The interdiffusion coefficient and the ratio of the intrinsic diffusivities with respect to the mole fixed frame of reference in Ag-Cd alloys have been determined by taking the volume change effects into account. The interdiffusivities obtained in this work are in good agreement with those obtained by previous workers. The ratio of the intrinsic diffusivities has been determined to be 1.50 at 8.6 at% Cd for Ag-15 at %Cd-Ag diffusion couple and 1.54 at 12.6 at% Cd for Ag-25 at% Cd-Ag diffusion couple. By using the ratios of the intrinsic diffusivities obtained in this work and those determined previously by the vapor thin plate method, the so-called vacancy flow factor, G, and the correlation factor, f;, in the infinitely dilute state have also been evaluated. ( Received August 13, 1986) Keywords: silver-cadmium alloy, interdiffusion, intrinsic diffusion, mole fixed frame, vacancy flow factor, correlation factor, ratio of intrinsic d(ffusivitiesThe authors(1) previously investigated the interdiffusion in the Ag-Zn alloys and evaluated the so-called vacancy flow factor, G, with the aid of the concentration dependence of the ratio of the intrinsic diffusivities, DNzn/DNAg, with respect to the mole fixed frame of reference. In the Ag-Zn system, it has been found that the experimental errors in G does not affect the value of correlation factor, fi, and therefore, fi has been favorably determined. The diffusion phenomena in Ag-Cd alloys are very similar to those in the Ag-Zn alloys. For an example, the activation energy for the impurity diffusion of Cd in Ag(2) is equivalent to the energy for the impurity diffusion of Zn in Ag(3), i.e., 174.5kJ/mol, and the is expected that the correlation factor, fi for impurity diffusion of Cd in Ag can also be determined favorably by evaluating the vacancy flow factor, G. The ratios DNcd/DNAg have been obtained previously by the vapor thin plate method(4). In addition to the data on the ratios DNca/DNAg, the ratios have been determined by the use of solid-solid diffusion couples in this experiment, and G and fi in the Ag-Cd system have been evaluated.Pure silver specimens about 11mm in diameter and 3mm in thickness were made by cutting a pure silver rod of 99.99% purity. The specimens were annealed in an evacuated furnace at 1073 K for about 10.8ks to yield the crystal grain growth. The grains thus obtained were about 1mm in diameter. A flat surface of each silver specimen was ground on a water proof abrasive paper and polished metallographically on a buff.For the preparation of the Ag-Cd alloys having 15 and 25 at% Cd, Ag chips of 99.99% purity and cadmium granules of 99.99% purity were molten at 1273 K in an alumina tube which was sealed in a quartz capsule together with purified argon gas. The alloys rods 10mm in diameter were then annealed at a temperature 50K below the solidus temperature for more than 1200ks to yield homogenization. The grain size of alloy rods thus obtained was about 3mm in diameter. Discs about 5-7mm in thickness were cut from the alloy rods. The homogen...

The impurity diffusion coefficients of Cu in Fe have been determined in the temperature range of 1073 - 1163 K by means of Laser Induced Breakdown Spectrometry (LIBS). The volume diffusion coefficients for Cu impurity diffusion in a-iron found in this work are in good agreement with the previously published result. The grain boundary diffusion coefficient gb D s d was also calculated using the volume diffusivity and processing the tails of the measured profiles. The values of the activation energy for volume and grain boundary diffusion were approximately 280 and 161 kJmol-1, respectively. This indicates the possibility of a monovacancy diffusion mechanism in case of volume diffusion. The results for the diffusion coefficients are Dv= 2.2 ×10-2exp(-280 kJmol-1/RT) m2s-1 and gb D s d = 2.6 ×10-11exp(-161 kJmol-1/RT) m3s-1.

The thermoelectric properties were examined of SiC specimens prepared by mixing -SiC powder with B 4 C, C, and Al 2 O 3 and then sintering at 2100 C. Sintered specimens containing Al 2 O 3 up to 3% with 0.5% B 4 C and 2.5% C exhibited the highest densities. The electrical conductivities of these specimens increased with the Al 2 O 3 content up to 3%. In contrast, the Seebeck coefficients of these specimens decreased with the addition of 1% Al 2 O 3 , but then barely decreased with the further addition of Al 2 O 3 . The maximum value of the power factor, 9:43 Â 10 À4 W/mK 2 at 800 C, was obtained with specimens sintered with 3% Al 2 O 3 as well as B 4 C and C. These results showed that the power factor of SiC ceramics could be enhanced by adding proper amounts of B 4 C, C, and Al 2 O 3 into them.

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