Kinetics of the Initial Stage of Sintering from Shrinkage Data: Simultaneous Determination of Activation Energy and Kinetic Model from a Single Nonisothermal Experiment

A new method for the kinetic analysis of the initial stage of sintering for constant-heating-rate data has been proposed. Unlike all of the methods previously reported in the literature, this new method proposed here allows the simultaneous determination of the activation energy and the kinetic model from a single dilatometric curve recorded under a linear-heating-rate program. The proposed method has been tested with simulated sintering curves and experimental results have been obtained for the sintering of a rutile sample.     

Synthesis of Dimethyl Carbonate from Methanol and Carbon dioxide using Potassium Methoxide as Catalyst under Mild Conditions

Pd-supported on WO₃–ZrO₂ (W/Zr atomic ratio=0.2) calcined at 1073 K was found to be highly active and selective for gas-phase oxidation of ethylene to acetic acid in the presence of water at 423 K and 0.6 MPa. Contact time dependence demonstrated that acetic acid is formed via acetaldehyde formed by a Wacker-type reaction, not through ethanol by hydration of ethylene.     

补强剂和共混工艺对PA/PVC/NBR三元共混弹性体性能的影响

在选择三元共聚尼龙（PA）、聚氯乙烯（PVC）、丁腈橡胶（NBR）为主体材料，制备PA／PVC／NBR（10／30／60）三元共混弹性体的工作基础上，进一步探讨了填料品种和用量，共混温度，加料顺序等因素PA／PVC／NBR三元共混弹性体的影响。试验结果表明：在PA／PVC／NBR（10／30／60）共混体系中，补强型填料的补强效果优于非补强型的填料，6种填料补强效果依次是：快压出炭黑＞半补强炭黑＞白炭黑＞活性重质，CaCO3＞陶土＞滑石粉，快压出炭黑的适宜用量是20－50份。在制备PA／PVC／NBR三元共混物时，适宜的共混温度是122－140℃，并且采用二段法混工艺制得的共混物性能优于采用一段法共混工艺。     

VAc/AA改性的VAE乳液高速接嘴卷烟胶的研制

介绍了VAc/AA改性的VAE乳液高速接嘴卷烟胶的制备方法。研究了各种因素对胶粘剂性能的影响。结果表明 :VAc/AA用量增加 ,VAE乳液的粘接性能增强。选择与VAE乳液相适应的乳化剂和控制适宜的pH值 ,可以增加VAE乳液的稳定性。采用滴加引发剂和混合单体的方法 ,可以避免过速反应产生及大粒径胶粒生成     

Propane oxydehydrogenation reaction on a VPO/TiO2 catalyst. Role of the nature of acid sites determined by dynamic in-situ IR studies

A VPO/TiO₂ catalyst tested in the oxydehydrogenation reaction (ODH) of propane between 300 and 400°C shows satisfactory performances (up to 80% of propene selectivity at 2% of propane conversion at 300°C or 56% of propene selectivity at 9% of propane conversion at 400°C). Addition of water or pyridine in the feed gas tends to decrease the propane conversion and enhances the propene selectivity. It is shown that water increases the number of Brönsted surface acid sites by dissociative adsorption which, in turn, enhances propene selectivity at the expense of the CO_x selectivity. These results are in good agreement with spectroscopic IR observations performed under catalytic conditions showing that the Lewis acid sites are linked to CO_xformation, whereas it seems that Brönsted sites would rather be linked to propene formation.     

Catalytic wet air oxidation of olive mill wastewater

Au-based catalysts, known for ambient temperature CO oxidation, have to provide stable performance of up to 5000 h in order to be commercially applicable in automotive fuel cells. In this report, the on-line deactivation characteristics of Au/TiO₂ in unconventional PROX conditions are discussed. As opposed to CO removal from air, results in this report suggests that carbonates have a minor effect on deactivation of Au/TiO₂ in dry H₂-rich conditions. Also, no conclusive correlation between surface hydration and deactivation was observed. Rather, deactivation appeared to have occurred as a result of an intrinsic transformation in the oxidation state of the active species in the reducing operating conditions; a process which was reversible in an oxidizing atmosphere.     

Determination of Binder Decomposition Kinetics for Specifying Heating Parameters in Binder Burnout Cycles

The decomposition kinetics of poly(vinyl butyral) binder from barium titanate multilayer ceramic capacitors with platinum metal electrodes were analyzed by thermogravimetric analysis as a function of the heating rate. The activation energy and pre-exponential factor for the decomposition kinetics were determined from two types of integral equations, from the Redhead method, and from the variation in heating rate method. The accuracy of the kinetic parameters determined from these methods was then evaluated for describing the observed rate of binder decomposition. Although the individual models yielded very different kinetic parameters, all were capable of describing the experimental data within ±15% accuracy. The kinetic parameters were then used in a coupled transport and kinetic model for describing the buildup of pressure within the ceramic green body as a function of the heating cycle. A methodology based on calculus of variations was also developed to predict the minimum duration for the binder burnout cycle.     

抄数系统在产品设计和模具制造中的应用

介绍高速抄数机的基本结构、功能、工作流程以及在新产品开发,模具型腔、型芯设计和制造中的具体应用.     

Ozone Contactor Hydrodynamics

Tracer tests were conducted at the 6,000 pounds of ozone per day Tucson, CAP Water Treatment Plant in Tucson, Arizona. The tests were designed to determine T₁₀ values through the contactors at various operating conditions. The tests were modeled using three techniques. Peclet Number was calculated for each of the runs, which would indicate the hydrodynamic conditions inside the ozone contactor. The results indicated that the increase in water flow rate and the number of cells with gas flow increased Peclet Number. The flow rate of liquid seemed to impact the Peclet Number more than gas flow. The headloss in each cell appeared to be important in controlling the distribution of liquid and gas through the cell. A correlation was developed between the product of gas and liquid phase Reynolds Number and Peclet Number.     

An improved light attenuation technique for measuring large interfacial areas

A laser-based light attenuation technique was successfully used to measure interfacial areas as high as 5832 m²/m³ and Sauter mean bubble diameter varying between 50 and 5600 μm. Good agreement between this approach and the photographic technique was obtained particularly at low gas holdups.