静电纺丝法制备LaFeO3微纳米纤维

采用静电纺丝技术并结合溶胶-凝胶方法制备了LaFeO3微纳米纤维. 用差热-热重分析(TG-DTA)、X射线衍射(XRD)、红外光谱(FTIR)、X射线光电子能谱和场发射扫描电镜(FE-SEM)对样品进行了表征. 实验结果表明, 390 ℃时钙钛矿结构的LaFeO3晶体开始形成, 同时伴有少量微弱的La2O2CO3和Fe2O3杂相存在, 600 ℃煅烧获得正交钙钛矿结构的LaFeO3微纳米纤维, 其纤维直径分布在300~600 nm之间, 其平均直径约为420 nm, 平均晶粒尺寸为28 nm.     

反胶束微乳液法合成纳米SrTiO3研究

The precursors of SrTiO3 were prepared by inverse micell microemulsion method. SrTiO3 nano-powders were synthesized by calcining the precursors at 800℃ in air for 4 hours and were characterized by XRD, IR,TG, SEM. The results show that the spherical SrTiO3 nano-particles have narrow distribution with an average size of 40 nm. The surfactants played an important role in controlling shape and size of nano-particles, and combined surfactants were more effective than single surfactant.     

四氧化三铁中空/螺旋纤维的制备及形成机理

以柠檬酸铁为原料, 利用有机凝胶热分解法在低升温速率下热处理并还原制备了Fe3O4中空/螺旋纤维. 通过TG/DTA, XRD和SEM对前驱体纤维热分解过程、产物物相和形貌进行了表征. 结果表明, 产物主要由80%的中空纤维和20%的螺旋纤维组成, 其中中空纤维的直径为6 μm左右, 壁厚为500 nm. 螺旋纤维的直径为6~10 μm, 螺旋纤维是由具有不同旋向的宽度为4~6 μm的带状纤维卷曲而成, 带状纤维的外表面壳层均匀密实, 其厚度为600 nm左右, 而内层疏松且不规则. Fe3O4中空/螺旋纤维是由晶粒尺寸为60 nm左右的纳米颗粒构成, 并有少量的介孔. 分析了中空纤维和螺旋纤维的形成机理, 直径较小的前驱体纤维在热处理过程中内部凝胶向表层迁移收缩形成中空纤维; 螺旋纤维是由直径较大的前驱体纤维在热处理过程中产生的强大的热应力导致纤维产生螺旋破裂形成的.     

气流诱导多晶铁纤维的可控制备及生长机理

仅通过控制Fe(CO)₃的热解温度(T_d),用气流诱导法制备了化学组成与结构可控的多晶铁纤维。研究了热解温度对多晶铁纤维的结构和化学组成的影响规律以及多晶铁纤维的形成机理。结果表明,多晶铁纤维的直径为100～300 nm、长径比为10～40,随热解温度的升高,多晶铁纤维的晶型结构更完整,晶粒尺寸在8～61 nm 内增大,组成多晶铁纤维的纳米晶粒子在600 ℃由颗粒状变为层片状,且在较高和较低的热解温度下易于获得铁元素含量高的多晶铁纤维。多晶铁纤维的形成是由于自发磁化的铁纳米晶粒子在气流的诱导作用下自组装成一维结构。     

Fe_3O_4/SrTiO_3复合光催化剂降解甲基橙

用共沉淀法制备了SrTiO3光催化剂及Fe3O4/SrTiO3复合光催化剂.通过紫外-可见漫反射光谱、XRD、SEM-EDX对其进行表征,以甲基橙为探针分子考察其光催化性能.结果表明,适量Fe3O4的掺入可明显提高Sr-TiO3光催化剂对可见光的吸收,从而增强其光催化性能;在光降解甲基橙的反应中,掺杂10%Fe3O4的SrTiO3光催化剂其催化活性是纯SrTiO3光催化剂的两倍.     

