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Sample records for sub-micron agglomerate-free alumina

  1. Deformation Behavior of Sub-micron and Micron Sized Alumina Particles in Compression.

    SciTech Connect

    Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay; Mook, William; Boyce, Brad; Kotula, Paul Gabriel; McKenzie, Bonnie Beth; Bufford, Daniel Charles; Hall, Aaron Christopher.

    2014-09-01

    The ability to integrate ceramics with other materials has been limited due to high temperature (>800degC) ceramic processing. Recently, researchers demonstrated a novel process , aerosol deposition (AD), to fabricate ceramic films at room temperature (RT). In this process, sub - micro n sized ceramic particles are accelerated by pressurized gas, impacted on the substrate, plastically deformed, and form a dense film under vacuum. This AD process eliminates high temperature processing thereby enabling new coatings and device integration, in which ceramics can be deposited on metals, plastics, and glass. However, k nowledge in fundamental mechanisms for ceramic particle s to deform and form a dense ceramic film is still needed and is essential in advancing this novel RT technology. In this wo rk, a combination of experimentation and atomistic simulation was used to determine the deformation behavior of sub - micron sized ceramic particle s ; this is the first fundamental step needed to explain coating formation in the AD process . High purity, singl e crystal, alpha alumina particles with nominal size s of 0.3 um and 3.0 um were examined. Particle characterization, using transmission electron microscopy (TEM ), showed that the 0.3 u m particles were relatively defect - free single crystals whereas 3.0 u m p articles were highly defective single crystals or particles contained low angle grain boundaries. Sub - micron sized Al 2 O 3 particles exhibited ductile failure in compression. In situ compression experiments showed 0.3um particles deformed plastically, fractured, and became polycrystalline. Moreover, dislocation activit y was observed within the se particles during compression . These sub - micron sized Al 2 O 3 particles exhibited large accum ulated strain (2 - 3 times those of micron - sized particles) before first fracture. I n agreement with the findings from experimentation , a tomistic simulation s of nano - Al 2 O 3 particles showed dislocation slip and

  2. Gelcasting of sub-micron alumina, sialon, and silicon nitride powders

    SciTech Connect

    Omatete, O.O.; Strehlow, R.A.; Walls, C.A.

    1990-01-01

    Gelcasting is a near-net-shape forming technique that is applicable to various types of powders. It is accomplished by casting a concentrated suspension of a commercial ceramic powder in a solution of a polymerizable monomer and then polymerizing. A filled gel is formed, which is dried and processed further. Alumina, sialon, and silicon nitride parts of various geometries have been made and are described. Emphasis is placed on the unit-operations of the process. Because a requirement of the process is a castable suspension of more than 50 vol % solids loading, good dispersion is crucial. Drying, another key process, has been studied extensively. Shrinkage from the cast size occurs during drying and further shrinkage occurs during sintering. Data on the relationship of physical properties of products to some of the more significant processing variables is discussed. Emphasis is also placed on the machinability of the dried gelled body. Because the body at this stage is quite durable, green part machining is feasible. The monomer used in the process is acrylamide, which undergoes a vinyl polymerization. Environmental, safety and hygiene issues are summarized. 9 refs., 6 figs.

  3. Sub-micron filter

    DOEpatents

    Tepper, Frederick; Kaledin, Leonid

    2009-10-13

    Aluminum hydroxide fibers approximately 2 nanometers in diameter and with surface areas ranging from 200 to 650 m.sup.2/g have been found to be highly electropositive. When dispersed in water they are able to attach to and retain electronegative particles. When combined into a composite filter with other fibers or particles they can filter bacteria and nano size particulates such as viruses and colloidal particles at high flux through the filter. Such filters can be used for purification and sterilization of water, biological, medical and pharmaceutical fluids, and as a collector/concentrator for detection and assay of microbes and viruses. The alumina fibers are also capable of filtering sub-micron inorganic and metallic particles to produce ultra pure water. The fibers are suitable as a substrate for growth of cells. Macromolecules such as proteins may be separated from each other based on their electronegative charges.

  4. Method for sampling sub-micron particles

    DOEpatents

    Gay, Don D.; McMillan, William G.

    1985-01-01

    Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar.RTM. and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis.

  5. Sub-micron particle sampler apparatus

    DOEpatents

    Gay, Don D.; McMillan, William G.

    1987-01-01

    Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar.RTM. and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis.

  6. Sub-micron particle sampler apparatus and method for sampling sub-micron particles

    DOEpatents

    Gay, D.D.; McMillan, W.G.

    1984-04-12

    Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however, the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis. 6 figures.

  7. Scanning SQUID susceptometers with sub-micron spatial resolution

    NASA Astrophysics Data System (ADS)

    Kirtley, John R.; Paulius, Lisa; Rosenberg, Aaron J.; Palmstrom, Johanna C.; Holland, Connor M.; Spanton, Eric M.; Schiessl, Daniel; Jermain, Colin L.; Gibbons, Jonathan; Fung, Y.-K.-K.; Huber, Martin E.; Ralph, Daniel C.; Ketchen, Mark B.; Gibson, Gerald W.; Moler, Kathryn A.

    2016-09-01

    Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between this area and the sample surface. In this paper we describe scanning SQUID susceptometers that achieve sub-micron spatial resolution while retaining a white noise floor flux sensitivity of ≈2μΦ0/Hz1/2. This high spatial resolution is accomplished by deep sub-micron feature sizes, well shielded pickup loops fabricated using a planarized process, and a deep etch step that minimizes the spacing between the sample surface and the SQUID pickup loop. We describe the design, modeling, fabrication, and testing of these sensors. Although sub-micron spatial resolution has been achieved previously in scanning SQUID sensors, our sensors not only achieve high spatial resolution but also have integrated modulation coils for flux feedback, integrated field coils for susceptibility measurements, and batch processing. They are therefore a generally applicable tool for imaging sample magnetization, currents, and susceptibilities with higher spatial resolution than previous susceptometers.

  8. Discovering sub-micron ice particles across Dione' surface

    NASA Astrophysics Data System (ADS)

    Scipioni, Francesca; Schenk, Pual; Tosi, Federico; Clark, Roger; Dalle Ore, Cristina; Combe, Jean-Philippe

    2015-11-01

    Water ice is the most abundant component of Saturn’s mid-sized moons. However, these moons show an albedo asymmetry - their leading sides are bright while their trailing side exhibits dark terrains. Such differences arise from two surface alteration processes: (i) the bombardment of charged particles from the interplanetary medium and driven by Saturn’s magnetosphere on the trailing side, and (ii) the impact of E-ring water ice particles on the satellites’ leading side. As a result, the trailing hemisphere appears to be darker than the leading side. This effect is particularly evident on Dione's surface. A consequence of these surface alteration processes is the formation or the implantation of sub-micron sized ice particles.The presence of such particles influences and modifies the surfaces' spectrum because of Rayleigh scattering by the particles. In the near infrared range of the spectrum, the main sub-micron ice grains spectral indicators are: (i) asymmetry and (ii) long ward minimum shift of the absorption band at 2.02 μm (iii) a decrease in the ratio between the band depths at 1.50 and 2.02 μm (iv) a decrease in the height of the spectral peak at 2.6 μm (v) the suppression of the Fresnel reflection peak at 3.1 μm and (vi) the decrease of the reflection peak at 5 μm relative to those at 3.6 μm.We present results from our ongoing work mapping the variation of sub-micron ice grains spectral indicators across Dione' surface using Cassini-VIMS cubes acquired in the IR range (0.8-5.1 μm). To characterize the global variations of spectral indicators across Dione' surface, we divided it into a 1°x1° grid and then averaged the band depths and peak values inside each square cell.We will investigate if there exist a correspondence with water ice abundance variations by producing water ice' absorption band depths at 1.25, 1.52 and 2.02 μm, and with surface morphology by comparing the results with ISS color maps in the ultraviolet, visible and infrared

  9. Sub-Micron Velocity Measurements near a Moving Contact Line

    NASA Astrophysics Data System (ADS)

    Zimmerman, Jeremiah; Weislogel, Mark M.; Tretheway, Derek C.

    2010-03-01

    The displacement of one fluid by an immiscible second fluid (i.e. dynamic wetting), governs many natural and technological processes. Despite extensive studies, understanding and modeling the displacement process remains one of the outstanding problems in fluid mechanics. In this work, we explore the physics of the moving contact line (the idealized line of intersection between two fluids and a solid) with micron resolution particle image velocimetry (μPIV), which enables sub-micron two-dimensional velocity measurements. The measured flow is generated by dynamic wetting in a glass microchannel. The microchannel is mounted on an automated microscope stage with precise velocity control allowing for the static placement of the contact line within the field of view. Full-field velocity measurements within 1 μm of the contact line were made in water/glycerol and fructose/glucose/water solutions. Preliminary results appear to show remarkable similarity to controversial theoretical predictions.

  10. Separating the signal from the noise: Expanding flow cytometry into the sub-micron range.

    EPA Science Inventory

    Cytometry Part A Special Section: Separating the signal from the noise: Expanding flow cytometry into the sub-micron range. The current Cytometry Part A Special Section presents three studies that utilize cytometers to study sub-micron particles. The three studies involve the 1...

  11. Anisotropic transport and magnetic properties of arrays of sub-micron wires

    NASA Astrophysics Data System (ADS)

    Piraux, L.; Dubois, S.; Ferain, E.; Legras, R.; Ounadjela, K.; George, J. M.; Maurice, J. L.; Fert, A.

    1997-01-01

    We report a comparative study of anisotropic magnetoresistance and magnetic properties in arrays of sub-micron Ni and Co wires electro-deposited in the cylindrical pores of track-etched polymer membranes. The variation of coercivity and squareness as a function of wire diameter for arrays of almost isolated sub-micron wires is reported in the range 30-500 nm. The Ni and Co-based systems demonstrate different magnetic and magnetoresistive behaviors except for the smallest diameter. It is believed that the observed difference originates from the presence of competing crystal anisotropy in the Co-based system.

  12. Geometric effects on the mechanical strengths of strong nanocrystalline rhodium sub-micron structures

    NASA Astrophysics Data System (ADS)

    Tsui, Ting Y.; Jahed, Zeinab; Evans, R. D.; Burek, Michael J.

    2015-06-01

    Sub-micron scale nanocrystalline rhodium pillars were fabricated by electron beam lithography and electroplating techniques. The fabricated specimens included solid core pillars and columnar structure with more complex cross-sectional geometries, including x-shaped and annulus shaped. Among these specimens, two groups of sub-micron scale annulus structures with sidewall thicknesses of 250 and 205 nm were fabricated. All of the structures have outer diameters of ~1 μm and consist of average grain size smaller than 22 nm. Uniaxial compression results reveal these rhodium pillars are very strong with true flow stresses exceeding 5 GPa and are not sensitive to the sample cross-sectional geometries.

  13. Membrane fouling caused by sub-micron particles in a mixed liquor suspension of an MBR.

    PubMed

    Kimura, K; Ogyu, R; Miyoshi, T; Naruse, T; Tsuyuhara, T; Watanabe, Y

    2013-01-01

    Membrane fouling needs to be mitigated for widespread use of membrane bioreactors (MBRs). It has been pointed out that particles with small sizes found in supernatants (sub-micron particles) of mixed liquor suspensions of MBRs are important in the evolution of membrane fouling of this technology. However, information on characteristics of sub-micron particles in MBRs is still insufficient. In this study, a pilot-scale MBR treating municipal wastewater was used to investigate and characterize sub-micron particles in an MBR and to identify the size fraction(s) responsible for irreversible fouling in an MBR. It was clearly shown that characteristics of sub-micron particles in the MBR varied considerably depending on their sizes. Results of Fourier transform infrared (FTIR) analysis and monosaccharide analysis suggested that irreversible fouling in this study was mainly caused by the specific size fraction of 0.1-0.45 μm, which was close to the size of micropores of the membrane used. Pore plugging might explain this to some extent. PMID:23752395

  14. Hydrogels containing metallic glass sub-micron wires for regulating skeletal muscle cell behaviour.

    PubMed

    Ahadian, Samad; Banan Sadeghian, Ramin; Yaginuma, Shin; Ramón-Azcón, Javier; Nashimoto, Yuji; Liang, Xiaobin; Bae, Hojae; Nakajima, Ken; Shiku, Hitoshi; Matsue, Tomokazu; Nakayama, Koji S; Khademhosseini, Ali

    2015-11-01

    Hydrogels with tunable electrical and mechanical properties have a wide range of biological applications in tissue engineering, biosensing, and biorobotics. In this work, palladium-based metallic glass sub-micron wires (PdMGSMWs) were employed to enhance the conductivity and mechanical strength of gelatin methacryloyl (GelMA) gels. The values of electrical resistivity and stiffness of hybrid GelMA-PdMGSMW hydrogels were varied by the concentration of the sub-micron wires in the gels. Compared with pristine GelMA gels, hybrid GelMA-PdMGSMW gels were more efficient in regulating adhesion and spreading of C2C12 myoblasts. Formation, contractility, and metabolic activity of C2C12 myotubes in GelMA hydrogels also increased upon inclusion of the PdMGSMWs and applying electrical stimulation. The latter phenomenon is likely because of the electrical conductivity of hybrid GelMA gels.

  15. Generating Sub-Micron Features On Rough Surfaces Using Optical Trap Assisted Nanopatterning

    NASA Astrophysics Data System (ADS)

    Tsai, Yu-Cheng; Fardel, Romain; Arnold, Craig B.

    2010-10-01

    Near-field intensity enhancement enables laser modification of materials with feature sizes below the classical diffraction limit. However, the need to maintain close distances between the objective element and the substrate typically limit demonstrations of this technology to flat surfaces, even though there are many cases where the ability to produce sub-micron features on rough or structured surfaces are needed. Here, we show the use of a new technique, optical trap assisted nanopatterning (OTAN), for the production of nanoscale features on rippled substrates. The ability to position a microbead near-field objective close to the surface without the need for active feedback and control allows one to continuously move the bead across a rough surface without sticking. Sub-micron patterning of polyimide is demonstrated on surfaces with 1.1 μm steps showing good uniformity. Finally, the enabling technology allows for straightforward parallelization where multiple patterns can be created simultaneously over surface.

  16. Generating Sub-Micron Features On Rough Surfaces Using Optical Trap Assisted Nanopatterning

    SciTech Connect

    Tsai, Yu-Cheng; Fardel, Romain; Arnold, Craig B.

    2010-10-08

    Near-field intensity enhancement enables laser modification of materials with feature sizes below the classical diffraction limit. However, the need to maintain close distances between the objective element and the substrate typically limit demonstrations of this technology to flat surfaces, even though there are many cases where the ability to produce sub-micron features on rough or structured surfaces are needed. Here, we show the use of a new technique, optical trap assisted nanopatterning (OTAN), for the production of nanoscale features on rippled substrates. The ability to position a microbead near-field objective close to the surface without the need for active feedback and control allows one to continuously move the bead across a rough surface without sticking. Sub-micron patterning of polyimide is demonstrated on surfaces with 1.1 {mu}m steps showing good uniformity. Finally, the enabling technology allows for straightforward parallelization where multiple patterns can be created simultaneously over surface.

  17. The fabrication of sub-micron size cesium iodide x-ray scintillator

    NASA Astrophysics Data System (ADS)

    Hun, Chien Wan; Chen, Po Chun; Huang, Ker Jer; Chen, Chien Chon

    2015-05-01

    The cesium iodide (CsI) scintillator can converts incident X-ray into visible light with very high conversion efficiency of optical photons. The incident energy, response time, film thickness, sample size, and spatial resolution require in engineering and medical applications are difference. A smooth and flat surface and single crystal structure of CsI enhance the X-ray to visible light conversion. However, the regular CsI is soft and extremely hygroscopic; it is very difficult to polish to obtain a smooth and optical flat plane. In order to obtain a good quality of CsI scintillator for X-ray application we used an ordering channel as template and formed sub-micron CsI wire in the template. The fabrication process including: (1) Ordering structure of nano or sub-micron channels were made by an anodization method; (2) fill CsI scintillated film on the channel by CsI solution, (3) fill CsI melt into the channel formation single crystal of sub-micron crystalline scintillator after solidification. The non-vacuum processes of anodization and solidication methods were used for the sub-micron CsI scintillator column formation that is cost down the scintillator fabrication. In addition, through the fabrication method, the ordering structure scintillator of scintillator can be made by anodic treatment and die casting technology with low cost and rapid production; moreover, the film oxidized metal tubes of the tubular template can be further manufactured to nano tubes by adjusting electrolyte composition, electrolysis voltage, and processing time of anodic treatment, and the aperture size, the thickness and the vessel density of the nano tube can be controlled and ranged from 10 nm to 500 nm, 0.1 μm to 1000 μm, and hundred million to thousand billion tube/cm2, respectively.

  18. Oxidation of synthesized sub-micron pyrite (FeS2) in seawater

    NASA Astrophysics Data System (ADS)

    Gartman, Amy; Luther, George W.

    2014-11-01

    Synthesized sub-micron pyrite was oxidized in 0.2 μm-filtered Sargasso seawater in order to investigate the rate of oxidation and reaction end-products. Over the initial phase of the reaction, the sub-micron pyrite behaved as a soluble entity as the initial rate of oxidation was determined to be first order with respect to both pyrite and oxygen concentration, where the rate is described as -dFeS2/dt = k[FeS2][O2] and k, the rate constant, is 7.60 × 10-5 + 6.29 × 10-5 μM-1 day-1 at 25 °C. Oxidation proceeds inward from an initial surface oxidation of the pyrite and the formation of an amorphous mixed valence Fe(II)/(III) oxide surrounding the remaining pyrite core. The oxidation rates obtained through this study are up to two orders of magnitude slower than reported in previous pyrite oxidation studies using ground rather than synthesized pyrite at similar pH values. These results may be applied anywhere seawater and sub-micron pyrite are found, including hydrothermal vents, salt marshes and marine sediments.

  19. Generation of sub-micron particles and secondary pollutants from building materials by ozone reaction

    NASA Astrophysics Data System (ADS)

    Aoki, Taisuke; Tanabe, Shin-ichi

    This study reports results from two different experiments examining reactions between ozone and common building materials that can lead to the formation of secondary products and particulate-phase materials. Monitored species include sub-micron particles and volatile organic compounds (VOCs). In the first set of experiments, various building materials were placed in a 20 L stainless-steel chamber and exposed to ozone. The materials included expanded polystyrene, a natural rubber adhesive, cedar board, Japanese Cyprus board and silver fir board, as well as d-limonene, which is a known constituent of certain woods and cleaning products. The combination of ozone and either d-limonene, cedar board or cypress board produced sub-micron particles, with most of the increase occurring in the size range of 0.01- 0.5μm diameter. This was not observed for the other materials. In the case of cedar board, the consequence of ozone exposure over an extended time interval was monitored. As the exposure time elapsed, the concentration of sub-micron particles moderately decreased. In the second set of experiments, unwaxed or waxed plastic tiles were placed in the 20 L chamber and exposed to ozone. Sub-micron particles and organic compounds were measured during the course of the experiments. In the case of the waxed tile, the number of 0.01- 1.0μm size particles grew about 50×108particlesm-3; particle growth was significantly less for the un-waxed tile. For both the waxed and un-waxed tiles, the emission rates of heptane, nonane, nonanal, and decanal increased after ozone was added to the supply air. (However, it is not clear if some or all of this production was due to ozone reacting with the sorbent used for sampling or with compounds captured by the sorbent.) This study provides further evidence that ozone-initiated reactions with building materials can be a significant source of both sub-micron particles and secondary organic compounds in indoor environments.

  20. Enhanced endothelial cell density on NiTi surfaces with sub-micron to nanometer roughness

    PubMed Central

    Samaroo, Harry D; Lu, Jing; Webster, Thomas J

    2008-01-01

    The shape memory effect and superelastic properties of NiTi (or Nitinol, a nickel-titanium alloy) have already attracted much attention for various biomedical applications (such as vascular stents, orthodontic wires, orthopedic implants, etc). However, for vascular stents, conventional approaches have required coating NiTi with anti-thrombogenic or anti-inflammatory drug-eluting polymers which as of late have proven problematic for healing atherosclerotic blood vessels. Instead of focusing on the use of drug-eluting anti-thrombogenic or anti-inflammatory proteins, this study focused on promoting the formation of a natural anti-thrombogenic and anti-inflammatory surface on metallic stents: the endothelium. In this study, we synthesized various NiTi substrates with different micron to nanometer surface roughness by using dissimilar dimensions of constituent NiTi powder. Endothelial cell adhesion on these compacts was compared with conventional commercially pure (cp) titanium (Ti) samples. The results after 5 hrs showed that endothelial cells adhered much better on fine grain (<60 μm) compared with coarse grain NiTi compacts (<100 μm). Coarse grain NiTi compacts and conventional Ti promoted similar levels of endothelial cell adhesion. In addition, cells proliferated more after 5 days on NiTi with greater sub-micron and nanoscale surface roughness compared with coarse grain NiTi. In this manner, this study emphasized the positive pole that NiTi with sub-micron to nanometer surface features can play in promoting a natural anti-thrombogenic and anti-inflammatory surface (the endothelium) on a vascular stent and, thus, suggests that more studies should be conducted on NiTi with sub-micron to nanometer surface features. PMID:18488418

  1. Suppression of transient enhanced diffusion in sub-micron patterned silicon template by dislocation loops formation

    SciTech Connect

    Hu, Kuan-Kan; Woon, Wei Yen; Chang, Ruey-Dar

    2015-10-15

    We investigate the evolution of two dimensional transient enhanced diffusion (TED) of phosphorus in sub-micron scale patterned silicon template. Samples doped with low dose phosphorus with and without high dose silicon self-implantation, were annealed for various durations. Dopant diffusion is probed with plane-view scanning capacitance microscopy. The measurement revealed two phases of TED. Significant suppression in the second phase TED is observed for samples with high dose self-implantation. Transmission electron microscopy suggests the suppressed TED is related to the evolution of end of range defect formed around ion implantation sidewalls.

  2. Suppression of transient enhanced diffusion in sub-micron patterned silicon template by dislocation loops formation

    NASA Astrophysics Data System (ADS)

    Hu, Kuan-Kan; Chang, Ruey-Dar; Woon, Wei Yen

    2015-10-01

    We investigate the evolution of two dimensional transient enhanced diffusion (TED) of phosphorus in sub-micron scale patterned silicon template. Samples doped with low dose phosphorus with and without high dose silicon self-implantation, were annealed for various durations. Dopant diffusion is probed with plane-view scanning capacitance microscopy. The measurement revealed two phases of TED. Significant suppression in the second phase TED is observed for samples with high dose self-implantation. Transmission electron microscopy suggests the suppressed TED is related to the evolution of end of range defect formed around ion implantation sidewalls.

  3. Quantitative X-ray phase tomography with sub-micron resolution

    NASA Astrophysics Data System (ADS)

    McMahon, P. J.; Peele, A. G.; Paterson, D.; Lin, J. J. A.; Irving, T. H. K.; McNulty, I.; Nugent, K. A.

    2003-03-01

    Tomographic X-ray phase reconstructions of an atomic force microscope tip with a spatial resolution of better than 900 nm are presented. The data was acquired using an X-ray energy of 1.83 keV using a zone plate based microscope at a third generation synchrotron, the Advanced Photon Source at the Argonne National Laboratory. The phase tomographic data is quantitatively accurate and we confirm that the deduced refractive index is in agreement with the known properties of the sample. Our results open the way for full 3D imaging of the complex refractive index with sub-micron spatial resolution.

  4. Characterization of the mean force on sub-micron particles in a standing wave field

    NASA Astrophysics Data System (ADS)

    Imani Jajarmi, Ramin; Robert, Etienne; KTH Mechanics Team

    2014-11-01

    The concentration of submicron particles suspended in air by means of a standing wave field is investigated experimentally. The focus in on molecular effects for very small particles and the quantification of the acoustophoretic force as particle size enters the sub-micron range. The experiment consists of a rectangular cross-section channel, with variable height, through which air seeded with TiO2 and salt particles is circulated. An electrostatic transducer generates a standing wave with frequencies in the 40--100 KHz range and the particle concentration is measured qualitatively using laser light scattering. Quantitative measurements of the particle number density and size distribution is obtained by isokinetic sampling downstream of the transducer. A Scanning Mobility Particle Sizer (SMPS) is used for the characterization of the aerosol as a function of position in the standing wave. The results gathered include the effects of acoustic (frequency, amplitude) and flow (bulk velocity, turbulence intensity) parameters on the separation efficiency. This allows for the estimation of the acoustic force acting on sub-micron particles and comparison with existing theoretical models that do not take into account molecular effects.

  5. Sub-micron alignment for nuclear emulsion plates using low energy electrons caused by radioactive isotopes

    NASA Astrophysics Data System (ADS)

    Miyamoto, S.; Ariga, A.; Fukuda, T.; Kazuyama, M.; Komatsu, M.; Nakano, T.; Niwa, K.; Sato, O.; Takahashi, S.

    2007-06-01

    Nuclear emulsion plates are employed in three-dimensional charged particle detectors that have sub-micron position resolution over 1 m2 with no dead space and no dead time. These detectors are suitable for the study of short-lived particle decays, and direct detection of neutrino interactions of all flavors. Typically emulsion plates are used in a stacked structure. Precise alignment between plates is required for physics analysis. The most accurate alignment method is to use tracks passing through the emulsion plates. The accuracy is about 0.2 μm. However, in an experiment with low track density alignment accuracy decreases to 20 μm because of plate distortion and it becomes more difficult to perform the analysis. This paper describes a new alignment method between emulsion plates by using trajectories of low energy electrons originating from environmental radioactive isotopes. As a trial emulsion plates were exposed to β-rays and γ-rays from K40. The trajectories which passed through emulsion layers were detected by a fully automated emulsion readout system. Using this method, the alignment between emulsion plates is demonstrated to be sub-micron. This method can be applied to many nuclear emulsion experiments. For example, the location of neutrino interaction vertices in the OPERA experiment can benefit from this new technique.

  6. Hybridization between nanocavities for a polarimetric color sorter at the sub-micron scale.

    PubMed

    Segal, Elad; Weissman, Adam; Gachet, David; Salomon, Adi

    2016-08-18

    Metallic hole arrays have been recently used for color generation and filtering due to their reliability and color tunability. However, color generation is still limited to several microns. Understanding the interaction between the individual elements of the whole nanostructure may push the resolution to the sub-micron level. Herein, we study the hybridization between silver nanocavities in order to obtain active color generation at the micron scale. To do so, we use five identical triangular cavities which are separated by hundreds of nanometers from each other. By tuning either the distance between the cavities or the optical polarization state of the incoming field, the transmitted light through the cavities is actively enhanced at specific frequencies. Consequently, a rainbow of colors is observed from a sub-micron scale unit. The reason for this is that the metallic surface plays a vital role in the hybridization between the cavities and contributes to higher frequency modes. Cathodoluminescence measurements have confirmed this assumption and have revealed that these five triangular cavities act as a unified entity surrounded by the propagated surface plasmons. In such plasmonic structures, multi-color tuning can be accomplished and may open the possibility to improve color generation and high-quality pixel fabrication. PMID:27500634

  7. Simultaneous sizing and electrophoretic mobility measurement of sub-micron particles using Brownian motion.

    PubMed

    Palanisami, Akilan; Miller, John H

    2010-10-01

    The size and surface chemistry of micron scale particles are of fundamental importance in studies of biology and air particulate pollution. However, typical electrophoretic measurements of these and other sub-micron scale particles (300 nm-1 μm) cannot resolve size information within heterogeneous mixtures unambiguously. Using optical microscopy, we monitor electrophoretic motion together with the Brownian velocity fluctuations - using the latter to measure size by either the Green-Kubo relation or by calibration from known size standards. Particle diameters are resolved to ±12% with 95% confidence. Strikingly, the size resolution improves as the particle size decreases due to the increased Brownian motion. The sizing ability of the Brownian assessed electrophoresis method described here complements the electrophoretic mobility resolution of the traditional CE. PMID:20882556

  8. Recording oscillations of sub-micron size cantilevers by extreme ultraviolet Fourier transform holography.

    PubMed

    Monserud, Nils C; Malm, Erik B; Wachulak, Przemyslaw W; Putkaradze, Vakhtang; Balakrishnan, Ganesh; Chao, Weilun; Anderson, Erik; Carlton, David; Marconi, Mario C

    2014-02-24

    We recorded the fast oscillation of sub-micron cantilevers using time-resolved extreme ultraviolet (EUV) Fourier transform holography. A tabletop capillary discharge EUV laser with a wavelength of 46.9 nm provided a large flux of coherent illumination that was split using a Fresnel zone plate to generate the object and the reference beams. The reference wave was produced by the first order focus while a central opening in the zone plate provided a direct illumination of the cantilevers. Single-shot holograms allowed for the composition of a movie featuring the fast oscillation. Three-dimensional displacements of the object were determined as well by numerical back-propagation, or "refocusing" of the electromagnetic fields during the reconstruction of a single hologram. PMID:24663740

  9. Occurrence of weak, sub-micron, tropospheric aerosol events at high Arctic latitudes

    NASA Astrophysics Data System (ADS)

    O'Neill, N. T.; Pancrati, O.; Baibakov, K.; Eloranta, E.; Batchelor, R. L.; Freemantle, J.; McArthur, L. J. B.; Strong, K.; Lindenmaier, R.

    2008-07-01

    Numerous fine mode (sub-micron) aerosol optical events were observed during the summer of 2007 at the High Arctic atmospheric observatory (PEARL) located at Eureka, Nunavut, Canada. Half of these events could be traced to forest fires in southern and eastern Russia and the Northwest Territories of Canada. The most notable findings were that (a) a combination of ground-based measurements (passive sunphotometry, high spectral resolution lidar) could be employed to determine that weak (near sub-visual) fine mode events had occurred, and (b) this data combined with remote sensing imagery products (MODIS, OMI-AI, FLAMBE fire sources), Fourier transform spectroscopy and back trajectories could be employed to identify the smoke events.

  10. Progress towards sub-micron hard x-ray imaging using elliptically bent mirrors

    SciTech Connect

    MacDowell, A.A.; Celestre, R.; Chang, C.H.; Frank, K.

    1997-07-01

    Of the many methods used to focus x-rays, the use of mirrors with an elliptical curvature shows the most promise of providing a sub-micron white light focus. Our group has been developing the techniques of controlled bending of mirror substrates in order to produce the desired elliptical shape. We have been successful in producing surfaces with the required microradian slope error tolerances. Details of the bending techniques used, results from laboratory slope error measurements using a Long Trace Profiler (LTP) and data from the measurement of focus shape using knife edge and imaging methods using x-rays in the 5-12 KeV energy range are presented. The development of a white light focusing opens many possibilities in diffraction and spectroscopic studies.

  11. STARR: Stepper Test Alignment Resolution Reticle For The Lithographic Characterization Of A Sub-Micron Stepper

    NASA Astrophysics Data System (ADS)

    Hardin, Robert P.; Gulden, Mark P.

    1986-08-01

    This paper describes the design and implementation of a custom reticle developed as part of a sub-micron stepper evaluation program. The 5X reticle was designed so that all major commercially available steppers could be directly compared. It has a unique arrangement of optical and electrical registration test structures allowing for three levels of processing which provides a true measure of the registration capabilities of a system. The reticle has a number of structures which can be used to evaluate the imaging quality of a stepper system. These include a "Focus Star" structure designed to allow easy evaluation of resolution, focus, and astigmatism, a defect structure to measure the printability of commonly seen reticle defects, and L-bar patterns. The remainder of the reticle is intended for use in analyzing other lithographic problems such as proximity effects, substrate induced reflections, step coverage, and critical dimension control.

  12. An all-optical modulation method in sub-micron scale

    PubMed Central

    Yang, Longzhi; Pei, Chongyang; Shen, Ao; Zhao, Changyun; Li, Yan; Li, Xia; Yu, Hui; Li, Yubo; Jiang, Xiaoqing; Yang, Jianyi

    2015-01-01

    We report a theoretical study showing that by utilizing the illumination of an external laser, the Surface Plasmon Polaritons (SPP) signals on the graphene sheet can be modulated in the sub-micron scale. The SPP wave can propagate along the graphene in the middle infrared range when the graphene is properly doped. Graphene's carrier density can be modified by a visible laser when the graphene sheet is exfoliated on the hydrophilic SiO2/Si substrate, which yields an all-optical way to control the graphene's doping level. Consequently, the external laser beam can control the propagation of the graphene SPP between the ON and OFF status. This all-optical modulation effect is still obvious when the spot size of the external laser is reduced to 400 nm while the modulation depth is as high as 114.7 dB/μm. PMID:25777581

  13. Infrared Response of Sub-Micron-Scale Structures of Polyoxymethylene: Surface Polaritons in Polymers.

    PubMed

    Nagai, Naoto; Okawara, Makoto; Kijima, Yuta

    2016-08-01

    An investigation of the infrared (IR) spectra of polyoxymethylene (POM) mold plates was undertaken to determine the sub-micron-scale morphology and molecular orientation. The nest-structured cells concerned with the orientation were observed from scanning electron microscope (SEM) measurements with the aid of Raman spectroscopy. The intensity of the anomalous IR reflectance peak of the C-O stretching A2 mode depends on the widths of the POM layers in the SEM image along the orientation direction. The results suggest that the spectral features originate from the Berreman effect of the bulk polaritons and the radiative surface polaritons. Moreover, the IR spectra of certain treated samples suggest that enhancement of the electromagnetic fields from the gap modes and transition dipole-dipole coupling influence the spectral shapes. PMID:27469531

  14. Realization of sub-micron radius of curvature measurement in vertical interferometer workstation

    NASA Astrophysics Data System (ADS)

    Miao, Erlong; Wang, Rudong; Zhang, Wei; Peng, Shijun

    2014-09-01

    Radius of curvature (ROC) is one of the key parameters for optical elements and it is especially important for high quality optical system, in which the computer-aided integration is wildly used. ROC is one of the main input parameters and its measurement accuracy is a premise for high quality integration. In this paper, sub-micron ROC measurements are realized in a vertical interference workstation based on Fizeau interferometer. The error sources and uncertainty of the system are analyzed. Experiment results based on samples with difference ROC are presented and in accordance with the analysis. At last, a ROC comparing tests between the system and a three-coordinates measuring machine (CMM) are performed on a SiC ball to certify the workstation's measurement uncertainty.

  15. An all-optical modulation method in sub-micron scale.

    PubMed

    Yang, Longzhi; Pei, Chongyang; Shen, Ao; Zhao, Changyun; Li, Yan; Li, Xia; Yu, Hui; Li, Yubo; Jiang, Xiaoqing; Yang, Jianyi

    2015-01-01

    We report a theoretical study showing that by utilizing the illumination of an external laser, the Surface Plasmon Polaritons (SPP) signals on the graphene sheet can be modulated in the sub-micron scale. The SPP wave can propagate along the graphene in the middle infrared range when the graphene is properly doped. Graphene's carrier density can be modified by a visible laser when the graphene sheet is exfoliated on the hydrophilic SiO2/Si substrate, which yields an all-optical way to control the graphene's doping level. Consequently, the external laser beam can control the propagation of the graphene SPP between the ON and OFF status. This all-optical modulation effect is still obvious when the spot size of the external laser is reduced to 400 nm while the modulation depth is as high as 114.7 dB/μm. PMID:25777581

  16. Acoustic Emission Patterns and the Transition to Ductility in Sub-Micron Scale Laboratory Earthquakes

    NASA Astrophysics Data System (ADS)

    Ghaffari, H.; Xia, K.; Young, R.

    2013-12-01

    We report observation of a transition from the brittle to ductile regime in precursor events from different rock materials (Granite, Sandstone, Basalt, and Gypsum) and Polymers (PMMA, PTFE and CR-39). Acoustic emission patterns associated with sub-micron scale laboratory earthquakes are mapped into network parameter spaces (functional damage networks). The sub-classes hold nearly constant timescales, indicating dependency of the sub-phases on the mechanism governing the previous evolutionary phase, i.e., deformation and failure of asperities. Based on our findings, we propose that the signature of the non-linear elastic zone around a crack tip is mapped into the details of the evolutionary phases, supporting the formation of a strongly weak zone in the vicinity of crack tips. Moreover, we recognize sub-micron to micron ruptures with signatures of 'stiffening' in the deformation phase of acoustic-waveforms. We propose that the latter rupture fronts carry critical rupture extensions, including possible dislocations faster than the shear wave speed. Using 'template super-shear waveforms' and their network characteristics, we show that the acoustic emission signals are possible super-shear or intersonic events. Ref. [1] Ghaffari, H. O., and R. P. Young. "Acoustic-Friction Networks and the Evolution of Precursor Rupture Fronts in Laboratory Earthquakes." Nature Scientific reports 3 (2013). [2] Xia, Kaiwen, Ares J. Rosakis, and Hiroo Kanamori. "Laboratory earthquakes: The sub-Rayleigh-to-supershear rupture transition." Science 303.5665 (2004): 1859-1861. [3] Mello, M., et al. "Identifying the unique ground motion signatures of supershear earthquakes: Theory and experiments." Tectonophysics 493.3 (2010): 297-326. [4] Gumbsch, Peter, and Huajian Gao. "Dislocations faster than the speed of sound." Science 283.5404 (1999): 965-968. [5] Livne, Ariel, et al. "The near-tip fields of fast cracks." Science 327.5971 (2010): 1359-1363. [6] Rycroft, Chris H., and Eran Bouchbinder

  17. Spectral bluing on 101955 Bennu and implications for dynamics of sub micron regolith grains on asteroids

    NASA Astrophysics Data System (ADS)

    Brown, Adrian J.

    2015-11-01

    C and B class asteroids (including 101955 Bennu, the destination of the OSIRIS REx mission) display spectral bluing in the visible (Lantz et al. 2013). This spectral bluing effect has been found to be temporally variable on Bennu (Binzel et al. 2015). Binzel et al. suggested this is due to a fining of the ~45 micron grain size fraction, which causes spectral reddening. This finer grain size of the ~45 micron fraction may be associated with regolith migration during formation of Bennu's equatorial ridge.In Brown (2014) the effect of grain size and optical index on the albedo of small conservative and absorbing particles as a function of wavelength was examined. The conditions necessary for maximization of spectral bluing effects in real-world situations were identified.The spectral bluing to be discussed in this presentation was present in the Lantz et al. spectra, but not the Binzel et al. spectra, suggesting that in addition to finer grain ~45 micron material, a decrease in the sub micron grain sized fraction has taken place as Bennu's sub-Earth latitude changed between these observations. Observations of this effect may provide the strongest test yet for cohesive regolith models (e.g. Rositis et al. 2014).In this presentation, I will discuss: 1.) the evidence for spectral bluing on 101955 Bennu (in particular) and other bodies in our solar system and 2.) the implications of how the OVIRS instrument on OSIRIS-REx may be used to determine the spatial variability of this spectral feature on Bennu and 3.) the potential for OVIRS to augment our understanding of the dynamics of sub micron material on asteroids.Refs:Binzel, R. P. et al. "Spectral slope variations for OSIRIS-REx target Asteroid (101955) Bennu: Possible evidence for a fine-grained regolith equatorial ridge" Icarus 256 (2015), 22-29Brown, Adrian J. “Spectral Bluing Induced by Small Particles under the Mie and Rayleigh Regimes.” Icarus 239 (2014): 85-95.Lantz, C., et al. “Evidence for the Effects of

  18. A wet chemistry approach to sub-micron, removable flip chip interconnects.

    SciTech Connect

    Rowen, Adam M.; Barker, Joy M.; Gillen, J. Rusty; Orendorff, Christopher J.; Arrington, Christian L.; Yelton, William Graham

    2008-08-01

    Higher performance is the main driver in the integrated circuit (IC) market, but along with added function comes the cost of increased input/output connections and larger die sizes. Space saving approaches aimed at solving these challenges includes two technologies; 3D stacking (3D-ICs) and flip chip assemblies. Emerging ICs require sub-micron scale interconnects which include vias for 3D-ICs and bump bonds for flip chips. Photolithographic techniques are commonly used to prepare templates followed by metal vapor deposition to create flip chip bump bonds. Both the lithography step and the metal properties required for bump bonding contribute to limiting this approach to a minimum bump size of -10 ?m. Here, we present a wet chemistry approach to fabricating uniform bump bonds of tunable size and height down to the nanoscale. Nanosphere lithography (NSL), a soft lithographic technique, is used to create a bump bond template or mask for nanoscale bumps. Electrochemical deposition is also used through photoresist templates to create uniform bump bonds across large area wafers or dies. This template approach affords bumps with tunable diameters from 100s of nanometers to microns (allowing for tunable interconnect pitch and via diameters) while the use of constant current electroplating gives uniform bump height over large areas (>1 cm{sup 2}).

  19. Measuring Sub-micron Size Fractionated Particulate Matter on Aluminum Impactor Disks

    SciTech Connect

    Buchholz, B A; Zermeno, P; Hwang, H; Young, T M

    2009-07-28

    Sub-micron sized airborne particulate matter is not collected well on regular quartz or glass fiber filter papers. We used a micro-orifice uniform deposit impactor (MOUDI) to size fractionate particulate matter (PM) into six size fractions and deposit it on specially designed high purity thin aluminum disks. The MOUDI separated PM into fractions 56-100 nm, 100-180 nm, 180-320 nm, 320-560 nm, 560-1000 nm, and 1000-1800 nm. Since MOUDI have low flow rates, it takes several days to collect sufficient carbon on 47 mm foil disks. The small carbon mass (20-200 microgram C) and large aluminum substrate ({approx}25 mg Al) presents several challenges to production of graphite targets for accelerator mass spectrometry (AMS) analysis. The Al foil consumes large amounts of oxygen as it is heated and tends to melt into quartz combustion tubes, causing gas leaks. We describe sample processing techniques to reliably produce graphitic targets for {sup 14}C-AMS analysis of PM deposited on Al impact foils.

  20. Local structure of human hair spatially resolved by sub-micron X-ray beam

    NASA Astrophysics Data System (ADS)

    Stanić, Vesna; Bettini, Jefferson; Montoro, Fabiano Emmanuel; Stein, Aaron; Evans-Lutterodt, Kenneth

    2015-11-01

    Human hair has three main regions, the medulla, the cortex, and the cuticle. An existing model for the cortex suggests that the α-keratin- based intermediate filaments (IFs) align with the hair’s axis, but are orientationally disordered in-plane. We found that there is a new region in the cortex near the cuticle’s boundary in which the IFs are aligned with the hair’s axis, but additionally, they are orientationally ordered in-plane due to the presence of the cuticle/hair boundary. Further into the cortex, the IF arrangement becomes disordered, eventually losing all in-plane orientation. We also find that in the cuticle, a key diffraction feature is absent, indicating the presence of the β-keratin rather than that of the α-keratin phase. This is direct structural evidence that the cuticle contains β-keratin sheets. This work highlights the importance of using a sub-micron x-ray beam to unravel the structures of poorly ordered, multi-phase systems.

  1. Detection, imaging, and kinetics of sub-micron organelles of chondrocytes by multiple beam interference microscopy

    NASA Astrophysics Data System (ADS)

    Joshi, Narahari V.; Medina, Honorio; Barboza, J. M.; Colantuoni, Gladys; Quintero, Maritza

    2004-07-01

    Chondrocytes, obtained from testosterone treated human articular cartilage, were examined by a recently developed Multiple Beam Interference Microscopy (MBIM) attached to a confocal set up, Video-enhanced differential interference microphotography and also by cinematography. In the MBIM, the intensity of the transmitted pattern is given by the Airy function which increases the contrast dramatically as the coefficient of the reflectance of the parallel plates increases. Moreover, in this configuration, the beam passes several times through a specific organelle and increases its optical path difference both because of the increase in the trajectory and refractive index (high density) of the organelle. The improved contrast enhances the resolving power of the system and makes visible several structural details of sub micron dimensions like nucleolus, retraction fibers, podia, etc. which are not possible to reveal with such a clarity by conventional techniques such as bright field, phase contrast or DIC. This technique permits to detect the oscillatory and rotational motions of unstained cilia for the first time. The frequency of oscillations was found to be 0.8 Hz.

  2. Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics

    PubMed Central

    Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Yun Jaung, Jae; Kim, Yong-Hoon; Kyu Park, Sung

    2015-01-01

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics. PMID:26411932

  3. Block copolymer stabilized nonaqueous biocompatible sub-micron emulsions for topical applications.

    PubMed

    Atanase, Leonard Ionut; Riess, Gérard

    2013-05-20

    Polyethylene glycol (PEG) 400/Miglyol 812 non-aqueous sub-micron emulsions were developed due to the fact that they are of interest for the design of drug-loaded biocompatible topical formulations. These types of emulsions were favourably stabilized by poly (2-vinylpyridine)-b-poly (butadiene) (P2VP-b-PBut) copolymer with DPBut>DP2VP, each of these sequences being well-adapted to the solubility parameters of PEG 400 and Miglyol 812, respectively. This type of block copolymers, which might limit the Ostwald ripening, appeared to be more efficient stabilizers than low molecular weight non-ionic surfactants. The emulsion characteristics, such as particle size, stability and viscosity at different shear rates were determined as a function of the phase ratio, the copolymer concentration and storage time. It was further shown that Acyclovir, as a model drug of low water solubility, could be incorporated into the PEG 400 dispersed phase, with no significant modification of the initial emulsion characteristics. PMID:23566926

  4. Local structure of human hair spatially resolved by sub-micron X-ray beam.

    PubMed

    Stanić, Vesna; Bettini, Jefferson; Montoro, Fabiano Emmanuel; Stein, Aaron; Evans-Lutterodt, Kenneth

    2015-11-30

    Human hair has three main regions, the medulla, the cortex, and the cuticle. An existing model for the cortex suggests that the α-keratin- based intermediate filaments (IFs) align with the hair's axis, but are orientationally disordered in-plane. We found that there is a new region in the cortex near the cuticle's boundary in which the IFs are aligned with the hair's axis, but additionally, they are orientationally ordered in-plane due to the presence of the cuticle/hair boundary. Further into the cortex, the IF arrangement becomes disordered, eventually losing all in-plane orientation. We also find that in the cuticle, a key diffraction feature is absent, indicating the presence of the β-keratin rather than that of the α-keratin phase. This is direct structural evidence that the cuticle contains β-keratin sheets. This work highlights the importance of using a sub-micron x-ray beam to unravel the structures of poorly ordered, multi-phase systems.

  5. Laser smoothing of sub-micron grooves in hydroxyl-rich fused silica

    SciTech Connect

    Shen, N; Matthews, M J; Fair, J E; Britten, J A; Nguyen, H T; Cooke, D; Elhadj, S; Yang, S T

    2009-10-30

    Nano- to micrometer-sized surface defects on UV-grade fused silica surfaces are known to be effectively smoothed through the use of high-temperature localized CO{sub 2} laser heating, thereby enhancing optical properties. However, the details of the mass transport and the effect of hydroxyl content on the laser smoothing of defective silica at submicron length scales is still not completely understood. In this study, we examine the morphological evolution of sub-micron, dry-etched periodic surface structures on type II and type III SiO{sub 2} substrates under 10.6 {micro}m CO{sub 2} laser irradiation using atomic force microscopy (AFM). In-situ thermal imaging was used to map the transient temperature field across the heated region, allowing assessment of the T-dependent mass transport mechanisms under different laser-heating conditions. Computational fluid dynamics simulations correlated well with experimental results, and showed that for large effective capillary numbers (N{sub c} > 2), surface diffusion is negligible and smoothing is dictated by capillary action, despite the relatively small spatial scales studied here. Extracted viscosity values over 1700-2000K were higher than the predicted bulk values, but were consistent with the surface depletion of OH groups, which was confirmed using confocal Raman microscopy.

  6. Sub-micron Hard X-ray Fluorescence Imaging of Synthetic Elements

    PubMed Central

    Jensen, Mark P.; Aryal, Baikuntha P.; Gorman-Lewis, Drew; Paunesku, Tatjana; Lai, Barry; Vogt, Stefan; Woloschak, Gayle E.

    2013-01-01

    Synchrotron-based X-ray fluorescence microscopy (SXFM) using hard X-rays focused into sub-micron spots is a powerful technique for elemental quantification and mapping, as well as microspectroscopic measurement such as μ-XANES (X-ray absorption near edge structure). We have used SXFM to image and simultaneously quantify the transuranic element plutonium at the L3 or L2 edge as well as lighter biologically essential elements in individual rat pheochromocytoma (PC12) cells after exposure to the long-lived plutonium isotope 242Pu. Elemental maps reveal that plutonium localizes principally in the cytoplasm of the cells and avoids the cell nucleus, which is marked by the highest concentrations of phosphorus and zinc, under the conditions of our experiments. The minimum detection limit under typical acquisition conditions for an average 202 μm2 cell is 1.4 fg Pu/cell or 2.9 × 10−20 moles Pu/μm2, which is similar to the detection limit of K-edge SXFM of transition metals at 10 keV. Copper electron microscopy grids were used to avoid interference from gold X-ray emissions, but traces of strontium present in naturally occurring calcium can still interfere with plutonium detection using its Lα X-ray emission. PMID:22444530

  7. Scalable sub-micron patterning of organic materials toward high density soft electronics

    DOE PAGES

    Kim, Jaekyun; Kim, Myung -Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong -Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; et al

    2015-09-28

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. Inmore » this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. As a result, the successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.« less

  8. Scalable sub-micron patterning of organic materials toward high density soft electronics

    SciTech Connect

    Kim, Jaekyun; Kim, Myung -Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong -Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun -Hi; Noh, Yong -Young; Yun Jaung, Jae; Kim, Yong -Hoon; Kyu Park, Sung

    2015-09-28

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. As a result, the successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.

  9. Conformational transitions of cytochrome c in sub-micron-sized capsules at air/buffer interface.

    PubMed

    Jaganathan, Maheshkumar; Dhathathreyan, Aruna

    2014-09-30

    This work presents the design of sub-micron-sized capsules of Cytochrome c (cyt c) in the range 300-350 nm and the conformational transitions of the protein that occur when the films of these capsules spread at the air/buffer interface are subjected to repeated compression-expansion cycles. Steady state fluorescence, time-resolved fluorescence, and circular dichroic (CD) spectra have been used to study the highly compact native conformation (70% helicity) of the protein in the capsules and its stability has been analyzed using cyclic voltammetry. The capsules have been characterized using zeta sizer and high resolution transmission electron microscopy (HRTEM). Surface concentration-surface pressure (Γ-π) isotherms of the films of the capsules spread at air/buffer interface following compression-expansion show destabilizing effect on cyt c. FTIR and CD spectra of these films skimmed from the surface show that the protein transitions gradually from its native helical to an anomalous beta sheet aggregated state. This results from a competition between stabilizing hydrated polar segments of the protein in the capsule and destabilizing nonspecific hydrophobic interactions arising at the air/buffer interface. This 2D model could further our understanding of the spatial and temporal roles of proteins in confined spaces and also in the design of new drug delivery vehicles using proteins.

  10. Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics.

    PubMed

    Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Jaung, Jae Yun; Kim, Yong-Hoon; Park, Sung Kyu

    2015-09-28

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.

  11. An automated injection system for sub-micron sized channels used in shear-driven-chromatography.

    PubMed

    De Malsche, Wim; Clicq, David; Eghbali, Hamed; Fekete, Veronika; Gardeniers, Han; Desmet, Gert

    2006-10-01

    This paper describes a method to automatically and reproducibly inject sharply delimited sample plugs in the shallow (i.e., sub-micron) channels typically used in shear driven chromatography. The formation of asymmetric plugs, which typically occurs during loading of the sample in wide channels, is circumvented by etching a slit in the middle of the channel that is connected to a micro-well and a vacuum system with syringes for the supply of both the analyte and the mobile phase. The design of the injection slit was supported by a series of CFD simulations to optimize its shape and that of the corresponding injection well. The system was intensively tested experimentally and showed good reproducibility, both for the width and the area of the injected peaks (relative standard deviations are max. 4 and 6%, respectively). The concentration of the injected plug was found to be approximately 80% of the original sample concentration. It was also observed that with the current setup the lower limit of the peak width was about 120 microm. This is a consequence of the fact that the peak width originating from the convection filling step becomes negligible to the contribution of diffusion during the filling and flushing time. Being fully automated and perfectly closed, the presently proposed injection system also paves the way to integrate other functionalities in shear driven chromatography, i.e. gradient elution and parallelization. PMID:17102846

  12. Generation of a quasi-monoergetic proton beam from laser-irradiated sub-micron droplets

    SciTech Connect

    Ter-Avetisyan, S.; Ramakrishna, B.; Prasad, R.; Borghesi, M.; Nickles, P. V.; Steinke, S.; Schnuerer, M.; Popov, K. I.; Ramunno, L.; Zmitrenko, N. V.; Bychenkov, V. Yu.

    2012-07-15

    Proton bursts with a narrow spectrum at an energy of (2.8 {+-} 0.3 MeV) are accelerated from sub-micron water spray droplets irradiated by high-intensity ({approx}5 Multiplication-Sign 10{sup 19} W/cm{sup 2}), high-contrast ({approx}10{sup 10}), ultra-short (40 fs) laser pulses. The acceleration is preferentially in the laser propagation direction. The explosion dynamics is governed by a residual ps-scale laser pulse pedestal which 'mildly' preheats the droplet and changes its density profile before the arrival of the high intensity laser pulse peak. As a result, the energetic electrons extracted from the modified target by the high-intensity part of the laser pulse establish an anisotropic electrostatic field which results in anisotropic Coulomb explosion and proton acceleration predominantly in the forward direction. Hydrodynamic simulations of the target pre-expansion and 3D particle-in-cell simulations of the measured energy and anisotropy of the proton emission have confirmed the proposed acceleration scenario.

  13. Proton acceleration from high-contrast short pulse lasers interacting with sub-micron thin foils

    NASA Astrophysics Data System (ADS)

    Petrov, G. M.; McGuffey, C.; Thomas, A. G. R.; Krushelnick, K.; Beg, F. N.

    2016-02-01

    A theoretical study complemented with published experimental data of proton acceleration from sub-micron (thickness < 1 μm) foils irradiated by ultra-high contrast ( >1010 ) short pulse lasers is presented. The underlying physics issues pertinent to proton acceleration are addressed using two-dimensional particle-in-cell simulations. For laser energy ɛ≤4 J (intensity I ≤5 ×1020 W/cm 2 ), simulation predictions agree with experimental data, both exhibiting scaling superior to Target Normal Sheath Acceleration's model. Anomalous behavior was observed for ɛ>4 J ( I >5 ×1020 W/cm 2 ), for which the measured maximum proton energies were much lower than predicted by scaling and these simulations. This unexpected behavior could not be explained within the frame of the model, and we conjecture that pre-pulses preceding the main pulse by picoseconds may be responsible. If technological issues can be resolved, energetic proton beams could be generated for a wide range of applications such as nuclear physics, radiography, and medical science.

  14. Chemical Mapping of Proterozoic Organic Matter at Sub-Micron Spatial Resolution

    NASA Technical Reports Server (NTRS)

    Oehler, Dorothy Z.; Robert, Francois; Mostefaoui, Smail; Meibom, Anders; Selo, Madeleine; McKay, David S.

    2006-01-01

    We have used a NanoSIMS ion microprobe to map sub-micron-scale distributions of carbon, nitrogen, sulfur, silicon, and oxygen in organic microfossils and laminae from the approximately 0.85 Ga Bitter Springs Formation of Australia. The data provide clues about the original chemistry of the microfossils, the silicification process, and biosignatures of specific microorganisms and microbial communities. Chemical maps of fossil unicells and filaments reveal distinct wall-and sheath-like structures enriched in C, N and S, consistent with their accepted biological origin. Surprisingly, organic laminae, previously considered to be amorphous, also exhibit filamentous and apparently compressed spheroidal structures defined by strong enrichments in C, N and S. By analogy to data from the well-preserved microfossils, these structures are interpreted as being of biological origin, most likely representing densely packed remnants of microbial mats. Because the preponderance of organic matter in Precambrian sediments is similarly "amorphous," our findings open a large body of generally neglected material to in situ structural, chemical, and isotopic study. Our results also offer new criteria for assessing biogenicity of problematic kerogenous materials and thus can be applied to assessments of poorly preserved or fragmentary organic residues in early Archean sediments and any that might occur in meteorites or other extraterrestrial samples.

  15. Analysis of sub-micron mineral matter in coal via scanning transmission electron microscopy

    SciTech Connect

    Allen, R.M.; VanderSande, J.B.

    1982-01-01

    The Scanning Transmission Electron Microscope (STEM) is an instrument well suited for the characterization of the sub-micron sized mineral matter in coal and can also be used to identify inorganic elements atomically bound in the organic coal matrix. For the three coals studied, a random survey was taken of mineral inclusions < 100nm in mean diameter observed within coal particles in powdered coal samples. The results indicate that the predominant mineral species making up these inclusions differ from those species predominating in mineral particles at larger size ranges. Two of the coals examined showed characteristic matrix signatures of inorganic elements which were observed in greater than or equal to 90% of the matrix areas examined. The third coal did not. All three coals exhibited various elements with Z greater than or equal to 11, most notably S, which were only irregularly associated with the matrix signal (i.e., found <50% of the time). For all three coals, the predominant mineral species observed in the less than or equal to 100nm size range would not be predicted from the results of the chemical analyses of the high temperature ash of the coals. None of the major elements (Z greater than or equal to 11) observed (with the exception of sulfur in the Ba, s-rich particles) constitutes more than 10% of the HTA for the respective coals; indeed, Ba, in the lignite, Ti in the bituminous coal, and Ca in the semianthracite all make up less than 1% of the respective ashes. Encountering these elements as the major constituents in the predominant mineral species observed in a random sampling of particles <100nm in diameter indicates that the distribution of inorganic elements must not be uniform over all size ranges of mineral inclusions. In particular, for all three coals, the predominant mineral species observed in the <100nm size range must therefore differ from those species predominating at larger size ranges.

  16. Characterization of phosphorus in organisms at sub-micron resolution using X-ray fluorescence spectromicroscopy.

    SciTech Connect

    Diaz, J.; Ingall, E; Vogt, S; Paterson, D; DeJonge, M; Rao, C; Brandes, J

    2009-01-01

    X-ray spectromicroscopy (combined X-ray spectroscopy and microscopy) is uniquely capable of determining sub-micron scale elemental content and chemical speciation in minimally-prepared particulate samples. The high spatial resolutions achievable with this technique have enabled the close examination of important microscale processes relevant to the cycling of biogeochemically important elements. Here, we demonstrate the value of X-ray microscopy to environmental and biological research by examining the phosphorus and metal chemistry of complete individual cells from the algal genera Chlamydomonas sp. and Chlorella sp. X-ray analysis revealed that both genera store substantial intracellular phosphorus as distinct, heterogeneously distributed granules whose X-ray fluorescence spectra are consistent with that of polyphosphate. Polyphosphate inclusions ranged in size from 0.3-1.4 {micro}m in diameter and exhibited a nonspecies-specific average phosphorus concentration of 6.87 {+-} 1.86 {micro}g cm{sup -2}, which was significantly higher than the average concentration of phosphorus measured in the total cell, at 3.14 {+-} 0.98 {micro}g cm{sup -2} (95% confidence). Polyphosphate was consistently associated with calcium and iron, exhibiting average P:cation molar ratios of 8.31 {+-} 2.00 and 108 {+-} 34, respectively (95% confidence). In some cells, polyphosphate was also associated with potassium, zinc, manganese, and titanium. Based on our results, X-ray spectromicroscopy can provide high-resolution elemental data on minimally prepared, unsectioned cells that are unattainable through alternative microscopic methods and conventional bulk chemical techniques currently available in many fields of marine chemistry.

  17. Sources and characteristics of sub-micron aerosols in the San Joaquin Valley, CA

    NASA Astrophysics Data System (ADS)

    Bahreini, R.; Middlebrook, A. M.; Brioude, J.; Brock, C. A.; de Gouw, J. A.; Hall, K.; Holloway, J. S.; Neuman, J.; Nowak, J. B.; Pollack, I. B.; Ryerson, T. B.; Warneke, C.; Parrish, D. D.

    2010-12-01

    The NOAA WP-3D aircraft performed several flights in the San Joaquin Valley (SJV), California during the CalNex-2010 (California Research at the Nexus of Air Quality and Climate Change) field project in May-June 2010. SJV is generally a rural valley, with a high concentration of feedlots and agricultural sites as well as urbanized centers such as Fresno and Bakersfield. Preliminary results on size-resolved chemical composition of sub-micron aerosols measured using a compact time-of-flight aerosol mass spectrometer, measurements of trace gases affecting secondary production of aerosols, and FLEXPART back trajectory analyses are presented in order to identify sources of aerosols transported to or produced in the valley. Observed enhancements in various trace gases and aerosol species indicate a mixed influence from urban, industrial, and animal feedlots in the SJV. Three distinct observations suggest a complex transport pattern of pollutants with different origins to and within the valley: 1) CO and NOx mixing ratios were prominent downwind of the urban areas in the valley; 2) SO2, aerosol organics and sulfate were higher closer to the foothills of the Sierra Nevada Mountains on the east of the valley; 3) high concentration of aerosol phase ammonium and nitrate were observed in NH3-rich air masses, directly downwind of the feedlots in the central part of the valley. Aerosol enhancements in each of these air mass categories relative to the background determine the relative contribution and significance of different sources to aerosol loadings in the valley. Differences in VOC measurements and meteorology will be explored to investigate the observed variation in characteristics of organics on different days.

  18. Investigation of dislocation behavior in micron and sub-micron thin films

    NASA Astrophysics Data System (ADS)

    Hunter, Abigail

    Plastic deformation in crystalline materials is mediated by dislocation motion and their interaction with defects, such as second phase particles, dislocations, grain boundaries and voids. In addition, grain boundaries, free and passivated surfaces have a significant impact on the evolution of dislocations and their intricate structures. In polycrystalline materials, the influence of dislocation motion and interactions results in unique mechanical properties, such as high yield stress and fracture strength and a dependency on grain size. It is observed that for an average grain size in the micron and sub-micron regime, the yield stress increases as the grain size decreases following a power law. This size effect is known as Hall Petch effect. A reliable computational model that describes the mechanical response and failure mechanisms of micron and sub-micron scale devices should incorporate these size effects. A three-dimensional phase field dislocation dynamics model (3D PFDD) is developed. This is a dislocation based plasticity model that accounts for the motion and interactions of individual dislocations with material defects and interfaces, such as obstacles, and grain boundaries. This model is a valuable and efficient research tool that will help to understand plastic deformation on the mesoscopic level, bridging the gap between microscopic and macroscopic studies. For the research presented here, this model is used specifically to understand and simulate dislocation behavior in fcc (face-centered cubic) metal thin films, similar to those used in micro-electro-mechanical systems (MEMS). Incorporating microstructure, such as grain boundaries, is key to accurately predicting deformation behavior in any system. Plastic deformation is affected by both the thickness of the film layers and by the resolution of the film's internal microstructure. In MEMS devices and components that are generally on the micron scale (hundreds of microns in size), the internal

  19. Sub-micron silica diaphragm-based fiber-tip Fabry-Perot interferometer for pressure measurement.

    PubMed

    Liao, Changrui; Liu, Shen; Xu, Lei; Wang, Chao; Wang, Yiping; Li, Zhengyong; Wang, Qiao; Wang, D N

    2014-05-15

    We demonstrate a sub-micron silica diaphragm-based fiber-tip Fabry-Perot interferometer for pressure sensing applications. The thinnest silica diaphragm, with a thickness of ∼320  nm, has been achieved by use of an improved electrical arc discharge technique. Such a sub-micron silica diaphragm breaks the sensitivity limitation imposed by traditional all-silica Fabry-Perot interferometric pressure sensors and, as a result, a high pressure sensitivity of ∼1036  pm/MPa at 1550 nm and a low temperature cross-sensitivity of ∼960  Pa/°C are achieved when a silica diaphragm of ∼500  nm in thickness is used. Moreover, the all-silica spherical structure enhanced the mechanical strength of the micro-cavity sensor, making it suitable for high sensitivity pressure sensing in harsh environments. PMID:24978213

  20. Sub-micron resolution high-speed spectral domain optical coherence tomography in quality inspection for printed electronics

    NASA Astrophysics Data System (ADS)

    Czajkowski, J.; Lauri, J.; Sliz, R.; Fält, P.; Fabritius, T.; Myllylä, R.; Cense, B.

    2012-04-01

    We present the use of sub-micron resolution optical coherence tomography (OCT) in quality inspection for printed electronics. The device used in the study is based on a supercontinuum light source, Michelson interferometer and high-speed spectrometer. The spectrometer in the presented spectral-domain optical coherence tomography setup (SD-OCT) is centered at 600 nm and covers a 400 nm wide spectral region ranging from 400 nm to 800 nm. Spectra were acquired at a continuous rate of 140,000 per second. The full width at half maximum of the point spread function obtained from a Parylene C sample was 0:98 m. In addition to Parylene C layers, the applicability of sub-micron SD-OCT in printed electronics was studied using PET and epoxy covered solar cell, a printed RFID antenna and a screen-printed battery electrode. A commercial SD-OCT system was used for reference measurements.

