Nano-Localized Thermal Analysis and Mapping of Surface and Sub-Surface Thermal Properties Using Scanning Thermal Microscopy (SThM).

PubMed

Pereira, Maria J; Amaral, Joao S; Silva, Nuno J O; Amaral, Vitor S

2016-12-01

Determining and acting on thermo-physical properties at the nanoscale is essential for understanding/managing heat distribution in micro/nanostructured materials and miniaturized devices. Adequate thermal nano-characterization techniques are required to address thermal issues compromising device performance. Scanning thermal microscopy (SThM) is a probing and acting technique based on atomic force microscopy using a nano-probe designed to act as a thermometer and resistive heater, achieving high spatial resolution. Enabling direct observation and mapping of thermal properties such as thermal conductivity, SThM is becoming a powerful tool with a critical role in several fields, from material science to device thermal management. We present an overview of the different thermal probes, followed by the contribution of SThM in three currently significant research topics. First, in thermal conductivity contrast studies of graphene monolayers deposited on different substrates, SThM proves itself a reliable technique to clarify the intriguing thermal properties of graphene, which is considered an important contributor to improve the performance of downscaled devices and materials. Second, SThM's ability to perform sub-surface imaging is highlighted by thermal conductivity contrast analysis of polymeric composites. Finally, an approach to induce and study local structural transitions in ferromagnetic shape memory alloy Ni-Mn-Ga thin films using localized nano-thermal analysis is presented.

Density functional theory study of structural, electronic, and thermal properties of Pt, Pd, Rh, Ir, Os and PtPd X (X = Ir, Os, and Rh) alloys

NASA Astrophysics Data System (ADS)

Shabbir, Ahmed; Muhammad, Zafar; M, Shakil; M, A. Choudhary

2016-03-01

The structural, electronic, mechanical, and thermal properties of Pt, Pd, Rh, Ir, Os metals and their alloys PtPdX (X = Ir, Os and Rh) are studied systematically using ab initio density functional theory. The groundstate properties such as lattice constant and bulk modulus are calculated to find the equilibrium atomic position for stable alloys. The electronic band structure and density of states are calculated to study the electronic behavior of metals on making their alloys. The electronic properties substantiate the metallic behavior for all studied materials. The firstprinciples density functional perturbation theory as implemented in quasi-harmonic approximation is used for the calculations of thermal properties. We have calculated the thermal properties such as the Debye temperature, vibrational energy, entropy and constant-volume specific heat. The calculated properties are compared with the previously reported experimental and theoretical data for metals and are found to be in good agreement. Calculated results for alloys could not be compared because there is no data available in the literature with such alloy composition.

Preparation and properties of the multi-layer aerogel thermal insulation composites

NASA Astrophysics Data System (ADS)

Wang, Miao; Feng, Junzong; Jiang, Yonggang; Zhang, Zhongming; Feng, Jian

2018-03-01

Multi-layer insulation materials possess low radiation thermal conductivity, and excellent thermal insulation property in a vacuum environment. However, the spacers of the traditional multi-layer insulation materials are mostly loose fibers, which lead to more sensitive to the vacuum environmental of serviced. With the vacuum degree declining, gas phases thermal convection increase obviously, and the reflective screen will be severe oxidation, all of these make the thermal insulation property of traditional multi-layer insulation deteriorate, thus limits its application scope. In this paper, traditional multi-layer insulation material is combined with aerogel and obtain a new multi-layer aerogel thermal insulation composite, and the effects of the number, thickness and type of the reflective screens on the thermal insulation properties of the multi-layer composites are also studied. The result is that the thermal insulation property of the new type multi-layer aerogel composites is better than the pure aerogel composites and the traditional multi-layer insulation composites. When the 0.01 mm stainless steel foil as the reflective screen, and the aluminum silicate fiber and silica aerogel as the spacer layer, the layer density of composite with the best thermal insulation property is one layer per millimeter at 1000 °C.

Thermophysical properties study of micro/nanoscale materials

NASA Astrophysics Data System (ADS)

Feng, Xuhui

Thermal transport in low-dimensional structure has attracted tremendous attentions because micro/nanoscale materials play crucial roles in advancing micro/nanoelectronics industry. The thermal properties are essential for understanding of the energy conversion and thermal management. To better investigate micro/nanoscale materials and characterize the thermal transport, pulse laser-assisted thermal relaxation 2 (PLTR2) and transient electrothermal (TET) are both employed to determine thermal property of various forms of materials, including thin films and nanowires. As conducting polymer, Poly(3-hexylthiophene) (P3HT) thin film is studied to understand its thermal properties variation with P3HT weight percentage. 4 P3HT solutions of different weight percentages are compounded to fabricate thin films using spin-coating technique. Experimental results indicate that weight percentage exhibits impact on thermophysical properties. When percentage changes from 2% to 7%, thermal conductivity varies from 1.29 to 1.67 W/m·K and thermal diffusivity decreases from 10-6 to 5×10-7 m2/s. Moreover, PLTR2 technique is applied to characterize the three-dimensional anisotropic thermal properties in spin-coated P3HT thin films. Raman spectra verify that the thin films embrace partially orientated P3HT molecular chains, leading to anisotropic thermal transport. Among all three directions, lowest thermal property is observed along out-of-plane direction. For in-plane characterization, anisotropic ratio is around 2 to 3, indicating that the orientation of the molecular chains has strong impact on the thermal transport along different directions. Titanium dioxide (TiO2) thin film is synthesized by electrospinning features porous structure composed by TiO2 nanowires with random orientations. The porous structure caused significant degradation of thermal properties. Effective thermal diffusivity, conductivity, and density of the films are 1.35˜3.52 × 10-6 m2/s, 0.06˜0.36 W/m·K, and 25.8˜373 kg/m3, respectively, much lower than bulk values. Then single anatase TiO2 nanowire is synthesized to understand intrinsic thermophysical properties and secondary porosity. Thermal diffusivity of nanowires varies from 1.76 to 5.08 × 10-6 m 2/s, while thermal conductivity alters from 1.38 to 6.01 W/m·K. SEM image of TiO2 nanowire shows secondary porous surface structure. In addition, nonlinear effects are also observed with experimental data. Two methods, generalized function analysis and direct capacitance derivation, are developed to suppress nonlinear effects. Effective thermal diffusivities from both modified analysis agree well with each other.

Thermal Properties of Algerian Diatomite, Study of the Possibility to Its Use in the Thermal Insulation

NASA Astrophysics Data System (ADS)

Hamdi, Boualem; Hamdi, Safia

The chemical and physical properties of a Algerian diatomite were given before and after heat treatment and chemical with an aim of a use in the heat insulation of constructions. The preliminary results obtained showed that this material is extremely porous (porosity >70 %), characterized of a low density and a very low thermal conductivity. These promising properties support the use of this local material in the thermal insulation.

Electrical and Thermal Transport Property Studies of High-Temperature Thermoelectric Materials.

DTIC Science & Technology

1985-06-01

THERMAL TRANSPORT PROPERTY STUDIES OF HIGH-TEMPERATURE THERMOELECTRIC MATERIALS: INTERIM TECHNICAL REPORT FOR THE PERIOD MAY 15, 1984 TO MAY 15, 1985 J. L...transport property data base has been expanded oy continued measurements in several systems under study, and a theoretical model for thermoelectric ...6.0 REFERENCES . . . . . . . . . . . . 6.1 APPENDIX A - THERMOELECTRIC PROPERTY DATA . . . . . . . A. I 1l FIGURES 3.1 Dimensionless Figure of Merit

Thermal properties of light-weight concrete with waste polypropylene aggregate

NASA Astrophysics Data System (ADS)

Záleská, Martina; Pokorný, Jaroslav; Pavlíková, Milena; Pavlík, Zbyšek

2017-07-01

Thermal properties of a sustainable light-weight concrete incorporating high volume of waste polypropylene as partial substitution of natural aggregate were studied in the paper. Glass fiber reinforced polypropylene (GFPP), a by-product of PP tubes production, partially substituted fine natural silica aggregate in 10, 20, 30, 40, and 50 mass%. In order to quantify the effect of GFPP use on concrete properties, a reference concrete mix without plastic waste was studied as well. For the applied GFPP, bulk density, matrix density, and particle size distribution were measured. Specific attention was paid to thermal transport and storage properties of GFPP that were examined in dependence on compaction time. For the developed light-weight concrete, thermal properties were accessed using transient impulse technique, whereas the measurement was done in dependence on moisture content, from the dry state to fully water saturated state. Additionally, the investigated thermal properties were plotted as function of porosity. The tested light-weight concrete was found to be prospective construction material possessing improved thermal insulation function. Moreover, the reuse of waste plastics in concrete composition was beneficial both from the environmental and financial point of view considering plastics low biodegradability and safe disposal.

Monitoring the Thermal Parameters of Different Edible Oils by Using Thermal Lens Spectrometry

NASA Astrophysics Data System (ADS)

Jiménez-Pérez, J. L.; Cruz-Orea, A.; Lomelí Mejia, P.; Gutierrez-Fuentes, R.

2009-08-01

Several vegetable edible oils (sunflower, canola, soya, and corn) were used to study the thermal diffusivity of edible oils. Thermal lens spectrometry (TLS) was applied to measure the thermal properties. The results showed that the obtained thermal diffusivities with this technique have good agreement when compared with literature values. In this technique an Ar+ laser and intensity stabilized He-Ne laser were used as the heating source and probe beam, respectively. These studies may contribute to a better understanding of the physical properties of edible oils and the quality of these important foodstuffs.

Thermal properties of alkali-activated aluminosilicates

NASA Astrophysics Data System (ADS)

Florian, Pavel; Valentova, Katerina; Fiala, Lukas; Zmeskal, Oldrich

2017-07-01

The paper is focused on measurements and evaluation of thermal properties of alkali-activated aluminosilicates (AAA) with various carbon admixtures. Such composites consisting of blast-furnace slag, quartz sand, water glass as alkali activator and small amount of electrically conductive carbon admixture exhibit better electric and thermal properties than the reference material. Such enhancement opens up new practical applications, such as designing of snow-melting, de-icing or self-sensing systems that do not need any external sensors to detect current condition of building material. Thermal properties of the studied materials were measured by the step-wise transient method and mutually compared.

Tissue-mimicking gel phantoms for thermal therapy studies.

PubMed

Dabbagh, Ali; Abdullah, Basri Johan Jeet; Ramasindarum, Chanthiriga; Abu Kasim, Noor Hayaty

2014-10-01

Tissue-mimicking phantoms that are currently available for routine biomedical applications may not be suitable for high-temperature experiments or calibration of thermal modalities. Therefore, design and fabrication of customized thermal phantoms with tailored properties are necessary for thermal therapy studies. A multitude of thermal phantoms have been developed in liquid, solid, and gel forms to simulate biological tissues in thermal therapy experiments. This article is an attempt to outline the various materials and techniques used to prepare thermal phantoms in the gel state. The relevant thermal, electrical, acoustic, and optical properties of these phantoms are presented in detail and the benefits and shortcomings of each type are discussed. This review could assist the researchers in the selection of appropriate phantom recipes for their in vitro study of thermal modalities and highlight the limitations of current phantom recipes that remain to be addressed in further studies. © The Author(s) 2014.

Optimization of Rei-mullite Physical Properties

NASA Technical Reports Server (NTRS)

Tanzilli, R. A.; Musikant, S.; Bolinger, P. N.; Brazel, J. P.

1973-01-01

Micromechanical and thermal modeling studies prove that ceramic fiber mullite materials is the only system capable of shuttle thermal protection to 1644 K. Hafnia pigmentated mullite surface coatings meet both orbital and reentry thermal radiative requirements for reuse without refurbishment. Thermal and mechanical models show growths potentials associated with the mullite system for a factor of 2 improvement in mechanical properties, and a factor of 2 to 3 reduction in thermal conductivity.

Effect of electron beam irradiation on thermal and mechanical properties of aluminum based epoxy composites

NASA Astrophysics Data System (ADS)

Visakh, P. M.; Nazarenko, O. B.; Sarath Chandran, C.; Melnikova, T. V.; Nazarenko, S. Yu.; Kim, J.-C.

2017-07-01

The epoxy resins are widely used in nuclear and aerospace industries. The certain properties of epoxy resins as well as the resistance to radiation can be improved by the incorporation of different fillers. This study examines the effect of electron beam irradiation on the thermal and mechanical properties of the epoxy composites filled with aluminum nanoparticles at percentage of 0.35 wt%. The epoxy composites were exposed to the irradiation doses of 30, 100 and 300 kGy using electron beam generated by the linear electron accelerator ELU-4. The effects of the doses on thermal and mechanical properties of the aluminum based epoxy composites were investigated by the methods of thermal gravimetric analysis, tensile test, and dynamic mechanical analysis. The results revealed that the studied epoxy composites showed good radiation resistance. The thermal and mechanical properties of the aluminum based epoxy composites increased with increasing the irradiation dose up to 100 kGy and decreased with further increasing the dose.

Coating effects on thermal properties of carbon carbon and carbon silicon carbide composites for space thermal protection systems

NASA Astrophysics Data System (ADS)

Albano, M.; Morles, R. B.; Cioeta, F.; Marchetti, M.

2014-06-01

Many are the materials for hot structures, but the most promising one are the carbon based composites nowadays. This is because they have good characteristics with a high stability at high temperatures, preserving their mechanical properties. Unfortunately, carbon reacts rapidly with oxygen and the composites are subjected to oxidation degradation. From this point of view CC has to be modified in order to improve its thermal and oxidative resistance. The most common solutions are the use of silicon carbide into the carbon composites matrix (SiC composites) to make the thermal properties increase and the use of coating on the surface in order to protect the composite from the space plasma effects. Here is presented an experimental study on coating effects on these composites. Thermal properties of coated and non coated materials have been studied and the thermal impact on the matrix and surface degradation is analyzed by a SEM analysis.

Evaluating the effect of spinning systems on thermal comfort properties of modal fabrics

NASA Astrophysics Data System (ADS)

Seçil Aydın, İ.; Kertmen, M.; Marmarali, A.

2017-10-01

In recent years the importance of clothing comfort became one of the most important feature of the fabrics. The aim of this study is to characterize thermal comfort properties of single jersey fabrics were knitted using 100% modal yarns which were spun in various types of yarn spinning methods such as ring spinning, compact spinning, rotor spinning and airjet spinning. Thermal comfort properties like air permeability, thermal resistance, thermal absorptivity and water vapour permeability of fabrics were tested. The results indicate that compact spinning technology will be appropriate for the summer climate casual wear.

Electrical and Thermal Transport Property Studies of High-Temperature Thermoelectric Materials.

DTIC Science & Technology

1984-12-15

Transport Property Studies of High-Temperature Thermoelectric Mateial 12. PERSONAL AUTHIOR(S) 113. TYPE OF REPORT 13b. TIME COVERED Ai DATE OF REPORtT (Yr...with an ABO(3 perovskite structure. Transport properties have been determined for various doping ele- ments and for different compositions. These data...THERMAL TRANSPORT PROPERTY STUDIES Unannounced [j OF HIGH-TEMPERATURE THERMOELECTRIC MATERIALS Justi±icI iou. CONTRACT F-49620-83-0109 DEF By-- Battelle

Anisotropic thermal conductivity in epoxy-bonded magnetocaloric composites

NASA Astrophysics Data System (ADS)

Weise, Bruno; Sellschopp, Kai; Bierdel, Marius; Funk, Alexander; Bobeth, Manfred; Krautz, Maria; Waske, Anja

2016-09-01

Thermal management is one of the crucial issues in the development of magnetocaloric refrigeration technology for application. In order to ensure optimal exploitation of the materials "primary" properties, such as entropy change and temperature lift, thermal properties (and other "secondary" properties) play an important role. In magnetocaloric composites, which show an increased cycling stability in comparison to their bulk counterparts, thermal properties are strongly determined by the geometric arrangement of the corresponding components. In the first part of this paper, the inner structure of a polymer-bonded La(Fe, Co, Si)13-composite was studied by X-ray computed tomography. Based on this 3D data, a numerical study along all three spatial directions revealed anisotropic thermal conductivity of the composite: Due to the preparation process, the long-axis of the magnetocaloric particles is aligned along the xy plane which is why the in-plane thermal conductivity is larger than the thermal conductivity along the z-axis. Further, the study is expanded to a second aspect devoted to the influence of particle distribution and alignment within the polymer matrix. Based on an equivalent ellipsoids model to describe the inner structure of the composite, numerical simulation of the thermal conductivity in different particle arrangements and orientation distributions were performed. This paper evaluates the possibilities of microstructural design for inducing and adjusting anisotropic thermal conductivity in magnetocaloric composites.

Thermal conductivity of tubrostratic carbon nanofiber networks

DOE PAGES

Bauer, Matthew L.; Saltonstall, Chris B.; Leseman, Zayd C.; ...

2016-01-01

Composite material systems composed of a matrix of nano materials can achieve combinations of mechanical and thermophysical properties outside the range of traditional systems. While many reports have studied the intrinsic thermal properties of individual carbon fibers, to be useful in applications in which thermal stability is critical, an understanding of heat transport in composite materials is required. In this work, air/ carbon nano fiber networks are studied to elucidate the system parameters influencing thermal transport. Sample thermal properties are measured with varying initial carbon fiber fill fraction, environment pressure, loading pressure, and heat treatment temperature through a bidirectional modificationmore » of the 3ω technique. The nanostructures of the individual fibers are characterized with small angle x-ray scattering and Raman spectroscopy providing insight to individual fiber thermal conductivity. Measured thermal conductivity varied from 0.010 W/(m K) to 0.070 W/(m K). An understanding of the intrinsic properties of the individual fibers and the interactions of the two phase composite is used to reconcile low measured thermal conductivities with predictive modeling. This methodology can be more generally applied to a wide range of fiber composite materials and their applications.« less

Comparative study of the thermal properties of mud and peat solutions applied in clinical practice.

PubMed

Beer, A M; Grozeva, A; Sagorchev, P; Lukanov, J

2003-11-01

Different peloids as e.g. mud and peat have been traditionally used for therapeutic purposes successfully, especially of there thermal actions. It was the aim of the experimental study to compare the thermal properties of two peloids, mud and peat, with a view to assessing their thermal effects when they are applied in clinical practice. The studies were carried out using peat of the marsh type of peats (Hochmoor), and curative Pomorie (Bulgaria) mud. As important parameters were determined the specific thermal capacity at constant pressure (Cp), the density of solutions (rho), the cooling rate (m), the coefficient of temperature transfer (a) of solutions and the coefficient of thermal conductivity (lambda) of solutions of peat and curative mud, compared to water bath. The comparative studies of the thermal properties of water and water solutions of peat and curative mud show that the thermal effect of the water bath is substantially smaller than that of the peat and mud applications. This difference is due to a greater extent to the high values of the dynamic viscosity, not allowing cooling by convection and protecting the surface of the skin upon applications of peloid solutions with a higher temperature.

Thermal Properties of Jojoba Oil Between 20°C and 45°C

NASA Astrophysics Data System (ADS)

Lara-Hernández, G.; Flores-Cuautle, J. J. A.; Hernandez-Aguilar, C.; Suaste-Gómez, E.; Cruz-Orea, A.

2017-08-01

Vegetable oils have been widely studied as biofuel candidates. Among these oils, jojoba ( Simmondsia chinensis) oil has attracted interest because it is composed almost entirely of wax esters that are liquid at room temperature. Consequently, it is widely used in the cosmetic and pharmaceutical industries. To date, research on S. chinensis oil has focused on to its use as a fuel and its thermal stability, and information about its thermal properties is scarce. In the present study, the thermal effusivity and conductivity of jojoba oil between 20°C and 45°C were obtained using the inverse photopyroelectric and hot-ball techniques. The feasibility of an inverse photopyroelectric method and a hot-ball technique to monitor the thermal conductivity, and the thermal effusivity of the S. chinensis is demonstrated. The thermal effusivity decreased from 538 W\\cdot s^{1/2}\\cdot m^{-2}\\cdot K^{-1} to 378 W\\cdot s^{1/2}m^{-2}\\cdot K^{-1} as the temperature increased, whereas the thermal conductivity remained the same over the temperature range investigated in this study. The obtained results provide insight into the thermal properties of S. chinensis oil between 20°C and 45°C.

What is the copper thin film thickness effect on thermal properties of NiTi/Cu bi-layer?

NASA Astrophysics Data System (ADS)

Fazeli, Sara; Vahedpour, Morteza; Khatiboleslam Sadrnezhaad, Sayed

2017-02-01

Molecular dynamics (MD) simulation was used to study of thermal properties of NiTi/Cu. Embedded atom method (EAM) potentials for describing of inter-atomic interaction and Nose-Hoover thermostat and barostat are employed. The melting of the bi-layers was considered by studying the temperature dependence of the cohesive energy and mean square displacement. To highlight the differences between bi-layers with various copper layer thickness, the effect of copper film thickness on thermal properties containing the cohesive energy, melting point, isobaric heat capacity and latent heat of fusion was estimated. The results show that thermal properties of bi-layer systems are higher than that of their corresponding of pure NiTi. But, these properties of bi-layer systems approximately are independent of copper film thicknesses. The mean square displacement (MSD) results show that, the diffusion coefficients enhance upon increasing of copper film thickness in a linear performance.

Thermal transport in bismuth telluride quintuple layer: mode-resolved phonon properties and substrate effects

PubMed Central

Shao, Cheng; Bao, Hua

2016-01-01

The successful exfoliation of atomically-thin bismuth telluride (Bi2Te3) quintuple layer (QL) attracts tremendous research interest in this strongly anharmonic quasi-two-dimensional material. The thermal transport properties of this material are not well understood, especially the mode-wise properties and when it is coupled with a substrate. In this work, we have performed molecular dynamics simulations and normal mode analysis to study the mode-resolved thermal transport in freestanding and supported Bi2Te3 QL. The detailed mode-wise phonon properties are calculated and the accumulated thermal conductivities with respect to phonon mean free path (MFP) are constructed. It is shown that 60% of the thermal transport is contributed by phonons with MFP longer than 20 nm. Coupling with a-SiO2 substrate leads to about 60% reduction of thermal conductivity. Through varying the interfacial coupling strength and the atomic mass of substrate, we also find that phonon in Bi2Te3 QL is more strongly scattered by interfacial potential and its transport process is less affected by the dynamics of substrate. Our study provides an in-depth understanding of heat transport in Bi2Te3 QL and is helpful in further tailoring its thermal property through nanostructuring. PMID:27263656

Prediction of threshold pain skin temperature from thermal properties of materials in contact.

PubMed

Stoll, A M; Chianta, M A; Piergallini, J R

1982-12-01

Aerospace design engineers have long sought concrete data with respect to the thermal safety of materials in contact with human skin. A series of studies on this subject has been completed and some of the results have been reported earlier. In these studies over 2,000 observations were made of pain threshold during contact with materials at elevated temperatures. Six materials were used representing the full range of thermal properties from good conductors to good insulators. Previous reports gave methods for determining the maximum permissible temperatures for any material in safe contact with bare skin for 1-5 s solely from a knowledge of its thermal properties. This report presents the comparison of the theoretical and experimental contact temperatures at pain threshold and provides a method for deriving the skin temperature productive of threshold pain from the thermal properties of any material within the range of those studies. Ratios reflecting the heat transfer coefficient associated with the materials in contact are related to their thermal properties so that the skin temperature at pain threshold may be determined from that calculated from heat transfer theory. Tabular and graphical representation of these data permits interpolation within the range of properties so that any material of known thermal conductivity, density and specific heat may be assessed with respect to its effect on the skin temperature during contact to the end point of pain. These data, in conjunction with those already reported, constitute a system for the complete assessment of the thermal aspects of practically any material suitable for construction and manufacturing applications with respect to safe contact with human skin.

High pressure elasticity and thermal properties of depleted uranium

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

Jacobsen, M. K., E-mail: mjacobsen@lanl.gov; Velisavljevic, N., E-mail: nenad@lanl.gov

2016-04-28

Studies of the phase diagram of uranium have revealed a wealth of high pressure and temperature phases. Under ambient conditions the crystal structure is well defined up to 100 gigapascals (GPa), but very little information on thermal conduction or elasticity is available over this same range. This work has applied ultrasonic interferometry to determine the elasticity, mechanical, and thermal properties of depleted uranium to 4.5 GPa. Results show general strengthening with applied load, including an overall increase in acoustic thermal conductivity. Further implications are discussed within. This work presents the first high pressure studies of the elasticity and thermal properties ofmore » depleted uranium metal and the first real-world application of a previously developed containment system for making such measurements.« less

Distributed databases for materials study of thermo-kinetic properties

NASA Astrophysics Data System (ADS)

Toher, Cormac

2015-03-01

High-throughput computational materials science provides researchers with the opportunity to rapidly generate large databases of materials properties. To rapidly add thermal properties to the AFLOWLIB consortium and Materials Project repositories, we have implemented an automated quasi-harmonic Debye model, the Automatic GIBBS Library (AGL). This enables us to screen thousands of materials for thermal conductivity, bulk modulus, thermal expansion and related properties. The search and sort functions of the online database can then be used to identify suitable materials for more in-depth study using more precise computational or experimental techniques. AFLOW-AGL source code is public domain and will soon be released within the GNU-GPL license.

Thermophysical Properties of Polymer Materials with High Thermal Conductivity

NASA Astrophysics Data System (ADS)

Lebedev, S. M.; Gefle, O. S.; Dneprovskii, S. N.; Amitov, E. T.

2015-06-01

Results of studies on the main thermophysical properties of new thermally conductive polymer materials are presented. It is shown that modification of polymer dielectrics by micron-sized fillers allows thermally conductive materials with thermal conductivity not less than 2 W/(m K) to be produced, which makes it possible to use such materials as cooling elements of various electrical engineering and semiconductor equipment and devices.

Interlaminar shear strength and thermo-mechanical properties of nano-enhanced composite materials under thermal shock

NASA Astrophysics Data System (ADS)

Gkikas, G.; Douka, D.-D.; Barkoula, N.-M.; Paipetis, A. S.

2013-04-01

The introduction of nanoscaled reinforcement in otherwise conventional fiber reinforced composite materials has opened an exciting new area in composites research. The unique properties of these materials combined with the design versatility of fibrous composites may offer both enhanced mechanical properties and multiple functionalities which has been a focus area of the aerospace technology on the last decades. Due to unique properties of carbon nanofillers such as huge aspect ratio, extremely large specific surface area as well as high electrical and thermal conductivity, Carbon Nanotubes have benn investigated as multifunvtional materials for electrical, thermal and mechanical applications. In this study, MWCNTs were incorporated in a typical epoxy system using a sonicator. The volume of the nanoreinforcement was 0.5 % by weight. Two different levels of sonication amplitude were used, 50% and 100% respectively. After the sonication, the hardener was introduced in the epoxy, and the system was cured according to the recommended cycle. For comparison purposes, specimens from neat epoxy system were prepared. The thermomechanical properties of the materials manufactured were investigated using a Dynamic Mechanical Analyser. The exposed specimens were subjected to thermal shock. Thermal cycles from +30 °C to -30 °C were carried out and each cycle lasted 24 hours. The thermomechanical properties were studied after 30 cycles . Furthermore, the epoxy systems prepared during the first stage of the study were used for the manufacturing of 16 plies quasi isotropic laminates CFRPs. The modified CFRPs were subjected to thermal shock. For comparison reasons unmodified CFRPs were manufactured and subjected to the same conditions. In addition, the interlaminar shear strength of the specimens was studied using 3-point bending tests before and after the thermal shock. The effect of the nanoreinforcement on the environmental degradation is critically assessed.

Laser-assisted manufacturing of super-insulation materials

NASA Astrophysics Data System (ADS)

Wang, Zhen; Zhang, Tao; Park, Byung Kyu; Lee, Woo Il; Hwang, David

2017-02-01

Being lightweight materials with good mechanical and thermal properties, hollow glass micro-particles (HGMPs) have been widely studied for multiple applications. In this study, it is shown that by using reduced binder fraction diluted in solvent, enables minimal contacts among the HGMPs assisted by a natural capillary trend, as confirmed by optical and electron microscope imaging. Such material architecture fabricated in a composite level proves to have enhanced thermal insulation performance through quantitative thermal conductivity measurement. Mechanical strength has also been evaluated in terms of particle-binder bonding by tensile test via in-situ microscope inspection. Effect of laser treatment was examined for further improvement of thermal and mechanical properties by selective binder removal and efficient redistribution of remaining binder components. The fabricated composite materials have potential applications to building insulation materials for their scalable manufacturing nature, improved thermal insulation performance and reasonable mechanical strength. Further studies are needed to understand mechanical and thermal properties of the resulting composites, and key fabrication mechanisms involved with laser treatment of complex multi-component and multi-phase systems.

Space Shuttle Orbiter flight heating rate measurement sensitivity to thermal protection system uncertainties

NASA Technical Reports Server (NTRS)

Bradley, P. F.; Throckmorton, D. A.

1981-01-01

A study was completed to determine the sensitivity of computed convective heating rates to uncertainties in the thermal protection system thermal model. Those parameters considered were: density, thermal conductivity, and specific heat of both the reusable surface insulation and its coating; coating thickness and emittance; and temperature measurement uncertainty. The assessment used a modified version of the computer program to calculate heating rates from temperature time histories. The original version of the program solves the direct one dimensional heating problem and this modified version of The program is set up to solve the inverse problem. The modified program was used in thermocouple data reduction for shuttle flight data. Both nominal thermal models and altered thermal models were used to determine the necessity for accurate knowledge of thermal protection system's material thermal properties. For many thermal properties, the sensitivity (inaccuracies created in the calculation of convective heating rate by an altered property) was very low.

Investigation of Thermophysical Properties of Thermal Degraded Biodiesels

NASA Astrophysics Data System (ADS)

Regatieri, H. R.; Savi, E. L.; Lukasievicz, G. V. B.; Sehn, E.; Herculano, L. S.; Astrath, N. G. C.; Malacarne, L. C.

2018-06-01

Biofuels are an alternative to fossil fuels and can be made from many different raw materials. The use of distinct catalyst and production processes, feedstocks, and types of alcohol results in biofuels with different physical and chemical properties. Even though these diverse options for biodiesel production are considered advantageous, they may pose a setback when quality specifications are considered, since different properties are subject to different reactions during usage, storage and handling. In this work, we present a systematic characterization of biodiesels to investigate how accelerated thermal degradation affects fuel properties. Two different types of biodiesel, commercially obtained from distinct feedstocks, were tested. The thermal degradation process was performed by maintaining the temperature of the sample at 140°C under constant air flux for different times: 0 h, 3 h, 6 h, 9 h, 12 h, 24 h and 36 h. Properties such as density, viscosity, activation energy, volumetric thermal expansion coefficient, gross caloric value, acid value, infrared absorption, and temperature coefficient of the refractive index were used to study the thermal degradation of the biodiesel samples. The results show a significant difference in fuel properties before and after the thermal degradation process suggesting the formation of undesirable compounds. All the properties mentioned above were found to be useful to determine whether a biodiesel sample underwent thermal degradation. Moreover, viscosity and acid value were found to be the most sensitive characteristics to detect the thermal degradation process.

Optimal experimental designs for the estimation of thermal properties of composite materials

NASA Technical Reports Server (NTRS)

Scott, Elaine P.; Moncman, Deborah A.

1994-01-01

Reliable estimation of thermal properties is extremely important in the utilization of new advanced materials, such as composite materials. The accuracy of these estimates can be increased if the experiments are designed carefully. The objectives of this study are to design optimal experiments to be used in the prediction of these thermal properties and to then utilize these designs in the development of an estimation procedure to determine the effective thermal properties (thermal conductivity and volumetric heat capacity). The experiments were optimized by choosing experimental parameters that maximize the temperature derivatives with respect to all of the unknown thermal properties. This procedure has the effect of minimizing the confidence intervals of the resulting thermal property estimates. Both one-dimensional and two-dimensional experimental designs were optimized. A heat flux boundary condition is required in both analyses for the simultaneous estimation of the thermal properties. For the one-dimensional experiment, the parameters optimized were the heating time of the applied heat flux, the temperature sensor location, and the experimental time. In addition to these parameters, the optimal location of the heat flux was also determined for the two-dimensional experiments. Utilizing the optimal one-dimensional experiment, the effective thermal conductivity perpendicular to the fibers and the effective volumetric heat capacity were then estimated for an IM7-Bismaleimide composite material. The estimation procedure used is based on the minimization of a least squares function which incorporates both calculated and measured temperatures and allows for the parameters to be estimated simultaneously.

Calculation of thermal conductivity, thermal diffusivity and specific heat capacity of sedimentary rocks using petrophysical well logs

NASA Astrophysics Data System (ADS)

Fuchs, Sven; Balling, Niels; Förster, Andrea

2015-12-01

In this study, equations are developed that predict for synthetic sedimentary rocks (clastics, carbonates and evapourates) thermal properties comprising thermal conductivity, specific heat capacity and thermal diffusivity. The rock groups are composed of mineral assemblages with variable contents of 15 major rock-forming minerals and porosities of 0-30 per cent. Petrophysical properties and their well-logging-tool-characteristic readings were assigned to these rock-forming minerals and to pore-filling fluids. Relationships are explored between each thermal property and other petrophysical properties (density, sonic interval transit time, hydrogen index, volume fraction of shale and photoelectric absorption index) using multivariate statistics. The application of these relations allows computing continuous borehole profiles for each rock thermal property. The uncertainties in the prediction of each property vary depending on the selected well-log combination. Best prediction is in the range of 2-8 per cent for the specific heat capacity, of 5-10 per cent for the thermal conductivity, and of 8-15 for the thermal diffusivity, respectively. Well-log derived thermal conductivity is validated by laboratory data measured on cores from deep boreholes of the Danish Basin, the North German Basin, and the Molasse Basin. Additional validation of thermal conductivity was performed by comparing predicted and measured temperature logs. The maximum deviation between these logs is <3 °C. The thermal-conductivity calculation allowed an evaluation of the depth range in which the palaeoclimatic effect on the subsurface temperature field can be observed in the North German Basin. This effect reduces the surface heat-flow density by 25 mW m-2.

Mechanical, thermal, and moisture properties of plastics with bean as filler

USDA-ARS?s Scientific Manuscript database

Experiments on polymers using beans as fillers are reported herein. We are looking for desirable mechanical, thermal and moisture properties at economical costs. Poly(lactic acid) (PLA) is studied as the polymeric matrix because it is available and biodegradable. Although the physical properties are...

Thermophysical Properties of Matter - the TPRC Data Series. Volume 14. Master Index - To Materials and Properties

DTIC Science & Technology

1979-01-01

Chloropentalfluoroothane - - - - - - - 11 140 1 - Chloropropane - 69 22 -- - - - Chlorosi lane - 6s 22 - - - - - - a-Chlorotoluens - 6s 22 - - - - - - -Chlorotofuene - 6s...Properties,’ Touloukian, 1 .S. and Ho, C. Y., 197 pp., 1979. To further expand this Data Series and to facilitate current research studies, this Master...Editor Volume 1 . Thermal Conductivity-Metallic Elements and Alloys Volume 2. Thermal Conductivity-Nonmetallic Solids Volume 3. Thermal Conductivity

Thermal properties of graphite oxide, thermally reduced graphene and chemically reduced graphene

NASA Astrophysics Data System (ADS)

Jankovský, Ondřej; Sedmidubský, David; Lojka, Michal; Sofer, Zdeněk

2017-07-01

We compared thermal behavior and other properties of graphite oxide, thermally reduced graphene and chemically reduced graphene. Graphite was oxidized according to the Hofmann method using potassium chlorate as oxidizing agent in strongly acidic environment. In the next step, the formed graphite oxide was chemically or thermally reduced yielding graphene. The mechanism of thermal reduction was studied using STA-MS. Graphite oxide and both thermally and chemically reduced graphenes were analysed by SEM, EDS, elemental combustion analysis, XPS, Raman spectroscopy, XRD and BET. These findings will help for the large scale production of graphene with appropriate chemical composition.

Enhanced mechanical and thermal properties of regenerated cellulose/graphene composite fibers.

PubMed

Tian, Mingwei; Qu, Lijun; Zhang, Xiansheng; Zhang, Kun; Zhu, Shifeng; Guo, Xiaoqing; Han, Guangting; Tang, Xiaoning; Sun, Yaning

2014-10-13

In this study, a wet spinning method was applied to fabricate regenerated cellulose fibers filled with low graphene loading which was systematically characterized by SEM, TEM, FTIR and XRD techniques. Subsequently, the mechanical and thermal properties of the resulting fibers were investigated. With only 0.2 wt% loading of graphene, a ∼ 50% improvement of tensile strength and 25% enhancement of Young's modulus were obtained and the modified Halpin-Tsai model was built to predict the mechanical properties of composite fibers. Thermal analysis of the composite fibers showed remarkably enhanced thermal stability and dynamic heat transfer performance of graphene-filled cellulose composite fiber, also, the presence of graphene oxide can significantly enhance the thermal conductivity of the composite fiber. This work provided a facile way to improve mechanical and thermal properties of regenerated cellulose fibers. The resultant composite fibers have potential application in thermal insulation and reinforced fibrous materials. Copyright © 2014 Elsevier Ltd. All rights reserved.

Thermal rectification in thin films driven by gradient grain microstructure

NASA Astrophysics Data System (ADS)

Cheng, Zhe; Foley, Brian M.; Bougher, Thomas; Yates, Luke; Cola, Baratunde A.; Graham, Samuel

2018-03-01

As one of the basic components of phononics, thermal rectifiers transmit heat current asymmetrically similar to electronic rectifiers in microelectronics. Heat can be conducted through them easily in one direction while being blocked in the other direction. In this work, we report a thermal rectifier that is driven by the gradient grain structure and the inherent gradient in thermal properties as found in these materials. To demonstrate their thermal rectification properties, we build a spectral thermal conductivity model with complete phonon dispersion relationships using the thermophysical properties of chemical vapor deposited (CVD) diamond films which possess gradient grain microstructures. To explain the observed significant thermal rectification, the temperature and thermal conductivity distribution are studied. Additionally, the effects of temperature bias and film thickness are discussed, which shed light on tuning the thermal rectification based on the gradient microstructures. Our results show that the columnar grain microstructure makes CVD materials unique candidates for mesoscale thermal rectifiers without a sharp temperature change.

Thermal properties for the thermal-hydraulics analyses of the BR2 maximum nominal heat flux.

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

Dionne, B.; Kim, Y. S.; Hofman, G. L.

2011-05-23

This memo describes the assumptions and references used in determining the thermal properties for the various materials used in the BR2 HEU (93% enriched in {sup 235}U) to LEU (19.75% enriched in {sup 235}U) conversion feasibility analysis. More specifically, this memo focuses on the materials contained within the pressure vessel (PV), i.e., the materials that are most relevant to the study of impact of the change of fuel from HEU to LEU. This section is regrouping all of the thermal property tables. Section 2 provides a summary of the thermal properties in form of tables while the following sections presentmore » the justification of these values. Section 3 presents a brief background on the approach used to evaluate the thermal properties of the dispersion fuel meat and specific heat capacity. Sections 4 to 7 discuss the material properties for the following materials: (i) aluminum, (ii) dispersion fuel meat (UAlx-Al and U-7Mo-Al), (iii) beryllium, and (iv) stainless steel. Section 8 discusses the impact of irradiation on material properties. Section 9 summarizes the material properties for typical operating temperatures. Appendix A elaborates on how to calculate dispersed phase's volume fraction. Appendix B shows the evolution of the BR2 maximum heat flux with burnup.« less

Physical properties (particle size, rock abundance) from thermal infrared remote observations: Implications for Mars landing sites

NASA Technical Reports Server (NTRS)

Christensen, P. R.; Edgett, Kenneth S.

1994-01-01

Critical to the assessment of potential sites for the 1997 Pathfinder landing is estimation of general physical properties of the martian surface. Surface properties have been studied using a variety of spacecraft and earth-based remote sensing observations, plus in situ studies at the Viking lander sites. Because of their value in identifying landing hazards and defining scientific objectives, we focus this discussion on thermal inertia and rock abundance derived from middle-infrared (6 to 30 microns) observations. Used in conjunction with other datasets, particularly albedo and Viking orbiter images, thermal inertia and rock abundance provide clues about the properties of potential Mars landing sites.

Graphene-magnesium nanocomposite: An advanced material for aerospace application

NASA Astrophysics Data System (ADS)

Das, D. K.; Sarkar, Jit

2018-02-01

This work focuses on the analytical study of mechanical and thermal properties of a nanocomposite that can be obtained by reinforcing graphene in magnesium. The estimated mechanical and thermal properties of graphene-magnesium nanocomposite are much higher than magnesium and other existing alloys used in aerospace materials. We also altered the weight percentage of graphene in the composite and observed mechanical and thermal properties of the composite increase with increase in concentration of graphene reinforcement. The Young’s modulus and thermal conductivity of graphene-magnesium nanocomposite are found to be ≥165 GPa and ≥175 W/mK, respectively. Nanocomposite material with desired properties for targeted applications can also be designed by our analytical modeling technique. This graphene-magnesium nanocomposite can be used for designing improved aerospace structure systems with enhanced properties.

Low temperature thermoelectric properties of p-type doped single-crystalline SnSe

NASA Astrophysics Data System (ADS)

Wang, Si; Hui, Si; Peng, Kunling; Bailey, Trevor P.; Liu, Wei; Yan, Yonggao; Zhou, Xiaoyuan; Tang, Xinfeng; Uher, Ctirad

2018-04-01

SnSe single crystals have been widely studied lately as a result of their record high ZT and controversial low thermal conductivity. Much research has focused on the high-temperature properties of single crystals and polycrystalline SnSe, but few studies were carried out on the low-temperature properties of doped single-crystalline SnSe. To study the mechanism of the charge carrier and phonon scattering, and to eliminate the ambiguity of the high temperature thermal conductivity measurement, we performed low temperature transport characterization of Na-doped and Ag-doped single-crystalline SnSe by a longitudinal steady-state technique. The electronic transport property measurements suggest that Na is a more efficient p-type dopant in SnSe than Ag. In the thermal conductivity data, we observe pronounced dielectric peak around 10 K with magnitude dependent on the doping level. In the p-type doped samples, we found that our room temperature lattice thermal conductivities (>1.74 W m-1 K-1) are in general higher than those previously reported. Based on these findings, our study implies that the lattice thermal conductivity values of doped and pure single-crystalline SnSe were underestimated.

Effect of electron beam irradiation on thermal and mechanical properties of epoxy polymer

NASA Astrophysics Data System (ADS)

Nguyen, A. T.; Visakh, P. M.; Nazarenko, O. B.; Chandran, C. S.; Melnikova, T. V.

2017-01-01

This study investigates the thermal and mechanical properties of epoxy polymer after exposure to different doses of electron beam irradiation. The epoxy polymer was prepared using epoxy-diane resin ED-20 cured by polyethylenepolyamine. The irradiation of the samples was carried out with doses of 30, 100 and 300 kGy. The effects of doses on thermal and mechanical properties of the epoxy polymer were investigated by the methods of thermal gravimetric analysis, tensile test, and dynamic mechanical analysis. The thermal properties of the epoxy polymer slightly increased after irradiation at the heating in air. The tensile strength and Young’s modulus of the epoxy polymer increased by the action of electron beam up to dose of 100 kGy and then decreased. The elongation at break decreased with increasing the irradiation dose.

Mechanical and thermal properties of bulk ZrB2

NASA Astrophysics Data System (ADS)

Nakamori, Fumihiro; Ohishi, Yuji; Muta, Hiroaki; Kurosaki, Ken; Fukumoto, Ken-ichi; Yamanaka, Shinsuke

2015-12-01

ZrB2 appears to have formed in the fuel debris at the Fukushima Daiichi nuclear disaster site, through the reaction between Zircaloy cladding materials and the control rod material B4C. Since ZrB2 has a high melting point of 3518 K, the ceramic has been widely studied as a heat-resistant material. Although various studies on the thermochemical and thermophysical properties have been performed for ZrB2, significant differences exist in the data, possibly due to impurities or the porosity within the studied samples. In the present study, we have prepared a ZrB2 bulk sample with 93.1% theoretical density by sintering ZrB2 powder. On this sample, we have comprehensively examined the thermal and mechanical properties of ZrB2 by the measurement of specific heat, ultrasonic sound velocities, thermal diffusivity, and thermal expansion. Vickers hardness and fracture toughness were also measured and found to be 13-23 GPa and 1.8-2.8 MPa m0.5, respectively. The relationships between these properties were carefully examined in the present study.

Thermal diffusivity determination using heterodyne phase insensitive transient grating spectroscopy

NASA Astrophysics Data System (ADS)

Dennett, Cody A.; Short, Michael P.

2018-06-01

The elastic and thermal transport properties of opaque materials may be measured using transient grating spectroscopy (TGS) by inducing and monitoring periodic excitations in both reflectivity and surface displacement. The "phase grating" response encodes both properties of interest, but complicates quantitative analysis by convolving temperature dynamics with surface displacement dynamics. Thus, thermal transport characteristics are typically determined using the "amplitude grating" response to isolate the surface temperature dynamics. However, this signal character requires absolute heterodyne phase calibration and contains no elastic property information. Here, a method is developed by which phase grating TGS measurements may be consistently analyzed to determine thermal diffusivity with no prior knowledge of the expected properties. To demonstrate this ability, the wavelength-dependent 1D effective thermal diffusivity of pure germanium is measured using this type of response and found to be consistent with theoretical predictions made by solving the Boltzmann transport equation. This ability to determine the elastic and thermal properties from a single set of TGS measurements will be particularly advantageous for new in situ implementations of the technique being used to study dynamic materials systems.

THERMAL PROPERTIES AND HEATING AND COOLING DURABILITY OF REACTOR SHIELDING CONCRETE (in Japanese)

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

Hosoi, J.; Chujo, K.; Saji, K.

1959-01-01

A study was made of the thermal properties of various concretes made of domestic raw materials for radiation shields of a power reactor and of a high- flux research reactor. The results of measurements of thermal expansion coefficient, specific heat, thermal diffusivity, thermal conductivity, cyclical heating, and cooling durability are described. Relationships between thermal properties and durability are discussed and several photographs of the concretes are given. It is shown that the heating and cooling durability of such a concrete which has a large thermal expansion coefficient or a considerable difference between the thermal expansion of coarse aggregate and themore » one of cement mortar part or aggregates of lower strength is very poor. The decreasing rates of bending strength and dynamical modulus of elasticity and the residual elongation of the concrete tested show interesting relations with the modified thermal stress resistance factor containing a ratio of bending strength and thermal expansion coefficient. The thermal stress resistance factor seems to depend on the conditions of heat transfer on the surface and on heat release in the concrete. (auth)« less

Optical, electrochemical and thermal properties of Mn2+ doped CdS nanoparticles

NASA Astrophysics Data System (ADS)

Muruganandam, S.; Anbalagan, G.; Murugadoss, G.

2015-08-01

Mn2+ doped (1-5 and 10 %) CdS nanoparticles have been synthesized by the chemical precipitation method using polyvinylpyrrolidone as a capping agent. The particle size, morphology and optical properties have been studied by X-ray powder diffraction, transmission electron microscopy, UV-Visible and photoluminescence spectroscopy. Powder diffraction data have confirmed that the crystallite size is around 2-5 nm. The band gap of the nanoparticles has been calculated using UV-Visible absorption spectra. An optimum concentration, Mn2+ (3 %) has been selected by optical study. The functional groups of the capping agent have been identified by fourier transform infrared spectroscopy study. The presence of dopant (Mn2+) has been confirmed by electron paramagnetic resonance spectroscopy. Thermal properties of CdS:Mn2+ have been analyzed using thermogravimetric-differential thermal analyser. The electrochemical properties of the undoped and doped samples have been studied by cyclic voltammetry for electrode applications. In addition, magnetic properties of Mn2+ doped CdS have been studied using a vibrating sample magnetometer.

Thermophysical Properties of Sn-Ag-Cu Based Pb-Free Solders

NASA Astrophysics Data System (ADS)

Kim, Sok Won; Lee, Jaeran; Jeon, Bo-Min; Jung, Eun; Lee, Sang Hyun; Kang, Kweon Ho; Lim, Kwon Taek

2009-06-01

Lead-tin (Pb-Sn) alloys are the dominant solders used for electronic packaging because of their low cost and superior properties required for interconnecting electronic components. However, increasing environmental and health concerns over the toxicity of lead, combined with global legislation to limit the use of Pb in manufactured products, have led to extensive research and development studies of lead-free solders. The Sn-Ag-Cu ternary eutectic alloy is considered to be one of the promising alternatives. Except for thermal properties, much research on several properties of Sn-Ag-Cu alloy has been performed. In this study, five Sn-xAg-0.5Cu alloys with variations of Ag content x of 1.0 mass%, 2.5 mass%, 3.0 mass%, 3.5 mass%, and 4.0 mass% were prepared, and their thermal diffusivity and specific heat were measured from room temperature to 150 °C, and the thermal conductivity was calculated using the measured thermal diffusivity, specific heat, and density values. Also, the linear thermal expansion was measured from room temperature to 170 °C. The results show that Sn-3.5Ag-0.5Cu is the best candidate because it has a maximum thermal conductivity and a low thermal expansion, which are the ideal conditions to be a proper packaging alloy for effective cooling and thermostability.

Effect of Functionalization of Graphene Nanoplatelets on the Mechanical and Thermal Properties of Silicone Rubber Composites

PubMed Central

Zhang, Guangwu; Wang, Fuzhong; Dai, Jing; Huang, Zhixiong

2016-01-01

This study investigated the effect of silane and surfactant treatments of graphene nanoplatelets (GnPs) on the mechanical and thermal properties of silicone rubber (SR) composites. GnPs were modified with aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), and Triton X-100, and then the pristine GnPs and functionalized GnPs were individually incorporated into the SR. Compared with the pristine GnP/SR composite, the composites reinforced with modified GnP showed better tensile strength, elongation at break, and thermal conductivity properties due to better dispersion of modified GnPs and stronger interfacial interactions between the modified GnPs and matrix. The mechanical properties and thermal conductivity of the VTMS-GnP/SR composite were comparable to the properties of the Triton-GnP counterpart, but better than that of the APTES-GnP/SR composite. In addition, the VTMS-GnP/SR composite demonstrated the highest thermal stability and crystallization temperature among the four types of composites. The remarkable improvement of mechanical and thermal properties of the VTMS-GnP/SR composite was mainly due to the covalent linkage of VTMS-GnP with SR. The VTMS treatment was a more appropriate modification of GnP particles to improve the multifunctional properties of SR. PMID:28787891

Effect of Functionalization of Graphene Nanoplatelets on the Mechanical and Thermal Properties of Silicone Rubber Composites.

PubMed

Zhang, Guangwu; Wang, Fuzhong; Dai, Jing; Huang, Zhixiong

2016-02-02

This study investigated the effect of silane and surfactant treatments of graphene nanoplatelets (GnPs) on the mechanical and thermal properties of silicone rubber (SR) composites. GnPs were modified with aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), and Triton X-100, and then the pristine GnPs and functionalized GnPs were individually incorporated into the SR. Compared with the pristine GnP/SR composite, the composites reinforced with modified GnP showed better tensile strength, elongation at break, and thermal conductivity properties due to better dispersion of modified GnPs and stronger interfacial interactions between the modified GnPs and matrix. The mechanical properties and thermal conductivity of the VTMS-GnP/SR composite were comparable to the properties of the Triton-GnP counterpart, but better than that of the APTES-GnP/SR composite. In addition, the VTMS-GnP/SR composite demonstrated the highest thermal stability and crystallization temperature among the four types of composites. The remarkable improvement of mechanical and thermal properties of the VTMS-GnP/SR composite was mainly due to the covalent linkage of VTMS-GnP with SR. The VTMS treatment was a more appropriate modification of GnP particles to improve the multifunctional properties of SR.

Thermal Properties for the Thermal-Hydraulics Analyses of the BR2 Maximum Nominal Heat Flux

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

Dionne, B.; Bergeron, A.; Licht, J. R.

2015-02-01

This memo describes the assumptions and references used in determining the thermal properties for the various materials used in the BR2 HEU (93% enriched in 235U) to LEU (19.75% enriched in 235U) conversion feasibility analysis. More specifically, this memo focuses on the materials contained within the pressure vessel (PV), i.e., the materials that are most relevant to the study of impact of the change of fuel from HEU to LEU. Section 2 provides a summary of the thermal properties in the form of tables while the following sections and appendices present the justification of these values. Section 3 presents amore » brief background on the approach used to evaluate the thermal properties of the dispersion fuel meat and specific heat capacity. Sections 4 to 7 discuss the material properties for the following materials: i) aluminum, ii) dispersion fuel meat (UAlx-Al and U-7Mo-Al), iii) beryllium, and iv) stainless steel. Section 8 discusses the impact of irradiation on material properties. Section 9 summarizes the material properties for typical operating temperatures. Appendix A elaborates on how to calculate dispersed phase’s volume fraction. Appendix B provides a revised methodology for determining the thermal conductivity as a function of burnup for HEU and LEU.« less

Radiative-conductive inverse problem for lumped parameter systems

NASA Astrophysics Data System (ADS)

Alifanov, O. M.; Nenarokomov, A. V.; Gonzalez, V. M.

2008-11-01

The purpose of this paper is to introduce a iterative regularization method in the research of radiative and thermal properties of materials with applications in the design of Thermal Control Systems (TCS) of spacecrafts. In this paper the radiative and thermal properties (emissivity and thermal conductance) of a multilayered thermal-insulating blanket (MLI), which is a screen-vacuum thermal insulation as a part of the (TCS) for perspective spacecrafts, are estimated. Properties of the materials under study are determined in the result of temperature and heat flux measurement data processing based on the solution of the Inverse Heat Transfer Problem (IHTP) technique. Given are physical and mathematical models of heat transfer processes in a specimen of the multilayered thermal-insulating blanket located in the experimental facility. A mathematical formulation of the inverse heat conduction problem is presented too. The practical testing were performed for specimen of the real MLI.

Characterization of Polyester Matrix Reinforced with Banana Fibers Thermal Properties by Photoacoustic Technique

NASA Astrophysics Data System (ADS)

de Assis, Foluke S.; Netto, Pedro A.; Margem, Frederico M.; Monteiro, Artur R. P. Junior Sergio N.

Synthetic fibers are being replaced gradually by natural materials such as lignocellulosic fibers. Compared to synthetic fibers, natural fibers have shown advantages in technical aspects such as environmental and economic. So there is a growing international interest in the use of those fibers. The banana fiber presents significant properties to be studied, but until now few thermal properties on banana fiber as reinforcement of polyester matrix were performed. The present work had as its objective to investigate, by photoacoustic spectroscopy and photothermal techniques the thermal properties of diffusivity, specific heat capacity and conductivity for polyester composites reinforced with banana fibers. In the polyester matrix will be added up to 30% in volume of continuous and aligned banana fibers. These values show that the incorporation of banana fibers in the polyester matrix changes its thermal properties.

Multifunctional cyanate ester nanocomposites reinforced by hexagonal boron nitride after noncovalent biomimetic functionalization.

PubMed

Wu, Hongchao; Kessler, Michael R

2015-03-18

Boron nitride (BN) reinforced polymer nanocomposites have attracted a growing research interest in the microelectronic industry for their uniquely thermal conductive but electrical insulating properties. To overcome the challenges in surface functionalization, in this study, hexagonal boron nitride (h-BN) nanoparticles were noncovalently modified with polydopamine in a solvent-free aqueous condition. The strong π-π interaction between the hexagonal structural BN and aromatic dopamine molecules facilitated 15 wt % polydopamine encapsulating the nanoparticles. High-performance bisphenol E cyanate ester (BECy) was incorporated by homogeneously dispersed h-BN at different loadings and functionalities to investigate their effects on thermo-mechanical, dynamic-mechanical, and dielectric properties, as well as thermal conductivity. Different theoretical and empirical models were successfully applied to predict thermal and dielectric properties of h-BN/BECy nanocomposites. Overall, the prepared h-BN/BECy nanocomposites exhibited outstanding performance in dimensional stability, dynamic-mechanical properties, and thermal conductivity, together with the controllable dielectric property and preserved thermal stability for high-temperature applications.

Ultrasonication effect on thermophysical properties of Al2O3 nanofluids

NASA Astrophysics Data System (ADS)

Shah, Janki; Ranjan, Mukesh; Gupta, Sanjeev K.; Sonvane, Yogesh

2018-04-01

In this work, we studied the thermal conductivity and viscosity of alumina nanofluids for their excellent thermophysical properties. Here we considered the bath sonication time effects on thermal conductivity, viscosity and zeta potential of alumina nanofluid with different concentration (0.2, 0.3, 0.4, 0.5 Vol.%). We observed that the thermal conductivity of the nanofluids increased nonlinearly with an increased sonication time/energy as well as viscosity decreased. An enhancement of the thermal conductivity and viscosity at higher particle concentration is also observed. The results indicate that thermal properties of Al2O3 nanofluid enhances as the sonication time increases and prove Al2O3 nanofluid is one of the best thermostable heat transfer fluids compared to conventional cooling fluids.

The effects of stacking sequence and thermal cycling on the flexural properties of laminate composites of aluminium-epoxy/basalt-glass fibres

NASA Astrophysics Data System (ADS)

Abdollahi Azghan, Mehdi; Eslami-Farsani, Reza

2018-02-01

The current study aimed at investigating the effects of different stacking sequences and thermal cycling on the flexural properties of fibre metal laminates (FMLs). FMLs were composed of two aluminium alloy 2024-T3 sheets and epoxy polymer-matrix composites that have four layers of basalt and/or glass fibres with five different stacking sequences. For FML samples the thermal cycle time was about 6 min for temperature cycles from 25 °C to 115 °C. Flexural properties of samples evaluated after 55 thermal cycles and compared to non-exposed samples. Surface modification of aluminium performed by electrochemical treatment (anodizing) method and aluminium surfaces have been examined by scanning electron microscopy (SEM). Also, the flexural failure mechanisms investigated by the optical microscope study of fractured surfaces. SEM images indicated that the porosity of the aluminium surface increased after anodizing process. The findings of the present study showed that flexural modulus were maximum for basalt fibres based FML, minimum for glass fibres based FML while basalt/glass fibres based FML lies between them. Due to change in the failure mechanism of basalt/glass fibres based FMLs that have glass fibres at outer layer of the polymer composite, the flexural strength of this FML is lower than glass and basalt fibres based FML. After thermal cycling, due to the good thermal properties of basalt fibres, flexural properties of basalt fibres based FML structures decreased less than other composites.

Thermal stability of detonation-produced micro and nanodiamonds

NASA Astrophysics Data System (ADS)

Efremov, V. P.; Zakatilova, E. I.; Maklashova, I. V.; Shevchenko, N. V.

2018-01-01

Detonation nanodiamonds are produced at utilization of high explosives. When an explosive blasts in a water environment, the detonation products contain microdiamonds, and in a gaseous medium, nanodiamonds. It is known that with decreasing size the influence of the surface energy of particles on their properties increases. Thus, it is interesting to compare the properties of detonation nano and microdiamonds. In this study, we have examined the thermal stability of diamond materials by synchronous thermal analysis. The experiments were performed at atmospheric pressure in argon flow for different heating rates in a range from room temperature to 1500 °C. Samples of initial and annealed micro and nanomaterials were studied using electron microscopy, x-ray and x-ray-fluorescence analysis. It was established that thermal and structural properties of micro and nanodiamonds differ substantially.

High pressure elasticity and thermal properties of depleted uranium

DOE PAGES

Jacobsen, M. K.; Velisavljevic, N.

2016-04-28

Studies of the phase diagram of uranium have revealed a wealth of high pressure and temperature phases. Under ambient conditions the crystal structure is well defined up to 100 gigapascals (GPa), but very little information on thermal conduction or elasticity is available over this same range. This work has applied ultrasonic interferometry to determine the elasticity, mechanical, and thermal properties of depleted uranium to 4.5 GPa. Results show general strengthening with applied load, including an overall increase in acoustic thermal conductivity. Further implications are discussed within. Lastly, this work presents the first high pressure studies of the elasticity and thermalmore » properties of depleted uranium metal and the first real-world application of a previously developed containment system for making such measurements.« less

Ultrasonic and micromechanical study of damage and elastic properties of SiC/RBSN ceramic composites. [Reaction Bonded Silicon Nitride

NASA Technical Reports Server (NTRS)

Chu, Y. C.; Hefetz, M.; Rokhlin, S. I.; Baaklini, G. Y.

1992-01-01

Ultrasonic techniques are employed to develop methods for nondestructive evaluation of elastic properties and damage in SiC/RBSN composites. To incorporate imperfect boundary conditions between fibers and matrix into a micromechanical model, a model of fibers having effective anisotropic properties is introduced. By inverting Hashin's (1979) microstructural model for a composite material with microscopic constituents the effective fiber properties were found from ultrasonic measurements. Ultrasonic measurements indicate that damage due to thermal shock is located near the surface, so the surface wave is most appropriate for estimation of the ultimate strength reduction and critical temperature of thermal shock. It is concluded that bonding between laminates of SiC/RBSN composites is severely weakened by thermal oxidation. Generally, nondestructive evaluation of thermal oxidation effects and thermal shock shows good correlation with measurements previously performed by destructive methods.

Strain Modulation of Electronic and Heat Transport Properties of Bilayer Boronitrene

NASA Astrophysics Data System (ADS)

Yang, Ming; Sun, Fang-Yuan; Wang, Rui-Ning; Zhang, Hang; Tang, Da-Wei

2017-10-01

Strain engineering has been proven as an effective approach to modify electronic and thermal properties of materials. Recently, strain effects on two-dimensional materials have become important relevant topics in this field. We performed density functional theory studies on the electronic and heat transport properties of bilayer boronitrene samples under an isotropic strain. We demonstrate that the strain will reduce the band gap width but keep the band gap type robust and direct. The strain will enhance the thermal conductivity of the system because of the increase in specific heat. The thermal conductivity was studied as a function of the phonon mean-free path.

Enhancement of thermoelectric properties in the Nb–Co–Sn half-Heusler/Heusler system through spontaneous inclusion of a coherent second phase

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

Buffon, Malinda L. C., E-mail: mandibuffon@mrl.ucsb.edu; Verma, Nisha; Lamontagne, Leo

Half-Heusler XYZ compounds with an 18 valence electron count are promising thermoelectric materials, being thermally and chemically stable, deriving from relatively earth-abundant components, and possessing appropriate electrical transport properties. The typical drawback with this family of compounds is their high thermal conductivity. A strategy for reducing thermal conductivity is through the inclusion of secondary phases designed to minimize negative impact on other properties. Here, we achieve this through the addition of excess Co to half-Heusler NbCoSn, which introduces precipitates of a semi-coherent NbCo{sub 2}Sn Heusler phase. A series of NbCo{sub 1+x}Sn materials are characterized here using X-ray and neutron diffractionmore » studies and electron microscopy. Electrical and thermal transport measurements and electronic structure calculations are used to understand property evolution. We find that annealing has an important role to play in determining antisite ordering and properties. Antisite disorder in the as-prepared samples improves thermoelectric performance through the reduction of thermal conductivity, but annealing during the measurement degrades properties to resemble those of the annealed samples. Similar to the more widely studied TiNi{sub 1+x}Sn system, Co addition to the NbCoSn phase results in improved thermoelectric performance through a decrease in thermal conductivity which results in a 20% improvement in the thermoelectric figure of merit, zT.« less

Thermal properties of alkali-activated aluminosilicates with CNT admixture

NASA Astrophysics Data System (ADS)

Zmeskal, Oldrich; Trhlikova, Lucie; Fiala, Lukas; Florian, Pavel; Cerny, Robert

2017-07-01

Material properties of electrically conductive cement-based materials with increased attention paid on electric and thermal properties were often studied in the last years. Both electric and thermal properties play an important role thanks to their possible utilization in various practical applications (e.g. snow-melting systems or building structures monitoring systems without the need of an external monitoring system). The DC/AC characteristics depend significantly on the electrical resistivity and the electrical capacity of bulk materials. With respect to the DC/AC characteristics of cement-based materials, such materials can be basically classified as electric insulators. In order to enhance them, various conductive admixtures such as those based on different forms of carbon, can be used. Typical representatives of carbon-based admixtures are carbon nanotubes (CNT), carbon fibers (CF), graphite powder (GP) and carbon black (CB). With an adequate amount of such admixtures, electric properties significantly change and new materials with higher added value can be prepared. However, other types of materials can be enhanced in the same way. Alkali-activated aluminosilicates (AAA) based on blast furnace slag are materials with high compressive strength comparable with cement-based materials. Moreover, the price of slag is lower than of Portland cement. Therefore, this paper deals with the study of thermal properties of this promising material with different concentrations of CNT. Within the paper a simple method of basic thermal parameters determination based on the thermal transient response to a heat power step is presented.

Fluid property measurements study

NASA Technical Reports Server (NTRS)

Devaney, W. E.

1976-01-01

Fluid properties of refrigerant-21 were investigated at temperatures from the freezing point to 423 Kelvin and at pressures to 1.38 x 10 to the 8th power N/sq m (20,000 psia). The fluid properties included were: density, vapor pressure, viscosity, specific heat, thermal conductivity, thermal expansion coefficient, freezing point and bulk modulus. Tables of smooth values are reported.

Optical property degradation of anodic coatings in the Space Station low earth orbit

NASA Technical Reports Server (NTRS)

David, Kaia E.; Babel, Hank W.

1992-01-01

The anodic coatings and optical properties to be used for passive thermal control of the SSF are studied. Particular attention is given to the beginning-of-life optical properties for aluminum alloys suitable for structural and radiator applications, the statistical variation in the beginning-of-life properties, and estimates of the end-of-life properties of the alloys based on ultraviolet radiation testing and flight test results. It is concluded that anodic coatings can be used for thermal control of long life, low earth orbit spacecraft. Some use restrictions are defined for specific cases. Anodic coatings have been selected as baseline thermal control coating for large portions of the SSF.

Characterization of the mechanical and physical properties of TD-NiCr (Ni-20Cr-2ThO2) alloy sheet

NASA Technical Reports Server (NTRS)

Fritz, L. J.; Koster, W. P.; Taylor, R. E.

1973-01-01

Sheets of TD-NiCr processed using techniques developed to produce uniform material were tested to supply mechanical and physical property data. Two heats each of 0.025 and 0.051 cm thick sheet were tested. Mechanical properties evaluated included tensile, modulus of elasticity, Poisson's Ratio, compression, creep-rupture, creep strength, bearing strength, shear strength, sharp notch and fatigue strength. Test temperatures covered the range from ambient to 1589K. Physical properties were also studied as a function of temperature. The physical properties measured were thermal conductivity, linear thermal expansion, specific heat, total hemispherical emittance, thermal diffusivity, and electrical conductivity.

Parameter Identification Of Multilayer Thermal Insulation By Inverse Problems

NASA Astrophysics Data System (ADS)

Nenarokomov, Aleksey V.; Alifanov, Oleg M.; Gonzalez, Vivaldo M.

2012-07-01

The purpose of this paper is to introduce an iterative regularization method in the research of radiative and thermal properties of materials with further applications in the design of Thermal Control Systems (TCS) of spacecrafts. In this paper the radiative and thermal properties (heat capacity, emissivity and thermal conductance) of a multilayered thermal-insulating blanket (MLI), which is a screen-vacuum thermal insulation as a part of the (TCS) for perspective spacecrafts, are estimated. Properties of the materials under study are determined in the result of temperature and heat flux measurement data processing based on the solution of the Inverse Heat Transfer Problem (IHTP) technique. Given are physical and mathematical models of heat transfer processes in a specimen of the multilayered thermal-insulating blanket located in the experimental facility. A mathematical formulation of the IHTP, based on sensitivity function approach, is presented too. The practical testing was performed for specimen of the real MLI. This paper consists of recent researches, which developed the approach suggested at [1].

