Browsing by Organisation Author "Acar, Özden"

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    Scalable Production of Boron Nitride-Coated Carbon Fiber Fabrics for Improved Oxidation Resistance
    (MDPI, 2025-10-14) Yıldırım Elçin; Cennet; Arık; Muhammet Nasuh; Örs; Kaan; Nakaş; Uğur; Yakışık Özgüle; Zeliha Bengisu; Acar; Özden; Aslanlar; Salim; Altay; Özkan; Çelik; Erdal; Şahin; Korhan
    This study aimed to develop an industrially scalable coating route for enhancing the oxidation resistance of carbon fiber fabrics, a critical requirement for next-generation aerospace and high-temperature composite structures. To achieve this goal, synthesis of hexagonal boron nitride (h-BN) layers was achieved via a single wet step in which the fabric was impregnated with an ammonia–borane/THF solution and subsequently nitrided for 2 h at 1000–1500 ◦C in flowing nitrogen. Thermogravimetric analysis coupled with X-ray diffraction revealed that amorphous BN formed below ≈1200 ◦C and crystallized completely into (002)-textured h-BN (with lattice parameters a ≈ 2.50 Å and c ≈ 6.7 Å) once the dwell temperature reached ≥1300 ◦C. Complementary XPS, FTIR and Raman spectroscopy confirmed a near-stoichiometric B:N ≈ 1:1 composition and the elimination of O–H/N–H residues as crystallinity improved. Low-magnification SEM (100×) confirmed the uniform and large-area coverage of the BN layer on the carbon fiber tows, while high-magnification SEM revealed a progressive densification of the coating from discrete nanospheres to a continuous nanosheet barrier on the fibers. Oxidation tests in flowing air shifted the onset of mass loss from 685 ◦C for uncoated fibers to 828 ◦C for the coating produced at 1400 ◦C; concurrently, the peak oxidation rate moved ≈200 ◦C higher and declined by ~40%. Treatment at 1500 ◦C conferred no additional benefit, indicating that 1400 ◦C provides the optimal balance between full crystallinity and limited grain coarsening. The resulting dense h-BN film, aided by an in situ self-healing B2O3 glaze above ~800 ◦C, delayed carbon fiber oxidation by ≈140 ◦C. Overall, the process offers a cost-effective, large-area alternative to vapor-phase deposition techniques, positioning BN-coated carbon fiber fabrics for robust service in extreme oxidative environments.