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Sample records for thermal expansion materials

  1. Anisotropic thermal expansion in flexible materials

    Science.gov (United States)

    Romao, Carl P.

    2017-10-01

    A definition of the Grüneisen parameters for anisotropic materials is derived based on the response of phonon frequencies to uniaxial stress perturbations. This Grüneisen model relates the thermal expansion in a given direction (αi i) to one element of the elastic compliance tensor, which corresponds to the Young's modulus in that direction (Yi i). The model is tested through ab initio prediction of thermal expansion in zinc, graphite, and calcite using density functional perturbation theory, indicating that it could lead to increased accuracy for structurally complex systems. The direct dependence of αi i on Yi i suggests that materials which are flexible along their principal axes but rigid in other directions will generally display both positive and negative thermal expansion.

  2. Negative thermal expansion materials: technological key for control of thermal expansion

    Directory of Open Access Journals (Sweden)

    Koshi Takenaka

    2012-01-01

    Full Text Available Most materials expand upon heating. However, although rare, some materials contract upon heating. Such negative thermal expansion (NTE materials have enormous industrial merit because they can control the thermal expansion of materials. Recent progress in materials research enables us to obtain materials exhibiting negative coefficients of linear thermal expansion over −30 ppm K−1. Such giant NTE is opening a new phase of control of thermal expansion in composites. Specifically examining practical aspects, this review briefly summarizes materials and mechanisms of NTE as well as composites containing NTE materials, based mainly on activities of the last decade.

  3. Ultra-low thermal expansion realized in giant negative thermal expansion materials through self-compensation

    Science.gov (United States)

    Shen, Fei-Ran; Kuang, Hao; Hu, Feng-Xia; Wu, Hui; Huang, Qing-Zhen; Liang, Fei-Xiang; Qiao, Kai-Ming; Li, Jia; Wang, Jing; Liu, Yao; Zhang, Lei; He, Min; Zhang, Ying; Zuo, Wen-Liang; Sun, Ji-Rong; Shen, Bao-Gen

    2017-10-01

    Materials with zero thermal expansion (ZTE) or precisely tailored thermal expansion are in urgent demand of modern industries. However, the overwhelming majority of materials show positive thermal expansion. To develop ZTE or negative thermal expansion (NTE) materials as compensators has become an important challenge. Here, we present the evidence for the realization of ultra-low thermal expansion in Mn-Co-Ge-In particles. The bulk with the Ni2In-type hexagonal structure undergoes giant NTE owing to a martensitic magnetostructural transition. The major finding is that the thermal expansion behavior can be totally controlled by modulating the crystallinity degree and phase transition from atomic scale. Self-compensation effect leads to ultra-low thermal expansion with a linear expansion coefficient as small as +0.68 × 10-6/K over a wide temperature range around room temperature. The present study opens an avenue to reach ZTE particularly from the large class of giant NTE materials based on phase transition.

  4. Seal assembly for materials with different coefficients of thermal expansion

    Science.gov (United States)

    Minford, Eric [Laurys Station, PA

    2009-09-01

    Seal assembly comprising (a) two or more seal elements, each element having having a coefficient of thermal expansion; and (b) a clamping element having a first segment, a second segment, and a connecting segment between and attached to the first and second segments, wherein the two or more seal elements are disposed between the first and second segments of the clamping element. The connecting segment has a central portion extending between the first segment of the clamping element and the second segment of the clamping element, and the connecting segment is made of a material having a coefficient of thermal expansion. The coefficient of thermal expansion of the material of the connecting segment is intermediate the largest and smallest of the coefficients of thermal expansion of the materials of the two or more seal elements.

  5. Effective Thermal Expansion Property of Consolidated Granular Materials.

    Science.gov (United States)

    Küçük, Gülşad; Gonzalez, Marcial; Cuitiño, Alberto M

    2017-11-09

    Thermally-assisted compaction of granular materials is of keen interest in many engineering applications. A proper estimation of the material behavior of compacted granular materials is contingent upon the knowledge of microstructure formation, which is highly dependent on the bulk material properties and processing conditions, during the deformation stage. Originating from the pair interactions between particles, the macroscopic properties are obtained using various homogenization techniques and postulating continuum constitutive laws. While pioneers in this field have laid fundamental groundwork regarding effective medium descriptions, there exists a discrepancy between discrete and continuum level solutions. In our previous work, we elaborated a Particle Mechanics Approach (PMA) that integrates thermal contact and Hertzian deformation models to understand the thermo-mechanically-coupled consolidation problem. We also considered the analogous problem from the perspective of the conventional Continuum Mechanics Approach (CMA). In this study, following the multi-scale modeling framework, we propose an effective thermal expansion coefficient for the thermally-assisted compaction of granular materials.

  6. Thermal Expansion Studies of Selected High Temperature Thermoelectric Materials

    Science.gov (United States)

    Ravi, Vilupanur; Firdosy, Samad; Caillat, Thierry; Brandon, Erik; Van Der Walde, Keith; Maricic, Lina; Sayir, Ali

    2008-01-01

    Radioisotope thermoelectric generators (RTGs) generate electrical power by converting the heat released from the nuclear decay of radioactive isotopes (typically plutonium-238) into electricity using a thermoelectric converter. RTGs have been successfully used to power a number of space missions and have demonstrated their reliability over an extended period of time (tens of years) and are compact, rugged, radiation resistant, scalable, and produce no noise, vibration or torque during operation. System conversion efficiency for state-of-practice RTGs is about 6% and specific power less than or equal to 5.1 W/kg. Higher specific power would result in more on-board power for the same RTG mass, or less RTG mass for the same on-board power. The Jet Propulsion Laboratory has been leading, under the advanced thermoelectric converter (ATEC) project, the development of new high-temperature thermoelectric materials and components for integration into advanced, more efficient RTGs. Thermoelectric materials investigated to date include skutterudites, the Yb14MnSb11 compound, and SiGe alloys. The development of long-lived thermoelectric couples based on some of these materials has been initiated and is assisted by a thermo-mechanical stress analysis to ensure that all stresses under both fabrication and operation conditions will be within yield limits for those materials. Several physical parameters are needed as input to this analysis. Among those parameters, the coefficient of thermal expansion (CTE) is critically important. Thermal expansion coefficient measurements of several thermoelectric materials under consideration for ATEC are described in this paper. The stress response at the interfaces in material stacks subjected to changes in temperature is discussed, drawing on work from the literature and project-specific tools developed here. The degree of CTE mismatch and the associated effect on the formation of stress is highlighted.

  7. Negative thermal expansion materials related to cubic zirconium tungstate

    Science.gov (United States)

    Lind, Cora

    2001-12-01

    A non-hydrolytic sol-gel method for the preparation of ZrW2O 8 was developed. A new trigonal polymorph was discovered, which is structurally related to trigonal ZrMO2O8 and MnRe2O 8 as evidenced by powder x-ray diffraction and EXAFS studies. Seeding of the starting mixtures with cubic ZrW2O8 promoted crystallization of the cubic phase instead of trigonal material. Dehydration of ZrW2O7(OH)2·2H 2O gave cubic ZrW2O8 at 650°C, and a modification of this route led to the discovery of the new NTE materials cubic ZrMo 2O8 and HfMo2O8. These compounds crystallize in the same temperature range as the more stable trigonal AMo2O 8 polymorphs. To facilitate preparation of phase pure cubic molybdates, the influence of precursor chemistry on the crystallization behavior was investigated. The synthesis was extended to the solid solution system ZrxHf 1-xMoyW2-yO8 (0 ≤ x ≤ 1, 0 ≤ y ≤ 2). All compounds showed negative thermal expansion between 77 and 573 K. High-pressure in situ diffraction experiments were conducted on several AM2O8 polymorphs. With the exception of monoclinic ZrMo2O8, all materials underwent at least one pressure induced phase transition. Quasi-hydrostatic experiments on cubic AMo 2O8 led to a reversible transition to a new high-pressure structure, while low-pressure amorphization was observed under non-hydrostatic conditions. Isothermal kinetic studies of the cubic to trigonal transformation for ZrMo2O8 were carried out on four samples. Apparent activation energies of 170--290 kJ/mol were obtained using an Avrami model in combination with an Arrhenius analysis. This corresponds to 5% conversion levels after one year at temperatures between 220 and 315°C. Ex situ studies showed that the conversion at lower temperatures was considerably slower than what would be expected from extrapolation of the kinetic data. Drop solution calorimetry was carried out on several polymorphs of ZrMo 2O8, HfMo2O8 and ZrW2O 8. Only monoclinic ZrMo2O8 was enthalpically

  8. Design of materials with extreme thermal expansion using a three-phase topology optimization method

    DEFF Research Database (Denmark)

    Sigmund, Ole; Torquato, S.

    1997-01-01

    We show how composites with extremal or unusual thermal expansion coefficients can be designed using a numerical topology optimization method. The composites are composed of two different material phases and void. The optimization method is illustrated by designing materials having maximum therma...

  9. Composite material of electrocontuctor having controlled coefficient of thermal expansion

    OpenAIRE

    Torrecillas, Ramón; García Moreno, Olga; Borrell, Amparo; Fernández-Camacho, A.

    2009-01-01

    [ES] La presente invención se refiere a un material compuesto que comprende un componente cerámico, caracterizado por tener un coeficiente de expansión térmico negativo, y nano filamentos de carbono, a su procedimiento de obtención y a sus usos como electroconductor en microelectrónica, óptica de precisión, aeronáutica y aeroespacial.

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

    Directory of Open Access Journals (Sweden)

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

    2012-01-01

    Full Text Available 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.

  11. Removal properties of low-thermal-expansion materials with rotating-sphere elastic emission machining

    Directory of Open Access Journals (Sweden)

    Masahiko Kanaoka et al

    2007-01-01

    Full Text Available Optical mirrors used in extreme ultraviolet lithography systems require a figure accuracy and a roughness of about 0.1 nm rms. In addition, mirror substrates must be low-thermal-expansion materials. Thus, in this study, we processed two low-thermal-expansion materials, ULE [K. Hrdina, B. Hanson, P. Fenn, R. Sabia, Proc. SPIE 4688 (2002 454.] (Corning Inc. and Zerodur [I. Mitra, M.J. Davis, J. Alkemper, Rolf Müller, H. Kohlmann, L. Aschke, E. Mörsen, S. Ritter, H. Hack, W. Pannhorst, Proc. SPIE 4688 (2002 462.] (SCHOTT AG, with elastic emission machining (EEM in order to evaluate the removal properties. Consequently, we successfully calculated the respective removal rates, because removal volumes were found to be proportional to process times in EEM. Moreover, we demonstrated that the surface roughness of Zerodur is reduced to 0.1 nm rms in the spatial wavelength range from 100 μm to 1 mm.

  12. Colossal Positive and Negative Thermal Expansion in the Framework Material Ag3[Co(CN)6

    Science.gov (United States)

    Goodwin, Andrew L.; Calleja, Mark; Conterio, Michael J.; Dove, Martin T.; Evans, John S. O.; Keen, David A.; Peters, Lars; Tucker, Matthew G.

    2008-02-01

    We show that silver(I) hexacyanocobaltate(III), Ag3[Co(CN)6], exhibits positive and negative thermal expansion an order of magnitude greater than that seen in other crystalline materials. This framework material expands along one set of directions at a rate comparable to the most weakly bound solids known. By flexing like lattice fencing, the framework couples this to a contraction along a perpendicular direction. This gives negative thermal expansion that is 14 times larger than in ZrW2O8. Density functional theory calculations quantify both the low energy associated with this flexibility and the role of argentophilic (Ag+...Ag+) interactions. This study illustrates how the mechanical properties of a van der Waals solid might be engineered into a rigid, useable framework.

  13. Low-thermal expansion infrared glass ceramics

    Science.gov (United States)

    Lam, Philip

    2009-05-01

    L2 Tech, Inc. is in development of an innovative infrared-transparent glass ceramic material with low-thermal expansion (ZrW2O8) which has Negative Thermal Expansion (NTE). The glass phase is the infrared-transparent germanate glass which has positive thermal expansion (PTE). Then glass ceramic material has a balanced thermal expansion of near zero. The crystal structure is cubic and the thermal expansion of the glass ceramic is isotropic or equal in all directions.

  14. A Noncontact Measurement Technique for the Density and Thermal Expansion Coefficient of Solid and Liquid Materials

    Science.gov (United States)

    Chung, Sang K.; Thiessen, David B.; Rhim, Won-Kyu

    1996-01-01

    A noncontact measurement technique for the density and the thermal expansion refractory materials in their molten as well as solid phases is presented. This technique is based on the video image processing of a levitated sample. Experiments were performed using the high-temperature electrostatic levitator (HTESL) at the Jet Propulsion Laboratory in which 2-3 mm diameter samples can be levitated, melted, and radiatively cooled in a vacuum. Due to the axisymmetric nature of the molten samples when levitated in the HTESL, a rather simple digital image analysis can be employed to accurately measure the volumetric change as a function of temperature. Density and the thermal expansion coefficient measurements were made on a pure nickel sample to test the accuracy of the technique in the temperature range of 1045-1565 C. The result for the liquid phase density can be expressed by p = 8.848 + (6.730 x 10(exp -4)) x T (degC) g/cu cm within 0.8% accuracy, and the corresponding thermal expansion coefficient can be expressed by Beta=(9.419 x 10(exp -5)) - (7.165 x 10(exp -9) x T (degC)/K within 0.2% accuracy.

  15. A Micro-Test Structure for the Thermal Expansion Coefficient of Metal Materials

    Directory of Open Access Journals (Sweden)

    Qingying Ren

    2017-02-01

    Full Text Available An innovative micro-test structure for detecting the thermal expansion coefficient (TEC of metal materials is presented in this work. Throughout this method, a whole temperature sensing moveable structures are supported by four groups of cascaded chevrons beams and packed together. Thermal expansion of the metal material causes the deflection of the cascaded chevrons, which leads to the capacitance variation. By detecting the capacitance value at different temperatures, the TEC value of the metal materials can be calculated. A finite element model has been established to verify the relationship between the TEC of the material and the displacement of the structure on horizontal and vertical directions, thus a function of temperature for different values of TEC can be deduced. In order to verify the analytical model, a suspended-capacitive micro-test structure has been fabricated by MetalMUMPs process and tested in a climate chamber. Test results show that in the temperature range from 30 °C to 80 °C, the TEC of the test material is 13.4 × 10−6 °C−1 with a maximum relative error of 0.8% compared with the given curve of relationship between displacement and temperature.

  16. Parallel calculations of vibrational properties in complex materials: negative thermal expansion and elastic inhomogeneity

    Science.gov (United States)

    Vila, F. D.; Rehr, J. J.

    Effects of thermal vibrations are essential to obtain a more complete understanding of the properties of complex materials. For example, they are important in the analysis and simulation of x-ray absorption spectra (XAS). In previous work we introduced an ab initio approach for a variety of vibrational effects, such as crystallographic and XAS Debye-Waller factors, Debye and Einstein temperatures, and thermal expansion coefficients. This approach uses theoretical dynamical matrices from which the locally-projected vibrational densities of states are obtained using a Lanczos recursion algorithm. In this talk I present recent improvements to our implementation, which permit simulations of more complex materials with up to two orders of magnitude larger simulation cells. The method takes advantage of parallelization in calculations of the dynamical matrix with VASP. To illustrate these capabilities we discuss two problems of considerable interest: negative thermal expansion in ZrW2O8; and local inhomogeneities in the elastic properties of supported metal nanoparticles. Both cases highlight the importance of a local treatment of vibrational properties. Supported by DOE Grant DE-FG02-03ER15476, with computer support from DOE-NERSC.

  17. Design of materials with extreme thermal expansion using a three-phase topology optimization method

    DEFF Research Database (Denmark)

    Sigmund, Ole; Torquato, S.

    1997-01-01

    that optimizes an objective function (e.g. thermoelastic properties) subject to certain constraints, such as elastic symmetry or volume fractions of the constituent phases, within a periodic base cell. The effective properties of the material structures are found using the numerical homogenization method based......Composites with extremal or unusual thermal expansion coefficients are designed using a three-phase topology optimization method. The composites are made of two different material phases and a void phase. The topology optimization method consists in finding the distribution of material phases...... microstructures that realize the bounds. For three phases, the optimal microstructures are also compared with new rigorous bounds and again it is shown that the method yields designed materials with thermoelastic properties that are close to the bounds. The three-phase design method is illustrated by designing...

  18. Novel Materials through Non-Hydrolytic Sol-Gel Processing: Negative Thermal Expansion Oxides and Beyond

    Directory of Open Access Journals (Sweden)

    Cora Lind

    2010-04-01

    Full Text Available Low temperature methods have been applied to the synthesis of many advanced materials. Non-hydrolytic sol-gel (NHSG processes offer an elegant route to stable and metastable phases at low temperatures. Excellent atomic level homogeneity gives access to polymorphs that are difficult or impossible to obtain by other methods. The NHSG approach is most commonly applied to the preparation of metal oxides, but can be easily extended to metal sulfides. Exploration of experimental variables allows control over product stoichiometry and crystal structure. This paper reviews the application of NHSG chemistry to the synthesis of negative thermal expansion oxides and selected metal sulfides.

  19. Synthesis and characterization of some low and negative thermal expansion materials

    Science.gov (United States)

    Varga, Tamas

    2005-12-01

    The high-pressure behavior of several negative thermal expansion materials was studied by different methods. In-situ high-pressure x-ray and neutron diffraction studies on several compounds of the orthorhombic Sc 2W3O12 structure revealed an unusual "bulk modulus collapse" at the orthorhombic to monoclinic phase transition. In some members of the A2M3O12 family, a second phase transition and/or pressure-induced amorphization were also seen at higher pressure. The mechanism for volume contraction on compression is different from that on heating. A combined in-situ high pressure x-ray diffraction and absorption spectroscopic study has been carried out for the first time. The pressure-induced amorphization in cubic ZrW2O8 and ZrMo 2O8 was studied by following the changes in the local coordination environments of the metals. A significant change in the average tungsten coordination was found in ZrW2O8, and a less pronounced change in the molybdenum coordination in ZrMo2O8 on amorphization. A kinetically frustrated phase transition to a high-pressure crystalline phase or a kinetically hindered decomposition, are likely driving forces of the amorphization. A complementary ex-situ study confirmed the greater distortion of the framework tetrahedra in ZrW2O8, and revealed a similar distortion of the octahedra in both compounds. The possibility of stabilizing the low thermal expansion high-temperature structure in AM2O7 compounds to lower temperatures through stuffing of ZrP2O7 was explored. Although the phase transition temperature was suppressed in MIxZr 1-xMIIIxP2O7 compositions, the chemical modification employed was not successful in stabilizing the high-temperature structure to around room temperature. An attempt has been made to control the thermal expansion properties in materials of the (MIII0.5MV 0.5)P2O7-type through the choice of the metal cations and through manipulating the ordering of the cations by different heat treatment conditions. Although controlled heat

  20. Negative thermal expansion and low-frequency modes in cyanide-bridged framework materials

    Science.gov (United States)

    Goodwin, Andrew L.; Kepert, Cameron J.

    2005-04-01

    We analyze the intrinsic geometric flexibility of framework structures incorporating linear metal-cyanide-metal (M-CN-M') linkages using a reciprocal-space dynamical matrix approach. We find that this structural motif is capable of imparting a significant negative thermal expansion (NTE) effect upon such materials. In particular, we show that the topologies of a number of simple cyanide-containing framework materials support a very large number of low-energy rigid-unit phonon modes, all of which give rise to NTE behavior. We support our analysis by presenting experimental verification of this behavior in the family of compounds ZnxCd1-x(CN)2 , which we show to exhibit a NTE effect over the temperature range 25-375K more than double that of materials such as ZrW2O8 .

  1. TOPICAL REVIEW: Negative thermal expansion

    Science.gov (United States)

    Barrera, G. D.; Bruno, J. A. O.; Barron, T. H. K.; Allan, N. L.

    2005-02-01

    There has been substantial renewed interest in negative thermal expansion following the discovery that cubic ZrW2O8 contracts over a temperature range in excess of 1000 K. Substances of many different kinds show negative thermal expansion, especially at low temperatures. In this article we review the underlying thermodynamics, emphasizing the roles of thermal stress and elasticity. We also discuss vibrational and non-vibrational mechanisms operating on the atomic scale that are responsible for negative expansion, both isotropic and anisotropic, in a wide range of materials.

  2. Thermal Expansion of Polyurethane Foam

    Science.gov (United States)

    Lerch, Bradley A.; Sullivan, Roy M.

    2006-01-01

    Closed cell foams are often used for thermal insulation. In the case of the Space Shuttle, the External Tank uses several thermal protection systems to maintain the temperature of the cryogenic fuels. A few of these systems are polyurethane, closed cell foams. In an attempt to better understand the foam behavior on the tank, we are in the process of developing and improving thermal-mechanical models for the foams. These models will start at the microstructural level and progress to the overall structural behavior of the foams on the tank. One of the key properties for model characterization and verification is thermal expansion. Since the foam is not a material, but a structure, the modeling of the expansion is complex. It is also exacerbated by the anisoptropy of the material. During the spraying and foaming process, the cells become elongated in the rise direction and this imparts different properties in the rise direction than in the transverse directions. Our approach is to treat the foam as a two part structure consisting of the polymeric cell structure and the gas inside the cells. The polymeric skeleton has a thermal expansion of its own which is derived from the basic polymer chemistry. However, a major contributor to the thermal expansion is the volume change associated with the gas inside of the closed cells. As this gas expands it exerts pressure on the cell walls and changes the shape and size of the cells. The amount that this occurs depends on the elastic and viscoplastic properties of the polymer skeleton. The more compliant the polymeric skeleton, the more influence the gas pressure has on the expansion. An additional influence on the expansion process is that the polymeric skeleton begins to breakdown at elevated temperatures and releases additional gas species into the cell interiors, adding to the gas pressure. The fact that this is such a complex process makes thermal expansion ideal for testing the models. This report focuses on the thermal

  3. Unusual compressibility in the negative-thermal-expansion material ZrW2O8

    Science.gov (United States)

    Migliori, Albert; Pantea, C.; Ledbetter, H.; Zhao, Y.; Kimura, T.; Littlewood, Peter B.; van Duijn, J.; Kowach, G. R.

    2006-03-01

    The negative thermal expansion (NTE) compound ZrW2O8 has been well-studied because it remains cubic with a nearly constant, isotropic NTE coefficient over a broad temperature range. However, its elastic constants seem just as strange as its volume because NTE makes temperature acts as positive pressure, decreasing volume on warming and, unlike most materials, the thermally-compressed solidsoftens. Does ZrW2O8 also soften when pressure alone is applied? Using pulse-echo ultrasound in a hydrostatic SiC anvil cell, we determine the elastic tensor of monocrystalline ZrW2O8 near 300 K as a function of pressure. We indeed find an unusual decrease in bulk modulus with pressure. Our results are inconsistent with conventional lattice dynamics, but do show that the thermodynamically-complete constrained-lattice model can relate NTE to elastic softening as increases in either temperature or pressure reduce volume, establishing the predictive power of the model, and making it an important concept in condensed-matter physics.

  4. Low thermal expansion glass ceramics

    CERN Document Server

    1995-01-01

    This book is one of a series reporting on international research and development activities conducted by the Schott group of companies With the series, Schott aims to provide an overview of its activities for scientists, engineers, and managers from all branches of industry worldwide where glasses and glass ceramics are of interest Each volume begins with a chapter providing a general idea of the current problems, results, and trends relating to the subjects treated This volume describes the fundamental principles, the manufacturing process, and applications of low thermal expansion glass ceramics The composition, structure, and stability of polycrystalline materials having a low thermal expansion are described, and it is shown how low thermal expansion glass ceramics can be manufactured from appropriately chosen glass compositions Examples illustrate the formation of this type of glass ceramic by utilizing normal production processes together with controlled crystallization Thus glass ceramics with thermal c...

  5. MATERIALS THAT SHRINK ON HEATING: PRESSURE-INDUCED PHASE TRANSITIONS IN NEGATIVE THERMAL EXPANSION MATERIALS, AND THEIR ENERGETICS

    Energy Technology Data Exchange (ETDEWEB)

    Varga, Tamas

    2011-09-01

    Despite the fact that all chemical bonds expand on heating, a small class of materials shrinks when heated. These, so called negative thermal expansion (NTE) materials, are a unique class of materials with some exotic properties. The present chapter offers insight into the structural aspects of pressure- (or temperature-) induced phase transformations, and the energetics of those changes in these fascinating materials, in particular NTE compound cubic ZrW2O8, orthorhombic Sc2W3O12 and Sc2Mo3O12, as well as other members of the 'scandium tungstate family'. In subsequent sections, (i) combined in situ high-pressure synchrotron XRD and XAS studies of NTE material ZrW2O8; (ii) an in situ high-pressure synchrotron XRD study of Sc2W3O12, Sc2Mo3O12, and Al2W3O12; and (iii) thermochemical studies of the above materials are presented and discussed. In all of these studies, chemical bonds change, sometimes break and new ones form. Correlations between structure, chemistry, and energetics are revealed. It is also shown that (iv) NTE materials are good candidates as precursors to make novel solid state materials, such as the conducting Sc0.67WO4, using high-pressure, high-temperature synthesis, through modification of bonding and electronic structure, and thus provide vast opportunities for scientific exploration.

  6. High-pressure study on borides, nanocrystals and negative thermal expansion materials

    Science.gov (United States)

    Chen, Bin

    2001-07-01

    By the use of Mao-Bell diamond anvil cell, employed with x-ray diffraction, optical absorption, Raman and Fourier Transform Infrared (FTIR) spectroscopy, iron borides, nanocrystalline Ni, Fe, Ni3Fe, Al2O 3, Negative Thermal Expansion (NTE) materials such as HfW2O 8, ZrW2O8, ZrMo2O8 have been studied under high pressure. The results of a synchrotron x-ray diffraction study of Fe2B under quasi-hydrostatic conditions from 0 to 50 GPa are reported. Over this pressure range, no phase change or disproportionation has been observed. A value of the bulk modulus, K, of 192 +/- 14 GPa and the first pressure derivative of the bulk modulus, K', of 2.6 +/- 0.6, are obtained. The compression is found to be anisotropic, with the a-axis being more incompressible than the c-axis. X-ray diffraction data of nanocrystalline Ni, Fe and Ni3Fe, using a synchrotron source, was collected under nonhydrostatic and quasi-hydrostatic conditions up to 60 GPa. The bulk moduli, of 185.4 +/- 10 GPa, 171 +/- 5 GPa, 179.4 +/- 8.1 GPa, 168.3 +/- 2.6 GPa, are determined from quasi-hydrostatic compression data of nanocrystalline Ni, alpha-Fe, epsilon-Fe and Ni3Fe, respectively, which are found similar to those of large-grained counterparts. Their phase transformations are studied and compared with their bulk counterparts. A new phase of Al2O3 formed by compression of the nanocrystalline gamma-phase has been detected. This high-pressure phase is metastable upon decompression to ambient pressure, and has a bulk modulus of 251 +/- 10 GPa for Al2O3 of 67 nm. From hydrostatic compression, bulk moduli of K67 = 238 +/- 3 GPa and K37 = 172 +/- 3 GPa are obtained for the 67 nm and 37 nm gamma-Al2O3 particles, respectively, which are significantly higher than that found in a previous study of smaller sized nanocrystals of gamma-alumina (K20 = 162 +/- 14 GPa for 20 nm crystallites). High pressure optical absorption, Raman and FTIR measurements are carried out on negative thermal expansion materials: HfW2O8, ZrW2O

  7. Low Thermal Expansion Glass Ceramics

    CERN Document Server

    Bach, Hans

    2005-01-01

    This book appears in the authoritative series reporting the international research and development activities conducted by the Schott group of companies. This series provides an overview of Schott's activities for scientists, engineers, and managers from all branches of industry worldwide in which glasses and glass ceramics are of interest. Each volume begins with a chapter providing a general idea of the current problems, results, and trends relating to the subjects treated. This new extended edition describes the fundamental principles, the manufacturing process, and applications of low thermal expansion glass ceramics. The composition, structure, and stability of polycrystalline materials having a low thermal expansion are described, and it is shown how low thermal expansion glass ceramics can be manufactured from appropriately chosen glass compositions. Examples illustrate the formation of this type of glass ceramic by utilizing normal production processes together with controlled crystallization. Thus g...

  8. End plate for e.g. solid oxide fuel cell stack, sets thermal expansion coefficient of material to predetermined value

    DEFF Research Database (Denmark)

    2011-01-01

    .05-0.3 mm. USE - End plate for solid oxide fuel cell stack (claimed). Can also be used in polymer electrolyte fuel cell stack and direct methanol fuel cell stack. ADVANTAGE - The robustness of the end plate is improved. The structure of the end plate is simplified. The risk of delamination of the stack......NOVELTY - The end plate is made of material whose thermal expansion coefficient is corresponding to that of material of a cell (103). The thermal expansion coefficient of material is 9asterisk10-6 K-1 to 14asterisk10-6 K11. The thickness of the end plate is within the range of 0.001-1 mm and 0...

  9. Pressurized electrolysis stack with thermal expansion capability

    Science.gov (United States)

    Bourgeois, Richard Scott

    2015-07-14

    The present techniques provide systems and methods for mounting an electrolyzer stack in an outer shell so as to allow for differential thermal expansion of the electrolyzer stack and shell. Generally, an electrolyzer stack may be formed from a material with a high coefficient of thermal expansion, while the shell may be formed from a material having a lower coefficient of thermal expansion. The differences between the coefficients of thermal expansion may lead to damage to the electrolyzer stack as the shell may restrain the thermal expansion of the electrolyzer stack. To allow for the differences in thermal expansion, the electrolyzer stack may be mounted within the shell leaving a space between the electrolyzer stack and shell. The space between the electrolyzer stack and the shell may be filled with a non-conductive fluid to further equalize pressure inside and outside of the electrolyzer stack.

  10. Thermal Expansion of Hafnium Carbide

    Science.gov (United States)

    Grisaffe, Salvatore J.

    1960-01-01

    Since hafnium carbide (HfC) has a melting point of 7029 deg. F, it may have many high-temperature applications. A literature search uncovered very little information about the properties of HfC, and so a program was initiated at the Lewis Research Center to determine some of the physical properties of this material. This note presents the results of the thermal expansion investigation. The thermal-expansion measurements were made with a Gaertner dilatation interferometer calibrated to an accuracy of +/- 1 deg. F. This device indicates expansion by the movement of fringes produced by the cancellation and reinforcement of fixed wave-length light rays which are reflected from the surfaces of two parallel quartz glass disks. The test specimens which separate these disks are three small cones, each approximately 0.20 in. high.

  11. Molecular modeling of nanotube composite materials: Interface formation, interfacial strength, and thermal expansion

    Science.gov (United States)

    Marietta-Tondin, Olivier

    present in this resin system, such as molecular wrapping around the SWNTs. Second, existing MD simulation models of nanotube pullout are analyzed and modified to examine the energy of certain material systems more correctly, and to characterize interfacial shear strength in SWNT/polymer composites. The interfacial bonding and load transfer behaviors between the different SWNTs' configurations (open end, capped end, functionalized end) and three different matrices (polystyrene, polyethylene and Epon862) were examined using the modified models. The results of the modified models effectively reveal the effects of different tube configurations and resin matrices on the interfacial strength during a simulated pullout. Finally, we use MD simulation to investigate the coefficient of thermal expansion (CTE) of individual SWNTs, SWNT ropes, as well as SWNT nanocomposites. Experiments were also carried out in order to gain further insight in the results. It is found that, while the CTE of individual nanotubes is of low negative value, the CTE of the same tubes within a rope or a nanocomposite can significantly change. We also find that SWNTs can be utilized to tailor the CTE of the Epon862 resin system, depending on the functionalization of the SWNTs prior to their introduction in the resin. Finally, a new twisting vibration mode was revealed in SWNT ropes that should prove critical in further SWNT rope studies utilizing MD simulation.

  12. Thermal expansion and swelling of cured epoxy resin used in graphite/epoxy composite materials

    Science.gov (United States)

    Adamson, M. J.

    1980-01-01

    The paper presents results of experiments in which the thermal expansion and swelling behavior of an epoxy resin system and two graphite/epoxy composite systems exposed to water were measured. It was found that the cured epoxy resin swells by an amount slightly less than the volume of the absorbed water and that the swelling efficiency of the water varies with the moisture content of the polymer. Additionally, the thermal expansion of cured epoxy resin that is saturated with water is observed to be more than twice that of dry resin. Results also indicate that cured resin that is saturated with 7.1% water at 95 C will rapidly increase in moisture content to 8.5% when placed in 1 C water. The mechanism for this phenomenon, termed reverse thermal effect, is described in terms of a slightly modified free-volume theory in conjunction with the theory of polar molecule interaction. Nearly identical behavior was observed in two graphite/epoxy composite systems, thus establishing that this behavior may be common to all cured epoxy resins.

  13. Investigation of the thermal expansion of the refractory materials at high temperatures

    Science.gov (United States)

    Kostanovskiy, A.; Kostanovskaya, M.; Zeodinov, M.; Pronkin, A.

    2017-11-01

    We present the experimental investigation of the relative elongation and the coefficient of linear thermal expansion for monocrystaline alumina Al2O3 (1200 K – 1860 K), zirconia ZrO2 (1200 K – 2730 K) and siliconized silicon carbide SiC+Si (1150 K – 2500 K) in the specified range of temperatures. The following approach is used to measure the relative elongation: the through-cylindrical-marks located in the centre of isothermal part of the sample, and the measurement of temperature by two blackbody models, taken out of the area of the sample where the relative elongation is measured.

  14. Fundamentals of Thermal Expansion and Thermal Contraction

    OpenAIRE

    Liu, Zi-Kui; Shang, Shun-Li; Wang, Yi

    2017-01-01

    Thermal expansion is an important property of substances. Its theoretical prediction has been challenging, particularly in cases the volume decreases with temperature, i.e., thermal contraction or negative thermal expansion at high temperatures. In this paper, a new theory recently developed by the authors has been reviewed and further examined in the framework of fundamental thermodynamics and statistical mechanics. Its applications to cerium with colossal thermal expansion and Fe3Pt with th...

  15. Giant negative thermal expansion in magnetic nanocrystals

    Science.gov (United States)

    Zheng, X. G.; Kubozono, H.; Yamada, H.; Kato, K.; Ishiwata, Y.; Xu, C. N.

    2008-12-01

    Most solids expand when they are heated, but a property known as negative thermal expansion has been observed in a number of materials, including the oxide ZrW2O8 (ref. 1) and the framework material ZnxCd1-x(CN)2 (refs 2,3). This unusual behaviour can be understood in terms of low-energy phonons, while the colossal values of both positive and negative thermal expansion recently observed in another framework material, Ag3[Co(CN)6], have been explained in terms of the geometric flexibility of its metal-cyanide-metal linkages. Thermal expansion can also be stopped in some magnetic transition metal alloys below their magnetic ordering temperature, a phenomenon known as the Invar effect, and the possibility of exploiting materials with tuneable positive or negative thermal expansion in industrial applications has led to intense interest in both the Invar effect and negative thermal expansion. Here we report the results of thermal expansion experiments on three magnetic nanocrystals-CuO, MnF2 and NiO-and find evidence for negative thermal expansion in both CuO and MnF2 below their magnetic ordering temperatures, but not in NiO. Larger particles of CuO and MnF2 also show prominent magnetostriction (that is, they change shape in response to an applied magnetic field), which results in significantly reduced thermal expansion below their magnetic ordering temperatures; this behaviour is not observed in NiO. We propose that the negative thermal expansion effect in CuO (which is four times larger than that observed in ZrW2O8) and MnF2 is a general property of nanoparticles in which there is strong coupling between magnetism and the crystal lattice.

  16. Structural investigation of the negative-thermal-expansion material ZrW2O8.

    Science.gov (United States)

    Evans; David; Sleight

    1999-06-01

    High-resolution powder diffraction data have been recorded on cubic ZrW(2)O(8) [a = 9.18000 (3) Å at 2 K] at 260 temperatures from 2 to 520 K in 2 K steps. These data have confirmed that alpha-ZrW(2)O(8) has a negative coefficient of thermal expansion, alpha = -9.07 x 10(-6) K(-1) (2-350 K). A 'parametric' approach to Rietveld refinement is adopted and it is demonstrated that a full anisotropic refinement can be performed at each temperature, despite using a data collection time of only 5 min. Examination of the resulting structural parameters suggests that the origin of the contraction with increasing temperature can be traced straightforwardly to the rigid-body transverse librations of bridging O atoms. alpha-ZrW(2)O(8) undergoes a phase transition from P2(1)3 to Pa3; at 448 K that is associated with the onset of considerable oxygen mobility. The phase transition can be described in terms of a simple cubic three-dimensional Ising model. Unusual kinetics are associated with this phase transition. Hysteresis in the cell parameter through the phase transition is the opposite of that normally observed.

  17. Thermal expansion: Metallic elements and alloys. [Handbook

    Science.gov (United States)

    Touloukian, Y. S.; Kirby, R. K.; Taylor, R. E.; Desai, P. D.

    1975-01-01

    The introductory sections of the work are devoted to the theory of thermal expansion of solids and to methods for the measurement of the linear thermal expansion of solids (X-ray methods, high speed methods, interferometry, push-rod dilatometry, etc.). The bulk of the work is devoted to numerical data on the thermal linear expansion of all the metallic elements, a large number of intermetallics, and a large number of binary alloy systems and multiple alloy systems. A comprehensive bibliography is provided along with an index to the materials examined.

  18. ZrW2O8-doped epoxy as low thermal expansion insulating materials for superconducting feeder system

    Science.gov (United States)

    Chu, Xinxin; Wu, Zhixiong; Huang, Chuanjun; Huang, Rongjin; Zhou, Yuan; Li, Laifeng

    2012-12-01

    Epoxy resin insulating materials used in superconducting feeder system of fusion device are required to be low thermal expansion coefficient (TEC). In this paper, negative thermal expansion (NTE) material ZrW2O8 filled epoxy resins were fabricated. To improve the dispersion of fillers in epoxy matrix, plasma polymerization was performed on the surface of ZrW2O8 powders. Transmission electron microscope (TEM) and surface wettability analysis were performed before and after the surface modification of ZrW2O8 powders. The TEC of ZrW2O8/epoxy composites were measured from 77 K to room temperature. The results show the doping of ZrW2O8 can significantly reduce the TEC of epoxy resins. The sedimentation rate of ZrW2O8 before and after modified in epoxy was compared by density measurement. It can be seen that the ZrW2O8 surface modified by plasma polymerization can enhance its dispersion properties in epoxy matrix.

  19. Contribution of thermal expansion and

    Directory of Open Access Journals (Sweden)

    O.I.Pursky

    2007-01-01

    Full Text Available A theoretical model is developed to describe the experimental results obtained for the isobaric thermal conductivity of rare gas solids (RGS. The isobaric thermal conductivity of RGS has been analysed within Debye approximation with regard to the effect of thermal expansion. The suggested model takes into consideration the fact that thermal conductivity is determined by U-processes while above the phonon mobility edge it is determined by "diffusive" modes migrating randomly from site to site. The mobility edge ω0 is determined from the condition that the phonon mean-free path restricted by the U-processes cannot be smaller than half of the phonon wavelength.

  20. Heat capacity, lattice dynamics, and thermodynamic stability of the negative thermal expansion material HfMo2O8

    Science.gov (United States)

    Kennedy, Catherine A.; White, Mary Anne; Wilkinson, Angus P.; Varga, Tamas

    2007-06-01

    We explore the lattice dynamics of the negative thermal expansion material, cubic HfMo2O8 , through analysis of its heat capacity (measured from 0.5to300K ) and its room-temperature Raman spectrum. Its heat capacity is quantitatively very similar to that of ZrW2O8 , as is its Raman spectrum. The heat capacity of HfMo2O8 can be well represented by the present lattice dynamical assignment and by CP(HfW2O8)-CP(ZrW2O8)+CP(ZrMo2O8) , but not by CP(HfO2)+2CP(MoO3) , likely because the AB2O8 compounds have low-frequency optic modes, not present in HfO2 and MoO3 . The present thermodynamic data also allow an analysis of the thermodynamic stability of cubic HfMo2O8 , and it is shown to be unstable with respect to MoO3 and HfO2 at room temperature.

  1. Composite material having controlled coefficient of thermal expansion with oxidic ceramics and procedure for the obtainment thereof

    OpenAIRE

    Torrecillas, Ramón; García Moreno, Olga; Fernández, Adolfo

    2009-01-01

    [EN] The present invention relates to a composite material comprising a ceramic component, characterized in having a negative coefficient of thennal expansion, and oxidic ceramic particles, to the procedure for the obtainment thereof, and to the uses thereof in microelectronics, precision optics, aeronautics and aerospace.

  2. Correlated atomic motions in the negative thermal expansion material ZrW2O8: A local structure study

    Science.gov (United States)

    Cao, D.; Bridges, F.; Kowach, G. R.; Ramirez, A. P.

    2003-07-01

    Recent studies of zirconium tungstate, ZrW2O8, show an isotropic negative thermal expansion (NTE) over a wide temperature range. It has been proposed that the low-energy phonon vibrational modes, observed in both specific heat and phonon density-of-states measurements, are responsible for this unusual NTE. We have carried out x-ray-absorption fine-structure (XAFS) experiments at both the W LIII edge and Zr K edge to study the detailed local structure in ZrW2O8. Our XAFS results show a very small temperature dependence of the broadening parameter, σ, for the W-Zr atom pair and the W-O-Zr linkage; consequently, the displacements of the W, O, and Zr atoms must be correlated. The data show a much larger temperature dependence of σ for the nearest W1-W2 pair as well as for the nearest Zr-Zr pair. These combined results indicate that it is the correlated motion of a WO4 tetrahedron and its three nearest ZrO6 octahedra that leads to the NTE effect in this material instead of primarily transverse vibrations of the middle O atom in the W-O-Zr linkage. The data for both W-W and Zr-Zr atom pairs also indicate a hardening of the effective spring constant near 100 K, which is consistent with the shift of the lowest mode with T in the phonon density of states. A simple model is developed to explain the NTE in terms of the local structure results; it also provides a natural explanation for the lack of a soft-mode phase transition.

  3. Micro-architected Composite Lattices with Tunable Negative Thermal Expansions

    Science.gov (United States)

    Wang, Qiming

    Solid materials with minimum or negative thermal expansion (NTE) have broad applications, from dental fillings to thermal-sensitive precision instruments. Previous studies on NTE structures were mostly focused on theoretically design and 2D experimental demonstrations. Here, aided with multimaterial projection micro-stereolithography, we experimentally fabricate multi-material composite lattices that exhibit significant negative thermal expansion in three directions and over a large range of temperature variations. The negative thermal expansion is induced by the structural interaction of material components with distinct thermal expansion coefficients. The NTE performance can be tuned over a large range by varying the thermal expansion coefficient difference between constituent beams and geometrical arrangement. Our experimental results match qualitatively with a simple scaling law and quantitatively consistently with computational models.

  4. Impact of size and temperature on thermal expansion of nanomaterials

    Indian Academy of Sciences (India)

    A theoretical method has been discussed to study the size dependency of thermal expansion of nanomaterials at higher temperature by considering the surface effect. A thermodynamical analysis of the equation of state (EoS) is studied from the knowledge of thermal expansion of nano-materials based on theoretical ...

  5. New Nanocomposite Materials with Improved Mechanical Strength and Tailored Coefficient of Thermal Expansion for Electro-Packaging Applications

    Directory of Open Access Journals (Sweden)

    Abdollah Saboori

    2017-12-01

    Full Text Available In this research, copper nanocomposites reinforced by graphene nanoplatelets (GNPs were fabricated using a wet mixing method followed by a classical powder metallurgy route. In order to find the best dispersion technique, ball milling and wet mixing were chosen. Qualitative evaluation of the structure of the graphene after mixing indicated that the wet mixing is an appropriate technique to disperse the GNPs. Thereafter, the influence of graphene content on microstructure, density, hardness, elastic modulus, and thermal expansion coefficient of composites was investigated. It was shown that by increasing the graphene content the aggregation of graphene is more obvious and, thus, these agglomerates affect the final properties adversely. In comparison with the unreinforced Cu, Cu–GNP composites were lighter, and their hardness and Young’s modulus were higher as a consequence of graphene addition. According to the microstructural observation of pure copper and its composites after sintering, it was concluded that grain refinement is the main mechanism of strengthening in this research. Apart from the mechanical characteristics, the coefficient of thermal expansion of composites decreased remarkably and the combination of this feature with appropriate mechanical properties can make them a promising candidate for use in electronic packaging applications.

  6. Local lattice distortion in the giant negative thermal expansion material Mn3Cu1-xGexN.

    Science.gov (United States)

    Iikubo, S; Kodama, K; Takenaka, K; Takagi, H; Takigawa, M; Shamoto, S

    2008-11-14

    Giant negative thermal expansion is achieved in antiperovskite manganese nitrides when the sharp volume change associated with magnetic ordering is broadened by substitution. In this Letter, we address the unique role of the ''magic" element, Ge, for such broadening in Mn3Cu1-xGexN. We present evidence for a local lattice distortion well described by the low-temperature tetragonal (T4) structure of Mn3GeN for a range of x, where the overall structure remains cubic. This structural instability shows a strong correlation with the broadness of the growth of the ordered magnetic moment and, hence, is considered to trigger the broadening of the volume change.

  7. Thin metastructures with engineered thermal expansion

    Science.gov (United States)

    Gdoutos, Eleftherios E.

    The geometry and constituent materials of metastructures can be used to engineer the thermal expansion coefficient. In this thesis, we design, fabricate, and test thin thermally stable metastructures consisting of bi-metallic unit cells and show how the coefficient of thermal expansion (CTE) of these metastructures can be finely and coarsely tuned by varying the CTE of the constituent materials and the unit cell geometry. Planar and three-dimensional finite element method modeling is used to drive the design and inform experiments, and predict the response of these metastructures. We demonstrate computationally the significance of out-of-plane effects in the metastructure response. We develop an experimental setup using digital image correlation and an infrared camera to experimentally measure full displacement and temperature fields during testing and accurately measure the metastructures' CTE. We experimentally demonstrate high aspect ratio metastructures of Ti/Al and Kovar/Al which exhibit near-zero and negative CTE, respectively. We demonstrate robust fabrication procedures for thermally stable samples with high aspect ratios in thin foil and thin film scales. We investigate the lattice structure and mechanical properties of thin films comprising a near-zero CTE metastructure. The mechanics developed in this work can be used to engineer metastructures of arbitrary CTE and can be extended to three dimensions.

  8. Structure and thermal expansion of liquid bismuth

    Directory of Open Access Journals (Sweden)

    Mudry S.

    2015-12-01

    Full Text Available Experimental structural data for liquid Bi were used for estimation of the main structure parameters as well as the thermal expansion coefficient both in supercooled and superheated temperature ranges. It was shown that the equilibrium melt had a positive thermal expansion coefficient within a temperature range upon melting and a negative one at higher temperatures. The former was related to structure changes upon melting, whereas the latter with topologic disordering upon further heating. It was found that the superheated melt had a negative thermal expansion coefficient. The results obtained from structural data were compared with the thermal expansion coefficient calculated from the data of density for liquid Bi.

  9. Spontaneous thermal expansion of nematic elastomers

    Science.gov (United States)

    Tajbakhsh, A. R.; Terentjev, E. M.

    2001-10-01

    We study the monodomain (single-crystal) nematic elastomer materials, all side-chain siloxane polymers with the same mesogenic groups and crosslinking density, but differing in the type of crosslinking. Increasing the proportion of long di-functional segments of main-chain nematic polymer, acting as network crosslinking, results in dramatic changes in the uniaxial equilibrium thermal expansion on cooling from the isotropic phase. At higher concentration of main chains their behaviour dominates the elastomer properties. At low concentration of main-chain material, we detect two distinct transitions at different temperatures, one attributed to the main-chain, the other to the side-chain component. The effective uniaxial anisotropy of nematic rubber, r(T)=ell_{allel}/ell_{bot} proportional to the effective nematic order parameter Q(T), is given by an average of the two components and thus reflects the two-transition nature of thermal expansion. The experimental data is compared with the theoretical model of ideal nematic elastomers; applications in high-amplitude thermal actuators are discussed in the end.

  10. Study of negative thermal expansion and shift in phase transition temperature in Ti4+- and Sn4+-substituted ZrW2O8 materials.

    Science.gov (United States)

    Buysser, Klaartje De; Driessche, Isabel Van; Putte, Bart Vande; Vanhee, Paul; Schaubroeck, Joseph; Hoste, Serge

    2008-01-21

    The negative-thermal-expansion material ZrW(2)O(8) is known to undergo an order-disorder phase transition which affects its expansion behavior. In this study, Ti(4+) and Sn(4+) are examined as possible substituting ions for the Zr(4+) position in ZrW(2)O(8). This substitution leads to a decrease in cell parameters, as the ionic radii of the substituents are smaller than the Zr(4+) ionic radius. A remarkable decrease in transition temperature is noticed. DSC is used to quantify the enthalpy and entropy changes during the phase transition in order to reveal the mechanisms behind this decrease. It is shown that the strength of the M-O bond plays an important role, as it is a partner in the rigid unit mode motion and the order-disorder transition mechanism.

  11. 6th International Symposium on Thermal Expansion

    CERN Document Server

    1978-01-01

    This 6th International Symposium on Thermal Expansion, the first outside the USA, was held on August 29-31, 1977 at the Gull Harbour Resort on Hecla Island, Manitoba, Canada. Symposium Chairman was Ian D. Peggs, Atomic Energy of Canada Limited, and our continuing sponsor was CINDAS/Purdue University. We made considerable efforts to broaden the base this year to include more users of expansion data but with little success. We were successful, however, in establishing a session on liquids, an area which is receiving more attention as a logical extension to the high-speed thermophysical property measurements on materials at temperatures close to their melting points. The Symposium had good international representation but the overall attendance was, disappointingly, relatively low. Neverthe­ less, this enhanced the informal atmosphere throughout the meeting with a resultant frank exchange of information and ideas which all attendees appreciated. A totally new item this year was the presentation of a bursary to ...

  12. Thermal expansion and specific heat of a superior IR-SOFC cathode material Sr1-xCexCoO3-δ

    Science.gov (United States)

    Srivastava, Archana; Thakur, Rasna; Gaur, N. K.

    2017-05-01

    We present the specific heat (Cv) and thermal expansion (α) of lightly doped Sr1-xCexCoO3-δ (x=0.0-0.15) using Modified Rigid Ion Model (MRIM) and a novel atomistic approach of Atom in Molecules(AIM) theory. We partial replaced the A-site Strontium cation by other element (Cerium) of different size, valence and mass. The effect of Cerium doping on lattice specific heat (Cv)lat, thermal expansion(α) of Sr1-xCexCoO3-δ (x = 0.0-0.15) as a function of temperature (20K≤T≤ 1000K) is reported probably for the first time. The results indicate better thermal compatibility of Sr0.95Ce0.05CoO3 with Samaria doped Ceria (SDC) electrolyte than other studied compounds. The Debye temperature of these perovskite material as cathode for Intermediate Range Solid Oxide Fuel Cell (IR-SOFC) is also predicted.

  13. Thermal expansion of L-ascorbic acid

    Science.gov (United States)

    Nicolaï, B.; Barrio, M.; Tamarit, J.-Ll.; Céolin, R.; Rietveld, I. B.

    2017-04-01

    The specific volume of vitamin C has been investigated by X-ray powder diffraction as a function of temperature from 110 K up to complete degradation around 440 K. Its thermal expansion is relatively small in comparison with other organic compounds with an expansivity α v of 1.2(3) × 10-4 K-1. The structure consists of strongly bound molecules in the ac plane through a dense network of hydrogen bonds. The thermal expansion is anisotropic. Along the b axis, the expansion has most leeway and is about 10 times larger than in the other directions.

  14. Controlling Thermal Expansion: A Metal–Organic Frameworks Route

    Science.gov (United States)

    2016-01-01

    Controlling thermal expansion is an important, not yet resolved, and challenging problem in materials research. A conceptual design is introduced here, for the first time, for the use of metal–organic frameworks (MOFs) as platforms for controlling thermal expansion devices that can operate in the negative, zero, and positive expansion regimes. A detailed computer simulation study, based on molecular dynamics, is presented to support the targeted application. MOF-5 has been selected as model material, along with three molecules of similar size and known differences in terms of the nature of host–guest interactions. It has been shown that adsorbate molecules can control, in a colligative way, the thermal expansion of the solid, so that changing the adsorbate molecules induces the solid to display positive, zero, or negative thermal expansion. We analyze in depth the distortion mechanisms, beyond the ligand metal junction, to cover the ligand distortions, and the energetic and entropic effect on the thermo-structural behavior. We provide an unprecedented atomistic insight on the effect of adsorbates on the thermal expansion of MOFs as a basic tool toward controlling the thermal expansion. PMID:28190918

  15. Controlling Thermal Expansion: A Metal-Organic Frameworks Route.

    Science.gov (United States)

    Balestra, Salvador R G; Bueno-Perez, Rocio; Hamad, Said; Dubbeldam, David; Ruiz-Salvador, A Rabdel; Calero, Sofia

    2016-11-22

    Controlling thermal expansion is an important, not yet resolved, and challenging problem in materials research. A conceptual design is introduced here, for the first time, for the use of metal-organic frameworks (MOFs) as platforms for controlling thermal expansion devices that can operate in the negative, zero, and positive expansion regimes. A detailed computer simulation study, based on molecular dynamics, is presented to support the targeted application. MOF-5 has been selected as model material, along with three molecules of similar size and known differences in terms of the nature of host-guest interactions. It has been shown that adsorbate molecules can control, in a colligative way, the thermal expansion of the solid, so that changing the adsorbate molecules induces the solid to display positive, zero, or negative thermal expansion. We analyze in depth the distortion mechanisms, beyond the ligand metal junction, to cover the ligand distortions, and the energetic and entropic effect on the thermo-structural behavior. We provide an unprecedented atomistic insight on the effect of adsorbates on the thermal expansion of MOFs as a basic tool toward controlling the thermal expansion.

  16. Pressure-induced cubic-to-orthorhombic phase transformation in the negative thermal expansion material HfW2O8

    Science.gov (United States)

    Jorgensen, J. D.; Hu, Z.; Short, S.; Sleight, A. W.; Evans, J. S. O.

    2001-03-01

    The effect of pressure on the crystal structure of HfW2O8 has been investigated by neutron powder diffraction. At a hydrostatic pressure of 0.62 GPa at room temperature the cubic material transforms, with a 5% reduction in volume, to the same orthorhombic phase that is seen in the isostructural compound ZrW2O8 above 0.21 GPa. The transformation is sluggish, requiring about 24 h to complete at constant pressure. Once formed, the orthorhombic phase is retained upon release of pressure. Upon heating to 360 K, the metastable orthorhombic phase transforms back to the cubic phase. The substantially higher pressure for the cubic-to-orthorhombic transition in HfW2O8, compared to ZrW2O8, may be important for the application of this material in composites with controlled thermal expansion because rather large local pressures can occur in such composites.

  17. Impact of size and temperature on thermal expansion of nanomaterials

    Indian Academy of Sciences (India)

    Abstract. A theoretical method has been discussed to study the size dependency of thermal expan- sion of nanomaterials at higher temperature by considering the surface effect. A thermodynamical analysis of the equation of state (EoS) is studied from the knowledge of thermal expansion of nano- materials based on ...

  18. Thermal expansion of doped lanthanum gallates

    Indian Academy of Sciences (India)

    Thermal expansion of several compositions of Sr and Mg-doped LaGaO3 including an -site deficient composition (La0.9Sr0.1)0.98(Ga0.8Mg0.2)O2.821 were measured in the temperature range from 298 to 1273 K. The effect of doping on thermal expansion was studied by varying the composition at one site of the ...

  19. Negative thermal expansion in framework compounds

    Indian Academy of Sciences (India)

    2015-11-27

    Nov 27, 2015 ... We have studied negative thermal expansion (NTE) compounds with chemi- cal compositions of NX2O8 and NX2O7 (N=Zr, Hf and X=W, Mo, V) and M2O (M=Cu, Ag) using the techniques of inelastic neutron scattering and lattice dynamics. There is a large variation in the negative thermal expansion ...

  20. Negative thermal expansion near two structural quantum phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Occhialini, Connor A.; Handunkanda, Sahan U.; Said, Ayman; Trivedi, Sudhir; Guzmán-Verri, G. G.; Hancock, Jason N.

    2017-12-01

    Recent experimental work has revealed that the unusually strong, isotropic structural negative thermal expansion in cubic perovskite ionic insulator ScF3 occurs in excited states above a ground state tuned very near a structural quantum phase transition, posing a question of fundamental interest as to whether this special circumstance is related to the anomalous behavior. To test this hypothesis, we report an elastic and inelastic x-ray scattering study of a second system Hg2I2 also tuned near a structural quantum phase transition while retaining stoichiometric composition and high crystallinity. We find similar behavior and significant negative thermal expansion below 100 K for dimensions along the body-centered-tetragonal c axis, bolstering the connection between negative thermal expansion and zero-temperature structural transitions.We identify the common traits between these systems and propose a set of materials design principles that can guide discovery of newmaterials exhibiting negative thermal expansion

  1. Thermal expansion behaviour of barium and strontium zirconium ...

    Indian Academy of Sciences (India)

    Unknown

    Thermal expansion behaviour of barium and strontium zirconium phosphates. P SRIKARI TANTRI, K GEETHA†, A M UMARJI† and SHEELA K RAMASESHA*. Materials Science Division, National Aerospace Laboratories, Bangalore 560 017, India. †Materials Research Centre, Indian Institute of Science, Bangalore 560 ...

  2. Thermal expansion behaviour of granites

    Czech Academy of Sciences Publication Activity Database

    Plevová, Eva; Vaculíková, Lenka; Kožušníková, Alena; Ritz, M.; Simha Martynková, G.

    2016-01-01

    Roč. 123, č. 2 (2016), s. 1555-1561 ISSN 1388-6150 R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : thermomechanical analysis * differential thermal analysis * granites Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.953, year: 2016 http://link.springer.com/article/10.1007/s10973-015-4996-z

  3. Soft Manifold Dynamics behind Negative Thermal Expansion

    Science.gov (United States)

    Schlesinger, Z.; Rosen, J. A.; Hancock, J. N.; Ramirez, A. P.

    2008-07-01

    Minimal models are developed to examine the origin of large negative thermal expansion in underconstrained systems. The dynamics of these models reveals how underconstraint can organize a thermodynamically extensive manifold of low-energy modes which not only drives negative thermal expansion but extends across the Brillioun zone. Mixing of twist and translation in the eigenvectors of these modes, for which in ZrW2O8 there is evidence from infrared and neutron scattering measurements, emerges naturally in our model as a signature of the dynamics of underconstraint.

  4. The effect of leucite crystallization and thermal history on thermal expansion measurement of dental porcelains

    Science.gov (United States)

    Khajotia, Sharukh Soli

    1997-12-01

    Objectives. Measurement of thermal expansion in glassy materials is complicated by thermal history effects. The purpose of this research was to determine whether the occurrence of structural relaxation in glassy materials, such as dental porcelains, and changes in porcelain leucite content could interfere with the accurate measurement of the coefficient of thermal expansion during the thermal expansion measurement itself. Methods. In a randomized design, thermal expansion specimens were fabricated using six commercial body porcelains and the leucite-containing Component No. 1 frit (Weinstein et al. patent, 1962), and subjected to one of the following heat treatments: a single heating run at 3sp°C/min in a conventional dilatometer followed by air quenching; three successive low-rate heating and cooling thermal expansion runs at 3sp°C/min in a conventional dilatometer; or three successive high-rate heating and cooling thermal expansion runs at 600sp°C/min in a laser dilatometer. The remaining specimens were left untreated and served as controls. Potential changes in porcelain leucite content were monitored via quantitative X-ray diffraction. Thermal expansion data for each run over a temperature range of 25-500sp°C and the leucite content of all specimens were subjected to repeated measures analysis of variance. Results. The thermal expansion coefficient measured on first slow heating was significantly lower than the values for succeeding low-rate heating and cooling runs in all materials (p $ 0.05). No significant effect of dilatometer thermal treatments on leucite content (p >$ 0.05) was shown for all materials studied using both dilatometers. Significance. The crystallization of additional amounts of leucite during thermal expansion runs can be ruled out as a possible interference in the determination of the thermal expansion coefficient of dental porcelain. Conventional dilatometer measurements exhibited structural relaxation during the first heating run, as

  5. Negative thermal expansion in framework compounds

    Indian Academy of Sciences (India)

    electron microscopy, EXAFS and differential scanning calorimetry have been used to study structural properties as a function of temperature for these compounds. In this paper we report the results obtained from our study [14–20] of negative thermal expansion (NTE) compounds with chemical compositions of NX2O8 and.

  6. Thermal expansion method for lining tantalum alloy tubing with tungsten

    Science.gov (United States)

    Watson, G. K.; Whittenberger, J. D.; Mattson, W. F.

    1973-01-01

    A differential-thermal expansion method was developed to line T-111 (tantalum - 8 percent tungsten - 2 percent hafnium) tubing with a tungsten diffusion barrier as part of a fuel element fabrication study for a space power nuclear reactor concept. This method uses a steel mandrel, which has a larger thermal expansion than T-111, to force the tungsten against the inside of the T-111 tube. Variables investigated include lining temperature, initial assembly gas size, and tube length. Linear integrity increased with increasing lining temperature and decreasing gap size. The method should have more general applicability where cylinders must be lined with a thin layer of a second material.

  7. Symmetry Switching of Negative Thermal Expansion by Chemical Control.

    Science.gov (United States)

    Senn, Mark S; Murray, Claire A; Luo, Xuan; Wang, Lihai; Huang, Fei-Ting; Cheong, Sang-Wook; Bombardi, Alessandro; Ablitt, Chris; Mostofi, Arash A; Bristowe, Nicholas C

    2016-05-04

    The layered perovskite Ca3-xSrxMn2O7 is shown to exhibit a switching from a material exhibiting uniaxial negative to positive thermal expansion as a function of x. The switching is shown to be related to two closely competing phases with different symmetries. The negative thermal expansion (NTE) effect is maximized when the solid solution is tuned closest to this region of phase space but is switched off suddenly on passing though the transition. Our results show for the first time that, by understanding the symmetry of the competing phases alone, one may achieve unprecedented chemical control of this unusual property.

  8. The Origin of High Thermal Conductivity and Ultralow Thermal Expansion in Copper-Graphite Composites.

    Science.gov (United States)

    Firkowska, Izabela; Boden, André; Boerner, Benji; Reich, Stephanie

    2015-07-08

    We developed a nanocomposite with highly aligned graphite platelets in a copper matrix. Spark plasma sintering ensured an excellent copper-graphite interface for transmitting heat and stress. The resulting composite has superior thermal conductivity (500 W m(-1) K(-1), 140% of copper), which is in excellent agreement with modeling based on the effective medium approximation. The thermal expansion perpendicular to the graphite platelets drops dramatically from ∼20 ppm K(-1) for graphite and copper separately to 2 ppm K(-1) for the combined structure. We show that this originates from the layered, highly anisotropic structure of graphite combined with residual stress under ambient conditions, that is, strain-engineering of the thermal expansion. Combining excellent thermal conductivity with ultralow thermal expansion results in ideal materials for heat sinks and other devices for thermal management.

