[en] Highlights: •BMBIMI is an effective mixed-type inhibitor for mild steel in H₂SO₄ solution. •The inhibition efficiency increases with the increment of inhibitor concentration. •BMBIMI takes the flat mode adsorbed on the metal surface by benzimidazole ring. •The adsorption is an exothermic process and obeys Langmuir adsorption isotherm. -- Abstract: A newly benzimidazole derivative, 1-butyl-3-methyl-1H-benzimidazolium iodide (BMBIMI), has been tested as inhibitor for mild steel in 0.5 M H₂SO₄ 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

[en] Highlights: • Hardness and thermal conductivity of alloy can be improved by aging treatment. • The interface between precipitates and matrix transformed coherent into incoherent with increasing aging time. • Coherent interface would impede the improvement of thermal conductivity of alloy. - Abstract: How to simultaneously improve the thermal conductivity and mechanical properties of Mg alloys is an interesting and important issue topic. In the present study, the effect of aging treatment on the thermal conductivity and micro-hardness of Mg–12Gd alloy was investigated. Results indicated that the thermal conductivity and micro-hardness of the alloy could be significantly improved by aging treatment, and Mg–12Gd alloy exhibited a typical aging hardening response with the increasing aging time. At the early stage of aging (4 h), a large number of fine particles precipitated from α-Mg matrix, but thermal conductivity of alloy increased a little, which was attributed to the coherent interface hindering the increase of thermal conductivity. The thermal conductivity increased to the peak value of 75.7 W/(m·K) at the aging time of 300 h, which was about 2.17 times that of as-solutionized alloy. The huge increment in the thermal conductivity of as-aged Mg–12Gd alloy was related to the precipitation of particles and the incoherent interface between precipitates and α-Mg matrix.

[en] 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. (paper)

[en] Highlights: • We obtained the habit information of α-Fe obtained by the “Morphology” module. • The adsorption of pyrrole, furan, and thiophene on Fe(110) surface were studied by DFT calculations. • Our DFT modeling provided a reasonable micro-explanation to the empirical rule. - Abstract: Steel is an important material in industry. Adding heterocyclic organic compounds have proved to be very efficient for steel protection. There exists an empirical rule that the general trend in the inhibition efficiencies of molecules containing heteroatoms is such that O < N < S. However, an atomic-level insight into the inhibition mechanism is still lacked. Thus, in this work, density functional theory calculations was used to investigate the adsorption of three typical heterocyclic molecules, i.e., pyrrole, furan, and thiophene, on Fe(110) surface. The approach is illustrated by carrying out geometric optimization of inhibitors on the stable and most exposed plane of α-Fe. Some salient features such as charge density difference, changes of work function, density of states were detailedly described. The present study is helpful to understand the afore-mentioned experiment rule.

[en] Highlights: • OMIMBr and [AOIM]Br are modest cathodic inhibitors for mild steel in 0.5 M H_2SO_4. • AOIMBr shows better corrosion inhibition due to the allyl electron-donating group. • Inhibitor mainly physically adsorbs on steel surface via positively charged N atom. • The adsorption of inhibitor molecules obeys El-Awady thermodynamic–kinetic model. - Abstract: 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 H_2SO_4 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