  1. Sub-micron LiCoO 2 manufactured in a single synthetic step using eutectic self-mixing method

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Woo; Lee, Seung-Goo; Han, Kyoo-Seung

    Sub-micron LiCoO 2 as a cathode material for lithium rechargeable battery with high rates is easily and economically prepared using eutectic self-mixing method without any artificial mixing procedures of reactants and ultra-miniaturization of products. While the micro-sized LiCoO 2 exhibits the discharge capacities of 134.8 mAh g -1 at 0.1 C and 118.6 mAh g -1 at 5.0 C, those of the sub-micron LiCoO 2 are 137.2 mAh g -1 at 0.1 C and 131.7 mAh g -1 at 5.0 C.

  2. Sub-micron silica diaphragm-based fiber-tip Fabry-Perot interferometer for pressure measurement.

    PubMed

    Liao, Changrui; Liu, Shen; Xu, Lei; Wang, Chao; Wang, Yiping; Li, Zhengyong; Wang, Qiao; Wang, D N

    2014-05-15

    We demonstrate a sub-micron silica diaphragm-based fiber-tip Fabry-Perot interferometer for pressure sensing applications. The thinnest silica diaphragm, with a thickness of ∼320  nm, has been achieved by use of an improved electrical arc discharge technique. Such a sub-micron silica diaphragm breaks the sensitivity limitation imposed by traditional all-silica Fabry-Perot interferometric pressure sensors and, as a result, a high pressure sensitivity of ∼1036  pm/MPa at 1550 nm and a low temperature cross-sensitivity of ∼960  Pa/°C are achieved when a silica diaphragm of ∼500  nm in thickness is used. Moreover, the all-silica spherical structure enhanced the mechanical strength of the micro-cavity sensor, making it suitable for high sensitivity pressure sensing in harsh environments.

  3. Fabrication of broadband anti-reflective sub-micron structures using polystyrene sphere lithography on a Si substrate

    NASA Astrophysics Data System (ADS)

    Lee, Yeeu-Chang; Chang, Che-Chun; Chou, Yen-Yu

    2014-02-01

    Anti-reflective coatings are widely used on the surfaces of solar cells to increase the efficiency of photoelectric conversion. Sub-wavelength structures have gradually replaced conventional anti-reflective (AR) thin films due to their broadband AR properties. This paper successfully fabricated structures with a variety of surface morphologies on Si substrate using polystyrene sphere lithography in conjunction with two-step inductive coupling plasma (ICP) and high density plasma (HDP) etching processes. We successfully fabricated various sub-micron structures with heights of 700 nm and above. Experimental results show that the sub-micron pyramidal structure has the best anti-reflection performance with the average reflectance effectively suppressed to below 1% across the spectral range of 300-1200 nm.

  4. A simple and wide-range refractive index measuring approach by using a sub-micron grating

    NASA Astrophysics Data System (ADS)

    Liu, Chun-Wei; Wu, Chun-Che; Lin, Shih-Chieh

    2015-04-01

    This paper presents the design and simulation results of a high-precision low-cost refractometer that demonstrates the main advantage of a wide measurement range (1 ≤ n ≤ 2). The proposed design is based on the diffractive properties of sub-micron gratings and Snell's Law. The precision and uncertainty factors of the proposed system were tested and analyzed, revealing that the proposed refractometer demonstrates a wide measurement range with sensitivity of 10-4.

  5. A simple and wide-range refractive index measuring approach by using a sub-micron grating

    SciTech Connect

    Liu, Chun-Wei; Wu, Chun-Che; Lin, Shih-Chieh

    2015-04-13

    This paper presents the design and simulation results of a high-precision low-cost refractometer that demonstrates the main advantage of a wide measurement range (1 ≤ n ≤ 2). The proposed design is based on the diffractive properties of sub-micron gratings and Snell's Law. The precision and uncertainty factors of the proposed system were tested and analyzed, revealing that the proposed refractometer demonstrates a wide measurement range with sensitivity of 10{sup −4}.

  6. Prescribed 3-D Direct Writing of Suspended Micron/Sub-micron Scale Fiber Structures via a Robotic Dispensing System

    PubMed Central

    Yuan, Hanwen; Cambron, Scott D.; Keynton, Robert S.

    2015-01-01

    A 3-axis dispensing system is utilized to control the initiating and terminating fiber positions and trajectory via the dispensing software. The polymer fiber length and orientation is defined by the spatial positioning of the dispensing system 3-axis stages. The fiber diameter is defined by the prescribed dispense time of the dispensing system valve, the feed rate (the speed at which the stage traverses from an initiating to a terminating position), the gauge diameter of the dispensing tip, the viscosity and surface tension of the polymer solution, and the programmed drawing length. The stage feed rate affects the polymer solution’s evaporation rate and capillary breakup of the filaments. The dispensing system consists of a pneumatic valve controller, a droplet-dispensing valve and a dispensing tip. Characterization of the direct write process to determine the optimum combination of factors leads to repeatedly acquiring the desired range of fiber diameters. The advantage of this robotic dispensing system is the ease of obtaining a precise range of micron/sub-micron fibers onto a desired, programmed location via automated process control. Here, the discussed self-assembled micron/sub-micron scale 3D structures have been employed to fabricate suspended structures to create micron/sub-micron fluidic devices and bioengineered scaffolds. PMID:26132732

  7. 2D-ordered dielectric sub-micron bowls on a metal surface: a useful hybrid plasmonic-photonic structure

    NASA Astrophysics Data System (ADS)

    Lan, Yue; Wang, Shiqiang; Yin, Xianpeng; Liang, Yun; Dong, Hao; Gao, Ning; Li, Jian; Wang, Hui; Li, Guangtao

    2016-07-01

    Recently, it has been demonstrated that the combination of periodic dielectric structures with metallic structures provides an efficient means to yield a synergetic optical response or functionality in the resultant hybrid plasmonic-photonic systems. In this work, a new hybrid plasmonic-photonic structure of 2D-ordered dielectric sub-micron bowls on a flat gold surface was proposed, prepared, and theoretically and experimentally characterized. This hybrid structure supports two types of modes: surface plasmon polaritons bound at the metallic surface and waveguided mode of light confined in the cavity of bowls. Optical responses of this hybrid structure as well as the spatial electric field distribution of each mode are found to be strongly dependent on the structural parameters of this system, and thus could be widely modified on demand. Importantly, compared to the widely studied hybrid systems, namely the flat metallic surface coated with a monolayer array of latex spheres, the waveguided mode with strong field enhancement appearing in the cavities of bowls is more facilely accessible and thus suitable for practical use. For demonstration, a 2D-ordered silica sub-micron bowl array deposited on a flat gold surface was fabricated and used as a regenerable platform for fluorescence enhancement by simply accommodating emitters in bowls. All the simulation and experiment results indicate that the 2D-ordered dielectric sub-micron bowls on a metal surface should be a useful hybrid plasmonic-photonic system with great potential for applications such as sensors or tunable emitting devices if appropriate periods and materials are employed.Recently, it has been demonstrated that the combination of periodic dielectric structures with metallic structures provides an efficient means to yield a synergetic optical response or functionality in the resultant hybrid plasmonic-photonic systems. In this work, a new hybrid plasmonic-photonic structure of 2D-ordered dielectric sub-micron

  8. 2D-ordered dielectric sub-micron bowls on a metal surface: a useful hybrid plasmonic-photonic structure.

    PubMed

    Lan, Yue; Wang, Shiqiang; Yin, Xianpeng; Liang, Yun; Dong, Hao; Gao, Ning; Li, Jian; Wang, Hui; Li, Guangtao

    2016-07-21

    Recently, it has been demonstrated that the combination of periodic dielectric structures with metallic structures provides an efficient means to yield a synergetic optical response or functionality in the resultant hybrid plasmonic-photonic systems. In this work, a new hybrid plasmonic-photonic structure of 2D-ordered dielectric sub-micron bowls on a flat gold surface was proposed, prepared, and theoretically and experimentally characterized. This hybrid structure supports two types of modes: surface plasmon polaritons bound at the metallic surface and waveguided mode of light confined in the cavity of bowls. Optical responses of this hybrid structure as well as the spatial electric field distribution of each mode are found to be strongly dependent on the structural parameters of this system, and thus could be widely modified on demand. Importantly, compared to the widely studied hybrid systems, namely the flat metallic surface coated with a monolayer array of latex spheres, the waveguided mode with strong field enhancement appearing in the cavities of bowls is more facilely accessible and thus suitable for practical use. For demonstration, a 2D-ordered silica sub-micron bowl array deposited on a flat gold surface was fabricated and used as a regenerable platform for fluorescence enhancement by simply accommodating emitters in bowls. All the simulation and experiment results indicate that the 2D-ordered dielectric sub-micron bowls on a metal surface should be a useful hybrid plasmonic-photonic system with great potential for applications such as sensors or tunable emitting devices if appropriate periods and materials are employed.

  9. Thermal conductivities of sub-micron Bi2Te3 films sputtered on anisotropic substrates

    NASA Astrophysics Data System (ADS)

    Yan, Dan; Wu, Ping; Zhang, Shiping; Pei, Yili; Yang, Fan; Wang, Li

    2016-07-01

    Approximately 450 nm thick Bi2Te3 films were deposited on flat Al2O3 substrate and nanochannel alumina (NCA) templates with different pore diameters through radio-frequency magnetron sputtering. The structure and morphology of Bi2Te3 films were investigated by x-ray diffraction and field-emission scanning electron microscopy. Moreover, the thermal conductivities of the films deposited on anisotropic substrates were evaluated by micro-Raman method combined with numerical simulation and optimization conducted by COMSOL Multiphysics. The thermal conductivities of Bi2Te3 films deposited on NCA templates with discontinuous Φ20 and Φ100 nm pores and flat Al2O3 substrate were 0.80, 0.99 and 1.54 Wm‑1 K‑1, respectively. The lower thermal conductivities of Bi2Te3 films deposited on NCA templates are attributed to much smaller grain size, bottom porous layers, and rougher surfaces through analysis.

  10. Sub-micron resolution of localized ion beam induced charge reduction in silicon detectors damaged by heavy ions

    SciTech Connect

    Auden, Elizabeth C.; Pacheco, Jose L.; Bielejec, Edward; Vizkelethy, Gyorgy; Abraham, John B. S.; Doyle, Barney L.

    2015-12-01

    In this study, displacement damage reduces ion beam induced charge (IBIC) through Shockley-Read-Hall recombination. Closely spaced pulses of 200 keV Si++ ions focused in a 40 nm beam spot are used to create damage cascades within 0.25 μm2 areas. Damaged areas are detected through contrast in IBIC signals generated with focused ion beams of 200 keV Si++ ions and 60 keV Li+ ions. IBIC signal reduction can be resolved over sub-micron regions of a silicon detector damaged by as few as 1000 heavy ions.

  11. Sub-micron resolution of localized ion beam induced charge reduction in silicon detectors damaged by heavy ions

    DOE PAGES

    Auden, Elizabeth C.; Pacheco, Jose L.; Bielejec, Edward; Vizkelethy, Gyorgy; Abraham, John B. S.; Doyle, Barney L.

    2015-12-01

    In this study, displacement damage reduces ion beam induced charge (IBIC) through Shockley-Read-Hall recombination. Closely spaced pulses of 200 keV Si++ ions focused in a 40 nm beam spot are used to create damage cascades within 0.25 μm2 areas. Damaged areas are detected through contrast in IBIC signals generated with focused ion beams of 200 keV Si++ ions and 60 keV Li+ ions. IBIC signal reduction can be resolved over sub-micron regions of a silicon detector damaged by as few as 1000 heavy ions.

  12. Sub-micron fracture mechanism in silica-based glass activated by permanent densification from high-strain loading

    DOE PAGES

    Wereszczak, Andrew A.; Waters, Shirley B.; Parten, Randy J.; Pye, L. David

    2016-04-26

    Several silica-based glasses were fractured at high strain energy via drop-weight testing on small specimens. A cylindrical specimen geometry was chosen to promote initially simple, axisymmetric, and uniform compressive loading. The imposed uniaxial compressive strain at impact was sufficiently high to qualitatively cause permanent densification. Produced fragments were collected for postmortem and a fraction of them, for all the silica-based glasses, consistently had distinct sub-micron-sized fractures (~ 300–1000 nm), designated here as “microkernels”, on their surfaces. They would most often appear as a sub-micron pore on the fragment - apparently if the microkernel had popped out as a consequence ofmore » the local crack plane running through it, tensile-strain release, and the associated formation of the fragment it was on. No fractographic evidence was found to show the microkernels were associated with local failure initiation. However, their positioning and habit sometimes suggested they were associated with localized crack branching and that they could have influenced secondary fracturing that occurred during overall crushing and comminution and associated fragment size and shape creation. Furthermore, the size range of these microkernels is much too small to affect structural flexure strength of these glasses for most applications but are of a size and concentration that may affect their ballistic, shock, crush, and comminution responses when permanent densification is concomitantly occurring.« less

  13. Impact of Device Scaling on Deep Sub-micron Transistor Reliability: A Study of Reliability Trends using SRAM

    NASA Technical Reports Server (NTRS)

    White, Mark; Huang, Bing; Qin, Jin; Gur, Zvi; Talmor, Michael; Chen, Yuan; Heidecker, Jason; Nguyen, Duc; Bernstein, Joseph

    2005-01-01

    As microelectronics are scaled in to the deep sub-micron regime, users of advanced technology CMOS, particularly in high-reliability applications, should reassess how scaling effects impact long-term reliability. An experimental based reliability study of industrial grade SRAMs, consisting of three different technology nodes, is proposed to substantiate current acceleration models for temperature and voltage life-stress relationships. This reliability study utilizes step-stress techniques to evaluate memory technologies (0.25mum, 0.15mum, and 0.13mum) embedded in many of today's high-reliability space/aerospace applications. Two acceleration modeling approaches are presented to relate experimental FIT calculations to Mfr's qualification data.

  14. Analysis of functional failure mode of commercial deep sub-micron SRAM induced by total dose irradiation

    NASA Astrophysics Data System (ADS)

    Zheng, Qi-Wen; Cui, Jiang-Wei; Zhou, Hang; Yu, De-Zhao; Yu, Xue-Feng; Lu, Wu; Guo, Qi; Ren, Di-Yuan

    2015-10-01

    Functional failure mode of commercial deep sub-micron static random access memory (SRAM) induced by total dose irradiation is experimentally analyzed and verified by circuit simulation. We extensively characterize the functional failure mode of the device by testing its electrical parameters and function with test patterns covering different functional failure modes. Experimental results reveal that the functional failure mode of the device is a temporary function interruption caused by peripheral circuits being sensitive to the standby current rising. By including radiation-induced threshold shift and off-state leakage current in memory cell transistors, we simulate the influence of radiation on the functionality of the memory cell. Simulation results reveal that the memory cell is tolerant to irradiation due to its high stability, which agrees with our experimental result.

  15. Tracking sub-micron fluorescent particles in three dimensions with a microscope objective under non-design optical conditions

    NASA Astrophysics Data System (ADS)

    Luo, R.; Sun, Y. F.; Peng, X. F.; Yang, X. Y.

    2006-06-01

    A microscope objective designed for air medium has been used under non-design optical conditions to focus an exciting laser beam on sub-micron fluorescent particles with the emitted fluorescence received through a glass layer with a mismatched refractive index. The diffraction pattern with several clear interference fringes generated from the fluorescence emitted from a fluorescent particle changed with the particle's position along the optical axis. A scalar diffraction model developed by Gibson and Lanni (1991 J. Opt. Soc. Am. A 8 1601-13) was used to predict the diffraction patterns for various aberration conditions and to analyse the effects of the coherence properties of the fluorescence on the details of the diffraction pattern. The particle position along the optical axis, i.e. its defocus distance, could be determined based on the characteristic sizes of the particle's diffraction pattern to track the particle in three dimensions.

  16. Dust Diffusion and Settling in the Presence of Collisions: Trapping (sub)micron Grains in the Midplane

    NASA Astrophysics Data System (ADS)

    Krijt, Sebastiaan; Ciesla, Fred J.

    2016-05-01

    In protoplanetary disks, the distribution and abundance of small (sub)micron grains are important for a range of physical and chemical processes. For example, they dominate the optical depth at short wavelengths and their surfaces are the sites of many important chemical reactions, such as the formation of water. Based on their aerodynamical properties (i.e., their strong dynamical coupling with the surrounding gas) it is often assumed that these small grains are well-mixed with the gas. Our goal is to study the vertical (re)distribution of grains taking into account settling, turbulent diffusion, and collisions with other dust grains. Assuming a fragmentation-limited background dust population, we developed a Monte Carlo approach that follows single monomers as they move through a vertical column of gas and become incorporated in different aggregates as they undergo sticking and fragmenting collisions. We find that (sub)micron grains are not necessarily well-mixed vertically, but can become trapped in a thin layer with a scale height that is significantly smaller than that of the gas. This collisional trapping occurs when the timescale for diffusion is comparable to or longer than the collision timescale in the midplane and its effect is strongest when the most massive particles in the size distribution show significant settling. Based on simulations and analytical considerations, we conclude that for typical dust-to-gas ratios and turbulence levels, the collisional trapping of small grains should be a relatively common phenomenon. The absence of trapping could then indicate a low dust-to-gas ratio, possibly because a large portion of the dust mass has been removed through radial drift or is locked up in planetesimals.

  17. Stable, Free-space Optical Trapping and Manipulation of Sub-micron Particles in an Integrated Microfluidic Chip

    NASA Astrophysics Data System (ADS)

    Kim, Jisu; Shin, Jung H.

    2016-09-01

    We demonstrate stable, free-space optical trapping and manipulation in an integrated microfluidic chip using counter-propagating beams. An inverted ridge-type waveguide made of SU8 is cut across by an open trench. The design of the waveguide provides low propagation losses and small divergence of the trapping beam upon emergence from the facet, and the trench designed to be deeper and wider than the optical mode enables full utilization of the optical power with an automatic alignment for counter-propagating beams in a trap volume away from all surfaces. After integration with polydimethylsiloxane (PDMS) microfluidic channel for particle delivery, 0.65 μm and 1 μm diameter polystyrene beads were trapped in free space in the trench, and manipulated to an arbitrary position between the waveguides with a resolution of < 100 nm. Comparison with numerical simulations confirm stable trapping of sub-micron particles, with a 10 kBT threshold power of less than 1 mW and a stiffness that can be 1 order of magnitude larger than that of comparable fiber-based trapping methods.

  18. Exploitation of sub-micron cavitation nuclei to enhance ultrasound-mediated transdermal transport and penetration of vaccines.

    PubMed

    Bhatnagar, Sunali; Kwan, James J; Shah, Apurva R; Coussios, Constantin-C; Carlisle, Robert C

    2016-09-28

    Inertial cavitation mediated by ultrasound has been previously shown to enable skin permeabilisation for transdermal drug and vaccine delivery, by sequentially applying the ultrasound then the therapeutic in liquid form on the skin surface. Using a novel hydrogel dosage form, we demonstrate that the use of sub-micron gas-stabilising polymeric nanoparticles (nanocups) to sustain and promote cavitation activity during simultaneous application of both drug and vaccine results in a significant enhancement of both the dose and penetration of a model vaccine, Ovalbumin (OVA), to depths of 500μm into porcine skin. The nanocups themselves exceeded the penetration depth of the vaccine (up to 700μm) due to their small size and capacity to 'self-propel'. In vivo murine studies indicated that nanocup-assisted ultrasound transdermal vaccination achieved significantly (p<0.05) higher delivery doses without visible skin damage compared to the use of a chemical penetration enhancer. Transdermal OVA doses of up to 1μg were achieved in a single 90-second treatment, which was sufficient to trigger an antigen-specific immune response. Furthermore, ultrasound-assisted vaccine delivery in the presence of nanocups demonstrated substantially higher specific anti-OVA IgG antibody levels compared to other transdermal methods. Further optimisation can lead to a viable, safe and non-invasive delivery platform for vaccines with potential use in a primary care setting or personalized self-vaccination at home. PMID:27417040

  19. Prospects for Sub-Micron Solid State Nuclear Magnetic Resonance Imaging with Low-Temperature Dynamic Nuclear Polarization

    PubMed Central

    Thurber, Kent R.; Tycko, Robert

    2010-01-01

    Summary We evaluate the feasibility of 1H nuclear magnetic resonance (NMR) imaging with sub-micron voxel dimensions using a combination of low temperatures and dynamic nuclear polarization (DNP). Experiments are performed on nitroxide-doped glycerol/water at 9.4 T and temperatures below 40 K, using a 30 mW tunable microwave source for DNP. With DNP at 7 K, a 0.5 µl sample yields a 1H NMR signal-to-noise ratio of 770 in two scans with pulsed spin-lock detection and after 80 db signal attenuation. With reasonable extrapolations, we infer that 1H NMR signals from 1 µm3 voxel volumes should be readily detectable, and voxels as small as 0.03 µm3 may eventually be detectable. Through homonuclear decoupling with a frequency-switched Lee-Goldburg spin echo technique, we obtain 830 Hz 1H NMR linewidths at low temperatures, implying that pulsed field gradients equal to 0.4 G/d or less would be required during spatial encoding dimensions of an imaging sequence, where d is the resolution in each dimension. PMID:20458431

  20. Ethanol (C2H5OH) spray of sub-micron droplets for laser driven negative ion source

    NASA Astrophysics Data System (ADS)

    Prasad, R.; Borghesi, M.; Abicht, F.; Nickles, P. V.; Stiel, H.; Schnürer, M.; Ter-Avetisyan, S.

    2012-08-01

    Liquid ethanol (C2H5OH) was used to generate a spray of sub-micron droplets. Sprays with different nozzle geometries have been tested and characterised using Mie scattering to find scaling properties and to generate droplets with different diameters within the spray. Nozzles having throat diameters of 470 μm and 560 μm showed generation of ethanol spray with droplet diameters of (180 ± 10) nm and (140 ± 10) nm, respectively. These investigations were motivated by the observation of copious negative ions from these target systems, e.g., negative oxygen and carbon ions measured from water and ethanol sprays irradiated with ultra-intense (5 × 1019 W/cm2), ultra short (40 fs) laser pulses. It is shown that the droplet diameter and the average atomic density of the spray have a significant effect on the numbers and energies of accelerated ions, both positive and negative. These targets open new possibilities for the creation of efficient and compact sources of different negative ion species.

  1. Time-specific measurements of energy deposition from radiation fields in simulated sub-micron tissue volumes

    SciTech Connect

    Famiano, M.A.

    1997-07-07

    A tissue-equivalent spherical proportional counter is used with a modified amplifier system to measure specific energy deposited from a uniform radiation field for short periods of time ({approximately}1 {micro}s to seconds) in order to extrapolate to dose in sub-micron tissue volumes. The energy deposited during these time intervals is compared to biological repair processes occurring within the same intervals after the initial energy deposition. The signal is integrated over a variable collection time which is adjusted with a square-wave pulse. Charge from particle passages is collected on the anode during the period in which the integrator is triggered, and the signal decays quickly to zero after the integrator feedback switch resets; the process repeats for every triggering pulse. Measurements of energy deposited from x rays, {sup 137}Cs gamma rays, and electrons from a {sup 90}Sr/{sup 90}Y source for various time intervals are taken. Spectral characteristics as a function of charge collection time are observed and frequency plots of specific energy and collection time-interval are presented. In addition, a threshold energy flux is selected for each radiation type at which the formation of radicals (based on current measurements) in mammalian cells equals the rate at which radicals are repaired.

  2. Stable, Free-space Optical Trapping and Manipulation of Sub-micron Particles in an Integrated Microfluidic Chip

    PubMed Central

    Kim, Jisu; Shin, Jung H.

    2016-01-01

    We demonstrate stable, free-space optical trapping and manipulation in an integrated microfluidic chip using counter-propagating beams. An inverted ridge-type waveguide made of SU8 is cut across by an open trench. The design of the waveguide provides low propagation losses and small divergence of the trapping beam upon emergence from the facet, and the trench designed to be deeper and wider than the optical mode enables full utilization of the optical power with an automatic alignment for counter-propagating beams in a trap volume away from all surfaces. After integration with polydimethylsiloxane (PDMS) microfluidic channel for particle delivery, 0.65 μm and 1 μm diameter polystyrene beads were trapped in free space in the trench, and manipulated to an arbitrary position between the waveguides with a resolution of < 100 nm. Comparison with numerical simulations confirm stable trapping of sub-micron particles, with a 10 kBT threshold power of less than 1 mW and a stiffness that can be 1 order of magnitude larger than that of comparable fiber-based trapping methods. PMID:27653191

  3. Characterisation of sub-micron particle number concentrations and formation events in the western Bushveld Igeneous Complex, South Africa

    NASA Astrophysics Data System (ADS)

    Hirsikko, A.; Vakkari, V.; Tiitta, P.; Manninen, H. E.; Gagné, S.; Laakso, H.; Kulmala, M.; Mirme, A.; Mirme, S.; Mabaso, D.; Beukes, J. P.; Laakso, L.

    2012-01-01

    South Africa holds significant mineral resources, with a substantial fraction of these reserves occurring in a large geological structure termed the Bushveld Igeneous Complex (BIC). The majority of the world's platinum group metals (PGMs) and chromium originate from the BIC. Considering the importance of PGMs in the manufacturing of automotive catalytic converters, as well as the relatively poor current state of air quality and the general lack of atmospheric research in the BIC, atmospheric related research in this geographical area is of local (South African) and of international interest. The western limb of the BIC is the most exploited, with at least eleven pyrometallurgical smelters occurring within a 55 km radius. Due to the lure of employment in the industrialised BIC, the area is populated by informal, semi-formal and formal residential developments. In order to investigate the characteristics and processes affecting sub-micron particle number concentrations and formation events, air ion and aerosol particle size distribution and concentration measurements were conducted for over two years at Marikana in the heart of the western BIC. Our results indicated that high amounts of Aitken and accumulation mode particles originated from domestic burning for heating and cooking in the morning and evening, while during daytime SO2-based nucleation (from industrial emissions) was the most probable source for large number concentrations of nucleation and Aitken mode particles. Nucleation event day frequency was extremely high, i.e. 86% of the analysed days, which to the knowledge of the authors is the highest frequency ever reported. Secondary particle formation was influenced both by local pollution sources and regional ambient conditions. Therefore, our observation of the annual cycle and magnitude of the particle formation and growth rates during nucleation events were similar to the results from a semi-clean savannah site in South Africa.

  4. Synthesis and characterization of monodisperse, mesoporous, and magnetic sub-micron particles doped with a near-infrared fluorescent dye

    SciTech Connect

    Le Guevel, Xavier; Nooney, Robert; McDonagh, Colette; MacCraith, Brian D.

    2011-06-15

    Recently, multifunctional silica nanoparticles have been investigated extensively for their potential use in biomedical applications. We have prepared sub-micron monodisperse and stable multifunctional mesoporous silica particles with a high level of magnetization and fluorescence in the near infrared region using an one-pot synthesis technique. Commercial magnetite nanocrystals and a conjugated-NIR-dye were incorporated inside the particles during the silica condensation reaction. The particles were then coated with polyethyleneglycol to stop aggregation. X-ray diffraction, N{sub 2} adsorption analysis, TEM, fluorescence and absorbance measurements were used to structurally characterize the particles. These mesoporous silica spheres have a large surface area (1978 m{sup 2}/g) with 3.40 nm pore diameter and a high fluorescence in the near infrared region at {lambda}=700 nm. To explore the potential of these particles for drug delivery applications, the pore accessibility to hydrophobic drugs was simulated by successfully trapping a hydrophobic ruthenium dye complex inside the particle with an estimated concentration of 3 wt%. Fluorescence imaging confirmed the presence of both NIR dye and the post-grafted ruthenium dye complex inside the particles. These particles moved at approximately 150 {mu}m/s under the influence of a magnetic field, hence demonstrating the multifunctionality and potential for biomedical applications in targeting and imaging. - Graphical Abstract: Hydrophobic fluorescent Ruthenium complex has been loaded into the mesopores as a surrogate drug to simulate drug delivery and to enhance the multifunctionality of the magnetic NIR emitting particles. Highlights: > Monodisperse magnetic mesoporous silica particles emitting in the near infrared region are obtained in one-pot synthesis. > We prove the capacity of such particles to uptake hydrophobic dye to mimic drug loading. > Loaded fluorescent particles can be moved under a magnetic field in a

  5. Fabrication of a high-aspect-ratio sub-micron tool using a cathode coated with stretched-out insulating layers.

    PubMed

    Zeng, Yongbin; Wang, Yufeng; Qu, Ningsong; Zhu, Di

    2013-09-01

    This paper describes a method for preparing a high-aspect-ratio sub-micron tool using a cathode coated with stretched-out insulating layers and a straight reciprocating motion applied at the anode via the liquid membrane electrochemical machining (ECM). Simulation results indicate that the application of a cathode coated with stretched-out insulating layers is beneficial for the localization of ECM. Moreover, a mathematical model was derived to estimate the final average diameter of the fabricated tools. Experiments were conducted to verify the versatility and feasibility of the proposed method and its mathematical model. It was observed that the calculated and the experimental results are in good agreement with each other. A sub-micron tool with an average diameter 140.8 nm and an aspect ratio up to 50 was fabricated using the proposed method. PMID:24089857

  6. Fabrication of a high-aspect-ratio sub-micron tool using a cathode coated with stretched-out insulating layers

    NASA Astrophysics Data System (ADS)

    Zeng, Yongbin; Wang, Yufeng; Qu, Ningsong; Zhu, Di

    2013-09-01

    This paper describes a method for preparing a high-aspect-ratio sub-micron tool using a cathode coated with stretched-out insulating layers and a straight reciprocating motion applied at the anode via the liquid membrane electrochemical machining (ECM). Simulation results indicate that the application of a cathode coated with stretched-out insulating layers is beneficial for the localization of ECM. Moreover, a mathematical model was derived to estimate the final average diameter of the fabricated tools. Experiments were conducted to verify the versatility and feasibility of the proposed method and its mathematical model. It was observed that the calculated and the experimental results are in good agreement with each other. A sub-micron tool with an average diameter 140.8 nm and an aspect ratio up to 50 was fabricated using the proposed method.

  7. On the sub-micron aerosol size distribution in a coastal-rural site at El Arenosillo Station (SW - Spain)

    NASA Astrophysics Data System (ADS)

    Sorribas, M.; de La Morena, B. A.; Wehner, B.; López, J. F.; Prats, N.; Mogo, S.; Wiedensohler, A.; Cachorro, V. E.

    2011-11-01

    This study focuses on the analysis of the sub-micron aerosol characteristics at El Arenosillo Station, a rural and coastal environment in South-western Spain between 1 August 2004 and 31 July 2006 (594 days). The mean total concentration (NT) was 8660 cm-3 and the mean concentrations in the nucleation (NNUC), Aitken (NAIT) and accumulation (NACC) particle size ranges were 2830 cm-3, 4110 cm-3 and 1720 cm-3, respectively. Median size distribution was characterised by a single-modal fit, with a geometric diameter, median number concentration and geometric standard deviation of 60 nm, 5390 cm-3 and 2.31, respectively. Characterisation of primary emissions, secondary particle formation, changes to meteorology and long-term transport has been necessary to understand the seasonal and annual variability of the total and modal particle concentration. Number concentrations exhibited a diurnal pattern with maximum concentrations around noon. This was governed by the concentrations of the nucleation and Aitken modes during the warm seasons and only by the nucleation mode during the cold seasons. Similar monthly mean total concentrations were observed throughout the year due to a clear inverse variation between the monthly mean NNUC and NACC. It was related to the impact of desert dust and continental air masses on the monthly mean particle levels. These air masses were associated with high values of NACC which suppressed the new particle formation (decreasing NNUC). Each day was classified according to a land breeze flow or a synoptic pattern influence. The median size distribution for desert dust and continental aerosol was dominated by the Aitken and accumulation modes, and marine air masses were dominated by the nucleation and Aitken modes. Particles moved offshore due to the land breeze and had an impact on the particle burden at noon, especially when the wind was blowing from the NW sector in the morning during summer time. This increased NNUC and NAIT by factors of 3

  8. NBS K409: A potential reference material for sub-micron X-ray resolution by EPMA

    NASA Astrophysics Data System (ADS)

    Cathey, H. E.; Gopon, P.; Fournelle, J.

    2013-12-01

    With advances in electron beam instrumentation, there has been a trend toward higher resolution electron gun sources for electron microprobes. JEOL has been marketing field-emission gun (FEG) microprobes since 2003 (JXA 8500F), and CAMECA introduced their SX5FE microprobe in 2011. However, there remain questions about the full utilization of such tight beams as those afforded by the FEG applied to common rock-forming minerals (e.g. silicates, oxides, carbonates, phosphates, glasses), because the desired improvement in X-ray spatial resolution for quantitative determination of the compositions of sub-micron size objects necessitates operation at lower accelerating voltages and use of low-energy X-ray lines. The physics of electron scatter and ionization energies under such conditions is of primary concern regarding the spatial resolution of field-emission EPMA. In the 1970s, the U.S. National Bureau of Standards (now National Institute of Standards and Technology) developed a series of glass reference materials for microanalysis. The two glasses K411 and K412 were certified in 1982 (Marinenko, 1982) and contain SiO2, MgO, CaO and FeO/Fe2O3, with K412 additionally containing Al2O3. Both glasses were independently characterized and each found to be homogeneous. The composition of K411 is equivalent to stoichiometric pyroxene (augite). Decades later, with interest in microanalysis of particles, microspheres (2-40 um) of K411 composition were developed (Marinenko et al., 2000). Recently, a vial of NBS glass "K409" was unearthed at the University of Wisconsin; it was apparently a "failed experiment" for a sodium-rich microanalysis standard (D. Newbury, pers. comm.) with a nominal composition of SiO2 (55 wt%), Al2O3 (15 wt%), FeO (20 wt%) and Na2O (10 wt%). Close inspection of this sample by SEM reveals a plenitude of equant euhedral iron oxide microlites ≤ 1000 nm in diameter. This "failed experiment" fortuitously created a potential standard for higher resolution X

  9. In situ fabrication of depth-type hierarchical CNT/quartz fiber filters for high efficiency filtration of sub-micron aerosols and high water repellency

    NASA Astrophysics Data System (ADS)

    Li, Peng; Zong, Yichen; Zhang, Yingying; Yang, Mengmeng; Zhang, Rufan; Li, Shuiqing; Wei, Fei

    2013-03-01

    We fabricated depth-type hierarchical CNT/quartz fiber (QF) filters through in situ growth of CNTs upon quartz fiber (QF) filters using a floating catalyst chemical vapor deposition (CVD) method. The filter specific area of the CNT/QF filters is more than 12 times higher than that of the pristine QF filters. As a result, the penetration of sub-micron aerosols for CNT/QF filters is reduced by two orders of magnitude, which reaches the standard of high-efficiency particulate air (HEPA) filters. Simultaneously, due to the fluffy brush-like hierarchical structure of CNTs on QFs, the pore size of the hybrid filters only has a small increment. The pressure drop across the CNT/QF filters only increases about 50% with respect to that of the pristine QF filters, leading to an obvious increased quality factor of the CNT/QF filters. Scanning electron microscope images reveal that CNTs are very efficient in capturing sub-micron aerosols. Moreover, the CNT/QF filters show high water repellency, implying their superiority for applications in humid conditions.We fabricated depth-type hierarchical CNT/quartz fiber (QF) filters through in situ growth of CNTs upon quartz fiber (QF) filters using a floating catalyst chemical vapor deposition (CVD) method. The filter specific area of the CNT/QF filters is more than 12 times higher than that of the pristine QF filters. As a result, the penetration of sub-micron aerosols for CNT/QF filters is reduced by two orders of magnitude, which reaches the standard of high-efficiency particulate air (HEPA) filters. Simultaneously, due to the fluffy brush-like hierarchical structure of CNTs on QFs, the pore size of the hybrid filters only has a small increment. The pressure drop across the CNT/QF filters only increases about 50% with respect to that of the pristine QF filters, leading to an obvious increased quality factor of the CNT/QF filters. Scanning electron microscope images reveal that CNTs are very efficient in capturing sub-micron aerosols

  10. Hydrothermal Synthesis Au-Bi2Te3 Nanocomposite Thermoelectric Film with a Hierarchical Sub-Micron Antireflection Quasi-Periodic Structure.

    PubMed

    Tian, Junlong; Zhang, Wang; Zhang, Yuan; Xue, Ruiyang; Wang, Yuhua; Zhang, Zhijian; Zhang, Di

    2015-01-01

    In this work, Au-Bi(2)Te(3) nanocomposite thermoelectric film with a hierarchical sub-micron antireflection quasi-periodic structure was synthesized via a low-temperature chemical route using Troides helena (Linnaeus) forewing (T_FW) as the biomimetic template. This method combines chemosynthesis with biomimetic techniques, without the requirement of expensive equipment and energy intensive processes. The microstructure and the morphology of the Au-Bi(2)Te(3) nanocomposite thermoelectric film was analyzed by X-ray diffraction (XRD), field-emission scanning-electron microscopy (FESEM), and transmission electron microscopy (TEM). Coupled the plasmon resonances of the Au nanoparticles with the hierarchical sub-micron antireflection quasi-periodic structure, the Au-Bi(2)Te(3) nanocomposite thermoelectric film possesses an effective infrared absorption and infrared photothermal conversion performance. Based on the finite difference time domain method and the Joule effect, the heat generation and the heat source density distribution of the Au-Bi(2)Te(3) nanocomposite thermoelectric film were studied. The heterogeneity of heat source density distribution of the Au-Bi(2)Te(3) nanocomposite thermoelectric film opens up a novel promising technique for generating thermoelectric power under illumination. PMID:26047340

  11. In situ fabrication of depth-type hierarchical CNT/quartz fiber filters for high efficiency filtration of sub-micron aerosols and high water repellency.

    PubMed

    Li, Peng; Zong, Yichen; Zhang, Yingying; Yang, Mengmeng; Zhang, Rufan; Li, Shuiqing; Wei, Fei

    2013-04-21

    We fabricated depth-type hierarchical CNT/quartz fiber (QF) filters through in situ growth of CNTs upon quartz fiber (QF) filters using a floating catalyst chemical vapor deposition (CVD) method. The filter specific area of the CNT/QF filters is more than 12 times higher than that of the pristine QF filters. As a result, the penetration of sub-micron aerosols for CNT/QF filters is reduced by two orders of magnitude, which reaches the standard of high-efficiency particulate air (HEPA) filters. Simultaneously, due to the fluffy brush-like hierarchical structure of CNTs on QFs, the pore size of the hybrid filters only has a small increment. The pressure drop across the CNT/QF filters only increases about 50% with respect to that of the pristine QF filters, leading to an obvious increased quality factor of the CNT/QF filters. Scanning electron microscope images reveal that CNTs are very efficient in capturing sub-micron aerosols. Moreover, the CNT/QF filters show high water repellency, implying their superiority for applications in humid conditions. PMID:23467703

  12. Hydrothermal Synthesis Au-Bi2Te3 Nanocomposite Thermoelectric Film with a Hierarchical Sub-Micron Antireflection Quasi-Periodic Structure.

    PubMed

    Tian, Junlong; Zhang, Wang; Zhang, Yuan; Xue, Ruiyang; Wang, Yuhua; Zhang, Zhijian; Zhang, Di

    2015-01-01

    In this work, Au-Bi(2)Te(3) nanocomposite thermoelectric film with a hierarchical sub-micron antireflection quasi-periodic structure was synthesized via a low-temperature chemical route using Troides helena (Linnaeus) forewing (T_FW) as the biomimetic template. This method combines chemosynthesis with biomimetic techniques, without the requirement of expensive equipment and energy intensive processes. The microstructure and the morphology of the Au-Bi(2)Te(3) nanocomposite thermoelectric film was analyzed by X-ray diffraction (XRD), field-emission scanning-electron microscopy (FESEM), and transmission electron microscopy (TEM). Coupled the plasmon resonances of the Au nanoparticles with the hierarchical sub-micron antireflection quasi-periodic structure, the Au-Bi(2)Te(3) nanocomposite thermoelectric film possesses an effective infrared absorption and infrared photothermal conversion performance. Based on the finite difference time domain method and the Joule effect, the heat generation and the heat source density distribution of the Au-Bi(2)Te(3) nanocomposite thermoelectric film were studied. The heterogeneity of heat source density distribution of the Au-Bi(2)Te(3) nanocomposite thermoelectric film opens up a novel promising technique for generating thermoelectric power under illumination.

  13. Exploring the Role of Sub-micron-sized Dust Grains in the Atmospheres of Red L0–L6 Dwarfs

    NASA Astrophysics Data System (ADS)

    Hiranaka, Kay; Cruz, Kelle L.; Douglas, Stephanie T.; Marley, Mark S.; Baldassare, Vivienne F.

    2016-10-01

    We examine the hypothesis that the red near-infrared colors of some L dwarfs could be explained by a “dust haze” of small particles in their upper atmospheres. This dust haze would exist in conjunction with the clouds found in dwarfs with more typical colors. We developed a model that uses Mie theory and the Hansen particle size distributions to reproduce the extinction due to the proposed dust haze. We apply our method to 23 young L dwarfs and 23 red field L dwarfs. We constrain the properties of the dust haze including particle size distribution and column density using Markov Chain Monte Carlo methods. We find that sub-micron-range silicate grains reproduce the observed reddening. Current brown dwarf atmosphere models include large-grain (1–100 μm) dust clouds but not sub-micron dust grains. Our results provide a strong proof of concept and motivate a combination of large and small dust grains in brown dwarf atmosphere models.

  14. Hydrothermal Synthesis Au-Bi2Te3 Nanocomposite Thermoelectric Film with a Hierarchical Sub-Micron Antireflection Quasi-Periodic Structure

    PubMed Central

    Tian, Junlong; Zhang, Wang; Zhang, Yuan; Xue, Ruiyang; Wang, Yuhua; Zhang, Zhijian; Zhang, Di

    2015-01-01

    In this work, Au-Bi2Te3 nanocomposite thermoelectric film with a hierarchical sub-micron antireflection quasi-periodic structure was synthesized via a low-temperature chemical route using Troides helena (Linnaeus) forewing (T_FW) as the biomimetic template. This method combines chemosynthesis with biomimetic techniques, without the requirement of expensive equipment and energy intensive processes. The microstructure and the morphology of the Au-Bi2Te3 nanocomposite thermoelectric film was analyzed by X-ray diffraction (XRD), field-emission scanning-electron microscopy (FESEM), and transmission electron microscopy (TEM). Coupled the plasmon resonances of the Au nanoparticles with the hierarchical sub-micron antireflection quasi-periodic structure, the Au-Bi2Te3 nanocomposite thermoelectric film possesses an effective infrared absorption and infrared photothermal conversion performance. Based on the finite difference time domain method and the Joule effect, the heat generation and the heat source density distribution of the Au-Bi2Te3 nanocomposite thermoelectric film were studied. The heterogeneity of heat source density distribution of the Au-Bi2Te3 nanocomposite thermoelectric film opens up a novel promising technique for generating thermoelectric power under illumination. PMID:26047340

  15. Effect of epicuticular wax crystals on the localization of artificially deposited sub-micron carbon-based aerosols on needles of Cryptomeria japonica.

    PubMed

    Nakaba, Satoshi; Yamane, Kenichi; Fukahori, Mie; Nugroho, Widyanto Dwi; Yamaguchi, Masahiro; Kuroda, Katsushi; Sano, Yuzou; Wuled Lenggoro, I; Izuta, Takeshi; Funada, Ryo

    2016-09-01

    Elucidation of the mechanism of adsorption of particles suspended in the gas-phase (aerosol) to the outer surfaces of leaves provides useful information for understanding the mechanisms of the effect of aerosol particles on the growth and physiological functions of trees. In the present study, we examined the localization of artificially deposited sub-micron-sized carbon-based particles on the surfaces of needles of Cryptomeria japonica, a typical Japanese coniferous tree species, by field-emission scanning electron microscopy. The clusters (aggregates) of carbon-based particles were deposited on the needle surface regions where epicuticular wax crystals were sparsely distributed. By contrast, no clusters of the particles were found on the needle surface regions with dense distribution of epicuticular wax crystals. Number of clusters of carbon-based particles per unit area showed statistically significant differences between regions with sparse epicuticular wax crystals and those with dense epicuticular wax crystals. These results suggest that epicuticular wax crystals affect distribution of carbon-based particles on needles. Therefore, densely distributed epicuticular wax crystals might prevent the deposition of sub-micron-sized carbon-based particles on the surfaces of needles of Cryptomeria japonica to retain the function of stomata.

  16. A Novel Step-Doping Fully-Depleted Silicon-on-Insulator Metal-Oxide-Semiconductor Field-Effect Transistor for Reliable Deep Sub-micron Devices

    NASA Astrophysics Data System (ADS)

    Elahipanah, Hossein; Orouji, Ali A.

    2009-11-01

    For first time, we report a novel deep sub-micron fully-depleted silicon-on-insulator metal-oxide-semiconductor field-effect-transistor (FD SOI MOSFET) where the channel layer consists of two sections with a step doping (SD) region in order to increase performance and reliability of the device. This new structure that called SD FD SOI structure (SDFD-SOI MOSFET), were used for reaching suitable threshold voltage upon device scaling and reliability improvement. We demonstrate that the electric field was modified in the channel and common peak near the source junction have been reduced in the SDFD-SOI structure. The device demonstrates large enhancements in performance areas such as current drive capability, output resistance, hot-carrier reliability and threshold voltage roll-off. It was found that the device performance is very much dependent upon the SD region parameters. Simulation results show that the proposed structure improved on/off current ratio, and saturated output characteristics compared with conventional SOI structure (C-SOI MOSFET). Also, it was shown that substrate current of SDFD-SOI MOSFET is much lower than the C-SOI MOSFET which presented the lower hot-carrier degradation in proposed MOSFET. Results show that the most short-channel problems in very large scale integrated circuits (VLSI) could be solved and the proposed SDFD-SOI MOSFETs can work very well in deep sub-micron and nanoscale regime.

  17. Effect of epicuticular wax crystals on the localization of artificially deposited sub-micron carbon-based aerosols on needles of Cryptomeria japonica.

    PubMed

    Nakaba, Satoshi; Yamane, Kenichi; Fukahori, Mie; Nugroho, Widyanto Dwi; Yamaguchi, Masahiro; Kuroda, Katsushi; Sano, Yuzou; Wuled Lenggoro, I; Izuta, Takeshi; Funada, Ryo

    2016-09-01

    Elucidation of the mechanism of adsorption of particles suspended in the gas-phase (aerosol) to the outer surfaces of leaves provides useful information for understanding the mechanisms of the effect of aerosol particles on the growth and physiological functions of trees. In the present study, we examined the localization of artificially deposited sub-micron-sized carbon-based particles on the surfaces of needles of Cryptomeria japonica, a typical Japanese coniferous tree species, by field-emission scanning electron microscopy. The clusters (aggregates) of carbon-based particles were deposited on the needle surface regions where epicuticular wax crystals were sparsely distributed. By contrast, no clusters of the particles were found on the needle surface regions with dense distribution of epicuticular wax crystals. Number of clusters of carbon-based particles per unit area showed statistically significant differences between regions with sparse epicuticular wax crystals and those with dense epicuticular wax crystals. These results suggest that epicuticular wax crystals affect distribution of carbon-based particles on needles. Therefore, densely distributed epicuticular wax crystals might prevent the deposition of sub-micron-sized carbon-based particles on the surfaces of needles of Cryptomeria japonica to retain the function of stomata. PMID:27294967

  18. Out-of-plane actuation with a sub-micron initial gap for reconfigurable terahertz micro-electro-mechanical systems metamaterials.

    PubMed

    Isozaki, Akihiro; Kan, Tetsuo; Takahashi, Hidetoshi; Matsumoto, Kiyoshi; Shimoyama, Isao

    2015-10-01

    We propose a reconfigurable terahertz (THz) metamaterial that can control the transmittance by out-of-plane actuation with changing the sub-micron gap distance between electrically coupled metamaterial elements. By using the out-of-plane actuation, it was possible to avoid contact between the coupled metamaterial elements across the small initial gap during the adjustment of the gap size. THz spectroscopy was performed during actuation, and the transmission dip frequency was confirmed to be tunable from 0.82 to 0.92 THz for one linear polarization state and from 0.80 to 0.91 THz for the other linear polarization; the two polarizations were orthogonal. The proposed approach will contribute to the development of tunable metamaterials based on structural deformations. PMID:26480137

  19. Direct sub-micron microstructuring on cylinder using TiO2 sol-gel process and radial phase mask based lithography

    NASA Astrophysics Data System (ADS)

    Berthod, L.; Vocanson, F.; Langlet, M.; Veillas, C.; Reynaud, S.; Verrier, I.; Laukkanen, J.; Parriaux, O.; Jourlin, Y.

    2016-04-01

    Design and fabrication of a high efficiency phase mask have been performed for printing submicron period gratings along 8 mm diameter glass cylinders. In this article, the authors present the radial phase mask specially designed and manufactured for a cylindrical surface micro-structuring under UV photolithography. Its period is sub-micron (480 nm < ΛPM < 720 nm). The authors describe then the phase mask based UV lithography set-up using the interference between the transmitted beams of +1 and -1 orders generated by the phase mask. Preliminary results of printed gratings on a cylinder are described on a sol-gel TiO2 thin film layer, enabling direct photo patterning on functionalized layer. The feasibility of a grating printed with a period of Λcylin = 960 nm on an 8 mm diameter cylinder with this dedicated mask has been demonstrated.

  20. Magnetic and Mössbauer characterization of the magnetic properties of single-crystalline sub-micron sized Bi₂Fe₄O₉ cubes

    SciTech Connect

    Papaefthymiou, Georgia C.; Wong, Stanislaus S.; Viescas, Arthur J.; Le Breton, Jean-Marie; Chiron, Hubert; Juraszek, Jean; Park, Tae-Jin

    2014-11-25

    Magnetic and Mössbauer characterization of single crystalline, sub-micron sized Bi₂Fe₄O₉ cubes has been performed using SQUID magnetometry and transmission Mössbauer spectroscopy in the temperature range of 4.2 K ≤ T ≤ 300 K. A broad magnetic phase transition from the paramagnetic to the anti-ferromagnetic state is observed below 250 K, with the Mössbauer spectra exhibiting a superposition of magnetic, collapsed and quadrupolar spectra in the transition region of 200 K < T < 245 K. Room temperature Mössbauer spectra obtained in transmission geometry are identical to those recorded in back-scattering geometry via conversion electron Mössbauer spectroscopy, indicating the absence of strain at the surface. A small hysteresis loop is observed in SQUID measurements at 5 K, attributable to the presence of weak-ferromagnetism arising from the canting of Fe³⁺ ion sublattices in the antiferromagnetic matrix.

  1. An optoelectronic device in bulk LiF with sub-micron periodic gratings fabricated by interference of 400 nm femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Kurobori, T.; Obayashi, Y.; Kurashima, M.; Hirose, Y.; Sakai, T.; Aoshima, S.; Kojima, T.; Okuda, S.

    2008-06-01

    Sub-micron periodic gratings of transparent materials are holographically fabricated by interference with the second harmonic (400 nm) of a mode-locked Ti:sapphire oscillator-amplifier laser. As one optoelectronic application, a pulsed, room temperature laser action in bulk lithium fluoride is demonstrated, for the first time, in the green spectral region based on the laser-active F3+colour centres utilizing a distributed feedback structure encoded by interference of 400 nm femtosecond laser pulses. A lasing output with a linewidth of 1 nm is obtained at approximately 539 nm, which value reflects the selective laser resonator. Realization of green and red distributed feedback colour centre laser action based on the F3+and F2 centres in LiF excited by a single wavelength can be expected.

  2. Co-existence of a few and sub micron inhomogeneities in Al-rich AlGaN/AlN quantum wells

    SciTech Connect

    Iwata, Yoshiya; Oto, Takao; Banal, Ryan G.; Funato, Mitsuru; Kawakami, Yoichi; Gachet, David

    2015-03-21

    Inhomogeneity in Al-rich AlGaN/AlN quantum wells is directly observed using our custom-built confocal microscopy photoluminescence (μ-PL) apparatus with a reflective system. The μ-PL system can reach the AlN bandgap in the deep ultra-violet spectral range with a spatial resolution of 1.8 μm. In addition, cathodoluminescence (CL) measurements with a higher spatial resolution of about 100 nm are performed. A comparison of the μ-PL and CL measurements reveals that inhomogeneities, which have different spatial distributions of a few- and sub-micron scales that are superimposed, play key roles in determining the optical properties.

  3. Simulation and optimization of a sub-micron beam for macromolecular crystallography using SHADOW and XOP at GM/CA CAT at the APS

    NASA Astrophysics Data System (ADS)

    Liu, Zunping; Xu, Shenglan; Yoder, Derek W.; Fischetti, Robert F.

    2011-10-01

    The small, high intensity and low convergence beams available on beamlines at 3rd generation synchrotron sources have been a boon to macromolecular crystallography. It is now becoming routine to solve structures using a beam in the 5 - 20 micron (FWHM) range. However, many problems in structural biology suffer from poor S/N due to small (a few microns) crystals or larger inhomogenous crystals. In additional, theoretical calculations and experimental results have demonstrated that radiation damage may be reduced by using a micron-sized X-ray beam. At GM/CA CAT we are developing a sub-micron, low convergence beam to address these issues. The sub-micron beam capability will be developed on the existing beamline 23ID-D where the minimum beam size available to users is currently 5 microns in diameter. The target goals are a beam size of ~0.8 micron (FWHM) in diameter, with a beam convergence of less 0.6 milli-rads, a flux greater than 5×1010 photons/sec, and an energy range from 5 to 35 keV. Five optical systems will be compared: 1) a single set of highly demagnifying Kirkpatrick-Baez (K-B) mirrors, 2) multiple Fresnel Zone Plates (FZP), 3) a set of K-B mirrors focusing to a secondary source that is imaged by another set of K-B mirrors, 4) a set of K-B mirrors focusing to a secondary source that is imaged by a FZP, 5) a horizontal focusing mirror focusing to a secondary source that is imaged by another horizontal mirror together with a vertical focusing mirror. Here we will present the results of a design optimization based on ray trace simulations (SHADOW), flux calculations (XOP), and experimental results on 23ID.

  4. Rheological and filtration behavior of aqueous alumina casting slips dispersed with polyacrylate and polymethacrylate deflocculants

    NASA Astrophysics Data System (ADS)

    Shemo, David M.

    Dynamic stress-controlled rheometry methods and filtration analysis were used to characterize aluminum oxide suspensions relative to several process variables. These included dispersant molecular weight, dispersant concentration, solids concentration, alumina PSD, and aging time. It is believed that through rheological analysis, a better understanding of a slip's structure and dewatering behavior can be achieved. Based upon time- and stress-sweep data, structural models were developed for the build-up (gelation) and break-down (yielding) processes in alumina suspensions. Aqueous alumina suspensions dispersed with acrylate-based polyelectrolytes of average molecular weights of 2400, 3500, and 15000 were evaluated over an aging period of up to ten days. The aging-induced variations in their rheological, filtration, and electrochemical characteristics were quantified. These effects were related to changes in the structures of the suspensions over time. It was found that the aging effect was most pronounced for slips dispersed with higher molecular weight polyacrylate or polymethacrylate deflocculants. A mechanism was proposed to account for the aging behavior and the effect of dispersant molecular weight. Alumina slips were prepared with bimodal particle size compositions by combining two sub-micron alumina powders. Variation in rheological behavior with the composition was evaluated for slips at moderate and high solids concentration, and at fully dispersed and under dispersed states. The corresponding changes in the filtration behavior and cast density were measured. A structural model was constructed for the observed variations with alumina composition.

  5. Alumina-on-Alumina in THA

    PubMed Central

    Garcia-Rey, Eduardo; Murcia-Mazón, Antonio; Blanco-Pozo, Agustín; Martí, Eduardo

    2008-01-01

    Different bearing surfaces, including alumina-on-alumina, have been used to avoid osteolysis. We prospectively followed 288 patients (319 hips) in which an alumina-on-alumina cup was used with a hydroxyapatite stem. The patients’ mean age was 52.7 (range, 14–70 years), and the minimum followup was 3 years (mean, 4.7 years; range, 3–8 years). At final followup, five cups (including one with an alumina liner fracture) and two stems underwent revision. The cumulative probability of not having a revision of one or both components for any cause was 97% (95% confidence interval, 94.7%–99.1%). No patient spontaneously reported any noises from the hip and none reported noises when specifically questioned. All patients who had not undergone revision had good clinical results, but five of these patients had radiographic cup loosening at last followup. These data suggest alumina-on-alumina prostheses had reasonable outcomes after 5 years. One acetabular component fractured from trauma. We observed no linear femoral head penetration. Continued followup will be required to determine if reduction in wear between the alumina-on-alumina bearings results in less osteolysis and loosening. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. PMID:18196411

  6. Source apportionment of fine PM and sub-micron particle number concentrations at a regional background site in the western Mediterranean: a 2.5 yr study

    NASA Astrophysics Data System (ADS)

    Cusack, M.; Pérez, N.; Pey, J.; Alastuey, A.; Querol, X.

    2013-02-01

    The chemical composition and sources of ambient fine particulate matter (PM1) over a period of 2.5 yr for a regional background site in the western Mediterranean are presented in this work. Major components (such as SO12-, NO3-, NH4+, organic and elemental carbon) and trace elements were analysed and the emission sources affecting PM1 were determined using Positive Matrix Factorisation (PMF). Furthermore, sub-micron particle number concentrations and the sources of these particles are also presented. Sources of sub-micron particles were determined by Principal Component Analysis (PCA). The mean PM1 concentration for the measurement period was 8.9 μg m-3, with organic matter (OM) and sulphate comprising most of the mass (3.2 and 1.5 μg m-3). A clear seasonal variation was recorded with higher PM1 concentrations in summer (11.2 μg m-3) compared to winter (6.6 μg m-3). This summer increase was due to elevated levels of sulphate and OM. Six sources were identified by PMF: secondary organic aerosol, secondary nitrate, industrial, traffic + biomass burning, fuel oil combustion and secondary sulphate. The daily variations of these sources were also determined, whereby the typically anthropogenic sources displayed elevated concentrations during the week with reductions at weekends. Nitrate levels were elevated in winter and negligible in summer, whereas secondary sulphate levels underwent a contrasting seasonal evolution with highest concentrations in summer, similar to the fuel oil combustion source. The SOA source was influenced by episodes of sustained pollution as a result of anticyclonic conditions occurring during winter, giving rise to thermal inversions and the accumulation of pollutants in the mixing layer. Increased levels in summer were owing to higher biogenic emissions and regional recirculation of air masses. The industrial source decreased in August due to decreased emissions during the vacation period. Increases in the traffic + biomass burning source

  7. Source apportionment of fine PM and sub-micron particle number concentrations at a regional background site in the western Mediterranean: a 2.5 year study

    NASA Astrophysics Data System (ADS)

    Cusack, M.; Pérez, N.; Pey, J.; Alastuey, A.; Querol, X.

    2013-05-01

    The chemical composition and sources of ambient fine particulate matter (PM1) over a period of 2.5 years for a regional background site in the western Mediterranean are presented in this work. Furthermore, sub-micron particle number concentrations and the sources of these particles are also presented. The mean PM1 concentration for the measurement period was 8.9 μg m-3, with organic matter (OM) and sulphate comprising most of the mass (3.2 and 1.5 μg m-3 respectively). Six sources were identified in PM1 by Positive Matrix Factorisation (PMF): secondary organic aerosol, secondary nitrate, industrial, traffic + biomass burning, fuel oil combustion and secondary sulphate. Typically anthropogenic sources displayed elevated concentrations during the week with reductions at weekends. Nitrate levels were elevated in winter and negligible in summer, whereas secondary sulphate levels underwent a contrasting seasonal evolution with highest concentrations in summer, similar to the fuel oil combustion source. The SOA source was influenced by episodes of sustained pollution as a result of anticyclonic conditions occurring during winter, giving rise to thermal inversions and the accumulation of pollutants in the mixing layer. Increased levels in summer were owing to higher biogenic emissions and regional recirculation of air masses. The industrial source decreased in August due to decreased emissions during the vacation period. Increases in the traffic + biomass burning source were recorded in January, April and October, which were attributed to the occurrence of the aforementioned pollution episodes and local biomass burning emission sources, which include agriculture and domestic heating systems. Average particle number concentrations (N9-825 nm) from 5/11/2010 to 01/06/2011 and from 15/10/2011 to 18/12/2011 reached 3097 cm-3. Five emission sources of particle of sub-micron particles were determined by Principal Component Analysis (PCA); industrial + traffic + biomass

  8. The heterogeneous reaction of hydroxyl radicals with sub-micron squalane particles: a model system for understanding the oxidative aging of ambient aerosols

    NASA Astrophysics Data System (ADS)

    Smith, J. D.; Kroll, J. H.; Cappa, C. D.; Che, D. L.; Liu, C. L.; Ahmed, M.; Leone, S. R.; Worsnop, D. R.; Wilson, K. R.

    2009-02-01

    The heterogeneous reaction of OH radicals with sub-micron squalane particles, in the presence of O2, is used as a model system to explore the fundamental chemical mechanisms that control the oxidative aging of organic aerosols in the atmosphere. Detailed kinetic measurements combined with elemental mass spectrometric analysis reveal that the reaction proceeds sequentially by adding an average of one oxygenated functional group per reactive loss of squalane. The reactive uptake coefficient of OH with squalane particles is determined to be 0.3±0.07 at an average OH concentration of ~1×1010 molecules·cm-3. Based on a comparison between the measured particle mass and model predictions it appears that significant volatilization of a reduced organic particle would be extremely slow in the real atmosphere. However, as the aerosols become more oxygenated, volatilization becomes a significant loss channel for organic material in the particle phase. Together these results provide a chemical framework in which to understand how heterogeneous chemistry transforms the physiochemical properties of particle phase organic matter in the troposphere.

  9. The heterogeneous reaction of hydroxyl radicals with sub-micron squalane particles: a model system for understanding the oxidative aging of ambient aerosols

    NASA Astrophysics Data System (ADS)

    Smith, J. D.; Kroll, J. H.; Cappa, C. D.; Che, D. L.; Liu, C. L.; Ahmed, M.; Leone, S. R.; Worsnop, D. R.; Wilson, K. R.

    2009-05-01

    The heterogeneous reaction of OH radicals with sub-micron squalane particles, in the presence of O2, is used as a model system to explore the fundamental chemical mechanisms that control the oxidative aging of organic aerosols in the atmosphere. Detailed kinetic measurements combined with elemental mass spectrometric analysis reveal that the reaction proceeds sequentially by adding an average of one oxygenated functional group per reactive loss of squalane. The reactive uptake coefficient of OH with squalane particles is determined to be 0.3±0.07 at an average OH concentration of ~1×1010 molecules cm-3. Based on a comparison between the measured particle mass and model predictions it appears that significant volatilization of a reduced organic particle would be extremely slow in the real atmosphere. However, as the aerosols become more oxygenated, volatilization becomes a significant loss channel for organic material in the particle-phase. Together these results provide a chemical framework in which to understand how heterogeneous chemistry transforms the physiochemical properties of particle-phase organic matter in the troposphere.

  10. Magnetic and Mössbauer characterization of the magnetic properties of single-crystalline sub-micron sized Bi₂Fe₄O₉ cubes

    DOE PAGES

    Papaefthymiou, Georgia C.; Wong, Stanislaus S.; Viescas, Arthur J.; Le Breton, Jean-Marie; Chiron, Hubert; Juraszek, Jean; Park, Tae-Jin

    2014-11-25

    Magnetic and Mössbauer characterization of single crystalline, sub-micron sized Bi₂Fe₄O₉ cubes has been performed using SQUID magnetometry and transmission Mössbauer spectroscopy in the temperature range of 4.2 K ≤ T ≤ 300 K. A broad magnetic phase transition from the paramagnetic to the anti-ferromagnetic state is observed below 250 K, with the Mössbauer spectra exhibiting a superposition of magnetic, collapsed and quadrupolar spectra in the transition region of 200 K < T < 245 K. Room temperature Mössbauer spectra obtained in transmission geometry are identical to those recorded in back-scattering geometry via conversion electron Mössbauer spectroscopy, indicating the absence ofmore » strain at the surface. A small hysteresis loop is observed in SQUID measurements at 5 K, attributable to the presence of weak-ferromagnetism arising from the canting of Fe³⁺ ion sublattices in the antiferromagnetic matrix.« less

  11. Sub-micron and nanoscale feature depth modulates alignment of stromal fibroblasts and corneal epithelial cells in serum-rich and serum-free media

    PubMed Central

    Fraser, Sarah A.; Ting, Yuk-Hong; Mallon, Kelly S.; Wendt, Amy E.; Murphy, Christopher J.; Nealey, Paul F.

