异丙醇探针反应表征Ce－Mo－O催化剂的酸性与氧化还原性 Characterization of Acidic and Oxidative Properties of Ce-Mo-O Catalysts Using the Probe Reaction of Isopropanol Conversion

Acidic and redox properties are two important aspects of metal oxide catalysts for selective oxidation reactions. Various methods have been used to characterize these properties, of which the isopropanol conversion is a useful probe reaction that can give qualitative information. It is well known that acidicsites catalyze the dehydration of isopropanol to propylene and basic sites catalyze the dehydrogenation of isopropanol to acetone.     

Effects of Cerium Oxides on the Catalytic Performance of Pd/CNT for Methanol Oxidation

The carbon nanotubes supported palladium(Pd/CNT)nanocatalysts were modified by cerium oxides/ hydroxides and their catalytic performances for methanol oxidation were evaluated.Electrochemical measurements indicate that the introduction of cerium remarkably improves the catalytic activity of Pd/CNT catalysts towards methanol oxidation.X-Ray photoelectron spectra results reveal an interaction between palladium and cerium oxides.It is also observed that cerium-modified catalysts have excellent poison resistances,which is attributed to the poison-removal ability of cerium oxides/hydroxides.The highly oxidized cerium oxides/hydroxides have a strong ability to inhibit the accumulation of carbonaceous intermediates on the active sites of Pd catalysts.     

Electrochemical partial reduction of Ni(OH)2 to Ni(OH)2/Ni via coupled oxidation of an interfacing NiAl intermetallic compound for robust hydrogen evolution

Ni-based porous electrocatalysts have been widely used in the hydrogen evolution reaction(HER) in alkaline water electrolysis, and the catalysts are produced by selective leaching of Al from Ni-Al alloys. It is well known that chemical leaching of Ni-Al intermetallic compound(IMC) generates a high surface area in Ni(OH)₂. However, the Ni(OH)₂produced by leaching the Ni-Al intermetallic compound retards the hydrogen evolution reaction, which is attributed to its weak hydroge...     

Synergistic effect between Sn and K promoters on supported platinum catalyst for isobutane dehydrogenation

Catalytic dehydrogenation of isobutane has recently received considerable attention because of the increasing demand for isobutene.In this study,the synergistic effect between Sn and K on PtSnK/γ-Al2O3 catalysts has been investigated by changing the content of Sn.It was found that with the presence of potassium,suitable addition of Sn could not only increase the metal dispersion,but also reduce the catalyst acidity.In these cases,the synergistic effect could also strengthen the interactions between the metal and support,which resulted in an increase in both catalytic activity and stability.In our experiments,Pt-0.6SnK/Al catalyst exhibited the lowest deactivation rate (12.4%) and showed a selectivity to isobutene higher than 94% at the isobutane conversion of about 45.3% after running the reaction for 6 h.However,with the excessive loading of Sn,surface property of active sites and the interactions between metal and support were changed.As a result,the initial optimal ratio between the metallic function and acid function would be destroyed,which was disadvantageous to the reaction.     

Electrolessly Plated Ni-Zn（Fe）-P Alloy and Its Corrosion Resistance Properties

The autocatalytic deposition of Ni-Zn(Fe)-P alloys has been carried out on substrate of carbon steel from a bath containing nickel sulfate, zinc sulfate, sodium hypophosphite, sodium citrate and boric acid. The effects of pH and the molar ratio of NiSO4/ZnSO4 on the deposition rate and the composition of deposits have been studied. It was found that the presence of zinc sulfate in the bath has an inhibitory effect on the alloy deposition. The structure and the surface morphology of Ni-Zn(Fe)-P coatings were characterized with XRD and SEM, respectively. The alloys plated under the experimental conditions consisted of an amorphous phase coexisting with a crystalline cubic Ni phase (poly-crystalline). The surface morphology of the coating is dependent on the deposition parameters. The corrosion resistance of the Ni-Zn(Fe)-P deposits was examined via mass loss tests and anodic polarization measurements, respectively. The results show that the surface morphologies of the deposits and the corrosion resistance of the deposits have been improved. The results of mass loss tests almost accord with those of anodic polarization measurements. The corrosion mechanisms of Ni-Zn(Fe)-P alloys in NaCl and NaOH solutions were investigated by means of EDX. The deposit immersed in an NaCI or an NaOH solution contains more content of oxygen and less contents of the metals(except Fe) than that placed in air, which shows that the NaCl or NaOH solution can accelerate the oxidation of the deposit.     

