28 March 2014, Volume 32 Issue 9

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    Spescial Issues
  • ZHOU Zhenggan, SUN Guangkai, MA Baoquan, LI Yang
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    The applications of the ultrasonic phased array technique, the air-coupled ultrasonic technique and the laser ultrasonic technique for the non-destructive testing for advanced composite materials are reviewed. For the problems of the non-destructive testing for composite parts of aeronautical and astronautical sophisticated equipment in manufacture and service stages, such as the testing of the complex profile parts, the noncontact testing, the fast testing, the on-site testing, a series of self-developed novel ultrasonic testing systems are developed. The effective detection of the porosity and the delamination located at the corner of the Lshaped carbon fibre reinforced plastic (CFRP) composite parts is realized by using the ultrasonic phased array technique. The detection of the interface debonding in honeycomb sandwich composite parts is realized based on the air-coupled ultrasonic technique. The detection of the porosity, the impact-damage and the drilling-induced delamination in CFRP composite parts and the detection of the delamination in refractory composite parts are realized by using the laser ultrasonic technique. The key technical problems, the application scopes and the future development of these novel ultrasonic testing techniques are analysed. It is shown that the new ultrasonic testing techniques can be used for the complex profile detection, the noncontact detection, the fast detection and the on-site detection for composite parts.
  • WANG Hongyu, SUI Guoxin
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    The paper exploits the use of the Xanthoceras sorbifolia husk as the filler of the composite materials, optimizes the process of the composite preparation, and explores the trend of the mechanical properties changing with the filler content. The surfaces of the Xanthoceras sorbifolia husk fibers are treated with alkali, silane coupling agent and the alkali treatment, followed by that of the silane coupling agent. The Xanthoceras Sorbifolia Husk Fibers/ High Density Polyethylene composites are prepared via the twin screw extrusion and the injection molding. The influence of processing methods and fiber contents on the mechanical properties, such as the tensile strength, the elongation at break, the elastic modulus and the impact strength, of the composites are investigated. The tensile strength and the elongation at break are found to increase for the composites extruded twice. The tensile strength and the elongation at break are decreased, the elastic modulus is increased, and the impact strength is changed in a wavy form with the increasing fiber contents. The fiber fracture mechanism and the spall- off mechanism are observed coexisting on the fracture surface of the composites.
  • JIN Zhi, ZHAO Guangjie
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    The pore structural characteristics of the liquefied wood-based activated carbon fiber with water steam activations at different activation temperatures and activation times are studied. The pore structure is assessed by N2 adsorption/desorption isotherms at -196℃. The specific surface area and the burnt-off are increased with the increase of the activation temperature or the activation time, and are more dependent on the activation time when activated at higher temperatures. With increasing activation time, the total pore volume and micropore volume are increased more significantly when activated at 750℃ and 800℃, while the mesopore volume is high at the early stage of activations at 650℃ and 700℃ then is decreased, and does not develop until the later stage of activations at 750℃ and 800℃. The pore size distribution analysis indicates that the micropore size distribution becomes increasingly heterogeneous with increasing the activation time under all activation temperatures.
  • MENG Yangang, JIN Xueke, LU Panpan, WANG Haifu
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    The numerical simulation and the experiment of the effects of the enhanced PELE of reactive materials on a metal plate are carried out to investigate the influence of the ratio of length to diameter, the thickness of the plate and the impact velocity on the terminal effects. It is shown that the influence of the ratio of length to diameter on the lateral efficiency and the deflagration efficiency of the enhanced PELE of reactive materials is limited, but the damage effect will decline if the ratio of length to diameter is too small, With the speed of 800 m/s, the damage effect of the enhanced PELE of reactive materials on the plate in a range of 10-15 mm is better; The enhanced PELE of reactive materials performs better for intercepting a high speed target.
  • FAN Lei, TAN Feihu, CHEN Ping, CHEN Huahui, CAO Hongzhi
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    To obtain the ceramics of mullite purified from fly ash not only cuts its production cost, but also improves the environment contaminated by the accumulation of fly ash. Through ball milling, pressing, sintering, the ceramic materials are prepared with different chemical compositions of mullite powders purified from the fly ash. This paper studies the influences of the sintering temperature and the composition of the microcrystalline mullite ceramics on the body shrinkage, the ignition loss, the apparent density, the impact toughness, the Vickers microhardness and the microstructure of the prepared ceramics. It is shown that with sintering mullite at 1450℃the obtained ceramic material has the most dense body shrinkage, the maximum Vickers microhardness; the sample prepared from the S type samples has an even greater density and the optimum overall performance; but the S-type sample has a large calcium oxide content and is not conducive to the impact toughness of the mullite ceramic materials.
