Abstract: Antibacterial silver can be used against such micro-organisms as bacteria and molds. When Ag nanoparticles are attached to an inorganic carrier, e.g., silica long-term antimicrobial functionality can be gained. Such Ag-SiO2 particles are potential for water purification or bactericidal applications. In this work, submicron sized silica particles doped with Ag were prepared by the modified Stöber method. The as-prepared powder was air-dried and annealed for 75 minutes at 573, 673, 773, 873, 973, 1073, 1173, or 1273 K in air. The powders were studied by DSC/TGA, XRD, SEM, TEM and UV-vis methods. The as-prepared powder consisted of round silica particles having size around several hundred nanometers. XRD and SEM studies confirmed that the powder consisted of metallic silver nanoparticles on the submicron silica surface after annealing at 873 K or higher. According to the SEM study the silver particles had an average particle size between 19-400 nm depending on the annealing temperature. DSC was used to determine the phase transformation temperatures. After annealing the Ag-SiO2 powder at 873 K the TEM study suggested that the silver had crystalline structure. The XRD studies confirmed that silver appeared as a FCC crystal structure. The UV-vis measurements of Ag-SiO2 powder annealed at and below 773 K showed a steady increase in absorption with decreasing wavelength without absorption peaks. Annealing at 873 K and above resulted in a strong peak in between 404 nm and 416 nm. This peak can be attributed to the surface plasmon resonance of silver nanoparticles.
Abstract: Ca-based sorbents has good performance on retening SO2 during coal combustion. In this paper, the effect of Ca/S molar ratio, coal size, combustion temperature and pretreatment time of the materials on sulfur-retention efficiency has been investigated by the method of orthogonal experiment. The work shown that the sulfur-retention is promoted greatly as Ca/S molar ratio of Ca-based agent increased. Simultaneously, the optimum experiment reveals that CaO as sulfur-fixing agent, Ca/S molar ratio 2.0, combustion temperature of 900 °C, coal particle size of smaller than 180 mesh and pretreatment for 30min could attain the best results.
Abstract: In this study, it was aimed to investigate the effects of grain refining of 3003 core alloy on forming and brazing characteristics of 4343/3003/4343 aluminum clad sheet. Ti inoculation level was changed up to 0.1wt% by adding Al-10Ti master alloy into 3003 aluminum melt as grain refiner. The three-layer aluminum clad sheets of 0.7 mm thickness were fabricated by hot roll bonding process. The forming and brazing characteristics were evaluated by measuring FLD (forming limit diagram), bonding strength and sagging resistance.
Abstract: In order to resolve the soil polluted problem which were brought by polyethylene, the study focus on the effects of different molecular weight polyethylene powders to soil, and discuss the molecular weight change of polyethylene. This study made use of four kinds of molecular weight polyethylene powders as materials, added them into the soil of potted soybean to test efficient N content, efficient P content, efficient K content in every development period of soybean, and test the molecular weight of four kinds of polyethylene after the whole development periods of soybean. The Important findings in this study were that there are no significant differences among the efficient N content, efficient P content, efficient K of control group and every experimental group, the molecular weight of polyethylene are nearly no change. it means that the different molecular weight polyethylene powders have no effect to soil.
Abstract: In this paper, composites with different contents of epoxy resin/nano-SiO2 were fabricated, the influence of compounding process on nano-SiO2 dispersion was studied, the microstructure and the relationship between impact strength and nano-SiO2 content were investigated. The results showed that the distribution of nano-SiO2 particles in the composites could be improved efficiently using high-speed shearing dispersion method. To composites with or without the coupling agent treatment, the impact strength grew with increasing nano-SiO2 content, and increase to a maximum value when nano-SiO2 content was 3wt.%. The maximum value was 75.4%, and 45.5% higher than that of monolithic epoxy resin respectively. With the nano-SiO2 content increased continually, the impact strength of composite materials decreased. The coupling agent treatment of nano-SiO2 administered to improve the impact strength of the composites.