    2011-01-01

    Topographic features are generally accepted as being capable of modulating cell alignment. Of particular interest is the potential that topographic feature geometry induces cell alignment indirectly through impacting adsorbed proteins from the cell culture medium on the surface of the substrate. However, it has also been reported that micron-scale feature depth significantly impacts the level of alignment of cellular populations on topography, despite being orders of magnitude larger than the average adsorbed protein layer (nm). In order to better determine the impact of biomimetic length scale topography and adsorbed protein interaction on cellular morphology we have systematically investigated the effect of combinations of sub-micron to nanoscale feature depth and lateral pitch on corneal epithelial cell alignment. In addition we have used the unique properties of a serum-free media alternative in direct comparison to serum-rich medium to investigate the role of culture medium protein composition on cellular alignment to topographically patterned surfaces. Our observation that increasing groove depth elicited larger populations of corneal epithelial cells to align regardless of culture medium composition and of cell orientation with respect to the topography, suggests that these cells can sense changes in topographic feature depths independent of adsorbed proteins localized along ridge edges and tops. However, our data also suggests a strong combinatory effect of topography with culture medium composition, and also a cell type dependency in determining the level of cell elongation and alignment to nanoscale topographic features. PMID:18041718

  12. Free-standing millimetre-long Bi2Te3 sub-micron belts catalyzed by TiO2 nanoparticles.

    PubMed

    Schönherr, Piet; Zhang, Fengyu; Kojda, Danny; Mitdank, Rüdiger; Albrecht, Martin; Fischer, Saskia F; Hesjedal, Thorsten

    2016-12-01

    Physical vapour deposition (PVD) is used to grow millimetre-long Bi2Te3 sub-micron belts catalysed by TiO2 nanoparticles. The catalytic efficiency of TiO2 nanoparticles for the nanostructure growth is compared with the catalyst-free growth employing scanning electron microscopy. The catalyst-coated and catalyst-free substrates are arranged side-by-side, and overgrown at the same time, to assure identical growth conditions in the PVD furnace. It is found that the catalyst enhances the yield of the belts. Very long belts were achieved with a growth rate of 28 nm/min. A ∼1-mm-long belt with a rectangular cross section was obtained after 8 h of growth. The thickness and width were determined by atomic force microscopy, and their ratio is ∼1:10. The chemical composition was determined to be stoichiometric Bi2Te3 using energy-dispersive X-ray spectroscopy. Temperature-dependent conductivity measurements show a characteristic increase of the conductivity at low temperatures. The room temperature conductivity of 0.20 × 10(5) S m (-1) indicates an excellent sample quality. PMID:27342602

  13. Refractive lens based full-field x-ray imaging at 45-50 keV with sub-micron resolution

    NASA Astrophysics Data System (ADS)

    Shastri, S. D.; Kenesei, P.; Suter, R. M.

    2015-09-01

    Combining sub-micron spatial resolution full-field-imaging with the penetration property of high-energy x-rays (> 50 keV) offers numerous applications, such as the ability to observe cracks and voids associated with the onset of failure in engineering materials, complementing x-ray diffraction microscopy probes. Progress in the development of adding such an imaging capability at the Advanced Photon Source high-energy x-ray undulator beamline 1-ID is reported. An initially tested, long baseline configuration had 18-21× x-ray image magnification with compound refractive lenses (as objective) placed 1.8 m after the specimen, and a two-dimensional detector located at a 32-37 m additional distance, in a different experimental station. Later, a more compact set-up of 3.5× magnification with a ≍6 m sample-to-detector separation, fitting within a single end-station, was tested. Both set-ups demonstrated 500 nm level spatial resolutions at energies within the 45-50 keV range. Phase contrast artifacts are present, and are discussed in view of the goal of achieving tomography capability, at even higher resolution, in such an instrument with high x-ray energies.

  14. Free-standing millimetre-long Bi2Te3 sub-micron belts catalyzed by TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Schönherr, Piet; Zhang, Fengyu; Kojda, Danny; Mitdank, Rüdiger; Albrecht, Martin; Fischer, Saskia F.; Hesjedal, Thorsten

    2016-06-01

    Physical vapour deposition (PVD) is used to grow millimetre-long Bi2Te3 sub-micron belts catalysed by TiO2 nanoparticles. The catalytic efficiency of TiO2 nanoparticles for the nanostructure growth is compared with the catalyst-free growth employing scanning electron microscopy. The catalyst-coated and catalyst-free substrates are arranged side-by-side, and overgrown at the same time, to assure identical growth conditions in the PVD furnace. It is found that the catalyst enhances the yield of the belts. Very long belts were achieved with a growth rate of 28 nm/min. A ˜1-mm-long belt with a rectangular cross section was obtained after 8 h of growth. The thickness and width were determined by atomic force microscopy, and their ratio is ˜1:10. The chemical composition was determined to be stoichiometric Bi2Te3 using energy-dispersive X-ray spectroscopy. Temperature-dependent conductivity measurements show a characteristic increase of the conductivity at low temperatures. The room temperature conductivity of 0.20 × 105 S m -1 indicates an excellent sample quality.

  15. A Fast, Versatile Nanoprobe for Complex Materials: The Sub-micron Resolution X-ray Spectroscopy Beamline at NSLS-II (491st Brookhaven Lecture)

    SciTech Connect

    Thieme, Juergen

    2014-02-06

    Time is money and for scientists who need to collect data at research facilities like Brookhaven Lab’s National Synchrotron Light Source (NSLS), “beamtime” can be a precious commodity. While scanning a complex material with a specific technique and standard equipment today would take days to complete, researchers preparing to use brighter x-rays and the new sub-micron-resolution x-ray spectroscopy (SRX) beamline at the National Synchrotron Light Source II (NSLS-II) could scan the same sample in greater detail with just a few hours of beamtime. Talk about savings and new opportunities for researchers! Users will rely on these tools for locating trace elements in contaminated soils, developing processes for nanoparticles to deliver medical treatments, and much more. Dr. Thieme explains benefits for next-generation research with spectroscopy and more intense x-rays at NSLS-II. He discusses the instrumentation, features, and uses for the new SRX beamline, highlighting its speed, adjustability, and versatility for probing samples ranging in size from millimeters down to the nanoscale. He will talk about complementary beamlines being developed for additional capabilities at NSLS-II as well.

  16. Hygroscopicity of Chemically Aged, sub-micron Squalane Particles: On the Role of Size and Composition towards the Hygroscopicity Parameter κ

    NASA Astrophysics Data System (ADS)

    Harmon, C. W.; Smith, J. D.; Che, D. L.; Leone, S. R.; Wilson, K. R.

    2010-12-01

    Measurements presented herein explore cloud condensation nuclei (CCN) activity of sub-micron squalane particles chemically aged by hydroxyl radicals as a function of size and OH exposure. As squalane particles are exposed to OH radicals, size-selected 100, 150, and 200 nm particles monotically decrease in size with increasing OH exposure. Concurrently, their CCN derived hygroscopicity parameter values, κ, increase with OH exposure until saturating at 0.165 in the 100 nm data set, 0.140 in the 150 nm data set, and reach a maximum value of 0.075 in the 200 nm data set at the highest level of OH exposure. The critical super-saturation relative humidity (RH) at which CCN activity is achieved decreases initially with increasing OH exposure and then increases with OH exposure, most notably for the 100 nm data set and weakly with the 150 nm data set. Chemically aged squalane particles from the 200 nm data set show a monotonic decrease in critical super-saturation RH with all values of increasing OH exposure between 0.1-2.5 × 10^13 s molec./cc. The measured O:C ratios of 160 nm chemically aged squalane particles, which were reported previously, are compared to κ values by the CCN derived relationship reported in literature: κ = 0.30*O:C and reasonable agreement is attained in the size-selected 150 nm data set. These values are also compared with the hygroscopic growth factor derived relationship in literature: κ = 0.49*(O:C -0.25) and reasonable agreement is attained at O:C > 0.35.

  17. Bauxite and alumina

    USGS Publications Warehouse

    Bray, E.L.

    2009-01-01

    The article provides information on bauxite and alumina mining. U.S. states like Alabama, Arkansas and Georgia produced small amounts of bauxite and bauxitic clays for nonmetallurgical uses. Total metallurgical-grade bauxite imports in 2008 is cited. The leading suppliers of bauxite to the U.S. are Jamaica, Guinea and Brazil. The estimated domestic production of alumina in 2008 is mentioned. It also discusses consumption and prices of both bauxite and alumina.

  18. Room Temperature Deformation Mechanisms of Alumina Particles Observed from In Situ Micro-compression and Atomistic Simulations

    NASA Astrophysics Data System (ADS)

    Sarobol, Pylin; Chandross, Michael; Carroll, Jay D.; Mook, William M.; Bufford, Daniel C.; Boyce, Brad L.; Hattar, Khalid; Kotula, Paul G.; Hall, Aaron C.

    2016-01-01

    Aerosol deposition (AD) is a solid-state deposition technology that has been developed to fabricate ceramic coatings nominally at room temperature. Sub-micron ceramic particles accelerated by pressurized gas impact, deform, and consolidate on substrates under vacuum. Ceramic particle consolidation in AD coatings is highly dependent on particle deformation and bonding; these behaviors are not well understood. In this work, atomistic simulations and in situ micro-compressions in the scanning electron microscope, and the transmission electron microscope (TEM) were utilized to investigate fundamental mechanisms responsible for plastic deformation/fracture of particles under applied compression. Results showed that highly defective micron-sized alumina particles, initially containing numerous dislocations or a grain boundary, exhibited no observable shape change before fracture/fragmentation. Simulations and experimental results indicated that particles containing a grain boundary only accommodate low strain energy per unit volume before crack nucleation and propagation. In contrast, nearly defect-free, sub-micron, single crystal alumina particles exhibited plastic deformation and fracture without fragmentation. Dislocation nucleation/motion, significant plastic deformation, and shape change were observed. Simulation and TEM in situ micro-compression results indicated that nearly defect-free particles accommodate high strain energy per unit volume associated with dislocation plasticity before fracture. The identified deformation mechanisms provide insight into feedstock design for AD.

  19. Room temperature deformation mechanisms of alumina particles observed from in situ micro-compression and atomistic simulations.

    SciTech Connect

    Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay D.; Mook, William M.; Bufford, Daniel Charles; Boyce, Brad L.; Hattar, Khalid Mikhiel; Kotula, Paul G.; Hall, Aaron Christopher

    2015-09-22

    Aerosol deposition (AD) is a solid-state deposition technology that has been developed to fabricate ceramic coatings nominally at room temperature. Sub-micron ceramic particles accelerated by pressurized gas impact, deform, and consolidate on substrates under vacuum. Ceramic particle consolidation in AD coatings is highly dependent on particle deformation and bonding; these behaviors are not well understood. In this work, atomistic simulations and in situ micro-compressions in the scanning electron microscope, and the transmission electron microscope (TEM) were utilized to investigate fundamental mechanisms responsible for plastic deformation/fracture of particles under applied compression. Results showed that highly defective micron-sized alumina particles, initially containing numerous dislocations or a grain boundary, exhibited no observable shape change before fracture/fragmentation. Simulations and experimental results indicated that particles containing a grain boundary only accommodate low strain energy per unit volume before crack nucleation and propagation. In contrast, nearly defect-free, sub-micron, single crystal alumina particles exhibited plastic deformation and fracture without fragmentation. Dislocation nucleation/motion, significant plastic deformation, and shape change were observed. Simulation and TEM in situ micro-compression results indicated that nearly defect-free particles accommodate high strain energy per unit volume associated with dislocation plasticity before fracture. As a result, the identified deformation mechanisms provide insight into feedstock design for AD.

  20. Room temperature deformation mechanisms of alumina particles observed from in situ micro-compression and atomistic simulations.

    DOE PAGES

    Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay D.; Mook, William M.; Bufford, Daniel Charles; Boyce, Brad L.; Hattar, Khalid Mikhiel; Kotula, Paul G.; Hall, Aaron Christopher

    2015-09-22

    Aerosol deposition (AD) is a solid-state deposition technology that has been developed to fabricate ceramic coatings nominally at room temperature. Sub-micron ceramic particles accelerated by pressurized gas impact, deform, and consolidate on substrates under vacuum. Ceramic particle consolidation in AD coatings is highly dependent on particle deformation and bonding; these behaviors are not well understood. In this work, atomistic simulations and in situ micro-compressions in the scanning electron microscope, and the transmission electron microscope (TEM) were utilized to investigate fundamental mechanisms responsible for plastic deformation/fracture of particles under applied compression. Results showed that highly defective micron-sized alumina particles, initially containingmore » numerous dislocations or a grain boundary, exhibited no observable shape change before fracture/fragmentation. Simulations and experimental results indicated that particles containing a grain boundary only accommodate low strain energy per unit volume before crack nucleation and propagation. In contrast, nearly defect-free, sub-micron, single crystal alumina particles exhibited plastic deformation and fracture without fragmentation. Dislocation nucleation/motion, significant plastic deformation, and shape change were observed. Simulation and TEM in situ micro-compression results indicated that nearly defect-free particles accommodate high strain energy per unit volume associated with dislocation plasticity before fracture. As a result, the identified deformation mechanisms provide insight into feedstock design for AD.« less

  1. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  2. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, M.A.; Guangyao Sheng.

    1993-05-04

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  3. Reuse of activated alumina

    SciTech Connect

    Hobensack, J.E.

    1991-12-31

    Activated alumina is used as a trapping media to remove trace quantities of UF{sub 6} from process vent streams. The current uranium recovery method employs concentrated nitric acid which destroys the alumina pellets and forms a sludge which is a storage and disposal problem. A recently developed technique using a distilled water rinse followed by three dilute acid rinses removes on average 97% of the uranium, and leaves the pellets intact with crush strength and surface area values comparable with new material. Trapping tests confirm the effectiveness of the recycled alumina as UF{sub 6} trapping media.

  4. Agglomeration-Free Distributor for Fluidized Beds

    NASA Technical Reports Server (NTRS)

    Ouyang, F.; Sinica, A.; Levenspiel, O.

    1986-01-01

    New gas distributor for fluidized beds prevents hot particles from reacting on it and forming hard crust. In reduction of iron ore in fluidized bed, ore particles do not sinter on distributor and perhaps clog it or otherwise interfere with gas flow. Distributor also relatively cool. In fluidized-bed production of silicon, inflowing silane does not decompose until within bed of hot silicon particles and deposits on them. Plates of spiral distributor arranged to direct incoming gas into spiral flow. Turbulence in flow reduces frequency of contact between fluidized-bed particles and distributor.

  5. Alumina fiber strength improvement

    NASA Technical Reports Server (NTRS)

    Pepper, R. T.; Nelson, D. C.

    1982-01-01

    The effective fiber strength of alumina fibers in an aluminum composite was increased to 173,000 psi. A high temperature heat treatment, combined with a glassy carbon surface coating, was used to prevent degradation and improve fiber tensile strength. Attempts to achieve chemical strengthening of the alumina fiber by chromium oxide and boron oxide coatings proved unsuccessful. A major problem encountered on the program was the low and inconsistent strength of the Dupont Fiber FP used for the investigation.

  6. Bauxite and alumina

    USGS Publications Warehouse

    Bray, E.L.

    2011-01-01

    The article discusses the latest developments in the bauxite and alumina industry, particularly in the U.S., as of June 2011. It claims that the U.S. mainly relies on imports for its bauxite consumption. Several states, including Alabama, Arkansas and Georgia, however, produce small amounts of bauxite and bauxitic clays for nonmetallurgical purposes. The major exporters of alumina to the U.S. include Australia, Brazil and Jamaica.

  7. Large pore alumina

    SciTech Connect

    Ternan, M. )

    1994-04-01

    Earlier the authors reported preparation conditions for an alumina material which contained large diameter macropores (0.1-100 [mu]). The preparation variable that caused the formation of the uncommonly large macropores was the large acid/alumina ratios which were very much greater than the ones used in the preparation of conventional porous aluminas. The alumina material had large BET surface areas (200 m[sup 2]/g) and small mercury porosimetry surface areas (1 m[sup 2]/g). This indicated that micropores (d[sub MIP]<2 nm) were present in the alumina, since they were large enough for nitrogen gas molecules to enter, but too small for mercury to enter. As a result they would be too small for significant diffusion rates of residuum molecules. In earlier work, the calcining temperature was fixed at 500[degrees]C. In the current work, variations in both calcining temperature and calcining time were used in an attempt to convert some of the micropores into mesopores. 12 refs., 2 figs., 1 tab.

  8. Bauxite and alumina

    USGS Publications Warehouse

    Bray, E.L.

    2010-01-01

    The article reports on the global market performance of bauxite and alumina in 2009 and presents an outlook for their 2010 performance. There were only several U.S. states that could produce bauxite and bauxitic clays including Georgia, Arkansas, and Alabama. The prices for imported refractory-grade calcined bauxite ranged between 426 U.S. dollars and 554 dollars per ton.

  9. Solid Lubricant For Alumina

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher; Pepper, Stephen V.; Honecy, Frank S.

    1993-01-01

    Outer layer of silver lubricates, while intermediate layer of titanium ensures adhesion. Lubricating outer films of silver deposited on thin intermediate films of titanium on alumina substrates found to reduce sliding friction and wear. Films provide effective lubrication for ceramic seals, bearings, and other hot sliding components in advanced high-temperature engines.

  10. Alumina Technology Roadmap

    SciTech Connect

    none,

    2002-02-01

    The Alumina Technology Roadmap outlines a comprehensive long-term research and development plan that defines the industry's collective future and establishes a clear pathway forward. It emphasizes twelve high-priority R&D areas deemed most significant in addressing the strategic goals.

  11. High Temperature Stability of Potassium Beta Alumina

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Kisor, A.; Ryan, M. A.

    1996-01-01

    None. From Objectives section: Evaluate the stability of potassium beta alumina under potassium AMTEC operating conditions. Evaluate the stability regime in which potassium beta alumina can be fabricated.

  12. Calcium aluminate in alumina

    NASA Astrophysics Data System (ADS)

    Altay, Arzu

    The properties of ceramic materials are determined not only by the composition and structure of the phases present, but also by the distribution of impurities, intergranular films and second phases. The phase distribution and microstructure both depend on the fabrication techniques, the raw materials used, the phase-equilibrium relations, grain growth and sintering processes. In this dissertation research, various approaches have been employed to understand fundamental phenomena such as grain growth, impurity segregation, second-phase formation and crystallization. The materials system chosen was alumina intentionally doped with calcium. Atomic-scale structural analyses of grain boundaries in alumina were carried on the processed samples. It was found that above certain calcium concentrations, CA6 precipitated as a second phase at all sintering temperatures. The results also showed that abnormal grain growth can occur after precipitation and it is not only related to the calcium level, but it is also temperature dependent. In order to understand the formation mechanism of CA6 precipitates in calcium doped alumina samples, several studies have been carried out using either bulk materials or thin films The crystallization of CA2 and CA6 powders has been studied. Chemical processing techniques were used to synthesize the powders. It was observed that CA2 powders crystallized directly, however CA6 powders crystallized through gamma-Al 2O3 solid solution. The results of energy-loss near-edge spectrometry confirmed that gamma-Al2O3 can dissolve calcium. Calcium aluminate/alumina reaction couples have also been investigated. All reaction couples were heat treated following deposition. It was found that gamma-Al2O3 was formed at the interface as a result of the interfacial reaction between the film and the substrate. gamma-Al 2O3 at the interface was stable at much higher temperatures compared to the bulk gamma-Al2O3 formed prior to the CA6 crystallization. In order to

  13. Bauxite Mining and Alumina Refining

    PubMed Central

    Frisch, Neale; Olney, David

    2014-01-01

    Objective: To describe bauxite mining and alumina refining processes and to outline the relevant physical, chemical, biological, ergonomic, and psychosocial health risks. Methods: Review article. Results: The most important risks relate to noise, ergonomics, trauma, and caustic soda splashes of the skin/eyes. Other risks of note relate to fatigue, heat, and solar ultraviolet and for some operations tropical diseases, venomous/dangerous animals, and remote locations. Exposures to bauxite dust, alumina dust, and caustic mist in contemporary best-practice bauxite mining and alumina refining operations have not been demonstrated to be associated with clinically significant decrements in lung function. Exposures to bauxite dust and alumina dust at such operations are also not associated with the incidence of cancer. Conclusions: A range of occupational health risks in bauxite mining and alumina refining require the maintenance of effective control measures. PMID:24806720

  14. Impact of smoking on guided tissue regeneration using a biocomposite poly (lactic-co-glycolic) acid/sub-micron size hydroxyapatite with a rubber dam as an alternative barrier.

    PubMed

    Stramazzotti, D; Coiana, C; Zizzi, A; Spazzafumo, L; Sauro, S; D'Angelo, A B; Rubini, C; Aspriello, S D

    2015-03-01

    The purpose of our study was to critically evaluate the results obtained from a guided tissue regeneration technique after 12 months using a bocomposite poly (lactic-co-glycolic) acid/sub-micron size hydroxyapatite (PLGA/HA) with a rubber dam as a barrier in smoking and non-smoking patients. We selected 36 patients (18 current smokers and 18 non-smokers) diagnosed with chronic advanced periodontitis with a periodontal site (probing depth [PD] >5) amenable to regenerative surgery. Twelve months after surgery, the periodontal parameters were found to have statistically improved, when non-smokers were compared with smokers, in: PD reduction (6.3 ± 2.1 mm vs. 3.6 ± 1.9 mm); CAL gain (4.4 ± 1.1 vs. 2.8 ± 2.2 mm); recession (1.8 ± 1.4 mm vs. 0.8 ± 0.9 mm); and hard tissue fill (4.7 ± 0.8 mm vs. 2.8 ± 2.1 mm). Furthermore, since we found PD baseline differences between groups, smoking seemed not to influence the outcomes achieved (CAL gain and ΔREC) 12 months post surgery with respect to PD baseline. The use of PLGA/HA with a rubber dam significantly improved the periodontal parameters in both smoking and non-smoking subjects. This improvement was nevertheless lower in smokers than the non-smokers, confirming the negative impact of smoking on periodontal regeneration.

  15. A Novel sub-micron electrostatic motor

    NASA Astrophysics Data System (ADS)

    Wright, J. H.

    2002-11-01

    Mathematical models in one dimension are developed for a recently proposed device [1] that utilizes the electric field energy of a thermally-charged open-gap p-n junction, in violation of the second law. The first model relies on an unstable steady-state representation of the dynamics of the machine to illuminate regions of viability in parameter space. This model admits a representation of the dynamics of the system by means of a second order nonlinear ODE whose phase plane trajectories are plotted and analyzed, but which does not address such practical issues as startup, loading, friction, etc. The second, improved, model is based on a coupled system of partial differential equations, and better captures the dynamics. The two models are compared, and suggestions for future directions in research and development are presented.

  16. Gelcasting Polycrystalline Alumina

    SciTech Connect

    Janney, M.A.; Zuk, K.J.; Wei, G.C.

    2000-01-01

    OSRAM SYLVANIA INC. is a major U.S. manufacturer of high-intensity lighting. Among its products is the Lumalux TM line of high-pressure sodium vapor arc lamps, which are used for industrial, highway, and street lighting. The key to the performance of these lamps is the polycrystalline alumina (PCA) tube that is used to contain the plasma that is formed in the electric arc. That plasma consists of ionized sodium, mercury, and xenon vapors. The key attributes of the PCA tubes are their transparency ({approximately}97% total transmittance in the visible), their refractoriness (inner wall temperature can reach l2OOC), and their chemical resistance (sodium and mercury vapor are extremely corrosive). The current efficiency of the lamps is very high, up to 100 initial lumens per watt. (Compare incandescent lamps 10-20 lumens per watt, fluorescent lamps 25-90 lumens per watt.)

  17. Alumina-Reinforced Zirconia Composites

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Bansal, Narottam P.

    2003-01-01

    Alumina-reinforced zirconia composites, used as electrolyte materials for solid oxide fuel cells, were fabricated by hot pressing 10 mol percent yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina particulates and platelets each containing 0 to 30 mol percent alumina. Major mechanical and physical properties of both particulate and platelet composites including flexure strength, fracture toughness, slow crack growth, elastic modulus, density, Vickers microhardness, thermal conductivity, and microstructures were determined as a function of alumina content either at 25 C or at both 25 and 1000 C. Flexure strength and fracture toughness at 1000 C were maximized with 30 particulate and 30 mol percent platelet composites, respectively, while resistance to slow crack growth at 1000 C in air was greater for 30 mol percent platelet composite than for 30 mol percent particulate composites.

  18. Gelcast zirconia-alumina composites

    SciTech Connect

    Omatete, O.O.; Bleier, A.; Westmoreland, C.G.; Young, A.C.

    1991-01-01

    Near net-shaped parts of zirconia-alumina composites have been successfully formed by gelcasting, a technique which utilizes in situ polymerization of acrylamide monomers. The high solids loading required for gelcasting ({approximately}50 vol %) was obtained by controlling the pH-dependent stability of the aqueous zirconia-alumina suspensions. A strong correspondence was found among the surface charges on the particles, colloidal stability, and the maximum solids loading. 14 refs., 3 figs., 2 tabs.

  19. Gelcasting polycrystalline alumina

    SciTech Connect

    Janney, M.A.

    1997-04-01

    This work is being done as part of a CRADA with Osram-Sylvania, Inc. (OSI) OSI is a major U.S. manufacturer of high-intensity lighting. Among its products is the Lumalux{reg_sign} line of high-pressure sodium vapor arc lamps, which are used for industrial, highway, and street lighting. The key to the performance of these lamps is the polycrystalline alumina (PCA) tube that is used to contain the plasma that is formed in the electric arc. That plasma consists of ionized sodium, mercury, and xenon vapors. The key attributes of the PCA tubes are their transparency (95% total transmittance in the visible region), their refractoriness (inner wall temperature can reach 1400{degrees}C), and their chemical resistance (sodium and mercury vapor are extremely corrosive). The current efficiency of the lamps is very high, on the order of several hundred lumens / watt. (Compare - incandescent lamps -13 lumens/watt fluorescent lamps -30 lumens/watt.) Osram-Sylvania would like to explore using gelcasting to form PCA tubes for Lumalux{reg_sign} lamps, and eventually for metal halide lamps (known as quartz-halogen lamps). Osram-Sylvania, Inc. currently manufactures PCA tubes by isostatic pressing. This process works well for the shapes that they presently use. However, there are several types of tubes that are either difficult or impossible to make by isostatic pressing. It is the desire to make these new shapes and sizes of tubes that has prompted Osram-Sylvania`s interest in gelcasting. The purpose of the CRADA is to determine the feasibility of making PCA items having sufficient optical quality that they are useful in lighting applications using gelcasting.

  20. Nickel in high-alumina basalts

    USGS Publications Warehouse

    Hedge, C.E.

    1971-01-01

    New analyses of high-alumina basalts reveal an average nickel content higher than previously indicated. Ni in high-alumina basalts correlates with magnesium in the same way as it does in other basalt types. There is therefore no reason, based on Ni contents, to hypothesize a special origin for high-alumina basalts and it is permissible (based on Ni contents) to form andesites by fractional crystallization from high-alumina basalts. ?? 1971.

  1. Attrition resistant gamma-alumina catalyst support

    DOEpatents

    Singleton, Alan H.; Oukaci, Rachid; Goodwin, James G.

    2006-03-14

    A .gamma.-alumina catalyst support having improved attrition resistance produced by a method comprising the steps of treating a particulate .gamma.-alumina material with an acidic aqueous solution comprising water and nitric acid and then, prior to adding any catalytic material thereto, calcining the treated .gamma.-alumina.

  2. Alumina-Enhanced Thermal Barrier

    NASA Technical Reports Server (NTRS)

    Smith, Marnell; Leiser, Dan; Goldstein, Howard

    1989-01-01

    Rigid, fibrous ceramic tile material called "alumina-enhanced thermal barrier" (AETB) extends temperature capability of insulating materials. Material has obvious potential for terrestrial use in kilns, furnaces, heat engines, and other applications in which light weight and high operating temperature are specified. Three kinds of ceramic fibers are blended, molded, and sintered to make refractory tiles.

  3. Alumina as a Thermoluminescent Material

    SciTech Connect

    Uzun, Erdem; Yarar, Yasemin

    2007-04-23

    Thermoluminescence dosimeters are extensively used for quantitative dose measurements in various irradiation fields. They are also important for environmental monitoring after nuclear accident and weapon tests. In this work, the principles of TLD dosimeter and characteristics of several TLD materials are presented. Besides, taken into account the importance as a raw material, the utilization of domestic alumina (Al2O3) in TLDs as a thermoluminescent material is discussed.

  4. Method for preparing Pb-. beta. ''-alumina ceramic

    DOEpatents

    Hellstrom, E.E.

    1984-08-30

    A process is disclosed for preparing impermeable, polycrystalline samples of Pb-..beta..''-alumina ceramic from Na-..beta..''-alumina ceramic by ion exchange. The process comprises two steps. The first step is a high-temperature vapor phase exchange of Na by K, followed by substitution of Pb for K by immersing the sample in a molten Pb salt bath. The result is a polycrystalline Pb-..beta..''-alumina ceramic that is substantially crack-free.

  5. Physical chemistry of carbothermic reduction of alumina

    SciTech Connect

    Frank, Robert A.

    1985-09-01

    Production of aluminium, by means of carbothermic reduction of alumina, is discussed. By employing a solvent metal bath to absorb the alumina metal, carbothermic reduction of alumina was accomplished at temperatures 300/degree/C lower than the temperatures reported in the literature. Reduction occurred without the formation of intermediate compounds and without the high volatilization of aluminum bearing species. Reduction of alumina immersed in a solvent bath appeared to be rate limited by chemical reaction control. The rates seemed to be a function of the activity of aluminum in the solvent metal bath. Reduction of alumina particles, above the surface of the bath, seemed to occur via vapor transport with carbon in the particles or in the crucible walls. Mass transport in the gas phase appeared to be rate limiting. The rates seemed to be a function of the distance separating the alumina and carbon sources. With both submerged alumina and alumina particles, increasing the surface area of the alumina increased the rate of reduction. 58 refs., 65 figs., 9 tabs.

  6. Perfluoropolyalkylether decomposition on catalytic aluminas

    NASA Technical Reports Server (NTRS)

    Morales, Wilfredo

    1994-01-01

    The decomposition of Fomblin Z25, a commercial perfluoropolyalkylether liquid lubricant, was studied using the Penn State Micro-oxidation Test, and a thermal gravimetric/differential scanning calorimetry unit. The micro-oxidation test was conducted using 440C stainless steel and pure iron metal catalyst specimens, whereas the thermal gravimetric/differential scanning calorimetry tests were conducted using catalytic alumina pellets. Analysis of the thermal data, high pressure liquid chromatography data, and x-ray photoelectron spectroscopy data support evidence that there are two different decomposition mechanisms for Fomblin Z25, and that reductive sites on the catalytic surfaces are responsible for the decomposition of Fomblin Z25.

  7. Nanohardness of Sintered and Shock Deformed Alumina

    NASA Astrophysics Data System (ADS)

    Chakraborty, Riya; Dey, Arjun; Mukhopadhyay, Anoop K.; Joshi, Keshaw D.; Rav, Amit; Mandal, Ashok K.; Bysakh, Sandip; Biswas, Sampad K.; Gupta, Satish C.

    2012-02-01

    To understand how high-strain rate, flyer-plate impact affects the nanohardness of a coarse (~10 μm) grain, high-density (~3.978 gm cc-1) alumina, load controlled nanoindentation experiments were conducted with a Berkovich indenter on as-sintered disks and shock-recovered alumina fragments obtained from an earlier flyer-plate shock impact study. The nanohardness of the shock-recovered alumina was much lower than that of the as-sintered alumina. The indentation size effect was severe in the shock-recovered alumina but only mild in the as-sintered alumina. Extensive additional characterization by field emission scanning electron microscopy, transmission electron microscopy, and analysis of the experimental load depth data were used to provide a new explanation for the presence of strong indentation size effect in the shock-recovered alumina. Finally, a qualitative model was proposed to provide a rationale for the whole scenario of nanoindentation responses in the as-sintered and shock-recovered alumina ceramics.

  8. Hydrogen and the structure of transition aluminas

    SciTech Connect

    Sohlberg, K.; Pennycook, S.J.; Pantelides, S.T.

    1999-08-25

    {alpha}-Alumina results from the complete dehydration of several minerals of the form Al{sub 2}O{sub 3}{center{underscore}dot}nH{sub 2}O. The ``transition'' aluminas, {gamma}-alumina, {eta}-alumina, and {delta}-alumina are known to have a spinel structure but the possibility that they contain hydrogen (H) has been the subject of debate. The authors present a series of density-functional theory calculations which, together with available experimental data, show that the spinel aluminas exist over a range of hydrogen content captured by the empirical formula H{sub 3m}Al{sub 2{minus}m}O{sub 3}, with a different greek-letter phases corresponding to different distributions of the Aluminum (Al) ions on the two cation sublattices. Calculations of densities and vibrational frequencies of bulk OH bonds are in excellent agreement with available data. The theory reconciles seemingly inconsistent data and reveals a remarkable property of the spinel aluminas: They are ``reactive sponges'' in that they can store and release water in a reactive way. This chemical activity offers a basis for understanding long-standing puzzles in the behavior of aluminas in catalytic systems.

  9. Effects of Impurities on Alumina-Niobium InterfacialMicrostructures

    SciTech Connect

    McKeown, Joseph T.; Sugar, Joshua D.; Gronsky, Ronald; Glaeser,Andreas M.

    2005-06-20

    Optical microscopy, scanning electron microscopy, and transmission electron microscopy were employed to examine the interfacial microstructural effects of impurities in alumina substrates used to fabricate alumina-niobium interfaces via liquid-film-assisted joining. Three types of alumina were used: undoped high-purity single-crystal sapphire; a high-purity, high-strength polycrystalline alumina; and a lower-purity, lower-strength polycrystalline alumina. Interfaces formed between niobium and both the sapphire and high-purity polycrystalline alumina were free of detectable levels of impurities. In the lower-purity alumina, niobium silicides were observed at the alumina-niobium interface and on alumina grain boundaries near the interface. These silicides formed in small-grained regions of the alumina and were found to grow from the interface into the alumina along grain boundaries. Smaller silicide precipitates found on grain boundaries are believed to form upon cooling from the bonding temperature.

  10. Alumina forming iron base superalloy

    DOEpatents

    Yamamoto, Yukinori; Muralidharan, Govindarajan; Brady, Michael P.

    2014-08-26

    An austenitic stainless steel alloy, consists essentially of, in weight percent 2.5 to 4 Al; 25 to 35 Ni; 12 to 19 Cr; at least 1, up to 4 total of at least one element selected from the group consisting of Nb and Ta; 0.5 to 3 Ti; less than 0.5 V; 0.1 to 1 of at least on element selected from the group consisting of Zr and Hf; 0.03 to 0.2 C; 0.005 to 0.1 B; and base Fe. The weight percent Fe is greater than the weight percent Ni. The alloy forms an external continuous scale including alumina, and contains coherent precipitates of .gamma.'-Ni.sub.3Al, and a stable essentially single phase FCC austenitic matrix microstructure. The austenitic matrix is essentially delta-ferrite-free and essentially BCC-phase-free.

  11. Fabrication of thin layer beta alumina

    NASA Technical Reports Server (NTRS)

    Tennenhouse, G. J.

    1977-01-01

    Beta alumina tubes having walls 700 microns, 300 microns, and 140 microns were processed by extrusion and sintering utilizing Ford proprietary binder and fabrication systems. Tubes prepared by this method have properties similar to tubes prepared by isostatic pressing and sintering, i.e. density greater than 98% of theoretical and a helium leak rate less than 3 x 10 to the -9th power cc/sq cm/sec. Ford ultrasonic bonding techniques were used for bonding beta alumina end caps to open ended beta -alumina tubes prior to sintering. After sintering, the bond was hermetic, and the integrity of the bonded area was comparable to the body of the tube.

  12. Nanoporous alumina enhanced surface plasmon resonance sensors

    NASA Astrophysics Data System (ADS)

    Koutsioubas, Alexandros G.; Spiliopoulos, Nikolaos; Anastassopoulos, Dimitris; Vradis, Alexandros A.; Priftis, George D.

    2008-05-01

    The signal enhancement of an easy to fabricate, nanoporous alumina assisted surface plasmon resonance (SPR) sensor is investigated. It is theoretically shown that the presence of a thin (under 200nm) porous alumina layer on top of an aluminum film supporting the surface plasmons, may significantly increase (over one order of magnitude) the sensitivity of the SPR method in the case where the adsorption of relatively small molecules is probed. The comparative experimental investigation of self-assembled monolayer formation on planar metal films and porous alumina layers verifies the theoretical predictions. Based on these results, we discuss the extended applicability of this setup in biosensor and other related applications.

  13. Effect of alumina composition on interfacial chemistry and strength of direct bonded copper-alumina

    SciTech Connect

    Holowczak, J.E.; Greenhut, V.A.; Shanefield, D.J.

    1989-10-01

    The gas-metal eutectic method was used to bond copper to sintered high alumina ceramics which had different sintering aid compositions in the magnesia-calcia-silica system. The highest average copper-alumina peel adhesion strength, 205 N/cm, was observed for alumina which contained 0.2 percent magnesia and 0.2 percent calcia. The lowest peel adhesion strength, 103 N/cm, was observed for copper bonded to 95 percent alumina which contained magnesia, calcia, and silica additions. This bond strength was similar to that for commercial 96 percent alumina. Statistical matrix experiments showed that alumina containing calcium silicate had significantly lower copper bond strength. This may be attributed to the formation of a transition compound other than the copper aluminate phase identified for well bonded samples in this study. 10 refs.

  14. Use of fracture mechanics theory in lifetime predictions for alumina and bioglass-coated alumina.

    PubMed

    Ritter, J E; Greenspan, D C; Palmer, R A; Hench, L L

    1979-03-01

    The fatigue behavior of alumina and bioglass-coated alumina was determined in air and biological test environments by the dynamic fatigue test technique in which strength is measured as a function of stressing rate. The good correlation found between the test data and fracture mechanics theory indicates that fatigue failure is controlled by the slow crack growth of preexisting flaws and that fracture mechanics theory can be used in making failure predictions for alumina and bioglass-coated alumina in biological environments. Thus, it is believed that lifetime predictions can be made for ceramic implants on the basis of short-term test data utilizing fracture mechanics principles.

  15. Sorption of metal ions on alumina

    SciTech Connect

    Baumgarten, E.; Kirchhausen-Duesing, U.

    1997-10-01

    The adsorption of metal ions on aluminas is of great interest in different fields such as geochemistry, oceanography, limnology, and pollution control. Precipitation and adsorption of metal ions (Co(II), Ni(II), Cu(II), and Cr(III)) on {gamma}-alumina were investigated experimentally. A surface chemical reaction model to calculate concentrations of aluminum ions, metal ions, and pH as variables depending on amount of alumina, volume of liquid and gas phase, initial metal concentration, and amount of acid or base added is presented. In the case of Co(II) the pH dependence of rest concentrations with and without alumina is equal; adsorption may be disregarded. For the other ions adsorption is important. Considering the charge of the surface does not improve the fit. In the pH region, where adsorption leads to lower rest concentrations than precipitation, adsorption may be described by a Henry isotherm.

  16. Loss tangent measurements on unirradiated alumina

    SciTech Connect

    Zinkle, S.J.; Goulding, R.H.

    1996-04-01

    Unirradiated room temperature loss tangent for sapphire and several commercial grades of polycrystalline alumina are complied for frequencies between 10{sup 5} and 4x10{sup 11} Hz. Sapphire exhibits significantly lower values for the loss tangent at frequencies up to 10{sup 11} Hz. The loss tangents of 3 different grades of Wesgo alumina (AL300, AL995, AL998) and 2 different grades of Coors alumina (AD94, AD995) have typical values near {approx}10{sup -4} at a frequency of 10{sup 8} Hz. On the other hand, the loss tangent of Vitox alumina exhibits a large loss peak tan d{approx} 5x10{sup -3} at this frequency.

  17. Processing of Alumina-Toughened Zirconia Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Choi, Sung R.

    2003-01-01

    Dense and crack-free 10-mol%-yttria-stabilized zirconia (10YSZ)-alumina composites, containing 0 to 30 mol% of alumina, have been fabricated by hot pressing. Release of pressure before onset of cooling was crucial in obtaining crack-free material. Hot pressing at 1600 C resulted in the formation of ZrC by reaction of zirconia with grafoil. However, no such reaction was observed at 1500 C. Cubic zirconia and -alumina were the only phases detected from x-ray diffraction indicating no chemical reaction between the composite constituents during hot pressing. Microstructure of the composites was analyzed by scanning electron microscopy and transmission electron microscopy. Density and elastic modulus of the composites followed the rule-of-mixtures. Addition of alumina to 10YSZ resulted in lighter, stronger, and stiffer composites by decreasing density and increasing strength and elastic modulus.

  18. Everlasting Dark Printing on Alumina by Laser

    NASA Astrophysics Data System (ADS)

    Penide, J.; Quintero, F.; Arias-González, F.; Fernández, A.; del Val, J.; Comesaña, R.; Riveiro, A.; Lusquiños, F.; Pou, J.

    Marks or prints are needed in almost every material, mainly for decorative or identification purposes. Despite alumina is widely employed in many different industries, the need of printing directly on its surface is still a complex problem. In this sense, lasers have largely demonstrated their high capacities to mark almost every material including ceramics, but performing dark permanent marks on alumina is still an open challenge. In this work we present the results of a comprehensive experimental analysis on the process of marking alumina by laser. Four different laser sources were used in this study: a fiber laser (1075 nm) and three diode pumped Nd:YVO4 lasers emitting at near-infrared (1064 nm), visible (532 nm) and ultraviolet (355 nm) wavelengths, respectively. The results obtained with the four lasers were compared and physical processes involved were explained in detail. Colorimetric analyses allowed to identify the optimal parameters and conditions to produce everlasting and high contrast marks on alumina.

  19. A negative surface energy for alumina.

    PubMed

    Łodziana, Zbigniew; Topsøe, Nan-Yu; Nørskov, Jens K

    2004-05-01

    The surface energy of a solid measures the energy cost of increasing the surface area. All normal solids therefore have a positive surface energy-if it had been negative, the solid would disintegrate. For this reason it is also generally believed that when certain ceramics can be found in a highly porous form, this is a metastable state, which will eventually sinter into the bulk solid at high temperatures. We present theoretical evidence suggesting that for theta-alumina, the surface energy is strongly dependent on the size of the crystallites, and that for some facets it is negative for thicknesses larger than approximately 1 nm. This suggests a completely new picture of porous alumina in which the high-surface-area, nanocrystalline form is the thermodynamic ground state. The negative surface energy is found to be related to a particularly strongly adsorbed state of dissociated water on some alumina surfaces. We also present new experimental evidence based on infrared spectroscopy, in conjunction with X-ray diffraction and surface-area measurements, that theta-alumina has indeed very stable surface OH groups at high temperatures, and that this form of alumina does not sinter even at temperatures up to 1,300 K.

  20. Effect of alumina contents on phase stability and mechanical properties of magnesium fluorapatite/alumina composites.

    PubMed

    Hejazi, M S; Ahmadian, M; Meratian, M; Fathi, M H

    2014-12-01

    The aim of the present work was twofold: to prepare biphasic magnesium fluorapatite (MFA) composites with different amounts of alumina using a two-step sintering process, and to evaluate the effects of various amounts of alumina on the mechanical properties, phase stability, and densification of the composite samples. Initially, MFA powders were prepared with different amounts of alumina by mechanical activation and the MFA composite samples were subsequently prepared using the two-step sintering (TSS) method. In order to determine the appropriate temperature of the first step sintering, conventional sintering of MFA/50% alumina was carried out at temperatures in the range of 1000-1300°C. X-ray diffraction and scanning electron microscopy (SEM) techniques were used to characterize the prepared MFA/alumina composites. The results showed fracture toughness and hardness in the MFA/50% alumina composite samples to increase as a result of alumina addition to their maximum values of 5.82±1.05MPam(1/2) and 22.09±3.5GPa, respectively. PMID:25218990

  1. Dielectric Performance of a High Purity HTCC Alumina at High Temperatures - a Comparison Study with Other Polycrystalline Alumina

    NASA Technical Reports Server (NTRS)

    Chen, Liangyu

    2014-01-01

    A very high purity (99.99+%) high temperature co-fired ceramic (HTCC) alumina has recently become commercially available. The raw material of this HTCC alumina is very different from conventional HTCC alumina, and more importantly there is no glass additive in this alumina material for co-firing processing. Previously, selected HTCC and LTCC (low temperature co-fired ceramic) alumina materials were evaluated at high temperatures as dielectric and compared to a regularly sintered 96% polycrystalline alumina (96% Al2O3), where 96% alumina was used as the benchmark. A prototype packaging system based on regular 96% alumina with Au thickfilm metallization successfully facilitated long term testing of high temperature silicon carbide (SiC) electronic devices for over 10,000 hours at 500 C. In order to evaluate this new high purity HTCC alumina for possible high temperature packaging applications, the dielectric properties of this HTCC alumina substrate were measured and compared with those of 96% alumina and a previously tested LTCC alumina from room temperature to 550 C at frequencies of 120 Hz, 1 KHz, 10 KHz, 100 KHz, and 1 MHz. A parallel-plate capacitive device with dielectric of the HTCC alumina and precious metal electrodes were used for measurements of the dielectric constant and dielectric loss of the co-fired alumina material in the temperature and frequency ranges. The capacitance and AC parallel conductance of the capacitive device were directly measured by an AC impedance meter, and the dielectric constant and parallel AC conductivity of the dielectric were calculated from the capacitance and conductance measurement results. The temperature and frequency dependent dielectric constant, AC conductivity, and dissipation factor of the HTCC alumina substrate are presented and compared to those of 96% alumina and a selected LTCC alumina. Other technical advantages of this new co-fired material for possible high packaging applications are also discussed.

  2. Iron films deposited on porous alumina substrates

    NASA Astrophysics Data System (ADS)

    Yamada, Yasuhiro; Tanabe, Kenichi; Nishida, Naoki; Kobayashi, Yoshio

    2016-12-01

    Iron films were deposited on porous alumina substrates using an arc plasma gun. The pore sizes (120 - 250 nm) of the substrates were controlled by changing the temperature during the anodic oxidation of aluminum plates. Iron atoms penetrated into pores with diameters of less than 160 nm, and were stabilized by forming γ-Fe, whereas α-Fe was produced as a flat plane covering the pores. For porous alumina substrates with pore sizes larger than 200 nm, the deposited iron films contained many defects and the resulting α-Fe had smaller hyperfine magnetic fields. In addition, only a very small amount of γ-Fe was obtained. It was demonstrated that the composition and structure of an iron film can be affected by the surface morphology of the porous alumina substrate on which the film is grown.

  3. Nanoporous alumina-based interferometric transducers ennobled

    NASA Astrophysics Data System (ADS)

    Dronov, Roman; Jane, Andrew; Shapter, Joseph G.; Hodges, Alastair; Voelcker, Nicolas H.

    2011-08-01

    A high fidelity interferometric transducer is designed based on platinum-coated nanoporous alumina films. The ultrathin metal coating significantly improves fidelity of the interferometric fringe patterns in aqueous solution and increases the signal-to-noise ratio. The performance of this transducer is tested with respect to refractive index unit (RIU) sensitivity measured as a change in effective optical thickness (EOT) in response to a solvent change and compared to porous silicon based transducers. RIU sensitivity in the order of 55% is attainable for porous alumina providing excellent signal-to-noise ratio, which exceeds the sensitivity of current interferometric transducers. Finally, as a proof-of-principle, we demonstrate biosensing with two distinct immunoglobulin antibodies.A high fidelity interferometric transducer is designed based on platinum-coated nanoporous alumina films. The ultrathin metal coating significantly improves fidelity of the interferometric fringe patterns in aqueous solution and increases the signal-to-noise ratio. The performance of this transducer is tested with respect to refractive index unit (RIU) sensitivity measured as a change in effective optical thickness (EOT) in response to a solvent change and compared to porous silicon based transducers. RIU sensitivity in the order of 55% is attainable for porous alumina providing excellent signal-to-noise ratio, which exceeds the sensitivity of current interferometric transducers. Finally, as a proof-of-principle, we demonstrate biosensing with two distinct immunoglobulin antibodies. Electronic supplementary information (ESI) available: EOT sensorgram of adsorption of BSA and normal human IgG onto hydroxylated porous alumina, FWHM of interferometric spectra, and theoretical comparison of calculated RIU sensitivities for 1 µm thick porous alumina and porous silicon films. See DOI: 10.1039/c0nr00897d

  4. Chlorination of alumina in kaolinitic clay

    NASA Astrophysics Data System (ADS)

    Grob, B.; Richarz, W.

    1984-09-01

    The chlorination of alumina in kaolinitic clay with Cl2 and CO gas mixtures was studied gravimetrically. The effects of the calcination method and of NaCl addition on the reactivity of the clay were examined. Fast reaction rates were achieved only with samples previously exposed to a sulfating treatment. Optimum conditions, with maximum yield and selectivity to A1C13 and minimum SiO2 conversion, were found between 770 and 970 K. At higher temperatures the SiCl4 formed poisons the reactive alumina surface by selective chemisorption with a marked decrease of the reaction rate.

  5. Erosion damage in glass and alumina

    SciTech Connect

    Ritter, J.E.; Strzepa, P.; Jakus, K.; Rosenfeld, L.; Buckman, K.J.

    1984-08-14

    The effect of room-temperature erosion on material removal from and strength properties of soda-lime glass and sintered alumina was determined. The results were compared to the elastic/plastic indentation fracture model. The dependence of erosion rate and strength of soda-lime glass on the kinetic energy of the impacting particles was in good agreement with predictions. The lack of agreement between theory and experiment for sintered alumina was attributed to microstructural aspects of the erosion damage that are not modeled by indentation fracture.

  6. Delayed Failure in a Shock Loaded Alumina

    SciTech Connect

    Cooper, G. A.; Millett, J. C. F.; Bourne, N. K.; Dandekar, D. P.

    2006-07-28

    Manganin stress gauges have been used to measure the lateral stress in a shock-loaded alumina. In combination with known longitudinal stresses, these have been used to determine the shear strength of this material, behind the shock front. The two-step nature of the lateral stress traces shows a slow moving front behind the main shock, behind which shear strength undergoes a significant decrease. Results also show that this front decreases markedly in velocity as the HEL is crossed, suggesting that limited plasticity occurs during inelastic deformation. Finally, comparison of measured shear strengths with other aluminas shows a high degree of agreement.

  7. Structural transformations in reactively sputtered alumina films

    SciTech Connect

    Nayar, P. Khanna, A.

    2014-04-24

    Thin films of amorphous alumina of thickness ∼350 nm were prepared on silicon wafer by DC cathode reactive sputtering. The effects of thermal annealing on the structural properties were investigated at annealing temperatures of 600°C, 800°C, 1100°C and 1220°C. X-ray diffraction showed that crystallization starts at 800°C and produces δ and θ alumina phases, the latter phase grows with heat treatment and the film was predominantly δ-phase with small amount of a-phase after annealing at 1220°C. AFM studies found that the surface of thin films smoothened upon crystallization.

  8. 40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Siloxane modified alumina... Specific Chemical Substances § 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this...

  9. 40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Siloxane modified alumina... Specific Chemical Substances § 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this...

  10. 40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Siloxane modified alumina... Specific Chemical Substances § 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this...

  11. 40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Siloxane modified alumina... Specific Chemical Substances § 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this...

  12. REMOVING RADIUM FROM WATER BY PLAIN AND TREATED ACTIVATED ALUMINA

    EPA Science Inventory

    The research determined the feasibility of using BaSO4-impregnated activated alumina and plain activated alumina for radium removal from groundwater by fixed-bed adsorption. The major factors influencing radium adsorption onto the two types of alumina were identified. The radium ...

  13. 21 CFR 73.1010 - Alumina (dried aluminum hydroxide).

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Alumina (dried aluminum hydroxide). 73.1010... GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity. (1) The color additive alumina (dried aluminum hydroxide) is a white,...

  14. 21 CFR 73.1010 - Alumina (dried aluminum hydroxide).

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Alumina (dried aluminum hydroxide). 73.1010... GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity. (1) The color additive alumina (dried aluminum hydroxide) is a white,...

  15. 21 CFR 73.1010 - Alumina (dried aluminum hydroxide).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Alumina (dried aluminum hydroxide). 73.1010... GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity. (1) The color additive alumina (dried aluminum hydroxide) is a white,...

  16. 21 CFR 73.1010 - Alumina (dried aluminum hydroxide).

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Alumina (dried aluminum hydroxide). 73.1010... GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity. (1) The color additive alumina (dried aluminum hydroxide) is a white,...

  17. 21 CFR 73.1010 - Alumina (dried aluminum hydroxide).

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Alumina (dried aluminum hydroxide). 73.1010... GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity. (1) The color additive alumina (dried aluminum hydroxide) is a white,...

  18. Alumina-on-alumina Total Hip Arthroplasty in Young Patients: Diagnosis is More Important than Age

    PubMed Central

    Garcia-Rey, Eduardo; Cruz-Pardos, Ana

    2009-01-01

    Abstract Total hip arthroplasty (THA) in young patients has a high loosening rate, due in part to acetabular deformities that may compromise bone fixation and polyethylene wear. We therefore asked whether wear or osteolysis and loosening differ in patients under 40 years of age with alumina-on-alumina THA compared to those who are older. We prospectively followed 56 patients (63 hips) younger than 40 years (Group 1) and 247 patients (274 hips) older than 40 (Group 2) who had an alumina-on-alumina THA. The minimum followup was 4 years (mean, 5.6 years; range, 4–9 years). The two groups differed in various features: there were no patients with primary osteoarthritis in Group 1 and they had worse preoperative function and range of mobility, while weight, activity level, and implant size were greater in Group 2. The survival rate for cup loosening at 80 months postsurgery was 90.8% (95% confidence interval, 82.9–98.6%) for Group 1 and 96.5% (95% confidence interval, 94.2–98.7%) for Group 2. Cup loosening was less frequent with primary osteoarthritis than with severe developmental dysplasia of the hip. Although an alumina-on-alumina THA provided similar midterm survival and radiographic loosening in both age groups, the preoperative diagnosis seems more important than age for outcome. Continued followup will be required to determine if the alumina-on-alumina bearings in young patients result less risk of osteolysis and loosening. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. PMID:19495898

  19. Ordered mesoporous alumina-supported metal oxides.

    PubMed

    Morris, Stacy M; Fulvio, Pasquale F; Jaroniec, Mietek

    2008-11-12

    The one-pot synthesis of alumina-supported metal oxides via self-assembly of a metal precursor and aluminum isopropoxide in the presence of triblock copolymer (as a structure directing agent) is described in detail for nickel oxide. The resulting mesoporous mixed metal oxides possess p6 mm hexagonal symmetry, well-developed mesoporosity, relatively high BET surface area, large pore widths, and crystalline pore walls. In comparison to pure alumina, nickel aluminum oxide samples exhibited larger mesopores and improved thermal stability. Also, long-range ordering of the aforementioned samples was observed for nickel molar percentages as high as 20%. The generality of the recipe used for the synthesis of mesoporous nickel aluminum oxide was demonstrated by preparation of other alumina-supported metal oxides such as MgO, CaO, TiO 2, and Cr 2O 3. This method represents an important step toward the facile and reproducible synthesis of ordered mesoporous alumina-supported materials for various applications where large and accessible pores with high loading of catalytically active metal oxides are needed.

  20. Method of making nanocrystalline alpha alumina

    DOEpatents

    Siegel, Richard W.; Hahn, Horst; Eastman, Jeffrey A.

    1992-01-01

    Method of making selected phases of nanocrystalline ceramic materials. Various methods of controlling the production of nanocrystalline alpha alumina and titanium oxygen phases are described. Control of the gas atmosphere and use of particular oxidation treatments give rise to the ability to control the particular phases provided in the aluminum/oxygen and titanium/oxygen system.

  1. Thermal Conductivity of Alumina-Toughened Zirconia Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Zhu, Dong-Ming

    2003-01-01

    10-mol% yttria-stabilized zirconia (10YSZ)-alumina composites containing 0 to 30 mol% alumina were fabricated by hot pressing at 1500 C in vacuum. Thermal conductivity of the composites, determined at various temperatures using a steady-state laser heat flux technique, increased with increase in alumina content. Composites containing 0, 5, and 10-mol% alumina did not show any change in thermal conductivity with temperature. However, those containing 20 and 30-mol% alumina showed a decrease in thermal conductivity with increase in temperature. The measured values of thermal conductivity were in good agreement with those calculated from simple rule of mixtures.

  2. Sub-micron surface plasmon resonance sensor systems

    NASA Technical Reports Server (NTRS)

    Glazier, James A. (Inventor); Amarie, Dragos (Inventor)

    2011-01-01

    A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multi-channel sensor for detecting the presence of several targets with a single micro-chip sensor is described. A multi-channel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

  3. Sub-micron surface plasmon resonance sensor systems

    NASA Technical Reports Server (NTRS)

    Glazier, James A. (Inventor); Dragnea, Bogdan (Inventor); Amarie, Dragos (Inventor)

    2010-01-01

    A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multi-channel sensor for detecting the presence of several targets with a single microchip sensor is described. A multi-channel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

  4. Sub-micron surface plasmon resonance sensor systems

    NASA Technical Reports Server (NTRS)

    Glazier, James A. (Inventor); Dragnea, Bogdan (Inventor); Amarie, Dragos (Inventor)

    2010-01-01

    A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multi-channel sensor for detecting the presence of several targets with a single micro-chip sensor is described. A multi-channel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

  5. Sub-micron surface plasmon resonance sensor systems

    NASA Technical Reports Server (NTRS)

    Glazier, James A. (Inventor); Amarie, Dragos (Inventor)

    2011-01-01

    A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multichannel sensor for detecting the presence of several targets with a single microchip sensor is described. A multichannel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

  6. Sub-micron surface plasmon resonance sensor systems

    NASA Technical Reports Server (NTRS)

    Glazier, James A. (Inventor); Amarie, Dragos (Inventor)

    2012-01-01

    A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multi-channel sensor for detecting the presence of several targets with a single microchip sensor is described. A multi-channel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

  7. Advanced composite applications for sub-micron biologically derived microstructures

    NASA Technical Reports Server (NTRS)

    Schnur, J. M.; Price, R. R.; Schoen, P. E.; Bonanventura, Joseph; Kirkpatrick, Douglas

    1991-01-01

    A major thrust of advanced material development is in the area of self-assembled ultra-fine particulate based composites (micro-composites). The application of biologically derived, self-assembled microstructures to form advanced composite materials is discussed. Hollow 0.5 micron diameter cylindrical shaped microcylinders self-assemble from diacetylenic lipids. These microstructures have a multiplicity of potential applications in the material sciences. Exploratory development is proceeding in application areas such as controlled release for drug delivery, wound repair, and biofouling as well as composites for electronic and magnetic applications, and high power microwave cathodes.

  8. Sub-Micron Long HTS Ho Electron Mixers

    NASA Technical Reports Server (NTRS)

    Harnack, 0.; Karasik, B. S.; McGrath, W. R.; Kleinsasser, A. W.; Barner, J. B.

    2000-01-01

    The hot-electron bolometer mixer made from a high-T, superconductor (HTS) was introduced recently as an alternative to a Schottky mixer at THz frequencies. The performance of the mixer depends on the total thermal conductance for heat removal from the phonon sub-system due to either length-dependent phonon diffusion or phonon escape to the substrate. We have measured both the length and temperature dependencies of the IF bandwidth of the mixers fabricated from 25-35 mn thick YBCO films on MgO and sapphire substrates. The films were grown by a laser deposition technique and electron-beam lithography was used to define bridge lengths down to 50 nm. Mixer measurements were done using signal frequencies in the range of 1-100 GHz. For 50 nm and 400 nm long devices on MgO, the 3-dB bandwidth was about 100 MHz. At temperatures below 60 K, the hot-electron plateau was clearly seen starting around 2-3 GHz. At temperatures above 70 K, the flux-flow effects begin to dominate and the IF bandwidth increases to 1-8 GHz, while the conversion efficiency drops by several dB. This temperature dependence of the IF bandwidth can account for previously reported unexpectedly high bandwidth of HTS mixers.

  9. Sub-micron surface plasmon resonance sensor systems

    NASA Technical Reports Server (NTRS)

    Glazier, James A. (Inventor); Amarie, Dragos (Inventor)

    2013-01-01

    Wearable or implantable devices combining microfluidic control of sample and reagent flow and micro-cavity surface plasmon resonance sensors functionalized with surface treatments or coatings capable of specifically binding to target analytes, ligands, or molecules in a bodily fluid are provided. The devices can be used to determine the presence and concentration of target analytes in the bodily fluids and thereby help diagnose, monitor or detect changes in disease conditions.

  10. Fabrication of biodegradable elastomeric scaffolds with sub-micron morphologies

    PubMed Central

    Stankus, John J.; Guan, Jianjun; Wagner, William R.

    2010-01-01

    The native extracellular matrix (ECM) of elastic tissues is strong and flexible and supports cell adhesion and enzymatic matrix remodeling. In an attempt to convey these ECM properties to a synthetic scaffold appropriate for soft tissue engineering applications, a biodegradable, elastomeric poly(ester urethane)urea (PEUU) was combined with type I collagen at various ratios (2.5, 5, 10, 20, 50, 60, 70, 80, and 90 wt% collagen) and electrospun to construct elastic matrices. Randomly orientated fibers in the electrospun matrices ranged in diameter from 100–900 nm, dependent on initial polymer concentration. Picrosirius red staining of matrices and CD spectroscopy of released collagen confirmed collagen incorporation and preservation of collagen structure at the higher collagen mass fractions. Matrices were strong and distensible possessing strengths of 2–13 MPa with breaking strains of 160–280% even with low PEUU content. Collagen incorporation significantly enhanced smooth muscle cell adhesion onto electrospun scaffolds. An approach has been demonstrated that mimics elastic extracellular matrices by using a synthetic component to provide mechanical function together with a biomacromolecule, collagen. Such matrices may find application in engineering soft tissue. PMID:15307165

  11. The Columbia University Sub-micron Charged Particle Beam.

    PubMed

    Randers-Pehrson, Gerhard; Johnson, Gary W; Marino, Stephen A; Xu, Yanping; Dymnikov, Alexander D; Brenner, David J

    2009-10-11

    A lens system consisting of two electrostatic quadrupole triplets has been designed and constructed at the Radiological Research Accelerator Facility (RARAF) of Columbia University. The lens system has been used to focus 6-MeV (4)He ions to a beam spot in air with a diameter of 0.8 µm. The quadrupole electrodes can withstand voltages high enough to focus (4)He ions up to 10 MeV and protons up to 5 MeV. The quadrupole triplet design is novel in that alignment is made through precise construction and the relative strengths of the quadrupoles are accomplished by the lengths of the elements, so that the magnitudes of the voltages required for focusing are nearly identical. The insulating sections between electrodes have had ion implantation to improve the voltage stability of the lens. The lens design employs Russian symmetry for the quadrupole elements.

  12. Virtual Impactor for Sub-micron Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Bolshakov, A. A.; Strawa, A. W.; Hallar, A. G.

    2005-12-01

    The objective of a virtual impactor is to separate out the larger particles in a flow from the smaller particles in such a way that both sizes of particles are available for sampling. A jet of particle-laden air is accelerated toward a collection probe so that a small gap exists between the acceleration nozzle and the probe. A vacuum is applied to deflect a major portion of the airstream away form the collection probe. Particles larger than a certain size have sufficient momentum so that they cross the deflected streamlines and enter the collection probe, whereas smaller particles follow the deflected streamlines. The result is that the collection probe will contain a higher concentration of larger particles than is in the initial airstream. Typically, virtual impactors are high-flow devices used to separate out particles greater than several microns in diameter. We have developed a special virtual impactor to concentrate aerosol particles of diameters between 0.5 to 1 micron for the purpose of calibrating the optical cavity ring-down instrument [1]. No similar virtual impactors are commercially available. In our design, we have exploited considerations described earlier [2-4]. Performance of our virtual impactor was evaluated in an experimental set-up using TSI 3076 nebulizer and TSI 3936 scanning mobility particle size spectrometer. Under experimental conditions optimized for the best performance of the virtual impactor, we were able to concentrate the 700-nm polystyrene particles no less than 15-fold. However, under experimental conditions optimized for calibrating our cavity ring-down instrument, a concentration factor attainable was from 4 to 5. During calibration experiments, maximum realized particle number densities were 190, 300 and 1600 cm-3 for the 900-nm, 700-nm and 500-nm spheres, respectively. This paper discusses the design of the impactor and laboratory studies verifying its performance. References: 1. A.W. Strawa, R. Castaneda, T. Owano, D.S. Baer, B.A. Paldus, J. Atm. Ocean. Technol., 20, 454-465 (2003). 2. V.A. Marple, K.L. Rubow, B.A. Olson, Aerosol Sci. Technol., 22, 140-150 (1995). 3. B.T. Chen, H.C. Yeh, Y.S. Cheng, J. Aerosol Sci., 16, 343-354 (1985). 4. V.A. Marple, C.M. Chien, Environ. Sci. Technol., 14, 976-985 (1980).

