HREM studies of the structure and the oxidation process of copper clusters created by inert gas aggregation

Structure and reactivity with oxigen of Cu clusters in the size range of 4.5±2.5 nm created by the inert gas aggregation technique were studied by HREM. The pure Cu clusters investigated under clean conditions show the structures of MTP's with a small lattice dilatation of the (111) plane of 1.25%. For icosahedral and decahedral particles this dilatation corresponds to a splitting of the nearest neighbour distance showing two different values, i.e. dilatation of 2.2% and contraction of 2.8% for the two edges of the deformed tetrahedral subunits, respectively. Oxidation at room temperature and air pressure of 1 bar only begins after a few minutes of exposure to air, after having undergone creation of probably non-stoichiometric intermediate states in the cuprite Cu₂O structure with the bulk values of the bond lengths.     

Size consistency in the dilute helium gas electronic structure

A new formula for correcting a double-excitation Cl result for the effects of higher excitations is suggested. The correct form of the effective hamiltonian for a coupled-electron-pair-approximation is discussed for a dilute gas of helium atoms.     

Ceramics with mayenite structure: Molecular sieve for helium gas

It was found that mayenite {ie536-1} has selective transmission of helium gas, which is associated with its unique structural features. The permeability of helium through mayenite is (16.5–17.0) × 10^?8 cm² s^?1 Pa^?1.     

Calculation of diatomic van der Waals systems inert gas Atom-Halogen type inert gas ion in the ground state

Interatomic potentials are calculated for the systems inert gas ion in the ground state-inert gas atom Ne⁺, Xe⁺ -Ne, Ar, Kr, Xe, Fr. The calculation is performed by the effective pseudopotential method using the new form of the polarization interaction potential obtained by calculating the most important polarization diagrams of perturbation theory in the Thomas-Fermi approximation. The quasimolecular states of these van der Waals systems are calculated to refine the available data; some data are obtained for the first time. Translated fromZhumal Strukturnoi Khimii, Vol. 39, No. 4, pp. 591–595, July–August, 1998.     

The velocity distribution of clusters generated by inert gas condensation

The velocity distribution of sodium chloride clusters produced by inert gas condensation is determined by means of a mechanical chopping technique. It is found to be the same for all cluster sizes between 1 and more than 200 molecular units per cluster, ruling out the possibility of cluster mass separation by velocity filters. This is explained by an adiabatic expansion occuring during the cluster's exit from the condensation chamber into the high vacuum of the mass spectrometer.     

Measurement of the composition of gas desorbed from coal by gas chromatography

Summary Direct methods for the determination of the gas content of a coal seam are based upon extracting a coal sample, enclosing it in a sealed container and measuring the volume of the gas evolved. In our work we measured evolved gas as a function of time, type and quantity of low rank coal (lignite) at normal (atmospheric pressure and temperature) conditions. The evolved gas was, collected in gas sampling bags and analyzed by GC for its main components (carbon dioxide, methane and dimethyl sulfide). From the parameters obtained (gas volume, CH₄:CO₂ ratio, rate of gas desorption, time concentration profile and different lithotypes of lignite) a more detailed identification of hazardous areas in underground coal extraction could be ensured. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997.     

Application of reflectance micro-infrared spectroscopy in coal structure studies

Fourier transform infrared micro-scale analysis of organic matter has been applied to characterise individual petrographic components of coal. The use of an infrared microscope made it possible to study and compare different parts of a single individual grain of vitrinite. This method enables analysis of particular macerals without the need for previous separation from coals. For this purpose the polished grainy micro-sections of coal have been prepared. The results obtained indicated the progression of aromatisation in the vitrinite structure with an increase of coalification degree of the parent coals.     

Molecular-dynamics study of the density scaling of inert gas condensation

The initial stages of vapor condensation of Ge in the presence of a cold Ar atmosphere were studied by molecular-dynamics simulations. The state variables of interest included the densities of condensing vapor and gas, the density of clusters, and the average cluster size, while the temperatures of the vapor and the clusters were separately monitored with time. Three condensation processes were explicitly identified: nucleation, monomeric growth, and cluster aggregation. Our principal finding is that both the average cluster size and the number of clusters scale with the linear dimension of the computation cell, L, and Ln, with the scaling parameter n approximately 4, corresponding to a reaction order of nu approximately 2.33. This small value of n is explained by an unexpected nucleation path involving the formation of Ge dimers via two-body collisions.     

Rapid analysis of hydrocarbons and inert gases by a multidimensional gas chromatograph

A combination of a pressure switching system with multiple columns and photoionization detectors makes possible rapid analysis of a mixture of inorganic gases and hydrocarbons. Hydrocarbons are separated by a narrow bore capillary column. An alumina PLOT column is used for the separation of lower molecular weight hydrocarbons, especially C4 isomers, while a combination of a micro-packed column with Porapak N and a PLOT capillary column with Molecular Sieve 5A is used for the fast separation of inorganic gases. A photoionization detector is a powerful additional tool for organic gas analysis.     

On the theory of intermolecular forces between inert gas atoms

The method described by Gordon and Kim and modified by Rae has been further modified to restrict the self-exchange correction to an electron gas composed of the outer shell electrons. Revised results are presented for the interaction potentials between various pairs of inert gas atoms.     

Spectroscopy of large molecules in inert gas clusters

Aromatic hydrocarbons provide nucleation centers for the formation of clusters of inert gases in high-flow supersonic beams. Large clusters of Ar, each containing a single tetracene (T) molecule, were prepared by supersonic expansion of the seeded gas at pressures p = 3000–13000 Torr and interrogated by laser-induced fluorescence spectroscopy Evidence is reported for homogeneous line broadening of large TAr_n clusters prepared at p? 8000 Torr.     

