat and muscles had little effect on the TCL tensile strain and CAA changes. However, TCL tensile strain and CAA increased with decreased elastic modulus of TCL and increased intratunnel pressure. The TCL tensile strain and CAA increased linearly with increased pressure while increased exponentially with decreased elastic modulus of TCL. Softening the TCL by decreasing the elastic modulus may be an alternative clinical approach to carpal tunnel expansion to accommodate elevated intratunnel pressure and alleviate median nerve compression neuropathy. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of biaxial strains on electronic and elastic properties of hexagonal XSi2 (X = Cr, Mo, W) from first-principles

NASA Astrophysics Data System (ADS)

Zhu, Haiyan; Shi, Liwei; Li, Shuaiqi; Zhang, Shaobo; Xia, Wangsuo

2018-02-01

Structural, electronic properties and elastic anisotropy of hexagonal C40 XSi2 (X = Cr, Mo, W) under equibiaxial in-plane strains are systematically studied using first-principle calculations. The energy gaps show significant changes with biaxial strains, whereas they are always indirect band-gap materials for -6% <ɛxx < 6%. All elastic constants, bulk modulus, shear modulus, Young's modulus increase (decrease) almost linearly with increasing compressive (tensile) strains. The evolutions of BH /GH ratio and Poisson's ratio indicate that these compounds have a better (worse) ductile behaviour under compressive (tensile) strains. A set of 3D plots show a larger directional variability in the Young's modulus E and shear modulus G at different strains for the three compounds, which is consist with the values of anisotropy factors. Moreover, the evolution of Debye temperature and anisotropy of sound velocities with biaxial strains are discussed.

Thermodynamic changes in mechanochemically synthesized magnesium hydride nanoparticles.

PubMed

Paskevicius, Mark; Sheppard, Drew A; Buckley, Craig E

2010-04-14

The thermodynamic properties of magnesium hydride nanoparticles have been investigated by hydrogen decomposition pressure measurements using the Sieverts technique. A mechanochemical method was used to synthesize MgH(2) nanoparticles (down to approximately 7 nm in size) embedded in a LiCl salt matrix. In comparison to bulk MgH(2), the mechanochemically produced MgH(2) with the smallest particle size showed a small but measurable decrease in the decomposition reaction enthalpy (DeltaH decrease of 2.84 kJ/mol H(2) from DeltaH(bulk) = 74.06 +/- 0.42 kJ/mol H(2) to DeltaH(nano) = 71.22 +/- 0.49 kJ/mol H(2)). The reduction in DeltaH matches theoretical predictions and was also coupled with a similar reduction in reaction entropy (DeltaS decrease of 3.8 J/mol H(2)/K from DeltaS(bulk) = 133.4 +/- 0.7 J/mol H(2)/K to DeltaS(nano) = 129.6 +/- 0.8 J/mol H(2)/K). The thermodynamic changes in the MgH(2) nanoparticle system correspond to a drop in the 1 bar hydrogen equilibrium temperature (T(1 bar)) by approximately 6 degrees C to 276.2 +/- 2.4 degrees C in contrast to the bulk MgH(2) system at 281.8 +/- 2.2 degrees C. The reduction in the desorption temperature is less than that expected from theoretical studies due to the decrease in DeltaS that acts to partially counteract the effect from the change in DeltaH.

Modeling the high-frequency complex modulus of silicone rubber using standing Lamb waves and an inverse finite element method.

PubMed

Jonsson, Ulf; Lindahl, Olof; Andersson, Britt

2014-12-01

To gain an understanding of the high-frequency elastic properties of silicone rubber, a finite element model of a cylindrical piezoelectric element, in contact with a silicone rubber disk, was constructed. The frequency-dependent elastic modulus of the silicone rubber was modeled by a fourparameter fractional derivative viscoelastic model in the 100 to 250 kHz frequency range. The calculations were carried out in the range of the first radial resonance frequency of the sensor. At the resonance, the hyperelastic effect of the silicone rubber was modeled by a hyperelastic compensating function. The calculated response was matched to the measured response by using the transitional peaks in the impedance spectrum that originates from the switching of standing Lamb wave modes in the silicone rubber. To validate the results, the impedance responses of three 5-mm-thick silicone rubber disks, with different radial lengths, were measured. The calculated and measured transitional frequencies have been compared in detail. The comparison showed very good agreement, with average relative differences of 0.7%, 0.6%, and 0.7% for the silicone rubber samples with radial lengths of 38.0, 21.4, and 11.0 mm, respectively. The average complex elastic moduli of the samples were (0.97 + 0.009i) GPa at 100 kHz and (0.97 + 0.005i) GPa at 250 kHz.

The Response of Starch/gelatin/glycerin Aqueous Electrorheological Elastomer to Applied Electric Field

NASA Astrophysics Data System (ADS)

Gao, Lingxiang; Zhao, Xiaopeng

The aqueous ER elastomers, containing crude organic starch particles which dispersed in gelatin/glycerin/water matrix, were prepared with or without the applied DC electric field. The responses of the composite systems to the electric field were tested by the compression modulus and resistance of the elastomers. The result shows that they are enhanced and controlled evidently under an applied DC electric field. The strongest responses appear at 25% weight fraction of starch. In addition, the increment modulus of the elastomer increases with the strength of the applied field within 0.5~1.5 kV/mm, while after the field is stronger than 1.5 kV/mm it doesn't increase with field, appearing "saturation".

Strain-induced Weyl and Dirac states and direct-indirect gap transitions in group-V materials

NASA Astrophysics Data System (ADS)

Moynihan, Glenn; Sanvito, Stefano; O'Regan, David D.

2017-12-01

We perform comprehensive density-functional theory calculations on strained two-dimensional phosphorus (P), arsenic (As) and antimony (Sb) in the monolayer, bilayer, and bulk α-phase, from which we compute the key mechanical and electronic properties of these materials. Specifically, we compute their electronic band structures, band gaps, and charge-carrier effective masses, and identify the qualitative electronic and structural transitions that may occur. Moreover, we compute the elastic properties such as the Young’s modulus Y; shear modulus G; bulk modulus B ; and Poisson ratio ν and present their isotropic averages of as well as their dependence on the in-plane orientation, for which the relevant expressions are derived. We predict strain-induced Dirac states in the monolayers of As and Sb and the bilayers of P, As, and Sb, as well as the possible existence of Weyl states in the bulk phases of P and As. These phases are predicted to support charge velocities up to 106 m {{\\text{s}}-1} and, in some highly anisotropic cases, permit one-dimensional ballistic conductivity in the puckered direction. We also predict numerous band gap transitions for moderate in-plane stresses. Our results contribute to the mounting evidence for the utility of these materials, made possible by their broad range in tuneable properties, and facilitate the directed exploration of their potential application in next-generation electronics.

On the role of API in determining porosity, pore structure and bulk modulus of the skeletal material in pharmaceutical tablets formed with MCC as sole excipient.

PubMed

Ridgway, Cathy; Bawuah, Prince; Markl, Daniel; Zeitler, J Axel; Ketolainen, Jarkko; Peiponen, Kai-Erik; Gane, Patrick

2017-06-30

The physical properties and mechanical integrity of pharmaceutical tablets are of major importance when loading with active pharmaceutical ingredient(s) (API) in order to ensure ease of processing, control of dosage and stability during transportation and handling prior to patient consumption. The interaction between API and excipient, acting as functional extender and binder, however, is little understood in this context. The API indomethacin is combined in this study with microcrystalline cellulose (MCC) at increasing loading levels. Tablets from the defined API/MCC ratios are made under conditions of controlled porosity and tablet thickness, resulting from different compression conditions, and thus compaction levels. Mercury intrusion porosimetry is used to establish the accessible pore volume, pore size distribution and, adopting the observed region of elastic intrusion-extrusion at high pressure, an elastic bulk modulus of the skeletal material is recorded. Porosity values are compared to previously published values derived from terahertz (THz) refractive index data obtained from exactly the same tablet sample sets. It is shown that the elastic bulk modulus is dependent on API wt% loading under constant tablet preparation conditions delivering equal dimensions and porosity. The findings are considered of novel value in respect to establishing consistency of tablet production and optimisation of physical properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Temperature Dependence of Thermodynamic Properties of Thallium Chloride and Thallium Bromide

NASA Astrophysics Data System (ADS)

Kavanoz, H. B.

2015-02-01

Thermodynamic properties as lattice parameters, thermal expansion, heat capacities Cp and Cv, bulk modulus, and Gruneisen parameter of ionic halides TlCl and TlBr in solid and liquid phases were studied using classical molecular dynamics simulation (MD) with interionic Vashistha-Rahman (VR) model potential. In addition to the static and transport properties which have been previously reported by the author [13], this study further confirms that temperature dependence of the calculated thermophysical properties of TlCl and TlBr are in agreement with the available experimental data at both solid and liquid phases in terms of providing an alternative rigid ion potential. The results give a fairly good description of TlCl and TlBr in the temperature range 10-1000 K.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heffernan, Karina M.; Ross, Nancy L.; Spencer, Elinor C.

In this study, accurate elastic constants for gadolinium phosphate (GdPO 4) have been measured by single-crystal high-pressure diffraction methods. The bulk modulus of GdPO 4 determined under hydrostatic conditions, 128.1(8) GPa (K'=5.8(2)), is markedly different from that obtained with GdPO 4 under non-hydrostatic conditions (160(2) GPa), which indicates the importance of shear stresses on the elastic response of this phosphate. Finally, high pressure Raman and diffraction analysis indicate that the PO 4 tetrahedra behave as rigid units in response to pressure and that contraction of the GdPO 4 structure is facilitated by bending/twisting of the Gd–O–P links that result inmore » increased distortion in the GdO 9 polyhedra.« less

Nanocrystalline high-entropy alloy (CoCrFeNiAl 0.3 ) thin-film coating by magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liao, Weibing; Lan, Si; Gao, Libo

High-entropy CoCrFeNiAl0.3 alloy thin films were prepared by magnetron sputtering technique. The thin film surface was very smooth and homogeneous. The synchrotron X-ray experiment confirmed that (111) type of texture existed in the thin film, and the structure was face-centered cubic nanocrystals with a minor content of ordered NiAl-type body-centered cubic structures. Interestingly, the elastic modulus of the thin film was nearly the same to the bulk single-crystal counterpart, however, the nanohardness is about four times of the bulk single-crystal counterpart. It was found that the high hardness was due to the formation of nanocrystal structure inside the thin filmsmore » and the preferred growth orientation, which could be promising for applications in micro fabrication and advanced coating technologies.« less

Poly(ethylene glycol)-Mediated Collagen Gel Mechanics Regulates Cellular Phenotypes in a Microchanneled Matrix.

PubMed

Rich, Max H; Lee, Min Kyung; Ballance, William C; Boppart, Marni; Kong, Hyunjoon

2017-08-14

For the past few decades, efforts have been extensively made to reproduce tissue of interests for various uses including fundamental bioscience studies, clinical treatments, and even soft robotic systems. In these studies, cells are often cultured in micropores introduced in a provisional matrix despite that bulk rigidity may negatively affect cellular differentiation involved in tissue formation. To this end, we hypothesized that suspending cells within a soft fibrous matrix that is encapsulated within the microchannels of a provisional matrix would allow us to mediate effects of the matrix rigidity on cells and, in turn, to increase the cell differentiation level. We examined this hypothesis by filling microchannels interpenetrating alginate matrices with collagen gels of controlled elastic moduli (i.e., 125 to 1 Pa). Myoblasts used as a model predifferentiated cell were suspended within the collagen gels. The elastic modulus of the collagen gels was decreased through the addition of poly(ethylene glycol) during the gel preparation. Myoblasts loaded in the collagen gel exhibited a higher myogenic differentiation level than those adhered to the collagen-coated microchannel wall. Furthermore, the collagen gel softened by poly(ethylene glycol) further increased the volume of the multinucleated myofibers. The role of collagen gel softness on cell differentiation became more significant when the bulk elastic modulus of the alginate matrix was tuned to be close to that of muscle tissue (i.e., 11 kPa). We believe that the results of this study would be useful to understanding phenotypic activities of a wide array of cells involved in tissue development and regeneration.

