Advanced Materials Research Vols. 150-151

Abstract: In the paper the properties of concrete masonry unit (CMU) made from sedimentary lightweight aggregate (LWA) were investigated. The main variables include water to cementitious material ratio (W/CM), filling ratio of paste or mortar in voids between coarse aggregate particles (Fv), filling ratio of sand in mortar (Fm), and cement replacement level by slag (Sc). Test results of representative CMU specimens show that unit weight ranged from 1585 to 1743 kg/m3, which was 30-25% lower than that for a normal weight CMU (2300 kg/m3); compressive strengths ranged from 8.4 to 18.7 MPa; water absorption was found to vary between 0.05 to 0.13 g/cm3; and thermal conductivity ranged from 0.27 to 0.41 W/mK. The research findings demonstrate that the use of sedimentary LWA as coarse aggregate in various concrete mixtures could produce high performance lightweight CMU, which comply with the requirements of Chinese National Standards (CNS) standards.

Abstract: Magnetic fluid is a stable colloidal dispersion of ferromagnetic particles in a liquid carrier. Once a magnetic field is applied to magnetic fluids (MF), various structures of MF are formed. A detailed understanding of structures and particle distributions in gradient magnetic fields is much important. But very few works have been done on this. In the present study, the effects of magnetic field gradient and magnetic interaction among magnetic particles on the structures of MF are investigated using a two-dimensional Monte Carlo simulation. The results show that a gradient distribution of magnetic particles is formed under gradient magnetic fields. However, as the interaction between magnetic particles increases, the distribution gradient decreases, accompanied by the formation of chain-like clusters. Moreover, with increasing the magnetic interaction, particle distribution changes from grass-like clusters to needle-like ones.

Abstract: The desulfurization ash, fly ash and metakaolin were uesd to prepare the geopolymer. Compressive strength test demonstrated that the optimum mass ratio of desulfurization ash, fly ash and metakaolin was 30:55:10 and the max strength reached 17.3 MPa. The XRD and SEM show that there is not new crystalline phase. The main crystalline phase of the matrix is non-reacted mullite in the fly ash. It was suggested that the emission of CO2 and SO2 were rehabited from geopolymer by analysis of those compositions volatilizing using TG/MS.

Abstract: The variation of impedance property during the 1st charge/discharge course was investigated by electrochemical impedance spectroscopy (EIS). The results show that the proposed equivalent circuit of RS(Qdl(RCtZW))(QSEIRSEI) perfectly simulating the EIS measurement data and all the errors less than 5% can reasonably explain the course of the reaction between Li and NiO electrode. The SEI film which distinctly influences the electrochemical performance of lithium ion battery is free at open circuit voltage. It begins to slowly grow at polarization voltage of 1.5V and completely forms at 0.3V in the 1st discharge. To react further with NiO, the Li+ must pass through SEI film and generate the fine grains Ni and amorphous Li2O matrix. SEI film partially decomposes and the NiO and Li are formed by reversible reaction of Ni and Li2O in the charge course.

Abstract: The titania films codoped by aluminum and nitrogen have been prepared by cathodic vacuum arc with titanium aluminum alloy target in an O2/N2 gas mixture. The films were characterized by X-ray diffraction (XRD), X-rayphotoelectron spectra (XPS) and ultraviolet-visible spectra (UV–vis). The results showed that all films annealled were crystalline anatase structure with a (101) preferential orientation, XPS revealed that Al and N were successfully doped into the lattice of TiO2. The optical properties of the films revealed that the spectrum response of the Al, N-codoped TiO2 films extended from the UV region to the visible region. The absorption of the Al, N-codoped TiO2 film in the visible region(>400 nm) was enhanced, compared with the pure TiO2 film and N-doped TiO2 film. The Al, N-codoped TiO2 film showed the best photocatalytic activities for the oxidative destruction of Acid Fuchsin (AF) under visible light irradiation.

Abstract: The properties of composites reinforced by three dimensional braided preform are determined by braiding structure significantly. The main objective of this paper is to develop a general methodology for the determination of the design and analysis of three dimensional two-step braided tubular preform. The arrangement pattern of axial yarns with various finenesses is derived for the uniform braiding structure of preform, which offers a possibility for achieving preferable interior structures of braided tubular preforms. Then, the general structure parameters, including the interrelation between surface braiding angles and interior braiding angles and the fiber volume fraction, are investigated in some detail. The results derived from this paper can provide a useful method for the design of 3D two-step tubular braided preform.

Abstract: Transparent conducting Al-doped ZnO films were prepared by ultrasonic spray pyrolysis technique on amorphous glass substrates under atmospheric environment with substrate temperature ranging from 350 to 500 , and Al/ZnO molar ratio of 1, 3 and 5 %. The impacts of the substrate temperature and doping level on structural, optical and electrical properties of the ZnO:Al thin films were investigated. The texture coefficient calculated from XRD data indicates that the substrate temperature at 450 and the doping level of 3 at.% is beneficial for crystal growth along (002) orientation. The Band gap (Eg) and Urbach parameter (E0) deduced by the optical absorption edge increases and decreases with the increase of Al doping level, respectively. The increase in sheet resistance is assumed to be associated with the decrease in preferential orientation and formation of Al2O3-x clusters.

Abstract: The materials and structural characteristics of several kinds of wind turbine blades are introduced and analyzed as well as the advantages and disadvantages of blades composites in this paper. Then the manufacturing technologies between traditional and high-quality composite wind turbine blades are studied and compared in this paper.

Abstract: Using of the multiple scattering methods, we characterize the positive and negative multi-refraction and transmission properties of a solid-based phononic crystal composed of coated solid inclusions in view of its applications in tunable multimode filtering. The geometrical parameters are chosen so that a left-handed longitudinal wave mode and a right-handed transverse wave mode, are simultaneously obtained in this three-component phononic crystal. When multimode Gaussian beams are placed transmitting through the phononic crystal slab, both positive and negative refractions are observed. We then study the individual propagation behavior of different modes. The angle dependent transmission beams with different energy distributions are found at the other side of the slab. Transmitted transverse waves coming from different directions incidence finally walk together into four oriented beams. Meanwhile, longitudinal wave incidence with different directions behaves simply as negative refraction in the slab. A far-field longitudinal wave image can be achieved being excited by a longitudinal wave point source. The three-component phononic crystal slab thus can be served as an alternate in tunable multimode filtering devices.

Abstract: Mg2Si/AZ91D magnesium matrix composites are fabricated from AZ91D-Al2(SiO3)3 system by direct melt reaction method. The effects of the variation Al2(SiO3)3 addition contents to the microstructures and mechanical properties of the composites are investigated. The results show that the amounts of Mg2Si particles are increased and the structures of AZ91D magnesium alloy are refined with the Al2(SiO3)3 content increasing. When the additional content of Al2(SiO3)3 is 3wt.%, the tensile strength of the composite reaches 178.6MPa, which is increased by nearly 14.5% than that of AZ91D matrix alloy.