Characterization of phase transition of Ba2-xSrxIn2O5 by thermal analysis and high temperature X-ray diffraction

The phase transitions of Ba_2-xSr_xIn₂O₅ were investigated with various thermal analyses and high-temperature X-ray diffraction. It was clarified that crystal structure of Ba_2-xSr_xIn₂O₅ with x=0.0~0.4 varies from brownmillerite through distorted perovskite to another distorted perovskite with increase of temperature. The phase transition from brownmillerite to distorted perovskite was revealed to be first order, whereas transition from distorted perovskite to another one was second order. The specimen with x≥0.5 showed only one first order phase transition from brownmillerite to distorted perovskite. The phase diagram of Ba_2-xSr_xIn₂O₅ was established and existence of tricritical point at ~1100°C with x=0.4~0.5 was suggested. This revised version was published online in August 2006 with corrections to the Cover Date.     

Water Permeation of SiO2-CH3SiO3/2 Thin Films Modified with Trimethylsilyl Groups on Nylon-6 Substrates

SiO₂-CH₃SiO_3/2 thin films coated on nylon-6 substrates by the sol-gel method were modified with trimethylsilyl (TMS) groups and their water permeability was evaluated. The water permeability coefficient of the nylon-6 substrates coated with TMS-modified SiO₂-CH₃SiO_3/2 thin films was smaller than that of unmodified ones. The wettability for water of SiO₂-CH₃SiO_3/2 thin films modified with TMS was smaller than that of unmodified ones. The decrease in the wettability by the modification with TMS resulted in the decrease in water permeability. The measurements of pore size distribution and the water permeability coefficient of coating films with different pressures of upstream side suggested that the mechanism of permeation was governed by the capillary condensation flow. This mechanism was also supported by the result that the water permeability coefficient was decreased with a decrease in wettability.     

纳米CaCO3的改性、表面结构与流变行为研究

采用铝锆偶联剂和棕榈酸改性纳米CaCO₃ 粉体. 借助 XRD, FTIR, 接触角及流变学等测试方法对纳米CaCO₃ 的表面结构进行表征. XRD 分析表明: 改性纳米 CaCO₃保持原样品完整的体相结构, 为方解石型纳米微晶. FTIR 分析证明: 表面改性剂与纳米 CaCO₃ 表面是以化学键合和物理吸附方式相结合, 粒子表面存在羧基等有机官能团的红外吸收特征. 通过测定苯和水在改性纳米CaCO₃粉末压片上的接触角, 计算了改性纳米 CaCO₃的表面能和极性分量, 并与未改性纳米CaCO₃ 进行比较. 结果表明, 经表面改性, 纳米 CaCO₃ 的表面能和极性分量明显降低, 其在有机溶液中的吸附功增大, 界面张力大大降低; 经棕榈酸改性的纳米 CaCO₃ 表现出较好的亲油疏水性, 而铝锆偶联剂改性的纳米 CaCO₃ 同时具有亲水性和亲油性. 以液体石蜡为溶剂, 研究了表面改性对纳米CaCO₃悬浮液流变行为的影响. 实验发现: 经过表面处理, 纳米 CaCO₃ 粉体悬浮液流变行为发生较大的变化, 稳态剪切黏度大大降低, 表现出较小的动态弹性储能模量和黏性损耗模量, 而损耗因子较大.     

Hydrogen storage over alkali metal hydride and alkali metal hydroxide composites

Alkali metal hydroxide and hydride composite systems contain both protic(H bonded with O) and hydridic hydrogen. The interaction of these two types of hydrides produces hydrogen. The enthalpy of dehydrogenation increased with the increase of atomic number of alkali metals,i.e.,-23 kJ/molH2 for LiOH-LiH, 55.34 kJ/molH2 for NaOH-NaH and 222 kJ/molH2 for KOH-KH. These thermodynamic calculation results were consistent with our experimental results. H2 was released from LiOH-LiH system during ball milling. The dehydrogenation temperature of NaOH-NaH system was about 150℃; whereas KOH and KH did not interact with each other during the heating process. Instead, KH decomposed by itself. In these three systems, NaOH-NaH was the only reversible hydrogen storage system, the enthalpy of dehydrogenation was about 55.65 kJ/molH2, and the corresponding entropy was ca. 101.23 J/(molH2 K), so the temperature for releasing 1.0 bar H2 was as high as 518℃, showing unfavorable thermodynamic properties. The activation energy for hydrogen desorption of NaOH-NaH was found to be57.87 kJ/mol, showing good kinetic properties.     

