Advanced Materials Research Vols. 399-401

Abstract: Porous SiC/Si₃N₄ composite ceramic was prepared at different temperatures by pressureless using SiC and Si₃N₄ as raw materials. The effects of sintering temperature and different particle size of SiC on porosity SiC/Si₃N₄ composite ceramic were investigated. The phases, microstructure and mechanical property were characterized by XRD, SEM, and compressive tests respectively. The results indicate that the increase of sintering temperature is in favor of the formation of β-Si₃N₄ crystal phase, the porosity and the compression strengthof porous SiC/Si₃N₄ composite ; The porosity of Si₃N₄/SiC block which contain particle graded higher than single particle size, but weaker compression strength.

Abstract: Attapulgites (AT) were modified by coupling agent 3-(trimethoxysilyl) propyl methacrylate ( KH570 ). Then, the modified AT (MAT) and unmodified AT particles were compounded with Polypropylene (PP) to prepare PP/MAT and PP/AT composites respectively. Their structure and properties were characterized by mechanical testing, differntial scanning calorimetry (DSC) and Scanning electron microscopy (SEM). The results showed that the tensile strength of PP/MAT and PP/AT composites were both improved by filling of 1~7 wt% AT particles. The izod impact strength of PP/MAT composites were increased obviously than that of PP/AT composites with AT content of 1~7 wt% , and it attain the most at 1 wt% filler loading. The crystallization temperature of PP/MAT composites was increased than that of PP/AT composites and pure PP. The degree of supercooling was decreased indicates that the crystallization rate of polymer is improved. The crystallization rate of the PP phase is enhanced in the PP/MAT composites due to the introduction of homogeneous dispersed AT modified by KH570 and good interface adhesion between the AT and PP matrix.

Abstract: Polyamide 6 (PA6)/magnesium hydroxide (MH) nanoparticles composites have been prepared by in situ polymerization of ε-caprolactam in the presence of pristine MH and γ-aminopropyl-triethoxysilan ( KH550 ) grafted MHs (MMH). Compared with pure PA6, the tensile strength and elongation at break of PA6/MH and PA6/MMH composites shown obvious increasement and attain maximum at loading of 3 wt% MHs. The tensile strength and elongations at break of PA6/MMH composites exhibited notably enhancement contrast with that of PA6/MH composites. Comparing with PA6/MH composites, the izod impact strength of PA6/MMH composites were also improved. Scanning electron microscopy (SEM) shown that MMH particles were homogeneous dispersed in PA6 matrix due to the surface modification of grafting KH550.

Abstract: In this paper, the tensile strength of 3-dimension-4-direction braided/epoxy resin composites after accelerated aging for different period of time at 150°C was investigated. The tensile tests of 3-dimension-4-direction braided/epoxy resin composite samples without aging and aged 60 hours, 120 hours, 180 hours, at 150°C were carried out. The damage forms of braided composite samples tested were investigated. The experiment result indicates that the accelerated aging process at 150°C has some effect on the tensile strength of braided composite samples. The average tensile strengths of composite samples aged 60 hours, 120 hours, and 180 hours period of time at 150°C are 92.44%, 91.62% and 84.91% of average tensile strength of braided composite samples without aging, respectively. This means that the tensile strength will be decreased when the aging period of time increases at 150°C. The damage form of samples tested shows that when accelerated aging, the resin in the composite samples is damaged, which makes the adhesive force between fiber bundles and epoxy resin decline, so that the ability of fiber and resin bearing the tensile load together decreases.

Abstract: The B₄C/BN composites were fabricated by hot-pressing process in this research. The B4C/BN composites included the B₄C/BN microcomposites and the B₄C/BN nanocomposites. The B₄C/BN microcomposites were fabricated by hot-pressing process, and the B₄C/BN nanocomposites were fabricated by chemical reaction and hot-pressing process. In this research, the phase composition of the B₄C/BN microcomposites and the B₄C/BN nanocomposites were investigated by XRD analysis. The XRD patterns results showed that there existed the B₄C phase and h-BN phase in the hot-pressed composites. The microstructure of the B₄C/BN microcomposites and the B₄C/BN nanocomposites sintered bulks were investigated by SEM and TEM. The SEM micrographs showed that the B₄C/BN microcomposites and the B₄C/BN nanocomposites sintered bulks exhibited the homogenous and compact microstructure, and the h-BN particles were homogenously distributed in the B₄C matrix. The TEM micrographs showed that there existed the weak interface between the B₄C matrix grains and h-BN particles as well as the microcracks within the laminate structured h-BN particles.

