Advanced Materials Research Vols. 79-82

Abstract: Polyaniline/nano-SrFe12O19 composites were prepared by in situ polymerization method for the first time. Rod-like and flower-like morphologies composites were synthesized in the phase of an emulsion polymerization system. It was found that the morphology of obtained PANI/nano-SrFe12O19 composites depended on the content of SrFe12O19 of the reaction system. A possible mechanism for the formation of the different morphologic composites had been proposed. The magnetic properties of the PANI/nano- SrFe12O19 composites were inspected by VSM. The possible mechanism for magnetic variation had been proposed in the paper.

Abstract: Ti-Al based composite coating was fabricated on LY12 aluminum alloy surface by electrospark deposition (ESD) process, with γ-TiAl as electrode. The microstructural characteristics, element distribution, microhardness and wear resistance of the coating were investigated. The results show that the coating forms metallurgical bonding to the substrate, which consists of strengthened layer, transition layer and heat affected zone. Besides the Al phase, the coating is also composed of Ti-Al intermetallic compounds and a small mount of Ti/Al oxides and nitrides. The microhardness of composite coating decreases gradually along the depth direction. The sliding wear test results suggest that the worn volume loss of the coating is less than one third of that of the substrate. The abradability of LY12 aluminum alloy is significantly improved. The phases with higher hardness dispersed in the coating increase not only composite coating hardness but also the resistance to micro-cutting and plowing during the sliding wear test. In addition, the excellent sliding wear resistance of composite coating is also related to the metallurgical bonding between the coating and the substrate.

Abstract: Co68.25Fe4.5Si12.25B15 naked amorphous wires of 60μm in diameter are prepared by melt extraction technology and annealed by DC-Joule heat at current from 40mA to 250mA for 10min. Impedance response is measured at low frequencies(≤13MHz) using HP4192 impedance analyzer. We get better GMI effect by heating wires at 60mA and 180mA.The connection between GMI response and transformation of structure under different heat current has been discussed. After proper heat treatment, magneto impedance response is strong even at 0.5MHz with GMI amplitude of 193.1% and field sensitivity of 59.4%/Oe. The maximum △Z/Z reaches 476.9% and the largest field sensitivity is up to 91.8%/Oe. These results indicate proper annealed Co-based melt extraction wires are suitable for high sensitivity sensor applications.

Abstract: Nb2O5 ceramic pellets were prepared through sintering and hydrogen was introduced into Nb2O5 pellets through a process known as electrochemical hydrogen charging, in which Nb2O5 acted as the cathode in a 0.01 M NaOH solution. The color of Nb2O5 was found dramatically darkened after the treatment while X-ray diffraction indicated that there was no change in the crystal structure. I-V and R-T measurements showed that the resistivity was greatly decreased after hydrogen charging and the resistivity exhibited a negative-temperature-coefficient (NTC). It was proposed that hydrogen can be incorporated into Nb2O5 lattice and occupies at some interstitial site. Nb5+ of Nb2O5 is partially reduced to Nb4+ by hydrogen and the NTC-type conduction results from electron transfer between Nb5+ and Nb4+ through a hopping mechanism.

Abstract: Novel Y-shaped amphiphilic block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide), PEG-b-(PNIPAM)2, were successfully synthesized through atom transfer radical polymerization (ATRP). A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly(ethylene glycol) monomethyl ether (PEG). The copolymers were obtained via the ATRP of N-isopropylacrylamide (NIPAM) with CuCl/Me6TREN as catalyst and DMF/H2O (v/v = 3:1) mixture as solvent. The resulting polymers were characterized by gel permeation chromatography (GPC) and 1H NMR. These block copolymers show controllable molecular weights and narrow molecular weight distributions (PDI <1.15). Their phase transition temperatures and enthalpy changes in aqueous solution were measured by differential scanning calorimetry (DSC). The results indicate a significant influence of the macromolecular architecture on the phase transition. This is the first study into the effect of molecular architecture on the phase transition using Y-shaped amphiphilic block copolymer composed of PEG and PNIPAM.

Abstract: By phase inversion process, the polyvinylidene fluoride (PVDF) with polyvinyl chloride (PVC) blend membrane was prepared. In which, as pore-forming agents, the polyethylene glycol (PEG), poly(vinylpyrrolidone) (PVP) and lithium chloride (LiCl) was separately added into PVDF/PVC casting solution. The effect of each pore-forming agent on the kinetics of membrane formation and properties of PVDF/PVC blend membrane were investigated respectively. Using the capillary flow porometry, the microstructure and morphology of PVDF/PVC blend membrane were quantitatively characterized. The results show that by respectively adding PEG, PVP or LiCl, it emphasizes the rate of solvent diffusion from PVDF/PVC solution during the phase inversion or membrane formation, and the porosity of membrane gets increasing. The pure water flux of PVDF/PVC blend membrane achieves enhancement obviously. At the same time, the rejection is decreased in a certain degree. Comparison with PEG or LiCl, PVP has more effect on the membrane pore-forming action. The microstructure analysis indicates that based on the same formulation, by selecting PEG or LiCl as pore-forming agent, formatted PVDF/PVC blend membranes achieve equivalent mean pore size. However, there is a little larger mean pore size distributed in the membrane by using PVP instead of PEG or LiCl. The application of purifying ε-polylysine (ε-PL) by using the PVDF/PVC blend membrane with PVP, the results reveal that the protein removal rate can be around 62.33% and the filterable and permeated ε-PL kept at 70.79% yield.

