碳纤维表面原位SiC纳米纤维的合成与生长

基于化学气相反应法,以高纯Si和SiO₂为反应源材料,在碳纤维表面原位生长β-SiC纳米纤维。采用XRD、SEM和TEM 等分析测试手段对SiC纳米纤维进行了表征分析,研究了不同反应温度和时间对生成β-SiC纳米纤维微观形貌和结构的影响,并探讨了β-SiC纳米纤维的生长机制。研究结果表明：采取化学气相反应法能够制备高质量、高纯度的β-SiC纳米纤维,纳米纤维的直径约为100~300 nm。随着反应温度的提高和时间的延长,纳米纤维的产额增加,且微观组织形貌发生了变化。结合制备过程和纳米纤维微观结构的观察分析,表明气-固(VS)机制是SiC纳米纤维生长的主要机理。     

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。     

碳热还原温度对耐高温纤维增强碳化硅多孔材料组织结构的影响

本研究目的是开发一种耐高温纤维增强碳化硅多孔块状材料。以纤维增强间苯二酚-甲醛/氧化硅复合气凝胶为前驱体,经过1300~1500℃碳热还原制备了纤维增强碳化硅多孔材料。采用XRD、SEM、TEM、氮气吸附孔结构分析仪和压汞仪对纤维增强碳化硅多孔材料的物相组成、微观形貌和孔结构进行了表征,结果表明：纤维增强碳化硅多孔材料由β-SiC和莫来石纤维组成,随着碳热还原温度的升高,样品中的SiC纳米晶颗粒团聚成大块,最终在1500℃生成SiC晶须,升高碳热还原温度会导致样品中大孔的增多和纳米孔的消失以及比表面积的降低。热分析结果表明纤维增强碳化硅多孔材料在空气中的耐温性高达1300℃。纤维增强碳化硅多孔材料的密度为0.330~0.345g·cm^-3,孔隙率在89%以上,室温下热导率为0.06~0.07W·m^-1·K^-1。     

Fe-Co-Ni合金纳米粒子镶嵌的碳纳米纤维的简单制备及其吸波性能

通过在氩气中碳化含有乙酰丙酮金属盐的电纺聚丙烯腈纳米纤维合成了镶嵌（Fe_1-xCo_x）_0.8Ni_0.2（x=0.25,0.50,0.75）合金纳米粒子的碳纳米纤维,用X射线衍射（XRD）、扫描电镜（SEM）、透射电镜（TEM）、振动样品磁强计（VSM）和矢量网络分析仪（VNA）等对其物相、形貌、微观结构、静磁及电磁特性进行表征和分析,并根据传输线理论模拟计算了2~18 GHz频率范围内的微波吸收性能。结果表明：所制备的复合纳米纤维具有典型的铁磁特征,由无定形碳、石墨和面心立方结构Fe-Co-Ni合金三相组成,原位形成的合金纳米粒子沿纤维轴向均匀分布,且被有序石墨层所包覆。磁损耗和介电损耗间的协同作用及特殊的核/壳微观结构使仅含5%（w/w）的（Fe_1-xCo_x）_0.8Ni_0.2/C复合纳米纤维的硅胶基吸波涂层表现出优异的微波吸收性能。当涂层厚度为1.1~5.0 mm时,x=0.25、0.50和0.75的样品最小反射损耗分别达到-78.5、-80.2和-63.4 dB,反射损耗在-20 dB以下的吸收带宽分别为14.9、14.8和14.5 GHz,几乎覆盖整个S波段至Ku波段。通过调节合金的组成可对材料的电磁特性及微波吸收性能进行一定程度的控制。     

