Papers by Keyword: Reaction Rate

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Authors: Xiao De Guo, Feng Sheng Li, Gui Zhen Bian, Guan Peng Liu
Abstract: Double-coated Mg powders with a chloride and a polymer such as HTPB(hydroxy-terminated polybutadiene),NC(nitrocellulose),PVB(polyvinylbutyral) were fabricated by physical vapor deposition and solvent evaporation,respectively.The influence of the addition and the species of the first and second coating agents on the water reaction characteristics was investigated. The results show that both the hydrogen release during the reaction with water and the reaction rate increases distinctly with the increase of the chloride.Compared with those of the raw Mg powders and Mg powders coated with the chloride, the initial reaction temperature of the double-coated Mg powders increases to different extent.Moreover,the initial reaction temperature has an increase trend with the increase of the addition of coating agents.
2463
Authors: Cao Bing, Cui Nan, Wu Yang
Abstract: In this thesis,a series of oxidation experiments on galena are conducted under different condition such as pH is 2,temperature is 50°C and 25°C.After the experiment is completed,The rate constant,reaction order,reaction reaction rate and energy of activation are also analyzed and computed.The effects of temperature and oxidized medium on lead ore oxidation speed were studied. Under the condition of 50°C, The rate of oxidation reaction is increase when concentration is 100mg/l.The higher the concentration the more sulfuric acid ion,the easier to produce sediment of lead sulfate , so the reaction will be impeded .the reaction will be extremely slow or even can’t carry on at 25°C.
901
Authors: Yong Nam Kim, Jeong Hyun Park, Hyun Gyu Shin, Jun Kwang Song, Hee Soo Lee
Abstract: Nanosized ITO powder was fabricated by homogeneous precipitation which used formamide as a precipitator. ITO thin film was deposited by RF magnetron sputtering using ITO target which was prepared by sintering of nanosized ITO powder. From the accelerated degradation test with stress factor of temperature, the lifetime estimate, degradation rate/degree, activation energy and etc. were calculated. It was showed that under thermal condition, the prominent failure mechanism of degradation was the decrease of oxygen vacancies due to oxidation of ITO thin film.
285
Authors: Keiji Yasuda, Toa Kaji, Zheng Xu
Abstract: Hydrodynamic cavitation is expected to apply to the decomposition of chemicals and the disinfection in wastewater. In this study, the effects of upstream pressure, hole diameter and shape of orifice plate on the reaction rate of I3- formation were investigated. The reaction rate increases with increasing upstream pressure of orifice plate. The reaction rates have maximum values, when hole diameters of orifice plate are 2.7 mm at the upstream pressure of 0.9 MPa gauge and 3.0 mm at 0.7 MPa gauge. The reaction rate increases in the order of triangle < square < hexagon < circle shaped hole of orifice plate at the same hole area.
718
Authors: Porntip Sae Be, Suesat Jantip, Sirisin Chum Rum
Abstract: This study aimed to investigate the influence of NaOH concentration and temperature used for cellulose extraction from sweet-bamboo leaves on the kinetics of the extraction reaction. The NaOH concentration and the temperature used for the extraction were varied and their effect was examined. It was found that the extraction rate was accelerated by either the increase of NaOH concentration or extraction temperature. The NaOH concentration affected the reaction rate constant, k, and the activation energy, E and the order of the reaction, n. Increase of NaOH concentration enhanced the reaction to move forwards, thus reducing the k and E values of the reaction and the order of the reaction, n, was changed. The correlation of the temperature and the NaOH concentration with the k value showed that at the lower NaOH concentration, the temperature influenced on the k value more significantly. The influence of the NaOH concentration on the k value was lessened with increase of the extraction temperature.
