锰锌铁氧体磁流体粘磁特性实验研究

本文使用旋转粘度计在不同磁场强度和剪切速率下对不同体积分量的锰锌铁氧体磁流体粘度进行了测量。实验表明其粘度增量不符合经典的Shliomis流变特性模型。本文认为,实验所用磁流体中存在滴状聚合物,它具有极强烈的粘磁效应,剪切稀化现象也能说明聚合物的存在。     

锰锌铁氧体陶瓷纤维的制备与磁性能研究

以柠檬酸及金属盐为原料,采用有机凝胶.热分解法制备了Mn0.5zn0.5Fe2O4铁氧体陶瓷纤维.通过FTIR、TG/DSC、XRD、SEM分别对前驱体凝胶的结构、热分解过程及热处理产物的物相和形貌进行了表征,用VSM对纤维的磁性能进行了检测.结果显示所得Mn0.5zn0.5Fe2O4铁氧体陶瓷纤维由9.7～12 nm晶粒组成,直径从1μm到20μm,长径比可达1×103.纤维的晶粒大小在400～580℃范围内随焙烧温度的升高而增大.这些铁氧体纤维显示出了超顺磁性,超顺磁程度与组成纤维的晶粒大小有关.     

溶胶-凝胶法制备热敏锰锌铁氧体及其磁性研究

采用以硫酸锰、硫酸锌、硫酸亚铁以及柠檬酸为原料的溶胶-凝胶方法制备热敏锰锌铁氧体.在900℃煅烧,得到锰锌铁氧体的粉体.将粉体压成环形样品,在平衡气氛下,1350℃烧结.采用扫描电镜(SEM)分析锰锌铁氧体烧结体的显微结构;用HP4192,测量从室温到150℃的烧结体的磁导率.结果表明在800℃热处理,得到尖晶石结构的锰锌铁氧体粉体.在平衡气氛下,1300℃烧结2 h,得到尖晶石结构的锰锌铁氧体烧结体.扫描电镜(SEM)图谱显示烧结体显微结构致密,晶粒平均尺寸大约在5-10μm锰锌热敏铁氧体的磁导率μi在居里温度附近发生突变,说明锰锌热敏铁氧体的磁性由铁磁相转变为顺磁相在铁离子含量不变的条件下,随着锌离子含量(Zn2 )的增加,锰离子含量(Mn2 )的减少,锰锌热敏铁氧体的居里温度降低;锰锌热敏铁氧体的磁导率μi,随着锌离子含量(Zn2 )的增加而降低.     

水热法制备的锌锰铁氧体纳米晶的离子分布、缺陷与磁性能

采用XPS及氧化还原滴定等手段确定了一种锌锰铁氧体纳米晶的离子分布式。采用XRD测定的样品晶格常数(αM—0．8431nm)与通过理论计算的结果(α=O．8393nm)十分接近。样品在350，450和700℃经过4h热处理后，离子分布数相应发生了变化：阳离子空位数e在350℃时达到最大值0．05520；晶格常数α随晶体阳离子空位数e的增加而增大，当e大于0.05时，晶格常数α的增加变缓。热处理温度不同，样品比饱和磁化强度σm相应改变，在350℃有最小值58．5Am^2／kg。理论计算与实验结果表明，样品的比饱和磁化强度σm与晶体中阳离子空位数e和次晶格上各价态的离子分布方式有关。     

从废旧锌锰电池中回收锌和锰的工艺研究

废旧锌锰干电池经过剖开、焙烧处理，去除汞和碳粉，再用硫酸浸取，滤液采用沉淀法分离锌和锰。锌和锰的回收率分别为94．5％和93．6％。     

湿法制备锰锌铁氧体粉体的研究

以硫酸亚铁、硫酸锌和硫酸锰为原料,分别采用化学共沉淀法和溶胶-凝胶法制备锰锌铁氧体粉体.结果表明,溶液pH值是影响MnZn铁氧体合成的主要因素:草酸铵作为沉淀剂,溶液pH=4,柠檬酸作为络合剂,溶胶pH=5,在800℃均能获得高活性的锰锌铁氧体粉体.以溶胶-凝胶法制得粉体在1200℃煅烧获得单相、细晶、致密的MnZn铁氧体,材料矫顽力Hc=4.529×79.6 A/m.以共沉淀制备的粉体需较高温度(1250℃)烧结,晶粒尺寸较大,但粒径分布较均匀,铁氧体的饱和磁感应强度较大(Bs=57.62(A·m2)/kg.     

