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Eutectic Al–Si binary alloy is technically one of the most important Al casting alloys due to its high corrosion resistance, evident shrinkage reduction, low thermal expansion coefficient, high fluidity, and good weldability. In this work, multiphased Al–Si matrix nanocomposites reinforced with Al2O3 and multiwalled carbon nanotubes (MWCNTs) have been sintered by an in situ vacuum hot-pressing method. The alumina Al2O3 nanoparticles were introduced by an in situ reaction of Al with SiO2. Microstructure and mechanical properties of the sintered Al/Si/Al2O3/SiO2/MWCNTs nanocomposites with different alumina contents were investigated. The mechanical properties were determined by micro-Vickers hardness and compressive and shear strength tests. The results demonstrated that in situ alumina and MWCNTs had impacts on microstructure and mechanical properties of the nanocomposites. Based on the mechanical properties and microstructure of the nanocomposites, strengthening and fracture mechanisms by multiple reinforcements were analyzed. [ABSTRACT FROM AUTHOR]

In this work, BC particulate-reinforced Al composite was fabricated by a pressureless infiltration technique, and its interfacial microstructure was studied in detail by X-ray diffraction as well as by scanning and transmission electron microscopy. The BC phase was unstable in Al melt during the infiltration process, forming AlB-type AlBC or AlBC as a major reactant phase. The Al matrix was large grains (over 10 μm), which had no definite orientation relationships (ORs) with the randomly orientated BC or its reactant particles, except for possible nucleation sites with $$ \{ 011\}_{{{\text{B}}_{4} {\text{C}}}} $$ almost parallel to {111} at a deviation angle of 1.5 deg. Both BC-Al and reactant-Al interfaces are semicoherent and free of other phases. A comparison was made with the SiC/Al composite fabricated similarly by the pressureless infiltration. It was suggested that the lack of ORs between the Al matrix and reinforced particles, except for possible nucleation sites, is the common feature of the composites prepared by the infiltration method. [ABSTRACT FROM AUTHOR]

Titanium alloy/Hydroxyapatite (HA) composites have become a hot research topic in biomedical materials, while there are some challenges concerning bioactivity and mechanical properties such as low interface adhesion at the interface between metal and ceramic, complex interfacial reactions, and so on. Nevertheless, composites with reinforced phases can reach special properties that meet the requirements of biomedical materials due to the strong interfacial interactions between reinforcing phases (nano-carbon, partial oxides, and so on) and Titanium alloys or HA. This review summarizes the interface properties and mechanisms of Titanium alloy/HA composites, including interfacial bonding methods, strengthening and toughening mechanisms, and performance evaluation. On this basis, the interface characteristics and mechanisms of the Titaniumalloy/HA composites with enhanced phase are prospected. The results show that the interfacial bonding methods in the Titanium alloy/HA composites include chemical reactions and mechanical effects. The strengthening and toughening mechanisms contain grain refinement strengthening, second phase strengthening, solution strengthening, cracks and pulling out mechanisms, etc. This review provides a guidline for the fabrication of biocomposites with both mechanical properties and bioactivity. [ABSTRACT FROM AUTHOR]

Abstract: Composite membranes containing ePTFE matrix and short side chain perfluoronated sulfonated ionomers are introduced as electrolytes for proton exchange membrane fuel cell applications. The output voltage at 800mAcm−2 for single cell using composite membrane as electrolyte reaches 0.61V at 95°C under 40% relative humidity whereas it is only 0.41V for cell assembled from pristine short side chain perfluoronated sulfonated membrane at the same condition. The performance of fuel cell stack using composite membrane as electrolyte in kilowatts ranges has been experimentally investigated at 95°C under ambient pressure. With the increase in the inlet gas temperature, the performance of the stack is enhanced. The non-monotonic behavior in instantaneous average voltage of single cells in the stack has been observed and the peak value is appeared at the stack temperature of 90°C. The observed water accumulation phenomena suggest that the decrease in stack performance above 90°C is attributed to the lack of water in the system. The results observed in this study demonstrate that the composite membrane has the potential operating at 95°C under reduced relative humidity to 40%, which is a suitable operating condition for fuel cell vehicle applications. [Copyright &y& Elsevier]

ABSTRACT Multi-walled carbon nanotubes (MWCNTs) and graphene synergetically reinforced Cu–graphite matrix composites with alloying elements and the rare earth element lanthanum were fabricated by powder metallurgy, and their mechanical properties were evaluated. An innovative solution for dispersing the solution into the MWCNTs and graphene was adopted by surface modification with gallic acid solution or rutin solution, instead of strong acid and base solutions, respectively. The interfacial bonding between MWCNTs or graphene and the copper matrix, and the particle distribution uniformity, were enhanced by mechanical alloying and freeze-drying. Nearly complete densification of the MWCNTs and graphene synergetically reinforced Cu–graphite matrix composites was achieved by hot-pressing and hot isostatic pressing sintering. The microstructure and mechanical properties of the composites indicated that the interfaces between the reinforcing phases and matrix were tightly bonded, confirming that the interface bonding between the MWCNTs, graphene, and copper matrix was mainly established as mechanical locks. The dominant strengthening mechanisms in the composites were the fine grain strengthening, load transferring, and solution strengthening, followed by dislocation strengthening. Graphical abstract Unlabelled Image Highlights • The Cu–graphite matrix composites with isotropic microstructure and properties were prepared via HIP. • The synergetic effect of MWCNTs and graphene in the composites were investigated. • The alloying elements and Lanthanum rare earth were used to improve the matrix structure and interface. • Strengthening and fracture mechanisms of the composites were analysed systematically. [ABSTRACT FROM AUTHOR]

Abstract: Acid functionalized single walled carbon nanotubes were covalently grafted to chitosan by first reacting the oxidized carbon nanotubes with thionyl chloride to form acyl-chlorinated carbon nanotubes which are subsequently dispersed in chitosan and covalently grated to form composite material, CNT–chitosan, 1, which was washed several times to remove un-reacted materials. This composite has been characterized by FTIR, 13C NMR, TGA, SEM and TEM and has been shown to exhibit enhanced thermal stability. The reaction of 1, with poly lactic acid has also been accomplished to yield CNTchitosan–g-poly(LA), 2 and fully characterized by the above techniques. Results showed covalent attachment of chitosan and chitosan–poly lactic acid to the carbon nanotubes. [Copyright &y& Elsevier]