Integration of Succinic Acid and Ethanol Production With Potential Application in a Corn or Barley Biorefinery

Production of succinic acid from glucose by Escherichia coli strain AFP184 was studied in a batch fermentor. The bases used for pH control included NaOH, KOH, NH₄OH, and Na₂CO₃. The yield of succinic acid without and with carbon dioxide supplied by an adjacent ethanol fermentor using either corn or barley as feedstock was examined. The carbon dioxide gas from the ethanol fermentor was sparged directly into the liquid media in the succinic acid fermentor without any pretreatment. Without the CO₂ supplement, the highest succinic acid yield was observed with Na₂CO₃, followed by NH₄OH, and lowest with the other two bases. When the CO₂ produced in the ethanol fermentation was sparged into the media in the succinic acid fermentor, no improvement of succinic acid yield was observed with Na₂CO₃. However, several-fold increases in succinic acid yield were observed with the other bases, with NH₄OH giving the highest yield increase. The yield of succinic acid with CO₂ supplement from the ethanol fermentor when NH₄OH was used for pH control was equal to that obtained when Na₂CO₃ was used, with or without CO₂ supplementation. The benefit of sparging CO₂ from ethanol fermentation on the yield of succinic acid demonstrated the feasibility of integration of succinic acid fermentation with ethanol fermentation in a biorefinery for production of fuels and industrial chemicals.     

Synthesis and reactions of [tris(trimethylsilyl)methyl]ethyl dichlorosilane

The crowded dichlorosilane TsiSiEtCl₂, (1), (Tsi = (Me₃Si)₃C) was prepared from the reaction between EtSiCl₃ and TsiLi, then it was reduced with LiAlH₄ to give TsiSiEtH₂, (2). The hydride (2) was then treated with two equivalents of ICl/CCl₄ or Br₂/CCl₄ to produce TsiSiEtI₂, (3), and TsiSiEtBr₂, (4), respectively. The reaction of compound (2) with one equivalent of ICl/CCl₄ gives TsiSiEtHI, (5). This product reacted with H₂O/dioxane in the presence of AgClO₄ or with dry MeOH to produce TsiSiEtHOH, (6), and TsiSiEtHOMe, (7), respectively. The compound (3) reacted with H₂O in DMSO/CH₃CN to give TsiSiEt(OH)₂, (8), and the compound TsiSiEtIOMe, (9), was prepared from the reaction of the compound (7) with ICl/CCl₄. When the dichloride (1) was treated with NaOMe/MeOH it gave (Me₃Si)₂CHSiEt(OMe)₂. It is suggested that the reaction proceeds through an elimination-addition mechanism. The dichloride (1) was also treated with KSCN, NaN₃ or NaOCN in CH₃CN to give S_N2 substitution products. All the new products were characterized by FTIR, ¹H NMR, and ¹³C NMR spectroscopy, mass spectrometry and elemental analysis.     

Pigmentary properties of rutile TiO2 modified with cerium, phosphorus, potassium, and aluminium

The influence of different modifiers, phosphorus, potassium, aluminium, and cerium on the pigmentary properties of TiO₂ was studied. The phase composition and distribution of modifiers in prepared TiO₂ products was investigated using XRD analysis, the selective leaching method, and ICP-AES technique. The optical properties, photoactivity, morphology, and surface area of modified TiO₂ were determined by spectrophotometric, fluorescent, SEM, and BET measurements. The research was directed towards obtaining a pigmentary TiO₂ with the highest possible photostability. It was found that the final calcination temperature, at which the anatase-rutile transformation rate was > 97 %, depended on the kind and amount of the modifiers introduced into hydrated titanium dioxide. In comparing the colour of TiO₂ products modified with Ce, it was found that the addition of K to the TiO₂ series caused an increase in all the optical properties examined. The presence of K and Al in TiO₂ modified with Ce resulted in decreased photocatalytic activity. The photostability of TiO₂ modified with Ce and K improved with an increase in P₂O₅ content. The highest photostability was measured for the TiO₂-CePKAl series. It was concluded that the differences in both the optical properties and photoactivity of TiO₂ depended on its phase composition and the distribution of modifiers in the products obtained.     