A molecularly imprinted polymer receptor for the enantiomeric recognition of amino acid hydantoins mimicking cooperative hydrogen bonds between nucleotide bases

Using acrylamide as hydrogen bonding functional monomer and (5R)-5-benzylhydantoin as template, a molecularly imprinted polymer was prepared in a polar solvent, which exhibited good enantiomeric recognition properties. The binding characteristics and selectivity of the polymer were evaluated by batch methods. Scatchard analysis showed that two classes of binding sites were produced in the polymer matrix and their dissociation constants were calculated to be 3.5 × 10-5mol/L and 4.3 ×10-4 mol/L, respectively, by utilizing the model of multiple independent classes of binding sites. These results were more reasonable than those obtained by Scatchard analysis , which was in agreement with the prediction of the binding characteristics of the polymer by exploring the effect of acrylamide on UV spectra of (5R)-5-benzylhydantoin. The substrate- and enantio-selectivity of the polymer was investigated. Finally, the study of effect of water on the chiral separation factor of the polymer further proved that the hy     

Phase Evolution and Magnetic Properties of Sn_(1-2x)Fe_xNb_xO_2(0.45≤x≤0.50)

Sn1-2xFexNbxO2(0.45≤x≤0.50) samples were prepared at 1000 ℃ via a simple chemical co-precipitation method.The effects of the concentrations of Sn doped on the structures and magnetic properties of the samples have been investigated.A systematic variation from monoclinic to orthorhombic FeNbO4 structure was observed with increasing Sn content.The phase evolutions were observed from monoclinic structure with x=0.50 to the coexistence of monoclinic and orthorhombic structures with x=0.48,0.47,0.46,and then to orthorhombic structure with x=0.45.Antiferromagnetic behavior was observed for all the samples,and the magnetic ordering temperatures decrease with increasing Sn concentration,which further indicated the sequence of phase transitions.The results suggest that the incorporation of Sn can stabilize the orthorhombic FeNbO4.     

SOLUBLE POLY-(o, m)-TOLUIDINE

The soluble poly-o-toluidine (POT) and poly-m-toluidine (PMT) have been success-fully prepared under controlled conditions of polymerization and post-treatment, andcharacterized by IR, VPO and elemental analysis. It is found that the soluble and insol-uble polymers obtained with two different methods (Ⅰ and Ⅱ) have the similar conduc-tivity and molecular chain structure. VPO measurement shows that the number averagemolecular weight (Mn) of soluble polymers is about 3000. The mole ratio of benzoidto quinoid is about 3:1 according to ~1H-NMR and elemental analysis. Free-standingfilms of intrinsic POT and PMT have been obtained by casting their CHCl_3, THF orDMF solutions onto a glass surface.     

Conversion of N2O to N2 on MgO （001） Surface with Vacancy： A DFT Study

The adsorption and decomposition of NzO at regular and defect sites of MgO (001) surface have been studied using cluster models embedded in a large array of point charges (PCs) by DFT/B3LYP method. The results indicate that the MgO (001)surface with oxygen vacancies exhibits high catalytic reactivity toward N2O adsorptive-decomposition. It is different from the regular MgO surface or the surface with magnesium vacancies.Much elongation of O—N bond of N2O after adsorption at oxy-gen vacancy site with O end down shows that O—N bond has been broken with concurrent production of N2, leaving a regu-lar site instead of the original oxygen vacancy site (F center ).The MgO (001) surface with magnesium vacancies hardly ex-hibits catalytic reactivity. It can be concluded that N2O dissoci-ation likely occurs at oxygen vacancy sites of MgO (001) sur-face, which is consistent with the generally accepted viewpoint in the experiments. The potential energy surface (PES) reflects that the dissociation process of N2O does not virtually need to surmount a given energy barrier.     

