电子对Cl2的离解附着

在电子平均能量为3—5电子伏的范围内,测定了Ar/Cl₂混合物中,电子对Cl₂的离解附着速率常数。结果表明,电子平均能量为3.5电子伏时,离解附着速率常数为(3.2±0.4)×10^-10厘米³/秒,并考察了速率常数与电子平均能量的关系。这些实验结果与最近Los Alamos国家实验室研究者们的类似工作的结果是一致的。 关键词：     

电子对Cl_2的离解附着

在电子平均能量为3—5电子伏的范围内,测定了Ar/Cl_2混合物中,电子对Cl_2的离解附着速率常数。结果表明,电子平均能量为3.5电子伏时,离解附着速率常数为(3.2±0.4)×10~(-10)厘米~3/秒,并考察了速率常数与电子平均能量的关系。这些实验结果与最近Los Alamos国家实验室研究者们的类似工作的结果是一致的。     

基于全维高精度势能面对H+SO_2→OH+SO反应的动力学研究（英文）

H+SO_2→OH+SO反应在燃烧、大气和星际化学中都扮演着重要角色.它还是具有深势阱中间体形成的典型反应,是检验速率理论和提供有趣反应动力学现象的理想候选反应.基于之前构建的全维高精度势能面,本文对该反应进行了准经典动力学研究.在1400 K≤T≤2200 K的温度范围内,计算值重现了实验速率常数.当反应物SO_2处于振-转基态,在31.0～40.0 kcal/mol的碰撞能范围内,计算得到的积分反应截面随碰撞能增加;在40.0～55.0 kcal/mol的碰撞能范围内,积分反应截面几乎不受碰撞能影响.产物角度分布呈现对称的前后向双峰结构.本文还分析了产物OH和SO的振动态分布.     

H+Li2: 一个典型的释能反应体系及其含时动力学研究

利用含时量子波包动力学理论在HLi₂ 基态势能面上研究了H+Li₂ → LiH+Li 反应的动力学性质. 计算得到了体系在0-0.4 eV 范围内J = 0 不同振动量子数(v = 0, 1, 2, 3), v = 0 不同转动量子数(J = 0, 5, 10,15) 下的反应概率、积分反应截面和热速率常数, 在此基础上讨论了释能反应的反应阈能随总角动量量子数的变化规律以及振动量子数对反应概率的影响等问题. 研究发现, 随着转动量子数的增大, 反应阈能也在逐渐增大; 然而随着振动量子数的增大, 由于反应为释能反应, 反应发生的概率却在逐渐减小. 分析了碰撞能对积分散射截面的影响以及温度对反应速率常数影响的规律.     

基于全维高精度势能面对H+SO2→OH+SO反应的动力学研究

H+SO₂→OH+SO反应在燃烧、大气和星际化学中都扮演着重要角色. 它还是具有深势阱中间体形成的典型反应,是检验速率理论和提供有趣反应动力学现象的理想候选反应. 基于之前构建的全维高精度势能面,本文对该反应进行了准经典动力学研究. 在1400 K≤T≤2200 K的温度范围内,计算值重现了实验速率常数. 当反应物SO₂处于振-转基态,在31.0∽40.0 kcal/mol的碰撞能范围内,计算得到的积分反应截面随碰撞能增加;在40∽55 kcal/mol的碰撞能范围内,积分反应截面几乎不受碰撞能影响. 产物角度分布呈现对称的前后向双峰结构. 本文还分析了产物OH和SO的振动态分布.     

H_2O分子在HONO+OH→NO_2+H_2O反应中的催化机制研究

本文采用CCSD(T)-F12a/cc-p VDZ-F12//M06-2X/6-311+G(2df,2p)方法并结合过渡态理论对HONO+OH→H_2O+NO_2抽氢反应以及H_2O参与该反应的微观机理和速率常数进行了理论研究.结果表明,由于复合物HONO…H_2O的高浓度和稳定性,我们预测HONO…H_2O+OH反应的大气相关性将比H_2O…HONO+OH和H_2O…OH+cis-HONO明显得多.进一步的速率常数计算结果表明,cisHONO…H_2O+OH反应的速率常数比H_2O…cis-HONO+OH和H_2O…OH+cis-HONO反应大了8～4个数量级.然而,cis-HONO…H_2O+OH反应的有效速率常数比无催化剂主反应cis-HONO+OH低了7～3个数量级.表明在实际大气环境中,H_2O对HONO+OH反应的催化效果并不明显.     

