Advanced Materials Research Vols. 335-336

Abstract: 40 wt. %WC steel-bonded carbides were prepared by microwave sintering. The sintering behavior and mechanical properties of 40 wt. %WC-Fe were investigated in comparison with 0 wt. %WC-Fe. The green compact of 40 wt. %WC-Fe sintered at 1280 °C, the phase transition between WC and Fe is observed, generating new Fe₂W₂C phase. The phase transition promotes the densification of the sample, which plays a strengthening effect on the material. Microwave sintering possesses even quicker densification than conventional sintering, as well as substantially higher mechanical properties. The microhardness and bending strength of steel-bonded carbides prepared by microwave sintering are 10% ~ 20% higher than the conventional sintering. The microhardness of 40 wt. %WC-Fe is up to 544 HV, eight times higher than that of 0 wt. %WC-Fe and the bending strength of 40 wt. %WC-Fe is three times higher than that of 0 wt. %WC-Fe. Strengthening mechanism of 40 wt. %WC-Fe samples is that the Fe2W2C rigid phase dispersed over the steel matrix is not deformation, and plays the effect of hindering dislocation motion. The fracture mode is mixed intergranular fracture and transgranular fracture, belonging to brittle fracture.

Abstract: The Microstructure of Cu-Bi master alloy with different melt processes, such as different melting temperature and holding time, was observed by PHILIPS-XL30 scanning electron microscopy (SEM); phase analysis was conducted by Miniflex X-ray diffraction(XRD); Magix(PW2424) X-ray fluorescence analyzer(XRF) was used to analyze chemical compositions of Cu-Bi master alloy. The results show that there are Cu and Bi two phases in the Cu-Bi master alloy; The yielding rate of bismuth decreases with the rising melting temperature. It decreases slowly between 1100 °C to 1150 °C,while it decreases rapidly between 1150 °C to 1200 °C.The bismuth particles in the Cu-Bi master alloy prepared at 1100 °C are much larger than those prepared at 1150 °C,while the size of bismuth particles change little from 1150 °C to 1200 °C. So the better melting temperature of preparing Cu-Bi master alloy is 1150 °C.The yielding rate of bismuth decreases with the holding time increasing. But when the holding time is too short, there are large bismuth particles in Cu-Bi alloy .So the better holding time is 120s.

Abstract: Recycled aluminum industry has great prospects in china. Early identification of key technologies for recycled aluminum plays a very important role in the healthy development of recycled aluminum industry. This paper studies the key technologies of recycled aluminum by technology roadmap method. Recycled aluminum technologies are evaluated by hierarchical analysis model, which is established by Delphi method, and then the key technologies of recycled aluminum industry are determined. Preliminary results and conclusions from this study point out the direction of technology research and technology upgradation for recycled aluminum industry.

Abstract: A series of hyperbranched polyester (HBPE) modified shape memory epoxies (SMEPs) were prepared for the first time. The materials’ toughness, mechanical properties and heat resistance were investigated by impact test, tensile test and DSC analysis. Besides, the possible effect of hyperbranched structure on SMEP’s shape memory property was studied by fold-deploy shape memory test. The results showed 5wt. % HBPE modified SMEP had the optimum properties. Its impact strength, tensile strength and elongation at break were increased by 51.8, 11.4 and 25.4%, respectively, without negative effect on SMEP’s heat resistance and shape memory property. All the samples had high shape retention ratio and 100% shape recovery ratio.

Abstract: Alumina (Al₂O₃) matrix composites reinforced with 10%, 20% and 40% of 10µm size aluminum particles were fabricated by two processes, namely cold pressing and sintering process and Sol-Gel process. Al2O3, Al, 5% volume fraction of cobalt was mixed together, compacted and then sintered at 400-500oC for 30 minutes to fabricate the CMC. In the Sol-Gel fabrication route the Al₂O₃, Al, Co were blended with water and aged for 2-3 days to remove all the moisture and to enable oxidation of Al reinforcement. The mixture was cold pressed and sintered at 400-500oC to produce the CMC. The composition analysis of the CMC carried out by EDAX clearly showed that Al₂O₃ particles were formed by oxidation of Al reinforced in the matrix, effectively forming Al₂O₃/Al₂O₃ particulate reinforced ceramic matrix composite. The nature of the bonding at the interface was characterized using Scanning Electron Microscopy (SEM). The amount of porosity was determined using image analyzer based on ASTM B 276 standard. The average micro hardness of the samples was measured. The optimum volume fraction of aluminum for better interface bonding and reduced porosity was determined using the results obtained.

