Peter Hing

Synthesis of nanostructured β-Ni(OH)2 by electrochemical dissolution–precipitation and its application as a water oxidation catalyst

A straightforward electrochemical dissolution-precipitation approach has been developed to synthesize nanostructured β-Ni(OH)2 powders (particle size 10-100 nm, specific surface area ∼100 m(2) g(-1)) from Ni metal anodes. The approach differs from existing electrochemical synthesis methods in that it predominantly results in bulk precipitation of nanoparticles, without significant film growth on either of the electrodes. Heat treatment of the as-synthesized β-Ni(OH)2 afforded NiO with mostly preserved nanostructure and very high specific surface area (≤100 m(2) g(-1), depending on calcination temperature). The as-synthesized β-Ni(OH)2 was found to be an excellent catalyst for the oxygen evolution reaction (OER) in the technologically important water electrolysis process, apparently contradicting recent reports that the α polymorph is required for such high activity. With catalyst loadings <0.1 mg cm(-2), OER current densities of 10 mA cm(-2) were sustained at overpotentials as low as 340 mV, with Tafel slopes of only ∼38 mV/decade. The catalyst was highly stable in alkaline media over the course of electrolysis experiments lasting for several hours. This performance surpasses that of many previously reported earth-abundant OER catalysts and is comparable to that obtained with state-of-the-art RuO2 and IrO2 catalysts.

Optimization of a Novel Composite Cathode for Intermediate Temperature SOFCs Applications

Ba0.95FeY0.05O2.81 was prepared by solid state reaction method to study its structure, conductivity and thermal expansion coefficients. X-ray powder diffraction at elevated temperatures showed the pure phase at 100 - 600 °C, then the phase changed at 700 - 800 °C. Electrical conductivity measurements at different temperatures showed that the conductivity increased with an increasing amount of Co2O3. The highest conductivity was observed for 10 wt%Ba0.95FeY0.05O2.81 + 90 wt%Co2O3. Thermal expansion coefficients were measured for different compositions to determine the compatibility with Ce0.9Gd0.1O1.95 electrolyte. Results showed that the conductivity and thermal expansion coefficient were sensitive to the composition. The optimum composition was 10 wt%BFY532 + 90 wt%Co2O3, which gave the highest conductivity at 600 - 800 °C. The thermal expansion coefficient was 12.79×10 -6 o C -1 at 40 - 800 °C, which is compatible with the Ce0.9Gd0.1O1.95 electrolyte.

Overview and Functional Characterization of Pb–Free Solders

There are now new legislations emerging or being contemplated to restrict the use of Pb in electronic devices. This development has provided the impetus for the development of Pb- free solder alloys and efforts are now geared towards characterizing their operational and functional properties. The most common alloys being recommended and investigated are those primarily based on the Sn-Ag-Cu (SAC) system. These SAC alloys generally have higher melting points than conventional Pb-Sn alloy. Additionally they are susceptible to microstructural evolution of inter-metallic compounds that have been implicated in thermal fatigue life, mechanical strength and fracture toughness of the soldered joints. We have studied the Sn rich corner of the Sn-Ag-Cu system with minor additions aimed at minimizing detrimental microstructural development and improving the solderability and the mechanical strength of soldered joints. Some of the SAC alloys with minor additions showed some interesting properties. Their shear strength measured ranged from 30 – 60 MPa. The combined properties of strength and conductivity recorded compared favorably with that of traditional Pb-Sn solders.

Synthesis and Characterization of La10Si6O27 and Ce0.9Gd0.1O1.95 Solid Oxide Fuel Cell Electrolyte Material

A Composite oxide ionic conductor consisting of La10Si6O27 (LASIO) and Ce0.9Gd0.1O1.95 (GDC) was synthesized by a modified sol-gel method. The La10Si6O27 powders prepared by modified sol-gel synthesis were coated with GDC gel and latter calcined to form a La10Si6O27 - Ce0.9Gd0.1O1.95 composite material. The structural and microstructural properties of the composite were investigated using powder XRD, SEM and TMA. EIS was conducted in air on the sintered pellets to evaluate the electrochemical performance of the pellets. The conductivity of the composite electrolyte at 973 K was 26 mS /cm which is two orders of magnitudes higher than that for the pure LASIO but lower than that of the GDC (30 mS/cm). The thermal expansion of the composite electrolyte is similar to that obtained for the LASIO.

Ultra Rapid Sintering of Ceramics

The paper presents some preliminary investigations on the sintering of alumina ceramics to translucency in a low thermal mass furnace. It is found that extremely fast sintering occurs in a forming gas atmosphere. Rapid densification occurs in minutes rather than hours normally encountered in conventional sintering of ceramics.