An Innovative Design for the Fabrication of Flexible Composite Films from Si3N4 Fiber Paper

A high-temperature-resistant flexible substrate is a critical component of high-performance flexible electronic components. Herein, a method that does not require flowing gas and which is suitable for volume production is presented for the preparation of several-millimeter-long silicon nitride (Si₃N₄) fibers with a cross-sectional dimension of 0.1–1.0 μm. Further, a square sheet of paper with a weight of 0.050 g, side lengths of 105 mm each, and thickness of 15 μm is fabricated using the Si₃N₄ fibers via a conventional laboratory paper-making method. Subsequently, the Si₃N₄ paper is coated with an LaNiO₃ sol using a blade-coating machine, dried at 80 °C for 10 min, and then annealed at 650 °C for 60 min to prepare Si₃N₄ fiber paper/LaNiO₃ composite films to evaluate the feasibility of applying the paper as a substrate for fabricating flexible functional films. The experimental results confirm that the Si₃N₄ fiber paper has excellent high-temperature resistance during annealing in air, and the Si₃N₄ paper/LaNiO₃ composite film presents excellent flexibility and conductivity. Thus, membranous flexible electronic components can be fabricated from Si₃N₄ fiber paper/LaNiO₃ paper by a regular high-temperature annealing process.     

Experimental investigation on dyeing wastewater treatment and by-product hydrogen with a reverse electrodialysis flocculator

Hydrogen production and dye degradation can be achieved simultaneously in a hybrid system of reverse electrodialysis（RED）and electrocoagulation (EC), using current derived from the salinity gradient energy. Under the current, Fe electrode is used as the anode to produce Fe²⁺(subsequently oxidized to Fe³⁺) which combines with OH⁻ produced from the cathode to remove the dyes, while the hydrogen gas produced by the cathode is collected by a hydrogen collection device. The experiments are carried out to investigate the effects of different initial concentrations, pH, currents, electrode rinse solution (ERS) flow rates and the addition of chlorine on the degradation rate and hydrogen production. The results indicate that the degradation rate and hydrogen production could reach 98.3% and 150 m h⁻¹ at alkaline condition (pH = 11) and acidic condition (pH = 3) respectively, with a current of 0.4 A. The degradation rate and hydrogen production increase significantly with an increase in current.     

A quantitative risk assessment of hydrogen fuel cell forklifts

With the increasing deployment of hydrogen fuel cell forklifts, it is essential to understand the risks of incidents involving these systems. A quantitative risk assessment (QRA) study was conducted to determine the potential hydrogen release scenarios, probabilities, and consequences in fuel cell forklift operations. QRA modeling tools, such as fault tree analysis (FTA) and event sequence diagrams (ESD), were used together with hydrogen systems data. This work provides insights into the fatality risk from a hydrogen fuel cell forklift and the reliability of its design and components. The analysis shows that the expected fatal accident rate of a hydrogen forklift is considerably higher than current fatal injury rates observed by the Bureau of Labor Statistics for industrial truck operators and material handling occupations. Nevertheless, the average individual risk posed to forklift drivers was found to be likely tolerable based on current risks accepted by industrial truck operators. Jet fires are found to dominate the system's risk, however, the risk of explosions is also considerable. An importance measures analysis shows that these risks could be mitigated by improving the design and reliability of pressure relief devices, as well as other components prone to leak such as filters and check valves. We also identify sources of uncertainty and conservatisms in the QRA process that can guide future research in hydrogen systems. These results provide powerful insight into improvements in the design of fuel cell forklifts to reduce risk and enable the safe deployment of this key technology for a decarbonized future.     

