多元醇法合成具有不同长径比的棒状LiFePO4/C材料

以三价铁盐为铁源,采用多元醇还原法在低温下制备出了具有不同长径比的棒状LiFePO₄材料. 通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、循环伏安(CV)、交流阻抗谱(EIS)和恒电流充放电测试等手段分析了不同回流反应时间下制备出的前驱体和最终的LiFePO₄/C 样品. 结果表明：回流反应时间对LiFePO₄的形貌和特性有明显的影响. 通过把回流反应时间从4 h延长至16 h,材料的形貌由不规则的短棒状颗粒变为规则的长棒状颗粒,且棒的直径明显变小. 当回流反应时间为10 h 时,样品复合了多种形貌,有利于电子的传输,在低倍率下具有优秀的性能,0.1C放电比容量为163 mAh·g^-1;当回流反应时间为16 h 时,样品具有最大的长径比,有利于锂离子的扩散,在高倍率下具有良好的性能,1C、3C、5C、10C、20C倍率下放电比容量分别为135、125、118、110、98 mAh·g^-1,循环性能良好,几乎无衰减.     

B-Co3O4/C复合纳米材料的制备及其电催化析氧性能

本文以雪莲果为碳源,采用热解法制备碳材料(C),以硝酸钴、四硼酸钠和碳材料为原料,通过热解法合成硼掺杂四氧化三钴/碳(B-Co₃O₄/C)复合纳米材料。运用XRD、FTIR、SEM、XPS等手段对其结构、形貌和组成进行表征。利用线性扫描(LSV)和Tafel曲线等电化学测试方法研究了B-Co₃O₄/C复合纳米材料的电催化析氧反应(OER)性能。结果表明,该材料具有较好的电催化OER活性。在1.0mol/L的KOH电解液和10mA·cm^-2的电流密度下,B-Co₃O₄/C复合纳米材料的过电位为293mV,Tafel斜率为45.0mV·dec^-1。在10mA·cm^-2电流密度下连续测试10h, B-Co₃O₄/C的电位变化不大,通过法拉第效率测试该催化剂的产氧效率为94%,说明硼原子的掺入改变了B-Co₃O₄...     

A study of the compounds present in the three-component system Dy2O3-SeO2-H2O at 100°C

The solubility isotherm of the system Dy₂O₃-SeO₂-H₂O at 100°C was studied and drawn. The selenites present in the system were identified and isolated. A thorough TG, DTG and DTA analysis was made. By modelling the conditions of TG, DTG and DTA analysis, the phases of the thermal decomposition were isolated and identified. The chemistry of the reaction was described.     

Li4Ti5O12/(Ag+C)电极材料的固相合成及电化学性能

以Li₂CO₃,TiO₂为原料,葡萄糖为碳源,采用固相煅烧工艺合成了亚微米级的Li₄Ti₅O₁₂/C复合负极材料。并将之与AgNO₃复合,采用固相方法制备出了Ag表面修饰的Li₄Ti₅O₁₂/(Ag+C)复合材料。采用XRD、SEM和TEM测试方法对材料的微结构进行了表征。结果表明,C的存在对Ag单质在Li₄Ti₅O₁₂/C颗粒表面的大量形成起到了积极的促进作用,从而很大程度地提高了Li₄Ti₅O₁₂/C的电导率,因此有效地改善了其电化学性能。在1C倍率下,Li₄Ti₅O₁₂/(Ag+C)复合材料的首次放电容量达到了164 mAh·g^-1。     

Domino Aza-Michael-SNAr-Heteroaromatization Route to C5-Substituted 1-Alkyl-1H-Indole-3-Carboxylic Esters

A new synthesis of C5-substituted 1-alkyl-1H-indole-3-carboxylic esters is reported. A series of methyl 2-arylacrylate aza-Michael acceptors were prepared with aromatic substitution to activate them towards S_NAr reaction. Subsequent reaction with a series of primary amines generated the title compounds. Initially, the sequence was expected to produce indoline products, but oxidative heteroaromatization intervened to generate the indoles. The reaction proceeded under anhydrous conditions in DMF at 23–90 °C using equimolar quantities of the acrylate and the amine with 2 equiv. of K₂CO₃ to give 61–92% of the indole products. The reaction involves an aza-Michael addition, followed by S_NAr ring closure and heteroaromatization. Since the reactions were run under nitrogen, the final oxidation to the indole likely results from reaction with dissolved oxygen in the DMF. Substrates incorporating a 2-arylacrylonitrile proved too reactive to prepare using our protocol. The synthesis of the reaction substrates, their relative reactivities, and mechanistic details of the conversion are discussed.     

