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Active constituents of Chinese yam peel (CYPE), namely, diosgenin (DOG), batatasin-I (BTS-I), batatasin-III (BTS-III), and yam polysaccharide (Y-PS), were extracted via an ultrasonic soaking strategy. The synergetic anticorrosion mechanism among these compounds for copper in artificial seawater (ASW) was clarified by gravimetric measurements, electrochemical evaluations, surface analyses, quantum chemical calculations under a dominant solvent model, and molecular dynamics (MD) simulations. The results of weight loss revealed that CYPE strongly inhibited the corrosion of copper in ASW, and the elevating temperature boosted the anticorrosion efficacy of CYPE. The inhibition efficiency could attain 96.33% with 900 mg/L CYPE in ASW at 298 K due to effective adsorption. CYPE simultaneously suppressed the anodic and cathodic reactions for copper in ASW, which could be categorized as the mixed-type corrosion inhibitor with the predominant anodic effect. Similar electrochemical kinetics was evidenced by electrochemical frequency modulation (EFM). Electrochemical impedance spectroscopy (EIS) indicated that CYPE prominently increased the charge-transfer resistance at the copper/electrolyte interface without altering the corrosion mechanism. Extending the immersion time was also conducive for CYPE to further minimize the corrosion of copper in ASW, which was demonstrated by the time-course polarization, EIS, and EFM tests. Owing to the adsorption of CYPE, the copper surface was well-protected and showed reduced wettability and limited variation of roughness. From the outcomes of quantum chemical calculations, global and local reactive descriptors of DOG implied the cross-linked deposition of actually formed dioscin on the copper surface; otherwise, those of BTS-I/-III showed the propensity for parallel adsorption, which could chemically anchor on the voids uncovered by dioscin and thereby synergistically inhibit the corrosion process. The adsorption orientations of DOG, BTS-I, and BTS-III were also consolidated by MD simulations. The findings of this study might be beneficial to inspire the development of eco-friendly corrosion inhibitors from plant wastes for copper in marine environments.

The inhibitive effect and inhibition mechanism of l-lysine derivatives, namely α-N-benzyloxycarbonyl-l-lysine (α-NL) and e-N-benzyloxycarbonyl-l-lysine (e-NL), on the corrosion of carbon steel in 0.5 M H2SO4 solution were investigated by electrochemical technique, weightlessness test, scanning electron microscope, atomic force microscope, infrared attenuated reflectance spectroscopy and quantum chemical calculation. The results showed that α-NL and e-NL as moderate cathodic inhibitors mainly inhibited the cathodic reaction of carbon steel in 0.5 M H2SO4 solution, and the terminal substituted e-NL showed better corrosion inhibition than the α-N-benzyloxycarbonyl protected α-NL. Their inhibition efficiencies increased with the increase in inhibitor concentration, and the inhibition efficiency of α-NL and e-NL with concentration of 10 mmol can reach 53.4% and 61.5%, respectively, but decreased with rising temperature. The adsorption of investigated inhibitors on the surface of carbon steel obeyed the modified Langmuir isotherm and El-Awady thermodynamic-kinetic model, and the thermodynamic and kinetic parameters were determined to discuss the mechanism of inhibition of α-NL and e-NL. Moreover, Quantum chemical calculation gave further insight into the inhibition mechanism of α-NL and e-NL and was employed to reveal the reasons for their differences in inhibition performance.

To improve the poor adhesion and the ensuing insufficient anticorrosion efficacy of electropolymerized polypyrrole (PPy) on copper surface, an inverted-electrode strategy was applied after the passivation procedure, for which the compact coating (PPy-I) was deposited on the substrate in a cathodic window. Morphological and physical characterizations revealed that PPy-I exerted satisfactory adhesion strength and suitable thickness and conductivity compared with the analogue prepared via the traditional protocol (PPy-T). Potentiodynamic polarization, electrochemical impedance spectroscopy and frequency modulation were employed to ascertain the propitious protection of PPy-I for copper in artificial seawater (ASW). Due to the dominant electroactivity, the PPy-I-coated sample possessed higher apparent current density and lower charge transfer resistance than its PPy-T-protected counterpart, which maintained the passivation of the substrate. Surface analysis also supported the viability of PPy-I for copper in ASW for a well-protected surface with inferior water wettability. Molecular dynamics simulations evidenced that PPy-I with the higher density retained efficient anticorrosion capacity on copper at elevated temperatures. Therein, the derived time-dependent spatial diffusion trajectories of ions were locally confined with low diffusion coefficients. Highly twisted pore passages and anodic protection behavior arising respectively from the tight coating architecture and electroactivity contributed to the adequate corrosion resistance of PPy-I-coated copper.

