Fracture Toughness of Ceramics Fired at Different Temperatures

Peter SIN, Renno VEINTHAL, Fjodor SERGEJEV, Maksim ANTONOV, Igor STUBNA

Abstract


The fracture toughness test was performed at room temperature on sets of 5 ceramic samples made from material for high voltage insulators (kaolin 36 wt. %, Al2O3 30 wt. %, clay 12 wt. % and feldspar 22 wt. %) fired at temperatures 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1250, 1300, 1400, 1500 °C at heating and cooling rate of 5 °C/min. The precrack was made to each sample by indentation under the loads 10 N 200 N, the dwell time was 45 s and the loading rate was 10 N/s. Results of the fracture toughness tests were in accordance with changes of structure of the samples after the partial firings. Fracture toughness from 20 °C to 500 °C is almost constant and it varies between 0.1 MPa·m0.5and 0.2 MPa·m0.5. Dehydroxylation (420 °C 600 °C) does not influence the value of fracture toughness. At temperature interval where we assume sintering (700 °C 1250 °C) we observe exponential dependence of fracture toughness up to 1.5 MPa·m0.5. From comparison of the fracture toughness, Young’s modulus and flexural strength follows a correlation and proporcionality of these mechanical properties.

DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1349


Keywords


ceramics; fracture toughness; mechanical strength; solid-state sintering; liquid-state sintering; dehydroxylation

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Print ISSN: 1392–1320
Online ISSN: 2029–7289