Local structure of NiTi naocrystals studied by EXAFS and XRD 收费下载 A series of NiTi nanocrystals with different annealing temperatures,prepared by sputtering method,were investigated by extended x-ray absrption fine structure(EXAFS) and x-ray diffraction.It was found that the structure of nano-phase powder is different from bulk NiTi alloy with bcc structure as targent materials.When increasing the annealing temperature,a small fraction of the (Ni,Ti) type nanocrystal with the hexagonal structure was presented except target materials and Ni,and it is atomic occupation in random.Finally there were four Ti and two Ni atoms around central Ni atoms,and the bond length of Ni-Ti and Ni-Ni were 0.2462nm and 0.2585nm at 800℃ annealed.Preparation and photoluminescence of nanowire array and films of cadmium sulfied by electrodepositing in organic solvent 收费下载 Nanowir array and film of cadmium sulfide were prepared by eletroplating in organic solvent dimethyl sulfoxide with CdCl2 and element sulfur under different temperature and current density.The UV-VIS absorption spectra show that increasing the electroplating temperature is benefit to forming perfect crystallites of energy shift for the lowest sveral excitons is given and compared with th experiment.The photoluminescence spectrum consists of two parts:the first is produced by recombination of the defcets and the second by recombination of excitons.Evidence for change of the interfacially local structure of titanium oxide／bis[（4,4’—carboxy—2,2’—bipyridine）（thiocyanato）]ruthenium nanocomposite^＋ 收费下载 Tianium oxide/bis[(4，4’-carboxy-2,2’-bigyridine)(thiocyanato)]ruthenium(cis-(NCS)2RuL2)nancomposites were prepared by the self-assembly method.In this system,their interfacially local structures were probed by x-ray absorption spectroscopy (XAS)and the Ti-O interatomic distance and the coordination number of the O atoms around the Ti central atoms were extracted.Copared with TiO2 annoparticles,the Ti local structure in the nanocomposite was changed,Which is responsible for binding cis(NCS)2RuL2 to the surface of TiO2 nanoparticles.copyright 2001 John Wiley and Sons,Ltd.机械球磨硒非晶化的XAFS研究 收费下载 利用低温EXAFS和XANES方法研究了晶态Se在机械球磨过程中的结构变化—结果显示在球磨过程中引入链状分子间的中程无序，破坏了分子间的结合，而分子内Se原子以共价键结合，不易被打破．γ—Mo2N和分子筛负载的钼氮化物的结构表征 收费下载 采用程序升温氮化的方法制备了分子筛负载的钼氮化物催化剂，并用EXAFS方法研究了氮化前后Mo原子的局城配位情况．氮化前负载MoO3样品的径向结构函数中有三个峰，其中前两个嫁对应着最近的Mo-O配位壳层，但是第一个峰与第二个峰的比例比晶体MoO3中的比例大很多，表明分子筛负载的MoO3具有更露密的结构．氮化以后,Mo2N样品的径向结构函数中有三个峰，对应于一个Mo-N和两个Mo-N配位壳层，与面心立方模型符合得很好．根据XRD和EXAFS谱的计算表明，Mo2N中的N原子使Mo-Mo键拉长并削弱．分子筛负载的Mo2N样品具有与非负载Mo-N样品近似相同的径向结构函数，只是对应于Mo—N壳层的峰较弱，表明负载的Mo2N具有更大的结构无序性．Mechanism of SO2 Promotion for NO Reduction With NH3 over Activaed Carbon—Supported Vanadium Oxide Catalyst 收费下载 SO2 shows a significant promoting effect on the activity of V2O5/AC catlayst for No reduction with ammonia at low temperatrures (180-250℃）.In the present study,the mechanism of the SO2 promotion was studied.It was found that the promoting effect of SO2 on the catalytic activity is due to the formation of a sulfate species on the catalyst surace.The sulfate species is linked to carbon surfaces other the vanadium or mineral surfaces.There is a synergetic role between carbon and V2O5 for the formation of surface sulfate species.A possilbe mechanism is proposed.SO2 is adsorbed and oxidized by oxygen to SO3 on the vanadium surface, and the formed SO3 shifts to the carbon surface and converts into sulfate species.The formed sulfate species acts as a new acid site,improves significantly the NH3 adsorption,and hence promotes the activity of the catalyst.During the reaction in the presence of SO2 at low temperatures,the sulfate species stays on the catalyst surface,while the ammonium ions react with NO continuously to avoid the formation and deposition of excess ammonium sulfate salts on the catalyst surface.Symmetry dependence of x—ray absorption near—edge structure at rhe metal K edge of 3d transition metal compounds 收费下载 The pre-edge features in system with “even” symmetry,apart from quadrupolar tranition contribution,are mainly dipolar in character,associated with the existence of unoccupied states made up of mixed cation np with higher-neighboring cation-(n-l)d orbitals,and reflect the density of states due to the medium-range order of the system,while in “ood” symmetry materials these pre-edge features are the result of a transition from the 1s to final denisty of states of p symmetry due to an unsymmetrical mixing of the ligand wave functions with the central cation d orbitals.In the latter case,they contain not only the p but also the d base of orbitals,similar to a tetrahedral configuration.These results are validated for Fe as a photoabsorber by comparing x-ray absorption near-edge spectra of Fe2SiO4(fayalite) and Fe2O3(hematite) to ab initio full multiple scattering calculations at the Fe K edge,but pertain to all systems containing sixfold-coordinated cations.Experimental and theoretical