  9. Numerical evaluation of the coefficients of thermal expansion of fibers in composite materials using a lamina-scale cost function with quasi-analytical gradients

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Jae Hyuk [Korea Aerospace Research Institute, Daejeon (Korea, Republic of); Charpentier, Jean Baptiste [École Nationale Supérieur des Mines de Saint-Étienne, Saint-Étienne (France); Sohn, Dong Woo [Korea Maritime and Ocean University, Busan (Korea, Republic of)

    2015-03-15

    In this work, the coefficients of thermal expansion (CTEs) of fibers in composite materials that contain microstructures are numerically evaluated using a lamina-scale cost function with quasi-analytical gradients. To consider the effects of fiber arrangements and local defects, such as interface debonding and voids, a variety of representative volume elements are modeled with a number of finite element meshes. Then, the CTEs of fibers are evaluated by minimizing a lamina-scale cost function that represents the difference between the measured CTEs and the computed CTEs by means of a computational homogenization scheme for the composite lamina. The descent direction of the cost function is obtained using quasi-analytical gradients that take partial derivatives from prediction models, such as the Schapery model and Hashin model defined in an explicit manner, which accelerates the minimization procedure. To verify the performance of the proposed scheme in terms of accuracy and efficiency, the CTEs of constituents calculated using the proposed scheme in a unidirectional composite lamina are compared with experimental values reported in the literature. Furthermore, the convergence behavior of the proposed scheme with quasi-analytical gradients is also investigated and compared with other minimization methods.

  10. Synthesis of Defect Perovskites (He2-x□x)(CaZr)F6 by Inserting Helium into the Negative Thermal Expansion Material CaZrF6.

    Science.gov (United States)

    Hester, Brett R; Dos Santos, António M; Molaison, Jamie J; Hancock, Justin C; Wilkinson, Angus P

    2017-09-27

    Defect perovskites (He2-x□x)(CaZr)F6 can be prepared by inserting helium into CaZrF6 at high pressure. They can be recovered to ambient pressure at low temperature. There are no prior examples of perovskites with noble gases on the A-sites. The insertion of helium gas into CaZrF6 both elastically stiffens the material and reduces the magnitude of its negative thermal expansion. It also suppresses the onset of structural disorder, which is seen on compression in other media. Measurements of the gas released on warming to room temperature and Rietveld analyses of neutron diffraction data at low temperature indicate that exposure to helium gas at 500 MPa leads to a stoichiometry close to (He1□1)(CaZr)F6. Helium has a much higher solubility in CaZrF6 than silica glass or crystobalite. An analogue with composition (H2)2(CaZr)F6 would have a volumetric hydrogen storage capacity greater than current US DOE targets. We anticipate that other hybrid perovskites with small neutral molecules on the A-site can also be prepared and that they will display a rich structural chemistry.

  11. Frostless heat pump having thermal expansion valves

    Science.gov (United States)

    Chen, Fang C [Knoxville, TN; Mei, Viung C [Oak Ridge, TN

    2002-10-22

    A heat pump system having an operable relationship for transferring heat between an exterior atmosphere and an interior atmosphere via a fluid refrigerant and further having a compressor, an interior heat exchanger, an exterior heat exchanger, a heat pump reversing valve, an accumulator, a thermal expansion valve having a remote sensing bulb disposed in heat transferable contact with the refrigerant piping section between said accumulator and said reversing valve, an outdoor temperature sensor, and a first means for heating said remote sensing bulb in response to said outdoor temperature sensor thereby opening said thermal expansion valve to raise suction pressure in order to mitigate defrosting of said exterior heat exchanger wherein said heat pump continues to operate in a heating mode.

  12. Frequency dependent thermal expansion in binary viscoelasticcomposites

    Energy Technology Data Exchange (ETDEWEB)

    Berryman, James G.

    2007-12-01

    The effective thermal expansion coefficient beta* of abinary viscoelastic composite is shown to be frequency dependent even ifthe thermal expansion coefficients beta A and beta B of both constituentsare themselves frequency independent. Exact calculations for binaryviscoelastic systems show that beta* is related to constituent valuesbeta A, beta B, volume fractions, and bulk moduli KA, KB, as well as tothe overall bulk modulus K* of the composite system. Then, beta* isdetermined for isotropic systems by first bounding (or measuring) K* andtherefore beta*. For anisotropic systems with hexagonal symmetry, theprincipal values of the thermal expansion beta*perp and beta*para can bedetermined exactly when the constituents form a layered system. In allthe examples studied, it is shown explicitly that the eigenvectors of thethermoviscoelastic system possess non-negative dissipation -- despite thecomplicated analytical behavior of the frequency dependent thermalexpansivities themselves. Methods presented have a variety ofapplications from fluid-fluid mixtures to fluid-solid suspensions, andfrom fluid-saturated porous media to viscoelastic solid-solidcomposites.

  13. Advanced thermal management materials

    CERN Document Server

    Jiang, Guosheng; Kuang, Ken

    2012-01-01

    ""Advanced Thermal Management Materials"" provides a comprehensive and hands-on treatise on the importance of thermal packaging in high performance systems. These systems, ranging from active electronically-scanned radar arrays to web servers, require components that can dissipate heat efficiently. This requires materials capable of dissipating heat and maintaining compatibility with the packaging and dye. Its coverage includes all aspects of thermal management materials, both traditional and non-traditional, with an emphasis on metal based materials. An in-depth discussion of properties and m

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

    Science.gov (United States)

    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.

  15. Magnetic structure and local lattice distortion in giant negative thermal expansion material Mn{sub 3}Cu{sub 1-x}Ge{sub x}N

    Energy Technology Data Exchange (ETDEWEB)

    Iikubo, S; Kodama, K; Takenaka, K; Takagi, H; Shamoto, S, E-mail: iikubo@life.kyutech.ac.jp

    2010-11-01

    Magnetic and local structures in an antiperovskite system, Mn{sub 3}Cu{sub 1-x}Ge{sub x}N, with a giant negative thermal expansion have been studied by neutron powder diffraction measurement. We discuss (1) an importance of an averaged cubic crystal structure and a {Gamma}G{sup 5g} antiferromagnetic spin structure for the large magneto-volume effect (MVE) in this itinerant electron system, (2) an unique role of a local lattice distortion well described by the low temperature tetragonal structure of Mn{sub 3}GeN for the broadening of MVE.

  16. Negative thermal expansion and its relation to high pressures

    Science.gov (United States)

    Sikka, S. K.

    2004-04-01

    Most materials expand when heated. However, many exceptions are now known. Recently, interest in this has been revived with the discovery of isotropic negative thermal expansion (NTE) in ZrW2O8. From equation of state considerations, one can relate NTE to negative Grüneisen parameters (thermal or electronic). Under pressure, these lead to equation of state anomalies with the pressure derivative of the bulk modules being small or negative. Many of these materials undergo pressure-induced amorphization. This in some of them can be understood on the steric constraint model. It is also argued that NTE in most materials may be understood from the fact that these materials have two degenerate or nearly degenerate energy states. On increase of temperature, the material then samples the lower volume state, leading to NTE.

  17. Tuning of a cavity in a silicon photonic crystal by thermal expansion of an elastomeric infill

    NARCIS (Netherlands)

    Erdamar, A.K.; Van Leest, M.M.; Picken, S.J.; Caro, J.

    2011-01-01

    We use an elastomer as infill material for a photonic crystal. As a result of the thermal-expansion-induced strongly negative thermal optical coefficient, this material is highly suitable for thermal tuning of the transmission of a cavity. This is demonstrated by global infilling of a hole-type

  18. Copper-based conductive composites with tailored thermal expansion.

    Science.gov (United States)

    Della Gaspera, Enrico; Tucker, Ryan; Star, Kurt; Lan, Esther H; Ju, Yongho Sungtaek; Dunn, Bruce

    2013-11-13

    We have devised a moderate temperature hot-pressing route for preparing metal-matrix composites which possess tunable thermal expansion coefficients in combination with high electrical and thermal conductivities. The composites are based on incorporating ZrW2O8, a material with a negative coefficient of thermal expansion (CTE), within a continuous copper matrix. The ZrW2O8 enables us to tune the CTE in a predictable manner, while the copper phase is responsible for the electrical and thermal conductivity properties. An important consideration in the processing of these materials is to avoid the decomposition of the ZrW2O8 phase. This is accomplished by using relatively mild hot-pressing conditions of 500 °C for 1 h at 40 MPa. To ensure that these conditions enable sintering of the copper, we developed a synthesis route for the preparation of Cu nanoparticles (NPs) based on the reduction of a common copper salt in aqueous solution in the presence of a size control agent. Upon hot pressing these nanoparticles at 500 °C, we are able to achieve 92-93% of the theoretical density of copper. The resulting materials exhibit a CTE which can be tuned between the value of pure copper (16.5 ppm/°C) and less than 1 ppm/°C. Thus, by adjusting the relative amount of the two components, the properties of the composite can be designed so that a material with high electrical conductivity and a CTE that matches the relatively low CTE values of semiconductor or thermoelectric materials can be achieved. This unique combination of electrical and thermal properties enables these Cu-based metal-matrix composites to be used as electrical contacts to a variety of semiconductor and thermoelectric devices which offer stable operation under thermal cycling conditions.

  19. High Thermal Conductivity Materials

    CERN Document Server

    Shinde, Subhash L

    2006-01-01

    Thermal management has become a ‘hot’ field in recent years due to a need to obtain high performance levels in many devices used in such diverse areas as space science, mainframe and desktop computers, optoelectronics and even Formula One racing cars! Thermal solutions require not just taking care of very high thermal flux, but also ‘hot spots’, where the flux densities can exceed 200 W/cm2. High thermal conductivity materials play an important role in addressing thermal management issues. This volume provides readers a basic understanding of the thermal conduction mechanisms in these materials and discusses how the thermal conductivity may be related to their crystal structures as well as microstructures developed as a result of their processing history. The techniques for accurate measurement of these properties on large as well as small scales have been reviewed. Detailed information on the thermal conductivity of diverse materials including aluminum nitride (AlN), silicon carbide (SiC), diamond, a...

  20. The Elusive Coefficients of Thermal Expansion in PBX 9502

    Energy Technology Data Exchange (ETDEWEB)

    C.B. Skidmore; T.A. Butler; C.W. Sandoval

    2003-05-01

    PBX 9502 has been in war reserve service for over two decades. Ninety-five percent of the solid phase of this insensitive high explosive is composed of energetic crystallites designated as TATB (1,3,5-triamino-2,4,6-trinitrobenzene), held together by the remaining solid fraction--an inert, polymeric binder named Kel-F 800. The unusual combination of extreme insensitivity and adequate performance characteristics is not the only enigmatic feature of such TATB-based materials. In this report, we describe the difficulty and progress to date in reliably determining the coefficients of thermal expansion for consolidated components of PBX 9502. We provide bulk linear coefficient of thermal expansion (CTE) values for PBX 9502 consolidated to a density of approximately 1.890 g/cm{sup 3} and offer a simple set of equations for calculating dimensional changes for temperatures from 218 to 347 K (-55 C to 74 C).

  1. Anisotropic thermal expansion in crystals of different categories

    Science.gov (United States)

    Zamkovskaya, A.; Maksimova, E.

    2015-12-01

    The three-dimensional (3D) indicatory surfaces of thermal expansion in crystals of different categories were constructed in program MathCad. Indicatory surface of thermal expansion is a sphere, spheroid, ellipsoid or surface of multiple parts, depending on the category of the crystal symmetry. The symmetry elements of thermal expansion include the symmetry elements of the point group of the crystal according Neumann's Principle.

  2. Thermal expansion and magnetostriction studies on iron pnictides

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Liran

    2010-09-19

    In this work, a 3-terminal capacitance dilatometer was set up and used for measurements of the thermal expansion and magnetostriction of novel superconducting iron pinictides and related materials. In particular, RFeAsO with R = La, Ce, Pr, Sm, Gd, LaFeASO{sub 1-x}F{sub x} and Ca(F{sub 1-c}Co{sub x}){sub 2}As{sub 2} have been investigated. The data on polycrystalline LaFeAsO{sub 1-x} are the first published thermal expansion data on this material. The lattice effects at the structural and the magnetic phase transition have been investigated and the phase diagram upon F-doping has been studied. A main result is the observation of a previously unknown fluctuation regime for the doping level x ≤ 0.04 over a large T range above the structural transition temperature T{sub S}. The absence of any structural anomalies in the normal state of the superconducting LaFeAlO{sub 1-x}F{sub x} samples with x ≥ 0.05 corroborates the discontinuous character of the phase boundary not only for the magnetism but also for the structural degrees of freedom. Similarly, the presence of high-temperature fluctuations is found for all RFeAsO undoped materials under study. The discussion of the probable origin of the fluctuations as well as the definition of the structural transition temperature T{sub S} are done. The low temperature features shown by the thermal expansion data for RFeAsO are caused by the onset of long range magnetic order of the 4f-moments and their different configurations. In particular, PrFeAsO, which has a very pronounced anomaly associated with Pr-ordering exhibits a large magnetostriction at low temperatures. By discussing this effect along with the magnetization, resistivity and other measurements, it is found that this large magneto-elastic effect may originate from the correlations between the momentum from Fe{sup 3+} and Pr{sup 3+}. Last, the thermal expansion of Ca(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} 122 single crystals is investigated. Ca(Fe{sub 1-x}Co{sub x

  3. Exploring the thermal expansion of fluorides and oxyfluorides with rhenium trioxide-type structures: From negative to positive thermal expansion

    Science.gov (United States)

    Greve, Benjamin K.

    This thesis explores the thermal expansion and high pressure behavior of some materials with the ReO3 structure type. This structure is simple and has, in principle, all of the features necessary for negative thermal expansion (NTE) arising from the transverse thermal motion of the bridging anions and the coupled rotation of rigid units; however, ReO 3 itself only exhibits mild NTE across a narrow temperature range at low temperatures. ReO3 is metallic because of a delocalized d-electron, and this may contribute to the lack of NTE in this material. The materials examined in this thesis are all based on d 0 metal ions so that the observed thermal expansion behavior should arise from vibrational, rather than electronic, effects. In Chapter 2, the thermal expansion of scandium fluoride, ScF3 , is examined using a combination of in situ synchrotron X-ray and neutron variable temperature diffraction. ScF3 retains the cubic ReO3 structure across the entire temperature range examined (10 - 1600 K) and exhibits pronounced negative thermal expansion at low temperatures. The magnitude of NTE in this material is comparable to that of cubic ZrW2O8, which is perhaps the most widely studied NTE material, at room temperature and below. This is the first report of NTE in an ReO3 type structure across a wide temperature range. Chapter 3 presents a comparison between titanium oxyfluoride, TiOF 2, and a vacancy-containing titanium hydroxyoxyfluoride, Ti x(O/OH/F)3. TiOF2 was originally reported to adopt the cubic ReO3 structure type under ambient conditions, therefore the initial goal for this study was to examine the thermal expansion of this material and determine if it displayed interesting behavior such as NTE. During the course of the study, it was discovered that the original synthetic method resulted in Tix(O/OH/F)3, which does adopt the cubic ReO3 structure type. The chemical composition of the hydroxyoxyfluoride is highly dependent upon synthesis conditions and subsequent

  4. Determination of coefficient of thermal expansion effects on Louisiana's PCC pavement design : research project capsule.

    Science.gov (United States)

    2009-01-01

    PROBLEM: The coefficient of thermal expansion (CTE) is a fundamental property of construction : materials such as steel and concrete. Although the CTE of steel is a well-defined : constant, the CTE of concrete varies substantially with aggregate type...

  5. Porous composite with negative thermal expansion obtained by photopolymer additive manufacturing

    Science.gov (United States)

    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.

  6. Porous composite with negative thermal expansion obtained by photopolymer additive manufacturing

    Directory of Open Access Journals (Sweden)

    Akihiro Takezawa

    2015-07-01

    Full Text Available 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.

  7. Negative Thermal Expansion and Ferroelectric Oxides in Electronic Device Composites

    Science.gov (United States)

    Trujillo, Joy Elizabeth

    Electronic devices increasingly pervade our daily lives, driving the need to develop components which have material properties that can be designed to target a specific need. The principle motive of this thesis is to investigate the effects of particle size and composition on three oxides which possess electronic and thermal properties essential to designing improved ceramic composites for more efficient, high energy storage devices. A metal matrix composite project used the negative thermal expansion oxide, ZrW2O 8, to offset the high thermal expansion of the metal matrix without sacrificing high thermal conductivity. Composite preparation employed a powder mixing technique to achieve easy composition control and homogenous phase distribution in order to build composites which target a specific coefficient of thermal expansion (CTE). A tailorable CTE material is desirable for overcoming thermomechanical failure in heat sinks or device casings. This thesis also considers the particle size effect on dielectric properties in a common ferroelectric perovskite, Ba1-xSrxTiO 3. By varying the Ba:Sr ratio, the Curie temperature can be adjusted and by reducing the particle size, the dielectric constant can be increased and hysteresis decreased. These conditions could yield anonymously large dielectric constants near room temperature. However, the ferroelectric behavior has been observed to cease below a minimum size of a few tens of nanometers in bulk or thin film materials. Using a new particle slurry approach, electrochemical impedance spectroscopy allows dielectric properties to be determined for nanoparticles, as opposed to conventional methods which measure only bulk or thin film dielectric properties. In this manner, Ba1-xSrxTiO3 was investigated in a new size regime, extending the theory on the ferroelectric behavior to < 10 nm diameter. This knowledge will improve the potential to incorporate high dielectric constant, low loss ferroelectric nanoparticles in many

  8. The origin of uniaxial negative thermal expansion in layered perovskites

    Science.gov (United States)

    Ablitt, Chris; Craddock, Sarah; Senn, Mark S.; Mostofi, Arash A.; Bristowe, Nicholas C.

    2017-10-01

    Why is it that ABO3 perovskites generally do not exhibit negative thermal expansion (NTE) over a wide temperature range, whereas layered perovskites of the same chemical family often do? It is generally accepted that there are two key ingredients that determine the extent of NTE: the presence of soft phonon modes that drive contraction (have negative Grüneisen parameters); and anisotropic elastic compliance that predisposes the material to the deformations required for NTE along a specific axis. This difference in thermal expansion properties is surprising since both ABO3 and layered perovskites often possess these ingredients in equal measure in their high-symmetry phases. Using first principles calculations and symmetry analysis, we show that in layered perovskites there is a significant enhancement of elastic anisotropy due to symmetry breaking that results from the combined effect of layering and condensed rotations of oxygen octahedra. This feature, unique to layered perovskites of certain symmetry, is what allows uniaxial NTE to persist over a large temperature range. This fundamental insight means that symmetry and the elastic tensor can be used as descriptors in high-throughput screening and to direct materials design.

  9. Controllable rectification of the axial expansion in the thermally driven artificial muscle

    Science.gov (United States)

    Yue, Donghua; Zhang, Xingyi; Yong, Huadong; Zhou, Jun; Zhou, You-He

    2015-09-01

    At present, the concept of artificial muscle twisted by polymers or fibers has become a hot issue in the field of intelligent material research according to its distinguishing advantages, e.g., high energy density, large-stroke, non-hysteresis, and inexpensive. The axial thermal expansion coefficient is an important parameter which can affect its demanding applications. In this letter, a device with high accuracy capacitive sensor is constructed to measure the axial thermal expansion coefficient of the twisted carbon fibers and yarns of Kevlar, and a theoretical model based on the thermal elasticity and the geometrical features of the twisted structure are also presented to predict the axial expansion coefficient. It is found that the calculated results take good agreements with the experimental data. According to the present experiment and analyses, a method to control the axial thermal expansion coefficient of artificial muscle is proposed. Moreover, the mechanism of this kind of thermally driven artificial muscle is discussed.

  10. Two Decades of Negative Thermal Expansion Research: Where Do We Stand?

    Directory of Open Access Journals (Sweden)

    Cora Lind

    2012-06-01

    Full Text Available Negative thermal expansion (NTE materials have become a rapidly growing area of research over the past two decades. The initial discovery of materials displaying NTE over a large temperature range, combined with elucidation of the mechanism behind this unusual property, was followed by predictions that these materials will find use in various applications through controlled thermal expansion composites. While some patents have been filed and devices built, a number of obstacles have prevented the widespread implementation of NTE materials to date. This paper reviews NTE materials that contract due to transverse atomic vibrations, their potential for use in controlled thermal expansion composites, and known problems that could interfere with such applications.

  11. Thermal expansion of spinel-type Si3N4

    DEFF Research Database (Denmark)

    Paszkowics, W.; Minkikayev, R.; Piszora, P.

    2004-01-01

    The lattice parameter and thermal expansion coefficient (TEC) for the spinel-type Si3N4 phase prepared under high-pressure and high-temperature conditions are determined for 14 K......The lattice parameter and thermal expansion coefficient (TEC) for the spinel-type Si3N4 phase prepared under high-pressure and high-temperature conditions are determined for 14 K...

  12. Advances in LED packaging and thermal management materials

    Science.gov (United States)

    Zweben, Carl

    2008-02-01

    Heat dissipation, thermal stresses and cost are key light-emitting diode (LED) packaging issues. Heat dissipation limits power levels. Thermal stresses affect performance and reliability. Copper, aluminum and conventional polymeric printed circuit boards (PCBs) have high coefficients of thermal expansion, which can cause high thermal stresses. Most traditional low-coefficient-of-thermal-expansion (CTE) materials like tungsten/copper, which date from the mid 20th century, have thermal conductivities that are no better than those of aluminum alloys, about 200 W/m-K. An OIDA LED workshop cited a need for better thermal materials. There are an increasing number of low-CTE materials with thermal conductivities ranging between that of copper (400 W/m-K) and 1700 W/m-K, and many other low-CTE materials with lower thermal conductivities. Some of these materials are low cost. Others have the potential to be low cost in high-volume production. High-thermal-conductivity materials enable higher power levels, potentially reducing the number of required LEDs. Advanced thermal materials can constrain PCB CTE and greatly increase thermal conductivity. This paper reviews traditional packaging materials and advanced thermal management materials. The latter provide the packaging engineer with a greater range of options than in the past. Topics include properties, status, applications, cost, using advanced materials to fix manufacturing problems, and future directions, including composites reinforced with carbon nanotubes and other thermally conductive materials.

  13. Strong anisotropic thermal expansion in cristobalite-type BPO 4

    Science.gov (United States)

    Achary, S. N.; Tyagi, A. K.

    2004-11-01

    In this communication, the thermal expansion behavior of cristobalite-type BPO 4, determined from high-temperature X-ray diffraction studies, is being reported. BPO 4 crystallizes in tetragonal lattice, with space group I-4 (No. 82) at room temperature, with unit cell parameters: a=4.3447(2), c=6.6415(5) Å and V=125.37(1) Å 3. The tetragonal unit cell parameters at 900 °C are: a=4.3939(2), c=6.6539(6) Å and V=128.46(1) Å 3. The results show a very strong anisotropic expansion in the lattice, with the typical thermal expansion coefficients along a- and c-axis 12.9×10 -6 and 2.1×10 -6/°C, respectively. The volume thermal expansion coefficient of the lattice is 28.2×10 -6/°C in the temperature range of 25-900 °C. The variation of the crystal structure with temperature and the thermal expansion behavior are explained in this manuscript. The role of inter-polyhedral angle on the thermal expansion behavior has also been established.

  14. Thermal Expansion Behavior of Hot-Pressed Engineered Matrices

    Science.gov (United States)

    Raj, S. V.

    2016-01-01

    Advanced engineered matrix composites (EMCs) require that the coefficient of thermal expansion (CTE) of the engineered matrix (EM) matches those of the fiber reinforcements as closely as possible in order to reduce thermal compatibility strains during heating and cooling of the composites. The present paper proposes a general concept for designing suitable matrices for long fiber reinforced composites using a rule of mixtures (ROM) approach to minimize the global differences in the thermal expansion mismatches between the fibers and the engineered matrix. Proof-of-concept studies were conducted to demonstrate the validity of the concept.

  15. Development of Low Thermal Expansion Tungsten UO 2 Cermet Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Marlowe, M O; Kaznoff, A I

    1970-03-31

    An attempt was made to develop a tungsten-uranium dioxide cermet of high fue 1 loading with thermal expansion approaching that of tungsten and with good dimensional stability on thermal cycling. These goals were sought through the use of tungsten-coated uranium dioxide particles with sufficient locally available void volume to accommodate the difference in thermal expansion between the uranium dioxide and the tungsten matrix and through limitation of plastic deformation in the particles during fabrication to avoid mechanical keying of the particles and the matrix. The particles were vibratorily compacted prior to hot pressing. The thermal expansion of the cermets was determined and they were thermal cycle tested. The thermal expansion of the cermets was considerably closer to that of tungsten than was observed with previously reported specimens of similar composition. However, the thermal cycling of the cermets resulted in intolerable growth. This growth could be accounted for by the agglomeration of gases trapped in the uranium dioxide particles during deposition of the tungsten coating.

  16. The role of static disorder in negative thermal expansion in ReO3

    Science.gov (United States)

    Rodriguez, Efrain E.; Llobet, Anna; Proffen, Thomas; Melot, Brent C.; Seshadri, Ram; Littlewood, Peter B.; Cheetham, Anthony K.

    2009-06-01

    Time-of-flight neutron powder diffraction and specific heat measurements were used to study the nature of thermal expansion in rhenium trioxide, an electrically conducting oxide with cubic symmetry. The temperature evolution of the lattice parameters shows that ReO3 can exhibit negative thermal expansion below room temperature and that the transition from negative to positive thermal expansion depends on sample preparation; the single crystal sample demonstrated the highest transition temperature, 294(19) K, and largest negative value for the coefficient of thermal expansion, α =-10(1)×10-7 K-1. For the oxygen atoms, the atomic displacement parameters are strongly anisotropic even at 15 K, indicative of a large contribution of static disorder to the displacement parameters. Further inspection of the temperature evolution of the oxygen displacement parameters for different samples reveals that the static disorder contribution is greater for the samples with diminished negative thermal expansion (NTE) behavior. In addition, specific heat measurements show that ReO3 lacks the low energy Einstein-type modes seen in other NTE oxides such as ZrW2O8. The thermal expansion behavior in other NTE materials such as ZrW2O8, cuprite-type oxides, and the Prussian blue cyanides are discussed and compared with that of our ReO3 samples.

  17. Glass-ceramic hermetic seals to high thermal expansion metals

    Science.gov (United States)

    Kramer, D.P.; Massey, R.T.

    1987-04-28

    A process for forming glass-ceramic materials from an alkaline silica-lithia glass composition comprising 60-72 mole-% SiO/sub 2/, 18-27 mole-% Li/sub 2/O, 0-5 mole-% Al/sub 2/O/sub 3/, 0-6 mole-% K/sub 2/O, 0-3 mole-% B/sub 2/O/sub 3/, and 0.5-2.5 mole-% P/sub 2/O/sub 5/, which comprises heating said glass composition at a first temperature within the 950-1050/degree/C range for 5-60 minutes, and then at a devitrification temperature within the 700-900/degree/C range for about 5-300 minutes to obtain a glass-ceramic having a thermal expansion coefficient of up to 210 x 10/sup /minus/7///degree/C. These ceramics form strong, hermetic seals with high expansion metals such as stainless steel alloys. An intermediate nucleation heating step conducted at a temperature within the range of 675-750/degree/C for 10-120 minutes may be employed between the first stage and the devitrification stage. 1 fig., 2 tabs.

  18. Zirconium titanate: stability and thermal expansion; Titanato de circonio: estabilidad termodinamica y expansion termica

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Lopez, E.; Moreno, R.; Baudin, C.

    2011-07-01

    Zirconium titanate is a well known compound in the field of electro ceramics, although it has also been used in catalyst and sensors applications. The crystallographic thermal expansion anisotropy of this compound makes it a potential candidate as constituent of structural components. In general, to assure the structural integrity and microstructural homogeneity of a ceramic piece, relatively low cooling rates from the fabrication temperature are required. This requirement is essential for zirconium titanate because thermal expansion as well as phase distribution is affected by small variations in the composition and cooling rate. This work reviews the available data on the phase equilibrium relationships in the systems ZrO{sub 2}-TiO{sub 2} and ZrO{sub 2}-TiO{sub 2}-Y{sub 2}O{sub 3}. The main discrepancies as well as the possible origins of them are discussed. Additionally, the crystallographic thermal expansion data in the current literature are reviewed. (Author) 56 refs.

  19. Glass ceramics for sealing to high-thermal-expansion metals

    Energy Technology Data Exchange (ETDEWEB)

    Wilder, Jr., J. A.

    1980-10-01

    Glass ceramics were studied, formulated in the Na/sub 2/O CaO.P/sub 2/O/sub 5/, Na/sub 2/O.BaOP/sub 2/O/sub 5/, Na/sub 2/O.Al/sub 2/O/sub 3/.P/sub 2/O/sub 5/, and Li/sub 2/O.BaO.P/sub 2/O/sub 5/ systems to establish their suitability for sealing to high thermal expansion metals, e.g. aluminum, copper, and 300 series stainless steels. Glass ceramics in Na/sub 2/O.CaO.P/sub 2/O/sub 5/ and Na/sub 2/O.BaO.P/sub 2/O/sub 5/ systems have coefficients of thermal expansion in the range 140 x 10/sup -1/ per /sup 0/C less than or equal to ..cap alpha.. less than or equal to 225 x 10/sup -7/ per /sup 0/C and fracture toughness values generally greater than those of phosphate glasses; they are suitable for fabricating seals to high thermal expansion metals. Crystal phases include NaPo/sub 3/, (NaPO/sub 3/)/sub 3/, NaBa(PO/sub 3/)/sub 3/, and NaCa(PO/sub 3/)/sub 3/. Glass ceramics formed in the Na/sub 2/O.Al/sub 2/O/sub 3/.P/sub 2/O/sub 5/ systems have coefficients of thermal expansion greater than 240 x 10/sup -7/ per /sup 0/C, but they have extensive microcracking. Due to their low thermal expansion values (..cap alpha.. less than or equal to 120 x 10/sup -7/ per /sup 0/C), glass ceramics in the Li/sub 2/O.BaO.P/sub 2/O/sub 5/ system are unsuitable for sealing to high thermal expansion metals.

  20. DYN3D thermal expansion models for SFR applications

    Energy Technology Data Exchange (ETDEWEB)

    Nikitin, Evgeny; Fridman, Emil [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Div. Reactor Safety

    2016-07-01

    The nodal diffusion code DYN3D is under extension for SFR applications. As a part of the extension a new model for axial thermal expansion of fuel rods was developed. The new model provides a flexible way of handling the axial fuel rod expansion, because each sub-assembly and node can be treated independently. The performance of the model was tested on a large oxide SFR core, and the results were compared to the reference full core Serpent solution. The test results indicated that the proposed model can accurately account for the axial expansion effects on full core level.

  1. Investigation of thermal properties of raw materials of asphalt mixtures

    Science.gov (United States)

    Géber, R.; Simon, A.; Kocserha, I.

    2017-02-01

    Asphalt mixtures are composite materials, which are made of different grades of mineral aggregates and bitumen. During the mixing process mineral materials were blended with bitumen at relatively high temperature (∼200 °C). As the binding process come off in these higher temperature range, thermal properties of asphaltic materials are important. The aim of this project is to reveal the thermal properties of raw materials. During our research two types of mineral aggregates were tested (limestone and dolomite) by different methods. Differential thermal analysis, thermal expansion and thermal conductivity were investigated at technologically important temperatures. The results showed that the structure of mineral materials did not change at elevated temperatures, expansion of samples was neglible, while thermal conductivity changed by temperature.

  2. [Determination of major expansion properties of refractory die material compatible with slip casting core of sintered titanium powder].

    Science.gov (United States)

    Chao, Y; Kuang, X; Liao, Y; Wang, H

    1999-02-01

    To determinate major expansion properties of refractory die material. The setting expansion ratio of refractory die material for slip casting core of sintered titanium powder at room temperature was performed, as well as thermal expansion ratio from room temperature to 800 degrees C. The maximum setting expansion ratio in 2 hours reached 0.3407%; The final setting expansion ratio in 24 hours was 0.3117%; The mean thermal expansion coefficient was mainly in range of 8 x 10(-6)-11 x 10(-6)/degree C; The expansion property seemed very stable after sintering repeatedly and the small shrinkage after sintering could be compensated with the die spacer and setting expansion. The expansion properties of the refractory die material that we synthesized can fulfil the application requirements of slip casting core of sintered titanium powder.

  3. Theory of low-temperature thermal expansion of glasses

    Science.gov (United States)

    Galperin, Yu. M.; Gurevich, V. L.; Parshin, D. A.

    1985-11-01

    We have developed a theory of low-temperature thermal expansion of glasses explaining a number of existing experimental data. We assume that thermal expansion, like many other low-temperature properties of glasses, is determined by associated two-level systems (TLS's) this concept has been introduced to explain these properties by Anderson, Halperin, and Varma and by Phillips. Our theory is based on the Karpov-Klinger-Ignat'ev model of two-level systems in glasses. The deformation potential of the TLS's is calculated. We have shown that it consists of two parts: The larger part (of the order of 0.3 eV) is responsible for the observed transport properties of glasses; however, it does not contribute to the thermal expansion of glasses. The latter is caused by a relatively small second part of the deformation potential which is, within logarithmic accuracy, proportional to the TLS's interlevel spacing E. This is why at low temperatures the coefficient of thermal expansion of glasses is approximately a linear function of the temperature. Its sign is determined by a microscopic structure of the TLS. We have calculated the Grüneisen parameter Γ. It appears to be of the order of (scrEa/ħωD)2/3~=100, where scrEa is an energy of the order of 30 eV and ωD is the Debye frequency. Such large values of Γ are connected with the softness of local anharmonic potentials that produce the TLS's in glasses. Our principal result is the dependence of the coefficient of thermal expansion α on the time of experiment, τexpt. It is shown that if α<0, then after heating glass it is at first contracted and afterwards, after the time about 10-8 sec (at T=0.3 K), a slow expansion begins. At τexpt~=1 sec the parameter Γ can have the absolute value of about (1/3) of that at τexpt~=10-8 sec. Such behavior of the thermal expansion coefficient is due to the fact that the contribution of the TLS's with large relative tunnel splitting (Δ0/E~=1) is negative while that of the TLS's with

  4. Effect of high thermal expansion glass infiltration on mechanical ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. This work studies the effect on the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabilized) composite by infiltrating glass of a higher thermal expansion (soda lime glass) on the surface at high temperature. The glass improved the strength of composite at room temperature as well as at high.

  5. Quantum elasticity of graphene: Thermal expansion coefficient and specific heat

    NARCIS (Netherlands)

    Burmistrov, I.S.; Gornyi, I.V.; Kachorovskii, V.Y.; Katsnelson, M.I.; Mirlin, A.D.

    2016-01-01

    We explore thermodynamics of a quantum membrane, with a particular application to suspended graphene membrane and with a particular focus on the thermal expansion coefficient. We show that an interplay between quantum and classical anharmonicity-controlled fluctuations leads to unusual elastic

  6. Thermal Expansion and Aging Effects in Neuromorphic Signal Processor

    NARCIS (Netherlands)

    Zjajo, A.; van Leuken, T.G.R.M.

    2016-01-01

    In this paper, we propose an efficient methodology based on a real-time estimator and predictor-corrector scheme for accurate thermal expansion profile and aging evaluation of a neuromorphic signal processor circuit components. As the experimental results indicate, for comparable mesh size, the

  7. Bioinspired engineering of thermal materials.

    Science.gov (United States)

    Tao, Peng; Shang, Wen; Song, Chengyi; Shen, Qingchen; Zhang, Fangyu; Luo, Zhen; Yi, Nan; Zhang, Di; Deng, Tao

    2015-01-21

    In the development of next-generation materials with enhanced thermal properties, biological systems in nature provide many examples that have exceptional structural designs and unparalleled performance in their thermal or nonthermal functions. Bioinspired engineering thus offers great promise in the synthesis and fabrication of thermal materials that are difficult to engineer through conventional approaches. In this review, recent progress in the emerging area of bioinspired advanced materials for thermal science and technology is summarized. State-of-the-art developments of bioinspired thermal-management materials, including materials for efficient thermal insulation and heat transfer, and bioinspired materials for thermal/infrared detection, are highlighted. The dynamic balance of bioinspiration and practical engineering, the correlation of inspiration approaches with the targeted applications, and the coexistence of molecule-based inspiration and structure-based inspiration are discussed in the overview of the development. The long-term outlook and short-term focus of this critical area of advanced materials engineering are also presented. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Thermal Expansion and Swelling of Cured Epoxy Resin Used in Graphite/Epoxy Composite

    Science.gov (United States)

    Adamson, M. J.

    1979-01-01

    The thermal expansion and swelling of resin material as influenced by variations in temperature during moisture absorption is discussed. Comparison measurements using composites constructed of graphite fibers and each of two epoxy resin matrices are included. Polymer theory relative to these findings is discussed and modifications are proposed.

  9. Fabrication of low thermal expansion SiC/ZrW2O8 porous ceramics

    Science.gov (United States)

    Poowancum, A.; Matsumaru, K.; Juárez-Ramírez, I.; Torres-Martínez, L. M.; Fu, Z. Y.; Lee, S. W.; Ishizaki, K.

    2011-03-01

    Low or zero thermal expansion porous ceramics are required for several applications. In this work near zero thermal expansion porous ceramics were fabricated by using SiC and ZrW2O8 as positive and negative thermal expansion materials, respectively, bonded by soda lime glass. The mixture of SiC, ZrW2O8 and soda lime glass was sintered by Pulsed Electric Current Sintering (PECS, or sometimes called Spark Plasma Sintering, SPS) at 700 °C. Sintered samples with ZrW2O8 particle size smaller than 25 μm have high thermal expansion coefficient, because ZrW2O8 has the reaction with soda lime glass to form Na2ZrW3O12 during sintering process. The reaction between soda lime glass and ZrW2O8 is reduced by increasing particle size of ZrW2O8. Sintered sample with ZrW2O8 particle size 45-90 μm shows near zero thermal expansion.

  10. Anion-mediated negative thermal expansion in lanthanum hexaboride

    Science.gov (United States)

    Mattox, Tracy M.; Groome, Chloe; Doran, Andrew; Beavers, Christine M.; Urban, Jeffrey J.

    2017-10-01

    Lanthanum hexaboride (LaB6) is well known for its thermionic emission, mechanical hardness, and intriguing optical properties. Though this material has been studied for decades, it is difficult to design LaB6 to meet application needs because little is understood about the mechanistic details of the synthesis. The ability to observe lattice formation during the reaction through in-situ x-ray diffraction is helping improve our knowledge. We report here the strong influence of anion size of the lanthanum precursor in the solid state reaction of LaX3 (X = Cl or I) and NaBH4. The Cl atom of the precursor remains within LaB6 post-synthesis and causes negative thermal expansion when the lattice is heated. Replacing Cl with the larger I atom has a larger impact on crystal growth; however, I does not remain within the lattice post-synthesis. These results suggest subtle new synthetic knobs may be available to optimize the synthesis of LaB6 that have previously gone unexplored.

  11. Compressibility and thermal expansion of cubic silicon nitride

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Lindelov, H.; Gerward, Leif

    2002-01-01

    The compressibility and thermal expansion of the cubic silicon nitride (c-Si3N4) phase have been investigated by performing in situ x-ray powder-diffraction measurements using synchrotron radiation, complemented with computer simulations by means of first-principles calculations. The bulk...... compressibility of the c-Si3N4 phase originates from the average of both Si-N tetrahedral and octahedral compressibilities where the octahedral polyhedra are less compressible than the tetrahedral ones. The origin of the unit cell expansion is revealed to be due to the increase of the octahedral Si-N and N-N bond...

  12. Synthesis, Structure, and Rigid Unit Mode-like Anisotropic Thermal Expansion of BaIr2In9.

    Science.gov (United States)

    Calta, Nicholas P; Han, Fei; Kanatzidis, Mercouri G

    2015-09-08

    This Article reports the synthesis of large single crystals of BaIr2In9 using In flux and their characterization by variable-temperature single-crystal and synchrotron powder X-ray diffraction, resistivity, and magnetization measurements. The title compound adopts the BaFe2Al9-type structure in the space group P6/mmm with room temperature unit cell parameters a = 8.8548(6) Å and c = 4.2696(4) Å. BaIr2In9 exhibits anisotropic thermal expansion behavior with linear expansion along the c axis more than 3 times larger than expansion in the ab plane between 90 and 400 K. This anisotropic expansion originates from a rigid unit mode-like mechanism similar to the mechanism of zero and negative thermal expansion observed in many anomalous thermal expansion materials such as ZrW2O8 and ScF3.

  13. Comparison of High Temperature Crystal Lattice and Bulk Thermal Expansion Measurements of LGT Single Crystal

    Energy Technology Data Exchange (ETDEWEB)

    Beaucage, Timothy R [University of Maine; Beenfeldt, Eric P [University of Maine; Speakman, Scott A [ORNL; Porter, Wallace D [ORNL; Payzant, E Andrew [ORNL; Pereira da Cunha, Mauricio [University of Maine

    2006-01-01

    Among the langasite family of crystals (LGX), the three most popular materials are langasite (LGS, La3Ga5SiO14), langatate (LGT, La3Ga5.5Ta0.5O14) and langanite (LGN, La3Ga5.5Nb0.5O14). The LGX crystals have received significant attention for acoustic wave (AW) device applications due to several properties, which include: (1) piezoelectric constants about two and a half times those of quartz, thus allowing the design of larger bandwidth filters; (2) existence of temperature compensated orientations; (3) high density, with potential for reduced vibration and acceleration sensitivity; and (4) possibility of operation at high temperatures, since the LGX crystals do not present phase changes up to their melting point above 1400degC. The LGX crystals' capability to operate at elevated temperatures calls for an investigation on the growth quality and the consistency of these materials' properties at high temperature. One of the fundamental crystal properties is the thermal expansion coefficients in the entire temperature range where the material is operational. This work focuses on the measurement of the LGT thermal expansion coefficients from room temperature (25degC) to 1200degC. Two methods of extracting the thermal expansion coefficients have been used and compared: (a) dual push-rod dilatometry, which provides the bulk expansion; and (b) x-ray powder diffraction, which provides the lattice expansion. Both methods were performed over the entire temperature range and considered multiple samples taken from <001> Czochralski grown LGT material. The thermal coefficients of expansion were extracted by approximating each expansion data set to a third order polynomial fit over three temperature ranges reported in this work: 25degC to 400degC, 400degC to 900degC, 900degC to 1200degC. An accuracy of fit better than 35ppm for the bulk expansion and better than 10ppm for the lattice expansion have been obtained with the aforementioned polynomial fitting. The

  14. Modeling the thermal deformation of TATB-based explosives. Part 1: Thermal expansion of “neat-pressed” polycrystalline TATB

    Energy Technology Data Exchange (ETDEWEB)

    Luscher, Darby J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-05-08

    thermal deformation of engineered components whose consolidation process is generally more complex than isostatic or die-pressed specimens. Finally, an envisioned application of the modeling approach to simulating thermal expansion of weapon systems and components is outlined along with necessary future work to introduce the effects of binder and ratcheting behavior. Key conclusions from this work include the following. Both porosity and grain aspect ratio have an influence on the thermal expansion of polycrystal TATB considering realistic material variability. Thepreferred orientation of the single crystal TATB [001] poles within a polycrystal gives rise to pronounced anisotropy of the macroscopic thermal expansion. The extent of this preferred orientation depends on the magnitude of deformation, and consequently, is expected to vary spatially throughout manufactured components much like porosity. The modeling approach presented here has utility toward bringing spatially variable microstructural features into macroscale system engineering modelsAbstract Not Provided

  15. Lattice thermal expansion and anisotropic displacements in -sulfur from diffraction experiments and first-principles theory.

    Science.gov (United States)

    George, Janine; Deringer, Volker L; Wang, Ai; Müller, Paul; Englert, Ulli; Dronskowski, Richard

    2016-12-21

    Thermal properties of solid-state materials are a fundamental topic of study with important practical implications. For example, anisotropic displacement parameters (ADPs) are routinely used in physics, chemistry, and crystallography to quantify the thermal motion of atoms in crystals. ADPs are commonly derived from diffraction experiments, but recent developments have also enabled their first-principles prediction using periodic density-functional theory (DFT). Here, we combine experiments and dispersion-corrected DFT to quantify lattice thermal expansion and ADPs in crystalline α-sulfur (S8), a prototypical elemental solid that is controlled by the interplay of covalent and van der Waals interactions. We begin by reporting on single-crystal and powder X-ray diffraction measurements that provide new and improved reference data from 10 K up to room temperature. We then use several popular dispersion-corrected DFT methods to predict vibrational and thermal properties of α-sulfur, including the anisotropic lattice thermal expansion. Hereafter, ADPs are derived in the commonly used harmonic approximation (in the computed zero-Kelvin structure) and also in the quasi-harmonic approximation (QHA) which takes the predicted lattice thermal expansion into account. At the PPBE+D3(BJ) level, the QHA leads to excellent agreement with experiments. Finally, more general implications of this study for theory and experiment are discussed.

  16. Investigation of the relationship between negative thermal expansion and other thermal properties of framework oxides

    Science.gov (United States)

    Kennedy, Catherine Anne

    2005-07-01

    Several framework solids exhibit negative thermal expansion (NTE) over a wide temperature range, e.g. ZrW2O 8 exhibits NTE from 0.3 to 1050 K. Although NTE is observed in other materials, it occurs over much smaller temperature ranges. NTE in ZrW 2O8 is associated with the low-energy modes corresponding to the correlated vibrations of the [WO4]2- tetrahedra and their three nearest [ZrO6]8- octahedra. This involves translation as well as libration, and low-energy optic modes play a central role. Thermal expansion and resistance to heat flow both originate in the anharmonic terms of the lattice dynamics. The influence of NTE in these framework materials on thermal conductivity was investigated by measuring thermal properties (thermal conductivity, kappa, from ca. 2 to 390 K and heat capacity, CP, from ca. 0.4 to 300 K) of ZrW2O8 and HfMo2O8. Literature values of the CP of ZrW2 O8 showed more disagreement than one might expect. In this research, it was found that the discrepancy could be due to low thermal conductivity of ZrW2O8. The CP of HfMo 2O8 is reported here for the first time. Analysis of CP reveals low-frequency modes that are not present in the binary oxides. A calculation of CP of HfMo 2O8 from HfMo2O8, ZrW2O 8, and ZrMo2O8 fits experimental C P of HfMo2O8 better since each AB 2O8 compound exhibits NTE and therefore has the low-frequency modes attributed to NTE. The thermodynamic calculations of the production of ZrW2O8 and HfMo2O8 from the appropriate oxides confirm that both are thermodynamically unstable with respect to the oxides. The kappa values of both ZrW2O8 and HfMo 2O8 are exceptionally low: kappadense(ZrW 2O8) is 0.91 W m-1 K-1 and kappadense(HfMo2O8) is 0.64 W m-1 K-1 at T = 300 K. Temperature-dependent kappa values of ZrW2O8 and HfMo2O8 are glass-like, despite polycrystalline morphology. Through consideration of the CP, phonon mean free path, and Gruneisen parameter, the kappa behavior is attributed to the low-frequency modes which are also

  17. Thermal expansion of vitrified blood vessels permeated with DP6 and synthetic ice modulators.

    Science.gov (United States)

    Eisenberg, David P; Taylor, Michael J; Jimenez-Rios, Jorge L; Rabin, Yoed

    2014-06-01

    This study provides thermal expansion data for blood vessels permeated with the cryoprotective cocktail DP6, when combined with selected synthetic ice modulators (SIMs): 12% polyethylene glycol 400, 6% 1,3-cyclohexanediol, and 6% 2,3-butanediol. The general classification of SIMs includes molecules that modulate ice nucleation and growth, or possess properties of stabilizing the amorphous state, by virtue of their chemical structure and at concentrations that are not explained on a purely colligative basis. The current study is part of an ongoing effort to characterize thermo-mechanical effects on structural integrity of cryopreserved materials, where thermal expansion is the driving mechanism to thermo-mechanical stress. This study focuses on the lower part of the cryogenic temperature range, where the cryoprotective agent (CPA) behaves as a solid for all practical applications. By combining results obtained in the current study with literature data on the thermal expansion in the upper part of the cryogenic temperature range, unified thermal expansion curves are presented. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Comparison of the Thermal Expansion Behavior of Several Intermetallic Silicide Alloys Between 293 and 1523 K

    Science.gov (United States)

    Raj, S. V.

    2015-03-01

    Thermal expansion measurements were conducted on hot-pressed CrSi2, TiSi2, WSi2 and a two-phase Cr-Mo-Si intermetallic alloy between 303 and 1523 K during three heat-cool cycles. The corrected thermal expansion, (Δ L/ L 0)thermal, varied with the absolute temperature, T, as where, A, B, C, and D are regression constants. Excellent reproducibility was observed for most of the materials after the first heat-up cycle. In some cases, the data from first heat-up cycle deviated from those determined in the subsequent cycles. This deviation was attributed to the presence of residual stresses developed during processing, which are relieved after the first heat-up cycle.

  19. Thermal expansion behavior of fluor-chlorapatite crystalline solutions

    Science.gov (United States)

    Hovis, G.; Harlov, D.; Gottschalk, M.; Hudacek, W.; Wildermuth, S.

    2009-04-01

    Apatite Ca5(PO4)3(F,Cl,OH,CO3) occurs widely as an accessory mineral in many igneous and metamorphic rocks and in nature displays a wide range of F-Cl-OH-CO3 mixtures (e.g., O'Reilly and Griffin, 2000) that have been used to interpret the role of fluids, e.g. Cl, F, and OH activities, during metamorphic and igneous processes (e.g., Harlov and Förster, 2002). It is important, therefore, to understand the thermodynamic behavior of these solid solutions, including their thermal expansion properties. Fluorapatite - chlorapatite samples were synthesized at the GFZ-Potsdam (Hovis, Harlov, Hahn and Steigert, 2007) using an adaptation of the molten flux method of Cherniak (2000). Dry CaF2 and CaCl2 (0.1 mole total) were mixed with Ca3(PO4)2 (0.03 moles), placed in a Pt crucible, equilibrated for 15 hours at 1375 °C, cooled to 1220 °C at 3 °C/hour, removed from the oven and cooled in air. Crystals were separated from the flux by boiling the quenched product in water. F:Cl fractions for each sample were determined via Rietveld refinement of X-ray powder diffraction data. Chemical homogeneity was confirmed by Rietveld refinement and high-contrast back-scattered electron imaging. Room-temperature unit-cell volumes were determined at the GFZ-Potsdam through Rietveld analysis of X-ray powder diffraction data and also at Lafayette College by standard unit-cell refinement techniques (Holland and Redfern, 1997) using NBS/NIST 640a Si as an internal standard. High-temperature unit-cell dimensions were calculated from X-ray powder diffraction data collected at Cambridge University from room temperature to 1000 °C on a Bruker D8 X-ray diffractometer. NBS Si again was utilized as an internal standard; high-temperature Si peak positions were taken from Parrish (1953). Results indicate that despite the considerable size difference between fluorine and chlorine ions, reflected by substantially different unit-cell sizes at room temperature, the coefficient of thermal expansion across

  20. Negative thermal expansion properties in tetragonal NbPO5 from the first principles studies

    Directory of Open Access Journals (Sweden)

    Tao Li

    2017-03-01

    Full Text Available By using the first-principles calculations based on density functional theory combined with quasi-harmonic approximation, we have studied the geometric structural, thermal properties, and the negative thermal expansion (NTE properties of tetrahedral NbPO5. The variations of cell parameter and cell volume of tetrahedral NbPO5 with temperature show that it displays NTE behavior in the range of 473-800 K along a-axis and the corresponding average coefficient of thermal expansion (CTE is approximately -0.766 ×10−6 K−1, while the c cell parameter and the cell volume display positive thermal expansion behaviors. These results are in consistent well with the experiment observations. Further vibrational modes analysis, together with Grüneisen parameters calculations, revealed that the transverse vibration of O corner atoms accompanying the rocking motions of corner-shared NbO6 octahedron and PO4 tetrahedron dominate the negative thermal properties of tetrahedral NbPO5. Our findings will provide an understanding for the underlying mechanisms of the NTE in oxides materials.

  1. With respect to coefficient of linear thermal expansion, bacterial vegetative cells and spores resemble plastics and metals, respectively

    Science.gov (United States)

    2013-01-01

    Background If a fixed stress is applied to the three-dimensional z-axis of a solid material, followed by heating, the amount of thermal expansion increases according to a fixed coefficient of thermal expansion. When expansion is plotted against temperature, the transition temperature at which the physical properties of the material change is at the apex of the curve. The composition of a microbial cell depends on the species and condition of the cell; consequently, the rate of thermal expansion and the transition temperature also depend on the species and condition of the cell. We have developed a method for measuring the coefficient of thermal expansion and the transition temperature of cells using a nano thermal analysis system in order to study the physical nature of the cells. Results The tendency was seen that among vegetative cells, the Gram-negative Escherichia coli and Pseudomonas aeruginosa have higher coefficients of linear expansion and lower transition temperatures than the Gram-positive Staphylococcus aureus and Bacillus subtilis. On the other hand, spores, which have low water content, overall showed lower coefficients of linear expansion and higher transition temperatures than vegetative cells. Comparing these trends to non-microbial materials, vegetative cells showed phenomenon similar to plastics and spores showed behaviour similar to metals with regards to the coefficient of liner thermal expansion. Conclusions We show that vegetative cells occur phenomenon of similar to plastics and spores to metals with regard to the coefficient of liner thermal expansion. Cells may be characterized by the coefficient of linear expansion as a physical index; the coefficient of linear expansion may also characterize cells structurally since it relates to volumetric changes, surface area changes, the degree of expansion of water contained within the cell, and the intensity of the internal stress on the cellular membrane. The coefficient of linear expansion holds

  2. Coefficient of Thermal Expansion of Pressed PETN Pellets

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Darla Graff [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); DeLuca, Racci [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-03-11

    The PETN single crystal coefficient of thermal expansion (CTE) values were measured and reported by Cady in 1972 [1] over the temperature range of -160 to 100°C. Measurements were made in the (001) and (100) crystallographic directions, see Figure 1 (a replicate of Figure 1 from the Cady paper). Cady used his single-crystal data to calculate the linear CTE for a randomly-oriented multi-crystal pressing of PETN, and his values ranged from 76.5 με/°C (at 20°C) to 89.9 5 με/°C (at 90°C).

  3. Modulus of Elasticity and Thermal Expansion Coefficient of ITO Film

    Energy Technology Data Exchange (ETDEWEB)

    Carter, Austin D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Elhadj, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-06-24

    The purpose of this experiment was to determine the modulus of elasticity (E) and thermal expansion coefficient (α) of RF sputtered Indium Tin Oxide (ITO) as a function of temperature (T), and to collect ITO film stress data. In order to accomplish that goal, the Toho FLX-2320-S thin film stress measurement machine was used to collect both single stress and stress-temperature data for ITO coated fused silica and sapphire substrates. The stress measurement function of the FLX-2320-S cannot be used to calculate the elastic modulus of the film because the Stoney formula incorporates the elastic modulus of the substrate, rather than of the film itself.

  4. Deformation analysis considering thermal expansion of injection mold

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jun Hyung; Yi, Dae Eun; Jang, Jeong Hui; Lee, Min Seok [Samsung Electronics Co., LTD., Seoul (Korea, Republic of)

    2015-09-15

    In the design of injection molds, the temperature distribution and deformation of the mold is one of the most important parameters that affect the flow characteristics, flash generation, and surface appearance, etc. Plastic injection analyses have been carried out to predict the temperature distribution of the mold and the pressure distribution on the cavity surface. As the input loads, we transfer the temperature and pressure results to the structural analysis. We compare the structural analysis results with the thermal expansion effect using the actual flash and step size of a smartphone cover part. To reduce the flash problem, we proposed a new mold design, and verified the results by performing simulations.

  5. Negative Thermal Expansion Coefficient of Graphene Measured by Raman Spectroscopy

    OpenAIRE

    Yoon, Duhee; Son, Young-Woo; Cheong, Heonsik

    2011-01-01

    The thermal expansion coefficient (TEC) of single-layer graphene is estimated with temperature-dependent Raman spectroscopy in the temperature range between 200 and 400 K. It is found to be strongly dependent on temperature but remains negative in the whole temperature range, with a room temperature value of -8.0x10^{-6} K^{-1}. The strain caused by the TEC mismatch between graphene and the substrate plays a crucial role in determining the physical properties of graphene, and hence its effect...

  6. Negative thermal expansion coefficient of graphene measured by Raman spectroscopy.

    Science.gov (United States)

    Yoon, Duhee; Son, Young-Woo; Cheong, Hyeonsik

    2011-08-10

    The thermal expansion coefficient (TEC) of single-layer graphene is estimated with temperature-dependent Raman spectroscopy in the temperature range between 200 and 400 K. It is found to be strongly dependent on temperature but remains negative in the whole temperature range with a room temperature value of (-8.0 ± 0.7) × 10(-6) K(-1). The strain caused by the TEC mismatch between graphene and the substrate plays a crucial role in determining the physical properties of graphene, and hence its effect must be accounted for in the interpretation of experimental data taken at cryogenic or elevated temperatures.

  7. Evaluating the coefficient of thermal expansion using time periods of minimal thermal gradient for a temperature driven structural health monitoring

    Science.gov (United States)

    Reilly, J.; Abdel-Jaber, H.; Yarnold, M.; Glisic, B.

    2017-04-01

    Structural Health Monitoring aims to characterize the performance of a structure from a combination of recorded sensor data and analytic techniques. Many methods are concerned with quantifying the elastic response of the structure, treating temperature changes as noise in the analysis. While these elastic profiles do demonstrate a portion of structural behavior, thermal loads on a structure can induce comparable strains to elastic loads. Understanding this relationship between the temperature of the structure and the resultant strain and displacement can provide in depth knowledge of the structural condition. A necessary parameter for this form of analysis is the Coefficient of Thermal Expansion (CTE). The CTE of a material relates the amount of expansion or contraction a material undergoes per degree change in temperature, and can be determined from temperature-strain relationship given that the thermal strain can be isolated. Many times with concrete, the actual amount of expansion with temperature in situ varies from the given values for the CTE due to thermally generated elastic strain, which complicates evaluation of the CTE. To accurately characterize the relationship between temperature and strain on a structure, the actual thermal behavior of the structure needs to be analyzed. This rate can vary for different parts of a structure, depending on boundary conditions. In a case of unrestrained structures, the strain in the structure should be linearly related to the temperature change. Thermal gradients in a structure can affect this relationship, as they induce curvature and deplanations in the cross section. This paper proposes a method that addresses these challenges in evaluating the CTE.

  8. Molecular dynamics study of the thermal expansion coefficient of silicon

    Science.gov (United States)

    Nejat Pishkenari, Hossein; Mohagheghian, Erfan; Rasouli, Ali

    2016-12-01

    Due to the growing applications of silicon in nano-scale systems, a molecular dynamics approach is employed to investigate thermal properties of silicon. Since simulation results rely upon interatomic potentials, thermal expansion coefficient (TEC) and lattice constant of bulk silicon have been obtained using different potentials (SW, Tersoff, MEAM, and EDIP) and results indicate that SW has a better agreement with the experimental observations. To investigate effect of size on TEC of silicon nanowires, further simulations are performed using SW potential. To this end, silicon nanowires of different sizes are examined and their TEC is calculated by averaging in different directions ([100], [110], [111], and [112]) and various temperatures. Results show that as the size increases, due to the decrease of the surface effects, TEC approaches its bulk value.

  9. ZrO2-ZrW2O8 Composites with tailor-made thermal expansion

    Directory of Open Access Journals (Sweden)

    K. De Buysser

    2004-12-01

    Full Text Available Most of the materials expand upon heating. There are a few families of materials which exhibit negative thermal expansion (NTE. ZrW2O8 is an example which gained a lot of interest in international literature recently. This cubic material has an exceptionally large and isotropic negative thermal expansion over its entire stability range (0.5 to 1050 K. At 430 K a phase transition occurs from a-ZrW2O8 (a = -9.1 x 10-6 K-1 to b-ZrW2O8 (b = -5.4 x 10-6 K-1. At high pressures an orthorhombic phase is formed, g-ZrW2O8, which possesses a small negative expansion coefficient. A broad range of applications have been suggested for these NTE materials. In composites, their thermal expansion coefficient can be tailor-made by combining a NTE material with a positive expansion material. Adjusting the volume fraction of the different phases results in a positive, negative or even zero thermal expansion. The ZrW2O8 - ZrO2 - composites studied in this paper were prepared in two ways. The first synthesis method applied, started from off-stoichiometry mixtures of the pure oxide powders of ZrO2 and WO3. This novel in situ process included a heating step up to 1450 K which combines the formation and sintering of ZrW2O8. In the conventional synthesis the starting materials were ZrO2 and ZrW2O8. ZrW2O8 was first obtained using an optimised spray drying technique. Obviously, our "in situ" method does not require such an additional step. The crystal structure, morphology, thermal expansion behaviour and mechanical properties of these composites were tested and compared.

  10. Sound velocity of high-strength polymer with negative thermal expansion coefficient

    Science.gov (United States)

    Nomura, R.; Ueno, M.; Okuda, Y.; Burmistrov, S.; Yamanaka, A.

    2003-05-01

    Sound velocities of fiber reinforced plastics (FRPs) were measured along the fiber axis at temperatures between 360 and 77 K. We used two kinds of the high-strength crystalline polymer fibers, polyethylene (Dyneema) and polybenzobisoxazole (Zylon), which have negative thermal expansion coefficients. They also have high thermal conductivities and high resistances for flash over voltage, and are expected as new materials for coil bobbins or spacers at cryogenic temperatures. They have very large sound velocities of about 9000 (m/s) at 77 K, which are 4.5 times larger than that of the ordinary polyethylene fiber.

  11. Thermal expansion investigation of tourmaline-group minerals

    Science.gov (United States)

    Hovis, G.; Scott, B.; Altomare, C.; Tomaino, G.

    2012-04-01

    In recent years one aim of this laboratory has been the characterization of thermal expansion in various mineral groups with an eye toward evaluation of the extent to which chemical composition affects expansion behaviour. We have undertaken studies on various mineral series including alkali feldspar, plagioclase, Ba/K-feldspar, Rb/K feldspar, nepheline/kalsilite minerals of various excess Si contents, and F/Cl/OH apatite. We turn our attention now to the tourmaline mineral system, which is of interest because of its wide variation in chemical composition, as well as its structural complexity. We have obtained multiple chemically-characterized tourmaline specimens from the U.S. National Museum of Natural History and also from George Rossman. Six specimens have been investigated so far, including elbaite, rossmanite, uvite, buergerite, schorl, and foitite. High-temperature X-ray powder diffraction measurements have been made from room temperature to 1000 °C at 75° intervals. X-ray peak positions were corrected utilizing NIST SRM 640a silicon as an internal standard. Peaks were indexed manually based on data in the literature; unit-cell dimensions were computed utilizing the software of Holland and Redfern (1997, Mineralogical Magazine). V-T relationships are generally linear, or close to it, up to the breakdown temperatures of all specimens. Coefficients of thermal expansion have been computed as (ΔV/ΔT)*(1/V0C), where V0C is the extrapolated volume intercept at 0 °C based on the various linear V-T relationships. Among the six specimens, all except foitite give thermal expansion coefficients between 23 and 26 x 10-6 deg-1. Foitite has a flatter V-T slope and thus expands less, giving a thermal expansion coefficient of 18 x 10-6. Based on the initial data, the relative uniformity of expansion behaviour in this system implies that any volumes of mixing in this system will be essentially constant with temperature, recognizing that this conclusion is based on the

  12. Metal-Matrix Nanocomposites with Tailored Coefficients of Thermal Expansion for Improved Thermomechanical Reliability

    Science.gov (United States)

    Trujillo, J. E.; Kim, J. W.; Lan, E. H.; Sharratt, S.; Ju, Y. S.; Dunn, B.

    2012-06-01

    Ensuring the thermomechanical reliability of various interfaces in thermoelectric (TE) devices during manufacture and operation is challenging, especially for those incorporating TE materials with small coefficients of thermal expansion (CTEs). In this paper, we describe our recent progress in the development of metal-matrix nanocomposites with tailorable CTEs, for use as electrodes or as interfacial bonding layers for creating segmented TE elements. The composites incorporate ceramic nanoscale fillers with isotropic negative thermal expansion (NTE) to effectively offset the high CTE of the metal phase. The NTE fillers, synthesized using a sol-gel route, were mixed with metal powders and hot pressed to yield nanocomposites having CTE values decreasing approximately linearly with filler volume fraction. Composites with 54/46 v/v Ag/zirconium tungstate (ZrW2O8) achieved average CTE of 7.2 ppm/K, with electrical and thermal conductivities approximately 50% of that of Ag nanopowders hot pressed under identical conditions. X-ray diffraction (XRD) analyses suggest that the composites are thermally stable at temperatures as high as 920 K. This research provides a foundation upon which to investigate alternative electrode and interface materials with tailored CTEs for achieving improved thermomechanical reliability of TE modules and other thermal and electronic devices.

