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77 results on '"Xu, L.F."'

48. Drilling of SiCp/Al Metal Matrix Composites with Polycrystalline Diamond (PCD) Tools.

Author

Huang, S.T., Zhou, L., Chen, J., and Xu, L.F.

Subjects
DRILLING & boring, METALLIC composites, POLYCRYSTALS, INDUSTRIAL diamonds, SILICON carbide, ALUMINUM composites, METAL cutting
Abstract

High-volume-fraction SiCp/Al composites have attracted considerable interest for their excellent thermo-physical properties. However, popularization of high volume fraction SiCp/Al composites is still hampered by their poor machinability. In this study, the influences of the cutting speed and feed rate on the drilling performance of SiCp/Al composites with 56% SiC particles were investigated experimentally. The drilling characteristics were evaluated in terms of drilling forces, tool wear, and the surface quality of drilled-hole. It was found that the feed rate is one of the main cutting parameters that affect the drilling performance, while the cutting speed has no significant effect on the thrust force. [ABSTRACT FROM AUTHOR]

Published
2012
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50. Dielectric properties of bismuth doped CaCu3Ti4O12 ceramics

Author

Xu, L.F., Qi, P.B., Chen, S.S., Wang, R.L., and Yang, C.P.

Subjects
*BISMUTH, *DOPED semiconductors, *ELECTRIC properties, *CERAMIC materials, *CALCIUM compounds, *SOLID state chemistry, *X-ray diffraction
Abstract

Abstract: Ca1−3x/2Bi x Cu3Ti4O12 (x =0.0–0.3) ceramics were prepared by the conventional solid-state reaction method. X-ray powder diffraction analysis confirmed the formation of cubic CCTO phase except for subtle peaks of CuO. SEM micrographs suggested that the morphologies of doped CCTO ceramics had been sheet-like for high Bi-doping amount, and the dominant grain size decreasing could be seen for the small content of Bi-doping CCTO. Dielectric properties of pure and doped CCTO were investigated in a broad temperature range of 20–420K. The results showed that bismuth doping could decrease the dielectric loss but suppress the dielectric temperature stability at the same time. Bi doped CCTO ceramics presented different relaxation properties. As to pure CCTO and BCCTO (x =0.3) only one MW relaxation (Relaxation I) could be found, which moves to higher frequency with temperature increasing. However, two relaxation processes (Relaxation I and II) appear for BCCTO (x =0.1–0.2). By means of complex impedance spectra analysis and Arrhenius fitting, we successfully separated the different conductive segments and explained the mechanisms of the two relaxation processes. Relaxation I appeared at low temperature could be attributed to the V O nergies inside CCTO grains which did not showed significant changing of activation energy after bismuth doping. For Relaxation II at higher temperature than Relaxation I, with activation energy obviously depending on the Bi-ion concentration, may be related with the V O fects at the grain boundaries. [Copyright &y& Elsevier]

Published
2012
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