煅烧温度对NiCuZn铁氧体粉末微观结构和磁性的影响

通过草酸盐共沉淀法制备了纳米级别的NiCuZn铁氧体粉末,采用X射线衍射和振动样品磁强计分析研究了不同煅烧温度对试样的微观结构和饱和磁化强度的影响。试验结果表明：通过草酸盐共沉淀法制备的Ni0.4Cu0.2Zn0.4Fe2O4铁氧体粉末,在一定煅烧条件下能够得到单一尖晶石相的粉末;随着煅烧温度的增加,试样的饱和磁化强度增加,矫顽力减小。     

制备条件对NiZn铁氧体纳米晶材料磁性能的影响

利用溶胶-凝胶法制备尖晶石结构的Ni1-xZnxFe2O4铁氧体纳米粉体材料,同时系统研究Ni/Zn比、溶液pH值以及煅烧温度对制备的Ni1-xZnxFe2O4铁氧体纳米材料微结构及磁性能影响。结果表明,随着Ni含量的增加,生成物中未反应的氧化铁不断增多。当x=0.3时,NiZn铁氧体的饱和磁化强度(Ms)最大。但随着温度的增加,氧化铁的含量减少,NiZn铁氧体的生成量增加。同时发现溶液pH值对Ni0.7Zn0.3Fe2O4铁氧体微结构及性能影响较大,当溶液的pH=5时,Ni0.7Zn0.3Fe2O4纳米材料的Ms最大。实验得到了NiZn铁氧体的最佳制备条件:Ni/Zn比为0.7/0.3,溶液pH值为5,最佳烧结温度为900℃。     

预烧温度及Ca含量对La-Ca-Co系铁氧体磁粉结构及磁性能的影响

采用常规的陶瓷工艺制备了La_0.572Ca_xSr₍(0.658-x))Co_0.356Fe_12.4O₁₉(x=0.1,0.2,0.3,0.4,0.5,0.6,0.658)磁粉,研究了预烧温度和Ca元素含量对磁粉晶体结构、显微组织和磁性能的研究。研究表明,在1 190～1 230℃的温度下预烧,磁粉均可形成具有典型M型六角晶系SrM铁氧体晶体结构的单一相结构。其中,在1 220℃预烧的磁粉具有最佳磁性能。Ca²⁺取代Sr²⁺导致M相的晶胞体积缩小,但是相结构稳定不变,随着Ca含量的升高,磁粉的饱和磁化强度出现了先升高后降低的变化规律,当x=0.5时M_s=59.30 emu/g,磁粉的矫顽力则变化不大。显微组织观察发现,磁粉颗粒主要呈现为等轴状,平均粒径为0.7μm。     

Cu及Mn掺杂NiZn铁氧体的合成及磁性能研究

利用溶胶-凝胶法制备尖晶石结构的Ni0.7-yZn0.3CuyFe2O4(y=0,0.1,0.2及0.3)。经微结构以及磁性能的研究发现,铜掺杂使样品在700℃时就形成了完全的尖晶石相,并且当铜掺入量为y=0.1时,样品的晶粒最大,最大值Ms达到66.7(A·m2)/kg。在此基础上,研究Mn掺杂对制备的样品(Ni0.6Zn0.3Cu0.1)1-xMnxFe2O4(x=0,0.01,0.02,0.03)的磁性能以及微观结构的影响。结果发现,铁氧体粉体的Ms随着Mn的增加基本保持不变;而环状样品的Bs,Br和Hc与锰含量以及烧结温度有着明显的变化关系,Bs和Br随着锰含量的增大先减小后增大,最小值分别达到Bs=305mT,Br=242mT。而矫顽力随锰含量的增大而增大。另外,Br与Bs都随着烧结温度的增大而增加,Hc减小。当烧结温度达到1050℃时,Hc,Bs和Br都趋于一个恒定的值。     

稀土La^3＋离子取代对M型锶铁氧体的结构和磁性的影响

采用陶瓷工艺，制备了Sr1-xLaxFe12O19M型锶铁氧体，系统地研究了稀土La^3 取代Sr^2 对M型六角铁氧体的结构和磁性的影响，La^3 离子取代部分的Sr^2 离子能明显改善M型铁氧体的内禀磁性。     

