Zircon (Hf, O isotopes) as melt indicator: Melt infiltration and abundant new zircon growth within melt rich layers of granulite-facies lenses versus solid-state recrystallization in hosting amphibolite-facies gneisses (central Erzgebirge, Bohemian Massif)

NASA Astrophysics Data System (ADS)

Tichomirowa, Marion; Whitehouse, Martin; Gerdes, Axel; Schulz, Bernhard

2018-03-01

partial Hf isotope homogenization in the melt, and melt infiltration from an external source. New zircon was most likely formed by a peritectic reaction with melt above the wet solidus (peritectic zircon). Conversely, the amphibolite-facies host gneisses lack indications of significant melt production. Pre-metamorphic zircons experienced mainly solid-state recrystallization and variable Pb loss with only minor new zircon formation. However, subtle changes in cathodoluminescence pattern, in the Hf and O isotopes, and in the Lu/Hf, Yb/Hf ratios of zircons suggest that small volumes of melt were locally present. In difference to granulites, melt was internally produced. The detection of low degree melts (inferred from zircon geochemistry) is extremely important for the rheology because these amphibolite-facies rocks could act as large scale ductile shear zones. The new zircon data support a different P-T path for closely spaced amphibolite- and granulite-facies rocks.

Thermocapillary convection in zone-melting crystal growth - An open-boat physical simulation

NASA Technical Reports Server (NTRS)

Kim, Y. J.; Kou, Sindo

1989-01-01

Thermocapillary convection in a molten zone of NaNO3 contained in a boat with a free horizontal surface, that is heated from above by a centered wire heater, was studied to simulate flow in zone-melting crystal growth. Using a laser-light-cut technique and fine SiO powder as a tracer, convection in the melt zone was visualized in two different cases. In the first case, the entire melt surface was free, while in the second the melt surface was free only in the immediate vicinity of one vertical wall and was covered elsewhere, this wall being to simulate the melt/crystal interface during crystal growth. It was observed that thermocapillary convection near this wall prevailed in the first case, but was reduced significantly in the second. Since thermocapillary rather than natural convection dominated in the melt, the effect of the partial covering of the melt surface on thermocapillary convection in the melt observed in this study is expected to be similar under microgravity.

Recrystallized arrays of bismuth nanowires with trigonal orientation.

PubMed

Limmer, Steven J; Yelton, W Graham; Erickson, Kristopher J; Medlin, Douglas L; Siegal, Michael P

2014-01-01

We demonstrate methods to improve the crystalline-quality of free-standing Bi nanowires arrays on a Si substrate and enhance the preferred trigonal orientation for thermoelectric performance by annealing the arrays above the 271.4 °C Bi melting point. The nanowires maintain their geometry during melting due to the formation of a thin Bi-oxide protective shell that contains the molten Bi. Recrystallizing nanowires from the melt improves crystallinity; those cooled rapidly demonstrate a strong trigonal orientation preference.

Deformation Enhanced Recrystallization of Titanite: Insight from the Western Gneiss Region Ultrahigh-Pressure Terrane

NASA Astrophysics Data System (ADS)

Gordon, S. M.; Reddy, S. M.; Blatchford, H.; Whitney, D. L.; Kirkland, C. L.; Teyssier, C.; Evans, N. J.; McDonald, B.

2017-12-01

Titanite readily recrystallizes due to metamorphism, deformation, and/or fluids making it an ideal chronometer for tracking the exhumation of high-grade rocks. The Western Gneiss Region (WGR), Norway, is a giant UHP terrane exhumed as a fairly coherent slab. Parts of the WGR underwent little deformation during exhumation; however, meters-scale shear zones, located across the WGR, deformed over a range of pressures, from (U)HP to amphibolite facies. Titanite from quartzofeldpathic gneiss within, directly adjacent to, and 300 m away from a mylonitic shear zone within the southern WGR have been analyzed to track exhumation and investigate effects of deformation on recrystallization and trace-element mobility. EBSD was used to characterize the microstructural evolution of the gneisses, and trace-element concentrations and timing of recrystallization were estimated by split-stream LA-ICPMS. Titanite grain size decreases from outside (>200) to inside (<75 µm) the shear zone. Gneiss in and directly adjacent to the shear zone contain partially to completely recrystallized grains, with 207-corrected 206Pb/238U ages of <405 Ma. Gneiss within the shear zone shows a greater percentage of recrystallized grains. EBSD data indicate that some titanite comprises multiple subgrains within an optically coherent single grain. Subgrains in titanite cores show evidence of inherited radiogenic Pb, whereas subgrains in rims and tails of deformed sigma grains were recrystallized. In a gneiss directly adjacent to the shear zone, optically coherent grains are zoned, with increasing Sr and decreasing Zr from core to rim; titanite subgrains within the shear-zone gneiss are too small to analyze. In comparison, titanite from the gneiss outside the shear zone does not show any internal microstructures or evidence for Scandian recrystallization and has low U and high 204Pb. These results show that most trace elements are unaffected by deformation of titanite; however, Pb is mobile. Deformation

Deformation Enhanced Recrystallization of Titanite: Insight from the Western Gneiss Region Ultrahigh-Pressure Terrane

NASA Astrophysics Data System (ADS)

Gordon, S. M.; Reddy, S. M.; Blatchford, H.; Whitney, D. L.; Kirkland, C. L.; Teyssier, C.; Evans, N. J.; McDonald, B.

2016-12-01

Titanite readily recrystallizes due to metamorphism, deformation, and/or fluids making it an ideal chronometer for tracking the exhumation of high-grade rocks. The Western Gneiss Region (WGR), Norway, is a giant UHP terrane exhumed as a fairly coherent slab. Parts of the WGR underwent little deformation during exhumation; however, meters-scale shear zones, located across the WGR, deformed over a range of pressures, from (U)HP to amphibolite facies. Titanite from quartzofeldpathic gneiss within, directly adjacent to, and 300 m away from a mylonitic shear zone within the southern WGR have been analyzed to track exhumation and investigate effects of deformation on recrystallization and trace-element mobility. EBSD was used to characterize the microstructural evolution of the gneisses, and trace-element concentrations and timing of recrystallization were estimated by split-stream LA-ICPMS. Titanite grain size decreases from outside (>200) to inside (<75 µm) the shear zone. Gneiss in and directly adjacent to the shear zone contain partially to completely recrystallized grains, with 207-corrected 206Pb/238U ages of <405 Ma. Gneiss within the shear zone shows a greater percentage of recrystallized grains. EBSD data indicate that some titanite comprises multiple subgrains within an optically coherent single grain. Subgrains in titanite cores show evidence of inherited radiogenic Pb, whereas subgrains in rims and tails of deformed sigma grains were recrystallized. In a gneiss directly adjacent to the shear zone, optically coherent grains are zoned, with increasing Sr and decreasing Zr from core to rim; titanite subgrains within the shear-zone gneiss are too small to analyze. In comparison, titanite from the gneiss outside the shear zone does not show any internal microstructures or evidence for Scandian recrystallization and has low U and high 204Pb. These results show that most trace elements are unaffected by deformation of titanite; however, Pb is mobile. Deformation

