Papers by Keyword: Composite

Abstract: A kind of graphitized carbon black 40B2 was incorporated in natural rubber matrix and vulcanizates were prepared. The content of carbon black varied from 4 to 100phr for 100phr of natural rubber. Thermal conductivity of the CB/rubber composites was studied as a function of CB loadings and temperature. TEM and SEM were employed to explore the morphology of the carbon black and the composites. It was found that percolation phenomenon existed in thermal conductivity of CB/rubber composites at different filler loadings, which was much similar with percolation behavior in electrical conductivity properties of many composites, and the percolation threshold was about 13.63%. The influence of temperature on thermal conductivity was more obviously within the region from the percolation threshold to the volume fraction of 26.2%.However, no great effect could be found on the percolation behavior of the composites in thermal conductivity. The result of TEM indicated that the mean size of CB particles was about 25nm, the maximum size of CB aggregates was about 125nm, and the CB aggregates were multichain in shape. The results of SEM showed that the distribution of CB differed at different filler loadings. Before the percolation threshold, the CB aggregates existed isolatedly, nevertheless at the percolation threshold, some long chains made up of CB aggregates ran through the rubber matrix, which resulted in the rapid increase in thermal conductivity value, and then with the addition of CB loadings, the number of chains increased. When the volume fraction was up to 26.2%, some three dimensional networks formed.

Abstract: On the investigations on the flexural properties,color stability and melting properties,the effects of treating ramie fiber with silane coupling agent on the anti-thermo-oxidative aging properties of high density polyethylene(HDPE)/ ramie fiber composites were studied.The results show that,treating the fiber with 3% coupling agent can improve the flexural strength and modulus of the composites before the aging test by 15.9% and 21.7% respectively,and also it can improve the flexural properties of the composites after the aging test;the modified composites will be more color stable,less color difference,and less disminish of the color during the aging test;the peak melting temperatures of the modified composites when aged for 0,500,1000,1500 and 3000h will be increased by 0.6，0.2， 0.5,2.3 and 3.8 oC from those of the unmodified composites;the flexural properties,color stability and melting properties of HDPE / ramie fiber composites during thermo-oxidative aging tests all indicate that treating ramie fiber with coupling agent can improve the anti-thermo-oxidative properties of the composites.

Abstract: Ramie fiber and polypropylene were used as raw materials,ramie fiber/polypropylene composites were prepared by compression molding process,the effects of treating the ramie fiber with silane coupling agent and compatibilizing the composite with maleic anhydride gafted polypropylene(MAPP) on the structure, melting and mechanical properties of the composites were studied，the effects of immersion time in water on the mechanical properties of the composites were also investigated.The results show that,both the modification with coupling agent and by means of compatibilizing agent can strengthen the interfacial bonding between the fiber and matrix in the composite,and also improve its thermal stability.All the modified composites have greater strengths and moduli than the unmodified ones when immersed in water for any periods,especially the impact strength of the MAPP compatibilized composite not only increases with immersion time in water dramatically,but also is improved from that of the unmodified one by 104.84%,239.40%,294.48% and 320.01% respectively when immersed in water for 0,7,14 and 21d.

Abstract: Damping of foamed Al composite filled epoxy resin in the holes is researched by experimental and theoretical analysis. The results are showed that foamed Al damping can be improved by Filling epoxy resin in the holes, and with porosity increasing or diameter decreasing, the composite’s Damping is increased, but the change of damping with frequency is non- monotone function. The results can provide reference for optimization and application of the composite.

Abstract: The use of composite materials, mainly reinforced thermoplastic has increased on the polymer industry, mainly the polypropylene resins (PP) reinforced by glass fibers (GF). The ionizing radiation can promote alterations in the polymeric chains by scission and crosslinking reactions. The objective of this work is to study the effect of the ionizing radiation in the properties of the polypropylene long fiber glass reinforced thermoplastic. Pellets with 1,3 cm of length, contend 15wt% of the unidirectional long glass fiber were obtained by extrusion and, subsequently, the samples were molded by injection, irradiated and submitted to thermal and mechanical tests. The mechanical (tensile and impact) properties and thermal (HDT and Vicat softening temperature) of irradiated and non irradiated reinforced thermoplastic were determined. The doses of the irradiation of the samples were 30, 50 and 100 kGy in a source of 60Co. The results showed a reduction in the thermal and mechanical performances indicating a degradation of the polymeric matrix.

