Advanced Materials Research Vols. 79-82

Abstract: The soybean protein fiber is a new textile material. Thanks to its fine denier, light specific gravity, high strength and silk-like luster，it has so excellent cashmere handle, silk softness and heat resistant properties that it has been called manmade cashmere and found wide application. In order to understand the relationship between the inner structure and the mechanical property and the effect of bleaching and dyeing to the soybean protein fibers，four mechanical models are chosen. The tensile and relaxation property of the soybean protein fibers are analyzed. The tensile and relaxation cures are fitted with the suitable model. It shows that the relaxation property of SPF is in accordance with the standard linear solid model. Estimates of the Hookean spring modulus at 8% and at 10% are different, so some structural modifications could be produced by the strain. Bleached fibers show a higher level of relaxation than raw fibers and dyed fibers. Bleaching has a remarkable influence on decreasing tenacity at break for each test modality. Knotted and looped modalities decrease fiber tenacity remarkably in all three samples.

Abstract: In this paper, microstructure and mechanical properties of the chafer cuticle were investigated. The microstructures of the chafer cuticle were first observed with a SEM. It showed that the cuticle is a kind of chitin-fiber-reinforced biocomposite with protein matrix. There are some holes existing in the chafer cuticle and the fibers around hole are continuous. Based on the observed results of the SEM, the analyses of 3D models on the simple composite elements with fiber-round hole were conducted. The result showed the microstructures of composite laminates with fiber-round holes can decrease the stress concentration and well transfer the stress. So it can improve the strength and toughness of the composite laminates included holes. These conclusions may present a bio-inspired approach for design and development of advanced man-made fiber-reinforced composites.

Abstract: The modification of liquid metal by electric pulse (EP, EPM) is a novel method for grain refinement. In this study, based on the reported structural heredity of EP-modified liquid aluminium, the structure tests of EP-modified liquid aluminium with different technique parameters were conducted by using high temperature X-ray diffractometer. The results show that the quantitative structure changes of EP-modified liquid aluminium have a close relationship with the modifying time and modifying temperature. The decrease of modifying time could result in an obvious weaker principal peak in structure factor curve compared with the optimal EP technique parameters, but a slight increase of coordination number (Ns), correlation radius (rc) and average atom number per cluster (Nat) is still observed under this condition. These facts indicate that the EP-modified liquid aluminum could gain an increasing order degree, and thus have an advantage during the formation of a stable nucleus, eventually leading to a grain-refining solidification structure. On the other hand, the structure factor curve of EP-modified liquid aluminum at the high modifying temperature of 850°C tends to be overlapped with that of the unmodified during the principal peak range. In this case, the competition result between the EP strengthening effect and the destruction of superheating would determine the final structure of EP-modified liquid aluminum.

Abstract: The high brittleness of cement-based materials is the dominant reason that causes cracking, corrosion, and even losing the load bearing capacity of the structure. PVA fiber reinforced Strain-hardening Cement-based Materials (SHCC) which is characterized by strain-hardening and multi-micro cracking significantly improves the mechanics performance of cement-based materials. In this paper, 3-point-bending and direct tensile tests were conducted to contrast influence of the material mechanics on SHCC by aggregate gradation. Tests results demonstrate that appropriate particle gradation may improve the strain hardening section in the stress-strain curve. Therefore, the maximum diameter of aggregate can be enlarged from 110μm to 1.25mm. Comparatively large aggregate will be convenient for such materials in the practical application and popularization.

Abstract: The silk fabric was chemically modified with 3-(trimethoxysilyl) propyl dodecyl dimethyl ammonium chloride (HSQA), a cationic modifying agent, to promote antibacterial property against S. aureus and E. coli. The dyeing and colorfastness properties of modified fabrics with commercial synthetic dyes, that is, acid and reactive dyes were also improved. The modified silk fabrics also exhibited some improved resiliency. Therefore, the wear properties of fabrics were expected to be improved by the technique of modification. However, the modification caused a slight decrease in the tensile strength of silk fabrics, as well as the whiteness and wettability because of introducing hydrophobic siloxane chains into amorphous regions of silk fibroin. The surface structure of modified silk fiber was studied by X-ray photoelectron spectra (XPS) and FT-IR spectra. Key words: Silk fabric; multiple-function; Wear property; antibacterial property; X-ray photoelectron spectrum; FT-IR spectrum

