水热合成MoO3纳米带的生长机理研究

以离子交换法制备的氧化钼溶胶为前驱体，在水热条件下制备了单晶MoO₃纳米带，对样品进行了XRD、SEM和TEM分析。通过考察水热反应温度和时间对产物结构和形貌的影响，结合材料热力学和动力学理论，探讨了MoO₃纳米带在水热条件下的生长机理。离子交换法制备的溶胶在水热条件下首先转变为热力学亚稳相h-MoO₃六角柱，随着温度的升高和时间的延长，h-MoO₃按照溶解-重结晶过程转变为稳定相α-MoO₃纳米带。     

Utilization of inverse approach in the design of materials over nano‐ to macro‐scale

In the light of recent developments in computer technology, a promising and efficient way to design a material with a desired property would be to solve the inverse problem: use a physical property to predict structure. Here, we discuss the basic idea and mathematical foundation of the inverse approach, and proposed strategies for its utilization in the design of materials over nano‐ to macro‐scales. At the nano‐scale, analyzed strategies include scanning of a high‐dimensional space of chemical compounds for those compounds that have a targeted property, and identification of correlations in large databases of materials. However, unlike utilization of inverse approach at nano‐scale where full structural information ‐ atoms and their positions‐ is linked to targeted properties, at the meso‐ and macro‐scale, only partial structural information, manifested via structural motifs or representative volume elements, is available. We discuss the role of partial structural information in the inverse approach to the design of materials at those scales. Risks and limitations of the inverse approach are analyzed and dependence of the approach on factors such as structure parametrization, approximations in theoretical models, and feedback from structural characterization, is addressed.

     

Fe/MgO催化裂解甲烷制备碳纳米带

采用溶胶-凝胶法制备了Fe/MgO催化剂(E)。以甲烷为碳源,通过催化化学气相沉积法在E上生长出了碳纳米带(F),其结构和形貌经SEM和TEM表征。在最佳制备条件[E中Fe负载量为50%,甲烷流速70mL·min-1,于870℃反应1 h]下制备的F宽度约135 nm,厚约89 nm,长度在几十微米量级。     

Hydrothermal synthesis of MoO3 nanobelt‐graphene composites

A composite of graphene sheets decorated with molybdenum trioxide (MoO₃) nanobelts has been fabricated via a facile and efficient hydrothermal route in the presence of NaCl. The structure, morphology of these promising composites were investigated by means of field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), Raman spectroscopy and thermogravimetric (TG) analysis. FESEM and TEM studies suggest the presence of uniform crystalline MoO₃ nanobelts and graphene sheets in as‐prepared hybrid materials. XRD and Raman results confirm the reduction of graphite oxide (GO) sheets to graphene sheets accompanying by the formation of MoO₃ nanobelts. Moreover, thermal properties of GO and MoO₃ nanobelt‐graphene composites reveal that thermal stability of the obtained MoO₃ nanobelt‐graphene composites is obviously higher than that of GO due to the transformation of GO sheets to highly stable graphene sheets in the hybrids. This work could provide new insights into the fabrication of high quality MoO₃‐graphene hybrid nanomaterials and facilitate their potential applications in different fields. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

样品的形貌对CeO2湿度传感器性能的影响

使用Ce(NO3)3·6H2O为前驱物,采用水热合成法和溶胶凝胶法分别制备了不同形貌的CeO2纳米晶体(纳米带和球形颗粒).通过XRD、SEM和TEM技术表征了材料的相成分、微结构和形貌.将样品制备成湿度传感器后对传感器性能进行了测试,结果表明:具有纳米带形貌的样品所制备的传感器展示了良好的传感性能,其响应-回复时间分别为7 s 和7 s(在15;~95;湿度范围内),最大迟滞为4;,这些性能都要好于球形颗粒所制备的样品.其主要原因是纳米带样品具有较大的比表面积.     

