Preparation of small particle stabilized zirconia by aerosol pyrolysis
- PDF / 372,008 Bytes
- 3 Pages / 593.28 x 841.68 pts Page_size
- 64 Downloads / 256 Views
(Received 15 November 1989; accepted 21 December 1989) Yttria stabilized zirconia powder was synthesized by aerosol pyrolysis of an Y-Zr-nitrate solution. The particles were spherical and had a narrow size distribution, peaking at 0.4 /xm. Material made by this process is phase-pure (cubic) and has high chemical purity.
the respective oxides. The solution contained 0.02 mol/1 Zr and 0.004 mol/1 Y consistent with the composition of the desired product, viz., ZrO2-10 mol% Y2O3 or ZrY0.2O23. The aerosol reaction system is schematically illustrated in Fig. 1. It includes a modified DeVilbis (DeVilbis, Somerset, PA 15501-0635) ULTRA-NEB99™ ultrasonic humidifier for generating the aerosol, a multiple pass quartz reactor for converting the solution droplets into oxide particles, and a heated microfilter assembly for collecting the product. The solution was dispersed at a rate of 1.2 cm3/min in an oxygen carrier flow of 4 1/min and passed through the 180-cm-long flow reactor which was held at 950 °C. Under these conditions, the residence time of the particles in the hot zone was about 15 s. Infrared heat lamps were used to keep the filter assembly above the dew point estimated to be 66 °C. The product was characterized by XRD and TEM. After a 340-min-long production run, close to the expected amount of oxide was recovered. An XRD diagram of the nearly colorless material is shown in Fig. 2 and is in excellent agreement with a reference spectrum (Powder Diffraction File #30-1468) of yttria stabilized zirconia. The average crystallite size was estimated from the XRD line broadening using the Scherrer equation,
Stabilized zirconia is an important high-performance ceramic material because of its outstanding thermal stability, chemical resistance, mechanical strength, and electrical characteristics (ion conductivity). The standard method of preparing stabilized zirconia by reaction sintering of the individual oxides is very time-consuming and may result in material with undesirable particle size, particle distribution, and purity. More recent methods are based on sol/gel processes, hydrolysis of alkoxides, and hydrothermal synthesis. In each case the process parameters must be controllable to the extent that powders of defined purity, shape, and size can be produced. There is room for novel approaches for processing stabilized zirconia powder. The author was recently involved in developing a process for synthesizing superconductive oxide powders, specifically YBa2Cu3O7^, by aerosol pyrolysis of an ultrasonically dispersed aqueous solution of the appropriate metal nitrates1 or metal chelates.2 Key to the process is the generation of a fine mist of droplets of relatively narrow size distribution with a submerged ultrasonic transducer. The method is expected to be applicable to other mixed oxide systems. This paper describes a first attempt to demonstrate the production of stabilized zirconia by this process. The solution was prepared from Fisher reagent zirconyl nitrate, ZrO(NO3)2 • xH2O, yttrium nitrate, Y(NO3)3 • 6H2O, and res
Data Loading...
