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Revealing the residual mechanism of switchable solvents in heavy oil
No full textThe entrainment of residual switchable hydrophilicity solvents (e.g., N, N, N ', N '-tetraethyl-1,3-propanediamine (TEPDA)) in the oil phase after solvent extraction was considered as one of the main challenges hindering the application of switchable solvents. Herein, the residual behavior of TEPDA in bitumen has been systematically investigated with experimental tests and molecular dynamic (MD) simulation. According to the experimental tests, it is found that the TEPDA could be entrained in bitumen in two different ways: i) a small amount of solvents are dissolved in the water droplets dispersed in the bitumen, and ii) most of the neutral solvents remain in the bitumen in the form of mutual solubility. The partial dissolution of asphaltene by TEPDA is the main factor affecting solvent protonation via solubility experiments. To comprehensively understand the process and formation mechanism of solvent residue, molecular dynamic simulation was used to analyze the wrapping mechanisms. By studying the interaction between different oil fractions and solvent molecules, it is found that asphaltene plays an important role in blocking reversible solvents and hinders their diffusion to the surface, which is consistent with the solubility tested. Intermolecular interaction analysis is used to understand the mechanism of solvent residue. It is observed that the van der Waals (vdW) forces between heteroatoms (O, N, S) in asphaltenes and methyl group in TEPDA as well as hydrogen bond (N...O-H) between TEPDA and asphaltene, play an important role in the binding of asphaltene-TEPDA. This finding provides molecular mechanisms for the residue of switchable solvents during heavy oil extraction. It would also shed light on developing new methods of solving the switchable solvent residues in other extraction processes
Effect of heat treatment on microstructure and tribological behavior of Ti?6Al?4V alloys fabricated by selective laser melting
No full textIn this paper, the effect of heat treatment (760?1060 ?C) on tribological behavior of selective laser melted Ti6Al4V alloy against Si3N4 counter-ball under different applied loads was investigated. Results show the wear rate of as-built Ti6Al4V alloy increased firstly and then gradually decreased with increasing the heat-treatment temperature, which obtained the lowest value when the heat treatment temperature was 1060 ?C, exhibiting the best wear resistance. The higher applied load led to larger wear rate and lower coefficient of friction. The wear mechanism was strongly dependent on the microstructure transformation, micro-hardness and applied load, which was discussed in detail
Designed glass frames full color in white light-emitting diodes and laser diodes lighting
No full textPhosphor-in-glass (PiGs) is one of the most important strategies to overcome thermal influence in high-power white light-emitting diodes and laser diodes. By carefully designing the glass composition of Na2O-CaO-B2O3-SiO2, the multi-color PiGs are successfully fabricated by a single-step co-sintering strategy at a relative low temperature (850 degrees C), most of PiGs maintain a high internal quantum efficiency approaching 90% of original phosphors. Under the 450 nm blue laser diodes (LDs) excitation, the luminous efficacy of YAG:Ce-PiG reaches 239.3 lm/W, which is almost the best result in white laser diodes (WLDs) so far. Outstandingly, the designed glass overcomes the oxidation, corrosion and decomposition of commercial nitride red phosphors, and realizes broadband emission from 500 to 700 nm by compositing red/yellow/green phosphors in an entire glass. Correspondingly, this work paves the way to achieve ideal white light with a high color rendering index of 94 in WLDs
High Temperature Resistant and Soluble Polyimide Resins and Their Composites
No full textTwo soluble imide oligomers and their composites were prepared, and their processability, the interfacial morphology, and thermal, dielectric and mechanical properties were systematically investigated. The results revealed that the oligomers possessed excellent processability, evidenced by their good solubility in aprotic solvents and low melt viscosities. The 5% mass loss temperatures of the cured resins were higher than 550 degrees C. The temperature of glass transition (T-g) values of cured PI-1 and PI-2 were 430 and 380 degrees C, respectively. The quartz fiber reinforced composites displayed relatively low dielectric constant and dielectric loss at a frequency of 1-3 GHz. Carbon fiber/PI-1 composite retained 62% of its original flexural strength and 48% of its original inter-laminar shear strength at 420 degrees C, indicative of their excellent mechanical properties at elevated temperatures. Composites with a thickness higher than 45 mm were fabricated through compress-molding, which further demonstrates the excellent processability of the resins
A novel strategy for the fabrication of high-performance nanostructured Ce-Fe-B magnetic materials via electron-beam exposure
No full textCe2Fe14B compound has a great potential to serve as a novel permanent magnet alternative thanks to the abundant and inexpensive rare-earth element (cerium), while its low magnetocrystalline anisotropy and energy product severely restrict its applications. In this work, a novel strategy combining melt-spinning and electron-beam exposure (EBE) aiming for fabricating high-performance Ce-Fe-B magnetic materials is reported to solve the above-mentioned problem. Remarkably, this strategy facilitates developing a suitable grain boundary configuration without using any additional heavy rare-earth element. Under the optimal EBE condition, the maximum energy product ((BH)(max)) of pure Ce-Fe-B alloy is 6.5 MGOe, about four times higher than that obtained after conventional rapid thermal processing method for the same precursor. The enhanced intergranular magnetostatic coupling effect in the EBE sample is validated by mapping the first-order-reversal-curve (FORC) diagrams. The in-situ observation of magnetic domain wall motion for Ce-Fe-B alloy using Lorentz transmission electron microscopy reveals that the boundary layers are very effective in pinning the motion of domain walls, leading to the increased coercivity under EBE, and this pinning effect is further verified by micromagnetic simulations. Our results suggest that CeFeB materials using EBE could be a promising candidate after further processing, which could fill the performance gap between hexaferrite and Nd-Fe-B-based magnets
