稀磁半导体Zn_（1-x）Ni_xO,Zn_（1-2x）Mn_xNi_xO及Zn_（1-2x）Co_xNi_xO纳米晶体的制备与磁性研究

利用溶胶-凝胶法制备了一系列的稀磁半导体材料如Zn1-xNixO、n1-2xMnxNixO及Zn1-2xCoxNixO晶体粉末,通过震荡样品磁强计（VSM）、X射线衍射仪（XRD）、扫描电子显微镜（SEM）和能量色散谱（EDS）分别对样品的磁性、晶相结构、形貌和成分进行了表征分析,讨论了获得本征铁磁性Zn1-xNixO样品的制备条件,比较了Mn、Co共掺杂对Zn1-xNixO磁性的影响,给出了Ni在ZnO中的固溶度以及实际掺杂浓度与名义掺杂浓度的关系。     

一种新型功能材料——二维层状磁性锌铝水滑石的制备及表征

采用共沉淀法将磁性基质与锌铝水滑石组装制备二维层状磁性锌铝水滑石,考察了不同n(Zn2 )/n(Fe2 )比及焙烧温度对合成磁性锌铝水滑石结构的影响,并借助XRD、FT-IR、VSM、HRTEM等手段对其晶型结构、磁学性能及结晶度等进行表征,结果表明:锌铝水滑石在赋予磁性后,并没有改变其典型的层状结构,证实了将磁性基质与层状材料组装合成的可行性.     

纳米Co_(1-x)Zn_xFe_2O_4/SiO_2复合材料的结构和磁性

为了研究Zn2+含量对CoZn铁氧体结构和磁性的影响,以正硅酸乙酯和硝酸盐为原料,用溶胶-凝胶法制备了纳米Co1-xZnxFe2O4/Si O2(0≤x≤1)复合材料。利用XRD、TEM、VSM和M ssbauer效应分析了样品的结构、形貌和磁性。结果表明,经900℃热处理后,Co1-xZnxFe2O4/Si O2复合材料中Co1-xZnxFe2O4为晶粒分布均匀的尖晶石铁氧体结构。Zn2+替代Co2+后引起Co1-xZnxFe2O4晶格膨胀。随Zn2+含量的增加,样品的矫顽力减小,而比饱和磁化强度先增大后减小,样品从磁有序状态转变为顺磁状态。Zn2+的掺杂对Fe3+核处的s电子密度有较大的影响,对尖晶石结构对称性影响较小。     

溶剂热法合成粒径可控的Fe3O4磁性介孔/空心球

采用简便的溶剂热法合成粒径可控的Fe3O4磁性介孔/空心球(mesoporous/hollow spheres of magne-tite,MHSM),粒径从80 nm至400 nm可调.通过调节反应时间、NH4HCO3与NH4Ac的摩尔比来控制MHSM的形貌、粒径以及介孔-空心的程度.采用XRD、SEM、TEM、VSM多种表征手段对MHSM进行了表征,结果表明NH4HCO3和NH4Ac的摩尔比对MHSM结构的形成、形貌、粒径起关键性的作用;NH4+的浓度对MHSM的粒径和磁性有决定性的影响;保持NH4HCO3和NH4Ac的摩尔比不变,延长反应时间对MHSM的结构与空腔生长有一定的影响.     

锌掺杂钴铁氧体:硬磁→软磁

采用共沉淀法制备了不同Zn2+掺杂量的Co1-xZnxFe2O4,研究了Zn2+掺杂量对其结构和磁性的影响。X射线衍射测试表明Co1-xZnxFe2O4成相良好,结晶随烧结温度增加而愈加完善。经400℃热处理2h的Co0.7Zn0.3Fe2O4晶粒尺寸由谢乐公式计算为8.57nm。利用振动样品磁强计研究其静态磁性,结果表明,Zn2+掺杂量对Co1-xZnxFe2O4磁性有显著影响,Zn2+含量越高矫顽力越低,同时饱和磁化强度越大,当x=0.3时,矫顽力仅为1352.82A/m,磁化强度为42A.m2/kg,实现了CoFe2O4从硬磁性到软磁性的转变,可作为潜在的高频软磁材料。     

纳米晶Co1-xZnxFe2O4薄膜的结构、磁性及温度特性

采用sol-gel方法制备了纳米晶Co1-xZnxFe2O4(x=0～0.3)薄膜.样品的结构、磁性及表面形貌分别用X射线衍射仪(XRD)、振动样品磁强计(VSM)和原子力显微镜(AFM)进行了表征.研究结果表明,400℃退火薄膜已生成单一的尖晶石结构,且样品的晶粒尺寸较小,平均晶粒尺寸在35nm以下.Zn2 离子含量的增加使样品的晶格常数有少许增大.Zn2 离子含量对样品的磁性能有较强的影响,样品的比饱和磁化强度在Zn2 离子含量x=0.2时达极大值(74.3(A·m2)/kg).变温测量显示,样品的磁化强度随温度升高呈下降趋势.当Zn2 含量从零增加到0.3,居里温度从530.0℃降至341.6℃.     

