Advanced Materials Research Vols. 79-82

Abstract: The feasibility of manufacturing microfibrillar composites (MFCs) and their novel applications have been studied to a significant extend. In order to achieve commercially viable production rate of MFC materials, consistent fabrication has to be guaranteed. However, it has been shown that continuous production of MFC materials has certain difficulties need to be overcome. This study aims at identifying the production problems and improving the efficiency of manufacturing MFC materials. MFC manufacturing has been reasonably successful by drawing poly(ethylene terephthalate) (PET)/polypropylene (PP) blends. However, when the PP in the polymer blends is replaced by polyethylene (PE) for its ease of subsequent manufacturing, irregular breakage persistently occurs during drawing and this phenomenon also occasionally happens for PP/PET blends. This study involves melt blending of linear low density polyethylene and linear medium density polyethylene with PET in a single screw extruder with 70/30 wt%. Drawing was conducted at temperatures ranging from room temperature to 70°C and with draw ratios of between 1:5 and 1:7. The test results, when comparing MFC with pure PE, show 60% and 80% increase in specific tensile strength and specific tensile stiffness, respectively. It is concluded that by carefully controlling the temperature profile within the drawing chamber and using a moderate draw ratio (1:5), an efficient drawing process can be achieved to produce commercial MFC materials.

Abstract: The work aims to investigate the anti-corrosion behavior of silane treated LY12 aluminum alloy (AA LY12) and optimize the process conditions of silane treatment. The silane films were prepared on AA LY12 from γ-aminopropyltriethoxysilane (γ-APS) hydrolized in ethanol/water mixture by dip coating method. The optimum process parameters were obtained from the orthogonal designs in terms of silane solution concentration, ethanol/water ratio, dipping time, curing temperature and curing time. Prior and after silane treatment, the surface of AA LY12 was characterized by contact angle measurements and scan electron microscopy (SEM). The potentiodynamic polarization tests and electrochemical impedance spectroscopy measurements (EIS) were employed to study the anti-corrosion characteristics of silane films on AA LY12. The impedance plots were fitted with the different equivalent circuits. Furthermore, the influence of the above process parameters of silane treatment on film formation and anti-corrosion performance was explored. The results indicate that the γ-APS treated AA LY12 significantly improved the corrosion resistance, compared to the untreated one.

Abstract: The thermal parameters of sweat self-lubricating composite and its effect on high temperature rolling bearing have been investigated in the paper. A new expression of describing the contact area of the rolling bearings has been developed and used to calculate the change value of the contact area with temperature. The result indicates that the thermal parameters of the sweat self-lubricating composite greatly improve the contact area of the bearings by comparing with the material M50, the increase rate of contact area is lower than that of M50.

Abstract: Based on the structures and composition of ceramic materials, the microstructure design and new preparations were used to induce in situ grain growth by adjusting the main factors which had impacts on grain morphology. By adding CAS (CaO-Al2O3-SiO2) and Nb2O5, the complex toughened alumina ceramics with columnar grain was fabricated under pressureless sintering systematically. The influences of additives on the alumina ceramics with columnar grain were analyzed by means of TEM, SEM, XRD etc. The dynamic conditions of anisotropic growth of columnar grain were researched, and superior growth in some grain directions was induced by doping CAS and Nb2O5. The growth mechanism of columnar grains of alumina ceramics was explored, and established growth model.

Abstract: In order to explore a new kind of high anti-corrosion and environmentally benign materials to protect steel, zinc-silica composite coatings were prepared by plating technique. In this paper, experiments on electrodeposited zinc-silica composite coatings are reported, effects of cathodic current density, agitation, additive, anode number, space between anode and cathode on the appearance of coatings are discussed, composition and property of zinc-silica composite coatings are investigated. The electrolyte composition and operating conditions are: ZnCl2　80 g/L, KCl　220 g/L, additive 10 ml/L, SiO2 2~3 g/L, pH 4~5, current density 140~180 A/m2, temperature 15~35°C, 20~30 cm space between anodes and cathodes, once plating time is 60 min.The content of silica in coatings is 0.47~0.56%(mass), the thickness of coatings is 20~23 μm, and the time of composite coatings appearing red rust in neutral salt spray test(NSS) keeps more than 410 h. During the experiment lasting for 30 days, pH value and composition of the electrolyte and deposition speed of coatings all keep relatively stable. Further more, this composite plating technique can reach the first National Entironment Standard(GB 8978–1996). All the results show that zinc-silica composite coatings with no chromate treatment have better corrosion resistance than zinc coatings, stability of this composite plating technique is satisfactory, maintenance operation is convenient, and the plating process is innocuous and safe, so this technique will undoubtedly has a great future in application.

