Dispersion analysis of triclinic K2Cr2O7

Polarized IR-reflection spectra of a single crystal of K₂Cr₂O₇ were recorded at near normal incidence. Dispersion analysis was applied, taking fully into account the triclinic symmetry of the crystal and the measuring conditions, to determine the oscillator parameters. The oscillator parameters and the dielectric background tensor were proven valid by comparison between measured and based on these parameters modeled spectra of a randomly oriented polycrystalline sample.     

Equilibrium,kinetics and thermodynamics studies of Cd sorption onto a dithizone-impregnated Amberchrom CG-300m polymer resin

Amberchrom CG-300m, a styrene acrylic ester polymer resin, was studied for the first time as sorbent for metal ion sorption in a solid-phase extraction system. The polymer sorbent was modified via impregnation with dithizone to improve its efficiency. Efficiency of the modified sorbent improved by more than 47%. The loading capacity of the resin is 3.2 mg dithizone per gram of sorbent. The mechanisms of Cd(II) sorption from aqueous solutions are presented. Capacity of the modified resin for Cd(II) was investigated in batch experiments as a function of pH, initial metal ion concentration, temperature and time. Maximum capacity of 0.551 mg Cd(II) per gram of sorbent was achieved. The dimensionless separation factor, 0 < R_L < 1, associated with the Langmuir isotherm (at T = 294 K) signifies sorption of Cd(II) was favorable, as do negative values of free energy of sorption (ΔG) at temperatures exceeding 293 K. Sorption was endothermic (ΔH > 0) while ΔS > 0 reflects the affinity of the sorbent towards Cd(II). The pseudo-second order model proved to be the best fit model for Cd(II) sorption kinetics data. Particle-diffusion models suggest sorption follows film as well as pore diffusion mechanisms.     

Diffusion of Acetic Acid Across Oil/Water Interface in Emulsification-Internal Gelation Process for Preparation of Alginate Gel Beads

Alginate has been widely used in cell microencapsulation and drug delivery systems in the form of gel beads or microcapsules.Although an alternative novel emulsification-internal gelation technology has been established and both the properties and the potential applications of the beads in drug delivery systems have been studied,the mechanism has not been well understood compared with the traditional droplet method(external gelation technology).On the basis of our previous knowledge that the novel technology is composed of complicatedly consecutive processes with multistep diffusion and reaction,and the diffusion of acetic acid across oil/water interface being the prerequisite that determines the occurrence and rate for the reactions and the structures and properties of final produced gel beads,a special emphasis was placed on the diffusion process.With the aid of diffusion modeling and simple experimental design,the diffusion rate constant and diffusion coefficient of acetic acid across oil/water interface were determined to be in the orders of magnitude of 10-6 and 10-16,respectively.This knowledge will be of particular importance in understanding and interpreting the formation,structure of the gel beads and the relationship between the structure and properties and guiding the preparation and quality control of the gel beads.     

黄铁矿处理重金属废水的光谱表征

将反射光谱和吸收光谱用于黄铁矿处理酸性重金属废水的研究,探讨了黄铁矿的表面反应以及黄铁矿与重金属的相互作用。漫反射红外光谱分析证实,在处理废水过程中,黄铁矿中表面羟基与重金属离子发生反应;并通过考察黄铁矿中碳酸盐,合理解释了黄铁矿处理酸性重金属废水后的溶液自然均趋于中性(pH 7)的现象。可见区的反射光谱用于表征处理过程中的黄铁矿的颗粒及比表面变化,解释了黄铁矿在重复使用时其活性反而增强的原因。吸收光谱及XPS表征表明,黄铁矿处理含Cr(Ⅵ)废水,是一个由Cr(Ⅵ)到Cr3+再到Cr(OH)₃的吸附沉淀过程。     

原位漫反射红外光谱表征钛硅分子筛TS-1催化苯乙烯氧化反应

采用高温漫反射红外光谱考察了钛硅分子筛TS-1的稳定性,发现960 cm-1吸收峰在673 K时没有变化,表明所表征的骨架钛具有一定的高温稳定性,而表征分子筛骨架振动的两个吸收峰在673 K下向低波数位移了约13 cm-1。探讨了H₂O₂吸附对TS-1分子筛骨架钛的影响,发现960 cm-1处的吸收峰在吸附H₂O₂后强度减弱,并且向高波数位移了11 cm-1;抽真空或加热,吸收峰又复原,表明骨架钛可能存在TiO结构,H₂O₂与分子筛中的TiO作用,使相应的960 cm-1吸收峰向高波数位移。原位漫反射红外光谱考察了TS-1催化苯乙烯氧化反应,谱图分析表明,苯甲醛是主要产物,TS-1催化氧化的关键是H₂O₂吸附在TS-1的骨架钛上形成活性中心。     