Measurement of Thermal Properties of Triticale Starch Films Using Photothermal Techniques

NASA Astrophysics Data System (ADS)

Correa-Pacheco, Z. N.; Cruz-Orea, A.; Jiménez-Pérez, J. L.; Solorzano-Ojeda, S. C.; Tramón-Pregnan, C. L.

2015-06-01

Nowadays, several commercially biodegradable materials have been developed with mechanical properties similar to those of conventional petrochemical-based polymers. These materials are made from renewable sources such as starch, cellulose, corn, and molasses, being very attractive for numerous applications in the plastics, food, and paper industries, among others. Starches from maize, rice, wheat, and potato are used in the food industry. However, other types of starches are not used due to their low protein content, such as triticale. In this study, starch films, processed using a single screw extruder with different compositions, were thermally and structurally characterized. The thermal diffusivity, thermal effusivity, and thermal conductivity of the biodegradable films were determined using photothermal techniques. The thermal diffusivity was measured using the open photoacoustic cell technique, and the thermal effusivity was obtained by the photopyroelectric technique in an inverse configuration. The results showed differences in thermal properties for the films. Also, the films microstructures were observed by scanning electron microscopy, transmission electron microscopy, and the crystalline structure determined by X-ray diffraction.

Thermal conductivity model for nanofiber networks

NASA Astrophysics Data System (ADS)

Zhao, Xinpeng; Huang, Congliang; Liu, Qingkun; Smalyukh, Ivan I.; Yang, Ronggui

2018-02-01

Understanding thermal transport in nanofiber networks is essential for their applications in thermal management, which are used extensively as mechanically sturdy thermal insulation or high thermal conductivity materials. In this study, using the statistical theory and Fourier's law of heat conduction while accounting for both the inter-fiber contact thermal resistance and the intrinsic thermal resistance of nanofibers, an analytical model is developed to predict the thermal conductivity of nanofiber networks as a function of their geometric and thermal properties. A scaling relation between the thermal conductivity and the geometric properties including volume fraction and nanofiber length of the network is revealed. This model agrees well with both numerical simulations and experimental measurements found in the literature. This model may prove useful in analyzing the experimental results and designing nanofiber networks for both high and low thermal conductivity applications.

Thermal conductivity model for nanofiber networks

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

Zhao, Xinpeng; Huang, Congliang; Liu, Qingkun

Understanding thermal transport in nanofiber networks is essential for their applications in thermal management, which are used extensively as mechanically sturdy thermal insulation or high thermal conductivity materials. In this study, using the statistical theory and Fourier's law of heat conduction while accounting for both the inter-fiber contact thermal resistance and the intrinsic thermal resistance of nanofibers, an analytical model is developed to predict the thermal conductivity of nanofiber networks as a function of their geometric and thermal properties. A scaling relation between the thermal conductivity and the geometric properties including volume fraction and nanofiber length of the network ismore » revealed. This model agrees well with both numerical simulations and experimental measurements found in the literature. This model may prove useful in analyzing the experimental results and designing nanofiber networks for both high and low thermal conductivity applications.« less

Thermal and Tribological Properties of Jatropha Oil as Additive in Commercial Oil

NASA Astrophysics Data System (ADS)

Gallardo-Hernández, E. A.; Lara-Hernández, G.; Nieto-Camacho, F.; Domínguez-Pacheco, A.; Cruz-Orea, A.; Hernández-Aguilar, C.; Contreras-Gallegos, E.; Torres, M. Vite; Flores-Cuautle, J. J. A.

2017-04-01

The recent use that has been given to bio-oil as an additive, in a commercial engine oil, raises the necessity to study its physical properties. The present study is aimed to obtain thermal properties of blends made with Jatropha-Curcas L. Oil, Crude, and Refined, at different concentrations using SAE40W oil (EO) as a lubricant base. By using photothermal techniques, thermal effusivity and diffusivity were obtained. The obtained results show that thermal effusivity increases from 455 Ws^{1/2}{\\cdot }m^{-2}{\\cdot }K^{-1} to 520 Ws^{1/2}{\\cdot }m^{-2}{\\cdot }K^{-1} as the percentage of additive increases as well, whereas thermal diffusivity values range from 7× 10^{-8}m2{\\cdot }s^{-1} to 10× 10^{-8}m2{\\cdot }s^{-1}. In the present study, four balls test was used in order to obtain friction coefficient and wear scar values for studied samples, the obtained results point out that in general refined Jatropha-Curcas L. oil presents smaller wear scars than the crude one.

Thermal Expansion and Thermal Conductivity of Rare Earth Silicates

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Lee, Kang N.; Bansal, Narottam P.

2006-01-01

Rare earth silicates are considered promising candidate materials for environmental barrier coatings applications at elevated temperature for ceramic matrix composites. High temperature thermophysical properties are of great importance for coating system design and development. In this study, the thermal expansion and thermal conductivity of hot-pressed rare earth silicate materials were characterized at temperatures up to 1400 C. The effects of specimen porosity, composition and microstructure on the properties were also investigated. The materials processing and testing issues affecting the measurements will also be discussed.

Electro-optical and physic-mechanical properties of colored alicyclic polyimide

NASA Astrophysics Data System (ADS)

Kravtsova, V.; Umerzakova, M.; Korobova, N.; Timoshenkov, S.; Timoshenkov, V.; Orlov, S.; Iskakov, R.; Prikhodko, O.

2016-09-01

Main optical, thermal and mechanical properties of new compositions based on alicyclic polyimide and active bright red 6C synthetic dye have been studied. It was shown that the transmission ratio of the new material in the region of 400-900 nm and 2.0 wt.% dye concentration was around 60-70%. Thermal, mechanical and electrical properties of new colored compositions were comparable with the properties of original polyimide.

Nonreciprocal Thermal Material by Spatiotemporal Modulation

NASA Astrophysics Data System (ADS)

Torrent, Daniel; Poncelet, Olivier; Batsale, Jean-Chirstophe

2018-03-01

The thermal properties of a material with a spatiotemporal modulation, in the form of a traveling wave, in both the thermal conductivity and the specific heat capacity are studied. It is found that these materials behave as materials with an internal convectionlike term that provides them with nonreciprocal properties, in the sense that the heat flux has different properties when it propagates in the same direction or in the opposite one to the modulation of the parameters. An effective medium description is presented which accurately describes the modulated material, and numerical simulations support this description and verify the nonreciprocal properties of the material. It is found that these materials are promising candidates for the design of thermal diodes and other advanced devices for the control of the heat flow at all scales.

Multi-modality gellan gum-based tissue-mimicking phantom with targeted mechanical, electrical, and thermal properties.

PubMed

Chen, Roland K; Shih, A J

2013-08-21

This study develops a new class of gellan gum-based tissue-mimicking phantom material and a model to predict and control the elastic modulus, thermal conductivity, and electrical conductivity by adjusting the mass fractions of gellan gum, propylene glycol, and sodium chloride, respectively. One of the advantages of gellan gum is its gelling efficiency allowing highly regulable mechanical properties (elastic modulus, toughness, etc). An experiment was performed on 16 gellan gum-based tissue-mimicking phantoms and a regression model was fit to quantitatively predict three material properties (elastic modulus, thermal conductivity, and electrical conductivity) based on the phantom material's composition. Based on these material properties and the regression model developed, tissue-mimicking phantoms of porcine spinal cord and liver were formulated. These gellan gum tissue-mimicking phantoms have the mechanical, thermal, and electrical properties approximately equivalent to those of the spinal cord and the liver.

Proton irradiation effects on beryllium – A macroscopic assessment

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

Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong

Beryllium, due to its excellent neutron multiplication and moderation properties, in conjunction with its good thermal properties, is under consideration for use as plasma facing material in fusion reactors and as a very effective neutron reflector in fission reactors. While it is characterized by unique combination of structural, chemical, atomic number, and neutron absorption cross section it suffers, however, from irradiation generated transmutation gases such as helium and tritium which exhibit low solubility leading to supersaturation of the Be matrix and tend to precipitate into bubbles that coalesce and induce swelling and embrittlement thus degrading the metal and limiting itsmore » lifetime. Utilization of beryllium as a pion production low-Z target in high power proton accelerators has been sought both for its low Z and good thermal properties in an effort to mitigate thermos-mechanical shock that is expected to be induced under the multi-MW power demand. To assess irradiation-induced changes in the thermal and mechanical properties of Beryllium, a study focusing on proton irradiation damage effects has been undertaken using 200 MeV protons from the Brookhaven National Laboratory Linac and followed by a multi-faceted post-irradiation analysis that included the thermal and volumetric stability of irradiated beryllium, the stress-strain behavior and its ductility loss as a function of proton fluence and the effects of proton irradiation on the microstructure using synchrotron X-ray diffraction. The mimicking of high temperature irradiation of Beryllium via high temperature annealing schemes has been conducted as part of the post-irradiation study. This study focuses on the thermal stability and mechanical property changes of the proton irradiated beryllium and presents results of the macroscopic property changes of Beryllium deduced from thermal and mechanical tests.« less

Proton irradiation effects on beryllium – A macroscopic assessment

DOE PAGES

Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong; ...

2016-07-01

Beryllium, due to its excellent neutron multiplication and moderation properties, in conjunction with its good thermal properties, is under consideration for use as plasma facing material in fusion reactors and as a very effective neutron reflector in fission reactors. While it is characterized by unique combination of structural, chemical, atomic number, and neutron absorption cross section it suffers, however, from irradiation generated transmutation gases such as helium and tritium which exhibit low solubility leading to supersaturation of the Be matrix and tend to precipitate into bubbles that coalesce and induce swelling and embrittlement thus degrading the metal and limiting itsmore » lifetime. Utilization of beryllium as a pion production low-Z target in high power proton accelerators has been sought both for its low Z and good thermal properties in an effort to mitigate thermos-mechanical shock that is expected to be induced under the multi-MW power demand. To assess irradiation-induced changes in the thermal and mechanical properties of Beryllium, a study focusing on proton irradiation damage effects has been undertaken using 200 MeV protons from the Brookhaven National Laboratory Linac and followed by a multi-faceted post-irradiation analysis that included the thermal and volumetric stability of irradiated beryllium, the stress-strain behavior and its ductility loss as a function of proton fluence and the effects of proton irradiation on the microstructure using synchrotron X-ray diffraction. The mimicking of high temperature irradiation of Beryllium via high temperature annealing schemes has been conducted as part of the post-irradiation study. This study focuses on the thermal stability and mechanical property changes of the proton irradiated beryllium and presents results of the macroscopic property changes of Beryllium deduced from thermal and mechanical tests.« less

Structural and thermal properties of γ - irradiated Bombyx mori silk fibroin films

NASA Astrophysics Data System (ADS)

Madhukumar, R.; Asha, S.; Sarojini, B. K.; Somashekar, R.; Rao, B. Lakshmeesha; Shivananda, C. S.; Harish, K. V.; Sangappa

2015-06-01

The gamma radiation-induced change in structural and thermal properties of Bombyx mori silk fibroin films were investigated and have been correlated with the applied radiation doses. Irradiation of samples were carried out in dry air at room temperature using Co-60 source, and radiation doses are in the range of 0 - 300 kGy. Structural and thermal properties of the irradiated silk films were studied using X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TGA) and compared with unirradiated sample. Interesting results are discussed in this report.

A one-dimensional model for gas-solid heat transfer in pneumatic conveying

NASA Astrophysics Data System (ADS)

Smajstrla, Kody Wayne

A one-dimensional ODE model reduced from a two-fluid model of a higher dimensional order is developed to study dilute, two-phase (air and solid particles) flows with heat transfer in a horizontal pneumatic conveying pipe. Instead of using constant air properties (e.g., density, viscosity, thermal conductivity) evaluated at the initial flow temperature and pressure, this model uses an iteration approach to couple the air properties with flow pressure and temperature. Multiple studies comparing the use of constant or variable air density, viscosity, and thermal conductivity are conducted to study the impact of the changing properties to system performance. The results show that the fully constant property calculation will overestimate the results of the fully variable calculation by 11.4%, while the constant density with variable viscosity and thermal conductivity calculation resulted in an 8.7% overestimation, the constant viscosity with variable density and thermal conductivity overestimated by 2.7%, and the constant thermal conductivity with variable density and viscosity calculation resulted in a 1.2% underestimation. These results demonstrate that gas properties varying with gas temperature can have a significant impact on a conveying system and that the varying density accounts for the majority of that impact. The accuracy of the model is also validated by comparing the simulation results to the experimental values found in the literature.

General Properties for an Agrawal Thermal Engine

NASA Astrophysics Data System (ADS)

Paéz-Hernández, Ricardo T.; Chimal-Eguía, Juan Carlos; Sánchez-Salas, Norma; Ladino-Luna, Delfino

2018-04-01

This paper presents a general property of endoreversible thermal engines known as the Semisum property previously studied in a finite-time thermodynamics context for a Curzon-Ahlborn (CA) engine but now extended to a simplified version of the CA engine studied by Agrawal in 2009 (A simplified version of the Curzon-Ahlborn engine, European Journal of Physics 30 (2009), 1173). By building the Ecological function, proposed by Angulo-Brown (An ecological optimization criterion for finite-time heat engines, Journal of Applied Physics 69 (1991), 7465-7469) in 1991, and considering two heat transfer laws an analytical expression is obtained for efficiency and power output which depends only on the heat reservoirs' temperature. When comparing the existing efficiency values of real power plants and the theoretical efficiencies obtained in this work, it is observed that the Semisum property is satisfied. Moreover, for the Newton and the Dulong-Petit heat transfer laws the existence of the g function is demonstrated and we confirm that in a Carnot-type thermal engine there is a general property independent of the heat transfer law used between the thermal reservoirs and the working substance.

Thermal Property Measurement of Semiconductor Melt using Modified Laser Flash Method

NASA Technical Reports Server (NTRS)

Lin, Bochuan; Zhu, Shen; Ban, Heng; Li, Chao; Scripa, Rosalla N.; Su, Ching-Hua; Lehoczky, Sandor L.

2003-01-01

This study further developed standard laser flash method to measure multiple thermal properties of semiconductor melts. The modified method can determine thermal diffusivity, thermal conductivity, and specific heat capacity of the melt simultaneously. The transient heat transfer process in the melt and its quartz container was numerically studied in detail. A fitting procedure based on numerical simulation results and the least root-mean-square error fitting to the experimental data was used to extract the values of specific heat capacity, thermal conductivity and thermal diffusivity. This modified method is a step forward from the standard laser flash method, which is usually used to measure thermal diffusivity of solids. The result for tellurium (Te) at 873 K: specific heat capacity 300.2 Joules per kilogram K, thermal conductivity 3.50 Watts per meter K, thermal diffusivity 2.04 x 10(exp -6) square meters per second, are within the range reported in literature. The uncertainty analysis showed the quantitative effect of sample geometry, transient temperature measured, and the energy of the laser pulse.

Properties of Polymer-Infiltrated Carbon Foams

NASA Astrophysics Data System (ADS)

Adams, W. A.; Bunning, T. J.; Farmer, B. L.; Kearns, K. M.; Anderson, D. A.; Roy, A. K.; Banerjee, T.; Jeon, H. G.

2001-03-01

There is considerable interest in extending the use-temperatures of both commodity and high performance polymers. There is also interest in improving the mechanical strength of carbon foams. Composites prepared by infiltrating carbon foam with polymers may offer significant improvements in both, the polymer helping to rigidize the foam and the foam providing thermal protection by virtue of its high thermal conductivity. The mechanical properties and thermal stability of carbon foams of various densities infiltrated with polyurethane have been studied. When used with a heat sink, the composite is able to maintain a substantial thermal gradient which provides stability of the polymer nominally above its decomposition temperature. The composite also has much improved strength properties without sacrificing tensile modulus. The composites may be very well suited for thermal management applications.

Thermal conductivity of wurtzite and zinc blende cubic phases of BeO from ab initio calculations

NASA Astrophysics Data System (ADS)

Malakkal, Linu; Szpunar, Barbara; Siripurapu, Ravi Kiran; Zuniga, Juan Carlos; Szpunar, Jerzy A.

2017-03-01

The structural, mechanical, thermal and thermodynamic properties of Beryllium oxide (BeO) in the zinc blende (ZB) and wurtzite (WZ) form have been calculated using the density functional theory (DFT) in the general gradient approximation (GGA). The ground state structural and elastic properties of wurtzite BeO (w-BeO) is calculated using the new GGA ultrasoft pseudopotentials for solids (pbesol); the simulated results have shown excellent agreement with the experiments. The thermodynamic properties are studied using quasi-harmonic approximation (QHA), and the predicted properties agree well for the WZ phase for which the experimental data are available, while for ZB phase it remains to be validated with future experiments. Both Boltzmann transport equation (BTE) and Slack model were used to calculate the lattice thermal conductivity of wurtzite BeO (w-BeO). Furthermore, the thermal conductivity along the crystallographic 'a' and 'c' axis of wurtzite BeO is investigated using BTE. Our calculation of w-BeO agrees well with the available experimental measurements. Apart from these studies on w-BeO, we have also compared the mechanical, structural and phonon dispersions of z-BeO with previously reported theoretical studies. Additionally we report the volume thermal expansion and the heat capacity at constant pressure of z-BeO for the first time and the bulk thermal conductivity of zinc blende BeO (z-BeO) using BTE.

Thermal Properties of Starch From New Corn Lines as Impacted by Environment and During Line Development

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

Lenihan, Elizabeth M

The objectives of this research were to further characterize exotic by adapted corn inbreds by studying the impact of environment on their starch thermal properties, and investigating the development of starch thermal properties during kernel maturation by using differential scanning calorimetry (DSC). A method to expedite identification of unusual starch thermal traits was investigated by examining five corn kernels at a time, instead of one kernel, which the previous screening methods used. Corn lines with known thermal functions were blended with background starch (control) in ratios of unique starch to control starch, and analyzed by using DSC. Control starch wasmore » representative of typical corn starch. The values for each ratio within a mutant type were unique (α < 0.01) for most DSC measurements. These results supported the five-kernel method for rapidly screening large amounts of corn germplasm to identify unusual starch traits. The effects of 5 growing locations on starch thermal properties from exotic by adapted corn and Corn Belt lines were studied using DSC. The warmest location, Missouri, generally produced starch with greater gelatinization onset temperature (T oG), narrower range of gelatinization (R G), and greater enthalpy of gelatinization (ΔH G). The coolest location, Illinois, generally resulted in starch with lower T oG, wider R G, and lower ΔH G. Starch from the Ames 1 farm had thermal properties similar to those of Illinois, whereas starch from the Ames 2 farm had thermal properties similar to those of Missouri. The temperature at Ames 2 may have been warmer since it was located near a river; however, soil type and quality also were different. Final corn starch structure and function change during development and maturity. Thus, the changes in starch thermal properties during 5 stages of endosperm development from exotic by adapted corn and Corn Belt lines at two locations were studied by using DSC. The T oG tended to decrease during maturation of the kernel, whereas theΔH G tended not to change. Retrogradation parameters did not vary greatly among days after pollination (DAP) and between locations. Genotypes were affected differently by environments and significant interactions were found between genotype, environment,and DAP.« less

Native Cellulose: Structure, Characterization and Thermal Properties

PubMed Central

Poletto, Matheus; Ornaghi Júnior, Heitor L.; Zattera, Ademir J.

2014-01-01

In this work, the relationship between cellulose crystallinity, the influence of extractive content on lignocellulosic fiber degradation, the correlation between chemical composition and the physical properties of ten types of natural fibers were investigated by FTIR spectroscopy, X-ray diffraction and thermogravimetry techniques. The results showed that higher extractive contents associated with lower crystallinity and lower cellulose crystallite size can accelerate the degradation process and reduce the thermal stability of the lignocellulosic fibers studied. On the other hand, the thermal decomposition of natural fibers is shifted to higher temperatures with increasing the cellulose crystallinity and crystallite size. These results indicated that the cellulose crystallite size affects the thermal degradation temperature of natural fibers. This study showed that through the methods used, previous information about the structure and properties of lignocellulosic fibers can be obtained before use in composite formulations. PMID:28788179

Laboratory measurements of gravel thermal properties. A methodology proposal

NASA Astrophysics Data System (ADS)

Cultrera, Matteo; Peron, Fabio; Bison, Paolo; Dalla Santa, Giorgia; Bertermann, David; Muller, Johannes; Bernardi, Adriana; Galgaro, Antonio

2017-04-01

Gravel thermal properties measurements at laboratory level is quite challenging due to several technical and logistic issues, mainly connected to the sediment sizes and the variability of their mineralogical composition. The direct measurement of gravel thermal properties usually are not able to involve a representative volume of geological material, consequently the thermal measurements performed produce much dispersed results and not consistent due to the large interstitial voids and the poor physical contact with the measuring sensors. With the aim of directly provide the measurement of the gravel thermal properties, a new methodology has been developed and some results are already available on several gravel deposits samples around Europe. Indeed, a single guarded hot plate Taurus Instruments TLP 800 measured the gravel thermal properties. Some instrumental adjustments were necessary to adapt the measuring devices and to finalize the thermal measurements on gravels at the IUAV FISTEC laboratory (Environmental Technical Physics Laboratory of Venice University). This device usually provides thermal measurements according to ISO 8302, ASTM C177, EN 1946-2, EN 12664, EN 12667 and EN 12939 for building materials. A preliminary calibration has been performed comparing the outcomes obtained with the single guarded hot plate with a needle probe of a portable thermal conductivity meter (ISOMET). Standard sand (ISO 67:2009) is used as reference material. This study is provided under the Cheap-GSHPs project that has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement no. 657982

Investigating the effectiveness of using agricultural wastes from empty fruit bunch (EFB), coconut fibre (CF) and sugarcane baggasse (SB) to produce low thermal conductivity clay bricks

NASA Astrophysics Data System (ADS)

Hamzah, Mohamad Hazmi; Deraman, Rafikullah; Saman, Nor Sarwani Mat

2017-12-01

In Malaysia, 45% of the average household electricity was consumed by air conditioners to create an acceptable indoor environment. This high energy consumption was mostly related to poor thermal performance of the building envelope. Therefore, selecting a low thermal conductivity of brick wall was of considerable importance in creating energy efficient buildings. Previously, numerous researchers reported the potential used of agricultural waste as an additive in building materials to enhance their thermal properties. The aim of this study is to examine how agricultural wastes from empty fruit bunch (EFB), coconut fibre (CF) and sugarcane bagasse (SB) can act as additive agents in a fired clay brick manufacturing process to produce a low thermal conductivity clay brick. In this study, these agricultural wastes were individually mixed with clay soil in different proportions ranging from 0%, 2.5%, 5%, 7.5% and 10% by weight. Physical and mechanical properties including soil physical properties, as well as thermal conductivity were performed in accordance with BS 1377: Part 2: 1990, BS 3921: 1985 and ASTM C518. The results reveal that incorporating 5% of EFB as an additive component into the brick making process significantly enhances the production of a low thermal conductivity clay brick as compared to other waste alternatives tested. This finding suggests that EFB waste was a potential additive material to be used for the thermal property enhancement of the building envelope.

Dispersion of SiC nanoparticles in cellulose for study of tensile, thermal and oxygen barrier properties.

PubMed

Kisku, Sudhir K; Dash, Satyabrata; Swain, Sarat K

2014-01-01

Cellulose/silicon carbide (cellulose/SiC) nanobiocomposites were prepared by solution technique. The interaction of SiC nanoparticles with cellulose were confirmed by Fourier transformed infrared (FTIR) spectroscopy. The structure of cellulose/SiC nanobiocomposites was investigated by X-ray diffraction (XRD), and transmission electron microscopy (TEM). The tensile properties of the nanobiocomposites were improved as compared with virgin cellulose. Thermal stabilities of cellulose/SiC nanobiocomposites were studied by thermogravimetric analysis (TGA). The cellulose/SiC nanobiocomposites were thermally more stable than the raw cellulose. It may be due to the delamination of SiC with cellulose matrix. The oxygen barrier properties of cellulose composites were measured using gas permeameter. A substantial reduction in oxygen permeability was obtained with increase in silicon carbide concentrations. The thermally resistant and oxygen barrier properties of the prepared nanobiocomposites may enable the materials for the packaging applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

Efficiency of thermoelectric conversion in ferroelectric film capacitive structures

NASA Astrophysics Data System (ADS)

Volpyas, V. A.; Kozyrev, A. B.; Soldatenkov, O. I.; Tepina, E. R.

2012-06-01

Thermal heating/cooling conditions for metal-insulator-metal structures based on barium strontium titanate ferroelectric films are studied by numerical methods with the aim of their application in capacitive thermoelectric converters. A correlation between the thermal and capacitive properties of thin-film ferroelectric capacitors is considered. The time of the temperature response and the rate of variation of the capacitive properties of the metal-insulator-metal structures are determined by analyzing the dynamics of thermal processes. Thermophysical calculations are carried out that take into consideration the real electrical properties of barium strontium titanate ferroelectric films and allow estimation of thermal modulation parameters and the efficiency of capacitive thermoelectric converters on their basis.

Study of the thermal properties of low k dielectric thin films

NASA Astrophysics Data System (ADS)

Hu, Chuan

The integration of low k material is of great importance for the performance of an electronic device as the result of shrink in the device size. The thermal conductivity of low k materials is usually much lower than that of the traditionally used SiO2 and thus a tradeoff has to be properly evaluated. The thermal conduction in amorphous thin films is not only industrially important but also scientifically interesting. Many efforts have been done to understand the "phonon" propagation in an amorphous medium. Two experimental tools to study thermal properties are developed. The photothermal technique is an optical far field method and the 3o technique is an electrical near field method. The free standing and on-wafer photothermal techniques measure the out-of-plane thermal diffusivity directly and the 3o technique measures the out-of-plane thermal conductivity under our typical experimental configurations. The thermal diffusivities of a rigid rod like polyimide PI2611 and a flexible PI2545 are measured using the photothermal technique. The thermal anisotropy is studied by comparing our measurements with the result from in-plane measurements. The porosity dependence of thermal conductivity of Xerogel is studied by 3o technique. The fast drop in thermal conductivity is explained as the result of porosity and thermal contact in solid phase. A scaling rule of thermal conductivity as a function of porosity is proposed to the show the tradeoff between the thermal and the electrical properties. The possible impact of integrating low k materials in an interconnect structure is evaluated. The effective thermal conductivity of polymeric thin films as thin as 70 A is measured by 3o technique. The interfacial thermal resistances of Al/polymer/Si sandwich structure are found to be about 2 to 10 times larger than that of Al/SiO2/Si and the bulk thermal conductivities of polymers are found to be about 5 to 10 times smaller than that of SiO 2. The thermal conductivity of amorphous material is explained using the minimum thermal length model. The interfacial thermal resistance is explained using the acoustic and diffuse mismatch models as well as roughness and inelastic scattering at the interface.

Thermal stability of Mn-Ir-based specular spin valve structure

NASA Astrophysics Data System (ADS)

Yoon, S. Y.; Lee, D. H.; Jeon, D. M.; Kim, J. H.; Yoon, D. H.; Suh, S. J.

2004-05-01

We studied the thermal properties of specular and conventional spin valves. The specular spin valve showed better thermal properties (e.g. slow MR degradation and sheet resistance increment) than those of conventional spin valve. It is considered that the Mn-Co-Fe-O is formed in the NOL at 543-578 K and this acts as a diffusion barrier for Mn during high-temperature annealing process.

Assembly of DNA Architectures in a Non-Aqueous Solution

DTIC Science & Technology

2012-08-31

environment, where butanol was chosen for optical compatibility and thermal properties. The retention of DNA hierarchical structure and thermal stability...transitioned to a non-aqueous environment, where butanol was chosen for optical compatibility and thermal properties. The retention of DNA hierarchical...techniques were first validated using a more widely studied DNA system, genomic salmon sperm DNA (saDNA) [19]. The saDNA samples were reacted with two

Review on effect of chemical, thermal, additive treatment on mechanical properties of basalt fiber and their composites

NASA Astrophysics Data System (ADS)

Jain, Naman; Singh, Vinay Kumar; Chauhan, Sakshi

2017-12-01

Basalt fiber is emerging out the new reinforcing material for composites. To overcome some of the disadvantages of fibers such as poor bonding to polymers, low thermal stability and high moisture absorption fiber characteristics are modified with chemical, thermal and additive treatments. Chemical treatment corrosive resistance to alkali and acid were investigated which were used to clean and modify the surface of fiber for higher bonding with resins. To improve the thermal stability and reduce moisture uptake thermal treatment such as plasma and non thermal plasma were used which increased the surface roughness and change the chemical composition of surface of basalt fiber. Additive treatment is used to improve the mechanical properties of fibers, in basalt fiber additive treatment was done with SiO2 additive because of its chemical composition which contains major content of SiO2. In present investigation review on the effect of different treatment such as chemical, thermal and additive were studied. Effect of these treatment on chemical composition of the surface of basalt fiber and corrosion to acidic and alkali solution were studied with their effect on mechanical properties of basalt fiber and their composite.

Improved thermal conductivity of TiO2-SiO2 hybrid nanofluid in ethylene glycol and water mixture

NASA Astrophysics Data System (ADS)

Hamid, K. A.; Azmi, W. H.; Nabil, M. F.; Mamat, R.

2017-10-01

The need to study hybrid nanofluid properties such as thermal conductivity has increased recently in order to provide better understanding on nanofluid thermal properties and behaviour. Due to its ability to improve heat transfer compared to conventional heat transfer fluids, nanofluids as a new coolant fluid are widely investigated. This paper presents the thermal conductivity of TiO2-SiO2 nanoparticles dispersed in ethylene glycol (EG)-water. The TiO2-SiO2 hybrid nanofluids is measured for its thermal conductivity using KD2 Pro Thermal Properties Analyzer for concentration ranging from 0.5% to 3.0% and temperature of 30, 50 and 70°C. The results show that the increasing in concentration and temperature lead to enhancement in thermal conductivity at range of concentration studied. The maximum enhancement is found to be 22.1% at concentration 3.0% and temperature 70°C. A new equation is proposed based on the experiment data and found to be in good agreement where the average deviation (AD), standard deviation (SD) and maximum deviation (MD) are 1.67%, 1.66% and 5.13%, respectively.

Structural, electronic and thermal properties of super hard ternary boride, WAlB

NASA Astrophysics Data System (ADS)

Rajpoot, Priyanka; Rastogi, Anugya; Verma, U. P.

2018-04-01

A first principle study of the structural, electronic and thermal properties of Tungsten Aluminum Boride (WAlB) using full-potential linearized augmented plane wave (FP-LAPW) in the frame work of density function theory (DFT) have been calculated. The calculated equilibrium structural parameters are in excellent agreement with available experimental results. The calculated electronic band structure reveals that WAlB is metallic in nature. The quasi-harmonic Debye model is applied to study of the temperature and pressure effect on volume, Debye temperature, thermal expansion coefficient and specific heat at constant volume and constant pressure. To the best of our knowledge theoretical investigation of these properties of WAlB is reported for the first time.

A study on thermal properties of biodegradable polymers using photothermal methods

NASA Astrophysics Data System (ADS)

Siqueira, A. P. L.; Poley, L. H.; Sanchez, R.; da Silva, M. G.; Vargas, H.

2005-06-01

In this work is reported the use of photothermal techniques applied to the thermal characterization of biodegradable polymers of Polyhydroxyalkanoates (PHAs) family. This is a family of polymer produced by bacteria using renewable resources. It exhibits thermoplastic properties and therefore it can be an alternative product for engineering plastics, being also applied as packages for food industry and fruits. Thermal diffusivities were determined using the open photoacoustic cell (OPC) configuration. Specific heat capacity measurements were performed monitoring temperature of the samples under white light illumination against time. Typical values obtained for the thermal properties are in good agreement with those found in the literature for other polymers. Due to the incorporation of hydroxyvalerate in the monomer structure, the thermal diffusivity and thermal conductivity increase reaching a saturation value, otherwise the specific thermal capacity decreases as the concentration of the hydroxyvalerate (HV) increases. These results can be explained by polymers internal structure and are allowing new applications of these materials.

Thermal and Mechanical Characteristics of Polymer Composites Based on Epoxy Resin, Aluminium Nanopowders and Boric Acid

NASA Astrophysics Data System (ADS)

Nazarenko, O. B.; Melnikova, T. V.; Visakh, P. M.

2016-01-01

The epoxy polymers are characterized by low thermal stability and high flammability. Nanoparticles are considered to be effective fillers of polymer composites for improving their thermal and functional properties. In this work, the epoxy composites were prepared using epoxy resin ED-20, polyethylene polyamine as a hardener, aluminum nanopowder and boric acid fine powder as flame-retardant filler. The thermal characteristics of the obtained samples were studied using thermogravimetric analysis and differential scanning calorimetry. The mechanical characteristics of epoxy composites were also studied. It was found that an addition of all fillers enhances the thermal stability and mechanical characteristics of the epoxy composites. The best thermal stability showed the epoxy composite filled with boric acid. The highest flexural properties showed the epoxy composite based on the combination of boric acid and aluminum nanopowder.

Thermophysical Properties and Corrosion Characterization of Low Cost Lithium Containing Nitrate Salts Produced in Northern Chile for Thermal Energy Storage

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

Fernandez, Angel G.; Gomez, Judith C.; Galleguillos, Hector

In recent years, lithium containing salts have been studied for thermal energy storage (TES) systems applications, because of their optimal thermophysical properties. In solar power plants, lithium is seen as a way to improve the properties of molten salts used today. Lithium nitrate is a good candidate for sensible heat storage, due to its ability to increase the salt mixture's working temperature range. In the present research, thermophysical properties characterization of lithium nitrate containing salts, produced in Chile, have been carried out. Corrosion evaluations of carbon and low chromium steels were performed at 390 degrees C for 1000 hours. Thermophysicalmore » properties of the salt mixtures, such as thermal stability and heat capacity, were measured before and after corrosion tests. Chemical composition of the salts was also determined and an estimation of Chilean production costs is reported. Results showed that purity, thermal stability and heat capacity of the salts were reduced, caused by partial thermal decomposition and incorporation of corrosion products from the steel.« less

Improving the thermal and physical properties of fire clay refractory bricks by added magnesia

NASA Astrophysics Data System (ADS)

Ibrahim, Sarmad I.; Ali, Nahedh M.; Abood, Tamara W.

2018-05-01

In this study, the Local natural Iraqi rocks kaolin with the addition of different proportions of MgO along with its effects on the physical and thermal properties of the prepared refractories were investigated. kaolin/MgO mixture was milled and classified into various size fractions, the kaolin (less than 105 µm) and MgO (less than 50µm). The specimens were mixed from kaolin and MgO in range M1 (95+5)%, M2 (90+10) %, M3(85+15)% and M4(80+20)% respectively. The green specimens were shaped by the semi-dry method using a hydraulic press and a molding pressure of (5)Ton with addition of (9-12) %wt. of pva solution ratio. After molding and drying, the specimens were fired at (1100, 1200 and 1300)°C. Physical properties (density, porosity, Water Absorption) and thermal properties (thermal conductivity) were measured for all the prepared samples. The results showed that the porosity was increased and the density was decreased, such increase &decrease affected on to the thermal properties for refractory.

Application of Glass Fiber Waste Polypropylene Aggregate in Lightweight Concrete – thermal properties

NASA Astrophysics Data System (ADS)

Citek, D.; Rehacek, S.; Pavlik, Z.; Kolisko, J.; Dobias, D.; Pavlikova, M.

2018-03-01

Actual paper focus on thermal properties of a sustainable lightweight concrete incorporating high volume of waste polypropylene aggregate as partial substitution of natural aggregate. In presented experiments a glass fiber reinforced polypropylene (GFPP) which is a by-product of PP tubes production, partially substituted fine natural silica aggregate in 10, 20, 30, 40 and 50 mass %. Results were compared with a reference concrete mix without plastic waste in order to quantify the effect of GFPP use on concrete properties. Main material physical parameters were studied (bulk density, matrix density without air content, and particle size distribution). Especially a thermal transport and storage properties of GFPP were examined in dependence on compaction time. For the developed lightweight concrete, thermal properties were accessed using transient impulse technique, where the measurement was done in dependence on moisture content (from the fully water saturated state to dry state). It was found that the tested lightweight concrete should be prospective construction material possessing improved thermal insulation function and the reuse of waste plastics in concrete composition was beneficial both from the environmental and financial point of view.

Thermal stability of poly(ethylene-co-vinyl acetate) based materials

DOE PAGES

Patel, Mogon; Pitts, Simon; Beavis, Peter; ...

2013-03-26

The thermal stability properties of poly (ethylene-co-vinyl acetate) composites have been studied in support of our core programmes in materials qualification and life assessment. The material is used as a binder phase for boron particles in highly filled (70 wt %) composites. Our studies show that the uncured resin readily accumulates acetic acid through hydrolysis of the pendent acetate groups which alters the acidity (pH) of the material. Thermal desorption studies in combination with gas-chromatography-mass spectrometry show that the resin readily evolves acetic acid when thermally aged to temperatures up to 75°C. Gel Permeation Chromatography (GPC) suggests that thermal ageingmore » induces a gradual reduction in resin molecular weight and confirms the susceptibility of the material to chain scission. Heating at elevated temperatures in excess of 300oC is required to induce significant changes in the carbon skeleton through deacetylation and dehydration processes and the production of unsaturated main chain double bonds. Overall, the mechanical response of these filled composites are found to be relatively complex with the extent of polymer-filler interactions possibly playing an important role in determining key engineering properties. Mechanical property studies confirm a small but significant decrease in modulus presumably linked to thermally induced chain scission of the EVA binder.« less

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

Bauer, Stephen J.; Urquhart, Alexander

Reconsolidated crushed salt is being considered as a backfilling material placed upon nuclear waste within a salt repository environment. In-depth knowledge of thermal and mechanical properties of the crushed salt as it reconsolidates is critical to thermal/mechanical modeling of the reconsolidation process. An experimental study was completed to quantitatively evaluate the thermal conductivity of reconsolidated crushed salt as a function of porosity and temperature. The crushed salt for this study came from the Waste Isolation Pilot Plant (WIPP). In this work the thermal conductivity of crushed salt with porosity ranging from 1% to 40% was determined from room temperature upmore » to 300°C, using two different experimental methods. Thermal properties (including thermal conductivity, thermal diffusivity and specific heat) of single-crystal salt were determined for the same temperature range. The salt was observed to dewater during heating; weight loss from the dewatering was quantified. The thermal conductivity of reconsolidated crushed salt decreases with increasing porosity; conversely, thermal conductivity increases as the salt consolidates. The thermal conductivity of reconsolidated crushed salt for a given porosity decreases with increasing temperature. A simple mixture theory model is presented to predict and compare to the data developed in this study.« less

A review on the effects of different parameters on contact heat transfer

NASA Astrophysics Data System (ADS)

Abdollahi, H.; Shahraki, S.; Motahari-Nezhad, M.

2017-07-01

In this paper, a complete literature review for thermal contact between fixed and periodic contacting surfaces and also thermal contact between exhaust valve and its seat in internal combustion engines is presented. Furthermore, the effects of some parameters such as contact pressure, contact frequency, the contacting surfaces topography and roughness, curvature radius of surfaces, loading-unloading cycles, gas gap conductance and properties, interface interstitial material properties, surfaces coatings and surfaces temperature on thermal contact conductance are investigated according to the papers presented in this field. The reviewed papers and studies included theoretical/ analytical/experimental and numerical studies on thermal contact conductance. In studying the thermal contact between exhaust valve and its seat, most of the experimental studies include two axial rods as the exhaust valve, and seat and the one ends of both rods are considered at constant and different temperatures. In the experimental methods, the temperatures of multi-points on rods are measured in different conditions, and thermal contact conductance is estimated using them.

Heat treatment versus properties studies associated with the Inconel 718 PBF acoustic filters

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

Smolik, G.R.; Reuter, W.G.

PBF acoustic filter Unit No. 1 cracked when heat treatment was attempted. The effects of prior thermal cycling, solution anneal temperature, and cooling rate from solution anneals were investigated. The investigations concerned influences of the above variables upon both 1400$sup 0$F stress rupture solution- annealed properties and room temperature age-hardened properties. 1400$sup 0$F stress rupture properties were of interest to assist the prevention of cracking during heat treatments. Room temperature age-hardened properties were needed to ensure that design requirement would be provided. Prior thermal cycling was investigated to determine if extra thermal cycles would be detrimental to the repaired filter.more » Slow furnace cools were considered as a means of reducing thermal stresses. Effects of solution annealing at 2000 and 1900$sup 0$F were also determined. Test results showed that slow cooling rates would not only reduce thermal stresses but also improve 1400$sup 0$F ductility. A modified aging treatment was established which provided the required 145 ksi room temperature yield strength for the slowly cooled material. Prior cooling did not degrade final age-hardened room temperature tensile or impact properties. (auth)« less

Analytical estimation of ultrasound properties, thermal diffusivity, and perfusion using magnetic resonance-guided focused ultrasound temperature data

PubMed Central

Dillon, C R; Borasi, G; Payne, A

2016-01-01

For thermal modeling to play a significant role in treatment planning, monitoring, and control of magnetic resonance-guided focused ultrasound (MRgFUS) thermal therapies, accurate knowledge of ultrasound and thermal properties is essential. This study develops a new analytical solution for the temperature change observed in MRgFUS which can be used with experimental MR temperature data to provide estimates of the ultrasound initial heating rate, Gaussian beam variance, tissue thermal diffusivity, and Pennes perfusion parameter. Simulations demonstrate that this technique provides accurate and robust property estimates that are independent of the beam size, thermal diffusivity, and perfusion levels in the presence of realistic MR noise. The technique is also demonstrated in vivo using MRgFUS heating data in rabbit back muscle. Errors in property estimates are kept less than 5% by applying a third order Taylor series approximation of the perfusion term and ensuring the ratio of the fitting time (the duration of experimental data utilized for optimization) to the perfusion time constant remains less than one. PMID:26741344

Effects of functionalization on thermal properties of single-wall and multi-wall carbon nanotube-polymer nanocomposites.

PubMed

Gulotty, Richard; Castellino, Micaela; Jagdale, Pravin; Tagliaferro, Alberto; Balandin, Alexander A

2013-06-25

Carboxylic functionalization (-COOH groups) of carbon nanotubes is known to improve their dispersion properties and increase the electrical conductivity of carbon-nanotube-polymer nanocomposites. We have studied experimentally the effects of this type of functionalization on the thermal conductivity of the nanocomposites. It was found that while even small quantities of carbon nanotubes (~1 wt %) can increase the electrical conductivity, a larger loading fraction (~3 wt %) is required to enhance the thermal conductivity of nanocomposites. Functionalized multi-wall carbon nanotubes performed the best as filler material leading to a simultaneous improvement of the electrical and thermal properties of the composites. Functionalization of the single-wall carbon nanotubes reduced the thermal conductivity enhancement. The observed trends were explained by the fact that while surface functionalization increases the coupling between carbon nanotube and polymer matrix, it also leads to formation of defects, which impede the acoustic phonon transport in the single-wall carbon nanotubes. The obtained results are important for applications of carbon nanotubes and graphene flakes as fillers for improving thermal, electrical and mechanical properties of composites.

The Effect of Temperature Dependent Material Nonlinearities on the Response of Piezoelectric Composite Plates

NASA Technical Reports Server (NTRS)

Lee, Ho-Jun; Saravanos, Dimitris A.

1997-01-01

Previously developed analytical formulations for piezoelectric composite plates are extended to account for the nonlinear effects of temperature on material properties. The temperature dependence of the composite and piezoelectric properties are represented at the material level through the thermopiezoelectric constitutive equations. In addition to capturing thermal effects from temperature dependent material properties, this formulation also accounts for thermal effects arising from: (1) coefficient of thermal expansion mismatch between the various composite and piezoelectric plies and (2) pyroelectric effects on the piezoelectric material. The constitutive equations are incorporated into a layerwise laminate theory to provide a unified representation of the coupled mechanical, electrical, and thermal behavior of smart structures. Corresponding finite element equations are derived and implemented for a bilinear plate element with the inherent capability to model both the active and sensory response of piezoelectric composite laminates. Numerical studies are conducted on a simply supported composite plate with attached piezoceramic patches under thermal gradients to investigate the nonlinear effects of material property temperature dependence on the displacements, sensory voltages, active voltages required to minimize thermal deflections, and the resultant stress states.

Effective Thermal Property Estimation of Unitary Pebble Beds Based on a CFD-DEM Coupled Method for a Fusion Blanket

NASA Astrophysics Data System (ADS)

Chen, Lei; Chen, Youhua; Huang, Kai; Liu, Songlin

2015-12-01

Lithium ceramic pebble beds have been considered in the solid blanket design for fusion reactors. To characterize the fusion solid blanket thermal performance, studies of the effective thermal properties, i.e. the effective thermal conductivity and heat transfer coefficient, of the pebble beds are necessary. In this paper, a 3D computational fluid dynamics discrete element method (CFD-DEM) coupled numerical model was proposed to simulate heat transfer and thereby estimate the effective thermal properties. The DEM was applied to produce a geometric topology of a prototypical blanket pebble bed by directly simulating the contact state of each individual particle using basic interaction laws. Based on this geometric topology, a CFD model was built to analyze the temperature distribution and obtain the effective thermal properties. The current numerical model was shown to be in good agreement with the existing experimental data for effective thermal conductivity available in the literature. supported by National Special Project for Magnetic Confined Nuclear Fusion Energy of China (Nos. 2013GB108004, 2015GB108002, 2014GB122000 and 2014GB119000), and National Natural Science Foundation of China (No. 11175207)

Experimental methods of determining thermal properties of granite

USDA-ARS?s Scientific Manuscript database

Determination of thermal properties of granite using the block method is discussed and compared with other methods. Problems that limit the accuracy of contact method in determining thermal properties of porous media are evaluated. Thermal properties of granite is determined in the laboratory with a...

Non-destructive thermal wave method applied to study thermal properties of fast setting time endodontic cement

NASA Astrophysics Data System (ADS)

Picolloto, A. M.; Mariucci, V. V. G.; Szpak, W.; Medina, A. N.; Baesso, M. L.; Astrath, N. G. C.; Astrath, F. B. G.; Santos, A. D.; Moraes, J. C. S.; Bento, A. C.

2013-11-01

The thermal wave method is applied for thermal properties measurement in fast endodontic cement (CER). This new formula is developed upon using Portland cement in gel and it was successfully tested in mice with good biocompatibility and stimulated mineralization. Recently, thermal expansion and setting time were measured, conferring to this material twice faster hardening than the well known Angelus Mineral trioxide aggregate (MTA) the feature of fast hardening (˜7 min) and with similar thermal expansion (˜12 μstrain/ °C). Therefore, it is important the knowledge of thermal properties like thermal diffusivity, conductivity, effusivity in order to match thermally the tissue environment upon its application in filling cavities of teeth. Photothermal radiometry technique based on Xe illumination was applied in CER disks 600 μm thick for heating, with prepared in four particle sizes (25, 38, 45, and 53) μm, which were added microemulsion gel with variation volumes (140, 150, 160, and 170) μl. The behavior of the thermal diffusivity CER disks shows linear decay for increase emulsion volume, and in contrast, thermal diffusivity increases with particles sizes. Aiming to compare to MTA, thermal properties of CER were averaged to get the figure of merit for thermal diffusivity as (44.2 ± 3.6) × 10-3 cm2/s, for thermal conductivity (228 ± 32) mW/cm K, the thermal effusivity (1.09 ± 0.06) W s0.5/cm2 K and volume heat capacity (5.2 ± 0.7) J/cm3 K, which are in excellent agreement with results of a disk prepared from commercial MTA-Angelus (grain size < 10 μm using 57 μl of distilled water).

Non-destructive thermal wave method applied to study thermal properties of fast setting time endodontic cement

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

Picolloto, A. M.; Mariucci, V. V. G.; Szpak, W.

The thermal wave method is applied for thermal properties measurement in fast endodontic cement (CER). This new formula is developed upon using Portland cement in gel and it was successfully tested in mice with good biocompatibility and stimulated mineralization. Recently, thermal expansion and setting time were measured, conferring to this material twice faster hardening than the well known Angelus Mineral trioxide aggregate (MTA) the feature of fast hardening (∼7 min) and with similar thermal expansion (∼12 μstrain/ °C). Therefore, it is important the knowledge of thermal properties like thermal diffusivity, conductivity, effusivity in order to match thermally the tissue environment upon its applicationmore » in filling cavities of teeth. Photothermal radiometry technique based on Xe illumination was applied in CER disks 600 μm thick for heating, with prepared in four particle sizes (25, 38, 45, and 53) μm, which were added microemulsion gel with variation volumes (140, 150, 160, and 170) μl. The behavior of the thermal diffusivity CER disks shows linear decay for increase emulsion volume, and in contrast, thermal diffusivity increases with particles sizes. Aiming to compare to MTA, thermal properties of CER were averaged to get the figure of merit for thermal diffusivity as (44.2 ± 3.6) × 10{sup −3} cm{sup 2}/s, for thermal conductivity (228 ± 32) mW/cm K, the thermal effusivity (1.09 ± 0.06) W s{sup 0.5}/cm{sup 2} K and volume heat capacity (5.2 ± 0.7) J/cm{sup 3} K, which are in excellent agreement with results of a disk prepared from commercial MTA-Angelus (grain size < 10 μm using 57 μl of distilled water)« less

Mechanical, Thermal and Dynamic Mechanical Properties of PP/GF/xGnP Nanocomposites

NASA Astrophysics Data System (ADS)

Ashenai Ghasemi, F.; Ghorbani, A.; Ghasemi, I.

2017-03-01

The mechanical, thermal, and dynamic mechanical properties of ternary nanocomposites based on polypropylene, short glass fibers, and exfoliated graphene nanoplatelets were studied. To investigate the mechanical properties, uniaxial tensile and Charpy impact tests were carried out. To study the crystallinity of the compositions, a DSC test was performed. A dynamic mechanical analysis was used to characterize the storage modulus and loss factor (tan δ). The morphology of the composites was studied by a scanning electron microscope (SEM). The results obtained are presented in tables and graphics.

Preparation of poly(vinyl alcohol)/chitosan/starch blends and studies on thermal and surface properties

NASA Astrophysics Data System (ADS)

Nasalapure, Anand V.; Chalannavar, Raju K.; Malabadi, Ravindra B.

2018-05-01

Biopolymers are abundantly available from its natural sources of extraction. Chitosan(CH) is one of the widely used natural polymer which is perspective natural polysaccharide. Natural polymer blend with synthetic polymer enhances property of the material such as polyvinyl alcohol (PVA). PVA is nontoxic degradable synthetic polymer and very good film forming polymer. In this study prepared hybrid based film by adding starch into Chitosan/PVA which slighlty increased the surface and thermal property of ternary blend film.

Assessment of structural, thermal, and mechanical properties of portlandite through molecular dynamics simulations

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

Hajilar, Shahin, E-mail: shajilar@iastate.edu; Shafei, Behrouz, E-mail: shafei@iastate.edu

The structural, thermal, and mechanical properties of portlandite, the primary solid phase of ordinary hydrated cement paste, are investigated using the molecular dynamics method. To understand the effects of temperature on the structural properties of portlandite, the coefficients of thermal expansion of portlandite are determined in the current study and validated with what reported from the experimental tests. The atomic structure of portlandite equilibrated at various temperatures is then subjected to uniaxial tensile strains in the three orthogonal directions and the stress-strain curves are developed. Based on the obtained results, the effect of the direction of straining on the mechanicalmore » properties of portlandite is investigated in detail. Structural damage analysis is performed to reveal the failure mechanisms in different directions. The energies of the fractured surfaces are calculated in different directions and compared to those of the ideal surfaces available in the literature. The key mechanical properties, including tensile strength, Young's modulus, and fracture strain, are extracted from the stress-strain curves. The sensitivity of the obtained mechanical properties to temperature and strain rate is then explored in a systematic way. This leads to valuable information on how the structural and mechanical properties of portlandite are affected under various exposure conditions and loading rates. - Graphical abstract: Fracture mechanism of portlandite under uniaxial strain in the z-direction. - Highlights: • The structural, thermal, and mechanical properties of portlandite are investigated. • The coefficients of thermal expansion are determined. • The stress-strain relationships are studied in three orthogonal directions. • The effects of temperature and strain rate on mechanical properties are examined. • The plastic energy required for fracture in the crystalline structure is reported.« less

Tailoring thermal conductivity via three-dimensional porous alumina

PubMed Central

Abad, Begoña; Maiz, Jon; Ruiz-Clavijo, Alejandra; Caballero-Calero, Olga; Martin-Gonzalez, Marisol

2016-01-01

Three-dimensional anodic alumina templates (3D-AAO) are an astonishing framework with open highly ordered three-dimensional skeleton structures. Since these templates are architecturally different from conventional solids or porous templates, they teem with opportunities for engineering thermal properties. By establishing the mechanisms of heat transfer in these frameworks, we aim to create materials with tailored thermal properties. The effective thermal conductivity of an empty 3D-AAO membrane was measured. As the effective medium theory was not valid to extract the skeletal thermal conductivity of 3D-AAO, a simple 3D thermal conduction model was developed, based on a mixed series and parallel thermal resistor circuit, giving a skeletal thermal conductivity value of approximately 1.25 W·m−1·K−1, which matches the value of the ordinary AAO membranes prepared from the same acid solution. The effect of different filler materials as well as the variation of the number of transversal nanochannels and the length of the 3D-AAO membrane in the effective thermal conductivity of the composite was studied. Finally, the thermal conductivity of two 3D-AAO membranes filled with cobalt and bismuth telluride was also measured, which was in good agreement with the thermal model predictions. Therefore, this work proved this structure as a powerful approach to tailor thermal properties. PMID:27934930

Thermal Properties of West Siberian Sediments in Application to Basin and Petroleum Systems Modeling

NASA Astrophysics Data System (ADS)

Romushkevich, Raisa; Popov, Evgeny; Popov, Yury; Chekhonin, Evgeny; Myasnikov, Artem; Kazak, Andrey; Belenkaya, Irina; Zagranovskaya, Dzhuliya

2016-04-01

Quality of heat flow and rock thermal property data is the crucial question in basin and petroleum system modeling. A number of significant deviations in thermal conductivity values were observed during our integral geothermal study of West Siberian platform reporting that the corrections should be carried out in basin models. The experimental data including thermal anisotropy and heterogeneity measurements were obtained along of more than 15 000 core samples and about 4 500 core plugs. The measurements were performed in 1993-2015 with the optical scanning technique within the Continental Super-Deep Drilling Program (Russia) for scientific super-deep well Tyumenskaya SG-6, parametric super-deep well Yen-Yakhinskaya, and deep well Yarudeyskaya-38 as well as for 13 oil and gas fields in the West Siberia. Variations of the thermal conductivity tensor components in parallel and perpendicular direction to the layer stratification (assessed for 2D anisotropy model of the rock studied), volumetric heat capacity and thermal anisotropy coefficient values and average values of the thermal properties were the subject of statistical analysis for the uppermost deposits aged by: T3-J2 (200-165 Ma); J2-J3 (165-150 Ma); J3 (150-145 Ma); K1 (145-136 Ma); K1 (136-125 Ma); K1-K2 (125-94 Ma); K2-Pg+Ng+Q (94-0 Ma). Uncertainties caused by deviations of thermal conductivity data from its average values were found to be as high as 45 % leading to unexpected errors in the basin heat flow determinations. Also, the essential spatial-temporal variations in the thermal rock properties in the study area is proposed to be taken into account in thermo-hydrodynamic modeling of hydrocarbon recovery with thermal methods. The research work was done with financial support of the Russian Ministry of Education and Science (unique identification number RFMEFI58114X0008).

Optimal Experiment Design for Thermal Characterization of Functionally Graded Materials

NASA Technical Reports Server (NTRS)

Cole, Kevin D.

2003-01-01

The purpose of the project was to investigate methods to accurately verify that designed , materials meet thermal specifications. The project involved heat transfer calculations and optimization studies, and no laboratory experiments were performed. One part of the research involved study of materials in which conduction heat transfer predominates. Results include techniques to choose among several experimental designs, and protocols for determining the optimum experimental conditions for determination of thermal properties. Metal foam materials were also studied in which both conduction and radiation heat transfer are present. Results of this work include procedures to optimize the design of experiments to accurately measure both conductive and radiative thermal properties. Detailed results in the form of three journal papers have been appended to this report.

Room temperature thermal conductivity measurements of neat MOF-5 compacts with high pressure hydrogen and helium

DOE PAGES

Semelsberger, Troy Allen; Veenstra, Mike; Dixon, Craig

2016-02-09

Metal-organic frameworks (MOFs) are a highly porous crystalline material with potential in various applications including on-board vehicle hydrogen storage for fuel cell vehicles. The thermal conductivity of MOFs is an important parameter in the design and ultimate performance of an on-board hydrogen storage system. However, in-situ thermal conductivity measurements have not been previously reported. The present study reports room temperature thermal conductivity and thermal diffusivity measurements performed on neat MOF-5 cylindrical compacts (ρ = 0.4 g/mL) as a function of pressure (0.27–90 bar) and gas type (hydrogen and helium). The transient plane source technique was used to measure both themore » non-directional thermal properties (isotropic method) and the directional thermal properties (anisotropic method). High pressure measurements were made using our in-house built low-temperature, high pressure thermal conductivity sample cell. The intrinsic thermal properties of neat MOF-5 measured under vacuum were—Isotropic: k isotropic = 0.1319 W/m K, α isotropic = 0.4165 mm 2/s; Anisotropic: k axial = 0.1477 W/m K, k radial = 0.1218 W/m K, α axial = 0.5096 mm 2/s, and α radial = 0.4232 mm 2/s. The apparent thermal properties of neat MOF-5 increased with increasing hydrogen and helium pressure, with the largest increase occurring in the narrow pressure range of 0–10 bar and then monotonically asymptoting with increasing pressures up to around 90 bar. On average, a greater than two-fold enhancement in the apparent thermal properties was observed with neat MOF-5 in the presence of helium and hydrogen compared to the intrinsic values of neat MOF-5 measured under vacuum. The apparent thermal properties of neat MOF-5 measured with hydrogen were higher than those measured with helium, which were directly related to the gas-specific thermal properties of helium and hydrogen. Neat MOF-5 exhibited a small degree of anisotropy under all conditions measured with thermal conductivities and diffusivities in the axial direction being higher than those in the radial direction. As a result, the low temperature specific heat capacities of neat MOF-5 were also measured and reported for the temperature range of 93–313 K (–180–40 °C).« less

Room temperature thermal conductivity measurements of neat MOF-5 compacts with high pressure hydrogen and helium

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

Semelsberger, Troy Allen; Veenstra, Mike; Dixon, Craig

Metal-organic frameworks (MOFs) are a highly porous crystalline material with potential in various applications including on-board vehicle hydrogen storage for fuel cell vehicles. The thermal conductivity of MOFs is an important parameter in the design and ultimate performance of an on-board hydrogen storage system. However, in-situ thermal conductivity measurements have not been previously reported. The present study reports room temperature thermal conductivity and thermal diffusivity measurements performed on neat MOF-5 cylindrical compacts (ρ = 0.4 g/mL) as a function of pressure (0.27–90 bar) and gas type (hydrogen and helium). The transient plane source technique was used to measure both themore » non-directional thermal properties (isotropic method) and the directional thermal properties (anisotropic method). High pressure measurements were made using our in-house built low-temperature, high pressure thermal conductivity sample cell. The intrinsic thermal properties of neat MOF-5 measured under vacuum were—Isotropic: k isotropic = 0.1319 W/m K, α isotropic = 0.4165 mm 2/s; Anisotropic: k axial = 0.1477 W/m K, k radial = 0.1218 W/m K, α axial = 0.5096 mm 2/s, and α radial = 0.4232 mm 2/s. The apparent thermal properties of neat MOF-5 increased with increasing hydrogen and helium pressure, with the largest increase occurring in the narrow pressure range of 0–10 bar and then monotonically asymptoting with increasing pressures up to around 90 bar. On average, a greater than two-fold enhancement in the apparent thermal properties was observed with neat MOF-5 in the presence of helium and hydrogen compared to the intrinsic values of neat MOF-5 measured under vacuum. The apparent thermal properties of neat MOF-5 measured with hydrogen were higher than those measured with helium, which were directly related to the gas-specific thermal properties of helium and hydrogen. Neat MOF-5 exhibited a small degree of anisotropy under all conditions measured with thermal conductivities and diffusivities in the axial direction being higher than those in the radial direction. As a result, the low temperature specific heat capacities of neat MOF-5 were also measured and reported for the temperature range of 93–313 K (–180–40 °C).« less

Thermal remediation alters soil properties - a review.

PubMed

O'Brien, Peter L; DeSutter, Thomas M; Casey, Francis X M; Khan, Eakalak; Wick, Abbey F

2018-01-15

Contaminated soils pose a risk to human and ecological health, and thermal remediation is an efficient and reliable way to reduce soil contaminant concentration in a range of situations. A primary benefit of thermal treatment is the speed at which remediation can occur, allowing the return of treated soils to a desired land use as quickly as possible. However, this treatment also alters many soil properties that affect the capacity of the soil to function. While extensive research addresses contaminant reduction, the range and magnitude of effects to soil properties have not been explored. Understanding the effects of thermal remediation on soil properties is vital to successful reclamation, as drastic effects may preclude certain post-treatment land uses. This review highlights thermal remediation studies that have quantified alterations to soil properties, and it supplements that information with laboratory heating studies to further elucidate the effects of thermal treatment of soil. Notably, both heating temperature and heating time affect i) soil organic matter; ii) soil texture and mineralogy; iii) soil pH; iv) plant available nutrients and heavy metals; v) soil biological communities; and iv) the ability of the soil to sustain vegetation. Broadly, increasing either temperature or time results in greater contaminant reduction efficiency, but it also causes more severe impacts to soil characteristics. Thus, project managers must balance the need for contaminant reduction with the deterioration of soil function for each specific remediation project. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of anisotropic thermal conduction on wind properties in hot accretion flow

NASA Astrophysics Data System (ADS)

Bu, De-Fu; Wu, Mao-Chun; Yuan, Ye-Fei

2016-06-01

Previous works have clearly shown the existence of winds from black hole hot accretion flow and investigated their detailed properties. In extremely low accretion rate systems, the collisional mean-free path of electrons is large compared with the length-scale of the system, thus thermal conduction is dynamically important. When the magnetic field is present, the thermal conduction is anisotropic and energy transport is along magnetic field lines. In this paper, we study the effects of anisotropic thermal conduction on the wind production in hot accretion flows by performing two-dimensional magnetohydrodynamic simulations. We find that thermal conduction has only moderate effects on the mass flux of wind. But the energy flux of wind can be increased by a factor of ˜10 due to the increase of wind velocity when thermal conduction is included. The increase of wind velocity is because of the increase of driving forces (e.g. gas pressure gradient force and centrifugal force) when thermal conduction is included. This result demonstrates that thermal conduction plays an important role in determining the properties of wind.

Review of Recent Developments on Using an Off-Lattice Monte Carlo Approach to Predict the Effective Thermal Conductivity of Composite Systems with Complex Structures

PubMed Central

Gong, Feng; Duong, Hai M.; Papavassiliou, Dimitrios V.

2016-01-01

Here, we present a review of recent developments for an off-lattice Monte Carlo approach used to investigate the thermal transport properties of multiphase composites with complex structure. The thermal energy was quantified by a large number of randomly moving thermal walkers. Different modes of heat conduction were modeled in appropriate ways. The diffusive heat conduction in the polymer matrix was modeled with random Brownian motion of thermal walkers within the polymer, and the ballistic heat transfer within the carbon nanotubes (CNTs) was modeled by assigning infinite speed of thermal walkers in the CNTs. Three case studies were conducted to validate the developed approach, including three-phase single-walled CNTs/tungsten disulfide (WS2)/(poly(ether ether ketone) (PEEK) composites, single-walled CNT/WS2/PEEK composites with the CNTs clustered in bundles, and complex graphene/poly(methyl methacrylate) (PMMA) composites. In all cases, resistance to heat transfer due to nanoscale phenomena was also modeled. By quantitatively studying the influencing factors on the thermal transport properties of the multiphase composites, it was found that the orientation, aggregation and morphology of fillers, as well as the interfacial thermal resistance at filler-matrix interfaces would limit the transfer of heat in the composites. These quantitative findings may be applied in the design and synthesis of multiphase composites with specific thermal transport properties. PMID:28335270

Overview of thermal conductivity models of anisotropic thermal insulation materials

NASA Astrophysics Data System (ADS)

Skurikhin, A. V.; Kostanovsky, A. V.

2017-11-01

Currently, the most of existing materials and substances under elaboration are anisotropic. It makes certain difficulties in the study of heat transfer process. Thermal conductivity of the materials can be characterized by tensor of the second order. Also, the parallelism between the temperature gradient vector and the density of heat flow vector is violated in anisotropic thermal insulation materials (TIM). One of the most famous TIM is a family of integrated thermal insulation refractory material («ITIRM»). The main component ensuring its properties is the «inflated» vermiculite. Natural mineral vermiculite is ground into powder state, fired by gas burner for dehydration, and its precipitate is then compressed. The key feature of thus treated batch of vermiculite is a package structure. The properties of the material lead to a slow heating of manufactured products due to low absorption and high radiation reflection. The maximum of reflection function is referred to infrared spectral region. A review of current models of heat propagation in anisotropic thermal insulation materials is carried out, as well as analysis of their thermal and optical properties. A theoretical model, which allows to determine the heat conductivity «ITIRM», can be useful in the study of thermal characteristics such as specific heat capacity, temperature conductivity, and others. Materials as «ITIRM» can be used in the metallurgy industry, thermal energy and nuclear power-engineering.

Humidity Effects on Soluble Core Mechanical and Thermal Properties (Polyvinyl Alcohol/Microballoon Composite)

NASA Technical Reports Server (NTRS)

1993-01-01

This document constitutes the final report for the study of humidity effects and loading rate on soluble core (PVA/MB composite material) mechanical and thermal properties. This report describes test results, procedures employed, and any unusual occurrences or specific observations associated with this test program.

Extraction of Curcumin Pigment from Indonesian Local Turmeric with Its Infrared Spectra and Thermal Decomposition Properties

NASA Astrophysics Data System (ADS)

Nandiyanto, A. B. D.; Wiryani, A. S.; Rusli, A.; Purnamasari, A.; Abdullah, A. G.; Ana; Widiaty, I.; Hurriyati, R.

2017-03-01

Curcumin is one of the pigments which is used as a spice in Asian cuisine, traditional cosmetic, and medicine. Therefore, process for getting curcumin has been widely studied. Here, the purpose of this study was to demonstrate the simple method for extracting curcumin from Indonesian local turmeric and investigate the infrared spectra and thermal decomposition properties. In the experimental procedure, the washed turmeric was dissolved into an ethanol solution, and then put into a rotary evaporator to enrich curcumin concentration. The result showed that the present method is effective to isolate curcumin compound from Indonesian local turmeric. Since the process is very simple, this method can be used for home industrial application. Further, understanding the thermal decomposition properties of curcumin give information, specifically relating to the selection of treatment when curcumin must face the thermal-related process.

Significant aspects on thermal degradation of hybrid biocomposite material

NASA Astrophysics Data System (ADS)

Bavan, D. Saravana; Kumar, G. C. Mohan

2013-06-01

Interest in use of bio fibers is increasing rapidly in structural and automotive applications because of few important properties such as low density, mechanical properties, renewability, biodegradation and sustainability. The present work is focused on fabricating a hybrid bio-composite material processed through compression molding technique. Natural fibers of maize and jute with bio polymeric resin of epoxidized soya bean oil are used as a matrix in obtaining a hybrid bio composite material. Thermal degradation of the prepared material is studied through Thermal gravimetric analyzer. Chemical treatment of the fibers was performed to have a better adhesion between the fibers and the matrix. The work is also surveyed on various parameters influencing the thermal properties and other aspects for a hybrid bio composite material.

