The insufficient soluble silicon and heavy metal contamination in soil severely threaten the yield and quality of crops, which urgently requires dual-functional materials to address the above issues. Herein, a high-performance hierarchical magnesium silicate/diatomite (Si/Mg/xK) composite is synthesized via a one-step hydrothermal method. Natural diatomite serves as both a porous support and silicon source, while cost-effective magnesium sulfate concentrate derived from flue gas desulfurization (FGD) waste provides the magnesium source and weak alkalinity condition. Potassium hydroxide is introduced as an alkaline activator to accelerate the in-situ formation of magnesium silicate nanostructure on diatomite, creating hierarchical porosity that significantly enhances the specific surface area and increases the interaction interface with target solutions. The resulting composite achieves a remarkable citrate-soluble silicon content of 391.89 mg/L, representing a 39-fold improvement over raw diatomite, while concurrently releasing beneficial soluble magnesium (253.33 mg/L). Furthermore, the composite demonstrates exceptional heavy metal ion adsorption performance with a maximum cadmium ion (Cd2+) adsorption capacity of 184.5 mg/L, indicating dual-functional potential for soil remediation. This work establishes a sustainable pathway to valorize natural diatomite and FGD waste into dual-functional materials capable of efficient silicon/magnesium release and Cd2+ adsorption.

A bunching system utilizing a heterodyne combiner is designed to generate a sawtooth waveform with three harmonics to increase the beam current intensity of medical cyclotron accelerators. The design incorporates a low-pass filter, helical bandpass filters, and a broadband matching network, producing a sawtooth waveform exceeding 1200 V, which meets the requirements for efficient bunching. This buncher substitutes the design and manufacturing requirements for high linearity broadband power amplifiers with three narrowband single-frequency power amplifiers for amplification. The digital direct synthesizer achieves coherent amplitude and phase adjustment of these three frequency signals. The broadband matching network is based on transmission line transformers to avoid the design of large-sized coaxial resonant cavities, which satisfy the spatial constraints of the cyclotron injection line.

The transformation of cementite significantly impacts performances of the steels during both preparation and application. It is particularly crucial to acquire a comprehension of the cementite's characteristics. This study systematically investigated the structural evolution from isolated to restrained cementite under thermal environments, utilizing characterization techniques such as X-ray Diffraction, Raman, Optical Microscopy, Scanning Electron Microscopy, and Transmission Electron Microscopy. The research findings demonstrated that when exposed to temperatures above 600 degrees C, fully isolated lamellar cementite with the nano-scaled size can undergo graphitization from the surface to the interior in a short time, resulting in a sandwich structure of "carbon-ironcarbon". The cementite that was fully restrained by the iron matrix could undergo spheroidization after undergoing a long time annealing. The persu-isolated cementite with meso-scaled size exhibited an alternating pattern of graphitization and spheroidization. As an individual thick lamellar cementite decomposed into a few numbers of carbon-coated iron capsules, and the large spheroidal cementite transformed into an interwoven core-shell structure with multi-chambers. Eventually, a selective evolution mechanism of cementite under the thermal environment was provided expressly.

Sulfur hexafluoride (SF6) is widely used in gas-insulated equipment due to its excellent electrical properties. However, SF6 is a potent greenhouse gas, and with the implementation of the "dual carbon" strategy, reducing SF6 emissions has become imperative. This article analyzes the interaction between SF6 and the ZnO surface through simulation calculations and studies the effects of ZnO-filled systems on SF(6 )degradation by dielectric barrier discharge (DBD) through experiments. The results demonstrate that the charge transfer of individual fluorine atoms is relatively weak, with no significant charge transfer occurring before and after the adsorption of each fluorine atom. Furthermore, after adsorption on the ZnO surface, the SF6 molecule does not undergo noticeable deformation, indicating that the adsorption of SF6 on the ZnO surface is physical adsorption. Under the conditions of a 2% SF6 concentration, a gas flow rate of 150 mL/min, and an input power of 90 W, the SF6 degradation rate (DR) and equivalent capacitance with ZnO filling were found to be 96.6% and 79.31 pF, respectively. At an input power of 80 W, the energy yield (EY) reached a maximum value of 12.41 g/kWh, and the main decomposition products of SF6 were SO2, SO2F2, and SOF2. This study provides a theoretical basis for the efficient degradation and harmless treatment of SF6.