Abstract: This work involved a study of polymer-fiber composites as biodegradable packaging made from recycled polyethylene (r-PE) and chemical-treated cotton fabric waste micro fibers. A compatibilizer, polyethylene-graft-maleic anhydride (PE-g-MA), was used to improve properties of the composites. Factors affecting composite properties were investigated including % PE-g-MA loading, and % fiber loading. The fiber composites were prepared by melt-blending technique. The materials were first mixed by a twin-screw extruder and shaped into samples by an extrusion blow molding machine. The samples were then characterized for mechanical, and morphological properties. It was found that properties of the composites were improved by adding the compatibilizer. Optimum properties of the composites were found at 10% (wt%) PE-g-MA loading. It was also revealed that tensile strength and modulus was found to increase as the % fiber loading was increased. SEM micrographs confirmed that interfacial bonding between the cellulose fibers and the r-PE matrix was enhanced as fewer voids at the interfaces were revealed by adding the PE-g-MA compatibilizer to the composites. Film formation occurred on all composites even if the polymer itself was inert biodegradation. The microbial colonization affected mainly of surface properties r-PE composites while changes were monitored also in the bulk properties of cellulose microfiber.
Abstract: High temperature low friction materials are sought for use in engines in order to reduce energy consumption of the machines. Due to the high service temperatures solid lubricating materials are necessary. This study is designed to find the optimal processing conditions for preparing these materials by pulsed electric current sintering. In this study, the Al2O3 - 15wt% ZrO2 (AZ) nanocomposite was modified with 3 wt% of self-lubricating component (CaF2, BaF2, MoS2, WS2, h-BN, or graphite). After the preparation of the alumina-zirconia powder mixture solid lubricant powder was added. Powders were then mixed in ethanol for 24 h, dried in a rotary evaporator, and in oven at 80°C for 24 h. The particle size distribution of the powders was established with the laser method. Powders were compacted by using pulsed electric current sintering technique at 1300 °C with 50 MPa for 5 min in vacuum. The structure of the materials was studied with XRD and SEM. Density of the compacts was measured with the Archimedes method and their hardness was evaluated by applying HV1 hardness with the instrumented indentation techniques. Their mechanical behavior was further studied with the instrumented scratch testing.
Abstract: The development trend for diagnostics is reducing the diameter of coaxial signal cables that comprise the probe cable. The thinner super-fine coaxial cable which is offering superior electronic and mechanical properties, such as 75 %IACS(International Annealed Copper Standard, electrical conductivity) and 700 ~ 800 MPa in tensile strength has to be developed. Cu-Ag based system is one of the most promising systems for high strength and high conductivity Cu alloys. In order to find the optimum conditions to obtain Cu-Ag-Zr-Co alloy with high strength and high electrical conductivity, the aging characteristics including work hardening of micro-Vickers hardness, tensile strength and electrical conductivity of this alloy were systematically measured at room temperature. Also the influence of aging treatment was investigated by transmission electron microscopy(TEM) and scanning electron microscopy(SEM) in this study. The aging treatment for precipitation was divided into two steps and carried out at various time and at different temperature and the multi-step aging treatment coupled with cold rolling was proposed for realizing Cu-Ag-Zr-Co alloys with high strength and high electrical conductivity. The electrical conductivity was improved from 31 %IACS to 91 %IACS remarkably and the tensile strength was increased from 230Mpa to 690Mpa greatly by an optimization of alloy composition and manufacturing process including aging.
Abstract: There is very strong ultraviolet radiation in western desert of China. In order to study the behavior of ultraviolet aging for bitumen, three type of bitumen were aged in the laboratory. The ultraviolet aging and thermal aging under the condition of artificial intensive ultraviolet radiation environment test and the rolling thin-film oven test (RTFOT) were comparative investigated. The results showed that the impact of ultraviolet aging manifests longer time than that of thermal aging for bitumen.
Abstract: Titania(B) nanobelt and anatase titania nanobelt could be prepared by calcining hydrogen titanate nanobelt at 450 °C and 550 °C respectively. When the hydrogen titanate was previously treated with HNO3 for some time before calcination at 450 °C, titania(B) and anatase mixed phase titania could be obtained. The ratio of anatase phase in the product could be changed by control the time of HNO3 treating. TEM images show that the mixed phase product was anatase nanocrystals doted on titania(B) nanobelts. The mixed phase product shows higher photocatalytic activity on the decomposition of Methylene Blue (MB) than the pure titania(B) nanobelt and anatase nanobelt.