Search

The luminescence properties and temperature sensing performances of Mg5Al7O16:Cr3+ are systematically studied in this paper, synthesized using the solid-state sintering method. Based on X-ray diffraction and first-principles calculations, Cr3+ is verified to occupy the octahedral Mg2+ and Al3+ sites in the host Mg5Al7O16. From the Tanable–Sugano diagram, Cr3+ is in a strong crystal environment to induce sharp line emissions of Cr3+ around 700 nm. As the temperature rises, the excitation and emission ranging from 303 to 543 K are recorded, and overlapping of emissions from 2E → 4A2 and 4T2 → 4A2 is observed. The emissions in the 303–543 K range are separated using deconvolution. The emission from 2E → 4A2 decreases with increasing temperature, which is a normal thermal quenching behavior. However, the emission from 4T2 → 4A2 increases with temperature until 523 K. Energy transfer through phonon assistance from 2E to 4T2 is verified using temperature-dependent excitation and decay curves. It is used for the temperature-reading method based on the luminescence intensity ratio (LIR). The highest relative sensitivity is 1.80% K−1 at 303 K and is retained at above 1.00% K−1 in the 303–403 K range. [ABSTRACT FROM AUTHOR]

The CaZr0.990−x(Zn1/3Nb2/3)xTi0.01O3 (CZT-xZN, x = 0, 0.025, 0.05, 0.1, 0.2 mol) ceramics were successfully prepared by substituting (Zn1/3Nb2/3)4+ for Zr4+. With the increase of x, the crystals are orthorhombic structure. And, the cell volume and lattice constant decrease with the increase of x. Based on the SEM results, the grains become uneven and fine with the increase of x. Based on the Raman, it is found that the 1:2 ordered structure degree increases. With the increase of x, the dielectric constant (εr) increases, the Q × f values first increase and then decreases. the temperature coefficient of resonance (τf) is in inverse proportion to tolerance factor (t). When the sintering temperature is 1520°C, the microwave dielectric properties of the CZT-0.025ZN and CZT-0.05ZN ceramics are excellent, which are εr = 30.6, Q × f = 37,360 GHz, τf = 1.5 ppm/°C and εr = 31.6, Q × f = 36280 GHz, τf = 1 ppm/°C, respectively. [ABSTRACT FROM AUTHOR]

Vinyl units intrinsically featuring less steric, nonpolarity, and unsaturated character, are well‐known π‐bridge used in the synthesis of high‐performance semiconducting materials. Two‐dimensional (2D) vinylene‐linked covalent organic frameworks (COFs) represent a promising class of π‐conjugated structures, however, the range of available monomers for the reversible formation of carbon‐carbon double bonds remains limited. In this study, a new class of 2D vinylene‐linked COFs were synthesized using dimethyldiketopyrrolopyrrole (DM‐DPP) as the key monomer. The strong electron deficiency of diketopyrrolopyrrole (DPP) makes its methyl substituents readily activated upon the cocatalysis of L‐proline and 4‐dimethylaminopyridine in aqueous solution to conduct dynamic condensation with tritopic aromatic aldehydes. The resulting COFs crystallized in an eclipsed AA stacking arrangement and featured abundant, regular nanochannels. Their robust vinyl DPP‐linking mode enhanced donor‐π‐acceptor conjugation and promoted π‐stacked alignment along the vertical direction. Consequently, the synthesized COFs exhibited band gaps as narrow as 1.02 eV and demonstrated excellent light‐harvesting capability across the visible to near‐infrared I (NIR‐I) regions. Furthermore, the COFs could be converted into free‐standing thin pellets through simple pressure casting, and show excellent photothermal response and cycling stability under different light sources. [ABSTRACT FROM AUTHOR]