  • WENG Duan, WAN Jie, ZHANG Zhijun, RAN Rui, CONG Shuchen
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    Sulfides exist widely in petrochemicals and have considerable influences on the processing parameters and the product quality of petrochemicals. Sulfides also affect the safety of the operating personnel and the environment. The controls of the sulfide content and the desulfurization technologies are currently the research focus in both petroleum industry and related environmental protection fields. This paper reviews the progress in the desulfurization technology of the light hydrocarbon and the solvent oil. The major forms of the sulfides in the light hydrocarbon and the solvent oil are discussed, together with the related control measures of the sulfide content. The commonly used desulfurization technology is reviewed. Progress and developing trends of the novel desulfurization technology are commented.
  • XIONG Dehua, CHEN Wei, LI Hong
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    It is urgent to solve the problem of energy shortage and the growing environmental problems, and to effectively utilize the clean and renewable solar energy via the photothermal conversion. The highly efficient solar selective absorber coating is the most critical part of solar thermal conversion devices, the property of which plays a decisive role in the device performance. This paper reviews the recent development of the solar- thermal selective absorber coatings, including the material selections, the coating structures, their preparation methods and their commercial applications. The existing problems of the solar selective coatings and their possible solutions are commented.
  • CHEN Zhaofeng, LI Chengdong, CHEN Qing, XU Tengzhou, LI Binbin, WANG Lei
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    In recent years, the technologies of the thermal insulation in our country are developed in a large extent; accompanied with researches and production capacities of novel thermal insulation materials. The vacuum insulation panel (VIP) enjoys an excellent thermal resistance, about 10 times higher than that of conventional insulators, and is now the most advanced thermal insulation and preservation material in refrigeration, freezing, and heat preservation areas, widely used in fields like buildings, household appliances and aerospace. The core material is the skeleton of the VIPs; it determines the thermal insulation properties of the VIPs and provides a guarantee for the long service life of the VIPs. This paper discusses the types and the functions of the core material, and the application requirements of the VIP core material. The differences in the properties and characteristics among traditional thermal insulation materials are compared, including the particle insulation materials, the foam insulation materials, and the fibrous insulation materials. A novel core material composed of fibers and different- sized particles is proposed. This kind of core material enjoys excellent compressive and bending resistances, and low elastic resilience. In addition, it has the advantages of both the fibrous insulation material and the particle insulation material,,to overcome the shortcomings of easy-collapsibility in the particle material and easy-resilience in the fibrous material, and becomes an optimizing core material for the VIPs in building up the exterior wall thermal insulation.
  • TONG Wangshu, ZHANG Yihe, ZHANG Qian, LÜ Fengzhu, YU Li, AN Qi, GAO Di, LIU Leipeng
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    The research progresses for the low dielectric constant polyimide and the composites are reviewed in this paper. The mesoporous silica, the silica tube and the polyhedral oligomeric silsesquioxane are discussed in the context of decreasing the dielectric constant of PI, and the prospects for the development of low dielectric constant PI materials The preparation by adding porous materials into PI can produce pores with supporting structures, leading to low dielectric properties and good mechanical properties of the composite. It is a new way to prepare PI of low dielectric constant.
  • ZHU Xixi, WANG Li
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    The bi- metal pillared montmorillonite is an important type of the pillared montmorillonite. It has application prospects in both adsorption and catalysis. This paper reviews the preparation of the pillaring agent, the approach of the pillared montmorillonite as well as the application in catalysis and adsorption. The long preparation period, the unsatisfactory thermal and hydrothermal stability and the uneven distribution of pores are the major problems. In future studies, the multimetal pillared structure or the introduction of rare earth metals, the mechanism, the retationship between structure and properties and the preparation of high-performance, multifunctional montmorillonite materials are the main subjects.
  • HU Haining
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    The studies of the structural colors of the anodic alumina membrane (AAM) fabricated by electrochemical oxidation of Al are reviewed in this paper. The color tuning of the AAM is predominantly due to the interference enhancement of the nanostructure and the colors obtained cover the whole light range and can be precisely tuned. These properties are of technological importance for applications in the fields of painting, color display, decoration, anti-counterfeiting and textiles. Recently, a considerable attention is paid to the construction of man-made systems with interference colors, such as multilayer structures, metal-coated or carbon-coated thin anodic alumina templates, anodic alumina membranes embedded with metal. The relationship between the brilliant colors and the microstructures is obtained for each man-made system.
  • Articles
  • LIU Jianmin, WANG Jiren, HE Zhiliang
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    In order to figure out the source of bursting water in an accurate manner, the multivariate mixed models theory and hydrochemical analysis were used to build the multivariate mixed models for aquifer and bursting water source. By combining the built equations, numerical analysis was taken for the bursting water source. The gained result was compared with those gained by the BP neural network method and the fuzzy comprehensive evaluation method. The comparison shows that these results are basically consistent with each other, proving that the multivariate mixed models can well be counted upon as a reliable tool. The tool is able to accurately figure out the source of coal mine water invasion and the calculation process is simple and accurate; it is less restricted by water chemical analysis of sample size and ionic species number, thus making a great contribution to the improvement of the safety production of coal mine.