Advanced Materials Research Vols. 150-151

Abstract: Due to the poor thermal conduction of polytetrafluoroethylene (PTFE), some fillers are often added into PTFE matrix to improve its thermal conduction and enhance its tribological performance. In our work, to increase their thermal conduction, the PTFE composites with different contents of copper particles were prepared. The friction and wear properties of the composites were tested. The effect of thermal conduction on tribological properties of the PTFE based composites was analyzed, and the wear mechanisms were also discussed. The results showed that with the increase of the thermal conductivity of the PTFE based composites, the coefficient of friction of the materials reduced, and the wear of the materials was dramatically decreased.

Abstract: Isolation technology is widely applied in civil engineering nowadays, while it is indicated by seismic damage investigations that the effect of vertical motion on buildings under earthquake couldn’t be ignored. In order to study the 3D isolation effect on high-rise buildings subjected to near-field ground motions, the finite element analysis of an 11-story reinforced concrete frame-shear wall building is conducted, three ground motions are selected, three kinds of structural model are calculated, which are without isolation, with horizontal isolation and with three-dimensional isolation. By analyzing and comparing the seismic response results of models, the 3D isolation effect is studied, and some conclusions are obtained.

Abstract: The Ce-Zr solid solution was prepared by co-precipitation method and ion exchange resin method. The properties of samples were characterized by XRD and SEM. Both the preparation methods can generate solid solution, and the particle size in the sample prepared by ion exchange resin is better than another when Ce-Zr solution formed. Besides, the effect of calcined temperature and feeding order on the formation of solid solution was discussed.

Abstract: The paper expounds the special properties of the nanomaterials, introduces the properties of the melt blown nonwovens and the advantages of nanomaterials and melt blown nonwovens composites, summarizes the methods of incorporating the nanoparticles into the melt blown webs at home and aboard and the advantages, disadvantages of different methods, finally, introduces the new method we taking in the study and the result of our study. The results show that activated carbon is good distributed on the meltblown nonwoven and activated carbon particles embedded within the fiber.

Abstract: A Cu–10Fe–3Ag alloy was produced by means of induction melting. The effects of aging processes on microhardness and conductivity of Cu–10Fe–3Ag alloy were studied. The microstructure of the alloy was examined using transmission electron microscope (TEM). The results show that: presence of Ag can accelerate γ-Fe precipitation from in the Cu matrix, but also reduces the thermal stability of Fe fibers. As the annealing temperature increasing, the microhardness and conductivity of Cu-10Fe-3Ag in-situ composite increase at first and then decrease. Annealed at 475 for 6h, the alloy has an excellent combination of microhardness and conductivity, the microhardness and conductivity reach 209HV and 58.4% IACS, respectively. The Fractures of the alloy are all ductile rupture and the dimples are smaller with the annealing temperature increasing.

Abstract: The erosion behaviors of a hydraulic concrete under high-speed abrasive waterjets at different impact angles were investigated in this paper. The worn surfaces were observed by a scanning electron microscope (SEM). It was found that the defects in the matrix are often the nucleation sites of the microcracks during the erosion. The erosion mechanisms of hydraulic concrete at different impact angles were discussed. The results showed that the erosion process is mainly the microcutting at small impact angles, but peeling off at large impact angles, or mixed mechanism, i. e. microcutting and peeling, at medium impact angles.

Abstract: A series of Co–Cu composite oxides with different susceptibility were prepared by a microemulsion method. XRD, TEM, EDS，FT-IR spectra , TG-DSC and magnetic balance were used to characterize the structure , thermostability and susceptibility of the composite oxides. The results indicate that sintering temperature has an apparent effect on the formation of the spinel structure, As the composite powders are annealed at 500 °C,the Co–Cu composite oxide was CuO 、CoO、 Cu2CoO3 and Co3O4 , but the susceptibilities of Co-Cu composite were found decreased with the annealing, and particle sizes of the composite oxides were increased in the beginning, and then became lower with the annealing .The element Co is found when the calcinations temperature is lower than 300°C.particle sizes of the composite oxides were increased at beginning, then reduced, and increased when over 500°C

Abstract: The effect of microstructure on transport properties of nano-polycrystalline La0.7Sr0.3MnO3-δ films, which were prepared by DC magnetron sputtering at various working pressures and followed by air annealing at 973K for 1h, has been investigated. The result indicates that the change of working pressure can change the microstructure, metal-insulator transition temperature (TIM) and peak resistance but does not change the transport mechanism for the films. The vacancy defects have an important effect on the transport properties of the films. Higher working pressure tends to decrease the density of vacancy defects. Low vacancy defects account for the high TIM and low resistance of the films. In the region of T > TIM, the charge carriers are moving in variable range hopping mode. The behavior of resistance decreasing with the increasing of temperature at low temperature (T<23K) can be explained on the basis of thermal excitation tunneling effect. The minimum resistance results from the combined effect of the tunneling effect and intrinsic metallic transport characteristic of the films.

Abstract: A new kind of lower-branched liquid crystalline polyester (LLCP) containing polyester mesogenic units was synthesized by p-hydroxybenzoic acid, terephthalyl chloride and trimellitic anhydride (TMA), then was used as collaborative modifier for the epoxy resin (E-51) with γ-azyl polyhedral oligomeric silsesquioxane (POSS). The experimental results showed that the LLCP / POSS could act as an effective toughening modifier for the epoxy resin. The impact strength of the composites modified with LLCP and POSS was 1.1 times higher than that of the unmodified system. The temperature of starting decomposition and maximum decomposition rate improved about 20 oC and 13 oC , respectively.

Abstract: Lanthanum hexaboride (LaB6) nanopowders were synthesized at 1200 for 2 hours in the vacuum hot resistor furnace with lanthanum chloride (LaCl3) and sodium borohydride (NaBH4). As-prepared nanopowders were surface modified first by silane coupling agent and then were used as fillers for PMMA to fabricate poly methyl methacrylate (PMMA)/LaB6 nanocomposites via melt extrusion using a twin-screw extruder. X-ray powder diffraction (XRD), transmission electron microscopy (TEM) indicated a pure cubic phase with the average size of 70 nm. Fourier transform infrared spectra (FTIR) proved silane coupling agent was grafted onto nanoparticles. The comparision of field emission scanning electron microscopy (FESEM) of unmodified and modified nanoparticles showed that surface modification prevented agglomeration of nanoparticles, making more evenly-distributed inorganic nanoparticles within organic matrix as LaB6 mass fraction equaled 0.010%. In addition, LaB6 nanoparticles played a vital role in the absorption range from ultraviolet (UV) to NIR and the composite with a higher content of LaB6 was beneficial for rejecting heat.