Activated sintering of zirconium dioxide

A new phenomenon has been observed — the activated sintering of a zirconium ceramic in the hydrogen-nitrogen plasma of a glow discharge. It is shown that the activation energy is considerably lower than the activation energy for sintering in a vacuum furnace. This makes it possible to reduce sintering temperature, refine the grains, and improve the mechanical properties of the ceramic. It is proposed that the mechanism by which sintering is activated is connected with the activating effect of hydrogen during a structural transformation involving the formation of oxynitride phases.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 65–69, February, 1996.     

Structural transformations in nanocrystalline zirconium dioxide

Peculiar features of the phase composition and structure of nanocrystalline powders based on zirconium dioxide, which appear during heating, have been studied. The oscillation of lattice microdistortions has been found, which is caused by variation in the crystallite defect structure. The phase composition of this material is determined according to the level of microdistortions.     

Structure of zirconium dioxide based porous glasses

This study is devoted to investigation of the micro- and mesostructure (including fractal properties) of porous zirconia glasses synthesized by precipitation from zirconium n-propoxide solutions in the presence of different hydrolyzing-agent (H₂O) quantities at different temperatures. Analysis of small-angle neutron, ultra-small-angle neutron and X-ray scattering, scanning electron microscopy allows concluding that the synthesized glasses are complex systems with a three-level hierarchical fractal structure. It is revealed that both the temperature of synthesis and the H₂O concentration in the initial solution significantly affect the structural characteristics of the glasses.     

Memory electrical switching in hydrated amorphous vanadium dioxide

Experimental data for the effect of memory electrical switching in a metal—oxide—metal structure based on hydrated vanadium dioxide obtained by the method of anodic—cathodic polarization are discussed. A model that assumes the key role of the ion current in the switching mechanism is suggested. This model makes it possible to determine the critical parameters of the material (the concentration and mobility of impurity ions) that influence the origination of the effect. The field dependence of the ion mobility derived by simulating the switching effect is explained through the hopping transfer mechanism in terms of the percolation theory.     

Dispersion of zirconium dioxide by pulsed laser radiation

A technique for producing ZrO₂ dioxide nanoparticles under the action of pulsed laser radiation is developed. By the methods of transmission electron microscopy and X-ray phase analysis, it is shown that the high-temperature cubic phase of ZrO₂ is formed during laser ablation. The dependence of the size of ZrO₂ dispersed particles on the laser radiation intensity is determined. A thermodynamic one-dimensional model of laser ablation of zirconium dioxide is analyzed. The results of analytical computations of ablation of ZrO₂ particles are confirmed by experimental data.     

Formation of zirconium dioxide in molybdenum alloy tsm-6

The formation of zirconium dioxide was observed during annealing of deformed molybdenum alloy TsM-6. Particles of ZrO₂ are formed in former subboundaries, grain boundaries, and within the grains. The size, shape, and distribution of particles at different depths after annealing at different temperatures were determined. The crystallographic orientation of ZrO₂ particles in relation to the matrix was determined. The results indicate penetration of oxygen into the alloy during annealing (in vacuum of 1 · 10^–4 to 7 · 10^–5 mm Hg) through enrichment of the subboundaries in oxygen and internal oxidation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 107–112, August, 1973.Our thanks to A. D. Korotaev, on whose initiative this work was undertaken.     

Relative humidity influence on proton conduction of hydrated pellicular zirconium phosphate in hydrogen form

Admittance measurements have been carried out as a function of temperature (20/-20°C) and relative humidity (5–90%) on pellets made up of pressed sheets of hydrated α-zirconium phosphate (pellicular zirconium phosphate). Their dc conductivities have been calculated on the basis of a suitable equivalent circuit using a nonlinear least squares procedure: at 20°C and 90% relative humidity they lie in the range 3-0.9×10^-4 S cm^-1 when the sheets are oriented parallel to the electric field and are about seven times lower in the case of perpendicular orientation. Changes in relative humidity from 90 to 5% cause the conductivity to decrease by two orders of magnitude and the activation energy to rise from 6.7 to 12.2 kcal/mol. A comparison of the Arrhenius equation parameters with those previously determined for polycrystalline α-Zr(HPO₄)₂·H₂O reveals that the same transport mechanism is present in both materials, the higher conductivity of pellicular zirconium phosphate arising from a larger effective number of carriers.     