纳米Eu_(0.12)Y_(1.88-x)La_xO_(3-δ)的光致发光性能及晶粒生长动力学

以超声波作用下的均匀沉淀法制备了Eu0.12Y1.88-xLaxO3-δ纳米晶荧光粉,用X射线粉末衍射(XRD)、透射电镜(TEM)、荧光光谱对其进行表征,考察了不同La3+掺杂含量下Eu0.12Y1.88-xLaxO3-δ(x=0～0.30)的晶格常数及晶粒尺寸的变化,研究了掺杂含量对样品激发光谱及发射光谱的影响.结果表明,Eu0.12Y1.88-xLaxO3-δ的晶格常数在1.060～1.068nm之间,晶粒尺寸在6.8～26.1nm之间,当x=0.10时,Eu0.12Y1.78La0.10O3-δ的平均粒径为35nm,发光性能优于未掺杂的Y2O3∶Eu3+荧光材料.根据晶粒生长动力学理论计算Eu0.12Y1.78La0.10O3-δ晶粒长大的活化能为9.24kJ·mol-1,表明热处理过程中纳米晶粒的长大为扩散生长机制.     

CoO/SrTiO3的合成及光催化分解水制氢性能

通过添加碱金属化合物矿化剂,以Sr(NO3)2和钛酸四丁酯的水解产物TiO(OH)2为原料进行固态反应,制得结晶完整性较好的SrTiO3粉末.再由浸渍法负载CoO,制备出光催化分解水催化剂CoO/SrTiO3,在400 W高压汞灯照射下,产氢速率可达到480μmol•g cat－1•h－1. SEM、UV-Vis漫反射光谱表征结果显示,合成SrTiO3时加入KOH矿化剂可使固态反应完全,SrTiO3结晶完整性提高,进而促进其光催化活性提高.确定了适宜的KOH矿化剂用量为2.0％(w).     

低温甲烷氧化偶联钙钛矿型SrTiO3纳米催化剂

 采用溶胶-凝胶法制备了Sr/Ti摩尔比为1.2的纳米钙钛矿型复合氧化物SrTiO3催化剂,比较了纳米SrTiO3催化剂和相同组成的常规SrTiO3催化剂对甲烷氧化偶联(OCM)反应的催化性能,并采用XRD,TEM和原位ESR技术对催化剂进行了表征. 结果表明,纳米SrTiO3催化剂具有较好的低温催化OCM反应性能. 在反应气氛下催化剂表面形成的吸附氧物种和F-中心能够活化甲烷生成C2烃,但吸附氧物种最终导致反应中间体和C2烃完全氧化; F-中心则能在低温下活化甲烷,并高选择性地生成C2烃. 纳米SrTiO3催化剂不仅含有吸附氧物种,而且含有高浓度的F-中心,而常规SrTiO3催化剂上只有吸附氧物种.     

锌掺杂对SrTiO_3光催化性能的影响

制备了锌掺杂的SrTiO3光催化剂,测试了掺杂样品在400 W高压汞灯照射下,分解纯水制氢的活性。考察了锌的掺杂量及样品的焙烧温度对其光催化活性的影响,并对掺锌与未掺杂样品进行了XRD、UV-vis、XPS及SEM表征分析。结果表明,Zn掺入可显著提高SrTiO3的光催化活性,适宜的锌掺杂摩尔分数为1%左右,相应的掺杂量下,适宜的焙烧温度为950℃左右,上述条件制得掺锌SrTiO3的产氢速率较未掺杂样品提高了120%左右。表征结果显示,掺摩尔分数1%的锌未改变SrTiO3的晶体结构及结晶完整性,但样品表面发生了锌的富集,而且在一定的掺杂范围内,锌掺杂使SrTiO3催化剂的粒度有所增大。推测掺入的Zn与存在于SrTiO3表面的富钛相反应生成Zn2TiO4,使SrTiO3表面的缺陷浓度降低,光催化活性提高。     