Abstract: In nanocrystalline materials the grain boundaries must be considered as regions of finite thickness with properties different from the crystalline bulk material present in the crystallite cores. Thus, dense (i.e. pore-free) single-phase nanocrystalline materials can be considered as quasi-twophase systems whose effective properties can be calculated when quantitative thickness information is available and the property value of the grain boundary phase can be reliably estimated. Similarly, dense two-phase nanocomposites may be considered as quasi-three-phase systems and their effective properties can be predicted using an analogous phase mixture modeling approach. In this contribution this is done for the thermal conductivity of alumina-zirconia nanocomposites. A twostage homogenization procedure is applied, consisting of a first step in which the alumina-zirconia composite is treated as a symmetric-cell material, and a second step in which the highly disordered grain boundary phase is treated as a matrix-phase, coating the crystallite cores. The individual averaging steps are discussed with respect to the two- and three-point bounds, and the resulting grain size dependence is compared with that of pure alumina and zirconia, and literature data.

Abstract: MoO3-x nanowires belong to photocromic materials and are promising candidates for lithium intercalation, hydrogen sensing, and smart windows. We report on a successful preparation of liquid single crystal elastomers (LSCE) containing MoO3-x nanowires, mostly the conductive Mo5O14 phase. Preparation and basic chemical and physical properties of these materials are discussed in view of the potentiality of these composites as actuators. The particular combination of molybdenum based nanowires and LSCE enables functionalization of liquid single crystal elastomers preventing the pristine mechanical and optical properties of the host matrix.

Abstract: One of the most recent alternatives in the development of materials with high mechanical properties and wear resistance is the addition of nanometric and/or micrometric particles of a secondary phase into ceramic matrices. Nanostructured materials can be defined as systems that have at least one microstructural characteristic of nanometric dimensions (less than 100nm). In this work, alumina-diamond nanocomposites were produced using nanometric diamond powder obtained by high energy milling in a SPEX mixer mill for 6h. The crystallite size was 30nm. After deagglomeration, the diamond powder was added to the alumina matrix in a ratio of 5wt%. The samples were isostatically pressed and high-vacuum sintered. The resulting nanocomposites and composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and by microhardness, diametral compression and wear resistance tests. The results confirmed the promising wear characteristics of the alumina-diamond nanocomposite.

Abstract: The earlier studies showed that addition of different chromium carbides to nonstoichiometric fine titanium carbide improve sintering in the similar way. The phase, structural and microstructural changes for addition of various chromium carbides were also similar. In the present work the composite materials were made of various carbon quantity saturated titanium carbide (as matrix) and commercial chromium carbide Cr3C2 (as additive). The titanium carbide powders with variable content of carbon in structure were synthesized by the SHS method. The chromium carbide in quantity of 7.5 % by volume was added to the initial mixture. The influence of various stoichiometry of titanium carbide on onset temperature of sintering was examined by use of high temperature dilatometer. The phase and structural changes of examined materials during sintering were made using XRD and Rietveld method. The evolution of microstructure, versus of different stoichiometry titanium carbides, was observed by use of scanning electron microscopy.

Abstract: Hexagonal boron nitride (h-BN) is a very versatile material that is used in a number of applications due to its unique combination of properties. This paper reviews typical h-BN qualities and their applications as functional particle in coatings and as sintered parts. As an example, the EKamold® coating family is presented in detail for a variety of substrate types and applications. Furthermore a general overview is given of the effect of the binder phase for hot-pressed h-BN qualities. And finally the use of h-BN as a composite with a) zirconium oxide for side dams in steel thin-strip casting and b) with titanium diboride as evaporation boats is described in more detail.