Advanced Materials Research Vols. 123-125

Abstract: The composites of (1-x)La0.7Ca0.3MnO3/xCoO and (1-x)La0.7Sr0.3MnO3/xCoO (x =0 ~ 0.09) were fabricated by conventional solid state reaction method, and their electrical transport and magnetoresistance (MR%) properties were investigated by physical property measurement system (PPMS). The result of x-ray diffraction (XRD) and scanning electronic microscopy (SEM) indicated that no new phase appeared in the composites except manganites matrix and CoO phases. CoO is mainly distributed at the grain boundaries and surfaces of the matrix. The resistivity LCMO and LSMO based composites were measured in the range 90-320K and 90-400K, respectively. The applied magnetic field is 0T and 0.5T. The observed variation of MR with varying Ca and Sr concentration has been qualitatively investigated.

Abstract: The effects of Si on the interfacial characteristics of Al-6.25 Si alloy/SiC and Al-11.12 Si alloy / SiC were investigated. The different compositions of aluminium and silicon carbide samples were prepared at various processing temperatures with constant holding time. The characteristics of interface between Al alloy and SiC were evaluated using tensile test and microhardness test. The interface morphologies were evaluated using scanning electron microscope and energy dispersive spectroscopy. The results shown that the interface fracture strength and microhardness values increased at the interface when Si concentration levels were increased.

Abstract: The interfacial property between graphite/epoxy laminate and multi-walled carbon nanotubes (MWNTs)/polymer nanocomposites was investigated. For the graphite/epoxy laminate, the fiber orientations were varied. For the MWNTs/polymer nanocomposites, the epoxy resins were used as the matrix material and the MWNTs were used as the reinforcement. The weight percentage of MWNTs in the MWNTs/polymer nanocomposites beam specimen was varied. The graphite/epoxy laminate and the MWNTs/polymer nanocomposite beam were glued together by epoxy to make the test specimens. To determine the interfacial property, the end notch flexure (ENF) method was used, and the specimen was placed in a three-point bending test to evaluate the critical strain energy release rate Gc. In analysis, the finite element method was used to obtain the numerical values of the critical strain energy release rate Gc and compared with the experimental ones.

Abstract: The nonwoven waste coming from textile industry takes up 5% of the total waste amount, so to recycle and to regenerate the waste is the prior obligation of the factory to reduce the waste. Nonwoven selvages waste can be buried or burnt but these two methods result in environmental pollution. This research proposes to reuse these waste nonwoven selvages effectively, and is designed as follows. Each piece of thermal-bonding material comprised a sandwich structure, with two layers of 7.0d PET matrices enclosing a layer of PP nonwoven selvage and nylon geogrid. After needle-punching and thermal-pressing, it forms a laminate structure of PET nonwoven/ PP selvage/ PET nonwoven in that it decreases the impact by the environmental pollution and protects the environment ultimately. In addition, thermal-bonding reinforces the mechanical properties of the composite fabric structure. The results of the experiment suggest the optimum manufacture parameters (selvage content: 10 %; thermal-bonding temperature: 220°C; needle-punching density: 400 needles/ cm2). The composite fabric undergoes the burst strength test and permeable coefficient measurement, evaluating its applications in geotextile filed.

Abstract: In this work, rice husk silica (RHS), obtained from rice husk waste, was used as a reinforcing filler for preparing PBAT composites. The RHS surface was modified using a silane coupling agent, i.e. γ-methacryloxypropyltrimethoxysilane (MPS), in order to facilitate interfacial adhesion between PBAT matrix and RHS filler. The contents of MPS were varied between 0.5 - 5.0 % based on weight of RHS. FTIR spectra indicated the appearance of MPS molecules on RHS surface. Untreated RHS and MPS treated RHS were used to produced RHS/PBAT composites containing 30%wt RHS. The results showed that mechanical properties of the PBAT composites can be enhanced by treating RHS surface with 2 %wt MPS.

