Effect of AlF3 Content on the Properties of In-situ Generated Mullite Whisker Reinforced High Aluminum Castables

Abstract The mullite whiskers have excellent high temperature resistance and high heat characteristics, the melting point is above 2000°C, and the maximum use temperature is 1500°C to 1700°C. In this paper, mullite whiskers were prepared by in-situ growth method. High aluminum castables were prepared by injecting mullite whiskers in situ at high temperature by adding Al(NO 3 ) 3 ·9H 2 O and NH 4 F to high alumina castables. It is 0, 0.5 wt%, 1 wt%, 2 wt%, 4 wt%. The materials were mixed, stirred, cast, and demolded and then fired at 1400°C. By testing the bulk density, apparent porosity and residual flexural strength of the samples, the properties, microstructure and microstructure of the fired samples were analyzed and characterized by means of XRD and SEM. The study focused on AlF 3 to mullite whiskers. The effect of microstructure and flexural strength. The results show that the introduction of AlF 3 promotes the formation of mullite whiskers. With the increase of AlF 3 content, the aspect ratio of whiskers increases first and then decreases, and when the AlF 3 content is 1wt%, the aspect ratio of whiskers The maximum is 6.67. Excessive AlF 3 causes the mullite whiskers to become thick and rod-shaped. The in-situ mullite whiskers form an interlocking structure, which enhances the flexural strength of mullite high-aluminum castables when AlF 3 content When the weight is 1wt%, the flexural strength of the model reaches the maximum value of 35.92MPa, and the residual flexural strength of the sample after 5, 10, and 15 thermal shocks reaches the maximum, which are respectively 2.07 MPa, 1.95 MPa, 1.19. MPa.