首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 234 毫秒
1.
用固态反应法制备了M(Pr,Ag)替代的La212型化合物,发现La2-xSrzC0.5Pr0.5Cu2O6,La176Pr0.4Ca1-xPr2Cu2O6和La2-xPrxCa0.5S0。.5Cu2Oε单相范围的x值分别是0.4-1.1,0-0.5和0-1.5。  相似文献   

2.
合成了La212型新化合物La2-xSrxCa0.5Cu2O6;发现Sr对La的替代量为0.4-1.1。通过LAZY程序结构研究发现该化合物具有典型La212型合物的晶体结构。  相似文献   

3.
基于碘量法测定高温超导氧化物氧含量的方法,总结出固溶化合物Sm(1+x)Ba(2-x)Cu3On的氧含量n随固溶度x变化的规律性;从理论分析和实验测定得出在固溶区域内,Sm(1+x)Ba(2-x)Cu3On的氧含量n与替代程度x呈线性关系,超出固溶极限x0,直线斜率将发生明显变化。此结果与X射线粉末衍射结果基本一致.  相似文献   

4.
基于碘量法测定高温超导氧化物氧含量的方法,总结出固溶化合物Sm1+xBa2-xCu3On的氧含量n随固溶度x变化的规律性,从理论分析和实验测定得出在固溶区域内,Sm^1+xBa2-xCu3On的氧含量n与替代程序x呈线性关系,超出固溶极限x0,直线斜率将发生明显变化。此结果与X射线粉末衍射结果基本一致。  相似文献   

5.
合成了La212型新化合物La2-xSrxCa0.5Pr0.5Cu2O6;发现Sr对La的替代量为0.4~1.1。通过LAZY程序结构研究发现该化合物具有典型La212型化合物的晶体结构。  相似文献   

6.
合成了通式为(C15H15N2O3)xRE(NO3)y(H2O)z(当RE=La~Pr时,x=3,y=6,z=0;RE=Nd时,x=2,y=5,z=1;RE=Sm~Lu,Y时,x=2,y=5,z=0)的一系列15种标题配合物.通过元素分析,IR,UV,1HNMR,TG-DTA,摩尔电导和X射线粉末衍射分析等对配合物的性质进行了表征.认为可能生成包含一分子水的11配位钕配合物的原因在于抗衡阳离子的空间效应,使其与络阴离子间的vanderWaals力增强的结果  相似文献   

7.
LaBa2FeCu2Oy的结构是立方相,晶格常数为,电子衍射表明这种化合物具有非公度调制结构.调制波矢q1=0.367a*,q2=0.367b*,并且推测q3=0.367c*,电阻测试表明该化合物为半导体.  相似文献   

8.
30只健康麻醉犬动脉血和脑脊液(CSF)酸碱变量及主要电解质检测结果分析发现:CSFpH、[K~+]<pHa和[K~+]_a,相互之间相关显著,其回归方程分别为CSFpH=0.477×pHa+3.78,CSF[K~+]=0.418×[K~+]_a+1.12。CSFPCO2、[Cl~-]、[乳酸][Lact]>PaCO2、[Cl-]_a和[Lact]_a,相互之间相关显著。其回归方程分别为CSFPCO2=0.564×PaCO2+3.5325,CSF[Cl~-]=0.5×[Cl~-]_a+76.7,CSF[Lact]+0.95×[Lact]_a+1.0。CSF[HCO_3~-]与CSFPCO2相关显著,回归方程为CSF[HCO_3~-]=1.898×CSFPCO2+10.6。  相似文献   

9.
镧锰系钙钛矿可脱附氧与催化氧化活性   总被引:2,自引:0,他引:2  
用热分解法合成La0.8Me0.2MnO3(Me:Na,K,Ca,Sr,Ba)和La0.8Sr0.2Mn0.7M0.3O3(M:Fe,Co,Ni,Cu)系统的钙钛矿型复合氧化物,用TPD方法研究部分取代对样品的氧吸-脱附性能的影响,对于La0.8Me0.2MnO3系列,氧的吸-脱附特性由A位的离子半径、价态和物化性质决定,对于B位取代基活性与可脱α氧量并不成比例关系,其活性的决定因素可能是B位离子的自氧化还原循环能力。  相似文献   

10.
本文用Sol-Gel法合成了Bi1.6Pb0.3Sb0.1Sr2Ca2Cu3Ox体系的高Tc超导原粉,对于不同的烧结时间,材料的超导性有不同程度的差异,并与同种方法合成的Bi1.7Pb0.3Sr2Ca2Cu3Ox体系进行了比较。用Sol-gel法,在Bi系中掺杂Pb,同样会缩短烧结时间,促进高温相的形成,同时掺杂Pb,Sb,形成超导材料所需的烧结时间进一步缩短。  相似文献   

11.
Utilization of novel materials, particularly high-Tc (critical temperature) superconductors, is essential to pursue the United Nations' Sustainable Goals, as well as to meet the increasing worldwide demand for clean and carbon-free electric power technologies. Superconduct-ing magnets are beneficial in several real-life applications including transportation, energy production, magnetic resonance imaging (MRI), and drug delivery systems. To achieve high performance, one must develop uniform, large-grain, infiltration-growth (IG) processed bulk YBa2Cu3Oy (Y-123) super-magnets. In this study, we report the magnetic and microstructural properties of a large-grain, top-seeded, IG-pro-cessed Y-123 pellet, which is 20 mm in diameter and 6 mm in height; the pellet is produced utilizing liquid Yb-123+Ba3Cu5O8 as the liquid source. All the samples cut from the top of the bulk exhibit a sharp superconducting transition (approximately 1 K wide) with the onset Tc of approximately 90 K. However, in the samples cut from the bottom surface, the onset Tc values slightly decreased to between 88 and 90 K, al-though still exhibiting a sharp superconducting transition. The top and bottom samples exhibited the highest remnant value of Jc (critical cur-rent density) at 77 K H//c-axis of 50 and 55 kA/cm2, respectively. The remnant Jc and irreversibility field values significantly fluctuated, being fairly low in some bottom samples. Scanning electron microscopy identified nanometer size Y-211 (Y2BaCuO5) secondary-phase particles dis-persed in the Y-123 matrix. Energy-dispersive spectroscopy clarified that the decreased both Tc and Jc for the bottom samples were attributed to liquid phase dispersion within the Y-123 phase.  相似文献   

