•Pure aluminum was reinforced with graphene-platelets by using mechanical milling.•The composites were studied after sintering condition.•Milling time and graphene-platelet enhance the mechanical ...behavior of the composites.
Graphene can be considered as an ideal reinforcement for the production of composites due to its outstanding mechanical properties. These characteristics offer an increased opportunity for their study in the production of metal matrix composites (MMCs). In this research, the studied composites were produced by mechanical alloying (MA). The employed milling times were of 1, 3 and 5h. GNPs were added in 0.25, 0.50 and 1.0wt% into an aluminum powder matrix. Milled powders were cold consolidated and subsequently sintered. Composites were microstructurally characterized with Raman spectroscopy and electron microscopy and X-ray diffraction. The hardness behavior in composites was evaluated with a Vickers micro-hardness test. A homogeneous dispersion of graphene during MA and the proper selection of sintering conditions were considered to produce optimized composites. The obtained results with electron microscopy indicate a homogeneous dispersion of GNPs into the aluminum matrix. Analyses showed GNPs edges where the structure of the graphene layers conserved after MA is observed.
Novel Al-based nanocomposites reinforced with multi-walled carbon nanotubes were produced by mechanical milling. Next, pressure-less sintering at 823
K under vacuum and hot extrusion at 773
K were ...carried out. The interface between Al matrix and the multi-walled carbon nanotubes was examined using transmission electron microscopy. The values of yield strength (
σ
y), maximum strength (
σ
max) and microhardness Vickers (HVN) of the composites were evaluated and reported as a function of carbon nanotubes content. The concentration of multi-walled carbon nanotubes has an important effect on the mechanical properties of the nanocomposite. Formation of aluminum carbide in the nanocomposites was observed. Possible strengthening mechanisms are presented and discussed.
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The decrease of the interfacial tension between water and oil by addition of nonionic and cationic surfactants known to be optimal for enhanced oil recovery is studied here using ...dissipative particle dynamics numerical simulations. Three nonionic surfactants are modeled: Neodol nonylphenol ethoxylate, Neodol Propoxate, and nonylphenol ethoxylate, and the cationic dodecyl trimethyl ammonium bromide (DTAB). To model DTAB accurately the electrostatic interactions are included explicitly. The interfacial tension is calculated as a function of surfactant concentration, at constant temperature and volume. DTAB is found to be more efficient in lowering the interfacial tension than the nonionic surfactants, at the same concentration. Our simulations show that their different performance is due to their adsorption mechanisms at the interface. The nonionic surfactants adsorb mostly as monolayers, while DTAB adsorbs in multilayers. An equation for the interfacial tension as a function of surfactant concentration equivalent to Szyszkowski’s equation is proposed for multilayer adsorption at the water-oil interface. The two – dimensional potentials of mean force calculated at the water-oil interface reveal a homogeneous interface when DTAB is present. This is in contrast with the nonionic surfactants, whose potentials of mean force show separate regions of hydrophobic and hydrophilic regions at the interface. Lastly, synergistic combinations of the cationic and nonionic surfactants are tested, yielding optimal mixtures that can reduce more the interfacial tension at lower surfactant concentrations. It is argued that our conclusions are useful to researchers designing new surfactants not only for enhanced oil recovery but also for other soft matter applications.
