用机械合金化方法制备纳米晶Ni-Zn铁氧体

用机械合金化方法球磨金属氧化物,通过机械化学反应合成了Ni-Zn铁氧体.XRD,DSC,TG等分析发现,在600℃空气中退火后样品完全转变成单相的尖晶石结构.球磨后粉末样品的平均颗粒尺寸为15～32 nm,在不同温度退火后晶粒有所长大.在空气中低于1000℃的温度下退火后的样品具有较高的比饱和磁化强度,最高σs=63.4 emu·g-1,可与块状样品相比.也讨论了真空退火对样品磁性的影响,800℃真空退火后样品的分子磁矩计算值为3.4～3 7μB.     

高能球磨法制备纳米晶Zn铁氧体

用高能球磨法制备了纳米晶Ｚｎ铁氧体。通过样品的Ｍｏｅｓｓｂａｕｅｒ谱及ＸＲＤ谱的测定,研究了纳米晶的形成过程。结果表明：球磨的３ｈα－Ｆｅ２Ｏ３即与ＺｎＯ发生机械化学反应生成Ｚｎ铁氧体,这种反应是通过先形成α－Ｆｅ２Ｏ３－ＺｎＯ固溶体而进行的。制得的纳米晶铁氧体有一定的晶格畸变。     

机械化学合成铁酸盐纳米晶的新进展

铁酸盐是一种重要的功能材料。本文介绍了纳米铁酸盐性质、应用及合成方法的特点。着重论述了机械化学法合成铁酸盐纳米晶的机制，并展望了该领域的发展趋势。     

高能球磨法合成纳米晶NiZn铁氧体的结构和磁性

报告了作者利用机械球磨方法成功制备纳米晶NiZn铁氧体软磁材料的实验结果。实验样品具有很好的单相结构,所形成材料典型晶粒尺度为10～50nm。结合纯Fe3O4球磨样品,初步估算其样品的合成效率大约为27%～44%,这一结果可利用两步合成及中间纳米颗粒的高活性给予理解。对本实验利用球磨方法直接获得的NiZn铁氧体样品表现出较低的磁化强度σm和较大的矫顽力Hc,其典型值为43Am2kg-1和377×103(4π)-1A/m。从实用化角度而言,必要的热处理将是必要的。实验进一步证明,除了传统的机械合金化制备纳米晶软磁合金材料以外,利用高能球磨制备纳米晶NiZn软磁铁氧体也将是一种有效可行的新方法。     

BaTiO3纳米晶机械力化学合成

在氮气保护下，采用高能球磨BaO，锐钛矿型TiO2混合粉体，机械力化学法成功地合成了BaTiO3纳米晶，并讨论了反应机制。发现在一定操作参数条件下，粉磨初期为无定形形成期（15h以前），混合物颗粒粒度减小，晶格畸变，转变为无定形；粉磨中期为固相反应期（15－30h），BaO与TiO2在机械力的作用下产生固相反应生成BaTiO3，同时BaTiO3晶粒长大；粉磨后期又转入动态平衡期（30h以后），固相反应基本结束，已生成的BaTiO3的晶粒生长与粉磨引起的晶粒减小处于动态平衡；XRD，SEM，TEM研究表明：合成BaTiO3纳米晶体的晶粒尺寸为10－30nm。     

锂铁氧体纳米晶的磁性能研究

我们用ＰＥＧ凝胶法合成出的ＬｉＦｅ＿５Ｏ＿３纳米晶，用ＸＲＤ和ＴＥＭ观测其粒径和形貌。用振动样品磁强计考察其比饱和磁化强度σ＿ｓ，随粒径口变化，得到样品的σ＿ｓ随Ｄ的减小而下降。     

用化学合成法制备ZnS：Mn纳米晶

报道了一种用化学合成法制备ＺｎＳ：Ｍｎ纳米晶的方法。制得纳米晶直径分别为３．０ｎｍ和３．６ｎｍ，紫外吸收峰分别在２６７ｎｍ和２７５ｎｍ，相对于体材料吸收带边３４０ｎｍ有明显的兰移。     

流变相法合成纳米晶Li铁氧体

以LiOH-H2O，Fe2O3和草酸为原料，通过流变相反应，制得草酸盐结构的Li铁氧体前驱体。将前驱体在远低于通常的固相反应的温度下进行热处理，得到Li铁氧体纳米粒子。这一反应通过LiFeO2作为中间相来完成。用XRD和VSM对制得的Li铁氧体粉体进行了表征。结果表明，所得铁氧体为纳米粒子，具有有序结构，且具有较高的饱和磁化强度和矫顽力。纳米晶Li铁氧体粉料表现出良好的微波吸收特性。     

