Tungsten thermal properties

In appUcations in which electrical conductivity is required, metals, copper, tungsten, molybdenum, and Kovar [12606-16-5] are the preferred chip-carrier materials. Metals have exceUent thermal conductivities. Tables 2 and 3 Ust the various materials used for substrates, along with their mechanical, electrical, and thermal properties. 

Tip assemblies used for work at helium temperatures may be modified as shown in Fig. 12. The inclusion of the nichrome sections is necessary if temperature control is desired. Since both the heat capacity and the electrical resistivity of tungsten at helium temperatures are extremely low and its heat conductivity is very high, a rise in temperature from I K to about 1000°K corresponds to changes of a few milliamperes in the heating current if all-tungsten assemblies are used. The nichrome sections act as thermal barriers, since alloys do not lose their high-temperature thermal properties at 4°K, and permit fine control of temperature. For... 

Tungsten metal exhibits outstanding thermal properties, which makes it attractive for a broad range of applications. However, for certain applications, its electrical and thermal conductivity, sensitivity toward oxidation, and poor workability are unsatisfactory. These limitations have led to the development of two-phase alloys, in which the useful properties of tungsten are combined with those of the additive. 

Tungsten is mainly used for heating conductors, electric bulbs, thermionic valves and electrodes. Because of its suitable electrical and thermal properties, molybdenum is used in high temperature furnaces. 

The transition metal carbides (TMC) are interesting because of their prominent properties such as great hardness, high electrical and thermal conductivities, stable field-electron emission1 and efficient catalysis.2 These properties are closely related to their electronic structures, yet the Fermi surfaces of TMC are not yet well established experimentally. In the case of hexagonal tungsten carbide (WC), there is only one reported experiment on the observation of de Haas-van Alphen oscillations.3... 

Pentacarbonyl(methoxymethylcarbene)tungsten(0) is a dull-yellow, crystalline solid mp 52°. It is appreciably more stable thermally and oxidatively than its chromium analog in the solid state at room temperature and may be stored at 5° for a period of 1 or 2 weeks without significant decomposition. It is soluble in aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and other common laboratory solvents such as benzene, 1,4-dioxane, tetrahydrofuran, chloroform, dichloromethane, and methanol it is slightly soluble in ethanol. The infrared spectrum (cyclohexane solution) has v(CO) bands at 2075, 1980, 1960, and 1947 cm"1. The nmr spectrum in chloroform-d has the methoxy proton resonance at t6.17 and the methyl proton resonance at t7.69. Other physical properties are reported in the literature.6,7... 

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