Study on the Microstructure of β‘—Sialon／SiC（w） Composites

The phase composition and microstructure of β‘-Sialon/SiC whisker compostie materials were studied by means of XRD ,SEM,EDAX and HREM.Besides β‘-Sialon and β-SiC as main crys-talline phases,15R AIN polytypoids presented in the materials,Yttrium,added in Y2O3 as sintering aid,was concetrated mainly in glassy phase,A mosaic structure of SiC whisker in β‘-Sialon grains was observed,Two kinds of grain boundaries were also observed:one was a direct-contact grain boundry between β‘-Sialon and β-SiC,while the other was a boundary between β‘-Sialon grains wqith glassy phases.     

The Effect of Al2O3（Mul.） on Phase Compositions of O′—Sialon Cermics

O′-Sialon Cermics are formed by reaction sintering of silicon nitride and silica with Al2O3(Y2O3) additive,The phase compositions of O′-Sialon Cermics are highly affected by addition of Al2O3( mul.) and are measured by X-ray diffraction techinque.The range of additions which could impaire the stucture of O′-Sialon Cermics is given in this article.     

Effects of Boron Bearing Additives on Oxidation and Corrosion Resistance of Doloma—based carbon bonded Refractories

Oxidation of the added graphite and the bonding carbon is an imortant degradation mode of doloma-carbon refractories in service,In this work,the behavior and effects of various boron bearing materials(CaB6,ZrB2,Bc and colemanite)as an-tioxidants have been investigated and compared to the effect of Al-Mg alloy,For CaO-MgO-C mate-rials,the effect of boron bearingadditives is better than Al-Mg alloy,The borate melt formed at high temperature would retard or prevent carbon oxidation,thus contributing to improved oxidation resistance,Preliminary investigations on the effect of boron bearing additives and Al-Mg alloy on corrosion resistance of doloma-carbon materials have indicated that simultaneous addition of the two types of additives would lead to pronounced improvement of slag corrosion resistance.     

Slag Corrosion Resistace of β－Sialon－Al2O3 Composites－Part I. Thermodynamics and Mechanism

Slag corrosion resistance of β－Sialon and β－Sialon-Al2O3 composites has been studied .The effects of FeO content and temperature on corrosion rate have been investi-gated by mens of dip method(static and self-rotating).The corrosion process and microstructural analysis.It is shown that FeO preferentially attacks β-Sialon in the composite and the protruded corundum grains would gradualy fall off into the slag.     

Abstracts from Naihuo Cailiao(Refractories)——A Chinese-Language Bimonthly

Development and properties of β-Sialon-Al_2O_3-SiCcomposite materials(1～4). -β-Sialon, Al_2O_3, SiC,Composite material, Advanced refractories. -The nitri-dation sintering technique of β-Sialon-Al_2O_3-SiC compos-ites was studied by using Si powder, Al powder, Al_2O_3 finepowder, corundum and SiC particles as raw materials at1500℃ under flowing nitrogen. SEM and XRD analysisconfirm that the microstructure of β-Sialon as bondingphase changes from fiber-like to hexagonal prism-like de-pending on the increasing amount of corundum. The hotMOR of the composites at 800～1400℃ is higher than     

Effect of Metal Additives on Performance of Low-Carbon Magnesia-Carbon Materials

In this paper,both oxidation and corrosion resistance of low-carbon magnesia-carbon materials containing 4.0wt% graphite with metallic Al and Mg-Al alloy powders as antioxidants were investigated.Meanwhile,the microstructures of samples corroded by slag were observed with optical microscope as well.The test results revealed the properties of oxidation and corrosion resistance of low-carbon magnesia-carbon materials could be improved obviously by adding metal Al powder and Mg-Al alloy powder.The rule of improving oxidation resistance was illegibility when metal Al powder and Mg-Al alloy powder were added together.It was harmful to corrosion resistance by mixed adding metal Al powder and Mg-Al alloy powder into the materials,at the same time,the corrosion resistance would decreased with the increasing of Mg-Al alloy content.The corrosion resistance of samples with 0.5wt% or 3.0wt% Mg-Al alloy was better. The oxidation resistance and corrosion resistance of materials with metal Al or Mg-Al alloy respectively were better than that with mixed metal Al and Mg-Al alloy. As a result, Mg-Al alloy was more suitable for low-carbon composite materials than metal Al as additives.     

