Microstructure observation on corrosion behavior of liquid phase sintered silicon carbide ceramics
JIANG Yong, WU Lan-er, CHEN Yu-hong, LU You-jun(School of MSE, The north University for nationalities, Yinchuan Ningxia 750021, China)
The corrosion behavior of LPS (liquid phase sintered) silicon carbide with AlN-R_2O_3(Y_2O_3+La_2O_3) as sintering additives were investigated. The samples were tested by putting into HF, HCl, NaOH, KOH, K_3Fe(CN)_6, etc. or mixed solution of them. The weight loss of samples after corrosion are measured. The SEM photo of the experimental specimen before and after corrosion are compared. The result shows that under both room and boiling temperature, the corrosion of LPS-SiC in HF, or in HCl, in NaOH,in KOH, all shows mainly intercrystalline liquid phase corrosion. Because glass phase of intercrystalline were etched off, the SiC crystals left look like islands. Tight connected grain boundary did not be etched. The corrosion extent of samples in acid are heavier than those in alkali. The erosion in room temperature developed much slower than it did in boiling temperature. Corrosion did not appeare in K_3Fe(CN)_6. But in the mixture aqueous solution of K_3Fe(CN)_6 and KOH, corrosion did happen in the intercrystalline, angularity and scratch. So it is good to show the profile of the crystals by this erosion method. The weight loss of the samples in strong acid solution slow down with the process going on. In the strong alkali solution, the samples seldom have weight loss.