C/g-C3N4/MoS2复合材料的制备及光催化性能

首先以尿素和葡萄糖为前驱体,通过热缩合方法制备了C/g-C₃N₄,然后利用溶剂热法合成C/g-C₃N₄/MoS₂三元复合材料。通过不同的手段对其进行了表征,结果表明,与C/g-C₃N₄相比,该三元复合材料不仅具有更强的光吸收性能和更大的表面积,而且更有利于电子的转移。同时对其可见光催化降解甲基橙性能进行研究,结果发现,C/g-C₃N₄/MoS₂-2.0%复合材料(含有质量分数为2.0%的MoS₂)表现出最高的反应速率常数(0.0086 min^-1),分别为g-C₃N₄/MoS₂-2.0%(0.0015 min^-1)和C/g-C₃N₄(0.0036min^-1)的5.7倍和2.3倍。     

V2O5/C catalyst for liquid phase oxidation of glyoxal to glyoxylic acid

A study of the catalytic activity of V₂O₅/C catalyst for the oxygen oxidation of glyoxal has been made, showing that glyoxylic acid can be formed without control of pH value and there is little oxalic acid from the excessive oxidation of glyoxylic acid. The studies of XRD and TEM have shown that V₂O₅ diffraction peaks gradually strengthen with the increase of the content of V₂O₅. With the content of 3% V₂O₅ and the calcination temperature of 573 K, V₂O₅/C catalyst displayed the best activity and selectivity. The conversion of glyoxal and the selectivity of glyoxylic acid reached 18.76% and 77.70% after 5 h, respectively. Moreover, V₂O₅/C catalyst showed small deactivation after recycling three times, which indicates that V₂O₅/C has a higher stability than noble metal catalysts in the reaction medium. Supported by the Technology Research and Development Project for University of Shanxi Province of China (Grant No. 20051272)     

Water-soluble polyketones and esters as the main stable products of ozonolysis of fullerene C60 solutions

Stable ozonolysis products of C₆₀ solutions in CCl₄, toluene, and hexane were studied by elemental analysis, HPLC, and UV and IR spectroscopy. Polyketones and esters were established for the first time to be the main stable products, whose content increased during the whole ozonolysis time (1 h). Epoxides C₆₀O _n (n = 1—6) are accumulated within 1—3 min, and after 5 min of ozonolysis their concentration decreases to zero. Fullerene C₆₀ disappears from the reaction solution due to its conversion to oxides and mechanical capturing of C₆₀ by these oxides to form a precipitate. The oxidation of C₆₀ is completed in the solid phase by the formation of the C₆₀O₁₆ oxide in which 9.68 O atoms fall on fullerene polyketones, 6 O atoms are attributed to esters, and 0.32 O atoms fall per epoxides. The optimum medium for preparation of the C₆₀ oxides is CCl₄ rather than traditional toluene, which reacts with ozone in the side reaction to form products containing active oxygen. The C₆₀ cage is raptured during ozonolysis because of the C=C bond cleavage to form two C=O groups at the ends of the open hexagon. Ozonolysis of C₆₀ solutions in CCl₄ is efficient for synthesis of water-soluble fullerene oxides due to the high yield and solubility of polyketones and esters in water.     

ZnCl2 and Pd/C catalyzed synthesis of 2-substituted indoles

A facile, mild, efficient, and copper-free method has been developed for the synthesis of 2-substituted indoles via domino Sonogashira coupling/cyclization reaction catalyzed by ZnCl₂ and palladium on carbon with simultaneous formations of C–C and C–N bonds.     

Thermal properties and kinetics study of charged LiCoO2 by TG and C80 methods

The thermal stability of lithium-ion battery cathode could substantially affect the safety of lithium-ion battery. In order to disclose the decomposition kinetics of charged LiCoO₂ used in lithium ion batteries, thermogravimetric analyzer (TG) and C80 microcalorimeter were employed in this study. Four stages of mass losses were detected by TG and one main exothermic process was detected by C80 microcalorimeter for the charged LiCoO₂. The chemical reaction kinetics is supposed to fit by an Arrhenius law, and then the activation energy is calculated as E _a=148.87 and 88.87 kJ mol⁻¹ based on TG and C80 data, respectively.     

