Cano-Crespo Rafael, Rivero-Antúnez Pedro, Gómez-García Diego, Moreno Rodrigo, Domínguez-Rodríguez Arturo
Departament de Física de la Materia Condensada, Universidad de Sevilla, Apartado 1065, 41080 Sevilla, Spain.
Instituto de Ciencia de Materiales de Sevilla, CSIC-USE, Avenida Américo Vespucio 49, 41092 Sevilla, Spain.
Materials (Basel). 2021 Feb 19;14(4):984. doi: 10.3390/ma14040984.
This paper is aims to give an answer to the following question: is the oxidation of graphene a critical issue for high-temperature plasticity in graphene-reinforced ceramics? To give a convincing reply, we will focus on two very different graphene-based ceramic composites: reduced graphene oxide (rGO)-reinforced alumina (α-AlO) and reduced graphene oxide (rGO)-reinforced yttria tetragonal zirconia (t-ZrO). The processing of the powders has been made using a colloidal route, and after that, a spark plasma sintering process was performed in order to densify the samples. Creep tests were performed at temperatures between 1200-1250 °C in an argon atmosphere. The microstructure obtained by an SEM of the sintered and tested specimens was characterized quantitatively to elucidate the deformation mechanism. Raman spectroscopy was carried out to check the integrity of the graphene. The average grain size was in the order of 1 µm and the shape factor was 0.7 for all the studied materials. The integrity of the graphene was checked before and after the creep experiments. The careful analysis of the creep tests shows that graphene oxide or its reduced version are not efficient phases for creep resistance improvement in general, contrary to what is reported elsewhere. However, the results permit the suggestion of a creep improvement in nanocomposites at a very high temperature regime due to an enhanced reactivity of oxygen between carbon and alumina interfaces. In the case of zirconia, the results give us the conclusion that the oxidation of graphene is a highly detrimental issue regarding the improvement of high-temperature plasticity.
石墨烯的氧化对于石墨烯增强陶瓷的高温可塑性而言是否是一个关键问题？为给出一个有说服力的答复，我们将聚焦于两种截然不同的基于石墨烯的陶瓷复合材料：还原氧化石墨烯（rGO）增强氧化铝（α - AlO）和还原氧化石墨烯（rGO）增强氧化钇四方氧化锆（t - ZrO）。粉末的加工采用了胶体路线，之后进行了放电等离子烧结工艺以使样品致密化。在氩气气氛中于1200 - 1250°C的温度下进行了蠕变试验。对烧结和测试后的试样进行扫描电子显微镜（SEM）观察所得到的微观结构进行了定量表征，以阐明变形机制。进行了拉曼光谱分析以检查石墨烯的完整性。所有研究材料的平均晶粒尺寸约为1 µm，形状因子为0.7。在蠕变实验前后检查了石墨烯的完整性。对蠕变试验的仔细分析表明，与其他地方所报道的情况相反，氧化石墨烯或其还原形式通常并非提高抗蠕变性的有效相。然而，结果表明由于碳与氧化铝界面之间氧的反应性增强，在非常高的温度范围内纳米复合材料的蠕变性能有所改善。对于氧化锆的情况，结果使我们得出结论，就高温可塑性的改善而言，石墨烯的氧化是一个极其有害的问题。
