Mechanical Properties and Thermal Shock Resistance of Alumina/Hexagonal Boron Nitride Composite Refractories

Abstract

Alumina/hexagonal boron nitride (Al 2 O 3 /h-BN) composite refractories were fabricated with various h-BN contents, to study the effects on the mechanical properties and thermal shock resistance (TSR) of the composite refractories. The results showed that the mechanical properties of the composite refractories, including fracture strength, Young's modulus, fracture toughness, work of fracture, and decreased with the increase of h-BN amount. However, the residual flexural strength ratio after thermal shock test was increased with increasing the h-BN content, showing an improvement of TSR. The resistance to fracture propagation caused by the thermal stresses was increased, as supported by the R IV and R ST parameters.

Microstructure and mechanical properties of h-BN/Yb4Si2O7N2 composites

“…Hexagonal boron nitride (h-BN), a layered material similar to graphite, is well known as an important ceramic because of its unique properties, such as thermal stability, high thermal conductivity, good thermal shock resistance [1][2][3][4][5][6], reliable electrical insulation, chemical inertness, excellent machinability [7][8][9][10][11], etc. h-BN is also used to improve the thermal shock resistance, machinability, and electrical insulation of other ceramics [12][13][14].…”

Effect of short carbon fiber content on strength and toughness of Al2O3–C refractories

“…The fracture toughness K IC of the as‐prepared samples was calculated from the maximum load and other parameters by the following equation: $$$$\begin{equation}{K}_{{\mathrm{IC}}} = \frac{{3FS{a}^{1/2}}}{{2B{W}^2}}Y\end{equation}$$$$ $$$$\begin{eqnarray}Y = {A}_0 &&+ {A}_1\left( {a/W} \right) + {A}_2{\left( {a/W} \right)}^2 + {A}_3{\left( {a/W} \right)}^3\nonumber\\ &&+ {A}_4{\left( {a/W} \right)}^4,\end{eqnarray}$$$$where F is the load force at fracture of the SENB specimen, S is the length of support span, a is the notch depth, B is the specimen width, W is the specimen thickness, and Y is the dimensionless number, which is dependent on the geometry of the loading and the crack configuration ( A 0 , A 1 , A 2 , A 3 , and A 4 are calculation parameters related to S / W ). When S / W = 4, A 0 = 1.93, A 1 = −3.07, A 2 = 14.53, A 3 = −25.11, A 4 = 25.8 15 …”

“…A 1 , A 2 , A 3 , and A 4 are calculation parameters related to S/W). 15 γ wof is a measure of the resistance to the propagation of a crack over a large area, 16 calculated from loaddeflection curves obtained from notched bars deformed in three-point bend by measuring the area (U) under the load-deflection curve. γ wof is given by the following equation:…”