Showing papers on "Thermal expansion published in 1981"
TL;DR: In this paper, the role of elastic, thermoelastic and interfacial properties in the toughening of a brittle matrix by metallic second-phase particles was studied, and two composites were studied: glass+partly oxidized Ni particles (thermal expansion coefficient of the glasses lower than, equal to, and higher than that of Ni) and glass + partly oxidised Al particles (the thermal expansion and elastic moduli equal).
Abstract: The role of elastic, thermoelastic, and interfacial properties in the toughening of a brittle matrix by metallic second-phase particles was studied. Two composites were studied: glass+partly oxidized Ni particles (thermal expansion coefficient of the glasses lower than, equal to, and higher than that of Ni) and glass+partly oxidized Al particles (thermal expansion and elastic moduli equal). Weak interfacial bonding between the nickel and its oxide and developed stress concentrations are the major toughness limitations found in the glass/Ni composites. When the thermal expansion coefficient and elastic modulus of the second phase are sufficiently greater than that of the glass matrix, a propagating crack will bypass the particles. When the thermal and elastic stresses are minimized and satisfactory bonding is achieved (glass/Al composites), a 60x toughness increase was realized.
221 citations
TL;DR: SiC-AIN alloys were prepared by the carbothermal reduction of silica and alumina, derived from an intimate mixture of silicon, aluminium chloride and starch, and the resulting single-phase SiC-ain powder was hot-pressed without additives to a high density.
Abstract: SiC-AIN alloys were prepared by the carbothermal reduction of silica and alumina, derived from an intimate mixture of silica, aluminium chloride and starch. The resulting single-phase SiC-AIN powder was hot-pressed without additives to a high density. The dense bodies had a fine-grained uniform microstructure. The Young's elastic modulus, microhardness, fracture toughness, thermal expansion and thermal conductivity were measured as functions of composition. The creep behaviour of the SiC-AIN alloy was compared with that of silicon carbide.
147 citations
TL;DR: In this paper, the authors show that fracture surface morphology, mechanical data, and the controlled crack growth analogues suggest that thermal fracture in solidifying basalt is an incremental and cyclic process, involving three steps: (1) the accumulation of elastic strain energy in cooling rock at temperatures below that required for stress relaxation due to viscous flow in the intercrystalline liquid phase, (2) fracture at a ΔT determined primarily by the aggregate thermal expansion coefficient αυ and Young's modulus E, (3) the penetration by the advancing crack tip, of
Abstract: The glass transition has been experimentally detected in basalt as (1) an increase in the aggregate linear thermal expansion coefficient αL, (2) an abrupt change in the temperature dependence of Young's modulus dE/dT, and (3) a change in stress relaxation behavior that effectively separates the T> TG and T TG. Collectively, the mechanical results suggest that for Hawaiian olivine tholeiite at 1-atm pressure, the principal material responses are (1) elastic (T ≤ 600°C), (2) reduced creep (600 980°C). Fracture surface morphologies developed during solidification suggest that the presence of the supercooled melt grain boundary phase may participate in the regulation of the thermal cracking process. Well-preserved fracture surfaces formed by incremental crack growth are found to be covered with striations that correspond to the inferred sequential stopping positions of the advancing fracture front. These striae may be rationalized in terms of experimental analogues that have been produced in viscoelastic polymers by cyclic tension-tension loading. The fracture surface morphology, mechanical data, and the controlled crack growth analogues suggest that thermal fracture in solidifying basalt is an incremental and cyclic process, involving three steps: (1) the accumulation of elastic strain energy in cooling rock at temperatures below that required for stress relaxation due to viscous flow in the intercrystalline liquid phase, (2) fracture at a ΔT determined primarily by the aggregate thermal expansion coefficient αυ and Young's modulus E, (3) the penetration by the advancing crack tip, of the thermal horizon capable of relaxing stress due to the creep of intercrystalline supercooled melt, producing the rough surface texture associated with the termination of a striation. Further crack growth must now await the migration of the solidus. The cycle then repeats. Striations measured in deep Hawaiian lava lakes have been compared with the crack advance increments expected in the vicinity of the glass transition, based on two tests: (1) thermal gradients measured in Kilauea Iki, combined with the mechanical properties of olivine tholeiite evaluated near TG, and (2) the crack advance required to match the recorded seismic stopping phases for prexisting cracks of the dimensions expected for Kilauea Iki. The observed versus predicted comparisons are (1) 31 versus 36 cm; and (2) 31 versus 30 cm. We envision this incremental crack growth process as contributing to the control on the downward movement of the thermal cracking front—and its associated hydrothermal circulation zone—in the upper portions of solidifying subaerial and submarine ponded basalt.