Flow sensors found in animals often feature soft and slender structures (e.g. fish neuromasts, insect hairs, mammalian stereociliary bundles, etc) that bend in response to the slightest flow disturbances in their surroundings and heighten the animal’s vigilance with respect to prey and/or predators. However, fabrication of bioinspired flow sensors that mimic the material properties (e.g. low elastic modulus) and geometries (e.g. high-aspect ratio (HAR) structures) of their biological counterparts remains a challenge. In this work, we develop a facile and low-cost method of fabricating HAR cantilever flow sensors inspired by the mechanotransductory flow sensing principles found in nature. The proposed workflow entails high-resolution 3D printing to fabricate the master mould, replica moulding to create HAR polydimethylsiloxane (PDMS) cantilevers (thickness = 0.5–1 mm, width = 3 mm, aspect ratio = 20) with microfluidic channel (150 μm wide × 90 μm deep) imprints, and finally graphene nanoplatelet ink drop-casting into the microfluidic channels to create a piezoresistive strain gauge near the cantilever’s fixed end. The piezoresistive flow sensors were tested in controlled airflow (0–9 m s−1) inside a wind tunnel where they displayed high sensitivities of up to 5.8 kΩ m s−1, low hysteresis (11% of full-scale deflection), and good repeatability. The sensor output showed a second order dependence on airflow velocity and agreed well with analytical and finite element model predictions. Further, the sensor was also excited inside a water tank using an oscillating dipole where it was able to sense oscillatory flow velocities as low as 16–30 μm s−1 at an excitation frequency of 15 Hz. The methods presented in this work can enable facile and rapid prototyping of flexible HAR structures that can find applications as functional biomimetic flow sensors and/or physical models which can be used to explain biological phenomena.

An enantioselective ring-closing C(sp3 )-H amination of 2-azidoacetamides is catalyzed by a chiral-at-metal ruthenium complex and provides chiral imidazolidin-4-ones in 31-95 % yield, with enantioselectivities of up to 95 % ee, and at catalyst loadings down to 0.1 mol % (turnover number (TON)=740). To our knowledge, this is the first example of a highly enantioselective C(sp3 )-H amination with aliphatic azides. Mechanistic experiments reveal the importance of the amide group, which presumably enables initial bidentate coordination of the 2-azidoacetamides to the catalyst. DFT calculations show that the transition state leading to the major enantiomer features a better steric fit and favorable π-π stacking between the substrate and the catalyst framework.

The normal growth of Nelumbo nucifera, a widely planted aquatic crop in Asia, was severely ruined by replant disease. The mechanism of replant disease was still unknown in aquatic crops. Complementary transcriptomic and proteomic analyses were performed by comparing seedings of first-year planting (FP) and consecutive planting (CP). 9810 differentially expressed genes (DEGs) were identified between FP and CP. Additionally, 975 differentially expressed proteins (DEPs) were obtained. The correlation of proteome and transcriptome illustrated phenylpropanoid biosynthesis, flavonoid biosynthesis, metabolic pathways, and MAPK signaling pathways were significantly activated. Peroxidase, determined as one of the key proteins in replant disease of N. nucifera, was phylogenetically analyzed. A new depiction of the molecular mechanism causing replant disease in N. nucifera was illustrated. A consecutive monoculture stimulated the generation of reactive oxygen species (ROS) and ethylene, altered the metabolic balance of lignin and flavonoid, and attenuated the activity of antioxidant enzymes through DNA methylation. Therefore, the accumulation of autotoxic allelochemicals and the deficiency of antioxidant enzymes unavoidably suppressed the normal growth and development of replanted N. nucifera.

The liquid metal magneto-hydro-dynamic (LMMHD) system is a promising power generation converter for a variety of heat sources. This paper presents a novel concept of the self-evaporating-driving LMMHD system, in which the liquid metal is driven by the vapor from its own evaporation. It has advantages of safety, higher electrical conductivity, a simplified structure without mixer and separator, and therefore a more reliable and higher efficiency. First, the basic principles of this system were introduced, in comparison with that of a conventional LMMHD system. Second, simulations were conducted to study the physical process of the evaporation of liquid metal in the heater and the characteristics of vapor–liquid flow in the following tube. Finally, three main impacting factors, namely inlet velocity, inlet temperature of liquid sodium, and temperature of the pipe wall, were discussed, respectively. The findings verify the feasibility of the proposed self-evaporating-driving LMMHD system and present the outl...

In this work, four allyl imidazolium-based ionic liquids (ILs) with various length of alkyl chains were developed for the corrosion inhibition of copper in 0.5 M sulfuric acid. Electrochemical techniques, morphological characterization, theoretical caculations were combined to investigate the inhibition performance and mechanism. The results show that corrosion circumstance of copper in sulfuric aqueous solution is efficiently inhibited by these ILs. Their favorable performance is ascribed to formation of ILs-adsorption films, which follow the Langmuir adsorption isotherm. Besides, the inhibition efficiencies of the investigated inhibitors increase with the augment of alkyl chain length attached to the imidazolium ring.

