Fabrication, Mechanical and Wear Properties of Aluminum (Al6061)-Silicon Carbide-Graphite Hybrid Metal Matrix Composites

In recent times, the use of aluminum alloy-based Hybrid Metal Matrix Composites (HMMCs) is being increased in aerospace and automotive applications. HMMCs compensate for the low desirable properties of each filler used. However, the mechanical properties of HMMCs are not well understood. In particular, microstructural investigations and wear optimization studies of HMMCs are not clear. Therefore, further studies are required. The present study is aimed at fabricating and mechanical and wear characterizing and microstructure investigating of Silicon Carbide (SiC) and Graphite (Gr) added in Aluminum (Al) alloy Al6061 HMMCs. The addition of SiC particles was in the range from 0 to 9 weight percentage (wt.%) in steps of 3, along with the addition of 1 wt.% Gr in powder form. The presence of alloying elements in the Al6061 alloy was identified using the Energy Dispersive X-Ray Analysis (EDX). The dispersion of SiC and Gr particles in the alloy was investigated using metallurgical microscope and Scanning Electron Microscopy (SEM). The gain in strength can be attributed to the growth in dislocation density. The nature of fracture was quasi-cleavage. The microstructure examination reveals the uniform dispersion of the reinforcement. Density, hardness, and Ultimate Tensile Strength values observed to be increased with increased contents of SiC reinforcement. Besides, wear studies were performed in dry sliding conditions. Optimization studies were performed to investigate the effect of parameters that affecting the wear. The sliding wear resistance was noticed to be improved concerning higher amounts of reinforcement leading to a decrease in delamination and adhesive wear. The predicted values for the wear rate have also been compared with the experimental results and good correlation is obtained

Thermal deoxygenation causes Photoluminescence shift from UV to blue region in lyophilized graphene oxide

Lyophilized graphene oxide (GO) was thermally exfoliated in stages at predefined temperatures up to 400 degrees C, and photoluminescence (PL) study of GO and thermally reduced GO (TGO) was carried out at each step. A significant red shift in the PL emission peak (412 nm) was found on annealing GO at 400 degrees C in comparison to as-synthesized GO (365 nm). In addition, the PL emission at 457 nm in case of as synthesized GO, which is related to topological defects was quenched conspicuously. Samples were characterized using X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy, Fourier-transform infrared (FTIR) spectroscopy and Raman spectroscopy. Morphological characterization was performed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The detailed analysis presented might help in highlighting and understanding the structural changes related to deoxygenation and the PL emission mechanism of graphene derivatives synthesized at lower temperatures. The study can also be used a tool for comprehending tunable PL emissions for future optoelectronic applications

Enhancement of electro-optical response of ferroelectric liquid crystal: the role of graphene quantum dots

We present a pioneer study depicting a significant improvement in the photoluminescence (PL) intensity and display of an expeditious electro-optic response of ferroelectric liquid crystal (FLC) when doped with graphene quantum dots (GQDs). Significant threefold enhancement in PL intensity of GQDs/FLC composite material can be ascribed to the additive combination of emissions from GQDs and FLCs. Furthermore, promptness in electro-optical response by a factor of 34% can be attributed to the lowering of rotational viscosity of the FLC material due to the incorporation of GQDs. These results would certainly be helpful in realisation of highly luminescent and faster generation of LC systems

Exfoliation of graphene oxide and its application in improving the electro-optical response of ferroelectric liquid crystal

Near complete exfoliation and reduction of lyophilized graphene oxide (GO) has been carried out at temperature as low as 400 degrees C. The structural characterizations of the reduced GO have been performed using X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy techniques. The morphological studies were carried out using scanning electron microscopy. The synthesized GO finds an application in improving the switching performance of a liquid crystal (LC) mixture by remarkably modifying the physical properties, such as spontaneous polarization and rotational viscosity of the ferroelectric LC (FLC) material which in turn resulted into faster response of the FLC. The present study explores the possibility of low temperature thermal reduction of GO along with its application in improving the properties of LC based display systems

Restructural confirmation and photocatalytic applications of graphene oxide-gold composites synthesized by Langmuir-Blodgett method

We present a first report on the use of Langmuir Blodgett (LB) technique for the synthesis of edge decorated graphene oxide gold (GO-Au) nanostructures by simple manipulation of electrostatic interactions. The GO-Au nanostructures when characterized using spectroscopy, surface, chemical and micro structural techniques, displayed unique physical and structural properties. The results re-established the theoretical corroboration that the carboxyl groups are primarily located at the edges of the 2D sheets of GO. The exploitation of air-water interface platform makes this process novel and fundamentally different from existing protocols for synthesis of GO-metal composites. These GO-Au hybrid materials favoured visible-light driven plasmonic photo catalysis together with enhanced charge separation and transportation properties, resulting in the augmentation of photocatalytic activity and conductivity with high transmittance. A plausible reaction mechanism for the degradation of pollutant dye and the role of gold nanoparticles (NPs) on GO has been established

Investigation of the Tribological Characteristics of Aluminum 6061-Reinforced Titanium Carbide Metal Matrix Composites

The current trend in the materials engineering sector is to develop newer materials that can replace the existing materials in various engineering sectors in order to be more and more efficient. Therefore, the present research work is aimed at fabricating and determining the physical, mechanical, and dry sliding wear properties of titanium carbide (TiC)-reinforced aluminum alloy (Al6061) metal matrix composites (MMCs). For the study, the Al6061-TiC microparticle-reinforced composites were fabricated via the liquid metallurgy route through the stir casting method, where the reinforcement of the TiC particles into the Al6061 alloy matrix was added in the range of 0 to 8.0 wt.%, i.e., in the steps of 2.0 wt.%. The synthesis procedure followed the investigation of the various mechanical properties of Al6061-TiC MMCs, such as the density and structure, as well as mechanical and dry wear experimentation. The tests performed on the casted Al6061, as well as its TiC composites, were in harmony with ASTM standards. As per the experimental outcome, it can be confirmed that the increase in the weight percentage of TiC into the Al6061 alloy substantially increases the density, hardness, and tensile strength, at the expense of the percentage of elongation. In addition, the dry wear experiments, performed on a pin-on-disc tribometer, showed that the Al6061-TiC MMCs have superior wear-resistance properties, as compared to those of pure Al6061 alloy. Furthermore, optical micrograph (OM), powdered X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) analyses were employed for the developed Al6061-TiC MMCs before and after the fracture and wear test studies. From the overall analysis of the results, it can be observed that the Al6061-TiC composite material with higher TiC reinforcement displays superior mechanical characteristics