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Showing papers on "Thermal expansion published in 1990"


Journal ArticleDOI
TL;DR: In this article, the melting curve of iron to 1.2 Mbar was remeasured in a laser-heated diamond anvil cell using a defocused 35 W Nd∶YAG laser beam provided low-temperature gradients which were measured within an area of 2 μm in diameter with a chromatically corrected optical geometry.
Abstract: The melting curve of iron to 1.2 Mbar was remeasured in a laser-heated diamond anvil cell. A defocused 35 W Nd∶YAG laser beam provided low-temperature gradients which were measured within an area of 2 μm in diameter with a chromatically corrected optical geometry. Argon to 350 kbar and A12O3 to 1.2 Mbar were used as pressure media. Melting was detected by in situ measurements of optical reflectivity and electrical resistivity and by visual observation of the surface texture. At 1.2 Mbar, iron melts at 3000 ± 100 K. The same laser-heating technique was used to measure volumes of fcc-(γ)-iron to 168 kbar and 2000 K using synchrotron radiation, leading to a decrease in the thermal expansion coefficient of γ-iron represented by (∂ In α/∂ In V)T = 6.5±0.5. The α-e transition of iron has been studied by X ray and by the change in resistivity of a fine wire using a variety of pressure media. The hysteresis of the transition changes systematically with the shear strength of the pressure medium with an equilibrium transition pressure at 130±10 kbar.

251 citations


Journal ArticleDOI
TL;DR: In this paper, high-temperature x-ray diffraction, differential thermal analysis, and differential scanning calorirmetry have been performed on LaGaO3, NdGaO-3, PrGaO 3, SmAlO3 and LaAlO 3 single crystals.
Abstract: Dilatometry, high-temperature x-ray diffraction, differential thermal analysis, and differential scanning calorirmetry have been performed on LaGaO3, NdGaO3, PrGaO3, SmAlO3, and LaAlO3 single crystals grown by the Czochralski technique. First order phase transitions have been located at 145°C for LaGaO3 and 785°C for SmAlO3, and ΔH has been measured for the LaGaO3 transition. Second order transitions have been identified for LaGaO3, PrGaO3, NdGaO3, and LaAlO3. The usefulness of these compounds as substrates for high temperature superconducting films is discussed in terms of thermal expansion matching.

186 citations


Journal ArticleDOI
TL;DR: The thermal expansion coefficients of transition-metal-free sinter mullite and fused mullite are measured between 25° and 900°C by high-temperature Guinier X-ray diffraction techniques as discussed by the authors.
Abstract: The thermal expansion coefficients of transition-metal-free sinter mullite and fused mullite, and of chromium-doped (11.5 wt% Cr2O3) and iron-doped (10.3 wt% Fe2O3) sinter mullites are measured between 25° and 900°C by high-temperature Guinier X-ray diffraction techniques. Most mullites display low and nonlinear thermal expansions below, but larger and linear expansion above, ∼300°C. Although the temperature-induced c-axis expansion coefficients seem to be less dependent on the compositional state x and on transition-metal incorporation of the Al4+2xSi2–2xO10–x mullite-type phases (α(c) = 5.6 × 10−6/°C to 6.1 × 10−6/°C), thermal a- and b-axis expansion coefficients change more significantly (α(a) = 3.1 × 10−6/°C to 4.1 × 10−6/°C and α(b) = 5.6 × 10−6/°C to 7.0 × 10−6/°C, where the values were calculated between 300° and 900°C). The larger temperature-induced b than c and a expansions probably are caused by intense lengthening of the relatively long and elastic octahedral Al(1)–O(D) bonds in mullite, which form at an angle of about 30° with b, but of about 60° with a. With increasing x value of the transition-metal-free mullites, the volume thermal expansion decreases, while the anisotropy of thermal expansion is reduced simultaneously. We believe that the variation of the thermal expansion coefficients is controlled by the Al* occupancy and by the number of O(C) vacancies in the mullite structure, and also by the disordering distribution of both structural elements. Transition-metal incorporation into mullite has no distinct influence on thermal expansion anisotropy, but does reduce thermal volume expansion. A prestressing of the crystal structure by substitution of Al3+ by the larger Fe3+ and Cr3+ ions may be the main reason for the latter effect.

