Recycling B4C grinding waste to fabricate high-performance ceramics by modification treatments and hot pressing

B4C grinding waste, originated from the fine grinding process of sapphire wafers, is discarded without reutilization, which causes environmental pollution and resource waste. This work proposes new methods on recycling B4C grinding waste to fabricate high-performance ceramics by first modification treatments via ball-milling mixing or microwave digestion with sulfuric acid and then hot pressing. The characteristic of B4C grinding waste is studied and Al2O3 is the main impurity. The direct hot pressing of B4C grinding waste is performed and the obtained ceramic is fragile. The large-size and unevenly distributed Al2O3 is verified to cause the fracture according to the structure analysis. Ball-milling mixing can break the Al2O3 agglomerate and make Al2O3 distribute evenly, and microwave digestion with sulfuric acid can remove most Al2O3. The ceramics fabricated via hot pressing with B4C grinding waste treated with ball-milling mixing or microwave digestion show good microstructure and mechanical property. The relative density, hardness, flexural strength and fracture toughness of the ceramics fabricated with grinding waste treated with ball-milling mixing are 98.82%, 32.42 GPa, 439.44 MPa, 4.82 MPam1/2, respectively, higher than those of the ceramics fabricated with grinding waste treated with microwave digestion, which are 98.69%, 29.54 GPa, 368.18 MPa, 4.20 MPam1/2, respectively. This work not only realizes the secondary utilization of waste and avoids pollution, but also provides another way supplying the high-cost B4C powder and ceramic, which has high economic benefits.