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81.
Mukil V. Ayyasamy Jeroen A. Deijkers Haydn N.G. Wadley Prasanna V. Balachandran 《Journal of the American Ceramic Society》2020,103(8):4489-4497
Density functional theory (DFT) calculations and machine learning (ML) methods are used to establish a relationship between the crystal structures of rare-earth (RE) disilicates (RE2Si2O7) and their coefficient of thermal expansion (CTE). The DFT total energy data predict the presence of several energetically competing crystal structures, which is rationalized as one of the reasons for observing polymorphism. An ensemble of support vector regression models is trained to rapidly predict the CTE as a function of RE2Si2O7 crystal chemistry. Experiments subsequently validated the structure and CTE predictions for Sm2Si2O7. 相似文献
82.
Marek Berezowski 《化学工程与技术》2020,43(12):2523-2529
The first and second Lyapunov methods were adapted to analyze the stability of a tubular chemical reactor with recycle. The criterion of local stability in the form of inequalities was derived using Lyapunov's first method. It is an explicit algebraic form, despite the fact that the mathematical model of the reactor is a partial differential problem with a boundary condition. As part of the second Lyapunov method, a mathematical criterion for non-local stability was derived in the form of an increase of Lyapunov's function. Both criteria are presented on graphs. 相似文献
83.
84.
Preston C. Bowes Jonathon N. Baker Douglas L. Irving 《Journal of the American Ceramic Society》2020,103(2):1156-1173
Unintentional impurities often found in strontium titanate (doped or undoped) have hindered efforts to study individual impurities experimentally. To fill this gap, a computational survey of acceptor-type point defects of common intentional or unintentional impurities (Al, Cu, Fe, K, Mg, Mn, N, Na, Ni, and Zn) is presented. Utilizing defect formation energies from density functional theory using hybrid exchange correlation functionals in a grand canonical model of the defect chemistry, the equilibrium Fermi level (μe) was calculated as a function of processing conditions for pure SrTiO3, SrTiO3 individually doped with each impurity, and SrTiO3 co-doped with Al and N. Above a certain concentration, each impurity reduced the maximum predicted hole concentration relative to the intrinsic case. Al, Mg, Zn, K, and Na exhibited similar trends and behaved more like ideal acceptors while N, Ni, Fe, Mn, and Cu were all unique and pinned μe near or above the mid-gap in most conditions. Al/N:SrTiO3 also exhibited similar trends at 800°C for all Al/N ratios, but more variation at 25°C. Additionally, the behavior of Al:SrTiO3 was not recovered until Al/N = 104. This suggests that to achieve SrTiO3 with free holes at room temperature, the concentration of most impurities must be controlled. 相似文献
85.
Rosa Colucci Cante Marianna Gallo Federica Nigro Francesca Passannanti Dana Salameh Andrea Budelli Roberto Nigro 《加拿大化工杂志》2020,98(9):1955-1961
In recent years, scientific interest in the development of non-dairy-based functional foods is increasing progressively and the fermentation of cereals, legumes, fruits and vegetable-based foods is becoming an important scientific research topic for the production of new probiotic products. In particular, legumes represent a possible alternative to protein foods from animal origins and an adequate fermentation substrate as they contain high amount of nutrients, such as proteins, carbohydrates, fibres, vitamins, and minerals, which are all useful to the growth and metabolic activity of certain microorganisms. This work focuses on the feasibility of developing a dry legume-based functional product using a fermentation process carried out on a 10% w/v navy bean suspension, in a lab-scale stirred batch reactor. After soaking and cooking dried navy beans, the fermentation tests performed on the resulting medium using Lactobacillus paracasei CBA L74 showed a maximum bacterial count of 109 CFU/mL after 20 hours and a maximum lactic acid concentration of 1.9 g/L after 16 hours of process time. A freeze-drying process was performed on the fermented bean suspension, showing a 2-log microbial reduction and a bacterial viability in the resulting probiotic powder of 3.7 × 108 CFU/g. 相似文献
86.
介绍了稀土晶体的科学内涵,包括稀土晶体的概念、学科特色和分类。阐述了稀土晶体材料的研发现状,包括稀土磁学材料、光学材料、电学材料、催化材料、能源材料、合金材料以及稀土原料。指出中国已建成从稀土矿产勘探开采、选矿、萃取、分离、冶炼等稀土原材料生产技术到下游稀土结构与功能材料研发和工业生产体系,形成了全球门类最齐全、规模第一的稀土新材料产业体系,但是仍未系统掌握稀土高技术材料和器件领域的核心技术。针对创新引领能力不足、稀土资源高端利用能力不强等系列问题,中国还需要在基础科学研究、应用基础研究、产业发展、资源回收等方面进一步加强战略规划。 相似文献
87.