圆筒内氢等离子体非定常化学反应羽流场DSMC分析

利用直接模拟Monte Carlo方法研究圆筒侧壁注入氢等离子体羽流场在8×10^-6s内的非定常流动特性.根据Bird的化学反应模型考虑离解-复合反应模型和电荷转移反应模型.在流场中注入H₂、H、金属原子X、H₂⁺和H⁺五种组分,研究离解-复合反应对流场中粒子分布和密度的影响,结果表明离解-复合反应使H₂数密度降低,H数密度增加,说明在流场中H₂的离解反应速率大于H的复合反应速率.加入电荷转移反应后H₂⁺数密度降低,H⁺数密度增加,对其他组分数密度没有显著影响.     

复合胺砜溶液吸收CO_2传质动力学研究

利用湿壁塔法测量复合胺砜溶液吸收CO_2的动力学特性,实验工况包括不同的反应温度(293.15～323.15 K)和不同的溶液浓度(0.5～6.6 mol/L)。本文简化了气液传质模拟,计算了不同工况下的吸收速率常数、总反应速率常数、二级反应速率常数及增强因子等动力学参数,同时根据实验结果拟合得到了二级反应速率常数和增强因子的经验公式,并得到了复合胺砜溶液与CO_2反应的表观反应活化能为为20.38 kJ/mol。     

碰撞诱导离解(CID)(Ⅱ) I_2(B~3∏_(o+u))在高振动态(v''''=62)的碰撞猝灭机理实验研究

本文研究了B~5∏_(o+u)激发态I_2分子在高振动态v=62时的碰撞猝灭过程。实验中得到了该能级I_2分子和其自身以及与其他气体分子(He,Ar,Kr,H_2,CO,N_2,O_2,CH_4,NH_3,C_2H_6,CCl_4)的碰撞猝灭速率常数,并且发现,在I_2与NH_3的碰撞过程中非稳态中间体的形成可能是碰撞猝灭的主要途径之一。极性分子CO与I_2碰撞的猝灭效率较非极性分子(如与之等电子的N_2)大,表明分子间偶极-诱导偶极相互作用对促进分子反应起着不可忽视的作用。更为重要的是,文献[2]中提出的分子碰撞诱导离解(CID)理论能较圆满地模拟实验结果,说明在此高振动能态,分子碰撞直接离解是猝灭过程的主要途径。     

CH3+NO的反应机理和动力学研究

在G2(B3LYP/MP2/CC)理论水平上研究了CH3自由基与一氧化氮分子(NO)的反应.计算了反应体系最低势能面上各驻点的构型参数、振动频率和能量,全面研究了此反应的反应机理及各个可能的反应通道;利用多通道TST RRKM理论计算了300～2500K的总包反应速率常数的温度效应、压力效应和各反应通道的分支比.详细讨论了活化分子碰撞失活对反应速率的贡献,计算结果和实验数据符合得较好.     

Homogeneous ignition of CH4/air and H2O and CO2-diluted CH4/O2 mixtures over Pt; an experimental and numerical investigation at pressures up to 16 bar

The homogeneous ignition of CH₄/air, CH₄/O₂/H₂O/N₂, and CH₄/O₂/CO₂/N₂ mixtures over platinum was investigated experimentally and numerically at pressures 4 bar p 16 bar, temperatures 1120 K T 1420 K, and fuel-to-oxygen equivalence ratios 0.30 0.40. Experiments have been performed in an optically accessible catalytic channel-flow reactor and included planar laser induced fluorescence (LIF) of the OH radical for the determination of homogeneous (gas-phase) ignition and one-dimensional Raman measurements of major species concentrations across the reactor boundary layer for the assessment of the heterogeneous (catalytic) processes preceding homogeneous ignition. Numerical predictions were carried out with a 2D elliptic CFD code that included elementary heterogeneous and homogeneous chemical reaction schemes and detailed transport. The employed heterogeneous reaction scheme accurately captured the catalytic methane conversion upstream of the gaseous combustion zone. Two well-known gas-phase reaction mechanisms were tested for their capacity to reproduce measured homogeneous ignition characteristics. There were substantial differences in the performance of the two schemes, which were ascribed to their ability to correctly capture the p–T– parameter range of the self-inhibited ignition behavior of methane. Comparisons between measured and predicted homogeneous ignition distances have led to the validation of a gaseous reaction scheme at 6 bar p 16 bar, a pressure range of particular interest to gas-turbine catalytically stabilized combustion (CST) applications. The presence of heterogeneously produced water chemically promoted the onset of homogeneous ignition. Experiments and predictions with CH₄/O₂/H₂O/N₂ mixtures containing 57% per volume H₂O have shown that the validated gaseous scheme was able to capture the chemical impact of water in the induction zone. Experiments with CO₂ addition (30% per volume) were in good agreement with the numerical simulations and have indicated that CO₂ had only a minor chemical impact on homogeneous ignition.     

