Papers by Keyword: Zircon

Abstract: The structures of sodium zirconate were studied in this research, which formed after the alkali fusion process. In this process, zircon is decomposed using sodium hydroxide (NaOH) at high temperatures to separate zirconium from impurities, resulting in high-purity zirconia which has potential as a dental material. The study aims to control the formation of Na₂ZrO₃ phase and to minimize the reactions between Zircon, NaOH, and crucible materials, such as porcelain, silicon carbide (SiC), and alumina to prevent contamination. To enhance reaction efficiency, a pre-treatment process was introduced, including wet milling and NaOH leaching. Then, the pre-treated zircon sand was reacted with NaOH in a 1 ZrSiO₄ : 6 NaOH molar ratio. Results showed color changes in the crucibles, indicating interactions between crucible materials and NaOH. But there is no change observed in alumina crucible which means that it is not reacted with either NaOH or ZrSiO₄. Different pre-treatment and crucible materials influenced the crystal size of Na₂ZrO₃ phase which give the lowest crystal size of 24.69 nm when using porcelain crucible. After the recovery process was finished high-purity full tetragonal zirconia phase is achieved which can be further processed as a artificial dental application. In artificial tooth application, pure zirconia with high strength is needed, thus controlling crystal and grain sizes is a crucial factor which affect the properties.

Abstract: The potential of zircon minerals in Indonesia as valuable adsorbent materials has not been properly developed. Seeing its high potential as an excellent adsorbent for anions/cations in water treatment and industrial wastewater, the raw zircon minerals into zircon oxides which will later be composited with magnetic nanoparticles using one-pot solvothermal processes (Fe₃O₄@ZrO₂). Cadmium is one of the most substances heavy metals toxic at lower concentrations. It is used in many industries, including textiles, paint, and dyes. In drinking water and industrial wastewater, the permissible concentration has been set the concentration level at 0.003 mg/L by the World Health Organization.The adsorbent characterizations of SEM and XRF analysis showed that the Fe₃O₄@ZrO₂ had many different chemical composition and a possibility of high specific surface area due to the nanosize particle for adsorption processes. The Fe₃O₄@ZrO₂ showed high adsorption uptake capacity and selectivity for the cadmium in the aqueous solution. The highest cadmium adsorption capacity was achieved (24.85 mg/g) at pH 6 using the Fe₃O₄@ZrO₂ as adsorbent. The removal efficiency of the Fe₃O₄@ZrO₂ for Cd remains almost 80% after three cycles. Therefore, the Fe₃O₄@ZrO₂ has the potential to be used as an adsorbent in water and wastewater treatment.

Abstract: Zircon (ZrSiO₄) is one of Indonesia's most abundant mineral reserves that have yet to be fully utilized since zircon mine production in Indonesia is only 110.000 tons/year while Australia produces zircon up to 500.000 tons/year. Indonesia has 167 million tons of zircon sand reserves, especially in West Kalimantan. One of the most efficient methods of zircon sand processing in terms of energy use and environmental pollution is the alkali fusion of NaOH. This study used zircon sand with NaOH, a stoichiometric ratio of 1:4 (excess 1.5), to be roasted in a muffle furnace at 600°C for 120 min. The following process is washing the frit with water, and the frit is dissolved with aquades with ratio frit: H₂O=1g:10 ml at 30°C and stirring 300 rpm for 60 min. The frit leaching solution is filtered to obtain Na₂ZrO₃. The water-wash product is leached using HNO₃ as the leaching agent with the ratio of water-wash product: HNO₃=1:5, the acid concentration is 6 M, at 90°C, agitation use 260 rpm with the variation of time 60, 120, 180, 240, and 300 minutes. The pregnant leach solution is deposited with NH₄OH and calcinated. According to the results of this experiment, the optimum time to obtain high Zr extraction is 240 minutes. This research produced single-phase zirconia with a cubic crystal structure containing 91.23% ZrO₂ and 1.18% SiO₂.

Abstract: Refractory coating is widely used in metal casting process to protect the mold from direct contact with molten metal. This coating also could improve the surface quality of casting product. Zircon is common materials that used as filler, but the materials cost is quite high. Therefore, alternative material is needed to make partial substitution of the filler. Silica Fused can be considered as filler because it has good refractoriness. This study aims to determine silica fused is reliable as an alternative to substitute zircon filler. The samples were made with 16%, 18%, and 20% silica fused addition and different treatment which were heated and non-heated drying. Particle size and distributions of the filler were analyzed using Particle Size Analysis. Viscosity measurement has been done to coating slurry to analyze the rheological characteristics of the slurry. The surface morphology of dried coating was taken using Scanning Electron Microscope. XRD test also has been done to analyse the compound. The quality of coating was determined from the thermal stability of the coating that was analyzed using Simultaneous Thermal Analysis. The result shows that silica fused is reliable as an alternative material for filler partial substitution.

