Advanced Materials Research Vols. 399-401

Abstract: Monocrystal nano-sliver lamella were prepared by hydrothermal method with the precursor Ag₂C₂O₄ and the surface active agent polyvinyl alcohol (PVA). The influence of the dosage of PVA on the film thickness and yield of nano-sliver lamella (NSL) were analyzed. And the morphology, the film thickness and electron diffraction pattern of NSL were characterized by scanning electron microscopy (SEM) and transmission electron microscope (TEM) respectively . Furthermore,the same sample was respectively characterized by the parallel optical path and the focus optical path of X-ray diffraction (XRD), and the difference between the diffraction data of these two paths was compared. The results show that the dosage of PVA has significant effect on the thickness and yield of monocrystal nano-sliver lamella. The reason that the great difference between diffraction data of the parallel light path and focusing light path can be mainly owing to the preferential orientation in space of NSL.

Abstract: WPCs are wood plastic composites materials. Currently most of WPCs are manufactured by extrude technology. In order to enhance the production efficiency, a new manufacture technology called hot press molding (HPM) has been developed. The remarkable advantages of the so-called HPM WPCs are that large dimension board from 600mm×600mm×3mm to 3500mm×3500mm ×60mm can be multi-moulded in one time. In this paper, the HPM WPCs’ process mechanism and technology is introduced, and the physical and mechanical behavior of the HPM WPCs board is tested and studied. Test and research have shown that the physical and mechanical property of HPM WPCs is good. It is an idea substitute material of timber. The water absorption of HPM WPCs is only 10.3%, the moisture dilation is only 1.10%, the dimensional changes after heated is 2.31%, etc. , physical behavior is better than that of normal timber. Besides that, the mechanical behavior is better than that of timber as well. The ultimate bending strength can reach 14.1MPa, the ultimate compression strength can reach 31.3MPa, and the compression modulus is 3618MPa.

Abstract: This paper presents the design, development and characterization of the spinel ferrite [Mn_0.2Zn_0.8Fe₂O₄] powders and Nickel (Ni)-coated multiwall carbon nanotubes (MWNTs). A combination of Mn_0.2Zn_0.8Fe₂O₄ spinel ferrites particles and Nickel (Ni)-coated multiwall carbon nanotubes (MWNTs) were introduced into epoxy resin to be a microwave absorber. The structural characterizations and surface morphology of Mn_0.2Zn_0.8Fe₂O₄ and MWNTs were investigated by X-ray diffraction (XRD) and scanning electron microscopy respectively. The electromagnetic wave absorption characteristics of the composites have been studied in the frequency interval of 12-15GHz.The results for Mn0.2Zn0.8Fe2O4/EP, Mn_0.2Zn_0.8Fe₂O₄/MWNTs/EP and Mn_0.2Zn_0.8Fe₂O₄/Ni-coated MWNTs/EP microwave absorbers for the same thickness have been reported. It has been found that the Mn_0.2Zn_0.8Fe₂O₄/Ni-coated MWNTs/EP composites show the broadband characteristics with minimum absorption of 5 dB about 2.6 GHz and the maximum absorption of 37.05 dB at 14 GHz for a coating thickness of 2 mm. Therefore, Mn0.2Zn0.8Fe2O4/Ni-coated MWNTs/EP composites will be a suitable microwave absorptive material for 12-15GHz.

Abstract: The aim of this paper is to propose a microstructure modeling for prediction of thermal conductivity of plain weave C/SiC fibre bundles considering manufacturing flaws. Utilizing photomicrographs taken by scanning electron microscope (SEM), we established an accurate sub representative volume element (sub-RVE) model for carbon fiber bundles and RVE for the plain weave C/SiC composite with consideration of four classes of manufacturing porosity. The thermal expansion coefficient of carbon fibre bundles on axial and transverse coefficient of thermal expansion is calculated, respectively. Based on which thermal expansion coefficient of plain weave C/SiC is obtained with the value of 2.71×10^-6 in-plain, which has a good correlation with experimental value. The influences of different manufacturing flaws on material’s thermal expansion coefficient are studied. The study shows that as the matrix porosity or crack volume fraction is increasing, thermal expansion coefficient of plain weave C/SiC is decreasing correspondingly while the speed gradually slows.

Abstract: This thesis does research on a method which can produce a kind of polyxymethylene composite material with fine performance. Nanometer Silicon Oxide Whisker is used as stuffing filler to intensify the strength and tenacity of polyxymethylene, the proper amount can be determined by the test of Sio2W’s influence on polyxymethylene’s characteristics. In the test ,Sio2w is used as toughening agent, MgO/Triethylene glycol dimethacrylate/dicyandiamide are used as thermal stabilizer, from the proportioning test, polyxymethylene Sio2w poly basic Thermal Stabilizer composite Material can be produced, which has high strength, .hardness impact toughness and thermal stability.

