A comparative study of ZnNb2O6 nanoceramics synthesized by high energy ball milling and subsequent conventional and microwave annealing

Ball-milling and subsequent conventional and microwave assisted heating processes have been applied to synthesize ZnNb2O6 nanoceramic. X-ray diffraction, simultaneous thermal analysis, scanning electron microscope (SEM), transmission electron microscope (TEM) and BET techniques were utilized to characterize the as-milled and annealed samples. Characterization of synthesized powders revealed that in spite of the very short heating time in the microwave process without soaking time, the powder heated at 550 A degrees C had all physical properties similar to powders synthesized in conventional heating at the 650 A degrees C temperature with a heating rate of 10 A degrees C/min and a soaking time of 1 h. In addition, SEM, TEM and BET observations of synthesized powders showed that the particle size of powders lies in the nano meter range

Reaction sintering of nano-sized ZnO-Nb2O5 powder mixture: sintering, microstructure and microwave dielectric properties

Sintering behavior, microstructures and microwave dielectric properties of ZnNb2O6 (ZN) ceramics prepared by reaction-sintering method were investigated. The X-ray diffraction patterns of the sintered samples revealed single-phase formation with a columbite structure after 1-5 h sintering at 1,025-1,125 A degrees C. After sintering at 1,125 A degrees C for 5 h, the ZN ceramics with the density of 5.56 g/cm(3) (98.9 % of the theoretical density) and good microwave dielectric properties of epsilon(r) = 23.9, Q x f = 51,000 and tau(f) = -62 ppm/A degrees C were obtained. The obtained results demonstrated that the reaction-sintering process is a simple and effective method to prepare the ZN ceramics for applications on microwave dielectric resonators

3D-printed barium strontium titanate-based piezoelectric scaffolds for bone tissue engineering

In order to promote bone healing, new generations of biomaterials are under development. These biomaterials should demonstrate proper biological and mechanical properties preferably similar to the natural bone tissue. In this research, 3D-printed barium strontium titanate (BST)/β-tricalcium phosphate (β-TCP) composite scaffolds have been synthesized as an alternative strategy for bone regeneration to not only induce appropriate bioactive characteristics but also piezoelectric behavior. The physical, chemical and biological performance of the scaffolds have been examined in terms of mechanical, dielectric properties, apatite-forming ability, Alizarin Red Staining (ARS), Alkaline Phosphatase activity (ALP), and cytotoxicity. The samples composed of 60 BST and 40 β-TCP showed the highest compressive strength, bending module, elastic modulus and the Young's modulus. The dielectric constant increased with further addition of the BST phase in the constructs. Scanning Electron Microscope (SEM) and energy dispersive X-ray (EDX) analyses showed that 60 BST/40 β-TCP sample had the highest amount of bone-like apatite formation after 28 days in simulated body fluid (SBF). Moreover, the results of ARS proved that 60 BST/40 β-TCP composite could present higher quantities of mineral deposition. The ALP activity of osteosarcoma cells on 60 BST/40 β-TCP sample showed higher activities compare with the other composites. None of the samples demonstrated any sign of toxicity using MTT test. It can be suggested that BST/β-TCP composite scaffolds can be potentially used as the next generation of bone tissue engineering scaffold materials. © 2019 Elsevier Ltd and Techna Group S.r.l

Microwave sintering of nanopowder ZnNb2O6: Densification, microstructure and microwave dielectric properties

High density ZnNb2O6 ceramics were successfully fabricated by microwave sintering of ZnO-Nb2O5 and ZnNb2O6 nanopowclers. Phase formation, microstructure and microwave electrical properties of the microwave sintered (MS) and microwave reaction sintered (MRS) specimens were examined using X-ray diffraction, field emission scanning electron microscopy and microwave dielectric properties measurement. Specimens were sintered in a temperature range from 950 to 1075 degrees C for 30 min at an interval of 25 degrees C using a microwave furnace operated at 245 GHz frequency, 3 kW power. XRD pattern revealed the formation of pure columbite phase of ZnNb2O6. The SEM micrographs show grain growth and reduction in porosity of specimens with the increase in sintering temperature. Good combination of microwave dielectric properties (epsilon(r)similar to 23.6, Q(f)similar to 64,300 GHz and tau(f)similar to 66 ppm/degrees C and epsilon(r)similar to 24, Q(f)similar to 75,800 GHz and tau(f)similar to -64 ppm/ degrees C) was obtained for MS- and MRS-prepared samples at 1000 degrees C and 1050 degrees C for 30 min, respectively. (C) 2014 Elsevier B.V. All rights reserved