S.Z. Othman

Effect of calcination time on NiAl-Al2O3 using gel combustion synthesis method

This study was conducted in order to investigate the effect of calcination time on phase and microstructural characteristics of intermetallic matric composite (IMC), NiAl-Al2O3 powder. This powder was synthesized using gel combustion method with octyl alcohol as fuel. Upon completion of the combustion process, the loose powder was calcined at 1050°C for 1, 2 and 4 hours and characterized using XRD, FESEM and TEM. The crystallite size was calculated to be in the range of 29-30 nm. It was found that NiAl-Al2O3 exhibits high crystalline structure after calcination for 4 hours. Furthermore, longer calcination time also cause growth of the particle size. Findings indicate that high crystalline nanostructured NiAl-Al2O3 powder consisting of submicron particles can be successfully produced using gel combustion synthesis with longer calcination time.

Synthesis and Characterizations of SiO2-Ag Core-Shell Nanostructure Using Fatty Alcohols as Surface Modifiers

SiO2-Ag core-shell nanostructure with silica core (SiO2) and silver shell (Ag) nanoparticles with spherical morphology were successfully synthesized using a modified self-assembly sol-gel method. Ag nanoparticles at ca.10-50 nm were successfully attached on monodispersed silica spheres (SiO2) with diameter of ca. 450 nm. Renewable resources of palm oil, derived fatty alcohols (octyl-alcohol (C8), decyl-alcohol (C10) and dodecyl-alcohol (C12)) were employed as nonsurfactant surface modifiers prior to coating with Ag nanoparticles. X-ray diffraction (XRD) patterns of calcined SiO2-Ag core-shell nanostructure prepared with surface modifiers exhibited amorphous structure of SiO2 (core) and face-centered cubic (FCC) structure of metallic Ag nanoparticles (shell). The results obtained in the present work demonstrated the feasibility of employing fatty alcohols as potential nonsurfactant surface modifiers in synthesizing SiO2-Ag core-shell.

Effect of NH3 on Structural and Optical Properties of SiO2-CuO Core-Shell Nanostructure

CuO nanoparticles at ca. 20-50 nm were successfully coated on monodispersed silica spheres prepared by modified sol-gel method. A renewable palm oil based decyl-alcohol (C10) was employed as nonsurfactant surface modifier prior to coating with CuO. Various amounts of ammonia (NH3) (0-1 ml) was as catalyst during the modification process to study the effect in homogeneous deposition of CuO on silica surfaces. The homogeneous depositions of CuO on silica were achieved with the addition of 0.9 ml of NH3. The optical absorption peak and energy band gap (Eg) values were at ca. 1.8-2.18 eV suitable for semiconductor and optical sensor materials.

Facile Method of Enzyme Immobilization on Silica Quasi-Nanospheres (SiO2) Synthesized Using PODFA for Biosensing Applications

In this study, silica spheres (SiO2) nanomaterials were introduced as the support materials for glucose sensors. Glucose oxidase (GOx) was immobilized onto SiO2 spheres (SiO2/GOx) using physical adsorption (electrostatic interaction) method. The SiO2 spheres were synthesized in-house using a nonsurfactant template of palm oil derived fatty alcohols (PODFA). Based on FT-IR analyses, SiO2/GOx exhibited N-H absorbance at ca. 2990 cm-1 and O-H absorbance at ca. 3330 cm-1. One new absorbance peak was observed at ca. 2320 cm1 attributed to the bending vibration (νbend)of silane molecules (Si-H) obtained by the interaction of GOx and the surface silanols (Si-OH). UV-Vis analysis results exihibited the presence of a new broad peak for GOx/SiO2 sample at ca. 250 nm to 280 nm suggested to be assigned to H2O2, C=C and benzene ring from GOx. The optimum pH and optimum temperature for SiO2/GOx for GOx activity were ca. 7.0 and ca. 50°C respectively. The increase of glucose concentration from 2mM to 5mM resulted to the increment of absorbance value for both GOx and SiO2/GOxsuggesting succesful immobilization of GOx on SiO2 spheres. These materials were suitable for glucose detection at very small glucose concentrations particularly in salivary glucose detection.

Synthesis and characterizations of MOF-199 using PODFA as porogen for CO2 adsorption applications

Copper-based metal-organic framework (MOF-199, also known as Cu-BTC and HKUST-1) materials were successfully synthesized by hydrothermal method using renewable straight-chain fatty alcohol with eight carbon chain length (i.e. octyl alcohol). The addition of palm oil derived fatty alcohol (PODFA) was suggested to act as porogen (structure directing agent) that aided the particle formation and flexible porous structure. This synthesis approach was environmental-friendly and sustainable by utilizing the fatty alcohols originated from biomass such as palm oil. The resulting MOF-199 materials exhibited single crystalline octahedral morphology structure by X-ray diffraction analyses and SEM images. The optimum ratio of octyl alcohol exhibited well-defined single octahedral particles at size range of ca. 10-50 µm and reduced by-product formation of cuprous oxide at high temperature synthesis. The nature of MOF-199 having apparently high surface area, high pore volume and low density provided the possibility in carbon capture storage. The CO2 adsorption capacity of MOF-199 investigated using high pressure volumetric analyser (HPVA-II) at ambient temperature (i.e. 25 °C) was found to be at maximum working capacity.

