ABSTRACT
Solution mixing, which is one of the standard methods of producing Graphene-based Nanocomposites (GPC) may not be as efficient as it is expected due to the presence of residual solvent in the cured product. Therefore, the influence of including acetone in the preparation of Graphene Oxide-based epoxy coating (GO-EP) on the curing behaviour, mechanical and corrosive behaviour was studied. FTIR and TGA analysis confirmed that the GO-EP prepared by ultrasonication (GO-EP U) indicated the presence of more low-molecular-weight/low crosslinked (LMW/LC) sites than GO-EP prepared by stirring (GO-EP MS). Meanwhile, the tensile strength and hardness of GO-EP MS was 20% and 10% better than GO-EP U which confirmed that the presence of a lower number of LMW/LC could prevail over the agglomeration of GO sheets in the GO-EP MS. Pull-off adhesion tests also confirms that the presence of remaining acetone would cause the poor bonding between metal and coating in GO-EP U. This is reflected on the electrochemical impedance spectroscopy (EIS) results, where the GO-EP U failed to provide substantial barrier protection for carbon steel after 140 days of immersion in 3.5 wt% NaCl. Therefore, it is essential to consider the solvent effect when solvent is used in the preparation of a coating to prevent the premature failure of high-performance polymer coatings.
ABSTRACT
The utilisation of rice husk ash (RHA) as an aluminosilicate source in fire-resistant coating could reduce environmental pollution and can turn agricultural waste into industrial wealth. The overall objective of this research is to develop a rice-husk-ash-based geopolymer binder (GB) fire-retardant additive (FR) for alkyd paint. Response surface methodology (RSM) was used to design the experiments work, on the ratio of RHA-based GB to alkyd paint. The microstructure behaviour and material characterisation of the coating samples were studied through SEM analysis. The optimal RHA-based GB FR additive was formulated at 50% wt. FR and 82.628% wt. paint. This formulation showed the result of 270 s to reach 200 °C and 276 °C temperature at equilibrium for thermal properties. Furthermore, it was observed that the increased contents of RHA showed an increment in terms of the total and open porosities and rough surfaces, in which the number of pores on the coating surface plays an important role in the formation of the intumescent char layer. By developing the optimum RHA-based GB to paint formulation, the coating may potentially improve building fire safety through passive fire protection.
ABSTRACT
Porous metal structures have emerged as a promising solution in repairing and replacing damaged bone in biomedical applications. With the advent of additive manufacturing technology, fabrication of porous scaffold architecture of different unit cell types with desired parameters can replicate the biomechanical properties of the natural bone, thereby overcoming the issues, such as stress shielding effect, to avoid implant failure. The purpose of this research was to investigate the influence of cube and gyroid unit cell types, with pore size ranging from 300 to 600 µm, on porosity and mechanical behavior of titanium alloy (Ti6Al4V) scaffolds. Scaffold samples were modeled and analyzed using finite element analysis (FEA) following the ISO standard (ISO 13314). Selective laser melting (SLM) process was used to manufacture five samples of each type. Morphological characterization of samples was performed through micro CT Scan system and the samples were later subjected to compression testing to assess the mechanical behavior of scaffolds. Numerical and experimental analysis of samples show porosity greater than 50% for all types, which is in agreement with desired porosity range of natural bone. Mechanical properties of samples depict that values of elastic modulus and yield strength decreases with increase in porosity, with elastic modulus reduced up to 3 GPa and yield strength decreased to 7 MPa. However, while comparing with natural bone properties, only cube and gyroid structure with pore size 300 µm falls under the category of giving similar properties to that of natural bone. Analysis of porous scaffolds show promising results for application in orthopedic implants. Application of optimum scaffold structures to implants can reduce the premature failure of implants and increase the reliability of prosthetics.
