Thermal expansion coefficients measurement

Figure 1. Thermal-expansion coefficients measured on cooling (300-77K and 4.2-2K) and heating (4.2-77K) along (OOl)e directions for In-26.5 at%Tl in the temperature range 2-3 OOK, with different external stress fields applied. (From reference 7)...

Hardness was estimated by Vickers indentation on sintered gradient samples, thermal expansion coefficient measurements and elastic behaviour was tested on the different dispersions. Preliminary mechanical testing (single edge notched beam, 3PB-SENB) and oxidation tests were performed on sintered FGM s. 

The authors would like to thank Prof. S.R. Wang for the thermal expansion coefficient measurement. This work was financially supported by NSEC Project No. 50672114, Research Project of Chinese Science and Technology Ministry No. 2007BAA07B01 and 973 Project of China No. 2007CB209700. 

T. Ocher changes occur at this temperature that can be monitored to identify the T experimentally. These include changes in specific volume of the polymer, index of refraction, gas diffusion coefficients, thermal expansion coefficients (measured by dilatomeCry), and specific heat (measured by differential scanning calorimetry (DSC) or by differential thermal analysis (DTA)). General discussions of the elastic properties of polymers can be found in references (4.2)-... 

The temperature dependence of the lattice constants a and c and the thermal expansion coefficients of hexagonal ZnO have been determined by the capacitive method [138]. The thermal expansion coefficients measured between 4 and 800 Rare shown in Figure 1.25. Reeber [30] has employed X-ray powder diffraction methods instead to measure the temperature dependence of the lattice parameters of ZnO in the range of 4.2-296 K. The results are shown in Figure 1.26. When analyzing the dependence of the lattice parameters on temperature, fourth-order polynomials... 

ASTM E831, Standard Test Method for Linear Thermal Expansion of Solid Materials by Thermomechanical Analysis For thermal expansion coefficient measurement. 

Dimensional Stability. Plastics, ia general, are subject to dimensional change at elevated temperature. One important change is the expansion of plastics with increa sing temperature, a process that is also reversible. However, the coefficient of thermal expansion (GTE), measured according to ASTM E831, frequendy is not linear with temperature and may vary depending on the direction in which the sample is tested, that is, samples may not be isotropic (Eig. 7). 

The Rheometric Scientific RDA II dynamic analy2er is designed for characteri2ation of polymer melts and soHds in the form of rectangular bars. It makes computer-controUed measurements of dynamic shear viscosity, elastic modulus, loss modulus, tan 5, and linear thermal expansion coefficient over a temperature range of ambient to 600°C (—150°C optional) at frequencies 10 -500 rad/s. It is particularly useful for the characteri2ation of materials that experience considerable changes in properties because of thermal transitions or chemical reactions. 

A summary of physical and chemical constants for beryUium is compUed ia Table 1 (3—7). One of the more important characteristics of beryUium is its pronounced anisotropy resulting from the close-packed hexagonal crystal stmcture. This factor must be considered for any property that is known or suspected to be stmcture sensitive. As an example, the thermal expansion coefficient at 273 K of siagle-crystal beryUium was measured (8) as 10.6 x 10 paraUel to the i -axis and 7.7 x 10 paraUel to the i -axis. The actual expansion of polycrystalline metal then becomes a function of the degree of preferred orientation present and the direction of measurement ia wrought beryUium. 

Thermal expansion values can be calculated from measurements of thermal deflection of enamel—metal composites. The cubical thermal expansion coefficient ia the temperature range of 0—300°C can also be calculated usiag the additive formula ... 

It is clear that nonconfigurational factors are of great importance in the formation of solid and liquid metal solutions. Leaving aside the problem of magnetic contributions, the vibrational contributions are not understood in such a way that they may be embodied in a statistical treatment of metallic solutions. It would be helpful to have measurements both of ACP and A a. (where a is the thermal expansion coefficient) for the solution process as a function of temperature in order to have an idea of the relative importance of changes in the harmonic and the anharmonic terms in the potential energy of the lattice. 

On the experimental side, one may expect most progress from thermodynamic measurements designed to elucidate the non-configurational aspects of solution. The determination of the change in heat capacity and the change in thermal expansion coefficient, both as a function of temperature, will aid in the distinction between changes in the harmonic and the anharmonic characteristics of the vibrations. Measurement of the variation of heat capacity and of compressibility with pressure of both pure metals and their solutions should give some information on the... 

However, since measurements of Tg s and the thermal expansion coefficients are not very sensitive and accurate, the results derived from such model present some scattering and their reliability needs further proof for its validity. Therefore, in the following we shall concentrate to the unfolding models for fiber composites, as they have been extended from the respective models for particulates, which present significant stability and unquestionned reliability. 

Since the glass transition corresponds to a constant value of the relaxation time [15], dTjdP is just the pressure coefficient of Tg. Comparing Equations 24.10 and 24.13, we see that the scaling exponent is related to quantities—thermal pressure coefficient, thermal expansion coefficient, Tg, and its pressure coefficient—that can all be determined from PVT measurements... 

The measure of the thermal expansion coefficient below room temperature is particularly difficult for low-expansion materials (see Section 3.9). Remember also how newly produced composite materials show extremely low-expansion coefficient of both sign. 

To measure the thermal expansion coefficients, a 0.125 in. thick sample was taken from the cured plates. The Increase in length with temperatures was measured by use of a Dupont 941 Thermomechanical Analyzer (TMA), with a heating rate of 5°C/min. The instrument was calibrated with an aluminum standard. Three runs were made for each sample and standard deviations calculated. 

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