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The macroscopic and microscopic melt-crystallization kinetics of poly(trimethylene terphthalate) (PTT)/poly-carbonate (PC) blends have been measured by differential scanning calorimetry (DSC), and optical microscopy (OM). The results are analyzed in terms of the Avrami equation and the Hoffman-Lauritzen crystallization theory (HL model). Blending with PC did not change the crystallization mechanism of PTT, but reduced the crystallization rate compared with that of neat PTT at the same crystallization temperature. The crystallization rate decreased with increasing crystallization temperature. The spherulitic morphology of PTT was influenced apparently by the crystallization temperature and by the addition of PC. X-ray diffraction shows no change in the unit cell dimension of PTT was observed after blending. Through the HL theory, the classical regime II →III transition was detected for the neat PTT and the blends. The nucleation parameter ([K.sub.g]), the fold-surface free energy ([σ.sub.e]), and the work of chain folding (q) were calculated. Blending with PC decreased all the aforementioned parameters compared with those of neat PTT. POLYM. ENG. SCI., 50:1036-1046, 2010. [C] 2010 Society of Plastics Engineers, INTRODUCTION Polymer blends and composites is a rapidly growing field in polymer science and have attracted a lot of attention in both the academic and industrial communities. The fact that [...]

It has been argued that for antifreeze proteins (AFPs) to stop ice crystal growth, they must irreversibly bind to the ice surface. Surface-adsorbed AFPs should also prevent ice from melting, but to date this has been demonstrated only in a qualitative manner. Here we present the first quantitative measurements of superheating of ice in AFP solutions. Superheated ice crystals were stable for hours above their equilibrium melting point, and the maximum superheating obtained was 0.44[degrees]C. When melting commenced in this superheated regime, rapid melting of the crystals from a point on the surface was observed. This increase in melting temperature was more appreciable for hyperactive AFPs compared to the AFPs with moderate antifreeze activity. For each of the AFP solutions that exhibited superheating, the enhancement of the melting temperature was far smaller than the depression of the freezing temperature. The present findings clearly show that AFPs adsorb to ice surfaces as part of their mechanism of action, and this absorption leads to protection of ice against melting as well as freezing. Gibbs-Thomson effect | ice recrystallization | irreversible binding | melting hysteresis | thermal hysteresis www.pnas.org/cgi/doi/10.1073/pnas.0909456107

Blends of poly-ζ-caprolactam (nylon6) and poly{2,6-diimi-dazo[4,5-b:4'5'-e]pyridinylene-1,4(2,5-dihydroxy) phenyl-ene} (PIPD/nylon 6) have been prepared via a controlled polymer solution crystallization method. The crystallization behavior of nylon 6 in the blends was investigated using differential scanning calorimetry (DSC), x-ray diffraction (XRD), and polarizing microscopy (PLM). The results indicated that the presence of PIPD inhibited the nucleation rate of the crystallization of nylon 6, resulting in reduction in crystallization temperature, degree of crystallinity, and the perfection of crystal. Such influence was attributed to the formation of hydrogen bonds between nylon 6 and PIPD molecules. POLYM. ENG. SCI., 50:396-401, 2010. [C]2009 Society of Plastics Engineers, INTRODUCTION A novel rigid-rod polymer was synthesized by the workers at Akzo Nobel, namely poly{2,6-diimidazo[4,5-b:4'5'-e]pyridinylene-1,4(2,5-dihydroxy) phenylene), referred as PIPD or M5 (1), PIPD possesses high modulus, high tensile strength, and [...]

We report here crystallization at long range in networks of like-charge supramolecular peptide filaments mediated by repulsive forces. The crystallization is spontaneous beyond a given concentration of the molecules that form the filaments but can be triggered by x-rays at tower concentrations. The crystalline domains formed by x-ray irradiation, with interfilament separations of up to 320 angstroms, can be stable for hours after the beam is turned off, and ions that screen charges on the filaments suppress ordering. We hypothesize that the stability of crystalline domains emerges from a balance of repulsive tensions linked to native or x-ray--induced charges and the mechanical compressive entrapment of filaments within a network. Similar phenomena may occur naturally in the cytoskeleton of cells and, if induced externally in biological or artificial systems, lead to possible biomedical and lithographic functions. 10.1126/science.1182340

ABSTRACT The ca. 1315 Ma Hosenbein massif-type anorthosite pluton (Nain, Labrador) shows complete exposure of a vertical section, described here for the first time, comprising a ~2000 m-thick Main Zone [...]

