Abstract Boron and nitrogen doped expanded graphite (B-doped EG & N-doped EG) were synthesized for the first time by annealing the mixtures, obtained from the suspensions of expanded graphite (EG) with boric acid and urea, respectively. Afterwards, the doped EG were introduced into Al 2 O 3 -C refractories by partially replacing the graphite flake. Synthesized materials were characterized using SEM-EDS, XPS, XRD, TG-DSC and Raman Spectroscopy. Also, evaluation of various mechanical properties and oxidation resistance tests were conducted. Boron (B) and Nitrogen (N) were successfully introduced into the C skeleton via different C-B bonds (B4C, B-sub-C and BC2O) and C-N bonds (pyridine-N, amino-N and graphitic-N) respectively, maintaining the hexagonal graphitic lattice and lower reactivity. Compared to as-received EG, the B-doped EG and N-doped EG remained relatively intact structure in Al 2 O 3 -C refractories at high temperature due to their less defects and lower reactivity. Addition of B-doped EG and N-doped EG into Al 2 O 3 -C refractories showed improved mechanical properties such as modulus of rupture (CMOR), force, displacement and thermal shock resistance. Besides, the Al 2 O 3 -C specimens containing B-doped EG and N-doped EG exhibited significantly better oxidation resistance, which further promote the reinforcement effect of doped EG in Al 2 O 3 -C refractories during actual service condition.

中文翻译：

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硼和氮掺杂膨胀石墨的合成作为 Al 2 O 3 -C 耐火材料的有效增强剂

摘要 通过对分别由膨胀石墨 (EG) 与硼酸和尿素的悬浮液制备的混合物进行退火，首次合成了掺硼和掺氮膨胀石墨 (B 掺杂 EG 和 N 掺杂 EG)。然后，通过部分替换石墨薄片，将掺杂的EG引入到Al 2 O 3 -C耐火材料中。使用 SEM-EDS、XPS、XRD、TG-DSC 和拉曼光谱对合成材料进行表征。此外，还进行了各种机械性能和抗氧化试验的评价。硼 (B) 和氮 (N) 分别通过不同的 CB 键（B4C、B-sub-C 和 BC2O）和 CN 键（吡啶-N、氨基-N 和石墨-N）成功地引入到 C 骨架中，保持六方石墨晶格和较低的反应性。与收到的 EG 相比，B掺杂的EG和N掺杂的EG在高温下在Al 2 O 3 -C耐火材料中保持相对完整的结构，因为它们的缺陷较少和反应性较低。向Al 2 O 3 -C 耐火材料中添加掺B EG 和掺N EG 显示出改进的机械性能，例如断裂模量(CMOR)、力、位移和抗热震性。此外，含有B掺杂EG和N掺杂EG的Al 2 O 3 -C试样表现出明显更好的抗氧化性，这进一步促进了掺杂EG在实际使用条件下在Al 2 O 3 -C耐火材料中的补强作用。向Al 2 O 3 -C 耐火材料中添加掺B EG 和掺N EG 显示出改进的机械性能，例如断裂模量(CMOR)、力、位移和抗热震性。此外，含有B掺杂EG和N掺杂EG的Al 2 O 3 -C试样表现出明显更好的抗氧化性，这进一步促进了掺杂EG在实际使用条件下在Al 2 O 3 -C耐火材料中的补强作用。向Al 2 O 3 -C 耐火材料中添加掺B EG 和掺N EG 显示出改进的机械性能，例如断裂模量(CMOR)、力、位移和抗热震性。此外，含有B掺杂EG和N掺杂EG的Al 2 O 3 -C试样表现出明显更好的抗氧化性，这进一步促进了掺杂EG在实际使用条件下在Al 2 O 3 -C耐火材料中的补强作用。