Pd取代对Mg2Ni及其氢化物结构和性能影响的第一性原理研究

利用基于第一性原理的密度泛函理论,计算了镁基储氢合金Mg2 Ni以及Pd取代的合金Mg12 Ni6-xPdx(x1,2,3)及其氢化物H2-Mg12 Ni6-xPdx(x=0,1,2,3)的晶体结构和电子结构.结果表明,Pd取代Mg2 Ni中的Ni原子,使其晶胞体积有所膨胀.同时,Pd的取代对Mg-Ni和Ni-Ni间的...     

A New Family of Nonstoichiometric Layered Rare-Earth Tin Antimonides, RESn(x)()Sb(2) (RE = La, Ce, Pr, Nd, Sm): Crystal Structure of LaSn(0.75)Sb(2)

A new class of nonstoichiometric layered ternary rare-earth tin antimonides, RESn(x)()Sb(2) (RE = La, Ce, Pr, Nd, Sm), has been synthesized through reaction of the elements at 950 degrees C. In the lanthanum series LaSn(x)()Sb(2), tin can be incorporated from a maximum content of x approximately 0.7 or 0.8 to as low as x approximately 0.10. The structure of lanthanum tin diantimonide with the maximum tin content, LaSn(0.75)Sb(2), has been determined by single-crystal X-ray diffraction methods. It crystallizes in the orthorhombic space group -Cmcm with a = 4.2425(5) ?, b = 23.121(2) ?, c = 4.5053(6) ?, and Z = 4. The isostructural rare-earth analogues were characterized by powder X-ray diffraction. The structure of LaSn(0.75)Sb(2) comprises layers of composition "LaSb(2)" in which La atoms are coordinated by Sb atoms in a square-antiprismatic geometry. Between these layers reside chains of Sn atoms distributed over three crystallographically independent sites, each partially occupied at about 20%. The structure of LaSn(0.75)Sb(2) can be regarded as resulting from the excision of RE-Sb and Sb-Sb bonds in the related structures of binary rare-earth diantimonides, RESb(2), and then intercalation of Sn atoms between layers.     

Co-Sn合金作为锂离子电池负极材料的研究

采用高能机械球磨法合成了富Co的Co3Sn2合金, 测试了Co-Sn合金作为锂离子电池负极材料的充放电性能. 考察了在机械球磨过程中加入碳和高温处理球磨后样品对合金组成和电化学性能的影响. XRD测试结果表明, 加入碳后所得样品的主要成分为CoSn2. 于400和600 ℃处理后主要成分转变为CoSn和Co3Sn2. CoSn2, CoSn和Co3Sn2的充放电容量随着Sn含量的降低依次降低, 但循环性能得到提高.     

