纳米二氧化硅包覆颜料黄的研究

采用静电自组装技术成功地将纳米二氧化硅粒子包覆在颜料黄的表面.研究结果表明,预吸附的聚电解质层数显著影响纳米二氧化硅的吸附量.随着包覆二氧化硅层数的增加,覆盖率逐渐增加,但包覆三层二氧化硅后,覆盖趋于平衡.吸附的纳米二氧化硅不仅可以提高颜料黄的亲水性,而且还能够散射紫外线,尤其是波长小于270nm的紫外线,提高了颜料黄的耐候性,同时又不影响颜料黄本身的颜色.     

Molecular investigation of water adsorption on graphene and graphyne surfaces

In this paper the adsorption action of a water droplet on the graphene and graphyne externals has been examined. Conclusions received from the calculation of the water contact angle on the graphene and the graphynes surfaces have demonstrated that graphyne is more hydrophobic than graphene. Sketching the contour maps of the water interaction showed different behaviors of water droplet on these surfaces. The results show that water molecules, form a sub_layer of water on the graphyne substrate while this sub_layer does not exist on the graphene. Molecular investigations of the water on the surfaces show that the attendance of a sub_layer of water on the substrate can cause changes, such as the number of hydrogen bonds per water molecule in the water droplet, the order of molecules in different layers of water droplet, and parallel forces to the surface between surface water molecules and substrate, in the structural properties of water droplet. In this study the interaction between first layer and sub-layer of water was investigated. Water drops on surface can affect on the behavior of water sub-layer.     

Investigation on femtosecond laser irradiation energy in inducing hydrophobic polymer surfaces

This study investigates the use of ultrashort femtosecond laser pulses to induce hydrophobic properties on PMMA surfaces. The modification of surface wetting property exhibits a strong dependence on the amount of energy deposited on the PMMA surface. A simple equation has been deduced from the laser parameters to express the energy deposition. It was revealed that water contact angle (WCA) of more than 120°, with a maximum of around 125°, could be achieved when the total energy deposited per unit area on the PMMA surface ranged from 600 J/cm² to 900 J/cm² at an energy deposition rate of around 50 J/cm²/s. Beyond this range, WCA reduced with increasing amount of energy deposition. Furthermore, with higher energy deposition rate or higher laser fluence, total energy required to induce hydrophobic surfaces was reduced. Under different energy deposition, the quantity of polar groups or non-polar groups induced was responsible for the changes in WCA and thus the different surface hydrophobicity.     

Controllable wettability of poly(ethylene terephthlate) film modified by oxygen combined inductively and capacitively coupled radio-frequency plasma

Poly(ethylene terephthalate) (PET) film was modified by using oxygen combined inductively coupled radio-frequency plasma (ICP) and capacitively coupled radio-frequency plasma (CCP) at the radio-frequency (RF) power of 200 W and 100 W, respectively, for a treatment time up to 300 s. The RF plasma modification under the combined ICP and CCP mode with the controllable oxygen plasma density and oxygen ion-flux energy significantly improved the wettability of PET film, due to the creation of the polar functional groups containing oxygen, such as C-O and O-CO, and the increase of the surface roughness. At a low surface roughness, the polar functional groups on the PET film affected both the advancing contact angles and receding contact angles. When the surface roughness increased over a threshold, the advancing contact angles mainly depended on the polar functional groups, and the receding contact angles were particularly dependent on the surface roughness. Therefore, the controllable advancing contact angles and receding contact angles on the plasma-modified PET film were independently determined by plasma functionalization and plasma etching under the combined ICP and CCP mode.     

Investigating the effect of different asphaltene structures on surface topography and wettability alteration

This paper aims at investigation of the effect of asphaltene structure on wettability and topography alteration of a glass surface as a result of asphaltene precipitation. In order to provide a better insight into the topography alteration, a bi-fractal approach was employed. Such an approach is capable of discriminating topography alteration in two different surface types, namely, macro-asperities and micro-asperities. The observed variation of the fractal dimension in the two surface types could be considered as the consequence of different asphaltene sources. Therefore, the structure of different asphaltene sources was carefully examined. The effect of asphaltene structure is more pronounced for asphaltene precipitation at higher pressure. It was revealed that asphaltene particles of high complexity and with larger poly-aromatic rings tend to be detached easier at higher pressure than those with smaller poly-aromatic rings. Another evidence to emphasize the significance of asphaltene structure was given through wettability alteration. It was found that asphaltene particles with larger poly-aromatic rings turn the surface less oil wet at higher pressure. It seems that the difference in wetting condition and surface topography alteration of different asphaltene sources roots in their different structures.     

