Advanced Materials Research Vols. 239-242

Abstract: Asphalt mixture is a kind of typical elastic-viscoplastic material. Environment temperature and loading condition will greatly affect its performance. As the temperature falls, asphalt pavement will engender a shrinkage deformation under the action of temperature stress. When the accumulated temperature stress exceeds tensile strength, the asphalt pavement will be cracked. Based on the results of the bending creep test in low temperature, the Burgers model was established and the viscoelastic parameters in the model were given, and the relaxation modulus of asphalt mixture was also determined in this paper. The study indicated that SBR modified asphalt mixtures have the advantage over common asphalt mixture in low-temperature performance.

Abstract: A novel synthesis route for a MCM-41 structure with Y zeolite seeds colloidal has been developed. The route is different from conversational method of highly ordered MCM-41 assembled from Y zeolite seed colloidal. The material was characterized by various techniques. The results indicate that the material has well-ordered hexagonal structure, with a thicker wall than that of the sample synthesized by a direct hydrothermal route (N-MCM-41). SEM images show a very uniform net-like morphology, which is different from the loose appearance of N-MCM-41. Furthermore, it has a stronger acid strength and a higher hydrothermal stability. The sample was used as the support of a Pd-Pt catalyst for the polyaromatics hydrogenation. It was demonstrated that the introduction of building units of Y zeolite enhances the activity of polyaromatics hydrogenation. It can be concluded that the pore structure and acidity of support is a key factor for the design of a sulfur tolerant noble metal catalyst for aromatics saturation of diesel.

Abstract: This study focuses on the conditions of preparation of C/C-SiC composites through polymer infiltration and pyrolysis method using hydrogen-containing polysiloxane as the precursor and divinylbenzene as cross-linking agent. The densities of different C/C composites (ρ=1.02, 1.21, 1.60, 1.78g·cm^-3) increased to 1.24, 1.36, 1.69, 1.84g·cm^-3 respectively after infiltration and pyrolysis four times. The appropriate ratio of hydrogen-containing polysiloxane and divinylbenzene was 1/0.5. The appropriate cross-linking temperature was 250°C. In pyrolysis process, the appropriate increasing rate of pyrolysis temperature should be 50°C/h in the range of 300-800°C. SiC was formed when pyrolysis temperature reached 1550°C.The linear ablation rate and mass ablation rate of C/C-SiC composites were much lower than those of C/C composites.

Abstract: On the base of electroless plating on fabric, the Ni-Co-Fe was plated on the PU membrane of coated polyamide fabric and the respiratory electromagnetic shielding fabric was developed. The functionality and wear-ability of electromagnetic shielding fabric was tested and analyzed. The results showed that it has good electrical conductivity, water vapor permeability, electromagnetic shielding performance and durability and so on. With the weight increasing rate goes up, the shielding effectiveness, vapor permeability and electrical conductivity increases obviously, then prone to slow increment. The plated layer on fabric has an adverse effect on the wear performance and on the premise of meeting respiratory and electromagnetic shielding performance, the thickness of plated layer should be decreased to the least extend.

Abstract: Flower-like LLM-105 three-dimensional microstructures, which consisted of LLM-105 microrods with rectangular cross-sections, were prepared via a smiple template- and surfactant-free recrystallization process using [Bmim]CF₃SO₃ as good solvent and water as poor solvent. A tentative mechanism for the growth of the flower-like LLM-105 three-dimensional microstructures was proposed on the basis of the analysis of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Comparing with LLM-105 raw material, the thermal decomposition took place at lower temperature and the weight loss has increased for the flower-like three-dimensional microstructures in the differential scanning calorimetric/thermogravimetric (DSC/TG) measurements.

