掺钽对二氧化钛压敏电阻性能的影响

研究了钽对二氧化钛压敏电阻性能的影响。研究中发现掺入 0 .2 5mol %Ta2 O5的样品显示出最低的反转电压 (Eb= 6V/mm)、最高的非线性常数 (α =8.8)以及最高的相对介电常数 (εr=6 .2× 10 4 ) ,与样品电容和电阻的频谱特性相一致。样品的性能变化可用Ta5+ 对Ti4 + 的掺杂取代和该取代存在的饱和值来解释     

CSD法制备SrBi2Ta2O9粉体

为了解决乙醇钽、醋酸锶、硝酸铋在乙二醇中的溶解问题,分别以醋酸、乙醇胺、吡啶、甘露醇作为络合剂,对比研究了4种络合剂对溶液稳定性和粉体物相的影响,利用X射线衍射、透射电镜和热重-差热仪分析了粉体的相组成、微观形态和热分解历程,结果表明,以乙醇胺作为络合剂,通过化学溶液分解(CSD)法可以获得稳定的SBT溶液;稳定的SBT溶液经干燥,300℃焙烧30min和800℃煅烧1h,可获得粒径约为100nm的钙钛矿相SBT粉体。     

Pyrolytic Synthesis of Carbon Nanotubes from Sucrose on a Mesoporous Silicate

Multi-wall carbon nanotubes were synthesized from sucrose by a pyrolytic technique using mesopourous MCM-41 silicate templates without transition metal catalysts. The nanotubes were examined in the carbon/silicate composite and after dissolution of the silicate. High-resolution transmission electron microscopy study of the multi-wall nanotubes showed them to be 15 nm in diameter, 200 nm in length and close-ended. There was variation in crystallinity with some nanotubes showing disordered wall structures.     

化学气相沉积法制备Ta2O5薄膜的研究进展

Ta2O5是重要的介电材料和光波导材料.从前驱体的选择方面综述了化学气相沉积法制备Ta2O5薄膜的研究进展,说明了五卤化钽和Ta金属有机化合物对CVD过程的影响,对这两类前驱体的优缺点进行了比较和评述,讨论了Ta2O5的生成机理,并对其发展方向作了简要的展望.     

Production and superconducting properties of laboratory scale NbTi and NbTiTa multifilamentary cables

A comparison of high field, low temperature superconducting properties between a Nb47^w/o Ti and two NbTiTa alloys as bases of laboratory scale cables was carried out Optimization cycles needed to obtain fair superconducting properties imply intermediate thermal treatments in the range 380–400°C during deformation at cold-work of 70%. The ternary alloys exhibit excellent ductile properties as do NbTi alloys. After an adequate optimization cycle the alloy Nb38^w/o Ti34^w/o Ta showed the best high field superconducting properties with values of more than 600 A mm^?2 at 12 Tesla and 2.15 K.     

还原氧化钽制备钽粉工艺研究进展

评述了几种由氧化钽还原制取钽粉的新工艺。并阐述了不同方法的工艺原理、特点和产品特性。钠还原法反应时间短,还原温度范围广,能过得到高纯度高比表面的钽粉。FFC法具有工艺简单,污染小,成本低的特点,可以用来制备电容器级粉末。SOM法电解速度快,具有很好的发展前景。采用镁蒸汽还原能够得到性能好的钽粉,但是还原时间长,还原装置复杂。     

电解液的循环使用对阳极氧化Ta2O5纳米管形貌的影响

以高纯钽片为原料,将其依次放入体积比为9:1的H2 SO4/HF电解液中进行阳极氧化,制备了五氧化二钽(Ta2 O5)纳米管.采用扫描电子显微镜(SEM)表征了第2、10、25、35、50片上制备的Ta2 O5纳米管的形貌,研究了电解液的循环使用对阳极氧化Ta2 O5纳米管形貌的影响规律.实验结果表明,随着电解液循环使用次数的增加,Ta2 O5纳米管顶部由团簇变为松散、管长变长、管径基本保持稳定,纳米管之间缝隙逐渐增大,这都与电解液中溶质F-的浓度及分布均匀性的变化相关.     

薄壁碳纳米管的制取

采用催化裂解法,以二氯苯为碳源,二茂铁为催化剂,制取了薄壁碳纳米管.引入多壁碳纳米管的薄壁指数?来表征多壁碳纳米管的薄壁程度.研究了氢气流量、反应温度和催化剂浓度对薄壁碳纳米管制取的影响.确定了制取薄壁碳纳米管的优化参数:反应温度为850℃,催化剂浓度为0.06g/ml,氩气流量为500ml/min,氢气流量为200ml/min,反应溶液进给量为0.012ml/min.制备出薄壁指数达5.6的大中空薄壁碳纳米管.     

聚乙烯亚胺功能化多壁碳纳米管的制备及对硫化氢气体的吸附性能

采用聚乙烯亚胺(PEI)对多壁碳纳米管(MWCNTs)进行功能化,并用红外、热失重、拉曼对聚乙烯亚胺改性的碳纳米管进行表征,红外光谱和热失重曲线表明聚乙烯亚胺成功键合到多壁碳纳米管上,拉曼光谱中碳纳米管的D/G比(D峰面积比G峰面积)从0.8398变成1.2364,说明碳纳米管的缺陷程度明显增加,这种缺陷的增加是由碳纳米管表面引入了PEI导致的。利用紫外吸收光谱探究聚乙烯亚胺功能化的多壁碳纳米管(MWCNTs-PEI)对硫化氢的吸收及其可逆性。MWCNTs-PEI对硫化氢的首次吸收效率为0.16 mmol/g,2次重复吸收后仍有0.13 mmol/g的吸收效率,说明MWCNTs-PEI能够对硫化氢起到吸收作用并且具有很好的可逆性。     

