Norhayati Ahmad

Mechanical properties of stabilized zirconia nanocrystalline EB-PVD coating evaluated by micro and nano indentation

Yttria-stabilized zirconia (YSZ) thin nanocrystalline coatings at different substrate preheating temperatures were deposited via electron beam-physical vapour deposition (EB-PVD). Nanocrystalline ZrO2-Y2O3 was deposited on the bond coat in order to compensate for the coefficient of thermal expansion (CTE), which can be functionalized as a thermal barrier coating (TBC). The aim of this study was to evaluate mechanical properties with respect to adhesion of zirconia nanocrystalline’s top ceramic layer to the interfacial bond coat by utilizing micro and nano indentation tests. In the present paper, the structural studies were carried out using X-ray diffraction (XRD) analysis of coating content (8 mol% of Y2O3). The tetragonal phase of stabilized zirconia was observed. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were employed to characterize the coatings’ morphology and microstructure. The mechanical behavior of ZrO2-Y2O3 thin films under point loading conditions was studied by nanoindentation using a Berkovich indenter with 130 nm tip radius. Therefore, adhesion of top coat to the interfacial underlying metallic bond coat known as MCrAlY (M = Ni, Co) was estimated according to the highest peak load tests; for a 120 mN peak load, the film manifested tolerable adhesion properties. Moreover, nanoindentation of ZrO2-Y2O3 nanostructure deposited at 1050 °C substrate preheating temperature produced the highest hardness value of about 21.7 GPa. Vickers micro hardness was utilized with the aid of the Tabor equation in order to achieve deeper insight into the correlation between adhesion and deposition process parameters.

Bio-corrosion behavior and mechanical characteristics of magnesium-titania-hydroxyapatite nanocomposites coated by magnesium-oxide flakes and silicon for use as resorbable bone fixation material

This study was aimed to improve of the corrosion resistance and mechanical properties of Mg/15TiO2/5HA nanocomposite by silicon and magnesium oxide coatings prepared using a powder metallurgy method. The phase evolution, chemical composition, microstructure and mechanical properties of uncoated and coated samples were characterized. Electrochemical and immersion tests used to investigate the in vitro corrosion behavior of the fabricated samples. The adhesion strength of ~36MPa for MgO and ~32MPa for Si/MgO coatings to substrate was measured by adhesion test. Fabrication a homogenous double layer coating with uniform thicknesses consisting micro-sized particles of Si as outer layer and flake-like particles of MgO as the inner layer on the surface of Mg/15TiO2/5HA nanocomposite caused the corrosion resistance and ductility increased whereas the ultimate compressive stress decreased. However, after immersion in SBF solution, Si/MgO-coated sample indicates the best mechanical properties compared to those of the uncoated and MgO-coated samples. The increase of cell viability percentage of the normal human osteoblast (NHOst) cells indicates the improvement in biocompatibility of Mg/15TiO2/5HA nanocomposite by Si/MgO coating.

Characterization and Modification of Mesoporous Silica Nanoparticles Prepared by Sol-Gel

Mesoporous silica nanoparticles (MSNs) were synthesized by sol-gel reaction at normal pressure by using TEOS as a silica source and CTAB as a directing agent in ammonia solution at 323 K subsequently calcined at 823 K. Then inorganic pores were modified with metal-supported MSN with attention to the acidity, surface area, pore size, and ability of ion exchange. Crystalline size was shown to decrease up to 20 molar ratios of Si/Al followed by increasing while further adding nanoparticles-aluminium. Moreover, the XRD patterns revealed the mesostructured material for all with 2D hexagonal structure. The obtained results from the XRD patterns were confirmed by using BET and EDX. The BET surface areas revealed the spherical shape for all samples with a decrease in the pore volume and surface area for various AlMSNs which emphasized that the loading of Al and was compatible with XRD results. MSN was prepared by sol-gel methods followed by loading of Al in order to prepare AlMSN which possess strong Lewis acidic sites. This modification occurred by using various molar ratios of 0, 5, 10, 20, 50, and 100 Si/Al, respectively. The XRD patterns of various ratios of Si/Al were interpreted in terms of strain, nanocrystalline size, and distribution of the particle size by deriving Wiliamson Hall equation.