The good dispersion of functionalized multiwalled carbon nanotube (f-MWCNT) in polyamide 6,6 (PA 6,6) matrix was prepared by solution mixing techniques. The crystalline structure and crystallization behaviors of PA 6,6 and PA 6,6/f-MWCNT nanocomposites were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and polarized optical microscopy (POM) analysis. DSC isothermal results revealed that the overall isothermal crystallization rates of PA 6,6 increased as well as the activation energy of PA 6,6 extensively decreased by adding f-MWCNT into PA 6,6, suggesting that the addition of f-MWCNT probably induces the heterogeneous nucleation. The effect of f-MWCNT on the chain arrangement for the crystallization of PA 6,6/f-MWCNT nanocomposites was also discussed. POLYM. ENG. SCI., 49:2447-2453, 2009. [C] 2009 Society of Plastics Engineers, INTRODUCTION Organic/inorganic nanocomposites have attracted a lot of interest because they normally exhibit unexpected hybrid properties synergistically derived from two components. One of the most promising composite systems would be [...]

Phase transformation generally begins with nucleation, in which a small aggregate of atoms organizes into a different structural symmetry. The thermodynamic driving forces and kinetic rates have been predicted by classical nucleation theory, but observation of nanometer-scale nuclei has not been possible, except on exposed surfaces. We used a statistical technique called fluctuation transmission electron microscopy to detect nuclei embedded in a glassy solid, and we used a laser pump-probe technique to determine the role of these nuclei in crystallization. This study provides a convincing proof of the time- and temperature-dependent development of nuclei, information that will play a critical role in the development of advanced materials for phase-change memories. 9 June 2009; accepted 11 September 2009 10.1126/science.1177483

Shear-induced melting and crystallization were investigated by confocal microscopy in concentrated colloidal suspensions of hard-sphere-like particles. Both silica and polymethylmethacrylate suspensions were sheared with a constant rate in either a counter-translating parallel plate shear cell or a counterrotating cone-plate shear cell. These instruments make it possible to track particles undergoing shear for extended periods of time in a plane of zero velocity. Although on large scales, the flow profile deviated from linearity, the crystal flowed in an aligned sliding layer structure at low shear rates. Higher shear rates caused the crystal to shear melt, but, contrary to expectations, the transition was not sudden. Instead, although the overall order decreased with shear rate, this was due to an increase in the nucleation of localized domains that temporarily lost and regained their ordered structure. Even at shear rates that were considered to have melted the crystal as a whole, ordered regions kept showing up at times, giving rise to very large fluctuations in 2D bond-orientational order parameters. Low shear rates induced initially disordered Suspensions to crystallize. This time, the order parameter increased gradually in time without large fluctuations, indicating that shear-induced crystallization of hard spheres does not proceed via a nucleation and growth mechanism. We conclude that the dynamics of melting and crystallization under shear differ dramatically from their counterparts in quiescent suspensions.

Protein crystallization is of strategic and commercial relevance in the post-genomic era because of its pivotal role in structural proteomics projects. Although protein structures are crucial for understanding the function of proteins and to the success of rational drug design and other biotechnology applications, obtaining high quality crystals is a major bottleneck to progress. The major means of obtaining crystals is by massive-scale screening of a target protein solution with numerous crystallizing agents. However, when crystals appear in these screens, one cannot easily know if they are crystals of protein, salt, or any other molecule that happens to be present in the trials. We present here a method based on Attenuated Total Reflection (ATR)-FT-IR imaging that reliably identifies protein crystals through a combination of chemical specificity and the visualizing capability of this approach, thus solving a major hurdle in protein crystallization. ATR-FT-IR imaging was successfully applied to study the crystallization of thaumatin and lysozyme in a high-throughput manner, simultaneously from six different solutions. This approach is fast as it studies protein crystallization in situ and provides an opportunity to examine many different samples under a range of conditions.

In this work, in situ Raman spectroscopy is applied in a quantitative manner to crystal suspensions during crystallization in order to monitor a solvent-mediated polymorph transformation without the use of a calibration model. Assuming a linear dependency of the Raman signal intensity on the solute and on the solid concentrations of both solid-state forms, the measured time-resolved Raman spectra are fitted directly using a detailed model that describes the time evolution of the process. The applicability of this novel method is demonstrated thoroughly through the application to synthetic data of unseeded and seeded transformations as well as to various seeded polymorph transformation experiments. The resulting concentration profiles show a good agreement with the concentrations obtained by a multivariate calibration model. Additionally, the estimated kinetic parameters are compared to parameters obtained through fitting the solid-phase composition profiles that result from the calibration. The discrepancy between the estimated model parameters is small, and essentially the same descriptive process model is obtained. However, by fitting the time-resolved Raman spectra directly, a significant amount of calibration effort can be avoided.

Semiconducting nanowires offer the possibility of nearly unlimited complex bottom-up design (1,2), which allows for new device concepts (3,4). However, essential parameters that determine the electronic quality of the wires, [...]

