Effect of acidic environment on glass-ceramic-metal composite materials

Abstract

Ceramic materials are often used in very aggressive and corrosive environments due to their high chemical inertness and corrosion resistance. However, even if corrosion progresses slowly, it still occurs. Corrosion usually depends on the structural properties of the materials. For example, more compact or tightly bonded materials corrode less, whether glass or crystalline materials. With the dramatic increase in nitrogen and sulphide oxide emissions, acid rain pollution has become one of the world's biggest environmental problems. One of the methods used to measure the corrosion resistance of ceramic materials and ceramic matrix composites (CMCs) is the immersion method, which studies their behaviour by immersing them in corrosive media and measuring the concentration of ions released. Adding different particles to basalt before sintering to obtain CMCs can increase fracture toughness. The aim of this work was to investigate the effects of the content of 316L stainless steel powder in sintered basalt on its structural properties and resistance to the release of metal ions in acidic environments. The andesite-basalt-based samples were prepared by adding 5, 10, 15, and 20 wt.% of steel powder, respectively, before sintering. The basalt aggregate and the pure sintered basalt served as reference materials. The metal concentrations in the solution were studied for 15 weeks at room temperature and a pH of 3.13±0.01. The major elements Fe, Cr, Mn, and Ni were monitored, while the others were below the limit of quantification. We found that the concentration of metal ions released from the basalt aggregate increases exponentially, implying that the release rate is constant over time. However, the concentration of metal ions released from the sintered samples follows the Weibull cumulative distribution function (CDF), which means that the release rate changes over time and allows us to calculate the characteristic times of ion release. The presence of 5 wt.% steel powder in the sintered basalt accelerates the release of metal ions by about six times. If the steel powder content increases, the metal release rate does not change further. These findings are positive since the highest toughness of sintered basalt is expressed at 20 wt.% of steel powder. The corrosion stability of glass-ceramic-metal-based composites was found to be satisfactory compared to natural andesite-basalt aggregate. These composites can be used in conditions of acid rain exposure where higher fracture toughness is required.