六方相氧化钨纳米线的制备及氨敏特性

采用简易水热法制备直径为10～20 nm、长几百纳米至几微米的六方相氧化钨纳米线,比表面积高达130.69 m~2/g.将该纳米线采用丝网印刷法制备成敏感膜,经350 ℃烧结1 h后测试其氨敏性能并分析其敏感机制.结果表明:在200～350 ℃的温度范围内,该敏感膜对低浓度氨气(1～100) μL/L具有较高的灵敏度(R_(air)/R_(NH_3)=4.0～18.8)、良好的重复性和很好的稳定性;对同一浓度的氨气,随测试温度的升高其灵敏度不断增大;在同一温度下,灵敏度随氨气浓度的增加基本上呈线性不断增大.     

纳米氧化钨薄膜的制备及光致变色特性的研究进展

过渡金属氧化物WO3因具有优异的光致变色特性而倍受重视.本文介绍了氧化钨薄膜的电致变色机理,综述了氧化钨薄膜的制备方法,总结了纳米氧化钨薄膜光致变色特性的一些实际应用,并对今后的发展方向提出了一些看法.     

以锯齿状碳纳米管为模板原位合成微/纳米球状氧化钨

以锯齿状CNTs管束作为模板担载H_2WO_4前驱体。在液相沉积过程中H_2WO_4被锯齿状CNTs包裹,所得H_2WO_4/CNTs团簇的平均尺寸为500 nm,由直径10～20 nm的H_2WO_4组成,比表面积和孔容分别为85.24 m~2·g~(-1)和0.2933 m~3·g~(-1)。将H_2WO_4/CNTs置于氧气气氛中进行热处理,除去CNTs后,得到了由纳米颗粒组成的WO_3微米球,比表面积和孔容分别为18.7 m~2·g~(-1)和0.2055 m~3·g~(-1)。结果表明,锯齿状CNTs对有效调节分层结构WO_3发挥重要作用,对制备微纳米结构材料具有广阔的应用前景。     

ZnS纳米晶须的溶剂热法制备及机理研究

在120℃下反应12 h,用乙二胺为溶剂,通过溶解热法制备出六方纤锌矿型的ZnS纳米晶须.ZnS纳米晶须的结构为定向排列的条纹状纹理.ZnS纳米晶须在乙二胺中的生长过程可以用溶剂配位分子模板机理加以解释.并讨论了乙二胺作为样品形态结构导向配位分子模板的作用.采用X射线衍射(XRD),透射电子显微镜(TEM),红外吸收光谱(IR)对样品进行了表征.     

氧化钨纳米颗粒和纳米线的选择合成及光致发光研究

采用无机盐辅助水热法选择调控合成了WO3纳米颗粒和纳米线.通过SEM,TEM,EDX和XRD等手段对产物进行了表征.研究了形貌和尺寸对WO3的光致发光性能的影响,并探讨了形貌和尺寸对WO3光致发光性能影响的机制.     

绒球状结构氧化钨的制备

通过W粉和Ni(NO3)2·6H2O在钼包套内反应,制备出微米尺度的绒球状结构氧化钨.绒球状结构由长度达数百微米、外径1～10 μm的微米管和直径100～500 nm的亚微米纤维组成.X射线衍射和透射电子显微镜分析表明:产物为具有良好晶体结构的沿[010]方向生长的单斜结构的W18O49.这些通过Vapor-Solid(V-S)生长机制形成的绒球状结构氧化钨因为具有巨大的表面积,在微型半导体敏感元件方面具有巨大的应用前景.     

纳米级SiC晶须的微波合成

以酚醛树脂、超细炭黑和超细ＳｉＯ２为原料，用微波加热的方法合成了直径在纳米级的ＳｉＣ晶须。用Ｘ射线衍射、分析电镜等手段对ＳｉＣ晶须进行了结构测定。比较并分析了不同的炭源和温度对ＳｉＣ晶须性能的影响．     

孪晶SiC纳米线的制备、结构及光致发光(英文)

以含碳的二氧化硅干凝胶为原料,采用碳热还原法制备了孪晶结构β-SiC纳米线。通过场发射扫描电镜、X射线衍射和高分辨透射电镜等测试分析表明,SiC纳米线具有六角形的横截面,直径50～300nm,沿着纳米线生长方向具有准周期性的(111)面孪晶结构。结合气-固生长机理及(111)密排面堆垛次序的变化讨论了孪晶纳米线的生长机理。光致发光谱表明,SiC纳米线在470nm附近有数个相对β-SiC体单晶的发光特征蓝移,且分裂的发光峰。这种发光现象可解释为堆垛层错导致相互隔离的β-SiC纳米片段的量子尺寸效应。     

