A thermoanalysis of phase transformations and linear shrinkage kinetics of ceramics made from ultrafine plasmochemical ZrO2(Y)-Al 2O3 powders

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Abstract

The methods of X-ray diffraction analysis, thermogravimetric analysis, differential scanning calorimetry, and dilatometry are used to study special features of the structural-phase state of the 80 mass% ZrO2(Y)-20 mass% Al2O3 plasmochemical powders (PCPs) and their effects on the sintering of composite ceramics. It is revealed that the ZrO 2(Y)-Al2O3 powder composite represents a mechanical mixture containing crystalline tetragonal zirconium dioxide and aluminum oxide nanoparticles, the latter found in an amorphous state and partially included into the ZrO2(Y) lattice, thus forming metastable solid solutions of variable composition. Heating of the composite powder within the temperature range 740-1,000 C reveals an exothermal effect associated with decomposition of metastable states of aluminum oxide. This is accompanied by the formation of the corundum-phase nuclei having subcritical dimensions. They achieve the critical sizes at higher temperatures T > 1200 C, when α-Al2O3 is finally crystallized. The shrinkage response of the powder compacts during non-isothermal sintering is measured in a sensitive dilatometer. It is shown that the shrinkage curve consists of several stages that closely correlate with the concurrent structural-phase transformation in the composite ZrO2(Y)-Al2O3 powder mixture. The decisive contribution into shrinkage during non-isothermal sintering of composite comes from the high-temperature stages with the maximum shrinkage rate at the temperatures 1,250 and 1,550 C. It is found out that the regime of sintering the ultrafine PCPs (T = 1,600 C, t = 1 h) allows producing composite ceramic materials with a porosity of Q ≈ (5-7) %, microhardness H v = 12.3 GPa, and crack resistance š 1c = (10-11) MPa m0.5.

Original languageEnglish
Pages (from-to)1439-1445
Number of pages7
JournalJournal of Thermal Analysis and Calorimetry
Volume115
Issue number2
DOIs
Publication statusPublished - 1 Feb 2014

Fingerprint

shrinkage
Powders
Thermoanalysis
phase transformations
Phase transitions
ceramics
Kinetics
composite materials
Aluminum Oxide
sintering
Composite materials
kinetics
Sintering
aluminum oxides
dilatometry
Temperature
extensometers
Dilatometers
Ceramic materials
dioxides

Keywords

  • Alumina toughened zirconia ceramics
  • Dilatometry
  • DSC
  • Phase transformations
  • Shrinkage
  • Sintering
  • TG

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

Cite this

@article{5dece48db55a49dda58288c0de9743d9,
title = "A thermoanalysis of phase transformations and linear shrinkage kinetics of ceramics made from ultrafine plasmochemical ZrO2(Y)-Al 2O3 powders",
abstract = "The methods of X-ray diffraction analysis, thermogravimetric analysis, differential scanning calorimetry, and dilatometry are used to study special features of the structural-phase state of the 80 mass{\%} ZrO2(Y)-20 mass{\%} Al2O3 plasmochemical powders (PCPs) and their effects on the sintering of composite ceramics. It is revealed that the ZrO 2(Y)-Al2O3 powder composite represents a mechanical mixture containing crystalline tetragonal zirconium dioxide and aluminum oxide nanoparticles, the latter found in an amorphous state and partially included into the ZrO2(Y) lattice, thus forming metastable solid solutions of variable composition. Heating of the composite powder within the temperature range 740-1,000 C reveals an exothermal effect associated with decomposition of metastable states of aluminum oxide. This is accompanied by the formation of the corundum-phase nuclei having subcritical dimensions. They achieve the critical sizes at higher temperatures T > 1200 C, when α-Al2O3 is finally crystallized. The shrinkage response of the powder compacts during non-isothermal sintering is measured in a sensitive dilatometer. It is shown that the shrinkage curve consists of several stages that closely correlate with the concurrent structural-phase transformation in the composite ZrO2(Y)-Al2O3 powder mixture. The decisive contribution into shrinkage during non-isothermal sintering of composite comes from the high-temperature stages with the maximum shrinkage rate at the temperatures 1,250 and 1,550 C. It is found out that the regime of sintering the ultrafine PCPs (T = 1,600 C, t = 1 h) allows producing composite ceramic materials with a porosity of Q ≈ (5-7) {\%}, microhardness H v = 12.3 GPa, and crack resistance š 1c = (10-11) MPa m0.5.",
keywords = "Alumina toughened zirconia ceramics, Dilatometry, DSC, Phase transformations, Shrinkage, Sintering, TG",
author = "Surzhikov, {Anatoly Petrovich} and Frangulyan, {T. S.} and Ghyngazov, {S. A.}",
year = "2014",
month = "2",
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doi = "10.1007/s10973-013-3455-y",
language = "English",
volume = "115",
pages = "1439--1445",
journal = "Journal of Thermal Analysis and Calorimetry",
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TY - JOUR

