Kinetics of Fe_3O_4 formation by air oxidation

1　INTRODUCTIONFe3O4 hasanumberofnovelpropertiesandper formances ,itsuniquemagnetic ,thermalandtribolog icalpropertiesmakeitanewtypeofmaterialspromis inginvariousapplicationssuchaspigment,toner ,in formationstorage ,ferrofluids ,bioprocessing ,elec tronicsandcatalyst[1,2 ] .Owingtothewideapplica tion ,majorityofresearchersfocusedontheprepara tionmethodsofmagnetite[310 ] ,however ,themech anismandkineticsofFe3O4 formationwerescarcelystudied .Thekineticsandmechanismofoxyhydrox idesformatio…     

光亮Fe—Ni合金电沉积工艺的研究

介绍了一种新的电沉积光亮Ｆｅ－Ｎｉ合金的方法。用这种方法在室温下电沉积出外观接近镜面的Ｆｅ－Ｎｉ合金镀层，其厚度可达３７μｍ。经Ｘ－ｒａｙ衍射及等离子光谱分析证实，所获得的合金镀层为γ（Ｆｅ－Ｎｉ）合金相，镀层中含Ｆｅ和Ｎｉ的量分别为２３．５％￣４５．７％和７６．２％￣５３．８％，同时含有少量的Ｐ和Ｂ元素。文中对电沉积的工艺条件、光亮剂ＨＢ、添加剂ＨＴ的作用和影响进行了分析和探讨。     

Synthesis of Ni-Zn ferrite and its microstructure and magnetic properties

1 INTRODUCTION Ni-Zn ferrite with spinel structure is a versatile technological material due to their high-resistivity and low-eddy current losses, particularly suitable for high-frequency applications. Ni-Zn ferrites have been commercially used in recording heads, antennas rods, loading coils, microwave devices and telecommunication applications fields, and so on[1?2]. Ni-Zn ferrites are usually prepared by the conventional ceramic method[3] and the wet-chemical method[4?16]. The cerami…     

在三价铬Cl--SO2-4体系中电沉积厚镀层的研究

研究了在新型尿素氯化物硫酸盐混合物三价铬溶液中电镀铬的工艺条件对镀层的影响,详细考察了电流密度、pH值、络合剂浓度、恒电流/恒电位方式对电流效率和镀层外观质量的影响.结果表明:pH值在1.9～2.3之间、电流密度在7～11 A/dm2范围内、络合剂浓度为2 mol/L时获得的镀层能达到较大厚度和较高的电流效率,镀层光亮致密.在此工艺条件下,可获得30～40 μm的镀层.提出了三价铬电化学聚合的新假设.     

Ni-Fe合金共沉积的电化学行为

通过线性扫描、循环伏安、交流阻抗方法,研究了柠檬酸溶液中Ni-Fe合金共沉积的电化学行为.结果表明,Ni-Fe合金的共沉积为异常共沉积,Fe发生了欠电位沉积;增大FeSO4浓度,阴极极化增大,镀层中Fe含量升高,镀层的耐蚀性降低;柠檬酸起增大电流密度、减小阴极极化、促进Ni-Fe合金共沉积的作用;光亮剂增大阴极极化,对Fe2 离子的阻碍作用大于对Ni2 离子的阻碍作用;陈化作用有利于阴极极化的增大和镀层光亮度的提高;Ni-Fe合金的共沉积过程为电化学步骤控制.XRD表明Ni-Fe合金为面心立方固溶体晶体结构,SEM表明镀层表面光亮平滑.     

粗硫酸镍脱除钙镁的工艺研究

研究了用化学沉淀法脱除粗硫酸镍中的Ｃａ、Ｍｇ。实验表明，络合沉淀剂是一种效果较好的沉淀剂，在６０℃、ＰＨ值在３．０－６．０之间、用量系数为１．５、反应时间１ｈ以上时，其脱除Ｃａ、Ｍｇ的效果良好，能达到电池用酸镍标准。     

用含铁废料制备软磁用高纯α-Fe2O3工艺的探讨

通过介绍以钛白副产硫酸亚铁、工业酸洗废液、平炉红尘等为原料制备软磁用α-Fe2O3的工艺，探讨了工艺方法、工艺参数及影响因素等。     

加大思想政治工作力度造就跨世纪的师资队伍

加大思想政治工作力度造就跨世纪的师资队伍中南工业大学龚竹青王章华客观现实要求青年教师迅速成长，在教学、科研中挑大梁，接好老一辈教师的班。认真研究他们的思想情况，进一步提高青年教师政治觉悟和思想素质，探讨和创造有利于他们健康成长的途径和环境，具有十分重...     

Preparation of cobalt-modified magnetite and its magnetic properties

Magnetite was modified by reaction with alkaline solution containing Co^2 and Fe^2 to obtain a cobalt ferrite layer on the surface of particles. The influences of modification conditions on the properties were investigated. The as-prepared particles were characterized by X-ray diffraction(XRD) and transmission electron microscope(TEM). The results show that pH value influences the particles composition directly, the desirable CoFe2O4 is obtained as pH value is 12. The coercivity of particles increases with the increase of cobalt content, and the cobalt efficiency reaches a maximum value at cobalt content of 2.71% (mass fraction). With cobalt modification, the magnetite particles have the similar lattice constant and structure to that without cobalt modification, and the squareness ratio is almost 0.5. The increase of the coercivity is attributed to the uniaxial magnetic anisotropy and magnetocrystalline anisotropy of cobalt-ferrite itself.     

含银废料中银的综合回收和利用工艺方法

综述含银废料中银的综合回收和利用工艺。分析银浸出、银回收和富集、银产品制备的各种工艺方法的特点和适用性。