水/有机溶剂双相中固定化啤酒酵母细胞催化三甲基硅乙酮不对称还原

Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied,The effects of shake speed,hydrophobictiy of organic solvent ,volume ratio of water phase to organic phase,pH value of aqueous phase and reaction temperature on the initial reaction rate,maximum yield and enantiomeric excess(ee) of the product were systematically explored,All the above-mentioned factors had significant infuence on the reaction.n-Hexane was found to be the best organic solvent for the reaction.The optimum shake speed,volume ratio of water phase to organic phase,pH value and reaction temperature were 150 r.min^-1,1/2,8 and 30℃ respectively,under which the maximum yield and enantiomeric excess of the product were as high as 96.8% and 95.7%,which are 15% and 16% higher than those of the corresponding reaction performed in aqueous phase ,To our best knowledge,this is the most satisfactory result obtained.     

超短接触反应器气固快分装置的数值模拟

A gas-solids fast separator was studied for its potential application in the process of coal pyrolysis to acetylene in plasma. The CFD method was employed to simulate the flow behavior in the gas-solids fast separator based on the realizable k-ε turbulence model and the discrete particle model（DPM）.The separation efficiency and residence time of gas phase in the gas-solids fast separator could be calculated. The numerical simulations were validated by the experimental results at a low velocity of the inlet gas（e. g. ,4 m·s^-1）.With the increase of gas velocity at the inlet,the separation efficiency was increased,and the residence time of gas phase was reduced accordingly. The separation efficiency approached 100% when particle diameter was larger than 20 μm. When inlet velocity was 100 m·s^-1,the mean residence time of gas phase was about 35 ms. To be noted,the performance of the gas-solids fast separator could be improved,for example by shortening the length of the separator,with a reduced residence time of gas phase at ～20 ms. It is expected that the gas-solids fast separator can meet the stringent demand of the coal pyrolysis to acetylene process for the milliseconds reaction,quench and separation.     

Analysis of H2S Tolerance of Pd-Cu Alloy Hydrogen Separation Membranes

The presence of a limited amount of H2S in H2-rich feed adversely affects the Pd-Cu membrane per-meation performance due to the sulphidization of the membrane surface. A theoretical model was proposed to pre-dict the S-tolerant performance of the Pd-Cu membranes in presence of H2S under the industrial water-gas-shift （WGS） reaction conditions. The ideas of surface coverage and competitive adsorption thermodynamics of H2S and H2 on Pd-Cu surface were introduced in the model. The surface sulphidization of the Pd-Cu membranes mainly de-pended on the pressure ratio of H2S to H2, temperature and S-adsorbed surface coverage, i.e., the occurrence of sulphidization on the surface was not directly related with the bulk compositions and structures [body centered cu-bic and face centered cubic （bcc or fcc）] of Pd-Cu alloy membranes because of the surface segregation phenomena. The resulting equilibrium equations for the H2S adsorption/sulphidization reactions were solved to calculate the pressure ratio of H2S to H2 over a wide range of temperatures. A validation of the model was performed through a comparison between lots of literature data and the model calculations over a rather broad range of operating condi-tions. An extremely good agreement was obtained in the different cases, and thus, the model can serve to guide the development of S-resistant Pd alloy membrane materials for hydrogen separation.     