EXAFS研究Ni-B和Ni-Ce-B超细非晶态合金的退火晶化

采用同步辐射EXAFS技术定量地研究化学还原法制备的Ni-B和Ni-Ce-B超细非晶态合金中Ni原子的局域环境结构随退火温度升高而产生的变化,结果表明,对于Ni-B和Ni-Ce-B超细非晶态合金初始样品：Ni-Ni最邻近配位壳层的平均键长RNi-Ni、配位数N、热无序σT、结构无序σs分别为0．275nm,11.9.0.0069nm,0.034nm;0.276nm,12.4,0.0067nm,0.035nm,Ni-B最邻近配位壳层的RNi-B,N, σT,σs分别为0．215nm,2.7,0.0055nm,0.0048nm;0.214nm,2.0,0.0058nm,0.0042nm,Ni-Ni配位的σs很大,是其σT的4－5倍,比Ni－B配位的σs大近一个数量级,在300℃退火后,Ni－B样品开始发生晶化生成晶态Ni3B,其RNi-Ni和σs分别为0．254nm和0．011nm,σs降低近2倍;而．3％原子比的Ce掺入后使Ni-Ce-B超细非晶态合金的晶化温度升高100℃左右。在500℃退火后,Ni－B样品的结构参数与Ni箔的相近,但Ni-Ce-B样品中的Ni-Ni配位的σs仍为0．0073nm,Ni-B配位的N为1．2,表明稀土元素Ce（以CeO2)显著增强了Ni与B的相互作用,且同时使退火晶化成的Ni晶结构产生畸变。     

Segregation of Sn in the binary CuSn and ternary CuSnSb alloy systems

Progression studies have been followed from Cu(111)‐ and Cu(100)Sn binaries to Cu(111)‐ and Cu(100)SnSb ternary‐alloy systems under the same experimental conditions. The segregation behaviour of Sn in the two orientations are explained. It is found that the kinetic segregation profiles of Sn in the ternary alloys shift to lower temperatures as compared to that in the binary. The Sn profile shift is mainly due to the decrease in the activation energy of Sn in the ternary systems. For a particular Cu orientation, the other segregation parameters that the Sn profiles depend on, like the pre‐exponential factor, segregation energy and the interaction coefficient, are found to be the same in the two systems. There is also a change in the equilibrium segregation profiles of Sn. In the ternary system, site competition between Sn and Sb causes the Sn to suffer exponential desegregation and eventual displacement from the surface. Copyright © 2006 John Wiley & Sons, Ltd.     

NiB和NiP超细非晶合金的退火晶化行为及催化性能

 采用X射线吸收精细结构（XAFS）,X射线衍射（XRD）和差热分析（DTA）等方法研究了以化学还原法制备的NiB和NiP超细非晶态合金催化剂在退火过程中的结构变化．XRD结果表明,在300℃下退火时,NiB超细非晶态合金晶化生成纳米晶Ni3B亚稳物相,NiP超细非晶态合金则主要晶化生成金属Ni和部分晶态Ni3P的混合物相;在500℃退火且近于完全晶化的条件下,大部分超细非晶态合金都晶化为金属Ni．XAFS结果定量地说明,对于NiB和NiP初始样品,第一近邻Ni－Ni配位的平均键长Rj分别为0.274和0.271nm,其结构无序度σS很大,分别为0.033和0.028nm,其热无序度σT分别为0.0069和0.0060nm．300℃退火后,晶化生成的Ni3B的Ni－Ni配位的σS降低到初始样品的33％,仅为0.011nm．500℃退火后,NiB样品的结构参数与金属Ni基本一致,但NiP样品的Ni－Ni配位的σS还远大于σT,仍为0.0125nm,表明NiB和NiP超细非晶态合金的退火晶化行为有很大的差别．纳米晶Ni3B催化苯加氢反应的转化率比超细Ni－B非晶态合金或多晶金属Ni更高,表明纳米晶Ni3B中的Ni与B原子组成了苯加氢催化反应的活性中心．     

Effects of Ca and Ag addition and heat treatment on the corrosion behavior of Mg-7Sn alloys in 3.5 wt.% NaCl solution

