Papers by Keyword: Hydrophobicity

Abstract: We report the fabrication of porous hydrophobic flat sheet membranes composed of polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP), which is incorporated with graphene (GNP) concentrations of (0.2, 0.5, and 0.8 wt.%) as the hydrophobic filler. FTIR, XRD, and SEM results were used to analyze the composites' functional groups, crystallinity and surface morphology. The water contact angles were 116 ±1.2°; 120 ±0.9°; 126 ±0.7°; 130 ±0.6° for pristine, 0.2 wt%, 0.5 wt%, and 0.8 wt% of GNP membranes, respectively. Moreover, the graphene incorporation enhanced the fabricated polymer's ultimate tensile strength (UTS). The UTS was as follows 2.4±0.01, 5.43±0.02, 7.485±0.015 and 6±0.01MPa for pristine, 0.2 wt% GNP, 0.5 wt% GNP and 0.8 wt% GNP respectively. The highest UTS was (7.485 ±0.015 MPa) for the 0.5 wt% GNP. Graphene incorporation (0.5 wt%) enhanced the membranes’ porosity (78 ±1.9%). This study explored the effect of graphene to improve the flat sheet membranes' mechanical strength, hydrophobicity, and porosity, which can then be applied in desalination using membrane distillation to mitigate clean water shortages and crises.

Abstract: The use of additive manufacturing by fused deposition is a versatile, cost-effective and simple prototyping and manufacturing technique that is generating and accelerating a revolution in equipment and filaments. However, materials are limited to a small number of polymers. It is a scientific challenge to bring new characteristics and properties to the parts obtained. In this work, a new filament has been designed with the combination of PLA (poly lactic acid) as matrix and PTFE (polytetrafluoroethylene) as filler. This filament has improved the water repellency of the parts obtained. Cleaning, demoulding, anti-adherence, anti-frost, anti-humidity and anti-bacterial applications can be deployed with this new filament. Extruded filaments have been obtained with PLA beads and PTFE micropowder. Flat test tubes have been produced with this filament. The experiments included PTFE fillers (1% to 40% by weight). The surfaces have been characterised by sliding angle (SA) and static contact angle (CA) tests, surface roughness (Sa and Sz), flatness error and % water adsorption. The results indicate, as expected, that the higher the fluoropolymer content, the higher the hydrophobicity, reaching values of 125° for CA and 9° for SA, and the % adsorption decreases. In terms of roughness, the surfaces are less rough when the PTFE load increases. On the other hand, the flatness is a property strongly affected by the % PTFE load and at values higher than 15% it produces intense warping and deformation of the specimens. Finally, the PTFE loading thresholds in the PLA matrix have been obtained below which the wettability and dimensional reproduction properties are balanced and optimal.

Abstract: Polylactidacid (PLA) is a type of bio-based and bio-degradable plastic. This substance is commonly used in the medical field since it is biocompatible and does not hurt bodily tissues. In this study, PLA plastic will be combined with chitosan (CS) via injection molding. The addition of CS to compensate for the absence of PLA with hydrophobic characteristics. CS has hydrophilic characteristics, which allow it to absorb water and bond with biological tissues. The contact angle test revealed that pure PLA is a hydrophobic material, but the PLA: CS alloy is a hydrophilic alloy.

Abstract: The photovoltaic panel is one of the most promising advancements when it comes to sustaining energy. However, being exposed to extreme and harmful atmospheric conditions can decrease its efficient transmittance. Therefore, an anti-reflective coating is added to a PV panel to provide different promising properties for the PV panel. It is used to reduce the reflection of light for more efficient transmittance. It can also possess several properties like hydrophobic self-cleaning and abrasion resistance when further modified. With these properties, PV panels become more effective and maintain their high transmission for a long time. Different materials are used in fabricating ARCs, but this review focused on silica due to its low refractive index of 1.52 using the dip-coating fabrication technique. This review focused on introducing additives such as CTAB, PMHS, and PDMS and their effects on the hydrophobicity and abrasion resistance of ARCs. Moreover, studies gathered for each additive were analyzed and compared to determine the advantages and disadvantages of each additive. Insights and perspectives were also given by focusing on the factors affecting the hydrophobicity and abrasion resistance of ARCs which may help future researchers to fabricate more efficient ARCs.

