In situ reaction synthesis and control during interdiffusion

Composite materials are usually complex multiphase materials systems that are required to serve multifunctional purposes. In developing composite systems, the clear understanding of the internal interface reactions together with the kinetic behavior of the components is one of the crucial factors to produce a desirable materials combination. In this study, Ti-Al-Si and Si-C-Metal together with Cu-Se-In systems are examined as model systems.; The interface reaction of the TiSi₂ and TiAl phases was investigated in order to produce the Ti₅Si₃ phase in a TiAl matrix. After annealing of TiSi₂/TiAl at 1373K, the sequence of products was obtained as TiSi, porous Ti₅Si₄, TiAl2, Ti ₂Al₅ and TiAl₃. The formation of Ti₅Si ₃ required an enhanced Ti flux which was provided by a kinetic bias layer of Ti. In the Ti-biased reaction, the Ti₅Si₃ phase was produced along with several other product phases. The reaction products of the biased reaction showed stability under long term annealing at 1373K.; For the SiC/Metal reactions, the diffusion pathway and kinetics governing the SiC/metal reaction have been examined to identify systematic behavior. With respect to the metal components, two separate reaction modes were identified—formation of carbides and development of silicides or formation of silicides and free carbon (periodic morphology). In each case, the diffusion pathway is dictated by the formation of carbon or carbides, and mass balance requirements. The analysis of the separate reaction modes was confirmed by experiments on SiC/Ni, SiC/Cu/Ni and SiC/Cr/Ni reactions and was used to control interface reactions.; Finally, the reactive diffusion Of Cu₂Se/In2Se₃ reaction couples was investigated in order to examine the component behavior during interdiffusion. The product phases obtained from Cu₂Se/In ₂Se₃ diffusion couples were observed as CuInSe₂ and β phase. The diffusion pathway of the Cu₂Se/In ₂Se₃ couple did not follow the pseudobinary plane. An irregular shape CuInSe₂ phase formed as a product in the Cu₂Se phase, indicating that In is the fastest component in diffusion.