Formation and Growth of Intermetallic Compounds during Reactions between Liquid Gallium and Solid Nickel

Liquid metals, such as Ga and eutectic Ga-In, have been extensively studied for various applications, including flexible and wearable devices. For applying liquid metal to electronic devices, interconnection with the various metal electrodes currently in use, and verifying their mechanical reliability are essential. Here, detailed investigations of the formation and growth of intermetallic compounds (IMCs) during the reactions between liquid Ga and solid nickel were conducted. Ga and Ni were reacted at 250, 300, and 350 °C for 10–240 min. The IMC double layer observed after the reactions contained a Ga7Ni3 bottom layer formed during the reactions, and a GaxNi top layer (with 89–95 at.% of Ga) precipitated during cooling. Numerous empty channels exist between the rod-type Ga7Ni3 IMCs. Ga7Ni3 growth occurred only in the vertical direction, without lateral coarsening and merging between the rods. The time exponents were measured at 1.1–1.5, implying that the reaction kinetics were near-interface reaction-controlled. The activation energy for Ga7Ni3 growth was determined as 49.1 kJ/mol. The experimental results of the Ga-Ni reaction study are expected to provide important information for incorporating liquid metals into electronic devices in the future.

THE EFFECTS OF DISSOLUTION OF THE SOLID NICKEL IN LIQUID ALUMINUM

<p class="Adressess">The preparation of a large number of materials trough the propagating exothermic reactions has been the objective of numerous investigation. Self-propagating reactions are typically associated with high temperatures and extremely steep thermal gradients and thus offer the opportunity to investigate the formation of intermediate and metastable phases. Such reactions are also of interest from a practical point of view since, as has been described in numerous literature accounts, they provide the opportunity to prepare materials with unique properties.</p><p class="Adressess">In this study the thermal effects of dissolution on the solid nickel in liquid aluminum and formation intermetallic phases was studied by simple experimental procedure. The thermal effects generated by exothermic solid-liquid metal interaction was judged by the rise of temperature in the system. Depending on experimental conditions, two different regimes of behavior were found: solid-liquid interaction leading to the considerable rise of the temperature in the system, and characterized by continuos decrease of the temperature in the system with time. The results of the experiments on the heat effects during the interaction of solid nickel with different particle size and liquid aluminum, with and without external mixing, are presented. It has been shown that, depending on experimental conditions, the evolved heat may influence the structure of a zone near to the solid-liquid interface. The experimental procedure correlates with the practical conditions of semi-industrial production of aluminum-nickel master alloys with relatively high percentage of nickel.</p>

The Effect of Heat Temperature on the Structure of Plasma Coating of the Ni-Cr-Si-B System

The powder of the Ni-Cr-Si-B system was applied on tubes of low carbon steel (0.2 % C) with the help of air-plasma spraying. The effect of heating temperature on the microstructure of obtained coatings was analyzed in this paper. The coatings were heated up to 500, 600, 700, 800, 900, 1000, and 1100 °C and cooled in the air. It was shown by the method of optical and scanning electron microscopy (SEM) and the X-ray diffraction analysis (XRD) that the same phases (γ-Ni, Ni3B, Ni3Si and Cr2B) were present in the coatings before and after heating. Chromium carbide Cr7C3 was observed in the coating structure after heating to above 1000 °C. Coatings which were heated to 1000 °C consisted of grains of the solid nickel base solution, micro volumes of the Ni+Ni3Si eutectic with inclusions of Ni3B and particles of Cr7C3. The coatings which were crystallized from a liquid state (heated up to 1100 °C) consisted of large areas of the solid nickel base solution and particles of chromium carbide Cr7C3. The space between nickel areas is filled by the Ni3Si+Ni3B eutectic.