The Okanogan gneiss dome, Washington. is located in the hinterland of the North American Cordillera and is part of a chain of metamorphic core complexes containing gneiss and migmatite drones exhumed during Eocene extension of thickened crust. U-Ph sensitive high-resolution ion microprobe (SHRIMP) analyses of zircon, monazite, and titanite, and [sup.40]Ar-[sup.39]Ar analyses of biotite from migmatites exposed in the footwall of the Okanogan detachment, coupled with a detailed structural analysis, document the timing and duration of migmatite crystallization and indicate coeval crystallization, extensional deformation, and exhumation of the dome. Okanogan migmatites are folded and deformed, and preserve successive generations of leucosomes generated by synkinematic anatexis. Analyses of migmatite samples from a high-melt fraction subdome near Stowe Mountain suggest that the Okanogan dome records a history of migmatite crystallization spanning at least 12 m.y., as indicated by [sup.206]Pb/[sup.238]U ages ranging from ca. 61 to 49 Ma for new zircon growth and rim overgrowths attributed to migmatite crystallization. Zircons from a granodiorite in a domain of diatexite near Stowe Mountain preserve rims that have a mean [sup.206]Pb/[sup.238]U age of 51.1 [+ or -] 1.0 Ma for the youngest population attributed to migmatite crystallization. Zircon from folded and discordant granitic leucosome in the diatexite domain yields a calculated [sup.206]Pb/[sup.238]U age of 53.5 [+ or -] 0.5 Ma for migmatite crystallization. Zircon from discordant leucosome of the metatexite domain has a mean [sup.206]Pb/[sup.238]U age of 59.8 [+ or -] 0.5 Ma, with ages as young as ca. 53 Ma attributed to final crystallization of the leucosome. Core domains of zircon samples have [sup.206]Pb/[sup.238]U ages that range from ca. 85 to 70 Ma and are interpreted to he related to an earlier phase of the orogeny. Monazite from two samples gives [sup.206]Pb/[sup.238]U crystallization ages of 52.9 [+ or -] 0.6 Ma for the granodiurite diatexite and 52.0 [+ or -] 0.6 Ma for nearby boudinaged and foliated layers of biotite granodiorite. One sample of folded granitic leucosome in metatexite contains titanite with a mean [sup.206]Pb/[sup.238]U age of 47.1 [+ or -] 0.5 Ma. The ca. 47 Ma age for titanite is similar to biotite [sup.40]Ar-[sup.39]Ar ages of 48.0 [+ or -] 0.1 Ma, 47.9 [+ or -] 0.2 Ma, and 47.1 [+ or -] 0.2 Ma for samples collected from the upper detachment surface downward over 1.5 km of structural thickness into the migmatite domain. Crystallization of the Okanogan migmatites was therefore coeval in part with upper crustal extension and ductile flow of the mid-crust. Leucosome crystallization largely ceased by ca. 49 Ma, followed by rapid cooling of footwall rocks through ~325[degrees]C by ca. 47 Ma. These data are similar to crystallization ages in migmatites from other domes in the northern Cordillera hinterland, suggesting that crustal anatexis was widespread over much of the mid-crust during Paleocene to Eocene time, coeval with extension and exhumation of orogenic middle crust. Keywords: Omineca belt, geochronology, partial melting, gneiss dome, metamorphic core complex, migmatite, Okanogan dome, continental tectonics.

Flexing a metallic disk triggers the crystallization of the supercooled sodium acetate solution contained in commercial heat pads. Many mechanisms have been proposed to explain the apparent nucleation of crystalline material. In this paper a simple experiment is described that demonstrates that nucleation is triggered by preserving seed crystals clamped between opposing metal surfaces. An explanation for the retention of the crystalline particles is the elevated melting point caused by very high local pressures. A series of thermophysical properties of the sodium acetate solution is also measured, including the available enthalpy upon crystallization of the supercooled substance, and liquid and solid phase specific heat capacities.

We investigated the effects of surface-treated organophilic clay on the crystallization of poly(L-lactide) (PLLA) in their hybrids. The natural nano-clay in PLLA/clay hybrids acts as a heterogeneous nucleating agent to facilitate crystallization. On the contrary, extensive distributions of induction periods for nucleation are observed in the individual spherulites of neat PLLA and PLLA/organophilic clay hybrids. Therefore, it is suggested that nucleation type of neat PLLA and PLLA/organophilic clay hybrids implies nearly growth geometry as a homogeneous one. Further, under the presence of nano-clay in their composites, PLLA matrix form the orthorhombic lattice structure corresponded to the α-form crystal. Since this experimental fact implies little effect of the clay particles on polymorphism of PLLA crystal, the nucleating effect of the organophilic clay seems weaker than the natural clay itself. However, an increase in clay content enhances the growth rates of spherulite for hybrids. Consequently, most of hybrids exhibit an increase in overall crystallization rates at any crystallization temperature in spite of relatively lower nucleation rate of PLLA crystallites itself. In addition, the Avrami exponents (n) obtained by relatively low crystallization temperature ranged from 4 to 6, implying that the growth geometry was dominated sheaf-like structure in early stage of isothermal crystallization. POLYM. ENG. SCI., 48:1103-1111, 2008. [C] 2008 Society of Plastics Engineers, INTRODUCTION Poly(L-lactide) (PLLA) has been known a biodegradable and biocompatible crystalline polymer with applications such as surgical suture and drug delivery systems [1-4]. The combination of PLLA and low-level loadings [...]