  13. Physics of sub-micron cosmic dust particles

    NASA Technical Reports Server (NTRS)

    Roy, N. L.

    1974-01-01

    Laboratory tests with simulated micrometeoroids to measure the heat transfer coefficient are discussed. Equations for ablation path length for electrically accelerated micrometeoroids entering a gas target are developed which yield guidelines for the laboratory measurement of the heat transfer coefficient. Test results are presented for lanthanum hexaboride (LaB sub 6) microparticles in air, argon, and oxygen targets. The tests indicate the heat transfer coefficient has a value of approximately 0.9 at 30 km/sec, and that it increases to approximately unity at 50 km/sec and above. Test results extend to over 100 km/sec. Results are also given for two types of small particle detectors. A solid state capacitor type detector was tested from 0.61 km/sec to 50 km/sec. An impact ionization type detector was tested from 1.0 to 150 km/sec using LaB sub 6 microparticles.

  14. Transducers for Sub-Micron Displacement Measurements at Cryogenic Temperatures

    NASA Astrophysics Data System (ADS)

    Nyilas, A.

    2006-03-01

    This paper deals with recent developments of extensometers working in cryogenic environments down to 4 K capable to transfer accurate, high resolution, and reproducible signals for a variety of engineering measurement tasks such as tensile, fracture, compression, fatigue, flexural, and component tests. Based on strain gauge technology it was possible to manufacture extensometers with resolutions lower than 20 nm. The extensometers foreseen for uniaxial tensile tasks were designed as a twin extensometer system firmly attached onto the specimen and providing for bending during loading by averaging the signals either via software or by special electrical wiring. In particular, for structural component tests, different types of extensometer designs were represented. With the production of a new series of small, low weight, worldwide first twin extensometer system of ˜ 0.5 g mass it was possible to resolve the local strains of fragile Nb3Sn wires. Besides the measurement of distances, it was possible to develop ultra sensitive load cells (resolution < 0.01 N) using a similar technique working inside a cryostat capable of avoiding the loads resulting from the friction between the 4 K rig and the machine actuator. In addition, modern laser technology based on an averaging extensometer system is presented for future generation high sensitivity transducer systems to be used in materials testing.

  15. Dielectric Performance of High Purity HTCC Alumina at High Temperatures - A Comparison Study with Other Polycrystalline Alumina

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu

    2012-01-01

    A very high purity (99.99+) high temperature co-fired ceramic (HTCC) alumina has recently become commercially available. The raw material of this HTCC alumina is very different from conventional HTCC alumina, and more importantly there is no glass additive in this co-fired material. Previously, selected HTCC and LTCC (low temperature co-fired ceramic) alumina materials were evaluated at high temperatures as dielectric and compared to a regularly sintered 96 polycrystalline alumina (96 Al2O3), where 96 alumina was used as the benchmark. A prototype packaging system based on regular 96 alumina with Au thick-film metallization successfully facilitated long term testing of high temperature silicon carbide (SiC) electronic devices for over 10,000 hours at 500C. In order to evaluate this new HTCC alumina for possible high temperature packaging applications, the dielectric properties of this HTCC alumina substrate were measured and compared with those of 96 alumina and a LTCC alumina from room temperature to 550C at frequencies of 120 Hz, 1 KHz, 10 KHz, 100 KHz, and 1 MHz. A parallel-plate capacitive device with dielectric of the HTCC alumina and precious metal electrodes were used for measurements of the dielectric constant and dielectric loss of the co-fired alumina material in the temperature and frequency ranges. The capacitance and AC parallel conductance of the capacitive device were directly measured by an AC impedance meter, and the dielectric constant and parallel AC conductivity of the dielectric were calculated from the capacitance and conductance measurement results. The temperature and frequency dependent dielectric constant, AC conductivity, and dissipation factor of the HTCC alumina substrate are presented and compared to those of 96 alumina. Other technical advantages of this new co-fired material for possible high packaging applications are also discussed.

  16. Rheological Properties of Aqueous Nanometric Alumina Suspensions

    SciTech Connect

    Li, Chuanping

    2004-01-01

    Colloidal processing is an effective and reliable approach in the fabrication of the advanced ceramic products. Successful colloidal processing of fine ceramic powders requires accurate control of the rheological properties. The accurate control relies on the understanding the influences of various colloidal parameters on the rheological properties. Almost all research done on the rheology paid less attention to the interactions of particle and solvent. However, the interactions of the particles are usually built up through the media in which the particles are suspended. Therefore, interactions of the particle with the media, the adsorbed layers on the particle surface, and chemical and physical properties of media themselves must influence the rheology of the suspension, especially for the dense suspensions containing nanosized particles. Relatively little research work has been reported in this area. This thesis addresses the rheological properties of nanometric alumina aqueous suspensions, and paying more attention to the interactions between particle and solvent, which in turn influence the particle-particle interactions. Dense nanometric alumina aqueous suspensions with low viscosity were achieved by environmentally-benign fructose additives. The rheology of nanometric alumina aqueous suspensions and its variation with the particle volume fraction and concentration of fructose were explored by rheometry. The adsorptions of solute (fructose) and solvent (water) on the nanometric alumina particle surfaces were measured and analyzed by TG/DSC, TOC, and NMR techniques. The mobility of water molecules in the suspensions and its variation with particle volume fractions and fructose additive were determined by the 17O NMR relaxation method. The interactions between the nanometric alumina particles in water and fructose solutions were investigated by AFM. The results indicated that a large number of water layers were physically bound on the particles

  17. Mechanisms of enhanced osteoblast adhesion on nanophase alumina involve vitronectin.

    PubMed

    Webster, T J; Schadler, L S; Siegel, R W; Bizios, R

    2001-06-01

    The role, including concentration, conformation, and bioactivity, of adsorbed vitronectin in enhancing osteoblast adhesion on nanophase alumina was investigated in the present study. Vitronectin adsorbed in a competitive environment in the highest concentration on nanophase alumina compared to conventional alumina. Enhanced adsorption of vitronectin on nanophase alumina was possibly due to decreased adsorption of apolipoprotein A-I and/or increased adsorption of calcium on nanophase alumina. In a novel manner, the present study utilized surface-enhanced Raman scattering (SERS) to determine the conformation of vitronectin adsorbed on nanophase alumina. These results provided the first evidence of increased unfolding of vitronectin adsorbed on nanophase alumina. Increased adsorption of calcium on nanophase alumina may affect the conformation of adsorbed vitronectin specifically to promote unfolding of the macromolecule to expose cell-adhesive epitopes recognized by specific cell-membrane receptors. Results of the present study also provided evidence of dose-dependent inhibition of osteoblast adhesion on nanophase alumina pretreated with vitronectin following preincubation (and thus blocking respective cell-membrane receptors) with either Arginine-Glycine-Aspartic Acid-Serine (RGDS) or Lysine-Arginine-Serine-Arginine (KRSR). These events, namely, enhanced vitronectin adsorption, comformation, and bioactivity, may explain the increased osteoblast adhesion on nanophase alumina.

  18. Impact of AD995 alumina rods

    SciTech Connect

    Chhabildas, L.C.; Furnish, M.D.; Reinhart, W.D.; Grady, D.E.

    1997-10-01

    Gas guns and velocity interferometric techniques have been used to determine the loading behavior of an AD995 alumina rod 19 mm in diameter by 75 mm and 150 mm long, respectively. Graded-density materials were used to impact both bare and sleeved alumina rods while the velocity interferometer was used to monitor the axial-velocity of the free end of the rods. Results of these experiments demonstrate that (1) a time-dependent stress pulse generated during impact allows an efficient transition from the initial uniaxial strain loading to a uniaxial stress state as the stress pulse propagates through the rod, and (2) the intermediate loading rates obtained in this configuration lie between split Hopkinson bar and shock-loading techniques.

  19. Activation of consolidation processes of alumina ceramics

    NASA Astrophysics Data System (ADS)

    Matrenin, S. V.; Zenin, B. S.; Tayukin, R. V.

    2016-02-01

    The methods for activating sintering ceramics based on Al2O3 by mechanical activation in the planetary mill, by adding in the mixture of nanopowders (NP) Al, Al2O3, and submicron powder TiO2, and by applying the technology of spark plasma sintering (SPS) are developed. It has been shown that adding the nanopowder up to 20 wt. % Al2O3 in a coarse powder α-Al2O3 activates the sintering process resulting in increased density and hardness of the sintered alumina ceramics. Substantial effect of increasing density of alumina ceramics due to adding the submicron powder TiO2 in the compound of initial powder mixtures has been established.

  20. Fracture toughness and strength of 96% alumina

    SciTech Connect

    Price, D.B.; Chinn, R.E.; McNerney, K.R.; Brog, T.K.; Kim, C.Y.; Krutyholowa, M.W.; Chen, N.W.; Haun, M.J.

    1997-05-01

    There exists a need to understand the controlling factors that simultaneously impact strength and toughness in 96% alumina. The enhancement of both strength and toughness enables designers to extend the use limits and reliability for structural ceramics. This article presents mechanical property results from a group study examining the use of different alkaline-earth aluminosilicate intergranular compositions containing magnesium, calcium and strontium oxides (RO) in 96% alumina. Principal results address trends in indentation strength toughness and modulus of rupture. Trends in the data are presented relative to existing theories of thermal expansion mismatch toughening, grain-bridging crack-wake effect and crack deflection mechanisms. Strength is addressed in terms of strength after indentation, crack growth of indentation flaws and Weibull characterization for the strength distribution.

  1. Li + ion diffusion in nanoscale alumina coatings

    NASA Astrophysics Data System (ADS)

    Johannes, Michelle; Bernstein, Noam

    Nanoscale coatings of alumina are used to stabilize surfaces for a variety of technologies. Diffusion of ions through these coatings is of primary importance: in some cases, diffusion is unwanted (e.g. corrosion) and in others (e.g. electrode materials), it is necessary. In this work DFT and AIMD calculations are used to investigate Li+ ion diffusion through a nano-layer of alumina, examining the phase (alpha, gamma, and amorphous), ion concentration, and electron count dependence. We look at the role of the surface itself in promoting diffusion. One of our main findings is that as the number of ions or charge increases, the diffusivity rises. We show how our data can explain electrochemical data from coated LiCoO2 cathodes and may point toward better and more efficient coatings for stabilizing electrodes.

  2. Nanoparticles in alumina: Microscopy and Theory

    NASA Astrophysics Data System (ADS)

    Idrobo, Juan C.; Halabica, Andrej; Rashkeev, Sergey; Glazoff, Michael V.; Boatner, Lynn A.; Haglund, Richard F.; Pennycook, Stephen. J.; Pantelides, Sokrates T.

    2007-03-01

    Transition-metal nanoparticles formed by ion implantation in alumina can be used to modify the optical properties of naturally oxidized and anodized aluminum. Here, we report atomic-resolution Z-contrast images using a scanning transmission electron microscope (STEM) of CoFe and other metal nanoparticles in alumina. We also report electron energy loss spectra (EELS) and relate them to visual appearance and optical properties. Finally, we report first-principles density- functional calculations of nucleation mechanisms for these nanoparticles. This research was sponsored by the Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, U.S. Department of Energy, under contract DE-AC05- 00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, by NSF grant No. DMR-0513048, and by Alcoa Inc.

  3. Tribology of alumina-graphite composites

    NASA Astrophysics Data System (ADS)

    Yu, Chih-Yuan

    Alumina-graphite composites, which combine high wear resistance and self-lubricity, are a potential and promising candidate for advanced tribological applications. The processing, mechanical properties and tribology of alumina-graphite composites are discussed. Full density is difficult to achieve by a pressureless sintering route. Porosity of the composites increases with graphite content which causes the strength, modulus of elasticity, and hardness of the composites to decrease. The increased porosity does cause the fracture toughness to slightly increases. Tribology of alumina-graphite composites was studied with a pin-on-disk tribometer with emphasis on the following aspects: the graphite content in both pin and disk, the graphite flake size and the orientation of the graphite flakes. Scan electronic microscopy (SEM) and X-ray diffraction are utilized to examine and characterize the wear debris and the worn surface. Results confirmed that it is necessary to optimize the structure and the supply of lubricant to improve the tribological behavior and that the arrangements of sliding couples also affect the tribology of self-lubricated ceramic composites. Continuous measurements of the friction coefficients were collected at high frequency in an attempt to correlate the tribology of alumina-graphite composites to vibrations introduced by friction. While these measurements indicate that the time frequency behavior of tribology is an important area of study, conclusions regarding the frequency response of different sliding couples could not be definitively stated. Finally, a new concept connecting instantaneous wear coefficient and instantaneous contact stress is proposed for prediction of wear behavior of brittle materials.

  4. Bar Impact Tests on Alumina (AD995)

    NASA Astrophysics Data System (ADS)

    Cazamias, James U.; Reinhart, William D.; Konrad, Carl H.; Chhabildas, Lalit C.; Bless, Stephan J.

    2002-07-01

    Dynamic strength may be inferred from bar impact tests, although interpretation of the data is affected by the time-to-failure of the target bar. To clarify the mechanics, tests with graded density impactors were conducted on bare and confined bars, 12 and 19 mm in diameter, cut from blocks of AD995 alumina. Manganin gauge and VISAR diagnostics were employed. Larger rods displayed higher strength. In some tests the "true" yield stress of ˜4.5 GPa was achieved.

  5. Fast Glazing of Alumina/Silica Tiles

    NASA Technical Reports Server (NTRS)

    Creedon, J. F.; Gzowski, E. R.; Wheeler, W. H.

    1986-01-01

    Technique for applying ceramic coating to fibrous silica/alumina insulation tiles prevents cracks and substantially reduces firing time. To reduce thermal stresses in tile being coated, high-temperature, shorttime firing schedule implemented. Such schedule allows coating to mature while substrate remains at relatively low temperature, reducing stress differential between coating and substrate. Technique used to repair tiles with damaged coatings and possibly used in heat-treating objects made of materials having different thermal-expansion coefficients.

  6. High contrast laser marking of alumina

    NASA Astrophysics Data System (ADS)

    Penide, J.; Quintero, F.; Riveiro, A.; Fernández, A.; del Val, J.; Comesaña, R.; Lusquiños, F.; Pou, J.

    2015-05-01

    Alumina serves as raw material for a broad range of advanced ceramic products. These elements should usually be identified by some characters or symbols printed directly on them. In this sense, laser marking is an efficient, reliable and widely implemented process in industry. However, laser marking of alumina still leads to poor results since the process is not able to produce a dark mark, yielding bad contrast. In this paper, we present an experimental study on the process of marking alumina by three different lasers working in two wavelengths: 1064 nm (Near-infrared) and 532 nm (visible, green radiation). A colorimetric analysis has been carried out in order to compare the resulting marks and its contrast. The most suitable laser operating conditions were also defined and are reported here. Moreover, the physical process of marking by NIR lasers is discussed in detail. Field Emission Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy were also employed to analyze the results. Finally, we propose an explanation for the differences of the coloration induced under different atmospheres and laser parameters. We concluded that the atmosphere is the key parameter, being the inert one the best choice to produce the darkest marks.

  7. Compression Testing of Alumina Fiber Insulation

    NASA Technical Reports Server (NTRS)

    Vaughn, Wallace L.

    2006-01-01

    A series of tests were conducted to measure the response of alumina fiber insulation to compression loading. The alumina fiber insulation is a candidate gasket material for the Space Shuttle Government Furnished Equipment (GFE) Tile Overlay Repair. Tests were conducted at room temperature and 2300 F. The alumina fiber insulation is a fibrous insulation blanket which was supplied to Langley in two forms, a nominal 3 lb/ft3 version and a nominal 9 lb/ft3 version. The 3 lb/ft3 material was tested as sheets 0.15 and 0.25 inches thick and the 9 lb/ft3 material in sheets 1 inch thick. The material showed very non-linear compression behavior with the compressive resistance of the material increasing as the material was compressed. The 3 lb/ft3 0.15-inch thick material required 4.1 psi to reach the nominal installation thickness of 0.045 inches and retain a load of 2.1 lbs during unloading. Testing at 2300 F resulted in a stiffer more board-like material. The 3 lb/ft3 0.15-inch thick material retained 1 psi of compressive resistance after a 10 minute hold at 2300 F and 0.045 inches thickness.

  8. Free-standing alumina nanobottles and nanotubes pre-integrated into nanoporous alumina membranes

    NASA Astrophysics Data System (ADS)

    Fang, Jinghua; Levchenko, Igor; (Ken Ostrikov, Kostya

    2014-08-01

    A novel interfacial structure consisting of long (up to 5 μm), thin (about 300 nm), highly-ordered, free-standing, highly-reproducible aluminum oxide nanobottles and long tubular nanocapsules attached to a rigid, thin (less than 1 μm) nanoporous anodic alumina membrane is fabricated by simple, fast, catalyst-free, environmentally friendly voltage-pulse anodization. A growth mechanism is proposed based on the formation of straight channels in alumina membrane by anodization, followed by neck formation due to a sophisticated voltage control during the process. This process can be used for the fabrication of alumina nanocontainers with highly controllable geometrical size and volume, vitally important for various applications such as material and energy storage, targeted drug and diagnostic agent delivery, controlled drug and active agent release, gene and biomolecule reservoirs, micro-biologically protected platforms, nano-bioreactors, tissue engineering and hydrogen storage.

  9. Method for preparing Pb-.beta."-alumina ceramic

    DOEpatents

    Hellstrom, Eric E.

    1986-01-01

    A process is disclosed for preparing impermeable, polycrystalline samples of Pb-.beta."-alumina ceramic from Na-.beta."-alumina ceramic by ion exchange. The process comprises two steps. The first step is a high-temperature vapor phase exchange of Na by K, followed by substitution of Pb for K by immersing the sample in a molten Pb salt bath. The result is a polycrystalline Pb-.beta."-alumina ceramic that is substantially crack-free.

  10. Synthesis of Co2+ and Ni2+ stabilized beta alumina

    SciTech Connect

    Chen, S.; White, D.R.; Sato, H.; Sandberg, C.J.; Harrison, H.R.

    1983-10-01

    By using a skull melting technique, both single crystalline Ni(2+) and Co(2+) stabilized beta double prime-aluminas and doped beta-aluminas have been synthesized. Both Ni(2+) and Co(2+) beta-aluminas are blue in color, although the Co(2+) material has a deeper hue. Analysis of their visible absorption spectra indicated that the divalent transition metal ions are situated in tetrahedral sites of the spinel blocks.

  11. Sintering of beta-type alumina bodies using alpha-alumina encapsulation

    DOEpatents

    McEntire, Bryan J.; Virkar, Anil V.

    1981-01-01

    A method of sintering a shaped green, beta-type alumina body comprising: (A) inserting said body into an open chamber prepared by exposing the interior surface of a container consisting essentially of at least about 50 weight percent of alpha-alumina and a remainder of other refractory material to a sodium oxide or sodium oxide producing environment; (B) sealing the chamber; and heating the chamber with the shaped body encapsulated therein to a temperature and for a time necessary to sinter said body to the desired density. The encapsulation chamber prepared as described above is also claimed.

  12. Low-temperature thermal conductivity of composites: Alumina fiber/epoxy and alumina fiber/PEEK

    SciTech Connect

    Rule, D.L.; Sparks, L.L.

    1989-05-01

    The thermal conductivities of poly-ether-ether-ketone (PEEK), of alumina fiber in a matrix of PEEK, and of alumina fiber in a matrix of epoxy, were determined along with the effects of fiber orientation and thermal cycling. Thermal conductivity was measured over the temperature range of 4.2 to 310 K using a steady-state apparatus. Data are presented and discussed relative to specimen characteristics. It appears that, after accounting for different fiber fractions in the specimens, the thermal conductivity of the PEEK composite material is less than that of the epoxy composite material in particular temperature ranges.

  13. Conduction mechanism of single-crystal alumina

    NASA Technical Reports Server (NTRS)

    Will, Fritz G.; Delorenzi, Horst G.; Janora, Kevin H.

    1992-01-01

    The fully guarded three-terminal technique was used to perform conductivity measurements on single-crystal alumina at temperatures of 400-1300 C. The conductivity was also determined as a function of time at various temperatures and applied fields. Further, the fractions of the current carried by Al and O ions (ionic transference numbers) were determined from long-term transference experiments in the temperature range 1100-1300 C. A mathematical model of the conduction mechanism is proposed, and model predictions are compared with experimental results.

  14. Anisotropic shrinkage characteristics of tape cast alumina

    NASA Astrophysics Data System (ADS)

    Patwardhan, Jaideep Suresh

    Dimensional control during sintering is a major issue in ceramics processing to avoid high post-sintering costs associated with machining of the fired ceramic part to desired tolerances and dimensions. Ceramic forming processes such as tape casting, injection molding, and extrusion involve shear of anisotropic particles resulting in preferential alignment of the particles in the green body. This preferential alignment causes directionality in mechanical, electrical, optical, and magnetic properties and most importantly warpage or distortion during sintering. A large effort has been devoted to synthesizing ceramic green bodies with minimal density gradients and uniform packing and modeling the sintering behavior evolution but little effort has been devoted to characterizing orientation of particles and the effect of preferential alignment on sintering shrinkage anisotropy. A systematic study was initiated to study the effect of processing variables such as shear rate, solids loading, temperature, and binder content on aqueous tape cast alumina. Three different alumina systems: A16-SG, Baikowski RC-UFX DBM and RC-LS DBM were investigated. Aqueous tapes of high solids loading alumina (56 vol. %) were tape cast at various speeds and thicknesses and assuming plane Couette flow a shear rate regime of 21--270 s-1 was investigated. Higher shear rates and high solids loading resulted in higher in-plane anisotropy whereas the anisotropy in the thickness direction was higher for low solids loading systems. The anisotropy was found to be fairly constant above a certain critical shear rate (˜100 s-1) irrespective of the temperature and the solids loading and this correlated with the viscosity-shear rate relationship of the cast slips. The higher shrinkage anisotropy in the thickness direction for the low solids loading systems (35 and 45 vol. %) was attributed to the higher amount of organics in the slip required to sustain the suitable viscosity for tape casting and

  15. Improved Synthesis Of Potassium Beta' '-Alumina

    NASA Technical Reports Server (NTRS)

    Williams, Roger M.; Jeffries-Nakamura, Barbara; Ryan, Margaret A.; O'Connor, Dennis E.; Kisor, Adam; Underwood, Mark

    1996-01-01

    Improved formulations of precursor materials synthesize nearly-phase-pure potassium beta' '-alumina solid electrolyte (K-BASE) powder. Materials are microhomogeneous powders (or, alternatively, gels) containing K(+,) Mg(2+), and Al(3+). K-BASE powder produced used in potassium-working-fluid alkali-metal thermal-to-electric conversion (K-AMTEC), in which heat-input and heat-rejection temperatures lower than sodium-working-fluid AMTEC (Na-AMTEC). Additional potential use lies in purification of pottassium by removal of sodium and calcium.

  16. Porosity in plasma sprayed alumina coatings

    SciTech Connect

    Ilavsky, J.; Herman, H.; Berndt, C.C.; Goland, A.N.; Long, G.G.; Krueger, S.; Allen, A.J.

    1994-03-01

    Small-angle neutron scattering (SANS) was used to study the porosity of plasma sprayed deposits of alumina in as-sprayed and heat-treated conditions. SANS results were compared with mercury intrusion porosimetry (MIP) and water immersion techniques. Multiple small-angle neutron scattering yields a volume-weighted effective pore radius (R{sub eff}), for pores with sizes between 0.08 and 10{mu}m, the pore volume in this size region, and from the Porod region, the surface area of pores of all sizes.

  17. Intercalation of water into lithium. beta. -alumina

    SciTech Connect

    Dudney, N J; Bates, J B; Wang, J C; Brown, G M; Larson, B C; Engstrom, H

    1981-01-01

    Infrared absorption, neutron diffraction and weight loss techniques have been used to investigate the hydration of single crystals of Li ..beta..-alumina. The hydration is a reversible intercalation reaction. Up to approximately two water molecules per formula unit can penetrate the conduction plane. Other protonated species are formed from the dissociation of the molecular water. The rate of hydration is controlled by the diffusion of water in the conduction plane. A likely diffusion mechanism requires dissociation of the water and an interstitialcy motion of the oxygen.

  18. Depositing Adherent Ag Films On Ti Films On Alumina

    NASA Technical Reports Server (NTRS)

    Honecy, Frank S.

    1995-01-01

    Report discusses cleaning of ceramic (principally, alumina) substrates in preparation for sputter deposition of titanium intermediate films on substrates followed by sputter deposition of outer silver films. Principal intended application, substrates sliding parts in advanced high-temperature heat engines, and outer silver films serve as solid lubricants: lubricating properties described in "Solid Lubricant for Alumina" (LEW-15495).

  19. Process for the recovery of alumina from fly ash

    DOEpatents

    Murtha, M.J.

    1983-08-09

    An improvement in the lime-sinter process for recovering alumina from pulverized coal fly ash is disclosed. The addition of from 2 to 10 weight percent carbon and sulfur to the fly ash-calcium carbonate mixture increase alumina recovery at lower sintering temperatures.

  20. Evaluation of nano-porous alumina membranes for hemodialysis application.

    PubMed

    Attaluri, Anil Chandra; Huang, Zhongping; Belwalkar, Amit; Van Geertruyden, William; Gao, Dayong; Misiolek, Wojciech

    2009-01-01

    Globally, kidney failure has consistently been a major health problem. The number of patients suffering from kidney failure is radically increasing. Some studies forecast an exponential growth in the number of kidney failure patients during the coming years. This emphasizes the importance of hemodialysis (HD) membranes. Current dialysis membranes (cellulose based and synthetic polymer membranes) have irregular pore shapes and sizes, nonuniform pore distribution and limited reusable capability, which leads to low efficiency of toxin removal. New alumina membranes with uniform, controllable and well-structured nanoscale pores, channeled pores aligned perpendicular to the membrane plane, high porosity, high thermal and chemical resistance, and better mechanical properties are certainly preferable to currently used membranes. Determination of transport properties of alumina membranes will assist in the development of the alumina membranes for enhancing hemodialysis. Experiments were performed to evaluate hydraulic permeability, solute diffusive permeability, sieving coefficient, and clearance of four solutes (urea, creatinine, Vancomycin, and inulin) for alumina membrane. Based on comparison of these values against those of polyethersulfone (PES) membranes, transport performance of alumina membrane was determined. Hydraulic conductivity of the alumina membrane was approximately twice that of the PES membrane and inulin sieving coefficient for alumina membrane is approximately 21% higher than that for PES membrane. Alumina membrane has higher solute clearances and no albumin leakage, which makes it an effective replacement for current dialysis membranes. PMID:19293709

  1. Microstructural and Mechanical Characterization of Actively Brazed Alumina Specimens

    SciTech Connect

    Hosking, F.M.; Cadden, C.H.; Stephens, J.J.; Glass, S.J.; Yang, N.Y.C.; Vianco, P.V.; Walker, C.A.

    1999-08-26

    Alumina (94 and 99.8% grade compositions) was brazed directly to itself with gold-based active brazing alloys (ABA's) containing vanadium additions of 1,2 and 3 weight percent. The effects of brazing conditions on the joint properties were investigated. Wetting behavior, interfacial reactions, microstructure, hermeticity and tensile strength were determined. Wetting was fair to good for the ABA and base material combinations. Microanalysis identified a discontinuous Al-V-O spinel reaction product at the alumina-braze interface. Tensile strength results for 94% alumina were uniformly good and generally not sensitive to the vanadium concentration, with tensile values of 85-105 MPa. There was more variability in the 99.8% alumina strength results, with values ranging from 25-95 MPa. The highest vanadium concentration (3 wt. %) yielded the highest joint strength for the brazed 99.8% alumina. Failures in the 99.8% alumina samples occurred at the braze-alumina interface, while the 94% alumina specimens exhibited fracture of the ceramic substrate.

  2. Dynamic compressive and tensile strengths of spark plasma sintered alumina

    SciTech Connect

    Girlitsky, I.; Zaretsky, E.; Kalabukhov, S.; Dariel, M. P.; Frage, N.

    2014-06-28

    Fully dense submicron grain size alumina samples were manufactured from alumina nano-powder using Spark Plasma Sintering and tested in two kinds of VISAR-instrumented planar impact tests. In the first kind, samples were loaded by 1-mm tungsten impactors, accelerated to a velocity of about 1 km/s. These tests were aimed at studying the Hugoniot elastic limit (HEL) of Spark Plasma Sintering (SPS)-processed alumina and the decay, with propagation distance, of the elastic precursor wave. In the tests of the second kind, alumina samples of 3-mm thickness were loaded by 1-mm copper impactors accelerated to 100–1000 m/s. These tests were aimed at studying the dynamic tensile (spall) strength of the alumina specimens. The tensile fracture of the un-alloyed alumina shows a monotonic decline of the spall strength with the amplitude of the loading stress pulse. Analysis of the decay of the elastic precursor wave allowed determining the rate of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of the shock-induced inelastic deformation and to clarify the mechanisms responsible for the deformation. The 1-% addition of Cr{sub 2}O{sub 3} decreases the HEL of the SPS-processed alumina by 5-% and its spall strength by 50% but barely affects its static properties.

  3. 40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... nanoparticles (generic). 721.10120 Section 721.10120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this...

  4. Thermal Conductivity of Alumina-reinforced Zirconia Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    2005-01-01

    10-mol% yttria-stabilized zirconia (10SZ) - alumina composites containing 0-30 mol% alumina were fabricated by hot pressing at 1500 C in vacuum. Thermal conductivity was determined at various temperatures using a steady-state laser heat flux technique. Thermal conductivity of the composites increased with increase in alumina content. Composites containing 0, 5, and 10-mol% alumina did not show any change in thermal conductivity with temperature. However, those containing 20 and 30-mol% alumina showed a decrease in thermal conductivity with increase in temperature. The measured values of thermal conductivity were in good agreement with those calculated from the Maxwell-Eucken model where one phase is uniformly dispersed within a second major continuous phase.

  5. Properties of Transition Metal Doped Alumina

    NASA Astrophysics Data System (ADS)

    Nykwest, Erik; Limmer, Krista; Brennan, Ray; Blair, Victoria; Ramprasad, Rampi

    Crystallographic texture can have profound effects on the properties of a material. One method of texturing is through the application of an external magnetic field during processing. While this method works with highly magnetic systems, doping is required to couple non-magnetic systems with the external field. Experiments have shown that low concentrations of rare earth (RE) dopants in alumina powders have enabled this kind of texturing. The magnetic properties of RE elements are directly related to their f orbital, which can have as many as 7 unpaired electrons. Since d-block elements can have as many as 5 unpaired electrons the effects of substitutional doping of 3d transition metals (TM) for Al in alpha (stable) and theta (metastable) alumina on the local structure and magnetic properties, in addition to the energetic cost, have been calculated by performing first-principles calculations based on density functional theory. This study has led to the development of general guidelines for the magnetic moment distribution at and around the dopant atom, and the dependence of this distribution on the dopant atom type and its coordination environment. It is anticipated that these findings can aid in the selection of suitable dopants help to guide parallel experimental efforts. This project was supported in part by an internship at the Army Research Laboratory, administered by the Oak Ridge Institute for Science and Education, along with a grant of computer time from the DoD High Performance Computing Modernization Program.

  6. Pseudopotential Computations for Metal/Alumina Interfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Wenqing

    2003-03-01

    Metal/alumina interfaces are found, for example, in electronic devices, as thermal barrier coatings in gas turbines, and in coatings to inhibit corrosion and wear. Of particular importance to their performance is their adhesion. Ultrasoft pseudopotentials combined with plane wave methods and density-functional theory have been employed to compute the properties of these relatively complex interfaces, including effects of impurity segregation. Interfacial stoichiometry and impurity content affect interfacial properties importantly. Thermodynamic links between our first principles results and metallurgical variables such as oxygen activity and oxygen partial pressure are established. This allows for a comparison between theoretical predictions and experimental measurements. Good agreement is obtained for predicted interfacial variables such as atomic structure and adhesive bond strengths on comparison with results of sessile drop, fracture, and other experiments on interfaces of Ni, Cu, Al, and Ag with alumina [1-3], including effects of water and sulfur interfacial impurities. Understanding of the nature of the adhesive bonding at the atomic level is obtained by the pseudopotential first principles approach. [1] W.Zhang, and J.R.Smith, and A.G.Evans, Acta Mater., 50,3803(2002). [2] W.Zhang, and J.R.Smith, Phys. Rev. Lett. 85, 3225(2000). [3] W.Zhang, and J.R.Smith, Phys. Rev. B61, 16883(2000).

  7. Combination for electrolytic reduction of alumina

    DOEpatents

    Brown, Craig W.; Brooks, Richard J.; Frizzle, Patrick B.; Juric, Drago D.

    2002-04-30

    An electrolytic bath for use during the electrolytic reduction of alumina to aluminum. The bath comprises molten electrolyte having the following ingredients: AlF.sub.3 and at least one salt selected from the group consisting of NaF, KF, and LiF; and about 0.004 wt. % to about 0.2 wt. %, based on total weight of the molten electrolyte, of at least one transition metal or at least one compound of the metal or both. The compound is, a fluoride; oxide, or carbonate. The metal is nickel, iron, copper, cobalt, or molybdenum. The bath is employed in a combination including a vessel for containing the bath and at least one non-consumable anode and at least one dimensionally stable cathode in the bath. Employing the instant bath during electrolytic reduction of alumina to aluminum improves the wetting of aluminum on a cathode by reducing or eliminating the formation of non-metallic deposits on the cathode.

  8. Parsing abnormal grain growth in specialty aluminas

    NASA Astrophysics Data System (ADS)

    Lawrence, Abigail Kremer

    Grain growth in alumina is strongly affected by the impurities present in the material. Certain impurity elements are known to have characteristic effects on abnormal grain growth in alumina. Specialty alumina powders contain multiple impurity species including MgO, CaO, SiO2, and Na 2O. In this work, sintered samples made from alumina powders containing various amounts of the impurities in question were characterized by their grain size and aspect ratio distributions. Multiple quantitative methods were used to characterize and classify samples with varying microstructures. The grain size distributions were used to partition the grain size population into subpopulations depending on the observed deviation from normal behavior. Using both grain size and aspect ratio a new visual representation for a microstructure was introduced called a morphology frequency map that gives a fingerprint for the material. The number of subpopulations within a sample and the shape of the distribution on the morphology map provided the basis for a classification scheme for different types of microstructures. Also using the two parameters a series of five metrics were calculated that describe the character of the abnormal grains in the sample, these were called abnormal character values. The abnormal character values describe the fraction of grains that are considered abnormal, the average magnitude of abnormality (including both grain size and aspect ratio), the average size, and variance in size. The final metric is the correlation between grain size and aspect ratio for the entire population of grains. The abnormal character values give a sense of how different from "normal" the sample is, given the assumption that a normal sample has a lognormal distribution of grain size and a Gaussian distribution of aspect ratios. In the second part of the work the quantified measures of abnormality were correlated with processing parameters such as composition and heat treatment conditions. A

  9. Terbium luminescence in alumina xerogel fabricated in porous anodic alumina matrix under various excitation conditions

    SciTech Connect

    Gaponenko, N. V.; Kortov, V. S.; Orekhovskaya, T. I.; Nikolaenko, I. A.; Pustovarov, V. A.; Zvonarev, S. V.; Slesarev, A. I.; Prislopski, S. Ya.

    2011-07-15

    Terbium-doped alumina xerogel layers are synthesized by the sol-gel method in pores of a porous anodic alumina film 1 {mu}m thick with a pore diameter of 150-180 nm; the film is grown on a silicon substrate. The fabricated structures exhibit terbium photoluminescence with bands typical of trivalent terbium terms. Terbium X-ray luminescence with the most intense band at 542 nm is observed for the first time for such a structure. Morphological analysis of the structure by scanning electron microscopy shows the presence of xerogel clusters in pore channels, while the main pore volume remains unfilled and pore mouths remain open. The data obtained confirm the promising applications of fabricated structures for developing matrix converters of X-rays and other ionizing radiations into visible light. The possibilities of increasing luminescence intensity in the matrix converter are discussed.

  10. Essentials of specifications for activated alumina in defluoridation technology.

    PubMed

    Misra, S K

    2006-10-01

    Worldwide, fluoride occurs naturally in some aquifers at concentrations above the WHO guideline values or Bureau of Indian Standards or CPHEEO - MUD - GOI parametric values. Fluoride in excess of the permissible limits in drinking water causes a number of endemic conditions referred to collectively as "fluorosis". Endemic fluorosis remains a challenging national health problem in India and Rajasthan is one of the worst affected states in India though a wide range of chemical and physical defluoridation systems were evolved and tried. Still activated alumina is one of the most widely used and liked defluoridation material currently available. Boom in the advanced and versatile alumina technology has opened new vistas to avail the strong potential of selective alumina adsorbents which are application-specific. Non-regenerable and specialty alumina offer tremendous scope to defluoridate drinking water. Indian industries are manufacturing regenerable activated alumina for defluoridation of drinking water. In order to ensure application of an adsorbent, which caters the desired results with minimum interferences, health risks and long service life span, it is inevitable to draw out dimensions which define precisely the attributes of activated alumina. Specifications for activated alumina intended for defluoridation of drinking water, specific operating and performance requirements, and limitations expressed by critical analysis of cardinal characteristics pave way for adoption of acceptable specifications and code of practice at national level.

  11. Deformation Behaviour of Coarse Grain Alumina under Shock Loading

    NASA Astrophysics Data System (ADS)

    Gupta, Satish

    2013-06-01

    To develop better understanding of the shock wave induced deformation behavior of coarse grain alumina ceramics, and for measurement of its Hugoniot Elastic Limit (HEL), in-situ and recovery gas gun experiments have been carried out on coarse grain alumina (grain size ~ 10 μm), prepared in the form of discs (>99.9% TMD) by pressure-less sintering of alpha alumina powder at 1583 K. The HEL value of 1.9 GPa has been determined from the kink in the pressure history recorded using piezoresistance gauge and also from the free surface velocity history of the sample shocked to 9 GPa. The nano-indentation measurements on the alumina samples shocked to 6.5 GPa showed hardness value 15% lower than 21.3 GPa for unshocked alumina, and strong Indentation Size Effect (ISE); the hardness value was still lower and the ISE was stronger for the sample shocked to 12 GPa. The XRD measurements showed reduced particle size and increased microstrains in the shocked alumina fragments. SEM, FESEM and TEM measurements on shock treated samples showed presence of grain localized micro- and nano-scale deformations, micro-cleavages, grain-boundary microcracks, extensive shear induced deformations, and localized micro-fractures, etc. These observations led to the development of a qualitative model for the damage initiation and its subsequent growth mechanisms in shocked alumina. The work performed in collaboration with K.D. Joshi of BARC and A.K. Mukhopadhyay of CGCRI.

  12. Fracture of the alumina-bearing couple delta ceramic liner.

    PubMed

    Taheriazam, Afshin; Mohajer, Mohammad Azizbaig; Aboulghasemian, Mansoour; Hajipour, Babak

    2012-01-01

    The fracture rate of third-generation ceramic liners is greatly reduced compared with first- and second-generation liners because of improvements in the design and manufacturing process. Fractures of the alumina-bearing couple are rare for the same reason.This article describes a case of a fracture of an alumina-bearing couple delta ceramic liner without trauma history that was treated with ceramic-on-polyethylene revision total hip arthroplasty. A 57-year-old man was admitted to the hip ward because of an alumina-bearing couple delta ceramic liner fracture. He underwent hip replacement by anterior approach 18 months previously in the same center because of left hip primary osteoarthritis. He received a 54×36-mm modular press-fit cup ceramic alumina-bearing couple delta insert. Probable causes of such fractures are manufacture production failure and edge loading based on cup inclination, but in our patient, inacceptable range of motion, failure of the locking mechanism during implantation insertion, or cracking were possible causes of fracture.Although the fracture rate of third-generation alumina-bearing couples is low, we believe that it may not be possible to eliminate the actual risk of alumina head fracture. Patients should be informed about the potential for this complication before receiving an alumina-bearing couple.

  13. Scattering and absorption coefficients of silica-doped alumina aerogels.

    PubMed

    Fu, Tairan; Tang, Jiaqi; Chen, Kai; Zhang, Fan

    2016-02-01

    Alumina-based aerogels are especially useful in many applications due to their excellent stability at high temperatures. This study experimentally analyzed the radiative properties of silica-doped alumina aerogels through spectral directional-hemispherical measurements for wavelengths of 0.38-25 μm. The silica-doped alumina aerogel samples were prepared with a 1.4∶1 molar ratio of silica to alumina. A two-flux model was used to describe the radiation propagation in a 1D scattering absorbing sample to derive expressions for the normal-hemispherical transmittances and reflectances based on the transport approximation. The normal-hemispherical transmittances and reflectances were measured at various spectral wavelengths and sample thicknesses using the integrating sphere method. The spectral absorption and transport scattering coefficients of silica-doped alumina aerogels were then determined from the measured normal-hemispherical data. The absorption and transport scattering coefficients of silica-doped alumina aerogels are (0.1  cm-1, 36  cm-1) and (0.1  cm-1, 112  cm-1) for wavelengths of 0.38-8.0 μm. The spectral transport scattering coefficient varies in the opposite direction from the spectral absorption coefficient for various wavelengths. The radiative properties for silica and alumina aerogels were quite different for the absorption coefficient for wavelengths of 2.5-8.0 μm and for the transport scattering coefficient for wavelengths of 0.38-2.5 and 3.5-6.0 μm. The measured radiative properties were used to predict the spectral normal-hemispherical reflectance and transmittance of the silica-doped alumina aerogels for various sample thicknesses and wavelengths. The predicted values do not change for the sample thicknesses greater than a critical value. The analysis provides valuable reference data for alumina aerogels for high-temperature applications. PMID:26836071

  14. Dermal Toxicity of Flake-Like α-Alumina Pigments.

    PubMed

    Kwon, TaeWoo; Seo, HyunJeong; Jang, Seongwan; Lee, Sang-Geun; Park, Sungkyun; Park, Kang Hyun; Youn, BuHyun

    2015-02-01

    Aluminum is one of the most widely used nonferrous metals and an important industrial material, especially for automotive coatings. However, potential toxicity caused by aluminum in humans limits the used of this metal. α-alumina is the most stable form of aluminum in various phases. Although the results of studies evaluating the dermal toxicity of α-alumina remained unclear, this compound can still be used as a pigment in cosmetics for humans. In the current study, we further evaluated the dermal cytotoxic effects of α-alumina on human skin cells and an in vivo mouse model. We also measured the in vitro penetration profile of flake-like α-alumina in porcine skin and assessed the degree of cellular metabolic disorders. Our findings demonstrated that treatment with flake-like α-alumina did not significantly affect cell viability up to 24 h. This compound was found to have a non-penetration profile based on a Franz modified diffusion cell assay. In addition, flake-like α-alumina was not found to induce dermal inflammation as assessed by histology of epidermal architecture, hyperplasia, and the expression of Interleukin-1β and Cyclooxygenase-2. Results of the cellular metabolic disorder assay indicated that flake-like α-alumina does not exert a direct effect on human skin cells. Taken together, our findings provided not only evidence that flake-like α-alumina may serve as a pearlescent pigment in cosmetics but also experimental basis utilizing α-alumina for human application. Our results also obviously provide new insight of the further toxicity study to aluminum based nanoparticles for skin. PMID:26353706

  15. Interfacial fracture toughness of alumina/niobium systems

    SciTech Connect

    Stout, M.G. ); O'Dowd, N.P.; Shih, C.F. . Div. of Engineering)

    1991-01-01

    The interfacial fracture toughness of an alumina/niobium composite has been measured as a function of phase angle. The interface was formed by solid-state bonding bulk Coor's AD-999 fine-grain alumina with a commercial purity niobium at 1600{degrees}C for 0.5 hr under a pressure of 10.5 MPa. The alumina/niobium system has a number of features which makes it ideal for an investigation of interfacial fracture toughness. From HREM data we estimate that the width of the interface is no more than 10 atomic planes. Furthermore the thermal expansion coefficients of the two materials differ by less than 5% so residual stresses due to the bonding process are small. Using symmetric and asymmetric four point bend specimens we have measured the fracture toughness of homogenous alumina and that of the alumina/niobium bimaterial in combinations of in-plane shear and tension. The fracture toughness of the homogenous alumina is relatively insensitive to the loading phase. The measured fracture toughness K{sub c} of the interface, however, depended strongly on phase angle. We were unable to obtain valid alumina/niobium interfacial toughness data at negative phase angles as the fracture initiates in the alumina and not at the interface. In symmetric bending at a phase angle {approx}5{degrees}, we measured a nominal interface toughness of 4.0 MPa{radical}m, comparable to the homogeneous alumina. We found that the toughness increased with loading phase angle to a value of K{sub c} {approx} 9 MPa{radical}m at a phase between 25{degrees} and 40{degrees}. Preliminary calculations and experiments suggest that this effect is due to an asymmetric stress distribution, with respect to the interface, and plastic deformation in the niobium. 12 refs., 9 figs., 1 tab.

  16. Residual Stress Predictions in Polycrystalline Alumina

    SciTech Connect

    VEDULA,VENKATA R.; GLASS,S. JILL; SAYLOR,DAVID M.; ROHRER,GREGORY S.; CARTER,W. CRAIG; LANGER,STEPHEN A.

    1999-12-13

    Microstructure-level residual stresses arise in polycrystalline ceramics during processing as a result of thermal expansion anisotropy and crystallographic disorientation across the grain boundaries. Depending upon the grain size, the magnitude of these stresses can be sufficiently high to cause spontaneous microcracking during the processing of these materials. They are also likely to affect where cracks initiate and propagate under macroscopic loading. The magnitudes of residual stresses in untextured and textured alumina samples were predicted using object oriented finite (OOF) element analysis and experimentally determined grain orientations. The crystallographic orientations were obtained by electron-backscattered diffraction (EBSD). The residual stresses were lower and the stress distributions were narrower in the textured samples compared to those in the untextured samples. Crack initiation and propagation were also simulated using the Griffith fracture criterion. The grain boundary to surface energy ratios required for computations were estimated using AFM groove measurements.

  17. Optimized alumina coagulants for water treatment

    DOEpatents

    Nyman, May D.; Stewart, Thomas A.

    2012-02-21

    Substitution of a single Ga-atom or single Ge-atom (GaAl.sub.12 and GeAl.sub.12 respectively) into the center of an aluminum Keggin polycation (Al.sub.13) produces an optimal water-treatment product for neutralization and coagulation of anionic contaminants in water. GaAl.sub.12 consistently shows .about.1 order of magnitude increase in pathogen reduction, compared to Al.sub.13. At a concentration of 2 ppm, GaAl.sub.12 performs equivalently to 40 ppm alum, removing .about.90% of the dissolved organic material. The substituted GaAl.sub.12 product also offers extended shelf-life and consistent performance. We also synthesized a related polyaluminum chloride compound made of pre-hydrolyzed dissolved alumina clusters of [GaO.sub.4Al.sub.12(OH).sub.24(H.sub.2O).sub.12].sup.7+.

  18. Tensile creep behavior of polycrystalline alumina fibers

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; Goldsby, J. C.

    1993-01-01

    Tensile creep studies were conducted on polycrystalline Nextel 610 and Fiber FP alumina fibers with grain sizes of 100 and 300 nm, respectively. Test conditions were temperatures from 800 to 1050 C and stresses from 60 to 1000 MPa. For both fibers, only a small primary creep portion occurred followed by steady-state creep. The stress exponents for steady-state creep of Nextel 610 and Fiber FP were found to be about 3 and 1, respectively. At lower temperatures, below 1000 C, the finer grained Nextel 610 had a much higher 0.2 percent creep strength for 100 hr than the Fiber FP; while at higher temperatures, Nextel 610 had a comparable creep strength to the Fiber FP. The stress and grain size dependencies suggest Nextel 610 and Fiber FP creep rates are due to grain boundary sliding controlled by interface reaction and Nabarro-Herring mechanisms, respectively.

  19. Crystallography of Alumina-YAG-Eutectic

    NASA Technical Reports Server (NTRS)

    Farmer, Serene C.; Sayir, Ali; Dickerson, Robert M.; Matson, Lawrence E.

    2000-01-01

    Multiple descriptions of the alumina-YAG eutectic crystallography appear in the ceramic literature. The orientation between two phases in a eutectic system has direct impact on residual stress, morphology, microstructural stability, and high temperature mechanical properties. A study to demonstrate that the different crystallographic relationships can be correlated with different growth constraints was undertaken. Fibers produced by Laser-Heated Float Zone (LHFZ) and Edge-defined Film-fed Growth (EFG) were examined. A map of the orientation relationship between Al2O3 and Y3Al5O12 and their relationship to the fiber growth axis as a function of pull rate are presented. Regions in which a single orientation predominates are identified.

  20. Alumina strength degradation in the elastic regime

    SciTech Connect

    Furnish, M.D.; Chhabildas, L.C.

    1997-08-01

    Measurements of Kanel et. al. [1991] have suggested that deviatoric stresses in glasses shocked to nearly the Hugoniot Elastic limit (HEL) relax over a time span of microseconds after initial loading. Failure (damage) waves have been inferred on the basis of these measurements using time-resolved manganin normal and transverse stress gauges. Additional experiments on glass by other researchers, using time-resolved gauges, high-speed photography and spall strength determinations have also lead to the same conclusions. In the present study the authors have conducted transmitted-wave experiments on high-quality Coors AD995 alumina shocked to roughly 5 and 7 GPa (just below or at the HEL). The material is subsequently reshocked to just above its elastic limit. Results of these experiments do show some evidence of strength degradation in the elastic regime.

  1. Compositional characterization of atomic layer deposited alumina

    SciTech Connect

    Philip, Anu; Thomas, Subin; Kumar, K. Rajeev

    2014-01-28

    As the microelectronic industry demands feature size in the order of few and sub nanometer regime, the film composition and other film properties become critical issues and ALD has emerged as the choice of industry. Aluminum oxide is a material with wide applications in electronic and optoelectronic devices and protective and ion barrier layers. Al{sub 2}O{sub 3} is an excellent dielectric because of its large band gap (8.7eV), large band offsets with silicon. We have deposited thin layers of alumina on silicon wafer (p-type) for gate dielectric applications by ALD technique and compositional characterizations of the deposited thin films were done using EDS, XPS and FTIR spectra.

  2. Viscoelasticity of nano-alumina dispersions

    SciTech Connect

    Rand, B.; Fries, R.

    1996-06-01

    The flow and viscoelastic properties of electrostatically stabilized nano-alumina dispersions have been studied as a function of ionic strength and volume fraction of solids. At low ionic strength the suspensions were deflocculated and showed a transition from viscous to elastic behavior as the solid content increased associated with the onset of double layer interpenetration. The phase transition was progressively shifted to higher solids fractions with increasing ionic strength. At higher ionic strength, above the critical coagulation concentration, the suspensions formed attractive networks characterized by high elasticity. Two independent methods of estimating the effective radius of electrostatically stabilized {open_quotes}soft{close_quotes} particles, a{sub eff}, are presented based on phase angle data and a modified Dougherty-Krieger equation. The results suggest that a{sub eff} is not constant for a given system but changes with both solids fraction and ionic strength.

  3. Aluminum-Alloy-Matrix/Alumina-Reinforcement Composites

    NASA Technical Reports Server (NTRS)

    Kashalikar, Uday; Rozenoyer, Boris

    2004-01-01

    Isotropic composites of aluminum-alloy matrices reinforced with particulate alumina have been developed as lightweight, high-specific-strength, less-expensive alternatives to nickel-base and ferrous superalloys. These composites feature a specific gravity of about 3.45 grams per cubic centimeter and specific strengths of about 200 MPa/(grams per cubic centimeter). The room-temperature tensile strength is 100 ksi (689 MPa) and stiffness is 30 Msi (206 GPa). At 500 F (260 C), these composites have shown 80 percent retention in strength and 95 percent retention in stiffness. These materials also have excellent fatigue tolerance and tribological properties. They can be fabricated in net (or nearly net) sizes and shapes to make housings, pistons, valves, and ducts in turbomachinery, and to make structural components of such diverse systems as diesel engines, automotive brake systems, and power-generation, mining, and oil-drilling equipment. Separately, incorporation of these metal matrix composites within aluminum gravity castings for localized reinforcement has been demonstrated. A composite part of this type can be fabricated in a pressure infiltration casting process. The process begins with the placement of a mold with alumina particulate preform of net or nearly net size and shape in a crucible in a vacuum furnace. A charge of the alloy is placed in the crucible with the preform. The interior of the furnace is evacuated, then the furnace heaters are turned on to heat the alloy above its liquidus temperature. Next, the interior of the furnace is filled with argon gas at a pressure about 900 psi (approximately equal to 6.2 MPa) to force the molten alloy to infiltrate the preform. Once infiltrated, the entire contents of the crucible can be allowed to cool in place, and the composite part recovered from the mold.

  4. Processing of silicon nitride and alumina nanosize powders

    SciTech Connect

    Gonzalez, E.J.; Piermarini, G.; Hockey, B.; Malghan, S.G.

    1995-08-01

    The effects of pressure on the compaction and subsequent processing of nanosize {gamma} alumina powders were studied. A 3 mm diameter piston/cylinder die was used to compact the nanosize powders to pressures of 1 and 2.5 GPa. The green bodies were sintered at temperatures up to 1600{degrees}C. Results show that green body density can be increased by higher compaction pressures. It appears that as a result of the {gamma}-to-{alpha} transformation in alumina, higher green density does not necessarily produce a higher density sintered alumina body. The microstructures of the sintered bodies are described in terms of porosity and phase content.

  5. Alumina Paste Sublimation Suppression Barrier for Thermoelectric Device

    NASA Technical Reports Server (NTRS)

    Paik, Jong-Ah (Inventor); Caillat, Thierry (Inventor)

    2014-01-01

    Alumina as a sublimation suppression barrier for a Zintl thermoelectric material in a thermoelectric power generation device operating at high temperature, e.g. at or above 1000K, is disclosed. The Zintl thermoelectric material may comprise Yb.sub.14MnSb.sub.11. The alumina may be applied as an adhesive paste dried and cured on a substantially oxide free surface of the Zintl thermoelectric material and polished to a final thickness. The sublimation suppression barrier may be finalized by baking out the alumina layer on the Zintl thermoelectric material until it becomes substantially clogged with ytterbia.

  6. Porous alumina based ordered nanocomposite coating for wear resistance

    NASA Astrophysics Data System (ADS)

    Yadav, Arti; Muthukumar, M.; Bobji, M. S.

    2016-08-01

    Uniformly dispersed nanocomposite coating of aligned metallic nanowires in a matrix of amorphous alumina is fabricated by pulsed electrodeposition of copper into the pores of porous anodic alumina. Uniform deposition is obtained by controlling the geometry of the dendritic structure at the bottom of pores through stepwise voltage reduction followed by mild etching. The tribological behaviour of this nanocomposite coating is evaluated using a ball on flat reciprocating tribometer under the dry contact conditions. The nanocomposite coating has higher wear resistance compared to corresponding porous alumina coating. Wear resistant nanocomposite coating has wide applications especially in protecting the internal surfaces of aluminium internal combustion engines.

  7. Fabrication of alumina films with laminated structures by ac anodization

    NASA Astrophysics Data System (ADS)

    Segawa, Hiroyo; Okano, Hironaga; Wada, Kenji; Inoue, Satoru

    2014-02-01

    Anodization techniques by alternating current (ac) are introduced in this review. By using ac anodization, laminated alumina films are fabricated. Different types of alumina films consisting of 50-200 nm layers were obtained by varying both the ac power supply and the electrolyte. The total film thickness increased with an increase in the total charge transferred. The thickness of the individual layers increased with the ac voltage; however, the anodization time had little effect on the film thickness. The laminated alumina films resembled the nacre structure of shells, and the different morphologies exhibited by bivalves and spiral shells could be replicated by controlling the rate of increase of the applied potentials.

  8. Preparation of Carbon Nanotube—Toughened Alumina Composites

    NASA Astrophysics Data System (ADS)

    Yamamoto, G.; Omori, M.; Hashida, T.

    2008-02-01

    With multi-walled carbon nanotubes (MWCNTs) as reinforcement, MWCNT/alumina composites were prepared at the MWCNTs mass% of 0.5. A flexural strength of 572.1±28.3 MPa and fracture toughness of 4.80±0.42 MPaṡm1/2, 1.2 times that of MWCNT-free monolithic alumina prepared under the same processing condition, was achieved. Experimental results showed that the dispersibility of the MWCNTs in the composite was crucially important in order to improve the mechanical properties of the MWCNT/alumina composite material.

  9. Magnesia-alumina-aluminum phosphate-zeolite catalyst

    SciTech Connect

    Reynolds, E.H.; Stanulonis, J.J.; Swift, H.E.

    1980-09-16

    A catalyst for cracking gasoline feedstock with superior selectivity to gasoline production and greater metals tolerance comprises a magnesia-alumina-aluminum phosphate matrix composited with a zeolite having cracking activity.

  10. Alumina-on-Polyethylene Bearing Surfaces in Total Hip Arthroplasty

    PubMed Central

    Jung, Yup Lee; Kim, Shin-Yoon

    2010-01-01

    The long-term durability of polyethylene lining total hip arthroplasty (THA) mainly depends on periprosthetic osteolysis due to wear particles, especially in young active patients. In hip simulator study, reports revealed significant wear reduction of the alumina ceramic-on-polyethylene articulation of THA compared with metal-on-polyethylene bearing surfaces. However, medium to long-term clinical studies of THA using the alumina ceramic-on-polyethylene are few and the reported wear rate of this articulation is variable. We reviewed the advantages and disadvantages of ceramicon- polyethylene articulation in THA, hip simulator study and retrieval study for polyethylene wear, in vivo clinical results of THA using alumina ceramic-on-polyethylene bearing surfaces in the literature, and new trial alumina ceramic-onhighly cross linked polyethylene bearing surfaces. PMID:20224739

  11. Structure and surface properties of praseodymium modified alumina

    NASA Astrophysics Data System (ADS)

    Tankov, I.; Pawelec, B.; Arishtirova, K.; Damyanova, S.

    2011-10-01

    Mixed PrO 2-Al 2O 3 oxides with different PrO 2 content (1-20 wt.%) were prepared by wetness impregnation of γ-alumina with aqueous solution of praseodymium nitrate. The samples were characterized by different techniques, using surface adsorption-desorption of N 2 ( SBET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR) and temperature-programmed desorption of CO 2 (TPD-CO 2). TGA and XRD showed the presence of small praseodymium oxide species on the alumina surface. XPS and DRS detected electron deficient interaction between deposited praseodymium oxide and alumina. It was observed a lower reduction temperature for supported Pr oxide species compared to that of the bulk Pr 6O 11. TPD-CO 2 studies suggested that the deposition of Pr oxide on alumina leaded to increase of the basicity of mixed oxides.

  12. Potassium Beta-Alumina/Molybdenum/Potassium Electrochemical Cells

    NASA Technical Reports Server (NTRS)

    Williams, R.; Kisor, A.; Ryan, M.; Nakamura, B.; Kikert, S.; O'Connor, D.

    1994-01-01

    potassium alkali metal thermal-to-electric converter (K-AMTEC) cells utilizing potassium beta alumina solid electrolyte (K-BASE) are predicted to have improved properties for thermal to electric conversion at somewhat lower temperatures than sodium AMTEC's.

  13. Removing Fluoride Ions with Continously Fed Activated Alumina.

    ERIC Educational Resources Information Center

    Wu, Yeun C.; Itemaking, Isara Cholapranee

    1979-01-01

    Discussed is the mathematical basis for determining fluoride removal during water treatment with activated alumina. The study indicates that decreasing particle size decreases the pore diffusion effect and increases fluoride removal. (AS)

  14. New Phenomena Observed in Plate Impacts onto Alumina Bars

    NASA Astrophysics Data System (ADS)

    Beno, T.; Bless, S.; Nichols, S.

    2006-07-01

    Steel flyer plates were used to impact alumina bars at 275 m/s, nominally. Manganin gauges were used to monitor stress waves in the bars. Geometry of the impact was varied in an attempt to extend gauge records. Gauge life was best improved by careful alignment. The longest gauge records indicated that alumina retains a strength level of about 2 GPa after initial failure. Stress levels of over 5 GPa were obtained with impact-zone confinement.

  15. Carbon dioxide pressure swing adsorption process using modified alumina adsorbents

    DOEpatents

    Gaffney, T.R.; Golden, T.C.; Mayorga, S.G.; Brzozowski, J.R.; Taylor, F.W.

    1999-06-29

    A pressure swing adsorption process for absorbing CO[sub 2] from a gaseous mixture containing CO[sub 2] comprises introducing the gaseous mixture at a first pressure into a reactor containing a modified alumina adsorbent maintained at a temperature ranging from 100 C and 500 C to adsorb CO[sub 2] to provide a CO[sub 2] laden alumina adsorbent and a CO[sub 2] depleted gaseous mixture and contacting the CO[sub 2] laden adsorbent with a weakly adsorbing purge fluid at a second pressure which is lower than the first pressure to desorb CO[sub 2] from the CO[sub 2] laden alumina adsorbent. The modified alumina adsorbent which is formed by depositing a solution having a pH of 3.0 or more onto alumina and heating the alumina to a temperature ranging from 100 C and 600 C, is not degraded by high concentrations of water under process operating conditions. 1 fig.

  16. Carbon dioxide pressure swing adsorption process using modified alumina adsorbents

    DOEpatents

    Gaffney, Thomas Richard; Golden, Timothy Christopher; Mayorga, Steven Gerard; Brzozowski, Jeffrey Richard; Taylor, Fred William

    1999-01-01

    A pressure swing adsorption process for absorbing CO.sub.2 from a gaseous mixture containing CO.sub.2 comprising introducing the gaseous mixture at a first pressure into a reactor containing a modified alumina adsorbent maintained at a temperature ranging from 100.degree. C. and 500.degree. C. to adsorb CO.sub.2 to provide a CO.sub.2 laden alumina adsorbent and a CO.sub.2 depleted gaseous mixture and contacting the CO.sub.2 laden adsorbent with a weakly adsorbing purge fluid at a second pressure which is lower than the first pressure to desorb CO.sub.2 from the CO.sub.2 laden alumina adsorbent. The modified alumina adsorbent which is formed by depositing a solution having a pH of 3.0 or more onto alumina and heating the alumina to a temperature ranging from 100.degree. C. and 600.degree. C., is not degraded by high concentrations of water under process operating conditions.

  17. Procoagulant behavior and platelet microparticle generation on nanoporous alumina.

    PubMed

    Ferraz, Natalia; Hong, Jaan; Karlsson Ott, Marjam

    2010-05-01

    In the present work, we have investigated platelet microparticle (PMP) generation in whole blood after contact with nanoporous alumina. Alumina membranes with pore sizes of 20 and 200 nm in diameter were incubated with whole blood and the number of PMP in the fluid phase was determined by flow cytometry. The role of the complement system in PMP generation was investigated using an analog of the potent complement inhibitor compstatin. Moreover, the procoagulant activity of the two pore size membranes were compared by measuring thrombin formation. Results indicated that PMP were not present in the fluid phase after whole blood contact with either of the alumina membranes. However, scanning electron microscope micrographs clearly showed the presence of PMP clusters on the 200 nm pore size alumina, while PMP were practically absent on the 20 nm membrane. We probed no influence of complement activation in PMP generation and adhesion and we hypothesize that other specific material-related protein-platelet interactions are taking place. A clear difference in procoagulant activity between the membranes could also be seen, 20 nm alumina showed 100% higher procoagulant activity than 200 nm membrane. By combining surface evaluation and flow cytometry analyses of the fluid phase, we are able to conclude that 200 nm pore size alumina promotes PMP generation and adhesion while the 20 nm membrane does not appreciably cause any release or adhesion of PMP, thus indicating a direct connection between PMP generation and nanoporosity.

