Advanced Ceramics Progress
Volume:5 Issue: 1, Winter 2019

Sol-gel process was chosen to produce a photocatalytic film to degrade methylene blue. In order to study structural and morphological properties of the coatings, a base sol of TTIP, I-PrOH, and DEA was prepared. Then with addition of 45g/L PEG 2000, 30g/L TiO2 and 15g/L PEG 2000 + 30g/L TiO2, to the base sol, three other sols were produced. The results of this study indicated that substrate can affect photocatalytic behavior of the coatings. Then different parameters (Sol types, number of dip coating cycles, initial concentration, two wavelengths of 265 and 254 nm and pH) of the study were modified and an equation was derived for each parameter. At last, using all the derived equations, a more general equation was calculated to predict the rate of corrosion based on pH, initial concentration of methylene blue, and number of dip coating cycles. A reactor was designed and tested to investigate the effect of continuous degradation. It was realized that the rate of all photocatalytic reactions were inhibited as a result of higher evaporation and decreased exposure time to coating and ultraviolet light.

The effect of zinc phosphate (ZP) and zinc calcium phosphate (ZCP) coatings on the reinforcing mechanisms of smooth steel fiber in cementitious matrix have been studied. The results of pull out tests illustrated that by coating smooth steel fiber the pull-out load may be increased up to 100%. The effect of zinc phosphate coating on interface bonding was more than zinc-calcium phosphate coating. This could be due to formation of large crystals in zinc phosphate coating and its tendency to react in alkaline environment of cementitious matrix. This behavior was also confirmed by SEM analysis. The obtained results from a mathematical model for pull-out energy were in good agreement with the experimental results. The results indicated that coating of fibers with zinc based ceramics could improve the composite's mechanical properties as well as its chemical stability.

In particular, chalcogenide glasses and glass-ceramics are new materials that exhibit good transparency in infrared region (0.8-12µm). We can overcome the main weakness of these glasses by improving the hardness through controlling crystallization. In this paper, we report results of a study on chalcogenide glasses in the ternary system of As-Se-Ge with nominal composition of Snx (Se0.6As0.1Ge0.3)100-x (x=0, 2, 4 and 6 mol %) which is suitable for use in optical devices. Melt quench technique was used for preparing alloy specimens. Glass-ceramics were made using an appropriate heat-treatment temperature and time from Snx (Se60As10Ge30)100-x glasses in order to improve the mechanical properties. The temperature of the heat treatment started with the peak temperature (Tp) for glasses and different characteristics of prepared glasses such as glass transition temperature, hardness, density, transmittance, and microstructure were determined. Initially, Tg temperature was decreased with the addition of Sn, but with an increase of Sn up to 6 mol%, Tg was increased due to structural cohesion and formation of long chains of selenium. In this study, the highest value of the hardness for the Se60Ge30As10Sn6 glass was obtained after heat treatment and forming a crystalline phase while maintaining the initial transmittance.

In present research, the foam glass-ceramic composites fabricated by window glass, steel slag and SiC, CaCO3 foaming agents were investigated by press–sintering method. The optimum sintering temperature was obtained at 1200°C with a 3-minutes holding time and 20°C/min heating rate. The optimum pressure level of 80 MPa for achieving the 70 % of relative density was selected. The effect of particle size distribution of starting materials on the green and fired density of resulted glass-ceramics composites was evaluated. The composite's green density was 1.7g/cm3 obtained using the following particle size (49 wt. % 150μm, 21wt. % 85μm, 21wt. % 65μm, 9wt. % 45μm). It was shown that using medium-fine grade of the slag powder, the compaction and green densities of samples were increased up to 16% while in the case of slag/glass composites (due to the high hardness of the glass powder), the compaction of composite was  increased 11% compared to the coarse grade particles bearing samples. It was observed that finer particle sizes (below 75 μm) significantly cause more foaming and lower density (about 80 wt.% porosity). This can be due to the faster coalescence process and gases trapping which was arisen from the decomposition of foam agent.

Flash sintering is one of the newest techniques for sintering ceramics to near full density. It occurs in an appropriate combination of temperature and electric field. Temperature measurement is one of the most serious challenges in this process. In the present study, we tried to model a flash sintering process of 8YSZ and 3YSZ with finite element method to make an assessment for temperature distribution and also to estimate the critical values of temperature and electric field intensity. Results indicated the correlation between furnace temperature and electric field intensity and also uniformity of current passage through the sample can be observed by simulation modeling.

In this research study, the effects of aluminum nitride (AlN) additive on the densification behavior and microstructure development of titanium diboride (TiB2) based ceramic matrix composite were investigated. In this way, a monolithic TiB2 ceramic and a TiB2–5 wt% AlN ultrahigh temperature ceramic composite were fabricated by spark plasma sintering (SPS) process at a temperature of 1900 °C for a dwell time of 7 min under an externally applied pressure of 40 MPa in vacuum conditions. The relative density measurements were carried out using the Archimedes principles for evaluation of bulk density and rule of mixtures for calculation of theoretical one. Compared to the additive-free monolithic TiB2 ceramic sample with a relative density of ~96%, the addition of AlN as a sintering aid greatly improved the sinterability of TiB2 matrix composite so that a near fully dense sample with a relative density of ~100% were obtained by the spark plasma sintering process. The removal of harmful oxide impurities of titania (TiO2) and boria (B2O3) from the surfaces of starting TiB2 powder particles and in-situ formation of new phases such as aluminum diboride (AlB2) and Al2Ti as an intermetallic compound of aluminum and titanium, not only improved the sinterability of the composite ceramic, but also significantly prevented the extreme growth of TiB2 grains.