467
Authors: Hideaki Sano, Hajime Karasuyama, Guo Bin Zheng, Yasuo Uchiyama
Abstract: A thin film including β-silicon carbide was synthesized by a reaction of silicon monoxide gas and carbon source derived from polyimide film (PIF) at 1400°, 1500°, 1600°, 1700° and 1800°C. Formation mechanism of the SiC film was investigated thermodynamically and kinetically through the relationships among the conversion ratio of SiC, synthesis temperature and time. The formation processes were simulated based on the calculation of differential equations concerning thermodynamic and kinetic constants of 7 chemical equations. The sample obtained had a film shape similar to that of the carbon source film. The results of the time dependence curves of the conversion ratio of SiC calculated from 7 chemical equations, 14 rate constants, 2 diffusion constants, 10 chemical species and 10 differential equations are in good agreement with the experimental results of the SiC conversion ratio as a function of synthesis time. The calculation results of solving each constant suggest that the formation processes of SiC are "rate-controlled reaction at the interface" at the initial stage of the reaction, and then they gradually change to "diffusion-controlling reaction in the reacted region". In the long term synthesis, we recognized that the waste SiO with non-stoichiometric oxygen can also be used as a silicon source.
930
Authors: Chih Ming Ma, Gui Bing Hong, Yong Chuan Lo, Chang Tang Chang
Abstract: This study evaluated the performance of a photoreactor packed with TiO2/Quartz and ZrO2/Quartz, ZnO/Quartz, initiated by UV irradiation. The experimental results showed that the concentration of VOCs increased and the degration efficiency decreased at the same residence time. Additionally, as the residence time increased, degration efficiency increased. According to the Langmuir-Hinshelwood Model’s predicted results, the reaction rate constant (kc) was 50.1, 7.2, and 3.0 ppm min-1 for TiO2/Quartz, ZrO2/Quartz and ZnO/Quartz, respectively. In contrast, the adsorption equilibrium constant (K) was 10.0, 21.9, and 2.4 ppm-1 with the previous catalyst, individually.
35
Authors: Ming Chun Li, Chen Wang, Jia Tao Liu, Yu Jing
Abstract: Based on the pore size distribution simulation and the derivation of the effective diffusion coefficient, a mathematical model describing the mass transfer and chemical reaction in a cylindrical gas sensitive porous medium is formulated. The reaction features and the effective utilization of the gas sensitive porous medium are analyzed under different pore size distribution. The results indicate that, an increase in porosity or in the most probably pore diameter leads to a higher mass transfer rate of the target gas, while the surface chemical reaction ability decreases. Depending on the calculated value of the Thiele number, the variation of the gas sensitivity and the effective surface utilization can be analyzed. The gas sensitivity and the effective utilization coefficient of the gas sensitive porous medium can be controlled by adjusting pore structure parameters. This will be useful for the pore structure design of gas sensor and choosing the most reasonable operation conditions.
2972
Authors: Jean Philibert
Abstract: The first part of this paper presents a brief historical account of the Arrhenius law, starting from the seminal paper by Arrhenius (1889) up to theoretical developments mainly based on the rate theory. The second part describes the so called compensation rule (Meyer-Neldel rule), a correlation between activation enthalpy and entropy (or between pre-exponential factor and activation energy) , and discusses whether this correlation is trivial or bears some physical meaning.
61
Authors: Peng Huo, Fan Xue, Li Xuan Wang, Yan Kun Cheng, He Xiao Yun
Abstract: The adsorption capability of Cd2+ with δ-MnO2 was studied in water. The results indicated: the adsorption strongly relied on pH values. At 303K, the pH values were above 6.05, adsorption percentages of Cd2+ were nearly 100%. When pH values were below 2.3, adsorption rates of Cd2+ was below 20%. The adsorption processes was completely controlled by reaction rate and diffusion factor. The reaction rate of adsorption increased with pH values and temperatures. The adsorption activated energy of Cd2+ was 54.66 KJ•mol -1 at pH value 3.28, and it was 31.98 KJ•mol -1 at pH value 6.05. δ-MnO2 may be effectively desorpted after adsorption Cd2+ at the pH values below 2.05. The desorption rates were about 75%.
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