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61.
A comprehensive kinetic model describing photopolymerization is developed which allows variation of temperature, species concentrations, and light intensity through the thickness of a photopolymerized film. Heat and mass transfer effects are included, as is the generation of heat by both reaction and light absorption. In addition to initiation, propagation, and termination mechanisms, both primary radical termination and inhibition are incorporated into the model. The possible presence and diffusion of an inert solvent are also accounted for. Thus, the model is useful for examining complex polymerization kinetics and behavior in industrially and commercially important thick film photopolymerizations, such as the curing of contact lenses, dental restorative materials, photolithographic resists, and optoelectronic coatings. The comprehensive model is used to predict polymerization rate, temperature, and conversion profiles in a variety of systems. The effects of heat generation and the thermal boundary conditions are explored, with the result that heat generation in thick samples leads to greatly increased conversions approaching 100 percent. Increased temperature in these samples also may lead to the appearance of two rate maxima, with the first due to the temperature increase and the second caused by the autoacceleration process. The magnitude of the temperature increase, along with the resultant effects, is more pronounced in insulated systems. 相似文献
62.
在环已烷中,以正丁基锂引发的丁二烯阴离子聚合,采用1G/2G复合调节剂,研究了1G/2G复合调节剂对聚丁二烯微观结构及聚合动力学的影响。实验结果表明:1G与2G复合调节剂对聚丁二烯微观结构的调节能力强于1G或2G单一调节剂。聚合速度与单体浓度呈一次方关系,并分别求得不同温度下的单体一级反应速度常数(K″p)及表观增长活化能(E′p)。 相似文献
63.
微铬含量CO中温变换催化剂本征动力学的研究崔波,赵素芳,刘鹏照,宋世英,张洪全(青岛化工学院化学工程系,青岛266042)关键词:催化剂,一氧化碳变换反应,铁催化剂,动力学1前言一氧化碳变换反应是化学工业中制氢的重要反应,长期以来所用的一氧比碳中变催... 相似文献
64.
Zan-guo?Peng Kus?Hidajat Mohammad?ShahabuddinEmail author 《Korean Journal of Chemical Engineering》2003,20(5):896-901
A colloidal suspension of magnetic particles coated with double layer surfactant molecules was prepared, characterized and
used for separation of some chemicals. The aqueous magnetic fluid was prepared by chemical precipitation method and characterized
by total organic carbon analyzer (TOC), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). The TOC
and TGA measurements indicate that the prepared magnetic particles are coated with surfactant molecules in double layers.
The outer surfactant layer has free polar heads. TEM measurement results show that magnetic particles are nanosized. A mixture
of 2-hydroxyphenol (strong polar) and 2-nitrophenol (weak polar) was chosen as the target system. Results show that the magnetic
fluid can selectively adsorb 2-hydroxyphenol from the mixture, whereas the adsorption of 2-nitrophenol is insignificant. For
2-hydroxyphenol, the adsorption equilibrium can be described well by Langmuir isotherm, and the adsorption kinetic can be
fitted well by a linear driving force mass transfer model. 相似文献
65.
Hugues Duncan 《Electrochimica acta》2007,52(21):6195-6205
Hydrogen adsorption and absorption at thin palladium deposits of 0.8-10 monolayers (ML) on Au(1 1 1) was studied in 0.1 M H2SO4 and HClO4 using cyclic voltammetry, ac voltammetry, and impedance spectroscopy in the absence and in the presence of poison, crystal violet. Hydrogen adsorption on palladium is more reversible in sulfuric acid than in perchloric acid but it occurs at potentials 30 mV more positive in latter. The charge-transfer resistance exhibits a minimum at ∼0.27 V versus RHE and decreases with increasing in Pd deposit thickness in both acids. Adsorption capacitance at 0.8 ML Pd reaches maximum at the same potential. At other deposits the pseudo-capacitance starts to increase at lower overpotentials indicating the beginning of absorption, even at 2 ML Pd. The double layer capacitance is similar for all the deposits in sulfuric acid and it has a sharp maximum at 0.27 V versus RHE. In perchloric acid a broad maximum is observed. Crystal violet inhibits hydrogen adsorption but makes hydrogen absorption more reversible. The results suggest a fast direct hydrogen absorption mechanism that proceeds in parallel with slower hydrogen adsorption and indirect absorption. 相似文献
66.