Abstract: Electric charges exist on the clay particle surfaces and induce a micro-electric field which leads to the formation of adsorbed water surrounding clay particles and exerts an influence on the movement pattern of ions in pore water, resulting in the ion effect of seepage in clay. The two factors above will obviously change the characteristics of seepage in micropore of clays. The change of seepage property caused by the factors mentioned above is defined as micro-electric field effect on seepage (MEFES) in clay. The electric potential on the surface of micro particles of clay amounts to tens or hundreds of mV, and then the electric field on the particle surface greatly affects the regulation of seepage. Using theoretical analyses, MEFES in micro particle clays is discussed in this paper. A theoretical model of seepage is proposed for the quantitative description of MEFES. The theoretical model shows the influences of particle surface electric potential, pore sizes, soil conductance, ion concentration in pore water, ion valence , viscosity etc. on seepage characteristics. The equivalent permeability coefficient derived from the theoretical model can be also simplified to that of Darcy’s law without regard to MEFES.

Abstract: In the paper, ultrafine quartz, sericite and wollastonite modified with silane coupling agents KH-570 were incorporated into natural rubber(NR). The synergisitc effect on reinforcing NR caused by the three types of fillers was investigated under a same vulcanizing formulation and process. The mechanical properties and microstructure of the vulcanizates were conducted through mechanical testing and scanning electron microscopy(SEM). The results of mechanical properties tests showed that when one of these three fillers was loaded within NR alone, the tear strength and permanent set of NR vulcanizates filled with quartz could reach 27.61 kN m^-1 and 16.0%, respectively, stress at 300% elongation of NR vulcanizates filled with sericite could attain 4.69 MPa, and the tensile strength and elongation at break of NR vulcanizates filled with wollastonite could get to16.64 MPa and 951.21%, respectively. Under the condition that the filler loadings were 40 parts per hundred parts of rubber(phr), and the mass ratio of quartz, sericite, wollastonite was 1:1:3, the tensile strength and tear strength could come up to 17.33MPa and 27.54 kN m^-1. The mechanical properties of NR composites filled with mixtures were found to be complemented by those three types of minerals. SEM results revealed that the fillers are well dispersed in the rubber matrix in the parallel arrangement with a densest stack, and the synergistic reinforcment effect of the fillers on NR was obvious.

Abstract: The vinyl ester resin sizing agents modified with epoxidized polybutadiene or epoxy terminated butadiene-acrylonitrile oligomer were prepared. The influence of the sizing agents on the performances of carbon fiber and its composite was studied. Surface topography of carbon fiber was characterized by scanning electron microscope (SEM). Fluffs and breakage, stiffness test were used to analyze the workability in later process of carbon fiber. The results indicated that the sizing agents had important influence to the carbon fiber and its composite. SEM images demonstrated that the sized carbon fiber had smooth surface. The sizing agent could significantly improve not only handling characteristics of carbon fiber due to the increase of fiber flexibility and reduction of fluffs and breakage, but also the interfacial adhesion of carbon fiber/vinyl ester resin composite.

Abstract: Effect of Mn doping on the structural, photoluminescence and photocatalytic photodegradation properties of Zn_1−xMn_xO have been studied. The Zn_1−xMn_xO powders and thin films were synthesized by the sol-gel, spin coating and high temperature annealing processes. The samples were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), photoluminescence and UV-visible (UV-Vis) spectroscopy. XRD analysis showed that Zn_1−xMn_xO can keep a single phase of wurtzite structure at low Mn doping. UV-Vis spectra of Mn-doped samples showed that Mn doping can enhance the decolorization efficiency of methyl orange at optimal Mn doping levels.

Abstract: Ni(OH)₂/multiwalled carbon nanotubes (Ni(OH)₂/MWNTs) nanocomposites were synthesized by hydrothermal method. The microstructures of such nanocomposites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical properties studies were carried out using cyclic voltammetry (CV), galvanostaitc charge/discharge and electrochemical impedance spectroscopy method. The presence of MWNTs network in the Ni(OH)₂ significantly improved the electrical conductivity of the host Ni(OH)₂ by the fromation of conducting network of MWNT and the active sites for the redox rection of the metal hydroxide. The specific capacitance of the new composites was significantly improved (MWNTs of 20 wt.%, 2144 F/g) compared to Ni(OH)₂ (MWNTs of 0 wt.%, 1772 F/g) in 6 M KOH solution at a charge-discharge current density of 4 mA/cm². Therefore, the Ni(OH)₂/MWNTs nanocomposites can be a potential application electrode material for electrochemical capacitors.