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Reaction sintered SiC ceramics were prepared by the silicon melt infiltration method over temperatures of 1450−1550°C. The effects of the carbon and silicon contents of the starting materials as well as the sintering temperature and time on the thermal conductivities and microstructures of the ceramic materials were studied. The thermal conductivities and microstructures of the samples were characterised using thermal conductivity measurements, X-ray diffraction analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy and mercury injection porosimetry. The results showed that sintering temperature and time as well as the carbon and silicon contents of the green specimens are the main factors affecting the microstructure and porosity of reaction bonded SiC ceramics. Increasing the reaction temperature and time decreased the porosity of the ceramics. This was due to the infiltration of the silicon melt into the ceramic specimens. The thermal conductivity and porosity of the sample sintered at 1550°C for 3 h in an argon atmosphere were 102·5 W m K−1and 0·3% respectively.

The coagulation process of PAN (poly(acrylonitrile)) wet-spinning was modeled and simulated based on the numerical analysis of the coagulation of a viscous polymer solution by diffusional interchange with a bath. Experiments were performed with gelled solutions of PAN in nitric acid to determine the diffusion rate of solvent and nonsolvent (water) during the coagulation. The experimental data were analyzed by using equations of diffusion coefficient which are a function of the solvent concentrations of the coagulation bath and the filament. The concentration profile of solvent in moving filament was predicted by solving the diffusion model equation numerically. A simplex method was used in the computation of the parameters of the diffusion equations to minimize the difference between the numerical results and experimental data.

This paper deals with the simulation and optimization of composite distillation columns for the waste nitric acid recovery process. The composite distillation columns which consist of a multistage vacuum column and an atmospheric pressure column, half of which, consists of a packed bed, were modeled by using an equilibrium stage method and a nonequilibrium stage method. The required physical properties of a nitric acid solution for simulation were obtained from correlations based on experimental data. Simulation results using the nonequilibrium model showed better agreement with actual plant data than those of the equilibrium model. Based on the simulation results, the optimal operation conditions were studied. In the optimization reflux ratio was employed as the key variable to maximize the operating profit.

Direct irradiation of 2‐vinylnaphthalene (I) and fumaronitrile (II) in benzene or acetonitrile yields predominantly the copolymer (III).