Kinetics and Mechanism of Nanostructures in Oxidation of Si1—xGex Alloys

We investigate the oxidation behaviour of Si1-xGex alloys(x=0.05,0.15,and 0.25),The oxidation of SiGe films with different compositions was carried out in O2(dry)atmosphere at 800,900 and 1000℃,respectively,for various lengths of time,The thickness and property of the nanoparticle and nanolayer in oxide films and germanium segregation in oxidation of SiGe alloys are measured by using a high precision ellipsometer.The results are in good agreement with the Rutherford backscattering spectrometry,profile dektak instrument and high-resolution scanning transmission electron microscopy.We found that the Ge content in the oxide layer increases with the Ge content in SiGe alloys,and that the Ge content in the oxide film decreases with the increasing oxidation temperature and time,Rejection of Ge results in Piling up of Ge at the interface etween the growing SiO2 and the remaining SiGe,which forms a nanometre Ge-rich layer.Substantial interdiffusion of Si and Ge takes place in the remaining SiGe,which leads to the complicated distribution of Ge segregation.We find a nanometre cap layer over the oxide film after fast oxidation,in which there are many Ge nanoparticles,We analyse the kinetics and mechanism of the nanostructure of the oxide and Ge segregation in oxidation of Si1-xGex alloys.     

Kinetics of ß-phase transformation in the heat treatment of FeSi2- and Fe2Si5-based thermoelectric alloys

FeSi₂- and Fe₂Si₅-based thermoelectric alloys have been fabricated by melt spinning and levitation melting. It was found that the levitation-melted FeSi₂-based alloy must be annealed at 800°C for 10 h to complete transformation of the β phase, while an anneal for only 6 h was needed for the melt-spun alloy. On the other hand, annealing the levitation-melted Fe₂Si₅-based alloy for 4 h was enough to complete β-phase formation, whereas 14 h was required for the melt-spun alloy. Annealing temperature dependence of the Seebeck coefficient showed that the maximum rate of transformation to β phase occurred at about 800°C for all samples. Application of the Johnson-Mehl-Avrami equation revealed that grain-boundary nucleation was predominant in the levitation-melted FeSi₂-based alloy (time exponent n = 1.1), while the zero nucleation mechanism was operative in the melt-spun alloy (n = 3.1). For the eutectoid reactions in the Fe₂Si₅-based alloys, several kinds of nucleation site were active. However, nuclei formed at grain edges were dominant in the melt-spun alloy since n = 1.6.     

Rotational and Vibrational State Distributions of CsH and Relative Reactivity in Reactions of Cs（6^2D,7^2D） with H2

By using a pump-probe technique, the nascent rotational and vibrational state distributions of CsH are obtained in the Cs（6^2 D,7^2 D） plus H2 reaction. The nascent CsH molecules are found to populate the lowest two vibrational （v″ = 0 and 1） levels of the ground electronic state. By comparing the spectral intensities of the CsH action spectra with those of pertinent Cs atomic fluorescence excitation spectra, the relative reactivity with 1-12 is in an order of6^2D3/2 〉 6^2D5/2 〉 7^2D3/2 〉 7^2D5/2. The rotational temperatures are found to be slightly below the cell temperature. The relative fractions （〈fV〉, 〈fR〉, 〈fT〉） of average energy disposal are derived as （0.2,0.12,0.68）, （0.2,0.12,0.68）, （0.07,0.04,0.89） and （0.07,0.04,0.89） for the 6^2D3/2, 6^2D5/2, 7^2D3/2 and 7^2D5/2, respectively. The major available energy is released as translation. These results support that the reaction mechanism of Cs（6^2 D,7^2 D） plus 112 is primarily a eollinear abstraction and not an insertion.     

A Quantum Monte Carlo Study on Mixed-Spin Chains of 1／2-1／2-1-1 and 3／2-3／2-1-1

The ground-state and thermodynamic properties of quantum mixed-spin chains of 1/2-1/2-1-1 and 3/2-3/2-1-1 are investigated by a quantum Monte Carlo simulation with the loop-cluster algorithm. For 1/2-1/2-1-1 chain, we find it hastwo phases separated by an energy-gap vanishing point in the ground-state. For 3/2-3/2-1-1 chain,the numerical results show two energy-gap vanishing points isolated by different phases in its ground-state. Our calculations indicate that all these ground state phases can be understood by means of valence-bond-solid picture, and the thermodynamic behavior at finite temperatures is continuous as a function of parameter α=J2/J1.     