Abstract: The inorganic-organic hybrid polymer PAFC–CPAM with 100∶1 (w/w) and basicity 1.5 was synthesized and the comparison with AlCl₃ and CPAM for flocculation effect in coking wastewater regeneration treatment was also performed. The hybrid polymer was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Raman spectroscopy. The results showed that the optimum value of CODCr removal rate for PAFC–CPAM was 52.17%, higher than that of AlCl₃ and CPAM with 50% and 40.91%, respectively, meanwhile settling time and sludge volume were improved. Characterizations suggested that PAFC was grafted onto CPAM chains through coordinate bonds due to hydroxyl crosslinking.

Abstract: Effect of sintering temperatures on reaction-bonded Si3N4/SiC composite ceramics under pressureless was investigated. Si₃N₄/SiC composite ceramics were sintered at different temperatures from 1450 to 1700 °C under nitrogen atmosphere by using SiC with different particle sizes, Si and additives Y₂O₃ as raw materials. The phases, microstructure and mechanical property were characterized by XRD, SEM, and compressive strength tests. The results demonstrated that when the particle gradation consists of silicon carbide of 74 μm (5 wt.%), 44 μm (10 wt.%) and 0.5 μm(35 wt.%) and silicon powder of 74 μm (42 wt.%), the more dense samples with the bulk density of 2.43 g/cm³ and the higher compressive strength of 324 MPa could be obtained at the sintering temperature of 1550 °C for 3h as the optimum processing parameters.

Abstract: The effect of graphite content on formation of decarbonization layer and corrosion resistance of zirconia graphite materials were studied by the corrosion test in induction furnace, and the effect of decarbonization layer on corrosion of zirconia graphite materials was also analysed by the kinetic models for the corrosion of SEN in mold, the result show that: (1) Thickness of decarbonization layer of slag line is decreasing with the increase of graphite content. When the mold fluxes for high carbon steel is used, decarbonization layer is thin and graphite content has little effect on corrosion resistance of zirconia graphite materials, and 10wt%graphite is better. When the mold fluxes for low carbon steel is used, decarbonization layer is thick and 14wt% graphite is the best. (2) Corrosion of zirconia graphite materials in mold is characterized by the features of consecutive reaction:original layer (k₁) decarbonization layer (k₂) corrosion layer . If k₁<2, there is no decarbonization layer forming and decarbonization is the key step for the corrosion; If k₁>>k₂, there is decarbonization layer on the hot surface of zirconia graphite materials and the corrosion of the layer is the key step. Graphite content is too high or too low is all harmful for the corrosion resistance of zirconia graphite materials.

Abstract: The organic-inorganic composite of oleic acid embedded layered magnesium borate was synthesized by low temperature hydrothermal method with magnesium chloride (MgCl₂•6H₂O), borax (Na₂B₄O₇•10H2O) as reactants, oleic acid as the embedded agent. The structure and morphologies of the synthesized samples were investigated by X-ray diffraction, N2 adsorption-desorption isotherms, scanning electron microscopy and Fourier transform infrared spectroscopy techniques. The results suggest that the structure of oleic acid embedded magnesium borate is layered-by-layered, and the interlayer spacing was about 6 nm. And the sizes of the lamellar magnesium borate are in the range of 100 nm to 200 nm. The average pore diameter of the prepared product is 22.4 nm. The BET surface area and pore volume are 50.31 m²/g and 0.275 m³/g, respectively. The molecular structure model of oleic acid embedded layered magnesium borate is established.

Abstract: AlN-ZrO₂ composites were prepared by hot pressed sintering with AlN particle (d≈2mm, d≈1.5mm and d≈1mm) and ZrO₂ powder as material. Its phase composition, thermal conductivity and sintering performance were investigated by XRD, SEM, EDS and performance testing. The results showed that AlN could be reserved in samples, and the thermal conductivity and the apparent porosity of the samples ascended with increase of the content of AlN, and the bending strength of the samples with same AlN particle occurred change according to V-shape with content of AlN increasing. Thereinto, the thermal conductivity of the samples with 1.5mm AlN was most excellent, amang samples with AlN particle of 2mm, 1.5mm and 1mm, and sintering performance of the samples with 1mm AlN was best. Particle interface of AlN and ZrO₂ was high concentration area of elements Ca and O, and was a structural loose crack area with CaAl₁₂O₁₉ formed. The area is abominable for performances of AlN-ZrO₂ composites such as thermal conductivity, density and strength. It is more appropriate for preparation of AlN-ZrO₂ composites with AlN particle of 1.5mm and 1mm as materials.