纳米SCR催化剂Ce-V/TiO_2的制备与研究

采用溶胶-凝胶法和浸渍法制备选择性催化还原(SCR)脱硝反应复合纳米催化剂Ce-V/TiO_2,在不同的实验条件下制备出一系列的TiO_2凝胶用作催化剂载体.然后通过浸渍法依次负载CeO_2和V_2O_5于多孔TiO_2载体.用氨气作为还原性气体,对选择性催化还原NOx进行实验研究.在不同的TiO_2载体煅烧温度、CeO_2和V_2O_5负载量以及催化还原反应温度等条件下,对催化剂的表面结构和催化性能采用BET、XRD、SEM等手段进行表征分析.结果表明,纳米Ce-V/TiO_2固溶体复合催化剂以及对其制备工艺技术参数的优化可增大催化剂的比表面积和微孔体积,使催化剂的催化活性有很大的提高.此外,相当数量的多孔纳米TiO_2大大增加了光催化活性的有效面积,有利于增大与反应物的接触面积和提高光催化活性.当载体TiO_2 的煅烧温度和催化还原反应温度为500 ℃时,5%Ce-10%V/TiO_2催化剂反应的NO_x转化率可达96.2%.     

纳米WO_3/DWCNTs材料的制备及其光催化性能

通过液相法制备出钨酸/DWCNTs和纯钨酸2种前驱体,然后在氮气气氛下焙烧至700℃,保温2 h,分别生成了WO_3/DWCNTs和WO_3粉末。采用扫描电子显微镜和X射线衍射仪对产物的形貌和结构进行表征。在11 W可见光的照射下,分别利用WO_3/DWCNTs和WO_3粉末对有机染料亚甲基蓝进行光催化降解反应;利用紫外-可见分光光度计测定出样品的紫外可见吸收光谱,通过朗伯比尔定律计算出光催化降解率。当光照时间为30 min时,WO_3/DWCNTs降解率达到87.50%,纯WO_3降解率仅为25.39%。结果表明,DWCNTs的加入可以有效抑制颗粒的团聚,减小颗粒尺寸,增大WO3的比表面积,增强WO_3的吸附能力,显著提高WO_3对亚甲基蓝的光催化降解效率。     

Direct solid-state synthesis of tungsten carbide nanoparticles from mechanically activated tungsten oxide and graphite

Solid-state carbothermic reduction of tungsten oxide (WO₃) to nano-sized tungsten carbide (WC) particles was achieved by calcining mechanically activated mixtures of WO₃ and graphite at 1215 °C under vacuum condition. By experiments and thermodynamic calculations, the intermediate phases, WO_2.72, WO₂ and metallic tungsten (W), were observed at 741 °C, which decomposed to synthesize the final product (WC). Homogeneity increase and associated decrease in the diffusion path by mechanical milling and formation of these intermediates are mainly responsible for the successful production of WC. The process indicates that solid-state synthesis of WC nanoparticles directly from as-milled mixtures of tungsten oxide and graphite powder is possible.     

Preparation of ultrafine tungsten powders by in-situ hydrogen reduction of nano-needle violet tungsten oxide

Ultrafine tungsten powders with a grain size below 0.5 μm are key raw materials for fabricating ultrafine cemented carbides. Conventional hydrogen reduction technique has been utilized to prepare the ultrafine tungsten powders. In the present work, highly pure nano-needles of violet tungsten oxide (WO_2.72) were reduced by dry hydrogen. Nucleation and growth of the metallic tungsten in the early stage of hydrogen reduction have been studied by XRD, FESEM and HRTEM. Mechanism of formation of nano-size tungsten powders is proposed and a concept of in-situ hydrogen of the nano-needle WO_2.72 is presented. Empirical relations between an average diameter of nano-needle WO_2.72 and an average particle size of the resultant tungsten powders in both stage of nucleation and industrial conduction have been established. These empirical relations could be a reasonable guidance for suitably choosing the raw materials of nano-needle WO_2.72 to prepare ultrafine tungsten powders. It has been determined that the BET special surface areas of the in-situ hydrogen-reduced tungsten powders with the average particle size of 0.2 μm and 0.3 μm, which were produced from the raw nano-needle WO_2.72 powders with the average diameter of 60 nm and 80 nm, are 6.03 m²/g and 4.65 m²/g, and the oxygen contents are 0.35% and 0.29%, respectively.     