136 citations
TL;DR: In this paper, the effects of confining pressure and temperature on the stresses and displacements in and around a spherical inclusion embedded in a matrix of different elasticity and thermal expansion were investigated.
95 citations
TL;DR: In this article, the coefficient of linear thermal expansion of pure polycrystalline silicon was measured with a polarization interferometer and a platinum resistance thermometer with an estimated error of less than 0.01 × 10-6 K-1.
Abstract: Measurements of the coefficient of linear thermal expansion of pure polycrystalline silicon were made with a polarization interferometer and a platinum resistance thermometer with an estimated error of less than 0.01 × 10-6 K-1.
90 citations
TL;DR: In this article, the dielectric constant, specific heat and thermal expansion of CsHSeO 4 were measured as functions of temperature, and X-ray examination was also made.
Abstract: The dielectric constant, specific heat and thermal expansion of CsHSeO 4 were measured as functions of temperature, and X-ray examination was also made. It was found that CsHSeO 4 undergoes a phase transition at 128°C. The crystal at room temperature is monoclinic with a space group P2/ c . The transition entropy was estimated from the specific heat to be Δ S =16.1 J·mol -1 deg -1 .
64 citations
TL;DR: In this article, at constant strain rate (10 −5 s −1 ), at 210 −250 MPa confining pressure and at 560 −900°C, deformation tests were performed on an aplite with varying water contents.
62 citations
TL;DR: In this article, an X-ray diffraction technique was used to measure the residual stresses of an aluminum matrix-graphite fiber composite, and the results can be related to interface structures and transverse properties of the composites.
61 citations
TL;DR: In this article, the authors measured the thermal expansion of single-crystal fayalite at temperatures between 25 °C and 850 °C. The results show the presence of anomalous expansion in the b axis, which is correlated to the anomalous variation of elastic moduli with temperature.
Abstract: Thermal expansion of single-crystal fayalite has been measured by a dilatometric method at temperatures between 25 °C and 850 °C. The results show the presence of anomalous expansion in the b axis, which is correlated to the anomalous variation of elastic moduli with temperature. Gruneisen's parameter is 1.10 and the thermal Debye temperature is 565 K, which is close to the acoustic Debye temperature of 511 K.
59 citations
TL;DR: In this paper, the analysis of the X-ray Debye-Scherrer lines of the fine gold particles of which sizes are in a range from 60 to 230 A, it was found that the thermal expansion coefficient as well as the lattice parameter are not different from those of the bulk crystal, while the characteristic temperature decreases monotonously with the decrease of the particle size.
58 citations
Patent•
10 Sep 1981TL;DR: In this article, an improved epoxy molding composition for encapsulating microelectronic devices is presented, where the molding mixture, after conversion to a thermoset condition, displays a low coefficient of thermal expansion and a high thermal conductivity.
