稀土Invar合金热力学性质研究

制备了稀土Invar（因瓦）合金YFe_(12-x)V_x（x＝1.6，2.0；2.4，2.8，3.2）和SmFe_(12－x_V_x（x=2.4, 2.8）采用电动势法以CaF_2单晶作为固体电解质，测定了钇和钐在相应合金中的活度．计算了偏摩尔自由能等热力学性质．测定温度对两类合金分别为920－1020 K和900－1000 K．     

金属石墨层间化合物的量子化学和热力学研究

采用量子化学密度泛函B3LYP方法,对碱金属、碱土金属和过渡金属石墨层间化合物(A-GIC,AE-GIC和T-GIC)进行计算.从原子净电荷、Mulliken重叠布居和轨道电子数等角度讨论了A-GIC和AE-GIC的电子结构与成键特性,初步阐明了结构与性能的关系.根据计算结果,结合热力学分析,讨论实验上尚未知的过渡金属石墨层间化合物合成的可能性.     

Thermodynamic Analysis of Combustible Formulations Forming Gaseous Metals in Combustion Products

A thermodynamic analysis of the burning temperatures and products formed in combustion of formulations containing zinc or lead was made in relation to the elemental composition and total enthalpy of formation of the starting mixture in order to develop programs searching in the existing database for such formulations whose combustion will produce a prescribed fraction of a metal in gaseous state.     

Behavior of the Concentrate of Rare Platinum Metals in Autoclave Conditions

Russian Journal of Applied Chemistry - Behavior of the concentrate of platinum-accompanying metals in autoclave conditions was studied with the use of various solvents: water and aqueous solutions...     

Electrocrystallization of Metals under Ideal and Real Conditions

Ideal conditions during electrocrystallization, which are only approximately attainable, would lead to a perfect single crystal, whereas real conditions yield a monocrystalline or polycrystalline product containing many structural defects. The electrolytic production of quasi-ideal single crystals requires an overpotential that supplies at least the activation energy necessary for the formation of two-dimensional nuclei, since growth otherwise proceeds via screw dislocations with formation of a “real” crystal. The potential deviation in electrocrystallization under real conditions is due to electrochemical and/or crystallization overpotential, which can be determined separately. The investigation of electrocrystallization also offers possibilities for a systematic study of the formation of imperfections in real crystals.     

Thermodynamic Properties of Aqueous Potassium Sulfate under Superambient Conditions

Using the ion-interaction or virial coefficient approach developed by Pitzer, the pressure dependencies of the osmotic and activity coefficients for K₂SO₄(aq) up to 225°C and 0.65 mol-kg^–1 have been calculated from recent literature data on the apparent molar volumes of K₂SO₄(aq). These pressure dependencies were combined with the osmotic and activity coefficients at 1 bar or P _sat, obtained from the model of Holmes and Mesmer to yield a comprehensive set of thermodynamic properties of K₂SO₄(aq) at temperatures from 25 to 225°C, pressures 100, 200, and 300 bars, and molalities to 0.65 mol-kg^–1.On leave from the     

Thermodynamic Properties of Aqueous Potassium Fluoride under Superambient Conditions

Using the ion-interaction or virial coefficient approach developed by Pitzer, the pressure dependences of the osmotic and activity coefficients for KF (aq.) up to 473.15 K and 2.5.0 mol-kg^-1 have been calculated from literature data for the apparent molar volumes of KF (aq.). These pressure dependencies were combined with the osmotic and activity coefficient at 0.1 MPa or p_sat, obtained from the model of Saluja et al. to yield a comprehensive set of thermodynamic properties for KF (aq.) at temperatures from 298.15 through 473.15 K, pressures 10, 20, and 30 MPa, and molalities to 2.5 mol-kg^-1.     

Siloxane Compounds of the Transition Metals

Heterosiloxanes of transition metals contain the characteristic grouping Si? O? X; in the compounds known so far, X may be Au, Zn, Cd, Hg, Ti, Zr, Hf, V, Nb, Ta, Cr, U, Re, Fe, Co, Ni, or Pt. Most of these compounds are obtained from silanols, metal silanolates, acyloxysilanes, disiloxanes, or alkoxysilanes, i.e. from compounds that already contain an Si? O bond. The transition metal may be introduced e.g. as a halide, as an organometailic compound, as an alkoxy compound, or as an oxide. Heterosiloxanes are also formed on reaction of many silicon compounds that do not contain oxygen with transition metal compounds containing oxygen. Some of these compounds, e.g. some titanosiloxanes, are very stable, whereas others decompose explosively. Oligomeric and polymeric heterosiloxanes exist in addition to the monomeric compounds.     

