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1.
Han F Zhu X Mu G Zeng B Cheng P Shen B Wen HH 《Journal of the American Chemical Society》2011,133(6):1751-1753
We successfully synthesized the copper-based pnictide LiCu(2)P(2), which was reported as a superconductor with T(c) = 3.7 K before. The temperature dependence of resistivity and DC magnetization was measured on both polycrystalline and single-crystalline LiCu(2)P(2). However, our repeatable synthesizing and measurements showed no superconducting transition either in resistivity or DC magnetization above 2 K. A metallic behavior can be seen in resistivity, and a Curie-Weiss behavior was observed in DC magnetization from 2 to 300 K. We have also carried out the Hall effect and MR measurements on the sample, from which we conclude that the LiCu(2)P(2) has a single-band character. We also synthesized the polycrystalline Li(1-x)Cu(2)P(2), LiCu(2-x)P(2), and Li(1+x)Cu(2-x)P(2) with different stoichiometries, and observed no superconductivity in all the samples. 相似文献
2.
Furić K Stoch L Dutkiewicz J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(7):1653-1659
Tough glass-ceramic material of special mechanical properties with nanosize crystal phases formed by appropriately controlled crystallization was studied by Raman spectroscopy. It was obtained by TiO2 activated crystallization of Mg-aluminosilicate glass of SiO2-Al2O3-MgO-TiO2-ZnO composition. Crystallization was preceded by a change in the TiO2 structural position and state, which is manifested by a changed color of glass from yellow into blue shortly before the glass transformation (Tg) temperature. Raman spectroscopy was applied to explain the mechanism of this process and to establish the role of TiO2 in the early stage of glass crystallization that precedes a complete crystal phase formation. The starting glasses were found in almost complete disorder, since all bands were weak, broad and dominated by a Bose band at about 90 cm-1. After the sample annealing all bands turned out better resolved and the Bose band practically disappeared, both confirming the amorphous structure reorganization process. A multiplet observed in the vicinity of 150 cm-1 we assigned to the anatase and other titania structures that can be considered prime centers of crystallization. Finally, in the closest neighborhood of the Rayleigh line the low frequency mode characterizing nanoparticles was observed. According to this band theory, the mean size of initial titania crystallites is about 10nm for all samples, but the size distribution varies within factor two among them. 相似文献
3.
V. A. Osyanin E. A. Ivleva Yu. N. Klimochkin 《Russian Journal of Organic Chemistry》2011,47(11):1686-1689
2-Substituted 4H-1,3-benzoxazines were obtained by the condensation of 2-(2-hydroxyphenyl)-2-adamantanol with aromatic and aliphatic nitriles
in trifluoroacetic acid. With acetonitrile the classic product of Ritter reaction, a secondary amide, was isolated. 相似文献
4.
I. Ya. Zaitseva I. S. Kovaleva V. A. Fedorov 《Russian Journal of Inorganic Chemistry》2014,59(11):1340-1342
The interaction in the HgBr2-CdBr2-PbBr2 ternary system was studied by differential thermal analysis; the isoconcentration section of the system at 50 mol % CdBr2 was investigated. Based on the results of the study, a projection of the liquidus surface of the HgBr2-CdBr2-PbBr2 ternary system to the composition triangle was constructed; the boundaries of the primary crystallization fields were determined for three phases: HgBr2 (degenerate field), solid solution α based on CdBr2, and solid solution β based on PbBr2; and isotherms were drawn. A ternary eutectic has the composition 93 mol % HgBr2-1 mol % CdBr2-6 mol % PbBr2 and melts at 235°C. 相似文献
5.
近 1 0年来 ,人们对于具有纳米尺度聚合物自组装结构的研究日益增多 .其中 ,嵌段共聚物在选择性溶剂中的胶束行为的研究非常引人瞩目 [1~ 3] .其表现出诸多常规尺寸所不具备的特殊性能 ,使得纳米胶束不仅在理论上有研究价值 ,而且在材料化学、生物医学和环境科学等领域都具有广阔的应用前景 .Ma等[4 ] 对聚丙烯酸和聚苯乙烯接枝共聚物的研究发现聚合物接枝率和聚合物浓度以及溶液离子强度对胶束结构有影响 ;Zhang等 [1,5] 对不同嵌段比例的苯乙烯 -丙烯酸嵌段共聚物的自组装行为的研究 ,发现不同嵌段比例所对应的纳米结构不同 ;而胶束表面… 相似文献
6.
N. A. Anisimova N. G. Makarova G. A. Berkova V. M. Berestovitskaya 《Russian Journal of General Chemistry》2006,76(10):1545-1549
The reactions of phosphorylated 2-nitro-and 2-bromo-2-nitroethenes with sodium azide involve 1,3-dipolar cycloaddition to form triazoles, aziridines and isomeric vinyl azides. The latter products were isolated as a mixture of structural isomers. The structure of the obtained compounds was determined by IR and 1H and 31P NMR spectroscopy. 相似文献
7.
