Advanced Materials Research Vols. 1120-1121

Abstract: In this study, the (Fe,Cr)₇C₃ particles strengthened gradient composite was produced by in situ synthesis process with subsequent heat treatment from gray cast iron (HT300) and high purity chrome plate. The microstructure, phase composition and wear resistance of the composite were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and scratch tester. The results showed that the thickness of the gradient layer was about 758 μm after heat treatment at 900 °Cfor 4 h. And it can be divided into three areas depending on microstructure. The outermost layer which was ~60 μm of thickness, was the dense ceramic layer with high volume fraction of (Fe,Cr)₇C₃ ~90%. No obvious grain boundaries were observed. The subsurface layer was the particles dispersed layer, which was ~525 μm of thickness, with the volume fraction of (Fe,Cr)₇C₃ decreased to 70%. The lowermost layer was ferrite, with about 173 μm thickness. A good metallurgical bond generated between the composite layer and matrix. The depth and the width of surface scratch increased with the raising loads from 0 to 100 N, and the cracks mainly included micro-crack, tiny dens crack, mixture crack and through-wall crack. The (Fe,Cr)₇C₃ particles were broken and scraped when the load exceeded 80 N.

Abstract: The branched polyethylene (br-PE) was synthesized by [ArN=C(An)-C(An)=NAr]NiBr₂ (An = acenaphthyl, Ar = 2,6-C₆H₃(iPr)₂) in the presence of modified methylaluminoxane (MMAO) and methylaluminoxane (MAO). The effects of experimental conditions in which ethylene pressure, temperature and time were varied on ethylene polymerization were investigated. The structures of the obtained polyethylene were characterized by high-temperature NMR, high-temperature GPC and DSC. It was found that the activities from MMAO were higher than that from MAO about 10 times, which reaches 10⁷(g/mol Ni·h). The branches of polyethylene prepared from MMAO were about 60/1000C, while that from MAO were about 80/1000C. The branched polyethylene with 84 branches / 1000C was used to toughen isotactic polypropylene (i-PP). The results show that the impact strength of blends improves as the content of branched PE increases. When the content of br-PE is 40%, the impact strength of the blend reaches to 50.24 KJ/m², which is about twenty times that of PP (2.24 KJ/m²).

Abstract: A novel kind of rubber toughened epoxy was prepared by in situ pre-crosslinking carboxyl-terminated butadiene-acrylonitrile copolymer (CTBN) in the epoxy matrix. The in situ pre-crosslinking of CTBN was initiated by BPO, followed by the curing reaction of epoxy to form the final pre-crosslinked CTBN/epoxy composites. Mechanical properties of epoxy are further improved by the incorporation of pre-crosslinked CTBN compared with its traditional CTBN/epoxy counterparts due to the improved interfacial strength between rubber and epoxy. SEM shows that the size of phase separated rubber particles of pre-crosslinked CTBN/epoxy decreases significantly.

Abstract: An innovative spray deposition technique has been applied to produce in situ TiB₂/Zn-30Al-1Cu composites. The microstructures of the spray-deposited composite were studied using optical microscopy, scanning electron microscopy, and X-ray diffraction. Both theoretical and experimental results have shown that the TiB₂ particulates are formed in the microstructure. It was found that the TiB₂ particles were distributed in Zn-30Al-1Cu matrix uniformly, and the TiB₂ particles are about 2 μm in size. Moreover, the presence of the TiB₂ particles was led to increasing of α’ phase with less 2 μm size in the composites which have a tendency to decompose to α+η structure.

Abstract: As flame-retardant Polyacrylonitrile (PAN) fibers was one of the most important differential fibers, it was of great importance to make research on the modification of flame-retardant PAN fibers to improve its characteristics. In this present study, the flame-retardant PAN fiber with good moisture absorption and mechanical properties has been prepared treated by blending solution of sodium hydroxide and hydrazine hydrate. FTIR spectra presented that new amide and cyclization-crosslinking pyridine group band peaks appeared. X-ray diffraction showed that the crystal structure of PAN fibers has been converted from quasi-crystalline structure into partially crystallized structure after modification treatment. SEM micrographs indicated that the original longitudinal surface microgroove has changed to layered structure by surficial etchant.

Abstract: Differential scanning calorimetry (DSC) measurement is used to investigate the nonisothermal crystallization behavior of poly (vinylidene fluoride) (PVDF)/polysulfone (PSF)/diethylene glycol dibenzoate (DEDB)/dibutyl phthalate (DBP) system via solid-liquid (S-L) phase separation during a thermally induced phase separation process. The effect of benzene ring in PSF on PVDF crystallization for PVDF/PSF/DEDB/DBP system is investigated. It is found that the Ozawa model can describe nonisothermal crystallization behavior of PVDF/PSF/DEDB/DBP system in a certain crystallization temperature range. Jeziorny method indicates that the secondary crystallization of PVDF exists in the process of nonisothermal crystallization and is enhanced by the increase of cooling rate.

Abstract: The conductive and fiction properties of overbased calcium sulfonate complex grease and lithium grease containing carbon black (CB) additive were investigated in detail. The results indicate that CB can dramatically improve the conductivities of the greases. Also the tribol-test results indicate that the CB can dramatically improve the tribological properties of the greases. The lithium greases containing CB, have better tribological properties than overbased calcium sulfonate complex greases. Among the lithium greases, 5% CB contained grease performs the best friction reduction properties, and among the overbased calcium sulfonate complex greases, 6% CB contained grease performs the best friction reduction properties.

Abstract: In this work, study on impact damage FEM model of composite structure was performed. From the finite element method analysis results of composite laminate, it was confirmed that the results of analysis was reasonable. The velocity of impactor to initiate damage was estimated, and in order to investigate the damage at the predicted velocity, impact analysis using finite element method was performed. According to the impact analysis results of composite laminate, it was confirmed that the damage was generated at the estimated impact velocity. Finally, the comparison of the numerical results with those measured by the experiment showed good agreement.

Abstract: The absorbed liquids in the substrate material may have a potential influence on atmospheric pressure plasma treatment. In order to investigate how the influence of ethanol pretreatment affects atmospheric pressure plasma treatment, nylon 6 films were treated by helium/oxygen plasma using atmospheric pressure plasma jet (APPJ). Water contact angle of the ethanol pretreated samples was close to that of the control. Scanning electron microscopy (SEM) showed that the ethanol pretreated sample surface had a little change on the surface. X-ray photoelectron spectroscopy (XPS) showed that the carbon component decreased and the oxygen component increased after plasma treatment. With the ethanol pretreatment, the T-peel strength values for the samples were similar to that of the control.

Abstract: To improve the preparation technology and mechanical properties of carbon/carbon composites, a kind of Zirconium dioxide modified Carbon/carbon (C/C–ZrO2) composites were prepared by Sol-Gel Process combined with isothermal chemical vapor infiltration (ICVI) method. This method could shorten preparation cycle greatly to reduce the cost. The microstructures and mechanical properties of the C/C–ZrO2 composites were investigated. The results indicate that the ZrO2 modified phase is uniformly distributed in the carbon matrix, the bending strength and modulus of C/C–ZrO2 composites are much higher than unmodified C/C composites due to its particle toughening and fiber toughening.