Advanced Ceramics Progress
Volume:7 Issue: 2, Spring 2021

The present study aims to introduce Niobium pentoxide-Titanium nanotube (Nb2O5-TNTs) composite as a novel anode material synthesized through hydrothermal method. In this respect, Nb2O5 nanoparticles and TNTs are separately synthesized through sonochemical and anodizing processes, respectively. According to FESEM images, the well-oriented TNTs with inner and outer diameters of 70 and 88 nm, respectively, are well decorated by Nb2O5 nanoparticles. The Nb2O5-TNTs anode shows the areal charge and discharge capacities of 0.167 mAh/cm2 and 0.146 mAh/cm2, respectively, at 0.113 mA/cm2 as well as 60% capacitive storage in 20 mV/s. High power Nb2O5-TNT anode reveals 86% reversible capacity in the 16th cycle with a columbic efficiency of 84% for the 16th cycle. In addition, the charge transfer resistance in TNTs declines from 750 Ω to 680 Ω after decorating by Nb2O5. The superior performance of Nb2O5-TNT composites is taken into account to derive higher charge storage from a capacitive charge storage which is dominant in the diffusion-controlled process. Therefore, Nb2O5-TNT composite can be applied to the next-generation pseudocapacitive anode in lithium-ion batteries.

Owing to their high strength-to-weight ratio, aluminum-ceramic composites, are widely used in various industries. In this study, aluminum matrix composite was fabricated with only 2 wt% micron-sized SiC particles as the reinforcing phase using electromagnetic stir casting. Prior to mixing, the surface of SiC particles were chemically etched by HF, NaOH, and KOH at two heat treatment temperatures of 460 and 510 °C for 30 min. The obtained results indicated better wettability and interaction between the etched SiC particles and Al matrix. In addition, etched SiC particle as a ceramic phase at 460 °C enhanced the mechanical properties of Al as a metal matrix, such as enhancing hardness and E about of 6.6 and 26.6%, respectively, mainly due to the increasing inhibition against movement of dislocation confirmed by the observed brittle behavior of fracture surface.

Fused silica ceramics are widely used in electronics and aerospace industries. In the present study, 70 µm of fused silica powder was milled to 10 µm through fast milling. The appropriate slurry was prepared for slip casting with the powder-to-water ratio of 80:20. After drying the specimens, the samples were sintered at different temperatures of 1100 °C to 1400 °C. The density increased upon increasing the temperature from 1.79 to 1.98 g/cm3. The phase transformation of the samples was investigated using XRD. The structure of the samples was analyzed using FTIR, and their microstructure was examined using a Field Emission Scanning Electron Microscope (FESEM). The bending strength of the samples was measured using the three-point method. According to the results, the cristobalite phase increased upon increasing the sintering temperature. The best flexural strength value (48.7 MPa) was obtained for the sample sintered at 1300 °C. The dielectric constants of the fused silica ceramics were about 3-3.8 in the frequency range of 8 to 12 GHz.

In ceramic additive manufacturing, it is important to fabricate parts with high solid contents to guarantee defect-free sintered parts. In stereolithography, low viscosity and especially shear-thinning behavior of the ink are the key factors in producing ceramic-resin parts. Therefore, there should be a correlation between solid loading and viscosity. In this study, Alumina-glass inks were printed using bottom-up and top-down approaches, and the rheological properties were investigated. The main objective of this study was to print a highly filled ceramic-resin part with a viscosity suitable for DLP printing. While use of suspensions with low viscosity was recommended for top-down digital light processing (DLP) printing, a new setup was designed to study the feasibility of the top-down approach for pastes for the top-down approach. According to the findings, ceramic-resin pastes with the solid content of maximum 75 wt% and viscosity of 47.64 Pa.s at the shear rate of 30 s-1 were easily printable via our hand-made top-down DLP printer. However, it was not possible to print inks with solid contents more than 60 wt% using the bottom-up DLP, mainly because the detachment force grew dramatically with an increase in viscosity.

Flexible and printed electronics have been widely applied due to their low cost, scalability in manufacturing, and usability in biosensors as well as wearable electronics. However, there are some limitations on fabrication of these devices including thermal limitations. Thermal constraints are of significance since ion implantation at high temperatures is one of the most important stages of fabrication; therefore, despite these limitations, fabrication of flexible BJT is practically impossible through conventional methods. In this study, copper oxide was used for the collector and emitter area of Double Heterojunction Bipolar Transistor (DHBT) due to the low-temperature deposition of copper oxide through the printing method, and the ability to adjust the doping according to the deposition conditions. DC and high-frequency specifications of two transistors with PNP and NPN structures were simulated using two-dimensional semiconductor simulator atlas module of SILVACO software.

The present study aims to investigate the optical properties and crystallization behavior of oxy-fluoride glasses with different amounts of Bi2O3. Glasses with compositions of 45SiO2-15Al2O3-25BaO-15BaF2-xBi2O3 (x=0, 1, 2.5, 4, and 6) (mole ratio) were prepared using melt-quenching method. Owing to the network modifying role of Bi2O3 and increasing number of Non-Bridging Oxygens (NBOs), the molar volume increased from 27.69 to 31.60 cm3 and microhardness was reduced from 720.21 to 613.10 MPa. In order to study the structural changes, the FTIR spectra were recorded, and increment of NBOs by adding Bi2O3 as well as the presence of Bi˚ particles in the sample containing six mole ratios of Bi2O3 were proved. The UV-Vis transmittance spectra were employed to determine the optical properties including Fermi energy, direct and indirect optical band gaps, and Urbach energy. The Fermi energy and optical band gaps were reduced as the Bi2O3 content increased. The degree of structural disorderliness (Urbach energy) increased from 0.170 to 0.212 eV followed by creating more NBOs through Bi2O3 addition. On the basis of UV-Vis-IR transmittance results, the sample containing four mole ratios of Bi2O3 exhibited the highest transmittance in IR region and its IR cut-off shifted to longer wavelengths. Further, the sample with six mole ratios of Bi2O3 was characterized as the highest refractive index (1.7) among other glasses. Finally, evaluation of crystallization behavior of specimens revealed that it was impossible to prepare transparent glass ceramics containing BaF2 nanocrystals due to the surface crystallization in these glasses.