Defect engineering has attracted significant interest in perovskite oxides because it can be applied to op-timize the content of intrinsic oxygen vacancies (V-O) for improving their recoverable energy-storage density (W-rec). Herein, we design 0.84Bi(0.5+x)Na(0.5-x)TiO(3)-0.16KNbO(3) (-0.02 <=& nbsp;x <=& nbsp;0.08) relaxor ferroelectric ceramics with A-site defects and discuss the influence of VO on W-rec. The composition with x = 0.02 has a high W-rec (3.35 J/cm(3)) as well as a high efficiency (eta = 91%) at 240 kV/cm, and exhibits excellent temperature, fre-quency, and fatigue stabilities. This optimized composition also provides a large discharge-energy-density (W-D = 1.0 J/cm(3)), a high power-density (P-D = 66 MW/cm(3)), a fast discharge-rate (122 ns) at 150 kV/cm, and favorable temperature-induced charge-discharge properties (CDPs). Electron paramagnetic resonance, X-ray photoelectron, and Raman spectroscopic results reveal that the outstanding comprehensive perfor-mance of the designed materials is attributed to the coupling effect of low contents of dimeric (Ti'(Ti -& nbsp;) V-O center dot )(x) & BULL; clusters and high contents of trimeric (Ti'(Ti)& nbsp;- V-O center dot center dot & nbsp;- Ti'(Ti))(x) clusters. This work provides key insights relevant for developing lead-free ceramics with excellent energy-storage properties (ESPs). (C)& nbsp;2022 Elsevier B.V. All rights reserved.

Surface functionalization of piezoelectric greatly determines its piezo-catalytic activity and selectivity in that functional group affect specific reactants’ surface adsorption and activation abilities. Herein, we propose chemical functionalization on the surface of nano-scaled BaTiO3 piezoelectric via a one-pot hydrothermal process using polyethylene glycol as surfactant, and evaluate its piezo-catalytic activity and selectivity by degrading model antibiotic and dye reactants under ultrasonic vibrations. Acetate or/and oxalic unidentate ligands on the surface of BaTiO3 nanobelts can be formed by controlling precursor and hydrothermal parameters. Particularly, oxalic acid functionalized BaTiO3 nanobelts presented a high piezo-catalytic rate constant of 0.068 min−1 for Rhodamine B solution and maintained >87% degradation efficiency within 30 min under the condition of ultrasonic bath with 40 kHz and 100 W, which was mainly ascribed to piezo-sensitization effect. This work provides references for the preparation of chemical functionalized catalysts and also contributes to the development of novel catalysts for special applications.

Stainless steels are an important class of alloys, and are already used in a broad range of applications, especially used as electronic information materials. To take advantage of their magnetic characteristics, many fundamental magnetic problems involving stainless steels must be further studied. In this paper, magnetic measuring of ferrite stainless steels are conducted using the ring samples and bar samples in different magnetic fields, which are both frequently used in industry for quality control. From the magnetic parameters obtained from the major loops of both samples, such as Br, Hc, mu(r), Js and H mu(max), large differences were found, revealing that, in ferrite stainless steel two kinds of samples can get quite a different result. The reasons are discussed. Furthermore, the benefits of both kinds of samples are discussed in terms of sample dimensions, anisotropy, demagnetization field, and inclusions. Moreover, the typical magnetic data obtained from the major and minor hysteresis loops are also discussed.

(续上期) 2 磁粉芯的磁学理论基础 我们已经知道,金属软磁磁粉芯主要用来制作用于各个科技领域的各种高性能电感元件,其优异的性能来源于其独特的微观结构.磁粉芯的理论之所以复杂,并不是因为所涉及的理论有多么高深,而是因为涉及的领域比较多,一个人很难一下子就能懂这么多学科领域.涉及的行业也比较多,不是一个人很快就能熟悉的.

With the development of modern industry, more and more permanent magnetic materials are used at elevated temperatures. Thus it has become more and more important to measure their magnetic properties accurately both at room temperature and elevated temperatures. In this paper, for a better understanding of temperature coefficients, measuring of the magnetic properties at elevated temperatures and related problems are reviewed and discussed qualitatively. Advices on magnetizing permanent magnets at elevated temperatures are also given. In addition, principal problems and new advances involved in measuring techniques at elevated temperatures are also discussed. Furthermore, problems associated with testing magnets at elevated temperatures using a vibrating sample magnetometer (VSM) are also presented.

本文从理论和生产实际出发,对粘结磁体作了简要介绍,主要综述了粘结磁体的研究背景、生产和研究现状及发展趋势,并对粘结磁体的原料及生产工艺现状进行了概括,涉及原料(永磁磁粉、粘结剂及配合剂等几个方面)及原料配比、制备工艺过程等产品生产的全过程,也对不同成型工艺的适用对象和优缺点作了简单描述,以便使人们对粘结磁体的现状及发展趋势能有基本的认识.最后,对粘结磁体的发展趋势和存在的问题进行了总结并提出了一些看法,以供研究和生产粘结磁体的同行参考.

