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Crystallization Studies (crystallization + studies)
Selected AbstractsFormation of High-Quality, Epitaxial La2Zr2O7 Layers on Biaxially Textured Substrates by Slot-Die Coating of Chemical Solution PrecursorsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2007Sung-Hun Wee Crystallization studies were performed of epitaxial La2Zr2O7 (LZO) films on biaxially textured Ni,3at.%W substrates having thin Y2O3 (10 nm) seed layers. LZO films were deposited under controlled humid atmosphere using reel-to-reel slot-die coating of chemical solution precursors. Controlled crystallization under various processing conditions has revealed a broad phase space for obtaining high-quality, epitaxial LZO films without microcracks, with no degradation of crystallographic texture and with high surface crystallinity. Crack-free and strong c -axis aligned LZO films with no random orientation were obtained even at relatively low annealing temperatures of 850°,950°C in flowing one atmosphere gas mixtures of Ar,4% H2 with an effective oxygen partial pressure of P(O2),10,22 atm. Texture and reflection high-energy electron diffraction analyses reveal that low-temperature-annealed samples have strong cube-on-cube epitaxy and high surface crystallinity, comparable to those of LZO film annealed at high temperature of 1100°C. In addition, these samples have a smoother surface morphology than films annealed at higher temperatures. Ni diffusion rate into the LZO buffer film is also expected to be significantly reduced at the lower annealing temperatures. [source] Morphology and thermal properties of a PC/PE blend with reactive compatibilizationPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2007Bo Yin Abstract Reactive compatibilization of immiscible polymers is becoming increasingly important and hence a representative study of a polycarbonate/high density polyethylene (PC/HDPE) system is the focus of this paper. A grafted copolymer PC- graft -ethylene- co -acrylic acid (PC- graft -EAA) was generated as a compatibilizer in situ during processing operation by ester and acid reaction between PC and ethylene-acrylic acid (EAA) in the presence of the catalyst dibutyl tin oxide (DBTO). As the polyethylene (PE) matrix does not play any part during the synthesis of the copolymer and since PC and EAA are also immiscible, to simplify the system, the influence of this copolymer formation at the interface between PC and EAA on rheological properties, phase morphology, and crystallization behavior for EAA/PC binary blends was first studied. The equilibrium torque increased with the DBTO content increasing in EAA/PC blends on Haake torque rheometer, indicating the in situ formation of the graft copolymer. Scanning electron microscopy (SEM) studies of cryogenically fractured surfaces showed a significant change at the distribution and dispersion of the dispersed phase in the presence of DBTO, compared with the EAA/PC blend without the catalyst. Differential scanning calorimetry (DSC) studies suggested that the heat of fusion of the EAA phase in PC/EAA blends with or without DBTO reduced with the formation of the copolymer compared with pure EAA. Then morphological studies and crystallization behavior of the uncompatibilized and compatibilized blends of PC/PE were studied as functions of EAA phase concentration and DBTO content. Morphological observations in PC/PE blends also revealed that on increasing the EAA content or adding the catalyst DBTO, the number of microvoids was reduced and the interface was intensive as compared to the uncompatibilized PC/PE blends. Crystallization studies indicated that PE crystallized at its bulk crystallization temperature. The degree of crystallinity of PE phase in PC/PE/EAA blends was also reduced with the addition of EAA and DBTO compared to the uncompatibilized blends of PC/PE, indicating the decrease in the degree of crystallinity was more in the presence of PC- graft -EAA. Copyright © 2007 John Wiley & Sons, Ltd. [source] Analytical Techniques for Nucleation Studies in Lipids: Advantages and DisadvantagesJOURNAL OF FOOD SCIENCE, Issue 9 2004M. Cerdeira ABSTRACT: Crystallization is generally considered a 2-step process. The 1st step, nucleation, involves the formation of molecular aggregates with a critical size great enough to become stable. During the 2nd step, nuclei grow and develop into crystals. Distinguishing between nucleation and growth constitutes a major challenge in lipid crystallization studies. Thus, it is of great importance to discuss the information obtained from the different techniques that are usually used to study nucleation behavior such as nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), rheological techniques, light-scattering techniques such as turbidimetry and scanning diffusive light scattering (SDLS), polarized light microscopy (PLM), and laser polarized optical sets such as laser polarizedlight turbidimetry (LPLT). Techniques to describe the nucleation process must be very sensitive to disregard growth. When crystallization is followed by methods such as DSC, NMR, and rheological measurements, at times, small amounts of crystals are present in the melt before any solids are detected. Clearly, at this stage, well beyond the induction time for nucleation (,), these methods are measuring crystal growth. Techniques of low sensitivity for solid fat contents lower than 0.1% must not be used to evaluate nucleation effects. Sensitive turbidimeters with detectors that saturate below 0.3% solid fat content give good results as do scanning diffusive light-scattering equipment. Although the PLM technique is sensitive enough for these kinds of studies, an understanding of important basic concepts is essential. Laser optical sets are the most appropriated methods to study nucleation in fats systems. [source] Density Fluctuations during the Early Stages of Polymer Crystallization: An OverviewMACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2008Jimmy Baert Abstract The present work provides a critical review of polymer crystallization studies using SALS; experimental methods, analysis techniques, observations and their relations with respect to other techniques are discussed. Furthermore, the fact that nucleation might be accompanied by large scale density fluctuations has been investigated for the flow-induced crystallization of iPB. SALS was applied to measure density and orientation fluctuations, whereas complementary results were obtained from optical microscopy. The observations from both crystallization and melting experiments seem to indicate that the detected density fluctuations result from the presence of weakly anisotropic structures, rather than being an indication of densification before the onset of crystallization. [source] Polypropylene/Clay nanocomposites: Effect of compatibilizer on the thermal, crystallization and dynamic mechanical behaviorPOLYMER ENGINEERING & SCIENCE, Issue 9 2002Sangeeta Hambir Polypropylene (PP)/clay nanocomposites are prepared using different grades of PP, compatibilizers, and organically modified clays. The melt intercalation of the PP is carried out in presence of a compatibilizer. The nanocomposites are characterized using various techniques for the structure and properties. X-ray diffraction results indicate well-defined structures. Thermogravimetric analysis indicates improved thermal stability of PP/clay nanocomposites. Isothermal crystallization studies carried out using differential scanning calorimeter illustrate enhanced crystallization of PP in all the nanocomposites. Optical microscopic study demonstrates that the nanocomposites can be crystallized at higher temperatures, exhibiting well-defined birefringent structures. The dynamic mechanical analysis reveals higher storage moduli over a temperature range of ,400C to 1200C for nanocomposites, and the extent of increase in the storage modulus is dependent on the type of compatibilizer used. [source] Image-based crystal detection: a machine-learning approachACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2008Roy Liu The ability of computers to learn from and annotate large databases of crystallization-trial images provides not only the ability to reduce the workload of crystallization studies, but also an opportunity to annotate crystallization trials as part of a framework for improving screening methods. Here, a system is presented that scores sets of images based on the likelihood of containing crystalline material as perceived by a machine-learning algorithm. The system can be incorporated into existing crystallization-analysis pipelines, whereby specialists examine images as they normally would with the exception that the images appear in rank order according to a simple real-valued score. Promising results are shown for 319,112 images associated with 150 structures solved by the Joint Center for Structural Genomics pipeline during the 2006,2007 year. Overall, the algorithm achieves a mean receiver operating characteristic score of 0.919 and a 78% reduction in human effort per set when considering an absolute score cutoff for screening images, while incurring a loss of five out of 150,structures. [source] | |||||||||||||