Fast Pyrolysis of Biomass in a Spout-fluidized Bed Reactor--Analysis of Composition and Combustion Characteristics of Liquid Product from Biomass

In order to gain insight into the fast pyrolysis mechanism of biomass and the relationship between bio-oil composition and pyrolysis reaction conditions, to assess the possibility for the raw bio-oil to be used as fuel, and to evaluate the concept of spout-fluidized bed reactor as the reactor for fast pyrolysis of biomass to prepare fuel oil, the composition and combustion characteristics of bio-oil prepared in a spout-fluidized bed reactor with a designed maximum capacity 5 kg/h of sawdust as feeding material, were investigated by GC-MS and thermogravimetry. 14 aromatic series chemicals were identified. The thermogravimetric analysis indicated that the bio-oil was liable to combustion, the combustion temperature increased with the heating rate, and only minute ash was generated when it burned. The kinetics of the combustion reaction was studied and the kinetic parameters were calculated by both Ozawa-Flynn-Wall and Popsecu methods. The results agree well with each other. The most probable combustion mechanism functions determined by Popescu method are f(a)=k(1-a)2 (400~406℃), f(a)=1/2k(1-a)3 (406~416℃) and f(a)=2k(1-a)3/2 (416~430℃) respectively.     

Thermal conductivity of boron carbide under fast neutron irradiation

Due to the complex products and irradiation-induced defects, it is hard to understand and even predict the thermal conductivity variation of materials under fast neutron irradiation, such as the abrupt degradation of thermal conductivity of boron carbide (B₄C) at the very beginning of the irradiation process. In this work, the contributions of various irradiation-induced defects in B₄C primarily consisting of the substitutional defects, Frenkel defect pairs, and helium bubbles were re-evaluated separately and quantitatively in terms of the phonon scattering theory. A theoretical model with an overall consideration of the contributions of all these irradiation-induced defects was proposed without any adjustable parameters, and validated to predict the thermal conductivity variation under irradiation based on the experimental data of the unirradiated, irradiated, and annealed B₄C samples. The predicted thermal conductivities by this model show a good agreement with the experimental data after irradiation. The calculation results and theoretical analysis in light of the experimental data demonstrate that the substitutional defects of boron atoms by lithium atoms, and the Frenkel defect pairs due to the collisions with the fast neutrons, rather than the helium bubbles with strain fields surrounding them, play determining roles in the abrupt degradation of thermal conductivity with burnup.     

Reconstruction of electrical capacitance tomography images based on fast linearized alternating direction method of multipliers for two-phase flow system

Electrical capacitance tomography (ECT) has been applied to two-phase flow measurement in recent years. Image reconstruction algorithms play an important role in the successful applications of ECT. To solve the il-posed and nonlinear inverse problem of ECT image reconstruction, a new ECT image reconstruction method based on fast lin-earized alternating direction method of multipliers (FLADMM) is proposed in this paper. On the basis of theoretical analysis of compressed sensing (CS), the data acquisition of ECT is regarded as a linear measurement process of permittivity distribution signal of pipe section. A new measurement matrix is designed and L1 regularization method is used to convert ECT inverse problem to a convex relaxation problem which contains prior knowledge. A new fast alternating direction method of multipliers which contained linearized idea is employed to minimize the objective function. Simulation data and experimental results indicate that compared with other methods, the quality and speed of reconstructed images are markedly improved. Also, the dynamic experimental results in-dicate that the proposed algorithm can fulfil the real-time requirement of ECT systems in the application.     

DIFFUSION MODES IN A DIFFUSION-CELL ADSORBER

1 INTRODUCTIONDiffusion-cells have been widely used for the measurement of the effective diffusivitiesin porous catalysts.Compared with other methods,diffusion-cell presents itself as asimple,fast and reliable technique and its response curve is very sensitive to the valueof effective diffusivity of the porous catalyst.     

Study on oxygen transport and titanium oxidation in coating cracks under parallel gas flow based on LBM modelling

The oxygen transportation from surrounding air to coating cracks is an important factor in the oxidation and ignition of titanium alloy. In this work, the oxygen transport and surface oxidation of titanium in inclined cracks of coating under parallel airflow are studied with the lattice Boltzmann method(LBM).A boundary scheme of LBM about surface reaction is developed. The conversion factors are utilized to build the relationship between the physical scale and the lattice scale. The reliability ...     

