Zn_(1-x)Cd_xSe/ZnSe 应变层超晶格光学特性(英文)

分析了用分子束外延法生长在ＧａＡｓ（１００） 衬底上的Ｚｎ１ － ｘＣｄｘＳｅ／ＺｎＳｅ 应变层超晶格光学特性．对光致发光谱的温度效应进行了详细的研究．光致发光谱的峰位和线形展宽的温度效应的实验结果与理论分析相一致．从光致发光谱的发光强度得出了该样品的激活能．     

Fex(CoyNi1-y)1-x微细磁粉微波电磁参数的影响因素

采用多元醇化学法制备了FeX(CoyNi1-y)1-x系列磁性合金粉，借助矢量网络分析仪测量了该系列合金微粉的的电磁参数，分析了合金组分、微观特性、填充率等因素对其微波电磁参量的影响，结果表明，对微粉进行包覆后热处理工艺可降低杂质含量，改善合金粉的微观形貌，提高合金粉的微波电磁参数。     

Li（Ni（1/3）Co（1/3）Mn（1/3））（1-x）ZnxO2固溶体的XRD及XPS研究

采用共沉淀法制备了不同Zn掺杂量的Li（Ni1/3Co1/3Mn1/3）1-xZnxO2（x=0-0.08）固溶体,通过X射线衍射（XRD）和光电子能谱（XPS）分析,研究了不同Zn掺杂量对Li（Ni1/3Co1/3Mn1/3）1-xZnxO2固溶体晶体结构和过渡金属表面化学状态的影响。实验结果表明：当Zn掺杂量x小于0.006时,固溶体材料具有稳定的层状结构;微量Zn的掺杂能够增强晶体材料的整体键能。     

Equivalent circuit models using CPE for impedance spectroscopy of electronic ceramics

Complex immittance (Impedance Z, Modulus M, Admittance Y, Permittivity ?) spectra for some equivalent circuit models involving resistances, capacitances and constant phase angle elements (CPE) are calculated for different ratios of the parameters. A comparison of experimentally obtained complex immittance plots with these diagrams greatly facilitates the search for the most appropriate equivalent circuit representing the electrical properties of electronic ceramics. An equivalent circuit for Ba_1-xSr_xTiO₃ (x = 0.35) ceramic system is developed by using these simulated plots.     

2：17型结构的Ho2（Fe1—xCox）15Al2化合物的结构与磁性

用电弧熔炼的方法制备了Ｈｏ２（Ｆｅ１－ｘＣｏｘ）１５Ａｌ５（ｘ＝０,０．２,０．４,０．６,０．７,０．８,０．９,１．０）化的,用Ｘ射线衍射和磁性测量研究了它们的结构和磁性,结果表明所有样品为单相２：１７型Ｔｈ２Ｎｉ１７六角结构,随Ｃｏ含量的增加,Ｈｏ２（Ｆｅ１－ｘＣｏｘ）１５Ａｌ２化合物的单胞体积Ｖ,晶格常数ａ、,ｃdisplay structure     

尖晶石LiCoxMn2-xO4的电化学阻抗谱分析

用溶胶-凝胶法合成尖晶石LiCoxMn2-xO4(x=0.1、0.2、0.3和0.4)。随着Co掺杂量x的提高,样品的首次比容量降低,循环性能提高。LiCo0.1Mn1.9O4的电化学阻抗谱(EIS)高频区域拉长压扁的半圆由两个半圆重叠而成,分别归属于Li+通过SEI膜的迁移和LiMn2O4的电子电导率。在首次充放电过程中,3.95~3.70 V时SEI膜的阻抗增大,可能是Li+嵌入时颗粒膨胀导致晶体畸变所致;随着电极电位升高,电子传输电阻Re总体减小,电荷传递电阻Rct先减小,后增大。     

Impact of pH Value on Structural,Thermal, Optical and Raman Studies of Neodymium Phosphate (NdP) Nanoparticles Synthesized by Co-Precipitation Technique

Abstract

The present study deals with the impact of pH value on neodymium phosphate (NdP) nanoparticles which have been successfully synthesized via wet chemical co precipitation technique. PXRD revealed the formation of monoclinic phase, purity and crystallinity. TEM reveals spherical morphology with the formation of slight agglomeration and grain size decrease at low pH as compared to high pH. TGA/DTA suggests that as synthesized nanoparticle shows phase transition above 800^°C. FTIR and Raman spectroscopy signifies slight shifting of bands towards lower wave number at high pH and gives relevant peaks of phosphates (PO₄^3?) group. Optical absorption with selected value of pH were studied in UV-VIS spectrophotometer and showed a strong absorbance with a tendency towards blue shift.     

