Advanced Materials Research Vols. 284-286

Abstract: Zeolites mordenite (MOR) and β decorated with high dispersion degree and loading content of CuO composite (symbolized as CuO/zeolite) were prepared via a novel method-the stepped hydrothermal synthesis. The resultant composite were characterized with details by powder XRD, ICP-AES, H₂-TPR and TEM techniques. Shown by experiment, the stepped hydrothermal synthetic method adopted in the present research using urea as alkali source as well as benefiting from the ultrasonic wash treatment hardly damages the zeolitic framework structure. Compared with ammonia, high dispersion degree and loading level of CuO are yielded as a consequence of the employment of urea as alkali source. Besides, the ultrasonic wash treatment not only removes some CuO precursors that deposit on the external surface of the porous support but also produces a uniform distribution of CuO particles with smaller dimension on the surface of zeolites: CuO are dispersed in nanoscale of about 4-8 nm on mordenite and 2-5 nm on zeolite β. The present synthetic strategy could be therefore applied as a novel general method for the manufacture of functional materials in a wide spectrum.

Abstract: Wear resistant NiMo/Mo₂Ni₃Si intermetallic composite with a microstructure of ternary metal silicide Mo₂Ni₃Si primary dendritic, the long strip-like NiMo intermetallic phase, and a small amount of Ni/NiMo eutectics structure were designed and fabricated. Wear resistance of NiMo/Mo₂Ni₃Si composites were evaluated under different load at room-temperature dry-sliding wear test conditions. Results indicate that NiMo/Mo₂Ni₃Si composites have excellent wear resistance and sluggish wear-load dependence. The dominant wear mechanisms of NiMo/Mo₂Ni₃Si composites are soft abrasion and slightly superficial oxidative wear.

Abstract: Nitrides(Si₃N₄/Sialon) bonded alumina castables were fabricated by in situ nitridation reaction. Effects of the formation of nitrides on the physical properties, hot strength and thermal shock resistance were investigated. The results show that the phase composition of castables is alumina, a-Si₃N₄, b-Si₃N₄ and Si₂N₂O after fired at 1400^ºC and 1450^ºC, and is alumina, b-Sialon and O’-Sialon after fired at 1500^ºC. Hot modulus of rupture and thermal shock resistance of specimens are noticeably improved due to the formation of nitrides.

Abstract: Based on SiC grains and powder, flake graphite, AlN powder, Silicon powder, sintered alumina ultra-fine powder as the starting materials, the sample of SiAlON-Graphite-SiC composites was prepared by firing under N₂ atmosphere at 1 550°C and then analyzed in terms of high temperature performances by XRD, SEM and EDAX etc. The interrelation between composition, structure and performance of the material was also investigated. It indicates that this material provides excellent thermal shock resistance and molten alkali resistance, also proper oxidation resistance and applicable as the inner lining of the blast furnace.

Abstract: The fabrication of assorted fibers barrel-type pre-formed shape which contain of ZLl09 alloy with alumina fibers and short carbon fibers by vacuum coining and extrusion casting in this study. The examination results show that it can be produced Al₂O_3f+C_f/ZL109 assorted fibers composite material whose the structures are fine and close and the fibers distribute uniformly by squeeze casting technology. The interface between wild phase and matrix is good combination and no inclusions in the composite material. The fiber reinforcement is uniformly distributed in the matrix, and mainly in 2-dimension distribution.

Abstract: The adsorptive capability of β-Cyclodextrin-cross-linked polymer(β-CDCP) for cadmium was assessed in this work using column method. It was found that the complex (Cd(II)-5-Br-PADAP) could be quantitatively retained on the β-CDCP in the pH 8.5, eluted completely with 1.5 mol×L^-1 HCl. Under the optimum conditions, the linear range, detection limit (DL) and the relative standard deviation (R.S.D.) was 2.0-60.0 μg×L^-1, 7.8 ng×L^-1 and 2.20% (n=3, c=20.0 μg×L^-1) respectively. The separation of Cd(II) was achieved from water samples with an enhancement factor of 20. Moreover, the β-CDCP could be used repeatedly and offered better recovery. The method was validated using a certified reference material, and applied for the determination of trace cadmium in water samples.

Abstract: A novel fine inclusion removal technology due to the dispersed in-situ phase induced by the composite ball explosive reaction was put forward. A composite ball with this function has been designed and prepared using a laboratory model batch type balling disc (at 12 rpm) and the composite ball has been fed at the end of RH refining. The results indicate that feeding composite ball in RH ladle is a novel technology and the inclusion in the IF molten steel can be removed effectively. Compared with conventional inclusion removal technology, the number of the oxide inclusion can be decreased to a lower level and the inclusion size becomes finer. Using this novel technology, the total oxygen in the as-cast slab can approach to 5ppm and the steel production cost for per ton can be reduced by 5 ~12 RMB.

Abstract: (Al₂O₃+Al₃Zr)_P/Al composites were in situ synthesized from Al-Zr(CO₃)₂ system. In the process of in situ reaction, electromagnetic stirring (EMS) is employed to improve the conditions of reaction between reactants powder and melt. The results indicate that the Lorenz force improves the kinetic condition and accelerates the nucleation of endogenetic particulates. The optimized electromagnetic density is 0.025T. Scanning electronic microscope (SEM) observation demonstrates that the sizes of reinforced particulates are controlled at 1~2 μm. Moreover, the particulates are well distributed in Al matrix.

Abstract: Al₂O₃·SiO_2f/A356 composites contained La were fabricated by squeeze casting, and effect of La on the solute segregation and microstructure were researched. The results indicate that the microstructure in the composite can be refined by La, which enriches near the interface to be favorable to improve the wettability between the fiber and Al alloy. The phases RE-richening do not formed at the interface. There is no special influence of La on the Mg segregation in the matrix alloy. The distribution of Mg and La in the composite are near the interface.

Abstract: This work investigated the effects of fumed titanium oxide on thermal stability of nano-silica thermal insulating composites prepared by dry process. The results showed that the composites could keep excellent thermal stability at the temperatures below 800°C. However, when the samples were used at higher temperatures (>800°C), the volume shrinkage increased sharply, which directly led to a serious deformation and then affected thermal insulating properties in applications. The utilization of fumed titanium oxide could significantly improve thermal stability of the composites. When 10wt% fumed titanium oxide was added, the service temperature can increase from 800°C to 900°C. The desirable results would be achieved by adjusting the amount of additives according to practical using temperature. In addition, field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) were employed to characterize the microstructure and phase transformations of the composites treated at different temperatures.