In the present review, the recent progress in describing the intricacies of mechanical and thermal properties of all types of graphene- and modified graphene-based polymer nanocomposites has been comprehensively examined. The effectiveness of microscopy bouquet for the intrinsic characterization of graphene family and their composites was clearly demonstrated in this research. Furthermore, the utility of the dynamic mechanical analysis and thermo-gravimetric analysis employed for thermal characterization that has been reported by various researchers was exhaustively analyzed in this paper. This research primarily focused on the analyses of several good articles concerned with hybrid graphene composites and the synergetic effect of graphene with other nanofiller to assess its effect on the mechanical properties of its corresponding composites. Such systematic analysis of previous literatures imparted a direction to the researchers about the solution of improved interfacial properties as well as the enhanced dispersion into the vicinity of the matrix. This current research has suggested that the presence of the graphene filler even at very low loadings has shown considerable improvement in the overall mechanical properties of graphene. Further studies to optimize the value of the filler need to be addressed in order to gain complete understanding of the properties of graphene. The potential applications, current challenges, and future perspectives pertaining to these nanocomposites were elaborately discussed in the current study with regard to the multi-scale capabilities and promising developments of the graphene-family-based nanocomposites materials.

A review of the mechanical and thermal properties of graphene and its hybrid polymer nanocomposites for structural applications

Nanocomposites of epoxy with 3 and 5 wt% graphene nanoplatelets (GnPs) were fabricated with GnP sizes of ~5 and <1 μm dispersed within an epoxy resin using a sonication process followed by three-roll milling. The morphology, mechanical, and thermal properties of the composites were investigated. Tensile and flexural properties measurements of these nanocomposites indicated higher modulus and strength with increasing concentration of small GnPs sizes (<1 μm, GnP-C750). The incorporation of larger GnPs sizes (~5 μm, GnP-5) significantly improved the tensile and flexural modulus but reduced the strength of the resulting composites. At 35 °C, the dynamic storage modulus of GnP-5/epoxy composites increased with increasing platelet concentration, and improved by 12 % at 3 wt% and 23 % at 5 wt%. The smaller GnP-C750 increased the storage modulus by 5 % at 3 wt% loading but only 2 % at 5 wt% loading. The glass transition temperatures of the composites increased with increasing platelet concentration regardless of the GnP particle size. A marked improvement in thermal conductivity was measured with the incorporation of the larger GnP size reaching 115 % at 5 wt% loading. The effects of different platelet sizes of the GnP reinforcement on the damage mechanisms of these nanocomposites were studied by scanning electron microscopy.

Mechanical properties and thermal conductivity of graphene nanoplatelet/epoxy composites

Handbook of Industrial Mixing: Science and Practice

An algal feedstock or biomass may contain a very high oil fraction, and thus could be used for the production of advanced biofuels via different conversion processes. Its major advantage apart from its large oil fraction is the ability to convert almost all the energy from the feedstock into different varieties of useful products. In the research to displace fossil fuels, algae feedstock has emerged as a suitable candidate not only because of its renewable and sustainable features but also for its economic credibility based on the potential to match up with the global demand for transportation fuels. Cultivating this feedstock is very easy and could be developed with little or even no supervision, with the aid of wastewater not suitable for human consumption while absorbing CO2 from the atmosphere. The overall potential for algae applications generally shows that this feedstock is still an untapped resource, and it could be of huge commercial benefits to the global economy at large because algae exist in millions compared to terrestrial plants. Algae applications are evident for everyday consumption via foods products, non-foods products, fuel, and energy. Biofuels derived from algae have no impact on the environment and the food supply unlike biofuels produced from crops. However, any cultivation method employed could control the operating cost and the technicalities involved, which will also influence the production rate and strain. The scope of this paper is to review the current status of algae as a potential feedstock with diverse benefit for the resolution of the global energy demand, and environmental pollution control of GHG.

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Algae biofuel: Current status and future applications

Monolithic epoxy, because of its brittleness, cannot prevent crack propagation and is vulnerable to fracture. However, it is well established that when reinforced—especially by nano-fillers, such as metallic oxides, clays, carbon nanotubes, and other carbonaceous materials—its ability to withstand crack propagation is propitiously improved. Among various nano-fillers, graphene has recently been employed as reinforcement in epoxy to enhance the fracture related properties of the produced epoxy–graphene nanocomposites. In this review, mechanical, thermal, and electrical properties of graphene reinforced epoxy nanocomposites will be correlated with the topographical features, morphology, weight fraction, dispersion state, and surface functionalization of graphene. The factors in which contrasting results were reported in the literature are highlighted, such as the influence of graphene on the mechanical properties of epoxy nanocomposites. Furthermore, the challenges to achieving the desired performance of polymer nanocomposites are also suggested throughout the article.

