Evaluation of Nano-Scale ZnO Coatings Prepared via the Sol–Gel Method on Cast Iron Piston Rings: Tribological Performance. ENERGY: JURNAL ILMIAH ILMU-ILMU TEKNIK, [S. l.], v. 16, n. 2, p. 501–518, 2026. DOI: 10.51747/energy.v16i2.p501-518. Disponível em: https://e-journal.upm.ac.id/index.php/energy/article/view/energy.v16i2.p501-518. Acesso em: 27 sep. 2026.