High speed steel has been widely used in various fields due to their excellent red hardness and good wear resistance. However, the influence of mischmetal （Ce-La） on the as-cast microstructures and mechanical proper...High speed steel has been widely used in various fields due to their excellent red hardness and good wear resistance. However, the influence of mischmetal （Ce-La） on the as-cast microstructures and mechanical properties of high speed steel has rarely been reported. Thus, the microstructure and mechanical properties of M2 high speed steel with addition of mischmetal （Ce-La） were investigated. The morphology and distribution of the eutectic carbides of the steel were observed by using optical microscopy and scanning electron microscopy, and the impact toughness and bending strength were tested. The results show that adding mischmetal has an obvious effect on the microstructure and mechanical properties of M2 high speed steel. The coarse eutectic structure is refined, the weak connection of the carbide networks is broken and the flake carbides become short and fine. More networks of eutectic carbides dissolve into the matrix. When a suitable adding content of mischmetal is selected, for example, 0.3 mass%, the impact strength and bending strength can increase by 27% and 10.76% compared with that without misehmetal, respectively.展开更多
目的探讨球囊扩张或血管支架补救治疗对急性大脑中动脉M1段机械取栓治疗失败患者的安全性和有效性,并分析患者预后的影响因素。方法回顾性分析2014年1月至2018年6月中国人民解放军陆军军医大学第二附属医院综合卒中中心和其他19家综合...目的探讨球囊扩张或血管支架补救治疗对急性大脑中动脉M1段机械取栓治疗失败患者的安全性和有效性,并分析患者预后的影响因素。方法回顾性分析2014年1月至2018年6月中国人民解放军陆军军医大学第二附属医院综合卒中中心和其他19家综合卒中中心80例急性大脑中动脉M1段机械取栓治疗失败并行补救治疗达到闭塞血管血流改良脑梗死溶栓分级(modi?ed thrombolysis in cerebral infarction score,m TICI)≥2b级患者的临床资料,根据补救治疗方法将其分为球囊扩张组(30例)和血管支架植入组(50例)。比较两组患者90 d改良Rankin量表(modi?ed Rankin scale,m RS)评分、血管再闭塞率、症状性颅内出血发生率及死亡率,并对影响患者预后的相关因素进行多因素Logistic回归分析。结果球囊扩张组中90 d mRS评分0～2分患者占比明显高于血管支架植入组(P <0.05);两组患者血管再闭塞率、死亡率及症状性颅内出血发生率比较均无显著差异(P_均> 0.05)。多因素Logistic回归分析显示:卒中病史(OR=8.968,95%CI:1.162～69.196,P=0.035)、补救治疗方式(OR=0.243,95%CI:0.066～0.894,P=0.033)、侧支循环(OR=3.873,95%CI:1.029～14.576,P=0.045)及基线美国国立卫生研究院卒中量表(National Institute of Health stroke scale,NIHSS)评分(OR=0.809,95%CI:0.701～0.934,P=0.004)均为急性大脑中动脉M1段闭塞取栓失败后行补救治疗患者神经功能预后的独立危险因素(P_均<0.05)。结论机械取栓联合球囊扩张能够有效改善急性大脑中动脉M1段闭塞性缺血性脑卒中患者神经功能,并未增加手术风险,且补救治疗方式是影响患者治疗后神经功能的独立危险因素。展开更多
Lithium metal batteries(LMBs) with a high theoretical capacity are seen as a type of the most potential energy storage system.Unfortunately,the growth of lithium dendrite,the irreversible side reactions,and the infini...Lithium metal batteries(LMBs) with a high theoretical capacity are seen as a type of the most potential energy storage system.Unfortunately,the growth of lithium dendrite,the irreversible side reactions,and the infinite volume alteration still curb the practical utilization of lithium metal anodes,resulting in low Coulombic efficiency(CE) and safety problems,etc.Herein,we synthesize a lithiophilic 3D copper foam host with uniformly distributed nano-flower-like ZnO particles(CuF/ZnO) and obtain the composite lithium metal anode containing the Li_(2)O,LiZn alloy,and pure Li by the infusion of molten Li(CuF/Li_(2)O-LiZn@Li).Benefitting from the advantages of the 3D structure of copper foam and the lithiophilicity of ZnO sites,the composite lithium metal anode can restrain the volume alternation and regulate the uniform deposition of lithium.The symmetrical cells of the composite lithium metal anode have a 1600 h long cycle life with a low polarization voltage of 15 mV,and the Coulombic efficiency can maintain about 97.8% at 1.0 mA·cm^(-2),1.0mAh·cm^(-2).展开更多
为研究脉冲等离子爆炸工艺制备H13钢(4Cr5Mo Si V1)表面改性层的组织和性能,通过对显微组织形貌、相结构、残余应力、硬度和耐磨性的分析,对脉冲等离子爆炸工艺的改性机制和影响进行了讨论。结果表明,脉冲等离子爆炸工艺使H13钢表面发...为研究脉冲等离子爆炸工艺制备H13钢(4Cr5Mo Si V1)表面改性层的组织和性能,通过对显微组织形貌、相结构、残余应力、硬度和耐磨性的分析,对脉冲等离子爆炸工艺的改性机制和影响进行了讨论。结果表明,脉冲等离子爆炸工艺使H13钢表面发生快速熔凝和快速淬火过程,在材料表面形成厚度均匀、组织致密、高硬度的改性层;改性层中马氏体细化,同时由于不同物理变化过程分别形成残余奥氏体和逆变奥氏体;随着脉冲次数的增加,材料表面的残余应力经历了由压应力先增大后减小然后转变成拉应力的过程;改性层的厚度和硬度随脉冲次数的增加而提高,但同时表面熔化程度加剧,表层低硬度熔凝区厚度增加。当脉冲次数为8次时,H13钢具有最优的耐磨损性能。展开更多
基金Item Sponsored by Key Project of National Research Program of China(2011BAC10B04)National Natural Science Foundation of China(51201075)
文摘High speed steel has been widely used in various fields due to their excellent red hardness and good wear resistance. However, the influence of mischmetal （Ce-La） on the as-cast microstructures and mechanical properties of high speed steel has rarely been reported. Thus, the microstructure and mechanical properties of M2 high speed steel with addition of mischmetal （Ce-La） were investigated. The morphology and distribution of the eutectic carbides of the steel were observed by using optical microscopy and scanning electron microscopy, and the impact toughness and bending strength were tested. The results show that adding mischmetal has an obvious effect on the microstructure and mechanical properties of M2 high speed steel. The coarse eutectic structure is refined, the weak connection of the carbide networks is broken and the flake carbides become short and fine. More networks of eutectic carbides dissolve into the matrix. When a suitable adding content of mischmetal is selected, for example, 0.3 mass%, the impact strength and bending strength can increase by 27% and 10.76% compared with that without misehmetal, respectively.