XANES study of the effcets of Fe—Mg solid solution in the enstatit—ferrosilite series 收费下载 Synthetic orthopyroxenes in the join enstatite-ferrosilite (Mg2Si2O6-Fe2Si2O6)have been studied by XANES with the aim to interpret the variations found in the spectra and evaluate the effects of the Mg-Fe substitution in the orthopyroxene(OPX) structure.The experimental Fe-and Mg-K edge XANES spectra show variations of the peaks intensity as a function of the chemical composition of the samples along the EN-FS join.In the region of the Fe edge,the intensity ratio between peak A and B(IB/IA)varies linearly(R=0.99) with the Mg/Fe substitution. Multiple scattering calculation have been performed both at the Fe and Mg K-edge,to study the geometrical modifications of the M1 and M2 octahedral sites induced by the Mg-Fe substitutions.The spectra,obtained locating Fe(or Mg)in both M1 and M2 and weighing the contributions using the occupancy data for the M1 and M2 sites determined by XRD,allow to discriminate the effects to the total spectrum due to Fe(Mg) located in each sites separately.Symmetry role on the preedge X—ray absorption fine structure at the metal K edge 收费下载 The preedge features in a system with “even”symmetry,apart from quadrupolar transition contribution,are mainly dipolar in character,associated with the existence of unoccupied states made up of mixed cation-4p with higher-neighboring cation-3d orbitals,and reflect the density of states due to the medium-range order of the system.In “odd“symmetry materials these preedge features ate the result of a transition from the ls to a final density of states of p symmetry due to an unsymmetrical mixing of the ligand wave functions with the central cation 3d orbitals,similar to atetrahedral configuration.These results are validated for Fe as a photoabsorber by comparing XAS spectra of Fe2SiO4(fayalite) to ab initio full multiple scattering calculations at the fe K edge,but pertain to all systems containing sixfold-coordinated cations.Hg L3 edge absorption study of the HgBa2CuO4＋δsuperconductor 收费下载 The HgBa2CuO4+δ superconductor has been studied by high resolution Hg L3 x-ray absorption near-edge structure(XANES)spectroscopy.The XANES spectrum has been simulated by full multiple-scattering calculations in order to xplore the origin of different features in the experimental spectrum.The experimental Hg L3-edge spectrum could be ewll reproduced by considering a cluster of 85 atoms,containing 10 shell,within a radius of about 7 A from the central Hg atom.The low energy spectral feature in the XANES spectrum is found to be due to aransition from the Hg p states to the electronic states hybridized with higher shell Ba atoms.This implies that the transition features in the Hg L3-edge XANES are strongly influenced by medium range order effects unlike the case of L3 edge of 3d transition metals where short-range order is enough to describe the main transition feansition featrues.Experimental and theoretical XANES and EXAFS study of tetra—ferriphologopite 收费下载 Experimental and theoretical EXAFS and XANES data on Fe coordination and bond istances have been obtained for a natural tetra-ferriphlogopite.XANES data show a predominance of trivalent iron in tetrahedral coordination.the use of theoretical multiple scattering calculations helps distinguish the contributions to the total spectrum coming from the different iron atoms.EXAFS spectra were reduced and analyzed using the GNXAS prograns and Fe has been confirmed to be in tetrahedral coordination,with refined struchural data Fe-O=1.86A,Fe-Si=3.24A,Fe-O-Si=138°.Moreover,a further contribution from Fe is detected corresponding to a Fe-O distance equal to 2.22A.This latter contribution (20mol?of the total Fe ca.)is interpreted to arise from divalent Fe in octahedral coordination,in excellent agreement with the structural and chemical data.On the change of electronic states at the Fermi level by Ce doping in the intermetallic LaRu2 收费下载 Variation of electronic structure at the Fermi level in superconducting LaRu2 intermetallic system has been studied by X-ray absorption near edge structure(XANES) spectroscopy.The high resolution Ru K-edge XANES have been measured by fluorescence yield method using multi-element solid state detector assembly allowing to reach a signal to noise ratio of the order of △α/α-10^-4.The results show decrease of the superconducting transition temperature.2001 Elsevier Science B.V.All rights reserved.EXAFS study of molybdenum oxide on the structure Al2O3 收费下载 In this paper,MoO3 dispersed on an alumina support was studied.The dispersion threshold was determined by x-ray diffraction and the Mo-O coordination structure was detected by extended x-ray absorption fine structure(EXAFS),which shows that the preferred dispersion phase is madu up of [MoO4] polyhedrons.Copyright 2001 John Wiley and sons,Lad.Structures of surface—and bulk—dispersion phases of