从废旧锌锰电池中回收锌和锰的工艺研究

废旧锌锰干电池经过剖开、焙烧处理,去除汞和碳粉,再用硫酸浸取,滤液采用沉淀法分离锌和锰.锌和锰的回收率分别为94.5%和93.6%.     

锌锰镍铁氧体纳米粉体的制备与磁性

采用化学共沉淀法制备锌锰镍铁氧体纳米粉体,用X射线衍射仪（XRD）、红外光谱仪（FT-IR）、透射电镜（TEM）和振动样品磁强计（VSM）等表征产物的结构、形貌和磁性能。结果表明：锌锰镍铁氧体的饱和磁化强度随着镍的相对含量（x）的增加呈现先缓慢增大（x=0～0．2）后急剧减小（x=0.2-0．3）然后再增大（x=0．3-0．4）的变化规律,这说明纳米铁氧体的磁性与其微观结构、颗粒尺寸、晶界和结构缺陷等因素有关。     

沉淀法合成纳米CeO2的晶粒生长动力学

以Ce(NO3)3·6HzO为铈源,(NH4)2CO3·H2O为沉淀剂,并加入一定量表面活性剂PEG4000,采用液相沉淀法制备前驱体Ce2(CO3)3·H2O,前驱体经热处理合成纳米CeO2.根据XRD线宽法研究了纳米CeO2热处理过程的晶粒生长动力学,结果表明随焙烧温度升高,CeO2晶粒尺寸显著增大;300℃下焙烧时间对CeO2晶粒尺寸影响不明显,700℃下CeO2晶粒随焙烧时间延长而长大,且焙烧初期粒径增长较快,超过180 min后增长速率变慢;700℃时CeO2晶粒生长指数为5,即符合5次方动力学方程,晶粒生长速率常数为1.986 5×104 nm5/min;由于纳米尺寸效应,使得CeO2晶粒生长活化能在低温区和高温区不同,低于400℃时为25.64 kJ/mol,高于400℃时为87.64 kJ/mol;认为热处理过程CeO2的晶粒生长为扩散生长机制.     

铁氧体磁性材料

超声波喷雾热分解法制取纳米Mn-Zn铁氧体颗粒;六方晶U型铁氧体Ba4Me2Fe36O60制造方法及磁性;烧结温度对锂铬铁氧体磁性的影响;六方晶铁氧体Ba4Me2Fe36O60制造方法及其磁性;Redox电容器锰铁氧体电极的电化学性能     

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.     

Microstructure and magnetic performance of Ni-substituted high density MnZn ferrite

The effects of NiO on microstructure and magnetic properties of Mn-Zn ferrite with a nominal composition of Zn0.32Mn0.60-xNixFe2.08O4 were investigated. The calcined powder of Mn-Zn ferrite was characterized by X-ray diffraction (XRD), the fracture surface of Mn-Zn ferrite was checked by scanning electronic microscope (SEM), and then the magnetic properties were measured. As a result, the substitution of Ni can cause the crystallattice constant of MnZn ferrite to decline, and the grain size to decrease, therefore improve the magnetic performance of MnZn ferrite whose density exceeds 5.0 g·cm-3.     

Preparation and properties of nanosize MnZn ferrite from δ-FeOOH

Ferrous ion was transformed into feroxyhyte (δ-FeOOH) by oxidation. Then, manganese sulfate and zinc sulfate in some ratio were added to the feroxyhyte solution. The co-precipitation was boiling reflux conditions sometime under constant stirring. The nanosize MnZn ferrite powder was formed. The mechanism of preparation of the nanosize MnZn ferrite was discussed, and the formation of feroxyhyte which was playing a key role during the process was mentioned. The properties of powder was tested by means of X-ray diffraction, transmission electron microscopy and vibrating sample magnetometer. The results show that the samples of spherical particles about 20 nm, which have characteristics of ferrimagnetism, has larger saturation magnetization, but the remanent magnetization and coercivity are comparatively smaller. The spinel MnZn ferrite nanosize powder was successfully prepared from δ-FeOOH at low temperature, with low-carbon steel and peroxide as main material.     