对Ga_(1-x)Al_xAs/GaAs太阳电池结构的一点新看法

用液相外延技术制备p-Ga_(1-x)Al_x/p-GaAs/n-GaAs结构的太阳电池,并获得AM1效率20.2%,AM0效率16%～17%.现已用研制出的GaAs电池单片,组装成组件,安装在我国1994年2月8日发射的实践4号卫星上作挂片实验.作者对此结构太阳电池提出一点新看法,同时提出北场GaAs太阳电池构想.     

Piezoelectric ceramics of (Bi1/2Na1/2)TiO3-PbTiO3-BaTiO3 system

Piezoelectric and ferroelectric properties of bismuth sodium titanate, (Bi_1/2Na_1/2)TiO₃(BNT)-based solid solution, that is, (Bi_1/2Na_1/2)(_1-x)(Pb_a Ba_b)_xTiO₃(a + b = 1) [BNPB(100x-100a/100b)], are studied from the viewpoint of a new group of lead-free or low-lead content piezo-electric ceramics with a rhombohedral(F_a-tetragonal (F_β) morphotropic phase boundary (MPB). It is evident that the MPB seems to be remarkably efficacious in promoting piezoelectric and pyroelectric activities by electrical poling. X-ray diffraction data, dielectric properties and D-E hysteresis loops show that the MPB exist near (Bi_1/2Na_1/2)TiO₃[BNT] at x = 0.13–0.14, 0.08–0.09 and 0.06–0.07 in the case of b = 0, b = 0.5 and b = 1, respectively. BNPB ceramics are superior for piezoelectric ceramics in high-frequency ultrasonic uses, or special piezoelectric actuator materials with a lower free permittivity ε₃₃Tε₀, and a high electromechanical coupling factor k₃₃, along with a high mechanical strength.     

锂离子蓄电池LiNi1/3Co1/3Mn1/3O2正极材料的性能表征

采用共沉淀法制备了层状Li1.05Ni1/3Co1/3Mn1/3O2正极材料.以C为负极,在1 C、2.7～4.2 V下的初始放电比容量达145.5 mAh·g-1,循环100次后容量保持率为98.4%.并采用X光电子能谱(XPS)、循环伏安法(CV)和交流阻抗法(EIS)对层状LiN1/3Co1/3Mn1/3O2材料中的各元素氧化态分布和嵌/脱锂动力学过程进行了系统研究.XPS实验结果表明LiN1/3Co1/3Mn1/3O2中Co,Ni,Mn的主要氧化态分别为 3. 2, 4价.还有少量的Ni3 和Mn3 ,并从晶体场理论解释了其氧化态分布机制.而LiN1/3Co1/3Mn1/3O2的循环伏安曲线上主要存在3.95 V氧化峰和3.69 V还原峰,分别对应于Ni3 /Ni4 的氧化还原反应.     

Ml_xMm_(1-x)(NiCoMnTi)_5贮氢合金的电化学性能和Rietveld分析

在ＡＢ５型混合稀土－镍系贮氢多元合金的研究中，为设计高性能价廉的ＡＢ５型贮氢电极合金，人们对其Ｂ侧多元合金化和Ａ（＝ＲＥ）侧稀土组元分别进行了系统的研究。本文通过对ＲＥ（ＮｉＣｏＭｎＴｉ）５合金中稀土组元（ＲＥ＝ＭｌｘＭｍ１－ｘ）进行组合优化研究，主要依赖于市售的混合稀土金属（Ｍｌ和Ｍｍ）原材料，利用不同种类的混合稀土中Ｌａ、Ｃｅ、Ｎｄ和Ｐｒ组元相应变化，来调整其稀土成分。结果表明，Ｍｌ∶Ｍｍ比例对其电化学性能有显著影响。Ｍｌ０．８５Ｍｍ０．１５（ＮｉＣｏＭｎＴｉ）５对应合金具有最高放电容量为２８０ｍＡｈ／ｇ和较好的循环寿命，而合金电化学性能与相应的结构有关。因此，采用Ｒｉｅｔｖｅｌｄ法（多晶衍射图形拟合法）对其精细结构分析具有重要意义。分析表明，合金仍保持母体合金ＬａＮｉ５的ＣａＣｕ５型六方晶系结构，空间群为Ｐ６／ｍｍｍ；合金中Ｌａ、Ｃｅ、Ｎｄ、Ｐｒ（１ａ）－Ｎｉ、Ｃｏ、Ｍｎ、Ｔｉ（２ｃ）键长对其电化学容量起决定作用     

