F.J.J. van Loo

Pattern formation in Pt-SiC diffusion couples

Abstract The morphology of reaction zones between platinum metal and silicon carbide ceramic at 973 and 1023 K is considered in detail. A periodic pattern of carbon bands embedded in Pt7Si3 is observed at both temperatures. The growth of platinum silicides at 973 and 1023 K is compared. Cross-sections of the Pt-Si-C phase diagram at those temperatures are presented. The periodic layered morphology is explained via a ‘repeated splitting’ mechanism.

Periodic pattern formation in solid state reactions related to the Kirkendall effect

Abstract The periodic layered morphology for solid state reactions is shown to occur in various ternary and higher order material systems including metal/metal and metal/ceramic diffusion couples. The experimental results on different systems where the periodic pattern formation has been observed are systematized and early explanations for this peculiar phenomenon are discussed. It is shown that a special class of structures periodic in time and in space can be considered as a manifestation of the Kirkendall effect accompanying reactive phase formation in the solid state.

Interactions in the Co–Ni–Si system at 800°C

Abstract The isothermal cross-section through the ternary phase diagram Co–Ni–Si at 800°C was constructed. No ternary phases exist in the system at this temperature. The topology of the Co–Ni–Si isotherm is determined by the formation of continuous solid solutions between isomorphous Co 2 Si and Ni 2 Si intermetallics and cubic CoSi 2 and NiSi 2 phases and by rather extensive cobalt/nickel exchanges in other binary silicides. The CoSi intermetallic compound was found to be a dominant growing phase in the binary Co/Si as well as ternary Co–Ni/Si couples with the initial end-members containing up to 50 at.% of Ni. When the Co–Ni solid solution with 30–70 at.% of nickel was used, the formation of NiSi 2 and NiSi (instead of CoSi 2 ) intermetallics next to the Si-substrate was observed after interaction at 800°C.

Solid state diffusion and reactive phase formation

Thermodynamic and diffusion models were developed to describe the morphological evolution of the diffusion zone during interaction between inorganic materials. The application of these models is demonstrated for a number of metal/metal and metal/ceramic systems.

On the relation between interdiffusion and tracer diffusion coefficients in ternary solid solutions

This article is meant as a warning message for those scientists who are working in the area of ternary diffusion. This thorough experimental study has shown the large errors that arise when the four interdiffusion coefficients are calculated from crossing diffusion paths. Even larger is the scatter in values of the tracer diffusion coefficients derived from these interdiffusion coefficient. The practical value of these coefficients is probably low. The effects of theoretical improvements, like taking into account the vacancy wind, cannot be verified because of this large scatter in the experimental values.

Diffusion Bonding of Si3N4-Ceramic to Transition Metals: Interfacial Microchemistry

Understanding and control of the behaviour of interfaces formed between metals and ceramics during diffusion bonding and service at elevated temperature is of fundamental importance in defining (and improving) the performance of a variety of bonded components.

Reaction and Diffusion in Multiphase Systems: Phenomenology and Frames

The Kirkendall effect is well-known and documented for the diffusion in a single-phased substitutional solid soln. Also in multiphased systems, much exptl. evidences for the occurrence of the Kirkendall effect can also be found in the literature. However, the relevant observations are not always analyzed in terms of differing vacancy fluxes in the differing parts of such diffusion couple. The anal. recently proposed by the authors shows that the interface must be able both to create or annihilate the point defects involved in the diffusion process within the two adjoining phases. The implication of this model on the relative motion of the phase lattice with respect to the vol. center (Matano frame) and to the interface will be described and discussed. The specific case of the growth of an intermediate phase in binary systems is also considered. Some specific aspects for the case of ternary systems are discussed.