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Mechanical, Thermal, and Electrical Properties of Graphene-Epoxy Nanocomposites—A Review

Impacts of Biodiesel Storage Duration on Fuel Properties and Emissions

Effect of Ambient Temperature and Oxygen Concentration on Ignition and Combustion Process of Diesel Spray

The mixture formation prior to the ignition process is a key element in the diesel combustion because it significantly influences throughout the combustion process and exhaust emissions. Purpose of this study is to clarify the effects of ambient temperature, oxygen concentration and air entrainment into the spray on the heat release process during ignition delay periods.
This study investigated diesel combustion fundamentally using a rapid compression machine and high speed digital video camera. The detail behavior of spray evaporation, spray interference and mixture formation during ignition delay period was investigated using the schlieren photography system. Ignition process, flame development and images of the spray ignition with extremely dark flame were investigated by light sensitivity direct photography method. Heat release processes were analyzed by pressure measurement in the chamber. 
Results show that short endothermic process produces slow heat recovery, leading to gentle increase of initial heat release rate. Low oxygen concentration produces slow heat recovery process rather than long endothermic period, which suggests fuel-air mixing is required to promote chemical reaction for the case of low oxygen-concentration atmosphere. Initial heat release is activated to some extent by increase of air entrainment into spray during ignition delay period. However, excessive air entrainment increases initial heat release little and rather affects diffusion combustion.

Effect of Air Entrainment and Oxygen Concentration on Endothermic and Heat Recovery Process of Diesel Ignition

The development of aerospace and automotive industries requests lightweight, high-performance materials, and polymer nanocomposites are ideal candidates in this case, which is shown by the increasingly more publications in this research field over the past two decades. However, the performance of nanocomposite not only depend on the properties of their individual constituents, but on their morphology and surface characteristics of fillers as well. Selections of nanofillers geometries, e.g. particulate, fibrous or layered have a tremendous influence on the properties of nanocomposites and their processing methods. In this paper, we review the chronological works performed in the field of polymer nanocomposites, in particular epoxy nanocomposites reinforced with layered fillers, such as clay and graphene. Surprisingly layered fillers are commercially available and more cost-effective than nanoparticles and carbon nanofibres, and these make them to the most extensively studied fillers that can be geared toward future applications, particularly in large-scale polymer nanocomposite production.

From clay to graphene for polymer nanocomposites—a survey

Many technologies for reducing exhaust emissions of wide variety of diesel engines from small size to large size ones have been considered with the improvement throughout the combustion process. To reduce emissions, mixing of fuel and air is still important phenomena. Purpose of this study is to clarify the relation between mixture formation during the ignition delay period and burning process in diesel combustion that strongly affects the exhaust emissions. In this study, a rapid compression machine was used to simulate actual phenomenon inside the combustion chamber with changing ambient density. In addition, swirl velocity and injection pressure were changed as experimental parameters to improve mixture formation at high ambient density. This study constructed schlieren photography system with a high-speed digital video camera to investigate the detail behavior of mixture formation during ignition delay period. This method can capture spray evaporation, spray interference and mixture formation process clearly. Ignition process and flame development were investigated by direct photography method using a light sensitive high-speed color digital video camera. The sensitive camera can capture flame development clearly with the mixture of dark and bright flames. Moreover, the mechanism and behavior of flame pattern were analyzed by newly developed image analysis technique. Flame images reveals that spray ignition occurs with dark flame between sprays at the middle and downstream of the spray where combustible mixture is first formed; then bright flame appears near the centerline of each spray where fuel is continuously injected to rich and high temperature atmosphere. Increasing ambient density restrains spray tip penetration, resulting that mixture is only formed at the center region of the combustion chamber. It is necessary for high ambient density condition to improve mixture formation. High-pressure injection is most effective in improvement of mixture formation under condition of high ambient density.

Amir Khalid

Papers

Impacts of Biodiesel Storage Duration on Fuel Properties and Emissions

Effect of Ambient Temperature and Oxygen Concentration on Ignition and Combustion Process of Diesel Spray

Effect of Air Entrainment and Oxygen Concentration on Endothermic and Heat Recovery Process of Diesel Ignition

From clay to graphene for polymer nanocomposites—a survey

Analysis of relation between mixture formation during ignition delay period and burning process in diesel combustion