Shearing single crystal magnesium in the close-packed basal plane at different temperatures

NASA Astrophysics Data System (ADS)

Han, Ming; Li, Lili; Zhao, Guangming

2018-05-01

Shear behaviors of single crystal magnesium (Mg) in close-packed (0001) basal plane along the [ 1 bar 2 1 bar 0 ], [ 1 2 bar 10 ], [ 10 1 bar 0 ] and [ 1 bar 010 ] directions were studied using molecular dynamics simulations via EAM potential. The results show that both shear stress-strain curves along the four directions and the motion path of free atoms during shearing behave periodic characteristics. It reveals that the periodic shear displacement is inherently related to the crystallographic orientation in single crystal Mg. Moreover, different temperatures in a range from 10 to 750 K were considered, demonstrating that shear modulus decreases with increasing temperatures. The results agree well with the MTS model. It is manifested that the modulus is independent with the shear direction and the size of the atomic model. This work also demonstrates that the classical description of shear modulus is still effective at the nanoscale.

Assessment of dynamic material properties of intact rocks using seismic wave attenuation: an experimental study

PubMed Central

Wanniarachchi, W. A. M.; Perera, M. S. A.; Rathnaweera, T. D.; Lyu, Q.; Mahanta, B.

2017-01-01

The mechanical properties of any substance are essential facts to understand its behaviour and make the maximum use of the particular substance. Rocks are indeed an important substance, as they are of significant use in the energy industry, specifically for fossil fuels and geothermal energy. Attenuation of seismic waves is a non-destructive technique to investigate mechanical properties of reservoir rocks under different conditions. The attenuation characteristics of five different rock types, siltstone, shale, Australian sandstone, Indian sandstone and granite, were investigated in the laboratory using ultrasonic and acoustic emission instruments in a frequency range of 0.1–1 MHz. The pulse transmission technique and spectral ratios were used to calculate the attenuation coefficient (α) and quality factor (Q) values for the five selected rock types for both primary (P) and secondary (S) waves, relative to the reference steel sample. For all the rock types, the attenuation coefficient was linearly proportional to the frequency of both the P and S waves. Interestingly, the attenuation coefficient of granite is more than 22% higher than that of siltstone, sandstone and shale for both P and S waves. The P and S wave velocities were calculated based on their recorded travel time, and these velocities were then used to calculate the dynamic mechanical properties including elastic modulus (E), bulk modulus (K), shear modulus (µ) and Poisson's ratio (ν). The P and S wave velocities for the selected rock types varied in the ranges of 2.43–4.61 km s−1 and 1.43–2.41 km h−1, respectively. Furthermore, it was observed that the P wave velocity was always greater than the S wave velocity, and this confirmed the first arrival of P waves to the sensor. According to the experimental results, the dynamic E value is generally higher than the static E value obtained by unconfined compressive strength tests. PMID:29134090

Assessment of dynamic material properties of intact rocks using seismic wave attenuation: an experimental study.

PubMed

Wanniarachchi, W A M; Ranjith, P G; Perera, M S A; Rathnaweera, T D; Lyu, Q; Mahanta, B

2017-10-01

The mechanical properties of any substance are essential facts to understand its behaviour and make the maximum use of the particular substance. Rocks are indeed an important substance, as they are of significant use in the energy industry, specifically for fossil fuels and geothermal energy. Attenuation of seismic waves is a non-destructive technique to investigate mechanical properties of reservoir rocks under different conditions. The attenuation characteristics of five different rock types, siltstone, shale, Australian sandstone, Indian sandstone and granite, were investigated in the laboratory using ultrasonic and acoustic emission instruments in a frequency range of 0.1-1 MHz. The pulse transmission technique and spectral ratios were used to calculate the attenuation coefficient ( α ) and quality factor ( Q ) values for the five selected rock types for both primary ( P ) and secondary ( S ) waves, relative to the reference steel sample. For all the rock types, the attenuation coefficient was linearly proportional to the frequency of both the P and S waves. Interestingly, the attenuation coefficient of granite is more than 22% higher than that of siltstone, sandstone and shale for both P and S waves. The P and S wave velocities were calculated based on their recorded travel time, and these velocities were then used to calculate the dynamic mechanical properties including elastic modulus ( E ), bulk modulus ( K ), shear modulus ( µ ) and Poisson's ratio ( ν ). The P and S wave velocities for the selected rock types varied in the ranges of 2.43-4.61 km s -1 and 1.43-2.41 km h -1 , respectively. Furthermore, it was observed that the P wave velocity was always greater than the S wave velocity, and this confirmed the first arrival of P waves to the sensor. According to the experimental results, the dynamic E value is generally higher than the static E value obtained by unconfined compressive strength tests.

Assessment of dynamic material properties of intact rocks using seismic wave attenuation: an experimental study

NASA Astrophysics Data System (ADS)

Wanniarachchi, W. A. M.; Ranjith, P. G.; Perera, M. S. A.; Rathnaweera, T. D.; Lyu, Q.; Mahanta, B.

2017-10-01

The mechanical properties of any substance are essential facts to understand its behaviour and make the maximum use of the particular substance. Rocks are indeed an important substance, as they are of significant use in the energy industry, specifically for fossil fuels and geothermal energy. Attenuation of seismic waves is a non-destructive technique to investigate mechanical properties of reservoir rocks under different conditions. The attenuation characteristics of five different rock types, siltstone, shale, Australian sandstone, Indian sandstone and granite, were investigated in the laboratory using ultrasonic and acoustic emission instruments in a frequency range of 0.1-1 MHz. The pulse transmission technique and spectral ratios were used to calculate the attenuation coefficient (α) and quality factor (Q) values for the five selected rock types for both primary (P) and secondary (S) waves, relative to the reference steel sample. For all the rock types, the attenuation coefficient was linearly proportional to the frequency of both the P and S waves. Interestingly, the attenuation coefficient of granite is more than 22% higher than that of siltstone, sandstone and shale for both P and S waves. The P and S wave velocities were calculated based on their recorded travel time, and these velocities were then used to calculate the dynamic mechanical properties including elastic modulus (E), bulk modulus (K), shear modulus (µ) and Poisson's ratio (ν). The P and S wave velocities for the selected rock types varied in the ranges of 2.43-4.61 km s-1 and 1.43-2.41 km h-1, respectively. Furthermore, it was observed that the P wave velocity was always greater than the S wave velocity, and this confirmed the first arrival of P waves to the sensor. According to the experimental results, the dynamic E value is generally higher than the static E value obtained by unconfined compressive strength tests.

Biomimicry in biomedical research

PubMed Central

Zhang, Ge

2012-01-01

Biomimicry (literally defined as the imitation of life or nature) has sparked a variety of human innovations and inspired countless cutting-edge designs. From spider silk-made artificial skin to lotus leaf-inspired self-cleaning materials, biomimicry endeavors to solve human problems. Biomimetic approaches have contributed significantly to advances biomedical research during recent years. Using polyacrylamide gels to mimic the elastic modulus of different biological tissues, Disher’s lab has directed meschymal stem cell differentiation into specific lineages.1 They have shown that soft substrates mimicking the elastic modulus of brain tissues (0.1~1 kPa) were neurogenic, substrates of intermediate elastic modulus mimicking muscle (8 ~17 kPa) were myogenic, and substrates with bone-like elastic modulus (25~40 kPa) were osteogenic. This work represents a novel way to regulate the fate of stem cells and exerts profound influence on stem cell research. Biomimcry also drives improvements in tissue engineering. Novel scaffolds have been designed to capture extracellular matrix-like structures, binding of ligands, sustained release of cytokines, and mechanical properties intrinsic to specific tissues for tissue engineering applications.2,3 For example, tissue engineering skin grafts have been designed to mimic the cell composition and layered structure of native skin.4 Similarly, in the field of regenerative medicine, researchers aim to create biomimetic scaffolds to mimic the properties of a native stem cell environment (niche) to dynamically interact with the entrapped stem cells and direct their response.5 PMID:23275257

A new model linking elastic properties and ionic conductivity of mixed network former glasses.

PubMed

Wang, Weimin; Christensen, Randilynn; Curtis, Brittany; Martin, Steve W; Kieffer, John

2018-01-17

Glasses are promising candidate materials for all-solid-state electrolytes for rechargeable batteries due to their outstanding mechanical stability, wide electrochemical stability range, and open structure for potentially high conductivity. Mechanical stiffness and ionic conductivity are two key parameters for solid-state electrolytes. In this study, we investigate two mixed-network former glass systems, sodium borosilicate 0.2Na 2 O + 0.8[xBO 1.5 + (1 - x)SiO 2 ] and sodium borogermanate 0.2Na 2 O + 0.8[xBO 1.5 + (1 - x)GeO 2 ] glasses. With mixed-network formers, the structure of the network changes while the network modifier mole fraction is kept constant, i.e., x = 0.2, which allows us to analyze the effect of the network structure on various properties, including ionic conductivity and elastic properties. Besides the non-linear, non-additive mixed glass former effect, we find that the longitudinal, shear and Young's moduli depend on the combined number density of tetrahedrally and octahedrally coordinated network former elements. These units provide connectivity in three dimensions, which is required for the networks to exhibit restoring forces in response to isotropic and shear deformations. Moreover, the activation energy for modifier cation, Na + , migration is strongly correlated with the bulk modulus, suggesting that the elastic strain energy associated with the passageway dilation for the sodium ions is governed by the bulk modulus of the glass. The detailed analysis provided here gives an estimate for the number of atoms in the vicinity of the migrating cation that are affected by elastic deformation during the activated process. The larger this number and the more compliant the glass network, the lower is the activation energy for the cation jump.

Dielectric, Impedance and Conduction Behavior of Double Perovskite Pr2CuTiO6 Ceramics

NASA Astrophysics Data System (ADS)

Mahato, Dev K.; Sinha, T. P.

2017-01-01

Polycrystalline Pr2CuTiO6 (PCT) ceramics exhibits dielectric, impedance and modulus characteristics as a possible material for microelectronic devices. PCT was synthesized through the standard solid-state reaction method. The dielectric permittivity, impedance and electric modulus of PCT have been studied in a wide frequency (100 Hz-1 MHz) and temperature (303-593 K) range. Structural analysis of the compound revealed a monoclinic phase at room temperature. Complex impedance Cole-Cole plots are used to interpret the relaxation mechanism, and grain boundary contributions towards conductivity have been estimated. From electrical modulus formalism polarization and conductivity relaxation behavior in PCT have been discussed. Normalization of the imaginary part of impedance ( Z″) and the normalized imaginary part of modulus ( M″) indicates contributions from both long-range and localized relaxation effects. The grain boundary resistance along with their relaxation frequencies are plotted in the form of an Arrhenius plot with activation energy 0.45 eV and 0.46 eV, respectively. The ac conductivity mechanism has been discussed.