The effects of 1 wt.% Ca or 1 wt.% Ca + 1 wt.% Ag addition and heat treatment on the corrosion behavior of Mg-7Sn (wt.%) alloy in 3.5 wt.% NaCl solution were investigated by electrochemical measurements and immersion tests. The alloys were characterized by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). It was found that all alloys were corroded by pitting corrosion and grain boundary corrosion and further corroded with time going. Loose layers of compounds, including Mg (OH)₂, MgO, SnO₂, and other compounds containing Ca and Ag elements, were calibrated on the surface of corroded Mg-7Sn-1Ca-1Ag alloy. The Ca addition improved the corrosion resistance of Mg-7Sn alloy due to the formation of relatively stable compounds containing calcium element and grains refinement. Furthermore, the solid solutioned alloys obtained a superior corrosion resistance due to the dissolve of eutectic Mg₂Sn phase and homogenization treatment. However, the aging treatment is slightly detrimental to the corrosion resistance of Mg-7Sn alloys with the formation of Mg₂Sn precipitates. In conclusion, the aged Mg-7Sn-1Ca-1Ag alloy exhibited a better corrosion resistance and a noticeable micro-hardness property compared with those of as-cast Mg-7Sn alloy. And this study provides an important idea for the research on the comprehensive properties of Mg-Sn alloys.     

Probing Cation and Vacancy Ordering in the Dry and Hydrated Yttrium-Substituted BaSnO(3) Perovskite by NMR Spectroscopy and First Principles Calculations: Implications for Proton Mobility

Hydrated BaSn(1-x)Y(x)O(3-x/2) is a protonic conductor that, unlike many other related perovskites, shows high conductivity even at high substitution levels. A joint multinuclear NMR spectroscopy and density functional theory (total energy and GIPAW NMR calculations) investigation of BaSn(1-x)Y(x)O(3-x/2) (0.10 ≤ x ≤ 0.50) was performed to investigate cation ordering and the location of the oxygen vacancies in the dry material. The DFT energetics show that Y doping on the Sn site is favored over doping on the Ba site. The (119)Sn chemical shifts are sensitive to the number of neighboring Sn and Y cations, an experimental observation that is supported by the GIPAW calculations and that allows clustering to be monitored: Y substitution on the Sn sublattice is close to random up to x = 0.20, while at higher substitution levels, Y-O-Y linkages are avoided, leading, at x = 0.50, to strict Y-O-Sn alternation of B-site cations. These results are confirmed by the absence of a "Y-O-Y" (17)O resonance and supported by the (17)O NMR shift calculations. Although resonances due to six-coordinate Y cations were observed by (89)Y NMR, the agreement between the experimental and calculated shifts was poor. Five-coordinate Sn and Y sites (i.e., sites next to the vacancy) were observed by (119)Sn and (89)Y NMR, respectively, these sites disappearing on hydration. More five-coordinated Sn than five-coordinated Y sites are seen, even at x = 0.50, which is ascribed to the presence of residual Sn-O-Sn defects in the cation-ordered material and their ability to accommodate O vacancies. High-temperature (119)Sn NMR reveals that the O ions are mobile above 400 °C, oxygen mobility being required to hydrate these materials. The high protonic mobility, even in the high Y-content materials, is ascribed to the Y-O-Sn cation ordering, which prevents proton trapping on the more basic Y-O-Y sites.     

镁对La1-xMgxNi2.5Co0.5（x=0～0.4）合金循环过程中电化学性能的影响

采用充放电测试、高倍率放电等方法,系统分析了Mg对合金在循环过程中的电化学性能影响规律,结果表明La1-xMgxNi2.5Co0.5(x=0～0.4)合金在初始阶段的高倍率放电性能随着Mg含量的增加先增大后减小,La1-xMgxNi2.5Co0.5(x=0～0.4)合金经90次循环后的放电容量保持率先从x=0时的28.0%增加到x=0.2时的59.1%,然后下降到x=0.4时的45.7%。     

M_2M_2′Te_4型层状异金属簇合物的SCC—DV—Xα研究(M=Co、Ni;M′=Ta、Nb)

标题簇合物的电子结构采用电荷自洽离散变分Xα方法(SCC—DV—Xα)计算得到。在前线区轨道密集,具有半导体的特征;层状结构内存在离域性d-p(π+α)键,这是该类簇合物导电的依据;Ni—Ni或Co—Co之间不存在成键。描述了它们的态密度图,并说明了与合金的DOS图相似点。