原位漫反射红外光谱研究SAPO-34分子筛的吸附性能

采用漫反射红外光谱原位考察了298－773K范围H2O，NH3和NO在SAPO－34分子筛上的吸附行为结果表明，SAPO－34对水的吸附是可逆的，对NH3和NO的吸附则是不可逆的。吸附水在623K完全脱附，脱水后的分子筛在3625－3600cm^-1出现表征桥式羟基（Si-OH-Al）的特征峰。发现SAPO－34对NH3和NO均有良好的吸附－催化活性。吸附NH3后，桥式羟基消失，位于3135，3032和1399cm^-1处在423K时出现三个吸收峰，在673K达最大，且峰高分别是SAPO－34骨架峰高的3.9,1.7和6.7倍；吸附NO后，在室温下位于1364cm^-1也观测到一强而尖锐的峰，其强度与骨架峰强度相当。对这些峰进行归属表明，吸附NH3和NO后产生了新的物种NO3^-。     

晶化时间及硅源对SAPO-5分子筛的结构及模板剂状态的影响

通过改变硅源和晶化时间的方法,采用水热法合成了系列SAPO-5分子筛材料,用X光衍射(XRD)和²⁷Al MAS NMR对产物的晶相结构进行表征,用¹³C CP MAS NMR研究了不同阶段的产物中模板剂的存在状态。结果可见:以SiO₂凝胶为硅源时;薄水铝石反应物有较高的活性,在48h的晶化时间内,延长晶化时间有助于SAPO-5分子筛的完整结晶,当晶化时间超过48h时,其中已形成的SAPO-5的结构部分被破坏,并转化为SAPO-34.且SAPO-34的量随晶化时间的延长而增多。当以Si(OEt)₄为硅源时,铝反应物的反应活性较低,在72h的晶化时间范围内,延长晶化时间有助于SAPO-5产物的形成,使其结构愈加完整,在SAPO-5分子筛的形成过程中,模板剂的状态随分子筛结构的变化而变化,由于三乙胺(Et₃N)模板剂中的甲基和亚甲基所处位置不同,其弛豫时间受分子筛结构的影响较大,可用其中甲基的¹³C MAS NMR诺线的强度及化学位移来表示分子筛结构的完整性。     

Ce-EU-1分子筛的合成和表征

采用水热法,以溴化六甲双铵（HMBr2）为模板剂,硅溶胶、偏铝酸钠为硅铝源,以六水硝酸铈为铈源合成了稀土Ce-EU-1分子筛,并通过XRD、FTIR、紫外-可见漫反射光谱、热重分析（TG-DTG）和氮气吸附-脱附等测试手段对合成样品的孔道结构、物化性能及Ce的存在状态进行了表征。XRD结果表明,合成样品不仅具有很高的纯度和结晶度,为典型的立方有序排列的EU-1结构,而且部分Ce已取代Si或Al进入微孔分子筛的骨架。样品的FTIR图谱在980cm-1附近有明显的Si—O—Ce特征吸收峰,证明Ce存在于分子筛的骨架中。紫外-可见漫反射图谱显示,在253nm附近出现O—Ce之间的电子跃迁特征峰,进一步证明了Ce进入了分子筛骨架。氮气吸附-脱附结果表明了Ce的掺入对分子筛的物化性能和孔道结构产生了影响。同时考察了镧系其他金属离子（Ln：La、Nd、Sm和Gd）对EU-1分子筛的影响,发现随着镧系离子半径的减小,Ln-EU-1分子筛的相对结晶度逐渐降低,晶胞体积减小。     

MASNMR研究钯添加剂对SAPO-5分子筛的影响

通过在SAPO-5分子筛的前身体中加入不同含量不同形式的钯盐方式,直接合成出了分子筛上担载贵金属的双功能催化剂,X光衍射(XRD)结果表明把的加入并不影响SAPO-5分子筛的生成,但降低了分子筛结晶度。当把以碱性介质加入反应物时,使产物中有少量SAPO-34伴生,由MASNMR实验结果可见,反应物中把的加入抑制了硅进入分子筛骨架,使骨架铝配位环境更加对称,并使三乙胺模板分解,改变了其在分子筛中的存在状态。从而导致分子筛结晶度的降低.     