Abstract: The plasma nitriding conditions and processing parameters were controlled to attain the high-density nitrogen ion and NH-radical populations and to form the nitrogen supersaturated layer into AISI420 type martensitic stainless steel mold substrate at 673 K for 14.4 ks and 28.8 ks. Thicker nitrided layer than 80 mm was attained for fine machining of the optical diffraction elements onto this nitrided AISI420 mold surface. The average hardness in this nitrogen supersaturated layer reached 1400 HV. After this hardness testing and microstructure analysis, the machinability test was performed to describe the ductile mode cutting behavior of nitrogen-supersaturated work by using the PCD (Poly-Crystalline Diamond)-chip tool. Higher average nitrogen solute content than 4 mass% was responsible for fine turning by PCD-chip and CVD (Chemical Vapor Deposition)-diamond coated cutting tools without any damages and for precisely finishing the mold surface with the lower maximum surface roughness than 10 nm on the machined mold surface. The low roughness and homogeneous machined surface profile proved that the nitrogen supersaturated AISI420 series stainless steel was adaptive as a stamping mold of chalcogenide glasses with high dimensional accuracy and demolding capacity.

Abstract: The common reed, Phragmites australis, is a plant species quite similar to the currently used bio-based aggregates and available on most continents. The purpose of this work is to characterise this common reed and compare its properties to other plants already studied for building use. This study presents the different properties focussing on Phragmites australis chemical composition, hydrophobicity nature and how this character could be explained. To that end, wettability and also water adsorption measurements were carried out on plant flour and aggregates in comparison to miscanthus, wood and hemp shiv properties. Formulations based on reeds of different origins and using different binders (lime and earth) were tested in compression and with thermal conductivity measurements in order to evaluate the behaviour of the reed as a material for building use.

Abstract: In this research, pure silica powder has been synthesized from the sand of the Bangka-Belitung Islands. Natural sand is extracted with permanent magnets and immersed with HCl to obtain pure silica, followed by coprecipitation and calcination processes at a temperature of 900 °C for 10 hours. The final result of the synthesis process is pure silica powder in the cristobalite phase (83.03% wt) and the tridymite phase (16.97% wt). The synthesized silica powder is used as a modification on topcoat of steel to increase the hydrophobicity of steel plate surface so that it can reduce the rate of corrosion. Steel plate has been painted by using the brush painting method and consists of three layers, namely the primary layer, midcoat and topcoat. The variation in this research is the concentration of silica powder on the topcoat of steel such as 0% wt (sample 1), 3% wt (sample 2), 6% wt (sample 3), 9% wt (sample 4), and 12% wt. (sample 5). These variations have an effect on the surface geometry of the steel plate, namely the surface gets rougher as the concentration of silica powder is mixed. The hydrophobicity of the steel plate can be seen from the measurement Water Contact Angle (WCA). The WCA using fresh water in sample first until five’th are 75,828 ̊, 90 ̊, 91,397 ̊ 96,520 ̊, and 104 ̊, respectively. While the WCA using seawater in sample first, second and fourth are 80.618 ̊, 102 ̊, and 104.56 ̊, respectively.

Abstract: Wet etching in nanometer-sized three-dimensional spaces creates new challengesbecause of the scaling of semiconductor devices with complex 3D architecture. Wet etching withinspaces is affected by the mass transport of the etchant ions that are impacted by the hydrophobicityand surface potential of surface. However, the kinetics of chemical reactions within the spaces is stillunclear.In this paper, we studied the effect of hydrophobicity and surface potential of silicon surface on SiO2etching in nanometer-sized narrow spaces by adding various additive components to etching solutions.We found that the transport of etchant ions into narrow spaces is governed by controlling thehydrophobicity and surface potential of the confined system walls.

Abstract: The developing nanotechnology is getting infiltrated into a wide area of industries. A variety of nanotextiles can be produced from different materials (e.g. polymers, SiO₂). Their applications are possible in many industrial branches as well as civil engineering. Silica-based nanotextiles can play a fundamental role in civil engineering. The potential utilization of nanotextiles in civil engineering is promising as surface protective layers. Wettability of SiO₂ nanotextiles was studied on different thicknesses of samples and were tested under static conditions by determination of the water contact angle. Their water contact angle, which indicates the degree of wetting, was measured using an optical tensiometer.

Abstract: New materials based on oligooxidridsilmethylensiloxysilane nanostructured with ethyl ester of orthosilicic acid – tetraethoxysilane have been studied in the research. Tetraethoxysilane introduction into the composition is supposed to cause its decomposition up to nanoparticles of silicon oxide. The alkoxysilane hydrolytic destruction kinetics and the impact of the composition and nature of the polymer composition components on the physical properties have been studied. Atomic force microscopy was used to study the structurization kinetics of the polymer composition. The composition hydrophobicity was determined by the edge wetting angle. To study the adhesion characteristics of the obtained material, the method of disc separation from the substrate has been used. The relative rigidity has been determined by a pendulum device M3. Atomic force microscopy revealed the presence of nanoscale neoplasms (at average of one hundred twenty per one square micrometer) in diameter from two to five nanometers in the surface structure of the composition, modified with tetraethoxysilane. Herewith the physical properties of the material change: rigidity increases, the edge angle of wetting increases as well. The studied nanostructured compositions can also be applied. For example – they can be used as a protective coating with a set of special properties, such as high hydrophobicity.