用化学合成法制备ZnS∶Mn纳米晶

报道了一种用化学合成法制备ＺｎＳ∶Ｍｎ纳米晶的方法。制得纳米晶直径分别为３．０ｎｍ和３．６ｎｍ，紫外吸收峰分别在２６７ｎｍ和２７５ｎｍ，相对于体材料吸收带边的３４０ｎｍ有明显的兰移。３１０ｎｍ光激发的发射光谱峰值分别为５７９ｎｍ和５８２ｎｍ，表明Ｍｎ已掺入ＺｎＳ纳米晶之内。     

自蔓延高温合成Ni-Zn铁氧体中Zn挥发的研究

研究了在用不同方法（SHS方法和传统固相反应法）制备Ni-Zn软磁铁氧体粉体的过程中，Zn挥发量的变化。采用能谱分析（EDAX）和火焰原子吸收光谱法分别对两种方法的产物的Zn挥发量进行测定，结果表明，以SHS方法合成Ni-Zn铁氧体粉体可以有效地抑制Zn的挥发，确保材料配比的准确性，提高材料性能。     

La掺杂纳米晶Ni-Zn铁氧体的制备及电磁性能

采用高分子凝胶法制备了Ni0.5Zn0.5LaxFe2-xO4（x=0,0.02,0.05和0.08）纳米晶铁氧体.采用X射线衍射仪（XRD）、透射电镜（TEM）和HP8510网络分析仪分别对其结构、形貌和电磁性能进行了研究.结果表明,当x=0,0.02和0.05时,所得粉体为纯立方晶系尖晶石结构.Ni0.5Zn0.5Fe2O4粉体平均粒径为70nm.随着La离子掺杂量的增加,红外光谱中550cm-1处吸收峰向高波数移动,420cm-1处吸收峰向低波数移动.La离子的掺杂对Ni-Zn铁氧体的电磁性能有一定的影响.在X波段,与Ni0.5Zn0.5Fe2O4铁氧体相比,掺杂La的Ni-Zn铁氧体的tanδm值降低,tanδε值升高.Ni0.5Zn0.5La0.02Fe1.98O4铁氧体的tanδε平均值为0.616.     

Combustion Synthesis: Effect of Urea on the Reaction and Characteristics of Ni-Zn Ferrite Powders

The purpose of this study was to evaluate the effect of the urea content (fuel) on the reaction and the characteristics of Ni-Zn ferrite powders obtained by combustion synthesis. Several batches were prepared with different fuel contents, ranging from the stoichiometric composition between 20 and 100% (excess), while the desired molar proportion of the metal precursors was kept constant. The solutions were heated on a hot plate and then transferred to a muffle furnace preheated to 700°C, in which ignition took place. The resulting powders were characterized by XRD, BET, SEM, and sedimentation, aided by rotation measured through an optic light. The crystalline hematite (-Fe₂O₃) and Ni-Zn ferrite phases were present in all the compositions studied, and the appearance of the agglomerates varied from soft to hard with increasing urea content. The increased urea content, which promoted a longer flame time, influenced the growth and/or formation of hard agglomerates. After sintering at 1200°C/2 h using the stoichiometric composition, only the spinel structure Ni-Zn ferrite, with homogeneous microstructure, was present.     

Mechanochemical Synthesis of Double Hydroxides

It has been demonstrated that the formation of magnesium-aluminium double hydroxides [Mg_{(1 – X)}Al _X (OH)₂] ^X+(A ^n– _X/n ) m H₂O, (A–Cl^–, NO^– ₃, SO^2– ₄) occurs during mechanical activation of the mixture of magnesium hydroxide (brucite) with aluminium chloride, nitrate and sulphate in high-energy planetary-type activators. The effect of activation time on the formation of the double hydroxide has been investigated. Thermal decomposition of the chloride form of the double hydroxide has been studied.     

EDTA络合法制备Ni-Zn铁氧体及其磁学性质(英文)

以金属硝酸盐为原料,通过乙二胺四乙酸(EDTA)络合法制备了尖晶石型Ni1-xZnxFe2O4(x=0.0-0.7)晶体。通过TG-DTA考察了制备过程,采用XRD、FT-IR、SEM和VSM等对产物进行了表征,研究了热处理温度和Zn取代量对晶型结构和磁学性质的影响。同传统的固相法相比(1300℃/20h),制备单相Ni-Zn铁氧体所需的焙烧温度降至700℃,焙烧时间缩短至2h。随着Zn取代量的增加,晶胞参数递增,而矫顽力(Hc)和居里温度(Tc)逐渐下降。饱和磁化强度(Ms)随Zn取代量呈先递增至x=0.4后再逐渐下降。在1.5MHz的交变磁场中,所制粒子的感应温度接近设计的居里温度,能够适于感应加热的应用。     