MgH_2-Ti/Cr(AMORPHOUS)COMPOSITE FOR HYDROGEN STORAGE

Ti/Cr (atomic ratio 3:4) amorphous alloy was prepared by ball milling the rapidly quenched Ti/Cr ribbons for 30h, and then milled with MgH_2 for 50 h under Ar atmosphere to obtain MgH_2-30wt. % Ti/Cr composite. The XRD results indicate that MgH_2 decomposed partly during ball milling process. The brittle MgH_2 and the mechanical driving force resulted in a highly dispersive distribution of the Ti/Cr amorphous phase in the Mg matrix. The favorable hydrogenation performance is mainly attributed to the combined effects of the catalytic efficiency of Ti/Cr amorphous alloy and defects on the surface and/or in the interior of Mg formed during ball milling process.     

聚醚与含氢硅油的硅氢加成反应的动力学研究

The hydrosilylation of polyhydrosiloxane and unsaturated allylic polyether terminated with ester group is processed with chloroplatinic acid as catalyst and ethyl acetate as solvent to exclude the mass transfer resistance in the system. The kinetic study is performed by means of Gel Permeation Chromatography. Within the experimental range （mass ratio of the whole reactants to solvent is 1：4, the tool ratio of Si-H bond to carbon-carbon double bond is 1： 1.3, the catalyst concentration from 1.0×10^-4mol·L^-1 （Pt） to 3.1×10^-4mol·L^-1 （Pt）, temperature between 338.15K and 350.35K）, a kinetic model of zero-th order reaction is built up and the evaluated model parameters are found to change linearly with the catalyst concentration.     

拟稳态模型用于间歇萃取精馏的数值模拟

Batch extractive distillation (BED) is a special method used in the distillation process by adding a solvent into the batch distillation column to alter the relative volatility of the components and improve the separation. A comprehensive design and simulation method is required due to the complexity of BED. In this study, a quasi-steady-state model for BED is proposed, the derivation and solution of the model are presented. This shortcut model can be used to simulate the composition and temperature of the reboiler, the top and other plates of the column in a batch extractive distillation operation. The calculated values are in good agreement with the experi-mental data. The results show that the quasi-steady-state model is a practical method because of some advantages such as high precision and fast calculation.     

PtCo-based nanocatalyst for oxygen reduction reaction: Recent highlights on synthesis strategy and catalytic mechanism

Oxygen reduction reaction over Pt-based catalyst is one of the most significant cathode reactions in fuel cells. However, low reserves and high price of Pt have motivated researchers worldwide seeking enhanced utilization efficiency and durability by doping non-noble metals to form Pt-based alloy catalysts. Alloying Pt with Co has been recognized as one of the most effective approaches to achieve this goal.PtCo bimetal combination is one of the most promising candidates to synthesize highly effi...     

A computational toolbox for molecular property prediction based on quantum mechanics and quantitative structure-property relationship

Chemical industry is always seeking opportunities to efficiently and economically convert raw materials to commodity chemicals and higher value-added chemicalbased products.The life cycles of chemical products involve the procedures of conceptual product designs,experimental investigations,sustainable manufactures through appropriate chemical processes and waste disposals.During these periods,one of the most important keys is the molecular property prediction models associating molecular structures with product properties.In this paper,a framework combining quantum mechanics and quantitative structure-property relationship is established for fast molecular property predictions,such as activity coefficient,and so forth.The workflow of framework consists of three steps.In the first step,a database is created for collections of basic molecular information;in the second step,quantum mechanics-based calculations are performed to predict quantum mechanics-based/derived molecular properties(pseudo experimental data),which are stored in a database and further provided for the developments of quantitative structure-property relationship methods for fast predictions of properties in the third step.The whole framework has been carried out within a molecular property prediction toolbox.Two case studies highlighting different aspects of the toolbox involving the predictions of heats of reaction and solid-liquid phase equilibriums are presented.