原位聚合法制备聚吡咯-钴铜锌铁氧体复合材料及其电磁性能

采用自蔓延燃烧法和原位聚合法分别制备纳米Co0.7Cu0.1Zn0.2Fe2O4铁氧体和聚吡咯(PPy)-Co0.7Cu0.1Zn0.2Fe2O4纳米复合材料.采用X射线衍射仪(XRD)、透射电子显微镜(TEM)和傅里叶红外光谱(FTIR)对材料的结构和形貌进行表征,使用波导法和振动样品磁强计(VSM)研究了材料的介电性能、微波吸收性能和磁性能.结果表明,制得了纯相的尖晶石结构Co0.7Cu0.1Zn0.2Fe2O4铁氧体,少量Cu2+离子替代了铁氧体八面体位置上的Co2+离子,使得材料的晶格常数减小;2种粉体粒子分散性较好,它们的平均粒径分别约为15 nm和50 nm;在5.0~20.0 GHz频率范围内,PPy-Co0.7Cu0.1Zn0.2Fe2O4复合材料的反射损耗在-16.25dB到-20.27 dB之间,且在18 GHz处出现极大值-20.27 dB,带宽为2.0 GHz(最强峰的半高宽),PPyCo0.7Cu0.1-Zn0.2Fe2O4复合材料的反射损耗明显大于铁氧体;PPy-Co0.7Cu0.1Zn0.2Fe2O4的饱和磁化强度(Ms)和剩余磁化强度(Mr)分别为12.9 A/g和4.29 A/g,小于Co0.7Cu0.1Zn0.2Fe2O4铁氧体的相应值,但复合材料的矫顽力大于Co0.7Cu0.1Zn0.2Fe2O4铁氧体的,为38.96 kA/m.     

镍钴锌纳米铁氧体的制备及磁热性能

以乙酰丙酮盐为前驱体,三乙二醇为溶剂,采用多元醇法制备了纳米Ni0.5-xCoxZn0.5Fe2O4(x=0,0.1,0.2,0.3和0.4)铁氧体.通过X射线衍射仪(XRD)、透射电子显微镜(TEM)、傅里叶变换红外光谱仪(FTIR)和振动样品磁强计(VSM)等对样品的结构、形貌和磁性能进行了表征.结果表明,所得纳米Ni0.5-xCoxZn0.5Fe2O4铁氧体的分散性较好,尺寸均一.在室温下产物的剩磁和矫顽力均较小,表现出亚铁磁性.纳米Ni0.3Co0.2Zn0.5Fe2O4铁氧体的饱和磁化强度达到41.34 A·m2·kg-1,其在交变磁场中升温可达到55℃,表现出较好的磁热性能.     

镧掺杂锶铁氧体-聚吡咯复合物的制备及磁性研究

用溶胶-凝胶法和溶液原位合成法分别制备镧掺杂锶铁氧体(Sr1－xLaxFe11.5Ni0.5O19, x＝0.0, 0.1, 0.2, 0.3, 0.4)粉末及其吡咯相对质量分数为60%和80%的聚吡咯-铁氧体复合物微粒PPY (Polypyrrole)/Sr0.8La0.2Fe11.5Ni0.5O19. 借助X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、红外光谱(FTIR)和振动样品磁强计(VSM)等分析手段表征了铁氧体粉末和复合物微粒的结构、形貌和磁性能. 结果表明, 包覆的聚吡咯外层对复合物微粒的形貌和磁性有一定的影响. 在外加磁场作用下, 复合物的饱和磁化强度MS随吡咯含量的增加而减小, 当吡咯含量等于0%, 60%和80%时, 对应的MS分别为59.4, 18.7和10.3 emu/g.     