Zn铁氧体纳米晶的磁性及微结构研究

通过高能球磨方法由α－Ｆｅ２Ｏ２＋ＺｎＯ混合粉体制得的Ｚｎ铁氧体纳米晶具有非正型分布的尖晶石结构,表现为亚铁磁性,其比饱和磁化强度σｓ＝１６．４ｅｍｕ／ｇ。通过适当的热处理可以使Ｚｎ铁氧体的结构向正型分布转变;使其磁性向顺磁性转变。     

镍锌铁氧体纳米材料制备及其光催化性能研究

以金属硝酸盐、硝酸镍、硝酸铁、硝酸锌为原料,柠檬酸和葡萄糖作为分散剂和燃烧剂,通过溶胶-凝胶自蔓燃法在200℃下制备了纳米Ni0.5Zn0.5Fe2O4光催化剂。通过XRD、TEM、VSM分析表明,所制样品为纯相尖晶石型镍锌铁氧体,颗粒大小约为18nm,饱和磁强度Ms为31.14A·m2/kg,剩余磁强度Ms为2.08A·m2/kg,矫顽力Hc为4949A/m,表现为铁磁性。样品的光催化性能实验表明,在Ni-Zn铁氧体+H2O2+可见光系统中,亚甲基蓝的降解率在2h内达到98%。反应后的样品通过磁力回收,用去离子水和无水乙醇清洗,60℃烘干后,进行3次重复实验,样品的降解率没有降低,表明样品性能稳定,是一种可回收的光催化剂。     

喷射-沉淀法合成纳米晶Ni-Zn铁氧体及表征

采用喷射-沉淀法成功地制备了纳米晶Ni-Zn铁氧体粉料。通过XRD、TG．DSC、SEM、TEM和BET等测试手段分析了其微观结构和形貌．结果表明：沉淀剂种类和溶液pH值对喷射．共沉淀法制备Ni-zn铁氧体纳米粉的物相和结构有着显著影响。采用NaOH溶液为沉淀剂，pH值范围为7．0～7．5，可以获得颗粒细小均匀、形状完整的纳米晶Ni-Zn铁氧体粉料。在600℃煅烧1．5h，样品晶粒尺寸为30nm左右，平均颗粒尺寸小于100nm。     

Steady-shear magnetorheological response of fluids containing solution-combustion-synthesized Ni-Zn ferrite powder

Magnetically soft nickel-zinc ferrite (Ni_0.5Zn_0.5Fe₂O₄) powder with high saturation magnetization was synthesized by solution combustion route using metal nitrates as precursors and glycine as fuel. The particles were found to have irregular morphology. Three different concentrations of magnetorheological fluids (MRFs) were prepared by dispersing 10, 20 and 40?wt% of these particles in thin silicone oil. The behaviours of the MRFs were studied under steady shear conditions at different applied magnetic field strengths (B). The yield strength (τ_Y) and viscosity (η) of all the MRFs were found to increase with B and particle fill fraction ?, while the response of the MRFs was strongly influenced by the morphology, microstructure and saturation magnetization of the particles. Owing to the low density of the particles, the observed off-state viscosity is high. However, the excellent thermo-oxidative and chemical stabilities of these magnetic oxide particles than metallic magnetic particles make these MRFs dependable for applications in harsh working environments. In addition, the low cost and feasibility of large scale preparation of these magnetic oxides make these MRFs further attractive for industrial applications.     

Ni_(0.5)Zn_(0.5)Fe_2O_4铁氧体的制备及其电磁损耗性能

以Zn(NO3)2.6H2O、Ni(NO3)2.6H2O和Fe(NO3)3.9H2O及柠檬酸为原料,采用溶胶-凝胶法制备前驱体,在1 200℃下煅烧3 h合成ZnFe2O4和Ni0.5Zn0.5Fe2O4铁氧体粉体。利用差热分析、X射线衍射、扫描电镜、透射电镜和红外光谱等测试手段对产物进行分析和表征。结果表明:ZnFe2O4和Ni0.5Zn0.5Fe2O4属于立方晶系尖晶石结构,结晶完整,晶粒大小在100 nm左右。在0.2~1.8 GHz的频率下对产品进行了电磁损耗性能测试,发现Ni0.5Zn0.5Fe2O4具有较好的电磁损耗特性。     

XRD and IR analysis of nanocrystalline Ni-Zn ferrite synthesized by the sol-gel method

Nanocrystalline Ni_1−xZn_xFe₂O₄ (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) ferrites were synthesized by the sol-gel method. The obtained powder was annealed at temperatures from 500 to 1000 °C. X-ray diffraction (XRD) and infrared spectroscopy (IR) were used to study the structural changes taking place with varying Zn content x. The grain size decreased while the lattice parameter increases with the increase of the Zn content.