Advanced Ceramics Progress
Volume:5 Issue: 2, Spring 2019

In this report, the degradation of 1-Naphthol was studied under xenon irradiation for 2 h using WO3-rGO nanocomposite as photocatalyst. Raman spectroscopy and scanning electron microscopy demonstrated nanocomposite formation. Gas chromatography-mass spectrometry (GC-MS) technique which was utilized to analyze the degradation products, confirmed the formation of salicylic acid as an intermediate compound.

Phosphate-based glasses are suitable candidates for biomedical applications due to their porous structure. This study illustrates the properties and structural characterization of titanium-phosphate glass powders in the 55(P2O5)-25(CaO)-(20-x)(Na2O)-x(TiO2), (x= 5, 10, 15) systems, which were prepared via sol-gel method. For this purpose, precursors of P2O5, CaO, Na2O, and TiO2 were added together dropwise on the magnetic stirrer after diluting or dissolving in ethanol. After gel formation, drying was done for various time periods at 60, 120, 180 and 200 °C. The structural and thermal properties of the obtained stabilized sol-gel glass powders were characterized using X-Ray Diffraction (XRD), Fourier Transform Infrared (FT-IR) spectroscopy, Simultaneous Thermal Analysis (STA), Brunauer-Emmett-Teller surface area, porosity analyzer (BET), and Scanning Electron Microscopy (SEM). The XRD results confirmed the amorphous and glassy nature of the prepared samples. FT-IR Spectroscopy results showed that the local structure of glasses changed with increasing TiO2 content. As TiO2 content increased in the glass structure, the phosphate connectivity increased. It was indicated that the addition of TiO2 correlated unequivocally with an increase in glass stability. Also, to assess specimen’s bioactivity, the samples were soaked in Simulated Body Fluid (SBF) for 7 days. The results of this study suggested that glass composition had a significant influence on apatite-forming ability, indicating the possibility to customize the properties of this class of materials towards the biomedical applications.

The purpose of this research was to produce high-purity monodisperse barium titanate nanocrystals (BTO-NCs). To this end, a modified and very high-yield organosol precipitation method was developed. The novelty of this method was its purely organic approach, which stoped the application of inorganic bases such as caustic soda (NaOH) and avoided the risk of the presence of undesirable ions in the synthesized dielectric material. Results showed that an absolutely-organic base, such as the methylamine aqueous solution could ensure the basic condition required for high-yield organosol precipitation. X-ray diffraction, scanning electron microscopy, dynamic light scattering, and high-resolution transmission electron microscopy analyses were utilized to ensure the formation of monodisperse NCs. It was also found that monodisperse precursor crystals of about 3 nm have been achieved. Using oleic acid as the capping agent allowed generating uniformly small size and excellent dispersibility of the precipitate in the nonpolar solvents. Thus, the synthesized NCs could be easily redispersed in different nonpolar solvents to produce various suspensions of nm-size BTO-NCs without adding any surfactant. The obtained transparent suspensions, which include well-dispersed nm-size crystals, are promising for many applications in nanotechnology such as advanced electro-optic devices.

In this research, bimetallic catalysts including Pd and Pt was synthesized on the composite of carbon nanotube (CNT) with Nafion and compared with Pd-Pt synthesized on CNT considering the key role of catalysts in PEMFC electrodes. The difference between the electrodes fabricated from these two synthesized catalysts was in the adding time of Nafion. The synthesized catalyst can enhance the performance of gas diffusion electrode (GDE) in cathode reaction (Oxygen Reduction Reaction or ORR) of polymer electrolyte membrane fuel cell (PEMFC) compared to commercial Pt/C catalyst. The bimetallic catalyst was synthesized in two steps. Pd and Pt were reduced at the first and second step, respectively. To reduce metals on support, the impregnation method were used along with hydrothermal. The electrochemical performance of the electrodes in ORR was studied through the Linear Sweep Voltammetry (LSV), Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS). Inductively coupled plasma (ICP), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM) techniques were applied to characterize the catalyst. The results have confirmed that the timing of Nafion addition can influence the electrode performance for ORR.

The effect of samarium oxide was examined on the sintering, microstructure, and grain growth behaviors of (Co, Nb)-doped SnO2-based ceramics prepared by co-precipitation method. The sintered samples were studied through x-ray diffraction (XRD), scanning electron microscopy (SEM), and electron dispersive spectroscopy (EDS) analyses. The microstructure observations revealed that the samples were near fully dense at a sintering temperature of 1200°C for 1h. The samarium doping prevented accelerated grain growth of the SnO2-based ceramic in the final stage of the sintering. The mean grain size of the SnO2-based ceramic without Sm2O3 doping was 2.70µm, which was reduced to 0.887µm for the sample doped with 0.05mol% Sm2O3. The grain size reduction of samples doped with Sm2O3 could be attributed to the segregation of Sm2O3 at the grain boundaries.

Porous Si3N4 ceramics were prepared by a novel colloidal method called starch consolidation casting. In this method, starch plays both pore-forming and consolidating roles. The effect of starch content on the viscosity of Si3N4/starch slurry was investigated in this research. Rotational Rheometer was used to study the rheological behavior of Si3N4/starch slurry. Green samples with 5 to 10MPa flexural strength were shaped by casting slurries in a nonporous mold and held at 80°C for 120min. Afterward the samples burned-out and sintered at 1650°C for 4h in an air furnace under a nitride powder bed condition. Thermal behavior, phase evolution, and microstructure of sintered samples were characterized through Thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscope (SEM). The XRD results showed that was the main phase in the sintered samples. The  phase content was as much as 90wt% in the sintered samples. Finally, a porous silicon nitride sample was successfully produced with 44vol% open porosity and Flexural strength of 108.9MPa through the starch consolidation casting method.