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SiC-Glass涂层碳/碳复合材料的中低温氧化行为及机制研究
作者: 李龙, 曾燮榕, 李贺军, 熊信柏, 谢盛辉, 邹继兆, 唐汉玲 主题: 碳/碳复合材料, 抗氧化涂层, 氧化机制 年份: 2009
摘要: 为揭示具有良好高温(1300~1600℃)抗氧化性能的sic-glass涂层在中低温(500~1200℃)条件下的氧化防护性能,对sic-glass涂层碳/碳(c/c)复合材料的中低温氧化行为和机制进行了系统研究。结果表明,sic-glass涂层c/c复合材料的中低温氧化失重服从直线规律,但氧化机制存在温度依赖性,可分为2个区段:(1)低温区(500~800℃),氧化失重速率与温度服从arrhenius关系,氧化主要受控于氧在涂层缺陷内的扩散速率;(2)在中温区(800~1200℃),氧化失重速率与温度不服从arrhenius关系,氧化过程受氧在涂层缺陷中的扩散、sic内涂层材料的氧化、glass外涂层的部分熔融愈合等多种因素联合控制。对比分析表明,sic-glass涂层的中低温抗氧化性能不及其高温抗氧化性能优异。中低温下,涂层缺陷愈合不充分是导致这一现象的主要原因。
短切碳纤维增强碳化硅复合材料的氧化性能研究
作者: 唐汉玲, 曾燮榕, 熊信柏, 李龙, 邹继兆 主题: Csf/SiC复合材料, 等温氧化, 抗氧化性能 年份: 2009
摘要: 采用热压烧结法制备了致密的短切碳纤维增强碳化硅(csf/sic)复合材料.借助热重分析、xrd、sem等手段对该材料等温氧化性能进行了研究.研究结果表明,该复合材料在900℃氧化时失重最为严重;之后,随着氧化温度升高,失重率逐渐减少;在1450℃以上则表现为增重.复合材料在低于900℃氧化时,主要是由于碳纤维氧化造成的失重;在900~1450℃氧化区间,复合材料表面的短切碳纤维被氧化,基体生成保护性的氧化膜,材料内部的短切碳纤维受到基体和氧化膜的有效保护,能够继续发挥增韧作用.因此,csf/sic复合材料在此温度范围内具有良好的抗氧化能力;当复合材料在1600℃氧化时,氧化反应剧烈,材料破坏严重,失去了抗氧化能力.
碳/碳复合材料TaSi_2/SiC氧化保护涂层(英文)
作者: 史小红, 曾燮榕, 李贺军, 付前刚, 邹继兆 主题: 碳/碳复合材料, 涂层, TaSi2, SiC 年份: 2011
摘要: 为提高碳/碳复合材料在高温下的氧化防护性能,利用包埋技术在碳/碳复合材料表面制备了tasi2/sic复合涂层。通过xrd、sem和eds分析了涂层的晶相结构和形貌特征,在1773k的空气介质中对tasi2/sic涂层碳/碳复合材料进行等温氧化实验。结果表明,复合涂层厚度为200μm,涂层中含有sic,si和tasi2相,并且涂层中没有明显裂纹出现。eds结果显示外层tasi2相可有效地填充内层sic涂层的空隙,使得内外两层涂层之间没有明显的界面,等温氧化实验曲线说明tasi2/sic复合涂层在1773k的空气介质中可有效保护碳/碳复合材料233h。
制备温度对热解炭包覆磷酸铁锂/气相生长炭纤维复合正极材料的影响
作者: 邓飞, 曾燮榕, 邹继兆, 黎晓华 主题: 磷酸铁锂, 热解炭, 气相生长炭纤维, 微波化学气相沉积, 锂离子电池 年份: 2011
摘要: 采用微波化学气相沉积法一步合成了热解炭包覆磷酸铁锂/气相生长炭纤维复合正极材料.借助x射线衍射仪、场发射扫描电子显微镜、高分辨透射电镜和电化学测试仪等测试手段研究了不同制备温度对材料晶体结构、显微形貌和电化学性能的影响.结果表明,当制备温度由500℃升至600℃时,磷酸铁锂主晶相的颗粒尺寸没有发生明显变化,而原位vgcf的网络程度却明显增加,材料的放电比容量随之提高;当制备温度进一步升高到700℃时,磷酸铁锂颗粒异常生长现象加剧,vgcf直径较大且粗细不均,材料的电化学性能变差.研究发现,当温度为600℃时,材料表现出较优的电化学性能,25℃在0.2c、0.5c、1c和3c倍率下的放电比容量分别可达163、159、153和143mah/g.
Effect of melt superheating treatment on crystallization behavior and magnetic properties of melt-spun Fe-rich Nd-Fe-B ribbons
作者: 盛洪超, 曾燮榕, 胡强, 邓飞 主题: microstructure, nanocomposite magnets, melt superheating treatment, rare earths 年份: 2010
摘要: melt-spun nd7fe90b3 ribbons were prepared under different melt treatment conditions,i.e.,the melt temperature was varied prior to ejection onto the quenching wheel.the microstructure characteristics,crystallization behavior,and subsequent magnetic properties of α-fe/nd2fe14b-based exchange-spring magnets were investigated using x-ray diffraction,differential scanning calorimeter,transmission electron microscopy,and vibrating sample magnetometer.it was shown that melt spinning at different quenching temperatures caused the as-quenched ribbons to have distinctive crystallization behavior.under high quenching temperature,precipitation of tbcu7 type phase was inhibited during crystallization,resulting in remarkable reduction of grain size.this led to strengthening of exchange coupling effect between the magnetically hard and soft phase and improvement of magnetic properties of annealed ribbons.