介孔分子筛Al-MCM-41的合成与催化异构化性能

采用正硅酸乙酯(TEOS)为硅源,九水硝酸铝为铝源,十六烷基三甲基溴化胺(CTMABr)为模板剂,在室温条件下合成了介孔Al-MCM-41分子筛.通过XRD、N2等温吸附、SEM、FTIR等分析测试手段表征了分子筛的介孔结构和表面性质.结果表明所合成的分子筛有良好的介孔结构和较高的有序度,并且有较高的比表面积(达到816 m2·g-1)和窄的孔径分布.采用程序升温的焙烧方式、凝胶Al/Si比最大范围控制在0.06～0.13有利于合成高度有序的介孔Al-MCM-41分子筛.评价结果表明,所合成的Al-MCM-41分子筛对桥式四氢双环戊二烯(endo-TCD)异构化反应合成挂式异构体exo-TCD及金刚烷具有较高的催化活性和极高的选择性.     

Fe-ZSM-5杂原子分子筛的合成与表征

采用静态水热法分别以正丁胺、四丙基溴化铵为模板剂合成ZSM-5分子筛及Fe-ZSM-5杂原子分子筛；利用XRD与FT-IR对其结构进行表征；考察了Mo改性后分子筛催化剂上甲烷脱氢芳构化的反应性能。结果表明，Fe部分进入了分子筛的骨架，导致分子筛的结晶度及表面酸强度的下降，使Mo／Fe-ZSM-5催化剂的反应性能较Mo／HZSM-5显著下降。     

ZnO/MCM-41复合材料的制备及其光谱性质

以硅酸钠(NaSiO3·9H2O)为硅源,三甲基十六烷基溴化铵(CTAB)为模板剂在碱性条件下水热合成介孔分子筛MCM-41,然后以其为主体,采用锌盐浸渍-灼烧的方法.在介孔分子筛MCM-41上负载了氧化锌(ZnO)纳米微粒,并通过扫描电子显微镜,红外光谱(1R).紫外可见吸收光谱(UV-Vis),N2-吸附脱附和荧光光谱等手段对产品进行了系列表征.结果表明,分子筛平均直径约为1.7μm,对不同温度下灼烧后得到的ZnO/MCM-41组装体的光谱性质进行研究表明介孔分子筛MCM-41的尺寸所限,制备出的ZnO粒子粒径小于2 nm.量子尺寸效应使得ZnO/MCM-41组装体中的ZnO纳米粒子的紫外可见吸收光谱及荧光光谱均发生蓝移.通过红外光谱分析得知ZnO负载到MCM-41上并没有改变介孔分子筛原有的骨架结构.     

超声波酸性体系下MCM-41的合成及表征

以十六烷基三甲基溴化铵(CTAB)为模板剂,正硅酸乙酯(TEOS)为硅源,以超声波为辅助手段于酸性介质中制备出了MCM-41介孔分子筛,采用XRD、TEM、FTIR等手段对样品进行了分析表征.结果表明,所合成样品具备MCM-41所特有的六方排列的一维孔道结构和较高的有序度,所合成的MCM-41平均粒径为11nm,孔径约为2.7nm.     

Ce-MCM-48立方介孔分子筛结构的光谱表征

在碱性条件下,以混合模板剂pH调节水热合成了掺入铈的介孔分子筛Ce-MCM-48,并采用XRD,DRUV-Vis(紫外-可见漫反射),FTIR,XRF结合BET等测试手段对样品进行表征。实验结果表明,采用本方法所合成的掺铈介孔材料仍保持立方介孔的有序结构,同时适量的铈的掺入和pH调节使分子筛的有序性及吸附性能得到改善,晶胞参数增大,孔径更均一,孔壁增厚。从而可推出Ce-MCM-48的热稳定性、水热稳定性、催化活性及择形选择性可得到提高。掺入的铈以四配位状态高度分散在介孔的有序结构当中。红外光谱表明不同量的铈的掺入对骨架硅的各种振动扰动程度不同。     

一维取向LTL型分子筛荧光阵列的快速组装

通过有效控制合成液配比,合成出了形貌规则、结晶度高且具有不同长径比的LTL型分子筛晶粒。采用"瓶中造船法",在不同长径比的LTL型分子筛晶粒孔道中组装稀土有机配合物,制得LTL分子筛/Eu-TTA主-客体荧光材料。荧光光谱表征结果表明,在激发波长为350 nm时,长径比为0.2的LTL分子筛/Eu-TTA晶粒在617 nm处的5D0→7F2发光强度最大,而长径比为3的晶粒发光强度最小。最后,将长径比为0.2的LTL分子筛/Eu-TTA晶粒在PEI修饰的玻璃表面快速擦涂10 s后,就制得厘米尺寸的一维取向LTL型分子筛荧光阵列。SEM表征结果证实,该分子筛荧光阵列中几乎所有的LTL分子筛晶粒都沿着与底基表面垂直的c轴方向一维高密度、单层有序排列。在激发波长为365 nm时,该一维取向LTL分子筛荧光阵列发出鲜艳的红色荧光。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.