Using two-temperature synthesis method with the further directed crystallization under the radial and slight horizontal temperature gradients, facilitating the convection and mixing of the melt, the authors obtained monocrystals of n- and p-[CuInSe.sub.2] with controlled deviation from the stoichiometry using the excess In and Se. We have carried out the measurements of the conductivity and Hall coefficient in the temperature interval 70-415 K and investigated Hall mobility as the function of temperature, determining the dominating carrier scattering mechanisms. It was found that the electrical properties of n- and p-[CuInSe.sub.2] are caused by the defects of various types depending on the growth conditions and stoichiometry deviations. The energy position of the impurity levels was identified to be 0.055 [+ or -] 0.003 eV and 0.022 [+ or -] 0.003 eV above the valence band for acceptor levels and 0.010 [+ or -] 0.002 eV below the conduction band for the donor level. Keywords: [CuInSe.sub.2] monocrystals; Directed crystallization: Mobility; Scattering mechanisms; Impurity levels

Author(s): Kei Hirose (corresponding author) [1]; Guillaume Morard [2]; Ryosuke Sinmyo [1]; Koichio Umemoto [1]; John Hernlund [1]; George Helffrich [1]; Stphane Labrosse [3] The Earths core is about ten [...]

The partial crystallization of amorphous Hf[O.sub.2] and its application to polysilicon-oxide-nitride-oxide-silicon (SONOS)-type Flash memory as a charge storage layer is examined. Findings reveal the suitability of the partially crystallized Hf[O.sub.2] for multilevel/bit and multibit/cell application for next generation nonvolatile memory (NVM) technology.

The crystallization kinetics of the a-Si/Ni bilayer recording films with different thickness ratios 4:1 and 20:1 under thermal annealing and the recording mechanism of the write-once blue-ray disk are demonstrated.

The exploration of the structure-directing effects of small amines that are selective for the crystallization of MMT-type zeolite phases by employing molecular modeling is reported.

We report the results of x-ray-scattering studies of individual helical ribbons formed in multicomponent solutions of cholesterol solubilized by various surfactants. The solutions were chemically defined lipid concentrate (CDLC) and model bile. In these and many analogous multicomponent surfactant-cholesterol solutions, helical ribbons of two well defined pitch angles, namely 11[degrees] and 54[degrees], are formed. We have suggested previously that this remarkable stability results from an underlying crystalline structure of the sterol ribbon strips. Using a synchrotron x-ray source, we have indeed observed Bragg reflections from individual ribbons having 11 [degrees] pitch angle. We have been able to deduce the parameters of the unit cell. The crystal structure of these ribbons is similar to that of cholesterol monohydrate, with the important difference that the length of the unit cell perpendicular to the cholesterol layers is tripled. We discuss possible origins for this triplication as well as the connection between the crystalline structure and the geometrical form of the helical ribbons. crystal structure | x-ray diffraction | crystallization | surfactants

The time-of-flight secondary ion mass spectrometry and reflection absorption infrared spectroscopy were used to determine the properties of supercooled liquid water and the mechanism of crystallization. The supercooled water is found to contain two phases and undergoes immediate crystallization and dissolution of LiCl.

A new route is described for rapid decrystallization of cellulose without esterification or morphology change on the macrofiber in trifluoroacetic acid (TFA). The esterification of TFA monomers on the external surface of crystalline cellulose, agglomeration of cellulose macrofibrils as well as water released from the esterification reaction has prevented the diffusion rate of TFA into the cellulose crystalline region and decreased the TFA swelling capability at higher temperatures.

The transition path sampling molecular dynamics simulations are used to investigate the crystallization of sodium chloride from melt and mixtures with other sodium halides. The nucleation mechanisms of both the solidification and the melting process at the atomic level are explored.

The structure of isolated photosystem I (PSI) complexes was studied using small-angle X-ray scattering (SAXS). The solution conformation of PSI showed that the polypeptide subunits at the periphery of PSI complex were partially unfolded and associated with detergent micelles.

The morphology, magnetic properties, crystallization mechanism and applications of the nanoparticles of amorphous Iron oxide are studied. The size of these amorphous particles predetermines the structure of the initial crystalline polymorph.

Based on the [Ni[(f-rac-L).sup.2+] and [[Ni[(CN).sub.4]].sup.2-] building blocks (L=5,5,7,12,12,14-hexamehtyl -1,4,8,11-tetraazacyclotetradecane), three helical supramolecular stereoisomers of meso-2, [DELTA]-2 and [DELTA]-3 were constructed. Complete examination of the structure indicates that the interchain hydrogen bonding and hydrophobic interactions play an important role in the transfer of chirality between neighboring helical chains due to which one dimensional (1D) helical chains are packed in an achiral or homochiral manner.

