纤维状TiO2/Bi2O3光催化剂的制备及其光催化性能

以C₁₆H₃₆O₄Ti和Bi(NO₃)·5H₂O为原料,以棉花纤维为生物模板,合成了系列纤维状TiO₂/Bi₂O₃光催化剂．采用XRD、SEM、UV-Vis等测试技术对样品的相结构、形貌和吸光性能等进行了表征分析．结果表明,样品中的Bi₂O₃为单斜相和四方相共存的混晶,纤维长度达到毫米级,     

Hg1-xCdxTe的共振拉曼散射

当入射光的光子能量接近Hg_1-xCd_xTe的E₀+Δ₀时,发现了Hg_1-xCd_xTe的共振拉曼散射,观察到了“禁戒”共振增强拉曼散射,同时也观察到了二级共振拉曼散射.分析了非共振条件下能在样品的(100)面观察到微弱的“禁戒”TO₂模以及在共振条件下“禁戒”TO₂模大大增强的原因.通过分析,发现由双LO声子引起的二级共振拉曼散射主要     

Nd高掺杂锐钛矿相TiO2电子结构和吸收光谱的第一原理研究

基于密度泛函理论平面波超软赝势方法, 采用第一原理研究未掺杂和不同浓度Nd高掺杂锐钛矿相TiO₂的电子结构和吸收光谱. 计算结果表明, 在本文限定的Nd高掺杂浓度范围内, Nd高掺杂浓度越小, 锐钛矿相TiO₂的禁带宽度越窄, 吸收光谱发生红移越显著. 计算结果与实验结果变化趋势相一致.     

Cu掺杂AgSbTe2化合物的相稳定、晶体结构及热电性能

利用熔融快淬结合放电等离子烧结(SPS), 制备了Cu_xAg_1-xSbTe₂(x= 0---0.3)样品. 粉末X射线衍射(XRD)分析结果显示, SPS处理以前, 含Cu样品形成NaCl型结构的固溶体, 而未加入Cu的样品析出Ag₂Te第二相. 根据热分析和XRD测量结果, Cu的加入能够有效抑制Ag₂Te的析出, 但同时会在快淬样品中产生少量非晶相. 在温度升高到540 K左右时, 非晶相发生晶化, 形成Sb₇Te亚稳相, 并最终转变成Sb₂Te₃稳定相. 对快淬样品进行低温SPS快速处理后, x =0.1样品为面心立方结构的单相化合物, 但是x =0.2, 0.3的样品分别析出第二相Sb₇Te和Sb₂Te₃. 由于析出第二相, x=0.2, 0.3样品的电导率增大, Seebeck系数减小, 热导率相应升高, 综合热电性能降低. x=0.1单相样品的功率因子与文献报道的AgSbTe₂化合物相当. 元素替代的合金化效应 增强了Cu_0.1Ag_0.9SbTe₂化合物的声子散射, 有效降低了样品的热导率. 因此, 单相样品Cu_0.1Ag_0.9SbTe₂表现出较佳的热电性能, 在620 K时热电优值达到1.     

机械合金化过程对硫化铋块体热电性能的影响机理

以机械合金化法(MA)结合放电等离子烧结技术(SPS)制备了Bi₂S₃多晶块体热电材料. 研究了MA过程中干磨转速、湿磨时间和湿磨介质对Bi₂S₃多晶热电材料电传输性能的影响. 分析了样品的物相, 观察了显微组织, 测试了电传输性能和热传输性能. 研究表明, 以无水乙醇为湿磨介质时, 随着湿磨时间的延长, 出现了微量Bi₂O₃第二相, 样品的晶粒尺寸减小, 电阻率大幅增加, 功率因子下降. 以丙酮为湿磨介质时, 虽然不存在微氧化反应, 但是由于样品中存在大量孔洞, 导致功率因子降低. 425 r/min 干磨15 h后未湿磨的样品在573 K取得最大的ZT值0.25, 是目前文献报道的最高值.     

C3N4的高温高压同步辐射研究

利用激光加热金刚石对顶砧技术在高温高压条件下合成了纯beta相和立方相C₃N₄beta相C₃N₄所属对称群为P63/M (176).对石墨相与beta相C₃N₄的X射线衍射结果进行了精确分析, 得到优化晶胞参数.原位高压同步辐射X射线衍射分析表明, 在6GPa时由beta相到立方相C₃N₄的相转变已经发生, 之后两相共存直到19GPa时相变结束得到纯立方相C₃N₄.     

Eu掺杂量对锐钛矿相TiO2电子寿命和吸收光谱影响的第一性原理研究

采用基于密度泛函理论框架下的第一性原理平面波超软赝势方法,建立了不同Eu掺杂量的锐钛矿相TiO₂超胞模型,计算了其态密度、差分电荷密度、能带结构和吸收光谱.结果发现:掺杂后Eu在TiO₂的禁带中产生杂质能级.通过对比两种不同Eu掺杂量(1.39at%和2.08at%)下的锐钛矿TiO₂的能带结构,发现掺杂量越高,杂质能级越向深能级方向移动,说明电子复合率随杂质浓度增加而增加,即电子寿命变小,同时吸收光谱红移越显著,强度越强.根据实际需要,可在锐钛矿TiO₂中适量掺杂Eu,在适当减少电子寿命情况下,使吸收光谱红移.     

