Mohd Hafiz Mohd Zaid

Phase Transformations of α-Alumina Made from Waste Aluminum via a Precipitation Technique

We report on a recycling project in which α-Al2O3 was produced from aluminum cans because no such work has been reported in literature. Heated aluminum cans were mixed with 8.0 M of H2SO4 solution to form an Al2(SO4)3 solution. The Al2(SO4)3 salt was contained in a white semi-liquid solution with excess H2SO4; some unreacted aluminum pieces were also present. The solution was filtered and mixed with ethanol in a ratio of 2:3, to form a white solid of Al2(SO4)3·18H2O. The Al2(SO4)3·18H2O was calcined in an electrical furnace for 3 h at temperatures of 400–1400 °C. The heating and cooling rates were 10 °C/min. XRD was used to investigate the phase changes at different temperatures and XRF was used to determine the elemental composition in the alumina produced. A series of different alumina compositions, made by repeated dehydration and desulfonation of the Al2(SO4)3·18H2O, is reported. All transitional alumina phases produced at low temperatures were converted to α-Al2O3 at high temperatures. The X-ray diffraction results indicated that the α-Al2O3 phase was realized when the calcination temperature was at 1200 °C or higher.

Effect of ZnO on the Physical Properties and Optical Band Gap of Soda Lime Silicate Glass

This manuscript reports on the physical properties and optical band gap of five samples of soda lime silicate (SLS) glass combined with zinc oxide (ZnO) that were prepared by a melting and quenching process. To understand the role of ZnO in this glass structure, the density, molar volume and optical band gaps were investigated. The density and absorption spectra in the Ultra-Violet-Visible (UV-Visible) region were recorded at room temperature. The results show that the densities of the glass samples increased as the ZnO weight percentage increased. The molar volume of the glasses shows the same trend as the density: the molar volume increased as the ZnO content increased. The optical band gaps were calculated from the absorption edge, and it was found that the optical band gap decreased from 3.20 to 2.32 eV as the ZnO concentration increased.

Fabrication and Crystallization of ZnO-SLS Glass Derived Willemite Glass-Ceramics as a Potential Material for Optics Applications

Willemite glass-ceramics were successfully derived from conventional melt-quench ZnO-SLS precursor glass by an isothermal heat treatment process. The effect of heat treatment temperatures on the physical properties was investigated by Archimedes principle and linear shrinkage. The generation of willemite crystal phase and morphology with increase in heat treatment temperature was examined by X-ray diffraction (XRD), Fourier transform infrared (FTIR), and field emission scanning electron microscopy (FESEM) techniques. X-ray diffraction revealed that the metastable -Zn2SiO4 and thermodynamically stable zinc orthosilicate α-Zn2SiO4 phases can be observed at temperatures above 700°C. The experimental results indicated that the density and shrinkage of the glass-ceramic vary with increasing the sintering temperature. FTIR studies showed that the structure of glass-ceramic consists of SiO2 and ZnO4 units and exhibits the structural evolution of willemite glass-ceramics. The characteristic of strong vibrational bands can be related to the tetrahedron corresponding to reference spectra of willemite.

The Effect of Remelting on the Physical Properties of Borotellurite Glass Doped with Manganese

A systematic set of borotellurite glasses doped with manganese (1–x) [(B2O3)0.3(TeO2)0.7]-xMnO, with x = 0.1, 0.2, 0.3 and 0.4 mol%, were successfully synthesized by using a conventional melt and quench-casting technique. In this study, the remelting effect of the glass samples on their microstructure was investigated through density measurement and FT-IR spectra and evaluated by XRD techniques. Initial experimental results from XRD evaluation show that there are two distinct phases of glassy and crystallite microstructure due to the existence of peaks in the sample. The different physical behaviors of the studied glasses were closely related to the concentration of manganese in each phase. FTIR spectra revealed that the addition of manganese oxide contributes the transformation of TeO4 trigonal bipyramids with bridging oxygen (BO) to TeO3 trigonal pyramids with non-bridging oxygen (NBO).

Effect of Sintering Temperature on Structural and Morphological Properties of Europium (III) Oxide Doped Willemite

Willemite- (Zn2SiO4-) based glass ceramics doped with various amounts of europium oxide (Eu2O3) were prepared by solid state melting and quenching method. Effect of sintering temperature (600–1000°C) on structural and morphological properties of the doped samples was investigated. Phase composition, phase evolution, functional groups, and microstructure analysis were, respectively, characterized using X-ray diffractometer (XRD), fourier transform infrared spectroscopy, field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray. XRD analysis detected the presence of rhombohedral crystalline phase in the doped samples sintered at different temperatures. FE-SEM and bulk density results confirmed that doping of the willemite with Eu2O3 effectively enhanced densification. The microstructural analysis of the doped samples showed that the average grain size increased with the increase of sintering temperature.