NiO／Al2O3 收费下载 The structural features of surface-disperison and bulk-dispersion states of NiO on/in γ-Al2O3 have been studied by x-ray absorption fine structure (XAFS) in combination with x-ray diffraction(XRD) and XPS.The results obtained from XRD and XAFS show that surface and buld dispersions of Ni^2 ions need different conditions and have different diffraction features and different corrdination structures.In both the surace-dispersion phase and the solid solution,Ni^2 ions seem to prefer to keep the coordination mode in NiO,which is quite different from that in the stoichioetric spinel.The Ni/Ai intensity ratios of XPS at different etching depths of samples have a maximum and the distribution of Ni^2 ions in the solid solution is not homogeneous.Both it and the coordination features provide evidence of the transition process of dispersing from surface to bulk.Copyright 2001 John Wiley and Sons,Ltd.EXAFS study on the local atomic strucures around iron in glycosylated haemoglobin 收费下载 Samples with 5.1%9.8% and 15.3% HbA1c were extracted from normal subjects and patients with slight and serious diabetes respectively.Extended x-ray absorption fine structure spectra of Fe K absorption were collected at the EXAFS experimental station of the Beijing Synchrotron Radiation Facility.The step-by-step fluorescent mode was employed with a count time of 10s per point.Several independent scans were averageed to eliminate the statistical nosie.Reference backscattering amplitudes and phaseshifts were calculated using the curve wave theory (FEFF code) of EXAFS.Apart from the nitrogen neighbors around the central iron atom,oxygen neighbours are also found.The Fe-Nbond length increases by about 0.02A for the sample with 15.3% HbAlc Compared with the others,but the Fe-Obond length is almost unchanged.With increasing of HbAlc concentration,the content of Hb increases and the content of HbO2 decreases.This demonstrates that the glycosylation of haemoglobin will decrease its ability to carry oxygen.Structural Characteristics of Cerium Oxide Nanocrystals Prepared by the Microemulsion Method 收费下载 The aim of this work is to investigate the microstructure development of erium oxide nanocrystal,prepared by the microemulsion process,as a function of annealing temperature in air.Combined with the HRTEM and the thermogravimetric-differential thermal analysis in air.Combined withthe HRTEm and the thremogravimetric-differential thermal analysis(TG-DTA),the XRD patterns reveal that the sample annealed at 623 K is amorphous,and the formation of cerium oxide nanocrystal occurs above 773 K.The local structural and electronic properties in the nanocrystallization process are probed by X-ray absorption spectra (XAS) at the Ce L3 edge.It is found that the phase structure changes from triclinic to cubic (CeO2),and the electroic structure changes from Ce^3 to Ce^4 upon increasing the annealing temperature.XANES study on the valence transitions in cerium oxide nanoparticles 收费下载 The aim of this work is determination of Ce environment and valence state in Cerium oxide nanopartices prepared by the microemulsion method. X-ray absorption near-edge structure measurements at Ce L3 edge were performed on the nanoparticles as a function of annealing temperature,ranging from 298K to 873K under air condition.The experimental results support the conclusion that Ce ion,in the investigated systems,is in trivalence state when the annealing temperature is below 473K.As the temperature increases up to 623K,the XANEs spectrum shows the coexistence of Ce^3 and Ce^4 states.When the temperature is higher than 623K,the spectra become identical to that of CeO2 with a distinct double-peak structure,corresponding to the Ce^4 state.New observatios on the optical properties of PPV／TiO2 nanocomposites 收费下载 The optical properties of poly(phenylenevinylene)(PPV)/TiO2 nanocomosites,Pprepared form mixtures of PPV precursor and titanium butoxide ethanol solution in a sol-gel process,are investigated by UV-VIS,FT-IR,PL spectroscopy and TEM.The TEM images showed that the TiO2 nano-aggregates took the form of a sphere and finally ellipsoid with an alignment,as the content of TiO2 increased.FT-IR spectra indicated that the titanium butoxied hydrolyzed to from Ti organic compound,which can result in the alignment structure of TiO2 nanoparticles;at the same time,PPV in TiO2 matrix hab the trans-PPV configuration.PL spectra revealed that the light emission of the PPV/TiO2 nanocomposites was from PPv,and the relative intensity of the vibrant components changed with the fromation of the TiO2 alignment structure.These phenomena suggest that the TiO2 matrix can form confined environments to control PPV molecular aggregate states and further effect the optical property of PPV.2001 Elsevier Science Ltd.All rights reserved.Study on the optical properties of PPV／TiO2 nanocomposites 收费下载 The optical properties of poly(Phenylenevinylene)(PPV)/TiO2 