氧化铒稳定氧化铋纳米纤维的制备及性能

采用电纺丝法制备了20%氧化铒稳定氧化铋(ESB)纳米纤维电解质材料,并利用XRD,SEM,电化学工作站表征了其晶体结构,微观形貌和电导率等性能。研究结果表明,当不掺杂稀土离子时,只能得到单斜相(α-Bi_2O_3)与四方相(β-Bi_2O_3)共存的Bi_2O_3;而掺杂20mol%Er~(3+)时,可以在室温得到稳定的立方相δ-Bi_2O_3纳米纤维。通过扫描电镜结果可知,500,600℃煅烧后的ESB纳米纤维长径比高、直径均匀、表面光滑。500℃煅烧的ESB纳米纤维在500℃时电导率约为0.031 S·cm~(-1)。     

静电纺丝技术制备NiFe_2O_4纳米纤维的表征

采用溶胶-凝胶法与静电纺丝技术相结合制备了PVP/[Ni(NO3)2+Fe(NO3)3]复合纳米纤维,在一定温度下进行热处理,得到尖晶石结构的NiFe2O4纳米纤维。利用TG-DTA、XRD、FTIR、SEM、TEM等分析手段对样品的组成及结构进行表征。TG-DTA分析表明,PVP/[Ni(NO3)2+Fe(NO3)3]复合纳米纤维的热处理温度高于450℃以后,质量恒定,总失重率为87.8%。XRD与FTIR分析表明,热处理温度高于600℃时,复合纳米纤维已经完全转变成尖晶石结构的NiFe2O4纳米纤维。SEM分析表明,所制备的PVP/[Ni(NO3)2+Fe(NO3)3]复合纤维直径在250～300nm之间,NiFe2O4纳米纤维直径约100nm,长度大于200μm。对NiFe2O4纳米纤维的形成机理进行了探讨。     

One-Step Preparation of β-Ga2O3 Nanomaterial and Research the Electrical Transport Properties at High Temperature

用热蒸发化学气相沉积法成功制备了β-Ga2O3纳米材料, 并研究了该纳米材料在高温下的电学特性。Ｘ射线衍射分析显示, 产物为单斜结构的β-Ga2O3。扫描电子显微镜及透射电镜测试表明,纳米带的宽度小于100 nm, 长度有几微米; 较大氧流量时制备出β-Ga2O3纳米晶粒结构, 晶粒尺度在80~150 nm。电学特性的测试表明：当温度低于800 ℃时, 纳米带电导率几乎不变,当温度高于800 ℃以上时,电导率和温度呈指数关系     

纳米钡铁氧体的制备与磁性研究

采用溶胶凝胶法在不同pH值和煅烧温度条件下制备了M型纳米钡铁氧体样品,利用X射线衍射、场发射扫描电镜以及振动样品磁强计研究了溶液pH值和煅烧温度对纳米钡铁氧体的微结构和磁性能的影响.实验结果表明:溶液pH值及煅烧温度对钡铁氧体的相结构和磁性能都有很大影响.当溶液pH值在3以上时,有利于BaFe12O19相的形成,纳米钡铁氧体的晶粒尺寸约50 nm,饱和磁化强度Ms和矫顽力Hc在pH=7时达到最高.对于pH=7的样品,在700℃左右开始有BaFe12O19相形成,同时伴有较多量的α-Fe2O3和少量的BaFe2O4与BaCO3杂相.随着温度的升高,BaFe12O19主相不断形成积累,杂相逐渐减少,当煅烧温度为800℃时,样品基本上为纯BaFe12O19相,经900℃热处理后样品磁性能最佳:饱和磁化强度达到Ms=61.6(A·m2)/kg,矫顽力为Hc=4.56×105A/m.     