Effects of Mn Substitution on the Thermoelectric Properties and Thermal Excitations of the Electron-doped Perovskite Sr1-xLaxTiO3

NASA Astrophysics Data System (ADS)

Okuda, Tetsuji; Hata, Hiroto; Eto, Takahiro; Sobaru, Shogo; Oda, Ryosuke; Kaji, Hiroki; Nishina, Kousuke; Kuwahara, Hideki; Nakamura, Mitsutaka; Kajimoto, Ryoichi

2016-09-01

We studied how Mn substitution affects the thermoelectric properties and thermal excitations of the electron-doped perovskite Sr1-xLaxTiO3 by measuring its electrical and thermal transport properties, magnetization, specific heat, and inelastic neutron scattering. Slight Mn substitution with the lattice defects enhanced the Seebeck coefficient, perhaps because of coupling between itinerant electrons and localized spins or between itinerant electrons and local lattice distortion around Mn3+ ions, while it enhanced anharmonic lattice vibrations, which effectively suppressed thermal conductivity in a state of high electrical conductivity. Consequently, slight Mn substitution increased the dimensionless thermoelectric figure of merit for Sr1-xLaxTiO3 near room temperature.

Characterization of Thermal and Mechanical Impact on Aluminum Honeycomb Structures

NASA Technical Reports Server (NTRS)

Robinson, Christen M.

2013-01-01

This study supports NASA Kennedy Space Center's research in the area of intelligent thermal management systems and multifunctional thermal systems. This project addresses the evaluation of the mechanical and thermal properties of metallic cellular solid (MCS) materials; those that are lightweight; high strength, tunable, multifunctional and affordable. A portion of the work includes understanding the mechanical properties of honeycomb structured cellular solids upon impact testing under ambient, water-immersed, liquid nitrogen-cooled, and liquid nitrogen-immersed conditions. Additionally, this study will address characterization techniques of the aluminum honeycomb's ability to resist multiple high-rate loadings or impacts in varying environmental conditions, using various techniques for the quantitative and qualitative determination for commercial applicability.

Study of changes induced in thermal properties of starch by incorporating Ag nanoparticles

NASA Astrophysics Data System (ADS)

Meena, Sharma, Annu

2018-05-01

This report presents the study of thermal properties of starch and Ag-starch nanocomposite films fabricated via chemical reduction method followed by solution casting. Thermo gravimetric analysis was utilized to investigate the effect of varying concentration of Ag nanoparticles on thermal stability and activation energy of starch. Activation energy that is the energy required for initialization of degradation process of starch comes out to be 238.9 kJ/mol which decreases to a value of 174.6 kJ/mol for Ag-starch nanocomposite film containing 0.50 wt% of Ag nanoparticles. Moreover the thermal stability of starch increases with the increasing concentration of Ag nanoparticles.

Thermal characterization of TiCxOy thin films

NASA Astrophysics Data System (ADS)

Fernandes, A. C.; Vaz, F.; Gören, A.; Junge, K. H.; Gibkes, J.; Bein, B. K.; Macedo, F.

2008-01-01

Thermal wave characterization of thin films used in industrial applications can be a useful tool, not just to get information on the films' thermal properties, but to get information on structural-physical parameters, e.g. crystalline structure and surface roughness, and on the film deposition conditions, since the thermal film properties are directly related to the structural-physical parameters and to the deposition conditions. Different sets of TiCXOY thin films, deposited by reactive magnetron sputtering on steel, have been prepared, changing only one deposition parameter at a time. Here, the effect of the oxygen flow on the thermal film properties is studied. The thermal waves have been measured by modulated IR radiometry, and the phase lag data have been interpreted using an Extremum method by which the thermal coating parameters are directly related to the values and modulation frequencies of the relative extrema of the inverse calibrated thermal wave phases. Structural/morphological characterization has been done using X-ray diffraction (XRD) and atomic force microscopy (AFM). The characterization of the films also includes thickness, hardness, and electric resistivity measurements. The results obtained so far indicate strong correlations between the thermal diffusivity and conductivity, on the one hand, and the oxygen flow on the other hand.

Study of the effect of gamma irradiation on a commercial polycyclooctene I. Thermal and mechanical properties

NASA Astrophysics Data System (ADS)

García-Huete, N.; Laza, J. M.; Cuevas, J. M.; Vilas, J. L.; Bilbao, E.; León, L. M.

2014-09-01

A gamma radiation process for modification of commercial polymers is a widely applied technique to promote new physical, chemical and mechanical properties. Gamma irradiation originates free radicals able to induce chain scission or recombination of radicals, which induces annihilation, branching or crosslinking processes. The aim of this work is to research the structural, thermal and mechanical changes induced on a commercial polycyclooctene (PCO) when it is irradiated with a gamma source of 60Co at different doses (25-200 kGy). After gamma irradiation, gel content was determined by Soxhlet extraction in cyclohexane. Furthermore, thermal properties were evaluated before and after Soxhlet extraction by means of Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC), as well as mechanical properties were measured by Dynamic Mechanical Thermal Analysis (DMTA). The results showed the variations of the properties depending on the irradiation dose. Finally, a first approach to evaluate qualitatively the shape memory behaviour of all irradiated PCO samples was performed by a visually monitoring shape recovery process.

Sustainable hemp-based composites for the building industry application

NASA Astrophysics Data System (ADS)

Schwarzova, Ivana; Stevulova, Nadezda; Junak, Jozef; Hospodarova, Viola

2017-07-01

Sustainability goals are essential driving principles for the development of innovative materials in the building industry. Natural plant (e.g. hemp) fibers represent an attractive alternative as reinforcing material due to its good properties and sustainability prerequisites. In this study, hemp-based composite materials, designed for building application as non-load bearing material, providing both thermal insulation and physico-mechanical properties, are presented. Composite materials were produced by bonding hemp hurds with a novel inorganic binder (MgO-based cement) and then were characterized in terms of physical properties (bulk density, water absorption), thermal properties (thermal conductivity) and mechanical properties (compressive and tensile strength). The composites exhibited promising physical, thermal and mechanical characteristics, generally comparable to commercially available products. In addition, the hemp-based composites have the advantage of a significantly low environmental impact (thanks to the nature of both the dispersed and the binding phase) and no negative effects on human health. All things considered, the composite materials seem like very promising materials for the building industry application.

Effects of alkali treatment on the mechanical and thermal properties of Sansevieria trifasciata fiber

NASA Astrophysics Data System (ADS)

Mardiyati, Steven, Rizkiansyah, Raden Reza; Senoaji, A.; Suratman, R.

2016-04-01

In this study, Sansevieria trifasciata fibers were treated by NaOH with concentration 1%,3%, and 5wt% at 100°C for 2 hours. Chesson-Datta methods was used to determine the lignocellulose content of raw sansevieria fibers and to investigate effect of alkali treatment on lignin content of the fiber. Mechanical properties and thermal properties of treated and untreated fibers were measured by means of tensile testing machine and thermogravimetric analysis (TGA).The cellulose and lignin contents of raw sansevieria fiber obtained from Chesson-Datta method were 56% and 6% respectively. Mechanical testing of fibers showed the increase of tensile strength from 647 MPa for raw fibers to 902 MPa for 5wt% NaOH treated fibers. TGA result showed the alkali treatment increase the thermal resistance of fibers from 288°C for raw fibers to 307°C for 5% NaOH treated fiber. It was found that alkali treatment affect the mechanical properties and thermal properties of sansevieria fibers.

Thermophysical properties of low cost lithium nitrate salts produced in northern Chile for thermal energy storage

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

Fernández, Ángel G.; Gomez-Vidal, Judith C.

In recent years, lithium containing salts have been studied for thermal energy storage (TES) applications because of their excellent thermophysical properties. In solar power plants, lithium is seen as a way to improve the properties of state-of-the art molten salts used today. Lithium nitrate is a good candidate for sensible heat storage, because of its ability to increase the salt mixture's working temperature range. In the present research, thermophysical properties characterization of lithium nitrate containing salts, produced in Chile, have been carried out. Corrosion evaluations at 390° and 565 °C for 1000 h were performed for low chromium steel T22more » and stainless steels (AISI 430 and AISI 316), respectively. Chemical composition of the salts including identification of corrosion products and impurities was determined and an estimation of the Chilean production costs is reported. The study shows a loss of thermal properties after the corrosion tests. The heat capacity was reduced, possibly caused by the formation of oxides at high temperatures. As a result, the partial thermal decomposition of the salt was probably produced by the incorporation of corrosion products from the steel.« less

Thermophysical properties of low cost lithium nitrate salts produced in northern Chile for thermal energy storage

DOE PAGES

Fernández, Ángel G.; Gomez-Vidal, Judith C.

2016-09-01

In recent years, lithium containing salts have been studied for thermal energy storage (TES) applications because of their excellent thermophysical properties. In solar power plants, lithium is seen as a way to improve the properties of state-of-the art molten salts used today. Lithium nitrate is a good candidate for sensible heat storage, because of its ability to increase the salt mixture's working temperature range. In the present research, thermophysical properties characterization of lithium nitrate containing salts, produced in Chile, have been carried out. Corrosion evaluations at 390° and 565 °C for 1000 h were performed for low chromium steel T22more » and stainless steels (AISI 430 and AISI 316), respectively. Chemical composition of the salts including identification of corrosion products and impurities was determined and an estimation of the Chilean production costs is reported. The study shows a loss of thermal properties after the corrosion tests. The heat capacity was reduced, possibly caused by the formation of oxides at high temperatures. As a result, the partial thermal decomposition of the salt was probably produced by the incorporation of corrosion products from the steel.« less

Thermal properties of soils: effect of biochar application

NASA Astrophysics Data System (ADS)

Usowicz, Boguslaw; Lukowski, Mateusz; Lipiec, Jerzy

2014-05-01

Thermal properties (thermal conductivity, heat capacity and thermal diffusivity) have a significant effect on the soil surface energy partitioning and resulting in the temperature distribution. Thermal properties of soil depend on water content, bulk density and organic matter content. An important source of organic matter is biochar. Biochar as a material is defined as: "charcoal for application as a soil conditioner". Biochar is generally associated with co-produced end products of pyrolysis. Many different materials are used as biomass feedstock for biochar, including wood, crop residues and manures. Additional predictions were done for terra preta soil (also known as "Amazonian dark earth"), high in charcoal content, due to adding a mixture of charcoal, bone, and manure for thousands of years i.e. approximately 10-1,000 times longer than residence times of most soil organic matter. The effect of biochar obtained from the wood biomass and other organic amendments (peat, compost) on soil thermal properties is presented in this paper. The results were compared with wetland soils of different organic matter content. The measurements of the thermal properties at various water contents were performed after incubation, under laboratory conditions using KD2Pro, Decagon Devices. The measured data were compared with predictions made using Usowicz statistical-physical model (Usowicz et al., 2006) for biochar, mineral soil and soil with addition of biochar at various water contents and bulk densities. The model operates statistically by probability of occurrence of contacts between particular fractional compounds. It combines physical properties, specific to particular compounds, into one apparent conductance specific to the mixture. The results revealed that addition of the biochar and other organic amendments into the soil caused considerable reduction of the thermal conductivity and diffusivity. The mineral soil showed the highest thermal conductivity and diffusivity that decreased in soil with addition of biochar and pure biochar. The reduction of both properties was mostly due to decrease in both particle density and bulk density. Both biochar and the organic amendments addition resulted in a decrease of the heat capacity of the mixtures in dry state and considerable increase in wet state. The lowest and highest reduction in the thermal conductivity with decreasing water content was obtained for pure biochar and mineral soil, respectively. The thermal diffusivity had a characteristic maximum at higher bulk densities and lower water contents. The wetland soil higher in organic matter content exhibit smaller temporal variation of the thermal properties compared to soils lower in organic matter content in response to changes of water content. The statistical-physical model was found to be useful for satisfactory predicting thermal properties of the soil with addition of biochar and organic amendments. Usowicz B. et al., 2006. Thermal conductivity modelling of terrestrial soil media - A comparative study. Planetary and Space Science 54, 1086-1095.

A Method to Estimate the Hydraulic Conductivity of the Ground by TRT Analysis.

PubMed

Liuzzo Scorpo, Alberto; Nordell, Bo; Gehlin, Signhild

2017-01-01

The knowledge of hydraulic properties of aquifers is important in many engineering applications. Careful design of ground-coupled heat exchangers requires that the hydraulic characteristics and thermal properties of the aquifer must be well understood. Knowledge of groundwater flow rate and aquifer thermal properties is the basis for proper design of such plants. Different methods have been developed in order to estimate hydraulic conductivity by evaluating the transport of various tracers (chemical, heat etc.); thermal response testing (TRT) is a specific type of heat tracer that allows including the hydraulic properties in an effective thermal conductivity value. Starting from these considerations, an expeditious, graphical method was proposed to estimate the hydraulic conductivity of the aquifer, using TRT data and plausible assumption. Suggested method, which is not yet verified or proven to be reliable, should be encouraging further studies and development in this direction. © 2016, National Ground Water Association.

Palm oil based nanofluids for enhancing heat transfer and rheological properties

NASA Astrophysics Data System (ADS)

Hussein, A. M.; Lingenthiran; Kadirgamma, K.; Noor, M. M.; Aik, L. K.

2018-04-01

Colloidal suspensions of nanomaterials size not more than 100 nm in basefluid are defined as nanofluids. The thermal and rheological properties study of oil based nanofluid is conducted to develop stable transformers palm oil based nanofluid. This paper describes the analysis techniques to determine the enhancement of thermal properties of nanofluids. Titanium dioxide (TiO2) has dispersed in the palm oil to prepare nanofluids with volume concentration (0.01-0.09) percentage. Both thermal conductivity and viscosity of nanofluid have measured by using the hot wire method and viscometer equipment respectively. Results indicate that the stable nanofluids improve the thermal properties as compared to palm oil. Results showed that the friction factor decreases as the Reynolds number increases and increases as the volume concentration increases. Additionally, the Nusselt number increases as the Reynolds number and volume concentration of the nanofluid increases.

Proton irradiation effects on beryllium - A macroscopic assessment

NASA Astrophysics Data System (ADS)

Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong; Camino, Fernando

2016-10-01

Beryllium, due to its excellent neutron multiplication and moderation properties, in conjunction with its good thermal properties, is under consideration for use as plasma facing material in fusion reactors and as a very effective neutron reflector in fission reactors. While it is characterized by unique combination of structural, chemical, atomic number, and neutron absorption cross section it suffers, however, from irradiation generated transmutation gases such as helium and tritium which exhibit low solubility leading to supersaturation of the Be matrix and tend to precipitate into bubbles that coalesce and induce swelling and embrittlement thus degrading the metal and limiting its lifetime. Utilization of beryllium as a pion production low-Z target in high power proton accelerators has been sought both for its low Z and good thermal properties in an effort to mitigate thermos-mechanical shock that is expected to be induced under the multi-MW power demand. To assess irradiation-induced changes in the thermal and mechanical properties of Beryllium, a study focusing on proton irradiation damage effects has been undertaken using 200 MeV protons from the Brookhaven National Laboratory Linac and followed by a multi-faceted post-irradiation analysis that included the thermal and volumetric stability of irradiated beryllium, the stress-strain behavior and its ductility loss as a function of proton fluence and the effects of proton irradiation on the microstructure using synchrotron X-ray diffraction. The mimicking of high temperature irradiation of Beryllium via high temperature annealing schemes has been conducted as part of the post-irradiation study. This paper focuses on the thermal stability and mechanical property changes of the proton irradiated beryllium and presents results of the macroscopic property changes of Beryllium deduced from thermal and mechanical tests.

Thermal dose dependent optical property changes of ex vivo chicken breast tissues between 500 and 1100 nm.

PubMed

Adams, Matthew T; Wang, Qi; Cleveland, Robin O; Roy, Ronald A

2014-07-07

This study examines the effectiveness of the thermal dose model in accurately predicting thermally induced optical property changes of ex vivo chicken breast between 500-1100 nm. The absorption coefficient, μa, and the reduced scattering coefficient, μ's, of samples are measured as a function of thermal dose over the range 50 °C-70 °C. Additionally, the maximum observable changes in μa and μ's are measured as a function of temperature in the range 50 °C-90 °C. Results show that the standard thermal dose model used in the majority of high-intensity focused ultrasound (HIFU) treatments is insufficient for modeling optical property changes, but that the isodose constant may be modified in order to better predict thermally induced changes. Additionally, results are presented that show a temperature dependence on changes in the two coefficients, with an apparent threshold effect occurring between 65 °C-70 °C.

Review on factors influencing thermal conductivity of concrete incorporating various type of waste materials

NASA Astrophysics Data System (ADS)

Misri, Z.; Ibrahim, M. H. W.; Awal, A. S. M. A.; Desa, M. S. M.; Ghadzali, N. S.

2018-04-01

Concrete is well-known as a construction material which is widely used in building and infrastructure around the world. However, its widespread use has affected the reduction of natural resources. Hence, many approached have been made by researchers to study the incorporation of waste materials in concrete as a substitution for natural resources besides reducing waste disposal problems. Concrete is basically verified by determining its properties; strengths, permeability, shrinkage, durability, thermal properties etc. In various thermal properties of concrete, thermal conductivity (TC) has received a large amount of attention because it is depend upon the composition of concrete. Thermal conductivity is important in building insulation to measure the ability of a material to transfer heat. The aim of this paper is to discuss the methods and influence factors of TC of concrete containing various type of waste materials.

Effectively control negative thermal expansion of single-phase ferroelectrics of PbTiO3-(Bi,La)FeO3 over a giant range.

PubMed

Chen, Jun; Wang, Fangfang; Huang, Qingzhen; Hu, Lei; Song, Xiping; Deng, Jinxia; Yu, Ranbo; Xing, Xianran

2013-01-01

Control of negative thermal expansion is a fundamentally interesting topic in the negative thermal expansion materials in order for the future applications. However, it is a challenge to control the negative thermal expansion in individual pure materials over a large scale. Here, we report an effective way to control the coefficient of thermal expansion from a giant negative to a near zero thermal expansion by means of adjusting the spontaneous volume ferroelectrostriction (SVFS) in the system of PbTiO3-(Bi,La)FeO3 ferroelectrics. The adjustable range of thermal expansion contains most negative thermal expansion materials. The abnormal property of negative or zero thermal expansion previously observed in ferroelectrics is well understood according to the present new concept of spontaneous volume ferroelectrostriction. The present studies could be useful to control of thermal expansion of ferroelectrics, and could be extended to multiferroic materials whose properties of both ferroelectricity and magnetism are coupled with thermal expansion.

Effectively control negative thermal expansion of single-phase ferroelectrics of PbTiO3-(Bi,La)FeO3 over a giant range

PubMed Central

Chen, Jun; Wang, Fangfang; Huang, Qingzhen; Hu, Lei; Song, Xiping; Deng, Jinxia; Yu, Ranbo; Xing, Xianran

2013-01-01

Control of negative thermal expansion is a fundamentally interesting topic in the negative thermal expansion materials in order for the future applications. However, it is a challenge to control the negative thermal expansion in individual pure materials over a large scale. Here, we report an effective way to control the coefficient of thermal expansion from a giant negative to a near zero thermal expansion by means of adjusting the spontaneous volume ferroelectrostriction (SVFS) in the system of PbTiO3-(Bi,La)FeO3 ferroelectrics. The adjustable range of thermal expansion contains most negative thermal expansion materials. The abnormal property of negative or zero thermal expansion previously observed in ferroelectrics is well understood according to the present new concept of spontaneous volume ferroelectrostriction. The present studies could be useful to control of thermal expansion of ferroelectrics, and could be extended to multiferroic materials whose properties of both ferroelectricity and magnetism are coupled with thermal expansion. PMID:23949238

Mechanical and thermal properties of waterborne epoxy composites containing cellulose nanocrystals

Treesearch

Shanhong Xu; Natalie Girouard; Gregory Schueneman; Meisha L. Shofner; J. Carson Meredith

2013-01-01

Cellulose nanocrystals (CNCs) are reinforcing fillers of emerging interest for polymers due to their high modulus and potential for sustainable production. In this study, CNC-based composites with a waterborne epoxy resin matrix were prepared and characterized to determine morphology, water content, and thermal and mechanical properties. While some CNC aggregation was...

Seasonal and clonal variations in technological and thermal properties of raw Hevea natural rubber

USDA-ARS?s Scientific Manuscript database

This study was undertaken over a ten-month period, under the environmental conditions within the state of Mato Grosso, Brazil, to evaluate the causes of variation in technological and thermal properties of raw natural rubber from different clones of Hevea brasiliensis (GT 1, PR 255, FX 3864 and RRIM...

Vibrational and Thermal Properties of Oxyanionic Crystals

NASA Astrophysics Data System (ADS)

Korabel'nikov, D. V.

2018-03-01

The vibrational and thermal properties of dolomite and alkali chlorates and perchlorates were studied in the gradient approximation of density functional theory using the method of a linear combination of atomic orbitals (LCAO). Long-wave vibration frequencies, IR and Raman spectra, and mode Gruneisen parameters were calculated. Equation-of-state parameters, thermodynamic potentials, entropy, heat capacity, and thermal expansion coefficient were also determined. The thermal expansion coefficient of dolomite was established to be much lower than for chlorates and perchlorates. The temperature dependence of the heat capacity at T > 200 K was shown to be generally governed by intramolecular vibrations.

Thermal Properties of Consolidated Granular Salt as a Backfill Material

NASA Astrophysics Data System (ADS)

Paneru, Laxmi P.; Bauer, Stephen J.; Stormont, John C.

2018-03-01

Granular salt has been proposed as backfill material in drifts and shafts of a nuclear waste disposal facility where it will serve to conduct heat away from the waste to the host rock. Creep closure of excavations in rock salt will consolidate (reduce the porosity of) the granular salt. This study involved measuring the thermal conductivity and specific heat of granular salt as a function of porosity and temperature to aid in understanding how thermal properties will change during granular salt consolidation accomplished at pressures and temperatures consistent with a nuclear waste disposal facility. Thermal properties of samples from laboratory-consolidated granular salt and in situ consolidated granular salt were measured using a transient plane source method at temperatures ranging from 50 to 250 °C. Additional measurements were taken on a single crystal of halite and dilated polycrystalline rock salt. Thermal conductivity of granular salt decreased with increases in temperature and porosity. Specific heat of granular salt at lower temperatures decreased with increasing porosity. At higher temperatures, porosity dependence was not apparent. The thermal conductivity and specific heat data were fit to empirical models and compared with results presented in the literature. At comparable densities, the thermal conductivities of granular salt samples consolidated hydrostatically in this study were greater than those measured previously on samples formed by quasi-static pressing. Petrographic studies of the consolidated salt indicate that the consolidation method influenced the nature of the porosity; these observations are used to explain the variation of measured thermal conductivities between the two consolidation methods. Thermal conductivity of dilated polycrystalline salt was lower than consolidated salt at comparable porosities. The pervasive crack network along grain boundaries in dilated salt impedes heat flow and results in a lower thermal conductivity compared to hydrostatically consolidated salt.

Current Bypassing Properties by Thermal Switch for PCS Application on NMR/MRI HTS Magnets

NASA Astrophysics Data System (ADS)

Kim, S. B.; Takahashi, M.; Saito, R.; Park, Y. J.; Lee, M. W.; Oh, Y. K.; Ann, H. S.

We develop the compact NMR/MRI device using high temperature superconducting (HTS) wires with the persistent current mode operating. So, the joint techniques between 2G wires are very important issue and many studies have been carried out. Recently, the Kbigdot JOINS, Inc. has developed successfully the high performance superconducting joints between 2G wires by partial melting diffusion and oxygenation annealing process [1]. In this study, the current bypassing properties in a loop-shaped 2G wire are measured experimentally to develop the permanent current switch (PSC). The current bypassing properties of loop-shaped test coil wound with 2G wire (GdBCO) are evaluated by measured the self-magnetic field due to bypassed current by Hall sensors. The strain gauge was used as heater for persistent current switch, and thermal properties against various thermal inputs were investigated experimentally.

Thermal and ac electrical properties of N-methylanthranilic acid below room temperature

NASA Astrophysics Data System (ADS)

Abdel-Kader, M. M.; Basha, M. A. F.; Ramzy, G. H.; Aboud, A. I.

2018-06-01

In this study, we investigated the thermal and alternating current (ac) electrical properties of N-methylanthranilic acid. Based on data obtained by differential scanning calorimetry, we detected two endothermic transitions at ≈ 213 K and ≈265.41 K. The weakening of hydrogen bonds as the temperature increased appeared to be the main cause of these phase transitions. We also recorded the melting point at about 475.5 K. Both the ac conductivity (σac) and complex dielectric constant (ε∗ = ε ' - jε ' ') were studied as functions of temperature over the frequency range from 1 kHz to 100 kHz. We observed significant variations in the thermal and electrical properties before and after the transition temperature at 265.41 K. The conduction mechanism responsible for the ac electrical properties before this transition was due to overlapping large polarons. These novel results are expected to have impacts on the application of organic semiconductors and dielectrics.

The Impact of Halloysite on the Thermo-Mechanical Properties of Polymer Composites.

PubMed

Gaaz, Tayser Sumer; Sulong, Abu Bakar; Kadhum, Abdul Amir H; Al-Amiery, Ahmed A; Nassir, Mohamed H; Jaaz, Ahed Hameed

2017-05-20

Nanotubular clay minerals, composed of aluminosilicate naturally structured in layers known as halloysite nanotubes (HNTs), have a significant reinforcing impact on polymer matrixes. HNTs have broad applications in biomedical applications, the medicine sector, implant alloys with corrosion protection and manipulated transportation of medicines. In polymer engineering, different research studies utilize HNTs that exhibit a beneficial enhancement in the properties of polymer-based nanocomposites. The dispersion of HNTs is improved as a result of pre-treating HNTs with acids. The HNTs' percentage additive up to 7% shows the highest improvement of tensile strength. The degradation of the polymer can be also significantly improved by doping a low percentage of HNTs. Both the mechanical and thermal properties of polymers were remarkably improved when mixed with HNTs. The effects of HNTs on the mechanical and thermal properties of polymers, such as ultimate strength, elastic modulus, impact strength and thermal stability, are emphasized in this study.

Chromate conversion coating: Iridite 14-2 thermal/optical characterization

NASA Astrophysics Data System (ADS)

Rodriguez, Marcello

2012-10-01

Chromate Conversion Coating (CCC) BOL and EOL thermal properties (absorptance and emittance) have been unspecified throughout the industry and throughout its use here at GSFC. Being key values essential for thermal engineers to assess thermal space conditions, this study focuses on the current application process, its outputted properties and assess whether these properties can in turn be classified under proper documentation. The results show that wide variations in the process overcome any possibility in thermally classifying this coating. A new set of samples were fabricated (in preparation for space environmental studies) in which a more controlled approach to applying the CCC was made. The resulting thermal values continued to show variations indicating lack of bath agitation existing within the bath. From this study you can conclude that witness samples may not best represent the flight hardware for this coating. The study then turns to space environmental study testing samples to high temperature (80°C), high vacuum, and combination of both, and UV radiation totaling 1625 ESH. The results showed an extremely dynamic coating sensitive to every environmental condition it was exposed to. Though the initial changes to the coating are drastic, post initial changes appear to be minuscule making EOL predictions more attainable. These results show that the worst case alpha/emittance values are likely after ground processing and before space exposure. From the data obtained in this study greater understanding and more informed decisions can be made with respect to this coating.

Non-aggregated axially disubstituted silicon phthalocyanines bearing electropolymerizable ligands and their aggregation, electropolymerizaton and thermal properties.

PubMed

Biyiklioglu, Zekeriya; Bas, Huseyin; Alp, Hakan

2015-08-21

A novel series of axially disubstituted silicon(iv) phthalocyanines bearing electropolymerizable ligands were designed and synthesized for the first time. The silicon(iv) phthalocyanines were characterized by various spectroscopic techniques as well as elemental analysis. The aggregation behavior of the SiPcs were examined in different solvents and at different concentrations in chloroform. In all the studied solvents and concentrations, the SiPcs were non-aggregated. The thermal behavior of the silicon(iv) phthalocyanines was also studied. The electropolymerization properties of the silicon(iv) phthalocyanines were investigated by cyclic and square wave voltammetry. This study is the first example of the electropolymerization of axially disubstituted silicon phthalocyanines. The type of axial ligand on the phthalocyanine ring did not show any effect on the absorption and thermal properties but influenced the electropolymerization of the phthalocyanines.

Lattice stability and thermal properties of Fe2VAl and Fe2TiSn Heusler compounds

NASA Astrophysics Data System (ADS)

Shastri, Shivprasad S.; Pandey, Sudhir K.

2018-04-01

Fe2VAl and Fe2TiSn are two full-Heusler compounds with non-magnetic ground states. They have application as potential thermoelectric materials. Along with first-principles electronic structure calculations, phonon calculation is one of the important tools in condensed matter physics and material science. Phonon calculations are important in understanding mechanical properties, thermal properties and phase transitions of periodic solids. A combination of electronic structure code and phonon calculation code - phonopy is employed in this work. The vibrational spectra, phonon DOS and thermal properties are studied for these two Heusler compounds. Two compounds are found to be dynamically stable with absence of negative frequencies (energy) in the phonon band structure.

Thermoelectric properties and thermal stability of layered chalcogenides, TlScQ2, Q = Se, Te.

PubMed

Aswathy, Vijayakumar Sajitha; Sankar, Cheriyedath Raj; Varma, Manoj Raama; Assoud, Abdeljalil; Bieringer, Mario; Kleinke, Holger

2017-12-12

A few thallium based layered chalcogenides of α-NaFeO 2 structure-type are known for their excellent thermoelectric properties and interesting topological insulator nature. TlScQ 2 belongs to this structural category. In the present work, we have studied the electronic structure, electrical and thermal transport properties and thermal stability of the title compounds within the temperature range 2-600 K. Density functional theory (DFT) predicts a metallic nature for TlScTe 2 and a semiconducting nature for TlScSe 2 . DFT calculations also show significant lowering of energies of frontier bands upon inclusion of spin-orbit coupling contribution in the calculation. The electronic structure also shows the simultaneous occurrence of holes and electron pockets for the telluride. Experiments reveal that the telluride shows a semi-metallic behaviour whereas the selenide is a semiconductor. The thermoelectric properties for both the materials were also investigated. Both these materials possess very low thermal conductivity which is an attractive feature for thermoelectrics. However, they lack thermal stability and decompose upon warming above room temperature, as evidenced from high temperature powder X-ray diffraction and thermal analysis.

Residual Tensile Property of Plain Woven Jute Fiber/Poly(Lactic Acid) Green Composites during Thermal Cycling

PubMed Central

Katogi, Hideaki; Takemura, Kenichi; Akiyama, Motoki

2016-01-01

This study investigated the residual tensile properties of plain woven jute fiber reinforced poly(lactic acid) (PLA) during thermal cycling. Temperature ranges of thermal cycling tests were 35–45 °C and 35–55 °C. The maximum number of cycles was 103 cycles. The quasi-static tensile tests of jute fiber, PLA, and composite were conducted after thermal cycling tests. Thermal mechanical analyses of jute fiber and PLA were conducted after thermal cycling tests. Results led to the following conclusions. For temperatures of 35–45 °C, tensile strength of composite at 103 cycles decreased 10% compared to that of composite at 0 cycles. For temperatures of 35–55 °C, tensile strength and Young’s modulus of composite at 103 cycles decreased 15% and 10%, respectively, compared to that of composite at 0 cycles. Tensile properties and the coefficient of linear expansion of PLA and jute fiber remained almost unchanged after thermal cycling tests. From observation of a fracture surface, the length of fiber pull out in the fracture surface of composite at 103 cycles was longer than that of composite at 0 cycles. Therefore, tensile properties of the composite during thermal cycling were decreased, probably because of the decrease of interfacial adhesion between the fiber and resin. PMID:28773694

Nanoindentation and thermal characterization of poly (vinylidenefluoride)/MWCNT nanocomposites

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

Eggedi, Obulapathi; Valiyaneerilakkal, Uvais; Varghese, Soney, E-mail: soneyva@nitc.ac.in

2014-04-15

We report the preparation, thermal and micro/nanomechanical behavior of poly (vinylidine diflouride) (PVDF)/multiwalled carbon nanotube (MWCNT) nanocomposites. It has been found that the addition of MWCNT considerably enhances the β-phase formation, thermal and mechanical properties of PVDF. Atomic force microscope (AFM) studies have been performed on the composites under stress conditions to measure the mechanical properties. The nanoscale mechanical properties of the composites like Young's modulus and hardness of the nanocomposites were investigated by nanoindentation technique. Morphological studies of the nanocomposites were also studied, observations show a uniform distribution of MWCNT in the matrix and interfacial adhesion between PVDF andmore » MWCNT was achieved, which was responsible for enhancement in the hardness and Young's modulus. Differential scanning calorimetry (DSC) studies indicate that the melting temperature of the composites have been slightly increased while the heat of fusion markedly decreased with increasing MWCNT content.« less

Synthesis of thermal and chemical resistant oxygen barrier starch with reinforcement of nano silicon carbide.

PubMed

Dash, Satyabrata; Swain, Sarat K

2013-09-12

Starch/silicon carbide (starch/SiC) bionanocomposites were synthesized by solution method using different wt% of silicon carbide with starch matrix. The interaction between starch and silicon carbide was studied by Fourier transform infrared (FTIR) spectroscopy. The structure of the bionanocomposites was investigated by X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). Thermal property of starch/SiC bionanocomposites was measured and a significant enhancement of thermal resistance was noticed. The oxygen barrier property of the composites was studied and a substantial reduction in permeability was observed as compared to the virgin starch. The reduction of oxygen permeability with enhancement of thermal stability of prepared bionanocomposites may enable the materials suitable for thermal resistant packaging and adhesive applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

Thermal properties of graphene from path-integral simulations

NASA Astrophysics Data System (ADS)

Herrero, Carlos P.; Ramírez, Rafael

2018-03-01

Thermal properties of graphene monolayers are studied by path-integral molecular dynamics simulations, which take into account the quantization of vibrational modes in the crystalline membrane and allow one to consider anharmonic effects in these properties. This system was studied at temperatures in the range from 12 to 2000 K and zero external stress, by describing the interatomic interactions through the LCBOPII effective potential. We analyze the internal energy and specific heat and compare the results derived from the simulations with those yielded by a harmonic approximation for the vibrational modes. This approximation turns out to be rather precise up to temperatures of about 400 K. At higher temperatures, we observe an influence of the elastic energy due to the thermal expansion of the graphene sheet. Zero-point and thermal effects on the in-plane and "real" surface of graphene are discussed. The thermal expansion coefficient α of the real area is found to be positive at all temperatures, in contrast to the expansion coefficient αp of the in-plane area, which is negative at low temperatures and becomes positive for T ≳ 1000 K.

Application of millisecond pulsed laser for thermal fatigue property evaluation

NASA Astrophysics Data System (ADS)

Pan, Sining; Yu, Gang; Li, Shaoxia; He, Xiuli; Xia, Chunyang; Ning, Weijian; Zheng, Caiyun

2018-02-01

An approach based on millisecond pulsed laser is proposed for thermal fatigue property evaluation in this paper. Cyclic thermal stresses and strains within millisecond interval are induced by complex and transient temperature gradients with pulsed laser heating. The influence of laser parameters on surface temperature is studied. The combination of low pulse repetition rate and high pulse energy produces small temperature oscillation, while high pulse repetition rate and low pulse energy introduces large temperature shock. The possibility of application is confirmed by two thermal fatigue tests of compacted graphite iron with different laser controlled modes. The developed approach is able to fulfill the preset temperature cycles and simulate thermal fatigue failure of engine components.

Effects of KMnO4 Treatment on the Flexural, Impact, and Thermal Properties of Sugar Palm Fiber-Reinforced Thermoplastic Polyurethane Composites

NASA Astrophysics Data System (ADS)

Mohammed, A. A.; Bachtiar, D.; Rejab, M. R. M.; Jiang, X. X.; Abas, Falak O.; Abass, Raghad U.; Hasany, S. F.; Siregar, Januar P.

2018-05-01

Global warming has had a great impact on environmental changes since the last decade. Eco-friendly industrial products are of great importance to sustain life on earth, including using natural composites. Natural fibers used as fillers are also environmentally valuable because of their biodegradable nature. However, compatibility issues between the fiber and its respective matrix is a major concern. The present work focused on the study of the flexural, impact, and thermal behaviors of environmentally friendly sugar palm fibers (SPF) incorporated into a composite with thermoplastic polyurethane (TPU). Two techniques (extrusion and compression molding) were used to prepare these composites. The fiber size and dosage were kept constant at 250 µm and 30 wt.% SPF, respectively. The effects of potassium permanganate (KMnO4) treatment on the flexural, impact, and thermal behaviors of the treated SPF with 6% NaOH-reinforced TPU composites were investigated. Three different concentrations of KMnO4 (0.033%, 0.066%, and 0.125%) were studied for this purpose. The characterization of the flexural and impact properties of the new TPU/SPF composites was studied as per American Society for Testing Materials ASTM standards. Thermogravimetric analysis was employed for thermal behavior analysis of the TPU/SPF composites. The best flexural strength, impact strength, and modulus properties (8.118 MPa, 55.185 kJ/m2, and 262.102 MPa, respectively) were obtained with a 0.033% KMnO4-treated sample. However, all flexural strength, impact strength, and modulus properties for the KMnO4-treated samples were lower than the sample treated only with 6% NaOH. The highest thermal stability was also shown by the sample treated with 0.033% KMnO4. Therefore, this method enhanced the thermal properties of the TPU/SPF composites with clear deterioration of the flexural and impact properties.

Materials characterization study of conductive flexible second surface mirrors

NASA Technical Reports Server (NTRS)

Levadou, F.; Bosma, S. J.; Paillous, A.

1981-01-01

The status of prequalification and qualification work on conductive flexible second surface mirrors is described. The basic material is FEP Teflon witn either aluminium or silver vacuum deposited reflectors. The top layer has been made conductive by deposition of layer of a indium oxide. The results of a prequalification program comprised of decontamination, humidity, thermal cycling, thermal shock and vibration tests are presented. Thermo-optical and electrical properties. The results of a prequalification program comprised of decontamination, humidity, thermal cycling, thermal shock and vibration tests are presented. Thermo-optical and electrical properties, the electrostatic behavior of the materials under simulated substorm environment and electrical conductivity at low temperatures are characterized. The effects of simulated ultra violet and particles irradiation on electrical and thermo-optical properties of the materials are also presented.

Thermal characteristic investigation of eutectic composite fatty acid as heat storage material for solar heating and cooling application

NASA Astrophysics Data System (ADS)

Thaib, R.; Fauzi, H.; Ong, H. C.; Rizal, S.; Mahlia, T. M. I.; Riza, M.

2018-03-01

A composite phase change material (CPCM) of myristic acid/palmitic acid/sodium myristate (MA/PA/SM) and of myristic acid/palmitic acid/sodium laurate (MA/PA/SL) were impregnated with purified damar gum as called Shorea Javanica (SJ) to improve the thermal conductivity of CPCM. The thermal properties, thermal conductivity, and thermal stability of both CPCM have investigated by using a Differential Scanning Calorimetry (DSC) thermal analysis, hot disc thermal conductivity analyzer, and Simultaneous Thermal Analyzer (STA), simultaneously. However, a chemical compatibility between both fatty acid eutectic mixtures and SJ in composite mixtures measured by Fourier Transform Infra-Red (FT-IR) spectrophotometer. The results were obtained that the thermal conductivity of MA/PA/SM/SJ and MA/PA/SL/SJ eutectic composite phase change material (CPCM) were improved by addition 3 wt.% and 2 wt.% of Shorea javanica (SJ), respectively, without occur a significant change on thermal properties of CPCM. Moreover, the absorbance spectrum of FT-IR shows the good compatibility of SJ with both MA/PA/SM and MA/PA/SL eutectic mixtures, the composite PCM also present good thermal performance and good thermal stability. Therefore, it can be noted that the purified Shorea Javanica proposed, the as high conductive material in this study was able to improve the thermal conductivity of eutectic PCM without any significant reduction on its thermo-physical and chemical properties and can be recommended as novelty composite phase change material for thermal energy storage application.

Precise Heat Control: What Every Scientist Needs to Know About Pyrolytic Techniques to Solve Real Problems

NASA Technical Reports Server (NTRS)

Devivar, Rodrigo

2014-01-01

The performance of a material is greatly influenced by its thermal and chemical properties. Analytical pyrolysis, when coupled to a GC-MS system, is a powerful technique that can unlock the thermal and chemical properties of almost any substance and provide vital information. At NASA, we depend on precise thermal analysis instrumentation for understanding aerospace travel. Our analytical techniques allow us to test materials in the laboratory prior to an actual field test; whether the field test is miles up in the sky or miles underground, the properties of any involved material must be fully studied and understood in the laboratory.

Thermal and mechanical analysis of PVA / sulfonated carbon nanotubes composite

NASA Astrophysics Data System (ADS)

Yadav, Vikrant; Sharma, Prem P.; Rajput, Abhishek; Kulshrestha, Vaibhav

2018-04-01

Nanocomposites of polyvinyl alcohol (PVA) and sulfonated carbon nanotubes (s-CNT) with enhanced properties were synthesized successfully. Effect of different amount of sulfonated nanotubes on thermal and mechanical properties of resultant nanocomposites derived from s-CNT and PVA were studied. Structural analysis for functionalization of CNT was done by using FTIR spectra. Thermal and mechanical analysis were done by using TGA, DSC and UTM. Nanocomposite containing s-CNT shows higher elastic moduli, higher melting temperature in consort with lower weight loss at same temperature, compared with pristine PVA. The novelty of this work is to use PVA/s-CNT based composites with improved thermomechanical properties in different nanotechnologies.

Anisotropic in-Plane Thermal Conductivity Observed in Few-Layer Black Phosphorus

DTIC Science & Technology

2015-10-16

optoelectronic devices where the anisotropic properties might be used10,21–23. Although electronic and photovoltaic properties have been extensively...investigated, thermal transport studies of BP, especially experimental ones, are still lacking. Recently, the thermoelectric power of bulk BP has been...reported, indicating that BP could be used as an efficient thermoelectric material at around 380K24. Some recent first-principles studies also raised

Performance Properties of Graphite Reinforced Composites with Advanced Resin Matrices

NASA Technical Reports Server (NTRS)

Kourtides, Demetrius A.

1980-01-01

This article looks at the effect of different resin matrices on thermal and mechanical properties of graphite composites, and relates the thermal and flammability properties to the anaerobic char yield of the resins. The processing parameters of graphite composites utilizing graphite fabric and epoxy or other advanced resins as matrices are presented. Thermoset resin matrices studied were: aminecured polyfunctional glycidyl aminetype epoxy (baseline), phenolicnovolac resin based on condensation of dihydroxymethyl-xylene and phenol cured with hexamine, two types of polydismaleimide resins, phenolic resin, and benzyl resin. The thermoplastic matrices studied were polyethersulfone and polyphenylenesulfone. Properties evaluated in the study included anaerobic char yield, limiting oxygen index, smoke evolution, moisture absorption, and mechanical properties at elevated temperatures including tensile, compressive, and short-beam shear strengths. Generally, it was determined that graphite composites with the highest char yield exhibited optimum fire-resistant properties.

Lithium aluminosilicate reinforced with carbon nanofiber and alumina for controlled-thermal-expansion materials

NASA Astrophysics Data System (ADS)

Borrell, Amparo; García-Moreno, Olga; Torrecillas, Ramón; García-Rocha, Victoria; Fernández, Adolfo

2012-02-01

Materials with a very low or tailored thermal expansion have many applications ranging from cookware to the aerospace industry. Among others, lithium aluminosilicates (LAS) are the most studied family with low and negative thermal expansion coefficients. However, LAS materials are electrical insulators and have poor mechanical properties. Nanocomposites using LAS as a matrix are promising in many applications where special properties are achieved by the addition of one or two more phases. The main scope of this work is to study the sinterability of carbon nanofiber (CNFs)/LAS and CNFs/alumina/LAS nanocomposites, and to adjust the ratio among components for obtaining a near-zero or tailored thermal expansion. Spark plasma sintering of nanocomposites, consisting of commercial CNFs and alumina powders and an ad hoc synthesized β-eucryptite phase, is proposed as a solution to improving mechanical and electrical properties compared with the LAS ceramics obtained under the same conditions. X-ray diffraction results on phase compositions and microstructure are discussed together with dilatometry data obtained in a wide temperature range (-150 to 450 °C). The use of a ceramic LAS phase makes it possible to design a nanocomposite with a very low or tailored thermal expansion coefficient and exceptional electrical and mechanical properties.

Numerical Study on the Thermal Stress and its Formation Mechanism of a Thermoelectric Device

NASA Astrophysics Data System (ADS)

Pan, Tao; Gong, Tingrui; Yang, Wei; Wu, Yongjia

2018-06-01

The strong thermo-mechanical stress is one of the most critical failure mechanisms that affect the durability of thermoelectric devices. In this study, numerical simulations on the formation mechanism of the maximum thermal stress inside the thermoelectric device have been performed by using finite element method. The influences of the material properties and the thermal radiation on the thermal stress have been examined. The results indicate that the maximum thermal stress was located at the contact position between the two materials and occurred due to differential thermal expansions and displacement constraints of the materials. The difference in the calculated thermal stress value between the constant and the variable material properties was between 3% and 4%. At a heat flux of 1 W·cm-2 and an emissivity of 0.5, the influence of the radiation heat transfer on the thermal stress was only about 5%; however, when the heat flux was 20 W·cm-2 and the emissivity was 0.7, the influence of the radiation heat transfer was more than 30%.

Temperature-dependent thermal properties of ex vivo liver undergoing thermal ablation.

PubMed

Guntur, Sitaramanjaneya Reddy; Lee, Kang Il; Paeng, Dong-Guk; Coleman, Andrew John; Choi, Min Joo

2013-10-01

Thermotherapy uses a heat source that raises temperatures in the target tissue, and the temperature rise depends on the thermal properties of the tissue. Little is known about the temperature-dependent thermal properties of tissue, which prevents us from accurately predicting the temperature distribution of the target tissue undergoing thermotherapy. The present study reports the key thermal parameters (specific heat capacity, thermal conductivity and heat diffusivity) measured in ex vivo porcine liver while being heated from 20 ° C to 90 ° C and then naturally cooled down to 20 ° C. The study indicates that as the tissue was heated, all the thermal parameters resulted in plots with asymmetric quasi-parabolic curves with temperature, being convex downward with their minima at the turning temperature of 35-40 ° C. The largest change was observed for thermal conductivity, which decreased by 9.6% from its initial value (at 20 ° C) at the turning temperature (35 ° C) and rose by 45% at 90 ° C from its minimum (at 35 ° C). The minima were 3.567 mJ/(m(3) ∙ K) for specific heat capacity, 0.520 W/(m.K) for thermal conductivity and 0.141 mm(2)/s for thermal diffusivity. The minimum at the turning temperature was unique, and it is suggested that it be taken as a characteristic value of the thermal parameter of the tissue. On the other hand, the thermal parameters were insensitive to temperature and remained almost unchanged when the tissue cooled down, indicating that their variations with temperature were irreversible. The rate of the irreversible rise at 35 ° C was 18% in specific heat capacity, 40% in thermal conductivity and 38.3% in thermal diffusivity. The study indicates that the key thermal parameters of ex vivo porcine liver vary largely with temperature when heated, as described by asymmetric quasi-parabolic curves of the thermal parameters with temperature, and therefore, substantial influence on the temperature distribution of the tissue undergoing thermotherapy is expected. 2013. Published by Elsevier Inc

In-vitro Thermal Maps to Characterize Human Dental Enamel and Dentin.

PubMed

Lancaster, Paula; Brettle, David; Carmichael, Fiona; Clerehugh, Val

2017-01-01

The crown of a human tooth has an outer layer of highly-mineralized tissue called enamel, beneath which is dentin, a less-mineralized tissue which forms the bulk of the tooth-crown and root. The composition and structure of enamel and dentin are different, resulting in different thermal properties. This gives an opportunity to characterize enamel and dentin from their thermal properties and to visually present the findings as a thermal map. The thermal properties of demineralized enamel and dentin may also be sufficiently different from sound tissue to be seen on a thermal map, underpinning future thermal assessment of caries. The primary aim of this novel study was to produce a thermal map of a sound, human tooth-slice to visually characterize enamel and dentin. The secondary aim was to map a human tooth-slice with demineralized enamel and dentin to consider future diagnostic potential of thermal maps for caries-detection. Two human slices of teeth, one sound and one demineralized from a natural carious lesion, were cooled on ice, then transferred to a hotplate at 30°C where the rewarming-sequence was captured by an infra-red thermal camera. Calculation of thermal diffusivity and thermal conductivity was undertaken, and two methods of data-processing used customized software to produce thermal maps from the thermal characteristic-time-to-relaxation and heat-exchange. The two types of thermal maps characterized enamel and dentin. In addition, sound and demineralized enamel and dentin were distinguishable within both maps. This supports thermal assessment of caries and requires further investigation on a whole tooth.

Effect of thermal exposure on mechanical properties hypo eutectic aerospace grade aluminium-silicon alloy

NASA Astrophysics Data System (ADS)

Nagesh Kumar, R.; Ram Prabhu, T.; Siddaraju, C.

2016-09-01

The effect of thermal exposure on the mechanical properties of a C355.0 aerospace grade aluminum-silicon alloy (5% Si - 1.2% Cu - 0.5% Mg) was investigated in the present study. The alloy specimens were subjected to T6 (solution treatment and artificial ageing treatment) temper treatment to enhance the strength properties through precipitation hardening. The T6 temper treatment involved solution heat treatment at 520oC for 6h, followed by water quenching and ageing at 150oC. After the heat treatment, the specimens were exposed to various temperatures (50oC, 100oC, 150oC, 200oC and 250oC) for 5 and 10 h to study the structural applications of this alloy to the various Mach number military aircrafts. After the thermal exposure, specimens were tested for tensile, hardness and impact properties (Charpy). The microstructure of the thermal exposed specimens was examined in the optical microscopes and correlated with the mechanical properties results. In summary, an increase of exposure time has a different effect on the tensile and hardness properties of the alloy. For the exposure time 5h, the tensile and hardness properties increase upto 100oC and later decrease with an increase of temperature. In contrast, the tensile and hardness properties linearly decrease with an increase of temperature. Several factors such as matrix grain growth, diffusion rate, Si particles size and distribution, precipitate stability play a key role on deciding the tensile properties of the alloy. Comparing the relative effects of temperature and time, the temperature effects dominate more in deteriorating tensile properties of the alloy. There are no effects of exposure temperature and/or time on the impact properties of the alloy.

Strain-modulated electronic and thermal transport properties of two-dimensional O-silica

NASA Astrophysics Data System (ADS)

Han, Yang; Qin, Guangzhao; Jungemann, Christoph; Hu, Ming

2016-07-01

Silica is one of the most abundant materials in the Earth’s crust and is a remarkably versatile and important engineering material in various modern science and technology. Recently, freestanding and well-ordered two-dimensional (2D) silica monolayers with octahedral (O-silica) building blocks were found to be theoretically stable by (Wang G et al 2015 J. Phys. Chem. C 119 15654-60). In this paper, by performing first-principles calculations, we systematically investigated the electronic and thermal transport properties of 2D O-silica and also studied how these properties can be tuned by simple mechanical stretching. Unstrained 2D O-silica is an insulator with an indirect band gap of 6.536 eV. The band gap decreases considerably with bilateral strain up to 29%, at which point a semiconductor-metal transition occurs. More importantly, the in-plane thermal conductivity of freestanding 2D O-silica is found to be unusually high, which is around 40 to 50 times higher than that of bulk α-quartz and more than two orders of magnitude higher than that of amorphous silica. The thermal conductivity of O-silica decreases by almost two orders of magnitude when the bilateral stretching strain reaches 10%. By analyzing the mode-dependent phonon properties and phonon-scattering channel, the phonon lifetime is found to be the dominant factor that leads to the dramatic decrease of the lattice thermal conductivity under strain. The very sensitive response of both band gap and phonon transport properties to the external mechanical strain will enable 2D O-silica to easily adapt to the different environment of realistic applications. Our study is expected to stimulate experimental exploration of further physical and chemical properties of 2D silica systems, and offers perspectives on modulating the electronic and thermal properties of related low-dimensional structures for applications such as thermoelectric, photovoltaic, and optoelectronic devices.

Strain-modulated electronic and thermal transport properties of two-dimensional O-silica.

PubMed

Han, Yang; Qin, Guangzhao; Jungemann, Christoph; Hu, Ming

2016-07-01

Silica is one of the most abundant materials in the Earth's crust and is a remarkably versatile and important engineering material in various modern science and technology. Recently, freestanding and well-ordered two-dimensional (2D) silica monolayers with octahedral (O-silica) building blocks were found to be theoretically stable by (Wang G et al 2015 J. Phys. Chem. C 119 15654-60). In this paper, by performing first-principles calculations, we systematically investigated the electronic and thermal transport properties of 2D O-silica and also studied how these properties can be tuned by simple mechanical stretching. Unstrained 2D O-silica is an insulator with an indirect band gap of 6.536 eV. The band gap decreases considerably with bilateral strain up to 29%, at which point a semiconductor-metal transition occurs. More importantly, the in-plane thermal conductivity of freestanding 2D O-silica is found to be unusually high, which is around 40 to 50 times higher than that of bulk α-quartz and more than two orders of magnitude higher than that of amorphous silica. The thermal conductivity of O-silica decreases by almost two orders of magnitude when the bilateral stretching strain reaches 10%. By analyzing the mode-dependent phonon properties and phonon-scattering channel, the phonon lifetime is found to be the dominant factor that leads to the dramatic decrease of the lattice thermal conductivity under strain. The very sensitive response of both band gap and phonon transport properties to the external mechanical strain will enable 2D O-silica to easily adapt to the different environment of realistic applications. Our study is expected to stimulate experimental exploration of further physical and chemical properties of 2D silica systems, and offers perspectives on modulating the electronic and thermal properties of related low-dimensional structures for applications such as thermoelectric, photovoltaic, and optoelectronic devices.

Development of low thermal conductivity brick using rice husk, corn cob and waste tea in clay brick manufacturing

NASA Astrophysics Data System (ADS)

Saman, Nor Sarwani Mat; Deraman, Rafikullah; Hamzah, Mohamad Hazmi

2017-12-01

The consumption of energy for cooling the indoor environment of buildings in Malaysia is high and mostly related to poor thermal performance of the building envelope. It is evident that reducing energy consumption of buildings has become vital, taking into considerations the limitation of conventional energy resources and the adverse effects associated with the use of such type of energy on the environment. Therefore, selecting the proper thermal properties of a building envelope play a major role in determining the energy consumption patterns and comfort conditions in enclosed spaces. The objective of this study is to investigate the potential application of rice husk (RH), corn cob (CC) and waste tea (WT) as an additive agent in a fired clay brick manufacturing to produce an improved thermal conductivity of final brick product. In the execution of this study, these agricultural wastes were mixed together with clay soil in different percentages, ranging from 0 %, 2.5 %, 5 %, 7.5 % and 10 % by weight. Physical and mechanical properties including soil physical properties, density, shrinkage, water absorption, compressive strength as well as thermal conductivity were measured, reported and discussed in accordance with BS 1377: Part 2: 1990, BS 3921: 1985, MS 76: 1972: Part 2 and ASTM C 518. The results show that RH at 7.5 % is the most effective combination to achieve low thermal conductivity of fired clay brick. This finding suggests that RH waste is a potentially good additive material to be used for thermal properties enhancement of the building envelope.

Multiscale Modeling of Carbon/Phenolic Composite Thermal Protection Materials: Atomistic to Effective Properties

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Murthy, Pappu L.; Bednarcyk, Brett A.; Lawson, John W.; Monk, Joshua D.; Bauschlicher, Charles W., Jr.

2016-01-01

Next generation ablative thermal protection systems are expected to consist of 3D woven composite architectures. It is well known that composites can be tailored to achieve desired mechanical and thermal properties in various directions and thus can be made fit-for-purpose if the proper combination of constituent materials and microstructures can be realized. In the present work, the first, multiscale, atomistically-informed, computational analysis of mechanical and thermal properties of a present day - Carbon/Phenolic composite Thermal Protection System (TPS) material is conducted. Model results are compared to measured in-plane and out-of-plane mechanical and thermal properties to validate the computational approach. Results indicate that given sufficient microstructural fidelity, along with lowerscale, constituent properties derived from molecular dynamics simulations, accurate composite level (effective) thermo-elastic properties can be obtained. This suggests that next generation TPS properties can be accurately estimated via atomistically informed multiscale analysis.

Thermal insulation materials for inside applications: Hygric and thermal properties

NASA Astrophysics Data System (ADS)

Jerman, Miloš; Černý, Robert

2017-11-01

Two thermal insulation materials suitable for the application on the interior side of historical building envelopes, namely calcium silicate and polyurethane-based foam are studied. Moisture diffusivity and thermal conductivity of both materials, as fundamental moisture and heat transport parameters, are measured in a dependence on moisture content. The measured data will be used as input parameters in computer simulation studies which will provide moisture and temperature fields necessary for an appropriate design of interior thermal insulation systems.

Numerical Simulation of Thermal Response and Ablation Behavior of a Hybrid Carbon/Carbon Composite

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2017-09-01

The thermal response and ablation behavior of a hybrid carbon/carbon (C/C) composite are studied herein by using a numerical model. This model is based on the energy- and mass-conservation principles as well as on the calculation of the thermophysical properties of materials. The thermal response and ablation behavior are simulated from the perspective of the matrix and fiber components of a hybrid C/C composite. The thermophysical properties during ablation are calculated, and a moving boundary is implemented to consider the recession of the ablation surface. The temperature distribution, thermophysical properties, char layer thickness, linear ablation rate, mass flow rate of the pyrolysis gases, and mass loss of the hybrid C/C composite are quantitatively predicted. This numerical study describing the thermal response and ablation behavior provides a fundamental understanding of the ablative mechanism of a hybrid C/C composite, serving as a reference and basis for further designs and optimizations of thermoprotective materials.

Numerical Simulation of Thermal Response and Ablation Behavior of a Hybrid Carbon/Carbon Composite

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2018-06-01

The thermal response and ablation behavior of a hybrid carbon/carbon (C/C) composite are studied herein by using a numerical model. This model is based on the energy- and mass-conservation principles as well as on the calculation of the thermophysical properties of materials. The thermal response and ablation behavior are simulated from the perspective of the matrix and fiber components of a hybrid C/C composite. The thermophysical properties during ablation are calculated, and a moving boundary is implemented to consider the recession of the ablation surface. The temperature distribution, thermophysical properties, char layer thickness, linear ablation rate, mass flow rate of the pyrolysis gases, and mass loss of the hybrid C/C composite are quantitatively predicted. This numerical study describing the thermal response and ablation behavior provides a fundamental understanding of the ablative mechanism of a hybrid C/C composite, serving as a reference and basis for further designs and optimizations of thermoprotective materials.

Thermal properties of graphene under tensile stress

NASA Astrophysics Data System (ADS)

Herrero, Carlos P.; Ramírez, Rafael

2018-05-01

Thermal properties of graphene display peculiar characteristics associated to the two-dimensional nature of this crystalline membrane. These properties can be changed and tuned in the presence of applied stresses, both tensile and compressive. Here, we study graphene monolayers under tensile stress by using path-integral molecular dynamics (PIMD) simulations, which allows one to take into account quantization of vibrational modes and analyze the effect of anharmonicity on physical observables. The influence of the elastic energy due to strain in the crystalline membrane is studied for increasing tensile stress and for rising temperature (thermal expansion). We analyze the internal energy, enthalpy, and specific heat of graphene, and compare the results obtained from PIMD simulations with those given by a harmonic approximation for the vibrational modes. This approximation turns out to be precise at low temperatures, and deteriorates as temperature and pressure are increased. At low temperature, the specific heat changes as cp˜T for stress-free graphene, and evolves to a dependence cp˜T2 as the tensile stress is increased. Structural and thermodynamic properties display non-negligible quantum effects, even at temperatures higher than 300 K. Moreover, differences in the behavior of the in-plane and real areas of graphene are discussed, along with their associated properties. These differences show up clearly in the corresponding compressibility and thermal expansion coefficient.

Enhanced mechanical, thermal, and electric properties of graphene aerogels via supercritical ethanol drying and high-temperature thermal reduction.

PubMed

Cheng, Yehong; Zhou, Shanbao; Hu, Ping; Zhao, Guangdong; Li, Yongxia; Zhang, Xinghong; Han, Wenbo

2017-05-03

Graphene aerogels with high surface areas, ultra-low densities and thermal conductivities have been prepared to exploit their wide applications from pollution adsorption to energy storage, supercapacitor, and thermal insulation. However, the low mechanical properties, poor thermal stability and electric conductivity restrict these aerogels' applications. In this paper, we prepared mechanically strong graphene aerogels with large BET surface areas, low thermal conductivities, high thermal stability and electric conductivities via hydrothermal reduction and supercritical ethanol drying. Annealing at 1500 °C resulted in slightly increased thermal conductivity and further improvement in mechanical properties, oxidation temperature and electric conductivity of the graphene aerogel. The large BET surface areas, together with strong mechanical properties, low thermal conductivities, high thermal stability and electrical conductivities made these graphene aerogels feasible candidates for use in a number of fields covering from batteries to sensors, electrodes, lightweight conductor and insulation materials.

Advanced thermally stable jet fuels. Technical progress report, January 1995--March 1995

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

Schobert, H.H.; Eser, S.; Song, C.

Quantitative structure-property relationships have been applied to study the thermal stability of pure hydrocarbons typical of jet fuel components. A simple method of chemical structure description in terms of Benson groups was tested in searching for structure-property relationships for the hydrocarbons tested experimentally in this program. Molecular connectivity as a structure-based approach to chemical structure-property relationship analysis was also tested. Further development of both the experimental data base and computational methods will be necessary. Thermal decomposition studies, using glass tube reactors, were extended to two additional model compounds: n-decane and n-dodecane. Efforts on refining the deposit growth measurement and characterizationmore » of suspended matter in stressed fuels have lead to improvements in the analysis of stressed fuels. Catalytic hydrogenation and dehydrogenation studies utilizing a molybdenum sulfide catalyst are also described.« less

Direct fusion of geostationary meteorological satellite visible and infrared images based on thermal physical properties.

PubMed

Han, Lei; Wulie, Buzha; Yang, Yiling; Wang, Hongqing

2015-01-05

This study investigated a novel method of fusing visible (VIS) and infrared (IR) images with the major objective of obtaining higher-resolution IR images. Most existing image fusion methods focus only on visual performance and many fail to consider the thermal physical properties of the IR images, leading to spectral distortion in the fused image. In this study, we use the IR thermal physical property to correct the VIS image directly. Specifically, the Stefan-Boltzmann Law is used as a strong constraint to modulate the VIS image, such that the fused result shows a similar level of regional thermal energy as the original IR image, while preserving the high-resolution structural features from the VIS image. This method is an improvement over our previous study, which required VIS-IR multi-wavelet fusion before the same correction method was applied. The results of experiments show that applying this correction to the VIS image directly without multi-resolution analysis (MRA) processing achieves similar results, but is considerably more computationally efficient, thereby providing a new perspective on VIS and IR image fusion.

Direct Fusion of Geostationary Meteorological Satellite Visible and Infrared Images Based on Thermal Physical Properties

PubMed Central

Han, Lei; Wulie, Buzha; Yang, Yiling; Wang, Hongqing

2015-01-01

This study investigated a novel method of fusing visible (VIS) and infrared (IR) images with the major objective of obtaining higher-resolution IR images. Most existing image fusion methods focus only on visual performance and many fail to consider the thermal physical properties of the IR images, leading to spectral distortion in the fused image. In this study, we use the IR thermal physical property to correct the VIS image directly. Specifically, the Stefan-Boltzmann Law is used as a strong constraint to modulate the VIS image, such that the fused result shows a similar level of regional thermal energy as the original IR image, while preserving the high-resolution structural features from the VIS image. This method is an improvement over our previous study, which required VIS-IR multi-wavelet fusion before the same correction method was applied. The results of experiments show that applying this correction to the VIS image directly without multi-resolution analysis (MRA) processing achieves similar results, but is considerably more computationally efficient, thereby providing a new perspective on VIS and IR image fusion. PMID:25569749

Morphological and functional effects of graphene on the synthesis of uranium carbide for isotopes production targets.

PubMed

Biasetto, L; Corradetti, S; Carturan, S; Eloirdi, R; Amador-Celdran, P; Staicu, D; Blanco, O Dieste; Andrighetto, A

2018-05-29

The development of tailored targets for the production of radioactive isotopes represents an active field in nuclear research. Radioactive beams find applications in nuclear medicine, in astrophysics, matter physics and materials science. In this work, we study the use of graphene both as carbon source for UO 2 carbothermal reduction to produce UC x targets, and also as functional properties booster. At fixed composition, the UC x target grain size, porosity and thermal conductivity represent the three main points that affect the target production efficiency. UC x was synthesized using both graphite and graphene as the source of carbon and the target properties in terms of composition, grain size, porosity, thermal diffusivity and thermal conductivity were studied. The main output of this work is related to the remarkable enhancement achieved in thermal conductivity, which can profitably improve thermal dissipation during operational stages of UC x targets.

Thermal and mechanical properties of TPU/PBT reinforced by carbon fiber

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

Huang, Jintao; Liu, Huanyu; Lu, Xiang

2016-03-09

In this study, thermal, mechanical properties and processability were performed on a series of carbon fiber (CF) filled thermoplastic polyurethane (TPU)/poly (butylene terephthalate) (PBT) composites to identify the effect of CF weight fraction on the properties of TPU/PBT. Scanning Electronic Microscope (SEM) show that CFs are uniformly dispersed in TPU/PBT matrix and there are no agglomerations. Melt flow index (MFI) show that the melt viscosity increased with the CF loading. Thermogravimetric analysis (TGA) revealed that the introduction of CF into organic materials tend to improve their thermal stability. The mechanical properties indicated that tensile strength and modulus, flexural strength andmore » modulus, improved with an increase in CF loading, but the impact strength decreased by the loading of CF.« less

Investigation of Thermal Properties of High-Density Polyethylene/Aluminum Nanocomposites by Photothermal Infrared Radiometry

NASA Astrophysics Data System (ADS)

Koca, H. D.; Evgin, T.; Horny, N.; Chirtoc, M.; Turgut, A.; Tavman, I. H.

2017-12-01

In this study, thermal properties of high-density polyethylene (HDPE) filled with nanosized Al particles (80 nm) were investigated. Samples were prepared using melt mixing method up to filler volume fraction of 29 %, followed by compression molding. By using modulated photothermal radiometry (PTR) technique, thermal diffusivity and thermal effusivity were obtained. The effective thermal conductivity of nanocomposites was calculated directly from PTR measurements and from the measurements of density, specific heat capacity (by differential scanning calorimetry) and thermal diffusivity (obtained from PTR signal amplitude and phase). It is concluded that the thermal conductivity of HDPE composites increases with increasing Al fraction and the highest effective thermal conductivity enhancement of 205 % is achieved at a filler volume fraction of 29 %. The obtained results were compared with the theoretical models and experimental data given in the literature. The results demonstrate that Agari and Uno, and Cheng and Vachon models can predict well the thermal conductivity of HDPE/Al nanocomposites in the whole range of Al fractions.

