Abnormal Graphitization Behavior in Near-Surface/Interface Region of Polymer-Derived Ceramics

Prior research has shown that polymer-derived ceramics (PDCs) contain in situ free carbon, which influences their microstructure and properties. However, the role of surface and interface effects in carbon evolution remained unclear. Established knowledge includes the general behavior of carbon in PDCs during pyrolysis. This paper introduces a novel observation: the surface and interface can drastically alter carbon's graphitization behavior. The study fills a gap in understanding how surface interactions affect carbon enrichment and electrical properties. No prior work had resolved the extent of surface-driven graphitization in PDCs. This discovery challenges assumptions about uniformity in PDC properties. The findings open new possibilities for tailoring PDCs for high-temperature applications.

The aim of this work is to investigate how surface and interface effects influence the graphitization of free carbon in PDCs. The specific problem is the lack of understanding about how surface interactions alter carbon evolution and domain structure. The motivation stems from the need to control PDC properties for advanced applications. The study seeks to reveal how surface enrichment leads to abnormal electrical behavior. Researchers propose that surface/interface effects are key to enhancing conductivity. The goal is to demonstrate how these effects can be harnessed for functional materials. The work also aims to fabricate a PDC strain gauge that functions at extreme temperatures. This contributes to the broader goal of improving PDC performance through surface engineering.

The study uses in situ analysis to track carbon evolution in PDCs during pyrolysis. Both micro/nanoscale films and millimeter-scale bulk samples are examined. Surface and interface regions are specifically targeted for detailed characterization. Techniques include structural and electrical measurements to assess carbon enrichment. The researchers compare surface and interior regions to identify differences in graphitization. Electrical conductivity is measured to quantify the impact of surface effects. The fabrication of a strain gauge is used to test practical performance at high temperatures. The approach combines experimental observation with functional testing to validate findings.

The surface and interface regions of PDCs show enhanced graphitization of free carbon. A carbon-enriched layer forms in the near-surface area, leading to abnormal electrical properties. The current intensity in this region is orders of magnitude higher than in the bulk interior. Conductivity reaches up to 14.47 S cm⁻¹, which is 5–8 times higher than in the bulk material. This effect is attributed to surface-driven carbon enrichment and structural evolution. The strain gauge fabricated from PDCs survives butane flames at ≈1300°C. The skin effect and edge current are observed as direct consequences of surface enrichment. These findings highlight the role of surface/interface interactions in PDC behavior.

The authors state that surface and interface effects significantly alter carbon graphitization in PDCs. These effects lead to the formation of a carbon-enriched layer and abnormal electrical behavior. The study confirms that the near-surface region exhibits ultrahigh conductivity compared to the bulk. The skin effect and edge current are direct outcomes of surface enrichment. The fabricated strain gauge demonstrates the practical potential of surface-engineered PDCs. The findings suggest that surface interactions are critical for regulating PDC properties. The authors propose that these effects can be harnessed for high-temperature applications. The study emphasizes the importance of surface/interface control in PDC design.