The effect of metal substitution in La2C2Br2 by Lu (non-magnetic) and Ce (magnetic), respectively, on Tc was studied. The Lu substitution affects Tc, which decreases moderately with increasing amount of Lu. However Ce substitution affects Tc drastically, such that only 10% Ce substitution makes superconductivity disappear. 相似文献
8.
Catalytic reduction of NO2 with CO and/or propylene in the presence of NO and excess oxygen, a model mixture for flue gas, was studied over a series of CuO‐CeO2/SiO2 catalysts between 120–260 °C. The effect of HCl, an impurity in flue gas, on the activity of the catalysts was evaluated. It was found that a binary oxide catalyst, 2% CuO‐8% CeO2/SiO2, was active for the reduction of NO2 by CO and/or propylene. CO was effective for selective reduction of NO2 in the presence of NO and O2 in a temperature window between 160–200 °C while propylene was effective at temperature higher than 200 °C. In the presence of HCl, the activity of the catalyst for reduction of NO2 with CO was irreversibly deactivated. However, the activity for reduction of NO2 with propylene was not influenced by HCl. 相似文献
9.
10.
Ludwik Kreja 《Monatshefte für Chemie / Chemical Monthly》1987,118(6-7):717-726
The kinetics of the H2O2 decomposition in acidic medium and the electrochemical activity of different iron-polyphthalocyanine catalysts for the O2 reduction in fuel cells were studied. It was found that the reaction order of the H2O2 decomposition depends on the initial concentration. For lower concentrations a first order and for the higher ones a second order relationship was found. The change of the reaction order with the increase of H2O2 concentration can be explained by a varying cover of the catalyst surface. Catalytic and electrochemical activities of iron-polyphthalocyanine depend on the conditions of the synthesis. 相似文献
11.
V. K. Gamov V. A. Kaminskii M. N. Tilichenko 《Chemistry of Heterocyclic Compounds》1972,8(10):1253-1256
The reaction of 2,2'-methylenedicyclohexanone with HCN and hydrazine in aqueous alcohol was studied at various pH values. Conclusions were drawn regarding the spatial configurations of the reaction products.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1387–1390, October, 1972. 相似文献
12.
CO2与2-丁醇二元系统的高压相平衡模型 总被引:1,自引:0,他引:1
采用固定体积可视观察法测定了在323.2~353.2 K温度范围内2-丁醇在CO2中高压相平衡数据. 运用Peng-Robinson状态方程(PR)和van der Waals-2混合规则建立了相平衡模型, 并运用Chrastil半经验方程建立了溶解度方程. 通过优化计算得到了状态方程中的模型参数, 同时得到的Chrastil溶解度方程为c=ρ3.3617·exp(-2198.8193/T+6.5545). 二元体系的溶解热为-18.2809 kJ/mol. 相似文献
13.
The first high performance liquid chromatographic method for determination of the plasma concentration of 2-chloro-2'-deoxyadenosine (CdA) in patients, which is significantly more sensitive than the previously used RIA method, is presented. CdA is a purine analogue with useful clinical activity against lymphoproliferative disorders and it has recently been found to be the single most active agent in the treatment of hairy cell leukaemia. Guaneran (6-nitroimidazol-6-thioguanine) was added to 1 mL plasma as the internal standard and CdA was extracted using ethyl acetate. A Perkin-Elmer C18, 3 mu, 8 cm column was used for the separation of CdA and the internal standard from endogenous compounds in the sample with a mixture of sodium phosphate buffer 10 mM, methanol and acetonitrile (85:10:5, pH = 3.0) as the mobile phase. The sensitivity of the method (1 nM) allows the determination of CdA in plasma 24 h after the administration of 0.14 mg/kg as a 2 h infusion. 相似文献
14.
Differential scanning calorimetry (DSC) was used to study crystallization in Ge2Sb2Se4.5Te0.5 glass under non-isothermal conditions. The crystallization kinetics was described in terms of the autocatalytic ?esták–Berggren model. An extensive discussion of all aspects of a full-scale kinetic study for a crystallization process was undertaken. In particular, the effect of Te ? Se substitution on the complexity of the crystallization process was analyzed. The addition of tellurium enhances bulk crystallization originating from volume nuclei at the expense of the surface/defects-based crystallization mechanism. Significantly higher activation energy in the case of the Te-doped material was attributed to the larger mass of the combined Se–Te chains and the larger spatial restrictions for their movement. On the other hand, the slightly lower crystallization temperature of the Te-doped glass corresponds to its higher tendency for crystallization. A supplemental X-ray diffraction study confirmed the findings obtained by DSC. 相似文献
15.
