Papers by Keyword: Phase Separation

Abstract: Nano-hydroxyapatite/polyamide66 (n-HA/PA66) composite scaffolds are prepared using phase separation and phase separation in combination with particle leaching, and both the composite powder and paste are used as starting materials. The composite is characterized by IR and XRD. The micro-architecture of the scaffolds is observed by SEM, and the mechanisms that the formation of the porous structure follows have been investigated preliminarily. The results show that scaffold prepared by phase separation in combination with particle leaching method using composite powder as starting material possesses controllable porosity and interconnectivity, as well as good mechanical strength comparable to human cancellous bone, suitable for being the tissue-engineered scaffold for load-bearing bone repair. Furthermore, scaffold made by phase separation using composite paste as starting material exhibits an anisotropy both in morphology and mechanical properties, which indicates the potential of guiding cell seeding, distribution and new tissue formation in preferential direction.

Abstract: Organic-inorganic hybrid monoliths with well-defined macropores and/or mesopores have been synthesized by a sol-gel process accompanied by polymerization-induced phase separation. Using aklyltrialkoxysilanes and alkylene-bridged alkoxysilanes, two different categories of organo-siloxane networks have been characterized in view of macroporoisity based on phase separation as well as mesoporosity based on supramolecular templating by surfactants. The alkyl-terminated polysiloxane network exhibited substantial surface hydrophobicity together with the mechanical flexibility. On the other hand, the alkylene-bridged network behaved much more similarly to those prepared from tetraalkoxysilanes with regard to surface hydrophilicity, mechanical rigidness and mesopore-forming ability. Supramolecular templating of mesopores embedded in the gel skeletons comprising well-defined macroporous network has proven to give wide variety of hierarchically designed macro-mesoporous organic-inorganic hybrid materials.

Abstract: Ga0.81In0.19As0.14Sb0.86 layers were grown on (100)-Te doped GaSb substrates 2º missoriented towards (110), (111)A and (111)B directions by metalorganic vapour deposition (MOVPE) at 540 °C. X-ray reciprocal space maps done in symmetric (224) and asymmetric (115) directions show a super-lattice structure due to the phase separation with a 5 nm period and independent of substrate orientation. The x-ray maps show different stage of relaxation of the films and in same cases an interdiffusion region near the substrate. Despite of the phase separation, channelling experiments with H ions as projectiles showed a good quality of the films. Channelling experiments show that the crystalline quality gets worse with increasing the In and As concentration.

Abstract: MZFC, MFC magnetizations, χac susceptibility and resistance measurements have been carried out for various polycrystalline compounds of (AA’)(BB’)O3 perovskites with A = La, (Nd,Y); B = Mn,Co; A’ = Sr,Ca and B’= Fe, Ti. Analyses have been done to elucidate the metallic ferromagnetism (FM) established by Double Exchange interaction between B+3 ion and the B+4 ion that is induced by the substitution of A’ for A. It is shown that there is no ‘pure’ FM ordering existing in the compounds, in other words the materials consist of a FM and a non-FM phase. In case when the latter is an AFM phase, the coexistence and competition of the two phases result in spin-glass like appearances. Such phenomena have been observed in several compounds of both single- and/or mixed-element at B site. The studies on substitution of Mn for Co in La0.7Sr0.3Co1- yMnyO3 show no DE interaction between the two magnetic ions, which results in not only SG behavior at y = 0.1 concentration but a clear evidence on a phase separation in the high y region. An analysis of M(H,T) curves for this region suggests a structural scenario that the FM phase forms as islets (of volume fraction as small as 2.7 – 8.6%) embedded in isolating AFM matrix. For the case while B’= Ti the inhomogeneity evidence appears as an enhancement of the Low Field MagnetoResistance, which is commonly understood as an intergranular effect.

Abstract: The reaction induced phase separation aimed for the distribution of nano-structured particles has been investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) in ternary Ti-Si-N film via N+ implantation. The fabrication of Ti-20at%Si film has made on Si substrates by ion beam sputtering (IBS), and then N+ implantation with 50 keV has been conducted on these films. The selected area electron diffraction (SAED) from as-deposited film shows amorphous Ti-Si. As-deposited Ti-Si film exhibited high stability even for the heat treatment at 773K for 3600s. N+ implantation induced the direct formation of nano crystalline of fcc-TiNx within the Ti-Si film. The XPS depth profiling and chemical shift suggest that the preferential nitriding of Ti accompanied with the segregation of SiNx occurred during N-implantation.

Abstract: By paying attention to the hole-doped two-dimensional systems of antiferromagnetically (strongly) correlated electrons, we discuss the cause of hole-rich phase formation in association with phase separation. We show that the phase diagram obtained from Maxwell's construction in the plane of temperature vs. hole density is consistent with one derived from the evaluation of hole-rich and electron-rich phases in real space. We observe that the formation of a hole-rich phase is attributed to the aggregation of hole pairs induced by spin singlet pairs present in the pseudogap phase, and that the direct involvement of correlations between hole pairs is not essential for phase separation.

Abstract: Nanoparticles exhibit unusual properties in contrast with their bulk properties due to small particle size and quantum confinement. In the present work, ultrasonic velocity and density measurements have been carried out in solutions of silver nanoparticles in micellar dispersion of cetyl tri-metyl ammonium bromide, CTAB. Ultrasonic velocity measurements at different concentrations of surfactant and temperatures were carried out using Sing-Around technique, operated at 2MHz. It is observed that ultrasonic velocity and adiabatic compressibility show abnormal behaviour with increase in concentration of CTAB in the solution, indicating the existence of the phase separations in nano-colloidal solution.