微波水热辅助电沉积法制备Bi_2S_3薄膜
作者: 王艳, 黄剑锋, 朱辉, 曹丽云, 薛小霜, 曾燮榕 主题: Bi2S3, 薄膜, 电沉积, 微波水热 年份: 2010
摘要: 采用微波水热辅助电沉积法在ito导电玻璃表面制备了形貌均匀具有纳米棒、纳米板状结构的bi2s3薄膜。利用xrd、xps、场发射扫描显微镜(fesem)、tem和uv-vis-nearir对薄膜的结构、形貌、光学性能进行了表征。结果显示微波水热辅助电沉积法制备的bi2s3薄膜具有良好的结晶性能;随着微波水热温度的提高,所制备bi2s3薄膜的结晶性能先增强后降低,合适的温度是130℃。与电沉积法制得薄膜相比,采用微波水热辅助电沉积法制得bi2s3薄膜的禁带宽度由1.44ev增加到1.84ev。
Effect of super heat treatment on crystallization behavior and magnetic properties of Nd_(4.5)Fe_(77)B_(18.5) nanocomposites
作者: 盛洪超, 曾燮榕, 邹继兆, 谢盛辉 主题: nanocomposite magnets, amorphous alloys, superheat treatment, rare earths 年份: 2010
摘要: melt-spun nd4.5fe77b18.5 ribbons were prepared under various superheat temperatures.the microstructure characteristics,crystallization behavior,and subsequent magnetic properties of fe3b/nd2fe14b nanocomposite magnets were investigated using x-ray diffraction,differential thermal analysis,and vibrating sample magnetometry.it was shown that melt spinning at different quenching temperatures caused the as-quenched ribbons to have distinctive crystallization behavior.depending on superheat temperature,phase transformation of the ribbons during annealing may take place in one of the following sequences:(1) amorphous phase(am)→am'+fe3b→fe3b+ nd2fe23b3→ fe3b+nd2fe14b,or(2) amorphous phase(am)→am'+fe3b→fe3b+nd2fe14b.for the latter,the ribbon after optimal annealing exhibited single-phase magnetic behavior.in the first case,magnetic properties of the optimally heat treated ribbons deteriorated and an apparent kink could be seen along the demagnetization curves near the zero field.
Influence of deposition voltage on phase, microstructure and antioxidation property of cristobalite aluminum phosphate coatings
作者: 杨文冬, 黄剑锋, 曹丽云, 曾燮榕 主题: carbon/carbon composites, aluminum phosphate, hydrothermal electrophoretic deposition, deposition voltage, micro-structure, antioxidation 年份: 2010
摘要: cristobalite aluminum phosphate (c-alpo_4) coatings were prepared by a hydrothermal electrophoretic deposition process on sic-coated c/c composites. phase compositions and microstructures of the as-prepared coatings were characterized by xrd and sem analyses. the influence of deposition voltage on the phase, microstructure and antioxidation property of the cristobalite aluminum phosphate coatings was investigated. results show that the as-prepared coatings are composed of cristobalite aluminum phosphate crystallites. the thickness and density of cristobalite aluminum phosphate coatings are improved with the increase of deposition voltage. the deposition amount and bonding strength of the cristobalite aluminum phosphate coatings also increase with the increase of deposition voltage. the deposition mass per unit area of the coatings and the square root of the deposition time at different hydrothermal voltages satisfy linear relationship. the antioxidation property of the coated c/c composites is improved with t...
水热温度对碳/碳复合材料表面HAp/壳聚糖生物复合涂层的影响
作者: 李颖华, 黄剑锋, 曹丽云, 曾燮榕 主题: 水热电泳沉积, 水热温度, 羟基磷灰石, 壳聚糖, 碳/碳复合材料 年份: 2010
摘要: 以声化学法合成的纳米羟基磷灰石(hap)为起始原料,以异丙醇作为分散介质,采用水热电泳沉积法在经壳聚糖(cs)溶液改性后的碳/碳复合材料(c/c)表面沉积hap/cs生物复合涂层。重点研究水热温度对复合涂层晶相、形貌的影响及涂层的沉积动力学机理。采用x射线衍射仪(xrd)、透射电子显微镜(tem)、傅立叶变换红外光谱分析仪(ftir)和扫描电子显微镜(sem)对所制备的涂层进行表征。结果表明:随着水热温度的升高,涂层表面由微晶疏松结合的多孔结构向紧密结合的多孔结构转变,涂层的内聚力增强;涂层的沉积速率随水热温度的升高而增加,涂层的沉积活化能为43.58kj/mol。
块体非晶合金的剪切带演变与结构研究
作者: 谢盛辉, 郑子越, 曾燮榕, 胡强, 符冬菊 主题: 特种合金, 块体非晶合金, 塑性应变, 剪切带, 驰豫过剩自由体积, 纳米孔洞 年份: 2010
摘要: 研究单轴准静态压缩时zr基块体非晶合金的剪切带特征,结合热膨胀测试研究剪切引起的非晶合金结构变化.结果表明,初始剪切带彼此独立(εp<2%),形核和初始扩展方向具有随机性,然后分叉(εp>2%)和相互交割(εp≥6.49%),次生剪切带逐渐与受力方向成45°,剪切带的次生和扩展受切应力影响较大;变形初期(εp<3%),剪切变形伴随新生自由体积,对应的驰豫过剩自由体积增多,过冷液相区最大黏度增大;塑性应变进一步增大,剪切带相互交割,对应的驰豫过剩自由体积和黏度急剧减少.
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