Jolanta ?wiatowska-Mrowiecka 《Electrochimica acta》2005,50(9):1829-1840
Anodic dissolution of poly- and single-crystals of zinc was performed in methanol solution of lithium perchlorate by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The mechanism of anodic dissolution of zinc in organic solvents occurs in two oxidation steps. It is the first step that surface anodic product is created. Stability of the surface product is much better in anhydrous organic environments than in aqueous media; because the product is stable, a barrier layer composed of is formed at low anodic overvoltage. The formation of the layer is much stronger on the low index than on the high-index plane (0 0 0 1), where the adsorption of anodic product is more difficult. 相似文献
67.
Ten selected samples with varying types and amounts of organic matter from two Miocene lacustrine basins in northwestern Turkey were analyzed by programmed-temperature open-system pyrolysis to determine methane generation potential and reaction kinetics. Open-system pyrolysis was performed at heating rates 0.1, 0.7 and 5.0 K/min, where generated gases were measured using an on-line gas chromatograph. Frequency factors and activation energy distributions of reaction kinetics for methane generation from the investigated lacustrine coals and sedimentary rocks indicated that type of kerogen controls the sequential order of methane generation. Methane from Type-III kerogen is generated at lower temperatures, which will be followed by methane from Type-II and Type-I kerogen. Methane generation potentials in the range 14-35 mg CH4/g TOC correlates also with type of organic matter. For Type-III kerogen up to 28% of the total hydrocarbon generation potential belongs to methane. The respective value is only 2% for a Type-I kerogen. 相似文献
68.
The electrodeposition of Cu on Ru(0 0 0 1) from 0.1 M CuSO4/0.5 M H2SO4 solution has been studied by cyclic voltammetry, current-time transient measurements, and by in situ electrochemical atomic force microscopy (EC-AFM). Cyclic voltammetry measurements show that the as-prepared Ru(0 0 0 1) electrode exhibits a UPD peak, while EC-AFM data indicate a broadly terraced surface with step heights of atomic dimensions. Kinetic data show that the electrodeposition/nucleation process is not well described by 3D or 2D nucleation models. The EC-AFM data show that at potentials near the OPD/UPD threshold, Cu crystallites exhibit pronounced growth anisotropy, with lateral dimensions greatly exceeding vertical dimensions. AFM data also show that deposition at more cathodic potentials result in smaller crystallites. 相似文献
69.
The kinetics of growth of Mg(OH)2, seed crystals at 298, 308 and 318 K from an a~ueous supersaturated solution of initial concentrations of Mg(OH)2 0,48, 0.60 and 0.73 mol-3 were determined. The growth was followed by measuring the conductivity of a seeded system as a function of time. The growth kinetics satisfied a first order kinetic equation. Within the examined range of variables the kinetic constant is independent of temperature and the initial concentration and dependenl on the surface area of seeds added at the start of the experiment. The growth of crystals under the studied conditions is controlled by the surface reaction mechanism. 相似文献
70.
Fungisai Matemadombo 《Electrochimica acta》2007,52(24):6856-6864
Cobalt and iron phenylthiosubstituted phthalocyanines have been deposited on Au electrode surfaces through the self-assembled monolayer (SAM) technique. The so formed layers were studied using voltammetric and impedance techniques. These SAMs blocked a number of Faradic processes and electrocatalyzed the oxidation of nitrite. The electrocatalytic parameters of the cobalt and iron phenylthiosubstituted phthalocyanines deposited on Au electrodes in nitrite solution were studied. Nitrite overpotentials which are lower than ever reported were obtained in this work for the iron phenylthiosubstituted phthalocyanines with very high stability. 相似文献