The reliability standards for on-chip electrostatic discharge (ESD) protection in high-voltage industrial communication buses are stringent, and traditional ESD solutions cannot effectively meet the requirements for high holding voltage ( V-h ) and high-temperature tolerance in these applications. Therefore, this article presents a dual-direction silicon-controlled rectifier (DDSCR) featuring shallow snapback and high-temperature robustness. At the same size, V-h (38.4 V) of the parallel NPN-enhanced SCR (NPNE_DDSCR), which employs a metal short and no shallow trench isolation (STI), is significantly higher than that of the traditional structure (T_DDSCR) and the parallel NPN structure (NPN_DDSCR). Under high-temperature conditions ranging from 50 (degrees) C to 125 (degrees) C, the structure maintains nanoampere-level leakage current, and the device's ESD characteristics show no significant degradation. The electrostatic properties of three types of structures were verified based on the 0.18- mu m bipolar-CMOS-DMOS (BCD) process, and their operating mechanisms were further analyzed using technology computer-aided design (TCAD) simulations. The results show that the NPNE_DDSCR exhibits superior performance, with a human body model (HBM) level exceeding 8 kV, and is suitable for efficient on-chip ESD protection of industrial communication buses.

7075 aluminum alloys with varying TiC particle additions were fabricated by simultaneously depositing a standard 7075 wire and a TiC treated wire at different wire feed speed ratios. The effects of TiC content on the microstructure and mechanical properties of 7075 alloy were investigated. Results indicated that the addition of TiC particles can effectively refine the grain structure through heterogeneous nucleation, and the grain refinement effect was enhanced with increasing TiC particle content in the range of 0-0.70 wt%. Moreover, TiC particles can restrain the continuous distribution of second phase at grain boundaries. TiC particles tended to cluster at grain boundaries as its content exceeded 0.48 wt%, which adversely affected their beneficial effect on the improvement of mechanical properties. At an optimal TiC content of 0.48 wt%, the tensile strength and elongation in the horizontal direction exhibited remarkable enhancements of 27.2% and 319%, respectively, compared to those without the addition TIC particle.

As one of the fundamental components, hollow cathodes using noble gas propellant are widely used in electric thrusters. Iodine has become one of the ideal alternative propellants due to its economy and good chemical properties, while due to the complex reactions, characteristics and proper functioning of iodine-fed hollow cathodes are still unknown. Therefore, a model is needed to understand the physical-chemical process of the iodine-fed hollow cathode discharge. In this work, a self-consistent two-dimensional fluid model of the low-current iodine-fed hollow cathode discharge with detailed non-equilibrium plasma chemistry is developed and verified by the voltages of the keeper and anode obtained in the experiments. Simulations show that the electron impact ionization with iodine atoms dominates the discharge process as the density of iodine atoms is much higher than that of iodine molecules due to the electron impact dissociation and thermal dissociation. Moreover, the power balance analysis shows the heating of electrons contributed by the electric field mainly takes place near the keeper and the orifice. Ion current heating contributes significantly to the gas heating compared with the heating by the electron elastic collisions with I and I2 and the heat release or consumption during the neutral reactions. Furthermore, the influence of electronegativity on plasma characteristics is analysed. Simulations involving I- ions bring higher values of ionization degree, discharge power as well as maximum electron and gas temperatures compared with those without I-. This is similar to the differences in the plasma properties between the iodine-fed and xenon-fed hollow cathode to which the low ionization energy, large collision ionization cross-section and the electronegativity of iodine contribute together. In all, these findings can better predict the plasma behaviours in the iodine-fed hollow cathode discharge and may promote the development of the electric propulsion system using iodine propellant.

Rhenium-tungsten core-shell powder was prepared by solid-liquid mixing method and then osmium powder was added to salt, washed and annealed, a ternary mixed-base cathode of tungsten-rhenium osmium was prepared. After impregnation with 411 salt, the pulse emission test found that W2Re1Os1 cathode which is a ternary mixed-base cathode has the best electron emission performance and the current emission density can reach 35 A/cm(2) at 1050 degree celsius, which is slightly higher than that of the same type of binary mixed-base cathode, neither Re nor Os reacts with the active salt during the impregnation process of the ternary tungsten-rhenium-osmium mixed-base cathode, and the active substance is produced by the reaction of W and the active salt.

In this study Zn doping was applied to MgO thin films in order to improve the secondary electron emission (SEE) property via relieving the surface charging and modifying the electron structure of MgO. Pristine MgO and Mg 1-x Zn x O thin films (the Zn doping proportion x is within 11at.%) were prepared on Si substrates by a simple, cost effective aerosol assisted chemical vapor deposition method followed by annealing at elevated temperature. The surface morphology and microstructure of the Mg 1-x Zn x O films were characterized. Secondary electron yield (δ) as a function of primary electron energy the films was examined. First principles calculation based on the density functional theory was introduced to evaluate the electronic structure and work function of Mg 1-x Zn x O crystals. SEE testing results revealed that δ of the MgO film is effectively improved by Zn doping of proper concentration. The pristine MgO film with relatively smooth surface exhibits a maximum secondary electron yield (δ m ) of 5.1 at E p of 750 eV. The δ m of the Mg 1-x Zn x O film (x=0.09) is 7.0 at E p =1500 eV, which is 34.6% higher than that of the MgO film prepared under identical method. Improvement of δ of the Mg 1-x Zn x O films with x<0.1 is probably due to the unique surface morphology with protrusions and sharp edges and the increase of electrical conductivities of the films. Another factor contributing to the δ increase is the decrease of work function due to Zn doping, which is confirmed by first-principles calculations of Mg 1-x Zn x O crystals.

