溶胶凝胶自蔓延燃烧法制备NiZnCoCu铁氧体粉体

以金属硝酸盐和柠檬酸等为原料,利用溶胶凝胶自蔓延燃烧法制备了Ni0.5–xZn0.5Co0.1CuxFe1.9O4(x=0,0.10,0.15,0.20)粉体,将粉体在800℃下热处理2 h,通过FT-IR、XRD、SEM和VSM对粉体的物相结构和磁性能进行分析。结果表明,自蔓延燃烧粉体以Ni Zn Co铁氧体为主晶相,其中含有Fe2O3杂相,煅烧后杂相消失。煅烧有效推动了晶界移动,实现晶粒的长大。煅烧前后两类粉体的饱和磁化强度都随着Cu的含量增加而逐渐减小,同时矫顽力也都先减小后增加,其中煅烧粉体的磁性能较自蔓延粉体均得到提升。     

共沉淀法制备锰锌铁氧体微粉的研究

以硫酸亚铁、硫酸锰和硫酸锌为原料,采用碳酸盐共沉淀法制备了Mn1–xZnxFe2O4(x=0,0.2,0.4,0.5和0.6)铁氧体微粉。通过TGA-DSC、XRD和SEM等测试手段,分析其物相、微观结构和形貌,并用振动样品磁强计(VSM)测量其室温磁滞回线,重点探讨了锰锌铁氧体前驱粉在热处理过程中发生的反应。磁性能测试表明,随着Zn2+含量的增加,锰锌铁氧体微粉的比饱和磁化强度先增加后降低,当x(Zn2+)=0.2时,微粉的比饱和磁化强度最大,为84.24A·m2·kg–1。     

Fe_3O_4纳米棒的水热法制备及其磁性能研究

以柠檬酸钠作为添加剂,采用水热法制备了Fe3O4纳米棒,用XRD、SEM、TEM、HRTEM和ED等手段,对样品进行了表征,并对Fe3O4纳米棒的形成机理进行了探讨。结果表明:所制备之Fe3O4纳米棒的直径在50～80nm,长度大于2μm。Fe3O4纳米棒具有较高的饱和磁化强度和矫顽力,分别为77.8A·m2·kg–1和39.6kA·m–1。     

SiO2对纳米CoFe2O4结构和磁性能的影响

采用sol-gel法及经空气中热处理制备了CoFe2O4和CoFe2O4/SiO2纳米材料。利用XRD、SEM和振动样品磁强计(VSM)对样品的结构、晶粒尺寸及磁性能进行了研究。结果表明:SiO2的加入有助于降低CoFe2O4的形成温度,有效抑制CoFe2O4晶粒的长大,并使CoFe2O4的Hc提高。经900℃热处理的CoFe2O4/SiO2样品中已不存在杂相Fe2O3;CoFe2O4的晶粒尺寸从无SiO2时的78nm减小到15nm;样品的Hc由41.1kA·m–1提高到73.1kA·m–1。     

PLD生长Fe_3O_4薄膜的微结构及磁性能研究

以烧结α-Fe2O3为靶材,采用脉冲激光沉积(PLD)方法,在Si(100)基片上制备了Fe3O4薄膜。XRD分析表明,所得薄膜为立方尖晶石结构的Fe3O4,而且具有(311)和(440)择优取向;显微激光喇曼(Raman)光谱分析进一步证实薄膜中只出现单相Fe3O4;AFM分析表明,所得Fe3O4薄膜表面平整;采用VSM分析表明,Fe3O4薄膜的饱和磁化强度Ms约为170kA·m–1,而其矫顽力约为412kA·m–1。     

废旧镍氢电池在柠檬酸中的溶解条件及Ni_(0.5)Co_(0.5)Fe_2O_4的制备研究

研究了废旧镍氢电池正极材料在柠檬酸中的溶解条件。采用单因素和正交试验相结合的方法分析柠檬酸初始浓度、液固比、溶解温度、溶解时间等对钴、镍的溶解率的影响。实验结果表明:当柠檬酸浓度为2 mol/L,液固比(质量比)8:1,溶解温度90℃,溶解时间50 min,镍钴的溶解率最高。在最佳溶解条件下,采用微波水热法制备出性能较好的球形纳米级Ni0.5Co0.5Fe2O4,其磁性参数为:饱和磁化强度为50.312 A·m2/kg,剩余磁化强度15.306 A·m2/kg,矫顽力为0.052 726 T。     

