溴甲酚绿-稀土配合物的热变色性能及变色机理

以稀土金属离子(La3+、Ce3+和Nd3+等)为显色剂,溴甲酚绿为发色剂和配位剂,制备了一系列稀土配合物可逆热变色材料,测试其综合变色性能,讨论了显色剂种类及用量、溶剂用量对稀土配合物热变色性能的影响。FT-IR、UV-Vis和DSC测试结果表明,热变色机理可归结为分子间的电子得失,随着温度变化,溴甲酚绿的结构在内酯式和醌式之间转变,颜色随之改变。     

高比能锂离子电池富锂正极材料研究进展

富锂正极材料被认为是高比能锂离子电池的潜在正极材料之一,其能够提供约300 mA·h/g的可逆容量,相比于目前商业化正极材料具有明显优势.然而初始Coulombic效率低、电压衰减、容量衰减等阻碍了其实际应用.本综述针对2类富锂材料包括富锂锰基材料和富锂阳离子无序材料,详细介绍其晶体结构、阳离子氧化还原机制、阴离子氧化...     

超薄层超晶格GaAs/AlAs(001)的电子结构

本文讨论了SU(N.M)的空间对称性和布里渊区经折叠后的特殊性质。使用分区变分法计算了超薄层超晶格(GaAs)_n/(AlAs)_n(n=1,2,3)的能带,运用四个势场调整参数所算出的能带和实验结果基本相符。结果表明,(GaAs)_1—(AlAs)_1为间接能隙半导体,禁带宽度为1.87eV,导带底位于Z_x点(1,0,0)(2π/a)。而(GaAs)_n—(AlAs)(n≥2)则为直接能隙半导体,且禁带宽度E_g随着n的增大而减小。并将计算结果和别的理论结果、实验数据作了比较和分析。     

Electrical measurement on individual multi-walled carbon nanotubes

The characterization of electrical property of multi-walled carbon nanotubes （MWCNTs） on a nanometer scale is essential for their potential application in nano-electronic devices. The MWCNTs were synthesized on Fe2O3/SiO2/Si substrate and Pt plate substrate by simple thermal chemical vapor deposition （STCVD） technique and the electrical measurements of individual MWCNT grown on silicon substrate and Pt plate substrate were performed by home-made ＇nano-manipulator＇, respectively. According to current-voltage curves obtained in the experiments the current density that the MWCNTs can carry is calculated to be about 10^7 A/cm^2, which is much larger than that of normal metals.     

Growth of straight carbon nanotubes by simple thermal chemical vapor deposition

Straight carbon nanotubes （CNTs） were achieved by simple thermal chemical vapor deposition（STCVD） catalyzed by Mo-Fe alloy catalyst on silica supporting substrate at 700 ℃. High-resolution transmission electron microscopy images show that the straight CNTs are well graphitized with no attached amorphous carbon. Mo-Fe alloy catalyst particles play a very crucial role in the growth of straight CNTs. The straight carbon nanotubes contain much less defects than the curved nanotubes and might have potential applications for nanoelectrical devices in the future. The simple synthesis of straight CNTs may have benefit for large-scale productions.     

赤热石墨棒在乙醇中快速淬火制备多壁碳纳米管

为了满足各种纳米电子学应用的需求，发展新的制备碳纳米管的方法引起人们特别的关注。最近，作者研究了乙醇催化化学气相沉积法来制备多壁碳纳米管。然而，这种方法需要使用金属催化剂，这使得产物中带有杂质。提出了一种采用将赤热石墨棒在乙醇中快速淬火制备多壁碳纳米管的方法，利用这种方法制备的碳纳米管没有催化剂杂质。利用高分辨透射电子显微术对制备的碳纳米管进行了表征。实验结果表明，制备的产物是多壁碳纳米管。由于这种方法制备碳纳米管不需要催化剂，因此它是一种经济的制备碳纳米管的方法。     

软模板法制备纳米TiO2介孔材料

以三嵌段共聚物EO20PO70EO20(P123)为模板剂,异丙醇钛(简称TTIP)为无机钛源,在适量强酸的催化作用下,由软模板法合成出TiO2介孔材料的前驱体凝胶后,经老化、煅烧得到了TiO2介孔材料.分别利用X射线衍射仪、高分辨率透射电子显微镜以及比表面积与孔径分析仪对制得的TiO2介孔材料的结构、形貌、比表面积和孔径进行了表征,并探讨了煅烧温度对介孔形成的影响.结果表明:通过调整原料的比例,在400℃下煅烧可得到局部结晶有序、比表面积大的纳米TiO2介孔材料.     

超薄层超晶格GaAs/AIAs(001)的能带结构

<正> 自1970年Esaki和Tsu提出超晶格(SL)设想以来,超晶格薄膜和超晶格器件作为一种人工调制结构,正愈来愈受到人们的重视,取得了很大进展。 对于厚层超晶格SL(n,m),n,m均大于8,用Krong-Penny模型和有效质量方程在理论上获得了和实验一致的结果。但对于超薄层超晶格SL(n,m),2≤n+m≤12的研究则刚刚开始,在理论和实验上尚不完善。目前国外用紧束缚法、赝势法和自洽赝势法来计算超薄层超晶格的能带结构,计算工作量较大,且结果并不完全一致。笔者用分区变分法来计算超薄层超晶格的能带结构,方法简便,且获得了和实验结果基本符合的数据。     

Selective growth of carbon nanotube on silicon substrates

The carbon nanotube （CNT） growth of iron oxide-deposited trench-patterns and the locally-ordered CNT arrays on silicon substrate were achieved by simple thermal chemical vapor deposition（STCVD） of ethanol vapor. The CNTs were uniformly synthesized with good selectivity on trench-patterned silicon substrates. This fabrication process is compatible with currently used semiconductor-processing technologies, and the carbon-nanotube fabrication process can be widely applied for the development of electronic devices using carbon-nanotube field emitters as cold cathodes and can revolutionize the area of field-emitting electronic devices. The site-selective growth of CNT from an iron oxide nanoparticle catalyst patterned were also achieved by drying-mediated self-assembly technique. The present method offers a simple and cost-effective method to grow carbon nanotubes with self-assembled patterns.