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Diffusion experiments on Nb/Si couples were conducted at 1050°C, 1150°C, 1250°C for annealing for 8h, 10h and 15h. Two intermediate phases, NbSi2 and Nb5Si3, were found to develop and grow as parallel layers in the Nb/Si couples, according to the parabolic rate law. The diffusion properties of the different phases were evaluated in terms of alternative theories, which were demonstrated to be equivalent algebraically but complementary because they are expressed in terms of different experimental variables.

The structure and processes of mass, charge and heat transfer are investigated in an equiatomic Fe–Ni composite fabricated by electroconsolidation using the spark plasma sintering (SPS) technology. The system contains regions of almost pure Fe and Ni, separated by areas with variable concentration of components, formed in consequence of the interdiffusion in the electroconsolidation process. The interdiffusion coefficient of the Fe–Ni system has been revealed to be significantly higher than that of an alloy of a similar composition at the same temperature, which is likely the result of the employed SPS technology and the enhanced diffusion along the grain boundaries. The concentration dependence of the interdiffusion coefficient passes through a maximum at a Ni concentration of $\sim$70 at.%. The electrical and thermal conductivity of the studied system is significantly higher than that of an alloy of the same composition. The temperature dependence of the resistivity of the sample in the range 5–300 K is due to the scattering of electrons by defects and phonons, and the scattering of electrons by phonons fits well to the Bloch–Grüneisen–Wilson relation. The boundaries of the conductivity of the investigated composite correspond to the Hashin–Shtrikman boundaries for a three-phase system, if Fe, Ni and the FeNi alloy are selected as phases.

Intermetallic formation at 425°C in the aluminum–copper system has been studied by scanning electron microscopy using welded diffusion couples. Several Al–Cu phases predicted by the equilibrium phase diagram of the elements and voids taking place in the diffusion zone have been detected in the couples. The predominant phases were found to be Al₂Cu₃ and the solid solution of Al in Cu, α. The growth of the intermetallic layer obeyed the parabolic law.

The growth kinetics of the solid solution phase of aluminum in copper in diffusion couples of pure aluminum and copper has been investigated at 425°C using a scanning electron microscope. In the initial stage, the phase layer growth was found to obey the parabolic law, indicating that the rate-controlling process is diffusion. At longer times, the growth rate deviates from the kt^-1/2 behavior of the early stage.

The microstructure resulting from diffusion reactions, at solid-state temperatures, in Ni/Sn couples has been studied by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). The Ni₃Sn₄ phase was the only reaction product which formed in the couples at temperatures from 150${}^{\circ }$C to 220${}^{\circ }$C. The growth kinetics of Ni₃Sn₄ layer followed the parabolic law with an apparent activation energy of 104kJmol${}^{-1}$. The effect of the atmosphere on the microstructure of the interfacial layer was investigated at 220${}^{\circ }$C for a pressure of 10${}^{-8}$atm. A decrease in the growth rate of the phase layer was observed.

We report the study of the interdiffusion effect of quantum-dot (QD) heterostructures, focusing on the theoretical calculation of the electronic structure of interdiffused QDs. A computational model has been developed for QD superlattice system using Hamiltonian in reciprocal space domain to analyze the interdiffusion effect on electronic structure. The interdiffusion effects of QDs with various geometries having the same volume and the same lattice constant have been studied. In general, the interdiffusion effect in QDs is significantly pronounced since it occurs in three dimensions. Comparing the interdiffusion effect for the various shapes of QDs, it was found that the spherical QD has the lowest ground state and produces the largest blue-shift during the interdiffusion or intermixing process.