Static crystallization study was carried out on virgin and nucleated poly(m-xylylene adipamide) (MXD6) which were, respectively, named PA1 and PA2. For PA2, the nucleating additives consist in talc (1%) and PA66 (11%). The three used experimental techniques (rheometer, calorimetry, and a hot stage coupled with an optical microscope) showed complementary results as the DSC could not be used to measure the low crystallization kinetics of PA1. Characteristic crystallization times were measured according to the crystallization conditions (temperature, cooling rate). Isothermal crystallization study allowed the determination of the thermodynamic melting point of the MXD6 and the description of the lamellae growth rate by the Hoffman-Lauritzen equation. For PA2, the creation of a soft network due to PA66 crystallization prior to the MXD6 crystallization was highlighted thanks to a specific rheological study. Lastly, kinetic models, based on both Avrami and Hoffman-Lauritzen theories, were proposed to depict the crystallization process. POLYM. ENG. SCI., 47:365-373, 2007. © 2007 Society of Plastics Engineers, INTRODUCTION The poly(m-xylylene adipamide) (MXD6) shows interesting properties, such as good barrier properties to dioxygen [1, 2] or a good miscibility with other polymers [3, 4] or a good transparency [...]

The coordination assemblies resulting from the complexation of 1,3,5-tri(4-sulfophenyl)benzene, [L.sup.3-], with copper(II) in the presence of pyridine are analyzed. The results have given insights into the subtleties of designing coordination polymers and open-channel solids and three different single crystalline solids are obtained from an initial crystallization.

The effect of the electron beam of the microscope on the crystallization process of phase change materials was investigated. A continuous increase in the crystal growth velocity was found due to electron irradiation during the crystallization process.

The importance of the electrocrystallization approach in constructing and precisely controlling the morphology and stoichiometry of Co[[TCNQ].sub.2] (TCNQ = tetracyanoquinodimethane) based materials is presented. The findings show that the electrocrystallization process occurs through two distinctly different, potential-dependent nucleation-growth mechanisms.

An in situ study, using optical microscopy is employed to investigate the morphology and growth kinetics of the lysozyme spherulites that are grown from sodium nitrate and sodium thiocyanate solutions through heterogeneous nucleation. The analysis of the spherulitic growth of hen egg-white lysozyme crystals reveal that the surface processes act as the late-limiting step, hence proving that polymorphic forms of the spherulites are less stable than the monoclinic form.

A combination of the growth probability method and several three-dimensional (3D) nucleation simulations is used to study the formation of polymorphs, wherein the nucleus size acts as a function of the driving force for crystallization. The study has found application in a large number of fields that includes a yellow isoxazolone dye, paracetamol and L-glutamic acid, as they show dominant nucleation of their stable form at all driving forces.

The x-ray diffraction (XRD) and second harmonic generation are used to examine the correlation between heat-treatment temperature for crystallization and orientation of surface crystalline phase in 30BaO-15Ti[O.sub.2]-55Ge[O.sub.2] (BTG55) crystallized glass. The results have provided the guideline for the BTG55 crystallized glass with a large nonlinear optical susceptibility that has originated from the designed crystallized structure.

We show that knowledge of the phase behavior of a protein allows one to create a rational screen that increases the success rate of crystallizing challenging proteins. The strategy is based on using microfluidics to perform large numbers of protein solubility experiments across many different chemical conditions to identify reagents for crystallization experiments. Phase diagrams were generated for the identified reagents and used to design customized crystallization screens for every protein. This strategy was applied with a 75% success rate to the crystallization of 12 diverse proteins, most of which failed to crystallize when using traditional techniques. The overall diffraction success rate was 33%, about double what was achieved with conventional automation in large-scale protein structure consortia. The higher diffraction success rates are achieved by designing customized crystallization screens using the phase behavior information for each target. The identification of reagents based on an understanding of protein solubility and the use of phase diagrams in the design of individualized crystallization screens therefore promotes high crystallization rates and the production of diffraction-quality crystals. microfluidics | protein phase behavior

