Advanced Materials Research Vols. 328-330

Abstract: Surface nanocrystallization (SNC) is a novel method for improving materials properties. Nanostructured surface layers of about 20 μm thickness were produced in copper plate samples by means of surface mechanical attrition treatment (SMAT). The behaviors of the SMAT samples were investigated by using transmission electron microscopy (TEM), Vickers hardness testing and potentiodynamic anodic polarization tests. The experimental results showed that the longer the peening time was performed on the copper pate samples, the thicker the deformation layers formed. The microhardness results for the top surface layer of the copper plate sample are 1.723 GPa and 1.752 GPa for 45 and 60 min, respectively, which are about two times higher than that of the matrix. The primary passivate potential of nanocrystalline copper was more negative than that of coarse-grain copper.

Abstract: By grafting carbon black (CB) with multifunctional waterborne polyurethane acrylate (WPUA), a series of environmental-friendly CB/WPUA black coatings with different CB contents were prepared in this study. The chemical structures of the products at different synthesis stages were analyzed by Fourier-transform infrared spectroscopy (FT-IR), and the influence of carbon black content on the properties of coatings was systemically investigated. The experimental results demonstrated that the WPUA/CB composite coatings with more CB contents had higher viscosities and impaired unsaturation conversions of WPUA. However, the coating containing 4 wt% of CB obtained the best water resistance and tensile strength owing to incorporate organic-inorganic structures, which is of importance for practical application.

Abstract: The AZ31 magnesium alloy flow stresses have been investigated in the strain rates of 0.03~3s^-1 and temperature range of 300~400°C. The result showed that dynamic recovery and dynamic recrystallization occurred obviously during the hot compression of AZ31 magnesium alloy. In order to represent the flow stress of plastic deformation accurately, the constitutive equation was built by using the dynamic recovery model and dynamic recrystallization model, and its parameters of the constitutive equation were determined by multivariate nonlinear regression analysis. The two-step constitutive equation not only expressed the variation of flow stress with strain rate, deformation temperature and strain, but also revealed the characteristic of dynamic recrystallization kinetics of AZ31 magnesium alloy. Its accuracy was higher than the flow stress of hyperbolic sine model, and the maximum relative errors of two constitutive equation models calculation values compared with experiment data were 5% and 6.5% respectively.

Abstract: Focusing on the residual amount of liquid ammonia in modified cotton yarn, this paper presents a new method of drying the liquid ammonia by microwave. An experimental system is designed to find whether this new method is correct and to analyse the effect of microwave drying on the dyeing rate of cutton yarn. Firstly, the microwave drying experiment is carried out to prove that this new drying method is better than the traditional steam drying way. Then, another contrast experiment on the dyeing rate confirms the good effect of microwave drying. So it is concluded that microwave drying is an efficient and energy-saving way to remove the remaining liquid ammonia. Meanwhile, the experimental results provide the relevant data to make guiding sense to engineering application.

Abstract: Based on the problems emerged from market, 700mm×700mm super-large billet has been advanced. This paper calculated the casting speed and the depth of liquid core according to empirical formula for 700mm×700mm super-large billet, based on calculate and feasibility analysis acquired the appropriate casting speed is 0.2 m/min. A new mold has been advance based on mold thermoanalysis that is complex mold. Theoretically analyzed the function of setting inner cooling and deflected SEN, indicate that complex mold can improve heat transfer efficiency and equiaxed crystal ratio, reducing center segregation; level rotary flow can uniform molten steel ingredient and growth of shell, reduce the impact depth, achieve the effect of E-EMS; calculation show that reduce the depth of liquid core by applying complex mold, finally, reduce infrastructure fee of caster.

Abstract: Soil moisture detective probe is an important part of automatic irrigation system. Soil moisture probe is usually made of metal material which is easy to be corroded and passivated as long-term working in the damp soil, especially containing acid, alkali and salt. We developed a new soil moisture probe material - the graphite-based cementitious material. The mechanical properties and the conductive properties of the material were tested and we found the graphite-based cementitious material which contains 30% to 50% of graphite could be an applicable material for the soil moisture probe.

Abstract: The graft copolymer EPDM-g-MMA was synthesized and its compatibilization property for HPVC/EPDM blending materials was studied in this paper. The synthesis conditions were investigated, results showed that the optimum solvent was the mixture of toluene and n-heptane with volume ratio of 1:1; the optimum conditions were reaction temperature of 80°C, time of 7 hours, initiator BPO was 0.12% and monomer MMA was 12%. The synthesis product was characterized by infrared spectroscopy and showed that EPDM-g-MMA grafting copolymer was obtained. The mechanical property of HPVC/EPDM blending materials increased greatly with an increase of compatibilizer content, compared with HPVC/EPDM material with no compatibilizer, when the dosage of EPDM-g-MMA was 9%, the tensile strength of the system increased from 6.8 MPa to 13.65 Mpa, and elongation at break increased from 175.23% to 347.31%.

Abstract: The attractive performance-to-cost ratio associated with the incorporation of waste material in composite formulations used to produce brake pads has stimulated the idea of exploring the possible incorporation of additional waste materials in such formulations. Thus, the viability of adding palm slag to the composite formulation used in brake pads was investigated, and the results are reported in this paper. In addition, other fillers, such as calcium carbonate and dolomite, were used for comparative purposes. The properties examined included thermal properties, compressive strength, and wear behavior. The results showed that palm slag has significant potential for use as an alternative to the existing fillers in the composite formulations used to produce brake pads.

Abstract: Flexible graphite was prepared using the fine flake graphite that could go straight through 149-85μm mesh as raw material, using sulfate acid and nitrate acid as inserting agent and Potassium permanganate as oxidant. The best oxidation reaction conditions are as follows: V_{Sulfate acid}/V_{Nitrate acid} =5:1, m (fine graphite)/m (Potassium permanganate)=1/0.12, the limited temperature is about 1100-1200°C. Under such condition, the expansion volume of the fine flake graphite with 250-149μm can be reached to 341ml/g. The graphite with 149-85μm can be reached to 230ml/g, the qualities of flexible graphite sheet when intensity is 1.20 g/cm³ are as follows: tensile strength is 4.09 Mpa; ash ratio is 2.19%; recovery rate is 7.8%; compression ratio is 44.0%, TG at 450°C is 0.32%; TG at 600°C is 18.97%; Stress relaxation rate is 3.1%.

Abstract: This paper applies a symplectic method to study analytically the stress distributions of Composite laminated plates. Using variation principle and introducing separation of variables, dual equations were presented. Then in the symplectic space which consists of the original variables and their dual variables,the problem can be solved via effective mathematical physics methods such as the method of sepatation of variables and eigenfunction vector expansion. The transcendental equation and eigen-vector are deduced. The results of cross-ply and angle-ply laminated graphite–epoxy composite plate are shown, which is compared with established results. The parameters’ influences on mechanical property are also discussed.