Papers by Keyword: Monoclinic

Abstract: In this study, we investigated the impact of high-energy milling on the structural and dielectric properties of Pb[Zr_(1-x)Ti_x ]O₃ [PZT] ceramics synthesized using the solid-state reaction process. The sample was milled for 2, 4 & 6 hours using a high-energy ball milling machine. The unit cell structure for all of the samples was observed to be monoclinic, according to x-ray diffraction measurements (space group: C1m1). A significant reduction in crystallite size was observed, from 132 nm to 46 nm after 6 hours of milling. The dielectric study indicated a classical ferroelectric type behaviour for the un-milled sample and diffused phase transition for all milled samples. However dielectric constant dropped from 940 to 487 after 6 hours of milling.

Abstract: The objective of this research was to prepare multi–phase bismuth vanadate (BiVO₄) powder using the solvothermal method to be used as a photocatalyst. In the preparation step, bismuth nitrate and ammonium vanadate were used as the precursors with a mole ratio of 1:1. The mixed solution was diluted to 0.025 M with acetic acid and heated at 200 °C for 2 h in a Teflon–lined stainless steel autoclave vessel. Multi–phase BiVO₄ was obtained without calcination step. Multi–phase BiVO₄ was characterized by X–ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT–IR), and energy dispersive spectroscopy (EDS). The efficiency of multi–phase BiVO₄ for photocatalytic degradation of the mixed dye of methylene blue (MB) and rhodamine B (RhB) solution under UV light irradiation was studied. The concentration of the mixed dye solution was measured by UV–Vis spectrophotometry (UV–Vis). The effect of concentration of catalyst and pH of solution was studied. The optimum conditions for photocatalytic degradation of mixed dye solution were obtained at 0.8 g/L for concentration of multi–phase BiVO₄ and 7.78 for initial pH of the mixed dye solution.

Abstract: Graphene oxide (GO) powder was synthesized by modified Hummer’s method. Bismuth vanadate (BiVO₄) nanoparticle was synthesized by solvothermal method at 100 and 200°C for 3h. Composite graphene oxide and bismuth vanadate (GO/BiVO₄) nanoparticle were synthesized by mixed oxide method in weight ratio of 0.20:1.00. The physical and chemical properties were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) and surface area analyzer (BET). The photocatalytic degradation of methomyl performance was determined by high performance liquid chromatograph (HPLC). Composite GO/BiVO₄ nanoparticle at 200°C for 3h was the highest photocatalytic degradation of methomyl.

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.

Abstract: Bismuth vanadate (BiVO₄) powder was synthesized by a modified microwave method. Bismuth nitrate pentahydrate, ammonium metavanadate and 2-propanol were used as the starting precursors. The final pH of solution was adjusted to 7 and irradiation power at 600 Watt for 2 and 6 min. The yellow powder was filtered and dried at 100 °C for 24h. The phase of BiVO₄ powder was characterized by X-ray diffractometer (XRD). Multi-phase of monoclinic and tetragonal phase was obtained without calcination step. The morphology of BiVO₄ powder was investigated by scanning electron microscope (SEM). The BiVO₄ powder was irregular in shape and agglomerated with the range particle of 0.1–0.3 μm. The functional group of BiVO₄ powder was investigated by fourier transform infrared spectrometer (FTIR). The wavenumber at 498–502 cm^-1 and 746–762 cm^-1 was corresponding to the vibration of Bi-O bending and VO₄^3- stretching, respectively.

Abstract: We report successful synthesis of baddeleyite type monoclinic zirconium oxide nanocrystals formation. The product mixture of zirconium incubated at room temperature for 7 days were thoroughly investigated employing X-ray diffraction, Raman spectroscopy and transmission electron microscopy studies. XRD and Raman studies revealed the formation of baddeleyite type monoclinic zirconium oxide nanocrystals. TEM studies revealed the nanocrystal formation with size ranging from 100 nm to 200 nm.

Abstract: Bismuth vanadate (BiVO₄) powder was synthesized via the solvothermal method at 100200 °C for 26h by using acetic acid as solvent without calcination steps. The phase transition of BiVO₄ powder was studied by Xray diffraction (XRD). The morphology and chemical composition of BiVO₄ powder were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The functional groups of BiVO₄ powder was identified by Fourier transform infrared spectroscopy (FTIR).

Abstract: The highest piezoelectric and ferroelectric properties of lead zirconate titanate (PZT) occur in vicinity of morphotropic phase boundary (MPB). In MPB, crystalline phase ratios play a crucial role in determining the dielectric properties. In this paper, PZT nanoparticles were synthesized by a modified sol gel procedure and the effects of different solvents of methanol, ethanol, 1-propanol, and acetic acid on tetragonal, rhombohedral, and monoclinic phase ratios near the Pb (Zr_0.53Ti_0.47)O₃ were investigated. The X-ray diffraction results show the formation of almost pure perovskite structure in all samples. The volume fraction of tetragonal and rhombohedral phases, lattice constants, and lattice distortion were measured from the X-ray diffraction and Raman spectroscopic analysis for each solvent. Also, the domain size was compared between the solvents. A trace amount of monoclinic phase could be detected by Raman spectroscopy. The results show that acetic acid is the most appropriate solvent for synthesizing of PZT nanoparticles in which the tetragonal lattice parameters are c_t=4.16 Ǻ and a_t=4.02 Ǻ with a distortion of 3%. The tetragonal volume fraction is estimated about 77%. The particle size and degree of agglomeration were measured according to field emission electron microscopy and indicates that 70 nm particles were formed for acid-based sample.

Abstract: Bismuth-based oxides have attractive photocatalytic properties under visible light. Bismuth vanadate (BiVO4) particles as a visible light-responsive photocatalyst were prepared by a facile hydrothermal reaction method with the different solvent using Bi(NO3)3·5H2O and NH4VO3 as raw materials at 180°C for 18h. The as-prepared samples were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis absorption spectra (UV-vis). The photocatalytic activity of BiVO4 crystals was evaluated using the photocatalytic oxidation of methylene blue (MB) at room temperature under visible light irradiation. It was found that the morphology and the band gap adsorption edge of BiVO4 are different with the different solvent. The widest band gap energy of BiVO4 obtained with ethylene glycol as solvent is 2.405eV. In addition, the BiVO4 powders exhibit a certain photocatalytic properties to photodegrade MB and the maximum photocatalytic degradation rate is 34% using BiVO4 prepared with water as solvent for 2h.

Abstract: Monoclinic BiVO4 photocatalysts were synthesized via facile and straightforward co-precipitation method at room temperature without high temperature treatment and characterized with X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), flourier transfer infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), and transmission electron microscopy (TEM). The results indicate that through proper selection of synthesis conditions, it is possible to obtain high efficient BiVO4 nanoparticles. The as-prepared monoclinic BiVO4 photocatalysts have an average crystallite size of about 20 nm with the particle size of about 20 to 50 nm. Their photocatalytic activities were evaluated by decolorization of rhodamine B in aqueous solution under visible light irradiation, and the relationship between the photocatalytic activity of BiVO4 and their physicochemical properties were investigated.