There exists a close relationship between automatic control system and magnetic properties of soft magnetic materials, especially with the development of intelligent control technology, thus, soft magnetic measuring has become even more important. This is especially true for ferritic stainless steel, which traditionally is not regarded as soft magnetic material. We have found that, the contact surface of the samples with the magnetic poles should be as large as possible in order to reduce the measurement error. The shape of the magnetic poles will have distinct influences on the measured magnetic properties of the samples in low, middle and high magnetization fields, especially when their contact surface is small. For the value ofH(μmax), whereμmax gets its value, there is a obvious difference among the values measured at different magnetization field even using the same magnetic poles. But the shape of the poles has no effect on the value of maximum flux density, also maximum magnetic polarization. These results also can be used in magnetic circuit design.

The standard method for measuring magnetic properties of permanent magnets is the closed circuit method using an iron-cored electromagnet. With the advances of modern high quality permanent magnetic materials, it has become more and more important to measure their magnetic properties accurately both at room and elevated temperatures. Many problems have arisen when using this traditional DC hysteresigraph to test these new materials, such as those based on rare earth intermetallic compounds, bonded magnetic materials and nanocrystalline exchange-coupled magnets. The physical knowledge on these principal problems including magnetic properties of material, magnetic properties of product, specimen, uniform magnetization, saturation magnetization, the influence of the saturation of the poles, and the influence of Hall probe, etc., is important in the research and development of new materials and also nondestructive evaluation (NDE). These problems are discussed in this paper qualitatively and the current statuses to solve these problems are also presented.

A brief introduction of stainless steel was given in this paper, in addition, the microstructure of stainless steel and its influence on the properties were discussed in detail, with emphases on the relationship between the magnetic property of stainless steel and other properties. Moreover, factors that influence its magnetic property are also analyzed. Then a brief introduction of ferritic stainless steel and its physical property were given, with emphases on the classification and physical paramaters of modern ferritic stainless steel. Moreover, comparisons of ferritic stainless steel with commonly used soft magnetic alloys were given. Furthermore, the physical properties of the material were also discussed in detail. Based on these knowledge, a brief introduction of properties of ferritic stainless steel were given, with emphases on many problems associated with their applications, such as saturation magnetization, corrosive resistance, free-cutting machinability, and coercivity, etc. Finally, the Influences of alloy elements on material properties were also discussed in detail.

With the development of modern ferromagnetic technology, soft magnetic powder cores (MPCs) of amorphous and nanocrystalline alloys have been intensively studied for their excellent soft magnetic properties such as high flux density, low coercivity and reduced core loss due to amorphous state and nanocrystalline grains of 10–20nm dispersed in a residual amorphous matrix. In this paper, the microstructures and soft magnetic properties, i.e., maximum magnetic induction Bm, effective permeability μe, DC-bias properties and volume power losses PCV of MPCs made from amorphous powder of gas atomization and nanocrystalline powder of pulverized melt-spun ribbon were investigated and also compared on the basis of the same level of μe. It is found that μe of both kinds of MPC keeps unchanged up to 1MHz. The amorphous MPC has lower PCV at lower frequency range, while the nanocrystalline MPC has lower PCV at high frequency range instead. Also, the nanocrystalline MPC has better DC-bias property. Moreover, the DC magnetic properties and the changes of PCV of both MPCs with frequency and flux density are also studied. Furthermore, the electromagnetic characteristics, the microstructures and the mechanisms accounting for these phenomena of both MPCs are also discussed.

材料科学与工程学科是随着现代科技的发展而兴起的一门新兴学科,并受到人们的普遍重视和关注,由于与材料科学相关的各个专业方向的许多主干课程大都涉及到磁学知识,因此,我们非常有必要在材料科学与工程学科中把磁学知识做为一门单独学科进行讲授,以加深学生对材料科学的理解,也为学生今后对该学科的研究奠定基础。

作为材料科学与工程学科重要组成部分的磁性材料在该学科中占有越来越重要的比重,当前材料科学领域的研究热点集中磁性导体和磁电复合材料就是一个很好的证明,这也就使得在做为工学的材料科学与工程领域开设传统理学体系的《磁学》课程显得尤为必要.如何对理学背景不是很深的学生讲授《磁学》体系的课程,也就成为一个很重要的课题需要我们探索和实践.

The material properties and device properties of soft magnetic ferrite and the connections and differences between them are analyzed and discussed in theory and measuring point of view,and the measuring standards,measuring techniques and questions related to these two properties are also considered.In the meantime,problems arose in measuring these two properties are evaluated.In addition,the current advances in these fields are examined.

