CNTs grown on stainless steel mesh can dewater water–oil emulsion with 80% efficiency by blocking water droplets larger than the mesh opening due to superhydrophobicity of CNTs. Oil can penetrate ...through the mesh due to oleophilicity of CNTs. Some small water droplets can also leak through the mesh.
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► Carbon nanotubes grown on stainless steel mesh forms three-dimensional porous structures (SS-CNT meshes). ► The superhydrophobic SS-CNT meshes can dewater water–oil emulsion with 80% efficiency by blocking large water droplet. ► The superoleophilic SS-CNT meshes allow oil to leak through.
Vertically-aligned multi-walled carbon nanotubes (CNTs) were grown on stainless steel (SS) mesh by thermal chemical vapor deposition with a diffusion barrier of Al
2O
3 film. These three-dimensional porous structures (SS-CNT meshes) were found to be superhydrophobic and superoleophilic. Water advancing contact angles of 145–150° were determined for these SS-CNT meshes in air and oil (gasoline, isooctane). Oil, on the other hand, completely wet the SS-CNT meshes. This combined superhydrophobic and superoleophilic property repelled water while allowed the permeation of oil. Filtration tests demonstrated efficiencies better than 80% of these SS-CNT meshes as the filtration membranes of the water-in-oil emulsions. We have conducted quantitative analysis on the diameters of the oil droplets in both the feed emulsion and the filtrate. Then, we have evaluated the issue of water blockage and possible way to improve the filtration efficiency. Finally, the filtration and blockage mechanisms are proposed.
AbstractThe objective of this study is to evaluate the rheological properties and chemical bonding of nano-modified asphalt binders blended with nanosilica. In this study, the nanosilica was added to ...the control asphalt at contents of 4% and 6% based on the weight of asphalt binders. Superpave binder and mixture tests were utilized in this study to estimate the characteristics of the nano-modifed asphalt binder and mixture. The rotational viscosity (RV), dynamic shear rheometer (DSR), bending beam rhometer (BBR), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), asphalt pavement analyzer (APA), dynamic modulus (DM) and flow number (FN) tests were used to analyze rheological properties and chemical bonding changes of the nano-modified asphalt binder and the performance of the nano-modified asphalt mixture. In addition, the performance of nano-modified asphalt after rolling thin-film oven (RTFO) short-term and pressure-aging vessel (PAV) long-term aging was assessed as well. The dissipated work per load cycle for the asphalt binder was used to evaluate the rheological properties of the nano-modified asphalt binder. Based on the binder test results, it was found that the additional nanosilica in the control asphalt binder slightly decreased the viscosity of the control asphalt binder, maintained low dissipated work per load cycle, held a similar low-temperature performance to the control asphalt, and had a positive effect on antioxidation. From the mixture test results, the dynamic modulus and flow number of nano-modified asphalt mixtures improved, and the rutting susceptibility of nano-modified asphalt mixtures was reduced compared to the control asphalt mixture. In general, the findings from this study show that the antiaging property and rutting and fatigue cracking performance of nanosilica modified asphalt binders are enhanced, and the addition of nanosilica in the control asphalt mixture significantly improves the dynamic modulus, flow number, and rutting resistance of asphalt mixtures.
Celotno besedilo
Dostopno za:
DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
High-quality boron nitride nanotubes (BNNTs) were functionalized for the first time with water-soluble and biocompatible PEGylated phospholipid methoxy-poly(ethylene ...glycol)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N conjugates (mPEG-DSPE). We found that BNNTs can be suspended in water for more than 3 months without precipitation. By comparing the dispersion stability of mPEG-DSPE/BNNTs in various solvents and the related Hansen solubility parameters, we found that polarized and hydrogen bonds between water and the hydrophilic mPEG play important roles in maintaining stable dispersion of BNNTs and preventing aggregation of mPEG-DSPE/BNNTs in the solutions. This has led to the formation of composite films with well-dispersed BNNTs and the coating of self-assembled monolayer (SAM) BNNTs. Furthermore, the lengths of these functionalized BNNTs can be shorterned, for the first time, from >10 μm to ∼500 nm by ultrasonication. Experiments suggest that effective dispersion of BNNT in solution is necessary for such cutting, where effective energy transfer from the sonicator to nanotubes is achieved. Our results will form the basis for stable functionalization, dispersion, and effective cutting of BNNTs with water-soluble and biocompatible PEGylated phospholipid, which are important for biomedical and composite applications.