废旧电池溶胶-凝胶-水热耦合法制备Mn0.6Zn0.4Cr0.4Fe1.6O4

以硝酸溶解废旧碱性锌锰电池所得的溶液为原料,采用溶胶-凝胶-水热耦合法制备了Mn0.6Zn0.4Cr0.4Fe1.6O4。借助于IR、XRD、SEM和VSM对产物的结构、晶型、形貌及磁性能进行研究,进而探讨了不同制备条件对材料结构和性能的影响。结果表明,在柠檬酸与金属离子的摩尔比为0.6：1,溶胶的pH值为7,水热温度为240℃的条件下能制备出性能较好的Mn0.6Zn0.4Cr0.4Fe1.6O4。在该条件下制备的样品形貌近似为球形,分散均匀,其磁性能参数为：饱和磁化强度为60.586 A·m2/kg,剩余磁化强度为4.0104 A·m2/kg,矫顽力为41.786 kA/m。     

热处理时间对铁磁性微晶玻璃磁性能的影响

以Fe2O3-CaO-SiO2-B2O3-P2O5系统为基础,采用基础玻璃析晶法制备铁磁性微晶玻璃热种子材料。通过XRD,确定了热处理样品中的主晶相为磁铁矿、硅灰石和赤铁矿;采用振动样品磁强计(VSM),测试样品室温下的磁性能;通过SEM,观察样品中晶体的形貌。研究了热处理时间对其磁性能的影响。结果表明:合理的热处理时间为2h,制得的铁磁性微晶玻璃的比饱和磁矩为26.2A·m2·kg–1。     

Cu或Sn与Fe共掺杂对ZnO晶体形貌和磁性的影响

采用水热法,在前驱物Zn(OH)2中添加一定量的分析纯FeSO4·7H2O和CuCl2·2H2O或SnCl2·2H2O,以3 mol/L KOH溶液作为矿化剂,填充度为35%,反应温度430℃,经24 h反应合成ZnO晶体。掺杂Fe的ZnO晶体室温下测量无磁饱和现象和磁滞回线,不具备室温铁磁性。Cu与Fe共掺杂合成ZnO晶体,随温度的升高其比磁化强度下降的幅度减小,室温下测量具有磁饱和现象和磁滞回线。Sn与Fe共掺杂的晶体形貌最好,且比磁化强度较大,没有随温度升高而下降,存在室温铁磁性和顺磁性。Cu或Sn元素的加入增加了掺杂Fe的ZnO晶体的磁性,改善了晶体形貌。     

Ba_xNi_(1–x)La_yFe_(12–y)O_(19)铁氧体的制备与磁性能研究

首先利用溶胶-凝胶法制备了BaxNi1–xFe12O19(x=0.2,0.4,0.6,0.8)样品,通过热重-差示扫描量热仪(TG-DSC)、X射线衍射仪(XRD)和振动试样磁强计(VSM)分析,确定了最佳煅烧温度和最佳Ba-Ni摩尔比。然后利用同样的方法制备了Ba0.6Ni0.4LayFe12–yO19(y=0,0.1,0.3,0.5)样品,利用场发射扫描电镜(FESEM)、XRD和VSM对产物进行表征分析。结果表明Ni2+取代Ba2+,进入其晶格内部,改变了铁氧体的磁性能。La3+的加入改变了铁氧体的矫顽力Hc、饱和磁化强度Ms和剩余磁化强度Mr。当y=0.3时,其Ms和Mr达到最大值,分别为51.0 A.m2/kg和32.3 A·m2/kg。     

Dispersion of ZrO2 nanoparticles in polyacrylonitrile: Preparation of thermally-resistant electrically-conductive oxygen barrier nanocomposites

Polyacrylonitrile/zirconium dioxide (PAN/ZrO₂) nanocomposites were synthesized by dispersion of ZrO₂ nanoparticles through the in situ emulsifier-free emulsion polymerization technique. The thermal stability of PAN/ZrO₂ nanocomposites was enhanced with increasing concentrations of ZrO₂ which may be due to dispersion of nanoparticles in PAN matrix. The electrical conductivity of nanocomposites gradually increased with increase in the ZrO₂ loading. The gas barrier property of PAN/ZrO₂ nanocomposites was determined by using gas permeameter and it was found that, the gas barrier property was reduced to about 10 times with increase of ZrO₂ proportions. This is because ZrO₂ nanoparticles in PAN/ZrO₂ nanocomposites created a tortuous path for preventing oxygen permeation. The electrical conductive PAN/ZrO₂ nanocomposites may be used in semiconductor devices and packaging materials.     

