Sintering kinetics of zirconium dioxide

Conclusions We investigated the sintering of zirconium dioxide over the temperature range 2000–2350°K as a function of the purity of the material and the defectivity of the oxide crystal lattice. The activation energy of sintering and the vacancy diffusion constant were calculated.The decrease in activation energy resulting from distortion of the crystal lattice is, on the whole, inadequate for activation of sintering.Translated from Ogneupory, No.5, pp. 51–57, May, 1969.     

Dynamic synthesis of zirconium dioxide powders

We investigated the process of zirconium dioxide powder synthesis by shock wave loading of a porous metal and the subsequent dispersion. The synthesized powder consists of hollow spherical shells and highly porous conglomerates with a 500 μm mean dimension. The specific surface of the powder is independent of the particle size and is 1.25±0.35 m²/g. The tetragonal modification predominates for large dimensions, while the monoclinic is more common in the small. The possibility of stabilizing the oxides in the high-temperature phase is investigated. Deceased. Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, 660036 Krasnoyarsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 6, pp. 78–81, November–December, 1993.     

Adsorption of polyacrylamide on zirconium dioxide

The adsorption of an anionic-type polyelectrolyte (polyacrylamide) onto zirconium dioxide from aqueous dispersion has been studied as a function of pH. Polymer adsorption takes place in the acid region, obeying a Langmuir-type isotherm. Adsorption decreases with increasing pH. The zero-point of charge (zpc) at the ZrO₂–H₂O interface and the nature of the ionic charge on the polymer molecules were investigated. The behavior of polymer attachment is discussed on the grounds of a nonionic bonding mechanism including H bonding and of electrostatic interaction. It has been found that the zpc of ZrO₂ is at pH ～3.5 and that the ionic properties of the polymer molecules depend, to a noticeable extent, upon the pH of the medium.     

Stabilization of high-temperature modification of zirconium dioxide

Translated from Steklo i Keramika, No. 9, pp. 22–23, September, 1991.     

纳米级二氧化锆的制备和应用

纳米二氧化锆是一种新型的高科技材料,有着广泛而重要的用途。根据国内外研究制备的最新进展及其发展趋势,综述了纳米级二氧化锆的制备技术和近年来新的应用领域和研究前沿。     

Improving the crack resistance of zirconium dioxide

Translated from Steklo i Keramika, No. 6, pp. 17–18, June, 1991.     

Electrical conductivity of cement pastes

The electrical conductivity of cement- and clinker mineral pastes was measured during setting and hardening. Conductograms give interesting and structurally important data on the beginning period of cement hydration.     

Electrical conductivity of carbonaceous powders

The present paper deals with the electrical conductivity of a number of carbonaceous powders undergoing a low compaction. It is shown that the contributions to the conductivity of such samples are too numerous and too complex to be solved exactly. Hence, several criteria are proposed in order to quantify the behaviour of moderately compressed powders, and thus derive several useful parameters characterizing their grains. Thus, their morphological characterization is shown to be feasible from such electrical measurements. For that purpose, a known weight of material is poured into a thick glass cylinder and is moderately compressed between two stainless steel pistons. A number of different carbonaceous powders having various morphologies, from almost spherical to disk- or needle-shaped, have been investigated. During the compaction, both the electrical conductivity σ and the volume of the sample are simultaneously measured. The results are found to depend strongly on the initial height h of the powder column. The non-monotonic behaviour of σ versus h is studied for each available material. Arguments are given for retaining only the sample size which leads to the highest conductivity. The so-called general effective media (GEM) equation is then applied to the corresponding data of σ versus Φ, where Φ is the volume fraction of grains in the column. In this context, the grains are assumed to behave like either oblate or prolate spheroids, depending on the material. The fitting procedure requires the knowledge of both the apparent density of the powder in the non-compacted state, and that of the grains, and thus uses only two adjustable parameters. For each material, average aspect ratios are derived from the fits of the GEM equation and are shown to be strongly consistent with the expected morphologies.     

Electrical conductivity of diopside ceramics

Translated from Steklo i Keramika, No. 1, pp. 26–27, January, 1990.     

Electrical conductivity of some hydroxyapatites

The electrical conductivity of hydroxyapatite, M₁₀(PO₄)₆(OH)₂ (M = Ca, Sr, Ba, Cd, Pb….), has been measured in the temperature range from 200°C to 800°C. The nature of charge carriers in Ca₁₀(PO₄)₆(OH)₂ and Pb₁₀(PO₄)₆(OH)₂ is examined by the emf measurement and the electrolysis experiment. These results suggested that the OH^? ion is the charge carrier in calcium-hydroxyapatite, and the OH^? ion and the electron in lead—hydroxyapatite.