In recent years, self-healing materials have become popular for their repairable properties, which can stabilize the service performance and prolong lifetime. Ionic liquids, one of the most important ...self-healing agents, have attracted much attention because of their excellent conductive properties, high healing efficiency, and facile healing condition. In this review, the self-healing mechanism based on ionic liquids and the factors that affect their healing efficiency are explored. On the one hand, ionic liquids endow materials with self-healing character due to the presence of secondary bonds including hydrogen bonds, ion–dipole interactions, and ionic aggregation. One the other hand, ionic liquids are combined with other materials and impart self-healing properties due to reversible chemical reactions such as Diels–Alder, coordination, and electrochemical reaction. In addition, the effects on the self-healing function of ionic liquids are reviewed, including their ionic diffusion ability and environmental conditions. Last, challenges regarding self-healing materials concerning ionic liquids are presented.
Graphic abstract
In natural language processing and information retrieval tasks, the bag-of-words model is widely used to represent the semantics of texts. However, it is difficult for machines to sufficiently ...understand a bag of words as well as the corresponding text without explicit semantic explanation, thus hindering the power of the bag-of-words model in many scenarios. In this paper, we introduce the task of hierarchical conceptual labeling (HCL), which aims to generate a set of conceptual labels with a hierarchy to explicitly explain the semantics of a bag of words, where the candidate labels are selected from a large-scale knowledge base, i.e., Microsoft Concept Graph. To this end, we first propose a denoising algorithm to filter out the noise in a bag of words in advance. Then the hierarchical conceptual labels are generated for the clean bag of words based on a hierarchical clustering algorithm, i.e., Bayesian rose trees. We conduct extensive experiments and prove that (1) the proposed denoising algorithm can effectively delete the noise words from a bag of words, (2) the Bayesian rose trees based algorithm can generate hierarchical conceptual labels for a bag of words with a high accuracy.
Fourier transform infrared spectroscopy was used to characterize the structure of phenol formaldehyde (PF) resin pyrolyzed at different temperatures, and pyrolysis gas chromatography mass ...spectrometry was used to observe the volatiles. A pyrolysis mechanism has been consequently deduced, and several previous ambiguities have been clarified. The occurrence of carbon monoxide and carbon dioxide is attributed to the oxidization of methylene. However, not oxidization, but methylene scission is mainly responsible for the decomposition of PF resin. At the same time, methylene radicals combine with other small molecules and form some volatiles such as ethylene and methanol. With the elevation of heat treatment temperature, PF resin is progressively transformed into amorphous carbon by pyrolysis and polycyclic reactions.
The pyrolysis of pure phenol-formaldehyde (PF) resin and boron carbide (B
4C) modified PF resin was investigated by using thermogravimetry (TG) and pyrolysis gas-chromatography–mass-spectrometry ...(PY-GC/MS). Scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy were also employed to investigate the micro-structural evolution. It was shown from the TG analysis that the char residues of pure PF resin were 62.9 and 60.5% after being pyrolyzed at 700 and 1000
°C, respectively. The degradation and failure of the resin matrix were mainly resulted from the release of volatiles. The phenol and its methyl derivates took a large proportion in the amount of volatiles. In comparison with the pure PF resin, the char residues of B
4C modified PF resin were obviously higher, with the values of 71.9 and 68.4% at 700 and 1000
°C, respectively. Due to the oxidation–reduction reactions between B
4C additive and oxygen-containing volatiles including CO and H
2O, partial carbon and oxygen elements in the volatiles remained in the resin matrix in the forms of amorphous carbon and B
2O
3, respectively. The results of SEM and FT-IR characterization demonstrated the occurrence of the modification, and the amorphous carbon existed in the form of reticular substance. In addition, the amount of the released phenol and its methyl derivates was also decreased drastically due to the formation of borate.
Multiphase particle-reinforced strategy shows promise for efficiently improving the comprehensive properties of aluminum matrix composites (AMCs) such as thermophysical and mechanical properties. In ...this work, AMC reinforced with
β
-eucryptite (LAS), and silicon carbide (SiC) particles were successfully prepared via a powder forging process. The microstructure morphology, interface compatibility, and coefficient of thermal expansion (CTE) of these composites were evaluated. Microstructural characterization illustrated that the co-effect of SiC and LAS resulted in a discontinuous phase with a microporous and deformation-free structure. The microporous structure of these composites was conducive for inward expansion and the elimination of internal stress, effectively limiting the outward thermal expansion behavior of the Al alloys. Moreover, SiC and LAS exhibited tight interfacial bonds with the Al grains, enhancing interfacial bonding strength. These composites provided practical and robust tensile stress that limited the thermal expansion of the Al matrix under heating. A fine Al grain size (53.5 nm) and low micro-strain (0.4 × 10
–4
) were obtained with increasing LAS content. Consequently, the composites achieved a low CTE of 17.27 × 10
–6
K
−1
at 500 °C. The experimental CTE values were also compared with theoretical values calculated by a rule of mixture model to confirm that the excellent interfacial bonding between the LAS and SiC reinforcements and the Al matrix imposed an effective constraint on matrix expansion.
