Papers by Keyword: Phase Separation

Abstract: In this paper, we prepared an octadecyltrichlorosilane(OTS) super-hydrophobic film using phase separation method to demonstrate the anti-icing property of super-hydrophobic surfaces. We investigated the super-hydrophobicity of the surface in -5°C environment, as well as the icing process of water droplets on the surface which proceeded at the temperature low to -15°C. We found that the prepared OTS film retained its super-hydrophobicity in the -5°C environment by the measurement of contact angle. It was observed that the icing progress of water droplets on the super-hydrophobic surface was greatly retarded. Based on the classical heterogeneous nucleation theory, it concluded that the ice formation is directly related to the surface wettability. This research would be beneficial to the preparation of anti-icing films.

Abstract: The chitosan (CS) /poly-L-lactic (PLLA) acid blend scaffolds were prepared by two kinds of blend solutions through immersion precipitation phase inversion method. CS/PLLA blend scaffold was fabricated by mixing the CS-HAc solution and PLLA-DMF solution, CSP/PLLA blend scaffold was fabricated by mixing chitosan powder (CSP) and PLLA-DMF solution. The results revealed that CS content in CSP/PLLA scaffold was 126 times higher than that in CS/PLLA scaffold. The difference of CS content made the structures of CS/PLLA scaffold and CSP/PLLA scaffold exhibit an obvious discrepancy, which resulted from the different thermodynamics and phase separation behavior of two blend solutions. CS/PLLA scaffold with a higher porosity took on an unsymmetrical structure with a compact upper surface and a porous cross-section containing the fingerlike macrovoids, while CSP/PLLA scaffold displayed a symmetrical structure with a porous upper surface and the sponge-like cross-section. WVTR and equilibrium swelling of CSP/PLLA blend scaffold were higher than that of CS/PLLA blend scaffold. WAXD analysis revealed that PLLA and CS did not crystallize in the course of CS/PLLA scaffold formation, while there were the diffraction peaks of PLLA and CS in the CSP/PLLA scaffold.

Abstract: Tungsten silicides intermetallic compound (WSi₂) was synthesized in-situ by self-propagating high temperature synthesis-casting of WO₃-Si-Al system in Ar gas environment. It is proposed that the extent of phase separation between oxide ceramic and intermetallic compound depends on the reaction temperature that made a lower viscosity and longer lifetime of the melted. The effects of inert gas pressure on densification of the intemetallic product were investigated.

Abstract: High purity nanoporous silica was fabricated using Shirasu volcanic ash as a starting material. The starting materials were placed into a platinum crucible and were melted at 1400°C. A mother glass was formed by quenching the melt in pure water. Leaching was performed by immersing the mother glass into an HCl solution. Nonsilica phases formed by phase separation in the mother glass were leached out with acid solution. The obtained porous silica was more than 99% pure and had pore size smaller than 2 nm. In order to control the pore size, post heat treatment was performed. The pore size could be controlled from 3.1 to 21.7 nm by changing the post treatment temperature.

Abstract: Understanding the evaporation and combustion mechanisms of single droplets of gel propellant is the first stage to predict the burning characteristics in the combustion chamber. This paper, taking into account convection heat for freely falling gelled fuel droplets under normal gravity conditions, as well unsteady mass diffusion and thermal diffusion inside droplet, a theoretical model was developed to understand mass and heat transport mechanisms, and bubble growth within the gel droplet during processes of droplet combustion. The results show that at the first stage, shrinkage of the radius obeys the d2-law; steep temperature gradient and fuel mass concentration gradient appear within droplet, especially region near droplet surface. At the second stage, liquid fuel near the gellant layer within droplet starts to boiling, gellant layer formation resist the vaporizing fuel gas flow to extent; the vapor region appears between gellant layer and vaporizing surface within the droplet, and the droplet expands, swells, the layer thickness decreases until it ruptures.