Strengthening and toughening metallic glasses: The elastic perspectives and opportunities

NASA Astrophysics Data System (ADS)

Liu, Z. Q.; Zhang, Z. F.

2014-04-01

There exist general conflicts between strength and toughness in crystalline engineering materials, and various strengthening and toughening strategies have been developed from the dislocation motion perspectives. Metallic glasses (MGs) have demonstrated great potentials owing to their unique properties; however, their structural applications are strictly limited. One of the key problems is that the traditional strengthening and toughening strategies and mechanisms are not applicable in MGs due to the absence of dislocations and crystalline microstructures. Here, we show that the strength and toughness, or equivalently the shear modulus and Poisson's ratio, are invariably mutually exclusive in MGs. Accordingly, the MGs can be categorized into four groups with different levels of integrated mechanical properties. It is further revealed that the conflicts originate fundamentally from the atomic bonding structures and the levels of strength-toughness combinations are indeed dominated by the bulk modulus. Moreover, we propose novel strategies for optimizing the mechanical properties of MGs from the elastic perspectives. We emphasize the significance of developing high bulk modulus MGs to achieve simultaneously both high strength and good toughness and highlight the elastic opportunities for strengthening and toughening materials.

Powder processing and mechanical properties of Silver0.86Lead19Antimony telluride20 (LAST) and Lead0.95Tin0.05Tellurium - Lead sulfide 8% (Lead telluride -Lead sulfide) thermoelectric materials

NASA Astrophysics Data System (ADS)

Ni, Jennifer Elisabeth

Thermoelectric (TE) materials convert between thermal and electrical energy and when used with existing processes will increase the efficiency via waste heat recovery. Ag0.86Pb19SbTe20 (LAST) and Pb0.95Sn0.05Te - PbS 8% (PbTe-PbS) materials exhibit good thermoelectric (TE) properties and have potential applications as thermoelectric generators in waste heat recovery. However, to fully characterize the thermo-mechanical behavior of LAST and PbTe-PbS materials under in-service conditions, knowledge is needed of the mechanical and thermal properties at room and high temperature. As fracture strength is inversely proportional to the square root of grain size, cast ingots were powder processed to reduce powder particle size. Three different powder processing methods were used (1) dry milling only, (2) wet milling only, or (3) dry milling and wet milling The specimens were fabricated using hot pressing or pulsed electric current sintering (PECS) from planetary ball milled powders. In this study, elastic moduli, including Young's modulus, shear modulus, and Poisson's ratio, were measured dynamically using resonant ultrasound spectroscopy (RUS) at room temperature and as a function of temperature up to 663 K. The room temperature porosity dependence for Young's modulus followed the empirical exponential relationships common for brittle materials, with a material dependent constant bPE of 3.5 and 1.3 for LAST and PbTe-PbS, respectively. The room temperature Young's modulus for a theoretically dense specimen was 58.4 +/- 0.6 GPa and 56.2 +/- 0.4 GPa for for LAST and PbTe-PbS, respectively. For hot pressed PbTe-PbS specimens, the Vickers indentations mean hardness and fracture toughness was 1.18 + 0.09 GPa and 0.35 +/- 0.04 MPa·m 1/2. The coefficient of thermal expansion is important for understanding the mechanical response of a material to a thermal gradient or a thermal transient. For PbTe-PbS the coefficient of thermal expansion measured using dilatometry and high temperature x-ray diffraction was 21.5 x 10-6 K -1. Bloating during post-densification annealing was measured indirectly using resonant ultrasound spectroscopy and dilatometry and directly using scanning electron microscopy. Dry milled only PECS-processed PbTe-PbS specimens did not bloat during post-densification anneals up to 936 K. Hot pressed and PECS-processed specimens processed from wet milled and dry and wet milled powder bloated during densification anneals at temperatures over 603 K.

Mechanical characterization of human brain tumors from patients and comparison to potential surgical phantoms

PubMed Central

Rubiano, Andrés; Dyson, Kyle; Simmons, Chelsey S.

2017-01-01

While mechanical properties of the brain have been investigated thoroughly, the mechanical properties of human brain tumors rarely have been directly quantified due to the complexities of acquiring human tissue. Quantifying the mechanical properties of brain tumors is a necessary prerequisite, though, to identify appropriate materials for surgical tool testing and to define target parameters for cell biology and tissue engineering applications. Since characterization methods vary widely for soft biological and synthetic materials, here, we have developed a characterization method compatible with abnormally shaped human brain tumors, mouse tumors, animal tissue and common hydrogels, which enables direct comparison among samples. Samples were tested using a custom-built millimeter-scale indenter, and resulting force-displacement data is analyzed to quantify the steady-state modulus of each sample. We have directly quantified the quasi-static mechanical properties of human brain tumors with effective moduli ranging from 0.17–16.06 kPa for various pathologies. Of the readily available and inexpensive animal tissues tested, chicken liver (steady-state modulus 0.44 ± 0.13 kPa) has similar mechanical properties to normal human brain tissue while chicken crassus gizzard muscle (steady-state modulus 3.00 ± 0.65 kPa) has similar mechanical properties to human brain tumors. Other materials frequently used to mimic brain tissue in mechanical tests, like ballistic gel and chicken breast, were found to be significantly stiffer than both normal and diseased brain tissue. We have directly compared quasi-static properties of brain tissue, brain tumors, and common mechanical surrogates, though additional tests would be required to determine more complex constitutive models. PMID:28582392

Biocompatible tissue scaffold compliance promotes salivary gland morphogenesis and differentiation.

PubMed

Peters, Sarah B; Naim, Nyla; Nelson, Deirdre A; Mosier, Aaron P; Cady, Nathaniel C; Larsen, Melinda

2014-06-01

Substrate compliance is reported to alter cell phenotype, but little is known about the effects of compliance on cell development within the context of a complex tissue. In this study, we used 0.48 and 19.66 kPa polyacrylamide gels to test the effects of the substrate modulus on submandibular salivary gland development in culture and found a significant decrease in branching morphogenesis in explants grown on the stiff 19.66 kPa gels relative to those grown on the more physiologically compliant 0.48 kPa gels. While proliferation and apoptosis were not affected by the substrate modulus, tissue architecture and epithelial acinar cell differentiation were profoundly perturbed by aberrant, high stiffness. The glands cultured on 0.48 kPa gels were similar to developing glands in morphology and expression of the differentiation markers smooth muscle alpha-actin (SM α-actin) in developing myoepithelial cells and aquaporin 5 (AQP5) in proacinar cells. At 19.66 kPa, however, tissue morphology and the expression and distribution of SM α-actin and AQP5 were disrupted. Significantly, aberrant gland development at 19.66 kPa could be rescued by both mechanical and chemical stimuli. Transfer of glands from 19.66 to 0.48 kPa gels resulted in substantial recovery of acinar structure and differentiation, and addition of exogenous transforming growth factor beta 1 at 19.66 kPa resulted in a partial rescue of morphology and differentiation within the proacinar buds. These results indicate that environmental compliance is critical for organogenesis, and suggest that both mechanical and chemical stimuli can be exploited to promote organ development in the contexts of tissue engineering and organ regeneration.

Biocompatible Tissue Scaffold Compliance Promotes Salivary Gland Morphogenesis and Differentiation

PubMed Central

Peters, Sarah B.; Naim, Nyla; Nelson, Deirdre A.; Mosier, Aaron P.; Cady, Nathaniel C.

2014-01-01

Substrate compliance is reported to alter cell phenotype, but little is known about the effects of compliance on cell development within the context of a complex tissue. In this study, we used 0.48 and 19.66 kPa polyacrylamide gels to test the effects of the substrate modulus on submandibular salivary gland development in culture and found a significant decrease in branching morphogenesis in explants grown on the stiff 19.66 kPa gels relative to those grown on the more physiologically compliant 0.48 kPa gels. While proliferation and apoptosis were not affected by the substrate modulus, tissue architecture and epithelial acinar cell differentiation were profoundly perturbed by aberrant, high stiffness. The glands cultured on 0.48 kPa gels were similar to developing glands in morphology and expression of the differentiation markers smooth muscle alpha-actin (SM α-actin) in developing myoepithelial cells and aquaporin 5 (AQP5) in proacinar cells. At 19.66 kPa, however, tissue morphology and the expression and distribution of SM α-actin and AQP5 were disrupted. Significantly, aberrant gland development at 19.66 kPa could be rescued by both mechanical and chemical stimuli. Transfer of glands from 19.66 to 0.48 kPa gels resulted in substantial recovery of acinar structure and differentiation, and addition of exogenous transforming growth factor beta 1 at 19.66 kPa resulted in a partial rescue of morphology and differentiation within the proacinar buds. These results indicate that environmental compliance is critical for organogenesis, and suggest that both mechanical and chemical stimuli can be exploited to promote organ development in the contexts of tissue engineering and organ regeneration. PMID:24410370

Nano-indentation investigations of (As2Se3)1-x: Snx and (As4S3Se3)1-x: Snx glasses

NASA Astrophysics Data System (ADS)

Harea, D. V.; Harea, E. E.; Iaseniuc, O. V.; Iovu, M. S.

2015-02-01

Experimental results on some physical and optical properties of (As2Se3)1-x:Snx and (As4S3Se3)1-x:Snx (x = 0-10 at %) glasses and amorphous films (d~2.0 μm) are presented. The bulk chalcogenide glasses are studied by X-ray diffraction spectroscopy and nanoindentation methods. It is established that the addition of these amounts of tin (x = 0-10 at %) does not lead to significant changes in the physical properties of the glass, such as values of stress and Young's modulus related to the modification of the density and compactness. It has been found that the addition of these amounts of tin in (As4S3Se3)1-x:Snx does not lead to significant changes in the glass physical properties, such as values of stress and Young's modulus related to the modification of the density and compactness. The study of the photoplastic effect is performed in situ, with illumination of the bulk and thin film samples during indentation as well as their indentation after illumination with a green laser (λ = 532 nm) at a power of P = 50 mV/cm2. The hardness is calculated from load-displacement curves by the Oliver-Pharr method. A sharp increase in hardness is registered if the tin concentration exceeds a value of 34% Sn. The hardness H of (As2Se3)1-x:Snx films varies between 115 and 130 kg/mm2. It is found that the hardness H of amorphous thin films is generally higher than the hardness of bulk samples with the same chemical composition. In this study, we are focused on the mechanical characteristics of high-purity As2Se3: Snx thin films. Keyword: Chalcogenide glasses, hardness,

Compressibility and thermal expansion of hydrous ringwoodite with 2.5(3) wt% H[subscript 2]O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Yu; Brown, David A.; Smyth, Joseph R.