  13. Phase behaviour, thermal expansion and compressibility of SnMo 2 O 8

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Luiza R.; Gallington, Leighanne C.; Wilkinson, Angus P.; Evans, John S. O.

    2018-02-01

    The phase behaviour and thermoelastic properties of SnMo2O8, derived from variable temperature and pressure synchrotron powder diffraction data, are reported. SnMo2O8 is a member of the AM2O8 family of negative thermal expansion (NTE) materials, but unexpectedly, has positive thermal expansion. Over the P-T space explored (298–513 K, ambient to 310 MPa) four different forms of SnMo2O8 are observed: α, β, γ and γ'. The γ to β transition is temperature-, pressure-, and time-dependent. SnMo2O8 is a much softer material (α and γ form have BT = 29 and 26 GPa at 298 K) than other members of the AM2O8 family. Counter-intuitively, its high temperature β phase becomes stiffer with increasing temperature (BT ~36 GPa at 490 K). The pressure dependence of the thermal expansion for each phase is reported.

  14. Analysis of the thermal expansivity near the tricritical point in dilute chromium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yurtseven, H., E-mail: hamit@metu.edu.tr [Department of Physics, Middle East Technical University, 06531 Ankara-TURKEY (Turkey); Tari, Ö., E-mail: ozlemilgin@arel.edu.tr [Department of Mathematics and Computer Science, Istanbul Arel University, 34537 Büyükçekmece, Istanbul-TURKEY (Turkey)

    2016-03-25

    Chromium (Cr) undergoes a first order Neel transition as an antiferromagnetic material. When V, Mo and Mn atoms are substituted in the Cr lattice, a weak first order Neel transition in pure Cr changes toward a second order transition and a possible tricritical point in CrV occurs close to 0.2 at %V, as observed experimentally from the measurements of the thermal expansivity at various temperatures. In this study, we analyze the experimental data for the thermal expansivity from the literature as a function of temperature using the power - law formula for Cr alloys (Cr - 0.1V, 0.2V, 0.5V and Cr - 0.1Mn, Cr - 0.2Mo, 0.3Mo, 0.4Mo). Our results are interpreted near the tricritical point in dilute chromium alloys.

  15. Thermal Expansion of Fluorapatite-Chlorapatite Solid Solutions

    Science.gov (United States)

    Hovis, Guy; Abraham, Tony; Hudacek, William; Wildermuth, Sarah; Scott, Brian; Altomare, Caitlin; Medford, Aaron; Conlon, Maricate; Morris, Matthew; Leaman, Amanda; Almer, Christine; Tomaino, Gary; Harlov, Daniel

    2015-04-01

    X-ray powder diffraction experiments have been performed on fifteen fluorapatite-chlorapatite solid solutions synthesized and chemically characterized at the GeoForschungsZentrum - Potsdam (Hovis and Harlov, 2010; Schettler, Gottschalk, and Harlov, 2011), as well as two natural near-end-member samples, from room temperature to ~900 °C at 50 to 75 °C intervals. NIST 640a Si was employed as an internal standard; data from Parrish (1953) were used to determine Si peak positions at elevated temperatures. Unit-cell parameters calculated using the software of Holland and Redfern (1997) result in volume-temperature (V-T) plots that are linear or slightly concave up (V plotted as the vertical axis) over the T range investigated. Relations for the "a" and "c" unit-cell dimensions with T for these hexagonal minerals are nearly linear, but as with V, commonly improved by quadratic fits to the data. Coefficients of thermal expansion for volume (αV ), calculated as (1/V0°C) x (ΔV/ΔT) based on linear V-T relationships, mostly fall within the range 42 ± 2 x 10-6 deg-1 and show no obvious dependence on composition. Thermal expansion coefficients for individual unit-cell axes, however, do show clear relationships to composition, αa increasing from ~9.5 to ~13.5 x 10-6 deg-1 and αc decreasing from ~19.5 to ~13 x 10-6 deg-1 from the Cl to the F end member. Clearly, a compensating structural relationship accounts for the observed relationships. Such compositional dependence was not seen in the thermal expansion data for F-OH apatite solid solutions (Hovis, Scott, Altomare, Leaman, Morris, and Tomaino, American Mineralogist, in press). This difference can be explained by the similar sizes of F- and (OH)- versus the much greater size contrast between F- and Cl-. Sincere thanks to the National Science Foundation for support of this work, which has provided numerous research experiences for Lafayette College undergraduates. Thanks also to the Earth Sciences Department, University

  16. Physics of thermal wave NDE of semiconductor materials and devices

    Energy Technology Data Exchange (ETDEWEB)

    Opsal, J.; Rosencwaig, A.

    1988-04-01

    The fundamental physics of a modulated-reflectance thermal-wave NDE technique for semiconductor materials and devices is explored. In this method, an intensity-modulated laser beam produces a thermal wave in the material and in the air above it; the thermal expansion of the material is detected by a probe-beam interferometer or by the deflection of a probe beam by the thermoelastic deformation of the surface. The governing equations for these basic processes are examined in detail, with a focus on the sensitivity of thermal and plasma waves to variations in thermal and electrical transport properties and recombination effects. The applicability of this technique to on-line monitoring of ion implantation, measurement of near-surface damage from wafer polishing or dry etching, and detection of defect-related electronic surface states is indicated. 23 references.

  17. Local Thermal Insulating Materials For Thermal Energy Storage ...

    African Journals Online (AJOL)

    Thermal insulation is one of the most important components of a thermal energy storage system. In this paper the thermal properties of selected potential local materials which can be used for high temperature insulation are presented. Thermal properties of seven different samples were measured. Samples consisted of: ...

  18. Local Thermal Insulating Materials For Thermal Energy Storage

    African Journals Online (AJOL)

    Unknown User

    1. Introduction. It is necessary to use thermal insulating materials around thermal energy storage systems to minimize heat losses from the systems [1]. There are varieties of insulating materials which come in various forms like loose fill, rigid boards, pipe and foam. The thermal insulation is provided by embedding insulation ...

  19. A phenomenological model of starchy materials expansion by extrusion

    OpenAIRE

    2015-01-01

    During extrusion of starchy products, the molten material is forced through a die so that the sudden pressure drop causes part of the water to vaporize, giving an expanded cellular structure. The moisture is lost due to evaporation and heat transfer, as the material cools down. Thus, the material crosses glass transition Tg and becomes solid. No simple deterministic model is available to describe satisfactory dynamic, multiphysic and multiphase phenomena during expansion. Current models are...

  20. Molecular dynamics study of the thermal expansion coefficient of silicon

    Energy Technology Data Exchange (ETDEWEB)

    Nejat Pishkenari, Hossein, E-mail: nejat@sharif.edu; Mohagheghian, Erfan; Rasouli, Ali

    2016-12-16

    Due to the growing applications of silicon in nano-scale systems, a molecular dynamics approach is employed to investigate thermal properties of silicon. Since simulation results rely upon interatomic potentials, thermal expansion coefficient (TEC) and lattice constant of bulk silicon have been obtained using different potentials (SW, Tersoff, MEAM, and EDIP) and results indicate that SW has a better agreement with the experimental observations. To investigate effect of size on TEC of silicon nanowires, further simulations are performed using SW potential. To this end, silicon nanowires of different sizes are examined and their TEC is calculated by averaging in different directions ([100], [110], [111], and [112]) and various temperatures. Results show that as the size increases, due to the decrease of the surface effects, TEC approaches its bulk value. - Highlights: • MD simulations of TEC and lattice constant of bulk silicon. • Effects of four potentials on the results. • Comparison to experimental data. • Investigating size effect on TEC of silicon nanowires.

  1. Thermal expansion in the orthorhombic γ phase of ZrW2O8

    Science.gov (United States)

    Evans, J. S. O.; Jorgensen, J. D.; Short, S.; David, W. I. F.; Ibberson, R. M.; Sleight, A. W.

    1999-12-01

    The thermal expansion of the orthorhombic γ phase of ZrW2O8 has been measured using neutron powder diffraction from 4.6 to 410 K, where it transforms to the cubic α phase. At low temperature, γ-ZrW2O8 has a negative thermal expansion, but the thermal expansion becomes less negative with increasing temperature and is slightly positive at room temperature. This behavior can be explained in terms of the contributing phonon modes: At low temperature, the vibrational modes lead to a negative thermal expansion, but additional modes that become active upon increasing temperature add positive contributions. Above room temperature, the a and b axes increase more sharply while the c axis reverses its behavior and decreases with increasing temperature. This unusual behavior can be explained in terms of a thermally activated process, presumed to result from oxygen-atom migration, that makes an additional contribution to the thermal expansion.

  2. Ultra low and negative expansion glass–ceramic materials ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Ultra low and negative expansion glass–ceramic materials have been obtained from pyrophyllite and blast furnace slag. The batch composition was modified with the addition of lithium carbonate, hydrated alumina, boric acid and nucleating agent (titania). The batch was melted at 1400°C followed by casting in the.

  3. Ultra low and negative expansion glass–ceramic materials ...

    Indian Academy of Sciences (India)

    Ultra low and negative expansion glass–ceramic materials have been obtained from pyrophyllite and blast furnace slag. The batch composition was modified with the addition of lithium carbonate, hydrated alumina, boric acid and nucleating agent (titania). The batch was melted at 1400°C followed by casting in the form of ...

  4. Thermal expansion behaviour and phase stability of AFe2As2 (A ...

    Indian Academy of Sciences (India)

    The lattice parameter in the tetragonal phase (AT) of CaFe 2 As 2 contracts with increasing temperature, whereas CT expands. The rate of contraction in AT is lower than the rate of expansion in CT. Other compounds show normal thermal expansion behaviour along both a- and c-axes. In-plane expansion (i.e., along the ...

  5. Controlled thermal expansion printed wiring boards based on liquid crystal polymer dielectrics

    Science.gov (United States)

    Knoll, Thomas E.; Blizard, Kent; Jayaraj, K.; Rubin, Leslie S.

    1994-04-01

    Dielectric materials based on innovative Liquid Crystal Polymers (LCP's) have been used to fabricate surface mount printed wiring boards (PWB's) with a coefficient of thermal expansion matched to leadless ceramic chip carriers. Proprietary and patented polymer processing technology has resulted in self reinforcing material with balanced in-plane mechanical properties. In addition, LCP's possess excellent electrical properties, including a low dielectric constant (less than 2.9) and very low moisture absorption (less than 0.02%). LCP-based multilayer boards processed with conventional drilling and plating processes show improved performance over other materials because they eliminate the surface flatness problems of glass or aramid reinforcements. Laser drilling of blind vias in the LCP dielectric provides a very high density for use in direct chip attach and area array packages. The material is ideally suited for MCM-L and PCMCIA applications fabricated with very thin dielectric layers of the liquid crystal polymer.

  6. Measurement of the thermal expansion coefficient of AISI 420 stainless steel between 20 and 293 K

    Science.gov (United States)

    Martelli, Valentina; Bianchini, Giovanni; Ventura, Guglielmo

    2014-07-01

    The accurate measurement of thermal expansion coefficient at low temperatures is fundamental in applications where a high mechanical stability is required over the complete procedure of cooling. Here we report on our measurement of thermal expansion of AISI 420 between 20 and 293 K, measured by an interferometric dilatometer.

  7. Complex oxide with negative thermal expansion for producing ceramic matrix composites with invar effect

    Science.gov (United States)

    Dedova, Elena S.; Pertushina, Mariya U.; Kondratenko, Anton I.; Gorev, Mikhail V.; Kulkov, Sergei N.

    2016-11-01

    The article investigates the phase composition of (Al2O3-20 wt % ZrO2)-ZrW2O8 ceramic composites obtained by cold-pressing and sintering processes. Using X-ray analysis it has been shown that composites mainly have monoclinic modification of zirconium dioxide and orthorhombic phase of aluminum oxide. After adding zirconium tungstate the phase composition of sintered ceramics changes, followed by the formation of tungsten-aluminates spinel such as Alx(WOy)z. It has been shown that thermal expansion coefficient of material decreases approximatly by 30%, as compared with initial ceramics.

  8. DETERMINATION OF THERMAL RESPONSE OF CARRARA AND SNEZNIKOVSKY MARBLE USED AS A BUILDING MATERIALS

    Directory of Open Access Journals (Sweden)

    Veronika Petráňová

    2016-02-01

    Full Text Available Physical weathering of marble, widely used as a cladding material on buildings, is one of the most common damaging mechanism caused by anisotropic thermal expansion of calcite grains. The extent of marble deterioration depends mainly on stone fabric and texture. Dry cuboids of Carrara marble and marble from Dolni Morava quarry were subjected to microscopic analysis and thermal cycling, to determine the thermal expansion related to stone fabric and predominant lattice orientation of grains (i.e. texture.

  9. Giant extrinsic negative thermal expansion in vanadium pentoxide nanocrystalline films

    Energy Technology Data Exchange (ETDEWEB)

    Bahgat, A.A. [Department of Physics, Faculty of Science, King Khaled University, P.O. Box 9004, Abha (Saudi Arabia); Department of Physics, Faculty of Science, Al-Azhar University, Nasr City 11884, Cairo (Egypt); Al-Hajry, A. [Department of Physics, Faculty of Science, King Khaled University, P.O. Box 9004, Abha (Saudi Arabia); El-Desoky, M.M. [Department of Physics, Faculty of Science, King Khaled University, P.O. Box 9004, Abha (Saudi Arabia); Department of Physics, Faculty of Education, Suez Canal University, Al-Arish (Egypt)

    2006-06-15

    Vanadium pentoxide gels, V{sub 2}O{sub 5}.1.6H{sub 2}O, give rise to xerogel layers that exhibit a preferred orientation. X-ray diffraction of this xerogel displays the 00l peaks typical of a turbostratic stacking of the V{sub 2}O{sub 5} ribbons along a direction parallel to the substrate. The distance along the c-axis is observed from the interlayer spacing to decrease continuously with increasing temperature up to 180 C, as observed by high-temperature X-ray diffraction. This contraction may be described by an extrinsic mechanism of negative thermal expansion (NTE). The coefficient of NTE as large as -1.5 x 10{sup -3} K{sup -1} was observed. Full recovery of the interlayer spacing is obtained after cooling the sample to room temperature in open air, where water molecules are reabsorbed, indicating that the process is reversible and the heating process can be repeated without losing NTE. The structure of the xerogel was explored further using differential scanning calorimetry as well as infrared spectroscopy. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Thermal expansion of PBX 9501 and PBX 9502 plastic-bonded explosives

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Darla Graff [Los Alamos National Laboratory; Brown, Geoff W [Los Alamos National Laboratory; Deluca, Racci [Los Alamos National Laboratory; Giambra, Anna [Los Alamos National Laboratory; Sandstrom, Mary [Los Alamos National Laboratory

    2009-01-01

    Two applications of thermal expansion measurements on plastic-bonded explosive (PBX) composites are described. In the first dilatometer application, thermal expansion properties of HMX-based PBX 9501 are measured over a broad thermal range that includes glass and domain-restructuring transitions in the polymeric binder. Results are consistent with other thermal measurements and analyses performed on the composite, as well as on the binder itself. The second application used the dilatometer to distinguish the reversible and irreversible components of thermal expansion in PBX 9502, a TATB-based explosive. Irreversible expansion of the composite is believed to derive from the highly-anisotropic coefficient of thermal expansion (CTE) values measured on single T A TB crystals, although the mechanism is not well understood. Effects of specimen density, thermal ramp rate, and thermal range variation (warm first or cold first) were explored, and the results are presented and discussed. Dilatometer measurements are ongoing towards gaining insight into the mechanism(s) responsible for PBX 9502 irreversible thermal expansion.

  11. Hygroscopic Expansion of Aesthetic Restorative Materials: One-Year Report

    Science.gov (United States)

    Emamieh, S.; Ghasemi, A.; Torabzadeh, H.

    2011-01-01

    Objective: To measure the long-term linear hygroscopic expansion (LHE) of several materials using bulked and layered techniques. Materials and Methods: Seven materials were used; Fuji Cap II, Fuji II LC, Photac-Fil Aplicap, Vitremer, Dyract, Tetric and Z100. Ten specimens (6×4 mm) were made for each material using layered and bulked techniques (each group comprises five specimens). The specimens were stored in distilled water at 37°C. The length of each specimen was measured immediately after preparation, 24 hours, one week, one month, three months, six months, nine months and one year. This was used to calculate the percentage change in the length of materials. The mean LHE and standard deviation were calculated. Repeated measure analysis and paired sample t-test were used. Results: The type of material and time had a significant effect on LHE. Fuji Cap II and Fuji II LC exhibited no significant changes after one-year and one month, respectively. However, layered specimens of Photac-Fil Aplicap and Tetric showed constant expansion until six month, whereas bulked specimens reached the constant length at three months. Constant expansion was obtained for layered and bulked specimens of Dyract and Z100 at six month. Layered specimens of Vitremer showed no significant differences except between 24 hours and one year measurements. But in bulked specimens, the results at nine months and one year were significantly different from those obtained at three months and before. Conclusion: Fuji II showed no significant LHE and resin-modified glass ionomer cements (RMGICs) exhibited the highest LHE. Dyract maintained an intermediate LHE in comparison with RMGIC and composite resin. PMID:21998804

  12. Overview of thermal conductivity models of anisotropic thermal insulation materials

    Science.gov (United States)

    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.

  13. Technique for reduction of mechanical losses in AC superconducting coils due to thermal expansion properties of various FRP bobbins

    Science.gov (United States)

    Sekine, N.; Tada, S.; Higuchi, T.; Furumura, Y.; Takao, T.; Yamanaka, A.

    2005-10-01

    We reported about reduction of mechanical losses in AC superconducting coils. The method is the use of FRP bobbins fabricated with special fibers. Since their FRPs have negative thermal expansion coefficient to the fiber direction, the FRP bobbins expand to the circumferential direction during cooling down. In case of the superconducting coils with such FRP bobbins, the winding tensions do not decrease during cooling down. Therefore, the mechanical losses are reduced by the suppression of wire's vibration. Their special FRPs are a Dyneema® fiber reinforced plastic (DFRP), a Dyneema and glass fiber reinforced plastic (DGFRP), and a Zylon® fiber reinforced plastic (ZFRP). These materials have negative thermal expansion coefficient to the fiber direction, however, the amplitudes of thermal expansion are various by the quantity or quality of the fiber. In this paper, the values of thermal expansion were actually measured, and it was discussed about the influence on the mechanical losses. At the experimental results, the mechanical loss was small, so that the thermal strain to the circumferential direction on the coil was large. Moreover, in case of the coils with sufficiently strong winding tensions at coil-operating temperature, the mechanical losses vanished.

  14. Technique for reduction of mechanical losses in AC superconducting coils due to thermal expansion properties of various FRP bobbins

    Energy Technology Data Exchange (ETDEWEB)

    Sekine, N. [Tsukamoto Laboratory, Faculty of Engineering, Yokohama National University, 79-5, Tokiwadai, Hodogaya-ku, Yokohama 240-8501 (Japan)]. E-mail: n-sekine@tsukalab.dnj.ynu.ac.jp; Tada, S. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Higuchi, T. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Furumura, Y. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Takao, T. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Yamanaka, A. [Research Center, Toyobo, Co., Ltd, 2-1-1, Katata, Otsu, Shiga 520-0292 (Japan)

    2005-10-01

    We reported about reduction of mechanical losses in AC superconducting coils. The method is the use of FRP bobbins fabricated with special fibers. Since their FRPs have negative thermal expansion coefficient to the fiber direction, the FRP bobbins expand to the circumferential direction during cooling down. In case of the superconducting coils with such FRP bobbins, the winding tensions do not decrease during cooling down. Therefore, the mechanical losses are reduced by the suppression of wire's vibration. Their special FRPs are a Dyneema[reg] fiber reinforced plastic (DFRP), a Dyneema and glass fiber reinforced plastic (DGFRP), and a Zylon[reg] fiber reinforced plastic (ZFRP). These materials have negative thermal expansion coefficient to the fiber direction, however, the amplitudes of thermal expansion are various by the quantity or quality of the fiber. In this paper, the values of thermal expansion were actually measured, and it was discussed about the influence on the mechanical losses. At the experimental results, the mechanical loss was small, so that the thermal strain to the circumferential direction on the coil was large. Moreover, in case of the coils with sufficiently strong winding tensions at coil-operating temperature, the mechanical losses vanished.

  15. Anisotropic Thermal Expansion of Zirconium Diboride: An Energy-Dispersive X-Ray Diffraction Study

    Directory of Open Access Journals (Sweden)

    William A. Paxton

    2016-01-01

    Full Text Available Zirconium diboride (ZrB2 is an attractive material due to its thermal and electrical properties. In recent years, ZrB2 has been investigated as a superior replacement for sapphire when used as a substrate for gallium nitride devices. Like sapphire, ZrB2 has an anisotropic hexagonal structure which defines its directionally dependent properties. However, the anisotropic behavior of ZrB2 is not well understood. In this paper, we use energy-dispersive synchrotron X-ray diffraction to measure the thermal expansion of polycrystalline ZrB2 powder from 300 to 1150 K. Nine Bragg reflections are fit using Pseudo-Voigt peak profiles and used to compute the a and c lattice parameters using a nonlinear least-squares approximation. The temperature-dependent instantaneous thermal expansion coefficients are determined for each a-axis and c-axis direction and are described by the following equations: αa = (4.1507×10-6 + 5.1086 × 10-9(T-293.15/(1+4.1507 × 10-6(T-293.15 + 2.5543×10-9(T-293.152 and αc = (4.5374×10-6 + 4.3004×10-9(T-293.15/(1+4.5374×10-6(T-293.15 + 2.1502×10-9(T-293.152. Our results are within range of previously reported values but describe the temperature anisotropy in more detail. We show that anisotropic expansion coefficients converge to the same value at about 780 K and diverge at higher temperatures. Results are compared with other reported values.

  16. Hygroscopic expansion of aesthetic restorative materials: one-year report.

    Science.gov (United States)

    Emamieh, S; Ghasemi, A; Torabzadeh, H

    2011-01-01

    To measure the long-term linear hygroscopic expansion (LHE) of several materials using bulked and layered techniques. Seven materials were used; Fuji Cap II, Fuji II LC, Photac-Fil Aplicap, Vitremer, Dyract, Tetric and Z100. Ten specimens (6×4 mm) were made for each material using layered and bulked techniques (each group comprises five specimens). The specimens were stored in distilled water at 37°C. The length of each specimen was measured immediately after preparation, 24 hours, one week, one month, three months, six months, nine months and one year. This was used to calculate the percentage change in the length of materials. The mean LHE and standard deviation were calculated. Repeated measure analysis and paired sample t-test were used. The type of material and time had a significant effect on LHE. Fuji Cap II and Fuji II LC exhibited no significant changes after one-year and one month, respectively. However, layered specimens of Photac-Fil Aplicap and Tetric showed constant expansion until six month, whereas bulked specimens reached the constant length at three months. Constant expansion was obtained for layered and bulked specimens of Dyract and Z100 at six month. Layered specimens of Vitremer showed no significant differences except between 24 hours and one year measurements. But in bulked specimens, the results at nine months and one year were significantly different from those obtained at three months and before. Fuji II showed no significant LHE and resin-modified glass ionomer cements (RMGICs) exhibited the highest LHE. Dyract maintained an intermediate LHE in comparison with RMGIC and composite resin.

  17. Thermal-vacuum effects on polymer matrix composite materials

    Science.gov (United States)

    Tennyson, R. C.; Mabson, G. E.

    1991-01-01

    Results are presented on the thermal-vacuum response of a variety of fiber reinforced polymers matrix composites that comprised the UTIAS experiment on the LDEF satellite. Theoretical temperature-time predictions for this experiment are in excellent agreement with test data. Results also show quite clearly the effect of outgassing in the dimensional changes of these materials and the corresponding coefficients of thermal expansion. Finally, comparison with ground-based simulation tests are presented as well. Use of these data for design purposes are also given.

  18. Phase change material thermal capacitor clothing

    Science.gov (United States)

    Buckley, Theresa M. (Inventor)

    2005-01-01

    An apparatus and method for metabolic cooling and insulation of a user in a cold environment. In its preferred embodiment the apparatus is a highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The apparatus can be made to heat or cool the body or to act as a thermal buffer to protect the wearer from changing environmental conditions. The apparatus may also include an external thermal insulation layer and/or an internal thermal control layer to regulate the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the apparatus also provide 1) a path for evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) heat conductive pathways within the material for thermal equalization, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for quickly regenerating the thermal storage capacity for reuse of the material. Applications of the composite materials are also described which take advantage of the composite's thermal characteristics. The examples described include a diver's wet suit, ski boot liners, thermal socks, gloves and a face mask for cold weather activities, and a metabolic heating or cooling blanket useful for treating hypothermia or fever patients in a medical setting and therapeutic heating or cooling orthopedic joint supports.

  19. Switching Between Giant Positive and Negative Thermal Expansions of a YFe(CN)6 -based Prussian Blue Analogue Induced by Guest Species.

    Science.gov (United States)

    Gao, Qilong; Chen, Jun; Sun, Qiang; Chang, Dahu; Huang, Qingzhen; Wu, Hui; Sanson, Andrea; Milazzo, Ruggero; Zhu, He; Li, Qiang; Liu, Zhanning; Deng, Jinxia; Xing, Xianran

    2017-07-24

    The control of thermal expansion of solid compounds is intriguing but remains challenging. The effect of guests on the thermal expansion of open-framework structures was investigated. Notably, the presence of guest ions (K(+) ) and molecules (H2 O) can substantially switch thermal expansion of YFe(CN)6 from negative (αv =-33.67×10(-6)  K(-1) ) to positive (αv =+42.72×10(-6)  K(-1) )-a range that covers the thermal expansion of most inorganic compounds. The mechanism of such substantial thermal expansion switching is revealed by joint studies with synchrotron X-ray diffraction, X-ray absorption fine structure, neutron powder diffraction, and density functional theory calculations. The presence of guest ions or molecules plays a critical damping effect on transverse vibrations, thus inhibiting negative thermal expansion. An effective method is demonstrated to control the thermal expansion in open-framework materials by adjusting the presence of guests. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Lattice thermal expansion and anisotropic displacements in 𝜶-sulfur from diffraction experiments and first-principles theory

    Science.gov (United States)

    George, Janine; Deringer, Volker L.; Wang, Ai; Müller, Paul; Englert, Ulli; Dronskowski, Richard

    2016-12-01

    Thermal properties of solid-state materials are a fundamental topic of study with important practical implications. For example, anisotropic displacement parameters (ADPs) are routinely used in physics, chemistry, and crystallography to quantify the thermal motion of atoms in crystals. ADPs are commonly derived from diffraction experiments, but recent developments have also enabled their first-principles prediction using periodic density-functional theory (DFT). Here, we combine experiments and dispersion-corrected DFT to quantify lattice thermal expansion and ADPs in crystalline α-sulfur (S8), a prototypical elemental solid that is controlled by the interplay of covalent and van der Waals interactions. We begin by reporting on single-crystal and powder X-ray diffraction measurements that provide new and improved reference data from 10 K up to room temperature. We then use several popular dispersion-corrected DFT methods to predict vibrational and thermal properties of α-sulfur, including the anisotropic lattice thermal expansion. Hereafter, ADPs are derived in the commonly used harmonic approximation (in the computed zero-Kelvin structure) and also in the quasi-harmonic approximation (QHA) which takes the predicted lattice thermal expansion into account. At the PPBE+D3(BJ) level, the QHA leads to excellent agreement with experiments. Finally, more general implications of this study for theory and experiment are discussed.

  1. Effect of Microstructure Scale on Negative Thermal Expansion of Antiperovskite Manganese Nitride

    National Research Council Canada - National Science Library

    Zhonghua Sun Xiaoyan Song

    The negative thermal expansion (NTE) properties of the antiperovskite manganese nitrides with micron-scale, submicron-scale and nanometer-scale microstructures, respectively, were investigated using...

  2. Absolute thermal expansion of copper and aluminum between 5 K and 330 K

    Energy Technology Data Exchange (ETDEWEB)

    Kroeger, F.R. Jr.

    1976-02-01

    Theoretical and experimental results of experiments on thermal expansion of Al and Cu are presented. Experimental apparatus and procedures are described. Results are presented in graphs and plots and discussed. (JRD)

  3. Hygroscopic Expansion of Aesthetic Restorative Materials: One-Year Report

    Directory of Open Access Journals (Sweden)

    S. Emamieh

    2011-03-01

    Full Text Available Objective: To measure the long-term linear hygroscopic expansion (LHE of several materials using bulked and layered techniques.Materials and Methods: Seven materials were used; Fuji Cap II, Fuji II LC, Photac-Fil Aplicap, Vitremer, Dyract, Tetric and Z100. Ten specimens (6×4 mm were made for each material using layered and bulked techniques (each group comprises five specimens. The specimens were stored in distilled water at 37°C. The length of each specimen was measured immediately after preparation, 24 hours, one week, one month, three months, six months, nine months and one year. This was used to calculate the percentage change in the length of materials. The mean LHE and standard deviation were calculated. Repeated measure analysis and paired sample t-test were used.Results: The type of material and time had a significant effect on LHE. Fuji Cap II and Fuji II LC exhibited no significant changes after one-year and one month, respectively.However, layered specimens of Photac-Fil Aplicap and Tetric showed constant expansionuntil six month, whereas bulked specimens reached the constant length at three months.Constant expansion was obtained for layered and bulked specimens of Dyract and Z100 at six month. Layered specimens of Vitremer showed no significant differences except between 24 hours and one year measurements. But in bulked specimens, the results at ninemonths and one year were significantly different from those obtained at three months and before.Conclusion: Fuji II showed no significant LHE and resin-modified glass ionomer cements (RMGICs exhibited the highest LHE. Dyract maintained an intermediate LHE in comparison with RMGIC and composite resin.

  4. First-Principles Mode Gruneisen Parameters and Negative Thermal Expansion in α-ZrW2O8

    Science.gov (United States)

    Gava, V.; Martinotto, A. L.; Perottoni, C. A.

    2012-11-01

    Mode Grüneisen parameters were estimated for α-ZrW2O8 zone-center modes by means of density functional theory calculations and the temperature dependence of the coefficient of thermal expansion was obtained according to the Debye-Einstein model of the quasiharmonic approximation. The lowest energy optic modes were identified at 45 and 46cm-1, and were shown to be the main modes responsible for negative thermal expansion at low temperature. Experimental evidence of the lowest energy, triply degenerated infrared active optic mode, was also found in the far infrared spectrum of α-ZrW2O8. Upon increasing temperature, other optic modes with E<25meV (particularly at 96, 100, 133, 161, and 164cm-1) also contribute significantly to the coefficient of thermal expansion near room temperature. An analysis was made of selected zone-center modes in light of previously proposed models for explaining negative thermal expansion in open framework materials.

  5. Thermal Expansion and Diffusion Coefficients of Carbon Nanotube-Polymer Composites

    OpenAIRE

    Wei, Chenyu; Srivastava, Deepak; Cho, Kyeongjae

    2002-01-01

    Classical molecular dynamics (MD) simulations employing Brenner potential for intra-nanotube interactions and Van der Waals forces for polymer-nanotube interfaces are used to invetigate the thermal expansion and diffusion characteristics of carbon nanotube-polyethylene composites. Additions of carbon nanotubes to polymer matrix are found to increase the glass transition temperature Tg, and thermal expansion and diffusion coefficients in the composite above Tg. These findings could have implic...

  6. Effect of graphene nanoplatelets on coefficient of thermal expansion of polyetherimide composite

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huang, E-mail: huang.wu.84@gmail.com [Composite Materials and Structures Center, Michigan State University, East Lansing, MI 48864 (United States); Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI 48864 (United States); Drzal, Lawrence T. [Composite Materials and Structures Center, Michigan State University, East Lansing, MI 48864 (United States); Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI 48864 (United States)

    2014-07-01

    Thermal expansion is one of the major concerns for polymer composites. In this research, graphene nanoplatelets (GNPs) were added to polyetherimide (PEId) thermoplastic polymer in order to reduce the coefficient of thermal expansion (CTE) of the injection molded composite. First, the coefficient of linear thermal expansion (LTE) was measured in three directions in the anisotropic coupon: 0°, 90° and the out of plane Z direction. It is found that the GNP particles are very effective in terms of reducing the LTE in 0° direction due to high degree of alignment. After annealing above glass transition temperature, significant increase of 0° LTE and decrease of Z° LTE were observed. The bulk CTE was calculated by adding up the LTEs in all three directions and is found to be independent of annealing. Second, several models were applied to predict both CTE and LTE. It is found that Schapery's lower limit model fits the experimental CTE very well. Chow's model was applied for LTEs in three directions. The behavior of GNP-5/PEId composites is explained by the combination of Chow's model and morphology obtained by scanning electron microscope (SEM). - Highlights: • Coefficient of thermal expansion (CTE) of polymer composite is characterized. • Reduction of linear thermal expansion depends on filler orientation. • Filler orientation is characterized based on the location of the specimen. • Filler orientation is changed by annealing, causing subsequent change in CTE. • CTE and linear thermal expansion coefficient are modeled.

  7. Composite Laminate With Coefficient of Thermal Expansion Matching D263 Glass

    Science.gov (United States)

    Robinson, David; Rodini, Benjamin

    2012-01-01

    The International X-ray Observatory project seeks to make an X-ray telescope assembly with 14,000 flexible glass segments. The glass used is commercially available SCHOTT D263 glass. Thermal expansion causes the mirror to distort out of alignment. A housing material is needed that has a matching coefficient of thermal expansion (CTE) so that when temperatures change in the X-ray mirror assembly, the glass and housing pieces expand equally, thus reducing or eliminating distortion. Desirable characteristics of this material include a high stiffness/weight ratio, and low density. Some metal alloys show promise in matching the CTE of D263 glass, but their density is high compared to aluminum, and their stiffness/weight ratio is not favorable. A laminate made from carbon fiber reinforced plastic (CFRP) should provide more favorable characteristics, but there has not been any made with the CTE matching D263 Glass. It is common to create CFRP laminates of various CTEs by stacking layers of prepreg material at various angles. However, the CTE of D263 glass is 6.3 ppm/ C at 20 C, which is quite high, and actually unachievable solely with carbon fiber and resin. A composite laminate has been developed that has a coefficient of thermal expansion identical to that of SCHOTT D263 glass. The laminate is made of a combination of T300 carbon fiber, Eglass, and RS3C resin. The laminate has 50% uni-T300 plies and 50% uni-E-glass plies, with each fiber-layer type laid up in a quasi-isotropic laminate for a total of 16 plies. The fiber volume (percent of fiber compared to the resin) controls the CTE to a great extent. Tests have confirmed that a fiber volume around 48% gives a CTE of 6.3 ppm/ C. This is a fairly simple composite laminate, following well established industry procedures. The unique feature of this laminate is a somewhat unusual combination of carbon fiber with E-glass (fiberglass). The advantage is that the resulting CTE comes out to 6.3 ppm/ C at 20 C, which matches D

  8. Effects of Deep Cryogenic Treatment on Wear Mechanisms and Microthermal Expansion for the Material of Drive Elements

    Directory of Open Access Journals (Sweden)

    Yuh-Ping Chang

    2013-01-01

    Full Text Available By the composite heat treatments, the strength and the surface hardness of the materials of drive elements can be improved. Moreover, the high accurate and capable machines can be obtained. For the numerous composite heat treatments, the deep cryogenic treatment has been used widely for the purpose of low thermal expansion in the industry. Therefore, this paper is further to investigate the low friction, wear resistance, and low thermal expansion for the carburizing steels of drive elements with deep cryogenic treatment. According to the experimental results, martensitic transformation occurred after the deep cryogenic treatment. The effects of deep cryogenic treatment on wear mechanisms are significant. The shape of wear particles changes from slip tongue to smooth stratification. Moreover, the surface magnetization is smaller for the case of Carburizing-Deep cryogenic treatment. Hence, the wear mechanism becomes simple. Besides, the thermal expansion is significantly smaller for the case of Carburizing-Deep cryogenic treatment.

  9. A study of the coefficient of thermal expansion of nuclear graphites

    Energy Technology Data Exchange (ETDEWEB)

    Hacker, P.J

    2001-02-01

    This thesis presents the results of a study of the Coefficient of Thermal Expansion (CTE) of two grades of nuclear graphite that are used as the moderator in the Magnox and Advanced Gas-Cooled reactors operated in the UK. This work has two main aims, the first is to characterise those elements of the graphite microstructure that control CTE within these materials and to relate these to the effects induced within the reactor. The second is to develop a microstructural model, of general applicability, that can initially be applied to model the CTE changes within the graphites under reactor conditions (neutron irradiation and radiolytic oxidation). These aims have been met by study in three interlinked areas, theoretical, experimental and modelling. Previous to this study, a loose assembly of single crystals together with changes in small scale nanometric porosity (Mrozowski cracks) were used to describe CTE behaviour of nuclear graphite both as-received and under reactor conditions. Within the experimental part of this thesis the graphite nanostructure was studied using, primarily, Transmission Electron Microscopy (TEM). This work concluded that structure on this scale was complex and that the loose assembly of single crystals was a poor microstructural approximation for modelling the CTE of these materials. Other experimental programmes measured the CTE of highly oxidised samples and simulated the effects of irradiation. The former discovered that CTE remained largely unaffected to high weight losses. This insensitivity was explained by ''The Continuous Network Hypothesis'' that was also related to classical percolation theory. The final part of the thesis modelled an abstraction of the key microstructural features identified in the previous parts of the thesis. This approach has been applied to AGR moderator graphite where it has successfully modelled the thermal expansion behaviour of the as-received, irradiated and oxidised material. (author)

  10. Effect of prolonged thermal cycling on microleakage around Class V cavities restored with glass-ceramic inserts with different coefficients of thermal expansion: an in vitro study.

    Science.gov (United States)

    Santini, Ario; Ivanovic, Vladimir; Tan, Chuei Luan; Ibbetson, Richard

    2006-10-01

    Tetric Ceram (P<0.05). Comparisons between non-thermal cycled and thermal cycled groups showed there was no significant difference with the Cerana inserts (P=0.5590). The results indicate that, after thermal cycling, restorations restored with Cerana glass-ceramic inserts, which have a coefficient of thermal expansion approximating to that of enamel, show a decrease in marginal microleakage, compared with Beta-Quartz glass-ceramic inserts and Tetric Ceram resin-based composite material. Restorative materials, which have a coefficient of thermal expansion approximating to that of enamel, would seem to be the materials of choice in reducing the problem of marginal microleakege.

  11. Carbon fiber-reinforced cyanate ester/nano-ZrW2O8 composites with tailored thermal expansion.

    Science.gov (United States)

    Badrinarayanan, Prashanth; Rogalski, Mark K; Kessler, Michael R

    2012-02-01

    Fiber-reinforced composites are widely used in the design and fabrication of a variety of high performance aerospace components. The mismatch in coefficient of thermal expansion (CTE) between the high CTE polymer matrix and low CTE fiber reinforcements in such composite systems can lead to dimensional instability and deterioration of material lifetimes due to development of residual thermal stresses. The magnitude of thermally induced residual stresses in fiber-reinforced composite systems can be minimized by replacement of conventional polymer matrices with a low CTE, polymer nanocomposite matrix. Zirconium tungstate (ZrW(2)O(8)) is a unique ceramic material that exhibits isotropic negative thermal expansion and has excellent potential as a filler for development of low CTE polymer nanocomposites. In this paper, we report the fabrication and thermal characterization of novel, multiscale, macro-nano hybrid composite laminates comprising bisphenol E cyanate ester (BECy)/ZrW(2)O(8) nanocomposite matrices reinforced with unidirectional carbon fibers. The results reveal that incorporation of nanoparticles facilitates a reduction in CTE of the composite systems, which in turn results in a reduction in panel warpage and curvature after the cure because of mitigation of thermally induced residual stresses.

  12. Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates.

    Science.gov (United States)

    Krishnan, N M Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan; Pilon, Laurent; Bauchy, Mathieu; Sant, Gaurav

    2016-12-28

    Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C-S-H's nanostructure. We identify that confinement is dictated by the topology of the C-S-H's atomic network. Taken together, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.

  13. The Origin of Uni-axial Negative Thermal Expansion in a Layered Perovskite

    Science.gov (United States)

    Ablitt, Chris; Craddock, Sarah; Senn, Mark; Mostofi, Arash; Bristowe, Nicholas

    Using first-principles calculations within the quasi-harmonic approximation (QHA), we explain the origin of experimentally observed uni-axial negative thermal expansion (NTE) in a layered perovskite: the Ruddlesden-Popper (RP) oxide Ca2MnO4, which has anti-ferromagnetic ordering at low temperatures and is closely related to Ca3Mn2O7, which exhibits hybrid improper ferroelectricity and uni-axial NTE in competing phases. Dynamic tilts of MnO6 octahedra, common in many complex oxides, drive the expansion of the a axis and contraction of the c axis of the tetragonal NTE phase. We find that ferroelastic RP phases with a frozen octahedral rotation are unusually compliant to particular combinations of strains along different axes. The atomic mechanism responsible is characteristic of the perovskite/rock-salt interfaces present in the RP structure. We show that the contribution from this anisotropic elasticity must be taken into account in order to accurately predict NTE over the temperature range observed in experiment. A similar compliance to cooperative strains is found in other systems with uni-axial NTE. The development of this mechanistic understanding of NTE in complex oxides may pave the way for designing tunable multifunctional materials. The authors would like to acknowledge support from the EPSRC and the Centre for Doctoral Training in Theory and Simulation of Materials.

  14. An anisotropic linear thermo-viscoelastic constitutive law - Elastic relaxation and thermal expansion creep in the time domain

    Science.gov (United States)

    Pettermann, Heinz E.; DeSimone, Antonio

    2017-09-01

    A constitutive material law for linear thermo-viscoelasticity in the time domain is presented. The time-dependent relaxation formulation is given for full anisotropy, i.e., both the elastic and the viscous properties are anisotropic. Thereby, each element of the relaxation tensor is described by its own and independent Prony series expansion. Exceeding common viscoelasticity, time-dependent thermal expansion relaxation/creep is treated as inherent material behavior. The pertinent equations are derived and an incremental, implicit time integration scheme is presented. The developments are implemented into an implicit FEM software for orthotropic material symmetry under plane stress assumption. Even if this is a reduced problem, all essential features are present and allow for the entire verification and validation of the approach. Various simulations on isotropic and orthotropic problems are carried out to demonstrate the material behavior under investigation.

  15. Polyglutamine expansion in Drosophila: thermal stress and Hsp70 ...

    Indian Academy of Sciences (India)

    2007-03-15

    Mar 15, 2007 ... Repetitive DNA sequences that encode polyglutamine tracts are prone to expansion and cause highly deleterious phenotypes of neurodegeneration. Despite this tendency, polyglutamine tracts (``polyQs”) are conserved features of eukaryotic genomes. PolyQs are the most frequent protein-coding ...

  16. Vendor Capability for Low Thermal Expansion Mask Substrates for EUV Lithography

    Energy Technology Data Exchange (ETDEWEB)

    Blaedel, K L; Taylor, J S; Hector, S D; Yan, P Y; Ramamoorthy, A; Brooker, P D

    2002-04-12

    Development of manufacturing infrastructure is required to ensure a commercial source of mask substrates for the timely introduction of EUVL. Improvements to the low thermal expansion materials that compose the substrate have been made, but need to be scaled to production quantities. We have been evaluating three challenging substrate characteristics to determine the state of the infrastructure for the finishing of substrates. First, surface roughness is on track and little risk is associated with achieving the roughness requirement as an independent specification. Second, with new flatness-measuring equipment just coming on line, the vendors are poised for improvement toward the SEMI P37 flatness specification. Third, significant acceleration is needed in the reduction of defect levels on substrates. The lack of high-sensitivity defect metrology at the vendors' sites is limiting progress in developing substrates for EWL.

  17. Engineered high expansion glass-ceramics having near linear thermal strain and methods thereof

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Steve Xunhu; Rodriguez, Mark A.; Lyon, Nathanael L.

    2018-01-30

    The present invention relates to glass-ceramic compositions, as well as methods for forming such composition. In particular, the compositions include various polymorphs of silica that provide beneficial thermal expansion characteristics (e.g., a near linear thermal strain). Also described are methods of forming such compositions, as well as connectors including hermetic seals containing such compositions.

  18. Polymeric materials for solar thermal applications

    CERN Document Server

    Köhl, Michael; Papillon, Philippe; Wallner, Gernot M; Saile, Sandrin

    2012-01-01

    Bridging the gap between basic science and technological applications, this is the first book devoted to polymers for solar thermal applications.Clearly divided into three major parts, the contributions are written by experts on solar thermal applications and polymer scientists alike. The first part explains the fundamentals of solar thermal energy especially for representatives of the plastics industry and researchers. Part two then goes on to provide introductory information on polymeric materials and processing for solar thermal experts. The third part combines both of these fields, dis

  19. Luminescence Materials as Nanoparticle Thermal Sensors

    Science.gov (United States)

    2016-06-01

    6201 Fort Belvoir, VA 22060-6201 T E C H N IC A L R E P O R T DTRA-TR-16-71 Luminescence Materials as Nanoparticle Thermal Sensors ...10 12 joule (J) British thermal unit (Btu) (thermochemical) 1.054 350 × 10 3 joule (J) foot-pound-force (ft lbf) 1.355 818 joule (J) calorie...theoretical investigations on thermal history extraction III. Materials Testing TL in te ns ity Temperature (K) te m pe ra tu re time • nanophosphors

  20. Description of the RHIC p(perpendicular) spectra in a thermal model with expansion.

    Science.gov (United States)

    Broniowski, W; Florkowski, W

    2001-12-31

    The assumption of simultaneous chemical and thermal freeze-outs of the hadron gas leads to a surprisingly accurate, albeit entirely conventional, explanation of the recently measured RHIC p(perpendicular) spectra. The original thermal spectra are supplied with secondaries from cascade decays of all resonances, and subsequently folded with a suitably parametrized expansion involving longitudinal and transverse flow. The predictions of this thermal approach, with various parametrizations for the expansion, are in a striking quantitative agreement with the data in the whole available range of 0 < or = p(perpendicular) < or = 3.5 GeV.

  1. Evaluation of thermal insulation materials

    Science.gov (United States)

    Wilbers, O. J.; Conti, J. C.; Mcgee, J. V.; Mcpherson, J. I.

    1973-01-01

    Data was obtained on silicone-bonded fiberglass, isocyanurate foam, and two dozen other insulators. Materials were selected to withstand heat sterilization, outer space, and the Martian atmosphere. Significant environmental parameters were vibration, landing shock, and launch venting.

  2. Investigation of Thermal Expansion Properties of Single Walled Carbon Nanotubes by Raman Spectroscopy and Molecular Dynamics Simulation

    Science.gov (United States)

    Casimir, Daniel

    The mechanical properties of nano-sized materials seem to differ significantly from the predicted behavior of their bulk macroscopic counterparts (Smart, 2014, 16). The former tend to be stronger, more malleable and exhibit greater flexibility. The thermal properties of materials have also been shown to be altered significantly after having been shrunken to nanometer dimensions. The nano material that exhibits this peculiar behavior that is studied in this dissertation are single walled carbon nanotubes. Single walled carbon nanotubes are hollow cylindrical tubes that are one atomic layer in thickness and made up of sp2 hybridized carbon atoms. The majority of samples have diameters on the order 1 nm, with lengths ranging from 1 micron to sometimes a centimeter (Tomanek, 2008, v). The thermo-mechanical quantity that I specifically examine in this research is the linear and volume thermal expansion coefficients of SWCNTs. The mean linear thermal expansion coefficient is the ratio of the change in unit length in response to a 1 degree Celsius rise in temperature. The "true" value of this quantity is obtained in the theoretical limit of a vanishing temperature range DeltaT in the ratio stated above. However, this simply stated thermo-mechanical quantity for Carbon Nanotubes still remains a controversial topic, with widespread discrepancies among results of certain magnitudes - such as the temperature at the occurrence of maximum contraction, and at the transition from contraction to expansion. In conclusion, there is much incentive in examining the somewhat controversial variation in the behavior and quoted values of the thermal expansion of these quasi one-dimensional objects. In this study, I examine this important property of single walled carbon nanotubes using Resonant Raman Spectroscopy and Molecular Dynamics Simulation based on the Adaptive Intermolecular Reactive Empirical Bond Order potential. The latter is a well established potential that is well-suited to

  3. Origin of the colossal positive and negative thermal expansion in Ag{sub 3}[Co(CN){sub 6}]: an ab initio density functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Calleja, Mark [Cambridge eScience Centre, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Goodwin, Andrew L; Dove, Martin T [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom)], E-mail: mtd10@cam.ac.uk

    2008-06-25

    DFT calculations have been used to provide insights into the origin of the colossal positive and negative thermal expansion in Ag{sub 3}[Co(CN){sub 6}]. The results confirm that the positive expansion within the trigonal basal plane and the negative expansion in the orthogonal direction are coupled due to the existence of a network defined by nearly rigid bonds within the chains of Co-C-N-Ag-N-C-Co linkages. The origin of the colossal values of the coefficients of thermal expansion arise from an extremely shallow energy surface that allows a flexing of the structure with small energy cost. The thermal expansion can be achieved with a modest value of the overall Grueneisen parameter. The energy surface is so shallow that we need to incorporate a small empirical dispersive interaction to give ground-state lattice parameters that match experimental values at low temperature. We compare the results with DFT calculations on two isostructural systems: H{sub 3}[Co(CN){sub 6}], which is known to have much smaller values of the coefficients of thermal expansion, and Au{sub 3}[Co(CN){sub 6}], which has not yet been synthesized but which is predicted by our calculations to be another candidate material for showing colossal positive and negative thermal expansion.

  4. Structure and thermal stability of nanocrystalline materials

    Indian Academy of Sciences (India)

    In addition, study of the thermal stability of nanocrystalline materials against significant grain growth is both scientific and technological interest. A sharp increase in grain size (to micron levels) during consolidation of nanocrystalline powders to obtain fully dense materials may consequently result in the loss of some unique ...

  5. Crystal structure, electrical conductivity and thermal expansion of Ni and Nb co-doped LaCoO3.

    Science.gov (United States)

    Øygarden, Vegar; Grande, Tor

    2013-02-28

    The effect of co-doping LaCoO(3) with Ni and Nb has been investigated in the two solid solution series (1 - x)LaCoO(3)-xLaNi(2/3)Nb(1/3)O(3) and (1 - y)LaCo(2/3)Ni(1/3)O(3)-yLaNi(2/3)Nb(1/3)O(3). The materials were shown to be stoichiometric with respect to oxygen. The compositional effect on the evolution of the crystal structure, thermal expansion and electrical conductivity is reported. The chemical stability of LaCoO(3) in a reducing atmosphere was improved and the thermal expansion was suppressed at higher levels of Nb-substitution. The materials with mixed oxidation states on the B-site possessed superior electrical transport properties compared to solid solutions with cations in mainly isovalent oxidation states. The evolution of the electronic conductivity, thermal expansion and crystal structural is discussed with emphasis on the oxidation states of Ni and Co, and the spin transitions of Co.

  6. Negative thermal expansion in cubic ZrMo2 O8 : Inelastic neutron scattering and lattice dynamical studies

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Schober, H.; Kolesnikov, A. I.; Loong, C.-K.; Lind, C.; Wilkinson, A. P.

    2004-12-01

    Disordered cubic ZrMo2O8(Pa3¯,Z=4) is known to display isotropic negative thermal expansion (NTE) below 600 K. We report high-pressure inelastic neutron scattering experiments up to 2.5 kbar in this material using the IN6 spectrometer at Institut Laue-Langevin. The observed phonon softening of about 0.1-0.3 meV for phonons below 8 meV is able to account for the NTE below 100 K. The phonon spectrum in the entire energy range up to 150 meV has been measured using the HRMECS spectrometer at Argonne National Laboratory. The ordered phase (space group P213 ) of cubic ZrMo2O8 has not yet been synthesized. However, we have calculated the phonon spectrum and thermal expansion in this phase for comparison with the known ordered phase of cubic ZrW2O8 .

  7. Effect of particle size on the thermal expansion of nanostructured lead sulfide films

    Energy Technology Data Exchange (ETDEWEB)

    Sadovnikov, S.I.; Gusev, A.I., E-mail: gusev@ihim.uran.ru

    2014-10-15

    Highlights: • PbS nanofilms prepared by chemical deposition have a D0{sub 3}-type crystal structure. • Thermal expansion coefficient α of PbS nanofilm is twice as large as that of bulk PbS. • Large difference in the coefficients α is due to the small particle size in PbS film. • Small size of particles in PbS film increases the anharmonicity of atomic vibrations. - Abstract: The effect of particle size on the thermal expansion of nanostructured lead sulfide films produced by hydrochemical deposition has been studied. The coherent scattering region size and thermal expansion coefficients of PbS nanofilm have been measured depending on the annealing temperature in the interval 293–473 K and on the duration of annealing at a constant temperature of 423 K. It is found that the thermal expansion coefficient α of nanostructured PbS film is nearly twice as large as that of bulk lead sulfide. It is shown that the observed large difference in the coefficients α is due to the small size of PbS particles in the film that leads to the change of the phonon spectrum boundaries and to the growth of anharmonicity of atomic vibrations. The additional contribution to the thermal expansion coefficient caused by the small particle size in PbS nanofilm is estimated theoretically.

  8. Pressure-dependence of the phase transitions and thermal expansion in zirconium and hafnium pyrovanadate

    Energy Technology Data Exchange (ETDEWEB)

    Gallington, Leighanne C.; Hester, Brett R.; Kaplan, Benjamin S.; Wilkinson, Angus P. (GIT)

    2017-05-01

    Low or negative thermal expansion (NTE) has been previously observed in members of the ZrP2O7 family at temperatures higher than their order-disorder phase transitions. The thermoelastic properties and phase behavior of the low temperature superstructure and high temperature negative thermal expansion phases of ZrV2O7 and HfV2O7 were explored via in situ variable temperature/pressure powder x-ray diffraction measurements. The phase transition temperatures of ZrV2O7 and HfV2O7 exhibited a very strong dependence on pressure (~700 K GPa), with moderate compression suppressing the formation of their NTE phases below 513 K. Compression also reduced the magnitude of the coefficients of thermal expansion in both the positive and negative thermal expansion phases. Additionally, the high temperature NTE phase of ZrV2O7 was found to be twice as stiff as the low temperature positive thermal expansion superstructure (24 and 12 GPa respectively).

  9. Sprayable Phase Change Coating Thermal Protection Material

    Science.gov (United States)

    Richardson, Rod W.; Hayes, Paul W.; Kaul, Raj

    2005-01-01

    NASA has expressed a need for reusable, environmentally friendly, phase change coating that is capable of withstanding the heat loads that have historically required an ablative thermal insulation. The Space Shuttle Program currently relies on ablative materials for thermal protection. The problem with an ablative insulation is that, by design, the material ablates away, in fulfilling its function of cooling the underlying substrate, thus preventing the insulation from being reused from flight to flight. The present generation of environmentally friendly, sprayable, ablative thermal insulation (MCC-l); currently use on the Space Shuttle SRBs, is very close to being a reusable insulation system. In actual flight conditions, as confirmed by the post-flight inspections of the SRBs, very little of the material ablates. Multi-flight thermal insulation use has not been qualified for the Space Shuttle. The gap that would have to be overcome in order to implement a reusable Phase Change Coating (PCC) is not unmanageable. PCC could be applied robotically with a spray process utilizing phase change material as filler to yield material of even higher strength and reliability as compared to MCC-1. The PCC filled coatings have also demonstrated potential as cryogenic thermal coatings. In experimental thermal tests, a thin application of PCC has provided the same thermal protection as a much thicker and heavier application of a traditional ablative thermal insulation. In addition, tests have shown that the structural integrity of the coating has been maintained and phase change performance after several aero-thermal cycles was not affected. Experimental tests have also shown that, unlike traditional ablative thermal insulations, PCC would not require an environmental seal coat, which has historically been required to prevent moisture absorption by the thermal insulation, prevent environmental degradation, and to improve the optical and aerodynamic properties. In order to reduce

  10. Transient evolution of inter vessel gap pressure due to relative thermal expansion between two vessels

    Science.gov (United States)

    Natesan, K.; Selvaraj, P.; Chellapandi, P.; Chetal, S. C.

    2002-08-01

    In a typical liquid metal cooled fast breeder reactor (LMFBR), a cylindrical sodium filled main vessel, which carries the internals such as reactor core, pumps, intermediate heat exchangers etc. is surrounded by another vessel called safety vessel. The inter vessel gap is filled with nitrogen. During a thermal transient in the pool sodium, because of the relative delay involved in the thermal diffusion between MV and SV, they are subjected to relative thermal expansion or contraction between them. This in turn results in pressurisation and depressurisation of inter vessel gap nitrogen respectively. In order to obtain the external pressurization for the buckling design of MV, transient thermal models for obtaining the evolutions of MV, SV and inter gap nitrogen temperatures and hence their relative thermal expansion and inter vessel gap pressure have been developed. This paper gives the details of the mathematical model, assumptions made in the calculation and the results of the analysis.

  11. Pressure-induced amorphization and negative thermal expansion in ZrW2O8

    Science.gov (United States)

    Perottoni; Jornada

    1998-05-08

    It has recently been shown that zirconium tungstate (ZrW2O8) exhibits isotropic negative thermal expansion over its entire temperature range of stability. This rather unusual behavior makes this compound particularly suitable for testing model predictions of a connection between negative thermal expansion and pressure-induced amorphization. High-pressure x-ray diffraction and Raman scattering experiments showed that ZrW2O8 becomes progressively amorphous from 1.5 to 3.5 gigapascals. The amorphous phase was retained after pressure release, but the original crystalline phase returned after annealing at 923 kelvin. The results indicate a general trend between negative thermal expansion and pressure-induced amorphization in highly flexible framework structures.

  12. Anisotropic thermal expansion of Ni, Pd and Pt germanides and silicides

    Science.gov (United States)

    Geenen, F. A.; Knaepen, W.; Moens, F.; Brondeel, L.; Leenaers, A.; Van den Berghe, S.; Detavernier, C.

    2016-07-01

    Silicon or germanium-based transistors are nowadays used in direct contact with silicide or germanide crystalline alloys for semiconductor device applications. Since these compounds are formed at elevated temperatures, accurate knowledge of the thermal expansion of both substrate and the contact is important to address temperature depending effects such as thermal stress. Here we report the linear coefficients of thermal expansion of Ni-, Pd- and Pt-based mono-germanides, mono-silicides and di-metal-silicides as determined by powder-based x-ray diffraction between 300 and 1225 K. The investigated mono-metallic compounds, all sharing the MnP crystal structure, as well as Pd2Si and Pt2Si exhibit anisotropic expansion. By consequence, this anisotropic behaviour should be taken into account for evaluating the crystal unit’s cell at elevated temperatures.

  13. Application of double modulation for measurement of the thermal expansion coefficient of liquid metals

    Energy Technology Data Exchange (ETDEWEB)

    Blagonravov, L A; Karchevskiy, O O; Ivannikov, P V; Soboleva, A V [M. V. Lomonosov Moscow State University, Faculty of Physics, Lenin Hills, 1-2, GSP-2, Moscow, 119991 (Russian Federation)], E-mail: blagonravovla@mail.ru

    2008-02-15

    The first results of the thermal expansion coefficient measurement obtained for liquid conductors using a new modulation method are presented. The method is based on a superposition of two periodical influences on a liquid metal. The thermal expansion coefficient {alpha}{sub P} is determined by means of measuring the amplitudes of oscillations of electric current power w{sub {approx}} and pressure p{sub {approx}}. In the present work the K-Na alloy of the eutectic composition was used as a sample. Distinction of the experimental data obtained by authors from the literature data is 30 to 40%. Such a difference is in the range of error of determination of {alpha}{sub P} from the density data of K-Na alloy. The method allows direct determination of the thermal expansion coefficient of liquid conductors in absolute units.

  14. Tribological Studies of Dynamic Thermal Seal Materials

    Science.gov (United States)

    DeMange, Jeffrey J.; Taylor, Shawn C.

    2016-01-01

    Thermal seals are required on high-speed vehicles in many dynamic applications such as variable inlets in propulsion systems and control surfaces. These seals, often referred to as dynamic thermal seals, must not only mitigate inboard heat transfer, but must also exhibit sufficient durability when scrubbed against mating surfaces. For high-temperature high-speed vehicle applications, the mating surfaces are often made from thermal protection system (TPS) materials, which are typically rougher and more abrasive than TPS materials used at lower temperatures. The high-temperature TPS materials used can include non-ablative (e.g., lightweight porous oxides, ceramic matrix composites) andor ablative systems (e.g., phenolic systems). Due to the increased need for durable high-temperature dynamic seals, researchers working with the NASA Glenn Research Center embarked on an effort to (a) characterize the tribological performance of state-of-the-art thermal seal materials against a variety of TPS materials and (b) develop approaches for improved wear resistance. Tests were conducted using a recently upgraded high-temperature tribometer to assess wear resistance for a variety of tribopairs under multiple conditions. This data will begin to frame the challenges of using these materials and eventually permit an improved ability to design and implement these critical TPS components.

  15. Stopping, heating, thermalization and expansion at SPS energies

    CERN Document Server

    Gaardhoje, J J

    1997-01-01

    The Pb beam at 158AGeV from the CERN SPS accelerator which was taken into use in the fall of 1994 has opened a new dimension in the study of highly excited nuclear matter in heavy ion reactions. It has now become possible to form reasonably large volumes (containing more than 300 nucleons) in central collisions between heavy ions, with energy and matter densities in some parts of the volume exceeding those expected for the phase transition from hadronic matter to deconfined quark and gluon matter. In this talk we discuss some features of the expansion of the hot and compressed system that may be learned by analysing the single particle spectra of baryons and mesons with emphasis on data from the NA44 experiment.

  16. Dynamic thermal expansivity of liquids near the glass transition

    DEFF Research Database (Denmark)

    Niss, Kristine; Gundermann, Ditte; Christensen, Tage Emil

    2012-01-01

    ) in the ultraviscous regime. Compared to the method of Bauer et al., the dynamical range has been extended by making time-domain experiments and by making very small and fast temperature steps. The modeling of the experiment presented in this paper includes the situation in which the capacitor is not full because......Based on previous works on polymers by Bauer et al. [ Phys. Rev. E 61 1755 (2000)], this paper describes a capacitative method for measuring the dynamical expansion coefficient of a viscous liquid. Data are presented for the glass-forming liquid tetramethyl tetraphenyl trisiloxane (DC704...... the liquid contracts when cooling from room temperature down to around the glass-transition temperature, which is relevant when measuring on a molecular liquid rather than a polymer....

  17. COMPACT ATHERMAL OPTICAL WAVEGUIDE USING THERMAL EXPANSION AMPLIFICATION

    DEFF Research Database (Denmark)

    2001-01-01

    ; said negative expanding fixture comprising one or two V-shaped displacement amplifiers made from a material with a higher positive CTE mounted in a frame made of a material with lower positive CTE; the V-shaped displacement amplifier is mounted on a support in such a manner that its motion...

  18. The effect of interphase on residual thermal stresses. 2. Unidirectional fiber composite materials

    Science.gov (United States)

    Kushnevsky, V.; Bledzki, A. K.