Rh?MoS2 Nanocomposite Catalysts with Pt‐Like Activity for Hydrogen Evolution Reaction

High overpotentials and low efficiency are two main factors that restrict the practical application for MoS₂, the most promising candidate for hydrogen evolution catalysis. Here, Rh? MoS₂ nanocomposites, the addition of a small amount of Rh (5.2 wt%), exhibit the superior electrochemical hydrogen evolution performance with low overpotentials, small Tafel slope (24 mV dec^?1), and long term of stability. Experimental results reveal that 5.2 wt% Rh? MoS₂ nanocomposite, even exceeding the commercial 20 wt% Pt/C when the potential is less than ?0.18 V, exhibits an excellent mass activity of 13.87 A mg_metal^?1 at ?0.25 V, four times as large as that of the commercial 20 wt% Pt/C catalyst. The hydrogen yield of 5.2 wt% Rh? MoS₂ nanocomposite is 26.3% larger than that of the commercial 20 wt% Pt/C at the potential of ?0.25 V. The dramatically improved electrocatalytic performance of Rh? MoS₂ nanocomposites may be attributed to the hydrogen spillover from Rh to MoS₂.     

RhMoS2 Nanocomposite Catalysts with Pt‐Like Activity for Hydrogen Evolution Reaction

High overpotentials and low efficiency are two main factors that restrict the practical application for MoS₂, the most promising candidate for hydrogen evolution catalysis. Here, Rh?MoS₂ nanocomposites, the addition of a small amount of Rh (5.2 wt%), exhibit the superior electrochemical hydrogen evolution performance with low overpotentials, small Tafel slope (24 mV dec^?1), and long term of stability. Experimental results reveal that 5.2 wt% Rh?MoS₂ nanocomposite, even exceeding the commercial 20 wt% Pt/C when the potential is less than ?0.18 V, exhibits an excellent mass activity of 13.87 A mg_metal^?1 at ?0.25 V, four times as large as that of the commercial 20 wt% Pt/C catalyst. The hydrogen yield of 5.2 wt% Rh?MoS₂ nanocomposite is 26.3% larger than that of the commercial 20 wt% Pt/C at the potential of ?0.25 V. The dramatically improved electrocatalytic performance of Rh?MoS₂ nanocomposites may be attributed to the hydrogen spillover from Rh to MoS₂.     

聚苯胺/复合钒钼酸纳米复合材料的制备与表征

采用原位氧化聚合法制备了聚苯胺/复合钒钼酸纳米复合材料,并对其进行了XRD、FT-IR、SEM表征和复阻抗谱分析。结果表明,聚苯胺以单层方式插入复合钒钼酸层间,由于层间缝隙限制以较伸展的链构相存在。随着苯胺(An)含量的增加,复合材料的电导率增大,当m(An):m(H2V10Mo2O31±y)为4:1时,复阻抗Z′小于0.2M?,Z″小于0.1M?。     

Low Electrical Percolation Threshold of Silver and Copper Nanowires in Polystyrene Composites

Silver and copper nanowires have been synthesized using a scalable method of AC electrodeposition into porous aluminum oxide templates, which produces gram quantities of metal nanowires ca. 25 nm in diameter and up to 5 and 10 μm in length for Ag and Cu, respectively. The nanowires have been used to prepare polystyrene nanocomposites by solution processing. Electrical resistivity measurements performed on polymer nanocomposites containing different volume fractions of metal indicate that low percolation thresholds of nanowires are attained between compositions of 0.25 and 0.75 vol %.     

Fabrication of ZnO-NiO nanocomposite thin films and experimental study of the effect of the NiO,ZnO concentration on its physical properties

ZnO-NiO nanocomposites thin films were elaborated at different mixing concentrations using sol gel and spin coating methods. Their structural and morphological evolutions as well as the optical and electrical properties were investigated. XRD diffraction and Raman spectra allowed phase identifications of ZnO (zinc oxide) and NiO (nickel oxide) with no appearance of secondary phases and the crystallinity of elaborated nanocomposite films improved with doping concentration increase. The grain sizes of obtained ZnO-NiO nanocomposites are investigated by AFM (Atomic force microscopy); they increase in the range (10–65 nm) and they are observed to affect the optical and electrical properties. In fact, ZnO-NiO nanocomposites thin films optical reflectivity decreased in the range (10–5%) with the increasing of mixing proportion and their resistivity decreased up to 1.4 10² Ω cm. The optical band gaps were in the range (3.3–4 eV). The values obtained by UV–Vis spectroscopy and ellipsometry are quite similar. We remarked also that the NiO concentration increase on to the nanocomposite induced a red shift of the gap value while the ZnO increase led toward a blue shift     

Effect of Nano-Ce-Doped TiO<Subscript>2</Subscript> on AC Conductivity and DC Conductivity Modeling Studies of Poly (<Emphasis Type="Italic">n</Emphasis>-Butyl Methacrylate)

