片状钡铁氧体纳米磁粉的研究及应用

介绍了高密度磁记录媒体用的片状，替代式钡铁氧体纳米磁粉制备方法及其磁特性。分析，讨论了高密度记录对记录媒体磁特性的要求，介绍了最近研制的，先进的钡铁氧体纳米粉磁带及软磁盘的高密度度灵放特性。     

磁记录用Co—Sn替代钡铁氧体微粒的温度特性研究

为了减小磁记录介质在运行过程中因温度变化而引起的干扰以使其具有良好的磁记录特性,对用融盐法制备的化学组成为ＢａＦｅ１２－２ｘＣＯｘＳｎｘＯ１９（ｘ＝０￣１．４０）的Ｃｏ－Ｓｎ替代钡铁氧体微细磁粉的磁性及其与温度的依赖关系进行了测量与分析。讨论制备方法的不同对替代离子占位情况的影响。结果表明,作为一种高密度磁记录介质,替代量ｘ＝１．１０￣１．４０的Ｃｏ－Ｓｎ替代钡铁氧体磁粉不但具有合适的矫顽力Ｈｃ,     

磁记录用Co-Sn替代钡铁氧体微粉的温度特性研究

为了减小磁记录介质在运行过程中因温度变化而引起的干扰以使其具有良好的磁记录特性,对用融盐法制备的化学组成为ＢａＦｅ１２－ ２ｘＣｏｘＳｎｘＯ１９（ ｘ ＝ ０～１．４０）的Ｃｏ－Ｓｎ 替代钡铁氧体微细磁粉的磁性及其与温度的依赖关系进行了测量与分析。讨论了制备方法的不同对替代离子占位情况的影响。结果表明,作为一种高密度磁记录介质,替代量ｘ ＝ １．１０～１．４０的Ｃｏ－Ｓｎ 替代钡铁氧体磁粉不但具有合适的矫顽力Ｈｃ ,饱和磁化强度Ｍｓ 和适用的居里温度Ｔｃ ,而且在２７３～３３３Ｋ的范围内具有较低的矫顽力温度系数ΔＨｃ／ΔＴ ,并对ΔＨｃ／ΔＴ随ｘ 的变化机理做出了定性的解释     

钡铁氧体纳米微粒的微结构与磁性能

利用溶胶-凝胶自蔓延燃烧法制备了钡铁氧体纳米粉体,同时利用X射线衍射(XRD)、场发射扫描电子显微镜(FSEM)研究了钡铁氧体的微结构及形貌.结果显示制备的样品为单相磁铅石型结构钡铁氧体,晶粒尺寸在50nm左右.另外,利用振动样品磁强计(VSM)研究了样品的室温及高温磁性能,结果表明钡铁氧体在室温时具有较高的矫顽力(μ0Hc=0.557T)和饱和磁化强度(Ms=64.34Am2/kg),纳米钡铁氧体的磁性能随温度的升高而降低,其居里温度约730K.最后,探讨了纳米钡铁氧体颗粒间的相互作用,纳米钡铁氧体颗粒间不存在交换耦合作用,而是以长程静磁相互作用为主,这对于提高垂直磁记录材料的信噪比是非常有益的.     

钡铁氧体厚膜在自偏置微带结环行器中的应用

采用丝网印刷工艺制备钡铁氧体厚膜,研究了玻璃粉含量对钡铁氧体厚膜结构和磁性能的影响。基于所制备的钡铁氧体厚膜设计并制备了自偏置微带结环行器。结果表明,所制备的钡铁氧体厚膜具有明显的c轴择优取向,随着玻璃含量的适当增加,钡铁氧体厚膜的剩磁比和矫顽力增大,磁性能提高。钡铁氧体厚膜在c轴方向上的最大剩磁比为0.72,矫顽力最高为286.6kA/m。钡铁氧体厚膜应用于微带结环行器,在中心频率38.6GHz处插入损耗为18dB,隔离度为40dB。     

回转窑湿法烧结工艺探讨

目前,利用回转窑烧结磁粉大都采用先氧化,后造球,再烧结的工艺方法;本文从节能降耗、缩短工序、降低成本的角度,对用铁鳞作原料、用煤气回转窑直接烧结锶(钡)铁氧体磁粉的湿法生产工艺进行利弊讨论。     

