稀土掺杂改性镍锌铁氧体磁学性能研究

以黄钠铁矾为原料,稀土掺杂改性制备镍锌铁氧体。通过X射线衍射(XRD)、扫描电镜(SEM)、红外光谱分析(FT-IR)和振动样品磁强计(VSM)等对镍锌铁氧体进行表征,探究稀土掺杂对镍锌铁氧体磁学性能的影响。结果表明:稀土掺杂后镍锌铁氧体的晶格产生畸变,但是尖晶石型的形貌没有变化,软磁性能提高。并且镝掺杂量与软磁性能提高呈现正相关。掺杂3%镝的镍锌铁氧体软磁性能最好,矫顽力为2.082kA/m,剩余磁化强度1.73A·m~2/kg,饱和磁感应强度为42.59A·m~2/kg。     

镍锌铁氧体纳米材料制备及其光催化性能研究

以金属硝酸盐、硝酸镍、硝酸铁、硝酸锌为原料,柠檬酸和葡萄糖作为分散剂和燃烧剂,通过溶胶-凝胶自蔓燃法在200℃下制备了纳米Ni0.5Zn0.5Fe2O4光催化剂。通过XRD、TEM、VSM分析表明,所制样品为纯相尖晶石型镍锌铁氧体,颗粒大小约为18nm,饱和磁强度Ms为31.14A·m2/kg,剩余磁强度Ms为2.08A·m2/kg,矫顽力Hc为4949A/m,表现为铁磁性。样品的光催化性能实验表明,在Ni-Zn铁氧体+H2O2+可见光系统中,亚甲基蓝的降解率在2h内达到98%。反应后的样品通过磁力回收,用去离子水和无水乙醇清洗,60℃烘干后,进行3次重复实验,样品的降解率没有降低,表明样品性能稳定,是一种可回收的光催化剂。     

等离子体法沉积磁性铁涂层及其电磁性能的研究

用铝金属作衬底、FeSO4溶液浓度为20~30g/L和电压130~150V采用等离子体沉积的方法可以制备出磁性铁涂层。XRD分析表明磁性涂层主要由单质铁结晶相组成。8℃,磁性铁涂层比饱和磁化强度达169.0A·m2/kg、剩磁为25.6A·m2/kg和矫顽力为35.34kA/m。磁性铁涂层的饱和磁化强度、剩余磁化强度和矫顽力随着测量温度的升高而降低。磁性铁涂层具有较好的雷达波吸收性能。     

镍锰铁氧体的制备及其光催化性能研究

针对尖晶石型铁氧体与不同阳离子匹配,就有不同电荷的特点。利用化学共沉淀法,在NaOH溶液中添加MnCl_2·4H_2O、FeCl_3·6H_2O、Ni(NO_3)2·6H_2O溶液,制备镍锰铁氧体前驱体,在温度600℃煅烧3h得到镍锰铁氧体。利用SEM、XRD、FT-IR等方法对镍锰铁氧体的形貌和尺寸、结构进行表征分析。结果表明,生成的镍锰铁氧体为尖晶石型的软磁材料,禁带宽度约为1.14eV,饱和磁化强度(Ms)和矫顽力(Hc)为10A·m~2/kg、9 950A/m。制备的镍锰铁氧体可作有效的光催化剂。     

锶废渣直接制备锶钡铁氧体材料研究

以重庆市大足区天青石锶废渣为原料,采用化学共沉淀法制备了锶钡铁氧体(Sr_xBa_1-xFe₁₂O₁₉)。通过XRD、SEM对锶钡铁氧体进行表征,探究沉淀pH值、焙烧温度、焙烧时间对锶钡铁氧体物相组成、微观形貌的影响。实验结果表明,在沉淀pH值为12、焙烧温度900℃、焙烧时间2 h的条件下,制备出的锶钡铁氧体无杂相且呈明显的六角或近六角片状形貌,饱和磁化强度(Ms)60.29 Am²/kg,剩余磁化强度(Ms)32.16 Am²/kg,矫顽力(Hc)30.08 kA/m,具有永磁体高饱和磁化强度(Ms)和高矫顽力(Hc)的特性。     