Ringwoodite ({gamma}-Mg{sub 2}SiO{sub 4}) is the stable polymorph of olivine in the transition zone between 525-660 km depth, and can incorporate weight percent amounts of H{sub 2}O as hydroxyl, with charge compensated mainly by Mg vacancies (Mg{sup 2+} = 2H{sup +}), but also possibly as (Si{sup 4+} = 4H{sup +} and Mg{sup 2+} + 2H{sup +} = Si{sup 4+}). We synthesized pure Mg ringwoodite containing 2.5(3) wt% H{sub 2}O, measured by secondary ion mass spectrometry (SIMS), and determined its compressibility at 300 K by single-crystal and powder X-ray diffraction (XRD), as well as its thermal expansion behavior between 140 andmore » 740 K at room pressure. A third-order Birch-Murnaghan equation of state (BM3 EOS) fits values of the isothermal bulk modulus K{sub T0} = 159(7) GPa and (dK{sub T}/dP){sub P = 0} = K' = 6.7(7) for single-crystal XRD; K{sub T0} = 161(4) GPa and K' = 5.4(6) for powder XRD, with K{sub T0} = 160(2) GPa and K' = 6.2(3) for the combined data sets. At room pressure, hydrous ringwoodite breaks down by an irreversible unit-cell expansion above 586 K, which may be related to dehydration and changes in the disorder mechanisms. Single-crystal intensity data were collected at various temperatures up to 736 K, and show that the cell volume V(cell) has a mean thermal expansion coefficient {alpha}{sub V0} of 40(4) x 10{sup -6}/K (143-736 K), and 29(2) x 10{sup -6}/K (143-586 K before irreversible expansion). V(Mg) have {alpha}{sub 0} values of 41(3) x 10{sup -6}/K (143-736 K), and V(Si) has {alpha}{sub 0} values of 20(3) x 10{sup -6}/K (143-586 K) and 132(4) x 10{sup -6}K (586-736 K). Based on the experimental data and previous work from {sup 29}Si NMR, we propose that during the irreversible expansion, a small amount of H{sup +} cations in Mg sites transfer to Si sites without changing the cubic spinel structure of ringwoodite, and the substituted Si{sup 4+} cations move to the normally vacant octahedral site at (1/2, 1/2, 0). Including new SIMS data on this and several Mg-ringwoodite samples from previous studies, we summarize volume-hydration data and show that the Mg{sup 2+} = 2H{sup +} dominates up to about 2 wt% H{sub 2}O, where a discontinuity in the volume vs. H{sub 2}O content trend suggests that other hydration mechanisms become important at very high H{sub 2}O contents.« less

Theoretical investigations on structural, elastic and electronic properties of thallium halides

NASA Astrophysics Data System (ADS)

Singh, Rishi Pal; Singh, Rajendra Kumar; Rajagopalan, Mathrubutham

2011-04-01

Theoretical investigations on structural, elastic and electronic properties, viz. ground state lattice parameter, elastic moduli and density of states, of thallium halides (viz. TlCl and TlBr) have been made using the full potential linearized augmented plane wave method within the generalized gradient approximation (GGA). The ground state lattice parameter and bulk modulus and its pressure derivative have been obtained using optimization method. Young's modulus, shear modulus, Poisson ratio, sound velocities for longitudinal and shear waves, Debye average velocity, Debye temperature and Grüneisen parameter have also been calculated for these compounds. Calculated structural, elastic and other parameters are in good agreement with the available data.

The first principles study of elastic and thermodynamic properties of ZnSe

NASA Astrophysics Data System (ADS)

Khatta, Swati; Kaur, Veerpal; Tripathi, S. K.; Prakash, Satya

2018-05-01

The elastic and thermodynamic properties of ZnSe are investigated using thermo_pw package implemented in Quantum espresso code within the framework of density functional theory. The pseudopotential method within the local density approximation is used for the exchange-correlation potential. The physical parameters of ZnSe bulk modulus and shear modulus, anisotropy factor, Young's modulus, Poisson's ratio, Pugh's ratio and Frantsevich's ratio are calculated. The sound velocity and Debye temperature are obtained from elastic constant calculations. The Helmholtz free energy and internal energy of ZnSe are also calculated. The results are compared with available theoretical calculations and experimental data.

Synchrotron SAXS/WAXD and rheological studies of clay suspensions in silicone fluid.

PubMed

Zhang, Li-Ming; Jahns, Christopher; Hsiao, Benjamin S; Chu, Benjamin

2003-10-15

Suspensions of two commercial smectite clays, montmorillonite KSF and montmorillonite K10, in a low-viscosity silicone oil (Dow Corning 245 Fluid) were studied by simultaneous synchrotron small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) techniques and rheological measurements. In the 0.5% (w/v) KSF clay suspension and two K10 clay suspensions (0.5% and 1.0%), WAXD profiles below 2theta=10.0 degrees did not display any characteristic reflection peaks associated with the chosen montmorillonite clays, while corresponding SAXS profiles exhibited distinct scattering maxima, indicating that both clays were delaminated by the silicone oil. In spite of the large increase in viscosity, the clay suspensions exhibited no gel characteristics. Dynamic rheological experiments indicated that the clay/silicone oil suspensions exhibited the behavior of viscoelasticity, which could be influenced by the type and the concentration of the clay. For the K10 clay suspensions, the frequency-dependent loss modulus (G") was greater in magnitude than the storage modulus (G') in the concentration range from 0.5 to 12.0%. The increase in the clay concentration shifted the crossover point between G' and G" into the accessible frequency range, indicating that the system became more elastic. In contrast, the KSF clay suspension exhibited lower G' and G" values, indicating a weaker viscoelastic response. The larger viscoelasticity response in the K10 clay suspension may be due to the acid treatment generating a higher concentration of silanol groups on the clay surface.

Time and temperature dependent modulus of pyrrone and polyimide moldings

NASA Technical Reports Server (NTRS)

Lander, L. L.

1972-01-01

A method is presented by which the modulus obtained from a stress relaxation test can be used to estimate the modulus which would be obtained from a sonic vibration test. The method was applied to stress relaxation, sonic vibration, and high speed stress-strain data which was obtained on a flexible epoxy. The modulus as measured by the three test methods was identical for identical test times, and a change of test temperature was equivalent to a shift in the logarithmic time scale. An estimate was then made of the dynamic modulus of moldings of two Pyrrones and two polyimides, using stress relaxation data and the method of analysis which was developed for the epoxy. Over the common temperature range (350 to 500 K) in which data from both types of tests were available, the estimated dynamic modulus value differed by only a few percent from the measured value. As a result, it is concluded that, over the 500 to 700 K temperature range, the estimated dynamic modulus values are accurate.

Solid impingement erosion mechanisms and characterization of erosion resistance of ductile metals

NASA Technical Reports Server (NTRS)

Rao, V. P.; Buckley, D. H.

1982-01-01

Experimental results pertaining to spherical glass bead and angular crushed glass particle impingement are presented. A concept of energy adsorption to explain the failure of material is proposed. The erosion characteristics of several pure metals were correlated with the proposed energy parameters and with other properties. Correlations of erosion and material properties were also carried out with these materials to study the effect of the angle of impingement. Analyses of extensive erosion data indicate that surface energy, strain energy, melting point, bulk modulus, hardness, ultimate resilience, atomic volume and product of linear coefficient of thermal expansion, bulk modulus, and temperature rise required for melting, and ultimate resilience, and hardness exhibit the best correlations. It appears that both energy and thermal properties contribute to the total erosion.

FAST TRACK COMMUNICATION: Variation of equation of state parameters in the Mg2(Si1 - xSnx) alloys

NASA Astrophysics Data System (ADS)

Pulikkotil, J. J.; Alshareef, H. N.; Schwingenschlögl, U.

2010-09-01

Thermoelectric performance peaks up for intermediate Mg2(Si1 - xSnx) alloys, but not for isomorphic and isoelectronic Mg2(Si1 - xGex) alloys. A comparative study of the equation of state parameters is performed using density functional theory, Green's function technique, and the coherent potential approximation. Anomalous variation of the bulk modulus is found in Mg2(Si1 - xSnx) but not in the Mg2(Si1 - xGex) analogs. Assuming a Debye model, linear variations of the unit cell volume and pressure derivative of the bulk modulus suggest that lattice effects are important for the thermoelectric response. From the electronic structure perspective, Mg2(Si1 - xSnx) is distinguished by a strong renormalization of the anion-anion hybridization.

The development of new, low-cost perfluoroalkylether fluids with excellent low and high-temperature properties

NASA Technical Reports Server (NTRS)

Bierschenk, Thomas R.; Kawa, Hajimu; Juhlke, Timothy J.; Lagow, Richard J.

1988-01-01

A series of perfluoroalkylether (PFAE) fluids were synthesized by direct fluorination. Viscosity-temperature properties, oxidation stabilities, oxidation-corrosion properties, and lubricity were determined. The fluids were tested in the presence of common elastomers to check for compatibility. The bulk modulus of each was measured to determine if any could be used as nonflammable aircraft hydraulic fluid. It was determined that as the carbon to oxygen ratio decreases, the viscometric properties improve, the fluids may become poor lubricants, the bulk modulus increases, the surface tension increases, and the fluid density increases. The presence of difluoromethylene oxide units in the polymer does not seriously lower the oxidation and oxidation-corrosion stabilities as long as the difluoromethylene oxide units are separated by other units.

Computer Simulations of Bottlebrush Melts and Soft Networks

NASA Astrophysics Data System (ADS)

Cao, Zhen; Carrillo, Jan-Michael; Sheiko, Sergei; Dobrynin, Andrey

We have studied dense bottlebrush systems in a melt and network state using a combination of the molecular dynamics simulations and analytical calculations. Our simulations show that the bottlebrush macromolecules in a melt behave as ideal chains with the effective Kuhn length bK. The bottlebrush induced bending rigidity is due to redistribution of the side chains upon backbone bending. Kuhn length of the bottlebrushes increases with increasing the side-chain degree of polymerization nsc as bK ~nsc0 . 46 . This model of bottlebrush macromolecules is extended to describe mechanical properties of bottlebrush networks in linear and nonlinear deformation regimes. In the linear deformation regime, the network shear modulus scales with the degree of polymerization of the side chains as G0 ~nsc + 1 - 1 as long as the ratio of the Kuhn length to the size of the fully extended bottlebrush backbone between crosslinks, Rmax, is smaller than unity, bK /Rmax < < 1 . Bottlebrush networks with bK /Rmax ~ 1 demonstrate behavior similar to that of networks of semiflexible chains with G0 ~nsc- 0 . 5 . In the nonlinear deformation regime, the deformation dependent shear modulus is a universal function of the first strain invariant I1 and bottlebrush backbone deformation ratio β describing stretching ability of the bottlebrush backbone between crosslinks. Nsf DMR-1409710 DMR-1436201.

Gaussian curvature elasticity determined from global shape transformations and local stress distributions: a comparative study using the MARTINI model.

PubMed

Hu, Mingyang; de Jong, Djurre H; Marrink, Siewert J; Deserno, Markus

2013-01-01

We calculate the Gaussian curvature modulus kappa of a systematically coarse-grained (CG) one-component lipid membrane by applying the method recently proposed by Hu et al. [Biophys. J., 2012, 102, 1403] to the MARTINI representation of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). We find the value kappa/kappa = -1.04 +/- 0.03 for the elastic ratio between the Gaussian and the mean curvature modulus and deduce kappa(m)/kappa(m) = -0.98 +/- 0.09 for the monolayer elastic ratio, where the latter is based on plausible assumptions for the distance z0 of the monolayer neutral surface from the bilayer midplane and the spontaneous lipid curvature K(0m). By also analyzing the lateral stress profile sigma0(z) of our system, two other lipid types and pertinent data from the literature, we show that determining K(0m) and kappa through the first and second moment of sigma0(z) gives rise to physically implausible values for these observables. This discrepancy, which we previously observed for a much simpler CG model, suggests that the moment conditions derived from simple continuum assumptions miss the effect of physically important correlations in the lipid bilayer.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solozhenko, Vladimir L.; Kurakevych, Oleksandr O.; Le Godec, Yann

Cubic boron phosphide, BP, has been studied in situ by X-ray diffraction and Raman scattering up to 55 GPa at 300 K in a diamond anvil cell. The bulk modulus of B{sub 0} = 174(2) GPa has been established, which is in excellent agreement with our ab initio calculations. The data on Raman shift as a function of pressure, combined with equation-of-state (EOS) data, allowed us to estimate the Grüneisen parameters of the TO and LO modes of zinc-blende structure, γ{sub G}{sup TO }= 1.26 and γ{sub G}{sup LO }= 1.13, just like in the case of other A{sup III}B{sup V} diamond-like phases, for which γ{sub G}{sup TO }> γ{submore » G}{sup LO }≅ 1. We also established that the pressure dependence of the effective electro-optical constant α is responsible for a strong change in relative intensities of the TO and LO modes from I{sub TO}/I{sub LO} ∼ 0.25 at 0.1 MPa to I{sub TO}/I{sub LO} ∼ 2.5 at 45 GPa, for which we also find excellent agreement between experiment and theory.« less

Superior mechanical performance of highly porous, anisotropic nanocellulose-montmorillonite aerogels prepared by freeze casting.

