Two synthesis routes to graphene/polycaprolactone composites are introduced and the properties of the resulting composites compared. In the first method, mixtures are produced using solution processing of polycaprolactone and well dispersed, chemically reduced graphene oxide and in the second, an esterification reaction covalently links polycaprolactone chains to free carboxyl groups on the graphene sheets. This is achieved through the use of a stable anhydrous dimethylformamide dispersion of graphene that has been highly chemically reduced resulting in mostly peripheral ester linkages. The resulting covalently linked composites exhibit far better homogeneity and as a result, both Young's modulus and tensile strength more than double and electrical conductivities increase by 14 orders of magnitude over the pristine polymer at less than 10 per cent graphene content. In vitro cytotoxicity testing of the materials showed good biocompatibility resulting in promising materials for use as conducting substrates for the electrically stimulated growth of cells. Two synthesis routes to graphene/polycaprolactone composites are introduced and the properties of the resulting composites compared. In the first method, mixtures are produced using solution processing of polycaprolactone and well dispersed, chemically reduced graphene oxide and in the second, an esterification reaction covalently links polycaprolactone chains to free carboxyl groups on the graphene sheets. This is achieved through the use of a stable anhydrous dimethylformamide dispersion of graphene that has been highly chemically reduced resulting in mostly peripheral ester linkages. The resulting covalently linked composites exhibit far better homogeneity and as a result, both Young's modulus and tensile strength more than double and electrical conductivities increase by ≈ 14 orders of magnitude over the pristine polymer at less than 10 % graphene content. In vitro cytotoxicity testing of the materials showed good biocompatibility resulting in promising materials for use as conducting substrates for the electrically stimulated growth of cells.

Problem statement: Jatropha curcas is a wonder plant with a variety of applications and enormous economic potentials. Oil from the seeds can be used as alternative fuel and for making biodiesel which aims to overcome energy crisis problems. In this study, extraction of Jatropha oil from seeds was optimized using organic solvent based on the amount of the extracted oil. The kinetics of extraction was also investigated and its parameters were determined based on a second order model. Approach: The effects of five operating parameters on the oil extraction namely type of solvents, temperature, solvent to solid ratio, processing time and particle size of the meal were investigated to optimize the processing conditions for achieving maximum oil yield. The kinetics of extraction was assumed based on a second order mechanism. The initial extraction rate, the saturated extraction capacity, the rate constant of extraction and the activation energy were calculated using the model. Results:The optimum conditions were found at 8 h reaction time, temperature of around 68°C, coarse particle size (0.5-0.75 mm), solvent to solid ratio of 6:1 and hexane as solvent. The activation energy was found to be 8021.9 J moL −1 . Conclusion: Hexane was found to be the best solvent for the process as compared to petroleum ether, the kinetics of extraction conforms well to the second order model and the extraction of Jatropha seeds was an endothermic process.

Composites of graphene in a chitosan-lactic acid matrix were prepared to create conductive hydrogels that are processable, exhibit tunable swelling properties and show excellent biocompatibility. The addition of graphene to the polymer matrix also resulted in significant improvements to the mechanical strength of the hydrogels, with the addition of just 3 wt% graphene resulting in tensile strengths increasing by over 200%. The composites could be easily processed into three-dimensional scaffolds with finely controlled dimensions using additive fabrication techniques and fibroblast cells demonstrate good adhesion and growth on their surfaces. These chitosan-graphene composites show great promise for use as conducting substrates for the growth of electro-responsive cells in tissue engineering. Composites of graphene in a chitosan-lactic acid matrix were prepared to create conductive hydrogels that are processable, exhibit tunable swelling properties and show excellent biocompatibility. The addition of graphene to the polymer matrix also resulted in significant improvements to the mechanical strength of the hydrogels, with the addition of just 3 wt% graphene resulting in tensile strengths increasing by over 200 %. The composites could be easily processed into threedimensional scaffolds with finely controlled dimensions using additive fabrication techniques and fibroblast cells demonstrate good adhesion and growth on their surfaces. These chitosan-graphene composites show great promise for use as conducting substrates for the growth of electro-responsive cells in tissue engineering.

A 3D iron porphyrin/graphene hydrogel electrocatalyst affords highly efficient, durable and selective CO2 reduction to CO at a low overpotential.

Conductive, flexible graphene/poly­(trimethylene carbonate) (PTMC) composites were prepared. Addition of just 3 wt % graphene to PTMC oligomers functionalized with methacrylate end-groups followed by UV cross-linking resulted in more than 100% improvement in tensile strength and enhanced electrical conductivity by orders of magnitude without altering the processability of the host material. The addition of graphene also enhanced mesenchymal stem cell (MSC) attachment and proliferation. When electrical stimulation via the composite material was applied, MSC viability was not compromised, and osteogenic markers were upregulated. Using additive fabrication techniques, the material was processed into multilayer 3D scaffolds which supported MSC attachment. These conducting composites with excellent processability and compatibility with MSCs are promising biomaterials to be used as versatile platforms for biomedical applications.

A relative lack of printable materials with tailored functional properties limits the applicability of three-dimensional (3D) printing. In this work, a diamond−acrylonitrile butadiene styrene (ABS) composite filament for use in 3D printing was created through incorporation of high-pressure and hightemperature (HPHT) synthetic microdiamonds as a filler. Homogenously distributed diamond composite filaments, containing either 37.5 or 60 wt % microdiamonds, were formed through preblending the diamond powder with ABS, followed by subsequent multiple fiber extrusions. The thermal conductivity of the ABS base material increased from 0.17 to 0.94 W/(m•K), more than fivefold following incorporation of the microdiamonds. The elastic modulus for the 60 wt % microdiamond containing composite material increased by 41.9% with respect to pure ABS, from 1050 to 1490 MPa. The hydrophilicity also increased by 32%. A low-cost fused deposition modeling printer was customized to handle the highly abrasive composite filament by replacing the conventional (stainless-steel) filament feeding gear with a harder titanium gear. To demonstrate improved thermal performance of 3D printed devices using the new composite filament, a number of composite heat sinks were printed and characterized. Heat dissipation measurements demonstrated that 3D printed heat sinks containing 60 wt % diamond increased the thermal dissipation by 42%.

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Novel water-based nanolubricants using TiO2 nanoparticles (NPs) were synthesised by adding sodium dodecyl benzene sulfonate (SDBS) and glycerol, which exhibited excellent dispersion stability and wettability. The tribological performance of the synthesised nanolubricants was investigated using an Rtec ball-on-disk tribometer, and their application in hot steel rolling was evaluated on a 2-high Hille 100 experimental rolling mill, in comparison to those without SDBS. The water-based nanolubricant containing 4 wt% TiO2 and 0.4 wt% SDBS demonstrated superior tribological performance by decreasing coefficient of friction and ball wear up to 70.5% and 84.3%, respectively, compared to those of pure water. In addition to the lubrication effect, the suspensions also had significant effect on polishing of the work roll surface. The resultant surface improvement thus enabled the decrease in rolling force up to 8.3% under a workpiece reduction of 30% at a rolling temperature of 850 °C. The lubrication mechanisms were primarily ascribed to the formation of lubricating film and ball-bearing effect of the TiO2 NPs.