A novel method for synthesis of metastable tetragonal zirconia nano powder at low temperatures (original) (raw)
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A NOVEL METHOD FOR SYNTHESIS OF METASTABLE TETRAGONAL ZIRCONIA NANOPOWDERS AT LOW TEMPERATURES
Zirconia (ZrO 2 ) nanopowder was synthesized using sucrose and fructose as a chelating agent from zirconium hydroxide. The synthesized powders were characterized by X-ray diffraction (XRD), simultaneously thermal analysis (STA), BET surface area, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The above-experimental results showed that the synthesized powders had particle sizes in the range 40-60 nm and mean crystallite sizes of 7-8 nm. Finally, in this research, chelating agents of sucrose and fructose were compared and the obtained results demonstrated that using fructose, nanopowder of zirconia with tetragonal phase was obtained.
Journal of the Australian Ceramic Society, 2018
The metastable tetragonal zirconia is an interesting material exhibiting a high surface area and photoluminescence properties. The present work studies the characteristics of the metastable tetragonal zirconia nanoparticles that were successfully prepared from local zircon without using a template by a modified sodium carbonate sintering method, followed by leaching, slow hydrolysis, and calcination at a low temperature. Zircon and alkaline were combined at a mole ratio of 1:2 and sintered at 1000°C. The sintered material was washed with water to dissolve the silica and followed by leaching with sulfuric acid at pH 1-2 to dissolve the zirconia then followed by slow hydrolysis until pH 9 to precipitate zirconium hydroxide. The final product was evaluated including thermal behavior, phase transformation, chemical composition, infrared spectra, microstructure, and textural properties. Crystallization of zirconia occurred at 564.29°C. Good crystallinity of the zirconia phase was obtained at 800°C consisting of 80% tetragonal zirconia with a crystal size of 11 nm corresponding to its crystal plane of (101) and 20% monoclinic zirconia. At this temperature, zirconia attains 83.19% in purity, shows typical infrared spectrum, and consists of particles less than 40 nm in sizes that agglomerate, belongs to a mesoporous material exhibiting a high surface area of 46.990 m 2 /g. Increase in calcination temperature at 1050°C transformed the tetragonal phase to the monoclinic phase of zirconia. Overall, the present work reveals a promising template-free method on the preparation of the metastable tetragonal zirconia nanoparticles from local zircon.
2007
The present work deals with the synthesis and enhancement of metastable tetragonal zirconia nanocrystals through novel chemical routes. Nanocrystalline t-ZrO2 is a technologically significant material that finds extensive use as catalyst or catalyst support, oxygen sensor and structural components. In this work, ZrO2 nanoparticles are synthesized using both reduction and hydrolysis techniques. These techniques are known to result in the production of nanocrystalline materials. Also, promote the stabilization of t-phase of ZrO2 at the nano level at moderate temperature, which is one of the primary objective of this work. For reduction technique, the Zr-salts are reduced by the addition of strong (Sodium borohydride, NaBH4) and weak (Hydrazine hydrate, N2H5OH) reducing agents. However for hydrolysis technique, Zr-salts are hydrolyzed by adding ammonium hydroxide (NH4OH). In this process, geletion and precipitation occurred at low and high pH respectively with the addition of these age...
Bulletin of Materials Science, 1998
Powders of tetragonal (t)ZrO 2 have been prepared by a solid state reaction between sodium metazirconate and sodium metaphosphate. The reaction temperatures and times have been varied between 450 and 550°C and 5 and 75 h, respectively. Zirconia powder, mostly in the t and t" phases, is obtained. The yield of ZrO 2 powder increases monotonically with time at all reaction temperatures according to a phase boundary controlled kinetics. The fraction of t phase also increases with time at 450°C and 500°C but goes through a maximum at 550°C, the highest temperature employed. A maximum of 55% of the precursor monoclinic zirconia (used to prepare sodium meta zirconate) is converted to t phase at 500°C/75 h. The ZrO z powder consists of crystallites of size 9-25 nm agglomerated into particles having average size between 2 and 4/zm. The agglomerates have a breaking strength of 100 MPa. A hydrothermal treatment is found to break the agglomerates into smaller sizes. Grinding the powder in a mortar and pestle converts only 12% of the t phase into monoclinic, indicating that substantial fraction of the tetragonal phase is the non transformable variety t'. Heating experiments also confirm this.
Synthesis of nanocrystalline tetragonal zirconia by a polymeric organometallic method
Applied Organometallic Chemistry, 1999
A polymeric precursor method based on the Pechini process was successfully used to synthesize zirconia-12 mol% ceria ceramic powders. The influence of the main process variables (citric acid-ethylene glycol ratio, citric acidtotal oxides ratio and calcination temperature) on phase formation and powder morphology (surface area and crystallite size) were investigated. The thermal decomposition behavior of the precursor is presented. X-ray diffraction (XRD) patterns of powders revealed a crystalline tetragonal zirconia single-phase, with crystallite diameter ranging from 6 to 15 nm. The BET surface areas were relatively high, reaching 95 m 2 g À1 . Nitrogen adsorption/desorption on the powders suggested that nonaggregated powders could be attained, depending on the synthesis conditions.