Layering, melting, and recrystallization of a close-packed micellar crystal under steady and large-amplitude oscillatory shear flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

López-Barrón, Carlos R., E-mail: carlos.r.lopez-barron@exxonmobil.com; Wagner, Norman J.; Porcar, Lionel

2015-05-15

The rheology and three-dimensional microstructure of a concentrated viscoelastic solution of the triblock copolymer poly(ethylene oxide){sub 106}-poly(propylene oxide){sub 68}-poly(ethylene oxide){sub 106} (Pluronic F127) in the protic ionic liquid ethylammonium nitrate are measured by small angle neutron scattering (SANS) under flow in three orthogonal planes. This solution's shear-thinning viscosity is due to the formation of two-dimensional hexagonal close-packed (HCP) sliding layer structure. Shear-melting of the crystalline structure is observed without disruption of the self-assembled micelles, resulting in a change in flow properties. Spatially resolved measurements in the 1–2 plane reveal that both shear-melting and sliding are not uniform across the Couettemore » gap. Melting and recrystallization of the HCP layers occur cyclically during a single large amplitude oscillatory shear (LAOS) cycle, in agreement with the “stick-slip” flow mechanism proposed by Hamley et al. [Phys. Rev. E 58, 7620–7628 (1998)]. Analysis of 3D “structural” Lissajous curves show that the cyclic melting and sliding are direct functions of the strain rate amplitude and show perfect correlation with the cyclic stress response during LAOS. Both viscosity and structural order obey the Delaware–Rutgers rule. Combining rheology with in situ spatiotemporally resolved SANS is demonstrated to elucidate the structural origins of the nonlinear rheology of complex fluids.« less

Thermocapillary flow and melt/solid interfaces in floating-zone crystal growth under microgravity

NASA Technical Reports Server (NTRS)

Lan, C. W.; Kou, Sindo

1990-01-01

Computer simulation of steady-state axisymmetrical heat transfer and fluid flow was conducted to study thermocapillary flow and melt/solid interfaces in floating-zone crystal growth under microgravity. The effects of key variables on the extent of thermocapillary flow in the melt zone, the shapes of melt/solid interfaces and the length of the melt zone were discussed. These variables are: (1) the temperature coefficient of surface tension (or the Marangoni number), (2) the pulling speed (or the Peclet number), (3) the feed rod radius, (4) the ambient temperature distribution, (5) the heat transfer coefficient (or the Biot number), and (6) the thermal diffusivity of the material (or the Prandtl number).

Ocean stratification reduces melt rates at the grounding zone of the Ross Ice Shelf

NASA Astrophysics Data System (ADS)

Begeman, C. B.; Tulaczyk, S. M.; Marsh, O.; Mikucki, J.; Stanton, T. P.; Hodson, T. O.; Siegfried, M. R.; Powell, R. D.; Christianson, K. A.; King, M. A.

2017-12-01

Ocean-driven melting of ice shelves is often invoked as the primary mechanism for triggering ice loss from Antarctica. However, due to the difficulty in accessing the sub-ice-shelf ocean cavity, the relationship between ice-shelf melt rates and ocean conditions is poorly understood, particularly near the transition from grounded to floating ice, known as the grounding zone. Here we present the first borehole oceanographic observations from the grounding zone of Antarctica's largest ice shelf. Contrary to predictions that tidal currents near grounding zones should mix the water column, driving high ice-shelf melt rates, we find a stratified sub-ice-shelf water column. The vertical salinity gradient dominates stratification over a weakly unstable vertical temperature gradient; thus, stratification takes the form of a double-diffusive staircase. These conditions limit vertical heat fluxes and lead to low melt rates in the ice-shelf grounding zone. While modern grounding zone melt rates may presently be overestimated in models that assume efficient tidal mixing, the high sensitivity of double-diffusive staircases to ocean freshening and warming suggests future melt rates may be underestimated, biasing projections of global sea-level rise.

Surface premelting/recrystallization governing the collapse of open-cell nanoporous Cu via thermal annealing.

PubMed

Wang, L; Zhang, X M; Deng, L; Tang, J F; Xiao, S F; Deng, H Q; Hu, W Y

2018-06-04

We systematically investigate the collapse of a set of open-cell nanoporous Cu (np-Cu) materials with the same porosity and shape but different specific surface areas, during thermal annealing, by performing large-scale molecular dynamics simulations. Two mechanisms govern the collapse of np-Cu. One is direct surface premelting, facilitating the collapse of np-Cu, when the specific surface area is less than a critical value (∼2.38 nm-1). The other is recrystallization followed by surface premelting, accelerating the sloughing of ligaments and the annihilation of voids, when the critical specific surface area is exceeded. Surface premelting results from surface reconstruction by prompting localized "disordering" and "chaos" on the surface, and the melting temperature reduces linearly with the increase of the specific surface area. Recrystallization is followed by surface premelting as the melting temperature is below the supercooling point, where a liquid is unstable and instantaneously recrystallizes.

The Cora Lake Shear Zone: Strain Localization in an Ultramylonitic, Deep Crustal Shear Zone, Athabasca Granulite Terrain, Western Churchill Province, Canada

NASA Astrophysics Data System (ADS)

Regan, S.; Williams, M. L.; Mahan, K. H.; Orlandini, O. F.; Jercinovic, M. J.; Leslie, S. R.; Holland, M.

2012-12-01

Ultramylonitic shear zones typically involve intense strain localization, and when developed over large regions can introduce considerable heterogeneity into the crust. The Cora Lake shear zone (CLsz) displays several 10's to 100's of meters-wide zones of ultramylonite distributed throughout its full 3-5 km mylonitized width. Detailed mapping, petrography, thermobarometry, and in-situ monazite geochronology suggest that it formed during the waning phases of granulite grade metamorphism and deformation, within one of North America's largest exposures of polydeformed lower continental crust. Anastomosing zones of ultramylonite contain recrystallized grain-sizes approaching the micron scale and might appear to suggest lower temperature mylonitization. However, feldspar and even clinopyroxene are dynamically recrystallized, and quantitative thermobarometry of syn-deformational assemblages indicate high P and T conditions ranging from 0.9 -10.6 GPa and 775-850 °C. Even at these high T's, dynamic recovery and recrystallization were extremely limited. Rocks with low modal quartz have extremely small equilibrium volumes. This is likely the result of inefficient diffusion, which is further supported by the unannealed nature of the crystals. Local carbonate veins suggests that H2O poor, CO2 rich conditions may have aided in the preservation of fine grain sizes, and may have inhibited dynamic recovery and recrystallization. The Cora Lake shear zone is interpreted to have been relatively strong and to have hardened during progressive deformation. Garnet is commonly fractured perpendicular to host rock fabric, and statically replaced by both biotite and muscovite. Pseudotachylite, with the same sense of shear, occurs in several ultramylonitized mafic granulites. Thus, cataclasis and frictional melt are interpreted to have been produced in the lower continental crust, not during later reactivation. We suggest that strengthening of rheologically stiffer lithologies led to

Modeling Mantle Shear Zones, Melt Focusing and Stagnation - Are Non Volcanic Margins Really Magma Poor?