Kinetics of A1 ↔ B2 phase transformations in Cu-Pd alloys

The effect of different initial states on the kinetics of formation of an ordered structure in the Cu-Pd alloys with palladium contents of 47, 49, 50, and 55 at % is studied. The activation energy of atomic ordering in an equiatomic CuPd alloy after severe plastic deformation has been estimated. A nearly single-phase ordered B2-type state in the Cu-49 at % Pd and Cu-50 at % Pd alloy has been achieved. For this phase state of the alloys, the lowest reported room temperature resistivity has been achieved. The temperature boundaries of phase transformations in the investigated Cu-Pd alloys are found to be in contradiction with the generally accepted phase diagram.     

Analysis of the 1S and 2S states of AQ and ΘQ with QCD sum rules

In this article,we study the ground states and the first radial excited states of the flavor antitriplet heavy baryon states AQ and ΘQ with the spin-parity JP =...     

Collisional Reactions of Energetic Methane Molecules with Single-Walled Carbon Nanotubes

We study the collisions of energetic methane molecules with single-walled carbon nanotubes in the incident energyrange from 5 to 100 eV using classical molecular dynamics simulations combined with ab initio calculations. Themethane molecules can be decomposed into different hydrocarbon radicals, e.g. CHn (n = 1-3), in the collisionsdepending on the incident energy. Chemical functionalization of the single-walled carbon nanotubes resulting fromthe chemical adsorption of these hydrocarbon radicals on the outside wall of single-walled carbon nanotubes canbe achieved simultaneously. Some stable adsorption configurations of hydrocarbon-functionalized single-walledcarbon nanotubes are also presented based on ab initio calculations.     

Kinetics of isothermal decomposition of unirradiated and γ-irradiated zirconium acetylacetonate

In this study, isothermal decomposition of unirradiated and γ-irradiated zirconium acetylacetonate Zr(acac)₄ using 10³ kGy absorbed γ-ray dose was carried out in static air. The isothermal operating temperatures were selected to be 150, 170, 190 and 210°C. The kinetics of the decomposition were followed using both model-fitting and model-free approaches. The results of the model-fitting approach with regard to the investigated data showed that the decomposition behaviour was best described by a first-order (F1) reaction model. The analysis of the data using the model-free approach signified the dependency of activation energy E _a on the extent of conversion (α). Pre-γ-irradiation of zirconium acetylacetonate Zr(acac)₄ with 10³ kGy absorbed γ-ray dose had no significant effect on the thermal decomposition behaviour of Zr(acac)₄. The thermodynamic and kinetic parameters of the decomposition process were calculated and evaluated.     

Azo-hydrazo Tautomerism and Inclusion Complexation of 1-phenylazo-2-naphthols with Various Solvents and β-cyclodextrin

Spectral characteristics of sudan I (SDI), sudan II (SDII) and mordant violet-5 (MV5) have been studied in various solvents and β-cyclodextrin (β-CD). The inclusion complex of the above molecules with β-CD was analyzed by UV-visible, fluorometry, and DFT methods. The solvent study shows that azo-hydrazo tautomer is present in these molecules. The increase in the fluorescence intensity and a large bathochromic shift in the S₁ state indicate these molecules forms 1:1 inclusion complex with β-CD.     

Correction to: Design,fabrication, and characterization of thermal and optical properties of nano‑composite self‑cleaning smart window

Optical and Quantum Electronics - Optical properties of polymerized polyethylene layers deposited on glass substrates by PECVD technique at different radio frequency powers are studied through...     

Spectrophotometric Determination of Trace Amounts of Cobalt and Copper with 3- (2′-Thiazolylazo)- 2,6- Diaminopyridine

Abstract

Sensitive methods for the determination of trace amounts of cobalt and copper by complexation with 3-(2′-Thiazolylazo)-2,6- diaminopyridine (2,6-TADAP) are described. Copper forms a 1:2 violet complex with the reagent having a molar absorptivity of 1.00 × 10⁴ L mol^?1cm^?1, Baer's law is obeyed over the range 0 ?50.84 μg in the total volume of 10ml. Cobalt also forms a 1:1 green complex with a molar absorptivity of 1.07 × 10⁴L mol^?1cm^?1 and obeying Beer's law over the range 0 –23.57 μg in the total volume of 10 ml. The procedure is simple and rapid without any tedious extraction steps for copper and without oxidation of cobalt (II) to cobalt (III).     

Kinetics of energy deactivation in the O2(1Δ)-I medium

The kinetics of energy-exchange and quenching processes in the O₂(¹Δ)-I medium plays an important role in the operation of the chemical oxygen-iodine laser. However, up to now, many of the key processes in this medium are not fully understood. In this work, the flow tube technique is used to determine the rate of excitation energy deactivation in the O₂(¹Δ)-I medium in the presence of small concentrations of water and carbon dioxide. The concentrations of electronically excited species are measured with spectrometers calibrated in absolute spectral responsivity. The effective rate constant for the deactivation of O₂(¹Δ) molecules in processes involving iodine atoms is determined. The results are compared to those obtained in previous works.     