Electrical conductivity and chemical diffusion in Perovskite-type proton conductors in H2-H2O gas mixtures

The electrical conductivities of SrZr_0.9Y_0.1O_3-δ (SZY10) and BaCe_0.95Y_0.05O_3-δ(BCY5) were measured as a function of hydrogen partial pressure P(H₂), oxygen partial pressure P(O₂), steam partial pressure P(H₂O) and temperature. Their relaxation processes were analyzed using the solution of Fick's diffusion equation to determine the chemical diffusion coefficients and surface reaction rate constants. There were the differences in chemical relaxation kinetics and the conductivity dependence on P(H₂O) between the both oxides. The chemical diffusion coefficients depend on temperature but are essentially independent of P(H₂), P(O₂) and P(H₂O). The ambipolar diffusion treatment can explain the temperature dependence of chemical diffusion coefficients quantitatively. The chemical diffusion coefficients of SZY10 is one or two order of magnitude smaller than those of BCY5 at low temperature. The sluggish conductivity relaxation in SZY10 was due to considerably small oxygen vacancy diffusion coefficients at low temperatures. The total conductivity depends on P(H₂O) in the case of SZY10, but not for BCY5. This different dependence on P(H₂O) is caused by the difference in the ratio between proton mobility and oxide-ion mobility.     

Chemical etching investigation of polycrystalline p-type 6H-SiC in HF/Na2O2 solutions

In this work, an experimental study on the chemical etching reaction of polycrystalline p-type 6H-SiC was carried out in HF/Na₂O₂ solutions. The morphology of the etched surface was examined with varying Na₂O₂ concentration, etching time, agitation speed and temperature. The surfaces of the etched samples were analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) Fourier transform infrared spectroscopy (FT-IR) and photoluminescence. The surface morphology of samples etched in HF/Na₂O₂ is shown to depend on the solution composition and bath temperature. The investigation of the HF/Na₂O₂ solutions on 6H-SiC surface shows that as Na₂O₂ concentration increases, the etch rate increases to reach a maximum value at about 0.5 M and then decreases. A similar behaviour has been observed when temperature of the solution is increased. The maximum etch rate is found for 80 °C. In addition, a new polishing etching solution of 6H-SiC has been developed. This result is very interesting since to date no chemical polishing solution has been developed on the material.     

Monte Carlo simulations of electron dynamics in N2/CO2 mixtures

Motivated by experimental investigations of electrical discharges in N₂/CO₂/H₂O, Monte Carlo (MC) electron dynamics simulations in atmospheric N₂/CO₂ mixtures were performed. The goal was to obtain electron energy distribution functions (EEDFs), mean free path, drift velocity, collision frequency and mean energy of electrons, rate coefficients of electron-impact reactions, ionisation and attachment coefficients, as functions of the reduced electric field strength (E/N) and of the concentration of individual gas components. The results obtained by MC simulations were fitted with polynomials of up to the 3rd order with reasonable accuracy for E/N above 80 Td. The studied parameters below 80 Td were strongly non-linear as functions of E/N. This is mostly due to the influence of elastic collisions of electrons with CO₂ molecules prevailing in CO₂-dominant mixtures for E/N < 40 Td, and vibrational excitation collisions of N₂ species prevailing in N₂-dominant mixtures for E/N from 40 to 80 Td. The effect of these electron-impact processes was specific for each of the studied parameters.     