湿法制备机械取向型永磁铁氧体磁粉的工艺研究

高性能磁粉是生产各种特殊要求的粘结磁体的关键原料。本文叙述了湿法制备具有机械取向特性的铁氧体磁粉的工艺研究，并对磁粉进行了多方面的物化测试。     

磁盘生产中的颗粒表面分散技术

本文介绍近年研制和生产新型大容量的微机软磁盘过程中所采用的制取钡铁氧体超细磁粉以及将磁粉分散成磁浆的新工艺．     

永磁铁氧体粉碎制粉工艺分析

永磁铁氧体单畴颗粒制造方法可分二大类。一类是化学法,另一类是陶瓷法。陶瓷工艺制造单畴颗粒按粉碎设备不同又可分球磨法,振动磨法,气流磨法和砂磨法等。下面对陶瓷粉碎工艺制造永磁铁氧体单畴颗粒谈一些不成熟的意见。一、永磁铁氧体湿磨工艺改革我厂永磁锶钡铁氧体球磨工艺原来是封闭式,即把料、球、水按一定比例装在桶内     

共沉法制备铁氧体及其应用

共沉法的种类较多,本文主要介绍氧化法。用这种工艺不但能制备超优的Mn-Zn铁氧体材料,而且还能制备高性能的磁头材料、磁记录介质,耐腐蚀电极以及颜料等。此外,利用铁氧体的共沉工艺可以处理废水,并介绍了废水处理所得的付产品的应用。     

Multifunctional SrTiO3/NiZn ferrite/POE composites with eletromagnetic and flexible properties for RF applications

Multifunctional dielectric composites with electromagnetic and flexible properties for RF applications were investigated. A kind of low loss flexible dielectric and magnetic composite with SrTiO₃ (STO) ultrafine particles and NiZn ferrite (NZO) ultrafine particles embedded in a Thermoplastic Polyolefin Elastomer (POE) matrix was fabricated using the extrusion technology. The dielectric and magnetic properties of the as-prepared composites with different volume fraction of ceramic fillers were studied. The results indicate that when the volume of the ceramic fillers is fixed, the permittivity of the composites increase while the dielectric loss, permeability and magnetic loss decrease with the increasing of the ratio of STO to NZO. The cut-off frequencies of the composites are all above 1 GHz. The good frequency stability of the electromagnetic properties within a wide frequency range was observed. All the composites show very good flexibilities. With the increasing of the volume fraction of ceramic fillers, the tensile strength and elongation decrease. The obtained multifunctional flexible magnetic-dielectric composites are good candidates for the applications of the capacitor-inductor integrating devices in RF communications such as electromagnetic interference filters and antennas.     

离子取代对W型Ba铁氧体结构及磁性能的影响

采用柠檬酸溶胶-凝胶法制备了BaZn2-xNixFe16O27纳米六角铁氧体,利用X射线衍射(XRD)、扫描电镜(SEM)和振动样品磁强计(VSM)对其物相组成、显微结构和磁性能进行了表征和测量。结果表明,溶液在中性和适当的温度下形成溶胶,经热处理可获得晶型良好的W型六角铁氧体;随着Ni量的增加,材料的比饱和磁化强度上升,矫顽力下降,比剩余磁化强度在x=0.4时达到最大值。     

Transient electromagnetic interference in substations

Electromagnetic interference levels on sensitive electronic equipment are quantified experimentally and theoretically in air and gas insulated substations of different voltages. Measurement techniques for recording interference voltages and currents and electric and magnetic fields are reviewed and actual interference data are summarized. Conducted and radiated interference coupling mechanisms and levels in substation control wiring are described using both measurement results and electromagnetic models validated against measurements. The nominal maximum field and control wire interference levels expected in the switchyard and inside the control house from switching operations, faults, and an average lightning strike are estimated using high frequency transient coupling models. Comparisons with standards are made and recommendations given concerning equipment shielding and surge protection     