Enhanced transmittance of Y2O3 transparent ceramics from near-UV to near-infrared through reduced atmosphere annealing

Y₂O₃ transparent ceramics were annealed under different atmospheric conditions. The samples annealed in H₂ containing atmosphere were colorless and had high in-line transmittances from the near-UV to the mid-infrared wavelength range. This is due to the elimination of carbon contamination and preventing the formation of high concentration oxygen interstitial defects in the sintered samples. Annealing in oxygen containing atmosphere resulted in stronger optical absorption in the visible wavelength region. High temperature annealing in O₂ or hot isostatic pressing under high partial pressure of O₂ (O₂ HIP) led to obviously declining of transparency in a broader wavelength range of 230–800 nm. The Er:Y₂O₃ ceramics annealed in H₂ containing atmosphere had high in-line transmittance of about 80% at 400 nm as well. Room temperature laser oscillation at 2.7 µm was also obtained on the 5%H₂/95%Ar atmosphere annealed Er:Y₂O₃ ceramics.     

Design of the PID temperature controller for an alkaline electrolysis system with time delays

Electrolysis systems use proportional–integral–derivative (PID) temperature controllers to maintain stack temperatures around set points. However, because of heat transfer delays in electrolysis systems, the manual tuning of PID temperature controllers is time-consuming, and temperature oscillations often occur. This paper focuses on the design of the PID temperature controller for an alkaline electrolysis system to achieve fast and stable temperature control. A thermal dynamic model of an electrolysis system is established in the frequency domain for controller designs. Based on this model, the temperature stability is analysed by the root distribution, and the PID parameters are optimized considering the temperature overshoot and the settling time. The performance of the optimal PID controllers is experimentally verified. Furthermore, the simulation results show that the before-stack temperature should be used as the feedback variable for small lab-scale systems to suppress stack temperature fluctuations, and the after-stack temperature should be used for larger systems to improve the economy. This study helps ensure the temperature stability and control of electrolysis systems.     

Prospecting the biofuel potential of new microalgae isolates

The continued search and urgent need for renewable fuel sources have necessitated the exploration of microalgae to identify relevant species for making biofuels. The aim of the study was bioprospecting and screening native microalgae strains from freshwater habitats of the Almaty region, Kazakhstan, to assess the potential for producing biofuel. The studied strains demonstrated simultaneous biomass productivity, lipid productivity, suitable fatty acid composition, and biodiesel properties. The sequence analysis of the ribosomal DNA internal transcribed spacer partial region and ribulose-bisphosphate carboxylase gene (rbcL) led to the identification of five microalgae: Monoraphidium griffithii ZBD-01, Nephrochlamys subsolitaria ZBD-02, Ankistrodesmus falcatus ZBD-03, Parachlorella kessleri ZBD-04, and Desmodesmus pannonicus ZBD-05. P. kessleri had the highest biomass production (1.42 ± 0.08 g L⁻¹ day⁻¹), lipid productivity (29 ± 1.2 g L⁻¹day⁻¹), and C₁₆–C₁₈ fatty acid contents (90%), followed by A. falcatus and M. griffithi. Gas chromatography/mass spectrometry analysis indicated that the dominant fatty acids in these strains were palmitic, stearic, and oleic acids. The calculated biodiesel properties of P. kessleri and A. falcatus based on fatty acid methyl esters (FAME) profiles showed relatively good fuel properties (cetane numbers - 48 and 50; iodine and saponification values - 83.4 and 103.6 g I₂/100 g oil, 260.8 and 199.5 mg KOH g⁻¹), which correlate well with. Our results suggest that P. kessleri and A. falcatus are promising strains for biodiesel production due to their high lipid productivity, fatty acid profile with relatively high content of oleic acid, and suitable biodiesel properties. The isolated native species of microalgae from natural freshwater bodies of the Almaty region present opportunities for further exploitation for the sustainable production of biomass and biodiesel.     