NASA Astrophysics Data System (ADS)

Lavier, L. L.; Muntener, O.

2011-12-01

Mantle peridotites from ocean-continent transition zones (OCT's) and ultraslow spreading ridges question the commonly held assumption of a simple link between mantle melting and MORB. 'Ancient' and partly refertilized mantle in rifts and ridges illustrates the distribution of the scale of upper mantle heterogeneity even on a local scale. Upwelling of partial melts that enter the conductive lithospheric mantle inevitably leads to freezing of the melt and metasomatized lithosphere. Field data and petrology demonstrates that ancient, thermally undisturbed, pyroxenite-veined subcontinental mantle blobs formed parts of the ocean floor next to thinned continental crust. Similar heterogeneity might be created in the oceanic lithosphere where the thermal boundary layer (TBM) is thick and veined with metasomatic assemblages. This cold, ancient, 'subcontinental domain' is separated by ductile shear zones (or some other form of permeability barriers) from an infiltrated ('hot') domain dominated by refertilized spinel and/or plagioclase peridotite. The footwall of these mantle shear zones display complex refertilization processes and high-temperature deformation. We present numerical models that illustrate the complex interplay of km-scale refertilization with active deformation and melt focusing on top of the mantle. Melt lubricated shear zones focus melt flow in shear fractures (melt bands) occurring along grain boundaries. Continuous uplift and cooling leads to crystallization, and crystal plastic deformation prevails in the subsolidus state. Below 800oC if water is present deformation by shearing of phyllosilicates may become prevalent. We develop physical boundary conditions for which stagnant melt beneath a permeability barrier remains trapped rather than being extracted to the surface via melt-filled fractures. We explore the parameter space for fracturing and drainage and development of anastomozing impermeable shear zones. Our models might be useful to constrain the

Rapid hydrothermal cooling above the axial melt lens at fast-spreading mid-ocean ridge: Quantification through intra-plagioclase diffusion revealed by IODP Hole 1256D

NASA Astrophysics Data System (ADS)

Zhang, C.; Koepke, J.; Kirchner, C.; Götze, N.; Behrens, H.

2014-12-01

At fast-spreading mid-ocean ridges the axial melt lenses sandwiched between the lower oceanic crust and the sheeted dike sequences are assumed to be the major magma source of oceanic crust accretion. According to the widely discussed "gabbro glacier" model, the formation of the lower oceanic crust requires efficient cooling of the axial melt lens, resulting in partly crystallization and leading to crystal-melt mush which may subside down to form the lower crust. These processes are believed to be controlled dominantly by periodical magma supply and hydrothermal circulation above melt lens. Here we quantify the cooling rate above melt lens using chemical zoning of plagioclase from hornfelsic recrystallized sheeted dikes overlying the uppermost gabbros, which are part of the dike-gabbro transition zone drilled in Hole 1256D in the Eastern equatorial Pacific by the Integrated Ocean Drilling Program, where for the first time the dike-gabbro transition zone of an intact oceanic crust was penetrated and sampled. The measured zoning patterns are supposed to be a combined result of diffusion during both on-ridge and off-ridge cooling. We estimate the on-ridge cooling rate using a forward modelling approach based on CaAl-NaSi interdiffusion in plagioclase. The results show that the recrystallized sheeted dikes have been cooled from the peak thermal overprint at 1000-1050 °C to 600 °C within about 5-30 years as a result of hydrothermal circulation above a melt lens during a period of magma starvation, corresponding to a cooling rate of 30±15 °C/yr. Heat balance calculation also approves that in order to balance the heat output of a melt lens at a fast-spreading mid-ocean ridge similar to the case of IODP Hole 1256D, the cooling rate above the melt lens is required to be around 30 °C/yr. The estimated rapid hydrothermal cooling rate coincides with the observed annual to decal episodes of melt lens fluctuation and lava eruption, which favors the "gabbro glacier" model and

Purification of organic nonlinear optical materials for bulk crystal growth from melt

NASA Astrophysics Data System (ADS)

Gebre, Tesfaye; Bhat, Kamala N.; Batra, Ashok K.; Lal, Ravindra B.; Aggarwal, Mohan D.; Penn, Benjamin G.; Frazier, Donald O.

2002-10-01

The techniques developed for purification of nonlinear optical organic materials, such as benzil, 2-methyl-4-nitroaniline (MNA), Dicyanovinyl anisole (DIVA) and its derivatives, nitrophenyl prolinol (NPP) and other Schiff's base compounds, include Kugelrohy method, physical vapor transport, zone refining and recrystallization from the solvent are described. Purity of the materials is tested using differential thermal analysis, gas chromatograph/Mass detector, Fourier Transform Infrared spectroscopy and melting point measurements. The purified materials were later used in the growth of single crystal by Bridgman-Stockbarger and Czochralski techniques.

The structure of melting mushy zones, with implications for Earth's inner core (Invited)

NASA Astrophysics Data System (ADS)

Bergman, M. I.; Huguet, L.; Alboussiere, T.

2013-12-01

Seismologists have inferred hemispherical differences in the isotropic wavespeed, the elastic anisotropy, the attenuation, and the attenuation anisotropy of Earth's inner core. One hypothesis for these hemispherical differences involves an east-west translation of the inner core, with enhanced solidification on one side and melting on the other. Another hypothesis is that long term mantle control over outer core convection can lead to hemispherical variations in solidification that could even result in melting in some regions of the inner core boundary. It has also been hypothesized that the inner core is growing dendritically, resulting in an inner core that has the structure of a mushy zone (albeit one with a high solid fraction). It would therefore be helpful to understand how the structure of a melting mushy zone might look in comparison with one that is solidifying, in an effort to help interpret the seismic inferences. We have carried out experiments on the solidification of ammonium chloride from an aqueous solution, yielding a mushy zone. The experiments run in a centrifuge, in order to reach a more realistic ratio of convective velocity to phase change rate, expected to be very large at the boundary of the inner core. Hypergravity thus increases the experimental solid fraction of the mush. So far the maximum gravity we have achieved is 200 g. A Peltier cell provides cooling at one end of the cell, and after the mushy zone has grown we turn on a heater at the other end. Probes monitor the temperature along the height of the cell. As ammonium chloride in the mushy zone melts it produces more dense fluid, which results in convection in the mushy zone, a greater ammonium chloride concentration deeper in the mushy zone, and hence enhanced solidification there. This thus changes the solid fraction profile from that during solidification, which may be observable in the lab experiments using ultrasonic transducers and post-mortem under a microscope. The melting

Strain heating in process zones; implications for metamorphism and partial melting in the lithosphere

NASA Astrophysics Data System (ADS)

Devès, Maud H.; Tait, Stephen R.; King, Geoffrey C. P.; Grandin, Raphaël

2014-05-01

Since the late 1970s, most earth scientists have discounted the plausibility of melting by shear-strain heating because temperature-dependent creep rheology leads to negative feedback and self-regulation. This paper presents a new model of distributed shear-strain heating that can account for the genesis of large volumes of magmas in both the crust and the mantle of the lithosphere. The kinematic (geometry and rates) frustration associated with incompatible fault junctions (e.g. triple-junction) prevents localisation of all strain on the major faults. Instead, deformation distributes off the main faults forming a large process zone that deforms still at high rates under both brittle and ductile conditions. The increased size of the shear-heated region minimises conductive heat loss, compared with that commonly associated with narrow shear zones, thus promoting strong heating and melting under reasonable rheological assumptions. Given the large volume of the heated zone, large volumes of melt can be generated even at small melt fractions.

