Advanced Ceramics Progress
Volume:2 Issue: 1, Winter 2016

Electrical resistivity (ER) is a main parameter in the melting processes of glasses. However, its measurement is difficult at high temperatures. In this study the electrical resistivity of different cordierite glass samples in the molten state was measured in the temperature range of 1100˚C to 1550 ˚C using the two-wire method. It was attempted to decrease the electrical resistivity of the glass by adding Na2O to the base glass. In one sample 0.5% wt Na2O was added and in another 1%. It was observed that the electrical resistivity of the glass decreased as temperature increased. Also, it was found that the electrical resistivity of cordierite glass decreases with the addition of Na2O. This was attributed to the high mobility of Na ions and mixed alkali effect.

Rheological characteristics of powder injection molding PIM feedstocks play an important role in final properties of manufactured MMCs. In this study, six formulations composed of magnesium and SiC powder (99:1 wt.%) and a specific binder were prepared to investigate the influence of binder composition, powder to binder ratio, time and temperature on rheological properties of the feedstock. The binder system contained Paraffin wax, Bees wax, and Stearic acid. Flow chracteristics of the compounds were investigated versus shera rate, time and temperature via rheological studies using a rotary rheometer. Finally, a heat treatment schedule was determined to effectively remove the binder from feedstocks. Resault show that, Viscosity versus shear rate exhibited three different parts with different slopes for all of the studied feedstocks. 1SA yielded Newtonian behavior and increasing the amount of stearic acid up to 6 wt % contributed to the pseudoplastic behavior which is favorable from the view point of manufacturing intricate shapes. Addition of more than 6 wt % stearic acid to the feedstock increased the flow behavior index n and devastated rheological behavior of the feedstocks.

TaC and HfC are thought to have the highest melting point (~4000°C) among all refractory materials. The binary solid solution of TaC and HfC (Ta4HfC5) is also considered as the most refractory material with the melting point over 4000 °C and valuable physical and mechanical properties. The main goal of this work is to fabricate TaC/HfCbased composites which consolidated by means of spark plasma sintering (SPS) with addition of MoSi2 as sintering aid and carbon nanotubes (CNTs) as reinforcement at 2000 °C. The effects of additives were investigated in terms of densification, mechanical properties, phase and microstructural evolutions. It was demonstrated that the relative density could reach from 94 % TD (for binder less sample) to near 99 % for samples containing additives, respectively. The average Vickers hardness and fracture toughness values were in the range of 16-19 MPa and 2.9-5.3 MPa.m1/2. The samples containing CNTs showed improved fracture toughness and the survivability of CNTs, after spark plasma sintering, was proved by scanning electron microscopy of fractured surfaces in addition to the Raman spectroscopy analysis.

Structural, electrical and optical properties of indium tin oxide or ITO (In2O3:SnO2) thin films on different substrates are investigated. A 100-nm-thick pre-deposited zinc oxide (ZnO) buffer layer is utilized to simultaneously improve the electrical and optical properties of ITO films. High purity ZnO and ITO layers are deposited with a radio frequency sputtering in argon ambient with plasma powers of 150 W and 300 W, respectively. After deposition, samples are annealed in a high vacuum furnace at 400 ˚C. The effects of ZnO-coated substrates on the crystallinity and morphological properties of ITO films are analyzed by X-ray diffractometer, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). X-ray diffraction patterns confirm the hexagonal wurtzite type polycrystalline structure of the ZnO films. FESEM and AFM analyses indicate that the surface morphology of the ITO films is affected by the ZnO buffer layer. Results also reveal that the roughness of ITO thin films is decreased in presence of the ZnO buffer layers. It has been found that ZnO incorporation promotes the crystallization of the ITO layer reduces its resistivity without deteriorating the optical transmittance.

In this study, green or eco-friendly synthesis of TiO2 nanoparticles (NPs) was performed by using the aqueous extract of Acanthophyllum laxiusculum. The plant genus Acanthophyllumis one of the natural sources rich in nonionic surface active agents known as saponins. Sol-gel method as one of the most common techniques widely used in nano-field was applied to synthesize the titanium dioxide nanoparticles. TiO2 nanoparticles were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Energy Dispersive Analysis of X-rays (EDAX). Fourier Transform Infrared Spectroscopy (FTIR) was performed to confirm the lack of the surfactant templates in synthesized NPs. The optical band gap of synthesized TiO2nanospheres was determined using UV–Vis absorption spectra and further verified by diffuse reflectance spectroscopy analysis. The specific surface area and pore size distribution of this product were evaluated by employing the Brunauer– Emmett–Teller (BET) technique and the Barrett–Joyner–Halenda (BJH) model.

Nanoporous silicon powder was produced via efficient magnesiothermic reduction. In this work, the thermal effect and reduction process time were investigated on the porous silicon structure. The nanoporous silicon powders were characterized by X-ray diffraction analysis and field emission scanning electron microscopy. The results demonstrate that porous structure was changed to homogeneous and uniform porous structure when the heating ramp rate was controlled at 5 0C/min. The average pore size of uniform porous silicon was reported 195.8 nm.

A conducting lithium aluminum germanium phosphate (LAGP) glass-ceramic with a formula of Li1.5Al0.5Ge1.5(PO4)3 was synthesized by melt-quenching method and subsequent crystallization at 850 °C for 8 h. The prepared glass-ceramic was characterized using differential scanning calorimetry (DSC), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and AC impedance techniques. The XRD patterns exhibited the existence of LiGe2(PO4)3 as the dominant phase with a little impurity phase of GeO2. SEM images revealed the presence of large LAGP crystals. A high conductivity of 5.36×10-3 S/cm at 25 °C was obtained for the pristine LAGP. Furthermore, the stability of the LAGP was examined in 1 M LiNO3 aqueous solution by XRD and conductivity measurements. XRD pattern and ionic conductivities of the immersed LAGP showed no change as compared with the pristine LAGP, showing the good stability in aqueous electrolyte and great potential for aqueous lithium-air battery application.