Nickel and potassium co-modified β-Mo2C catalyst for CO conversion

Nickel and potassium co-modified -Mo2C catalysts were prepared and used for CO hydrogenation reaction. The major products over -Mo2C were C1–C4 hydrocarbons, only few alcohols were obtained. Addition of potassium resulted in remarkable selectivity shift from hydrocarbons to alcohols at the expense of CO conversion over -Mo2C. Moreover, it was found that potassium enhanced the ability of chain propagation with a higher C2+OH production. Modified by nickel, -Mo2C showed a relatively high CO conversion, however, the products were similar to those of pure -Mo2C. When co-modified by nickel and potassium, -Mo2C exhibited high activity and selectivity towards mixed alcohols synthesis, and also the whole chain propagation to produce alcohols especially for the stage of C1OH to C2OH was remarkably enhanced. It was concluded that the Ni and K had, to some extent, synergistic effect on CO conversion.     

Preparation and study of hydrides of fullerenes C60 and C70

Fullerene hydrides were prepared by hydrogenation of fullerences C₆₀ and C₇₀ using proton transfer from 9,10-dihydroanthracene to fullerene and were studied by mass spectrometry (electron impact, field desorption), IR, UV, and¹H and¹³C NMR spectroscopy. The main product of the hydrogenation of C₆₀ is C₆₀H₃₆, which is sufficiently stable. Hydrogenation of fullerene C₇₀ gives a series of polyhydrides C₇₀H _n (n=36–46), and the main product is C₇₀H₃₆. The dehydrogenation of C₆₀H₃₆ by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is not quantitative and results in the formation of fullerene derivatives along with C₆₀. The comparison of the IR and¹H and¹³C NMR spectral data for solid C₆₀H₃₆ with the theoretical calculations suggests that the fullerene hydride has aT-symmetric structure and contains four isolated benzenoid rings located at tetrahedral positions on the surface of the closed skeleton of the molecule. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 4, pp. 671–678, April, 1997.     

Simultaneous thermoanalytical investigations of (C6H5)4AsCl and (C6H5)4PCl under air and argon atmospheres

The thermoanalytical curves of (C₆H₅)₄AsCl (I) and (C₆H₅)₄PCl (II) were generated simultaneously by using a Netzsch simultaneous thermal analyser 409 under static air and dynamic argon atmospheres. The ranges of thermal stability of I and II were found to be 145–310°C and 137–365°C, respectively, and their melting points to be 261 and 278°C. The DTA profiles of I and II differ and can be used for their distinction.     

Reduction of C60 and C70 by primary amines: Optical and ESR studies

Radical anions C70- and C70 2- were obtained in vacuo by the reaction of I-amino3-propanol (AP) and 1,5-diaminopentane (DAP) with fullerene C70. The radical anions were identified by visible/near IR (X = I372 and I172 nm, respectively) and ESR spectroscopies. The temperature dependences of the ESR spectra were studied for the C₆₀-AP, C₇₀-AP, and C70-DAP systems. At low temperatures (I5-45 K), the ESR spectrum for C60 is close to that for species with axial symmetry of theg-factor (q_| = 2.000 and g, = I.995). The anisotropy of theg-factor is averaged, when the temperature increases. At T > I48 K the averaged line is broadened, and the sharp signal with g = 2.0001 overlaps this broad line. The intensity of the narrow line increases, when the temperature increases. The ESR spectrum observed in the C₇₀-AP system at I2.5 K may be tentatively described as a superposition of two ESR spectra, namely, the ESR spectra of a radical with g_| = 2.0042 and g, = 2.0015 (presumably a radical cation) and of C₇₀ ^– with q_| = 2.000 and g = I.994. The spectra of the sample in which C70 is present mainly as C₇₀ ^2– exhibit only a line with g = 2.0004.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. I, pp. 103–108, January, 1996.     

