Somjaijaroen, Natthawirot
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Preferred name
Somjaijaroen, Natthawirot
Alternative Name
Somjaijaroen, N.
Email
natthawirot.so@kmitl.ac.th
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Item type:Publication, Optimal AIN film deposition conditions for enhancing surface corrosion resistance and silver appearance(2026-05-01); ; ; This study investigates the development of AlN thin-film protective coatings for enhancing the corrosion resistance, surface hardness, and color stability of Ag 925 substrates used in decorative and wearable applications. AlN coatings were deposited by reactive DC magnetron sputtering, and the influences of working pressure and film thickness on bonding chemistry, oxygen incorporation, optical appearance, and artificial-sweat corrosion resistance were systematically evaluated. Increasing the working pressure promoted Al–O bond formation and noticeable surface discoloration, consistent with enhanced oxygen uptake that disrupted the near-surface Al–N bonding network. In contrast, films deposited within a moderate pressure window (2.5–7.5 × 10<sup>−1</sup> Pa) exhibited minimal color change (ΔE < 3), maintained stable Al–N bonding characteristics, and achieved a hardness of approximately 5.2 GPa. Film thickness further governed the protective performance: ultrathin AlN layers provided only limited resistance, whereas coatings thicker than ~ 300 nm significantly improved surface resistance, as supported by the reduced chloride-induced discoloration (ΔE decreased from ~ 33.6 to ~ 11) and the effective suppression of Ag and Cu oxidation, as confirmed by FE-SEM/EDS analysis. These results demonstrate that both an optimal working pressure regime and a sufficiently thick coating (> 300 nm) are essential for achieving long-term color stability and corrosion resistance in wearable silver applications. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Sputter-deposited AlN coatings for enhanced tarnish resistance and mechanical durability of silver jewelry(2026-04-01); ; ; Silver jewelry is prone to surface tarnishing caused by sulfur-containing species in ambient environments. In this study, a transparent aluminum nitride–based thin film was deposited by magnetron sputtering and evaluated as a protective barrier against silver tarnishing. Sheets of 99.9% pure silver were coated under various nitrogen flow conditions to optimize film composition and performance. An appropriate nitrogen flow rate of 25 standard cubic centimeters per minute (sccm), corresponding to an N₂/Ar gas ratio of approximately 1:1, was identified for forming AlN-rich films, while an AlN-based film thickness in the range of 80–110 nm was found to be suitable for jewelry protection. X-ray photoelectron spectroscopy analysis showed that insufficient nitrogen availability suppresses complete nitridation, resulting in residual metallic aluminum, which readily reacts with residual oxygen and moisture, increasing the oxygen content in the films. At an N₂ flow rate of 25 sccm, metallic aluminum was suppressed and the films were dominated by Al–N bonding with minor oxygen incorporation, accompanied by the development of a polycrystalline structure. Nanoindentation measurements performed on the 110 nm-thick film yielded a peak hardness of approximately 3.6 GPa, indicating enhanced mechanical durability compared with uncoated silver. Comparative evaluation of color difference, mechanical hardness, tarnish resistance, and environmental durability demonstrated improved performance of the AlN-coated silver. Finally, the practical applicability of the coating was demonstrated by depositing AlN-based films onto large and intricately designed silver jewelry items, indicating compatibility with industrial-scale processing. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Simultaneous O2 plasma and thermal treatment for improved surface conductivity of Cu-Doped SnO2 films(2019-08-01); ;