Thermal transport in boron nitride nanotorus—towards a nanoscopic thermal shield

NASA Astrophysics Data System (ADS)

Loh, G. C.; Baillargeat, D.

2013-11-01

Nanotori, or nanorings, are topological variants of nanotubes and are conceived to have different properties from their tubular form. In this study, the toroidal arrangement of boron nitride is introduced. Using classical molecular dynamics simulations, the thermal behaviour (thermal conductivity and thermal stability) of the boron nitride nanotorus and its relationship with the structural characteristics are investigated. Its circumferential thermal rectification strength displays a linear dependence on the bending coefficient of the nanostructure. Surface kinks are relatively inconsequential on its circumferential mode of conduction, as compared to its axial sense. The circumferential conductivity in the diffusive regime is calculated to be approximately 10 W/m K, while the axial conductivity is more than tenfold of this value. All nanotori with different toroidal characters show excellent thermal stability at extremely high temperatures approaching 3400 K. With consideration to its favourable properties, a thermal shield made up of a parallel row of nanotori is proposed as a nanoscale thermal insulation device.

Physical Properties of Normal Grade Biodiesel and Winter Grade Biodiesel

PubMed Central

Sadrolhosseini, Amir Reza; Moksin, Mohd Maarof; Nang, Harrison Lau Lik; Norozi, Monir; Yunus, W. Mahmood Mat; Zakaria, Azmi

2011-01-01

In this study, optical and thermal properties of normal grade and winter grade palm oil biodiesel were investigated. Surface Plasmon Resonance and Photopyroelectric technique were used to evaluate the samples. The dispersion curve and thermal diffusivity were obtained. Consequently, the variation of refractive index, as a function of wavelength in normal grade biodiesel is faster than winter grade palm oil biodiesel, and the thermal diffusivity of winter grade biodiesel is higher than the thermal diffusivity of normal grade biodiesel. This is attributed to the higher palmitic acid C16:0 content in normal grade than in winter grade palm oil biodiesel. PMID:21731429

Synthesis, Characterization and Application of Functional Carbon Nano Materials

DTIC Science & Technology

2014-05-05

properties All nanotubes are expected to be very good thermal conductors along the tube, exhibiting a 12 property known as "ballistic conduction ...by approximately the same value (2.3%) [86]. 5) Thermal properties [87] Graphene is a perfect thermal conductor . Its thermal conductivity at room...other fields of materials science and technology. In particular, owing to their extraordinary thermal conductivity and mechanical and electrical

Changes in the dielectric properties of ex vivo bovine liver during microwave thermal ablation at 2.45 GHz

NASA Astrophysics Data System (ADS)

Lopresto, Vanni; Pinto, Rosanna; Lovisolo, Giorgio A.; Cavagnaro, Marta

2012-04-01

In microwave thermal ablation (MTA) therapy, the dielectric properties of the target tissue play an important role in determining the radiation properties of the microwave ablation antenna. In this work, the ex vivo dielectric properties of bovine liver were experimentally characterized as a function of the temperature during MTA at the frequency of 2.45 GHz. The obtained data were compared with measurements performed at the end of the MTA treatment, and considering the heating achieved with a temperature-controlled water bath. Finally, measured data were used to perform a numerical study evaluating the effects of changes in tissue's dielectric properties during the MTA treatment on the radiation properties of a microwave interstitial ablation antenna, as well as on the obtained thermal lesion. Results evidenced a significant decrease of both relative permittivity (about 38%) and electric conductivity (about 33%) in the tissue during treatment as the temperature increased to over 60 °C, with a dramatic drop when the temperature approached 100 °C. Moreover, the numerical study evidenced that changes in tissue's dielectric properties during the MTA treatment affect the distribution of the power absorbed by the tissue (specific absorption rate—SAR, W kg-1) surrounding the microwave interstitial ablation antenna, leading to a peak SAR up to 20% lower, as well as to a thermal lesion up to 8% longer. This work may represent a preliminary step towards the future development of a procedure for MTA treatment planning.

Long life high reliability thermal control systems study data handbook

NASA Technical Reports Server (NTRS)

Scollon, T. R., Jr.; Carpitella, M. J.

1971-01-01

The development of thermal control systems with high reliability and long service life is discussed. Various passive and semi-active thermal control systems which have been installed on space vehicles are described. The properties of the various coatings are presented in tabular form.

Heat and Moisture transport of socks

NASA Astrophysics Data System (ADS)

Komárková, P.; Glombíková, V.; Havelka, A.

2017-10-01

Investigating the liquid moisture transport and thermal properties is essential for understanding physiological comfort of clothes. This study reports on an experimental investigation of moisture management transport and thermal transport on the physiological comfort of commercially available socks. There are subjective evaluation and objective measurements. Subjective evaluation of the physiological comfort of socks is based on individual sensory perception of probands during and after physical exertion. Objective measurements were performed according to standardized methods using Moisture Management tester for measuring the humidity parameters and C-term TCi analyzer for thermal conductivity and thermal effusivity. The obtained values of liquid moisture transport and thermal properties were related to the material composition and structure of the tested socks. In summary, these results show that objective measurement corresponds with probands feelings.

Thermophysical properties of U 3 Si 2 to 1773K

DOE PAGES

White, Joshua Taylor; Nelson, Andrew Thomas; Dunwoody, John Tyler; ...

2015-05-08

Use of U 3Si 2 in nuclear reactors requires accurate thermophysical property data to capture heat transfer within the core. Compilation of the limited previous research efforts focused on the most critical property, thermal conductivity, reveals extensive disagreement. Assessment of this data is challenged by the fact that the critical structural and chemical details of the material used to provide historic data is either absent or confirms the presence of significant impurity phases. This study was initiated to fabricate high purity U 3Si 2 to quantify the coefficient of thermal expansion, heat capacity, thermal diffusivity, and thermal conductivity from roommore » temperature to 1773 K. Here, the datasets provided in this manuscript will facilitate more detailed fuel performance modeling to assess both current and proposed reactor designs that incorporate U 3Si 2.« less

Electronic and magnetic properties of manganite thin films with different compositions and its correlation with transport properties: An X-ray resonant magnetic scattering study

DOE PAGES

Singh, Surendra; Freeland, J. W.; Fitzsimmons, M. R.; ...

2014-12-08

Here, we present x-ray resonant magnetic dichroism and x-ray resonant magnetic scattering measurements of the temperature dependence of magnetism in Pr-doped La-Ca-Mn-O films grown on (110) NdGaO3 substrates. We observed thermal hysteresis of the ferromagnetism in one film that also showed large thermal hysteresis of ~18K in transport measurements. While in a second film of a different nominal chemistry, which showed very small thermal hysteresis ~3K in transport measurements, no thermal hysteresis of the ferromagnetism was observed. As a result, these macroscopic properties are correlated with evolution of surface magnetization across metal insulator transition for these films as observed bymore » soft x-ray resonant magnetic scattering measurements.« less

Enhanced thermoelectric properties of N-type polycrystalline In4Se3-x compounds via thermally induced Se deficiency

NASA Astrophysics Data System (ADS)

Zhao, Ran; Shu, Yu-Tian; Guo, Fu

2014-03-01

In4Se3-x compound is considered as a potential thermoelectric material due to its comparably low thermal conductivity among all existing ones. While most studies investigated In4Se3-x thermoelectric properties by controlling selennium or other dopants concentrations, in the current study, it was found that even for a fixed initial In/Se ratio, the resulting In/Se ratio varied significantly with different thermal processing histories (i.e., melting and annealing), which also resulted in varied thermoelectric properties as well as fracture surface morphologies of In4Se3-x polycrystalline specimens. Single phase polycrystalline In4Se3-x compounds were synthesized by combining a sequence of melting, annealing, pulverizing, and spark plasma sintering. The extension of previous thermal history was observed to significantly improve the electrical conductivity (about 121%) and figure of merit (about 53%) of In4Se3-x polycrystalline compounds. The extended thermal history resulted in the increase of Se deficiency (x) from 0.39 to 0.53. This thermally induced Se deficiency was observed to associate with increasing carrier mobility but decreasing concentration, which differs from the general trend observed for the initially adjusted Se deficiency at room temperature. Unusually large dispersed grains with nanosize layers were observed in specimens with the longest thermal history. The mechanism(s) by which previous thermal processing enhances carrier mobility and affect microstructural evolution are briefly discussed.

Effect of cobalt doping on the structural, magnetic and abnormal thermal expansion properties of NaZn13-type La(Fe1-xCox)11.4Al1.6 compounds.

PubMed

Zhao, Yuqiang; Huang, Rongjin; Li, Shaopeng; Wang, Wei; Jiang, Xingxing; Lin, Zheshuai; Li, Jiangtao; Li, Laifeng

2016-07-27

Cubic NaZn13-type La(Fe1-xCox)11.4Al1.6 compounds were synthesized and extensively explored through crystal structure and magnetization analyses. By optimizing the chemical composition, the isotropic abnormal properties of excellent zero and giant negative thermal expansion in a pure form were both found at different temperature ranges through room temperature. Moreover, the temperature regions with the remarkable abnormal thermal expansion (ATE) properties have been broadened which are controlled by the dM/dT. The present study demonstrates that the ATE behavior mainly depends on special structural and magnetic properties. These diverse properties suggest the high potential of La(Fe1-xCox)11.4Al1.6 for the development of abnormal expansion materials.

A comparative study on the effects of air gap wind and walking motion on the thermal properties of Arabian Thawbs and Chinese Cheongsams.

PubMed

Cui, Zhiying; Fan, Jintu; Wu, Yuenshing

2016-08-01

This paper reports on an experimental investigation on the effects of air gap, wind and walking motion on the thermal properties of traditional Arabian thawbs and Chinese cheongsams. Total thermal resistance (It) and vapour resistance (Re) were measured using the sweating fabric manikin - 'Walter', and the air gap volumes of the garments were determined by a 3D body scanner. The results showed the relative changes of It and Re of thawbs due to wind and walking motion are greater than those of cheongsams, which provided an explanation of why thawbs are preferred in extremely hot climate. It is further shown that thermal insulation and vapour resistance of thawbs increase with the air gap volume up to about 71,000 cm(3) and then decrease gradually. Thawbs with higher air permeability have significantly lower evaporative resistance particularly under windy conditions demonstrating the advantage of air permeable fabrics in body cooling in hot environments. Practitioner Summary: This paper aims to better understand the thermal insulation and vapour resistance of traditional Arabian thawbs and Chinese cheongsams, and the relationship between the thermal properties and their fit and design. The results of this study provide a scientific basis for designing ethnic clothing used in hot environments.

An Atomistic-Scale Study for Thermal Conductivity and Thermochemical Compatibility in (DyY)Zr2O7 Combining an Experimental Approach with Theoretical Calculation.

PubMed

Qu, Liu; Choy, Kwang-Leong; Wheatley, Richard

2016-02-18

Ceramic oxides that have high-temperature capabilities can be deposited on the superalloy components in aero engines and diesel engines to advance engine efficiency and reduce fuel consumption. This paper aims to study doping effects of Dy(3+) and Y(3+)on the thermodynamic properties of ZrO2 synthesized via a sol-gel route for a better control of the stoichiometry, combined with molecular dynamics (MD) simulation for the calculation of theoretical properties. The thermal conductivity is investigated by the MD simulation and Clarke's model. This can improve the understanding of the microstructure and thermodynamic properties of (DyY)Zr2O7 (DYZ) at the atomistic level. The phonon-defect scattering and phonon-phonon scattering processes are investigated via the theoretical calculation, which provides an effective way to study thermal transport properties of ionic oxides. The measured and predicted thermal conductivity of DYZ is lower than that of 4 mol % Y2O3 stabilized ZrO2 (4YSZ). It is discovered that DYZ is thermochemically compatible with Al2O3 at 1300 °C, whereas at 1350 °C DYZ reacts with Al2O3 forming a small amount of new phases.

An Atomistic-Scale Study for Thermal Conductivity and Thermochemical Compatibility in (DyY)Zr2O7 Combining an Experimental Approach with Theoretical Calculation

PubMed Central

Qu, Liu; Choy, Kwang-Leong; Wheatley, Richard

2016-01-01

Ceramic oxides that have high-temperature capabilities can be deposited on the superalloy components in aero engines and diesel engines to advance engine efficiency and reduce fuel consumption. This paper aims to study doping effects of Dy3+ and Y3+on the thermodynamic properties of ZrO2 synthesized via a sol-gel route for a better control of the stoichiometry, combined with molecular dynamics (MD) simulation for the calculation of theoretical properties. The thermal conductivity is investigated by the MD simulation and Clarke’s model. This can improve the understanding of the microstructure and thermodynamic properties of (DyY)Zr2O7 (DYZ) at the atomistic level. The phonon-defect scattering and phonon-phonon scattering processes are investigated via the theoretical calculation, which provides an effective way to study thermal transport properties of ionic oxides. The measured and predicted thermal conductivity of DYZ is lower than that of 4 mol % Y2O3 stabilized ZrO2 (4YSZ). It is discovered that DYZ is thermochemically compatible with Al2O3 at 1300 °C, whereas at 1350 °C DYZ reacts with Al2O3 forming a small amount of new phases. PMID:26888438

Enhancement of thermal and mechanical properties of poly(MMA-co-BA)/Cloisite 30B nanocomposites by ultrasound-assisted in-situ emulsion polymerization.

PubMed

Sharma, Sachin; Kumar Poddar, Maneesh; Moholkar, Vijayanand S

2017-05-01

This study reports synthesis and characterization of poly(MMA-co-BA)/Cloisite 30B (organo-modified montmorillonite clay) nanocomposites by ultrasound-assisted in-situ emulsion polymerization. Copolymers have been synthesized with MMA:BA monomer ratio of 4:1, and varying clay loading (1-5wt% monomer). The poly(MMA-co-BA)/Cloisite 30B nanocomposites have been characterized for their thermal and mechanical properties. Ultrasonically synthesized nanocomposites have been revealed to possess higher thermal degradation resistance and mechanical strength than the nanocomposites synthesized using conventional techniques. These properties, however, show an optimum (or maxima) with clay loading. The maximum values of thermal and mechanical properties of the nanocomposites with optimum clay loading are as follows. Thermal degradation temperatures: T 10% =320°C (4wt%), T 50 =373°C (4wt%), maximum degradation temperature=384°C (4wt%); glass transition temperature=64.8°C (4wt%); tensile strength=20MPa (2wt%), Young's modulus=1.31GPa (2wt%), Percentage elongation=17.5% (1wt%). Enhanced properties of poly(MMA-co-BA)/Cloisite 30B nanocomposites are attributed to effective exfoliation and dispersion of clay nanoparticles in copolymer matrix due to intense micro-convection induced by ultrasound and cavitation. Clay platelets help in effective heat absorption with maximum surface interaction/adhesion that results in increased thermal resistivity of nanocomposites. Hindered motion of the copolymer chains due to clay platelets results in enhancement of tensile strength and Young's modulus of nanocomposite. Rheological (liquid) study of the nanocomposites reveals that nanocomposites have higher yield stress and infinite shear viscosity than neat copolymer. Nonetheless, nanocomposites still display shear thinning behavior - which is typical of the neat copolymer. Copyright © 2016 Elsevier B.V. All rights reserved.

A first principles study of the electronic structure, elastic and thermal properties of UB2

NASA Astrophysics Data System (ADS)

Jossou, Ericmoore; Malakkal, Linu; Szpunar, Barbara; Oladimeji, Dotun; Szpunar, Jerzy A.

2017-07-01

Uranium diboride (UB2) has been widely deployed for refractory use and is a proposed material for Accident Tolerant Fuel (ATF) due to its high thermal conductivity. However, the applicability of UB2 towards high temperature usage in a nuclear reactor requires the need to investigate the thermomechanical properties, and recent studies have failed in highlighting applicable properties. In this work, we present an in-depth theoretical outlook of the structural and thermophysical properties of UB2, including but not limited to elastic, electronic and thermal transport properties. These calculations were performed within the framework of Density Functional Theory (DFT) + U approach, using Quantum ESPRESSO (QE) code considering the addition of Coulomb correlations on the uranium atom. The phonon spectra and elastic constant analysis show the dynamic and mechanical stability of UB2 structure respectively. The electronic structure of UB2 was investigated using full potential linear augmented plane waves plus local orbitals method (FP-LAPW+lo) as implemented in WIEN2k code. The absence of a band gap in the total and partial density of states confirms the metallic nature while the valence electron density plot reveals the presence of covalent bond between adjacent B-B atoms. We predicted the lattice thermal conductivity (kL) by solving Boltzmann Transport Equation (BTE) using ShengBTE. The second order harmonic and third-order anharmonic interatomic force constants required as input to ShengBTE was calculated using the Density-functional perturbation theory (DFPT). However, we predicted the electronic thermal conductivity (kel) using Wiedemann-Franz law as implemented in Boltztrap code. We also show that the sound velocity along 'a' and 'c' axes exhibit high anisotropy, which accounts for the anisotropic thermal conductivity of UB2.

Study on processing immiscible materials in zero gravity

NASA Technical Reports Server (NTRS)

Reger, J. L.; Mendelson, R. A.

1975-01-01

An experimental investigation was conducted to evaluate mixing immiscible metal combinations under several process conditions. Under one-gravity, these included thermal processing, thermal plus electromagnetic mixing, and thermal plus acoustic mixing. The same process methods were applied during free fall on the MSFC drop tower facility. The design is included of drop tower apparatus to provide the electromagnetic and acoustic mixing equipment, and a thermal model was prepared to design the specimen and cooling procedure. Materials systems studied were Ca-La, Cd-Ga and Al-Bi; evaluation of the processed samples included the morphology and electronic property measurements. The morphology was developed using optical and scanning electron microscopy and microprobe analyses. Electronic property characterization of the superconducting transition temperatures were made using an impedance change-tuned coil method.

Characterization-curing-property studies of HBRF 55A resin formulations

NASA Technical Reports Server (NTRS)

Pearce, E. M.; Mijovic, J.

1985-01-01

Characterization curing property investigations on HBRF 55A resin formulations are reported. The initial studies on as received cured samples cut from a full-size FWC are reviewed. Inadequacies of as-received and aged samples are pointed out and additional electron microscopic evidence is offered. Characterization of as-received ingredients of HBRF 55A formulation is described. Specifically, Epon 826, Epon 828, EpiRez 5022, RD-2 and various amines, including Tonox and Tonox 60.40, were characterized. Cure kinetics of various formulations are investigated. Changes in physical/thermal properties (viscosity, specific heat, thermal conductivity and density) during cure are described.

Thermal properties and dynamic mechanical properties of ceramic fillers filled epoxy composites

NASA Astrophysics Data System (ADS)

Saidina, D. S.; Mariatti, M.; Juliewatty, J.

2015-07-01

This present study is aimed to enhance the thermal and dynamic mechanical properties of ceramic fillers such as Calcium Copper Titanate, CaCu3Ti4O12 (CCTO) and Barium Titanate (BaTiO3) filled epoxy thin film composites. As can be seen from the results, 20 vol% BaTiO3/epoxy thin film composite showed the lowest coefficient of thermal expansion (CTE) value, the highest decomposition temperature (T5 and Tonset) and weight of residue among the composites as the filler has low CTE value, distributed homogeneously throughout the composite and less voids can be seen between epoxy resin and BaTiO3 filler.

Comparative investigation of thermal and mechanical properties of cross-linked epoxy polymers with different curing agents by molecular dynamics simulation.

PubMed

Jeyranpour, F; Alahyarizadeh, Gh; Arab, B

2015-11-01

Molecular dynamics (MD) simulations were carried out to predict the thermal and mechanical properties of the cross-linked epoxy system composed of DGEBA resin and the curing agent TETA. To investigate the effects of curing agents, a comprehensive and comparative study was also performed on the thermal and mechanical properties of DGEBA/TETA and DGEBA/DETDA epoxy systems such as density, glass transition temperature (Tg), coefficient of thermal expansion (CTE) and elastic properties of different cross-linking densities and different temperatures. The results indicated that the glass transition temperature of DGEBA/TETA system calculated through density-temperature data, ∼ 385-395 °K, for the epoxy system with the cross-linking density of 62.5% has a better agreement with the experimental value (Tg, ∼ 400 °K) in comparison to the value calculated through the variation of cell volume in terms of temperature, 430-440 °K. They also indicated that CTE related parameters and elastic properties including Young, Bulk, and shear's moduli, and Poisson's ratio have a relative agreement with the experimental results. Comparison between the thermal and mechanical properties of epoxy systems of DGEBA/TETA and DGEBA/DETDA showed that the DGEBA/DETDA has a higher Tg in all cross linking densities than that of DGEBA/TETA, while higher mechanical properties was observed in the case of DGEBA/TETA in almost all cross linking densities. Copyright © 2015 Elsevier Inc. All rights reserved.

Estimation of groundwater flow from temperature monitoring in a borehole heat exchanger during a thermal response test

NASA Astrophysics Data System (ADS)

Yoshioka, Mayumi; Takakura, Shinichi; Uchida, Youhei

2018-05-01

To estimate the groundwater flow around a borehole heat exchanger (BHE), thermal properties of geological core samples were measured and a thermal response test (TRT) was performed in the Tsukuba upland, Japan. The thermal properties were measured at 57 points along a 50-m-long geological core, consisting predominantly of sand, silt, and clay, drilled near the BHE. In this TRT, the vertical temperature in the BHE was also monitored during and after the test. Results for the thermal properties of the core samples and from the monitoring indicated that groundwater flow enhanced thermal transfers, especially at shallow depths. The groundwater velocities around the BHE were estimated using a two-dimensional numerical model with monitoring data on temperature changes. According to the results, the estimated groundwater velocity was generally consistent with hydrogeological data from previous studies, except for the data collected at shallow depths consisting of a clay layer. The reasons for this discrepancy at shallow depths were predicted to be preferential flow and the occurrence of vertical flow through the BHE grout, induced by the hydrogeological conditions.

Thermal, Morphological and Rheological Properties of Rigid Polyurethane Foams as Thermal Insulating Materials

NASA Astrophysics Data System (ADS)

Kim, Ji Mun; Han, Mi Sun; Kim, Youn Hee; Kim, Woo Nyon

2008-07-01

The polyurethane foams (PUFs) were prepared by polyether polyols, polymeric 4,4'-diphenylmethane diisocyanate (PMDI), silicone surfactants, amine catalysts and cyclopentane as a blowing agent. Solid and liquid type fillers were used as a nucleating agent to decrease a cell size of the PUFs as well as improve the thermal insulating properties of the PUFs. The PUFs were prepared by adding solid and liquid type fillers in the range of 1 to 3 wt%. For the liquid type fillers, the cell size of the PUFs showed minimum and found to decrease compared the PUF without adding fillers. Also, thermal conductivity of the PUFs with adding fillers showed minimum. For the solid type fillers, cell size and thermal conductivity of the PUFs were observed to decrease with the filler content up to 3 wt%. From these results, it is suggested that the thermal insulating property of the PUFs can be improved by adding fillers as a nucleating agent. Also, storage and loss modulus of the PUFs will be presented to study gelling points of the PUFs.

Transient thermal effect, nonlinear refraction and nonlinear absorption properties of graphene oxide sheets in dispersion.

PubMed

Zhang, Xiao-Liang; Liu, Zhi-Bo; Li, Xiao-Chun; Ma, Qiang; Chen, Xu-Dong; Tian, Jian-Guo; Xu, Yan-Fei; Chen, Yong-Sheng

2013-03-25

The nonlinear refraction (NLR) properties of graphene oxide (GO) in N, N-Dimethylformamide (DMF) was studied in nanosecond, picosecond and femtosecond time regimes by Z-scan technique. Results show that the dispersion of GO in DMF exhibits negative NLR properties in nanosecond time regime, which is mainly attributed to transient thermal effect in the dispersion. The dispersion also exhibits negative NLR in picosecond and femtosecond time regimes, which are arising from sp(2)- hybridized carbon domains and sp(3)- hybridized matrix in GO sheets. To illustrate the relations between NLR and nonlinear absorption (NLA), NLA properties of the dispersion were also studied in nanosecond, picosecond and femtosecond time regimes.

USSR Report, Chemistry

DTIC Science & Technology

1985-08-16

of the thermal interaction of polonium - 210 with palladium and iridium. The vacuum-thermal method of direct synthesis was used, a study of the...ZHURNAL -PRIKLADNOY KHIMII, No k, Apr 85) Ik CATALYSIS Effect of Intermetallic Compounds Zr-Co Composition on Their Catalytic Properties in...KHIMICHESKAYA, No U, Apr 85) IT Effect of Stabilization on Adsorption and Catalytic Properties of Electrodeposited Platinum Catalysts (T. M. Grishina, Ye. V

Ab-initio study of thermal expansion in pure graphene

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

Mann, Sarita; Kumar, Ranjan; Jindal, V. K., E-mail: jindal@pu.ac.in

Graphene is a zero band gap semiconductor with exceptionally high thermal conductivity. The electronic properties having been studied, therole of phonon in contributing to thermal expansion, thermal conductivity and other thermodynamic properties, is required to be investigated. This paper focuses more on thermal expansion. Some others results like phonon dispersion, Grüneisenparameters and bulk modulus,which are essential to estimation of thermal expansion, are also presented. The dynamical matrix was calculated using VASP code using both DFT and DFPT and the phonon frequencies were calculated using phonopy code under harmonic approximation. The linear thermal expansion coefficient of graphene is found to bemore » strongly dependent on temperature but remains negative upto 470 K and positive thereafter, with a room temperature value of −1.44×10{sup −6}. The negative expansion coefficient is very interesting and is found to be in conformity with experimental as well as with recent theoretical estimates. There is only qualitative agreement of our results with experimental data and motivates further investigation, primarily on the high negative values of Grüneisen parameters.« less

Experimental characterization of thermal and hygric properties of hemp concrete with consideration of the material age evolution

NASA Astrophysics Data System (ADS)

Bennai, F.; Issaadi, N.; Abahri, K.; Belarbi, R.; Tahakourt, A.

2018-04-01

The incorporation of plant crops in construction materials offers very good hygrothermal performance to the building, ensuring substantial environmental and ecological benefits. This paper focuses on studying the evolution of hygrothermal properties of hemp concrete over age (7, 30 and 60 days). The analysis is done with respect to two main hygric and thermal properties, respectively: sorption isotherms, water vapor permeability, thermal conductivity and heat capacity. In fact, most of these parameters are very susceptible to change function of the age of the material. This influence of the aging is mainly due to the evolution of the microstructure with the binder hydration over time and the creation of new hydrates which can reduces the porosity of the material and consequently modify its properties. All the tested hemp concrete samples presented high moisture storage capacity and high-water vapor permeability whatever the age of such hygroscopic material. These hygric parameters increase significantly for high relative humidity requiring more consideration of such variability during the modeling of coupled heat and mass transfer within the material. By the same, the thermal conductivity and heat capacity tests highlighted the impact of the temperature and hygric state of the studied material.

Study on thermal properties and crystallization behavior of electron beam irradiated ethylene vinyl acetate (EVA)/waste tyre dust (WTD) blends in the presence of polyethylene graft maleic anhydride (PEgMAH)

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

Ramli, Syuhada; Ahmad, S. H.; Ratnam, C. T.

2013-11-27

The aim of this article is to show the effects of the electron beam irradiation dose and presence of a compatibiliser on the thermal properties and crystallinity of EVA/WTD blends. The purpose of applying electron beam radiation with doses range 50 to 200 kGy and adding a compatibiliser was to enhance the compatibility of the studied blends and at the same time to investigate the possibility of using this technique in the process of recycling polymeric materials. As the compatibilisers, the polyethylene grafted maleic anhydride (PEgMAH) was utilized, they were added at the amounts of 1-5 phr respectively. The enhancementmore » of thermal properties was accompanied by the following effects, discussed in this article: i) an irradiated EVA/WTD blend at 200kGy was found to improve the thermal properties of EVA, ii) the addition of PEgMAH in EVA/WTD blends and the subsequent irradiation allowed prevention of degradation mechanism. iii) the ΔH{sub f} and crystallinity percentage decrease at higher PEgMAH content.« less

Thermal Physical Property-Based Fusion of Geostationary Meteorological Satellite Visible and Infrared Channel Images

PubMed Central

Han, Lei; Shi, Lu; Yang, Yiling; Song, Dalei

2014-01-01

Geostationary meteorological satellite infrared (IR) channel data contain important spectral information for meteorological research and applications, but their spatial resolution is relatively low. The objective of this study is to obtain higher-resolution IR images. One common method of increasing resolution fuses the IR data with high-resolution visible (VIS) channel data. However, most existing image fusion methods focus only on visual performance, and often fail to take into account the thermal physical properties of the IR images. As a result, spectral distortion occurs frequently. To tackle this problem, we propose a thermal physical properties-based correction method for fusing geostationary meteorological satellite IR and VIS images. In our two-step process, the high-resolution structural features of the VIS image are first extracted and incorporated into the IR image using regular multi-resolution fusion approach, such as the multiwavelet analysis. This step significantly increases the visual details in the IR image, but fake thermal information may be included. Next, the Stefan-Boltzmann Law is applied to correct the distortion, to retain or recover the thermal infrared nature of the fused image. The results of both the qualitative and quantitative evaluation demonstrate that the proposed physical correction method both improves the spatial resolution and preserves the infrared thermal properties. PMID:24919017

Thermal physical property-based fusion of geostationary meteorological satellite visible and infrared channel images.

PubMed

Han, Lei; Shi, Lu; Yang, Yiling; Song, Dalei

2014-06-10

Geostationary meteorological satellite infrared (IR) channel data contain important spectral information for meteorological research and applications, but their spatial resolution is relatively low. The objective of this study is to obtain higher-resolution IR images. One common method of increasing resolution fuses the IR data with high-resolution visible (VIS) channel data. However, most existing image fusion methods focus only on visual performance, and often fail to take into account the thermal physical properties of the IR images. As a result, spectral distortion occurs frequently. To tackle this problem, we propose a thermal physical properties-based correction method for fusing geostationary meteorological satellite IR and VIS images. In our two-step process, the high-resolution structural features of the VIS image are first extracted and incorporated into the IR image using regular multi-resolution fusion approach, such as the multiwavelet analysis. This step significantly increases the visual details in the IR image, but fake thermal information may be included. Next, the Stefan-Boltzmann Law is applied to correct the distortion, to retain or recover the thermal infrared nature of the fused image. The results of both the qualitative and quantitative evaluation demonstrate that the proposed physical correction method both improves the spatial resolution and preserves the infrared thermal properties.

Utility of Thermal Infrared Satellite Data For Urban Landscapes

NASA Astrophysics Data System (ADS)

Xian, G.; Crane, M.; Granneman, B.

2006-12-01

Urban landscapes are comprised of a variety of surfaces that are characterized by contrasting radiative, thermal, aerodynamic, and moisture properties. These different surfaces possess diverse physical and thermal attributes that directly influence surface energy balance and our ability to determine surface characteristics in urban areas. Reflectance properties obtained from satellite imagery have proven useful for mapping urban land use and land cover change, as well as ecosystem health. Landsat reflectance bands are commonly used in regression tree models to generate linear equations that correspond to distinct land surface materials. However, urban land cover is generally a heterogeneous mix of bare soil, vegetation, rock, and anthropogenic impervious surfaces. Surface temperature obtained from satellite thermal infrared bands provides valuable information about surface biophysical properties and radiant thermal characteristics of land cover elements, especially for urban environments. This study demonstrates the improved characterization of land cover conditions for Seattle, Washington, and Las Vegas, Nevada, that were achieved by using both the reflectance and thermal bands of Landsat Enhanced Thematic Mapper Plus (ETM+) data. Including the thermal band in the image analysis increased the accuracy of discriminating cover types in heterogeneous landscapes with extreme contrasts, especially for mixed pixels at the urban interface.

Effect of Moisture Content on Thermal Properties of Porous Building Materials

NASA Astrophysics Data System (ADS)

Kočí, Václav; Vejmelková, Eva; Čáchová, Monika; Koňáková, Dana; Keppert, Martin; Maděra, Jiří; Černý, Robert

2017-02-01

The thermal conductivity and specific heat capacity of characteristic types of porous building materials are determined in the whole range of moisture content from dry to fully water-saturated state. A transient pulse technique is used in the experiments, in order to avoid the influence of moisture transport on measured data. The investigated specimens include cement composites, ceramics, plasters, and thermal insulation boards. The effect of moisture-induced changes in thermal conductivity and specific heat capacity on the energy performance of selected building envelopes containing the studied materials is then analyzed using computational modeling of coupled heat and moisture transport. The results show an increased moisture content as a substantial negative factor affecting both thermal properties of materials and energy balance of envelopes, which underlines the necessity to use moisture-dependent thermal parameters of building materials in energy-related calculations.

Synthesis and evaluation of lead telluride/bismuth antimony telluride nanocomposites for thermoelectric applications

NASA Astrophysics Data System (ADS)

Ganguly, Shreyashi; Zhou, Chen; Morelli, Donald; Sakamoto, Jeffrey; Uher, Ctirad; Brock, Stephanie L.

2011-12-01

Heterogeneous nanocomposites of p-type bismuth antimony telluride (Bi 2- xSb xTe 3) with lead telluride (PbTe) nanoinclusions have been prepared by an incipient wetness impregnation approach. The Seebeck coefficient, electrical resistivity, thermal conductivity and Hall coefficient were measured from 80 to 380 K in order to investigate the influence of PbTe nanoparticles on the thermoelectric performance of nanocomposites. The Seebeck coefficients and electrical resistivities of nanocomposites decrease with increasing PbTe nanoparticle concentration due to an increased hole concentration. The lattice thermal conductivity decreases with the addition of PbTe nanoparticles but the total thermal conductivity increases due to the increased electronic thermal conductivity. We conclude that the presence of nanosized PbTe in the bulk Bi 2- xSb xTe 3 matrix results in a collateral doping effect, which dominates transport properties. This study underscores the need for immiscible systems to achieve the decreased thermal transport properties possible from nanostructuring without compromising the electronic properties.

Accurate temperature measurement by temperature field analysis in diamond anvil cell for thermal transport study of matter under high pressures

NASA Astrophysics Data System (ADS)

Yue, Donghui; Ji, Tingting; Qin, Tianru; Wang, Jia; Liu, Cailong; Jiao, Hui; Zhao, Lin; Han, Yonghao; Gao, Chunxiao

2018-02-01

The study on the thermal transport properties of matter under high pressure is important but is hard to fulfill in a diamond anvil cell (DAC) because the accurate measurement of the temperature gradient within the sample of DAC is very difficult. In most cases, the sample temperature can be read accurately from the thermocouples that are directly attached to the lateral edges of diamond anvils because both the sample and diamond anvils can be uniformly heated up to a given temperature. But for the thermal transport property studies in DAC, an artificial temperature distribution along the compression axis is a prerequisite. Obviously, the temperature of the top or bottom surface of the sample cannot be substituted by that of diamond anvils although diamond anvils can be considered as a good medium for heat conduction. With temperature field simulation by finite element analysis, it is found that big measurement errors can occur and are fatal to the correct analysis of thermal transport properties of materials. Thus, a method of combining both the four-thermocouple configuration and temperature field analysis is presented for the accurate temperature distribution measurement in DAC, which is based on the single-function relationship between temperature distribution and sample thermal conductivity.

Red River Waterway Thermal Studies. Report 2. Thermal Stress Analyses

DTIC Science & Technology

1991-12-01

stress relaxation, q. Shrinkage of the concrete, and . Thermal properties of the concrete including coefficient of thermal expansion , specific heat...Finite-Element Code 12. The thermal stress analyses in this investigation was performed using ABAQUS , a general-purpose, heat-transfer and structural...model (the UMAT 9 subroutine discussed below) may be incorporated as an external subroutine linked to the ABAQUS library. 14. In order to model the

Influence of electron irradiation on the structural and thermal properties of silk fibroin films

NASA Astrophysics Data System (ADS)

Asha, S.; Sangappa, Sanjeev, Ganesh

2015-06-01

Radiation-induced changes in Bombyx mori silk fibroin (SF) films under electron irradiation were investigated and correlated with dose. SF films were irradiated in air at room temperature using 8 MeV electron beam in the range 0-150 kGy. Various properties of the irradiated SF films were studied using X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Electron irradiation was found to induce changes in the physical and thermal properties, depending on the radiation dose.

Multidimensional Tests of Thermal Protection Materials in the Arcjet Test Facility

NASA Technical Reports Server (NTRS)

Agrawal, Parul; Ellerby, Donald T.; Switzer, Mathew R.; Squire, Thomas H.

2010-01-01

Many thermal protection system materials used for spacecraft heatshields have anisotropic thermal properties, causing them to display significantly different thermal characteristics in different directions, when subjected to a heating environment during flight or arcjet tests. This paper investigates the effects of sidewall heating coupled with anisotropic thermal properties of thermal protection materials in the arcjet environment. Phenolic Impregnated Carbon Ablator (PICA) and LI-2200 materials (the insulation material of Shuttle tiles) were used for this study. First, conduction-based thermal response simulations were carried out, using the Marc.Mentat finite element solver, to study the effects of sidewall heating on PICA arcjet coupons. The simulation showed that sidewall heating plays a significant role in thermal response of these models. Arcjet tests at the Aerodynamic Heating Facility (AHF) at NASA Ames Research Center were performed later on instrumented coupons to obtain temperature history at sidewall and various radial locations. The details of instrumentation and experimental technique are the prime focus of this paper. The results obtained from testing confirmed that sidewall heating plays a significant role in thermal response of these models. The test results were later used to verify the two-dimensional ablation, thermal response, and sizing program, TITAN. The test data and model predictions were found to be in excellent agreement

Mechanical properties and negative thermal expansion of a dense rare earth formate framework

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

Zhang, Zhanrui; Jiang, Xingxing; Feng, Guoqiang

The fundamental mechanical properties of a dense metal–organic framework material, [NH{sub 2}CHNH{sub 2}][Er(HCOO){sub 4}] (1), have been studied using nanoindentation technique. The results demonstrate that the elastic moduli, hardnesses, and yield stresses on the (021)/(02−1) facets are 29.8/30.2, 1.80/1.83 and 0.93/1.01 GPa, respectively. Moreover, variable-temperature powder and single-crystal X-ray diffraction experiments reveal that framework 1 shows significant negative thermal expansion along its b axis, which can be explained by using a hinge–strut structural motif. - Graphical abstract: The structure of framework, [NH{sub 2}CHNH{sub 2}][Er(HCOO){sub 4}], and its indicatrix of thermal expansion. - Highlights: • The elastic modulus, hardness, and yieldmore » stress properties of a rare earth metal–organic framework material were studied via nanoindentation technique. • Variable-temperature powder X-ray diffraction experiments reveal that this framework shows significant negative thermal expansion along its b axis. • Based on variable-temperature single-crystal X-ray diffraction experiments, the mechanism of negative thermal expansion can be explained by a hinge–strut structural motif.« less

Role of chemical functional groups on thermal and electrical properties of various graphene oxide derivatives: a comparative x-ray photoelectron spectroscopy analysis

NASA Astrophysics Data System (ADS)

Balaji Mohan, Velram; Jakisch, Lothar; Jayaraman, Krishnan; Bhattacharyya, Debes

2018-03-01

In recent years, graphene and its derivatives have become prominent subject matter due to their fascinating combination of properties and potential applications in a number application. While several fundamental studies have been progressed, there is a particular need to understand how different graphene derivatives are influenced in terms of their electrical and thermal conductivities by different functional groups they end up with through their manufacturing and functionalisation methods. This article addresses of the role of different functional groups present of different of reduced graphene oxides (rGO) concerning their electrical and thermal properties, and the results were compared with elemental analyses of functionalised reduced graphene oxide (frGO) and graphene. The results showed that electrical and thermal conductivities of the rGO samples, highly dependent on the presence of residual functional groups from oxidation, reduction and functionalisation processes. The increase in reduction of oxygen, hydroxyl, carboxylic, epoxide moieties and heterocyclic compounds increase the specific surface area of the samples through which the mean electron path has increased. This improved both electrical and thermal conductivities together in all the samples which were highly dependent on the efficiency of different reductant used in this study.

Two-phase nanofluid-based thermal management systems for LED cooling

NASA Astrophysics Data System (ADS)

Kiseev, V.; Aminev, D.; Sazhin, O.

2017-04-01

This research focuses on two-phase thermal control systems, namely loop thermosyphons (LTS) filled with nanofluids, and their use as LED cooling devices. The behavior of the fluid in the thermosyphons and the mechanisms explaining the possible impact of nanoparticles on thermal properties of the working fluid as well as the processes in the LTS are addressed. Nanoparticle distribution in the nanofluid, methods of preparation of nanofluids and nanofluid degradation processes (aging) are studied. The results are obtained from a set of experiments on thermosyphon characteristics depending on the thermophysical properties of the working fluid, filling volume, geometry and materials of radiators. The impact of nanofluids on heat-transfer process occurring inside thermosyphon is also studied. Results indicate strong influence of nanoparticles on the thermal properties of the thermosyphons, with up to 20% increase of the heat transfer coefficient. Additionally, a method of calculating the hydrodynamic limit of the LTS is proposed, which allows for estimation of the maximum heat flux that can be transferred by means of the LTS. Possible ways for further improvement of the model are proposed. The nanofluids are shown to be effective means of enhancing two-phase systems of thermal management.

Photoemf in cadmium sulfide

NASA Technical Reports Server (NTRS)

Boeer, K. W.

1971-01-01

Theoretical and experimental investigations on CdS single crystals and CuxS:CdS photovoltaic cells prepared from CdS single crystals by a chemical-dip procedure are described. The studies are aimed at clarifying cell mechanisms which affect key cell properties (efficiency, reliability, and lifetime) by examining the properties of intrinsic and extrinsic defects in the junction and surface regions and their effects on carrier transport through these regions. The experimental research described includes studies of thermal, infrared, and field quenching of acceptor-doped CdS crystals; investigation of optical and electrical properties of CuxS:CdS photovoltaic cells (current-voltage characteristics, spectral distribution of photocurrent and photovoltage) and the dependence of these properties on temperature and light intensity; measurement of changes, as a result of heat treatment in ultrahigh vacuum, in the spectral distribution of photoconductivity at room temperature and liquid nitrogen temperature, the luminescence spectrum at liquid nitrogen temperature, and the thermally stimulated current curves of CdS crystals; determination of the effect of irradiation with 150 keV (maximum) X-rays on the spectral distribution of photoconductivity and thermally-stimulated current of CdS crystals; and studies of the effect of growth conditions on the photoconductive properties of CdS crystals.

In-situ Observation of Size and Irradiation Effects on Thermoelectric Properties of Bi-Sb-Te Nanowire in FIB Trimming

PubMed Central

Chien, Chia-Hua; Lee, Ping-Chung; Tsai, Wei-Han; Lin, Chien-Hung; Lee, Chih-Hao; Chen, Yang-Yuan

2016-01-01

In this report, the thermoelectric properties of a Bi0.8Sb1.2Te2.9 nanowire (NW) were in-situ studied as it was trimmed from 750 down to 490 and 285 nm in diameter by a focused ion beam. While electrical and thermal conductivities both indubitably decrease with the diameter reduction, the two physical properties clearly exhibit different diameter dependent behaviors. For 750 and 490 nm NWs, much lower thermal conductivities (0.72 and 0.69 W/m-K respectively) were observed as compared with the theoretical prediction of Callaway model. The consequence indicates that in addition to the size effect, extra phonon scattering of defects created by Ga ion irradiation was attributed to the reduction of thermal conductivities. As the NW was further trimmed down to 285 nm, both the electrical and thermal conductivities exhibited a dramatic reduction which was ascribed to the formation of amorphous structure due to Ga ion irradiation. The size dependence of Seebeck coefficient and figure of merit (ZT) show the maximum at 750 nm, then decrease linearly with size decrease. The study not only provides the thoroughly understanding of the size and defect effects on the thermoelectric properties but also proposes a possible method to manipulate the thermal conductivity of NWs via ion irradiation. PMID:27030206

Assesment of influncing factors on mechanical and electrical properties of Al/Cu joints

NASA Astrophysics Data System (ADS)

Selvaraj, R. Meby; Hynes, N. Rajesh Jesudoss

2018-05-01

Joining of dissimilar materials opens up challenging opportunities in todays technology. Al/Cu weldments are used in applications that demands corrosion resistance, thermal and electrical conducting properties. In dissimilar joining mechanical and thermal properties result in large stress gradients during heating. The Al-Cu joints are lighter, cheaper and have conductivity equal to copper alloy. The main scope of this study is to assess the influencing factors of Al/Cu joints in mechanical and electrical properties. It includes the influence of the dilution between the base metals, influence of physical properties, influence of welding parameters, influence of filler metal, influence of heat treatment, and influence of electrical properties

Cryogenic foam insulation: Abstracted publications

NASA Technical Reports Server (NTRS)

Williamson, F. R.

1977-01-01

A group of documents were chosen and abstracted which contain information on the properties of foam materials and on the use of foams as thermal insulation at cryogenic temperatures. The properties include thermal properties, mechanical properties, and compatibility properties with oxygen and other cryogenic fluids. Uses of foams include applications as thermal insulation for spacecraft propellant tanks, and for liquefied natural gas storage tanks and pipelines.

Nanocrystalline CuNi alloys: improvement of mechanical properties and thermal stability

NASA Astrophysics Data System (ADS)

Nogues, Josep; Varea, A.; Pellicer, E.; Sivaraman, K. M.; Pane, S.; Nelson, B. J.; Surinach, S.; Baro, M. D.; Sort, J.

2014-03-01

Nanocrystalline metallic films are known to benefit from novel and enhanced physical and chemical properties. In spite of these outstanding properties, nanocrystalline metals typically show relatively poor thermal stability which leads to deterioration of the properties due to grain coarsening. We have studied nanocrystalline Cu1-xNix (0.56 < x < 1) thin films (3 μm-thick) electrodeposited galvanostatically onto Cu/Ti/Si (100) substrates. CuNi thin films exhibit large values of hardness (6.15 < H < 7.21 GPa), which can be tailored by varying the composition. However, pure Ni films (x = 1) suffer deterioration of their mechanical and magnetic properties after annealing during 3 h at relatively low temperatures (TANN > 475 K) due to significant grain growth. Interestingly, alloying Ni with Cu clearly improves the thermal stability of the material because grain coarsening is delayed due to segregation of a Cu-rich phase at grain boundaries, thus preserving both the mechanical and magnetic properties up to higher TANN.

Solid Propellant Grain Structural Integrity Analysis

NASA Technical Reports Server (NTRS)

1973-01-01

The structural properties of solid propellant rocket grains were studied to determine the propellant resistance to stresses. Grain geometry, thermal properties, mechanical properties, and failure modes are discussed along with design criteria and recommended practices.

Physical and Thermal Comfort Properties of Viscose Fabrics made from Vortex and Ring Spun Yarns

NASA Astrophysics Data System (ADS)

Thilagavathi, G.; Muthukumar, N.; Kumar, V. Kiran; Sadasivam, Sanjay; Sidharth, P. Mithun; Nikhil Jain, G.

2017-06-01

Viscose fiber is frequently preferred for various types of inner and outer knitwear products for its comfort and visual characteristics. In this study, the physical and thermal comfort properties of viscose fabrics made from ring and vortex yarns have been studied to explore the impact of spinning process on fabric properties. 100% viscose fibers were spun into yarns by ring and vortex spinning and the developed yarns were converted to single jersey fabrics. The results indicated that fabrics made from vortex spun yarns had better pilling resistance over that of those from ring spun yarns. There was no significant difference between bursting strength values of vortex and ring spun yarn fabrics. Fabrics made from ring yarn had better dimensional stability compared to fabrics made from vortex yarn. The air permeability and water vapour permeability of vortex yarn fabrics were higher than ring spun yarn fabrics. The vortex yarn fabrics had better thermal comfort properties compared to ring yarn fabrics.

Modification of the electrical, optical and thermal properties of L-Arginine Perchlorate single crystals by 5 kGy and 8 kGy electron beam irradiation for optoelectronic devices

NASA Astrophysics Data System (ADS)

Thomas, Prince; Santhosh Kumar, R.; Sreekanth, G.; John, Bitto; Sanjeev, Ganesh; Joseph, Ginson P.

2017-11-01

This paper attempts to elucidate the effect of 5 kGy and 8 kGy electron irradiation on the optical, thermal and electrical properties of a prominent amino acid crystal, L-Arginine Perchlorate (LAPCl) grown by low-temperature solution growth technique. Optical absorption studies revealed that the UV lower cut-off wavelength shift towards the higher wavelength region (Red shift), the optical band gap of LAPCl were found to be decreasing while the Urbach energy was found to be increasing with increasing the dosage of irradiation. Fourier Transform Infrared (FT-IR) spectroscopic result showed that peak intensities corresponding to typical bonding increase with the increase in electron beam irradiation dosage. Electrical studies revealed that the dielectric constant, loss and conductivity of the sample increases with increasing the dosage of irradiation. The behaviour of electrical properties on temperature and thermal properties has also been investigated.

Effect of high pressure on rheological and thermal properties of quinoa and maize starches.

PubMed

Li, Guantian; Zhu, Fan

2018-02-15

Quinoa starch has small granules with relatively low gelatinization temperatures and amylose content. High hydrostatic pressure (HHP) is a non-thermal technique for food processing. In this study, effects of HHP up to 600MPa on physical properties of quinoa starch were studied and compared with those of a normal maize starch. Both starches gelatinized at 500 and 600MPa. The pressure of 600MPa completely gelatinized quinoa starch as revealed by thermal analysis. Dynamic rheological analysis showed that HHP improved the gel stability of both starches during cooling. HHP had little effects on amylopectin recrystallization and gel textural properties of starch. Overall, quinoa starch was more susceptible to HHP than maize starch. The effects of HHP on some rheological properties such as frequency dependence were different between these two types of starches. The differences could be attributed to the different composition, granular and chemical structures of starch, and the presence of granule remnants. Copyright © 2017 Elsevier Ltd. All rights reserved.

Morphological, Thermal, and Rheological Properties of Starches from Maize Mutants Deficient in Starch Synthase III.

PubMed

Zhu, Fan; Bertoft, Eric; Li, Guantian

2016-08-31

Morphological, thermal, and rheological properties of starches from maize mutants deficient in starch synthase III (SSIII) with a common genetic background (W64A) were studied and compared with the wild type. SSIII deficiency reduced granule size of the starches from 16.7 to ∼11 μm (volume-weighted mean). Thermal analysis showed that SSIII deficiency decreased the enthalpy change of starch during gelatinization. Steady shear analysis showed that SSIII deficiency decreased the consistency coefficient and yield stress during steady shearing, whereas additional deficiency in granule-bound starch synthase (GBSS) increased these values. Dynamic oscillatory analysis showed that SSIII deficiency decreased G' at 90 °C during heating and increased it when the paste was cooled to 25 °C at 40 Hz during a frequency sweep. Additional GBSS deficiency further decreased the G'. Structural and compositional bases responsible for these changes in physical properties of the starches are discussed. This study highlighted the relationship between SSIII and some physicochemical properties of maize starch.

Quantifying the Interactions Between Soil Thermal Characteristics, Soil Physical Properties, Hydro-geomorphological Conditions and Vegetation Distribution in an Arctic Watershed

NASA Astrophysics Data System (ADS)

Dafflon, B.; Leger, E.; Robert, Y.; Ulrich, C.; Peterson, J. E.; Soom, F.; Biraud, S.; Tran, A. P.; Hubbard, S. S.

2017-12-01

Improving understanding of Arctic ecosystem functioning and parameterization of process-rich hydro-biogeochemical models require advances in quantifying ecosystem properties, from the bedrock to the top of the canopy. In Arctic regions having significant subsurface heterogeneity, understanding the link between soil physical properties (incl. fraction of soil constituents, bedrock depth, permafrost characteristics), thermal behavior, hydrological conditions and landscape properties is particularly challenging yet is critical for predicting the storage and flux of carbon in a changing climate. This study takes place in Seward Peninsula Watersheds near Nome AK and Council AK, which are characterized by an elevation gradient, shallow bedrock, and discontinuous permafrost. To characterize permafrost distribution where the top of permafrost cannot be easily identified with a tile probe (due to rocky soil and/or large thaw layer thickness), we developed a novel technique using vertically resolved thermistor probes to directly sense the temperature regime at multiple depths and locations. These measurements complement electrical imaging, seismic refraction and point-scale data for identification of the various thermal behavior and soil characteristics. Also, we evaluate linkages between the soil physical-thermal properties and the surface properties (hydrological conditions, geomorphic characteristics and vegetation distribution) using UAV-based aerial imaging. Data integration and analysis is supported by numerical approaches that simulate hydrological and thermal processes. Overall, this study enables the identification of watershed structure and the links between various subsurface and landscape properties in representative Arctic watersheds. Results show very distinct trends in vertically resolved soil temperature profiles and strong lateral variations over tens of meters that are linked to zones with various hydrological conditions, soil properties and vegetation types. The interaction between these zones is of strong interest to understand the evolution of the landscape and the permafrost distribution. The obtained information is expected to be useful for improving predictions of Arctic ecosystem feedbacks to climate.

Composite materials for space applications

NASA Technical Reports Server (NTRS)

Rawal, Suraj P.; Misra, Mohan S.; Wendt, Robert G.

1990-01-01

The objectives of the program were to: generate mechanical, thermal, and physical property test data for as-fabricated advanced materials; design and fabricate an accelerated thermal cycling chamber; and determine the effect of thermal cycling on thermomechanical properties and dimensional stability of composites. In the current program, extensive mechanical and thermophysical property tests of various organic matrix, metal matrix, glass matrix, and carbon-carbon composites were conducted, and a reliable database was constructed for spacecraft material selection. Material property results for the majority of the as-fabricated composites were consistent with the predicted values, providing a measure of consolidation integrity attained during fabrication. To determine the effect of thermal cycling on mechanical properties, microcracking, and thermal expansion behavior, approximately 500 composite specimens were exposed to 10,000 cycles between -150 and +150 F. These specimens were placed in a large (18 cu ft work space) thermal cycling chamber that was specially designed and fabricated to simulate one year low earth orbital (LEO) thermal cycling in 20 days. With this rate of thermal cycling, this is the largest thermal cycling unit in the country. Material property measurements of the thermal cycled organic matrix composite laminate specimens exhibited less than 24 percent decrease in strength, whereas, the remaining materials exhibited less than 8 percent decrease in strength. The thermal expansion response of each of the thermal cycled specimens revealed significant reduction in hysteresis and residual strain, and the average CTE values were close to the predicted values.

The effects of MWNT on thermal conductivity and thermal mechanical properties of epoxy

NASA Astrophysics Data System (ADS)

Ismadi, A. I.; Othman, R. N.

2017-12-01

Multiwall nanotube (MWNT) was used as filler in various studies to improve thermal conductivity and mechanical properties of epoxy. Present study varied different weight loading (0, 0.1 %, 0.5 %, 1 %, 1.5 %, 3 % and 5 %) of MWNT in order to observe the effects on the epoxy. Nanocomposite was analyzed by dynamic-mechanical thermal analyser (DMTA) and KD2 pro analyzer. DMTA measured storage modulus (E') and glass transition temperature (Tg) of the nanocomposite. Result showed that Tg value of neat epoxy is higher than all MWNT epoxy nanocomposite. Tg values drop from 81.55 °C (neat epoxy) to 65.03 °C (at 0.1 wt%). This may happen due to the agglomeration of MWNT in the epoxy. However, Tg values increases with the increase of MWNT wt%. Tg values increased from 65.03 °C to 78.53 °C at 1 wt%. Increment of storage modulus (E') at 3 °C (glassy region) was observed as the MWNT loading increases. Maximum value of E' during glassy region was observed to be at 5 wt% with (7.26±0.7) E+08 Pa compared to neat epoxy. On the contrary, there is slight increased and slight decreased with E' values at 100 °C (rubbery region) for all nanocomposite. Since epoxy exhibits low thermal conductivity properties, addition of MWNT has enhanced the properties. Optimum value of thermal conductivity was observed at 3 wt%. The values increased up to 9.03 % compared to neat epoxy. As expected, the result showed decrease value in thermal conductivity at 5 wt% as a result of agglomeration of MWNT in the epoxy.

Comparison of thermal signatures of a mine buried in mineral and organic soils

NASA Astrophysics Data System (ADS)

Lamorski, K.; Pregowski, Piotr; Swiderski, Waldemar; Usowicz, B.; Walczak, R. T.

2001-10-01

Values of thermal signature of a mine buried in soils, which ave different properties, were compared using mathematical- statistical modeling. There was applied a model of transport phenomena in the soil, which takes into consideration water and energy transfer. The energy transport is described using Fourier's equation. Liquid phase transport of water is calculated using Richard's model of water flow in porous medium. For the comparison, there were selected two soils: mineral and organic, which differs significantly in thermal and hydrological properties. The heat capacity of soil was estimated using de Vries model. The thermal conductivity was calculated using a statistical model, which incorprates fundamental soil physical properties. The model of soil thermal conductivity was built on the base of heat resistance, two Kirchhoff's laws and polynomial distribution. Soil hydrological properties were described using Mualem-van Genuchten model. The impact of thermal properties of the medium in which a mien had been placed on its thermal signature in the conditions of heat input was presented. The dependence was stated between observed thermal signature of a mine and thermal parameters of the medium.

An International Round-Robin Study, Part II: Thermal Diffusivity, Specific Heat and Thermal Conductivity

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

Wang, Hsin; Porter, Wallace D; Bottner, Harold

2013-01-01

For bulk thermoelectrics, figure-of-merit, ZT, still needs to improve from the current value of 1.0 - 1.5 to above 2 to be competitive to other alternative technologies. In recent years, the most significant improvements in ZT were mainly due to successful reduction of thermal conductivity. However, thermal conductivity cannot be measured directly at high temperatures. The combined measurements of thermal diffusivity and specific heat and density are required. It has been shown that thermal conductivity is the property with the greatest uncertainty and has a direct influence on the accuracy of the figure of merit. The International Energy Agency (IEA)more » group under the implementing agreement for Advanced Materials for Transportation (AMT) has conducted two international round-robins since 2009. This paper is Part II of the international round-robin testing of transport properties of bulk bismuth telluride. The main focuses in Part II are on thermal diffusivity, specific heat and thermal conductivity.« less

Method for measuring thermal properties using a long-wavelength infrared thermal image

DOEpatents

Walker, Charles L [Albuquerque, NM; Costin, Laurence S [Albuquerque, NM; Smith, Jody L [Albuquerque, NM; Moya, Mary M [Albuquerque, NM; Mercier, Jeffrey A [Albuquerque, NM

2007-01-30

A method for estimating the thermal properties of surface materials using long-wavelength thermal imagery by exploiting the differential heating histories of ground points in the vicinity of shadows. The use of differential heating histories of different ground points of the same surface material allows the use of a single image acquisition step to provide the necessary variation in measured parameters for calculation of the thermal properties of surface materials.

Determination of the Thermal Properties of Sands as Affected by Water Content, Drainage/Wetting, and Porosity Conditions for Sands With Different Grain Sizes

NASA Astrophysics Data System (ADS)

Smits, K. M.; Sakaki, T.; Limsuwat, A.; Illangasekare, T. H.

2009-05-01

It is widely recognized that liquid water, water vapor and temperature movement in the subsurface near the land/atmosphere interface are strongly coupled, influencing many agricultural, biological and engineering applications such as irrigation practices, the assessment of contaminant transport and the detection of buried landmines. In these systems, a clear understanding of how variations in water content, soil drainage/wetting history, porosity conditions and grain size affect the soil's thermal behavior is needed, however, the consideration of all factors is rare as very few experimental data showing the effects of these variations are available. In this study, the effect of soil moisture, drainage/wetting history, and porosity on the thermal conductivity of sandy soils with different grain sizes was investigated. For this experimental investigation, several recent sensor based technologies were compiled into a Tempe cell modified to have a network of sampling ports, continuously monitoring water saturation, capillary pressure, temperature, and soil thermal properties. The water table was established at mid elevation of the cell and then lowered slowly. The initially saturated soil sample was subjected to slow drainage, wetting, and secondary drainage cycles. After liquid water drainage ceased, evaporation was induced at the surface to remove soil moisture from the sample to obtain thermal conductivity data below the residual saturation. For the test soils studied, thermal conductivity increased with increasing moisture content, soil density and grain size while thermal conductivity values were similar for soil drying/wetting behavior. Thermal properties measured in this study were then compared with independent estimates made using empirical models from literature. These soils will be used in a proposed set of experiments in intermediate scale test tanks to obtain data to validate methods and modeling tools used for landmine detection.

Two-Dimensional Thermal Boundary Layer Corrections for Convective Heat Flux Gauges

NASA Technical Reports Server (NTRS)

Kandula, Max; Haddad, George

2007-01-01

This work presents a CFD (Computational Fluid Dynamics) study of two-dimensional thermal boundary layer correction factors for convective heat flux gauges mounted in flat plate subjected to a surface temperature discontinuity with variable properties taken into account. A two-equation k - omega turbulence model is considered. Results are obtained for a wide range of Mach numbers (1 to 5), gauge radius ratio, and wall temperature discontinuity. Comparisons are made for correction factors with constant properties and variable properties. It is shown that the variable-property effects on the heat flux correction factors become significant

A study of the effect of gamma and laser irradiation on the thermal, optical and structural properties of CR-39 nuclear track detector

NASA Astrophysics Data System (ADS)

Nouh, S. A.; Atta, M. R.; El-Melleegy, W. M.

2004-08-01

A comparative study of the effect of gamma and laser irradiation on the thermal, optical and structural properties of the CR-39 diglycol carbonate solid state nuclear track detector has been carried out. Samples from CR-39 polymer were classified into two main groups: the first group was irradiated by gamma rays with doses at levels between 20 and 300 kGy, whereas the second group was exposed to infrared laser radiation with energy fluences at levels between 0.71 and 8.53 J/cm(2). Non-isothermal studies were carried out using thermogravimetry, differential thermogravimetry and differential thermal analysis to obtain activation energy of decomposition and transition temperatures for the non-irradiated and all irradiated CR-39 samples. In addition, optical and structural property studies were performed on non-irradiated and irradiated CR-39 samples using refractive index and X-ray diffraction measurements. Variation in the onset temperature of decomposition T-o, activation energy of decomposition E-a, melting temperature T-m, refractive index n and the mass fraction of the amorphous phase after gamma and laser irradiation were studied. It was found that many changes in the thermal, optical and structural properties of the CR-39 polymer could be produced by gamma irradiation via degradation and cross-linking mechanisms. Also, the gamma dose has an advantage of increasing the correlation between thermal stability of the CR-39 polymer and bond formation created by the ionizing effect of gamma radiation. On the other hand, higher laser-energy fluences in the range 4.27-8.53 J/cm(2) decrease the melting temperature of the CR-39 polymer and this is most suitable for applications requiring molding of the polymer at lower temperatures.

Nanofluid two-phase flow and thermal physics: a new research frontier of nanotechnology and its challenges.

PubMed

Cheng, Lixin; Bandarra Filho, Enio P; Thome, John R

2008-07-01

Nanofluids are a new class of fluids engineered by dispersing nanometer-size solid particles in base fluids. As a new research frontier, nanofluid two-phase flow and thermal physics have the potential to improve heat transfer and energy efficiency in thermal management systems for many applications, such as microelectronics, power electronics, transportation, nuclear engineering, heat pipes, refrigeration, air-conditioning and heat pump systems. So far, the study of nanofluid two-phase flow and thermal physics is still in its infancy. This field of research provides many opportunities to study new frontiers but also poses great challenges. To summarize the current status of research in this newly developing interdisciplinary field and to identify the future research needs as well, this paper focuses on presenting a comprehensive review of nucleate pool boiling, flow boiling, critical heat flux, condensation and two-phase flow of nanofluids. Even for the limited studies done so far, there are some controversies. Conclusions and contradictions on the available nanofluid studies on physical properties, two-phase flow, heat transfer and critical heat flux (CHF) are presented. Based on a comprehensive analysis, it has been realized that the physical properties of nanofluids such as surface tension, liquid thermal conductivity, viscosity and density have significant effects on the nanofluid two-phase flow and heat transfer characteristics but the lack of the accurate knowledge of these physical properties has greatly limited the study in this interdisciplinary field. Therefore, effort should be made to contribute to the physical property database of nanofluids as a first priority. Secondly, in particular, research on nanofluid two-phase flow and heat transfer in microchannels should be emphasized in the future.

Engineering and design properties of thallium-doped sodium iodide and selected properties of sodium-doped cesium iodide

NASA Technical Reports Server (NTRS)

Forrest, K.; Haehner, C.; Heslin, T.; Magida, M.; Uber, J.; Freiman, S.; Hicho, G.; Polvani, R.

1984-01-01

Mechanical and thermal properties, not available in the literature but necessary to structural design, using thallium doped sodium iodide and sodium doped cesium iodide were determined to be coefficient of linear thermal expansion, thermal conductivity, thermal shock resistance, heat capacity, elastic constants, ultimate strengths, creep, hardness, susceptibility to subcritical crack growth, and ingot variation of strength. These properties were measured for single and polycrystalline materials at room temperature.

Non-Contact Measurement of Thermal Diffusivity in Ion-Implanted Nuclear Materials

NASA Astrophysics Data System (ADS)

Hofmann, F.; Mason, D. R.; Eliason, J. K.; Maznev, A. A.; Nelson, K. A.; Dudarev, S. L.

2015-11-01

Knowledge of mechanical and physical property evolution due to irradiation damage is essential for the development of future fission and fusion reactors. Ion-irradiation provides an excellent proxy for studying irradiation damage, allowing high damage doses without sample activation. Limited ion-penetration-depth means that only few-micron-thick damaged layers are produced. Substantial effort has been devoted to probing the mechanical properties of these thin implanted layers. Yet, whilst key to reactor design, their thermal transport properties remain largely unexplored due to a lack of suitable measurement techniques. Here we demonstrate non-contact thermal diffusivity measurements in ion-implanted tungsten for nuclear fusion armour. Alloying with transmutation elements and the interaction of retained gas with implantation-induced defects both lead to dramatic reductions in thermal diffusivity. These changes are well captured by our modelling approaches. Our observations have important implications for the design of future fusion power plants.

Thermal control of electroosmotic flow in a microchannel through temperature-dependent properties.

PubMed

Kwak, Ho Sang; Kim, Hyoungsoo; Hyun, Jae Min; Song, Tae-Ho

2009-07-01

A numerical investigation is conducted on the electroosmotic flow and associated heat transfer in a two-dimensional microchannel. The objective of this study is to explore a new conceptual idea that is control of an electroosmotic flow by using a thermal field effect through the temperature-dependent physical properties. Two exemplary problems are examined: a flow in a microchannel with a constant vertical temperature difference between two horizontal walls and a flow in a microchannel with the wall temperatures varying horizontally in a sinusoidal manner. The results of numerical computations showed that a proper control of thermal field may be a viable means to manipulate various non-plug-like flow patterns. A constant vertical temperature difference across the channel produces a shear flow. The horizontally-varying thermal condition results in spatial variation of physical properties to generate fluctuating flow patterns. The temperature variation at the wall with alternating vertical temperature gradient induces a wavy flow.

Non-Contact Measurement of Thermal Diffusivity in Ion-Implanted Nuclear Materials

DOE PAGES

Hofmann, F.; Mason, D. R.; Eliason, J. K.; ...

