Synthesis of nanostructured gadolinium doped mixed ferrite: A novel catalyst for the mineralization of textile dyes

Herein, cobalt-nickel mixed ferrite (Co_0·5Ni_0·5Fe₂O₄, CNFO) and gadolinium doped cobalt-nickel mixed ferrite (Co_0·5Ni_0.5Gd_0.1Fe_1·9O₄, G-CNFO) materials have been synthesized at the nanoscale via the microemulsion technique. The physicochemical features of the CNFO and G-CNFO materials were examined by advanced structural (PXRD and FTIR), morphological (FESEM), elemental (EDX), and optical (UV/Vis and transient photocurrent) studies. Under visible light, the catalytic activity of CNFO and G-CNFO materials was compared using Congo red and Aniline blue dyes as model textile pollutants. The G-CNFO material showed better photocatalytic activity than CNFO material, as it eliminated almost 21% more dye than CNFO material under the same experimental conditions. In order to find the optimal parameter for the experiments, the variables affecting the catalytic properties of the G-CNFO material were investigated in considerable detail. These variables included pH, catalyst dosage, dye concentration, temperature, and irradiation time. Scavenging and transient photocurrent experiments were also carried out in order to determine the key reactive oxygen species and the formation of electron-hole pairs. The G-CNFO mineralized the Congo red dye almost three times faster than its counterpart and showed a negligible loss in its catalytic activity even after five successive catalytic cycles. The combined effects of the G-CNFO material's tuned band structure, high light harvesting abilities, reduced electron-hole recombination, and nanostructured morphology resulted in its enhanced photocatalytic activity.     

Tailoring hardness behaviors of BIT-based piezoceramics via doping and annealing strategies

Bismuth titanate (BIT) piezoelectric ceramics are perceived as a strong competitor in high temperature applications. Currently, a mass of work has been done to optimize the electrical performance of the ceramic utilizing different strategies. However, little attention has been paid to the mechanical behaviors of BIT ceramics, especially the research on mechanical hardness behaviors under doping and annealing, limiting the deep understanding for ceramics and its further development of practical applications. In this work, the mechanical hardness behaviors of a type of bismuth titanate-based ceramics [Bi_3.96Ce_0.04Ti_3-xW_xNb_xO₁₂ (BCTWN)] at different doping contents and selectively annealing temperatures were investigated using nanoindentation and Vickers indentation techniques. The results show that the hardness is strongly dependent doping contents, wherein the samples with smaller grain size and higher density exhibit bigger hardness. For the poled samples, a higher annealing temperature could restore more domain walls and induce more oxygen vacancies in the samples, along with higher elastic recovery and less remanent strain, shedding extra deformation resistance to make sample harder. Moreover, a schematic of defect assistant domain wall pinning mechanism is proposed to further rationalize the enhanced deformation resistance by annealing strategy. This work helps us deep understand the deformation mechanism of BIT ceramics beneath indentation, and provides insight into tailoring mechanical hardness behaviors via doping and annealing strategies.     

The energy storage mathematical models for simulation and comprehensive analysis of power system dynamics: A review. Part i

Energy storage systems are increasingly used as part of electric power systems to solve various problems of power supply reliability. With increasing power of the energy storage systems and the share of their use in electric power systems, their influence on operation modes and transient processes becomes significant. In this case, there is a need to take into account their properties in mathematical models of real dimension power systems in the study of various operation modes, design, etc. In this article the main types of energy storage devices, as well as the fields and applications of their use in electric power systems are considered. The principles of realization of detailed mathematical models, principles of their control systems are described for the presented types of energy storage systems. The article is an overview and can help in choosing a mathematical model of energy storage system to solve the necessary tasks in the mathematical modeling of storage systems in electric power systems.Information is presented on large hydrogen energy storage units for use in the power system.     

Thermo-enhanced afterglow emission in Tm3+ doped fluoride nanoparticles for anti-counterfeiting application after X-ray excitation

Multimodal luminescence has emerged as a promising solution in the realm of anti-counterfeiting techniques, which have gained global attention due to their association with information and data security. The conventional approach to achieving multimodal luminescence typically involves combining upconversion and downshifting luminescence, which necessitates the use of external excitation sources and costly detection equipment. Herein, we develop an anti-counterfeiting strategy based on the afterglow performance of NaLuF₄: Gd, Tm nanoparticles after X-ray excitation. The X-ray-induced Frenkel defects-base traps ensnare electrons with low kinetic energy, resulting in the creation of persistent photon traps that are responsible for the temperature-dependent afterglow intensity. The dual-band and thermo-enhanced afterglow emission can encrypt information well according to our proof-of-concept experiment and the visible light signal can be successfully captured by a smartphone camera. These unique features of NaLuF₄: Gd, Tm nanoparticles render them highly appealing for multilevel anti-counterfeiting applications.     