Pterocephin A is a natural triterpenoid saponin isolated from Pterocephalus hookeri, a traditional Tibetan medicine with slight toxicity, which can induce liver injury in rats. This study aimed to establish a sensitive and reliable UPLC-MS/MS method for exploring the toxicokinetics and tissue distribution of pterocephin A following single intravenous and intragastric administration. Pterocephin A and prosapogenin 1C (internal standard, IS) were extracted using a simple protein precipitation technique with methanol as the precipitant for plasma samples and methanol/acetonitrile = 1:1 (v/v) for tissue samples. UPLC separation was achieved by gradient elution with 0.3 mL/min and a mobile phase consisting of 5 mM ammonium formate (A) and acetonitrile (B) (0–2 min 30% B; 2–4 min: 30–80% B; 4–5 min: 80–98% B; 5–6.5 min: 98% B; 6.5–7 min: 98–30% B; and 7–8 min: 30% B, v/v) with a column temperature of 35 °C. MS spectrometry adopted negative ion scanning mode, primary MS spectrometry adopted full scan monitoring mode, and secondary MS spectrometry adopted targeted MS2 scan monitoring mode. The assay exhibited a linear dynamic range of 0.02–15 μg/mL for pterocephin A in biological samples, with the low limit of quantification set at 0.02 μg/mL. Non-compartmental toxicokinetic parameters indicated that pterocephin A was well absorbed into the systemic circulation and had a long residual time after intravenous (10 mg/kg) and intragastric (60 mg/kg) administration, as it could still be detected after 72 h. Tissue distribution analysis revealed detectable levels of pterocephin A in various tissues, and a high concentration was maintained in the liver after intravenous (10 mg/kg) administration, with the highest concentration being 610.95 ± 25.73 ng/mL and a specific distribution pattern of liver > lung > kidney > intestine > spleen > testes > heart > stomach. The toxicokinetic process and tissue distribution characteristics of pterocephin A were expounded in this study, which can provide relevant data support for further research and clinical application of pterocephin A with its slight toxicity. [ABSTRACT FROM AUTHOR]

Owing to its prominent π‐delocalization and stability, vinylene linkage holds great merits in the construction of covalent organic frameworks (COFs) with promising semiconducting properties. However, carbon‐carbon double bond formation reaction always exhibits relatively low reversibility, unfavorable for the formation of high crystalline frameworks through self‐error correction and assembling processes. In this work, we report a heteroatom‐tuned strategy to build up a series of two‐dimensional (2D) vinylene‐linked COFs by Knoevenagel condensation of an electron‐deficient methylthiazolyl‐based monomer with different triformyl substituted (hetero−)aromatic derivatives. The resulting COFs show high‐quality periodic mesoporous structures with high surface areas. Embedding heteroatoms into the backbones enables significantly improving their crystallinity, and finely tailoring their semiconducting structures. Upon visible light stimulation, one of the as‐prepared COFs with donor‐π‐acceptor structure could deliver a nearly seven‐fold increase in the catalytic activity of hydrogen generation as compared with the other two. Meanwhile, in combination with high crystallinity and the matched conduction band energy level, such kind of COFs can be able to selectively generate singlet oxygen and superoxide radicals in a high ratio of up to 30 : 1, allowing for catalyzing aerobic thioanisole oxidation in distinctly tunable activities through the substituent electronic effect of the substrates. [ABSTRACT FROM AUTHOR]

The rapid development of 5G and 6G technologies has led to an increased demand for microwave dielectrics ceramics. Microwave dielectrics ceramics with high Q value and low cost have attracted a lot of attention from researchers. Such as material sintered at relatively low temperature and cheap raw materials. Magnesium titanate (MgTiO3) is a material with excellent dielectric properties but requires high-temperature sintering. It is reported that substitution of Zn2+ for Mg2+ can lower sintering temperature and improve dielectric properties. Here, microwave dielectric properties and phase evolution of Zn-excess Mg0.95Zn0.05+xTiO3+x (x = 0, 0.025, 0.05, 0.075, 0.1) compositions were investigated. A moderate Zn-excess is found to promote formation of pure MgTiO3 phase with lower temperature. The composition with x = 0.05 sintered at 1300 °C possess optimal dielectric performance εr of 17.85, Q × f of 173,300 GHz (@11 GHz) and τf of − 52.04 ppm/°C with relative density of 97%. [ABSTRACT FROM AUTHOR]