Abstract: Polymer microcapsule is a kind of functional material with unique structure. Study on the preparation methods is growing obviously. An efficient and environmentally friendly method for the preparation of polymer microcapsules is presented in this article. PMMA microcapsules were prepared by ultrasonically initiated miniemulsion polymerization phase separation method. The morphology, size and its distribution of PMMA microcapsules were investigated by transmission electron microscopy (TEM), atomic force microscopy (AFM) and dynamic light scattering (DLS). And the polymerization kinetics was also discussed. The results show that PMMA microcapsules with size of ca. 100 nm can be obtained when the amount of coemulsifier is 3 times of that of the emulsifier, the amount of monomer is 3 wt% of the system and the reaction temperature is 80°C. In all experiments, N₂ was bubbled to protect the reaction system.

Abstract: The effects of temperature and relative humidity on regenerated cellulose had been investigated in detail in the present work. From experimental results, it was shown that with increasing of RH within temperature range of 35~65°C, storage modulus E_r decreased, loss tangent tanδ increased. This indicated that water molecules penetrate into cellulose and mask off inter- and intra-chain hydrogen bonds and make some motion units to move. More importantly, experimental results indicated that three regenerated cellulose samples had different microstructure and superstructure, which greatly affects the properties of regenerated cellulose. So it will be very valuable to further study the effect.

Abstract: Hexanoyl chitosan: LiClO₄: TiO₂ composite electrolyte films were prepared by the solution cast technique. The ac conductivity and dielectric properties of the samples prepared have been studied in the frequency range from 100 Hz to 1 MHz over the temperature range from 273 to 333 K. The exponent s in the Jonscher’s universal power law, σ(ω)=σ_dc+Aω^s was analyzed as a function of temperature and the analysis suggests that the conduction mechanism can be interpreted based on the correlated barrier hopping (CBH) model. The barrier heights, W_M were calculated. The values of W_M are found to decrease with increasing temperature in the same manner as the exponent s. Both dielectric constant and dielectric loss decrease with increase in frequency and increase with increase in temperature.

Abstract: A series of silicone modified polyurethane(Si-PU) block polymers were synthesized from using polybutylene adipate (PBA), methane-4-4’-diisocyanate(MDI), 1,4–butanediol(BDO) and hydroxyl terminated polysiloxane(HO-PDMS). The effect of synthesis condition on the shear strength was investigated. The influnce of the content of HO-PDMS on the absorption properties of PU was tested. The structure of the synthetic products was characterized by Infrared Spectrum, the surface hydrophobicity was examined by surface contact angle and the scanning electron microscopy(SEM), respectively. The results showed that the silicone chain segments were incorporated into PU macromolecule. The shear strength firstly decreased slightly and then decressed greatly with increasing the HO-PDMS content. But the modified polyurethane had low surface energy, surface water contact was improved by 25°C, and the water resistance was also improved.

Abstract: The crystallinity of PLA which was blended with POE and POE-g-MAH together with main mechanical properties were studied. Contact angles increase in the following sequence: PLA, POE-g-MAH, POE. The crystallinity of PLA which were blended with 5 wt% POE is higher than untreated PLA while POE-g-MAH bring down the crystallinity of PLA. For POE, The 15 wt% portion in the blend with PLA is enough to make optimal toughness. Tensile strength of the blends is not decline but increase a little when POE is used in small amount (less then 5wt%) on account of the high crystallinity. All of those lead to a result that not only the tougher, but also the crystallinity of PLA itself play important role in mechanical properties of the blends.