This work investigates the mechanism of the controllable wettability transition on laser ablated Ti-6Al-4V alloy surfaces with the vacuum treatment. The effects of surface morphologies, vacuum ...conditions and joint mechanisms are discussed. To achieve stable and controllable wettability transitions, the laser ablated Ti-6Al-4V alloy surfaces were placed in a low vacuum environment to adsorb non-polar organic molecules. The sample appeared an unstable wettability transition, which manifested itself as a change in the apparent contact angle (ACA) with time. High vacuum conditions can accelerate the assembly of organic molecules on the sample surface and achieve a stable wettability transition. Furthermore, by varying the surface morphologies of laser ablated Ti-6Al-4V alloy and the adsorption time of organic molecules, stable and controllable wettability transitions can be achieved at high vacuum conditions.
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Diamond wire saw silicon powder (DWSSP) is a waste produced during silicon wafer processing for photovoltaic (PV) modules, and it shows significant reutilization potential. However, the presence of ...moisture leads to silicon oxidation and the formation of a surface SiO2 layer that hinders the recovery of high-purity silicon. In this study, vacuum treatment (VT) was used to prepare low-oxygen silicon by controlling the oxidation and removing moisture from DWSSP waste, thus preventing SiO2 layer formation. The oxygen content in DWSSP decreased by 15.01 %, from 7.26 % to 6.17 %, and the SiO2 layer thickness also decreased by 10.29 %, from 2.04 nm to 1.83 nm after the VT process. Additionally, the VT process lowered the moisture boiling point, facilitating surface evaporation and internal diffusion of moisture. This increased the moisture effective diffusion coefficient from 5.16 × 10−10–6.16 × 10−9 m2 s−1 to 1.21 × 10−9–6.88 × 10−9 m2 s−1 and reduced the apparent activation energy from 32.17 kJ mol−1 to 16.05 kJ mol−1. The efficient moisture removal of VT inhibited the growth of the SiO2 layer to enable the preparation of low-oxygen silicon during silicon recovery.
•The low-oxygen Si preparation is significance for the PV sustainable development.•Discusses the effects of three methods of moisture removal on Si oxidation.•The low-oxygen Si was prepared via vacuum treatment.•The oxide layer thickness of Si decreased to 1.83 nm with an O content of 6.17 %.
TiO2 as an anode for sodium‐ion batteries (NIBs) has attracted much recent attention, but poor cyclability and rate performance remain problematic owing to the intrinsic electronic conductivity and ...the sluggish diffusivity of Na ions in the TiO2 matrix. Herein, a simple process is demonstrated to improve the sodium storage performance of TiO2 by fabricating a 1D, multichannel, porous binary‐phase anatase‐TiO2–rutile‐TiO2 composite with oxygen‐deficient and high grain‐boundary density (denoted as a‐TiO2−x/r‐TiO2−x) via electrospinning and subsequent vacuum treatment. The introduction of oxygen vacancies in the TiO2 matrix enables enhanced intrinsic electronic conductivity and fast sodium‐ion diffusion kinetics. The porous structure offers easy access of the liquid electrolyte and a short transport path of Na+ through the pores toward the TiO2 nanoparticle. Furthermore, the high density of grain boundaries between the anatase TiO2 and rutile TiO2 offer more interfaces for a novel interfacial storage. The a‐TiO2−x/r‐TiO2−x shows excellent long cycling stability (134 mAh g−1 at 10 C after 4500 cycles) and superior rate performance (93 mAh g−1 after 4500 cycles at 20 C) for sodium‐ion batteries. This simple and effective process could serve as a model for the modification of other materials applied in energy storage systems and other fields.
A 1D, multichannel, porous binary‐phase anatase‐TiO2–rutile‐TiO2 composite with oxygen‐deficient and high grain‐boundary density (a‐TiO2−x/r‐TiO2−x) are fabricated via electrospinning and subsequent vacuum treatment. The introduction of numerous oxygen vacancies and the high density of grain boundaries between the anatase‐ and rutile‐phase TiO2 are favorable for enhanced electrochemical performance with excellent long cycling stability and superior rate performance.
Inorganic CsPbI3 perovskite is an important photovoltaic material. However, growing high-quality CsPbI3 perovskite by using dimethyl sulfoxide as solvent, that is environmentally-friendly with ...considerably higher complexation capability, is still a great challenge. In this work, we overcome the challenge by introducing a vacuum treatment to induce the formation of DMAPbI3 (DMA = (CH3)2NH2+) intermediate, which could be subsequently transitioned to high-quality CsPbI3 perovskite. As a result, the CsPbI3 perovskite solar cells based on carbon electrode achieve a record efficiency of 16.7%.
