Interfacial Reaction between Sn and Cu-Ti Alloy (C1990HP)

The interfacial reaction between pure tin and substrate with the composition of Cu-4.3 at% Ti (C1990HP) was investigated using the reaction couple technique from 240 °C until 270 °C in the range 0.5~4.0h. The SEM images show the Cu6Sn5 and small precipitated Ti2Sn3 phase formed at the Sn/C1990HP interface. In addition of Ti substantially increased the amount of intermetallic compound (IMC) at the interface which separated parts of Cu6Sn5 compounds with the inner region containing more Ti than the outer. The existence of Sn/C1990HP on the liquid/solid state reaction indicates that spalling occurred with changes in reaction time and temperature. With increased reaction temperature and time, the grain produced an abnormal condition resulting in Cu6Sn5 not accumulating at the interface and spalling into the solder in addition to grain ripening and an increase in total layer thickness. The hexagonal prism-shaped Cu6Sn5 phase is found on the top of the C1990HP substrate when the Cu6Sn5 layer detaches. The reaction phase formation, detachment, and split mechanisms are proposed in this study.

Cycle Stability and Hydration Behavior of Magnesium Oxide and Its Dependence on the Precursor-Related Particle Morphology

Thermochemical energy storage is considered as an auspicious method for the recycling of medium-temperature waste heat. The reaction couple Mg(OH)2–MgO is intensely investigated for this purpose, suffering so far from limited cycle stability. To overcome this issue, Mg(OH)2, MgCO3, and MgC2O4·2H2O were compared as precursor materials for MgO production. Depending on the precursor, the particle morphology of the resulting MgO changes, resulting in different hydration behavior and cycle stability. Agglomeration of the material during cyclization was identified as main reason for the decreased reactivity. Immersion of the spent material in liquid H2O decomposes the agglomerates restoring the initial reactivity of the material, thus serving as a regeneration step.

Growth Kinetics of Intermetallic Compounds Between Sn and Fe Liquid–Solid Reaction Couples

Growth behavior of the intermetallic compound (IMC), FeSn2, was investigated in the liquid Sn/solid Fe reaction couple over the annealing temperatures from 250 °C to 400 °C. Low-carbon steel AISI 1018 was chosen to make Fe samples. The morphology and thickness of the IMC formed between Sn and Fe were examined using scanning electron microscopy (SEM). In addition, energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were used to confirm that the IMC is FeSn2. The growth kinetics of FeSn2 was modeled by parabolic law and empirical power law. Based on the models, the growth constants, the activation energy, and the time exponents were established at different annealing temperatures. It was found that the time exponent values obtained by fitting with empirical power law deviate from 0.5, meaning that volume (bulk) diffusion is not the only rate-controlling process in the liquid Sn/solid Fe reaction couple. Also, a variation in the time exponent values is indicative that the growth behavior is correlated with grain size growth and irregular grain morphology at different annealing stages. The results of this research show that AISI 1018 steel can readily react with Sn to form IMC on the interface. This is an essential requirement of soldering action using Sn-rich solders.

Development of the CaO–SrO–ZrO2–B2O3–SiO2 sealing glasses for solid oxide fuel cell applications: structure–property correlation

The Cr6+ fraction in the glass/Cr2O3 reaction couple decreases significantly with increasing ZrO2 content at 700 °C because of the condensed glass structure and increases at 750 and 800 °C due to the increase in residual glass content in the glass–ceramics.