Materials Science and Engineering Applications

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Authors: Ju An Zhao
Abstract: A multi-layer coating SiC/ Si - MoSi2 /MoSi2 with good oxidation resistance has been developed by using the slurry-sintering method on the surface of graphite to improve the oxidation resistance performance at 1700 °C for more than 200 h. Microstructure and anti-oxidation property of the as-received coating were investigated. It was found that functionally gradient SiC/ Si - MoSi2 /MoSi2 coating was formed on the surface of the graphite substrate. The coating characterized by excellent thermal shock resistance can effectively protect the graphite from oxidation at 1700 °C for 200 h. The mechanism of the oxidation resistance of the coated graphite is also dicussed, and a dense SiO2 layer was formed on the surface of coating at 1700°C during the isotheral oxidation, which can protect graphite from oxidation at longer time.
Authors: Yi Da Tang, Wen Heng Zheng, Zhong Hua Tang, Ling Wang
Abstract: The nano-microencapsulated phase change materials were prepared ,with butyl stearate as core material, styrene-maleic anhydride copolymer (SMA) as dispersant and emulsifier, polyurea resin as shell material which was synthesized from monomer 2, 4- toluene diisocyanate (TDI) and diethylen etriamine (DETA),and was modified by glycerol, nanometer material(TiO2) as functional material. We have analyzed the compactness, stabilities, phase transition temperature, and bactericidal efficiency of microcapsules. The results show that the compactness properties and stabilities properties of the modified microcapsule, when the ratio of core material and shell material is 3:4, such as washing stability properties and thermal stability properties are obviously improved than that of non-modified, phase transition temperature rises from 23.2°C to 24.2°C,bactericidal efficiency of Nano-Micro-PCMs is 7~8 times more than that of separate using of nanometer material (TiO2), modified polyurea Nano-Micro-PCMs may have extensive application prospects in the fields of architecture, textile and air-conditioning filtering materials.
Authors: Jiao Jiao Chen, Lin Jiang, Yi Ping Zhao, Qing Song Zhang, Li Chen
Abstract: A serious of poly(NIPA-co-NALPE) hydrogels containing chiral group (L-Phenylalanine ethyl ester) were prepared by copolymerization of N-isopropylacrylamide(NIPA) and acrylic acid derivatived L-Phenylalanine ethyl ester (NALPE) in ethanol with different feed ratios. The kinetics adsorption approach, isothermal adsorption and chiral separation experiment of hydrogels on D/L-phenylalanine were investigated, and the results showed that the chiral hydrogels exhibited enantioselectivity for D/L-phenylalanine and the absorption capability increased with the rising temperature and increasing contents of NALPE due to the temperature-sensitive NIPA molecular chains and the chiral monomer NALPE, respectively. Furthermore, the poly(NIPA-co-NALPE) hydrogels were also used to separate DL-alanine and DL-tartaric acid, which suggested that the gels are also applicable to other chiral molecules besides DL-phenylalanine and have potential applications in separation of chiral drugs.
Authors: Tian Chun Zou, Zhen Yu Feng
Abstract: Microwave absorbing materials (MAMs) is a key component for weapon systems such as aircrafts, warships, and missiles to achieve the stealth performance by absorbing electromagnetic waves incident on. In this work, activated carbon fibers (ACFs) with average length of 1-3mm were prepared, and ACFs dielectric properties were investigated. The results show that ACFs have the frequency response effect, which is helpful for broadening the absorbing bands. According to ACF permittivity, the optimal design is carried out for four-layer microwave absorbing composites with thickness of 4mm based on the impedance matching design method. Following the optimization results the four-layer absorbing material was prepared, and it obtains a reflection loss below -10dB over 8GHz and the minimum value reaches -39.3dB in 2-18GHz.
Authors: Zhen Zhong Sun, Wei Feng He, Hai Bin Chen
Abstract: The surface deflection is an important disadvantage issue in the automobile outer panels forming. It can be controlled effectively through forming process. It is difficult to study the surface deflection because of the complexity of automobile panels. In this paper, a model of cylinder shallow shell is founded, and the measured method and evaluated standard of surface deflection for drawing parts are presented. The influence law of process techniques on surface deflection such as binder force, draw-bead, local force, and shape of blank-hold surface is achieved, which give a basic reference for controlling surface deflection.
Authors: Bai Ming Chen, Zheng Yu Zhang, Ming Xu Wang, Guo Cai Han, Liang An
Abstract: The Cu based friction composites using graphite as solid lubricant with different weight rations of Ti, i.e. 8 wt.%, 12 wt.%, 16 wt.%, 20 wt.%, were sintered by powder metallurgy (P/M) method. The structure of the composites was characterized by X-ray diffraction (XRD) and the tribological properties was studied on block-on-ring tester. XRD results verified presence of TiC phase which was in-situ synthesized through reaction of Ti and graphite in the composites, and the content of TiC was increased with the increased Ti content. The in-situ synthesized TiC phase which was fine and distributed uniformly improved tribological properties of Cu based friction composites significantly. The hardness, wear rates and friction coefficient of composites were increased with increasing amount of in-situ synthesized TiC.
Authors: Yan Li, Heng Qin Xu
Abstract: As an important part of the social logistics, reverse logistics plays an important role in socio-economic development. In this paper, we took discarded Haier refrigerator as the object of study, and investigated the operating conditions of electrical appliance industry and recycling situation of discarded appliances enterprises in Harbin. Through the reference to the domestic and international recycling technology of discarded refrigerators, we analysed the haier home appliance in financial crisis in Harbin, introduced the concept of reverse logistics and constructed the recycling system of Haier refrigerators based on reverse logistics. After the analysis of the system, we find out its feasibility and practical operability and prospect the future research of logistics industry.
Authors: Fan Li, Feng Tian, Chang Jun Liu
Abstract: Poly(3-hydroxybutyrate) (PHB) based microspheres were prepared via double emulsion solvent evaporation using polyethylene glycol (PEG), poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV), polylactide (PLA), poly(dl-lactic-co-glycolic acid) (PLGA) or chitosan (CTS) as the additive of wall polymers. It was found that additives had distinct effect on the properties of microspheres, such as the yield, drug loading, average diameter, crystallization states microstructure and surface morphological characters. PHB based microspheres using PEG as the additive had the lowest yield, the smallest average diameter, and the highest drug loading which reached 12.2% thereinto. At the same time it had the lowest crystallinity of PHB, and the diameter of the crystal particles was only 11.44 nm. It was feasible to prepare PHB based microspheres using PEG and PHBV as additives, which had relatively high protein loading but different microstructures and surface morphologies, and they were anticipated to have a good effect of controlled release.

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