Thermal aspects are becoming increasingly important for the reliability of the electronic components due to the continuous progress of the electronic industries. Therefore, the effective thermal management is a key issue for packaging of high performance semiconductors. The ideal material working as heat sink and heat spreader should have a CTE of (4-8) × 10 −6 K −1 and a high thermal conductivity. Metal matrix composites offer the possibility to tailor the properties of a metal by adding an appropriate reinforcement phase and to meet the demands in thermal management.Copper/SiC and copper/diamond composites have been produced by powder metallurgy. The major challenge in development of Cu/SiC is the control of the interfacial interactions. Silicon carbide is not stable in copper at the temperature needed for the fabrication of Cu/SiC. It is known that the bonding between diamond and copper is very weak in the Cu/diamond composite. Improvements in bonding strength and thermo-physical properties of the composites have been achieved by • a vapour deposited molybdenum coating on SiC powders to control interface reactions, • using atomized Cu(X) alloys with minor additions of carbide formers, e.g. X = Cr, B, to improve the interfacial bonding in Cu-diamond composites.
Titanium alloys exhibit high specific strength and stiffness that fit structural applications demanding lightweight construction. Ceramic reinforcements can improve specific strength and stiffness, and also the wear resistance. Higher specific strength and Young's modulus is expected when reinforcing titanium by SiC particles compared to other reinforcements. The production of a SiC reinforced titanium alloy using conventional powder metallurgy methods (PM) yields porosity and silicides formation. PM processing methods are discussed in this work: equal channel angular pressing, Spark plasma sintering, sintering using an induction oven and hot extrusion. Consolidation time and temperature are considerably decreased avoiding the silicide formation, while consolidation loads were increased to obtain a denser Ti-SiC composite. Hot extruded samples show the best results, without any reaction zone and a density near to the theoretical one. Entnommen aus TEMA
A 10-year research and development program was conducted by the BioEnergy Development Corporation, USDA Forest Service, and U.S. Department of Energy on the island of Hawaii, where nearly 230,000 acres are suitable for growing biomass in short-rotation Eucalyptus plantations. Successful techniques are described for seedling production, plantation establishment (site preparation, weed control, planting), maintenance (weed control, fertilization), biomass yield estimation, and harvest. Basic biological relationships are described to aid decisions on site selection, initial spacing, fertilizer schedules, and rotation length. Environmental issues likely to be faced by growers of Eucalyptus plantations are discussed, including soil erosion, nutrient depletion, and monocultures. Continuing programs for tree improvement, monitoring, and silviculture research are recom mended. Production costs for biomass yields are estimated for three promising management regimes, representing pure Eucalyptus plantings at dense and wide spacings and a mixed species plantation where Albizia is used as a nurse crop to provide nitrogen needed for optimum Eucalyptus growth. This information will help prospective investors decide whether to invest in Eucalyptus plantations, and will help growers develop or choose among alternative management regimes.
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