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Inorganic CsPbI3 perovskite is an important photovoltaic material due to its suitable band gap and high chemical stability. However, it is a challenge to grow high-quality CsPbI3 perovskite because the stability of perovskite phase is low and is sensitive to solvent. So far, most of CsPbI3 perovskites in high-performance perovskite solar cells (PSCs) were prepared from N,N-dimethylformamide, a highly toxic solvent, and no successful case has been reported for dimethyl sulfoxide (DMSO), which is environmentally-friendly with considerably higher complexation capability. Herein, we reveal that forming DMSO-based adduct is the main cause for limiting the quality of CsPbI3 perovskite from DMSO-based solutions, which would inhibit the formation of DMAPbI3 (DMA = dimethylammonium, (CH3)2NH2+) intermediate. Then, by introducing a vacuum treatment, DMSO molecules could be efficiently extracted from the adduct to induce the formation of DMAPbI3 intermediate. After annealing, the intermediate is transitioned to the CsPbI3 perovskite with enhanced crystallinity, high orientation, low defect density, and high uniformity. By using the CsPbI3 perovskite as a light absorber, the PSCs based on carbon electrode (C-PSCs) achieve an efficiency of 16.7%, a new record for inorganic C-PSCs.
•Two-stage thermotreatment improves yield and spinnability of derived mesophase pitch.•Interaction among sub-fractions of mesophase facilitates its fusible deformability.•Rapid mesophase development ...at second stage produces semi-rigid oligomeric mesogen.•Excessive polymerization at the later stage is mainly induced by α-methyl cleavage.
The comparative study of different two-stage heat treatments was conducted to illustrate the modified effects on improving yield and spinnability of mesophase pitch. In such two-stage thermotreatments, a pressured condensation is employed to involve low-molecular-weight species into the formation of mesogens, thereby increasing pitch yields. Subsequently, vacuum polymerization could contribute to rapid development of mesophase and then reduce the residence time. The results indicate that the short duration could decrease occurrence of the intramolecular aromatization and intermolecular polymerization reactions that are readily induced by elimination of α-methyl and dehyroaromatization of naphthenic rings during the later stage of heat treatment. Consequently, the formed semi-rigid molecules in QS sub-fraction (i.e., fusible component) are seldom transformed into rigid ones mainly constituting QI sub-fraction (i.e., infusible component). Ultimately, sufficient QS sub-fraction, with a higher average Mw and a large amount of short alkyl and naphthenic substituents, is more likely to completely dissolve QI sub-fraction. Thus, the resultant mesophase exhibits an excellent fusible deformability. Besides, the structural feature of semi-rigid oligomer could somewhat loosen molecular association of layered stacking and contribute to the slippage between stacked mesogens due to its steric effects, thereby decreasing the softening points of mesophase pitch. Above modified effects are easily implementable during a suitable process of two-stage thermotreatment, such as the processes of preparing MP-4-0.01-1.0, MP-4-0.005-1.0 and MP-3-0.01-2.0 in this study. It is worthwhile to mention that the vacuum treatment is required to be conducted prior to large-scale coalescence of mesophase spheres in order to obtain spinnable mesophase pitch.
Development of materials with excellent separation performances remains an ongoing challenge in methane/nitrogen (CH4/N2) separation science. Herein, a facile and effective method for enhancing CH4 ...uptake, binding, and CH4/N2 selectivity using the surface‐carbonized and stiffened zeolitic imidazolate framework‐8 (CSZ) via high‐vacuum‐resistance calcination (HVRC) was demonstrated. Such vacuum‐treated CSZ nanoparticles, with carbonized structures that contain Zn‐rich sites, high stability, and satisfactory compatibility with polymers, were then uniformly mixed with the strong basic polymer polyvinylamine (PVAm) to obtain large‐area mixed‐matrix membranes (1120 cm2, which is ca. 2 pieces of A4‐size paper). Owing to the presence of Zn‐rich sites and amino groups, CH4 molecules were bound more readily to CSZ and PVAm than N2, as confirmed by gas adsorption isotherms and DFT calculations. The obtained MMM modules (ca. 2000 cm2) exhibited outstanding CH4 separation performances at 85 wt% CSZ loading, achieving a CH4 permeance of 7600 GPU and CH4/N2 selectivity of 4.35.