Controlled Synthesis of One‐Dimensional Inorganic Nanostructures Using Pre‐Existing One‐Dimensional Nanostructures as Templates

Template‐directed strategy has become one of the most popular methods for the fabrication of one‐dimensional (1D) nanostructures with uniform size and controllable physical dimensions in recent years. This Review article describes the recent progress in the synthesis of 1D inorganic nanostructures by using suitable templates. A brief survey on the templating method based on the organic templates and porous membrane is firstly given. Then, the article is focused on recent emerging synthetic strategies by templating against the pre‐existing 1D nanostructures using different physical and chemical transformation techniques, including epitaxial growth, nonepitaxial growth, direct chemical transformation, solid‐state interfacial diffusion reaction, and so on. The important reactivity role of the 1D nanostructures will be emphasized in such transformation process. Finally, we conclude this paper with some perspectives and outlook on this research topic.     

Polydopamine Spheres as Active Templates for Convenient Synthesis of Various Nanostructures

In this work, monodisperse polydopamine (PDA) spheres with tunable diameters have been synthesized through a facile and low cost method using a deionized water and alcohol mixed solvent. The PDA spheres possess surface functional groups (–OH, –NH₂), exhibiting an extraordinary versatile active nature. It is demonstrated that the PDA spheres could serve as an active template for the convenient synthesis of various nanostructures, e.g., MnO₂ hollow spheres or PDA/Fe₃O₄ and PDA/Ag core/shell nanostructures. No surface modification or special treatment is required for the synthesis of these nanostructures, which makes the fabrication process simple and very convenient. The novel application of PDA/Fe₃O₄ spheres as fillers in nanocomposites for high‐performance capacitors is demonstrated, indicating a promising practicality. The PDA spheres provide a new general platform not only for the facile assembly of nanostructures but also a green synthetic template for practical applications.     

Light‐Induced Motion of Microengines Based on Microarrays of TiO2 Nanotubes

An electrochemical approach for manufacturing light‐driven nanostructured titanium dioxide (TiO₂) microengines with controlled spatial architecture for improved performance is reported. The microengines based on microscale arrays of TiO₂ nanotubes with variable (50–120 nm) inner diameter show a quasi‐ordered arrangement of nanotubes, being the smallest tubular entities for catalytic microengines reported to date. The nanotubes exhibit well defined crystalline phases depending upon the postfabrication annealing conditions that determine the microengines' efficiency. When exposed to UV‐light, the microarrays of TiO₂ nanotubes exhibiting conical internal shapes show directed motion in confined space, both in the presence and absence of hydrogen peroxide. In the former case, two different motion patterns related to diffusiophoresis and localized nanobubble generation inside of the tubes due to the photocatalytic decomposition of H₂O₂ are disclosed. Controlled pick‐up, transport, and release of individual and agglomerated particles are demonstrated using the UV light irradiation of microengines. The obtained results show that light‐driven microengines based on microarrays of TiO₂ nanotubes represent a promising platform for controlled micro/nanoscale sample transportation in fluids as well as for environmental applications, in particular, for the enhanced photocatalytic degradation of organic pollutants due to the improved intermixing taking place during the motion of TiO₂ microengines.     

碳纳米管及碳纳米管纤维的性能与应用

碳纳米管是由单层或多层石墨片卷曲而成的无缝纳米级管状壳层结构。扼要介绍了碳纳米管、碳纳米管纤维的合成方法及近几年来国内外制备的各种碳纳米管产品。碳纳米管、碳纳米管纤维由于其优良的力学、电学特性可以制成气体吸附体、生物模板、传动装置、增强复合体、催化剂载体、探测器、传感器、纳米反应器等产品，在航空、能源、医药、化学等技术领域广泛应用。     

尿素-过氧化氢混合模板法合成介孔二氧化硅

以尿素-过氧化氢为混合模板、正硅酸乙酯为硅源,在酸性条件下,通过溶胶-凝胶过程合成二氧化硅介孔材料。采用煅烧法除去模板剂,用红外光谱、XRD、N2吸附-脱附、HRTEM等分析测试手段对介孔材料的结构和形态进行了表征。结果表明:与以尿素为单一模板相比,采用混合模板剂所合成介孔材料为蠕虫状,孔径分布基本保持不变、比表面积相近(分别为445、431m2/g)、孔径(分别为7.04、8.11nm)和孔体积(分别为0.783、0.874cm3/g)明显增大。     

Formation of monodispersed Ta2O5 powders

The Ta₂O₅ powders synthesized by the hydrolysis of tantalum pentaethoxide, Ta(OC₂H₅)₅ in alcoholic solution were monodispersed fine oxide particles, which were a uniform, spherical shape, non-agglomerate, and had a narrow size distribution. They grew to 1.2m after ageing for 1 h after hydrolysis. Powder X-ray diffraction and differential thermal analysisthermogravimetric analysis showed the particles were amorphous and hydrated. These particles lost the water at 290° C and gave well-crystalline Ta₂O at 740° C. Throughout these thermal processes, the particle morphology was kept almost the same.     

多壁碳纳米管复合V2O5材料的制备及性能研究

将多壁碳纳米管(MWCNTs)与V2O5气凝胶复合,以V2O5粉末、苯甲醇(BA)、异丙醇(IP)和MWC-NTs为原料,采用溶胶-凝胶和溶剂替换技术制备V2O5复合气凝胶材料.利用透射电子显微镜、扫描电子显微镜、热失重分析等表征手段,研究了MWCNTs复合V2O5气凝胶材料的结构和性能.