    1997-03-01

    In real composite materials an additional phase may exist between the fiber and the matrix. This phase, commonly known as the interphase, is a local region that results from the matrix bonds with the fiber surface or the fiber sizing. The differing thermal expansions or contractions of the fiber and matrix cause thermally induced stresses in composite materials. In the present study, a four-cylinder model is proposed for the determination of residual thermal stresses in unidirectional composite materials. The elastic modulus of the interphase is a function of the interphase radius and thickness. The governing equations in terms of displacements are solved in the form of expansion into a series [1]. The effective elastic characteristics are obtained using the finite element approach. The effect of the interphase thickness and different distributions of the interphase Young's modulus on the thermal residual stress field in unidirectional composite materials is investigated.

  19. Coprecipitation synthesis and negative thermal expansion of NbVO5.

    Science.gov (United States)

    Wang, Jinrui; Deng, Jinxia; Yu, Ranbo; Chen, Jun; Xing, Xianran

    2011-04-07

    We develop a coprecipitation synthesis route to prepare NbVO(5) with simple oxide Nb(2)O(5) and NH(4)VO(3) as starting materials. No metal alkoxide or organometallic substance was used in the process. Nano-crystal NbVO(5) was obtained by calcination of the coprecipitates at 550 °C for 2 h. DSC/TG and XRD investigations indicate that the target compound NbVO(5) is completely formed up to 504.5 °C and is thermally stable below 658 °C. Rietveld XRD refinements give an orthorhombic structure with space group Pnma and lattice parameters, a=11.8453(2), b=5.5126(3) and c=6.9212(2) Å, respectively. In particular, HTXRD determinations show a negative thermal expansion in NbVO(5) with a TEC of -6.63 × 10(-6) °C(-1) in the temperature range of RT-600 °C. This fact is ascribed to the tilting of NbO(6) octahedra and VO(4) tetrahedra in the flexible framework structure. The present synthesis route is facile and easy to be extended to prepare analogues such as TaVO(5), etc. © The Royal Society of Chemistry 2011

  20. About Utilization Efficiency Evaluation of Gas-Expansion and Generator Units at Thermal Power Stations

    Directory of Open Access Journals (Sweden)

    S. A. Kachan

    2007-01-01

    Full Text Available The paper considers methods for determination of gas-expansion and generator unit indices when they are applied at a thermal power station. It is shown, that while relating the effect of additional power-and-heat generation output due to heat taking-off from steam turbines to gas-expansion and generator unit to the operation of this unit a specific fuel consumption of power supply from gas-expansion and generator unit can be lower than fuel equivalent of kilowatt-hour.

  1. Anomalous thermal expansion of InSe layered semiconductors in the low-temperature region

    Energy Technology Data Exchange (ETDEWEB)

    Krynetskii, I. B.; Kulbachinskii, V. A. [Moscow State University (Russian Federation); Shabanova, N. P., E-mail: shaban@sci.lebedev.ru; Tsikunov, A. V.; Kovalenko, R. I.; Rodin, V. V.; Gavrilkin, S. Yu. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2013-05-15

    The temperature dependence of the linear thermal expansion coefficient (TEC) of an InSe single crystal in the (001) plane is measured in the temperature range 7-50 K. A peak in the thermal expansion is detected near T = 10 K, after which the sample shrinks upon heating. The effect of an external magnetic field of up to 6 T, which is parallel to the (001) plane, on the TEC is investigated. The observed partial suppression of the peak and crystal compression by the field indicates the relation of these anomalies to possible electron ordering in InSe layers.

  2. Measurements on thermal expansion with strain gauge; yugami geji wo mochiita gokuteion netsubochoritsu no keisoku

    Energy Technology Data Exchange (ETDEWEB)

    Numazawa, T.; Sato, A. [National Research Inst. for Metals, Tokyo (Japan); Arai, O.; Okuda, Y. [Tokyo Inst. of Tech., Tokyo (Japan)

    1999-11-10

    As the part of very low temperature thermophysical property measurement technique standardization by the intelligent basis promotion system, very low temperature coefficient of thermal expansion measurement method using the strain gauge was examined. Here, DyVO4 that that it has the unique temperature dependency as a sample for the test at 20K or less was expected was taken up. The strain gauge, which constituted bridge circuit using strain sensor of 4 used by fatigue test of very low temperature, was produced, and the measurement of coefficient of thermal expansion was tried. (NEDO)

  3. Hybrid Composites from Wheat Straw, Inorganic Filler, and Recycled Polypropylene: Morphology and Mechanical and Thermal Expansion Performance

    National Research Council Canada - National Science Library

    Yu, Min; Huang, Runzhou; He, Chunxia; Wu, Qinglin; Zhao, Xueni

    2016-01-01

    .... The effects of individual filler (WS) and combined fillers (WS and inorganic filler) on morphological, mechanical, and thermal expansion and water absorption properties of hybrid composites were investigated...

  4. Standard Practice for Evaluating Thermal Insulation Materials for Use in Solar Collectors

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1994-01-01

    1.1 This practice sets forth a testing methodology for evaluating the properties of thermal insulation materials to be used in solar collectors with concentration ratios of less than 10. Tests are given herein to evaluate the pH, surface burning characteristics, moisture adsorption, water absorption, thermal resistance, linear shrinkage (or expansion), hot surface performance, and accelerated aging. This practice provides a test for surface burning characteristics but does not provide a methodology for determining combustibility performance of thermal insulation materials. 1.2 The tests shall apply to blanket, rigid board, loose-fill, and foam thermal insulation materials used in solar collectors. Other thermal insulation materials shall be tested in accordance with the provisions set forth herein and should not be excluded from consideration. 1.3 The assumption is made that elevated temperature, moisture, and applied stresses are the primary factors contributing to the degradation of thermal insulation mat...

  5. Dynamics of plasma expansion in the pulsed laser material interaction

    Indian Academy of Sciences (India)

    process results from the anisotropic expansion velocities associated with different species. These velocities are mainly controlled by the initial dimension of the expanding plasma. An attempt was undertaken to estimate the length of the plume at different ambient gas pressures using an adiabatic expansion model. The rate.

  6. High pressure studies of A{sub 2}Mo{sub 3}O{sub 12} negative thermal expansion materials (A{sub 2}=Al{sub 2}, Fe{sub 2}, FeAl, AlGa)

    Energy Technology Data Exchange (ETDEWEB)

    Young, Lindsay; Gadient, Jennifer; Gao, Xiaodong; Lind, Cora, E-mail: cora.lind@utoledo.edu

    2016-05-15

    High pressure powder X-ray diffraction studies of several A{sub 2}Mo{sub 3}O{sub 12} materials (A{sub 2}=Al{sub 2}, Fe{sub 2}, FeAl, and AlGa) were conducted up to 6–7 GPa. All materials adopted a monoclinic structure under ambient conditions, and displayed similar phase transition behavior upon compression. The initial isotropic compressibility first became anisotropic, followed by a small but distinct drop in cell volume. These patterns could be described by a distorted variant of the ambient pressure polymorph. At higher pressures, a distinct high pressure phase formed. Indexing results confirmed that all materials adopted the same high pressure phase. All changes were reversible on decompression, although some hysteresis was observed. The similarity of the high pressure cells to previously reported Ga{sub 2}Mo{sub 3}O{sub 12} suggested that this material undergoes the same sequence of transitions as all materials investigated in this paper. It was found that the transition pressures for all phase changes increased with decreasing radius of the A-site cations. - Graphical abstract: Overlay of variable pressure X-ray diffraction data of Al{sub 2}Mo{sub 3}O{sub 12} collected in a diamond anvil cell. Both subtle and discontinuous phase transitions are clearly observed. - Highlights: • The high pressure behavior of A{sub 2}Mo{sub 3}O{sub 12} (A=Al, Fe, (AlGa), (AlFe)) was studied. • All compounds undergo the same sequence of pressure-induced phase transitions. • The phase transition pressures correlate with the average size of the A-site cation. • All transitions were reversible with hysteresis. • Previously studied Ga{sub 2}Mo{sub 3}O{sub 12} undergoes the same sequence of transitions.

  7. Effect of high thermal expansion glass infiltration on mechanical ...

    Indian Academy of Sciences (India)

    Department of Information and Electronic Materials Engineering, College of Engineering, Paichai University, Daejeon 302-735, Republic of Korea; Division of Metrology for Emerging Technology, Korea Research Institute of Standards and Science, 1 Doryong-Dong, Yuseong-Gu, Daejeon 305-340, Republic of Korea ...

  8. Giant negative thermal expansion covering room temperature in nanocrystalline GaNxMn3

    Science.gov (United States)

    Lin, J. C.; Tong, P.; Zhou, X. J.; Lin, H.; Ding, Y. W.; Bai, Y. X.; Chen, L.; Guo, X. G.; Yang, C.; Song, B.; Wu, Y.; Lin, S.; Song, W. H.; Sun, Y. P.

    2015-09-01

    Nanocrystalline antiperovskite GaNxMn3 powders were prepared by mechanically milling. The micrograin GaNxMn3 exhibits an abrupt volume contraction at the antiferromagnetic (AFM) to paramagnetic (PM) (AFM-PM) transition. The temperature window of volume contraction (ΔT) is broadened to 50 K as the average grain size (⟨D⟩) is reduced to ˜30 nm. The corresponding coefficient of linear thermal expansion (α) reaches ˜ -70 ppm/K, which are comparable to those of giant NTE materials. Further reducing ⟨D⟩ to ˜10 nm, ΔT exceeds 100 K and α remains as large as -30 ppm/K (-21 ppm/K) for x = 1.0 (x = 0.9). Excess atomic displacements together with the reduced structural coherence, revealed by high-energy X-ray pair distribution functions, are suggested to delay the AFM-PM transition. By controlling ⟨D⟩, giant NTE may also be achievable in other materials with large lattice contraction due to electronic or magnetic phase transitions.

  9. Properties of Expansive Porous Materials Based on Aluminate Cement for Underground Mining

    Science.gov (United States)

    Klimas, Wojciech

    2017-06-01

    The paper presents the results of laboratory tests of expansive mineral binding materials based on calcium aluminate with mineral additive and carbonate expander. The expansion size can be controlled by the amount of expander as well as by water-binder ratio. The study describes the method of measuring the expansion size and selected technical parameters of obtained expansive binders together with the proposed scope of their use in underground construction.

  10. How important is thermal expansion for predicting molecular crystal structures and thermochemistry at finite temperatures?

    Science.gov (United States)

    Heit, Yonaton N; Beran, Gregory J O

    2016-08-01

    Molecular crystals expand appreciably upon heating due to both zero-point and thermal vibrational motion, yet this expansion is often neglected in molecular crystal modeling studies. Here, a quasi-harmonic approximation is coupled with fragment-based hybrid many-body interaction calculations to predict thermal expansion and finite-temperature thermochemical properties in crystalline carbon dioxide, ice Ih, acetic acid and imidazole. Fragment-based second-order Möller-Plesset perturbation theory (MP2) and coupled cluster theory with singles, doubles and perturbative triples [CCSD(T)] predict the thermal expansion and the temperature dependence of the enthalpies, entropies and Gibbs free energies of sublimation in good agreement with experiment. The errors introduced by neglecting thermal expansion in the enthalpy and entropy cancel somewhat in the Gibbs free energy. The resulting ∼ 1-2 kJ mol(-1) errors in the free energy near room temperature are comparable to or smaller than the errors expected from the electronic structure treatment, but they may be sufficiently large to affect free-energy rankings among energetically close polymorphs.

  11. Copper-zirconium tungstate composites exhibiting low and negative thermal expansion influenced by reinforcement phase transformations

    Science.gov (United States)

    Balch, Dorian K.; Dunand, David C.

    2004-03-01

    A fully-dense Cu-75 vol pct ZrW2O8 metal matrix composite was fabricated by hot isostatic pressing of Cu-coated ZrW2O8 particles. A small amount of the high-pressure γ-ZrW2O8 phase was created during the cooldown and depressurization following densification; near complete transformation to γ-ZrW2O8 was achieved by subsequent cold isostatic pressing. The thermal expansion behavior of the composite between 25°C and 325°C was altered by the cold isostatic pressing treatment, and also depended on the length of time that had passed between thermal cycles. The measured thermal expansion coefficients within specific temperature ranges varied from -6·10-6 K-1 to far above the thermal expansion coefficient of the copper matrix. The complex temperature-dependent expansion/contraction behavior could be justified by considering the evolution of phase transformations taking place in the ZrW2O8 phase, which were observed by in-situ synchrotron X-ray diffraction measurements.

  12. Isotropic Zero Thermal Expansion and Local Vibrational Dynamics in (Sc,Fe)F3.

    Science.gov (United States)

    Qin, Feiyu; Chen, Jun; Aydemir, Umut; Sanson, Andrea; Wang, Lu; Pan, Zhao; Xu, Jiale; Sun, Chengjun; Ren, Yang; Deng, Jinxia; Yu, Ranbo; Hu, Lei; Snyder, G Jeffrey; Xing, Xianran

    2017-09-18

    Scandium fluoride (ScF3) exhibits a pronounced negative thermal expansion (NTE), which can be suppressed and ultimately transformed into an isotropic zero thermal expansion (ZTE) by partially substituting Sc with Fe in (Sc0.8Fe0.2)F3 (Fe20). The latter displays a rather small coefficient of thermal expansion of -0.17 × 10(-6)/K from 300 to 700 K. Synchrotron X-ray and neutron pair distribution functions confirm that the Sc/Fe-F bond has positive thermal expansion (PTE). Local vibrational dynamics based on extended X-ray absorption fine structure indicates a decreased anisotropy of relative vibration in the Sc/Fe-F bond. Combined analysis proposes a delicate balance between the counteracting effects of the chemical bond PTE and NTE from transverse vibration. The present study extends the scope of isotropic ZTE compounds and, more significantly, provides a complete local vibrational dynamics to shed light on the ZTE mechanism in chemically tailored NTE compounds.

  13. XRD- and infrared-probed anisotropic thermal expansion properties of an organic semiconducting single crystal.

    Science.gov (United States)

    Mohanraj, J; Capria, E; Benevoli, L; Perucchi, A; Demitri, N; Fraleoni-Morgera, A

    2018-01-17

    The anisotropic thermal expansion properties of an organic semiconducting single crystal constituted by 4-hydroxycyanobenzene (4HCB) have been probed by XRD in the range 120-300 K. The anisotropic thermal expansion coefficients for the three crystallographic axes and for the crystal volume have been determined. A careful analysis of the crystal structure revealed that the two different H-bonds stemming from the two independent, differently oriented 4HCB molecules composing the unit cell have different rearrangement patterns upon temperature variations, in terms of both bond length and bond angle. Linearly Polarized Mid InfraRed (LP-MIR) measurements carried out in the same temperature range, focused on the O-H bond spectral region, confirm this finding. The same LP-MIR measurements, on the basis of a semi-empirical relation and of geometrical considerations and assumptions, allowed calculation of the -CNH-O- hydrogen bond length along the a and b axes of the crystal. In turn, the so-calculated -CNH-O- bond lengths were used to derive the thermal expansion coefficients along the corresponding crystal axes, as well as the volumetric one, using just the LP-MIR data. Reasonable to good agreement with the same values obtained from XRD measurements was obtained. This proof-of-principle opens interesting perspectives about the possible development of a rapid, low cost and industry-friendly assessment of the thermal expansion properties of organic semiconducting single crystals (OSSCs) involving hydrogen bonds.

  14. Contrast Enhanced Microscopy Digital Image Correlation: A General Method to Contact-Free Coefficient of Thermal Expansion Measurement of Polymer Films

    Science.gov (United States)

    Jairo A. Diaz; Robert J. Moon; Jeffrey P. Youngblood

    2014-01-01

    Thermal expansion represents a vital indicator of the processing history and dimensional stability of materials. Solvent-sensitive, thin, and compliant samples are particularly challenging to test. Here we describe how textures highlighted by contrast enhanced optical microscopy modes (i.e., polarized light (PL), phase contrast (PC)) and bright field (BF) can be used...

  15. Combustion synthesis and thermal expansion measurements of the rare earth-uranium ternary oxides RE 6UO 12 (RE=La, Nd and Sm)

    Science.gov (United States)

    Jena, Hrudananda; Asuvathraman, R.; Govindan Kutty, K. V.

    2000-08-01

    Rare earth-uranium ternary oxides were synthesized by a solution combustion route. The starting materials were the corresponding metal nitrates and urea. In these preparations, the metal nitrates act as oxidizer and urea as fuel. Highly exothermic decomposition of the metal nitrate-urea complexes on heating at about 500 K leads to a combustion process yielding RE 6UO 12 fine powders. Thermal expansion measurements of these compounds were carried out in the temperature range of 298-1173 K by high temperature X-ray powder diffractometry. The observed axial thermal expansion behaviour is explained on the basis of the crystal chemistry of the compounds.

  16. Waste Package Outer Barrier Stress Due to Thermal Expansion with Various Barrier Gap Sizes

    Energy Technology Data Exchange (ETDEWEB)

    M. M. Lewis

    2001-11-27

    The objective of this activity is to determine the tangential stresses of the outer shell, due to uneven thermal expansion of the inner and outer shells of the current waste package (WP) designs. Based on the results of the calculation ''Waste Package Barrier Stresses Due to Thermal Expansion'', CAL-EBS-ME-000008 (ref. 10), only tangential stresses are considered for this calculation. The tangential stresses are significantly larger than the radial stresses associated with thermal expansion, and at the WP outer surface the radial stresses are equal to zero. The scope of this activity is limited to determining the tangential stresses the waste package outer shell is subject to due to the interference fit, produced by having two different shell coefficients of thermal expansions. The inner shell has a greater coefficient of thermal expansion than the outer shell, producing a pressure between the two shells. This calculation is associated with Waste Package Project. The calculations are performed for the 21-PWR (pressurized water reactor), 44-BWR (boiling water reactor), 24-BWR, 12-PWR Long, 5 DHLW/DOE SNF - Short (defense high-level waste/Department of Energy spent nuclear fuel), 2-MCO/2-DHLW (multi-canister overpack), and Naval SNF Long WP designs. The information provided by the sketches attached to this calculation is that of the potential design for the types of WPs considered in this calculation. This calculation is performed in accordance with the ''Technical Work Plan for: Waste Package Design Description for SR (Ref.7). The calculation is documented, reviewed, and approved in accordance with AP-3.12Q, Calculations (Ref.1).

  17. 14 CFR 25.856 - Thermal/Acoustic insulation materials.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Thermal/Acoustic insulation materials. 25....856 Thermal/Acoustic insulation materials. (a) Thermal/acoustic insulation material installed in the... requirement does not apply to thermal/acoustic insulation installations that the FAA finds would not...

  18. Mechanical stability of the LHC dipole-dipole 50-75K thermal shield interconnect "floating" expansion joint concept

    CERN Document Server

    Skoczen, Blazej

    1998-01-01

    The LHC dipole cryostats are equipped with thermal shields carrying super-insulation. A cold helium transfer line equipped with expansion joints is integrated into the shield carrying trays (aluminium profiles supported on three composite feet). The stainless steel (316 L) expansion joints compensate for thermal contraction/expansion of the aluminium panels as well as for their misalignment. Design of the LHC thermal shield interconnect is based on the "floating" expansion joint concept (distance between the supports is of around 5 m). The present paper is dedicated to the analysis of mechanical stability of this large span system working at room and at cryogenic temperatures.

  19. Magnetic transition broadening and local lattice distortion in the negative thermal expansion antiperovskite Cu1-xSnxNMn3

    Science.gov (United States)

    Tong, P.; Louca, Despina; King, Graham; Llobet, Anna; Lin, J. C.; Sun, Y. P.

    2013-01-01

    The local distortion indicated by the split of the Cu/Sn-Mn bonds for the negative thermal expansion (NTE) materials Cu1-xSnxNMn3 (x = 0.1 and 0.5) was observed using neutron pair distribution function. The distribution of Cu/Sn-Mn bonds upon Sn doping is suggested to be attributable to the fluctuation in the hybridization of Mn d with Sn p orbitals. Accordingly, the antiferromagnetic (AFM) coupling mediated by the p-d hybridization fluctuates in strength. Consequently, the AFM transition closely coupled with the volume change is broadened, leading to the NTE.

  20. Thermal Ablation Modeling for Silicate Materials

    Science.gov (United States)

    Chen, Yih-Kanq

    2016-01-01

    A general thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in the ablation simulation of the meteoroid and the glassy ablator for spacecraft Thermal Protection Systems. Time-dependent axisymmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. The predicted mass loss rates will be compared with available data for model validation, and parametric studies will also be performed for meteoroid earth entry conditions.

  1. Measurements of thermal conductivity and the coefficient of thermal expansion for polysilicon thin films by using double-clamped beams

    Science.gov (United States)

    Liu, Haiyun; Wang, Lei

    2018-01-01

    In this paper, a test structure for simultaneously determining thermal conductivity and the coefficient of thermal expansion (CTE) of polysilicon thin film is proposed. The test structure consists of two double-clamped beams with different lengths. A theoretical model for extracting thermal conductivity and CTE based on electrothermal analysis and resonance frequency approach is developed. Both flat and buckled beams are considered in the theoretical model. The model is confirmed by finite element software ANSYS. The test structures are fabricated by surface micromachined fabrication process. Experiments are carried out in our atmosphere. Thermal conductivity and CTE of polysilicon thin film are obtained to be (29.96  ±  0.92) W · m · K‑1 and (2.65  ±  0.03)  ×  10‑6 K‑1, respectively, with temperature ranging from 300–400 K.

  2. Advanced materials for thermal protection system

    Science.gov (United States)

    Heng, Sangvavann; Sherman, Andrew J.

    1996-03-01

    Reticulated open-cell ceramic foams (both vitreous carbon and silicon carbide) and ceramic composites (SiC-based, both monolithic and fiber-reinforced) were evaluated as candidate materials for use in a heat shield sandwich panel design as an advanced thermal protection system (TPS) for unmanned single-use hypersonic reentry vehicles. These materials were fabricated by chemical vapor deposition/infiltration (CVD/CVI) and evaluated extensively for their mechanical, thermal, and erosion/ablation performance. In the TPS, the ceramic foams were used as a structural core providing thermal insulation and mechanical load distribution, while the ceramic composites were used as facesheets providing resistance to aerodynamic, shear, and erosive forces. Tensile, compressive, and shear strength, elastic and shear modulus, fracture toughness, Poisson's ratio, and thermal conductivity were measured for the ceramic foams, while arcjet testing was conducted on the ceramic composites at heat flux levels up to 5.90 MW/m2 (520 Btu/ft2ṡsec). Two prototype test articles were fabricated and subjected to arcjet testing at heat flux levels of 1.70-3.40 MW/m2 (150-300 Btu/ft2ṡsec) under simulated reentry trajectories.

  3. Study on radial core thermal expansion for MOX fuelled large LMFBRS

    Energy Technology Data Exchange (ETDEWEB)

    Ohkubo, Y. [Mitsubishi Heavy Industries, Yokohama (Japan); Watanabe, O. [Advanced Reactor Technology, Tokyo (Japan); Nakagawa, M. [Toshiba Co., Kawasaki (Japan); Fujimura, K. [Hitachi, Ltd., Ibarakiken (Japan); Ishida, M. [FBR Engineering Co., Ltd., Tokyo (Japan); Kotake, S. [The Japan Atomic Power Com., Tokyo (Japan)

    1998-07-01

    A study has been performed to evaluate radial core thermal expansion characteristics in ULOF (Unprotected Loss Of Flow) events of large LMFBRs with MOX fuel, which are expected as a passive safety feature of LMFBRs. The mechanism of radial core expansion is so complicated that the precise evaluation of its reactivity effect needs a sophisticated analytical tool system. An analytical code system has been developed in order to determine the best-estimate reactivity due to core radial expansion. The code system consists of the 3-D core thermal hydraulic transient analysis code with point kinetics, the 3-D core deflection analysis code and the 3-D core bowing reactivity analysis code. The core radial expansion reactivity in ULOF events of a large FBR with electric power of 1500MWe has been evaluated by iteration procedures among the three codes in order to study the negative reactivity insertion mechanism. It has been concluded that the core radial expansion reactivity feedback is not sufficient to prevent the coolant boiling in ULOF event of the MOX fuelled large LMFBR by itself but is considered to assist other passive safety measures to settle the core in a stable shutdown state by delaying the coolant boiling inception.

  4. Coefficient of Thermal Expansion of the Beta and Delta Polymorphs of HMX

    Energy Technology Data Exchange (ETDEWEB)

    Weese, R K; Burnham, A K

    2005-01-11

    Dimensional changes related to temperature cycling of the {beta} and {delta} polymorphs of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) are important for a variety of applications. The coefficient of thermal expansion (CTE) of the {beta} and {delta} phases are measured over a temperature range of -20 C to 215 C by thermo-mechanical analysis (TMA). Dimensional changes associated with the phase transition were also measured, and the time-temperature dependence of the dimensional change is consistent with phase transition kinetics measured earlier by differential scanning calorimetry (DSC). One HMX sample measured by TMA during its initial heating and again three days later during a second heating showed the {beta}-to-{delta} phase transition a second time, thereby indicating back conversion from {delta}-to-{beta} phase HMX during those three days. DSC was used to measure kinetics of the {delta}-to-{beta} back conversion. The most successful approach was to first heat the material to create the {delta} phase, then after a given period at room temperature, measure the heat absorbed during a second pass through the {beta}-to-{delta} phase transition. Back conversion at room temperature follows nucleation-growth kinetics.

  5. Effects of cation substitution on thermal expansion and electrical properties of lanthanum chromites

    Energy Technology Data Exchange (ETDEWEB)

    Ding Xifeng [College of Materials Science and Engineering, Nanjing University of Technology, Nanjing, Jiangsu, 210009 (China); Liu Yingjia [College of Materials Science and Engineering, Nanjing University of Technology, Nanjing, Jiangsu, 210009 (China); Gao Ling [College of Materials Science and Engineering, Nanjing University of Technology, Nanjing, Jiangsu, 210009 (China); Guo Lucun [College of Materials Science and Engineering, Nanjing University of Technology, Nanjing, Jiangsu, 210009 (China)]. E-mail: lc-guo@163.com

    2006-11-30

    The effects of cation substitution on the sintering characteristics, thermal expansion and electrical conductivity properties of La(AE)Cr(M)O{sub 3} (AE=Mg, Ca, Sr, M=Ni, Cu, Co) were investigated. The sinterability of alkaline metal earth (AE)-doped LaCrO{sub 3} increased with AE contents in a sequence of Ca > Sr > Mg. Sr-doped LaCrO{sub 3} sample had a TEC compatible with that of 8YSZ electrolyte. The transition metals of Ni, Co and Cu substituted in Cr-site further optimized the sinterability of La{sub 0.85}Sr{sub 0.15}CrO{sub 3} in air. Ni and Co could effectively enhance the electrical conductivity from room temperature to 1123 K though the concomitant increase in TEC was distinctively large with Co doping. The TEC was controlled by co-doping Ni and Co in Cr-site, and La{sub 0.85}Sr{sub 0.15}Cr{sub 0.95}Ni{sub 0.02}Co{sub 0.02}O{sub 3} exhibited a TEC of 10.9 x 10{sup -6}/K, which was matched with that of 8YSZ, indicating that it could be suitable to be used as an SOFC interconnect material.

  6. Multifunctional Hybrid Composites for Thermal Materials

    Science.gov (United States)

    2012-08-03

    Hierarchical carbon fiber morphology for tailored thermal properties in heterogeneous materials systems – Fiber reinforced composites – Sensors , Heat sink...Interfaces, 4 (2), 2012 • Metal – CNT interface – MD simulation, processing, measurements 5 MWCNT Graphite Interface (Hexagonal Crystal ED Patterns...Simulations • Values are low (metal-metal 300-1000 MW/m2/K) • Similar conductance found for MWCNT and SWCNT interfaces • Conductance is higher for

  7. Thermal contraction of superconducting magnet materials

    Science.gov (United States)

    Gladky, V. N.; Kozub, S. S.; Veshchikov, A. T.; Escher, U.

    This paper reports on the design of a quartz dilatometer used to measure the thermal contraction of structural glass cloth based laminates and of uniaxial glass fibre based laminates along and normal to the glass fibres within the 293-77 K and 293-4 K temperature ranges. The contraction of the structural and insulation materials and of the coil of the superconducting (SO magnets for the UNK was studied during cool-down from 300 to 4 K.

  8. Thermophysical Properties of Matter - the TPRC Data Series. Volume 13. Thermal Expansion - Nonmetallic Solids

    Science.gov (United States)

    1977-01-01

    to a high enough the near-zero expansivity of vitreous silica that makes temperature it will crystallize in the cristobalite it so useful. Methods for...John Wiley, 1961. 33. Matthias, B.T., Geballe, T.H., Corenzwit, E., Andres, K., and Hall, G.W., "Superconductivity of Beta -Uranium," Science, 151, 985...Thermal Expansion Coefficients of Beta -MnOt,ŕ J. Electro- chem. Soc., 109(7), 651, 1962. 125 52255 Mistler, R. E., Ploetz, G. L., and Smith, J. A

  9. Two-level systems and negative thermal expansion of lutetium borides

    Science.gov (United States)

    Novikov, V. V.; Mitroshenkov, N. V.; Kornev, B. I.; Matovnikov, A. V.

    2017-05-01

    The heat capacity Cv(T) and unit cell volume V(T) temperature dependencies of lutetium borides LuB2 and LuB4 in the region of 2-300 K were analysed in the Debye-Einstein approximation. The characteristic temperatures of the Debye and Einstein components of boride heat capacity and thermal expansion were found. The anomalous contribution to the borides' thermal characteristics was revealed. This contribution was attributed to the influence of two-level systems (TLS), formed in the subsystem of lutetium ions due to asymmetry in the way they are surrounded by the boron atoms in the boride crystal structure. The TLS influence is revealed on heat capacity temperature dependencies by the Schottky-type maxima at Tmax LuB2 =13.8 K, Tmax LuB4 =22.7 K, as well as by the negative contribution to the borides' thermal expansion. The borides' Grüneisen parameters corresponding to the heat capacity and thermal expansion TLS anomalies are negative, and amount to several 10 s of units.

  10. Spatial variability in the coefficient of thermal expansion induces pre-service stresses in computer models of virgin Gilsocarbon bricks

    Energy Technology Data Exchange (ETDEWEB)

    Arregui-Mena, José David, E-mail: jose.arreguimena@postgrad.manchester.ac.uk [School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Margetts, Lee, E-mail: lee.margetts@manchester.ac.uk [School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Griffiths, D.V., E-mail: d.v.griffiths@mines.edu [Colorado School of Mines, 1500 Illinois St, Golden, CO 80401 (United States); Lever, Louise, E-mail: louise.lever@manchester.ac.uk [Research Computing, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Hall, Graham, E-mail: graham.n.hall@manchester.ac.uk [School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Mummery, Paul M., E-mail: paul.m.mummery@manchester.ac.uk [School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)

    2015-10-15

    In this paper, the authors test the hypothesis that tiny spatial variations in material properties may lead to significant pre-service stresses in virgin graphite bricks. To do this, they have customised ParaFEM, an open source parallel finite element package, adding support for stochastic thermo-mechanical analysis using the Monte Carlo Simulation method. For an Advanced Gas-cooled Reactor brick, three heating cases have been examined: a uniform temperature change; a uniform temperature gradient applied through the thickness of the brick and a simulated temperature profile from an operating reactor. Results are compared for mean and stochastic properties. These show that, for the proof-of-concept analyses carried out, the pre-service von Mises stress is around twenty times higher when spatial variability of material properties is introduced. The paper demonstrates that thermal gradients coupled with material incompatibilities may be important in the generation of stress in nuclear graphite reactor bricks. Tiny spatial variations in coefficient of thermal expansion (CTE) and Young's modulus can lead to the presence of thermal stresses in bricks that are free to expand. - Highlights: • Open source software has been modified to include random variability in CTE and Young's modulus. • The new software closely agrees with analytical solutions and commercial software. • Spatial variations in CTE and Young's modulus produce stresses that do not occur with mean values. • Material variability may induce pre-service stress in virgin graphite.

  11. Thermal stability, thermal expansion and grain-growth in exchange-coupled Fe-Pt-Ag-B bulk nanocomposite magnets

    Energy Technology Data Exchange (ETDEWEB)

    Nicula, R., E-mail: radu.nicula@empa.ch [Empa, Swiss Federal Laboratories for Materials Science and Technology, Advanced Materials Processing, Feuerwerkerstr. 39, CH-3602 Thun (Switzerland); Crisan, O.; Crisan, A.D.; Mercioniu, I. [National Institute for Materials Physics, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania); Stir, M. [University of Berne, Department of Chemistry and Biochemistry, Freiestrasse 3, CH-3012 Berne (Switzerland); Vasiliu, F. [National Institute for Materials Physics, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania)

    2015-02-15

    Highlights: • Formation of the L10 FePt hard-magnetic phase (>90%) directly in the as-cast state. • Specific alternating hard/soft nanostructure is stable to 600 °C without grain growth. • Anisotropic and non-linear thermal expansion effects. • The FePtAgB alloy behaves like a single magnetic phase (full exchange coupling). - Abstract: Rare-earth free (RE-free) exchange coupling nanocomposite magnets are intensively studied nowadays due to their potential use in applications demanding stable high-temperature operation and corrosion resistance. In this respect, the FePt alloy system is one of the most actively addressed potential permanent magnet solutions. In FePt alloys, promising magnetic features arise from the co-existence of hard magnetic L1{sub 0} FePt and soft magnetic L1{sub 2} Fe{sub 3}Pt phases emerged from the same metastable precursor. The present work deals with an in-situ temperature-resolved synchrotron radiation study of the thermal stability, thermal expansion and microstructure evolution in exchange-coupled FePtAgB alloys. The as-cast microstructural state as well as the optimized magnetic behavior are given as reference and correlated to the observed microstructural evolution with temperature. The melt-spun Fe{sub 48}Pt{sub 28}Ag{sub 6}B{sub 18} alloy ribbons were examined in situ by synchrotron X-ray powder diffraction from ambient temperature up to 600 °C. The FePt-Fe{sub 3}Pt exchange-coupled microstructure achieved by rapid solidification is not significantly altered during the high temperature exposure. The thermal expansion of the FePt L1{sub 0} unit cell has been found to be strongly anisotropic, being essentially an in-plane expansion which may be seen as an anisotropic invar effect. For the FePt L1{sub 0} phase, a significant deviation from linear thermal expansion is observed at the Curie temperature T{sub C} = 477 °C. This non-linear behavior above T{sub C} is tentatively linked to a diffusion/segregation mechanism of Ag

  12. Dynamics of plasma expansion in the pulsed laser material interaction

    Indian Academy of Sciences (India)

    It is seen from present computations that the forward directed nature of the laser evaporation process results from the anisotropic expansion velocities associated with different species. These velocities are mainly controlled by the initial dimension of the expanding plasma. An attempt was undertaken to estimate the length of ...

  13. Metallic Nanocomposites as Next-Generation Thermal Interface Materials: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xuhui [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Narumanchi, Sreekant V [National Renewable Energy Laboratory (NREL), Golden, CO (United States); King, Charles C [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Nagabandi, Nirup [Texas A& M University; Oh, Jun K. [Texas A& M University; Akbulut, Mustafa [Texas A& M University; Yegin, Cengiz [Texas A& M University

    2017-09-14

    Thermal interface materials (TIMs) are an integral and important part of thermal management in electronic devices. The electronic devices are becoming more compact and powerful. This increase in power processed or passing through the devices leads to higher heat fluxes and makes it a challenge to maintain temperatures at the optimal level during operation. Herein, we report a free standing nanocomposite TIM in which boron nitride nanosheets (BNNS) are uniformly dispersed in copper matrices via an organic linker, thiosemicarbazide. Integration of these metal-organic-inorganic nanocomposites was made possible by a novel electrodeposition technique where the functionalized BNNS (f-BNNS) experience the Brownian motion and reach the cathode through diffusion, while the nucleation and growth of the copper on the cathode occurs via the electrochemical reduction. Once the f-BNNS bearing carbonothioyl/thiol groups on the terminal edges come into the contact with copper crystals, the chemisorption reaction takes place. We performed thermal, mechanical, and structural characterization of these nanocomposites using scanning electron microcopy (SEM), diffusive laser flash (DLF) analysis, phase-sensitive transient thermoreflectence (PSTTR), and nanoindentation. The nanocomposites exhibited a thermal conductivity ranging from 211 W/mK to 277 W/mK at a filler mass loading of 0-12 wt.percent. The nanocomposites also have about 4 times lower hardness as compared to copper, with values ranging from 0.27 GPa to 0.41 GPa. The structural characterization studies showed that most of the BNNS are localized at grain boundaries - which enable efficient thermal transport while making the material soft. PSTTR measurements revealed that the synergistic combinations of these properties yielded contact resistances on the order of 0.10 to 0.13 mm2K/W, and the total thermal resistance of 0.38 to 0.56 mm2K/W at bondline thicknesses of 30-50 um. The coefficient of thermal expansion (CTE) of the

  14. Metallic Nanocomposites as Next-Generation Thermal Interface Materials

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xuhui [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Narumanchi, Sreekant V [National Renewable Energy Laboratory (NREL), Golden, CO (United States); King, Charles C [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Nagabandi, Nirup [Texas A& M University; Oh, Jun Kyun [Texas A& M University; Akbulut, Mustafa [Texas A& M University; Yegin, Cengiz [Texas A& M University

    2017-07-27

    Thermal interface materials (TIMs) are an integral and important part of thermal management in electronic devices. The electronic devices are becoming more compact and powerful. This increase in power processed or passing through the devices leads to higher heat fluxes and makes it a challenge to maintain temperatures at the optimal level during operation. Herein, we report a free standing nanocomposite TIM in which boron nitride nanosheets (BNNS) are uniformly dispersed in copper matrices via an organic linker, thiosemicarbazide. Integration of these metal-organic-inorganic nanocomposites was made possible by a novel electrodeposition technique where the functionalized BNNS (f-BNNS) experience the Brownian motion and reach the cathode through diffusion, while the nucleation and growth of the copper on the cathode occurs via the electrochemical reduction. Once the f-BNNS bearing carbonothioyl/thiol groups on the terminal edges come into the contact with copper crystals, the chemisorption reaction takes place. We performed thermal, mechanical, and structural characterization of these nanocomposites using scanning electron microcopy (SEM), diffusive laser flash (DLF) analysis, phase-sensitive transient thermoreflectence (PSTTR), and nanoindentation. The nanocomposites exhibited a thermal conductivity ranging from 211 W/mK to 277 W/mK at a filler mass loading of 0-12 wt.percent. The nanocomposites also have about 4 times lower hardness as compared to copper, with values ranging from 0.27 GPa to 0.41 GPa. The structural characterization studies showed that most of the BNNS are localized at grain boundaries - which enable efficient thermal transport while making the material soft. PSTTR measurements revealed that the synergistic combinations of these properties yielded contact resistances on the order of 0.10 to 0.13 mm2K/W, and the total thermal resistance of 0.38 to 0.56 mm2K/W at bondline thicknesses of 30-50 um. The coefficient of thermal expansion (CTE) of the

  15. APPLICATIONS OF THERMAL-WAVE PHYSICS TO SEMICONDUCTOR MATERIALS ANALYSIS

    OpenAIRE

    Rosencwaig, A.

    1983-01-01

    Nonspectroscopic applications of thermal-wave physics, in particular those involving materials analysis through thermal-wave imaging, and quantitative thin-film thickness measurements, are described for the study of semiconductor materials and devices.

  16. Dendritic solidification and thermal expansion of refractory Nb-Zr alloys investigated by electrostatic levitation

    Energy Technology Data Exchange (ETDEWEB)

    Yang, S.J.; Hu, L.; Wang, L.; Wei, B. [Northwestern Polytechnical University, Department of Applied Physics, Xi' an (China)

    2017-05-15

    The dendritic growth and thermal expansion of isomorphous refractory Nb-5%Zr, Nb-10%Zr, and Nb-15%Zr alloys were studied by electrostatic levitation technique. The obtained maximum undercoolings for the three alloys were 534 (0.2T{sub L}), 498 (0.19T{sub L}), and 483 K (0.18T{sub L}), respectively. Within these undercooling ranges, the dendritic growth velocities of the three alloys all exhibited power laws, and achieved 38.5, 34.0, and 27.1 m s{sup -1} at each maximum undercooling. The microstructures were characterized by coarse dendrites at small undercooling, while they transformed into refined dendrites under large undercooling condition. In addition, the measured thermal expansion coefficients of solid Nb-Zr alloys increased linearly with temperature. The values at liquid state were more than double of those at solid state, which also displayed linear dependence on temperature. (orig.)

  17. Uniaxial Negative Thermal Expansion and Mechanical Properties of a Zinc-Formate Framework

    Directory of Open Access Journals (Sweden)

    Hongqiang Gao

    2017-02-01

    Full Text Available The thermal expansion behavior of a metal-formate framework, Zn(HCOO2·2(H2O (1, has been systematically studied via variable temperature single-crystal X-ray diffraction. Our results demonstrate that this formate exhibits significant negative thermal expansion (NTE, −26(2 MK−1 along its c-axis. Detailed structural analyses reveal that the large NTE response is attributed to the ‘hinge-strut’ like framework motion. In addition, the fundamental mechanical properties of framework 1 have been explored via nanoindentation experiments. The measured elastic modulus and hardness properties on the (00-2/(100/(110 facets are 35.5/35.0/27.1 and 2.04/1.83/0.47 GPa, respectively. The stiffness and hardness anisotropy can be correlated well with the underlying framework structure, like its thermoelastic behavior.

  18. HAYNES 244 alloy – a new 760 ∘C capable low thermal expansion alloy

    OpenAIRE

    Fahrmann Michael G.; Srivastava S. Krishna; Pike Lee M.

    2014-01-01

    HAYNES® 244TM alloy is a new 760∘C capable, high strength low thermal expansion (CTE) alloy. Its nominal chemical composition in weight percent is Ni – 8 Cr – 22.5 Mo – 6 W. Recently, a first mill-scale heat of 244 alloy was melted by Haynes International, and processed to various product forms such as re-forge billet, plate, and sheet. This paper presents key attributes of this new alloy (CTE, strength, low-cycle fatigue performance, oxidation resistance, thermal stability) as they pertain t...

  19. HAYNES 244 alloy – a new 760 ∘C capable low thermal expansion alloy

    Directory of Open Access Journals (Sweden)

    Fahrmann Michael G.

    2014-01-01

    Full Text Available HAYNES® 244TM alloy is a new 760∘C capable, high strength low thermal expansion (CTE alloy. Its nominal chemical composition in weight percent is Ni – 8 Cr – 22.5 Mo – 6 W. Recently, a first mill-scale heat of 244 alloy was melted by Haynes International, and processed to various product forms such as re-forge billet, plate, and sheet. This paper presents key attributes of this new alloy (CTE, strength, low-cycle fatigue performance, oxidation resistance, thermal stability as they pertain to the intended use in rings and seals of advanced gas turbines.

  20. Thermal expansion and magnetostriction of superconducting URu{sub 2}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    van Dijk, N.H.; de Visser, A.; Franse, J.J.M.; Menovsky, A.A. [Van der Waals-Zeeman Laboratory, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands)

    1995-05-01

    Dilatation measurements have been performed on a single-crystalline sample of the heavy-fermion superconductor URu{sub 2}Si{sub 2} ({ital T}{sub {ital c}}=1.2 K). Thermal-expansion measurements in combination with specific-heat data reveal a thermal electronic Grueneisen parameter of {Gamma}{sub {ital T}}=27. A comparison with the magnetic electronic Grueneisen parameter derived from the magnetostriction, {Gamma}{sub {ital B}}=26, points to a single energy scale. The measured magnetostriction is strongly anisotropic with a peculiar hysteresis. Close to the upper critical field, a change of sign in the magnetostrictive hysteresis is observed.

  1. Low-temperature abnormal thermal expansion property of Mn doped cubic NaZn13-type La(Fe, Al)13 compounds

    Science.gov (United States)

    Zhao, Yuqiang; Huang, Rongjin; Shan, Yi; Wang, Wei; Li, Jiangtao; Li, Laifeng

    2017-09-01

    Low-temperature abnormal thermal expansion (ATE) materials have been recently developed because of their significant applications for cryogenic engineering. However, the challenge still remains for the control of ATE effect at cryogenic temperature and adjustable ATE is of fundamental interest. In this paper, we report the isotropic ATE in La(Fe, Al)13 compounds over a wide adjusting temperature range by partially substituting Fe by Mn. It is found that all samples crystallize in the cubic NaZn13-type structure with the Fm\\bar{3}c space group. The introduction of nonmagnetic Mn atoms reduces the Fe-Fe exchange interaction, therefore, the itinerant electron system needs less energy to break the magnetic order in ferromagnetic (FM) state at low temperature. The negative thermal expansion (NTE) operation-temperature window moves towards lower temperatures accompanied with the decrease of Curie temperature (T C) by increasing Mn elements. Moreover, the composite combining Mn 0 and Mn 57 broadens the zero thermal expansion (ZTE) behavior occurring in the whole tested temperature range. The present studies could be useful to control the thermal expansion, and indicate the potential applications of ATE materials in cryogenic engineering.

  2. Thermal stress fracturing of magma simulant materials

    Energy Technology Data Exchange (ETDEWEB)

    Wemple, R.P.; Longcope, D.B.

    1986-10-01

    Direct contact heat exchanger concepts for the extraction of energy from magma chambers are being studied as part of the DOE-funded Magma Energy Research Program at Sandia National Laboratories. These concepts require the solidification of molten material by a coolant circulated through a borehole drilled into the magma and subsequent fracture of the solid either as a natural consequence of thermal stress or by deliberate design (intentional flaws, high pressure, etc.). This report summarizes the results of several thermal stress fracturing experiments performed in the laboratory and compares the results with an analysis developed for use as a predictive tool. Information gained from this test series has been the basis for additional work now under way to simulate magma melt solidification processes.

  3. Thermal expansions in wurtzite AlN, GaN, and InN: First-principle phonon calculations

    Science.gov (United States)

    Xu, Li-Chun; Wang, Ru-Zhi; Yang, Xiaodong; Yan, Hui

    2011-08-01

    Using the first-principle phonon calculations under the quasiharmonic approximation, thermal expansions in III-nitrides with wurtzite AlN, GaN, and InN are reported. The results showed that it is different for each thermal expansion of three III-nitrides at low temperatures, which is consistent with their Grüneisen parameters as the function of temperature. Below 50 K, negative thermal expansions occur in InN, while GaN and AlN follow the rule of positive thermal expansion. To seek the origin of positive/negative thermal expansion distinction, the mode Grüneisen parameters and the phonon spectra are investigated. They indicate that different low-frequency phonon vibration modes correspond to the change of thermal expansions. Below 5 THz, the significant weighted negative values of mode Grüneisen parameters, caused by the weakening of mixing-mode constituted with two transverse acoustic (TA) modes and a small overlapped part of optical modes, directly lead to the negative thermal expansion at low temperatures.

  4. Thermal expansion in UO 2 determined by high-energy X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Guthrie, M.; Benmore, C. J.; Skinner, L. B.; Alderman, O. L. G.; Weber, J. K. R.; Parise, J. B.; Williamson, M.

    2016-10-01

    Here we present crystallographic analyses of high-energy X-ray diffraction data on polycrystalline UO2 up to the melting temperature. The Rietveld refinements of our X-ray data are in agreement with previous measurements, but are systematically located around the upper bound of their uncertainty, indicating a slightly steeper trend of thermal expansion compared to established values. This observation is consistent with recent first principles calculations.

  5. Coefficient of thermal expansion (CTE) in EUV lithography: LER and adhesion improvement

    Science.gov (United States)

    Higgins, Craig; Settens, Charles; Wolfe, Patricia; Petrillo, Karen; Auger, Robert; Matyi, Richard; Brainard, Robert

    2011-04-01

    Spin-on underlayers are currently being employed by the lithographic industry to improve the imaging performance of EUV resists. In this work, multiple examples have shown improved line-edge roughness (LER) of an open-source resist using new open-source underlayers in comparison to a primed silicon substrate. Additionally, several experiments demonstrate better resist adhesion on underlayers that have lower coefficients of thermal expansion (CTE). Both organic and inorganic underlayers provide better resist LER when their CTE is lower.

  6. Composite materials for thermal energy storage

    Science.gov (United States)

    Benson, David K.; Burrows, Richard W.; Shinton, Yvonne D.

    1986-01-01

    The present invention discloses composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations. These phase change materials do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions, such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

  7. The Study on Thermal Expansion of Ceramic Composites with Addition of ZrW2O8

    Science.gov (United States)

    Dedova, E. S.; Shadrin, V. S.; Petrushina, M. Y.; Kulkov, S. N.

    2016-02-01

    The studies on structure, phase composition and thermal properties of (Al2O3 - 20 wt% ZrO2) - ZrW2O8 ceramic composites obtained using nanosized, initial powders were conducted. Homogeneously distributed white particles on the polished surface of composites were observed. Phase composition of the composites was represented with corundum, monoclinic ZrO2 and two modifications of ZrW2O8 (tetragonal and cubic). Linear thermal expansion coefficient values of the composites were determined. The difference in experimental and calculated coefficient of thermal expansion values for composites obtained may be attributed to phase transformations, features of the structure, internal stresses due to thermal expansion mismatch, which contribute significantly to thermal expansion of the ceramic composites.

  8. Novel quantum criticality in CeRu2Si2 near absolute zero observed by thermal expansion and magnetostriction.

    Science.gov (United States)

    Yoshida, J; Abe, S; Takahashi, D; Segawa, Y; Komai, Y; Tsujii, H; Matsumoto, K; Suzuki, H; Onuki, Y

    2008-12-19

    We report linear thermal expansion and magnetostriction measurements for CeRu2Si2 in magnetic fields up to 52.6 mT and at temperatures down to 1 mK. At high temperatures, this compound showed Landau-Fermi-liquid behavior: The linear thermal expansion coefficient and the magnetostriction coefficient were proportional to the temperature and magnetic field, respectively. In contrast, a pronounced non-Fermi-liquid effect was found below 50 mK. The negative contribution of thermal expansion and magnetostriction suggests the existence of an additional quantum critical point.

  9. Smoldering combustion hazards of thermal insulation materials

    Energy Technology Data Exchange (ETDEWEB)

    Ohlemiller, T.J.; Rogers, F.E.

    1980-07-01

    Work on the smolder ignitability in cellulosic insulation and on thermal analytical characterization of the oxidation of this material is presented. Thermal analysis (TGA and DSC) shows that both retarded and unretarded cellulosic insulation oxidizes in two overall stages, both of which are exothermic. The second stage (oxidation of the char left as a residue of the first stage) is much more energetic on a unit mass basis than the first. However, kinetics and a sufficient exothermicity make the first stage responsible for ignition in most realistic circumstances. Existing smolder retardants such as boric acid have their major effect on the kinetics of the second oxidation stage and thus produce only a rather small (20/sup 0/C) increase in smolder ignition temperature. Several simplified analogs of attic insulations have been tested to determine the variability of minimum smolder ignition temperature. These employed planar or tubular constant temperature heat sources in a thermal environment quite similar to a realistic attic application. Go/no-go tests provided the borderline (minimum) ignition temperature for each configuration. The wide range (150/sup 0/C) of minimum ignition temperatures confirmed the predominant dependence of smolder ignition on heat flow geometry. Other factors (bulk density, retardants) produced much less effect on ignitability.

  10. Gene expression under thermal stress varies across a geographical range expansion front.

    Science.gov (United States)

    Lancaster, Lesley T; Dudaniec, Rachael Y; Chauhan, Pallavi; Wellenreuther, Maren; Svensson, Erik I; Hansson, Bengt

    2016-03-01

    Many ectothermic species are currently expanding their distributions polewards due to anthropogenic global warming. Molecular genetic mechanisms facilitating range expansion under these conditions are largely unknown, but understanding these could help mitigate expanding pests and disease vectors, or help explain why some species fail to track changing climates. Here, using RNA-seq data, we examine genomewide changes in gene expression under heat and cold stress in the range-expanding damselfly Ischnura elegans in northern Europe. We find that both the number of genes involved and levels of gene expression under heat stress have become attenuated during the expansion, consistent with a previously reported release from selection on heat tolerances as species move polewards. Genes upregulated under cold stress differed between core and edge populations, corroborating previously reported rapid adaptation to cooler climates at the expansion front. Expression of sixty-nine genes exhibited a region x treatment effect; these were primarily upregulated in response to heat stress in core populations but in response to cold stress at the range edge, suggesting that some cellular responses originally adapted to heat stress may switch to cold-stress functionality upon encountering novel thermal selection regimes during range expansion. Transcriptional responses to thermal stress involving heat-shock and neural function genes were largely geographically conserved, while retrotransposon, regulatory, muscle function and defence gene expression patterns were more variable. Flexible mechanisms of cold-stress response and the ability of some genes to shift their function between heat and cold stress might be key mechanisms facilitating rapid poleward expansion in insects. © 2016 John Wiley & Sons Ltd.

  11. Mechanical properties of thermal protection system materials.

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, Robert Douglas; Bronowski, David R.; Lee, Moo Yul; Hofer, John H.

    2005-06-01

    An experimental study was conducted to measure the mechanical properties of the Thermal Protection System (TPS) materials used for the Space Shuttle. Three types of TPS materials (LI-900, LI-2200, and FRCI-12) were tested in 'in-plane' and 'out-of-plane' orientations. Four types of quasi-static mechanical tests (uniaxial tension, uniaxial compression, uniaxial strain, and shear) were performed under low (10{sup -4} to 10{sup -3}/s) and intermediate (1 to 10/s) strain rate conditions. In addition, split Hopkinson pressure bar tests were conducted to obtain the strength of the materials under a relatively higher strain rate ({approx}10{sup 2} to 10{sup 3}/s) condition. In general, TPS materials have higher strength and higher Young's modulus when tested in 'in-plane' than in 'through-the-thickness' orientation under compressive (unconfined and confined) and tensile stress conditions. In both stress conditions, the strength of the material increases as the strain rate increases. The rate of increase in LI-900 is relatively small compared to those for the other two TPS materials tested in this study. But, the Young's modulus appears to be insensitive to the different strain rates applied. The FRCI-12 material, designed to replace the heavier LI-2200, showed higher strengths under tensile and shear stress conditions. But, under a compressive stress condition, LI-2200 showed higher strength than FRCI-12. As far as the modulus is concerned, LI-2200 has higher Young's modulus both in compression and in tension. The shear modulus of FRCI-12 and LI-2200 fell in the same range.

  12. Thermal-Structures and Materials Testing Laboratory

    Science.gov (United States)

    Teate, Anthony A.

    1997-01-01

    Since its inception and successful implementation in 1997 at James Madison University, the Thermal Structures and Materials Testing Laboratory (T-SaMTL) funded by the NASA Langley Research Center is evolving into one of the University's premier and exemplary efforts to increase minority representation in the sciences and mathematics. Serving ten (10) students and faculty directly and almost fifty (50) students indirectly, T-SAMTL, through its recruitment efforts, workshops, mentoring program, tutorial services and its research and computational laboratories has marked the completion of the first year with support from NASA totaling $ 100,000. Beginning as an innovative academic research and mentoring program for underrepresented minority science and mathematics students, the program now boasts a constituency which consists of 50% graduating seniors in the spring of 1998 with 50% planning to go to graduate school. The program's intent is to increase the number of underrepresented minorities who receive doctoral degrees in the sciences by initiating an academically enriched research program aimed at strengthening the academic and self actualization skills of undergraduate students with the potential to pursue doctoral study in the sciences. The program provides financial assistance, academic enrichment, and professional and personal development support for minority students who demonstrate the potential and strong desire to pursue careers in the sciences and mathematics. James Madison University was awarded the first $100,000, in April 1997, by The NASA Langley Research Center for establishment and support of its Thermal Structures and Materials Testing

  13. Ternary alloy material prediction using genetic algorithm and cluster expansion

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chong [Iowa State Univ., Ames, IA (United States)

    2015-12-01

    This thesis summarizes our study on the crystal structures prediction of Fe-V-Si system using genetic algorithm and cluster expansion. Our goal is to explore and look for new stable compounds. We started from the current ten known experimental phases, and calculated formation energies of those compounds using density functional theory (DFT) package, namely, VASP. The convex hull was generated based on the DFT calculations of the experimental known phases. Then we did random search on some metal rich (Fe and V) compositions and found that the lowest energy structures were body centered cube (bcc) underlying lattice, under which we did our computational systematic searches using genetic algorithm and cluster expansion. Among hundreds of the searched compositions, thirteen were selected and DFT formation energies were obtained by VASP. The stability checking of those thirteen compounds was done in reference to the experimental convex hull. We found that the composition, 24-8-16, i.e., Fe3VSi2 is a new stable phase and it can be very inspiring to the future experiments.

  14. Jupiter's North Equatorial Belt expansion and thermal wave activity ahead of Juno's arrival

    Science.gov (United States)

    Fletcher, L. N.; Orton, G. S.; Sinclair, J. A.; Donnelly, P.; Melin, H.; Rogers, J. H.; Greathouse, T. K.; Kasaba, Y.; Fujiyoshi, T.; Sato, T. M.; Fernandes, J.; Irwin, P. G. J.; Giles, R. S.; Simon, A. A.; Wong, M. H.; Vedovato, M.

    2017-07-01

    The dark colors of Jupiter's North Equatorial Belt (NEB, 7-17°N) appeared to expand northward into the neighboring zone in 2015, consistent with a 3-5 year cycle. Inversions of thermal-IR imaging from the Very Large Telescope revealed a moderate warming and reduction of aerosol opacity at the cloud tops at 17-20°N, suggesting subsidence and drying in the expanded sector. Two new thermal waves were identified during this period: (i) an upper tropospheric thermal wave (wave number 16-17, amplitude 2.5 K at 170 mbar) in the mid-NEB that was anticorrelated with haze reflectivity; and (ii) a stratospheric wave (wave number 13-14, amplitude 7.3 K at 5 mbar) at 20-30°N. Both were quasi-stationary, confined to regions of eastward zonal flow, and are morphologically similar to waves observed during previous expansion events.

  15. [The measurement of thermal expansion coefficient of Co-Cr alloy fabricated by selective laser melting].

    Science.gov (United States)

    Tian, Xiao-mei; Zeng, Li; Wei, Bin; Huang, Yi-feng

    2015-12-01

    To investigate the thermal expansion coefficient of different processing parameters upon the Co-Cr alloy prepared by selective laser melting (SLM) technique, in order to provide technical support for clinical application of SLM technology. The heating curve of self-made Co-Cr alloy was protracted from room temperature to 980°C centigrade with DIL402PC thermal analysis instrument, keeping temperature rise rate and cooling rate at 5 K/min, and then the thermal expansion coefficient of 9 groups of Co-Cr alloy was measured from 20°C centigrade to 500°C centigrade and 600°C centigrade. The 9 groups thermal expansion coefficient values of Co-Cr alloy heated from 20°C centigrade to 500°C centigrade were 13.9×10(-6)/K,13.6×10(-6)/K,13.9×10(-6)/K,13.7×10(-6)/K,13.5×10(-6)/K,13.8×10(-6)/K,13.7×10(-6)/K,13.7×10(-6)/K,and 13.9×10(-6)/K, respectively; when heated from 20°C centigrade to 600°C centigrade, they were 14.2×10(-6)/K,13.9×10(-6)/K,13.8×10(-6)/K,14.0×10(-6)/K,14.1×10(-6)/K,14.1×10(-6)/K,13.9×10(-6)/K,14.2×10(-6)/K, and 13.7×10(-6)/K, respectively. The results showed that the Co-Cr alloy has good matching with the VITA VMK 95 porcelain powder and can meet the requirement of clinic use.

  16. Density and anomalous thermal expansion of deeply cooled water confined in mesoporous silica investigated by synchrotron X-ray diffraction.

    Science.gov (United States)

    Liu, Kao-Hsiang; Zhang, Yang; Lee, Jey-Jau; Chen, Chia-Cheng; Yeh, Yi-Qi; Chen, Sow-Hsin; Mou, Chung-Yuan

    2013-08-14

    A synchrotron X-ray diffraction method was used to measure the average density of water (H2O) confined in mesoporous silica materials MCM-41-S-15 and MCM-41-S-24. The average density versus temperature at atmospheric pressure of deeply cooled water is obtained by monitoring the intensity change of the MCM-41-S Bragg peaks, which is directly related to the scattering length density contrast between the silica matrix and the confined water. Within MCM-41-S-15, the pore size is small enough to prevent the crystallization at least down to 130 K. Besides the well-known density maximum at 277 K, a density minimum is observed at 200 K for the confined water, below which a regular thermal expansion behavior is restored. Within MCM-41-S-24 of larger pore size, water freezes at 220.5 K. The average water/ice density measurement in MCM-41-S-24 validated the diffraction method. The anomalous thermal expansion coefficient (αp) is calculated. The temperature at which the αp reaches maximum is found to be pore size independent, but the peak height of the αp maximum is linearly dependent on the pore size. The obtained data are critical to verify available theoretical and computational models of water.

  17. Effect of space exposure of some epoxy matrix composites on their thermal expansion and mechanical properties (A0138-8)

    Science.gov (United States)

    Jabs, Heinrich

    1992-01-01

    Assessments of the behavior of the carbon/epoxy composites in space conditions are described. After an exposure of five years, the mechanical characteristics and the coefficient of thermal expansion are measured and compared to reference values.

  18. Thermal-vacuum facility with in-situ mechanical loading. [for testing space construction materials

    Science.gov (United States)

    Tennyson, R. C.; Hansen, J. S.; Holzer, R. P.; Uffen, B.; Mabson, G.

    1978-01-01

    The paper describes a thermal-vacuum space simulator used to assess property changes of fiber-reinforced polymer composite systems. The facility can achieve a vacuum of approximately .0000001 torr with temperatures ranging from -200 to +300 F. Some preliminary experimental results are presented for materials subjected to thermal loading up to 200 F. The tests conducted include the evaluation of matrix modulus and strength, coefficients of thermal expansion, and fracture toughness. Though the experimental program is at an early stage, the data appear to indicate that these parameters are influenced by hard vacuum.

  19. Material Based Structure Design: Numerical Analysis Thermodynamic Response of Thermal Pyrolytic Graphite /Al Sandwich Composites

    Science.gov (United States)

    Wang, Junxia; Yan, Shilin; Yu, Dingshan

    2016-12-01

    Amine-grafted multiwalled carbon nanotubes (MWCNTs) based thermally conductive adhesive (TCA) was studied in the previous paper and applied here in thermal pyrolytic graphite (TPG)/Al radiator due to its high thermal conductivity, toughness and cohesiveness. In this paper, in an attempt to confirm the application of TCA to TPG/Al sandwich radiator, the thermodynamic response in TPG/Al sandwich composites associated with key material properties and structural design was investigated using finite element simulation with commercial available ANSYS software. The induced thermal stress in TCA layer is substantial due to the thermal expansion mismatch between Al plate and TPG. The maximum thermal stress is located near the edge of TCA layer with the von Mises stress value of 4.02 MPa and the shear stress value of 1.66 MPa. The reasonable adjustment of physical-mechanical properties including thermal conductivity, thermal expansion, Young,s modulus and the thickness of TCA layer, Al plate and TPG are beneficial for reducing the temperature of the top surface of the upper skin and their effects on the reduction of thermal structural response in some ways. These findings will highlight the structural optimization of TPG/Al radiator for future application.

  20. Thermal properties of hemp fibre non-woven materials

    Science.gov (United States)

    Freivalde, Liga; Kukle, Silvija; Russell, Stephen

    2013-12-01

    This review considers the thermal properties analysis of hemp fiber non-woven materials made by three different manufacturing technologies - thermal bonding, needle-punching and hydro-entanglement. For non-wovens development two hemp fibers cultivars grown in Latvia were used - Purini and Bialobrzeskie. Thermal resistance, conductivity and the effects of several parameters on thermal performance are revised.