The purpose of this paper was to investigate the correlation between thermal treatment and tetragonal/monoclinic nanostructured zirconia powders obtained by sol-gel process. The originality of this work is in the evaluation of the temperature influence on the preparation of nanostructured zirconia powders. The structure of the zirconia produced is amorphous when the samples are heated below 400 °C. The zirconia powders were prepared using zirconium n-propoxide diluted in n-propanol under stirring and refluxed under controlled temperature at pH=5. The resulting gel was air-dried and annealed under air atmosphere at temperatures up to 800 °C for 12 h. The zirconia powders were characterized by means of differential thermal analysis, thermogravimetric analysis, X-ray diffraction, size distribution by laser diffraction, Fourier transform infrared spectroscopy, and scanning and transmission electron microscopy. Crystallite size was calculated by single-line technique using the mathematical function Pearson VII. The presence of the tetragonal phase was observed at a temperature higher than 400 °C. The monoclinic phase was formed at 600 °C, which resulted in a lowering of the content of tetragonal phase. At 800 °C, the particle showed D 50 =11.54 µm. The crystallite size was calculated using X-ray diffraction-single line and measured by TEM, both approximately 30 nm.
International Journal of NanoScience and Nanotechnology, 2012
In this study, isophthalic acid-zirconium(IV) nanocomposite has been prepared from zirconyl nitrate pentahydrate and potassium iodide, with isophthalic acid, (C 8 H 6 O 4 =Benzene-1,3-dicarboxylic acid) as a ligand, via sonochemical method in ethylene glycol and methanol as solvents. The crystalline tetragonal ZrO 2 has been produced by thermal decomposition of isophthalic acid-zirconium(IV) nanocomposite as precursor. Characterization of nanocomposite was carried out using element analysis, Fourier transfer infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA) techniques. The results demonstrated that, pure zirconia with particle size of about 49 nm was obtained in which methanol has been used as solvent during the reaction, particle sizes was significantly reduced to about 20 nm, when ethylene glycol used as solvent during formation of the nanocomposite isophthalic acid-zirconium (IV) as precursor.
Tetragonal zirconia powders from the zirconium n-propoxide-acetylacetone-water-isopropanol system
Journal of Non-Crystalline Solids, 1992
As a part of a work concerning densification and toughening of silicate ceramic products, this paper describes the preliminary characterization of a zirconia precursor fabricated through a sol-gel route in the zirconium n-propoxideacetylacetone-water-isopropanol system. When the molar ratio R =[acac]/[Zr] increases from R = 0 to R = 0.8, the precursor changes from a colloidal precipitate to a polymeric gel with an increasing gelation time. Drying and firing the precipitates leads to the monoclinic stable form of zirconia while the first crystalline phase obtained beyond 500°C from the gel is the metastable tetragonal one. Successive steps of the reactions are investigated by small angle X-ray scattering, differential thermal analysis, thermogravimetry and X-ray diffraction.
Glycothermal synthesis of nanocrystalline ZrO2 powders at low temperature without mineralizers
Journal of the Ceramic Society of Japan, 2012
Zirconia (ZrO 2) nanoparticles were synthesized at temperature as low as 200°C through a glycothermal reaction using amorphous zirconium hydrous gel precursors and 1,4-butanediol as solvent, XRD and TEM data support that glycothermal processing method provides a simple low temperature route for producing highly crystallized ZrO 2 nanoparticles without mineralizers, which could also be extended to other systems. XRD results also showed that ZrO 2 nanoparticles synthesized in glycothermal condition had tetragonal phase with small portion of monoclinic phase, where the tetragonality was confirmed by Raman spectroscopy. The as-prepared ZrO 2 nanoparticles have spherical morphology with an average crystal size of 1015 nm and agglomerated into bigger spheres with a diameter of about 100 nm. The tetragonal phase begins to transform to monoclinic phase at 600°C when the calcinations of the as-synthesized powder was carried out.
Comparative study of nanocrystalline zirconia prepared by precipitation and sol–gel methods
Catalysis Today, 2001
The crystalline properties of zirconia synthesized by the precipitation and sol-gel methods were comparatively studied. Samples were characterized with thermoanalysis and X-ray powder diffraction techniques. The tetragonal and monoclinic crystalline structures of zirconia were refined with the Rietveld technique, which provided the quantitative information concerning the lattice cell parameters, phase concentrations, average crystallite sizes and the concentrations of the cationic and anionic vacancies. Both synthesis methods gave rise to nanocrystalline zirconia. The samples calcined at 800 • C and prepared by the precipitation had average crystallite sizes less than 18 nm, which were two times smaller than the corresponding values obtained in the sol-gel samples. Both tetragonal and monoclinic nanocrystalline phases had atomic defects in concentrations that depended on the synthesis method and annealing temperature.