A. Latiff, M. I., et al. “Characteristics of Six Layered Al Si3N4 Functionally Graded Materials Prepared through Two-Step Pressureless Sintering Process”. Journal of Mechanical Engineering and Sciences, vol. 15, no. 4, Dec. 2021, pp. 8508-17, doi:10.15282/jmes.15.4.2021.04.0670.