Preparation of TiO2 Sol Using TiCl4 as a Precursor

A titanium dioxide sol with narrow particle size distribution was synthesized using TiCl₄ as the starting material. The sol was prepared by a process where HCl was added to a gel of hydrated titanium oxide to dissolve it. The resulting aqueous titanic acid solution was heated to form titanium dioxide sol. The effects of preparation parameters were investigated. TiCl₄ was slowly added to distilled water at 5°C. Aqueous solution of sodium hydroxide was added to adjust the pH of the system to 8–12. After aging for a period of time, the peptized sol was filtered and sufficiently washed. The filtered cake was repulped in water. Hydrochloric acid was slowly added to the solution with stirring. After condensation reaction and crystallization, a transparent sol with suspended TiO₂ was formed. XRD results show that the crystalline phase was anatase. The suspended TiO₂ particles were rhombus primary particles with the major axis ca. 20 nm and the minor axis ca. 5 nm. The TiO₂ particles prepared at pH 8 had the largest surface area of 141 cm³/g and it was microporous. The compositions of the solution which yielded the smallest suspended TiO₂ particles were TiO₂:HCl (35% HCl) = 1:1 (molar ratio), concentration of TiO₂ = 10%. Hydroxypropyl cellulose with viscosity of 150–400 cps was added as a dispersant. The sol was excellent in dispersibility and long-term stability. Transparent thin films could be obtained through dip-coating glass substrate in the sol. The dip-coating on glass can be less than three times to have one monolayer TiO₂. The transparent TiO₂ thin film had strong hydrophilicity after being illuminated by UV light.     

Influence of H2O on alternating copolymerization with the EtnAlCl3-n-VOCl3 catalyst system

The effect of the catalytic amount of H₂O was investigated with the Et_nAlCl_3-n-VOCl₃ catalyst system on the alternating copolymerization of acrylic monomers with diolefins and styrene. The presence of the catalytic amount of H₂O produced an improvement in the yield and in the molecular weight as well as the structure of copolymer with the Et_nAlCl_3-n-VOCl₃ catalyst system. The efficiency of the aluminum components in the Et_nAlCl_3-n-VOCl₃ system appears with AlEt₃ and especially with Et_1.5AlCl_1.5. The catalytic activity was found to depend upon the H₂O Et_nAlCl_3-n molar ratio and was also affected by the order of mixing of the catalyst components and the monomers. Effective catalyst could be prepared when the catalyst components (except VOCl₃) were premixed without presence of monomers. The possible catalytic behavior of H₂O was discussed.     

氧化环境和比例对改性Hummers法制备GO的影响

以鳞片石墨(GR)为原料,采用改性Hummers法液相氧化方法制备氧化石墨,通过超声剥离的方法剥离出片状的氧化石墨烯(GO),探讨了H₂SO₄环境与H₂SO₄+H₃PO₄混酸环境和KMnO₄与GR的比例对GO制备的影响。采用FTIR、UV、TG、XRD、SEM和XPS等分析手段对制备的GO进行分析。结果表明：GO外貌是呈褶皱片状,在片层上主要有C=O、C-OH、-COOH和C-O-C等官能团,以共价键形式存在石墨层间;通过TG与XPS数据分析表明在H₂SO₄ H₃PO₄混酸环境下制备的GO含氧官能团较多,并且(KMnO₄)与鳞片石墨的最佳比例是1:4。     

Preparation of Pt/K2La2Ti3O10 and its photo-catalytic activity for hydrogen evolution from methanol water solution

A layered perovskite-type oxide K₂La₂Ti₃O₁₀ was prepared with high-temperature solid-state reaction, and characterized with X-ray diffraction (XRD) and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). Platinum was loaded onto K₂La₂Ti₃O₁₀ as a co-catalyst with different methods. The dispersion of platinum on K₂La₂Ti₃O₁₀ was determined with HOT method. The photocatalytic activity of Pt/K₂La₂Ti₃O₁₀ was studied. This catalyst showed much higher activity in hydrogen evolution reaction than Ni/K₂La₂Ti₃O₁₀. The effects of different amounts of loaded platinum and several preparation methods were evaluated. The best achieved hydrogen evolution rate was 233.88 μmol·h⁻¹ by Pt(2%)/K₂La₂Ti₃O₁₀. A possible band structure and mechanism were discussed based on the results.     