β-Ga_2O_3纳米材料的制备及高温电学特性(英文)EI北大核心CSCD

用热蒸发化学气相沉积法成功制备了β-Ga2O3纳米材料,并研究了该纳米材料在高温下的电学特性.X射线衍射分析显示,产物为单斜结构的-Ga2O3.扫描电子显微镜及透射电镜测试表明,纳米带的宽度小于100 nm,长度有几微米;较大氧流量时制备出β-Ga2O3纳米晶粒结构,晶粒尺度在80～150 nm.电学特性的测试表明：当温度低于800℃时,纳米带电导率几乎不变,当温度高于800℃以上时,电导率和温度呈指数关系.     

液相包裹法制备Al2O3/Fe纳米复合粉体

利用液相包裹法制备了纳米Fe颗粒包裹Al2O3,纳米复合粉体,研究了不同的煅烧和还原温度对复合粉体物相组成的影响,利用X-ray衍射（XRD）、热重/差式-量热扫描法（TG/DSC）、Zeta电位和扫描电镜（SEM）对复合粉体的成分、热学特性以及形貌特征进行了分析.结果表明：煅烧温度为500℃,保温30min,在氢气气氛中700℃还原1h可以得到Fe包裹Al2O3的纳米复合粉体;经SEM发现,包裹层的Fe颗粒呈球形,尺寸约为30 nm,分布均匀.     

热处理工艺对纳米γ-Al2O3粉体的尺寸和形貌的影响

以异丙醇铝为原料采用溶胶凝胶技术制备水合氧化铝前驱体,经热处理制得纳米氧化铝粉体.采用正交实验设计研究了热处理工艺条件对纳米氧化铝粉体的尺寸和形貌的影响规律.结果表明,热处理工艺参数对Al2O3粒子颗粒特性的影响由强到弱的次序为:煅烧温度、水合氧化铝在300℃分解温度点的保温时间、在煅烧温度点的保温时间;通过控制其热处理工艺参数,可获得一定尺寸范围的大小均匀,分散性好的球形γ-Al2O3粉体;制备尺寸为8 nm的球形γ-Al2O3粉体的最佳的热处理工艺参数为:煅烧温度900℃,在煅烧温度点保温4 h,在300℃温度点不保温.     

用偏钛酸作原料制备纳米TiO2粉末以及颗粒相结构与光催化性能关系的研究

米用常温氨水水解TiOSO4过程中加入自制的表面活性剂制备了超细纳米TiO2粉末,用XRD,TEM和比表面仪对不同煅烧温度下的纳米TiO2粉末结构、粒径大小和比表面等进行了表征,研究了纳米TiO2粉末对甲基橙的光催化降解能力。研究表明煅烧温度在400℃～800℃时得到的纳米TiO2粉末呈锐钛矿结构,粒径约为5．5nm～9．6nm,比表面积高达189．45m^2/g;在850℃煅烧后所得的纳米TiO2粉末为锐钛矿与金红石型混晶结构;在l100℃时得到的纳米TiO2粉末为金红石型纳米TiO2粉末,同时微粒出现团聚且粒径变大。光催化实验表明：纳米TiO2粉末的光催化活性与煅烧温度密切相关,850℃煅烧1．5h所制得的混晶结构纳米TiO2粉末表现出较高的光催化活性。与国产商品纳米锐钛矿型TiO2相比,其降解甲基橙的速率约为国产商品纳米TiO2的1倍。     

