Eco-friendly approach for preparation of hybrid silica aerogel via freeze drying method

Journal of Materials Science - In this paper, an eco-friendly method of producing hybrid silica aerogels by freeze-drying method (FD) is proposed. In the freeze-drying system, deionized water was...     

Improved Algorithm for Solving Inverse Kinematics of Biped Robots

Mobile Networks and Applications - Inverse kinematics is an important basic theory in walking control of biped robot. This study focuses on the parameter setting using the improved algorithm in...     

Surface Reconstruction Engineering with Synergistic Effect of Mixed-Salt Passivation Treatment toward Efficient and Stable Perovskite Solar Cells

Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, a lack of passivation with mixture treatment has been investigated, as well as an in-depth understanding of its passivation mechanism. Here, a systematic study on a mixed-salt passivation strategy of formamidinium bromide (FABr) coupled with different F-substituted alkyl lengths of ammonium iodide is demonstrated. It is obtained better device performance with decreasing chain length of the F-substituted alkyl ammonium iodide in the presence of FABr. Moreover, they unraveled a synergistic passivation mechanism of the mixed-salt treatment through surface reconstruction engineering, where FABr dominates the reformation of the perovskite surface via reacting with the excess PbI₂. Meanwhile, ammonium iodide passivates the perovskite grain boundaries both on the surface and top perovskite bulk through penetration. This synergistic passivation engineer results in a high-quality perovskite surface with fewer defects and suppressed ion migration, leading to a champion efficiency of 23.5% with mixed-salt treatment. In addition, the introduction of the moisture resisted F-substituted groups presents a more hydrophobic perovskite surface, thus enabling the decorated devices with excellent long-term stability under a high humid atmosphere as well as operational conditions.     

Spontaneous Directional Self-Cleaning on the Feathers of the Aquatic Bird Anser cygnoides domesticus Induced by a Transient Superhydrophilicity

In nature, the feathers of the goose Anser cygnoides domesticus stay superhydrophobic over a long term, thought as the main reason for keeping the surface clean. However, contaminants, especially those that are oleophilic or trapped within textures, cannot be removed off the superhydrophobic feathers spontaneously. Here, a different self-cleaning strategy based on superhydrophilic feathers is revealed that is imparted by self-coating of the amphiphilic saliva, which enables removing away low-surface-tension and/or small-size contaminants by forming directional water sheeting depending on their unique anisotropic microstructures. Particularly, the surface superhydrophilicity is switchable to superhydrophobicity upon exposure to air for maintaining a clean surface for a long time, which is further enhanced by coating with self-secreted preening oil. By alternate switching between a transient superhydrophilicity and a long-term stable superhydrophobicity, the goose feathers exhibit an integrated smart self-cleaning strategy, which is also shared by other aquatic birds. An attractive point is the re-entrant structure of the feathers, which facilitates not only liquid spreading on superhydrophilic feathers, but also long-term stability of the cleaned surface by shedding water droplets off the superhydrophobicity feathers. Thus, artificial self-cleaning microtextures are developed. The result renews the common knowledge on the self-cleaning of aquatic bird feathers, offering inspiration for developing bioinspired self-cleaning microtextures and coatings.     

Contributions of oxygen vacancies to the hydrogen evolution catalytic activity of tungsten oxides

The tungsten trioxide attracts less attention due to the low electron transfer kinetics that hinders the interaction of electrons and ions during the hydrogen evolution reaction (HER). But the oxygen vacancy strategy can inspire its electrocatalytic activity for HER because it has a positive effect on improving the charge transfer and compensating for the weak hydrogen adsorption of the tungsten trioxide. By synthesizing a series of substoichiometric tungsten oxides, we reveal the linear relationship between the catalytic activity and the content of oxygen vacancies, which indicates that the oxygen vacancy strategy is an achievable route to enhance the HER for metal oxides.     

Different chemical effect of hydrogen addition on soot formation in laminar coflow methane and ethylene diffusion flames

Previous studies showed that adding hydrogen (H₂) can have an opposite chemical effect on soot formation: its chemical effect enhances and suppresses soot formation in methane (CH₄) and ethylene (C₂H₄) diffusion flames, respectively. Such opposite chemical effect of H₂ (CE-H₂) remains unresolved. The different CE-H₂ is studied numerically in the two laminar coflow diffusion flames. A detailed chemical mechanism with the addition of a chemically inert virtual species FH₂ is used to model the gas-phase combustion chemistry in this study. Particularly, a reaction pathway analysis was performed based on the numerical results to gain insights into how H₂ addition to fuel affects the pathways leading to the formation of benzene (A₁) in CH₄ and C₂H₄ flames. The numerical results show that the CE-H₂ in CH₄ diffusion flame to prompt soot formation is ascribed that the higher mole fraction of H atom promotes the formation of A₁ and Acetylene (C₂H₂) and leads to higher nucleation rate and eventually higher soot surface growth rate. In contrast, adding H₂ to C₂H₄ diffusion flames decreases soot nucleation and surface growth rate. The lower soot nucleation rate is due to the lower mole fractions of pyrene (A₄), while the lower soot surface growth rate is due to the lower mole fractions of H atom and C₂H₂, higher mole fraction of H₂ and lower soot nucleation rate. Furthermore, the CE-H₂ in C₂H₄ diffusion flames promotes the formation of A₁, but suppresses the formation of A₄.     

