Producing reflective screens for sapphire crystal growth furnaces requires high-purity (≥99.95%) molybdenum foil and precise processing to ensure high-temperature reflection efficiency and structural stability. The process includes: 1) Material Selection: Cold-rolled molybdenum foil (0.2-1 mm thick) with tensile strength of 800-1000 MPa and polished surface (roughness Ra<0.1 μm) is chosen to minimize heat absorption. 2) Cutting: Laser or wire cutting shapes the foil into designed dimensions (typically circular or curved), with ±0.01 mm precision. 3) Forming: Stamping or bending creates curved reflective structures, followed by annealing (800-1200°C, vacuum) to relieve stress and maintain ductility (elongation 10-20%). 4) Surface Treatment: Chemical cleaning removes oxides, and polishing enhances reflectivity (>90% for infrared light). 5) Assembly: The foil is fixed in the furnace, ensuring uniform spacing from the crucible, often using molybdenum bolts. Molybdenum’s high melting point (2623°C) and thermal conductivity (138 W/m·K) enable stable heat reflection at 2000°C, reducing energy consumption. Its low thermal expansion coefficient (4.8 × 10⁻⁶/K) minimizes thermal deformation. Inert gas protection is needed above 600°C to prevent oxidation. Quality control includes surface flatness testing, spectral analysis, and high-temperature performance checks to ensure screen durability. Advantages include efficient reflection and stability; disadvantages are complex processing and high cost.
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