nanocomposites,prepared via the sol-gel process,were investigated by UV-VIS,FT-IR,FL spectroscopy and TEM.TEM images indicated that the surfaces of TiO2 nanoparticles became rough,and finally formed the connected network as the TiO2 content increased.FT-IR spectra showed the titanium butoxide hydrolyzed to from Ti organic compound,which can result in the connected network of TiO2 nanoarticles.The conjugation of PPV polymer chains can be interrupted by the TiO2 network structure,as evdenced in UV-VIS spectra.The investigation of the PL spectra revealed that the emitted light of the PPV/TiO2 nanocoposites blue shifted wihout fine structure,and the PL intensity enhanced,when the TiO2 net work fromed.These phenomena suggested that the optical properties of the PPV/TiO2 nanocomposites were dependent on the interfacial structure between PPV and TiO2 nanoparticles.2001 Elsevier Science B.V.All rights reserved.Effect of cobalt promoter on Co—Mo—K／C catalysts used for mixed alcohol synthesis 收费下载 The structures of sulfided Co-Mo-K/C catalysts were studied by menas of X-ray diffraction (XRD),laser Raman spectra(LRS),and X-ray absorption fine structure(XAFS).Activities for alcohol synthesis via CO hydrogenation were used to characterize the catalytic performance of these catalysts.On the activeated carbon support,molybdenum is mainly resent as MoS2 species which shrinks with the cobalt loading,While cobalt is mainly present in the form of “Co-Mo-S”phase at the low Co loading and partly in a Co9S8--like structure at higher Co loading.The catalysts exhibit outstanding performance for higher alcohol synthesis due to addition of the promotion of cobalt.The catalysts exhibit outstanding performance for higher alcohol synthesis due to the addition of the promotion of cobalt.The activity for alcohol formation is optimized at a Co/Mo atomic ratio of 0.5.Co species operate as s synergistic system,rather than independently from the MoS2 phase.2001 Elsevier Science B.V.All rights reserved.Active Carbon Supported Mo—K Catalysts Used for Alcohol Synthesis 收费下载 The structre of oxidic and sulfided Mo catlysts supported on activated carbon was studied by means of X-ray diffraction(XRD),laser Raman spectroscopy(LRS),and extended X-ray absorption fine structure(EXAFS).The activity for mixed alcohol synthesis was also investigated.In oxidic state,the Mo phase on the sample with low Mo loading is mainly present as MoO2,due to the migration of the potassium anions into micropores of activated carbon and thd reducing nature of activated carbon at a high preparation temperature.AS the Mo loading increases,the interaction between potassium and molybdenum is enhanced.At the MoO3 loading of 72 wt?Mo mainly exists in the form of K2Mo2O7 species.After sulfidation,the O-S substitution takes place;the Mo sulfide phase is highly dispersed as tiny three-dimensional particles at higher loading.Indeed,the reults of XRD,LRS,and EXAFS demonstrate that MoS2 is the major phase present after sulfidation.The higher catalytic activity for Mo-K/AC compared to Mo-K/Al2O3 is explained by the difference in the structure of sulfide phase and in the interaction between these phases and the respective supports.活性炭担载的Rh—Mo—K合成醇催化剂 收费下载 采用XRD、EXAFS等技术研究微量贵金属Rh对活性炭担载的Rh-Mo-K合成醇催化剂结构的影响，并关联其催化性能。氧化态Rh-Mo-K／AC样品中Rh与Mo有着较强的相互作用，使得K2Mo2O7向MoO2转化。硫化还原后，Mo主要以MoS2微晶形式存在，其有序结构尺度随Rh含量的增加而减小。经Rh助剂修饰后，催化剂的合成醇催化性能有明显的提高。硫化态Co—Mo—K／AC合成醇催化剂的EXAES研究 收费下载 采用XRD、EXAFS等手段考察了Co载量对催化剂结构的影响，并关联其合成醇活性。活性炭担载的硫化态Co-Mo-K样品中，Mo主要以MoS2物种形式存在于活性炭的表面上，而Co在低Co载量时主要形成“Co-Mo-S”相，在高Co负载量会有部分类CO9S8的物相出现。经Co助剂修饰后的催化剂显示出良好的合成醇催化性能，Co助剂有利于合成C2醇。Co/Mo原于比为0．5时．表面“Co-Mo-S”相可能达到饱和，合成醇的收率也最高。Co物种是和MoS2物相以协同的方式起作用的。三氧化二铝含量对Ni／Zr0.4Ce0.6O2—Al2O3催化剂的CH4—CO2重整反应性能影响 收费下载 采用水热合成法．制备了不同Al2O3含量的Ni／Zr0.4Ce0.6O2-Al2O3催化剂。采用X-射线衍射(XRD)和扩展X光吸收精细结构(EXAFS)，对催化剂样品进行结构表征；考察了Al2O3的加入对催化剂结构和CH4-CO2重整反应活性的影响。结构表征和活性测试表明，催化剂中存在的主要晶相是Zr0.4Ce0.6O2.Al2O3的加入，使催化剂颗粒度变小，镍的分散度提高。并使反应活性有明显改进，而过量Al2O3的加入，却容易导致积炭．氧化铝负载高分散γ—Mo2N的制备及其微观结构的EXAFS表征 收费下载 采用氟化态Mo/γ-Al2O3与NH3的程序升温反应(TPR)制备了不同Mo担载量的氯化态Mo/γ-Al2O3催化剂，用XRD和EXAFS方法分别研究了样品在氮化前后的体相结构及Mo原子局域配位结构．结果表明，在氮化前样品的Mo边径向结构函数与非负载的MoO3类似，样品中Mo以高分散的MoO3形式存在；氮化后样品的径向结构函数与非负载的γ-Mo2N基本相同，只是峰强度有所降低，表明样品中Mo主要以分数度较高的γ-Mo2N形式存在，并且随担载量降低．γ-Mo2N的分散度更高．