161 citations


Journal ArticleDOI
V. L. Moruzzi1
TL;DR: In this paper, total energy band calculations that show the coexistence of a high-spin and low-spin state in fcc transition metals and alloys are presented, and the energy difference between the two states is shown to be a function of the electron concentration and to vanish at 8.6.
Abstract: Total-energy band calculations that show the coexistence of a high-spin and low-spin state in fcc transition metals and alloys are presented. The energy difference between the two states is shown to be a function of the electron concentration and to vanish at 8.6. At larger electron concentrations the low-temperature state is the high-spin state, and the thermal expansion is shown to pause at a system-dependent characteristic temperature. At lower electron concentrations the low-temperature state is the low-spin state, and enhanced thermal expansion is expected. An analysis that leads to a qualitative understanding of the thermal properties of Invar and that implies a connection with martensitic transformations and spin glasses in related alloys is presented. For Invar a magnetic collapse from the high-spin to the low-spin state at a pressure of 55 kbar is predicted.

121 citations


Journal ArticleDOI
TL;DR: In this article, the authors describe fundamental thermodynamic relations (Helmholtz free energy as a function of volume and temperature) for solids and liquids, simple physically based expressions which contain all thermodynamic information about a system.
Abstract: We describe fundamental thermodynamic relations (Helmholtz free energy as a function of volume and temperature) for solids and liquids, simple physically based expressions which contain all thermodynamic information about a system. The solid fundamental relation consists of Debye and Birch-Murnaghan finite-strain theory combined in the Mie-Gruneisen framework. The liquid fundamental relation is derived by taking the high-temperature limit of the solid expression. We derive the liquid equation of state, which contains only four parameters, from the liquid fundamental relation and show that it successfully describes measurements of liquid alkali metals, water, and liquid diopside over a wide range of pressure and temperature. We find optimal fundamental relation parameters for diopside, enstatite, ilmenite, and perovskite and find the solid relation to be in excellent agreement with data, including heat capacities, thermal expansion, and MgSiO3 phase equilibria. We then combine the liquid and solid fundamental relations to calculate the melting curves of diopside, enstatite, and perovskite, which are found to be in excellent agreement with experiment. All predicted melting curves have dT/dP slopes which decrease steadily with pressure, eventually becoming negative because of liquid-crystal density inversion. Our predicted melting temperature of perovskite in the D″ region (3750 K) at the base of the mantle is thousands of degrees lower than previous estimates, yet it is consistent with experimental data. The predicted melting curve, although consistent with the lack of widespread melting in the lower mantle, is much lower than recently proposed geotherms in the D″ layer at the base of the mantle. By combining our results with seismic observations of the deep mantle, we propose that the D″ layer consists of magnesiowustite and silica in the form of stishovite or its recently discovered high-pressure modification.

108 citations


Book ChapterDOI
TL;DR: In this paper, the authors summarized the magnetic phase diagrams of the most important binary and ternary alloy systems showing moment-volume instabilities in general and Invar or Elinvar behavior in special composition ranges.
Abstract: Publisher Summary The term “invar” stands for alloys showing minimum thermal expansion coefficients (maximum spontaneous volume magnetostriction) in certain ranges of composition and temperatures. Invar effect originates from investigations by Ch.E. Guillaume who found that ferromagnetic fcc FeNi alloys at concentrations around Fe 65 Ni 35 show almost constant thermal expansion as a function of temperature in a wide range around room temperature. According to his results, the linear thermal expansion coefficient α = (1/ l )/(d l /d T ) of Fe 65 Ni 35 Invar at 300 K is about 1.2 × 10 -6 K -1 , thus an order of magnitude smaller than in the pure components Fe and Ni and even smaller than in a Pt–10% Ir alloy, the material used for the prototype meter. The chapter summarizes the magnetic phase diagrams of the most important binary and ternary alloy systems showing moment–volume instabilities in general and Invar or Elinvar behavior in special composition ranges. Besides the magnetic-transition temperatures, Curie temperatures T C for ferromagnetic (FM) transitions, Neel temperatures T N for antiferromagnetic (AF) transitions, and T f for spin glass (SG) or re-entrant spin glass (RSG) like transitions, the diagrams contain information about the structural phases occurring in the systems.