复合添加剂对NiCoCuZn铁氧体高频磁导率色散行为的影响

用低温烧结法制备NiCoCuZn尖晶石铁氧体,并研究了不同复合添加剂(Bi2O3-V2O5,Bi2O3-PbO)对其磁导率色散行为的影响。结果表明:在Bi2O3-V2O5复合掺杂时,晶粒尺寸随Bi2O3含量的增大而增大。微观结构的变化导致了材料初始磁导率和截止频率的变化。磁导率的色散机制主要以畴壁位移为主。然而在Bi2O3-PbO复合掺杂下,晶粒尺寸随Bi2O3含量的减小而增大,材料的初始磁导率较Bi2O3-V2O5复合掺杂更小,截止频率更高。     

铁电性SBT和铁磁性NiCuZn铁氧体复合材料的制备

采用固相法成功制备了铁电性SBT和铁磁性NiCuZn铁氧体的复合材料。借助于TMA，XRD和SEM技术，对复合材料的共烧特性、物相组成以及显微结构进行了研究。共烧特性研究表明，SBT和NiCuZn铁氧体的烧成收缩和烧成收缩率存在差异。物相分析表明，复合体系均由NiCuZn铁氧体和SBT两相所组成。显微结构表明，复合材料具有较高的密度和良好的显微结构。NiCuZn铁氧体的平均晶粒尺寸比SBT要大。     

煅烧工艺和稀土掺杂对钡铁氧体微纳米结构的影响

采用静电纺丝技术,以PVP的冰醋酸溶液为助纺剂,以Ba(NO3)2、Fe(NO3)3·9H2O、La(NO3)3·6H2O和C6H8O7·H2O为基本原料获得了BaFe12O19/PVP一维复合纤维,并利用SEM、XRD对复合纤维煅烧前、后样品进行形貌和物相的表征。结果表明:煅烧前,BaFe12O19/PVP复合纤维平均直径为350～500nm。经800,850℃煅烧2h,均生成了六方晶系的M型BaFe12O19相。随着升温速率的提高,依次形成了棒状、片状、颗粒状、八面体锥状的BaFe12O19。掺杂稀土元素镧并煅烧后,产物除BaFe12O19相外,还有少量LaFe12O19相,但对结构和形貌无明显影响。     

有机凝胶先驱体转化法制备Ni-Zn-Cu铁氧体纤维

以柠檬酸和金属盐为原料,采用有机凝胶先驱体转化法制备了Nix-Zn0.8-x-Cu0.2(x=0.1～0.4)铁氧体纤维.通过FTIR,XRD,TG/DSC,SEM和VSM对纤维先躯体凝胶的结构、物相组成、热分解过程、热处理后产物的形貌及磁性能进行了表征.结果表明在凝胶形成过程中金属离子单齿配位于柠檬酸根阴离子,形成线型分子结构,使凝胶有较好的可纺性先驱体纤维经1000℃焙烧2 h可得直径约为2 μm、长径比可达1000、晶粒沿轴向有序排列的Ni-zn-Cu铁氧体纤维.这些纤维在室温下有良好的软磁特性,其磁性能与组成和热处理温度有关.所制备的有机凝胶先驱体在1200℃的热处理过程中Ni0.4Zn0.4Cu0.2Fe2O4晶粒的生长呈现出低过饱和度条件下晶体台阶生长特征.     

退火温度对钴铁氧体薄膜结构和性能的影响

采用溶胶-凝胶法结合匀胶旋涂工艺在复合基片(Pt/Ti/SiO2/Si)上制备了钴铁氧体(CoFe2O4)薄膜,利用XRD、SEM、VSM分析了薄膜的微结构以及磁性能,研究了不同退火温度对钴铁氧体薄膜的结构和磁性能的影响.结果表明,钴铁氧体在500℃时开始形成尖晶石相.随着退火温度的增高,钴铁氧体晶粒逐渐长大,饱和磁化...     

