Pitch and TiB2/C green composite cathode material were respectively analyzed with simultaneous DSC-TGA, and effects of three baking processes of TiB2/C composite cathode material, i.e. K25, K5 and M5, on properties of...Pitch and TiB2/C green composite cathode material were respectively analyzed with simultaneous DSC-TGA, and effects of three baking processes of TiB2/C composite cathode material, i.e. K25, K5 and M5, on properties of TiB2/C composite cathode material were investigated. The results show that thermogravimetrie behavior of pitch and TiB2/C green composite cathode is similar, and appears the largest mass loss rate in the temperature range from 200 to 600 ℃. The bulk density variation of sample K5 before and after baking is the largest （11.9%）, that of sample K25 is the second, and that of sample M5 is the smallest （6.7%）. The crushing strength of sample M5 is the biggest （51.2 MPa）, that of sample K2.5 is the next, and that of sample K5 is the smallest （32.8 MPa）. But, the orders of the electrical resistivity and electrolysis expansion of samples are just opposite with the order of crushing strength. The heating rate has a great impact on the microstructure of sample. The faster the heating rate is, the bigger the pore size and porosity of sample are. Compared with the heating rate between 200 and 600℃ of samples K25 and K5, that of sample M5 is slower and suitable for baking process of TiB2/C composite cathode material.展开更多
The cutting performance of particulate reinforced me tallic matrix composites(PRMMCs) SiC p/Al in ultrasonic vibration cutting and c ommon cutting with carbide tools and PCD tools was researched in the paper. Mic rost...The cutting performance of particulate reinforced me tallic matrix composites(PRMMCs) SiC p/Al in ultrasonic vibration cutting and c ommon cutting with carbide tools and PCD tools was researched in the paper. Mic rostructure of machined surface was described, the relation between cutting para meters and surface roughness was presented, and characteristic of the surface re mained stress was also presented. Furthermore, wear regularity and abrasion resi stance ability of tools in ultrasonic vibration cutting and common cutting o f PRMMCs were discussed in detail. The test results show: (1) The surface config urations are obviously different when using different tools to machine such PRMM Cs. The surface machined with carbide tools looks luminous and orderly and there are seldom surface defects on it. The reason is that the soft basal body is apt to flow during cutting, therefore a layer of Al matrix film covers machined sur face. On the contrary, the surface machined with PCD tools looks lackluster. But the profile of machined surface is very clear. Superfine grooves, pits and blac k reinforce particulates can be seen easily without obvious Al film. (2) Because of unstable cutting process in common cutting, the surface is easy to produce s ome defects such as burrs, built-up edges and so on so that the quality of surf ace becomes very poor. Vibration cutting can reduce the influence of tearing, pl astic deformation and built-up edge in cutting and can restrain flutter so as t o make cutting process more stable. Therefore, surface roughness of vibration cu tting is better than that of common cutting. (3) There is an optimum value of fe ed rate in vibration cutting of PRMMCs due to the influence of material characte ristics. Whether feed rate is more than or less than this optimum value, surface roughness will increase. (4) According to analyzing the wear rate of tools in v ibration cutting PRMMCs, it can be concluded that abrasion resistance of tools w ill be improved remarkably when vibration cutting composites have a lower pe rcentage of reinforce particulate. If the percentage of reinforce particulate is higher, the influence on abrasion resistance of carbide tool in vibration cut ting will not be obvious. The research result indicates that vibration cutting effect has a close relation with material characteristics.展开更多
基金Project (2005CB623703) supported by the Major State Basic Research and Development Program of ChinaProject (2008AA030502) supported by the National High-Tech Research and Development Program of China
文摘Pitch and TiB2/C green composite cathode material were respectively analyzed with simultaneous DSC-TGA, and effects of three baking processes of TiB2/C composite cathode material, i.e. K25, K5 and M5, on properties of TiB2/C composite cathode material were investigated. The results show that thermogravimetrie behavior of pitch and TiB2/C green composite cathode is similar, and appears the largest mass loss rate in the temperature range from 200 to 600 ℃. The bulk density variation of sample K5 before and after baking is the largest （11.9%）, that of sample K25 is the second, and that of sample M5 is the smallest （6.7%）. The crushing strength of sample M5 is the biggest （51.2 MPa）, that of sample K2.5 is the next, and that of sample K5 is the smallest （32.8 MPa）. But, the orders of the electrical resistivity and electrolysis expansion of samples are just opposite with the order of crushing strength. The heating rate has a great impact on the microstructure of sample. The faster the heating rate is, the bigger the pore size and porosity of sample are. Compared with the heating rate between 200 and 600℃ of samples K25 and K5, that of sample M5 is slower and suitable for baking process of TiB2/C composite cathode material.
文摘The cutting performance of particulate reinforced me tallic matrix composites(PRMMCs) SiC p/Al in ultrasonic vibration cutting and c ommon cutting with carbide tools and PCD tools was researched in the paper. Mic rostructure of machined surface was described, the relation between cutting para meters and surface roughness was presented, and characteristic of the surface re mained stress was also presented. Furthermore, wear regularity and abrasion resi stance ability of tools in ultrasonic vibration cutting and common cutting o f PRMMCs were discussed in detail. The test results show: (1) The surface config urations are obviously different when using different tools to machine such PRMM Cs. The surface machined with carbide tools looks luminous and orderly and there are seldom surface defects on it. The reason is that the soft basal body is apt to flow during cutting, therefore a layer of Al matrix film covers machined sur face. On the contrary, the surface machined with PCD tools looks lackluster. But the profile of machined surface is very clear. Superfine grooves, pits and blac k reinforce particulates can be seen easily without obvious Al film. (2) Because of unstable cutting process in common cutting, the surface is easy to produce s ome defects such as burrs, built-up edges and so on so that the quality of surf ace becomes very poor. Vibration cutting can reduce the influence of tearing, pl astic deformation and built-up edge in cutting and can restrain flutter so as t o make cutting process more stable. Therefore, surface roughness of vibration cu tting is better than that of common cutting. (3) There is an optimum value of fe ed rate in vibration cutting of PRMMCs due to the influence of material characte ristics. Whether feed rate is more than or less than this optimum value, surface roughness will increase. (4) According to analyzing the wear rate of tools in v ibration cutting PRMMCs, it can be concluded that abrasion resistance of tools w ill be improved remarkably when vibration cutting composites have a lower pe rcentage of reinforce particulate. If the percentage of reinforce particulate is higher, the influence on abrasion resistance of carbide tool in vibration cut ting will not be obvious. The research result indicates that vibration cutting effect has a close relation with material characteristics.
