Novel electrically conductive Al2O3–TiC ceramics for electrical discharge machining applications: Bimodal micro/nano-Al2O3 particle size grading enabling continuous 3D TiC networks

Conductive composite ceramics, consisting of an insulating matrix and a dispersed conductive phase, have become a major research frontier in structural–functional ceramics. These composites retain the favorable characteristics of traditional structural ceramics, such as high strength and hardness, while exhibiting electrical conductivity, enabling efficient machining via electrical discharge machining (EDM).

However, a long-standing trade-off exists: increasing the size disparity between the insulating matrix and the conductive phase favors the formation of continuous conductive networks and lowers electrical resistivity, but it usually requires coarse matrix powders that severely hinder densification. The resulting porosity not only degrades mechanical properties but also acts as an insulating barrier, disrupting conductive pathways. Conversely, using fine or nanosized powders improves densification but reduces the phase domain size disparity, making it difficult to form continuous conductive networks. As a typical conductive composite ceramic, Al₂O₃–TiC also suffers from this dilemma, which has become a critical bottleneck for developing high-performance, EDM-machinable Al₂O₃–TiC ceramics.

Recently, a team of materials scientists led by Songlin Ran from Anhui University of Technology, China, reported a bimodal matrix particle size grading strategy to overcome this limitation. They incorporated nano-Al₂O₃ into a micro-Al₂O₃ matrix, with TiC content fixed at 25 vol%, and consolidated the composites by spark plasma sintering. The work not only elucidates the synergistic microstructural evolution that promotes densification and constructs a continuous three-dimensional TiC network, but also provides a robust framework for developing advanced conductive ceramics tailored for EDM applications.

The team published their work in Journal of Advanced Ceramics on October 8, 2026.

“In this study, we proposed a bimodal matrix design strategy by incorporating highly active nano-Al₂O₃ particles into a coarse micro-Al₂O₃ skeleton,” said Songlin Ran, a professor at the School of Materials Science and Engineering at Anhui University of Technology. “The nano-Al₂O₃ particles fill interparticle spaces to promote densification and can pin TiC grain boundaries, thereby contributing to the refinement of the conductive phase domains. Concurrently, the micro-Al₂O₃ phase domains coarsen through consumption of nano-Al₂O₃, maximizing the phase domain size disparity and favoring the formation of a continuous three-dimensional TiC network.”

“With 10 vol% nano-Al₂O₃ addition, the calculated effective percolation threshold decreases from 15.54 vol% to 10.20 vol%, yielding an electrical conductivity of 4.02 × 10⁴ S/m,” said Ran. “Consequently, the composite exhibits enhanced EDM performance, achieving a material removal rate of 9.50 mm²/min along with high surface quality. The enhanced conductivity and densification also lead to improved mechanical properties, with a flexural strength of 450 MPa.”

“This strategy offers a robust framework for developing advanced conductive ceramics tailored for EDM applications,” said Ran. “By simply grading the matrix particle size, we can simultaneously achieve high densification, high electrical conductivity, and good mechanical properties, a combination that is traditionally difficult to achieve.”

Other contributors include Liangliang Liu, Xiaofeng Jia, Lei Zhao, Dong Wang, Xing Jin and Zhaoyang Wu from Anhui University of Technology, China.

About Author

Songlin Ran is a professor and doctoral supervisor at Anhui University of Technology. He was selected for the Anhui Provincial Talent Program. He received his PhD from the Shanghai Institute of Ceramics, Chinese Academy of Sciences, in July 2008, and conducted postdoctoral research at KULeuven, Belgium, from August 2008 to August 2010. His main research interests include structural–functional integrated composite ceramics, ceramic joining, and comprehensive utilization of solid waste. He has led more than 20 research projects, including four funded by the National Natural Science Foundation of China. He has published over 70 SCI-indexed papers as first or corresponding author, and has obtained 13 authorized Chinese invention patents and one US invention patent. He serves as an assistant editor of Journal of Advanced Ceramics.

Funding

This work was supported by the National Natural Science Foundation of China (Nos. 52472061 and 52072003), and the Natural Science Foundation of Anhui Provincial Education Department (No. 2024AH040031).

DOI LINK: 10.26599/JAC.2026.9221390

About Journal of Advanced Ceramics

Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen. JAC’s 2025 IF is 14, ranking in Top 1 (1/34, Q1) among all journals in “Materials Science, Ceramics” category, and its 2025 CiteScore is 24.6 (6/133) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508