Nucleation, growth and characterization of L-tartaric acid—nicotinamide NLO crystals

The solubility, metastable zone width and nucleation parameters of organic nonlinear optical material L-tartaric acid–nicotinamide (LTN) have been determined. The crystals of LTN are grown by the slow cooling method. The grown crystals are morphologically interpreted. The crystalline powder of the grown crystals has been examined by X-ray diffraction and thermogravimetric analysis. The different modes of vibrations present in the crystal are identified by the Fourier infrared spectroscopy analysis. The powder SHG efficiency of LTN is comparable with that of KDP.     

Investigation on growth,optical, thermal,mechanical and dielectric studies of Benzimidazolium L-aspartate NLO crystal

The organic salt of Benzimidazolium L-aspartate (BLA) has been synthesised and single crystals were grown by slow evaporation solution growth technique at room temperature using water as the solvent. The grown crystal was subjected to single crystal X-ray diffraction analysis and confirmed it belongs to monoclinic crystal system with space group P2₁/c. The crystalline perfection was studied using High resolution X-ray diffraction (HRXRD). The functional groups were analysed by FT-IR analysis. The optical transmittance and the lower cut-off wavelength of the BLA crystal have been identified by UV-Vis study. The thermal stability of the title crystal was investigated by TGA/DTA analyses. The Vickers microhardness analysis was carried out to study the mechanical strength of the crystal. The dielectric response of the crystal was studied in the frequency range 100 to 5 MHz at different temperatures. The surface morphology of the grown BLA crystal was studied by scanning electron microscopy (SEM). The second harmonic generation efficiency was measured in comparison with KDP by employing Kurtz Perry Powder method.     

溶胶-凝胶法制备紫外及蓝光双截止润眼镀膜玻璃

采用溶胶-凝胶法,在3 mm厚的普白玻璃含锡面镀制镶嵌Ag纳米粒子的氧化硅薄膜,达到吸收蓝光的效果,在其非锡面镀制纤锌矿结构的氧化锌薄膜,达到阻隔紫外效果.通过双膜层的相互作用,达到对紫外和短波蓝光有效阻隔吸收,从而获得具有紫外蓝光防护及润眼功能的镀膜玻璃.研究了热处理温度和膜层厚度对近紫外和蓝光阻隔率的影响.结果表明:随着退火温度的升高,膜层更加致密,且退火温度越高,蓝光的吸收率也逐渐提高,吸收峰位红移.利用浮法玻璃本体的富锡表面还原AgNO3成Ag纳米粒子分散镶嵌在氧化硅薄膜的结构,能有效吸收380～450 nm的短波蓝光.实验样品呈现出美观的淡金黄色,且随着膜厚的增大,金黄色程度逐渐加深.以样品a为例,所制备的氧化锌膜层为稳定的纤锌矿结构,膜厚为438 nm,表面为球状颗粒,对380 nm以下的紫外光阻隔率为98.83;;所制备氧化硅薄膜厚为200 nm,表面致密,对380～450 nm的蓝光阻隔率为90.73;,样品整体450～780 nm可见光透过率为77.8;.     

Mathematical modeling of impurity distribution in the melt meniscus in the growth of profiled sapphire crystals

The distribution of impurities in the growth of profiled sapphire crystals is simulated. The distribution of impurities was calculated with the use of the diffusion equation with convective terms. The melt flow was found by solving the Navier-Stokes equation. The distributions of impurities over the melt meniscus are obtained at different crystallization rates. The maximum concentration supersaturation in the meniscus is studied as a function of its geometric parameters.     

均匀共沉淀法制备NiO包覆Al粉体及性能研究

采用均匀共沉淀法制备了NiO包覆片状铝粉的NiO/Al复合粉末,系统研究了制备工艺对NiO/Al复合粉末红外发射率的影响。采用XRD和SEM对复合粒子的晶体结构及表面形貌进行了分析,利用傅里叶变换红外光谱仪和矢量网络分析仪对复合粉末的红外发射率和电磁参数进行了测试。结果表明:当铝粉的量为2.0 g,反应时间7.0 h,反应温度70℃,煅烧温度450℃时,所得复合粉末的红外发射率最低0.5556;复合粉末的表面NiO包覆较为完整,复合粉末呈片状,厚度基本均匀;复合粉末具有较好的电磁性能。     

Purification,isolation, crystallization,and preliminary X-ray diffraction study of the BTB domain of the centrosomal protein 190 from <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

The spatial organization of the genome is controlled by a special class of architectural proteins, including proteins containing BTB domains that are able to dimerize or multimerize. The centrosomal protein 190 is one of such architectural proteins. The purification, crystallization, and preliminary X-ray diffraction study of the BTB domain of the centrosomal protein 190 are reported. The crystallization conditions were found by the vapor-diffusion technique. The crystals diffracted to 1.5 Å resolution and belonged to sp. gr. P322₁. The structure was solved by the molecular replacement method. The structure refinement is currently underway.     

