Papers by Author: Sufizar Ahmad

Abstract: The effect of fabrication methods on polysiloxane (POS) composites were studied by analysing both method of casting (CA) and compression (CO). The POS composites were reinforced with 2-12 wt% of natural derived silica from rice husk (RHA SiO₂) as a filler which incinerated at 700°C. The composites behaviour were analysed through tensile testing (ASTM D412). Through comparison study on both CA and CO composites’s tensile behaviour it shows that both composites strength keep increasing with 2wt% - 10wt% RHA SiO₂ addition but strength decreased at 12wt% due to agglomeration of RHA SiO₂. Moreover, it was found that the tensile strength of CO composites had offer 23.56% higher compared to CA composites. The difference were influenced by the distribution of RHA SiO₂ as filler. The surface morphology of CO composites had showed that the most of RHA SiO₂ were embedded and less agglomeration, compared to CA composites that had lots of agglomeration which lead to higher tendency of crack propagation. The arrangement of filler due to the CO method that helps RHA SiO₂ to distributed homogenously and embedded in a matrix of POS to avoid agglomeration and lead better adhesion respectively. Thus, CO method had potential to offer in enhancing tensile behaviour compared to CA method by influencing filler distribution arrangement for vibration absorber application.

Abstract: Silica (SiO₂) foams have been widely applied in numerous fields, mainly filters and catalysts supports, due to their characteristics of high permeability, high porosity and specific surface area. In this study, foams of SiO₂ from rice husk ash (RHA) was fabricated via polymeric sponge replication method. Polymeric foam initially was used as template and dipped into SiO₂ slurry followed by drying and sintering to yield the replica of the original polymeric foam. Different solid loadings of SiO₂ as-derived from RHA (20 to 35 wt. %) slurry and sintering temperature of 1150 °C were applied. Phase identification and chemical composition of the green and sintered foams were conducted using X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF). Morphological observations were performed using Scanning Electron Microscopy (SEM). Density and porosity of the SiO₂ foams were characterized using Archimedes method. Compressive strengths of the foams were determined as per ASTM C773-88 (1999). XRD analyses confirmed that the SiO₂ as derived from the RHA were of tridymite and cristobalite phases with as high as 93% purity, as confirmed by XRF analyses. The density of SiO₂ foams fabricated was in the range of 0.614 to 0.989 g/cm³, whereas the porosity values was in the range of 70% to 82%%. Compressive strengths were found to increase from 0.05 to 0.30 MPa respectively, proportionate with the increased SiO₂ solid loading. Excellent properties of the SiO₂ foams definitely signifies that the polymeric replication method is indeed a promising technique for SiO₂ as derived from RHA foam fabrication.

Abstract: Naphthenic acid is a sort of organic acid which present in crude oil and cause severe corrosion in certain circumstances. This type of acid will lead to the corrosion phenomenon known as naphthenic acid corrosion (NAC). Damage mechanism by NAC attack can be analysed using Scanning Electron Microscope (SEM), Electron-dispersive X-ray (EDX) and X-ray Diffraction (XRD). These characterization methods aim to observe the morphology, element content, and crystal structure of the NAC. The objective of this research is to apply failure analysis (FA) on heat exchanger (HE) tube bundle made form stainless steel 410 (SS410). SEM reveals the inter-granular attack initiate to crack propagation. A particular result of interest is that nickel catalytically decomposes naphthenic acids at high temperatures (e.g. 270°C) via a catalytic mechanism. For XRD testing, the corrosion product have been known and the main causes that lead to the corrosion has been detected which there is a formation of chromium carbide continuously along the pipe tube. However there is also formation of iron sulphide and chromium sulphide obtained in the XRD analysis where both are the reaction element that can retard the formation of NAC. Material selection is the most crucial task to resists from corrosion attack especially in high temperature applications. The mechanism of resistance of these elements provides insight into the failure mode of 304 and 400 series stainless steel in NA service.