2015-11-03

Knowledge of mechanical and physical property evolution due to irradiation damage is essential for the development of future fission and fusion reactors. Ion-irradiation provides an excellent proxy for studying irradiation damage, allowing high damage doses without sample activation. Limited ion-penetration-depth means that only few-micron-thick damaged layers are produced. Substantial effort has been devoted to probing the mechanical properties of these thin implanted layers. Yet, whilst key to reactor design, their thermal transport properties remain largely unexplored due to a lack of suitable measurement techniques. Here we demonstrate non-contact thermal diffusivity measurements in ion-implanted tungsten for nuclear fusion armour. Alloying withmore » transmutation elements and the interaction of retained gas with implantation-induced defects both lead to dramatic reductions in thermal diffusivity. These changes are well captured by our modelling approaches. Our observations have important implications for the design of future fusion power plants.« less

Non-Contact Measurement of Thermal Diffusivity in Ion-Implanted Nuclear Materials

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

Hofmann, F.; Mason, D. R.; Eliason, J. K.

Knowledge of mechanical and physical property evolution due to irradiation damage is essential for the development of future fission and fusion reactors. Ion-irradiation provides an excellent proxy for studying irradiation damage, allowing high damage doses without sample activation. Limited ion-penetration-depth means that only few-micron-thick damaged layers are produced. Substantial effort has been devoted to probing the mechanical properties of these thin implanted layers. Yet, whilst key to reactor design, their thermal transport properties remain largely unexplored due to a lack of suitable measurement techniques. Here we demonstrate non-contact thermal diffusivity measurements in ion-implanted tungsten for nuclear fusion armour. Alloying withmore » transmutation elements and the interaction of retained gas with implantation-induced defects both lead to dramatic reductions in thermal diffusivity. These changes are well captured by our modelling approaches. Our observations have important implications for the design of future fusion power plants.« less

Thermal expansion and magnetostriction measurements at cryogenic temperature using the strain gage method

NASA Astrophysics Data System (ADS)

Wang, Wei; Liu, Huiming; Huang, Rongjin; Zhao, Yuqiang; Huang, Chuangjun; Guo, Shibin; Shan, Yi; Li, Laifeng

2018-03-01

Thermal expansion and magnetostriction, the strain responses of a material to temperature and a magnetic field, especially properties at low temperature, are extremely useful to study electronic and phononic properties, phase transitions, quantum criticality, and other interesting phenomena in cryogenic engineering and materials science. However, traditional dilatometers cannot provide magnetic field and ultra low temperature (＜77 K) environment easily. This paper describes the design and test results of thermal expansion and magnetostriction at cryogenic temperature using the strain gage method based on a Physical Properties Measurements System (PPMS). The interfacing software and automation were developed using LabVIEW. The sample temperature range can be tuned continuously between 1.8 K and 400 K. With this PPMS-aided measuring system, we can observe temperature and magnetic field dependence of the linear thermal expansion of different solid materials easily and accurately.

Non-Contact Measurement of Thermal Diffusivity in Ion-Implanted Nuclear Materials

PubMed Central

Hofmann, F.; Mason, D. R.; Eliason, J. K.; Maznev, A. A.; Nelson, K. A.; Dudarev, S. L.

2015-01-01

Knowledge of mechanical and physical property evolution due to irradiation damage is essential for the development of future fission and fusion reactors. Ion-irradiation provides an excellent proxy for studying irradiation damage, allowing high damage doses without sample activation. Limited ion-penetration-depth means that only few-micron-thick damaged layers are produced. Substantial effort has been devoted to probing the mechanical properties of these thin implanted layers. Yet, whilst key to reactor design, their thermal transport properties remain largely unexplored due to a lack of suitable measurement techniques. Here we demonstrate non-contact thermal diffusivity measurements in ion-implanted tungsten for nuclear fusion armour. Alloying with transmutation elements and the interaction of retained gas with implantation-induced defects both lead to dramatic reductions in thermal diffusivity. These changes are well captured by our modelling approaches. Our observations have important implications for the design of future fusion power plants. PMID:26527099

Lattice dynamics and lattice thermal conductivity of thorium dicarbide

NASA Astrophysics Data System (ADS)

Liao, Zongmeng; Huai, Ping; Qiu, Wujie; Ke, Xuezhi; Zhang, Wenqing; Zhu, Zhiyuan

2014-11-01

The elastic and thermodynamic properties of ThC2 with a monoclinic symmetry have been studied by means of density functional theory and direct force-constant method. The calculated properties including the thermal expansion, the heat capacity and the elastic constants are in a good agreement with experiment. Our results show that the vibrational property of the C2 dimer in ThC2 is similar to that of a free standing C2 dimer. This indicates that the C2 dimer in ThC2 is not strongly bonded to Th atoms. The lattice thermal conductivity for ThC2 was calculated by means of the Debye-Callaway model. As a comparison, the conductivity of ThC was also calculated. Our results show that the ThC and ThC2 contributions of the lattice thermal conductivity to the total conductivity are 29% and 17%, respectively.

Experimental and computational study of electronic, electrochemical and thermal properties of quinoline phosphate

NASA Astrophysics Data System (ADS)

Ben Issa, Takoua; Ben Ali Hassine, Chedia; Ghalla, Houcine; Barhoumi, Houcine; Benhamada, Latifa

2018-06-01

In this work, the electronic behavior, charge transfer, non linear optical (NLO) properties, and thermal stability of the quinoline phosphate (QP) have been investigated. The experimental UV-Vis spectrum has been recorded in the range of 200-800 nm. Additionally, the absorption spectrum was reproduced by time-dependent density functional theory (TD-DFT) method with B3LYP functional and with empirical dispersion corrections D3BJ in combination with the 6-311+G(d,p) basis set. The electronic properties such as HOMO-LUMO energy gap and chemical reactivity have been calculated. The electrochemical characterization of the title compound is investigated using cyclic voltammetry and impedance spectroscopy methods. Finally, the thermal stability of the QP is discussed in term of differential scanning calorimetry (DSC) measurement, which showed that QP compound is thermally stable up to 150 °C.

Effect of Continuous Multi-Walled Carbon Nanotubes on Thermal and Mechanical Properties of Flexible Composite Film

PubMed Central

Cha, Ji Eun; Kim, Seong Yun; Lee, Seung Hee

2016-01-01

To investigate the effect of continuous multi-walled carbon nanotubes (MWCNTs) on the thermal and mechanical properties of composites, we propose a fabrication method for a buckypaper-filled flexible composite film prepared by a two-step process involving buckypaper fabrication using vacuum filtration of MWCNTs, and composite film fabrication using the dipping method. The thermal conductivity and tensile strength of the composite film filled with the buckypaper exhibited improved results, respectively 76% and 275% greater than those of the individual MWCNT-filled composite film. It was confirmed that forming continuous MWCNT fillers is an important factor which determines the physical characteristics of the composite film. In light of the study findings, composite films using buckypaper as a filler and polydimethylsiloxane (PDMS) as a flexible matrix have sufficient potential to be applied as a heat-dissipating material, and as a flexible film with high thermal conductivity and excellent mechanical properties. PMID:28335310

Task 6 : material thermal input for Iowa materials.

DOT National Transportation Integrated Search

2008-02-01

The present research project was designed to determine thermal properties, such as coefficient of thermal expansion : (CTE) and thermal conductivity, of Iowa concrete pavement materials. These properties are required as input values by : the Mechanis...

Lamb Wave Assessment of Fatigue and Thermal Damage in Composites

NASA Technical Reports Server (NTRS)

Seale, Michael D.; Smith, Barry T.; Prosser, W. H.

2004-01-01

Among the various techniques available, ultrasonic Lamb waves offer a convenient method of evaluating composite materials. Since the Lamb wave velocity depends on the elastic properties of a structure, an effective tool exists to monitor damage in composites by measuring the velocity of these waves. Lamb wave measurements can propagate over long distances and are sensitive to the desired in-plane elastic properties of the material. This paper describes two studies which monitor fatigue damage and two studies which monitor thermal damage in composites using Lamb waves. In the fatigue studies, the Lamb wave velocity is compared to modulus measurements obtained using strain gage measurements in the first experiment and the velocity is monitored along with the crack density in the second. In the thermal damage studies, one examines samples which were exposed to varying temperatures for a three minute duration and the second includes rapid thermal damage in composites by intense laser beams. In all studies, the Lamb wave velocity is demonstrated to be an excellent method to monitor damage in composites.

Thermal energy storage in granular deposits

NASA Astrophysics Data System (ADS)

Ratuszny, Paweł

2017-10-01

Energy storage technology is crucial for the development of the use of renewable energy sources. This is a substantial constraint, however it can, to some extent, be solved by storing energy in its various forms: electrical, mechanical, chemical and thermal. This article presents the results of research in thermal properties of granular deposits. Correlation between temperature changes in the stores over a period of time and their physical properties has been studied. The results of the research have practical application in designing thermal stores based on bulk materials and ground deposits. Furthermore, the research results are significant for regeneration of the lower ground sources for heat pumps and provide data for designing ground heat exchangers for ventilation systems.

Influence of weathering effect in natural environment on thermal properties hybrid kenaf blast/glass fibre and unsaturated polyester composite

NASA Astrophysics Data System (ADS)

Mohammed, M.; Rozyanty, A. R.; Beta, B. O.; Adam, T.; Osman, A. F.; Salem, I. A. S.; Dahham, O. S.; Al-Samarrai, M. N.; Mohammed, A. M.

2017-10-01

Unprecedented growing on environmental concern has put research on completive driven effort to quest for new material in various application, the effort toward producing thermally stable polymer is ever gaining considerable interest. Thus, this study proposed the integration of glass fiber with kenaf based polymer to improve thermal properties. Based on the TGA and DSC results, the composites show slow and steady initial weight loss until major weight loss at 360°C. Thus, with incorporation of glass fiber extend region of degradation until 260-360 °Cshow no exothermic or endothermic changes, this reflected that the composites thermally stability have been improved.

Effects of thermal cycling on graphie-fiber-reinforced 6061 aluminum

NASA Technical Reports Server (NTRS)

Dries, G. A.; Tompkins, S. S.

1986-01-01

Graphite-reinforced aluminum alloy metal-matrix composites are among materials being considered for structural components in dimensionally stable space structures. This application requires materials with low values of thermal expansions and high specific stiffnesses. They must remain stable during exposures to the space environment for periods extending to 20 years. The effects of thermal cycling on the thermal expansion behavior and mechanical properties of Thornel P100 graphite 6061 aluminum composites, as fabricated and after thermal processing to eliminate thermal strain hysteresis, have been investigated. Two groups of composites were studied: one was fabricated by hot roll bonding and the other by diffusion bonding. Processing significantly reduced strain hysteresis during thermal cycling in both groups and improved the ultimate tensile strength and modulus in the diffusion-bonded composites. Thermal cycling stabilized the as-fabricated composites by reducing the residual fabrication stress and increased the matrix strength by metallurgical aging. Thermal expansion behavior of both groups after processing was insensitive to thermal cycling. Data scatter was too large to determine effects of thermal cycling on the mechanical properties. The primary effects of processing and thermal cycling can be attributed to changes in the metallurgical condition and stress state of the matrix.

The thermal expansion and thermophysical properties of an aluminum and Al/B4C composite

NASA Astrophysics Data System (ADS)

Gladkovsky, S. V.; Kamantsev, I. S.; Kuteneva, S. V.; Veselova, V. E.; Ryzhkov, M. A.

2017-12-01

The paper presents results of experimental studies of the thermal expansion and thermophysical properties of an Al/B4C composite with a boron carbide content of 20 wt% and technically pure aluminum in the temperature range from 100 to 600°C to evaluate the possible use of this composite as a neutron-protective material in the nuclear industry.

Properties of forced convection experimental with silicon carbide based nano-fluids

NASA Astrophysics Data System (ADS)

Soanker, Abhinay

With the advent of nanotechnology, many fields of Engineering and Science took a leap to the next level of advancements. The broad scope of nanotechnology initiated many studies of heat transfer and thermal engineering. Nano-fluids are one such technology and can be thought of as engineered colloidal fluids with nano-sized colloidal particles. There are different types of nano-fluids based on the colloidal particle and base fluids. Nano-fluids can primarily be categorized into metallic, ceramics, oxide, magnetic and carbon based. The present work is a part of investigation of the thermal and rheological properties of ceramic based nano-fluids. alpha-Silicon Carbide based nano-fluid with Ethylene Glycol and water mixture 50-50% volume concentration was used as the base fluid here. This work is divided into three parts; Theoretical modelling of effective thermal conductivity (ETC) of colloidal fluids, study of Thermal and Rheological properties of alpha-SiC nano-fluids, and determining the Heat Transfer properties of alpha-SiC nano-fluids. In the first part of this work, a theoretical model for effective thermal conductivity (ETC) of static based colloidal fluids was formulated based on the particle size, shape (spherical), thermal conductivity of base fluid and that of the colloidal particle, along with the particle distribution pattern in the fluid. A MATLAB program is generated to calculate the details of this model. The model is specifically derived for least and maximum ETC enhancement possible and thereby the lower and upper bounds was determined. In addition, ETC is also calculated for uniform colloidal distribution pattern. Effect of volume concentration on ETC was studied. No effect of particle size was observed for particle sizes below a certain value. Results of this model were compared with Wiener bounds and Hashin- Shtrikman bounds. The second part of this work is a study of thermal and rheological properties of alpha-Silicon Carbide based nano-fluids. The nano-fluid properties were tested at three different volume concentrations; 0.55%, 1% and 1.6%. Thermal conductivity was measured for the three-volume concentration as function of temperature. Thermal conductivity enhancement increased with the temperature and may be attributed to increased Brownian motion of colloidal particles at higher temperatures. Measured thermal conductivity values are compared with results obtained by theoretical model derived in this work. Effect of temperature and volume concentration on viscosity was also measured and reported. Viscosity increase and related consequences are important issues for the use of nano-fluids. Extensive measurements of heat transfer and pressure drop for forced convection in circular pipes with nano-fluids was also conducted. Parameters such as heat transfer coefficient, Nusselt number, pressure drop and a thermal hydraulic performance factor that takes into account the gains made by increase in thermal conductivity as well as penalties related to increase in pressure drop are evaluated for laminar and transition flow regimes. No significant improvement in heat transfer (Nusselt number) compared to its based fluid was observed. It is also observed that the values evaluated for the thermal-hydraulic performance factor (change in heat transfer/change in pressure drop) was under unity for many flow conditions indicating poor overall applicability of SiC based nano-fluids.

All-optical technique for measuring thermal properties of materials at static high pressure

NASA Astrophysics Data System (ADS)

Pangilinan, G. I.; Ladouceur, H. D.; Russell, T. P.

2000-10-01

The development and implementation of an all-optical technique for measuring thermal transport properties of materials at high pressure in a gem anvil cell are reported. Thermal transport properties are determined by propagating a thermal wave in a material subjected to high pressures, and measuring the temperature as a function of time using an optical sensor embedded downstream in the material. Optical beams are used to deposit energy and to measure the sensor temperature and replace the resistive heat source and the thermocouples of previous methods. This overcomes the problems introduced with pressure-induced resistance changes and the spatial limitations inherent in previous high-pressure experimentation. Consistent with the heat conduction equation, the material's specific heat, thermal conductivity, and thermal diffusivity (κ) determine the sensor's temperature rise and its temporal profile. The all-optical technique described focuses on room-temperature thermal properties but can easily be applied to a wide temperature range (77-600 K). Measurements of thermal transport properties at pressure up to 2.0 GPa are reported, although extension to much higher pressures are feasible. The thermal properties of NaCl, a commonly used material for high-pressure experiments are measured and shown to be consistent with those obtained using the traditional methods.

Mechanical Reinforcement, Shapestabilization and Thermal Improvement of Phase-Change Energy Storage Materials Using Graphene Oxide Aerogel

NASA Astrophysics Data System (ADS)

Schuman, Yue Xu

Paraffin is known as a good energy storage phase change material (PCM) because of its high energy storage capacity and low cost. However, the leakage of liquid paraffin beyond its melting point and its low thermal conductivity hinder applications of paraffin in energy storage systems. Recently, nanomaterials have been used to create PCM composites in order to enhance their thermal properties while shape stabilizing the PCMs. However, fundamental studies on the material structures and mechanical behavior of the thermally enhanced PCM composites are limited especially at the nanoscale. In this study, we developed a PCM composite using graphene oxide aerogel (GOxA) as the reinforcing 3D network. The GOxA functions thermally as a heat transfer path and mechanically as a nanofiller to reinforce the PCM matrix. We characterized the morphology, the crystal and molecular structures as well as the multiscale mechanical and thermal behavior of the GOxA-PCM composite to evaluate the role of GOxA in the PCM composite. The molecular and diffraction characterizations imply that the GOxA network may affect the paraffin's crystallization, potentially forming an interfacial phase at the surfaces of GOxA. Furthermore, the mechanical properties were studied using nanoindentation at the nano/microscale and a digital durometer at the macroscale from 25degree C to 80 degree C. The mechanical characterizations show that the GOxA-PCM composite is 3 7x harder than pure paraffin and maintains significant strength even above paraffin's melting point due to the support from the GoxA. Moreover, the composite is much less strain-rate sensitive than paraffin. The reinforcement via GOxA is much beyond the prediction by the rule of mixture, implying a strong GOxA-paraffin interfacial bonding. Finally, a thermal scanning microscopy (SThM) along with AFM was used to study the thermal properties at microscale. AFM and thermal images indicate that GOxA-PCM has a better thermal conductivity. The latent heats and thermal conductivities were analyzed using DSC and TPS at the macroscale. Results imply that there might be an interphase between the paraffin and the GOxA resulting in a greater latent heat storage ability and better thermal conductivity of the GOxA-PCM. We believe this is the first fundamental study on the mechanical and thermal behaviors of paraffin and GOxA-PCM composite at the multiscale. The enhancement in hardness, latent heat, and thermal conductivity are expected to aid the analysis and design of thermal energy storage composites with higher performance in the future.

Influence of Thermal Cycling on Flexural Properties and Simulated Wear of Computer-aided Design/Computer-aided Manufacturing Resin Composites.

PubMed

Tsujimoto, A; Barkmeier, W W; Takamizawa, T; Latta, M A; Miyazaki, M

The purpose of this study was to evaluate the influence of thermal cycling on the flexural properties and simulated wear of computer-aided design/computer-aided manufacturing (CAD/CAM) resin composites. The six CAD/CAM resin composites used in this study were 1) Lava Ultimate CAD/CAM Restorative (LU); 2) Paradigm MZ100 (PM); 3) CERASMART (CS); 4) Shofu Block HC (SB); 5) KATANA AVENCIA Block (KA); and 6) VITA ENAMIC (VE). Specimens were divided randomly into two groups, one of which was stored in distilled water for 24 hours, and the other of which was subjected to 10,000 thermal cycles. For each material, 15 specimens from each group were used to determine the flexural strength and modulus according to ISO 6872, and 20 specimens from each group were used to examine wear using a localized wear simulation model. The test materials were subjected to a wear challenge of 400,000 cycles in a Leinfelder-Suzuki device (Alabama machine). The materials were placed in custom-cylinder stainless steel fixtures, and simulated localized wear was generated using a stainless steel ball bearing (r=2.387 mm) antagonist in a water slurry of polymethyl methacrylate beads. Simulated wear was determined using a noncontact profilometer (Proscan 2100) with Proscan and AnSur 3D software. The two-way analysis of variance of flexural properties and simulated wear of CAD/CAM resin composites revealed that material type and thermal cycling had a significant influence (p<0.05), but there was no significant interaction (p>0.05) between the two factors. The flexural properties and maximum depth of wear facets of CAD/CAM resin composite were different (p<0.05) depending on the material, and their values were influenced (p>0.05) by thermal cycling, except in the case of VE. The volume losses in wear facets on LU, PM, and SB after 10,000 thermal cycles were significantly higher (p<0.05) than those after 24 hours of water storage, unlike CS, KA, and VE. The results of this study indicate that the flexural properties and simulated wear of CAD/CAM resin composites are different depending on the material. In addition, the flexural properties and simulated wear of CAD/CAM resin composites are influenced by thermal cycling.

Synthesis and characterization of new polyamides derived from alanine and valine derivatives

PubMed Central

2012-01-01

Background Many efforts have been recently devoted to design, investigate and synthesize biocompatible, biodegradable polymers for applications in medicine for either the fabrication of biodegradable devices or as drug delivery systems. Many of them consist of condensation of polymers having incorporated peptide linkages susceptible to enzymatic cleavage. Polyamides (PAs) containing α-amino acid residues such as L-leucine, L-alanine and L-phenylalanine have been reported as biodegradable materials. Furthermore, polyamides (PAs) derived from C10 and C14 dicarboxylic acids and amide-diamines derived from 1,6-hexanediamine or 1,12-dodecanediamine and L-phenylalanine, L-valyl-L-phenylalanine or L-phenylalanyl-L-valine residues have been reported as biocompatible polymers. We have previously described the synthesis and thermal properties of a new type of polyamides-containing amino acids based on eight new symmetric meta-oriented protected diamines derived from coupling of amino acids namely; Fomc-glycine, Fmoc-alanine, Fomc-valine and Fomc-leucine with m-phenylene diamine or 2,6-diaminopyridine. Results revealed that incorporation of pyridine onto the polymeric backbone of all series decreases the thermal stability. Here we describe another family of polyamides based on benzene dicarboxylic acid, pyridine dicarboxylic acid, and α-amino acid linked to benzidine and 4,4′-oxydianiline to study the effect of the dicarboxylic acid as well as the amino acids on the nature and thermal stability of the polymers. Results We report here the preparation of a new type of polyamides based on benzene dicarboxylic acid, pyridine dicarboxylic acid, and α-amino acid linked to benzidine and 4,4′-oxydianiline to study the effect of the dicarboxylic acid as well as the amino acids on the nature and thermal stability of polymers. The thermal properties of the polymers were evaluated by different techniques. Results revealed that structure-thermal property correlation based on changing the dicarboxylic acid monomer or the diamine monomer demonstrated an interesting connection between a single change (changing the dicarboxylic acids in each series while the diamine is fixed) and thermal properties. The newly prepared polymers may possess biodegradability and thus may find some applications as novel biomaterials. Conclusions The thermal properties of the new type of polyamides based on benzene dicarboxylic acid, pyridine dicarboxylic acid, and α-amino acid (alanine and valine) linked to benzidine and 4,4′-oxydianiline were evaluated by thermal gravimetric (TG), differential thermal gravimetric (DTG) and differential thermal analysis (DTA) techniques. Results revealed that the structure-thermal property correlation based on changing the dicarboxylic acid monomer or the diamine monomer demonstrated an interesting connection between a single change (changing the dicarboxylic acids in each series while the diamine is fixed) and thermal properties. In addition, pyridine-containing polymers exhibited semicrystalline characteristic with melting temperature, Tm. where none of the valine-containing polymers showed a melting and crystallization peak indicating that the polymers were amorphous. This is expected since L-valine side chain can inhibit close packing and eliminate crystallization. The newly prepared polymers may possess biodegradability and thus may find some applications as novel biomaterials. PMID:23122321

Parametric study of different contributors to tumor thermal profile

NASA Astrophysics Data System (ADS)

Tepper, Michal; Gannot, Israel

2014-03-01

Treating cancer is one of the major challenges of modern medicine. There is great interest in assessing tumor development in in vivo animal and human models, as well as in in vitro experiments. Existing methods are either limited by cost and availability or by their low accuracy and reproducibility. Thermography holds the potential of being a noninvasive, low-cost, irradiative and easy-to-use method for tumor monitoring. Tumors can be detected in thermal images due to their relatively higher or lower temperature compared to the temperature of the healthy skin surrounding them. Extensive research is performed to show the validity of thermography as an efficient method for tumor detection and the possibility of extracting tumor properties from thermal images, showing promising results. However, deducing from one type of experiment to others is difficult due to the differences in tumor properties, especially between different types of tumors or different species. There is a need in a research linking different types of tumor experiments. In this research, parametric analysis of possible contributors to tumor thermal profiles was performed. The effect of tumor geometric, physical and thermal properties was studied, both independently and together, in phantom model experiments and computer simulations. Theoretical and experimental results were cross-correlated to validate the models used and increase the accuracy of simulated complex tumor models. The contribution of different parameters in various tumor scenarios was estimated and the implication of these differences on the observed thermal profiles was studied. The correlation between animal and human models is discussed.

Investigation of thermal fatigue in fiber composite materials. [(thermal cycling tests)

NASA Technical Reports Server (NTRS)

Fahmy, A. A.; Cunningham, T. G.

1976-01-01

Graphite-epoxy laminates were thermally cycled to determine the effects of thermal cycles on tensile properties and thermal expansion coefficients of the laminates. Three 12-ply laminate configurations were subjected to up to 5,000 thermal cycles. The cumulative effect of the thermal cycles was determined by destructive inspection (electron micrographs and tensile tests) of samples after progressively larger numbers of cycles. After thermal cycling, the materials' tensile strengths, moduli, and thermal expansion coefficients were significantly lower than for the materials as fabricated. Most of the degradation of properties occurred after only a few cycles. The property degradation was attributed primarily to the progressive development of matrix cracks whose locations depended upon the layup orientation of the laminate.

The effect of replaced recycled glass on thermal conductivity and compression properties of cement

NASA Astrophysics Data System (ADS)

khalil, A. S.; Mahmoud, M. A.; AL-Hathal, A.; Jawad, M. K.; Mozahim, B. M.

2018-05-01

This study deal with recycling of waste colorless glass bottles which are prepared as a powder and use them as an alternative for cement to save the environment from west and reduce some of cement(ceramic) damage and interactions with conserving physical properties of block concrete. Different weight percentage (0%, 2%, 4%, 5%, 6%, 8%, 10%, 15%, 20% and 25%) of recycled glass bottle were use in this research to be replaced by a certain percentages of cement. Thermal conductivity was studied for prepared samples. Results show that the thermal conductivity decrease with the increase of weight percentage of glass powder comparing with the stander sample.

Complex Study of the Physical Properties of Reticulated Vitreous Carbon

NASA Astrophysics Data System (ADS)

Alifanov, O. M.; Cherepanov, V. V.; Morzhukhina, A. V.

2015-01-01

We give an example of using a two-level identifi cation system incorporating an augmented mathematical model covering the structure, the thermal, electrophysical, and optical properties of nonmetallic ultraporous reticulated materials. The model, when combined with a nonstationary thermal experiment and methods of the theory of inverse heat transfer problems, permits determining the little studied characteristics of the above materials. We present some of the results of investigations of reticulated vitreous carbon confirming the possibility of using it in a number of engineering applications.

PCM/wood composite to store thermal energy in passive building envelopes

NASA Astrophysics Data System (ADS)

Barreneche, C.; Vecstaudza, J.; Bajare, D.; Fernandez, A. I.

2017-10-01

The development of new materials to store thermal energy in a passive building system is a must to improve the thermal efficiency by thermal-regulating the indoor temperatures. This fact will deal with the reduction of the gap between energy supply and energy demand to achieve thermal comfort in building indoors. The aim of this work was to test properties of novel PCM/wood composite materials developed at Riga Technical University. Impregnation of PCM (phase change material) in wood increases its thermal mass and regulates temperature fluctuations during day and night. The PCM used are paraffin waxes (RT-21 and RT-27 from Rubitherm) and the wood used was black alder, the most common wood in Latvia. The PCM distribution inside wood sample has been studied as well as its thermophysical, mechanical and fire reaction properties. Developed composite materials are promising in the field of energy saving in buildings.

Information-theoretic equilibrium and observable thermalization

NASA Astrophysics Data System (ADS)

Anzà, F.; Vedral, V.

2017-03-01

A crucial point in statistical mechanics is the definition of the notion of thermal equilibrium, which can be given as the state that maximises the von Neumann entropy, under the validity of some constraints. Arguing that such a notion can never be experimentally probed, in this paper we propose a new notion of thermal equilibrium, focused on observables rather than on the full state of the quantum system. We characterise such notion of thermal equilibrium for an arbitrary observable via the maximisation of its Shannon entropy and we bring to light the thermal properties that it heralds. The relation with Gibbs ensembles is studied and understood. We apply such a notion of equilibrium to a closed quantum system and show that there is always a class of observables which exhibits thermal equilibrium properties and we give a recipe to explicitly construct them. Eventually, an intimate connection with the Eigenstate Thermalisation Hypothesis is brought to light.

Information-theoretic equilibrium and observable thermalization

PubMed Central

Anzà, F.; Vedral, V.

2017-01-01

A crucial point in statistical mechanics is the definition of the notion of thermal equilibrium, which can be given as the state that maximises the von Neumann entropy, under the validity of some constraints. Arguing that such a notion can never be experimentally probed, in this paper we propose a new notion of thermal equilibrium, focused on observables rather than on the full state of the quantum system. We characterise such notion of thermal equilibrium for an arbitrary observable via the maximisation of its Shannon entropy and we bring to light the thermal properties that it heralds. The relation with Gibbs ensembles is studied and understood. We apply such a notion of equilibrium to a closed quantum system and show that there is always a class of observables which exhibits thermal equilibrium properties and we give a recipe to explicitly construct them. Eventually, an intimate connection with the Eigenstate Thermalisation Hypothesis is brought to light. PMID:28266646

Information-theoretic equilibrium and observable thermalization.

PubMed

Anzà, F; Vedral, V

2017-03-07

A crucial point in statistical mechanics is the definition of the notion of thermal equilibrium, which can be given as the state that maximises the von Neumann entropy, under the validity of some constraints. Arguing that such a notion can never be experimentally probed, in this paper we propose a new notion of thermal equilibrium, focused on observables rather than on the full state of the quantum system. We characterise such notion of thermal equilibrium for an arbitrary observable via the maximisation of its Shannon entropy and we bring to light the thermal properties that it heralds. The relation with Gibbs ensembles is studied and understood. We apply such a notion of equilibrium to a closed quantum system and show that there is always a class of observables which exhibits thermal equilibrium properties and we give a recipe to explicitly construct them. Eventually, an intimate connection with the Eigenstate Thermalisation Hypothesis is brought to light.

Thermal properties of poly(3-hydroxybutyrate)/vegetable fiber composites

NASA Astrophysics Data System (ADS)

Vitorino, Maria B. C.; Reul, Lízzia T. A.; Carvalho, Laura H.; Canedo, Eduardo L.

2015-05-01

The present work studies the thermal properties of composites of poly(3-hydroxybutyrate) (PHB) - a fully biodegradable semi-crystalline thermo-plastic obtained from renewable resources through low-impact biotechno-logical process, biocompatible and non-toxic - and vegetable fiber from the fruit (coconut) of babassu palm tree. PHB is a highly crystalline resin and this characteristic leads to suboptimal properties in some cases. Consequently, thermal properties, in particular those associated with the crystallization of the matrix, are important to judge the suitability of the compounds for specific applications. PHB/babassu composites with 0-50% load were prepared in an internal mixer. Two different types of babassu fibers with two different particle size ranges were compounded with PHB and test specimens molded by compression. Melting and crystallization behavior were studied by differential scanning calorimetry (DSC) at heating/cooling rates between 2 and 30°C/min. Several parameters, including melting point, crystallization temperature, crystallinity, and rate of crystallization, were estimated as functions of load and heating/cooling rates. Results indicate that fibers do not affect the melting process, but facilitate crystallization from the melt. Crystallization temperatures are 30 to 40°C higher for the compounds compared with the neat resin. However, the amount of fiber added has little effect on crystallinity and the degree of crystallinity is hardly affected by the load. Fiber type and initial particle size do not have a significant effect on thermal properties.

Unravelling the distinct crystallinity and thermal properties of suberin compounds from Quercus suber and Betula pendula outer barks.

PubMed

Sousa, Andreia F; Gandini, Alessandro; Caetano, Ana; Maria, Teresa M R; Freire, Carmen S R; Neto, Carlos Pascoal; Silvestre, Armando J D

2016-12-01

The main purpose of this study was to investigate the potential of suberin (a naturally occurring aromatic-aliphatic polyester ubiquitous to the vegetable realm) as a renewable source of chemicals and, in particular, to assess their physical properties. A comparison between cork and birch suberin fragments obtained by conventional depolymerisation processes (hydrolysis or methanolysis) is provided, focusing essentially on their thermal and crystallinity properties. It was found that suberin fragments obtained by the hydrolysis depolymerisation of birch had a high degree of crystallinity, as indicated by their thermal analysis and corroborated by the corresponding XRD diffractions, as opposed to hydrolysis-depolymerised cork suberin counterparts, which were essentially amorphous. Copyright © 2016 Elsevier B.V. All rights reserved.

Fabrication methods and anisotropic properties of graphite matrix compacts for use in HTGR

NASA Astrophysics Data System (ADS)

Yeo, Sunghwan; Yun, Jihae; Kim, Sungok; Cho, Moon Sung; Lee, Young-Woo

2018-02-01

This study investigated the anisotropic microstructural, mechanical, and thermal properties of fabricated graphite matrix prismatic compacts for High Temperature Gas Cooled Reactor (HTGR) fuel. When the observed alignment of graphite grains and the coke derived from phenolic resin is in the transverse direction, the result is severely anisotropic thermal properties. Compacts with such orientation in the transverse direction exhibited increases of thermal expansion and conductivity up to 5.8 times and 4.82 times, respectively, more than those in the axial direction. The formation of pores due to the pyrolysis of phenolic resin was observed predominantly on upper region of the fabricated compacts. This anisotropic pore formation created anisotropic Vickers hardness on the planes with different directions.

Thermal Coatings Seminar Series Training Part 1: Properties of Thermal Coatings

NASA Technical Reports Server (NTRS)

Triolo, Jack

2015-01-01

This course will present an overview of a variety of thermal coatings-related topics, including: coating types and availability, thermal properties measurements, environmental testing (lab and in-flight), environmental impacts, contamination impacts, contamination liabilities, determination of BOLEOL values, and what does specularity mean to the thermal engineer.

Crosslinked bicontinuous biobased PLA/NR blends via dynamic vulcanization using different curing systems.

PubMed

Yuan, Daosheng; Chen, Kunling; Xu, Chuanhui; Chen, Zhonghua; Chen, Yukun

2014-11-26

In this study, blends of entirely biosourced polymers, namely polylactide (PLA) and natural rubber (NR), were prepared through dynamic vulcanization using dicumyl peroxide (DCP), sulphur (S) and phenolic resin (2402) as curing agents, respectively. The crosslinked NR phase was found to be a continuous structure in all the prepared blends. The molecular weight changes of PLA were studied by gel permeation chromatography. Interfacial compatibilization between PLA and NR was investigated using Fourier transform infrared spectroscopy and scanning electron microscopy. The thermal properties of blends were evaluated by differential scanning calorimetry and thermogravimetric analysis instrument. It was found that the molecular weight of PLA and interfacial compatibilizaion between PLA and NR showed a significant influence on the mechanical and thermal properties of blends. The PLA/NR blend (60/40 w/w) by DCP-induced dynamic vulcanization owned the finest mechanical properties and thermal stability. Copyright © 2014 Elsevier Ltd. All rights reserved.

Mechanical and thermal properties of polylactic acid composites reinforced with cellulose nanoparticles extracted from kenaf fibre

NASA Astrophysics Data System (ADS)

Ketabchi, Mohammad Reza; Khalid, Mohammad; Thevy Ratnam, Chantara; Walvekar, Rashmi

2016-12-01

Different approaches have been attempted to use biomass as filler for production of biodegradable polymer composites. In this study, cellulose nanoparticles (CNP) extracted from kenaf fibres were used to produce polylactic acid (PLA) based biodegradable nanocomposites. CNP concentration was varied from 1-5 wt. % and blended with PLA using Brabender twin-screw compounder. Effects of CNP loading on the mechanical, thermal and dynamic properties of PLA were investigated. Studies on the morphological properties and influence of CNP loading on the properties of CNP/PLA nanocomposite were also conducted. The results show an adequate compatibility between CNP and PLA matrix. Moreover, addition of 3 wt. % of CNP improved the PLA tensile strength by 25%.

Evaluating the performance of coupled snow-soil models in SURFEXv8 to simulate the permafrost thermal regime at a high Arctic site

NASA Astrophysics Data System (ADS)

Barrere, Mathieu; Domine, Florent; Decharme, Bertrand; Morin, Samuel; Vionnet, Vincent; Lafaysse, Matthieu

2017-09-01

Climate change projections still suffer from a limited representation of the permafrost-carbon feedback. Predicting the response of permafrost temperature to climate change requires accurate simulations of Arctic snow and soil properties. This study assesses the capacity of the coupled land surface and snow models ISBA-Crocus and ISBA-ES to simulate snow and soil properties at Bylot Island, a high Arctic site. Field measurements complemented with ERA-Interim reanalyses were used to drive the models and to evaluate simulation outputs. Snow height, density, temperature, thermal conductivity and thermal insulance are examined to determine the critical variables involved in the soil and snow thermal regime. Simulated soil properties are compared to measurements of thermal conductivity, temperature and water content. The simulated snow density profiles are unrealistic, which is most likely caused by the lack of representation in snow models of the upward water vapor fluxes generated by the strong temperature gradients within the snowpack. The resulting vertical profiles of thermal conductivity are inverted compared to observations, with high simulated values at the bottom of the snowpack. Still, ISBA-Crocus manages to successfully simulate the soil temperature in winter. Results are satisfactory in summer, but the temperature of the top soil could be better reproduced by adequately representing surface organic layers, i.e., mosses and litter, and in particular their water retention capacity. Transition periods (soil freezing and thawing) are the least well reproduced because the high basal snow thermal conductivity induces an excessively rapid heat transfer between the soil and the snow in simulations. Hence, global climate models should carefully consider Arctic snow thermal properties, and especially the thermal conductivity of the basal snow layer, to perform accurate predictions of the permafrost evolution under climate change.

Thermal conductivity of suspended single crystal CH3NH3PbI3 platelets at room temperature.

PubMed

Shen, Chao; Du, Wenna; Wu, Zhiyong; Xing, Jun; Ha, Son Tung; Shang, Qiuyu; Xu, Weigao; Xiong, Qihua; Liu, Xinfeng; Zhang, Qing

2017-06-22

Recently, organic-inorganic lead halide perovskites have gained great attention for their breakthrough in photovoltaic and optoelectronics. However, their thermal transport properties that affect the device lifetime and stability are still rarely explored. In this work, the thermal conductivity properties of single crystal CH 3 NH 3 PbI 3 platelets grown by chemical vapor deposition are studied via non-contact micro-photoluminescence (PL) spectroscopy. We developed a measurement methodology and derived expressions suitable for the thermal conductivity extraction for micro-sized perovskites. The room temperature thermal conductivity of ∼0.14 ± 0.02 W m -1 K -1 is extracted from the dependence of the PL peak energy on the excitation laser power. On changing the film thickness from 80 to 400 nm, the thermal conductivity does not show noticeable variations, indicating the minimal substrate effects due to the advantage of the suspended configuration. The ultra-low thermal conductivity of perovskites, especially thin films, suggests their promising applications for thermal isolation, such as thermal insulation and thermo-electricity.

Lattice thermal conductivity of silicate glasses at high pressures

NASA Astrophysics Data System (ADS)

Chang, Y. Y.; Hsieh, W. P.

2016-12-01

Knowledge of the thermodynamic and transport properties of magma holds the key to understanding the thermal evolution and chemical differentiation of Earth. The discovery of the remnant of a deep magma ocean above the core mantle boundary (CMB) from seismic observations suggest that the CMB heat flux would strongly depend on the thermal conductivity, including lattice (klat) and radiative (krad) components, of dense silicate melts and major constituent minerals around the region. Recent measurements on the krad of dense silicate glasses and lower-mantle minerals show that krad of dense silicate glasses could be significantly smaller than krad of the surrounding solid mantle phases, and therefore the dense silicate melts would act as a thermal insulator in deep lower mantle. This conclusion, however, remains uncertain due to the lack of direct measurements on the lattice thermal conductivity of silicate melts under relevant pressure-temperature conditions. Besides the CMB, magmas exist in different circumstances beneath the surface of the Earth. Chemical compositions of silicate melts vary with geological and geodynamic settings of the melts and have strong influences on their thermal properties. In order to have a better view of heat transport within the Earth, it is important to study compositional and pressure dependences of thermal properties of silicate melts. Here we report experimental results on lattice thermal conductivities of silicate glasses with basaltic and rhyolitic compositions up to Earth's lower mantle pressures using time-domain thermoreflectance coupled with diamond-anvil cell techniques. This study not only provides new data for the thermal conductivity of silicate melts in the Earth's deep interior, but is crucial for further understanding of the evolution of Earth's complex internal structure.

Study on Thermal and Mechanical Properties of EPDM Insulation

NASA Astrophysics Data System (ADS)

Zhang, Zhong-Shui; Xu, Jin-Sheng; Chen, Xiong; Jiang, Jing

As the most common insulation material of solid rocket motors, thermal and mechanical properties of ethylene propylene diene monomer (EPDM) composite are inspected in the study. Referring to the results of thermogravimetric analysis (TGA), composition and morphology of EPDM composite in different thermal degradation degree are investigated by scanning electron microscope (SEM) to inspect the mechanism of thermal insulation. Mechanical properties of EPDM composite in the state of pyrolysis are investigated by uniaxial tensile tests. At the state of initial pyrolysis, composite belongs to the category of hyperelastic-viscoelastic material. The tendency of tensile strength increased and elongation decreased with increasing of heating temperature. Composite behaves as the linear rule at the state of late pyrolysis, which belongs to the category of bittle. The elasticity modulus of curves are almost the same while the heating temperature ranges from 200°C to 300°C, and then gradually go down. The tensile strength of pyrolytic material reach the highest at the heating temperature of 300°C, and the virgin material has the largest elongation.

External fuel vaporization study, phase 2

NASA Technical Reports Server (NTRS)

Szetela, E. J.; Chiappetta, L.

1981-01-01

An analytical study was conducted to evaluate the effect of variations in fuel properties on the design of an external fuel vaporizaton system. The fuel properties that were considered included thermal stability, critical temperature, enthalpy a critical conditions, volatility, and viscosity. The design parameters that were evaluated included vaporizer weight and the impact on engine requirement such as maintenance, transient response, performance, and altitude relight. The baseline fuel properties were those of Jet A. The variation in thermal stability was taken as the thermal stability variation for Experimental Referee Broad Specification (ERBS) fuel. The results of the analysis indicate that a change in thermal stability equivalent to that of ERBS would increase the vaporization system weight by 20 percent, decrease oprating time between cleaning by 40 percent and make altitude relight more difficult. An increase in fuel critical temperature of 39 K would require a 40 percent increase in vaporization system weight. The assumed increase in enthalpy and volatility would also increase vaporizer weight by 40 percent and make altitude relight extremely difficult. The variation in fuel viscosity would have a negligible effect on the design parameters.

The Effects of Adding Elements of Zinc and Magnesium on Ag-Cu Eutectic Alloy for Warming Acupuncture

PubMed Central

Park, Il Song; Kim, Keun Sik; Lee, Min Ho

2013-01-01

The warming acupuncture for hyperthermia therapy is made of STS304. However, its needle point cannot be reached to a desirable temperature due to heat loss caused by low thermal conductivity, and the quantification of stimulation condition and the effective standard establishment of warming acupuncture are required as a heat source. Accordingly, in this study, after Ag-Cu alloys with different composition ratios were casted and then mixed with additives to improve their physical and mechanical properties, the thermal conductivity and biocompatibility of the alloy specimens were evaluated for selecting suitable material. Ag-Cu binary alloys and ternary alloys added 5 wt% Zn or 2 wt% Mg were casted and then cold drawn to manufacture needles for acupuncture, and their physical properties, thermal conductivity, and biocompatibility were evaluated for their potential use in warming acupuncture. The results of this study showed that the physical and mechanical properties of the Ag-Cu alloys were improved by additives and that the thermal conductivity, machinability, and biocompatibility of the Ag-Cu alloys were improved by Mg addition. PMID:24078827

The effects of adding elements of zinc and magnesium on ag-cu eutectic alloy for warming acupuncture.

PubMed

Kim, Yu Kyoung; Park, Il Song; Kim, Keun Sik; Lee, Min Ho

2013-01-01

The warming acupuncture for hyperthermia therapy is made of STS304. However, its needle point cannot be reached to a desirable temperature due to heat loss caused by low thermal conductivity, and the quantification of stimulation condition and the effective standard establishment of warming acupuncture are required as a heat source. Accordingly, in this study, after Ag-Cu alloys with different composition ratios were casted and then mixed with additives to improve their physical and mechanical properties, the thermal conductivity and biocompatibility of the alloy specimens were evaluated for selecting suitable material. Ag-Cu binary alloys and ternary alloys added 5 wt% Zn or 2 wt% Mg were casted and then cold drawn to manufacture needles for acupuncture, and their physical properties, thermal conductivity, and biocompatibility were evaluated for their potential use in warming acupuncture. The results of this study showed that the physical and mechanical properties of the Ag-Cu alloys were improved by additives and that the thermal conductivity, machinability, and biocompatibility of the Ag-Cu alloys were improved by Mg addition.

Mechanical and Thermal Characterization of Silica Nanocomposites

NASA Astrophysics Data System (ADS)

Cunningham, Anthony Lamar

Polymer nanocomposites are a class of materials containing nanoparticles with a large interfacial surface area. Only a small quantity of nanoparticles are needed to provide superior multifunctional properties; such as mechanical, thermal, electrical, and moisture absorption properties in polymers. Nanoparticles tend to agglomerate, so special techniques are required for homogeneous distribution. Nanosilica is now readily available as colloidal sols, for example; Nanopox RTM F400 (supplied by Evonik Nanoresins AG, Germany). The nanoparticles are first synthesized from aqueous sodium silicate solution, and then undergo a surface modification process with organosilane and matrix exchange. F400 contains 40%wt silica nanoparticles colloidally dispersed in a DGEBA epoxy resin. The mean particle diameter is about 20 nm with a narrow distribution range of about 5 to 35 nm. The objectives of this study are to develop a reproducible processing method for nanosilica enhanced resin systems used in the manufacturing of fiber reinforced composites that will be characterized for mechanical and thermal properties. Research has concluded that shows improvements in the properties of the matrix material when processed in loading variations of 0 to 25%wt silica nanoparticles. The loadings were also used to manufacture fiberglass reinforced nanocomposite laminates and also tested for mechanical and thermal properties.

Nitinol laser cutting: microstructure and functional properties of femtosecond and continuous wave laser processing

NASA Astrophysics Data System (ADS)

Biffi, C. A.; Tuissi, A.

2017-03-01

Thermal processing can affect the properties of smart materials, and the correct selection of the best manufacturing technology is fundamental for producing high tech smart devices, containing embedded functional properties. In this work cutting of thin superelastic Nitinol plates using a femtosecond (fs) and continuous wave (CW) laser was studied. Diamond shaped elements were cut to characterize the kerf qualitative features; microstructural analysis of the cross sections allowed identification of thermal damage characteristics introduced into the material during the laser processes. A thermally undamaged microstructure was observed for fs laser cutting, while CW was seen to be characterized by a large heat-affected zone. Functional properties were investigated by differential scanning calorimetry and tensile testing of laser cut microelements and of the reference material. It was seen that the martensitic transformation behavior of Nitinol is not affected by fs regime, while cw cutting provokes an effect equivalent to a high temperature thermal treatment in the material surrounding the cutting kerf, degradating the material properties. Finally, tensile testing indicated that superelastic performances were guaranteed by fs regime, while strong reduction of the recoverable strain was detected in the CW processed sample.

The experimental study of the effect of microwave on the physical properties of multi-walled carbon nanotubes

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

Haque, A.K.M. Mahmudul; Oh, Geum Seok; Kim, Taeoh

Highlights: • We study the microwave effect on the multi-walled carbon nanotubes (MWCNTs). • We examine the non uniform heating effect on the physical structure of MWCNTs. • We examine the purification of MWCNTs by microwave. • We analyze the thermal characteristics of microwave treated MWCNTs. - Abstract: This paper reports the effect of microwave on the physical properties of multi-walled carbon nanotubes (MWCNTs) where different power levels of microwave were applied on MWCNTs in order to apprehend the effect of microwave on MWCNTs distinctly. A low energy ball milling in aqueous circumstance was also applied on both MWCNTs andmore » microwave treated MWCNTs. Temperature profile, morphological analysis by field emission scanning electron microscopy (FESEM), defect analysis by Raman spectroscopy, thermal conductivity, thermal diffusivity as well as heat transfer coefficient enhancement ratio were studied which expose some strong witnesses of the effect of microwave on the both purification and dispersion properties of MWCNTs in base fluid distilled water. The highest thermal conductivity enhancement (6.06% at 40 °C) of MWCNTs based nanofluid is achieved by five minutes microwave treatment as well as wet grinding at 500 rpm for two hours.« less

Inorganic polymers from laterite using activation with phosphoric acid and alkaline sodium silicate solution: Mechanical and microstructural properties

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

Lassinantti Gualtieri, Magdalena, E-mail: magdalena.gualtieri@unimore.it; Romagnoli, Marcello; Pollastri, Simone

2015-01-15

Geopolymers from laterite, an iron-rich soil available in developing countries, have great potential as building materials. In this work, laterite from Togo (Africa) was used to prepare geopolymers using both phosphoric acid and alkaline sodium silicate solution. Microstructural properties were investigated by scanning electron microscopy, X-ray powder diffraction and mercury porosimetry, whereas thermal properties were evaluated by thermal analyses. The local environment of iron was studied by X-ray Absorption Spectroscopy (XANES region). The mechanical properties were determined. Modulus of Rupture and Young's modulus fell in the ranges 3.3–4.5 MPa and 12–33 GPa, respectively, rendering the materials good candidates for constructionmore » purposes. Heating above 900 °C results in weight-gain, presumably due to iron redox reactions. X-ray Absorption Spectroscopy data evidence changes in the chemical and structural environments of iron following thermal treatment of geopolymers. These changes indicate interaction between the geopolymer structure and iron during heating, possibly leading to redox properties. -- Highlights: •Geopolymerization of laterite is promising for fabrication of building materials. •Both phosphoric acid and alkaline sodium silicate solution can be used for activation. •Thermally activated redox properties of the inorganic polymers were observed.« less

Effect of Nanoparticles on the Morphology, Thermal, and Electrical Properties of Low-Density Polyethylene after Thermal Aging

PubMed Central

Wang, Youyuan; Zhang, Zhanxi; Xiao, Kun

2017-01-01

This paper investigates the morphology, thermal, and electrical properties of LDPE (low-density polyethylene)-based nanocomposites after thermal aging. The FTIR (Fourier transform infrared spectroscopy) spectra results show that thermo-oxidative reactions occur in neat LDPE and LDPE/SiO2 nanocomposites when the aging time is 35 days and in LDPE/MgO nanocomposites when the aging time is 77 days. Specifically, LDPE/MgO nanocomposites delay the appearance of thermo-oxidative reactions, showing anti-thermal aging ability. Furthermore, nanocomposites present lower onset degradation temperature than neat LDPE, showing better thermal stabilization. With regard to the electrical properties, nanocomposites maintain the ability to suppress space charge accumulation after thermal aging. Additionally, in comparison with SiO2 nanocomposites and neat LDPE, the permittivity of LDPE/MgO nanocomposites changes slightly after thermal aging. It is concluded that LDPE/MgO nanocomposites have better insulation properties than neat LDPE after thermal aging, which may be caused by the interface introduced by the nanoparticles. PMID:29023428

Effect of Nanoparticles on the Morphology, Thermal, and Electrical Properties of Low-Density Polyethylene after Thermal Aging.

PubMed

Wang, Youyuan; Wang, Can; Zhang, Zhanxi; Xiao, Kun

2017-10-12

This paper investigates the morphology, thermal, and electrical properties of LDPE (low-density polyethylene)-based nanocomposites after thermal aging. The FTIR (Fourier transform infrared spectroscopy) spectra results show that thermo-oxidative reactions occur in neat LDPE and LDPE/SiO₂ nanocomposites when the aging time is 35 days and in LDPE/MgO nanocomposites when the aging time is 77 days. Specifically, LDPE/MgO nanocomposites delay the appearance of thermo-oxidative reactions, showing anti-thermal aging ability. Furthermore, nanocomposites present lower onset degradation temperature than neat LDPE, showing better thermal stabilization. With regard to the electrical properties, nanocomposites maintain the ability to suppress space charge accumulation after thermal aging. Additionally, in comparison with SiO₂ nanocomposites and neat LDPE, the permittivity of LDPE/MgO nanocomposites changes slightly after thermal aging. It is concluded that LDPE/MgO nanocomposites have better insulation properties than neat LDPE after thermal aging, which may be caused by the interface introduced by the nanoparticles.

Investigation of thermal energy transport interface of hybrid graphene-carbon nanotube/polyethylene nanocomposites.

PubMed

Liu, Feng; Liu, Xuyang; Hu, Ning; Ning, Huiming; Atobe, Satoshi; Yan, Cheng; Mo, Fuhao; Fu, Shaoyun; Zhang, Jianyu; Wang, Yu; Mu, Xiaojing

2017-10-31

It is well known the thermal properties of three-dimensional (3-D) hybrid graphene (GR)-carbon nanotube (CNT) structures are not superior to that of the individual GR and CNT, however, the 3-D hybrid GR-CNT structures can effectively improve the thermal properties of polymer matrix. Therefore, understanding the thermal energy transport in the interface between polymer matrix and 3-D hybrid GR-CNT structure is essential. Here, the enhancement mechanism of interfacial thermal transport of hybrid GR-CNT structure was explored by applying non-equilibrium molecular dynamics (NEMD) simulations. Three different types of hybrid GR-CNT structures were built. The influences of CNT radius and CNT type for the hybrid GR-CNT on the interfacial thermal properties were also analyzed. Computational results show that among the three different types of hybrid GR-CNT structures, the Model-I, i.e., the covalent bond hybrid GR-CNT structures are of the best interfacial thermal properties. Meanwhile, the CNT radius of hybrid GR-CNT structure has a great influence on the interfacial thermal properties.

Waxy soft white wheat: extrusion characteristics and thermal and rheological properties

USDA-ARS?s Scientific Manuscript database

Waxy wheat flour was analyzed for its thermal and rheological properties and extruded to understand its processing characteristics. Comparisons were made with normal soft white wheat flour to identify extrusion differences under the same conditions. The thermal and rheological properties through Rap...

Understanding and Predicting the Thermal Explosion Violence of HMX-Based and RDX-Based Explosives - Experimental Measurements of Material Properties and Reaction Violence

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

Maienschein, J L; Wardell, J F; Weese, R K

The violence of thermal explosions with energetic materials is affected by many material properties, including mechanical and thermal properties, thermal ignition kinetics, and deflagration behavior. These properties must be characterized for heated samples as well as pristine materials. We present available data for these properties for two HMX-based formulations--LX-04 and PBX-9501, and two RDX-based formulations--Composition B and PBXN-109. We draw upon separately published data on the thermal explosion violence with these materials to compare the material properties with the observed violence. We have the most extensive data on deflagration behavior of these four formulations, and we discuss the correlation ofmore » the deflagration data with the violence results. The data reported here may also be used to develop models for application in simulation codes such as ALE3D to calculate and Dredict thermal explosion violence.« less

Thin-layer thermal insulation coatings based on high-filled spheroplastics with polyorganosiloxane binder

NASA Astrophysics Data System (ADS)

Chukhlanov, V. Yu; Selivanov, O. G.; Trifonova, T. A.; Ilina, M. E.; Chukhlanova, N. V.

2017-10-01

Thermal insulation coatings, based on polyorganosiloxane as a binder and hollow glass microspheres, have been studied in this research. The developed materials are widely applied in various branches of science and engineering basically in construction. Components interaction processes are comprehensively studied. Spraying production methods of thin layer thermal insulation coatings have been researched. Ideal technological parameters for polyorganosiloxane coatings hardening depending on components ratio, ambient temperature, solvent and curative concentration have been determined. Stress related characteristics of constructional energy saving materials containing polyorganosiloxane have been researched. Components structure and ratio concerning compound extension strength properties have been revealed. Substantiation of Danneberg model application for the strength characteristics enhancing, when hollow microspheres are introduced, has been suggested. Thermal properties of coating thermal insulation have been studied. To research these characteristics standard methods applying devices IT-S-400 and IT-λ-400 have been chosen. Filler concentration increase was stated to decrease the composition heat conductivity coefficient and to the reduction of temperature dependence of this index. The authors suggested to employ the developed thermal insulation materials for construction and power engineering facilities operating under high temperature and other unfavorable environment.

Thermal capacitator design rationale. Part 1: Thermal and mechanical property data for selected materials potentially useful in thermal capacitor design and construction

NASA Technical Reports Server (NTRS)

Bailey, J. A.; Liao, C. K.

1975-01-01

The thermal properties of paraffin hydrocarbons and hydrocarbon mixtures which may be used as the phase change material (PCM) in thermal capacitors are discussed. The paraffin hydrocarbons selected for consideration are those in the range from C11H24 (n-Undecane) to C20H42 (n-Eicosane). A limited amount of data is included concerning other properties of paraffin hydrocarbons and the thermal and mechanical properties of several aluminum alloys which may find application as constructional materials. Data concerning the melting temperature, transition temperature, latent heat of fusion, heat of transition, specific heat, and thermal conductivity of pure and commercial grades of paraffin hydrocarbons are given. An index of companies capable of producing paraffin hydrocarbons and information concerning the availability of various grades (purity levels) is provided.

Study of thermal and fire behavior of wood fiber/thermoplastic composite materials

NASA Astrophysics Data System (ADS)

Oladipo, Adedejo Bukola

The fire safety characteristics of wood fiber/thermoplastic composite materials were investigated in this study. Composites comprising wood fiber fillers and polymeric binders are known to offer many advantages such as good strength to weight ratio, ease of manufacture, low cost, and the possibility for recycling. In spite of these advantages however, the fire safety question of plastic-based materials is an important one since they can, under certain conditions, drip or run, under fire, thereby potentially spreading fire from one location to the other. It is important therefore to understand the fire behavior of such a composite if the advantages it offers are to be fully utilized. To this end, numerical and experimental studies of opposed flow flame spread over the composite were conducted with emphasis on the influences of gravity, material thermal property variations, and finite-rate chemistry on the rate of spread. The thermal properties of the composite material, needed for opposed flame spread computations, were first determined using a combination of inverse heat conduction and non-linear parameter estimation procedures. The influences of wood fiber mass fraction and temperature on the effective thermal properties of the composite were established. The means for predicting the effective properties from those of the individual constituents were also examined and the results showed that the composite is close to being isotropic. The experimental and numerical methods used to determine the thermal properties of the composite were also adapted for the investigation of various proprietary automobile sound blanket materials to assess their effectiveness as thermal barriers separating the engine compartment from the passenger cabin. The results of opposed flame spread study over the composite suggests that, for opposed flow velocities lower than about 245 cm/s, finite rate chemistry will dominate the spread process when the oxygen mass fraction is 70% or less. Above this limit, heat transfer from the flame to the unburned fuel ahead seems to be the dominant factor. Also, the composite was observed to exhibit wood-like fire behavior when the wood fiber mass fraction is 40% or more.

Roles of strain and domain boundaries on the phase transition stability of VO2 thin films

NASA Astrophysics Data System (ADS)

Jian, Jie; Chen, Aiping; Chen, Youxing; Zhang, Xinghang; Wang, Haiyan

2017-10-01

The fundamental phase transition mechanism and the stability of the semiconductor-to-metal phase transition properties during multiple thermal cycles have been investigated on epitaxial vanadium dioxide (VO2) thin films via both ex situ heating and in situ heating by transmission electron microscopy (TEM). VO2 thin films were deposited on c-cut sapphire substrates by pulsed laser deposition. Ex situ studies show the broadening of transition sharpness (ΔT) and the width of thermal hysteresis (ΔH) after 60 cycles. In situ TEM heating studies reveal that during thermal cycles, large strain was accumulated around the domain boundaries, which was correlated with the phase transition induced lattice constant change and the thermal expansion. It suggests that the degradation of domain boundary structures in the VO2 films not only caused the transition property reduction (e.g., the decrease in ΔT and ΔH) but also played an important role in preventing the film from fracture during thermal cycles.

Reactivity study on thermal cracking of vacuum residues

NASA Astrophysics Data System (ADS)

León, A. Y.; Díaz, S. D.; Rodríguez, R. C.; Laverde, D.

2016-02-01

This study focused on the process reactivity of thermal cracking of vacuum residues from crude oils mixtures. The thermal cracking experiments were carried out under a nitrogen atmosphere at 120psi between 430 to 500°C for 20 minutes. Temperature conditions were established considering the maximum fractional conversion reported in tests of thermogravimetry performed in the temperature range of 25 to 600°C, with a constant heating rate of 5°C/min and a nitrogen flow rate of 50ml/min. The obtained products were separated in to gases, distillates and coke. The results indicate that the behaviour of thermal reactivity over the chemical composition is most prominent for the vacuum residues with higher content of asphaltenes, aromatics, and resins. Finally some correlations were obtained in order to predict the weight percentage of products from its physical and chemical properties such as CCR, SARA (saturates, aromatics, resins, asphaltenes) and density. The results provide new knowledge of the effect of temperature and the properties of vacuum residues in thermal conversion processes.

Thermophysical properties of heat-treated U-7Mo/Al dispersion fuel

NASA Astrophysics Data System (ADS)

Cho, Tae Won; Kim, Yeon Soo; Park, Jong Man; Lee, Kyu Hong; Kim, Sunghwan; Lee, Chong Tak; Yang, Jae Ho; Oh, Jang Soo; Sohn, Dong-Seong

2018-04-01

In this study, the effects of interaction layer (IL) on thermophysical properties of U-7Mo/Al dispersion fuel were examined. Microstructural analyses revealed that ILs were formed uniformly on U-Mo particles during heating of U-7Mo/Al samples. The IL volume fraction was measured by applying image analysis methods. The uranium loadings of the samples were calculated based on the measured meat densities at 298 K. The density of the IL was estimated by using the measured density and IL volume fraction. Thermal diffusivity and heat capacity of the samples after the heat treatment were measured as a function of temperature and volume fractions of U-Mo and IL. The thermal conductivity of IL-formed U-7Mo/Al was derived by using the measured thermal diffusivity, heat capacity, and density. The thermal conductivity obtained in the present study was lower than that predicted by the modified Hashin-Shtrikman model due to the theoretical model's inability to consider the thermal resistance at interfaces between the meat constituents.

Porous composite with negative thermal expansion obtained by photopolymer additive manufacturing

NASA Astrophysics Data System (ADS)

Takezawa, Akihiro; Kobashi, Makoto; Kitamura, Mitsuru

2015-07-01

Additive manufacturing (AM) could be a novel method of fabricating composite and porous materials having various effective performances based on mechanisms of their internal geometries. Materials fabricated by AM could rapidly be used in industrial application since they could easily be embedded in the target part employing the same AM process used for the bulk material. Furthermore, multi-material AM has greater potential than usual single-material AM in producing materials with effective properties. Negative thermal expansion is a representative effective material property realized by designing a composite made of two materials with different coefficients of thermal expansion. In this study, we developed a porous composite having planar negative thermal expansion by employing multi-material photopolymer AM. After measurement of the physical properties of bulk photopolymers, the internal geometry was designed by topology optimization, which is the most effective structural optimization in terms of both minimizing thermal stress and maximizing stiffness. The designed structure was converted to a three-dimensional stereolithography (STL) model, which is a native digital format of AM, and assembled as a test piece. The thermal expansions of the specimens were measured using a laser scanning dilatometer. Negative thermal expansion corresponding to less than -1 × 10-4 K-1 was observed for each test piece of the N = 3 experiment.

The Effect of Multi Wall Carbon Nanotubes on Some Physical Properties of Epoxy Matrix

NASA Astrophysics Data System (ADS)

Al-Saadi, Tagreed M.; hammed Aleabi, Suad; Al-Obodi, Entisar E.; Abdul-Jabbar Abbas, Hadeel

2018-05-01

This research involves using epoxy resin as a matrix for making a composite material, while the multi wall carbon nanotubes (MWNCTs) is used as a reinforcing material with different fractions (0.0,0.02, 0.04, 0.06) of the matrix weight. The mechanical ( hardness ), electrical ( dielectric constant, dielectric loss factor, dielectric strength, electrical conductivity ), and thermal properties (thermal conductivity ) were studied. The results showed the increase of hardness, thermal conductivity, electrical conductivity and break down strength with the increase of MWCNT concentration, but the behavior of dielectric loss factor and dielectric constant is opposite that.

Thermal stresses in composite tubes using complementary virtual work

NASA Technical Reports Server (NTRS)

Hyer, M. W.; Cooper, D. E.

1988-01-01

This paper addresses the computation of thermally induced stresses in layered, fiber-reinforced composite tubes subjected to a circumferential gradient. The paper focuses on using the principle of complementary virtual work, in conjunction with a Ritz approximation to the stress field, to study the influence on the predicted stresses of including temperature-dependent material properties. Results indicate that the computed values of stress are sensitive to the temperature dependence of the matrix-direction compliance and matrix-direction thermal expansion in the plane of the lamina. There is less sensitivity to the temperature dependence of the other material properties.

Multidimensional Testing of Thermal Protection Materials in the Arcjet Test Facility

NASA Technical Reports Server (NTRS)

Agrawal, Parul; Ellerby, Donald T.; Switzer, Matt R.; Squire, Thomas Howard

2010-01-01

Many thermal protection system materials used for spacecraft heatshields have anisotropic thermal properties, causing them to display significantly different thermal characteristics in different directions, when subjected to a heating environment during flight or arcjet tests. The anisotropic effects are enhanced in the presence of sidewall heating. This paper investigates the effects of anisotropic thermal properties of thermal protection materials coupled with sidewall heating in the arcjet environment. Phenolic Impregnated Carbon Ablator (PICA) and LI-2200 materials (the insulation material of Shuttle tiles) were used for this study. First, conduction-based thermal response simulations were carried out, using the Marc.Mentat finite element solver, to study the effects of sidewall heating on PICA arcjet coupons. The simulation showed that sidewall heating plays a significant role in thermal response of these models. Arcjet tests at the Aerodynamic Heating Facility (AHF) at NASA Ames Research Center were performed later on instrumented coupons to obtain temperature history at sidewall and various radial locations. The details of instrumentation and experimental technique are the prime focus of this paper. The results obtained from testing confirmed that sidewall heating plays a significant role in thermal response of these models. The test results were later used to validate the two-dimensional ablation, thermal response, and sizing program, TITAN. The test data and model predictions were found to be in excellent agreement

Study of the thermal properties of filaments for 3D printing

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

Trhlíková, Lucie, E-mail: xctrhlikova@fch.vutbr.cz; Zmeskal, Oldrich, E-mail: zmeskal@fch.vutbr.cz; Florian, Pavel, E-mail: xcflorianp@fch.vutbr.cz

Various materials are used for 3D printing, most commonly Acrylonitrile butadiene styrene (ABS), Polylactic acid (PLA), Polyethylene (PET) and Polypropylene (PP). These materials differ mainly in their melting point, which significantly influences the properties of the final products. Filaments are melted in the print head during the printing process. The temperature range is from 150 °C to 250 °C depending on the technology used. The optimum temperature for the cooling substrate on which printing is carried out is chosen so as to ensure uniform cooling and deformation. It generally varies between (40 – 100) °C. From the above it ismore » clear that both temperatures can significantly affect the properties of the printed 3D object. It is therefore important to determine the thermal parameters (thermal conductivity, specific heat and thermal diffusivity) of the materials used across the entire range of temperatures. For evaluating the properties of different types of PLA materials, the step transient method was used, which allows determination of all required parameters using a fractal heat transfer model.« less

Estimating thermal maturity in the Eagle Ford Shale petroleum system using gas gravity data

USGS Publications Warehouse

Birdwell, Justin E.; Kinney, Scott A.