  18. Wetting and strength issues at Al/alpha-alumina interfaces

    SciTech Connect

    Saiz, Eduardo; Tomsia, Antoni P.; Suganuma, Katsuaki

    2003-04-15

    The wetting behavior and strength at aluminum/alumina interfaces has been an active subject of research. Al/alumina applications include ceramic-metal composites and several applications for electronic industries. In this paper the interface strength and microstructure of Al/alpha-alumina was investigated. We discovered that in a solid-state joining, the strength of the joint increases with increasing joining temperature. In a liquid-state joining, the strength of the joint gradually decreases due to the formation of unbonded areas. The strength, sigma sub b, is expressed by the following equation as a function of unbonded area, A: sigma sub b = 2.22 A + 143 (70 percent {le} A {le} 100 percent). The highest strength reached 400 MPa when the interface was formed at around the melting temperature of aluminum. An aluminum layer close to the interface became a single crystal when it was bonded to a sapphire. The following crystallographic orientation relationship is established: (1{bar 1}1){sub Al}//(001){sub {alpha}}-Al{sub 2} O{sub 3}, (110){sub Al}//<100>{sub {alpha}}-Al{sub 2}O{sub 3}. Amorphous alumina islands were formed at the interface. In the amorphous alumina, gamma-alumina nanocrystals grew from the sapphire, with the same orientation relationship to sapphire as above.

  19. The microstructure and mechanical reliability of alumina scales and coatings

    SciTech Connect

    Alexander, K.B.; Pruessner, K.; Tortorelli, P.F.

    1997-09-01

    Alumina scales on iron-aluminides (Fe{sub 3}Al-based) and NiCrAl- based alloys were characterized in order to develop the knowledge to control the oxidation performance of alloys by controlling the microstructure and microchemistry of their scales. Plasma-deposited amorphous alumina coatings on iron-aluminides were used to study phase transformations, transport processes in the scales, and S segregation to the scale/metal interface. It was found that during heat treatment in absence of oxidation, amorphous coatings first transform to {gamma}-Al{sub 2}O{sub 3} and eventually {alpha}-Al{sub 2}O{sub 3} nucleates at the scale/metal interface. Sulfur from the Zr- free alloy segregates to the scale/metal interface during heat treatment. Thermally grown scales on Zr-doped iron-aluminides were compared to those formed after oxidation of a specimen with an alumina coating. Microstructural and gravimetric results showed that the primarily amorphous alumina coating promoted the nucleation and growth of metastable alumina phases, which resulted in more rapid oxidation. The thermally grown oxide was found on top of the coating. The NiCrAl-based alloys formed columnar alumina scales underneath a layer of mixed oxides. Segregation of alloying elements like Y, Hf, and At was found at both oxide grain boundaries and scale/metal interfaces.

  20. Effect of alumina composition and surface integrity in alumina/epoxy composites on the ultrasonic attenuation properties.

    PubMed

    Cho, Eikhyun; Park, Gwanwoo; Lee, Jae-Wan; Cho, Sung-Min; Kim, Taekyung; Kim, Joongeok; Choi, Wonjoon; Ohm, Won-Suk; Kang, Shinill

    2016-03-01

    We report a method of fabricating backing blocks for ultrasonic imaging transducers, using alumina/epoxy composites. Backing blocks contain scatterers such as alumina particles interspersed in the epoxy matrix for the effective scattering and attenuation of ultrasound. Here, the surface integrity can be an issue, where the composite material may be damaged during machining because of differences in strength, hardness and brittleness of the hard alumina particles and the soft epoxy matrix. Poor surface integrity results in the formation of air cavities between the backing block and the piezoelectric element upon assembly, hence the increased reflection off the backing block and the eventual degradation in image quality. Furthermore, with an issue of poor surface integrity due to machining, it is difficult to increase alumina as scatterers more than a specific mass fraction ratio. In this study, we increased the portion of alumina within epoxy matrix by obtaining an enhanced surface integrity using a net shape fabrication method, and verified that this method could allow us to achieve higher ultrasonic attenuation. Backing blocks were net-shaped with various mass fractions of alumina to characterize the formability and the mechanical properties, including hardness, surface roughness and the internal micro-structure, which were compared with those of machined backing blocks. The ultrasonic attenuation property of the backing blocks was also measured.

  1. Processing, characterization and mechanical properties of alumina-based nanocomposites

    NASA Astrophysics Data System (ADS)

    Thomson, Katherine E.

    2007-12-01

    The present study focuses on improving the fracture toughness of nanocrystalline alumina by incorporating second phases---specifically niobium and carbon nanotubes. Ceramics have many properties that lend themselves well to load bearing and armor applications. Chemical inertness, high hardness and strength, low wear rates and low densities are examples of these properties that warrant potential substitution of metals and their alloys. In this study, nanocrystalline alumina was investigated based on its impressive elevated temperature properties and high hardness. Despite these promising structural properties, pure nanocrystalline alumina has low fracture toughness (˜2.5 MPa*m1/2) and is thus limited to non-structural applications. Alumina-based nanocomposites reinforced with niobium and/or carbon nanotubes (CNT) were fabricated by advanced powder processing techniques and consolidated by spark plasma sintering (˜1200°C, 4 min). Raman spectroscopy revealed that single-walled carbon nanotubes (SWCNTs) begin to break down at sintering temperatures above 1150°C. Nuclear magnetic resonance (NMR) showed that, although thermodynamically unlikely, no Al4C3 was formed in the CNT-alumina nanocomposites. Thus, the nanocomposite is purely a physical mixture and no chemical bond was formed between the nanotubes and matrix. In addition, in-situ 3-pt and standard 4-pt bend tests were conducted on niobium and/or carbon nanotube-reinforced alumina nanocomposites in order to assess their toughness. Although stable crack growth was not achieved in the 3-pt bend testing, average fracture toughness vales of 6.1 and 3.3 MPa·m 1/2 were measured for 10 vol%Nb and 10 vol%Nb-5 vol%SWCNT-alumina, respectively. The 4-pt bend testing measured average intrinsic fracture toughness of 2.95, 2.76, 3.33 and 3.95 MPa·m1/2 for alumina nanocomposites containing 5 vol%SWCNT, 10 vol%SWCNT, 5 vol%DWCNT and 10 vol% Nb, respectively. Although nanocrystalline alumina will never be able to compete with

  2. Mechanical properties of alumina porcelain during heating

    NASA Astrophysics Data System (ADS)

    Šín, Peter; Podoba, Rudolf; ŠtubÅa, Igor; Trník, Anton

    2014-11-01

    The mechanical strength and Young's modulus of green alumina porcelain (50 wt. % of kaolin, 25 wt. % of Al2O3, and 25 wt. % of feldspar) were measured during heating up to 900 °C and 1100 °C, respectively. To this end, we used the three point-bending method and modulated force thermomechanical analysis (mf-TMA). The loss liberation - of the physically bound water (20 - 250 °C) strengthens the sample and Young's modulus increases its values significantly. The dehydroxylation that takes place in the range of 400 - 650 °C causes a slight decrease in Young's modulus. On the other hand, the mechanical strength slightly increases in this temperature range, although it has a sudden drop at 420 °C. Beyond the dehydroxylation range, above 650 °C, both Young's modulus and mechanical strength increase. Above 950 °C, a sharp increase of Young's modulus is caused by the solid-state sintering and the new structure created by the high-temperature reactions in metakaolinite.

  3. Annealing Would Improve beta" - Alumina Solid Electrolyte

    NASA Technical Reports Server (NTRS)

    Williams, Roger; Homer, Margie; Ryan, Margaret; Cortez, Roger; Shields, Virgil; Kisor, Adam

    2003-01-01

    A pre-operational annealing process is under investigation as a potential means of preventing a sudden reduction of ionic conductivity in a Beta"-alumina solid electrolyte (BASE) during use. On the basis of tests, the sudden reduction of ionic conductivity, followed by a slow recovery, has been found to occur during testing of the solid electrolyte and electrode components of an alkali metal thermal-to-electric converter (AMTEC) cell. At this time, high-temperature tests of limited duration have indicated the superiority of the treated BASE, but reproducible tests over thousands of hours are necessary to confirm that microcracking has been eliminated. The ionic conductivity of the treated BASE is also measured to be higher than untreated BASE at 1,073 K in low-pressure sodium vapor. Microcracking resulting in loss of conductivity was not observed with treated BASE in one high-temperature experiment, but this result must be duplicated over very long testing times to be sure of the effect. Shorter annealing times (10 to 20 hours) were found to result in significantly less loss of mass; it may be necessary for the packed powder mixture to evolve some Na2O before the Na2O can leave the ceramic.

  4. Filter-pressing of alumina dispersions

    SciTech Connect

    Fries, R.; Rand, B.

    1996-06-01

    The filter-pressing characteristics of aqueous alumina dispersions containing either submicron or nano-sized particles have been compared with respect to ionic strength. The highest green densities for both systems were achieved at electrolyte concentrations < 0.01 mol dm{sup -3} where long-range repulsive interparticle forces stabilize the slips. A slight increase in density with ionic strength in this range was attributed to an increase in the ratio of particle radius-to-double layer thickness, Ka. At higher electrolyte concentrations, above the critical coagulation concentration, the green densities dropped to significantly lower values due to the onset of flocculation and the formation of open particle networks characterized by strong attraction which resisted rearrangement into a dense green microstructure. The green densities of the compacts consolidated from the submicron dispersions at ionic strength > 1 mol dm{sup -3} were significantly higher than those prepared close to the critical coagulation concentration although the slips exhibited properties typical for a flocculated structure. The results may indicate the presence of short-range repulsive forces at high salt concentration for the submicron slips not accounted for by the classical DLVO-theory. In order to characterize the early stages of filter-cake consolidation the initial cake permeability was determined from the compaction curves.

  5. Cast alumina forming austenitic stainless steels

    DOEpatents

    Muralidharan, Govindarajan; Yamamoto, Yukinori; Brady, Michael P

    2013-04-30

    An austenitic stainless steel alloy consisting essentially of, in terms of weight percent ranges 0.15-0.5C; 8-37Ni; 10-25Cr; 2.5-5Al; greater than 0.6, up to 2.5 total of at least one element selected from the group consisting of Nb and Ta; up to 3Mo; up to 3Co; up to 1W; up to 3Cu; up to 15Mn; up to 2Si; up to 0.15B; up to 0.05P; up to 1 total of at least one element selected from the group consisting of Y, La, Ce, Hf, and Zr; <0.3Ti+V; <0.03N; and, balance Fe, where the weight percent Fe is greater than the weight percent Ni, and wherein the alloy forms an external continuous scale comprising alumina, and a stable essentially single phase FCC austenitic matrix microstructure, the austenitic matrix being essentially delta-ferrite free and essentially BCC-phase-free. A method of making austenitic stainless steel alloys is also disclosed.

  6. Ion polarization behavior in alumina under pulsed gate bias stress

    SciTech Connect

    Liu, Yu; Diallo, Abdou Karim; Katz, Howard E.

    2015-03-16

    Alkali metal ion incorporation in alumina significantly increases alumina capacitance by ion polarization. With high capacitance, ion-incorporated aluminas become promising high dielectric constant (high-k) gate dielectric materials in field-effect transistors (FETs) to enable reduced operating voltage, using oxide or organic semiconductors. Alumina capacitance can be manipulated by incorporation of alkali metal ions, including potassium (K{sup +}), sodium (Na{sup +}), and lithium (Li{sup +}), having different bond strengths with oxygen. To investigate the electrical stability of zinc tin oxide-based transistors using ion incorporated alumina as gate dielectrics, pulsed biases at different duty cycles (20%, 10%, and 2% representing 5 ms, 10 ms, and 50 ms periods, respectively) were applied to the gate electrode, sweeping the gate voltage over series of these cycles. We observed a particular bias stress-induced decrease of saturation field-effect mobility accompanied by threshold voltage shifts (ΔV{sub th}) in potassium and sodium-incorporated alumina (abbreviated as PA and SA)-based FETs at high duty cycle that persisted over multiple gate voltage sweeps, suggesting a possible creation of new defects in the semiconductor. This conclusion is also supported by the greater change in the mobility-capacitance (μC) product than in capacitance itself. Moreover, a more pronounced ΔV{sub th} over shorter times was observed in lithium-incorporated alumina (abbreviated as LA)-based transistors, suggesting trapping of electrons in existing interfacial states. ΔV{sub th} from multiple gate voltage sweeps over time were fit to stretched exponential forms. All three dielectrics show good stability using 50-ms intervals (20-Hz frequencies), corresponding to 2% duty cycles.

  7. Ion polarization behavior in alumina under pulsed gate bias stress

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Diallo, Abdou Karim; Katz, Howard E.

    2015-03-01

    Alkali metal ion incorporation in alumina significantly increases alumina capacitance by ion polarization. With high capacitance, ion-incorporated aluminas become promising high dielectric constant (high-k) gate dielectric materials in field-effect transistors (FETs) to enable reduced operating voltage, using oxide or organic semiconductors. Alumina capacitance can be manipulated by incorporation of alkali metal ions, including potassium (K+), sodium (Na+), and lithium (Li+), having different bond strengths with oxygen. To investigate the electrical stability of zinc tin oxide-based transistors using ion incorporated alumina as gate dielectrics, pulsed biases at different duty cycles (20%, 10%, and 2% representing 5 ms, 10 ms, and 50 ms periods, respectively) were applied to the gate electrode, sweeping the gate voltage over series of these cycles. We observed a particular bias stress-induced decrease of saturation field-effect mobility accompanied by threshold voltage shifts (ΔVth) in potassium and sodium-incorporated alumina (abbreviated as PA and SA)-based FETs at high duty cycle that persisted over multiple gate voltage sweeps, suggesting a possible creation of new defects in the semiconductor. This conclusion is also supported by the greater change in the mobility-capacitance (μC) product than in capacitance itself. Moreover, a more pronounced ΔVth over shorter times was observed in lithium-incorporated alumina (abbreviated as LA)-based transistors, suggesting trapping of electrons in existing interfacial states. ΔVth from multiple gate voltage sweeps over time were fit to stretched exponential forms. All three dielectrics show good stability using 50-ms intervals (20-Hz frequencies), corresponding to 2% duty cycles.

  8. Alumina-on-alumina total hip replacement for femoral neck fracture in healthy patients

    PubMed Central

    2011-01-01

    Background Total hip replacement is considered the best option for treatment of displaced intracapsular fractures of the femoral neck (FFN). The size of the femoral head is an important factor that influences the outcome of a total hip arthroplasty (THA): implants with a 28 mm femoral head are more prone to dislocate than implants with a 32 mm head. Obviously, a large head coupled to a polyethylene inlay can lead to more wear, osteolysis and failure of the implant. Ceramic induces less friction and minimal wear even with larger heads. Methods A total of 35 THAs were performed for displaced intracapsular FFN, using a 32 mm alumina-alumina coupling. Results At a mean follow-up of 80 months, 33 have been clinically and radiologically reviewed. None of the implants needed revision for any reason, none of the cups were considered to have failed, no dislocations nor breakage of the ceramic components were recorded. One anatomic cementless stem was radiologically loose. Conclusions On the basis of our experience, we suggest that ceramic-on-ceramic coupling offers minimal friction and wear even with large heads. PMID:21284879

  9. Adsorption and reaction of sulfur dioxide on alumina and sodium-impregnated alumina

    SciTech Connect

    Mitchell, M.B.; Sheinker, V.N.; White, M.G.

    1996-05-02

    The adsorption and oxidation of SO{sub 2} on alumina and sodium-impregnated alumina has been examined using thermogravimetric analysis and diffuse reflectance infrared Fourier transform spectroscopy. Sulfur dioxide chemisorbs initially at basic sites to form an adsorbed sulfite, which is quantitatively converted to sulfate on oxidation. It has been observed that at low coverages, nearly 2.6 {mu}mol/m{sup 2}, sodium acts as a promoter for the formation of an adsorbed sulfite and sulfate which have structures similar to those of aluminum sulfite and sulfate, respectively. At higher sodium loadings, a second type of adsorbed SO{sub 2} is formed, similar to sodium sulfite and sulfate. The species with the aluminum sulfate structure appears to be more easily decomposed than does the sodium sulfate species and accounts for the regenerable adsorption capacity. Formation of the sodium sulfate species appears to account for the loss of adsorption capacity as the number of adsorption/regeneration cycles increases. Oxidation of the sulfite form to the sulfate form can occur in the absence of added oxygen, but it is an activated process and begins to occur in measurable amounts at temperatures between 150 and 300{degree}C. Partitioning of adsorbed SO{sub 2} between aluminum and sodium forms is not a function of temperature and depends on only sodium loading. 32 refs., 14 figs., 1 tab.

  10. Peltier heats in cryolite melts with alumina

    SciTech Connect

    Flem, B.E.; Ratkje, S.K.; Sterten, A.

    1996-10-01

    The Seebeck coefficient was measured for cells with electrolytes of molten mixtures of sodium fluoride and aluminum fluoride saturated with alumina. The electrodes were either a pair of oxygen electrodes or a pair of aluminum electrodes. For the molar ratio NaF/AlF{sub 3} equal to 1.8, 1.2 and 1.0, the authors obtained the Seebeck coefficients {minus}1.80 mV K{sup {minus}1} at 971 C, {minus}1.63 mV K{sup {minus}1} at 813.6 C and {minus}0.583 mV K{sup {minus}1} at 758 C, respectively, for the oxygen electrodes. For the aluminum electrodes, the authors obtained the Seebeck coefficient {minus}1.23 mV K{sup {minus}1} at 962 C, for the molar ratio NaF/AlF{sub 3} equal to 1.8. The results suggest that there is a substantial reversible heat consumption at the anode during aluminum electrolysis and a large reversible heat production at the cathode. The highest temperature in the Hall-Heroult cell is then closer to the cathode than the anode. The transported entropies of Al{sup 3+} and O{sup 2{minus}} were calculated to be 77 J mol{sup {minus}1} K{sup {minus}1} and 10 J mol{sup {minus}1} K{sup {minus}1}, respectively, when the molar ratio NaF/AlF{sub 3} was equal to 1.0.

  11. Aluminas with dispersoids. Tribologic properties and in vivo aging.

    PubMed

    Mandrino, A; Moyen, B; Ben Abdallah, A; Treheux, D; Orange, D

    1990-07-01

    Three base alumina ceramics with dispersoids: monoclinic zirconia alumina (A5Z), tetragonal zirconia alumina (A20Z) and aluminalon (Aa20) have been investigated because of their improved mechanical properties with reference to pure alumina (AI203). Bending strength and fracture toughness are twice higher than alumina for the most toughened. These two parameters were measured by four-points bending tests after 1 week, 1, 2, 3, 6, 12 months of non loaded in vivo aging in wistar rats. They showed a little decrease for AI203 and Aa20 and a total stability for A5Z and A20Z even after one year. For tribologic study of the ceramic/polyethylene combination, cylinder against plane and pin on flat tests were conducted on an alternative movement with hip parameters of speed and load in presence of ringer solution. For the most representative test (pin on disk), the friction coefficients were nearly the same for all materials but UHMWPE wear volume was twice lower against A20Z than against AI203. A20Z/UHMWPE combination would be very interesting as new friction couple for total hip arthroplasty. Further studies are currently conducted.

  12. Corrosion resistance characterization of porous alumina membrane supports

    SciTech Connect

    Dong Yingchao; Lin Bin; Zhou Jianer; Zhang Xiaozhen; Ling Yihan; Liu Xingqin; Meng Guangyao; Hampshire, Stuart

    2011-04-15

    Tubular porous alumina ceramic membrane supports were fabricated by an extrusion-drying-sintering process and then characterized in detail in terms of corrosion resistance in both H{sub 2}SO{sub 4} and NaOH aqueous solutions. Variations in the properties of the alumina supports such as mass loss percent, mechanical strength, open porosity and pore size distribution were studied before and after corrosion under different conditions. In addition, the microstructures were analyzed using scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction before and after corrosion. The fabricated porous alumina supports offer possibilities for some potential applications as micro-filtration or ultra-filtration membrane supports, as well as in the pre-treatment of strongly acidic industrial waste-liquids. - Research highlights: {yields} Porous alumina membrane supports fabricated by extrusion-drying-sintering process. {yields} Corrosion resistance in 20 wt.% H{sub 2}SO{sub 4} and 1, 5, 10 wt.% NaOH aqueous solutions. {yields} Rapid mass loss and loss of flexural strength occurred in hot NaOH solution. {yields} Resistant to strong acid corrosion with low mass loss, low flexural strength loss. {yields} Porous alumina supports have potential for treatment of strong acid waste liquids.

  13. The nature of hydrogen in γ-alumina

    SciTech Connect

    Li, Yunguo Lousada, Cláudio M. Korzhavyi, Pavel A.

    2014-05-28

    Gibbs free energy models are derived from the calculated electronic and phonon structure of two possible models of γ-alumina, a defective spinel phase and a hydrogenated spinel phase. The intrinsic vacancies and hydrogen in the two structural models give rise to a considerable configurational (residual) entropy and significantly contribute to thermodynamic stability and physical-chemical properties of γ-alumina, which was neglected in previous studies but considered in this work. The electronic densities of states, calculated using a hybrid functional for the two structural models of γ-alumina, are presented. The dynamic stability of the two phases is confirmed by full-spectrum phonon calculations. The two phases share many similarities in their electronic structure, but can be distinguished by their vibrational spectra and specific heat. The defective spinel is found to be the ground state of γ-alumina, while the hydrogenated spinel to be a metastable phase. However, dehydration of the metastable phase into the ground state is expected to be slow due to the low diffusion rate of H, which leaves hydrogen as a locked-in impurity in γ-alumina.

  14. The mechanical reliability of alumina scales and coatings

    SciTech Connect

    Alexander, K.B.; Pruebner, K.; Tortorelli, P.F.

    1996-08-01

    The mechanical integrity of oxide scales ultimately determines their ability to protect materials from corrosion and other environmental effects arising from deleterious reactions with gases and condensable products. The microstructure and mechanical behavior of alumina products thermally grown or deposited on Fe-28 at.% Al intermetallic alloys are being characterized in order to develop the knowledge and means to control the mechanical reliability of alumina scales by microstructural manipulation through design and processing. Mechanical characterization involved gravimetric data from cyclic oxidation experiments, in-situ observation of oxidized specimens undergoing flexural loading in a scanning electron microscope, and measurements of hardness, elastic modulus and cracking resistance by nanoindentation. Values of cracking thresholds for Al{sub 2}O{sub 3} scales were consistent with other measurements for surface and bulk alumina. The oxidation behavior of Fe{sub 3}Al alloys coated with a thin (0.5 - 1 {mu}m) alumina film deposited by plasma synthesis has been studied. During exposure in the oxidizing environment, new oxide was formed between the coating and the substrate. The presence of the deposited amorphous oxide inhibited the subsequent thermal oxidation of the metal. Because the thermally grown alumina forms under the deposit, the adherence of the coating is controlled by the strength of the metal/oxide interface that develops during oxidation.

  15. Excellent results with cementless total hip arthroplasty and alumina-on-alumina pairing: minimum ten-year follow-up

    PubMed Central

    Kress, Alexander M.; Schmidt, Rainer; Holzwarth, Ulrich; Forst, Raimund

    2010-01-01

    Ceramic-on-ceramic coupling is thought to be a durable alternative to metal- or alumina-on-polyethylene pairing. No evidence exists suggesting superior clinical and radiological results for hydroxyapatite-coated stems versus uncoated stems. The aim of this study is to report the performance of an alumina-on-alumina bearing cementless total hip arthroplasty and to compare stems with a tapered design with and without hydroxyapatite coating. We prospectively analysed the results of cementless tapered femoral stems (40 hydroxyapatite-coated versus 22 uncoated stems), a metal-backed fibre mesh hydroxyapatite-coated socket and alumina-on-alumina pairing. Of 75 hips studied, 62 were available for follow-up (mean of 10.5 years after surgery). The average Harris hip score was 90. Only one hydroxyapatite-coated stem was revised for aseptic loosening. One instance of non-progressive osteolysis was detected around a screw of a cup. All other components showed radiographic signs of stable ingrowth. Hydroxyapatite coating of the stem had no significant impact on the clinical or radiological results. Total hip arthroplasty with the presented implant and pairing provides a durable standard for all patients requiring hip joint replacement against which all newer generations of cementless implants should be judged. PMID:21079952

  16. Effects of stearic acid on the injection molding of alumina

    SciTech Connect

    Chan, T.Y.; Lin, S.T.

    1995-10-01

    This research investigated the influence of stearic acid on the injection molding of alumina, by varying the concentration of stearic acid. The interaction between stearic acid and alumina was identified using transmission infrared spectroscopy, indicating stearic acid preferentially adsorbed onto the alumina powder surface. In addition to slightly modifying the intrinsic binder viscosity, stearic acid adsorbed onto the powder surface changed the flow behavior of the mixtures from dilatant flow to pseudoplastic flow at low temperatures. As a result, inhomogeneous distribution of binder in the injection-molded parts was minimized with increased stearic acid concentration. However, the possibility of forming bubbles in the mixtures arising from vaporization of stearic acid was enhanced. Additionally, the binder burnout temperature range was broadened with the increase of stearic acid concentration.

  17. Plastic deformation and sintering of alumina under high pressure

    SciTech Connect

    Liu, Fangming; Liu, Pingping; Wang, Haikuo; Xu, Chao; Yin, Shuai; Yin, Wenwen; Li, Yong; He, Duanwei

    2013-12-21

    Plastic deformation of alumina (Al{sub 2}O{sub 3}) under high pressure was investigated by observing the shape changes of spherical particles, and the near fully dense transparent bulks were prepared at around 5.5 GPa and 900 °C. Through analyzing the deformation features, densities, and residual micro-strain of the Al{sub 2}O{sub 3} compacts prepared under high pressures and temperatures (2.0–5.5 GPa and 600–1200 °C), the effects of plastic deformation on the sintering behavior of alumina have been demonstrated. Under compression, the microscopic deviatoric stress caused by grain-to-grain contact could initiate the plastic deformation of individual particles, eliminate pores of the polycrystalline samples, and enhance the local atomic diffusion at the grain boundaries, thus produced transparent alumina bulks.

  18. Porous Alumina as a Promising Biomaterial for Public Health.

    PubMed

    Bragazzi, Nicola Luigi; Gasparini, Roberto; Amicizia, Daniela; Panatto, Donatella; Larosa, Claudio

    2015-01-01

    Porous aluminum is a nanostructured material characterized by unique properties, such as chemical stability, regular uniformity, dense hexagonal porous lattice with high aspect ratio nanopores, excellent mechanical strength, and biocompatibility. This overview examines how the structure and properties of porous alumina can be exploited in the field of public health. Porous alumina can be employed for fabricating membranes and filters for bioremediation, water ultrafiltration, and microfiltration/nanofiltration, being a promising technique for having clean and fresh water, which is essential for human health. Porous alumina-based nanobiosensor coated with specific antibodies or peptides seem to be a useful tool to detect and remove pathogens both in food and in water, as well as for environmental monitoring. Further, these applications, being low-energy demanding and cost-effective, are particularly valuable in resource-limited settings and contexts, and can be employed as point of use devices in developing countries, where there is an urgent need of hygiene and safety assurance.

  19. Effect of humic acid on sorption of technetium by alumina.

    PubMed

    Kumar, S; Rawat, N; Kar, A S; Tomar, B S; Manchanda, V K

    2011-09-15

    Sorption of technetium by alumina has been studied in absence as well as in presence of humic acid using (95)Tc(m) as a tracer. Measurements were carried out at fixed ionic strength (0.1M NaClO(4)) under varying pH (3-10) as well as redox (aerobic and reducing anaerobic) conditions. Under aerobic conditions, negligible sorption of technetium was observed onto alumina both in absence and in presence of humic acid. However, under reducing conditions (simulated with [Sn(II)] = 10(-6)M), presence of humic acid enhanced the sorption of technetium in the low pH region significantly and decreased at higher pH with respect to that in absence of humic acid. Linear additive as well as surface complexation modeling of Tc(IV) sorption in presence of humic acid indicated the predominant role of sorbed humic acid in deciding technetium sorption onto alumina.

  20. Improving fatigue damage resistance of alumina through surface grading.

    PubMed

    Ren, L; Liu, L; Bhowmick, S; Gerbig, Y B; Janal, M N; Thompson, V P; Zhang, Y

    2011-08-01

    Porcelain-veneered alumina crown restorations often fail from bulk fracture resulting from radial cracks that initiate at the cementation surface with repeated flexure of the stiffer crown layers on the soft dentin support. We hypothesized that bulk fracture may be substantially mitigated by grading the elastic modulus at the crown surfaces. In this study, we fabricated graded structures by infiltrating glass into dense alumina plates, resulting in a diminished modulus at the surface layers. The plates were then bonded to polycarbonate substrates and subjected to fatigue loading in water. Tests were terminated when fracture occurred at the cementation tensile surface or at the fatigue endurance limit (1 million cycles). Infiltrated specimens showed a significant increase in fatigue fracture loads over non-infiltrated controls. Our results indicate that controlled elastic gradients at the surface could be highly beneficial in the design of fracture-resistant alumina crowns.

  1. Origin of High-Alumina Basalt, Andesite, and Dacite Magmas.

    PubMed

    Hamilton, W

    1964-10-30

    The typical volcanic rocks of most island arcs and eugeosynclines, and of some continental environments, are basalt, andesite, and dacite, of high alumina content. The high-alumina basalt differs from tholeiitic basalt primarily in having a greater content of the components of calcic plagioclase. Laboratory data indicate that in the upper mantle, below the level at which the basaltic component of mantle rock is transformed by pressure to eclogite or pyroxenite, the entire basaltic portion probably is melted within a narrow temperature range, but that above the level of that transformation plagioclase is melted selectively before pyroxene over a wide temperature range. The broad spectrum of high-alumina magmas may represent widely varying degrees of partial melting above the transformation level, whereas narrow-spectrum tholeiite magma may represent more complete melting beneath it.

  2. Sodium-beta Alumina Batteries: Status and Challenges

    SciTech Connect

    Lu, XC; Lemmon, JP; Sprenkle, V; Yang, ZG

    2010-09-01

    This paper provides a review of materials and designs for sodium-beta alumina battery technology and discusses the challenges ahead for further technology improvement. Sodium-beta alumina batteries have been extensively developed in recent years and encouraging progress in performance and cycle life has been achieved. The battery is composed of an anode, typically molten sodium, and a cathode that can be molten sulfur (Na-S battery) or a transition metal halide incorporated with a liquid phase secondary electrolyte (e.g.. ZEBRA battery). In most cases the electrolyte is a dense solid beta ''-Al(2)O(3), sodium ion-conducting membrane. The issues' prohibiting widespread commercialization of sodium-beta alumina technology are rekited to the materials and methods of manufacturing that impact cost, safety, and performance characteristics.

  3. Origin of High-Alumina Basalt, Andesite, and Dacite Magmas.

    PubMed

    Hamilton, W

    1964-10-30

    The typical volcanic rocks of most island arcs and eugeosynclines, and of some continental environments, are basalt, andesite, and dacite, of high alumina content. The high-alumina basalt differs from tholeiitic basalt primarily in having a greater content of the components of calcic plagioclase. Laboratory data indicate that in the upper mantle, below the level at which the basaltic component of mantle rock is transformed by pressure to eclogite or pyroxenite, the entire basaltic portion probably is melted within a narrow temperature range, but that above the level of that transformation plagioclase is melted selectively before pyroxene over a wide temperature range. The broad spectrum of high-alumina magmas may represent widely varying degrees of partial melting above the transformation level, whereas narrow-spectrum tholeiite magma may represent more complete melting beneath it. PMID:17794034

  4. Temperature distribution in microwave sintering of alumina cylinders

    SciTech Connect

    Thomas, J.R. Jr.; Katz, J.D.; Blake, R.D.

    1994-04-01

    Small cylinders of high-purity alumina were encased in a `casket` of low-density zirconia insulation and heated to sintering temperature in a large multi-mode microwave oven. Optical fiber sensors were used to monitor the temperature at several locations in the system. It was found that the alumina samples heat faster than the zirconia insulation at temperatures above 1000 C, and that the temperature distribution in the sample is essentially uniform during the heating process. A two-dimensional mathematical model of the heat transfer process was developed which reproduces the essential features of the observed phenomena. Literature data for all temperature-dependent properties were incorporated into the model. The model suggests that the alumina samples absorb a significant fraction of the microwave energy.

  5. Modifying alumina red mud to support a revegetation cover

    NASA Astrophysics Data System (ADS)

    Xenidis, A.; Harokopou, A. D.; Mylona, E.; Brofas, G.

    2005-02-01

    Alumina red mud, a fine-textured, iron-rich, alkaline residue, is the major waste product of bauxite digestion with caustic soda to remove alumina. The high alkalinity and salinity as well as the poor nutrient status are considered to be the major constraints of red mud revegetation. This research was conducted to evaluate the ameliorating effect of gypsum, sewage sludge, ferrous sulfate, ammonium sulfate, ammonium nitrate, and calcium phosphate on alumina red mud. The effectiveness of the mixtures was evaluated by applying extraction tests and performing experiments using six plant species. Gypsum amendment significantly reduced the pH, electrical conductivity, and sodium and aluminum content of red mud. Sewage sludge application had an extended effect in improving both the soil structure and the nutrient status of the gypsum-amended red mud. Together with the gypsum and sewage sludge, calcium phosphate application into red mud enhanced plant growth and gave the most promising results.

  6. Origin of high-alumina basalt, andesite, and dacite magmas

    USGS Publications Warehouse

    Hamilton, W.

    1964-01-01

    The typical volcanic rocks of most island arcs and eugeosynclines, and of some continental environments, are basalt, andesite, and dacite, of high alumina content. The high-alumina basalt differs from tholeiitic basalt primarily in having a greater content of the components of calcic plagioclase. Laboratory data indicate that in the upper mantle, below the level at which the basaltic component of mantle rock is transformed by pressure to eclogite or pyroxenite, the entire basaltic portion probably is melted within a narrow temperature range, but that above the level of that transformation plagioclase is melted selectively before pyroxene over a wide temperature range. The broad spectrum of high-alumina magmas may represent widely varying degrees of partial melting above the transformation level, whereas narrow-spectrum tholeiite magma may represent more complete melting beneath it.

  7. The surface reaction kinetics of salicylate on alumina

    SciTech Connect

    Wang, Z.; Ainsworth, C.C.; Friedrich, D.M.; Joly, A.G.; Gassman, P.L.

    1997-12-31

    The kinetics of reaction of salicylate with colloidal alumina in aqueous suspension and with Al(III) in homogeneous aqueous solution were studied by stopped-flow laser fluorescence spectroscopy. The emission spectra confirmed the formation of both monodentate complexes and more stable bidentate chelates. Temporal evolution of the spectra indicated that the reaction was fast (within first few minutes) for both the homogeneous and heterogeneous reactions but slowed down afterwards for the latter. Reactions completed within 10 minutes in homogeneous phase at pH 3.3 but took more than 12 hours in alumina suspension. Analysis of the fluorescence intensity within first four minutes showed that in homogeneous phase the reaction followed a single pseudo-first-order kinetics. In alumina suspension log plots were nonlinear and characteristic of multiple heterogeneous reaction paths. The kinetics are interpreted in terms of the simultaneous formation of multiple species as well as subsequent conversion between species.

  8. Molecular dynamics studies of interfacial water at the alumina surface.

    SciTech Connect

    Argyris, Dr. Dimitrios; Ho, Thomas; Cole, David

    2011-01-01

    Interfacial water properties at the alumina surface were investigated via all-atom equilibrium molecular dynamics simulations at ambient temperature. Al-terminated and OH-terminated alumina surfaces were considered to assess the structural and dynamic behavior of the first few hydration layers in contact with the substrates. Density profiles suggest water layering up to {approx}10 {angstrom} from the solid substrate. Planar density distribution data indicate that water molecules in the first interfacial layer are organized in well-defined patterns dictated by the atomic terminations of the alumina surface. Interfacial water exhibits preferential orientation and delayed dynamics compared to bulk water. Water exhibits bulk-like behavior at distances greater than {approx}10 {angstrom} from the substrate. The formation of an extended hydrogen bond network within the first few hydration layers illustrates the significance of water?water interactions on the structural properties at the interface.

  9. Studies on synthesis of alumina nanopowder from synthetic Bayer liquor

    SciTech Connect

    Mazloumi, Mahyar; Arami, Hamed; Khalifehzadeh, Razieh; Sadrnezhaad, S.K. . E-mail: sadrnezh@sharif.edu

    2007-06-05

    Procedure for synthesis of alumina nanopowder from Bayer liquor (synthetic sodium aluminate solution) is investigated. Cooling, ageing and then addition of 3 ml/l Tiron (1,2-dihydroxy-3,5-benzene disulfonic acid disodium salt) to the supersaturated liquor affect purity and fineness of the nanopowder product. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX) analyses indicate that purity of the alumina nanopowder increases with the aging time. Experimental observations show that highly pure alumina nanopowders could be produced by direct calcination of cold gelatinous sodium aluminate solution followed by careful washing at a Tiron concentration of 3 ml/l NaOH.

  10. Improving Fatigue Damage Resistance of Alumina through Surface Grading

    PubMed Central

    Ren, L.; Liu, L.; Bhowmick, S.; Gerbig, Y.B.; Janal, M.N.; Thompson, V.P.; Zhang, Y.

    2011-01-01

    Porcelain-veneered alumina crown restorations often fail from bulk fracture resulting from radial cracks that initiate at the cementation surface with repeated flexure of the stiffer crown layers on the soft dentin support. We hypothesized that bulk fracture may be substantially mitigated by grading the elastic modulus at the crown surfaces. In this study, we fabricated graded structures by infiltrating glass into dense alumina plates, resulting in a diminished modulus at the surface layers. The plates were then bonded to polycarbonate substrates and subjected to fatigue loading in water. Tests were terminated when fracture occurred at the cementation tensile surface or at the fatigue endurance limit (1 million cycles). Infiltrated specimens showed a significant increase in fatigue fracture loads over non-infiltrated controls. Our results indicate that controlled elastic gradients at the surface could be highly beneficial in the design of fracture-resistant alumina crowns. PMID:21555776

  11. Factors contributing to the breakdown of sodium beta-alumina

    SciTech Connect

    Buechele, A.C.

    1982-05-01

    Clarification of the breakdown process occurring during charge transfer in sodium beta alumina solid electrolytes was derived from: (1) studying the effects of molten sodium contact at 350/sup 0/C on single crystal sodium beta alumina and polycrystalline sodium beta alumina; (2) determination of critical current density by monitoring acoustic emissions accompanying crack growth in sodium/sodium beta alumina/sodium cells subjected to linear current ramping at 1 mA cm/sup -2/ sec/sup -1/; (3) failure analysis conducted on cycled electrolytes, some from commercial sodium/sulfur cells, which had been subjected to up to 703 Ahr cm/sup -2/ of charge transfer. Gray coloration developing in beta aluminas in contact with molten sodium was found to be a consequence of formation, through reduction by sodium, of oxygen vacancies charge compensated by electrons. Electronic conductivity of the electrolyte increases as a result. No second phase formation was detected. Colored electrolytes from sodium/sulfur cells show evidence of a newly recognized degradation mechanism in which fracture occurs when sodium is reduced and deposited internally under pressure as metal in regions where an electronic conductivity gradient exists. Heating colored beta aluminas in air produces reoxidation and bleaching. Kinetics and other properties of the coloration and bleaching processes were determined. Critical current density was found to bear an inverse relation to average electrolyte grain size. Evidence was found in the cycled electrolytes for a slow crack growth mechanism and a progressive mode of degradation advancing from the sulfur electrode interface. Implications of the findings for the construction and operation of sodium/sulfur battery systems are discussed.

  12. Hydrogen removal from e-beam deposited alumina thin films by oxygen ion beam

    SciTech Connect

    Das, Arijeet Mukharjee, C. Rajiv, K. Bose, Aniruddha Singh, S. D. Rai, S. K.; Ganguli, Tapas; Joshi, S. C.; Deb, S. K.; Phase, D. M.

    2014-04-24

    Hydrogen interstitials and oxygen vacancies defects create energy levels in the band gap of alumina. This limits the application of alumina as a high-k dielectric. A low thermal budget method for removal of hydrogen from alumina is discussed. It is shown that bombardment of alumina films with low energy oxygen ion beam during electron beam evaporation deposition decreases the hydrogen concentration in the film significantly.

  13. Alumina over-coating on Pd nanoparticle catalysts by atomic layer deposition : enhanced stability and reactivity.

    SciTech Connect

    Feng, H.; Lu, J.; Stair, P. C.; Elam, J. W.

    2011-04-01

    ALD Alumina was utilized as a protective layer to inhibit the sintering of supported nano-sized ALD Pd catalysts in the methanol decomposition reaction carried out at elevated temperatures. The protective ALD alumina layers were synthesized on Pd nanoparticles (1-2 nm) supported on high surface area alumina substrates. Up to a certain over-coat thickness, the alumina protective layers preserved or even slightly enhanced the catalytic activity and prevented sintering of the Pd nanoparticles up to 500 C.

  14. Nanowatt threshold, alumina sensitized neodymium laser integrated on silicon

    PubMed Central

    Maker, Ashley J.; Armani, Andrea M.

    2013-01-01

    Low threshold lasers based on rare-earth elements have enabled numerous scientific discoveries and innovations in industry. However, pushing the threshold into the sub-microwatt regime has been stymied by a fundamental material phenomenon. Specifically, rare earth dopants form clusters which quench emission and reduce efficiency. Here, we fabricate resonant cavity lasers from neodymium-doped silica films containing alumina. The alumina prevents the clustering of the Neodymium, enabling the lasers to achieve thresholds of 530nanoWatts at room temperature. PMID:24216946

  15. Atomistic force field for alumina fit to density functional theory

    SciTech Connect

    Sarsam, Joanne; Finnis, Michael W.; Tangney, Paul

    2013-11-28

    We present a force field for bulk alumina (Al{sub 2}O{sub 3}), which has been parametrized by fitting the energies, forces, and stresses of a large database of reference configurations to those calculated with density functional theory (DFT). We use a functional form that is simpler and computationally more efficient than some existing models of alumina parametrized by a similar technique. Nevertheless, we demonstrate an accuracy of our potential that is comparable to those existing models and to DFT. We present calculations of crystal structures and energies, elastic constants, phonon spectra, thermal expansion, and point defect formation energies.

  16. Influence of grain boundary silica impurity on alumina toughness

    SciTech Connect

    Moya, J.S.; Kriven, W.M.; Pask, J.A.

    1980-08-01

    In a series of previous reports the effect of silica impurity on aggregation state and on electropheretic, pressing, filtering and sintering behavior on alumina powders was presented. The results obtained showed that the silica surface impurity plays an important role in the ceramic processing of powders by (a) decreasing the pH values of the isoelectric point (i.e.p.), which affects the aggregation state of the powder, and (b) decreasing the compactability and the activation energy for the initial stage of sintering. In the phase of the studies emphasis was given to the effect of the presence of silica impurity on the toughness and fracture behavior of alumina samples.

  17. The influence of aluminum grain size on alumina nanoporous structure

    SciTech Connect

    Feil, A. F.; Costa, M. V. da; Amaral, L.; Teixeira, S. R.; Migowski, P.; Dupont, J.; Machado, G.; Peripolli, S. B.

    2010-01-15

    An approach to control the interpore distances and nanopore diameters of 150-nm-thick thin aluminum films is reported here. The Al thin films were grown by sputtering on p-type silicon substrate and anodized with a conventional anodization process in a phosphoric acid solution. It was found that interpore distance and pore diameter are related to the aluminum grain size and can be controlled by annealing. The grain contours limit the sizes of alumina cells. This mechanism is valid for grain sizes supporting only one alumina cell and consequently only one pore.

  18. Photochromic isomerization of spirobenzopyran in nanoholes of anodic alumina

    SciTech Connect

    Saito, Mitsunori; Tsubokura, Yasuhiro

    2006-11-01

    A notable change in the photochromic characteristics was observed when the benzene solution of spirobenzopyran was put in nanoholes of anodic alumina. The absorption peak that appeared in the ultraviolet irradiation process shifted to a shorter wavelength, and the decay time of the decoloration process became?200 times longer than that of the original solution. After a preservation period of several days, however, both the absorption wavelength and the decay time recovered to those of the original solution. These experimental results suggest that the photochromic isomerization in the alumina nanoholes is affected by the large surface area of the matrix rather than the limited free volume.

  19. Synthesis and textural evolution of alumina particles with mesoporous structures

    SciTech Connect

    Liu Xun; Peng Tianyou; Yao Jinchun; Lv Hongjin; Huang Cheng

    2010-06-15

    Alumina particles with mesostructures were synthesized through a chemical precipitation method by using different inorganic aluminum salts followed by a heterogeneous azeotropic distillation and calcination process. The obtained mesoporous {gamma}-alumina particles were systematically characterized by the X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption measurement. Effects of the aluminum salt counter anion, pH value and the azeotropic distillation process on the structural or textural evolution of alumina particles were investigated. It is found that Cl{sup -} in the reaction solution can restrain the textural evolution of the resultant precipitates into two-dimensional crystallized pseudoboehmite lamellae during the heterogeneous azeotropic distillation, and then transformed into {gamma}-Al{sub 2}O{sub 3} particles with mesostructures after further calcination at 1173 K, whereas coexisting SO{sub 4}{sup 2-} can promote above morphology evolution and then transformed into {gamma}-Al{sub 2}O{sub 3} nanofibers after calcination at 1173 K. Moreover nearly all materials retain relatively high specific surface areas larger than 100 m{sup 2} g{sup -1} even after calcinations at 1173 K. - Graphical abstract: Co-existing Cl{sup -} is beneficial for the formation of {gamma}-alumina nanoparticles with mesostructures during the precipitation process. Interparticle and intraparticle mesopores can be derived from acidic solution and near neutral solution, respectively.

  20. Viscosity of alumina nanoparticles dispersed in car engine coolant

    SciTech Connect

    Kole, Madhusree; Dey, T.K.

    2010-09-15

    The present paper, describes our experimental results on the viscosity of the nanofluid prepared by dispersing alumina nanoparticles (<50 nm) in commercial car coolant. The nanofluid prepared with calculated amount of oleic acid (surfactant) was tested to be stable for more than 80 days. The viscosity of the nanofluids is measured both as a function of alumina volume fraction and temperature between 10 and 50 C. While the pure base fluid display Newtonian behavior over the measured temperature, it transforms to a non-Newtonian fluid with addition of a small amount of alumina nanoparticles. Our results show that viscosity of the nanofluid increases with increasing nanoparticle concentration and decreases with increase in temperature. Most of the frequently used classical models severely under predict the measured viscosity. Volume fraction dependence of the nanofluid viscosity, however, is predicted fairly well on the basis of a recently reported theoretical model for nanofluids that takes into account the effect of Brownian motion of nanoparticles in the nanofluid. The temperature dependence of the viscosity of engine coolant based alumina nanofluids obeys the empirical correlation of the type: log ({mu}{sub nf}) = A exp(BT), proposed earlier by Namburu et al. (author)

  1. Alumina-encapsulated vaccine formulation with improved thermostability and immunogenicity.

    PubMed

    Zhou, Hangyu; Wang, Guangchuan; Li, Xiao-Feng; Li, Yaling; Zhu, Shun-Ya; Qin, Cheng-Feng; Tang, Ruikang

    2016-05-11

    Developing vaccine formulations with excellent thermostability and immunogenicity remains a great challenge. By in situ encapsulating a live-attenuated strain of human enterovirus 71 (EV71) in alumina, we obtained a robust vaccine formulation named EV71@NanoAlum, which features significantly enhanced thermostability and immunogenicity. This attempt follows a material-based tactic for vaccine improvement. PMID:27098047

  2. Formation of {gamma}-alumina nanorods in presence of alanine

    SciTech Connect

    Dabbagh, Hossein A.; Rasti, Elham; Yalfani, Mohammad S.; Medina, Francesc

    2011-02-15

    Graphical abstract: Nanorod aluminas with a possible hexagonal symmetry, high surface area and relatively narrow pore size distribution were obtained. Research highlights: {yields} Research highlights {yields} Boehmite was prepared using a green sol-gel process in the presence of alanine. {yields} Nanorod aluminas with a high surface area were obtained. {yields} Addition of alanine would shape the size of the holes and crevices. {yields} The morphologies of the nanorods were revealed by transmission electron microscope. -- Abstract: Boehmite and alumina nanostructures were prepared using a simple green sol-gel process in the presence of alanine in water medium at room temperature. The uncalcined (dried at 200 {sup o}C) and the calcined materials (at 500, 600 and 700 {sup o}C for 4 h) were characterized using XRD, TEM, SEM, N{sub 2} physisorption and TGA. Nanorod aluminas with a possible hexagonal symmetry, high surface area and relatively narrow pore size distribution were obtained. The surface area was enhanced and crystallization was retarded as the alanine content increased. The morphologies of the nanoparticles and nanorods were revealed by a transmission electron microscope (TEM).

  3. Nanocomposite formed by titanium ion implantation into alumina

    SciTech Connect

    Spirin, R. E.; Salvadori, M. C. Teixeira, F. S.; Sgubin, L. G.; Cattani, M.; Brown, I. G.

    2014-11-14

    Composites of titanium nanoparticles in alumina were formed by ion implantation of titanium into alumina, and the surface electrical conductivity measured in situ as the implantation proceeded, thus generating curves of sheet conductivity as a function of dose. The implanted titanium self-conglomerates into nanoparticles, and the spatial dimensions of the buried nanocomposite layer can thus be estimated from the implantation depth profile. Rutherford backscattering spectrometry was performed to measure the implantation depth profile, and was in good agreement with the calculated profile. Transmission electron microscopy of the titanium-implanted alumina was used for direct visualization of the nanoparticles formed. The measured conductivity of the buried layer is explained by percolation theory. We determine that the saturation dose, φ{sub 0}, the maximum implantation dose for which the nanocomposite material still remains a composite, is φ{sub 0} = 2.2 × 10{sup 16 }cm{sup −2}, and the corresponding saturation conductivity is σ{sub 0} = 480 S/m. The percolation dose φ{sub c}, below which the nanocomposite still has basically the conductivity of the alumina matrix, was found to be φ{sub c} = 0.84 × 10{sup 16 }cm{sup −2}. The experimental results are discussed and compared with a percolation theory model.

  4. Development of Cast Alumina-Forming Austenitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Muralidharan, G.; Yamamoto, Y.; Brady, M. P.; Walker, L. R.; Meyer, H. M., III; Leonard, D. N.

    2016-09-01

    Cast Fe-Ni-Cr chromia-forming austenitic stainless steels with Ni levels up to 45 wt.% are used at high temperatures in a wide range of industrial applications that demand microstructural stability, corrosion resistance, and creep strength. Although alumina scales offer better corrosion protection at these temperatures, designing cast austenitic alloys that form a stable alumina scale and achieve creep strength comparable to existing cast chromia-forming alloys is challenging. This work outlines the development of cast Fe-Ni-Cr-Al austenitic stainless steels containing about 25 wt.% Ni with good creep strength and the ability to form a protective alumina scale for use at temperatures up to 800-850°C in H2O-, S-, and C-containing environments. Creep properties of the best alloy were comparable to that of HK-type cast chromia-forming alloys along with improved oxidation resistance typical of alumina-forming alloys. Challenges in the design of cast alloys and a potential path to increasing the temperature capability are discussed.

  5. Osseointegration of alumina bioceramic granules: A comparative experimental study

    NASA Astrophysics Data System (ADS)

    Rerikh, V. V.; Avetisyan, A. R.; Zaydman, A. M.; Anikin, K. A.; Bataev, V. A.; Nikulina, A. A.; Sadovoy, M. A.; Aronov, A. M.; Semantsova, E. S.

    2016-08-01

    To perform a comparative analysis of osseointegration of bioceramic alumina-based granules, hydroxyapatite-based granules, and deproteinized bone granules. The experiment was conducted on 52 adult male Kyoto-Wistar rats weighing 350 to 520 g. The animals were divided into five matched groups that differed only in the type of an implanted material. The granules were implanted in the lumbar vertebral bodies and in the distal right femur of each laboratory animal. Two months after surgery, the animals were euthanized, followed by tissue sampling for morphological studies. An examination of specimens from the groups with implanted alumina granules revealed the newly formed trabecular bone with remodeling signs. The bone tissue filled the intragranular space, tightly adhering to the granule surface. There was no connective tissue capsule on the border between bone tissue and alumina granules. Cylindrical bioceramic alumina-based granules with an open internal channel have a higher strength surpassing than that of analogs and the osseointegration ability close to that of hydroxyapatite and deproteinized bone granules.

  6. Structure factor changes in supercooled yttria-alumina

    SciTech Connect

    Wilding, Martin C.; Greaves, G. Neville; Quang Vu Van; Majerus, Odile; Hennet, Louis

    2009-01-29

    Changes in the structure factor of yttria-alumina liquids have been identified in the supercooled range. Different inter-polyhedral configurations between AlO{sub 4} and YO{sub 6} groups distinguish low density and high density liquid phases. The coexistence of phases at high temperatures have been identified in simultaneous measurements of small angle x-ray scattering.

  7. Ionic Segregation on Grain Boundaries in Thermally Grown Alumina Scales

    SciTech Connect

    Pint, Bruce A; Unocic, Kinga A

    2012-01-01

    This study first examined segregation behaviour in the alumina scale formed after 100 h at 1100 C on bare and MCrAlYHfSi-coated single-crystal superalloys with {approx}10 ppma La and Y. For the bare superalloy, Hf and Ti were detected on the grain boundaries of the inner columnar alumina layer. Increasing the oxidation temperature to 1200 C for 2 h did not change the segregation behavior. With the bond coating, both Y and Hf were segregated to the grain boundaries as expected. However, there was evidence of Ti-rich oxide particles near the gas interface suggesting that Ti diffused from the superalloy through the coating. To further understand these segregation observations with multiple dopants, other alumina-forming systems were examined. Alumina scale grain boundary co-segregation of Ti with Y is common for FeCrAl alloys. Co-segregation of Hf and Ti was observed in the scale formed on co-doped NiAl. No La segregation was detected in the scale formed on NiCrAl with only a 19 ppma La addition, however, the scale was adherent.

  8. On the electrical conductivity of Ti-implanted alumina

    SciTech Connect

    Salvadori, M. C.; Teixeira, F. S.; Cattani, M.; Nikolaev, A.; Savkin, K. P.; Oks, E. M.; Park, H.-K.; Phillips, L.; Yu, K. M.; Brown, I. G.

    2012-03-15

    Ion implantation of metal species into insulators provides a tool for the formation of thin, electrically conducting, surface layers with experimenter-controlled resistivity. High energy implantation of Pt and Ti into alumina accelerator components has been successfully employed to control high voltage surface breakdown in a number of cases. In the work described here we have carried out some basic investigations related to the origin of this phenomenon. By comparison of the results of alumina implanted with Ti at 75 keV with the results of prior investigations of polymers implanted with Pt at 49 eV and Au at 67 eV, we describe a physical model of the effect based on percolation theory and estimate the percolation parameters for the Ti-alumina composite. We estimate that the percolation dose threshold is about 4 x 10{sup 16} cm{sup -2} and the maximum dose for which the system remains an insulator-conductor composite is about 10 x 10{sup 16} cm{sup -2}. The saturation electrical conductivity is estimated to be about 50 S/m. We conclude that the observed electrical conductivity properties of Ti-implanted alumina can be satisfactorily described by percolation theory.

  9. Alumina contribution to CO oxidation: A TPR and IR study

    NASA Astrophysics Data System (ADS)

    Ammendola, P.; Barbato, P. S.; Lisi, L.; Ruoppolo, G.; Russo, G.

    2011-10-01

    The alumina contribution to CO oxidation in the absence of O2 on metal oxide supported catalysts was investigated by CO TPR and in-situ FTIR and DRIFT studies up to 800 °C. These tests were performed on two Al2O3 supported catalysts (1 wt.% Pt/La/γ-Al2O3 and 8 wt.% Cu/γ-Al2O3) and on two corresponding alumina supports (5 wt.% La2O3 stabilised γ-Al2O3 and high mechanical resistant spherical γ-Al2O3 particles). The quantitative determination of CO consumption and CO2 and H2 formation on the alumina supports was in agreement with a WGS reaction occurring between surface OH and CO with a predominantly 2:1 stoichiometry. In the CO TPR of metal oxide supported catalysts, in addition to the reduction of the metal, a WGS reaction took place with enhanced kinetics. This enhancement was the result of a CO spillover phenomenon from the metal to alumina hydroxyls. This phenomenon significantly affected the evaluation of the reduction degree of the supported metal and could not be neglected in the subsequent calculations.

  10. Modelling precursor decay in AD-99.5 Alumina

    SciTech Connect

    Simha, C. Hari Manoj; Bless, S. J.; Bedford, A.

    1998-07-10

    In this paper we present a simple model to explain the absence of precursor decay in the Coor's AD-99 5 Alumina ceramic, as shown by Grady in his plate impact experiments. The model is incorporated into the Research EPIC 95 finite element code. The simulations compare well with Grady's results.

  11. Modelling precursor decay in AD-99.5 Alumina

    NASA Astrophysics Data System (ADS)

    Simha, C. Hari Manoj; Bless, S. J.; Bedford, A.

    1998-07-01

    In this paper we present a simple model to explain the absence of precursor decay in the Coor's AD-99 5 Alumina ceramic, as shown by Grady in his plate impact experiments. The model is incorporated into the Research EPIC 95 finite element code. The simulations compare well with Grady's results.

  12. Atomic scale insights on chlorinated gamma-alumina surfaces.

    PubMed

    Digne, Mathieu; Raybaud, Pascal; Sautet, Philippe; Guillaume, Denis; Toulhoat, Hervé

    2008-08-20

    The thermochemistry of chlorinated gamma-alumina surfaces is explored by means of density functional calculations as a function of relevant reaction conditions used in experiments and in high-octane fuel production in the refining industry such as hydrocarbon isomerization and reforming. The role of chlorine as a dope of the Brønsted acidity of gamma-alumina surfaces is investigated at an atomic scale. Combining infrared spectroscopy and density functional theory calculations, the most favorable location of chlorine atoms on the (110), (100) and (111) surfaces of gamma-alumina is found to result either from direct adsorption or from the exchange of basic hydroxyl groups. Moreover, the modification of the hydrogen bond network upon chlorine adsorption is put forward as a key parameter for changing the Brønsted acidity. In a second step, we use a thermodynamic approach based on DFT total energy calculations corrected by the chemical potentials of HCl and H2O to determine the adsorption isotherms of chlorine and the relative surface concentration of hydroxyl groups and chlorine species on the gamma-alumina surfaces. The determination of chlorine content as a function of temperature and partial pressures of H2O and HCl offers new quantitative data required for optimizing the state of the support surface in industrial conditions. The mechanisms of chlorination are also discussed as a function of reaction conditions. PMID:18646849

  13. Development of an imaging system for the detection of alumina on turbine blades

    NASA Astrophysics Data System (ADS)

    Greenwell, S. J.; Kell, J.; Day, J. C. C.

    2014-03-01

    An imaging system capable of detecting alumina on turbine blades by acquiring LED-induced fluorescence images has been developed. Acquiring fluorescence images at adjacent spectral bands allows the system to distinguish alumina from fluorescent surface contaminants. Repair and overhaul processes require that alumina is entirely removed from the blades by grit blasting and chemical stripping. The capability of the system to detect alumina has been investigated with two series of turbine blades provided by Rolls-Royce plc. The results illustrate that the system provides a superior inspection method to visual assessment when ascertaining whether alumina is present on turbine blades during repair and overhaul processes.

  14. Ambient-temperature mechanical response of alumina-fluoromica laminates

    SciTech Connect

    King, T.T.; Cooper, R.F. . Dept. of Materials Science and Engineering)

    1994-07-01

    Flexural delamination experiments were used to evaluate the mechanical performance of thermochemically stable alumina-fluoromica laminates. Hot-pressed, precracked laminate specimens, in which two MgAl[sub 2]O[sub 4]-spinel-coated alumina substrates were separated by a thin layer of fluorophlogopite (KMg[sub 3](AlSi[sub 3])O[sub 10]F[sub 2]), were tested in four-point flexure at room temperature. Two types of mechanical response were observed: steady-state delamination and brittle failure. Microstructural analysis showed that the delamination response was associated with fine ([le]5 [mu]m) grains of the mica; the brittle response occurred when the mica interphase consisted of large (> 30 [mu]m) grains that bridged the interphase. The steady-state strain-energy release rate (G[sub ss]) measured on the graceful, delaminating beams was 9.1 [+-] 0.4 J[center dot]m[sup [minus]2] for randomly oriented [approximately]5-[mu]m grains but only 2.8 [+-] 0.2 J[center dot]m[sup [minus]2] for [approximately]1-[mu]m grains that were aligned with easy-cleavage planes parallel to the laminate interfaces. The results suggested that debonding of the specimens occurred via cleavage of the mica grains. Observation of delamination cracks confirmed this point: propagation occurred within the fluoromica interphase rather than along the spinel/alumina or spinel/fluorophlogopite interfaces. The mechanical feasibility of laminate specimens without the protective spinel coating on the substrate containing the notch was also tested to address an issue related to the preparation of alumina fiber/mica interphase/alumina matrix composites. The delamination response again occurred for the case of a fine-grained mica interphase.

  15. Advanced morphological analysis of patterns of thin anodic porous alumina

    SciTech Connect

    Toccafondi, C.; Stępniowski, W.J.; Leoncini, M.; Salerno, M.

    2014-08-15

    Different conditions of fabrication of thin anodic porous alumina on glass substrates have been explored, obtaining two sets of samples with varying pore density and porosity, respectively. The patterns of pores have been imaged by high resolution scanning electron microscopy and analyzed by innovative methods. The regularity ratio has been extracted from radial profiles of the fast Fourier transforms of the images. Additionally, the Minkowski measures have been calculated. It was first observed that the regularity ratio averaged across all directions is properly corrected by the coefficient previously determined in the literature. Furthermore, the angularly averaged regularity ratio for the thin porous alumina made during short single-step anodizations is lower than that of hexagonal patterns of pores as for thick porous alumina from aluminum electropolishing and two-step anodization. Therefore, the regularity ratio represents a reliable measure of pattern order. At the same time, the lower angular spread of the regularity ratio shows that disordered porous alumina is more isotropic. Within each set, when changing either pore density or porosity, both regularity and isotropy remain rather constant, showing consistent fabrication quality of the experimental patterns. Minor deviations are tentatively discussed with the aid of the Minkowski measures, and the slight decrease in both regularity and isotropy for the final data-points of the porosity set is ascribed to excess pore opening and consequent pore merging. - Highlights: • Thin porous alumina is partly self-ordered and pattern analysis is required. • Regularity ratio is often misused: we fix the averaging and consider its spread. • We also apply the mathematical tool of Minkowski measures, new in this field. • Regularity ratio shows pattern isotropy and Minkowski helps in assessment. • General agreement with perfect artificial patterns confirms the good manufacturing.

  16. Synthesis and structural evaluation of freeze-cast porous alumina

    SciTech Connect

    Souza, Douglas F.; Nunes, Eduardo H.M.; Pimenta, Daiana S.; Vasconcelos, Daniela C.L.; Nascimento, Jailton F.; Grava, Wilson; Vasconcelos, Wander L.

    2014-10-15

    In this work we fabricated alumina samples by the freeze-casting technique using tert-butanol as the solvent. The prepared materials were examined by scanning electron microscopy and X-ray microtomography. Next, they were coated with sol–gel silica films by dip-coating. Permeability tests were carried out in order to assess the permeation behavior of the materials processed in this study. We observed that the sintering time and alumina loading showed a remarkable effect on both the structural properties and flexural strength of the freeze-cast samples. Nitrogen adsorption tests revealed that the silica prepared in this study exhibited a microporous structure. It was observed that the presence of silica coatings on the alumina surface decreased the CO{sub 2} permeance by about one order of magnitude. Because of the similar kinetic diameters of nitrogen and carbon dioxide, the CO{sub 2}/N{sub 2} system showed a separation efficiency that was lower than that observed for the He/CO{sub 2} and He/N{sub 2} systems. We noticed that increasing the feed pressure improved the separation capacity of the obtained materials. - Highlights: • Porous alumina samples obtained by the freeze-casting technique • Microporous silica coating prepared by a simple sol–gel dip-coating methodology • Samples examined by SEM, μ-CT, and nitrogen sorption tests • Mechanical tests were carried out in the freeze-cast samples. • The presence of silica coatings on the alumina surface decreased the CO{sub 2} permeance.

  17. Osteoblast function on nanophase alumina materials: Influence of chemistry, phase, and topography.

    PubMed

    Price, Rachel L; Gutwein, Luke G; Kaledin, Leonid; Tepper, Frederick; Webster, Thomas J

    2003-12-15

    Alumina is a material that has been used in both dental and orthopedic applications. It is with these uses in mind that osteoblast (bone-forming cell) function on alumina of varying particulate size, chemistry, and phase was tested in order to determine what formulation might be the most beneficial for bone regeneration. Specifically, in vitro osteoblast adhesion, proliferation, intracellular alkaline phosphatase activity, and calcium deposition was observed on delta-phase nanospherical, alpha-phase conventional spherical, and boehmite nanofiber alumina. Results showed for the first time increased osteoblast functions on the nanofiber alumina. Specifically, a 16% increase in osteoblast adhesion over nanophase spherical alumina and a 97% increase over conventional spherical alumina were found for nanofiber alumina after 2 h. A 29% increase in cell number after 5 days and up to a 57% greater amount of calcium was found on the surface of the nanofiber alumina compared with other alumina surfaces. Some of the possible explanations for such enhanced osteoblast behavior on nanofiber alumina may be attributed to chemistry, crystalline phase, and topography. Increased osteoblast function on nanofiber alumina suggests that it may be an ideal material for use in orthopedic and dental applications.