Among the unique properties of polymer nanocomposites, electrical conductivity deserves a prominent place due to their wide applications in conducting adhesive, electromagnetic shielding and sensors. The present work focuses on the effect of cerium-doped titanium dioxide (Ce-TiO₂) nanoparticles on the conductivity studies of poly (n-butyl methacrylate), or PBMA, nanocomposites at different temperatures. The frequency-dependent alternating current (AC) electrical conductivity of PBMA/Ce-TiO₂ nanocomposites has been found to increase with increase in temperature and the concentration of Ce-TiO₂ nanoparticles. The activation energy calculated from the AC electrical conductivity has been found to decrease with frequency and increasing temperatures. The frequency exponent factor also showed a decrease with frequency, indicating the hopping conduction in the nanocomposites. The maximum AC conductivity has been observed for the composites with 7 wt.% sample. The direct current (DC) conductivity of PBMA/Ce-TiO₂ composites was also enhanced with the addition of Ce-TiO₂ nanoparticles. Experimental and theoretical investigations based on Scarisbrick, Bueche, McCullough and Mamunya modeling were undertaken to understand the observed DC conductivity differences induced by the addition of Ce-doped TiO₂ nanoparticles to PBMA matrix. The experimental conductivity showed good agreement with the theoretical conductivity observed using the Mamunya model.     

Synthesis of Polythiophene/Poly(3,4-ethylenedioxythiophene) Nanocomposites and Their Application in Thermoelectric Devices

Polythiophene/poly(3,4-ethylenedioxythiophene) (PTh/PEDOT) nanocomposites with luminescent characteristics and high thermoelectric (TE) performance were successfully synthesized by two-step oxidative polymerization in aqueous medium. First, PTh nanoparticles (NPs) were synthesized by use of FeCl₃/H₂O₂ as catalyst/oxidant system with poly(4-styrene sulfonic acid) (PSSA) as surfactant. PTh/PEDOT nanocomposites were then synthesized by in situ oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) on the surface of PTh NPs. The composition of the nanocomposites was controlled by varying the concentration of EDOT. Electron microscopy imaging and dynamic light scattering experiments confirmed the nanocomposites had a PTh core and a PEDOT shell/matrix. Finally, the TE performance of the PTh/PEDOT nanocomposites was investigated. The electrical conductivity and power factor of the nanocomposites were found to increase from 0.0001 S/cm to 475 S/cm and from 0.001 μW/mK² to 22.9 μW/mK², respectively, at the optimum PEDOT concentration.     

Magnetic and electric properties of BFO–NFO nanocomposites

Multiferroic nanocomposites of (1−x)BiFeO₃–xNiFe₂O₄ for x=0.2, 0.4, and 0.6 were prepared by a sol gel technique. The synthesized nanocomposites were characterized by X-ray diffraction (XRD). XRD confirmed, they being nanocomposites having desired phase with crystallite size ranging from 14.0 nm to 3.6 nm. The morphological analysis was done with the help of Transmission electron microscopy (TEM), which revealed the particle size to be in the range of 10–7 nm. Polarization–electric field (P–E) loop tracer was used to determine the ferroelectric properties of the nanocomposites. The dielectric constant at room temperature was analyzed upto 1 MHz frequency and was found to increase with increasing concentration. In order to investigate the magnetic behavior, a superconducting quantum interference device (SQUID) was used. The nanocomposites were analyzed by increasing the magnetic field up to 25 kOe and the magnetization was found to increase from 6 emu/g for x=0.2–10 emu/g for x=0.6, which was found to be optimum for the technological applications. The appropriate combination of two phases gave rise to higher magnetization.     

Electrochemically Induced High Capacity Displacement Reaction of PEO/MoS2/Graphene Nanocomposites with Lithium

Nanocomposites comprised of poly(ethylene oxide), molybdenum disulfide, and graphene were prepared by the hydrolysis of lithiated molybdenum disulfide in an aqueous solution of PEO and graphene. Structural analysis by XRD shows the nanocomposites are disordered with an expansion of ～6 Å in the interlayer spacing. During the first discharge, the nanocomposites electrochemically dissociates irreversibly into Li₂S and Mo and are able to continously cycle as Li₂S +Mo/Li_x ? S + Mo + Li_x+2 as shown by XRD of the discharged electrodes at different depth of discharge (DOD), cyclic voltammetry (CV), and high resolution TEM. A significant increase of the reversible capacity is found in as‐prepared MoS₂/PEO/graphene composite. The results suggest a new electro‐interaction between lithium and molybdenum metal that only occurs in the nanoregime and is enhanced by PEO. The addition of 2 wt% of graphene to the nanocomposites greatly increases the rate capability with rates as high as 10000mA g^?1 yielding > 250mAh g^?1 and recovering to > 600 mAhr g^?1 at 50mA g^?1.