Controlled Firing of Reaction‐Bonded Aluminum Oxide (RBAO) Ceramics: Part II, Experimental Results

Abstract

The reaction‐bonded aluminum oxide (RBAO) process is an attractive alternative to conventional processing of ceramics, because of advantages such as lower costs, enhanced green machinability, near‐net‐shape forming, and broad microstructural variability. However, various problems are still encountered in the production of RBAO ceramics. Part I of the paper presented model predictions that may allow for the controlled firing of RBAO ceramics. The current work investigates the reaction behavior of RBAO ceramics under the model‐predicted conditions (i.e., for varying oxygen content, heat loss, heating cycles, and scale) via thermogravimetry, differential thermal analysis, and analysis of samples that have been fired in a box furnace. By controlling the reaction, one can produce large, crack‐free RBAO ceramics.

Andalusite‐Based High‐Alumina Castables

“…The addition of nonhydraulic bonding materials led to further mullite formation. 9 Metallic aluminum was used to assess if it might form a reaction-bonded aluminum oxide (RBAO) product, 10,11 and silicon carbide was used to compensate for shrinkage during sintering and to potentially form mullite through its oxidation in the presence of alumina. 12,13 The nonhydraulic bonding agent contents were fixed at 0, 2, and 4 wt% for the aluminum powder (Grade 120, Alcoa, Pittsburgh, PA) and at 2, 4, and 6 wt% for the silicon carbide (Exolon-ESK, Tonawanda, NY).…”

Strong ceramic foams from polyurethane templates

“…The exothermic peak temperature can be shifted by controlling parameters such as heating rate, partial O 2 pressure, volume of Al present and so on. [11][12][13] Mechanical strength Figure 4 shows the three point bend strength of Al 2 O 3 foams as a function of relative density, calculated from the model of Gibson and Ashby. 14 15 This simple model supposes a defect free strut structure.…”

Processing and Properties of ZrO2‐Containing Reaction‐Bonded Aluminum Oxide with High Initial Aluminum Contents

“…3 and must be avoided to obtain dense, crack‐free samples. To assess the validity of the low‐temperature isotherms commonly used to fire RBAO, 18 disc samples of AZ1 were subjected to 10 h isothermal treatments at 400° and 450°C, as shown in Fig. 6.…”