Sahin, B.;Soylu, S.;Kara, M.;Turkmen, M.;Aydin, R.;Cetin, H.
年/卷/期：2021 / 47 / 1
An easy and eco-friendly approach using Thymbra spicata var. spicata L. (TS) plant extract was developed for the formation of nanostructured ZnO. TS aqueous leaf extract was used for the green synthesis of nanostructured ZnO via the Successive ionic layer adsorption and reaction (SILAR) method. Electron microscope images exhibit the morphological adjustments of the samples with respect to change in TS concentration in the growth solution. The nanostructured ZnO grown by SILAR was observed to be polycrystalline with hexagonal crystal structure. The optical energy bandgap value of the samples varies from 3.21 to 3.09 eV as the content of TS increases from 2.5 to 5.0%. Also, the effect of TS additive to ZnO on electrical properties was investigated. It was determined by Van der Pauw measurements that TS contribution to ZnO significantly increased electrical resistance. In addi-tion, impedance analyzes of the produced films were carried out in the frequency range of 20Hz -1 MHz. Nyquist plots showed the single semicircle for all samples, and the values of capacitance and resistance were calculated. Its antibacterial activities was investigated against economically important Gram-positive (Clavibacter michiganensis subsp. Michiganensis) and negative (Pseudomonas syringae pv. Phaseolicola, Pseudomonas cichorii and Pectobacterium carotovorum subsp. Carotovorum) seed-borne plant bacterial disease agents by using paper disc diffusion assay for the first time. In vitro laboratory screenings of green synthesized nanostructured ZnO have given encouraging results, indicating their potential use in the management of seed-borne bacterial diseases.
Lithium-ion capacitors (LICs) composed of battery-type anodes with large energy densities and capacitor-type cathodes with high power densities are considered as appealing energy-storage devices. Here, a LIC with good performance is constructed using active carbon (AC) as the cathode and Li1.95La0.05ZnTi3O8 (LL5ZTO) as the anode. LL5ZTO doped with La is synthesized via a one-step solid-state route. The kinetics and structural stability of LZTO are enhanced by La-doping. Thus, LL5ZTO exhibits good Li-storage performance. The discharge specific capacity reaches 182.6 mAh g(-1) at 3 A g(-1) (120th cycle) for LL5ZTO. The LIC based on the LL5ZTO anode and the AC cathode delivers an energy density of 59.72 Wh kg(-1) at 846.4 W kg(-1), and a high power density of 8771 W kg(-1) at 19.49 Wh kg(-1). Furthermore, the capacity retention is over 90% after 3000 cycles for the LIC at 2 A g(-1). The good electrochemical performance indicates that the constructed LIC is expected to use in advanced energy storage devices.
The zirconia (ZrO2) ceramic dental implant abutment was prepared by DLP (Digital Light Processing) 3D printing technology. The effect of different heat treatment parameters on the sintering quality of ZrO2 was studied. According to TG-DSC, XRD, Raman, SEM and other characterization methods, it could be determined that best sintering parameter was set at 1450 degrees C for 1.5 h. The final product has a good morphology without holes and other defects, and the relative density is 99.48%. The ZrO2 samples printed in different directions have obvious anisotropy. The three-point bending strength of the sample in the horizontal direction is better than that in the vertical direction, and the strength is 600 MPa. The fatigue load simulation results show that the smaller the pre angle is, the smaller the maximum stress is and the higher the safety factor is.
This work presents phase-field modeling of quasi-static cracking in urania (UO2) ceramic nuclear fuel under neutron radiation at high temperatures. Considering the tightly coupled multi-physics processes within the fuel during reactor power operation, a diffusion model including Fickian and Soret effects is used to describe the oxygen hyper-stoichiometry (x in UO2+x), and the temperature field is given by a thermal model involving non-uniform fission-generated heat source and heat flow across fuel pellet, pellet-cladding gap and cladding to the outside heat sink. Both temperature and irradiation effects are taken into account for the basic thermomechanical properties and irradiation behaviors of the nuclear fuel. Especially, the acceleration of fuel thermal creep by oxygen hyper-stoichiometry is included. The fracture due to the above physical processes is approximated by a scalar phase-field variable based upon a cohesive phase-field fracture method. A granite fracture experiment is simulated to validate the thermo-fracture coupling approach. For the first time, the diffusion-thermo-mechanical-fracture coupling model is applied to UO2 fuel pellet cracking during reactor startup, power ramp and reactor shutdown. UO2 creep is found to play an important role on the fuel pellet fragmentation. The developed capability supports interpretation of experimental data and can guide material design of ceramic nuclear fuels.
Azad, Abul K.;Afroze, Shammya;Torino, Nico;Reza, Md Sumon;Radenahmad, Nikdalila;Cheok, Quentin;Henry, Paul F.
年/卷/期：2021 / 47 / 1
The structural and electrochemical properties of the double perovskite-type oxide, PrBaMnMoO6-delta, was in-vestigated using neutron diffraction with in-situ conductivity measurement under a dry Argon atmosphere from 25 degrees C to 700 degrees C. A Rietveld refinement of the neutron diffraction data confirmed monoclinic symmetry in the P2(1)/n space group. Rietveld refinement also confirms the unit cell parameters of a = 5.6567 (1) angstrom, b = 5.6065 (2) angstrom, c = 7.9344 (1) angstrom and beta = 84.43 degrees with reliable atomic positions and refinement factors (R-factors). Neutron diffraction data refinement shows two minor phases (< 5%), an orthorhombic AB(2)O(5) type phase of PrMn2O5 in the Pbam (No. 32) space group with unit cell parameters, a = 7.9672 (1) angstrom, b = 8.9043 (2) angstrom and c = 5.8540 (1) angstrom and a scheelite phase of BaMoO4 in the tetragonal I4(1)/a (88) space group with the unit cell parameters, a = b = 5.9522 (1) angstrom, and c = 12.3211 (2) angstrom. Morphological images revealed a porous and intertwined microstructure. In-situ conductivity measurement shows that the total conductivity of this material was 130.84 Scm(-1) at 700 degrees C.