Pressure dependence of elastic properties of low-silica calcium alumino-silicate glasses

The hydrostatic and uni-axial pressure dependence of elastic properties of a low-silica calcium alumino-silicate glass (LSCAS) is determined by ultrasonic pulse-echo techniques at room temperature. The experimental results are used to obtain the third-order elastic constants (TOECs) of these glasses. The pressure dependence of fractal bond connectivity of these glasses is discussed. The normal behavior of positive pressure dependence of ultrasonic velocities was observed for the glass. The pressure dependence of both shear modulus and bulk modulus are positive for these glasses.     

Chemical synthesis, characterization and transport properties of copolymer: Poly(aniline-co-m-methylaniline)

Poly(aniline-co-m-methylaniline) were copolymerized by chemical peroxidation of aniline and m-methylaniline in aqueous acidic medium under nitrogen atmosphere at 0–4oC. The molar feed ratio of the monomers were varied to prepare copolymers of different composition. The copolymers product were characterized by solubility, spectroscopic methods, elemental analysis and electrical conductivity measurements. The solubility and spectroscopic analysis suggested that the product is a copolymer of aniline and m-methylaniline. The optical spectra of the copolymer shows hypsochromic shift with the increase in dielectric constant of the solvent and with increasing the content of m-methylaniline in the copolymer chain. The electrical conductivity of copolymer salts were measured as a function of temperature. The conductivity of copolymer decreases with increasing the content of m-methylaniline in the copolymer chain, due to change in coplanarity of polymer and reduction of mobility of charge carrier along the main chain. The conduction mechanism of copolymer is polaron hopping conduction as similar to the case of polyaniline. The coherence, most probable hopping distance, hopping energy and localization length of copolymers have been compared to those of homopolymers.     

Synthesis,crystal growth,spectral, thermal and optical properties of acenaphthene picrate

The crystalline material of acenaphthene picrate (ACP) was synthesized and the single crystals of the title compound grown by slow evaporation solution growth technique. The solubility of the complex compound was estimated using different solvents as chloroform, ethanol, (1:1) chloroform ‐ acetone mixture. The material was characterized through elemental analysis; powder XRD, NMR and FTIR techniques. The various planes of reflection have been identified from the XRD powder pattern. The formation of the charge transfer complex was confirmed by UV‐VIS spectroscopy. The thermal stability of the crystals was studied using TG/DTA analyses techniques. The second harmonic generation (SHG) of the material was confirmed by using Nd: YAG laser. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

采用溶液沉积及快速退火制备LiMn2O4薄膜的研究

采用溶液沉积及快速退火制备了不同厚度的LiMn2O4薄膜,用X射线衍射及扫描电子显微镜检测分析薄膜的物相及形貌;采用恒电流充放电及交流阻抗技术研究了LiMn2O4薄膜的电化学性质.结果表明,制备的LiMn2O4薄膜均匀,晶粒大小相近,晶粒尺寸在20～50 nm之间.经热处理后LiMn2O4薄膜断面清晰,薄膜与基片之间扩散很轻微.随着薄膜厚度的增加,薄膜的粗糙度减小,平整度变好.不同厚度的LiMn2O4薄膜的比容量介于42～47 μAh/(cm2·μm)之间,经50次循环后,薄膜的容量损失率从0.18 μm的0.64;上升到1.04 μm的9.0;,循环性能随着薄膜厚度的增加而变差.电化学阻抗测试表明不同厚度的LiMn2O4薄膜锂离子扩散系数差别不大,数量级为10-11cm2/s.     

水热法白宝石晶体和籽晶界面研究

用分光光度计研究发现水热法白宝石晶体和籽晶界面使晶体透过率降低,用大视场偏光显微镜和原子力显微镜分析了该界面的包裹物分布以及界面的显微结构.结果表明平行于(1123)面的籽晶和生长层晶体界面包裹物含量少.界面的缺陷主要来自于晶格畸变及生长初期的温场不稳定所引起的结构缺陷,这也是引起晶体透过率下降的主要因素.     

LiVPO4F电子结构及锂离子扩散特性的理论研究

基于密度泛函理论第一性原理计算的方法研究了锂离子电池正极材料LiVPO4F的晶体结构、电子结构、磁性、插入电压与扩散特性.结果表明,P-O共价键的稳定性较强,在脱锂过程中LiVPO4F的晶体结构始终保持稳定, 体积变化率只有3;.费米能级附近的电子状态主要受V-3d轨道电子的影响,脱锂后体系带隙减小.体系脱锂前后都存在着自旋极化现象,脱锂后体系磁性减弱.LiVPO4F的平均插入电压为4.53 V,这与实验结果4.30 V比较吻合.Li比其他的原子有十分明显的向外扩散的趋势.     

SiO2双尺寸光子晶体的自组装及稳定性探索

采用St?ber法制备不同尺寸SiO2胶体球,利用多次垂直沉积法制备SiO2双尺寸光子晶体.通过场发射扫描电子显微镜(FE-SEM)对所得双尺寸光子晶体的形貌和排列方式进行表征.对双尺寸光子晶体的生长过程进行探讨,研究界面作用力及胶体球间相互作用力对制备稳定结构的影响.研究结果表明,SiO2双尺寸光子晶体具有更加有序稳定的结构.胶体球间的相互作用力随胶体球粒径增大而增大,大粒径胶体球更有利于形成稳定的结构.     

