SiC颗粒的高温氧化动力学

研究了SiC颗粒在927℃、1027℃和1127℃空气中的高温氧化动力学.结果表明,温度越高SiC颗粒的氧化速率常数越大,氧化反应越容易进行;SiC颗粒的高温氧化分为氧化前期和氧化后期两个阶段.氧化前期的反应速率受界面化学反应的控制;氧化后期受扩散控制,其表观活化能远比氧化前期的大.SiC颗粒的高温氧化过程符合两个阶段式模型:氧化前期的氧化速率常数k_c=143.37exp(-70994/RT)(mg·m~(-2)·min~(-1)),氧化后期的氧化速率常数k_D=3.61×10~8exp(-192758/RT)(mg·m~(-2)·min~(-1)).     

Parylene C膜的热降解行为

采用微分-积分法和裂解质谱研究了聚氯代对二甲苯(Parylene C膜)的非等温热降解行为.实验结果表明,Parylerie C膜在N2中的热降解符合二级化学反应,其动力学模型方程式为dα/dt=Aexp(-E/RT)(1-α)2,平均表观活化能E=139kJ/mol,在N2中裂解产物主要为芳香烃和芳香醛.     

炭分子筛的结构和表面性质对其吸附分离CH4/N2和CO2/N2的影响

对日本Takeda(CMS-1)、Kuraray(CMS-2)和德国BF(CMS-3)3种炭分子筛(CMS)的孔结构和表面官能团进行了表征,分析了它们对CH4/N2和CO2/N2的吸附平衡和吸附动力学分离性能,以及CMS的结构与表面性质对吸附性能的影响。结果表明,CMS-1和CMS-2可实现CH4/N2的动力学分离,还可实现N2/CO2的平衡分离;CMS-3平衡分离CH4/N2和CO2/N2的效果要优于动力学分离。孔结构是影响炭分子筛分离性能的直接因素,孔径分布的差异使CMS-1和CMS-2对CH4/N2的位阻-动力学分离效应表现得更为明显;表面含氧官能团有利于提高炭分子筛的吸附分离性能。     

DF化学激光器反应动力学模型的简化及其有效性分析

DF化学激光器涉及到多组分的高速化学反应流,组分、反应方程、速率常数的选择对计算结果有着重要影响.通过对DF化学激光器反应动力学模型的讨论,给出了简化模型的依据,并且分别运用几组简化反应模型进行数值模拟,分析与完全反应模型相比,简化对激光器小信号增益系数和DF激发态分子空间分布的影响.推荐了一个针对(NF_3+H_3+He)/D_2燃料体系,DF化学激光器"冷反应"系统的11组分23方程简化模型,在很大程度上减少了计算量,有利于反应流场数值仿真的编程实现.     

N80钢在川西某气井常温常压和高温高压下的腐蚀行为

管道钢在高温高压环境中的热力学条件和腐蚀动力学过程不同,因而其腐蚀规律及机理与常温常压下有很大不同.利用电化学方法研究了N80管道钢在川西某气井含饱和CO2的腐蚀介质中于常温常压和高温高压环境下的极化曲线和交流阻抗特征,通过对比发现:2种环境下的阳极反应机理相同而阴极反应机理不完全一样;高温高压条件下N80钢的腐蚀速率...     

SMA/PA6界面化学反应的流变学测试

采用流变学的方法研究了剪切作用下苯乙烯-马来()酐共聚物(SMA)/尼龙6(PA6)体系的界面化学反应.固定可反应界面面积,从化学反应动力学的角度分析剪切提高界面化学反应速率的原因.研究发现,随着SMA/PA6界面上施加角频率和应变的增大,界面化学反应速率增大,化学反应动力学由一级扩散控制反应向二级化学反应控制转变,表...     

紫外辐射合成CTs/AMPS/MA可降解型高吸水树脂

以壳聚糖(CTs)﹑马来酸酐(MA)﹑2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为原料,过硫酸铵(APS)为引发剂,N,N’-亚甲基双丙烯酰胺(NMBA)为交联剂,采用紫外光固化的方法合成CTs/AMPS/MA三元共聚高吸水树脂。研究了反应条件对树脂吸水性能的影响,结果表明,当固含量为15.87%,nAMPS∶nMA=14∶1,ω(CTs)=2%,ω(NMBA)=2.5%,ω(APS)=0.3%,pH=3,固化时间为5min时可得到具有较好吸水性的高吸水树脂,在蒸馏水中的最大吸水率为555g/g。采用FT-IR和TGA对树脂结构及热稳定性进行表征,并对其吸水速率及动力学进行分析,反吸液能力测定表明制备的树脂具有一定的降解性。     

CuO-CeO2-ZrO2/HZSM-5催化CO2加氢直接合成DME

采用共沉淀法制备了一系列不同n(Ce)/n(Zr)时的CuO-CeO2-ZrO2甲醇合成催化剂,运用X射线衍射(XRD)、N2物理吸附(BET)和H2程序升温还原(H2-TPR)等手段对催化剂进行了表征分析.将甲醇合成催化剂与HZSM-5分子筛按照一定质量比进行机械混合,CO2加氢直接合成DME双功能催化剂.在固定床反应器中,温度250℃、压力3MPa、H2/CO2=3/1以及空速1800h-1的条件下,对双功能催化剂进行了活性评价.结果表明,当n(Ce)/n(Zr)=1/1时,CO2转化率最高;当n(Ce)/n(Zr)-1/3时,DME的选择性最好,Ce的加入并未有效降低CO的含量.     

