In situ synthesis of melt-grown mullite ceramics using directed laser deposition


While mullite is a significant oxide ceramic material, its current preparation process has many limitations such as complicated process, low efficiency, and high cost. In this paper, directed laser deposition (DLD) was used to prepare mullite ceramics directly using α-Al2O3 and SiO2 powder as raw materials. The phase composition, microstructure, and primary defects of prepared samples were investigated by XRD, Raman spectroscopy, and SEM/EDS. Vickers indentation and three-point bending experiments were used to evaluate mechanical properties. The results showed that microstructure was mainly composed of a mullite crystal phase and Si-rich glass phase. It is shown that mullite ceramics were successfully synthesized in situ during the DLD process with the use of Al2O3 and SiO2 powder. Morphology of mullite crystal inside cylindrical sample was particular “tabular cellular,” which transformed into “rod cellular” at the edge. Two mullite crystals were arranged along deposition direction basically, surrounded by the Si-rich glass phase. The defects included pores with various sizes and crack, in which large pores were mainly distributed at the edge of the sample, and small pores were throughout the section. The crack was distributed in the center of the sample and spread to the edge. Mechanical properties test showed flexural strength, microhardness, and fracture toughness were 62.8 ± 30.3 MPa, 12.7 ± 0.34 GPa, and 1.84 ± 0.14 MPa·m1/2, respectively. It is considered that pores and crack were responsible for poor mechanical properties. This research is expected to provide a new option for the rapid preparation of mullite ceramics.

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The raw/processed data required to reproduce these findings cannot be shared at this time due to technical or time limitations.


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The authors would like to acknowledge the financial support from the National Natural Science Foundation of China (No. 51805070, No. 51790172), the Fundamental Research Funds for the Central Universities (DUT19RC(3)060) and the Liaoning Province Natural Science Foundation Guidance Program (2019-ZD-0010).

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Fangyong Niu helped in conceptualization, methodology, formal analysis, investigation, writing—review and editing, funding acquisition. Dongjiang Wu contributed to investigation, experiments, writing—review and editing, project administration, funding acquisition, supervision. Dake Zhao contributed to conceptualization, methodology, investigation, visualization, formal analysis, writing—original draft. Yunfei Huang helped in writing—review and editing. Jia Zhu helped in investigation, experiments, writing—review and editing. Guangyi Ma helped in writing—review and editing. All authors read and approved the manuscript.

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Correspondence to Fangyong Niu.

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Wu, D., Zhao, D., Niu, F. et al. In situ synthesis of melt-grown mullite ceramics using directed laser deposition. J Mater Sci 55, 12761–12775 (2020).

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