Strontium ferrite powders prepared from oily cold rolling mill sludge by solid-state reaction method

Oily cold rolling mill （CRM） sludge is one of the pollutants emitted by iron and steel plants. Recycling oily CRM sludge can not only reduce pollution but also bring social and environmental benefits. In this study, using oily CRM sludge as sources of iron oxide, the strontium ferrite powders were synthesized in multiple steps including vacuum distillation, magnetic separation, oxidizing roasting, and solidstate reaction. The optimal technological conditions of vacuum distillation and oxidizing roasting were studied carefully. To consider the effects of Fe203/ SrCO3 tool ratio, calcination temperature, milling time and calcination time on magnetic properties of prepared strontium ferrite powders, the orthogonal experimental method was adopted. The maximum saturation magneti- zation （62.6 mA-m2.g-1） of the synthesized strontium ferrite powders was achieved at the Fe203/SrCO3 mol ratio of 6, 5 h milling time, 1250 ~C calcination temperature, and 1 h calcination time. Strontium ferrite powders syn- thesis method not only provides a cheap, high quality raw material for the production of strontium ferrite powders, but also effectively prevents the environmental pollution.     

Study on sintering process and characteristic of nanosized soft magnetic MnZn ferrite powders

The effect of sintering process (especially the sintering temperature) on the magnetic property and microstructure of sintered sample of nanosized soft magnetic MnZn ferrite powder was investigated. The sintered sample of MnZn ferrite was prepared by both traditional pressing and cool isostatic pressing on MnZn ferrite nanoparticals. The sintering process of which was segmented. Thedensity, microstructure and phase composition of sintered sample were analyzed by Archimedes'law, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The grain growth and densification in sintering process of MnZn ferrite were investigated. The magnetic property was measured by vibrating sample magnetometer (VSM) and Nim2000 magnetic material testing system. The results show that the better sintering temperature is 850 ℃, at which the better magnetic property and microstructure of sintered compact were obtained.     

Cofiring behavior of NiCuZn ferrite／PMN ferroelectrics di-layer composites

The cofiring compatibility between ferrite and relaxor ferroelectrics materials is the key issue in the production of multilayer chip LC filters. The cofiring behavior, interracial microstructure and diffusion of di-layer composites of NiCuZn ferrite/PMN relaxor ferroelectrics are studied. In order to analyze the matching condition of thermodynamic properties between ferrite and relaxor ferroelectric ceramics, TMA is performed on PMN ferroelectrics and NiCuZn ferrite with certain percentage of Bi2O3, respectively. EDS results demonstrate that serious element diffusions exist at the interface, which is in accordance with the phase analysis based on XRD patterns.     

Low-temperature sintering method for NiCuZn ferrite and effect of Mn addition on electromagnetic properties

Low temperature sintering NiCuZn ferrite was employed at most cases due to its co-firability with Ag （below 960 ℃）. The NiCuZn ferrite sintered body with high-strength and high-frequency magnetic properties was fabricated. Firstly, NiCuZn ferrite powder was synthesized under CO2 atmosphere at 500 ℃from the mixed doxalate synthesized by liquid phase precipitation method. Then a small amount of boric acid （H3BO3） was added to the powder, and the NiCuZn ferrite powder compact was prepared with Newton press and CIP methods. Finally, NiCuZn ferrite sintered body was fabricated by sintering at 900 ℃ under CO2 atmosphere. The minimum sintering temperature （800 ℃） was determined by the study of high temperature shrinkage. By this method, NiCuZn ferrite sintered body with 0.5% （mass fraction） boric acid was obtained, which has the bending strength of 340 MPa. The effect of various Mn addition on electromagnetic properties were studied.     

针状铁素体对超细晶铁素体钢力学性能的影响

针对利用形变强化铁素体相变工艺制备出的超细晶铁素体钢,其抗拉强度很高但伸长率偏低的问题,对其进行了组织精细分析。精细分析结果表明,针状铁素体的形成主要与轧后冷速有关,冷速越大,针状铁素体越多,针状铁素体对钢的力学性能具有双重影响,一方面钢的抗拉强度随着针状铁素体体积比的增加而增加;另一方面又因针状铁素体其内部的精细结构特征、形态特征、针尖效应及其尺寸等影响因素,使钢的伸长率大为降低。当将试验钢中针状铁素体体积比控制在7.28%左右时,可使钢的抗拉强度在高达740 MPa时,仍具有26%的理想伸长率。     

Effects of Sn-substitution on the microstructure and magnetic properties of Bi-CVG ferrite with low temperature sintering