低温工况下蒸发器结霜特性的数值模拟及试验研究

结合 CFD 模拟和试验两种方法,研究制冷过程中蒸发器结霜这一常见的问题.提出了修正的组分传输和有限速率化学反应模型来对蒸发器的结霜过程进行 CFD 模拟,用升华潜热来替代化学反应的活化能,使H2O(g)←→H2O(s)这一物理反应变成有限速率的化学反应.考察了低温工况下(-20℃以下),湿空气进口速度分别为v=2 m/s,1.2 m/s,0.8 m/s;相对湿度分别为60%,80%时蒸发器结霜量的大小.低温工况下,蒸发器的结霜量随着蒸发器迎面风速的增大而增大,随着空气进口相对湿度的增加而增加,模拟结果和试验结果符合得很好.     

可降解聚碳酸亚丙酯马来酸酯载药微球的制备

采用阴离子配位聚合方法,合成了二氧化碳(CO2),环氧丙烷(PO)与马来酸酐(MA)的三元共聚物,聚碳酸亚丙酯马来酸酯 (PPCMA).采用复相乳液(W/O/W)溶剂挥发法制备了包裹水溶性模型药物葡萄糖(glucose)的可降解微球,并研究了壁材与囊心的比例、稳定剂明胶浓度、搅拌速率等因素对微球性能的影响.当v(PPCMA)∶v(glucose)=1∶2,gelatin质量分数为0.2%,第1次乳化搅拌速率为400r/min,第2次乳化搅拌速率为500r/min时,得到粒径较小、载药量和包封率分别为26.1%和76.1%的载药微球.     

Vibrational temperatures of carbon dioxide in products of the reaction of carbon monoxide with nitrous oxide under the conditions of a gasdynamic laser

The conditions under which the superequilibrium chemical pumping of the laser levels of CO₂ molecules occurs in a gasdynamic laser based on products of the reaction CO+N₂O are established experimentally.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 35, No. 6, pp. 1006–1011, December, 1978.     

Vibrational temperatures of carbon dioxide in the reaction products of carbon monoxide and nitrous oxide under gasdynamic laser conditions

A method is developed for the experimental determination of the vibrational temperatures of asymmetric and combined symmetric modes of carbon dioxide, based on the simultaneous recording of the spontaneous and stimulated radiation characteristics of the CO+N₂O reaction products under gasdynamic laser (GDL) conditions.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 35, No. 4, pp. 581–590, October, 1978.     

Picosecond laser-induced fluorescence measurement of rotational energy transfer of OH A (2)?(+) (v? = 2) in atmospheric pressure flames

Rate constants for total and state-specific rotational energy transfer (RET) of OH A(2) ?(+) (v? = 2) have been measured directly in atmospheric methane-air and methane-oxygen flames for the first time to our knowledge. We used a picosecond Raman-excimer laser (tau(l) = 300 ps, lambda = 268 nm) to excite the P(11) (12.5) and Q(11) (16.5) A -X transitions in the (2, 0) band of OH molecules. We analyzed the resultant fluorescence with a high-resolution spectrometer in combination with a fast-gated, intensified CCD camera (tau(g) = 400 ps). We recorded the temporal evolution of the emission spectrum by shifting the detection time with respect to the laser pulse. Measured emission spectra were inverted to yield the time-dependent population of rotational levels in the excited state. We calculated rate constants for RET from the results of the fit. The total RET in v? = 2 is similar to v? = 0, 1. The state-specific rates are represented well by a simple energy-gap law.     

Carbon analysis for inspecting carbonation of concrete using a TEA CO2 laser-induced plasma

It has been demonstrated that a spectrochemical analysis of carbon using the laser plasma method can be successfully applied to inspect the carbonation of concrete by detecting carbon produced in aged concrete by a chemical reaction of Ca(OH)2 with CO2 gas in environmental air, turning into CaCO3, which induces degradation of the quality of building concrete. A comparative study has been made using a TEA CO2 laser (500-1000 mJ) and a Q-switched Nd-YAG laser (50-200 mJ) to search for the optimum conditions for carbon analysis, proving the advantage of the TEA CO2 laser for this purpose. Also, it was clarified that laser irradiation with suitable defocusing conditions is a crucial point for obtaining high sensitivity in the detection of carbon. Practical experiments on the inspection of carbonation were carried out using both a concrete sample that had been intentionally carbonated by exposure to high concentrations of CO2 gas and a naturally carbonated concrete sample. As a result, good coincidence was observed between the laser method and the ordinary method, which uses the chemical indicator phenolphthalein, implying that this laser technique is applicable as an in situ quantitative method of inspection for carbonation of concrete.     

