Papers by Keyword: Hydrophilicity

Abstract: In this study, an organically modified montmorillonite (OMMT) hydrophilic clay was incorporated in PSf through non-solvent induced phase separation fabrication process to improve its properties. Afterwards, hand casting was done and the PSf/OMMT membranes produced were characterized to determine the effect of OMMT addition to its structural, mechanical and thermal properties, and hydrophilicity. Scanning electron microscope (SEM) images of the surfaces showed a denser surface as the OMMT content increases but the pores on the images were not pronounced unlike the SEM images of the cross-section which depicted spherical macrovoids for 1.0% while wider macrovoids were observed for 3.0% and 5.0% OMMT. The mechanical properties of the nanocomposite with clay content up to 3.0% were improved. The glass transition temperatures of the PSf/OMMT nanocomposites were lower than the pure PSf while no significant difference was observed for the melting point. By statistical analysis, the addition and variation of the clay concentrations has no significant effect to the thermal properties. The hydrophilicity of the membranes improved with the increasing OMMT concentration, but was found to be insignificant. The overall data gathered showed that the clay addition had improved characteristics compared to the pure PSf membrane, which implies that PSf/OMMT nanocomposite could be likely used in filtration applications.

Abstract: Investigations of microarc calcium phosphate (CaP) boehmite-containing biocoatings on the pure titanium (Ti) alloy were presented. There were discovered relationships of coating properties (morphology, elemental and phase composition, zeta-potential, wettability) on the boehmite deposition parameters. A variation of the modification parameters of boehmite nanoparticles deposition allowed producing hydrophilic boehmite-containing CaP coatings with the roughness of 2.2-3.1 μm and nanoscale morphology. The influence of boehmite nanoparticles on the surface zeta-potential of the coating was found.

Abstract: This paper reports studies to investigate the relationships between hydrophobicity of biochar surface and soil water retention. The studied biochars were produced from acacia wood, cashew wood and bamboo. The resulting materials were oxidized via liquid oxidation to generate hydrophilic biochars containing oxygenated functional groups on the surface. All biochars were characterized and their ability as soil additives to enhance water retention was assessed. Our results suggest that hydrophobicity/hydrophilicity of biochars is not the major factor governing water retention ability of this particular soil. However, hydrophilicity of biochar helps improve soil permeability by providing better wettability to the soil.

Abstract: The surface modification of microarc calcium phosphate coatings by boehmite nanoparticles deposition was studied. The powder of aluminium nitride AlN was deposited on the microarc calcium phosphate coatings, and then the hydrolysis reaction was initiated. The boehmite (AlO(OH)) was formed as a result of the reaction. The influence of boehmite nanoparticles deposition on the properties of calcium phosphate microarc coatings (i.e. the morphology, elemental and phase composition, wettability) was studied. Experimental results show that the introduction of boehmite nanoparticles affects the surface morphology and wettability of the coating.

Abstract: Polytetrafluoroethylene (PTFE) membrane, with high resistances to acid, alkali and other chemical corrosion, is the ideal filter material in water treatment, which can be used in a variety of harsh environment. However, the hydrophobictity of PTFE membrane limits its wide application in water treatment. Thus, the hydrophilic modification of PTFE membrane attracts much attention. In this work, the microporous PTFE membrane was treated by a novel strategy for enhancing its hydrophilicity. The pristine microporous PTFE membrane was modified by assembly of fluorocarbon surfactant. The structure and morphology of the membranes were characterized by attenuated Fourier Transform Infrared spectroscopy (ATR-FTIR) and scanning electron microscope (SEM). The variation of wettability was evaluated by the change of water contact angle (WCA). And the influences of the concentration of fluorocarbon surfactant and modification time on PTFE WCA were also investigated as well. The WCA of the pristine PTFE membrane is 156°. After modified by 5.0 g/L of fluorocarbon surfactants, the WCA reduced to 4.3°, indicating that the hydrophobic PTFE membrane was transformed into a hydrophilic one. FTIR and SEM results indicated that there were hydrophilic groups, such as carbonyl (-C=O) and hydroxyl (–OH) existing on the surface of PTFE membrane after modification. And WCA of the hydrophilic membrane showed a slight increase from 4.3°to 8° after a week, indicating that the hydrophilic PTFE membrane exhibiting a persistent durability.