近红外光谱法测定紫花苜蓿青贮鲜样的营养价值

应用近红外光谱技术(NIRS)直接分析新鲜饲草的营养价值,如饲草中干物质(DM),粗蛋白(CP),中性洗涤纤维(NDF),酸性洗涤纤维(ADF)含量,对畜牧业生产具有重要意义。鲜草中由于含有较多的水分,不易制备均一的样品和进行光谱中有用信息的提取,因此难于进行近红外光谱分析。本试验应用偏最小二乘回归法(PLS)、傅里叶变换近红外光谱技术和液氮冷冻制样技术,建立了适合于不同品种,不同生育期,不同茬次和不同青贮方法即时测定青贮苜蓿鲜样中DM,CP,NDF,ADF的模型,以期对NIRS在测定紫花苜蓿青贮鲜样品这些成分测定的可行性进行分析。所建DM,CP,NDF和ADF模型的交叉检验决定系数(R2_cv)为0.884 6～0.989 8,交叉检验标准误(RMSECV)为3.9～9.7 g·kg-1鲜重。用50个样品对模型进行外部检验,预测相关系数(r)为0.939 7～0.994 9,预测标准误为1.9～8.3 g·kg-1鲜重。结果表明： 采用适当的样品处理方法和光谱分析技术可以实现近红外光谱技术对苜蓿青贮鲜样的营养价值评定。     

基于彩色扫描仪的图像光谱重构

针对彩色扫描仪的特点,采用主元分析法(PCA)和反向传播(BP)人工神经网络(ANN)相结合的方法对图像光谱重构进行研究。选择IT8.7/2标准色卡作为训练样本,将该色卡中的另一组色靶作为检验样本以讨论不同网络结构以及不同主元数和训练样本数对光谱重构的影响,再以自然色系统(NCS)色卡为检验样本来分析不同种类的训练和检验样本与光谱重构性能的关系。实验结果表明,采用3-14-6网络结构和6个主元数是最佳选择,训练样本和扫描目标之间的一致性是基于彩色扫描仪图像光谱重构的关键所在。     

GaN基紫光LED的高反射率p型欧姆接触

研究用于GaN基大功率倒装焊(Flip-chip)紫光LED(UV-LED)的高反射率p型欧姆接触的电学和光学性能。用磁控溅射的方法在GaN基LED外延片表面沉积了不同厚度Ag,Al,Au和Pd四种金属,测量了样品的反射率和透射率。结合同步辐射高强度X射线衍射和AFM对金属薄膜的晶体结构进行分析,并对表面形貌进行了观测,对由金属薄膜构成的多层膜结构及其对光反射率的作用机理进行了研究。测量结果表明,在入射光波长为400nm时,Ni/Au/Ag和Ni/Au/Al电极的反射率比Ni/Au的反射率提高了三倍。同时与p-GaN有良好的欧姆接触特性。     

偏最小二乘法结合傅里叶变换红外漫反射光谱快速测定煤质

发热量、挥发分和灰分等是衡量煤质的质量指标。通常,烟煤的发热量、挥发分和灰分是按行业标准方法[1]分别进行测定的,操作过程繁琐,速度慢,且费用高。随着化学计量学多元校正方法的发展与广泛应用,董庆年采用最小二乘法结合红外光谱成功测定了灰分[2];而应用偏最小二乘法[3](P     

Properties of RhP predicted by first-principles

Using density functional theory combined with a global crystal structure search with the particle swarm optimization method, we propose three stable three-dimensional (3D) metallic RhP structures, namely, the Cmcm (RhP-I), P6/mmm (RhP-II), and P6₃mc (RhP-III) phases. All these structures are found to be dynamically stable through vibrational normal mode calculations, indicating that they could be successfully synthesized in experiments. We show that the RhP-I phase has a relatively high thermodynamic stability and high mechanical strength in comparison with the others. The RhP-II and RhP-III phases have porous structures which could accommodate small atoms or molecules. However their thermodynamics are poor, especially the RhP-III phase. The RhP-II structure is stable at 500 K, but the RhP-III fails to survive even at the freezing point of water. Importantly, all these materials have one dimensional conducting channels corresponding to ultrahigh Fermi velocities. Moreover, the porous hexagonal RhP-II and III structures exhibit excellent ability to trap lithium, hydrogen, oxygen, and boron atoms. The RhP-II structure could be especially useful for directly dissociating the hydrogen molecule into two atoms without an energy barrier. In the present study, we identify three new metallic structures to the family of RhP structures, and anticipate their potential for technological applications.