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Owing to energy conservation of waste heat, Lead telluride, PbTe, based materials have promising good thermoelectric properties around a range of middle temperature (Fig. 1, from 300 to 600°C), due to their high melting point, fine chemical stability, and the high figure of merit Z. The general physical properties and factors affecting the figure of merit have been reviewed. This research is focused on the n-type of PbTe materials and collocated with analysis of densities, hardness, elastic modulus, and thermoelectric properties thermoelectric figure of merit ZT=GS2T/κ (where G is electrical conductivity, S is Seebeck coefficient , T is absolute temperature, and κ is thermal conductivity). Room temperature hardness and Young’s modulus are measured by nano-indentation. In this study, the hot-press compacts under the pressure of 4 ton/cm2 can reach the maximum density about 8.2 g/cm3, and hardness and elastic modulus are 0.6 GPa and 70 GPa, respectively. The figure of merit value (ZT) of PbTe in low temperature (around 340°C) was found about 1 with carrier concentration above 1019 cm−3. These results also indicate that the powder metallurgy parameters provide potentialities for further increase of the high efficiency of energy conversion in PbTe materials.
The effect of graphite particles on the damping behavior of 6061 Al–graphite composites was investigated with an aim to develop a high damping, stiffness, and hardness material. The composites were processed by mixing 6061 alloy powder with graphite particles, hot pressed as a billet and consolidated by reciprocating extrusion 10 times. The results showed that the graphite particles were greatly refined and niformly distributed in the matrix. The graphite in situ reacted with the Al matrix to orm fine dispersed Al4C3 particles during both reciprocating extrusion and subsequent olution treatment. The Al4C3 phase could result in a pronounced dispersion trengthening effect. The damping capacity of the composite increased with increasing raphite content. The composite showed a peak in damping capacity during aging reatment. The 6061 Al–20% (graphite, Al4C3) composite solution-treated for 24 h and eak-aged displayed an excellent combination of damping capacity, stiffness, and ardness. The composite retained high damping while maintaining a high modulus ecause of the coexistence of graphite and Al4C3. The operative damping mechanisms, ncluding intrinsic damping of graphite particle, interface damping, dislocation amping, and grain boundary damping, are discussed with consideration of material icrostructure.
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