Preparation of LiDAR-detectable black pigments via recycling the silicon sludge generated from the semiconductor manufacturing processes

A novel LiDAR-detectable plate-like hollow black titanium dioxide (HbTiO₂) is developed by recycling silicon sludge generated from silicon wafer sawing. By employing TiCl₄ sol-gel synthesis, hydrofluoric acid etching, and NaBH₄ reduction, the hollow-structured black TiO₂ is successfully synthesized. Plate-like HbTiO₂ readily mixed with hydrophilic varnish, owing to its inherent hydrophilic properties. With monolayer coating, HbTiO₂-based paints exhibit the blackness (L* = 17.63) comparable to that of commercial black paints, indicating that NaBH₄ successfully changed the color of TiO₂ from white to black. In addition to its blackness, HbTiO₂ exhibits a superior near-infrared (NIR) reflectance of ca. 26.8 R% at 905 nm, making it suitable for integration with the LiDAR systems used in autonomous vehicles. This high NIR reflectance ensures that HbTiO₂ can effectively interact with the LiDAR sensors, attributing to the hollow structures and effective light reflection mechanism. Furthermore, the use of recycled silicon sludge not only offers a cost-effective alternative to traditional template materials but also promotes environmental sustainability by reducing solid waste. Our findings demonstrate the potential of HbTiO₂ as an innovative and practical LiDAR-detectable black pigment, paving the way for advanced applications in autonomous vehicle technologies.