Address to the by-product sulfuric acid in the pyrometallurgical smelting process of copper sulfide concentrate is difficult to be applied on a large scale in the unsalable area of sulfuric acid, the oxygen pressure leaching process of copper sulfide concentrate was studied. The composition, phase and occurrence state of valuable elements of a copper sulfide concentrate raw material were analyzed. The feasibility of oxygen pressure leaching of copper sulfide concentrate was analyzed theoretically. The leaching effects of one-stage oxygen pressure leaching and two-stage oxygen pressure leaching process were studied. The results show that the copper leaching rate is 90.49%-92.25% by two-stage countercurrent oxygen pressure leaching. In the first stage, the temperature is 135140 °C, the total pressure is 1.3-1.4 MPa, the time is 2-2.5 h, the amount of dispersant is 4‰-5‰, and the amount of precipitation agent is 2.5%-3%. In the second stage, the temperature is 165-170 °C, the total pressure is 1.4-1.5 MPa, the time is 2.5-3 h, the amount of dispersant is 6‰-7‰, and the amount of precipitation agent is 3%-3.5%. The leaching solution from the first stage contains copper 90.78-92.34 g/L, iron 10.81-13.84 g/L and H2SO4 28-30 g/L, which can be sent to subsequent iron removal purification-electrowinning to produce electrocopper. [ABSTRACT FROM AUTHOR]

We prepared a 3D FeZn–N–C based catalyst by green in situ growth of 1D Fe–N–C carbon nanotubes by introducing ferrocyanide ions on the surface of 2D exfoliated MOF-5. The 1D/2D FeZn–N–C based electrocatalyst is conducive to O2 diffusion and ionic/electron transfer, exhibiting an excellent ORR catalytic performance and a peak power density of 294 mW cm−2 for Zn–air batteries. [ABSTRACT FROM AUTHOR]

Calcium bismuth niobate (CBN) ceramic, as a core element of high-temperature piezoelectric sensors, has attracted widespread attention due to its high Curie temperature within the class of Aurivillius compounds. However, CBN usually faces two shortcomings: poor piezoelectric constant and low resistivity. In this work, CBN-based ceramics with donor–acceptor ions (W/Co) co-substituted at B-site were prepared by solid-state reaction method, and structure–property relationship of ceramics was studied in detail. Co-substitution of W/Co ions effectively improved the electrical property and hardness of CBN ceramics. CaBi2Nb 1. 9 1 (W 2 / 3 Co 1 / 3 ) 0. 0 9 O9 exhibits enhanced electrical and mechanical properties including high resistivity of ∼ 1 0 7 Ω ⋅ cm at 500°C, piezoelectric constant of ∼ 1 5. 3 pC/N and hardness value of ∼ 3. 5 7 GPa. These values are two orders of magnitude, over two times, and 1.36 times higher than those of pure CBN ceramic, respectively. This work provides a reference for exploring other bismuth-layered structural ceramics. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the impact of the Kovar glass content on the mechanical and electrical properties of Si3N4–Kovar composites sintering at air atmosphere. To achieve this, Si3N4–Kovar composites were prepared using molding technology with the Kovar glass powder ranging from 20 to 70 wt%. The phase composition, morphology, bulk density, apparent porosity, flexural strength at room temperature, dielectric constant, and dielectric loss of the composites were all examined in relation to changing the Kovar glass content. During the sintering process, the α‐quartz on the surface of Si3N4 particles acted as the crystal nucleus, inducing the crystallization of the glass at the wetting position that the Kovar glass and the surface of the Si3N4 particles. A small amount of the β‐quartz phase was crystallized at 750–850°C, followed by a large amount of the β‐quartz phase crystallizing above 900°C. Additionally, some β‐quartz phase transformed into the metastable β‐cristobalite phase that could exist below 1470°C. During the cooling process, the β‐cristobalite phase transformed into a low‐temperature α‐cristobalite phase, while the β‐quartz phase transformed into a low‐temperature α‐quartz phase. The results indicate that the Si3N4–Kovar glass composite with 60 wt% the Kovar glass content sintered at 900°C exhibits higher density (1.88 g/cm3), lower porosity (25.4%), higher flexural strength (55.34 MPa), lower dielectric constant (3.46), and lower dielectric loss (4.26 × 10−3). [ABSTRACT FROM AUTHOR]

Starting from the market rules of the pilot provinces of the domestic spot market, this paper analyzes the mechanism of market intervention and suspension, the mechanism of the power supply period, and the mechanism of market clearing anomaly. At the same time, combined with the real-time operation of the Inner Mongolia power grid, the traditional dispatching mode and the power spot market operation dispatching mode are compared. Given the abnormal frequency, section overload, and insufficient spinning reserve in real-time operation, an auxiliary decision mechanism of manual intervention in the power spot market is proposed. The mechanism includes load bias setting, section limit bias setting, deviation monitoring, and other auxiliary functions, which provide a method of quick intervention under the electric spot market to ensure the safe and stable operation of the power grid.