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The adsorption and decomposition of monoethylgermane (GeH3Et) on the Si(100)-(2×1) surface was investigated with the intent of elucidating the surface processes leading to the deposition of germanium. The low-temperature adsorption of the molecule was explored, as well as its thermal decomposition. H2 and C2H4 are observed as the desorption products in temperature-programmed desorption experiments. The ethylene is produced by a hydride elimination reaction within the adsorbed ethyl groups. The amount of Ge which can be deposited in a reaction cycle is correlated with the number of sites occupied by the ethyl groups upon the dissociation of GeH3Et.  相似文献
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An energy and mass balanced method of determining the pyrolysis temperature is proposed. The concept is to find the pyrolysis temperature that consumes the same amount of energy to produce the same amount of mass when using the pyrolysis front model as when using finite rate kinetics models for the entire charring process. The resulting pyrolysis temperature has the form of pyrolysis rate weighted average temperature. Comparisons between finite rate kinetics and pyrolysis front models for various boundary conditions, geometries, heats of decomposition, kinetic parameters and assumptions used in the literature were made to assess the proposed method. Models using energy and mass balanced pyrolysis temperature show good agreement with finite rate models and the experiments. Extensive numerical studies on various factors influencing the charring material pyrolysis show that heat flux, sample size, heat of decomposition and kinetic parameters are the most important factors for determining an appropriate pyrolysis temperature. Thermal conductivity, specific heat and density have a lesser effect on the pyrolysis temperature. For practical application, a non-dimensional correlation is developed to determine the appropriate pyrolysis temperature without solving the problem by using finite rate models. With this correlation the energy and mass balanced pyrolysis temperature can be determined with a standard deviation of 7.6 K. These predictions are validated by comparison with measurements of wood cylinder pyrolysis. A good agreement suggests that simpler pyrolysis front models yield practically useful and accurate results given an appropriate pyrolysis temperature.  相似文献
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利用ReaxFF分子动力学模拟方法对正庚烷在高温条件下的热解行为进行了研究.细致分析了温度对正庚烷高温裂解过程以及产物分布的影响.结果显示温度对正庚烷的热解过程的影响是分阶段的.高温能加速正庚烷的分解,但是当温度达到一定阶段之后这种影响逐渐变小.正庚烷的热解可以分为三个阶段.主要产物C2H4、C3和C4的质量百分数随转化率的变化规律与实验值符合很好.利用一阶动力学模型得到的正庚烷热解的表观活化能和指前因子分别为53.96 kcal/mol和55.34×1013 s-1,与实验值相符.  相似文献
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采用溶胶-凝胶方法制备了B掺杂ZnO(BZO)薄膜,系统研究了热解温度对薄膜的结晶行为和性能的影响. X射线衍射谱表明所有的BZO薄膜均具有六方纤锌矿结构,并沿c轴方向择优生长. 随着热解温度的升高,BZO薄膜的晶粒尺寸和RMS粗糙度增加. BZO薄膜的载流子浓度和载流子迁移率也随着热解温度的升高而增加,其可见光平均透过率均在90%以上.  相似文献
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 采用热重分析技术研究了4种聚-α-甲基苯乙烯原料和其它微球壳层材料的热降解温度。研究表明,聚-α-甲基苯乙烯原料主要失重温度范围为220~340 ℃,等离子体辉光放电涂层材料的降解温度为350~450 ℃。升温速率在20 ℃/min和30 ℃/min时,降解温度基本相同,升温速率不影响降解的温度范围,低于20 ℃/min时,随着升温速率升高,降解温度升高。  相似文献
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