Overview
Some products require glazing. We apply glass glaze evenly on the ceramic surface by physical or chemical methods, and form a strong bond between the glass glaze and the ceramic surface through high-temperature sintering. Glass glaze can enhance the smoothness, firmness and corrosion resistance of ceramics, and also make ceramics easier to clean.
Glass Glazing for Advanced Ceramics
Glass glazing is a surface treatment process where a glass-based coating is applied to advanced ceramics (e.g., alumina, zirconia, or silicon carbide) to enhance their thermal stability, chemical resistance, and mechanical durability. The glaze forms a vitrified layer during high-temperature sintering (1,200–1,500°C), sealing surface pores and preventing environmental degradation. This technique is critical for components in aerospace, energy, and biomedical industries exposed to extreme conditions.
Key Process Steps
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Glaze Formulation
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Composition: Glazes typically contain SiO₂ (50–70%), Al₂O₃ (10–20%), and fluxing agents (e.g., B₂O₃, Na₂O) to lower melting points. Additives like ZrO₂ or Y₂O₃ improve thermal shock resistance.
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Preparation: Raw materials are ball-milled into fine powders (<10 µm) and mixed with binders (e.g., polyvinyl alcohol) to form a slurry.
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Application Methods
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Spray Coating: Automated spray systems ensure uniform thickness (50–200 µm) for complex geometries like turbine blades.
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Dip Coating: Immersing ceramics in glaze slurry, ideal for small, high-volume components.
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Screen Printing: Precision patterning for electronic substrates or sensor surfaces.
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Sintering
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Temperature Profile: Gradual heating (5°C/min) to 1,400°C in oxidizing or inert atmospheres.
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Phase Formation: Glass phase densifies, bonding with the ceramic substrate via diffusion.
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Quality Control
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Defect Detection: X-ray tomography or ultrasonic testing identifies cracks or voids.
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Performance Testing: Thermal cycling (1,000°C ↔ room temperature) and corrosion resistance (acid/alkali immersion).
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Applications
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Aerospace: Thermal barrier coatings (TBCs) for engine components (e.g., SiC/SiC composites).
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Energy: Sealing layers for solid oxide fuel cells (SOFCs) to prevent gas leakage.
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Biomedical: Bioinert glazes for zirconia dental implants to reduce bacterial adhesion
Glass glazing enhances advanced ceramics by forming a dense, non-porous layer that blocks oxygen diffusion and chemical corrosion. For example, alumina components with SiO₂-B₂O₃ glaze show 40% lower oxidation rates at 1,200°C compared to uncoated samples. The glaze also reduces surface friction, improving wear resistance in industrial pump seals.
Choose glazes with high SiO₂ (≥60%) and Al₂O₃ (≥15%) for thermal stability. Additives like ZrO₂ (5–10%) mitigate thermal expansion mismatch. For aerospace TBCs, Y₂O₃-stabilized ZrO₂ glazes achieve thermal conductivity <1.5 W/m·K, outperforming traditional coatings.
Defects include pinholes (from trapped gases) and cracks (due to CTE mismatch). Solutions include optimizing sintering profiles (e.g., slow cooling at 2°C/min) and using nano-sized fillers (e.g., Si₃N₄) to refine microstructure.
Yes. Laser cladding or sol-gel recoating can repair minor defects. For severe damage, chemical etching (e.g., HF-based solutions) removes the glaze layer, allowing reapplication.