Metal additive manufacturing (metal-AM) has undergone a remarkable evolution over the past three decades. It was first used solely as an innovative resource of the prototype. Due to the technology maturity which allows combining various manufacturing processes for the production of a bespoke part that applied complex geometries, additive manufacturing (AM) technology has captured an increasing attention. For the past ten years, it has moved into the mainstream of the industrialised field such as biomedicine. The review covers the recent progress of metal-AM manufacturing technologies, main types of metallic biomaterials, and most common biomedical applications. The direction of the future potential of metal-AM in biomedical research and implementation are further discussed. Selective laser melting (SLM), selective laser sintering (SLS), electron beam melting (EBM), and laser engineered net shaping (LENS) are the most common metal-based additive manufacturing processes employed in the production of the biocompatible parts. The evolution and favourite trend of the metal-AM technologies are highlighted in this review. Additionally, the advancement of metallic biomaterials such as titanium and its alloys, cobalt-based alloys, 316L stainless steel, nickel-titanium, and other metallic biomaterials is also presented since it leads to the transpired of several new studies in the scope of metal-AM in the medical field. The rise of metal-AM in the biomedical industry has also been significant, especially in orthopaedics and dental. The metal-AM is predicted to continue to dominate and further benefit the biomedical industry development.

Posted on: March 2018

Authored: Faiz Ahmad

Intumescent coating is an insulating material designed to decrease heat transfer to a substrate structure. This research presents the results of different formulations developed to study the effects of kaolin clay on expansion of coating and heat shielding during the fire test. The intumescent coating formulations (ICFs) were tested at 950 °Cfor 1 h. The results showed that the coatings were stable and well bound with substrate. The coatings were characterized by using Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The morphology of char was studied by FESEM on the coating after fire test. XRD and FTIR showed the presence of carbon (graphite), boron phosphate, boron oxide, sassolite and kaolinite in the residual char. TGA showed that kaolin clay reinforced formulation; IF5-KC enhanced 49% residual weight than that of IF-Control formulation. XPS analysis showed that elemental composition of IF5-KC char residue gave 41.80% carbon content in the residual char. An accelerated weathering test ASTM D 6695-03 showed that IF5-KC coating sustained its integrity up to 90 days under accelerated weathering chamber.

Posted on: December 2014

Authored:Faiz Ahmad

Intumescent coating is an insulating material designed to decrease heat transfer to a substrate structure. The coating presented in this research article was based on expandable graphite, ammonium polyphosphate, melamine, and boric acid. Bisphenol A epoxy resin BE-188 was used as a binder with ACR hardener H-2310 polyamide amine. Different formulations were developed to study the effect of expansion and heat shielding after fire testing. The coating was tested at 950 °C for 1 h. The results show that the coating was stable and well bonded with the substrate. The coating was characterized with thermogravimetric analysis (TGA, Parkin Elmer, Norwalk, CT, 06859, USA), Fourier transform infrared (FTIR, Nicolet 400 D Shimadzu spectrometer) spectroscopy, X-ray diffraction (XRD, Bruker D8 advance Diffracto meter, Bruker Germany), and scanning electron microscopy (SEM, Carl Zeiss Leo 1430VP, UK). The morphology of char was studied by SEM on the coating after fire testing. XRD and FTIR spectroscopy showed the presence of graphite, boron phosphate, boron oxide, and sassolite in the residual char. TGA (Pyris 1, manufactured by Parkin Elmer, Norwalk, CT, 06859, USA) and differential thermal gravimetric analysis (DTGA) showed that boric acid enhanced the residual weight of the intumescent fire-retardant coating.

Posted on: September 2012

Authored: Faiz Ahmad

This research investigates the synthesis of new formulations of intumescent coating with improved thermal performance for steel structures. The coating formulations were based on the expandable graphite reinforced with wollastonite and bentonite. Ten samples of five formulations were synthesized by varying grinding time duration between 1 and 2 min. To analyse the substrate temperature of coated steel, fire test was performed according to ASTM-E119. The char morphology was observed by Field Emission Scanning Electron (FESEM) and Transmission Electron Microscopy (TEM). FTIR and X-ray Diffraction (XRD) test is conducted to analyse the composition of the residual char. The residual char mass was perceived by Thermogravimetric analysis (TGA) of the coating. X-ray Photo Electron Spectroscopy (XPS) was utilized for binding energy and elemental composition of the char. One-hour fire protection test showed 166 °C, the lowest substrate temperature of IFRC5-2 and 40.46% residual mass was obtained by TGA analysis. XRD analysis showed that residual char has aluminum borate and borophosphate and confirmed by functional group analysis using and FTIR. FESEM and TEM illustrated that char relates to hexagonal particles of wollastonite. XPS analysis of IFRC5-2 showed the carbon and oxygen contents were 41.40% and 51.20%. Pyrolysis-Gas Chromatography-Mass Spectrometry (Pyrolysis GC-MS) results showed IFRC-5 produced less concentration of the gaseous products compared to IFRC-C. The formulations developed by grinding solid ingredients for 2 min showed improved thermal performance compared with the formulation produced by grinding solid ingredients for 1 min. Longer grinding time and higher amount of filler improved the thermal properties of the intumescent coating.

Posted on: December 2019

Authored: Faiz Ahmad

The purpose of this research is to investigate the influence of different powder loadings of 316L stainless steel (SS) powders on rheological behavior of feedstocks required for low pressure powder injection molding (L-PIM) process. The main idea consists in development of various formulations by varying 316L SS powder contents in feedstocks and evaluating the temperature sensitivity of feedstock via flow behavior index and activation energy. For this purpose, the irregular shape, spherical shape, and combination of both shapes and sizes (bimodal approach) of 316L SS powders are compounded with wax based composite binder. Moreover, the influence of elemental nanosized boron (nB) addition (up to 1.5 wt.%) on rheological properties of irregular shape 316L SS powders is also evaluated using capillary rheometer method. It is observed that rheological parameters for solid powder loading of powder gas atomized (PGA) and bimodal powder P25/75 316L SS underwent sudden change from PGA-69 vol.% to PGA-72 vol.% and P25/75-67 vol.% to P25/75 316L SS 70 vol.%, respectively. Thus it is concluded that PGA-69 vol.% and P25/75-67 vol.% are optimal powder solid loadings corresponding to the lowest values of activation energies.

Posted on:January 2016

Authored:Faiz Ahmad