聚苯胺/Co_(0.5)Zn_(0.5)Fe_2O_4纳米复合材料的制备及电磁性能

采用高分子凝胶法制备尖晶石型Co0.5Zn0.5Fe2O4,原位聚合法制备纯聚苯胺和聚苯胺/Co0.5Zn0.5-Fe2O4纳米复合材料.使用傅立叶红外光谱(FTIR)、紫外可见吸收光谱(UV-Vis)、X射线衍射仪(XRD)和透射电子显微镜(TEM)对复合材料进行了表征.FTIR和XRD的结果表明样品为纯聚苯胺和聚苯胺/Co0.5Zn0.5-Fe2O4.UV-Vis光谱表明聚苯胺/Co0.5Zn0.5Fe2O4苯环上的π-π*和n-π*分别红移了23nm和5nm.TEM照片可知,聚苯胺和聚苯胺/Co0.5Zn0.5Fe2O4粒子的平均粒径分别约为50nm和70nm.在8.2～12.4GHz测试频率范围内,聚苯胺/Co0.5Zn0.5Fe2O4的ε″数值在9.2～12.3之间,u″数值在0.15～0.16之间;聚苯胺/Co0.5-Zn0.5Fe2O4介电损耗低于纯聚苯胺,而磁损耗高于纯聚苯胺.     

室温铁磁性Ni2+掺杂TiO2纳米带的制备与表征

通过水热离子交换方法, 制得不同含量的过渡金属离子Ni2+掺杂的、锐钛矿型的TiO2纳米带. 使用X射线衍射(XRD), 扫描电子显微镜(SEM), 透射电子显微镜(TEM), 高分辨透射电子显微镜(HRTEM), X射线光电子能谱(XPS), 傅立叶变换红外(FTIR)光谱和磁性测试等手段对样品进行了详尽的表征. 结果表明, 经过离子交换, Ni2+离子进入到了TiO2纳米带的晶格中, 其中并没有形成金属Ni团簇或纳米颗粒. 此外, 磁性测试的结果表明, 实验制备的Ni-TiO2样品具有室温铁磁性和磁滞回线特性, 并且, 由于TiO2纳米带中Ni2+离子有较好的分散性, 在相同的外磁场条件下, 样品的磁化强度随着掺杂Ni2+含量的增加而增大.     

温和条件下元素对M~(2+)/Fe~(2+)/Fe~(3+)-LDHs转化成尖晶石铁氧体过程的影响(英文)

研究了二价金属离子在温和条件下(低于100℃,暴露于空气中)从水滑石M2+/Fe2+/Fe3+-LDHs(M=Co,Ni,Mn,Zn)转化成尖晶石铁氧体的过程中所起的作用。结果表明,该转化过程不仅与晶化温度有关,还与M2+在元素周期表中所处的位置有关。当这些二价金属离子处于同一周期并且相邻较近时,M2+的半径越大,水滑石微晶向尖晶石铁氧体的转化就越容易。此外,Fe2+在转化过程中起着至关重要的作用,如果没有Fe2+的参与,在此条件下的转化将无法进行。     

多核超顺磁性Ni0.5Zn0.5Fe2O4/SiO2催化载体的制备与表征

采用化学共沉淀法与溶胶-凝胶法相结合, 在制备过程中改变磁性纳米粒子和TEOS的引入方式, 成功地制备了多核超顺磁性Ni0.5Zn0.5Fe2O4/SiO2催化剂载体. 采用透射电子显微镜(TEM)、氮气吸附、X射线衍射(XRD)及物理性质综合测试系统(PPMS)对样品进行了表征, 利用永磁铁对载体的分离效果进行了验证. 研究结果表明, 改进制备方法后, 制备的载体比表面积明显增大, 这有利于催化剂在载体上的分散与固载; 样品的饱和磁化强度明显增加, 表明样品具有很好的磁响应能力, 有利于催化剂的分离, 同时, 载体的超顺磁特性也有利于液相催化体系中催化剂的分散.     

掺杂Co2+和Sm3+对纳米ZnFe2O4铁氧体的电磁损耗性质的影响

采用NaHCO3与FeCl3?6H2O,ZnSO4?7H2O,Co(NO3)2?6H2O和Sm(NO3)3?6H2O进行室温固相反应制得碱式碳酸盐和氢氧化铁混合前驱物,先微波加热,再热分解分别制得复合氧化物ZnFe2O4,Co0.5Zn0.5Fe2O4和Co0.5Zn0.5Fe1.95-Sm0.05O4.由激光粒度分析仪、XRD和SEM表征:获得了颗粒分布均匀、平均粒度为62nm左右的立方晶系尖晶石结构的纳米铁氧体粉体.并测试样品的相对介电常数和相对磁导率,研究了它们的电磁损耗特性.结果表明:在ZnFe2O4中,掺入Co2 ,Sm3 元素可以在100～1800MHz测试频率范围内不同程度提高材料的电磁损耗特性.     

