Development and testing of an intermediate temperature glass sealant for use in mixed ionic and electronic conducting membrane reactors

High temperature ceramic membranes have interesting possibilities for application in areas of new and developing technologies such as hydrocarbon combustion with carbon dioxide capture and electrochemical promotion of catalysis (EPOC). However, membrane module sealing remains a significant technical challenge. In this work a borosilicate glass sealant (50SiO₂·25B₂O₃·25Na₂O, mol%) was developed to fit the requirements of sealing an air separation membrane system at intermediate temperatures (300-600 °C). The seal was assessed by testing the leak rates under a range of conditions. The parameters tested included the effect of flowrate on the leak rate, the heating and cooling rates of the reactor and the range of temperatures under which the system could operate. Tests for durability and reliability were also performed. It was found that the most favourable reactor configuration employed a reactor with the ceramic pellet placed underneath the inner chamber alumina tube (inverted configuration), using a quartz wool support to keep the membrane in place prior to sealing. Using this configuration the new glass-based seal was found to be a more suitable sealant than traditional alternatives; it produced lower leak rates at all desirable flowrates, with the potential for rapid heating and cooling and multiple cycling, allowing for prolonged usage. © 2010 Elsevier B.V. All rights reserved.

Hole-making Process and Its impacts on the Fatigue Response of Ti -6Al-4V Aircraft Alloy

In this work, the impact of conventional drilling and helical milling processes on the fatigue response Ti-6Al-4V (grade 5 titanium alloy) has been presented. Results show that the work pieces produced by helical milling has a 119% longer fatigue life compared with the drilled pieces under dry machining condition, and a 96% longer fatigue life for helical milled piece under lubricated condition. The use of cutting fluid has led to longer fatigue lives – 15% longer for drilling and 3% longer for helical milling. Other results such as the machined surface roughness, alloy surface and sub-surface microstructures have also been studied in details.

Robust Room Temperature Hysteresis in an FeIII Spin Crossover Metallomesogen

The high temperature magnetic and structural properties of an amphiphilic iron(III) spin crossover complex are reported. Thermal cycling reveals a scan rate-dependent 20 K thermal hysteresis in the mT vs. T data close to room temperature. A fast scan rate is essential for the hysteresis but it is robust and reproducible after multiple thermal cycles. Differential scanning calorimetry and cross polarized microscopy are used to show that the magnetic switching aligns with a material state change from solid to ordered liquid phase on warming.

Effect of reinforcement and heat treatment on elevated temperature sliding of electroless Ni–P/SiC composite coatings

The investigation is focused on the wear behaviour at elevated test temperature of composite Ni–P/SiC deposit, with varying concentration of the reinforcing SiC particles. The phase evolution measured by X-ray diffraction suggests slight crystallisation during wear testing at 200 °C. In coating without reinforcing particles, adhesive wear is accompanied by microcracks. The thermal heat generated and the cyclic loading could have induced sub-surface microcracks. Owing to the effective matrix-ceramics system in composite coatings, fine grooves, abrasive polishing and uniform wearing are observed. Reinforcing particles in the matrix hinder microcrack formation and significantly reduce the wear rate. Triboxidation is confirmed from energy dispersive X-ray spectrometry.

Corrosion Fatigue Behaviour of Laser-welded Shape Memory NiTi Wires in a Simulated Body Fluid

Corrosion fatigue is a fracture process as a consequence of synergistic interactions between the material structure, corrosive environment and cyclic loads/strains. It is difficult to be detected and can cause unexpected failure of engineering components in use. This study reveals a comparison of corrosion fatigue behaviour of laser-welded and bare NiTi wires using bending rotation fatigue (BRF) test coupled with a specifically-designed corrosion cell. The testing medium was Hanks’ solution (simulated body fluid) at 37.5 oC. Electrochemical impedance spectroscopic (EIS) measurement was carried out to monitor the change of corrosion resistance of sample during the BRF test at different periods of time. Experiments indicate that the laser-welded NiTi wire would be more susceptible to the corrosion fatigue attack than the bare NiTi wire. This study can serve as a benchmark for the product designers and engineers to understand the corrosion fatigue behaviour of the NiTi laser weld joint and determine the fatigue life safety factor for NiTi medical devices/implants involving laser welding in the fabrication process.