Advanced Materials Research Vols. 284-286

Abstract: Based on the classical diffuse mismatch model (DMM), the dedicated Monte Carlo model for Si/Ge superlattice is proposed and the method to cope with the scattering at the interface is provided. In this model, phonons transport between two different materials can be taken as the movements between the different phonon dispersion relationships. If there is a corresponding position in the other material, the phonon with a given frequency will be able to pass through the interface, otherwise it will be reflected.

Abstract: The environment which can have a great effect on the composite aircraft structure performances must be considered during the design and certification process. In this paper, the extreme temperature and humidity span of the worst environment conditions in aircraft structure design and certification are investigated, and some test methods involving environment influences are also discussed. The studying results can be used in design and certification for environment influences of composite aircraft structures.

Abstract: Mullite (3A1₂O₃·2SiO₂) is an aluminosilicate ceramic of great technological importance. We investigated its potential as fillers in rubber. Mullites untreated or treated with 3% γ-mecapto-propyltrimethoxysilane (A-189) were added into styrene-butadiene rubber (SBR) materials on a laboratory-sized two-roll mill. For comparison, commercial precipitated silica was also used. The effect of these fillers on the cure characteristics, processibility and mechanical properties of SBR at various loadings, ranging from 0 to 50 phr was investigated. The results showed that mullite was a semi-reinforcing filler for SBR materials and exhibits better overall cure properties, lower Mooney viscosity, lower tensile set, better resilience as compared to precipitated silica, while it is inferior to precipitated silica especially with regard to tensile strength, tear strength and abrasion resistance. The presence of the silane coupling agent can enhance mechanical properties of filled SBR vulcanizates to some extent.

Abstract: The diffusion coefficients of slag constituents were calculated using Eyring equation. The Urbain slag viscosity calculation method was modified by improving the constiuents dividing method based on slag depolymerisation degree NBO/T calculation. the amphoteric oxides such as TiO₂, Cr₂O₃, Fe₂O₃, B₂O₃ and Al₂O₃ were specifically dividied into glass former part and modifier part, and the diffusion dimension was calculated according to the value of NBO/T. The results of diffusion coefficients showed that, the modified method is more accurate than the Urbain method within the calculation conditions. Based on the modified diffusion coefficient calculation method, ladle slag composition was optimized to enhance the deoxidization rate.

Abstract: Gunpowder composite welding rod is a new type of welding material, which can accomplish welding without electricity and gas. In this article, the effect regularities of two types of thermite on the energy densities of gunpowder composite welding rod have been obtained with thermodynamical equilibrium equations. These results are very useful for the design of the main reaction system of this welding material.

Abstract: To meet the oilfield reinjection water quality for low and ultra-low permeability reservoirs in China, a hydrophilized polyvinylidene fluoride membrane manufactured by our laboratory was used for ultrafiltration of the produced water from polymer flooding in Daqing Oilfield. The results showed that a temperature of 37 °C, volume reduction factor (VRF) of 4, TMP of 0.20 MPa and crossflow velocity of 4.5 m/s were the feasible operation conditions for the membrane, and the average flux could reach 75 L/(m²h). In the permeate, the total suspension substance was consistently below detection limits (2.5 mg/L) and medium grain size was undetectable, and the content of hydrolyzed polyacrylamide, crude oil and turbidity were respectively lower than 50 mg/L, 1 mg/L and 1 NTU, all of which reached the highest oilfield reinjection water quality in China and demonstrated the membrane had a good anti-fouling characteristics.

Abstract: In the paper, the polyurethane/carbon nanotubes composites were prepared by solution-blending method. The polyurethane dissolution, carbon nanotubes dispersion agent, dispersion method and preparation of composites were analyzed. The results showed that the tetrahydrofuran and N-N-dimethylfomamide could used as the dissolution of polyurethane. The dissolution is most even with the ratio of tetrahydrofuran and N-N-dimethylfomamide of 1:1, and 1g polyurethane grains were resolved with 20ml solutions about 72 h. The N-N-dimethylfomamide was used as dispersion agent of carbon nanotubes by ultrasonic dispersion about 2h. The producing process of polyurethane/carbon nanotubes composites was successively heating, drying, and solidifing in the air, so the smooth surface could be received. The results indicated that the dispersion effect from good to poor is ultrasonic dispersion, magnetic dispersion and machining dispersion. With extension in time and increasing disperse frequency, the dispersion effect is better and better. But it also presented that the carbon nanotubes were reunited by magnetic and ultrasonic dispersion after the certainly scattered time, their best dispersion time were respectively two hours and one and a half hours.

Abstract: Two-step casting method was developed for preparing quasi constrained layer damping structural polymeric composite. Quasi constrained layer structural piezoelectric ceramic P82/carbon black(CB)/epoxy resin(EP) composites were successfully prepared when the ceramic content was less than 30% in volume. Dynamic mechanical analysis(DMA) showed that the composites with quasi constrained layer structure exhibited perfect damping properties. When the piezoelectric ceramic P82 volume fraction was 10%, the composite showed the highest loss factor peak value of 1.182, the widest damping temperature range of 44.2°C, and the largest loss area of 32.17. The storage moduli of composites with quasi constrained layer structures were higher than that with non quasi constrained layer structure.

Abstract: An unconstrained optimization model is established for assessing cylindricity errors by the minimum zone method based on radial deviation measurement. The properties of the objective function in the optimization model are thoroughly researched. On the basis of the modern theory on convex functions, it is strictly proved that the objective function is a continuous and non-differentiable and convex function defined on a subset of the four-dimensional Euclidean space. The minimal value of the objective function is unique and any of its minimal point must be its global minimal point. Thus, any existing optimization algorithm, so long as it is convergent, can be applied to solve the objective function in order to get the wanted cylindricity errors by the minimun zone assessment. An example is given to verify the theoretical results presented.

Abstract: Integral inference method for multi-state type-Ⅱcensored data is presented, which is used to evaluate the rupture life of composite material. The best unbiased estimators for the model parameters, the standard deviation and their covariance are also given. The confidence limits of the acceleration equation and the confidence intervals of percentiles for Weibull distribution are discussed in detail. According to the presented method, the experimental information of accelerated rupture life is fully exploited, and the cross information among test data in different stresses are analyzed as an integration.So its information quantity is much bigger than traditional group test method. The method provides a feasible and effective approach to rupture life evaluation and reliability estimation of composite material.