The performance of hybridized nano-ceramics on the microstructure and corrosion of Mg alloy in an auto-engine cooling system

This current novel research focuses on developing a hybrid magnesium-based composite through the spark plasma sintering process with an interest in the improvement of mechanical properties and corrosion resistance of Mg Alloy in an auto-cooling system. AZ91D was selected as the primary Mg alloy and it was reinforced with hybridized AlN-VB at a sintering temperature of 500 °C, a heating rate of 75 °C/min, a pressure of 30 MPa, and a dwell time of 5 min. The microstructure of the sintered composite at varying weight constituents shows a homogenous dispersion of the reinforcing material and refinement of the inherent eutectic β-Mg₁₇Al₁₂ phase. The refinement of the phase yielded a small grain size of 16.6 ± 0.20 μm by the MgAZ91D-8wt%AlN-8wt%VB composite compared to the coarse grain size of 36.1 ± 0.9 μm by the unreinforced MgAZ91D. likewise, a higher microstrain value of 7.57E-2 was achieved by the composite with the highest reinforcing constituents. The load-displacement curve shows a gradual shift to the left following the inclusion of the reinforcing substances, this implies a higher resistance to penetration as a result of higher nanohardness and elastic modulus. The corrosion behavior of the sintered composite was examined in a simulated auto-engine cooling system using ethylene-glycol and corrosive water. The Unreinforced MgAZ91D shows a high corrosion rate (Cr) of 2.2217 mm/year, a higher degree of disorderliness (n) of 0.8829, and a low charge resistance transfer (Rct) of 4.6143 kΩcm². However, the corrosion rate decreases rapidly to 0.0475 mm/year and the Rct to 20.9543 kΩcm² at MgAZ91D-8wt%AlN-8wt%VB composite.     

Enhancing the performance and stability of solid oxide fuel cells by adopting samarium-doped ceria buffer layer

In this work, the Sm_0.2Ce_0.8O_1.9 (SDC) buffer layer was used to replace the Gd_0.1Ce_0.9O_1.95 (GDC) buffer layer to improve the long-term stability and performance of the solid oxide fuel cells (SOFCs) in the intermediate temperature (550–750 °C). The buffer layer was prepared by screen printing method. The micromorphology of the SDC buffer layer and the cell structures was observed by scanning electron microscopy (SEM). The electrochemical impedance spectroscopy (EIS) results showed that the polarization resistance (R_P) of the cell with SDC buffer layer was smaller than that of the cell with GDC buffer layer, reducing the R_P values by 43.52% and 43.33%, respectively (SDC-cell: 0.12 Ω cm² at 650 °C and 0.27 Ω cm² at 600 °C). The maximum power density of the cell with SDC buffer layer is 560 mW cm⁻² at 650 °C, which was 25% higher than that with GDC buffer layer. The long-term durability of the cell with SDC buffer layer was better than that of the cell with GDC buffer layer. These provide an excellent prospect for utilizing SDC buffer layer.     

High performance aluminum-air battery for sustainable power generation

Metal-air battery is receiving vast attention due to its promising capabilities as an energy storage system for the post lithium-ion era. The electricity is generated through oxidation and reduction reaction within the anode and cathode. Among various types of metal-air battery, aluminum-air battery is the most attractive candidate due to its high energy density and environmentally friendly. In this study, a novel polypropylene-based dual electrolyte aluminum-air battery is developed. Polypropylene pads are used as a medium to absorb the electrolyte, isolate the anode and cathode, control the hydrogen generation in the parasitic reaction. Potassium hydroxide is used as anolyte and sulfuric acid is used as catholyte. Parametric study is conducted to investigate the effect of electrolyte concentration and polypropylene separator thickness on the performance of the battery. The results show that the dual-electrolyte system can boost the open circuit voltage to 2.2 V as compared to the single electrolyte system for 5 M of anolyte while maintaining specific discharge capacity of about 1390.92 mAh.g⁻¹. The maximum peak power density has improved dramatically from 100 mW.cm⁻² to 350 mW cm⁻² for the dual electrolyte system.     