The photocatalytic performance of TiO2 is significantly limited by its high recombination rate of photo-generated charge carriers, and therefore it is essential to further boost the photocatalytic activity of TiO2. In this paper, to enhance the separation efficiency of the photo-generated charge carriers by surface state regulation, a series of TiO2 photocatalysts were prepared by sol–gel method with the assistance of NH4Cl and studied by the Brunauer-Emmet Teller method, X-ray diffraction patterns, UV-VIS diffuse reflectance spectra, scanning electron microscopy with energy dispersive spectroscopy and surface photovoltage spectroscopy. The relative amount of •O2 − was measured using nitrotetrazolium blue chloride (NBT) method. The photocatalytic activities of the samples under the simulated sunlight irradiation were investigated using Rhodamine B as the model dye. The results reveal that all the samples prepared with the assistance of NH4Cl display better photocatalytic activity than the reference TiO2 and the enhancement mechanism was proposed.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

WOS: 000403012700051, One of the effective methods developed to inhibit the corrosion of steel is the use of organic molecules as corrosion inhibitors. In particular, the design and synthesis of large size organic corrosion inhibitors draws more and more attention. Unfortunately, an atomic-level insight into the inhibition mechanism is still lacking, and regular density functional theory method is found to be inefficient in dealing with large inhibitor-metal adsorption systems. Given this background, in this work, density functional based tight binding (DFTB) approach was used to investigate the adsorption properties of three large size inhibitors (i.e., chalcone derivatives) on an iron surface. The molecular activity of free chalcone derivatives was studied by means of Frontier molecular orbital theory. The growth characteristics of alpha-Fe habits were observed using the "Morphology" software. Some adsorption parameters such as charge density difference, density of states, and changes of molecular orbital were described in detail. The present study is helpful to understand the anticorrosive mechanism of similar organic inhibitors and provides a feasible way to develop novel corrosion inhibitors., Science and Technology Program of Guizhou Province [QKHJC 2016-1149]; Guizhou Provincial Department of Education Foundation [QJHKYZ2016105, 2016-009]; Research Fund for the Doctoral Program of Tongren University [trxyDH1510]; National Natural Science Foundation of China [51462030]; Student's Platform for Innovation and Entrepreneurship Training Program [2016106665]; Opening Project of Sichuan University of Science and Engineering [2016CL06], This research was sponsored by the Science and Technology Program of Guizhou Province (QKHJC 2016-1149), the Guizhou Provincial Department of Education Foundation (QJHKYZ2016105, 2016-009), the Research Fund for the Doctoral Program of Tongren University (trxyDH1510), the National Natural Science Foundation of China (51462030), the Student's Platform for Innovation and Entrepreneurship Training Program (2016106665), and the Opening Project of Sichuan University of Science and Engineering (2016CL06).

Design of lubrication systems, particularly of bearing chambers, requires a sufficient understanding of the physical characteristics of the air–oil two phase flow. Due to a high shaft rotating speed of micro UAV (Unmanned Aerial Vehicle) engines, the heat production of bearings often results in a poor cooling effect on the bearings. In the present work, numerical simulation was conducted on the above topic for a certain type of UAV engine. Firstly, the heat production in the bearings was theoretically analysed, and a three dimensional structural model of the bearing chamber was built by Unigraphics (UG) software. Then on the FLUENT platform, some key physical fields, such as path lines, velocity and temperature distributions were presented and discussed, with the simulated results were verified by measured values under typical working conditions. Afterwards, the influences of some important operating conditions, including revolving speed, oil supply, and air inlet velocity were investigated. Finally, optimal values were suggested for each operating condition, taking into consideration the cooling effect, lubrication effect and engine efficiency.

Liquid Metal Magneto-Hydro-Dynamic (LMMHD) power generation is a promising technology for waste heat recovery, solar thermal utilization, etc. In this system, a high-temperature liquid metal is mixed with a low-boiling point working fluid, which will evaporate and push the liquid metal to flow through the MHD generator channel. The characteristics of mixing and the vapor–liquid two phase flow will greatly affect the power generation efficiency and effectiveness. This paper firstly proposed a spherical mixer tank for the entire LMMHD system. Then CFD simulation was employed to investigate the above process, with liquid tin as the liquid metal and trifluorotrichloroethane (R113) as the low-boiling point working medium. The findings indicate that an appropriately higher inlet velocity of liquid tin can lead to both higher outlet velocity and larger volume fraction of liquid tin, which is beneficial to MHD power generation. Increasing the initial temperature of liquid tin or inlet velocity of R113 will, on the one hand, elevate the outlet velocity of liquid tin; on the other hand, it will reduce the outlet volume fraction of liquid tin, which was suggested be kept above 20% to avoid the undesirable annular flow. In addition, the inlet velocity of R113 should be kept above 0.05 m s−1; otherwise, liquid tin may flow downwards into its inlet pipeline and cause blockage. The present results will help guide the design, operation and optimization of the mixer, and improve the basic theory of multiphase flow in a LMMHD system.

