BiFeO3基铁磁电陶瓷的制备与性能研究进展

BiFeO3是一种典型的铁磁电材料,因在室温下同时具有铁电性与磁性而在新型存储器件、磁电传感器和自旋电子器件等方面具有很大的应用前景,人们从理论和实验上不断地进行探索.在对比分析现有资料的基础上,综述研究国内外在该领域取得的成果,以理清新近在BiFeO3基铁磁电陶瓷材料制备、性能等研究工作的进展.     

单相室温磁电材料BiFeO_3的研究现状

铁磁、铁电和多铁性材料,被称为信息存储终极材料,近来已成为国际上一个新的研究领域。多功能材料BiFeO3是著名的铁电、压电和磁电材料,在远高于室温的范围内具有良好的铁电性,其铁电极化是同类材料中最大的,因而受到科研人员的强烈关注,越来越多的新奇物理性质被发现。本文探讨A位稀土离子掺杂诱导与调控BiFeO3结构相变、物性变化研究的现状。     

层状复合材料NiMnGa/PZT的磁电耦合效应研究

选取NiMnGa合金和传统的压电材料PbZr0.52 Ti0.48 O3（PZT陶瓷）,制备出2-2型层状复合磁电材料NiMnGa／PZT。在室温下测量了其磁电耦合效应,得到了该材料的磁电耦合系数随频率和偏置磁场的变化曲线。由磁电耦合系数随偏置磁场的变化曲线选择合适的模型,对该结果进行了比较理想的拟合,分析了拟合过程及磁电耦合效应的物理机制。可以为设计样品以提高磁电耦合效应提供参考。     

新型磁电阻效应实验仪研制及应用

利用新型的磁电阻效应实验仪对多层膜巨磁电阻传感器、自旋阀巨磁电阻传感器以及各向异性磁电阻传感器的电阻随外加磁场的变化进行了研究,从而了解各种磁电阻的特性。该新型仪器可在高校实验中应用,有助于学生掌握磁电阻传感器的定标方法,测量并计算3种磁电阻传感器灵敏度,也可用于研究3种磁电阻传感器输出电压与通电导线电流的关系,以及磁电阻的其他效应。     

巨磁电阻效应及其应用

介绍了巨磁电阻效应的概念以及巨磁电阻材料在磁传感器、高密度读出磁头、磁性随机存储器等领域的应用.     

锰基钙钛矿型复合材料的电输运及低场磁电阻研究进展

锰基钙钛矿氧化物由于具有高的自旋极化率,其多晶样品表现出显著的低场磁电阻效应.通过把第二相材料引入到钙钛矿材料的表面或晶界,可以对颗粒边界进行表面改性,进而提高其电输运以及磁电阻性能.本文介绍了几类第二相材料,如绝缘体氧化物、金属材料、磁性材料和铁电材料.讨论了电输运性能和磁电阻提高的可能机制,展望了此类复合系统材料的良好前景.     

纳米材料的特性及进展

论述了纳米材料的分类和结构特征,介绍了纳米材料的尺寸效应,表面与界面效应,并阐述了纳米材料的进展,包括纳米光学材料,纳米催化材料,纳米敏感材料外,纳米储氢材料,纳米巨磁电阻材料。     

Nd_(0.5)Sr_(0.5)MnO_3/xZrO_2复合体系的磁电特性

用溶胶-凝胶法制备得到(1mol)Nd0.5Sr0.5MnO3/(xmol)ZrO2颗粒复合纳米材料.磁电测量结果表明,ZrO2含量对复合体系的磁电输运和磁电阻效应有显著影响,随ZrO2含量的增加,剩余磁逐渐减小;x=0.1的样品居里温度与纯磁性相材料相同,而对于其他成分的异质复合样品,居里温度略有下降;样品的电阻率随非磁含量的增加先迅速减小,而后增大,在x≥0.2时出现金属一绝缘转变,非磁ZrO2的加入使得样品在低温下磁电阻效应有很大的提高.     

钙钛矿锰氧化物磁电性质的研究进展

本文着重研究了钙钛矿锰氧化物磁电性质极为丰富的物理内涵,回顾了不同种类磁电阻效应的材料、特点及其重要的应用价值及其在国内外的研究进展．这一方面为研究揭示这些特定属性提供了良好的研究对象,另一方面也为运用这些属性来构筑特定功能材料和器件提供了很好的材料基础和广阔的应用前景．     

基于LabVIEW的磁电阻测试系统的设计

由于在基本理论研究和实际应用中的巨大意义与潜力,材料的磁电输运性质近20年来倍受材料物理和凝聚态物理的关注,特别是巨磁电阻(GMR)、隧穿电阻(TMR)的广泛研究更促进了自旋电子学(Spintronics)的兴起和飞速发展.随着实验的深人,提高磁电阻测试效率和自动化程度已成为研究与自旋相关的电磁输运效应的迫切要求.该文给出了一种基于LabVIEW平台下磁电阻测试系统的设计,使磁电阻测试效率有明显的提高.     

