Nanotextured Mold Surface with DLC Coating for Reduction in Residual Ceramic Particles

Ceramic manufacturing processes often face challenges with particle adhesion to mold surfaces, which leads to frequent cleaning and reduced productivity. Prior research has shown that surface treatments like texturing and coatings can influence adhesion properties. However, the specific effects of nanotexturing and tetrahedral amorphous carbon (ta-C) coatings on ceramic residue reduction remain unclear. This gap motivated the current investigation into how surface morphology and coating hardness affect ceramic particle retention. No prior work had resolved the optimal combination of texturing and coating parameters for ceramic mold applications. Existing studies have focused on general surface treatments but lacked specificity to ceramic particles like Al₂O₃ and SiO₂. The need for durable, low-adhesion mold surfaces persists in industrial settings. Current methods fail to address the dual challenges of high wear resistance and low particle adhesion. This paper aims to clarify how surface design and material choice influence ceramic residue levels in press molding.

The study aims to evaluate how nanotexturing and ta-C coatings can reduce ceramic particle adhesion on mold surfaces during press molding. The specific problem involves frequent mold cleaning due to residual ceramic particles, which lowers productivity. The motivation comes from the need for durable, low-maintenance mold surfaces in ceramic manufacturing. The researchers seek to determine whether surface morphology and coating hardness influence ceramic residue levels. They also aim to compare different ta-C variants and surface textures for effectiveness. The goal is to provide practical design guidelines for mold surfaces. This includes identifying optimal texturing pitch and coating hardness for minimal residue. The study addresses a specific industry need for improved mold performance.

The researchers tested two surface morphologies: 770 nm pitch nanotexturing and flat surfaces. They evaluated five materials: nonhardened steel, hardened steel, ta-C, and two types of nitrogen-doped ta-C (ta-CNx). Molding tests used Al₂O₃ and SiO₂ ceramic particles to measure residue amounts. Surface hardness was measured to correlate with residue reduction. The study compared residue levels across all combinations of texture and coating. Data collection focused on quantifying residual particle mass after molding. The experimental setup simulated typical press molding conditions. Results were analyzed to determine the most effective surface treatments.

The ta-C coating on flat surfaces with 30 GPa hardness showed the lowest Al₂O₃ residue of 5.9 μg. This is 82% less than nonhardened steel. For SiO₂ particles, ta-CNx₂₀ showed 234 μg residue, 81% less than nontextured ta-CNx₂₀. Nanotexturing at 770 nm pitch reduced SiO₂ residue by 81% compared to flat surfaces. The lowest surface energy per unit area correlated with reduced residue. Harder surfaces consistently showed lower particle adhesion. Residue levels varied significantly between ceramic types and surface treatments. The study found that surface hardness and texturing pitch are critical factors.

The authors propose that nanotextured mold surfaces with ta-C coatings reduce ceramic residue effectively. They suggest that texturing pitch should be small enough to trap ceramic particles. Surface hardness must be sufficient to resist wear and particle adhesion. Lower surface energy per unit area correlates with reduced residue. The findings indicate that ta-C coatings outperform nonhardened steel. The study supports using ta-CNx₂₀ for SiO₂ particles and ta-C for Al₂O₃. Design guidelines emphasize balancing hardness and surface energy. The results align with the goal of improving mold longevity and reducing cleaning frequency.