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Sputter-deposited AlN coatings for enhanced tarnish resistance and mechanical durability of silver jewelry
(2026-04-01)
Sudsawad, Kanyarat
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Somjaijaroen, Natthawirot
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Somdock, Nuttakrit
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Sakdanuphab, Rachsak
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Sakulkalavek, Aparporn
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.
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Multi-phase structure electrospun CNF@Ag/Mn/Bi/Fe composite nanofiber enhanced supercapacitor behavior
(2025-02-15)
Sinprachim, Tanayt
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Klompong, Narit
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Chanlek, Narong
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Kidkhunthod, Pinit
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Maensiri, Santi
This study presents the development of carbon-based multiphase metal oxide nanocomposites (CNF@MO<inf>x</inf>; M = Ag, Mn, Bi, and Fe) incorporating silver, manganese, bismuth, and iron nanoparticles within polyacrylonitrile (PAN)-derived carbon nanofibers. These nanocomposites were fabricated via the electrospinning technique with metal oxide concentrations of 10, 20, and 40 %w. This was followed by annealing in an argon atmosphere. The resulting nanofibers exhibited diameters ranging from 559 to 830 nm, with embedded nanoparticles measuring from 9 to 21 nm. Comprehensive characterization revealed that the nanofibers possessed uniform morphology, high porosity, and robust thermal stability. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) confirmed the valence states of the metal oxides (Ag⁰, Bi³⁺, Mn²⁺, Mn³⁺, Fe²⁺, and Fe³⁺), which are integral to redox reactions and charge storage mechanisms. Among the fabricated composites, CNF@Ag/Mn/Bi/Fe-20 demonstrated the best electrochemical performance, achieving a specific capacitance of 156 F g<sup>−1</sup> at a scan rate of 2 mV s<sup>−1</sup> and outstanding cycling stability with a capacity retention of over 96 % after 1400 charge-discharge cycles. The synergistic combination of double-layer capacitance and pseudocapacitance mechanisms in these nanofibers represents a significant improvement over conventional electrode material. This study highlights CNF@Ag/Mn/Bi/Fe nanocomposites as highly promising candidates for advanced energy storage applications, particularly in supercapacitor technologies.
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Enhancing the anti-tarnish and mechanical properties of gold-coated silver sheets for decorative applications using TiO2 film protection
(2024-12-01)
Khanwaeo, Sarocha
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Srirach, Pisan
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Limsuwan, Pichet
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Sakulkalavek, Aparporn
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Sakdanuphab, Rachsak
This study explores an innovative method to enhance the anti-tarnish and mechanical properties of gold-coated silver sheets, targeting decorative applications through the TiO<inf>2</inf> film coatings. The research focuses on gold films with a thickness of approximately 100 nm, and TiO<inf>2</inf> films ranging from 10 to 31 nm. It was observed that the color of the multilayer coatings exhibited significant sensitivity to variations in thickness, indicating that a TiO<inf>2</inf> coating with a thickness around 20 nm could be optimally applied to the gold film, maintaining an acceptable ΔE value. X-ray photoelectron spectroscopy analysis demonstrated the TiO<inf>2</inf> film's potential to inhibit the formation of Ag<inf>2</inf>S on the surface, thereby enhancing tarnish resistance. Furthermore, the application of a 20 nm TiO<inf>2</inf> layer reduced the friction coefficient from 0.28 to 0.24 for gold-coated silver. Durability tests involving 1,000 abrasion cycles revealed that the gold film without TiO<inf>2</inf> protection experienced delamination, with only about 57 % of the coated area remaining intact. In contrast, the samples protected with a TiO<inf>2</inf> layer retained approximately 90 % of the coating, underscoring the effectiveness of TiO<inf>2</inf> in preserving the structural integrity and appearance of the gold-coated silver sheets.

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