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Due to a high propensity of nano-particles to agglomerate, making aluminium matrix composites with a uniform dispersion of the nano-particles using liquid routes is an exceptionally difficult task. In this study, an innovative approach was utilised to prevent agglomeration of nano-particle by encapsulating SiC nanoparticles using graphene sheets during ball milling. Subsequently, the milled mixture was incorporated into A356 molten alloy using non-contact ultrasonic vibration method. Two different shapes for graphene sheets were characterised using HRTEM, including onion-like shells encapsulating SiC particles and disk-shaped graphene nanosheets. This resulted in 45% and 84% improvement in yield strength and tensile ductility, respectively. The former was ascribed to the Orowan strengthening mechanism, while the latter is due primarily to the fiber pull-out mechanism, brought about by the alteration of the solidification mechanism from particle pushing to particle engulfment during solidification as a consequence of high thermal conductive graphene sheets encapsulating SiC particles. Due to a high propensity of nano-particles to agglomerate, making aluminium matrix composites with 13 a uniform dispersion of the nano-particles using liquid routes is an exceptionally difficult task. In this 14 study, an innovative approach was utilised to prevent agglomeration of nano-particles by 15encapsulating SiC nano-particles using graphene sheets during ball milling. Subsequently, the milled 16 mixture was incorporated into A356 molten alloy using non-contact ultrasonic vibration method. Two 17 different shapes for graphene sheets were characterised using HRTEM, including onion-like shells 18encapsulating SiC particles and disk-shaped graphene nanosheets. This resulted in 45% and 84% 19improvement in yield strength and tensile ductility, respectively. The former was ascribed to the 20Orowan strengthening mechanism, while the latter is due primarily to the fiber pull-out mechanism, 21 brought about by the alteration of the solidification mechanism from particle pushing to particle

Size effect is a special phenomenon in metal micro-forming process. As the deformation process is scale down to micro/mesoscale, the characteristics of single grain involved in the deformed region play a significant role on the material mechanical behaviours resulting in the invalidation of classical theories in microforming. This paper presents a newly developed material model in microscale on the basis of the grained heterogeneity (e.g. grain size, shape and deformability) and specimen dimension. Voronoi tessellation has been employed to describe the polycrystalline aggregate. The grain shape is controlled by the centroidal-voronoi algorithm to drive grains into steady state. Hardness of the grains obtained from Nano-indentation is used to identify the scatter of the grained deformability. Applying the new material model, the micro-compression test of pure copper is numerically simulated by finite element method (FEM). The influences of grain size and feature size on the deformation behaviours are discussed. The numerical simulation results are in good agreement with the experimental results in terms of the flow stress curves and profile of deformed parts. Based on the novel material model, a FE model of microcross wedge rolling is established and the obtained results show the strain of specimen core region increases with the magnification of grain size. © 2013 Elsevier B.V. All rights reserved. AbstractSize effect is a special phenomenon in metal micro-forming process. As the deformation process is scale down to micro/meso scale, the characteristics of single grain involved in the deformed region play a significant role on the material mechanical behaviours resulting in the invalidation of classical theories in microforming. This paper presents a newly developed material model in micro scale on the basis of the grained heterogeneity (e.g. grain size, shape and deformability) and specimen dimension. Voronoi tessellation has been employed to describe the polycrystalline aggregate. The grain shape is controlled by the centroidal-voronoi algorithm to drive grains into steady state. Hardness of the grains obtained from Nano-indentation is used to identify the scatter of the grained deformability. Applying the new material model, the micro-compression test of pure copper is numerically simulated by finite element method (FEM). The influences of grain size and feature size on the deformation behaviours are discussed. The numerical simulation results are in good agreement with the experimental results in terms of the flow stress curves and profile of deformed parts. Based on the novel material model, a FE model of micro cross wedge rolling is established and the obtained results show the strain of specimen core region increases with the magnification of grain size.

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Polyurethane (PU)/silicate composite for grouting is prepared using toluene 2,4‐diisocyanate (TDI), polyoxypropylene glycol (PPG), and sodium silicate. The reaction temperature change, mechanical properties, flame resistance, thermal performance, chemical structure, and section morphology of PU/silicate composite are investigated by thermometer, mechanical test, LOI and vertical combustion tester, thermogravimetric analysis (TGA), FTIR, and scanning electron microscopy (SEM). The addition of sodium silicate reduced the maximum reaction temperature and improved the mechanical properties and flame resistance of PU composite dramatically. The best comprehensive performance can be achieved when the silicate fraction is 25 wt%, tensile strength is 19.3 MPa, bonding strength is 4.1 MPa, compression strength is 47.2 MPa, the value of LOI is 34.1% and reaches UL 94 V‐0 rating. Porous structures with microspheres and spherical crevices are observed in the section of PU/silicate composite, which contributes to the low reaction temperature and higher mechanical performance, the reaction equations and possible formation mechanism of the special microspheres reinforced structure are put forward finally. POLYM. ENG. SCI., 55:2322–2327, 2015. © 2015 Society of Plastics Engineers

In this study, a series of waterborne polyurethane/fumed silica (WPU/S) hybrids were prepared by an optimized in situ polymerization through a grafting process. Fourier transform infrared spectrum and X-ray diffraction confirmed the enhanced interfacial interactions between fumed silica particles and polyurethane (PU) segments. Atomic force microscopy demonstrated well dispersion of fumed silica in PU matrix and the rough surface of WPU/S hybrid films, which contributed to improved water resistance. The thermal stability of WPU was also improved by the incorporation of fumed silica, and the glass transition temperature of WPU/S increased compared with pure WPU. Moreover, as the content of fumed silica increased from 0% to 4%, the tensile strength of WPU/S increased from 29.0 MPa to 37.6 MPa without losing high elongation at break.