Replacing the expensive Sc in thermionic cathode with cheaper Y has come to be a widespread concern, but has no substantial breakthrough so far in previous studies. In this paper, several co-doped tungsten matrix cathodes with different weight ratio of Y 2 O 3 :Sc 2 O 3 were prepared and tested. The results indicate that addition of Y can enhance the emission performance of cathodes in some specific component ratios of Y to Sc. However, the surface analysis indicates that the added Y are not working as adsorption Y to adjust the chemical potential of O and Ba on the surface of cathode like Scandium, but just promote the generation of Sc.

The sintering of osmium is critical for the preparation of raw material targets for film coating, which is the main application area of osmium. In order to get a better understanding of the intrinsic mechanism of densification of osmium, a serial study on the sintering behavior of osmium has been made in this study. By the master sintering curve (MSC) and constant heating rate (CHR) method, the sintering activation energy of nanosized osmium is evaluated to be about 340 kJ/mol, which is higher than most other metals. The density–functional theory calculation indicates the higher energy barrier of the surface atom and vacancy migration and lacking migration tunnel of inner point vacancies. For example, the diffusion of osmium atoms on the surface of particles is mainly limited by Os (1010), which has an energy barrier as high as 1.14 eV, that is higher than the W atom on W (110) of 0.99 eV. The vacancy migration energy barrier inside osmium’s grains is higher than 3.0 eV, while that of W is only 1.7 eV. This means that it is more difficult for osmium to achieve a high density compared with W, which is consistent with the experimental results. Accordingly, the proposed strategy provides a new opportunity to design a sintering process for target fabrication with excellent properties for various applications.

The sintering of Os is critical for the preparation of raw material targets for film coating, which is the main application area of Os. Here we have made a serial study on the sintering behavior of Os. By constructing a Master Sintering Curve (MSC), the sintering activation energy of nano-sized Os is 340kJ/mol, higher than many other metals. By using density-functional theory, it is found that the higher energy barrier of the surface atom migration and surface vacancy migration, combined with lacking migration tunnel of inner point vacancies, leading to the high activation energy of Os. For example, the diffusion of atoms on the surface of particles is mainly limited by Os (1010), which has an energy barrier as high as 1.14eV. The vacancy migration energy barrier inside Os's grains is higher than 3.0eV, while that of W is only 1.7eV, indicating that Os is more difficult to get a high density compared with W, which is consistent with the experimental results.

The cathode in the magnetron should have good secondary emission property and a certain thermionic property. In this article, ZrH 2 was added as an activator to obtain rare earth-doped tungsten matrix impregnated cathode to improve the emission property. Cathodes with ZrH 2 (Y15-411-Zr cathode) or without ZrH 2 (Y15-411 cathode) were prepared by a spray drying method combined with high-temperature sintering in dry hydrogen atmosphere. The emission properties and emission mechanism have been studied. The results showed that thermionic emission performance and secondary emission performance of Y15-411-Zr cathode are 3.4 times and 1.2 times higher than those of Y15-411 cathode, respectively. With the addition of ZrH 2 , yttrium was produced during activating process, which contributed to the better emission properties of Y15-411-Zr cathode. Furthermore, the work function of barium and oxygen adsorbed on yttrium oxide and yttrium surface was calculated using the first principle. The results showed that the lowest work function of Ba-O absorbed on Y 2 O 3 and Y is 1.9 and 1.6 eV, respectively.

锇靶是制备M型阴极常用的一类靶材,须具有纯度高、致密度高、晶粒细小等特性,然而,传统工艺烧结因烧结温度较高获得的靶材晶粒较粗大,对阴极覆膜沉积不利.本研究对锇粉模压成圆饼压坯,之后采用微波烧结压坯.微波烧结锇压坯过程中以碳化硅、氧化锆作为辅助加热材料,氧化铝作为保温材料,升温速率在20～30 min/℃之间.结果 表明,当随着压强从100增加到300MPa,微波烧结1500℃保温60 min后,样品相对密度从80.61％快速增加到93.44％.当压强继续增加到400MPa时,相对密度随着压强的增长变缓达到94.25％.当压强从400增加到500MPa,烧结后样品的相对密度增长不明显,并有裂纹出现.锇烧结体的相对密度和直径收缩率随着保温时间的延长先快速增加,然后缓慢增加,最后增加趋于平缓.在微波烧结1500℃下,随着保温时间的延长直径收缩率从11.67％快速增加到14.99％,然后缓慢增加到15.56％,相对密度从87.97％快速增加到93.78％,然后缓慢增加到94.25％,而孔隙的数量和尺寸随着保温时间的延长而减小,最终呈球形,晶粒尺寸在1 μm左右.

