纳米晶复合永磁材料研发新进展与产业化前景

纳米晶复合永磁材料作为一种近几年来发展起来的一类新型磁性材料，在性能和技术手段上有许多普通永磁材料不具备的优势。这类材料具有高剩磁、高磁能积和相对高的矫顽力以及低的稀土含量和较好的化学稳定性，是一种有广泛应用前景的廉价永磁材料。[编按]     

新型稀土铁基纳米晶永磁材料的磁性

近日，由中国科学院物理研究所沈保根、成昭华、张宏伟等人完成了“新型稀土铁基纳米晶永磁材料的磁性”研究。新型铁基纳米晶符合永磁材料研究不但是国际上研究的热点，而且也能充分发挥我国稀土优势。物理所成功研制了快淬镨铁硼基纳米晶复相稀土永磁材料，磁粉的室温磁能积达176kJ／m^3（22．2MGOe），是国际实验室最好水平。在此基础上，进行了中试研究。利用国产设备制备的镨铁硼基纳米晶稀土永磁磁粉的磁性能可与美国麦格昆磁公司的商品MQ磁粉相比。     

纳米晶双相Nd3.6Pr5.4Fe83-xGaxCo3B5合金磁性能的研究

用熔体快淬法制备Nd3.6Pr5.4Fe83-xGaxCo3B5(%(原子分数),x=0～1.0)纳米晶双相永磁材料,研究其磁性能的变化.结果表明适量的添加Ga(x=0.25)可以细化晶粒,使快淬薄带中的Nd2Fe14B硬磁相和α-Fe软磁相发生较充分的交换耦合作用,获得较优异的磁性能,Ga含量过多或过少的快淬薄带的磁滞回线出现缩颈现象,低温退火使得该现象得以改善.     

北京稀土永磁材料产业发展研究

稀土永磁材料是一种新型优异、应用范围广阔的永磁材料,是由稀土金属和过渡金属组成的合金经过一定工艺制备而成。稀土永磁材料至今发展了4代,第1代和第2代为钐钴永磁材料,由于原料缺乏、价格昂贵,前2代稀土永磁材料主要用于军工领域。第3代为钕铁硼永磁材料,因为其剩磁高、矫顽力高、磁性能高等优点,从一出现就受到各国的高度重视,发展极为迅速,是目前应用最为广泛的稀土永磁材料。2010年,全球钕铁硼     

行星式球磨工艺参数对SmCo5粉体磁性能的影响研究

纳米晶SmCo₅粉体具有高矫顽力和强磁耦合的优点,是制备纳米复合永磁材料使用最广泛的硬磁材料之一。采用表面活性剂辅助球磨法制备SmCo₅微纳米片,采用行星式球磨机,系统研究了球磨时间、球料比和表面活性剂含量对SmCo₅粉体的形貌和磁性能的影响。结果表明随着球磨时间和球料比的增加,SmCo₅粉末的粒径和厚度减小并转化为微、纳米片,当球磨时间和球料比大于4 h和12∶1后,SmCo₅粉末的粒径和厚度变化不明显。选用球料比16∶1、球磨时间2 h、表面活性剂含量30%参数,SmCo₅粉体具有最优的磁性能,剩磁(Mr)为45.9 Am²/kg,矫顽力(Hc)为1.13×10⁶ A/m。     

稀土(R)—铁合金永磁材料及其在测试技术中的应用

论述了新型R-Fe合金化合物永磁材料的发展及近期成果,针对剩磁、矫顽力、最大磁能积、居里温度等硬磁材料的各项指标,对R-Fe合金永磁材料与传统的铁氧永磁材料、稀土—钴永磁材料等进行了比较和分析,展望了R-Fe永磁材料在测试技术中的应用前景。     

热变形温度对Nd14Fe80B6磁各向异性的影响

在850～880℃真空热变形4min、变形量70%制备了Nd14Fe80B6各向异性磁体,实验结果表明随着热变形温度的提高,磁体的各向异性先上升后降低,870℃热变形时磁体的(006)晶面峰为X衍射图谱的主峰、(004)相对极密度最大值达到130.01、I(006)/I(105)为1.88,获得(006)磁织构,磁体的饱和磁化强度达到1.453T。如热变形过程消除平均宽度为25μm的带状组织,减少与热变形压力垂直的片状晶之间夹角为19°左右的局部片状晶,则磁体的各向异性可望进一步提高。Nd2Fe14B相在热变形过程中从等轴晶变形为片状晶,且磁体宏观变形量≥65%时,才能形成(006)磁织构,局部富稀土相只起到有利晶粒滑移、有利片状晶形成的作用。细化热变形磁体的片状晶厚度可使磁体具有高矫顽力、高剩磁与饱和磁化强度之比值。850℃热变形Nd14Fe80B6磁体的片状晶平均厚度为76nm,磁体的矫顽力为450.6kA/m,Mr/Ms为0.92。     

纳米晶复合Pr2Fe14B/α-Fe合金薄带的磁性

研究了双相纳米晶复合Ｐｒ２Ｆｅ１４Ｂ／α－Ｆｅ永磁合金薄带的剩磁增强效应与α－Ｆｅ体积分类、合金晶粒平均尺寸ｄ、辊速υ以及薄带厚度之间的关系，讨论了起始磁化过程，Ｈｃｉ与Ｈｅｘｔ关系以及形核场与交换耦合钉扎场的物理模型和磁硬化机理。     

Sm(Co_(0.74)Cu_(0.12)Fe_(0.1)Zr_(0.04))_(7.5)纳米晶烧结磁体的结构和磁性能

采用放电等离子烧结技术制备了致密纳米晶SmCoCuFeZr烧结磁体,研究了磁体的结构和磁性能.X衍射结果表明,烧结磁体具有TbCu_7结构.TEM观察显示,烧结磁体平均晶粒尺寸为35nm.室温时磁体的剩磁为0.49T,矫顽力高达1.42T,而剩磁比Mr/Ms为0.63,表明在纳米晶之间存在晶间交换耦合作用.     

Fe73.5Cu1Nb3Si13.5B9纳米晶合金在NaCl溶液中耐腐蚀性能研究

研究了Fe73.5Cu1Nb3Si13.5B9纳米晶合金在0.1mol/L的NaCl溶液中的耐腐蚀性能,及对其软磁性能的影响。实验结果表明,Fe73.5Cu1Nb3Si13.5B9纳米晶合金经0.1mol/L的NaCl溶液腐蚀后溶液中有橙色沉淀物产生,XRD测试表明铁基纳米晶合金腐蚀后仍保留非晶纳米晶双相结构;铁基纳米晶合金有效磁导率μe随腐蚀时间的增加而降低,腐蚀30d后在频率为50Hz、1、100kHz时其有效磁导率μe较腐蚀前分别下降35.9%、35.3%、27.6%,矫顽力Hc由腐蚀前的0.7097A/m增加到1.117A/m,增加了57.4%,磁滞损耗Pu由腐蚀前的1.819J/m3增加到2.994J/m3,增加了64.6%,腐蚀后铁基纳米晶合金软磁性能有所下降。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。