A Rate-Theory-Phase-Field Model of Irradiation-Induced Recrystallization in UMo Nuclear Fuels

NASA Astrophysics Data System (ADS)

Hu, Shenyang; Joshi, Vineet; Lavender, Curt A.

2017-12-01

In this work, we developed a recrystallization model to study the effect of microstructures and radiation conditions on recrystallization kinetics in UMo fuels. The model integrates the rate theory of intragranular gas bubble and interstitial loop evolutions and a phase-field model of recrystallization zone evolution. A first passage method is employed to describe one-dimensional diffusion of interstitials with a diffusivity value several orders of magnitude larger than that of fission gas xenons. With the model, the effect of grain sizes on recrystallization kinetics is simulated. The results show that (1) recrystallization in large grains starts earlier than that in small grains, (2) the recrystallization kinetics (recrystallization volume fraction) decrease as the grain size increases, (3) the predicted recrystallization kinetics are consistent with the experimental results, and (4) the recrystallization kinetics can be described by the modified Avrami equation, but the parameters of the Avrami equation strongly depend on the grain size.

Infiltration of meteoric fluids in an extensional detachment shear zone (Kettle dome, WA, USA): How quartz dynamic recrystallization relates to fluid-rock interaction

NASA Astrophysics Data System (ADS)

Quilichini, Antoine; Siebenaller, Luc; Nachlas, William O.; Teyssier, Christian; Vennemann, Torsten W.; Heizler, Matthew T.; Mulch, Andreas

2015-02-01

We document the interplay between meteoric fluid flow and deformation processes in quartzite-dominated lithologies within a ductile shear zone in the footwall of a Cordilleran extensional fault (Kettle detachment system, Washington, USA). Across 150 m of shear zone section, hydrogen isotope ratios (δD) from synkinematic muscovite fish are constant (δD ˜ -130‰) and consistent with a meteoric fluid source. Quartz-muscovite oxygen isotope thermometry indicates equilibrium fractionation temperatures of ˜365 ± 30 °C in the lower part of the section, where grain-scale quartz deformation was dominated by grain boundary migration recrystallization. In the upper part of the section, muscovite shows increasing intragrain compositional zoning, and quartz microstructures reflect bulging recrystallization, solution-precipitation, and microcracking that developed during progressive cooling and exhumation. The preserved microstructural characteristics and hydrogen isotope fingerprints of meteoric fluids developed over a short time interval as indicated by consistent mica 40Ar/39Ar ages ranging between 51 and 50 Ma over the entire section. Pervasive fluid flow became increasingly channelized during detachment activity, leading to microstructural heterogeneity and large shifts in quartz δ18O values on a meter scale. Ductile deformation ended when brittle motion on the detachment fault rapidly exhumed the mylonitic footwall.

Optical Benson: Following the Impact of Melt Season Progression Using Landsat and Sentinel 2 - Snow Zone Formation Imaged

NASA Astrophysics Data System (ADS)

Fahnestock, M. A.; Shuman, C. A.; Alley, K. E.

2017-12-01

Snow pit observations on a glaciologically-focussed surface traverse in Greenland allowed Benson [1962, SIPRE (now CRREL) Research Report 70] to define a series of snow zones based on the extent of post-depositional diagenesis of the snowpack. At high elevations, Benson found fine-grained "dry snow" where melt (at that time) was absent year-round, followed down-elevation by a "percolation zone" where surface melt penetrated the snowpack, then a "wet snow zone" where firn became saturated during the peak of the melt season, and finally "superimposed ice" and "bare ice" zones where refrozen surface melt and glacier ice were exposed in the melt season. These snow zones can be discriminated in winter synthetic aperture radar (SAR) imagery of the ice sheet (e.g. Fahnestock et al. 2001), but summer melt reduces radar backscatter and makes it difficult to follow the progression of diagenesis beyond the initial indications of surface melting. While some of the impacts of surface melt (especially bands of blue water-saturated firn) are observed from time to time in optical satellite imagery, it has only become possible to map effects of melt over the course of a summer season with the advent of large-data analysis tools such as Google Earth Engine and the inclusion of Landsat and Sentinel-2 data streams in these tools. A map of the maximum extent of this blue saturated zone through the 2016 melt season is shown in the figure. This image is a true color (RGB) composite, but each pixel in the image shows the color of the surface when the "blueness" of the pixel was at a maximum. This means each pixel can be from a different satellite image acquisition than adjacent pixels - but it also means that the maximum extent of the saturated firn (Benson's wet snow zone) is visible. Also visible are percolation, superimposed and bare ice zones. This analysis, using Landsat 8 Operational Land Imager data, was performed using Google Earth Engine to access and analyze the entire melt

Characterization of frictional melting processes in subduction zone faults by trace element and isotope analyses

NASA Astrophysics Data System (ADS)

Ishikawa, T.; Ujiie, K.

2017-12-01

Pseudotachylytes found in exhumed accretionary complexes, which are considered to be formed originally at seismogenic depths, are of great importance for elucidating frictional melting and concomitant dynamic weakening of the fault during earthquake in subduction zones. However, fluid-rich environment of the subduction zone faults tends to cause extensive alteration of the pseudotachylyte glass matrix in later stages, and thus it has been controversial that pseudotachylytes are rarely formed or rarely preserved. Chemical analysis of the fault rocks, especially on fluid-immobile trace elements and isotopes, can be a useful means to identify and quantify the frictional melting occurred in subduction zone faults. In this paper, we report major and trace element and Sr isotope compositions for pseudotachylyte-bearing dark veins and surrounding host rocks from the Mugi area of the Shimanto accretionary complex (Ujiie et al., J. Struct. Geol. 2007). Samples were collected from a rock chip along the microstructure using a micro-drilling technique, and then analyzed by ICP-MS and TIMS. Major element compositions of the dark veins showed a clear shift from the host rock composition toward the illite composition. The dark veins, either unaltered or completely altered, were also characterized by extreme enrichment in some of the trace elements such as Ti, Zr, Nb and Th. These results are consistent with disequilibrium melting of the fault zone. Model calculations revealed that the compositions of the dark veins can be produced by total melting of clay-rich matrix in the source rock, leaving plagioclase and quartz grains almost unmolten. The calculations also showed that the dark veins are far more enriched in melt component than that expected from the source rock compositions, suggesting migration and concentration of frictional melt during the earthquake faulting. Furthermore, Sr isotope data of the dark veins implied the occurrence of frictional melting in multiple stages

Magma-assisted strain localization in an orogen-parallel transcurrent shear zone of southern Brazil

NASA Astrophysics Data System (ADS)

Tommasi, AndréA.; Vauchez, Alain; Femandes, Luis A. D.; Porcher, Carla C.