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。     

二氧化钛多孔纳米片在染料敏化太阳电池中的应用

运用连续吸附反应法和化学腐蚀-沉积法,用ZnO/FTO（氟掺杂氧化锡）多孔纳米片为模板,制备了TiO₂/FTO多孔纳米片。研究了吸附次数对形貌、光散射性能和染料敏化太阳电池性能的影响。最佳吸附次数为30,由此得到的太阳能电池的效率、短路电流密度J_sc、开路电压V_oc和填充因子FF分别为：5.57%、9.26mA·cm^-2、0.835V和72.04%。这个效率略高于P₂₅（5.32%）,但远高于ZnO（2.41%）。     

(Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05) O4+δ纳米纤维阴极的制备及电化学性质

采用静电纺丝法制备了（Pr_0.9La_0.1）₂（Ni_0.74Cu_0.21Ga_0.05）O_4+δ（PLNCG）氧化物纳米纤维。利用热重-差热分析（TG-DTA）、X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）和扫描电子显微镜（SEM）对材料的物相及微观形貌进行分析。研究表明950℃煅烧5 h得到平均直径420 nm、形貌均一的PLNCG氧化物纤维;1 000℃烧结2 h得到紧密附着在Ce_0.9Gd_0.1O_2-δ（CGO）电解质上的网状结构纤维阴极。电化学阻抗谱（EIS）测试结果表明纳米纤维阴极具有比粉体阴极更优越的性能。700℃的极化电阻（R_P）为0.134 Ω·cm²,比同组分的粉末阴极减少32%（R_P=0.197 Ω·cm²）。以纤维阴极构筑的电解质支撑单电池Ni-CGO/CGO/PLNCG在700℃的最大输出功率密度为231 mW·cm^-2。氧分压测试结果表明阴极反应的速率控制步骤为电荷转移过程。     

石墨基底对碳/碳化硼复合纳米绳形成的影响

利用邻碳硼烷(C₂H₁₂B₁₀)作为反应原料,二茂铁(C₁₀H₁₀Fe)作为催化剂,通过化学气相沉积法在石墨基片上生长出一种新颖的碳化硼纳米绳。用X射线衍射仪分析纳米绳的相结构,用场发射扫描电子显微镜(FESEM)和高分辨透射电子显微镜(HRTEM)观察纳米绳的微观形貌和结构,结果发现纳米绳的中心部分是碳化硼纳米线,在线的表面有非晶碳绳结,故纳米绳为碳/碳化硼复合物。研究了绳状产物的生长机理,表明石墨基片对产物的形成有至关重要的作用。     

纳米镍钴铁氧体空心微球的制备与性能

以乙二醇为溶剂,氯化铁、氯化钴、氯化镍和醋酸铵为反应试剂,采用溶剂热法制备纳米Ni_xCo_1-xFe₂O₄(x=0、0.3、0.5、0.7、1)铁氧体空心微球,研究镍含量对铁氧体空心球的磁性与吸波性能的影响。借助X-射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、振动样品磁强计(VSM)和网络分析仪对试样的物相组成、微观形貌和电磁特性进行表征。结果表明制备的镍钴铁氧体为尖晶石结构,且形貌为空心球,粒径在200 nm左右。当x=0时,镍钴铁氧体空心球饱和磁化强度最大为81.7 emu·g^-1,反射损耗在1 658.8 MHz有最小值为-16.9 dB。     

纳米镍钴铁氧体空心微球的制备与性能

以乙二醇为溶剂,氯化铁、氯化钴、氯化镍和醋酸铵为反应试剂,采用溶剂热法制备纳米Ni_xCo_1-xFe₂O₄(x=0、0.3、0.5、0.7、1)铁氧体空心微球,研究镍含量对铁氧体空心球的磁性与吸波性能的影响。借助X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、振动样品磁强计(VSM)和网络分析仪对试样的物相组成、微观形貌和电磁特性进行表征。结果表明制备的镍钴铁氧体为尖晶石结构,且形貌为空心球,粒径在200nm左右。当x=0时,镍钴铁氧体空心球饱和磁化强度最大为81.7emu·g^-1,反射损耗在1658.8MHz有最小值为-16.9dB。     

