Search

The study describes the successful development of a TiO2 ceramic substrate with a protective nano-Al2O3 coating using two different coating techniques: microwave combustion and polymeric methods. The coated ceramics demonstrate enhanced corrosion resistance compared to the uncoated substrate. The optimal TiO2 substrate was prepared by firing it at 1000 °C. This was done to give the desired physical properties of the TiO2 substrate for the coating procedures. Nano-Al2O3 powder was coated onto the surface of the TiO2 substrates. The TiO2 substrates with the Al2O3 coating were then calcined (heat-treated) at 800 and 1000 °C. The structures, morphology, phase composition, apparent porosity, bulk density, and compressive strength of the substrate and coated substrate were characterized. Upon firing at 1000 °C, it was discovered that the two phases of TiO2—rutile and anatase—combine in the substrate. Once the substrate has been coated with nano Al2O3 at 1000 °C, the anatase is transferred into rutile. When compared to the substrate, the coated substrate resulted in a decrease in porosity and an increase in strength. The efficiency of the ceramic metal nanoparticles Al2O3 as a good coating material to protect the TiO2 substrates against the effect of the corrosive medium 0.5 M solution of H2SO4 was measured by two methods: potentio-dynamic polarization (PDP) and the electrochemical impedance spectroscopy (EIS). The results indicated that the corrosion rate was decreased after the substrate coated with alumina from (67.71 to 16.30 C.R. mm/year) and the percentage of the inhibition efficiency recorded a high value reaching (78.56%). The surface morphology and composition after electrochemical measurements are investigated using SEM and EDX analysis. After conducting the corrosion tests and all the characterization, the results indicated that the coated TiO2 substrate prepared by the polymeric method at 800 °C displayed the best physical, mechanical, and corrosion-resistant behavior. [ABSTRACT FROM AUTHOR]

This study focuses on recycling of granite sludge for production of cordierite-spinel composites prepared by direct coagulation method. Furthermore, the effect of transition metal oxides (CuO, NiO, and MnO2) on their in-situ formation, sinterability and properties (mechanical and electrical) was studied. The granite sludge, talc, and calcined alumina were utilized to prepare cordierite-spinel composites. Firstly, talc and alumina were mixed and fired at 1350 °C, then mixed with granite sludge and transition metal oxides to be ready for casting by direct coagulation method after adjusting the appropriate conditions. The casted specimens were firstly dried then sintered at 1200 and 1250 °C. The phase composition and physical properties of sintered composites were investigated by x-ray diffraction technique (XRD) and Archimedes method, respectively. The microstructure was investigated by scanning electron microscope while the hardness was tested by Vickers indentation method. The electrical properties of sintered bodies were also evaluated. All XRD patterns showed formation of cordierite and spinel phases after addition of metal oxides and sintering at 1200 or 1250 °C. Also, the results indicated enhancement of densification parameters for CuO- and MnO2-containing composites after sintering at 1250 °C while for NiO-containing composites, they enhanced after sintering at 1200 °C. Furthermore, the densification parameters were improved with increasing metal oxides contents. The highest hardness value (8.3 GPa) was obtained for 6% NiO-containing composite. The composites that contained 6 wt.% CuO or MnO2 exhibited hardness values of 6.4 and 6.16 GPa, respectively. The trend of electrical conductivity values for sintered composites was as follows: CuO-containing composite > NiO-containing composite > MnO2-containing composites. [ABSTRACT FROM AUTHOR]

The present work focused on recycling the alum sludge which is one of the serious problems during the production of potable water. In this work, the alumina was extracted from alum sludge by using different chemical treatment methods after subjecting to different thermal treatments. XRD, XRF, SEM, TEM, IR and surface area measurements were used to detect the properties of the obtained alumina. Alpha alumina was obtained at 1400°C after treatment by NaOH followed by ammonium acetate as a precipitating agent for Al(OH)3 or by direct addition of NH4OH in one step method at pH 5.5–6. On the contrary, the treatment by NaOH followed by NaHCO3 for precipitation of Al(OH)3 led to the formation of sodium aluminate beside low percentage of alpha alumina after the heat treatment. [ABSTRACT FROM AUTHOR]