  1. Reactive thermal waves in energetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Hill, Larry G [Los Alamos National Laboratory

    2009-01-01

    Reactive thermal waves (RTWs) arise in several energetic material applications, including self-propagating high-temperature synthesis (SHS), high explosive cookoff, and the detonation of heterogeneous explosives. In this paper I exmaine ideal RTWs, by which I mean that (1) material motion is neglected, (2) the state dependence of reaction is Arrhenius in the temperature, and (3) the reaction rate is modulated by an arbitrary mass-fraction-based reaction progress function. Numerical simulations demonstrate that one's natural intuition, which is based mainly upon experience with inert materials and which leads one to expect diffusion processes to become relatively slow after a short time period, is invalid for high energy, state-sensitive reactive systems. Instead, theory predicts that RTWs can propagate at very high speeds. This result agrees with estimates for detonating heterogeneous explosives, which indicate that RTWs must spread from hot-spot nucleation sites at rates comparable to the detonation speed in order to produce experimentally-observed reaction zone thicknesses. Using dimensionless scaling and further invoking the high activation energy approximation, I obtain an analytic formula for the steady plane RTW speed from numerical calculations. I then compute the RTW speed for real explosives, and discuss aspects of their behavior.

  2. Anharmonic phonon quasiparticle theory of zero-point and thermal shifts in insulators: Heat capacity, bulk modulus, and thermal expansion

    Science.gov (United States)

    Allen, Philip B.

    2015-08-01

    The quasiharmonic (QH) approximation uses harmonic vibrational frequencies ωQ ,H(V ) computed at volumes V near V0 where the Born-Oppenheimer (BO) energy Eel(V ) is minimum. When this is used in the harmonic free energy, QH approximation gives a good zeroth order theory of thermal expansion and first-order theory of bulk modulus, where nth-order means smaller than the leading term by ɛn, where ɛ =ℏ ωvib/Eel or kBT /Eel , and Eel is an electronic energy scale, typically 2 to 10 eV. Experiment often shows evidence for next-order corrections. When such corrections are needed, anharmonic interactions must be included. The most accessible measure of anharmonicity is the quasiparticle (QP) energy ωQ(V ,T ) seen experimentally by vibrational spectroscopy. However, this cannot just be inserted into the harmonic free energy FH. In this paper, a free energy is found that corrects the double-counting of anharmonic interactions that is made when F is approximated by FH( ωQ(V ,T ) ) . The term "QP thermodynamics" is used for this way of treating anharmonicity. It enables (n +1 ) -order corrections if QH theory is accurate to order n . This procedure is used to give corrections to the specific heat and volume thermal expansion. The QH formulas for isothermal (BT) and adiabatic (BS) bulk moduli are clarified, and the route to higher-order corrections is indicated.

  3. Zirconium tungstate/epoxy nanocomposites: effect of nanoparticle morphology and negative thermal expansivity.

    Science.gov (United States)

    Wu, Hongchao; Rogalski, Mark; Kessler, Michael R

    2013-10-09

    The ability to tailor the coefficient of thermal expansion (CTE) of a polymer is essential for mitigating thermal residual stress and reducing microcracks caused by CTE mismatch of different components in electronic applications. This work studies the effect of morphology and thermal expansivity of zirconium tungstate nanoparticles on the rheological, thermo-mechanical, dynamic-mechanical, and dielectric properties of ZrW2O8/epoxy nanocomposites. Three types of ZrW2O8 nanoparticles were synthesized under different hydrothermal conditions and their distinct properties were characterized, including morphology, particle size, aspect ratio, surface area, and CTE. Nanoparticles with a smaller particle size and larger surface area led to a more significant reduction in gel-time and glass transition temperature of the epoxy nanocomposites, while a higher initial viscosity and significant shear thinning behavior was found in prepolymer suspensions containing ZrW2O8 with larger particle sizes and aspect ratios. The thermo- and dynamic-mechanical properties of epoxy-based nanocomposites improved with increasing loadings of the three types of ZrW2O8 nanoparticles. In addition, the introduced ZrW2O8 nanoparticles did not negatively affect the dielectric constant or the breakdown strength of the epoxy resin, suggesting potential applications of ZrW2O8/epoxy nanocomposites in the microelectronic insulation industry.

  4. Thermal expansion of solutions of deuteromethane in fullerite C60 at low temperatures. Isotopic effect

    Science.gov (United States)

    Dolbin, A. V.; Vinnikov, N. A.; Gavrilko, V. G.; Esel'Son, V. B.; Manzheliĭ, V. G.; Gadd, G. E.; Moricca, S.; Cassidy, D.; Sundqvist, B.

    2009-03-01

    The thermal expansion of CD4 solutions in the orientational glass C60 with molar concentration of deuteromethane 20 and 50% has been investigated in the temperature range 2.5-23K. The orientational glass CD4-C60 undergoes a first-order phase transition in the temperature interval 4.5-55K. This transition is manifested as hysteresis of the linear thermal expansion coefficient α as well as maxima in the temperature dependences α(T ) and τ1(T), where τ1 is the characteristic thermalization time of the experimental samples. The characteristic re-orientation times of the C60 molecules and the characteristic phase transformations occurring in the experimental solutions are determined. The results of the present study are compared with the results of a similar study of the solution CH4-C60. It is concluded that tunneling rotation of the CH4 and CD4 molecules occupying interstitial positions in the fullerite C60 lattice occurs.

  5. Novel technologies and materials for thermal management

    CERN Document Server

    Verlaat, B; The ATLAS collaboration

    2013-01-01

    Efficient thermal engineering solutions for the entire heat load path from source to sink (sensor to cooling plant) are crucial for the future silicon detectors, more than even before. The particularly demanding cooling requirements are coming from the extreme radiation environment, causing high leakage current in the silicon sensors, as well as from the high power dissipated in the front-end electronics, featuring enhanced functionality and high channel count. The need to carry out dedicated R&D has encouraged increased cooperation among the HEP experiments, to identify state-of-the-art materials and construction principles that can help fulfilling the requirements, and to develop more efficient active cooling systems like CO2 cooling, which is now widely accepted as an excellent detector cooling technology.

  6. Thermal energy storage in phase change material

    Science.gov (United States)

    White, P.; Buchlin, J. M.

    1982-03-01

    The present study deals with an experimental investigation of low temperature thermal storage based on macroencapsulation of Phase Change Material (PCM). The storage performance capabilities of capsule bed, tube bank and tubular single-pass heat exchanger are compared. The tests are conducted on the VKI Solar Utility Network (SUN) which is a closed loop facility designed to study air heating systems. An original data acquisition chain based on two conversing microprocessors is developed to carry out mass flow, pressure drop and temperature measurements. The experimental results are interpreted on the basis of comparison with numerical predictions and they allow to draw the following conclusions. Each type of matrix has its own range of operation for practical application but from a heat transfer standpoint, the PCM capsule packing unit is strongly recommended. It is suggested to extend this investigation to the effect of Reynolds number to find optimum range for thermomechanical efficiency.

  7. Integrated Thermal Structures and Materials Overview

    Science.gov (United States)

    Jensen, Brian

    2000-01-01

    The accomplishments of the project this viewgraph presentation summarizes (integrated thermal structures and materials) include the following: (1) Langley Research Center prepared five resins with Tgs as high as 625 F, less than 1% volatiles, moderate toughness, and low melt viscosity and sent to Boeing or Lockheed Martin; (2) Glenn Research Center prepared four resins with Tgs as high as 700 F, less than 10% volatiles, and low melt viscosity and sent to Boeing; (3) Boeing successfully fabricated 2'x2'x36 ply composites by resin infusion of stitched preforms from all NASA supplied resins; and (4) Lockheed Martin successfully fabricated 13"x14"x16 ply composites by resin transfer molding from all NASA supplied resins.

  8. Thermally stimulated photoluminescence in disordered organic materials

    Science.gov (United States)

    Kadashchuk, A.; Skryshevskii, Yu.; Vakhnin, A.; Ostapenko, N.; Arkhipov, V. I.; Emelianova, E. V.; Bässler, H.

    2001-03-01

    An analytical model of thermally stimulated photoluminescence (TSPL) in a random hopping system is formulated. The model is based on the assumption that TSPL originates from radiative recombination of sufficiently long geminate pairs of charge carriers created during photoexcitation of the sample at a low (helium) temperature. Since TSPL measurements are normally performed after some dwell time, the initial energy distribution of localized carriers is formed after low-temperature hopping relaxation of photogenerated carriers and, therefore, the first thermally assisted jumps of relaxed carriers are considered as the rate-limiting steps in the present model. Predictions of the model are found to be in good quantitative agreement with experimental data on molecularly doped polymers if a double-peak energy distribution of localized states is invoked for these materials. Comparing theoretical results with existing experimental data also reveals a somewhat slower low-temperature energy relaxation of charge carriers in these materials than predicted by the conventional theory of carrier random walk in random hopping systems. TSPL was also measured in a methyl-substituted ladder-type poly(paraphenylene). Both fluorescence and phosphorescence were found to contribute to the TSPL spectrum whereas only the latter was observed in the long isothermal afterglow following photoexcitation of the sample at helium temperature. This implies that the binding energy of a short off-chain geminate pair is higher than the binding energy of a singlet excitation but lower than that of a triplet exciton. The experimentally observed TSPL curve reveals an unusually low-temperature peak with the maximum at around 40 K. Interpretation of the experiment based on the hopping model of TSPL yields an effective density of states width of 0.055 eV, in good agreement with the value of 0.050 eV estimated from transport measurements.

  9. Composite Materials for Thermal Energy Storage: Enhancing Performance through Microstructures

    Science.gov (United States)

    Ge, Zhiwei; Ye, Feng; Ding, Yulong

    2014-01-01

    Chemical incompatibility and low thermal conductivity issues of molten-salt-based thermal energy storage materials can be addressed by using microstructured composites. Using a eutectic mixture of lithium and sodium carbonates as molten salt, magnesium oxide as supporting material, and graphite as thermal conductivity enhancer, the microstructural development, chemical compatibility, thermal stability, thermal conductivity, and thermal energy storage performance of composite materials are investigated. The ceramic supporting material is essential for preventing salt leakage and hence provides a solution to the chemical incompatibility issue. The use of graphite gives a significant enhancement on the thermal conductivity of the composite. Analyses suggest that the experimentally observed microstructural development of the composite is associated with the wettability of the salt on the ceramic substrate and that on the thermal conduction enhancer. PMID:24591286

  10. FEM Simulation of the Effect of Coefficient of Thermal Expansion and Heat Capacity on Prediction of Residual Stresses of Compression Molded Glass Lenses

    Science.gov (United States)

    Tao, Bo; Yuan, Ye

    2017-11-01

    In this research, the effects of the coefficient of thermal expansion (CTE) and heat capacity on the prediction of residual stresses in BK7 compression molded glass lenses were studied. Three different groups of CTE and two different kinds of heat capacity, which are constant and proportional to temperature, were chosen to investigate the impacts of residual stresses. The simulation results show a big difference and suggest that the properties of glass materials determine the residual stresses and should be measured carefully.

  11. Frustrated Soft Modes and Negative Thermal Expansion in ZrW2O8

    Science.gov (United States)

    Cao, D.; Bridges, F.; Kowach, G. R.; Ramirez, A. P.

    2002-11-01

    Negative thermal expansion (NTE) in cubic ZrW2O8 has generated much interest due to its large, isotropic, and temperature independent behavior. Here, x-ray absorption fine structure data are presented for various atom pairs, providing evidence that the low-energy modes causing NTE correspond to the correlated vibrations of a WO4 tetrahedron and its three nearest ZrO6 octahedra. This involves translations of the WO4 as a rigid unit along each of the four axes. The interconnectivity of these modes prevents an anisotropic soft mode from developing, a new geometrical phenomenon that we call the ``frustrated soft mode.''

  12. Effect of Inclusion Morphology on the Coefficient of Thermal Expansion in Filled Epoxy Matrix (Preprint)

    Science.gov (United States)

    2006-04-01

    Aeronautics and Astronautics 6 F. Effect of Inclusion Shape on Effective CTE There has been tremendous interest in Zirconium Tungstate ( ZrW2O8 ), a ceramic...with a strongly negative coefficient of thermal expansion (CTE). In contrast to most other ceramics exhibiting negative CTE, the CTE of ZrW2O8 is...unusual properties suggest the incorporation of ZrW2O8 into a polymeric matrix, to create a composite with very low CTE. The objective of the

  13. Control of biaxial strain in single-layer Molybdenite using local thermal expansion of the substrate

    OpenAIRE

    Plechinger, G.; Castellanos-Gomez, A.; Buscema, M.; van der Zant, H. S. J.; Steele, G. A.; Kuc, A.; Heine, T; Schüller, C.; Korn, T.

    2015-01-01

    Single-layer MoS2 is a direct-gap semiconductor whose electronic band structure strongly depends on the strain applied to its crystal lattice. While uniaxial strain can be easily applied in a controlled way, e.g., by bending of a flexible substrate with the atomically thin MoS2 layer on top, experimental realization of biaxial strain is more challenging. Here, we exploit the large mismatch between the thermal expansion coefficients of MoS2 and a silicone-based substrate to apply a controllabl...

  14. Solid state phase change materials for thermal energy storage in passive solar heated buildings

    Science.gov (United States)

    Benson, D. K.; Christensen, C.

    1983-11-01

    A set of solid state phase change materials was evaluated for possible use in passive solar thermal energy storage systems. The most promising materials are organic solid solutions of pentaerythritol, pentaglycerine and neopentyl glycol. Solid solution mixtures of these compounds can be tailored so that they exhibit solid-to-solid phase transformations at any desired temperature within the range from less than 25 deg to 188 deg. Thermophysical properties such as thermal conductivity, density and volumetric expansion were measured. Computer simulations were used to predict the performance of various Trombe wall designs incorporating solid state phase change materials. Optimum performance was found to be sensitive to the choice of phase change temperatures and to the thermal conductivity of the phase change material. A molecular mechanism of the solid state phase transition is proposed and supported by infrared spectroscopic evidence.

  15. Higher gradient expansion for linear isotropic peridynamic materials

    Czech Academy of Sciences Publication Activity Database

    Šilhavý, Miroslav

    2017-01-01

    Roč. 22, č. 6 (2017), s. 1483-1493 ISSN 1081-2865 Institutional support: RVO:67985840 Keywords : peridynamics * higher-grade theories * non-local elastic-material model * representation theorems for isotropic functions Subject RIV: BA - General Mathematics Impact factor: 2.953, year: 2016 http://journals.sagepub.com/doi/10.1177/1081286516637235

  16. Optical temperature sensor and thermal expansion measurement using a femtosecond micromachined grating in 6H-SiC.

    Science.gov (United States)

    DesAutels, G Logan; Powers, Peter; Brewer, Chris; Walker, Mark; Burky, Mark; Anderson, Gregg

    2008-07-20

    An optical temperature sensor was created using a femtosecond micromachined diffraction grating inside transparent bulk 6H-SiC, and to the best of our knowledge, this is a novel technique of measuring temperature. Other methods of measuring temperature using fiber Bragg gratings have been devised by other groups such as Zhang and Kahrizi [in MEMS, NANO, and Smart Systems (IEEE, 2005)]. This temperature sensor was, to the best of our knowledge, also used for a novel method of measuring the linear and nonlinear coefficients of the thermal expansion of transparent and nontransparent materials by means of the grating first-order diffracted beam. Furthermore the coefficient of thermal expansion of 6H-SiC was measured using this new technique. A He-Ne laser beam was used with the SiC grating to produce a first-order diffracted beam where the change in deflection height was measured as a function of temperature. The grating was micromachined with a 20 microm spacing and has dimensions of approximately 500 microm x 500 microm (l x w) and is roughly 0.5 microm deep into the 6H-SiC bulk. A minimum temperature of 26.7 degrees C and a maximum temperature of 399 degrees C were measured, which gives a DeltaT of 372.3 degrees C. The sensitivity of the technique is DeltaT=5 degrees C. A maximum deflection angle of 1.81 degrees was measured in the first-order diffracted beam. The trend of the deflection with increasing temperature is a nonlinear polynomial of the second-order. This optical SiC thermal sensor has many high-temperature electronic applications such as aircraft turbine and gas tank monitoring for commercial and military applications.

  17. Negative coefficient of thermal expansion in (epoxy resin)/(zirconium tungstate) nanocomposites

    Science.gov (United States)

    See, Erich; Kochergin, Vladimir; Neely, Lauren; Zayetnikov, Madrakhim; Ciovati, Gianluigi; Robinson, Hans

    2011-10-01

    The α-phase of zirconium tungstate (ZrW2O8) has the remarkable property that its coefficient of thermal expansion (CTE) takes on a nearly constant negative value throughout its entire range of thermal stability (0 -- 1050 K). Composites of ZrW2O8 nanoparticles and polymer resins have a reduced CTE compared to the pure polymer, but previous work has been restricted to measurements near room temperature. We show that the CTE of such composites can take on increasingly negative values as the temperature is lowered to cryogenic values. We used this phenomenon to fabricate a metal-free all-optical cryogenic temperature sensor by coating a fiber optic Bragg grating with the nanocomposite. This sensor has a sensitivity at 2 K that is at least six time better than any previous fiber-optic temperature sensor at this temperature.

  18. Negative Thermal Expansion in ZrW2O8: Mechanisms, Rigid Unit Modes, and Neutron Total Scattering

    Science.gov (United States)

    Tucker, Matthew G.; Goodwin, Andrew L.; Dove, Martin T.; Keen, David A.; Wells, Stephen A.; Evans, John S. O.

    2005-12-01

    The local structure of the low-temperature ordered phase of the negative thermal expansion (NTE) material ZrW2O8 has been investigated by reverse Monte Carlo (RMC) modeling of neutron total scattering data. We obtain, for the first time, quantitative measurements of the extent to which the WO4 and ZrO6 polyhedra move as rigid units, and we show that these values are consistent with the predictions of rigid unit mode theory. We suggest that rigid unit modes are associated with the NTE. Our results do not support a recent interpretation of x-ray-absorption fine structure spectroscopy data in terms of a larger rigid structural component involving the Zr-O-W linkage.

  19. Pulse thermal processing of functional materials using directed plasma arc

    Science.gov (United States)

    Ott, Ronald D.; Blue, Craig A.; Dudney, Nancy J.; Harper, David C.

    2007-05-22

    A method of thermally processing a material includes exposing the material to at least one pulse of infrared light emitted from a directed plasma arc to thermally process the material, the pulse having a duration of no more than 10 s.

  20. Use of steel slag as a granular material: volume expansion prediction and usability criteria.

    Science.gov (United States)

    Wang, George; Wang, Yuhong; Gao, Zhili

    2010-12-15

    The theoretical equation for predicting volume expansion of steel slag is deduced based on both chemical reaction and physical changes of free lime in steel slag during the hydration process. Laboratory volume expansion testing is conducted to compare the results with the theoretical volume expansion. It is proved that they correlated well. It is furthermore experimentally proved that certain volume expansion of steel slag can be absorbed internally by the void volume in bulk steel slag under external surcharge weight making the apparent volume expansion equal zero. The minimum (lowest) absorbable void volume is approximately 7.5%, which is unrelated to the free lime content. A usability criterion is then developed based on the volume expansion of steel slag (%) and the minimum percentage of the volume that can take the volume expansion of steel slag (%). Eventually the criterion (relationship) is established based on the free lime content, the specific gravity and bulk relative gravity of a specific steel slag sample. The criteria can be used as guidance and specification for the use of steel slag and other expansion-prone nonferrous slags, copper, nickel for instance as a granular material in highway construction. Copyright © 2010 Elsevier B.V. All rights reserved.

  1. Internal Thermal Control System Hose Heat Transfer Fluid Thermal Expansion Evaluation Test Report

    Science.gov (United States)

    Wieland, P. O.; Hawk, H. D.

    2001-01-01

    During assembly of the International Space Station, the Internal Thermal Control Systems in adjacent modules are connected by jumper hoses referred to as integrated hose assemblies (IHAs). A test of an IHA has been performed at the Marshall Space Flight Center to determine whether the pressure in an IHA filled with heat transfer fluid would exceed the maximum design pressure when subjected to elevated temperatures (up to 60 C (140 F)) that may be experienced during storage or transportation. The results of the test show that the pressure in the IHA remains below 227 kPa (33 psia) (well below the 689 kPa (100 psia) maximum design pressure) even at a temperature of 71 C (160 F), with no indication of leakage or damage to the hose. Therefore, based on the results of this test, the IHA can safely be filled with coolant prior to launch. The test and results are documented in this Technical Memorandum.

  2. Effective thermal conductivity of a thin composite material

    Energy Technology Data Exchange (ETDEWEB)

    Phelan, P.E. [Arizona State Univ., Tempe, AZ (United States). Dept. of Mechanical and Aerospace Engineering; Niemann, R.C. [Argonne National Lab., IL (United States)

    1996-12-31

    The thermal conductivity of a randomly oriented composite material is modeled using a probabilistic approach in order to determine if a size effect exists for the thermal conductivity at small composite thickness. The numerical scheme employs a random number generator to position the filler elements, which have a relatively high thermal conductivity, within a matrix having a relatively low thermal conductivity. Results indicate that, below some threshold thickness, the composite thermal conductivity increases with decreasing thickness, while above the threshold the thermal conductivity is independent of thickness. The threshold thickness increases for increasing filler fraction and increasing k{sub f}/k{sub m}, the ratio between filler and matrix thermal conductivities.

  3. Glass-Transition Temperature Profile Measured in a Wood Cell Wall Using Scanning Thermal Expansion Microscope (SThEM)

    Science.gov (United States)

    Antoniow, J. S.; Maigret, J.-E.; Jensen, C.; Trannoy, N.; Chirtoc, M.; Beaugrand, J.

    2012-11-01

    This study aims to assess the in situ spatial distribution of glass-transition temperatures ( T g) of the main lignocellulosic biopolymers of plant cell walls. Studies are conducted using scanning thermal expansion microscopy to analyze the cross-section of the cell wall of poplar. The surface topography is mapped over a range of probe-tip temperatures to capture the change of thermal expansion on the sample surface versus temperature. For different temperature values chosen between 20 °C and 250 °C, several quantitative mappings were made to show the spatial variation of the thermal expansion. As the glass transition affects the thermal expansion coefficient and elastic modulus considerably, the same data line of each topography image was extracted to identify specific thermal events in their topographic evolution as a function of temperature. In particular, it is shown that the thermal expansion of the contact surface is not uniform across the cell wall and a profile of the glass-transition temperature could thus be evidenced and quantified corresponding to the mobility of lignocellulosic polymers having a role in the organization of the cell wall structures.

  4. Cookoff Response of PBXN-109: Material Characterization and ALE3D Thermal Predictions

    Energy Technology Data Exchange (ETDEWEB)

    McClelland, M A; Tran, T D; Cunningham, B J; Weese, R K; Maienschein, J L

    2001-05-29

    Materials properties measurements are made for the RDX-based explosive, PBXN-109, and initial ALE3D model predictions are given for the cookoff temperature in a U.S. Navy test. This work is part of an effort in the U.S. Navy and Department of Energy (DOE) laboratories to understand the thermal explosion behavior of this material. Benchmark cookoff experiments are being performed by the U.S. Navy to validate DOE materials models and computer codes. The ALE3D computer code can model the coupled thermal, mechanical, and chemical behavior of heating, ignition, and explosion in cookoff tests. In our application, a standard three-step step model is selected for the chemical kinetics. The strength behavior of the solid constituents is represented by a Steinberg-Guinan model while polynomial and gamma-law expressions are used for the Equation Of State (EOS) for the solid and gas species, respectively. Materials characterization measurements are given for thermal expansion, heat capacity, shear modulus, bulk modulus, and One-Dimensional-Time-to-Explosion (ODTX). These measurements and those of the other project participants are used to determine parameters in the ALE3D chemical, mechanical, and thermal models. Time-dependent, two-dimensional results are given for the temperature and material expansion. The results show predicted cookoff temperatures slightly higher than the measured values.

  5. Cookoff Response of PBXN-109: Material Characterization and ALE3D Thermal Predictions

    Energy Technology Data Exchange (ETDEWEB)

    McClelland, M A; Tran, T D; Cunningham, B J; Weese, R K; Maienschein, J L

    2001-08-21

    Materials properties measurements are made for the RDX-based explosive, PBXN-109, and initial ALE3D model predictions are given for the cookoff temperature in a U.S. Navy test. This work is part of an effort in the U.S. Navy and Department of Energy (DOE) laboratories to understand the thermal explosion behavior of this material. Benchmark cookoff experiments are being performed by the U.S. Navy to validate DOE materials models and computer codes. The ALE3D computer code can model the coupled thermal, mechanical, and chemical behavior of heating, ignition, and explosion in cookoff tests. In our application, a standard three-step step model is selected for the chemical kinetics. The strength behavior of the solid constituents is represented by a Steinberg-Guinan model while polynomial and gamma-law expressions are used for the Equation Of State (EOS) for the solid and gas species, respectively. Materials characterization measurements are given for thermal expansion, heat capacity, shear modulus, bulk modulus, and One-Dimensional-Time-to-Explosion (ODTX). These measurements and those of the other project participants are used to determine parameters in the ALE3D chemical, mechanical, and thermal models. Time-dependent, two-dimensional results are given for the temperature and material expansion. The results show predicted cookoff temperatures slightly higher than the measured values.

  6. Bond thermal expansion and effective pair potential in crystals: the case of cadmium selenide.

    Science.gov (United States)

    Sanson, Andrea

    2011-08-10

    The local dynamics of cadmium selenide (CdSe) with wurtzite structure has been investigated by molecular dynamics simulations, using a many-body Tersoff potential. The radial distribution functions (i.e., the effective pair potentials) of the first seven coordination shells have been determined as a function of temperature, as well as their parallel and perpendicular mean-square relative atomic displacements. The bond thermal expansion of the first coordination shell is mainly due to the asymmetry of the effective pair potential. In contrast, the bond thermal expansion of the outer shells is mostly due to a rigid shift of the effective pair potential. This behavior, recently observed also in simple cubic monoatomic crystals, can be generalized and related to the correlation of atomic motion. Finally, a shift toward lower values of the first Se-Cd effective pair potential has been observed when increasing the temperature, confirming previous findings by extended x-ray absorption fine-structure measurements. Differently from superionic conductors like AgI and CuBr, in which this anomalous negative shift was tentatively explained by cluster distortion and cation diffusion, the negative shift of CdSe is related to the peculiar properties of the crystalline potential.

  7. Anomalous thermal expansion in rare-earth gallium perovskites: a comprehensive powder diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Senyshyn, A; Trots, D M; Engel, J M; Ehrenberg, H; Fuess, H [Institute for Materials Science, Darmstadt University of Technology, D-64287 Darmstadt (Germany); Vasylechko, L [Lviv Polytechnic National University, 12 Bandera Street, 79013 Lviv (Ukraine); Hansen, T [Institut Max von Laue-Paul Langevin, 38042 Grenoble Cedex 9 (France); Berkowski, M [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw (Poland)

    2009-04-08

    Crystal structures of rare-earth gallium perovskites LaGaO{sub 3}, PrGaO{sub 3}, NdGaO{sub 3} and Pr{sub 1-x}Nd{sub x}GaO{sub 3} (x = 0.25, 0.50, 0.75) solid solutions were investigated in the temperature range 12-300 K by high-resolution powder diffraction using synchrotron or neutron radiation. The previously reported negative thermal expansion in the b direction of the PrGaO{sub 3} lattice has been found to be persistent in Pr{sub 1-x}Nd{sub x}GaO{sub 3} solid solutions and its magnitude has been revealed as proportional to the amount of praseodymium. Evaluation of the obtained temperature evolution of cell dimensions indicated a weak anomalous behaviour of the b lattice parameter in NdGaO{sub 3}, and its origin is supposed to be the same as in PrGaO{sub 3}, i.e. a coupling of the crystal electric field levels with phonon excitations of about 23-25 meV energy. The performed bond length analysis revealed an anomalous behaviour of both LnO{sub 12} (Ln-rare-earth) and GaO{sub 6} coordination polyhedra, which can be a structural manifestation of anomalous thermal expansion in the considered compounds.

  8. TEV—A Program for the Determination of the Thermal Expansion Tensor from Diffraction Data

    Directory of Open Access Journals (Sweden)

    Thomas Langreiter

    2015-02-01

    Full Text Available TEV (Thermal Expansion Visualizing is a user-friendly program for the calculation of the thermal expansion tensor αij from diffraction data. Unit cell parameters determined from temperature dependent data collections can be provided as input. An intuitive graphical user interface enables fitting of the evolution of individual lattice parameters to polynomials up to fifth order. Alternatively, polynomial representations obtained from other fitting programs or from the literature can be entered. The polynomials and their derivatives are employed for the calculation of the tensor components of αij in the infinitesimal limit. The tensor components, eigenvalues, eigenvectors and their angles with the crystallographic axes can be evaluated for individual temperatures or for temperature ranges. Values of the tensor in directions parallel to either [uvw]’s of the crystal lattice or vectors (hkl of reciprocal space can be calculated. Finally, the 3-D representation surface for the second rank tensor and pre- or user-defined 2-D sections can be plotted and saved in a bitmap format. TEV is written in JAVA. The distribution contains an EXE-file for Windows users and a system independent JAR-file for running the software under Linux and Mac OS X. The program can be downloaded from the following link: http://www.uibk.ac.at/mineralogie/downloads/TEV.html (Institute of Mineralogy and Petrography, University of Innsbruck, Innsbruck, Austria

  9. Thermal expansion and decomposition of jarosite: a high-temperature neutron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Hongwu [Los Alamos National Laboratory; Zhao, Yusheng [Los Alamos National Laboratory; Vogel, Sven C [Los Alamos National Laboratory; Hickmott, Donald D [Los Alamos National Laboratory; Daemen, Luke L [Los Alamos National Laboratory; Hartl, Monika A [Los Alamos National Laboratory

    2009-01-01

    The structure of deuterated jarosite, KFe{sub 3}(SO{sub 4}){sub 2}(OD){sub 6}, was investigated using time-of-flight neutron diffraction up to its dehydroxylation temperature. Rietveld analysis reveals that with increasing temperature, its c dimension expands at a rate {approx}10 times greater than that for a. This anisotropy of thermal expansion is due to rapid increase in the thickness of the (001) sheet of [Fe(O,OH){sub 6}] octahedra and [SO{sub 4}] tetrahedra with increasing temperature. Fitting of the measured cell volumes yields a coefficient of thermal expansion, a = a{sub 0} + a{sub 1} T, where a{sub 0} = 1.01 x 10{sup -4} K{sup -1} and a{sub 1} = -1.15 x 10{sup -7} K{sup -2}. On heating, the hydrogen bonds, O1{hor_ellipsis}D-O3, through which the (001) octahedral-tetrahedral sheets are held together, become weakened, as reflected by an increase in the D{hor_ellipsis}O1 distance and a concomitant decrease in the O3-D distance with increasing temperature. On further heating to 575 K, jarosite starts to decompose into nanocrystalline yavapaiite and hematite (as well as water vapor), a direct result of the breaking of the hydrogen bonds that hold the jarosite structure together.

  10. Influence of soil consolidation and thermal expansion effects on height and gravity variations

    Science.gov (United States)

    Romagnoli, C.; Zerbini, S.; Lago, L.; Richter, B.; Simon, D.; Domenichini, F.; Elmi, C.; Ghirotti, M.

    2003-07-01

    The daily GPS height series of the Medicina station were analyzed for the period July 1996-September 2001. The station is located in the middle Po Plain on fine-grained alluvial deposits. A seasonal oscillation in the order of 18 mm (peak-to-peak amplitude) is present in the data. This crustal deformation has been modeled by including variations in the atmospheric, oceanic and hydrologic mass. The vertical positions can also be affected significantly by soil consolidation. Geotechnical parameters derived by in situ tests and laboratory analyses of the clayey soil collected at Medicina allowed the estimate of the soil settlement relevant to the seasonal oscillation of the surficial water table. Thermal expansion of the geodetic monument has to be taken into account in the case of high-precision vertical positioning. In this work models both for the soil consolidation and the thermal expansion effects are provided. The continuous gravity observations collected at Medicina by means of a superconducting gravimeter also exhibit a marked seasonal oscillation, which has been interpreted as the sum of loading and Newtonian attraction effects, as well as of the contribution due to soil consolidation. Especially the study concerning the soil consolidation effect has allowed a better insight on the seasonal vertical movements occurring at the Medicina station by providing quantitative information on soil behavior due to change of effective pressures. The results can be applied to those stations characterized by similar fine-grained soils and surficial hydrogeology.

  11. Bond thermal expansion and effective pair potential in crystals: the case of cadmium selenide

    Energy Technology Data Exchange (ETDEWEB)

    Sanson, Andrea, E-mail: andrea.sanson@unipd.it [Dipartimento di Fisica, Universita di Padova, Via Marzolo 8, I-35131 Padova (Italy)

    2011-08-10

    The local dynamics of cadmium selenide (CdSe) with wurtzite structure has been investigated by molecular dynamics simulations, using a many-body Tersoff potential. The radial distribution functions (i.e., the effective pair potentials) of the first seven coordination shells have been determined as a function of temperature, as well as their parallel and perpendicular mean-square relative atomic displacements. The bond thermal expansion of the first coordination shell is mainly due to the asymmetry of the effective pair potential. In contrast, the bond thermal expansion of the outer shells is mostly due to a rigid shift of the effective pair potential. This behavior, recently observed also in simple cubic monoatomic crystals, can be generalized and related to the correlation of atomic motion. Finally, a shift toward lower values of the first Se-Cd effective pair potential has been observed when increasing the temperature, confirming previous findings by extended x-ray absorption fine-structure measurements. Differently from superionic conductors like AgI and CuBr, in which this anomalous negative shift was tentatively explained by cluster distortion and cation diffusion, the negative shift of CdSe is related to the peculiar properties of the crystalline potential.

  12. The Conductive Thermal Control Material Systems for Space Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal is submitted to develop and demonstrate the feasibility of processing the space environment stable, multifunctional thermal control material system...

  13. Matrix-filler interfaces and physical properties of metal matrix composites with negative thermal expansion manganese nitride

    Science.gov (United States)

    Takenaka, Koshi; Kuzuoka, Kota; Sugimoto, Norihiro

    2015-08-01

    Copper matrix composites containing antiperovskite manganese nitrides with negative thermal expansion (NTE) were formed using pulsed electric current sintering. Energy dispersive X-ray spectroscopy revealed that the chemically reacted region extends over 10 μm around the matrix-filler interfaces. The small-size filler was chemically deteriorated during formation of composites and it lost the NTE property. Therefore, we produced the composites using only the nitride particles having diameter larger than 50 μm. The large-size filler effectively suppressed the thermal expansion of copper and improved the conductivity of the composites to the level of pure aluminum. The present composites, having high thermal conductivity and low thermal expansion, are suitable for practical applications such as a heat radiation substrate for semiconductor devices.

  14. Matrix-filler interfaces and physical properties of metal matrix composites with negative thermal expansion manganese nitride

    Energy Technology Data Exchange (ETDEWEB)

    Takenaka, Koshi, E-mail: takenaka@nuap.nagoya-u.ac.jp [Department of Applied Physics, Nagoya University, Nagoya 464-8603 (Japan); Department of Crystalline Materials Science, Nagoya University, Nagoya 464-8603 (Japan); Kuzuoka, Kota [Department of Applied Physics, Nagoya University, Nagoya 464-8603 (Japan); Sugimoto, Norihiro [Department of Crystalline Materials Science, Nagoya University, Nagoya 464-8603 (Japan)

    2015-08-28

    Copper matrix composites containing antiperovskite manganese nitrides with negative thermal expansion (NTE) were formed using pulsed electric current sintering. Energy dispersive X-ray spectroscopy revealed that the chemically reacted region extends over 10 μm around the matrix–filler interfaces. The small-size filler was chemically deteriorated during formation of composites and it lost the NTE property. Therefore, we produced the composites using only the nitride particles having diameter larger than 50 μm. The large-size filler effectively suppressed the thermal expansion of copper and improved the conductivity of the composites to the level of pure aluminum. The present composites, having high thermal conductivity and low thermal expansion, are suitable for practical applications such as a heat radiation substrate for semiconductor devices.

  15. Thermal conductivity of disperse insulation materials and their mixtures

    Science.gov (United States)

    Geža, V.; Jakovičs, A.; Gendelis, S.; Usiļonoks, I.; Timofejevs, J.

    2017-10-01

    Development of new, more efficient thermal insulation materials is a key to reduction of heat losses and contribution to greenhouse gas emissions. Two innovative materials developed at Thermeko LLC are Izoprok and Izopearl. This research is devoted to experimental study of thermal insulation properties of both materials as well as their mixture. Results show that mixture of 40% Izoprok and 60% of Izopearl has lower thermal conductivity than pure materials. In this work, material thermal conductivity dependence temperature is also measured. Novel modelling approach is used to model spatial distribution of disperse insulation material. Computational fluid dynamics approach is also used to estimate role of different heat transfer phenomena in such porous mixture. Modelling results show that thermal convection plays small role in heat transfer despite large fraction of air within material pores.

  16. Evaluation of Structure Influence on Thermal Conductivity of Thermal Insulating Materials from Renewable Resources

    Directory of Open Access Journals (Sweden)

    Jolanta VĖJELIENĖ

    2011-07-01

    Full Text Available The development of new thermal insulation materials needs to evaluate properties and structure of raw material, technological factors that make influence on the thermal conductivity of material. One of the most promising raw materials for production of insulation material is straw. The use of natural fibres in insulation is closely linked to the ecological building sector, where selection of materials is based on factors including recyclable, renewable raw materials and low resource production techniques In current work results of research on structure and thermal conductivity of renewable resources for production thermal insulating materials are presented. Due to the high abundance of renewable resources and a good its structure as raw material for thermal insulation materials barley straw, reeds, cattails and bent grass stalks are used. Macro- and micro structure analysis of these substances is performed. Straw bales of these materials are used for determining thermal conductivity. It was found that the macrostructure has the greatest effect on thermal conductivity of materials. Thermal conductivity of material is determined by the formation of a bale due to the large amount of pores among the stalks of the plant, inside the stalk and inside the stalk wall.http://dx.doi.org/10.5755/j01.ms.17.2.494

  17. Numerical homogenization of elastic and thermal material properties for metal matrix composites (MMC)

    Science.gov (United States)

    Schindler, Stefan; Mergheim, Julia; Zimmermann, Marco; Aurich, Jan C.; Steinmann, Paul

    2017-01-01

    A two-scale material modeling approach is adopted in order to determine macroscopic thermal and elastic constitutive laws and the respective parameters for metal matrix composite (MMC). Since the common homogenization framework violates the thermodynamical consistency for non-constant temperature fields, i.e., the dissipation is not conserved through the scale transition, the respective error is calculated numerically in order to prove the applicability of the homogenization method. The thermomechanical homogenization is applied to compute the macroscopic mass density, thermal expansion, elasticity, heat capacity and thermal conductivity for two specific MMCs, i.e., aluminum alloy Al2024 reinforced with 17 or 30 % silicon carbide particles. The temperature dependency of the material properties has been considered in the range from 0 to 500°C, the melting temperature of the alloy. The numerically determined material properties are validated with experimental data from the literature as far as possible.

  18. Measurement Techniques for Thermal Conductivity and Interfacial Thermal Conductance of Bulk and Thin Film Materials

    OpenAIRE

    Zhao, Dongliang; Qian, Xin; Gu, Xiaokun; Jajja, Saad Ayub; Yang, Ronggui

    2016-01-01

    Thermal conductivity and interfacial thermal conductance play crucial roles in the design of engineering systems where temperature and thermal stress are of concerns. To date, a variety of measurement techniques are available for both bulk and thin film solid-state materials with a broad temperature range. For thermal characterization of bulk material, the steady-state absolute method, laser flash diffusivity method, and transient plane source method are most used. For thin film measurement, ...

  19. Use of phase change materials during compressed air expansion for isothermal CAES plants

    Science.gov (United States)

    Castellani, B.; Presciutti, A.; Morini, E.; Filipponi, M.; Nicolini, A.; Rossi, F.

    2017-11-01

    Compressed air energy storage (CAES) plants are designed to store compressed air into a vessel or in an underground cavern and to expand it in an expansion turbine when energy demand is high. An innovative CAES configuration recently proposed is the isothermal process. Several methods to implement isothermal CAES configuration are under investigation. In this framework, the present paper deals with the experimental testing of phase change materials (PCM) during compressed air expansion phase. The experimental investigation was carried out by means of an apparatus constituted by a compression section, a steel pressure vessel, to which an expansion valve is connected. The initial internal absolute pressure was equal to 5 bar to avoid moisture condensation and the experimental tests were carried out with two paraffin-based PCM amounts (0.05 kg and 0.1 kg). Results show that the temperature change during air expansion decreases with increasing the PCM amount inside the vessel. With the use of PCM during expansions an increase of the expansion work occurs. The increase is included in the range from 9.3% to 18.2%. In every test there is an approach to the isothermal values, which represent the maximum theoretical value of the obtainable expansion work.

  20. Effect of Material Composition and Environmental Condition on Thermal Characteristics of Conductive Asphalt Concrete.

    Science.gov (United States)

    Pan, Pan; Wu, Shaopeng; Hu, Xiaodi; Liu, Gang; Li, Bo

    2017-02-23

    Conductive asphalt concrete with high thermal conductivity has been proposed to improve the solar energy collection and snow melting efficiencies of asphalt solar collector (ASC). This paper aims to provide some insight into choosing the basic materials for preparation of conductive asphalt concrete, as well as determining the evolution of thermal characteristics affected by environmental factors. The thermal properties of conductive asphalt concrete were studied by the Thermal Constants Analyzer. Experimental results showed that aggregate and conductive filler have a significant effect on the thermal properties of asphalt concrete, while the effect of asphalt binder was not evident due to its low proportion. Utilization of mineral aggregate and conductive filler with higher thermal conductivity is an efficient method to prepare conductive asphalt concrete. Moreover, change in thermal properties of asphalt concrete under different temperature and moisture conditions should be taken into account to determine the actual thermal properties of asphalt concrete. There was no noticeable difference in thermal properties of asphalt concrete before and after aging. Furthermore, freezing-thawing cycles strongly affect the thermal properties of conductive asphalt concrete, due to volume expansion and bonding degradation.

  1. Effect of Material Composition and Environmental Condition on Thermal Characteristics of Conductive Asphalt Concrete

    Directory of Open Access Journals (Sweden)

    Pan Pan

    2017-02-01

    Full Text Available Conductive asphalt concrete with high thermal conductivity has been proposed to improve the solar energy collection and snow melting efficiencies of asphalt solar collector (ASC. This paper aims to provide some insight into choosing the basic materials for preparation of conductive asphalt concrete, as well as determining the evolution of thermal characteristics affected by environmental factors. The thermal properties of conductive asphalt concrete were studied by the Thermal Constants Analyzer. Experimental results showed that aggregate and conductive filler have a significant effect on the thermal properties of asphalt concrete, while the effect of asphalt binder was not evident due to its low proportion. Utilization of mineral aggregate and conductive filler with higher thermal conductivity is an efficient method to prepare conductive asphalt concrete. Moreover, change in thermal properties of asphalt concrete under different temperature and moisture conditions should be taken into account to determine the actual thermal properties of asphalt concrete. There was no noticeable difference in thermal properties of asphalt concrete before and after aging. Furthermore, freezing–thawing cycles strongly affect the thermal properties of conductive asphalt concrete, due to volume expansion and bonding degradation.

  2. Flexible composite material with phase change thermal storage

    Science.gov (United States)

    Buckley, Theresa M. (Inventor)

    2001-01-01

    A highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The composite material can be made to heat or cool the body or to act as a thermal buffer to protect the wearer from changing environmental conditions. The composite may also include an external thermal insulation layer and/or an internal thermal control layer to regulate the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the PCM composite also provide 1) a path for evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) heat conductive pathways within the material for thermal equalization, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for quickly regenerating the thermal storage capacity for reuse of the material. Applications of the composite materials are also described which take advantage of the composite's thermal characteristics. The examples described include a diver's wet suit, ski boot liners, thermal socks, ,gloves and a face mask for cold weather activities, and a metabolic heating or cooling blanket useful for treating hypothermia or fever patients in a medical setting and therapeutic heating or cooling orthopedic joint supports.

  3. Non-adiabatic effects within a single thermally averaged potential energy surface: thermal expansion and reaction rates of small molecules.

    Science.gov (United States)

    Alonso, J L; Castro, A; Clemente-Gallardo, J; Echenique, P; Mazo, J J; Polo, V; Rubio, A; Zueco, D

    2012-12-14

    At non-zero temperature and when a system has low-lying excited electronic states, the ground-state Born-Oppenheimer approximation breaks down and the low-lying electronic states are involved in any chemical process. In this work, we use a temperature-dependent effective potential for the nuclei which can accommodate the influence of an arbitrary number of electronic states in a simple way, while at the same time producing the correct Boltzmann equilibrium distribution for the electronic part. With the help of this effective potential, we show that thermally activated low-lying electronic states can have a significant effect in molecular properties for which electronic excitations are oftentimes ignored. We study the thermal expansion of the Manganese dimer, Mn(2), where we find that the average bond length experiences a change larger than the present experimental accuracy upon the inclusion of the excited states into the picture. We also show that, when these states are taken into account, reaction-rate constants are modified. In particular, we study the opening of the ozone molecule, O(3), and show that in this case the rate is modified as much as a 20% with respect to the ground-state Born-Oppenheimer prediction.

  4. Effect of Aggregate Mineralogy and Concrete Microstructure on Thermal Expansion and Strength Properties of Concrete

    Directory of Open Access Journals (Sweden)

    Jinwoo An

    2017-12-01

    Full Text Available Aggregate type and mineralogy are critical factors that influence the engineering properties of concrete. Temperature variations result in internal volume changes could potentially cause a network of micro-cracks leading to a reduction in the concrete’s compressive strength. The study specifically studied the effect of the type and mineralogy of fine and coarse aggregates in the normal strength concrete properties. As performance measures, the coefficient of thermal expansion (CTE and compressive strength were tested with concrete specimens containing different types of fine aggregates (manufactured and natural sands and coarse aggregates (dolomite and granite. Petrographic examinations were then performed to determine the mineralogical characteristics of the aggregate and to examine the aggregate and concrete microstructure. The test results indicate the concrete CTE increases with the silicon (Si volume content in the aggregate. For the concrete specimens with higher CTE, the micro-crack density in the interfacial transition zone (ITZ tended to be higher. The width of ITZ in one of the concrete specimens with a high CTE displayed the widest core ITZ (approx. 11 µm while the concrete specimens with a low CTE showed the narrowest core ITZ (approx. 3.5 µm. This was attributed to early-age thermal cracking. Specimens with higher CTE are more susceptible to thermal stress.

  5. Lattice thermal expansion and anisotropic displacements in urea, bromomalonic aldehyde, pentachloropyridine, and naphthalene

    Science.gov (United States)

    George, Janine; Wang, Ruimin; Englert, Ulli; Dronskowski, Richard

    2017-08-01

    Anisotropic displacement parameters (ADPs) are commonly used in crystallography, chemistry, and related fields to describe and quantify thermal motion of atoms. Within the very recent years, these ADPs have become predictable by lattice dynamics in combination with first-principles theory. Here, we study four very different molecular crystals, namely, urea, bromomalonic aldehyde, pentachloropyridine, and naphthalene, by first-principles theory to assess the quality of ADPs calculated in the quasi-harmonic approximation. In addition, we predict both the thermal expansion and thermal motion within the quasi-harmonic approximation and compare the predictions with the experimental data. Very reliable ADPs are calculated within the quasi-harmonic approximation for all four cases up to at least 200 K, and they turn out to be in better agreement with the experiment than those calculated within the harmonic approximation. In one particular case, ADPs can even reliably be predicted up to room temperature. Our results also hint at the importance of normal-mode anharmonicity in the calculation of ADPs.

  6. Basic Thermal Parameters of Selected Foods and Food Raw Materials

    Directory of Open Access Journals (Sweden)

    Monika Božiková

    2017-01-01

    Full Text Available In general, processing and manipulation with foods and food raw materials have significant influence on their physical properties. The article is focused on thermophysical parameters measurement of selected foods and food raw materials. There were examined thermal conductivity and thermal diffusivity of selected materials. For detection of thermal parameters was used instrument Isomet 2104, which principle of measurement is based on transient methods. In text are presented summary results of thermal parameters measurement for various foods and food raw materials as: granular materials – corn flour and wheat flour; fruits, vegetables and fruit products – grated apple, dried apple and apple juice; liquid materials – milk, beer etc. Measurements were performed in two temperature ranges according to the character of examined material. From graphical relations of thermophysical parameter is evident, that thermal conductivity and diffusivity increases with temperature and moisture content linearly, only for granular materials were obtained non‑linear dependencies. Results shows, that foods and food raw materials have different thermal properties, which are influenced by their type, structure, chemical and physical properties. From presented results is evident, that basic thermal parameters are important for material quality detection in food industry.

  7. Thermal niche evolution and geographical range expansion in a species complex of western Mediterranean diving beetles.

    Science.gov (United States)

    Hidalgo-Galiana, Amparo; Sánchez-Fernández, David; Bilton, David T; Cieslak, Alexandra; Ribera, Ignacio

    2014-09-04

    Species thermal requirements are one of the principal determinants of their ecology and biogeography, although our understanding of the interplay between these factors is limited by the paucity of integrative empirical studies. Here we use empirically collected thermal tolerance data in combination with molecular phylogenetics/phylogeography and ecological niche modelling to study the evolution of a clade of three western Mediterranean diving beetles, the Agabus brunneus complex. The preferred mitochondrial DNA topology recovered A. ramblae (North Africa, east Iberia and Balearic islands) as paraphyletic, with A. brunneus (widespread in the southwestern Mediterranean) and A. rufulus (Corsica and Sardinia) nested within it, with an estimated origin between 0.60-0.25 Ma. All three species were, however, recovered as monophyletic using nuclear DNA markers. A Bayesian skyline plot suggested demographic expansion in the clade at the onset of the last glacial cycle. The species thermal tolerances differ significantly, with A. brunneus able to tolerate lower temperatures than the other taxa. The climatic niche of the three species also differs, with A. ramblae occupying more arid and seasonal areas, with a higher minimum temperature in the coldest month. The estimated potential distribution for both A. brunneus and A. ramblae was most restricted in the last interglacial, becoming increasingly wider through the last glacial and the Holocene. The A. brunneus complex diversified in the late Pleistocene, most likely in south Iberia after colonization from Morocco. Insular forms did not differentiate substantially in morphology or ecology, but A. brunneus evolved a wider tolerance to cold, which appeared to have facilitated its geographic expansion. Both A. brunneus and A. ramblae expanded their ranges during the last glacial, although they have not occupied areas beyond their LGM potential distribution except for isolated populations of A. brunneus in France and England. On

  8. Thermal expansion of the cryoprotectant cocktail DP6 combined with synthetic ice modulators in presence and absence of biological tissues.

    Science.gov (United States)

    Eisenberg, David P; Taylor, Michael J; Rabin, Yoed

    2012-10-01

    This study explores physical effects associated with the application of cryopreservation via vitrification using a class of compounds which are defined here as synthetic ice modulators (SIMs). The general classification of SIMs includes molecules that modulate ice nucleation and growth, or possess properties of stabilizing the amorphous state, by virtue of their chemical structure and at concentrations that are not explained on a purely colligative basis. A sub-category of SIMs, referred to in the literature as synthetic ice blockers (SIBs), are compounds that interact directly with ice nuclei or crystals to modify their structure and/or rate of growth. The current study is part of an ongoing effort to characterize thermo-mechanical effects during vitrification, with emphasis on measuring the physical property of thermal expansion-the driving mechanism to thermo-mechanical stress. Materials under investigation are the cryoprotective agent (CPA) cocktail DP6 in combination with one of the following SIMs: 12% polyethylene glycol 400, 6% 1,3 cyclohexanediol, and 6% 2,3 butanediol. Results are presented for the CPA-SIM cocktail in the absence and presence of bovine muscle and goat artery specimens. This study focuses on the upper part of the cryogenic temperature range, where the CPA behaves as a fluid for all practical applications. Results of this study indicate that the addition of SIMs to DP6 allows lower cooling rates to ensure vitrification and extends the range of measurements. It is demonstrated that the combination of SIM with DP6 increases the thermal expansion of the cocktail, with implications for the likelihood of fracture formation-the most dramatic outcome of thermo-mechanical stress. Copyright © 2012 Elsevier Inc. All rights reserved.

  9. Implications of Thermal Diffusity being Inversely Proportional to Temperature Times Thermal Expansivity on Lower Mantle Heat Transport

    Science.gov (United States)

    Hofmeister, A.

    2010-12-01

    Many measurements and models of heat transport in lower mantle candidate phases contain systematic errors: (1) conventional methods of insulators involve thermal losses that are pressure (P) and temperature (T) dependent due to physical contact with metal thermocouples, (2) measurements frequently contain unwanted ballistic radiative transfer which hugely increases with T, (3) spectroscopic measurements of dense samples in diamond anvil cells involve strong refraction by which has not been accounted for in analyzing transmission data, (4) the role of grain boundary scattering in impeding heat and light transfer has largely been overlooked, and (5) essentially harmonic physical properties have been used to predict anharmonic behavior. Improving our understanding of the physics of heat transport requires accurate data, especially as a function of temperature, where anharmonicity is the key factor. My laboratory provides thermal diffusivity (D) at T from laser flash analysis, which lacks the above experimental errors. Measuring a plethora of chemical compositions in diverse dense structures (most recently, perovskites, B1, B2, and glasses) as a function of temperature provides a firm basis for understanding microscopic behavior. Given accurate measurements for all quantities: (1) D is inversely proportional to [T x alpha(T)] from ~0 K to melting, where alpha is thermal expansivity, and (2) the damped harmonic oscillator model matches measured D(T), using only two parameters (average infrared dielectric peak width and compressional velocity), both acquired at temperature. These discoveries pertain to the anharmonic aspects of heat transport. I have previously discussed the easily understood quasi-harmonic pressure dependence of D. Universal behavior makes application to the Earth straightforward: due to the stiffness and slow motions of the plates and interior, and present-day, slow planetary cooling rates, Earth can be approximated as being in quasi

  10. Phase change thermal control materials, method and apparatus

    Science.gov (United States)

    Buckley, Theresa M. (Inventor)

    2001-01-01

    An apparatus and method for metabolic cooling and insulation of a user in a cold environment. In its preferred embodiment the apparatus is a highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The apparatus can be made to heat or cool the body or to act as a thermal buffer to protect the wearer from changing environmental conditions. The apparatus may also include an external thermal insulation layer and/or an internal thermal control layer to regulate the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the apparatus also provide 1) a path for evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) heat conductive pathways within the material for thermal equalization, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for quickly regenerating the thermal storage capacity for reuse of the material. Applications of the composite materials are also described which take advantage of the composite's thermal characteristics. The examples described include a diver's wet suit, ski boot liners, thermal socks, gloves and a face mask for cold weather activities, and a metabolic heating or cooling blanket useful for treating hypothermia or fever patients in a medical setting and therapeutic heating or cooling orthopedic joint supports.

  11. Recent patents on nano-enhanced materials for use in thermal energy storage (TES).

    Science.gov (United States)

    Cabeza, Luisa F; Ferrer, Gerard; Barreneche, Camila; Solé, Aran; Juliá, José Enrique

    2016-10-27

    Thermal energy storage (TES) systems using phase change materials (PCM) have been lately studied and are presented as one of the key solutions for the implementation of renewable energies. These systems take advantage of the latent heat of phase change of PCM during their melting/solidification processes to store or release heat depending on the needs and availability. Low thermal conductivity and latent heat are the main disadvantages of organic PCM, while corrosion, subcooling and thermal stability are the prime problems that inorganic PCM present. Nanotechnology can be used to overcome these drawbacks. Nano-enhanced PCM are obtained by the dispersion of nanoparticles in the base material and thermal properties such as thermal conductivity, viscosity and specific heat capacity, within others, can be enhanced. This paper presents a review of the patents regarding the obtaining of nano-enhanced materials for thermal energy storage (TES) in order to realize the development nanotechnologies have gained in the TES field. Patents regarding the synthesis methods to obtain nano-enhanced phase materials (NEPCM) and TES systems using NEPCM have been found and are presented in the paper. The few existing number of patents found is a clear indicator of the recent and thus low development nanotechnology has in the TES field so far. Nevertheless, the results obtained with the reviewed inventions already show the big potential that nanotechnology has in TES and denote a more than probable expansion of its use in the next years.

  12. Local Vibrations and Negative Thermal Expansion in ZrW2O8

    Science.gov (United States)

    Bridges, F.; Keiber, T.; Juhas, P.; Billinge, S. J. L.; Sutton, L.; Wilde, J.; Kowach, Glen R.

    2014-01-01

    We present an x-ray pair distribution function (XPDF) analysis and extended x-ray absorption fine structure (EXAFS) data for ZrW2O8 (10-500 K) with a focus on the stiffness of the Zr-O-W linkage. The XPDF is highly sensitive to W-Zr and W-W correlations, but much less so to O-O or W-O correlations. The Zr-W peak in the XPDF data has a weak temperature dependence and, hence, this linkage is relatively stiff and does not permit bending of the Zr-O-W link. We propose that the low energy vibrational modes that lead to negative thermal expansion involve correlated rotations of ZrO6 octahedra that produce large ⟨111⟩ translations of the WO4 tetrahedra, rather than a transverse motion of O atoms that imply a flexible Zr-O-W linkage.

  13. Negative-thermal-expansion ZrW2O8. Elasticity and pressure

    Science.gov (United States)

    Pantea, Cristian; Migliori, Albert; Littlewood, Peter; Zhao, Yusheng; Ledbetter, Hassel; Lashley, Jason; Kimura, Tsuyoshi; van Duijn, Joost; Kowach, Glen

    2007-03-01

    The elasticity of the negative thermal expansion (NTE) compound ZrW2O8 is rather strange: the solid softens as its volume decreases on warming. Does ZrW2O8 also soften when pressure alone is applied? Using pulse-echo ultrasound in a large-volume moissanite anvil cell, we find an unusual decrease in bulk modulus with pressure at 300K. Our results are inconsistent with conventional lattice dynamics, but a framework-solid-based non-linear model with many degrees of freedom predicts elastic softening as increases in either temperature or pressure reduce volume. The pressure-induced phase transition from α-ZrW2O8 (cubic) to γ-ZrW2O8 (orthorhombic) is found to take place at 0.5 GPa, result confirmed by Raman spectroscopy.

  14. Measurement of phonon dispersion relation in negative thermal expansion compound ZrW2O8

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Pintschovius, L.; Achary, S. N.; Kowach, G. R.

    2007-12-01

    Isotropic negative thermal expansion (NTE) is found in cubic AX2O8(A = Zr, Hf: X=W, Mo) up to high temperatures (1050 K). Anharmonicity of low energy phonon modes plays an important role in leading to the NTE behaviour. Earlier we verified our predictions of large phonon softening for low energy phonons (below 8 meV) through high-pressure inelastic neutron scattering measurements on powder samples at ILL, France. Now we have measured the phonon dispersion relation from a single crystal of ZrW2O8. The measurements are useful to verify our prediction of highly anharmonic nature of specific phonon branches, in particular the transverse acoustic branch, and other branches up to 10 meV. These modes below 10 meV mainly contribute to the NTE in ZrW2O8.

  15. Acute plasma volume expansion alters cardiovascular but not thermal function during moderate intensity prolonged exercise.

    Science.gov (United States)

    Roy, B D; Green, H J; Grant, S M; Tarnopolsky, M A

    2000-03-01

    To investigate the hypothesis that the increase in plasma volume (PV) that typically occurs with training results in improved cardiovascular and thermal regulation during prolonged exercise, eight untrained males (V(O2)peak = 3.52 +/- 0.12 L x min(-1)) performed 90 min of cycle ergometry at 62% V(O2)peak before and after acute PV expansion. Subjects were infused with a PV-expanding solution (dextran (6%) or Pentaspan (10%)) equivalent to 6.7 mL x kg(-1) body mass (PVX) or acted as their own control (CON) in a randomized order. PVX resulted in a calculated 15.8% increase in resting PV, which relative to CON, was maintained throughout the exercise (P performance without affecting the thermoregulatory response to prolonged cycle exercise.

  16. Biomedical photoacoustics beyond thermal expansion using triggered nanodroplet vaporization for contrast-enhanced imaging.

    Science.gov (United States)

    Wilson, Katheryne; Homan, Kimberly; Emelianov, Stanislav

    2012-01-10

    Since being discovered by Alexander Bell, photoacoustics may again be seeing major resurgence in biomedical imaging. Photoacoustics is a non-ionizing, functional imaging modality capable of high contrast images of optical absorption at depths significantly greater than traditional optical imaging techniques. Optical contrast agents have been used to extend photoacoustics to molecular imaging. Here we introduce an exogenous contrast agent that utilizes vaporization for photoacoustic signal generation, providing significantly higher signal amplitude than that from the traditionally used mechanism, thermal expansion. Our agent consists of liquid perfluorocarbon nanodroplets with encapsulated plasmonic nanoparticles, entitled photoacoustic nanodroplets. Upon pulsed laser irradiation, liquid perfluorocarbon undergoes a liquid-to-gas phase transition generating giant photoacoustic transients from these dwarf nanoparticles. Once triggered, the gaseous phase provides ultrasound contrast enhancement. We demonstrate in phantom and animal studies that photoacoustic nanodroplets act as dual-contrast agents for both photoacoustic and ultrasound imaging through optically triggered vaporization.

  17. Determination of Coefficient of Thermal Expansion (CTE) of 20MPa Mass Concrete Using Granite Aggregate

    Science.gov (United States)

    Chee Siang, GO

    2017-07-01

    Experimental test was carried out to determine the coefficient of thermal expansion (CTE) value of 20MPa mass concrete using granite aggregate. The CTE value was established using procedure proposed by Kada et al. 2002 in determining the magnitude of early-ages CTE through laboratory test which is a rather accurate way by eliminating any possible superimposed effect of others early-age thermal deformation shrinkages such as autogenous, carbonation, plastic and drying shrinkage. This was done by submitting granite concrete block samples instrumented with ST4 vibrating wire extensometers to thermal shocks. The response of the concrete samples to this shock results in a nearly instantaneous deformation, which are measured by the sensor. These deformations, as well as the temperature signal, are used to calculate the CTE. By repeating heat cycles, the variation in the early-ages of concrete CTE over time was monitored and assessed for a period of upto 7 days. The developed CTE value facilitating the verification and validation of actual maximum permissible critical temperature differential limit (rather than arbitrarily follow published value) of cracking potential. For thick sections, internal restraint is dominant and this is governed by differentials mainly. Of the required physical properties for thermal modelling, CTE is of paramount importance that with given appropriate internal restraint factor the condition of cracking due to internal restraint is governs by equation, ΔTmax= 3.663ɛctu / αc. Thus, it can be appreciated that an increase in CTE will lower the maximum allowable differential for cracking avoidance in mass concrete while an increase of tensile strain capacity will increase the maximum allowable temperature differential.

  18. Mantle dynamics with pressure- and temperature-dependent thermal expansivity and conductivity

    Science.gov (United States)

    Tosi, Nicola; Yuen, David A.; de Koker, Nico; Wentzcovitch, Renata M.

    2013-04-01

    In numerical simulations of mantle convection it is commonly assumed that the coefficients of thermal expansion α and thermal conduction k are either constant or pressure-dependent. Pressure changes are generally computed using parametrizations that rely on extrapolations of low-pressure data for a single upper-mantle phase. Here we collect data for both the pressure and temperature dependence of α from a database of first-principles calculations, and of k from recent experimental studies. We use these data-sets to construct analytical parametrizations of α and k for the major upper- and lower-mantle phases that can be easily incorporated into exisiting convection codes. We then analyze the impact of such parametrizations on Earth's mantle dynamics by employing two-dimensional numerical models of thermal convection. When α is the only variable parameter, both its temperature and pressure dependence enhance hot plumes and tend to inhibit the descent of cold downwellings. Taking into account a variable k leads to a strong increase of the bulk mantle temperature, which reduces the buoyancy available to amplify bottom boundary layer instabilities and causes mantle flow to be driven primarily by the instability of cold plates whose surface velocity also tends to rise. When both parameters are considered together, we observe an increased propensity to local layering which favors slab stagnation in the transition zone and subsequent thickening in the lower mantle. Furthermore, the values of k near the core-mantle boundary ultimately control the effect of this physical property on convection, which stresses the importance of determining the thermal conductivity of the post-perovskite phase.