To investigate the effect of water on phase relations and compositions in a basaltic system, we performed crystallization experiments at pressures of 100, 200 and 500 MPa in a temperature range of 940 to 1,220[degrees]C using four different water contents. Depending on the water activity, the oxygen fugacity varied between 1 and 4 log units above the quartz-magnetite-fayalite buffer. Addition of water to the dry system shifts the solidus > 250[degrees]C to lower temperatures and increases the amount of melt drastically. For instance, at 1,100[degrees]C and 200 MPa, the melt fraction increases from 12.5 wt% at a water content of 1.6 wt% to 96.3% at a water content of 5 wt% in the melt. The compositions of the experimental phases also show a strong effect of water. Plagioclase is shifted to higher anorthite contents by the addition of water. Olivine and clinopyroxene show generally higher MgO/FeO ratios with added water, which could also be related to the increasing oxygen fugacity with water. Moreover, water affects the partitioning of certain elements between minerals and melts, e.g., the Ca partitioning between olivine and melt. Plagioclase shows a characteristic change in the order of crystallization with water that may help to explain the formation of wehrlites intruding the lower oceanic crust (e.g., in Oman, Macquarie Island). At 100 MPa, plagioclase crystallizes before clinopyroxene at all water contents. At pressures > 100 MPa, plagioclase crystallizes before clinopyroxene at low water contents (e.g. < 3 wt%), but after clinopyroxene at [H.sub.2]O in the melt > 3 wt%. This change in crystallization order indicates that a paragenesis typical for wehrlites (olivine-clinopyroxerie-without plagioclase) is stabilized at low pressures typical of the oceanic crust only at high water contents. This opens the possibility that typical wehrlites in the oceanic crust can be formed by the fractionation and accumulation of olivine and clinopyroxene at 1,060[degrees]C and > 100 MPa in a primitive tholeiitic basaltic system containing more than 3 wt% water. The comparison of the experimental results with evolution trends calculated by the thermodynamic models 'MELTS' and 'Comagmat' shows that neither model predicts the experimental phase relations with sufficient accuracy.

The quantitative model is presented to describe the cyclic phase transformation kinetics. The mechanistic significance of the cyclic transformation kinetics is described on the basis of escape of an overdamped Brownian particle from a fluctuating barrier.

New experimental data are presented that allows the biotite-magnetite-sanidine equilibrium to be used for estimating water fugacity ([f.sub.[H.sub.2]O]) in hydrous phonolitic magmas. It is also demonstrated that the partly ionic model gives the best estimate for the annite activity ([a.sub.annite]). Crystallization experiments were carried out on a representative sample of peralkaline, phonolitic obsidian of Montana Blanca (MB) pumice deposit, Tenerife, Canary Islands. Experiments were performed from 720-810 [degrees]C and 50-250 MPa. Redox conditions were varied between NNO (nickel + nickel oxide) + 1 ([+ or -]0.2) and FMQ (fayalite + magnetite + quartz). The majority of the experiments were done under [H.sub.2]O saturation conditions ([P.sub.water] = [P.sub.total]). Several experiments were done using a mixed [H.sub.2]O-C[O.sub.2] fluid phase whereas in other experiments 10 or 20 wt% powdered alkali feldspar was added to the starting material. The pre-eruptive [f.sub.[H.sub.2]O] of the Montana Blanca magma is estimated at 676 [+ or -] 200 bars. The pre-emptive [f.sub.[H.sub.2]O] for the Fish Canyon tuff (753-2978 bars) and Bishop tuff rhyolite (1065-2440 bars) were also calculated, as well as [f.sub.[H.sub.2]O] for metamorphic biotite from Au Sable Forks ([approximately equal to] 130 bars). The results of this study suggest that this geohygrometer can be used in any magmatic system in which biotite-magnetite-sanidine is a stable assemblage. Keywords: Crystallization experiments, geohygrometer, pbonolitic magmas, water fugacity

A series of Ti-doped diopside samples synthesized by fluxgrowth methods under reducing conditions were investigated by microanalytical methods and optical absorption spectroscopy, to assess Ti incorporation mechanisms, valence states, and related electronic transitions. Chemical characterization show that Ti occurs both in the tri-and tetravalent states, with [Ti.sup.4+] preferentially ordered to the tetrahedral position whereas [Ti.sup.3+] is restricted to the M1 position. Charge-balance is maintained by incorporation of Na and minor B, stemming from the flux compound. Polarized optical absorption spectra reveal three major absorption features. Two relatively narrow bands centered at 18 500 and 15 700 [cm.sup.-1], mainly polarized in the crystallographic c-direction, display absorbance values that correlate with the calculated [Ti.sup.3+] (M1) concentration, and are assigned to spin-allowed d-d transitions in [Ti.sup.3+]. A broader band centered around 24 500 [cm.sup.-1] displays absorbance values that are well correlated with the product of [sup.VI][Ti.sup.3+] and [sup.IV][Ti.sup.4+]. Based on the spectral characteristics of this band, including a strong polarization in the crystallographic b-direction, we assign this band to an [sup.M1][Ti.sup.3+]-[Ti.sup.4+] intervalence charge transfer process. Keywords: Crystal synthesis, diopside, optical spectroscopy, pyroxene, major and minor elements, Ti in pyroxene, order-disorder