Inorganic ceramic/polymer ferroelectric composite electrets

Ferroelectric composites are now an established alternative to conventional ferroelectric ceramic materials and to the more recently discovered ferroelectric polymers. These materials due to their unique blending of polymetric properties of mechanical flexibility, formability and low cost with high electro-active properties have been been suggested to be a viable alternative both in piezoelectric and pyroelectric transducer applications. This review is devoted to the piezoelectric and pyroelectric properties exhibited by these type of composites with a special reference to those made of ceramic particles embedded in a polymer matrix (i.e. 0-3 connectivity type composite). A review of models predicting the electro-active properties of 0-3 composites is presented together with a proposal for a new mixed connectivity cubes model to be applicable to the case of high ceramic loading and/or when the ceramic grain size incorporated in the polymer matrix is comparable to the thickness of the sample. A review of the experimental results of the piezo- and pyroelectric properties of various ferroelectric composite materials, reported by several workers, is also presented in this paper. Special reference is made to composites made from calcium modified lead titanate and poly(vinyldene fluoride-trifluorethylene) emphasizing their advantages in the poling process which is a critical phase in the process of obtaining successful electro-active 0-3 composite electrets     

磁记录介质的表面形貌和磁结构的观测

使用磁力显微镜和偏光显微镜观测了硬磁盘，磁光盘，录像带，录音带和磁卡的表面形貌和磁结构，揭示了磁记录介质的信息存储状态，对于不同的记录模式，介质的磁结构截然不同，并且表面平整度也有差别，记录密度越高，介质表面越平整。     

Ba(ZnTi)_xFe_(12-2x)O_(19)铁氧体的磁特性

采用标准陶瓷工艺 ,并进行湿压磁场成型和氧气氛烧结 ,制备了高取向度、低介电损耗的各向异性 Ba(Zn Ti) x Fe12 - 2 x O19多晶六角铁氧体。根据分析 ,我们认为 M型六角钡铁氧体的六面体位 2 b位是一个特殊的四面体位 ,Zn2 +取代了 4f1和 2 b位上的 Fe3+,而 Ti4 +取代了1 2 k和 2 a位上的 Fe3+。     

Co离子添加对NiZn铁氧体电磁性能的影响

用传统的陶瓷工艺制备了Co掺杂Ni0.24Zn0.6Fe1.98O4铁氧体材料,研究了Co掺杂量对NiZn铁氧体磁性能的影响.实验发现,在掺杂少量Co的情况下,随着掺杂量的增加,NiZn铁氧体的晶粒均匀生长,截止频率增高,损耗减小,介电常数在较宽频率范围稳定.因而,添加适量的Co离子,能有效改善NiZn铁氧体的性能.     

Electrostatic atomization of conducting liquids using ACsuperimposed on DC fields

The objective of this study is to investigate the possibility of using electrostatic atomization to produce fine ceramic particles starting from highly conducting ceramic precursor solutions. The work was directed towards carrying out experimental investigation for the production of uniform droplets formed by the breakup of a permanent jet extending from the capillary nozzle. To control the atomization process an AC field (sine wave) was superimposed on a DC field. For given parameters of electrostatic field, capillary diameters, resistivity of liquids, and flowrate, the jet formation and breakup process was investigated. Several regimes were observed to be in synchronization with the applied potentials and frequencies. In these regimes uniform droplets were produced. Optical techniques were employed to study the breakup process     

Formation of ceramic thin films using electrospray in cone-jet mode

An electrostatic atomization technique has been developed to generate ultrafine spray droplets of ZrO₂ and SiC ceramic suspensions in a range of a few micrometers with a narrow size distribution. The aim of this paper is to deposit uniform thin films (from a few micrometers to a few tens of micrometers) of these ceramic materials on alloy substrates. Compared to some other thin-film deposition techniques, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), and plasma spray (PS), etc., the thin-film deposition process using electrostatic atomization is not only cheap but also capable of depositing a very thin multilayer with abrupt interfaces. CVD and PVD are expensive techniques. They require either a high vacuum, even an ultrahigh vacuum environment or complex gas handling system. Their deposition rate is also low. PS is normally used to grow thermal barrier coatings which usually have a thickness of a few tens to a few hundreds micrometers. Its application is limited by the quality of the coatings (high porosity, coarse and nonuniform microstructure). Preliminary results in this work have shown that, for low through-put atomization, the cone-jet is the most suitable method to produce a fine charged aerosol with a narrow size distribution, which is crucial to produce uniform thin films. It was found that the size of ceramic particles in ZrO₂ and SiC thin films is less than 10 μm. Microstructures of these thin films show very homogenous morphologies. These results indicate that ceramic thin films with high homogeneity can be deposited using electrostatic atomization. It was also observed that the morphology of the underlayer has some influence on the morphology of the top layer