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Amorphous Component (amorphous + component)
Selected AbstractsOutcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 2, 3, 4, synthetic bauxite, natural granodiorite and pharmaceuticalsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2002Nicola V. Y. Scarlett The International Union of Crystallography (IUCr) Commission on Powder Diffraction (CPD) has sponsored a round robin on the determination of quantitative phase abundance from diffraction data. The aims of the round robin have been detailed by Madsen et al. [J. Appl. Cryst. (2001), 34, 409,426]. In summary, they were (i) to document the methods and strategies commonly employed in quantitative phases analysis (QPA), especially those involving powder diffraction, (ii) to assess levels of accuracy, precision and lower limits of detection, (iii) to identify specific problem areas and develop practical solutions, (iv) to formulate recommended procedures for QPA using diffraction data, and (v) to create a standard set of samples for future reference. The first paper (Madsen et al., 2001) covered the results of sample 1 (a simple three-phase mixture of corundum, fluorite and zincite). The remaining samples used in the round robin covered a wide range of analytical complexity, and presented a series of different problems to the analysts. These problems included preferred orientation (sample 2), the analysis of amorphous content (sample 3), microabsorption (sample 4), complex synthetic and natural mineral suites, along with pharmaceutical mixtures with and without an amorphous component. This paper forms the second part of the round-robin study and reports the results of samples 2 (corundum, fluorite, zincite, brucite), 3 (corundum, fluorite, zincite, silica flour) and 4 (corundum, magnetite, zircon), synthetic bauxite, natural granodiorite and the synthetic pharmaceutical mixtures (mannitol, nizatidine, valine, sucrose, starch). The outcomes of this second part of the round robin support the findings of the initial study. The presence of increased analytical problems within these samples has only served to exacerbate the difficulties experienced by many operators with the sample 1 suite. The major difficulties are caused by lack of operator expertise, which becomes more apparent with these more complex samples. Some of these samples also introduced the requirement for skill and judgement in sample preparation techniques. This second part of the round robin concluded that the greatest physical obstacle to accurate QPA for X-ray based methods is the presence of absorption contrast between phases (microabsorption), which may prove to be insurmountable in some circumstances. [source] Isothermal Crystallization Kinetics of Poly(, -caprolactone) with Tetramethyl Polycarbonate and Poly(styrene- co -acrylonitrile) Blends Using Broadband Dielectric SpectroscopyMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 11 2006Samy A. Madbouly Abstract Summary: Phase behavior and isothermal crystallization kinetics of poly(, -caprolactone) (PCL) blends with tetramethyl polycarbonate (TMPC) and poly(styrene- co -acrylonitrile) with 27.5 wt.-% acrylonitrile content have been investigated using broadband dielectric spectroscopy and differential scanning calorimeter. An LCST-type phase diagram has been observed for PCL/SAN blend while all the different blend compositions of PCL/TMPC were optically clear without any phase separation structure even at high temperatures up to 300,°C. The composition dependence of Tgs for both blends has been well described by the Gordon-Taylor equation. The phase diagram of PCL/SAN was theoretically calculated using the Flory-Huggins equation considering that the interaction parameter is temperature and composition dependent. The equilibrium melting point of PCL depressed in the blend and the magnitude of the depression was found to be composition dependent. The interaction parameters of PCL with TMPC and SAN could not be calculated from the melting point depression based on Nishi-Wang approach. The isothermal crystallization kinetics of PCL and in different blends was also investigated as a function of crystallization temperature using broadband dielectric spectroscopy. For pure PCL the rate of crystallization was found to be crystallization temperature (Tc) dependent, i.e., the higher the Tc, the lower the crystallization rate. The crystallization kinetics of PCL/TMPC blend was much slower than that of PCL/SAN at a constant crystallization temperature. This behavior was attributed to the fact that PCL is highly interacted with TMPC than SAN and consequently the stronger the interaction the higher the depression in the crystallization kinetics. It was also attributed to the different values of Tg of TMPC (191,°C) and SAN (100,°C); therefore, the tendency for crystallization decreases upon increasing the Tg of the amorphous component in the blend. The analysis of the isothermal crystallization kinetics was carried out using the theoretical approach of Avrami. The value of Avrami exponent was almost constant in the pure state and in the blends indicating that blending simply retarded the crystallization rate without affecting the crystallization mechanism. Dielectric constant, ,,, of pure PCL, blends of PCL/TMPC,=,80/20 and PCL/SAN,=,80/20 as a function of crystallization time at 47,°C and 1 kHz. [source] The role of Raman microspectroscopy in the study of black gloss coatings on Roman potteryJOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2005Francesca Ospitali Abstract Raman microspectroscopy was adopted for the study of black gloss coatings on Roman pottery, found in Rimini (northern Italy) and in Suasa, near Ancona (central Italy), dated second century B.C. This non-destructive technique allowed a very accurate analysis of the crystalline and amorphous components of thin surface layers. The investigated coating is black, homogeneous and glazed, without any crystals, becoming red on approaching to the ceramic body. Magnetite and carbon are the main phases of the black zones, whereas hercynite, quartz, silicates and haematite are the secondary components. In the red zones, approaching the ceramic body, the amount of haematite increases and the amount of magnetite decreases. The presence of carbon, on the surface only, confirms the hypothesis of a firing cycle in a partial reducing atmosphere. Copyright © 2004 John Wiley & Sons, Ltd. [source] Effects of SBS on phase morphology of iPP/aPS blendsPOLYMER ENGINEERING & SCIENCE, Issue 10 2000The supermolecular structure of binary isotactic polypropylene/poly(styrene- b -butadiene- h -styrene) (iPP/SBS) and isotactic polypropylene/atactic polystyrene (iPP/aPS) compression molded blends and that of ternary iPP/aPS/SBS blends were studied by optical microscopy, scanning and transmission electron microscopy, wide-angle X-ray diffraction and differential scanning calorimetry. Nucleation, crystal growth, solidification and blend phase morphology are affected by the addition of amorphous components (SBS and aPS). As a compatiblizer in immiscible iPP/aPS blends, SBS formed interfacial layer between dispersed honeycomb-like aPS/SBS particles and the iPP matrix, thus influencing the crystallization process in iPP. The amount of SBS and aPS, and compatibilizing efficiency of SBS, determine the size of dispersed aPS, SBS, and aPS/SBS particles and, consequently, the final blend phase morphologies: well-developed spherulitic morphology, cross-hatched structure with blocks of sandwich lamellae and co-continuous morphology. The analysis of the relationship between the size of spherulites and dispersed particles gave the criterion relation, which showed that, in the case of a well-developed spherulitization, the spherulites should be about fourteen times larger than the incorporated dispersed particles; i.e. to be large enough to engulf dispersed inclusions without considerable disturbing of the spherulitic structure. [source] | |||||||||||||