Khaidzir Hamzah

Prediction of terrestrial gamma dose rate based on geological formations and soil types in the Johor State, Malaysia

This study aims to predict and estimate unmeasured terrestrial gamma dose rate (TGDR) using statistical analysis methods to derive a model from the actual measurement based on geological formation and soil type. The measurements of TGDR were conducted in the state of Johor with a total of 3873 measured points which covered all geological formations, soil types and districts. The measurements were taken 1 m above the soil surface using NaI [Ti] detector. The measured gamma dose rates ranged from 9 nGy h(-1) to 1237 nGy h(-1) with a mean value of 151 nGy h(-1). The data have been normalized to fit a normal distribution. Tests of significance were conducted among all geological formations and soil types, using the unbalanced one way ANOVA. The results indicated strong significant differences due to the different geological formations and soil types present in Johor State. Pearson Correlation was used to measure the relations between gamma dose rate based on geological formation and soil type (D(G,S)) with the gamma dose rate based on geological formation (D(G)) or soil type (D(s)). A very good correlation was found between D(G,S) and D(G) or D(G,S) and D(s). A total of 118 pairs of geological formations and soil types were used to derive the statistical contribution of geological formations and soil types to gamma dose rates. The contribution of the gamma dose rate from geological formation and soil type were found to be 0.594 and 0.399, respectively. The null hypotheses were accepted for 83% of examined data, therefore, the model could be used to predict gamma dose rates based on geological formation and soil type information.

Optical Absorption of Er3+/Nd3+ Co-Doped Tellurite Glass

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.

Luminescence Enhancement of Samarium-Doped Tellurite Glass Containing Silver Nanoparticles

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.

Chemical durability of Yb doped lead tellurite glass: Effect of solution pH

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.

Luminescence Properties of Magnesium Phosphate Glass Doped Samarium

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.

VHF-PECVD FABRICATION PARAMETERS DEPENDENT MORPHOLOGYVARIATION OF GOLD CATALYST ASSISTED SILICON THIN FILM GROWTH

Achieving two dimensional quantum structure of silicon with well-defined tunable morphology is an outstanding issue. We present the preliminary results on fabrication parameters dependent silicon thin film production using VHF-PECVD method. Five samples are prepared on Si(100) substrate with gold (Au) catalyst by adjusting different parameters such as deposition time, temperature and the flow of precursor gas. The samples morphology are analyzed using FESEM. The results reveal that the silicon thin film appear to be smooth and more uniform after an enormous amount of hydrogen is inserted together with the precursor gas (silane) during the deposition process. More interestingly, the films exhibit silicon nanowires as the deposition time is increased up to 1 hour. This morphological transformation is attributed to the vapor-liquid-solid (VLS) mechanism related to the deposition process.

Study of Crystallization Kinetics of TeO2-Na2O-MgO Glass Using Ozawa Method: Influence of Europium

. 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.