化学溶液沉积法制备WO3•2H2O薄膜及其电致变色性能

目的研究具有不同微观结构的WO_3·2H_2O薄膜的电致变色性能。方法采用化学溶液沉积法在FTO玻璃上制备WO_3·2H_2O薄膜,通过加入不同的形貌控制剂(柠檬酸或草酸铵),制备不同纳米结构的WO_3·2H_2O薄膜。采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)分析薄膜的成分结构和微观形貌,利用紫外可见光分光光度计对薄膜在波长为200～1000nm范围内的透光性进行研究,并通过电化学工作站对薄膜进行电化学性能分析。结果采用柠檬酸作为形貌控制剂制备的WO_3·2H_2O薄膜的透光性高达82%左右,其在着色和褪色状态的透过率差值为36.2%。通过添加柠檬酸或草酸铵作为形貌控制剂制备的WO_3·2H_2O薄膜均呈现出纳米片状结构,纳米片的厚度分别为5～15 nm和50～60 nm,但是采用柠檬酸制备的WO_3·2H_2O具有较多的间隙和裂缝,使其表现出了较好的电致变色性能。结论具有间隙和裂缝的纳米WO_3·2H_2O薄膜增加了薄膜与电解质的接触面积,减少了离子扩散的路径距离,更小的纳米结构可以提供更多的化学活性位点,从而表现出较好的电致变色性能。     

改进溶剂热法制备锂离子电池负极材料用多级孔Co3O4微球

将溶剂热法与高温煅烧法相结合制备多级孔Co3O4微球,采用XRD、SEM、TEM和电化学测试等技术研究该多级孔Co3O4微球的结构和性能.结果表明:当煅烧温度为700℃时,所合成的Co3O4(Co3O4-700)是由丰富的纳米颗粒(50～200 nm)和大量孔洞(～100 nm)构成的微米级微球(1～2μm);该Co3...     

Effects of iron catalyst on the formation of crystalline domain during carbonization of electrospun acrylic nanofiber

To investigate the effects of introducing the iron compound on the carbonization behavior polyacrylonitile (PAN)-based electrospun nanofibers were carbonized with or without iron(III) acetylacetonate (AAI) over the temperature range of 900–1500 °C in nitrogen atmosphere. The morphological characteristics of the carbon nanofibers were investigated using X-ray diffractometer (XRD), Raman spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The electrical conductivity of the carbon nanofiber web was measured by four-point probe method. The iron catalyst had a profound effect on the crystal structure of the carbonized nanofiber. In the presence of AAI the nanofibers carbonized at 1300 °C developed graphite structure, which could be obtained at the temperature higher than 2000 °C in the absence of the catalyst. The in-plane size of the graphite crystals (L_a) was measured to be about 6.5 nm by Raman spectroscopy and the (0 0 2) spacing by XRD was 0.341 nm.     

Characterization of polymer nanofibers coated by reactive sputtering of zinc

The surface properties of polymer nanofibers are of importance in various applications. In this work, electrospun polyamide nanofibers were used as substrates for creating functional nanostructures on the nanofiber surfaces. The surface functionalization of polymer nanofibers was made by reactive sputtering of zinc (Zn). The surface structures of the sputter-coated nanofibers were examined by atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM). AFM results revealed the formation of functional coatings on the nanofiber surface. A full energy dispersive X-ray analysis (EDX) mounted on the ESEM confirmed the chemical compositions of the nanofiber surfaces. The electrical conductivity and light transmittance of the functional nanofibers were also investigated. The results indicated that the nanofibers deposited with zinc films significantly improved the surface conductivity and the reactive sputter coating of zinc oxide obviously enhanced the ultra-violet absorption.     

浸渍法制备Ag_2O-TiO_2纳米纤维及其光催化活性

采用浸渍法制备直径约20nm,长度达到微米级,且形态分布均匀的Ag2O-TiO2纳米纤维。以TEM、XRD、DRS及XPS手段对样品晶型结构、微观形貌以及化学组成进行表征,探讨掺杂对TiO2纤维结构和性质的影响。结果表明:未掺杂纤维表面平滑,浸渍法制备的Ag2O-TiO2纤维表面有明显的球状颗粒存在,颗粒直径为2～5nm,分布均匀,且其XRD谱出现Ag2O的衍射峰。与未掺杂样品相比,掺杂纤维的DRS谱线发生蓝移,光催化降解亚甲基蓝实验表明Ag2O-TiO2纤维光催化活性较高。     

Enhanced photocatalytic properties of ultra-long nanofiber synthesized from pure titanium powders