Santanu Mondal Andriy Durygin Vadym Drozd Jose Belisario Zhe Cheng 《Journal of the American Ceramic Society》2020,103(9):4876-4893
In this research, near fully dense single phase bulk multicomponent transition metal nitride (Nb1/3Ta1/3Ti1/3)N1−δ has been successfully synthesized from mixed commercial powders of NbN, TaN and TiN via reaction flash sintering technique. This was performed with an applied pressure of ~ 35 MPa at 25°C under a constant DC electric field (~24-32 V/cm). The flash event, which is the abrupt increase in current (up to ~ 25.2 A/mm2) and temperature, occurred without preheating. The threshold power dissipation on the sample right before the flash is ~ 0.7 W/mm3. The formation of single phase (Nb1/3Ta1/3Ti1/3)N1−δ random solid solution and its compositional uniformity were confirmed by XRD and EDS, respectively. The effects of ball milling duration and limiting current density on phase formation were studied. Simulation based on Joule heating provides an estimate of the ultimate sample temperature of ~ 1850°C. Vickers hardness of the obtained (Nb1/3Ta1/3Ti1/3)N1−δ is 17.6 ± 0.6 GPa, which is comparable to similarly flash sintered ingredient binary nitrides of TaN and NbN. TGA in air shows that the oxidation resistance of (Nb1/3Ta1/3Ti1/3)N1−δ is better than that of TaN and NbN but inferior to TiN. The study demonstrates that reaction flash sintering can be a highly efficient technique for synthesizing bulk multicomponent ceramics for both material fundamental investigations and application development. 相似文献
88.
Gabriela Ben-Melech Stan Kapil Dhaka Maytal Caspary Toroker 《Israel journal of chemistry》2020,60(8-9):888-896
Two-dimensional transistors are promising candidates for the next generation of nanoscale devices. Like the other alternatives, they also encounter problems such as instability under standard condition (STP), low channel mobility, small band gaps, and difficulty to integrate metal contacts. The latter poses a great challenge since metal/semiconductor interface significantly affects the transistor‘s performance. Some of these obstacles can be solved by using two-dimensional transition metal di-chalcogenides (TMDC) materials. In this study, we performed charge transport calculation based on density functional theory (DFT) followed by wave dynamics to evaluate the performance of six two-dimensional TMDC metal/semiconductor/metal systems. Each semiconductor monolayer was laterally connected, at both ends to metal contacts consisting of VS2 or FeS2 monolayers. We found that charge transport was more efficient in systems containing a CrS2 semiconductor monolayer compared to systems with MoS2 or WS2 as the semiconductor monolayer. The electronic characterization of the monolayer TMDC materials by DFT estimates well the trend in charge transport efficiency calculated using wave packet dynamics. 相似文献
89.
Jing Zhao Chunliang Zhou Yiju Li Kui Cheng Kai Zhu Ke Ye Jun Yan Dianxue Cao Ying Xie Guiling Wang 《国际能源研究杂志》2020,44(5):3883-3892
Sodium-ion hybrid capacitors are a prospective energy storage device candidate that couples the superiorities of battery-type and capacitive storage mechanisms. In this study, we fabricate a composite of NiCo2O4 nanowires with carbon tubular bundles (CTBs) via a facile hydrothermal and annealing procedure. The density functional theory (DFT) calculations are performed to evaluate the bonding strength between the two components of the composite, the binding energy of the NiCo2O4 is calculated to be −0.952 J m−2, indicating that the NiCo2O4 nanowires can be stabilized on both sides of the carbon tubular bundles, which leads to a good cycling performance. Moreover, the composite in this work exhibits a metallic property because of the introduction of carbon material. As expected, when used for sodium storage, the NiCo2O4/CTBs shows a high capacity of 298 mA h g−1 at 1 A g−1 and high capacity retention of 92% after 500 cycles, which are superior than the bare NiCo2O4 electrode. Consequently, the sodium-ion hybrid capacitor is also assembled with NiCo2O4/carbon tubular bundles and commercial activated carbon, which achieves high energy density of 99 Wh kg−1 in a wide potential range from 0.5 V to 4.0 V. 相似文献
90.