The compatibility of TiB2 protective coatings with SiC fibre and Ti-6Al-4V

TiB₂ coatings have been studied as prospective protective layers to inhibit the interfacial reaction between SiC fibres and Ti-alloy matrices. This protective coating has been deposited onto SiC monofilament fibres using a chemical vapour deposition (CVD) technique. The fibre-matrix compatibility of these TiB₂-coated SiC fibres in Ti-6Al-4V composites was evaluated by incorporating the coated fibres into Ti-6Al-4V using a diffusion bonding technique. The interfaces of this composite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe microanalysis, to evaluate the interfacial microstructures, chemical stability and the efficiency of TiB₂ as a protective coating for SiC fibres in Ti-alloy matrices, and to study the effects of deposition temperature on the interface of the coated fibre. Results show that stoichiometric TiB₂ coatings are stable chemically to both SiC fibres and Ti-6Al-4V and hinder the deleterious fibre-matrix reactions effectively. Boron-rich TiB₂ coatings should be avoided, as they lead to the formation of a needle-like TiB phase at the fibre–matrix interface. These findings provide promising evidence for the value of further exploration of the use of stoichiometric TiB₂ as a protective coating for SiC fibre in Ti-based composites.     

Reaction of HF with Porous Glass

Infrared spectra were used to follow the reaction of HF with porous glass which had been dehydroxylated to various degrees. The fluoridation proceeded smoothly, and the surface hydroxyls were eliminated completely with samples which were not degassed or were degassed mildly (at temperatures up to approximately 500°C) so that appreciable amounts of water and hydroxyls were on the surface before the HF treatment. Samples which had been severely dehydroxylated before exposure to HF behaved differently, and several HF treatments were required to effect complete fluoridation. Experiments suggest that the replacement of hydroxyls by fluoride is negligible at room temperature, the dominant reaction being the formation of B-OH and B-F groups. The latter are unstable at higher temperatures and release HF, so that dehydroxylation can continue after physically adsorbed HF has been desorbed and pumped away.     

DETERMINATION OF IRON LOSS DISTRIBUTION IN INVERTER FED INDUCTION MOTORS

ABSTRACT

An approach based on the temperature-time method was used to investigate the iron loss density distribution in a 4 kW, 415V, 3-phase, 4-pole induction motor under both sinusoidal and inverter fed conditions. A test rig was constructed to allow loss densities to be evaluated at discrete points within the machine. A model based on interpolate functions was constructed to give the full loss density distribution throughout the stator iron. It is shown that iron losses increase considerably towards the ends of the stator core stack, particularly for the inverter fed case. The results are verified with those obtained from established models based on an equivalent circuit representations.     

DETERMINATION OF IRON AND STRAY LOAD LOSSES IN INDUCTION MOTORS USING A THERMOMETRIC METHOD

Abstract

In an induction motor, losses in the magnetic materials account for 10% to 20% of total losses. The iron loss effectively reduces both the output capability and possibly the life span of the machine. To limit these undesirable effects a prior requirement is to accurately assess the iron losses, and understand their nature and, ideally, their spatial location. An experimental method for determining the iron and stray load losses is presented. The test motor is a 3 phase, 4 pole, 4 KW induction motor which was heavily instrumented with thermocouples to map the loss distribution.     

Heritage from Below

Current research into the peri-urbanisation associated with the rapid population growth of preferred Australian metropolitan regions has shown that their landscape values are put at risk and the region's quality of life (QoL) and the community's standards of liveability are consequently threatened. Whilst the concept of a landscape framework as an analytical, policy and management tool has general acceptance, there appears to be few if any working examples where this concept has been operationalised. To date, the conventional approaches utilised by regional planning agencies and local government have not been able to deliver the necessary tools to incorporate the essential landscape planning principles let alone planning processes to address the regional landscape values at risk in the peri-urban areas of rapidly growing regions. However, promising initiatives have emerged from allied planning fields such as landscape planning. Despite shortcomings in the theoretical development of this conceptual framework, a regional landscape framework has been incorporated into the recently released SEQ Regional Plan 2005–2026, a statutory planning instrument for the South East Queensland (SEQ) region, Australia's fastest growing metropolitan region. Whilst it is conceivable that in the SEQ case, practice may be ahead of theory, there is now an imperative to develop this framework in a manner that it can be utilised as a regional policy framework and as an integrating instrument to address the values of regional landscapes including the range of existing and emerging rural values of the critical urban–rural interface.     

Utilization of pre-gelatinized tapioca starch in the manufacture of a snackfood, fish cracker ('keropok')

The use of pre-gelatinized tapioca starch for the manufacture of 'keropok' by drumdrying has been investigated. Processing variables were examined by using five different slurries of water: starch, with ratios of 50:50, 60:40, 70:30, 80:20, and 90:10 at four different temperatures: 120.2°C, 133.5°C, 143.6°C, and 151.8°C. Only 'keropok' made from a slurry with a water: starch ratio of 70:30 pre-gelatinized at 133.5°, 143.6°C and 151.8°C had linear expansion greater than the minimum acceptable value of 77%. 'Keropok' containing pre-gelatinized starch produced at 133.5°C was the most acceptable to a sensory panel.     

Synthesis and properties of spodumene-modified mullite ceramics formed by sol-gel processing

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Reduction of Glucose Content in Potatoes with Glucose Oxidase

Two commercial glucose oxidase preparations, DeeO 1500 and Fermcozyme CBB-750, were investigated for their activities and use in decreasing glucose levels in Norland and Shepody potatoes. When DeeO was added at 0.01% by weight of peeled potatoes, glucose of potato extracts of both cultivars was decreased by about 22% when the extracts were first blanched, and about 15% if not blanched, indicating the presence of some inhibitors in raw potatoes. When applied to steam-blanched potato strips, 0.10% (v/v) solution of Fermcozymc reduced glucose by 25–35%. These experiments showed a potential use of glucose oxidase as a processing aid to reduce nonenzymatic browning in potato products.     

Reaction of Cyanogen with SiO2 Surfaces

Infrared spectra (4000 to 1300 cm⁻¹) of SiO₂ specimens with high surface areas which had been exposed to (CN)₂ at 25° to 600°C were recorded. Sorption was slight at 25°, but extensive reaction occurred at higher temperatures. The main effects of the sorption were the decrease of the 3747 cm⁻¹ band of surface Si-OH groups and the buildup of a prominent band at 2310 cm⁻¹ thought to be caused by surface Si-NCO species rather than Si-OCN species. The data suggest that, in addition to the isocyanate formed in the dehydroxylation reaction, HCN produced in that reaction led to the formation of Si-CN and Si-OH