Using Ti powder as reagent,ultra-long TiO2 nanofibers were prepared via hydrothermal method in NaOH solution.The samples were char-acterized respectively by means of field emission scanning electron microscopy (FESEM),transmission electron microscopy (TEM) with selected area electron diffraction (SAED),and X-ray diffraction (XRD).The diameter and the length of the ultra-long TiO2 nanofiber were ～100 nm and >200μm,respectively.The ultra-long TiO2 nanofibers were anatase after heat treatment at 450 ?C for 1 h.Moreover,the optical properties of the products were investigated by UV-visible light absorption spectrum.Furthermore,methyl orange was used as a target molecule to estimate the photocatalytic activity of the specimens.Under the same testing conditions,the photocatalytic activity of the ultra-long TiO2 nanofibers was higher than that of P25.Direct electrical pathway and improved light-harvesting efficiency were crucial for the superior photocatalytic activity of the ultra-long TiO2 nanofibers.     

Properties of composite films of titania nanofibers and Safranin O dye

Titania (TiO₂) nanofibers and composite thin films of titania nanofibers and Safranin O dye (SAF) were studied. TiO₂ nanofibers were prepared by electrospinning technique from titanium tetra-isopropoxide precursor solution in ethanol. Surface topology of the nanofibers was observed using scanning electron microscopy (SEM), their crystal structure was studied by X-ray diffraction (XRD) and the chemical composition by X-ray photoelectron spectroscopy (XPS). Properties of the TiO₂ nanofibers were studied in dependence on the values of relative air humidity in the range from 15% to 55%. It was necessary to maintain the relative humidity lower than 30% during electrospinning in order to obtain high quality nanofiber films. The average minimum diameter of the as-prepared TiO₂ nanofibers was found to be around 100 nm. Nanofiber diameter diminishes to about 50 nm after annealing at 420 °C for 1 h. The as-prepared titania nanofiber films were completely amorphous while anatase crystal phase was detected in the films after annealing. In order to prepare the composite films, solution of SAF dye with poly(vinylpyrrolidone) in ethanol/water was dropped off on the prepared titania nanofibers surface. Opto-electrical properties of SAF dye and the resulting nanocomposite films were studied by UV–Vis spectroscopy and current–voltage characteristics. Safranin O is characterized by two strong absorption peaks; one at 274 nm and a wide band with splitting between 420 nm and 600 nm. The optical energy band gap of titania nanofibers was estimated from the UV–Vis measurements to be 3.4 eV. The charge transport in the composite films is influenced by the space charge limited currents due to the very high resistance of the materials.     

Polyaniline nanofibers synthesized in compressed CO2

Polyaniline (PANI) nanofibers were synthesized in compressed liquid carbon dioxide without any template or surfactant. The polymerization of aniline took place at the interface between CO₂ and aqueous solution in a high-pressure stirred reactor. The prepared PANI nanofibers were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), electrical conductivity (EC), Fourier-transform infrared (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) analyses. The yield of polymerization was high enough to reach 63.04% while maintaining small diameters of the PANI nanofibers. This result is very important for the preparation of the PANI nanofibers because no other previous investigations have achieved both high yield and small diameter of fibers at the same time. Through SEM and TEM analyses, we observed that the PANI nanofibers had diameter range of 30–70 nm and a length range of 0.3–1 μm, which caused them to disperse well in various solvents such as water, ethanol, 2-propanol, m-cresol and toluene. The electrical conductivity of the PANI nanofibers was 4.34 S/cm at 20 °C. The XRD diffraction pattern showed that the PANI nanofibers had crystalline one-dimensional structures, which gave high thermal stabilities as confirmed by TGA.     