Simultaneous Improvement of Efficiency and Stability of Organic Photovoltaic Cells by using a Cross-Linkable Fullerene Derivative
No full textImproving power conversion efficiencies (PCEs) and stability are two main tasks for organic photovoltaic (OPV) cells. In the past few years, although the PCE of the OPV cells has been considerably improved, the research on device stability is limited. Herein, a cross-linkable material, cross-linked [6,6]-phenyl-C61-butyric styryl dendron ester (c-PCBSD), is applied as an interfacial modification layer on the surface of zinc oxide and as the third component into the PBDB-TF:Y6-based OPV cells to enhance photovoltaic performance and long-term stability. The PCE of the OPV cells that underwent the two-step modification increased from 15.1 to 16.1%. In particular, such OPV cells exhibited much better stability under both thermal and air conditions because of the decreased number of interfacial defects and stable interfacial and active layer morphologies. The results demonstrated that the introduction of a cross-linkable fullerene derivative into the interfacial and active layers is a feasible method to improve the PCE and stability of OPV cells
Comparison of the in vitro corrosion behavior of biodegradable pure Zn in SBF, 0.9% NaCl, and DMEM
No full textZn-based alloys are considered to be the new biodegradable implant materials due to their suitable degradation rate and good biocompatibility. The biocorrosion behavior of pure Zn in 0.9% NaCl, simulated body fluid, and Dulbecco's modified Eagle's medium (DMEM) was investigated by electrochemical and immersion tests. These tests revealed that pure Zn has the lowest corrosion rate in DMEM and the highest in 0.9% NaCl. Aggressive Cl- has an important effect on the corrosion process. Buffering agents, amino acids, and glucose have a close connection with corrosion resistance. Among the three solutions, DMEM with a similar ion concentration and necessary nutriments is recommended as the more suitable choice for estimating biodegradable alloys' in vitro degradation
Annihilation and Regeneration of Defects in (11(2)over-bar2) Semipolar AlN via High-Temperature Annealing and MOVPE Regrowth
No full textSemipolar III-nitrides have attracted great attention due to their weak polarization field for optoelectronic devices. High-quality AlN is a perfect template in the epitaxial growth of AlGaN-based ultraviolet optical devices. In this work, (11 (2) over bar2) semipolar AlN was grown on m-plane sapphire by the hierarchical growth mode. A high density of extended defects due to the lattice mismatch and anisotropic growth rate is identified in the as-grown AlN thin film. The influence of thermal annealing and AlN regrowth on the evolution of stacking faults and dislocations in AlN was thoroughly investigated by high-resolution transmission electron microscopy. Extending defects turned into partial dislocations after high-temperature treatment, by which the stacking faults were buried inside the AlN template, incapable of propagating into the AlN regrowth layer. As a result, the AlN regrowth layer exhibits superior crystalline quality. However, compressive strain is found after high-temperature annealing (HTA), which introduces new defects in the AlN regrowth layer. Strain management is demonstrated to be crucial for the quality control of the AlN layer. Overall, high-temperature annealing and regrowth processes proved to be stable and repeatable techniques in the realization of high-efficiency semipolar UV semiconductor devices
A green Brassica oleracea L extract as a novel corrosion inhibitor for Q235 steel in two typical acid media
No full textBased on the eco-friendly, sustainable, and high-efficiency themes, an aqueous extract of Brassica oleracea L (BOLE) was employed to retard Q235 steel corrosion in two harsh acid environments (0.5 M H2SO4 and 1 M HCl) for the first time. The ingredient and corrosion inhibition ability of BOLE had been testified via Fourier-transform infrared spectroscopy (FT-IR), Ultraviolet-visible spectroscopy (UV-vis), conventional and in-situ electrochemical techniques, surface topography research, and X-ray diffraction (XRD). The experimental results showed that BOLE was a mixed-type inhibitor and possesses superior inhibition ability due to the compact BOLE protective film. The inhibition efficiency was 92.3% in H2SO4 and 93.8% in HCl when the added dose of BOLE was merely 300 mg/L. Meanwhile, the chemical adsorption reaction of the BOLE/steel surface was demonstrated by the N? Fe bond from X-ray photoelectronic spectroscopy (XPS). In theoretical calculation, the calculated values of low energy gap (?E) and high dipole moment (?), as well as Ebinding in neutralization and protonation conditions related to powerful interaction between BOLE and steel, which also revealed the excellent anti-corrosion ability of BOLE at the micro-level
PdO-modified alpha-Fe2O3 nanoparticles with enhanced gas performance for dimethyl disulfide
No full textNoble metal modification was a very promising way to enhance the gas-sensing properties of semiconductor materials. Therefore, gas sensors based on noble metal modified semiconductor materials had received much attention. In this work, PdO-modified alpha-Fe2O3 (denoted as PdO-alpha-Fe2O3) composite nanocrystals were fabricated by simple hydrothermal approach and wet impregnation means. The outcome disclosed that the 1.0 wt% PdO-alpha-Fe2O3 sensor exhibited better response in detecting dimethyl disulfide (DMDS) than that of pure alpha-Fe2O3 sensor and other PdO-alpha-Fe2O3 sensors based on different content of palladium oxide. Specially, the maximum response value in testing 100 ppm DMDS for 1.0 wt% PdO-alpha-Fe2O3 sensor can reach 113.1, and that of original alpha-Fe2O3 sensor was 11.1. Moreover, the outstanding selectivity, fast response recovery time (1 s/68 s), superior repeatability and stable long-term stability toward 100 ppm DMDS distinguished this 1.0 wt% PdO-alpha-Fe2O3 sensor from pristine alpha-Fe2O3 sensor. Here, the function and sensing mechanism of 1.0 wt% PdO-alpha-Fe2O3 were also discussed. (C) 2020 Elsevier B.V. All rights reserved