107 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of temperature (4 −400 K), hydrostatic pressure and frequency on the dielectric constant, e.g., loss, and loss of single crystals of LaAlO3 and cubic yttria (9.5 mol) −stabilized zirconia (ZrO2) were investigated.
Abstract: The effects of temperature (4–400 K), hydrostatic pressure and frequency on the dielectric constant, e’, and dielectric loss of single crystals of LaAlO3 and cubic yttria(9.5 mol %)‐stabilized zirconia (ZrO2) were investigated. Both crystals are relatively low‐loss, low‐dispersion dielectrics in the temperature range (T<150 K) of most interest for high‐temperature superconductors. The pressure results make it possible to evaluate the various contributions to the temperature dependence of e’. It is found that this dependence is dominated by the change of polarizability with volume. The dielectric properties of the two crystals are compared with those of other candidate substrate materials.

92 citations


Journal ArticleDOI
TL;DR: An empirical embedded-atom potential for a bcc metal (vanadium) has been developed by fitting the embedding function, electron density, and pair interaction to the lattice constant, cohesive energy, elastic constants, and vacancy-formation energy.
Abstract: An empirical embedded-atom potential for a bcc metal (vanadium) has been developed by fitting the embedding function, electron density, and pair interaction to the lattice constant, cohesive energy, elastic constants, and vacancy-formation energy. This potential has been used to calculate vacancy and divacancy properties, interstitial properties, thermal expansion, bulk-phonon dispersion, surface relaxation, surface energy, and liquid volume; in all cases the calculations are in reasonable agreement with experiment.

92 citations


Journal ArticleDOI
A. Chopelas1
01 Mar 1990
TL;DR: In this article, the effect of pressure on the heat capacity, Cv, and entropy, S, of MgO was determined using vibrational spectroscopy to over 200 kbar by the measurement of several vibronic bands in the fluorescence of Cr3+ doped into the mgO lattice.
Abstract: The effect of pressure on the heat capacity, Cv, and entropy, S, of MgO was determined using vibrational spectroscopy to over 200 kbar by the measurement of several vibronic bands in the fluorescence of Cr3+ doped into the MgO lattice. The results for Cv and S demonstrate that the high pressure thermodynamic properties of MgO can be accurately estimated using a Debye model even at room temperature.

86 citations


Patent
11 Dec 1990
TL;DR: In this article, a method of controlling deposition quality of line-of-sight and specimen surrounding surfaces in a plasma-enhanced chemical vapor deposition apparatus is presented, which is improved by avoiding differential thermal expansion of the film and the underlying surfaces, controlling geometry of the surfaces to eliminate edges which generate stress in the deposited film, and using material for the surface which provides strong adhesion.
Abstract: A method of controlling deposition quality of line-of-sight and specimen surrounding surfaces in a plasma-enhanced chemical vapor deposition apparatus. Adhesion and integrity of deposited film on the surfaces is improved by one or more of (1) avoiding differential thermal expansion of the film and the underlying surfaces, (2) controlling geometry of the surfaces to eliminate edges which generate stress in the deposited film, and (3) using material for the surface which provides strong adhesion of the deposited film. For instance, differential thermal expansion can be avoided by maintaining the surfaces at a substantially constant temperature such as ambient temperature.

