Effect of Cu Doping on the Formation of Metastable Al2O3 Nanoparticles Synthesized through Plasma Arc Imam Sholahuddin (1*), Rudy Soenoko (2), Djarot B. Darmadi (2), Lilis Yuliati (2), Haidzar Nurdiansyah (1)
1. Department of Mechanical Engineering, Jember University, Jember 68121, Indonesia
*imam.teknik[at]unej.ac.id
2. Department of Mechanical Engineering, Brawijaya University, Malang 65145, Indonesia
Abstract
We report the successful synthesis of Cu-doped metastable Al2O3 nanoparticles using a plasma arc technique, where Cu was introduced in situ via electrode erosion during high-temperature processing. The airflow rate of both plasma and carrier gas was introduced at 16 lpm and 5 lpm, respectively, to sustain the arc discharge and served as the primary oxidizing medium. The aluminum precursor was atomized, oxidized, and doped simultaneously at a feed rate of 6 g/min. EDX analysis and Rietveld refinement of XRD patterns confirmed Cu incorporation (2.1-4.0%) into the Al2O3 lattice. This Cu affects the difference in the increase of gamma-Al2O3 and theta-Al2O3, and decreases delta-Al2O3 phases at 14.1%, 8.1%, and 22.2%, respectively. These are changes due to the presence of minor Cu atoms occupying interstitial sites in the spinel lattice framework. The presence of polymorphic Al2O3 phase coexistence was also detected through SAED patterns, as exhibited by diffuse rings. The spatial distributions of Al2O3 phases revealed extending to the particle surface, suggesting the influence of uneven cooling rates during in-flight plasma processing, as shown by the Fast Fourier Transform examination of HR-TEM images. These findings demonstrate the role of minor Cu doping in tailoring metastable Al2O3 nanostructures through plasma arc, offering the functional properties for broader applications, with promise for scalable production of advanced materials.
Keywords: Metastable Al2O3- Cu dopant- Plasma arc- Polymorphic nanoparticles
