Advanced Materials Research Vols. 562-564

Abstract: A N-containing additive, amide type modified rapeseed oil (named as NRO), was prepared by chemical modification of rapeseed oil and characterized by infrared spectrum The friction and wear performances of AZ91D magnesium alloy against GCr15 bearing steel under the lubrication of rapeseed oil formulated with NRO were evaluated on a SRV tribotester. The topographies and the chemical species of the worn surfaces of magnesium alloy were analyzed by a scanning electron microscope (SEM) and an X-ray photoelectron spectroscope (XPS), respectively. The results indicated that the friction and wear of the magnesium alloy—steel tribomates could be effectively reduced by formulating NRO into rapeseed oil lubricant. The friction coefficients and the wear volumes of magnesium alloy decreased with increasing contents of NRO. The surface lubricated with NRO-doped rapeseed oil was characterized by less wear as compared with that lubricated with neat rapeseed oil. The enhanced anti-wear and friction-reducing abilities of rapeseed oil by NRO in the lubrication of magnesium alloy against steel were ascribed to the formation of a composite boundary lubrication film due to the strong adsorption of NRO and rapeseed oil onto the lubricated surfaces and their tribochemical reactions with magnesium alloy.

Abstract: Sizing removal of silica fibers was carried out by air heat-treatment, and the mechanical strength, surface condition, microstructures were studied by tensile breaking force measurement, X-ray photoelectron spectroscopy, field emission scanning electron microscope and high-resolution transmission electron microscope. Heat-treatment at 600°C in air was suitable for sizing removal of silica fibers, with the residual strength ratio of 26.6%. The effects of sizing removal by air heat-treatment on the silica fibers are: (a) the sizing acts as an protective layer for the silica fibers to cover the surface defects and decrease the sensitivity under external forces, and the tensile strength drops a lot after the sizing removal; (b) the decomposition and combustion of the epoxy sizing also lead to the embrittlement of the silica fibers.

Abstract: Ceramic honeycomb regenerator as a critical component about the coalmine ventilation air methane thermal oxidation was proposed for a self-developed thermal reverse-flow reactor. A three-dimensional simulation model was established to obtain the distribution of temperature and velocity of gas, and the temperature variation of honeycomb at the length direction. The outlet temperature of gas variation with time was also obtained. The result could provide valuable reference for design calculation of the oxidizer unit and the later study of the thermal shock resistance.

Abstract: The obvious characteristics of transcritical CO2 cycle are that the heat rejection process takes place in the supercritical region. The thermophysical properties of supercritical CO2 change dramatically with the temperature and pressure near the critical region, which results in the momentum and energy exchange and buoyant force change in the heat flux direction, so it should be treated as “variable properties”. According to the characteristics of CO2 specific heat, the correlation of the pseudocritical temperature is obtained and the pseudocritical region is defined. The heat transfer features of CO2 under supercritical pressure are different from those of the conventional refrigerants. In order to compare the heat transfer performance of supercritical CO2 fluid and the conventional refrigerants, the contrast investigation on the heat transfer treatment principle, the heat transfer mechanism and the thermophysical properties are mainly presented in this paper.

Abstract: Oil and natural gas are important energy and chemical raw materials, its resources are gradually reduced. With the rapid development of the global economy, the conventional oil resources can’t meet the rapid growth of oil demand, people began turning to unconventional oil resources, one of which is the oil sands. Oil sands is unconventional oil resources, if its proven reserves are converted into oil, it will be much larger than the world's proven oil reserves. Canadian oil sands reserves stand ahead in the world, followed by the former Soviet Union, Venezuela, the United States and China. However, due to its special properties, different mining and processing technology, and higher mining costs compared with conventional oil, the research of oil sands makes slow progress. At present, due to the rising of world oil price, oil sands mining technology have attracted more and more attention, and have developed a lot.

Abstract: Functionally graded material is a new kind of inhomogeneous material whose material properties change continuously with spatial positions. As a result of its excellent performance, it’s widely used in aerospace, nuclear engineering, biomedicine and some other fields that requirement of material is very strict. Classification based on different applications and research actuality are shown in this article.

Abstract: The influence of calcined temperature and sintered technology on the properties of 0.85 （ Na0.5Bi0.5 ） TiO3-0.144(K0.5Bi0.5)TiO3-0.006BaTiO3(NBT-KBT-BT) lead-free piezoelectric ceramics was investigated by conventional solid state method, and the relationship between calcined temperature, sintered technology and properties of NBT-KBT-BT lead-free piezoelectric ceramics was obtained. The influence of calcined temperature on the material phase was investigated by X-ray diffraction(XRD), the influence of sintered technology on the microstructure of ceramics was investigated by scanning electron microscopy (SEM). Results show that there are impurity phase Na0.5Bi4.5Ti4O15 and main crystal phase （Na0.5Bi0.5）TiO3 while calcined temperature is 830-870°C, the impurity phase decreases while calcined temperature increases, there is pure （Na0.5Bi0.5）TiO3 phase while calcined temperature is more than 890°C. The density of ceramics first increases and then decreases, the crystal grain size first increases and then decreases while sintered temperature increases. The crystal grain size increases straight while soaking time prolonges. When calcined temperature is 890°C, sintered temperature is 1160°C and soaking time is 2 h, the comprehensive properties is good which the dielectric constant(εr) is 1055, the piezoelectric constant(d33) is 144 pC/N, the dielectric loss(tanδ) is 4.0%.

Abstract: The durability of the asphalt is of great significance to its pavement performance, so more and more effort has been addressed on improving the asphalt anti-aging performance. In this work, the effects of antioxidant type and formula on the asphalt anti-aging performance were investigated through various measurements before and after aging process including needle penetration, softening point and ductility. Furthermore, the aging mechanism was analyzed via the FTIR (Fourier Transform Infrared) test. As a result, composite antioxidant can observably improve aging resistance of the asphalt. When the formula is 1.2%B+1.5%C+1.2%D, the needle penetration, ductility, softening point are as follows: 39.4×10-1mm, 148.1cm, 52.1°C. FTIR shows that carbonyl absorption peak reduced. Moreover, composite antioxidant can be more stable improvement of asphalt aging effect due to the cooperativity.

Abstract: Rigid polyurethane foam has many advantages such as low thermal conductivity, good thermal insulation, good antisepsis ability, non-toxic, and light quality. Based on the above reasons, this paper systematically summarized the processing technologies of rigid polyurethane foam, and research progress of its reinforced technology by inorganic materials was briefly discussed.

Abstract: The damping properties of glass and carbon fiber reinforced composites with epoxy and unsaturated polyester resin matrices were studied experimentally in this paper. It is found that temperature and frequency have significant effects on damping properties of these fiber reinforced resin composites. In the frequency range of 0Hz~30Hz, the damping factors of pure resin materials are higher than those of fiber reinforced resin composites. In the temperature range of -300C~500C, the epoxy resin composite shows the lower damping factors at about 200C, and the damping factors of unsaturated polyester resin composites keep increasing with the increase of temperature. Additionally, the storage modulus of the fiber reinforced resin composites decreases slowly with increasing temperature before the curing temperature is reached and it increases slowly with the increase of frequency.