Key Engineering Materials Vols. 575-576

Abstract: This paper presents a novel fabrication process that combines SHS with V-EPC (vacuum expandable pattern casting) and microstructural features of TiB₂+TiC duplex particulates reinforced surface composite with carbon steel matrix. Macro structural observation shows that the surface composite is dense and there are no obvious defects. Microstructural investigation demonstrates that the composite from surface to core is consisted of three different layers, i.e., the top surface compound layer, the interim transitional layer and the bottom carbon steel matrix. A large amount of fine TiB₂ and TiC duplex particles are evenly distributed in the composite matrix, while the concentration are significantly decreased and non-uniform distribution increased for these particles in the interim layer.

Abstract: The polytetrafluoroethylene (PTFE) matrix composites which filled with polyphenylene sulfide (PPS) fiber, poly-p-phenelenferephthalamide (PPTA) fibre or glass fiber (GF)) and graphite at various mass fractions were prepared by the processes of mechanical blending, compression molding and sintering. The mechanical properties of the composites, such as tensile strength, impact strength and hardness were investigated. The results show that tensile strength and elongation at break markedly decrease but elasticity increases by filling with fibers. Impact strength decreases by filling with PPS and GF, and the composite displays brittle characteristic. However, the impact strength rapidly increases by filling with PPTA fiber. Hardness increases with the fibers content increases, and decreases with graphite content increases. Filling graphite into PTFE has light effect on the impact and tensile strength of composites. The tribological properties of the composites were investigated on M-2000 wear tester at dry friction condition. The wear mechanism was also discussed and the wear surfaces were examined by SEM. The result indicates that fibers which diffused in PTFE matrix wind with PTFE molecule chain, and then form grid structure. The load-bearing capacity of composites can be obviously enhanced and the trend of block fragmentations slide is inhibited, so that the tribological properties are improved markedly.

Abstract: Carbon coated micro/nanostructure FePO₄ composite materials were synthesized by hydrothermal methode, in which citric acid was used as both complexant and carbon resource. The dependence of synthesis process and complexant on the structure and morphology of composite materials were investigated by X ray diffraction (XRD) and scanning electronmicroscopy (SEM). The results showed that the sample consisted of dispersive microspheres with a quite uniform size distribution of 10μm through hydrothermal reaction at 130°C for 24h, when solution concetration was 0.03mol/L and pH value was nearly 2. After calcinated at 550°C for 3h, the microspheres were comprised of nanosticks, and their specific surface area can reach nearly 14 m²/g. Due to their micro/nanomicrosphere structure, the composite materials will benefit to the increase of lithium diffusion rate meanwhile preserve high tap density.

Abstract: In this paper, Stöber silica particles were decorated with polyethyleneimine and silver nanoparticles and Eu-polyoxometalates were grafted on the surface of polyethyleneimine/silica spheres. The hybrid SiO₂/Eu-polyoxometalates/Ag particles were characterized by IR, UVvis, luminescent spectra, scanning electron microscopy, transmission electron microscope, and cyclic voltammetry (CV), respectively. The hybrid particles show the bright red emission under UV light which can be observed by naked eyes. The luminescent properties of particles have been investigated which show that Ag nanoparticles have an influences on the luminescence of europium ions. The electrochemical activities of SiO₂/Eu-polyoxometalates/Ag particles have been demonstrated by CV measurement. The catalytic results indicate that the hybrid particles show the catalytic properties in the oxidation of styrene and benzaldehyde is the main product of the reaction.

Abstract: A novel composite photocatalyst g-C₃N₄/α-Fe₂O₃ was prepared through calcination method. The photocatalysts were characterized by thermogravimetric analysis (TG), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The obtained g-C₃N₄/α-Fe₂O₃ composites show high efficiency for the degradation of Rhodamine B (RHB). The optimum photocatalytic activity of g-C₃N₄/Fe₂O₃ at a g-C₃N₄ content of 8.6% under visible light irradiation is almost 4.8 times as high as that of pure α-Fe₂O₃. The enhancement in visible light photoactivity of g-C₃N₄/α-Fe₂O₃ composites was attributed to the introduction of g-C₃N₄ and the interaction between g-C₃N₄ and α-Fe₂O₃.