Sn3InSb4合金嵌Li性能的第一性原理研究

采用第一性原理超软赝势平面波方法计算了Sn₃InSb₄的嵌Li性能,得到各种嵌Li相的嵌Li形成能、理论质量比容量、体积膨胀率、能带结构、态密度和差分电荷密度等.从能量角度分析,Li在嵌入时,优先占据晶胞的四面体间隙位置,然后逐步挤出处于节点位置的Sn原子和In原子.在嵌Li过程中,材料表现出较大的体积膨胀率(11.74%-43.40%),这是导致Sn₃InSb₄作为Li离子电极材料循环性能差的重要原因.态密度计算表明,体系的导电性能首先随嵌Li量的增加而增加,当所有的间隙位置被Li填满,发生Sn的替换反应时,富Li态合金相的导电性反而下降.     

BaFe0.4Sn0.6O3/BaBiO3负温度系数复合热敏陶瓷阻抗分析

以BaBiO₃为导电相,BaFe_0.4Sn_0.6O₃为高阻相,采用固态反应法制备了不同BaBiO₃含量的BaFe_0.4Sn_0.6O₃/BaBiO₃负温度系数(NTC)热敏复合陶瓷.为获得在渗流阈值(即BaBiO₃含量为12 mol%)前后复合陶瓷的内部导电机理,对复合陶瓷进行了阻抗分析.分     

第一原理研究Sn(O1-xNx)2材料的光电磁性质

基于第一原理的密度泛函理论, 以量子化学从头计算软件 为平台研究了Sn(O_1-xN_x)₂材料的光电磁性能, 分析了体系的态密度、 能带结构、 磁性、 介电虚部及折射率. 计算结果表明, N替代O后, 随着掺杂浓度的增加, 体系的带隙先减小后增大, 掺杂量为12.50%时带隙最窄. 由于N 2p轨道电子的贡献, 在0.55-1.05 eV范围内产生了浅受主能级, 价带和导带处的能级均出现了劈裂及轨道的重叠现象, Sn-O键的键强大于N-O键的键强. 从磁性来看, N原子决定了磁矩的大小. 从介电虚部可知, 掺杂后体系的光学吸收边增宽, 主跃迁峰发生红移, 反射率和介电谱相对应, 各峰值与电子的跃迁吸收有关.     

Shot-to-shot interferometry of pulsed reproducible quasi-monochromatic signals

A procedure for constructing interferograms on a shot-by-shot basis is proposed. It is shown how Michelson's fringe visibility criterion can be applied to a sequence of interferometer signals to test whether or not their Fourier transform properly represents the pulse frequency spectrum. The ideas discussed are illustrated by experiments with 50 ns CO₂ TEA laser pulses.     

Knotted pictures of the GHZ states on the surface of trivial torus

By means of the method of torus knot theory, this paper presents the complete process of obtaining the knotted pictures of eight GHZ states on the surface of trivial torus from the knotted pictures of eight basic three-qubit states on the surface of trivial torus. Thus, we obtain eight knotted pictures 12₁ linkage on the ordinary plane.     

Testing a large aspheric surface based on analysis of scanning 3D interferogram

A new method based on new reconstruction algorithm and new interferogram fringe analysis was proposed for testing a large aspheric surface. In the testing process, firstly, the interferometer or the tested aspheric surface was shifted relatively for measurement of the whole aperture of the tested aspheric surface to obtain a series of interferograms. Then these interferograms were analyzed to extract the best matching point, where the annular sub-surface was tangent with the corresponding reference sphere of the reference wavefront. Finally, the wavefront aberration of the whole aperture was figured out to describe the deformation information of the tested surface. Without any additional null optical elements, this method can perform the measurement directly. So, this method provides an effective and convenient means of testing the large-aperture aspheric surface. The mathematical model of this method is described, and the results of simulation tests are presented to verify it.     

长干涉腔波长移相计算的自适应相位筛选法

波长移相干涉仪可用于大口径光学元件的测试。其移相量需经过标定方可采用定步长移相算法计算相位分布。在长腔长测试条件下,由于激光器的波长调谐驱动源的精度有限,采用定步长移相算法求解相位分布的精度不高。在分析干涉腔长和波面计算误差的基础上,提出了一种自适应相位筛选计算方法。根据电压-相位标定曲线采集多组周期干涉图,对干涉图中的光强值进行均匀分布抽样后,对其进行随机移相计算,求取每帧干涉图精确的步进移相量,从中筛选出移相量为π/2的四帧干涉图,利用四步移相计算公式求得精确的相位分布。实验结果表明,在波长移相干涉仪中运用该方法,可以很好地解决长腔长测试条件下的相位计算问题,与未进行筛选的计算结果比较,其测试精度得到了显著提高。     

Phase conjugation of CO2-laser radiation by a three-beam interaction

The distortion correction of a CO₂-laser radiation wavefront is studied by using forward resonant parametric scattering in gaseous SF₆ and retrace after retroreflection from a mirror.     

