Salt-assisted solution combustion synthesis of NiFe2O4: Effect of salt type

The effects of three types of salt including NaF, KCl, and NaCl on the properties of NiFe₂O₄ nanoparticles using salt-assisted solution combustion synthesis (SSCS) have been investigated. The synthesized powders were evaluated by SEM, TEM, FTIR, XRD, and VSM analysis. Also, the specific surface area (SSA), as well as size distribution and volume of the porosities of NiFe₂O₄ powders were determined by the BET apparatus. The visual observations showed that the intensity and time of combustion synthesis of nanoparticles have been severely influenced by the type of salt. The highest crystallinity was observed in the synthesized powder using NaCl. The SSA has also been correlated completely to the type of salt. The quantities of SSA was achieved about 91.62, 64.88, and 47.22 m²g^-1 for the powders synthesized by KCl, NaCl, and NaF respectively. Although the magnetic hysteresis loops showed the soft ferromagnetic behavior of the NiFe₂O₄ nanoparticles in all conditions, KCl salt could produce the particles with the least coercivity and remanent magnetization. Based on the present study, the salt type is a key parameter in the SSCS process for the preparation of spinel ferrites. Thermodynamic evaluation also showed that the melting point and heat capacity are important parameters for the proper selection of the salt.     

响应面法优化α-淀粉酶的酶反应体系

目的:采用单因素实验及响应面法优化α-淀粉酶的反应体系。方法:以淀粉为底物对象，以可溶性淀粉浓度、α-淀粉酶浓度、反应时间为考察因素，在单因素实验基础上，运用Box-behnken实验设计方法研究各因素及其交互作用对α-淀粉酶作用底物时的反应速度的影响。结果:建立α-淀粉酶酶反应体系的最佳反应条件为12.0 mg/mL可溶性淀粉、1.50 U/mL α-淀粉酶、10.0 min反应时间，在此条件下，α-淀粉酶表现出的反应速度达到（19.53±1.74） mmol/（L·min），接近模型中的预测数值18.75 mmol/（L·min）。结论:此优化α-淀粉酶酶反应体系的方法可行，能够使α-淀粉酶在反应过程中发挥的酶活最大化，为日后在此体系下进行糖苷酶抑制剂的研究奠定了基础，具有一定的指导意义。     

Poly(ether-block-amide) membrane with deformability and adjustable surface hydrophilicity for water purification

Freshwater resources are currently insufficient, and another form of freshwater resources, namely, ice, is very interesting except for the issue of how to use new materials for effective purification during the processing procedure. In this article, a new membrane material with multisize pore structure in the cross-section and intact thin skin layer on the upper and lower surfaces was successfully prepared by adding porogen, filler and setting heating environment during the phase separation process. The membrane exhibits excellent axial deformability, and its elongation at break can reach to 160% strain. Meanwhile, they all show elastic deformation behavior in the range from −60 to 100°C. Even if high content of hydrophobic filler is compounded into these membranes, that is, 5.7 wt% carbon tube content, water contact angle of membrane's surface is only 72.5°, demonstrating obvious hydrophilicity. In addition, in the water purification process, the adsorption rate constant reached ideal value of 0.26 s⁻¹, and the equilibrium adsorption capacity was about 2.8 g/g, showing fast and efficient water purification ability. In the mode of external heating source or the membrane's heat dissipation, these prepared membranes can melt the ice to obtain purified water and exhibit a controllable purification ability in this process.     

Position-varying surface roughness prediction method considering compensated acceleration in milling of thin-walled workpiece

Machined surface roughness will affect parts’ service performance. Thus, predicting it in the machining is important to avoid rejects. Surface roughness will be affected by system position dependent vibration even under constant parameter with certain toolpath processing in the finishing. Aiming at surface roughness prediction in the machining process, this paper proposes a position-varying surface roughness prediction method based on compensated acceleration by using regression analysis. To reduce the stochastic error of measuring the machined surface profile height, the surface area is repeatedly measured three times, and Pauta criterion is adopted to eliminate abnormal points. The actual vibration state at any processing position is obtained through the single-point monitoring acceleration compensation model. Seven acceleration features are extracted, and valley, which has the highest R-square proving the effectiveness of the filtering features, is selected as the input of the prediction model by mutual information coefficients. Finally, by comparing the measured and predicted surface roughness curves, they have the same trends, with the average error of 16.28% and the minimum error of 0.16%. Moreover, the prediction curve matches and agrees well with the actual surface state, which verifies the accuracy and reliability of the model.     

Process parameter dependencies of continuous and pulsed laser modes on surface polishing of additive manufactured aluminium AlSi10Mg parts

Laser powder bed fusion is a well-established 3D printing technique for metal alloys, but exhibits a poor surface quality. Laser polishing provides the possibility of a fast contact-free and fully-automatable surface treatment. This paper deals with the experimental investigation of laser polishing of laser powder bed fusion parts made of aluminium AlSi10Mg. Laser polishing is done with a 4 kW solid state disc laser in combination with a multi-axis system and a one dimensional scanner optic. The laser is operated at continuous and pulsed operation mode. The parameter study reveals a high dependency of the achievable roughness on the laser beam intensity, the track and pulse overlap, the energy density and the number of polishing passes and polishing directions. Pulsed laser polishing mode with up to four passes from different directions revealed the lowest surface roughness of 0.14 μm Ra. With respect to the initial average surface roughness of Ra = 8.03 μm a reduction of the surface roughness of greater than 98 % could be achieved. Polishing with continuous laser radiation at one polishing pass resulted in Ra = 0.23 μm at an area rate of 20 cm²/min. Laser polishing using four passes achieved a further improvement up to Ra = 0.14 μm.     

