Phenolic resin pyrolytic carbon is a key matrix phase in carbon-based refractories and carbon/carbon composites; however, its defect-rich glassy carbon structure exhibits poor oxidation resistance at elevated temperatures. In this work, we report a facile one-step thermal-treatment strategy using melamine as a nitrogen source to prepare nitrogen-modified phenolic resin pyrolytic carbon (NC). The structural evolution and oxidation behavior of samples carbonized at 500–800 °C were systematically investigated by XRD, SEM, TEM, FT-IR, Raman, XPS, BET, and TG-DSC. The results reveal that melamine-derived nitrogen exists in two distinct forms: at 500–700 °C, a carbon nitride-rich phase consistent with graphitic carbon nitride (g-C₃N₄) forms sheet- and belt-like structures on the carbon surface and partially fills the internal pores; at 800 °C, its long-range crystalline signature disappears, while pyridinic, pyrrolic, and graphitic nitrogen remain in the carbon framework. From 500 to 800 °C, the relative N 1s fraction of pyridinic N decreases from 72.33% to 44.38%, whereas graphitic N increases from 0.47% to 24.09%. Meanwhile, the pore structure evolves from a mesopore-dominated architecture with a limited accessible surface area at 500–600 °C to a micropore-rich structure at 700–800 °C. Relative to unmodified PR-800, NC-800 exhibits an approximately 30 °C higher onset oxidation temperature and an approximately 40 °C higher complete oxidation temperature, together with a lower maximum mass-loss rate and a delayed, broadened exothermic response. These results show that melamine-derived pore regulation and skeletal nitrogen doping jointly retard oxygen transport and suppress oxidation-active defect sites, providing a simple and potentially scalable route for improving the high-temperature oxidation resistance of phenolic resin pyrolytic carbon.

Silicon carbide (SiC) whiskers are effective reinforcements for carbon-containing refractories; however, their application is restricted by the inherently low reactivity of graphite, which is commonly used as an internal carbon source. In this study, low-cost coke and silicon powder were used as the carbon and silicon sources to synthesize SiC whiskers via a graphite-burial heat treatment process. The structural evolution of coke and the reaction behavior of the coke–Si system at different temperatures were systematically characterized. The results reveal that coke exhibits a TG-DSC mass loss of 16.01% and undergoes progressive structural rearrangement and enhanced short-range ordering at 1200–1400 °C while retaining a predominantly turbostratic carbon structure and morphological stability. At 1100–1200 °C, SiC whiskers form predominantly within pores, and this distribution is consistent with a gas-phase-assisted VS-type growth pathway; the normalized crystalline SiC fractions remain relatively low (~4–11%). A pronounced enhancement of SiC formation occurs at 1300 °C, where the crystalline Si phase becomes undetectable by XRD and abundant SiC whiskers spread from localized pore regions to the matrix surface. The enhanced whisker formation at 1300–1400 °C is attributed to accelerated reaction and mass-transfer processes at elevated temperatures. The synthesized whiskers consist of crystalline β-SiC, and those formed at 1400 °C exhibit high-density stacking faults and pronounced radial coarsening, with representative diameters of approximately 35–80 nm in the TEM images. The structural evolution of coke from a defect-rich state toward a more ordered turbostratic structure occurs concurrently with the temperature-dependent evolution of SiC nucleation and growth and may contribute to the availability of reaction sites and transport pathways, establishing coke as a promising carbon source for the in-situ synthesis of SiC whiskers in refractory applications.