Late-stage rims of magmatic pyroxenes from some martian basalts show decreases in Li and B contents relative to earlier-formed pyroxene cores. This behavior is different than expected from their documented incompatible element behavior. Previous workers interpreted such depletions to reflect the loss of several wt% magmatic water during basalt crystallization. This interpretation has profound implications for the nature of the martian mantle and recent exchange of volatiles between the martian mantle and atmosphere. To assess alternative mechanisms that may influence the behavior of Li and B in the absence of aqueous fluid activity, the effects of changing pyroxene composition during crystallization, shock pressure, and shock-associated thermal metamorphism were studied. Lithium and B depletions are documented in late-stage rims of pyroxenes from anhydrous lunar basalts indicating that mechanisms other than aqueous fluid activity must have influenced Li and B partitioning in these pyroxenes. Depletions of Li and B are most likely associated with changing pyroxene composition during crystallization, and occur in lunar and martian pyroxenes with late-stage Fe-enrichment. It is interesting that pyroxenes without late-stage Fe-enrichment show no concomitant Li and B increases. Lithium loss may occur during breakdown of metastable pyroxferroite. Additionally, changes in Cr content may influence the substitution mechanism involved for incorporating Li. Shock does not redistribute Li or B but may facilitate subsequent thermally driven diffusion by the introduction of mechanical defects in grains. Thermally metamorphosed pyroxenes exhibit higher Li and lower B contents relative to unheated pyroxenes. It is likely, therefore, that Li and B are redistributed through interactions between pyroxenes and surrounding zones of mesostasis during thermal metamorphism. Keywords: Lithium, boron, lunar mare basalts, martian basalts, shock pressure, thermal metamorphism, crystal chemistry, pyroxenes

A theoretical study related to the main features of solid solution formation from aqueous solutions starting from the equilibrium and quasi-equilibrium in 'solid solution - aqueous solution' system (SS-AS systems), looking at crystallization kinetics under the simplest growth conditions and under more complicated ones, is presented. The theory developed is found to predict the growth/dissolution rate of a mixed crystal based on the knowledge of phase diagram and growth kinetics of the end members of the series.

The orbicular rock at Slattemossa, southeastern Sweden, has a quartz monzodioritic composition. The cores of the orbicules crystallized directly from the orbicule-forming magma; cores made up of xenoliths have not been observed. Outside the core follow first an inner mafic, a felsic and then an outer mafic shell. The orbicules occur in a matrix, which is similar to the core. They grew simultaneously and show an almost perfect parallelism in evolution. After initial 'normal' crystallization of the magma, superheating probably triggered by a sudden addition of volatiles destroyed earlier formed nuclei and also affected the already crystallized part of the rock. Cooling caused heterogeneous nucleation and rapid crystallization, which formed the inner mafic shell. This is enriched in mafic minerals, especially biotite, compared to the core. At the same time the grain size becomes significantly smaller. Depletion in mafic components, possibly intensified by a sudden change in physical conditions, destabilized biotite and amphibole crystallization, causing oversaturation in plagioclase components, forming a felsic shell having a sharp boundary with the mafic shell. Plagioclase is extremely altered. Mafic minerals were then stabilized, probably due to depletion of plagioclase components, and an outer mafic shell formed. With the return to homogeneous nucleation, matrix formation concluded the crystallization. Orbicules might have moved in the magma causing some squeezing of magma surrounding the orbicules, but major movements involved the settling of the whole package of orbicules and matrix in the surrounding non-orbicular magma. Keywords: orbicular, monzodiorite, Proterozoic, Sweden

Abstract: Metapelites of the parautochthonous Gagnon terrane at the footwall of the high-pressure (high-P) belt in the Manicouagan area (central Grenville Province) preserve an impressive textural record of partial melting [...]

Differential scanning calorimeter (DSC) and polarized optical microscopy (POM) have been used to investigate the isothermal and nonisothermal crystallization behavior of poly(ζ-caprolactone) (PCL)/multi-walled carbon nanotube (MWNT) composites. PCL/MWNT composites have been prepared by mixing the PCL polymer with carboxylic groups containing multi-walled carbon nanotubes (c-MWNTs) in tetrahydrofuran solution. Raman spectrum of c-MWNT indicated the possible presence of carboxylic acid groups at both ends and on the sidewalls of the MWNTs. The TEM micrograph showed that the c-MWNT is well separated and uniformly dispersed in the PCL matrix. DSC isothermal results showed that the introduction of c-MWNT into the PCL initiates strongly heterogeneous nucleation, which induced a change of the crystal growth process. The activation energy of PCL significantly decreases by adding 0.25 wt% c-MWNT into PCL/c-MWNT composites and then increases as c-MWNT content increases. The result demonstrates that the addition of c-MWNT into PCL induces the heterogeneous nucleation at lower c-MWNT content and then inhibits the polymer chain transportation ability during crystallization at higher c-MWNT content. In this study, we have also studied the nonisothermal crystallization kinetics and melting behavior of PCL/c-MWNT composites at various cooling rates. The correlation among isothermal and nonisothermal crystallization kinetics and melting behavior of PCL/c-MWNT composites can be also discussed. POLYM. ENG. SCI., 46: 1309-1317, 2006. [C] 2006 Society of Plastics Engineers, INTRODUCTION Carbon nanotubes (CNTs), a new discovery of Iijima and Ichihashi [1], have received great interest for their potential use in probe tips for SPMs [2], field emitters [3], nanoelectronic [...]