Abstract: Development of lightweight materials becomes essential and has been applied for various structural and functional applications in industrial field since last decade. Porous metal can contribute to lightweight material with great mechanical, thermal and electrical properties. In this study, porous stainless steel was fabricated by using powder metallurgy technique and egg shell as a new potential space holder material. Stainless steel 316L was used as metal matrix powder, egg shells as space holder material, and polyethylene glycol (PEG) as binder to increase the green density of the preforms. The material was mixed using roller mill before the mixtures are ready to the next process of compaction by using uniaxial pressing machine. The samples were sintered to two-stage sintering at temperature 1000°C in a tube furnace. Physical properties of porous stainless steel were studies by performing density and porosity test. Scanning Electron Microscopy (SEM) apparatus was used to characterize morphology properties. The results show that, porous stainless steel with the composition of 30 wt. % of egg shells added into formulation yields the highest porosity compared to other compositions and the distribution of pores can be classify as micro-pores.

Abstract: Porous ceramic body is broadly utilized in the engineering discipline in this globalization era especially in the industrial applications. This is due to the advantages of one of the ceramic foams characteristics that can exhibit highly open pore and have a good interconnectivity. At the present study, the formation of Silica-Nickel oxide (SiO₂-NiO) foams was developed by using the replication method with various solid loadings of 20wt. %, 25wt. %, 30wt. %, 35wt. % by adding a fixed amount of 5wt. % composition of Nickel Oxide (NiO) and sintered at a temperature of 1250°C. The Polyethylene Glycol (PEG) and Carboxymethyl Cellulose (CMC) as the binders to bind the particles and as thickening agent for the slurries formation. The cylindrical shape polyurethane acts as a template of the SiO₂-NiO foams. The properties of physical and mechanical of the SiO₂-NiO foams are being characterized through the morphology analysis via the Scanning Electron Microscope (SEM). Bulk density and apparent porosity tests are determined by adapting the Archimedes Principles. The compressive test has been carried out to identify the compressive strength of SiO₂-NiO foams. The results obtained during the morphology analysis show the size of the pores appeared differently between the ranges of 268.81µm to 516.17µm. The result of the density and porosity of the porous SiO₂-NiO foams recorded results between the ranges of 0.452g/cm³ to 0.775g/cm³ and 68.5% to 81.2%. This indicates that the variable of solid loading reveals the effect on the properties of the SiO₂-NiO foams. Thus, the increasing of the solid loading will decrease the average size of the pores. However, with the decreasing of the average size of the pores will increase the density and the compressive strength of SiO₂-NiO foams.

Abstract: The correlation between calcination temperature with the morphological, porosity and density of Sm_0.5Sr_0.5CoO_3−δ/ Sm_0.2 Ce_0.8O_1.9 incorporation with binary carbonate prepared by high energy ball milling (HEBM) method has been investigated. The composite cathode, samarium strontium cobaltite-samarium doped ceria carbonate (SSC:SDCc), was developed and scrutinised as for potential cathode materials in solid oxide fuel cell (SOFC) applications. This research studied the influence of carbonate in composite electrolyte, SDCc towards the composite cathode properties. The composition of 50 wt.% of SSC was chosen to be added with 50 wt.% of SDCc powder. The prepared powders of composite cathode SSC5:SDCc5 were then undergone calcination process at different operating temperatures which has been varied from 600°C, 650°C, 700°C and 750°C and all prepared pellets were sintered at 600 °C. The morphological properties of the composite cathode powders were observed via FESEM micrograph, and the average particle sizes of the composite powders were measured via SmartTiff Software. The total porosity (%) of the SSC5:SDCc5 composite cathode pellets was determined using the Archimedes method. The FESEM micrograph revealed that the obtained composite cathode powder is homogeneous, fine with average of agglomerates sizes of 70–100 nm. By increased on calcination temperatures, the agglomerates size of the composite cathode and the density of the pellet increased. Meanwhile the results collected from porosity value are decreased. The porosity percentage lies in the range from 32.3% until 38.7%. Based on the overall results, lower calcination temperature, which is 600° lead to better morphological and physical results. In conclusion, the calcination temperature has a direct effect on the average size of SSC-SDCc composite cathode, porosity and density value but still in line within the acceptable range to serve as effective potential cathode materials for solid oxide fuel cells.