1994-04-01

In a lithospheric-scale, orogen-parallel transcurrent shear zone of the Pan-African Dom Feliciano belt of southern Brazil, two successive generations of magmas, an early calc-alkaline and a late peraluminous, have been emplaced during deformation. Microstructures show that these granitoids experienced a progressive deformation from magmatic to solid state under decreasing temperature conditions. Magmatic deformation is indicated by the coexistence of aligned K-feldspar, plagioclase, micas, and/or tourmaline with undeformed quartz. Submagmatic deformation is characterized by strain features, such as fractures, lattice bending, or replacement reactions affecting only the early crystallized phases. High-temperature solid-state deformation is characterized by extensive grain boundary migration in quartz, myrmekitic K-feldspar replacement, and dynamic recrystallization of both K-feldspar and plagioclase. Decreasing temperature during solid-state deformation is inferred from changes in quartz crystallographic fabrics, decrease in grain size of recrystallized feldspars, and lower Ti amount in recrystallized biotites. Final low-temperature deformation is characterized by feldspar replacement by micas. The geochemical evolution of the synkinematic magmatism, from calc-alkaline metaluminous granodiorites with intermediate 87Sr/86Sr initial ratio to peraluminous granites with very high 87Sr/86Sr initial ratio, suggests an early lower crustal source or a mixed mantle/crustal source, followed by a middle to upper crustal source for the melts. Shearing in lithospheric faults may induce partial melting in the lower crust by shear heating in the upper mantle, but, whatever the process initiating partial melting, lithospheric transcurrent shear zones may collect melt at different depths. Because they enhance the vertical permeability of the crust, these zones may then act as heat conductors (by advection), promoting an upward propagation of partial melting in the crust

Surface Melt and Firn Density Evolution in the Western Greenland Percolation Zone Over the Past 50 Years

NASA Astrophysics Data System (ADS)

Graeter, K.; Osterberg, E. C.; Hawley, R. L.; Thundercloud, Z. R.; Marshall, H. P.; Ferris, D. G.; Lewis, G.

2016-12-01

Predictions of the Greenland Ice Sheet's (GIS) contribution to sea-level rise in a warming climate depend on our ability to model the surface mass balance (SMB) processes occurring across the ice sheet. These processes are poorly constrained in the percolation zone, the region of the ice sheet where surface melt refreezes in the firn, thus preventing that melt from directly contributing to GIS mass loss. In this way, the percolation zone serves as a buffer to higher temperatures increasing mass loss. However, it is unknown how the percolation zone is evolving in a changing climate and to what extent the region will continue to serve as a buffer to future runoff. We collected seven shallow ( 22-30 m) firn cores from the Western Greenland percolation zone in May-June 2016 as part of the Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) project. Here we present data on melt layer stratigraphy, density, and annual accumulation for each core to determine: (1) the temporal and spatial accumulation and melt refreeze patterns in the percolation zone of W. Greenland over the past 40 - 55 years, and (2) the impacts of changing melt and refreeze patterns on the near-surface density profile of the percolation zone. Three of the GreenTrACS firn cores re-occupy firn core sites collected in the 1970's-1990's, allowing us to more accurately quantify the evolution of the percolation zone surface melt and firn density during the most recent decades of summertime warming. This work is the basis for broader investigations into how changes in W. Greenland summertime climate are impacting the SMB of the Greenland Ice Sheet.

Gelatinization and freeze-concentration effects on recrystallization in corn and potato starch gels.

PubMed

Ronda, Felicidad; Roos, Yrjö H

2008-04-07

Freeze-concentration of starch gels was controlled by temperature and gelatinization with glucose and lactose. The aim of the study was to evaluate the effects of freezing temperature and gel composition on starch recrystallization behaviour of corn and potato starch gels (water content 70%, w/w) in water or glucose or lactose (10%, w/w) solutions. Starch gels were obtained by heating in differential scanning calorimetry (DSC). Samples of starch gels were frozen at -10 degrees C, -20 degrees C and -30 degrees C for 24h and, after thawing, stored at +2 degrees C for 0, 1, 2, 4 and 8 days. The extent of starch recrystallization was taken from the enthalpy of melting of the recrystallized starch by DSC. Freezing temperatures, glucose, lactose and the origin of the starch affected the recrystallization behaviour greatly. The recrystallization of amorphous starch during storage was enhanced by freeze-concentration of gels at temperatures above T'(m). Molecular mobility was enhanced by unfrozen water and consequently molecular rearrangements for nucleation could take place. Further storage at a higher temperature enhanced the growth and the maturation of crystals. In particular, glucose decreased the T'(m) of the gels and consequently lower freezing temperatures were needed to reduce enhanced recrystallization during storage. Freeze-concentration temperatures also showed a significant effect on the size and the perfection of crystals formed in starch recrystallization.

Origins of ultralow velocity zones through slab-derived metallic melt

PubMed Central

Liu, Jiachao; Li, Jie; Smith, Jesse S.

2016-01-01

Understanding the ultralow velocity zones (ULVZs) places constraints on the chemical composition and thermal structure of deep Earth and provides critical information on the dynamics of large-scale mantle convection, but their origin has remained enigmatic for decades. Recent studies suggest that metallic iron and carbon are produced in subducted slabs when they sink beyond a depth of 250 km. Here we show that the eutectic melting curve of the iron−carbon system crosses the current geotherm near Earth’s core−mantle boundary, suggesting that dense metallic melt may form in the lowermost mantle. If concentrated into isolated patches, such melt could produce the seismically observed density and velocity features of ULVZs. Depending on the wetting behavior of the metallic melt, the resultant ULVZs may be short-lived domains that are replenished or regenerated through subduction, or long-lasting regions containing both metallic and silicate melts. Slab-derived metallic melt may produce another type of ULVZ that escapes core sequestration by reacting with the mantle to form iron-rich postbridgmanite or ferropericlase. The hypotheses connect peculiar features near Earth's core−mantle boundary to subduction of the oceanic lithosphere through the deep carbon cycle. PMID:27143719

Recrystallization texture in nickel heavily deformed by accumulative roll bonding

NASA Astrophysics Data System (ADS)

Mishin, O. V.; Zhang, Y. B.; Godfrey, A.

