MICROSTRUCTURES DEVELOPED IN SOLID-LIQUID REACTIONS - USING CU-SN REACTION, NI-BI REACTION, AND CU-IN REACTION AS EXAMPLES

In this study Cu was reacted with pure liquid Sn and liquid Sn saturat ed with Cu at 240 degrees, 250 degrees, and 275 degrees C. Different m icrostructures were observed for different liquid Sn baths. For reacti on in the Sn bath saturated with Cu, Cu6Sn5 and Cu3Sn with the layered structure formed. The growth follows the parabolic kinetics, suggesti ng the growth is diffusion-controlled. The apparent activation energy for the parabolic growth constant is 29 kJ mol(-1). For reaction in pu re Sn, the reaction produced a very thin and irregular Cu3Sn layer and a thicker Cu6Sn5 region with long protrusions into the Sn region. In addition to the diffusional reaction, Cu dissolved very rapidly into t he pure liquid Sn bath. It is proposed that the formation of the non-p lanar structure is due to the rapid dissolution of Cu6Sn5 into the liq uid Sn. Similar behaviors were observed for the reaction between Ni an d liquid Bi as well as between Cu and liquid In. For Ni reacted in liq uid Bi saturated with Ni at 300 degrees C, NiBi3, formed with the laye red structure. For Ni reacted in pure liquid Bi, NiBi3 formed with an irregular structure. For Cu reacted in liquid In saturated with Cu at 200 degrees C, Cu11In9 formed with the layered structure. For Cu react ed in pure liquid In, Cu11In9 formed with an irregular structure; Cu7I n3 and Cu2In also formed but were very thin, only a few microns in thi ckness. (C) 1997 Elsevier Science S.A.