Acta Chimica Slovaca (ACS) publishes papers on fundamental and applied aspects of chemistry, biochemistry, chemical technology, chemical engineering and process control, biotechnology and food technology. Welcome are also topics which include chemical aspects of materials, physical chemistry and chemical physics, analytical chemistry, macromolecular chemistry and biomedical engineering.

Comparison of two β-SiAlON ceramics prepared from synthetic and natural raw materials

Maha S. M. Noaman, Zoltan Lences a, Martin Vitkovič, Z. Gabrišová b, Martin Palou *

Institute of Inorganic Chemistry, Technology and Materials, Faculty of Chemical and Food Technology Slovak University of Technology Radlinského 9, 812 37 Bratislava, Slovak Republic
a Institute of Inorganic Chemistry, Slovak Academy of Sciences Dúbravska cesta 9,84536 Bratislava Slovak Republic
b Faculty of Mechanical Engineering, Slovak University of Technology Pionerska 15, 812 31 Bratislava, Slovak Republic

E-mail: *

Abstract: Two types of β-SiALON ceramics (denoted SiALON-S and SiAlON -N) were synthesized by carbothermal reduction and nitridation. The starting raw materials used were commercial synthetic powders (AlN, Al2O3 and Si3N4) for SiAlON-S and natural aluminosilicate raw materials (pyrophilite) for SiAlON-N. Sintering of materials has been achieved by hot- isostatical pressing procedure at 1730 °C using Y2O3 as a sintering additive. In this study XRD and SEM methods were used. XRD method showed that SiAlON-S is pure aluminum silicon nitride oxide, while sample from natural pyrophilite is composed of two aluminum silicon nitride oxides and corundum. Hardness and fracture toughness values were measured for all samples, the average values (means of 10 measurements) of SiAlON-S and SiAlON -N were HV = 12.28 GPa and 12.34 GPa, KIC = 4.11 MPa m1/2 and 3.77 MPa m1/2 respectively. A new testing method was used to assess the resistance of SiAlON samples to repeated thermal shocks. Samples with initiated cracks by Vickers’s indentor were cyclically heated to 1000 °C and cooled to 500 °C. Apart from phase composition, the source of raw materials has a little influence on the properties of ceramic samples. Therefore, pyrophilite could be a potential natural source to synthesize SiAlON ceramics.

Keywords: SiAlON ceramics, starting materials, hardness, fracture toughness, thermal shock resistance

Full paper in Portable Document Format: acs_0042.pdf

Acta Chimica Slovaca, Vol. 2, No. 2, 2009, pp. 3—13