2017-07-01

The recrystallization behavior of Ni processed by accumulative roll bonding to a total accumulated von Mises strain of 4.8 has been examined, and analyzed with respect to heterogeneity in the deformation microstructure. The regions near the bonding interface are found to be more refined and contain particle deformation zones around fragments of the steel wire brush used to prepare the surface for bonding. Sample-scale gradients are also observed, manifested as differences between the subsurface, intermediate and central layers, where the distributions of texture components are different. These heterogeneities affect the progress of recrystallization. While the subsurface and near-interface regions typically contain lower frequencies of cube-oriented grains than anywhere else in the sample, a strong cube texture forms in the sample during recrystallization, attributed to both a high nucleation rate and fast growth rate of cube-oriented grains. The observations highlight the sensitivity of recrystallization to heterogeneity in the deformation microstructure and demonstrate the importance of characterizing this heterogeneity over several length scales.

Integrated melt inclusion and crystal zoning study to track the timescales and pre-eruption dynamics of violent Strombolian eruptions at Llaima volcano, Chile

NASA Astrophysics Data System (ADS)

Ruth, D. C.; Costa Rodriguez, F.; Bouvet de Maisonneuve, C.; Calder, E. S.

2013-12-01

Melt inclusion compositions in crystals from many volcanic systems are notoriously variable and some times difficult to interpret. Their compositions can be a combination of rapid crystal growth, entrapment of local melt, and diffusive re-equilibration, among other processes. Additionally, chemical zoning in olivine records changing environmental conditions, most importantly temperature and magma composition. Many geochemical studies focus on either melt inclusion data or chemical zoning data to ascertain volcanic processes. Here we combine melt inclusion data with that of chemical zoning of the olivine host crystals from the 2008 violent Strombolian eruption of Llaima volcano, Chile, to obtain a more refined understanding of the processes related to crystal growth, melt inclusion formation, and magma dynamics. We investigated zoning characteristics in a suite of olivine crystals, created X-ray element maps (Al, Ca, Mg, P, Fe), and collected quantitative elemental abundances across chemical zones for detailed diffusion modeling. Melt inclusion compositions were collected via electron microprobe analysis and LA-ICPMS. We observe three types of zoning in the host olivine crystals: normal, reverse, and multiple zones with fluctuating Fo content. Reverse zoning was more common than the other types. Regardless of zoning character, multiple melt inclusions are present within a given olivine, often found near the crystal rim. For some of these melt inclusions, the olivine surrounding the melt inclusion was also zoned, often to a similar composition as the olivine rim. This implies that these inclusions remained connected with interstitial matrix melt until melt inclusion closure. These ';open' melt inclusions exhibited slightly different major (higher SiO2, Na2O+K2O, TiO2) and trace elements (positive Eu and Sr anomalies) compared to melt inclusions in the same olivine that were not surrounded by compositional zoning. Quantitative elemental profiles produce modeled

Rapid hydrothermal cooling above the axial melt lens at fast-spreading mid-ocean ridge

NASA Astrophysics Data System (ADS)

Zhang, Chao; Koepke, Juergen; Kirchner, Clemens; Götze, Niko; Behrens, Harald

2014-09-01

Axial melt lenses sandwiched between the lower oceanic crust and the sheeted dike sequences at fast-spreading mid-ocean ridges are assumed to be the major magma source of oceanic crust accretion. According to the widely discussed ``gabbro glacier'' model, the formation of the lower oceanic crust requires efficient cooling of the axial melt lens, leading to partial crystallization and crystal-melt mush subsiding down to lower crust. These processes are believed to be controlled by periodical magma replenishment and hydrothermal circulation above the melt lens. Here we quantify the cooling rate above melt lens using chemical zoning of plagioclase from hornfelsic recrystallized sheeted dikes drilled from the East Pacific at the Integrated Ocean Drilling Program Hole 1256D. We estimate the cooling rate using a forward modelling approach based on CaAl-NaSi interdiffusion in plagioclase. The results show that cooling from the peak thermal overprint at 1000-1050°C to 600°C are yielded within about 10-30 years as a result of hydrothermal circulation above melt lens during magma starvation. The estimated rapid hydrothermal cooling explains how the effective heat extraction from melt lens is achieved at fast-spreading mid-ocean ridges.

Electrical conductivity of hydrous andesitic melts pertinent to subduction zones

NASA Astrophysics Data System (ADS)

Guo, Xuan; Li, Bin; Ni, Huaiwei; Mao, Zhu

2017-03-01

Andesitic magmatism and rocks are widespread at convergent plate boundaries. Electrically conductive bodies beneath subduction zone arc volcanoes, such as the Uturuncu Volcano, Bolivia, may correspond to active reservoirs of H2O-bearing andesitic magma. Laboratory measurements of electrical conductivity of hydrous andesitic melts are required to constrain the physicochemical conditions of these magma reservoirs in combination with magnetotelluric data. This experimental study investigates electrical conductivity of andesitic melts with 0.01-5.9 wt % of H2O at 1164-1573 K and 0.5-1.0 GPa in a piston cylinder apparatus using sweeping-frequency impedance spectroscopy. Electrical conductivity of andesitic melt increases with increasing temperature and H2O concentration but decreases with pressure. Across the investigated range of H2O concentration, electrical conductivity varies by 1.2-2.4 log units, indicating stronger influence of H2O for andesitic melt than for rhyolitic and dacitic melts. Using the Nernst-Einstein equation, the principal charge carrier is inferred to be Na in anhydrous melt but divalent cations in hydrous andesitic melts. The experimental data are regressed into a general electrical conductivity model for andesitic melt accounting for the pressure-temperature-H2O dependences altogether. Modeling results show that the conductive layer at >20 km depths beneath the surface of the Uturuncu Volcano could be interpreted by the presence of less than 20 vol % of H2O-rich andesitic melt (with 6-9 wt % H2O).

Recrystallized Impact Glasses of the Onaping Formation and the Sudbury Igneous Complex, Sudbury Structure, Ontario, Canada

NASA Technical Reports Server (NTRS)

Dressler, B. O.; Weiser, T.; Brockmeyer, P.

1996-01-01

The origin of the Sudbury Structure and of the associated heterolithic breccias of the Onaping Formation and the Sudbury Igneous Complex have been controversial. While an impact origin of the structure has gained wide acceptance over the last 15 years, the origin of the recrystallized Onaping Formation glasses and of the igneous complex is still being debated. Recently the interpretation of the breccias of the Onaping Formation as suevitic fall-back impact breccias has been challenged. The igneous complex is interpreted either as a differentiated impact melt sheet or as a combination of an upper impact melt represented by the granophyre, and a lower, impact-triggered magmatic body consisting of the norite-sublayer formations. The Onaping Formation contains glasses as fluidal and nonfluidal fragments of various shapes and sizes. They are recrystallized, and our research indicates that they are petrographically heterogeneous and span a wide range of chemical compositions. These characteristics are not known from glasses of volcanic deposits. This suggests an origin by shock vitrification, an interpretation consistent with their association with numerous and varied country rock clasts that exhibit microscopic shock metamorphic features. The recrystallized glass fragments represent individual solid-state and liquid-state vitrified rocks or relatively small melt pods. The basal member lies beneath the Gray and Black members of the Onaping Formation and, where not metamorphic, has an igneous matrix. Igneous-textured melt bodies occur in the upper two members and above the Basal Member. A comparison of the chemical compositions of recrystallized glasses and of the matrices of the Basal Member and the melt bodies with the components and the bulk composition of the igneous complex is inconclusive as to the origin of the igneous complex. Basal Member matrix and Melt Bodies, on average, are chemically similar to the granophyre of the Sudbury Igneous Complex, suggesting that

Stress in recrystallized quartz by electron backscatter diffraction mapping

NASA Astrophysics Data System (ADS)

Llana-Fúnez, S.