79 citations


Journal ArticleDOI
TL;DR: It is shown that the spin-orbit splitting of the 5{ital f} band gives rise to a considerable increase of the thermal expansion and to a large extent explains the observed anomalously large thermal expansion for the neptunium and plutonium metals.
Abstract: The room-temperature linear thermal-expansion coefficient is calculated for the light actinides thorium, protactinium, uranium, neptunium, and plutonium for the fcc crystal structure. The relativistic spin-orbit interaction is included in these calculations. We show that the spin-orbit splitting of the 5{ital f} band gives rise to a considerable increase of the thermal expansion and to a large extent explains the observed anomalously large thermal expansion for the neptunium and plutonium metals.

Journal ArticleDOI
TL;DR: In this paper, the temperature dependence of lattice constants for a NdGaO3 single crystal grown by the Czochralski method and thermal expansion coefficients were obtained for the first time.
Abstract: We report the temperature dependence of lattice constants for a NdGaO3 single crystal grown by the Czochralski method and thermal expansion coefficients which were obtained for the first time. Lattice mismatch between the NdGaO3 substrate and YBa2Cu3Ox superconducting film is 0.27% at elevated temperatures and the appropriate expansivities are similar. The crystalline quality of deposited YBa2Cu3Ox films on NdGaO3 by the laser ablation method was extremely good. NdGaO3 is, therefore, an excellent candidate for epitaxial high‐Tc superconducting films.

Journal ArticleDOI
TL;DR: In this article, a method was developed for calculating hydraulic pressures induced by thermal expansion of liquid binders early in the removal cycle, when evaporative losses are negligible and fully saturated conditions prevail.
Abstract: A method has been developed for calculating hydraulic pressures induced by thermal expansion of liquid binders early in the removal cycle, when evaporative losses are negligible and fully saturated conditions prevail. Specific results were obtained for flat compacts containing a common wax binder, mixed with varying amounts of low-density polyethylne. In general, these results show how the risk of hydraulic fracture increases with heating rate and compact thickness. Although pressures are minimal when the binder consists entirely of wax, the continual addition of polyethylene eventually gives rise to unacceptable risk levels, even for relatively thin compacts. Binder removal at elevated temperatures is considered subsequently. In this case, vapor pressures eventually approach a critical level, thereby allowing mass removal by evaporation to overcome the effect of thermal expansion in maintaining full saturation. With the onset of void formation, the developing capillary pressure supersedes hydraulic pressure as the driving force in liquid transport. Besides representing capillary flow, the present formulation also accounts for thermal degradation of the binder during removal. The resulting system of equations was solved numerically for a variety of representative debinding conditions. Predictions for flat compact containing a balanced wax/polyethylene binder indicate that thermal degradation of the polyethylene can give rise to a marked improvement in debinding rates. It turns out, however, that this enhancement is far more effective in thinner compacts.

Journal ArticleDOI
TL;DR: In this paper, high-resolution x-ray diffraction data were collected from 10 to 433K on a homogeneous polycrystalline specimen of Mg{sub 0.9}Fe{ sub 0.1}SiO{sub 3}-perovskite.
Abstract: High-resolution x-ray diffraction data were collected from 10 to 433K on a homogeneous polycrystalline specimen of Mg{sub 0.9}Fe{sub 0.1}SiO{sub 3}-perovskite. Rietveld structural refinement and x-ray absorption fluorescence measurements demonstrate that Fe substitutes for Mg and not Si. The thermal expansion behavior is anisotropic, with the orthorhombic distortion becoming less with increasing temperature. The volumetric thermal expansion, which is dominated by the decrease in octahedral tilts, is 1.9 {times} 10{sup {minus}5} K{sup {minus}1} between 150 and 373K. No evidence of conversion to enstatite could be found up to 873 K.

