Advanced Materials Research Vols. 299-300

Abstract: Concrete filled tubular columns are widely used all over the world, due to their significant advantages, including attractive appearance, structural efficiency, reduced column footing, fast construction and high fire resistance without external fire protection. An experimental study has been carried out on the performance of joints between steel beams and concrete filled tubular columns in simple construction under fire conditions. The failure modes of the test specimens were always in the joint regions. Therefore, if the joints are appropriately designed and protected so that they possess sufficient strength, it is possible for the steel beam to develop catenary action and survive very high temperatures even without fire protection.

Abstract: The physico-chemical characterization of two types of alkali lignin from different origin, namely L1 and L2, were studied by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectrometry (1H NMR) and gel permeation chromatography (GPC) analysis. FT-IR spectra show that they have the characteristics of absorption peaks of syringyl and guaiacyl. ¹H NMR spectra indicate that acetylated L1 exhibits higher content of aromatic protons than L2, as the former is mainly composed by G units. L2 presents high quantities of methoxyl groups. GPC results show that L1 has much higher weight average than L2. They had similar functional groups, however, there were differences in the relative contents of functional groups.

Abstract: A thermoplastic elastomer of EPDM/HPVC with excellent properties was prepared by dynamic vulcanization. The effects of the rubber/plastics ratio, the content of plasticizer and vulcanizing agent on the mechanical properties of EPDM/HPVC were investigated in detail. Results indicate when the mass ratio of EPDM/HPVC was 30/70, CPE was 9 phr, sulfur was 0.4 phr, EPDM/HPVC had an excellent mechanical property and aging resistance. EPDM/HPVC prepared by dynamic vulcanization had a typical sea-island two phase structure in which smaller EPDM particle dispersed uniformly in the continuous phase of HPVC.

Abstract: The viscoelastic property of the CTC composite cores was investigated through dynamic mechanical thermal analysis (DMTA) in single cantilever mode. The effect of the frequency on the glass transition temperature (T_g) was studied. The results show that the peaks were shifted to higher temperatures with increasing frequencies. T_g of CTC was approximately 180 ^°C, much higher than that of a home-made composite core (Composite I). The activation energy ΔH of CTC is also greater than that of Composite I. The CTC sample exhibit better stiffness and toughness.

Abstract: The effect of DLC film on tribological properties of C/C composites was investigated with a ball-on-disk tribometer in dry air, compared with the result of specimen without DLC film. The DLC film was prepared on the surface of C/C composites substrate by plasma enhanced chemical vapor deposition method (PECVD). After PECVD, structural characterization of the film, adhesion strength of film to substrate, surface morphology and linear wear were studied by Raman spectroscopy, Rockwell-C apparatus, Scanning Electron Microscopy (SEM) and Optical Microscopy (OM), respectively. The result showed that the film deposited on the surface of C/C substrate exhibited typical Raman spectroscopy fingerprints of DLC films and a good adhesion to the substrate surface was found. A stable friction coefficient was observed during the friction tests. With the DLC film, the friction and wear properties of C/C composites were improved significantly. The average friction coefficient of the C/C specimen with DLC film (0.08637) was reduced by 65.56% than that of the one without DLC film (0.2508) and the linear wear was decreased by 84.7% ( from 148.47μm to 22.71 μm) as well.

Abstract: Natural zeolites combined with the magnetic iron oxides are prepared by a chemical coprecipitation process. A detailed characterization of our magnetically modified zeolite (MMZ) is given, including powder X-ray diffraction (XRD), nitrogen adsorption and vibrating sample magnetometer (VSM). The results reveal that in comparison with Na-zeolite, the structure of MMZ has no obvious change but its surface area increases from 25.13 m² g^-1 to 100.90 m² g^-1. The adsorption properties of MMZ to Pb²⁺ and Cu²⁺ were studied. The results show that the maximum loading capacities for Pb²⁺ and Cu²⁺ in the initial concentration range are 123.74 and 14.633 mg g^-1, respectively. The MMZ can be used as an adsorbent for removal of heavy metal ions from industrial effluents or municipal waters, and the saturated adsorbent is separated from the medium by a simple magnetic process.

Abstract: Porous asphalt pavement (PAC) is constructed with an open-graded porous mixture with 15–25% designed air void and 4–5 cm surface thickness. This paper presents paving material selection and requirements of porous asphalt concrete in the cold regions. Through a series of laboratory tests, optimum gradation of the aggregates and bitumen content (BC) were selected, which met all aspects of performance indexes. Uniform experiment design methods, including Marshall test, immersion Marshall test and Freezing–thaw indirect tensile test, were applied to analyze road performance of PAC, such as temperature stability, water stability, resistance to Freezing and thawing and so on. The results confirmed that PAC studied is an effective pavement surfacing materials in cold climate regions.

Abstract: Casting of a wire-inserted strip was tried by a downward melt drag twin roll caster. Some numbers of wires of 0.3 mm diameter were inserted. Effects of the wire-interval, matrix alloy and melt temperature on the ability of the insertion of the wire were investigated. Minimum interval of the wire, with which the insertion of the wires was able, was 1.6 mm. Insertion of the wire became easy as the roll speed becomes higher. Superheat of the melt was not important factor for the insertion of the wire.

Abstract: The deformation depends on twinning in Mg alloy, and twins will be the dominant recrystallization nucleation site. Tension twinning proceeds much more easily than compression twinning since its volume fraction is much higher than that of compression twins, which may have a promotive effect on the recrystallization to a certain degree. Based on the previous research on the static recrystallization at compression twins, the evolution of microstructure and texture in AZ31 magnesium alloy during its static recystallization at tension twins was further investigated; and the orientational characteristics of new grains formed at tension twins in the early stage of static recrystallization were analyzed by EBSD technique. The results showed that the strong basal texture was retained and weakened with no new texture component being detected during annealing. New grains were observed to nucleate preferentially at the intersections of tension twin variants or the intersection between tension twins and compression twins. Their orientations are relatively random and are strongly scattered from those of original tension twins or compression twins. A comparison of the recrystallization at tension twins and compression twins was further made.

Abstract: Well-aligned ZnO nanorod arrays had been successfully prepared by using hydrothermal methods. XRD and SEM analysis showed ZnO nanorod arrays had well orientation along the [0 0 1] direction of ZnO nanorods. The length to diameter is biggest among these samples and is about 25 when solution concentration is 0.8mol/l. The UV emission caused mainly by exciton combination. Furthermore the formation mechanism of ZnO nanorob arrays was studied in detail.