Flow structure of the active medium of a HF laser with a radially expanding nozzle unit

Measurements have been made of gasdynamic characteristics of the flow of the active medium as well as energy and spectral characteristics of radiation generated by a continuous chemical HF laser with a radially expanding nozzle unit. Based on the analysis of measurement results, the flow structure of the active medium has been determined, which is formed by the “nozzle–injector” reactant mixing scheme. It has been shown that only a part of the active medium is involved in the radiation generation. Measures for improving the efficiency of its use have been proposed.     

Calculation of the characteristics of a mixing CO2 gasdynamic laser with a nozzle unit of honeycomb construction

A mathematical model of a gasdynamic laser with parallel supersonic mixing of the components and its applications to the choice of the geometrical characteristics of the nozzle unit of honeycomb construction are presented.Notation T static temperature - u velocity - P pressure - molecular weight - e_i average number of vibrational quanta - k amplification ratio for a weak signal - I radiation intensity - _i molar fraction of the component in the mixture - ^* displacement thickness - r, d current radius and diameter of the nozzle - angle of inclination of the generating profile of the nozzle and characteristic temperature - h enthalpy - G flow rate - L characteristic length - A/A* expansion ratio of the nozzle - T_w wall temperature - ¯T_w=¯T_w/T_o temperature factor - =E _a /E_* nozzle efficiency - E stored vibrational energy - X=X/(r_a1 + r_a2) dimensionless coordinate Indices 1 radiating gas stream - 2 exciting gas stream - 0 stagnation value - a, *, values at the cut of the nozzle, in its critical cross section, and beyond the compression shock in the cross section of the nozzle cut Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 1, pp. 53–59, July, 1984.     

Application of the particle-in-cell method to calculate the parameters of molecular beams from gasdynamic sources

The particle-in-cell method is used to calculate the flow fields of gases formed by supersonic nozzles of different shapes under flow conditions typical of gasdynamic sources of molecular beams. The proposed calculation scheme is tested by comparing the calculated flow fields from an acoustic nozzle with the semiempirical calculations made by Ashkenas and Sherman. For a nozzle with a conical supersonic section the calculations are compared with the results of time-of-flight measurements made using the molecular beam generator at the St. Petersburg Institute of Nuclear Physics of the Russian Academy of Sciences. Prospects for the further use of these calculation methods to develop and optimize gasdynamic sources of molecular beams are discussed. Pis’ma Zh. Tekh. Fiz. 24, 66–72 (August 26, 1998)     

高产率低成本激光合成硅基纳米陶瓷粉

本文采用激光诱导大分子有机硅熔（ＨＭＤＳ）气相反应，通过加入附加反应气和工艺参数的优化控制，在不同合成条件下制得单相非晶Ｓｉ３Ｎ４，β—ＳｉＣ纳米粉和宽组份变化范围的ＳｉＮＸＣＹ纳米复合粉（平均粒径：１０－３０ｎｍ）。与通常采用的硅烷相比，采用此有机硅烷激光合成在等同实验条件下粉产率可提高３－５倍．成本降低１倍，且具有粉体组成，结构易于控制等优点，是一种具有商业化应用前景的高性能硅基纳米陶瓷粉制备技术。     

Pulsed laser photofragment emission for detection of mercuric chloride

The viability of pulsed laser photofragment emission (PFE) is evaluated for the in situ measurement of vapor-phase mercuric chloride (HgCl(2)) concentration in combustion flue gas. Dispersed emissions from both the Hg (6(3)P(1)) and HgCl (B(2)Sigma(+)) photoproducts are presented, and the dependence of the HgCl(2) PFE signal originating from Hg (6(3)P(1)) on the collisional environment is examined for buffer-gas mixtures of N(2), O(2), and CO(2). Integrated PFE intensity measurements as a function of buffer gas pressure support the assumption that the primary effect of the relevant flue gas constituents is to quench emission from Hg (6(3)P(1)). The quenching rate constants for PFE from HgCl(2) were measured to be 1.37 (+/-0.16) x 10(5) Torr(-1) s(-1) for N(2), 9.35 (+/-0.25) x 10(6) Torr(-1) s(-1) for O(2), and 1.49 (+/-0.29) x 10(6) Torr(-1) s(-1) for CO(2). These values are in good accord with literature values for the quenching of Hg (6(3)P(1)). The emission cross section for Hg (6(3)P(1)) generated by photodissociation of HgCl(2) in 760 Torr N(2) is found to be 1.0 (+/-0.2) x 10(-25) m(2) by comparing the PFE signal to N(2) Raman scattering.