添加Al2O3对Ni0.5Zn0.5Fe2O4纳米纤维结构和磁性能的影响

采用静电纺丝技术制备了添加0～20wt%Al2O3的Ni0.5Zn0.5Fe2O4纳米纤维。通过XRD、FESEM、TEM和VSM对样品的物相结构、形貌和磁性能进行了表征。结果表明,所合成的复合纳米纤维的直径都分布在40～150 nm之间,添加到纤维中的Al2O3主要以非晶态形式分布于铁氧体晶粒边界;随着Al2O3添加量的增加,可观察到γ-Fe2O3相逐渐析出,Ni-Zn铁氧体的晶格常数单调减小,说明有一些Al2O3进入到尖晶石晶格中取代了B位的Fe3+离子,Ni-Zn铁氧体的平均晶粒尺寸先增大后减小,在Al2O3添加量为8wt%时达到最大值39.2 nm;比饱和磁化强度和矫顽力随Al2O3添加量的增加呈现出相同的变化规律,先减小后增大,当Al2O3添加量超过5wt%时又开始变小。     

负载型双金属催化剂的制备及其等离子体催化氨分解制氢性能

利用等体积浸渍法制备了Fe-Co、Fe-Ni、Mo-Co、Mo-Ni双金属催化剂(总金属含量均为10%(w,质量分数),双金属摩尔比均为1:1),考察了其在等离子体条件下氨分解活性,结果表明Fe-Ni双金属催化剂表现出较好的协同作用。在此基础上,进一步考察了Fe/Ni摩尔比对其活性的影响。结果表明:当Fe/Ni摩尔比为6/4时,氨分解活性最好,而且该双金属催化剂稳定性良好。采用N_2物理吸附、X射线衍射(XRD)、H_2-程序升温还原(H_2-TPR)和高分辨透射电子显微镜(HRTEM)对催化剂的物化性质、还原性能、微观形貌等进行了研究。结果表明:活性较好的Fe-Ni双金属催化剂中,Fe与Ni形成尖晶石结构NiFe_2O_4,该结构有利于Fe和Ni的还原,即活性组分易恢复金属态,这可能是其活性较高的原因。     

Preparation of MnxNi0.5-xZn0.5Fe2O4 Nanorods by the Co-precipitation Method

Mn_xNi_0:5-xZn_0:5Fe₂O₄ nanorods were successfully synthesized by the thermal treatment of rod-like precursors that were fabricated by the co-precipitation of Mn²⁺, Ni²⁺, and Fe²⁺ in the lye. The phase, morphology, and particle diameter were examined by the X-ray diffrac-tion and transmission electron microscopy. The magnetic properties of the samples were stud-ied using a vibrating sample magnetometer. The results indicated that pure Ni_0:5Zn_0:5Fe₂O₄ nanorods with a diameter of 35 nm and an aspect ratio of 15 were prepared. It was found that the diameter of the Mn_xNi_0:5-xZn_0:5Fe₂O₄ (0≤x≤0.5) samples increased, the length and the aspect ratio decreased, with an increase in x value. When x=0.5, the diameter and the aspect ratio of the sample reached up to 50 nm and 7～8, respectively. The coercivity of the samples first increased and then decreased with the increase in the x value. The coer-civity of the samples again increased when the x value was higher than 0.4. When x=0.5,the coercivity of the Mn_xNi_0:5-xZn_0:5Fe₂O₄ sample reached the maximal value (134.3 Oe)at the calcination temperature of 600 oC. The saturation magnetization of the samples first increased and then decreased with the increase in the x value. When x=0.2, the satura-tion magnetization of the sample reached the maximal value (68.5 emu/g) at the calcination temperature of 800 oC.     

