Advanced Materials Research Vols. 150-151

Abstract: Fiber reinforced composites have been an important way to utilize agriculture plant fibers. Flax fiber is plant fiber and strong, biodegradable, anti-fungi and bacterial. Flax fiber reinforced PP fiberboard is thermoplastic with the advantages of low density, low cost, low energy consumption, and recyclable. The influences of flax / PP fiber blending ratio, molding temperature, molding time on the mechanical properties of flax / PP board were carefully investigated. After mathematical manipulations and experimental validation, it was found that the thermoplastic composite board had maximum tensile and bending strengths when the flax fibers were at 50% of the total weight, the molding temperature was 181 ， and the molding time was 48 minutes.

Abstract: This paper presented the composite coatings of nickel with graphite particle on the aluminum substrate using a nickel sulfamate bath. Effects of graphite particle concentration on the surface morphologies of the composite coatings were investigated. The inclusion of graphite particle into metal deposits was dependent on many process parameters, including particle concentration, current density, pH and temperature. Results of SEM and XRD demonstrated that graphite particle had successfully deposited on that nickel matrix; besides, the surface morphology of coatings obtained from sulfamate bath containing 2g/L graphite particle dispersed more uniformly than the ones with higher concentration.

Abstract: Copolymers of styrene (St), n-butyl acrylate (BA) and vinyltrimethoxysilane (VTMS) have been synthesized by emulsifier-free emulsion copolymerization using ammonium persulfate (APS) as initiator. Acrylic acid used as functional monomer was also added into the emulsion polymerization system. The effects of varying the concentrations of initiator and VTMS as well as the polymerization temperature on the polymerization conversion were investigated in detail. The copolymer was characterized by Fourier transform infrared spectrometer (FTIR). Copolymerization of VTMS with St and BA was confirmed by the appearance of an absorption peak between 1000 cm-1 to 1200 cm-1 (due to Si-O-C bonds) in the IR spectrum. The siloxane segments in the copolymer chain underwent hydrolysis and self-condensation, resulting in a change in the structure of the copolymers from linear into a cross-linked network. As a result, the organic and inorganic hybrid material was formed. The water absorption of emulsion decreased with increasing VTMS concentration. The polymerization conversion increased with increasing polymerization temperature, molar concentration of initiator and decreased with increasing molar concentration of VTMS.

Abstract: A small amount of nickel ions is added to trivalent chromium chloride plating bath to study effect of Ni ions on trivalent chromium electrodeposition. The obtained Cr-Ni alloy coatings and Cr coatings are characterized by means of EDS and SEM. Cathodic polarization curves of trivalent chromium chloride plating bath show that right amount of Ni ions contained in bath make the LSV more positive, exerting a catalytic effect on electrodeposition of Cr ( ) ions. EDS results of the obtained coatings also demonstrate the catalytic effect of Ni ions on trivalent chromium electrodeposition. Analysis of SEM indicate that the surface morphology of coatings obtained from Cr( ) bath containing 0.03g/L Ni2+ bath are similar to the ones obtained from pure Cr( ) ions bath.

Abstract: Aligned carbon nanotubes (ACNTs) array is synthesized by plasma-enhanced hot filament chemical vapor deposition of the stainless steel substrate covered by ferric nitrate. The morphology and structure of the carbon nanotubes array are characterized by Scanning Electron Microscope and Transmission Electron Microscope. Cyclic voltammetry, constant current charge-discharge technique are employed to test the electrochemical performance of the button-like super-capacitor fabricated using the ACNTs array as electrode. The specific capacitance of the ACNTs array electrode reached 160.9F/g in the potential range of -0.2~+0.8V, at a scan rate of 1mV/s in 1mol/L Na2SO4 aqueous electrolyte.

Abstract: The geopolymer was chosen to immobilize the municipal solid waste incineration (MSWI) fly ash because of its strong fixing capacity for heavy metals. The fly ash-based geopolymer was synthesized from metakaolinite with MSWI fly ash under activation of sodium silicate solution, and then cured at relative humidity (RH) between 40% and 90% at 20°C. The ability of immobilization of heavy metals in MSWI fly ash with the geopolymer was evaluated in terms of the compressive strength and leaching concentration. The experimental results confirmed that the compressive strength of the resulting solidified body could achieve 35.13 MPa after 7 days of curing. Meanwhile, the leaching concentrations of Pb, Zn, Cu and Cr were 0.0230 mg/kg, 0.186 mg/kg, 0.231 mg/kg, and 6.56 mg/kg, respectively. We confirm that geopolymerisation is an effective alternative in the disposal of various hazardous wastes containing heavy metals.

Abstract: The evaluation on energy characteristics of earthquake-excited building structures with seismic protection devices is actively carried out in this study. The mechanical model of passive friction dampers is first introduced and the dynamic model of building-damper system is proposed. The evaluation criteria of energy responses are developed and applied to the earthquake response mitigation of a real multi-story building incorporated with friction dampers. The observations indicate that the earthquake-induced vibration of the structure can be substantially suppressed and the proposed energy evaluation criteria can be effectively utilized in the examination on seismic mitigation performance.

Abstract: Short mullite fiber reinforced Al-Cu-Si alloy composites were produced by squeeze casting. The interfacial microstructure and microchemistry of the testing composites were studied by means of X-ray diffraction (XRD), transmission electron microscope (TEM) and energy disperse spectrum (EDS) equipped with TEM, respectively. It is shown that chopped mullite fibers in the composites are polycrystalline in structure composed of many fine mullite crystal particles which are orthorhombic in structure with lattice constants of a = 0.749 nm, b = 0.927 nm and c = 0.581 nm based on electron diffraction (ED) analysis and high resolution transmission electron microscope (HRTEM). There are much denser dislocations in the near vicinity of both fiber/matrix interface and silicon/matrix interface. But interfacial reaction products at fiber/matrix interface in (3Al2O32SiO2)/Al-4.0Cu-5.0Si composites have not been observed yet.

Abstract: The degradation of a steel dome due to strong earthquake may lead to a sudden loss of structural stiffness in a structure and cause a discontinuity in acceleration response time histories recorded in the vicinity of damage location at damage time instant. A damage detection approach based on discrete wavelet transform is developed and implemented in this paper to detect the damage time instant and location of a steel dome due to sudden seismic damage. To examine the feasibility of the wavelet-based detection approach, parameter studies are carried out to investigate the detection quality for different noise intensities. The time instant and location of sudden damage event are detected through the distribution of discrete wavelet coefficients in the time domain and spatial distribution along the structural span.

Abstract: The dense TiC-Fe coating was fabricated by combustion synthesis on surface of a plane iron, and the phase composition of the TiC-Fe coating was determined by X-ray diffraction. The predominant TiC and a small quantity of α-Fe phases without others phases in an XRD spectrum were observed, indicating that chemical reaction was complete. The microstructure of TiC-Fe coating on surface of a plane iron is characterized by the grey TiC particles and white Fe phase, and the grey TiC particles appeared to be uniformly dispersed in the white Fe matrix. The increase in hardness and bond strength is due to the formation of the TiC phase.