A novel sintering additive system for porous mullite-bonded SiC ceramics: High mechanical performance with controllable pore structure

In situ formation of mullite strengthened SiC porous ceramics via gelcasting with high strength and good alkali resistance

“…Anorthite intermediate phase was observed. The overall reaction mechanism in mullitization was determined as 23 : $$\begin{eqnarray}&& 1.5{\rm{Ca}}{{\rm{F}}_2}\left( {\rm{s}} \right) + 2{\rm{A}}{{\rm{l}}_2}{{\rm{O}}_3}\left( {\rm{s}} \right) + 3{\rm{Si}}{{\rm{O}}_2}\left( {\rm{s}} \right)\mathop \to \limits^{\quad \quad }\nonumber \\ && \quad 1.5{\rm{CaO}}\cdot{\rm{A}}{{\rm{l}}_2}{{\rm{O}}_3}\cdot2{\rm{Si}}{{\rm{O}}_2}\left( {{\rm{s}},{\rm{\;anorthite}}} \right) + {\rm{Al}}{{\rm{F}}_3}\left( {\rm{g}} \right){\rm{\;}}\end{eqnarray}$$ $$\begin{eqnarray}&& 6{\rm{Al}}{{\rm{F}}_3}{\rm{\;}}\left( {\rm{g}} \right) + {\rm{\;}}6.5{\rm{Si}}{{\rm{O}}_2}\left( {\rm{s}} \right)\mathop \to \limits^{\quad \quad } 3{\rm{A}}{{\rm{l}}_2}{{\rm{O}}_3}\nonumber \\ && \quad \cdot2{\rm{Si}}{{\rm{O}}_2}\left( {{\rm{s}},{\rm{\;mullite}}} \right) + 4.5{\rm{Si}}{{\rm{F}}_4}\left( {\rm{g}} \right){\rm{\;}}\end{eqnarray}$$…”

“…Based on our previous work, 23 the optimized weight ratio of SiC, Al(OH) 3 and Y 2 O 3 was expected to be 50:25:1 for all specimens so as to obtain best conversion. The addition amount of CaF 2 was 0, 1.0, 1.5, 2.0, and 2.5 weight percent (listed in Table 1), and these samples were marked as 0 CaF 2 , 1.0 CaF 2 , 1.5 CaF 2 , 2.0 CaF 2 , and 2.5 CaF 2 , accordingly.…”

“…Anorthite intermediate phase was observed. The overall reaction mechanism in mullitization was determined as 23 :…”

“…In our previous work, 23 composite sintering additives of Al(OH) 3 + Y 2 O 3 + CaF 2 were developed to promote the transformation of cristobalite to mullite phase by dry‐pressing method. Y 2 O 3 was introduced to form a Y‐Al‐Si‐O liquid phase.…”

EFFECTS OF BORIC ACID DOSAGE AND REACTION TEMPERATURE ON THE PHASE COMPOSITION AND MICROSTRUCTURE OF Si C-B₄C COMPOSITE POWDERS SYNTHESISED BY THE CARBOTHERMAL REDUCTION METHOD

“…Silicon carbide (SiC) ceramics, as a kind of highperformance structural ceramic, has high hardness and strength at high temperatures, and other excellent properties, such as a high melting point, high thermal conductivity, low coefficient of thermal expansion, and good corrosion resistance. Thus, it is widely used in the fields of machinery, aviation, petroleum, chemical industry, energy and so on [1][2][3]. However, the strong covalent property of SiC itself makes it lack a plastic deformation ability, resulting in low strength and fracture toughness of SiC ceramics at room temperature, thereby limiting its application range [4][5].…”