Carbothermal Synthesis, Characterization, and Mechanical Properties of Sparkplasma Sintered Β-Sialon (Z = 2) Powder Prepared from Mechanochemically Activated Precursors

Based on technological capabilities, b-SiAlON ceramics are one of the most valuable compounds formed in the Si-Al-O-N system, which can be synthesized from various raw materials using different methods. The findings described in this paper provide an affordable approach for the elaboration of aluminosilicate precursor necessary for the synthesis of b-Si 4 Al 2 O 2 N 6 (z=2) from Aluminum Chloride hexahydrate, Ammonium Chloride and Sodium Metasilicate nonahydrate used as starting materials. The results obtained by XRD and FTIR revealed the amorphous precursor prepared by mechanochemical processing originally is originally crystallized as mullite and silica phases at 1200 o C/2h and then, with continuing heating to 1500 o C/2h, it is progressively converted into high-quality SiAlON powders b-Si 4 Al 2 O 2 N 6 and b-Si 2 Al 4 O 4 N 4 with a small amount of α-Al 2 O 3 through the reduction and nitridation of mullite and intermediate phases, produced at lower temperatures. The evaluation of sintering and mechanical properties of as-prepared SiAlON powder sintered by spark plasma sintering (SPS) at 1750 o C exhibits a significant improvement in densification (3.19 gcm -3 ) and also in the hardness number (15.70 GPa) and fracture toughness (6.9 MPa m 1/2 ), ascribed to the nanometric particles smaller than 50 nm well distributed throughout the microstructure of sintered sample