Abstract: An improved epoxy molding composition for encapsulating microelectronic devices wherein the molding composition, after conversion to a thermoset condition, i.e., infusible state, by the application of heat and pressure, displays a low coefficient of thermal expansion and a high thermal conductivity. The dual properties of low coefficient of thermal expansion and high thermal conductivity are imparted to the molding composition by the incorporation therein of a specific anisotropic, polycrystalline, sintered ceramic product which is relatively non-abrasive and free of ionic contaminants and which has cordierite as its primary phase, consisting essentially on an analytical oxide basis of 11.5 to 16.5% RO, 33 to 41% Al2 O3 and 46.6 to 53% SiO2.
TL;DR: In this article, anomalous thermal expansion of FeNi alloy is calculated on the basis of Liberman-Pettifor's virial theorem and the full single site approximation in the functional integral method.
Abstract: Anomalous thermal expansion of FeNi alloy is calculated on the basis of Liberman-Pettifor's virial theorem and the full single site approximation in the functional integral method. Results explain well the Invar effect. In general, the electronic contribution to the thermal expansion consists of three terms, i.e. the positive term proportional to the specific heat, the local moment term caused by the temperature variation of the amplitudes of the local moments and the term due to the s - d charge transfer. It is verified that the large negative thermal expansion of the electron system is caused by the local moment term. The lattice parameter, the bulk modulus at T =0 K and other magnetic quantities are also calculated, which are consistent with the experimental results.
TL;DR: Within the accuracy of the data on thermal expansion, bulk modulus, and specific heat, Gruneisen's gamma at constant volume for 21 metals is shown to be independent of temperature, at least to a substantial fraction of the melt temperature.
Abstract: Within the accuracy of the data on thermal expansion, bulk modulus, and specific heat, Gruneisen’s gamma at constant volume for 21 metals is shown to be independent of temperature, at least to a substantial fraction of the melt temperature.
TL;DR: In this paper, the specific heat, thermal expansion and resistivity were measured for the intermediate valence compound YbCuAl and its reference compound LuCuAl between 1.5 and 400 K. All quantities show strong anomalies.
Abstract: The specific heat, thermal expansion and resistivity was measured for the intermediate valence compound YbCuAl and its reference compound LuCuAl between 1.5 and 400 K. All quantities show strong anomalies. The entropy of the specific heat anomaly is found to be nearR·ln9, the value expected for the entropy of a high temperature mixture of Yb-ions in the ratio dictated by the degeneracies of the Hund's rule groundstates of 4f
14 and 4f
13. TheT
3 coefficient of the low temperature specific heat of YbCuAl contains a large electronic contribution. The integrated thermal expansion anomaly indicates a shift of the valence by at least 3.5% towards 3+ between 1.5 and 310 K.
TL;DR: In this article, the quenching of a thick-walled viscoplastic cylinder cooled from To −1 −320°C down to room temperature is examined. The transient thermomechanical problem is partitioned into the staggered solution of thermal-heat conduction and elastic-viscoplastic response behavior using finite elements.
Abstract: The quenching of a thick-walled viscoplastic cylinder cooled from To = 320° C down to room temperature is examined. The transient thermomechanical problem is partitioned into the staggered solution of thermal-heat conduction and elastic-viscoplastic response behavior using finite elements. Fully implicit time operators are applied to both field problems, which are coupled on one side by the mechanical heat production of thermoelasticity and thermoviscoplasticity and on the other by the ensuing thermal expansion due to temperature transients. In both analysis steps a quasi-Newton technique (BFGS algorithm) is applied for solving the implicit nonlinear problem within each time step. In this way the entire coupled thermomechanical response is monitored incrementally, starting from the initially pressurized condition at elevated temperature up to the steady-state behavior at room temperature after quenching.
TL;DR: In this paper, a model of coarsening of the closed pores based on a vacancy migration mechanism is proposed, and the superposition method after correcting the thermal expansion induced surface area change and the curve fitting method give an activation energy of 64 ± 10 kcal / mole.
