In this study,femtosecond laser assisted-chemical vapor infiltration(LA-CVI)was employed to produce C/SiC composites with 1,3,and 5 rows of mass transfer channels.The effect of laser machining power on the quality of ...In this study,femtosecond laser assisted-chemical vapor infiltration(LA-CVI)was employed to produce C/SiC composites with 1,3,and 5 rows of mass transfer channels.The effect of laser machining power on the quality of produced holes was investigated.The results showed that the increase in power yielded complete hole structures.The as-obtained C/SiC composites with different mass transfer channels displayed higher densification degrees with flexural strengths reaching 546±15 MPa for row mass transfer channel of 3.The strengthening mechanism of the composites was linked to the increase in densification and formation of"dense band"during LA-CVI process.Multiphysics finite element simulations of the dense band and density gradient of LA-CVI C/SiC composites revealed C/SiC composites with improved densification and lower porosity due to the formation of"dense band"during LA-CVI process.In sum,LA-CVI method is promising for future preparation of ceramic matrix composites with high densities.展开更多
以某铅蓄电池厂污染场地5个铅污染区域(WS、A、B、C及BZ)的土壤为研究对象,对土壤中铅全量及各形态含量进行分析.在0.1 mol.L-1EDTA,30 min,25℃相同条件下,使用超声波辅助化学洗脱(ultrasonic-assisted chemical extraction,UCE)与传...以某铅蓄电池厂污染场地5个铅污染区域(WS、A、B、C及BZ)的土壤为研究对象,对土壤中铅全量及各形态含量进行分析.在0.1 mol.L-1EDTA,30 min,25℃相同条件下,使用超声波辅助化学洗脱(ultrasonic-assisted chemical extraction,UCE)与传统化学洗脱(conventional chemical extraction,CCE)两种不同的作用方式,对铅的去除效率进行比较,并对两种不同清洗方式后铅的形态变化进行了探讨.结果表明,UCE对铅的去除效率显著优于CCE.在CCE作用下,5份污染土壤WS、A、B、C、BZ铅的去除效率依次为10.06%、48.29%、48.69%、53.28%及36.26%,而UCE作用下铅的去除效率依次为22.42%、69.31%、71.00%、74.49%及71.58%,平均效率高出22%.通过对比两种清洗方式后土壤中的铅形态发现,酸可提取态在UCE作用后持平或有所降低,但CCE后使酸溶态有增高的趋势;对于铁锰氧化态,UCE对其有着极好的去除能力,可达98%左右,同时对有机物及硫化物结合态、残渣态也具有较好的去除能力.因此,UCE在化学萃取中的应用具有一定的可行性,是一种简单、极快速去除污染场地中重金属铅的增效手段.展开更多
为了有效改善硅基负极材料的性能及降低制备成本,以微米级单质硅为原料,通过金属辅助化学刻蚀法制备多孔硅负极材料,该方法步骤简单可控、成本低廉,易于大规模生产。采用场发射扫描电镜和电池测试系统,对比分析不同工艺参数下制得的硅...为了有效改善硅基负极材料的性能及降低制备成本,以微米级单质硅为原料,通过金属辅助化学刻蚀法制备多孔硅负极材料,该方法步骤简单可控、成本低廉,易于大规模生产。采用场发射扫描电镜和电池测试系统,对比分析不同工艺参数下制得的硅负极材料的形貌和性能差异,从而进行工艺优化,并得出较优的工艺参数:Ag NO_(3)浓度约为0.015 mol/L、伽伐尼反应时间选择1~4 min、刻蚀剂中C_(HF)/(C_(H_(2)O_(2))+C_(HF))为70%~90%。在合适的工艺参数下制备的多孔硅负极材料电化学性能明显优于硅负极材料,在0.5C倍率下循环50次后容量仍有1 130.7 m A·h/g,在2C、5C的倍率下仍有929、669 m A·h/g的较高比容量。该方法得到的多孔硅负极材料能够有效缓解单质硅负极材料体积膨胀严重和导电性差的问题,从而有效提高其电化学性能。展开更多
基金support from the National Natural Science Foundation of China(Nos.51972269 and 51672217)the Fundamental Research Funds for the Central Universities(No.3102019ghxm014)the Creative Research Foundation of the Science and Technology on Thermostructural Composite Materials Laboratory(No.JCKYS2020607001)。
文摘In this study,femtosecond laser assisted-chemical vapor infiltration(LA-CVI)was employed to produce C/SiC composites with 1,3,and 5 rows of mass transfer channels.The effect of laser machining power on the quality of produced holes was investigated.The results showed that the increase in power yielded complete hole structures.The as-obtained C/SiC composites with different mass transfer channels displayed higher densification degrees with flexural strengths reaching 546±15 MPa for row mass transfer channel of 3.The strengthening mechanism of the composites was linked to the increase in densification and formation of"dense band"during LA-CVI process.Multiphysics finite element simulations of the dense band and density gradient of LA-CVI C/SiC composites revealed C/SiC composites with improved densification and lower porosity due to the formation of"dense band"during LA-CVI process.In sum,LA-CVI method is promising for future preparation of ceramic matrix composites with high densities.
文摘以某铅蓄电池厂污染场地5个铅污染区域(WS、A、B、C及BZ)的土壤为研究对象,对土壤中铅全量及各形态含量进行分析.在0.1 mol.L-1EDTA,30 min,25℃相同条件下,使用超声波辅助化学洗脱(ultrasonic-assisted chemical extraction,UCE)与传统化学洗脱(conventional chemical extraction,CCE)两种不同的作用方式,对铅的去除效率进行比较,并对两种不同清洗方式后铅的形态变化进行了探讨.结果表明,UCE对铅的去除效率显著优于CCE.在CCE作用下,5份污染土壤WS、A、B、C、BZ铅的去除效率依次为10.06%、48.29%、48.69%、53.28%及36.26%,而UCE作用下铅的去除效率依次为22.42%、69.31%、71.00%、74.49%及71.58%,平均效率高出22%.通过对比两种清洗方式后土壤中的铅形态发现,酸可提取态在UCE作用后持平或有所降低,但CCE后使酸溶态有增高的趋势;对于铁锰氧化态,UCE对其有着极好的去除能力,可达98%左右,同时对有机物及硫化物结合态、残渣态也具有较好的去除能力.因此,UCE在化学萃取中的应用具有一定的可行性,是一种简单、极快速去除污染场地中重金属铅的增效手段.
文摘为了有效改善硅基负极材料的性能及降低制备成本,以微米级单质硅为原料,通过金属辅助化学刻蚀法制备多孔硅负极材料,该方法步骤简单可控、成本低廉,易于大规模生产。采用场发射扫描电镜和电池测试系统,对比分析不同工艺参数下制得的硅负极材料的形貌和性能差异,从而进行工艺优化,并得出较优的工艺参数:Ag NO_(3)浓度约为0.015 mol/L、伽伐尼反应时间选择1~4 min、刻蚀剂中C_(HF)/(C_(H_(2)O_(2))+C_(HF))为70%~90%。在合适的工艺参数下制备的多孔硅负极材料电化学性能明显优于硅负极材料,在0.5C倍率下循环50次后容量仍有1 130.7 m A·h/g,在2C、5C的倍率下仍有929、669 m A·h/g的较高比容量。该方法得到的多孔硅负极材料能够有效缓解单质硅负极材料体积膨胀严重和导电性差的问题,从而有效提高其电化学性能。