2017-07-01

The long-term state of stress at middle and lower crustal depths can be estimated through the study of the microstructure of exhumed rocks from active and/or ancient shear zones. Constitutive equations for deformation mechanisms in experimentally deformed rocks relate differential stress to the size of recrystallized grains. Cross et al. (2017) take advantage of electron backscatter diffraction mapping to systematically separate new recrystallized grains from host grains on the basis of the measurable lattice distorsion within the grains. They produce the first calibrated piezometer for quartz with this technique, reproducing within error a previous calibration based on optical microscopy.

Recrystallization and grain growth in NiAl

NASA Technical Reports Server (NTRS)

Haff, G. R.; Schulson, E. M.

1982-01-01

Aluminide intermetallics, because of their strength, microstructural stability, and oxidation resistance at elevated temperatures, represent potential structural materials for use in advanced energy conversion systems. This inherent potential of the intermetallics can currently not be realized in connection with the general brittleness of the materials under ambient conditions. It is pointed out, however, that brittleness is not an inherent characteristic. Single crystals are ductile and polycrystals may be, too, if their grains are fine enough. The present investigation is concerned with an approach for reducing material brittleness, taking into account thermal-mechanically induced grain refinement in NiAl, a B2 aluminide which melts at 1638 C and which retains complete order to its melting point. Attention is given to the kinetics of recrystallization and grain growth of warm-worked, nickel-rich material.

Unlocking the Secrets of the Mantle Wedge: New Insights Into Melt Generation Processes in Subduction Zones

NASA Astrophysics Data System (ADS)

Grove, T. L.

2007-05-01

Recent laboratory studies of the melting and crystallization behavior of mantle peridotite and subduction zone lavas have led to new insights into melting processes in island arc settings. Melting of the mantle wedge in the presence of H2O begins at much lower temperatures than previously thought. The solidus of mantle peridotite at 3 GPa is ~ 800 °C, which is 200 °C below previous estimates. At pressures greater than 2.4 GPa chlorite becomes a stable phase on the solidus and it remains stable until ~ 3.5 GPa. Therefore, melting over this pressure range occurs in the presence of chlorite, which contains ~ 12 wt. % H2O. Chlorite stabilized on the peridotite solidus by slab-derived H2O may be the ultimate source of H2O for subduction zone magmatism. Thus, chlorite could transport large amounts of H2O into the descending mantle wedge to depths where it can participate in melting to generate hydrous arc magmas. Our ability to identify primitive mantle melts at subduction zones has led to the following observations. 1) Primitive mantle melts show evidence of final equilibration at shallow depths near the mantle - crust boundary. 2) They contain variable amounts of dissolved H2O (up to 6 wt. %). 3) They record variable extents of melting (up to > 25 wt. %). To produce melts with such variable characteristics requires more than one melting process and requires consideration of a new type of melting called hydrous flux melting. Flux melting occurs when the H2O - rich melt initially produced on the solidus near the base of the mantle wedge ascends and continuously reacts with overlying hotter, shallower mantle. The mantle melts and magmatic H2O content is constantly diluted as the melt ascends and reacts with shallower, hotter mantle. Anhydrous mantle melts are also found in close temporal and spatial proximity to hydrous flux melts. These melts are extracted at similar depths near the top of the mantle wedge when mantle is advected up and into the wedge corner and melted

Origins of ultralow velocity zones through slab-derived metallic melt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jiachao; Li, Jie; Hrubiak, Rostislav

2016-05-03

Understanding the ultralow velocity zones (ULVZs) places constraints on the chemical composition and thermal structure of deep Earth and provides critical information on the dynamics of large-scale mantle convection, but their origin has remained enigmatic for decades. Recent studies suggest that metallic iron and carbon are produced in subducted slabs when they sink beyond a depth of 250 km. Here we show that the eutectic melting curve of the iron-carbon system crosses the current geotherm near Earth’s core-mantle boundary, suggesting that dense metallic melt may form in the lowermost mantle. If concentrated into isolated patches, such melt could produce themore » seismically observed density and velocity features of ULVZs. Depending on the wetting behavior of the metallic melt, the resultant ULVZs may be short-lived domains that are replenished or regenerated through subduction, or long-lasting regions containing both metallic and silicate melts. Slab-derived metallic melt may produce another type of ULVZ that escapes core sequestration by reacting with the mantle to form iron-rich post-bridgmanite or ferropericlase. The hypotheses connect peculiar features near Earth’s core-mantle boundary to subduction of the oceanic lithosphere through the deep carbon cycle.« less

Trace Elements in Basalts From the Siqueiros Fracture Zone: Implications for Melt Migration Models

NASA Astrophysics Data System (ADS)

Pickle, R. C.; Forsyth, D. W.; Saal, A. E.; Nagle, A. N.; Perfit, M. R.

2008-12-01

Incompatible trace element (ITE) ratios in MORB from a variety of locations may provide insights into the melt migration process by constraining aggregated melt compositions predicted by mantle melting and flow models. By using actual plate geometries to create a 3-D thermodynamic mantle model, melt volumes and compositions at all depths and locations may be calculated and binned into cubes using the pHMELTS algorithm [Asimow et al., 2004]. These melts can be traced from each cube to the surface assuming several migration models, including a simplified pressure gradient model and one in which melt is guided upwards by a low permeability compacted layer. The ITE ratios of all melts arriving at the surface are summed, averaged, and compared to those of the actual sample compositions from the various MOR locales. The Siqueiros fracture zone at 8° 20' N on the East Pacific Rise (EPR) comprises 4 intra-transform spreading centers (ITSCs) across 140 km of offset between two longer spreading ridges, and is an excellent study region for several reasons. First, an abundance of MORB data is readily available, and the samples retrieved from ITSCs are unlikely to be aggregated in a long-lived magma chamber or affected by along-axis transport, so they represent melts extracted locally from the mantle. Additionally, samples at Siqueiros span a compositional range from depleted to normal MORB within the fracture zone yet have similar isotopic compositions to samples collected from the 9-10° EPR. This minimizes the effect of assuming a uniform source composition in our melting model despite a heterogeneous mantle, allowing us to consistently compare the actual lava composition with that predicted by our model. Finally, it has been demonstrated with preliminary migration models that incipient melts generated directly below an ITSC may not necessarily erupt at that ITSC but migrate laterally towards a nearby ridge due to enhanced pressure gradients. The close proximity of the

Recrystallization of polycrystalline silicon

NASA Technical Reports Server (NTRS)

Lall, C.; Kulkarni, S. B.; Graham, C. D., Jr.; Pope, D. P.