K. Zbudniewek J. Góralski J. Rynkowski 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(13):2057-2062
The development of industry induced a massive increase in the emission of carbon dioxide into the atmosphere. A large amount of CO2 and its general availability causes that it could be a cheap reactant in a reaction that runs in a way similar to photosynthesis in plants. Pure TiO2 and metal doped TiO2 are the most studied semiconductor catalysts for photoreduction of CO2. The TiO2/SiO2 and Pd/TiO2/SiO2 catalysts were prepared and studied by temperature-programmed desorption, X-ray diffraction analysis, SEM-EDS, temperature-programmed reduction and then used for the methanol synthesis. The photoactivity of Pd/TiO2/SiO2 catalysts in the reduction of CO2 with H2O was tested at room temperature using photoreactor equipped with 16 lamps. The wavelength was characteristic of near ultraviolet. Post-reaction products were identified with gas chromatograph equipped with the flame ionization detector. Pd doping made the catalysts photoactive and the photoactivity of catalysts was changing as follows: 1%Pd/5%TiO2/SiO2 > 1% Pd/10% TiO2/SiO2 > 1% Pd/15% TiO2/SiO2. Optimum ultraviolet radiation time in the photoreduction of CO2 to methanol was 7 h. An addition of Pd does not change the surface of the carrier. 相似文献
16.
利用柠檬酸三钠还原硝酸银制备了银纳米颗粒(AgNPs),然后通过氨水水解正硅酸乙酯(TEOS)的方法,在AgNPs上沉积SiO2,制备出以Ag为核,SiO2为壳的复合纳米颗粒(Ag@SiO2).调节TEOS用量,可以控制SiO2层的厚度.根据AgNPs的局域表面等离激元共振(LSPR)效应,将制得的Ag@SiO2颗粒用于H2O2的检测,检测下限为1μmol/L,并可以通过控制SiO2层的厚度方便地调节Ag@SiO2颗粒与H2O2反应的速率.与传统方法相比,具有简单、快速、成本低的优点.分别运用TEM、紫外-可见分光光度计对反应前后Ag@SiO2颗粒形貌及反应过程中其LSPR吸收的变化进行了表征. 相似文献
17.
During the investigation of the reaction of dichloroketene with cyclic enoxy-lactones and acyclic enoxy-ester substrates it was found that only the acylic variants effectively participated in the [2+2]-cycloaddition. Although a complete understanding of the reasons for this are lacking, molecular mechanics calculations do suggest that an out of plane twist of the cabonyl group in the acyclic compounds may be partially responsible. After screening a variety of chiral auxiliaries it was found that useful levels of diastereoselectivity (2.6-10.8:1) could be obtained in this cycloaddition reaction when (R)-2,2-diphenylcyclopentanol was used as the chiral auxiliary. 相似文献
18.
Summary A method for the determination of 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI) in
plasma was developed. 5-HNMP and 2-HMSI are metabolites to the widely used organic solvent N-methyl-2pyrrolidone (NMP). The
5-HNMP and 2-HMSI were purified from plasma by C8 solid phase extraction, derivatised by bistrimethylsilyl trifluoroacetamid,
and analysed by gas chromatography with mass spectrometric detection. For 5-HNMP, the precision was 2–7 % (120 and 780 ng
mL−1) and the detection limit was 6 ng mL−1 (m/z 98). For 2-HMSI, the precision was 2–9 % (160 and 1000 ng mL−1) and the detection limit was 4 ng mL−1 (m/z 144). The method is applicable for analysis of plasma samples from workers exposed to NMP. 相似文献
19.
DSC was used for heat capacity measurements of pure RuO2 in the temperature range from 300 to 1170 K of solid solutions corresponding to the compositions of (Ti1−x Rux )O2 (x ≤0.15 and x ≥0.85) and in the temperature range from 300 to 1550 K of pure TiO2. The analysis of experimental data obtained within ±2%
of accuracy has shown that the characteristic temperatures representing the harmonic lattice vibrations do not strongly depend
on the chemical composition x . It was demonstrated that non-harmonic heat capacity is strongly correlated to x. The existence of additional excess heat
capacity was observed with the mixed oxide solid solution samples of low Ru content and explained by the defect formation
model.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
L. P. Krul’ E. A. Murashko L. B. Yakimtsova O. I. Yankovich I. A. Oleinikova E. K. Fomina E. V. Grinyuk A. P. Polikarpov 《High Energy Chemistry》2009,43(4):274-277
The dependence of the yield of polymer and its molecular mass on the absorbed dose of γ-irradiation of a 0.8 M 2-acrylamido-2-methylpropanesulfonic acid aqueous solution was determined, as well as the gel fraction of the polymer produced. The feasibility of obtaining a crosslinked polymer via radiation polymerization of 2-acrylamido-2-methylpropanesulfonic acid in the presence of N,N′-methylenebisacrylamide admixtures was shown. It was found that the maximal degree of crosslinking is reached at a dose on the order of 20 kGy and the maximal water uptake (1150 g/g) is achieved at a dose of 1.25 kGy. 相似文献