具有高耐蚀性和导电性的掺Cr类金刚石非晶碳的化学式解析

Cr掺杂的类金刚石非晶碳具有良好的导电性和耐腐蚀性,这对于燃料电池金属双极板涂层改性特别重要。使用团簇加连接原子模型对其非晶结构进行了详细解析,在该模型中,良好的玻璃形成材料由覆盖特征性最近邻团簇加上几个下一壳层原子的结构单元来表述。根据文献,在Cr掺杂的类金刚石非晶碳中占优势的团簇是Cr中心和C壳层的Cr-C4]四面体团簇,然后将该团簇与适当的连接原子匹配,以满足电子轨道饱和原理。由此推导出了两个最优组成式,即Cr-C4]CrC3(22.2%Cr)和Cr-C4]Cr3C2(40%Cr),它们显示出良好的非晶态结构稳定性。实验结果显示,所提出的这两组化学组成的涂层材料兼具低电阻率(低至10-4Ω·cm)和优异的耐腐蚀性(腐蚀电流密度~10^-2μA/cm^2)。在sp2键含量和渗流理论的框架内讨论了导电和耐蚀的协同行为。这项工作验证了团簇加连接原子模型在具有高耐腐蚀性和高导电性的涂层材料成分设计中的可行性。

Chemical Formulas of Cr-doped Diamond-like Amorphous Carbon Possessing High Corrosion Resistance and Electrical Conductivity

Cr-doped diamond-like amorphous carbon,possessing good electrical conductivity and corrosion resistance,are especially important for bipolar plates coating for fuel cells.The present work addresses its amorphous structure using the cluster-plus-glue-atom model,where a good glass forming materials described by a structural unit covering a characteristic nearest-neighbor cluster plus a few next-shell glue atoms.According to the literature,the prevailing cluster in Cr-doped diamond-like amorphous carbon is Cr-centered and C-shelledCr-C4]tetrahedral cluster.Then,this cluster is matched with appropriate glue atoms to satisfy the electron orbital saturation principle.Two composition formulas are thus proposed,Cr-C4]CrC3(22.2 at.%Cr)andCr-C4]Cr3C2(40 at.%Cr)that show good amorphous structural stabilities.It is pointed out that the coatings of the proposed chemical compositions show simultaneously low electrical resistivity(down to 10-4Ω·cm)and superior corrosion resistance(corrosion current density^10^-2μA/cm^2).The synergetic electrical and corrosion behavior is discussed within the framework of sp2 bond content and of the percolation theory.This work verifies the feasibility of the cluster-plusglue-atom model in composition design of coatings with high corrosion resistance and electrical conductivity.