2017-01-01

Basin-wide datasets that provide information on the geochemical properties of petroleum systems, such as source rock quality, product composition, and thermal maturity, are often difficult to come by or assemble from publically available data. When published studies are available and include these kinds of properties, they generally have few sampling locations and limited numbers and types of analyses. Therefore, production-related data and engineering parameters can provide useful proxies for geochemical properties that are often widely available across a play and in some states are reported in publically available or commercial databases. Gas-oil ratios (GOR) can be calculated from instantaneous or cumulative production data and can be related to the source rock geochemical properties like kerogen type (Lewan and Henry, 1999) and thermal maturity (Tian et al., 2013; U.S. Energy Information Administration [EIA], 2014). Oil density or specific gravity (SG), often reported in American Petroleum Institute units (°API = 141.5 /SG – 131.5), can also provide information on source rock thermal maturity, particularly when combined with GOR values in unconventional petroleum systems (Nesheim, 2017).

Using of Aerogel to Improve Thermal Insulating Properties of Windows

NASA Astrophysics Data System (ADS)

Valachova, Denisa; Zdrazilova, Nada; Panovec, Vladan; Skotnicova, Iveta

2018-06-01

For the best possible thermal-technical properties of building structures it is necessary to use materials with very low thermal conductivity. Due to the increasing thermal-technical requirements for building structures, the insulating materials are developed. One of the modern thermal insulating materials is so-called aerogel. Unfortunately, this material is not used in the field of external thermal insulation composite systems because of its price and its properties. The aim of this paper is to present possibilities of using this insulating material in the civil engineering - specifically a usage of aerogel in the production of windows.

Review of temperature dependence of thermal properties, dielectric properties, and perfusion of biological tissues at hyperthermic and ablation temperatures.

PubMed

Rossmanna, Christian; Haemmerich, Dieter

2014-01-01

The application of supraphysiological temperatures (>40°C) to biological tissues causes changes at the molecular, cellular, and structural level, with corresponding changes in tissue function and in thermal, mechanical and dielectric tissue properties. This is particularly relevant for image-guided thermal treatments (e.g. hyperthermia and thermal ablation) delivering heat via focused ultrasound (FUS), radiofrequency (RF), microwave (MW), or laser energy; temperature induced changes in tissue properties are of relevance in relation to predicting tissue temperature profile, monitoring during treatment, and evaluation of treatment results. This paper presents a literature survey of temperature dependence of electrical (electrical conductivity, resistivity, permittivity) and thermal tissue properties (thermal conductivity, specific heat, diffusivity). Data of soft tissues (liver, prostate, muscle, kidney, uterus, collagen, myocardium and spleen) for temperatures between 5 to 90°C, and dielectric properties in the frequency range between 460 kHz and 3 GHz are reported. Furthermore, perfusion changes in tumors including carcinomas, sarcomas, rhabdomyosarcoma, adenocarcinoma and ependymoblastoma in response to hyperthmic temperatures up to 46°C are presented. Where appropriate, mathematical models to describe temperature dependence of properties are presented. The presented data is valuable for mathematical models that predict tissue temperature during thermal therapies (e.g. hyperthermia or thermal ablation), as well as for applications related to prediction and monitoring of temperature induced tissue changes.

Review of temperature dependence of thermal properties, dielectric properties, and perfusion of biological tissues at hyperthermic and ablation temperatures

PubMed Central

Rossmann, Christian; Haemmerich, Dieter

2016-01-01

The application of supraphysiological temperatures (>40°C) to biological tissues causes changes at the molecular, cellular, and structural level, with corresponding changes in tissue function and in thermal, mechanical and dielectric tissue properties. This is particularly relevant for image-guided thermal treatments (e.g. hyperthermia and thermal ablation) delivering heat via focused ultrasound (FUS), radiofrequency (RF), microwave (MW), or laser energy; temperature induced changes in tissue properties are of relevance in relation to predicting tissue temperature profile, monitoring during treatment, and evaluation of treatment results. This paper presents a literature survey of temperature dependence of electrical (electrical conductivity, resistivity, permittivity) and thermal tissue properties (thermal conductivity, specific heat, diffusivity). Data of soft tissues (liver, prostate, muscle, kidney, uterus, collagen, myocardium and spleen) for temperatures between 5 to 90°C, and dielectric properties in the frequency range between 460 kHz and 3 GHz are reported. Furthermore, perfusion changes in tumors including carcinomas, sarcomas, rhabdomyosarcoma, adenocarcinoma and ependymoblastoma in response to hyperthmic temperatures up to 46°C are presented. Where appropriate, mathematical models to describe temperature dependence of properties are presented. The presented data is valuable for mathematical models that predict tissue temperature during thermal therapies (e.g. hyperthermia or thermal ablation), as well as for applications related to prediction and monitoring of temperature induced tissue changes. PMID:25955712

Optimizing Compliance and Thermal Conductivity of Plasma Sprayed Thermal Barrier Coatings via Controlled Powders and Processing Strategies

NASA Astrophysics Data System (ADS)

Tan, Yang; Srinivasan, Vasudevan; Nakamura, Toshio; Sampath, Sanjay; Bertrand, Pierre; Bertrand, Ghislaine

2012-09-01

The properties and performance of plasma-sprayed thermal barrier coatings (TBCs) are strongly dependent on the microstructural defects, which are affected by starting powder morphology and processing conditions. Of particular interest is the use of hollow powders which not only allow for efficient melting of zirconia ceramics but also produce lower conductivity and more compliant coatings. Typical industrial hollow spray powders have an assortment of densities resulting in masking potential advantages of the hollow morphology. In this study, we have conducted process mapping strategies using a novel uniform shell thickness hollow powder to control the defect microstructure and properties. Correlations among coating properties, microstructure, and processing reveal feasibility to produce highly compliant and low conductivity TBC through a combination of optimized feedstock and processing conditions. The results are presented through the framework of process maps establishing correlations among process, microstructure, and properties and providing opportunities for optimization of TBCs.

Simulation studies on structural and thermal properties of alkane thiol capped gold nanoparticles.

PubMed

Devi, J Meena

2017-06-01

The structural and thermal properties of the passivated gold nanoparticles were explored employing molecular dynamics simulation for the different surface coverage densities of the self-assembled monolayer (SAM) of alkane thiol. The structural properties of the monolayer protected gold nanoparticles such us overall shape, organization and conformation of the capping alkane thiol chains were found to be influenced by the capping density. The structural order of the thiol capped gold nanoparticles enhances with the increase in the surface coverage density. The specific heat capacity of the alkane thiol capped gold nanoparticles was found to increase linearly with the thiol coverage density. This may be attributed to the enhancement in the lattice vibrational energy. The present simulation results suggest, that the structural and thermal properties of the alkane thiol capped gold nanoparticles may be modified by the suitable selection of the SAM coverage density. Copyright © 2017 Elsevier Inc. All rights reserved.

Spectral properties of thermal fluctuations on simple liquid surfaces below shot-noise levels.

PubMed

Aoki, Kenichiro; Mitsui, Takahisa

2012-07-01

We study the spectral properties of thermal fluctuations on simple liquid surfaces, sometimes called ripplons. Analytical properties of the spectral function are investigated and are shown to be composed of regions with simple analytic behavior with respect to the frequency or the wave number. The derived expressions are compared to spectral measurements performed orders of magnitude below shot-noise levels, which is achieved using a novel noise reduction method. The agreement between the theory of thermal surface fluctuations and the experiment is found to be excellent, elucidating the spectral properties of the surface fluctuations. The measurement method requires relatively only a small sample both spatially (few μm) and temporally (~20 s). The method also requires relatively weak light power (~0.5 mW) so that it has a broad range of applicability, including local measurements, investigations of time-dependent phenomena, and noninvasive measurements.

Thermal aging effect of vanadyl acetylacetonate precursor for deposition of VO{sub 2} thin films with thermochromic properties

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

Yu, Jung-Hoon; Nam, Sang-Hun; Kim, Donguk

Highlights: • 7 day aged VO(acac){sub 2} sol shows enhanced adhesivity on the SiO{sub 2} compared with non-aged sol. • The aging process has significantly affected the morphologies of VO{sub 2} films. • From the FT-IR spectra, thermal aging process provides the deformation of precursor. • The metal insulator transition (MIT) efficiency (ΔT{sub at2000} {sub nm}) reached a maximum value of 51% at 7 day aging. • Thermal aging process could shorten the aging time of sol solution. - Abstract: Thermochromic properties of vanadium dioxide (VO{sub 2}) have been studied extensively due to their IR reflection applications in energy smartmore » windows. In this paper, we studied the optical switching property of VO{sub 2} thin film, depending on the thermal aging time of the vanadyl acetylacetonate (VO(acac){sub 2}) precursor. We found the alteration of the IR spectra of the precursor by tuning the aging time as well as heat treatments of the precursor. An aging effect of vanadium precursor directly affects the morphologies, optical switching property and crystallinity of VO{sub 2} films. The optimum condition was achieved at the 7 day aging time with metal insulator transition (MIT) efficiency of 50%.« less

First principles study on structural, lattice dynamical and thermal properties of BaCeO3

NASA Astrophysics Data System (ADS)

Zhang, Qingping; Ding, Jinwen; He, Min

2017-09-01

BaCeO3 exhibits impressive application potentials on solid oxide fuel cell electrolyte, hydrogen separation membrane and photocatalyst, owing to its unique ionic and electronic properties. In this article, the electronic structures, phonon spectra and thermal properties of BaCeO3 in orthorhombic, rhombohedral and cubic phases are investigated based on density functional theory. Comparisons with reported experimental results are also presented. The calculation shows that orthorhombic structure is both energetically and dynamically stable under ground state, which is supported by the experiment. Moreover, charge transfer between cations and anions accompanied with phase transition is observed, which is responsible for the softened phonon modes in rhombohedral and cubic phases. Besides, thermal properties are discussed. Oxygen atoms contribute most to the specific heat. The calculated entropy and specific heat at constant pressure fit well with the experimental ones within the measured temperature range.

Battery Thermal Characterization

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

Keyser, Matthew; Saxon, Aron; Powell, Mitchell

2016-06-07

This poster shows the progress in battery thermal characterization over the previous year. NREL collaborated with U.S. DRIVE and USABC battery developers to obtain thermal properties of their batteries, obtained heat capacity and heat generation of cells under various power profiles, obtained thermal images of the cells under various drive cycles, and used the measured results to validate thermal models. Thermal properties are used for the thermal analysis and design of improved battery thermal management systems to support achieve life and performance targets.

Predicting the Thermal Conductivity of AlSi/Polyester Abradable Coatings: Effects of the Numerical Method

NASA Astrophysics Data System (ADS)

Bolot, Rodolphe; Seichepine, Jean-Louis; Qiao, Jiang Hao; Coddet, Christian

2011-01-01

The final target of this study is to achieve a better understanding of the behavior of thermally sprayed abradable seals such as AlSi/polyester composites. These coatings are used as seals between the static and the rotating parts in aero-engines. The machinability of the composite coatings during the friction of the blades depends on their mechanical and thermal effective properties. In order to predict these properties from micrographs, numerical studies were performed with different software packages such as OOF developed by NIST and TS2C developed at the UTBM. In 2008, differences were reported concerning predictions of effective thermal conductivities obtained with the two codes. In this article, a particular attention was paid to the mathematical formulation of the problem. In particular, results obtained with a finite difference method using a cell-centered approach or a nodal formulation allow explaining the discrepancies previously noticed. A comparison of the predictions of the computed effective thermal conductivities is thus proposed. This study is part of the NEWAC project, funded by the European Commission within the 6th RTD Framework programm (FP6).

Building Energy Storage Panel Based on Paraffin/Expanded Perlite: Preparation and Thermal Performance Study.

PubMed

Kong, Xiangfei; Zhong, Yuliang; Rong, Xian; Min, Chunhua; Qi, Chengying

2016-01-25

This study is focused on the preparation and performance of a building energy storage panel (BESP). The BESP was fabricated through a mold pressing method based on phase change material particle (PCMP), which was prepared in two steps: vacuum absorption and surface film coating. Firstly, phase change material (PCM) was incorporated into expanded perlite (EP) through a vacuum absorption method to obtain composite PCM; secondly, the composite PCM was immersed into the mixture of colloidal silica and organic acrylate, and then it was taken out and dried naturally. A series of experiments, including differential scanning calorimeter (DSC), scanning electron microscope (SEM), best matching test, and durability test, have been conducted to characterize and analyze the thermophysical property and reliability of PCMP. Additionally, the thermal performance of BESP was studied through a dynamic thermal property test. The results have showed that: (1) the surface film coating procedure can effectively solve the leakage problem of composite phase change material prepared by vacuum impregnation; (2) the optimum adsorption ratio for paraffin and EP was 52.5:47.5 in mass fraction, and the PCMP has good thermal properties, stability, and durability; and (3) in the process of dynamic thermal performance test, BESP have low temperature variation, significant temperature lagging, and large heat storage ability, which indicated the potential of BESP in the application of building energy efficiency.

Building Energy Storage Panel Based on Paraffin/Expanded Perlite: Preparation and Thermal Performance Study

PubMed Central

Kong, Xiangfei; Zhong, Yuliang; Rong, Xian; Min, Chunhua; Qi, Chengying

2016-01-01

This study is focused on the preparation and performance of a building energy storage panel (BESP). The BESP was fabricated through a mold pressing method based on phase change material particle (PCMP), which was prepared in two steps: vacuum absorption and surface film coating. Firstly, phase change material (PCM) was incorporated into expanded perlite (EP) through a vacuum absorption method to obtain composite PCM; secondly, the composite PCM was immersed into the mixture of colloidal silica and organic acrylate, and then it was taken out and dried naturally. A series of experiments, including differential scanning calorimeter (DSC), scanning electron microscope (SEM), best matching test, and durability test, have been conducted to characterize and analyze the thermophysical property and reliability of PCMP. Additionally, the thermal performance of BESP was studied through a dynamic thermal property test. The results have showed that: (1) the surface film coating procedure can effectively solve the leakage problem of composite phase change material prepared by vacuum impregnation; (2) the optimum adsorption ratio for paraffin and EP was 52.5:47.5 in mass fraction, and the PCMP has good thermal properties, stability, and durability; and (3) in the process of dynamic thermal performance test, BESP have low temperature variation, significant temperature lagging, and large heat storage ability, which indicated the potential of BESP in the application of building energy efficiency. PMID:28787870

Mechanical Properties of Nylon Harp Strings

PubMed Central

Lynch-Aird, Nicolas; Woodhouse, Jim

2017-01-01

Monofilament nylon strings with a range of diameters, commercially marketed as harp strings, have been tested to establish their long-term mechanical properties. Once a string had settled into a desired stress state, the Young’s modulus was measured by a variety of methods that probe different time-scales. The modulus was found to be a strong function of testing frequency and also a strong function of stress. Strings were also subjected to cyclical variations of temperature, allowing various thermal properties to be measured: the coefficient of linear thermal expansion and the thermal sensitivities of tuning, Young’s modulus and density. The results revealed that the particular strings tested are divided into two groups with very different properties: stress-strain behaviour differing by a factor of two and some parametric sensitivities even having the opposite sign. Within each group, correlation studies allowed simple functional fits to be found to the key properties, which have the potential to be used in automated tuning systems for harp strings. PMID:28772858

Mechanical Properties of Nylon Harp Strings.

PubMed

Lynch-Aird, Nicolas; Woodhouse, Jim

2017-05-04

Monofilament nylon strings with a range of diameters, commercially marketed as harp strings, have been tested to establish their long-term mechanical properties. Once a string had settled into a desired stress state, the Young's modulus was measured by a variety of methods that probe different time-scales. The modulus was found to be a strong function of testing frequency and also a strong function of stress. Strings were also subjected to cyclical variations of temperature, allowing various thermal properties to be measured: the coefficient of linear thermal expansion and the thermal sensitivities of tuning, Young's modulus and density. The results revealed that the particular strings tested are divided into two groups with very different properties: stress-strain behaviour differing by a factor of two and some parametric sensitivities even having the opposite sign. Within each group, correlation studies allowed simple functional fits to be found to the key properties, which have the potential to be used in automated tuning systems for harp strings.

Thermal and optical characterization of biologically synthesized ZnS nanoparticles synthesized from an endophytic fungus Aspergillus flavus: A colorimetric probe in metal detection

NASA Astrophysics Data System (ADS)

Uddandarao, Priyanka; Balakrishnan, Raj Mohan

2017-03-01

Nanostructured semiconductor materials are of great importance for several technological applications due to their optical and thermal properties. The design and fabrication of metal sulfide nanoparticles with tunable properties for advanced applications have drawn a great deal of attention in the field of nanotechnology. ZnS is a potential II-IV group material which is used in hetero-junction solar cells, light emitting diodes, optoelectronic devices, electro luminescent devices and photovoltaic cells. Due to their multiple applications, there is a need to elucidate their thermal and optical properties. In the present study, thermal and optical properties of biologically synthesized ZnS nanoparticles are determined in detail with Thermal Gravimetric Analysis (TGA), Derivative Thermogravimetric Analysis (DTG), Differential Scanning Calorimeter (DSC), Diffuse Reflectance Spectroscopy (DRS), Photoluminescence (PL) and Raman spectroscopy. The results reveal that ZnS NPs exhibit a very strong quantum confinement with a significant increase in their optical band gap energy. These biologically synthesized ZnS NPs contain protein residues that can selectively bind with metal ions in aqueous solutions and can exhibit an aggregation-induced color change. This phenomenon is utilized to quantitatively measure the metal concentrations of Cu2 + and Mn2 + in this study. Further the stability of nanoparticles for the metal sensing process is accessed by UV-Vis spectrometer, zeta potential and cyclic voltammeter. The selectivity and sensitivity of ZnS NPs indicate its potential use as a sensor for metal detection in the ecosystem.

Novel elastic, lattice dynamics and thermodynamic properties of metallic single-layer transition metal phosphides: 2H-M 2P (Mo2P, W2P, Nb2P and Ta2P)

NASA Astrophysics Data System (ADS)

Yin, Jiuren; Wu, Bozhao; Wang, Yanggang; Li, Zhimi; Yao, Yuanpeng; Jiang, Yong; Ding, Yanhuai; Xu, Fu; Zhang, Ping

2018-04-01

Recently, there has been a surge of interest in the research of two-dimensional (2D) phosphides due to their unique physical properties and wide applications. Transition metal phosphides 2H-M 2Ps (Mo2P, W2P, Nb2P and Ta2P) show considerable catalytic activity and energy storage potential. However, the electronic structure and mechanical properties of 2D 2H-M 2Ps are still unrevealed. Here, first-principles calculations are employed to investigate the lattice dynamics, elasticity and thermodynamic properties of 2H-M 2Ps. Results show that M 2Ps with lower stiffness exhibit remarkable lateral deformation under unidirectional loads. Due to the largest average Grüneisen parameter, single-layer Nb2P has the strongest anharmonic vibrations, resulting in the highest thermal expansion coefficient. The lattice thermal conductivities of Ta2P, W2P and Nb2P contradict classical theory, which would predict a smaller thermal conductivity due to the much heavier atom mass. Moreover, the calculations also demonstrate that the thermal conductivity of Ta2P is the highest as well as the lowest thermal expansion, owing to its weak anharmonic phonon scattering and the lowest average Grüneisen parameter. The insight provided by this study may be useful for future experimental and theoretical studies concerning 2D transition metal phosphide materials.

Ab initio study of the structural, electronic, elastic and thermal conductivity properties of SrClF with pressure effects

NASA Astrophysics Data System (ADS)

Lv, Zhen-Long; Cui, Hong-Ling; Wang, Hui; Li, Xiao-Hong; Ji, Guang-Fu

2017-04-01

SrClF is an important optical crystal and can be used as pressure gauge in diamond anvil cell at high pressure. In this work, we performed a systematic study on the structural, electronic and elastic properties of SrClF under pressure, as well as its thermal conductivity, by first-principles calculation. Different exchange-correlation functionals were tested and PBESOL was finally chosen to study these properties of SrClF. Studies reveal that SrClF has a bulk modulus of about 56.2 GPa (by fitting equation of states) or 54.3 GPa (derived from elastic constants), which agree well with the experimental result. SrClF is mechanically and dynamically stable up to 50 GPa. Its elastic constants increase with the applied pressure, but its mechanical anisotropy deteriorates as the pressure increases. Investigation of its electronic properties reveals that SrClF is a direct band-gap insulator with a gap value of 5.73 eV at 0 GPa, which decreases with the increasing pressure and the reason is found by analysing the partial density of states. Based on the calculated phonon dispersion curves, thermal conductivity of SrClF is predicated. At ambient conditions, the predicted thermal conductivity is about 3.74 Wm-1 K-1, while that obtained using the simplified Slack model give a slightly larger value of 4.62 Wm-1 K-1.

Growth, structural, optical, thermal and laser damage threshold studies of an organic single crystal: 1,3,5 – triphenylbenzene (TPB)

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

Raja, R. Subramaniyan; Babu, G. Anandha; Ramasamy, P., E-mail: E-mail-ramasamyp@ssn.edu.in

2016-05-23

Good quality single crystals of pure hydrocarbon 1,3,5-Triphenylbenzene (TPB) have been successfully grown using toluene as a solvent using controlled slow cooling solution growth technique. TPB crystallizes in orthorhombic structure with the space group Pna2{sub 1}. The structural perfection of the grown crystal has been analysed by high resolution X-ray diffraction measurements. The range and percentage of the optical transmission are ascertained by recording the UV-vis spectrum. Thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study its thermal properties. Powder second harmonic generation studies were carried out to explore its NLO properties. Laser damage threshold valuemore » has been determined using Nd:YAG laser operating at 1064 nm.« less

Photo-thermal and cytotoxic properties of inkjet-printed copper sulfide films on biocompatible latex coated substrates

NASA Astrophysics Data System (ADS)

Sarfraz, Jawad; Borzenkov, Mykola; Niemelä, Erik; Weinberger, Christian; Törngren, Björn; Rosqvist, Emil; Collini, Maddalena; Pallavicini, Piersandro; Eriksson, John; Peltonen, Jouko; Ihalainen, Petri; Chirico, Giuseppe

2018-03-01

Inkjet-printing of metal nanoparticles is a particularly promising technique for the fabrication and modification of surfaces with a multifunctional nature. Recently copper sulfide nanoparticles (CuS NPs) have attracted wide interest due to a range of valuable properties including long term stability, photo-thermal activity, ease of synthesis and low cost. In the present study, printed CuS patterns were successfully fabricated on latex coated paper substrates and characterized by means of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), UV-Vis-NIR spectroscopy, and grazing incidence X-ray diffraction (GID). The resulted patterns displayed pronounced photo-thermal effect under Near Infrared Irradiation (NIR) even with relatively low laser power. Finally, by utilizing an automated real-time imaging platform it was possible to verify that the CuS printed film was not cytotoxic to human dermal fibroblast cells (HDF). The pronounced photo-thermal properties and nontoxic nature of these printed low-cost flexible CuS films make them promising candidates for fabrication of devices with localized photo-thermal effect suitable for biomedical applications.

Influence of geologic layering on heat transport and storage in an aquifer thermal energy storage system

NASA Astrophysics Data System (ADS)

Bridger, D. W.; Allen, D. M.

2014-01-01

A modeling study was carried out to evaluate the influence of aquifer heterogeneity, as represented by geologic layering, on heat transport and storage in an aquifer thermal energy storage (ATES) system in Agassiz, British Columbia, Canada. Two 3D heat transport models were developed and calibrated using the flow and heat transport code FEFLOW including: a "non-layered" model domain with homogeneous hydraulic and thermal properties; and, a "layered" model domain with variable hydraulic and thermal properties assigned to discrete geological units to represent aquifer heterogeneity. The base model (non-layered) shows limited sensitivity for the ranges of all thermal and hydraulic properties expected at the site; the model is most sensitive to vertical anisotropy and hydraulic gradient. Simulated and observed temperatures within the wells reflect a combination of screen placement and layering, with inconsistencies largely explained by the lateral continuity of high permeability layers represented in the model. Simulation of heat injection, storage and recovery show preferential transport along high permeability layers, resulting in longitudinal plume distortion, and overall higher short-term storage efficiencies.

Physical characteristics of cometary dust from optical studies

NASA Technical Reports Server (NTRS)

Hanner, M. S.

1980-01-01

Observations of the sunlight scattered and thermal emission from cometary dust, which may be used to infer the physical properties of the dust grains, are reviewed. Consideration is given to the observed wavelength dependence of the scattered light from cometary coma and tails, the average scattering function of the dust grains, the average grain Bond albedo, the polarization of the scattered light, and grain temperatures deduced from thermal infrared emission. The thermal properties of dust grains are illustrated for models based on magnetite or olivine grain materials, with consideration given to the variation of thermal properties with particle radius and heliocentric distance. Comparison of the models with observations indicates that a disordered or amorphous olivine composition can give a reasonable fit to the data for appropriate grain sizes and temperatures. The observations acquired are noted to indicate an optically important particle size of 1 micron, with silicate particles not larger than a few microns usually present although pure silicate grains can not be responsible for the thermal emission, and the cometary dust grains are most likely not spherical. Further observations needed in the infrared are indicated.

Thermal properties of oil palm nano filler/kenaf reinforced epoxy hybrid nanocomposites

NASA Astrophysics Data System (ADS)

Saba, N.; Paridah, M. T.; Abdan, K.; Ibrahim, N. A.

2016-11-01

The aim of this research study was to fabricate nano oil palm empty fruit bunch (OPEFB)/kenaf/epoxy hybrid nanocomposites and to make comparative study on the thermal properties of nano OPEFB/kenaf/epoxy hybrid nanocomposites with the montmorillonite (MMT)/kenaf/epoxy hybrid nanocomposites and organically modified MMT (OMMT)/kenaf/epoxy hybrid nanocomposites. Epoxy based kenaf hybrid nanocomposites was prepared by dispersing the nano filler (nano OPEFB filler, MMT, OMMT) at 3% loading through high speed mechanical stirrer followed by hand lay-up technique. Thermal properties of hybrid nanocomposites were analyzed through thermogravimetry analyzer (TGA), and differential scanning calorimetry (DSC). Obtained results specified that addition of nano OPEFB filler improves the thermal stability and char yield of kenaf/epoxy composites. Furthermore, the increase in decomposition temperature by the nano OPEFB filler was quite comparable to the MMT/kenaf/epoxy but relatively less than OMMT/kenaf/epoxy hybrid nanocomposites. We concluded from overall consequences that the nano OPEFB filler can be used as the promising and innovative alternative of existing expensive nano filler, with relatively lesser impact on the environment having marked pronounced impact on the construction, automotive, aerospace, electronics and semiconducting sectors as future industries based on bio-wastes with satisfactory light weight and thermal stability on other side.

Numerical simulation study on thermal response of PBX 9501 to low velocity impact

NASA Astrophysics Data System (ADS)

Lou, Jianfeng; Zhou, Tingting; Zhang, Yangeng; Zhang, Xiaoli

2017-01-01

Impact sensitivity of solid high explosives, an important index in evaluating the safety and performance of explosives, is an important concern in handling, storage, and shipping procedures. It is a great threat for either bare dynamite or shell charge when subjected to low velocity impact involved in traffic accidents or charge piece drops. The Steven test is an effective tool to study the relative sensitivity of various explosives. In this paper, we built the numerical simulation method involving mechanical, thermo and chemical properties of Steven test based on the thermo-mechanical coupled material model. In the model, the stress-strain relationship is described by dynamic plasticity model, the thermal effect of the explosive induced by impact is depicted by isotropic thermal material model, the chemical reaction of explosives is described by Arrhenius reaction rate law, and the effects of heating and melting on mechanical properties and thermal properties of materials are also taken into account. Specific to the standard Steven test, the thermal and mechanical response rules of PBX 9501 at various impact velocities were numerically analyzed, and the threshold velocity of explosive initiation was obtained, which is in good agreement with experimental results. In addition, the effect of confine condition of test device to the threshold velocity was explored.

N-vinylpyrrolidone modified glass-ionomer resins for improved dental restoratives

NASA Astrophysics Data System (ADS)

Xie, Dong

The studies described in this dissertation focus on improvement of mechanical properties of current glass-ionomer cements. Thermal properties and microstructures of the cements were correlated with their mechanical strengths. The first study evaluated mechanical properties of selected commercial glass-ionomer cements and examined their microstructures. The results showed that resin-modified glass-ionomer cements (RM GICs) exhibited much higher flexural (FS) and diametral tensile strengths (DTS), compared to conventional GICs (C GICs). In addition, they exhibited comparable compressive strength (CS), relatively low microhardness and less wear resistance than C GICs. The C GICs exhibited brittle behavior, whereas the RM GICs underwent substantial plastic deformation in compression. The mechanical properties of the GICs were closely related to their microstructures. Factors such as the density of the microstructure, the integrity of the interface between the glass particles and polymer matrix, particle size and the number and size of voids have important roles in determining the mechanical properties. The second study evaluated thermal properties of these GICs. The results showed that the RM GICs exhibited higher thermal transition temperatures than those of the C GICs, thermal expansion coefficients of these cements were close to those of human teeth, and the indentation creep of the RM GICs were higher than the C GICs. The third study explored and evaluated the effect of a water-soluble monomer, N-vinylpyrrolidone (NVP), on the performance of current C GICs, indicating a significant improvement in both mechanical and working properties. The fourth study demonstrated the process of determining the optimal molar ratio of the NVP-containing copolymers, using design of experiment. The results showed that the optimal molar ratio for these copolymers was 7:1:3 for poly(acrylic acid-co-itaconic acid-co-N-vinylpyrrolidone), based on the FS test. The molar ratio of 8:2:1 (AA:IA:NVP) was considered as the best molar ratio for these copolymers, based on the DTS and CS tests. The fifth study formulated the NVP-containing RM GICs using a statistical design of experiment. The results indicated that the best graft ratio for 2-isocyanatoethyl methacrylate (IEM) in this system was 15% of the terpolymer by a molar ratio. The optimal formulation was found to be at the weight ratio of 55:15:30 (RM NVP-containing terpolymer: 2-hydroxyethyl methacrylate (HEMA): Hsb2O). Stress-strain curves showed that a relatively high amount of water in the formulation led to higher elastic modulus and proportional limit and lower malleability, whereas a relatively high amount of HEMA gave the opposite results. The sixth study evaluated the NVP modified GICs (NVPM GICs) with the best molar ratios and optimal formulations in the mechanical, thermal and working properties. The results showed that the effect of molecular weight on mechanical properties of the NVPM GICs were evident. Different glass powders exhibited different effects on properties of the NVPM GICs, due to different compositions, size and affinity. Powder/liquid ratios had significant effects on the mechanical properties of NVPM GICs, especially on FS. P/W ratios are only beneficial to the NVPM GICs mixed with the Fuji II glass powders. The NVPM GICs showed a higher WT than the models, due to water retention of the NVP ring. Thermal expansion coefficients for the NVPM GICs were close to those for the natural tooth. Mismatch between the glass powders used and the polymer matrix was a big concern in this study and should be solved in the future.

Study of the thermal-optics parameters of Nd3+-doped phosphate glass as a function of temperature

NASA Astrophysics Data System (ADS)

Filho, J. C.; Pilla, V.; Messias, D. N.; Lourenço, S. A.; Silva, A. C. A.; Dantas, N. O.; Andrade, A. A.

2017-02-01

The spectroscopic properties of rare earth ions in many different hosts have been investigated, including surveys of Nd3+ in silicate, phosphate, fluorophosphates and fluoride glasses. Some of the thermal-optical properties of materials are influenced by temperature change, such as thermal diffusivity, specific heat and luminescence quantum efficiency. In this work the luminescence quantum efficiency of PANK: Nd3+, as a function of temperature (80- 480 K), was investigated using the normalized lifetime thermal lens technique. This system presents high quantum efficiency at low Nd3+ concentration and at ambient temperature, 100%, which decrease as temperature increase. Below room temperature the effects are not in accord with the maximum value of η, which must be unity.

Thermal properties of silica-filled high density polyethylene composites compatibilized with glut palmitate

NASA Astrophysics Data System (ADS)

Samsudin, Dalina; Ismail, Hanafi; Othman, Nadras; Hamid, Zuratul Ain Abdul

2017-07-01

A study of thermal properties resulting from the utilization of Glut Palmitate (GP) on the silica filled high density polyethylene (HDPE) composites was carried out. The composites with the incorporation of GP at 0.5, 1.0, 2.0 and 3.0 phr were prepared by using an internal mixer at the temperature 180 °C and the rotor speed of 50 rpm. The thermal behaviours of the composites were then investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was found that the crystallinity and the thermal stability of the composites increased with the incorporation of GP. The highest crystallinity contents and decomposition temperatures were observed at the 1 phr GP loading.

Solution of the equation of heat conduction with time dependent sources: Programmed application to planetary thermal history

NASA Technical Reports Server (NTRS)

Conel, J. E.

1975-01-01

A computer program (Program SPHERE) solving the inhomogeneous equation of heat conduction with radiation boundary condition on a thermally homogeneous sphere is described. The source terms are taken to be exponential functions of the time. Thermal properties are independent of temperature. The solutions are appropriate to studying certain classes of planetary thermal history. Special application to the moon is discussed.

Thermal Analysis of Filler Reinforced Polymeric Composites

NASA Astrophysics Data System (ADS)

Ghadge, Mahesh Devidas

Improving heat dissipating property of composite materials is becoming increasingly important in domains ranging from the automotive industry, electronic devices to aeronautical industry. Effective heat dissipation is required especially in aircraft and racing tires to guarantee high performance and good service life [1]. The present study is focused on improving the thermal conductivity of Emulsion-styrene butadiene rubber (ESBR) which is a cheap alternative to other rubber composites. The disadvantages of ESBR are low thermal conductivity and high heat generation. Adding fillers with high thermal conductivity to ESBR is proposed as a technique for improving the thermal conductivity of ESBR. The purpose of the research is to predict the thermal conductivity of ESBR when filled with fillers of much higher thermal conductivity and also to find out to what extent the filler properties affect the heat transfer capabilities of the composite matrix. The influence of different filler shapes i.e. spherical, cylindrical and platelets on the overall thermal capability of composite matrix is studied, the finite element modelings are conducted using Abaqus. Three-dimensional and two-dimensional models are created in Abaqus to simulate the microstructure of the composite matrix filled with fillers. Results indicate that the overall thermal conductivity increases with increasing filler loading i.e. for a filler volume fraction of 0.27, the conductivity increased by around 50%. Filler shapes, orientation angle, and aspect ratio of the fillers significantly influences the thermal conductivity. Conductivity increases with increasing aspect ratio (length/diameter) of the cylindrical fillers since longer conductive chains are able to form at the same volume percentage as compared to spherical fillers. The composite matrix reaches maximum thermal conductivity when the cylindrical fillers are oriented in the direction of heat flow. The heat conductivity predicted by FEM for ESBR is compared with that predicted by mean field theories. At low volume fractions the FEM and mean field theory results are matching. However, at high volume fractions, the results obtained by the two methods are not in agreement. This is due to the fact that mean field theory do not consider the particle interactions happening at higher volume fractions. The present analysis can be used to tailor the thermal properties of ESBR for required thermal conductivity for a wide range of applications such as racing tires, electronic gadgets or aeronautical components. In addition, the proposed FEM models can be used to design and optimize the properties of new composite materials providing more insight into the thermal conductivity of composite polymers and aid in understanding heat transfer mechanism of reinforced polymers.

Lightweight Ablative and Ceramic Thermal Protection System Materials for NASA Exploration Systems Vehicles

NASA Technical Reports Server (NTRS)

Valentine, Peter G.; Lawrence, Timothy W.; Gubert, Michael K.; Milos, Frank S.; Kiser, James D.; Ohlhorst, Craig W.; Koenig, John R.

2006-01-01

As a collaborative effort among NASA Centers, the "Lightweight Nonmetallic Thermal Protection Materials Technology" Project was set up to assist mission/vehicle design trade studies, to support risk reduction in thermal protection system (TPS) material selections, to facilitate vehicle mass optimization, and to aid development of human-rated TPS qualification and certification plans. Missions performing aerocapture, aerobraking, or direct aeroentry rely on advanced heatshields that allow reductions in spacecraft mass by minimizing propellant requirements. Information will be presented on candidate materials for such reentry approaches and on screening tests conducted (material property and space environmental effects tests) to evaluate viable candidates. Seventeen materials, in three classes (ablatives, tiles, and ceramic matrix composites), were studied. In additional to physical, mechanical, and thermal property tests, high heat flux laser tests and simulated-reentry oxidation tests were performed. Space environmental effects testing, which included exposures to electrons, atomic oxygen, and hypervelocity impacts, was also conducted.

High throughput integrated thermal characterization with non-contact optical calorimetry

NASA Astrophysics Data System (ADS)

Hou, Sichao; Huo, Ruiqing; Su, Ming

2017-10-01

Commonly used thermal analysis tools such as calorimeter and thermal conductivity meter are separated instruments and limited by low throughput, where only one sample is examined each time. This work reports an infrared based optical calorimetry with its theoretical foundation, which is able to provide an integrated solution to characterize thermal properties of materials with high throughput. By taking time domain temperature information of spatially distributed samples, this method allows a single device (infrared camera) to determine the thermal properties of both phase change systems (melting temperature and latent heat of fusion) and non-phase change systems (thermal conductivity and heat capacity). This method further allows these thermal properties of multiple samples to be determined rapidly, remotely, and simultaneously. In this proof-of-concept experiment, the thermal properties of a panel of 16 samples including melting temperatures, latent heats of fusion, heat capacities, and thermal conductivities have been determined in 2 min with high accuracy. Given the high thermal, spatial, and temporal resolutions of the advanced infrared camera, this method has the potential to revolutionize the thermal characterization of materials by providing an integrated solution with high throughput, high sensitivity, and short analysis time.

Determination of the thermal and physical properties of black tattoo ink using compound analysis.

PubMed

Humphries, Alexander; Lister, Tom S; Wright, Philip A; Hughes, Michael P

2013-07-01

Despite the widespread use of laser therapy in the removal of tattoos, comparatively little is known about its mechanism of action. There is a need for an improved understanding of the composition and thermal properties of the tattoo ink in order that simulations of laser therapy may be better informed and treatment parameters optimised. Scanning electron microscopy and time-of-flight secondary ion mass spectrometry identified that the relative proportions of the constituent compounds of the ink likely to exist in vivo are the following: carbon black pigment (89 %), carvacrol (5 %), eugenol (2 %), hexenol (3 %) and propylene glycol (1 %). Chemical compound property tables identify that changes in phase of these compounds lead to a considerable reduction in the density and thermal conductivity of the ink and an increase in its specific heat as temperature increases. These temperature-dependent values of density, thermal conductivity and specific heat are substantially different to the constant values, derived from water or graphite at a fixed temperature, which have been applied in the simulations of laser therapy as previously described in the literature. Accordingly, the thermal properties of black tattoo ink described in this study provide valuable information that may be used to improve simulations of tattoo laser therapy.

Investigation of the Effect of Oil Modification on Critical Characteristics of Asphalt Binders

NASA Astrophysics Data System (ADS)

Golalipour, Amir

Thermally induced cracking of asphalt pavement continues to be a serious issue in cold climate regions as well as in areas which experience extreme daily temperature differentials. Low temperature cracking of asphalt pavements is attributed to thermal stresses and strains developed during cooling cycles. Improving asphalt binder low temperature fracture and stiffness properties continues to be a subject of particular concern. Therefore, significant amount of research has been focused on improving asphalt binder properties through modification. In recent years, wide ranges of oil based modifications have been introduced to improve asphalt binder performance, especially at the low service temperatures. Although, significant use of these oils is seen in practice, knowledge of the fundamental mechanisms of oil modification and their properties for achieving optimum characteristics is limited. Hence, this study focuses on better understanding of the effect of oil modifiers which would help better material selection and achieve optimum performance in terms of increasing the life span of pavements. In this study, the effect of oil modification on the rheological properties of the asphalt binder is investigated. To examine the effect of oil modification on binder characteristics, low temperature properties as well as high temperature performance of oil modified binders were evaluated. It is found that oils vary in their effects on asphalt binder performance. However, for all oils used in the study, adding an oil to binder can improve binder low temperature performance, and this result mainly attributed to the softening effect. In addition to that, a simple linear model is proposed to predict the performance grade of oil modified binder based on the properties of its constituents at high and low temperatures. Another part of this study focuses on the oil modification effect on asphalt binder thermal strain and stresses. A viscoelastic analytical procedure is combined with experimentally derived failure stress and strain envelopes to determine the controlling failure mechanism, strain tolerance or critical stress, in thermal cracking of oil modified binders. The low temperature failure results depict that oil modification has a good potential of improving the cracking resistance of asphalt binders during thermal cycles.

Characterizing Thermal Properties of Melting Te Semiconductor: Thermal Diffusivity Measurements and Simulation

NASA Technical Reports Server (NTRS)

Zhu, Shen; Li, C.; Su, Ching-Hua; Lin, B.; Ben, H.; Scripa, R. N.; Lehoczky, S. L.; Curreri, Peter A. (Technical Monitor)

2002-01-01

Tellurium is an element for many II-VI and I-III-VI(sub 2) compounds that are useful materials for fabricating many devices. In the melt growth techniques, the thermal properties of the molten phase are important parameter for controlling growth process to improve semiconducting crystal quality. In this study, thermal diffusivity of molten tellurium has been measured by a laser flash method in the temperature range from 500 C to 900 C. A pulsed laser with 1064 nm wavelength is focused on one side of the measured sample. The thermal diffusivity can be estimated from the temperature transient at the other side of the sample. A numerical simulation based on the thermal transport process has been also performed. By numerically fitting the experimental results, both the thermal conductivity and heat capacity can be derived. A relaxation phenomenon, which shows a slow drift of the measured thermal conductivity toward the equilibrium value after cooling of the sample, was observed for the first time. The error analysis and the comparison of the results to published data measured by other techniques will be discussed.

Characterizing Thermal Properties of Melting Te Semiconductor: Thermal Diffusivity Measurements and Simulation

NASA Technical Reports Server (NTRS)

Zhu, Shen; Su, Ching-Hua; Li, C.; Lin, B.; Ben, H.; Scripa, R. N.; Lehoczky, S. L.; Curreri, Peter A. (Technical Monitor)

2002-01-01

Tellurium is an element for many II-VI and I-III-VI(sub 2) compounds that are useful materials for fabricating many devises. In the melt growth techniques, the thermal properties of the molten phase are important parameter for controlling growth process to improve semiconducting crystal quality. In this study, thermal diffusivity of molten tellurium has been measured by a laser flash method in the temperature range from 500 C to 900 C. A pulsed laser with 1064 nm wavelength is focused on one side of the measured sample. The thermal diffusivity can be estimated from the temperature transient at the other side of the sample. A numerical simulation based on the thermal transport process has been also performed. By numerically fitting the experimental results, both the thermal conductivity and heat capacity can be derived. A relaxation phenomenon, which shows a slow drift of the measured thermal conductivity toward the equilibrium value after cooling of the sample, was observed for the first time. The error analysis and the comparison of the results to published data measured by other techniques will be discussed in the presentation.

Mapping Thermal Habitat of Ectotherms Based on Behavioral Thermoregulation in a Controlled Thermal Environment

NASA Astrophysics Data System (ADS)

Fei, T.; Skidmore, A.; Liu, Y.

2012-07-01

Thermal environment is especially important to ectotherm because a lot of physiological functions rely on the body temperature such as thermoregulation. The so-called behavioural thermoregulation function made use of the heterogeneity of the thermal properties within an individual's habitat to sustain the animal's physiological processes. This function links the spatial utilization and distribution of individual ectotherm with the thermal properties of habitat (thermal habitat). In this study we modelled the relationship between the two by a spatial explicit model that simulates the movements of a lizard in a controlled environment. The model incorporates a lizard's transient body temperatures with a cellular automaton algorithm as a way to link the physiology knowledge of the animal with the spatial utilization of its microhabitat. On a larger spatial scale, 'thermal roughness' of the habitat was defined and used to predict the habitat occupancy of the target species. The results showed the habitat occupancy can be modelled by the cellular automaton based algorithm at a smaller scale, and can be modelled by the thermal roughness index at a larger scale.

Applications of graphite-enabled phase change material composites to improve thermal performance of cementitious materials

NASA Astrophysics Data System (ADS)

Li, Mingli; Lin, Zhibin; Wu, Lili; Wang, Jinhui; Gong, Na

2017-11-01

Enhancing the thermal efficiency to decrease the energy consumption of structures has been the topic of much research. In this study, a graphite-enabled microencapsulated phase change material (GE-MEPCM) was used in the production of a novel thermal energy storage engineered cementitious composite feathering high heat storage capacity and enhanced thermal conductivity. The surface morphology and particle size of the microencapsulated phase change material (MEPCM) were investigated by scanning electron microscopy (SEM). Thermal properties of MEPCM was determined using differential scanning calorimetry (DSC). In addition, thermal and mechanical properties of the cementitious mortar with different admixtures were explored and compared with those of a cementitious composite. It was shown that the latent heat of MEPCM was 162 J/g, offering much better thermal energy storage capacity to the cementitious composite. However, MEPCM was found to decrease the thermal conductivity of the composite, which can be effectively solved by adding natural graphite (NG). Moreover, the incorporation of MEPCM has a certain decrease in the compressive strength, mainly due to the weak interfaces between MEPCM and cement matrix.

Theoretical investigation of the structural, electronic, dynamical and thermal properties of YSn3 and YPb3

NASA Astrophysics Data System (ADS)

Kılıçarslan, Aynur; Salmankurt, Bahadır; Duman, Sıtkı

2017-02-01

We have performed an ab initio study of the structural, electronic, dynamical and thermal properties of the cubic AuCu3-type YSn3 and YPb3 by using the density functional theory, plane-wave pseudopotential method and a linear response scheme, within the generalized gradient approximation. An analysis of the electronic density of states at the Fermi level is found to be governed by the p states of Sn and Pb atoms with some contributions from the d states of Y atoms. The obtained phonon figures indicate that these material are dynamically stable in the cubic structure. Due to the metallic behavior of the compounds, the calculated zone-center phonon modes are triply degenerate. Also the thermal properties have been examined.

Lattice distortions in complex oxides and their relation to the thermal properties

NASA Astrophysics Data System (ADS)

Srivastava, Archana; Gaur, N. K.

2018-05-01

We have investigated the various lattice distortions in complex oxides Ca1-xLaxMnO3 and its effect on elastic and thermal properties of these perovskite manganites, especially Debye temperature of these complex oxides. The revealed data on Bulk modulus and Debye temperature studied as a function of lattice distortions using a novel atomistic approach of Atom in Molecules(AIM) theory and Modified Rigid Ion Model (MRIM) are in closer agreement with the available experimental data for some concentrations (x) of Ca1-xLaxMnO3. We demonstrate that the distortions introduced due to electron concentration, size mismatch and JT effects are the dominant factor, whereas charge mismatch and buckling of Mn-O-Mn angle influence the thermal properties to a lesser degree in the ferromagnetic state.

Another Demo of the Unusual Thermal Properties of Rubber

ERIC Educational Resources Information Center

Liff, Mark I.

2010-01-01

The unusual thermal behavior of rubbers, though discovered a long time ago, can still be mind-boggling for students and teachers who encounter this class of polymeric systems. Unlike other solids, stretched elastic polymers shrink upon heating. This is a manifestation of the Gough-Joule (G-J) effect. Joule in the 1850s studied the thermal behavior…

Constraining the physical properties of compositionally distinctive surfaces on Mars from overlapping THEMIS observations

NASA Astrophysics Data System (ADS)

Ahern, A.; Rogers, D.

2017-12-01

Better constraints on the physical properties (e.g. grain size, rock abundance, cohesion, porosity and amount of induration) of Martian surface materials can lead to greater understanding of outcrop origin (e.g. via sedimentary, effusive volcanic, pyroclastic processes). Many outcrop surfaces on Mars likely contain near-surface (<3 cm) vertical heterogeneity in physical properties due to thin sediment cover, induration, and physical weathering, that can obscure measurement of the bulk thermal conductivity of the outcrop materials just below. Fortunately, vertical heterogeneity within near-surface materials can result in unique, and possibly predictable, diurnal and seasonal temperature patterns. The KRC thermal model has been utilized in a number of previous studies to predict thermal inertia of surface materials on Mars. Here we use KRC to model surface temperatures from overlapping Mars Odyssey THEMIS surface temperature observations that span multiple seasons and local times, in order to constrain both the nature of vertical heterogeneity and the underlying outcrop thermal inertia for various spectrally distinctive outcrops on Mars. We utilize spectral observations from TES and CRISM to constrain the particle size of the uppermost surface. For this presentation, we will focus specifically on chloride-bearing units in Terra Sirenum and Meridiani Planum, as well as mafic and feldspathic bedrock locations with distinct spectral properties, yet uncertain origins, in Noachis Terra and Nili Fossae. We find that many of these surfaces exhibit variations in apparent thermal inertia with season and local time that are consistent with low thermal inertia materials overlying higher thermal inertia substrates. Work is ongoing to compare surface temperature measurements with modeled two-layer scenarios in order to constrain the top layer thickness and bottom layer thermal inertia. The information will be used to better interpret the origins of these distinctive outcrops.

Variation of microstructural and optical properties in SILAR grown ZnO thin films by thermal treatment.

PubMed

Valanarasu, S; Dhanasekaran, V; Chandramohan, R; Kulandaisamy, I; Sakthivelu, A; Mahalingam, T

2013-08-01

The influence of thermal treatment on the structural and morphological properties of the ZnO films deposited by double dip Successive ionic layer by adsorption reaction is presented. The effect of annealing temperature and time in air ambient is presented in detail. The deposited films were annealed from 200 to 400 degrees C in air and the structural properties were determined as a function of annealing temperature by XRD. The studies revealed that films were exhibiting preferential orientation along (002) plane. The other structural parameters like the crystallite size (D), micro strain (epsilon), dislocation density (delta) and stacking fault (alpha) of as-deposited and annealed ZnO films were evaluated and reported. The optical properties were also studied and the band gap of the ZnO thins films varied from 3.27 to 3.04 eV with the annealing temperature. SEM studies revealed that the hexagonal shaped grains with uniformly distributed morphology in annealed ZnO thin films. It has been envisaged using EDX analysis that the near stoichiometric composition of the film can be attained by thermal treatment during which microstructural changes do occur.

Method and apparatus for implementing material thermal property measurement by flash thermal imaging

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

Sun, Jiangang

A method and apparatus are provided for implementing measurement of material thermal properties including measurement of thermal effusivity of a coating and/or film or a bulk material of uniform property. The test apparatus includes an infrared camera, a data acquisition and processing computer coupled to the infrared camera for acquiring and processing thermal image data, a flash lamp providing an input of heat onto the surface of a two-layer sample with an enhanced optical filter covering the flash lamp attenuating an entire infrared wavelength range with a series of thermal images is taken of the surface of the two-layer sample.

Compatibility tests between Jarytherm DBT synthetic oil and solid materials from wastes

NASA Astrophysics Data System (ADS)

Fasquelle, Thomas; Falcoz, Quentin; Neveu, Pierre; Flamant, Gilles; Walker, Jérémie

2016-05-01

Direct thermocline thermal energy storage is the cheapest sensible thermal energy storage configuration. Indeed, a thermocline tank consists in one tank instead of two and reduces costs. Thermocline thermal energy storages are often filled with cheap solid materials which could react with the heat transfer fluid in the case of incompatibility. PROMES laboratory is building a pilot-scale parabolic trough solar loop including a direct thermocline thermal energy storage system. The working fluid will be a synthetic oil, the Jarytherm® DBT, and the thermal energy storage tank will be filled with stabilized solid materials elaborated from vitrified wastes. Compatibility tests have been conducted in order to check on one hand if the thermo-mechanical properties and life time of the energy storage medium are not affected by the contact with oil and, on the other hand, if the thermal oil performances are not degraded by the solid filler. These experiments consisted in putting in contact the oil and the solid materials in small tanks. In order to discriminate the solid materials tested in the shortest time, accelerating aging conditions at 330 °C for 500 hours were used. The measurements consisted in X-Ray Diffraction and Scanning Electron Microscopy for the solids, and thermo-physical and chemical properties measurements for the oil. Regarding the solid samples, their crystalline structure did not change during the test, but it is difficult to conclude about their elementary composition and they seem to absorb oil. While thermal properties still makes Jarytherm® DBT a good heat transfer fluid after the accelerated aging tests, this study results in differentiating most compatible materials. Thus according to our study, Jarytherm® DBT can be used in direct thermocline thermal energy storage applications when compatibility of the solid material has been demonstrated.

Synthesis, structural, thermal and optical properties of TeO2-Bi2O3-GeO2-Li2O glasses

NASA Astrophysics Data System (ADS)

Dimowa, Louiza; Piroeva, Iskra; Atanasova-Vladimirova, S.; Petrova, Nadia; Ganev, Valentin; Titorenkova, Rositsa; Yankov, Georgi; Petrov, Todor; Shivachev, Boris L.

2016-10-01

In this study, synthesis and characterization of novel quaternary tellurite glass system TeO2-Bi2O3-GeO2-Li2O is presented. The compositions include TeO2 and GeO2 as glass formers while different proportion of Bi2O3 and Li2O act as network modifiers. Differential thermal analysis, X-ray diffraction, scanning electron microscopy energy dispersive X-ray spectroscopy, laser ablation inductively coupled plasma mass spectrometry, UV-Vis and Raman spectroscopy are applied to study the structural, thermal and optical properties of the studied glasses. Obtained glasses possess a relatively low glass transition temperature (around 300 °C) if compared to other tellurite glasses, show good thermal transparency in the visible and near infra-red (from 2.4 to 0.4 μm) and can double the frequency of laser light from its original wavelength of 1064 nm to its second-harmonic at 532 nm (i.e. second harmonic generation).

Studies on the growth aspects, structural, thermal, dielectric and third order nonlinear optical properties of solution grown 4-methylpyridinium p-nitrophenolate single crystal

NASA Astrophysics Data System (ADS)

Devi, S. Reena; Kalaiyarasi, S.; Zahid, I. MD.; Kumar, R. Mohan

2016-11-01

An ionic organic optical crystal of 4-methylpyridinium p-nitrophenolate was grown from methanol by slow evaporation method at ambient temperature. Powder and single crystal X-ray diffraction studies revealed the crystal system and its crystalline perfection. The rocking curve recorded from HRXRD study confirmed the crystal quality. FTIR spectral analysis confirmed the functional groups present in the title compound. UV-visible spectral study revealed the optical window and band gap of grown crystal. The thermal, electrical and surface laser damage threshold properties of harvested crystal were examined by using TGA/DTA, LCR/Impedance Analyzer and Nd:YAG laser system respectively. The third order nonlinear optical property of grown crystal was elucidated by Z-scan technique.

Intermetallic Al-, Fe-, Co- and Ni-Based Thermal Barrier Coatings Prepared by Cold Spray for Applications on Low Heat Rejection Diesel Engines

NASA Astrophysics Data System (ADS)

Leshchinsky, E.; Sobiesiak, A.; Maev, R.

2018-02-01

Conventional thermal barrier coating (TBC) systems consist of a duplex structure with a metallic bond coat and a ceramic heat insulating topcoat. They possess the desired low thermal conductivity, but at the same time they are very brittle and sensitive to thermal shock and thermal cycling due to the inherently low coefficient of thermal expansion. Recent research activities are focused on the developing of multilayer TBC structures obtained using cold spraying and following annealing. Aluminum intermetallics have demonstrated thermal and mechanical properties that allow them to be used as the alternative TBC materials, while the intermetallic layers can be additionally optimized to achieve superior thermal physical properties. One example is the six layer TBC structure in which cold sprayed Al-based intermetallics are synthesized by annealing in nitrogen atmosphere. These multilayer coating systems demonstrated an improved thermal fatigue capability as compared to conventional ceramic TBC. The microstructures and properties of the coatings were characterized by SEM, EDS and mechanical tests to define the TBC material properties and intermetallic formation mechanisms.

Improving the Performance of Heat Insulation Polyurethane Foams by Silica Nanoparticles

NASA Astrophysics Data System (ADS)

Nikje, M. M. Alavi; Garmarudi, A. Bagheri; Haghshenas, M.; Mazaheri, Z.

Heat insulation polyurethane foam materials were doped by silica nano particles, to investigate the probable improving effects. In order to achieve the best dispersion condition and compatibility of silica nanoparticles in the polymer matrix a modification step was performed by 3-aminopropyltriethoxysilane (APTS) as coupling agent. Then, thermal and mechanical properties of polyurethane rigid foam were investigated. Thermal and mechanical properties were studied by tensile machine, thermogravimetric analysis and dynamic mechanical analysis.

Thermal properties measurements in biodiesel oils using photothermal techniques

NASA Astrophysics Data System (ADS)

Castro, M. P. P.; Andrade, A. A.; Franco, R. W. A.; Miranda, P. C. M. L.; Sthel, M.; Vargas, H.; Constantino, R.; Baesso, M. L.

2005-08-01

In this Letter, thermal lens and open cell photoacoustic techniques are used to measure the thermal properties of biodiesel oils. The absolute values of the thermal effusivity, thermal diffusivity, thermal conductivity and the temperature coefficient of the refractive index were determined for samples obtained from soy, castor bean, sunflower and turnip. The results suggest that the employed techniques may be useful as complementary methods for biodiesel certification.

Applications of photoacoustic techniques to the study of jet fuel residue

NASA Technical Reports Server (NTRS)

Claspy, P. C.

1983-01-01

It has been known for many years that fuels for jet aircraft engines demonstrate thermal instability. One manifestation of this thermal instability is the formation of deleterious fuel-derived thermally-induced deposits on surfaces of the aircraft's fuel-handling system. The results of an investigation of the feasibility of applying photoacoustic techniques to the study of the physical properties of these thermal deposits are presented. Both phase imaging and magnitude imaging and spectroscopy were investigated. It is concluded that the use of photoacoustic techniques in the study of films of the type encountered in this investigation is not practical.

The effect of thermal cycling on the structure and properties of a Co, Cr, Ni-TaC directionally solidified eutectic composite

NASA Technical Reports Server (NTRS)

Dunlevey, F. M.; Wallace, J. F.

1973-01-01

The effect of thermal cycling on the structure and properties of a cobalt, chromium, nickel, tantalum carbide directionally solidified eutectic composite is reported. It was determined that the stress rupture properties of the alloy were decreased by the thermal cycling. The loss in stress rupture properties varied with the number of cycles with the loss in properties after about 200 cycles being relatively high. The formation of serrations and the resulting changes in the mechanical properties of the material are discussed.

Surface chemistry of Au/TiO2: Thermally and photolytically activated reactions

NASA Astrophysics Data System (ADS)

Panayotov, Dimitar A.; Morris, John R.

2016-03-01

The fascinating particle size dependence to the physical, photophysical, and chemical properties of gold has motivated thousands of studies focused on exploring the ability of supported gold nanoparticles to catalyze chemical transformations. In particular, titanium dioxide-supported gold (Au/TiO2) nanoparticles may provide the right combination of electronic structure, structural dynamics, and stability to affect catalysis in important practical applications from environmental remediation to selective hydrogenation to carbon monoxide oxidation. Harnessing the full potential of Au/TiO2 will require a detailed atomic-scale understanding of the thermal and photolytic processes that accompany chemical conversion. This review describes some of the unique properties exhibited by particulate gold before delving into how those properties affect chemistry on titania supports. Particular attention is given first to thermally driven reactions on single crystal system. This review then addresses nanoparticulate samples in an effort begin to bridge the so-called materials gap. Building on the foundation provided by the large body of work in the field of thermal catalysis, the review describes new research into light-driven catalysis on Au/TiO2. Importantly, the reader should bear in mind throughout this review that thermal chemistry and thermal effects typically accompany photochemistry. Distinguishing between thermally-driven stages of a reaction and photo-induced steps remains a significant challenge, but one that experimentalists and theorists are beginning to decipher with new approaches. Finally, a summary of several state-of-the-art studies describes how they are illuminating new frontiers in the quest to exploit Au/TiO2 as an efficient catalyst and low-energy photocatalyst.

Photophysical, electrochemical, thermal and aggregation properties of new metal phthalocyanines

NASA Astrophysics Data System (ADS)

Jeong, Jaemyeng; Kumar, Rangaraju Satish; Mergu, Naveen; Son, Young-A.

2017-11-01

In this study, the synthesis of di(ethylene glycol) naphthalene substituted metal-phthalocyanines was reported. These novel phthalocyanines were characterized by elemental and spectroscopic analysis, including 1H NMR, FT-IR, UV-Vis spectral and MALDI-TOF mass data. The aggregation behavior of these phthalocyanines was examined in chloroform at different concentrations, and we confirmed that the phthalocyanines were non-aggregated. Further thermal stability, electrochemical, theoretical studies and metal sensing properties also investigated. In addition, we successfully prepared phthalocyanine (6d) blended polyurethane electrospun (ES) nanofibers.

Laser Treatment of Benign Prostatic Hyperplasia: Dosimetric and Thermodynamic Considerations

NASA Astrophysics Data System (ADS)

Anvari, Bahman

1993-01-01

Benign prostatic hyperplasia (BPH) is the most commonly occurring neoplastic disease in the aging human male. Currently, surgical treatment of BPH is the primary therapeutic method. However, due to surgical complications, less invasive methods of treatment are desirable. In recent years, thermal coagulation of the hyperplastic prostate by a laser has received a considerable amount of attention. Nevertheless, the optimum laser irradiation parameters that lead to a successful and safe treatment of BPH have not been determined. This dissertation studies the physics of laser coagulation of prostate from both basic science and practical perspectives. Optical properties of prostatic tissue are determined over a spectrum of wavelengths. Knowledge of these properties allows for selection of appropriate laser wavelengths and provides a basis for performing dose equivalency studies among various types of lasers. Furthermore, knowledge of optical properties are needed for development of computer simulation models that predict the extent of thermal injury during laser irradiation of prostate. A computer model of transurethral heating of prostate that can be used to guide the clinical studies in determining an optimum dosimetry is then presented. Studies of the effects of non-laser heating devices, optical properties, blood perfusion, surface irrigation, and beam geometry are performed to examine the extent of heat propagation within the prostate. An in vitro model for transurethral laser irradiation of prostate is also presented to examine the effects of an 810 nm diode laser, thermal boundary conditions, and energy deposition rate during Nd:YAG laser irradiation. Results of these studies suggest that in the presence of laminar irrigation, the convective boundary condition is dominated by thermal diffusion as opposed to the bulk motion of the irrigation fluid. Distinct phases of thermal events are also identified during the laser irradiation. The in vivo studies of transurethral laser irradiation of prostate in canine models are also performed to search for an optimum dosimetry that will result in a maximum zone of coagulation necrosis.

Research on thermal conductivity of HGMs at vacuum in room temperature

NASA Astrophysics Data System (ADS)

Wang, Ping; Liao, Bin; An, Zhenguo; Yan, Kaiqi; Zhang, Jingjie

2018-05-01

Hollow glass microspheres (HGMs) can be used as thermal insulation materials owing to its hollow structure which brings excellent thermal insulation property and low density. At present, most researches on thermal conductivity of HGMs are focused on polymer matrix/HGMs composite materials. However, thermal conductivity of HGMs at vacuum in room temperature has rarely been investigated. In this work, thermal conductivity of six types of HGMs (T17 (0.17g/cm3), T20 (0.20g/cm3), T22 (0.22g/cm3), T25 (0.25g/cm3), T32 (0.32g/cm3) and T40 (0.40g/cm3)) at vacuum in room temperature were calculated by heat transfer of solid conduction and radiation. The calculation results showed that thermal conductivity of HGMs would be decreased by an order of magnitude compared with no vacuum. In order to verify the calculation and study vacuum thermal insulation properties of HGMs, thermal conductivity of above-mentioned HGMs at no vacuum and high vacuum in room temperature were measured by a self-made thermal conductivity measuring apparatus which was based on the transient plane source (TPS) method. The experimental results showed that thermal conductivity of HGMs were in the range of 4.2030E-02 to 6.3300E-02 W/m.K (at no vacuum) and 3.8160E-03 to 4.9660E-03 W/m.K (at high vacuum). The results indicated that experimental thermal conductivity was consistent with the calculation results and both of them were all decreased by 8-13 times at vacuum compared with no vacuum. In addition, the relationship with physical properties and thermal conductivity of HGMs has been discussed in detail. In conclusion, HGMs possess excellent thermal insulation performance at high vacuum in room temperature and have potential to further reduce thermal conductivity at the same conditions.

Crystallization and mechanical properties of reinforced PHBV composites using melt compounding: Effect of CNCs and CNFs.

PubMed

Jun, Du; Guomin, Zhao; Mingzhu, Pan; Leilei, Zhuang; Dagang, Li; Rui, Zhang

2017-07-15

Nanocellulose reinforced poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composites were prepared using melt compounding. The effects of nanocellulose types (CNCs and CNFs) and nanocellulose content (1, 2, 3, 4, 5, 6 and 7wt%) on the crystallization, thermal and mechanical properties of PHBV composites were systematically compared in this study. The thermal stability of PHBV composites was improved by both CNCs and CNFs. CNFs with a higher thermal stability leaded to a higher thermal stability of PHBV composites. Both CNCs and CNFs induced a reduction in the crystalline size of PHBV spherulites. Furthermore, CNCs could act as a better nucleating agent for PHBV than did CNFs. CNCs and CNFs showed reinforcing effects in PHBV composites. At the equivalent content of nanocellulose, CNCs led to a higher tensile modulus of PHBV composites than did CNFs. 1wt% CNCs/PHBV composites exhibited the most optimum mechanical properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

Long-term impacts of prescribed burns on soil thermal conductivity and soil heating at a Colorado Rocky Mountain site: a data/model fusion study

Treesearch

W. J. Massman; J. M. Frank; N. B. Reisch

2008-01-01

Heating any soil during a sufficiently intense wild fire or prescribed burn can alter that soil irreversibly, resulting in many significant, and well studied, long-term biological, chemical, and hydrological effects. On the other hand, much less is known about how fire affects the thermal properties and the long-term thermal regime of soils. Such knowledge is important...

Thermal Effects on the Bearing Behavior of Composite Joints

NASA Technical Reports Server (NTRS)

Walker, Sandra Polesky

2001-01-01

Thermal effects on the pin-bearing behavior of an IM7/PET15 composite laminate are studied comprehensively. A hypothesis presents factors influencing a change in pin-bearing strength with a change in temperature for a given joint design. The factors include the change in the state of residual cure stress, the material properties, and the fastener fit with a change in temperature. Experiments are conducted to determine necessary lamina and laminate material property data for the IM7/PET15 being utilized in this study. Lamina material properties are determined between the assumed stress free temperature of 460 F down to -200 F. Laminate strength properties are determined for several lay-ups at the operating temperatures of 350 F, 70 F, and -200 F. A three-dimensional finite element analysis model of a composite laminate subject to compressive loading is developed. Both the resin rich layer located between lamina and the thermal residual stresses present in the laminate due to curing are determined to influence the state of stress significantly. Pin-bearing tests of several lay-ups were conducted to develop an understanding on the effect of temperature changes on the pin-bearing behavior of the material. A computational study investigating the factors influencing pin-bearing strength was performed. A finite element model was developed and used to determine the residual thermal cure stresses in the laminate containing a hole. Very high interlaminar stress concentrations were observed two elements away from the hole boundary at all three operating temperatures. The pin-bearing problem was modeled assuming a rigid frictionless pin and restraining only radial displacements at the hole boundary. A uniform negative pressure load was then applied to the straight end of the model. A solution, where thermal residual stresses were combined with the state of stress due to pin-bearing loads was evaluated. The presence of thermal residual stresses intensified the interlaminar stresses predicted at the hole boundary in the pin-bearing problem. This dissertation shows that changes in material properties drives pin-bearing strength degradation with increasing temperature.