Revealing and Eliminating the Light-Soaking Issue in Metal Oxide-Based Inverted Organic Solar Cells

Inverted organic solar cells (i-OSCs) provide an exciting opportunity for commercialization owing to their excellent device air stability. However, light soaking (LS) issue generally occurs in metal oxide based i-OSCs, causing drastically decreased performance. The underlying root of LS effect is not clearly clarified until now. Herein, it is demonstrated that the surface oxygen defects on metal oxide nanoparticles, such as chemisorbed superoxide (O²⁻) and hydroxide (OH) dangling bonds, are the main reasons for LS issue in i-OSCs. The O²⁻ layer induces band bending at the cathode interface and increases the work function (WF) of metal oxide, thus leading to inefficient charge transport. The dangling bonds serve as interfacial trap states and cause non-radiative recombination, thus leading to the reduced open circuit voltage (V_oc). With ultraviolet (UV) illumination, the surface oxygen defects are interacted with photogenerated carriers, thereby improving the photovoltaic performance. Additionally, UV pretreatment of metal oxide films is employed to eliminate the LS issue and the resulting device yields significantly improved fill factors from 50.20% to 73.50% in the pristine SnO₂ based i-OSCs. This study reveals the origin of LS effect in i-OSCs and proposes a suggested model for LS mechanism.     

A first-principles study of doping effect on enhancing ORR performance of Sr–Ni–Nb co-doped LaFeO3 perovskite

The development of oxygen reductive reaction (ORR) electrocatalyst with high-stability, conductivity and activity is of great importance for improving the conversion efficiency of Solid Oxide Fuel Cell (SOFC). Although the ORR performance of LaFeO₃ perovskite (LFO) is not excellent, it is a promising cathode for SOFC duo to its low-cost peculiarity and adequate compatibility with electrolyte. In this work, the Ni–Nb and Sr were partially doped to Fe and La sites of LFO, respectively, to evaluate the doping effect on ORR ability. The increased formation energy illustrated that Nb-doping significantly enhanced the stability of LFO, while Ni-3d band emerged as the minimum conductive band mainly contributed to reduce the band gap. Moreover, the overpotential of LFO with Sr-doping (LSFO) was sharply reduced from 0.60 V to 0.34 V, which was possibly attributed to the decrease of e_g-filling (less than 2), and hence increased the binding energy. Although surface O-vacancy (O_v) is more favorable to be induced than sublayer, the sublayer O_v facilitates to reduce the ORR overpotential. The electron variation exploration of Sr–Ni–Nb co-doped LFO provides important guidance for the design of high-efficient ORR catalyst for SOFC with high stability, and superior conductivity, as well as low overpotential.     

Phase formation and magnetic properties of M-type lanthanum substituted strontium ferrites