AbstractThis paper aims to investigate the viability of using swine waste binder to improve the rheological properties of bituminous asphalt binder. Due to rising bituminous asphalt binder costs, ...diminishing reserves of crude oil from which asphalt binder is derived, and the gradual paradigm shift toward more environmentally friendly and energy efficient hot-mix asphalt (HMA) mixtures, the asphalt pavement industry is exploring different sustainable alternative binders. Biobinder has the potential to partially or fully replace typical crude-based asphalt. In this paper, biobinder from swine manure is produced by thermochemical liquefaction process at 380°C and 40 MPa (approximately 400 atm) pressure in the absence of oxygen. A Superpave PG 64-22 is then modified with 5% biobinder by total weight of asphalt binder to produce the biobinder. Samples of the base asphalt binder (nonmodified PG 64-22) and samples of asphalt modified with biobinder are characterized by running the Superpave rotational viscosity (RV), dynamic shear rheometer (DSR), and the bending beam rheometer (BBR) tests. Furthermore, Fourier transform infrared (FTIR) spectroscopy investigations were used to validate the chemical bond initiations that caused changes in stiffness and viscosity of the asphalt modified with 5% biobinder from those of base asphalt binder (PG 64-22). The modification resulted in 27% decrease in viscosity of the base binder. The rolling thin film (RTFO)–aged samples of modified binder experienced a 28.9% decrease in average viscosity change when compared with the RTFO-aged samples from the base binder. Additionally, the pressure aging vessel (PAV)–aged samples of modified binder experienced a 62.9% decrease in average viscosity change when compared with the PAV-aged samples of base binder. The rotational viscosity results proved that the addition of biobinder (swine waste asphalt binder) can reduce the viscosity of the asphalt binder. Furthermore, the modified binder had lower complex moduli and phase angles compared with the base binder (based on DSR results). The BBR results indicated that biobinder had the potential to improve the thermal cracking performance of conventional asphalt binders by reducing the creep stiffness and increasing m-value. The BBR results proved that the modification of the PG 64-22 induces a one grade jump on the lower temperature side. The functional groups in typical petroleum-based asphalt binders remained unchanged after the addition of the biobinder to the PG 64-22 binder. Additionally, the FTIR spectra showed that addition of biobinder decreased the stiffness of the PG 64-22 binder through the reduction in molecular carbonyl and sulphoxide bond chains at high temperature. This research investigation provides useful rheological and morphological guidance on the use of swine waste binder as an asphalt binder and mixture modifier.
Celotno besedilo
Dostopno za:
DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
A comprehensive overview of current research progress on boron nitride nanotubes (BNNTs) is presented in this article. Particularly, recent advancements in controlled synthesis and large-scale ...production of BNNTs will first be summarized. While recent success in mass production of BNNTs has opened up new opportunities to implement the appealing properties in various applications, concerns about product purity and quality still remain. Secondly, we will summarize the progress in functionalization of BNNTs, which is the necessary step for their applications. Additionally, selected potential applications in structural composites and biomedicine will be highlighted.
For the first time, patterned growth of boron nitride nanotubes is achieved by catalytic chemical vapor deposition (CCVD) at 1200 °C using MgO, Ni, or Fe as the catalysts, and an Al2O3 diffusion ...barrier as underlayer. The as-grown BNNTs are clean, vertically aligned, and have high crystallinity. Near band-edge absorption ∼6.0 eV is detected, without significant sub-band absorption centers. Electronic transport measurement confirms that these BNNTs are perfect insulators, applicable for future deep-UV photoelectronic devices and high-power electronics.
Partially vertical aligned boron nitride nanotubes (BNNTs) on Si substrates are found to be superhydrophobic in contrast to boron nitride (BN) thin films. While the hexagonal-phase BN films are ...partially wetted by water with advancing contact angle of about 50°, partially vertically aligned BNNTs can achieve superhydrophobic state with advancing water contact angle exceeding 150°. Our results show that the pH value of water does not affect the wetting characteristics of BNNTs. Since BN is chemically inert, resistive to oxidation up to 900 °C, and transparent to visible−UV light, BNNTs could potentially be useful as self-cleaning, transparent, insulating, anticorrosive coatings under rigorous chemical and thermal conditions.
Superhydrophobic surfaces are attractive as self-cleaning protective coatings in harsh environments with extreme temperatures and pH levels. Hexagonal phase boron nitride (h-BN) films are promising ...protective coatings due to their extraordinary chemical and thermal stability. However, their high surface energy makes them hydrophilic and thus not applicable as water repelling coatings. Our recent discovery on the superhydrophobicity of boron nitride nanotubes (BNNTs) is thus contradicting with the fact that BN materials would not be hydrophobic. To resolve this contradiction, we have investigated BNNT coatings by time-dependent contact angle measurement, thermogravimetry, IR spectroscopy, and electron microscopy. We found that the wettability of BNNTs is determined by the packing density, orientation, length of nanotubes, and the environmental condition. The origins of superhydrophobicity of these BNNT coatings are identified as (1) surface morphology and (2) hydrocarbon adsorbates on BNNTs. Hydrocarbon molecules adsorb spontaneously on the curved surfaces of nanotubes more intensively than on flat surfaces of BN films. This means the surface energy of BNNTs was enhanced by their large curvatures and thus increased the affinity of BNNTs to adsorb airborne molecules, which in turn would reduce the surface energy of BNNTs and make them hydrophobic. Our study revealed that both high-temperature and UV-ozone treatments can remove these adsorbates and lead to restitution of hydrophilic BN surface. However, nanotubes have a unique capability in building a hydrophobic layer of adsorbates after a few hours of exposure to ambient air.
Effective growth of multiwalled boron nitride nanotubes (BNNTs) has been obtained by thermal chemical vapor deposition (CVD). This is achieved by a growth vapor trapping approach as guided by the ...theory of nucleation. Our results enable the growth of BNNTs in a conventional horizontal tube furnace within an hour at 1200 °C. We found that these BNNTs have an absorption band edge of 5.9 eV, approaching that of single h-BN crystals, which are promising for future nanoscale deep-UV light emitting devices.
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