Alloys specific heat values

Specific heat can be predicted fairly accurately by mathematical models through statistical mechanics and quantum theory. For solids, the Debye model gives a satisfactory representation of the specific heat with temperature. Difficulties, however, are encountered when the Debye theory is applied to alloys and compounds. Plastics and glasses are other classes of solids that fail to follow this theory. In such cases, only experimental test data will provide sufficiently reliable specific heat values. 

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... 

As an example for the specific case of vanadium alloys with palladium, the trend of the average atomic volume of the alloys is shown in Fig. 4.20 and compared with the phase diagram. These data were obtained by Ellner (2004) who studied the solid solutions of several metals (Ti, V, Cr, Mn, Fe, Co and Ni) in palladium. The alloys were heat treated at 800°C and water-quenched. From the unit cell parameters measured by X-ray diffraction methods, the average atomic volume was obtained Vat = c 14 (see Table 4.3). These data together with those of the literature were reported in a graph, and the partial molar (atomic) value of the vanadium volume in Pd solid solution (Fv)... 

Dowden and Reynolds (49,50) in further experimental work on the hydrogenation of benzene and styrene with nickel-copper alloys as catalysts, found a similar dependence. The specific activities of the nickel-copper alloy catalysts decreased with increasing copper content to a negligible value at 60% copper and 30-40% copper for benzene and styrene, respectively. Low-temperature specific heat data indicated a sharp fall (1) in the energy density of electron levels N(E) at the Fermi surface, where the d-band of nickel becomes filled at 60 % copper, and (2) from nickel to the binary alloy 80 nickel -)- 20 iron. Further work by these authors (50) on styrene hydrogenation with nickel-iron alloy... 

Figure 3. Generalized thermodynamic quantities calculated for a Lennard-Jones KrAr binary mixture (left) and molten LiF alloy (right) the generalized dilatation 6(k) the generalized linear thermal expansion coefficient ckt (fc) the generalized specific heat at constant volume Cy (fc) (the filled boxes at k = 0 correspond to the values obtained directly in MD simulations) and the generalized ratio of specific heats 7(k).

In this study, thermal diffusivity and specific heat of Be/Cu mixture sintered compacts were measured by laser flash method, then thermal conductivity was obtained from calculation of those measured values. And thermal expansion coefficient was measured by laser interferometry method. These thermophysical properties were measured in order to characterized those compacts as interlayer between beryllium and copper alloy used in the plasma facing components. The obtained results are as follows. 

A 25.0-g sample of an alloy was heated to 100.0 °C and dropped into a beaker containing 90 g of water at 25.32 °C. The temperature of the water rose to a final value of 27.18 °C. Neglecting heat loses to the room and the heat capacity of the beaker itself, what is the specific heat of the alloy ... 

The results of applying this method to the present 10 Fe-Ni-base alloys are given in Table VII, where they are compared with those of direct measurement. The percentage differences between the calculated and measured specific heats are the bracketed quantities. Table VII shows that room-temperature specific heats calculated from liquid helium data are reliable to within 4%. Universal plots of C, vs. T/do (e.g., ReL 8) show that specific heat varies most rapidly with temperature for values of T/do between about 0.1 and 0.3, i.e., for a temperature range... 

Table IV. Low-Temperature Specific Heats (Fitted Values) for Ten Fe-Ni-Base Alloy Samples at Specified Temperatures...

The specific heat of chromium rich Cr-Ni and Cr-Fe-Mo alloys was measured by [1971Bau] in the temperature range 1.3-4.2 K. Measurements were made for compositions of 20 mass% Mo and 0-20 mass% Fe. This experimental program was intended primarily for the determination of the electronic band stmcture of 3d transition elements. It is known that Cr-Fe alloys exhibit unusual electron specific heat coefficients and an abnormally low Debye temperature, which is attributed to a complex magnetic stmcture of these alloys. The addition of 20 at.% Mo may avoid such complications, as the alloy becomes paramagnetic at liquid He temperatures. The results of the measurements are shown in Table 4. The temperature dependence of the specific heat is expressed as C = 234 R (770) + where R is the gas constant and 0 is the apparent Debye temperature. The authors concluded that the values of the specific heat coefficients and the Debye temperature are rather unusual (a low value of the apparent Debye temperature). They cannot be caused by... 

Recently, DeLong et al. (1976) reported measurements of the depression of T, the magnetic susceptibility, specific heat and pressure dependence of for (LaSm)Sn3 alloys. The extremely large value of the initial depression of Tc was confirmed by ac susceptibility and specific heat measurements in the superconducting state. 

The change of the specific heat of the transition from amorphous solid to supereooled liquid as well as the temperature dependence of the specific heat in the amorphous solid and supercooled liquid has been examined for the La-Al-Ni amorphous alloys through detailed differential scanning calorimetric measurements (Inoue et al. 1989f). As an example, fig. 115 shows the thermograms of the amorphous La5sAl25Ni2o alloy with the widest supercooled liquid region. The Cp value of the as-quenched phase is 24 J/mol K... 

The Cp s curve of the reheated (control) sample is unaffected by thermal changes and consists of configurational contributions as well as those arising from purely thermal vibrations. Therefore, the vibrational specific heat, Cp,v, for the amorphous alloy is extrapolated from the Cp values in the low-temperature region and is a linear function of temperature, viz.,... 

Kasaya et al. (1983b) measured the specific heat of La doped SmBe. For a compo.sition Smo,75Lao.25B6 where the valence of Sm is about 2.5 the energy gap in the SmBs lattice disappears and the y value of the specific heat amounts to 45mJ/molK. Whether the Fermi level has moved out of the gap into the density of states peaks on either side of the gap or that the gap has collapsed cannot be decided in this chapter. But the fact that the hybridization gap disappears upon alloying due to a reduction of the coherence in the lattice is well known and reported by Marabelli et al. (1992b). 

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