Advanced Ceramics Progress
Volume:1 Issue: 3, Fall 2015

BaO -SiO2-Al2O3 glass ceramics containing K2O and B2O3 were prepared using conventional melting of powered batches, quenching in water and crystallization of sintered glass. XRD patterns introducehexacelsian and celsian as two major crystallized phases in sintered glass-ceramics. Presence of K2O enhances crystallization of hexacelsianin comparison withB2O3.Observations showed sintering temperature decreases with 4% wt K2O 4% wt B2O3 and 2% wt B2O3amount of additivesbesides condensation starts from 850 ºC.Glass-ceramics containing 4% wtK2O 4% wtB2O3exhibitedmore sinterability in comparison with2% wtB2O3glass ceramics. SEM micrograph of glass and glass ceramic samples depicted morphology of serrated phase and hexacelsian respectively.

Lead free potassium sodium niobate (KNN) piezoceramics were synthesized via conventional solid state sintering route. Nano and micron WO3 were separately added to KNN through ball-milling. Dielectric and piezoelectric properties of samples sintered in the temperature range of 1110°-1145°C were measured by precision LCR-meter and APC d33-meter devices. The results revealed that micron WO3 particles were effective in inhibiting the grain growth in KNN ceramics. Micron WO3-added KNN obtained much finer microstructure and the sintering process terminated at higher temperature compared to pure KNN and nano WO3-added KNN. Densification and electrical properties of KNN were considerably affected by using nano and micron WO3. Nano WO3-added KNN obtained its maximum density at lower sintering temperature compared to micron WO3-added KNN. With increasing the sintering temperature over optimum amounts, the density of both WO3-added KNN samples decreased due to the evaporation of alkalis. Finally, at 1125ºC KNNW3n showed d33, εr, tanδ, and Qm of 75 pC/N, 345, 2%, and 50, respectively. For KNNW3m sample at 1135ºC these values were 81 pC/N, 773, 3.3%, and 30, respectively.

Over the past decades, bioactive glass (BG) has been of a great interest in the bone regeneration field, due to its excellent biocompatibility, bioactivity and osteoconductivity. Herein, fabrication of bioactive glass as one-dimensional fibers by employing an Electrospinning process is reported. The Sol-Gel method was chosen considering the final fibers smoothness and homogeneity. Starting sol was prepared by mixing Tetraethyl orthosilicate (TEOS), Triethyl phosphate (TEP) and Calcium Nitrate Tetrahydrate as precursors in an adequate solvent. Fibers were obtained via electrospinning the mixture of different ratios of BG and polymer solutions. Biocompatible Poly(vinyl alcohol) (PVA) was used in order to investigate the polymer effect. Furthermore, electrospinning parameters such as voltage and working distance were examined. Following the heat treatment and depolymerization, X-ray diffractometery (XRD) was done. Besides, fibers morphology before and after calcination was observed in detail employing Optical Microscopy (OM) and Field Emission Scanning Electron Microscopy (FE-SEM). XRD patterns revealed the presence of bioactive glass. Results indicated that the fibers diameter and homogeneity were reduced after calcination showing an intensification as polymer increased.

A single phased Y-type hexagonal ferrite Sr2Co1.7Mg0.3Fe11.2Sn0.4Zn0.4O22 was synthesized by the sol–gel auto combustion method. Structural and magnetic properties of this composition of Y-type hexagonal ferrite have been investigated. The X-ray diffraction (XRD) patterns confirm single phase Y-type hexagonal ferrite and various parameters such as lattice constants and cell volume have been calculated from XRD data. The morphology and size distribution of the particles have been studied using high resolution field emission scanning electron microscopy (FESEM). The Fourier transform infrared (FTIR) spectra show the characteristics absorption ferrite peaks of the sintered sample. The thermo gravimetric (TG) and differential thermal analysis (DTA) are used to study the systematic weight loss and subsequent transformation during heat treatment. Magnetic properties were determined using a vibrating sample magnetometer (VSM). Single phase Y-type ferrite powders were obtained after calcinations at 1000 °C. The XRD results showed that the crystallite size of particles is 44 nm. The microstructures of the pure powders appeared as a hexagonal platelet-like structure. The saturation magnetization (Ms) and the coercivity (Hc) of the samples were in the range, 26.58–50.42 emu/g and 546-1108 Oe, respectively. The effect of the heat treatment temperature was to increase the magnetization, following a slight coercivity decrease due to replacing of intermediate phases by single Y-type hexaferrite. Which it can be used as soft magnetic materials for multilayer inductors for high frequency applications.

Titanium and titanium alloys are often used in orthopedic surgery and dentistry because of their especial characteristics such as biocompatibility, mechanical properties, and corrosion resistance. However, their bio- inertness is the most serious drawback for biomedical applications. Therefore, a bioactive coating like hydroxyapatite (HA) is coated on their surface. In this regard, in the present study, laser induced liquid deposition (LLD) technique was used to deposit nanocrystalline HA films on titanium substrates at room temperature and various exposure times (20, 30, and 60 min) were examined. The LLD method was employed via applying a laser irradiation into a liquid precursor and depositing the HA films on titanium substrates immersed in the liquid precursor. Materials characterization was examined by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) equipped Electron Dispersive X-ray (EDX). Also, corrosion behaviors of coating were evaluated by potentiodynamic polarization test in simulated body fluid (SBF). Results showed that by choosing the appropriate exposure time, the corrosion resistance of coated substrates improves by HA coatings versus uncoated Ti substrates.

Among bioactive ceramics, the apatite/wollastonite (A/W) glass ceramic, containing apatite and wollastonite crystals in the glassy matrix, has been largely studied because of good bioactivity and used in some fields of medicine, especially in orthopedics and dentistry. However, medical applications of bioceramic are limited to non-load bearing applications because of their poor mechanical properties. Apatite/wollastonite coatings on 316 alloys substrates were prepared by plasma spraying and incubated in simulated body fluids for different periods to investigate the nucleation and growth of apatite on their surface. The morphology and the microstructure of the coatings were observed by SEM and the phase composition was examined by X-ray diffraction and FT-IR. The bioactivity of the coatings was evaluated by soaking the samples in a simulated body fluid (SBF) for 7 and 14 days. The results obtained showed that carbonate hydroxyapatite can be formed on the surface of the coating soaked in SBF for 7 days. With longer immersion periods, the coating surface was covered by carbonate hydroxyapatite, which indicated that the apatite/wollastonite coating possesses good bioactivity.

Spark plasma sintering (SPS) is a sintering process that is capable of sintering hard worked powders in short times. This technique was used to fabricate bulk Cu and Cu-SiC nanocomposites. Pure Cu and mixed powders of Cu including 4 vol% of SiC nanoparticles were mechanically alloyed for 25 h and sintered at 750˚C under vacuum condition by SPS method. Microstructures of the materials were characterized using optical and scanning electron microscopes and x-ray diffraction patterns, and mechanical properties were evaluated by micro hardness tests. The results showed density values of 8.69 and 8.30 g/cm3 and hardness values over 105 and 128Hv for Cu and its nanocomposite respectively. The addition of nanoparticles retarded Cu matrix grain growth during SPS process and resulted in higher hardness of nanocomposite compared to non-reinforced copper.