PubMed

Donius, Amalie E; Liu, Andong; Berglund, Lars A; Wegst, Ulrike G K

2014-09-01

Directionally solidified nanofibrillated cellulose (NFC)-sodium-montmorillonite (MMT) composite aerogels with a honeycomb-like pore structure were compared with non-directionally frozen aerogels with equiaxed pore structure and identical composition and found to have superior functionalities. To explore structure-property correlations, three different aerogel compositions of 3wt% MMT, and 0.4wt%, 0.8wt%, and 1.2wt% NFC, respectively, were tested. Young׳s modulus, compressive strength and toughness were found to increase with increasing NFC content for both architectures. The modulus increased from 25.8kPa to 386kPa for the isotropic and from 2.13MPa to 3.86MPa for the anisotropic aerogels, the compressive yield strength increased from 3.3kPa to 18.0kPa for the isotropic and from 32.3kPa to 52.5kPa for the anisotropic aerogels, and the toughness increased from 6.3kJ/m(3) to 24.1kJ/m(3) for the isotropic and from 22.9kJ/m(3) to 46.2kJ/m(3) for the anisotropic aerogels. The great range of properties, which can be achieved through compositional as well as architectural variations, makes these aerogels highly attractive for a large range of applications, for which either a specific composition, or a particular pore morphology, or both are required. Finally, because NFC is flammable, gasification experiments were performed, which revealed that the inclusion of MMT increased the heat endurance and shape retention functions of the aerogels dramatically up to 800°C while the mechanical properties were retained up to 300°C. Copyright © 2014 Elsevier Ltd. All rights reserved.

The B → πK puzzle and the bulk Randall-Sundrum model

NASA Astrophysics Data System (ADS)

Chang, Sanghyeon; Kim, C. S.; Song, Jeonghyeon

2011-02-01

The recent measurements of the direct CP asymmetries (ACP) in the penguin-dominated B → Kπ decays show some discrepancy from the standard model (SM) prediction. While ACP of B+ →π0K+ and that of B0 →π-K+ in the naive estimate of the SM are expected to have very similar values, their experimental data are of the opposite sign and different magnitudes. We study the effects of the custodial bulk Randall-Sundrum model on this ACP. In this model, the misalignment of the five-dimensional (5D) Yukawa interactions to the 5D bulk gauge interactions in flavor space leads to tree-level flavor-changing neutral current by the Kaluza-Klein gauge bosons. In a large portion of the parameter space of this model, the observed non-zero ACP (B+ →π0K+) -ACP (B0 →π-K+) can be explained only with low Kaluza-Klein mass scale MKK around 1 TeV. Rather extreme parameters is required to explain it with MKK ≃ 3 TeV. The new contributions to well-measured branching ratios of B → Kπ decays are also shown to be suppressed.

Characterization of Inorganic Filler Content, Mechanical Properties, and Light Transmission of Bulk-fill Resin Composites.

PubMed

Fronza, B M; Ayres, Apa; Pacheco, R R; Rueggeberg, F A; Dias, Cts; Giannini, M

The aims of this study were to characterize inorganic content (IC), light transmission (LT), biaxial flexural strength (BFS), and flexural modulus (FM) of one conventional (layered) and four bulk-fill composites at different depths. Bulk-fill composites tested were Surefil SDR flow (SDR), Filtek Bulk Fill (FBF), Tetric EvoCeram Bulk Fill (TEC), and EverX Posterior (EXP). Herculite Classic (HER) was used as a control. Energy dispersive x-ray analysis and scanning electron microscopy were used to characterize filler particle composition and morphology. The LT through different composite thicknesses (1, 2, 3, and 4 mm) was measured using a laboratory-grade spectral radiometer system (n=5). For the BFS and FM tests, sets of eight stacked composite discs (0.5-mm thick) were prepared simulating bulk filling of a 4-mm-thick increment (n=8). SDR demonstrated larger, irregular particles than those observed in TEC or HER. Filler particles in FBF were spherical, while those in EXP were composed of fiberglass strands. The LT decreased with increased composite thickness for all materials. Bulk-fill composites allowed higher LT than the HER. Furthermore, HER proved to be the unique material, having lower BFS values at deeper regions. SDR, FBF, and TEC bulk-fill composites presented reduced FM with increasing composite depth. The bulk-fill composites investigated exhibited higher LT, independent of different filler content and characteristics. Although an increase in composite thickness reduced LT, the BFS of bulk-fill composites at deeper layers was not compromised.

A high-sensitivity torsional pendulum for polymeric films and fibres

NASA Technical Reports Server (NTRS)

Aghili-Kermani, H.; Obrien, T.; Armeniades, C. D.; Roberts, J. M.

1976-01-01

A free oscillation torsion pendulum is described, which has been designed to measure accurately the dynamic shear modulus and logarithmic decrement of polymeric thin films and fibers, at frequencies of 0.1 to 10 Hz and a temperature range of 4.2 to 450 K. The instrument can also provide in situ tensile deformations of up to 5%. The specimen geometry necessary to obtain reliable modulus measurements with thin films is discussed, and typical data are presented which exhibit hitherto unreported relaxation processes, discernible by this instrument.

First-principles calculations of dynamical and thermodynamic properties of cuprite doped with silver (Cu2(1‑x)Ag2xO)

NASA Astrophysics Data System (ADS)

Musari, A. A.; Joubert, D. P.; Adebayo, G. A.

2018-04-01

Cuprite (Cu2O) is a solid mineral and a compound whose simplicity of preparation, non toxic nature, low band gap and its abundance has made it a prospective candidate for the realisation of low cost photovoltaic applications. The present work successfully dopes Cuprite with Ag ({{{Cu}}}2(1-{{x})}{{{Ag}}}2{{x}}{{O}}) at different concentrations x = 0, 0.25, 0.5, 0.75 and 1, their first-principle calculations of their electronic, dynamical and thermodynamic properties have been investigated extensively within the generalised gradient approximation. Direct band gap energies at {{Γ }} are predicted for all the studied systems. A small bowing parameter for lattice constants ba and bulk modulus bB of 0.4245 \\mathring{{A}} and 0.8747 GPa were obtained when compared to Vegard’s law. The results of phonon dispersion when x = 0 and 1 indicate stability, these agree with available theoretical and experimental results while negative frequencies observed along the Brillouin zone for the doped systems when x = 0.25, 0.5 and 0.75 imply that they are dynamically unstable. The thermodynamic properties between 0 to 800 K were determined using the calculated phonon density of states within the harmonic approximation and the values of the specific heat capacity at constant volume at ambient temperature and the temperature at which lattice vibrations and thermal motion of electrons contribute to the constant volume specific heat capacity are presented for all the systems.

Note: All solid-state high repetitive sub-nanosecond risetime pulse generator based on bulk gallium arsenide avalanche semiconductor switches.

PubMed

Hu, Long; Su, Jiancang; Ding, Zhenjie; Hao, Qingsong; Fan, Yajun; Liu, Chunliang

2016-08-01

An all solid-state high repetitive sub-nanosecond risetime pulse generator featuring low-energy-triggered bulk gallium arsenide (GaAs) avalanche semiconductor switches and a step-type transmission line is presented. The step-type transmission line with two stages is charged to a potential of 5.0 kV also biasing at the switches. The bulk GaAs avalanche semiconductor switch closes within sub-nanosecond range when illuminated with approximately 87 nJ of laser energy at 905 nm in a single pulse. An asymmetric dipolar pulse with peak-to-peak amplitude of 9.6 kV and risetime of 0.65 ns is produced on a resistive load of 50 Ω. A technique that allows for repetition-rate multiplication of pulse trains experimentally demonstrated that the parallel-connected bulk GaAs avalanche semiconductor switches are triggered in sequence. The highest repetition rate is decided by recovery time of the bulk GaAs avalanche semiconductor switch, and the operating result of 100 kHz of the generator is discussed.

Self-interaction corrected LDA + U investigations of BiFeO3 properties: plane-wave pseudopotential method

NASA Astrophysics Data System (ADS)

Yaakob, M. K.; Taib, M. F. M.; Lu, L.; Hassan, O. H.; Yahya, M. Z. A.

2015-11-01

The structural, electronic, elastic, and optical properties of BiFeO3 were investigated using the first-principles calculation based on the local density approximation plus U (LDA + U) method in the frame of plane-wave pseudopotential density functional theory. The application of self-interaction corrected LDA + U method improved the accuracy of the calculated properties. Results of structural, electronic, elastic, and optical properties of BiFeO3, calculated using the LDA + U method were in good agreement with other calculation and experimental data; the optimized choice of on-site Coulomb repulsion U was 3 eV for the treatment of strong electronic localized Fe 3d electrons. Based on the calculated band structure and density of states, the on-site Coulomb repulsion U had a significant effect on the hybridized O 2p and Fe 3d states at the valence and the conduction band. Moreover, the elastic stiffness tensor, the longitudinal and shear wave velocities, bulk modulus, Poisson’s ratio, and the Debye temperature were calculated for U = 0, 3, and 6 eV. The elastic stiffness tensor, bulk modulus, sound velocities, and Debye temperature of BiFeO3 consistently decreased with the increase of the U value.

First-principles study of structural and electronic properties of Be0.25Zn0.75S mixed compound

NASA Astrophysics Data System (ADS)

Paliwal, U.; Joshi, K. B.

2018-05-01

In this work the first-principles study of structural and electronic properties of Be0.25Zn0.75S mixed compound is presented. The calculations are performed applying the QUANTUM ESPRESSO code utilizing the Perdew, Becke, Ernzerhof generalized gradient approximation in the framework of density functional theory. Adopting standard optimization strategy, the ground state equilibrium lattice constant and bulk modulus are calculated. After settling the structure the electronic band structure, bandgap and static dielectric constant are evaluated. In absence of any experimental work on this system our findings are compared with the available theoretical calculations which are found to follow well anticipated general trends.

Molecular dynamics simulations of melting and the glass transition of nitromethane.