Abstract: Zirconia (ZrO₂) is one of the refractory ceramic materials that have applications in several fields. The aim of this study was to synthesis ZrO₂ from natural zircon sand collected from Kereng Pangi, Central Kalimantan with a variation of pH deposition using alkali fusion co-precipitation method. The synthesized ZrO₂ began with the preparation process involved magnetic separation, milling, and leaching with HCl. Furthermore, the alkali fusion process was used KOH solution and heated in an electrical furnace at 700°C for 3 h whereas the co-precipitation process was carried out using a filtrate mixed with the NH₄OH solution to reach a pH variation between 3–11 and then precipitated for 12 h. The precipitates were dried in an oven and then calcined at 800°C for 3 h. The structure of synthesized ZrO₂ was characterized using XRD and the particle sizes were measured using particle size analyzer (PSA). The XRD analysis showed that the identified phase of zirconia powder is tetragonal with a crystal size in nanometer size. Result of PSA measurement revealed that the crystal size decreased in the range pH of 3 - 7, but increased in the range pH of 7 - 11. The biggest powder particle size could be achieved at 260 nm with pH 7 whereas the smallest size was at 143 nm occurred at pH 3.

Abstract: ZrB₂-ZrC composite powders were synthesized from zircon sand by self-propagating high-temperature synthesis (SHS). The reactions were verified and the feasibility of obtaining the predicted products was calculated from the adiabatic temperature (T_ad) and the equilibrium composition using the HSC^® chemistry program. The results show that the SHS products consisted of ZrB₂, ZrC, ZrO₂, ZrSiO₄, MgO, and Mg₂SiO₄. Leaching the products with 0.5 M of HCl solution eliminated the by-product of MgO and the intermediate Mg₂SiO₄ phases. The phase composition of the products was characterized by X-ray diffraction (XRD) and the morphologies were characterized by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray (EDX).

Abstract: Zircon samples from Ubon Ratchathani, Thailand; Rattanakiri, Cambodia and Dak Nong, Vietnam change their color from light brown and reddish-brown to blue color after thermal enhancement at 1000 ^๐C in reducing condition for 60 min. The high temperature is one of the factors for the zircon structure to recrystallize. The objective of this study is to describe the crystal structure of zircon samples before and after thermal enhancement. Zircon is a metamict mineral whose structure is destroyed by some trace elements. There are radioactive elements such as U and Th in the zircon structure. In this study, Raman spectroscopy was used to analyze the molecular vibration in zircon structure before and after thermal enhancement. As a result, the Raman spectra of zircon samples after thermal enhancement show the Raman shift at peak position of V₃(SiO₄) stretching around 1008cm^-1 to higher wavenumber concerning to the full width at half maximum (FWHM) values calculated by PyMCA software. The results could be summarized that the metamict zircon will be recrystallized to the crystalline zircon after thermal enhancement. The advantage of this study is about the identification of zircon before and after thermal enhancement.

Abstract: In this work, chamotte with dispersions of up to 30wt% zircon is sintered at 1500 °C to investigate the effect of zircon content on the microstructure and physical properties of chamotte refractories. The microstructure and physical properties of samples are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), three-point bending and dilatometer. The result shows that the main phases of chamotte with and without sintering at 1500 °C are mullite and cristobalite, the addition of zircon has no impact on the main phase compositions of chamotte matrix. For the sintered samples, zircon grains are wrapped with glass and no obvious bonding are detected between the interface of zircon and mullite grains. Increasing zircon content leads to the increase in bulk density and has a negative effect on the flexural strength, besides, linear thermal expansion ratio decreases as the zircon content increases.

Abstract: Zircon whiskers were synthesized via non-hydrolytic sol-gel process combined with molten salt method by using anhydrous zirconium tetrachloride as zirconium source, TEOS as silicon source, anhydrous ethanol as solvent, and sodium molybdate as molten salt. The effects of heat treatment mode and cooling rate on the synthesis of zircon whiskers have been studied by means of XRD, FE-SEM, TG and TEM. The results indicate that well-developed whiskers can be prepared through heat treating the sample at 850°C for 3 h followed by a furnace cooling process. The zircon whiskers which were fabricated by this heat treatment mode grew along the [001] direction and showed diameter of 50~100 nm and aspect ratio of 20~30.

Abstract: The high temperature phase transition of zirconia produced from commercial zirconyl chloride chemical was compared with that produced from a Malaysian zircon mineral. Zirconyl chloride was produced from zircon by using the hydrothermal fusion method. Initial XRD diffractogram of these samples at room temperature show that they are of amorphous structure. High temperature XRD studies was then performed on these samples; heated up to 1500°C. The XRD diffractograms shows that the crystalline structure of tetragonal zirconia was first observed and the monoclinic zirconia becomes more visible at higher heating temperature.