The MAX phase Ti3SiC2 has broad application prospects in the field of rail transit,nuclear protective materials and electrode materials due to its excellent electrical conductivity,selflubricating properties and wear ...The MAX phase Ti3SiC2 has broad application prospects in the field of rail transit,nuclear protective materials and electrode materials due to its excellent electrical conductivity,selflubricating properties and wear resistance.Cu–Ti3SiC2 co-continuous composites have superior performance due to the continuous distribution of 3 D network structures.In this paper,the Cu/Ti3SiC2(Ti C/Si C)co-continuous composites are formed via vacuum infiltration process from Cu and Ti3SiC2 porous ceramics.The co-continuous composites have significantly improved the flexural strength and conductivity of Ti3SiC2 due to the addition of Cu,with the conductivity up to 5.73×10^5 S/m,twice as high as the Ti3SiC2 porous ceramics and five times higher than graphite.The reaction between ingredients leads to an increase in the friction coefficient,while the hard reaction products(Ti Cx,Si C)lower the overall wear rate(1×10^–3 mm^3/(N·m)).Excellent electrical conductivity and wear resistance make co-continuous composites more advantageous in areas such as rail transit.展开更多
Investigation has been made on the process of synthesizing SiC/Al co-continuous composite by spontaneous melt infiltration. It is found that nitrogen atmosphere is an indispensable factor for spontaneous infiltration ...Investigation has been made on the process of synthesizing SiC/Al co-continuous composite by spontaneous melt infiltration. It is found that nitrogen atmosphere is an indispensable factor for spontaneous infiltration of melt Al into SiC preform with continuous porosity. The critical temperature for spontaneous infiltration occurrence can be lowered and spontaneous infiltration rate increased by doping a small amount of Mg into the Al alloy. Adding fine SiO2 powders into the ceramic preform can play the similar role as Mg-doping by increasing wetting through the chemical reaction of 3SiO2+4AI=2Al2O3+3Si at the infiltration front. Infiltration rate can also be increased by Si-doping to lower the viscosity of the molten Al alloy. In addition, sufficient Si content in the molten Al is also indispensable to avoid the formation of Al4C in the synthesized composite.展开更多
文摘The MAX phase Ti3SiC2 has broad application prospects in the field of rail transit,nuclear protective materials and electrode materials due to its excellent electrical conductivity,selflubricating properties and wear resistance.Cu–Ti3SiC2 co-continuous composites have superior performance due to the continuous distribution of 3 D network structures.In this paper,the Cu/Ti3SiC2(Ti C/Si C)co-continuous composites are formed via vacuum infiltration process from Cu and Ti3SiC2 porous ceramics.The co-continuous composites have significantly improved the flexural strength and conductivity of Ti3SiC2 due to the addition of Cu,with the conductivity up to 5.73×10^5 S/m,twice as high as the Ti3SiC2 porous ceramics and five times higher than graphite.The reaction between ingredients leads to an increase in the friction coefficient,while the hard reaction products(Ti Cx,Si C)lower the overall wear rate(1×10^–3 mm^3/(N·m)).Excellent electrical conductivity and wear resistance make co-continuous composites more advantageous in areas such as rail transit.
基金National Natural Sciellce Foundation of China under grant !No. 59601001
文摘Investigation has been made on the process of synthesizing SiC/Al co-continuous composite by spontaneous melt infiltration. It is found that nitrogen atmosphere is an indispensable factor for spontaneous infiltration of melt Al into SiC preform with continuous porosity. The critical temperature for spontaneous infiltration occurrence can be lowered and spontaneous infiltration rate increased by doping a small amount of Mg into the Al alloy. Adding fine SiO2 powders into the ceramic preform can play the similar role as Mg-doping by increasing wetting through the chemical reaction of 3SiO2+4AI=2Al2O3+3Si at the infiltration front. Infiltration rate can also be increased by Si-doping to lower the viscosity of the molten Al alloy. In addition, sufficient Si content in the molten Al is also indispensable to avoid the formation of Al4C in the synthesized composite.
文摘目的比较不同浓度罗哌卡因切口持续浸润对乳腺癌患者术后镇痛的效果,以期筛选提高乳腺癌患者术后镇痛的最佳方法。方法选择行乳腺癌根治术的患者156例作为研究对象,根据手术顺序编号,采用随机数字表法随机分为A、B、C 3组,每组52例,所有患者均由同一组医护人员行乳腺癌根治术。A组患者术后采用0.2%浓度罗哌卡因持续浸润手术切口,B组患者采用0.3%浓度罗哌卡因持续浸润手术切口,C组患者采用0.4%浓度罗哌卡因持续浸润手术切口,比较3组患者术后12、24、48、72 h视觉模拟评分(VAS),术后12、24、48 h血清前列腺素(PG)、一氧化氮(NO)、5-羟色胺(5-HT)、神经肽Y(NPY)、β-内啡肽(β-EP)水平。结果术后12、24、48、72 h,B、C组患者VAS评分均低于A组患者,差异均有统计学意义(P﹤0.05),C组患者VAS评分略低于B组患者,但两组比较差异均无统计学意义(P﹥0.05)。3组患者术前PG、NO、5-HT、NPY、β-EP水平比较,差异均无统计学意义(P﹥0.05);3组患者术后12、24、48 h血清PG水平均低于术前,血清NO、5-HT、NPY、β-EP水平均高于术前,差异均有统计学意义(P﹤0.05)。C组患者术后12、24、48 h PG水平均高于A组、B组,NO、5-HT、NPY、β-EP水平均低于A组、B组;B组患者术后12、24、48 h PG水平均高于A组,NO、5-HT、NPY、β-EP水平均低于A组,差异均有统计学意义(P﹤0.05)。结论浓度0.4%的罗哌卡因对乳腺癌根治术患者术后镇痛的效果更为明显,可能由于患者对VAS测试的主观性较强,与0.3%浓度比较VAS评分的差异未能体现,需进一步制定合理研究方案进行验证。