PubMed

Zheng, Lianqing; Luo, Sheng-Nian; Thompson, Donald L

2006-04-21

Molecular dynamics simulations have been used to investigate the thermodynamic melting point of the crystalline nitromethane, the melting mechanism of superheated crystalline nitromethane, and the physical properties of crystalline and glassy nitromethane. The maximum superheating and glass transition temperatures of nitromethane are calculated to be 316 and 160 K, respectively, for heating and cooling rates of 8.9 x 10(9) Ks. Using the hysteresis method [Luo et al., J. Chem. Phys. 120, 11640 (2004)] and by taking the glass transition temperature as the supercooling temperature, we calculate a value of 251.1 K for the thermodynamic melting point, which is in excellent agreement with the two-phase result [Agrawal et al., J. Chem. Phys. 119, 9617 (2003)] of 255.5 K and measured value of 244.73 K. In the melting process, the nitromethane molecules begin to rotate about their lattice positions in the crystal, followed by translational freedom of the molecules. A nucleation mechanism for the melting is illustrated by the distribution of the local translational order parameter. The critical values of the Lindemann index for the C and N atoms immediately prior to melting (the Lindemann criterion) are found to be around 0.155 at 1 atm. The intramolecular motions and molecular structure of nitromethane undergo no abrupt changes upon melting, indicating that the intramolecular degrees of freedom have little effect on the melting. The thermal expansion coefficient and bulk modulus are predicted to be about two or three times larger in crystalline nitromethane than in glassy nitromethane. The vibrational density of states is almost identical in both phases.

Investigation of the commensurate magnetic structure in the heavy-fermion compound CePt 2 In 7 using magnetic resonant x-ray diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gauthier, Nicolas; Wermeille, Didier; Casati, Nicola

In this paper, we investigated the magnetic structure of the heavy-fermion compound CePt 2In 7 below T N = 5.34 (2) K using magnetic resonant x-ray diffraction at ambient pressure. The magnetic order is characterized by a commensurate propagation vector k 1/2 = (1/2, 1/2, 1/2) with spins lying in the basal plane. Our measurements did not reveal the presence of an incommensurate order propagating along the high-symmetry directions in reciprocal space but cannot exclude other incommensurate modulations or weak scattering intensities. The observed commensurate order can be described equivalently by either a single-k structure or by a multi-k structure.more » Furthermore we explain how a commensurate-only ordering may explain the broad distribution of internal fields observed in nuclear quadrupolar resonance experiments [Sakai et al., Phys. Rev. B 83, 140408 (2011)] that was previously attributed to an incommensurate order. We also report powder x-ray diffraction showing that the crystallographic structure of CePt 2In 7 changes monotonically with pressure up to P = 7.3 GPa at room temperature. The determined bulk modulus B 0 = 81.1 (3) GPa is similar to those of the Ce-115 family. Broad diffraction peaks confirm the presence of pronounced strain in polycrystalline samples of CePt 2In 7. Lastly, we discuss how strain effects can lead to different electronic and magnetic properties between polycrystalline and single crystal samples.« less

Investigation of the commensurate magnetic structure in the heavy-fermion compound CePt 2 In 7 using magnetic resonant x-ray diffraction

DOE PAGES

Gauthier, Nicolas; Wermeille, Didier; Casati, Nicola; ...

2017-08-10

In this paper, we investigated the magnetic structure of the heavy-fermion compound CePt 2In 7 below T N = 5.34 (2) K using magnetic resonant x-ray diffraction at ambient pressure. The magnetic order is characterized by a commensurate propagation vector k 1/2 = (1/2, 1/2, 1/2) with spins lying in the basal plane. Our measurements did not reveal the presence of an incommensurate order propagating along the high-symmetry directions in reciprocal space but cannot exclude other incommensurate modulations or weak scattering intensities. The observed commensurate order can be described equivalently by either a single-k structure or by a multi-k structure.more » Furthermore we explain how a commensurate-only ordering may explain the broad distribution of internal fields observed in nuclear quadrupolar resonance experiments [Sakai et al., Phys. Rev. B 83, 140408 (2011)] that was previously attributed to an incommensurate order. We also report powder x-ray diffraction showing that the crystallographic structure of CePt 2In 7 changes monotonically with pressure up to P = 7.3 GPa at room temperature. The determined bulk modulus B 0 = 81.1 (3) GPa is similar to those of the Ce-115 family. Broad diffraction peaks confirm the presence of pronounced strain in polycrystalline samples of CePt 2In 7. Lastly, we discuss how strain effects can lead to different electronic and magnetic properties between polycrystalline and single crystal samples.« less

Self-organized carbon-rich stripe formation from competitive carbon and aluminium segregation at Fe0.85Al0.15(1 1 0) surfaces

NASA Astrophysics Data System (ADS)

Dai, Zongbei; Borghetti, Patrizia; Mouchaal, Younes; Chenot, Stéphane; David, Pascal; Jupille, Jacques; Cabailh, Gregory; Lazzari, Rémi

2018-06-01

By combining Scanning Tunnelling Microscopy, Low Energy Electron Diffraction and X-ray Photoelectron Spectroscopy, it was found that the surface of A2 random alloy Fe0.85Al0.15(1 1 0) is significantly influenced by the segregation of aluminium but also of carbon bulk impurities. Below ∼ 900 K, carbon segregates in the form of self-organized protruding stripes separated by ∼ 5 nm that run along the [ 0 0 1 ] B bulk direction and cover up to 34% of the surface. Their C 1s spectroscopic signature that is dominated by graphitic carbon peaks around 900 K. Above this temperature, the surface carbon concentration decays by redissolution in the bulk, whereas an intense aluminium segregation is observed giving rise to a hexagonal superstructure. The present findings is interpreted by a competitive segregation between the two elements.

The surface stability of Cr 2O 3 (0 0 0 1)

DOE PAGES

Cao, Shi; Wu, Ning; Echtenkamp, William; ...

2015-05-28

The surface of chromia (Cr 2O 3) has a surface electronic structure distinct from the bulk and a packing density distinct from the bulk. More than a demarcation between the solid and the vacuum, the surface differs from the bulk of chromia, not just because of a partial occupancy of chromium sites, but also because of an increased number of unoccupied surface oxygen sites (vacancy sites), evident in angle-resolved core level photoemission. In spite of the structural differences that exist at the surface, there is, as yet, no evidence that these complications affect the surface Debye temperature beyond the mostmore » simple of assumptions regarding the lower coordination of the surface. Using low-energy electron diffraction (LEED), the effective surface Debye temperature (similar to 490 K) is found to be lower than the bulk (similar to 645 K) Debye temperature of Cr 2O 3(0 0 0 1). This surface effective Debye temperature, indicative of vibrations along the surface normal, uncorrected for anharmonic effects, has a value reduced from the effective bulk Debye temperature yet close to the value root 2 expected from a simple mean field argument.« less

A Focused Fundamental Study of Predicting Materials Degradation & Fatigue. Volume 1

DTIC Science & Technology

1997-05-31

physical properties are: bulk modulus, shear strength, coefficient of friction, modulus of elasticity/ rigidity and Poisson’s ratio. Each of these physical...acting on a subsurface crack when abrasive motion occurs on the surface using linear elastic fracture mechanics theory. Both mechanisms involve a...The body of the scattering 5 cell was a 4-way Swagelok*(Crawford Fitting Co., Solon, OH) connector with a 1.5 mm hole drilled in the top for

Density and mechanical properties of calcium aluminate cement

NASA Astrophysics Data System (ADS)

Ahmed, Syed Taqi Uddin; Ahmmad, Shaik Kareem

2018-04-01

Calcium aluminate cements are a special type of cements which have their composition mainly dominated by the presence of Monocalcium Aluminates. In the present paper for the first time we have shown theoretical density and elastic constants for various calcium aluminate cements. The density of the present CAS decrease with aluminates presents in the cement. Using the density data, the elastic moduli namely Young's modulus, bulk and shear modulus show strong linear dependence as a function of compositional parameter.

Hydromechanics in dentine: role of dentinal tubules and hydrostatic pressure on mechanical stress-strain distribution.

PubMed

Kishen, A; Vedantam, S

2007-10-01

This investigation is to understand the role of free water in the dentinal tubules on the mechanical integrity of bulk dentine. Three different experiments were conducted in this study. In experiment 1, three-dimensional models of dentine with gradient elastic modulus, homogenous elastic modulus, and with and without hydrostatic pressure were simulated using the finite element method. Static compressive loads of 15, 50 and 100 N were applied and the distribution of the principal stresses, von Mises stresses, and strains in loading direction were determined. In experiment 2, experimental compression testing of fully hydrated and partially dehydrated dentine (21 degrees C for 72 h) was conducted using a Universal testing machine. In experiment 3, Fourier transform infrared spectroscopic analysis of hydrated and partially dehydrated dentine was carried out. The finite element analysis revealed that the dentine model with simulated hydrostatic pressure displayed residual tensile stresses and strains in the inner region adjacent to the root canal. When external compressive loads were applied to the model, the residual stresses and strains counteracted the applied loads. Similarly the hydrated specimens subjected to experimental compression loads showed greater toughness when compared to the partially dehydrated specimens. The stress at fracture was significantly higher in partially dehydrated specimens (p=0.014), while the strain at fracture was significantly higher in hydrated dentine specimens (p=0.037). These experiments highlighted the distinct role of free water in the dentinal tubules and hydrostatic pressure on the stress-strain distribution within the bulk dentine.

Laboratory experiments simulating poroelastic stress changes associated with depletion and injection in low-porosity sedimentary rocks

NASA Astrophysics Data System (ADS)

Ma, Xiaodong; Zoback, Mark D.

2017-04-01

We characterized the poroelastic deformation of six cores from three formations associated with the Bakken play in the Williston Basin (the Lodgepole, Middle Bakken, and Three Forks formations). All are low-porosity, low-permeability formations, but vary considerably in clay, kerogen, and carbonate content. The experimental program simulated reservoir stress changes associated with depletion and injection via cycling both the confining pressure (Pc) and pore pressure (Pp). We measured volumetric strain, derived the corresponding bulk modulus, and calculated the Biot coefficient (α). We found α, which generally ranges between 0.3 and 0.9, to vary systematically with Pc and Pp for each of the specimens tested. The effect of pore pressure on α is much larger at low simple effective stress (σ = Pc-Pp) during depletion than injection. The α decreases with σ for all pore pressures. For the same Pc and Pp, the Biot coefficient is consistently higher during injection than during depletion. Given the observed variations of α with Pc and Pp, the modeling of reservoir stress changes using a constant α could be problematic as poroelastic stress changes during depletion and injection are not likely to follow the same path. Scanning electron microscope examination of microstructures suggests that the variations of the bulk modulus and the Biot coefficient can be attributed to the abundance of compliant components (pores, microcracks, clays, and organic matter) and how they are distributed throughout the rock matrix.

High pressure study of a highly energetic nitrogen-rich carbon nitride, cyanuric triazide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laniel, Dominique; Desgreniers, Serge; Downie, Laura E.

Cyanuric triazide (CTA), a nitrogen-rich energetic material, was compressed in a diamond anvil cell up to 63.2 GPa. Samples were characterized by x-ray diffraction, Raman, and infrared spectroscopy. A phase transition occurring between 29.8 and 30.7 GPa was found by all three techniques. The bulk modulus and its pressure derivative of the low pressure phase were determined by fitting the 300 K isothermal compression data to the Birch-Murnaghan equation of state. Due to the strong photosensitivity of CTA, synchrotron generated x-rays and visible laser radiation both lead to the progressive conversion of CTA into a two dimensional amorphous C=N network,more » starting from 9.2 GPa. As a result of the conversion, increasingly weak and broad x-ray diffraction lines were recorded from crystalline CTA as a function of pressure. Hence, a definite structure could not be obtained for the high pressure phase of CTA. Results from infrared spectroscopy carried out to 40.5 GPa suggest the high pressure formation of a lattice built of tri-tetrazole molecular units. The decompression study showed stability of the high pressure phase down to 13.9 GPa. Finally, two CTA samples, one loaded with neon and the other with nitrogen, used as pressure transmitting media, were laser-heated to approximately 1100 K and 1500 K while compressed at 37.7 GPa and 42.0 GPa, respectively. In both cases CTA decomposed resulting in amorphous compounds, as recovered at ambient conditions.« less

Elasticity of water-saturated rocks as a function of temperature and pressure.