This article presents the effects of nanoclay and supercritical nitrogen on the crystallization and thermal behavior of microcellular injection-molded polyamide-6 (PA6) nanocomposites with 5 and 7.5 wt% nanoclay. Differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and polarized optical microscopy (POM) were used to characterize the thermal behavior and crystalline structure. The isothermal and nonisothermal crystallization kinetics of neat resin and its corresponding nanocomposite samples were analyzed using the Avrami and Ozawa equations, respectively. The activation energies determined using the Arrhenius equation for isothermal crystallization and the Kissinger equation for nonisothermal crystallization were comparable. The specimen thickness had a significant influence on the nonisothermal crystallization especially at high scanning rates. Nanocomposites with an optimal amount of nanoclay possessed the highest crystallization rate and a higher level of nucleation activity. The nanoclay increased the magnitude of the activation energy but decreased the overall crystallinity. The dissolved SCF did not alter the crystalline structure significantly. In contrast with conventionally injection-molded solid counterparts, microcellular neat resin parts and microcellular nanocomposite parts were found to have lower crystallinity in the core and higher crystallinity near the skin. POLYM. ENG. SCI., 46:904-918, 2006. © 2006 Society of Plastics Engineers, INTRODUCTION Polyamide-6 (PA6)/montmorillonite (MMT) nanocomposites have attracted much attention because of the inherent compatibility between the polymer and the silicate nanoclay that involves ionic bonds and of their outstanding properties [...]

The effects of exposure time and vapor pressure on the crystallization behaviors of bisphenol-A polycarbonate (BAPC) films were investigated at 25°C by using differential scanning calorimetry (DSC). Double melting peaks were observed for various BAPC samples after vapor-induced crystallization. The low temperature melting peak shifted to higher temperature and became sharper with increasing exposure time, and could be assigned to defective crystals with smaller crystal size. Crystallinity and average crystal dimension normal to (020) were calculated from wide-angle X-ray diffraction spectra. A good agreement was obtained between crystallinity values obtained from WAXD and those from DSC. The morphology of crystallized samples after various exposure time periods was examined by means of polarized optical microscopy. Nucleation occurred at the initial stage of vapor-induced crystallization. Poor crystals become perfect through segment reorganization with increasing exposure time, and spherulites' growth was observed. The average diameter of spherulites increased from 2 µm for 1 h, to 7 and 16 µm after 3 and 56 h, respectively. POLYM. ENG. SCI., 46:729-734, 2006. © 2006 Society of Plastics Engineers, INTRODUCTION The crystallization behavior of bisphenol-A polycarbonate (BAPC) is of considerable scientific and technical interest and has been extensively investigated [1-8]. It is well known that the ability of polymers [...]

A study conducted shows that the [.sup.17.O]-enriched water vapor involves during the crystallization of molecular sieves by the dry-gel conversion methods. [.sup.17.O] NMR is a sensitive technique for monitoring the role of water in the formation of molecular sieves by dry-gel conversion methods.

The networks of mesoporous high-surface-area silicates and zeolites undergo a deep depolymerization process in glycerol, near 200 degree Celsius. However, some local ordering subsists as demonstrated by a striking similarity between the silicon and aluminum high-resolution solid-state NMR spectra before and after the reaction.

Crystallization processes in indomethacin can be observed below T(sub g) leading to different forms depending on the thermal treatment. A rapid and deep quench below T(sub g) leads to the metastable alpha-phase and a slow cooling close to T(sub g) gives rise to the stable gamma-phase.

The crystallization kinetics of a melt-miscible blend, consisting of poly(trimethylene terephthalate) (PTT) and poly(ether imide) (PEI) prepared by solution precipitation, has been investigated by means of optical polarized microscopy and differential scanning calorimeter. It was found that both the PTT spherulitic growth rate (G) and overall crystallization rate constant ([k.sub.n]) were depressed, with increasing PEI composition or crystallization temperature ([T.sub.c]). The kinetic retardation was attributed to the decrease in PTT molecular mobility, and the dilution of PTT concentration due to the addition of PEI, which has a higher glass transition temperature ([T.sub.g]). According to the Lauritzen-Hoffman theory of secondary nucleation, the crystallization of PTT in blends was similar to that of neat PTT as regime III, n = 4 and regime II, n = 2 growth processes, while the transition point of regime III to II has been shifted from 194°C for neat PTT to 190°C for blends. POLYM. ENG. SCI., 46:89-96, 2006. © 2005 Society of Plastics Engineers, INTRODUCTION Crystallization kinetics in melt-miscible blends of crystalline and amorphous polymers has been extensively studied [1-15]. When crystallization occurs below the melting point of the crystalline component, the process involves [...]