Journal ArticleDOI
TL;DR: In this paper, the magnetization and thermal expansion measurements have been made on the same samples of Fe x Co 1-x Si alloys and they have been analyzed on the basis of the spin fluctuation theory developed by Takahashi to obtain information on the nature of spin fluctuations of this system.
Abstract: Both magnetization and thermal expansion measurements have been made on the same samples of Fe x Co 1- x Si alloys. The magnetization data is analyzed on the basis of the spin fluctuation theory developed by Takahashi to obtain information on the nature of spin fluctuations of this system. We found that concentration variation of magnetic behaviors of the ferromagnetic alloys, such as the Arrott plots and the temperature dependence of spontaneous magnetization, is quantitatively well explained by the theory. Magnetovolume coupling constant is also estimated from thermal expansion coefficient on the basis of the SCR theory over the wide concentration range. The magnetovolume effect is also in good accordance with the predictions of Takahashi's theory, even quantitatively.

Journal ArticleDOI
TL;DR: In this article, the anisotropy of thermal expansion of spin-coated thin polyimide (PI) films was investigated, and the lateral thermal expansion coefficient was derived from the measurement of the thermal stress by the Fizeau interference method.

Journal ArticleDOI
TL;DR: In this article, two sets of Al2TiO5-based composites were prepared by reaction sintering of powder mixtures containing both ZrSiO4 and MgO.
Abstract: Two sets of Al2TiO5-based composites were prepared by reaction sintering of (a) Al2O3/TiO2/ZrSiO4 and (b)Al2O3/TiO2/ZrSiO4/MgO powder mixtures. The influence of the variation of ZrSiO4 content (0 to 10wt%) and the addition of 2 wt% MgO on the reaction-sintering process, microstructure, mechanical and thermal properties, were evaluated. ZrSiO4 addition shifted the Al2TiO5 formation to higher temperatures, whereas MgO accelerated both Al2TiO5 formation and ZrSiO4 decomposition. The presence of ZrSiO4 and an excess of Al2O3 generated a dispersion of ZrO2 and mullite particles in the grain boundaries and enhanced simultaneously the densification process. After sintering in the temperature range 1350 to 1500 ° C, the obtained composites exhibited significantly higher bending strength than the monophasic aluminium titanate (up to 80 M Pa). Al2TiO5 (80wt%)-mullite-ZrO2 composites which combined good mechanical strength (55MPa), low thermal expansion (α20−1000C < 1 × 10−6 K−1) and excellent thermal stability were obtained by reaction and sintering of powder mixtures containing both ZrSiO4 and MgO.

Journal ArticleDOI
TL;DR: In this article, the complete thermodynamic functions for MgO are presented for the temperature range 300-2000 K and the pressure range 0-150 GPa, both as tables and as graphs.
Abstract: The complete thermodynamic functions for MgO are presented for the temperature range 300–2000 K and the pressure range 0–150 GPa, both as tables and as graphs. Careful attention is given to the temperature and pressure dependence of the coefficient of thermal expansion α and the isothermal bulk modulus KT, which are the major corrections to the thermodynamic functions in extreme conditions. Our equations efficiently use the fact that the product αKT varies only slightly with either temperature or with volume, although scrupulous care is taken to account for the actual numbers. The corrections are now possible due to recent measurements of the bulk modulus up to 1800 K. The Birch–Murnaghan equation of state is used to account for certain terms in the expressions for internal energy and enthalpy. The parameters used in the Birch–Murnaghan equation of state are given as functions of temperature. The parameters which presently limit the calculations of thermodynamic functions to even higher temperatures and p...

Journal ArticleDOI
TL;DR: The thermal lattice expansion of calcined hydroxyapatite and β-tricalcium phosphate single-phase powder was investigated by high-temperature X-ray diffractometry as discussed by the authors.

Journal ArticleDOI
TL;DR: In this article, measurements of density, linear thermal expansion coefficient, elastic moduli, and Poisson's ratio were made on ζ-phase, eutectic, and δ-phase specimens.
Abstract: The Au-Sn eutectic alloy, composed of the ζ and δ phases, has been used for many years in the sealing of hermetic parts. Recently, it was shown that the ζ phase undergoes an ordering transformation to ζ′. Since this transformation may affect hermeticity, measurements of density, linear thermal expansion coefficient, elastic moduli, and Poisson’s ratio were made on ζ-phase, eutectic, and δ-phase specimens. Measurements were made over a temperature range that includes the ζ → ζ′ transformation. Abrupt changes in these thermophysical properties, near the phase transformation temperature, are noted for ζ and eutectic specimens but not for the δ specimen.