The Reactions of Nickel ion with n-Alkane in the Gas Phase

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Kinetics and dynamics of the S(1D2) + H2 → SH + H reaction at very low temperatures and collision energies

We report combined studies on the prototypical S(1D2) + H2 insertion reaction. Kinetics and crossed-beam experiments are performed in experimental conditions approaching the cold energy regime, yielding absolute rate coefficients down to 5.8 K and relative integral cross sections to collision energies as low as 0.68 meV. They are supported by quantum calculations on a potential energy surface treating long-range interactions accurately. All results are consistent and the excitation function behavior is explained in terms of the cumulative contribution of various partial waves.     

Crystallization Kinetics of Linear and Long‐Chain Branched Polypropylene

Isothermal crystallization kinetics of linear polypropylene (PP) and long‐chain branched (LCB) PPs were investigated on the basis of the Avrami theory. The Avrami exponents of LCB PPs are smaller than that of linear PP; moreover, they decrease with an increasing LCB level. The crystallization half‐time of LCB PP depends more strongly on the crystallization temperature than does that of linear PP. The Lauritzen‐Hoffman theory was used to study the effect of LCB on the crystal growth rate of PP. The fold surface free energy of LCB PP is lower than that of linear PP; moreover, it decreases with an increasing LCB level. However, when the LCB level is over a certain value, the fold surface free energy increases again. Furthermore, the crystal structures of linear PP and LCB PPs were studied by wide‐angle X‐ray diffraction (WAXD); it was observed that linear PP can crystallize in the α and β forms, while LCB PPs have only the α crystalline form. Moreover, the relative intensities of different α peaks were also influenced by the LCB level.     

Reactions of COO− radical-ion with M+ and M3+ states produced in the radiolysis of aqueous solutions

Pure nickel and lithium-implanted nickel were irradiated with 1 MeV electrons at the Argonne HVEM-Tandem facility. The lithium-implanted nickel was not damaged as readily as the pure nickel under 1 MeV electron irradiation in the temperature range 20–600°C. The decreased damage accumulation in the lithiated nickel could arise from both the precipitated lithium and that in solution. The latter could slow down the nickel interstitials produced during irradiation by association, thus enhancing their recombination with vacancies. The interfaces of the precipitated lithium could also act as unbiased sinks for the vacancies and interstitials. Above 600°C, under electron irradiation, a melting process which created small irregular shaped regions occurred in the lithium-implanted nickel. Electron diffraction analysis showed that the compound Li₂NiO₂ was formed inside these regions.     

Interaction of 1-(β-oxyethyl)-2-methyl-5-nitroimidazole with the surface of highly dispersed silica

Using the IR spectroscopy method, it has been established that formation of a monolayer 1-(β-oxyethyl)-3-methyl-5-nitroimidazole (metronidazole) on the surface of nonporous amorphous highly dispersed silica (S_sp = 230 m²/g) occurs during its absorption in an amount of 0.6 mmole/g. Such a content of adsorbate corresponds to the concentration of free silanol groups that are main active centers of the surface. Based on the analysis of the IR spectra of the specimens obtained and the dependence of the degree of perturbation of silanol groups on the content of adsorbed metronidazole, the structure of the surface adsorption complexes is suggested. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 717–721, November–December, 2005.     

Kinetics of 1H→13C NMR cross-polarization in polymorphs and solvates of the antipsychotic drug olanzapine

The (1)H→(13)C NMR cross-polarization (CP) was studied under magic-angle spinning at 7.5 kHz in various crystal forms of the antipsychotic drug olanzapine: two polymorphs (metastable I and stable II) and eight solvates containing organic solvent and water molecules. The CP kinetics followed the non-classical I-I(*)-S model, in which CP begins in a spin cluster of proximate abundant spins I(*) and rare spins S, then is controlled by spin diffusion of the abundant spins I from bulk to the I(*) spins of the spin cluster and finally is governed by spin-lattice relaxation of the abundant spins in the rotating frame. The corresponding CP kinetics parameters were determined and analyzed. It was demonstrated that the, λ and T(df) values (the CP time constant, the cluster composition parameter and the (1)H spin-diffusion constant, respectively) were very useful to discriminate the functional groups, especially in the 3D parameter space. In order to conveniently analyze the large amount (175) of the collected CP parameters, the number of the observed variables was reduced using the principal component (PC) analysis. The 2D plot of PC2 vs. PC1 showed adequate separation of the CH(3), CH(2), CH and C cases (C stands for carbons without adjacent hydrogens). It was demonstrated that those cases were located along the PC1 axis in the order of increasing (1)H-(13)C dipolar couplings: C相似文献