Growth and Chemical Thermodynamics Analysis of SiC Film on Si Substrate by Heating Polystyrene/Silica Bilayer Method

采用改进的PS/OCS/Si(111)叠层热解法,在石英高温管式炉中,常压流通Ar气氛下,于1300 o C制备出了无层错空洞缺陷的晶态SiC薄膜．采用红外、X射线衍射和扫描电镜等分析方法对薄膜样品进行了表征．并研究了这种方法制备SiC薄膜的化学热力学过程．通过对反应平衡常数和吉布斯自由能的计算,初步确定了生成SiC的主反应的发生顺序以及反应体系的平衡状态,并论证了流通的Ar气氛对于反应的持续进行是必须的．该方法制备的薄膜为SiO2/SiC/Si(111)结构,这种结构对于半导体MOS器件的应用是非常有利的．该SiO2层形成反应后期降温阶段,并且可以通过RCA清洗工艺(标准半导体清洗工艺)彻底清除．目前还没有发现用这种方法生长SiC薄膜的报道．     

傅里叶红外光谱法研究AP的快速热分解

用T-Jump/FTIR联用技术研究了模拟燃烧条件下AP的快速热裂解。在不同压力的高纯氮气条件下,以1000K.s-1的升温速率达到设定的温度(874和1274K)快速分解,用快速扫描傅里叶变换红外光谱原位实时分析分解产物的种类和浓度变化。结果表明,AP热裂解主要气相产物为NO2,N2O,NO,HCl和NOCl等,实验温度和压力都使AP快速热裂解气相产物N2O/NO2,NO/NO2和NO/NOCl的比值提高,因此认为AP不但存在凝聚相和非均相的气相/凝聚相反应,而且还有主要气相产物之间的"后续反应"。     

炭/碳粒在CO_2/O_2气氛中燃烧速率的研究

１引言大量的研究表明,近一个世纪以来,大气中温室气体（主要是ＣＯ２）含量的迅速增加是引起全球气候变化的一个重要因素。而且,在今后若干年内,随着人类从矿物燃料中获取能源的进一步增加,ＣＯ２的排放量亦将持续增长。其中煤的利用量及在燃烧过程中ＣＯ２的排放量...     

A quantum chemical study of ZrO2 atomic layer deposition growth reactions on the SiO2 surface

Zirconium oxide (ZrO₂) is one of the leading candidates to replace silicon oxide (SiO₂) as the gate dielectric for future generation metal-oxide-semiconductor (MOS) based nanoelectronic devices. Experimental studies have shown that a 1–3 monolayer SiO₂ film between the high permittivity metal oxide and the substrate silicon is needed to minimize electrical degradation. This study uses density functional theory (DFT) to investigate the initial growth reactions of ZrO₂ on hydroxylated SiO₂ by atomic layer deposition (ALD). The reactants investigated in this study are zirconium tetrachloride (ZrCl₄) and water (H₂O). Exchange reaction mechanisms for the two reaction half-cycles were investigated. For the first half-reaction, reaction of gaseous ZrCl₄ with the hydroxylated SiO₂ surface was studied. Upon adsorption, ZrCl₄ forms a stable intermediate complex with the surface SiO₂–OH^* site, followed by formation of SiO₂–O–Zr–Cl^* surface sites and HCl. For the second half-reaction, reaction of H₂O on SiO₂–O–Zr–Cl^* surface sites was investigated. The reaction pathway is analogous to that of the first half-reaction; water first forms a stable intermediate complex followed by evolution of HCl through combination of a Cl atom from the surface site and an H atom from H₂O. The results reveal that the stable intermediate complexes formed in both half-reactions can lead to a slow film growth rate unless process parameters are adjusted to lower the stability of the complex. The energetics of the two half-reactions are similar to those of ZrO₂ ALD on ZrO₂ and as well as the energetics of ZrO₂ ALD on hydroxylated silicon. The energetics of the growth reactions with two surface hydroxyl sites are also described.     

Degradation of Y2SiO5:Ce phosphor powders

The degradation of the cathodoluminescence (CL) intensity of cerium-doped yttrium silicate (Y₂SiO₅:Ce) phosphor powders was investigated for possible application in low voltage field emission displays (FEDs). Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and CL spectroscopy were used to monitor changes in the surface chemical composition and luminous efficiency of commercially available Y₂SiO₅:Ce phosphor powders. The degradation of the CL intensity for the powders is consistent with a well-known electron-stimulated surface chemical reaction (ESSCR) model. It was shown with XPS and CL that the electron stimulated reaction led to the formation of a luminescent silicon dioxide (SiO₂) layer on the surface of the Y₂SiO₅:Ce phosphor powder. XPS also indicated that the Ce concentration in the surface layer increased during the degradation process and the formation of CeO₂ and CeH₃ were also part of the degradation process. The CL intensity first decreased until about 300 C cm⁻² and then increased due to an extra peak arising at a wavelength of 650 nm.