Journal ArticleDOI
TL;DR: In this paper, an equation of state is proposed which has been found to be applicable at high pressures and high temperatures, and the proposed equation has been used to compute the pressure-volume behaviour, the isothermal bulk modulus and its pressure derivative, the coefficient of thermal expansion and the Anderson-Gruneisen parameter of NaCl and CsCl.
Abstract: In the present paper, an equation of state is proposed which has been found to be applicable at high pressures and high temperatures. The proposed equation of state has been used to compute the pressure-volume behaviour, the isothermal bulk modulus and its pressure derivative, the coefficient of thermal expansion and the Anderson-Gruneisen parameter of NaCl and CsCl at high pressures (up to 400 kbar) and high temperatures (up to 1073 K). The results obtained for V(P,T)/V(0,T) are found to be in very good agreement with Decker's data in the whole ranges of pressure and temperature. Further, the other calculated results are also found to be in good agreement with the experimental data. The present calculations definitely lend support to the proposed equation of state and to the method used to extend the applicability at higher temperatures.

Journal ArticleDOI
TL;DR: In this paper, a single crystal of calcium tartrate has been grown using silica gel and it has been shown that the crystals are ferroelectric, which is supported by dielectric and thermal expansion measurements.

Journal ArticleDOI
TL;DR: In this paper, high resolution specific heat measurements and thermal expansion data of YBa 2 Cu 3 O 7-δ polycrystalline samples in the temperature range 20-300 K were presented.
Abstract: We present high resolution specific heat measurements and thermal expansion data of YBa 2 Cu 3 O 7-δ polycrystalline samples in the temperature range 20–300 K. The specific heat anomaly at T c shows strong deviations from mean field behavior due to superconducting fluctuations. The fluctuation behaviour seems to be more complicated than simply Gaussian. The thermal expansion shows clear anomalies at the T c 's of the samples. Additionally we give an estimate of the Gruneisen functions and discuss data of the low field DC Meissner effect in connection with the grain structure of the samples.

Journal ArticleDOI
TL;DR: These results directly confirm that a large anharmonicity in the interatomic potential develops on metal surfaces and that it may be a precursor to various surface disordering transitions.
Abstract: We show that the high-temperature Ni(001) surface undergoes a large vertical expansion. LEED experiments indicate that the surface thermal-expansion coefficient α surf increases rapidly between 900 and 1300 K, reaching a value nearly 20 times larger than in the bulk. These results directly confirm that a large anharmonicity in the interatomic potential develops on metal surfaces and that it may be a precursor to various surface disordering transitions

Journal ArticleDOI
TL;DR: In this article, the anisotropic thermal expansion of LiB3O5 has been studied along the principal crystallographic directions over the temperature range of 17 to 790 degrees C by means of high-temperature X-ray powder diffraction.
Abstract: The anisotropic thermal expansion of LiB3O5 has been studied along the principal crystallographic directions over the temperature range of 17 to 790 degrees C by means of high-temperature X-ray powder diffraction. This orthorhombic crystal exhibits strongly anisotropic expansion with coefficients of 108.2*10-6 K-1 for (100), 33.6*10-6 K-1 for (010) and -88.0*10-6 K-1 for (001) at 50 degrees C. The coefficients tend to zero when the temperature approaches the crystal's peritectic reaction point.