Effect of temperature treatment on the optical characterization of ZnO-Bi2O3-TiO2 varistor ceramics

The optical band-gap energy ( Eg) is an important feature of semiconductors which determines their applications in optoelectronics. So, it is necessary to investigate the electronic states of ceramic ZnO and effect of doped impurities at different processing conditions. Eg of the ceramic ZnO + xBi 2O3 + xTiO 2 where x = 0.5 mol%, was determined using UV-Vis spectrophotometer. The samples was prepared using solid-state route and sintered at the sintering temperatures from 1140 to 1260°C for 45 min in open air. Eg was decreased with increase of sintering temperature. XRD analysis indicates that there is hexagonal ZnO and few small peaks of inter granular layers of secondary phases, namely, Bi 4Ti 3O12 and Zn 2Ti 3O8. The relative density of the sintered ceramics decreased and the average grain size increased with the increase of sintering temperature. The variation of sintering temperatures and XRD findings are correlated with the UV-Vis spectrophotometer results of ZnO doped with 0.5 mol% of Bi 2O3 and TiO 2 due to the formation of interface states at all sintering temperatures.

Investigation on Structural and Optical Properties of Willemite Doped Mn2

Mn-doped willemite (Zn2SiO4:Mn2+) glass-ceramics derived from ZnO-SLS glass system were prepared by a conventional melt-quenching technique followed by a controlled crystallization step employing the heat treatment process. Soda lime silica (SLS) glass waste, ZnO, and MnO were used as sources of silicon, zinc, and manganese, respectively. The obtained glass-ceramic samples were characterized using the X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared (FTIR), UV-Visible (UV-Vis), and photoluminescence (PL) spectroscopy. The results of XRD revealed that ZnO crystal and willemite (β-Zn2SiO4) were presented as major embedded crystalline phases. This observation was consistent with the result of FESEM which showed the presence of irregularity in shape and size of willemite crystallites. FTIR spectroscopy exhibits the structural evolution of willemite based glass-ceramics. The optical band gap shows a decreasing trend as the Mn-doping content increased. Photoluminescent technique was applied to characterize the role of Mn2+ ions when entering the willemite glass-ceramic structure. By measuring the excitation and emission spectra, the main emission peak of the glass-ceramic samples located at a wavelength of 585 nm after subjecting to 260 nm excitations. The following results indicate that the obtained glass-ceramics can be applied as phosphor materials.

Studying the Effect of ZnO on Physical and Elastic Properties of (ZnO)x(P2O5)1−x Glasses Using Nondestructive Ultrasonic Method

Binary zinc phosphate glass system with composition of (ZnO)x(P2O5)1−x, ( = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mol%) was successfully prepared using a conventional melt-quenching method. Composition dependence of physical properties and elastic properties in the (ZnO)x(P2O5)1−x were discussed in association with the effects of adding zinc oxide (ZnO) as a modifier. The addition of ZnO modifier was expected to produce substantial changes on physical properties of the phosphate glasses. An increase in density values of the phosphate glasses was observed. Elastic moduli were studied by measuring ultrasonic longitudinal and shear velocities ( and ) of the glasses at room. Longitudinal modulus, shear modulus, bulk modulus, Young’s modulus, Poisson’s ratio, and Debye temperature were derived from both data of velocities and respective density of all of the samples. Findings from present work showed dependence of density and elastic moduli of each ZnO-P2O5 series on glass composition.

Manganese modified structural and optical properties of zinc soda lime silica glasses.

A series of MnO-doped zinc soda lime silica glass systems was prepared by a conventional melt and quenching technique. In this study, the x-ray diffraction analysis was applied to confirm the amorphous nature of the glasses. Fourier transform infrared spectroscopy shows the glass network consists of MnO4, SiO4, and ZnO4 units as basic structural units. The glass samples under field emission scanning electron microscopy observation demonstrated irregularity in shape and size with glassy phase-like structure. The optical absorption studies revealed that the optical bandgap (Eopt) values decrease with an increase of MnO content. Through the results of various measurements, the doping of MnO in the glass matrix had effects on the performance of the glasses and significantly improved the properties of the glass sample as a potential host for phosphor material.

Effects of Calcination Holding Time on Properties of Wide Band Gap Willemite Semiconductor Nanoparticles by the Polymer Thermal Treatment Method

Willemite is a wide band gap semiconductor used in modern day technology for optoelectronics application. In this study, a new simple technique with less energy consumption is proposed. Willemite nanoparticles (NPs) were produced via a water–based solution consisting of a metallic precursor, polyvinylpyrrolidone (PVP), and underwent a calcination process at 900 °C for several holding times between 1–4 h. The FT–IR and Raman spectra indicated the presence of metal oxide bands as well as the effective removal of PVP. The degree of the crystallization and formation of the NPs were determined by XRD. The mean crystallite size of the NPs was between 18.23–27.40 nm. The morphology, particle shape and size distribution were viewed with HR-TEM and FESEM analysis. The willemite NPs aggregate from the smaller to larger particles with an increase in calcination holding time from 1–4 h with the sizes ranging between 19.74–29.71 nm. The energy values obtained from the experimental band gap decreased with increasing the holding time over the range of 5.39 eV at 1 h to at 5.27 at 4 h. These values match well with band gap obtained from the Mott and Davis model for direct transition. The findings in this study are very promising and can justify the use of these novel materials as a potential candidate for green luminescent optoelectronic applications.