Characterization of gel grown iron‐manganese‐cobalt ternary levo‐tartrate crystals

In the present investigation, iron–manganese–cobalt ternary levo‐tartrate crystals of different compositions have been grown by single‐diffusion gel growth technique in silica hydrogel medium. The metallic composition in the crystals was estimated by EDAX. The coloration of the crystals changed with composition of metallic content. The powder XRD study suggested the crystalline nature and indicated the presence of some extra phases. The grown crystals were characterized by FT‐IR spectroscopy, TGA, dielectric and Vibrating Sample Magnetometer (VSM) studies. The FT‐IR study suggested the presence of O‐H, C=O, C‐O and metal‐oxygen bonds. The effect of composition of metallic content was observed in certain absorption regions in FT‐IR spectra. The thermal stability of the crystals was studied by thermogravimetry and the kinetic and thermodynamic parameters of dehydration were calculated. The effect of composition of ternary levo‐tartrate was observed in dielectric study. The dielectric study was carried out in the frequency range of applied field from 500 Hz to 1 MHz. The variations in dielectric constant, dielectric loss, a.c. resistivity and a.c. conductivity with frequency of applied field were studied. VSM study suggested that all crystals were of paramagnetic nature. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Er3+离子在多孔模板内的发光特性

利用两次阳极氧化的方法制备多孔氧化铝模板,然后采用溶胶-凝胶法将铒的乙酰丙酮配合物掺人多孔氧化铝的模板内,制得了Er3 离子的SiO2凝胶。用扫描电镜(SEM)观察了多孔氧化铝模板的形貌,并测试了乙酰丙酮合铒的红外吸收谱以及Er3 离子在多孔模板内的室温荧光谱。初步结果显示纳米孔洞导致了荧光峰变窄。     

白光发光二极管用CaAl2B2O7:Eu3+微晶的发光性质

利用高温固相法合成了CaAl2B2O7:Eu3+微晶.X射线衍射分析表明我们得到了纯相的CaAl2B2O7基质.样品在近紫外光和蓝光激发下能发出红光.发射光谱的主峰位于614nm,对应于Eu3+的5D0→7F2跃迁.激发光谱中两个主峰位于401nm和471nm,分别与紫外和蓝光LED相匹配.并研究了电荷补偿剂和Eu3+的浓度对样品发光强度的影响.所有掺入电荷补偿剂(Li+,Na+和K+)样品的发光强度都比没有掺入电荷补偿剂的样品高.其中掺入Li+的样品的发光强度最高.Eu3+的最佳浓度为6;.CaAl2B2O7:Eu3+是一种有应用前景的白光LED用红色荧光粉.     

电场辅助电化学法沉积ZnO纳米线

采用电场辅助电化学沉积的方法成功的在阳极氧化铝模板中沉积出ZnO纳米线阵列.透射电子显微镜(TEM)、X射线衍射(XRD)测试结果表明,制备的纳米线是单晶ZnO纳米线,形貌均匀,直径大约为60nm,并且择优于(101)晶面.我们对生长过程中所加辅助电场的作用给出了初步的解释.     

Dynamical aspects of Czochralski growth of alkali halides

The variation of the crystal diameter in KC1, KBr, and KI after a sudden small temperature step was measured by means of an optical diameter controller using a laser beam. The diameter reaches exponentially a new equilibrium with time constants of about 30 to 60 min in the given Czochralski apparatus. The time constants increase with the length of the grown crystal. The same exponential behaviour and time constants were obtained from photographs of the solid-liquid interface after a temperature step. The maximum diameter changes for a given temperature step also increase with the length of the grown crystal. The results can be used for a construction of an automatic Czochralski growth apparatus.     

用化学气相沉积法制备红外体块晶体ZnS

本文报道了采用化学气相沉积法制备红外ZnS体块晶体的工艺及其性能.并用傅立叶红外光谱仪测试了材料的红外性能,研究了晶体缺陷对材料红外透过率的影响.结果表明:通过优化生长工艺,使反应室的压力在500～1000Pa之间变化,沉积温度控制在550～650℃之间,可以制备出厚度均匀,红外透过率(3-5μm和8～12μm)在70;以上,尺寸达250mm×250mm×15mm高质量的ZnS体块晶体.     

热处理温度对溶胶凝胶法制备LiNi0.5Mn1.5O4电化学性能的影响

在传统溶胶凝胶法的基础上,通过高温热处理LiNi0.5Mn1.5O4前驱体,合成了高性能的LiNi0.5Mn1.5O4材料.通过X射线衍射仪测试材料的结构,经过超高温热处理后,获得了晶体发育完好的LiNi0.5Mn1.5O4.经电化学测试,高温热处理显著提高了材料的循环性能.经过900℃处理的LiNi0.5Mn1.5O4首次充放电容量达到123 mAh/g,在1C倍率下循环一百次以后容量仍在121.6 mAh/g左右,容量保持率达到98.9;,高温热处理显著的改善了材料的循环性能.