Magnetic properties and thermal stability of CoFeNi-based amorphous films

CoNiFe-based amorphous films were magnetron-sputtered to investigate their structural and magnetic properties, including annealing-induced effects and interfacial influence from additional layers of Ta and Cu. The amorphous structure was confirmed by diffraction experiments. The magnetic measurements showed a well-defined uniaxial anisotropy in plane, arising possibly from atom oblique incidence effects competing with the stray field of the magnetron. The anisotropy could be influenced by using a Ta buffer layer, though the interfacial reaction gives rise to a dead layer. A coercive force H _c of 1–2 Oe and a magnetization of 680 emu/cm³ were measured at room temperature; properties which show promise for application in magnetotunneling junction devices. Thermal analyses showed a two-stage crystallization behavior, which started at 400°C and ended at about 600°C. The Curie temperature of the amorphous phase was estimated to be about 440°C.     

Modelling induction skull melting design modifications

Induction Skull Melting (ISM) is used for heating, melting, mixing and, possibly, evaporating reactive liquid metals at high temperatures when a minimum contact at solid walls is required. The numerical model presented here involves the complete time dependent process analysis based on the coupled electromagnetic, temperature and turbulent velocity fields during the melting and liquid shape changes. The simulation is validated against measurements of liquid metal height, temperature and heat losses in a commercial size ISM furnace. The often observed limiting temperature plateau for ever increasing electrical power input is explained by the turbulent convective heat losses. Various methods to increase the superheat within the liquid melt, the process energy efficiency and stability are proposed.     

Sensors for chemicals based on electrically conductive immiscible HIPS/TPU blends containing carbon black

Carbon Black (CB)-containing immiscible polymer blends based on high-impact polystyrene/thermoplastic polyurethane (HIPS/TPU) were studied as sensing materials for an homologous series of alcohols, including, methanol, ethanol and 1-propanol. The studied immiscible blend was designed to exhibit a double-continuity structure i.e., the CB particles form chain-like network structures within the TPU phase, which forms a continuous phase within the HIPS matrix. Extruded HIPS/TPU/CB filaments produced by a capillary rheometer process at various shear rate levels were used for the sensing experiments. All filaments displayed a selective resistance changes upon exposure to the various alcohols combined with reproducibility and recovery behaviour. An attempt is made to identify the dominant mechanisms controlling the sensing process in a CB-containing immiscible polymer blend characterized by a double-continuity structure. The distinct structure and composition of the HIPS/TPU interphase region were found to have a crucial role in the sensing mechanism, determining the selectivity of the filaments toward the studied alcohols. Additionally, the sensing performance of HIPS/TPU/CB system is compared to recent results for TPU/CB compounds, polypropylene/TPU/CB and HIPS/ethylene vinyl acetate/CB immiscible polymer blends.     

High speed propulsion: Performance advantage of advanced materials

High-speed air breathing propulsion systems have many attractive military and civil applications. The high propulsive efficiency of these systems allows the exploitation of speed, distance, and bigger payloads, or any combination of the three. The severe operating conditions of these systems require particular attention to overall thermal management of the engine/air-frame. Fuel-cooling the engine structure is a viable way of maintaining thermal balance over a range of flight conditions. Air Force applications have focused on using endothermic hydrocarbon fuels to address this issue because of their compatibility with the military operations. Recent ground tests of scramjet engines have demonstrated adequate performance utilizing state-of-the-art technology in materials. This progress has paved the way for an expendable flight test vehicle in the near future. In order to take full advantage of the capabilities of this propulsion system, advances in fuel-cooled structures, high temperature un-cooled materials, and increased heat capacity of hydrocarbon fuels will be needed to enable expendable systems to reach higher Mach numbers. An additional benefit would be realized in future reusable systems.     

Synthesis of new sulphides of transition metal ions in presence of sun light

New sulphides of transition metal ions [M⁺ⁿ = Cu⁺¹, Cu⁺² and Zn⁺²] have been synthesised in sunlight. XRD patterns show that these compounds are not MxSy but are mercaptyl, hydroxyl metal sulphides [M(SH)(OH)(H₂O)₂] which is further ascertained by I.R. spectra showing bands due to T _d-symmetry. ESCA of compound of copper in solid state shows presence of Cu¹⁺ and Cu²⁺ ion. The presence of hydroxyl, mercaptyl, aqua and S^–2 groups has finally been confirmed with TGA, DTA and ESCA. Conductivity and Seebeck coefficient measurements show that compound of copper is p-type semiconductor and compound of zinc is n-type semiconductor. The production of these low cost materials opens an interesting area of research and development for their use in solar cell devices.