铸造RE17Fe76.5B5Cu1.5（RE=Pr,Nd）热压及其热处理的研究

在热压温度Ｔ〈１１７３Ｋ，ε＝１０＾－４－１０＾－３ｓ＾－１条件下，首次得到铸造Ｐｒ１７Ｆｅ７６．Ｂ５Ｃｕ１．５「００６」织构，而在其它条件下得到的均为「１０５」织构。热压试样经较低温度热处理，不仅热压Ｐｒ１７Ｆｅ７６．５Ｂ６Ｃｕ１．５而且Ｎｄ１７Ｆｅ７６．５Ｂ５Ｃｕ１．５均得到更加显著的「００６」织构，包括在内绝大多数晶面的峰消失，磁体的剩磁大幅度提高，达１３２０－１３３０ｍＴ。     

基于灰色GM(1,1)模型预测固废气化焚烧污染物排放

基于灰色理论,建立了有机固体废物气化处理气化燃料燃烧气态污染物部分组分浓度的GM(1,1)预测模型、预测精度评估,并编制了相应的M atlab应用程序。以氧气流量为3 m3/h,混合固废物料(12.9%稻壳、15.8纸屑、17.5%树叶、24.8%蒿草、29.0%内胎)在不同温度(650℃、700℃、750℃、800℃、850℃)气化时焚烧气结果为例,建立了不同温度下NO、NO2、NOX、SO2含量的GM(1,1)模型,利用该模型预测混合固废物料900℃气化焚烧气的产气组分中NO、NO2、NOX、SO2的含量分别是57.133 9 ppm、9.911 1 ppm、69.764 3ppm、28.774 7 ppm,残差百分率最大的是NOX,仅为-2.9534%,说明GM(1,1)模型预测精度较好。     

ICP-AES测定Ni_xCo_yMn_(1-x-y)(OH)_2中硫酸根的含量

采用电感耦合等离子体发射光谱(ICP-AES)法测定Ni_xCo_yMn_(1-x-y)(OH)_2中硫酸根的含量。探讨高速吹扫时间、镍钴锰基体干扰及测定波长等对结果的影响。优化条件为:高速吹扫2.5 h,镍钴锰基体匹配方法,测定波长为S180.669 nm。该方法与重量法测定的结果吻合,回收率为102.25%~106.00%,相对标准偏差(RSD)为4.64%。     

Li(Ni1/3Co1/3Mn1/3)1-2xMgxAlxO2的合成与电化学性能

采用溶胶-凝胶法在900℃于空气中煅烧合成了层状复合掺杂型正极材料Li(Ni1/3Co1/3Mn1/3)1-2xMgxAlxO2(x=0,0.01,0.02,0.05).通过X-射线衍射(XRD)、扫描电镜(SEM)和电化学测试等研究了掺杂元素对Li(Ni1/3Co1/3Mn1/3)O2的结构和电化学性能的影响.结果表明,适量Mg、Al掺入Li(Ni1/3Co1/3Mn1/3)O2后降低了材料的阳离子混排程度,且晶胞参数随着掺杂量的增加而增加.合成材料颗粒分布比较均匀,平均粒径约为0.5 μm.在充放电倍率为0.1 C和电压范围为3.0～4.3 V的条件下,与未掺杂样品相比,Mg-Al复合掺杂的样品具有更好的电化学性能和容量保持率.当x=0.02时,复合掺杂样品的首次放电容量和库仑效率分别为153 mAh/g和93.0%,20个循环后容量保持率达93.4%.因此Mg-Al复合掺杂锂离子电池正极材料Li(Ni1/3Co1/3Mn1/3)1-2xMgxAlxO2是很有前景的.     