  18. Processing and Mechanical Properties of Various Zirconia/Alumina Composites for Fuel Cell Applications

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Bansal, Narottam P.

    2002-01-01

    Various electrolyte materials for solid oxide fuel cells were fabricated by hot pressing 10 mol% yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina, particulates and platelets, each containing 0 to 30 mol% alumina. Flexure strength and fracture toughness of both particulate and platelet composites at ambient temperature increased with increasing alumina content, reaching a maximum at 30 mot% alumina. For a given alumina content, strength of particulate composites was greater than that of platelet composites, whereas, the difference in fracture toughness between the two composite systems was negligible. No virtual difference in elastic modulus and density was observed for a given alumina content between particulate and platelet composites. Thermal cycling up to 10 cycles between 200 to 1000 C did not show any effect on strength degradation of the 30 mol% platelet composites, indicative of negligible influence of CTE mismatches between YSZ matrix and alumina grains.

  19. Interactions of dispersants and binders with {alpha}-alumina in aqueous suspensions

    SciTech Connect

    Hidber, P.; Graule, T.; Gauckler, L.

    1995-12-31

    Citric acid and poly(vinyl alcohol) (PVA) are commonly used as dispersant and binder for aqueous alumina slurries. The interaction of citric acid and PVA with the alumina surface as well as the competitive reaction of these two additives on the alumina surface have been studied by measurements of the adsorption density and electrophoretic mobility. By variation of the citric acid concentration, it is possible to adjust the isoelectric point (IEP) of alumina to any pH-value between 9 and 3. For citric acid, a high adsorption density on alumina was measured over a broad pH range, whereas the adsorption of PVA is very low. The adsorption density of citric acid on alumina is not influenced by the presence of PVA, whereas the polymer is displaced by citric acid from the alumina surface. Enhanced binder migration in wet green bodies during the drying process is a consequence of this displacement.

  20. High alumina metamorphic rocks of the Kings Mountain district, North Carolina and South Carolina

    USGS Publications Warehouse

    Potter, Donald Brandreth

    1954-01-01

    The following evidence suggests that high alumina quartzite in this district is of metasedimentary origin: high alumina quartzite occurs as well defined thin beds that can be traced up to three and one half miles along strike; many outcrops of high alumina quartzite exhibit compositional layering (i.e., kyanigte quartzite is interlayered with staurolite quartzite, and with non-kyanitic magnetiferous quartzite); high alumina quartzite beds occur in a conformable sequence of high alumina metasedimentary and metavolcanic schists. It is suggested that the high alumina quartzite beds are metamorphosed beds of sandy or silty clay; these beds probably represent one stage in the deposition of fine grained clayey clastic sediments. No evidence was found to support the view of Smith and Newcombe (1951) that the kyanite at Henry Knob developed by hudrothermal introduction of alumina. The present study indicates that kyanite in the kyanite quartzite here, as throughout the district, is of metasedimentary origin.

  1. Porous alumina, zirconia and alumina/zirconia for bone repair: fabrication, mechanical and in vitro biological response.

    PubMed

    Hadjicharalambous, Chrystalleni; Buyakov, Ales; Buyakova, Svetlana; Kulkov, Sergey; Chatzinikolaidou, Maria

    2015-04-23

    Zirconia (ZrO2) and alumina (Al2O3) based ceramics are widely used for load-bearing applications in bone repair due to their excellent mechanical properties and biocompatibility. They are often regarded as bioinert since no direct bone-material interface is created unless a porous structure intercedes, leading to better bone bonding. In this regard, investigating interactions between cells and porous ceramics is of great interest. In the present study, we report on the successful fabrication of sintered alumina A-61, zirconia Z-50 and zirconia/alumina composite ZA-60 ceramics with medium porosities of 61, 50 and 60%, respectively, indicating a bimodal pore size distribution and good interconnectivity. They exhibit elastic moduli of 3-10 GPa and compressive strength values of 60-240 MPa, similar to those of human cortical bone.We performed in vitro cell-material investigations comparing the adhesion, proliferation and differentiation of mouse pre-osteoblasts MC3T3-E1 on the three porous materials. While all three ceramics demonstrate a strong cell attachment, better cell spreading is observed on zirconia-containing substrates. Significantly higher cell growth was quantified on the latter ceramics, revealing an increased alkaline phosphatase activity, higher collagen production and increased calcium biomineralization compared to A-61. Hence, these porous zirconia-containing ceramics elicit superior biological responses over porous alumina of similar porosity, promoting enhanced biological interaction, with potential use as non-degradable bone grafts or as implant coatings.

  2. Synthesis of highly ordered mesoporous alumina thin films and their framework crystallization to γ-alumina phase.

    PubMed

    Jiang, Xiangfen; Oveisi, Hamid; Nemoto, Yoshihiro; Suzuki, Norihiro; Wu, Kevin C-W; Yamauchi, Yusuke

    2011-11-01

    Here we report the preparation of highly ordered mesoporous alumina films existing both as P6(3)/mmc and Fm-3m mesostructures by using triblock copolymer Pluronic P123 as the structure-directing agent. 2D grazing-incidence small-angle X-ray scattering (GI-SAXS) completely proves the existence of two different mesopore structures (i.e., [001]-oriented P6(3)/mmc and [111]-oriented Fm-3m symmetries). After calcination at 1000 °C, the amorphous alumina framework is successfully converted to γ-alumina crystals. During the crystallization process, large uniaxial shrinkage occurs along the direction perpendicular to the substrate with the retention of horizontal mesoscale periodicity, thereby resulting in formation of partially vertical mesoporosity in the film. Through detailed electron microscopic study, we discuss the formation mechanism for the vertical mesoporosity upon calcination. The obtained mesoporous γ-alumina film shows high thermal stability up to 1000 °C, which is highly useful in wide research areas such as catalyst supports and separators.

  3. Structure of δ-Alumina: Toward the Atomic Level Understanding of Transition Alumina Phases

    SciTech Connect

    Kovarik, Libor; Bowden, Mark; Genc, Arda; Szanyi, János; Peden, Charles H. F.; Kwak, Ja Hun

    2014-08-07

    Transition Al2O3 derived from thermal decomposition of AlOOH Boehmite have complex structures and to a large extent remain poorly understood. Here, we report a detailed atomic level analysis of δ-Al2O3 for the first time using a combination of high-angle annular dark field electron microscopy imaging, X-ray diffraction refinement, and density functional theory calculations. We show that the structure of δ-Al2O3 represents a complex structural intergrowth from two main crystallographic variants, which are identified as δ1-Al2O3 and δ2-Al2O3. The two main variants are fully structurally described, and in addition, we also derive their energy of formation. On the basis of comparison with other relevant transition Al2O3 phases, it is shown how energetic degeneracy leads to the structural disorder and complex intergrowths among several transition Al2O3. Finally, the results of the work have important implications for understanding thermodynamic stability and transformation processes in transition alumina.

  4. Unoxidized Graphene/Alumina Nanocomposite: Fracture- and Wear-Resistance Effects of Graphene on Alumina Matrix

    PubMed Central

    Kim, Hyo Jin; Lee, Sung-Min; Oh, Yoon-Suk; Yang, Young-Hwan; Lim, Young Soo; Yoon, Dae Ho; Lee, Changgu; Kim, Jong-Young; Ruoff, Rodney S.

    2014-01-01

    It is of critical importance to improve toughness, strength, and wear-resistance together for the development of advanced structural materials. Herein, we report on the synthesis of unoxidized graphene/alumina composite materials having enhanced toughness, strength, and wear-resistance by a low-cost and environmentally benign pressure-less-sintering process. The wear resistance of the composites was increased by one order of magnitude even under high normal load condition (25 N) as a result of a tribological effect of graphene along with enhanced fracture toughness (KIC) and flexural strength (σf) of the composites by ~75% (5.60 MPa·m1/2) and ~25% (430 MPa), respectively, compared with those of pure Al2O3. Furthermore, we found that only a small fraction of ultra-thin graphene (0.25–0.5 vol%, platelet thickness of 2–5 nm) was enough to reinforce the composite. In contrast to unoxidized graphene, graphene oxide (G-O) and reduced graphene oxide (rG-O) showed little or less enhancement of fracture toughness due to the degraded mechanical strength of rG-O and the structural defects of the G-O composites. PMID:24898792

  5. Strain-Induced Deformation in Magnesia-Alumina Layered Composites

    SciTech Connect

    Kim, Chang Soo; Lombardo, Stephen J; Winholtz, Robert A

    2008-06-18

    Ceramic beams are induced in situ to form complex shapes at elevated temperature without the application of an external stress. This process has been demonstrated for thin alumina substrates coated with a layer of magnesia. The internal strain causing the substrates to deform at elevated temperature arises as a consequence of strain mismatch accompanying the penetration of the coating into the substrate. The magnitude of the deformation depends on the amount of coating applied, on the thickness of the substrate, on the density of the substrate, and on the temperature. During exposure of the beams to elevated temperature, the magnesia coating reacts with the alumina substrate to form the spinel phase; the resulting volume change accompanying the phase transformation is likely the predominant driving force for deformation.

  6. Conduction in alumina with atomic scale copper filaments

    NASA Astrophysics Data System (ADS)

    Xu, Xu; Liu, Jie; Anantram, M. P.

    2014-10-01

    The conductance of atomic scale filaments with three and seven Cu atoms in α-alumina are calculated using ab initio density functional theory. We find that the filament with 3 Cu atoms is sufficient to increase the conductance of 1.3 nm thick alumina film by more than 103 times in linear response. As the applied voltage increases, the current quickly saturates and differential resistance becomes negative. Compared to the filament with three Cu atoms, while the conductance of the filament with seven Cu atoms is comparable in linear response, they carry as much as twenty times larger current at large biases. The electron transport is analyzed based on local density of states, and the negative differential resistance in the seven Cu filaments occurs due to their narrow bandwidth.

  7. Adsorption of copper on a γ-alumina support

    NASA Astrophysics Data System (ADS)

    Papas, Brian N.; Whitten, Jerry L.

    2016-09-01

    The interaction of a Cu atom with two model γ-alumina surfaces was examined using configuration interaction theory. These two surfaces are centered on Td and Oh coordinated Al atoms near the surface, with both surfaces fully hydroxylated. Copper was found to bind to non-hydrogenated oxygen atoms in the surface by 25 kcal/mol, with the possibility that an under coordinated aluminum site may bind copper much more strongly. Vacancies formed by the removal of hydrogen atoms, or by removal of OH groups, were found to bind Cu by values ranging from 40 to 98 kcal/mol. The interaction of a planar Cu7 particle with an exposed Td coordinated Al atom at an OH vacancy site was found to lead to decomposition of the particle and partial absorption of the Cu into the alumina surface.

  8. Fracture behavior of 20% Nb particulate reinforced alumina composite

    SciTech Connect

    Lane, S.; Biner, S.B.; Buck, O.

    1993-11-01

    The composites consist of alumina matrix with 0.05 wt % MgO and 20 Vol % Nb with an average particle size of 30 to 100 microns produced by dry mixing and sintering to near their theoretical densities. Fracture toughness tests were carried out in three point bending on chevron notched samples. Results indicate that R-curve of the composites exhibited more than 300% increase in crack growth resistance compared to crack growth resistance of alumina produced with the identical procedures. Crack growth resistance curve of the composites increased with increasing Nb particle size. Metallorgraph indicated that failure of Nb particles in crack path ranges from full interface separation without any significant deformation of Nb particles to cleavage failure without any evidence of interface separation.

  9. Capillarity in isothermal infiltration of alumina fiber preforms with aluminum

    SciTech Connect

    Michaud, V.J.; Mortensen, A. . Dept. of Materials Science); Compton, L.M. )

    1994-10-01

    Models derived in petroleum engineering and soil science for flow of two immiscible fluids in a porous medium are extended to the infiltration of ceramic preforms by a liquid metal. SAFFIL alumina fiber preforms are infiltrated with an aluminum matrix in a series of interrupted unidirectional and isothermal experiments at various low applied pressures, to measure profiles of the volume fraction of metal along the length of the preforms. Comparison of experimental data with theory reveals the existence of a pressure-dependent incubation time for wetting of the alumina preforms by molten aluminum at 973 K. If this incubation time is taken into account, experimental curves of metal distribution are well predicted by theory, confirming the validity of the models after initiation of flow.

  10. Deterministic processing of alumina with ultra-short laser pulses

    SciTech Connect

    Furmanski, J; Rubenchik, A M; Shirk, M D; Stuart, B C

    2007-06-27

    Ultrashort pulsed lasers can accurately ablate materials which are refractory, transparent, or are otherwise difficult to machine by other methods. The typical method of machining surfaces with ultrashort laser pulses is by raster scanning, or the machining of sequentially overlapping linear trenches. Experiments in which linear trenches were machined in alumina at various pulse overlaps and incident fluences are presented, and the dependence of groove depth on these parameters established. A model for the machining of trenches based on experimental data in alumina is presented, which predicts and matches observed trench geometry. This model is then used to predict optimal process parameters for the machining of trenches for maximal material removal rate for a given laser.

  11. Observation of dislocations and twins in explosively compacted alumina

    SciTech Connect

    Yust, C.S.; Harris, L.A.

    1980-01-01

    The microstructure at the half-radius position of a polycrystalline alumina rod formed by explosive compaction has been studied by transmission electron microscopy. The as-compacted lattice is composed of differently misoriented bands aligned predominantly in one direction. Such bands may correspond to frequently observed shock lamellae. The band edges are defined by dislocation arrays lying on the basal planes of the hexagonal alumina lattice. The dislocations have Burgers vectors of the type (1120) and (1010), which are the Burgers vectors of slip dislocations in the basal plane. Basal plane twinning is also observed, and the twin boundaries are found to contain interfacial dislocations. While dislocation generation occurs primarily on basal planes, some dislocation activity is also noted on prism, (1100), and on rhombohedral, (1101), planes. Nonbasal twinning, however, has not been detected. The lattice damage is discussed in terms of possible dislocation and twinning mechanisms.

  12. Real-time polarimetric biosensing using macroporous alumina membranes

    NASA Astrophysics Data System (ADS)

    Álvarez, Jesús; Sola, Laura; Platt, Geoff; Cretich, Marina; Swann, Marcus; Chiari, Marcella; Hill, Daniel; Martínez-Pastor, Juan

    2013-05-01

    We report the first demonstration of real-time biosensing in free standing macroporous alumina membranes. The membranes with their 200 nm diameter pores are ideal candidates for biosensing applications where fast response times for small sample volumes are needed as they allow analytes to flow through the pores close to the bioreceptors immobilized on the pores walls. A bulk refractive index sensitivity of 5.2x10-6 refractive index units was obtained from signal responses to different concentrations of NaCl solutions flowing through the pores. Finally, after functionalizing the alumina pore surfaces with an epoxysilane and then spotting it with β-Lactoglobulin protein, the interactions between the β-lactoglobulin and rabbit anti-β-lactoglobulin, as well as the interaction between the rabbit anti-β-lactoglobulin and a secondary antibody anti-rabbit Immunoglobulin G were monitored in real-time.

  13. Process for High-Rate Fabrication of Alumina Nanotemplates

    NASA Technical Reports Server (NTRS)

    Myung, Nosang; Fleurial, Jean-Pierre; Yun, Minhee; West, William; Choi, Daniel

    2007-01-01

    An anodizing process, at an early stage of development at the time of reporting the information for this article, has shown promise as a means of fabricating alumina nanotemplates integrated with silicon wafers. Alumina nanotemplates are basically layers of alumina, typically several microns thick, in which are formed approximately regular hexagonal arrays of holes having typical diameters of the order of 10 to 100 nm. Interest in alumina nanotemplates has grown in recent years because they have been found to be useful as templates in the fabrication of nanoscale magnetic, electronic, optoelectronic, and other devices. The present anodizing process is attractive for the fabrication of alumina nanotemplates integrated with silicon wafers in two respects: (1) the process involves self-ordering of the holes; that is, the holes as formed by the process are spontaneously arranged in approximately regular hexagonal arrays; and (2) the rates of growth (that is, elongation) of the holes are high enough to make the process compatible with other processes used in the mass production of integrated circuits. In preparation for fabrication of alumina nanotemplates in this process, one first uses electron-beam evaporation to deposit thin films of titanium, followed by thin films of aluminum, on silicon wafers. Then the alumina nanotemplates are formed by anodizing the aluminum layers, as described below. In experiments in which the process was partially developed, the titanium films were 200 A thick and the aluminum films were 5 m thick. The aluminum films were oxidized to alumina, and the arrays of holes were formed by anodizing the aluminum in aqueous solutions of sulfuric and/or oxalic acid at room temperature (see figure). The diameters, spacings, and rates of growth of the holes were found to depend, variously, on the composition of the anodizing solution, the applied current, or the applied potential, as follows: In galvanostatically controlled anodizing, regardless of the

  14. Conduction in alumina with atomic scale copper filaments

    SciTech Connect

    Xu, Xu; Liu, Jie; Anantram, M. P.

    2014-10-28

    The conductance of atomic scale filaments with three and seven Cu atoms in α-alumina are calculated using ab initio density functional theory. We find that the filament with 3 Cu atoms is sufficient to increase the conductance of 1.3 nm thick alumina film by more than 10{sup 3} times in linear response. As the applied voltage increases, the current quickly saturates and differential resistance becomes negative. Compared to the filament with three Cu atoms, while the conductance of the filament with seven Cu atoms is comparable in linear response, they carry as much as twenty times larger current at large biases. The electron transport is analyzed based on local density of states, and the negative differential resistance in the seven Cu filaments occurs due to their narrow bandwidth.

  15. Measurements of prompt radiation induced conductivity of alumina and sapphire.

    SciTech Connect

    Hartman, E. Frederick; Zarick, Thomas Andrew; Sheridan, Timothy J.; Preston, Eric F.

    2011-04-01

    We performed measurements of the prompt radiation induced conductivity in thin samples of Alumina and Sapphire at the Little Mountain Medusa LINAC facility in Ogden, UT. Five mil thick samples were irradiated with pulses of 20 MeV electrons, yielding dose rates of 1E7 to 1E9 rad/s. We applied variable potentials up to 1 kV across the samples and measured the prompt conduction current. Analysis rendered prompt conductivity coefficients between 1E10 and 1E9 mho/m/(rad/s), depending on the dose rate and the pulse width for Alumina and 1E7 to 6E7 mho/m/(rad/s) for Sapphire.

  16. Decomposition of halomethanes on [alpha]-alumina at stratospheric temperatures

    SciTech Connect

    Robinson, G.N.; Freedman, A.; Kolb, C.E.; Worsnop, D.R. )

    1994-03-01

    The authors present data that suggest the possibility of a previously unsuspected heterogeneous process involving the decomposition of halocarbon source gases on alumina solid-propellant rocket motor exhaust particles deposited in the stratosphere. These results, obtained under ultrahigh vacuum conditions, provide evidence that halomethane compounds undergo dissociative chemisorption on [alpha]-alumina surfaces at stratospheric temperatures, leading to the release of more reactive halogen containing species. Simple calculations indicate that halocarbon concentrations will be severely depleted in the immediate wake of the rocket plume; any serious global impact at current projected launch rates requires the existence of one or more processes that regenerate active sites on the surface subsequent to the dissociative chemisorption of halocarbons. 19 refs., 3 figs., 1 tab.

  17. Mechanical properties of alumina-zirconia-silver composites

    SciTech Connect

    Tuan, W.H.; Chen, W.R.

    1995-02-01

    Either ceramic inclusions or metallic inclusions can be used to enhance the mechanical properties of ceramics. In the present study, both silver inclusions and zirconia agglomerates have been added to alumina. The presence of the inclusions inhibits the grain growth of the alumina matrix. The strength of Al{sub 2}O{sub 3}-ZrO{sub 2}-Ag composites is increased by microstructural refinement. Together with the plastic deformation of silver inclusions and the phase transformation of tetragonal zirconia agglomerates, the toughness of the composites is enhanced. Because silver inclusions and zirconia agglomerates are attached after sintering, the toughness increase for the Al{sub 2}O{sub 3}-ZrO{sub 2}-Ag composites is less than the sum of the toughness increments for Al{sub 2}O{sub 3}-Ag and Al{sub 2}O{sub 3}-ZrO{sub 2} composites.

  18. Protective coating for alumina-silicon carbide whisker composites

    DOEpatents

    Tiegs, Terry N.

    1989-01-01

    Ceramic composites formed of an alumina matrix reinforced with silicon carbide whiskers homogenously dispersed therein are provided with a protective coating for preventing fracture strength degradation of the composite by oxidation during exposure to high temperatures in oxygen-containing atmospheres. The coating prevents oxidation of the silicon carbide whiskers within the matrix by sealing off the exterior of the matrix so as to prevent oxygen transport into the interior of the matrix. The coating is formed of mullite or mullite plus silicon oxide and alumina and is formed in place by heating the composite in air to a temperature greater than 1200.degree. C. This coating is less than about 100 microns thick and adequately protects the underlying composite from fracture strength degradation due to oxidation.

  19. Melt processing of Bi--2212 superconductors using alumina

    DOEpatents

    Holesinger, Terry G.

    1999-01-01

    Superconducting articles and a method of forming them, where the superconducting phase of an article is Bi.sub.2 Sr.sub.2 CaCu.sub.2 O.sub.y (Bi-2212). Alumina is combined with Bi-2212 powder or Bi-2212 precursor powder and, in order to form an intimate mixture, the mixture is melted and rapidly cooled to form a glassy solid. The glassy solid is comminuted and the resulting powder is combined with a carrier. An alternative to melting is to form the mixture of nanophase alumina and material having a particle size of less than about 10 microns. The powder, with the carrier, is melt processed to form a superconducting article.

  20. Low-temperature synthesis of berlinite-bonded alumina ceramics.

    SciTech Connect

    Grover, S. E.

    1999-08-03

    Alumina ceramics, in which berlinite (aluminum orthophosphate, AlPO{sub 4}) is the bonding phase, were synthesized at 150 C. Differential thermal analysis of a mixture of Al{sub 2}O{sub 3} and H{sub 3}PO{sub 4} solution indicated that a minimum temperature of 118 C was necessary for a chemical reaction to occur. Therefore, we hydrothermally cured a mixture of Al{sub 2}O{sub 3} and H{sub 3}PO{sub 4} solution between 130 C and 150 C to form a hard and dense berlinite-bonded alumina ceramic. The intermediate phase of aluminum phosphate hydrate (AlH{sub 3}(PO{sub 4}){sub 2}H{sub 2}O) was also identified. Physical and mechanical properties of this material are discussed.

  1. Diffusion bonding of titanium-titanium aluminide-alumina sandwich

    SciTech Connect

    Wickman, H.A.; Chin, E.S.C.; Biederman, R.R.

    1995-12-31

    Diffusion bonding of a metallic-intermetallic-ceramic sandwich is of interest for potential armor applications. Low cost titanium, titanium diboride reinforced titanium aluminide (Ti-48at.%Al), and aluminum oxide are diffusion bonded in a vacuum furnace between 1,000 C and 1,400 C. Metallographic examination of the prior bonding interface showed excellent metallurgical coupling between the Ti-48at.%Al composite and the low cost Ti. A series of microstructures representative of phases consistent with a hypothetical Ti-Al-B phase diagram is visible. The alumina-Ti-48at.%Al interfacial bond is achieved through penetration of titanium-aluminum phases into the existing alumina porosity. A detailed microstructural analysis identifying mechanisms of interfacial bonding will be presented for each interfacial zone.

  2. Proton Adsorption onto Alumina: Extension of Multisite Complexation (MUSIC) Theory.

    PubMed

    Nagashima; Blum

    1999-09-01

    The adsorption isotherm of protons onto a commercial gamma-alumina sample was determined in aqueous nitric acid with sodium nitrate as a background electrolyte. Three discrete regions could be discerned in the log-log plots of the proton isotherm determined at the solution pH 5 to 2. The multisite complexation (MUSIC) model was modified to analyze the simultaneous adsorption of protons onto various kinds of surface species. Copyright 1999 Academic Press. PMID:10441408

  3. Proton adsorption onto alumina: extension of multisite complexation (MUSIC) theory

    SciTech Connect

    Nagashima, K.; Blum, F.D.

    1999-09-01

    The adsorption isotherm of protons onto a commercial {gamma}-alumina sample was determined in aqueous nitric acid with sodium nitrate as a background electrolyte. Three discrete regions could be discerned in the log-log plots of the proton isotherm determined at the solution pH 5 to 2. The multisite complexation (MUSIC) model was modified to analyze the simultaneous adsorption of protons onto various kinds of surface species.

  4. Plasma synthesis of alumina films on metal and ceramic substrates

    SciTech Connect

    Brown, I.; Zhi Wang

    1995-04-01

    The authors are exploring the feasibility of the plasma synthesis of highly-adherent films of alumina and chromia on SiC and FeAl substrates. A magnetically-filtered cathodic arc plasma deposition technique is used in which a high density metal plasma (Al or Cr) is formed and deposited on the substrate in the presence of a low pressure gaseous oxygen background. The substrate is simultaneously repetitively pulse biased, providing a means of controlling the incident ion energy. In the early stages of the process the ion energy is held in the keV range so as to produce atomic mixing at the film-substrate interface (ion stitching), and in the latter stages of deposition the energy is reduced to {approximately}200 eV (IBAD range) to provide a means of controlling the film structure and morphology. Films that are dense and highly adherent can be formed in this way. The authors have produced near-stoichiometric films of alumina and chromia on small SiC and FeAl substrates and characterized the films in a number of ways, including RBS, X-ray diffraction and adhesion, and we`ve also done some preliminary temperature cycling experiments. The alumina films are of thickness from 0.2 to 1.5.{micro}, amorphous prior to heat treatment, and show an {alpha}-alumina phase after heat treating at 1,000 C for up to 16 hours. The film substrate adhesion is typically greater then {approximately}70 MPa prior to heating, and initial results indicate that the films maintain their adhesion after repetitive cycling in temperature between ambient and 1,000 C. Here they describe the plasma processing method and outline the experimental results obtained to-date.

  5. Characterization of glass-infiltrated alumina-based ceramics

    PubMed Central

    Bona, Alvaro Della; Mecholsky, John J; Barrett, Allyson A; Griggs, Jason A

    2010-01-01

    Objective characterize the microstructure, composition, and important properties of glass-infiltrated alumina-based ceramics similar to the In-Ceram system. Methods Materials used were: IA- In-Ceram Alumina (Vita); IAE- IA electrophoretically deposited (Vita); AEM- IA using a vacuum driven method (Vita); VC- Vitro-Ceram (Angelus); TC- Turkom-Cera (Turkom-Ceramic); CC- Ceramcap (Foto-Ceram); and AG- Alglass (EDG). Ceramic specimens were fabricated following manufacturers’ instructions and ISO6872 standard and polished successively through 1μm alumina abrasive. Semi-quantitative and qualitative analyses were performed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and stereology (Vv). The elastic modulus (E) and Poisson’s ratio (ν) were determined using time-of-flight data measured in an ultrasonic pulser/receiver and the density (ρ) was determined using a helium pycnometer. Vicker’s indentation was used to calculate hardness (H). Bar specimens (25×4×1.2mm3) were loaded in three-point bending to fracture using a universal testing machine with cross-head speed of 1mm/min. Flexural strength (σ3P) was calculated and statistically analyzed using ANOVA, Tukey (α=0.05) and Weibull (m= modulus, σ0= characteristic strength). Results SEM and EDS analyses revealed similar microstructure for all ceramics, except for a lead-based matrix in CC and a zirconia phase in VC. TC, AG and CC showed significantly lower mean σ3P values than the other ceramics (p 0.05). AEM showed the greatest m (16). Conclusion Despite few differences in microstructure and composition, the IA, IAE, AEM and VC ceramics have similar properties. Significance The glass-infiltrated alumina-based ceramics from different manufacturers presented distinct characteristics. It is necessary to characterize new commercially available materials to understand their properties. PMID:18692231

  6. Single Crystal Structure Determination of Alumina to 1 Mbar

    NASA Astrophysics Data System (ADS)

    Dong, H.; Zhang, L.; Prakapenka, V.; Mao, H.

    2014-12-01

    Aluminum oxide (Al2O3) is an important ceramic material and a major oxide in the earth. Additionally, alumina is a widely used pressure standard in static high-pressure experiments (Cr3+-bearing corundum, ruby). The changes of its crystal structure with pressure (P) and temperature (T) are important for its applications and understanding its physical properties in the deep Earth. There have been numerous reports on the high P-T polymorphs of alumina. Previous theoretical calculations and experiments suggest that the crystal structure of Al2O3 evolves greatly at high P-T. In this study, we used the newly developed multigrain crystallography method combined with single-crystal x-ray diffraction analysis technique for the structure determination of alumina at high P-T to provide single-crystal structure refinement for high-pressure phases of Al2O3. Alumina powder was mixed with ~10% Pt and Ne was used as both pressure transmitting media and thermal insulating layers during laser-heating. Coarse-grained aggregates of Al2O3 were synthesized in a laser-heated diamond anvil cell. The structure change of Al2O3 was monitored by in situ x-ray diffraction at ~1 Mbar and 2700 K. The results allow us to distinguish the structural differences between the Rh2O3 (II) structure (space group Pbcn) and perovskite structure (space group Pbnm) for the first high-pressure phase of Al2O3. More detailed results will be discussed in the later work.

  7. Moisture-Induced Alumina Scale Spallation: The Hydrogen Factor

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    2010-01-01

    For some time the oxidation community has been concerned with interfacial spallation of protective alumina scales, not just upon immediate cool down, but as a time-delayed phenomenon. Moisture-induced delayed spallation (MIDS) and desktop spallation (DTS) of thermal barrier coatings (TBCs) refer to this process. It is most apparent for relatively adherent alumina scales that have survived initial cool down in a dry environment, have built up considerable thickness and strain energy, and have been somewhat damaged, such as by cyclic oxidation cracking. Indeed, a "sensitive zone" can be described that maximizes the observed effect as a function of all the relevant factors. Moisture has been postulated to serve as a source of interfacial hydrogen embrittlement. Hydrogen is derived from reaction with aluminum in the alloy at an exposed interface. The purpose of this monograph is to trace the close analogy of this phenomenon to other hydrogen-induced effects, such as embrittlement of aluminides and blistering of alloys and anodic alumina films. A formalized, top-down, logic-tree structure is presented as a guide to this discussion. A theoretical basis for interfacial weakening by hydrogen is first cited, as are demonstrations of hydrogen detection as a reaction product or interfacial species. Further support is provided by critical experiments that recreate the moisture effect, but by isolating hydrogen from other potential causative factors. These experiments include tests in H 2-containing atmospheres or cathodic hydrogen charging. Accordingly, they strongly indicate that interfacial hydrogen, derived from moisture, is the key chemical species accounting for delayed alumina scale spallation.

  8. Fluorine-mediated acidity of alumina-pillared fluorohectorite

    SciTech Connect

    Butruille, J.R.; Pinnavaia, T.J. ); Michot, L.J.; Barres, O. )

    1993-02-01

    Structural fluorine atoms in the 2:1 layered silicate framework of fluorohectorite have a profound effect on the acidity of alumina-pillared derivatives prepared by intercalation of Al[sub 13] polycations and subsequent calcination at elevated temperatures. The alumina-pillared clay formed by calcination at 350[degrees]C exhibits greatly enhanced catalytic activity for propylene alkylation of biphenyl, relative to nonfluorinated smectite hosts. However, calcination of the Al[sub 13] intercalate at 500[degrees]C results in a relatively inactive clay with greatly diminished NH[sub 3] and pyridine chemisorption properties. The effect of the calcination process on the clay layer structure was carefully studied by [sup 27]Al, [sup 29]Si, and [sup 19]F MAS-NMR and FTIR spectroscopic methods and by mass spectrometric analysis of volatile by-products. It was shown that between 30 and 500[degrees]C, specific lattice fluorine atoms adjacent to charged sites in the octahedral sheet of the layers are replaced by hydroxyl groups. At calcination temperatures below 350[degrees]C the Broensted acidity of protonated hydroxyl groups in the layers is enhanced by the electron-withdrawing effect of near-neighbor fluorine atoms at neutral sites in the octahedral sheet. A mechanism for fluorine hydrolysis is proposed in which gallery water molecules, formed by the dehydroxylation of the alumina pillars, migrate to hexagonal oxygen cavities above the reactive fluorine positions. Between 350 and 500[degrees]C, a second process occurs that causes dehydroxylation of the layers, and this results in a sharp decrease in the acidity and catalytic activity of the pillared clay. The relationships between structure and reactivity suggest that the acid-catalytic activity of an alumina-pillared clay can be mediated by controlling the relative amounts of hydroxyl groups at charged octahedral sites and fluorine atoms at neutral octahedral sites in the host clay. 22 refs., 13 figs., 3 tabs.

  9. Directional solidification of the alumina-zirconia ceramic eutectic system

    SciTech Connect

    Boldt, C.

    1994-07-27

    It is possible to produce alumina-zirconia ceramic samples through existing solidification techniques. The resulting microstructures typically consist of rods of zirconia in an alumina matrix, although a lamellar structure has been noted in some cases. In nearly all cases, colony growth was present which may possibly result from grain size, repeated nucleation events, and lamellar oscillations. In the same vein, it appears that the amount of impurities within the system might be the underlying cause for the colony growth. Colony growth was diminished through impurity control as the higher purity samples exhibited colony free behavior. In addition to colony formations, faceted alumina dendrites or nonfaceted zirconia dendrites may result in the ceramic if the sample is solidified out of the coupled zone. In all cases, for larger-sized Bridgman samples, a lower limit in the eutectic spacing was noted. The solidification model which includes the kinetic effect has been developed, although the effect appears to be negligible under present experimental conditions. A spacing limit might also occur due to the result of heat flow problems. Heat flow out of the ceramic is difficult to control, often causing radial and not axial growth. This behavior is exaggerated in the presence of impurities. Thus, higher purity powders should always be used. Higher purity samples, in addition to yielding a more microstructurally uniform ceramic, also showed increased directionality. In the future, the kinetic model needs to be examined in more detail, and further research needs to be accomplished in the area of molten ceramics. Once better system constants are in place, the kinetic model will give a better indication of the behavior in the alumina-zirconia system.

  10. The multiple applications of hydrocyclones in alumina production

    SciTech Connect

    Oeberg, N.; Kelton, G.P.; Rawlins, C.H.

    1996-10-01

    Hydrocyclones are used in many alumina refineries to enhance efficiency. A partial list of applications includes bauxite grinding, bauxite refinement sands separations from red muds, sand washing, hydrate classification and product size control, seed size control, hydrate thickening and deliquoring, agglomeration, preferential separation/reduction of oxalates, spent liquor solids recovery, cooling tower water clean-up, and lime slurry degritting. This paper reviews these applications including viable flowsheets and operating experience; and summarizes basic hydrocyclone selection including the main factors affecting performance.

  11. Advances in Zirconia Toughened Alumina Biomaterials for Total Joint Replacement

    PubMed Central

    Kurtz, Steven M.; Kocagöz, Sevi; Arnholt, Christina; Huet, Roland; Ueno, Masaru; Walter, William L.

    2014-01-01

    The objective of this article is to provide an up-to-date overview of zirconia-toughened alumina (ZTA) components used in total hip arthroplasties. The structure, mechanical properties, and available data regarding the clinical performance of ZTA are summarized. The advancements that have been made in understanding the in vivo performance of ZTA are investigated. This article concludes with a discussion of gaps in the literature related to ceramic biomaterials and avenues for future research. PMID:23746930

  12. Proton Adsorption onto Alumina: Extension of Multisite Complexation (MUSIC) Theory.

    PubMed

    Nagashima; Blum

    1999-09-01

    The adsorption isotherm of protons onto a commercial gamma-alumina sample was determined in aqueous nitric acid with sodium nitrate as a background electrolyte. Three discrete regions could be discerned in the log-log plots of the proton isotherm determined at the solution pH 5 to 2. The multisite complexation (MUSIC) model was modified to analyze the simultaneous adsorption of protons onto various kinds of surface species. Copyright 1999 Academic Press.

  13. Synthesis and textural evolution of alumina particles with mesoporous structures

    NASA Astrophysics Data System (ADS)

    Liu, Xun; Peng, Tianyou; Yao, Jinchun; Lv, Hongjin; Huang, Cheng

    2010-06-01

    Alumina particles with mesostructures were synthesized through a chemical precipitation method by using different inorganic aluminum salts followed by a heterogeneous azeotropic distillation and calcination process. The obtained mesoporous γ-alumina particles were systematically characterized by the X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption measurement. Effects of the aluminum salt counter anion, pH value and the azeotropic distillation process on the structural or textural evolution of alumina particles were investigated. It is found that Cl - in the reaction solution can restrain the textural evolution of the resultant precipitates into two-dimensional crystallized pseudoboehmite lamellae during the heterogeneous azeotropic distillation, and then transformed into γ-Al 2O 3 particles with mesostructures after further calcination at 1173 K, whereas coexisting SO 42- can promote above morphology evolution and then transformed into γ-Al 2O 3 nanofibers after calcination at 1173 K. Moreover nearly all materials retain relatively high specific surface areas larger than 100 m 2 g -1 even after calcinations at 1173 K.

  14. Moisture-Induced Alumina Scale Spallation: The Hydrogen Factor

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    2009-01-01

    For some time our community has been concerned with interfacial spallation of protective alumina scales, not just upon immediate cooldown, but as a time-delayed phenomenon. Moisture-induced delayed spallation (MIDS) and desktop spallation (DTS) of TBC's refer to this process. It is most apparent for relatively adherent alumina scales that have survived cool down in a dry environment, built up considerable thickness and strain energy, and have been somewhat damaged, such as by cyclic oxidation cracking. Indeed, a "sweet zone" can be defined that maximizes the observed effect as a function of all the relevant factors. Moisture has been postulated to serve as a source of interfacial hydrogen embrittlement derived from reaction with aluminum in the alloy at an exposed interface. The purpose of this monograph is to trace the close analogy of this phenomenon to other hydrogen effects, such as embrittlement of aluminides and blistering of alloys and anodic alumina films. A formalized, top-down, logic tree structure is presented as a guide to this discussion. A theoretical basis for interfacial weakening by hydrogen is first cited, as are demonstrations of hydrogen as a reaction product or detected interfacial species. Further support is provided by critical experiments that produce the same moisture effect, but by isolating hydrogen from other potential causative factors. These experiments include tests in H2-containing atmospheres or cathodic hydrogen charging.

  15. Alumina Based 500 C Electronic Packaging Systems and Future Development

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu

    2012-01-01

    NASA space and aeronautical missions for probing the inner solar planets as well as for in situ monitoring and control of next-generation aeronautical engines require high-temperature environment operable sensors and electronics. A 96% aluminum oxide and Au thick-film metallization based packaging system including chip-level packages, printed circuit board, and edge-connector is in development for high temperature SiC electronics. An electronic packaging system based on this material system was successfully tested and demonstrated with SiC electronics at 500 C for over 10,000 hours in laboratory conditions previously. In addition to the tests in laboratory environments, this packaging system has more recently been tested with a SiC junction field effect transistor (JFET) on low earth orbit through the NASA Materials on the International Space Station Experiment 7 (MISSE7). A SiC JFET with a packaging system composed of a 96% alumina chip-level package and an alumina printed circuit board mounted on a data acquisition circuit board was launched as a part of the MISSE7 suite to International Space Station via a Shuttle mission and tested on the orbit for eighteen months. A summary of results of tests in both laboratory and space environments will be presented. The future development of alumina based high temperature packaging using co-fired material systems for improved performance at high temperature and more feasible mass production will also be discussed.

  16. Preparation, characterization, and activity of fluorinated aluminas for halogen exchange

    SciTech Connect

    Hegde, R.I.; Barteau, M.A. )

    1989-12-01

    Fluorinated aluminas with {alpha}-AlF{sub 3} contents up to 90+% were prepared by treatment with the fluoroalkanes CHF{sub 3} or C{sub 2}HF{sub 5} at 773 K. XPS results suggest that nearly complete fluorination of the surface occurs even at low extents of bulk fluorination. Neither {gamma}-Al{sub 2}O{sub 3} nor {alpha}-AlF{sub 3} exhibits significant activity for reaction of CHF{sub 3} following adsorption at 300 K and subsequent temperature-programmed desorption. In contrast, partially fluorinated aluminas strongly adsorb CHF{sub 3}, CHClF{sub 2}, and CHCl{sub 2}F. TPD experiments indicate that all three C{sub 1}-HCFCs desorb from partially fluorinated alumina above 500 K; all react to liberate HF and CO{sub 2}, and the chlorine-containing species undergo fluorine-for-chlorine exchange to produce CHF{sub 3}. These results suggest that halogen-exchange reactions of HCFCs can be carried out with materials resembling conventional fluorination catalysts.

  17. Mild hydrotreating of heavy oils with modified alumina based catalysts

    SciTech Connect

    Dai, E.P.; Campbell, C.N.

    1994-12-31

    The decreasing demand for heavy fuels oils requires that refiners find ways for converting heavy hydrocarbon feedstocks to higher value mid-distillate products. To increase mid-distillate production, the refiner can choose from several processing options such as hydrocracking, fluid catalytic cracking, and coking. All of these options, however, require heavy capital investments. Because of these high investment costs, refiners are continually searching for conversion processes which may be utilized in existing units. One such process is mild hydrocracking (MHC). The general objective of this work is to identify an MHC catalyst which gives a higher conversion level for heavy hydrocarbon feedstocks, especially that fraction of the feedstock that boils above 1,000 F (538 C), while maintaining the same amount of sediment production. The conventional hydrocracking catalysts that consist of acidic cracking components such as Y zeolite, though exhibiting conversion improvements over alumina based catalysts, were not suitable for processing of heavy oils in the mild hydrocracking mode because of high sediment formation. In contrast, alumina catalysts containing basic oxides (alkali metal and alkaline earth metal) not only improve heavy oil conversion but, also maintain the sediment make at the same level as alumina based catalysts. The sediment make generally decreased with increasing macroporosity.

  18. Crystallographic and morphological textures in laser surface modified alumina ceramic

    NASA Astrophysics Data System (ADS)

    Harimkar, Sandip P.; Dahotre, Narendra B.

    2006-07-01

    Laser surface modification is an advanced technique for improving the surface performance of alumina ceramics in refractory and abrasive machining applications. Surface performance is expected to be greatly influenced by the crystallographic and morphological textures of surface grains generated during rapid solidification associated with laser processing. In this study, an investigation of the evolution of crystallographic and morphological textures during laser surface modifications of alumina ceramic was carried out using a 4kW Nd:YAG laser with fluences in the range of 458-726J/cm2. In these regimes of laser surface processing, the formation of equilibrium α-alumina was found to be assisted by catalytic sites provided by the substrate. Microstructure evolution was explored in terms of the development of crystallographic and morphological (size and shape) textures of surface grains as a function of laser processing parameters. The interdependence of crystallographic and morphological textures of the surface grains is discussed within the framework of faceted growth model suggesting that the formation of crystal shapes is governed by the relative velocities of certain crystallographic facets. Also, the effect of thermal aspects of laser processing on the morphology of the surface grains is discussed from the viewpoint of existing solidification theories.

  19. Development of Alumina-Forming Austenitic Stainless Steels

    SciTech Connect

    Brady, Michael P; Yamamoto, Yukinori; Bei, Hongbin; Santella, Michael L; Maziasz, Philip J

    2009-01-01

    This paper presents the results of the continued development of creep-resistant, alumina-forming austenitic (AFA) stainless steel alloys, which exhibit a unique combination of excellent oxidation resistance via protective alumina (Al2O3) scale formation and high-temperature creep strength through the formation of stable nano-scale MC carbides and intermetallic precipitates. Efforts in fiscal year 2009 focused on the characterization and understanding of long-term oxidation resistance and tensile properties as a function of alloy composition and microstructure. Computational thermodynamic calculations of the austenitic matrix phase composition and the volume fraction of MC, B2-NiAl, and Fe2(Mo,Nb) base Laves phase precipitates were used to interpret oxidation behavior. Of particular interest was the enrichment of Cr in the austenitic matrix phase by additions of Nb, which aided the establishment and maintenance of alumina. Higher levels of Nb additions also increased the volume fraction of B2-NiAl precipitates, which served as an Al reservoir during long-term oxidation. Ageing studies of AFA alloys were conducted at 750 C for times up to 2000 h. Ageing resulted in near doubling of yield strength at room temperature after only 50 h at 750 C, with little further increase in yield strength out to 2000 h of ageing. Elongation was reduced on ageing; however, levels of 15-25% were retained at room temperature after 2000 h of total ageing.

  20. EFFECT OF GRAIN SIZE ON DYNAMIC SCRATCH RESPONSE IN ALUMINA

    SciTech Connect

    Wang, Hong; Wereszczak, Andrew A; Lance, Michael J

    2006-01-01

    The machining and wear of ceramics and ceramic components are obviously influenced by abrasive damage. One parameter that can affect the abrasion process is the grain size of the ceramic material. To investigate this, single-grit pendulum scratch testing was used to investigate the dynamic scratch response in three 99.9% aluminas that each had a tight size distribution about mean grain sizes of 2, 15, or 25 m, respectively. The scratch speeds generated had an order of magnitude of ~ 1 m/s and the maximum scratch depths were several tens of micrometers. Tangential and normal scratch forces were monitored during each test and interpreted in conjunction with postmortem SEM and profilometry results. It was observed that both plastic deformation and brittle fracture participated in the scratching process and the relative activity of each was dependent on depth of penetration. At a specific depth of penetration, the material removal of alumina prevailingly relies on the generation and interaction of oblique radial and lateral cracks. Chip formation is greatly enhanced when the created cracks interact and that interaction itself depends on grain size. Larger grain size gives rise to larger lateral cracks, more severe fracture at the groove's bottom, and larger amplitude of scratch force oscillation. Lastly, the cutting pressure and the scratch hardness of alumina exhibit sensitivity to both grain size and the groove depth.

  1. Dielectric properties of KDP filled porous alumina nanocomposite thin films.

    PubMed

    Boni, O; Berger, S

    2001-12-01

    A new concept of a composite dielectric thin film fabrication is presented. The fabrication process consists of two stages. The first stage is anodizing a thin aluminum film to produce a porous alumina film that contains an array of nanometer sized parallel pores. The second stage is filling the pores with a saturated KDP (KH2PO4) liquid solution due to capillary forces. After drying KDP nanocrystals are formed inside the pores. This process results in a formation of a composite dielectric thin film composed of the alumina pores walls as one dielectric material and the KDP nanocrystals inside the pores as another dielectric material. The dielectric permittivity of this composite film is higher than that of the porous alumina film at all applied frequencies. The dielectric enhancement is more pronounced at low frequencies due to an interface polarization mechanism. This fabrication process enables controlling the size, composition, and microstructure of the composite dielectric film constituents and thus changing its dielectric properties over a wide range of values.

  2. High strength alumina produced by direct coagulation casting

    SciTech Connect

    Baader, F.H.; Will, J.; Tieche, D.

    1995-09-01

    Direct Coagulation Casting is a new colloidal forming technique. Double layer stabilized, concentrated alumina suspensions are solidified by shifting the suspensions pH from 4 towards the isoelectric point at 9 using the in situ enzyme-catalyzed decomposition of urea. This reaction minimizes the repulsive forces between the suspended particles. The remaining, attractive Van der Waals forces form a stiff particle network. Suspensions with low viscosities (0.3 Pa*s, 59 vol%) were prepared at pH 4. Deagglomeration of the suspensions by ball milling reduced the agglomerate size below 5 pm. The coagulation kinetics could be influenced either by the urease concentration or by the suspension temperature. Process variables were established, providing long idle times, which allowed additional filtration and degassing steps. Coagulation was followed by drying and sintering, whereby densities of more than 3.97 g/cm{sup 3}, a 4-point bending strength of 685 MPa (HIPed) and a high reliablility (m = 40) for high purity alumina were achieved. DCC has the potential to improve the reliability of alumina components of complex shape, as well as to avoid expensive molding.

  3. A New Mechanism for ISE in Alumina Shock Deformed at 6.5 GPa

    NASA Astrophysics Data System (ADS)

    Chakraborty, R.; Dey, A.; Mukhopadhyay, A. K.; Joshi, K. D.; Rav, A.; Ghosh, J.; Mandal, A. K.; Bysakh, S.; Biswas, S. K.; Gupta, S. C.

    2012-07-01

    With a view to understand how high strain rate flyer plate impact affects the nanohardness of a coarse (10 μm) grain high density (3.978 gm.cc-1) alumina, load controlled nanoindentation experiments were conducted with a Berkovich indenter on as received alumina (ARA) and shocked alumina fragments (SA) of obtained from a flyer plate shock impact study at 6.5 GPa. The results showed that the nanohardness of the shocked alumina (SA) samples was much lower than that of the as received alumina (ARA) samples and that the indentation size effect (ISE) was mild in the ARA but quite severe in the SA samples. Extensive additional characterization by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and a physical model based analysis of the experimental load depth data were utilized to provide a new explanation for the presence of strong indentation size effect in the shock recovered alumina.

  4. Load-bearing increase in alumina evoked by introduction of a functional glass gradient

    PubMed Central

    Dorthé, Erik; Zhang, Yu

    2011-01-01

    Alumina is the most commonly used ceramic in orthopedics due mainly to its wear resistance and chemical inertness. However, alumina has relatively low load-bearing capacity compared to other advanced ceramics, such as zirconia. We hypothesized that grading the elastic modulus at the surfaces may substantially increase the load-bearing capacity of alumina. In this study, graded structures were fabricated by infiltrating glass into dense alumina plates, resulting in a diminished modulus at the surface layers. The plates were then bonded to polycarbonate substrates and subjected to flexural loading with various loading rates spanning five orders of magnitude (dynamic fatigue) in water. Infiltrated specimens showed an increase in flexural load over homogenous controls for all loading rates, despite the graded alumina exhibiting greater load rate dependence than their homogenous counterparts. Our results indicate that controlled elastic gradients at the surface could be highly beneficial in improving the load-bearing capacity of alumina ceramics. PMID:22639492

  5. Role of metal oxides in chemical evolution: interaction of ribose nucleotides with alumina.

    PubMed

    Arora, Avnish Kumar; Kamaluddin

    2009-03-01

    Interaction of ribonucleotides--namely, 5'-AMP, 5'-GMP, 5'-CMP, and 5'-UMP--with acidic, neutral, and basic alumina has been studied. Purine nucleotides showed higher adsorption on alumina in comparison with pyrimidine nucleotides under acidic conditions. Adsorption data obtained followed Langmuir adsorption isotherm, and X(m) and K(L) values were calculated. On the basis of infrared spectral studies of ribonucleotides, alumina, and ribonucleotide-alumina adducts, we propose that the nitrogen base and phosphate moiety of the ribonucleotides interact with the positive charge surface of alumina. Results of the present study may indicate the importance of alumina in concentrating organic molecules from dilute aqueous solutions in primeval seas in the course of chemical evolution on Earth.

  6. Effects of particle size and coating on decomposition of alumina-extracted residue from high-alumina fly ash.

    PubMed

    Wang, Zehua; Ma, Shuhua; Tang, Zhenhua; Wang, Xiaohui; Zheng, Shili

    2016-05-01

    The effective removal of alkali in the alumina-extracted reside (AER) obtained by extracting alumina from high-alumina fly ash is the premise for realizing the utilization of the silicon component in the fly ash. Sodium was removed from the AER by a decomposition reaction. The effects of the particle size and reactant coating on the decomposition reaction of AER were studied, and the results showed that by decreasing the particle size, the decomposition reaction rate of AER could be enhanced obviously and the Na2O content of the products could be decreased effectively. In addition, the process and mechanism of the decomposition reaction of AER and the reaction kinetics were investigated. The results revealed that the decomposition reaction of AER started from the outer surface of the AER particles. The reaction kinetics corresponded with shrinking unreacted core models. Furthermore, the decomposition reaction rate of AER could be enhanced obviously by decreasing the particle size because the effect of product layer diffusion was weakened when the particle size of AER was decreased.

  7. Viscosity of aqueous and cyanate ester suspensions containing alumina nanoparticles

    SciTech Connect

    Lawler, Katherine

    2009-01-01

    The viscosities of both aqueous and cyanate ester monomer (BECy) based suspensions of alumina nanoparticle were studied. The applications for these suspensions are different: aqueous suspensions of alumina nanoparticles are used in the production of technical ceramics made by slip casting or tape casting, and the BECy based suspensions are being developed for use in an injection-type composite repair resin. In the case of aqueous suspensions, it is advantageous to achieve a high solids content with low viscosity in order to produce a high quality product. The addition of a dispersant is useful so that higher solids content suspensions can be used with lower viscosities. For BECy suspensions, the addition of nanoparticles to the BECy resin is expected to enhance the mechanical properties of the cured composite. The addition of saccharides to aqueous suspensions leads to viscosity reduction. Through DSC measurements it was found that the saccharide molecules formed a solution with water and this resulted in lowering the melting temperature of the free water according to classic freezing point depression. Saccharides also lowered the melting temperature of the bound water, but this followed a different rule. The shear thinning and melting behaviors of the suspensions were used to develop a model based on fractal-type agglomeration. It is believed that the structure of the particle flocs in these suspensions changes with the addition of saccharides which leads to the resultant viscosity decrease. The viscosity of the BECy suspensions increased with solids content, and the viscosity increase was greater than predicted by the classical Einstein equation for dilute suspensions. Instead, the Mooney equation fits the viscosity behavior well from 0-20 vol% solids. The viscosity reduction achieved at high particle loadings by the addition of benzoic acid was also investigated by NMR. It appears that the benzoic acid interacts with the surface of the alumina particle which may

  8. Synthesis of Cubic Alpha-Alumina Using a Blocking Reagent of Tetraethyl Ammonium Hydroxide.

    PubMed

    Kim, Hyun Soo; Park, No-Kuk; Lee, Tae Jin; Kang, Misook

    2015-02-01

    This study was an attempt to obtain a stable and reproducible cubic primary alumina by a hydrothermal method using various aluminum precursors, AIP, AlO(OH), and Al(OH)3. Tetraethyl ammonium hydroxide was introduced as a blocking reagent to control the shape of alumina. The synthesized primary alumina powders from Al precursors showed a boehmite structure after hydrothermal treatment at 200 °C for 1 h. The primary alumina powders synthesized using the precursors of AIP and AlO(OH) had irregular shapes, however the cubic-shape of approximately 300 nm was observed in the primary alumina powder synthesized using Al(OH)3 precursor. The cubic primary alumina samples were transformed to different solid phases like gamma-, delta-, theta-, and alpha-phases according to the calcined temperatures. The theta-phase alumina formed at 1100 °C continually kept the cubic shape, but the shape was collapsed at 1200 °C. However the cubic alpha-alumina alpha-alumina was stably remained by thermal treatment at 1100 °C under the fierce oxygen atmosphere. PMID:26353660

  9. Near-infrared optical properties of a porous alumina ceramics produced by hydrothermal oxidation of aluminum

    NASA Astrophysics Data System (ADS)

    Lisitsyn, Aleksey V.; Dombrovsky, Leonid A.; Mendeleyev, Vladimir Ya.; Grigorenko, Anatoly V.; Vlaskin, Mikhail S.; Zhuk, Andrey Z.

    2016-07-01

    The measured spectral normal-hemispherical reflectance of an optically thick sample of porous alumina ceramics produced by hydrothermal oxidation of aluminum and subsequent high-temperature treatment of boehmite (or böhmite), AlO(OH), is used in a combination with the published data for absorption coefficient of alumina to retrieve the near-infrared optical properties of the alumina ceramics at both room and elevated temperatures. The spectral emissivity of porous alumina ceramics is also determined. An approximate model based on the Mie theory for single grains is suggested to estimate the transport scattering coefficient and the radiative conductivity of the material at high temperatures.

  10. Electromotive force measurements on cells involving beta-alumina solid electrolyte

    NASA Technical Reports Server (NTRS)

    Choudhury, N.

    1973-01-01

    Open circuit emf measurements have been made to demonstrate that a two-phase, polycrystalline mixture of beta- alumina and alpha-alumina could be used as a solid electrolyte in galvanic cells with reversible electrodes fixing oxygen or aluminum chemical potentials. These measurements indicate that such a two phase solid electrolyte can be used to monitor oxygen chemical potentials as low as that corresponding to Al, Al2O3 coexistence. The activity of Na2O in beta-alumina in coexistence with alpha-alumina was also determined by emf measurements.

  11. Method to produce alumina aerogels having porosities greater than 80 percent

    DOEpatents

    Poco, John F.; Hrubesh, Lawrence W.

    2003-09-16

    A two-step method for producing monolithic alumina aerogels having porosities of greater than 80 percent. Very strong, very low density alumina aerogel monoliths are prepared using the two-step sol-gel process. The method of preparing pure alumina aerogel modifies the prior known sol method by combining the use of substoichiometric water for hydrolysis, the use of acetic acid to control hydrolysis/condensation, and high temperature supercritical drying, all of which contribute to the formation of a polycrystalline aerogel microstructure. This structure provides exceptional mechanical properties of the alumina aerogel, as well as enhanced thermal resistance and high temperature stability.

  12. The Effect of Novel Synthetic Methods and Parameters Control on Morphology of Nano-alumina Particles.

    PubMed

    Xie, Yadian; Kocaefe, Duygu; Kocaefe, Yasar; Cheng, Johnathan; Liu, Wei

    2016-12-01

    Alumina is an inorganic material, which is widely used in ceramics, catalysts, catalyst supports, ion exchange and other fields. The micromorphology of alumina determines its application in high tech and value-added industry and its development prospects. This paper gives an overview of the liquid phase synthetic method of alumina preparation, combined with the mechanism of its action. The present work focuses on the effects of various factors such as concentration, temperature, pH, additives, reaction system and methods of calcination on the morphology of alumina during its preparation.

  13. Oxidation behavior in reaction-bonded aluminum-silicon alloy/alumina powder compacts

    SciTech Connect

    Yokota, S.H.

    1992-12-01

    Goal of this research is to determine the feasibility of producing low-shrinkage mullite/alumina composites by applying the reaction-bonded alumina (RBAO) process to an aluminum-silicon alloy/alumina system. Mirostructural and compositional changes during heat treatment were studied by removing samples from the furnace at different steps in the heating schedule and then using optical and scanning electron microscopy, EDS and XRD to characterize the powder compacts. Results suggest that the oxidation behavior of the alloy compact is different from the model proposed for the pure Al/alumina system.

  14. Electromotive force measurements on cells involving beta-alumina solid electrolyte

    NASA Technical Reports Server (NTRS)

    Choudhury, N. S.

    1973-01-01

    Open-circuit emf measurements have been made to demonstrate that a two-phase, polycrystalline mixture of beta-alumina and alpha-alumina could be used as a solid electrolyte in galvanic cells with reversible electrodes fixing oxygen or aluminum chemical potentials. These measurements indicate that such a two-phase solid electrolyte may be used to monitor oxygen chemical potentials as low as that corresponding to Al and Al2O3 coexistence (potentials of about 10 to the minus 47th power atm at 1000 K). The activity of Na2O in beta-alumina in coexistence with alpha-alumina was also determined by emf measurements.

  15. The Effect of Novel Synthetic Methods and Parameters Control on Morphology of Nano-alumina Particles.

    PubMed

    Xie, Yadian; Kocaefe, Duygu; Kocaefe, Yasar; Cheng, Johnathan; Liu, Wei

    2016-12-01

    Alumina is an inorganic material, which is widely used in ceramics, catalysts, catalyst supports, ion exchange and other fields. The micromorphology of alumina determines its application in high tech and value-added industry and its development prospects. This paper gives an overview of the liquid phase synthetic method of alumina preparation, combined with the mechanism of its action. The present work focuses on the effects of various factors such as concentration, temperature, pH, additives, reaction system and methods of calcination on the morphology of alumina during its preparation. PMID:27206644

  16. The Effect of Novel Synthetic Methods and Parameters Control on Morphology of Nano-alumina Particles

    NASA Astrophysics Data System (ADS)

    Xie, Yadian; Kocaefe, Duygu; Kocaefe, Yasar; Cheng, Johnathan; Liu, Wei

    2016-05-01

    Alumina is an inorganic material, which is widely used in ceramics, catalysts, catalyst supports, ion exchange and other fields. The micromorphology of alumina determines its application in high tech and value-added industry and its development prospects. This paper gives an overview of the liquid phase synthetic method of alumina preparation, combined with the mechanism of its action. The present work focuses on the effects of various factors such as concentration, temperature, pH, additives, reaction system and methods of calcination on the morphology of alumina during its preparation.

  17. Rational engineering of nanoporous anodic alumina optical bandpass filters

    NASA Astrophysics Data System (ADS)

    Santos, Abel; Pereira, Taj; Law, Cheryl Suwen; Losic, Dusan

    2016-08-01

    Herein, we present a rationally designed advanced nanofabrication approach aiming at producing a new type of optical bandpass filters based on nanoporous anodic alumina photonic crystals. The photonic stop band of nanoporous anodic alumina (NAA) is engineered in depth by means of a pseudo-stepwise pulse anodisation (PSPA) approach consisting of pseudo-stepwise asymmetric current density pulses. This nanofabrication method makes it possible to tune the transmission bands of NAA at specific wavelengths and bandwidths, which can be broadly modified across the UV-visible-NIR spectrum through the anodisation period (i.e. time between consecutive pulses). First, we establish the effect of the anodisation period as a means of tuning the position and width of the transmission bands of NAA across the UV-visible-NIR spectrum. To this end, a set of nanoporous anodic alumina bandpass filters (NAA-BPFs) are produced with different anodisation periods, ranging from 500 to 1200 s, and their optical properties (i.e. characteristic transmission bands and interferometric colours) are systematically assessed. Then, we demonstrate that the rational combination of stacked NAA-BPFs consisting of layers of NAA produced with different PSPA periods can be readily used to create a set of unique and highly selective optical bandpass filters with characteristic transmission bands, the position, width and number of which can be precisely engineered by this rational anodisation approach. Finally, as a proof-of-concept, we demonstrate that the superposition of stacked NAA-BPFs produced with slight modifications of the anodisation period enables the fabrication of NAA-BPFs with unprecedented broad transmission bands across the UV-visible-NIR spectrum. The results obtained from our study constitute the first comprehensive rationale towards advanced NAA-BPFs with fully controllable photonic properties. These photonic crystal structures could become a promising alternative to traditional optical

  18. Rational engineering of nanoporous anodic alumina optical bandpass filters.

    PubMed

    Santos, Abel; Pereira, Taj; Law, Cheryl Suwen; Losic, Dusan

    2016-08-01

    Herein, we present a rationally designed advanced nanofabrication approach aiming at producing a new type of optical bandpass filters based on nanoporous anodic alumina photonic crystals. The photonic stop band of nanoporous anodic alumina (NAA) is engineered in depth by means of a pseudo-stepwise pulse anodisation (PSPA) approach consisting of pseudo-stepwise asymmetric current density pulses. This nanofabrication method makes it possible to tune the transmission bands of NAA at specific wavelengths and bandwidths, which can be broadly modified across the UV-visible-NIR spectrum through the anodisation period (i.e. time between consecutive pulses). First, we establish the effect of the anodisation period as a means of tuning the position and width of the transmission bands of NAA across the UV-visible-NIR spectrum. To this end, a set of nanoporous anodic alumina bandpass filters (NAA-BPFs) are produced with different anodisation periods, ranging from 500 to 1200 s, and their optical properties (i.e. characteristic transmission bands and interferometric colours) are systematically assessed. Then, we demonstrate that the rational combination of stacked NAA-BPFs consisting of layers of NAA produced with different PSPA periods can be readily used to create a set of unique and highly selective optical bandpass filters with characteristic transmission bands, the position, width and number of which can be precisely engineered by this rational anodisation approach. Finally, as a proof-of-concept, we demonstrate that the superposition of stacked NAA-BPFs produced with slight modifications of the anodisation period enables the fabrication of NAA-BPFs with unprecedented broad transmission bands across the UV-visible-NIR spectrum. The results obtained from our study constitute the first comprehensive rationale towards advanced NAA-BPFs with fully controllable photonic properties. These photonic crystal structures could become a promising alternative to traditional optical

  19. Intermetallic strengthened alumina-forming austenitic steels for energy applications

    NASA Astrophysics Data System (ADS)

    Hu, Bin

    In order to achieve energy conversion efficiencies of >50 % for steam turbines/boilers in power generation systems, materials required are strong, corrosion-resistant at high temperatures (>700°C), and economically viable. Austenitic steels strengthened with Laves phase and Ni3Al precipitates, and alloyed with aluminum to improve oxidation resistance, are potential candidate materials for these applications. The creep resistance of these alloys is significantly improved through intermetallic strengthening (Laves-Fe 2Nb + L12-Ni3Al precipitates) without harmful effects on oxidation resistance. This research starts with microstructural and microchemical analyses of these intermetallic strengthened alumina-forming austenitic steels in a scanning electron microscope. The microchemistry of precipitates, as determined by energy-dispersive x-ray spectroscopy and transmission electron microscope, is also studied. Different thermo-mechanical treatments were carried out to these stainless steels in an attempt to further improve their mechanical properties. The microstructural and microchemical analyses were again performed after the thermo-mechanical processing. Synchrotron X-ray diffraction was used to measure the lattice parameters of these steels after different thermo-mechanical treatments. Tensile tests at both room and elevated temperatures were performed to study mechanical behaviors of this novel alloy system; the deformation mechanisms were studied by strain rate jump tests at elevated temperatures. Failure analysis and post-mortem TEM analysis were performed to study the creep failure mechanisms of these alumina-forming austenitic steels after creep tests. Experiments were carried out to study the effects of boron and carbon additions in the aged alumina-forming austenitic steels.