The electrochemical reduction of CO2 on a copper electrode in 1‐n‐butyl‐3‐methyl imidazolium tetrafluoroborate (BMI.BF4) monitored by surface‐enhanced Raman scattering (SERS)

The electrochemical conversion of CO₂ into value‐added products using room temperature ionic liquids as solvent/electrolyte has been proposed as an alternative to minimize the environmental effects of CO₂ emissions. A key issue in the design of electrochemical systems for the reduction of CO₂ is the in situ identification of intermediate surface species as well as reaction products. Copper electrodes, besides being used as cathodes in the electrochemical reduction of CO₂, present surface‐enhanced Raman scattering (SERS) when properly activated. In this sense, the electrochemical reduction of CO₂ over a copper electrode in the room temperature ionic liquids 1‐n‐butyl‐3‐methyl imidazolium tetrafluoroborate (BMI.BF₄) was investigated by cyclic voltammetry and by in situ SERS. The cyclic voltammetries have shown that the presence of CO₂ on the BMI.BF₄ anticipates the reduction of BMI⁺ to the corresponding carbene. Fourier‐transform‐SERS spectra excited at 1064 nm and SERS spectra excited at 632.8 nm have shown vibrational signals from adsorbed CO. These SERS results indicated that CO adsorbs on the copper surface at two different surface sites. The observation of a 2275 cm⁻¹ vibration in the SERS spectra also confirmed the presence of chemically adsorbed CO₂. Other products of CO₂ reduction in BMI.BF₄, besides CO, were identified, including BMI carbene and the BMI‐CO₂ adduct. The SERS results also suggest that the presence of a thin film of Cu₂O on the copper surface anticipates the reduction of CO₂ to CO, an important component of syngas. Copyright © 2016 John Wiley & Sons, Ltd.     

Visible luminescence of Er2O3 induced by CO2 laser radiation with a wavelength of 10.6 µm

The visible luminescence of Er₂O₃ powder induced by CO₂ laser radiation with a wavelength of 10.6 μm is observed and spectrally studied. The mechanisms for the CO₂ laser radiation’s conversion into the luminescence are discussed. The experimental results can be used for the creation of large-screen devices for displaying, visualization, and digital photo and video detection of the intensity distributions, spectra, and interferograms of laser radiation. Original Text ? Astro, Ltd., 2006.     

Temperature Dependence of the Vibrational Relaxation Rate Constants of CO2 (0001) in Binary Mixtures

The rate constants of intramolecular intermode relaxation of the CO₂ molecule (00⁰1) in pure CO₂ and in binary mixtures with He, Ar, H₂, O₂, N₂, CO, NO, N₂O, and H₂O were measured in the temperature range 300–1000 K by means of a laser-induced luminescence method. It is shown that these relaxation rate constants K for all the gas mixtures investigated increase with increase in the gas temperature in this range; the most efficient in deactivation of the 00⁰1 level are the collisions of CO₂ molecules with H₂O molecules; the mechanisms of relaxation of the 00⁰1 level of CO₂ and their channels depend not only on the temperature but also on the parameters of colliding particles; for each of the colliding partners of the CO₂ molecules there is a certain temperature T _c above which the temperature dependence of K is coordinated with the Landau–Teller dependence, and, moreover, the simpler the structure of the colliding partner of the CO₂ molecule, the higher the temperature T _c. Deviations from these dependences at temperatures T < T _c are attributed to the influence of intermolecular forces of attraction, change of relaxation channels, and formation of molecular clusters. For all the colliding partners of the CO₂ molecules, the interaction radii are determined from the intermolecular potentials of interaction used in the theoretical model.     

Determination of the fractal dimension of activated carbons: Two alternative methods

The fractal dimension of three samples of activated carbon has been determined according to two different experimental methods. The first method is based on the vaporization of gas species from the sample into a CO₂ flow up to a constant temperature of 573 K, and the adsorption of CO₂ from the CO₂ flow onto the surface of the sample under cooling. The second method is based on the application of the equation proposed by Frankel, Halsey and Hill. The degree of concordance between both methods is excellent.     

Properties of hollow bent output tips in CO2 laser light delivery system

In order to change the output direction of laser light in a small operation space, two types of hollow bent output tips are proposed for medical laser light delivery system. One is the hollow fiber insert-type, which is of the minimum bending radius of 3 cm. The other type, based on a fixed-bent pyrex glass tube, is of the minimum bending radius of 2 mm. Both types of tips are inner-coated with a silver layer and a cyclic olefin polymer (COP) layer. Loss properties for CO₂ laser light are clarified for the insert-type tips with various bending angles and radii. For the fixed-bent tips, the losses are around 0.7 dB, which are almost not dependent on the bending angles and radii. Transmissions of the tips remain undamaged after 1-h-delivery of 5 W output CO₂ laser light. A nickel layer is coated on the outside wall of fixed-bent tips so as to increase the mechanical strength and lower the surface temperature. Characteristics of surface temperature distribution and time response were experimentally discussed. Transmission properties of pilot beams are also evaluated.