Advanced Materials Research Vols. 335-336

Abstract: The B4C/BN nanocomposite powders were fabricated by chemical reaction and heat treatment process in this research. The starting powders was composed of B₄C powders, H₃BO₃ and CO(NH₂)₂. The mixture powders were reacted at 550°C for 15h and heat treated at 850°C for 6h. So the B4C/BN nanocomposite powders were prepared by above process. In this research, the B₄C/BN nanocomposite powders were heat treated at 850°C, 1300°C, 1500°C, 1750°C. The phase composition and microstructure of the B₄C/BN nanocomposite powders fabricated by heat treatment at high temperature were investigated by XRD and TEM. The XRD patterns results showed that there existed the B4C phase and amorphous BN phase after chemical reaction at 550°C and heat treatment at 850°C. Then the amorphous BN phase gradually transformed into the hexagonal BN (h-BN) phase with the increase of heat treatment temperature from 1300°C to 1750°C. The amorphous BN phase completely transformed into the h-BN phase after the hot-pressing process at 1850°C. The IR spectrum results showed that there existed the B₄C phase and BN phase in the produced composite powders and sintered bulks. The microstructure of the synthesized B₄C/BN composite powders showed that the B₄C particles were surrounded with the amorphous BN coated layer after the heat treatment at 850°C, then the amorphous BN coated layer gradually transformed into the nano-sized h-BN particles with the increase of heat treatment temperature. So the B₄C/BN nanocomposite powders were fabricated by chemical reaction and heat treatment process.

Abstract: Abstract: Composite materials are playing a greater role in engineering application due to their optimized structure and mechanical characteristics. Study here aims at composite design which enables the fabricated composite to have excellent mechanical behavior even in extremely corrosive environment, for example, environment with extremely high ozone gas concentration. To take advantage of the great anticorrosion property of pure aluminum (Al), PET thin film coated with pure aluminum (Al) on its surface has been introduced as the top layer of the fabricated composite with polyester textile as the middle layer. To bond these layers together, the composites with this sandwiched structure are manufactured at different temperature. Main purpose of the study is to evaluate the influence of processing temperatures on the mechanical properties of the manufactured composites, and on their failure behavior. In this way, optimized processing temperature may be found.

Abstract: Polystyrene composites containing polyhedral oligomeric silsesquioxane (POSS1) were prepared by bulk free radical polymerization under magnetic field and no magnetic field. XRD studies indicate dispersion of POSS1 in PS/POSS1 97/3 nanocomposites prepared under magnetic field is better than those prepared without magnetic field. The PS/POSS1 nanocomposites also display much higher initial decomposed temperature in comparison with neat PS. The initial decomposed temperature of PS/POSS1 nanocomposites prepared under magnetic filed are higher than those with same content of POSS1 without magnetic field.

Abstract: Adding microelements Ag In Ga and Sb into Sn-20Bi solder, the changes of melting properties and microstructures of the solder were observed. The experimental result showed that when the content of Ag was 0.7% (wt%), In was 0.1% , Ga was 0.5% and Sb was 0.5%, the melting points of the solder reduced to the bottom and the segregation of Bi obviously decreased. Sb was not suitable to add solely but when it was added together with Ag In and Ga, it can produce a good effect on reinforcement of solid solution, furthermore it can restrain the phase change of Sn. The Sn-Bi-X solder with the best compositions of Ag In Ga and Sb has a near melting point to Sn-37Pb. The solder is close to practicality without segregation of Bi.

Abstract: The new type of solid superacid S₂O₈^2-/SnO₂-SiO₂ was prepared by precipitation and hydrothermal aging method with ammonium persufate as soaker instead of sulphuric acid. The samples with different tin oxide content were characterized by FT-IR, XRD, BET, TG/DTA and Hammett indicators techniques. Catalytic activities for esterification of butanol and acetic acid were also investigated. As a result, most sulfate-ion in surface of S₂O₈^2-/SnO₂-SiO₂ coordinate with Sn bidentatly, and the acidic strength of S₂O₈^2-/SnO₂-SiO₂ is related to the content of tin oxide. Besides, introducing appropriate Si can improve the combination of the tin with SO₄^2- thus increases the amount of acid. Catalyst S₂O₈^2-/SnO₂-SiO₂ reveals high catalytic activity and stability in the esterification at very large range of composition.

Abstract: The electrochemical property of molybdenum disulphide (MoS₂) as anode materials for lithium ion batteries was studied using two-electrode Li-ion cell. The first reversible capacity of MoS₂ treated by using ball milling and doped graphite was 617mAhg^-1 and 506mAhg^-1 respectively. But the reversible capacity of pristine MoS₂ was 661mAhg^-1. The results indicated that the processes of ball milling and doped graphite of MoS₂ can not widely enhance the reversible capacity.

Abstract: It has studied the subsidence characteristics of the geogrid-reinforced and pile-supported foundation through eleven loading model tests, and analyzed the effects that varied pile spacing, reinforced floors, the paving position of the reinforcement, underlayer thickness have had on the subsidence of the geogrid-reinforced and pile-supported foundation.

Abstract: In this paper, low-velocity impact residual tensile strength of carbon fiber composite laminates are investigated by experiment. The triple-plate-string-element finite element model was used to calculate the strength of repaired structures of the damage. The corresponding strength tests were conducted to verify the computational results. According to the computational and experimental results, the influence of the repair parameters on the repair efficiency was analyzed, such as the overlap length and the thickness of the patch.

Abstract: There is little information about removal soil Pb from EDTA leachate. Modified bentonite was successfully synthesized from original bentonite and iron (Fe) in this study. Removal efficiency of Pb from the EDTA leachate using the modified bentonite was higher than that of original bentonite. The highest removal efficiency of Pb was 65% with modified bentonite with pH 3.0. The results of this work proposed a potential way for removal of soil Pb from the EDTA leachates.

Abstract: Structures of CaSO₄ whisker(A) and CaSO₄ whisker(B) were characterized by IR and XRD, and the morphologies were observed by optical microscope. The results showed that the modified CaSO₄ whisker(B) has perfect crystal structure, high crystallinity and less defects. Mechanical properties and static thermal stability time(190 °C) of two composites which were prepared by CaSO₄ whisker(A) / PVC and CaSO₄ whisker(B) / PVC were tested separately, and the degradation processes were analyzed by TG at 50 °C-400°C, N₂ atmosphere, and the dispersing states of two whiskers in the composites were observed by means of optical microscope and SEM. The research results showed that the tensile strength and elongation at break increased over 3 MPa and 40% separately, and the static thermal stability time was over 90 min of CaSO₄ whisker(B) / PVC, the initial degradation time was delayed comparing with CaCO₃ / PVC composite. The consistency and interfacial configuration between whisker and PVC resin were perfect, and the toughness and thermal stability of the composite was improved after CaSO₄ whisker was modified. The research results indicated that modified CaSO₄ whisker has better toughness and thermal stability actions for PVC.