Advanced Materials Research Vols. 295-297

Abstract: The optical properties of composites, formed by filling the high density polyethylene (HDPE) with carbon black (CB), multi-walled carbon nanotubes (MWNTs) and fullerene (C₆₀), respectively, in the frequence region from 0.3 to 2.0 terahertz (THz) were characterized with THz time-domain spectroscopy (THz-TDS). It is found that the optical parameters and the details of their variation with frequence and filler concentration are significantly different for different kinds of carbon materials. The MWNTs filled composites have the biggest absorption coefficient value, refractive index and real conductivity. The C₆₀/HDPE composite shows very little changes in absorption and refractive index compared to that of the HDPE even at a filler-content of 12.3% in volume fraction. These phenomena are related to the special properties of the fillers as well as their particulate structures, such as aspect ratio, particle size, and aggregate structure, etc. The results are analyzed by using Cole-Cole theory of dipole relaxation under the assumption that carbon particles dispersed in the matrix behave like dipoles.

Abstract: The nanocrystals Ce_0.5Zr_0.5O₂ solid solutions with various morphologies and crystal structures have been synthesized via a modified sol-gel method assisted with a template. Aerosol OT and/or ionic liquids ([MMIM]Cl] and [BMIM]Cl]) was used as a template. The characterization results of the X-ray diffraction, transmission electron microscopy and N₂ adsorption at 77 K indicate that the physical properties of the solid solutions were significantly affected by the templates used and the calcination temperatures. The Ce_0.5Zr_0.5O₂ calcined at 773 K possessed bimodal mesopores, narrow pore size distributions, and tetragonal phase.

Abstract: Fused quartz powder (size<0.04mm) was used as raw material, nano-Y₂O₃, nano-CeO₂ and nano-La₂O₃ (size<0.08μm) were dividedly used as additives with dosage of 2% each. Fused quartz ceramic materials were sintered in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1h. The effect of rare earth nano-oxides on sintering and crystallization of the fused quartz ceramic were researched by measurements of apparent porosity, bending strength and thermal expansion rate, and analyses of XRD and SEM. The results showed that additives nano-Y₂O₃, nano-CeO₂ and nano-La₂O₃ had obvious effect of inhibiting crystallization of fused quartz, and the samples added nano-Y₂O₃ and nano-La₂O₃ were better. Sample added nano-Y₂O₃ had least thermal expansion rate. Sample added nano-La₂O₃ had higher bending strength, and it showed that nano-La₂O₃ had better effect on sintering of fused quartz ceramic. It can be deduced that nano-La₂O₃ plays the excellent role as the crystallization inhibitor of fused quartz materials.

Abstract: SiC is fabricated by chemical vapor deposition (CVD) on graphite and Si₃N₄ ceramic respectively. The morphology, composition, grain size and electrical conductivity of SiC deposited on graphite (CVD-SiC_(C)) and on Si₃N₄ ceramic (CVD-SiC_(N)) are investigated and compared. The morphology of CVD-SiC_(C) and CVD-SiC_(N) is much different with each other. The grain size of CVD-SiC_(C) is bigger than that of CVD-SiC_(N). It is nearly stoichiometric in CVD-SiC_(C), while carbon-rich in CVD-SiC_(N), so the electrical conductivity and dielectric loss of CVD-SiC_(N) are much higher than that of CVD-SiC_(C). As the annealing temperature increases, the grain size and electrical conductivity of CVD-SiC_(C) and CVD-SiC_(N) both increase.

Abstract: The purpose of this paper is used Ansys to simulate the temperature field of laser brazing by FEM. The 3-D solid elements are used in FEM model, and nonlinear factors of temperature-dependent material properties are considered. The surface temperature grades have been attained, and the brazing experiment have been conducted, the results show that the wetting of Ni-Cr alloy to diamond is good. This study is useful for selecting reasonable processing parameters on laser brazing.

Abstract: (Tetracarboxyphthalocyaninato) cobalt (Ⅱ) was used as dye to enhance the photocatalytic activity of nano-TiO₂ in visible light. The photocatalyzer was prepared by phthlocyanine Co and TiO₂, which was called TPC. The photocatalytic process of removal of benzene was investigated in visible light and ultraviolet. Results reveal that TPC can enhance photocatalytic activity of TiO₂. The Benzene removal of TPC catalyst at 4.5 h was 52.80 % in incandescent lamp, at the same time it was 41.86% higher than nano-TiO₂. The Benzene removal of TPC catalyst at 4.5 h was 43.53% in fluorescent lamp, at then 28.03% higher than nano-TiO₂. The Benzene removal of TPC catalyst at 4.5 h was 36.58% under ultraviolet, at then 5.50% lower than nano-TiO₂. The Benzene removal of TPC catalyst at 4.5 h was 10.69% in incandescent lamp, at then 2.15% higher than nano-TiO₂. TPC catalyst should enhance ability of liquid photocatalytic oxidation TiO₂. The highest photocatalytic degradation of nitrobenzene and methylene blue were separately 76.60 % and 21.02 % under incandescent light.

Abstract: By testing the mechanical properties, microstructure observation, accelerated corrosion test, the effect of alloying element nickel on microstructure and properties of weathering steels was studied. The results showed that nickel content from 0 to 0.44%（mass percent）have little influence on microstructure and mechanical properties of weathering steels.The corrosion resistance enhanced with increasing nickel content, and nickel content of 0.11% or more had significant enfluence on corrosion resistant performance of weathering steels.

Abstract: Study on the mechanics performance of ancient Chinese timber structure is of great significance. The paper based on P’ai-lou of Xi'an Great Mosque as the research object, and used spring elements to simulate semi-rigid of mortise-tenon joints, just answered to the finite element numerical analysis. The stiffness values of mortise-tenon joints were got by nonlinear contact analysis; Under the vertical load, the inner force of structure is far less than its design value, and the safety margin of structure is above 60%; The differential motion equation of structure was given, the first six natural frequencies and the vibration performance of the P’ai-lou were got by the model analysis; Based on Spectrum analysis and time-history analysis , the results show that the ancient Chinese timber structure is soft, and has a better energy consumption performance as well as a "meet strong a strong" intelligent shock absorption characteristics. Analysis and calculation results provide the theory basis for maintenance and protection of ancient Chinese timber structure.

Abstract: Using ·OH from Fenton’s reagent, the strong oxidation treatment of methylene blue dye wastewater can destruct the chromophore in organic compounds, and yield CO₂, H₂O and small molecule inorganic compounds by oxidative degradation finally. The influence of Fenton's reagent dosage, initial pH, and reaction time on the degradation effect was studied. The experimental results show that the decolorization rate of 100mL 20mg/L methylene blue dye wastewater can achieve 96% in the conditions of 0.02g FeSO₄·7H₂O, 1mL 30% H₂O₂, initial pH at 3.0 ~4.0, reaction time is 30 min, at room temperature. This treatment of dye wastewater is easy to operate and with good effect.

Abstract: By the tight-binding method, we study the transport properties of right-angle L-shaped graphene nanoribbons. We found a universal conclusion is that the resonance of electron tunneling will present at the Dirac point when the system is metallic and the ribbons widths satisfy (NB_AB=2NB_ZB-1). Further research suggests that the conductance resonance effect will be destroyed by impurity scatterer, especially the impurity concentration and strength are nontrivially large. We also found that antiresonance effect will result in a strong conductance suppression when the width difference () of the two ribbons is very big. In addition, when the system is semiconducting, the center of the well-defined insulating band can be easily tuned by a gate bias exerted on the armchair-edged graphene nanoribbon.