Thermal analysis of microlens formation on a sensitized gelatin layer

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

Muric, Branka; Pantelic, Dejan; Vasiljevic, Darko

2009-07-01

We analyze a mechanism of direct laser writing of microlenses. We find that thermal effects and photochemical reactions are responsible for microlens formation on a sensitized gelatin layer. An infrared camera was used to assess the temperature distribution during the microlens formation, while the diffraction pattern produced by the microlens itself was used to estimate optical properties. The study of thermal processes enabled us to establish the correlation between thermal and optical parameters.

Wood products : thermal degradation and fire

Treesearch

R.H. White; M.A. Dietenberger

2001-01-01

Wood is a thermally degradable and combustible material. Applications range from a biomass providing useful energy to a building material with unique properties. Wood products can contribute to unwanted fires and be destroyed as well. Minor amounts of thermal degradation adversely affect structural properties. Therefore, knowledge of the thermal degradation and fire...

The effect of radiation on the thermal properties of chitosan/mimosa tenuiflora and chitosan/mimosa tenuiflora/multiwalled carbon nanotubes (MWCNT) composites for bone tissue engineering

NASA Astrophysics Data System (ADS)

Martel-Estrada, S. A.; Santos-Rodríguez, E.; Olivas-Armendáriz, I.; Cruz-Zaragoza, E.; Martínez-Pérez, C. A.

2014-07-01

The purpose of this study is to examine the effect of gamma radiation and UV radiation on the microstructure, chemical structure and thermal stability of Chitosan/Mimosa Tenuiflora and Chitosan/Mimosa Tenuiflora/MWCNT composites scaffolds produced by thermally induced phase separation. The composites were irradiated and observed to undergo radiation-induced degradation through chain scission. Morphology, thermal properties and effects on chemical and semi-crystalline structures were obtained by scanning electronic microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), FT-IR analysis and X-ray Diffraction. A relationship between radiation type and the thermal stability of the composites, were also established. This relationship allows a more accurate and precise control of the life span of Chitosan/Mimosa Tenuiflora and Chitosan/Mimosa Tenuiflora/MWCNT composites through the use of radiation in materials for use in tissue engineering.

Thermal Degradation and Combustion Behavior of Polypropylene/MWCNT Composites

NASA Astrophysics Data System (ADS)

Zaikov, G. E.; Rakhimkulov, A. D.; Lomakin, S. M.; Dubnikova, I. L.; Shchegolikhin, A. N.; Davidov, E. Ya.

2010-06-01

Studies of thermal and fire-resistant properties of the polypropylene/multi-walled carbon nanotube composites (PP/MWCNT) prepared by means of melt intercalation are discussed. The sets of the data acquired with the aid of non-isothermal TG experiments have been treated by the model kinetic analysis. The thermal-oxidative degradation behavior of PP/MWCNT and stabilizing effect caused by addition of MWCNT has been investigated by means of TGA and EPR spectroscopy. The results of cone calorimetric tests lead to the conclusion that char formation plays a key role in the mechanism of flame retardation for nanocomposites. This could be explained by the specific antioxidant properties and high thermal conductivity of MWCNT which determine high-performance carbonization during thermal degradation process. Comparative analysis of the flammability characteristics for PP-clay/MWCNT nanocomposites was provided in order to emphasize the specific behavior of the nanocomposites under high-temperature tests.

Facile Preparation of Carbon Microcapsules Containing Phase-Change Material with Enhanced Thermal Properties

PubMed Central

Tahan Latibari, Sara; Mehrali, Mohammad; Mehrali, Mehdi; Mahlia, Teuku Meurah Indra; Metselaar, Hendrik Simon Cornelis

2014-01-01

This study describes the hydrothermal synthesis of a novel carbon/palmitic acid (PA) microencapsulated phase change material (MEPCM). The field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) images confirm that spherical capsules of uniform size were formed with a mean diameter of 6.42 μm. The melting and freezing temperature were found to be slightly lower than those of pure PA with little undercooling. The composite retained 75% of the latent heat of pure PA. Thermal stability of the MEPCM was found to be better than that of pure PA. The thermal conductivity of MEPCM was increased by as much as 41% at 30°C. Due to its good thermal properties and chemical and mechanical stability, the carbon/PA MEPCM displays a good potential for thermal energy storage systems. PMID:25054179

Measurement of elastic and thermal properties of composite materials using digital speckle pattern interferometry

NASA Astrophysics Data System (ADS)

Kumar, Manoj; Khan, Gufran S.; Shakher, Chandra

2015-08-01

In the present work, application of digital speckle pattern interferometry (DSPI) was applied for the measurement of mechanical/elastic and thermal properties of fibre reinforced plastics (FRP). Digital speckle pattern interferometric technique was used to characterize the material constants (Poisson's ratio and Young's modulus) of the composite material. Poisson ratio based on plate bending and Young's modulus based on plate vibration of material are measured by using DSPI. In addition to this, the coefficient of thermal expansion of composite material is also measured. To study the thermal strain analysis, a single DSPI fringe pattern is used to extract the phase information by using Riesz transform and the monogenic signal. The phase extraction from a single DSPI fringe pattern by using Riesz transform does not require a phase-shifting system or spatial carrier. The elastic and thermal parameters obtained from DSPI are in close agreement with the theoretical predictions available in literature.

The magnetic-nanofluid heat pipe with superior thermal properties through magnetic enhancement

PubMed Central

2012-01-01

This study developed a magnetic-nanofluid (MNF) heat pipe (MNFHP) with magnetically enhanced thermal properties. Its main characteristic was additional porous iron nozzle in the evaporator and the condenser to form a unique flowing pattern of MNF slug and vapor, and to magnetically shield the magnet attraction on MNF flowing. The results showed that an optimal thermal conductivity exists in the applied field of 200 Oe. Furthermore, the minor thermal performance of MNF at the condenser limited the thermal conductivity of the entire MNFHP, which was 1.6 times greater than that filled with water for the input power of 60 W. The feasibilities of an MNFHP with the magnetically enhanced heat transfer and the ability of vertical operation were proved for both a promising heat-dissipation device and the energy architecture integrated with an additional energy system. PMID:22716909

Improving the Mechanical Performance and Thermal Stability of a PVA-Clay Nanocomposite by Electron Beam Irradiation

NASA Astrophysics Data System (ADS)

Shokuhi Rad, A.; Ebrahimi, D.

2017-07-01

The effects of electron beam irradiation and presence of clay on the mechanical properties and thermal stability of montmorillonite clay-modified polyvinyl alcohol nanocomposites were studied. By using the X-ray diffraction (XRD) and transmission electron microscopy (TEM), the microstructure of the nanocomposites was investigated. The results obtained from TEM and XRD tests showed that montmorillonite clay nanoparticles were located in the polyvinyl alcohol phase. The XRD analysis confirmed the formation of an exfoliated structure in nanocomposites samples. Increasing the amount of clay to 20 wt.% increased the tensile strength and modulus of the nanocomposite. Irradiation up to an absorbed dose of 100 kGy increased its mechanical properties and thermal stability, but at higher irradiation levels, the mechanical strength and thermal stability declined. The sample with 20 wt.% of the nanofiller, exposed to 100 kGy, showed the highest mechanical strength and thermal stability.

Phonon Surface Scattering and Thermal Energy Distribution in Superlattices.

PubMed

Kothari, Kartik; Maldovan, Martin

2017-07-17

Thermal transport at small length scales has attracted significant attention in recent years and various experimental and theoretical methods have been developed to establish the reduced thermal conductivity. The fundamental understanding of how phonons move and the physical mechanisms behind nanoscale thermal transport, however, remains poorly understood. Here we move beyond thermal conductivity calculations and provide a rigorous and comprehensive physical description of thermal phonon transport in superlattices by solving the Boltzmann transport equation and using the Beckman-Kirchhoff surface scattering theory with shadowing to precisely describe phonon-surface interactions. We show that thermal transport in superlattices can be divided in two different heat transport modes having different physical properties at small length scales: layer-restricted and extended heat modes. We study how interface conditions, periodicity, and composition can be used to manipulate the distribution of thermal energy flow among such layer-restricted and extended heat modes. From predicted frequency and mean free path spectra of superlattices, we also investigate the existence of wave effects. The results and insights in this paper advance the fundamental understanding of heat transport in superlattices and the prospects of rationally designing thermal systems with tailored phonon transport properties.

Comparison of Thermal Stability of Dry High-strength Concrete and Wet High-strength Concrete

NASA Astrophysics Data System (ADS)

Musorina, Tatiana; Katcay, Aleksandr; Selezneva, Anna; Kamskov, Victor

2018-03-01

High-strength concrete is a modern material, which occupies it`s own niche on the construction material market. It is applicable in a large-scale high-rise construction, particularly an underground construction is a frequently used solution for a space saving. Usually underground structure is related to a wet usage environment. Though not all properties of the high-strength concrete are investigated to the full extent. Under adverse climatic conditions of the Russian Federation one of the most important properties for constructional materials is a thermal capacity. Therefore, the main purpose of the paper is to compare a thermal capacity of the high-strength concrete in humid conditions and a thermal capacity of the high-strength concrete in dry operational condition. During the study dependency between thermal capacity and design wall thickness and ambient humidity has to be proven with two experiments. As a result the theoretical relation between thermal capacity characteristic - thermal inertia and wall thickness and ambient humidity was confirmed by the experimental data. The thermal capacity of a building is in direct ratio to the construction thickness. It follows from the experiments and calculations that wet high-strength concrete has less thermal stability.

Thermal Transport in Graphene Oxide – From Ballistic Extreme to Amorphous Limit

PubMed Central

Mu, Xin; Wu, Xufei; Zhang, Teng; Go, David B.; Luo, Tengfei

2014-01-01

Graphene oxide is being used in energy, optical, electronic and sensor devices due to its unique properties. However, unlike its counterpart – graphene – the thermal transport properties of graphene oxide remain unknown. In this work, we use large-scale molecular dynamics simulations with reactive potentials to systematically study the role of oxygen adatoms on the thermal transport in graphene oxide. For pristine graphene, highly ballistic thermal transport is observed. As the oxygen coverage increases, the thermal conductivity is significantly reduced. An oxygen coverage of 5% can reduce the graphene thermal conductivity by ~90% and a coverage of 20% lower it to ~8.8 W/mK. This value is even lower than the calculated amorphous limit (~11.6 W/mK for graphene), which is usually regarded as the minimal possible thermal conductivity of a solid. Analyses show that the large reduction in thermal conductivity is due to the significantly enhanced phonon scattering induced by the oxygen defects which introduce dramatic structural deformations. These results provide important insight to the thermal transport physics in graphene oxide and offer valuable information for the design of graphene oxide-based materials and devices. PMID:24468660

Thermophysical modeling of main-belt asteroids from WISE thermal data

NASA Astrophysics Data System (ADS)

Hanuš, J.; Delbo', M.; Ďurech, J.; Alí-Lagoa, V.

2018-07-01

By means of a varied-shape thermophysical model of Hanuš et al. (2015) that takes into account asteroid shape and pole uncertainties, we analyze the thermal infrared data acquired by the NASA's Wide-field Infrared Survey Explorer of about 300 asteroids with derived convex shape models. We utilize publicly available convex shape models and rotation states as input for the thermophysical modeling. For more than one hundred asteroids, the thermophysical modeling gives us an acceptable fit to the thermal infrared data allowing us to report their thermophysical properties such as size, thermal inertia, surface roughness or visible geometric albedo. This work more than doubles the number of asteroids with determined thermophysical properties, especially the thermal inertia. In the remaining cases, the shape model and pole orientation uncertainties, specific rotation or thermophysical properties, poor thermal infrared data or their coverage prevent the determination of reliable thermophysical properties. Finally, we present the main results of the statistical study of derived thermophysical parameters within the whole population of main-belt asteroids and within few asteroid families. Our sizes based on TPM are, in average, consistent with the radiometric sizes reported by Mainzer et al. (2016). The thermal inertia increases with decreasing size, but a large range of thermal inertia values is observed within the similar size ranges between D ∼ 10-100 km. We derived unexpectedly low thermal inertias ( < 20 J m-2 s- 1 / 2 K-1) for several asteroids with sizes 10 < D < 50 km, indicating a very fine and mature regolith on these small bodies. The thermal inertia values seem to be consistent within several collisional families, however, the statistical sample is in all cases rather small. The fast rotators with rotation period P ≲ 4 h tend to have slightly larger thermal inertia values, so probably do not have a fine regolith on the surface. This could be explained, for example, by the loss of the fine regolith due to the centrifugal force, or by the ineffectiveness of the regolith production(e.g., by the thermal cracking mechanism of Delbo' et al. 2014).

Black Versus Gray T-Shirts: Comparison of Spectrophotometric and Other Biophysical Properties of Physical Fitness Uniforms and Modeled Heat Strain and Thermal Comfort

DTIC Science & Technology

2016-09-01

test method for measuring the thermal insulation of clothing using a heated manikin. 2010. 2. ASTM International. F2370-10 Standard test method for...PROPERTIES OF PHYSICAL FITNESS UNIFORMS AND MODELED HEAT STRAIN AND THERMAL COMFORT DISCLAIMER The opinions or assertions contained herein are the...SHIRTS: COMPARISON OF SPECTROPHOTOMETRIC AND OTHER BIOPHYSICAL PROPERTIES OF PHYSICAL FITNESS UNIFORMS AND MODELED HEAT STRAIN AND THERMAL COMFORT

Thermal radiative and thermodynamic properties of solid and liquid uranium and plutonium carbides in the visible-near-infrared range

NASA Astrophysics Data System (ADS)

Fisenko, Anatoliy I.; Lemberg, Vladimir F.

2016-09-01

The knowledge of thermal radiative and thermodynamic properties of uranium and plutonium carbides under extreme conditions is essential for designing a new metallic fuel materials for next generation of a nuclear reactor. The present work is devoted to the study of the thermal radiative and thermodynamic properties of liquid and solid uranium and plutonium carbides at their melting/freezing temperatures. The Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, pressure, and normal total emissivity are calculated using experimental data for the frequency dependence of the normal spectral emissivity of liquid and solid uranium and plutonium carbides in the visible-near infrared range. It is shown that the thermal radiative and thermodynamic functions of uranium carbide have a slight difference during liquid-to-solid transition. Unlike UC, such a difference between these functions have not been established for plutonium carbide. The calculated values for the normal total emissivity of uranium and plutonium carbides at their melting temperatures is in good agreement with experimental data. The obtained results allow to calculate the thermal radiative and thermodynamic properties of liquid and solid uranium and plutonium carbides for any size of samples. Based on the model of Hagen-Rubens and the Wiedemann-Franz law, a new method to determine the thermal conductivity of metals and carbides at the melting points is proposed.

Time resolved thermal lens in edible oils

NASA Astrophysics Data System (ADS)

Albuquerque, T. A. S.; Pedreira, P. R. B.; Medina, A. N.; Pereira, J. R. D.; Bento, A. C.; Baesso, M. L.

2003-01-01

In this work time resolved thermal lens spectrometry is applied to investigate the optical properties of the following edible oils: soya, sunflower, canola, and corn oils. The experiments were performed at room temperature using the mode mismatched thermal lens configuration. The results showed that when the time resolved procedure is adopted the technique can be applied to investigate the photosensitivity of edible oils. Soya oil presented a stronger photochemical reaction as compared to the other investigated samples. This observation may be relevant for future studies evaluating edible oils storage conditions and also may contribute to a better understanding of the physical and chemical properties of this important foodstuff.

Energy Storage Analysis of a Mixed R161/MOF-5 Nanoparticle Nanofluid Based on Molecular Simulations

PubMed Central

Wang, Qiang; Tang, Shengli; Li, Leilei

2018-01-01

The thermal properties of refrigerants can be modified by adding porous nanoparticles into them. Here, molecular simulations, including molecular dynamics and grand canonical Monte Carlo, were employed to study the thermal energy storage properties of an R161/MOF-5 nanofluid. The results show that the thermodynamic energy change of MOF-5 nanoparticles is linear to the temperature. The adsorption heat calculated by grand canonical Monte Carlo is close to that calculated by the Clausius–Clapeyron equation. Additionally, a negative enhancement of the thermal energy storage capacity of the R161/MOF-5 nanofluid is found near the phase transition area. PMID:29783773

Energy Storage Analysis of a Mixed R161/MOF-5 Nanoparticle Nanofluid Based on Molecular Simulations.

PubMed

Wang, Qiang; Tang, Shengli; Li, Leilei

2018-05-20

The thermal properties of refrigerants can be modified by adding porous nanoparticles into them. Here, molecular simulations, including molecular dynamics and grand canonical Monte Carlo, were employed to study the thermal energy storage properties of an R161/MOF-5 nanofluid. The results show that the thermodynamic energy change of MOF-5 nanoparticles is linear to the temperature. The adsorption heat calculated by grand canonical Monte Carlo is close to that calculated by the Clausius⁻Clapeyron equation. Additionally, a negative enhancement of the thermal energy storage capacity of the R161/MOF-5 nanofluid is found near the phase transition area.

Electrical and Thermal Transport in Inhomogeneous Luttinger Liquids

DOE PAGES

DeGottardi, Wade; Matveev, K. A.

2015-06-12

In this paper, we study the transport properties of long quantum wires by generalizing the Luttinger liquid approach to allow for the finite lifetime of the bosonic excitations. Our theory accounts for long-range disorder and strong electron interactions, both of which are common features of experiments with quantum wires. We obtain the electrical and thermal resistances and thermoelectric properties of such quantum wires and find a strong deviation from perfect conductance quantization. Finally, we cast our results in terms of the thermal conductivity and bulk viscosity of the electron liquid and give the temperature scale above which the transport canmore » be described by classical hydrodynamics.« less

Time-temperature-stress capabilities of composites for supersonic cruise aircraft applications

NASA Technical Reports Server (NTRS)

Haskins, J. F.; Kerr, J. R.; Stein, B. A.

1976-01-01

A range of baseline properties was determined for representatives of 5 composite materials systems: B/Ep, Gr/Ep, B/PI, Gr/PI, and B/Al. Long-term exposures are underway in static thermal environments and in ones which simultaneously combine programmed thermal histories and mechanical loading histories. Selected results from the environmental exposure studies with emphasis placed on the 10,000-hour thermal aging data are presented. Results of residual strength determinations and changes in physcial and chemical properties during high temperature aging are discussed and illustrated using metallographic, fractographic and thermomechanical analyses. Some initial results of the long-term flight simulation tests are also included.

Atomic-scale to Meso-scale Simulation Studies of Thermal Ageing and Irradiation Effects in Fe- Cr Alloys

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

Stanley, Eugene; Liu, Li

In this project, we target at three primary objectives: (1) Molecular Dynamics (MD) code development for Fe-Cr alloys, which can be utilized to provide thermodynamic and kinetic properties as inputs in mesoscale Phase Field (PF) simulations; (2) validation and implementation of the MD code to explain thermal ageing and radiation damage; and (3) an integrated modeling platform for MD and PF simulations. These two simulation tools, MD and PF, will ultimately be merged to understand and quantify the kinetics and mechanisms of microstructure and property evolution of Fe-Cr alloys under various thermal and irradiation environments

The Effect of Alloying Elements on Thermal Conductivity and Casting Characteristic in High Pressure Die Casting of Aluminum Alloy

NASA Astrophysics Data System (ADS)

Kim, Cheol-Woo; Cho, Jae-Ik; Choi, Se-Weon; Kim, Young-Chan; Kang, Chang-Seog

Recently, demand of aluminum alloys for use in high thermal conductivity application is increases but the most aluminum die casting alloys exhibit very lower thermal properties because of their high concentrations of alloying elements. However, those alloying elements are essential to obtain sufficient fluidity and mechanical strength. Therefore, the purpose of this study is to analyze the effect of alloying elements in die casting alloys, Si, Cu, Mg, Fe and Mn, in thermal conductivity, die casting characteristics and mechanical properties and find out the appropriate amount of each alloying element for development of heat sink component. The results showed that Mn had the most deleterious effect in thermal conductivity and Si and Fe contents were important to improve strength and limit casting defects, such as hot tearing and die soldering. The alloy with 0.2 1.0wt%Cu, 0.3 0.6wt%Fe and 1.0 2.0wt%Si showed very good combination of high thermal conductivity and good casting characteristics.

Thermotropic Properties of Thermophilic, Mesophilic, and Psychrophilic Blue-green Algae

PubMed Central

Chen, Chang-Hwei; Berns, Donald S.

1980-01-01

Thermotropic properties of blue-green algae grown at high, room, and low temperatures in H2O and D2O media were studied by highly sensitive differential scanning microcalorimetry. The thermograms of these organisms contain an endothermal peak in the temperature range of 50 to 70 C with an endothermal heat ranging from 0.14 to 1.91 joules per gram organism. The temperature at which the endothermal peak occurs is comparable with the thermal denaturation temperature of phycocyanin, the major biliprotein isolated from these algae. A good correlation can be found for the relative thermal stability of various organisms with that of the isolated biliproteins. The ability of these algae to resist thermal disruption is correlated with the thermal environments in which these algal cells grow. The thermal stability of normal algae is in the order of thermophile > mesophile > psychrophile. It was found that the deuterated mesophilic algae were less able to resist thermal disruption than ordinary mesophilic algae. PMID:16661485

Effects of thermal energy harvesting on the human - clothing - environment microsystem

NASA Astrophysics Data System (ADS)

Myers, A. C.; Jur, J. S.

2017-10-01

The objective of this work is to perform an in depth investigation of garment-based thermal energy harvesting. The effect of human and environmental factors on the working efficiency of a thermal energy harvesting devices, or a thermoelectric generator (TEG), placed on the body is explored.. Variables that strongly effect the response of the TEG are as follows: skin temperature, human motion or speed, body location, environmental conditions, and the textile properties surrounding the TEG. In this study, the use of textiles for managing thermal comfort of wearable technology and energy harvesting are defined. By varying the stitch length and/or knit structure, one can manipulate the thermal conductivity of the garment in a specific location. Another method of improving TEG efficiency is through the use of a heat spreader, which increases the effective collection area of heat on the TEG hot side. Here we show the effect of a TEG on the thermal properties of a garment with regard to two knit stitches, jersey and 1 × 1 rib.

Thermal conductance of Teflon and Polyethylene: Insight from an atomistic, single-molecule level

PubMed Central

Buerkle, Marius; Asai, Yoshihiro

2017-01-01

The thermal transport properties of teflon (polytetrafluoroethylene) and its polyethylene counterparts are, while highly desirable and widely used, only superficially understood. Here, we aim therefore to provide rigorous insight from an atomistic point of view in context of single-molecule devices. We show that for vinyl polymers adsorbed on metal-surfaces the thermal transport strongly depends on the properties of the metal-molecule interface and that the reduced thermal conductance observed for teflon derivatives originates in a reduced phonon injection life time. In asymmetric molecules phonon blocking on the intra molecular interface leads to a further reduction of thermal conductance. For hetrojunctions with different electrode materials we find that thermal conductance is suppressed due to a reduced overlap of the available phonon modes in the different electrodes. A detailed atomistic picture is thereby provided by studying the transport through perfluorooctane and octane on a single-molecule level using first principles transport calculations and nonequilibrium molecular dynamic simulations. PMID:28150738

Determining in-situ thermal conductivity of coarse textured materials through numerical analysis of thermal

NASA Astrophysics Data System (ADS)

Saito, H.; Hamamoto, S.; Moldrup, P.; Komatsu, T.

2013-12-01

Ground source heat pump (GSHP) systems use ground or groundwater as a heat/cooling source, typically by circulating anti-freezing solution inside a vertically installed closed-loop tube known as a U-tube to transfer heat to/from the ground. Since GSHP systems are based on renewable energy and can achieve much higher coefficient of performance (COP) than conventional air source heat pump systems, use of GSHP systems has been rapidly increasing worldwide. However, environmental impacts by GSHP systems including thermal effects on subsurface physical-chemical and microbiological properties have not been fully investigated. To rigorously assess GSHP impact on the subsurface environment, ground thermal properties including thermal conductivity and heat capacity need to be accurately characterized. Ground thermal properties were investigated at two experimental sites at Tokyo University of Agriculture and Technology (TAT) and Saitama University (SA), both located in the Kanto area of Japan. Thermal properties were evaluated both by thermal probe measurements on boring core samples and by performing in-situ Thermal Response Tests (TRT) in 50-80 m deep U-tubes. At both TAT and SU sites, heat-pulse probe measurements gave unrealistic low thermal conductivities for coarse textured materials (dominated by particles > 75 micrometers). Such underestimation can be partly due to poor contact between probe and porous material and partly to markedly decreasing sample water content during drilling, carrying, and storing sandy/gravelly samples. A more reliable approach for estimating in-situ thermal conductivity of coarse textured materials is therefore needed, and may be based on the commonly used TRT test. However, analyses of TRT data is typically based on Kelvin's line source model and provides an average (effective) thermal property for the whole soil profile around the U-tube but not for each geological layer. The main objective of this study was therefore to develop a method for estimating thermal conductivity values of coarse textured layers by numerically analyzing TRT data. A numerical technique combining three-dimensional conductive heat transport and one-dimensional convective heat transport to simulate heat exchange processes between the U-tube and the ground was used. In the numerical simulations, the thermal conductivities for the fine textured layers were kept at the probe-measured values, while the thermal conductivity for the coarse textured layers (constituting around half of the profile depth at both sites) was calibrated. The numerically-based method yielded more reasonable thermal conductivity values for the coarse-textured materials at both TAT and SU sites as compared to the heat pulse probe measurements, while the temperature changes of the heat carry fluid inside the U-tubes were also well simulated.

Comparative study of the functional properties of three legume seed isolates: adzuki, pea and soy bean.

PubMed

Barac, Miroljub B; Pesic, Mirjana B; Stanojevic, Sladjana P; Kostic, Aleksandar Z; Bivolarevic, Vanja

2015-05-01

The aim of this work was to compare functional properties including solubility, emulsifying and foaming properties of native and thermally treated adzuki, soy and pea protein isolates prepared under the same conditions. These functional properties were tested at four pH values: pH 3.0, pH 5.0, pH 7.0 and pH 8.0. The lowest solubility at all pH values were obtained for isolate of adzuki whereas isolates of soybean had the highest values at almost all pHs. Thermal treatment reduced solubility of soy and pea isolates at all pH values, whereas solubility of adzuki isolate was unchanged, except at pH 8. Native isolate of adzuki had the best emulsifying properties at pH 7.0 whereas at the other pH values some of native pea and soybean protein isolates were superior. After thermal treatment, depending on tested pH and selected variety all of three species could be a good emulsifier. Native soy protein isolates formed the most stable foams at all pHs. Thermal treatment significantly improved foaming properties of adzuki isolate, whereas reduced foaming capacity of soy and pea isolates, but could improve foam stability of these isolates at specific pH. Appropriate selection of legume seed as well as variety could have great importance in achievement of desirable functional properties of final products. All three tested species could find specific application in wide range of food products.

Thermoelectric Properties of High-Doped Silicon from Room Temperature to 900 K

NASA Astrophysics Data System (ADS)

Stranz, A.; Kähler, J.; Waag, A.; Peiner, E.

2013-07-01

Silicon is investigated as a low-cost, Earth-abundant thermoelectric material for high-temperature applications up to 900 K. For the calculation of module design the Seebeck coefficient and the electrical as well as thermal properties of silicon in the high-temperature range are of great importance. In this study, we evaluate the thermoelectric properties of low-, medium-, and high-doped silicon from room temperature to 900 K. In so doing, the Seebeck coefficient, the electrical and thermal conductivities, as well as the resulting figure of merit ZT of silicon are determined.

Atomistic modeling of BN nanofillers for mechanical and thermal properties: a review.

PubMed

Kumar, Rajesh; Parashar, Avinash

2016-01-07

Due to their exceptional mechanical properties, thermal conductivity and a wide band gap (5-6 eV), boron nitride nanotubes and nanosheets have promising applications in the field of engineering and biomedical science. Accurate modeling of failure or fracture in a nanomaterial inherently involves coupling of atomic domains of cracks and voids as well as a deformation mechanism originating from grain boundaries. This review highlights the recent progress made in the atomistic modeling of boron nitride nanofillers. Continuous improvements in computational power have made it possible to study the structural properties of these nanofillers at the atomistic scale.

Thermal Property Parameter Estimation of TPS Materials

NASA Technical Reports Server (NTRS)

Maddren, Jesse

1998-01-01

Accurate knowledge of the thermophysical properties of TPS (thermal protection system) materials is necessary for pre-flight design and post-flight data analysis. Thermal properties, such as thermal conductivity and the volumetric specific heat, can be estimated from transient temperature measurements using non-linear parameter estimation methods. Property values are derived by minimizing a functional of the differences between measured and calculated temperatures. High temperature thermal response testing of TPS materials is usually done in arc-jet or radiant heating facilities which provide a quasi one-dimensional heating environment. Last year, under the NASA-ASEE-Stanford Fellowship Program, my work focused on developing a radiant heating apparatus. This year, I have worked on increasing the fidelity of the experimental measurements, optimizing the experimental procedures and interpreting the data.

Thermodynamic nonequilibrium phase change behavior and thermal properties of biological solutions for cryobiology applications.

PubMed

Han, Bumsoo; Bischof, John C

2004-04-01

Understanding the phase change behavior of biomaterials during freezing/thawing including their thermal properties at low temperatures is essential to design and improve cryobiology applications such as cryopreservation and cryosurgery. However, knowledge of phase change behavior and thermal properties of various biomaterials is still incomplete, especially at cryogenic temperatures (< or = -40 degrees C). Moreover, in these applications, chemicals are often added to improve their outcome, which can result in significant variation in the phase change behavior and thermal properties from those of the original biomaterials. These chemical additives include cryoprotective agents (CPAs), antifreeze protein (AFP), or cryosurgical adjuvants like sodium chloride (NaCl). In the present study, phase change behavior and thermal properties of saline solutions--either water-NaCl or phosphate buffered saline (PBS)--with various chemical additives were investigated. The chemical additives studied are glycerol and raffinose as CPAs, an AFP (Type III, molecular weight = 6500), and NaCl as a cryosurgical adjuvant. The phase change behavior was investigated using a differential scanning calorimeter (DSC) and a cryomicroscope. The specific and latent heat of these solutions were also measured with the DSC. The saline solutions have two distinct phase changes--water/ice and eutectic phase changes. During freezing, eutectic solidification of both water-NaCl and PBS are significantly supercooled below their thermodynamic equilibrium eutectic temperatures. However, their melting temperatures are close to thermodynamic equilibrium during thawing. These eutectic phase changes disappear when even a small amount (0.1 M glycerol) of CPA was added, but they are still observed after the addition of an AFP. The specific heats of these solutions are close to that of ice at very low temperatures (< or = -100 degrees C) regardless of the additives, but they increase between -100 degrees C and -30 degrees C with the addition of CPAs. The amount of latent heat, which is evaluated with sample weight, generally decreases with the addition of the additives, but can be normalized to approximately 300 J/g based on the weight of water which participates in the phase change. This illustrates that thermal properties, especially latent heat, of a biomaterial should be evaluated based on the understanding of its phase change behavior. The results of the present study are discussed in the context of the implications for cryobiology applications.

First-principles study of thermal transport in nitrogenated holey graphene.

PubMed

Ouyang, Tao; Xiao, Huaping; Tang, Chao; Zhang, Xiaoliang; Hu, Ming; Zhong, Jianxin

2017-01-27

Nitrogenated holey graphene (NHG), a new two-dimensional graphene variant with a large fundamental direct band gap, has recently been successfully synthesized via a simple wet-chemical reaction. Motivated by its unique geometry and novel properties, we investigated the phonon transport properties of the material by combining first-principle calculations and the phonon Boltzmann transport equation. The lattice thermal conductivity of NHG at room temperature is predicted to be about 82.22 W mK -1 , which is almost two orders of magnitude lower than that of graphene (about 3500 W mK -1 ). Deviating from the traditional understanding that thermal transport is usually largely contributed by the acoustic phonon modes for most suspended 2D materials, both out-of-plane flexural acoustic (ZA) and optical phonon modes make a more or less equal contribution, and their combination abnormally dominates the overall thermal transport in NHG. The major three-phonon process in NHG is further analyzed and the scattering between the acoustic and optical phonon modes like [Formula: see text] is the main phonon process channel. Meanwhile, the mean free path distribution of different phonon modes is calculated for the purpose of the thermal management of NHG-based devices. Our results elucidate the unusual thermal transport properties of NHG as compared with the representative case of graphene, and underpin its potential application for use by the thermal management community.

First-principles study of thermal transport in nitrogenated holey graphene

NASA Astrophysics Data System (ADS)

Ouyang, Tao; Xiao, Huaping; Tang, Chao; Zhang, Xiaoliang; Hu, Ming; Zhong, Jianxin

2017-01-01

Nitrogenated holey graphene (NHG), a new two-dimensional graphene variant with a large fundamental direct band gap, has recently been successfully synthesized via a simple wet-chemical reaction. Motivated by its unique geometry and novel properties, we investigated the phonon transport properties of the material by combining first-principle calculations and the phonon Boltzmann transport equation. The lattice thermal conductivity of NHG at room temperature is predicted to be about 82.22 W mK-1, which is almost two orders of magnitude lower than that of graphene (about 3500 W mK-1). Deviating from the traditional understanding that thermal transport is usually largely contributed by the acoustic phonon modes for most suspended 2D materials, both out-of-plane flexural acoustic (ZA) and optical phonon modes make a more or less equal contribution, and their combination abnormally dominates the overall thermal transport in NHG. The major three-phonon process in NHG is further analyzed and the scattering between the acoustic and optical phonon modes like {{ZA}}/{{TA}}/{{LA}}+{{O}}≤ftrightarrow {{O}} is the main phonon process channel. Meanwhile, the mean free path distribution of different phonon modes is calculated for the purpose of the thermal management of NHG-based devices. Our results elucidate the unusual thermal transport properties of NHG as compared with the representative case of graphene, and underpin its potential application for use by the thermal management community.

Effect of gamma irradiation on the thermal, mechanical and structural properties of chlorinated polyvinyl chloride

NASA Astrophysics Data System (ADS)

Nouh, S. A.

Non isothermal studies were carried out using thermogravimetry (TG) and differential thermogravimetry (DTG) to obtain the activation energy of decomposition for chlorinated polyvinyl chloride (CPVC) before and after exposure to gamma doses at levels between 5.0 and 50.0 KGy. Thermal gravitational analysis (TGA) indicated that the CPVC polymer decomposes in one main breakdown stage and a decrease in activation energies was observed followed by an increase on increasing the gamma dose. The variation of melting temperatures with the gamma dose has been determined using differential thermal analysis (DTA). Also, mechanical and structural property studies were performed on all irradiated and non-irradiated CPVC samples using stress-strain relations and X-ray diffraction. The results indicated that the exposure to gamma doses at levels between 27.5 and 50 KGy leads to further enhancement of the thermal stability, tensile strength and isotropic character of the polymer samples due to the crosslinking phenomenon. This suggests that gamma radiation could be a suitable technique for producing a plastic material with enhanced properties that can be suitable for high temperature applications and might be a suitable candidate for dosimetric applications.

The technology for creating of decorative plywood with low formaldehyde emission

NASA Astrophysics Data System (ADS)

Safin, R. R.; Khasanshin, R. R.; Shaikhutdinova, A. R.; Ziatdinov, R. R.

2015-10-01

The development of new technologies of processing of industrial art products to improve their functional, ergonomic and aesthetic properties is one of the important directions of improvement of product design. The article presents the technology of preliminary contact thermal modification of sheets of veneer in the production of low-toxic decorative plywood and laminated products, which lets significantly improve their water resistance. It has been established that thermal modification of wood material causes a decrease in density with increasing temperature and duration of treatment. A mathematical model describing the process of heat treatment of wood veneer and allowing predicting the degree of thermal modification of wood material depending on the modes of modification has been developed. Several studies to determine the basic properties of plywood made on the basis of heat-treated veneer were conducted in the work. Studies have shown that the thermal effect on veneer in the manufacture of plywood provides improves water-repellent properties of it, while not increasing its toxicity. It has also been found that the alternating of layers of wood with varying degrees of heat treatment when creating laminated products greatly enhances the decorative features of the products.

Assessing the perception and reality of arguments against thermal waste treatment plants in terms of property prices

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

Phillips, K.J.O.; Longhurst, P.J.; Wagland, S.T., E-mail: s.t.wagland@cranfield.ac.uk

Highlights: • Previous research studies have shown that EfW facilities negatively impact the local house prices. • In this study property prices surrounding 3 operational EfW plants were analysed. • No significant negative effect on property prices due to an incinerator was found. - Abstract: The thermal processing of waste materials, although considered to be an essential part of waste management, is often sharply contested in the UK. Arguments such as health, depletion of resources, cost, noise, odours, traffic movement and house prices are often cited as reasons against the development of such facilities. This study aims to review themore » arguments and identify any effect on property prices due to the public perception of the plant. A selection of existing energy from waste (EfW) facilities in the UK, operational for at least 7 years, was selected and property sales data, within 5 km of the sites, was acquired and analysed in detail. The locations of the properties were calculated in relation to the plant using GIS software (ArcGIS) and the distances split into 5 zones ranging from 0 to 5 km from the site. The local property sale prices, normalised against the local house price index, were compared in two time periods, before and after the facility became operational, across each of the 5 zones. In all cases analysed no significant negative effect was observed on property prices at any distance within 5 km from a modern operational incinerator. This indicated that the perceived negative effect of the thermal processing of waste on local property values is negligible.« less

Thermal Conductivity of a Nanoscale Yttrium Iron Garnet Thin-Film Prepared by the Sol-Gel Process

PubMed Central

2017-01-01

The thermal conductivity of a nanoscale yttrium iron garnet (Y3Fe5O12, YIG) thin-film prepared by a sol-gel method was evaluated using the ultrafast pump-probe technique in the present study. The thermoreflectance change on the surface of a 250 nm thick YIG film, induced by the irradiation of femtosecond laser pulses, was measured, and curve fitting of a numerical solution for the transient heat conduction equation to the experimental data was performed using the finite difference method in order to extract the thermal property. Results show that the film’s thermal conductivity is 22–83% higher than the properties of bulk YIG materials prepared by different fabrication techniques, reflecting the microstructural characteristics and quality of the film. PMID:28858249

Synthesis and photophysical characterizations of thermal-stable naphthalene benzimidazoles.

PubMed

Erten-Ela, Sule; Ozcelik, Serdar; Eren, Esin

2011-07-01

Microwave-assisted synthesis, photophysical and electrochemical properties of thermal-stable naphthalene benzimidazoles and naphthalimides are studied in this paper. Microwave-assisted synthesis of naphthalene benzimidazoles provide higher yields than the conventional thermal synthesis. Comparative photophysical properties of naphthalene benzimidazoles and naphthalimides are revealed that conjugation of electron-donating group onto naphthalimide moiety increases fluorescence quantum yields. Fluorophore-solvent interactions are also investigated using Lippert-Mataga equation for naphthalimides and naphthalene benzimidazoles. Thermal stabilities of naphthalene benzimidazoles are better than naphthalimides due to increased aromaticity. The experimental E(LUMO) levels of naphthalene benzimidazoles are found to be between 3.15 and 3.28 eV. Therefore, naphthalene benzimidazole derivatives consisting of anchoring groups are promising materials in organic dye sensitized solar cells. © Springer Science+Business Media, LLC 2011

Thermal Conductivity of Polyimide/Carbon Nanofiller Blends

NASA Technical Reports Server (NTRS)

Ghose, S.; Watson, K. A.; Delozier, D. M.; Working, D. C.; Connell, J. W.; Smith, J. G.; Sun, Y. P.; Lin, Y.

2007-01-01

In efforts to improve the thermal conductivity (TC) of Ultem(TM) 1000, it was compounded with three carbon based nano-fillers. Multiwalled carbon nanotubes (MWCNT), vapor grown carbon nanofibers (CNF) and expanded graphite (EG) were investigated. Ribbons were extruded to form samples in which the nano-fillers were aligned. Samples were also fabricated by compression molding in which the nano-fillers were randomly oriented. The thermal properties were evaluated by DSC and TGA, and the mechanical properties of the aligned samples were determined by tensile testing. The degree of dispersion and alignment of the nanoparticles were investigated with high-resolution scanning electron microscopy. The thermal conductivity of the samples was measured in both the direction of alignment as well as perpendicular to that direction using the Nanoflash technique. The results of this study will be presented.

Thermal Conductivity of Polyimide/Nanofiller Blends

NASA Technical Reports Server (NTRS)

Ghose, S.; Watson, K. A.; Delozier, D. M.; Working, D. c.; Connell, J. W.; Smith, J. G.; Sun, Y. P.; Lin, Y.

2006-01-01

In efforts to improve the thermal conductivity of Ultem(TM) 1000, it was compounded with three carbon based nano-fillers. Multiwalled carbon nanotubes (MWCNT), vapor grown carbon nanofibers (CNF) and expanded graphite (EG) were investigated. Ribbons were extruded to form samples in which the nano-fillers were aligned. Samples were also fabricated by compression molding in which the nano-fillers were randomly oriented. The thermal properties were evaluated by DSC and TGA, and the mechanical properties of the aligned samples were determined by tensile testing. The degree of dispersion and alignment of the nanoparticles were investigated with high-resolution scanning electron microscopy. The thermal conductivity of the samples was measured in both the direction of alignment as well as perpendicular to that direction using the Nanoflash technique. The results of this study will be presented.

Effects of Long-Term Thermal Exposure on Commercially Pure Titanium Grade 2 Elevated-Temperature Tensile Properties

NASA Technical Reports Server (NTRS)

Ellis, David L.

2012-01-01

Elevated-temperature tensile testing of commercially pure titanium (CP Ti) Grade 2 was conducted for as-received commercially produced sheet and following thermal exposure at 550 and 650 K (531 and 711 F) for times up to 5000 h. The tensile testing revealed some statistical differences between the 11 thermal treatments, but most thermal treatments were statistically equivalent. Previous data from room temperature tensile testing was combined with the new data to allow regression and development of mathematical models relating tensile properties to temperature and thermal exposure. The results indicate that thermal exposure temperature has a very small effect, whereas the thermal exposure duration has no statistically significant effects on the tensile properties. These results indicate that CP Ti Grade 2 will be thermally stable and suitable for long-duration space missions.

Enhanced thermal and pyroelectric properties in 0-3 TGS:PVDF composites doped with graphene for infrared application

NASA Astrophysics Data System (ADS)

Feng, Xiaodong; Wang, Minqiang; Li, Le; Yang, Zhi; Cao, Minghui; Cheng, Z.-Y.

Pyroelectric composites of triglycine sulfate (TGS)-polyvinylidene difluoride (PVDF) doped with graphene are studied. It is found that the graphene can effectively improve the polling efficiency and thermal property of the composites so that the infrared detective performance can be significantly improved. For example, by adding about 0.83 wt.% of graphene, the infrared detective property can be improved by more than 30%. It is also found that the size of the graphene plays a critical role on the property improvement. For example, the small-sized graphene prepared by ultrasonic exfoliation (UE) method is more effective than the big-sized graphene prepared by electrochemical exfoliation (EE) method.

Production of thermal insulation blocks from bottom ash of fluidized bed combustion system.

PubMed

Mandal, A K; Sinha, O P

2017-08-01

The issues of disposal and environmental problems are increased by the generation of bottom ash from the thermal power plants day by day; hence, its recycling is required. The present study aimed to make thermal insulation blocks using as raw material bottom ash and iron ore slime as a binder and to characterize their engineering properties. Two different fineness values of bottom ash were considered with varying amounts of iron ore slime (0-10%) to make the blocks. Blocks were dried followed by firing at 1000, 1100 and 1200°C, respectively. Cold crushing strength, density and thermal conductivity of these fired blocks showed increasing behaviour with firing temperature, fineness of bottom ash and iron ore slime content. In contrast, a reverse trend was observed in the case of porosity. With increasing firing temperature, the formation of lower melting phases like iron silicate followed by iron aluminium silicate was observed, which imparts the strength inside the blocks. The coarser particles of bottom ash increase the interparticle spaces, which enhances the apparent porosity, resulting in higher thermal insulation property in the blocks. Blocks having better thermal insulation property could be possible to make effectively from coarse bottom ash by adding iron ore slime as a binder.

The use of polyimide-modified aluminum nitride fillers in AlN@PI/Epoxy composites with enhanced thermal conductivity for electronic encapsulation

PubMed Central

Zhou, Yongcun; Yao, Yagang; Chen, Chia-Yun; Moon, Kyoungsik; Wang, Hong; Wong, Ching-ping

2014-01-01

Polymer modified fillers in composites has attracted the attention of numerous researchers. These fillers are composed of core-shell structures that exhibit enhanced physical and chemical properties that are associated with shell surface control and encapsulated core materials. In this study, we have described an apt method to prepare polyimide (PI)-modified aluminum nitride (AlN) fillers, AlN@PI. These fillers are used for electronic encapsulation in high performance polymer composites. Compared with that of untreated AlN composite, these AlN@PI/epoxy composites exhibit better thermal and dielectric properties. At 40 wt% of filler loading, the highest thermal conductivity of AlN@PI/epoxy composite reached 2.03 W/mK. In this way, the thermal conductivity is approximately enhanced by 10.6 times than that of the used epoxy matrix. The experimental results exhibiting the thermal conductivity of AlN@PI/epoxy composites were in good agreement with the values calculated from the parallel conduction model. This research work describes an effective pathway that modifies the surface of fillers with polymer coating. Furthermore, this novel technique improves the thermal and dielectric properties of fillers and these can be used extensively for electronic packaging applications. PMID:24759082

Thermophysical properties of LiCoO₂-LiMn₂O₄ blended electrode materials for Li-ion batteries.

PubMed

Gotcu, Petronela; Seifert, Hans J

2016-04-21

Thermophysical properties of two cathode types for lithium-ion batteries were measured by dependence on temperature. The cathode materials are commercial composite thick films containing LiCoO2 and LiMn2O4 blended active materials, mixed with additives (binder and carbon black) deposited on aluminium current collector foils. The thermal diffusivities of the cathode samples were measured by laser flash analysis up to 673 K. The specific heat data was determined based on measured composite specific heat, aluminium specific heat data and their corresponding measured mass fractions. The composite specific heat data was measured using two differential scanning calorimeters over the temperature range from 298 to 573 K. For a comprehensive understanding of the blended composite thermal behaviour, measurements of the heat capacity of an additional LiMn2O4 sample were performed, and are the first experimental data up to 700 K. Thermal conductivity of each cathode type and their corresponding blended composite layers were estimated from the measured thermal diffusivity, the specific heat capacity and the estimated density based on metallographic methods and structural investigations. Such data are highly relevant for simulation studies of thermal management and thermal runaway in lithium-ion batteries, in which the bulk properties are assumed, as a common approach, to be temperature independent.

Evaluation of thermal stress in hydroxyapatite film fabricated by powder jet deposition.

PubMed

Akatsuka, Ryo; Matsumura, Ken; Noji, Miyoko; Kuriyagawa, Tsunemoto; Sasaki, Keiichi

2013-10-01

This study aimed to create a thick hydroxyapatite (HA) film on the surface of a human tooth via a powder jet deposition (PJD) device for dental handpieces, and to examine the microstructural and mechanical properties of the HA film. In particular, the effects of thermal stress on this film were evaluated. The HA film was created by blasting 3.18-μm HA particles, calcinated at 1,200°C, onto the enamel substrate at room temperature and atmospheric pressure. An HA film with an area of 3 mm × 3 mm was prepared and polished. The following HA film parameters were evaluated from the three-dimensional surface profile: surface roughness, Vickers hardness, and bonding strength before and after artificial aging induced by 500 cycles of thermal cycling (5-55°C). The HA particles in the deposited film were densely packed, and the surface of the HA film was unchanged after thermal cycling. There were also no significant differences in the hardness and the bonding strength of the HA film before and after thermal cycling. The HA film created in this study demonstrated excellent microstructural and mechanical properties, even after the application of thermal stress. © 2013 Eur J Oral Sci.

Influence of post-deposition annealing on structural, morphological and optical properties of copper (II) acetylacetonate thin films.

PubMed

Abdel-Khalek, H; El-Samahi, M I; El-Mahalawy, Ahmed M

2018-05-21

In this study, the effect of thermal annealing under vacuum conditions on structural, morphological and optical properties of thermally evaporated copper (II) acetylacetonate, cu(acac) 2 , thin films were investigated. The copper (II) acetylacetonate thin films were deposited using thermal evaporation technique at vacuum pressure ~1 × 10 -5  mbar. The deposited films were thermally annealed at 323, 373, 423, and 473 K for 2 h in vacuum. The thermogravimetric analysis of cu(acac) 2 powder indicated a thermal stability of cu(acac) 2 up to 423 K. The effects of thermal annealing on the structural properties of cu(acac) 2 were evaluated employing X-ray diffraction method and the analysis showed a polycrystalline nature of the as-deposited and annealed films with a preferred orientation in [1¯01] direction. Fourier transformation infrared (FTIR) technique was used to negate the decomposition of copper (II) acetylacetonate during preparation or/and annealing up to 423 K. The surface morphology of the prepared films was characterized by means of field emission scanning electron microscopy (FESEM). A significant enhancement of the morphological properties of cu(acac) 2 thin films was obtained till the annealing temperature reaches 423 K. The variation of optical constants that estimated from spectrophotometric measurements of the prepared thin films was investigated as a function of annealing temperature. The annealing process presented significantly impacted the nonlinear optical properties such as third-order optical susceptibility χ (3) and nonlinear refractive index n 2 of cu(acac) 2 thin films. Copyright © 2018 Elsevier B.V. All rights reserved.

Mechanical properties and shape memory effect of thermal-responsive polymer based on PVA

NASA Astrophysics Data System (ADS)

Lin, Liulan; Zhang, Lingfeng; Guo, Yanwei

2018-01-01

In this study, the effect of content of glutaraldehyde (GA) on the shape memory behavior of a shape memory polymer based on polyvinyl alcohol chemically cross-linked with GA was investigated. Thermal-responsive shape memory composites with three different GA levels, GA-PVA (3 wt%, 5 wt%, 7 wt%), were prepared by particle melting, mold forming and freeze-drying technique. The mechanical properties, thermal properties and shape memory behavior were measured by differential scanning calorimeter, physical bending test and cyclic thermo-mechanical test. The addition of GA to PVA led to a steady shape memory transition temperature and an improved mechanical compressive strength. The composite with 5 wt% of GA exhibited the best shape recoverability. Further increase in the crosslinking agent content of GA would reduce the recovery force and prolong the recovery time due to restriction in the movement of the soft PVA chain segments. These results provide important information for the study on materials in 4D printing.

Properties of Multifunctional Hybrid Carbon Nanotube/Carbon Fiber Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Cano, Roberto J.; Kang, Jin Ho; Grimsley, Brian W.; Ratcliffe, James G.; Siochi, Emilie J.

2016-01-01

For aircraft primary structures, carbon fiber reinforced polymer (CFRP) composites possess many advantages over conventional aluminum alloys due to their light weight, higher strength- and stiffness-to-weight ratios, and low life-cycle maintenance costs. However, the relatively low electrical and thermal conductivities of CFRP composites fail to provide structural safety in certain operational conditions such as lightning strikes. Carbon nanotubes (CNT) offer the potential to enhance the multi-functionality of composites with improved thermal and electrical conductivity. In this study, hybrid CNT/carbon fiber (CF) polymer composites were fabricated by interleaving layers of CNT sheets with Hexcel® IM7/8852 prepreg. Resin concentrations from 1 wt% to 50 wt% were used to infuse the CNT sheets prior to composite fabrication. The interlaminar properties of the resulting hybrid composites were characterized by mode I and II fracture toughness testing. Fractographical analysis was performed to study the effect of resin concentration. In addition, multi-directional physical properties like thermal conductivity of the orthotropic hybrid polymer composite were evaluated.

Effect of the interface on the mechanical properties and thermal conductivity of bismuth telluride films

NASA Astrophysics Data System (ADS)

Lai, Tang-Yu; Wang, Kuan-Yu; Fang, Te-Hua; Huang, Chao-Chun

2018-02-01

Bismuth telluride (Bi2Te3) is a type of thermoelectric material used for energy generation that does not cause pollution. Increasing the thermoelectric conversion efficiency (ZT) is one of the most important steps in the development of thermoelectric components. In this study, we use molecular dynamics to investigate the mechanical properties and thermal conductivity of quintuple layers of Bi2Te3 nanofilms with different atomic arrangements at the interface and study the effects of varying layers, angles, and grain boundaries. The results indicate that the Bi2Te3 nanofilm perfect substrate has the ideal Young’s modulus and thermal conductivity, and the maximum yield stress is observed for a thickness of ∼90 Å. As the interface changed, the structural disorder of atomic arrangement affected the mechanical properties; moreover, the phonons encounter lattice disordered atomic region will produce scattering reduce heat conduction. The results of this investigation are helpful for the application of Bi2Te3 nanofilms as thermoelectric materials.

Production and properties of high strength Ni free Zr-based BMGs

NASA Astrophysics Data System (ADS)

Iqbal, M.; Wang, W. H.

2014-06-01

Bulk metallic glasses (BMGs) are well known for very attractive physical, mechanical and thermal properties. Zr-based BMGs are used as structural materials in sports goods, electronics, jewelry, medical and aerospace applications. Ni free Zr48Cu36Al8M8 (M = Nb, Ti and Ta) BMGs are successfully synthesized by Cu mold casting technique. Differential scanning calorimetery (DSC) results show that the Zr48Cu36Al8Nb8 BMG have good thermal stability, wide supercooled liquid region of 80 K and contain the double stage crystallization. The alloy has fracture strength of 1.953 GPa. Shear angle was measured to be in the range of 43.5±5° for the alloy studied. Vicker's hardness of the BMGs was found to be over 500 Hv for the as cast alloy which enhanced about 11 % more by annealing up to 600 °C/20 min. Intersected shear bands were observed. The observed promising mechanical and thermal properties showed that BMG studied can be used for industrial applications.

Novel natural super-lattice materials with low thermal conductivity for thermoelectric applications: A first principles study

NASA Astrophysics Data System (ADS)

Sreeparvathy, P. C.; Kanchana, V.

2017-12-01

A systematic study which reveals the low thermal conductivity and high thermopower on a series of natural superlattice structures in the form BaXFCh (X: Cu, Ag, Ch: S, Se, Te), LaXSO (X: Cu, Ag) and SrCuTeF are presented. Low thermal conductivity is predicted by combining elastic constants and few well established models. The electronic properties reveal the highly two dimensional nature of band structure in the valence band, and this is confirmed through effective mass calculations. The huge difference in effective mass along different crystallographic directions in valence band introduces anisotropy in the transport properties for hole doping, and 'a' axis is found to be more favourable. In addition to these, the parameter A (S2σ/τT/κe /τ), which can decouple the relaxation time is also calculated, and it reveals the possibility of good thermoelectric properties in these compounds. Our results are comparable with prototype thermoelectric materials, and show better values than traditional TE materials.

Electrical, Thermal, and Magnetic Properties of Single Crystal CaMn2O4 Marokite

NASA Astrophysics Data System (ADS)

White, B. D.; Neumeier, J. J.; Souza, J. A.; Chiorescu, C.; Cohn, J. L.

2008-03-01

CaMn2O4 was first described [1] in 1963 as a natural mineral called Marokite. Since its discovery, it has been studied as a minor structural impurity phase in CMR- related CaMnO3 and for its structural similarities to high-pressure phases of spinel-oxide compounds. However, little attention has previously been paid to physical properties beyond its temperature-dependent magnetization. We will present a detailed physical properties study of CaMn2O4 single crystals grown by the optical floating zone method. [2] These measurements, several of which display anisotropy as a result of an orthorhombic crystal structure, include electrical transport, thermal transport, thermal expansion, heat capacity, and magnetization. [1] C. Gaudefroy, G. Jouravsky, F. Permingeat, Bull. Soc. Franc. Min'er. Crist. 86 (1963) 359. [2] B. D. White, C. A. M. dos Santos, J. A. Souza, K. J. McClellan, J. J. Neumeier submitted to J. Cryst. Growth.

Female upper body and breast skin temperature and thermal comfort following exercise.

PubMed

Ayres, B; White, J; Hedger, W; Scurr, J

2013-01-01

Breast support reduces breast pain and movement during exercise, however, an extra layer of clothing may affect thermoregulation. This preliminary study investigated female upper body and breast skin temperature and thermal comfort following short-duration exercise. Eight female participants with C-cup breasts had thermal images (infra-red camera, FLIR systems) of the bare breasts, the breasts in two sports bras (composite and polyester) and the abdomen, taken before and after 20 min of exercise at 28(o)C. Following exercise, bare-breast, bra and abdomen temperatures reduced by 0.61(o)C, 0.92(o)C and 2.06(o)C, respectively. The polyester sports bra demonstrated greater thermal comfort and enabled a greater change in skin temperature than the composite sports bra. It is concluded that following short-duration exercise, sports bras reduced the cooling ability of the breast. Material properties of the bras affect thermal comfort and post-exercise skin temperature; this should be an important consideration for sports bra manufacturers. This study investigates the effect of sports bras on thermal regulation of the breast following exercise. Sports bras negatively affected the cooling ability of the skin on the breast, with the material properties of the bra affecting thermal comfort following exercise. These results present important considerations for sports bra manufacturers.

Structural, electronic, elastic, and thermal properties of CaNiH3 perovskite obtained from first-principles calculations

NASA Astrophysics Data System (ADS)

Benlamari, S.; Bendjeddou, H.; Boulechfar, R.; Amara Korba, S.; Meradji, H.; Ahmed, R.; Ghemid, S.; Khenata, R.; Omran, S. Bin

2018-03-01

A theoretical study of the structural, elastic, electronic, mechanical, and thermal properties of the perovskite-type hydride CaNiH3 is presented. This study is carried out via first-principles full potential (FP) linearized augmented plane wave plus local orbital (LAPW+lo) method designed within the density functional theory (DFT). To treat the exchange–correlation energy/potential for the total energy calculations, the local density approximation (LDA) of Perdew–Wang (PW) and the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) are used. The three independent elastic constants (C 11, C 12, and C 44) are calculated from the direct computation of the stresses generated by small strains. Besides, we report the variation of the elastic constants as a function of pressure as well. From the calculated elastic constants, the mechanical character of CaNiH3 is predicted. Pertaining to the thermal properties, the Debye temperature is estimated from the average sound velocity. To further comprehend this compound, the quasi-harmonic Debye model is used to analyze the thermal properties. From the calculations, we find that the obtained results of the lattice constant (a 0), bulk modulus (B 0), and its pressure derivative ({B}0^{\\prime }) are in good agreement with the available theoretical as well as experimental results. Similarly, the obtained electronic band structure demonstrates the metallic character of this perovskite-type hydride.

The effect of filler parameters on the healing of thermal conductivity and mechanical properties of a thermal interface material based on a self-healable organic-inorganic polymer matrix

NASA Astrophysics Data System (ADS)

Zhong, Nan; Garcia, Santiago J.; van der Zwaag, Sybrand

2016-08-01

Thermal interface materials (TIMs) are widely used in all kinds of electronic devices to handle the heat dissipation and the mechanical anchoring of the heat producing component. The aging of TIMs may lead to delamination and internal crack formation causing a loss of heat transfer and mechanical integrity both leading to premature device failure. In the present work, a novel TIM system based on a self-healing organic-inorganic polymer matrix filled with spherical glass beads is presented which is capable of healing both the thermal conductivity and the mechanical properties upon thermal activation. The effect of particle volume concentration (PVC) and particle size on tensile strength and thermal conductivity healing behavior is investigated. The results show that a higher PVC increases the mechanical property but decreases mechanical healing. For the same PVC, bigger particles lead to lower mechanical properties but higher thermal conductivities and higher mechanical healing efficiencies.

Analysis of simplified heat transfer models for thermal property determination of nano-film by TDTR method

NASA Astrophysics Data System (ADS)

Wang, Xinwei; Chen, Zhe; Sun, Fangyuan; Zhang, Hang; Jiang, Yuyan; Tang, Dawei

2018-03-01

Heat transfer in nanostructures is of critical importance for a wide range of applications such as functional materials and thermal management of electronics. Time-domain thermoreflectance (TDTR) has been proved to be a reliable measurement technique for the thermal property determinations of nanoscale structures. However, it is difficult to determine more than three thermal properties at the same time. Heat transfer model simplifications can reduce the fitting variables and provide an alternative way for thermal property determination. In this paper, two simplified models are investigated and analyzed by the transform matrix method and simulations. TDTR measurements are performed on Al-SiO2-Si samples with different SiO2 thickness. Both theoretical and experimental results show that the simplified tri-layer model (STM) is reliable and suitable for thin film samples with a wide range of thickness. Furthermore, the STM can also extract the intrinsic thermal conductivity and interfacial thermal resistance from serial samples with different thickness.

Bio-composites of cassava starch-green coconut fiber: part II-Structure and properties.

PubMed

Lomelí-Ramírez, María Guadalupe; Kestur, Satyanarayana G; Manríquez-González, Ricardo; Iwakiri, Setsuo; de Muniz, Graciela Bolzon; Flores-Sahagun, Thais Sydenstricker

2014-02-15

Development of any new material requires its complete characterization to find potential applications. In that direction, preparation of bio-composites of cassava starch containing up to 30 wt.% green coconut fibers from Brazil by thermal molding process was reported earlier. Their characterization regarding physical and tensile properties of both untreated and treated matrices and their composites were also reported. Structural studies through FTIR and XRD and thermal stability of the above mentioned composites are presented in this paper. FT-IR studies revealed decomposition of components in the matrix; the starch was neither chemically affected nor modified by either glycerol or the amount of fiber. XRD studies indicated increasing crystallinity of the composites with increasing amount of fiber content. Thermal studies through TGA/DTA showed improvement of thermal stability with increasing amount of fiber incorporation, while DMTA showed increasing storage modulus, higher glass transition temperature and lower damping with increasing fiber content. Improved interfacial bonding between the matrix and fibers could be the cause for the above results. Copyright © 2013 Elsevier Ltd. All rights reserved.

Molecular Dynamics Simulation of the Thermophysical Properties of Quantum Liquid Helium Using the Feynman-Hibbs Potential

NASA Astrophysics Data System (ADS)

Liu, J.; Lu, W. Q.

2010-03-01

This paper presents the detailed MD simulation on the properties including the thermal conductivities and viscosities of the quantum fluid helium at different state points. The molecular interactions are represented by the Lennard-Jones pair potentials supplemented by quantum corrections following the Feynman-Hibbs approach and the properties are calculated using the Green-Kubo equations. A comparison is made among the numerical results using LJ and QFH potentials and the existing database and shows that the LJ model is not quantitatively correct for the supercritical liquid helium, thereby the quantum effect must be taken into account when the quantum fluid helium is studied. The comparison of the thermal conductivity is also made as a function of temperatures and pressure and the results show quantum effect correction is an efficient tool to get the thermal conductivities.

Electronic and Transport Properties of LaNi4Sb12 Skutterudite: Modified Becke-Johnson Approach

NASA Astrophysics Data System (ADS)

Bhat, Tahir Mohiuddin; Singh, Srishti; Gupta, Dinesh C.

2018-05-01

We carried out an ab initio study of structural, electronic, thermodynamic, and thermoelectric properties of the lanthanum-filled skutterudite, LaNi4Sb12. Generalized gradient approximation and modified Becke-Johnson potentials were employed for the exchange-correlation potential. The electronic structure calculations display the metallic behavior of the compound. The alloy offers low lattice thermal conductivity along with a high Seebeck coefficient with a value of - 158 (μVK-1) at room temperature. The effect of high pressure and temperature on thermal properties like thermal expansion coefficient, heat capacity, and Grüneisen parameter are also investigated by means of a quasi-harmonic Debye model. The large Seebeck coefficient and high power factor exhibited by LaNi4Sb12 make it an attractive candidate for thermoelectric materials.

Sustainability of Recycled ABS and PA6 by Banana Fiber Reinforcement: Thermal, Mechanical and Morphological Properties

NASA Astrophysics Data System (ADS)

Singh, Rupinder; Kumar, Ranvijay; Ranjan, Nishant

2018-01-01

In the present study efforts have been made to prepare functional prototypes with improved thermal, mechanical and morphological properties from polymeric waste for sustainability. The primary recycled acrylonitrile butadiene styrene (ABS) and polyamide 6 (PA6) has been selected as matrix material with bio-degradable and bio-compatible banana fibers (BF) as reinforcement. The blend (in form of feed stock filament wire) of ABS/PA6 and BF was prepared in house by conventional twin screw extrusion (TSE) process. Finally feed stock filament of ABS/PA6 reinforced with BF was put to run on open source fused deposition modelling based three dimensional printer (without any change in hardware/software of the system) for printing of functional prototypes with improved thermal/mechanical/morphological properties. The results are supported by photomicrographs, thermographs and mechanical testing.

Adaptive Photothermal Emission Analysis Techniques for Robust Thermal Property Measurements of Thermal Barrier Coatings

NASA Astrophysics Data System (ADS)

Valdes, Raymond

The characterization of thermal barrier coating (TBC) systems is increasingly important because they enable gas turbine engines to operate at high temperatures and efficiency. Phase of photothermal emission analysis (PopTea) has been developed to analyze the thermal behavior of the ceramic top-coat of TBCs, as a nondestructive and noncontact method for measuring thermal diffusivity and thermal conductivity. Most TBC allocations are on actively-cooled high temperature turbine blades, which makes it difficult to precisely model heat transfer in the metallic subsystem. This reduces the ability of rote thermal modeling to reflect the actual physical conditions of the system and can lead to higher uncertainty in measured thermal properties. This dissertation investigates fundamental issues underpinning robust thermal property measurements that are adaptive to non-specific, complex, and evolving system characteristics using the PopTea method. A generic and adaptive subsystem PopTea thermal model was developed to account for complex geometry beyond a well-defined coating and substrate system. Without a priori knowledge of the subsystem characteristics, two different measurement techniques were implemented using the subsystem model. In the first technique, the properties of the subsystem were resolved as part of the PopTea parameter estimation algorithm; and, the second technique independently resolved the subsystem properties using a differential "bare" subsystem. The confidence in thermal properties measured using the generic subsystem model is similar to that from a standard PopTea measurement on a "well-defined" TBC system. Non-systematic bias-error on experimental observations in PopTea measurements due to generic thermal model discrepancies was also mitigated using a regression-based sensitivity analysis. The sensitivity analysis reported measurement uncertainty and was developed into a data reduction method to filter out these "erroneous" observations. It was found that the adverse impact of bias-error can be greatly reduced, leaving measurement observations with only random Gaussian noise in PopTea thermal property measurements. Quantifying the influence of the coating-substrate interface in PopTea measurements is important to resolving the thermal conductivity of the coating. However, the reduced significance of this interface in thicker coating systems can give rise to large uncertainties in thermal conductivity measurements. A first step towards improving PopTea measurements for such circumstances has been taken by implementing absolute temperature measurements using harmonically-sustained two-color pyrometry. Although promising, even small uncertainties in thermal emission observations were found to lead to significant noise in temperature measurements. However, PopTea analysis on bulk graphite samples were able to resolve its thermal conductivity to the expected literature values.

Star-shaped azomethines based on tris(2-aminoethyl)amine. Characterization, thermal and optical study.

