Papers by Keyword: Contact Angle

Abstract: To investigate the wetting behavior of unsized carbon fibers with a sizing dispersion and the wettability of sized fibers with the liquid polymeric resin, contact angle measurements by capillary rise experiments are performed by tensiometry. First, the sizing behavior of fibers with different degrees of surface activation is analyzed. Increasing activation levels result in increasing oxygen surface concentrations and accordingly increasing polar components of the surface energies. These conditions result in a better wettability of the higher activated fibers. Secondly, the influence of the type of sizing dispersion is addressed by using two water-based epoxy sizing dispersions, i.e. a standard epoxy sizing and an advanced functional epoxy sizing with high reactivity. Using the functional sizing the wettability is further improved. Finally, the influence of the sizing on the wettability of the carbon fibers by the matrix polymer during resin infiltration is investigated using the differently sized fibers and a liquid epoxy resin. Carbon fibers with functional sizing show improved wettability by the resin compared to fibers with standard sizing. The results show that the wetting behavior of carbon fibers with respect to sizing and polymer matrix can be controlled by a suitable choice of surface activation of the fibers and reactivity of the polymeric sizing dispersion.

Abstract: The dimension stone industry produces large amount of residue. An alternative to reduce this environmental liability is to apply as glaze in coating ceramic. This research is about the wettability between glaze and red ceramic, applying the sessile drop method. The waste and additives were mixed, pressed, and put over red ceramic plate previously sintered. The system was heated until the melting point of the glaze and the contact angle decreasing was measured in function of the temperature, and in a function of the time at 750 °C and 800 °C. The minimum contact angle value was near 6 ° at 994 °C in the testing changing the temperature, and presents 19 ° and 10 °, respectively, at 750 °C and 800 °C, when the time was varied. The longitudinal section of the samples was analyzed using optical microscopy, showing physical wettability in all testing. This glaze presents good wettability on red ceramic with potential as coating ceramic.

Abstract: This work deals with the determination of basic waterproofing properties of nanofiber textiles with basis weights of up to 30 g/m². Samples used in this experiment were made from nanofiber textiles based on two polymers – PVDF and PUR. Each polymer was prepared in three basis weights. All samples were not treated prior to testing. One of the key properties was the contact angle of water and the resistance to penetration of liquid water. Water-resistance of nanofiber textiles was tested according to the harmonized European standard EN 13859-1., Underlays for discontinuous roofing in pitched roof constructions are tested according to this standard. In the position of underlays there has to be some layer with low diffusion resistance of water vapor and relatively high waterproofing. We suppose such properties of nanofiber textiles. Testing of the two groups of material basis shows correlation between the contact angle and water-resistance of the nanofiber textile.

Abstract: Presented work deals with the surface treatments and its effect on micro fibers using as randomly dispersed reinforcement in many types of composite materials. Cool oxygen plasma was used to surface wettability modification of chopped glass fibers having diameter equal to 14 μm. Plasma treatments were carried out at three different times of exposition equal to 4 min, 8 min and 16 min. The influence of executed treatments was observed by the horizontal direct optical method enabling static contact angle measurements on micro fibers which were submerged in a distilled water. The identified differences between the contact angles size of original fibers and the treated fibers were equal to several tens of percent.

Abstract: This work focuses on capillary-induced collapse of high-aspect-ratio silicon nanopillars. Modification of the surface chemistry is demonstrated to be an efficient approach for reducing capillary forces and consequently reduce pattern collapse. Special effort is spent on determination of the wetting state of chemically modified surfaces as complete structure wetting is of utmost importance in wet processing. In light of this, an ATR-FTIR based method has been developed to unambiguously distinguish between wetting and non-wetting states.

Abstract: A rapid repair process of plasma damaged SiCOH in combination with post-etch residue removal has been developed. The carbon depletion layer caused by plasma dry etching was repaired by subsequent surface modifying SAM treatment, which resulted in replenishment of carbon not only on the surface but also a few nm toward the bulk. This repairing technique provides a high-quality hydrophobic surface under conditions of low temperature and short process time. In addition, the SAM layer can be expected to act as an adhesion promotor with metal materials.

Abstract: Nanoweb fabricated by electrospinning has a large specific area and a small pore size which can be controlled through a spinning process to enable a strong adsorption and selective permeability. It is required to produce nanofiber of different polymer mixture with a limited miscibility for improvement of physical, chemical, or biological properties. In this study, poly (vinyl alcohol) (PVA)/polyurethane (PU) nanofibers were produced by coaxial electrospinning. PVA (core)/PU (shell) nanofibers were defect-free and had a uniform thickness. The pseudo core/shell structure of PVA/PU nanofibers was confirmed by transmission electron microscopy. The presence of PVA and PU in the nanofibers was identified by ¹³C solid state nuclear magnetic resonance spectroscopy, fourier transform infrared spectroscopy, and X-ray diffraction analysis. Water contact angle was reduced by incorporation of PVA in a core of PU nanofiber. For variety of biomedical applications, bioactive substances such as antibiotics and proteins can be incorporated in a core of hydrophobic PU nanofiber by coaxial electrospinning of water-soluble polymer/bioactive substance mixture.

Abstract: The effect of substrate surface roughness on the wettability of SAC237 (Sn 99.9%, Ag 0.3%, Cu 0.7%) with difference percentage of CNT on copper substrate was investigated. Solder paste of SAC 237 without CNT, 0.01% and 0.04% of CNT were reflowed at 270°C on different surface roughness of Cu substrate (abrasive number 240, 400, 600, 800). Contact angle of soldered samples measured by Infinite Focus Microscope (IFM). As a result, contact angle value of investigated solders range 7° to 20°. Contact angle obtained decreases with the increasing surface roughness of Cu substrate. This demonstrates that rougher substrate enhance the wettability of the solders. Addition of CNT also effects the wettability of investigated solders. Higher composition of CNT show better wettability.

Abstract: This paper reported the investigation on gallium, Ga addition into In-4.8Zn lead-free solder to improve its wettability performances. The effect of addition of Ga in In-4.8Zn solder alloy was studied. The results show with the addition of 0.5% Ga into the In-4.8Zn composition, the spreading area of In-4.8Zn-0.5Ga solder on copper increase between 35.71 and 43.75 %. Hence, as the spreading area increases, the contact angle decreased from between 22.09 to 39.71 %. Additionally, the addition of Ga as dopant increased the thickness of IMCs layer.

Abstract: The wetting behavior and the interaction at the liquid-solid interface are significant in preparation of metallic glass composite. In this paper, the wetting behavior and the interfacial interaction between Ti_32.8Zr_30.2Ni_5.3Cu₉Be_22.7 (denoted as ZT3) bulk metallic glass (BMG) alloy melt and Ti6Al4V (denoted as TC4) substrate at different temperatures were investigated using sessile drop method. The results show that ZT3 alloy melt wetted the substrate well. With the increase of temperature, the droplet spread out rapidly and then came to equilibrium gradually. The equilibrium contact angle under 1273 K stabilized at about 15°. Dendrite phase generated at the interface during the wetting progress. The composition of the interface product transformed from Ti_69.8Zr_24.2Al_2.2V₁Cu_2.8 to Ti_73.6Zr_15.3Al₅V_2.7Cu_2.6Ni_0.8 with the temperature rising from 973 K to 1273 K. Meanwhile, the dissolution of the TC4 substrate increased with increasing the temperature.