The pyrolytic carbon （PyC） coatings were fabricated on A1203 fiber fabrics by the method of chemical vapor deposition （CVD）. The microstructures of A1203 fibers with and without PyC coatings were characterized by ...The pyrolytic carbon （PyC） coatings were fabricated on A1203 fiber fabrics by the method of chemical vapor deposition （CVD）. The microstructures of A1203 fibers with and without PyC coatings were characterized by SEM and Raman spectroscopy. The influence of deposition time of PyC on the DC conductivity （ad） of A1203 filaments and complex permittivity of fabrics at X band （8.2-12.4 GHz） were investigated. The values of Crd and complex permittivity increase with increasing deposition time of PyC. The electron relaxation polarization and conductance loss were supposed to be contributed to the increase of ε＇ and ε＂, respectively. In addition, the reflection loss （RL） of fabrics was calculated. The results show that the microwave absorbing properties of Al2O3 fiber fabrics can be improved by PyC coatings. The best RL results are for 60 min-deposition sample, of which the minimum value is about -40.4 dB at about 9.5 GHz and the absorbing frequency band （AFB） is about 4 GHz.展开更多
Al2O3 short fiber reinforced La-bearing Al-5%Cu alloy was fabricated by squeeze casting, and the solidified structure and the solute segregation during alloy solidification were studied. The results indicated that La ...Al2O3 short fiber reinforced La-bearing Al-5%Cu alloy was fabricated by squeeze casting, and the solidified structure and the solute segregation during alloy solidification were studied. The results indicated that La has been enriched near the interface which is favorable to improve the wettability between the fiber and At alloy, but the RE-rich phase was not formed at the interface. At the end of the solidification of the composites, the change of the solute in the surplus liquid phase results in the type of matrix alloy being changed because of the selective crystallization, and the segregation at the interface is finally formed. There is no special influence by La on the Cu segregation in the matrix alloy.展开更多
A unique SiC whisker wheel was invented,in which the whiskers were aligned normally to the grinding wheel surface.In this paper,grindabilities of the SiC whisker wheel are investigated and compared with those of other...A unique SiC whisker wheel was invented,in which the whiskers were aligned normally to the grinding wheel surface.In this paper,grindabilities of the SiC whisker wheel are investigated and compared with those of other wheels of SiC grains,Al2O3 grains,as well as Al2O3 long and short fibres which were also aligned normally to the grinding wheel surface,respectively.The main research contents concern grinding characteristics of a directionally aligned SiC whisker wheel such as material-removal volume,wheel-wear rates,integrity of the ground surfaces,grinding ratios and grinding efficiency.Furthermore,grinding wheels of whiskers and fibres have a common disadvantage:they tend to load easily.The authors have proposed a simple method of loading-free grinding to overcome this propensity and investigate some related grinding characteristics under loading-free grinding conditions.展开更多
The effects of Al 2O 3 fiber on wear characteristics of eutectic Al-Si alloy composites were studied using a pin-on-disk tester under dry sliding condition. The results show that the Al 2O 3 fiber can make matrix grai...The effects of Al 2O 3 fiber on wear characteristics of eutectic Al-Si alloy composites were studied using a pin-on-disk tester under dry sliding condition. The results show that the Al 2O 3 fiber can make matrix grain be fine, specially the eutectic Si be finer and prevent the plastic flow of matrix and prohibit the crack propagation in the wear layer, thereby it can remarkably improve the mechanical property and the wear resistance of the MMCs. Since Al 2O 3 fiber plays a role of certain framework in protecting the matrix against crash, it can eliminate the severe wear of MMCs with higher φ f of fiber from the beginning of test. At mild stage, when φ f is in the range of 8%～10%, the wear rates are the lowest. With increasing φ f of Al 2O 3 fiber, the wear mechanism of MMCs can be transformed from adhesive delamination to brittle breakaway.展开更多
A number of nanostructured carbon materials were proposed as new effective promoters for preparing modified Cu/ZnO/Al 2O 3 catalyst system for efficient hydrogen production from methanol steam reforming. Compared to t...A number of nanostructured carbon materials were proposed as new effective promoters for preparing modified Cu/ZnO/Al 2O 3 catalyst system for efficient hydrogen production from methanol steam reforming. Compared to the catalysts modified by other type of carbon materials, the ACF-promoted catalyst prepared via carbonate-coprecipitation method exhibit the highest performance in the low-temperature steam reforming of methanol. It was suggested that the intrinsic high surface area nature of ACF material may favor the generation of modified catalysts with a high surface area and improved component dispersion, thus leading to improved performance for methanol steam reforming.展开更多