Enhanced photocatalytic H2 evolution over In2S3 via decoration with GO and Fe2P co-catalysts

In this study, GO and Fe₂P were used as co-catalysts to improve the separation efficiency of photogenerated electron-hole pairs in an In₂S₃ photocatalyst. The metallic character of Fe₂P provided a cheap substitute for traditional noble metal co-catalyst for H₂ production in aqueous media. The GO/Fe₂P/In₂S₃ composite demonstrated significantly enhanced photocatalytic activity compared to pure In₂S₃, delivering a H₂ production rate of 483.35 μmol h^?1 g^?1 and a quantum yield was 22.68% under visible light irradiation. The design of the photocatalyst was optimized using “Design Expert” software. The analysis showed that a GO loading of 1.18 wt%, a Fe loading of 5.36 wt%, and a calcination temperature of 180 °C were optimal.     

粗化床面非均匀沙推移质运动扩散特性研究

对泥沙颗粒运动规律的把握是准确估算推移质输沙率的基础。本文开展了粗化床面条件下的水槽试验，分析了非均匀沙颗粒的均方位移和速度自相关系数变化，并与已有均匀沙试验进行了对比。结果表明，粗化床面存在着由单个或多个粗颗粒组成的粗化结构体，形成比平整床面更复杂的底部边界，粗化结构体对泥沙颗粒运动造成较大影响，颗粒在运动过程中与水流动量交换强度大，泥沙颗粒运动与均匀沙试验“类弹道扩散”存在一定差异；受床面结构影响，部分颗粒表现出较强的横向运动，颗粒的横向扩散特性与流向扩散特性类似。与均匀沙平整床面不同，粗化床面上颗粒运动可能会相应改变床面结构，从而改变水流底部边界条件，进而对泥沙颗粒运动造成影响，泥沙颗粒运动存在较明显的记忆效应和反常扩散现象。     

Ni2V2O7 dandelion microsphere for a high-performance electrocatalyst in water splitting

Water splitting is an effective way to produce hydrogen to solve the energy crisis problem, and inorganic metal compounds are widely used in electrocatalysis field due to efficient hydrogen evolution reaction (HER). Herein, we synthesize Ni₂V₂O₇ dandelion microsphere from nickel nitrate and vanadium pentoxide by “one-step hydrothermal” way, which exhibits large specific surface area of 102.74 m² g⁻¹. The as-prepared Ni₂V₂O₇ microsphere shows good electrocatalysis performances including OER overpotential of 358 mV and good stability, as well as HER overpotential of 195 mV. Furthermore, the Ni₂V₂O₇ microsphere electrode is assembled to Ni₂V₂O₇ microsphere//Ni₂V₂O₇ microsphere system, showing the water splitting voltage of 1.50 V at 10 mA cm⁻² by two-electrode method, which is much lower than those of commercial RuO₂//Pt/C system and most of spinel oxides electrocatalysts. Our work opens up a new and facile avenue for fabricating inorganic microsphere electrocatalyst in hydrogen production field.     

Extended-state-observer-based dynamic surface control of flexible-joint robot systems with input saturation

This article presents an extended-state-observer-based dynamic surface control approach for flexible-joint robot systems with asymmetric input saturation and large unknown dynamic knowledge. Traditional controllers for flexible-joint robot systems usually use approximation technology to deal with unknown dynamics knowledge. Unlike the traditional control algorithm, this article utilizes an extended state observer to estimate the unknown dynamics. For the closed-loop system, the delay strategy handles the time-scale separation issue, the filtering system overcomes the “explosion of differentiation” caused by the repeated differentiation of auxiliary control signals, and the mean-value-theorem solves the input saturation problem of the actuator. The stability analysis implies that estimation errors of extended state observers (ESOs) and other state variables are semiglobally uniformly ultimately bounded. Compared with fuzzy control algorithms, the novel ESO-based dynamic surface control approach not only omits online learning time but also uses only a few control parameters to obtain satisfactory tracking performance. Finally, a comparison simulation experiment is provided to illustrate the effectiveness of the gained conclusions.     

Exploring the relationship between the physical properties of activated carbon catalysts and their efficiency in catalyzing hydrogen iodide decomposition to produce hydrogen

Using simple and efficient methods to synthesize biological activated carbon catalysts (ACCs) with the decomposition of hydrogen iodide (HI) in the sulfur-iodine cycle as a typical reaction is urgently needed for the commercialization of hydrogen energy production and development. In this study, a series of ACCs with different specific surface areas (SSAs) and pore structures are prepared by comparing and controlling the changes in carbonization and activation methods of activated carbon (AC) preparation process. Hierarchical porous AC with larger SSA has higher HI decomposition efficiency. The representative samples H240H1h and H240C4h are hierarchical porous ACCs with 48.96% and 46.88% micropores, respectively, and have the highest catalytic activity in the entire series. The nitrogen adsorption and desorption curve is combined with pore size distribution data and analyzed using the capillary aggregation (Kelvin) and monolayer adsorption (Langmuir) theories. And ACC pore grading coefficient—which can improve data visualization—is introduced.