Abstract: Recent research findings on the electron channeling contrast (ECC) characterization of various deformation microstructures in some metals were summarized. It is shown that the ECC technique can easily image, in a wide field of view, typical dislocation structures in fatigued Cu single crystals, as well as the relevant dislocation arrangements in deformation bands (DBs). The thermal instability of cyclic deformation induced dislocation structures in Cu single crystals under annealing, and microstructural instability of ultrafine-grained (UFG) Cu produced by equal channel angular pressing (ECAP) under annealing or deforming were also well detected by ECC observations. In addition, a trial observation of the plastic deformation micro-features around the fatigue crack (tip) in Al6XN super-austenitic stainless steels was also made by the ECC technique.

Abstract: Epoxidized castor oil-based polyurethane were synthesized with epoxidized castor oil (ECO) and isophorone diisocyanate (IPDI) as the main raw materials. Epoxidized castor oil-based polyurethane (ECOPU) films were impregnated in different concentrations of chitosan (CS) solution containing acetic acid to prepare CS/ECOPU composite film. The structure and morphologies of the film have been characterized by means of mass change test, infrared spectroscopy, and optical polarization microscope. The recalcification time and dynamic blood-clotting tests were used to characterize the blood compatibility of CS/ECOPU composition film. The result showed that CS has been grafted onto the surface of ECOPU film. The material had good blood compatibility, and can be used as biomedical materials.

Abstract: Physico-chemical and flocculating properties of a bioflocculant, producing by a Serratia plumuthica isolate, were studied. The bioflocculant was identified as an acid polysaccharide consisting of galactose, talose, glucose, mannose and galaturonic acid in a ratio of 34.5:5.1:24.5:29.6: 9.2. Its molecular weight was estimated to be 1.8×106. The bioflocculant was found to be effective for flocculation of a kaolin suspension, when added at a concentration of 1~10 mg/L, in a broad pH range of 2~9 and temperature range of 10~80°C. Its flocculating activity was synergistically stimulated by the bivalent or trivalent cations such as Ca2+, Mg2+, Al3+ and Fe3+. In addition, it could efficiently flocculate a variety of suspensions, including paper-making wastewater, oil-producing wastewater, black ink, alga cell suspension and activated sludge.

Abstract: Piezoelectric Pb(Sb1/2Nb1/2)O3-Pb(Mn1/3Nb2/3)O3-PbZrO3-PbTiO3 (PSN-PMN-PZT) quaternary ceramics with the various contents of Pb(Mn1/3Nb2/3)O3 from 4 to 10mol% were prepared. The phase structure of the system was delineated by X-ray diffraction analysis. The surface morphology was examined by SEM. The piezoelectric and dielectric properties were also measured. X-ray diffraction patterns showed that the PSN-PMN-PZT piezoelectric ceramics was composed of tetragonal phase with perovskite-type structure. Study on the influence of Pb(Mn1/3Nb2/3)O3 additives on dielectric and piezoelectric properties indicated that the PSN-PMN-PZT quaternary system exhibited a high mechanical quality factor and well-situated piezoelectric properties. The optimized results of d33 =332pC/N, d31= -105pC/N, Kp=0.58, K31=0.34 and Qm=1658 can be obtained at 6 mol% Pb(Mn1/3Nb2/3)O3. The obtained electrical properties make this composition a good candidate for underwater acoustic devices.

Abstract: Martensitic transformation (MT) and the internal friction (IF) behavior of the initially amorphous Ti-rich Ti-Ni-Cu melt-spun ribbon annealed at 400°C for 10 h were investigated by using DSC and dynamic mechanical analysis (DMA). The annealed ribbon shows B2 structure with strong preferential (110) orientation and exhibits B2↔B19 MT with the temperature hysteresis of 13°C. DMA tests show that the internal friction is frequencies dependence at 1-50 Hz. The tanδ values decrease with the increasing frequency, but it does not meet the 1/f dependence. Isothermal DMA tests show that the tanδ value at a temperature of 15°C in the MT zone increases quickly from 0.005 to 0.045 with the increasing isothermal intervals and keep stable subsequently. The isothermal time to complete the MT can be determined by the DMA tanδ curve directly.