Growth of hierarchical based ZnO micro/nanostructured films and their tunable wettability behavior

Hierarchical zinc oxide (ZnO) micro/nanostructured thin films were grown onto as-prepared and different annealed ZnO seed layer films by a simple two step chemical process. A cost effective successive ionic layer adsorption and reaction (SILAR) method was employed to grow the seed layer films at optimal temperature (80 °C) and secondly, different hierarchical based ZnO structured thin films were deposited over the seed layered films by chemical bath deposition (CBD). The influence of seed layer on the structural, surface morphological, optical and wettability behavior of the ZnO thin films were systematically investigated. The XRD analysis confirms the high crystalline nature of both the seed layer and corresponding ZnO micro/nanostructured films with a perfect hexagonal structure oriented along (0 0 2) direction. The surface morphology revels a complex and orientated hierarchical based ZnO structured films with diverse shapes from plates to hexagonal rod-like crystal to tube-like structure and even much more complex needle-like shapes during secondary nucleation, by changing the seed layer conditions. The water contact angle (WCA) measurements on hierarchical ZnO structured films are completely examined to study its surface wettability behavior for its suitability in future self-cleaning application. Photoluminescence (PL) spectra of the ZnO structured film exhibit UV and visible emissions in the range of 420-500 nm. The present approach demonstrates its potential for low-temperature, large-scale, controlled synthesis of crystalline hierarchical ZnO nanostructures films.     

Wettability of ZnO: A comparison of reactively sputtered; thermally oxidized and vacuum annealed coatings

We have studied the wettability of sputter deposited ZnO, thermally oxidized Zn-ZnO and vacuum annealed ZnO coatings. The X-ray diffraction patterns showed the formation of hexagonal-wurtzite structure of ZnO, which was further confirmed by micro-Raman spectroscopy data. The X-ray photoelectron spectroscopy data indicated that the sputter deposited ZnO coatings were more stoichiometric than thermally oxidized Zn-ZnO and vacuum annealed ZnO coatings. The wettability measurements indicated that water contact angles of 158.5° and 155.2° with sliding angles of 2° and 4° were achieved for thermally oxidized Zn-ZnO and vacuum annealed ZnO coatings, respectively. The superhydrophobicity observed in thermally oxidized Zn-ZnO and vacuum annealed coatings is attributed to the nanorod cluster like morphology along with the presence of high fraction of micron scale air pockets. The water droplet on such surfaces is mostly in contact with air pockets rather than solid surface, leading to high contact angle. Whereas, the sputter deposited ZnO coatings exhibited a maximum water contact angle of 110.3°. This is because the sputter deposited ZnO coatings exhibited a densely packed nanograin-like microstructure without any air pockets. The work of adhesion of water was very low for thermally oxidized Zn-ZnO (5.06 mJ/m²) and vacuum annealed ZnO coatings (6.71 mJ/m²) when compared to reactively sputtered ZnO coatings (90.41 mJ/m²). The apparent surface free energy (SFE) for these coatings was calculated using Neumann method and the SFE values for sputter deposited ZnO, thermally oxidized Zn-ZnO and vacuum annealed ZnO coatings were 32.95, 23.21 and 18.78 mJ/m², respectively.     

Modifications of roughness and wettability properties of metals induced by femtosecond laser treatment

Topographic and wetting properties of AISI 316L stainless steel and Ti-6Al-V alloys were modified via linearly polarized femtosecond laser pulse irradiation. In order to induce a gradual evolution of the surface topography and wettability, four samples of each alloy were irradiated with different number of pulses. From the topographic point of view, a multi-scale morphology made of nano- and micro-periodic ripples was induced. The increase in the number of pulses led to the appearance of a third scale structure of waviness that is due to the laser scanning. The wettability of alloys was changed from a hydrophilic behavior to a hydrophobic one without lowering surface energies by chemical coatings. The apparent contact angle (CA) increased with increasing the number of pulses. A rise of about 50° of the apparent CA of the Ti-6Al-V was noticed.     

Surface modification of PDMS using atmospheric glow discharge polymerization of tetrafluoroethane for immobilization of biomolecules

In this study an atmospheric glow discharge with a fluorocarbon gas as precursor was used to modify the surface of polydimethyl siloxane (PDMS -[(CH₃)₂SiO]_n-). The variation in protein immobilizing capability of PDMS was studied for different times of exposure. It was observed that the concentration of proteins adsorbed on the surface varied in an irregular manner with treatment time. The fluorination results in the formation of a thin film of fluorocarbon on the PDMS surface. The AFM and XPS data suggest that the film cracks due to stress and regains its uniformity thereafter. This Stranski-Krastanov growth model of the film was due to the high growth rate offered by atmospheric glow discharge.     

Thermally switchable thin films of an ABC triblock copolymer of poly(n-butyl methacrylate)-poly(methyl methacrylate)-poly(2-fluoroethyl methacrylate)

The thermo-responsive behavior of polymer films consisting of novel linear triblock copolymers of poly(n-butyl methacrylate)-poly(methyl methacrylate)-poly(2-fluoroethyl methacrylate) (PnBuMA-PMMA-P2FEMA) are reported using differential scanning calorimetry (DSC), atomic forcing microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contacting angle (CA) measurements. The surface morphology, wettability and chemical structure of thin films of these triblock copolymers on silicon wafers as a function of temperature have been investigated. It has been shown that the wettability of the films is thermally switchable. Detailed structural analysis shows that thermo-responsive surface composition changes are produced. The underlying mechanism of the thermoresponsive behavior is discussed.