低温烧结Bi-CVG铁氧体的微结构与性能研究

利用传统陶瓷工艺制备了Y1.05Bi0.75Ca1.2Fe44V0.6O12铁氧体,并对其低温烧结特性进行了研究。结果表明,选择适当的预烧温度可以有效提高铁氧体的密度;烧结温度对相稳定性和磁性能影响显著。在900℃预烧、1100℃烧结,可获得晶粒大小均匀、结构致密的烧结体,其磁特性为：B=4．84×10^-2T,B=3．76×10^-2T,Hc=364A／m。     

磁场对纳米MnZn铁氧体前驱体形貌的影响

采用SEM，XRD，TEM，TG等手段研究了磁场对共沉淀法制备纳米MnZn铁氧体前驱体形貌及晶态结构的影响。结果表明，随着磁感应强度增大并达到某一临界值时，纳米颗粒形貌由球状向链状转变，继续增加磁感应强度将获得针状、棒状或纤维状的颗粒，10T强磁场下获得棒状颗粒呈现单晶结构。热重分析表明10T磁场下获得的纳米颗粒由于单维尺寸增加而导致活性降低。根据晶体生长理论，讨论了磁场影响纳米颗粒形核和长大过程的机理。     

Co基非晶软磁合金的制备与晶化动力学行为研究

采用旋铸急冷工艺在大气环境中制备出Co6.85Fe4Si10B17.5非晶合金带材.XRD分析表明:样品为完全非晶.用DiamondTG/DTA差热分析仪在高纯氩气保护下测量了非晶薄带的等温晶化动力学曲线.采用JMA方程计算出了合金的晶化动力学参数,在不同的晶化温度下,Avrami指数的值在2.11～2.58之间,晶化激活能Ec为113.67 kJ/mol.Co6.85Fe4Si10B17.5非晶合金的晶化方式是初晶型(761、791、803 K)和共晶型晶化(813 K),合金的晶化百分比与退火时间的关系曲线均为S型曲线.     

Development of MnZn ferrites by combinatorial synthesis and high throughput screening method

In this paper, the application of combinatorial synthesis and high throughput screening method to prepare low loss MnZn ferrite is investigated. The combinatorial synthesis and high throughput screening method is regarded as a novel technical method to develop new materials. It seems to be an attractive approach to fabricate MnZn ferrite, for it can accelerate rapid development, shorten research periods and save research funds. We analyze the technical route of the development of low power loss MnZn ferrite by this method in detail. Meanwhile, the influence of different dopants combination and sintering temperatures on magnetic properties of MnZn ferrites are discussed. Using this method, the prepared samples display higher magnetic performance, which can be applied in wider frequencies and temperatures range.     

含Nb管线钢针状铁素体相变动力学研究

采用Gleeble 3500热模拟试验机,研究含Nb管线钢连续冷却过程中的针状铁素体转变行为。将试样加热到1 050℃奥氏体化,冷却至850℃并分别保温0,300,600,1 200 s后冷却到室温。根据热膨胀曲线,采用杠杆定律绘制了相转变量-温度曲线,建立含Nb针状铁素体相变Jeziorny动力学方程。结果表明:随保温时间的增加,由于Nb(C,N)的析出,Nb(C,N)颗粒为针状铁素体提供更多形核位置,提高相变温度,促进针状铁素体转变,抑制贝氏体转变,最终由贝氏体、针状铁素体的混合组织转变为针状铁素体组织;相变开始时间减少,同时相变完成时间缩短,针状铁素体体积分数增加。     

FeNiAlGaPBSiC非晶合金的晶化动力学

采用单辊急冷法制备了Fe68Ni1Al5Ga2P9.65B4.6Si3C6.75非晶薄带.用XRD、DSC研究合金的晶化动力学过程.结果表明:合金的玻璃转变和晶化行为均具有动力学效应,其晶化类型为初晶型和随后的共晶型反应.用Kissinger法计算得到的Eg、Ex、Ep1、Ep2分别为703、373、446、723 kJ/mol,Eg远大于Ex,表明该合金具有较高的热稳定性.     

晶内铁素体在夹杂物上形核机制的讨论

从夹杂物与金属之间的界面能和热膨胀系数不同导致的应变能,夹杂物周围基体局域溶质贫乏等角度对晶内铁素体在夹杂物上形核机制进行讨论．并试图分析解释不同夹杂物对铁素体形核作用的差别。