This study aimed to investigate the mechanical behavior of an environmentally friendly granulated blast furnace slag-based geopolymer matrix reinforced with modified multi-walled carbon nanotubes (MWCNTs). The modi-fied MWCNTs were obtained using a modification method combining nitric acid and sulfuric acid and were then dispersed using sodium dodecylsulfate (SDS) as a dispersant. Two types and three concentrations of MWCNTs were mixed directly into the aqueous solution, sonicated, and then mechanically mixed with waste granulated blast furnace slag to form the geopolymer matrix. Raman and Fourier transform infrared (FT-IR) spectroscopy were used to evaluate the ordered structure and crystallization degree of the modified MWCNTs. Then, the dispersity of the modified MWCNTs was characterized using transmission electron microscopy (TEM). The compressive and bending strengths were measured to evaluate the mechanical behavior of specimens. Moreover, the polycondensation products, polycondensation degree, pore structure, and microscopic morphology of the geopolymer matrix were analyzed using X-ray diffraction (XRD), FT-IR spectroscopy, nuclear magnetic resonance (NMR), mercury intrusion porosimetry (MIP), and field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDS). The experimental results showed that the incorporation of 0.1% functionalized MWCNTs had an optimal influence on the fluidity and mechanical behavior. The slump diameters of geopolymers with 0.1% functionalized MWCNTs with and without SDS were increased by 16.3% and 23.5%, respectively, compared with the reference geopolymer matrix. For geopolymer matrix samples at a curing age of 28 d, the compressive strength of geopolymers with 0.1% functionalized MWCNTs with and without SDS were increased by 16.3% and 17.6%, respectively. For the bending strength, the corresponding increases were 17.6% and 18.7%, respectively. It was found that functionalized MWCNTs could increase the degree of poly condensation, leading to a more traditional amorphous N-A-S-H phase, a finer C-S-H phase, more Q(4) (2Al) and Q(4) (3Al), and lower porosity. In addition, the propagation of micro-cracks in the geopolymers was inhibited by the incorporation of functionalized MWCNTs.
Bi12GeO20 nanowires uniformly decorated with ultrafine Ag3PO4 nanoparticles (Bi12GeO20/Ag3PO4) were syn-thesized. The Bi12GeO20/Ag3PO4 nanowire composite with 10 wt% of Ag3PO4 exhibited significantly improved photocatalytic performance and excellent stability over pure Bi12GeO20, Ag3PO4 and other composites, with the RhB dye decomposition efficiency reaching 94.2%. The electrochemical and photocurrent response measurements suggested that the electrons generated in Bi12GeO20 during the photocatalytic reaction could be quickly transferred to the Ag3PO4 surface, resulting in increased electron/hole separation. The trapping experiments with different scavengers and ESR results revealed that holes and center dot O-2 were the dominant active species for the photocatalytic decomposition of RhB, and the presence of Ag3PO4 was beneficial to generate more center dot O-2 species and enlarge the active surface area, leading to significantly improved photocatalytic performance. The presented photocatalyst heterostructure composed of appropriate semiconductor nanoparticles and one-dimensional nanowires in this study could be extended to the construction of other photocatalysts for a wide variety of photocatalytic applications.
In this work, we investigate the synthesis of LiGa5O8 ceramic powders through a polyvinyl alcohol-based sol-gel technique and their optical properties when doped with high Cr3+ concentrations (5, 25 and 50 mol% with respect to the Ga3+ sites). The results indicate that the main crystalline phase, LiGa5O8, is obtained after calcining the samples at 1000 degrees C/2 h in a static air atmosphere. Via X-ray photoelectron spectroscopy, Cr is confirmed to exist in its trivalent oxidation state and the evaluation of the optical properties is performed via photoluminescence excited from visible to vacuum ultraviolet energy range and with X-ray excited optical luminescence, indicating the typical Cr3+ emission at the near-infrared energy range. The crystal field and Racah parameters are calculated and the influence of Cr3+ concentration in the host material indicates luminescence suppression/quenching and a redshift for a higher amount of these ions.
TiO2 and ZnO are photocatalysts that degrade organic chemicals into smaller hydrocarbons in the presence of UV irradiation. Metal meshes have been previously used to harvest fog droplets from air streams. By merging these two observations, we hypothesize that TiO2/ZnO-coated metal meshes installed in the path of a fog-laden wind carrying contaminants, such as volatile organic compounds (VOCs), will degrade these VOCs providing pollution abatement.
Direct foam writing allows the fabrication of highly porous and hierarchical ceramic structures with high specific mechanical properties. This manufacturing technique, however, has mainly used stabilized Al2O3 foam inks. In this work, we pressent a novel foam ink based on TiO2. This ink uses polyvinyl alcohol (PVA) as a binder and a small amount of zinc as a frothing agent. We used this ink to produce cylindrical foam samples via direct foam writing. The foams had a porosity of up to 65% and a mean pore size of 180 mu m, which is significantly larger than previously reported for direct foam writing with Al2O3. The foams were tested in compression and were found to have an elastic modulus of 0.5 GPa and a compressive strength of 12-18 MPa. These mechanical properties are similar to those of porous ceramics produced by conventional manufacturing routes. Therefore, this work represents a step forward by broadening the direct foam writing process to a wider range of porous ceramics.