NASA Technical Reports Server (NTRS)

Takeuchi, S.; Simmons, G.

1973-01-01

Compressional and shear wave velocities of water-saturated rocks were measured as a function of both pressure and temperature near the melting point of ice to confining pressure of 2 kb. The pore pressure was kept at about 1 bar before the water froze. The presence of a liquid phase (rather than ice) in microcracks of about 0.3% porosity affected the compressional wave velocity by about 5% and the shear wave velocity by about 10%. The calculated effective bulk modulus of the rocks changes rapidly over a narrow range of temperature near the melting point of ice, but the effective shear modulus changes gradually over a wider range of temperature. This phenomenon, termed elastic anomaly, is attributed to the existence of liquid on the boundary between rock and ice due to local stresses and anomalous melting of ice under pressure.

The Pressure Dependence of Structural, Electronic, Mechanical, Vibrational, and Thermodynamic Properties of Palladium-Based Heusler Alloys

NASA Astrophysics Data System (ADS)

Çoban, Cansu

2017-08-01

The pressure dependent behaviour of the structural, electronic, mechanical, vibrational, and thermodynamic properties of Pd2TiX (X=Ga, In) Heusler alloys was investigated by ab initio calculations. The lattice constant, the bulk modulus and its first pressure derivative, the electronic band structure and the density of states (DOS), mechanical properties such as elastic constants, anisotropy factor, Young's modulus, etc., the phonon dispersion curves and phonon DOS, entropy, heat capacity, and free energy were obtained under pressure. It was determined that the calculated lattice parameters are in good agreement with the literature, the elastic constants obey the stability criterion, and the phonon dispersion curves have no negative frequency which shows that the compounds are stable. The band structures at 0, 50, and 70 GPa showed valence instability at the L point which explains the superconductivity in Pd2TiX (X=Ga, In).

Elastic properties and optical absorption studies of mixed alkali borogermanate glasses

NASA Astrophysics Data System (ADS)

Taqiullah, S. M.; Ahmmad, Shaik Kareem; Samee, M. A.; Rahman, Syed

2018-05-01

First time the mixed alkali effect (MAE) has been investigated in the glass system xNa2O-(30-x)Li2O-40B2O3- 30GeO2 (0≤x≤30 mol%) through density and optical absorption studies. The present glasses were prepared by melt quench technique. The density of the present glasses varies non-linearly exhibiting mixed alkali effect. Using the density data, the elastic moduli namely Young's modulus, bulk and shear modulus show strong linear dependence as a function of compositional parameter. From the absorption edge studies, the values of optical band gap energies for all transitions have been evaluated. It was established that the type of electronic transition in the present glass system is indirect allowed. The indirect optical band gap exhibit non-linear behavior with compositional parameter showing the mixed alkali effect.

Influence of Ag, Cd or Pb Addition on Electrical and Dielectric Properties of Bulk Glassy Se-Ge

NASA Astrophysics Data System (ADS)

El-Metwally, E. G.; Shakra, A. M.

2018-05-01

Bulk glassy samples of Se0.7Ge0.3 and Se0.7Ge0.25 X 0.05 (X = Ag, Cd or Pb) chalcogenide glass have been prepared by melt-quenching method. The studied compositions were examined in powder form by x-ray diffraction analysis. The direct-current (dc) conductivity σ_{{dc}} was measured for bulk samples in the temperature range from 303 K to 433 K, revealing enhancement with temperature for all samples. The results indicate two values of activation energy ( Δ E_{{σ1 }} and Δ E_{{σ2 }} ) due to two conduction mechanisms. Measurements of the alternating-current (ac) conductivity σ_{{ac}} ( ω ) and dielectric properties for bulk samples were carried out in the temperature range from 303 K to 433 K and frequency range from 1 kHz to 1 MHz. The ac conductivity σ_{{ac}} ( ω ) was temperature dependent and proportional to ωS , where S is the frequency exponent, which reduced with rising temperature, and ω is the angular frequency. These results are discussed based on a correlated barrier hopping model. The calculated values of the maximum height of the barrier W_{{M}} for each composition are consistent with carrier hopping over a potential barrier. The density of localized states N( {E_{{F}} } ) at the Fermi level lay in the range from 1019 eV-1 cm-3 to 1020 eV-1 cm-3, and increased with temperature. The dielectric constant ɛ1 ( ω ) and loss ɛ2 ( ω ) increased with temperature but decreased with frequency. The values of σ_{{dc}} , σ_{{ac}} ( ω ) , ɛ1 ( ω ) , and ɛ2 ( ω ) increased with temperature and with addition of Ag, Cd or Pb. The observed increase was greater for Se0.7Ge0.25Pb0.05 than for Se0.7Ge0.25Cd0.05, which was greater than for Se0.7Ge0.25Ag0.05.

Pressure dependence of thermal physical properties of A-type R2O3 (R=Y, La): A first-principles study

NASA Astrophysics Data System (ADS)

Li, Y. F.; Xiao, B.; Sun, L.; Gao, Y. M.; Ma, S. Q.; Yi, D. W.

2017-04-01

The mechanical, electronic and thermal physical properties of A-type R2O3 (R=Y, La) under hydrostatic pressure are studied by first-principles calculations. The calculated band gap is 6.3 eV (5.9 eV) for Y2O3 (La2O3). Under hydrostatic pressure, both phases show anisotropic elasticity in different crystallographic directions. The isothermal bulk modulus of R2O3 decreases monotonically with the increasing of temperature from 300 K to 1500 K. The intrinsic ductile nature of both phases is confirmed by the obtained B/G ratio. The temperature dependence of linear TECs of La2O3 is stronger than that of Y2O3, and the linear TECs in [001] direction show larger values in both phases than those in [010] direction. At room temperature, the average linear TECs for Y2O3 and La2O3 are 8.40×10-6 K-1 and 8.42×10-6 K-1, respectively. Other thermal physical properties such as specific heats (CV, and CP), entropy (S), sound velocity and Debye temperature are also obtained.

Ultrahigh lattice thermal conductivity in topological semimetal TaN caused by a large acoustic-optical gap

NASA Astrophysics Data System (ADS)

Guo, San-Dong; Liu, Bang-Gui

2018-03-01

Topological semimetals may have potential applications such as in topological qubits, spintronics and quantum computations. Efficient heat dissipation is a key factor for the reliability and stability of topological semimetal-based nano-electronics devices, which is closely related to high thermal conductivity. In this work, the elastic properties and lattice thermal conductivity of TaN are investigated using first-principles calculations and the linearized phonon Boltzmann equation within the single-mode relaxation time approximation. According to the calculated bulk modulus, shear modulus and C 44, TaN can be regarded as a potential incompressible and hard material. The room-temperature lattice thermal conductivity is predicted to be 838.62 W~m-1~K^{-1} along the a axis and 1080.40 W~m-1~K^{-1} along the c axis, showing very strong anisotropy. It is found that the lattice thermal conductivity of TaN is several tens of times higher than other topological semimetals, such as TaAs, MoP and ZrTe, which is due to the very longer phonon lifetimes for TaN than other topological semimetals. The very different atomic masses of Ta and N atoms lead to a very large acoustic-optical band gap, and then prohibit the scattering between acoustic and optical phonon modes, which gives rise to very long phonon lifetimes. Calculated results show that isotope scattering has little effect on lattice thermal conductivity, and that phonons with mean free paths larger than 20 (80) μm along the c direction at 300 K have little contribution to the total lattice thermal conductivity. This work implies that TaN-based nano-electronics devices may be more stable and reliable due to efficient heat dissipation, and motivates further experimental works to study lattice thermal conductivity of TaN.

Cohesive Strength of Gas-hydrate-bearing Marine Sediments

NASA Astrophysics Data System (ADS)

Cook, A. E.; Goldberg, D.

2005-12-01

We examine the relationship between gas hydrate saturation and the cohesive strength of marine sediments in a variety of continental margin settings. The cohesive strength (cohesion) is a fundamental physical property controlling sediment resistance to compressive failure. The cohesion (Co), is typically defined by the uncompressive rock strength and the friction angle, but it can also be related to the dynamic Young's modulus (ED), where: Co = 1.5*10-3 ED. The dynamic Young's modulus is computed using in situ Vp, Vs, and bulk density borehole logs. The Co profiles are compared to estimates of the in situ hydrate saturation, Sh, calculated using electrical resistivity logs and the modified Archie formula: Sh = 1 - (aRw/RΦm)1/n. We will present results of these comparisons from data collected during Ocean Drilling Program Legs at Cascadia margin (204 & 168) and Blake Ridge (164), the JIP gas hydrate drilling project in the Gulf of Mexico, and Malik permafrost wells. In general, at all the sites investigated, Co steadily increases downhole as sediments compact due to overburden. In marine sediments, cohesion ranges from 500-2000kPa above the BSR, with a baseline gradient usually between 5 and 10 kPa/m. Preliminary results show at Cascadia margin that sediments with Sh > 15%, Co increases dramatically, at least 200kPa greater than the general trend of the downhole gradient. This suggests that Co is affected directly by Sh, and may be related to the rate of change in Sh (e.g. gradual or sharp) as a function of depth. Further study on the relationship between Co and Sh may provide information on the growth habit of gas hydrates in sediment pore spaces.

Growth and giant coercive field of spinel-structured Co3- x Mn x O4 thin films

NASA Astrophysics Data System (ADS)

Kwak, Yongsu; Song, Jonghyun; Koo, Taeyeong

2016-08-01

We grew epitaxial thin films of CoMn2O4 and Co2MnO4 on Nb-doped SrTiO3(011) and SrTiO3(001) single crystal substrates using pulsed laser deposition. The magnetic Curie temperature ( T c ) of the Co2MnO4 thin films was ~176 K, which is higher than that of the bulk whereas CoMn2O4 thin films exhibited a value of T c (~151 K) lower than that of the bulk. For the Co2MnO4 thin films, the M - H loop showed a coercive field of ~0.7 T at 10 K, similar to the value for the bulk. However, the M -H loop of the CoMn2O4(0 ll) thin film grown on a Nb-doped SrTiO3(011) substrate exhibited a coercive field of ~4.5 T at 30 K, which is significantly higher than those of the Co2MnO4 thin film and bulk. This giant coercive field, only observed for the CoMn2O4(0 ll) thin film, can be attributed to the shape anisotropy and strong spin-orbit coupling.

Robustness in spin polarization and thermoelectricity in newly tailored Mn2-based Heusler alloys

NASA Astrophysics Data System (ADS)

Yousuf, S.; Gupta, D. C.

