Effects of debinding and sintering atmosphere on properties and corrosion resistance of powder injection molded 316 L - stainless steel

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

Influences of flame-retardant fillers on fire protection and mechanical properties of intumescent coatings

A combination of acrylic binder and flame-retardant ingredients was used to synthesize the solvent-borne intumescent coatings designed for steel substrates. The influences of individual and various combinations of flame-retardant fillers on the fire protection and mechanical properties of the coatings were characterized by using Bunsen burner, thermogravimetric analysis, limiting oxygen index, field emission scanning electron microscopy, freeze thaw cycles, static immersion and pull-off type equipment. It was found that the combination of aluminium hydroxide (Al(OH)(3)) and titanium dioxide (TiO2) has significantly improved the fire protection, thermal stability and water resistance of the coating. This formulation had an LOI value of 34, which indicated good flammability resistance of the coating. The adhesion strength tests showed that the coating added with magnesium hydroxide (Mg(OH)(2)) exhibited maximum bonding strength to the metal surface due to its effective interface adhesion. Hence, the findings from this study revealed that the selection of appropriate combinations of flame-retardant fillers strongly influenced the physical and chemical properties of the coatings. (C) 2014 Elsevier B.V. All rights reserved

Eggshells: A novel bio-filler for intumescent flame-retardant coatings

The aim of this study was to develop intumescent flame-retardant coatings that incorporate chicken eggshell (CES) waste as a novel eco-friendly bio-filler. Three flame-retardant additives, namely, ammonium polyphosphate phase II, pentaerythritol and melamine were mixed with flame-retardant fillers and acrylic binder to synthesize the intumescent coatings. The fire performance of the coatings was evaluated in accordance with 'BS 476: Part 6-Fire Propagation' and 'BS 476: Part 7-Surface Spread of Flame' test standards. It was found that 4 out of 5 of the coated specimens (B, C, D and E) neither showed surface spread of flame nor any afterglow combustion upon fire exposure. The addition of 5.0 wt and 2.5 wt eggshell bio-filler into formulations B and E, respectively, improved fire protection due to char formation, with better morphology, height and structure of the protecting shield. The filler compositions of samples D (3.4 wt TiO2/3.3 wt Al(OH)3/3.3 wt Mg(OH)(2)) and E (2.5 wt TiO2/2.5 wt Al(OH)(3)/2.5 wt Mg(OH)(2)/2.5 wt CES) applied at a thickness of 1.5 +/- 0.2 mm achieved the lowest fire propagation index with a value of 4.5 and 5.0, respectively (BS 476 Part 6, Class 0 materials) which indicates excellent fire-stopping properties. The results showed that the coatings were effective in fire protection, with good qualities of water resistance, thermal stability, and adhesion strength. Significantly, coating E (with CES) has proved to be efficient in the protection of plywood against fire. (C) 2015 Elsevier B.V. All rights reserved

Multi-component MWCNT/NG/EP-based bipolar plates with enhanced mechanical and electrical characteristics fabricated by compression moulding

In this work, multi-walled carbon nanotubes (MWCNTs), natural graphite (NG) and epoxy (EP) were used to fabricate bipolar plates by the compression moulding technique. The mechanical and thermal behaviours of the as-developed material were investigated in terms of the effects of temperature on the morphological, mechanical and electrical properties. It was observed that the flexural strength of the MWCNT/NG/EP composite decreased with increasing temperature. The highest flexural strength (27.05 MPa) was recorded at 25 ?C. When heated to 200 ?C, the flexural strength of the material decreased by up to 2.40 MPa. The shore hardness of the MWCNT/NG/EP composite decreased with increasing temperature. The highest shore hardness (69.7 HD) was recorded at a temperature of 25 ?C, while the lowest shore hardness (31.3 HD) was recorded at 200 ?C. The temperature-dependent through-plane and in-plane electrical conductivities of the MWCNT/NG/EP composite were also investigated, although its contact, bulk and forward resistivity values were found to decrease. The experimental results revealed that the effect of temperature on the thermal and mechanical properties of the bipolar plate material was different at different temperatures. The synergistic electrical nature of the as-designed material may be ascribed to the phenomenon of electron transfer among the channels of natural graphite and MWCNTs. The enhanced mechanical behaviour was attributed to the presence of EP in the composite material. ? 2018 Elsevier Ltd and Techna Group S.r.l.We acknowledge the financial support provided by the Ministry of Education of Malaysia under Grant Nos. DIP-2014-006 and LRGS-USM-UKM/PT/05 .Scopu

Investigation on solvent-borne intumescent flame-retardant coatings for steel

This paper presents an investigation on solvent-borne intumescent flame-retardant coatings that can provide good bonding strength, water resistance and fire protection to the steel substrate. The fire protection performance and characterisations of the coatings were investigated by using the Bunsen burner test, thermogravimetry analysis, field emission scanning electron microscope, static immersion test and Instron Micro Tester. It was found that the fire protection and foam structure of the coating significantly improved by adding the combination of Mg(OH)(2) and TiO2 flame-retardant fillers to the flame-retardant additives and acrylic binder. The formation of uniform foam structure and reaction of the coating which decompose into voluminous and multicellular char layers with thermal insulation properties contribute an important fire protection to the steel substrate from reaching its critical temperature. However, the combination of [Al(OH)(3) and Mg(OH)(2)] flame-retardant fillers to the flame-retardant additives and epoxy binder led to maximum adhesion strength. The improvement in the bonding properties of the coating to the metal surface was attributed to the effective [Mg(OH)(2) and TiO2] fillers/epoxy binder interface adhesion. Hence, the findings of this study reveal that the selection of appropriate combination of binders and flame-retardant fillers strongly influenced the fire protection, water resistance and mechanical properties of intumescent coatings