  20. Near-field radiative heat transfer in mesoporous alumina

    NASA Astrophysics Data System (ADS)

    Jing, Li; Yan-Hui, Feng; Xin-Xin, Zhang; Cong-Liang, Huang; Ge, Wang

    2015-01-01

    The thermal conductivity of mesoporous material has aroused the great interest of scholars due to its wide applications such as insulation, catalyst, etc. Mesoporous alumina substrate consists of uniformly distributed, unconnected cylindrical pores. Near-field radiative heat transfer cannot be ignored, when the diameters of the pores are less than the characteristic wavelength of thermal radiation. In this paper, near-field radiation across a cylindrical pore is simulated by employing the fluctuation dissipation theorem and Green function. Such factors as the diameter of the pore, and the temperature of the material are further analyzed. The research results show that the radiative heat transfer on a mesoscale is 2˜4 orders higher than on a macroscale. The heat flux and equivalent thermal conductivity of radiation across a cylindrical pore decrease exponentially with pore diameter increasing, while increase with temperature increasing. The calculated equivalent thermal conductivity of radiation is further developed to modify the thermal conductivity of the mesoporous alumina. The combined thermal conductivity of the mesoporous alumina is obtained by using porosity weighted dilute medium and compared with the measurement. The combined thermal conductivity of mesoporous silica decreases gradually with pore diameter increasing, while increases smoothly with temperature increasing, which is in good agreement with the experimental data. The larger the porosity, the more significant the near-field effect is, which cannot be ignored. Project supported by the National Natural Science Foundation of China (Grant No. 51422601), the National Basic Research Program of China (Grant No. 2012CB720404), and the National Key Technology Research and Development Program of China (Grant No. 2013BAJ01B03).

  1. Aqueous dual-tailed surfactants simulated on the alumina surface.

    PubMed

    Liu, Zhen; Yu, Jian-Guo; O'Rear, Edgar A; Striolo, Alberto

    2014-08-14

    Atomistic molecular dynamics (MD) simulations were used to compare the morphology of aqueous surfactant self-assembled aggregates on a flat alumina substrate. The substrate was modeled using the CLAYFF force field, and it was considered fully protonated. Three ionic surfactants were considered, all with a sulfate headgroup. The first surfactant was the single-tailed, widely studied sodium dodecyl sulfate (SDS), for which previous simulation results are available on several substrates. The results obtained for this surfactant were used for benchmarking the behavior of two dual-tailed surfactants. These latter surfactants have equal structure, except that in one case both linear tails are composed by seven fully protonated carbon atoms [CH3(CH2)6CHOSO3(CH2)6CH3(-), 2H7], whereas in the other, one tail is composed by seven fully protonated carbon atoms and the other tail is composed by seven fully fluorinated carbon atoms [CF3(CF2)6CHOSO3(CH2)6CH3(-), H7F7]. Our results suggest that preferential interactions lead to surfactant aggregates for H7F7 that differ compared to both those obtained for SDS and 2H7. Although molecular-level geometric structural differences can be invoked to explain differences between H7F7 and SDS aggregates, those between H7F7 and 2H7 aggregates can only be ascribed to atomic-scale interactions. Because as the adsorbed amount of surfactant increases, the self-assembled surfactant aggregates change, suggesting that the substrate on which adsorption occurs effectively evolves as adsorption progresses, compared to bare alumina. The morphological differences observed in our simulations coupled with molecular-level microphase separation might explain, in part, the unusual retrograde adsorption isotherm that has been observed experimentally for H7F7 surfactants on alumina. PMID:25089638

  2. Optical properties of porous anodic alumina embedded Cu nanocomposite films

    NASA Astrophysics Data System (ADS)

    Liu, Huiyuan; Sun, Huiyuan; Liu, Lihu; Hou, Xue; Jia, Xiaoxuan

    2015-06-01

    Porous anodic alumina embedded Cu with iridescent colors were fabricated in copper sulfate electrolyte. The films display highly saturated colors after being synthesized by an ac electrodeposition method. Tunable color in the films is obtained by adjusting anodization time, and can be adjusted across the entire visible range. Theoretical results of the changes in the structural color according to the Bragg-Snell formula are consistent with the experimental results. The films could be used in many areas including decoration, display and multifunctional anti-counterfeiting applications.

  3. Method for thermal processing alumina-enriched spinel single crystals

    DOEpatents

    Jantzen, C.M.

    1995-05-09

    A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly. 12 figs.

  4. Method for thermal processing alumina-enriched spinel single crystals

    DOEpatents

    Jantzen, Carol M.

    1995-01-01

    A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly.

  5. HIGH FREQUENCY ULTRASOUND OF ARMOR-GRADE ALUMINA CERAMICS

    SciTech Connect

    Bottiglieri, S.; Haber, R. A.

    2009-03-03

    Different lots of high density, commercial, armor-grade alumina (Al{sub 2}O{sub 3}) were tested using high frequency ultrasound in order to determine any correlation between measured properties and ballistic performance. C-scan images were taken using a 15 MHz ultrasonic transducer in order to form attenuation coefficient and elastic property maps. These samples were further characterized by using quantitative analysis. The results indicate that attenuation coefficient values appear to have the strongest correlation, of every property measured, to ballistic classifications.

  6. Specific heat capacity of molten salt-based alumina nanofluid.

    PubMed

    Lu, Ming-Chang; Huang, Chien-Hsun

    2013-06-21

    There is no consensus on the effect of nanoparticle (NP) addition on the specific heat capacity (SHC) of fluids. In addition, the predictions from the existing model have a large discrepancy from the measured SHCs in nanofluids. We show that the SHC of the molten salt-based alumina nanofluid decreases with reducing particle size and increasing particle concentration. The NP size-dependent SHC is resulted from an augmentation of the nanolayer effect as particle size reduces. A model considering the nanolayer effect which supports the experimental results was proposed.

  7. Preparation Of Strong, Dense Potassium Beta''-Alumina Ceramic

    NASA Technical Reports Server (NTRS)

    Williams, Roger M.; Jeffries-Nakamura, Barbara; Ryan, Margaret A.; O'Connor, Dennis E.; Kisor, Adam; Kikkert, Stanley J.; Losey, Robert; Suitor, Jerry W.

    1995-01-01

    Improved process for making mechanically strong, dense, phase-pure potassium beta''-alumina solid electrolyte (K-BASE) results in material superior to all previous K-BASE preparations and similar to commercial Na-BASE in strength, phase purity and high-temperature ionic conductivity. Potassium-based alkali-metal thermal-to-electric conversion (AMTEC) cells expected to operate efficiently at lower heat-input temperatures and lower rejection temperatures than sodium-based AMTEC cells, making them appropriate for somewhat different applications.

  8. Measurement of the radiative transport properties of reticulated alumina foams

    SciTech Connect

    Hale, M.J.; Bohn, M.S.

    1992-12-01

    This paper presents a method for determining radiative transport properties of reticulated materials. The method has both experimental and analytical components. A polar nephelometer is used to measure the scattering profile of a sample of the reticulated material. The results of a Monte Carlo simulation of the experiment are then combined with the experimental results to give the scatter albedo and extinction coefficient. This paper presents the results of using this method to determine the radiative transport properties of four different porosities (10, 20, 30, 65 pores per inch) of cylindrical reticulated alumina samples ranging in thickness form 0.5 inches to 2. 5 inches.

  9. Luminescent properties of alumina ceramics doped with chromium oxide

    NASA Astrophysics Data System (ADS)

    Kortov, V.; Kiryakov, A.; Pustovarov, V.

    2016-08-01

    Ceramics doped with chromium oxide were synthesized from alumina nanopowder at high heating and cooling rates. XRD analysis of the obtained samples shows that they consist mainly of Al2O3 α-phase. Photoluminescence (PL) spectra in the visible spectral region and thermoluminescence (TL) curves were measured. An effect of the dopant concentration on the intensity and shape of the PL bands as well as on the TL yield was found. Annealing of the quenching defects which emerged during the synthesis changed the PL spectra. The centers responsible for PL and TL in the synthesized ceramics were identified.

  10. Silicon carbide whisker-zirconia reinforced mullite and alumina ceramics

    DOEpatents

    Becher, Paul F.; Tiegs, Terry N.

    1987-01-01

    The flexural strength and/or fracture toughness of SiC whisker-reinforced composites utilizing mullite or alumina as the matrix material for the composite are increased by the addition of zirconia in a monoclinic or tetragonal phase to the matrix. The zirconia addition also provides for a lower hot-pressing temperature and increases the flexural strength and/or fracture toughness of the SiC whisker-reinforced composites over SiC whisker-reinforced composites of the similar matrix materials reinforced with similar concentrations of SiC whiskers.

  11. Functionally graded alumina-based thin film systems

    DOEpatents

    Moore, John J.; Zhong, Dalong

    2006-08-29

    The present invention provides coating systems that minimize thermal and residual stresses to create a fatigue- and soldering-resistant coating for aluminum die casting dies. The coating systems include at least three layers. The outer layer is an alumina- or boro-carbide-based outer layer that has superior non-wettability characteristics with molten aluminum coupled with oxidation and wear resistance. A functionally-graded intermediate layer or "interlayer" enhances the erosive wear, toughness, and corrosion resistance of the die. A thin adhesion layer of reactive metal is used between the die substrate and the interlayer to increase adhesion of the coating system to the die surface.

  12. Fractal dimension of alumina aggregates grown in two dimensions

    NASA Technical Reports Server (NTRS)

    Larosa, Judith L.; Cawley, James D.

    1992-01-01

    The concepts of fractal geometry are applied to the analysis of 0.4-micron alumina constrained to agglomerate in two dimensions. Particles were trapped at the bottom surface of a drop of a dilute suspension, and the agglomeration process was directly observed, using an inverted optical microscope. Photographs were digitized and analyzed, using three distinct approaches. The results indicate that the agglomerates are fractal, having a dimension of approximately 1.5, which agrees well with the predictions of the diffusion-limited cluster-cluster aggregation model.

  13. Interaction of hydrogen chloride with alumina. [atmospheric effluent concentrations and interaction of solid rocket propellants used in space shuttle

    NASA Technical Reports Server (NTRS)

    Bailey, R. R.; Wightman, J. P.

    1978-01-01

    The influence of temperature, pressure, and outgas conditions on the absorption of hydrogen chloride and water vapor on both alpha and gamma alumina was studied. Characterization of the adsorbents was performed using X-ray powder diffraction, scanning electron microscopy (SEM), low temperature nitrogen adsorption desorption measurements, BET nitrogen surface area measurements and electron spectroscopy for chemical analysis (ESCA). Water vapor adsorption isotherms at 30, 40, and 50 C were measured on alpha and gamma alumina after outgassing at 80, 200, and 400 C. Both outgas temperature and adsorption temperature influenced the adsorption of water vapor on the aluminas. The water vapor adsorption was completely reversible. Alpha alumina absorbed more water per unit area than gamma alumina. Differences in the adsorption capacity for water vapor of the two aluminas were explained on the basis of ideal surface models of alpha and gamma alumina. Isosteric heats of adsorption for water vapor on the aluminas were determined over a limited range of surface coverage.

  14. Design Manual: Removal of Fluoride from Drinking Water Supplies by Activated Alumina

    EPA Science Inventory

    This document is an updated version of the Design Manual: Removal of Fluoride from Drinking Water Supplies by Activated Alumina (Rubel, 1984). The manual is an in-depth presentation of the steps required to design and operate a fluoride removal plant using activated alumina (AA)...

  15. The Formation and Dissolution of Crust Upon Alumina Addition into Cryolite Electrolyte

    NASA Astrophysics Data System (ADS)

    Yang, Youjian; Gao, Bingliang; Wang, Zhaowen; Shi, Zhongning; Hu, Xianwei

    2015-09-01

    The properties of the alumina agglomerate/crust formed upon smelting grade alumina feeding and the corresponding dissolution rates in cryolite electrolyte were studied using a suspended weighing device. A series of experiments was designed to investigate the dissolution rate of the crust at various temperatures and the effects of initial alumina concentration in the electrolyte on the formation process and properties of the crust. Initial results showed that under experimental non-stirring conditions, a large proportion as high as 54-64% of the fed alumina participated in the formation of the crust upon feeding at 1233-1238 K (960-965°C). The dissolution rate of the crust decreased greatly with the increase of initial alumina concentration and the decrease of operating temperature. The mass of the crust increased significantly at high initial alumina concentrations and decreased temperature, while the alumina content of the crust showed a slight decreasing trend. Other parameters of the crust such as volume density and gas-filling fraction were also measured. The influence of physical stirring on alumina dissolution rate was also discussed.

  16. A Review of Alumina Feeding and Dissolution Factors in Aluminum Reduction Cells

    NASA Astrophysics Data System (ADS)

    Lavoie, Pascal; Taylor, Mark P.; Metson, James B.

    2016-08-01

    Modern aluminum reduction cells use point feeding technology to replenish alumina as it is consumed by the electrolytic process. The dissolution of alumina has become increasingly difficult to control as the cell sizes and electrolysis intensity have increased. The mass of alumina added per unit time is now much higher than a decade ago, and must take place within a smaller electrolyte mixing volume. In order to replenish the alumina concentration evenly, the alumina needs to be delivered, dispersed, dissolved, and distributed throughout the reduction cell. The dissolution itself follows a 4-step process that can be limited by a multitude of factors. The status of the research on each of these factors is reviewed in the present paper. Although research in laboratory cells has been conducted many times, and the impact of many factors on dissolution has been measured, published observations of alumina feeding on industrial cells are very sparse, especially regarding the dissolution dynamics in the space-time domain and the impact of the feeder hole condition. The present paper therefore presents a qualitative model of the factors governing alumina dissolution in industrial cells and offers the hypothesis that maintenance of the feeder hole condition is central to ensuring alumina dissolution and prevention of sludging.

  17. [Research on bending strength and fracture toughness of alumina-glass composite].

    PubMed

    Luo, X; Zhao, Y; Tian, J; Chao, Y; Zhang, S; Zhang, Y

    1998-12-01

    To develop a new ceramic material that can be machined and infiltrated with glass, a porous alumina blank sintered at 1350 degrees C was made of high purity, super fine alpha-alumina and then infiltrated with glass in this study. The density, bending strength and fracture toughness of the partially sintered alumina and alumina-glass composite were determined. The results indicated that the porous alumina density was 2.12 g/cm3, the three point bending strength 102 MPa, the fracture toughness 1.61 MPam1/2; that the alumina-glass composite density was 3.85 g/cm3, the three point bending strength 385 MPa, and the fracture toughness 4.05 MPam1/2. By SEM and EDXA analysis, lanthanum boroslicate glass was completely infiltrated into the 3 mm thick porous alumina blank for 6 h at 1150 degrees C. These suggest that the new developed alumina blank is suited for clinical use. PMID:10743233

  18. Effects of Variable Aspect-Ratio Inclusions on the Electrical Impedance of an Alumina Zirconia Composite at Intermediate Temperatures

    NASA Technical Reports Server (NTRS)

    Goldsby, Jon C.

    2010-01-01

    A series of alumina-yttria-stabilized zirconia composites containing either a high aspect ratio (5 and 30 mol%) hexagonal platelet alumina or an alumina low aspect ratio (5 and 30 mol%) spherical particulate was used to determine the effect of the aspect ratio on the temperature-dependent impedance of the composite material. The highest impedance across the temperature range of 373 to 1073 K is attributed to the grain boundary of the hexagonal platelet second phase in this alumina zirconia composite.

  19. Micromechanics of deformation in porous liquid phase sintered alumina under hertzian contact

    SciTech Connect

    DIGIOVANNI,ANTHONY A.; CHAN,HELEN M.; HARMER,MARTIN P.; NIED,HERMAN F.

    2000-05-15

    A series of fine-grained porous alumina samples, with and without a liquid phase, were fabricated in compositions matched closely to commercially available alumina used as a microelectronic substrates. Hertzian indentation on monolithic specimens of the glass-containing samples produced a greater quasi-ductile stress-strain response compared to that observed in the pure alumina. Maximum residual indentation depths, determined from surface profilometry, correlated with the stress-strain results. Moreover, microstructural observations from bonded interface specimens revealed significantly more damage in the form of microcracking and under extreme loading, pore collapse, in the glass-containing specimens. The absence of the typical twin faulting mechanism observed for larger-grained alumina suggests that the damage mechanism for quasi-ductility in these fine-grained porous alumina derived from the pores acting as a stress concentrator and the grain boundary glass phase providing a weak path for short crack propagation.

  20. Thermodynamic study of solid copper nickel alloys by use of copper beta-alumina

    NASA Astrophysics Data System (ADS)

    Oishi, Toshio; Tagawa, Shinya; Tanegashima, Soichiro

    2005-02-01

    Copper β″-alumina was prepared by ion exchange reactions starting with a sodium β″-alumina. Exchange from sodium ion to copper ion was done by immersing the sample in liquid cuprous chloride. Exchange of Na+ ion in β″-alumina to Cu+ ion was not complete as Na+ ion remained within the β″-alumina. Copper activity in solid copper nickel alloys was measured by electromotive force (EMF) technique incorporating the partially exchanged (Cu+ Na+) β″-alumina as a solid electrolyte for temperatures between 870 and 1300 K. The activities of copper and nickel in the solid solution at these temperatures exhibited positive deviations from Raoult's law. The activity coefficients of copper and nickel at infinite dilution at 973 K were estimated to be 5.55 and 3.71, respectively. Furthermore, the free energies, enthalpies and entropies of mixing were derived from EMF data.

  1. Final report on DSA methods for monitoring alumina in aluminum reduction cells with cermet anodes

    SciTech Connect

    Windisch, C.F. Jr.

    1992-04-01

    The Sensors Development Program was conducted at the Pacific Northwest Laboratory (PNL) for the US Department of Energy, Office of Industrial Processes. The work was performed in conjunction with the Inert Electrodes Program at PNL. The objective of the Sensors Development Program in FY 1990 through FY 1992 was to determine whether methods based on digital signal analysis (DSA) could be used to measure alumina concentration in aluminum reduction cells. Specifically, this work was performed to determine whether useful correlations exist between alumina concentration and various DSA-derived quantification parameters, calculated for current and voltage signals from laboratory and field aluminum reduction cells. If appropriate correlations could be found, then the quantification parameters might be used to monitor and, consequently, help control the alumina concentration in commercial reduction cells. The control of alumina concentration is especially important for cermet anodes, which have exhibited instability and excessive wear at alumina concentrations removed from saturation.

  2. Porous alumina scaffold produced by sol-gel combined polymeric sponge method

    NASA Astrophysics Data System (ADS)

    Hasmaliza, M.; Fazliah, M. N.; Shafinaz, R. J.

    2012-09-01

    Sol gel is a novel method used to produce high purity alumina with nanometric scale. In this study, three-dimensional porous alumina scaffold was produced using sol-gel polymeric sponge method. Briefly, sol gel alumina was prepared by evaporation and polymeric sponge cut to designated sizes were immersed in the sol gel followed by sintering at 1250 and 1550°C. In order to study the cell interaction, the porous alumina scaffold was sterilized using autoclave prior to Human Mesenchymal Stem Cells (HMSCs) seeding on the scaffold and the cell proliferation was assessed by alamarBlue® assay. SEM results showed that during the 21 day period, HMSCs were able to attach on the scaffold surface and the interconnecting pores while maintaining its proliferation. These findings suggested the potential use of the porous alumina produced as a scaffold for implantation procedure.

  3. Quantitative structure-retention relationship study of tetrazolium salts on alumina support.

    PubMed

    Cserháti, T; Kosa, A; Balogh, S

    1998-01-01

    The retention of 7 monotetrazolium and 9 ditetrazolium salts was determined on alumina and reversed-phase (RP) alumina layers using n-hexane-2-propanol and water-2-propanol mixtures as eluents. The retention capacity and the specific surface area of solutes in contact with the stationary phases were calculated. Quantitative structure-retention relationship calculations indicated that the retention capacity of solutes on RP alumina layers depended not only on the molecular hydrophobicity but also on the hydrogen-donor and acceptor properties. Specific surface areas were related to the electronic and steric parameters of the solutes. Calculations suggested that the retention on both alumina and RP alumina layers is of mixed character, hydrophobic, electronic and steric parameters are equally involved in the retention.

  4. Regeneration and recovery of spent Claus alumina catalyst

    SciTech Connect

    George, Z.M.

    1982-09-01

    Alberta, Canada recovers about seven million tons of elemental sulfur each year as a by-product of sour natural gas processing. Hydrogen sulfide is separated from the sour gas and subject to a sub-stoichiometric combustion in a reaction furnace at around 1000 degrees C, where about 60% of the sulfur present in the H/sub 2/S is recovered as sulfur. The residue, which is basically a mixture of H/sub 2/S and SO/sub 2/ in the stoichiometric ration of 2:1 together with significant quantities of water vapor and nitrogen is passed through a series of Claus adiabatic catalytic converters containing activated alumina or bauxite at around 250 degrees whereby the Claus reaction takes place: 2H/sub 2/S + SO/sub 2/ in equilibrium 2H/sub 2/O + 3/x s/sub x/ where x refers to the sulfur species at equilibrium. Employing four catalytic convertors in series, equilibrium conversions of over 98% are possible. Since the H/sub 2/S contains small quantities of heavier hydrocarbons, these undergo cracking and polymerization leading to carbon deposits on the catalyst and hence significant decrease in Claus catalytic activitiy. Presented is the results of research at the Alberta Research Council to regenerate spent Claus alumina catalysts. The process involves removal of the water soluble sulfates followed by an oxidate burn off to remove carbon and sulfur deposits. (JMT)

  5. Dynamics of Ice/Water Confined in Nanoporous Alumina.

    PubMed

    Suzuki, Yasuhito; Steinhart, Martin; Graf, Robert; Butt, Hans-Jürgen; Floudas, George

    2015-11-19

    Dielectric (DS), IR spectroscopy, and (1)H MAS NMR are employed in the study of ice/water confined in nanoporous alumina with pore diameters ranging from 400 nm down to 25 nm. Within nanoporous alumina there is a transformation from heterogeneous nucleation of hexagonal ice in the larger pores to homogeneous nucleation of cubic ice in the smaller pores. DS and IR show excellent agreement in the temperature interval and pore size dependence of the transformation. DS further revealed two dynamic processes under confinement. The "fast" and "slow" processes with an Arrhenius temperature dependence are attributed to ice and supercooled water relaxation, respectively. The main relaxation process of ice under confinement ("slow" process) has an activation energy of 44 ± 2 kJ/mol. The latter is in agreement with the reported relaxation times and activation energy of cubic ice prepared following a completely different route (by pressure). (1)H MAS NMR provided new insight in the state of ice structures as well as of supercooled water. Under confinement, a layer of liquid-like water coexists with ice structures. In addition, both ice structures under confinement appear to be more ordered than bulk hexagonal ice. Supercooled water in the smaller pores is different from bulk water. It shows a shift of the signal toward higher chemical shift values which may suggest stronger hydrogen bonding between the water molecules or increasing interactions with the AAO walls. PMID:26511073

  6. Protection of enzymes from photodegradation by entrapment within alumina.

    PubMed

    Shapovalova, Olga E; Levy, David; Avnir, David; Vinogradov, Vladimir V

    2016-10-01

    Most enzymes are highly sensitive to UV-light in all of its ranges and their activity can irreversibly drop even after a short time of exposure. Here we report a solution of this problem by using sol-gel matrices as effective protectors against this route of enzyme inactivation and denaturation. The concept presented here utilizes several modes of action: First, the entrapment within the rigid ceramic sol-gel matrix, inhibits denaturation motions, and the hydration shell around the entrapped protein provides extra protection. Second, the matrix itself - alumina in this report - absorbs UV light. And third, sol-gel materials have been shown to be quite universal in their ability to entrap small molecules, and so co-entrapment with well documented sun-screening molecules (2-hydroxybenzophenone, 2,2'-dihydroxybenzophenone, and 2,2'-dihydroxy-4-methoxybenzophenone) is an additional key protective tool. Three different enzymes as models were chosen for the experiments: carbonic anhydrase, acid phosphatase and horseradish peroxidase. All showed greatly enhanced UV (regions UV-A, UV-B, and UV-C) stabilization after entrapment within the doped sol-gel alumina matrices. PMID:27442952

  7. Strain measurements in thermally grown alumina scales using ruby fluorescence

    SciTech Connect

    Veal, B.W.; Natesan, K.; Koshelev, I.; Grimsditch, M.; Renusch, D. Hou, P.Y.

    1996-12-31

    We have measured strains in alumina scales thermally grown on Fe-Cr- Al alloys by exploiting the strain dependence of the ruby luminescence line. Measurements were done on Fe-5Cr-28Al and Fe-18Cr-10Al (at.%, bal. Fe) oxidized between 300-1300 C with periodic cycling to room temperature. Significantly different levels of strain buildup were observed in scales on these alloys. Results on similar alloys containing a dilute reactive element (Zr or Hf) are also presented. We observe that scales on alloys containing a reactive element (RE) can support higher strains than scales on RE-free alloys. With the luminescence technique, strain relief associated with spallation thresholds is readily observed. In early stage oxidation, the evolution of transition phases is monitored using Raman and fluorescence spectroscopies. The fluorescence technique also provides a sensitive probe of early stage formation of {alpha}-Al{sub 2}O{sub 3}. It appears that, in presence of Cr{sub 2}O{sub 3} or Fe{sub 2}O{sub 3}, the {alpha}-alumina phase can form at anomalously low temperatures.

  8. Joining of alumina via copper/niobium/copper interlayers

    SciTech Connect

    Marks, Robert A.; Chapman, Daniel R.; Danielson, David T.; Glaeser, Andreas M.

    2000-03-15

    Alumina has been joined at 1150 degrees C and 1400 degrees C using multilayer copper/niobium/copper interlayers. Four-point bend strengths are sensitive to processing temperature, bonding pressure, and furnace environment (ambient oxygen partial pressure). Under optimum conditions, joints with reproducibly high room temperature strengths (approximately equal 240 plus/minus 20 MPa) can be produced; most failures occur within the ceramic. Joints made with sapphire show that during bonding an initially continuous copper film undergoes a morphological instability, resulting in the formation of isolated copper-rich droplets/particles at the sapphire/interlayer interface, and extensive regions of direct bonding between sapphire and niobium. For optimized alumina bonds, bend tests at 800 degrees C-1100 degrees C indicate significant strength is retained; even at the highest test temperature, ceramic failure is observed. Post-bonding anneals at 1000 degrees C in vacuum or in gettered argon were used to assess joint stability and to probe the effect of ambient oxygen partial pressure on joint characteristics. Annealing in vacuum for up to 200 h causes no significant decrease in room temperature bend strength or change in fracture path. With increasing anneal time in a lower oxygen partial pressure environment, the fracture strength decreases only slightly, but the fracture path shifts from the ceramic to the interface.

  9. Synthesis of magnesium aluminate spinel by periclase and alumina chlorination

    SciTech Connect

    Orosco, Pablo; Barbosa, Lucía; Ruiz, María del Carmen

    2014-11-15

    Highlights: • Use of chlorination for the synthesis of magnesium aluminate spinel. • The reagents used were alumina, periclase and chlorine. • Isothermal and non-isothermal assays were performed in air and Cl{sub 2}–N{sub 2} flows. • The chlorination produced magnesium aluminate spinel at 700 °C. • Selectivity of the chlorination reaction to obtain spinel is very high. - Abstract: A pyrometallurgical route for the synthesis of magnesium aluminate spinel by thermal treatment of a mechanical mixture containing 29 wt% MgO (periclase) and 71 wt% Al{sub 2}O{sub 3} (alumina) in chlorine atmosphere was developed and the results were compared with those obtained by calcining the same mixture of oxides in air atmosphere. Isothermal and non-isothermal assays were performed in an experimental piece of equipment adapted to work in corrosive atmospheres. Both reagents and products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD) and X-ray fluorescence (XRF). Thermal treatment in Cl{sub 2} atmosphere of the MgO–Al{sub 2}O{sub 3} mixture produces magnesium aluminate spinel at 700 °C, while in air, magnesium spinel is generated at 930 °C. The synthesis reaction of magnesium aluminate spinel was complete at 800 °C.

  10. Dynamics of Ice/Water Confined in Nanoporous Alumina.

    PubMed

    Suzuki, Yasuhito; Steinhart, Martin; Graf, Robert; Butt, Hans-Jürgen; Floudas, George

    2015-11-19

    Dielectric (DS), IR spectroscopy, and (1)H MAS NMR are employed in the study of ice/water confined in nanoporous alumina with pore diameters ranging from 400 nm down to 25 nm. Within nanoporous alumina there is a transformation from heterogeneous nucleation of hexagonal ice in the larger pores to homogeneous nucleation of cubic ice in the smaller pores. DS and IR show excellent agreement in the temperature interval and pore size dependence of the transformation. DS further revealed two dynamic processes under confinement. The "fast" and "slow" processes with an Arrhenius temperature dependence are attributed to ice and supercooled water relaxation, respectively. The main relaxation process of ice under confinement ("slow" process) has an activation energy of 44 ± 2 kJ/mol. The latter is in agreement with the reported relaxation times and activation energy of cubic ice prepared following a completely different route (by pressure). (1)H MAS NMR provided new insight in the state of ice structures as well as of supercooled water. Under confinement, a layer of liquid-like water coexists with ice structures. In addition, both ice structures under confinement appear to be more ordered than bulk hexagonal ice. Supercooled water in the smaller pores is different from bulk water. It shows a shift of the signal toward higher chemical shift values which may suggest stronger hydrogen bonding between the water molecules or increasing interactions with the AAO walls.

  11. Stability of amorphous silica-alumina in hot liquid water.

    PubMed

    Hahn, Maximilian W; Copeland, John R; van Pelt, Adam H; Sievers, Carsten

    2013-12-01

    Herein, the hydrothermal stability of amorphous silica-alumina (ASA) is investigated under conditions relevant for the catalytic conversion of biomass, namely in liquid water at 200 °C. The hydrothermal stability of ASA is much higher than that of pure silica or alumina. Interestingly, the synthetic procedure used plays a major role in its resultant stability: ASA prepared by cogelation (CG) lost its microporous structure, owing to hydrolysis of the siloxane bonds, but the resulting mesoporous material still had a considerable surface area. ASA prepared by deposition precipitation (DP) contained a silicon-rich core and an aluminum-rich shell. In hot liquid water, the latter structure was transformed into a layer of amorphous boehmite, which protected the particle from further hydrolysis. The surface area showed relatively minor changes during the transformation. Independent of the synthetic method used, the ASAs retained a considerable concentration of acid sites. The concentration of acid sites qualitatively followed the changes in surface area, but the changes were less pronounced. The performance of different ASAs for the hydrolysis of cellobiose into glucose is compared. PMID:24124062

  12. Stress-rupture behavior of small diameter polycrystalline alumina fibers

    NASA Technical Reports Server (NTRS)

    Yun, Hee Mann; Goldsby, Jon C.; Dicarlo, James A.

    1993-01-01

    Continuous length polycrystalline alumina fibers are candidates as reinforcement in high temperature composite materials. Interest therefore exists in characterizing the thermomechanical behavior of these materials, obtaining possible insights into underlying mechanisms, and understanding fiber performance under long term use. Results are reported on the time-temperature dependent strength behavior of Nextel 610 and Fiber FP alumina fibers with grain sizes of 100 and 300 nm, respectively. Below 1000 C and 100 hours, Nextel 610 with the smaller grain size had a greater fast fracture and rupture strength than Fiber FP. The time exponents for stress-rupture of these fibers were found to decrease from approximately 13 at 900 C to below 3 near 1050 C, suggesting a transition from slow crack growth to creep rupture as the controlling fracture mechanism. For both fiber types, an effective activation energy of 690 kJ/mol was measured for rupture. This allowed stress-rupture predictions to be made for extended times at use temperatures below 1000 C.

  13. Protection of enzymes from photodegradation by entrapment within alumina.

    PubMed

    Shapovalova, Olga E; Levy, David; Avnir, David; Vinogradov, Vladimir V

    2016-10-01

    Most enzymes are highly sensitive to UV-light in all of its ranges and their activity can irreversibly drop even after a short time of exposure. Here we report a solution of this problem by using sol-gel matrices as effective protectors against this route of enzyme inactivation and denaturation. The concept presented here utilizes several modes of action: First, the entrapment within the rigid ceramic sol-gel matrix, inhibits denaturation motions, and the hydration shell around the entrapped protein provides extra protection. Second, the matrix itself - alumina in this report - absorbs UV light. And third, sol-gel materials have been shown to be quite universal in their ability to entrap small molecules, and so co-entrapment with well documented sun-screening molecules (2-hydroxybenzophenone, 2,2'-dihydroxybenzophenone, and 2,2'-dihydroxy-4-methoxybenzophenone) is an additional key protective tool. Three different enzymes as models were chosen for the experiments: carbonic anhydrase, acid phosphatase and horseradish peroxidase. All showed greatly enhanced UV (regions UV-A, UV-B, and UV-C) stabilization after entrapment within the doped sol-gel alumina matrices.

  14. Microwave absorption properties of carbon nanotubes dispersed in alumina ceramic

    NASA Astrophysics Data System (ADS)

    Chojnacki, E.; Huang, Q.; Mukherjee, A. K.; Holland, T. B.; Tigner, M.; Cherian, K.

    2011-12-01

    Ceramic nanocomposites of alumina and carbon nanotubes (CNTs) are experimentally studied for use as microwave absorbers in particle accelerators. The weight percentage of multi-walled CNTs in SPS sintered nanocomposite samples is varied from 0.5 to 10% and the complex permittivity is measured. The RF absorption is strong and relatively flat in the frequency band 1-40 GHz for a CNT weight percentage in the range 1-2.5%, which is just above the percolation threshold. The permittivity is observed to increase dramatically with increasing CNT weight percentage above the percolation threshold as observed elsewhere, and in accordance with theoretical treatments. The electromagnetic properties of the nanocomposites are little changed in going from 294 K to 77 K. The DC conductivity of the alumina-CNT nanocomposite is also sufficient to drain static charge in particle accelerator beamline environments, even at cryogenic temperatures. Fabrication of the nanocomposites using an industrial RF sintering process compatible with large sizes shows that the microwave absorption properties of small samples are similar to those of the SPS sintered samples.

  15. Bath for electrolytic reduction of alumina and method therefor

    DOEpatents

    Brown, Craig W.; Brooks, Richard J.; Frizzle, Patrick B.; Juric, Drago D.

    2001-07-10

    An electrolytic bath for use during the electrolytic reduction of alumina to aluminum. The bath comprises a molten electrolyte having the following ingredients: (a) AlF.sub.3 and at least one salt selected from the group consisting of NaF, KF, and LiF; and (b) about 0.004 wt. % to about 0.2 wt. %, based on total weight of the molten electrolyte, of at least one transition metal or at least one compound of the metal or both. The compound may be, for example, a fluoride, oxide, or carbonate. The metal can be nickel, iron, copper, cobalt, or molybdenum. The bath can be employed in a combination that includes a vessel for containing the bath and at least one non-consumable anode and at least one dimensionally stable cathode in the bath. Employing the bath of the present invention during electrolytic reduction of alumina to aluminum can improve the wetting of aluminum on a cathode by reducing or eliminating the formation of non-metallic deposits on the cathode.

  16. Bath for electrolytic reduction of alumina and method therefor

    DOEpatents

    Brown, Craig W.; Brooks, Richard J.; Frizzle, Patrick B.; Juric, Drago D.

    2002-11-26

    An electrolytic bath for use during the electrolytic reduction of alumina to aluminum. The bath comprises a molten electrolyte having the following ingredients: (a) AlF.sub.3 and at least one salt selected from the group consisting of NaF, KF, and LiF; and (b) about 0.004 wt. % to about 0.2 wt. %, based on total weight of the molten electrolyte, of at least one transition metal or at least one compound of the metal or both. The compound may be, for example, a fluoride, oxide, or carbonate. The metal can be nickel, iron, copper, cobalt, or molybdenum. The bath can be employed in a combination that includes a vessel for containing the bath and at least one non-consumable anode and at least one dimensionally stable cathode in the bath. Employing the bath of the present invention during electrolytic reduction of alumina to aluminum can improve the wetting of aluminum on a cathode by reducing or eliminating the formation of non-metallic deposits on the cathode. Removing sulfur from the bath can also minimize cathode deposits. Aluminum formed on the cathode can be removed directly from the cathode.

  17. Extraction and characterization of alumina nanopowders from aluminum dross by acid dissolution process

    NASA Astrophysics Data System (ADS)

    Sarker, Md. Saifur Rahman; Alam, Md. Zahangir; Qadir, Md. Rakibul; Gafur, M. A.; Moniruzzaman, Mohammad

    2015-04-01

    A significant amount of aluminum dross is available as a waste in foundry industries in Bangladesh. In this study, alumina was extracted from aluminum dross collected from two foundry industries situated in Dhamrai and Manikgang, near the capital city, Dhaka. Aluminum dross samples were found to approximately contain 75wt% Al2O3 and 12wt% SiO2. An acid dissolution process was used to recover the alumina value from the dross. The effects of various parameters, e.g., temperature, acid concentration, and leaching time, on the extraction of alumina were studied to optimize the dissolution process. First, Al(OH)3 was produced in the form of a gel. Calcination of the Al(OH)3 gel at 1000°C, 1200°C, and 1400°C for 2 h produced γ-Al2O3, (α+γ)-Al2O3, and α-alumina powder, respectively. Thermal characterization of the Al(OH)3 gel was performed by thermogravimetric/differential thermal analysis (TG/DTA) and differential scanning calorimetry (DSC). The phases and crystallite size of the alumina were determined by X-ray diffraction analysis. The dimensions of the alumina were found to be on the nano level. The chemical compositions of the aluminum dross and alumina were determined by X-ray fluorescence (XRF) spectroscopy. The microstructure and morphology of the alumina were studied with scanning electron microscopy. The purity of the alumina extracted in this study was found to be 99.0%. Thus, it is expected that the obtained alumina powders can be potentially utilized as biomaterials.

  18. Additive manufacturing of scaffolds with sub-micron filaments via melt electrospinning writing.

    PubMed

    Hochleitner, Gernot; Jüngst, Tomasz; Brown, Toby D; Hahn, Kathrin; Moseke, Claus; Jakob, Franz; Dalton, Paul D; Groll, Jürgen

    2015-06-12

    The aim of this study was to explore the lower resolution limits of an electrohydrodynamic process combined with direct writing technology of polymer melts. Termed melt electrospinning writing, filaments are deposited layer-by-layer to produce discrete three-dimensional scaffolds for in vitro research. Through optimization of the parameters (flow rate, spinneret diameter, voltage, collector distance) for poly-ϵ-caprolactone, we could direct-write coherent scaffolds with ultrafine filaments, the smallest being 817 ± 165 nm. These low diameter filaments were deposited to form box-structures with a periodicity of 100.6 ± 5.1 μm and a height of 80 μm (50 stacked filaments; 100 overlap at intersections). We also observed oriented crystalline regions within such ultrafine filaments after annealing at 55 °C. The scaffolds were printed upon NCO-sP(EO-stat-PO)-coated glass slide surfaces and withstood frequent liquid exchanges with negligible scaffold detachment for at least 10 days in vitro.

  19. Fabrication of large area gratings with sub-micron pitch using mold micromachining

    SciTech Connect

    Fleming, J.G.; Barron, C.C.; Stallard, B.; Kaushik, S.

    1997-03-01

    In this work, the authors have applied mold micromachining and standard photolithographic techniques to the fabrication of parts integrated with 0.4 micron pitch diffraction gratings. In principle, the approach should be scaleable to considerably finer pitches. They have achieved this by relying on the thickness of deposited or grown films, instead of photolithography, to determine the grating pitch. The gratings can be made to extend over large areas and the entire process is compatible with batch processing. Literally thousands of parts can be batch fabricated from a single lot of six inch wafers. In the first stage of the process they fabricate a planarized silicon dioxide pad over which the silicon nitride wave guide runs. The grating is formed by first patterning and etching single crystalline silicon to form a series of trenches with well defined pitch. The silicon bounding the trenches is then thinned by thermal oxidation followed by stripping of the silicon dioxide. The trenches are filled by a combination of polysilicon depositions and thermal oxidations. Chemical mechanical polishing (CMP) is used to polish back these structures resulting in a series of alternating 2000 {angstrom} wide lines of silicon and silicon dioxide. The thickness of the lines is determined by the oxidation time and the polysilicon deposition thickness. The silicon lines are selectively recessed by anisotropic reactive ion etching, thus forming the mold for the grating. The mold is filled with low stress silicon nitride deposited by chemical vapor deposition. A wave guide is then patterned into the silicon nitride and the mold is locally removed by a combination of deep silicon trench etching and wet KOH etching. This results in a suspended diffraction grating/membrane over the KOH generated pit.

  20. Free-Standing Organic Transistors and Circuits with Sub-Micron Thicknesses

    NASA Astrophysics Data System (ADS)

    Fukuda, Kenjiro; Sekine, Tomohito; Shiwaku, Rei; Morimoto, Takuya; Kumaki, Daisuke; Tokito, Shizuo

    2016-06-01

    The realization of wearable electronic devices with extremely thin and flexible form factors has been a major technological challenge. While substrates typically limit the thickness of thin-film electronic devices, they are usually necessary for their fabrication and functionality. Here we report on ultra-thin organic transistors and integrated circuits using device components whose substrates that have been removed. The fabricated organic circuits with total device thicknesses down to 350 nm have electrical performance levels close to those fabricated on conventional flexible substrates. Moreover, they exhibit excellent mechanical robustness, whereby their static and dynamic electrical characteristics do not change even under 50% compressive strain. Tests using systematically applied compressive strains reveal that these free-standing organic transistors possess anisotropic mechanical stability, and a strain model for a multilayer stack can be used to describe the strain in this sort of ultra-thin device. These results show the feasibility of ultimate-thin organic electronic devices using free-standing constructions.

  1. Seasonality of ultrafine and sub-micron aerosols and the inferences on particle formation processes

    NASA Astrophysics Data System (ADS)

    Cheung, H. C.; Chou, C. C.-K.; Chen, M.-J.; Huang, W.-R.; Huang, S.-H.; Tsai, C.-Y.; Lee, C. S.-L.

    2015-08-01

    The aim of this study is to investigate the seasonal variations in the physicochemical properties of atmospheric ultrafine particles (UFPs, d ≤ 100nm) and submicron particles (PM1, d ≤ 1 μm) in an East-Asian urban area, which are hypothesized to be affected by the interchange of summer and winter monsoons. An observation experiment was conducted at the TARO, an urban aerosol station in Taipei, Taiwan, from October 2012 to August 2013. The measurements included the mass concentration and chemical composition of UFPs and PM1, as well as the particle number concentration (PNC) and size distribution (PSD) with size range of 4-736 nm. The results indicate that the mass concentration of PM1 was elevated during cold seasons with peak level of 18.5 μg m-3 in spring, whereas the highest UFPs concentration was measured in summertime with a seasonal mean of 1.62 μg m-3. Moreover, chemical analysis revealed that the UFPs and PM1 were characterized by distinct composition; UFPs were composed mostly of organics, whereas ammonium and sulfate were the major constituents in PM1. The seasonal median of total PNCs ranged from 13.9 × 103 cm-3 in autumn to 19.4 × 103 cm-3 in spring. The PSD information retrieved from the corresponding PNC measurements indicates that the nucleation mode PNC (N4-25) peaked at 11.6 × 103 cm-3 in winter, whereas the Aitken mode (N25-100) and accumulation mode (N100-736) exhibited summer maxima at 6.0 × 103 and 3.1 × 103 cm-3, respectively. The shift in PSD during summertime is attributed to the enhancement in the photochemical production of condensable organic matter that, in turn, contributes to the growth of aerosol particles in the atmosphere. In addition, remarkable photochemical production of particles was observed in spring and summer seasons, which was characterized with averaged particle growth and formation rates of 4.3 ± 0.8 nm h-1 and 1.6 ± 0.8 cm-3 s-1, respectively. The prevalence of new particle formation (NPF) in summer is suggested as a result of seasonally enhanced photochemical oxidation of SO2, which contributes to the production of H2SO4, and low level of PM10 (d ≤ 10 μm) that serves as the condensation sink. Regarding the sources of aerosol particles, correlation analysis upon the PNCs against NOx revealed that the local vehicular exhaust was the dominant contributor of the UFPs throughout a year. On the contrary, the Asian pollution outbreaks can have significant influence in the PNC of accumulation mode particles during the seasons of winter monsoons. The results of this study underline the significance of secondary organic aerosols in the seasonal variations of UFPs and the influences of continental pollution outbreaks in the downwind areas of Asian outflows.

  2. Heavy ion acceleration driven by the Interaction between ultraintense Laser pulse and sub-micron foils

    NASA Astrophysics Data System (ADS)

    Yu, Jinqing; McGuffey, C.; Beg, F. N.; High Energy Density Group Team

    2015-11-01

    For ion acceleration at the intensity exceeding 1021W/cm2, Radiation Pressure Acceleration (RPA) could offer advantages over Target Normal Sheath Acceleration (TNSA) and Break-Out Afterburner (BOA). In this ultra-relativistic regime, target electrons become highly relativistic and the results are sensitive to many parameters. Especially for heavy ions acceleration, the understanding of the most important parameter effects is limited due to the lack of experiments and modeling. To further understand the key parameters and determine the most suitable regimes for efficient acceleration of heavy ions, we have carried out two-dimensional Particle-in-Cell simulations with the epoch code. In the simulations, effects of preplasma and optimal targets thicknesses for different laser pulse have been studied in detail. Based on the understanding of ion RPA, we propose some new target parameters to achieve higher ion energy. This work was performed with the support of the Air Force Office of Scientific Research under grant FA9550-14-1-0282.

  3. Optical detection of sub-micron and nanoscale particles in liquids

    NASA Astrophysics Data System (ADS)

    Pradhan, Subechhya; McGrath, Matthew; Hertel, Tobias

    2006-03-01

    We discuss a scheme for detection of submicron and nanoscale particles using light scattering in combination with lock-in filtering for increased sensitivity and signal-to-noise ratio. In this experiment, suspended submicron and nanoscale particles flow downstream a microfluidic cell until they enter the detection volume where particles are subjected to forced oscillatory motion perpendicular to the flow direction. Scattered light can then be detected in the forward direction by a position sensitive detector or in backscattering geometry using an interferometric confocal setup. The signal to noise ratio is improved over previous experiments making use of low pass filtering by lock-in amplification. We explore the potential of this technique for nanoparticle detection in liquid environment and present preliminary results on the detection of low and high index spherical particles such as polystyrene beads or colloidal gold as well as of high aspect ratio particles such as carbon nanotubes and tobacco mosaic virus.

  4. Openstage: A Low-Cost Motorized Microscope Stage with Sub-Micron Positioning Accuracy

    PubMed Central

    Campbell, Robert A. A.; Eifert, Robert W.; Turner, Glenn C.

    2014-01-01

    Recent progress in intracellular calcium sensors and other fluorophores has promoted the widespread adoption of functional optical imaging in the life sciences. Home-built multiphoton microscopes are easy to build, highly customizable, and cost effective. For many imaging applications a 3-axis motorized stage is critical, but commercially available motorization hardware (motorized translators, controller boxes, etc) are often very expensive. Furthermore, the firmware on commercial motor controllers cannot easily be altered and is not usually designed with a microscope stage in mind. Here we describe an open-source motorization solution that is simple to construct, yet far cheaper and more customizable than commercial offerings. The cost of the controller and motorization hardware are under $1000. Hardware costs are kept low by replacing linear actuators with high quality stepper motors. Electronics are assembled from commonly available hobby components, which are easy to work with. Here we describe assembly of the system and quantify the positioning accuracy of all three axes. We obtain positioning repeatability of the order of in X/Y and in Z. A hand-held control-pad allows the user to direct stage motion precisely over a wide range of speeds ( to ), rapidly store and return to different locations, and execute “jumps” of a fixed size. In addition, the system can be controlled from a PC serial port. Our “OpenStage” controller is sufficiently flexible that it could be used to drive other devices, such as micro-manipulators, with minimal modifications. PMID:24586468

  5. Sub-micron period metal lattices fabricated by interfering ultraviolet femtosecond laser processing

    NASA Astrophysics Data System (ADS)

    Nakata, Yoshiki; Matsuba, Yoshiki; Miyanaga, Noriaki

    2016-05-01

    The interference pattern of a femtosecond laser has been utilized to fabricate nanostructures in the lattice. In this paper, SH (second-harmonic) waves (λ = 392.5 {{nm}}) of a femtosecond laser were applied to four beams interfering laser processing using a demagnification system as a beam correlator. The lattice constant of the resultant matrix was shortened to 760 nm. The unit structures fabricated on gold thin films were nanoholes, nanobumps, nanodrops or nanowhiskers, and their unit size was minimized compared to the case with a greater lattice constant formed by fundamental wavelengths. The radius of a nanoball on top of a nanodrop was between 42 and 76 nm, and the radius of metallic hole arrays (MHA) was 220 nm. The energy efficiency of the laser increased by 4.79 times due to better absorption coefficient of gold at ultraviolet wavelengths. In addition, the smallest lattice constant was estimated with the use of a commercial plano-convex fused-silica lens and a NIR (near-infrared) achromatic lens.

  6. Deep sub-micron stud-via technology for superconductor VLSI circuits

    NASA Astrophysics Data System (ADS)

    Tolpygo, Sergey K.; Bolkhovsky, V.; Weir, T.; Johnson, L. M.; Oliver, W. D.; Gouker, M. A.

    2014-05-01

    A fabrication process has been developed for fully planarized Nb-based superconducting inter-layer connections (vias) with minimum size down to 250 nm for superconductor very large scale integrated (VLSI) circuits with 8 and 10 superconducting layers on 200-mm wafers. Instead of single Nb wiring layers, it utilizes Nb/Al/Nb trilayers for each wiring layer to form Nb pillars (studs) providing vertical connections between the wires etched in the bottom layer of the trilayer and the next wiring layer that is also deposited as a Nb/Al/Nb trilayer. This technology makes possible a dramatic increase in the density of superconducting digital circuits by reducing the area of interconnects with respect to presently utilized etched contact holes between superconducting layers and by enabling the use of stacked vias. Results on the fabrication and size dependence of electric properties of Nb studs with dimensions near the resolution limit of 248-nm photolithography are presented. Superconducting critical current density in the fabricated stud-vias is about 0.3 A/μm2 and approaches the depairing current density of Nb films.

  7. Deviation from threshold model in ultrafast laser ablation of graphene at sub-micron scale

    SciTech Connect

    Gil-Villalba, A.; Xie, C.; Salut, R.; Furfaro, L.; Giust, R.; Jacquot, M.; Lacourt, P. A.; Dudley, J. M.; Courvoisier, F.

    2015-08-10

    We investigate a method to measure ultrafast laser ablation threshold with respect to spot size. We use structured complex beams to generate a pattern of craters in CVD graphene with a single laser pulse. A direct comparison between beam profile and SEM characterization allows us to determine the dependence of ablation probability on spot-size, for crater diameters ranging between 700 nm and 2.5 μm. We report a drastic decrease of ablation probability when the crater diameter is below 1 μm which we interpret in terms of free-carrier diffusion.

  8. Sub-micron scale patterning of fluorescent silver nanoclusters using low-power laser

    PubMed Central

    Kunwar, Puskal; Hassinen, Jukka; Bautista, Godofredo; Ras, Robin H. A.; Toivonen, Juha

    2016-01-01

    Noble metal nanoclusters are ultrasmall nanomaterials with tunable properties and huge application potential; however, retaining their enhanced functionality is difficult as they readily lose their properties without stabilization. Here, we demonstrate a facile synthesis of highly photostable silver nanoclusters in a polymer thin film using visible light photoreduction. Furthermore, the different stages of the nanocluster formation are investigated in detail using absorption and fluorescence spectroscopy, fluorescence microscopy, and atomic force microscopy. A cost-effective fabrication of photostable micron-sized fluorescent silver nanocluster barcode is demonstrated in silver-impregnated polymer films using a low-power continuous-wave laser diode. It is shown that a laser power of as low as 0.75 mW is enough to write fluorescent structures, corresponding to the specifications of a commercially available laser pointer. The as-formed nanocluster-containing microstructures can be useful in direct labeling applications such as authenticity marking and fluorescent labeling. PMID:27045598

  9. A biological sub-micron thickness optical broadband reflector characterized using both light and microwaves

    PubMed Central

    Vukusic, P.; Kelly, R.; Hooper, I.

    2008-01-01

    Broadband optical reflectors generally function through coherent scattering from systems comprising one of three designs: overlapped; chirped; or chaotic multilayer reflectors. For each, the requirement to scatter a broad band of wavelengths is met through the presence of a variation in nanostructural periodicity running perpendicular to the systems' outer surfaces. Consequently, the requisite total thickness of the multilayer can often be in excess of 50 μm. Here, we report the discovery and the microwave-assisted characterization of a natural system that achieves excellent optical broadband reflectivity but that is less than 1 μm thick. This system, found on the wing scales of the butterfly Argyrophorus argenteus, comprises a distinctive variation in periodicity that runs parallel to the reflecting surface, rather than perpendicular to it. In this way, the requirement for an extensively thick system is removed. PMID:19042180

  10. Free-Standing Organic Transistors and Circuits with Sub-Micron Thicknesses

    PubMed Central

    Fukuda, Kenjiro; Sekine, Tomohito; Shiwaku, Rei; Morimoto, Takuya; Kumaki, Daisuke; Tokito, Shizuo

    2016-01-01

    The realization of wearable electronic devices with extremely thin and flexible form factors has been a major technological challenge. While substrates typically limit the thickness of thin-film electronic devices, they are usually necessary for their fabrication and functionality. Here we report on ultra-thin organic transistors and integrated circuits using device components whose substrates that have been removed. The fabricated organic circuits with total device thicknesses down to 350 nm have electrical performance levels close to those fabricated on conventional flexible substrates. Moreover, they exhibit excellent mechanical robustness, whereby their static and dynamic electrical characteristics do not change even under 50% compressive strain. Tests using systematically applied compressive strains reveal that these free-standing organic transistors possess anisotropic mechanical stability, and a strain model for a multilayer stack can be used to describe the strain in this sort of ultra-thin device. These results show the feasibility of ultimate-thin organic electronic devices using free-standing constructions. PMID:27278828

  11. Assembly of spherical, sub-micron Stober silica spheres into hexagonal arrays in ethoxylated trimethylolpropane triacrylate

    NASA Astrophysics Data System (ADS)

    Brubaker, Gill

    This dissertation will examine and explain the hexagonal ordering of spin coated Stober silica particles in ethoxylated trimethylolpropane triacrylate (ETPTA) monomer. It will document the fact that these arrays are formed primarily by settling and self ordering to minimize their gravitational energy, constrained by monomer mediated interparticle repulsion. It will use the fact that these arrays partially self assemble to explain the ordering produced by spin coating of the Stober silica-triacrylate suspensions. The final ordering produces vertically compact, horizontally non-close packed, simple hexagonal arrays of silica particles, in a polymer produced by ultraviolet light initiated, free radical polymerization of the ETPTA triacrylate monomer.

  12. Detection of Sub-Micron Radiation from the Surface of Venus by Cassini/VIMS

    USGS Publications Warehouse

    Baines, K.H.; Bellucci, G.; Bibring, J.-P.; Brown, R.H.; Buratti, B.J.; Bussoletti, E.; Capaccioni, F.; Cerroni, P.; Clark, R.N.; Coradini, A.; Cruikshank, D.P.; Drossart, P.; Formisano, V.; Jaumann, R.; Langevin, Y.; Matson, D.L.; McCord, T.B.; Mennella, V.; Nelson, R.M.; Nicholson, P.D.; Sicardy, B.; Sotin, C.; Hansen, G.B.; Aiello, J.J.; Amici, S.

    2000-01-01

    We report the first detection and profile characterization of thermal emission from the surface of Venus at 0.85 and 0.90 ??m, observed in the first planetary spectrum acquired by the Visual-Infrared Mapping Spectrometer onboard the Cassini spacecraft en route to the Saturn system. The strength and shape of these two newly observed nightside emissions agree with theoretical predictions based on the strength of the strong emission observed at 1.01 ??m. These emissions, together with previously-reported surface emission features at 1.01, 1.10, and 1.18 ??m, potentially provide a new technique for remotely mapping the mineralogical composition of the venusian surface. ?? 2000 Academic Press.

  13. Characterization and source identification of sub-micron particles at the HKUST Supersite in Hong Kong.

    PubMed

    Cheung, K; Ling, Z H; Wang, D W; Wang, Y; Guo, H; Lee, B; Li, Y J; Chan, C K

    2015-09-15

    Particle size distribution measurements were conducted continuously at a 30-second interval using the Fast Mobility Particle Sizer (FMPS) in August, September, November and December of 2011 at a coastal background site in Hong Kong. Concurrent measurements of CO, NOx, O3, SO2 and volatile organic compounds (VOCs) were used to determine the causes of high particle number concentration (PNC) events. In all sampling months, PNC were usually higher in the evening, likely resulting from the arrival of upwind air pollutants as wind direction changed in the late afternoon. On the more polluted days, the PNC were usually higher around noon, particularly in August, similar to the diurnal trend of O3. The mode diameter at noon was smaller than in other time periods in all sampling months, further highlighting the role of secondary formation at this urban background site. A prolonged period of pollution episode occurred in late August. High PNC resulted from the arrival of pollution laden air from the PRD region or super regions. In December, new particle formation followed by subsequent growth accounted for most of the polluted days. Overall, meteorology was the most important parameter affecting particle concentrations and formation at this Hong Kong background site.

  14. Sub-micron scale patterning of fluorescent silver nanoclusters using low-power laser

    NASA Astrophysics Data System (ADS)

    Kunwar, Puskal; Hassinen, Jukka; Bautista, Godofredo; Ras, Robin H. A.; Toivonen, Juha

    2016-04-01

    Noble metal nanoclusters are ultrasmall nanomaterials with tunable properties and huge application potential; however, retaining their enhanced functionality is difficult as they readily lose their properties without stabilization. Here, we demonstrate a facile synthesis of highly photostable silver nanoclusters in a polymer thin film using visible light photoreduction. Furthermore, the different stages of the nanocluster formation are investigated in detail using absorption and fluorescence spectroscopy, fluorescence microscopy, and atomic force microscopy. A cost-effective fabrication of photostable micron-sized fluorescent silver nanocluster barcode is demonstrated in silver-impregnated polymer films using a low-power continuous-wave laser diode. It is shown that a laser power of as low as 0.75 mW is enough to write fluorescent structures, corresponding to the specifications of a commercially available laser pointer. The as-formed nanocluster-containing microstructures can be useful in direct labeling applications such as authenticity marking and fluorescent labeling.

  15. Sub-micron lateral topography affects endothelial migration by modulation of focal adhesion dynamics.

    PubMed

    Antonini, S; Meucci, S; Jacchetti, E; Klingauf, M; Beltram, F; Poulikakos, D; Cecchini, M; Ferrari, A

    2015-06-24

    Through the interaction with topographical features, endothelial cells tune their ability to populate target substrates, both in vivo and in vitro. Basal textures interfere with the establishment and maturation of focal adhesions (FAs) thus inducing specific cell-polarization patterns and regulating a plethora of cell activities that govern the overall endothelial function. In this study, we analyze the effect of topographical features on FAs in primary human endothelial cells. Reported data demonstrate a functional link between FA dynamics and cell polarization and spreading on structured substrates presenting variable lateral feature size. Our results reveal that gratings with 2 µm lateral periodicity maximize contact guidance. The effect is linked to the dynamical state of FAs. We argue that these results are readily applicable to the rational design of active surfaces at the interface with the blood stream.

  16. Sub-micron solid air tracers for quantum vortices and liquid helium flows

    NASA Astrophysics Data System (ADS)

    Fonda, Enrico; Sreenivasan, Katepalli R.; Lathrop, Daniel P.

    2016-02-01

    The dynamics of quantized vortices in superfluids has received increased attention recently because of novel techniques developed to visualize them directly. One of these techniques [G. P. Bewley et al., Nature 441, 588 (2006)] visualized quantized vortices and their reconnections in superfluid flows of 4He by using solid hydrogen tracers of micron-size or larger. The present work improves upon the previous technique by using substantially smaller particles created by injecting atmospheric air diluted in helium gas. These smaller particles are detectable thanks to the higher index of refraction of nitrogen compared to hydrogen and thanks to an improved visualization setup. The optical counting estimate, which agrees with terminal velocity estimates, suggests that the tracer diameter is typically 400 ± 200 nm and could be as small as 200 nm; being smaller, but not so small as to be influenced by thermal motion, the particles get trapped on the vortices faster, perturb the vortices less, possess smaller Stokes drag, and stay trapped on fast-moving vortices, as also on vortices generated closer to the superfluid transition temperature. Unlike the past, the ability to create particles in the superfluid state directly (instead of creating them above the λ-point and cooling the fluid subsequently), ensures greater temperature stability for longer periods, and enables the tracking of long and isolated vortices. These advantages have also led to the direct visualization of Kelvin waves. The use of other seed gases could lead to the visualization of even smaller tracers for quantized vortices. We discuss the visualization setup and provide suggestions for further improvement.

  17. Suspension Plasma Spraying of Sub-micron Silicon Carbide Composite Coatings

    NASA Astrophysics Data System (ADS)

    Mubarok, F.; Espallargas, N.

    2015-06-01

    Thermal spraying of silicon carbide (SiC) material is a challenging task since SiC tends to decompose during atmospheric spraying process. The addition of metal or ceramic binders is necessary to facilitate the bonding of SiC particles, allowing SiC composite coating to be deposited. In the conventional procedures, the binders are added through mechanical mixing of powder constituents, making it difficult to achieve homogeneous distribution. In the new procedure proposed in this work, the binder is delivered as a nano-film of the surface of the individual SiC particles through co-precipitation treatment. Suspension plasma spray (SPS) coating technique has been used with the aim at avoiding the decomposition of SiC typically expected with atmospheric techniques, such as atmospheric plasma spray. The deposited SiC coatings by SPS showed identical SiC phase peak as identified in the suspension feedstock, indicating that the nano-film binder was able to protect SiC particles from decomposition. Further analysis by XPS revealed that SiC particles underwent some minor oxidation. Unfortunately, all the SiC coatings exhibited poor mechanical performance due to low cohesive strength, high porosity, and powdery structure making the coatings vulnerable to grain pull-out. This was due to the absence of sintering process during the spraying process contributing to the low performance of SiC SPS coatings.