T1 - A thermoanalysis of phase transformations and linear shrinkage kinetics of ceramics made from ultrafine plasmochemical ZrO2(Y)-Al 2O3 powders

AU - Surzhikov, Anatoly Petrovich

AU - Frangulyan, T. S.

AU - Ghyngazov, S. A.

PY - 2014/2/1

Y1 - 2014/2/1

N2 - The methods of X-ray diffraction analysis, thermogravimetric analysis, differential scanning calorimetry, and dilatometry are used to study special features of the structural-phase state of the 80 mass% ZrO2(Y)-20 mass% Al2O3 plasmochemical powders (PCPs) and their effects on the sintering of composite ceramics. It is revealed that the ZrO 2(Y)-Al2O3 powder composite represents a mechanical mixture containing crystalline tetragonal zirconium dioxide and aluminum oxide nanoparticles, the latter found in an amorphous state and partially included into the ZrO2(Y) lattice, thus forming metastable solid solutions of variable composition. Heating of the composite powder within the temperature range 740-1,000 C reveals an exothermal effect associated with decomposition of metastable states of aluminum oxide. This is accompanied by the formation of the corundum-phase nuclei having subcritical dimensions. They achieve the critical sizes at higher temperatures T > 1200 C, when α-Al2O3 is finally crystallized. The shrinkage response of the powder compacts during non-isothermal sintering is measured in a sensitive dilatometer. It is shown that the shrinkage curve consists of several stages that closely correlate with the concurrent structural-phase transformation in the composite ZrO2(Y)-Al2O3 powder mixture. The decisive contribution into shrinkage during non-isothermal sintering of composite comes from the high-temperature stages with the maximum shrinkage rate at the temperatures 1,250 and 1,550 C. It is found out that the regime of sintering the ultrafine PCPs (T = 1,600 C, t = 1 h) allows producing composite ceramic materials with a porosity of Q ≈ (5-7) %, microhardness H v = 12.3 GPa, and crack resistance š 1c = (10-11) MPa m0.5.

AB - The methods of X-ray diffraction analysis, thermogravimetric analysis, differential scanning calorimetry, and dilatometry are used to study special features of the structural-phase state of the 80 mass% ZrO2(Y)-20 mass% Al2O3 plasmochemical powders (PCPs) and their effects on the sintering of composite ceramics. It is revealed that the ZrO 2(Y)-Al2O3 powder composite represents a mechanical mixture containing crystalline tetragonal zirconium dioxide and aluminum oxide nanoparticles, the latter found in an amorphous state and partially included into the ZrO2(Y) lattice, thus forming metastable solid solutions of variable composition. Heating of the composite powder within the temperature range 740-1,000 C reveals an exothermal effect associated with decomposition of metastable states of aluminum oxide. This is accompanied by the formation of the corundum-phase nuclei having subcritical dimensions. They achieve the critical sizes at higher temperatures T > 1200 C, when α-Al2O3 is finally crystallized. The shrinkage response of the powder compacts during non-isothermal sintering is measured in a sensitive dilatometer. It is shown that the shrinkage curve consists of several stages that closely correlate with the concurrent structural-phase transformation in the composite ZrO2(Y)-Al2O3 powder mixture. The decisive contribution into shrinkage during non-isothermal sintering of composite comes from the high-temperature stages with the maximum shrinkage rate at the temperatures 1,250 and 1,550 C. It is found out that the regime of sintering the ultrafine PCPs (T = 1,600 C, t = 1 h) allows producing composite ceramic materials with a porosity of Q ≈ (5-7) %, microhardness H v = 12.3 GPa, and crack resistance š 1c = (10-11) MPa m0.5.

KW - Alumina toughened zirconia ceramics

KW - Dilatometry

KW - DSC

KW - Phase transformations

KW - Shrinkage

KW - Sintering

KW - TG

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U2 - 10.1007/s10973-013-3455-y

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JO - Journal of Thermal Analysis and Calorimetry

JF - Journal of Thermal Analysis and Calorimetry

SN - 1388-6150

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