XAFS CHARACTERIZATION ON THE ACTIVE SITES OF Ni／γ—Al2O3 CATALYSTS FOR NO—SCR BY PROPENE 收费下载 Ni/γ-Al2O3 catalysts show high catalytic activity for the selective catalytic reduction of NO by C3H6.The microstructures of nickel species were characterized by the spectroscopy of X-ray Absorption Near Edge Structures(XANES) and Extended X-ray Absorption Fine Structures(EXAFS).The resuts of XANES and EXAFS indicate that the nickel species in the sample calcined at 500℃mainly exist as highly dispersed NiO phase,Whereas in the samples calcined at750 and 950℃,the nickel species mainly exist as NiAl2O4-like spinel.The surace NiAl2O4-like spinel is the main active site for the selective reduction of No,and the highly dispersed NiO phase is the main active site for C3H6 oxidation. The formation of subsurface or buld NiAl2O4 spinel results in the reduction of surface spinel and cuases the decrease of activity for the selective catalytic reduction of NO by propene.Synthesis of zincosilicate mordenite using citric acid as complexing agent 收费下载 The zincosilicate analog of zeolite mordenite was hydrothermally synthesized in the presence of citric acid and characterized with several spectroscopic techniques.The zeolite thus prepared had a higher crystallinity and Zn concentration in the framework compared with the one obtained in the absence of citric acid.XRD and FTIR provided evidence for the incorporation of Zn in the framework.Results of XAFS indicated a tetrahedral structure of Zn in the lattice framework with a Zn-O distancd of 0.1938nm.It is speculated that the citric acid might decrease the concentration of Zn^2 in the synthesis mixture,there by preventing the unfavorable-formation of oxide or hydroxide species.2001 Elsevier Science B.V.All rights reserved.Determination of double decker sanwich structured La—substituted chlorophyll a by EXAFS 收费下载 As a representative naural porphyrin derivative,it is interesting to know the chemical form of lanthanide in chlorophyll a.We select the natural fern dicranopteris dichotoma,the most lanthanide-concentrated plant known,to isolate the chlorophyll a for our study. It is found by EXAFS that lanthanum substutes in the magnesium position in chorophyll and coordinates with the porphyrin ring.The lanthanum is seen to have a similar coordination structure to a sandwich-type lanthanide complex,with the La surrounded by eight nitrogen atoms from two porphyrin rings with average La-N bond length of 2.65A.A beam position monitor and slit combination for synchrotron radiation 收费下载 At BSRF we have designed and constructed a four-blade slit for 4W1B XAFS beamline to improve its performance.The slit also functions as a beam position monitor by detecting the signal of photoemission from the blades.The key features of this design are:(1) adopting a new mechanism for blade adjustment;(2) combining the functions of two types of BPM (the single wire monitor and the double blade monitor) with the slit.Those features enable us firstly to accurately align the slit with the center of the beam,secondly to monitor the stability of the beam position during operation,and thirdly to diagnose the beam characteristics with this single device.The principle,the features and the testing results are presented in the following sections.2001 Elsevier Science B.V.All rights reserved.Monochromator development at 4W1B beamiline of BSRF 收费下载 The 4W1B is a X-ary monochromator beamline for XAFS at BSRF.During the upgrading phase,we have redsigned the monochromator to improve the performnce of beamline.It is a goniometer based,fixed exit double crystal monochromator.A mechanical linkage is employed to adjust the distance between the surfaces of the two crystals as the Bragg angle is changed to keep the outgoing beam direction constant.The whole mechanism is driven by only one stepping motor.The testing result shows that over the scanning range of 5-30°,the shift of outgoing beam position is less then 70μm in the vertical direction.The basic principle,the mechanical realization,and the error analysis are discussed in detail.The performance and the testing results are also presented in this paper.2001 Elsevier Science B.V.All rights reserved.BSRF XAFS的新进展——全反射XAFS实验方法 收费下载 开展全反射XAFS研究是BSRF XAFS实验站的发展课题之一．目前关键设备全反射实验样品台已加工完成，正处于安装及系统调试阶段．本文介绍了样品台的结构原理，全反射实验系统的构成、设置调整方案及初步实验结果．此外还讨论了应用该设备可开展的全反射XAFS，DAFS等实验方法．不同方法制备的硫化态K—Co—Mo催化剂的EXAFS研究 收费下载 采用共沉淀法和溶胶-凝胶法制备了同组分的硫化态K-Co-Mo催化剂，并用EXAFS研究了体系中Mo原子和Co原子的局域配位情况．结果表明，硫化态K-Co-Mo样品中Mo原子以类似于MoS2结构的物种存在，而Co原子除了以Co9S8形式存在外，还以一种Co-Mo-S相的形式存在，Co-Mo-S的晶相结构与MoS2类似．结合活性测试结果认为Co-Mo-S的形成促进了样品催化活性的提高．此外，EXAFS结果还表明，不同制备方法对K-Co-Mo样品中Mo物种晶粒尺寸具有较大的影响，而对CogS8粒子则影响不明显．其中，采用溶胶—凝胶方法制备，并且在氢气中处理过的样品中Mo物种具有最小的晶粒尺寸．不同热处理方式对超细粒子K—Co—Mo催化剂性能和结构的影响 收费下载 以柠檬酸为络合剂，采用溶胶-凝胶法制备Co-Mo超细粒子氧化物，所得干凝胶分别置于空气和氩气中进行焙烧，然后经K2CO3助化后硫化。使用X射线衍射（XRD）比表面测试和扩展X光吸收精细结构（EXAFS）对样品进行结构表征，同时测试硫化态样品的CO加氢合成低碳混合醇活性。XRD结果表明，在空气中焙烧的样品为单一的CoMoO4物种，其晶粒尺寸约为60nm。在氩气中焙烧的样品，柠檬酸的分解对样品起到还原作用，主要物种为CoMoO3，同时存在少量的CoMoO4，晶粒尺寸约为20nm。BET结果表明，在氩气中焙烧的样品具有较大的比表面积。硫化态样品中主要物种为MoS2和Co9S8，此外，还可能存在CoMoS3.13物种。XRD和EXAFS结果均表明，在氩气中焙烧的样品硫化后，其晶粒尺寸相对较小。活性测试结果表明，催化剂晶粒尺寸的降低明显促进了合成醇的活性和选择性的提高。