Solid loading and post-sintered cooling rates are two effective parameters used to control the mechanical properties of powder-injection molded parts. In the case of 316 L stainless steel (SS), these parameters also influence mechanical properties and corrosion resistance. In this study, four formulations with powder loading above and below the critical powder loading were prepared and sintered at 1325 °C in vacuum with cooling rates varying from 3 °C/min to 10 °C/min. Solid loadings above the critical loading caused reductions in final properties (i.e. mechanical properties and corrosion resistance) because of increased porosity. The high cooling rate of 10 °C/min improved the mechanical properties due to the formation of large number of grains and corrosion resistance due to formation of chromium oxide layer at the surface of PIM 316 L SS. Solid loading of 65 vol.%, sintered at 1325 °C with a cooling rate of 10 °C/min showed improvements in terms of mechanical properties and corrosion resistance compared with conventional 316 L SS. Such improvements were considered due to reduced grain sizes and formation of a chromium oxide layer on the sample surface. This study identifies the solid loading (65 vol.%) below the critical powder loading and a high post-sintered cooling rate, i.e., 10 °C/min, are suitable to achieve optimum mechanical properties and corrosion resistance in 316 L SS. The developed material may be recommended for biomedical applications.

Posted on:February 2016

Authored:Faiz Ahmad

316L stainless steel is a common biomedical material. Currently, biomedical parts are produced through powder injection molding (PIM). Carbon control is the most critical in PIM. Improper debinding can significantly change the properties of the final product. In this work, thermal debinding and sintering were performed in two different furnaces (i.e. laboratory and commercially available furnaces) to study the mechanical properties and corrosion resistance. Debounded samples were sintered in different atmospheres. The samples sintered in inert gas showed enhanced mechanical properties compared with wrought 316L stainless steel and higher corrosion rate than those sintered in the vacuum furnace. The densification and tensile strength of the hydrogen sintered samples increased up to 3% and 51%, respectively, compared with those of the vacuum-sintered samples. However, the samples sintered in inert gas also exhibited reduced ductility and corrosion resistance. This finding is attributed to the presence of residual carbon in debonded samples during debinding.

Posted on: February 2017

Authored:Faiz Ahmad

The electromagnetic inference is a problem for a longer span. Various composites were formed to eliminate this problem by developing electromagnetic shielding material. For this purpose, a systematic review was performed to provide a general understanding of graphene and iron-based composites as a shielding material. Scopus database was selected to extract the articles with the only limitation to consider only those articles which were written in the English language. The interpretation of the articles revealed that most of the researchers have worked on the X-band frequency range, where still, there is a need to work on a higher frequency range. Also, the inclusion of polymers into graphene and iron showed promising results, yet still, need further exploration.

Posted on: November 2020

Authored: Faiz Ahmad

Dolomite Clay was introduced in a traditional intumescent flame retardant system which contains ammonium polyphosphate/expandable graphite/melamine (APP-EG-MEL) to evaluate its effects on char morphology and fire performance. The effect of dolomite clay on the fire-resistance and thermal properties of expandable graphite based Intumescent fire retardant coatings has been investigated by using Bunsen burner fire test and thermal gravimetric (TG) techniques. The current study describes the effects of Dolomite Clay on the heat shielding performance of intumescent passive fireproofing coatings during fire testing. The fire performance of dolomite clay reinforced intumescent coating formulations were evaluated by Bunsen burner fire test according to ASTM E-119. Results showed that the dolomite reinforcement in IFRC formulation significantly reduced the steel substrate temperature up to 180 °Cafter 1 hour of fire exposure. The coating degradation was studied using thermogravimetric analysis (TGA). The physical morphology and alignment of intumescent char residue were studied by field emission scanning electron microscopy (FESEM). TGA analysis revealed that IFD (8) containing 8 wt. % of dolomite clay enhanced residual weight by 37.30%. It is suggested that Dolomite clay can enhance the fire performance and can significantly affect the formation of dense and continuous char if incorporated as a filler in conventional intumescent fire resistive systems.

Posted on: 2016

Authored:Faiz Ahmad

Advancement of novel electromagnetic inference (EMI) materials is essential in various industries. The purpose of this study is to present a state-of-the-art review on the methods used in the formation of graphene-, metal- and polymer-based composite EMI materials. The study indicates that in graphene- and metal-based composites, the utilization of alternating deposition method provides the highest shielding effectiveness. However, in polymer-based composite, the utilization of chemical vapor deposition method showed the highest shielding effectiveness. Furthermore, this review reveals that there is a gap in the literature in terms of the application of artificial intelligence and machine learning methods. The results further reveal that within the past half-decade machine learning methods, including artificial neural networks, have brought significant improvement for modelling EMI materials. We identified a research trend in the direction of using advanced forms of machine learning for comparative analysis, research and development employing hybrid and ensemble machine learning methods to deliver higher performance.

Posted on: July 2021

Authored:Faiz Ahmad