A Thermodynamic Frame for the Kinetics of Polymer Crystallization under Processing Conditions

A retrospective view is given on work, which has been carried out at the Johannes Kepler University during the last two decades on the structure formation in crystallizable polymers during their processing. Emphasis is laid on some useful principles lend from basic physical chemistry: use of the T,S-diagram and of the temperature dependent courses of (effective) surface tensions along coexistence lines of phases. These considerations should be helpful in creating an overview, where a deficiency of direct experimental crystallization kinetics data exists. For a series of industrially important, mostly fast crystallizing, polymers data are given in the present paper for the quiescent melt (temperature dependences of number densities of nuclei and of growth speeds). Critical minimum cooling speeds for bypassing crystallization are given on the basis of the given data. These critical cooling speeds vary by almost six decades from HDPE to i-PS. These results are also helpful in the formulation of a viable classification of materials in the light of their processing conditions. This classification includes metals and glass forming minerals as limiting cases for extremely fast and extremely slowly crystallizing materials.     

A Thermodynamic Frame for the Kinetics of Polymer Crystallization under Processing Conditions

Summary. A retrospective view is given on work, which has been carried out at the Johannes Kepler University during the last two decades on the structure formation in crystallizable polymers during their processing. Emphasis is laid on some useful principles lend from basic physical chemistry: use of the T,S-diagram and of the temperature dependent courses of (effective) surface tensions along coexistence lines of phases. These considerations should be helpful in creating an overview, where a deficiency of direct experimental crystallization kinetics data exists. For a series of industrially important, mostly fast crystallizing, polymers data are given in the present paper for the quiescent melt (temperature dependences of number densities of nuclei and of growth speeds). Critical minimum cooling speeds for bypassing crystallization are given on the basis of the given data. These critical cooling speeds vary by almost six decades from HDPE to i-PS. These results are also helpful in the formulation of a viable classification of materials in the light of their processing conditions. This classification includes metals and glass forming minerals as limiting cases for extremely fast and extremely slowly crystallizing materials.     

The Effect of Oxygen Impurities on the Formation of Intercalated Compounds of Graphite with an Ultrahigh Content of Alkali Metals under Mild Conditions

A fundamentally new interpretation is proposed for the mechanism of the effect of small amounts of oxygen [and also, probably, other elements (S, Se, As, P)] on the formation of ultradense modifications of intercalated compounds of alkali metals with graphite. It was shown by the semiempirical AM1 self-consistent field method that the formation of the intercalated compounds of graphite of such a type must begin with partial oxidation of the edge carbon atoms in the graphene layers and the formation of the corresponding phenolate and carboxylate groups [and in the presence of other elements (S, Se, As, P) the corresponding "edge" sulfides, phosphides, selenides, or arsenides].     

质子转移反应质谱在线检测痕量挥发性有机物

质子转移反应质谱是近年来兴起的一种痕量挥发性有机物在线检测技术,它可以在秒量级的时间内获得ppt量级的探测灵敏度,已经广泛的应用在环境污染监测、医学诊断、食品成分和质量检验等领域。本文介绍了它的工作原理和装置结构,给出了一些痕量挥发性有机物检测的例子,以及作者实验室使用该技术检测挥发性有机物的初步研究结果,并对该在线检测技术的发展方向进行了展望。     

钯催化下活性亚甲基化合物的烯丙基化相转移反应

钯催化下活性亚甲基化合物的烯丙基化反应在有机合成中是一种十分有用的方法。例如在双三苯基膦二氯化钯催化下丙二酸二乙酯、α-砜基乙酸乙酯等活性亚甲基化     

Gasification of Powdered Solid Fuel in the Filtration Combustion Mode

A new procedure for gasification of powdered solid fuel in a flow of a gaseous oxidant in the course of filtration of the mixture through an inert packing was suggested and tested. This procedure allows the productive capacity of a single reactor to be increased owing to acceleration of the reactions, i.e., to an increase in the reaction surface area with a decrease in the fuel particle size. As shown in cold (without ignition) experiments, the powdered fuel was partially accumulated in the inert porous packing, which led to the pressure buildup in the reactor. In gasification experiments with ignition, the powdered fuel was not accumulated in the reactor if the temperature in the fuel feeding zone was no less than 500°С. In this case, the linear velocity of the gas increased owing to thermal expansion, and this velocity was sufficient for the coal particles fed to the reactor to be entrained by the flow.