Study of the Antioxidative Properties of Several Amino Acid-Type Surfactants and their Synergistic Effect in Mixed Micelle

Cysteine and methionine, two sulfur-containing amino acids (AA), were introduced in their surfactant forms as potential antioxidants. The antioxidative (AOX) properties of lauroyl methionine (C12-Met) and lauroyl cysteine (C12-Cys) was investigated by means of the oxygen radical absorbance capacity assay. Both the surfactants exhibited excellent AOX behavior at the premicellar state and micellar medium. The AOX behavior was found to be comparable for both the surfactants at their premicellar states. However, in micellar medium, C12-Met showed better AOX property than C12-Cys. The AOX power of the surfactants was compared with other previously developed AA-type surfactants. The order of the AOX power was found to be: C12-tryptophan > C12-tyrosine ≈ C12-methionine ≈ C12-cysteine > C12-histidine at the premicellar state and C12-tryptophan > C12-tyrosine > C12-methionine > C12-cysteine > C12-histidine at the micellar state. C12-Cys displayed lower AOX property in micellar medium due to its dimer formation tendency. Based on the HPLC and UPLC-Q-TOF-MS analysis, the dimer formation of C12-Cys was found to be accelerated due to the micellar environment and results into negative synergistic effect on other aromatic AA-type surfactants. However, the presence of C12-His in the micellar solution of C12-Cys resulted no synergistic effect due to stronger H-bonding between the surfactants and resulting less dimer formation.     

Flame Front Deformation Instabilities of Filtration Combustion for Initial Thermal Perturbation

The flame front deformation instability of low-velocity filtration combustion within an inert packed bed is studied based on the initial preheating non-uniformity. Based on the experimental phenomena, an initial thermal perturbation model is numerically proposed so as to predict the deformation behaviors of the flame front instabilities. The numerical prediction indicates that the assumption of an initial thermal perturbation is a feasible explanation as the cause of the flame front inclination instability. As the initial thermal perturbation increases, the phenomena of the flame front break and shrinking instabilities could easily occur at high filtration velocity or low equivalence ratio. Moreover, the evolutions of the flame front break rate and the shrinking rate are quantitatively analyzed.     

Phase-transition induced optimization of electrostrain,electrocaloric refrigeration and energy storage of LiNbO3 doped BNT-BT ceramics

((Bi_0.5Na_0.5TiO₃)_0.88-(BaTiO₃)_0.12)_(1-x)-(LiNbO₃)_x (x = 0.0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, and 0.07; abbreviated as LiNbO₃-doped BNT-BT) ceramics possessing many excellent performances (large electrostrain, negative electrocaloric effect and energy storage density with high efficiency) was fabricated by the conventional solid-state reaction method. A large electrostrain (maximum ~ 0.34% at 100 kV/cm and room temperature) with high thermal stability over a broad temperature range (~80 K) is obtained at x = 0.03. A large energy storage density (maximum W_energy ~ 0.665 J/cm³ at 100 kV/cm and room temperature) with a high efficiency (η ~ 49.3%) is achieved at x = 0.06. Moreover, a large negative electrocaloric (EC) effect (maximum ΔT ~ 1.71 K with ΔS ~ - 0.22 J/(K kg) at 70 kV/cm)) is also obtained at x = 0.04. Phase transition (from ferroelectric to antiferroelectric and then to relaxor) induced by increasing the doping amount of LiNbO₃ plays a very key role on the optimization of these performances. These findings and breakthroughs make the LiNbO₃-doped BNT-BT ceramics very promising candidates as multifunctional materials.     

Constraint effect caused by graphene on in situ grown Gr@WO3 -nanobrick hybrid material

This work reported the abnormal constraint effect of graphene on the structural and optical properties of in situ grown Gr@WO₃ nanobrick (NB) hybrid nanomaterials. Stable hybrid Gr@WO₃ nanomaterials were synthesized through a one-step hydrothermal method, in which different graphene contents (0.1, 0.3 and 0.5 wt%) were directly introduced into the precursor solution of tungsten oxide. The existence of graphene in the nucleation phase of tungsten oxide NB decreased the crystallite size from 49.5 nm to 45.3 nm, increased the microstrain from 1.10% to 1.44% and the optical bandgap of the hybrid samples from 2.68 eV to 2.78 eV, and reduced the radiative recombination efficiency of tungsten oxide NB. The hybridization between graphene and tungsten oxide NBs was confirmed by X-ray diffraction and Raman scattering analysis. The optical properties of materials were studied based on the absorbance and diffuse reflectance spectra. In this work, we also proposed a reliable method to estimate the optical bandgap of the sample from the diffuse reflectance spectrum. These findings would introduce an alternative method of fabrication and enhance the understanding of in situ hybrid materials.     