PubMed

Iwan, Agnieszka; Janeczek, Henryk; Kaczmarczyk, Bozena; Jarzabek, Bozena; Sobota, Michal; Rannou, Patrice

2010-02-01

The synthesis and detailed (physico)-chemical ((1)H/(13)C NMR, FTIR, UV-vis and elemental analysis) characterizations of new star-shaped compounds based on tris(2-aminoethyl)amine, including in their structure an azomethine function (HCN-) and alkoxysemiperfluorinated (-O-(CH(2))(3)-(CF(2))(7)-CF(3)), octadecyloxy aliphatic (-O-(CH(2))(17)-CH(3)) chain or two phenyl rings (-Ph-Ph-) as a terminal group, were reported. The mesomorphic behavior was investigated by means of differential scanning calorimetry (DSC), polarized optical microscopy (POM) and additionally by FTIR(T) and UV-vis(T) spectroscopy. Wide-angle X-ray diffraction (WAXD) technique was used to probe the structural properties of the azomethines. Moreover, the azomethine A1 was electro-spun to prepare fibers with poly(methyl methacrylate) (PMMA) and investigated by DSC and POM. Additionally, a film of the A1 with PMMA was cast from chloroform and the thermal properties of the film were compared with the thermal properties of the fiber and powder. It was showed that terminal groups dramatically influence the thermal and optical properties of the star-shaped azomethines. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Humidity effects on soluble core mechanical and thermal properties (polyvinyl alcohol/microballoon composite) type CG extendospheres, volume 2

NASA Technical Reports Server (NTRS)

1993-01-01

This document constitutes the final report for the study of humidity effects and loading rate on soluble core (PVA/MB composite material) mechanical and thermal properties under Contract No. 100345. This report describes test results procedures employed, and any unusual occurrences or specific observations associated with this test program. The primary objective of this work was to determine if cured soluble core filler material regains its tensile and compressive strength after exposure to high humidity conditions and following a drying cycle. Secondary objectives include measurements of tensile and compressive modulus, and Poisson's ratio, and coefficient of thermal expansion (CTE) for various moisture exposure states. A third objective was to compare the mechanical and thermal properties of the composite using 'SG' and 'CG' type extendospheres. The proposed facility for the manufacture of soluble cores at the Yellow Creek site incorporates no capability for the control of humidity. Recent physical property tests performed with the soluble core filler material showed that prolonged exposure to high humidity significantly degradates in strength. The purpose of these tests is to determine if the product, process or facility designs require modification to avoid imparting a high risk condition to the ASRM.

Thermal transport and thermoelectric properties of beta-graphyne nanostructures.

PubMed

Ouyang, Tao; Hu, Ming

2014-06-20

Graphyne, an allotrope of graphene, is currently a hot topic in the carbon-based nanomaterials research community. Taking beta-graphyne as an example, we performed a comprehensive study of thermal transport and related thermoelectric properties by means of nonequilibrium Green's function (NEGF). Our simulation demonstrated that thermal conductance of beta-graphyne is only approximately 26% of that of the graphene counterpart and also shows evident anisotropy. Meanwhile, thermal conductance of armchair beta-graphyne nanoribbons (A-BGYNRs) presents abnormal stepwise width dependence. As for the thermoelectric property, we found that zigzag beta-graphyne nanoribbons (Z-BGYNRs) possess superior thermoelectric performance with figure of merit value achieving 0.5 at room temperature, as compared with graphene nanoribbons (~0.05). Aiming at obtaining a better thermoelectric coefficient, we also investigated Z-BGYNRs with geometric modulations. The results show that the thermoelectric performance can be enhanced dramatically (figure of merit exceeding 1.5 at room temperature), and such enhancement strongly depends on the width of the nanoribbons and location and quantity of geometric modulation. Our findings shed light on transport properties of beta-graphyne as high efficiency thermoelectrics. We anticipate that our simulation results could offer useful guidance for the design and fabrication of future thermoelectric devices.

A Comparative Study on the Mechanical, Thermal and Morphological Characterization of Poly(lactic acid)/Epoxidized Palm Oil Blend

PubMed Central

Giita Silverajah, V. S.; Ibrahim, Nor Azowa; Yunus, Wan Md Zin Wan; Hassan, Hazimah Abu; Woei, Chieng Buong

2012-01-01

In this work, poly(lactic acid) (PLA) a fully biodegradable thermoplastic polymer matrix was melt blended with three different epoxidized palm oil (EPO). The aim of this research was to enhance the flexibility, mechanical and thermal properties of PLA. The blends were prepared at various EPO contents of 1, 2, 3, 4 and 5 wt% and characterized. The SEM analysis evidenced successful modification on the neat PLA brittle morphology. Tensile tests indicate that the addition of 1 wt% EPO is sufficient to improve the strength and flexibility compared to neat PLA. Additionally, the flexural and impact properties were also enhanced. Further, DSC analysis showed that the addition of EPO results in a decrease in Tg, which implies an increase in the PLA chain mobility. In the presence of 1 wt% EPO, TGA results revealed significant increase in the thermal stability by 27%. Among the three EPOs used, EPO(3) showed the best mechanical and thermal properties compared to the other EPO’s, with an optimum loading of 1 wt%. Conclusively, EPO showed a promising outcome to overcome the brittleness and improve the overall properties of neat PLA, thus can be considered as a potential plasticizer. PMID:22754338

A comparative study on the mechanical, thermal and morphological characterization of poly(lactic acid)/epoxidized Palm Oil blend.

PubMed

Giita Silverajah, V S; Ibrahim, Nor Azowa; Yunus, Wan Md Zin Wan; Hassan, Hazimah Abu; Woei, Chieng Buong

2012-01-01

In this work, poly(lactic acid) (PLA) a fully biodegradable thermoplastic polymer matrix was melt blended with three different epoxidized palm oil (EPO). The aim of this research was to enhance the flexibility, mechanical and thermal properties of PLA. The blends were prepared at various EPO contents of 1, 2, 3, 4 and 5 wt% and characterized. The SEM analysis evidenced successful modification on the neat PLA brittle morphology. Tensile tests indicate that the addition of 1 wt% EPO is sufficient to improve the strength and flexibility compared to neat PLA. Additionally, the flexural and impact properties were also enhanced. Further, DSC analysis showed that the addition of EPO results in a decrease in T(g), which implies an increase in the PLA chain mobility. In the presence of 1 wt% EPO, TGA results revealed significant increase in the thermal stability by 27%. Among the three EPOs used, EPO(3) showed the best mechanical and thermal properties compared to the other EPO's, with an optimum loading of 1 wt%. Conclusively, EPO showed a promising outcome to overcome the brittleness and improve the overall properties of neat PLA, thus can be considered as a potential plasticizer.

Microbial production, ultrasound-assisted extraction and characterization of biopolymer polyhydroxybutyrate (PHB) from terrestrial (P. hysterophorus) and aquatic (E. crassipes) invasive weeds.

PubMed

Pradhan, Sushobhan; Borah, Arup Jyoti; Poddar, Maneesh Kumar; Dikshit, Pritam Kumar; Rohidas, Lilendar; Moholkar, Vijayanand S

2017-10-01

This study reports synthesis of biodegradable poly(3-hydroxybutyrate) (PHB) polymer from two invasive weeds, viz. P. hysterophorus and E. crassipes. The pentose and hexose-rich hydrolyzates obtained from acid pretreatment and enzymatic hydrolysis of two biomasses were separately fermented using Ralstonia eutropha MTCC 8320 sp. PHB was extracted using sonication and was characterized using FTIR, 1 H and 13 C NMR and XRD. PHB content of dry cell mass was 8.1-21.6% w/w, and the PHB yield was 6.85×10 -3 -36.41×10 -3 % w/w raw biomass. Thermal properties of PHB were determined by TGA, DTG and DSC analysis. PHB obtained from pentose-hydrolyzate had glass transition temperatures of 6°-9°C, while PHB from hexose-rich hydrolyzate had maximum thermal degradation temperatures of 370°-389°C. These thermal properties were comparable to the properties of commercial PHB. Probable causes leading to differences in thermal properties of pentose and hexose-derived PHB are: extent of crystallinity and presence of impurity in the polymer matrix. Copyright © 2017 Elsevier Ltd. All rights reserved.

Surface Chemistry Manipulation of Gold Nanorods Displays High Cellular Uptake In Vitro While Preserving Optical Properties for Bio-Imaging and Photo-Thermal Applications

DTIC Science & Technology

2016-03-28

PROPERTIES FOR BIO -IMAGING AND PHOTO-THERMAL APPLICATIONS ANTHONY B. POLITO III, Maj, USAF, BSC, PhD, MT(ASCP)SBB March 2016 Final Report for March...HIGH CELLULAR UPTAKE IN VITRO WHILE PRESERVING OPTICAL PROPERTIES FOR BIO -IMAGING AND PHOTO-THERMAL APPLICATIONS. 5a. CONTRACT NUMBER 5b...These findings identify MTAB-TA GNRs as prime candidates for use in nano-based bio -imaging and photo-thermal applications. 15. SUBJECT TERMS

Structural, chemical and physical properties of pure and La3+ doped L-Threonine acetate crystals

NASA Astrophysics Data System (ADS)

Senthamizhan, A.; Sambathkumar, K.; Nithiyanantham, S.; Venkatachalapathy, M.; Rajkamal, N.

2017-12-01

The pure and La3+ doped L- Threonine crystals can be grown by slow evaporation techniques. The crystal structure were examined through X-Ray diffraction (XRD) analysis, confirmed the P212121 system. The quantitative nature of dopant can be analyzed with Inductively Coupled Plasma (ICP) study. The Fourier Transform Infra-Red (FTIR) and Fourier Transform (FT- Raman) investigations yields the possible stretching/bonding with their functional groups and the qualitative/quantitative nature of both crystals is analyzed. The optical behavior of crystals can be studied through Ultra Violet (UV) - Visible spectrometer. The mechanical, thermal and decomposition studies can be carried out through Vickers hardness test, Thermo Gravometric Analysis (TGA) and Differential Thermal Analysis (DTA). The Non Linear Optical (NLO) properties are found more than Potassium Phosphate (KDP) through Kurtz powders technique. The dielectric and optical absorption studies for both pure and L-doped crystals were studied and interpreted all the properties. The La3+ dopant increases the properties are investigated.

36 CFR 21.3 - Use of thermal water.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 36 Parks, Forests, and Public Property 1 2013-07-01 2013-07-01 false Use of thermal water. 21.3 Section 21.3 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR HOT SPRINGS NATIONAL PARK; BATHHOUSE REGULATIONS § 21.3 Use of thermal water. (a) The use of the thermal...

Contribution to the study of thermal properties of clay bricks reinforced by date palm fiber

NASA Astrophysics Data System (ADS)

Mekhermeche, A.; Kriker, A.; Dahmani, S.

2016-07-01

The Saharan regions of Algeria are characterized by a hot and dry climate. The most used cement materials such as theconcrete or the mortar blocks have bad thermal characteristic. However, these regions have several local materials: clay, dune sand and some natural fibers, which are formerly proved their thermal efficiency. The price of construction material used therefore depends on the international market constantly destabilized by theeconomic crisis coupled with the energy crisis in recent times. To produce a framework of life at a lower cost, it is important, therefore, to circumvent the influence of the cost of energy by upgrading the local materials of construction. In order to improve thermal performances in Saharan building materials this study was lanced. The aim of this research isthen to fabricate some bricks using three local materials: namely the clay, sand dune and the fibers of date palm. The percentage of sand and fibers varies from 0% to 40% and 0% to 3% by mass respectively. A sand dune of Ain El Beida of Ouargla of Algeria was used. Clay was extracted from Beldet Amer of Touggourt Ouargla Algérie. The fibers used in this study were vegetable fibers from date palm of Ouargla Algeria. The results showed that increasing in the mass fraction of sand and of fiber were beneficial for improving thermal properties. As function of increasing the percentage of sand dune and fibers there were: A decrease in: thermal conductivity, specific heat, heat capacity, thermal effusivity and thermal diffusivity and there were an increase in the thermal resistance.

Effect of titanium addition on the thermal properties of diamond/cu-ti composites fabricated by pressureless liquid-phase sintering technique.

PubMed

Chung, Chih-Yu; Chu, Chao-Hung; Lee, Mu-Tse; Lin, Chun-Ming; Lin, Su-Jien

2014-01-01

In this study, minor-addition elements such as Si, Co, Cr, W, Mo, and Ti were added to matrix to improve the wettability between the diamonds and Cu matrix. The pressureless liquid-phase sintering technique adopted in this study provides a low-cost method for producing diamond/Cu composites with high potential for industrial mass production. Thermal properties of the diamond/Cu-Ti composites fabricated by pressureless liquid-phase sintering at 1373 K with variation in Ti contents were thoroughly investigated. XRD and TEM analysis show that TiC layer formed in the interface between Cu and diamond. The composites exhibited thermal conductivity as high as 620 W/m · K for 50 vol% diamond/Cu-0.6 at % Ti composite with diamond particle size of 300 µm. This value comes up to 85% of the thermal conductivity calculated by the Hasselman and Johnson (H-J) theoretical analysis. Under these conditions, a suitable coefficient of thermal expansion of 6.9 ppm/K was obtained.

Effect of Titanium Addition on the Thermal Properties of Diamond/Cu-Ti Composites Fabricated by Pressureless Liquid-Phase Sintering Technique

PubMed Central

Chung, Chih-Yu; Chu, Chao-Hung; Lee, Mu-Tse; Lin, Chun-Ming; Lin, Su-Jien

2014-01-01

In this study, minor-addition elements such as Si, Co, Cr, W, Mo, and Ti were added to matrix to improve the wettability between the diamonds and Cu matrix. The pressureless liquid-phase sintering technique adopted in this study provides a low-cost method for producing diamond/Cu composites with high potential for industrial mass production. Thermal properties of the diamond/Cu-Ti composites fabricated by pressureless liquid-phase sintering at 1373 K with variation in Ti contents were thoroughly investigated. XRD and TEM analysis show that TiC layer formed in the interface between Cu and diamond. The composites exhibited thermal conductivity as high as 620 W/m·K for 50 vol% diamond/Cu-0.6  at % Ti composite with diamond particle size of 300 µm. This value comes up to 85% of the thermal conductivity calculated by the Hasselman and Johnson (H-J) theoretical analysis. Under these conditions, a suitable coefficient of thermal expansion of 6.9 ppm/K was obtained. PMID:24715816

Thermophysical properties of heat-treated U-7Mo/Al dispersion fuel

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

Cho, Tae Won; Kim, Yeon Soo; Park, Jong Man

In this study, the effects of interaction layer (IL) on thermophysical properties of U-7Mo/Al dispersion fuel were examined. Microstructural analyses revealed that ILs were formed uniformly on U-Mo particles during heating of U-7Mo/Al samples. The IL volume fraction was measured by applying image analysis methods. The uranium loadings of the samples were calculated based on the measured meat densities at 298 K. The density of the IL was estimated by using the measured density and IL volume fraction. Thermal diffusivity and heat capacity of the samples after the heat treatment were measured as a function of temperature and volume fractionsmore » of U-Mo and IL. The thermal conductivity of IL-formed U-7Mo/Al was derived by using the measured thermal diffusivity, heat capacity, and density. The thermal conductivity obtained in the present study was lower than that predicted by the modified Hashin–Shtrikman model due to the theoretical model’s inability to consider the thermal resistance at interfaces between the meat constituents.« less

Measurement of Thermal Conductivities of Two Cryoprotective Agent Solutions for Vitreous Cryopreservation of Organs at the Temperature Range of 77 K-300 K Using a Thermal Sensor Made of Microscale Enamel Copper Wire.

PubMed

Li, Yufang; Zhao, Gang; Hossain, S M Chapal; Panhwar, Fazil; Sun, Wenyu; Kong, Fei; Zang, Chuanbao; Jiang, Zhendong

2017-06-01

Biobanking of organs by cryopreservation is an enabling technology for organ transplantation. Compared with the conventional slow freezing method, vitreous cryopreservation has been regarded to be a more promising approach for long-term storage of organs. The major challenges to vitrification are devitrification and recrystallization during the warming process, and high concentrations of cryoprotective agents (CPAs) induced metabolic and osmotic injuries. For a theoretical model based optimization of vitrification, thermal properties of CPA solutions are indispensable. In this study, the thermal conductivities of M22 and vitrification solution containing ethylene glycol and dimethyl sulfoxide (two commonly used vitrification solutions) were measured using a self-made microscaled hot probe with enameled copper wire at the temperature range of 77 K-300 K. The data obtained by this study will further enrich knowledge of the thermal properties for CPA solutions at low temperatures, as is of primary importance for optimization of vitrification.

Study of hot thermally fissile nuclei using relativistic mean field theory

NASA Astrophysics Data System (ADS)

Quddus, Abdul; Naik, K. C.; Patra, S. K.

2018-07-01

We have studied the properties of hot 234,236U and 240Pu nuclei in the framework of relativistic mean field formalism. The recently developed FSUGarnet and IOPB-I parameter sets are implemented for the first time to deform nuclei at finite temperature. The results are compared with the well known NL3 set. The said isotopes are structurally important because of the thermally fissile nature of 233,235U and 239Pu as these nuclei (234,236U and 240Pu) are formed after the absorption of a thermal neutron, which undergoes fission. Here, we have evaluated the nuclear properties, such as shell correction energy, neutron-skin thickness, quadrupole and hexadecapole deformation parameters and asymmetry energy coefficient for these nuclei as a function of temperature.

Dynamic properties of polydisperse colloidal particles in the presence of thermal gradient studied by a modified Brownian dynamic model

NASA Astrophysics Data System (ADS)

Song, Dongxing; Jin, Hui; Jing, Dengwei; Wang, Xin

2018-03-01

Aggregation and migration of colloidal particles under the thermal gradient widely exists in nature and many industrial processes. In this study, dynamic properties of polydisperse colloidal particles in the presence of thermal gradient were studied by a modified Brownian dynamic model. Other than the traditional forces on colloidal particles, including Brownian force, hydrodynamic force, and electrostatic force from other particles, the electrostatic force from the asymmetric ionic diffusion layer under a thermal gradient has been considered and introduced into the Brownian dynamic model. The aggregation ratio of particles (R A), the balance time (t B) indicating the time threshold when {{R}A} becomes constant, the porosity ({{P}BA} ), fractal dimension (D f) and distributions of concentration (DISC) and aggregation (DISA) for the aggregated particles were discussed based on this model. The aggregated structures formed by polydisperse particles are less dense and the particles therein are loosely bonded. Also it showed a quite large compressibility as the increases of concentration and interparticle potential can significantly increase the fractal dimension. The thermal gradient can induce two competitive factors leading to a two-stage migration of particles. When t<{{t}B} , the unsynchronized aggregation is dominant and the particles slightly migrate along the thermal gradient. When t>{{t}B} , the thermophoresis becomes dominant thus the migrations of particles are against the thermal gradient. The effect of thermophoresis on the aggregate structures was found to be similar to the effect of increasing particle concentration. This study demonstrates how the thermal gradient affects the aggregation of monodisperse and polydisperse particles and can be a guide for the biomimetics and precise control of colloid system under the thermal gradient. Moreover, our model can be easily extended to other more complex colloidal systems considering shear, temperature fluctuation, surfactant, etc.

Calibration of a thin metal foil for infrared imaging video bolometer to estimate the spatial variation of thermal diffusivity using a photo-thermal technique.

PubMed

Pandya, Shwetang N; Peterson, Byron J; Sano, Ryuichi; Mukai, Kiyofumi; Drapiko, Evgeny A; Alekseyev, Andrey G; Akiyama, Tsuyoshi; Itomi, Muneji; Watanabe, Takashi

2014-05-01

A thin metal foil is used as a broad band radiation absorber for the InfraRed imaging Video Bolometer (IRVB), which is a vital diagnostic for studying three-dimensional radiation structures from high temperature plasmas in the Large Helical Device. The two-dimensional (2D) heat diffusion equation of the foil needs to be solved numerically to estimate the radiation falling on the foil through a pinhole geometry. The thermal, physical, and optical properties of the metal foil are among the inputs to the code besides the spatiotemporal variation of temperature, for reliable estimation of the exhaust power from the plasma illuminating the foil. The foil being very thin and of considerable size, non-uniformities in these properties need to be determined by suitable calibration procedures. The graphite spray used for increasing the surface emissivity also contributes to a change in the thermal properties. This paper discusses the application of the thermographic technique for determining the spatial variation of the effective in-plane thermal diffusivity of the thin metal foil and graphite composite. The paper also discusses the advantages of this technique in the light of limitations and drawbacks presented by other calibration techniques being practiced currently. The technique is initially applied to a material of known thickness and thermal properties for validation and finally to thin foils of gold and platinum both with two different thicknesses. It is observed that the effect of the graphite layer on the estimation of the thermal diffusivity becomes more pronounced for thinner foils and the measured values are approximately 2.5-3 times lower than the literature values. It is also observed that the percentage reduction in thermal diffusivity due to the coating is lower for high thermal diffusivity materials such as gold. This fact may also explain, albeit partially, the higher sensitivity of the platinum foil as compared to gold.

Calibration of a thin metal foil for infrared imaging video bolometer to estimate the spatial variation of thermal diffusivity using a photo-thermal technique

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

Pandya, Shwetang N., E-mail: pandya.shwetang@LHD.nifs.ac.jp; Sano, Ryuichi; Peterson, Byron J.

A thin metal foil is used as a broad band radiation absorber for the InfraRed imaging Video Bolometer (IRVB), which is a vital diagnostic for studying three-dimensional radiation structures from high temperature plasmas in the Large Helical Device. The two-dimensional (2D) heat diffusion equation of the foil needs to be solved numerically to estimate the radiation falling on the foil through a pinhole geometry. The thermal, physical, and optical properties of the metal foil are among the inputs to the code besides the spatiotemporal variation of temperature, for reliable estimation of the exhaust power from the plasma illuminating the foil.more » The foil being very thin and of considerable size, non-uniformities in these properties need to be determined by suitable calibration procedures. The graphite spray used for increasing the surface emissivity also contributes to a change in the thermal properties. This paper discusses the application of the thermographic technique for determining the spatial variation of the effective in-plane thermal diffusivity of the thin metal foil and graphite composite. The paper also discusses the advantages of this technique in the light of limitations and drawbacks presented by other calibration techniques being practiced currently. The technique is initially applied to a material of known thickness and thermal properties for validation and finally to thin foils of gold and platinum both with two different thicknesses. It is observed that the effect of the graphite layer on the estimation of the thermal diffusivity becomes more pronounced for thinner foils and the measured values are approximately 2.5–3 times lower than the literature values. It is also observed that the percentage reduction in thermal diffusivity due to the coating is lower for high thermal diffusivity materials such as gold. This fact may also explain, albeit partially, the higher sensitivity of the platinum foil as compared to gold.« less

Optical and thermal properties in ultrafast laser surface nanostructuring on biodegradable polymer

NASA Astrophysics Data System (ADS)

Yada, Shuhei; Terakawa, Mitsuhiro

2015-03-01

We investigate the effect of optical and thermal properties in laser-induced periodic surface structures (LIPSS) formation on a poly-L-lactic acid (PLLA), a biodegradable polymer. Surface properties of biomaterials are known to be one of the key factors in tissue engineering. Methods to process biomaterial surfaces have been studied widely to enhance cell adhesive and anisotropic properties. LIPSS formation has advantages in a dry processing which is able to process complex-shaped surfaces without using a toxic chemical component. LIPSS, however, was difficult to be formed on PLLA due to its thermal and optical properties compared to other polymers. To obtain new perspectives in effect of these properties above, LIPSS formation dependences on wavelength, pulse duration and repetition rate have been studied. At 800 nm of incident wavelength, high-spatial frequency LIPSS (HSFL) was formed after applying 10000 femtosecond pulses at 1.0 J/cm2 in laser fluence. At 400 nm of the wavelength, HSFL was formed at fluences higher than 0.20 J/cm2 with more than 3000 pulses. Since LIPSS was less formed with lower repetition rate, certain heat accumulation may be required for LIPSS formation. With the pulse duration of 2.0 ps, higher laser fluence as well as number of pulses compared to the case of 120 fs was necessary. This indicates that multiphoton absorption process is essential for LIPSS formation. Study on biodegradation modification was also performed.

Thermophysical Properties of Lithium Alloys for Thermal Batteries

NASA Astrophysics Data System (ADS)

Swift, Geoffrey A.

2011-10-01

Thermal batteries are electrochemical systems primarily used in defense applications. The long-term storage capability afforded by the electrically inert low-temperature properties of the electrolyte-separator enables the use of this technology for military purposes. The current state-of-the art for thermal batteries relies upon the Li/FeS2 couple for power generation with the anode typically an Li-Si or Li-Al alloy. Thermal modeling of these primary battery systems is crucial to allowing the predictive capability of thermal evolution both in terms of the battery lifetime and thermal profile for the proper design of internal insulation and the surrounding environment. However, thermophysical properties for the anode alloys are not available in the literature. Thermophysical measurements of the alloys used in thermal batteries are essential for thermal modeling and simulation. The laser-flash method was used to determine the specific heat, thermal diffusivity, and thermal conductivity for Li-Si and Li-Al alloys as a function of temperature.

Performance benefits from pulsed laser heating in heat assisted magnetic recording

NASA Astrophysics Data System (ADS)

Xu, B. X.; Cen, Z. H.; Goh, J. H.; Li, J. M.; Toh, Y. T.; Zhang, J.; Ye, K. D.; Quan, C. G.

2014-05-01

Smaller cross track thermal spot size and larger down track thermal gradient are desired for increasing the density of heat assisted magnetic recording. Both parameters are affected significantly by the thermal energy accumulation and diffusion in the recording media. Pulsed laser heating is one of the ways to reduce the thermal diffusion. In this paper, we describe the benefits from the pulsed laser heating such as the dependences of the cross track thermal width, down track thermal gradient, the required laser pulse/average powers, and the transducer temperature rise on the laser pulse width at different media thermal properties. The results indicate that as the pulse width decreases, the thermal width decreases, the thermal gradient increases, the required pulse power increases and the average power decreases. For shorter pulse heating, the effects of the medium thermal properties on the thermal performances become weaker. This can greatly relax the required thermal properties of the media. The results also show that the pulsed laser heating can effectively reduce the transducer temperature rise and allow the transducer to reach its "dynamically" stable temperature more quickly.

Measurement of Thermal Properties of Rocks at Temperature up to 1,000°C with Transient Plane Source Techniques

NASA Astrophysics Data System (ADS)

Kim, S. K.; Lee, Y.

2017-12-01

A set of devices that can measure thermal properties of rocks over a temperature range from room temperature up to 1,000°C with transient plane source techniques (also known as a Hot Disk method) is introduced. It consists of a main control system (e.g., TPS 2500 S from Hot Disk), mica-insulated sensor, tubular furnace, N2 gas supplier, and pressure regulator. The TPS 2500 S is the core instrument designed for precise analysis of thermal transport properties including thermal conductivity, thermal diffusivity, and volumetric heat capacity. The mica-insulated sensor is composed of an insulated nickel double spiral, which is utilized for both transient heating and precise temperature reading; a mica insulator protects the sensor against mechanical and thermal damage at high temperatures. The tubular furnace can hold two rock core samples of 50-mm-diameter and 25-mm-height with increasing temperatures up to 1,000°C. N2 gas supplier and pressure regulator are used to keep the inside the furnace away from oxygen. Thermal properties of most rocks and minerals vary with increasing temperatures. Experimental measurements of thermal properties at high temperatures have been made mostly using laser flash, needle probe, and divided bar methods in the previous researches, and no previous measurements with the Hot Disk method have been reported yet. We report thermal conductivities, thermal diffusivities, and volumetric heat capacities determined by a transient plane heat source method for fused silica and mafic rock samples using the introduced transient plane source apparatus. The thermal properties of fused silica have been measured mainly over the temperature range from ambient temperature to 500°C. The results seem to agree moderately with the previously reported values by Birch and Clark (Am. J. Sci., 1940). We now check the possible causes of measurement errors in our measurements and prepare to measure thermal properties of the mafic rock samples at temperatures up to 1,000°C using the hot disk method.

The effects of temperature on fiber composite bridge decks.

DOT National Transportation Integrated Search

2009-01-01

In this study the fiber composite bridge decks were subjected to thermal gradients to obtain the temperature difference between the top and bottom surface of the decks and to determine the thermal properties of the deck. The fiber composite bridge de...

Preparation and physical properties of tara gum film reinforced with cellulose nanocrystals.

PubMed

Ma, Qianyun; Hu, Dongying; Wang, Lijuan

2016-05-01

Cellulose nanocrystals (CNC) prepared from microcrystalline cellulose were blended in tara gum solution to prepare nanocomposite films. The morphology, crystallinity, and thermal properties of the CNC and films were evaluated by using transmission electron microscopy, X-ray diffractometry, and thermogravimetric analysis, respectively. The resultant CNC was rod-shaped with diameters of around 8.6 nm. The effect of CNC content on physical and thermal properties of films was studied. The composite film tensile strength increased from 27.86 to 65.73 MPa, elastic modulus increased from 160.98 MPa to 882.49 MPa and the contact angle increased from 55.8° to 98.7° with increasing CNC content from 0 to 6 wt%. However, CNC addition increased the thermal stability slightly and CNC content above 6 wt% decreased the tensile strength by CNC aggregation in the matrix. The nanocomposite film containing 6 wt% CNC possessed the highest light transmittance, mechanical properties, and lowest oxygen permeability. CNC addition is a suitable method to modify tara gum matrix polymer properties. Copyright © 2016 Elsevier B.V. All rights reserved.

A Study on a Novel Phase Change Material Panel Based on Tetradecanol/Lauric Acid/Expanded Perlite/Aluminium Powder for Building Heat Storage

PubMed Central

Wang, Enyu; Kong, Xiangfei; Rong, Xian; Yao, Chengqiang; Yang, Hua; Qi, Chengying

2016-01-01

Phase change material (PCM) used in buildings can reduce the building energy consumption and indoor temperature fluctuation. A composite PCM has been fabricated by the binary eutectic mixture of tetradecanol (TD) and lauric acid (LA) absorbed into the expanded perlite (EP) using vacuum impregnation method, and its thermal conductivity was promoted by aluminium powder (AP) additive. Besides, the styrene-acrylic emulsion has been mixed with the composite PCM particles to form the protective film, so as to solve the problem of leakage. Thus, a novel PCM panel (PCMP) has been prepared using compression moulding forming method. The thermal property, microstructure characteristic, mechanical property, thermal conductivity, thermal reliability and leakage of the composite PCM have been investigated and analysed. Meanwhile, the thermal performance of the prepared PCMP was tested through PCMPs installed on the inside wall of a cell under outdoor climatic conditions. The composite PCM has a melting temperature of 24.9 °C, a freezing temperature of 25.2 °C, a melting latent heat of 78.2 J/g and a freezing latent heat of 81.3 J/g. The thermal conductivity test exposed that the thermal conductivity has been enhanced with the addition of AP and the latent heat has been decreased, but it still remains in a high level. The leakage test result has proven that liquid PCM leaking has been avoided by the surface film method. The thermal performance experiment has shown the significant function of PCMP about adjusting the indoor temperature and reducing the heats transferring between the wall inside and outside. In view of the thermal performance, mechanical property and thermal reliability results, it can be concluded that the prepared PCMP has a promising building application potential. PMID:28774020

Thermochemical characterization of some thermally stable thermoplastic and thermoset polymers

NASA Technical Reports Server (NTRS)

Kourtides, D. A.; Gilwee, W. J., Jr.; Parker, J. A.

1979-01-01

The thermochemical and flammability properties of some thermally stable polymers considered for use in aircraft interiors are described. The properties studied include: (1) thermomechanical properties such as glass transition and melt temperature; (2) dynamic thermogravimetric analysis in anaerobic environment; (3) flammability properties such as oxygen index, flame spread, and smoke evolution; and (4) selected physical properties. The thermoplastic polymers evaluated include polyphenylene sulfide, polyaryl sulfone, 9,9-bis(4-hydroxyphenyl)-fluorene polycarbonate-poly(dimethylsiloxane) and polyether sulfone. The thermoset polymers evaluated include epoxy, bismaleimide, a modified phenolic, and polyaromatic melamine resin. These resins were primarily used in the fabrication of glass-reinforced prepregs for the construction of experimental panels. Test results and relative rankings of some of the flammability parameters are presented, and the relationship of the molecular structure, char yield, and flammability properties of these polymers are discussed.

New approaches in the indirect quantification of thermal rock properties in sedimentary basins: the well-log perspective

NASA Astrophysics Data System (ADS)

Fuchs, Sven; Balling, Niels; Förster, Andrea

2016-04-01

Numerical temperature models generated for geodynamic studies as well as for geothermal energy solutions heavily depend on rock thermal properties. Best practice for the determination of those parameters is the measurement of rock samples in the laboratory. Given the necessity to enlarge databases of subsurface rock parameters beyond drill core measurements an approach for the indirect determination of these parameters is developed, for rocks as well a for geological formations. We present new and universally applicable prediction equations for thermal conductivity, thermal diffusivity and specific heat capacity in sedimentary rocks derived from data provided by standard geophysical well logs. The approach is based on a data set of synthetic sedimentary rocks (clastic rocks, carbonates and evaporates) composed of mineral assemblages with variable contents of 15 major rock-forming minerals and porosities varying between 0 and 30%. Petrophysical properties are assigned to both the rock-forming minerals and the pore-filling fluids. Using multivariate statistics, relationships then were explored between each thermal property and well-logged petrophysical parameters (density, sonic interval transit time, hydrogen index, volume fraction of shale and photoelectric absorption index) on a regression sub set of data (70% of data) (Fuchs et al., 2015). Prediction quality was quantified on the remaining test sub set (30% of data). The combination of three to five well-log parameters results in predictions on the order of <15% for thermal conductivity and thermal diffusivity, and of <10% for specific heat capacity. Comparison of predicted and benchmark laboratory thermal conductivity from deep boreholes of the Norwegian-Danish Basin, the North German Basin, and the Molasse Basin results in 3 to 5% larger uncertainties with regard to the test data set. With regard to temperature models, the use of calculated TC borehole profiles approximate measured temperature logs with an error of <3°C along a 4 km deep profile. A benchmark comparison for thermal diffusivity and specific heat capacity is pending. Fuchs, Sven; Balling, Niels; Förster, Andrea (2015): Calculation of thermal conductivity, thermal diffusivity and specific heat capacity of sedimentary rocks using petrophysical well logs, Geophysical Journal International 203, 1977-2000, doi: 10.1093/gji/ggv403

Study of an experimental methodology for thermal properties diagnostic of building envelop

NASA Astrophysics Data System (ADS)

Yang, Yingying; Sempy, Alain; Vogt Wu, Tingting; Sommier, Alain; Dumoulin, Jean; Batsale, Jean Christophe

2017-04-01

The building envelope plays a critical role in determining levels of comfort and building efficiency. Its real thermal properties characterization is of major interest to be able to diagnose energy efficiency performance of buildings (new construction and retrofitted existing old building). Research and development on a possible methodology for energy diagnostic of the building envelop is a hot topic and necessary trend. Many kinds of sensors and instruments are used for the studies. The application of infrared (IR) thermography in non-destructive evaluation has been widely employed for qualitative evaluations for building diagnostics; meanwhile, the IR thermography technology also has a large potentiality for the evaluation of the thermal characteristics of the building envelope. Some promising recent research studies have been carried out with such contactless measurement technique. Nevertheless, research efforts are still required for in situ measurements under natural environmental conditions. In order to develop new solutions for non-intrusive evaluation of local thermal performance, enabling quantitative assessment of thermal properties of buildings and materials, experiments were carried out on a multi-layer pratical scale wall fixed on a caisson placed in a climatic chamber. Six halogen lamps (1.5 kW for each lamp) placed in front of objective wall were used to emulate sunny conditions. The radiative heat flux emitted was monitored and modulated with time according to typical weather data set encountered in France. Both steady state and transient regime heat transfer were studied during these experiments. Contact sensors (thermocouples, heat flux meters, Peltier sensors) and non-contact sensors (thermal IR camera, pyranometer) were used to measure the temperatures and heat flux density evolution. It has to be noticed that the Peltier sensors have been tuned and used with a specific processing to set them compliant for heat flux density measurements. The measured data from different sensors were analysed and compared. The emissivity of wall surface and treated sensor surfaces were evaluated by using an IR camera with an adapted post-processing. Then, convective and radiative heat fluxes, at wall level, were estimated. Finally, the wall thermal properties can be calculated by using the measured temperatures and estimated heat fluxes using a dedicated thermal quadrupoles heat transfer model and an inverse method. This study aims at providing some guidelines for the choice of sensors, measurements protocol and adapted inverse model to be tested in real conditions on pilot situ scale. Aknowledgments : The Authors are very grateful to H2020 Built2Spec project for supporting this work.

Designing energy dissipation properties via thermal spray coatings

DOE PAGES

Brake, Matthew R. W.; Hall, Aaron Christopher; Madison, Jonathan D.

2016-12-14

The coefficient of restitution is a measure of energy dissipation in a system across impact events. Often, the dissipative qualities of a pair of impacting components are neglected during the design phase. This research looks at the effect of applying a thin layer of metallic coating, using thermal spray technologies, to significantly alter the dissipative properties of a system. We studied the dissipative properties across multiple impacts in order to assess the effects of work hardening, the change in microstructure, and the change in surface topography. The results of the experiments indicate that any work hardening-like effects are likely attributablemore » to the crushing of asperities, and the permanent changes in the dissipative properties of the system, as measured by the coefficient of restitution, are attributable to the microstructure formed by the thermal spray coating. Furthermore, the microstructure appears to be robust across impact events of moderate energy levels, exhibiting negligible changes across multiple impact events.« less

Triphenylamine-Thienothiophene Organic Charge-Transport Molecular Materials: Effect of Substitution Pattern on their Thermal, Photoelectrochemical, and Photovoltaic Properties.

PubMed

Le, Thi Huong; Dao, Quang-Duy; Nghiêm, Mai-Phuong; Péralta, Sébastien; Guillot, Regis; Pham, Quoc Nghi; Fujii, Akihiko; Ozaki, Masanori; Goubard, Fabrice; Bui, Thanh-Tuân

2018-04-25

Two readily accessible thienothiophene-triphenylamine charge-transport materials have been synthesized by simply varying the substitution pattern of the triphenylamine groups on a central thienothiophene π-linker. The impact of the substitution pattern on the thermal, photoelectrochemical, and photovoltaic properties of these materials was evaluated and, based on theoretical and experimental studies, we found that the isomer in which the triphenylamine groups were located at the 2,5-positions of the thienothiophene core (TT-2,5-TPA) had better π-conjugation than the 3,6-isomer (TT-3,6-TPA). Whilst the thermal, morphological, and hydrophobic properties of the two materials were similar, their optoelectrochemical and photovoltaic properties were noticeably impacted. When applied as hole-transport materials in hybrid perovskite solar cells, the 2,5-isomer exhibited a power-conversion efficiency of 13.6 %, much higher than that of its 3,6-counterpart (0.7 %) under the same standard conditions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Acid-functionalized carbon nanofibers for high stability, thermoelectrical and electrochemical properties of nanofluids.

PubMed

Said, Zafar; Allagui, Anis; Abdelkareem, Mohammad Ali; Alawadhi, Hussain; Elsaid, Khaled

2018-06-15

Carbon-based nanofluids are viewed as promising thermal fluids for heat transfer applications. However, other properties, such as electrical conductivity and electrochemical behavior, are usually overlooked and rarely investigated despite their importance for the overall performance characterization of a given application. In this study, we synthesized PAN-based carbon nanofibers (CNF) by electrospinning, and characterized them using electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric analysis. Thermoelectrical and electrochemical measurements were carried out on nanofluids. We found that, although CNF nanofluids exhibit good thermal and electrical properties with a negligible corrosive effect, the suspensions tend to sediment within a few days. However, acid treatment of CNF (F-CNF), which resulted in the shortening of the fibers and the appearance of surface-oxygenated species, made F-CNF-based nanofluids exhibit superior stability in water that extended for more than 90 days, with consistent and superior thermal and electrical properties. Copyright © 2018 Elsevier Inc. All rights reserved.

Designing energy dissipation properties via thermal spray coatings

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

Brake, Matthew R. W.; Hall, Aaron Christopher; Madison, Jonathan D.

The coefficient of restitution is a measure of energy dissipation in a system across impact events. Often, the dissipative qualities of a pair of impacting components are neglected during the design phase. This research looks at the effect of applying a thin layer of metallic coating, using thermal spray technologies, to significantly alter the dissipative properties of a system. We studied the dissipative properties across multiple impacts in order to assess the effects of work hardening, the change in microstructure, and the change in surface topography. The results of the experiments indicate that any work hardening-like effects are likely attributablemore » to the crushing of asperities, and the permanent changes in the dissipative properties of the system, as measured by the coefficient of restitution, are attributable to the microstructure formed by the thermal spray coating. Furthermore, the microstructure appears to be robust across impact events of moderate energy levels, exhibiting negligible changes across multiple impact events.« less

Ab initio studies of structural, electronic, optical, elastic and thermal properties of silver gallium dichalcogenides (AgGaX{sub 2}: X = S, Se, Te)

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

Sharma, Sheetal; Department of Physics, Panjab University, Chandigarh 160014; Verma, A.S., E-mail: ajay_phy@rediffmail.com

2014-05-01

Graphical abstract: - Highlights: • FP-LAPW method has been used to compute the solid state properties of AgGaX{sub 2} (X = S, Se, Te). • Electronic and optical properties reported with recently developed mBJ potential. • Thermal expansion, heat capacity, Debye temperature, entropy and Grüneisen parameter were evaluated. • Hardness was calculated for the first time at different temperature and pressure. - Abstract: We have performed ab initio calculations for the structural, electronic, optical, elastic and thermal properties of the silver gallium dichalcogenides (AgGaX{sub 2}: X = S, Se, Te). In this study, we have used the accurate full potentialmore » linearized augmented plane wave (FP-LAPW) method to find the equilibrium structural parameters and to compute the six elastic constants (C{sub 11}, C{sub 12}, C{sub 13}, C{sub 33}, C{sub 44} and C{sub 66}). We have reported electronic and optical properties with the recently developed density functional theory of Tran and Blaha, and this theory is used along with the Wu-Cohen generalized gradient approximation (WC-GGA) for the exchange-correlation potential. Furthermore, optical features such as dielectric functions, refractive indices, extinction coefficient, optical reflectivity, absorption coefficients and optical conductivities were calculated for photon energies up to 40 eV. The thermodynamical properties such as thermal expansion, heat capacity, debye temperature, entropy, Grüneisen parameter and bulk modulus were calculated employing the quasi-harmonic Debye model at different temperatures (0–900 K) and pressures (0–8 GPa) and the silent results were interpreted. Hardness of the materials was calculated for the first time at different temperatures and pressures.« less

Anomalous behaviour of thermodynamic properties at successive phase transitions in (NH4)3GeF7

NASA Astrophysics Data System (ADS)

Bogdanov, Evgeniy V.; Kartashev, Andrey V.; Pogoreltsev, Evgeniy I.; Gorev, Mikhail V.; Laptash, Natalia M.; Flerov, Igor N.

2017-12-01

Heat capacity, thermal dilatation, susceptibility to hydrostatic pressure and dielectric properties associated with succession of three phase transitions below room temperature in double fluoride salt (NH4)3GeF7 were studied. A possible transformation into the parent Pm-3m cubic phase was not observed up to the decomposition of compound. Nonferroelectric nature of structural distortions was confirmed. The DTA under pressure studies revealed a high temperature stability of two phases: P4/mbm and Pbam. The entropies of the phase transitions agree well with the model of structural distortions. Analysis of the thermal properties associated with the individual phase transitions in the framework of thermodynamic equations has shown a high reliability of the data obtained.

Electrical Transport Properties of Liquid Al-Cu Alloys

NASA Astrophysics Data System (ADS)

Thakore, B. Y.; Khambholja, S. G.; Suthar, P. H.; Jani, A. R.

2010-06-01

Electrical transport properties viz. electrical resistivity, thermoelectric power and thermal conductivity of liquid Al-Cu alloys as a function of Cu concentration have been studied in the present paper. Ashcroft empty core model potential has been used to incorporate the ion-electron interaction. To incorporate the exchange and correlation effects, five different forms of local field correction functions viz. Hartree, Taylor, Ichimaru et al., Farid et al. and Sarkar et al. have been used. The transport properties of binary system have been studied using Faber-Ziman formulation combined with Ashcroft-Langreth (AL) partial structure factor. The computed values of electrical resistivity are compared with experimental data and for low Cu concentration, good agreement has been observed. Further, thermoelectric power and thermal conductivity have also been predicted.

Effect of thermal processing practices on the properties of superplastic Al-Li alloys

NASA Technical Reports Server (NTRS)

Hales, Stephen J.; Lippard, Henry E.

1993-01-01

The effect of thermal processing on the mechanical properties of superplastically formed structural components fabricated from three aluminum-lithium alloys was evaluated. The starting materials consisted of 8090, 2090, and X2095 (Weldalite(TM) 049), in the form of commercial-grade superplastic sheet. The experimental test matrix was designed to assess the impact on mechanical properties of eliminating solution heat treatment and/or cold water quenching from post-forming thermal processing. The extensive hardness and tensile property data compiled are presented as a function of aging temperature, superplastic strain and temper/quench rate for each alloy. The tensile properties of the materials following superplastic forming in two T5-type tempers are compared with the baseline T6 temper. The implications for simplifying thermal processing without degradation in properties are discussed on the basis of the results.

Dynamical effects on the core-mantle boundary from depth-dependent thermodynamical properties of the lower mantle

NASA Technical Reports Server (NTRS)

Zhang, Shuxia; Yuen, David A.

1988-01-01

A common assumption in modeling dynamical processes in the lower mantle is that both the thermal expansivity and thermal conductivity are reasonably constant. Recent work from seismic equation of state leads to substantially higher values for the thermal conductivity and much lower thermal expansivity values in the deep mantle. The dynamical consequences of incorporating depth-dependent thermodynamic properties on the thermal-mechanical state of the lower mantle are examined with the spherical-shell mean-field equations. It is found that the thermal structure of the seismically resolved anomalous zone at the base of the mantle is strongly influenced by these variable properties and, in particular, that the convective distortion of the core-mantle boundary (CMB) is reduced with the decreasing thermal expansivity. Such a reduction of the dynamically induced topography from pure thermal convection would suggest that some other dynamical mechanism must be operating at the CMB.

A study of the effect of selected material properties on the ablation performance of artificial graphite

NASA Technical Reports Server (NTRS)

Maahs, H. G.

1972-01-01

Eighteen material properties were measured on 45 different, commercially available, artificial graphites. Ablation performance of these same graphites were also measured in a Mach 2 airstream at a stagnation pressure of 5.6 atm. Correlations were developed, where possible, between pairs of the material properties. Multiple regression equations were then formulated relating ablation performance to the various material properties, thus identifying those material properties having the strongest effect on ablation performance. These regression equations reveal that ablation performance in the present test environment depends primarily on maximum grain size, density, ash content, thermal conductivity, and mean pore radius. For optimization of ablation performance, grain size should be small, ash content low, density and thermal conductivity high, and mean pore radius large.

Characterization of anisotropic thermal conductivity of suspended nm-thick black phosphorus with frequency-resolved Raman spectroscopy

NASA Astrophysics Data System (ADS)

Wang, Tianyu; Han, Meng; Wang, Ridong; Yuan, Pengyu; Xu, Shen; Wang, Xinwei

2018-04-01

Frequency-resolved Raman spectroscopy (FR-Raman) is a new technique for nondestructive thermal characterization. Here, we apply this new technique to measure the anisotropic thermal conductivity of suspended nm-thick black phosphorus samples without the need of optical absorption and temperature coefficient. Four samples with thicknesses between 99.8 and 157.6 nm are studied. Based on steady state laser heating and Raman measurement of samples with a specifically designed thermal transport path, the thermal conductivity ratio (κZZ/κAC) is determined to be 1.86-3.06. Based on the FR-Raman measurements, the armchair thermal conductivity is measured as 14-22 W m-1 K-1, while the zigzag thermal conductivity is 40-63 W m-1 K-1. FR-Raman has great potential for studying the thermal properties of various nanomaterials. This study significantly advances our understanding of thermal transport in black phosphorus and facilitates the application of black phosphorus in novel devices.

Effect of thermal cycling in a Mach 0.3 burner rig on properties and structure of directionally solidified gamma/gamma prime - delta eutectic

NASA Technical Reports Server (NTRS)

Gray, H. R.; Sanders, W. A.

1975-01-01

Tensile and stress rupture properties at 1040 C of a thermally cycled gamma/gamma prime - delta eutectic were essentially equivalent to the as-grown properties. Tensile strength and rupture life at 760 C appeared to decrease slightly by thermal cycling. Thermal cycling resulted in gamma prime coarsening and Widmanstatten delta precipitation in the gamma phase. An unidentified precipitate, presumably gamma prime, was observed within the delta phase. The eutectic alloy exhibited a high rate of oxidation-erosion weight loss during thermal cycling in the Mach 0.3 burner rig.

Deleterious Thermal Effects due to Randomized Flow Paths in Pebble Bed, and Particle Bed Style Reactors

NASA Technical Reports Server (NTRS)

Moran, Robert P.

2013-01-01

Reactor fuel rod surface area that is perpendicular to coolant flow direction (+S) i.e. perpendicular to the P creates areas of coolant stagnation leading to increased coolant temperatures resulting in localized changes in fluid properties. Changes in coolant fluid properties caused by minor increases in temperature lead to localized reductions in coolant mass flow rates leading to localized thermal instabilities. Reductions in coolant mass flow rates result in further increases in local temperatures exacerbating changes to coolant fluid properties leading to localized thermal runaway. Unchecked localized thermal runaway leads to localized fuel melting. Reactor designs with randomized flow paths are vulnerable to localized thermal instabilities, localized thermal runaway, and localized fuel melting.

Thermal conductivity and combustion properties of wheat gluten foams.

PubMed

Blomfeldt, Thomas O J; Nilsson, Fritjof; Holgate, Tim; Xu, Jianxiao; Johansson, Eva; Hedenqvist, Mikael S

2012-03-01

Freeze-dried wheat gluten foams were evaluated with respect to their thermal and fire-retardant properties, which are important for insulation applications. The thermal properties were assessed by differential scanning calorimetry, the laser flash method and a hot plate method. The unplasticised foam showed a similar specific heat capacity, a lower thermal diffusivity and a slightly higher thermal conductivity than conventional rigid polystyrene and polyurethane insulation foams. Interestingly, the thermal conductivity was similar to that of closed cell polyethylene and glass-wool insulation materials. Cone calorimetry showed that, compared to a polyurethane foam, both unplasticised and glycerol-plasticised foams had a significantly longer time to ignition, a lower effective heat of combustion and a higher char content. Overall, the unplasticised foam showed better fire-proof properties than the plasticized foam. The UL 94 test revealed that the unplasticised foam did not drip (form droplets of low viscous material) and, although the burning times varied, self-extinguished after flame removal. To conclude both the insulation and fire-retardant properties were very promising for the wheat gluten foam. © 2012 American Chemical Society

Physical and thermal behavior of cement composites reinforced with recycled waste paper fibers

NASA Astrophysics Data System (ADS)

Hospodarova, Viola; Stevulova, Nadezda; Vaclavik, Vojtech; Dvorsky, Tomas

2017-07-01

In this study, three types of recycled waste paper fibers were used to manufacture cement composites reinforced with recycled cellulosic fibers. Waste cellulosic fibers in quantity of 0.2, 0.3, and 0.5 wt.% were added to cement mixtures. Physical properties such as density, water capillarity, water absorbability and thermal conductivity of fiber cement composites were studied after 28 days of hardening. However, durability of composites was tested after their water storage up to 90 days. Final results of tested properties of fiber cement composites were compared with cement reference sample without cellulosic fibers.

Alkali-resistant calcium iron phosphate glass fibers for concrete reinforcement

DOT National Transportation Integrated Search

2008-02-01

The physical properties and alkaline corrosion resistant properties of calcium-ironphosphate glasses were studied. Iron addition decreases the thermal expansion coefficient and increases the Youngs modulus in comparison with the addition of calciu...

Studying the processes relating to oxidation of organic substances contained in the coolant of thermal and nuclear power stations

NASA Astrophysics Data System (ADS)

Khodyrev, B. N.; Krichevtsov, A. L.; Sokolyuk, A. A.

2010-07-01

A radical-chain mechanism governing thermal-oxidation destruction of organic substances contained in the coolant of thermal and nuclear power stations is considered. Hypotheses on the chemical nature of antioxidation properties of amines are presented. Theoretical conjectures about the fundamental processes through which protective amine films are formed on the surface of metals are suggested.

The roles of thermal insulation and heat storage in the energy performance of the wall materials: a simulation study.

PubMed

Long, Linshuang; Ye, Hong

2016-04-07

A high-performance envelope is the prerequisite and foundation to a zero energy building. The thermal conductivity and volumetric heat capacity of a wall are two thermophysical properties that strongly influence the energy performance. Although many case studies have been performed, the results failed to give a big picture of the roles of these properties in the energy performance of an active building. In this work, a traversal study on the energy performance of a standard room with all potential wall materials was performed for the first time. It was revealed that both heat storage materials and insulation materials are suitable for external walls. However, the importances of those materials are distinct in different situations: the heat storage plays a primary role when the thermal conductivity of the material is relatively high, but the effect of the thermal insulation is dominant when the conductivity is relatively low. Regarding internal walls, they are less significant to the energy performance than the external ones, and they need exclusively the heat storage materials with a high thermal conductivity. These requirements for materials are consistent under various climate conditions. This study may provide a roadmap for the material scientists interested in developing high-performance wall materials.

The roles of thermal insulation and heat storage in the energy performance of the wall materials: a simulation study

PubMed Central

Long, Linshuang; Ye, Hong

2016-01-01

A high-performance envelope is the prerequisite and foundation to a zero energy building. The thermal conductivity and volumetric heat capacity of a wall are two thermophysical properties that strongly influence the energy performance. Although many case studies have been performed, the results failed to give a big picture of the roles of these properties in the energy performance of an active building. In this work, a traversal study on the energy performance of a standard room with all potential wall materials was performed for the first time. It was revealed that both heat storage materials and insulation materials are suitable for external walls. However, the importances of those materials are distinct in different situations: the heat storage plays a primary role when the thermal conductivity of the material is relatively high, but the effect of the thermal insulation is dominant when the conductivity is relatively low. Regarding internal walls, they are less significant to the energy performance than the external ones, and they need exclusively the heat storage materials with a high thermal conductivity. These requirements for materials are consistent under various climate conditions. This study may provide a roadmap for the material scientists interested in developing high-performance wall materials. PMID:27052186

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

Madhukumar, R.; Asha, S.; Rao, B. Lakshmeesha

The gamma radiation-induced change in structural and thermal properties of Bombyx mori silk fibroin films were investigated and have been correlated with the applied radiation doses. Irradiation of samples were carried out in dry air at room temperature using Co-60 source, and radiation doses are in the range of 0 - 300 kGy. Structural and thermal properties of the irradiated silk films were studied using X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TGA) and compared with unirradiated sample. Interesting results are discussed in this report.

Synchronous infrared imaging methods to characterize thermal properties of materials

NASA Astrophysics Data System (ADS)

Ouyang, Zhong

1999-11-01

A fundamental thermal property of a material is its thermal conductivity. The current state-of-the art for measurement of thermal conductivity is inadequate, especially in the case of composite materials. This dissertation addresses the need for a rapid and accurate measurement of thermal conductivity that can provide values for three orthogonal directions in a single measurement. The theoretical approach is based on three-dimensional thermal wave propagation and scattering treatments that have been developed earlier at Wayne State University. The experimental approach makes use of a state-of-the-art focal-plane-array infrared camera, which is used to follow the time- and spatial-progression of the planar heat pulse on both surfaces of the slab. The method has been used to determine the thermal diffusivity of six pure elemental single crystal materials (Cu, Ti, Bi, Al, Ag, Pb). The results are in good agreement (better than 1%) with the diffusivities calculated from the handbook. The diffusivities of some alloys and unidirectional graphite-fiber-reinforced-polymer composite also are determined by this method. As a byproduct of one of the experimental approaches measuring the IR radiation from the heated surface, direct evidence is obtained for the presence of a thermal wave "echo". The theory and confirming measurements in this dissertation represent its first clear confirmation. A second experimental method which is studied in this dissertation, and which may be used to characterize thermal properties of materials, is that of lock-in thermal wave imaging. In this technique, pioneered earlier at Wayne State University, a periodic heat source is applied to the surface of the material, and synchronous, phase-sensitive detection of the IR radiation from that surface is used to determine the effects of thermal wave propagation to subsurface features, and the effects of reflected thermal waves from those features on the observed IR radiation from the surface. The rationale for re-visiting this technique is the availability of the focal-plane-array IR camera, with its "snapshot" capability, its high spatial resolution, and its high pixel rate. A lock-in imaging method is developed for use with this camera, which can be used at frequencies that considerably exceed the maximum frame rate, with illustrative applications to characterize the thermal properties of printed circuits and electronic packages.

Investigating the Differential Emission Measure and Energetics of Microflares with Combined SDO/AIA and RHESSI Observations

NASA Technical Reports Server (NTRS)

Inglis, A. R.; Christe, S.

2014-01-01

An important question in solar physics is whether solar microflares, the smallest currently observable flare events in X-rays, possess the same energetic properties as large flares. Recent surveys have suggested that microflares may be less efficient particle accelerators than large flares, and hence contribute less non-thermal energy, which may have implications for coronal heating mechanisms. We therefore explore the energetic properties of microflares by combining EUV and X-ray measurements. We present forward-fitting differential emission measure (DEM) analysis of 10 microflares. The fitting is constrained by combining, for the first time, high-temperature Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observations and flux data from the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA). Two fitting models are tested for the DEM; a Gaussian distribution and a uniform DEM profile. A Gaussian fit proved unable to explain the observations for any of the studied microflares. However, 8 of 10 events studied were reasonably fit by a uniform DEM profile. Hence microflare plasma can be considered to be significantly multi-thermal, and may not be significantly peaked or contain resolvable fine structure, within the uncertainties of the observational instruments. The thermal and non-thermal energy is estimated for each microflare, comparing the energy budget with an isothermal plasma assumption. From the multi-thermal fits the minimum non-thermal energy content was found to average approximately 30% of the estimated thermal energy. By comparison, under an isothermal model the non-thermal and thermal energy estimates were generally comparable. Hence, multi-thermal plasma is an important consideration for solar microflares that substantially alters their thermal and non-thermal energy content.

Thermal Properties of SiOC Glasses and Glass Ceramics at Elevated Temperatures

PubMed Central

Stabler, Christina; Reitz, Andreas; Stein, Peter; Albert, Barbara; Riedel, Ralf

2018-01-01

In the present study, the effect of the chemical and phase composition on the thermal properties of silicon oxide carbides (SiOC) has been investigated. Dense monolithic SiOC materials with various carbon contents were prepared and characterized with respect to their thermal expansion, as well as thermal conductivity. SiOC glass has been shown to exhibit low thermal expansion (e.g., ca. 3.2 × 10−6 K−1 for a SiOC sample free of segregated carbon) and thermal conductivity (ca. 1.5 W/(m∙K)). Furthermore, it has been observed that the phase separation, which typically occurs in SiOC exposed to temperatures beyond 1000–1200 °C, leads to a decrease of the thermal expansion (i.e., to 1.83 × 10−6 K−1 for the sample above); whereas the thermal conductivity increases upon phase separation (i.e., to ca. 1.7 W/(m∙K) for the sample mentioned above). Upon adjusting the amount of segregated carbon content in SiOC, its thermal expansion can be tuned; thus, SiOC glass ceramics with carbon contents larger than 10–15 vol % exhibit similar coefficients of thermal expansion to that of the SiOC glass. Increasing the carbon and SiC content in the studied SiOC glass ceramics leads to an increase in their thermal conductivity: SiOC with relatively large carbon and silicon carbides (SiC) volume fractions (i.e., 12–15 and 20–30 vol %, respectively) were shown to possess thermal conductivities in the range from 1.8 to 2.7 W/(m∙K). PMID:29439441

Oligosilylarylnitrile: The Thermoresistant Thermosetting Resin with High Comprehensive Properties.

PubMed

Wang, Mingcun; Ning, Yi

2018-04-11

One of the highest thermoresistant thermosetting resins ever studied so far, oligosilylarylnitrile resin, was investigated first in this study. Oligosilylarylnitrile was synthesized by lithium-reduced Wurtz-Fittig condensation reaction, and the prepared viscous resin exhibited moderate rheological behaviors while heated purely or together with 20% polysilazane as a cross-linking agent. The thermal curing temperatures were found by differential scanning calorimetry at 268 °C (pure) and 158 °C (with the polysilazane cross-linking agent), which is comparably close to that of polysilylarylacetylene resin (normally at 220-250 °C) but much lower than those of polyimide and phthalonitrile resins (normally >300 °C), indicating the admirable material processability of oligosilylnitrile. The cured oligosilylarylnitrile resins have extremely high thermal resistance, indicated by the results of thermogravimetric analysis (the mass residue at 800 °C is >90% under N 2 ) and dynamic mechanical analysis (the glass-transition temperature is >420 °C). The mechanical property of the oligosilylarylnitrile-matrixed silica-cloth reinforced laminate is comparably close to those of polyimide and phthalonitrile but much higher than that of polysilylarylacetylene, indicating the enviable thermal and mechanical properties of oligosilylnitrile. Thus, among the high-temperature resins ever studied so far, the oligosilylarylnitrile resin was found to have the almost best comprehensive characteristics of processability and properties.

Effect of epoxidised soybean oil loading as plasticiser on physical, mechanical and thermal properties of polyvinylchloride

NASA Astrophysics Data System (ADS)

Rahmah, M.; Nurazzi, N. Mohd; Farah Nordyana, A. R.; Syed Anas, S. M.

2017-07-01

The aim of this paper is to study the effect of epoxidised soybean oil (ESO) as an alternative plasticizer on physical, mechanical and thermal properties of plasticised polyvinyl chloride (PPVC). Samples were prepared using 10, 20, 30 and 40% by weight percent of ESO. The samples were characterized for density, water absorption, tensile, hardness and thermal properties. The addition of ESO as plasticizer in PVC had caused significant effect on the physical and mechanical properties of PPVC. Increasing of ESO loading had resulted in decreased density, tensile strength, tensile modulus but increased in elongation at break and shore hardness. From water absorption study, it was observed that the all the samples reached the plateau absorption at days 8 to 10 with absorption percentages of between 1.8 to 2%. In general the crystallinity of PPVC maintained between 10 to 13% with increase in ESO loading while the melting point ( Tm) is slightly decreased about 3 to 6°C. In this study, ESO which acts as plasticiser were found to result in lower glass transition temperature (Tg). The enhancements of super cooling with higher ESO loading were found to increase the crystallization temperature, promoting crystallisation and act as nucleating agent.

Thermal Transport in Self-Assembled Nanostructures

DTIC Science & Technology

2011-01-01

2:1 smectite clay family which can be exfoliated into large aspect ratio (>1000:1) ~1 nm thick sheets (Figure 4a). Each montmorillonite sheet...measurements. While it was suggested earlier that study of the thermal transport properties of similarly modified smectite clays other than montmorillonite

Thermodynamic properties of rhodium at high temperature and pressure by using mean field potential approach

NASA Astrophysics Data System (ADS)

Kumar, Priyank; Bhatt, Nisarg K.; Vyas, Pulastya R.; Gohel, Vinod B.

2016-10-01

The thermophysical properties of rhodium are studied up to melting temperature by incorporating anharmonic effects due to lattice ions and thermally excited electrons. In order to account anharmonic effects due to lattice vibrations, we have employed mean field potential (MFP) approach and for thermally excited electrons Mermin functional. The local form of the pseudopotential with only one effective adjustable parameter rc is used to construct MFP and hence vibrational free energy due to ions - Fion. We have studied equation of state at 300 K and further, to access the applicability of present conjunction scheme, we have also estimated shock-Hugoniot and temperature along principle Hugoniot. We have carried out the study of temperature variation of several thermophysical properties like thermal expansion (βP), enthalpy (EH), specific heats at constant pressure and volume (CP and CV), specific heats due to lattice ions and thermally excited electrons ( and , isothermal and adiabatic bulk moduli (BT and Bs) and thermodynamic Gruneisen parameter (γth) in order to examine the inclusion of anharmonic effects in the present study. The computed results are compared with available experimental results measured by using different methods and previously obtained theoretical results using different theoretical philosophy. Our computed results are in good agreement with experimental findings and for some physical quantities better or comparable with other theoretical results. We conclude that local form of the pseudopotential used accounts s-p-d hybridization properly and found to be transferable at extreme environment without changing the values of the parameter. Thus, even the behavior of transition metals having complexity in electronic structure can be well understood with local pseudopotential without any modification in the potential at extreme environment. Looking to the success of present scheme (MFP + pseudopotential) we would like to extend it further for the study of liquid state properties as well as thermophysical properties of d and f block metals.

Thermal Exposure Effects on Properties of Al-Li Alloy Plate Products

NASA Technical Reports Server (NTRS)

Shah, Sandeep; Wells, Douglas; Wagner, John; Babel, Henry

2003-01-01

The objective of this viewgraph representation is to evaluate the effects of thermal exposure on the mechanical properties of both production mature and developmental Al-Li alloys. The researchers find for these alloys, the data clearly shows that there is no deficit in mechanical properties at lower exposure temperatures in some cases, and a signficant deficit in mechanical properties at higher exposure temperatures in all cases. Topics considered include: Al-Li alloys composition, key characteristics of Al-Li alloys and thermal exposure matrix.

Optical Constants of Crystallized TiO2 Coatings Prepared by Sol-Gel Process

PubMed Central

Wang, Xiaodong; Wu, Guangming; Zhou, Bin; Shen, Jun

2013-01-01

Titanium oxide coatings have been deposited by the sol-gel dip-coating method. Crystallization of titanium oxide coatings was then achieved through thermal annealing at temperatures above 400 °C. The structural properties and surface morphology of the crystallized coatings were studied by micro-Raman spectroscopy and atomic force microscopy, respectively. Characterization technique, based on least-square fitting to the measured reflectance and transmittance spectra, is used to determine the refractive indices of the crystallized TiO2 coatings. The stability of the synthesized sol was also investigated by dynamic light scattering particle size analyzer. The influence of the thermal annealing on the optical properties was then discussed. The increase in refractive index with high temperature thermal annealing process was observed, obtaining refractive index values from 1.98 to 2.57 at He-Ne laser wavelength of 633 nm. The Raman spectroscopy and atomic force microscopy studies indicate that the index variation is due to the changes in crystalline phase, density, and morphology during thermal annealing. PMID:28811410

Optical Constants of Crystallized TiO₂ Coatings Prepared by Sol-Gel Process.

PubMed

Wang, Xiaodong; Wu, Guangming; Zhou, Bin; Shen, Jun

2013-07-12

Titanium oxide coatings have been deposited by the sol-gel dip-coating method. Crystallization of titanium oxide coatings was then achieved through thermal annealing at temperatures above 400 °C. The structural properties and surface morphology of the crystallized coatings were studied by micro-Raman spectroscopy and atomic force microscopy, respectively. Characterization technique, based on least-square fitting to the measured reflectance and transmittance spectra, is used to determine the refractive indices of the crystallized TiO₂ coatings. The stability of the synthesized sol was also investigated by dynamic light scattering particle size analyzer. The influence of the thermal annealing on the optical properties was then discussed. The increase in refractive index with high temperature thermal annealing process was observed, obtaining refractive index values from 1.98 to 2.57 at He-Ne laser wavelength of 633 nm. The Raman spectroscopy and atomic force microscopy studies indicate that the index variation is due to the changes in crystalline phase, density, and morphology during thermal annealing.