low temperature sintering (rus. низкотемпературное спекание) — sintering of powder-based compacts and suspension mouldings in atmospheric pressure without any additional high-energy exposures (pressure, electric discharge) carried out in temperatures more than 100 degrees lower than temperature of sintering conventional sources of raw materials.

Description

The most common techniques of reducing the sintering temperature are as follows:

1. introduction of low-melting dopants that help crystallites slide more freely at the initial sintering stages and promote an inter-grain mass transfer through a fluid film coating grains at later stages;

2. increase of the dispersion of base powder, which also facilitates the movement of particles at the initial stages of sintering and leads to an increased importance of surface and grain-boundary diffusion compared to bulk diffusion as a result of the higher specific surface of raw pressing material;

3. heterovalent doping of base compounds to increase the concentration of crystalline lattice defects and the subsequent increase of the diffusion mobility of the material.

The dispersion of base powders can usually be increased when such powders are synthesised using chemical homogenisation or intensive mechanical/mechanochemical treatment.

Nanosintering is a very effective type of low-temperature sintering, although it is seldom used. Nanosintering is based on spontaneous compaction of non-aggregated monodisperse nanopowders of certain materials when exposed to temperatures 300-500 degrees lower than the temperature of traditional (high-temperature) sintering.

Low-temperature sintering is one of the key methods of producing nanoceramics.

Illustrations

BiNbO4 ceramics obtained during low-temperature
BiNbO4 ceramics obtained during low-temperature sintering at 720 °С. Author: Oleg A. Shlyakhtin, Lomonosov Moscow State University, Department of Materials Science. From personal files.

Author

  • Shlyakhtin Oleg A.

Sources

  1. Kingery W.D.et al. Introduction to Ceramics. 2-nd ed. — Wiley-Interscience, 1976, 1056 pp.
  2. Mayo M. J., Hague D.C., Chen D.-J . Processing nanocrystalline ceramics for applications in superplasticity // Materials Science and Engineering. 1993. V. A166, №1–2. 145–159 pp.
  3. Watari K., Hwang H. J., Toriyama M., Kanzaki S. Effective sintering aids for low-temperature sintering of AlN ceramics // J. Mater. Res. 1999. V. 14, №4. 1409–1417 pp.

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