Matrix derived from resin after carbonization in rigid carbon felt thermal insulation has many advantages. The microstructures and properties of these materials were investigated in this paper. Results showed that matrix tend to accumulate at the intersections of fibers. This can improve mechanical properties and have a little influence on thermal conductivities of the composites. The excellent bending strength of 2.66MPa, compressive strength of 0.91MPa and a high thermal conductivity of 0.81W/(m·K) (at 1500°C) with a matrix concentration of 32.7% is achieved. However, high thermal conductivity is harmful for those materials which are used as thermal insulators.
Five-layered Al/Al-Cu functionally graded material (FGM) was fabricated by powder metallurgy technology. The microstructure and composition of the prepared specimen were studied. Vickers hardness, flexural strength and fracture surface morphology were also measured. The results showed that Al/Al-Cu graded material with dense structure and compositional continuous change was obtained by solution-precipitation method. The graded materials presented a compositional continuous change along the graded direction because of the diffusion effect, and the Vickers hardness was liner proportional to the distribution of Cu content. Compared with pure sintered Al, remarkable improvement on hardness and fracture strength was achieved due to the CuAl2 phase dispersively distributed in the matrix. With the increase of Cu content, the fracture mode changed from tough fracture to the tendency of brittle fracture.
This paper proposes a new wireless sensor routing algorithm by combining the ant colony algorithm with the mobile agent technology. This algorithm considers the distance and path energy overhead among nodes and residual node energy, equalizes the energy overhead in the network, improves the update rule of the ant colony information elements and speeds up convergence of the ant colony algorithm to get the optimal values. The simulation results indicate that this algorithm can improve the globalization and convergence speed, effectively reduce redundant data transmission and communication overhead, extend the network lifecycle and be very suitable for a large-scale wireless sensor network compared to other mobile agent routing algorithms.
This article provides a method to determinate boron (B) impurity in silicon by inductively coupled plasma emission spectrometry (ICP-AES), in which the element spectral and analytical parameters were optimized. Three factors that influence testing results were discussed, including the amount of mannitol (C6H14O6) addition, concentration of nitric acid (HNO3) and evaporated temperature. As a result, the experimental parameters and conditions were optimized. The method of the detection limit, recovery and precision were all awarded with satisfactory results.
Effect of heat treatment in atmosphere on the resistivity of polycrystalline silicon has been investigated in this paper. After heat treatment at 1050oC for 10h, there is no obvious change of the resistivity in the N-type region of polycrystalline silicon, which could be contributed to the complicated influence factors, such as more impurities content and defects. On the other hand, an obvious increase of the resistivity was observed in the P-type region which could be contributed the redistribution of Al and B in the Si-SiO2 interface. The resistivity of the P-type region increased from less than 1Ω·cm to several hundreds Ω·cm.
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