Abstract: Achievement of exfoliated structure of polymer/ Clay nanocomposites is of particular interest for the improvement of mechanical properties. In this work, the morphology and mechanical properties of epoxy/ clay nanocomposites has been investigated. Diglycidyl ether of bis-phenol A (DGEBA) epoxy resin (EPON828) and Jeffamine D400 curing agent was used. To obtain perfect dispersion, nanoclay (Cloisite 30B) was sonicated in acetone. The mixture was then mixed with polymer. Afterwards, the curing process was performed by addition of curing agent and degassing. Disappearing of peaks in X-Ray diffraction patterns of nanocomposites containing less than 5wt% nanoclay, is a good evidence of perfect dispersion of layered silicates in matrix, i.e. formation of exfoliated morphology. Based on tensile test results, it is deduced that as the amount of nanoclay increases, the elastic modulus and elongation at break of the nanocomposites containing 1wt% and 5wt% nanoclay increases by 12% and 31%, respectively. Therefore, obtaining perfect dispersion of layered silicates in epoxy matrix and exfoliated morphology, results in better mechanical properties of the nanocomposites.

Abstract: This paper presents the development of a braided reinforced composite rod (BCR) able to both reinforce and monitor the stress state of concrete elements. Carbon fibers have been used as sensing and reinforcing material along with glass fiber. Various composites rods have been produced using an author patented technique based on a modified conventional braiding machine. The materials investigated were prepared with different carbon fiber content as follows: BCR2 (77% glass/23% carbon fiber), BCR3 (53% glass/47% carbon fiber), BCR4 (100% carbon fiber). BCRs have been tested under bending while the variation of the electrical resistance was simultaneously monitored. The correlations obtained between deformation and electrical resistance show the suitability of the rods to be used as sensors. The fractional resistance change versus strain plots show that the gage factor increases with decreasing carbon fiber content.

Abstract: Several polymer inorganic nanocomposites were specially designed for protecting oil formation, enhancing oil recovery in the low permeable strata and solar cell efficicency. The inorganic phase with different load was introduced to the polymer matrix through either the intercalation process of the layered silicates or core-shell particle affinity.Several novel nanoeffects were discovered in such polymers as polyacrylamide, poly(ethylene terephthalate),starch, polynucleic aromatic resins–montmorrilonite or SiO2 nanocomposites. In the nanocomposites, the nano size was 10-70nm, the nanoeffects of particle encapsulation, dispersion, molecular weight growth, barrier, and specially solar absorption and solar power transformation efficiency,etc.were presented and reviewed. The tunable nanoeffects of the nanocomposites and some very obvious practical efficicnecy to traditional and new enenergy were first reported.

Abstract: “Green” multiferroic BaTiO3/FeBSi composite films were grown by pulsed laser deposition and ion beam sputtering on general Pt/Ti/SiO2/Si substrates. Room temperature X-ray diffraction and Raman scattering show that the crystal structures of BaTiO3 and FeBSi are tetragonal and amorphous, respectively, and no additional or intermediate phase peaks appears in the composite films. A cross-sectional scanning electron microscopy image clearly demonstrates a 2-2 type structure with sharp interface between the top FeBSi layer and bottom BaTiO3 layer. The magnetic properties of the top FeBSi are obviously modified by the bottom BaTiO3. The composite films show obvious ferroelectric feature.

Abstract: Periodic and non-periodic 1-3 type cement based piezoelectric composites were fabricated by cut and filling technique, using P(MN)ZT ceramic as functional material and cement as matrix. The influences of periodicity of piezoelectric ceramic rods in the composites on electrical properties of all the composites were discussed. The results show that the non-periodic composites have larger dielectric factor and piezoelectric strain constant than those of the periodic composite. The impedance-frequency spectra analysis indicates that the non-periodic arrangement of ceramic rods can effectively restrict the lateral structural mode of the composite, accordingly reduces the coupling resonant between the thickness resonant mode and lateral resonant mode. The thickness electromechanical coupling coefficient of non-periodic composites is larger than that of the periodic composite. With increasing the non-periodic level of P(MN)ZT ceramic in the composites, the mechanical quality factor of the composites increases gradually. Therefore, 1-3 type cement based piezoelectric composites with different special abilities can be obtained by varying the periodic arrangement of P(MN)ZT ceramic rods in the composites.