Inherent safer design for chemical process of 1,4-dioldiacetate-2-butene oxidized by ozone

Abstract

Oxidation reaction is the typical thermal runaway reaction, and the reaction of 1, 4-dioldiacetate-2-Butene oxidized by ozone was investigated in this study. Firstly, the thermal hazards of the oxidative exothermic reactions were identified and evaluated combined process risk assessment method. The Qualitative Assessment for Inherently Safer Design (QAISD) was used to identify the risk of the reaction process. Meanwhile, the Reaction Calorimeter (RC1^e) was used to obtain the thermal properties of the oxidation reaction. Then the inherent safer designs (ISD) were proposed according to the risk assessment results to increase the level of safety of chemical industry technique. 1) ISD I: reaction temperature was improved to –5?°C, and ventilation rate was improved to 200?L?h^?1. 2) ISDII: using a tubular reactor as reaction vessel. The results indicated that the severity of the reaction hazard was reduced by 43%, and safety was improved significantly via two ISDs. Moreover, the inherent safety level of the reaction was increased by 63% and 43.4% via ISD Iand II, respectively. The reaction process get closer to inherent safety theories of “minimize,” “substitute,” and “moderate”.     

High-yield water-phase exfoliated few-defect graphene for high performance polymer nanocomposites

Application of graphene requires a high-yield, low-cost, scalable production method, but it remains highly challenging. We here report a water-phase technique to produce few-defect graphene nanosheets (FGS) with a high exfoliation yield (92%), based on the chemically expanded graphite with ultrahigh specific surface areas, and demonstrate the application in graphene-polymer nanocomposites. The exfoliated FGS has low degree of oxidation and preserves good mechanical and electrical properties, revealing promising potential for improving comprehensive properties of polymer composites. When 0.5 wt% FGS was incorporated to poly(methyl methacrylate) (PMMA), the 5% weight loss temperature and storage modulus increase by 87°C and 21%, respectively, relative to the neat polymer. With increasing the content of FGS to 4.6 wt%, the glass transition temperature of the composite increases by 25°C. In addition, the composites show a percolation threshold as low as 0.25 vol% and excellent electrical conductivity (50 S/m for 2.7 vol% FGS-PMMA composite).     

一种新型随钻轨迹仪的研制

针对现有随钻轨迹仪工作时间短、需人工同步、"数钻杆"记录钻孔深度不足等问题,采用深度实时测量技术、电源智能管理技术和数据自动同步与成图等关键技术,研制了新型随钻轨迹仪。该仪器由直线位移传感器、压力传感器、霍尔开关等组成,具有钻孔深度自动测量、电源智能管理、测量数据与深度自动匹配等功能。试验结果表明:新型钻孔轨迹仪工作稳定可靠、无需人工干预、工作时间长、生产效率高。     

Remarkable Antibacterial Activity of Reduced Graphene Oxide Functionalized by Copper Ions

Despite long-term efforts for exploring antibacterial agents or drugs, potentiating antibacterial activity and meanwhile minimizing toxicity to the environment remains a challenge. Here, it is experimentally shown that the functionality of reduced graphene oxide (rGO) through copper ions displays selective antibacterial activity that is significantly stronger than that of rGO itself and no toxicity to mammalian cells. Remarkably, this antibacterial activity is two-orders-of-magnitude greater than the activity of its surrounding copper ions. It is demonstrated that rGO is functionalized through the cation–π interaction to massively adsorb copper ions to form a rGO–copper composite and result in an extremely low concentration level of surrounding copper ions (less than ≈0.5 µm ). These copper ions on rGO are positively charged and strongly interact with negatively charged bacterial cells to selectively achieve antibacterial activity, while rGO exhibits the functionality to not only actuate rapid delivery of copper ions and massive assembly onto bacterial cells but also result in the valence shift in the copper ions from Cu²⁺ into Cu⁺, which greatly enhances the antibacterial activity. Notably, this rGO functionality through cation–π interaction with copper ions can similarly achieve algaecidal activity but does not exert cytotoxicity against neutrally charged mammalian cells.