Coatings

Yttrium oxide (Y₂O₃) is a crucial protective material for the inner walls of semiconductor etching chambers. This study employed Suspension Plasma Spray (SPS) technology to deposit Y₂O₃ coatings on AISI 304 stainless steel substrates. A water ring guide cover, which injects deionized water toward the center of the plasma flame at the torch outlet, was installed. The critical parameter ratio between the water ring flow rate and the suspension feed rate was investigated, with a specific focus on its influence on the coating’s microstructure and mechanical properties. The findings reveal that this parameter exhibits a significant positive correlation with porosity, with the coefficient of determination R² for their linear fit reaching 0.91236. When the water ring flow rate ratio was reduced to 79.66%, the porosity decreased to 0.946%, while the primary composition of the coating remained unchanged. Bond strength tests demonstrated that the adhesion strength of the coating exhibits an upward trend with increasing proportion of water ring flow. The adhesion strength reached its maximum value of 27.02 MPa when the water ring flow rate proportion was increased to 85.45%. Roughness exhibits a non-monotonic variation trend within the ratio range, attaining its optimal minimum value at the lower end of the ratio, indicating complex interrelationships among process characteristics. This work concludes that a low water ring flow rate ratio is essential for fabricating dense, well-adhered, and smooth Y₂O₃ coatings via SPS, providing a critical guideline for process optimization for applications such as semiconductor protection.

This paper explores the structural, mechanical, thermal, and electrochemical properties of copper matrix composites (CMCs) enhanced by Crassostrea madrasensis seashell powder, which were produced via powder metallurgy and resistance sintering. FESEM images showed a uniform distribution of bio-ceramic particles in the copper matrix composites (CMCs), leading to an improved microstructure and enhanced mechanical behavior. Mechanical tests showed that after incorporating 12 wt.% seashell powder, the average hardness increased to 56 HV, and compressive strength improved to 686 MPa. Density analysis showed a decrease in porosity, which was attributed to better particle diffusion during sintering. The corrosion resistance was evaluated using electrochemical techniques, including OCPT, Tafel polarization, EIS, LSV, and chronocoulometry, which were employed in 3.5 wt.% NaCl media with varying concentrations of the extract of Allium sativum (garlic) as a green inhibitor. Garlic-derived phytochemicals facilitated surface passivation, which was proven by shifts in potential, reduced corrosion rates, and minor charge transfer. The findings confirm that Crassostrea madrasensis bio-ceramic reinforcements and garlic extract-based corrosion inhibition provide a sustainable method for improving the performance and durability of copper matrix composites.

Diamond-like carbon (DLC) films exhibit superior tribological properties; however, their widespread adoption in precision manufacturing is hampered by inherent brittleness and a lack of reliable toughness characterization methods at the micrometer scale. This review critically examines existing techniques for evaluating DLC film toughness, highlighting limitations due to film thickness constraints and subjective failure definitions. We focus on two prominent micro-scale methods: impact testing and scratch testing. Impact toughness is assessed through energy absorption analysis based on impact crater morphology, including crack patterns and delamination areas. Scratch toughness is evaluated using critical loads (Lc₁, Lc₂) and the derived Crack Propagation Resistance (CPRS) parameter, complemented by microscopic failure analysis. We argue that neither method alone suffices for comprehensive toughness assessment. Instead, we propose a synergistic strategy integrating both techniques to provide a practical and comprehensive evaluation encompassing energy- and stress-based failure mechanisms under varying loading conditions. This approach offers a practical framework for developing tougher DLC coatings.