EFFECTS OF HEAT TREATMENT ON STRUCTURE AND PROPERTIES OF ULTRAFINE K—Co—Mo CATTALYSTS 收费下载 Co-Mo ultrafine particles were prepared by sol-gel method with citric acid as a complexant.The obtained dried gel was calcined in air and argon atmospheres,respectively.After promoting by K2CO3 and sulifiding,the two catalysts were single CoMoO4 crystallites with average size of 60nm.For the sample treated in argon,the main species in the sample were CoMoO3,besides,some Co-MoO4 existed,and the average size was about 20nm.These results indicated that the decomposition of citric acid reduced the CoMoO4 species and decreased the particle size remarkalby.BET measurements showed that,trating the dried gel in argon,the obtained Co-Mo particle and corresxponding sulifded sample possessed a larger surface area.For the sulfided catalysts,MoS2 and EXAFS results indicated that the sulfided sample whose precursor treated in argon possessed smaller average size.The catalytic activity measurement showed that the decrease of the particle sizes resulted in better properties for mixed alcohol synthesis.Eu^3 和Tb^3 在LnBaB9O16中的紫外和真空紫外发光性质 收费下载 研究了Tb^3 和Eu^3 在LnBaB9O16(Ln=La,Gd,Y,Lu)中的紫外和真空紫外光谱性质。X射线粉末衍射数据指标化结果表明，LnBaB9O16(Ln=La,Gd,Y,Lu)系列化合物属于三方晶系.Eu^3 的荧光光谱结果表明，LaBaB9O16和GdBaB9O16中稀土离子占据非中心对称的格位,Eu^3 在其中的特征发射以^5D0→^7F2电偶极跃迁为主；而在YBaB9O16和GdBaB9O16中稀土离子占据中心对铱性的格位，E^3 在其中的特征发射以^5D0→^7F1磁偶极跃迁为主．Tb^3 在LaBaB9O16和GdBaB9O16中的发射为^5D3→^7F0和^5D4→FJ(J=0-6)辐射跃迁，在YBaB9O16和LuBaB9O16中只能观察到^D4→^7FJ(J=3-6)辐射跃迁。与Eu^3 的发光性质相反,Tb^3 占据非中心对称的格位时的发射强度比占据中心对称的格位时要弱得多．Eu^3 和Tb^3 掺杂的样品在真空紫外波段的吸收弱。SrB4O7：Pr^3 中Pr^3 的发光性质 收费下载 本研究报道Pr^3 在SrB4O7中的发光性质，在SrB4O7中Pr^3 离子的4f5d能态高^1S0能级，因此，在207nm UV光激发下，Pr^3 能够把所吸收的一个高能量的UV光子转换为两个可见光子的发射(光子倍增)；在此氧化物基质中的光子倍增主要是由于田离子处于弱的晶体场格位之中；由于与稀土弱联结相关的声于振动频串低(hωmax-1200cm^-1)，因此还能观察到从^3P0能级向低能级的跃迁．第一个光子的发射由1^S0→1^G4(313nm),^1S0→^1D2(338nm)和^1S0→^1I6(405nm)的辐射跃迁组成；第二个光子的发射由^3P0和^1D2能级向低能级的辐射跃迁组成[^3P0→(^3HJ,^3FJ)和^1D2→（^3H4,^3H5)].Gd203：（Ce^3 ，En^3 ）微晶中稀土离子间的级联能量传递 收费下载 本文报道了纳米Gd203：(Ce^3 ，En^3 )的紫外与真空紫外（UV-VUV)激发谱及其选择激发下的荧光光谱。这些光谱实数表明，除了Gd2O3基质与Ce^3 ,Eu^3 离子之间的能量传递外，还存在着Gd^3 与Ce^3 、Eu^3 间的能量传递，即存在Gd^3 →Ce^3 →Eu^3 三种稀土离子间的级联传递。Gorwth and characterization of SrMoO3 thin films 收费下载 Highly conductive SrMoO3 thin films with good crystallinity and somooth surface were grown on SrTiO3(001)substrates by pulsed laser deposition.The effects of ubstrate temperature and oxygen pressure on the stucture,Surface morphology,and eletrical properties were studied.In the range of substrate temperatures form 560℃ to 640℃ and oxygen pressure from 10^-3 to 10^-4 Pa studied in our experiments,high-quality SrMoO3 thin films were produced. Beyond the top temperature or oxygen pressure limit,SrMoO4 appears as an impurity phase.High-resolution transmission electron microscopy(HRTEM) study shows that the SrMoO3 film has high-quality crystallinity and an epitaxial nature.The root-mean-square surface roughness of the film deposited at 2.5×10^-4 Pa is 3.9A.The films exhibit metallic conduction,which results from the delocalized electrons from Mo.X-ray photoelectron spectroscopy (XPS) measurements characterized its core level spectra and the valence band.2001 Elsevier Science B.V.All rights reserved.Bei四羧酸铈在TiO2纳米晶膜上的光电转化性质 收费下载 报道了Ce^3 和Ce^4 两种金属离子桥联Bei四羧酸在二氧化钛纳米晶电极上自组装膜的制备，并利用紫外可见光谱、红外光谱、光电子能谱等手段对自组装膜进行了表征．通过同步辐射光电子能谱确定了自组装膜的HOMO能级．基于自组装膜缺化二氧化钛纳米晶电极的薄层三明治型太阳能电池具有较好的光电传化性质．在480nm，Bei四羧酸敏化二氯化钛电极产生了26．9％的入射单色光子-电子转化效率(IPCE)，而由Ce^4 离子或Ce^3 离子桥联所形成的自组装膜分别产生了55．8％和39.1％的IPCE．金属离子桥联Bei四羧酸自组装膜相当于一种配合物，其HOM0能级比Bei四羧酸自组装膜的高，这是形成铈离子桥联Bei四羧酸后IPCE提高的一个主要原因，Self—assembly and photoelectric properties of cerium compleses with 3,4,9,10—perylenetetracarboxylic acid on nanocrystalline TiO2 films 收费下载 Self-assembled(SA)films (PMP,M=Ce^3 or Ce^4 )of 3,4,9,10-perylenetetracarboxylic acid(PTA)on nanocrystalline TiO2 films with Ce^3 or Ce^4 as a bridge were fabricated and characterized with UV-Vis,IR,and XPS synchrotron radiation photoelectron spectroscopy (SRPES) which gave the HOMO energy levels for the SA films.It was shown that thin-layer sndwich-type solar cells based on these SA films possess good properties for photoelectric conversion.While PTA-loaded TiO2 electrode(P) generated 26.9?f incident monochromatic phototo-to-electron conversion efficiency (IPCE),PMP-sensitized TiO2 electrodes yielded 55.8?and 39.1?for Ce^4 and Ce^3 respectively.PMP films can be considered as a kind of complexes whose HOMO energy levels were proved to eb higher than that of film P,which is one of the major reasons for the increase in IPCE form film P to film PMP.Ultrathin Pb film growth on Cu（111） studied by photoemission 收费下载 The valence bands and the Pb 5d,Cu 3p core levels of Pb films evaporated on Cu(111) were measured by synchrotron radiation photoemission and characterized by low-energy electron diffraction(LEED) and Auger electron spectroscopy(AES).The variation of the surafce state at the center of the surface Brillouin zone (SBZ) of Cu(111) with Pb coverage shows that the submonolayer Pb grows on Cu(111) at room temperature(RT) as two-dimensional(2D) islands.With the Pb coverage increasing,the Pb 5d5/2 core level shifts to higher binding energy monotonically.While the Cu 3p3/2 core level is shifted toward higher binding energy by about 120 meV due to the deposition of 1.0ML Pb.At low Ph coverage,subsequent annealing at 200℃ gives rise to Pb-Cu surface alloy formation in the first layer of Cu(111).The Pb 5d core level is shifted toward Fermi level by 20-30 meV due to the surface alloying.An assumption about electron charge transfer from Cu to Pb was adopted to interpret the observed cored level shifts.2001 Published by Elsevier Science Ltd.