制备方法对MoO_3／ZrO_2结构的影响及MoO_3／ZrO_2固体超强酸的结构特征 Ⅰ．ZrO_2的形态与样品比表面的研究

ＸＲＤ，ＤＴＡ，比表面测定等结果表明，制备方法对ＭｏＯ３／ＺｒＯ２结构有决定性影响．仲钼酸铵浸渍仅经干燥的Ｚｒ（ＯＨ）４再经高温焙烧所得团体超强酸ＭｏＯ３／ＺｒＯ２（Ⅰ）与浸渍晶态ＺｒＯ２所得部分氧化催化剂ＭｏＯ３／ＺｒＯ２（Ⅱ）的载体形态有明显不同．（１）ＭｏＯ３／ＺｒＯ２（Ⅰ）的比表面数倍于ＭｏＯ３／ＺｒＯ２（Ⅱ）；（２）ＭｏＯ３含量增加时，ＭｏＯ３／ＺｒＯ２（Ⅰ）的比表面逐步增大至一极大值再缓缓下降，而ＭｏＯ３／ＺｒＯ２（Ⅱ）的比表面随ＭｏＯ３含量增加而单调下降；（３）在ＭｏＯ３／ＺｒＯ２（Ⅰ）中，ＺｒＯ２以介稳四方相存在，而在ＭｏＯ３／ＺｒＯ２（Ⅱ）中则是稳定的单斜相．在此基础上研究了事先引入的活性组分在载体织构形成过程中的作用，包括延迟ＺｒＯ２晶化，阻碍晶粒长大及与之相关的相变等，并讨论了ＭｏＯ３／ＺｒＯ２（Ⅰ）中ＭｏＯ３最佳含量的科学含义．     

Optimization of the electrophoretic deposition of YBa2Cu3O7−x superconducting large area coatings

Large area coatings (>10cm²) of the high temperature superconductor YBa₂Cu₃O_7–x (x = 0.1 – 0.2) (YBCO) have been prepared by scale up an electrophoretic deposition technique using silver sheets and Si-wafers coated with Ag or Au as substrates. Several parameters, like the kind of the solvent, the applied voltage, the distance between the electrodes, the initial concentration of the suspension and the temperature during the electrophoresis were investigated in order to attain high deposition rates, as well as uniform YBCO coatings with the proper stoichiometry. To obtain a strongly adherent and dense coating a subsequent appropriate sintering and annealing procedure has been developed. The coatings obtained were characterized for their stoichiometry and superconducting properties by X-ray diffraction (XRD), Raman spectroscopy and magnetic measurements. The homogeneity and thickness of the films and the average grain size of the deposited particles have been investigated by optical and scanning electron microscopy (SEM).     

Methods for the synthesis of mono- and polynuclear NH-tetrazoles. (Review)

Data on methods for the synthesis of monocyclic and polynuclear NH-unsubstituted tetrazoles are reviewed.Dedicated to Prof. H. Elguero on the occasion of his 65th birthday.St. Petersburg State Technological Institute (Technical University), St. Petersburg 198013, Russia; Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 867–884, July, 2000.     

Preparation of Titania from Tetrakis(diethylamino)titanium via Hydrolysis

The conversion of tetrakis(diethylamino)titanium (Ti(NEt₂)₄) into titania via either a combination of hydrolysis (Ti(NEt₂)₄ : THF : H₂O = 1 : 10 : x, x = 2, 4, 10) at ambient conditions and calcination (method A) or hydrolysis in a water-tetrahydrofuran (THF) mixture (Ti(NEt₂)₄ : THF : H₂O = 1 : 10 : 100) at reflux (method B) was investigated. Titanium tertiary butoxide (Ti(O ^t Bu)₄) was also used as a substitute for Ti(NEt₂)₄. The hydrolysis via method A resulted in the formation of amorphous solids containing organics. Thermal analyses showed that the hydrolysis products showed mass losses up to 500°C probably due to the presence of diethylamine (Et₂NH) formed via the hydrolysis of Ti(NEt₂)₄ in the hydrolysis products, while a mass loss of the hydrolysis product from Ti(O ^t Bu)₄ was completed up to about 200°C. After calcination at 600°C, anatase or a mixture of anatase and rutile was obtained. The crystallization behavior of the hydrolysis products from Ti(NEt₂)₄ was different from that of the hydrolysis product from Ti(O ^t Bu)₄. The hydrolysis via method B gave only an amorphous material from Ti(NEt₂)₄, while a crystalline titania (anatase and brookite) formed from Ti(O ^t Bu)₄.     