CMAS corrosion resistance,thermal shock resistance and numerical simulation of novel surface micromesh thermal barrier coatings

Thermal barrier coatings (TBCs) are widely used as insulating layers to protect the underlying metallic structure of gas turbine blades. However, the thermal cycling performance of TBCs is affected by their complex working environments, which may shorten their service life. Previous studies have shown that preparing a mesh structure in the bonding layer can relieve thermal stress and improve the bonding strength, thereby prolonging the service life of TBCs. In this paper, a micromesh structure was prepared on the surface of the bonding layer via wet etching. The microstructure and failure mechanism of the micromesh TBCs after CMAS (CaO-MgO-Al₂O₃-SiO₂) thermal erosion were investigated. Numerical simulation was combined with thermal shock experiments to study the stress distribution of the micromesh-structured TBCs. The results showed that the circular convex structure can effectively improve the CMAS corrosion resistance and thermal shock resistance of TBCs.     

Interfacial Engineering of Polycrystalline Pt5P2 Nanocrystals and Amorphous Nickel Phosphate Nanorods for Electrocatalytic Alkaline Hydrogen Evolution

Electrocatalytic hydrogen evolution reaction (HER) in alkaline media is important for hydrogen economy but suffers from sluggish reaction kinetics due to a large water dissociation energy barrier. Herein, Pt₅P₂ nanocrystals anchoring on amorphous nickel phosphate nanorods as a high-performance interfacial electrocatalyst system (Pt₅P₂ NCs/a-NiPi) for the alkaline HER are demonstrated. At the unique polycrystalline/amorphous interface with abundant defects, strong electronic interaction, and optimized intermediate adsorption strength, water dissociation is accelerated over abundant oxophilic Ni sites of amorphous NiPi, while hydride coupling is promoted on the adjacent electron-rich Pt sites of Pt₅P₂. Meanwhile, the ultra-small-sized Pt₅P₂ nanocrystals and amorphous NiPi nanorods maximize the density of interfacial active sites for the Volmer–Tafel reaction. Pt₅P₂ NCs/a-NiPi exhibits small overpotentials of merely 9 and 41 mV at −10 and −100 mA cm⁻² in 1 M KOH, respectively. Notably, Pt₅P₂ NCs/a-NiPi exhibits an unprecedentedly high mass activity (MA) of 14.9 mA µg_Pt⁻¹ at an overpotential of 70 mV, which is 80 times higher than that of Pt/C and represents the highest MA of reported Pt-based electrocatalysts for the alkaline HER. This work demonstrates a phosphorization and interfacing strategy for promoting Pt utilization and in-depth mechanistic insights for the alkaline HER.     

Design of luminescence in(Sr,Gd)Li(Al,Mg)3N4:Eu2+ deep red phosphors via crystal field engineering for full-spectrum WLEDs

Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)₃N₄:Eu²⁺ were designed from the initial model of SrLiAl₃N₄:Eu²⁺ by structural modification.The correlations among structural evolution,crystal-field environment,and luminescence properties were elucidated.Replacing Sr²⁺ with Gd³⁺in(Sr,Gd)LiAl₃N₄:Eu²⁺ leads...     

Extremely high corrosion resistance of ZnxNi1–xCr2O4 spinel as sidewalls in the aluminum electrolyte

The sidewall material is a key component in new electrolytic cell with an inert electrode for the aluminum electrolysis industry. The continuous development of novel sidewall materials with excellent corrosion resistance in molten salts electrolyte is an important topic. Herein, a new system of sidewall material, spinel structured Zn_xNi_1–xCr₂O₄ (x = 0 – 1), is prepared by solid-phase reaction and the corrosion-resistance enhancement is investigated. The results prove that Zn²⁺ plays two roles in the Zn_xNi_1–xCr₂O₄ spinels. Firstly, Zn²⁺ tunes the surface energies of spinels resulting in the octahedral grains, which suppresses the cation diffusion in the corrosion process. Secondly, Zn²⁺ stabilizes the Cr³⁺ in the spinels. As a result, the Zn_0.5Ni_0.5Cr₂O₄ spinel displays an extremely low corrosion rate ～0.007 cm·a^–1 in NaF-KF-AlF₃ bath at 800 °C comparing with other sidewall materials. The as-obtained spinel shows great potential as a novel sidewall material for the new electrolytic cell.     

Synthesis,microstructure and electromagnetic properties of Hf-based SiBCN ceramics

In this work, two kinds of ceramic polymers, polyborosilazane and polyhafnoxane, were mixed by a precursor blending method, followed by curing and pyrolysis to obtain Hf-based SiBCN ceramics. Through FTIR and NMR characterization of cured product, it can be found that the two precursors underwent cross-linking reaction during the curing process, resulting in the increase of crystallization temperature of HfO₂ and β-SiC, and the formation of new components (HfB₂ and HfN) during pyrolysis. When the pyrolysis temperature increases, the average values of the real part and imaginary part of the dielectric constant of Hf-based SiBCN ceramics increased from 7.2 to 4.9 to 9.0 and 6.6, respectively, resulting from the precipitation of HfB₂ and HfC(N) with high dielectric constants. The effective absorption width decreased from 3.4 to 2.5 GHz, and the minimum value of reflection coefficient increased from −14.9 to −12.2 dB, which is caused by poor impedance matching. After being oxidized at 500 °C for 50 h in air, the free carbon basically disappears, and the full X-band absorption can be realized for the Hf-based SiBCN ceramic pyrolyzed at 1500 °C with a thickness of 2.8 mm.