Journal of the Australian Ceramic Society最新文献

To gain high dielectric constant, polymer composites with 1D fillers are researched for energy storage. However, high leakage conduction from polymer/filler interface and filler interconnection can induce high dielectric loss. For high dielectric constant and low dielectric loss, in this work, we raised a strategy of morphological synergy of fillers (1D catenulate semi-conductive CuO nano-filler and 0D insulating alumina nano-particles) to fabricate polymer-based ternary composites. Instead of 0D CuO, 1D CuO nano-chains with the improved specific surface area were employed for high dielectric constant via polymer/CuO interface polarization. Spherical alpha-alumina nano-particles were used for reducing polymer/CuO interface leakage conduction and depressing CuO percolation to gain low dielectric loss. Compared with rather high dielectric constant and dielectric loss in polymer/CuO binary composites, moderately high dielectric constant and rather low dielectric loss were achieved in ternary composites. Via excellent synergy of CuO and alumina, ternary composites showed more promising dielectric properties. Ternary composite with 9 wt% CuO and 3 wt% alumina exhibited a high dielectric constant of ~ 64 and low dielectric loss of ~ 0.16 at 20 Hz. This work might pave a road for large-scale preparation of high-performance composite dielectrics by morphological synergy of fillers.

In this work, AlN nanoparticles were prepared by arc discharge method and transformer oil-based nanofluids containing different concentrations of these nanostructures were prepared and their thermal conductivities and stabilities were investigated at various temperatures. Two aluminum rods were used as the electrodes and nitrogen gas was used as the arc atmosphere. To investigate the factors that influence the size and purity of the nanoparticles, the nitrogen gas pressure and the current flowing through the electrodes were changed. Based on XRD measurements, it was observed that at the pressure of 2 atm. and current of 100 A, the highest purity phase was achieved. Scanning electron microscope (SEM) images indicated that the smallest samples were the ones that were made at a pressure of 3 atm. and arc current of 400 A and had an average particle size of about 67 nm. The band gap of nanoparticles was obtained at 5.6 eV using the Tauc method. Then, transformer oil-based nanofluids with concentrations of 0.5, 1, 2, and 4 wt.% of AlN were prepared and their thermal conductivities and stabilities were investigated. The nanofluid with 4 wt.% of AlN nanoparticles at 60 °C showed a maximum thermal conductivity enhancement of 9.4%. Nanofluids were completely stable for up to a week.

Abstract

When ceramic-matrix composites (CMCs) are under tension-tension cyclic fatigue loading, stochastic matrix cracking evolves with applied cycles and the closure of cracks occurs upon unloading. Evolution, opening, and closure of matrix cracking affect the reliability and safety of CMC components during operation. The objective of this paper is to establish the relationship between the hysteresis loops, cracking evolution, opening, and closure based on a new hysteresis constitutive model. Multiple micro damage parameters, e.g., unloading/reloading inverse tangent modulus (UITM/RITM), interface reverse slip ratio (IRSR), and interface new slip ratio (INSR), are developed to characterize the hysteresis loops with cracking evolution and closure. Upon unloading, the closure of matrix cracking decreases the UITMs and IRSR of the tension-tension fatigue hysteresis loops; upon reloading, the opening of matrix cracking increases the RITMs and IRSR of the tension-tension fatigue hysteresis loops. Experimental tension-tension fatigue hysteresis loops in different CMCs are predicted for different peak stresses and cycles. Effects of fiber volume, interface properties, peak stress, and stress ratio on ITM, IRSR, and IRSR are discussed. The developed approach can be used for cracking evolution, opening, and closure identification in CMCs.

Abstract

This paper goes into extensive detail about the theoretical and experimental characterization of (mathrm{Sr}) doped hydroxyapatite ((mathrm{HAp})) samples that have been doped with (mathrm{Sm}) in various amounts. To accomplish this, five (mathrm{HAps}) containing a constant (0.133mathrm{ at}. %) of (mathrm{Sr}) were additionally doped with (mathrm{Sm}) at varied amounts and synthesized by a method of wet chemical. In addition, the density functional theory (DFT) was used to model all of these samples. According to theoretical results, the bandgap energy declined continuously from (4.6297) to (4.4034mathrm{ eV}). The linear absorption coefficient increased with increasing amounts of (mathrm{Sm}) in all samples, while this parameter decreased with increasing photon energy. There was a reduction in both the lattice parameter (a) and the volume of the unit cell, but there was also an increase in the lattice parameter (c) and theoretical density. Accordingly, the experiment’s results were as follows:(mathrm{HAp}) phase (above (98mathrm{%}) for all of the samples) and beta-tricalcium phosphate (upbeta -mathrm{TCP}) were both confirmed as the major phase and minor phase, respectively, by X-ray diffraction ((mathrm{XRD })), FT-Raman spectroscopy and the Fourier transform infrared ((mathrm{FTIR})) measurements. The addition of (mathrm{Sm}) increased in the (upbeta -mathrm{TCP}) phase from (0.62) to (0.86%.) Same as theoretical results, it was also found that density was increasing and the volume of the unit cell decreased. An increase in anisotropic energy density and a decrease in crystallinity were discovered. The values are calculated based on the molar ratio, which was discovered to be close to those for stoichiometric (mathrm{HAp}) in all samples ((1.67).) Based on the results of the thermal study, all samples were confirmed to be thermally stable. (mathrm{Sm}) content was discovered to have an effect on cell viability.

Abstract

Tin-doped zinc sulfide was coated onto glass plates and subjected to a post-air annealing treatment at 300 °C for 2 h. The air-annealed thin films were characterized for observing the tailoring in structural, surface, chemical, optical, photoluminescence, and magnetic properties due to annealing. The properties of thin films after air-annealing were compared with as-synthesized Kumar et al. (J. Supercond. Novel Magn. 32(6), 1725-1734, 2019), and vacuum-annealed Kunapalli et al. (Opt. Mater.114, 110961, 2021) thin films. Annealing in presence of air leads to finer crystallite structures of ZnS thin films. The air annealing also enhanced the transmittance property of the thin films. Two prominent peaks at 420 nm and 440 nm were observed in photoluminescence spectra. From magnetic studies, it was found that the films were paramagnetic in nature, and magnetization increased with an increase in the applied field.

Abstract

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