Typical superparamagnetism with improved electrical properties of nano modified bismuth ferrite multiferroic composites

Multiferroic composites with the chemical formula, (0.5) BiFeO₃ + (0.5) Ni_0.5Zn_0.5Fe₂O₄, in bulk and nano forms were synthesized by preparing bismuth ferrite (BiFeO₃ or BFO) in bulk (B) and nano (N) forms and nickel zinc ferrite (Ni_0.5Zn_0.5Fe₂O₄or NZFO) in nano form. Single phase BFO was synthesized using conventional solid-state reaction as well as sol-gel autocombustion methods and NZFO powders were prepared by using sol-gel autocombustion method, respectively. X-ray diffraction (XRD) studies reveal the existence of rhombohedrally distorted perovskite structure for BFO and cubic spinel phase for NZFO in single phase as well as composite samples. Microstructural studies and energy dispersive spectroscopy (EDS) data reveal the formation of grains, intergranular porosities and chemical purity of the synthesized samples. Dielectric and AC conductivity measurements confirm the existence of space charge polarization along with the small polaron model in these composites. Ferroelectric and magnetic studies show that there was a considerable enhancement in the ferroelectric and magnetic orders for the nano form of the BFO (N) + NZFO composite. The observed remnant polarization values 2.80388 & 7.75901 μC/cm², saturation magnetization values 37.96072 & 40.47491emu/gm for bulk BFO (B) + NZFO and nano BFO (N) + NZFO composites, respectively. Interestingly, both the samples exhibit superparamagnetic behaviour at room temperature with coercivities close to zero. This typical behaviour is attributed to the corresponding anisotropic contributions originated from the individual constituents. The observed variations in BFO (N) + NZFO sample attributed to the corresponding structural modifications brought about by the variations due to its size effect in the present work.     

Ultrasonic-assisted synthesis of PMMA/Ni0.5Zn0.5Fe2O4 nanocomposite in mixed surfactant system

PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite with superparamagnetic behavior was synthesized by in situ emulsion polymerization of methylmethacrylate (MMA) monomer in the presence of Ni_0.5Zn_0.5Fe₂O₄ colloidal suspension assisted by ultrasonic irradiation. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). XRD and FT-IR spectra confirmed the formation of PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite. TEM images showed that Ni_0.5Zn_0.5Fe₂O₄ nanoparticles with the particle sizes of about 12 nm were well dispersed in the polymer matrix. The nanocomposite at room temperature exhibited superparamagnetic behavior under applied magnetic field. The formation mechanism of PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite was proposed as well.     

A highly coercive carbon nanotube coated with Ni0.5Zn0.5Fe2O4 nanocrystals synthesized by chemical precipitation-hydrothermal process

Novel magnetic composites (Ni_0.5Zn_0.5Fe₂O₄-MWCNTs) of multi-walled carbon nanotubes (MWCNTs) coated with Ni_0.5Zn_0.5Fe₂O₄ nanocrystals were synthesized by chemical precipitation-hydrothermal process. The composites were characterized by X-ray powder diffractometer (XRD), X-ray photoelectron spectrometer (XPS), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy (MS), transmission electron microscopy (TEM), and selected area electron diffraction (SAED), etc. A temperature of about 200 °C was identified to be an appropriate hydrothermal condition to obtain Ni_0.5Zn_0.5Fe₂O₄-MWCNTs, being lower than the synthesis temperature of a single-phase Ni_0.5Zn_0.5Fe₂O₄ nanocrystals. The sizes of Ni_0.5Zn_0.5Fe₂O₄ in the composites were smaller than those of Ni_0.5Zn_0.5Fe₂O₄ nanocrystals in single phase. The composites exhibited more superparamagnetic than Ni_0.5Zn_0.5Fe₂O₄ nanocrystals in their relaxation behaviors. The magnetic properties measured by a vibrating sample magnetometer showed that the composites had a high coercive field of 386.0 Oe at room temperature, higher than those of MWCNT and Ni_0.5Zn_0.5Fe₂O₄ nanocrystals.     