Patent•
30 Nov 1981TL;DR: In this paper, a thermal coefficient control fabric embedded in a resin matrix and composed of yarns with positive and negative coefficients of thermal expansion is proposed for a composite circuit board constructed of the composite and matched to a particular chip carrier material, such as aluminum oxide.
Abstract: A composite characterized by a controlled coefficient of thermal expansion and comprising a thermal coefficient control fabric embedded in a resin matrix and composed of yarns with positive and negative coefficients of thermal expansion. A composite circuit board constructed of the composite and having a coefficient of thermal expansion matched to a particular integrated chip carrier material, such as aluminum oxide.
TL;DR: In this paper, the transition of condensed hydrogen from an insulating molecular crystal phase to a metallic liquid phase, at zero temperature and high pressure, appears possible, and the low-temperature specific heat, compressibility, thermal expansion coefficient and spin susceptibility are given.
Abstract: It is reported that the transition of condensed hydrogen from an insulating molecular crystal phase to a metallic liquid phase, at zero temperature and high pressure, appears possible. Liquid metallic hydrogen (LMH), comprising interpenetrating proton and electron fluids, would constitute a two-component Fermi liquid with both a very high component-mass ratio and long-range, species-dependent bare interactions. The low-temperature equilibrium properties of LMH are examined by means of a generalization to the case of two components of the phenomenological Landau Fermi-liquid theory, and the low-temperature specific heat, compressibility, thermal expansion coefficient and spin susceptibility are given. It is found that the specific heat and the thermal expansion coefficient are vastly greater in the liquid than in the corresponding solid, due to the presence of proton quasiparticle excitations in the liquid.
TL;DR: In this article, the Liberman-Pettifor virial theorem is extended to the finite temperatures, and expressions for the spontaneous volume magnetostriction and the electronic contribution to the thermal expansion coefficient are given by using the functional integral method within the static approximation.
Abstract: The Liberman-Pettifor virial theorem is extended to the finite temperatures, and the expressions for the spontaneous volume magnetostriction and the electronic contribution to the thermal expansion coefficient are given by using the functional integral method within the static approximation. The temperature variations of these quantities are determined mainly by the amplitude of the local magnetic moment and the s-d charge transfer. Two types of the thermal expansion, the αFe type and the Weiss model type, appear within the CPA-LSA and their properties are examined and discussed.
01 Jul 1981
TL;DR: In this paper, thermal expansion data for several composite materials, including generic epoxy resins, various graphite, boron, and glass fibers, and unidirectional and woven fabric composites in an epoxy matrix, were compiled.
Abstract: Thermal expansion data for several composite materials, including generic epoxy resins, various graphite, boron, and glass fibers, and unidirectional and woven fabric composites in an epoxy matrix, were compiled. A discussion of the design, material, environmental, and fabrication properties affecting thermal expansion behavior is presented. Test methods and their accuracy are discussed. Analytical approaches to predict laminate coefficients of thermal expansion (CTE) based on lamination theory and micromechanics are also included. A discussion is included of methods of tuning a laminate to obtain a near-zero CTE for space applications.
TL;DR: In this paper, the authors used direct mechanical tests to estimate both the coefficient of thermal expansion and the elastic modulus of hydrogenated amorphous silicon (a-Si:H) thin films.
TL;DR: In this paper, the effective thermal stress and thermal expansion coefficients of unidirectional short-fiber composites were derived based on the known local elastic field solution derived by the perturbation expansion of the Green's tensor function.
TL;DR: A survey of the more recent experimental measurements of the viscosity, density, thermal expansion coefficient, thermal conductivity, and specific heat of liquid 4He from the λ region up to 4.2 K can be found in this article.
Abstract: A survey has been made of the more recent experimental measurements of the viscosity, density, thermal expansion coefficient, thermal conductivity, and specific heat of liquid 4He from the λ region up to 4.2 K. Cubic spline fits to these data are provided using a mean squares approach. The fits are used to plot the temperature dependence of the kinematic viscosity, the thermal diffusivity, and the Prandtl number.