2018-02-01

Investigation of electronic structure, magnetism, hybridization and thermoelectricity of Mn2-based Heusler alloys within the framework of DFT simulation technique have been carried out. Through the optimized ground state parameters viz., lattice constant, total energy and bulk's modulus, electronic properties, magnetic properties and thermoelectric response of new tailored materials is reported. Mechanically stable with ductile nature and 100% spin polarization could favor their use in future spintronic materials. Thermoelectric properties are investigated through the variation of carrier concentration and temperature. Power factor analysis show a way for the selection of the optimal carrier concentration responsible for increasing their thermoelectric response with temperature. The power factor of 857.51 (966.16) × 109µW K-2 m-1 s-1 at an optimal concentration of 1018 cm-3 and temperature of 800 K for Mn2YSn (Mn2ZnSn) respectively is obtained. The Seebeck coefficient portray them as p-type materials and show a linear increase with temperature and vice versa for the carrier concentrations.

Robustness in spin polarization and thermoelectricity in newly tailored Mn2-based Heusler alloys

NASA Astrophysics Data System (ADS)

Yousuf, S.; Gupta, D. C.

2018-07-01

Investigation of electronic structure, magnetism, hybridization and thermoelectricity of Mn2-based Heusler alloys within the framework of DFT simulation technique have been carried out. Through the optimized ground state parameters viz., lattice constant, total energy and bulk's modulus, electronic properties, magnetic properties and thermoelectric response of new tailored materials is reported. Mechanically stable with ductile nature and 100% spin polarization could favor their use in future spintronic materials. Thermoelectric properties are investigated through the variation of carrier concentration and temperature. Power factor analysis show a way for the selection of the optimal carrier concentration responsible for increasing their thermoelectric response with temperature. The power factor of 857.51 (966.16) × 109µW K-2 m-1 s-1 at an optimal concentration of 1018 cm-3 and temperature of 800 K for Mn2YSn (Mn2ZnSn) respectively is obtained. The Seebeck coefficient portray them as p-type materials and show a linear increase with temperature and vice versa for the carrier concentrations.

Superconductivity under high pressure in the binary compound CaLi2

NASA Astrophysics Data System (ADS)

Debessai, M.; Matsuoka, T.; Hamlin, J. J.; Gangopadhyay, A. K.; Schilling, J. S.; Shimizu, K.; Ohishi, Y.

2008-12-01

Feng predicted for CaLi2 highly anomalous properties with possible superconductivity under very high pressures, including for the hcp polymorph a significant lattice bifurcation at pressures above 47 GPa. More recently, however, Feng suggested that for pressures exceeding 20 GPa CaLi2 may dissociate into elemental Ca and Li. Here we present for hcp CaLi2 measurements of the electrical resistivity and ac susceptibility to low temperatures under pressures as high as 81 GPa. Pressure-induced superconductivity is observed in the pressure range of 11-81 GPa, with Tc reaching values as high as 13 K. X-ray diffraction studies to 54 GPa at 150 K reveal that hcp CaLi2 undergoes a structural phase transition above 23 GPa to orthorhombic but does not dissociate into elemental Ca and Li. In the hcp phase a fit of the equation of state with the Murnaghan equation yields the bulk modulus Bo=15(2)GPa and dBo/dP=3.2(6) .

Formation of collapsed tetragonal phase in EuCo₂As₂ under high pressure.

PubMed

Bishop, Matthew; Uhoya, Walter; Tsoi, Georgiy; Vohra, Yogesh K; Sefat, Athena S; Sales, Brian C

2010-10-27

The structural properties of EuCo₂As₂ have been studied up to 35 GPa, through the use of x-ray diffraction in a diamond anvil cell at a synchrotron source. At ambient conditions, EuCo₂As₂ ) (I4/mmm) has a tetragonal lattice structure with a bulk modulus of 48 ± 4 GPa. With the application of pressure, the a axis exhibits negative compressibility with a concurrent sharp decrease in c-axis length. The anomalous compressibility of the a axis continues until 4.7 GPa, at which point the structure undergoes a second-order phase transition to a collapsed tetragonal (CT) state with a bulk modulus of 111 ± 2 GPa. We found a strong correlation between the ambient pressure volume of 122 parents of superconductors and the corresponding tetragonal to collapsed tetragonal phase transition pressures.

Characterization of solid particle erosion resistance of ductile metals based on their properties

NASA Technical Reports Server (NTRS)

Rao, P. V.; Buckley, D. H.

1985-01-01

This paper presents experimental results pertaining to spherical glass bead and angular crushed glass particle impingement. A concept of energy absorption to explain the failure of material is proposed and is correlated with the erosion characteristics of several pure metals. Analyses of extensive erosion data indicate that the properties - surface energy, specific melting energy, strain energy, melting point, bulk modulus, hardness, atomic volume - and the product of the parameters - linear coefficient of thermal expansion x bulk modulus x temperature rise required for melting, and ultimate resilience x hardness - exhibit the best correlations. The properties of surface energy and atomic volume are suggested for the first time for correlation purposes and are found to correlate well with erosion rates at different angles of impingement. It further appears that both energy and thermal properties contribute to the total erosion.

Computer simulation of the matrix-inclusion interphase in bulk metallic glass based nanocomposites

NASA Astrophysics Data System (ADS)

Kokotin, V.; Hermann, H.; Eckert, J.

2011-10-01

Atomistic models for matrix-inclusion systems are generated. Analyses of the systems show that interphase layers of finite thickness appear interlinking the surface of the nanocrystalline inclusion and the embedding amorphous matrix. In a first approximation, the interphase is characterized as an amorphous structure with a density slightly reduced compared to that of the matrix. This result holds for both monatomic hard sphere systems and a Cu47.5Zr47.5Al5 alloy simulated by molecular dynamics (MD). The elastic shear and bulk modulus of the interphase are calculated by simulated deformation of the MD systems. Both moduli diminish with decreasing density but the shear modulus is more sensitive against density reduction by one order of magnitude. This result explains recent observations of shear band initiation at the amorphous-crystalline interface during plastic deformation.

Atomistic modeling of structure II gas hydrate mechanics: Compressibility and equations of state

NASA Astrophysics Data System (ADS)

Vlasic, Thomas M.; Servio, Phillip; Rey, Alejandro D.

2016-08-01

This work uses density functional theory (DFT) to investigate the poorly characterized structure II gas hydrates, for various guests (empty, propane, butane, ethane-methane, propane-methane), at the atomistic scale to determine key structure and mechanical properties such as equilibrium lattice volume and bulk modulus. Several equations of state (EOS) for solids (Murnaghan, Birch-Murnaghan, Vinet, Liu) were fitted to energy-volume curves resulting from structure optimization simulations. These EOS, which can be used to characterize the compressional behaviour of gas hydrates, were evaluated in terms of their robustness. The three-parameter Vinet EOS was found to perform just as well if not better than the four-parameter Liu EOS, over the pressure range in this study. As expected, the Murnaghan EOS proved to be the least robust. Furthermore, the equilibrium lattice volumes were found to increase with guest size, with double-guest hydrates showing a larger increase than single-guest hydrates, which has significant implications for the widely used van der Waals and Platteeuw thermodynamic model for gas hydrates. Also, hydrogen bonds prove to be the most likely factor contributing to the resistance of gas hydrates to compression; bulk modulus was found to increase linearly with hydrogen bond density, resulting in a relationship that could be used predictively to determine the bulk modulus of various structure II gas hydrates. Taken together, these results fill a long existing gap in the material chemical physics of these important clathrates.

Atomistic modeling of structure II gas hydrate mechanics: Compressibility and equations of state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vlasic, Thomas M.; Servio, Phillip; Rey, Alejandro D., E-mail: alejandro.rey@mcgill.ca

2016-08-15

This work uses density functional theory (DFT) to investigate the poorly characterized structure II gas hydrates, for various guests (empty, propane, butane, ethane-methane, propane-methane), at the atomistic scale to determine key structure and mechanical properties such as equilibrium lattice volume and bulk modulus. Several equations of state (EOS) for solids (Murnaghan, Birch-Murnaghan, Vinet, Liu) were fitted to energy-volume curves resulting from structure optimization simulations. These EOS, which can be used to characterize the compressional behaviour of gas hydrates, were evaluated in terms of their robustness. The three-parameter Vinet EOS was found to perform just as well if not better thanmore » the four-parameter Liu EOS, over the pressure range in this study. As expected, the Murnaghan EOS proved to be the least robust. Furthermore, the equilibrium lattice volumes were found to increase with guest size, with double-guest hydrates showing a larger increase than single-guest hydrates, which has significant implications for the widely used van der Waals and Platteeuw thermodynamic model for gas hydrates. Also, hydrogen bonds prove to be the most likely factor contributing to the resistance of gas hydrates to compression; bulk modulus was found to increase linearly with hydrogen bond density, resulting in a relationship that could be used predictively to determine the bulk modulus of various structure II gas hydrates. Taken together, these results fill a long existing gap in the material chemical physics of these important clathrates.« less

Phosphate-based glasses: Prediction of acoustical properties

NASA Astrophysics Data System (ADS)

El-Moneim, Amin Abd

2016-04-01

In this work, a comprehensive study has been carried out to predict the composition dependence of bulk modulus and ultrasonic attenuation coefficient in the phosphate-based glass systems PbO-P2O5, Li2O-TeO2-B2O3-P2O5, TiO2-Na2O-CaO-P2O5 and Cr2O3-doped Na2O-ZnO-P2O5 at room temperature. The prediction is based on (i) Makishima-Mackenzie theory, which correlates the bulk modulus with packing density and dissociation energy per unit volume, and (ii) Our recently presented semi-empirical formulas, which correlate the ultrasonic attenuation coefficient with the oxygen density, mean atomic ring size, first-order stretching force constant and experimental bulk modulus. Results revealed that our recently presented semi-empirical formulas can be applied successfully to predict changes of ultrasonic attenuation coefficient in binary PbO-P2O5 glasses at 10 MHz frequency and in quaternary Li2O-TeO2-B2O3-P2O5, TiO2-Na2O-CaO-P2O5 and Cr2O3-Na2O-ZnO-P2O5 glasses at 5 MHz frequency. Also, Makishima-Mackenzie theory appears to be valid for the studied glasses if the effect of the basic structural units that present in the glass network is taken into account.

First principles investigation of structural, mechanical, dynamical and thermodynamic properties of AgMg under pressure

NASA Astrophysics Data System (ADS)

Cui, Rong Hua; Chao Dong, Zheng; Gui Zhong, Chong

2017-12-01

The effects of pressure on the structural, mechanical, dynamical and thermodynamic properties of AgMg have been investigated using first principles based on density functional theory. The optimized lattice constants agree well with previous experimental and theoretical results. The bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and Debye temperature under pressures were calculated. The calculated results of Cauchy pressure and B/G ratio indicate that AgMg shows ductile nature. Phonon dispersion curves suggest the dynamical stability of AgMg. The pressure dependent behavior of thermodynamic properties are calculated, the Helmholtz free energy and internal energy increase with increase of pressure, while entropy and heat capacity decrease.

Radion stabilization in higher curvature warped spacetime

NASA Astrophysics Data System (ADS)

Das, Ashmita; Mukherjee, Hiya; Paul, Tanmoy; SenGupta, Soumitra

2018-02-01

We consider a five dimensional AdS spacetime in presence of higher curvature term like F(R) = R + α R^2 in the bulk. In this model, we examine the possibility of modulus stabilization from the scalar degrees of freedom of higher curvature gravity free of ghosts. Our result reveals that the model stabilizes itself and the mechanism of modulus stabilization can be argued from a geometric point of view. We determine the region of the parametric space for which the modulus (or radion) can to be stabilized. We also show how the mass and coupling parameters of radion field are modified due to higher curvature term leading to modifications of its phenomenological implications on the visible 3-brane.