Effects of annealing on bandgap and surface plasmon resonance enhancement in Au/SnO2 quantum dots

Au/SnO₂ quantum dots (AuSQDs) were synthesized, and the effects of annealing on their structural and optical properties were examined. Significant changes were observed in the bandgap and surface plasmon resonance (SPR) of the AuSQDs after thermal treatment at different temperatures (400, 500, and 600 °C). The properties of the as-prepared and annealed samples were characterized via X-ray diffraction analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy, and diffuse reflectance spectroscopy. Annealing reduced the bandgap from 3.03 to 2.33 eV and increased the crystallinity while maintaining an average crystallite size below 10 nm. XPS valence band (VB) profiles provided information regarding the VB edge potentials, which helped to determine the conduction band edge potentials. An enhancement in the SPR of the Au nanoparticles was observed for AuSQD-500, which had the smallest bandgap among the samples investigated.     

Synergistic effect of iodide ions and bark resin of Schinus molle for the corrosion inhibition of API5L X70 pipeline steel in H2SO4

The synergistic effect of bark resin of Schinus molle (BRSM) and iodide ions in 0.5 M sulfuric acid has been studied for the first time by potentiodynamic polarization and electrochemical impedance spectroscopy measurements; also, the surface morphology has been analyzed by scanning electron microscopy–energy-dispersive X-ray spectroscopic analysis in the present work. The results show that the BRSM and iodide ions have an evident synergistic inhibition effect in a 0.5-M sulfuric acid solution. The adsorption of the BRSM/iodide ion system follows the Langmuir adsorption isotherm and acts as a mixed-type inhibitor in sulfuric acid. The BRSM/iodide ion system is an effective inhibitor for API5L X70 pipeline steel in the 0.5-M sulfuric acid solution. The maximum percentage inhibition efficiency is equal to 99% at 1 g/L BRSM + 2 mM KI.     

考虑黏压效应的风电齿轮热弹流分析

在线接触热弹流润滑的基础上，考虑黏压效应，对风电行星轮系齿轮副进行热弹流润滑数值分析，并采用热弹流润滑数值方法和ISO/TS 6336-22计算了齿轮副的最小油膜厚度、安全系数和闪温温度，并比较各主要啮合点的压力和油膜厚度分布。结果表明：与使用ISO/TS 6336-22计算的结果对比，采用热弹流润滑理论计算的油膜更厚，但安全系数更小；在风电齿轮副热弹流润滑分析时应考虑压力对黏度的影响；风电主齿轮箱齿面因啮合产生油膜厚度随温度增加会迅速降低，最小油膜厚度会随载荷增加迅速减小，因此风电齿轮箱要保证足够的润滑，并尽量避免在高于额定载荷下长时间持续运行     

瓦斯抽采钻孔水射流协同修护技术研究与应用

瓦斯抽采钻孔普遍存在因变形、煤渣积聚及塌孔等导致钻孔堵塞和抽采效果差的问题。通过分析钻孔塌堵失稳机制,得出煤岩体性质、地质构造及多应力耦合条件是造成钻孔失稳的主要因素,进而推断相应堵孔段情形。利用高压水射流解堵作用,提出了水射流疏通-筛管护孔协同修护技术,并研制出轻型气动钻孔修复装备。应用结果表明,该协同修护技术能有效解决瓦斯抽采钻孔塌堵后无法有效抽采的技术难题,试验钻孔修护深度达到50 m,修护完成后单孔抽采瓦斯浓度和瓦斯纯流量比修复前提高0.57~3.67倍和0.99~5.15倍,抽采效果大幅改善,实现了塌堵钻孔的快速便捷修复进而确保了瓦斯流动通道的畅通。     

New observations and critical assessments of incipient plasticity events and indentation size effect in nanoindentation of ceramic nanocomposites

The ceramic nanocomposites (CNCs) like zirconia toughened alumina (ZTA) ceramics are important futuristic materials for structural and functional applications in advanced strategic systems, structural components, biomedical prostheses and devices. In all structural materials including the ZTA CNCs, the very early stages of plastic deformation i.e., the incipient plasticity events (IPE) are most important to be understood so that the microstructure and mechanical properties can be tuned to suit a given end application. Here we report for the first time the mechanisms of IPE in the nanoindentation experiments conducted at 10–1000 mN loads in the 40 ZTA CNCs. Here 40 ZTA CNC stands for 40 vol% of 3 mol% Yttria partially stabilized zirconia toughened alumina (40ZTA) CNC. The role of load ranges in variations of the IPE related parameters in the 40 ZTA CNCs is also studied. Further, an attempt is made to assess how the amount of zirconia content in ZTA CNCs affects the variations of the IPE related parameters. Through the extensive usage of field emission scanning electron microscopy (FESEM) and theoretical estimations, efforts are also directed to check out the linkage, if any, between the localized shear deformation and/or microcracking with the IPE events that occur in the present CNCs. In addition, a new concept of damage resistance is introduced for the first time in the present work to explain the presence of a strong indentation size effect (ISE) in the 40 ZTA CNCs. Finally, an attempt is also directed to understand how the indentation load (P) controls the relative size of interaction zones of dislocation loops as well as the damage resistance and thereby, engineer the acuteness of the ISE in ZTA CNCs. The implication of these findings in futuristic design of especially the ZTA CNCs for various applications is also discussed.