Abstract: Composite coating containing HA was fabricated on AZ91 biomedical magnesium alloy by plasma electrolytic oxidation in aluminate electrolyte with HA power in electrolyte. The microstructure of the coating including phase composition and surface morphology was investigated. The results showed that the coating consisted of MgO and MgAl₂O₄ and some HA. The whole coating surface was covered by many micro-pores but the surface are relatively uniform. The diameters of most pores were below 5um, and a few pores were bigger than 10 um.

Abstract: Mg-0.5Mn-1Nd (wt.%) alloy has been prepared by zone purifying method followed by backward extrusion (BE) technique. The microstructures, recrystallization behavior from 150 to 400 °C and mechanical properties of Mg-0.5Mn-1Nd alloy were investigated. The alloy exhibited bimodal microstructures after BE deformation. The equiaxed grains changed to more homogeneous after annealing treatment in range of 150 to 250 °C. The similar trend was confirmed after thermal annealing treatment at different annealing temperatures. The abnormal grains growth was clearly observed when the temperature was higher than 350 °C. Compared with BE-Mg-0.5Mn-1Nd alloy, both yield strength and ultimate tensile strength were reduced after annealing treatment, whereas the elongation was increased correspondingly. These results were mostly related to the fine grain size and homogeneous secondary precipitate.

Abstract: This paper presents the partial results of an experimental program undertaken to investigate the behavior of square and rectangular ultra-high-strength concrete (UHSC)-filled fiber reinforced polymer (FRP) tubes (UHSCFFTs) under axial compression. The effects of the amount of confinement, cross-sectional aspect ratio and corner radius were investigated experimentally through the tests of 24 concrete-filled FRP tubes (CFFTs) that were manufactured using unidirectional carbon fiber sheets and UHSC with 108 MPa average compressive strength. Test results indicate that sufficiently confined square and rectangular UHSCFFTs can exhibit highly ductile behavior. The results also indicate that HSCFFTs having tubes of low confinement effectiveness may experience a significant strength loss at the point of transition on their stress-strain curves. Examination of the test results have led to a number of important observations on the influence of corner radius and sectional aspect ratio, which are presented and discussed in the paper.

Abstract: Gemini surfactants generally exhibit superior properties to those of their single-chain analogues with a similar chain length and head group, especially for gemini cationic surfactants. Gemini cationic surfactants have recently attracted considerable attention due to the increasing microbial resistance to common quaternary ammonium compounds. A novel symmetrical gemini cationic surfactant based on n-hexadecyldimethylamine was synthesized through epichlorohydrin and n-hexadecyldimethylamine as rude materials. The chemical structure of the product was confirmed using ¹H-NMR and FT-IR. The minimum inhibitory concentration of the surfactant to escherichia coli rises to 100 ppm, and a higher concentration surely contributes to increase its effect, but staphylococcus aureus is immune to this surfactant.

Abstract: It is found thatManganese Deuteroporphyrin (Mn(Ⅲ)DP) can greatly enhance the chemiluminescence intensity of luminol-hydrogen peroxide system in alkaline conditions. Basing on that fact a flow injection chemiluminescence (CL) method has been developed for the determination of acetaminophen. With the peak height as a quantitative parameter applying optimum conditions, the relative CL intensity was linear with acetaminophen concentration in the range of 1.0×10^-9～1.0×10^-7 g/mL with a detection limit of 2.8×10^-10 g/mL. The relative standard deviation (RSD) was 2.7% for 2.0 x10^-8 g/mL acetaminophen (n = 11). The proposed method held low detection limit and was successfully applied to determination of acetaminophen in pharmaceutical preparations.