Chemical in situ polymerization of polypyrrole on bacterial cellulose nanofibers

Conducting porous nanofibrous composite membranes of bacterial cellulose (BC) and polypyrrole (PPy) were prepared through in situ oxidative chemical polymerization of pyrrole (Py) on the surface of synthetized BC nanofibers by using FeCl₃ as oxidant agent. The influence of polymerization conditions on electrical conductivity, morphological and thermal stability of the BC/PPy composites was investigated. The amount of PPy deposited on the BC nanofibers increased with increasing the monomer concentration and reaction time while the electrical resistivity of the composites decreased due to the formation of a continuous layer that coated the nanofiber surface. Fourier transform infrared (attenuated total reflectance mode) spectroscopy (FTIR-ATR) of the composites revealed strong interaction between PPy and BC, as characterized by a blue-shift of C–N band of PPy towards pure PPy with increasing Py concentration. BC/PPy composites showed higher thermal stability than BC membrane due to the protective effect of the conducting polymer coating. Scanning electron microscopy (SEM) analysis of the composites revealed that PPy consisted of particles of mean size of 35 nm that form a continuous coating that fully encapsulates the BC nanofibers. The material properties obtained by the method described in this work for the BC/PPy composites open interesting possibilities for novel applications of electrically conducting bio-based composites, particularly those that may exploit the biocompatible nature of the BC/PPy membranous composite.     

电纺法制备PAN基高比表面积活性纳米碳纤维

将聚丙烯腈(PAN)粉末配制为PAN/DMF溶液,通过静电纺丝工艺制备了PAN纳米纤维,然后依次进行预氧化、碳化处理得到纳米碳纤维;采用CO₂作为活化剂制备了超大比表面积活性碳纤维。使用扫描电镜、场发射透射电镜、拉曼光谱,傅里叶红外光谱和N₂吸附等手段对样品的形貌、成分和结构进行了全面表征,研究了聚合物溶液浓度和静电压对PAN纳米纤维形貌和直径的影响。活性碳纤维独特的孔结构使其作为电极材料在多种电解液中保持了较高的比容量。结果表明活化后的碳纤维的比表面积、总孔容和微孔孔容都明显增加,本研究所制备的活性碳纤维具有极高的比面积和良好的电导率,使其在超级电容器电极材料领域有着进一步的应用。     

Fluorescence studies of electrospun MEH-PPV/PEO nanofibers

We report a study of the fluorescence properties of the conjugated polymer poly [2-methoxy-5-(2′-ethyl hexyloxy)-p-phenylene vinylene] (MEH-PPV) and polyethylene oxide (PEO) nanofibers. MEH-PPV/PEO nanofibers with different compositions have been fabricated by the electrospinning technique. The fluorescence spectra of the nanofibers show that the emission shoulder at ∼630 nm blue-shifts ∼45 nm, whereas the main emission peak around 590 nm blue-shifts ∼15 nm with decreasing concentration of MEH-PPV in the nanofiber. In addition, confocal microscopic studies of a single MEH-PPV/PEO electrospun nanofiber indicate that the fluorescence spectra of the nanofiber do not show any polarization dependence. The results are discussed in terms of the aggregation of MEH-PPV in an inert matrix.     

Electrospinning of carbon nanofiber supported Fe/Co/Ni ternary alloy nanoparticles

Polyacrylonitrile (PAN)-based carbon nanofiber supported Fe/Co/Ni ternary alloy nanoparticles were prepared by using the electrospinning technique for potential fuel cell applications. The solution was prepared by adding pre-solved catalytic precursor into PAN/DMF solution. The effect of PAN and catalyst precursor concentration on solution properties (viscosity and conductivity) and heat stabilization temperature has been investigated. Electrospun nanofibers were characterized by field emission scanning electron microscope, transmission electron microscope, energy dispersive spectrometer and X-ray diffractometer. It has been found that ternary nanoparticle size is in the range of 5–115 nm (average: 20 nm) and is a crystal alloy of Fe, Co and Ni. Also, TEM results demonstrate that in some regions metal nanoparticles tend to agglomerate into larger particles mainly due to the non-uniform distribution of nanoparticles in as-spun condition. PAN-derived carbon nanofiber mean diameter was measured as 200 nm by varying from 40 nm to 420 nm.