Biexponential and diffusional kurtosis imaging, and generalised diffusion-tensor imaging (GDTI) with rank-4 tensors: a study in a group of healthy subjects

Object Clinical diffusion imaging is based on two assumptions of limited validity: that the radial projections of the diffusion propagator are Gaussian, and that a single directional diffusivity maximum exists in each voxel. The former can be removed using the biexponential and diffusional kurtosis models, the latter using generalised diffusion-tensor imaging. This study provides normative data for these three models. Materials and methods Eighteen healthy subjects were imaged. Maps of the biexponential parameters D _fast, D _slow and f _slow, of D and K from the diffusional kurtosis model, and of diffusivity D′ were obtained. Maps of generalised anisotropy (GA) and scaled entropy(SE) were also generated, for second and fourth rank tensors. Normative values were obtained for 26 regions. Results In grey versus white matter, D _slow and D′ were higher and D _fast, f _slow and K were lower. With respect to maps of D′, anatomical contrast was stronger in maps of D _slow and K. Elevating tensor rank increased SE, generally more significantly than GA, in: anterior limb of internal capsule, corpus callosum, deep frontal and subcortical white matter, along superior longitudinal fasciculus and cingulum. Conclusion The values reported herein can be used for reference in future studies and in clinical settings.     

Structural, Electrical and Dielectric Behavior of Pb(Mg1/4 Ni1/4 W1/2)O3 Ceramics

Polycrystalline samples of Pb(Mg_1/4 Ni_1/4 W_1/2)O₃ (PMNW) have been prepared by a conventional solid-state reaction. Preliminary room temperature X-ray study shows the formation of single-phase compound with cell parameters a = 9.8045 (28) Å, b = 13.1280 (28) Å and c = 14.42072 (28) Å. Dielectric anomaly and ferroelectric phase transition observed at 76°C was supported by our polarization study. The variation of dc resistivity of the material with temperature shows its semiconducting behaviour.     

Characterization and dielectric properties of Ba5LnNiTa9O30 (Ln = La, Nd and Sm) ceramics

Three novel Ba₅LnNiTa₉O₃₀ (Ln = La, Nd and Sm) ceramics were prepared and characterized in the BaO-Ln₂O₃-NiO-Ta₂O₅ system. All three compounds adopted the filled tetragonal tungsten bronze (TB) structure at room temperature. The present ceramics exhibited relaxor behavior, and the Curie temperature (at 10kHz) were −130, −80 and −45°C for Ba₅LaNiTa₉O₃₀, Ba₅NdNiTa₉O₃₀, and Ba₅SmNiTa₉O₃₀ respectively. At room temperature, Ba₅LnNiTa₉O₃₀ ceramics have a high dielectric constants in the range 102∼118, a low dielectric loss in range 0.0019∼0.0036, and the temperature coefficients of the dielectric constant (τ_ɛ) in the range −320∼−460 ppm°C⁻¹ (at 1 MHz).     

Design and control of LCL filter interfaced grid connected solar photovoltaic (SPV) system using power balance theory

In this paper solar photovoltaic (SPV) system connected to the utility grid is designed and simulated. The utility grid and SPV system are coupled with current controlled voltage source converter (VSC) and LCL filter. The design of LCL filter, MPPT algorithm and power quality improvements are discussed and simulation results are shown for the performance analysis of grid-coupled PV system under different load condition. The system is controlled through power balance theory method. The principle behind the control implementation is to evacuate the solar power generated during the daytime and the reactive power demand for the load should be supplied by the PV. The grid coupled system consists of SPV system, dc–dc boost converter, maximum power point tracking (MPPT), voltage source converter (VSC), LCL filter, different loads and three phase utility grid. This system is capable of eliminating harmonic and load balancing by supplying unbalanced current from the PV as a compensator. The system is simulated with 10 kW SPV array using indirect current control scheme.     

2.38 Tbit/s, 1.49 bit/s/Hz, and (16×4×40 Gbit/s) RZ-DQPSK polarization division multiplex transmission over 273 km of fiber

We report on transmission of a net aggregate data rate of 2.38 Tbit/s (excluding an assumed ~7% FEC overhead) over 273 km of fiber with just 16 100-GHz-spaced WDM channels. Due to polarization division multiplex and RZ-DQPSK modulation, each channel carries 160 Gbit/s (including the assumed FEC overhead) although the symbol rate is only 40 Gbaud. Polarizations are demultiplexed using automatic polarization control with a LiNbO₃ polarization transformer. In-phase and quadrature data are demodulated in a 1-bit interferometer.