[Bi_0.75Y_1.05−xCa_1.2+x](Fe_4.4−xSn_xV_0.6)O₁₂ (Sn_x:Bi-CVG) ferrite materials were prepared by conventional ceramic technique. The bulk density, microstructure and the magnetic properties of the obtained samples were analyzed. The results showed that moderate addition of Sn⁴⁺ in Bi-CVG could lower the sintering temperature and enhance the soft magnetic properties obviously. With the increase of Sn⁴⁺ content, the saturation magnetization first increased and then decreased, while the coercivity and the ferromagnetic resonance linewidth (ΔH) first sharply decreased and then slightly increased. Additionally, the specimen of [Bi_0.75Y_0.65Ca_1.6](Fe_4.0Sn_0.4V_0.6)O₁₂ sintered at 1075 °C possessed the highest density and the optimum magnetic properties: RD (the relative density) = 98.49%, H_c = 152.3 A/m, 4πM_s = 711.3 × 10⁻⁴ T, ΔH = 2.1 kA/m.     

Influence of surfactants on co-precipitation synthesis of strontium ferrite

Strontium ferrite (SrFe₁₂O₁₉) particles were prepared by co-precipitation method. The ferrite precursors were produced from aqueous mixtures of ferric chloride and strontium nitrate by co-precipitation, using 3 mol/L sodium hydroxide aqueous solutions as precipitant. Three surfactants sodium dodecyl sulfate (SDS), polyethylene glycol 6000 (PEG-6000), cetyltrimethylammonium bromide (CTAB), were applied and the influence of surfactants on the properties of the strontium ferrite particles was studied. The ferrite precursors were first precalcined in a muffle furnace at 400 °C and then mixed with KCl and NaCl using a planetary milling machine in order to lower the calcination temperature. Subsequently the mixtures were calcined at various temperatures. Structure and magnetic properties of the particles were characterized by X-ray powder diffraction, transmission electron microscopy and vibrating sample magnetometer. In this paper, effects of Fe³⁺/Sr²⁺ mole ratio were first verified and annealing temperatures were then discussed. The results show the strontium ferrite phase begins to form at 650 °C and complete at 800 °C after calcination, and the particles prepared using CTAB exhibit the best properties with respect to particle size and dispersibility.     

固溶处理温度对Fe-Mn-Al-C铁素体基轻质钢耐蚀性能的影响

利用光学显微镜、扫描电镜、X射线衍射仪等研究了热轧态、850、950和1050℃固溶处理Fe-Mn-Al-C铁素体基轻质钢的微观组织.通过测试固溶处理试样的极化曲线和阻抗曲线,以及观察试样在3.5％NaCl溶液中腐蚀后的表面状态,分析其耐蚀性.结果表明,试样经850℃固溶处理后的组织为铁素体+κ碳化物;950℃固溶处理...     

淬火温度对1Cr13马氏体不锈钢中铁素体含量的影响

通过JmatPro软件模拟及热处理试验,研究了1Cr13马氏体不锈钢中铁素体随淬火温度变化的规律。结果表明,1Cr13马氏体不锈钢淬火组织主要由马氏体+铁素体+少量碳化物组织成。淬火组织中相组成的相对含量主要受淬火温度的影响,当淬火温度为970 ℃时,铁素体含量最少,晶粒也较小,在这一温度淬火,调质后能够得到良好的综合性能,尤其能够保证高的低温冲击性能。     

针状铁素体钢的高温屈服应力及弹性模量

用热模拟试验机研究了C-Mn-Mo-Nb针状铁素体钢的相变特性,采用拉伸和压缩方法检测了试验钢在奥氏体化加热后冷却至不同温度时的屈服应力和弹性模量,采用高温拉伸试验机对比检测了加热至奥氏体化以下,试验温度时钢的屈服应力和弹性模量。结果表明：在奥氏体化后冷却过程中,钢的屈服应力在650～500℃相变温度范围内从约75 MPa提高至约450 MPa,但弹性模量在针状铁素体相变温度区间（600℃左右）出现谷值。在550℃以上,从室温加热至试验温度拉伸方法获得钢的屈服应力和弹性模量较奥氏体化加热法的高。相变过程中,晶体结构转变及位错密度增加是弹性模量波谷产生的主要原因;晶体结构转变、位错密度增加和析出使屈服应力急剧增加。而相同组织状态下,钢的屈服强度和弹性模量主要受温度影响。不同测试方法所得数据的差异,主要是由不同的组织结构转变而非测试方法造成。