Iranian Journal of Materials Science and Engineering

Coatings based on chromium borides and chromium carbides are commonly employed in applications requiring mechanical performance, such as high hardness and low friction coefficient, as well as corrosion resistance. In this work, we made layers of chromium borides and chromium carbides on the surface of low carbon steel through some specific treatments. For chromium borides, the boriding treatment in a solid medium at 900 °C for 4 hours followed by chromium electroplating on the steel surface and finally the application of annealing treatment at temperatures at 950 °C for 1 and 2 hours. For chromium carbides, the cementation in a solid medium followed by electroplating of chromium on the surface and finally the application of annealing treatment at temperatures between 500 and 1100 °C for 1 hour. The obtained results show that, in the first case, boron diffusion and chromium deposition lead to chromium borides on the treated surface. Similarly, for the second case, the cemented layer and the chromium deposited on the surface combine to form chromium carbides on the treated surface after annealing. The characteristics of the chromium borides and chromium carbides obtained are very similar to those of chromium borides and chromium carbides obtained by other processes.

Our study is to highlight the effect of the acid-base character and the redox potential of two clays, synthetic anionic Layered Double Hydroxides Zn₃Al-CO₃ (LDH) clay, and natural commercial cationic clay "Ghassoul" on their antioxidant and antibacterial activities. The antibacterial effect was tested on two Gram-positive bacteria: Staphylococcus aureus and Enterococcus faecalis. Then it was tested on a Gram-negative bacterium: Escherichia coli. The determination of the minimum inhibitory concentration of the two materials was carried out using the microplatemicrotitration technique. The antioxidant activities of clays are assessed by the methods 2.2-diphenyl-1-picrylhydrazyl and the reducing power of iron (Fe³⁺). The redox potential (Eh) was measured and the redox strength (rH2) was evaluated. The results showed that these materials have an antibacterial effect on the three bacteria tested, the measured zero charge point of Ghassoul (pH_zpc =8.75) more basic than that of double layer hydroxide (pH_zpc =7.5), redox potential of LDH (-27mV) was higher than that of Gh (- 103mV), and the rH2 of Gh (14.04) was higher compared to anionic clay (13.33).
Keywords: LDHs, Ghassoul, Redox Potential, Zero point of Charge, Antibacterial.