Among materials able to withstand ablation in extreme environments, the class of compounds commonly known as Ultra-High Temperature Ceramics (UHTCs) is a potential candidate, thanks to melting temperatures above 3000°C. However, research on UHTCs has generally stumbled across two major issues: the low fracture toughness and the oxidation resistance. Recent advancements in high temperature mechanical properties have been achieved through addition of W-based compounds, thanks to the formation of highly refractory secondary phases and to a particular configuration of the matrix grains. On the other hand, in order to increase the intrinsic brittleness, long and short fibers have been added to UHTC matrices. However, cautious choice of the sintering parameters must be paid, owing to the tendency of the fibers to react with the matrix at increasing temperatures, change their characteristic structure and thus lose their properties. This work presents a series of UHTCs exhibiting outstanding high temperature mechanical strength, or improved fracture toughness and oxidation resistance. In particular, the microstructure evolution upon sintering or oxidation has been studied by SEM and TEM and correlated to the specific thermo-mechanical performances.

Ceramic Composites for Extreme Environments: effect of W doping

L Silvestroni
2017

Abstract

Among materials able to withstand ablation in extreme environments, the class of compounds commonly known as Ultra-High Temperature Ceramics (UHTCs) is a potential candidate, thanks to melting temperatures above 3000°C. However, research on UHTCs has generally stumbled across two major issues: the low fracture toughness and the oxidation resistance. Recent advancements in high temperature mechanical properties have been achieved through addition of W-based compounds, thanks to the formation of highly refractory secondary phases and to a particular configuration of the matrix grains. On the other hand, in order to increase the intrinsic brittleness, long and short fibers have been added to UHTC matrices. However, cautious choice of the sintering parameters must be paid, owing to the tendency of the fibers to react with the matrix at increasing temperatures, change their characteristic structure and thus lose their properties. This work presents a series of UHTCs exhibiting outstanding high temperature mechanical strength, or improved fracture toughness and oxidation resistance. In particular, the microstructure evolution upon sintering or oxidation has been studied by SEM and TEM and correlated to the specific thermo-mechanical performances.
2017
Istituto di Scienza, Tecnologia e Sostenibilità per lo Sviluppo dei Materiali Ceramici - ISSMC (ex ISTEC)
UHTC
W-doping
HT strength
fracture toughness
oxidation resistance
extreme environment
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/344956
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