TL;DR: In this article, a precise determination of the lattice parameters of silver indium selenide was made in the temperature range 28-478 °C using a 19 cm Unicam high temperature powder camera and Cu Kα radiation.
Abstract: A precise determination of the lattice parameters of silver indium selenide was made in the temperature range 28–478 °C using a 19 cm Unicam high temperature powder camera and Cu Kα radiation. Cohen's least-squares method was adopted for determining the lattice parameters at each temperature. The data were used to evaluate the coefficients of thermal expansion, perpendicular ( α ⊥ and parallel ( α ∥ ) to the principal axis, at various temperatures. The parameter a decreases non-linearly with increasing temperature whilst the parameter c increases from room temperature to about 360 °C and then decreases non-linearly. The unit cell volume decreases non-linearly with temperature throughout the temperature range studied. The negative value of α ⊥ increases linearly with increasing temperature; the positive value of α ∥ decreases non-linearly, becomes zero at about 360 °C and above 360 °C it becomes negative and increases numerically with increasing temperature.
TL;DR: In this article, the authors used a wedge-shaped air gap between reference and specimen gratings to measure the thermal expansion of graphite-epoxy laminates in the temperature range of 297-422 K.
Abstract: Moire interferometry by reflection is described and demonstrated for the case of a real reference grating of 1200 lines/mm. Extraneous beams can be displaced and stopped by using a wedge-shaped air gap between reference and specimen gratings. Double-order dominance, the use of diffraction sequences for reflection, the isolation of preferred sequences, and the use of two-beam interference are discussed. Experimental accuracy is enhanced significantly by using several data points to establish displacements along a line, and random errors characterized by one standard deviation can be as small as one microstrain. The method is well adapted to thermal environments, coefficients of thermal expansion of selected graphite-epoxy laminates being determined in the temperature range of 297-422 K. Very good precision was achieved for a wide range of thermal expansion coefficients, from approximately zero to 27 microstrains/K.
TL;DR: In this article, the modulus and Poisson ratio of polystyrene-polyethylene blends with different compositions have been determined using the Kerner packed grains model, which is used to predice accurately both modulus of these blends.
TL;DR: In this article, thermal expansion measurements on synthetic orthorhombic Mg-cordierite (low cordierite), Mg2Al4Si5O18, were carried out with a high-temperature X-ray Guinier camera.
Abstract: Thermal expansion measurements on synthetic orthorhombic Mg-cordierite (“low cordierite”), Mg2Al4Si5O18, were carried out with a high-temperature X-ray Guinier camera. The measurements confirm previous studies reporting low thermal expansion and suggesting a closer relationship with ring rather than framework silicates. No indication for structural modifications correlated with symmetry changes was observed. However, two discontinuities in the thermal expansion function at 275±25° and 600±50° C were detected and are assumed to represent higher-order phase transitions. The first discontinuity is related to a minimum in specific volume, implying unusual expansion behavior (negativ thermal coefficient) at low temperatures. An estimate of the dP/dT-slope of the established discontiniuties yields a positive sign for the one at 275° C and a negative one for that at 600° C.
TL;DR: In this paper, a precise X-ray determination of the lattice parameters of silver gallium telluride, AgGaTe2, has been made in the temperature range 301 to 667 K with a Unicam 190 mm high-temperature powder camera.
Abstract: A precise X-ray determination of the lattice parameters of silver gallium telluride, AgGaTe2, has been made in the temperature range 301 to 667 K with a Unicam 190 mm high-temperature powder camera. The data have been used to evaluate the coefficients of thermal expansion, α⊥ and α\parallel, at various temperatures. It has been observed that the `c' parameter decreases while the `a' parameter increases with increasing temperature as in the case of AgGaSe2 and AgGaS2, which also have a chalcopyrite-type structure. The magnitudes of both α⊥ and α\parallel increase non-linearly with increasing temperature.