Effect of Sintering Temperature on Membrane Properties of Sayong Ball Clay

Sayong ball clay membrane can be fabricated as a cheap membrane material and available commonly at Malaysia. This work was concerned with the study of Sayong ball clay membrane as a water filtration by gel casting technique. Gel casting involves mixing process of Sayong ball clay with the solvent, monomer, dispersant, initiator and catalyst in a certain composition. Tubular membrane was fabricated by controlling the sintering temperature (1000, 1100, 1200, 1300°C). The physical measurements (shrinkage, apparent porosity, and bulk density), microstructure analysis, filtration process (flow rate) and water quality assessments (pH, color, Chemical Oxygen Demand (COD), solid suspended (SS)) were carried out at different sintering temperature. Apparent porosity and bulk density of the samples were measured by using Archimedes method. The effect of sintering temperature on microstructure of the membranes has been investigated using SEM. The experimental results showed that the shrinkage and bulk density increase with increasing sintering temperature. It gives the improvement in water quality with the lowest SS (192 mg/L), lowest COD (4 mg/L) and most colorless (1.1 Gardner units) filtered wastewater as compared to others.

Mesoporosity, thermochemical and probabilistic failure analysis of fired locally sourced kaolinitic clay

Abstract A dense and mesoporous ceramic from locally sourced Nigerian clay under fracture-strength test were produced and the reliability analysis of the fractured strength was conducted using a three-parameter Weibull probability distribution. The samples were prepared by addition of starch (0–20wt%), pressed at 60 MPa and fired at 1300 °C. The as-received Nigerian clay, dense and porous ceramic were characterized using XRD, XRF, TGA/DTA, PSD, multi-point BET and FESEM. The fracture strength of the samples (33 each) was determined using a three-point bending test. The fracture strength data were analyzed using three-parameter Weibull probability distribution. From the characterization results, a mullite ceramic formed at a sintering temperature of 1300 °C. The threshold strength for the three-parameter Weibull provides the strength below which the dense and the porous ceramic will not fail. The Weibull moduli of the ceramics at different starch compositions show that failure modes in these materials are not identical. The Weibull modulus increases with increase in percentage starch from 0% to 15%. However, the value decreases with 20% starch addition. Reliability analysis provides a detailed interpretation and assessment of the fracture strength of the porous ceramics.

Application of Sayong Ball Clay Membrane Filtration for Ni (II) Removal from Industrial Wastewater

Abstract Wastewater containing heavy metals, such as nickel ions (Ni2+), discharged from industry to water streams poses a serious threat because even at low concentrations, it does not naturally degrade and is toxic to human and aquatic life. This article reviews a novel technique for wastewater treatment using a Sayong ball clay (SBC) membrane to remove nickel from industrial wastewater. SBC powder was achieved through milling using a planetary ball mill (milling time; 10, 20 and 30 h), further labelled as SBC 10, SBC 20 and SBC 30, with a ball-to-powder of ratio 7:1 and rotation speed of 300 rpm. The physical characteristics of the apparent porosities, bulk density and shrinkage were investigated. XRD was used to study the phase, while FESEM was used to analyse the microstructure of the fired membrane. The FESEM microstructure indicates a decreased particle size (SB30). Filtration was conducted using a dead-end filtration system. The fabricated SBC 10, 20 and 30 membranes showed significant removal of nickel from industrial wastewater—88.87%, 82.96% and 85.13%, respectively. This study revealed that the SBC membrane is a promising membrane to remove nickel from industrial wastewater. The results also indicate the possibility of highlighting the introduced technique as a new technique for the treatment of industrial wastewater. As a new trend for waste management, pollution prevention could be applied in Malaysia as one of the advanced biotechnologies to solve various environmental problems.

