Papers by Author: Khaidzir Hamzah

Abstract: Biodiesel fuel can be used in diesel engine in accordance to the standard provided. However, a significant issue with biodiesel fuel was noted. Some of the fuel quality were outside the accepted range of the specification stated in the standard. Thus, this can be lead to the problem of utilization them in diesel engine. Moreover, material compatibility is the main concern whenever the fuel composition is altered in the fuel system. A large variety of metals and non-metals are worn as the material of construction for the various components of the fuel system. Introduction of biodiesel fuel often generate many problems in the components of the fuel system. This paper attempts to present the compatibility issue related to the use of biodiesel with automotive materials.

Abstract: . Achieving tunable optical properties of inorganic glasses via optimized doping of rare earth ions is ever-demanding in photonics. Control and inhibition of luminescence quenching, nonradiative decay and multi-phonon relaxation responsible of reduction of optical performance remains challenging. Doping/co-doping of different rare earth ions, variation of modifiers and embedding metallic nanoparticles (NPs) are thought as alternative routes to enhance optical response are still underway. We examine the influence of samarium ion concentrations on the optical properties of oxy-chlorite tellurite glasses of the form (70-x)TeO₂-15MgO-5Li₂O-10LiCl-xSm₂O₃ with 0.0 x 2.5 mol% prepared using melt-quenching method. The structural and optical characterizations are performed via X-ray diffraction (XRD), Ultraviolet-Visible (UV-Vis) absorption and photoluminescence (PL) spectroscopy. The glass density increased from 4.509 - 4.770 with the increase of Sm₂O₃ contents from 0.0 2.5 mol %. The XRD spectra confirm the amorphous nature of the glass. The absorption spectra exhibit nine prominent peaks corresponding to the transitions from the ground to excited states and the PL spectra reveal four peaks. The optical energy band gap for direct and indirect transitions are increased and Urbach energy decreased from 3.448 - 3.497, 3.165 - 3.232 and 0.217 - 0.175, respectively with the increase of Sm³⁺ ion concentrations. Furthermore, the significant enhancement in UV-Vis and PL response display the strong influence of samarium ion on optical and structural properties. The mechanism responsible for enhanced optical properties are analyzed and discussed. The results suggest that our careful experimental studies may contribute towards the development of tellurite glass based solid state lasers.

Abstract: Series of glass based on (80-x)TeO₂-10PbO-10PbCl₂-xYb₂O₃ where 0.0 ≤ x ≤ 3.0 were successfully prepared via melt quenching technique. The corrosion rate measurement was carried out by immersing the glass in various pH solutions in the range of pH 2 to 11. The alteration in surface morphology and structural characteristics was examined using field emission scanning electron microscopic and X-ray diffraction measurements. The corrosion investigations showed that the corrosion rate of the glass decreased over time due to the formation of protective layer on the glass surface. Furthermore, the increase in Yb amount in the glass network was found to enhance the corrosion resistance. This attributed to the enhancement of glass compactness. However, as the amount reached 2 mol%, the ability to resist corrosion decreased due to inability of Yb to participate in the structure. The FESEM micrographs indeed revealed the differences of surface morphology of glass after immersion in various pH solutions. It is demonstrated that the corrosion of acid and alkali occurred differently where acidic attacks were faster compared to alkali and distilled water.

Abstract: Samarium-doped tellurite glass embedded with silver nanoparticles are synthesized by melt quenching technique and optically characterized. The effect of silver nanoparticles on the luminescent properties of the samarium-doped sodium tellurite glass is investigated. Upon pumping with 406 nm radiation, it is found that there are four distinctive emission bands centered at 562 nm, 599 nm, 645 nm and 705 nm. In the presence of silver nanoparticles in the glass substrates, we observe significant enhancement in the intensity of these emission bands. The enhancement tends to increase with the increasing of silver nanoparticles concentration. The mechanism of luminescence enhancement is discussed in terms of localized surface plasmon resonance.

Abstract: Samarium doped magnesium phosphate glass having a composition of [P2O5]50-x-[MgO]50-[Sm2O3]x, with 0≤x≤4 mol% were prepared by melt-quenching method. The emission spectra were recorded using the photoluminescence spectrometer in the range of 540-730 nm at room temperature after being excited at 403 nm. It was found that the emission spectrum of Sm3+consisted of four emission bands at ~559.76 nm, ~597.32 nm, ~641.55 nm and ~705.57 nm which were assign as a transition of 4G5/2→6H5/2, 4G5/2 →6H7/2, 4G5/2→6H9/2 and 4G5/2→6H11/2 respectively. The transition of 4G5/2→6H7/2 is detected as the strongest orange (597.32 nm) luminescence peaks thus dominates the transition.

Abstract: . The study of the crystallization kinetics of rare-earth doped glass stimulated much interest especially for crystallization process. In this work transparent Eu2O3 doped glasses with composition TeO2 - Na2O – MgO were prepared using conventional melt-quenching technique. The amorphous nature of glass was confirmed using X-ray diffraction method. The influence of Eu3+ content on the crystallization kinetics of the glass such as activation energy (Ea) was thoroughly evaluated under non-isothermal conditions using DTA. The crystallization kinetic at different heating rate from 5 °C min-1 to 25 °C min-1 at different crystallization temperature (Tp) were examined and verified using Ozawa method. The result showed that the activation energy (Ea) was decreased with the increasing of the dopant concentration from 319.8 eV to 93.5 eV.

Abstract: Tellurite glasses of varying Er3+/Nd3+ concentration were successfully prepared by melt-quenching method. The X-Ray diffraction pattern was determined by using Siemens Diffractometer D5000 while the optical properties were measured using Shimadzu 3101 pc UV-VIS NIR scanning spectrophotometer. It was found that the diffraction patterns of all samples showed glasses characteristics. The optical band gap, Eopt¬ increased proportionally with the content of Er¬2O3 but Urbach energy, ∆E decreased due to the increasing Er2O3 contents.

Abstract: Series of glass based on (80-x)TeO2-10PbO-10PbCl2-xYb2O3 where 0.0 ≤ x ≤ 3.0 has been successfully prepared by melt quenching technique. The amorphous nature of glass has been determined by X-ray diffraction method. Their corrosion behavior was investigated using the FTIR spectroscopy technique on the sample that has been immersed in distilled water and in aqueous solution of pH 4 and pH 9 for 10 days. There were three major absorption peaks around 3600 cm-1, 889 cm-1 and 470 cm-1 has been observed. The intensity of each peak was found to vary with the Yb3+ content.