Thermal expansion materials

Low thermal expansion material High thermal expansion material... 

Evans, J. S. O., Negative thermal expansion materials, J. Chem. Soc., Dalton Trans. 1999, 3317-3326. 

Senbhagaraman, S., Guru Row, T.N., and Umarji, A.M. (1993) Structural refinement using high-resolution powder x-ray diffraction data of Ca05Ti2P3O12, a low thermal expansion material. /. Mater. Chem., 3, 309-314. 

Lightweight and isotropic near-zero thermal expansion materials can be obtained by adding metallic particles to a negative thermal expansion glass-ceramic matrix [95]. These materials find applications in mirrors and general optics, sensors, microwave components and antennae because of their impressive thermal and dimensional stability. 

Negative thermal expansion - Materials that reduce in size with heating are said to display negative thermal expansion (NTE). An example of an NTE compound is Zn(CN)2 in which as the temperature rises the Zn Zn distance is reduced due to vibration of the CN ligands around the Zn-Zn vector. 

Silicon steel sheets with low electromagnetic core loss are supplied with a surface layer of low thermal expansion material such as boron nitride. This can be done by ion implantation, ion plating, chemical vapor deposition (CVD), and secondary recrystallization annealing in a nonoxidative atmosphere [72 to 77]. 

Some materials will undergo a change of state while stiU soKd. As it is heated, pure iron changes from body centered cubic to face centered cubic at 912°C with a corresponding increase in atomic radius from 0.12 to 0.129 nm due to thermal expansion. Materials that can have two or more distinct types of crystals with the same composition are caMed polymorphic. 

Linear coefficient of thermal expansion Material parameter indicating dimensional change as a function of increasing temperature. 

M. B. Jakubinek, C. A. Whitman, and M. A. White, Negative thermal expansion materials Thermal properties and imphcations for composite materials, J. Therm. Anal. Calorim., DOI 1.1007/sl0973-009-0458-9, Japan Symposium, 2008. 

Kim I. J., Kim H. C.(2004) Zero level thermal expansion materials based on ZrTi04-Al2TiQ5 ceramics synthesized by reaction sintering. / Ceram Proc Res 5 308-12. 

Dimensional stability Is an Important attribute of space materials. High-performance carbon fibers possess a small, negative coefficient of thermal expansion at all temperatures below 375°C. That property, combined with their high modulus, permits a composites engineer to design a near-zerc thermal expansion material by combining carbon fibers with one of a variety of matrices. 

Rely on inherent and passive safety features including the use of enhanced thermal expansion materials, a fast expansion module, a very low reactivity swing, and other reactivity feedback mechanisms to achieve a high degree of reactor self-control in the ATWS scenarios. 

Apart from crystal structure, the bond strength also decides the thermal expansion. Materials such as tungsten possess high bond strength. Consequently, their thermal coefficient is low. Oxide structures have dense crystal structures. Their linear thermal expansion coefficients at room temperature are in the range of 6 to 8 x 10 per °C. 

As indicated in Figure 13, the sample is placed in a heater or furnace surrounded by a coolant or heat sink and insulation. For the measurement of linear thermal expansivity the bottom of the probe is perfectly flat, and the probe acts merely as a push rod. Connected to the upper end of the probe is an Ivdt and some mechanism for maintaining the probe-lvdt system vertical. The sample is heated at a controlled or programmed rate, and its change in linear dimension is measured by the displacement of the Ivdt core. The sample probe and outer tube are made of a low thermal-expansion material, usually fused quartz, and are... 

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