乙烯在Ru（1010）表面价带电子特性研究 收费下载 在200K以下乙烯(C2H4)可以在Ru（1010）表面上以分子状态稳定吸附，200K以上乙烯发生了脱氢分解反应生成乙炔(C2H2)。乙烯分解生成乙炔后，σCC和σCH分子轨道能级向高结合能方向分别移动了0．5和1.1eV。偏振角分辨紫光电子谱（ARUPS)结果表明：在RM（1010）表面上，乙烯和脱氨反应后生成的乙炔分子的C—C键轴都不平行于表面，而是沿表面(0001)晶向倾斜。C2H2,C2H4与K在Ru（1010）表面上共吸附的UPS研究 收费下载 利用紫外光电子谱(UPS)对乙烯(C2H4)和乙烯(C2H2)气体在Ru(1010)表面的吸附及与K的共吸附进行了研究，实验结果表明：当衬底温度超过200K，乙烯即发生脱氢反应后，σCH和σCC能级均高结合方向移动．在室温下、σCH和σCC能级位置与乙炔在Ru(1010)表面的吸附时的分子能级完全一致．乙烯发生脱氢反应后的主要产物为乙炔。衬底温度从120K升到室温，Ru(1010)表面上乙炔的σCH和σCC能级均未发现变化．室温下乙炔仍然可以在Ru(1010)表面以分子状态稳定吸附．在有K的Ru(1010）表面上．室温时σCH谱峰几乎消失．碱金属K的存在促进了乙炔的分解．INVESTIGATION OF BONDING IN NANO—SiO2 BY Si L2，3 X—RAY ABSORPTION NEAR—EDGE STRUCTURE SPECTROSCOPY 收费下载 The Si L2,3 X-ray absorption near-edge structure(XANES) can be used to probe the local structure around Si and derive electronic information of the unoccupied s- and d-like partial density of states in nano-size SiO2.We present Si L2,3-edge for three different size silicates acquired by total electron yield(TEY) at the photoemission atation of Beijing Synchrotron Radiation Facility (BSRF).The Si L2,3-edge spectra are interpreted based on ab initio full multiple-scattering(MS) calculation.The Si L2,3-edge of nano-size materials has XANES similar to that of α-quartz.The similarities between the Si L2,3-edge shapes attest to a common molecular-orbital picture of their Si-O bonding and the same coordination state.However,a considerable broadening of Si L2,3-edge XANES spectra as decrease of particle size is also an indicative of polyhedral distortions.Oxygen 1s ELNES study of perovskites （Ca,Sr,Ba）TiO3 收费下载 The O K-edge spectra of perovskites XTiO3 with X=Ca,Sr and Ba have been measured using electro energy-loss spectroscopy (EELS) and are analyzed using the ab initio full mulitiple-scattering(MS) calculations.The near-edge structures arise mainly from covalency by direct and/or indirect interaction between oxygen and metal.The coordination number of the cation and the site symmetry also infuence the spectral shape and structures.Comparison of full MS simulations of different clusters around the excited atom allows to interpret and correlate the features present in the spectra of each compound to its specific atomic arrangement and electronic structure.NEXAFS multiple scattering calculations of KO2 收费下载 Since many years the oxidation of alkali metals has being attracted much interest due to the catalytic properties of metal promoters and the simple electronic structure of alkali atoms.The alkali-oxides phase diagram indicates that the interaction of oxygen with alkali metals can lead to the formation of different atomic O^2 ions and molecular O2 and O2^2- ions.Potassium superoxide has been prepared in situ and high resolution O e-edge absorption NEXAFS spectra have been measured at the VUV beam-Line at ELETTRA facility.The experimental data have been analyzed by multiple scattering approach deriving many geometrical and electronic is of the KO2 type with an O-O distance of about 1.35A and that the transition involving singleπ molecular empty state of the superoxied O2 anion has a fine structure.Multiple Scattering self consistent calculation indicates that the bond between oxygen anion adn K atom is totally ionic and that the fine structure is essentially due to solid state effects.RESONANT PHOTOEMISSION OF BULK CeO2 AND NANO—CeO2 FILMS 收费下载 Photoemission behaviors of nano-CeO2 films with parlicle sizes ranging from 8nm to 50nm and bulk CeO2 in Ce 4d-4f absorption region have been investigated.Resonant enhancements of Ce 4f valance band and Ce 5p bands for nano film and bulk material have been observed.The variation of electron density of Ce 4d-4f resonace.INVESTIGATION ON THE VALEN CE STATE OF Ce ATOM IN BULK AND nANOCRYSTAL CeO2 BY X—RAY ABSORPTION AND PHOTOEMISSION 收费下载 Valence band photoemission spectra(PES) for both bulk and nanocrystal CeO2 have been masured on and off resonance of Ce 4d-4f absorption edge.The PES show that the bulk and nanocrystal CeO2 of diameter ranging from 8nm to 50nm exhibit a peak near Fermi edge with binding energy of abiyt 1.8eV peak shows a strong dependence on excitation energy,although it looks like the contribution of Ce^3 ion following the data reported in literatures.However,According to the results of resonance photoemission and X-ray absorption spectra at O 1s edge,this electronic structure may be associated to the intermediate state charge transfer effcets.弧光放电法原位清洗光学元件 收费下载 光学元件受到污染后其光学性能会变差，如何对其进行清洗，尽可能地恢复其原来的性能，使其能够重新使用显得很重要。本文介绍—种碳污染的原位清洗方法——射频弧光放电法，利用原子氧与光学元件表面所沉积的碳反应以达到清洗的目的。清洗装置建立后对北京同步辐射装置（BSRF)上所使用的光学元件进行了清洗，取得了较好的效果。