Abstract: Porous ceramic is a type of material that has highly open and partially interconnected pores. It has a wide range of applications which include catalyst support, electrical conductivity, refractory insulation of furnaces, filtration, adsorption, and separation. There are many conventional methods for producing silica foam including direct forming, steam heating, freeze casting and the polymeric sponge method which is also known as the replication method. In this study, SiO₂-NiO foam was fabricated using 25wt. %, 30wt % and 35wt.% of SiO₂ and 5wt.% of NiO under different sintering temperatures (850 °C and 1050 °C) via replication method. The morphologies of SiO₂-NiO foams were observed using Scanning Electron Microscopy (SEM) while the identification of the different phases of foam was analysed using X-Ray Diffraction (XRD). The XRD analysis indicated that there were only SiO₂ and NiO present and no additional phases were detected after sintering. The effects of sintering temperature (850 °C, 1050 °C) and SiO₂ solid loading on properties such as apparent porosity, bulk density and shrinkage were investigated. It was found that when the solid loading of SiO₂ and sintering temperature increased, the density of SiO₂-NiO foams increased in the range of 0.6373 g/cm³ to 0.8165 g/cm³. On the other hand, the porosity percentage obtained increased from 78.51 % to 81.63 %. The density and porosity analyses showed that the density of foam increases when the porosity of SiO₂-NiO foam decreases. However, the shrinkage after sintering ranged between 3.5081cm to 6.9975 cm at 850C ̊ and 7.3618 cm to 8.3704 cm at 1050 °C respectively. Thus, this proves that SiO₂-NiO foam can be successfully fabricated through the replication method.

Abstract: This study presents the preparation of barium strontium cobalt ferrite (BSCF)–samarium doped ceria (SDC) added samarium doped ceria carbonate (SDCC) cathode for solid oxide fuel cell (SOFC). The aim of this study is to investigate the effect of heat treatment on compatibility and characterization of BSCF composite. Calcined BSCF was mixed with SDCC and SDC by ball milling at 150 and 200 rpm respectively. Subsequently, both were uniaxially pressed to form pellets and sintered at 600°C for 2 hours. The BSCF behavior of composite samples was characterized via X-ray diffraction to determine the crystalline phase of BSCF composite. Fourier transform infrared spectroscopy was used to determine the existence of carbonate bond. Field emission scanning electron microscopy was used to examine the grain morphology. The crystalline BSCF phase percentage increased and secondary phases reduced when the milling speed decreased. After milling, BSCF composites still displayed uniform elemental distribution. Heat treatment has an impaired crystalline phase of perovskite BSCF. Without heat treatment, the BSCF composites showed agglomerate and unmolded particles.

Abstract: Porous materials with open and interconnected pores are very interesting for biomedical applications as it provides a good base for the formation of bone ingrowth naturally. Besides, it also allows for body fluid transportation through the interconnected network. Therefore, in this work, foam replication method has been used to produce porous SS316L. The SS316L slurries were prepared by ball milling and mechanical stirring method. The polyurethane (PU) foam has been used as a sacrificial template. Sintering process was carried in a high vacuum furnace at 1200°C, 1250°C and 1300°C. The overall results show that increasing the sintering temperature from 1200°C to 1300°C and the using of different slurry mixing methods did not significantly affect the physical and mechanical properties of the porous SS316L produced. The density, porosity percentage and compression strength found for this porous SS316L were in the range of 1.35g/cm3-3g/cm3, 62% - 83%, and 30.6MPa-79MPa respectively. The SEM images also show that the microstructure of this porous SS316L mostly consisted of open and interconnected pores. Therefore, these results are very promising for biomedical implant application.

Abstract: Metal foams are a cellular structure that has a solid matrix made of metal and has pores in their structure. Metal foams offer excellent combination of properties which led researchers interested in investigation in recent years. Closed-cell stainless steel (SS316L) foams for biomedical application were prepared by space holder method and the physical and morphological properties of SS316L foams were studied. Stainless steel (SS316L) powders as metallic material, polyethylene glycol (PEG) as a binder and Urea as a space holder material were mixed homogenously to avoid the particle wrecked. This mixture was compacted using uniaxial pressing machine and pressurized to 8 tons to formed the green body. By using tube furnace, the SS316L foams was two-stage sintered, the first phase at 600°C for 2 hours to decompose the urea, and the second phase at 1000°C, 1100°C, and 1200°C respectively to sinter the steel. The porosity and density test was carried out by applying Archimedean principles, while morphological observation was done by using Field Emission Scanning Electron (FESEM). The samples with 40wt.% SS316L composition and sintered at temperature of 1100°C, leads to porosities of about 44.539% and show the potential as the best metal foams.