Corrosion of Si3N4–MoSi2 ceramic composite in acid- and basic-aqueous environments: surface modification and properties degradation

Degradation of mechanical and electrical properties after long-term oxidation and corrosion of non-oxide structural ceramic composites

“…30,32 After corrosion in acidic environment the failing of the Si 3 N 4 -35 vol.% MoSi 2 composite (the strength is about 79% of the as-sintered value) is due to the presence of the porous and thick subsurface layer affected by corrosion, while after the tests in NaOH the strength degradation (87% of the as-sintered value) is due to the increased surface population of defects caused by the leaching of the superficial MoSi 2 particles.…”

“…30,32 The chemical attack in sulphuric acid solution at RT and at 40 • C involves only the progressive chemical dissolution of grain boundary phases. The attack on TiN and on MoSi 2 occurs only at 70 • C and is more enhanced for TiN.…”

“…26 Oxidation and corrosion of non-oxide ceramic composites results in different behaviours and mechanisms depending on the temperature, besides the matrix microstructure and type and amount of the electroconductive particles. [18][19][20][21][22][23][24][25][27][28][29][30][31][32] In particular, chemical reactions leading to oxidation of silicon nitride or aluminium nitride matrices containing titanium nitride or molybdenum disilicide are accompanied by several diffusion phenomena, therefore, the complex interactions among the involved species at the reaction interface and inside the growing oxide scale and the development of complex product layers affect the overall oxidation behaviour. This paper shows the results of long-term oxidation and corrosion in aqueous basic or acid solutions on flexural strength and electrical resistivity of full dense composites in the systems: AlN SiC, AlN SiC MoSi 2 , Si 3 N 4 MoSi 2 and Si 3 N 4 TiN.…”

Corrosion of pressureless sintered ZrB2–MoSi2 composite in H2SO4 aqueous solution

“…3 Literature is very scarce about aqueous corrosion of structural ceramic composites. [4][5][6][7][8][9] Previous studies on monolithic ZrB 2 6 and ZrB 2 -SiC composite 7 demonstrated that the addition of SiC as secondary phase did not modify the corrosion behaviour of the ZrB 2 phase in aqueous environments. However, the addition of * Corresponding author.…”

“…a secondary phase was found to influence the overall corrosion of ceramic composites because of its individual and specific corrosion characteristic, such as MoSi 2 in AlN-SiC and Si 3 N 4 matrices. 8,9 In this study, the corrosion behaviour of a pressureless sintered ZrB 2 + 20 vol% MoSi 2 composite was investigated in 1.8 M sulphuric acid aqueous solution at room temperature, 40 and 70 • C up to 90 h.…”