AxMn1-xFe2O4铁氧体(A=Zn,Ni)中阳离子的占位有序化行为研究

基于尖晶石晶体结构信息,本文采用热力学三亚晶格模型,将材料热力学计算和第一性原理计算相结合,研究了Zn_xMn_1-x Fe₂O₄和Ni_xMn_1-xFe₂O₄立方相中的Zn²⁺、Ni²⁺、Mn²⁺以及Fe³⁺在8a和16d亚晶格上的占位有序化行为。结果表明:在锰铁氧体中,室温下Mn²⁺完全占据在8a亚晶格上,Fe³⁺完全占据在16d亚晶格上,属于正尖晶石结构;随着热处理温度升高,在1 273 K达到热处理平衡时的占位构型为(Fe_0.09³⁺Mn_0.91²⁺)[Fe_1.91³⁺Mn_0.09²⁺]O₄,在热处理温度升至1 473 K时,达到热处理平衡时的占位构型为(Fe_0.11³⁺ Mn_0.89²⁺)[Fe_1.89³⁺Mn_0.11²⁺]O₄,均与实验结果符合较好。在锌铁氧体中,室温下Zn²⁺完全占据在8a亚晶格上,Fe³⁺完全占据在16d亚晶格上,属于正尖晶石结构;在热处理温度较高时,Zn²⁺和Fe³⁺发生部分置换,符合实验结果。在镍铁氧体中,半数的Fe³⁺在室温下占据在8a亚晶格上,Ni²⁺与剩下另一半的Fe³⁺共同占据在16d亚晶格上,仅在热处理温度较高的时候发生微弱变化,亦与已有的实验结果吻合。在此基础上,本文进一步通过热力学预测建立了立方相尖晶石结构的Zn_xMn_1-xFe₂O₄、Ni_xMn_1-xFe₂O₄复合体系中阳离子占位行为与热处理温度对占位的影响。     

单分散NixZn1-xFe2O4纳米颗粒的制备及其磁热效应

以乙酰丙酮金属盐为前驱体,三乙二醇为溶剂,采用多元醇法制备了镍锌不同配比的Ni_xZn_(1-x)Fe_2O_4(x=0,0.3,0.5,0.7和1.0)铁氧体,并通过X射线衍射仪(XRD),透射电子显微镜(TEM)和振动样品磁强计(VSM)等对样品的结构、形貌、磁性能和磁热性能进行了表征。结果表明:Ni_xZn_(1-x)Fe_2O_4铁氧体分散性较好,尺寸均一,形状近似球形,平均粒径为4~5 nm。Ni_xZn_(1-x)Fe_2O_4纳米颗粒在室温下表现出亚铁磁性,饱和磁化强度随着镍含量的增加先增大后减小,当x=0.5时达到最大值29.38 emu·g~(-1)。在382k Hz交变磁场作用下,Ni_(0.5)Zn_(0.5)Fe_2O_4铁氧体温度可升温至313 K,表现出较好的磁热性能。     

Preparation and optical properties of TiO2?xNx/Ni0.5Zn0.5Fe2O4 core–shell nanocatalyst from sol–gel-hydrothermal process

A nitrogen doped TiO₂/Ni_0.5Zn_0.5Fe₂O₄ core–shell structure nanoparticles was prepared by low temperature sol–gel-hydrothermal process. The characterizations of the catalyst indicate that the Ni_0.5Zn_0.5Fe₂O₄ nanocrystals of about 25 nm are well-coated with crystalline N-doped titania. The absorption edges in the diffusion reflectance spectra of TiO_0.98N_1.02 and TiO_1.37N_0.63/Ni_0.5Zn_0.5Fe₂O₄ shift to visible light region. The core–shell nanocatalysts can effectively photodegrade organic pollutants in the dispersion system and can be recycled easily by an external magnetic field.     