静电纺丝法制备Y2O3纳米纤维与表征

采用静电纺丝法制备了PVA/Y(NO3)3复合纳米纤维,在适当的温度下进行热处理,得到Y2O3纳米纤维. 利用XRD,SEM,TG-DTA,FTIR等现代分析手段对样品进行了表征. XRD分析表明,PVA/Y(NO3)3复合纤维为无定型,焙烧温度在600 ℃以上得到晶态单相的Y2O3纳米纤维,属于立方晶系,空间群为Ia3. SEM分析表明,PVA/Y(NO3)3复合纤维表面光滑,平均直径为110 nm. 焙烧温度对Y2O3纳米纤维的形成有重要影响. 600 ℃焙烧得到的Y2O3纳米纤维的平均直径约50 nm,900 ℃焙烧得到的Y2O3纳米纤维由纳米颗粒堆积而成,部分已断裂. TG-DTA和FTIR分析表明,PVA,Y(NO3)3以及水分在600 ℃以上时完全分解挥发,最终样品为晶态单相的Y2O3纳米纤维.     

原位水热合成SrTiO3/TiO2复合纳米纤维及光催化性能

以利用静电纺丝技术制备的TiO2纳米纤维为模板和反应物,原位水热合成了具有异质结构的SrTiO3/TiO2复合纳米纤维.采用X射线衍射(XRD)、扫描电子显微镜(SEM)、能量散射光谱(EDS)、高分辨透射电子显微镜( HRTEM)和X射线光电子能谱(XPS)等测试手段对样品的结构和形貌进行了表征.用罗丹明B(RB)模...     

Fabrication and photocatalytic activity of LaFeO3 ribbon-like nanofibers

LaFeO₃ ribbon-like nanofibers were synthesized via a sol–gel-assisted electrospinning method. The differences in morphology and photocatalytic property of LaFeO₃ nanofibers prepared through different needles were investigated. At the same time, the morphology and photocatalytic activity of porous LaFeO₃ nanobelts formed at different calcination temperatures were also investigated. Scanning electron microscopy results revealed that the obtained ribbon-like LaFeO₃ nanofibers made using a coaxial needle contained a large number of pores. Moreover, with the increase of calcination temperature, the morphology of the fibers also changed. X-ray diffraction analysis showed a series of fibers all in orthorhombic LaFeO₃ phase but no other impurities. In addition, the photocatalytic activity of LaFeO₃ nanofibers was studied for the degradation of methylene blue under visible light. The results demonstrated that ribbon-like nanofibers exhibited excellent photocatalytic activity compared with the others and the LaFeO₃ nanobelts calcined at 500°C had the best photocatalytic activity. Based on the experimental results, possible forming mechanisms involving in LaFeO₃ nanofibers through different needles are also discussed.     

Influence of processing conditions on the thermal decomposition of SrTiO<Subscript>3</Subscript> precursors

The present work investigates the influence of milling and calcination atmosphere on the thermal decomposition of SrTiO3 powder precursors. Both pure and neodymium-modified SrTiO3 samples were studied. Milling did not significantly influence numerical mass loss value, but reduced the number of decomposition steps, modifying the profiles of the TG and DTA curves. On the other hand, milling increases the amount of energy liberated by the system upon combustion of organic matter. It was also observed that the milling process, associated to the calcination in an oxygen atmosphere, considerably decreases the amount of organic matter and increases the final mass loss temperature.     

静电纺丝法制备NiO纳米纤维及其表征

纳米级NiO因具有优良的催化和热敏等性能而被广泛用于催化剂^[1]、电池电极^[2,3]、光电转化材料^[4～6]、电化学电容器^[7～8]等诸多方面.迄今,已成功地制备出N iO的纳米颗粒^[9]、纳米线^[10]及纳米薄膜^[11],但是对于具有准一维结构的NiO纳米纤维的制备及性能研究尚未见报道.     