基金Project (51072165) supported by the National Natural Science Foundation of ChinaProject (KP200901) supported by the Fund of the State Key Laboratory of Solidification Processing,China
文摘The pyrolytic carbon （PyC） coatings were fabricated on A1203 fiber fabrics by the method of chemical vapor deposition （CVD）. The microstructures of A1203 fibers with and without PyC coatings were characterized by SEM and Raman spectroscopy. The influence of deposition time of PyC on the DC conductivity （ad） of A1203 filaments and complex permittivity of fabrics at X band （8.2-12.4 GHz） were investigated. The values of Crd and complex permittivity increase with increasing deposition time of PyC. The electron relaxation polarization and conductance loss were supposed to be contributed to the increase of ε＇ and ε＂, respectively. In addition, the reflection loss （RL） of fabrics was calculated. The results show that the microwave absorbing properties of Al2O3 fiber fabrics can be improved by PyC coatings. The best RL results are for 60 min-deposition sample, of which the minimum value is about -40.4 dB at about 9.5 GHz and the absorbing frequency band （AFB） is about 4 GHz.
基金The study is supported by the Key Research Program of the Ministry of National Education(Authorized No.:00191)the Natural Science Foundation of Jiangxi Province(Authorized No.:0150032).
文摘Al2O3 short fiber reinforced La-bearing Al-5%Cu alloy was fabricated by squeeze casting, and the solidified structure and the solute segregation during alloy solidification were studied. The results indicated that La has been enriched near the interface which is favorable to improve the wettability between the fiber and At alloy, but the RE-rich phase was not formed at the interface. At the end of the solidification of the composites, the change of the solute in the surplus liquid phase results in the type of matrix alloy being changed because of the selective crystallization, and the segregation at the interface is finally formed. There is no special influence by La on the Cu segregation in the matrix alloy.
文摘A unique SiC whisker wheel was invented,in which the whiskers were aligned normally to the grinding wheel surface.In this paper,grindabilities of the SiC whisker wheel are investigated and compared with those of other wheels of SiC grains,Al2O3 grains,as well as Al2O3 long and short fibres which were also aligned normally to the grinding wheel surface,respectively.The main research contents concern grinding characteristics of a directionally aligned SiC whisker wheel such as material-removal volume,wheel-wear rates,integrity of the ground surfaces,grinding ratios and grinding efficiency.Furthermore,grinding wheels of whiskers and fibres have a common disadvantage:they tend to load easily.The authors have proposed a simple method of loading-free grinding to overcome this propensity and investigate some related grinding characteristics under loading-free grinding conditions.
文摘The effects of Al 2O 3 fiber on wear characteristics of eutectic Al-Si alloy composites were studied using a pin-on-disk tester under dry sliding condition. The results show that the Al 2O 3 fiber can make matrix grain be fine, specially the eutectic Si be finer and prevent the plastic flow of matrix and prohibit the crack propagation in the wear layer, thereby it can remarkably improve the mechanical property and the wear resistance of the MMCs. Since Al 2O 3 fiber plays a role of certain framework in protecting the matrix against crash, it can eliminate the severe wear of MMCs with higher φ f of fiber from the beginning of test. At mild stage, when φ f is in the range of 8%～10%, the wear rates are the lowest. With increasing φ f of Al 2O 3 fiber, the wear mechanism of MMCs can be transformed from adhesive delamination to brittle breakaway.
文摘A number of nanostructured carbon materials were proposed as new effective promoters for preparing modified Cu/ZnO/Al 2O 3 catalyst system for efficient hydrogen production from methanol steam reforming. Compared to the catalysts modified by other type of carbon materials, the ACF-promoted catalyst prepared via carbonate-coprecipitation method exhibit the highest performance in the low-temperature steam reforming of methanol. It was suggested that the intrinsic high surface area nature of ACF material may favor the generation of modified catalysts with a high surface area and improved component dispersion, thus leading to improved performance for methanol steam reforming.