12.
研究分别由 CeO_2和 Ce_2(C_2O_4)_3作为起始原料制备的名义成分为 CeBa_2Cu_3Oy样品以及 Ce(Y,Eu)-Ba-Cu-O 系列样品的工艺过程和测量结果.实验表明,Ce和 Ba 氧化物具有极强的形成 BaCeO_3的趋势,阻止了缺氧钙钛矿结构的形成.在 CeBa_2Cu_3Oy 中非化学计量添加 Y 获得了转变温度为85K 的超导体,本文给出了其电阻、磁化率及元素含量分析结果.  相似文献   

13.
用固相反应法制备123相YBa2-xSrxCu3O7-δ(YBCO)和掺Sr的YBa2-xSrxCu3O7-δ系列超导样品.利用四端引线电阻法测量样品的电阻温度曲线,得到Sr元素替代Ba位时超导转变温度Tc降低且Tc随掺杂量单调变化,从实验上验证了CuO2面的耦合可能是维持高温超导电性的一个重要条件.  相似文献   

14.
利用扩展X射线吸收精细结构(EXAFS),研究了Bi2(Sr,Ca)2Cu2Oy超导体中Cu原子与Bi原子的局域结构.结果表明:Cu原子第一配位层是五配位的氧原子,第二配位层是四配位的Ca原子和一配位的Cu原子,但不含Sr原子的结构信息,这是Sr-O层与Cu-O层层间距较大所致;同时测定Bi原子第一配住层含有2.3个氧原子,用非公度调制结构模型解释了Bi原子的配位状况.  相似文献   

15.
Autoigniting synthesis of gel from Ba(NO3)2, TiO(NO3)2 and C6H8O7H2O aqueous solution was investigated at an initial temperature of 600℃ and tetragonal BaTiO3 nanopowder with particle size of 80nm was prepared. It is indicated that the specific surface area of the combustion product before and after calcination is 14.74 m2/g and 12.49 m2/g, respectively. The combustion wave is composed of solid phase reaction zone and gaseous phase flame reaction zone. The combustion flametemperature is 1 123 K derived from thermocouple measurement. The characteristics and densification behavior of the sol-gel autoigniting synthesized BaTiO3 nanopowder were investigated.  相似文献   

16.
La2O3对Ni基合金激光熔覆层组织和耐磨性的影响   总被引:9,自引:0,他引:9  
在Ni基自熔合金粉末中添加不同量的La2O3,并利用激光形成熔覆层。利用扫描电镜、X射线能谱仪、X射线衍射仪、显微硬度计和环块摩擦磨损实验机等对激光熔覆层显微组织、化学成分、相结构、显微硬度和摩擦磨损性能进行了研究。结果表明,在激光熔覆层中添加La2O3能细化和净化显微组织;降低基材对熔覆层的稀释率;减小固溶体的晶格常数;提高熔覆层的显微硬度;降低熔覆层摩擦系数并提高其耐磨性能。该文还探讨了La2O3作用的机理。  相似文献   

17.
用碘滴定法测定了高温氧化物超导体LLa2-xBaxCuO4-y在不同掺杂浓度下和YBa2Cu3O7-y在不同淬火温度下的氧含量,得到了氧含量与掺杂浓度x和淬火温度T的关系.  相似文献   

18.
采用共沉淀法制备了不同稀土元素改性的Ce0.6Zr0.35RE0.05O2(RE=Y,La,Nd,Pr)固溶体,并用XRD,H2-TPR等方法对其晶相结构、还原性能和高温热稳定性进行研究.结果表明,稀土元素Y,La,Nd,Pr掺入Ce0.6Zr0.4O2固溶体,所形成的三元混合氧化物均为萤石型立方晶相结构的均相固溶体,并未出现所掺杂稀土氧化物的晶相,且高温老化后,物相结构稳定.与Ce0.6Zr0.4O2固溶体比较,稀土元素的掺杂,明显改善了其还原性能及高温热稳定性.  相似文献   

19.
Kinetics of carbothermic reduction of manganese oxide and the catalytic effect of La2O3 on the reduction have been studied by the measurement of mass loss in N2 atmosphere at different temperatures and followed by SEM analysis. It is concluded that the kinetics of carbothermic reduction of manganese oxide is divided into three stages: gas diffusion controlling stage, carbon gasification controlling stage and solid state diffusion controlling stage. La2O3 has catalytic effect on the reduction. The catalytic effect of La2O3 increases with the added amount of La2O3. SEM analysis shows that the catalytic mechanism is that Laa2O3 promotes the transfer of oxygen ions so that carbon gasifying is catalyzed and thus carbothermic reduction of MnO3 is catalyzed.  相似文献   

20.
利用复杂晶体化学键电介质的平均能带模型研究了(La_(1-x)M_x)_2CuO_4(M=Ba,Sr)的化学键特性,得到Cu-O键的平均共价性为0.3,La-O键的平均共价性为0.03。应用由共价性和极化率定义的化学环境因子计算了~(57)Fe在La_2CuO_4中的Mossbauer同质异能位移,确定了~(57)Fe在La_2CuO_4中的价态和占位情况。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号