磁电式万用表的组装调试经验

通过对磁电式万用表组装调试过程中的故障分析,提出了一些有效的排除故障的方法,重点介绍了磁电式万用表表头的维修方法。     

关于磁电系电表的放置问题

文章根据力矩平衡条件初步分析了磁电系电表的放置问题,为仪表的工作原理提供了理论基础。     

霍尔效应及应用

霍尔效应是一种发现、研究和应用都很早的磁电效应。霍尔效应的研究在当今已取得了许多突破性的进展，在科学技术的许多领域都有着广泛的应用。     

磁电系电表内阻的温度误差及其补偿

磁电系电表的扩程实验,通常采用串联分压电阻或并联分流电阻的方法。在实验中发现,表头的内阻在不同环境温度下,其值有很大的偏差,这种偏差引起改装表测量结果的误差,称为温度误差。文章给出了电表的温度误差原因,并给出了扩展较大量限,准确度等级要求不高(如1.5级)的电表温度补偿方法,进一步提高和完善磁电系电表扩程实验,为修理和制作大量程电表提供参考技术。     

Evaluation of in-plane shear test methods for composite material laminates

In-plane shear properties of composite material laminates are very important in structural design of composite material. Four commonly used in-plane shear test methods were introduced in this paper. In order to study the differences of various shear test methods, two ASTM standard in-plane shear test methods for composite material laminates were experimentally investigated. They are ±45° tensile shear test (ASTM D3518) and V-notched rail shear test (ASTM D7078). Five types of composite material laminates composed of E-glass fiber fabric and vinyl ester resin were utilized, whose stacking sequences are 03s, 0/903s, CSM/0/902s, ±453s and (0/90)2/(±45)2/(0/90)2s, respectively. The test results indicate that the ±45° tensile shear test can predict shear moduli of composite material laminates accurately. However, the predictions of shear strength using ±45° tensile shear test are significantly lower than those of V-notched rail shear test.     

大学生手机使用状况及对其物质主义价值观影响的实证调查

为了解大学生手机使用的现实状况以及大学生物质主义价值观的基本特点,特别是大学生手机使用对其物质主义价值观的影响作用,采用物质主义价值观量表和大学生手机使用问卷对1543名大学生进行问卷调查,采用描述性统计、T检验和方差分析技术对研究所得数据进行统计处理,结果发现:(1)随着手机的广泛使用,越来越多的大学生加入手机用户的行列,成为"手机世代";(2)大学生的物质主义价值观处于中等水平,受物质主义的影响不是特别强烈;(3)手机媒体对大学生物质主义价值观具有正向影响。在此基础上探讨了本研究对现实的启示和价值。     

双峰中密度聚乙烯/纳米碳酸钙复合材料的流变行为与力学性能

研究了双峰中密度聚乙烯(BMDPE)与纳米碳酸钙不同配比复合物的流变行为与力学性能.讨论了复合物的组成、剪切应力和剪切速率以及温度对熔体粘度和膨胀比的影响,测定了不同配比熔体的非牛顿指数(n)、熔体流动速率(MFR)、粘流活化能以及习用屈服应力,断裂应力和断裂伸长率,用扫描电镜观察了纳米碳酸钙在复合材料中的分散情况.结果发现:纳米碳酸钙可以均匀地分散在BMDPE中,少量的纳米碳酸钙就可以明显提高材料的力学性能,在较高的剪切速率下还可以改善材料的加工性能.     

Spiritual beliefs among Chinese junior high school students

Objective: To explore the characteristics of the spiritual beliefs among junior high school students. Method: 431 junior high school students are measured by Students’ Basic Information Questionnaire (SBIQ) and Middle School Students’ Spiritual Beliefs Questionnaire (MSSSBQ). Results: (1) The overall characteristics of the spiritual beliefs among junior high school students are as follows: social beliefs rank first, practical faith second, and supernatural beliefs last. The ranks of the seven beliefs from high to low are nationalism, political conviction, family’s doctrine, life worship, religious beliefs, money/material and gods worship. (2) Boy students have higher political conviction and money/material faith than girl students. Girl students have higher religious beliefs than boy students. (3) On the beliefs of money/material and life worship, students in Grade 9 take the first place, Grade 8 second and Grade 7 last. (4) Non-student cadres have stronger money/material faith than cadres. (5) League members have higher political beliefs than non-members. (6) Students who are good at studies have stronger national faith than students who are average or poor at studies. Students who are poor at studies have stronger money/material faith than other students. Conclusion: The spiritual beliefs of junior high school students are positive. __________ Translated from Psychology Development and Education, 2005:2.     

On Wooden Pillows: Multiple Classification and Children''s Category-based Inductions

Previous research has indicated that preschoolers do not distinguish between properties that are generalizable within a given category and those that are not. 2 possible general constraints on children's cognition are proposed to account for these findings. 3 studies are reported that argue against the presence of such general constraints. We examine preschoolers' understanding of the properties associated with material (e.g., wood, cotton) and object (e.g., chair, pillow) categories. In Study 1, subjects consistently made inductions based on the material compositions of items when asked to predict texture and fragility. In Study 2, the same subjects judged that items that shared material would share an unfamiliar dispositional property (e.g., gets sodden in water), but items that shared object kind would share a novel functional property (e.g., used for accelerating). Study 3 tested a younger sample of 3-year-olds and found the same sensitivity to category type, albeit with larger individual differences. By age 3, children use different modes of categorization to generalize different kinds of phenomena. These results argue against general limitations on children's abilities to use categories to make inductions. Even when children lack specific theoretical knowledge, the ability to organize phenomena into domains allows children to recognize which categories are relevant in different situations. This understanding can provide a basis for the development of more specific theories.