Compositional change in human enamel irradiated with MIR free electron laser 收费下载 The purpose of this study was to investigate compositional changes in human enamel irradiated with the free electron laser (FEL).The exposure on dental enamel at the wavelength of 9.64μm was observed with the Beijing free electron laser.The distribution of elements in the irradiated or non-irradiated enamel was measured by scanning electron microscope (SEM) with energy-dispersive spectroscopy and synchrotron radiation X-ray fluorescence(SRXRF) in Beijing Synchrotron Radiation Facility (BSRF).The results showed that the P/Ca ratio in the ablation region of enamel at the maximum wavelength of infrared absorption of enalmel at the maximum wavelength of infrared absorption was obviously smaller than that at the non-maximum wavelength.In the ablation region the ratios of P/Ca and Ca/Sr were smaller than those in the non-ablation region.The distribution of P,Ca and Sr in the ablation region were heterogeneous due to the element change caused by FEL irradiation.Synchrotron radiation XRF microprobe investigation of elemental distribution in femoral head slice with osteoporsis 收费下载 This note deals with the scanning of femoral head slices form both normal and osteoporosis subjects using synchrotron radiation X-ray fluorescence (SRXRF) microprobe technique.the sample preparation and experimental apparatus are described in detail.The quantitative computerized tomography(QCT) of elemental distribution,such as Ca,P,K,Fe,Zn,Sr and Pb in bone slice tissue including cartilage,substantial compact and substantial spongy,is investigated.Combined with the correlation between P,K,Zn,Sr and Ca,the loss way of minerals and the physiological functions of some metal elements in bone are also discussed.南极菲尔德斯半岛六种藻类和地衣植物的X荧光分析 收费下载 为了研究南极的植物与环境间的关系，探讨植物在南极环境监测中的作用。在无标样条件下，利用微束X荧光分析法对南极菲尔德斯半岛的6种藻类和地衣植物进行了元素分析．其中藻类植物有孔石莼(Ulva pertusa)、海膜（Halymenia sp.)和大型鞘丝藻（Lyngbya maijor),地衣植物有筛石蕊(Cladonia borealis)、喇叭石蕊（C.fimbriata)和松萝(Usnea sp.)．研究结果发现，不同的藻类植物对各种元素的吸收能力不同，在XRF（X射线荧光)谱中，孔石莼比海膜含有更多的元素，象As、Br和Rb,Cu和Zn的含量也较高。在大型鞘丝藻中，K比Ca少，Zn的含量较高．在3种地衣植物中，其XRF谱中的元素种类组成非常相似，只是Mn、Fe、Cu和Zn等元素的相对含量有些差异。南极乔治王岛六种苔藓植物的X荧光分析 收费下载 在无标样条件下，我们利用微束X荧光分析法对南极乔治王岛的6种苔藓植物的叶和茎进行重元素分析。它们是：Adreaca regularis,Bryum muehlenbeckii,Drepanocladus uncinatus,Brachythecium subpilosum,Tortula sxiola,Ditrichum austro-georgicum。研究结果发现，不同苔藓植物对各种不同重元素的吸收能力不同，即使是同一种植物，叶和茎中的重元素成分也有差异。在6种苔藓中，Andreaea regularis体内的重元素种类最少，但其对Fe有较强的吸收。由于南极环境条件优越，在苔藓植物体内，尚未发现大量有毒重金属元素的存在。用同步光微束作激发源的PSS性能研究 收费下载 用同步光微束作激发源，对所研制的平面晶体波长色散位置灵敏谱仪(PSS)性能进行了研究。结果表明，用LjF(200)晶体测得Ti Kα的能量分辨率达14．2eV，比Si(Li)探测器的能量分辨率好一个多量级；用Si(Li)观察不锈钢样品中的Cr Kβ与Mn Kα两X线为一重叠的峰，而用PSS能清楚地分辨它们；对K2CrO7，样品中Cr的探测限<200μg/g对一气溶胶样品中Ti的可检测量达10^9-10^10g量级。结果表明，随着实验条件的改善使PSS的探测限进一步降低，在同步光束线上用Pss开展高能量分辨的数量元素分析将是可行的。同步辐射X射线荧光分析在植物微量元素分析中的应用 收费下载 利用同步辐射X射线荧光分析方法的信噪比高、检测限小、无损伤等特点，对采集自南极、青岛和安徽地区多种植物的茎、叶和花被样品进行了元素分析，在检测出的20多种元素中，有Ca，Mn，Fe,Cu，Zn，Br，Rb和Sr等。结果显示，南极苔藓中重元素的低含量与其环境污染低相一致，苔藓中K，Ca和Fe的峰强依次有数量级的提高。青岛红藻门的鸭毛藻对Br有很强的吸收倾向。将1985年和1999年获取的样品进行对比，说明这些植物的金属元素峰强有明显增加．淮河沉水植物金鱼藻对K，Ca，Mn和Fe都有较强的富集能力，所富集的元素含量和种类随水环境污染元素浓度的变化而有显著的不同。Single fluid inclusion study by SRXRF microprobe 收费下载 The nondestructive analysis technique of single fluid inclusions by SRXRF microprobe at BSRF was developed.To test the method,A canning analysis reult of a single fluid inclusion in quartz crystal was presented.With this technique,the semi-quantitative inorganic ompositions of two typical individual organic fluid inclusions were also determined by using a thin glass film of known compositions as a standard.2001 Elsevier Science B.V.All rights reserved.Study of human bone tumor slice by SRXRF microprobe 收费下载 The SRXRF microprobe at the BSRF is described.The minimum detection limits (MDLs) of trace elements were measured to deermine the capability for biological sample analysis.the changes of the trace elements and their ratios in the normal and tumor parts of a human osteosarcoma tissue were investigated.It was found that our results were in agreement with those of other analytical methods,such as spectrophotometric analysis,NAA and PIXE as well as an early clinic study of serum.2001 Elsevier Science B.V.All rights reserved.Beijing synchrotron radiation total—reflection X—ray fluorescence analysis facility and its applications on trace element study of cells 收费下载 The feasibility of total-reflection X-ray fluorescence(TXRF) analysis excited by synchrotron radiation applied to trace element analysis of biological cells is investigated.The Beijing synchrotron radiation TXRF facility and the related xperimental method are also described.The elemental mininum detection limits of some standard reference materials are determined.The elemental compositions of a cluster of small intestine cells of a small white mouse are given,and hence the average trace element contents of the single small intestine cell are also obtained.With this technique,the changes of some trace elements in the cells of lung and cervix cancer before and after apoptosis are also preliminarily studied.2001 Elsevier Science B.V.All rights Reserved.