光电振荡器是一种能够稳定产生自激振荡的微波光子共振系统,近年来得到了广泛的研究,工作频率达到数百GHz,相位噪声性能达到-163 dBc/Hz at 6 kHz,调谐范围达到数十千兆赫兹。文章回顾了光电振荡器问世以来的部分研究进展和重要应用,重...光电振荡器是一种能够稳定产生自激振荡的微波光子共振系统,近年来得到了广泛的研究,工作频率达到数百GHz,相位噪声性能达到-163 dBc/Hz at 6 kHz,调谐范围达到数十千兆赫兹。文章回顾了光电振荡器问世以来的部分研究进展和重要应用,重点介绍了近年来集成化光电振荡器的研究现状,并提出了一种可应用于集成化光电振荡器的新型电光晶体材料。展开更多
以柠檬酸为螯合剂和还原剂,NH4VO3为钒源,通过溶胶-凝胶法制备了锂离子电池正极材料Li3V2(PO4)3及其三元掺杂体系Li2.85Na0.15V1.9Al0.1(PO4)2.9F0.1.分别采用X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)、能量损失谱(EELS)、拉曼(Ram...以柠檬酸为螯合剂和还原剂,NH4VO3为钒源,通过溶胶-凝胶法制备了锂离子电池正极材料Li3V2(PO4)3及其三元掺杂体系Li2.85Na0.15V1.9Al0.1(PO4)2.9F0.1.分别采用X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)、能量损失谱(EELS)、拉曼(Raman)光谱、扫描电子显微镜(SEM)、X射线能谱(EDS)、恒流充放电、循环伏安(CV)和交流阻抗谱(EIS)等技术对材料的微观结构、颗粒形貌和电化学性能进行分析.结果表明:在残余碳包覆的基础上,Na、Al、F三元掺杂有利于稳定Li3V2(PO4)3的晶体结构,进一步减少颗粒团聚和提升材料导电特性,促进第三个锂离子的脱出和嵌入,从而显著改善Li3V2(PO4)3的实用电化学性能.未经掺杂的Li3V2(PO4)3原粉在1/9C、1C和6C倍率下的可逆比容量分别为141、119和98 m Ah g–1,而三元掺杂改性材料在1/9C、1C、8C和14C倍率下的比容量分别为172、139、119和115 m Ah g–1.在1C倍率下循环300圈后,掺杂体系的比容量依然高达118 m Ah g–1,比原粉高出32.6%.值得注意的是,这种三元掺杂还使Li3V2(PO4)3的多平台放电曲线近似转变为一条斜线,显示出可能不同的储锂机制.展开更多
ZnSe nanocrystals doped in silica were prepared by using sol-gel process and in situ growth technique. It was found that when n(Zn)∶n(Se)=1∶1 in the sol precursor, the resultant ZnSe nanocrystals were rather instabl...ZnSe nanocrystals doped in silica were prepared by using sol-gel process and in situ growth technique. It was found that when n(Zn)∶n(Se)=1∶1 in the sol precursor, the resultant ZnSe nanocrystals were rather instable and after several days the color of the ZnSe nanocrystals-doped SiO 2 glass changed from yellow to red. According to the analysis results of XRD, UV-Vis transmission spectra and XPS, the existence of many zinc vacancies in the ZnSe nanocrystals was considered as the reason of the instability. Based on this reason, the synthesis process was improved by introducing much larger amount of zinc to the precursor sol and this made the stability of the ZnSe nanocrystals improved greatly from several days to more than 6 months.展开更多
文摘光电振荡器是一种能够稳定产生自激振荡的微波光子共振系统,近年来得到了广泛的研究,工作频率达到数百GHz,相位噪声性能达到-163 dBc/Hz at 6 kHz,调谐范围达到数十千兆赫兹。文章回顾了光电振荡器问世以来的部分研究进展和重要应用,重点介绍了近年来集成化光电振荡器的研究现状,并提出了一种可应用于集成化光电振荡器的新型电光晶体材料。
文摘以柠檬酸为螯合剂和还原剂,NH4VO3为钒源,通过溶胶-凝胶法制备了锂离子电池正极材料Li3V2(PO4)3及其三元掺杂体系Li2.85Na0.15V1.9Al0.1(PO4)2.9F0.1.分别采用X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)、能量损失谱(EELS)、拉曼(Raman)光谱、扫描电子显微镜(SEM)、X射线能谱(EDS)、恒流充放电、循环伏安(CV)和交流阻抗谱(EIS)等技术对材料的微观结构、颗粒形貌和电化学性能进行分析.结果表明:在残余碳包覆的基础上,Na、Al、F三元掺杂有利于稳定Li3V2(PO4)3的晶体结构,进一步减少颗粒团聚和提升材料导电特性,促进第三个锂离子的脱出和嵌入,从而显著改善Li3V2(PO4)3的实用电化学性能.未经掺杂的Li3V2(PO4)3原粉在1/9C、1C和6C倍率下的可逆比容量分别为141、119和98 m Ah g–1,而三元掺杂改性材料在1/9C、1C、8C和14C倍率下的比容量分别为172、139、119和115 m Ah g–1.在1C倍率下循环300圈后,掺杂体系的比容量依然高达118 m Ah g–1,比原粉高出32.6%.值得注意的是,这种三元掺杂还使Li3V2(PO4)3的多平台放电曲线近似转变为一条斜线,显示出可能不同的储锂机制.
文摘ZnSe nanocrystals doped in silica were prepared by using sol-gel process and in situ growth technique. It was found that when n(Zn)∶n(Se)=1∶1 in the sol precursor, the resultant ZnSe nanocrystals were rather instable and after several days the color of the ZnSe nanocrystals-doped SiO 2 glass changed from yellow to red. According to the analysis results of XRD, UV-Vis transmission spectra and XPS, the existence of many zinc vacancies in the ZnSe nanocrystals was considered as the reason of the instability. Based on this reason, the synthesis process was improved by introducing much larger amount of zinc to the precursor sol and this made the stability of the ZnSe nanocrystals improved greatly from several days to more than 6 months.