Abstract: An electrical sheet resistance and water contact angle of titanium dioxide nanoparticle thin films were prepared by sparking process. The experiments were carried out by the titanium wires as electrodes of sparking process and varied the sparking time of 1-4 h and the annealing temperature of 200-400 ^OC for 2 h. The as-deposited and as-annealed of thin films on glass substrate were measured a water contact angle and a sheet resistance whereas a surface was analyzed by a scanning electron microscopy. The results found that the optimum as-deposited TiO₂ NP thin films was shown the homogeneity surface, the minimum sheet resistance and the duplicate water contact at the sparking time of 3 h. The optimum as-deposited TiO₂ NP thin films was annealed which the water contact angle and the sheet resistance of the as-annealed TiO₂ NP thin films decreased with increasing the annealing temperature. However, the hydrophilic property was shown optimum at the annealing temperature of 400 ^OC.

Abstract: Bio-absorbable materials have been strongly needed in bone regenerative surgery. β-TCP ceramics have been widely used as bone tissue scaffold materials, due to their bio-compatibility and bio-degradation. The aims of this study are to estimate blood permeation into different porous β-TCP blocks (75% and 67% in porosity), and to evaluate the behaviors of the 75% porous β-TCP block in rat subcutaneous tissue and sheep iliac bone defect by histological observation and 3-dimensional (3D) imaging analysis by μ-CT. The 75% β-TCP block revealed better performance in blood permeation than the 67% β-TCP in a dish including 3ml of sheep blood at 2 and 10 minutes. Almost area of the 75% β-TCP block turned to red at 10 minutes. In rat subcutaneous tissue, the bulk region of the 75% β-TCP was stained with HE. TRAP-positive multinucleated giant cells appeared on the surface of bulk at 4 weeks. In sheep iliac bone defect (10×15×9 mm³) model, μ-CT showed bone ingrowth into almost pores of the 75% β-TCP block at 2 months, and the block was absorbed and replaced by new bone until 4 months. The block was reduced to one-third in horizontal length and from 10 mm to 4 mm in vertical length at 2 months by 3D images. Body fluid stained by HE was found in the bulk region. We believe the body fluid permeation inside the bulk of the 75% porous β-TCP should contribute to the initial cell adhesion, proliferation and differentiation, and its biodegradation. It was concluded that the super porous β-TCP block with hydrophilic property might be a biological scaffold, harmonized with bone remodeling.

Abstract: The transparent nanosized TiO₂ film was fabricated by a layer-by-layer assembly method starting from the highly dispersed anatase oppositely charged TiO₂ nanoparticles without using anypoly electrolytes. The positively charged TiO₂ nanoparticles (ca.7 nm) and negatively charged TiO₂ nanoparticles (ca.7 nm) were synthesized by a subsequently hydrothermal process. Field-emission scanning electron microscopy, UV-vis transmittance spectra and Contact angle measurement were employed to characterize TiO₂films.By the treatment of 500°C for 2hrs, the nanostructured TiO₂ film showed a water contact angle of below 10°andthe relative transmittance to quartz glass of over 90%.

Abstract: The influence of the microarc oxidation parameters as electrical voltage and process duration on the surface morphology and topography, wettability and chemical composition of calcium phosphate coatings on the low elastic module Ti-40mas.%Nb (Ti-40Nb) alloy surface has been investigated. The linear growth of thickness and roughness and the linear decrease of the free surface energy with increasing process electrical voltage have been obtained. It was shown that calcium phosphate coatings have low contact angle with liquids and high free surface energy, as a consequence. It indicates a high hydrophilicity. X-ray diffraction analyses showed that the coatings after deposition have X-ray amorphous state that indicates high rate of coating dissolution. The coatings have maximum Ca/P ratio is 0.6. The optimal range of the oxidation voltage from 200 to 250 V and process duration from 5 to 10 min has been found. Such parameters allow to form the coating with the specific morphology, roughness and thickness and high hydrophylicity.

Abstract: In this study, surface modification of stainless steel flat plates was performed using nanoscale bilayers assembly method to increase the surface’s hydrophilicity and enhance evaporation. Thin layers of SiO₂ nanoparticles layered onto the stainless steel surfaces were used to modify their surface properties, and the relationship between the number of layers (0~20) and water’s hydrophilicity (surface tension) was investigated. The effects of modification on evaporation were then tested using de-ionized water. According to experimental results, surface modification was able to reduce the contact angle of water on stainless steel flat plate from the unmodified 87o to 7o at 18 layers, significantly increasing the hydrophilicity of the surface. Evaporation experiments show that the evaporation heat transfer enhancement for droplets on stainless steel plates is at least 300%.Keywords: bilayers assembly, hydrophilicity, surface modification, evaporation performance