Abstract: Aquatic Larvae of Stenopsychid caddisfly (Stenopsychie marmorata) survive by attaching its catching nets at the bottom of the rocks in the flowing water. It was hypothesized that S. marmorata larva connects small pebbles by producing both silk-like protein and strong adhesive protein simultaneously. A 98 kDa protein（Smap-98k）was identified as an adhesive component by constructing a silk gland –specific cDNA library of S. marmorata. The cDNA sequence of Smap-98k was 2,679 bp long and encoding a 893 amino acids–long open reading frame (ORF) in which the first 19 residues are predict to be the signal peptide. The alignment of the Cys residues indicated the primary structure of this protein to consist of 15 degenerated repeats, each about 50 residues long and contains 6 conserved Cys residues. The Smap-98k was characterized by an abundance of Cys residues and charged amino acids with epidermal growth factor-like (EGF-like) structure. The most common amino acid of this protein was Cys (11.98%), with Pro (9.91%) and Glu (9.26%) following order of magnitude. Cys was assumed to play a role in maintaining the topology of charged amino acids on the molecular surface by intramolecular disulphide-bond formation. The gene was expressed specially in the silk gland similarity to the major silk proteins such like heavy fibroin (H-fibroin) and Light fibroin (L-fibroin) of S. marmorata larvae. The sequence of the protein showed certain homology to the silk-185 kDa of Chironomus pallidivittatus (Midge) which also spin silk underwater. The characterizations of abundance of Cys residues and charged amino acids also shared by Megabalanus rosa cement protein (Mrcp-20k ) and Mytilus galloprovincialis foot protein 2 (Mgfp 2) which both were produced in the marine environment. Although the similarity among Smap-98k, Mrcp-20k and Mgfp 2 sequences were very low, the functional relationship in underwater adhesion of these proteins should be noted.

Abstract: In this paper it was investigated that silicon be electrodeposited in the room temperature from propylene carbonate solvent. Cyclic voltammograms indicated that it was possible to electrochemical reduction of silicon chloride at -2.3984V versuHg/Hg2Cl2/ KCl (saturation) quasi-reference electrode. Potentiostatic electrolysis yielded deposits, accompanied by the change in electrolyte color from transparent to brown. Scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS) were used to characterize the physical properties of the silicon. The EDS analysis performed simultaneously with SEM observation demonstrates that the deposit consists of Si, O and Cl.

Abstract: Reactive sintering of elemental powders was used to form Y-doped Mg2Si (Y: 1000, 2000, 3000ppm) using a field-activated pressure assisted synthesis (FAPAS) method. XRD analysis, and the calculation of lattice constant (a) indicates that 1000ppm is the solid solubility of Y in Mg2Si. Sample doped with 2000ppm Y owns better performances, the absolute value of Seebeck Coefficient increases in the temperature of 288-580K and is higher than that of non-doped Mg2Si, and it got higher electric conductivity and higher power factor, which reaches up to 1.67 times of non-doped Mg2Si at 438K and 2.03 times of that of non-doped Mg2Si at about 408K. Meanwhile, the introduction of Y can decrease thermo-conductivity obviously, proving that the introduction of Y is favorable for both electrical and thermal properties.

Abstract: The amorphous calcium phosphate (ACP)/tricalcium silicate (Ca3SiO5, C3S) composite powders were synthesized in this paper. The exothermal behavior of C3S determined by isothermal conduction calorimetry indicated that the ACP could be synthesis by chemical precipitation method during the induction period (stage II) of C3S. The composite powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results indicated that nanosized ACP particles deposited on the surface of C3S particles to form core-shell structure at pH=10.5, and the nCa/nP of ACP could be controlled between 1.0 and 1.5. The core-shell structure is stable after sintered at 500 oC for 3 h to remove the β-cyclodextrin (β-CD). As compared with the irregular C3S particles (1~5 μm), the composite powders particles are spherical with a diameter of 40~150 μm. Therefore, to obtain the smaller size of composite powders, it is expected to avoid the aggregate of C3S particles in the aqueous solution by addition of dispersant. As compared with C3S, the composite powders may contribute better injectability, strength and biocompatibility.