Abstract: Porous activated carbon was prepared from orange wastes using zinc chloride as an activating agent by one-step carbonization method. Effects of impregnation ratio, carbonization temperature and heat preservation time on pore characteristics of activated carbon were studied. The porous structures of the orange wastes activated carbon were investigated by BET, D-R equations, BJH equations and Kelvin theory. The morphology was observed using transmission electron microscopy (TEM). The mesoporous activated carbon is gained when the impregnation ratio is 3:1; the carbonization temperature is 550°Cand heat preservation time is 1.0 h. The activated carbon has total pore volume 2.098 cm3/g, mesoporous pore volume 1.438 cm3/g, with a high BET surface area 1476m2/g. The pore distribution of the mesoporous activated carbon is very concentrative, with average pore diameter of 3.88nm. While, the high specific surface area activated carbon is gained when the impregnation ratio is 2:1; the carbonization temperature is 550°Cand heat preservation time is 1.0 h. The activated carbon has high BET surface area 1909 m2/g, while the total pore volume is only 1.448cm3/g and microporous pore volume is 0.889cm3/g, with average pore diameter of 2.29 nm.

Abstract: This paper discussed the effects of different cooling rate on the microstructure of the 4Y32 aluminum alloy and the refinement and modification on 4Y32 aluminum alloy by using Na and Al-10%Sr master alloys in various treatment states. And also the effect of Al-10Sr and Al-3Ti-1B compound modification on microstructures of 4Y32 aluminum alloy has also been studied. The results showed that: the primary silicon was eliminated during slow cooling. As the cooling rate increased, the number of primary silicon was also growing, but the size of primary silicon and eutectic silicon were significantly refined; when without modification, the shape of eutectic silicon was needle and flake; 4Y32 aluminum alloy could be effectively refined after Na modification, under the optimum addition amount of 0.8wt%. The best modification was achieved with 15 minutes, that is, the shape of primary silicon changed to small granular or oval and the primary silicon was eliminated; the as-cast structure has been improved after Al-10Sr modification, under the optimum addition amount of 0.2wt. %, the shape of eutectic silicon changed to fine short rod or point and the primary silicon was eliminated; However, in the compound modification, efficiency of Sr was decreased with the increasing additional amount of AI-3Ti-1B master alloy, which was attribute to the interaction of Sr and Ti.

Abstract: The corrosion behavior of Fe3Al intermetallic compounds annealed at various temperatures in sea water was studied. The results indicated that both structure ordering and surface oxidation film can significantly improve the anti-corrosion performance of Fe3Al alloys. Furthermore, there was no significant difference in anti-corrosion performance between Fe3Al samples of DO3 and B2 structure. The corrosion mechanism of Fe3Al alloys in seawater was probably as follows: Al element is preferentially corroded, Fe corrosion followed when Al element has been corroded away from the sample surface as well as the reduce ratio of Al becomes smaller than the dissolution ratio of Fe.

Abstract: H-beam is widely used in the construction in virtue of its excellent sectional properties. Because of its complex section, flange and web are deformed in different zones in rolling process. The traditional elongation ratio between flange and web is 1.03~1.05, which obtained from experience. Web wave, crack, or flange crack, and the large residual stress exist in the H-beam production. The problems are mainly caused by the uneven elongation of flange and web. It is necessary to keep uniform elongation of flange and web to solve these problems. The modified reduction ratio between flange and web is provided in this paper. The ratios improve the quality of H-beam by simulation and experiment.

Abstract: Present paper deals with the delayed fracture in woven GFRP underwater at elevated temperature. The tensile test of GFRP after water immersion was conducted to evaluate the residual strength ater immersion at various water temperatures. The residual strength of GFRP decreased with the increase in the water temperature and the immersion time. In fact, the transition in failure mode with water immersion was ascertained from SEM observation of the fracture surface. Additionally, creep test in air and under hot water at 95°C was conducted. The creep rupture time decreased drastically with water immersion, in contrast, creep rupture wasn’t observed from the creep test in air. It was clarified that the water immersion generated the transition in the failure mode of GFRP and therefore led to the acceleration of the strength degradation.