essential. This was the reason that the subject of this study was the examination of the in uence the volume fraction of Room temperature compressive tests have been SiC particles, as well as the in uence of aging, directly on carried out on metal matrix composites (MMCs) the compressive the characteristics of composites based based on an Al alloy (CW67 alloy). The particulate on a high strength aluminium alloy (commercial name CW67) reinforcements used were SiC in three volume fractions at room temperature. (5%, 10%, and 15%) with an average size of 15 mm. Two matrix aging conditions were studied: peak aged and equivalent underaged conditions. The presence and
EXPERIMENTAL PROCEDURE increasing volume fraction of SiC particles increasesThe composites examined in this study were consolidated elastic modulus and yield stress but decreases ultimate via powder metallurgy processing. Aluminium alloy powder compressive strength and ductility of the W67 alloy (CW67-8•25 wt-%Zn-2•23 wt-%Mg-1•22 wt-%Cu) has been characterised under compression in both peak aged and used as a composite matrix while SiC particles (average underaged conditions. Higher compressive strength size of 15 mm) in three volume fractions (5%, 10%, and and lower ductility have been achieved in the matrix sub-15%) have been used as reinforcement. mitted to peak aging in comparison to the matrix thatThe prealloyed, atomised aluminium powder, with a size underwent underaging.PM/0983 range of about 50 mm (Fig. 1a), forms the composite matrix. SEM analysis showed the powder particles to be nodular,
Magnesium carbon nanocomposites for hydrogen storage have been synthesized by ball milling with different amount of benzene, acting as a lubricant. Their microstructure has been studied by X-ray diffraction and scanning electron microscopy, while the hydrogen desorption temperature has been tested by differential scanning calorimetry. Experimental results show that the microstructure after milling, the hydrogenation capabilities of the material and the reactivity with the air are related to the amount of additives. In particular the carbon to benzene ratio seems to play a major role. In fact, with an optimum value of carbon to benzene weight ratio of 1/6, the amount of carbon being 15 wt% of the milled mixture, a decomposition heat equal to 57% of pure MgH2 was measured, even after air manipulation of the sample.
The hydrogen storage performances of Mg-C nanocomposites have been studied on
materials synthesized by ball milling with and without addition of an organic additive. The main purpose of this work is to study in more detail the cooperative effect observed when both graphite and benzene are added to the milled blend. In fact, when both components are added to Mg in the ball milling process, good catalyzing properties of the composite surface allow improved sorptiondesorption behavior of the synthesized material. The processed materials have been characterized by XRD to assess the details of the phase structure by Rietveld analysis, while surface features have been studied by XPS, which evidences structural modifications of both the surface Mg oxide and the graphite particles. The hydrogen desorption behavior has been correlated with the surface structure which appears to depend on the carbon to benzene ratio. Thermal stability and hydrogen desorption properties were investigated by DSC. Experimental results on nanocomposites with the same Mg to C weight ratio (70:30) show improved performances for a proper choice of carbon to benzene ratio weight (1/3), even after manipulation of the milled material in air.
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