Thermal expansion amorphous metals

This can only be decided by experiment, or, failing that, by a suitable hypothesis whose consequences are in agreement with experiment. Properties which appear to approach infinity at the absolute zero are, for example, the electrical and thermal conductivity of metals and the thermal conductivity of crystals (Eucken ), while the thermal conductivity of amorphous bodies, the specific heat, and the coefficient of expansion appear to approach zero. 

Grayish-white, lustrous, brittle, crystalline solid, hexagonal, rhombohedral structure, or dark-gray to brown, amorphous powder with metal characteristics, d (cryst) 6.tl-6.27. mp 449.8". bp 989.9". Electrical resistivity (19.6") 200,000, -ohms-cm. Latent heat of fusion 4,27 keal/mote. Linear coefficient of thermal expansion 16.8 x 10- /°C. 

Thermal expansion curves for amorphous metals closely resemble those of non-metallic glasses. Expansion coefficients for the composition Fe4oNi4oPi4Bg are almost identical in the amorphous and crystalline... 

Because of the great difference in the thermal expansion of polymers and metals or glass, significant problems can arise when thermal stress is applied to composites of these materials. The so-called dimensional stability of the polymer is also of technological importance. Dimensionally stable polymers must not only possess a small coefficient of thermal expansion They should also not exhibit recrystallization phenomena. Recrystallizations lead to distortions because of the difference in densities between amorphous and crystalline regions. 

Colorless amorphous (i.e., fused silica) or crystalline (i.e., quartz) material having a low thermal expansion coefficient and excellent optical transmittance in far UV. Silica is insoluble in strong mineral acids and alkalis except HE, concentrated HjPO, NH HE, concentrated alkali metal hydroxides. Owing to its good corrosion resistance to liquid metals such as Si, Ge, Sn, Pb, Ga, In, Tl, Rb, Bi, and Cd, it is used as crucible container for melting these metals, while silica is readily attacked in an inert atmosphere by molten metals such as Li, Na, K Mg, and Al. Quartz crystals are piezoelectric and pyroelectric. Maximum service temperature 1090°C... 

These thermoplastic polymers are generally characterized by their toughness in respect to resistance to heat and UV exposure. Of importance also are their transparency, warp resistance, excellent flexural recovery, high elastic limits, and good electrical and mechanical properties, including outstanding creep resistance. They have as well excellent radiation and oxidation resistance. Their thermal expansion rate is close to Uiat of metal. This amorphous material is subject to environmental stress cracking, however, particularly in the presence of aromatic or aliphatic hydrocarbons. 

Values of linear thermal expansion coefficients of commonly used non-metallic thin film, interlayer or substrate materials are given in Table 2.1 over a broad range of temperatures of practical interest. Table 2.2 provides corresponding values of linear thermal expansion coefficients for polycrys-talline metals. Table 2.3 lists the room temperature values of elastic modulus and Poisson s ratio for a wide variety of polycrystalline and amorphous materials with isotropic elastic properties, which are commonly used as thin films, interlayers or substrates. The anisotropic elastic properties of cubic and hexagonal single crystals are given in Tables 3.1 and 3.2, respectively, in the next chapter. 

The coefficient of linear expansion of unfilled polymers is approximately 10 X 10 5 cm/cm K. These values are reduced by the presence of fillers or reinforcements. The thermal conductivity of the polymers is about 5 X 10 4 cal/sec cm K. These values are increased by the incorporation of metal flake fillers. The specific heat is about 0.4 cal/g K, and these values are slightly lower for crystalline polymers than for amorphous polymers. 

Properties Colorless crystals or white powder odorless and tasteless. D 2.2-2.6 thermal conductivity about half that of glass, mp 1710C, bp 2230C, high dielectric constant, high heat and shock resistance. Insoluble in water and acids except hydrogen fluoride soluble in molten alkai when finely divided and amorphous. Combines chemically with most metallic oxides melts to a glass with lowest known coefficient of expansion (fused silica). Noncombustible. 

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