High Strength Electrospun Single Copolyacrylonitrile (coPAN) Nanofibers with Improved Molecular Orientation by Drawing

High-performance carbon nanofibers are highly dependent on the performance of their precursors, especially polyacrylonitrile (PAN).In this work, the copolymer of PAN (coPAN) was synthesized for electrospinning. A self-assembling set-up was used for the stretching of single coPAN nanofibers. FTIR and Raman spectroscopies were used to characterize the chemical structure of coPAN nanofibers. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to monitor the morphology of single coPAN nanofibers under different drawing times. Micro-tensile test was used to determine the mechanical properties of single coPAN nanofibers. The results indicated that the drawing led to an increase in degree of molecular orientation along the fiber axis from 0.656 to 0.808, tensile strength from 304 MPa to 595 MPa, and modulus from 3.1 GPa to 12.4 GPa. This research would provide fundamental information of high-performance electrospun coPAN nanofibers and offer opportunities for the preparation of high-performance carbon nanofibers.     

CVD Growth of Carbon Nanotubes and Nanofibers: Big Length and Constant Diameter

Summary: We report mass production of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) with relatively high length and aspect ratio. We synthesized carbon nanomaterials by chemical vapor deposition (CVD) of methane as the feeding gas on Fe/Mo nanoparticles that use alumina-aerogel support. Alumina-aerogel-supported Fe/Mo catalyst was prepared using sol-gel. Drying step performed using rotary evaporation and freeze-drying. CVD was performed using a quartz tube furnace. Samples were analyzed using scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Raman spectroscopy.     

一步法溶剂热催化合成纳米碳纤维

利用四氢呋喃为溶剂和碳源,通过溶剂热催化方法在500 ℃一步合成了纳米碳纤维,X-射线衍射（XRD）分析显示此法合成的碳纤维晶型为碳的六方石墨相,场发射电镜(FESEM)和透射电镜(TEM)照片进一步表明碳纤维平均直径为100 nm,长度达几百纳米至几微米,高分辨电镜照片揭示产品中碳的晶间距为0.34 nm;产品纯度通过热重法（TGA）分析;同时,拉曼光谱图显示在1 347和1 584 cm^-1处有2个强峰,这与石墨相碳的典型拉曼光谱图是一致的。     

Template‐Synthesized Copper Nanotubes via Electroless Plating

Template synthesis method of preparing copper nanotubes via electroless plating has been investigated in this paper. The tubular structures were obtained by calcinring copper‐coated carbon nanofibers. The final products were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), and x‐ray diffractometer (XRD). The results show that copper nanotubes can be synthesized by this method. The inner diameter of the prepared copper nanotubes is about 100 nm, and the wall thickness is about 25 nm. In this method, it is convenient to control the dimension or the shape of the obtained copper nanotubes by using different nanofibers as templates.     

手性聚苯胺纳米纤维的电化学制备

采用恒电位电聚合法制备了樟脑磺酸(CSA)掺杂的旋光异构性聚苯胺(PANI)纳米纤维. 用扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 紫外-可见吸收光谱(UV-Vis)和圆二色光谱(CD)对PANI纳米纤维的形貌和光学性质进行表征, 结合电聚合溶液胶束平均粒径和ζ电位的测定, 研究了具有旋光异构性PANI纳米纤维的形成机理和具有增强旋光异构性的原因. 所制备的PANI纳米纤维具有无双螺旋结构, 其形貌不随着苯胺浓度的改变而变化. 不同手性樟脑磺酸掺杂制备的PANI纳米纤维具有镜像对称的旋光异构性, 且具有较高的椭圆偏振率. 这种手性PANI纳米纤维的颜色和旋光性均可通过化学掺杂/去掺杂或电化学掺杂改变氧化还原态而呈现可逆变化.     