Analysis of amine compounds by capillary gas chromatography using ammonia–helium carrier gas

The use of 10%, 1%, and 0.1% ammonia in helium as carrier gas was investigated as a means of improving poor chromatographic peak shape often associated with low level determinations of amine compounds using thin film capillary columns. The 1% ammonia in helium was found suitable for improving the peak shape of sterically unhindered amine compounds, such as urethane and certain aliphatic primary amines, during gas chromatographic analysis on thin film columns. There was a negligible effect on the peak tailing arising on thick film columns. The 0.1% ammonia in helium was suitable, but not as efficient as the 1% ammonia in helium, in eliminating the peak tailing associated with low level analysis of amine compounds. The signal-to-noise (S/N) ratio improved from < 1 using helium carrier gas to 20–25 (for certain test amine compounds) using 1% ammonia in carrier gas. The 10% ammonia in helium carrier gas had an effect on the chromatographic performance similar to that of the 1% ammonia in helium, but the baseline level was very high and this mixture was not used in further studies.     

Effects of inert gas CO2/N2 injection on coal low-temperature oxidation characteristic: Experiments and simulations

To deeply understand the mechanism of inert gases in inhibiting coal spontaneous combustion, the effects of dry air, CO₂, and N₂ on coal spontaneous combustion were analyzed experimentally. To this end, bituminous coal prepared from Dongrong No. 2 Coal Mine was considered the research object. Based on the adsorption configuration of the oxygen-containing coal, the displacement behavior of O₂ by CO₂ /N₂ was studied using the grand canonical Monte-Carlo (GCMC) and molecular dynamics (MD) methods. The obtained results show that the injection of CO₂ and N₂ reduces the ability of spontaneous combustion of coal. It is found that among the studied gases, CO₂ has a stronger inhibition effect on coal spontaneous combustion, which increases the temperature of CO occurrence by 5℃, decreases the concentration of CO by 29.91%, and inhibits low-temperature oxidation of coal. From the microscopic point of view, CO₂ /N₂ gases can effectively displace O₂ by diffusion and occupying adsorption sites. It is found that after the injection of CO₂, the concentration of O₂ molecules increases significantly in the vacuum layer. Compared with N₂, injection of CO₂ increases the diffusion activation of O₂ by 5.89%. This indicates that the injection of an inert gas significantly reduces the oxygen absorption capacity of coal, thereby decreasing the coal-oxygen combination reaction and preventing the spontaneous combustion of coal. The performed analyses demonstrate that CO₂ outperforms N₂ in restraining the spontaneous combustion of coal.     

惰气熔融-红外吸收光谱法测定镧铈稀土钢中氧含量

高品质稀土钢要求进行精确低氧含量控制,而依据现有GB/T11261-2006标准进行氧含量测定,检测结果具有较大的不准确性。本研究以具有不同镧、铈稀土元素含量的稀土钢为对象,以其氧含量精确测定为目标,基于惰气熔融-红外吸收法,开展了分析功率、助熔剂和称样量对镧铈稀土钢中氧含量分析结果的影响研究。结果表明,对于不同镧、铈元素含量的稀土钢,需要采用不同的分析方法：当稀土钢中的镧、铈含量较低时,通过降低分析功率即可较为精确的测定稀土钢中的氧含量;对于镧、铈含量较高的稀土钢,在调控分析功率（分析功率在4000W～4500W）的基础上,需同时采用锡作为助熔剂,并将助熔剂与样品比例设定为1:1（称样量为0.3g～0.6g）,即可实现氧含量的精确测定。精密度验证实验结果显示,采用本研究所建立的方法,氧含量测试结果相对标准偏差（RSD）小于8.0%;采用钢标样进行回收率实验,回收率值在97%～108%,而加标回收率略有升高的原因在于助熔剂Sn降低了合金熔点,使少量难熔氧化物中的氧得到更充分释放。本研究所建立的分析方法可准确测定不同镧、铈元素含量稀土钢中的氧含量。     

Complex-coordinate studies of helium autoionizing resonances

Several aspects of the numerical application of the complex-coordinate method for calculating helium autoionizing resonances are discussed. A direct-search algorithm is used to locate resonance eigensolutions that satisfy the virial theorem, and the influence of the basis set on the accuracy of the calculated positions and widths is investigated. The complex-coordinate method is related to the stabilization method of Holøien and Midtdal.     

The Vapour Pressure and the Enthalpy of Sublimation: Determination by inert gas flow method

A new device, based on the inert gas flow method, for measuring the vapour pressure and the determination of the enthalpy of sublimation in a wide range of temperatures (up to 573 K) is described in this paper. The limits of the flow rate as important experimental parameter were determined for the given instrument. The results of calibration showed a good precision and reproducibility of the measurements of the enthalpy of sublimation. The results of the determination of some derivatives of pyrimidine were presented.This revised version was published online in November 2005 with corrections to the Cover Date.     

Self-association of N-methyltrifluoromethanesulfonamide in the gas phase and in inert solvents

IR spectroscopy and quantum-chemical calculations (B3LYP/6-31G*) were used to show that N-methyltrifluoromethanesulfonamide in the gas phase and in a low-polarity inert solvent (CCl₄) exists as an equilibrium mixture of monomers and cyclic dimers. In a more polar solvent (CH₂Cl₂), highly polar open-chain dimers are stabilized.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1659–1664.Original Russian Text Copyright © 2004 by Chipanina, Sherstyannikova, Turchaninov, Shainyan.This revised version was published online in April 2005 with a corrected cover date.