Search

The Cu-12Al-4Ni-1Mn-xB（x=0%，0.1%，0.2%，0.3%，mass fraction，the same below） shape memory alloys were prepared by vacuum arc melting furnace after introducing trace boron element into the alloy. The influence of boron addition on the microstructure， phase transformation， and mechanical properties of the alloy was investigated. The results show that the addition of boron significantly refines the grain size， with the grain size decreasing from hundreds of microns to （11±3.45） μm. The phase transformation temperature shifts to the high-temperature side after boron is added， indicating that the phase transformation process requires higher thermal activation energy. When the boron content is 0.2%， the microhardness of the alloy is enhanced， from （301.7±2.6）HV without adding boron element to （334.3±3.4）HV， which is attributed to grain refinement and the precipitation of hard and brittle borides. The tensile fracture strength and elongation are greatly improved， with the fracture strength increasing from （320±2.6） MPa to （788±17） MPa， and the elongation increasing from （1.44±0.05）% to （3.74±0.12）%. After solid solution annealing， the fracture strength and the elongation are both further increased to （856±10.7）MPa and （5.78±0.16）%， respectively. Analysis indicates that grain refinement strengthening， precipitation strengthening of borides， and solid solution strengthening are the main mechanisms for the improvement of mechanical properties. The fracture mode of the alloy shifts from brittle fracture to ductile fracture.

CuAlMn shape memory alloys have specific target demands in various fields due to excellent thermal stability and high damping properties.However， the mechanical property of the alloy is severely weakened due to the intergranular fracture arising from the coarse grain size. To improve the mechanical properties， the Cu-11.36Al-5Mn-xY （x=0-3， mass fraction/%，the same below） alloys were prepared by using a vacuum arc melting furnace by introducing rare earth Y element. The microstructure of the as-cast CuAlMn alloy was subsequently tailored and homogenized through solid solution and aging treatment. The phase transformation， phase composition， and microstructure of the alloy were respectively characterized by DSC， XRD， metallography and SEM observations. The hardness and mechanical properties of the alloy were tested by using a microhardness tester and a universal materials testing machine. Results show that the addition of Y element effectively refines the CuAlMn alloy grain， and the grain size even reduces from several hundred μm to around 10 μm. The grain refinement is mainly associated with the increased grain nucleation areas and the inhibition of grain growth during the cooling process. Moreover， quite numbers of Y-containing precipitates with the network structure are formed and distributed along the grain boundaries. The hardness of the alloy increases with the enhancement of Y element addition， which is associated with the precipitation of a large amount of hard and brittle containing Y phases.The hardness of the solution-aged sample is higher than that of the cast sample， due to the precipitate distribution throughout the entire matrix and higher volume fraction of precipitates for the former sample.In addition， the compressive and tensile fracture strength of the alloy are significantly improved when the Y content is in the range of 0.1%-0.4%. The strengthening mechanism can be understood by grain refinement strengthening， precipitation strengthening and solution strengthening. The compressive fracture strain of the alloy reaches its maximum when the Y content is 0.4%， while the elongation after fracture exhibits the maximum value with Y content of 0.1%. The changing trend is closely related to the coupling effect between grain refinement and precipitation phases.

BaBiNb5O15- based oxide ion conductors have shown promise for solid fuel cell applications at medium temperatures. In this study, BaBi0.98Sr0.02Nb5-xTixO15-δ (x = 0.02, 0.04, 0.05, 0.06, 0.08) samples were prepared by the conventional solid-state synthesis with two-step sintering method. The electrical properties and oxygen relaxation behaviors of the BaBi0.98Sr0.02Nb5-xTixO15-δ samples were investigated. With increasing the Ti content, the bulk conductivity of the BaBi0.98Sr0.02Nb5-xTixO15-δ samples showed a trend of increasing first and then decreasing. When the doped Ti content reached 5 mol%, the highest bulk conductivity of BaBi0.98Sr0.02Nb5-xTixO15-δ samples can be got, 5.27 × 10−5 S/cm at 773 K. According to the dielectric relaxation spectroscopy measurement, the BaBi0.98Sr0.02Nb4.95Ti0.05O15-δ sample exhibits the higher moveable oxygen vacancy concentration and mobility of oxygen vacancies. This could be the possible reason that there is the highest bulk conductivity in the BaBi0.98Sr0.02Nb4.95Ti0.05O15-δ sample. Additionally, the influence of sintering temperature on the electrical properties of the BaBi0.98Sr0.02Nb4.95Ti0.05O15-δ compound was investigated. When the BaBi0.98Sr0.02Nb4.95Ti0.05O15-δ sample is sintered at a temperature of 1423 K, it exhibits the best bulk conductivity and total conductivity. [ABSTRACT FROM AUTHOR]

Acute lung injury (ALI) remains a significant global health issue, necessitating novel therapeutic interventions. In our latest study, we pioneered the use of D-mannitol–cerium–quercetin/rutin coordination polymer nanoparticles (MCQ/R NPs) as a potential treatment for ALI. The MCQ/R NPs, which integrate rutin and quercetin for their therapeutic potential and D-mannitol for its pulmonary targeting, displayed exceptional efficacy. By utilizing cerium ions for optimal nanoparticle assembly, the MCQ/R NPs demonstrated an average size of less than 160 nm. Impressively, these nanoparticles outperformed conventional treatments in both antioxidative capabilities and biocompatibility. Moreover, our in vivo studies on LPS-induced ALI mice showed a significant reduction in lung tissue inflammation. This groundbreaking research presents MCQ/R NPs as a promising new approach in ALI therapeutics. [ABSTRACT FROM AUTHOR]

Offshore wind farm (OWF) is considered as a perfect zero‐carbon energy source for the future power system. However, the growing offshore distance and water depth of OWF make the OWF HVDC transmission technique a more promising solution than HVAC due to higher cost‐efficiency and reliability. In this paper, the current situation of OWF‐HVDC projects is introduced at first. Then, novel converter topologies with the higher power density and cost‐efficiency are presented, including the hybrid modular multilevel converter (MMC), alternative arm converter (AAC), and diode rectifier (DR). Next, several OWF HVDC transmission system topologies are introduced, including terminal‐hybrid, station‐hybrid and all‐DC delivered system. Furthermore, the key technologies for OWF HVDC operation and control are summarized, including grid‐forming control strategy for offshore wind turbines, stability analysis method, corresponding stability enhancement measures and frequency support control strategies. Additionally, the fault ride‐through and protection strategies for different fault locations have been presented. Finally, the main conclusions and prospects for OWF HVDC are summarized. [ABSTRACT FROM AUTHOR]