载镍羟基硅酸镁微粉的制备与表征

利用亚临界水热法合成了粒径为100nm～1μm、利蛇纹石相的顺磁性羟基硅酸镁微粉,采用扫描电子显微镜、X射线衍射、红外光谱和磁性检测等手段进行了表征.探讨了表面活性剂油酸、体系酸碱度、水热温度及时间、磁性掺杂与合成样品形貌、物相、结构、性能之间的关系,结果表明:油酸可有效控制微粉团聚,强碱环境下提高水热温度和延长反应时间可窄化产物粒径分布,相同水热条件下改变初始配比对产物主相无影响,掺镍可提高产物的顺磁特性,使之具有特殊的磁性润滑能力.     

Sol-gel法制备NiZnCu铁氧体性能的研究

采用溶胶-凝胶自燃法制备了Ni0.4Zn0.4Cu0.2Fe2O4铁氧体,使用HP4191A阻抗分析仪测试了材料高频磁谱;结合快速热处理(RTP)工艺制备了Ni0.4Zn0.4Cu0.2Fe2O4磁性薄膜,使用AFM、XRD、AGM系统地研究了制备工艺对薄膜样品表面形貌、晶相结构和准静态磁性的影响。测试结果表明:Ni0.4Zn0.4Cu0.2Fe2O4可适用于射频领域,截止频率fr在1GHz以上,1GHz处起始磁导率μ′=5.3,μ″=3.45;sol-gel法制备磁性薄膜最佳晶化温度为600℃左右,在此温度下制备的薄膜晶粒大小为13nm左右,饱和磁化强度Ms=2.29×105A/m,矫顽力Hc=1.24×103A/m。     

尖晶石型铁氧体纤维的制备及磁性能

以柠檬酸和金属盐为原料,采用有机凝胶-热分解法制备了MeFe2O4(Me=Zn,Ni0.5Zn0.5,Ni0.4Zn0.4Cu0.2)铁氧体纤维.通过FT-IR、XRD,TG-DSC,SEM和VSM等测试技术对纤维前驱体凝胶的结构,热分解过程及热处理产物的物相、形貌以及纤维的磁性能等进行了表征.结果表明,在凝胶形成过程中,金属离子单齿或双齿螯合配位于柠檬酸根阴离子,形成线型分子结构,使凝胶有较好的可纺性.所制得的纤维具有较大的长径比,纤维直径在0.5-20.0μm之间.这些纤维在室温下都具有软磁特性,化学组成、晶粒大小及形貌对纤维的磁性能有着显著影响.ZnFe2O4、Ni0.5Zn0.5Fe2O4和Ni0.4Zn0.4Cu0.2Fe2O4纤维的饱和磁化强度分别为2.6、12.7和40.0A.m2.kg-1,相应的矫顽力分别为4.77、5.82和4.04kA·m-1.     

MSn (M＝ Fe,Cd,Zn)微纳米结构材料的溶剂热合成与表征

以单质硫粉为硫源,乙醇为溶剂,在不添加任何络合剂和表面活性剂的条件下使之与MCln(M=Fe、Cd、Zn,n=2,3)金属盐发生溶剂热反应并成功制备了MS (M=Fe、Cd、Zn,n=1,2)微纳米结构材料.并用XRD、SEM对所得产物进行一系列的表征,研究和讨论了反应温度、反应时间、尤其是溶剂对所得产物的形貌和纯度等...     

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.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.     

卧式金属罐容量的测量结果不确定度

本文根据多年的实践检定经验 ,参照JJF1 0 59- 1 999《测量不确定度评定与表示》以及《测量不确定度表达 1 0讲》 ,对卧式金属罐容量的测量结果不确定度进行了评定。     

盐酸浓度不确定度的评估

通过对盐酸浓度标定的过程分析，找出影响结果的各个分量，进行不确定度的评定，按照计量技术规范给出标准的表示法。     

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.     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.