Studies on novel cyclodextrans: Inclusion of C60 and C70

Cycloisomalto-heptaose (CI-7) and cycloisomalto-octaose (CI-8) are two novel cyclodextrans. Treatment with C₆₀ or C₇₀ by kneading leads to the formation of four distinct water-soluble inclusion complexes: CI-7/C₆₀ (2: 1), CI-8/C₆₀ (2: 1), CI-7/C₇₀ (2: 1) and CI-8/C₇₀ (2: 1). Their formation and structures have been examined by UV vis spectroscopy, X-ray powder diffraction and fluorescence spectral studies. The reaction is a reversible process.     

Redox-induced hydrogen transfer from hydrofullerene C60H36 to fullerene C60

The possibility of hydrogen transfer from hydrofullerene C₆₀H₃₆ to electrogenerated radical anion C₆₀ ^.− or dianion C₆₀ ²⁻ in propylene carbonate-toluence (3∶2, v/v) was demonstrated by cyclic voltammetry. The process affords C₆₀H₂ as the product. The reaction found is the typical redox-induced process. Translated fromIzvestiya Akodemii Nauk. Seriya Khimicheskaya, No. 6, pp. 1136–1139, June, 1998.     

Rigid Nanoporous Urea-Based Covalent Triazine Frameworks for C2/C1 and CO2/CH4 Gas Separation

C2/C1 hydrocarbon separation is an important industrial process that relies on energy-intensive cryogenic distillation methods. The use of porous adsorbents to selectively separate these gases is a viable alternative. Highly stable covalent triazine frameworks (urea-CTFs) have been synthesized using 1,3-bis(4-cyanophenyl)urea. Urea-CTFs exhibited gas uptakes of C₂H₂ (3.86 mmol/g) and C₂H₄ (2.92 mmol/g) at 273 K and 1 bar and is selective over CH₄. Breakthrough simulations show the potential of urea-CTFs for C2/C1 separation.     

Hydration of C3a in the presence of CaCO3

The hydration of C₃A with and without CaCO₃ was studied. The techniques used were X-ray diffraction, thermogravimetry, differential thermogravimetry and calorimetry.In the presence of CaCO₃, the hydration of C₃A is accelerated. The hexagonal hydrates are formed first. They react with CaCO₃ to form calcium carboaluminate hydrate. This reaction blocks formation of the cubic hydrate. The latter appears when CaCO₃ is completely consumed.     

Li3V2(PO4)3/C的P123辅助流变相法制备及电化学性能

以V₂O₅、NH₄H₂PO₄、LiOH、柠檬酸、三嵌段聚合物表面活性剂P123为原料, 用流变相(RPR)法制备了Li₃V₂(PO₄)₃/C正极材料. 用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)等方法表征, 结果表明: 材料为单一纯相的单斜晶体结构, 颗粒均匀并呈现珊瑚结构; 恒流充放电, 循环伏安(CV)及电化学交流阻抗(EIS)等电化学性能测试表明, 采用P123 辅助合成材料电化学性能明显优于未采用P123 辅助合成材料. 3.0-4.3 V放电区间, 0.1C充放电下P123 辅助合成Li₃V₂(PO₄)₃/C材料首次放电比容量为129.8 mAh·g^-1, 经过50 次循环后容量只衰减0.9%; 倍率性能及循环性能优异, 1C、10C、25C的首次放电比容量分别为128.2、121.3、109.1 mAh·g^-1, 50次循环后容量保持率分别为99.1%, 96.9%, 90.7%. 这归因于三嵌段聚合物P123 作为分散剂的同时也作为有机碳源在颗粒表面及间隙形成碳网络, 有利于材料导电率的改善, 降低了其电荷转移阻抗, 减小了电极充放电过程的极化现象.     

Determination of cyclo C6 and C7 peroxides and hydroperoxides by gas chromatography

Summary A method for determining cyclo C₆-C₇-peroxides and hydroperoxides by high-resolution capillary GC has been developed. The compounds were synthesized in the liquid phase and identified in chromatograms of the reaction mixture of cyclohexyl hydroperoxide and cycloheptane using GC-MS. Peroxy compounds were determined using an FID. The effective carbon number (ECN) concept was used to calculate response factors of the peroxy compounds analysed. The experimentally determined response factor for cyclohexyl hydroperoxide was identical (within error limits) with that calculated.