Modern high-frequency electronic technology demands Mn-Zn soft ferrite for high DC-bias and low power loss applications owing to the needs for smaller electronic devices. In this study,DMR50B ferrite material with very attractive DC-bias property and lower power loss at high frequency up to 3MHz was developed employing a conventional ceramic powder processing technique based on our previous study of DMR50 material. The magnetic properties can be further improved by optimizing composition,additives,production technique and microstructure. The core loss is around 200 kW/m3 at 3 MHz,10 mT and 100℃ ,and only around 20 kW/m3 at 700 kHz,30 mT and 100 ℃; its cutoff frequency fr is about 4MHz and its incremental permeability μΔ remains constant until HDC=100 A/m. Furthermore,the electromagnetic characteristics and the microstructure of this new DMR50B material were also discussed.

Modern high-frequency electronic technology demands Mn–Zn soft ferrite for high DC-bias and low power loss applications. In this study, DMR50B ferrite material with a very attractive DC-bias property and with a lower power loss at high frequency up to 3MHz was developed employing a conventional ceramic powder processing technique based on our previous study of DMR50 material, indicating its magnetic properties can be further improved by microstructure homogeneity. The core loss is around 200kW/m3 at 3MHz, 10mT and 100°C, and only around 20kW/m3 at 700kHz, 30mT and 100°C; its cutoff frequency fr is ∼4MHz and its incremental permeability μΔ remains constant until HDC=100A/m. Furthermore, the electromagnetic characteristics and the microstructure of this new DMR50B material are also discussed.

(Ni(1-x)) Zn(x)Fe(2)O(4) ferrite powders with the spinel structure were prepared by a sol-gel method, and then the influence of the ratio of Ni/Zn, the pH value of the solution and the sintering temperature on the microstructure and magnetic properties of the as-prepared NiZn ferrite nanoparticles was mainly discussed. The impurity Fe(2)O(3) phase presented with the increasing Ni content; the saturation magnetization (M,) of the Ni(1-x)Zn(x)Fe(2)O(4) reached maximum at x=0.3. And the impurity Fe(2)O(3) decreased with the sintering temperature. At the same time, the pH value also affected the magnetic properties of the Ni(0.7)Zn(0.3)Fe(2)O(4) ferrite, and M(s) reached max at pH=5. Therefore, from the above results, the optimized conditions are obtained as the following: the ratio of Ni/Zn= 0.7:0.3, pH=5 and the sintering temperature of 900 degrees C.

Low Mn-doped NiCuZn ferrites with compositions of (Ni0.6Zn0.3Cu0.1)1−xMnxFe2O4 (where x=0, 0.01, 0.02 and 0.03) were synthesized directly with sol–gel method. The influence of the Mn2+ content (parameter x) and the sintered temperature on the microstructure and the magnetic properties of these ferrites were mainly discussed. With the increasing Mn2+ content, saturation magnetization (Ms) of the powder samples decreased. Saturation magnetic flux density (Bs) and remnant magnetic flux density (Br) of the toroidal specimens decreased with the Mn2+ content up to x=0.02, followed by increasing. Br and Bs both increased with the increasing sintered temperature, while coercivity (Hc) decreased. The real part of permeability (μ′) of the toroidal specimens increased up to x=0.01, followed by decreasing. The sintered temperature also affected the resonance frequency and the useable frequency (from which the value of tanδ increased more) obviously. Furthermore, the low-frequency permeability and the secondary maximum (the maximum of the permeability appearing the secondary time) both increased with the sintered temperature from 70 to 120 and 150 to about 600.

The lamellar Fe/Al2O3 catalysts were prepared by sol–gel method, and then with these prepared catalysts, carbon nanotubes (CNTs) were synthesized by catalytic chemical vapor deposition (CCVD) method using C2H2 as precursor. The as-prepared CNTs and Fe/Al2O3 catalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and Raman spectrum. The results proved that the as-prepared CNTs actually existed in bundles. And the growth of CNTs bundles should be attributed to the lamellar catalysts, which supported the bottom growth mechanism of CNTs. The transition metal of Mo was not introduced in catalysts to produce CNTs bundles, which was different with others’ results.

Three dimensional (3D) SiO2 photonic crystals films were fabricated on quartz substrate by vertical deposition method. The effects of various preparation parameters on optical properties were studied by optical transmission measurements. Bragg reflection on parallel sets of (111) planes were observed in all the samples. The center wavelength of [111] photonic band gap (PBG) varied from 450 nm to 680 nm with the increasing sphere size. For a given sphere size, the (111) Bragg reflection of as-deposited sample shifted towards lower wavelengths as the sintering temperature T increased. The role of evaporation temperature on the optical properties of the film was also investigated. The PBG can be correspondingly modulated in visible region by changing various preparation parameters.

With the advance of modern electronic technology, there has been a critical need for Mn–Zn ferrites with even higher permeability and even lower power loss at higher frequencies. In this study, ferrite with extremely low losses than conventional ferrite materials at high frequency was developed employing a conventional ceramic powder processing technique. As a result, the core loss at 3MHz, 10mT and 100°C is around 300kW/m3, and its cutoff frequency is 4MHz. Furthermore, the electromagnetic characteristics and the microstructure of this new DMR50 material are also discussed.