High Temperature Oxidation of Fe22Cr-alloy

The isothermal and constant heating rate oxidation behaviour of the alloy Fe₇₈Cr₂₂ was examined in air with 1% H₂O and in 7% H₂/93% Ar with 1% or 12% H₂O. The measurements were performed in the temperature range 700–1300°C. The effect of surface treatment prior to oxidation was examined. A Cr₂O₃ scale developed slowly up to900°C. At 1100°C a catastrophic oxidation was observed after heat treatment for 70 h in air with 1% H₂O and in 7% H₂/93% Ar with 12% H₂O. The scale developed in these cases consisted of iron rich oxides such as Fe₂O₃ or FeCr₂O₄, in contrast to the more protective Cr₂O₃ scale seen under other test conditions. Possible causes for the catastrophic oxidation are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

The reaction between [RuCl<Subscript>2</Subscript>(PPh<Subscript>3</Subscript>)<Subscript>3</Subscript>] and hydroxyquinoline carboxylic acid

The reactions of [RuCl₂(PPh₃)₃] with 8-hydroxy-2-methyl-quinoline-7-carboxylic acid was examined, and a novel ruthenium(II) complex—[Ru(PPh₃)₂(C₅H₈NO)₂]—was obtained. The compound was studied by IR, UV–vis spectroscopy, and X-ray crystallography. The molecular orbital diagram of the complex was calculated with the density functional theory (DFT) method. The spin-allowed singlet–singlet electronic transitions of the compound were calculated using the time-dependent DFT method, and the UV–vis spectrum of the compound was discussed, on this basis. The luminescence property of the [Ru(PPh₃)₂(C₅H₈NO)₂]was examined.     

Microcalorimetry, energetics and binding studies of DNA-dimethyltin dichloride complexes

The interaction of dimethyltin dichloride (Me₂SnCl₂) with calf thymus DNA was studied at 27 °C, pH 7.6 using various techniques including isothermal titration calorimetry (ITC) and UV-Vis, fluorescence and IR spectrophotometries. The binding isotherm and enthalpy curve for Me₂SnCl₂-DNA interaction was a biphasic transition process. This was determined by the analysis of the binding data with the Hill equation. The first phase of the enthalpy curve (exothermic process) was consistent with the first set of binding site, the second phase (endothermic process, less exothermicity) was consistent with second set of binding site from the cited interactions. Our results showed that the first set of binding sites is occupied by one mole of ligand bound per near 1 base pair of DNA. The DNA-ethidium bromide (EB) complex, in the presence of Me₂SnCl₂, caused the quenching of the fluorescence emission. The Scatchard plots illustrated a non-intercalating manner for such quenching. The DNA-EB complex results indicated that the binding of Me₂SnCl₂ is with the phosphate groups of DNA at low ligand concentrations (<9 mM). This was confirmed with the IR spectrophotometric spectra. However, the binding at higher ligand concentrations (>9 mM) was with the base groups of DNA. Therefore, these results suggest that the Me₂SnCl₂ binding to DNA at low concentrations occurs through an outside interaction by an exothermic process. However, the partial unfolding of the DNA caused at higher concentrations of Me₂SnCl₂ is through an endothermic process involving interactions with the base groups.     

沉淀法制备不同形貌和结构的纳米BiVO4

采用液相沉淀法，通过选择不同起始原料并控制反应温度和pH值，制备得到不同形貌和结构的纳米BiVO₄。采用X-射线衍射(XRD)、透射电子显微镜(TEM)和紫外-可见吸收光谱(UV-Vis)技术对产物进行分析表征。结果表明，采用NH₄VO₃作V源，室温下可直接制备得到结晶好的四方晶系硅酸锆型BiVO₄球形纳米颗粒，提高反应液pH值或升高温度，可得到单斜晶系白钨矿型BiVO₄，采用NaVO₃作为V源，室温下可直接得到单斜晶系白钨矿型片状BiVO₄。加入不同类型表面活性剂则得到不同形貌的BiVO₄。     

THE EFFECT AND FUNCTION OF AliBu_2OR'''' ON BUTADIENE-PROPYLENE ALTERNATING COPOLYMERIZATION CATALYZED BY VO(OR)_2Cl-AIiBu_3 SYSTEM

Four kinds of AliBu_2OB' with different R' were synthesized. The effect of AliBu_2OR'/AliBu_3 mole ratio on the conversion, the [η] of copolymer and catalytic efficiency were studied. The conversion was increased obviously and the catalytic efficiency was 2.7 times higher than before. The effect of the amount of AliBu_2OR' on the valence state of vanadium ion and the change of the valence state of vanadium ion with reaction temperature and time were studied. The VIS and IR spectra of the trinary-component catalyst system were measured. The model of active center including AliBu_2OR' was proposed. The function of AliBu_2OB was explained.     