文摘目的探讨球囊扩张或血管支架补救治疗对急性大脑中动脉M1段机械取栓治疗失败患者的安全性和有效性,并分析患者预后的影响因素。方法回顾性分析2014年1月至2018年6月中国人民解放军陆军军医大学第二附属医院综合卒中中心和其他19家综合卒中中心80例急性大脑中动脉M1段机械取栓治疗失败并行补救治疗达到闭塞血管血流改良脑梗死溶栓分级(modi?ed thrombolysis in cerebral infarction score,m TICI)≥2b级患者的临床资料,根据补救治疗方法将其分为球囊扩张组(30例)和血管支架植入组(50例)。比较两组患者90 d改良Rankin量表(modi?ed Rankin scale,m RS)评分、血管再闭塞率、症状性颅内出血发生率及死亡率,并对影响患者预后的相关因素进行多因素Logistic回归分析。结果球囊扩张组中90 d mRS评分0～2分患者占比明显高于血管支架植入组(P <0.05);两组患者血管再闭塞率、死亡率及症状性颅内出血发生率比较均无显著差异(P_均> 0.05)。多因素Logistic回归分析显示:卒中病史(OR=8.968,95%CI:1.162～69.196,P=0.035)、补救治疗方式(OR=0.243,95%CI:0.066～0.894,P=0.033)、侧支循环(OR=3.873,95%CI:1.029～14.576,P=0.045)及基线美国国立卫生研究院卒中量表(National Institute of Health stroke scale,NIHSS)评分(OR=0.809,95%CI:0.701～0.934,P=0.004)均为急性大脑中动脉M1段闭塞取栓失败后行补救治疗患者神经功能预后的独立危险因素(P_均<0.05)。结论机械取栓联合球囊扩张能够有效改善急性大脑中动脉M1段闭塞性缺血性脑卒中患者神经功能,并未增加手术风险,且补救治疗方式是影响患者治疗后神经功能的独立危险因素。
基金financially supported by the School Research Startup Expenses of Harbin Institute of Technology (Shenzhen) (Nos.DD29100027 and DD45001022)the National Natural Science Foundation of China (No.52002094)+4 种基金Guangdong Basic and Applied Basic Research Foundation (No. 2019A1515110756)Shenzhen Science and Technology Program (Nos.JCYJ20210324121411031,JSGG202108021253804014 and RCBS20210706092218040)the Open Fund of Guangdong Provincial Key Laboratory of Advanced Energy Storage materials (No. asem202107)the Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering (No.2022-K16)Shenzhen Steady Support Plan (No. GXWD20201230155427003-20200824103000001)。
文摘Lithium metal batteries(LMBs) with a high theoretical capacity are seen as a type of the most potential energy storage system.Unfortunately,the growth of lithium dendrite,the irreversible side reactions,and the infinite volume alteration still curb the practical utilization of lithium metal anodes,resulting in low Coulombic efficiency(CE) and safety problems,etc.Herein,we synthesize a lithiophilic 3D copper foam host with uniformly distributed nano-flower-like ZnO particles(CuF/ZnO) and obtain the composite lithium metal anode containing the Li_(2)O,LiZn alloy,and pure Li by the infusion of molten Li(CuF/Li_(2)O-LiZn@Li).Benefitting from the advantages of the 3D structure of copper foam and the lithiophilicity of ZnO sites,the composite lithium metal anode can restrain the volume alternation and regulate the uniform deposition of lithium.The symmetrical cells of the composite lithium metal anode have a 1600 h long cycle life with a low polarization voltage of 15 mV,and the Coulombic efficiency can maintain about 97.8% at 1.0 mA·cm^(-2),1.0mAh·cm^(-2).
文摘为研究脉冲等离子爆炸工艺制备H13钢(4Cr5Mo Si V1)表面改性层的组织和性能,通过对显微组织形貌、相结构、残余应力、硬度和耐磨性的分析,对脉冲等离子爆炸工艺的改性机制和影响进行了讨论。结果表明,脉冲等离子爆炸工艺使H13钢表面发生快速熔凝和快速淬火过程,在材料表面形成厚度均匀、组织致密、高硬度的改性层;改性层中马氏体细化,同时由于不同物理变化过程分别形成残余奥氏体和逆变奥氏体;随着脉冲次数的增加,材料表面的残余应力经历了由压应力先增大后减小然后转变成拉应力的过程;改性层的厚度和硬度随脉冲次数的增加而提高,但同时表面熔化程度加剧,表层低硬度熔凝区厚度增加。当脉冲次数为8次时,H13钢具有最优的耐磨损性能。