Journal ArticleDOI
R. Chanchani1, P. Hall1
TL;DR: In this article, the X-Y expansivity of aluminas of different purities (92-99.5%), low-temperature co-fired ceramics, aluminum nitride, and beryllia was measured.
Abstract: The X-Y (in-plane) expansivity was measured over the -40-140 degrees C range for several of the ceramics used in modern hybrids, single-chip packages, and multichip modules. These thermal expansion data were compared to those of silicon and the materials used for leads, lids, heat spreaders, and sinks. The expansivity of aluminas of different purities (92-99.5%), low-temperature cofired ceramics, aluminum nitride, and beryllia was measured. A k=4.8 sample was expansivity-matched to Si, and a k=8.0 sample matched to alumina. No significant effect of metallization of the multilayers on the expansivity was found. Aluminum nitride was found to be well matched to silicon, whereas beryllia was found to be well matched to alumina, Kovar, Invar, Alloy 42, molybdenum, and two composites, namely copper-molybdenum-copper and copper-Invar-copper, were measured. Kovar is well matched to alumina ceramic at room temperature; below and above room temperature, however, the expansivity of Kovar diverges from that of alumina. >

Journal ArticleDOI
TL;DR: In this article, the temperature dependence of the unit cell parameters of two newly identified hexagonal structure clathrate hydrates of hexamethylethane (HME) and 2,2-dimethylbutane (DMB) have been measured by X-ray powder diffraction.
Abstract: The temperature dependence of the unit cell parameters of two newly identified hexagonal structure clathrate hydrates of hexamethylethane (HME) and 2,2-dimethylbutane (DMB) have been measured by X-ray powder diffraction. The thermal expansion of the two distinct crystallographic axes was found to be inequivalent. However, the coefficients of cubic expansion are comparable to that in the cubic structure I and II hydrates. The larger thermal expansivity in the clathrate hydrates relative to ice is attributed to the weakening of the host lattice due to the internal pressure generated by the rattling motions of the encaged guests.

Journal ArticleDOI
TL;DR: In this article, the thermal expansion curves of a composite consisting of an Al-3% Mg matrix reinforced by 30 vol.% continuous SiC fibres (Nicalon) were used to provide quantitative data on the internal stresses and on the temperature dependence of the yield stress of the matrix.
Abstract: In a study of the thermal expansion behaviour of a variety of metal matrix composites, it appeared to the authors that a wealth of information could be extracted from thermal expansion curves. In the present work they aim at showing how a fairly straightforward analysis of these curves can provide quantitative data on the internal stresses and on the temperature dependence of the yield stress of the matrix. The method is illustrated on the basis of the thermal expansion curves of a composite consisting of an Al-3% Mg matrix reinforced by 30 vol.% continuous SiC fibres (Nicalon).

Patent
25 May 1990
TL;DR: In this paper, a heat-conductive composite material consisting of a metal sheet of high thermal expansion sandwiched between two metal sheets of low thermal expansion, each having a number of through-holes in the direction of the thickness, is presented.
Abstract: A heat-conductive composite material usable as a substrate (heat sink) for mounting a semiconductor thereon or a lead frame includes which comprises a core sheet and metal foil layers welded to the both surfaces of the core sheet. The core sheet is composed of a metal sheet of high thermal expansion sandwiched between two metal sheets of low thermal expansion, each having a number of through-holes in the direction of the thickness, and the three layers are laminated and integrated so that a part of the metal sheet of high thermal expansion is exposed out to the metal surfaces of low thermal expansion through the through-holes of the metal sheets of low thermal expansion The metal foil layers each are made of a metal of high thermal expansion, which are same as or different from the metal of high thermal expansion of constituting the core sheet. Varying the thickness ratio of the respective constitutional metal sheets and the surface area ratio of the exposed metal spots on the surfaces of the core sheet, heat-conductive composite materials having any desired thermal expansion coefficient and thermal conductivity can be obtained. Additionally, by providing outermost metal foil layers on both surfaces of the core sheet, the heat-conductive composite material has an improved uniform heat-receiving effect and an improved excellent heat-diffusing effect. Further, the material is free from fine pores on the both surfaces thereof and therefore has an excellent weldability.

Journal ArticleDOI
TL;DR: In this paper, the lattice parameters of CsH 2 PO 4 (CDP) crystals have been determined in the temperature range from RT to 504K and the temperature dependence of the thermal expansion coefficients has also been determined.