High-resolution X-ray diffractometry(HRXRD)was used to assess the quality of 6H-SiC crystals grown by sublimation method.The results show the occurrence of low-angle grain boundaries(LB)is close relative to the inclin...High-resolution X-ray diffractometry(HRXRD)was used to assess the quality of 6H-SiC crystals grown by sublimation method.The results show the occurrence of low-angle grain boundaries(LB)is close relative to the inclination of the crystal interface.At the central faceted region with 0°inclination the crystal is of high structural perfection.However,at the region close to the facet with less than 5°inclination LB occurs slightly and at the region close to the peripheral polytype ring with more than 5°inclination LB defect occurs heavily.The density of LB can be drastically reduced by decreasing radial temperature gradient that determines the shape of the crystal growth interface.展开更多
Under electron beam irradiation,the in-situ formation of 2H-SiC dentritic nanocrystals from amorphous silicon carbide at room temperature was observed.The homogenous transition mainly occurs at the thin edge and on th...Under electron beam irradiation,the in-situ formation of 2H-SiC dentritic nanocrystals from amorphous silicon carbide at room temperature was observed.The homogenous transition mainly occurs at the thin edge and on the surface of specimen where the energy obtained from electron beam irradiation is high enough to cause the amorphous crystallizing into 2H-SiC.展开更多
基于CiteSpace软件对CNKI和Web of science数据库中关于三峡库区消落带的已发表文献进行可视化分析,从文献计量视角探讨了三峡库区消落带研究的现状、进展及热点演变。结果表明,(1)截止2019年底,检索到相关中文文献936篇,英文文献225篇...基于CiteSpace软件对CNKI和Web of science数据库中关于三峡库区消落带的已发表文献进行可视化分析,从文献计量视角探讨了三峡库区消落带研究的现状、进展及热点演变。结果表明,(1)截止2019年底,检索到相关中文文献936篇,英文文献225篇;国内外三峡消落带研究论文数量均存在缓慢增长-快速增长-波动稳定的发展过程,中文文献年发文量近两年有降低趋势;(2)研究团队主要集中在重庆、湖北地区的高校和研究所,以西南大学、重庆大学、中国地质大学、中国科学院等为主,形成了较为稳定的研究团队,但各机构及团队之间合作交流较薄弱;(3)发文期刊,中文以《生态学报》、《环境科学》、《长江流域资源与环境》为主,外文以《Environmental Science and Pollution Research》《Ecological Engineering》《PLoS One》发文较多,外文高水平期刊发文较少;(4)研究热点主要以植物、土壤两大生态要素为轴心,高频关键词有“水位变化”“水淹”“土壤”“重金属”“狗牙根”“riparian zone”“vegetation”“sediment”等;分析表明三峡水库消落带研究内容主要包括水位波动下植物群落逆向演替与格局变化、植物对水淹胁迫的生理生态响应、植被恢复技术研发、消落带微生物群落演变、土壤养分或重金属的赋存与迁移过程以及溶解性有机质特征等,近年来消落带重金属环境行为、消落带生境异质性的生态效应、生态格局与水库安全的关系等问题成为研究热点。然而,单一要素和单一过程研究限制了消落带研究的系统性,相关研究陷入瓶颈;新技术方法的运用以及生态系统观的引入是未来三峡消落带研究突破的关键,应开展消落带生境异质性带来的生态过程的复杂性研究,同时加强消落带植物-土壤-水耦合长期观测,探索消落带生态恢复技术及其持续的生态影响。展开更多
基金Project supported National Natural Science Foundation of China(60025409 and 50472068)National"863"High Technology Plan(2001AA311080)
文摘High-resolution X-ray diffractometry(HRXRD)was used to assess the quality of 6H-SiC crystals grown by sublimation method.The results show the occurrence of low-angle grain boundaries(LB)is close relative to the inclination of the crystal interface.At the central faceted region with 0°inclination the crystal is of high structural perfection.However,at the region close to the facet with less than 5°inclination LB occurs slightly and at the region close to the peripheral polytype ring with more than 5°inclination LB defect occurs heavily.The density of LB can be drastically reduced by decreasing radial temperature gradient that determines the shape of the crystal growth interface.
基金Project supproted by the National Natural Science Foundation of China(60025409 and 50472068)National"863"High Technology Plan(2001AA311080)Program for New Century Excellent Talents in Shangdong University
文摘Under electron beam irradiation,the in-situ formation of 2H-SiC dentritic nanocrystals from amorphous silicon carbide at room temperature was observed.The homogenous transition mainly occurs at the thin edge and on the surface of specimen where the energy obtained from electron beam irradiation is high enough to cause the amorphous crystallizing into 2H-SiC.
文摘基于CiteSpace软件对CNKI和Web of science数据库中关于三峡库区消落带的已发表文献进行可视化分析,从文献计量视角探讨了三峡库区消落带研究的现状、进展及热点演变。结果表明,(1)截止2019年底,检索到相关中文文献936篇,英文文献225篇;国内外三峡消落带研究论文数量均存在缓慢增长-快速增长-波动稳定的发展过程,中文文献年发文量近两年有降低趋势;(2)研究团队主要集中在重庆、湖北地区的高校和研究所,以西南大学、重庆大学、中国地质大学、中国科学院等为主,形成了较为稳定的研究团队,但各机构及团队之间合作交流较薄弱;(3)发文期刊,中文以《生态学报》、《环境科学》、《长江流域资源与环境》为主,外文以《Environmental Science and Pollution Research》《Ecological Engineering》《PLoS One》发文较多,外文高水平期刊发文较少;(4)研究热点主要以植物、土壤两大生态要素为轴心,高频关键词有“水位变化”“水淹”“土壤”“重金属”“狗牙根”“riparian zone”“vegetation”“sediment”等;分析表明三峡水库消落带研究内容主要包括水位波动下植物群落逆向演替与格局变化、植物对水淹胁迫的生理生态响应、植被恢复技术研发、消落带微生物群落演变、土壤养分或重金属的赋存与迁移过程以及溶解性有机质特征等,近年来消落带重金属环境行为、消落带生境异质性的生态效应、生态格局与水库安全的关系等问题成为研究热点。然而,单一要素和单一过程研究限制了消落带研究的系统性,相关研究陷入瓶颈;新技术方法的运用以及生态系统观的引入是未来三峡消落带研究突破的关键,应开展消落带生境异质性带来的生态过程的复杂性研究,同时加强消落带植物-土壤-水耦合长期观测,探索消落带生态恢复技术及其持续的生态影响。