Advantages of using a modified orthogonal sampling configuration originally designed for LC-ESI-MS to couple CE and MS for the determination of antioxidant phenolic compounds found in virgin olive oil

A ThermoFinnigan sheath liquid flow capillary electrophoresis-mass spectrometry system designed for coupling via a co-axial interface was coupled through an adapted via an alternative, commercially available interface for orthogonal sampling. The affordable, reversible structural alterations made in the commercial LC-MS interface resulted in improved analytical performance.The results of a conventional capillary electrophoresis (CE) method using a commercial co-axial source to determine antioxidant phenolic acids present in virgin olive oil, were compared with those obtained by using a modified orthogonal sampling position. In both cases, separations were done using a 10 mM ammonium acetate/ammonium hydroxide buffer solution at pH 10.0 and a constant applied voltage of 25 kV. The operating variables for the mass spectrometry interface were re-optimized for the modified orthogonal orientation. This allowed the sheath liquid, sheath gas flow rates and capillary voltage to be lowered with respect to the co-axial coupling configuration. In addition, the orthogonal sampling position provided a higher selectivity by effect of ion sampling excluding larger droplets—with an increased momentum along the axis—which were drained through the sink at the bottom of the ion source. Also, the new configuration facilitated sample ionization, improved electrospray stability and led to stronger signals as a result.The new system was validated in terms of precision (repeatability), linearity, and limits of detection and quantification. A comparison of the validation data with the results previously obtained by using a commercial co-axial configuration revealed the adapted orthogonal sampling position to provide better repeatability in both migration times and relative peak areas (<1% and 7% respectively with n = 15 replicates), a good linear range (with levels in the microgram-per-litre region) and lower limits of detection—especially for the compounds detected with the lowest sensitivity when co-axial ESI was used, as HFA, GEN, FER and VAN finding LOD among 24-3.0 μg L⁻¹ respectively.     

~(12)CO_2/~(13)CO_2体系中碳同位素的显微激光拉曼光谱研究

采用自行设计的装置制备了一系列不同比例的12CO2/13 CO2混合物,对混合物样品进行显微激光拉曼测试,获得CO2气体碳同位素分子的拉曼特征峰。对实验数据分析发现,12CO2的摩尔分数[x(12CO2)]与12CO2/13 CO2混合物中拉曼特征峰峰面积比之间存在数学关系式。根据拟合的关系式,利用显微激光拉曼光谱可以预测CO2气体碳同位素的组成,并为以后预测单个流体包裹体中12CO2的摩尔分数奠定了理论基础。     

A New Diterpene Acid from the Flowers of Heteropappus altaicus

A new compound, named heteraltaic acid was isolated from the flowers of Heteropappus altaicus (willd) Novopokr. The compound was elucidated as (5R, 6S, 8aS) -5-[2-(3-furyl) ethyl-5, 6, 8a-trimethyl-4a, 5, 6, 7, 8, 8a -hexahydro-l-naphthalenecarboxylic acid] by the combination of 1D and 2D NMR techniques (HSQC, HMBC) and X-ray analysis.     

Solvation of amino acid residues in water and urea-water mixtures: Volumes and heat capacities of 20 amino acids in water and in 8 molar urea at 25°C

The limiting partial molar volumes V ^o and heat capacities C _p ^o of 20 amino acids have been determined in water and in 8 molar urea at 25.0°C using flow calorimetry and flow densimetry. The side chain contributions to V ^o and C _p ^o were obtained as the difference between the properties of the various amino acids and those of glycine, both in water and in 8M urea. The solvent accessible surface area of the amino acid residues were obtained using a method developed by Hermann, and the total surface areas were separated into their hydrophobic A _Hb and hydrophilic components. In water, C _p ^o values for the various residues C _p ^o (R) were found well correlated with A _Hb , though much less so in the urea solution. Hence, C _p ^o (R) values, in water yield a good estimate of side chain hydrophobicity, but the (waterurea) transfer heat capacities appear strongly affected by specific solvation effects in the urea solution.Presented at the sixth Italian meeting on Calorimetry and Thermal Analysis (AICAT) held in Naples, December 4–7, 1984.     

Interaction of iodine species with glycogen at high concentrations of iodine

Glycogen–iodine (GI) complex formation has been studied at different concentrations of iodine and glycogen. For each glycogen concentration (0.25, 0.125, 0.0625, 0.0313 g/L), the iodine concentration was varied from 0.0317 to 1.59 g/L and the absorbance readings were taken at 453 and 560 nm (GI wavelengths of maximum absorbance). The 453 nm absorbance curves for the GI solution (GI complex and unreacted iodine), and that of the pure iodine solution (without glycogen) level off at a high iodine concentration, and give a peak in the subtracted curve. The 560 nm curves consistently increase in absorbance, and no peak is noticed in the subtracted curve. The spectra of concentrated iodine solutions in water and alcohol suggest the formation of neutral iodine clusters. We suggest that these iodine clusters do not react with glycogen, and that the GI complex formation takes place by the addition of I₂ molecules. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 927–931, 1997     

Past and Present of Sol-Gel Science and Technology

In the last twenty years sol-gel science has undergone a spectacular development. The various stages of the sol-gel process have been scrutinised in considerable detail and a sound basis for future technological developments established. In the beginning the studies centred mainly on silica and silicate glasses and were progressively extended to many ceramics and composites. A turning point was reached with the emergence of ormosils and of organic-inorganic nanocomposites. This opened the gateway to whole classes of new materials. The present studies show a definite tendency towards very specialised high-tech applications.