Graphical abstract
The potential damage during the pyrolysis of phenol–formaldehyde (PF) resin in the manufacturing of carbon/carbon components is serious. Accurately modeling the kinetics of the pyrolysis reaction can ...lead to improvements in processing. To study the pyrolysis kinetics of PF resin, non-isothermal pyrolysis kinetics is investigated using thermogravimetric analysis (ТGA) at controlled heating rates. The research indicates that the pyrolysis process consists of three consecutive and overlapping stages. PEAKFIT was employed to separate overlapping regions, and then pyrolysis kinetic triplet of PF resin is calculated. With the determined apparent activation energies, the most probable mechanism functions and the corresponding pre-exponential factor, the model agrees well with the experimental data.
The hydrophobic surface on aluminum alloy fabricated by anodizing and polymeric coating. Display omitted
► Anodizing and polymeric coating were used to prepare a superhydrophobic surface on aluminum ...alloy. ► Superhydrophobic surfaces with a high water contact angle of 162° and a low rolling angle of 2° were obtained. ► The method is facile, and the materials are inexpensive, and is expected to be used widely.
We reported the preparation of the superhydrophobic surface on aluminum alloy via anodizing and polymeric coating. Both the different anodizing processes and different polymeric coatings of aluminum alloy were investigated. The effects of different anodizing conditions, such as electrolyte concentration, anodization time and current on the superhydrophobic surface were discussed. The results showed that a good superhydrophobic surface was facilely fabricated by polypropylene (PP) coating after anodizing. The optimum conditions for anodizing were determined by orthogonal experiments. When the concentration of oxalic acid was 10g/L, the concentration of NaCl was 1.25g/L, anodization time was 40min, and anodization current was 0.4A, the best superhydrophobic surface on aluminum alloy with the contact angle (CA) of 162° and the sliding angle of 2° was obtained. On the other hand, the different polymeric coatings, such as polystyrene (PS), polypropylene (PP) and polypropylene grafting maleic anhydride (PP-g-MAH) were used to coat the aluminum alloy surface after anodizing. The results showed that the superhydrophobicity was most excellent by coating PP, while the duration of the hydrophobic surface was poor. By modifying the surface with the silane coupling agent before PP coating, the duration of the superhydrophobic surface was improved. The morphologies of the superhydrophobic surface were further confirmed by optical microscope (OM) and scanning electron microscope (SEM). Combined with the material of PP with the low surface free energy, the micro/nano-structures of the surface resulted in the superhydrophobicity of the aluminum alloy surface.
This study aimed to obtain a high yield and purity of Sargassum pallidum polyphenol extracts (SPPE) and study its enzyme activity. Fresh Sargassum pallidum seaweed was selected for optimization of ...ultrasound-assisted extraction (UAE) conditions and purification conditions using macroporous resin and Sephadex LH20 to obtain SPPE. The SPPE was characterized using UPLC-QTOF-MS/MS and α-amylase, α-glucosidase, tyrosinase, and AchE inhibitory activity were determined. The maximum extraction rate of SPPE was 7.56 mg GAE/g and the polyphenol purity reached 70.5% after macroporous resin and Sephadex LH-20 purification. A total of 50 compounds were identified by UPLC-QTOF-MS/MS. The IC50 values of SPPE were 334.9 μg/mL, 6.290 μg /mL, 0.834 mg /mL and 0.6538 mg /mL for α-amylase, α-glucosidase, tyrosinase and AchE, respectively. Molecular docking technology further revealed the effects of SPPE on the above enzymes. This study provided information on the potential hypoglycemic, whitening and anti-Alzheimer's disease biological activities of SPPE, which had guiding significance for the purification and development of other seaweed polyphenols.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Deep eutectic solvents (DES) doping is an important method to realize the preparation and modification of PEDOT:PSS films in aqueous solution, but there is no systematic research focusing on its ...action mechanism in polymerization process. A series of in-situ characterizations were conducted to investigate the effect of DES doping on properties and structure. The UV–Vis spectra indicated the DES doping can strengthen the π−π* stacking interaction and conjugation stabilization of PEDOT:PSS, and then lead to stronger photovoltaic conversion ability. The in situ FTIR spectra revealed the hydrogen bonds were incorporated into the polymer chain during polymerization process. The CV and SEM analysis results suggested that DES doping delayed passivation nucleation stage of PEDOT:PSS film in the thickness direction and remained a stable polymerization rate. The XPS spectra of S 2p proved DES doping decrease the interaction between PEDOT and PSS. Comprehensive experiments demonstrate that the structure-induced effects of DES can trigger structural reorganization in line conformation of PEDOT:PSS/DESs. It is structure-induced effects of DES that delays passivation nucleation stage in polymerization and improves the optical absorption contrast, maximum current density and some other properties efficently.