Three-dimensional (3D) Nitrogen-doped carbon coated hierarchically porous silicon (hp-Si@NC) composite with cocontinuous skeletons and abundant interconnected macropores was prepared by a sol-gel route, followed by a magnesiothermic reduction and a polydopamine pyrolyzation. The BET specific surface area and pore volume of the obtained hp-Si@NC composite are calculated to be around 220.4 m(2).g(-1) and 0.247 cm(3).g(-1), respectively. Both hierarchically porous Si monolith and hp-Si@NC composite possess great electrochemical performances. The hierarchically porous Si monolith exhibits an initial discharge and charge capacity of about 1943 and 1621 mAh.g(-1), and maintains a reversible capacity of about 125 mAh.g(-1) in the 100th cycle. The hp-Si@NC composite reveals a discharge capacity of about 1077 mAh.g(-1) and a charge capacity of 723 mAh.g(-1) in the first cycle, and a reversible capacity of around 700 mAh.g(-1) remains after 100 cycles. The coulombic efficiency increases from 67.1% in the first cycle to 97% in the second cycle and to 99% in the 100th cycle, with a great rate performance. All these favorable electrochemical characterizations benefit from unique pore structure and N-doped carbon layer. The hp-Si@NC composite obtained by integrating with sol-gel process, magnesiothermic reduction and polydopamine pyrolyzation can be promisingly applied as an anode in Li-ion batteries with a bright prospect. (C) 2021 Elsevier B.V. All rights reserved.

Dictyophora-shaped porous Mn2SnO4/C composite materials were prepared by a sol–gel process accompanied by phase separation. The samples possess a well-defined interconnected micro–meso–macroporous structure which benefits the cycling performance for Li-ion batteries.

教师的职责之一就是教书育人,从专业基础课生理学与其他医学基础课程的融合、与临床知识的融合、与日常生活常识的融合以及与学生专业知识的融合四个维度,探讨在培养人才的过程中,在讲授基础知识的同时如何更好地拓展学生的知识结构,与培养学生的能力相结合,达到学有所获、学有所用的目的,教师"真正把教学当作科学研究在做",从中领悟到教好书、育好人的真谛和内涵.

Os sintered body was prepared by microwave sintering process. The influences of the green compact pressure and the microwave sintering parameters (heating rate, sintering temperature, and holding time) on the microstructure and relative density of Os sintered bodies were investigated. The densification mechanism of Os microwave sintering was analyzed. The results show that, the average grain size of Os after microwave sintering at 1350 ℃ is about 0.22 μm, which is close to the average particle size of the Os powders. With the increase of the sintering temperature to 1500 ℃, the grain size grows to 0.76 μm. The relative density of the Os sintered body increases rapidly at first and then slowly after prolonging the holding time sintered at 1500 ℃. After microwave sintering at 1500 ℃ for 60 min, the relative density of the Os sintered body is 94.3%, and the average particle size is less than 1 μm. The sintering kinetics analysis shows that the densification process of Os is the result of the combined action of volume diffusion and grain boundary diffusion. With the increase of the sintering temperature, the diffusion mechanism gradually transfers from grain boundary diffusion to volume diffusion.

In this study, the structural, elastic, and thermodynamic properties of DO19 and L12 structured Co3X (X = W, Mo or both W and Mo) and μ structured Co7X6 were investigated using the density functional theory implemented in the pseudo-potential plane wave. The obtained lattice constants were observed to be in good agreement with the available experimental data. With respect to the calculated mechanical properties and Poisson’s ratio, the DO19-Co3X, L12-Co3X, and μ-Co7X6 compounds were noted to be mechanically stable and possessed an optimal ductile behavior; however, L12-Co3X exhibited higher strength and brittleness than DO19-Co3X. Moreover, the quasi-harmonic Debye–Grüneisen approach was confirmed to be valid in describing the temperature-dependent thermodynamic properties of the Co3X and Co7X6 compounds, including heat capacity, vibrational entropy, and Gibbs free energy. Based on the calculated Gibbs free energy of DO19-Co3X and L12-Co7X6, the phase transformation temperatures for DO19-Co3X to L12-Co7X6 were determined and obtained values were noted to match well with the experiment results.