Photoactive Earth‐Abundant Iron Pyrite Catalysts for Electrocatalytic Nitrogen Reduction Reaction

The generation of ammonia, hydrogen production, and nitrogen purification are considered as energy intensive processes accompanied with large amounts of CO₂ emission. An electrochemical method assisted by photoenergy is widely utilized for the chemical energy conversion. In this work, earth‐abundant iron pyrite (FeS₂) nanocrystals grown on carbon fiber paper (FeS₂/CFP) are found to be an electrochemical and photoactive catalyst for nitrogen reduction reaction under ambient temperature and pressure. The electrochemical results reveal that FeS₂/CFP achieves a high Faradaic efficiency (FE) of ≈14.14% and NH₃ yield rate of ≈0.096 µg min^?1 at ?0.6 V versus RHE electrode in 0.25 m LiClO₄. During the electrochemical catalytic reaction, the crystal structure of FeS₂/CFP remains in the cubic pyrite phase, as analyzed by in situ X‐ray diffraction measurements. With near‐infrared laser irradiation (808 nm), the NH₃ yield rate of the FeS₂/CFP catalyst can be slightly improved to 0.1 µg min^?1 with high FE of 14.57%. Furthermore, density functional theory calculations demonstrate that the N₂ molecule has strong chemical adsorption energy on the iron atom of FeS₂. Overall, iron pyrite‐based materials have proven to be a potential electrocatalyst with photoactive behavior for ammonia production in practical applications.     

The application of convergent beam electron diffraction (CBED) analysis on transformation‐induced plasticity (TRIP) steels

Convergent beam electron diffraction (CBED) in transmission electron microscopy (TEM) was applied to determine local carbon concentrations in low‐carbon transformation‐induced plasticity (TRIP) steels. High‐order Laue‐zone (HOLZ) lines were experimentally obtained for comparison with simulation results. A new procedure for calculating carbon content is thus proposed. Retained austenite (RA) is classified into three types by morphology; the relationship between the carbon content and the corresponding RA morphology is discussed based on CBED results. Furthermore, results of X‐Ray diffractometry measurements are also used for comparison.     

基于高岭土多孔基板的In2O3微米梳制备及其气敏性能

采用模压-烧结法制备高岭土多孔基板，考察烧结温度对高岭土多孔基板表面形貌与孔隙结构的影响，通过热蒸发法在高岭土多孔基板上制备出In₂O₃微米材料，并采用XRD、SEM、FTIR、阿基米德排水法等检测手段考察多孔基板及In₂O₃微米材料的形貌与结构。结果表明，在烧结温度1 200 ℃时所获高岭土多孔基板的孔径尺寸在45 μm左右，显气孔率为32.71%，体积密度为1.48 g/cm³，抗弯强度为15.08 MPa。在该多孔基板上所制备的In₂O₃产物呈梳状结构，梳齿直径和长度分别在1~10 μm和20~80 μm范围内，梳柄长度约为1 mm，结晶良好。对In₂O₃微米梳的气敏检测结果表明：In₂O₃微米梳对NO₂气体具有良好的选择性、可逆性和重复性；其对浓度为0.001%的NO₂气体的灵敏度随着工作温度的升高呈先升高后降低的趋势，响应时间和恢复时间随之减少，且在最佳工作温度200 ℃时达到最大值，为44.4，此时的响应时间和恢复时间分别为21 s和106 s；In₂O₃微米梳对NO₂气体的灵敏度随着NO₂浓度的增加而增加，两者之间呈线性相关，响应时间随着NO₂浓度的增加而缩短，恢复时间则随之增长。     

分析位于沉积地层中建物产生过大沉降量之新观念

在软弱地基土层上设计建筑物时，除了考虑基础下土层的承载力必须达到安全要求外，地基土的长期沉降变形也同样重要。本文在追踪一工程实例中，发现依据传统土力学观念在深厚沉积土层中，标准贯入击数Ｎ值已达１５～２５之地层，设计４５ｍ长摩擦桩基础之谷仓结构物，在使用１９年后仍产生因差异沉降过量导致之严重结构破坏。传统土力学较偏于可靠的承载力，对于各土层的先期固结应力，仅能由单向度固结试验求得，但实际工作时，取得完全不扰动土样几乎不可能，因而亦很难取得正确的先期固结应力，便无法计算正确沉降量。故设计者常因本身主观的观念，造成研判的疏忽。本文提出“由Ｎ值判断各土层超固结比（ＯＣＲ）法及应力还原法”观念，由不同深度土层的标准贯入击数Ｎ值及地质历史，可协助设计者于设计阶段便能轻易而明确地判断不同深度土层的固结比（ＯＣＲ），精确计算各土层沉降量，以便能事先设计出防止类似本实例于１９年后才发现的疏忽。     

Specific power bound of a finite-time closed Brayton cycle

The purpose of this paper is to define a finite-time closed Brayton cycle and apply it to an indirect gas-cooled nuclear reactor plant for its optimization. Practical engineering heat engine power optimization usually takes the form of determining minimum heat exchanger area per unit net power output or minimum cost per unit power output, rather than determining the maximum cycle efficiency. The objective function of the optimization described in this paper is specific power, power output per total heat exchanger surface area. The specific power output of a real indirect gas-cooled nuclear reactor plant coupled with its heat source and sink is analyzed. It is found that there is an upper bound on the specific power output of the nuclear power plant. This bound can guide the evaluation of existing real plants or influence design of future power plants.     

Heating load and COP optimisations for a universal steady flow endoreversible heat pump model

The heating load and coefficient of performance (COP) of a class of universal steady flow endoreversible heat pump cycle model, which consists of one heating branch, two cooling branches and two adiabatic branches, are optimised using the theory of finite time thermodynamics. The analytical formulae for heating load and COP versus temperature ratio as well as COP versus heating load of the cycle model are derived. Effects of the total heat exchanger inventory on performances of heat pump cycles are shown by detailed numerical examples. The results obtained herein include the optimal performances of endoreversible Otto, Brayton, Atkinson, Diesel, Dual and Carnot heat pump cycles.     

Optimal performance for a steady-flow endoreversible refrigerator model including five typical cycles

The optimal performance of a universal endoreversible steady-flow refrigerator cycle consisting of a constant thermal-capacity heating branch, a constant thermal-capacity cooling branch and two adiabatic branches with heat transfer loss was analysed using finite-time thermodynamics. The analytical formulae about cooling load, coefficient of performance, exergy loss rate, exergy output rate and ecological criterion of the endoreversible steady-flow refrigerator cycle are derived. Moreover, analysis and optimisation of the model were carried out in order to investigate the effect of the cycle process on the performance of the cycles using numerical examples. The results obtained include the performance characteristics of endoreversible steady-flow Carnot, Diesel, Otto, Atkinson and Brayton refrigeration cycles. The results can provide some theoretical guidance for the design of practical refrigerators.     

Biosynthesis of di-(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) from red alga--Bangia atropurpurea

The contents of di-(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) of red alga, Bangia atropurpurea, filaments cultured in artificial sea water medium were similar to those cultured in natural sea water medium. In the culture experiment, B. atropurpurea filaments were found to synthesize de novo phthalate esters. Additionally, DEHP and DBP contents in different species of algae grown in the same environment were different significantly, suggesting that it was due to the intrinsic nature of algae.