Metals specific heat values

For non-magnetic actinide metals, specific heat data have been employed very usefully to corroborate 5 f localization starting with Am, as indicated by the sudden drop in y values (ypu 12 mJ/mol K, yAm 2 mJ/mol K ). It allowed also the discovery of superconductivity in Pa and Am metals ... 

For most plastics the specific heat value (calories per gram per °C) lies between 0.3 and 0.4. On a weight basis this value is much higher than that of most metals. Both iron and copper, for example, have specific heats of about 0.1 at ordinary temperatures. However, along a volume basis, the specific heats of plastics are lower than those of common metals, because of the substantially lower density of plastics. 

Deformation potential coupling constants are of the order of fip, (Ziman 1960). To observe deformation potential effects in the temperature dependence of elastic constants several conditions have to be met as discussed above dpA(,(0) must be large and - Eq has to be of the order of k T. This excludes normal metals and only d-band metals with rather narrow bands can exhibit this behavior. Typical examples have been given above. In intermetallic rare-earth compounds simple density of states arguments show why elastic constant effects can be observed only for CsCl-type and Th3P4-type materials. In table 4 electronic specific heat values are listed for various rare earth compounds. This is an updated list of a previous work, see Liithi et al. (1982). This table indicates that monopnictides and monochalcogenides have smaller values of y than CsCl- and Th3P4-structure materials, i.e., the 5d band of the former structure is more hybridized than in the latter. 

Dulong and Pedt s law The product of the atomic weight and the specific heat of a metal is constant of value approximately 6-2. Although not true for all metals at ordinary temperatures, these metals and several non-metals approximate to the law at high temperatures. 

The expansion coefficient of a solid can be estimated with the aid of an approximate thermodynamic equation of state for solids which equates the thermal expansion coefficient with the quantity where yis the Griineisen dimensionless ratio, C, is the specific heat of the solid, p is the density of the material, and B is the bulk modulus. For fee metals the average value of the Griineisen constant is near 2.3. However, there is a tendency for this constant to increase with atomic number. 

Whereas heat capacity is a measure of energy, thermal diffusivity is a measure of the rate at which energy is transmitted through a given plastic. It relates directly to processability. In contrast, metals have values hundreds of times larger than those of plastics. Thermal diffusivity determines plastics rate of change with time. Although this function depends on thermal conductivity, specific heat at constant pressure, and density, all of which vary with temperature, thermal diffusivity is relatively constant. 

The most marked effect of change of temperature on the specific heat is, however, exhibited by the non-metals, carbon, boron, and silicon. The following values were obtained by H. F. Weber (1875) ... 

Let ado be the heat developed per second in a portion of a homogeneous conductor the ends of which are at temperatures 6 and 6 + d6, when unit current passes from the warmer to the colder end. a is called the specific heat of electricity in the metal. Let the values of [Pg.451]

By means of the experimental methods briefly referred to in 9 a large number of specific-heat measurements have been made at very low temperatures. In Fig. 91 we haye the atomic heats of some metals, and of the diamond, represented as functions of the temperature. The peculiar shape of the curves will. be at once apparent. At a more or less low temperature, the atomic heat decreases with extraordinary rapidity, then apparently approaches tangentially the value zero in the vicinity of T = 0. The thin curves represent the atomic heats calculated from the equation ... 

It is a matter of speculation as to whether or not the activity would pass through a significant maximum at a surface composition between 0 and 30% Rh. It is interesting to note in this connection that the magnetic susceptibility (156, 157) and the electronic specific heat coefficient (156) increase from low values at 60% Ag-Pd through pure palladium and reach a maximum at - 5% Rh-Pd, thereafter decreasing smoothly to pure rhodium. Activity maxima have also been reported for reduced mixed oxides and supported alloys of group VIII metal pairs. For example, in the... 

What is unique about metal particles burning in oxygen is that the flame temperature developed is a specific known value—the vaporization-dissociation or volatilization temperature of the metal oxide product. This temperature could be referred to as a boiling point. This interesting observation is attributable to the physical fact that the heat of vaporization-dissociation or decomposition of the metal oxide formed is greater than the heat available to raise the condensed state of the oxide above its boiling point. That is, if <2r is the heat of reaction of the metal at the reference temperature 298 K and (H° - H gi) is the... 

As an example of the use of the heat capacity values, calculate the calories required to heat 1 kilogram of aluminum from 10° C to 70° C. Multiply the grams of metal by the 60° C increase by the specific heat capacity ... 

A linear term has been observed in the specific heats of the larger metal cluster compounds measured down to 20 mK [49, 56], The value of the linear term of these cluster compounds, which have metal cores of Pt309 and Pd 551, is only a fraction ( 1/3) of the bulk value. We might extrapolate to AU55, and use a fraction smaller than 1/3. But even using 1/3, the linear term would only become equal to the cubic term at about 15 mK. 

Table 3. Density of states at the Fenni level for actinide metals from band calculations (model) from the electronic contribution y to the specific heat from magnetic susceptibility measurements. The increasing values indicate a decreasing 5 f bandwidth pinned at Ep for americium metal (not shown) there is a sudden decrease in N(np)...

The amount of heat required to raise the temperature of a material is related to the vibrational and rotational motions thermally excited within the sample. Polymers typically have relatively (compared with metals) large specific heats, with most falling within the range of 1 to 2 kJ kg-1 K . Replacement of hydrogen atoms by heavier atoms such as fluorine or chlorine leads to lower Cp values. The Cp values change as materials undergo phase changes (such as that at the T ) but remain constant between such transitions. 

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. 

Determining the Approximate Value of the Atomic Mass of Lead from Its Specific Heat Capacity. To determine the specific heat capacity of a metal, use a calorimeter and a device for heating the metal. A very simple calorimeter can be made from several beakers inserted one into another (Fig. 38). The inner beaker should have a volume of 100 ml, the middle one—300-400 ml, and the outer one—500 ml. Water is poured into the small beaker, while the others are needed to produce an air thermal-insulating layer. 

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