Fabrication of carbon fibers with nanoporous morphologies from electrospun polyacrylonitrile/poly(L‐lactide) blends

Porous carbon nanofibers were prepared through electrospinning a blend solution of polyacrylonitrile and poly(L ‐lactide), followed by carbonization at different temperatures and in different atmospheres. Structural features of these porous carbon nanofibers were characterized using scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, X‐ray powder diffraction, and Raman spectroscopy. Surface area and pore structure were evaluated using the nitrogen adsorption technique. It was found that carbon fibers prepared by this scalable and relatively economical method exhibited a porous surface morphology with high specific surface area and large pore volume. The fiber diameter, surface area, pore volume, bulky crystalline structure, and surface crystalline structure of these carbon nanofibers showed a strong dependence on the polymer precursor composition and carbonization condition. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 493–503, 2009     

Synthesis of polypyrrole micro/nanofibers via a self-assembly process

Novel polypyrrole (PPy) micro/nanofibers were synthesized via a self-assembly process by using 4-hydroxy-3-[(4-sulfo-1-naphthalenyl) azo]-1-naphthalenesulfonic acid (Acid Red B) as dopant and ferric chloride (FeCl₃) as oxidant. Experimental conditions, including the concentration of the dopant, reaction temperature and stirring state have been investigated for their influences on the morphology of the synthesized PPy micro/nanofibers. The products were characterized by scanning electron microscopy, transmission electron microscopy and Fourier-transform infrared spectroscopy. The formation mechanism of micro/nanofibers was studied. It is believed that the micelles formed by the dopant and pyrrole monomer act as templates during the synthesis process. Two functions of aggregation and synthesis are proposed in the reaction system simultaneously, and the morphologies of micro/nanofibers are the co-operations of these two functions. The maximum conductivity value of the PPy micro/nanofibers was 8.56 S cm^?1     

Highly Porous Amidoximed Carbon Nanofibers Supported Palladium(0) Nanoparticle Catalyzed Heck Reaction

Highly porous amidoximed carbon nanofibers(AOCNFs), which were fabricated via a conventional electrospinning technique followed by chemically modification, impregnation-reduction and carbonization process, had been used for the immobilization of palladium nanoparticles(Pd NPs) catalyst. During the carbonization process, polystyrene(PS) was selectively decomposed from bicomponent fibers, generating porous fibers. Fourier transform infrared spectroscopy(FTIR) result revealed the functional groups on PAN-PS fibers(PAN=polyacrylonitrile), AOPAN-PS fibers and AOCNFs; scanning electron microscopy(SEM) was used to observe the morphology of all stages of nanofibers; transmission electron microscopy(TEM) result gave the structure of through-hole morphology clearly visible and the dispersion of Pd NPs on the surface of nanofibers; and X-ray photoelectron spectra(XPS) confirmed that Pd nanoparticles on the surface of AOCNFs was of the metallic state. Moreover, the as-prepared catalyst exhibited high catalytic activity and efficient recycle for Heck coupling reactions between iodobenzene and acrylates.     

Fabrication of polyacrylonitrile/lignin-based carbon nanofibers for high-power lithium ion battery anodes

Low-cost carbon nanofibers are fabricated from lignin, the second most abundant raw material in wood after cellulose and polyacrylonitrile mixture as a carbon precursor by electrospinning, followed by suitable heat treatments. As the lignin content in the precursor increases, the carbon nanofibers become thinner, as seen from scanning electron microscopy images. However, their carbon structure and electrochemical performance are found to be very similar, even though surface functional groups on carbon nanofibers are slightly different from each other. For example, in the initial charge (lithium insertion) and discharge (lithium deinsertion) process, the reversible specific capacities of the various carbon nanofibers come from different precursor ratios of lignin and polyacrylonitrile are similar. Even at a fast (7 min) charge and discharge condition, the carbon nanofibers prepared from the lignin-containing precursors show a discharge capacity of 150 mAh g^?1. The lignin-based carbon nanofibers thus show promise for use in high-power lithium ion battery anodes with low price.