CH4/N2 separation is considered a feasible method for reducing the greenhouse effect, but its utility in industrial applications has limited by the low permselective performance. In this work, a ...novel method for enhancing CH4/N2 separation performance using amorphous UIO-66-NH2 with a carbonized structure (ACU) via high vacuum resistance calcination is proposed. Owing to the presence of carbonized framework that contains rich Zr4+ active sites, these vacuum-treated ACU nanoparticles showed high IAST CH4/N2 selectivity, good alkaline stability and satisfactory compatibility with polymers. Then, ACU were uniformly dispersed in polyvinyl alcohol (PVA) to obtain defect-free mixed matrix membranes (MMMs), the resulting ACU-based MMMs exhibited an enhanced CH4 separation performance. Remarkably, the PVA/ACU-120A/MPSf MMM that consisted of 80 wt% ACU-120A exhibited the outstanding CH4 permselectivity, achieving a CH4 permeance of 5584 GPU and CH4/N2 selectivity of 3.43.
The PVA/ACU-120A/MPSf MMM fabricated by vacuum treated amorphous UiO-66 (ACU) showed unprecendent CH4 permeance and good CH4/N2 selectivity. Display omitted
•High vacuum-resistance calcination treated amorphous UiO-66 (ACU) by carbonization was used as filler of MMM.•ACU shows good membrane-forming property and high alkaline stability.•PVA/ACU-120A/MPSf MMM showed unprecendent CH4 permeance and good CH4/N2 selectivity.
•MV treatment induced varying degrees of LSPIs unfolding with a decrease of α-helix.•Highly-ordered LSPIs were dissociated under a moderate microwave-vacuum field.•LSPIs treated by MV-100 W had the ...highest solubility and smallest protein size.•Low power (50–100 W) MV treatment improved the emulsifying properties of LISPs.
The present study investigated the changes in structural and emulsifying properties of lotus seed protein isolates (LSPIs) under different microwave-vacuum (MV) treatments. A decrease of fluorescence peak intensity with blue-shift of the fluorescence emission maximum indicated that MV treatment induced unfolding of LSPIs so that more hydrophobic residues were exposed. Raman spectra showed that the ordered secondary structures (α-helix, β-sheet) gradually converted into β-turns and random coils during 50–150 W MV treatment. Particle size distribution and atomic force microscope revealed that the amounts of small subunits increased when the LSPIs were modified by 50–100 W MV treatment. Emulsions prepared by 100-W-MV-LSPIs exhibited the optimal emulsifying ability with the smallest oil droplet sizes. Confocal laser scanning microscopy and analytical centrifugal analyzer further proved 50–100 W MV-treatment enhanced the flocculation and creaming stability. Our findings provide a certain theoretical foundation to apply MV technology for developing desirable LSPIs-stabilized emulsions.
The research presents the results of data analysis on degassing of wheel grades of steels in a tank degasser with a capacity of 120 tons, operated at the JSC “Ural Steel”. The volume of the analyzed ...sample included 754 steels for railway wheels (steel grades “2” and “T” according to State standard GOST 10791-2011) weighing more than 80 thousand tons received in November-December 2019.It was established that in order to guarantee the production of hydrogen content of less than 1.5 ppm and nitrogen before 0.007%, it is necessary to carry out vacuum treatment of metal with overheating of 110-130°C at the residual pressure of up to 3 mbar for 20-25 minutes and argon flow rate of at least 0.05 m3/ton. The regression equation was obtained, which allows to predict the results of degassing, as well as select the values of vacuum treatment parameters in order to achieve a given content of dissolved gases - hydrogen and nitrogen.
Passiflora edulis, commonly known as passion fruit, is a popular all‐weather fruit eaten fresh or processed. Its shells, which currently are mostly discarded as waste and hurt the environment, ...account for more than half of the passion fruit. The shells contain gamma‐aminobutyric acid (GABA) which is the main inhibitory neurotransmitter and has many proven medical values such as antidepressant, anti‐anxiety, etc. Many studies have shown that GABA production in plants can be significantly increased by reverse stress. Taking Tainong 1 as a typical passion fruit cultivar, this study explored the optimal anoxic vacuum treatment for increasing the GABA content of passion fruit shells. The content increased to 2139.25 ± 26.69 mg/100 g on day 4 of chill storage after vacuum packing (63.68% higher than the control). The activities of glutamate decarboxylase (GAD) and diamine oxidase (DAO) were significantly higher in the vacuum‐treated group than in the control group after 4 days of vacuum‐chill storage. On day 5 of vacuum‐chill storage, the activities of all measured enzymes decreased except for the increase of GABA transaminase (GABA‐T), which was accompanied by a decrease in GABA content. Vacuum treatment and subsequent chill storage increased the content of GABA, thereby increasing functional value of passion fruit shells.