Abstract: Chromium powder reinforced geopolymer composite (Cr/geopolymer) was prepared in order to enhance its thermal conductivity and mechanical properties. The phase composition, microstructure and mechanical properties of Cr/geopolymer before and after heat treatment at 900, 1000, 1100 and 1200°C were investigated by the X–ray diffraction (XRD), scanning electron microscopy (SEM) and three–point bending test. With increasing heat treatment temperature from 900 to 1100°C, mechanical property of Cr/geopolymer increased gradually and at 1100°C flexural strength got the peak value, which was 325% higher than that of specimens without heat treatment. Cr/geopolymer treated at 900°C did not completely transform into crystalline phase, and many micro cracks around the chromium particles were observed. Cr/geopolymer treated at 1000–1100°C completely crystallized into leucite phase, and the metal chromium remained its original state. Meanwhile, most of the micro cracks were closed. When the temperature further increased to 1200°C, many visible defects were observed in Cr/geopolymer, and chromium oxide appeared in the interface of Cr/geopolymer, which had detrimental effect on the heat conduction and mechanical property of the composite.

Abstract: Jute fibers reinforced friction materials were prepared by mold and heat treatment. The friction coefficients of 3wt.%,9wt.% and 12wt.% jute fibers reinforced friction materials were bigger than that of the materials without jute fibers in the heating condition. The friction coefficient of 6 wt.% jute fibers reinforced friction materials was bigger than that of the materials without jute fibers below 250°C. The friction coefficient of jute fibers reinforced friction materials deceased with the temperature decrease in the cooling condition. The friction coefficient of the materials with free-jute fibers raised from 350-250°C and reduced at the temperature lower than 250°C.Wear rates of the friction materials raised with temperature rise for jute fibers carbonization led to the matrix became loose. With jute fibers content rise worn surface of the reinforced materials became from smooth to rough. There were pits, grooves, abrasive particles, pulled out fibers and wear debris on the worn surfaces. Abrasive wear was the main wear mechanism.

Abstract: The mechanical properties of 3D woven interlock composites (3DWIC) can be tailored via design of their weave architecture. This paper presents a geometric model called Generic Geometric Model (GG-Model) which delineates the weave architecture of 3DWIC based on its realistic internal geometry i.e. geometry of the cross-section and path of tows. In GG-Model, the cross-section of tows has been described through a novel shape function called “Generic Shape Function (GSF)”. The GG-Model uses manufacturer and weaver specified data to calculate geometric parameters of the 3DWIC and the reinforcing fabric. The GG-Model is then validated by comparing modeled parameters with experimental data. Strong correlation is found between modeled parameters and experimental data.

Abstract: A series of polyurethaneurea (PUU) nanocomposites based on clay-like sepiolite (Sp) with the modification of γ-aminopropyltriethoxysilane (KH550) were prepared via in situ polymerization from poly(propylene glycol), tolylene-2,4-diisocyanate (TDI) and 3,3'-dichloro-4,4'- diamino-diphenylmethane(MOCA). Morphology and structure of nanocomposites were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results indicated that KH550-Sp was dispersed homogeneously in the PUU matrix, which facilitated the formation of chemical bonds between KH550-Sp and the hard segment of PUU. The thermostability and mechanical properties were studied by the thermogravimetric (TG) analysis and tensile tests. The results showed that the onset decomposition temperature and tensile strength of nanocomposites was higher than those of pure PUU.

Abstract: Abstract:The paper makes use of the ANSYS analysis software to simulate[1] the temperature field and calculate , and further proof the Synergy Effects of flame - retardant effect on OMMT and APP for PP/PA6 composts on the basis of the oxygen index (LOI),UL-94 testing and thermo gravimetric analysis (TGA) test. According to simulation and analysis , the simulation result of temperature field corresponds with the oxygen index (LOI), UL - 94 test results.