  19. Thermal energy storage using phase change materials fundamentals and applications

    CERN Document Server

    Fleischer, Amy S

    2015-01-01

    This book presents a comprehensive introduction to the use of solid‐liquid phase change materials to store significant amounts of energy in the latent heat of fusion. The proper selection of materials for different applications is covered in detail, as is the use of high conductivity additives to enhance thermal diffusivity. Dr. Fleischer explores how applications of PCMS have expanded over the past 10 years to include the development of high efficiency building materials to reduce heating and cooling needs, smart material design for clothing, portable electronic systems thermal management, solar thermal power plant design and many others. Additional future research directions and challenges are also discussed.

  20. New wrought Ni-based superalloys with low thermal expansion for 700C steam turbines

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, R.; Kadoya, Y. [Takasago Research and Development Center, Mitsubishi Heavy Industries, Ltd., Takasago, Hyogo (Japan); Kawai, H.; Magoshi, R. [Takasago Machinery Works, Mitsubishi Heavy Industries, Ltd., Takasago, Hyogo (Japan); Noda, T.; Hamano, S.; Ueta, S.; Isobe, S. [Research and Development Lab., Daido Steel Co., Ltd., Minamiku, Nagoya (Japan)

    2002-07-01

    Advanced 700C class steam turbines require austenitic alloys to replace conventional ferritic 12Cr steels, which lose creep strength and oxidation resistance above 650C. The austenitic alloys, however, possess a higher thermal expansion coefficient than ferritic 12Cr steels. Therefore, Ni-based superalloys were tailored to reduce their coefficients to the level of 12Cr steels. A regression analysis of commercial superalloys proves that Ti, Mo and Al decrease the coefficient quantitatively in this order, while Cr increases it so significantly that Cr should be limited to 12wt% to secure oxidation resistance. The newly designed Ni-18Mo-12Cr-1.1Ti-0.9Al alloy is strengthened by gamma-prime [Ni{sub 3}(Al,Ti)] and also Laves [Ni{sub 2}(Mo,Cr)] phase precipitates. It bears a RT/700C mean expansion coefficient equivalent to that of 12Cr steels and far lower than that of low-alloyed heat resistant steels. It surpasses a current turbine alloy, Refractaloy 26, in tensile strength at RT to 700C and SCC life in 330C deaerated pure water. Its creep rupture life at 700C is equivalent to that of Refractaloy 26. The developed alloy will be suitable for fasteners and/or blades in steam turbines at present and future USC power plants. (orig.)

  1. Investigation of the Negative Thermal Expansion of ZrW2O8

    Science.gov (United States)

    Ulbrich, N.; Tröger, W.; Butz, T.; Blaha, P.

    2000-02-01

    The negative thermal expansion in ZrW2O8 was investigated on a microscopic scale by temperature dependent measurements of the electric field gradients at the nuclear probe 187W(β-) 187Re using time differential perturbed angular correlation spectroscopy. Two distinct nuclear quadrupole interactions I VzzRe1 l= 18.92(4) • 10 21 V/m2 , ηRe1 = 0.0 and I VzzRe1 l = 4.55(2) • 1021 V/m2 , ηRe1 = 0.053(3) were observed at 295 K, which are assigned to the two crystallographically distinct W0 4 tetrahedra of the room temperature structure. Ab initio calculations of electron densities and electric field gradients with 1:7 Re-impurities using the full potential linearized augmented plane wave package WIEN97 yield the electric field gradients VzzRe1 = 12.63 • 10 21 V/m2 , ηRe1 = 0.0 and VzzRe2 =4.90 • 10 21 V/m2 , ηRe2 =0.0. The observed temperature dependence of the nuclear quadrupole interactions agrees well with the structural phase transition at 428 K observed by neutron and x-ray diffraction. Our experiments corroborate the suggested mechanism of coupled librations of rigid ZrO6 octahedra and WO4 tetrahedra, which is an alternative description of transverse vibrations of oxygen atoms in Zr-O-W bonds, for the negative thermal expansion in ZrW2 O8

  2. The Thermal Expansion and Tensile Properties of Nanofiber-ZrW2O8 Reinforced Epoxy Resin Nanocomposites

    Science.gov (United States)

    Shan, Xinran; Huang, Chuanjun; Yang, Huihui; Wu, Zhixiong; Li, Jingwen; Huang, Rongjin; Li, Laifeng

    Zirconium tungstate/epoxy (ZrW2O8/EP) nanocomposites were prepared and their thermal expansion properties were investigated within the temperature range of 4-300 K. Compared to unmodified epoxy resin, zirconium tungstate/epoxy composites lowers the thermal expansion coefficient (CTEs). The tensile strength was investigated at room temperature (300 K) and liquid nitrogen temperature (77 K). The fracture surfaces were examined by scanning electron microscopy (SEM). Results showed that the tensile strength and elongation at break increases with the increasing ZrW2O8 content.

  3. Origin of the Giant Negative Thermal Expansion in Mn3(Cu0.5Ge0.5N

    Directory of Open Access Journals (Sweden)

    B. Y. Qu

    2012-01-01

    Full Text Available The giant negative thermal expansion in the Ge-doped antiperovskite Mn3CuN compound is theoretically studied by using the first principles calculations. We propose that such a negative thermal expansion property is essentially attributed to the magnetic phase transition, rather than to the lattice vibration of the Ge-doped compound. Furthermore, we found that the doped Ge atoms in the compound significantly enhance the antiferromagnetic couplings between the nearest neighboring Mn ions, which effectively stabilizes the magnetic ground states. In addition, the nature of the temperature-dependent changes in the volume of the Ge-doped compound was revealed.

  4. Negative thermal expansion behavior in single crystal and ceramic of Nb{sub 2}O{sub 5}-based compositions.

    Energy Technology Data Exchange (ETDEWEB)

    Choosuwan, H.; Guo, R.; Bhalla, A. S.; Balachandran, U.; Energy Technology; Pennsylvania State Univ.

    2002-04-15

    The thermal expansion coefficients of a single crystal and ceramic of Nb{sub 2}O{sub 5} are measured in the temperature range of -200-500 C by the dilatometer technique. Both single crystals and ceramics of Nb{sub 2}O{sub 5} and Nb{sub 2}O{sub 5}(1-x):xTiO{sub 2} show negative thermal expansion in this temperature range. Some contribution to the result could be due to the presence of the Magneli phases. The main phase transition temperature, which also matches with the dielectric anomaly, occurs at {approx}150 C.

  5. A model to estimate volume change due to radiolytic gas bubbles and thermal expansion in solution reactors

    Energy Technology Data Exchange (ETDEWEB)

    Souto, F.J. [NIS-6: Advanced Nuclear Technology, Los Alamos National Lab., Los Alamos, NM (United States); Heger, A.S. [ESA-EA: Engineering Sciences and Application, Los Alamos National Lab., Los Alamos, NM (United States)

    2001-07-01

    To investigate the effects of radiolytic gas bubbles and thermal expansion on the steady-state operation of solution reactors at the power level required for the production of medical isotopes, a calculational model has been developed. To validate this model, including its principal hypotheses, specific experiments at the Los Alamos National Laboratory SHEBA uranyl fluoride solution reactor were conducted. The following sections describe radiolytic gas generation in solution reactors, the equations to estimate the fuel solution volume change due to radiolytic gas bubbles and thermal expansion, the experiments conducted at SHEBA, and the comparison of experimental results and model calculations. (author)

  6. Extreme ultraviolet optical properties of two SiO2 based low-expansion materials

    Science.gov (United States)

    Rife, J.; Osantowski, J.

    1980-01-01

    The reflectances of two low-expansion materials, a recrystallized glass ceramic and a high silica glass, have been measured at five angles of incidence from 15 to 85 deg in the wavelength region from 80 to 310 A and in some cases up to 1050 A. Optical constants are derived and silicon core-level transitions analyzed.

  7. Green Building Construction Thermal Isolation Materials (Rockwool)

    OpenAIRE

    M. Itewi

    2011-01-01

    Problem statement: Building insulation consisting roughly to anything in a structure that is utilizes as insulation for any reason. Thermal insulation in structures is a significant feature to attaining thermal comfort for its tenants. Approach: Insulation decreases unnecessary warmth loss or gain and can reduce the power burdens of heating and cooling structures. It does not automatically having anything to do with problems of sufficient exposure to air and might or might...

  8. Robust high pressure stability and negative thermal expansion in sodium-rich antiperovskites Na{sub 3}OBr and Na{sub 4}OI{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yonggang, E-mail: yyggwang@gmail.com, E-mail: yangwg@hpstar.ac.cn, E-mail: yusheng.zhao@unlv.edu [High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Nevada 89154 (United States); Institute of Nanostructured Functional Materials, Huanghe Science and Technology College, Zhengzhou, Henan 450006 (China); High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Wen, Ting [Institute of Nanostructured Functional Materials, Huanghe Science and Technology College, Zhengzhou, Henan 450006 (China); Park, Changyong; Kenney-Benson, Curtis [High Pressure Collaborative Access Team (HPCAT), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Pravica, Michael; Zhao, Yusheng, E-mail: yyggwang@gmail.com, E-mail: yangwg@hpstar.ac.cn, E-mail: yusheng.zhao@unlv.edu [High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Nevada 89154 (United States); Yang, Wenge, E-mail: yyggwang@gmail.com, E-mail: yangwg@hpstar.ac.cn, E-mail: yusheng.zhao@unlv.edu [High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China)

    2016-01-14

    The structure stability under high pressure and thermal expansion behavior of Na{sub 3}OBr and Na{sub 4}OI{sub 2}, two prototypes of alkali-metal-rich antiperovskites, were investigated by in situ synchrotron X-ray diffraction techniques under high pressure and low temperature. Both are soft materials with bulk modulus of 58.6 GPa and 52.0 GPa for Na{sub 3}OBr and Na{sub 4}OI{sub 2}, respectively. The cubic Na{sub 3}OBr structure and tetragonal Na{sub 4}OI{sub 2} with intergrowth K{sub 2}NiF{sub 4} structure are stable under high pressure up to 23 GPa. Although being a characteristic layered structure, Na{sub 4}OI{sub 2} exhibits nearly isotropic compressibility. Negative thermal expansion was observed at low temperature range (20–80 K) in both transition-metal-free antiperovskites for the first time. The robust high pressure structure stability was examined and confirmed by first-principles calculations among various possible polymorphisms qualitatively. The results provide in-depth understanding of the negative thermal expansion and robust crystal structure stability of these antiperovskite systems and their potential applications.

  9. Robust high pressure stability and negative thermal expansion in sodium-rich antiperovskites Na3OBr and Na4OI2

    Science.gov (United States)

    Wang, Yonggang; Wen, Ting; Park, Changyong; Kenney-Benson, Curtis; Pravica, Michael; Yang, Wenge; Zhao, Yusheng

    2016-01-01

    The structure stability under high pressure and thermal expansion behavior of Na3OBr and Na4OI2, two prototypes of alkali-metal-rich antiperovskites, were investigated by in situ synchrotron X-ray diffraction techniques under high pressure and low temperature. Both are soft materials with bulk modulus of 58.6 GPa and 52.0 GPa for Na3OBr and Na4OI2, respectively. The cubic Na3OBr structure and tetragonal Na4OI2 with intergrowth K2NiF4 structure are stable under high pressure up to 23 GPa. Although being a characteristic layered structure, Na4OI2 exhibits nearly isotropic compressibility. Negative thermal expansion was observed at low temperature range (20-80 K) in both transition-metal-free antiperovskites for the first time. The robust high pressure structure stability was examined and confirmed by first-principles calculations among various possible polymorphisms qualitatively. The results provide in-depth understanding of the negative thermal expansion and robust crystal structure stability of these antiperovskite systems and their potential applications.

  10. High resolution steady-state measurements of thermal contact resistance across thermal interface material junctions

    Science.gov (United States)

    Warzoha, Ronald J.; Donovan, Brian F.

    2017-09-01

    Thermal interface materials (TIMs) are meant to reduce the interfacial thermal resistance (RT) across bare metal contacts in commercial electronics packaging systems. However, there is little scientific consensus governing material design for optimized thermal performance. This is principally due to the inability to separate the effects of the intrinsic material thermal properties from the magnitude of heat flow crossing the TIM-substrate junction (RC). To date, efforts to isolate these effects using standard thermal interface material characterization techniques have not been successful. In this work, we develop an infrared thermography-based steady-state heat meter bar apparatus with a novel in situ thickness measurement system having 0.5 nm sensitivity. These in situ thickness measurements allow us to simultaneously determine RT and RC independently across current state-of-the-art TIMs with ±5% uncertainty. In this work, thermal pastes with bond line thicknesses ranging between 5 and 50 μ m are used to illustrate the capability of the apparatus to measure extremely thin materials that are expected to achieve relatively low values of RT. Results suggest that the contribution of the thermal contact resistance to the total thermal resistance can range from 5% to 80% for these materials. This finding highlights the need for appropriate metrology and independent measurements of RC and RT to better optimize thermal interface materials for a number of important electronics applications.

  11. Summary of thermal properties for casting alloys and mold materials

    Science.gov (United States)

    Pehlke, R. D.; Jeyarajan, A.; Wada, H.

    1982-12-01

    A review of thermal properties of casting alloys and mold materials was conducted for the purpose of stimulating activity in computer aided design for castings. A summary of thermal data; thermal conductivity, specific heat, density, and heats of fusion was prepared for metals and casting alloys, and for primary molding materials. This summary represents an initial step in the development of data bases for support of computer aided design systems for castings. Additional information is required, in particular for thermal properties of commercial casting alloy systems.

  12. Evaluation of thermal energy storage materials for advanced compressed air energy storage systems

    Energy Technology Data Exchange (ETDEWEB)

    Zaloudek, F.R.; Wheeler, K.R.; Marksberry, L.

    1983-03-01

    Advanced Compressed-Air Energy Storage (ACAS) plants have the near-term potential to reduce the fuel consumption of compressed-air plants from 33 to 100%, depending upon their design. Fuel is saved by storing some or all of the heat of compression as sensible heat which is subsequently used to reheat the compressed air prior to expansion in the turbine generator. The thermal storage media required for this application must be low cost and durable. The objective of this project was to screen thermal store materials based on their thermal cycle durability, particulate formation and corrosion resistant characteristics. The materials investigated were iron oxide pellets, Denstone pebbles, cast-iron balls, and Dresser basalt rock. The study specifically addressed the problems of particle formation and thermal ratcheting of the materials during thermal cycling and the chemical attack on the materials by the high temperature and moist environment in an ACAS heat storage bed. The results indicate that from the durability standpoint Denstone, cast iron containing 27% or more chromium, and crushed Dresser basalt would possibly stand up to ACAS conditions. If costs are considered in addition to durability and performance, the crushed Dresser basalt would probably be the most desirable heat storage material for adiabatic and hybrid ACAS plants, and more in-depth longer term thermal cycling and materials testing of Dresser basalt is recommended. Also recommended is the redesign and costing analysis of both the hybrid and adiabatic ACAS facilities based upon the use of Dresser basalt as the thermal store material.

  13. Local Chemical Ordering and Negative Thermal Expansion in PtNi Alloy Nanoparticles.

    Science.gov (United States)

    Li, Qiang; Zhu, He; Zheng, Lirong; Fan, Longlong; Wang, Na; Rong, Yangchun; Ren, Yang; Chen, Jun; Deng, Jinxia; Xing, Xianran

    2017-12-13

    An atomic insight into the local chemical ordering and lattice strain is particular interesting to recent emerging bimetallic nanocatalysts such as PtNi alloys. Here, we reported the atomic distribution, chemical environment, and lattice thermal evolution in full-scale structural description of PtNi alloy nanoparticles (NPs). The different segregation of elements in the well-faceted PtNi nanoparticles is convinced by extended X-ray absorption fine structure (EXAFS). Atomic pair distribution function (PDF) study evidences the coexistence of the face-centered cubic and tetragonal ordering parts in the local environment of PtNi nanoparticles. Further reverse Monte Carlo (RMC) simulation with PDF data obviously exposed the segregation as Ni and Pt in the centers of {111} and {001} facets, respectively. Layer-by-layer statistical analysis up to 6 nm for the local atomic pairs revealed the distribution of local tetragonal ordering on the surface. This local coordination environment facilitates the distribution of heteroatomic Pt-Ni pairs, which plays an important role in the negative thermal expansion of Pt41Ni59 NPs. The present study on PtNi alloy NPs from local short-range coordination to long-range average lattice provides a new perspective on tailoring physical properties in nanomaterials.

  14. Zero thermal expansion and ferromagnetism in cubic Sc(1-x)M(x)F3 (M = Ga, Fe) over a wide temperature range.

    Science.gov (United States)

    Hu, Lei; Chen, Jun; Fan, Longlong; Ren, Yang; Rong, Yangchun; Pan, Zhao; Deng, Jinxia; Yu, Ranbo; Xing, Xianran

    2014-10-01

    The rare physical property of zero thermal expansion (ZTE) is intriguing because neither expansion nor contraction occurs with temperature fluctuations. Most ZTE, however, occurs below room temperature. It is a great challenge to achieve isotropic ZTE at high temperatures. Here we report the unconventional isotropic ZTE in the cubic (Sc1-xMx)F3 (M = Ga, Fe) over a wide temperature range (linear coefficient of thermal expansion (CTE), αl = 2.34 × 10(-7) K(-1), 300-900 K). Such a broad temperature range with a considerably negligible CTE has rarely been documented. The present ZTE property has been designed using the introduction of local distortions in the macroscopic cubic lattice by heterogeneous cation substitution for the Sc site. Even though the macroscopic crystallographic structure of (Sc0.85Ga0.05Fe0.1)F3 adheres to the cubic system (Pm3̅m) according to the results of X-ray diffraction, the local structure exhibits a slight rhombohedral distortion. This is confirmed by pair distribution function analysis of synchrotron radiation X-ray total scattering. This local distortion may weaken the contribution from the transverse thermal vibration of fluorine atoms to negative thermal expansion, and thus may presumably be responsible for the ZTE. In addition, the present ZTE compounds of (Sc1-xMx)F3 can be functionalized to exhibit high-Tc ferromagnetism and a narrow-gap semiconductor feature. The present study shows the possibility of obtaining ZTE materials with multifunctionality in future work.

  15. Giant negative thermal expansion covering room temperature in nanocrystalline GaN{sub x}Mn{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Lin, J. C.; Tong, P., E-mail: tongpeng@issp.ac.cn; Chen, L.; Guo, X. G.; Yang, C.; Song, B.; Wu, Y.; Lin, S.; Song, W. H. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Zhou, X. J.; Lin, H., E-mail: linhe@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 200120 (China); Ding, Y. W.; Bai, Y. X. [Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026 (China); Sun, Y. P., E-mail: ypsun@issp.ac.cn [High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China); Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-09-28

    Nanocrystalline antiperovskite GaN{sub x}Mn{sub 3} powders were prepared by mechanically milling. The micrograin GaN{sub x}Mn{sub 3} exhibits an abrupt volume contraction at the antiferromagnetic (AFM) to paramagnetic (PM) (AFM-PM) transition. The temperature window of volume contraction (ΔT) is broadened to 50 K as the average grain size (〈D〉) is reduced to ∼30 nm. The corresponding coefficient of linear thermal expansion (α) reaches ∼ −70 ppm/K, which are comparable to those of giant NTE materials. Further reducing 〈D〉 to ∼10 nm, ΔT exceeds 100 K and α remains as large as −30 ppm/K (−21 ppm/K) for x = 1.0 (x = 0.9). Excess atomic displacements together with the reduced structural coherence, revealed by high-energy X-ray pair distribution functions, are suggested to delay the AFM-PM transition. By controlling 〈D〉, giant NTE may also be achievable in other materials with large lattice contraction due to electronic or magnetic phase transitions.

  16. Phase change thermal energy storage material

    Science.gov (United States)

    Benson, David K.; Burrows, Richard W.

    1987-01-01

    A thermal energy storge composition is disclosed. The composition comprises a non-chloride hydrate having a phase change transition temperature in the range of 70.degree.-95.degree. F. and a latent heat of transformation of at least about 35 calories/gram.

  17. Synthesis and thermal expansion hysteresis of Ca1–xSrxZr4P6O24

    Indian Academy of Sciences (India)

    Unknown

    and Roy 1984; Lenain et al 1984; Roy et al 1984), controlled lattice thermal expansion anisotropy (Oota and ... hexagonal lattice with structural holes that are partially or fully, depending upon the composition, occupied ..... Wurst J C and Nelson J A 1972 J. Am. Ceram. Soc. 55. 109. Yamai I and Ota T 1985 J. Am. Ceram.

  18. Thermal Expansion of ZrO2-ZrW2O8 Composites Prepared Using Co-Precipitation Route

    Science.gov (United States)

    Liu, Hongfei; Zhang, Zhiping; Cheng, Xiaonong; Yang, Juan

    In this work, a series of ZrO2/ZrW2O8 ceramic composites with different amounts of ZrW2O8 were successfully prepared by calcining the precursors synthesized using co-precipitation route at 1150°C for 3 h. The X-ray diffraction (XRD) data confirmed that the composites only consisted of α-ZrW2O8 phase and m-ZrO2 phase. The scanning electron microscopy (SEM) analysis of the synthesized ZrO2/ZrW2O8 composites showed that the specimens had good mixed-uniformities. In addition, the thermal expansion coefficients of the composites decreased with increased amounts of negative thermal expansion ZrW2O8, specimen with 26wt% ZrW2O8 shows almost zero thermal expansion and its average thermal expansion coefficient is -0.5897×10-6K-1 in the temperature range from 30°C to 600°C.

  19. A MODEL TO ESTIMATE VOLUME CHANGE DUE TO RADIOLYTIC GAS BUBBLES AND THERMAL EXPANSION IN SOLUTION REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    F. SOUTO; A HEGER

    2001-02-01

    Aqueous homogeneous solution reactors have been proposed for the production of medical isotopes. However, the reactivity effects of fuel solution volume change, due to formation of radiolytic gas bubbles and thermal expansion, have to be mitigated to allow steady-state operation of solution reactors. The results of the free run experiments analyzed indicate that the proposed model to estimate the void volume due to radiolytic gas bubbles and thermal expansion in solution reactors can accurately describe the observed behavior during the experiments. This void volume due to radiolytic gas bubbles and fuel solution thermal expansion can then be used in the investigation of reactivity effects in fissile solutions. In addition, these experiments confirm that the radiolytic gas bubbles are formed at a higher temperature than the fuel solution temperature. These experiments also indicate that the mole-weighted average for the radiolytic gas bubbles in uranyl fluoride solutions is about 1 {micro}m. Finally, it should be noted that another model, currently under development, would simulate the power behavior during the transient given the initial fuel solution level and density. The model is based on Monte Carlo simulation with the MCNP computer code [Briesmeister, 1997] to obtain the reactor reactivity as a function of the fuel solution density, which, in turn, changes due to thermal expansion and radiolytic gas bubble formation.

  20. Numerical simulation for thermal shock resistance of thermal protection materials considering different operating environments.

    Science.gov (United States)

    Li, Weiguo; Li, Dingyu; Wang, Ruzhuan; Fang, Daining

    2013-01-01

    Based on the sensitivities of material properties to temperature and the complexity of service environment of thermal protection system on the spacecraft, ultrahigh-temperature ceramics (UHTCs), which are used as thermal protection materials, cannot simply consider thermal shock resistance (TSR) of the material its own but need to take the external constraint conditions and the thermal environment into full account. With the thermal shock numerical simulation on hafnium diboride (HfB2), a detailed study of the effects of the different external constraints and thermal environments on the TSR of UHTCs had been made. The influences of different initial temperatures, constraint strengths, and temperature change rates on the TSR of UHTCs are discussed. This study can provide a more intuitively visual understanding of the evolution of the TSR of UHTCs during actual operation conditions.

  1. Numerical Simulation for Thermal Shock Resistance of Thermal Protection Materials Considering Different Operating Environments

    Directory of Open Access Journals (Sweden)

    Weiguo Li

    2013-01-01

    Full Text Available Based on the sensitivities of material properties to temperature and the complexity of service environment of thermal protection system on the spacecraft, ultrahigh-temperature ceramics (UHTCs, which are used as thermal protection materials, cannot simply consider thermal shock resistance (TSR of the material its own but need to take the external constraint conditions and the thermal environment into full account. With the thermal shock numerical simulation on hafnium diboride (HfB2, a detailed study of the effects of the different external constraints and thermal environments on the TSR of UHTCs had been made. The influences of different initial temperatures, constraint strengths, and temperature change rates on the TSR of UHTCs are discussed. This study can provide a more intuitively visual understanding of the evolution of the TSR of UHTCs during actual operation conditions.

  2. Quasi-coherent thermal emitter based on refractory plasmonic materials

    DEFF Research Database (Denmark)

    Liu, Jingjing; Guler, Urcan; Lagutchev, Alexei

    2015-01-01

    The thermal emission of refractory plasmonic metamaterial - a titanium nitride 1D grating - is studied at high operating temperature (540 degrees C). By choosing a refractory material, we fabricate thermal gratings with high brightness that are emitting mid-infrared radiation centered around 3 mu m...

  3. Cryogenic thermal conductivity measurements on candidate materials for space missions

    Science.gov (United States)

    Tuttle, James; Canavan, Edgar; Jahromi, Amir

    2017-12-01

    Spacecraft and instruments on space missions are built using a wide variety of carefully-chosen materials. It is common for NASA engineers to propose new candidate materials which have not been totally characterized at cryogenic temperatures. In many cases a material's cryogenic thermal conductivity must be known before selecting it for a specific space-flight application. We developed a test facility in 2004 at NASA's Goddard Space Flight Center to measure the longitudinal thermal conductivity of materials at temperatures between 4 and 300 K, and we have characterized many candidate materials since then. The measurement technique is not extremely complex, but proper care to details of the setup, data acquisition and data reduction is necessary for high precision and accuracy. We describe the thermal conductivity measurement process and present results for ten engineered materials, including alloys, polymers, composites, and a ceramic.

  4. Switchable Shape Memory Alloys (SMA) Thermal Materials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Shape memory alloys applies to a group of materials that demonstrate the ability to return to some previously defined shape when subjected to the appropriate thermal...

  5. Advanced Thermal Interface Material Systems for Space Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The ultimate aim of proposed efforts are to develop innovative material and process (M&P) engineering technology to reduce thermal resistance between space power...

  6. Thermal Energetic Reactor with High Reproduction of Fission Materials

    Directory of Open Access Journals (Sweden)

    Vladimir M. Kotov

    2012-01-01

    On the base of thermal reactors with high fission materials reproduction world atomic power engineering development supplying higher power and requiring smaller speed of raw uranium mining, than in the variant with fast reactors, is possible.

  7. Graphene-based filament material for thermal ionization

    Energy Technology Data Exchange (ETDEWEB)

    Hewitt, J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Shick, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Siegfried, M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-09-19

    The use of graphene oxide materials for thermal ionization mass spectrometry analysis of plutonium and uranium has been investigated. Filament made from graphene oxide slurries have been 3-D printed. A method for attaching these filaments to commercial thermal ionization post assemblies has been devised. Resistive heating of the graphene based filaments under high vacuum showed stable operation in excess of 4 hours. Plutonium ion production has been observed in an initial set of filaments spiked with the Pu 128 Certified Reference Material.

  8. Using thermal power plants waste for building materials

    Science.gov (United States)

    Feduik, R. S.; Smoliakov, A. K.; Timokhin, R. A.; Batarshin, V. O.; Yevdokimova, Yu G.

    2017-10-01

    The recycled use of thermal power plants (TPPs) wastes in the building materials production is formulated. The possibility of using of TPPs fly ash as part of the cement composite binder for concrete is assessed. The results of X-ray diffraction and differential thermal analysis as well as and materials photomicrographs are presented. It was revealed that the fly ash of TPPs of Russian Primorsky Krai is suitable for use as a filler in cement binding based on its chemical composition.

  9. Advanced materials for thermal management of electronic packaging

    CERN Document Server

    Tong, Xingcun Colin

    2011-01-01

    The need for advanced thermal management materials in electronic packaging has been widely recognized as thermal challenges become barriers to the electronic industry's ability to provide continued improvements in device and system performance. With increased performance requirements for smaller, more capable, and more efficient electronic power devices, systems ranging from active electronically scanned radar arrays to web servers all require components that can dissipate heat efficiently. This requires that the materials have high capability of dissipating heat and maintaining compatibility

  10. Method and apparatus for implementing material thermal property measurement by flash thermal imaging

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jiangang

    2017-11-14

    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.

  11. Thermal and Thermoelectric Properties of Nanostructured Materials and Interfaces

    Science.gov (United States)

    Liao, Hao-Hsiang

    Many modern technologies are enabled by the use of thin films and/or nanostructured composite materials. For example, many thermoelectric devices, solar cells, power electronics, thermal barrier coatings, and hard disk drives contain nanostructured materials where the thermal conductivity of the material is a critical parameter for the device performance. At the nanoscale, the mean free path and wavelength of heat carriers may become comparable to or smaller than the size of a nanostructured material and/or device. For nanostructured materials made from semiconductors and insulators, the additional phonon scattering mechanisms associated with the high density of interfaces and boundaries introduces additional resistances that can significantly change the thermal conductivity of the material as compared to a macroscale counterpart. Thus, better understanding and control of nanoscale heat conduction in solids is important scientifically and for the engineering applications mentioned above. In this dissertation, I discuss my work in two areas dealing with nanoscale thermal transport: (1) I describe my development and advancement of important thermal characterization tools for measurements of thermal and thermoelectric properties of a variety of materials from thin films to nanostructured bulk systems, and (2) I discuss my measurements on several materials systems done with these characterization tools. First, I describe the development, assembly, and modification of a time-domain thermoreflectance (TDTR) system that we use to measure the thermal conductivity and the interface thermal conductance of a variety of samples including nanocrystalline alloys of Ni-Fe and Co-P, bulk metallic glasses, and other thin films. Next, a unique thermoelectric measurement system was designed and assembled for measurements of electrical resistivity and thermopower of thermoelectric materials in the temperature range of 20 to 350 °C. Finally, a commercial Anter Flashline 3000 thermal

  12. Model for thermal stress resistance of truly elastic materials containing more than one crack. Ph.D. Thesis

    Science.gov (United States)

    Lineback, L. D.

    1974-01-01

    The model was developed upon the physical properties of surface energy and intrinsic modulus of elasticity of a material containing a number of equal sized microcracks which are independent of one another. The effect of these cracks upon the strain energy per unit volume of material necessary to continue simultaneous crack growth as well as the measured physical properties was established, and the thermal stress resistance is developed in terms of this energy. The model is expressed in its final form in terms of the measured physical properties of fracture strength, effective modulus of elasticity, and coefficient of thermal expansion. The model was applied to existent thermal stress data of ceramic materials for which these physical properties had been measured. On the basis of these data it was concluded that the thermal stress resistance of a material may be improved by increasing the fracture strength.

  13. Instrument for Measuring Thermal Conductivity of Materials at Low Temperatures

    Science.gov (United States)

    Fesmire, James; Sass, Jared; Johnson, Wesley

    2010-01-01

    With the advance of polymer and other non-metallic material sciences, whole new series of polymeric materials and composites are being created. These materials are being optimized for many different applications including cryogenic and low-temperature industrial processes. Engineers need these data to perform detailed system designs and enable new design possibilities for improved control, reliability, and efficiency in specific applications. One main area of interest is cryogenic structural elements and fluid handling components and other parts, films, and coatings for low-temperature application. An important thermal property of these new materials is the apparent thermal conductivity (k-value).

  14. The crystallization behavior and thermal expansion properties of {beta}-eucryptite prepared by sol-gel route

    Energy Technology Data Exchange (ETDEWEB)

    Xia Long [School of Material Science and Engineering, Harbin Institute of Technology at Weihai, 2 Wenhua West Road, Weihai 264209 (China); Wen Guangwu, E-mail: wgw@hitwh.edu.cn [School of Material Science and Engineering, Harbin Institute of Technology at Weihai, 2 Wenhua West Road, Weihai 264209 (China); Song Liang; Wang Xinyu [School of Material Science and Engineering, Harbin Institute of Technology at Weihai, 2 Wenhua West Road, Weihai 264209 (China)

    2010-02-15

    Lithium-aluminosilicate glass-ceramics in the form of eucryptite were synthesized through sol-gel technique by mixing boehmite sol, silica sol and lithium salt and sintering at different temperatures for further analysis. Thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction (XRD), IR analysis and dilatometry were done to study sintering characteristics, phase transformation and thermal expansion behavior on the sintered specimens. XRD and FTIR results confirmed that crystallization of {beta}-eucryptite took place at about 600 deg. C, substantial increase of {beta}-eucryptite was observed in the specimens sintered at temperatures from 800 to 1300 deg. C. Trace amount of cristobalite also emerged at 600 deg. C and disappeared at 1300 deg. C. The thermal expansion behavior characteristics were found to be strongly influenced by crystalline phases in the specimens which depended on the sintering temperatures.

  15. Non-contact measurement of the coefficient of thermal expansion of Al 6061-T6 with fiber Bragg grating sensors

    Energy Technology Data Exchange (ETDEWEB)

    Hayat, Khazar; Ha, Sung Kyu [Hanyang University, Ansan (Korea, Republic of)

    2014-02-15

    An experimental study describing the non-contact measurement of the coefficient of thermal expansion of an aluminum (Al-6061-T6) specimen with two fiber Bragg grating sensors using a pair of C-lens collimators was carried out. The collimators were used for the free space coupling between the fiber Bragg sensors and the optical sensing interrogator. During the experiment, the wavelength distortion of the optical signals was observed. Consequently, the measured thermal strains were corrected using an estimated collimator correction factor of 0.8466. The coefficient of thermal expansion of the specimen was then calculated to be (22.0 ± 0.1)X10{sup -60} C{sup -1} for every 5 .deg. C step in the range 35 .deg. C ∼ 75 .deg. C, which was in good agreement with the typical value of 23.6X10{sup -60}C{sup -1} for aluminum.

  16. Shape forming by thermal expansion mismatch and shape memory locking in polymer/elastomer laminates

    Science.gov (United States)

    Yuan, Chao; Ding, Zhen; Wang, T. J.; Dunn, Martin L.; Qi, H. Jerry

    2017-10-01

    This paper studies a novel method to fabricate three-dimensional (3D) structure from 2D thermo-responsive shape memory polymer (SMP)/elastomer bilayer laminate. In this method, the shape change is actuated by the thermal mismatch strain between the SMP and the elastomer layers upon heating. However, the glass transition behavior of the SMP locks the material into a new 3D shape that is stable even upon cooling. Therefore, the second shape becomes a new permanent shape of the laminate. A theoretical model that accounts for the temperature-dependent thermomechanical behavior of the SMP material and thermal mismatch strain between the two layers is developed to better understand the underlying physics. Model predictions and experiments show good agreement and indicate that the theoretical model can well predict the bending behavior of the bilayer laminate. The model is then used in the optimal design of geometrical configuration and material selection. The latter also illustrates the requirement of thermomechanical behaviors of the SMP to lock the shape. Based on the fundamental understandings, several self-folding structures are demonstrated by the bilayer laminate design.

  17. Development of reduced-variable master curves for estimating tensile stresses of encapsulated solar cells caused by module deflection or thermal expansion

    Energy Technology Data Exchange (ETDEWEB)

    Cuddihy, E.F.

    1981-10-01

    Complex computer programs are being used by Spectrolab, Inc., to achieve encapsulation engineering optimization of photovoltaic modules. Optimization involves structural adequacy, electrical isolation (safety), maximum optical transmission, and minimum module temperature, at the lowest life-cycle energy cost. A goal of this activity is the generation, where possible, of encapsulation engineering generalities, principles, and design aids (tables or graphs) that would permit a ready, desktop capability of an engineering evaluation of encapsulation options involving materials or designs. The first efforts to generate reduced-variable mater curves for thermal expansion and deflection stress to serve as structural-analysis design aids are reported.

  18. Voltage tunability of thermal conductivity in ferroelectric materials

    Science.gov (United States)

    Ihlefeld, Jon; Hopkins, Patrick Edward

    2016-02-09

    A method to control thermal energy transport uses mobile coherent interfaces in nanoscale ferroelectric films to scatter phonons. The thermal conductivity can be actively tuned, simply by applying an electrical potential across the ferroelectric material and thereby altering the density of these coherent boundaries to directly impact thermal transport at room temperature and above. The invention eliminates the necessity of using moving components or poor efficiency methods to control heat transfer, enabling a means of thermal energy control at the micro- and nano-scales.

  19. Thermal transmittance of a cellulose loose-fill insulation material

    Energy Technology Data Exchange (ETDEWEB)

    Nicolajsen, A. [Danish Building and Urban Research, Hoersholm (Denmark). Department of Building Technology and Productivity

    2005-07-15

    The thermal performance of cellulose insulation material was investigated and compared with the thermal performance of stone wool batts. The moisture content in selected facade elements insulated with cellulose loose-fill insulation material and stone wool, was investigated as well as the influence of the moisture content on thermal transmittance. The investigation was carried out as a full-scale test under normal climate conditions in a moisture test house facility. Facade elements were built as timber frame constructions. Heat flow through the facade elements was measured with built-in heat flowmeters and the moisture content in the thermal insulation behind the wind barrier was measured with moisture measuring dowels. The test showed that the thermal performance of the tested type of cellulose loose-fill insulation material was significantly lower than the thermal performance of stone wool batts. The maximum moisture content of the insulation material was below, what in Denmark is considered critical for the onset of rot and growth of wood decaying fungi. The thermal transmittance did not change with changes in the moisture content within the investigated hygroscopic range. (author)

  20. Control of biaxial strain in single-layer molybdenite using local thermal expansion of the substrate

    Science.gov (United States)

    Plechinger, Gerd; Castellanos-Gomez, Andres; Buscema, Michele; van der Zant, Herre S. J.; Steele, Gary A.; Kuc, Agnieszka; Heine, Thomas; Schüller, Christian; Korn, Tobias

    2015-03-01

    Single-layer MoS2 is a direct-gap semiconductor whose electronic band structure strongly depends on the strain applied to its crystal lattice. While uniaxial strain can be easily applied in a controlled way, e.g., by bending of a flexible substrate with the atomically thin MoS2 layer on top, experimental realization of biaxial strain is more challenging. Here, we exploit the large mismatch between the thermal expansion coefficients of MoS2 and a silicone-based substrate to apply a controllable biaxial tensile strain by heating the substrate with a focused laser. The effect of this biaxial strain is directly observable in optical spectroscopy as a redshift of the MoS2 photoluminescence. We also demonstrate the potential of this method to engineer more complex strain patterns by employing highly absorptive features on the substrate to achieve non-uniform heat profiles. By comparison of the observed redshift to strain-dependent band structure calculations, we estimate the biaxial strain applied by the silicone-based substrate to be up to 0.2%, corresponding to a band gap modulation of 105 meV per percentage of biaxial tensile strain.

  1. Thermal expansion and magnetostriction measurements on PrIr{sub 2}Zn{sub 20}

    Energy Technology Data Exchange (ETDEWEB)

    Woerl, Andreas; Stingl, Christian; Sakai, Akito; Gegenwart, Philipp [Experimentalphysics VI, Center for Electronic Correlations and Magnetism, University of Augsburg (Germany); Matsumoto, Keisuke T.; Onimaru, Takahiro [Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima (Japan); Takabatake, Toshiro [Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima (Japan); Institute for Advanced Materials Research, Hiroshima University, Higashi-Hiroshima (Japan)

    2016-07-01

    Strong hybridization between electric quadrupole moments and conduction electrons gives rise to interesting physical phenomena such as new quantum phases and novel metallic properties. Non-fermi-liquid behavior based on the two channel Kondo effect is predicted by theory. PrIr{sub 2}Zn{sub 20} crystallizes in the CeCr{sub 2}Al{sub 20}-type structure, where the Pr{sup 3+} ions are surrounded by the highly symmetric cubic crystal field of 16 Zn atoms. The ground state is the non-magnetic Γ{sub 3} doublet and carries only electric quadrupole and a magnetic octupole moment. At T{sub Q}=0.11 K the electric quadrupole moments order in a antiferroquadrupolar way. A superconducting transition occurs at T{sub c}=0.05 K. The phase transition at T{sub Q}=0.11 K can be suppressed by high magnetic fields parallel to the [100] direction. We investigate the thermal expansion and magnetostriction at low temperatures. By applying high magnetic fields the system is tuned towards a quadrupolar quantum critical point. Furthermore the reaction of the system on breaking the cubic symmetry by compressive stress is explored.

  2. Coefficient of Thermal Expansion of the Beta and Delta Polymorphs of HMX

    Energy Technology Data Exchange (ETDEWEB)

    Weese, R K; Burnham, A K; Maienschein, J L

    2004-08-05

    Dimensional changes related to temperature cycling of the beta and delta polymorphs of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) are important for a variety of applications. The coefficient of thermal expansion (CTE) of the beta and delta phases are measured and reported in this work over a temperature range of -20 C to 215 C. In addition, dimensional changes associated with the phase transition were measured, both through the transition and back down. Initially, differential scanning calorimetry (DSC) was used to investigate back conversion of the delta phase to the beta phase polymorph. The most successful approach was first to measure the amount of the beta to delta conversion, then after a given cooling period a repeat analysis, to measure the heat consumed by a second pass through the beta to delta phase transition. In addition, TMA is used to measure the dimensional change of a 0.20-gram sample of HMX during its initial heating and then three days later during a 2nd heating. This HMX shows the beta to delta phase transition a second time, thereby confirming the back conversion from delta to beta phase HMX.

  3. Structural investigation of the negative thermal expansion in yttrium and rare earth molybdates

    Energy Technology Data Exchange (ETDEWEB)

    Guzman-Afonso, Candelaria; Torres, Manuel Eulalio; Sabalisck, Nanci; Sanchez-Fajardo, VIctor [Departamento de Fisica Basica, Universidad de La Laguna, Tenerife (Spain); Gonzalez-Silgo, Cristina; Gonzalez-Platas, Javier [Departamento de Fisica Fundamental II, Universidad de La Laguna, Tenerife (Spain); Lozano-GorrIn, Antonio Diego [Servicio Integrado de Difraccion de Rayos X, Universidad de La Laguna, Tenerife (Spain); Campo, Javier [Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza (Spain); RodrIguez-Carvajal, Juan, E-mail: csilgo@ull.es [Institut Laue-Langevin, Grenoble (France)

    2011-08-17

    The Sc{sub 2}(WO{sub 4}){sub 3}-type phase (Pbcn) of Y{sub 2}(MoO{sub 4}){sub 3}, Er{sub 2}(MoO{sub 4}){sub 3} and Lu{sub 2}(MoO{sub 4}){sub 3} has been prepared by the conventional solid-state synthesis with preheated oxides and the negative thermal expansion (NTE) has been investigated along with an exhaustive structural study, after water loss. Their crystal structures have been refined using the neutron and x-ray powder diffraction data of dehydrated samples from 150 to 400 K. The multi-pattern Rietveld method, using atomic displacements with respect to a known structure as parameters to refine, has been applied to facilitate the interpretation of the NTE behavior. Polyhedral distortions, transverse vibrations of A{center_dot}{center_dot}{center_dot}O-Mo (A = Y and rare earths) binding oxygen atoms, non-bonded distances A{center_dot}{center_dot}{center_dot}Mo and atomic displacements from the high temperature structure, have been evaluated as a function of the temperature and the ionic radii.

  4. Thermal expansion and magnetic properties of benzoquinone-bridged dinuclear rare-earth complexes.

    Science.gov (United States)

    Moilanen, Jani O; Mansikkamäki, Akseli; Lahtinen, Manu; Guo, Fu-Sheng; Kalenius, Elina; Layfield, Richard A; Chibotaru, Liviu F

    2017-10-10

    The synthesis and structural characterization of two benzoquinone-bridged dinuclear rare-earth complexes [BQ(MCl2·THF3)2] (BQ = 2,5-bisoxide-1,4-benzoquinone; M = Y (1), Dy (2)) are described. Of these reported metal complexes, the dysprosium analogue 2 is the first discrete bridged dinuclear lanthanide complex in which both metal centres reside in pentagonal bipyramidal environments. Interestingly, both complexes undergo significant thermal expansion upon heating from 120 K to 293 K as illustrated by single-crystal X-ray and powder diffraction experiments. AC magnetic susceptibility measurements reveal that 2 does not show the slow relation of magnetization in zero dc field. The absent of single-molecule behaviour in 2 arises from the rotation of the principal magnetic axis as compared to the pseudo-C5 axis of the pentagonal bipyramidal environment as suggested by ab initio calculations. The cyclic voltammetry and chemical reduction experiments demonstrated that complexes 1 and 2 can be reduced to radical species containing [BQ(3)˙(-)]. This study establishes efficient synthetic strategy to make bridged redox-active multinuclear lanthanide complexes with a pentagonal bipyramidal coordination environment that are potential precursors for single-molecule magnets.

  5. Direct observation of a transverse vibrational mechanism for negative thermal expansion in Zn(CN)2: an atomic pair distribution function analysis.

    Science.gov (United States)

    Chapman, Karena W; Chupas, Peter J; Kepert, Cameron J

    2005-11-09

    The instantaneous structure of the cyanide-bridged negative thermal expansion (NTE) material Zn(CN)(2) has been probed using atomic pair distribution function (PDF) analysis of high energy X-ray scattering data (100-400 K). The temperature dependence of the atomic separations extracted from the PDFs indicates an increase of the average transverse displacement of the cyanide bridge from the line connecting the Zn(II) centers with increasing temperature. This allows the contraction of non-nearest-neighbor Zn...Zn' and Zn...C/N distances despite the observed expansion of the individual direct Zn-C/N and C-N bonds. Thus, this analysis provides definitive structural confirmation that an increase in the average displacement of bridging atoms is the origin of the NTE behavior. The lattice parameters reveal a slight reduction in the NTE behavior at high temperature from a minimum coefficient of thermal expansion (alpha = dl/ldT) of -19.8 x 10(-6) K(-1) below 180 K, which is attributed to interaction between the doubly interpenetrated frameworks that comprise the structure.

  6. Real-space distribution of local WO4 ordering in negative thermal expansive ZrW2O8.

    Science.gov (United States)

    Sato, Yukio; Yamamura, Yasuhisa; Saito, Kazuya; Ikuhara, Yuichi

    2012-08-29

    Solids usually expand when they are heated. This is quite common behavior of solids; however, there are some exceptions. Zirconium tungstate (ZrW(2)O(8)) is a prototype material among them, because it has the highest degree of negative thermal expansion (NTE) over broad temperature range. Intensive investigation of NTE mechanisms has suggested the importance of metal-oxygen polyhedra. However, most of the studies have been done with volume-averaged techniques, and microscopic information has been lacking. Here, our electron microscopy observations have unraveled the real-space distribution of local WO(4) tetrahedra ordering for the first time. We have found that (i) the WO(4) ordering is partly inverted; (ii) WO(4) is disordered on the nanoscale; and (iii) doping with scandium enhances the WO(4) disordering. These findings led to construction of a microstructure model for ZrW(2)O(8), providing a new structural perspective for better understanding of local structure and its role in phase transitions.

  7. An Ag based brazing system with a tunable thermal expansion for the use as sealant for solid oxide cells

    DEFF Research Database (Denmark)

    Kiebach, Wolff-Ragnar; Engelbrecht, Kurt; Grahl-Madsen, Laila

    2016-01-01

    An Ag-Al2TiO5 composite braze was developed and successfully tested as seal for solid oxide cells. The thermo-mechanical properties of the Ag-Al2TiO5 system and the chemical compatibility between this composite braze and relevant materials used in stacks were characterized and the leak rates...... as a function of the operation temperature were measured. The thermal expansion coefficient in the Ag-Al2TiO5 system can be tailored by varying the amount of the ceramic filler. The brazing process can be carried out in air, the joining partners showed a good chemical stability and sufficient low leak rates...... were demonstrated. Furthermore, the long-term stability of the Ag-Al2TiO5 composite braze was studied under relevant SOFC and SOEC conditions. The stability of brazed Crofer/Ag-Al2TiO5/NiO-YSZ assemblies in reducing atmosphere and in pure oxygen was investigated over 500 h at 850 °C. Additionally...

  8. The world's smallest capacitive dilatometer, for high-resolution thermal expansion and magnetostriction in high magnetic fields.

    Science.gov (United States)

    Küchler, R; Wörl, A; Gegenwart, P; Berben, M; Bryant, B; Wiedmann, S

    2017-08-01

    For the characterization of novel quantum phases of matter, it is often required to study materials under multi-extreme conditions, in particular down to very low temperatures and in very high magnetic fields. We developed the world's smallest high-resolution capacitive dilatometer suitable for temperatures down to 10 mK and usage in high magnetic fields up to 37.5 T. Despite the extreme miniaturization, the capacitive dilatometer can resolve length changes down to 0.01 Å. This is an unprecedented resolution in a capacitive dilatometer of this compact size. Many cryogenic devices have limited space. Due to the extremely reduced cell size (3 cm3, 12 g), implementation or new applications in many of these sample space lacking devices are now possible. As an important example, the minute device can now be rotated in any standard cryostat, including dilution refrigerators or the commercial physical property measurement system. The present super compact design provides also for high resolution thermal expansion and magnetostriction measurements in a 15.2 mm diameter tube, enabling its use in the 32 mm bore, 37.5 T Bitter magnet at the High Field Magnet Laboratory in Nijmegen down to a temperature of 300 mK.

  9. Anisotropic properties of high-temperature polyimide thin films: Dielectric and thermal-expansion behaviors

    Science.gov (United States)

    Ree, M.; Chen, K.-J.; Kirby, D. P.; Katzenellenbogen, N.; Grischkowsky, D.

    1992-09-01

    Multilayer poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) polyimide films of 172 μm total thickness (11.4 μm per layer) were prepared from the poly(amic acid) precursor solution through repetition of a spin-coat/softbake/cure process. Wide-angle x-ray diffraction results indicate that the polyimide molecules in the multilayer films are highly ordered along the chain axes as well as in the lateral direction and furthermore are highly oriented in the film plane as observed in a single-layer film of 11.4 μm thickness. The multilayer films showed the same dynamic mechanical properties and glass transition behavior (Tg = 330 °C) as a single-layer film. For the multilayer films both the in-plane dielectric constant (ɛ'XY) and out-of-plane thermal-expansion coefficient (αZ) were measured using time-domain spectroscopy and conventional thermal mechanical analysis, respectively. The ɛ'XY at room temperature was 3.69 (±0.08) over a frequency range of 0.35-2.50 THz. A similar ɛ'XY is predicted at frequencies of ≤0.35 THz. In contrast to the ɛ'XY, a relatively lower out-of-plane dielectric constant (ɛ'Z) was observed: ɛ'Z = 2.96-3.03 (±0.02) at 1 MHz, depending on moisture content in the film. The dielectric loss ɛ`Z at 1 MHz was 0.011-0.014 (±0.001), depending on moisture content. The measured αZ was 74 ppm/°C over the temperature range of 25-150 °C, which was much higher than αXY = 2.6-5 ppm/°C. Consequently, large anisotropic ɛ' and α have been observed in the in plane and out of plane of the thermally imidized BPDA-PDA films. The anisotropic ɛ' and α were caused by high in-plane orientation of the polyimide molecules highly ordered along the chain axes in the films.

  10. MISSE Thermal Control Materials with Comparison to Previous Flight Experiments

    Science.gov (United States)

    Finckenor, Miria; Pippin, H. Gary; Frey, George

    2008-01-01

    Many different passive thermal control materials were flown as part of the Materials on International Space Station Experiment (MISSE), including inorganic coatings, anodized aluminum, and multi-layer insulation materials. These and other material samples were exposed to the low Earth orbital environment of atomic oxygen, ultraviolet radiation, thermal cycling, and hard vacuum, though atomic oxygen exposure was limited for some samples. Materials flown on MISSE-1 and MISSE-2 were exposed to the space environment for nearly four years. Materials flown on MISSE-3, MISSE-4, and MISSE-5 were exposed to the space environment for one year. Solar absorptance, infrared emittance, and mass measurements indicate the durability of these materials to withstand the space environment. Effects of short duration versus long duration exposure on ISS are explored, as well as comparable data from previous flight experiments, such as the Passive Optical Sample Assembly (POSA), Optical Properties Monitor (OPM), and Long Duration Exposure Facility (LDEF).

  11. Phase Change Material Thermal Power Generator

    Science.gov (United States)

    Jones, Jack A. (Inventor); Chao, Yi (Inventor); Valdez, Thomas I. (Inventor)

    2014-01-01

    An energy producing device, for example a submersible vehicle for descending or ascending to different depths within water or ocean, is disclosed. The vehicle comprises a temperature-responsive material to which a hydraulic fluid is associated. A pressurized storage compartment stores the fluid as soon as the temperature-responsive material changes density. The storage compartment is connected with a hydraulic motor, and a valve allows fluid passage from the storage compartment to the hydraulic motor. An energy storage component, e.g. a battery, is connected with the hydraulic motor and is charged by the hydraulic motor when the hydraulic fluid passes through the hydraulic motor. Upon passage in the hydraulic motor, the fluid is stored in a further storage compartment and is then sent back to the area of the temperature-responsive material.

  12. Thermal-Mechanical and Thermal Behavior of High-Temperature Structural Materials.

    Science.gov (United States)

    1979-12-31

    Physical Constants of Porcelain ," Nagoya Kogyo Gijutsu Shikensko Hokoku, 8 [5] 37-43 (1959); Ceram. Abstracts, 1959, Nov. p. 287a. 6. F. P. Knudsen...engineering materials appropriate for conditions which require high thermal shock resistance in combination with good thermal insulating ability"C. Finally

  13. Effect of dynamic and thermal prehistory on aerodynamic characteristics and heat transfer behind a sudden expansion in a round tube

    Science.gov (United States)

    Terekhov, V. I.; Bogatko, T. V.

    2017-03-01

    The results of a numerical study of the influence of the thicknesses of dynamic and thermal boundary layers on turbulent separation and heat transfer in a tube with sudden expansion are presented. The first part of this work studies the influence of the thickness of the dynamic boundary layer, which was varied by changing the length of the stabilization area within the maximal extent possible: from zero to half of the tube diameter. In the second part of the study, the flow before separation was hydrodynamically stabilized and the thermal layer before the expansion could simultaneously change its thickness from 0 to D1/2. The Reynolds number was varied in the range of {Re}_{{{{D}}1 }} = 6.7 \\cdot 103 {{to}} 1.33 \\cdot 105, and the degree of tube expansion remained constant at ER = ( D 2/ D 1)2 = 1.78. A significant effect of the thickness of the separated boundary layer on both dynamic and thermal characteristics of the flow is shown. In particular, it was found out that with an increase in the thickness of the boundary layer the recirculation zone increases and the maximal Nusselt number decreases. It was determined that the growth of the heat layer thickness does not affect the hydrodynamic characteristics of the flow after separation but does lead to a reduction of heat transfer intensity in the separation area and removal of the coordinates of maximal heat transfer from the point of tube expansion. The generalizing dependence for the maximal Nusselt number at various thermal layer thicknesses is given. Comparison with experimental data confirmed the main trends in the behavior of heat and mass transfer processes in separated flows behind a step with different thermal prehistories.

  14. Porous materials produced from incineration ash using thermal plasma technology.

    Science.gov (United States)

    Yang, Sheng-Fu; Chiu, Wen-Tung; Wang, To-Mai; Chen, Ching-Ting; Tzeng, Chin-Ching

    2014-06-01

    This study presents a novel thermal plasma melting technique for neutralizing and recycling municipal solid waste incinerator (MSWI) ash residues. MSWI ash residues were converted into water-quenched vitrified slag using plasma vitrification, which is environmentally benign. Slag is adopted as a raw material in producing porous materials for architectural and decorative applications, eliminating the problem of its disposal. Porous materials are produced using water-quenched vitrified slag with Portland cement and foaming agent. The true density, bulk density, porosity and water absorption ratio of the foamed specimens are studied here by varying the size of the slag particles, the water-to-solid ratio, and the ratio of the weights of the core materials, including the water-quenched vitrified slag and cement. The thermal conductivity and flexural strength of porous panels are also determined. The experimental results show the bulk density and the porosity of the porous materials are 0.9-1.2 g cm(-3) and 50-60%, respectively, and the pore structure has a closed form. The thermal conductivity of the porous material is 0.1946 W m(-1) K(-1). Therefore, the slag composite materials are lightweight and thermal insulators having considerable potential for building applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Applying infrared measurements in a measuring system for determining thermal parameters of thermal insulation materials

    Science.gov (United States)

    Chudzik, S.

    2017-03-01

    The paper presents results of research on an innovative method for determining thermal parameters of thermal insulating materials. The method is based on harmonic thermal excitations. Temperature measurements at selected points of a specimen under test are performed by means of semiconductor infrared sensors. The study also employs a 3D model of thermal diffusion. To obtain a solution of the coefficient inverse problem a method based on an artificial neural network is presented. The heat transfer coefficient on the specimen surface is estimated on the basis of a reference specimen. The validity of the adopted model of heat diffusion and the usefulness of the method proposed are verified experimentally.

  16. Porous materials for thermal management under extreme conditions.

    Science.gov (United States)

    Clyne, T W; Golosnoy, I O; Tan, J C; Markaki, A E

    2006-01-15

    A brief analysis is presented of how heat transfer takes place in porous materials of various types. The emphasis is on materials able to withstand extremes of temperature, gas pressure, irradiation, etc. i.e. metals and ceramics, rather than polymers. A primary aim is commonly to maximize either the thermal resistance (i.e. provide insulation) or the rate of thermal equilibration between the material and a fluid passing through it (i.e. to facilitate heat exchange). The main structural characteristics concern porosity (void content), anisotropy, pore connectivity and scale. The effect of scale is complex, since the permeability decreases as the structure is refined, but the interfacial area for fluid-solid heat exchange is, thereby, raised. The durability of the pore structure may also be an issue, with a possible disadvantage of finer scale structures being poor microstructural stability under service conditions. Finally, good mechanical properties may be required, since the development of thermal gradients, high fluid fluxes, etc. can generate substantial levels of stress. There are, thus, some complex interplays between service conditions, pore architecture/scale, fluid permeation characteristics, convective heat flow, thermal conduction and radiative heat transfer. Such interplays are illustrated with reference to three examples: (i) a thermal barrier coating in a gas turbine engine; (ii) a Space Shuttle tile; and (iii) a Stirling engine heat exchanger. Highly porous, permeable materials are often made by bonding fibres together into a network structure and much of the analysis presented here is oriented towards such materials.

  17. Energy Consumption of Insulated Material Using Thermal Effect Analysis

    OpenAIRE

    Fadzil M. A.; Norliyati M. A.; Hilmi M. A.; Ridzuan A. R.; Wan Ibrahim M. H.; Assrul R. Z.

    2017-01-01

    Wall is one of the structures elements that resist direct heat from the atmosphere. Modification on several structures is relevance to reduce filtrate thermal movement on wall. Insulation material seems to be suitable to be implemented since its purpose meets the heat resistance requirement. Insulation material applied as to generate positive impact in energy saving through reduction in total building energy consumption. Fiberglass is one of the insulation materials that can be used to insula...

  18. Effect of colouring green stage zirconia on the adhesion of veneering ceramics with different thermal expansion coefficients

    Science.gov (United States)

    Aktas, Guliz; Sahin, Erdal; Vallittu, Pekka; Özcan, Mutlu; Lassila, Lippo

    2013-01-01

    This study evaluated the adhesion of zirconia core ceramics with their corresponding veneering ceramics, having different thermal expansion coefficients (TECs), when zirconia ceramics were coloured at green stage. Zirconia blocks (N=240; 6 mm×7 mm×7 mm) were manufactured from two materials namely, ICE Zirconia (Group 1) and Prettau Zirconia (Group 2). In their green stage, they were randomly divided into two groups. Half of the specimens were coloured with colouring liquid (shade A2). Three different veneering ceramics with different TEC (ICE Ceramic, GC Initial Zr and IPS e.max Ceram) were fired on both coloured and non-coloured zirconia cores. Specimens of high noble alloys (Esteticor Plus) veneered with ceramic (VM 13) (n=16) acted as the control group. Core–veneer interface of the specimens were subjected to shear force in the Universal Testing Machine (0.5 mm⋅min−1). Neither the zirconia core material (P=0.318) nor colouring (P=0.188) significantly affected the results (three-way analysis of variance, Tukey's test). But the results were significantly affected by the veneering ceramic (P=0.000). Control group exhibited significantly higher mean bond strength values (45.7±8) MPa than all other tested groups ((27.1±4.1)−(39.7±4.7) and (27.4±5.6)−(35.9±4.7) MPa with and without colouring, respectively) (Pzirconia–veneer test groups, predominantly mixed type of failures were observed with the veneering ceramic covering 1/3 of the metal surface. Colouring zirconia did not impair adhesion of veneering ceramic, but veneering ceramic had a significant influence on the core–veneer adhesion. Metal–ceramic adhesion was more reliable than all zirconia–veneer ceramics tested. PMID:24158142

  19. Effect of colouring green stage zirconia on the adhesion of veneering ceramics with different thermal expansion coefficients.

    Science.gov (United States)

    Aktas, Guliz; Sahin, Erdal; Vallittu, Pekka; Ozcan, Mutlu; Lassila, Lippo

    2013-12-01

    This study evaluated the adhesion of zirconia core ceramics with their corresponding veneering ceramics, having different thermal expansion coefficients (TECs), when zirconia ceramics were coloured at green stage. Zirconia blocks (N=240; 6 mm×7 mm×7 mm) were manufactured from two materials namely, ICE Zirconia (Group 1) and Prettau Zirconia (Group 2). In their green stage, they were randomly divided into two groups. Half of the specimens were coloured with colouring liquid (shade A2). Three different veneering ceramics with different TEC (ICE Ceramic, GC Initial Zr and IPS e.max Ceram) were fired on both coloured and non-coloured zirconia cores. Specimens of high noble alloys (Esteticor Plus) veneered with ceramic (VM 13) (n=16) acted as the control group. Core-veneer interface of the specimens were subjected to shear force in the Universal Testing Machine (0.5 mm⋅min(-1)). Neither the zirconia core material (P=0.318) nor colouring (P=0.188) significantly affected the results (three-way analysis of variance, Tukey's test). But the results were significantly affected by the veneering ceramic (P=0.000). Control group exhibited significantly higher mean bond strength values (45.7±8) MPa than all other tested groups ((27.1±4.1)-(39.7±4.7) and (27.4±5.6)-(35.9±4.7) MPa with and without colouring, respectively) (Pveneer test groups, predominantly mixed type of failures were observed with the veneering ceramic covering veneering ceramic was left adhered >1/3 of the metal surface. Colouring zirconia did not impair adhesion of veneering ceramic, but veneering ceramic had a significant influence on the core-veneer adhesion. Metal-ceramic adhesion was more reliable than all zirconia-veneer ceramics tested.

  20. THERMAL CONDUCTIVITY OF HIGHLY POROUS MATERIALS

    Directory of Open Access Journals (Sweden)

    Rumyantsev Boris Mikhaylovich

    2012-10-01

    Heat fluxes inside aerated concrete are determined by the heat transfer driven by the filtration of the mixture of vapour and air and its convection inside cells. Products made of mineral cotton demonstrate accessible porosity; therefore, heat fluxes are determined by the properties of gas, or the air-vapour mixture under constant pressure. A convective heat flux is primarily dependent on the air permeability of the media and the characteristics (pressures and concentrations of internal and external surfaces of the material under research.

  1. Effects of waste eggshells and SiC addition on specific strength and thermal expansion of hybrid green metal matrix composite.