Influence of phase components of tungsten oxide on homogeneity of ultrafine tungsten powder

1　ＩＮＴＲＯＤＵＣＴＩＯＮＨｙｄｒｏｇｅｎｒｅｄｕｃｔｉｏｎｏｆｔｕｎｇｓｔｅｎｏｘｉｄｅｓ,ｓｕｂｓｅｑｕｅｎｔｍｉｘｉｎｇｗｉｔｈｃａｒｂｏｎｂｌａｃｋａｎｄｃａｒｂｕｒａｔｉｎｇｉｓｔｈｅｍｏｓｔｃｏｍｍｏｎｗａｙｔｏｐｒｏｄｕｃｅｔｕｎｇｓｔｅｎｃａｒｂｉｄｅｐｏｗｄｅｒｓｆｏｒｔｈｅｈａｒｄｍｅｔａｌｉｎｄｕｓｔｒｙ.Ｔｈｉｓｔｅｃｈｎｉｑｕｅｈａｓｂｅｅｎｐｒａｃｔｉｃｅｄｆｏｒｄｅｃａｄｅｓａｎｄｃａｌｌｅｄ“ｃｏｎｖｅｎｔｉｏｎａｌｈｙｄｒｏｇｅｎｒｅｄｕｃｔｉｏｎｐｒｏｃｅｓｓ…     

碱式氯化镁晶须的水热制备及热分解机理研究

采用水热法以氯化镁溶液、氢氧化钠为原料制备了碱式氯化镁晶须。通过SEM和SAED观察样品的显微形貌及晶体结构,晶须长度150μm以上,直径0.5~1μm,为单晶物质。通过XRD测定样品的晶相结构,产物为碱式氯化镁9Mg(OH)_2·MgCl_2·5H_2O。通过红外光谱考察了不同镁离子浓度产物官能团的不同。升温速率为2~5℃/min,高温程序煅烧前驱体碱式氯化镁,制备出氧化镁晶须,很好的保持了碱式氯化镁晶须的形貌,仍为单晶物质,并推测了其可能的热分解的机理过程。     

钨渣回收制备四氧化三锰新工艺

研究从钨渣中回收锰的新工艺,通过钨渣的低温硫酸化焙烧、烧结块浸出、浸出液除杂、溶液中水解沉锰及氢氧化锰氧化获得Mn3O4粉末,采用SEM和XRD对产品粉末进行分析。结果表明:在浓硫酸过量150%、焙烧时间90 min、浸出温度98℃、浸出时间120 min的条件下,Mn浸出率达到88.9%。浸出液可以通过硫化物沉淀除重金属、硫酸复盐沉淀法深度净化除杂、中和水解除Fe,水解沉锰也有一定的净化作用,溶液pH值为6.56时,除铁率达到99.91%。净化液经水解沉锰后采用10%H2O2氧化,在氢氧化锰氧化过程中,溶液pH值对产物物相的影响较大;溶液pH值为8时在50℃沉锰,并以过量150%的H2O2氧化反应20min,获得粒度小于0.1μm的Mn3O4粉末。     

Synthesis of ZnO whiskers via hydrothermal decomposition route

ZnO whiskers with a length of 30-40μm and a diameter of about 1μm were synthesized by co-precipitation of ZnSO 4 and Na2CO3 solution at room temperature followed by hydrothermal treatment of the as-prepared Zn5(CO3)2(OH)6 precursor at 160 ℃for 6 h.The increase of the initial solution pH promotes the hydrothermal conversion of the particulate Zn5(CO3)2(OH)6 to ZnO whiskers.The presence of minor amount of EDTA in the hydrothermal solution promotes the one dimensional growth of ZnO whiskers,leading to the formation of ZnO whiskers with a length of 50-60μm and a diameter of 1-2μm.     

Preparation of tungsten powder by the combustion of CaWC4/Mg

Tungsten powder was prepared by a Self-Propagating High-Temperature Synthesis(SHS) Process of a CaWO₄-Mg mixture. Mg vapor was discovered to significantly affect such combustion parameters as the combustion temperature(T_c), the combustion velocity(U), the relative mass change(δm) and the relative elongation(δh) of the sample. These effects could be reduced by decreasing the internal Ar pressure, sample density and reducing agent content. The oxygen content in tungsten was decreased by using 5% excess Mg; the carbon content was diminished when the combustion process occurred under P_Ar=0.1 MPa. The MgO and CaO in the product was leached with an HC1 solution. Such parameters as combustion temperature(T_c), U, Am, and milling time(τ) were found to affect the tungsten particle size and morphology.     

水热法制备超细焦绿石型三氧化钨及其表征

在水热条件下利用纯WO3作为添加剂能够直接从钨酸钠溶液中制备出超细焦绿石型三氧化钨(WO3-0.5H2O)粉体。结果表明:往100 g/L的钨酸钠溶液中添加WO3,在密闭压力容器内,在140℃下反应24 h,反应率能达到80%左右。采用XRD和SEM等测试手段对水热产物进行表征,产物为结晶良好的立方体结构,颗粒的平均尺寸小于1μm。EDS检测表明:所得产品含微量的Na元素,经盐酸洗涤后可得到几乎不含杂质Na的WO3-0.5H2O粉体。利用IR光谱测定水热条件下钨酸钠溶液的离子结构变化,初步认为制备WO3-0.5H2O的生长基元为WO42-。