• Proceedings of the SCSK Conference
• /
• 1999.10a
• /
• pp.65-74
• /
• 1999

We have studied the stability of W/O high internal phase emulsions(HIPE) containing water, cetyl dimethicone copolyol and oils varying magnesium sulfate in the range 0 to 0.5wt% and oil polarities, respectively. The rheological consistency was mainly destroyed by the coalescence of the deformed water droplets. The greater the increase of concentrated modulus was, the less coalescence occurred and the more consistent the concentrated emulsions were. The increasing pattern of complex modulus versus volume fraction has been explained with the resistance to coalescence of the deformed interfacial film of water droplets in concentrated W/O emulsion. The stability is dependent on: (i) the choice of the oil is important, the requirements coincide with the requirements for the formation of the rigid liquid crystalline phases :5; and (ii) addition of salts the aqueous phase opposes the instability due to coalescence:. Increasing the salt concentration increases the refractive index of the aqueous phase. It lowers the difference in the refractive index between the oil and aqueous phases. This decreases the attraction between the water domains, thus increasing the stability.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1998.06a
• /
• pp.95-95
• /
• 1998

• Applied Chemistry for Engineering
• /
• v.22 no.1
• /
• pp.37-44
• /
• 2011

The critical micelle concentration (CMC) of sorbitan laurate SP 20 surfactant in this paper was near $7.216{\times}10^{-4}mol/L$ and the surface tension at CMC was about 26.0 mN/m, which showed higher CMC and lower surface tension than those of octylphenol ethoxylate octylphenol ethoxylate (OPE) 10 surfactant. Dynamic surface tension measurement using a maximum bubble pressure tensiometer showed that the adsorption rate at the interface between air and surfactant solution was found to be slower with SP 20 surfactant, presumably due to a low mobility of SP 20 surfactant monomer. The contact angle of SP 20 surfactant solution was observed to decrease with an increase in surfactant concentration and showed a larger value than that of OPE 10 surfactant solution. Half-life time for foams generated with 1 wt% surfactant solution was also larger with SP 20 surfactant, which indicated higher foam stability with SP 20 surfactant. Dynamic behavior study reveals that the solubilization of n-decane oil was much lower with SP 20, which is in good agreement with experimental results of foam stability, contact angle and CMC. Dynamic interfacial tension measurement by a spinning drop tensiometer shows that interfacial tensions at equilibrium condition in both systems were almost the same but the time required to reach equilibrium was longer with SP 20.

• Applied Chemistry for Engineering
• /
• v.32 no.3
• /
• pp.260-267
• /
• 2021

In this study, a carboxylate-based anionic surfactant SLEC-3 was prepared from coconut oil and the structure was elucidated by using FT-IR, ¹H-NMR and ¹³C-NMR analysis. Measurements of interfacial properties such as critical micelle concentration, static and dynamic surface tensions, emulsification index, and foam stability have shown that SLEC-3 is better in terms of interfacial activity and more effective in lowering interfacial free energy than those of SLES, which has been widely used as a conventional anionic surfactant in the detergent industry. Biodegradability, acute oral toxicity and dermal irritation tests also revealed that SLEC-3 surfactant possesses excellent mildness and low toxicity, indicating the potential applicability in detergents and cleaner products formulation.

• Korean Journal of Materials Research
• /
• v.26 no.12
• /
• pp.751-756
• /
• 2016

Graphite was diffusion-bonded by hot-pressing to W-25Re alloy using a Ti interlayer. For the joining, a uniaxial pressure of 25 MPa was applied at $1600^{\circ}C$ for 2 hrs in an argon atmosphere with a heating rate of $10^{\circ}C\;min^{-1}$. The interfacial microstructure and elemental distribution of the W-25Re/Ti/Graphite joints were analyzed by scanning electron microscopy (SEM). Hot-pressed joints appeared to form a stable interlayer without any micro-cracking, pores, or defects. To investigate the high-temperature stability of the W-25Re/Ti/Graphite joint, an oxy-acetylene torch test was conducted for 30 seconds with oxygen and acetylene at a 1.3:1 ratio. Cross-sectional analysis of the joint was performed to compare the thickness of the oxide layer and its chemical composition. The thickness of W-25Re changed from 250 to $20{\mu}m$. In the elemental analysis, a high fraction of rhenium was detected at the surface oxidation layer of W-25Re, while the W-25Re matrix was found to maintain the initial weight ratio. Tungsten was first reacted with oxygen at a torch temperature over $2500^{\circ}C$ to form a tungsten oxide layer on the surface of W-25Re. Then, the remaining rhenium was subsequently reacted with oxygen to form rhenium oxide. The interfacial microstructure of the Ti-containing interlayer was stable after the torch test at a temperature over $2500^{\circ}C$.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.12
• /
• pp.2227-2238
• /
• 2000

The interfacial features of suspension system made of $CaCO_3$ particles have been investigated for the purpose of designing its effective treatment process. For the examination of variation of electrokinetic potential as a function of pH. the value of potential was observed to shift in the negative direction, which was thought to be due to the adsorption of hydroxide ion on the particle surface. Adsorption of surfactant on suspended particles resulted in the change of surface charge and shift in electrokinetic potential, which was dependent upon the sign of head charge and concentration of surfactant. Addition of inorganic salts affected stability of suspension greatly and sedimentation rate of suspension was influenced by the electric valence and amount of ions produced by dissolution of inorganic coagulants. DLVO theory made it possible to construct a energy profile diagram and a close correlation was found between experimental result and theoretically derived consequences. Non-specific adsorption of indifferent electrolyte resulted in the compression of electrical double layer and specific adsorption induced the shift of IEP and PZC in the opposite direction.

