Copper-graphite composites were prepared by spark plasma sintering(SPS)using coppercoated graphite powder.Hydrophobic surfaces were successfully constructed by chemical etching and surface treatment.The density,metall...Copper-graphite composites were prepared by spark plasma sintering(SPS)using coppercoated graphite powder.Hydrophobic surfaces were successfully constructed by chemical etching and surface treatment.The density,metallographic structure,microstructure,Shore hardness,resistivity,water contact angle,and friction/wear properties of the composites were investigated using the Archimedes drainage method,a metallographic microscope,a scanning electron microscope,a hardness tester,a resistometer,a surface science tester,and a friction tester.The results showed that the relative density and Shore hardness of the copper-graphite composites increased slightly from 90.04%and 56 HSD to 92.66%and 59 HSD,respectively,when the sintering temperature increased from 700 to 900℃.The copper and graphite phases in the copper-graphite composites were uniformly distributed with a continuous and network-like structure at various sintering temperatures.The interface between the copper and graphite was in good condition,without any obvious cracks or voids.The optimum process for hydrophobic surface construction included etching with a 1 mol/L K_(2)Cr_(2)O_(7)-H_(2)SO_(4)solution for 1 min,and soaking in a 0.09 mol/L cetylbenzene sulfonic acid alcohol solution for 1 h.The contact angle of the copper-graphite composite reached 130°.Hydrophobic treatment was beneficial for reducing the friction coefficient(from 0.18-0.19 to 0.13-0.15)and the wear rate(from 4.1-6.2×10^(-3)to 1.1-2.1×10^(-3)mm^(3)/(N·m)),demonstrating obvious antifriction and wear-resisting properties.The resistivities of the hydrophobic-treated samples increased slightly,from(4-8)×10^(-7)Ω·m to(5-15)×10^(-7)Ω·m,meeting the resistivity requirements of copper-graphite composite pantograph sliders and current receiver sliders in actual working conditions.展开更多
背景热带岛礁特殊气候与当地常见病的发生相关,热带常见病特征的研究报道较少。目的回顾性分析热带岛礁某二级医院门诊就诊情况,探讨与大陆常见疾病谱的差异性,为热带岛礁常见病精准化防治提供参考。方法按照国际疾病分类(International...背景热带岛礁特殊气候与当地常见病的发生相关,热带常见病特征的研究报道较少。目的回顾性分析热带岛礁某二级医院门诊就诊情况,探讨与大陆常见疾病谱的差异性,为热带岛礁常见病精准化防治提供参考。方法按照国际疾病分类(International Classification of Diseases,ICD)-10标准,统计分析热带岛礁某二级医院2016年1月-2019年12月门诊病历中62870例次诊断信息。结果就诊人群18~30岁年龄段占比最高(60.15%),男性(95.83%)占比远高于女性(4.17%)。按人体系统分,排名前5位的是肌肉骨骼系统和结缔组织疾病(19.15%)、呼吸系统疾病(17.57%)、消化系统疾病(15.50%)、皮肤和皮下组织疾病(10.24%)、损伤和中毒(8.13%)。按疾病类型分,排名前5位的是上呼吸道感染(9.81%)、腰痛(5.64%)、意外事故(5.58%)、皮炎(2.96%)、陈旧性肌肉劳损(2.08%)。结论热带岛礁常见疾病中上呼吸道感染是主要疾病类型,病原体不明确,存在流感暴发风险,应提高检测能力,予以针对性防控;同时应提高肌肉骨骼系统疾病和皮肤、皮下组织疾病的防治。展开更多
基金the Open Subject of The State Key Laboratory of Heavy Duty AC Drive Electric Locomotive Systems Integration(No.172195100710)。
文摘Copper-graphite composites were prepared by spark plasma sintering(SPS)using coppercoated graphite powder.Hydrophobic surfaces were successfully constructed by chemical etching and surface treatment.The density,metallographic structure,microstructure,Shore hardness,resistivity,water contact angle,and friction/wear properties of the composites were investigated using the Archimedes drainage method,a metallographic microscope,a scanning electron microscope,a hardness tester,a resistometer,a surface science tester,and a friction tester.The results showed that the relative density and Shore hardness of the copper-graphite composites increased slightly from 90.04%and 56 HSD to 92.66%and 59 HSD,respectively,when the sintering temperature increased from 700 to 900℃.The copper and graphite phases in the copper-graphite composites were uniformly distributed with a continuous and network-like structure at various sintering temperatures.The interface between the copper and graphite was in good condition,without any obvious cracks or voids.The optimum process for hydrophobic surface construction included etching with a 1 mol/L K_(2)Cr_(2)O_(7)-H_(2)SO_(4)solution for 1 min,and soaking in a 0.09 mol/L cetylbenzene sulfonic acid alcohol solution for 1 h.The contact angle of the copper-graphite composite reached 130°.Hydrophobic treatment was beneficial for reducing the friction coefficient(from 0.18-0.19 to 0.13-0.15)and the wear rate(from 4.1-6.2×10^(-3)to 1.1-2.1×10^(-3)mm^(3)/(N·m)),demonstrating obvious antifriction and wear-resisting properties.The resistivities of the hydrophobic-treated samples increased slightly,from(4-8)×10^(-7)Ω·m to(5-15)×10^(-7)Ω·m,meeting the resistivity requirements of copper-graphite composite pantograph sliders and current receiver sliders in actual working conditions.
文摘背景热带岛礁特殊气候与当地常见病的发生相关,热带常见病特征的研究报道较少。目的回顾性分析热带岛礁某二级医院门诊就诊情况,探讨与大陆常见疾病谱的差异性,为热带岛礁常见病精准化防治提供参考。方法按照国际疾病分类(International Classification of Diseases,ICD)-10标准,统计分析热带岛礁某二级医院2016年1月-2019年12月门诊病历中62870例次诊断信息。结果就诊人群18~30岁年龄段占比最高(60.15%),男性(95.83%)占比远高于女性(4.17%)。按人体系统分,排名前5位的是肌肉骨骼系统和结缔组织疾病(19.15%)、呼吸系统疾病(17.57%)、消化系统疾病(15.50%)、皮肤和皮下组织疾病(10.24%)、损伤和中毒(8.13%)。按疾病类型分,排名前5位的是上呼吸道感染(9.81%)、腰痛(5.64%)、意外事故(5.58%)、皮炎(2.96%)、陈旧性肌肉劳损(2.08%)。结论热带岛礁常见疾病中上呼吸道感染是主要疾病类型,病原体不明确,存在流感暴发风险,应提高检测能力,予以针对性防控;同时应提高肌肉骨骼系统疾病和皮肤、皮下组织疾病的防治。