Deposition and growth kinetics studies of thin zirconium dioxide films by UVILS-CVD

We report the deposition of thin zirconium dioxide films on Si(1 0 0) by a technique of ultraviolet-assisted injection liquid source chemical vapor deposition (UVILS-CVD) by using ultraviolet with 222 nm radiation. The alkoxide zirconium(IV) tert-butoxide (Zr[OC(CH₃)₃]₄) was used as precursor while nitrous oxide was driven into the reaction chamber as an oxidizing agent. The ZrO₂ films were deposited under various conditions and characterized by ellipsometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. The growth rate decreased with the increasing of substrate temperatures from 200 to 400 °C. Deposition rate of 20 nm/min was observed at a substrate temperature of 350 °C. There was a liner relation between the thicknesses of the films and deposition times. As a result the thicknesses can be accurately controlled by changing the number of drops of precursor introduced by the injection liquid source. The growth rate increased with the increasing concentrations of the precursor, nevertheless the trend stopped when the concentration exceeded 8.5%. The growth kinetics were also studied and the results were fit to a three-step kinetic model involving a photo chemical reaction, a reversible precursor absorption process and a following irreversible deposition reaction.     

Properties of Foamglass with Fullerene-Like Mesostructure

Russian Physics Journal -     

Performance enforcement of gel polymer electrolyte for lithium ion battery with co-doping silicon dioxide and zirconium dioxide nanoparticles

In this work, we report a new method to enforce the comprehensive performances of gel polymer electrolyte (GPE) for lithium ion battery. Poly(methyl methacrylate-acrylonitrile-vinyl acetate) [P(MMA-AN-VAc)] is synthesized as polymer matrix. The physical and electrochemical performances of the matrix and the corresponding GPEs, doped with nano-SiO₂ and nano-ZrO₂ particles individually or simultaneously, are investigated by scanning electron microscopy, thermogravimetry, electrochemical impedance spectroscopy, and charge/discharge test. It is found that the membrane co-doped with 5 wt.% nano-SiO₂?+?5 wt.% nano-ZrO₂ and the corresponding GPE combine the advantages of those doped individually with 10 wt.% nano-SiO₂ or 10 wt.% nano-ZrO₂. Accordingly, the comprehensive performances of the membrane and the corresponding GPE, in terms of thermal stability, ionic conductivity, and electrochemical stability on the anode and cathode of lithium ion battery, is enforced by co-doping 5 wt.% nano-SiO₂ and 5 wt.% nano-ZrO₂.     

Synthesis of zirconium dioxide by ultrasound assisted precipitation: effect of calcination temperature

Nanostructured zirconium dioxide was synthesized from zirconyl nitrate using both conventional and ultrasound assisted precipitation in alkaline medium. The synthesized samples were calcinated at temperatures ranging from 400°C to 900°C in steps of 100°C. The ZrO(2) specimens were characterized using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The thermal characteristics of the samples were studied via Differential Scanning Calorimetry-Thermo-Gravimetry Analysis (DSC-TGA). The influence of the calcination temperature on the phase transformation process from monoclinic to tetragonal to cubic zirconia and its consequent effect on the crystallite size and % crystallinity of the synthesized ZrO(2) was studied and interpreted. It was observed that the ultrasound assisted technique helped to hasten to the phase transformation and also at some point resulted in phase stabilization of the synthesized zirconia.     

Lateral layer-by-layer nanostructuring of thermal barrier coatings of zirconium dioxide during plasma spraying

Results of experiments on development of the method of the lateral layer-by-layer nanostructuring of coatings prepared by plasma spraying in order to improve their working characteristics under thermal cycling loads are presented. Coating deposition is performed through a mask with holes while maintaining dynamic vacuum in the chamber. Analysis of the morphology of the zirconium-oxide coatings using a scanning electron microscope shows that the structure of the coating obtained in the “shaded” regions almost completely consists of submicron particles and nanoparticles. An estimate explaining the formation of regions in the coating consisting of nanoparticles due to heterogeneous condensation of the vapor phase of the sprayed material in the Prandtl-Meyer expansion formed in the supersonic plasma flow around the barrier is given.     

Phase transitions in zirconium dioxide powder after being subjected to impulsive loads

We study the structure of zirconium dioxide powder, initially in tetragonal form, subjected to shock waves up to 43 MPa in amplitude. It is shown that after shock-wave loading a complicated structure is formed with monoclinic and x-ray-amorphous phases. The amount of the monoclinic phase reaches a maximum at a pressure of 10 GPa, while the amount of the x-ray-amorphous phase increases monotonically with increasing pressure. It is shown that the x-ray-amorphous phase results from mixing of different polytypes after shock waves pass through the material.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 51–55, January, 1995.