    Science.gov (United States)

    Sharma, Satpal; Dwivedi, Shashi Prakash

    2017-07-05

    Chicken eggshell waste is an industrial byproduct, and its disposal constitutes a serious environmental hazard. Chicken eggshell can be used in commercial products to produce new materials with low cost and density. Low density material which can sustain at higher temperature is a remarkable area of research. Keeping these facts in the mind, the present investigation aims to study the physical behaviour, specific strength and thermal expansion of AA2014/SiC/carbonized eggshell hybrid green metal matrix composites. Microstructure of hybrid green metal matrix shows that the reinforcement particles (SiC particulates and carbonized eggshells particles) are uniformly distributed in the matrix AA2014 alloy. Specific strength for the composites containing 2.5wt.% SiC and up to 7.5wt.% carbonized eggshell was observed to be higher than that of the other selected composites. While for the same composition (AA2014/2.5% SiC/7.5% carbonized eggshell composites), porosity was observed lower than other selected composites. The results revealed that sample of AA2014/2.5% SiC/7.5% carbonized eggshell showed minimum cross sectional area reduction after the thermal expansion at 450°C among all the selected samples. Overall costs of hybrid metal matrix composites were also calculated. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Thermal expansion and the heat capacity of nanocrystalline and coarse-crystalline silver sulfide Ag2S

    Science.gov (United States)

    Sadovnikov, S. I.; Gusev, A. I.

    2017-09-01

    The thermal expansion and the heat capacity of coarse-crystalline and nanocrystalline silver sulfide Ag2S were studied by dilatometry and differential scanning calorimentry for the first time in the temperature range 290-970 K. It is found that the thermal expansion coefficient and the heat capacity of nanocrystalline silver sulfide in this temperature range are higher than those in the case of the coarse-crystalline sulfide. It is revealed that the transformation of α-Ag2S acanthite to β-Ag2S argentite and β-Ag2S argentite to γ-Ag2S phase are the first-order phase transitions; the temperatures and the enthalpies of these transformations have been determined.

  3. Origin of Negative Thermal Expansion in Cubic ZrW2O8 Revealed by High Pressure Inelastic Neutron Scattering

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Schober, H.; Mary, T. A.

    2001-05-01

    Isotropic negative thermal expansion has been reported in cubic ZrW2O8 over a wide range of temperatures (0-1050 K). Here we report the direct experimental determination of the Grüneisen parameters of phonon modes as a function of their energy, averaged over the whole Brillouin zone, by means of high pressure inelastic neutron scattering measurements. We observe a pronounced softening of the phonon spectrum at P = 1.7 kbar compared to that at ambient pressure by about 0.1-0.2 meV for phonons of energy below 8 meV. This unusual phonon softening on compression, corresponding to large negative Grüneisen parameters, is able to account for the observed large negative thermal expansion.

  4. Unusual Low-Energy Phonon Dynamics in the Negative Thermal Expansion Compound ZrW2O8

    Science.gov (United States)

    Hancock, Jason N.; Turpen, Chandra; Schlesinger, Zack; Kowach, Glen R.; Ramirez, Arthur P.

    2004-11-01

    An infrared study of the phonon spectra of ZrW2O8 as a function of temperature which includes the low-energy (2 10meV) region relevant to negative thermal expansion is reported and discussed in the context of specific heat and neutron density of state results. The prevalence of infrared active phonons at low energy and their observed temperature dependence are highly unusual and indicative of exotic low-energy lattice dynamics. Eigenvector calculations indicate a mixing of librational and translational motion within each low-frequency IR mode. The role of the underconstrained structure in establishing the nature of these modes and the relationship between the IR spectra and the large negative thermal expansion in ZrW2O8 are discussed.

  5. Linear thermal expansion data for tuffs from the unsaturated zone at Yucca Mountain, Nevada; Yucca Mountain Site Characterization Project

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, B.M.; Chocas, C.S.

    1992-07-01

    Experiment results are presented for linear thermal expansion measurements on tuffaceous rocks from the unsaturated thermal expansion measurements could not be determined.

  6. An alternative empirical model for the relationship between the bond valence and the thermal expansion rate of chemical bonds.

    Science.gov (United States)

    Sidey, Vasyl

    2015-08-01

    The relationship between the bond valence s and the thermal expansion rate of chemical bonds (dr/dT) has been closely approximated by using the alternative three-parameter empirical model (dr/dT) = (u + vs)(-1/w), where u, v and w are the refinable parameters. Unlike the s-(dr/dT) model developed by Brown et al. [(1997), Acta Cryst. B53, 750-761], this alternative model can be optimized for particular s-(dr/dT) datasets in the least-squares refinement procedure. For routine calculations of the thermal expansion rates of chemical bonds, the alternative model with the parameters u = -63.9, v = 2581.0 and w = 0.647 can be recommended.

  7. The fabrication and thermal expansion properties of 4H-Ag nanowire arrays in porous anodic alumina templates.

    Science.gov (United States)

    Zhou, Ye; Fei, Guang Tao; Cui, Ping; Wu, Bing; Wang, Biao; Zhang, Li De

    2008-07-16

    Hexagonal silver nanowire (4H-Ag NW) arrays with preferred orientation are fabricated into the holes of porous anodic alumina membranes (AAMs) by direct current electrodeposition. The addition of tartaric acid and low deposition temperature are crucial conditions for the growth of 4H-Ag NWs. The thermal expansion properties of the as-prepared and annealed 4H-Ag NWs are studied by in situ x-ray diffraction in the temperature range from room temperature to 800 °C. The axial thermal expansion coefficient (TEC) of the as-prepared sample decreases initially and increases subsequently, while that of the annealed sample consistently increases during the whole measuring process.

  8. The fabrication and thermal expansion properties of 4H-Ag nanowire arrays in porous anodic alumina templates

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Ye; Fei Guangtao; Cui Ping; Wu Bing; Wang Biao; Zhang Lide [Key Laboratory of Materials Physics and Anhui Key Laboratory of Nanomaterials and Nanostructures, Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, PO Box 1129, Hefei, 230031 (China)], E-mail: gtfei@issp.ac.cn

    2008-07-16

    Hexagonal silver nanowire (4H-Ag NW) arrays with preferred orientation are fabricated into the holes of porous anodic alumina membranes (AAMs) by direct current electrodeposition. The addition of tartaric acid and low deposition temperature are crucial conditions for the growth of 4H-Ag NWs. The thermal expansion properties of the as-prepared and annealed 4H-Ag NWs are studied by in situ x-ray diffraction in the temperature range from room temperature to 800 deg. C. The axial thermal expansion coefficient (TEC) of the as-prepared sample decreases initially and increases subsequently, while that of the annealed sample consistently increases during the whole measuring process.

  9. Effect of micro-cracking on the thermal conductivity and thermal expansion of tialite (Al2TiO5 ceramics

    Directory of Open Access Journals (Sweden)

    Ramanathan Papitha

    2013-09-01

    Full Text Available The pure and magnesium silicate (Mg2+/Si4+ doped tialite ceramics were prepared from the homogenized mixture of alumina and titania by uniaxial pressing and pressure-less sintering at 1550 °C in air. Thermal conductivity and thermal expansion of the doped and undoped tialite ceramics were measured from 30 to 700 °C. The identical trend in the behaviour of these thermal properties most probably is influenced by the population, size and shape of microcracks present throughout the grain and grain boundaries as complemented by the microstructural observations. The observed decrease in thermal properties of the doped in comparison to the pure tialite can be attributed to the substitutional Mg2+ and Si4+ at Al3+ site in Al2TiO5 which promotes the phonon scattering and causes modifications in micro-crack density and the morphology of the cracks.

  10. PHASE CHANGE MATERIALS IN FLOOR TILES FOR THERMAL ENERGY STORAGE

    Energy Technology Data Exchange (ETDEWEB)

    Douglas C. Hittle

    2002-10-01

    Passive solar systems integrated into residential structures significantly reduce heating energy consumption. Taking advantage of latent heat storage has further increased energy savings. This is accomplished by the incorporation of phase change materials into building materials used in passive applications. Trombe walls, ceilings and floors can all be enhanced with phase change materials. Increasing the thermal storage of floor tile by the addition of encapsulated paraffin wax is the proposed topic of research. Latent heat storage of a phase change material (PCM) is obtained during a change in phase. Typical materials use the latent heat released when the material changes from a liquid to a solid. Paraffin wax and salt hydrates are examples of such materials. Other PCMs that have been recently investigated undergo a phase transition from one solid form to another. During this process they will release heat. These are known as solid-state phase change materials. All have large latent heats, which makes them ideal for passive solar applications. Easy incorporation into various building materials is must for these materials. This proposal will address the advantages and disadvantages of using these materials in floor tile. Prototype tile will be made from a mixture of quartz, binder and phase change material. The thermal and structural properties of the prototype tiles will be tested fully. It is expected that with the addition of the phase change material the structural properties will be compromised to some extent. The ratio of phase change material in the tile will have to be varied to determine the best mixture to provide significant thermal storage, while maintaining structural properties that meet the industry standards for floor tile.

  11. The infrared camera application for calculating the impact of the feed screw thermal expansion on machining accuracy

    Science.gov (United States)

    Matras, A.

    2017-08-01

    The paper discusses the impact of the feed screw heating on the machining accuracy. The test stand was built based on HASS Mini Mill 2 CNC milling machine and a Flir SC620 infrared camera. Measurements of workpiece were performed on Talysurf Intra 50 Taylor Hobson profilometer. The research proved that the intensive work of the milling machine lasted 60 minutes, causing thermal expansion of the feed screw what influence on the dimension error of the workpiece.

  12. Thermal expansion of LaFeAsO1-xFx: evidence for high temperature fluctuations

    NARCIS (Netherlands)

    Wang, L.; Köhler, U.; Leps, N.; Kondrat, A.; Nale, M.; Gasparini, A.; de Visser, A.; Behr, G.; Hess, C.; Klingeler, R.; Büchner, B.

    2009-01-01

    We present measurements of the thermal expansion coefficient α of polycrystalline LaFeAsO1−xFx (x≤0.1). The magnetic and structural transitions of the samples with x≤0.04 give rise to large anomalies in α(T) while the onset of superconductivity in the crystals with x≥0.05 is not resolved. Above the

  13. Determination of the coefficient of thermal expansion of jp-4 fuels. Interim report, April 1983-July 1985

    Energy Technology Data Exchange (ETDEWEB)

    Duvall, D.S.; Hale, M.D.; Lewis, D.J.; Snyder, A.D.

    1985-12-01

    Precise density determinations were made on 100 JP-4 jet fuels using a Mettler/Paar Model ADS-55 density-measuring system. Statistical analysis of the density measurements was performed using a computerized nonlinear regression technique; and coefficient of thermal expansion values were calculated for each fuel at 60 F. A majortiy of the fuels (88 out of 100) were consistent with the API published volume series correction for crude oils.

  14. FINITE ELEMENT METHOD ANALYSIS OF PIPE MATERIAL TEMPERATURE CHANGES INFLUENCE ON LINE EXPANSION LOOPS IN HYDRAULIC INSTALLATIONS ON MODERN TANKERS

    Directory of Open Access Journals (Sweden)

    Bartlomiej Zylinski

    2011-01-01

    Full Text Available Finite element method analysis of main lines of hydraulic central loading system installation expansion loops mounted on product and chemical tankers has been presented in the paper. The axial forces problem in installations mounted along the ship's open decks executed from hull deformations on waves and thermal stresses is given. Use of "U" type expansion loops is described. Results of forces in anchor points and stresses of Mises due to expansion loop deformations are shown. Calculations were made by ABAQUS Ver.6.7 FEM computer program.

  15. Effective Thermal Conductivity of Insulating Material made from Recycled Newspapers

    Science.gov (United States)

    Yamada, Etsuro; Takahashi, Kaneko; Sato, Mitsuo; Ishii, Yukihiro

    In this paper, the experimental results are represented on the effective thermal conductivity of cellulose insulation powder which is made from recycled newspapers. This insulating material is useful for energy and resources saving. The steady state cylindrical absolute method is employed by considering the accuracy of measurement. The experimental results are compared with the ones measured previously by other methods. The main results obtained are as follows (1) The effective thermal conductivity of this insulating material increases with increasing temperature and effective specific density, respectively. But, these increasing rate is not so large. (2) The effective thermal conductivity is about 0.04-0.06[W/mK] at the range of the effective specific density less than 100 [kg/m3]. This value is comparable with other industrial insulating materials.

  16. Exercises in 80223 Numerical Modelling of Thermal Processing of Materials

    DEFF Research Database (Denmark)

    Frandsen, Jens Ole

    Processing of Materials'. The original copy is kept in the archives of TM on the ground floor of building 425. A copy of the exercise book can be made available by contacting the secretary on the ground floor of building 425. Please give the following number: TM 00.01 (TM = Thermal processing of Materials)......This exercise book contains exercise instructions for the 7 compulsory exercises (Exercise 1-7) and the final exercise (Exercise 8) in the course 80223 'Numerical Modelling of Thermal Processing of Materials'. The exercise book also contains written program examples in 'C' and 'Pascal'. Finally......, guidelines are given on how to write the report which has to be handed in at the end of the course. The exercise book is a updated version of the exercise book from 1999. The exercise book is used in the course 42224 'Numerical Process Modelling' which earlier was called 80223 'Numerical Modelling of Thermal...

  17. Optimal Experiment Design for Thermal Characterization of Functionally Graded Materials

    Science.gov (United States)

    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.

  18. Inelastic neutron scattering and lattice dynamical calculation of negative thermal expansion in HfW2O8

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Kolesnikov, A. I.; Loong, C.-K.; Mary, T. A.

    2003-08-01

    The compounds ZrW2O8 and HfW2O8 undergo large isotropic negative thermal expansion (NTE) over a wide range of temperatures up to 1443 K and 1050 K, respectively. We have showed previously that large softening of low-energy phonons in ZrW2O8 is responsible for its anomalous thermal expansion behavior. In order to understand the effect of replacing Zr by Hf on NTE behavior we report lattice dynamical calculations and neutron time-of-flight spectroscopic measurements of the phonon density of states for cubic HfW2O8. The calculated phonon spectrum for cubic HfW2O8 is in fair agreement with the experimental data. The phonon spectra in the Zr and Hf compounds differ at low energies largely due to the mass difference. The calculated negative thermal expansion for HfW2O8 is in good agreement with experimental data from the literature. We further report a calculation of the pressure dependence of the detailed phonon dispersion relation which reveals large softening of several phonon branches on compression associated with the NTE.

  19. Analysis of the Effect of Construction and Operation of Thermal Expansion System Compounds on Steam Turbines Reliability

    Science.gov (United States)

    Murmansky, B. E.; Sosnovsky, A. Yu.; Brodov, Yu. M.

    2017-11-01

    The inspection results are presented of turbines of different types and capacity, showing the influence of various factors (such as increased frictional forces on the mating surfaces, clearance changes in the joints elements, TES elements design, state of the thermal expansions compensation system of pipelines) on the operation both of thermal expansion system and of the turbine as a whole. The data are presented on the effectiveness of various measures aimed to eliminate the causes of the turbine thermal expansion system deviations from its normal operation. The results are shown of the influence simulation of various factors (such as flanges and piping warming, ratio of clearance changes in the elements) on the probability of turbine TES hindrance. It is shown that clearance ratios employed in most turbines do not provide the stability of turbine TES against the external action of connected pipes. The simulation results permit to explain the bearing housings turns observed during inspections, resulting in a jam on the longitudinal keys, in temperature distribution changes on the thrust bearing pads, and in some cases in false readings of instruments rotor axial displacement.

  20. Role of bond strength on the lattice thermal expansion and oxide ion conductivity in quaternary pyrochlore solid solutions.

    Science.gov (United States)

    Radhakrishnan, A N; Prabhakar Rao, P; Mahesh, S K; Thampi, D S Vaisakhan; Koshy, Peter

    2012-02-20

    Quaternary pyrochlore-type solid solutions, CaGdZrNb(1-x)Ta(x)O(7) (x = 0, 0.2, 0.4, 0.6, 0.8, 1), were prepared by a high-temperature ceramic route. The pyrochlore phases of the compounds were confirmed by powder X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy. The crystallographic parameters of the pyrochlore compounds were accurately determined by Rietveld analysis of the powder XRD data. The isovalent substitution of Ta in place of Nb at the B site can reveal the effect of chemical bonding on lattice thermal expansion and oxide ion conductivity because both Nb and Ta have the same ionic radius (0.64 Å). Lattice thermal expansion coefficients of the samples were calculated from high-temperature XRD measurements, and it was found that the thermal expansion coefficient decreases with substitution of Ta. Oxide ion conductivity measured by a two-probe method also shows the same trend with substitution of Ta, and this can be attributed to the high bond strength of the Ta-O bond compared to that of the Nb-O bond. Microstructural characterization using scanning electron microscopy proves that the size of the grains has a small effect on the oxide ion conductivity. Our studies established the role of chemical bonding in deciding the conductivity of pyrochlore oxides and confirmed that the 48f-48f mechanism of oxide ion conduction is dominant in pyrochlore oxides.

  1. Thermal stress fracture in elastic-brittle materials

    Science.gov (United States)

    Emery, A. F.

    1980-01-01

    The reported investigation shows that the assessment of the possibility of the thermal fracture of brittle materials depends upon an accurate evaluation of the thermal stresses and the determination of the resulting stress intensity factors. The stress intensity factors can be calculated in a variety of ways ranging from the very precise to approximate, but only for a limited number of geometries. The main difficulty is related to the determination of the thermal stress field because of its unusual character and its dependence upon boundary conditions at points far from the region of thermal activity. Examination of a number of examples suggests that the best visualization of the thermal stresses and any associated fracture can be made by considering the problem to be the combination of thermal and isothermal problems or by considering that the prime effect of the temperature is in the generation of thermal strains and that the thermal stresses are simply the result of the region trying to accommodate these strains.

  2. Determining in-situ thermal conductivity of coarse textured materials through numerical analysis of thermal

    Science.gov (United States)

    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

  3. Thermal conductivity measurements of particulate materials under Martian conditions

    Science.gov (United States)

    Presley, M. A.; Christensen, P. R.

    1993-01-01

    The mean particle diameter of surficial units on Mars has been approximated by applying thermal inertia determinations from the Mariner 9 Infrared Radiometer and the Viking Infrared Thermal Mapper data together with thermal conductivity measurement. Several studies have used this approximation to characterize surficial units and infer their nature and possible origin. Such interpretations are possible because previous measurements of the thermal conductivity of particulate materials have shown that particle size significantly affects thermal conductivity under martian atmospheric pressures. The transfer of thermal energy due to collisions of gas molecules is the predominant mechanism of thermal conductivity in porous systems for gas pressures above about 0.01 torr. At martian atmospheric pressures the mean free path of the gas molecules becomes greater than the effective distance over which conduction takes place between the particles. Gas particles are then more likely to collide with the solid particles than they are with each other. The average heat transfer distance between particles, which is related to particle size, shape and packing, thus determines how fast heat will flow through a particulate material.The derived one-to-one correspondence of thermal inertia to mean particle diameter implies a certain homogeneity in the materials analyzed. Yet the samples used were often characterized by fairly wide ranges of particle sizes with little information about the possible distribution of sizes within those ranges. Interpretation of thermal inertia data is further limited by the lack of data on other effects on the interparticle spacing relative to particle size, such as particle shape, bimodal or polymodal mixtures of grain sizes and formation of salt cements between grains. To address these limitations and to provide a more comprehensive set of thermal conductivities vs. particle size a linear heat source apparatus, similar to that of Cremers, was assembled to

  4. Thermal conductivity enhancement of phase change materials for thermal energy storage: A review

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Liwu; Khodadadi, J.M. [Department of Mechanical Engineering, Auburn University, 270 Ross Hall, Auburn, AL 36849-5341 (United States)

    2011-01-15

    A review of experimental/computational studies to enhance the thermal conductivity of phase change materials (PCM) that were conducted over many decades is presented. Thermal management of electronics for aeronautics and space exploration appears to be the original intended application, with later extension to storage of thermal energy for solar thermal applications. The present review will focus on studies that concern with positioning of fixed, stationary high conductivity inserts/structures. Copper, aluminum, nickel, stainless steel and carbon fiber in various forms (fins, honeycomb, wool, brush, etc.) were generally utilized as the materials of the thermal conductivity promoters. The reviewed research studies covered a variety of PCM, operating conditions, heat exchange and thermal energy storage arrangements. The energy storage vessels included isolated thermal storage units (rectangular boxes, cylindrical and annular tubes and spheres) and containers that transferred heat to a moving fluid medium passing through it. A few studies have focused on the marked role of flow regimes that are formed due to the presence of thermally unstable fluid layers that in turn give rise to greater convective mixing and thus expedited melting of PCM. In general, it can be stated that due to utilization of fixed high conductivity inserts/structures, the conducting pathways linking the hot and cold ends must be minimized. (author)

  5. Preparation, characterization, and thermal properties of microencapsulated phase change material for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Alkan, Cemil; Sari, Ahmet; Karaipekli, Ali [Department of Chemistry, Gaziosmanpasa University, 60240 Tokat (Turkey); Uzun, Orhan [Department of Physics, Gaziosmanpasa University, 60240 Tokat (Turkey)

    2009-01-15

    This study is focused on the preparation, characterization, and determination of thermal properties of microencapsulated docosane with polymethylmethacrylate (PMMA) as phase change material for thermal energy storage. Microencapsulation of docosane has been carried out by emulsion polymerization. The microencapsulated phase change material (MEPCM) was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Thermal properties and thermal stability of MEPCM were measured by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). DSC analysis indicated that the docosane in the microcapsules melts at 41.0 C and crystallizes at 40.6 C. It has latent heats of 54.6 and -48.7 J/g for melting and crystallization, respectively. TGA showed that the MEPCM degraded in three distinguishable steps and had good chemical stability. Accelerated thermal cycling tests also indicated that the MEPCM had good thermal reliability. Based on all these results, it can be concluded that the microencapsulated docosane as MEPCMs have good potential for thermal energy storage purposes such as solar space heating applications. (author)

  6. Thermal cyclic durability testing of ceramic materials for turbine engines

    Science.gov (United States)

    Lindberg, L. J.

    1986-01-01

    The thermal cyclic durability of commercial ceramic materials for turbine engines was under evaluation since 1978. Ceramic materials are exposed to cyclic diesel-fired burner exhaust at either 1204 or 1371 C (2200 or 2500 F) for up to 3500 hours. The test conditions are selected to simulate the environment experienced by the hot flow path components in an automotive gas turbine engine. The silicon nitride and silicon carbide materials tested are the same ceramic materials currently used on the AGT100 and AGT101 ceramic turbine engine program.

  7. Possibility of Using Metakaolin as Thermal Insulation Material

    Science.gov (United States)

    Rashad, Alaa M.

    2017-08-01

    The use of energy in the building sector accounts a significant part of the world's total energy and greenhouse gas emissions. In order to meet the demands of improved energy efficiency, thermal insulation of buildings plays an important role. To attain the highest possible thermal insulation, new insulation plaster types with low thermal conductivity values have been investigated and developed. In the current investigation, the possibility of using new plaster types based on metakaolin (MK) as heat insulation material and elevated temperature resistance has been studied and compared with that of traditional Portland cement plaster. Either cement or gypsum was used as a binder material. Three different plaster types containing MK were investigated as well as the traditional cement plaster (TC), which was used as a reference. Density and thermal conductivity values were measured. The compressive strength values before and after exposure to 600°C for 2 h were identified. The results showed that it is possible to produce different plaster types based on MK as heat insulation materials as well as elevated temperature resistance. MK plaster types exhibited approximately 65.7 % to 72 % lower thermal conductivity than that of TC plaster.

  8. Handbook on dielectric and thermal properties of microwaveable materials

    CERN Document Server

    Komarov, Vyacheslav V

    2012-01-01

    The application of microwave energy for thermal processing of different materials and substances is a rapidly growing trend in modern science and engineering. In fact, optimal design work involving microwaves is impossible without solid knowledge of the properties of these materials. Here s a practical reference that collects essential data on the dielectric and thermal properties of microwaveable materials, saving you countless hours on projects in a wide range of areas, including microwave design and heating, applied electrodynamics, food science, and medical technology. This unique book provides hard-to-find information on complex dielectric permittivity of media at industrial, scientific, and medical frequencies (430 MHz, 915MHz, 2.45GHz, 5.8 GHz, and 24.125GHz). Written by a leading expert in the field, this authoritative book does an exceptional job at presenting critical data on various materials and explaining what their key characteristics are concerning microwaves.

  9. Preparation, thermal properties and thermal reliability of microencapsulated n-eicosane as novel phase change material for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Alkan, Cemil; Sari, Ahmet; Karaipekli, Ali [Department of Chemistry, Gaziosmanpasa University, 60240 Tokat (Turkey)

    2011-01-15

    This study deals with preparation, characterization, thermal properties and thermal reliability of n-eicosane microcapsules as novel phase change material (PCM) for thermal energy storage. The microcapsulated PCMs were prepared by coating n-eicosane with polymethylmethacrylate (PMMA) shell. Fourier transform infrared (FT-IR), scanning electron microscope (SEM) and particle size distribution (PSD) analysis were used to characterize the PMMA/eicosane microcapsules as microcapsulated PCMs. The PSD analysis indicated that the average diameter of microcapsules was found to be 0.70 {mu}m under the stirring speed of 2000 rpm. Thermal properties and thermal reliability of the microcapsules were determined using differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) methods. From DSC analysis, the melting and freezing temperatures and the latent heats of the microcapsules were measured as 35.2 C and 34.9 C, 84.2 and -87.5 J/g, respectively. TGA analysis indicated that PMMA/eicosane microcapsules degrade in three steps at considerably high temperatures. Accelerated thermal cycling tests have been also applied to show the thermal reliability of the microcapsules. All results showed that thermal properties make the PMMA/eicosane microcapsules potential PCM for thermal energy storage. (author)

  10. An Ag based brazing system with a tunable thermal expansion for the use as sealant for solid oxide cells

    Science.gov (United States)

    Kiebach, Ragnar; Engelbrecht, Kurt; Grahl-Madsen, Laila; Sieborg, Bertil; Chen, Ming; Hjelm, Johan; Norrman, Kion; Chatzichristodoulou, Christodoulos; Hendriksen, Peter Vang

    2016-05-01

    An Ag-Al2TiO5 composite braze was developed and successfully tested as seal for solid oxide cells. The thermo-mechanical properties of the Ag-Al2TiO5 system and the chemical compatibility between this composite braze and relevant materials used in stacks were characterized and the leak rates as a function of the operation temperature were measured. The thermal expansion coefficient in the Ag-Al2TiO5 system can be tailored by varying the amount of the ceramic filler. The brazing process can be carried out in air, the joining partners showed a good chemical stability and sufficient low leak rates were demonstrated. Furthermore, the long-term stability of the Ag-Al2TiO5 composite braze was studied under relevant SOFC and SOEC conditions. The stability of brazed Crofer/Ag-Al2TiO5/NiO-YSZ assemblies in reducing atmosphere and in pure oxygen was investigated over 500 h at 850 °C. Additionally, a cell component test was performed to investigate the durability of the Ag-Al2TiO5 seal when exposed to dual atmosphere. The seals performed well over 900 h under electrolysis operation conditions (-0.5 A cm2, 850 °C), and no cell degradation related to the Ag-Al2TiO5 sealing was found, indicating that the developed braze system is applicable for the use in SOFC/SOEC stacks.

  11. Influence of thermal expansion mismatch on residual stress profile in veneering ceramic layered on zirconia: Measurement by hole-drilling.

    Science.gov (United States)

    Mainjot, Amélie K; Najjar, Achref; Jakubowicz-Kohen, Boris D; Sadoun, Michaël J

    2015-09-01

    Mismatch in thermal expansion coefficient between core and veneering ceramic (Δα=αcore-αveneer, ppm/°C) is reported as a crucial parameter influencing veneer fractures with Yttria-tetragonal-zirconia-polycrystal (Y-TZP) prostheses, which still constitutes a misunderstood problem. However, the common positive Δα concept remains empirical. The objective of this study is to investigate the Δα dependence of residual stress profiles in veneering ceramic layered on Y-TZP frameworks. The stress profile was measured with the hole-drilling method in bilayered disc samples of 20mm diameter with a 0.7mm thick Y-TZP framework and a 1.5mm thick veneer layer. 3 commercial and 4 experimental veneering ceramics (n=3 per group) were used to obtain different Δα varying from -1.3ppm/°C to +3.2ppm/°C, which were determined by dilatometric analyses. Veneer fractures were observed in samples with Δα≥+2.3 or ≤-0.3ppm/°C. Residual stress profiles measured in other groups showed compressive stresses in the surface, these stresses decreasing with depth and then becoming more compressive again near the interface. Small Δα variations were shown to induce significant changes in residual stress profiles. Compressive stress near the framework was found to decrease inversely to Δα. Veneer CTE close to Y-TZP (+0.2ppm/°C Δα) gived the most favorable stress profile. Yet, near the framework, Δα-induced residual stress varied inversely to predictions. This could be explained by the hypothesis of structural changes occurrence within the Y-TZP surface. Consequently, the optimum Δα value cannot be determined before understanding Y-TZP's particular behavior when veneered. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  12. Cellular and Porous Materials Thermal Properties Simulation and Prediction

    CERN Document Server

    Öchsner, Andreas; de Lemos, Marcelo J S

    2008-01-01

    Providing the reader with a solid understanding of the fundamentals as well as an awareness of recent advances in properties and applications of cellular and porous materials, this handbook and ready reference covers all important analytical and numerical methods for characterizing and predicting thermal properties. In so doing it directly addresses the special characteristics of foam-like and hole-riddled materials, combining theoretical and experimental aspects for characterization purposes.

  13. Measurement of thermal conductivity of polymeric nanocomposite materials

    OpenAIRE

    Gannoum, Misel

    2016-01-01

    A measuring device of the thermal conductivity of Polymeric nanocomposite materials is presented. This project is a continuation of a previous master student work. The goal of this project is to build a miniaturized version of the previous device in order to overturn certain limitations and improve its overall performance. The new device uses much smaller size samples, which ensures sample integrity/rigidity and saves material which in the case of nanoadditives may be expensive or scarce. In ...

  14. Pattern-free thermal modulator via thermal radiation between Van der Waals materials

    Science.gov (United States)

    Liu, Xianglei; Shen, Jiadong; Xuan, Yimin

    2017-10-01

    Modulating heat flux provides a platform for a plethora of emerging devices such as thermal diodes, thermal transistors, and thermal memories. Here, a pattern-free noncontact thermal modulator is proposed based on the mechanical rotation between two Van der Waals films with optical axes parallel to the surfaces. A modulation contrast can reach a value higher than 5 for hexagonal Boron Nitride (hBN) films separated by a nanoscale gap distance. The dominant radiative heat exchange comes from the excitation of both Type I and Type II hyperbolic surface phonon polaritons (HSPhPs) at the vacuum-hBN interface for different orientations, while the large modulation contrast is mainly attributed to the mismatching Type I HSPhPs induced by rotation. This work opens the possibility to design cheap thermal modulators without relying on nanofabrication techniques, and paves the way to apply natural Van der Waals materials in manipulating heat currents in an active way.

  15. Arc Jet Testing of Thermal Protection Materials: 3 Case Studies

    Science.gov (United States)

    Johnson, Sylvia; Conley, Joe

    2015-01-01

    Arc jet testing is used to simulate entry to test thermal protection materials. This paper discusses the usefulness of arc jet testing for 3 cases. Case 1 is MSL and PICA, Case 2 is Advanced TUFROC, and Case 3 is conformable ablators.

  16. Natural analogues for expansion due to the anaerobic corrosion of ferrous materials

    Energy Technology Data Exchange (ETDEWEB)

    Smart, N.R.; Adams, R. [Serco Assurance, Culham Science Centre (United Kingdom)

    2006-10-15

    In Sweden, spent nuclear fuel will be encapsulated in sealed cylindrical canisters, consisting of a cast iron insert and a copper outer container. The canisters will be placed in a deep geologic repository and surrounded by bentonite. If a breach of the outer copper container were to occur the cast iron insert would undergo anaerobic corrosion, forming a magnetite film whose volume would be greater than that of the base metal. In principle there is a possibility that accumulation of iron corrosion product could cause expansion of the copper canister. Anaerobic corrosion rates are very slow, so in the work described in this report reference was made to analogous materials that had been corroding for long periods in natural anoxic aqueous environments. The report considers the types of naturally occurring environments that may give rise to anoxic environments similar to deep geological groundwater and where ferrous materials may be found. Literature information regarding the corrosion of iron archaeological artefacts is summarised and a number of specific archaeological artefacts containing iron and copper corroding in constrained geometries in anoxic natural waters are discussed in detail. No evidence was obtained from natural analogues which would suggest that severe damage is likely to occur to the SKB waste canister design as a result of expansive corrosion of cast iron under repository conditions.

  17. Comparative study of hygrothermal properties of five thermal insulation materials

    Directory of Open Access Journals (Sweden)

    Laure Ducoulombier

    2017-09-01

    Full Text Available The objective of this article is to carry out a comparative study of the main hygrothermal properties of five thermal insulation materials for buildings. These properties are necessary for a correct prediction of heat and moisture transfers through the walls and the selection of the most appropriate materials according to the specific buildings. The studied materials were glass wool, rock wool, expanded polystyrene, wood fiberboard and polyester fiberfill. The article is divided into three parts. The first part presents the phenomena of hygrothermal transfers in walls in order to understand the need for determining specific properties of the insulating materials. The second part describes in details the five studied insulating materials and the methods used for the characterization and identification of their main properties. Finally, the last part presents the experimental results and makes comparisons between materials. The differences between the insulating materials are brought out, such as the strong dependence of the thermal conductivity of polystyrene on temperature, or the good permeability of fibrous insulating materials to water vapor. A detailed analysis of the obtained results is presented.

  18. From Tomography to Material Properties of Thermal Protection Systems

    Science.gov (United States)

    Mansour, Nagi N.; Panerai, Francesco; Ferguson, Joseph C.; Borner, Arnaud; Barnhardt, Michael; Wright, Michael

    2017-01-01

    A NASA Ames Research Center (ARC) effort, under the Entry Systems Modeling (ESM) project, aims at developing micro-tomography (micro-CT) experiments and simulations for studying materials used in hypersonic entry systems. X-ray micro-tomography allows for non-destructive 3D imaging of a materials micro-structure at the sub-micron scale, providing fiber-scale representations of porous thermal protection systems (TPS) materials. The technique has also allowed for In-situ experiments that can resolve response phenomena under realistic environmental conditions such as high temperature, mechanical loads, and oxidizing atmospheres. Simulation tools have been developed at the NASA Ames Research Center to determine material properties and material response from the high-fidelity tomographic representations of the porous materials with the goal of informing macroscopic TPS response models and guiding future TPS design.

  19. Mode Grüneisen parameters and negative thermal expansion of cubic ZrW2O8 and ZrMo2O8

    Science.gov (United States)

    Wang, Kai; Reeber, Robert R.

    2000-04-01

    Thermal expansion for ZrW2O8 and ZrMo2O8 is analyzed by a multifrequency Einstein model. Vibrational modes that contribute significantly to the thermal expansion are empirically identified. For ZrW2O8, a negative Grüneisen parameter mode is consistent with the observed Raman spectral peak of 40 cm-1. Experimental confirmation of the results is proposed.

  20. Outgassing of solid material into vacuum thermal insulation spaces

    Science.gov (United States)

    Wang, Pao-Lien

    1994-01-01

    Many cryogenic storage tanks use vacuum between inner and outer tank for thermal insulation. These cryogenic tanks also use a radiation shield barrier in the vacuum space to prevent radiation heat transfer. This shield is usually constructed by using multiple wraps of aluminized mylar and glass paper as inserts. For obtaining maximum thermal performance, a good vacuum level must be maintained with the insulation system. It has been found that over a period of time solid insulation materials will vaporize into the vacuum space and the vacuum will degrade. In order to determine the degradation of vacuum, the rate of outgassing of the insulation materials must be determined. Outgassing rate of several insulation materials obtained from literature search were listed in tabular form.

  1. Development of thermal energy storage materials for biomedical applications.

    Science.gov (United States)

    Shukla, A; Sharma, Atul; Shukla, Manjari; Chen, C R

    2015-01-01

    The phase change materials (PCMs) have been utilized widely for solar thermal energy storage (TES) devices. The quality of these materials to remain at a particular temperature during solid-liquid, liquid-solid phase transition can also be utilized for many biomedical applications as well and has been explored in recent past already. This study reports some novel PCMs developed by them, along with some existing PCMs, to be used for such biomedical applications. Interestingly, it was observed that the heating/cooling properties of these PCMs enhance the quality of a variety of biomedical applications with many advantages (non-electric, no risk of electric shock, easy to handle, easy to recharge thermally, long life, cheap and easily available, reusable) over existing applications. Results of the present study are quite interesting and exciting, opening a plethora of opportunities for more work on the subject, which require overlapping expertise of material scientists, biochemists and medical experts for broader social benefits.

  2. Calculating Cutting Thermal Physics Parameters of Plastic Materials

    Directory of Open Access Journals (Sweden)

    S. V. Grubyi

    2017-01-01

    Full Text Available The thermal physics parameters and a cutting temperature belong to the output performances to characterise a process and allow a rational selection of machining modes and conditions. In machining hard-to-cut materials the utmost cutting temperature is a technological restriction and defines tool wear rate and intensity. The cutting temperature also has impact on the heat extension of tool and the finished machining.The subject is to study thermal physics parameters and cutting temperature when machining the plastic materials by a hard-alloy tool. The objective is to develop a technique to calculate these parameters. A calculation method for the analysis of process parameters is used.Calculation results for the cutting temperature were compared with experimental ones published in the literature sources. A novelty of the technique is that there is no need in conducting the experimental studies to calculate the thermal physics parameters. Calculation is based on using known mechanical and thermal physics characteristics of machined and tool materials. The calculation results are parameters, namely heat flow intensities in the conditional shear plane, on the contact surfaces of tool, temperatures of theses surfaces, averaged cutting temperature - depending on the cutting speed, thickness of cutting layer, tool wear value.A sequence of calculations is implemented in the developed software in the programming algorithmic language with results in graphic and tabular representations. The calculation technique is designed for conducting research activities and engineering designs in the field of machining.

  3. Laser ablation in CdZnTe crystal due to thermal self-focusing: Secondary phase hydrodynamic expansion

    Energy Technology Data Exchange (ETDEWEB)

    Medvid’, A., E-mail: mychko@latnet.lv [Riga Technical University, 3 Paula Valdena Str., LV-1048 Riga (Latvia); Mychko, A.; Dauksta, E. [Riga Technical University, 3 Paula Valdena Str., LV-1048 Riga (Latvia); Kosyak, V. [Sumy State University, 2, Rymskogo-Korsakova St., 40007 Sumy (Ukraine); Grase, L. [Riga Technical University, 3 Paula Valdena Str., LV-1048 Riga (Latvia)

    2016-06-30

    Highlights: • We found two laser induced threshold intensity for CdZnTe crystal. • The laser beam self-focusing lead to increase of intensity of laser radiation at exit surface. • Laser ablation is a result of Te inclusion hydrodynamic expansion. - Abstract: The present paper deals with the laser ablation in CdZnTe crystal irradiated by pulsed infrared laser. Two values of threshold intensities of the laser ablation were determined, namely of about 8.5 and 6.2 MW/cm{sup 2} for the incident and the rear surfaces, correspondingly. Lower intensity of the laser ablation for the rear surface is explained by thermal self-focusing of the laser beam in the CdZnTe crystal due to heating of Te inclusions with a following hydrodynamic expansion.

  4. Diffraction phase microscopy imaging and multi-physics modeling of the nanoscale thermal expansion of a suspended resistor.

    Science.gov (United States)

    Wang, Xiaozhen; Lu, Tianjian; Yu, Xin; Jin, Jian-Ming; Goddard, Lynford L

    2017-07-04

    We studied the nanoscale thermal expansion of a suspended resistor both theoretically and experimentally and obtained consistent results. In the theoretical analysis, we used a three-dimensional coupled electrical-thermal-mechanical simulation and obtained the temperature and displacement field of the suspended resistor under a direct current (DC) input voltage. In the experiment, we recorded a sequence of images of the axial thermal expansion of the central bridge region of the suspended resistor at a rate of 1.8 frames/s by using epi-illumination diffraction phase microscopy (epi-DPM). This method accurately measured nanometer level relative height changes of the resistor in a temporally and spatially resolved manner. Upon application of a 2 V step in voltage, the resistor exhibited a steady-state increase in resistance of 1.14 Ω and in relative height of 3.5 nm, which agreed reasonably well with the predicted values of 1.08 Ω and 4.4 nm, respectively.

  5. Mechanical properties and coefficient of thermal expansion of β-eucryptite sintered by microwave technique; Propiedades mecanicas y coeficiente de dilatacion termica de la β-eucriptita sinterizada por la tecnica de microondas

    Energy Technology Data Exchange (ETDEWEB)

    Benavente, R.; Borrell, A.; Salvador, M. D.; Garcia-Moreno, O.; Penaranda-Foix, F. L.; Catala-Civera, J. M.

    2014-10-01

    Microwave non-conventional sintering technique allows obtaining fully dense glass-free β-eucryptite bulk material (∼99 %). A considerable difference in the densification, microstructure, coefficient of thermal expansion behaviour and mechanical properties, between conventional and non-conventional sintered specimens was observed. The hardness and Young's modulus values obtained by microwaves at 1200 degree centigrade-5min have been relatively high, 6.8 GPa and 101 GPa, respectively, compared to conventional sintering (3.9 GPa and 58 GPa, respectively). Very low thermal expansion materials have been obtained in a wide temperature range including cryogenic temperatures (from -150 degree centigrade to 150 degree centigrade). The high heating rate along with the lower energy consumption makes microwave technique a clear alternative to other types of sintering methods. (Author)

  6. Carbon nanotubes for thermal interface materials in microelectronic packaging

    Science.gov (United States)

    Lin, Wei

    As the integration scale of transistors/devices in a chip/system keeps increasing, effective cooling has become more and more important in microelectronics. To address the thermal dissipation issue, one important solution is to develop thermal interface materials with higher performance. Carbon nanotubes, given their high intrinsic thermal and mechanical properties, and their high thermal and chemical stabilities, have received extensive attention from both academia and industry as a candidate for high-performance thermal interface materials. The thesis is devoted to addressing some challenges related to the potential application of carbon nanotubes as thermal interface materials in microelectronics. These challenges include: 1) controlled synthesis of vertically aligned carbon nanotubes on various bulk substrates via chemical vapor deposition and the fundamental understanding involved; 2) development of a scalable annealing process to improve the intrinsic properties of synthesized carbon nanotubes; 3) development of a state-of-art assembling process to effectively implement high-quality vertically aligned carbon nanotubes into a flip-chip assembly; 4) a reliable thermal measurement of intrinsic thermal transport property of vertically aligned carbon nanotube films; 5) improvement of interfacial thermal transport between carbon nanotubes and other materials. The major achievements are summarized. 1. Based on the fundamental understanding of catalytic chemical vapor deposition processes and the growth mechanism of carbon nanotube, fast synthesis of high-quality vertically aligned carbon nanotubes on various bulk substrates (e.g., copper, quartz, silicon, aluminum oxide, etc.) has been successfully achieved. The synthesis of vertically aligned carbon nanotubes on the bulk copper substrate by the thermal chemical vapor deposition process has set a world record. In order to functionalize the synthesized carbon nanotubes while maintaining their good vertical alignment

  7. A finite element technique for non-deterministic thermal deformation analyses including temperature dependent material properties

    Science.gov (United States)

    Case, W. R., Jr.; Walston, W. H., Jr.

    1977-01-01

    A technique utilizing the finite element displacement method is developed for the static analysis of structures subjected to non-deterministic thermal loading in which the material properties, assumed isotropic, are temperature dependent. Matrix equations are developed for the first two statistical moments of the displacements using a third order series expansion for the displacements in terms of the random temperatures. Sample problems are included to demonstrate the range of applicability of the third order series solutions. These solutions are compared with results from Monte Carlo analyses and also, for some problems, with solutions obtained by numerically integrating equations for the statistical properties of the displacements. In general, it is shown that the effect of temperature dependent material properties can have a significant effect on the covariances of the displacements.

  8. Conformal surface coatings to enable high volume expansion Li-ion anode materials.

    Science.gov (United States)

    Riley, Leah A; Cavanagh, Andrew S; George, Steven M; Jung, Yoon Seok; Yan, Yanfa; Lee, Se-Hee; Dillon, Anne C

    2010-07-12

    An alumina surface coating is demonstrated to improve electrochemical performance of MoO(3) nanoparticles as high capacity/high-volume expansion anodes for Li-ion batteries. Thin, conformal surface coatings were grown using atomic layer deposition (ALD) that relies on self-limiting surface reactions. ALD coatings were tested on both individual nanoparticles and prefabricated electrodes containing conductive additive and binder. The coated and non-coated materials were characterized using transmission electron microscopy, energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, and galvanostatic charge/discharge cycling. Importantly, increased stability and capacity retention was only observed when the fully fabricated electrode was coated. The alumina layer both improves the adhesion of the entire electrode, during volume expansion/contraction and protects the nanoparticle surfaces. Coating the entire electrode also allows for an important carbothermal reduction process that occurs during electrode pre-heat treatment. ALD is thus demonstrated as a novel and necessary method that may be employed to coat the tortuous network of a battery electrode.

  9. Preparation and properties of negative thermal expansion zirconium tungstate thin films deposited by radio frequency magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hong-Fei; Cheng, Xiao-Nong; Zhang, Zhi-Ping [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China)

    2008-11-15

    Zirconium tungstate (ZrW{sub 2}O{sub 8}) thin films were deposited on quartz substrates by radio frequency magnetron sputtering followed by annealing at various temperatures. The effects of post-deposition annealing temperature on the phase, morphology and negative thermal expansion properties of the ZrW{sub 2}O{sub 8} thin films were investigated. X-ray diffraction data confirmed that the as-deposited ZrW{sub 2}O{sub 8} films were amorphous, and crystalline ZrW{sub 2}O{sub 8} films could be obtained at high annealing temperature. Trigonal ZrW{sub 2}O{sub 8} films could be prepared at 740 C and cubic ZrW{sub 2}O{sub 8} films could be prepared at 1200 C. The surface morphologies of the ZrW{sub 2}O{sub 8} thin films were evaluated using scanning electron microscopy. The results indicated that amorphous ZrW{sub 2}O{sub 8} films were uniform and dense, and the grain size of the crystalline ZrW{sub 2}O{sub 8} films became larger with increasing annealing temperature. The resulting cubic ZrW{sub 2}O{sub 8} films showed negative thermal expansion, the average value of thermal expansion coefficient being -8.18 x 10{sup -6} K{sup -1} in the temperature range 15-700 C. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Thermal Transport in Nanoporous Materials for Energy Applications

    Science.gov (United States)

    Fang, Jin

    The present study investigates the complex relationship between nanostructures and microscale thermal transport in nanoporous thin films for energy applications. It experimentally and numerically demonstrates that the effective thermal conductivity of nanoporous materials can be tuned by controlling their nanoscale architectures including porosity, pore diameter, wall thickness, nanocrystal size, and crystallinity as well as surface passivation. This study reports measurements of the cross-plane thermal conductivity of nanoporous thin films with various architectures between 25 and 315 K. Physics-based models combining phonon transport theory and effective medium approximations were developed to interpret the experimental data. Ordered mesoporous titania and silicon thin films were prepared based on evaporation-induced self-assembly method. Pure silica zeolite films were produced by either in-situ growth or by spin coating a zeolite nanoparticle suspension followed by crystal growth upon heating. These synthesized thin films were systematically and fully characterized. They featured ordered nanopores with porosity, pore diameter, and film thickness ranging from 30% to 59%, 0.5 to 25 nm, and 120 to 370 nm, respectively. Their dense matrix was amorphous, polycrystalline, or consisted of an aggregate of nanocrystals. The thermal conductivity of all synthesized nanoporous films increased monotonically with temperature within the temperature range considered. At low temperatures, the nanoporous films behaved like amorphous or strongly disordered materials and their thermal conductivity was proportional to Tn with n varied between 1 and 2.3. At high temperatures, the thermal conductivity increased slowly with temperature or reached a plateau due to strong phonon Umklapp scattering and the saturation of phonon modes. The presence of pores in amorphous mesoporous thin films had a purely geometrical effect by reducing the cross-sectional area through which heat can diffuse

  11. Experimental measurements of thermal properties of high-temperature refractory materials used for thermal energy storage

    Science.gov (United States)

    El-Leathy, Abdelrahman; Jeter, Sheldon; Al-Ansary, Hany; Abdel-Khalik, Said; Golob, Matthew; Danish, Syed Noman; Saeed, Rageh; Djajadiwinata, Eldwin; Al-Suhaibani, Zeyad

    2016-05-01

    This paper builds on studies conducted on thermal energy storage (TES) systems that were built as a part of the work performed for a DOE-funded SunShot project titled "High Temperature Falling Particle Receiver". In previous studies, two small-scale TES systems were constructed for measuring heat loss at high temperatures that are compatible with the falling particle receiver concept, both of which had shown very limited heat loss. Through the course of those studies, it became evident that there was a lack of information about the thermal performance of some of the insulating refractory materials used in the experiments at high temperatures, especially insulating firebrick and perlite concrete. This work focuses on determining the thermal conductivities of those materials at high temperatures. The apparatus consists of a prototype cylindrical TES bin built with the same wall construction used in previous studies. An electric heater is placed along the centerline of the bin, and thermocouples are used to measure temperature at the interfaces between all layers. Heat loss is measured across one of the layers whose thermal conductivity had already been well established using laboratory experiments. This value is used to deduce the thermal conductivity of other layers. Three interior temperature levels were considered; namely, 300°C, 500°C, and 700°C. Results show that the thermal conductivity of insulating firebrick remains low (approximately 0.22 W/m.K) at an average layer temperature as high as 640°C, but it was evident that the addition of mortar had an impact on its effective thermal conductivity. Results also show that the thermal conductivity of perlite concrete is very low, approximately 0.15 W/m.K at an average layer temperature of 360°C. This is evident by the large temperature drop that occurs across the perlite concrete layer. These results should be useful for future studies, especially those that focus on numerical modeling of TES bins.

  12. Thermal expansion measurements by x-ray scattering and breakdown of Ehrenfest's relation in alloy liquids

    Energy Technology Data Exchange (ETDEWEB)

    Gangopadhyay, A. K.; Blodgett, M. E.; Johnson, M. L.; Vogt, A. J.; Mauro, N. A.; Kelton, K. F. [Department of Physics and Institute of Materials Science and Engineering, Washington University in St. Louis, St. Louis, Missouri 63130 (United States)

    2014-05-12

    Measurements of sharp diffraction peaks as a function of temperature are routinely used to obtain precise linear expansion coefficients of crystalline solids. In this case, the relation between temperature dependent changes in peak position in momentum transfer (q{sub 1}) and volume expansion is straightforward (Ehrenfest's relation: q{sub 1} = K(2π/d), where K is a constant and d is the interatomic spacing) and the data obtained are usually in close agreement with more direct measurements. With high intensity synchrotron x-ray and spallation neutron sources, it is also possible to accurately measure the positions of the much broader peaks for liquids and glasses. This has led to a debate on whether linear expansion coefficients derived from these data are an accurate representation of the volume expansion coefficients. We present here volume thermal expansion and x-ray diffraction data for a large number of glass-forming alloy liquids acquired in a containerless environment using the beamline electrostatic levitation technique. The data show a large difference in the values obtained from the two different techniques. Moreover, the position of the first peak (q{sub 1}) in the scattered intensity in the structure factor (S(q)) and the atomic volume v for all liquids follow a simple relationship, v∝(q{sub 1}){sup −ε}. The exponent, ε = 2.28 (±0.11), is much different from the expected value of 3 from Ehrenfest's relation and shows no temperature dependence over the temperature range of the data collected.

  13. Iridescent cellulose nanocrystal/polyethylene oxide composite films with low coefficient of thermal expansion

    Science.gov (United States)

    Jairo A. Diaz; Julia L. Braun; Robert J. Moon; Jeffrey P. Youngblood

    2015-01-01

    Simultaneous control over optical and thermal properties is particularly challenging and highly desired in fields like organic electronics. Here we incorporated cellulose nanocrystals (CNCs) into polyethylene oxide (PEO) in an attempt to preserve the iridescent CNC optical reflection given by their chiral nematic organisation, while reducing the composite thermal...

  14. Analysis of thermal expansivity of iron (Fe) metal at ultra high ...

    Indian Academy of Sciences (India)

    Abstract. In the present investigation we have explained the thermal and compression properties of HCP iron (Fe) at high pressure with variable temperature (isobars) and at high temperature with variable pressure (isotherm). The usual Tait equation of state is modified by incorporating the effect of thermal pressure.

  15. Influence of thermal stress on marginal integrity of restorative materials

    Directory of Open Access Journals (Sweden)

    Maximiliano Sérgio Cenci

    2008-04-01

    Full Text Available The aim of this study was to evaluate the influence of thermal stress on the marginal integrity of restorative materials with different adhesive and thermal properties. Three hundred and sixty Class V cavities were prepared in buccal and lingual surfaces of 180 bovine incisors. Cervical and incisal walls were located in dentin and enamel, respectively. Specimens were restored with resin composite (RC; glass ionomer (GI or amalgam (AM, and randomly assigned to 18 groups (n=20 according to the material, number of cycles (500 or 1,000 cycles and dwell time (30 s or 60 s. Dry and wet specimens served as controls Specimens were immersed in 1% basic fuchsine solution (24 h, sectioned, and microleakage was evaluated under x40 magnification. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests: Thermal cycling regimens increased leakage in all AM restorations (p<0.05 and its effect on RC and GI restorations was only significant when a 60-s dwell time was used (p<0.05. Marginal integrity was more affected in AM restorations under thermal cycling stress, whereas RC and GI ionomer restoration margins were only significantly affected only under longer dwell times.

  16. Encapsulation of High Temperature Phase Change Materials for Thermal Energy Storage

    Science.gov (United States)

    Nath, Rupa

    Thermal energy storage is a major contributor to bridge the gap between energy demand (consumption) and energy production (supply) by concentrating solar power. The utilization of high latent heat storage capability of phase change materials is one of the keys to an efficient way to store thermal energy. However, some of the limitations of the existing technology are the high volumetric expansion and low thermal conductivity of phase change materials (PCMs), low energy density, low operation temperatures and high cost. The present work deals with encapsulated PCM system, which operates at temperatures above 500°C and takes advantage of the heat transfer modes at such high temperatures to overcome the aforementioned limitations of PCMs. Encapsulation with sodium silicate coating on preformed PCM pellets were investigated. A low cost, high temperature metal, carbon steel has been used as a capsule for PCMs with a melting point above 500° C. Sodium silicate and high temperature paints were used for oxidation protection of steel at high temperatures. The emissivity of the coatings to enhance heat transfer was investigated.

  17. Seal accommodating thermal expansion between adjacent casings in gas turbine engine

    Science.gov (United States)

    Marra, John J. (Inventor)

    1992-01-01

    A casing around a turbine and a casing around discharge nozzles have a concentrically arranged shell portion. The seal contains internal pressure while accommodating eccentric, expansion and axial travel. Arcuate seal segments have one leg sealing against a radial surface extending from the inner shell and the other leg against the outer shell. A linkage guides travel of the segments.

  18. A theoretical analysis of local thermal equilibrium in fibrous materials

    Directory of Open Access Journals (Sweden)

    Tian Mingwei

    2015-01-01

    Full Text Available The internal heat exchange between each phase and the Local Thermal Equilibrium (LTE scenarios in multi-phase fibrous materials are considered in this paper. Based on the two-phase heat transfer model, a criterion is proposed to evaluate the LTE condition, using derived characteristic parameters. Furthermore, the LTE situations in isothermal/adiabatic boundary cases with two different heat sources (constant heat flux and constant temperature are assessed as special transient cases to test the proposed criterion system, and the influence of such different cases on their LTE status are elucidated. In addition, it is demonstrated that even the convective boundary problems can be generally estimated using this approach. Finally, effects on LTE of the material properties (thermal conductivity, volumetric heat capacity of each phase, sample porosity and pore hydraulic radius are investigated, illustrated and discussed in our study.

  19. Characteristic of Thermally Reduced Graphene Oxide as Supercapacitors Electrode Materials

    Science.gov (United States)

    Marcelina, Vika; Syakir, Norman; Wyantuti, Santhy; Hartati, Yeni W.; Hidayat, Rahmat; Fitrilawati

    2017-05-01

    We investigated graphene like material named reduced graphene oxide (RGO) as an electrode material by employed graphene oxide (GO). Thin film of GO was prepared on the indium thin oxide (ITO) substrate by spin-coating method using varied concentration of GO that dispersed in water. In order to remove its oxygen contained, GO film was thermally reduced at 200 °C for 1 hour. We used cyclic voltammetry to measure its CV characteristic and estimated its specific capacitance. We obtained the highest specific capacitance of 6.53 mF g-1 that measured from 4 mg ml-1 RGO thin film at scan rate 25 mVs-1.

  20. Exercises in 80223 Numerical Modelling of Thermal Processing of Materials

    DEFF Research Database (Denmark)

    Frandsen, Jens Ole

    This exercise book contains exercise instructions for the 7 compulsory exercises (Exercise 1-7) and the final exercise (Exercise 8) in the course 80223 'Numerical Modelling of Thermal Processing of Materials'. The exercise book also contains written program examples in 'C' and 'Pascal'. Finally, ...... by contacting the secretary on the ground floor of building 425. Please give the following number: TM 99.05 (TM = Thermal processing of Materials)......This exercise book contains exercise instructions for the 7 compulsory exercises (Exercise 1-7) and the final exercise (Exercise 8) in the course 80223 'Numerical Modelling of Thermal Processing of Materials'. The exercise book also contains written program examples in 'C' and 'Pascal'. Finally......, guidelines are given on how to write the report which has to be handed in at the end of the course. The exercise book exists in a newer, updated version from 2000. The original copy is kept in the archives of TM on the ground floor of building 425. A copy of the exercise book can be made available...

  1. Influence of specimens' geometry and materials on the thermal stresses in dental restorative materials during thermal cycling.

    Science.gov (United States)

    Fabris, Douglas; Souza, Júlio C M; Silva, Filipe S; Fredel, Márcio; Gasik, Michael; Henriques, Bruno

    2018-02-01

    Thermal cycling is widely used to simulate the aging of restorative materials corresponding to the changes of temperature in the oral cavity. However, test parameters present in literature vary considerably, which prevents comparison between different reports. The aim of this work is to assess the influence of the specimens' geometry and materials on the thermal stresses developed during thermal cycling tests. Finite elements method was used to simulate the conditions of thermal cycling tests for three different sample geometries: a three-points bending test sample, a cylinder rod and more complex shape of a restoration crown. Two different restorative systems were considered: all-ceramic (zirconia coupled with porcelain) and metal-ceramic (CoCrMo alloy coupled with porcelain). The stress state of each sample was evaluated throughout the test cycle. The results show that the sample geometry has great influence on the stress state, with difference of up to 230% in the maximum stress between samples of the same composition. The location of maximum stress also changed from the interface between materials to the external wall. Maximum absolute stress values were found to vary between 2 and 4MPa, which might not be critical even for ceramics. During multi-cycle testing these stresses would cause different fatigue in various locations. The zirconia-based specimens and zirconia-based restoration (crown) exhibited the most similar stress states. Thus it might be recommended to use these geometries for fast screening of the materials for this type of restorations. The selection of specimens' geometry and materials should be carefully considered when aging conditions close to clinical ones want to be simulated. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Testing of High Thermal Cycling Stability of Low Strength Concrete as a Thermal Energy Storage Material

    Directory of Open Access Journals (Sweden)

    Chao Wu

    2016-09-01

    Full Text Available Concrete has the potential to become a solution for thermal energy storage (TES integrated in concentrating solar power (CSP systems due to its good thermal and mechanical properties and low cost of material. In this study, a low strength concrete (C20 is tested at high temperatures up to 600 °C. Specimens are thermally cycled at temperatures in the range of 400–300 °C, 500–300 °C, and 600–300 °C, which TES can reach in operation. For comparison, specimens also cycled at temperature in the range of 400–25 °C (room temperature, 500–25 °C, and 600–25 °C. It is found from the test results that cracks are not observed on the surfaces of concrete specimens until the temperature is elevated up to 500 °C. There is mechanical deterioration of concrete after exposure to high temperature, especially to high thermal cycles. The residual compressive strength of concrete after 10 thermal cycles between 600 °C and 300 °C is about 58.3%, but the specimens remain stable without spalling, indicating possible use of low strength concrete as a TES material.

  3. Applications of graphite-enabled phase change material composites to improve thermal performance of cementitious materials

    Science.gov (United States)

    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.

  4. Hybrid Composites from Wheat Straw, Inorganic Filler, and Recycled Polypropylene: Morphology and Mechanical and Thermal Expansion Performance

    Directory of Open Access Journals (Sweden)

    Min Yu

    2016-01-01

    Full Text Available Reinforcing effect of hybrid filler including wheat straw (WS and inorganic filler (heavy calcium carbonate, silicon dioxide, and fly ash in recycled polypropylene (R-PP has been investigated. The effects of individual filler (WS and combined fillers (WS and inorganic filler on morphological, mechanical, and thermal expansion and water absorption properties of hybrid composites were investigated. The flexural modulus and flexural strength were both reduced when reinforced with three kinds of inorganic fillers, respectively, which was possibly due to the poor interphase adhesion as observed in SEM. The high surface energy of heavy calcium carbonate due to its high acidic character provides an opportunity of better PP-heavy calcium carbonate interfacial interactions compared to PP-straw, PP-fly ash, and PP-SiO2 interface. The water absorption at saturation increased markedly by introduction of WS in it. The hybrid composites from WS and inorganic fillers showed better water absorption compared to those WS/PP composites. The thermal expansion of composites decreased with the increase of WS loading. Heavy calcium and SiO2 can obviously reduce the LCTE value of composite. At the 25% inorganic filler content, composites had the smallest LCTE values.

  5. An Investigation of the Thermal Expansion Coefficient for Resin Concrete with ZrW2O8

    Directory of Open Access Journals (Sweden)

    Kuangzhe Lin

    2015-08-01

    Full Text Available This paper presents a novel resin concrete obtained by adding cubic zirconium tungstate (ZrW2O8 as filler. A prediction algorithm on the thermal expansion coefficient (CTE of resin concrete (including filler was established on the basis of the meso-mechanics method and a three-phase model for concrete. The concept of twice mixing was also proposed for prediction accuracy. Then, a 2D and 3D irregular polygon aggregate particles packing model was set up by Matlab and the properties of the packing model were simulated by finite element analysis. Finally, resin concrete samples were made and their CTE were measured. Mix proportion and addition of ZrW2O8 as influencing factors were considered in this experiment. The CTE of resin concrete was verified by comparing results of the prediction model, simulation model and experiment. The optimum CTE obtained from the experiment was 1.504 × 10−6/K. Compared with 6.817 × 10−6/K without ZrW2O8, it was found that the addition of ZrW2O8 to resin concrete can make it perform significantly better in thermal expansion.

  6. Spin-glass-like behavior and negative thermal expansion in antiperovskite Mn3Ni1-xCuxN compounds

    Science.gov (United States)

    Ding, Lei; Wang, Cong; Sun, Ying; Colin, Claire V.; Chu, Lihua

    2015-06-01

    The Cu-doping effect on the lattice and magnetic properties in Mn3Ni1-xCuxN (x = 0, 0.3, 0.5, 0.7, 1.0) was extensively investigated. We observed that the Cu-doping at the Ni site complicated the magnetic ground states, which induced the competition of antiferromagnetic and ferromagnetic interactions. Spin-glass-like behavior, arising from possible site-randomness and competing interactions of magnetism, was observed in compounds with x = 0.3, 0.5, and 0.7, and typically discussed by means of the measurement of ac magnetic susceptibility for x = 0.7. The negative thermal expansion (NTE) behavior, due to the magnetic ordering transition, was observed in Mn3Ni1-xCuxN compounds using variable temperature x-ray diffraction. It reveals that the introduction of Cu effectively broadens the temperature range displaying negative thermal expansion. The relationship between the local lattice distortion and the competing magnetic ground states might play an important role in broadening the NTE temperature range in this antiperovskite compound.