Line defects (LDs) which are commonly present in two-dimensional materials play an important role in spintronic applications for generating and transporting spin current. We theoretically predict of the electronic and magnetic properties of n-type doped monolayers of hexagonal boron nitride (h-BN) with 4|8 LDs. The LDs can create two deep narrow bands in the band gap of the h-BN sheet with an energy separation about 2.75 eV at Γ point. Interestingly, at a certain concentration of electrons introduced by n-type doping, a tantalizing spontaneous one-dimensional ferromagnetic ordering emerges due to the partially-occupied narrow conduction band. Moreover, it is found that this electron doping induced spin polarization (of charge current) is up to 90% in the bias voltage range from 0.1 V to 0.4 V. Our findings indicate that the h-BN monolayer can functionalize a semiconductor for spintronic devices applications, which is beyond a common sense of h-BN tunneling barrier.

The inhibition performance and mechanism of 1-octyl-3-methylimidazolium bromide ([OMIM]Br) and 1-allyl-3-octylimidazolium bromide ([AOIM]Br) for the corrosion of mild steel in 0.5 M H2SO4 were investigated using weight loss method, electrochemical measurements, scanning electron microscope (SEM) and quantum chemical calculation. The results revealed that [OMIM]Br and [AOIM]Br acted as modest cathodic inhibitors, and due to the electron-donating effect of allyl group, [AOIM]Br showed better inhibitive performance. The adsorption of both inhibitors on steel surface obeyed El-Awady thermodynamic–kinetic model, thus the thermodynamic and kinetic parameters were calculated and discussed. Moreover, theoretical calculation was used to investigate inhibition mechanism of studied inhibitors.

The work presents the combined effect of methionine molecules and cuprous oxide passive film on the corrosion inhibition of copper in 1 M NaOH solution by using potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy/energy dispersive X-ray analysis and theoretical calculations. The results reveal that methionine is an effective inhibitor for copper in 1 M NaOH solution and its inhibition efficiency is increased by increasing its concentration. Also, the electrochemical results showed that methionine mainly suppresses the cathodic process as a cathodic-typed inhibitor by adsorption, and the adsorption of methionine can occur on the passive film surface (cuprous oxide) of copper. The adsorbed film of inhibitors combines with the cuprous oxide passive film, and provides a double-layer protection for copper in alkaline solution. Quantum chemical calculation was applied to investigate the inhibition mechanism of methionine, and molecular dynamics simulation was further performed to illustrate the double-layer protection system for copper in alkaline solution.

A newly amino acid ionic liquid, 1-octyl-3-methylimidazolium l-prolinate ([Omim]Lpro), was investigated as the inhibitor for mild steel in 0.5 M H2SO4 solution using weight loss method, electrochemical measurements, scanning electron microscopy (SEM), and quantum chemical calculation. The obtained results revealed that [Omim]Lpro was a mixed-type inhibitor with a predominantly cathodic action for mild steel in 0.5 M H2SO4 solution, and inhibition efficiency reached nearly 80% at the concentration of 10 mM, in which the Omim cation played a major role in the corrosion inhibition of [Omim]Lpro. The adsorption of [Omim]Lpro on the mild steel surface was found to obey the El-Awady thermodynamic-kinetic model and Flory–Huggins isotherm equations; thus the thermodynamic and kinetic parameters governing the adsorption process were calculated and discussed. Moreover, quantum chemical calculation gave further insight into the mechanism of inhibition of [Omim]Lpro.

A newly benzimidazole derivative, 1-butyl-3-methyl-1 H -benzimidazolium iodide (BMBIMI), has been tested as inhibitor for mild steel in 0.5 M H 2 SO 4 solution via various approaches including weight loss, electrochemical measurements, scanning electron microscope (SEM), atomic force microscope (AFM) and theoretical calculations. The obtained results reveal that BMBIMI is an effective mixed-type corrosion inhibitor for mild steel, and the adsorption of BMBIMI on the mild steel surface is found to obey the Langmuir adsorption isotherm, thus the thermodynamic and kinetic parameters governing the adsorption process are calculated and discussed. Moreover, theoretical calculations give further insight into the mechanism of inhibition of BMBIMI.