Hierarchically porous carbon from biomass tar as sustainable electrode material for high-performance supercapacitors

The byproduct tar from biomass gasification process had seriously impeded development and applications of this technology, thus novel path for biomass tar valorization is had been continuously pursued. Given its high carbon content, this work attempted to convert biomass tar into hierarchically porous carbon by thermal activation with acetate potassium. The optimal product produced with mass ratio of biomass tar to acetate potassium of 1:3 and activation temperature at 800 °C was revealed as excellent electrode material for high-performance supercapacitor, which demonstrated electrochemical capacitance up to 310.4 F/g at 0.2 A/g, whilst preserved 91% of initial capacitance after 5000 charge-discharge circles at current density of 5 A/g. These excellent properties had arisen from the open and hierarchical porosity and large surface area. This work disclosed the great potential of biomass tar as sustainable and competent candidate for fabricating high-performance electrode material for electrochemical energy devices, and may bring up new opportunities to development of biomass gasification technologies.     

掺杂Bi的β-Cu2Se薄膜的微观结构与热电性能

目的 探究在β-Cu2Se薄膜中掺杂元素Bi对其组织结构及其热电性能的影响，探求Bi元素对载流子传输过程和热电性能的影响规律，为将来该类热电薄膜的研究和应用提供宝贵的经验。方法 使用粉末烧结制得Cu-Bi-Se合金靶材，使用磁控溅射的方法在含有SiO2层的单晶Si衬底上制备了不同Bi含量的β-Cu2‒xBixSe热电薄膜。利用X射线衍射仪、扫描电子显微镜、能谱仪分别研究了沉积薄膜的XRD谱、表面与截面形貌以及元素含量与分布。利用LSR-3电阻率/塞贝克系统测量了沉积薄膜的Seebeck系数与电导率。利用霍尔试验测量了沉积薄膜的室温载流子浓度和迁移率。结果 沉积薄膜主要由单一的β-Cu2Se相构成，在Bi掺杂量最大为1.07%(原子数分数)的薄膜还含有非常少量的α-Cu2Se相;在β-Cu2Se相薄膜中Bi的掺杂没有生成单质相而是替换点阵中的Cu而形成替位式固溶体。在沉积的β-Cu2‒xBixSe薄膜中，([Bi]+[Cu])/[Se]＞2.0且具有p型导电特征。随着温度的增加，电导率降低而Seebeck系数增加，彰显沉积薄膜的简并或半简并半导体的导电特性。当温度低于225 ℃时，沉积薄膜功率因子随Bi掺杂量的增加而增大;当温度高于225 ℃时，掺杂量为0.29%(原子数分数)的薄膜具有最大的功率因子，进一步增加Bi掺杂量，沉积薄膜的功率因子却逐渐减小。结论 使用磁控溅射的方法可制备β-Cu2Se薄膜，掺杂适量的Bi可显著提高薄膜的功率因子。     

Three-dimensional numerical simulation of oxygen isotope transport in lanthanum strontium manganese - Yttria-stabilized zirconia cathode of solid oxide fuel cell

Distribution of oxygen isotope ¹⁸O concentration which was labeled in lanthanum strontium manganese (LSM) – yttria-stabilized zirconia (YSZ) cathode of a solid oxide fuel cell (SOFC) is predicted through numerical simulations using a three-dimensional microstructure which was reconstructed by a focused ion beam-scanning electron microscopy (FIB-SEM). The electrochemical reaction under the SOFC operation is first numerically simulated, then the unsteady ¹⁸O transport is simulated by coupling self-diffusion by concentration gradient, migration by the electrochemical potential field, and electrochemical reaction at the triple phase boundaries. Predicted results were compared with the measured ¹⁸O concentration by a secondary ion mass spectrometry taken at the intermediate plane of the reconstructed 3D microstructure, which showed qualitative consistency between them. Thus, from the direct correlation of the electrochemical reaction and ¹⁸O concentration in an actual electrode microstructure, influence of electrochemical reaction was discussed. The present approach provides useful information for the interpretation of the oxygen labeling experiment results, which can cultivate better understanding of the electrochemical reaction mechanism in the SOFC electrodes.