Nanofibers of LiMn2O4 by electrospinning

Through sol-gel processing and electrospinning technique, extrathin fibers of poly(vinyl alcohol) (PVA)/lithium chloride/manganese acetate composite fibers were prepared. After calcination of the above precursor fibers at 600 degrees C, the spinel lithium manganese oxide (LiMn2O4) nanofibers, with a diameter of 100-200 nm, were successfully obtained. The fibers were investigated by TG-DTA, XRD, FT-IR, and SEM, respectively. The results showed that the crystalline phase and morphology of the fibers were largely influenced by the calcination temperature.     

Electrospun Nickel Oxide Hollow Nanostructured Fibers

The citric acid/nickel acetate composite hollow fibers were prepared by using sol-gel processing and co-electrospinning technique. The polycrystalline NiO hollow nanostructured fibers were prepared after calcination. The obtained hollow nanostructured fibers made up of 17～25 nm nanocrystals were about 150 nm to several micrometers in outer diameter. The hollow NiO nanostructured fibers have been characterized by TG, DSC, SEM, FTIR, and XRD techniques. The results showed that the morphology of NiO hollow fibers was obviously influenced by the calcination temperature.     

Formation of Ultrafine Apatite Fibers by Sol-gel/Electrospinning

Ultrafine apatite fibers were prepared by electrospinning of sol-gel precursor/poly（ vinyl pyrrolidone） （PVP） solutions followed by subsequent calcination. The as-electrospun and calcinated fibers were observed under a scanning electron microscope and an optical polarizing microscope. Results show that the morphology and the diameter of as-electrospun fibers strongly depend on the viscosity and the surface tension of sol-gel precursor/PVP solutions. After calcination, the smooth as-electrospun fibers shrink and the fiber diameter decreases because of the removal of the polymer. The chemical evolution upon the transformation of the precursor from a gel to the final apatite fibers was investigated by thermogravimetric-differenfial thermal analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. It is thus suggested that the crystalline structure of the calcined fibers is largely influenced by the calcination temperature. After being calcined at 600 ℃, the apatite fibers with a diameter of about 280 nm containing β-tricalcium phosphate were obtained.     

可见光驱动Au/SrTiO3纳米等离子体光催化剂分解水制氢

采用水热法和光沉积法制备了Au/SrTiO_3纳米等离子体光催化剂。通过XRD、XPS、SEM、TEM、EDS和DRS等技术对光催化剂的结构、组成、形貌、粒子大小和光吸收性质等进行了表征,考察了Au/SrTiO_3纳米光催化剂在可见光照下的制氢性能。结果表明,采用水热法成功合成了SrTiO_3纳米粒子,通过负载Au纳米粒子后,由于表面等离子体共振效应,增强了其对可见光的吸收。此外,测试了不同Au负载量对SrTiO_3光催化剂在可见光照下制氢活性的影响,其中,5%Au/SrTiO_3光催化剂在可见光照下制氢活性最高,并对其光催化反应机理进行了进一步的探讨。     

Preparation of Mn2O3 and Mn3O4 nanofibers via an electrospinning technique

Thin PVA/manganese acetate composite fibers were prepared by using sol-gel processing and electrospinning technique. After calcinations of the above precursor fibers, Mn₂O₃ and Mn₃O₄ nanofibers with a diameter of 50-200 nm could be successfully obtained. The fibers were characterized by TG-DTA, Scanning electron microscopy, FT-IR, WAXD, respectively. The results showed that the crystalline phase and morphology of nanofibers were largely influenced by the calcination temperature.     

静电纺丝法制备MgO纳米纤维

以聚乙烯醇(PVA)作为络合剂与醋酸镁反应制得前驱体，采用静电纺丝法制得聚乙烯醇(PVA)／醋酸镁复合纤维，经焙烧后得到分布均匀、具有较高比表面积和多孔结构的。MgO纳米纤维．对所制得的纳米纤维的结晶度、纯度和表面形貌，分别采用X射线粉末衍射、差热一热重分析(TG-DTA)、红外光谱(IR)、扫描电镜(SEM)等分析测试手段进行了表征．结果表明，煅烧温度对纳米纤维的结晶度和形貌有很大影响．