فهرست مطالب

Advanced Ceramics Progress - Volume:5 Issue: 3, 2019
  • Volume:5 Issue: 3, 2019
  • تاریخ انتشار: 1398/06/10
  • تعداد عناوین: 6
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  • L. Farahinia, M. Rezvani * Pages 1-7
    In the present study, the oxyfluoride glasses of SiO2-Al2O3-CaF2 system containing different amounts of Y3+ ions were prepared through the convenient melting method. The crystallization temperatures and size of the CaF2 nanocrystals were obtained from DTA curves and XRD patterns, respectively. As a consequence, the optimum amount of Y2O3 dopant (0.5wt%) and the suitable composition for basic glass were determined from the viewpoints of better crystallization behavior and higher transparency. The FTIR spectra approved the presence of oxyfluoride glass-ceramic structure in samples. The optical parameters (Fermi energy level, Urbach energy, direct and indirect band gaps) were calculated using UV-Vis spectra. The decreasing trend of Fermi energy level for glass-ceramic samples crystallized at higher temperatures is related to better semiconducting behavior. Urbach energy and optical band gap of the glass-ceramic samples were reduced due to the increment of the structural order and the emergence of dangling bonds, respectively.
    Keywords: band gap energy, Urbach tailing, Y2O3 dopant, Oxyfluoride glass
  • H. Mohebbi, S. M. Mirkazemi * Pages 8-14
    Flash sintering has been investigated as a modern sintering method through examining the effect of processing parameters such as current density, temperature, and contact paste on the flash sintered 8YSZ characteristic. 95% of theoretical density was achieved at 800°С in 30sec with a field intensity of 100V.cm-1 and a current density of 160mA.mm-2. Such relative density in conventional sintering achieved at 1450°С for 4 hours. Results indicated that the temperature and flash current density have positive effects on the relative density. Contact paste had a significant effect on the relative density. 8YSZ samples with LSM contact paste had a higher relative density in comparison with those flash sintered with Pt contact paste. The positive effect of LSM contact paste was more significant, especially at lower current density.
    Keywords: flash sintering, 8YSZ
  • F. Zerafati, H. Majidian *, L. Nikzad Pages 15-22
    In the present research, the aqueous suspensions of nano-sized YSZ particles were prepared using a common and available dispersant (Dolapix CE64) at different pH values and their stability were evaluated through the sedimentation height, viscosity measurement, and microstructural observation. Different amounts of dispersant were tested and the optimum percentage was examined by measuring the viscosity of suspensions. It was found that the use of Dolapix CE64 resulted in a suspension with a low sedimentation height and viscosity. The suspension prepared at pH = 4 with the optimum amount of dispersant (Dolapix CE64 0.1wt%) indicated a reasonable value of zeta potential. Moreover, the packing of particles in sediment layers was evaluated by sedimentation parameters (sedimentation volume and packing density) and the sediment layers were characterized by the microstructural observation. The microstructural observation revealed homogeneous packing of particles in the sedimentation layer, demonstrating the suspension stability, and proper dispersion of particles.
    Keywords: YSZ suspension, Dolapix, Viscosity, Microstructure of sedimentation layer
  • H. Ajamein, F. Assa, L. Sharifi, S. H. Mirhosseini * Pages 23-29
    The inkjet printing machine was initially used on ceramic parts as a small device in designing and advertising offices limitedly. In recent years, this device has been applied professionally to create high-quality patterns in the industry. In this method, liquid ceramic ink is sprayed on the specified parts by piezoelectric nozzles and after drying and discharging, the organic matter is baked at a different temperature. The ink of the digital print consists of two parts of the pigment and solvent. In this article, the effect of pigment and solvent additives has been investigated as the main factors affecting the physical properties of digital ink. The results of this study indicate that pigment is known as the main component of the physical properties of digital ink. The amount of pigment in ink can have a definite effect on density, viscosity, and surface tension while its effect on surface tension is lower than other properties.
    Keywords: digital ink, ceramic tile, pigment, Solvent
  • M. M. Kalantarian *, H. Yousefi Mashhour Pages 30-35

    In this study, theoretical investigations of Li2MSiO4 family cathode materials, including Li2MnSiO4, Li2FeSiO4, Li2CoSiO4, and Li2NiSiO4 are performed using density functional theory (DFT), by GGA and GGA+U methods. The materials properties including electrical conductivity and rate capability were investigated. To evaluate electrical conductivity, we use here a noble approach in DFT established in our previous work, which is related to intrinsic/extrinsic band gap concepts in solid state physics. Also, using lithiated-delithiated junction, aligning Fermi levels, and the difference between conduction bands value is the basis of the comparison of rate-capability, which is also a noble approach. To perform a quantitative investigation of electrical rate-capability, Fermi levels of obtained DOS diagrams of lithiated and delithiated structures were aligned. The difference between maximum of valance band (MVB) of lithiated and delithiated structures was considered as the criteria of rate-capability. The obtained values for the considered materials were fairly close. It was concluded that electron conductivity and rate-capability of this family of Li-ion cathode material is in the same range and do not strictly relate to the transition metal.

    Keywords: Band gap, Rate capability, Density of states, Lithium Ion Batteries, Cathode Materials
  • H. Aliasghari, A. M. Arabi *, H. Haratizadeh Pages 36-46
    Tungsten oxide (WO3) and tungsten oxide hydrate (WO3.H2O) nanoparticles were synthesized via microwave-assisted solution combustion in comparison with the acidic precipitation method. Oxalic acid was used as a surfactant and forming agent in the acidic precipitation method. In addition to oxalic acid, glycine and citric acid were also used as fuels in the microwave-assisted combustion method. The synthesis process was investigated by thermogravimetric (TG) and Differential Thermal Analysis (DTA) analysis. The obtained nanoparticles were analyzed using the scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The sample synthesized via the acidic precipitation method showed an orthorhombic crystal structure. One of the samples synthesized via the microwave-assisted solution combustion method was monoclinic and the two others were amorphous. The acidic precipitation method resulted in uniform plate-like structures while the combusted samples indicated irregular spherical morphology. Fourier-transform infrared (FTIR) analysis revealed stretching-vibrating bands relating to W-O bonds in the synthesized tungsten oxide nanoparticles. The bandgap energy of the nanoparticles calculated using UV-Vis spectra and Tauc plot extrapolation increased with decreasing the particle size. The data of reflectance and colorimetry had good agreement with the maximum peak position in the absorption spectra. The results indicated that the acidic precipitation method controls the particle's morphology as well as the size distribution. Although the combustion of fuels releases a lot of heat, the synthesis by solution combustion can control the size and shape of the nanoparticles, which can be an appropriate method for mass production of nanoparticles.
    Keywords: Microwave-assisted solution combustion synthesis, WO3, WO3.H2O, Optical properties, colorimetric characteristics