化学共沉淀法制备MnZn铁氧体前驱物微粉及其性能

首先对Me(Me=Fe2+、Mn2+、Zn2+)在Me-NaOH-H2O体系中的沉淀行为进行了必要的热力学分析,在此基础上,通过化学共沉淀法制备了尖晶石型的MnZn铁氧体前驱物微粉。利用XRD、SEM对前驱物粉料的粒度分布、物相以及表面形貌进行了表征与测试,并结合TG-DSC(热重与差热扫描分析)对前驱物微粉的煅烧温度进行了分析。前驱物微粉的磁性能由振动样品磁强计(VSM)来表征。实验表明Me在Me-NaOH-H2O体系中共沉范围为10.0～10.7。在此pH范围内,配以一定的盐溶液流速及搅拌速度下,可直接制备出具有尖晶石结构的前驱物微粉,并有效地解决了共沉淀制粉中的洗涤困难的问题。前驱物粉的磁性能测试表明,比饱和磁化强度σs≈64.09A.m2/kg,比剩余磁化强度σr≈3.08A.m2/kg,矫顽力Hc≈0.51A/m。     

纳米晶 Ni1-x ZnxFe2O4铁氧体粉料的制备及其磁性能研究

采用喷射-共沉淀法制备了纳米晶Ni1-xZnxFe2O4（0≤x≤1.0）铁氧体粉料.通过TG-DSC、XRD、SEM、TEM、BET等测试手段分析了其微观结构和形貌,用振动样品磁强计测量其室温下磁性能.结果表明：喷射-共沉淀法制备的粉料颗粒细小均匀、形状完整.600℃下煅烧1.5h,样品晶粒尺寸为30nm左右,平均颗粒尺寸＜100nm.室温下,样品比饱和磁化强度随Zn^2＋含量增加而变化,当x=0.5时,最大比饱和磁化强度σs为66.8A·m^2/kg.当晶粒大小为41nm时,纳米晶Ni0.5Zn0.5Fe2O4铁氧体矫顽力达到最大值5.06kA/m,随后又随晶粒尺寸增大而减小.这归因于纳米晶软磁材料中强烈的无序磁晶各向异性模式的影响.     

热分解法制备Ni_(0.5)Zn_(0.5)Fe_2O_4纳米颗粒

采用热分解法制备Ni_(0.5)Zn_(0.5)Fe_2O_4纳米颗粒,研究表面活性剂用量、回流温度和回流时间对产物尺寸、形貌以及分散性的影响。通过X射线衍射仪(XRD)、透射电子显微镜(TEM)和振动样品磁强计(VSM)对样品的结构、形貌与磁性能进行了表征。结果表明:增加表面活性剂的用量,产物的粒径减小,分散性明显提高,而提高回流温度和延长回流时间则会使产物粒径增加,但粒径分布也会变宽。在三辛基氧化膦(TOPO)用量为0.6mmol,260℃回流1h条件下制备产物的饱和磁化强度为49.38A·m2/kg,矫顽力为7143.20A/m,剩余磁化强度为5.76A·m2/kg,表现为亚铁磁性。     

喷射-共沉淀法合成纳米晶CoFe2O4及磁性能

用喷射-共沉淀法成功地制备了纳米晶CoFe2O4铁氧体粉料.研究了不同合成温度对产物晶体结构、微观形貌和磁性能影响.结果表明:喷射-共沉淀法制备的粉料颗粒细小均匀、形状完整.600℃下煅烧1.5h,样品晶粒尺寸为29nm左右,平均颗粒尺寸小于100nm.室温下,样品比饱和磁化强度随煅烧温度增加而增大.850℃煅烧1.5 h时,其比饱和磁化强度Ms为88.6A·m2·kg-1.当晶粒大小为29nm时,纳米晶CoFe2O4铁氧体矫顽力达到最大值64.5kA·m-1,随后又随晶粒尺寸增大而减小.这可能归因于纳米磁性材料存在强烈的晶粒尺寸效应.     

锰锌铁氧体制备工艺及其对磁性玻璃陶瓷性能的影响

采用氧化物煅烧法、共沉淀法和溶胶-凝胶法制备锰锌铁氧体前驱体,并将其与生物玻璃陶瓷复合,制备磁性玻璃陶瓷。研究了不同工艺制备的铁氧体对材料磁性、生物活性和细胞亲和性的影响。结果表明,充磁至7.96×105 A/m,材料的饱和磁化强度在7.49～6.46A.m2/kg之间,矫顽力在9.95×103～1.60×104 A/m之间。其中使用共沉淀法制备铁氧体前驱体使复合材料磁滞回线包围面积最大,预期有最好的生热能力。而各铁氧体的掺入均导致材料生物活性下降,但在浸泡入模拟体液21d后,各材料表面均能生成类磷灰石层。将ROS17/2.8细胞与共沉淀法制备的铁氧体复合材料共同培养7d,材料显示出良好的细胞亲和性。     

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.     

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.     

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.     

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)。