Effect of Synthesis Methods Using Renewable PODFA on Structural Characteristics of Metal-Organic Framework (MOF-5)

In this work, metal-organic framework (MOF-5) syntheses were successfully synthesized with three different methods namely i) modified direct-mixing method ii) microwave assisted method and iii) autoclave assisted method without using surfactants. Palm oil derived fatty alcohol (PODFA), dodecyl alcohol (C8) was used as renewable non-surfactant template. Four prominent peaks were observed in all three samples attributable to the reflection planes of (200), (220), (400) and (420) of a cubic structure at ca. 2θ = 6.9°, 9.6°, 13.7° and 15.2°. The morphology of MOF-5 produced using modified direct-mixing method was faceted structure with average size of ca. 1 µm. In addition, the morphology of MOF-5 produced using microwave assisted synthesis was cubic structure with average size of ca. 8.34 µm. However, the morphology of MOF-5 using autoclave assisted method was interpenetrated cubic with average size of ca. 22.65 µm.

Characterizations of NiAl-Al2O3 Produced Using Gel Combustion Synthesis Method

NiAl is widely used for elevated temperature application because it gives better properties, especially in the gas turbine application. This study was done in order to investigate the effects of calcination temperature on NiAl and α-Al2O3 formation using gel combustion synthesis method. This method used fatty alcohol and fatty acid ester for producing NiAl powders. X-Ray diffraction patterns of calcined samples exhibited NiAl and α-Al2O3 at temperature 1050°C. Therefore, nanostructured NiAl-α- Al2O3 can be successfully produced with the gel combustion method using less expensive and more environmental friendly fatty alcohol and fatty acid ester as fuels.

Settlement Prediction of Soil at Closed Dumping area using Power Creep Function

In Malaysia, total dumping sites are 73 sites, controlled dumping sites are 71 sites and sanitary landfill are 11 sites. These disposal sites will increase over time because population in Malaysia has been increased at a rate of 2.4% per annum or about 600,000 per annum since 1994. The increase in population would increase the amount of waste generated. Thus, it will increase the number of dumping sites. The dumping area which has a full capacity of waste will eventually closed. These closed dumping area which are to be developed for new development are prone to settlement. The settlement at dumping area are to be predicted and simulated using Power Creep Function. The heterogeneous content of waste soil from dumping area are complicated to characterize and classified. The content of waste dumped at the dumping area is important to analyse because the degradation process changes with time. The degradation process are called power creep function. Power Creep Function (PCF) is time dependent deformation which is under constant stress. The two constant variables which are M’ and N’. M’ is the compressibility constant and N’ is rate of compression varies with age placement condition. The input parameters for PCF are H0, ∆σ, t, Tr, M’ and N’. These parameters are simulated based on two cases whereby, case 1 where M’ and N’ are kept constant and time (t) increases from 25 days to 75 days. Tr is kept constant at 1 day. Case 2 is where M’, N’ and Tr are kept constant and time (t) increases from 240 days to 730 days. The settlement prediction at the dumping area for Case 1 is 0.024 meters to 0.042 meters and for Case 2 the settlement is in the range of 0.074 meters to 0.130 meters. The prediction of total settlement for dumping area would be used to determine the depth of foundation for the new development at the dumping area.

Review on Immobilization of Nanoparticles for Fabrication of Glucose Biosensor

Glucose biosensor has been improvised from time to time in order to provide fast and accurate detection of glucose concentration especially for diabetic patients. Recently, nanoparticles have rising attention engaging with biosensor application. Nanoparticles serve as the carrier of enzyme immobilization whereas; enzyme is a biological catalyst that reacts with specific substrate in metabolic reaction. Glucose oxidase (GOx) in particular, is the most common enzyme used for fabrication of biosensor. Glucose measurement was done by using amperometric measurement that converted corresponding biochemical reaction between glucose and GOx into electrical output. Response behavior studies were conducted in order to compare the successfulness of GOx immobilization onto GOx-biosensor. Immobilization of glucose oxidase onto nanoparticles can lead towards tremendous impacts especially in new, high sensitivity biosensor.

Hydrothermal Synthesis and Characterizations of MOF-199 Using Renewable Template

A three-dimensional (3D) copper-based metal-organic frameworks or MOF-199 were successfully synthesized by utilizing palm oil based fatty alcohols that acted as renewable template. The synthesis of MOF-199 employed different length of straight chain of fatty alcohols namely octyl, decyl, lauryl, myristyl and cetyl alcohols derived from palm oil using similar method to those reported earlier with some modifications. The microstructure of MOF-199 exhibited single particles with fine octahedral morphology at various particle sizes in the range of ca. 15-60 μm. The nitrogen adsorption isotherms were conducted to estimate the surface area and pore volume of the materials and were at ca. 400 – 1100 m2g-1 and 0.17 – 0.43 mLg-1 respectively. The surface area and pore volume of the materials decreased with longer straight chain fatty alcohol possibility due to mobility of the long carbon chain.