由钛酸盐纳米带水热制备锐钛矿型TiO2纳米带

研究了水热处理具有层状结构的钛酸钠纳米带或钛酸纳米带转化为锐钛矿型TiO₂的制备过程、难易程度和相转化机理. 实验结果表明, 当水热反应温度和时间分别在160 ℃ 和24 h以内, 钛酸钠纳米带很难完全转化为锐钛矿型TiO₂, 若升高反应温度并延长反应时间, 则可制得纯的锐钛矿型TiO₂, 但纳米带形貌被严重破坏; 当水热反应温度和时间分别为160 ℃ 和16 h时, 1次酸洗的钛酸纳米带能够完全转化为锐钛矿型TiO₂, 若钛酸纳米带经过3次强酸浸泡, 则在160 ℃下相转化时间就会缩短到12 h, 所有钛酸纳米带在转化为TiO₂后的形貌仍为纳米带, 但经3次酸浸后生成的TiO₂纳米带表面更光滑. 讨论了钛酸钠纳米带或钛酸纳米带转化为锐钛矿型TiO₂的相转化机理.     

溶胶凝胶法合成莫来石纳米带

Single-crystal mullite nanobelts were prepared by a simple sol-gel method using WO₃ as additive, and nanobelts were straight and uniform with width of 200 nm and length of 3~4 μm. The as-prepared products were characterized with XRD, SEM and TEM and the nanobelt formation mechanism was also discussed. The interphase of aluminium tungstate acted as seed crystals or epitaxial templates during the formation of nanobelts. The further experiments showed that there was a strong correlation between the formation of nanobelts and the presence of WO₃.     

Preparation of Single Crystalline V6O13 Nanobelts

Ultralong beltlike nanostructures was successfully synthesized for V6O13 crystal by a hydrothermal route. The products are characterized by means of X-ray powder diffraction, transmission electron microscopy and high-resolution transmission electron microscopy. The experimental results give the evidence that the V6O13 nanobelts are pure, structurally uniform and single crystalline, with typical widths of 50 to 300 nm and lengths of up to a few millimeters.     

铝热反应法制备双股类螺旋Zn2SnO4单晶纳米带

综合利用化学气相沉积、铝热反应法、汽-液-固生长法、极性面融合和稳态湍流动力学控制来大量制备双股类螺旋Zn₂SnO₄单晶纳米带. 该材料属于面心立方尖晶石型透明半导体, 在光伏器件和湿度与可燃气体传感器中有着广泛的应用. 扫描电镜、透射电镜、电子衍射、X射线衍射、拉曼光谱以及光发射等技术分析表明所得的双股类螺旋纳米带是由两个独立的Zn₂SnO₄纳米带通过扭曲纠缠和融合而成. 该双股类螺旋纳米带实际上是在轴向具有周期性的超晶格材料. 光致发光测量表明该纳米带在326.1 nm处出现强发射峰, 线宽约为1.5nm. 本研究所采用的综合制备法中的铝热反应法和稳态湍流微扰法可能有助于类似材料的控制制备.     

Controllable synthesis of ultrathin vanadium oxide nanobelts via an EDTA-mediated hydrothermal process

Ultrathin VO_2 nanobelts with rough alignment features are prepared on the induction layer-coated substrates by an ethylenediaminetetraacetic acid(EDTA)-mediated hydrothermal process. EDTA acts as a chelating reagent and capping agent to facilitate the one-dimensional(1D) preferential growth of ultrathin VO_2 nanobelts with high crystallinities and good uniformities. The annealed induction layer and concentration of EDTA are found to play crucial roles in the formation of aligned and ultrathin nanobelts. Variation in EDTA concentration can change the VO_2 morphology of ultrathin nanobelts into that of thick nanoplates. Mild annealing of ultrathin VO_2 nanobelts at 350℃ in air results in the formation of V_2O_5 nanobelts with a nearly unchanged ultrathin structure. The nucleation and growth mechanism involved in the formations of nanobelts and nanoplates are proposed. The ethanol gas sensing properties of the V_2O_5 nanobelt networks-based sensor are investigated in a temperature range from 100℃ to 300℃ over ethanol concentrations ranging from 3 ppm to 500 ppm.The results indicate that the V_2O_5 nanobelt network sensor exhibits high sensitivity, good reversibility, and fast responserecovery characteristics with an optimal working temperature of 250℃.