  7. Investigation of gold as a material for thermal radiation shielding

    Science.gov (United States)

    Munshi, Amit Harenkumar

    CdS/CdTe thin film solar cells technology is one of the fastest growing carbon neutral energy sources in the world today. Manufacturing of CdS/CdTe solar modules is carried out at temperature in the range of 620350°C under a vacuum of 40 millitorr using a Heated Pocket Deposition (HPD) system in the materials engineering laboratory. Since this system operates in vacuum, majority of the heat loss is due to thermal radiation. The concept here is to conserve the heat by reflecting the infrared radiation back into the deposition system thus increasing the thermal efficiency. Various metals may be used but calculations show that using a Gold thin film mirror can effectively reflect almost 97% of the incident radiation, thus conserving energy required for the manufacturing process. However, a phenomenon called thermal grooving or island formation inhibits its use. Thermal grooving occurs when the stress concentration at the grain boundaries causes grain separation. This phenomenon is observed in thin gold films that are exposed to a temperature in excess of 350°C for over 3 to 5 hours. In this study, these films are exposed to temperature upto 620350°C for cycles as long as 200 hours. The goal of this research is to explore the solutions for elimination of the phenomenon of thermal grooving and thus extract maximum life out of these thin gold films for conservation of heat. After carefully exploring literature on past research and conducting experiments it was found that within the range of the films that were tested, a 2000 A350° film with a 150 A350° of Indium underlay showed the best performance after thermal annealing and testing.

  8. The P-T conditions of garnet inclusion formation in diamond: thermal expansion of synthetic end-member pyrope

    Science.gov (United States)

    Milani, Sula; Mazzucchelli, Matteo; Nestola, Fabrizio; Alvaro, Matteo; Angel, Ross J.; Geiger, Charles A.; Domeneghetti, Chiara

    2013-04-01

    Pyrope, Mg3Al2Si3O12, due to the abundance of garnet in Earths's upper mantle, has been studied many times. A number of different investigations have measured its physical and thermodynamic properties at high temperature or pressure and, even more recently, under simultaneous high P-T conditions (e.g. Zou et al., 2012). This abstract reports thermal expansion results on pyrope, as part of a much wider project on the determination of the physical properties of garnet, in order to obtain geobarometric information on the formation conditions of its inclusion in diamond. Our experimental approach is based on the elastic method (e.g. Izraeli et al., 1999; Howell et al., 2010; Nestola et al., 2011; Howell et al., 2012), which takes into account the thermoelastic properties of both diamond and any tiny solid phase inclusion within it. The method requires accurate and precise knowledge of thermal expansion and compressibility behavior in order to calculate precisely the pressure and temperature formation conditions of the diamond-inclusion pair. Thus, in order to do this, we measured the thermal expansion of an end-member synthetic single crystal of pyrope up to 1100 K at 52 different temperatures. This was done by measuring the ao unit-cell edge with high precision and accuracy under heating and cooling conditions. This allows excellent experimental reproducibility, which is also checked by monitoring any diffraction peak broadening over the entire range of temperatures. Fitting the temperature-volume data to the thermal expansion equation of Berman (1988), we obtained a room temperature volume-thermal expansion coefficient equal to 2.72(2)×10-5K-1. Using the same pyrope crystal, in situ high-pressure measurements are now in progress in order to determine its isothermal bulk modulus. The use of our results, along with the dK/dT data of Zou et al ( 2012), we plan to calculate the pressure of formation of diamonds containing pyrope-rich garnet inclusions. References Berman

  9. Thermal wave imaging techniques for inspection of plywood materials

    Science.gov (United States)

    Mulaveesala, Ravibabu; Venkata Nagarjuna, P.; Ravi, Dadda; Amarnath, Muniyappa

    2012-06-01

    Infrared non-destructive testing and evaluation (IRNDT&E) is an emerging approach for materials characterization due to its capability to test wide variety of solid materials such as metals, composites and semiconductors of industrial interest. Further it supports thorough inspection and evaluation by its unique remote and fast and whole field testing capabilities. Wood is one of the most commonly used house hold building material it has both structural and decorative applications. It is used both in natural and processed form like ply wood, veneer, ply-board etc. Defects like knots, worm track, delaminations, glue smear etc. influences its in-service capabilities. Even though various non-destructive methods such as optical, ultrasonic and radiography are commonly used to inspect wooden materials, infrared imaging has its own advantage due to its safe, whole field inspection capabilities. This paper describes the applicability of the transient thermal wave imaging (TWI) method for inspection of ply wood. This paper highlights applicability of transient pulsed thermal imaging approach for finding out the hidden defects. Capability of the proposed method and its defect detection capabilities have been highlighted through experimental results.

  10. Fabrication, characterization, and thermal-property measurements of ThO/sub 2/--UO/sub 2/ fuel materials (LWBR Development Program)

    Energy Technology Data Exchange (ETDEWEB)

    Springer, J R; Eldridge, E A; Goodyear, M U; Wright, T R; Lagedrost, J F

    1967-10-01

    Thermophysical-property specimens of ThO/sub 2/, ThO/sub 2/-10 wt % UO/sub 2/, and ThO/sub 2/-20 wt % UO/sub 2/ were fabricated and characterized. Each material composition was represented by specimens with nominal densities of 95, 85, and 75 percent of theoretical. Thermal-diffusivity, linear-thermal-expansion, and specific-heat measurements were made at 300 to 1900/sup 0/C and used to determine thermal conductivity. Results of linear-thermal-expansion and specific-heat measurements were approximately the same for all materials. Values of linear thermal expansion ranged up to 2.2 percent in heating from room temperature to 2000/sup 0/C. The specific heat ranged from 0.055 cal/(g) (C) at 0/sup 0/C to 0.080 cal/(g) (C) at 2000/sup 0/C. Thermal-diffusivity values ranged from 3.0 x 10/sup -2/ cm/sup 2/ per sec at 300/sup 0/C to 0.5 x 10/sup -2/ cm/sup 2/ per sec at 1900/sup 0/C. Thermal conductivities decreased in regular fashion with increased UO/sub 2/ content and porosity. An equation is given which fits all of the data obtained; it is anticipated that it will fit the data for other compositions within the given limits. (NSA 22: 47703)

  11. Using expanded real options analysis to evaluate capacity expansion decisions under uncertainty in the construction material industry

    Directory of Open Access Journals (Sweden)

    Momani, Amer Mohammad

    2016-08-01

    Full Text Available Capacity expansion generally requires large capital expenditure on illiquid assets. Therefore, decisions to enlarge capacity must support the organisation’s strategic objectives and provide valuable input for the budgeting process. This paper applies an expanded form of Real Options Analysis (ROA to generate and evaluate capacity expansion strategies under uncertainty in the construction material industry. ROA is applied to different expansion strategies associated with different demand scenarios. Evaluating a wider variety of strategies can reduce risk and sponsor decisions that maximise the firm’s value. The case study shows that the execution of a lead expansion strategy with 10-year intervals under a 50 per cent demand satisfaction scenario produces superior results.

  12. Standard Practice for Evaluating Solar Absorptive Materials for Thermal Applications

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This practice covers a testing methodology for evaluating absorptive materials used in flat plate or concentrating collectors, with concentrating ratios not to exceed five, for solar thermal applications. This practice is not intended to be used for the evaluation of absorptive surfaces that are (1) used in direct contact with, or suspended in, a heat-transfer liquid, (that is, trickle collectors, direct absorption fluids, etc.); (2) used in evacuated collectors; or (3) used in collectors without cover plate(s). 1.2 Test methods included in this practice are property measurement tests and aging tests. Property measurement tests provide for the determination of various properties of absorptive materials, for example, absorptance, emittance, and appearance. Aging tests provide for exposure of absorptive materials to environments that may induce changes in the properties of test specimens. Measuring properties before and after an aging test provides a means of determining the effect of the exposure. 1.3 Th...

  13. In Situ Diffraction from Levitated Solids Under Extreme Conditions-Structure and Thermal Expansion in the Eu 2 O 3 -ZrO 2 System

    Energy Technology Data Exchange (ETDEWEB)

    Maram, Pardha S. [Peter A. Rock Thermochemistry Laboratory and Neat ORU, University of California, Davis, One Shields Avenue 4415 Chemistry Annex Davis California 95616; Ushakov, Sergey V. [Peter A. Rock Thermochemistry Laboratory and Neat ORU, University of California, Davis, One Shields Avenue 4415 Chemistry Annex Davis California 95616; Weber, Richard J. K. [Materials Development, Inc., 3090 Daniels Court Arlington Heights Illinois 60004; X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue Lemont Illinois 60439; Benmore, Chris J. [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue Lemont Illinois 60439; Navrotsky, Alexandra [Peter A. Rock Thermochemistry Laboratory and Neat ORU, University of California, Davis, One Shields Avenue 4415 Chemistry Annex Davis California 95616; Raveau, B.

    2014-12-31

    The accurate determination of structure and thermal expansion of refractory materials at temperatures above 1500 degrees C is challenging. Here, for the first time, we demonstrate the ability to reliably refine the structure and thermal expansion coefficient of oxides at temperatures to 2200 degrees C using in situ synchrotron diffraction coupled with aerodynamic levitation. Solid solutions in the Eu2O3-ZrO2 binary system were investigated, including the high-temperature order-disorder transformation in Eu2Zr2O7. The disordered fluorite phase is found to be stable above 1900 degrees C, and a reversible phase transition to the pyrochlore phase is noticed during cooling. Site occupancies in Eu2Zr2O7 show a gradual increase in disorder on both cation and anion sublattices with increasing temperature. The thermal expansion coefficients of all cubic solid solutions are relatively similar, falling in the range 8.6-12.0x10(-6)C(-1). These studies open new vistas for in situ exploration of complex structural changes in high-temperature materials.

  14. Electric vehicles batteries thermal management systems employing phase change materials

    Science.gov (United States)

    Ianniciello, Lucia; Biwolé, Pascal Henry; Achard, Patrick

    2018-02-01

    Battery thermal management is necessary for electric vehicles (EVs), especially for Li-ion batteries, due to the heat dissipation effects on those batteries. Usually, air or coolant circuits are employed as thermal management systems in Li-ion batteries. However, those systems are expensive in terms of investment and operating costs. Phase change materials (PCMs) may represent an alternative which could be cheaper and easier to operate. In fact, PCMs can be used as passive or semi-passive systems, enabling the global system to sustain near-autonomous operations. This article presents the previous developments introducing PCMs for EVs battery cooling. Different systems are reviewed and solutions are proposed to enhance PCMs efficiency in those systems.

  15. Current Situation Development of Lightweight Ablation Materials for Thermal Protection

    Directory of Open Access Journals (Sweden)

    XUE Hua- fei

    2017-02-01

    Full Text Available In view of demand of lighter thermal protection system for our national space vehicle,recent development of investigation and practical application of lightweight thermal protection ablation materials are summarized systematically at home and abroad,in which the silicon or resin reinforced with honeycomb structural reinforcement and resin impregnated fibrous substrate ablators are included,focuses On silicone resin reinforced with glass,silica or carbon fiber/phenolic honeycomb as well as silicon,phenolic and Silicone Impregnated Reusable tendency Ceramic Ablator(SIRCA and Phenolic Impregnated Carbon Ablator( in the future of aboard lightweight ablators is proposed,which can PICA,finally the development directly borrow or simply draw inspiration for our country in this field.

  16. Fiber Optic Thermal Health Monitoring of Aerospace Structures and Materials

    Science.gov (United States)

    Wu, Meng-Chou; Winfree, William P.; Allison, Sidney G.

    2009-01-01

    A new technique is presented for thermographic detection of flaws in materials and structures by performing temperature measurements with fiber Bragg gratings. Individual optical fibers with multiple Bragg gratings employed as surface temperature sensors were bonded to the surfaces of structures with subsurface defects or thickness variations. Both during and following the application of a thermal heat flux to the surface, the individual Bragg grating sensors measured the temporal and spatial temperature variations. The investigated structures included a 10-ply composite specimen with subsurface delaminations of various sizes and depths. The data obtained from grating sensors were further analyzed with thermal modeling to reveal particular characteristics of the interested areas. These results were found to be consistent with those from conventional thermography techniques. Limitations of the technique were investigated using both experimental and numerical simulation techniques. Methods for performing in-situ structural health monitoring are discussed.

  17. Study of improving the thermal response of a construction material containing a phase change material

    Science.gov (United States)

    Laaouatni, A.; Martaj, N.; Bennacer, R.; Elomari, M.; El Ganaoui, M.

    2016-09-01

    The use of phase change materials (PCMs) for improving the thermal comfort in buildings has become an attractive application. This solution contributes to increasing the thermal inertia of the building envelope and reducing power consumption. A building element filled with a PCM and equipped with ventilation tubes is proposed, both for increasing inertia and contributing to refreshing building envelope. A numerical simulation is conducted by the finite element method in COMSOL Multiphysics, which aims to test the thermal behaviour of the developed solution. An experimental study is carried out on a concrete block containing a PCM with ventilation tubes. The objective is to see the effect of PCM coupled with ventilation on increasing the inertia of the block. The results show the ability of this new solution to ensure an important thermal inertia of a building.

  18. High-Temperature Oxidation-Resistant and Low Coefficient of Thermal Expansion NiAl-Base Bond Coat Developed for a Turbine Blade Application

    Science.gov (United States)

    2003-01-01

    Many critical gas turbine engine components are currently made from Ni-base superalloys that are coated with a thermal barrier coating (TBC). The TBC consists of a ZrO2-based top coat and a bond coat that is used to enhance the bonding between the superalloy substrate and the top coat. MCrAlY alloys (CoCrAlY and NiCrAlY) are currently used as bond coats and are chosen for their very good oxidation resistance. TBC life is frequently limited by the oxidation resistance of the bond coat, along with a thermal expansion mismatch between the metallic bond coat and the ceramic top coat. The aim of this investigation at the NASA Glenn Research Center was to develop a new longer life, higher temperature bond coat by improving both the oxidation resistance and the thermal expansion characteristics of the bond coat. Nickel aluminide (NiAl) has excellent high-temperature oxidation resistance and can sustain a protective Al2O3 scale to longer times and higher temperatures in comparison to MCrAlY alloys. Cryomilling of NiAl results in aluminum nitride (AlN) formation that reduces the coefficient of thermal expansion (CTE) of the alloy and enhances creep strength. Thus, additions of cryomilled NiAl-AlN to CoCrAlY were examined as a potential bond coat. In this work, the composite alloy was investigated as a stand-alone substrate to demonstrate its feasibility prior to actual use as a coating. About 85 percent of prealloyed NiAl and 15 percent of standard commercial CoCrAlY alloys were mixed and cryomilled in an attritor with stainless steel balls used as grinding media. The milling was carried out in the presence of liquid nitrogen. The milled powder was consolidated by hot extrusion or by hot isostatic pressing. From the consolidated material, oxidation coupons, four-point bend, CTE, and tensile specimens were machined. The CTE measurements were made between room temperature and 1000 C in an argon atmosphere. It is shown that the CTE of the NiAl-AlN-CoCrAlY composite bond coat

  19. Thermal Stability and Material Balance of Nanomaterials in Waste Incineration

    Science.gov (United States)

    Paur, H.-R.; Baumann, W.; Hauser, M.; Lang, I.; Teuscher, N.; Seifert, H.; Stapf, D.

    2017-06-01

    Nanostructured materials are widely used to improve the properties of consumer products such as tires, cosmetics, light weight equipment etc. Due to their complex composition these products are hardly recycled and thermal treatment is preferred. In this study we investigated the thermal stability and material balance of nanostructured metal oxides in flames and in an industrial waste incinerator. We studied the size distribution of nanostructured metal oxides (CeO2, TiO2, SiO2) in a flame reactor and in a heated reaction tube. In the premixed ethylene/air flame, nano-structured CeO2 partly evaporates forming a new particle mode. This is probably due to chemical reactions in the flame. In addition sintering of agglomerates takes place in the flame. In the electrically heated reaction tube however only sintering of the agglomerated nanomaterials is observed. Ceria has a low background in waste incinerators and is therefore a suitable tracer for investigating the fate of nanostructured materials. Low concentrations of Ceria were introduced by a two-phase nozzle into the post-combustion zone of a waste incinerator. By the incineration of coal dust in a burning chamber the Ceria nanoparticles are mainly found in the size range of the fly ash (1 - 10 µm) because of agglomeration. With gas as a fuel less agglomeration was observed and the Ceria nanoparticles were in the particle size range below 1 µm.

  20. Characterization of Encapsulated Phase Change Materials for Thermal Energy Storage

    Science.gov (United States)

    Zhao, Weihuan

    Solar energy is receiving a lot of attentions at present since it is a kind of clean, renewable and sustainable energy. A major limitation however is that it is available for only about 2,000 hours a year in many places. One way to improve this situation is to use thermal energy storage (TES) system for the off hours. A novel method to store solar energy for large scale energy usage is using high melting temperature encapsulated phase change materials (EPCMs). The present work is a study of thermal energy storage systems with phase change materials (PCMs). It is hoped that this work is to help understand the storage capability and heat transfer processes in the EPCM capsules in order to help design large EPCM based thermoclines. A calorimeter system was built to test the energy stored in EPCM capsules and examine the storage capabilities and potential for storage deterioration in EPCM capsules to determine the types of EPCMs suitable for TES. To accomplish this, the heat transfer performances of the EPCMs are studied in detail. Factors which could affect the heat transfer performance including the properties of materials, the sizes of capsules, the types of heat transfer fluids, the gravity effect of solid PCM, the buoyancy-driven convection in the molten PCM, void space inside the capsule are given attention. Understanding these characteristics for heat transfer process could help build the EPCM based thermoclines to make energy storage economical for solar energy and other applications.

  1. 24 CFR 3280.207 - Requirements for foam plastic thermal insulating materials.

    Science.gov (United States)

    2010-04-01

    ... mineral fiber insulation or an equivalent thermal barrier; or (3) The foam plastic insulating material has... thermal insulating materials. 3280.207 Section 3280.207 Housing and Urban Development Regulations Relating... SAFETY STANDARDS Fire Safety § 3280.207 Requirements for foam plastic thermal insulating materials. (a...

  2. Identification and analysis of factors affecting thermal shock resistance of ceramic materials in solar receivers

    Science.gov (United States)

    Hasselman, D. P. H.; Singh, J. P.; Satyamurthy, K.

    1980-01-01

    An analysis was conducted of the possible modes of thermal stress failure of brittle ceramics for potential use in point-focussing solar receivers. The pertinent materials properties which control thermal stress resistance were identified for conditions of steady-state and transient heat flow, convective and radiative heat transfer, thermal buckling and thermal fatigue as well as catastrophic crack propagation. Selection rules for materials with optimum thermal stress resistance for a particular thermal environment were identified. Recommendations for materials for particular components were made. The general requirements for a thermal shock testing program quantitatively meaningful for point-focussing solar receivers were outlined. Recommendations for follow-on theoretical analyses were made.

  3. Improved Compressive, Damping and Coefficient of Thermal Expansion Response of Mg–3Al–2.5La Alloy Using Y2O3 Nano Reinforcement

    Directory of Open Access Journals (Sweden)

    Amit Kumar

    2017-03-01

    Full Text Available In the present study, the effects of the addition of Y2O3 nanoparticles on Mg–3Al–2.5La alloy were investigated. Materials were synthesized using a disintegrated melt deposition technique followed by hot extrusion. The samples were then characterized for microstructure, compression properties, damping properties, CTE (coefficient of thermal expansion and fracture morphology. The grain size of Mg–3Al–2.5La was significantly reduced by the addition of the Y2O3 nano-sized reinforcement (~3.6 μm, 43% of Mg–3Al–2.5La grain size. SEM and X-ray studies revealed that the size of uniformly distributed intermetallic phases, Al 11 La 3 , Al 2 La , and Al 2.12 La 0.88 reduced by the addition of Y2O3 to Mg–3Al–2.5La alloy. The coefficient of thermal expansion (CTE was slightly improved by the addition of nanoparticles. The results of the damping measurement revealed that the damping capacity of the Mg–3Al–2.5La alloy increased due to the presence of Y2O3. The compression results showed that the addition of Y2O3 to Mg–3Al–2.5La improved the compressive yield strength (from ~141 MPa to ~156 MPa and the ultimate compressive strength (from ~456 MPa to ~520 MPa, which are superior than those of the Mg–3Al alloy (Compressive Yield Strength, CYS ~154 MPa and Ultimate Compressive Strength, UCS ~481 MPa. The results further revealed that there is no significant effect on the fracture strain value of Mg–3Al–2.5La due to the addition of Y2O3.

  4. Phase Change Materials for Thermal Management of IC Packages

    Directory of Open Access Journals (Sweden)

    P. Fiala

    2007-06-01

    Full Text Available This paper deals with the application of phase change materials (PCM for thermal management of integrated circuits as a viable alternative to active forced convection cooling systems. The paper presents an analytical description and solution of heat transfer, melting and freezing process in 1D which is applied to inorganic crystalline salts. There are also results of numerical simulation of a real 3D model. These results were obtained by means of the finite element method (FEM. Results of 3D numerical solutions were verified experimentally.

  5. Aspects of corrosion testing of thermal-insulating materials

    Energy Technology Data Exchange (ETDEWEB)

    Sheppard, K.G.; Weil, R.

    1983-01-01

    The literature dealing with corrosion by thermal-insulating materials in residential buildings is reviewed. Current corrosiveness test methods are discussed. In view of their shortcomings, the need for a new procedure is evident. Possible methods applicable to various types of insulation are considered. The program for developing the new procedure is outlined. Preliminary test results indicate relationships between existing coupon and rapidly executable electrochemical tests. Field data, which are beginning to be collected, are needed to establish the validity of the new test and its ability to predict behavior under service conditions.

  6. Thermal Stress Analysis of W/Cu Functionally Graded Materials by Using Finite Element Method

    Science.gov (United States)

    Yang, Zhenxiao; Liu, Min; Deng, Chunming; Zhang, Xiaofeng; Deng, Changguang

    2013-03-01

    Copper alloys with tungsten coating shows an excellent plasma irradiation resistance, however, the difference of coefficient thermal expansion between W and Cu makes it really a difficult job to prepare over 1 mm W coating with high adhesive strength. Functionally graded material (FGM) seems to be an effective method to improve the adhesive strength of thick W coating. This paper focused on the finite element simulation on thermal stress for W/Cu FGM with different graded layers, composition and thicknesses. In addition, the variance of stresses for functionally graded coatings with the steady state heat flux were simulated by finite element analysis (ANSYS Workbench). The results showed that the W/Cu FGM was effectively beneficial for the stress relief of W coating. Meanwhile, the maximum von mises stress decreased approximately by 52.8 % compared to monolithic W plasma facing material. And the four-layer FGM with a compositional exponent of 2 was optimum for 1.5 mm W coating.

  7. Analysis of the phenomenon of material expansiveness in tunnels built in anhydrite. Outcomes and experiences

    Directory of Open Access Journals (Sweden)

    del Campo, J. M.

    2012-12-01

    Full Text Available The serious geotechnical problems arising in many tunnels bored in material giving rise to stability problems as a result of being expansive, makes the water channelizers. These are materials which are easily washed with sulphates dissolving with water causing the massif to become decompressed and to remould, aggravating and transferring the problem beyond the tunnel’s immediate environment. In the particular case of layers of anhydrite between argillite, it also happens that the primary support and subsequent lining must have exceptional strength to resist the pressures the terrain may transmit in the medium to long term. This article describes the most relevant aspects of the hydromechanical behaviour of sulphated soil and rock and presents some experiments, concluding with various aspects associated to the phenomenon of swelling in tunnels and its possible treatment.

    Los graves problemas geotécnicos sucedidos en numerosos túneles europeos excavados en materiales que generan problemas de estabilidad, como consecuencia de su expansividad, los convierten en canalizadores de aguas. Estos materiales son fácilmente lavables al disolverse los sulfatos con el agua, provocando una decompresión y remoldeo del macizo, agravando y trasladando el problema más allá del inmediato entorno del túnel. En el caso particular de presencia de capas de anhidrita entre argilitas, además de la adopción de medidas de sostenimiento y revestimiento especiales, el sostenimiento primario y el revestimiento posterior deben ser excepcionalmente resistentes a las presiones que pueden llegar a transmitir el terreno a medio y largo plazo. En este artículo se describen los aspectos más relevantes de comportamiento hidromecánico de los suelos y las rocas sulfatadas y se presentan algunas experiencias, concluyendo sobre aspectos asociados al fenómeno de hinchamiento en túneles y su posible tratamiento.

  8. Mechanical Testing of Carbon Based Woven Thermal Protection Materials

    Science.gov (United States)

    Pham, John; Agrawal, Parul; Arnold, James O.; Peterson, Keith; Venkatapathy, Ethiraj

    2013-01-01

    Three Dimensional Woven thermal protection system (TPS) materials are one of the enabling technologies for mechanically deployable hypersonic decelerator systems. These materials have been shown capable of serving a dual purpose as TPS and as structural load bearing members during entry and descent operations. In order to ensure successful structural performance, it is important to characterize the mechanical properties of these materials prior to and post exposure to entry-like heating conditions. This research focuses on the changes in load bearing capacity of woven TPS materials after being subjected to arcjet simulations of entry heating. Preliminary testing of arcjet tested materials [1] has shown a mechanical degradation. However, their residual strength is significantly more than the requirements for a mission to Venus [2]. A systematic investigation at the macro and microstructural scales is reported here to explore the potential causes of this degradation. The effects of heating on the sizing (an epoxy resin coating used to reduce friction and wear during fiber handling) are discussed as one of the possible causes for the decrease in mechanical properties. This investigation also provides valuable guidelines for margin policies for future mechanically deployable entry systems.

  9. Studies on compatibility of energetic materials by thermal methods

    Directory of Open Access Journals (Sweden)

    Maria Alice Carvalho Mazzeu

    2010-04-01

    Full Text Available The chemical compatibility of explosives, pyrotechnics and propellants with those materials is studied to evaluate potential hazards when in contact with other materials during production, storage and handling. Compatibility can be studied by several thermal methods as DSC (differential scanning calorimetry, TG (Thermogravimetry, VST (Vacuum stability test and others. The test methods and well defined criteria are the most important elements when a compatibility study is being accomplished. In this paper, the compatibility of two very important high explosives used in ammunition, RDX (Cyclo-1,3,5-trimethylene-2,4,6-trinitramine and HMX (Cyclotetramethylene tetranitramine was studied with the materials: fluoroelastomer (Viton and powdered aluminum (Al, using DSC and VST methods. The criteria to judge the compatibility between materials is based on a standardization agreement (STANAG 4147, 2001, and the final conclusion is that explosives and this materials are compatible, but in DSC it was observed that the peak of decomposition temperature of the admixture of RDX with Al decreased in 3º C and another peak appeared after the decomposition peak.

  10. Graphene nanocomposites as thermal interface materials for cooling energy devices

    Science.gov (United States)

    Dmitriev, A. S.; Valeev, A. R.

    2017-11-01

    The paper describes the technology of creating samples of graphene nanocomposites based on graphene flakes obtained by splitting graphite with ultrasound of high power. Graphene nanocomposites in the form of samples are made by the technology of weak sintering at high pressure (200-300 bar) and temperature up to 150 0 C, and also in the form of compositions with polymer matrices. The reflection spectra in the visible range and the near infrared range for the surface of nanocomposite samples are studied, the data of optical and electronic spectroscopy of such samples are givenIn addition, data on the electrophysical and thermal properties of the nanocomposites obtained are presented. Some analytical models of wetting and spreading over graphene nanocomposite surfaces have been constructed and calculated, and their effective thermal conductivity has been calculated and compared with the available experimental data. Possible applications of graphene nanocomposites for use as thermal interface materials for heat removal and cooling for power equipment, as well as microelectronics and optoelectronics devices are described.

  11. Effective Thermal Conductivity of Graphite Materials with Cracks

    Science.gov (United States)

    Pestchaanyi, S. E.; Landman, I. S.

    The dependence of effective thermal diffusivity on temperature caused by volumetric cracks is modelled for macroscopic graphite samples using the three-dimensional thermomechanics code Pegasus-3D. At high off-normal heat loads typical of the divertor armour, thermostress due to the anisotropy of graphite grains is much larger than that due to the temperature gradient. Numerical simulation demonstrated that the volumetric crack density both in fine grain graphites and in the CFC matrix depends mainly on the local sample temperature, not on the temperature gradient. This allows to define an effective thermal diffusivity for graphite with cracks. The results obtained are used to explain intense cracking and particle release from carbon based materials under electron beam heat load. Decrease of graphite thermal diffusivity with increase of the crack density explains particle release mechanism in the experiments with CFC where a clear energy threshold for the onset of particle release has been observed in J. Linke et al. Fusion Eng. Design, in press, Bazyler et al., these proceedings. Surface temperature measurement is necessary to calibrate the Pegasus-3D code for simulation of ITER divertor armour brittle destruction.

  12. Thermal expansion, internal stresses and porosity distribution in AlSiCp MMC; Thermische Ausdehnung, innere Spannungen und Porenverteilung in AlSiCp Metallmatrixverbundwerkstoffen

    Energy Technology Data Exchange (ETDEWEB)

    Requena, G.; Degischer, H.P.; Kaminski, H. [TU Wien, Institut fuer Werkstoffwissenschaft und Werkstofftechnologie (Austria); Buslaps, T.; Di Michiel, M. [Europ. Synchrotron-Strahlungsquelle (ESRF), Grenoble (France); Schoebel, M.

    2007-11-15

    AlSi7Mg/SiC/70p (AlSiC) is used for heat sinks because of its good thermal conductivity combined with a low coefficient of thermal expansion (CTE). These properties are important for power electronic devices where heat sinks have to provide efficient heat transfer to a cooling device. A low CTE is essential for a good surface bonding of the heat sink material to the isolating ceramics. Otherwise mismatch in thermal expansion would lead to damage of the bonding degrading the thermal contact within the electronic package. Therefore AlSiC replaces increasingly copper heat sinks. The CTE mismatch between isolation and a conventional metallic heat sink is transferred into the metal matrix composite (MMC). The stability of the external and internal interface bonding is essential for the heat sink function of AlSiC. In situ thermal cycling (RT - 400 C) measurements of an AlSi7Mg/SiC/70p MMC are reported yielding the pore volume fraction and internal stresses between the matrix and the reinforcements in function of temperature. The changes in pore volume fractions are determined by synchrotron tomography and residual stresses by synchrotron diffraction at ESRF-ID15A. The measurements show a relationship between thermal expansion, residual stresses and pore formation in the MMC. The results obtained from the in situ measurements reveal a thermo elastic range with inversion of the dominant tensile stresses in the matrix into compressive up to 200 C followed by plastic matrix deformation reducing the volume of pores during heating. A reverse process takes place during cooling from 500 C starting with elastic matrix strains converting into tensile stresses increasing the pore volume fraction again. Below 200 C, the CTE behaves again according to thermo elastic calculations. Damage like in low cycle fatigue could be observed after multiple extreme cooling-heating cycles between -100 C and +400 C, which increase the volume fraction and the size of the voids. (Abstract Copyright

  13. The evolution of magnetic transitions, negative thermal expansion and unusual electronic transport properties in Mn3AgxMnyN

    Science.gov (United States)

    Deng, Sihao; Sun, Ying; Yan, Jun; Shi, Zaixing; Shi, Kewen; Wang, Lei; Hu, Pengwei; Malik, Muhammad Imran; Wang, Cong

    2015-11-01

    The antiperovskite compounds Mn3AgxMnyN with Ag vacancies and Mn doping at Ag site were synthesized and investigated. The introduction of Ag vacancies has a very small influence on magnetic transitions. However, the magnetic transitions at TN (Néel temperature) and Tt (transition at lower temperature) gradually overlap with Mn doping accompanied by broadening of negative thermal expansion behavior. We also observed the nearly zero temperature coefficient of resistivity (NZ-TCR) behavior above magnetic order-disorder transition. The tunable TCR values from positive to negative could be achieved in Mn3AgxMnyN by reducing the contribution of (electron-phonon) e-p scattering in resistivity. Our results reveal the significance of e-p scattering for the evolution of TCR values, which could enrich the understanding of NZ-TCR behavior in antiperovskite manganese nitrides.

  14. An Adaptive Neuro-Fuzzy Inference System for Sea Level Prediction Considering Tide-Generating Forces and Oceanic Thermal Expansion

    Directory of Open Access Journals (Sweden)

    Li-Ching Lin Hsien-Kuo Chang

    2008-01-01

    Full Text Available The paper presents an adaptive neuro fuzzy inference system for predicting sea level considering tide-generating forces and oceanic thermal expansion assuming a model of sea level dependence on sea surface temperature. The proposed model named TGFT-FN (Tide-Generating Forces considering sea surface Temperature and Fuzzy Neuro-network system is applied to predict tides at five tide gauge sites located in Taiwan and has the root mean square of error of about 7.3 - 15.0 cm. The capability of TGFT-FN model is superior in sea level prediction than the previous TGF-NN model developed by Chang and Lin (2006 that considers the tide-generating forces only. The TGFT-FN model is employed to train and predict the sea level of Hua-Lien station, and is also appropriate for the same prediction at the tide gauge sites next to Hua-Lien station.

  15. THERMLIB: a material property data library for thermal analysis of radioactive material transport casks

    Energy Technology Data Exchange (ETDEWEB)

    Ikushima, Takeshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    The paper describes an heat conduction data library and graphical program for analysis of radioactive material transport casks. More than 1000 of material data are compiled in the data library which was produced by Lawrence Livermore Laboratory. Thermal data such as, density, thermal conductivity, specific heat, phase-change or solid-state, transition temperature and latent heat have been tabulated. Using this data library, a data library processing program THERMLIB for thermal analysis has been developed. Main features of THERMLIB are as follows: (1) data have been tabulated against temperature, (2) more than 1000 material data are available, (3) it is capable of graphical representations for thermal data and (4) not only main frame computer but also work stations (OS UNIX) and personal computer (OS Windows) are available for use of THERMLIB. In the paper, brief illustration of data library is presented in the first section. The second section presents descriptions of structural data. The third section provides an user`s guide for computer program and input data for THERMLIB. (author)

  16. Potassium lithium carbonate, KLiCO{sub 3}: single-crystal X-ray structure analysis and thermal expansion

    Energy Technology Data Exchange (ETDEWEB)

    Kirfel, A.; Euler, H.; Barbier, H.; Haegele, E.; Klapper, H. [Bonn Univ. (Germany). Mineralogisch-Petrologisches Inst. und Museum

    2000-07-01

    Single crystals of KLiCO{sub 3}, the intermediate compound in the eutectic system K{sub 2}CO{sub 3}-Li{sub 2}CO{sub 3}, were synthesized from the melt and the crystal structure was redetermined at room temperature by single-crystal X-ray diffraction: a = 7.232(1) A, b = 7.085(2) A, c = 6.579(1) A, {beta} = 113.40(1) , space group P2{sub 1}/n (No 14), Z = 4. Earlier literature results obtained by neutron time-of-flight powder diffraction are corroborated. The structure is composed of distorted face and edge sharing LiO{sub 5} and KO{sub 9} coordination polyhedra which are arranged in a layered manner and are connected by distorted but planar carbonate anions. In addition to the structure analysis, the thermal expansion of the crystal was measured and analyzed up to melting at 504.5 C. It exhibits a significant anisotropy with a maximum in direction c{sup *} about three times as large as the almost equal expansions in the a, b plane. This anisotropy is clearly understood from the distribution of bonds in the structure rather than from its layered nature. (orig.)

  17. A three-dimensional vertically aligned functionalized multilayer graphene architecture: an approach for graphene-based thermal interfacial materials.

    Science.gov (United States)

    Liang, Qizhen; Yao, Xuxia; Wang, Wei; Liu, Yan; Wong, Ching Ping

    2011-03-22

    Thermally conductive functionalized multilayer graphene sheets (fMGs) are efficiently aligned in large-scale by a vacuum filtration method at room temperature, as evidenced by SEM images and polarized Raman spectroscopy. A remarkably strong anisotropy in properties of aligned fMGs is observed. High electrical (∼386 S cm(-1)) and thermal conductivity (∼112 W m(-1) K(-1) at 25 °C) and ultralow coefficient of thermal expansion (∼-0.71 ppm K(-1)) in the in-plane direction of A-fMGs are obtained without any reduction process. Aligned fMGs are vertically assembled between contacted silicon/silicon surfaces with pure indium as a metallic medium. Thus-constructed three-dimensional vertically aligned fMG thermal interfacial material (VA-fMG TIM) architecture has significantly higher equivalent thermal conductivity (75.5 W m(-1) K(-1)) and lower contact thermal resistance (5.1 mm2 K W(-1)), compared with their counterpart from A-fMGs that are recumbent between silicon surfaces. This finding provides a throughout approach for a graphene-based TIM assembly as well as knowledge of vertically aligned graphene architectures, which may not only facilitate graphene's application in current demanding thermal management but also promote its widespread applications in electrodes of energy storage devices, conductive polymeric composites, etc.

  18. Thermal segregation of asphalt material in road repair

    Directory of Open Access Journals (Sweden)

    Juliana Byzyka

    2017-08-01

    Full Text Available This paper presents results from a field study of asphaltic pavement patching operations performed by three different contractors working in a total of ten sites. It forms part of an ongoing research programme towards improving the performance of pothole repairs. Thermal imaging technology was used to record temperatures of the patching material throughout the entire exercise, from the stage of material collection, through transportation to repair site, patch forming, and compaction. Practical complications occurring during patch repairs were also identified. It was found that depending on the weather conditions, duration of the travel and poor insulation of the transported hot asphalt mix, its temperature can drop as high as 116.6 °C over the period that the reinstatement team travel to the site and prepare the patch. This impacting is on the durability and performance of the executed repairs. Cold spots on the asphalt mat and temperature differentials between the new hot-fill asphalt mix and existing pavement were also identified as poorly compacted areas that were prone to premature failure. For example, over the five-minute period, the temperature at one point reduced by 33% whereas the temperatures of nearby areas decreased by 65% and 71%. A return visit to the repair sites, three months later, revealed that locations where thermal segregation was noted, during the patching operation, had failed prematurely.

  19. Thermal transport in phase-change materials from atomistic simulations

    Science.gov (United States)

    Sosso, Gabriele C.; Donadio, Davide; Caravati, Sebastiano; Behler, Jörg; Bernasconi, Marco

    2012-09-01

    We computed the thermal conductivity (κ) of amorphous GeTe by means of classical molecular dynamics and lattice dynamics simulations. GeTe is a phase change material of interest for applications in nonvolatile memories. An interatomic potential with close-to-ab initio accuracy was used as generated by fitting a huge ab initio database with a neural network method. It turns out that the majority of heat carriers are nonpropagating vibrations (diffusons), the small percentage of propagating modes giving a negligible contribution to the total value of κ. This result is in contrast with the properties of other amorphous semiconductors such as Si for which nonpropagating and propagating vibrations account for about one half of the value of κ each. This outcome suggests that the value of κ measured for the bulk amorphous phase can be used to model the thermal transport of GeTe and possibly of other materials in the same class also in nanoscaled memory devices. Actually, the contribution from propagating modes, which may endure ballistic transport at the scale of 10-20 nm, is negligible.

  20. Thermal expansion, thermal conductivity, and heat capacity measurements for boreholes UE25 NRG-4, UE25 NRG-5, USW NRG-6, and USW NRG-7/7A

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, N.S.; Riggins, M. [Sandia National Labs., Albuquerque, NM (United States); Connolly, J. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Geology and Inst. of Meteoritics; Ricci, P. [Holometrix, Inc., Bedford, MA (United States)

    1997-09-01

    Specimens were tested from four thermal-mechanical units, namely Tiva Canyon (TCw), Paintbrush Tuff (PTn), and two Topopah Spring units (TSw1 and TSw2), and from two lithologies, i.e., welded devitrified (TCw, TSw1, TSw2) and nonwelded vitric tuff (PTn). Thermal conductivities in W(mk){sup {minus}1} averaged over all boreholes, ranged (depending upon temperature and saturation state) from 1.2 to 1.9 for TCw, from 0.4 to 0.9 for PTn, from 1.0 to 1.7 for TSw1, and from 1.5 to 2.3 for TSw2. Mean coefficients of thermal expansion were highly temperature dependent and values, averaged over all boreholes, ranged (depending upon temperature and saturation state) from 6.6 {times} 10{sup {minus}6} to 49 {times} 10{sup {minus}6} C{sup {minus}1} for TCw, from the negative range to 16 {times} 10{sup {minus}6} {center_dot} {degree}C{sup {minus}1} for PTn, from 6.3 {times} 10{sup {minus}6} to 44 {times} 10{sup {minus}6} C{sup {minus}1} for TSw1, and from 6.7 {times} 10{sup {minus}6} to 37 {times} 10{sup {minus}6} {center_dot} {degree}C{sup {minus}1} for TSw2. Mean values of thermal capacitance in J/cm{sup 3}K (averaged overall specimens) ranged from 1.6 J to 2.1 for TSw1 and from 1.8 to 2.5 for TSw2. In general, the lithostratigraphic classifications of rock assigned by the USGS are consistent with the mineralogical data presented in this report.

  1. Distortions and stresses in thin shells due to anisotropic thermal expansion

    Science.gov (United States)

    Koenig, Manfred

    1992-10-01

    The considerable interest in the application of refractory anisotropic materials to the design of shell components, which are used in the very hot regions of future hypersonic flight and reusable reentry vehicle structures, is discussed. These materials are often homogeneous in the macroscopic scale but anisotropic. Typical examples are pyrolytic graphite (obtained by vapor deposition) and more recently, carbon fiber reinforced carbon (C/C) and carbon fiber reinforced silicon carbide (C/SiC). The carbon fiber reinforcement of C/C and C/SiC often consists of layers of fabrics (0/90 deg), resulting in a behavior that is nearly isotropic in the plane of the shell but differs in the perpendicular (thickness) direction. The study focuses on such transversely isotropic materials and deals with distortions and residual stresses in shells made of such materials and resulting from uniform temperature changes.

  2. Calcium pyroxenes at Mercurian surface temperatures: investigation of in-situ emissivity spectra and thermal expansion

    Science.gov (United States)

    Ferrari, S.; Nestola, F.; Helbert, J.; Maturilli, A.; D'Amore, M.; Alvaro, M.; Domeneghetti, M.; Massironi, M.; Hiesinger, H.

    2013-12-01

    The European Space Agency and Japan Aerospace Agency mission to Mercury, named BepiColombo, will carry on board the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) that will be able to provide surface Thermal Infra-Red (TIR) emissivity spectra from 7 to 14 μm. This range of wavelengths is very useful to identify the fine-scale structural properties of several silicates. For mineral families as pyroxenes, the emissivity peak positions are good indicators of the composition. A complication in the interpretation of MERTIS data could arise from the extreme daily surface temperature range of Mercury (70 to 725 K) that significantly affects the crystal structure and density of minerals and consequently should affect the TIR spectral signature of each single mineral present on the surface of the planet. In preparation for the MERTIS data analysis, we are extensively investigating at high temperatures conditions several mineral phases potentially detectable on the surface of Mercury. Two C2/c augitic pyroxenes, with constant calcium content and very different magnesium to iron ratio, were studied by in situ high-temperature thermal infrared spectroscopy (up to 750 K) and in situ high-temperature single-crystal X-ray diffraction (up to 770 K). The emissivity spectra of the two samples show similar band center shifts of the main three bands toward lower wavenumbers with increasing temperature. Our results indicate that the center position of bands 1 and 2 is strictly dependent on temperature, whereas the center position of band 3 is a strong function of the composition regardless the temperature. These data suggest that MERTIS spectra will be able to provide indications of C2/c augitic pyroxene with different magnesium contents and will allow a correct interpretation independently on the spectra acquisition temperature.

  3. Multi-functional materials by powder processing for a thermal protection system with self-cooling capability: Perspirable skin

    Science.gov (United States)

    Sun, Li

    Aerodynamic heating generated by the friction between the atmosphere and the space vehicle's surface at reentry can enhance the temperature on the surface as high as 1700°C. A Thermal Protection System (TPS) is needed to inhibit the heat entering into the vehicle. Presently, the completely passive thermal protection is used for TPS. The thermal ablation/erosion and oxidization reaction of the current TPS is the major threat to the safety of the space vehicle. Therefore, a new design for TPS with actively self-cooling capability was proposed by bio-mimicking the perspiration of the human body, henceforth called Perspirable skin. The design of Perspirable Skin consists of core material shrink-fitted into a skin panel such as Reinforced Carbon-Carbon (RCC) Composite. The core material contains a very small Coefficient of Thermal Expansion (CTE) compared to the panel material. As temperature increases, the gap between the core and the skin are produced due to the CTE difference. Compressed gas on board the space vehicle will blow out from the gap once the surface temperature reaches a critical value. The cold gas flows over the surface and mixes with the atmospheric air to compensate for the frictional heat. With Perspirable Skin, the highest temperature on the surface is expected to decrease, and we assumed it to be around half of the present temperature. This dissertation focuses on the selection of the core materials and their manufacturing by powder processing. Based on a series of experiments, several results were obtained: (1) the effect of powder mixing on the compaction capability and sintering capability was determined; (2) a flat 3-layered Al 2O3/ZrO2 Functionally Graded Material (FGM) without cracks was fabricated; (3) the factors contributing to the cracks in the multi-layered materials were investigated; (4) an isotropic negative thermal expansion material, ZrW2O8, as well as its composites with ZrO2 were processed by in-situ reaction of WO3 and ZrO2; (5

  4. Polymerization shrinkage and hygroscopic expansion of contemporary posterior resin-based filling materials--a comparative study.

    Science.gov (United States)

    Rüttermann, Stefan; Krüger, Sören; Raab, Wolfgang H-M; Janda, Ralf

    2007-10-01

    To investigate the polymerization shrinkage and hygroscopic expansion of contemporary posterior resin-based filling materials. The densities of SureFil (SU), CeramXMono (CM), Clearfil AP-X (CF), Solitaire 2 (SO), TetricEvoCeram (TE), and Filtek P60 (FT) were measured using the Archimedes' principle prior to and 15min after curing for 20, 40 and 60s and after 1h, 24h, 7 d, and 30 d storage at 37 degrees C in water. Volumetric changes (DeltaV) in percent after polymerization and after each storage period in water were calculated from the changes of densities. Water sorption and solubility were determined after 30 d for all specimens and their curing times. Two-way ANOVA was calculated for shrinkage and repeated measures ANOVA was calculated for hygroscopic expansion (pHygroscopic expansion depended on water sorption and solubility. Except for SU, all materials showed DeltaV approximately +1% after water storage. Polymerization shrinkage depended on the type of resin-based filling material but not on curing time. Shrinkage was not compensated by hygroscopic expansion.

  5. Energy Consumption of Insulated Material Using Thermal Effect Analysis

    Directory of Open Access Journals (Sweden)

    Fadzil M. A.

    2017-01-01

    Full Text Available Wall is one of the structures elements that resist direct heat from the atmosphere. Modification on several structures is relevance to reduce filtrate thermal movement on wall. Insulation material seems to be suitable to be implemented since its purpose meets the heat resistance requirement. Insulation material applied as to generate positive impact in energy saving through reduction in total building energy consumption. Fiberglass is one of the insulation materials that can be used to insulate a space from heat and sound. Fiberglass is flammable insulation material with R Value rated of R-2.9 to R-3.8 which meets the requirement in minimizing heat transfer. Finite element software, ABAQUS v6.13 employed for analyze non insulated wall and other insulated wall with different wall thicknesses. The several calculations related to overall heat movement, total energy consumption per unit area of wall, life cycle cost analysis and determination of optimal insulation thickness is calculated due to show the potential of the implementation in minimize heat transfer and generate potential energy saving in building operation. It is hoped that the study can contribute to better understanding on the potential building wall retrofitting works in increasing building serviceability and creating potential benefits for building owner.

  6. The response of the HMX-based material PBXN-9 to thermal insults: thermal decomposition kinetics and morphological changes

    Energy Technology Data Exchange (ETDEWEB)

    Glascoe, E A; Hsu, P C; Springer, H K; DeHaven, M R; Tan, N; Turner, H C

    2010-12-10

    PBXN-9, an HMX-formulation, is thermally damaged and thermally decomposed in order to determine the morphological changes and decomposition kinetics that occur in the material after mild to moderate heating. The material and its constituents were decomposed using standard thermal analysis techniques (DSC and TGA) and the decomposition kinetics are reported using different kinetic models. Pressed parts and prill were thermally damaged, i.e. heated to temperatures that resulted in material changes but did not result in significant decomposition or explosion, and analyzed. In general, the thermally damaged samples showed a significant increase in porosity and decrease in density and a small amount of weight loss. These PBXN-9 samples appear to sustain more thermal damage than similar HMX-Viton A formulations and the most likely reasons are the decomposition/evaporation of a volatile plasticizer and a polymorphic transition of the HMX from {beta} to {delta} phase.

  7. Zirconium tungstate/epoxy resin nanocomposites with negative coefficient of thermal expansion for all-dielectric cryogenic temperature sensors

    Science.gov (United States)

    See, Erich; Kochergin, Vladimir; Neely, Lauren; Zayetnikov, Madrakhim; Ciovati, Gianluigi; Robinson, Hans

    2012-02-01

    The α-phase of zirconium tungstate (ZrW2O8) has the remarkable property that its coefficient of thermal expansion (CTE) is negative over its entire range of thermal stability (0-1050K), and through this range it has a nearly constant negative CTE. When ZrW2O8 nanoparticles are mixed into a polymer resin, the resulting composite has a reduced CTE when compared with that of the pure polymer. However, previous research on such composites has occurred only near room temperature. We show that at cryogenic temperatures, it is possible to make ZrW2O8/resin nanocomposites with negative CTE. By coating a fiber-optic Bragg grating with such a composite, we were able to create an all-optical temperature sensor without the use of metals, which would be of particular use in superconducting RF cavities. The sensor has sensitivity down to at least 2 K, six times lower than previous fiber-optic temperature sensors.

  8. Disentangling random thermal motion of particles and collective expansion of source from transverse momentum spectra in high energy collisions

    Science.gov (United States)

    Wei, Hua-Rong; Liu, Fu-Hu; Lacey, Roy A.

    2016-12-01

    In the framework of a multisource thermal model, we describe experimental results of the transverse momentum spectra of final-state light flavor particles produced in gold-gold (Au-Au), copper-copper (Cu-Cu), lead-lead (Pb-Pb), proton-lead (p-Pb), and proton-proton (p -p) collisions at various energies, measured by the PHENIX, STAR, ALICE, and CMS Collaborations, by using the Tsallis-standard (Tsallis form of Fermi-Dirac or Bose-Einstein), Tsallis, and two- or three-component standard distributions which can be in fact regarded as different types of ‘thermometers’ or ‘thermometric scales’ and ‘speedometers’. A central parameter in the three distributions is the effective temperature which contains information on the kinetic freeze-out temperature of the emitting source and reflects the effects of random thermal motion of particles as well as collective expansion of the source. To disentangle both effects, we extract the kinetic freeze-out temperature from the intercept of the effective temperature (T) curve as a function of particle’s rest mass (m 0) when plotting T versus m 0, and the mean transverse flow velocity from the slope of the mean transverse momentum ( ) curve as a function of mean moving mass (\\overline{m}) when plotting versus \\overline{m}.

  9. Effects of thermal expansion of the crystal lattice on x-ray crystal spectrometers used for fusion research

    Science.gov (United States)

    Delgado-Aparicio, L.; Bitter, M.; Podpaly, Y.; Rice, J.; Burke, W.; Sanchez del Rio, M.; Beiersdorfer, P.; Bell, R.; Feder, R.; Gao, C.; Hill, K.; Johnson, D.; Lee, S. G.; Marmar, E.; Pablant, N.; Reinke, M. L.; Scott, S.; Wilson, R.

    2013-12-01

    X-ray imaging crystal spectrometers with high spectral and spatial resolution are currently being used on magnetically confined fusion devices to infer the time history profiles of ion and electron temperatures as well as plasma flow velocities. The absolute measurement of flow velocities is important for optimizing various discharge scenarios and evaluating the radial electric field in tokamak and stellarator plasmas. Recent studies indicate that the crystal temperature must be kept constant to within a fraction of a degree to avoid changes of the interplanar 2d-spacing by thermal expansion that cause changes in the Bragg angle, which could be misinterpreted as Doppler shifts. For the instrumental parameters of the x-ray crystal spectrometer on Alcator C-Mod, where those thermal effects were investigated, a change of the crystal temperature by 1 °C causes a change of the lattice spacing of the order of Δd = 1 × 10-5 Å introducing a fictitious velocity drift of the order of ˜3 km s-1. This effect must be considered for x-ray imaging crystals spectrometers installed on LHD, KSTAR, EAST, J-TEXT, NSTX and, in the future, W7-X and ITER.

  10. Non-adiabatic effects within a single thermally-averaged potential energy surface: Thermal expansion and reaction rates of small molecules

    CERN Document Server

    Alonso, J L; Clemente-Gallardo, J; Echenique, P; Mazo, J J; Polo, V; Rubio, A; Zueco, D

    2012-01-01

    At non-zero temperature and when a system has low-lying excited electronic states, the ground-state Born--Oppenheimer approximation breaks down and the low-lying electronic states are involved in any chemical process. In this work, we use a temperature-dependent effective potential for the nuclei which can accomodate the influence of an arbitrary number of electronic states in a simple way, while at the same time producing the correct Boltzmann equibrium distribution for the electronic part. With the help of this effective potential, we show that thermally-activated low-lying electronic states can have a significant effect in molecular properties for which electronic excitations are oftentimes ignored. We study the thermal expansion of the Manganese dimer, Mn$_2$, where we find that the average bond length experiences a change larger than the present experimental accuracy upon the inclusion of the excited states into the picture. We also show that, when these states are taken into account, reaction rate const...

  11. Cryogenic Refractive Index and Coefficient of Thermal Expansion for the S-TIH1 Glass

    Science.gov (United States)

    Quijada, Manuel A.; Leviton, Douglas; Content, David

    2013-01-01

    Using the CHARMS facility at NASA GSFC, we have measured the cryogenic refractive index of the Ohara S-TIH1 glass from 0.40 to 2.53 micrometers and from 120 to 300 K. We have also examined the spectral dispersion and thermo-optic coefficients (dn/dT). We also derived temperature-dependent Sellmeier models from which refractive index may be calculated for any wavelength and temperature within the stated ranges of each model. The S-TIH1 glass we tested exhibited unusual behavior in the thermo-optic coefficient. We found that for delta glass in order to understand its thermal properties. The CTE showed a monotonic change with a decrease in temperature.

  12. High-Temperature Structures, Adhesives, and Advanced Thermal Protection Materials for Next-Generation Aeroshell Design

    Science.gov (United States)

    Collins, Timothy J.; Congdon, William M.; Smeltzer, Stanley S.; Whitley, Karen S.

    2005-01-01

    National Laboratories. These tests are designed to validate aeroshell manufacturability using advanced material systems, and to demonstrate the maintenance of bondline integrity at realistically high temperatures and heating rates. Finally, a status is given of ongoing aeroshell modeling and analysis efforts which will be used to correlate with experimental testing, and to provide a reliable means of extrapolating to performance under actual flight conditions. The modeling and analysis effort includes a parallel series of experimental tests to determine TSP thermal expansion and other mechanical properties which are required for input to the analysis models.

  13. Development of Solution-Processable, Optically Transparent Polyimides with Ultra-Low Linear Coefficients of Thermal Expansion

    Directory of Open Access Journals (Sweden)

    Masatoshi Hasegawa

    2017-10-01

    Full Text Available This paper reviews the development of new high-temperature polymeric materials applicable to plastic substrates in image display devices with a focus on our previous results. Novel solution-processable colorless polyimides (PIs with ultra-low linear coefficients of thermal expansion (CTE are proposed in this paper. First, the principles of the coloration of PI films are briefly discussed, including the influence of the processing conditions on the film coloration, as well as the chemical and physical factors dominating the low CTE characteristics of the resultant PI films to clarify the challenges in simultaneously achieving excellent optical transparency, a very high Tg, a very low CTE, and excellent film toughness. A possible approach of achieving these target properties is to use semi-cycloaliphatic PI systems consisting of linear chain structures. However, semi-cycloaliphatic PIs obtained using cycloaliphatic diamines suffer various problems during precursor polymerization, cyclodehydration (imidization, and film preparation. In particular, when using trans-1,4-cyclohexanediamine (t-CHDA as the cycloaliphatic diamine, a serious problem emerges: salt formation in the initial stages of the precursor polymerization, which terminates the polymerization in some cases or significantly extends the reaction period. The system derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA and t-CHDA can be polymerized by a controlled heating method and leads to a PI film with relatively good properties, i.e., excellent light transmittance at 400 nm (T400 = ~80%, a high Tg (>300 °C, and a very low CTE (10 ppm·K−1. However, this PI film is somewhat brittle (the maximum elongation at break, εb max is about 10%. On the other hand, the combination of cycloaliphatic tetracarboxylic dianhydrides and aromatic diamines does not result in salt formation. The steric structures of cycloaliphatic tetracarboxylic dianhydrides significantly influence

  14. Evaluation of heat sink materials for thermal management of lithium batteries

    Science.gov (United States)

    Dimpault-Darcy, E. C.; Miller, K.

    1988-01-01

    Aluminum, neopentyl glycol (NPG), and resins FT and KT are evaluated theoretically and experimentally as heat sink materials for lithium battery packs. The thermal performances of the two resins are compared in a thermal vacuum experiment. As solutions to the sublimation property were not immediately apparent, a theoretical comparison of the thermal performance of NPG versus KT, Al, and no material, is presented.

  15. Evaluation of different measurements for effective thermal conductivity of fibrous materials

    Directory of Open Access Journals (Sweden)

    Tian Ming-Wei

    2014-01-01

    Full Text Available Effective thermal conductivity is generally recognized as the intrinsic factor to reveal the thermal responses of fibrous materials. Here, two typical measurements, the step-wise transient method and the guarded hot plate method, were utilized to identify their feasibility for the effective thermal conductivity of fibrous materials (non-woven fabric and twill fabric with different stacking layers.

  16. Thermal Interface Materials Selection and Application Guidelines: In Perspective of Xilinx Virtex-5QV Thermal Management

    Science.gov (United States)

    Suh, Jong-ook; Dillon, R. Peter; Tseng, Stephen

    2015-01-01

    The heat from high-power microdevices for space, such as Xilinx Virtex 4 and 5 (V4 and V5), has to be removed mainly through conduction in the space vacuum environment. The class-Y type packages are designed to remove the heat from the top of the package, and the most effective method to remove heat from the class-Y type packages is to attach a heat transfer device on the lid of the package and to transfer the heat to frame or chassis. When a heat transfer device is attached to the package lid, the surfaces roughness of the package lid and the heat transfer device reduces the effective contact area between the two. The reduced contact area results in increased thermal contact resistance, and a thermal interface material is required to reduce the thermal contact resistance by filling in the gap between the surfaces of the package lid and the heat transfer device. The current report describes JPL's FY14 NEPP task study on property requirements of TIM and impact of TIM properties on the packaging reliability. The current task also developed appratuses to investigate the performances of TIMs in the actual mission environment.

  17. Thermal and chemical degradation of inorganic membrane materials. Topical report

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, G.N.; Sanjurjo, A.; Wood, B.J.; Lau, K.H.

    1994-04-01

    This report describes the results of a literature review to evaluate the long-term thermal and chemical degradation of inorganic membranes that are being developed to separate gaseous products produced by the gasification or combustion of coal in fixed-, fluidized-, and entrained-bed gasifiers, direct coal-fired turbines, and pressurized-fluidized-bed combustors. Several impurities, such as H{sub 2}S, NH{sub 3}, SO{sub 2}, NO{sub x}, and trace metal compounds are generated during coal conversion, and they must be removed from the coal gas or the combustor flue gas to meet environmental standards. The use of membranes to separate these noxious gases is an attractive alternative to their removal by sorbents such as zinc titanate or calcium oxide. Inorganic membranes that have a high separation efficiency and exhibit both thermal and chemical stability would improve the economics of power generation from coal. The U.S. Department of Energy is supporting investigations to develop inorganic membranes for separating hydrogen from coal gas streams and noxious impurities from hot coal- and flue-gas streams. Membrane materials that have been investigated in the past include glass (silica), alumina, zirconia, carbon, and metals (Pd and Pt).

  18. THERMAL PERFORMANCE OF RADIOACTIVE MATERIAL PACKAGES IN TRANSPORT CONFIGURATION

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, N.

    2010-03-04

    Drum type packages are routinely used to transport radioactive material (RAM) in the U.S. Department of Energy (DOE) complex. These packages are designed to meet the federal regulations described in 10 CFR Part 71. The packages are transported in specially designed vehicles like Safe Secure Transport (SST) for safety and security. In the transport vehicles, the packages are placed close to each other to maximize the number of units in the vehicle. Since the RAM contents in the packagings produce decay heat, it is important that they are spaced sufficiently apart to prevent overheating of the containment vessel (CV) seals and the impact limiter to ensure the structural integrity of the package. This paper presents a simple methodology to assess thermal performance of a typical 9975 packaging in a transport configuration.

  19. Moisture Absorption and Thermal Expansion of Building Blocks Bound with Bitumen

    OpenAIRE

    Thanaya, I Nyoman Arya

    2009-01-01

    . This paper described about masonry wall building blocks that incorporate waste aggregate materials, namely steel slag, crushed glass, and coal fly ash. The binder used was 50 pen bitumen. The investigation was carried out at the University of Leeds United Kingdom (UK). The samples were produced by hot mixing the waste aggregates, compacting by static compaction, then applying heat curing to the compacted samples to harden the bitumen binder. The objective of the investigation was mainly to ...

  20. The structure, thermal expansion and phase transition properties of Ho{sub 2}Mo{sub 3−x}W{sub x}O{sub 12} (x = 0, 1.0, 2.0) solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X.Z.; Hao, L.J.; Wu, M.M.; Ma, X.B.; Chen, D.F.; Liu, Y.T., E-mail: ytliu@ciae.ac.cn

    2015-10-15

    Graphical abstract: A polymorph with Gd{sub 2}Mo{sub 3}O{sub 12}-type structure (space group: Pba2) for negative thermal expansion material Ho{sub 2}Mo{sub 3}O{sub 12} is observed above 700 °C, this polymorphism could be effectively supressed by W-substiution for Mo, the give the temperature dependence of Pba2 phase contents for Ho{sub 2}Mo{sub 3−x}W{sub x}O{sub 12} (x = 0.0, 1.0, 2.0). - Highlights: • The solid solution Ho{sub 2}Mo{sub 3−x}W{sub x}O{sub 12} was investigated by in situ X-ray diffraction. • It is found that the substitution slightly influence thermal expansion property. • A polymorph of Ho{sub 2}Mo{sub 3}O{sub 12} with Pba2 space group was observed above 700 °C. • The W-substitution for Mo effectively suppresses this transformation. - Abstract: Three solid solutions of Ho{sub 2}Mo{sub 3−x}W{sub x}O{sub 12}(x = 0, 1.0, 2.0) were prepared by solid state reaction method, the temperature dependent in-situ X-ray diffraction and thermal analysis were performed to investigate their structure and thermal expansion. All samples have orthorhombic structure(space group Pbcn# 60) with negative thermal expansion at the room temperature. the substitution of W for Mo enlarges the lattice constant and slightly influences the negative thermal expansion. An irreversible phase transformation to the Pba2 phase(Tb{sub 2}Mo{sub 3}O{sub 12} structure) was observed at high temperature for Mo-rich samples. This ploymorphism could be effectively suppressed by the W-substitution for Mo, this phenomenon could be explained by the lower electronegativity of W{sup 6+} than Mo{sup 6+}.