Abstract: Phase separation of the poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester(PCBM) active layer (ATL) was investigated by varying their relative ratio in the organic solar cells (OSCs).With the help of the UV/visible spectrophotometer, optical microscopy and scanning electron microscope,we found that the cluster of PCBM at the interface or surface was affected by Al cathode, the composition of the blends and thermal annealing. The disc-like shape crystals of PCBM substituted for the needle-like ones at higher PCBM compositions at the ATL/Al interface, which led to stronger contacts and bigger contact area. It could make short circuit current density increase, but may affect the blend morphology and result in parallel resistance and open circuit voltage decreased with the PCBM ratio increasing from 40 to 60%. The microstructure of the P3HT:PCBM ATL, determined by the composition dependent phase separation, supported the optimized performance of the OSCs with the composition of 40–50% PCBM.

Abstract: Phase diagram of aqueous two-phase system (ATPS) composed of polyethylene glycol (PEG) and gelatin is of paramount importance for the application of such system in microencapsulation of bioactive compounds. Phase separation of PEG/gelatin aqueous solution was investigated in the present work and the phase diagram of resultant ATPS was reported for the first time. The results show that phase separation will happen if the solid content of PEG/gelatin aqueous solution is higher than a critical value, resulting in an ATPS. The resultant ATPS consists of a low-density phase enriched in PEG and a dense phase enriched in gelatin. The phase compositions of the resultant ATPS were determined accurately using the method developed. The phase diagrams obtained show that higher solid content is required for the phase separation of PEG10,000/gelatin aqueous solution when compared with that of PEG20,000/gelatin one. And PEG is found to be more hydrophilic when compared with gelatin.

Abstract: The H₂SO₄ phase and HI_x phase solution produced from Bunsen reaction section in SI (Sulfur-iodine) process were supplied to the phase separator for the continuous operation of SI process. However, the separation of Bunsen products in the phase separator is difficult because an excess of HI_x phase solution existed in the phase separator than the H₂SO₄ phase solution. Therefore, the additional supply of H₂SO₄ to the phase separator as the phase separation method was considered for improvement of phase separation efficiency. In this work, the variations in volume ratio and composition of each phase solution were examined after the Bunsen product mixing on the HI_x phase/H₂SO₄ phase volume ratio. As the results, the variation in composition of products increases with increase of the HI_x phase/H₂SO₄ phase volume ratio after mixing. It was also found that the high variations in composition and volume ratio of Bunsen products by mixing in the presence of excess HI_x phase. From the results, we concluded that the phase separation method, additional supply of H₂SO₄ phase solution to the phase separator, is effective in Bunsen product separation when the variation in composition is little.

Abstract: The Sulfur-Iodine thermochemical hydrogen production process (SI process) has been focused as one of the most promising method for hydrogen production by water splitting. SI process consists of three sections as follow; (1) Bunsen reaction, (2) H₂SO₄ decomposition and (3) HI decomposition. The O₂ produced in a H₂SO₄ decomposition section could be supplied directly to the Bunsen reaction section without additional separation. Meanwhile, the reactant solution supplied to a Bunsen reaction section could be supplied as the type of a HI_x (I₂ + HI + H₂O) solution, since only the separation of I₂ in a HIx solution recycled from a HI decomposition section is very difficult. Therefore, we carried out the reaction using SO₂ and SO₂-O₂ mixture gases in presence of the HI_x solution to identify the effect of O₂ in the Bunsen reaction. From the results, the amount of I₂ unreacted under the feed of SO₂-O₂ mixture gases was very small higher than those under the feed of SO₂ gas only, while the amount of HI produced was relatively decreased. In addition, the amount of impurities in each phase produced from the Bunsen reaction with the HIx solution was hardly affected by the O₂/SO₂ molar ratios.

Abstract: Phase separation of the poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester(PCBM) active layer (ATL) was investigated by varying their relative ratio in the organic solar cells (OSCs).With the help of the UV/visible spectrophotometer, optical microscopy and scanning electron microscope,we found that the cluster of PCBM at the interface or surface was affected by Al cathode, the composition of the blends and thermal annealing. The disc-like shape crystals of PCBM substituted for the needle-like ones at higher PCBM compositions at the ATL/Al interface, which led to stronger contacts and bigger contact area. It could make short circuit current density increase, but may affect the blend morphology and result in parallel resistance and open circuit voltage decreased with the PCBM ratio increasing from 40 to 60%. The microstructure of the P3HT:PCBM ATL, determined by the composition dependent phase separation, supported the optimized performance of the OSCs with the composition of 40–50% PCBM.