Preparation Of Zirconia Powders Research Articles

Preparation of zirconia powders by sol–gel route of sodium glycozirconate complex

Zirconia powders were prepared by a sol–gel method, using sodium glycozirconate complex as precursor synthesized via the Oxide One Pot Synthesis (OOPS) process. Gelation of this precursor was achieved through the variation of the hydrolysis ratio without the use of the dopants. The gel samples were also calcined at different temperatures. The resulting zirconia was characterized using X-ray diffraction (XRD), SEM and nitrogen adsorption/desorption. The solid materials obtained after heat treatment at 500 °C by varying the hydrolysis ratio have large surface areas of 154–220 m 2 g −1 and a narrow pore size distribution in the mesopore region. By variation of the heat treatment, the zirconia xerogels existed in either an amorphous, tetragonal, or monoclinic form at room temperature. Based on XRD data the first identifiable crystalline structure developed from the amorphous phase was the tetragonal polymorph, which was formed between 500 and 800 °C. When the temperature was raised to 1000 °C, zirconia powder with a monoclinic structure was obtained. Surface areas about 280 m 2 g −1 was obtained after calcination at 400 °C, which drop to ca. 70 m 2 g −1 following treatment at 1000 °C.

Influence of synthesis conditions on the preparation of zirconia powder by the glycothermal method

Nanocrystalline zirconia powders have been prepared by the reaction of zirconium n-propoxide in 1,4-butanediol and 1,5-pentanediol at 300 °C for 2 h. The influences of concentration of zirconium n-propoxide in the solution and drying condition on primary and secondary particle size, and pore system of the powders were investigated. When 1,4-butanediol was used, increasing the concentration of zirconium n-propoxide increased the primary and secondary particle size and BET surface area while the physical properties of zirconia prepared in 1,5-pentanediol were not affected by such factors. To investigate the effect of drying method, glycol was removed from the autoclave at reaction temperature instead of by the conventional process in which the product is washed in methanol and air-dried. This change improved the pore system of powders prepared in 1,5-pentanediol, probably through the reduction of coagulation among the ultrafine particles during the drying process.

Study on a new, environmentally benign method and its feasibility of preparing nanometer zirconia powder

In this paper, a new method to prepare nanometer zirconia is described, and the mechanism is discussed briefly. It is proposed that the coordinated water of zirconium oxychloride acts as a microzone actuating medium in the preparation of zirconia powder. The method was realized by agitating a solid mixture of sodium hydroxide and zirconium oxychloride, whose intermediate and final products were studied by X-ray fluorescence analysis (XRF), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). It was found that the nuclei of zirconia were formed under the superalkaline condition and polycrystallized at 400°C. The experiments showed that the powder obtained was tetragonal/cubic zirconia, with narrow particle size distribution (average size about 7 nm), and contained and less than a trace (<10 ppm) of chlorion. The by-product of the new process can be recycled as chemical raw material after simple treatment. Compared with traditional methods, the new method is environmently benign, with low energy consumption, convenient manipulation, easy source recycling, and low pollution.

The acidic/basic effects on preparation of zirconia powders from molten salts

Influences of the acidity/basicity on the phase composition and the crystallite size of zirconia powders prepared in the NaNO3/KNO3 system was investigated by adding Lux-Flood bases (NaNO2/KNO2, Na2O2 and Na2CO3) to the system. It was found that the reaction occurred at lower temperatures in the system containing bases than in the pure NaNO3/KNO3 system. The phase composition of the tetragonal zirconia yielded varies with the concentration of the bases contained in the NaNO3/KNO3 melt. When the base concentration is above a certain value, 100% tetragonal phase can be produced. The crystallite size of the tetragonal phase decreases with increasing base concentration, i.e. basicity, in the melt. The crystallite size, was found to decrease in the order of added bases in the molten NaNO3/KNO3 system: Na2O2>Na2CO3>NaNO2/KNO2. The strength of the basicity of the commonly used molten nitrate and nitrite systems was found to decrease in the order: NaNO2/KNO2>LiNO3/KNO3>NaNO3/KNO3 and NaNO3. It appears that the acidity/basicity of a melt plays a very important role in the phase composition and crystallite size during the precipitation of zirconia from molten salts.

Preparation of zirconia powders from molten nitrites and nitrates

Finely dispersed ZrO2 powders with high purity have been prepared by the reactions of Zr(SO4)2 in molten nitrites and nitrates. The effects of the starting materials of α-Zr(SO4)2 and β-Zr(SO4)2, the different nitrate and nitrite melts, and reaction conditions such as temperature and time, on the structure and crystallite size of the ZrO2 powders produced were investigated. The processing of the prepared powders was also studied under different conditions; the results showed that very fine ZrO2 powders with soft agglomeration could be produced if the proper treatment of the powders was applied.

Development of Zirconia Based Transformation Toughened Ceramics

An account is given of the R & D activity at Bhabha Atomic Research Centre on transformation toughened zirconia ceramics. Special reference is made to the preparation of zirconia powders by the hydrothermal route. The details of compaction of powders obtained by hydrothermal and co-precipitation routes and their sintering behaviour in presence of stabilizing agents and other additives are described. The results on densification behaviour and observed microstructures of the ceramics are discussed at length. Thermal, mechanical and electrical properties of the ceramics are evaluated and some possible applications are suggested.

Preparation of zirconia powder by the pyrolysis of active carbon

Etude de la preparation des poudres d'oxyde de zirconium par impregnation du charbon actif par du zirconium puis par pyrolyse a 550°C dans l'air

44. Waxes, lubricants, cements, lacquers, paints, oils

In this paper, a new method to prepare nanometer zirconia is described, and the mechanism is discussed briefly. It is proposed that the coordinated water of zirconium oxychloride acts as a microzone actuating medium in the preparation of zirconia powder. The method was realized by agitating a solid mixture of sodium hydroxide and zirconium oxychloride, whose intermediate and final products were studied by X-ray fluorescence analysis (XRF), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). It was found that the nuclei of zirconia were formed under the superalkaline condition and polycrystallized at 400°C. The experiments showed that the powder obtained was tetragonal/cubic zirconia, with narrow particle size distribution (average size about 7 nm), and contained and less than a trace (<10 ppm) of chlorion. The by-product of the new process can be recycled as chemical raw material after simple treatment. Compared with traditional methods, the new method is environmently benign, with low energy consumption, convenient manipulation, easy source recycling, and low pollution.