• Journal of the Korean Magnetics Society
• /
• v.3 no.4
• /
• pp.305-309
• /
• 1993

Thermal stability of Co/Cu artificial superlattice (AS) prepared by RF-magnetron sputtering and the effect of low temperature annealing on the magnetoresistance of the AS have been investigated in this work. Dependence of annealing behavior on the Cu spacer thickness, Fe underlayer thickness, and kind of the underlayer was examined and the relationship between the interfacial reaction and magnetoresistance was studied. It turned out that when Co/Cu AS was annealed at low temperature ($<450^{\circ}C$), the magnetoresistance could increase in the case of AS with thick spacer Cu ($20~25\AA$) layer, whereas it decreased in the case of AS with thin spacer Cu ($7\AA$) layer, which of the former is in contrast with previous reports and the latter in consistent with them. The increase of magnetoresistance is due to increase of interfacial atomic sharpness, which is supported by low angle X-ray diffraction analysis. The thermal stability of Co/Cu AS was better in the case of thick Fe underlayered AS. Interfacial reaction (separation of intermixed Co and Cu) could be observed at lower temperature for (200)-textured samples than for (111)-textured samples, which can be interpreted in terms of interdiffusion kinetics depending on the crystallographic orientation.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.5
• /
• pp.644-654
• /
• 2003

An analytical solution for a vertically stratified viscous flow in a microchannel with a rectangular cross-section is constructed, assuming fully developed laminar flow where the interfaces between the fluid layers are flat. Although the solution is for n-layer flow, restricted results to symmetrical three-layer flow are presented to investigate the effects of the viscosity and thickness ratios of the fluid layers and the aspect ratio of the microchannel on the flow field. Relations between the flow rate and thickness ratios of the fluid layers with varying viscosity distributions are found, considering the cross -sectional velocity profiles which vary noticeably with the three parameters and differ significantly from the velocity profiles of the flow between infinite parallel plates. Interfacial instability induced by the viscosity stratification in the microchannel is discussed referring to previous studies on the instability analysis for plane multilayer flow. Exact solution derived in the present study can be used for examining a diffusion process and three -dimensional stability analysis. More works are needed to formulate the equations including the effects of interfacial' tension between immiscible liquids and surface wettability which are important in microscale transport phenomena.

• Composites Research
• /
• v.26 no.1
• /
• pp.54-59
• /
• 2013

This study deals with effect of plasma treatment on the properties of unidirectional ligno cellulosic fabric Hildegardia Populofolia (HDP) fabric. Thermal stability of the fabric was determined by differential scanning calorimetry (DSC) and Thermo gravimetric analysis (DSC). Morphological properties was analyzed by SEM analysis and found that the surface was rough upon plasma treatment which provides good interfacial adhesion with matrix during composite fabrication. Thermal stability and mechanical properties of the plasma treated fabric slightly increases compare to alkali and untreated fabric. It was observed that tensile properties of the fabric increases upon plasma treatment due to the formation of rough surface. SEM analysis indicates formation of rough surface on plasma treatment which helps in increasing the interfacial interaction between the matrix (hydrophobic) and fabric (hydrophilic).

• Journal of the Korean Society of Clothing and Textiles
• /
• v.21 no.3
• /
• pp.632-640
• /
• 1997

Changes in surface properties and detergency of sunactant mixtures were investigated in order to study the optimum mixing ratio of anionic and nonionic surfactants by measuring surface tension, interfacial tension, suspendability, and emulsification as a Amction of mixing ratio. Also, surface tension and detergency of the surfactant mixtures were determined with the increase of water-hardness or temperature. The results were as follows: the addition of NPE to anionic surfactant solutions (LAS or SDS) by 0.1 mole fraction remarkably decreased surface tension. NPE (n=15)/anionic surfactant mixtures showed a synergistic effect in lowering interfacial tension and emulsification, but NPE (n=7.5)/anionic surfactant mixtures did not. In suspension stability, however, synergism appeared when LAS or 505 was mixed with both of NPE's. With respect to the hydrophile of NPE, NPE (n=15) was more effective than NPE (n=i.5) in improving suspension stability. Detergency of LAS/NPE mixture changed almost linearly with mixing ratio, but that of SDS/NPE mixture increased remarkably by the addition of 0.1 or 0.2 mole fraction of NPE at all temperatures. As the temperature increased, surface tension of surfactant mixtures decreased and detergency was improved, but their synergistic effect decreased. In hard water, the mixtures showed better detergency than single surfactuant solutions.