高密度非球形和球形LiNi1/3Mn1/3Co1/3O2的合成和性能比较

利用二次干燥法和共沉淀法分别制备出了非球形的Ni_1/3Co_1/3Mn_1/3OOH前驱体和球形Ni_1/3Co_1/3Mn_1/3(OH)₂前驱体, 并分别和LiNO₃混合烧结合成高密度非球形和球形的锂离子正极材料Li(Ni_1/3Co_1/3Mn_1/3)O₂. XPS分析表明, 二次干燥法制备的非球形Ni_1/3Co_1/3Mn_1/3OOH前驱体其过渡金属Ni, Co和Mn的价态分别是＋2, ＋3和＋4, 而共沉淀法制备的球形Ni_1/3Co_1/3Mn_1/3(OH)₂前驱体其各金属价态为＋2; X射线衍射分析表明, 非球形的Ni_1/3Co_1/3Mn_1/3OOH前驱体比球形的前驱体具有较高的活性, 能够在低温下合成出Li(Ni_1/3Co_1/3Mn_1/3)O₂, 而且制备的产物结晶度高, 具有规整的层状α-NaFeO₂结构, 扫描电镜显示制备的非球形产物颗粒均匀, 颗粒间隙小, 振实密度高达2.95 g•cm^－3, 远高于球形的振实密度2.35 g•cm^－3; 充放电实验表明, 由非球形前驱体制备的Li(Ni_1/3Co_1/3Mn_1/3)O₂其充放电性能和循环性能以及体积比容量均高于球形正极材料.     

Determination of alkali, alkaline earth and transition metal ions in UO2, ThO2 powders and sintered (Th,U)O2 pellets by ion chromatography

An ion chromatographic method has been developed for the determination of traces of Li⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, Sr²⁺, Fe³⁺, Cu²⁺, Ni^2+, Co²⁺, Zn²⁺, Cd²⁺, Mn²⁺ in UO₂, ThO₂ powders and sintered (Th,U)O₂ pellets. This new method utilizes poly-(butadiene-maleic acid) (PBDMA) coated silica cation exchange column and mixed functionality column of anion and cation exchange to achieve the separation of alkali, alkaline earths and transition metal ions, respectively. It involves matrix separation after sample dissolution by solvent extraction with TBP (tri butyl phosphate)-TOPO (tri octyl phosphine oxide)/CCl₄. Interference of transition metal ions in the determination of alkali, alkaline earth metal ions are removed by using pyridine 2,6-dicarboxylic acid (PDCA) in the tartaric acid mobile phase. Mobile phase composition is optimized for the base line separation of alkali, alkaline earth and transition metal ions. Linear calibration graphs in the range 0.01–20 μg mL⁻¹ were obtained with regression coefficients better than 0.999. The respective relative standard deviations were also determined. Recoveries of the spiked samples are within ±10% of the expected value. The developed method is authenticated by comparison with certified standards of UO₂ and ThO₂ powders.     

Radar Absorption Properties of Ni0.5Zn0.5Fe2O4/PANI/epoxy Nanocomposites

A nitrate? citrate gel was prepared from metallic nitrates and citric acid by sol? gel process and was further used to synthesize Ni_0.5Zn_0.5Fe₂O₄ nanocrystalline powder by auto‐combustion. Then, two novel 15 and 35% (w/w) magnetic Ni_0.5Zn_0.5Fe₂O₄ containing polyaniline nanocomposites, named as PANI‐Ni15 and PANI‐Ni35, respectively, were prepared via in‐situ polymerization of aniline in an aqueous solution containing proper amount of Ni_0.5Zn_0.5Fe₂O₄ magnetic powder. The incorporation of the nanopowders to PANI matrix was confirmed by X‐ray diffraction (XRD), IR and SEM. Synthesized PANI‐NiZn ferrite composite particles were subsequently added to an epoxy resin matrix to produce related nanocomposites. The morphological properties of these nanocomposite materials were investigated by SEM and TEM. The electromagnetic‐absorbing properties were studied by measuring the reflection loss in the frequency range of 8.0 to 12.0 GHz. Results showed the reflection loss of the PANI‐Ni35 composite is higher than pure polyaniline and PANI‐Ni15. The good reflection loss of the nanocomposites suggests their potential applicability as radar absorber.