  18. Characterization and source identification of sub-micron particles at the HKUST Supersite in Hong Kong.

    PubMed

    Cheung, K; Ling, Z H; Wang, D W; Wang, Y; Guo, H; Lee, B; Li, Y J; Chan, C K

    2015-09-15

    Particle size distribution measurements were conducted continuously at a 30-second interval using the Fast Mobility Particle Sizer (FMPS) in August, September, November and December of 2011 at a coastal background site in Hong Kong. Concurrent measurements of CO, NOx, O3, SO2 and volatile organic compounds (VOCs) were used to determine the causes of high particle number concentration (PNC) events. In all sampling months, PNC were usually higher in the evening, likely resulting from the arrival of upwind air pollutants as wind direction changed in the late afternoon. On the more polluted days, the PNC were usually higher around noon, particularly in August, similar to the diurnal trend of O3. The mode diameter at noon was smaller than in other time periods in all sampling months, further highlighting the role of secondary formation at this urban background site. A prolonged period of pollution episode occurred in late August. High PNC resulted from the arrival of pollution laden air from the PRD region or super regions. In December, new particle formation followed by subsequent growth accounted for most of the polluted days. Overall, meteorology was the most important parameter affecting particle concentrations and formation at this Hong Kong background site. PMID:25965042

  19. Sub-micron scale patterning of fluorescent silver nanoclusters using low-power laser.

    PubMed

    Kunwar, Puskal; Hassinen, Jukka; Bautista, Godofredo; Ras, Robin H A; Toivonen, Juha

    2016-01-01

    Noble metal nanoclusters are ultrasmall nanomaterials with tunable properties and huge application potential; however, retaining their enhanced functionality is difficult as they readily lose their properties without stabilization. Here, we demonstrate a facile synthesis of highly photostable silver nanoclusters in a polymer thin film using visible light photoreduction. Furthermore, the different stages of the nanocluster formation are investigated in detail using absorption and fluorescence spectroscopy, fluorescence microscopy, and atomic force microscopy. A cost-effective fabrication of photostable micron-sized fluorescent silver nanocluster barcode is demonstrated in silver-impregnated polymer films using a low-power continuous-wave laser diode. It is shown that a laser power of as low as 0.75 mW is enough to write fluorescent structures, corresponding to the specifications of a commercially available laser pointer. The as-formed nanocluster-containing microstructures can be useful in direct labeling applications such as authenticity marking and fluorescent labeling. PMID:27045598

  20. Nanoparticulate, sub-micron and micron sized particles emanating from hydrothermal vents

    NASA Astrophysics Data System (ADS)

    Luther, G. W., III; Gartman, A.; Findlay, A.; Yucel, M.; Chan, C. S. Y.

    2015-12-01

    Recent data from Geotraces cruises over the MAR and SEPR indicate dissolved and particulate Fe enrichment in waters 1000 and 4000 km from their vent sources, respectively. Deep-sea hydrothermal vents and the waters in the reactive mixing zone above vent orifices have been suggested to be an important source of fine material that can pass through normal filters (0.2 and 0.4 μm). In this work, nanoparticles are defined operationally as that which can pass through a 0.2 μm filter. We investigated two vent sites (Lau Basin and the MAR). Chimneys from both vent sites have fluids that can be sulfide rich or metal rich. We also present chemical and physical chemical data (SEM-EDS, TEM, XRD, EELS) showing some of the materials found in these (nano)particulate phases including pyrite, metal sulfides, silicate and aluminosilicate material. Enrichment of Mg and K in the latter suggest that reverse weathering may occur in the waters within 1-2 meters of the vent orifice where vent waters mix with cold oxygenated bottom waters.

  1. Deep sub-micron stud-via technology of superconductor VLSI circuits

    NASA Astrophysics Data System (ADS)

    Tolpygo, Sergey K.; Bolkhovsky, V.; Weir, T.; Johnson, L. M.; Oliver, W. D.; Gouker, M. A.

    2014-02-01

    A fabrication process has been developed for fully planarized Nb-based superconducting interlayer connections (vias) with minimum size down to 250 nm for superconductor very large scale integrated (VLSI) circuits with 8 and 10 superconducting layers on 200-mm wafers. Instead of etched contact holes in the interlayer dielectric it employs etched and planarized Nb pillars (studs) as connectors between adjacent wiring layers. Detailed results are presented for one version of the process that utilizes Nb/Al/Nb trilayers for each wiring layer instead of single Nb wiring layers. Nb studs are etched in the top layer of the trilayer to provide vertical connections between the wires etched in the bottom layer of the trilayer and the next wiring layer that is also deposited as a Nb/Al/Nb trilayer. This technology makes possible a dramatic increase in the density of superconducting digital circuits by reducing the area of interconnects with respect to presently utilized etched contact holes between superconducting layers and by enabling the use of stacked vias. Results on the fabrication and size dependence of electric properties of Nb studs with dimensions near the resolution limit of 248-nm photolithography are presented in the normal and superconducting states. Superconducting critical current density in the fabricated stud-vias is about 0.3 A μm-2 and approaches the depairing current density of Nb films.

  2. Characterization and recovery of Deep Sub Micron (DSM) technologies behavior under radiation

    NASA Technical Reports Server (NTRS)

    Stoica, Adrian; Wang, Xiao

    2005-01-01

    This paper serves a twofold purpose: characterize the behavior of a reconfigurable chip exposed to radiation; and demonstrate a method for functionality recovery due to Total Ionizing Dose (TID) effects. The experiments are performed using a PL developed reconfigurable device, a Field Programmable Transistor Array (FPTA). The paper initially describes experiments on the characterization of the NMOS transistor behavior for TID values up to 300krad. The behavior of analog and digital circuits downloaded onto the FPTA chip is also assessed for TID effects. This paper also presents a novel approach for circuit functionality recovery due to radiation effects based on Evolvable Hardware. The key idea is to reconfigure a programmable device, in-situ, to compensate, or bypass its degraded or damaged components. Experiments with total radiation dose up to 300kRad show that while the functionality of a variety of circuits, including digital gates, a rectifier and a Digital to Analog Converter implemented on a FPTA-2 chip is degraded/lost at levels before 200kRad, the correct functionality can be recovered through the proposed evolutionary approach and the chips are able to survive higher radiation, for several functions in excess of total radiation dose of 250kRad.

  3. MSTAR: an absolute metrology sensor with sub-micron accuracy for space-based applications

    NASA Technical Reports Server (NTRS)

    Peters, Robert D.; Lay, Oliver P.; Dubovitsky, Serge; Burger, Johan P.; Jeganathan, Muthu

    2004-01-01

    The MSTAR sensor is a new system for measuring absolute distance, capable of resolving the integer cycle ambiguity of standard interferometers, and making it possible to measure distance with subnanometer accuracy.

  4. InAlAs/InGaAs/InP sub-micron HEMTs grown by CBE

    NASA Astrophysics Data System (ADS)

    Munns, G. O.; Sherwin, M. E.; Brock, T.; Haddad, G. I.; Kwon, Y.; Ng, G. I.; Pavlidis, D.

    1992-05-01

    The paper describes the growth of InGaAs/InAlAs and InP/InAlAs high-electron-mobility transistors (HEMTs), using InAlAs grown by chemical beam epitaxy (CBE) with trimethyl amine alane (TMAA). The InAlAs bulk layers showed background carrier concentrations of 2 x 10 exp 14/cu cm, with 15 K photoluminescence FWHM of only 18.5 meV. Planar doped InAlAs/InGaAS HEMTs grown by CBE showed f(t) values of 150 GHz and f(max) values of 160 GHz.

  5. The deformation of gum metal under nanoindentation and sub-micron pillar compression

    NASA Astrophysics Data System (ADS)

    Withey, Elizabeth Ann

    Reaching ideal strength has proven to be difficult in most materials. Dislocation slip, phase transformations, twinning, and fracture all tend to occur at stresses well below the ideal strength of a material. Only on very small scales has it been possible to approach ideal strength. Thus, it was of great interest when a set of beta-Ti alloys, Gum Metal, were found to have a bulk yield strength close to half of its ideal strength. However, some recent studies have questioned the reliability of this claim. Several studies have suggested Gum Metal deforms by dislocation slip. Others have suggested the possibility of transformation-induced plasticity. The present study was undertaken in order to help clarify if and how Gum Metal can reach ideal strength. Two different experiments, ex situ nanoindentation and quantitative in situ nanopillar compression in a transmission electron microscope to correlate real-time deformation behavior, were performed on a single composition of Gum Metal, Ti-23Nb-0.7Ta-2Zr-1.20 at. %, obtained from Toyota Central R&D Laboratories. Nanoindented specimens were thinned from the bottom surface until the pits of multiple indentations became electron-transparent allowing for qualitative analysis of the deformation microstructure in both fully cold-worked and solution-treated specimens. Real-time load-displacement behavior from the nanopillar compression tests was correlated with real-time video recorded during each compression to determine both the compressive strength of each pillar and the timing and strengths of different deformation behaviors observed. Combining the results from both experiments provided several important conclusions. First, Gum Metal approaches and can attain ideal strength in nanopillars regardless of processing condition. While dislocations exist in Gum Metal, they can be tightly pinned by obstacles with spacing less than ˜20 nm, which should inhibit their motion at strengths below the ideal shear strength. The plastic deformation of Gum Metal is not controlled by giant faults or by stress-induced phase transformations. Both of these phenomena, while active, are not the source of plasticity in Gum Metal.

  6. Sub micron area Nb/AlO(x)/Nb tunnel junctions for submillimeter mixer applications

    NASA Technical Reports Server (NTRS)

    Leduc, Henry G.; Bumble, B.; Cypher, S. R.; Judas, A. J.; Stern, J. A.

    1992-01-01

    In this paper, we report on a fabrication process developed for submicron area tunnel junctions. We have fabricated Nb/AlO(x)/Nb tunnel junctions with areas down to 0.1 sq micron using these techniques. The devices have shown excellent performance in receiver systems up to 500 GHz and are currently in use in radio astronomy observatories at 115, 230, and 500 GHz.

  7. Mechanoresponsive system based on sub-micron chitosan-functionalized ferromagnetic disks.

    SciTech Connect

    Kim, D-H.; Karavayev, P.; Rozhkova, E. A.; Pearson, J.; Yefremenko, V.; Bader, S. D.; Novosad, V.

    2011-01-01

    We report a doxorubicin loaded chitosan biopolymer-ferromagnetic disks hybrid system capable of on-demand magnetomechanically induced release of drug molecules. Gold covered ferromagnetic disks were encapsulated into the polymer scaffold through the assembly of the thiolated chitosan on the disk's gold surface followed by entrapping of the doxorubicin drug within a cross-linked polymer matrix. We demonstrate that the release process can be effectively tuned and controlled by varying the magnetic field characteristics: orientation, amplitude, frequency and duration.

  8. Aqueous processing of alumina and phase behavior of polymeric additives

    NASA Astrophysics Data System (ADS)

    Sundlof, Brian Richard

    Microstructures observed when dextran sulfate and PEG were added to an aqueous alumina suspension resulted from polymeric phase separation. A suspension can be processed outside the phase separating region, followed by induced phase separation via changes in suspension pH, electrolyte level, and temperature. The processing method can be used to control pore size, shape and connectivity. The dispersion of aqueous suspensions of two alpha-aluminas was investigated. APA-0.5 was of high purity, and A-16 S.G. had MgO added as a sintering aid and contained other impurities (e.g., Na2O). The rheology of the alumina suspensions was manipulated via electrostatic (HCl H2SO 4, NaOH, and NH4OH) and electrosteric stabilization (Na- and NH4-PMAA, Na- and NH4-PAA, citric acid neutralized to a pH of ˜9.0, sodium silicate, sodium hexa-metaphosphate, and sodium carbonate). Rheological phenomena correlated with zeta-potential measurements, the dissociation behavior of the polyelectrolytes, and powder surface chemistry. A method was developed to measure the critical coagulation concentration (CCC) of stabilized suspensions. A critical double layer thickness ( d = ˜0.96 run) was calculated as a function of the electrolyte concentration and valence of the counter-ion, using a capacitance model. CCC estimations using the critical d value agreed with experimental observations. Microstructure development was dependent upon the disperant used during processing. Bulk density, and linear shrinkage measurements were used to evaluate the densification process of pellets slip cast then fired to 1000°C, 1200°C, 1400°C, or 1600°C. SEM micrographs of pellets fired to 1400°C, polished, then thermally etched, display variations in morphology and grain size. The presence of sodium resulted in abnormal grain growth, organics inhibited grain growth, and the inorganic dispersants severely inhibited grain growth. Polymeric interactions were observed using microscopy and light scattering in aqueous

  9. Contact fatigue response of porcelain-veneered alumina model systems.

    PubMed

    Stappert, Christian F J; Baldassarri, Marta; Zhang, Yu; Stappert, Dina; Thompson, Van P

    2012-02-01

    Fatigue damage modes and reliability of hand-veneered (HV) and over-pressed (OP) aluminum-oxide layer structures were compared. Influence of luting cement thickness on mechanical performance was investigated. Sixty-four aluminum-oxide plates (10 × 10 × 0.5 mm) were veneered with hand built-up or pressed porcelain (0.7 mm) and adhesively luted (50- or 150-μm cement thickness) to water-aged composite resin blocks (12 × 12 × 4 mm). Single-load-to-failure and fatigue tests were performed with a spherical tungsten carbide indenter (d = 6.25 mm) applied in the center of the veneer layer. Specimens were inspected with polarized-reflected-light and scanning electron microscopy. Use-level probability Weibull curves were plotted with two-sided 90% confidence bounds, and reliability at 75,000 cycles and 250 N load was calculated. For all specimens but two OP with 50-μm cement thickness, failure was characterized by flexural radial cracks initiating at the bottom surface of the alumina core and propagating into the veneering porcelain before cone cracks could extend to the porcelain/alumina interface. HV specimens showed higher reliability compared to OP. Those with 50-μm cement thickness were more reliable relative to their 150-μm counterparts (HV_50 μm: 95% (0.99/0.67); HV_150 μm: 55% (0.92/0.01); OP_50 μm: 69% (0.84/0.48); OP_150 μm: 15% (0.53/0.004)). Similar failure modes were observed in HV and OP specimens. Radial cracks developing in the core and spreading into the veneer are suggested to cause bulk fracture, which is the characteristic failure mode for alumina core crowns. However, the highest resistance to fatigue loading was found for the HV specimens with thin cement thickness, while the lowest occurred for the OP with thick cement layer.

  10. Morphology-controlled electrochemical sensing amaranth at nanomolar levels using alumina.

    PubMed

    Zhang, Yuanyuan; Gan, Tian; Wan, Chidan; Wu, Kangbing

    2013-02-18

    Different-shaped aluminas were readily prepared via hydrothermal reaction. It was found that the morphology and the electrochemical sensing properties of alumina were heavily dependent on the reaction time. When extending the reaction time from 6 h to 24 h, the obtained alumina samples changed from amorphous bumps to regular microfibers in diameter of 200 nm, as confirmed by scanning electron microscopy. Transmission electron microscopy observation revealed that longer reaction time was beneficial for the formation of porous and uniform fiber-like structures. Electrochemical tests proved that alumina microfibers were more active for the oxidation of amaranth and exhibited much higher enhancement effect, compared with alumina bumps. On the surface of alumina microfibers, the oxidation peak currents of amaranth increased remarkably. The influences of pH value, amount of alumina microfibers, and accumulation time on the signal enhancement of amaranth were discussed. As a result, a novel electrochemical method was developed for the detection of amaranth. The linear range was from 1 to 150 nM, and the detection limit was 0.75 nM after 1-min accumulation. The analytical application in drink samples was investigated, and the results consisted with the values that obtained by high-performance liquid chromatography.

  11. Infrared radiative properties of alumina up to the melting point: A first-principles study

    NASA Astrophysics Data System (ADS)

    Yang, J. Y.; Xu, M.; Liu, L. H.

    2016-11-01

    The high thermal emission of alumina dominates the radiative heat transfer of rocket exhaust plume. Yet numerous experimental measurements on radiative properties of alumina at high temperatures vary considerably from each other and cannot provide physical insight into the underlying mechanism. In this work, the ab initio molecular dynamics (AIMD) method and ab initio parameterized Drude model are combined to predict the radiative properties of alumina for temperatures up to 2327 K (the melting point) in the spectral range 1-12 μm. Contributed by different microscopic processes, the optical absorption of alumina in the spectral range 1-4 and 4-12 μm is described by two distinct methods. In the spectral range 4-12 μm, the multi-phonon process mainly contributes to optical absorption and can be simulated by the AIMD method based on the linear response theory. While in the spectral range 1-4 μm, the optical absorption is mainly caused by intrinsic carriers and can be effectively described by the ab initio parameterized Drude model. The first-principles calculations can successfully predict the infrared radiative properties of alumina at high temperatures and well reproduce the literature experiments. Moreover, the theoretical simulations verify that alumina can retain its semiconducting character even in the liquid phase and there emerges sharp increase in the near-infrared optical absorption of alumina upon melting.

  12. Strength, Fracture Toughness, and Slow Crack Growth of Zirconia/alumina Composites at Elevated Temperature

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Bansal, Narottam P.

    2003-01-01

    Various electrolyte materials for solid oxide fuel cells were fabricated by hot pressing 10 mol% yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina particulates and platelets each containing 0 to 30 mol% alumina. Flexure strength and fracture toughness of platelet composites were determined as a function of alumina content at 1000 C in air and compared with those of particulate composites determined previously. In general, elevated-temperature strength and fracture toughness of both composite systems increased with increasing alumina content. For a given alumina content, flexure strength of particulate composites was greater than that of platelet composites at higher alumina contents (greater than or equal to 20 mol%), whereas, fracture toughness was greater in platelet composites than in particulate composites, regardless of alumina content. The results of slow crack growth (SCG) testing, determined at 1000 C via dynamic fatigue testing for three different composites including 0 mol% (10-YSZ matrix), 30 mol % particulate and 30 mol% platelet composites, showed that susceptibility to SCG was greatest with SCG parameter n = 6 to 8 for both 0 and 30 mol% particulate composites and was least with n = 33 for the 30 mol% platelet composite.

  13. Preparation and electrochemical performance of sulfur-alumina cathode material for lithium-sulfur batteries

    SciTech Connect

    Dong, Kang; Wang, Shengping; Zhang, Hanyu; Wu, Jinping

    2013-06-01

    Highlights: ► Micron-sized alumina was synthesized as adsorbent for lithium-sulfur batteries. ► Sulfur-alumina material was synthesized via crystallizing nucleation. ► The Al{sub 2}O{sub 3} can provide surface area for the deposition of Li{sub 2}S and Li{sub 2}S{sub 2}. ► The discharge capacity of the battery is improved during the first several cycles. - Abstract: Nano-sized sulfur particles exhibiting good adhesion with conducting acetylene black and alumina composite materials were synthesized by means of an evaporated solvent and a concentrated crystallization method for use as the cathodes of lithium-sulfur batteries. The composites were characterized and examined by X-ray diffraction, environmental scanning electron microscopy and electrochemical methods, such as cyclic voltammetry, electrical impedance spectroscopy and charge–discharge tests. Micron-sized flaky alumina was employed as an adsorbent for the cathode material. The initial discharge capacity of the cathode with the added alumina was 1171 mAh g{sup −1}, and the remaining capacity was 585 mAh g{sup −1} after 50 cycles at 0.25 mA cm{sup −2}. Compared with bare sulfur electrodes, the electrodes containing alumina showed an obviously superior cycle performance, confirming that alumina can contribute to reducing the dissolution of polysulfides into electrolytes during the sulfur charge–discharge process.

  14. Polyethylene wear particle generation in vivo in an alumina medial pivot total knee prosthesis.

    PubMed

    Minoda, Yukihide; Kobayashi, Akio; Iwaki, Hiroyoshi; Miyaguchi, Masatsugu; Kadoya, Yoshinori; Ohashi, Hirotsugu; Takaoka, Kunio

    2005-10-01

    Polyethylene wear particle generation is one of the most important factors affecting mid- to long-term results of total knee arthroplasties. It has been reported that the medial pivot total knee prosthesis (MP) design and alumina ceramic femoral component reduce polyethylene wear. The aim of this study is to evaluate in vivo polyethylene wear particle generation in the newly introduced alumina MP, in comparison with a metal MP. Synovial fluid was obtained from 11 knees with alumina MP and 15 knees with metal MP at nine months after the operation. Polyethylene particles were isolated, and examined using scanning electron microscope and image analyzer. Total number of particles in each knee was 7.10+/-2.86x10(6) in alumina (mean+/-standard error), and 5.70+/-2.82x10(7) in metal MP (p=0.048). Particle size (equivalent circle diameter) was 0.78+/-0.04 microm in alumina, and 0.66+/-0.06 microm in metal MP (p=0.120). Particle shape (aspect ratio) was 1.52+/-0.05 in alumina, and 1.88+/-0.11 in metal MP (p=0.014). Apart from the femoral component, the material and manufacturing method of polyethylene insert differed between the two groups, although the sterilization method was the same. Alumina MP generated fewer and rounder polyethylene wear particles than metal MP in early clinical stage, and could potentially reduce prevalence of osteolysis and aseptic loosening. PMID:15893371

  15. Contribution of aluminas and aluminosilicates to the formation of PCDD/Fs on fly ashes.

    PubMed

    Potter, Phillip M; Dellinger, Barry; Lomnicki, Slawomir M

    2016-02-01

    Chlorinated aromatics undergo surface-mediated reactions with metal oxides to form Environmentally Persistent Free Radicals (EPFRs) which can further react to produce polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Previous work using laboratory-made fly ash surrogates composed of transition metal oxides deposited on silica powder has confirmed their ability to mimic fly ash in the production of PCDD/Fs. However, little is known about the propensity of aluminas and aluminosilicates, other components of fly ash, to form PCDD/Fs. A fly ash sample containing both alumina and mullite, an aluminosilicate, was tested for PCDD/F formation ability and compared to PCDD/F yields from the thermal degradation of 2-monochlorophenol (2-MCP) precursor over γ-alumina, α-alumina, and mullite. A packed-bed flow reactor was used to investigate the thermal degradation of 2-MCP over the various catalysts at 200-600 °C. Fly ash gave similar PCDD/F yields to surrogates made with similar transition metal content. γ-alumina, which is thermodynamically unfavorable, was very catalytically active and gave low PCDD/F yields despite a high destruction of 2-MCP. Mullite and α-alumina, the thermodynamically favorable form of alumina, yielded higher concentrations of dioxins and products with a higher degree of chlorine substitution than γ-alumina. The data suggest that certain aluminas and aluminosilicates, commonly found in fly ash, are active catalytic surfaces in the formation of PCDD/Fs in the post-flame cool zones of combustion systems and should be considered as additional catalytic surfaces active in the process. PMID:26615490

  16. Contribution of aluminas and aluminosilicates to the formation of PCDD/Fs on fly ashes.

    PubMed

    Potter, Phillip M; Dellinger, Barry; Lomnicki, Slawomir M

    2016-02-01

    Chlorinated aromatics undergo surface-mediated reactions with metal oxides to form Environmentally Persistent Free Radicals (EPFRs) which can further react to produce polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Previous work using laboratory-made fly ash surrogates composed of transition metal oxides deposited on silica powder has confirmed their ability to mimic fly ash in the production of PCDD/Fs. However, little is known about the propensity of aluminas and aluminosilicates, other components of fly ash, to form PCDD/Fs. A fly ash sample containing both alumina and mullite, an aluminosilicate, was tested for PCDD/F formation ability and compared to PCDD/F yields from the thermal degradation of 2-monochlorophenol (2-MCP) precursor over γ-alumina, α-alumina, and mullite. A packed-bed flow reactor was used to investigate the thermal degradation of 2-MCP over the various catalysts at 200-600 °C. Fly ash gave similar PCDD/F yields to surrogates made with similar transition metal content. γ-alumina, which is thermodynamically unfavorable, was very catalytically active and gave low PCDD/F yields despite a high destruction of 2-MCP. Mullite and α-alumina, the thermodynamically favorable form of alumina, yielded higher concentrations of dioxins and products with a higher degree of chlorine substitution than γ-alumina. The data suggest that certain aluminas and aluminosilicates, commonly found in fly ash, are active catalytic surfaces in the formation of PCDD/Fs in the post-flame cool zones of combustion systems and should be considered as additional catalytic surfaces active in the process.

  17. Semimetal nanowires and their superlattices in anodic alumina membranes.

    PubMed

    Li, Liang; Dou, Xincun; Li, Guanghai

    2010-11-01

    Semimetal Bi and Sb are important thermoelectric materials. Since theoretical calculation predicted that thermoelectric efficiency can be improved as the dimension of materials decreases, the synthesis and physical properties of Bi-based nanostructures (nanowires, nanotubes, nanobelts, nanoplates) have attracted great interests. This review begins with a survey of the patents and reports on the recent developments of Bi-based nanowires. We focus on Bi-based nanowires fabricated by pulsed electrodeposition in anodic alumina membranes, which are main achievements in our group. Based on the literatures and patents, from synthesis of Bi-based nanowires and their alloys and superlattices, to physical properties including electronic transport, thermal expansion, and thermoelectricity will be demonstrated. PMID:20632961

  18. Kinetics of Ice Nucleation Confined in Nanoporous Alumina.

    PubMed

    Suzuki, Yasuhito; Steinhart, Martin; Butt, Hans-Jürgen; Floudas, George

    2015-09-01

    The nucleation mechanism of water (heterogeneous/homogeneous) can be regulated by confinement within nanoporous alumina. The kinetics of ice nucleation is studied in confinement by employing dielectric permittivity as a probe. Both heterogeneous and homogeneous nucleation, obtained at low and high undercooling, respectively, are stochastic in nature. The temperature interval of metastability extends over ∼4 and 0.4 °C for heterogeneous and homogeneous nucleation, respectively. Nucleation within a pore is spread to all pores in the template. We have examined a possible coupling of all pores through a heat wave and a sound wave, with the latter being a more realistic scenario. In addition, dielectric spectroscopy indicates that prior to crystallization undercooled water molecules relax with an activation energy of ∼50 kJ/mol, and this process acts as precursor to ice nucleation. PMID:26241561

  19. Synthesis and Characterization of Silica Alumina Supported Heteropolyoxometallets

    NASA Astrophysics Data System (ADS)

    Dangwal, A.; Singhal, S.; Semwal, S.; Shukla, S.

    2014-04-01

    Novel acid catalysts for alkane isomerization were synthesized with silica alumina supported heteropolyoxometallets by wet incipient method. Two series of catalysts were prepared by dispersing TPA or MPA. Characterization of catalysts was done by BET and TPD methods. Objective was to find high surface and acidity catalysts and to see the effect of synthesis parameter as loading or impregnation time on catalyst physicochemical properties as surface area, pore size, pore volume and acidity of HPA based oxide Seralox-5. TPA or MPA loading affected acidity and pore volume of catalysts, however no effect of impregnation time has been revealed. Surface area of catalysts was found in the range of 154-198 m2/g and acidity 10.1-17.7 ml/g of NH3 at STP. Among all the catalysts optimum characteristic catalysts were found from both the series, selecting one from each. These two catalysts exhibit high surface area, mesopore structure and high acidity.

  20. Tailorable advanced blanket insulation using aluminoborosilicate and alumina batting

    NASA Technical Reports Server (NTRS)

    Calamito, Dominic P.

    1989-01-01

    Two types of Tailorable Advanced Blanket Insulation (TABI) flat panels for Advanced Space Transportation Systems were produced. Both types consisted of integrally woven, 3-D fluted core having parallel faces and connecting ribs of Nicalon yarns. The triangular cross section flutes of one type was filled with mandrels of processed Ultrafiber (aluminoborosilicate) stitchbonded Nextel 440 fibrous felt, and the second type wall filled with Saffil alumina fibrous felt insulation. Weaving problems were minimal. Insertion of the fragile insulation mandrels into the fabric flutes was improved by using a special insertion tool. An attempt was made to weave fluted core fabrics from Nextel 440 yarns but was unsuccessful because of the yarn's fragility. A small sample was eventually produced by an unorthodox weaving process and then filled with Saffil insulation. The procedures for setting up and weaving the fabrics and preparing and inserting insulation mandrels are discussed. Characterizations of the panels produced are also presented.

  1. Acoustic phonon spectrum and thermal transport in nanoporous alumina arrays

    SciTech Connect

    Kargar, Fariborz; Ramirez, Sylvester; Debnath, Bishwajit; Malekpour, Hoda; Lake, Roger; Balandin, Alexander A.

    2015-10-28

    We report results of a combined investigation of thermal conductivity and acoustic phonon spectra in nanoporous alumina membranes with the pore diameter decreasing from D=180 nm to 25 nm. The samples with the hexagonally arranged pores were selected to have the same porosity Ø ≈13%. The Brillouin-Mandelstam spectroscopy measurements revealed bulk-like phonon spectrum in the samples with D = 180 nm pores and spectral features, which were attributed to spatial confinement, in the samples with 25 nm and 40 nm pores. The velocity of the longitudinal acoustic phonons was reduced in the samples with smaller pores. As a result, analysis of the experimental data and calculated phonon dispersion suggests that both phonon-boundary scattering and phonon spatial confinement affect heat conduction in membranes with the feature sizes D < 40 nm.

  2. Dynamic shear behavior of alumina-filled epoxy

    SciTech Connect

    Costin, L.S.

    1982-03-01

    Thin-walled tubular specimens of alumina-filled epoxy were loaded in torsion at a strain rate of approximately 10/sup 3/ s/sup -1/ using a stored-torque Kolsky bar. In addition to measuring the time resolved shear stress and shear strain in the specimen, the axial stress generated by the dilation of the material during shear deformation was also obtained as a function of time. Tests were conducted at room temperature and at -60/sup 0/C. At room temperature, a moderate amount of plastic deformation occurred before failure. Material dilation was associated with the plastic flow. At -60/sup 0/C, there was a marked increase in failure stress over the failure stress at room temperature. However, little or no plastic deformation or dilation occurred before failure.

  3. Porosity estimation of alumina samples based on resonant backscattering spectrometry

    NASA Astrophysics Data System (ADS)

    Mokhles Gerami, F.; Kakuee, O.; Mohammadi, S.

    2016-04-01

    In this work, columnar porous alumina samples were investigated using the 16O(α,α)16O resonance scattering at 3.045 MeV. If the incident energy is slightly above the resonance energy, a resonance peak appears in the energy spectra of the backscattered ions. The position and width of this peak for non-porous samples are mainly determined by the experimental setup, whilst for porous materials, the peak position shifts towards higher energies under certain conditions. This effect can be explained by the lower amount of material which the ions encounter along the backscattered trajectories. The energy shift of the resonance peak towards higher energies was revealed experimentally and discussed theoretically. The estimated porosities of the samples based on this energy shift were compared with those evaluated from the graphical analysis of the images obtained by field emission scanning electron microscopy.

  4. Age hardening of 6061/alumina-silica fiber composite

    SciTech Connect

    Khangaonkar, P.R.; Shamsul, J.B.; Azmi, R.

    1994-12-31

    Continuous alumina-silica fiber (Altex of Sumitomo) which yields high performance composites with some aluminium alloys was tried for squeeze cast 6061 based composites with volume fractions of 0.5 and 0.32, and the matrix microhardness and resistivity changes during age hardening were studied. The matrix in the composites hardened much more than the unreinforced alloy. Microhardness increases of up to 70 VPN above the solution treated condition at various aging temperatures were observed. The resistivity variation indicated an appreciable state of internal stress which continued to persist even when hardness fell by overaging. Energy dispersive X-ray analysis indicated that the regions close to the fibers had a higher silicon content than the matrix, and amorphous silica in the fiber may have a role in the formation of an enriched layer which may help the bonding and strength in the composite.

  5. Alumina Volatility in Water Vapor at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Myers, Dwight L.

    2003-01-01

    The volatility of alumina in high temperature water vapor was determined by a weight loss technique. Sapphire coupons were exposed at temperatures between 1250 and 1500 C, water partial pressures between 0.15 and 0.68 atm in oxygen, total pressure of 1 atm, and flowing gas velocities of 4.4 cm/s. The pressure dependence of sapphire volatility was consistent with AI(OH)3(g) formation. The enthalpy of reaction to form Al(OH)3(g) from sapphire and water vapor was determined to be 210 +/- 20 kJ/mol, comparing favorably to other studies. Microstructural examination of tested sapphire coupons revealed surface etching features consistent with a volatilization process.

  6. Preparation of silica or alumina pillared crystalline titanates

    SciTech Connect

    Udomsak, S.; Nge, R.; Dufner, D.C.; Anthony, R.G.; Lott, S.E.

    1994-05-01

    Layered crystalline titanates (CT) [Anthony and Dosch, US Patent 5 177 045 (1993)] are pillared with tetraethyl orthosilicate, 3-aminopropyltrimethoxysilane, and aluminum acetylacetonate to prepare porous and high surface area supports for sulfided NiMo catalyst. Tetra-ethyl orthosilicate or aluminum acetylacetonate intercalated CT are prepared by stepwise intercalation. First, the basal distance is increased by n-alkylammonium ions prior to intercalation with inorganic compounds. However, an aqueous solution of 3-aminopropyltrimethoxysilane could directly pillar CT without first swelling the titanate with n-alkylamine. The catalytic activities for hydrogenation of pyrene of sulfided NiMo supported silica or alumina pillared CT were higher than those of commercial catalysts (Shell324 and Amocat1C). The silicon and aluminum contents of the pillared CT, used as supports, have a considerable effect on the catalytic activities and physical properties of the supports.

  7. Characterization of ultra fine alumina powder produced by wet milling

    SciTech Connect

    Hofius, H.; Hofmann, H.; Foerster, H.

    1995-09-01

    Different raw alumina powders were wet milled in a ball mill and in an attrition mill. The influence of the raw material properties as well as the milling parameters on the properties of the final product was investigated by chemical analysis, XRD, surface characterization and sintering experiments. The results show the synthesis of nanoscaled powder with a specific surface area {ge} 50 m{sup 2}/g can be achieved by wet milling. In addition domains with diameters of a few nm could be detected by XRD. The sintering temperature could be lowered from 1650{degrees}C to 1424{degrees}C. The hydration of {alpha}-Al{sub 2}O{sub 3}, will also be discussed.

  8. Pore sizes and filtration rates from two alumina slips

    SciTech Connect

    Smith, P.A. . Materials Science Dept.); Kerch, H.; Krueger, S.; Long, G.G. . Ceramics Div.); Keller, J.; Haber, R.A. . Dept. of Ceramics)

    1994-07-01

    The relationship between filtration rate and the resultant green body microstructure was examined for aqueous alumina slips cast at two different deflocculation states. The volume loading of both slips was 40%. Slip viscosities of 500 and 60 mPa[center dot]s were produced by different tetrasodium pyrophosphate additions. The filtration rate of these slips varied by a factor of 2; however, mercury porosimetry results showed the same average pore size for both samples. Single and multiple small-angle neutron scattering results showed the specimen cast with the higher-viscosity slip to possess a bimodal pore size distribution. The body cast with the low-viscosity slip showed unimodal porosity and, consequently, the filtration is attributed to the toroidal region between the packed particles. These results showed that mercury porosimetry does not provide a pore size that predicts filtration behavior of slips with different degrees of dispersion.

  9. Removal of mercury from an alumina refinery aqueous stream.

    PubMed

    Mullett, Mark; Tardio, James; Bhargava, Suresh; Dobbs, Charles

    2007-06-01

    Digestion condensate is formed as a by-product of the alumina refinery digestion process. The solution exhibits a high pH and is chemically reducing, containing many volatile species such as water, volatile organics, ammonia, and mercury. Because digestion condensate is chemically unique, an innovative approach was required to investigate mercury removal. The mercury capacity and adsorption kinetics were investigated using a number of materials including gold, silver and sulphur impregnated silica and a silver impregnated carbon. The results were compared to commercial sorbents, including extruded and powdered virgin activated carbons and a sulphur impregnated mineral. Nano-gold supported on silica (88% removal under batch conditions and 95% removal under flow conditions) and powdered activated carbon (91% under batch conditions and 98% removal under flow conditions) were the most effective materials investigated. The silver and sulphur impregnated materials were unstable in digestion condensate under the test conditions used.

  10. Sodium-Beta Alumina Batteries: Status and Challenges

    SciTech Connect

    Lu, Xiaochuan; Lemmon, John P.; Sprenkle, Vincent L.; Yang, Zhenguo

    2010-09-05

    Sodium-beta alumina batteries, have been extensively developed for a few decades and encouraging progress has been achieved so far. The anode is typically molten sodium while the cathode can be molten sulfur (Na-S battery) or solid transition metal halides plus a liquid phase secondary electrolyte (e.g., ZEBRA battery). The electrolyte typically used is a β"-Al2O3 solid membrane. The issues prohibiting broad commercialization of this type of technology are dependent on the materials used, but can be broadly described as relatively high cost, safety (particularly for the Na-S couple), and low power. This paper offers a review on materials and designs for the batteries and discusses the challenges ahead for further technology improvement.

  11. Multi-Objective Optimization for Alumina Laser Sintering Process

    NASA Astrophysics Data System (ADS)

    Fayed, E. M.; Elmesalamy, A. S.; Sobih, M.; Elshaer, Y.

    2016-09-01

    Selective laser sintering processes has become one of the most popular additive manufacturing processes due to its flexibility in creation of complex components. This process has many interacting parameters, which have a significant influence on the process output. In this work, high purity alumina is sintered through a pulsed Nd:YAG laser sintering process. The aim of this work is to understand the effect of relevant sintering process parameters (laser power and laser scanning speed) on the quality of the sintered layer (layer surface roughness, layer thickness and vector/line width, and density). Design of experiments and statistical modeling techniques are employed to optimize the process control factors and to establish a relationship between these factors and output responses. Model results have been verified through experimental work and show reasonable prediction of process responses within the limits of sintering parameters.

  12. Stress determination in thermally grown alumina scales using ruby luminescence

    SciTech Connect

    Renusch, D.; Veal, B.W.; Koshelev, I.; Natesan, K.; Grimsditch; Hou, P.Y.

    1996-06-01

    By exploiting the strain dependence of the ruby luminescence line, we have measured the strain in alumina scales thermally grown on Fe-Cr- Al alloys. Results are compared and found to be reasonably consistent with strains determined using x rays. Oxidation studies were carried out on alloys Fe - 5Cr - 28Al and Fe - 18Cr - 10Al (at.%). Significantly different levels of strain buildup were observed in scales on these alloys. Results on similar alloys containing a ``reactive element`` (Zr or Hf) in dilute quantity are also presented. Scales on alloys containing a reactive element (RE) can support significantly higher strains than scales on RE-free alloys. With the luminescence technique, strain relief associated with spallation thresholds is readily observed.

  13. Electromagnetic absorption in anisotropic photonic crystal of alumina cylinders

    NASA Astrophysics Data System (ADS)

    Carbonell, J.; Sánchez-Dehesa, J.; Arriaga, J.; Gumen, L.; Krokhin, A.

    2011-06-01

    We present a theoretical and experimental study of the effective permittivity of a photonic crystal (PC) made of parallel dielectric rods in the long-wavelength limit. Using the plane-wave expansion method we derive an analytical expression for the imaginary part of the dielectric tensor. Angular dependence of the dissipative part of permittivity turns out to be more complicated than that for the real part. In particular, it exhibits stronger anisotropy for a PC with rectangular unit cell. Theoretical and numerical results are compared to the experimental measurements of microwave reflection and transmission through a PC fabricated from low-loss alumina rods. A good agreement between the theory and experiment was obtained in the limit where the effective medium approximation is valid.

  14. Corrosion performance of alumina scales in coal gasification environments

    SciTech Connect

    Natesan, K.

    1997-02-01

    Corrosion of metallic structural materials in complex gas environments of coal gasification is a potential problem. The corrosion process is dictated by concentrations of two key constituents: sulfur as H{sub 2}S and Cl as HCl. This paper examines the corrosion performance of alumina scales that are thermally grown on Fe-base alloys during exposure to O/S mixed-gas environments. The results are compared with the performance of chromia-forming alloys in similar environments. The paper also discusses the available information on corrosion performance of alloys whose surfaces were enriched with Al by the pack-diffusion process, by the electrospark deposition process, or by weld overlay techniques.

  15. Adsorption of chromium onto activated alumina: kinetics and thermodynamics studies.

    PubMed

    Marzouk, Ikhlass; Dammak, Lassaad; Hamrouni, Béchir

    2013-02-01

    In this study, the removal of chromium (VI) by adsorption on activated alumina was investigated and the results were fitted to Langmuir, Freundlich, Dubinin-Redushkevich, and Temkin adsorption models at various temperatures. The constants of each model were evaluated depending on temperature. Thermodynamic parameters for the adsorption system were determined at 10, 25 and 40 degrees C. (deltaH degrees = -21.18 kJ x mol(-1); deltaG degrees = -8.75 to -7.43 kJ x mol(-1) and deltaS degrees = -0.043 kJ x K(-1) x mol(-1)). The obtained values showed that chromium (VI) adsorption is a spontaneous and exothermic process. The kinetic process was evaluated by first-order, second-order and Elovich kinetic models.

  16. Modeling Lewis acidity of transition aluminas by numerical simulations

    SciTech Connect

    Alvarez, L.J.; Blumenfeld, A.L.; Fripiat, J.J.

    1998-01-01

    The bulk and surface features of an alumina particle obtained by molecular-dynamics simulation are used to support the experimental distribution of aluminums with respect to their coordination number obtained by NMR (nuclear magnetic resonance). This information was obtained by using results of various editing procedures of the {sup 27}Al nuclear magnetic resonance, such as the classical one-pulse (1P) magic angle spinning, the cross polarization (CP) from the protons of chemisorbed ammonia and the 1P or CP rotational echo double resonance (REDOR). Because the REDOR technique revealed that the acid Lewis sites are constituted by pairs of four or fivefold coordinated aluminum atoms about 3 {Angstrom} apart, these pairs were counted in the simulated particle. The agreement with experimental surface density of Lewis sites is satisfactory. {copyright} {ital 1998 American Institute of Physics.}

  17. Recovering metals from red mud generated during alumina production

    NASA Astrophysics Data System (ADS)

    Piga, Luigi; Pochetti, Fausto; Stoppa, Luisa

    1993-11-01

    There is growing interest in processing and utilizing the red mud by-product of the Bayer process for alumina extraction from bauxite. This interest stems largely from the environmental impacts associated with red mud and the storage costs involved. Furthermore, complete utilization of the raw materials, in this case bauxite, meets an ecological concept while ensuring raw material conservation. To prepare this article, the authors perused approximately 100 patents and articles in order to provide a concise description of the methods of storing red mud and its uses as a flocculant or construction material and in other minor applications. Special attention has been given to the methods developed for recovering metals contained in the red mud.

  18. Acoustic phonon spectrum and thermal transport in nanoporous alumina arrays

    SciTech Connect

    Kargar, Fariborz; Ramirez, Sylvester; Debnath, Bishwajit; Malekpour, Hoda; Lake, Roger; Balandin, Alexander A.

    2015-10-28

    We report results of a combined investigation of thermal conductivity and acoustic phonon spectra in nanoporous alumina membranes with the pore diameter decreasing from D=180 nm to 25 nm. The samples with the hexagonally arranged pores were selected to have the same porosity Ø ≈13%. The Brillouin-Mandelstam spectroscopy measurements revealed bulk-like phonon spectrum in the samples with D=180-nm pores and spectral features, which were attributed to spatial confinement, in the samples with 25-nm and 40-nm pores. The velocity of the longitudinal acoustic phonons was reduced in the samples with smaller pores. As a result, analysis of the experimental data and calculated phonon dispersion suggests that both phonon-boundary scattering and phonon spatial confinement affect heat conduction in membranes with the feature sizes D<40 nm.

  19. Ferromagnetic nanotubes by atomic layer deposition in anodic alumina membranes

    NASA Astrophysics Data System (ADS)

    Daub, M.; Knez, M.; Goesele, U.; Nielsch, K.

    2007-05-01

    In this paper, two methods for the synthesis of magnetic nanotubes inside the pores of anodic alumina membranes by atomic layer deposition (ALD) are compared. The precursors were nickelocene or cobaltocene, and H2O or O3. The first method consists of a three-step ALD cycle: First, the sample is exposed to the metal-organic precursor, subsequently to water, and finally, to hydrogen. In the second method, metal oxide is deposited by a conventional two-step ALD cycle. After the ALD process, the sample is reduced under hydrogen atmosphere. The magnetic nanotubes obtained by the second method have a smaller grain size and improved magnetic properties. The magnetic nanotubes with diameters ranging from 35to60nm exhibit a preferential magnetization direction along the nanowire axis. The Ni or Co nanotubes with larger diameters (around 160nm) show a nearly isotropic magnetic behavior, with the magnetic moments arranged in a vortex state at zero field.

  20. Acoustic phonon spectrum and thermal transport in nanoporous alumina arrays

    DOE PAGES

    Kargar, Fariborz; Ramirez, Sylvester; Debnath, Bishwajit; Malekpour, Hoda; Lake, Roger; Balandin, Alexander A.

    2015-10-28

    We report results of a combined investigation of thermal conductivity and acoustic phonon spectra in nanoporous alumina membranes with the pore diameter decreasing from D=180 nm to 25 nm. The samples with the hexagonally arranged pores were selected to have the same porosity Ø ≈13%. The Brillouin-Mandelstam spectroscopy measurements revealed bulk-like phonon spectrum in the samples with D = 180 nm pores and spectral features, which were attributed to spatial confinement, in the samples with 25 nm and 40 nm pores. The velocity of the longitudinal acoustic phonons was reduced in the samples with smaller pores. As a result, analysismore » of the experimental data and calculated phonon dispersion suggests that both phonon-boundary scattering and phonon spatial confinement affect heat conduction in membranes with the feature sizes D < 40 nm.« less

  1. Damping Behavior of Alumina Epoxy Nano-Composites

    NASA Astrophysics Data System (ADS)

    Katiyar, Priyanka; Kumar, Anand

    2016-05-01

    Polymer nano composites, consisting of a polymer matrix with nanoparticle filler, have been predicted to be one of the most beneficial applications of nanotechnology. Addition of nano particulates to a polymer matrix enhances its performance by capitalizing on the nature and properties of the nano-scale fillers. The damping behavior of composites with nano structured phases is significantly different from that of micro structured materials. Viscoelastic homopolymer exhibit a high material damping response over a relatively narrow range of temperature and frequencies. In many practical situations, a polymeric structure is required to possess better strength and stiffness properties together with a reasonable damping behavior. Viscoelastic polymers show higher loss factor beyond the glassy region which comes with a significant drop in the specific modulus. Addition of nano alumina particles to epoxy leads to improved strength and stiffness properties with an increase in glass transition temperature while retaining its damping capability. Experimental investigations are carried out on composite beam specimen fabricated with different compositions of alumina nano particles in epoxy to evaluate loss factor, tan δ. Impact damping method is used for time response analysis. A single point Laser is used to record the transverse displacement of a point on the composite beam specimen. The experimental results are compared with theoretical estimation of loss factor using Voigt estimation. The effect of inter phase is included in theoretical estimation of loss factor. The result reveals that the study of interface properties is very important in deriving the overall loss factor of the composite since interface occupies a significant volume fraction in the composite.

  2. Preparation and Various Characteristics of Epoxy/Alumina Nanocomposites

    NASA Astrophysics Data System (ADS)

    Kozako, Masahiro; Ohki, Yoshimichi; Kohtoh, Masanori; Okabe, Shigemitsu; Tanaka, Toshikatsu

    Epoxy/ alumina nanocomposites were newly prepared by dispersing 3, 5, 7, and 10 weight (wt) % boehmite alumina nanofillers in a bisphenol-A epoxy resin using a special two-stage direct mixing method. It was confirmed by scanning electron microscopy imaging that the nanofillers were homogeneously dispersed in the epoxy matrix. Dielectric, mechanical, and thermal properties were investigated. It was elucidated that nanofillers affects various characteristics of epoxy resins, when they are nanostructrued. Such nano-effects we obtained are summarized as follows. Partial discharge resistance increases as the filler content increases; e.g. 7 wt% nanofiller content creates a 60 % decrease in depth of PD-caused erosion. Weibull analysis shows that short-time electrical treeing breakdown time is prolonged to 265 % by 5 wt% addition of nanofillers. But there was more data scatter in nanocomposites than in pure epoxy. Permittivity tends to increase from 3.7 to 4.0 by 5 wt% nanofiller addition as opposed to what was newly found in the recent past. Glass transition temperature remains unchanged as 109 °C. Mechanical properties such as flexural strength and flexural modulus increase; e.g. flexural strength and flexural modulus are improved by 5 % and 8 % with 5 wt% content, respectively. Excess addition causes a reverse effect. It is concluded from permittivity and glass transition temperature characteristics that interfacial bonding seems to be more or less weak in the nanocomposite specimens prepared this time, even though mechanical strengths increase. There is a possibility that the nanocomposites specimens will be improved in interfacial quality.

  3. Lightweight alumina refractory aggregate. Phase 2, Pilot scale development

    SciTech Connect

    Swansiger, T.G.; Pearson, A.

    1994-11-01

    Kilogram quantities of refractory aggregate were prepared from both a paste and a pelletized form of extruder feed material in both bench and pilot-scale equipment. The 99{sup +} % alumina aggregate exhibited a bulk density approaching 2.5 g/cm{sup 3} and a fired strength slightly lower than fused alumina. Based on initial evaluation by two refractory manufacturers in brick or castable applications, the new aggregate offered adequate strength with thermal conductivity reductions up to 34%, depending on the temperature and application of the new aggregate in these initial trials. The new aggregate was simply substituted for Tabular{trademark} in the refractory formulation. Thus, there is room for improvement through formulation optimization with the lightweight aggregate. The new aggregate offers a unique combination of density, strength, and thermal properties not available in current aggregate. To this point in time, technical development has led to a pelletized formulation with borderline physical form leaving the Eirich mixer. The formulation requires further development to provide more latitude for the production of pelletized material without forming paste, while still reducing the bulk density slightly to reach the 2.5 g/cm{sup 3} target. The preferred, pelletized process flowsheet was outlined and a preliminary economic feasibility study performed based on a process retrofit into Alcoa`s Arkansas tabular production facilities. Based on an assumed market demand of 20,000 mt/year and an assumed selling price of $0.65/lb (25% more than the current selling price of Tabular{trademark}, on a volume basis), economics were favorable. Decision on whether to proceed into Phase 3 (full- scale demonstration) will be based on a formal market survey in 1994 October.

  4. Optical Basicity and Nepheline Crystallization in High Alumina Glasses

    SciTech Connect

    Rodriguez, Carmen P.; McCloy, John S.; Schweiger, M. J.; Crum, Jarrod V.; Winschell, Abigail E.

    2011-02-25

    The purpose of this study was to find compositions that increase waste loading of high-alumina wastes beyond what is currently acceptable while avoiding crystallization of nepheline (NaAlSiO4) on slow cooling. Nepheline crystallization has been shown to have a large impact on the chemical durability of high-level waste glasses. It was hypothesized that there would be some composition regions where high-alumina would not result in nepheline crystal production, compositions not currently allowed by the nepheline discriminator. Optical basicity (OB) and the nepheline discriminator (ND) are two ways of describing a given complex glass composition. This report presents the theoretical and experimental basis for these models. They are being studied together in a quadrant system as metrics to explore nepheline crystallization and chemical durability as a function of waste glass composition. These metrics were calculated for glasses with existing data and also for theoretical glasses to explore nepheline formation in Quadrant IV (passes OB metric but fails ND metric), where glasses are presumed to have good chemical durability. Several of these compositions were chosen, and glasses were made to fill poorly represented regions in Quadrant IV. To evaluate nepheline formation and chemical durability of these glasses, quantitative X-ray diffraction (XRD) analysis and the Product Consistency Test were conducted. A large amount of quantitative XRD data is collected here, both from new glasses and from glasses of previous studies that had not previously performed quantitative XRD on the phase assemblage. Appendix A critically discusses a large dataset to be considered for future quantitative studies on nepheline formation in glass. Appendix B provides a theoretical justification for choice of the oxide coefficients used to compute the OB criterion for nepheline formation.

  5. Iron migration from the anode surface in alumina electrolysis

    NASA Astrophysics Data System (ADS)

    Zhuravleva, Elena N.; Drozdova, Tatiana N.; Ponomareva, Svetlana V.; Kirik, Sergei D.

    2013-01-01

    Corrosion destruction of two-component iron-based alloys used as an anode in high-temperature alumina electrolysis in the melt of NaF/KF/AlF3 electrolyte has been considered. Ni, Si, Cu, Cr, Mn, Al, Ti in the amount of up to 10% have been tested as the dopants to an anode alloys. The composition of the corrosion products has been studied using X-ray diffraction, scanning electron microscopy and electron microprobe analysis. It has been established that the anode corrosion is induced by a surface electrochemical polarization and iron atom oxidation. Iron ions come into an exchange interaction with the fluoride components of the melted electrolyte, producing FeF2. The last interacts with oxyfluoride species transforming into the oxide forms: FeAl2O4, Fe3O4, Fe2O3. Due to the low solubility, the iron oxides are accumulated in the near-electrode sheath. The only small part of iron from anode migrates to cathode that makes an production of high purity aluminum of a real task. The alloy dopants are also subjected to corrosion in accordance with electromotive series resulting corrosion tunnels on the anode surface. The oxides are final compounds which collect in the same area. The corrosion products form an anode shell which is electronic conductor at electrolysis temperature. The electrolysis of alumina occurs beyond the corrosion shell. The rate limiting step in the corrosion is the electrolyte penetration through corrosion shell to the anode surface. The participation of the released oxygen in the corrosion has not been observed.

  6. Alumina-zirconia-silicon carbide-magnesia compositions and articles made through therefrom

    SciTech Connect

    Mehrotra, P.K.; Billman, E.R.

    1990-10-23

    This patent describes an alumina based ceramic composition. It comprises: about 1.5 to 17.5 v/o silicon carbide whiskers; about 5 to 17.5 v/o zirconia; a residue of a magnesia addition added in the amount of about 0.03 to 3 v/o; alumina forming essentially the remainder of the composition; wherein the silicon carbide whiskers, the zirconia and the residue of the magnesia addition are substantially homo-geneously dispersed in a matrix formed of the alumina; and wherein at least about 4.0 v/o of the ceramic composition is tetragonal zirconia.

  7. Ultrasonic Characterization of Custom Engineered Armor Grade Alumina (Al2O3)

    NASA Astrophysics Data System (ADS)

    Bottiglieri, S.; Haber, R. A.

    2010-02-01

    High frequency ultrasonic characterization was performed on a series of alumina samples of varying degrees of density. These samples were specifically fired to temperatures below and above what is considered to be appropriate for the sintering of alumina. Ultrasound attenuation coefficient and Young's modulus C-scan mapping and acoustic spectroscopy were employed in order to establish a baseline fingerprint for each temperature type. Characterization was performed using 20 MHz and 75 MHz planar transducers. This study showed the veracity of high frequency ultrasound as a diagnostic tool in characterizing the effect of densification on material properties for armor-grade alumina.

  8. Fabrication and evaluation of low fiber content alumina fiber/aluminum composites

    NASA Technical Reports Server (NTRS)

    Hack, J. E.; Strempek, G. C.

    1980-01-01

    The mechanical fabrication of low volume percent fiber, polycrystalline alumina fiber reinforced aluminum composites was accomplished. Wire preform material was prepared by liquid-metal infiltration of alumina fiber bundles. The wires were subsequently encapsulated with aluminum foil and fabricated into bulk composite material by hot-drawing. Extensive mechanical, thermal and chemical testing was conducted on preform and bulk material to develop a process and material data base. In addition, a preliminary investigation of mechanical forming of bulk alumina fiber reinforced aluminum composite material was conducted.

  9. Introduction of bridging and pendant organic groups into mesoporous alumina materials.

    PubMed

    Grant, Stacy M; Woods, Stephan M; Gericke, Arne; Jaroniec, Mietek

    2011-11-01

    Incorporation of organic functionalities into soft-templated mesoporous alumina was performed via organosilane-assisted evaporation induced self-assembly using aluminum alkoxide precursors and block copolymer templates. This strategy permits one to obtain mesoporous alumina-based materials with tailorable adsorption, surface and structural properties. Isocyanurate, ethane, mercaptopropyl, and ureidopropyl-functionalized mesoporous alumina materials were synthesized with relatively high surface area and large pore volume with uniform and wormhole-like mesopores. The presence of organosilyl groups within these hybrid materials was confirmed by IR or Raman spectroscopy and their concentration was determined by elemental analysis.

  10. Interaction of hydrogen chloride with alumina. [influence of outgas and temperature conditions on adsorption

    NASA Technical Reports Server (NTRS)

    Bailey, R. R.; Wightman, J. P.

    1975-01-01

    The influence of outgas conditions and temperature on the adsorptive properties of two aluminas Alon-c and Al6sG were studied using adsorption isotherm measurements. Alon-C and Al6SG were characterized using X-ray powder diffraction, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and BET nitrogen surface areas. Some of these techniques were applied to two other aluminas but no isotherm data was obtained. Isotherm data and techniques applied to each alumina are summarized in tabular form.

  11. Investigation of silver-impregnated alumina for removal of radioactive methyl iodide

    SciTech Connect

    Funabashi, Kiyomi; Fukasawa, Tetsuo; Kikuchi, Makoto

    1995-03-01

    The removal efficiency of methyl iodide for silver-impregnated alumina from gaseous waste has been experimentally evaluated as a function of atmospheric relative humidity. A new adsorbent has been developed for the iodine filter installed in the off-gas treatment system of a radioactive waste tank vent. To improve its removal efficiency under a highly humid atmosphere, the optimum average pore size of alumina was determined to be {approximately}60 nm, and the most effective chemical form of the impregnated silver was identified as silver nitrate. Holding capability of the impregnated silver was also improved by developing a double-pore-structure alumina.

  12. Influence of Alumina Reaction Tube Impurities on the Oxidation of Chemically-Vapor-Deposited Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth

    1995-01-01

    Pure coupons of chemically vapor deposited (CVD) SiC were oxidized for 100 h in dry flowing oxygen at 1300 C. The oxidation kinetics were monitored using thermogravimetry (TGA). The experiments were first performed using high-purity alumina reaction tubes. The experiments were then repeated using fused quartz reaction tubes. Differences in oxidation kinetics, scale composition, and scale morphology were observed. These differences were attributed to impurities in the alumina tubes. Investigators interested in high-temperature oxidation of silica formers should be aware that high-purity alumina can have significant effects on experiment results.

  13. First principles calculation of thermal expansion coefficients of pure and Cr doped α-alumina crystals

    NASA Astrophysics Data System (ADS)

    Tohei, Tetsuya; Watanabe, Yuito; Lee, Hak-Sung; Ikuhara, Yuichi

    2016-10-01

    We have performed theoretical analysis of thermal expansion behavior of alumina crystals under finite temperature based on first principles phonon state calculations. Liner thermal expansion coefficients of a pure α-alumina crystal have been evaluated based on quasi-harmonic approximation including crystalline anisotropy. The Cr doping effect on the alumina crystal has also been examined and found that the doping can cause a noticeable change on the thermal expansion coefficient. The present results demonstrate that the first principles theoretical approach can be helpful for reproducing or predicting thermal expansion behaviors including dopant effects, which may pave a way for possible control of thermal expansion of materials by doping or alloying.

  14. Integrating coal combustion and red mud sintering at an alumina refinery

    NASA Astrophysics Data System (ADS)

    Rayzman, Viktor L.; Filipovich, Igor K.

    1999-08-01

    The fuel cost at an alumina refinery can be significantly reduced by shifting steam generation from gas or oil to coal use. The sorbent that can be applied for the cleaning of fuel gases is a regular red mud copiously dumped at alumina refineries. It is possible to combine coal combustion and red mud low-temperature sintering to recover remaining alumina and caustic from a red mud. The integrated technology, based on a combination of known processes, will provide advantages over other methods that are currently being used.

  15. The Future of Alumina-Forming Alloys: Challenges and Applications for Power Generation

    SciTech Connect

    Pint, Bruce A

    2011-01-01

    Alumina-forming alloys have been studied for over 50 years and are now needed for high efficiency power generation applications operating at higher temperatures. Especially in the presence of water vapor, alumina-forming alloys outperform conventional chromia-forming alloys above 1000 C. However, alloy mechanical behavior is a significant issue and alumina-forming alloy development has been limited. The opportunity for alloy development is discussed as well as the factors that limit oxidation resistance, including alloy thermal expansion and optimizing reactive element additions. Finally, lifetime modeling is discussed for thick section components together with the need to address performance in more complex environments.

  16. Optimization of the textural characteristics of an alumina to capture contaminants in natural gas

    SciTech Connect

    Nedez, C.; Boitiaux, J.P.; Cameron, C.J.; Didillon, B.

    1996-08-07

    Capillary condensation of water can seriously impair the performance of an adsorbent intended for use in removing contaminants (mercury, arsenic, sulfur, etc.) in natural gas. Adsorption and desorption isotherms were used to determine how the nature and pore structure distribution of the adsorbent (alumina, active carbon) affect water adsorption. The contribution of the different phenomena involved (chemisorption, physisorption, capillary condensation) have been determined. The threshold of capillary condensation is reached much more rapidly on active carbon and microporous alumina (40% relative humidity) than on a highly mesoporous alumina (75-80% relative humidity). 44 refs., 9 figs., 1 tab.

  17. The low-temperature loss tangent of adsorbed water in alumina

    NASA Astrophysics Data System (ADS)

    Khasawneh, Mazin; Sarabi, Bahman; Khalil, M. S.; Stoutimore, M. J. A.; Gladchenko, Sergiy; Wellstood, F. C.; Lobb, C. J.; Osborn, Kevin

    2012-02-01

    Superconducting quantum information circuits use various amorphous dielectrics for capacitors, and alumina is the ubiquitous barrier material for Josephson junctions within these devices. The exposure of the devices to air allows water molecules to penetrate the dielectric films along grain boundaries, and become adsorbed onto internal surfaces. In this study we plan to use ALD-grown alumina and titanium oxide to study the penetration of water through films. Using blocking layers to selectively prevent water penetration, we then plan to measure the difference in the low-temperature loss tangent between an alumina film which is exposed to air and one which is not.

  18. Rational engineering of nanoporous anodic alumina optical bandpass filters

    NASA Astrophysics Data System (ADS)

    Santos, Abel; Pereira, Taj; Law, Cheryl Suwen; Losic, Dusan

    2016-08-01

    Herein, we present a rationally designed advanced nanofabrication approach aiming at producing a new type of optical bandpass filters based on nanoporous anodic alumina photonic crystals. The photonic stop band of nanoporous anodic alumina (NAA) is engineered in depth by means of a pseudo-stepwise pulse anodisation (PSPA) approach consisting of pseudo-stepwise asymmetric current density pulses. This nanofabrication method makes it possible to tune the transmission bands of NAA at specific wavelengths and bandwidths, which can be broadly modified across the UV-visible-NIR spectrum through the anodisation period (i.e. time between consecutive pulses). First, we establish the effect of the anodisation period as a means of tuning the position and width of the transmission bands of NAA across the UV-visible-NIR spectrum. To this end, a set of nanoporous anodic alumina bandpass filters (NAA-BPFs) are produced with different anodisation periods, ranging from 500 to 1200 s, and their optical properties (i.e. characteristic transmission bands and interferometric colours) are systematically assessed. Then, we demonstrate that the rational combination of stacked NAA-BPFs consisting of layers of NAA produced with different PSPA periods can be readily used to create a set of unique and highly selective optical bandpass filters with characteristic transmission bands, the position, width and number of which can be precisely engineered by this rational anodisation approach. Finally, as a proof-of-concept, we demonstrate that the superposition of stacked NAA-BPFs produced with slight modifications of the anodisation period enables the fabrication of NAA-BPFs with unprecedented broad transmission bands across the UV-visible-NIR spectrum. The results obtained from our study constitute the first comprehensive rationale towards advanced NAA-BPFs with fully controllable photonic properties. These photonic crystal structures could become a promising alternative to traditional optical

  19. Stabilized Alumina/Ethanol Colloidal Dispersion for Seeding High Temperature Air Flows

    NASA Technical Reports Server (NTRS)

    Wernet, Judith H.; Wernet, Mark P.

    1994-01-01

    Seeding air flows with particles to enable measurements of gas velocities via laser anemometry and/or particle image velocimetry techniques can be quite exasperating. The seeding requirements are compounded when high temperature environments are encountered and special care must be used in selecting a refractory seed material. The pH stabilization techniques commonly employed in ceramic processing are used to obtain stable dispersions for generating aerosols of refractory seed material. By adding submicron alumina particles to a preadjusted pH solution of ethanol, a stable dispersion is obtained which when atomized produces a high quality aerosol. Commercial grade alumina powder is used with a moderate size distribution. The technique is not limited to alumina/ethanol and is also demonstrated with an alumina/H2O system. Other ceramic powders in various polar solvents could also be used once the point of zero charge (pH(sub pzc)) of the powder in the solvent has been determined.

  20. Investigations of mechanical and wear properties of alumina/titania/fire-clay reinforced epoxy composites

    NASA Astrophysics Data System (ADS)

    Patel, Vinay Kumar; Chauhan, Shivani; Sharma, Aarushi

    2016-05-01

    In this work, the effect of various particulates (alumina, titania, fire clay) reinforcements on mechanical and wear properties of epoxy composites have been studied with a prime motive of replacing the costly alumina and titania by much economical fire clay for high mechanical strength and/or wear resistant materials. Fire clay based epoxy composites delivered better mechanical (both tensile and impact) properties than the alumina filled or neat epoxy composites and slightly lower than titania reinforced composites, which qualified the fire clay a very suitable cost effective alternatives of both alumina and titania for high mechanical strength based applications. However, the poor wear behavior of fire clay reinforced composites revealed its poor candidacy for wear and tear applications.