Flexural Strength Analysis of Dense and Porous Sintered Clay Using Weibull Probability Distribution

This research analyzed the results of flexural strength of dense and porous mullite ceramic prepared from kaolin clay by using two-parameter Weibull probability distribution with different estimates. Chemical and physical characterizations of the clay were conducted using XRF, XRD and FESEM. The samples were tested using three point bending tests. The different estimates used in analyzing the results include mean rank, median rank, modified Kaplan Meier and Kaplan Meier. Among the estimates, Kaplan Meier was found to give the best fit with the highest correlation coefficient (R2) value. The porous ceramic had the higher value of Weibull modulus in comparison to the dense ceramic, while the characteristic strength (scale parameter) of the dense ceramic was higher than that of the porous ceramic. The micrograph of the porous ceramic showed a relatively balanced distribution of rounded pores, which is associated with the higher Weibull modulus in the porous ceramic.

Fabrication and Characterization of Ceramic Membrane by Gel Cast Technique for Water Filtration

Sayong ball clay membrane can be fabricated without the assistance of high-tech sophisticated machineries and complicated production methods make the filters particularly attractive as a point-of-use treatment. This work was concerned with the study of Sayong ball clay membrane as a water filtration by Gel Cast technique. Gel cast involves mixing process of Sayong ball clay with the solvent, monomer, dispersant, initiator and catalyst in a certain composition Tubular membrane was designed and fabricated by controlling the Gel Cast monomer (5, 10, 15, 20 MAM percentage) at sintering temperature of 1300°C. The physical measurements (shrinkage, apparent porosity, bulk density), microstructure analysis, filtration process (flow rate) and water quality assessments (pH, color, COD, SS) were carried out at different percentage of MAM. The porosity and density of membranes were measured by using Archimedes method. The effect of monomer percentage on microstructure of the membranes has been investigated using FESEM. The experimental results showed that the apparent porosity and bulk density of Sayong Ball Clay Gel Cast with 5% MAM and sintered at temperature of 1300°C for 20 minutes were 15.39% and 1.87 g/cm3, respectively. It gives improvement in water quality with the lowest suspended solid (192 mg/L), lowest COD (4 mg/L) and most colorless (1.1 Gardner units) filtered wastewater as compared to others.

Glycerol as Plasticizer for Waste Polystyrene Based Metal Injection Molding (MIM) Binder

Except for the binder characteristics and molding conditions, the powder loading has a very important effect on the compact distortion. Three types of feedstocks consist of water atomised SS316L powder with 55% waste polystyrene, 35% palm stearin and 10% glycerol were prepared. The powder loading of each feedstocks are 63%, 64% and 65% respectively. Effect of glycerol at different powder loading on rheological properties in term of flowability (n), activation energy (E) and moldability (α) were investigated. It has been observed that all feedstocks possess pseudoplastic flow behavior which is one of the most crucial requirements in MIM process. The addition of glycerol decreases the flowability index while increased the activation energy.

The effect of organic solvent (Ethanol) on electroless Ni-P deposition

Use of electroless nickel for electronic applications continues to grow and is clearly the most diverse market segment. This project is aimed to investigate the possibility to coat nickel by using organic solvent for nickel composite coating deposition with undissolved-incorporated particles in water using electroless plating and to coat on water-dissolved materials. The work focuses on optimizing the coating parameters of electroless nickel phosphorous (Ni-P) in organic solvent which is ethanol on a copper substrate. The maximum concentration of ethanol was 50% to be added in an aqueous solution of plating bath to dissolve the entire Ni salt, complexing agent, stabilizer and reducing agent. The effect of 50% ethanol on electroless Ni-P deposition and characterization of Ni-P coating were studied. The characterization of coating materials was conducted using X-Ray Fluorescence (XRF) and Field Emission Scanning Microscopy (FESEM) with Energy Dispersive X-Ray (EDX). The result showed that the agglomerated Ni-P deposited on coating surface become bigger when the NiSO 4 concentration increases at the optimum plating time of 20 minutes. The performance of deposited Ni-P in this study showed highest adhesion level when the concentration of NiSO4 was 15 g/L while the thickest coating was formed at 40 minutes of 35 g/L NiSO 4 concentration.