Thermodynamic Study of the Solid-Liquid Equilibria in the Systems MIPO3-Pr(PO3)3 (MI=Na,Rb, Cs OR Ag)

A previously established equation of a stoichiometric phase liquidus curve was applied to determination of the phase diagrams of the systems M^IPO₃-Pr(PO₃)₃ (with M^I=Na, Rb, Cs or Ag). The temperature, enthalpy and entropy of fusion were calculated for each solid phase with the exception of silver polyphosphate, the crystallization field of which was very limited. The enthalpy of fusion of the polyphosphate Pr(PO₃)₃ was determined from the DTA curve. The melting enthalpy of Pr(PO₃)₃ calculated from the different binary systems was approximately equal to the measured value. The calculated temperatures and compositions were in good agreement with those determined experimentally. This revised version was published online in July 2006 with corrections to the Cover Date.     

纳米Re2O7的萃取法制备及光催化特性研究

本工作从N235-正庚烷萃取体系中，以饱和萃取法制得前体物和纳米粉体Re₂O₇，平均粒径30 nm。以此纳米粉为光催化剂，研究了光降解甲基橙染料的最佳条件，并在相同条件下，与非纳米Re₂O₇及工业常用的纳米TiO₂进行比较，光降解甲基橙能力大小为：纳米Re₂O₇ > 锐钛矿型纳米TiO₂ > 非纳米Re₂O₇。     

Construction of Protein Probe with a His-tag and an Electron-transfer Peptide for a Target Protein Sensing

A protein probe with an electron-transfer peptide and a His-tag was designed to electrochemically sense a target protein. We selected tyrosine-rich (Y₄C) and tryptophan-rich (W₄C) peptides for use as electron-transfer agents. The peak for oxidation was based on the oxidations of the phenolic hydroxy groups in Y₄C and on the indole rings in W₄C. Asialofetuin (ASF) with galactose residues was the protein probe, and a galactose recognition protein, soybean agglutinin (SBA), was the target protein. A protein probe composed of an amino acid and carbohydrate residue was expected to be biocompatible. When voltammetric measurements were performed using a glassy carbon electrode, the oxidation peaks of H₆Y₄C and ASF-H₆Y₄C appeared at the same potential. The peak current of ASF-H₆Y₄C was 4-fold that of H₆Y₄C because of the stronger adsorption of ASF-H₆Y₄C onto the electrode. The electrode response of ASF-H₆Y₄C with SBA was half that of ASF-H₆Y₄C alone. By contrast, the peak current of ASF-Y₄CH₆ was higher than that of ASF-H₆Y₄C, which was the result of a greater degree of contact between the Y₄C moieties and an electrode. On the other hand, the voltammetric behaviors of ASF with W₄C and a His-tag were similar to those with Y₄C and a His-tag. The sensitivity of SBA using ASF-Y₄CH₆ was at the 10⁻¹³ M level. To confirm the function of the sensing system, measurements were performed in human serum with SBA and ASF-Y₄CH₆. When SBA was added, the serum had a concentration that ranged between 5.0×10⁻¹³ and 4.0×10⁻¹² M, and the amount of SBA that could be recovered ranged from 97 to 101%. Consequently, this system could be applied to the detection of SBA in serum.     

TiO2微粒功能化多孔Al2O3膜的光电化学研究

用恒电位法制备了多孔Al₂O₃薄膜, 通过在Al₂O₃薄膜孔内水蒸汽水解钛酸异丙酯生成了锐钛矿型TiO₂微粒, 制备出了Al₂O₃与TiO₂微粒的复合薄膜. 用XRD, SEM, 光电化学方法进行了研究. 实验表明: 该复合薄膜具有光电转换特性, 在光催化、光电化学太阳能转换中具有应用价值.