Rare earth ion substitution is one of the most important methods for adjusting the magnetic properties of M-type hexagonal ferrites; however, the regularity of these phase formations has rarely been studied. In this work, La substituted Sr hexaferrite La_xSr_1-xO·nFe₂O₃ (La-SrM, 4.9 ≤ n ≤ 6.0, 0 ≤ x ≤ 0.6) was prepared using the traditional ceramic method. The effects of the Fe/Sr molar ratio (n), calcining temperature, and La³⁺ substitution (x) on SrM phase formation, the crystalline structure, and magnetic properties were investigated. With an increase of x up to a maximum value of 0.5–0.6, a higher calcining temperature is required to form the single M-phase of La-SrM samples. However, the optimal n values of single-phase La-SrM samples differ as the La substitution varies: when x = 0.1, n = 5.5–6.0; x = 0.2, n = 5.5–5.9; x = 0.3, 0.4 and 0.5, n = 5.7–5.8. The magnetic measurements show that La_0.2Sr_0.8O·5.8Fe₂O₃ has the highest specific saturation magnetization (σ_s), which is 2.2% higher than that of unsubstituted SrM (SrO·6Fe₂O₃), while the anisotropic field (H_A), the anisotropic constant (K₁), and Neel point (T_N) of La³⁺ substituted SrM decreased. Detailed structure analyses were conducted to explain the changes in magnetic properties. Fe³⁺ in the spin-up 2a sublattice of La_xSr_1-xO·5.8Fe₂O₃ decreased by approximately 5% from 98.5% (x = 0) to 93.85% (x = 0.4) with an increase in x. Additionally, a small amount of Fe³⁺ was reduced to Fe²⁺ in the spin-down 4f₂ sublattice with the maximum reduction amount of 4.13% reached at x = 0.2, thereby improving σ_s. The decrease in the bond angle of (4f₁) Fe3–O2–Fe5 (12k), (2a) Fe1–O4–Fe3 (4f₁), and (4f₁) Fe3–O4–Fe5 (12k) lead to the weakening of Fe–O–Fe superexchange of La-SrM so that H_A, K_1, and T_n decreased with increasing values of x. This work lays a solid foundation for the study of process regulation and ion substitution of permanent magnet ferrite.     

On the characterization and origin of the dislocations associated with the two way memory effect in CuZnAl thermoelastic alloys-I. Quantitative analysis of the dislocations

We have determined the Burgers vector of dislocations formed During the thermo-mechanical treatment needed to induce the two way memory effect in a CuZnAl alloy. This quantitative analysis was performed in the very highly anisotropic β₁, phase (A ∼- 15) by computer simulations of the contrast of dislocations observed in a transmission electron microscope. Interesting geometrical characteristics of the dislocations were found, which give a further information about their origin.     

Enhanced piezoelectricity and non-contact optical temperature sensing performance in Er3+ ion modified (K,Na)NbO3-based multifunctional ceramics

Rare earth ions doped ferroelectrics have attracted wide attentions due to their multifunction characteristics with both ferroelectric/piezoelectric properties and intriguing photoluminescence performance, which show great prospects for future multifunctional devices. In this work, a novel rare earth Er³⁺ ion modified potassium-sodium niobate (KNN) based ceramics were elaborately designed and prepared by the conventional solid-state reaction. The microstructure, phase structure, electric properties and photoluminescence performance of the Er³⁺ ion modified KNN-based ceramics were systematically investigated. Enhanced piezoelectricity (a considerable d₃₃ of exceeding 300 pC/N and a large d₃₃* up to 500 p.m./V) was realized through optimizing the substitution of BaZrO₃ by (Er_0.5,Na_0.5)ZrO₃. Both down-conversion and up-conversion photoluminescence emissions were detected in the optimal composition. The temperature-dependent upconversion emissions of the optimal Er³⁺ modified ceramic sample in the temperature range of 303–573K were verified to be applicable for non-contact optical temperature sensing with a maximum sensitivity S_a of 0.0028 K^-1 and a peak relative sensitivity S_r of 0.96% K⁻¹. Moreover, low-temperature sensing performance with a maximum S_r of 16.7% K⁻¹ in the temperature range of 80–280K was also presented based on the temperature-dependent down-conversion emissions. With both decent electrical properties and intriguing photoluminescence performance, the Er³⁺-modified KNN-based ferroelectrics exhibit good application potential in the future multifunctional optoelectronic devices.     

Effect of aluminum on microstructure and magnetic properties of sintered Nd-Fe-B magnets processed by grain boundary diffusion of Tb-Al

The grain boundary diffusion process(GBDP) of Tb can improve the coercivity of sintered Nd-Fe-B magnets.In this study,the effect of AI on the diffusion of Tb in the GBDP was investigated.The content of diffused Tb-Al was precisely controlled by adjusting the magnetron sputtering process.The Tb equivalent of Al was also studied.Results show that AI promotes the diffusion of Tb deeper into the magnet,reducing the thickness of the shell in the core-shell structure.This study is helpful for further ...