1981-01-01

Optical metallography is used to investigate the recrystallization properties of polycrystalline semiconductor-grade silicon. It is found that polycrystalline silicon recrystallizes at 1380 C in relatively short times, provided that the prior deformation is greater than 30%. For a prior deformation of about 40%, the recrystallization process is essentially complete in about 30 minutes. Silicon recrystallizes at a substantially slower rate than metals at equivalent homologous temperatures. The recrystallized grain size is insensitive to the amount of prestrain for strains in the range of 10-50%.

Hot 'nough for ya?: Controls and Constraints on modeling flux melting in subduction zones

NASA Astrophysics Data System (ADS)

Spiegelman, M.; Wilson, C. R.; van Keken, P.; Kelemen, P. B.; Hacker, B. R.

2012-12-01

The qualitative concept of flux-melting in subduction zones is well established. Progressive dehydration reactions in the down-going slab release fluids to the hot overlying mantle wedge, causing flux melting and the migration of melts to the volcanic front. However, the quantitative details of fluid release, migration, melt generation and transport in the wedge remain poorly understood. In particular, there are two fundamental observations that defy quantitative modeling. The first is the location of the volcanic front with respect to intermediate depth earthquake (e.g. ˜ 100±40 km; England et al., 2004, Syracuse and Abers, 2006) which is remarkably robust yet insensitive to subduction parameters. This is particularly surprising given new estimates on the variability of fluid release in global subduction zones (e.g. van Keken et al. 2011) which show great sensitivity of fluid release to slab thermal conditions. Reconciling these results implies some robust mechanism for focusing fluids/melts toward the wedge corner. The second observation is the global existence of thermally hot erupted basalts and andesites that, if derived from flux melting of the mantle requires sub-arc mantle temperatures of ˜ 1300° C over shallow pressures of 1-2 GPa which are not that different from mid-ocean ridge conditions. These thermodynamic constraints are also implicit in recent parameterizations of wet melting (e.g. Kelley et al, 2010) which tend to produce significant amounts of melt only near the dry solidus. These observations impose significant challenges for geodynamic models of subduction zones, and in particular for those that don't include the explicit transport of fluids and melts. We present new high-resolution model results that suggest that a more complete description of coupled fluid/solid mechanics (allowing the fluid to interact with solid rheological variations) together with rheologically consistent solutions for temperature and solid flow, may provide the

Solid State Research.

DTIC Science & Technology

1982-11-22

48 Fabricated in Zone-Melting-Recrystallized Si Films on Si0 2-Coated Si Substrates V 4. MICROELECTRONICS 55 4.1 Charge-Coupled Devices: Time...OMCVD to the CLEFT (cleavage of lateral epitaxial films for transfer) process, a continuous epitaxial GaAs layer 3 Ym thick has been grown over a...complete-island-etch or local-oxidation-of-Si isolation, that were fabricated in zone-melting-recrystallized Si films on Si02-coated Si substrates. As

Microstructural and rheological evolution of calcite mylonites during shear zone thinning: Constraints from the Mount Irene shear zone, Fiordland, New Zealand

NASA Astrophysics Data System (ADS)

Negrini, Marianne; Smith, Steven A. F.; Scott, James M.; Tarling, Matthew S.

2018-01-01

Layers of calc-mylonite in the Mount Irene shear zone, Fiordland, New Zealand, show substantial variations in thickness due to deflection of the shear zone boundaries around wall rock asperities. In relatively thick parts (c. 2.6 m) of the shear zone, calcite porphyroclasts are internally strained, contain abundant subgrain boundaries and have a strong shape preferred orientation (SPO) and crystallographic preferred orientation (CPO), suggesting that deformation occurred mainly by dislocation creep involving subgrain-rotation recrystallization. In relatively thin parts (c. 1.5 m) of the shear zone, aggregates of fine-grained recrystallized calcite surrounding flattened porphyroclasts have a weak SPO and CPO, and contain polygonal calcite grains with low degrees of internal misorientation. The recrystallized aggregates also contain microstructures (e.g. grain quadruple junctions, randomized misorientation axes) similar to those reported for neighbor-switching processes during grain-boundary sliding. Comparison of subgrain sizes in the porphyroclasts to published grain-size differential-stress relationships indicates that stresses and strain rates were substantially higher in relatively thin parts of the shear zone. The primary microstructural response to higher stresses and strain rates was an increase in the amount of recrystallization to produce aggregates that deformed by grain-boundary sliding. However, even after the development of interconnected networks of recrystallized grains, dislocation creep by subgrain-rotation recrystallization continued to occur within porphyroclasts. This behavior suggests that the bulk rheology of shear zones undergoing thinning and thickening can be controlled by concomitant grain-size insensitive and grain-size sensitive mechanisms. Overall, our observations show that shear zone thickness variations at constant P-T can result in highly variable stresses and strain rates, which in turn modifies microstructure, deformation mechanism

Surface recrystallization theory of the wear of copper in liquid methane

NASA Technical Reports Server (NTRS)

Bill, R. C.; Wisander, D. W.

1974-01-01

Copper was subjected to sliding against 440C in liquid methane. The normal load range was from 1/4 to 2 kilograms, and the sliding velocity range was from 3.1 to 25 meters per second. Over this range of experimental parameters, the wear rate of the copper rider was found to be proportional to the sliding velocity squared and to the normal load. Transmission electron microscopy was used to study the dislocation structure in the copper very near the wear scar surface. It was found that near the wear scar surface, the microstructure was characterized by a fine-cell recrystallized zone in which individual dislocations could be distinguished in the cell walls. The interiors of the cells, about 0.5 micrometer in diameter, were nearly dislocation free. Below the recrystallized layer was a zone that was intensely cold worked by the friction process. With increasing depth, this intensely cold worked zone gradually became indistinguishable from the partially cold worked bulk of the copper, representative of the initial condition of the material.

Separation of supercritical slab-fluids to form aqueous fluid and melt components in subduction zone magmatism.

PubMed

Kawamoto, Tatsuhiko; Kanzaki, Masami; Mibe, Kenji; Matsukage, Kyoko N; Ono, Shigeaki

2012-11-13

Subduction-zone magmatism is triggered by the addition of H(2)O-rich slab-derived components: aqueous fluid, hydrous partial melts, or supercritical fluids from the subducting slab. Geochemical analyses of island arc basalts suggest two slab-derived signatures of a melt and a fluid. These two liquids unite to a supercritical fluid under pressure and temperature conditions beyond a critical endpoint. We ascertain critical endpoints between aqueous fluids and sediment or high-Mg andesite (HMA) melts located, respectively, at 83-km and 92-km depths by using an in situ observation technique. These depths are within the mantle wedge underlying volcanic fronts, which are formed 90 to 200 km above subducting slabs. These data suggest that sediment-derived supercritical fluids, which are fed to the mantle wedge from the subducting slab, react with mantle peridotite to form HMA supercritical fluids. Such HMA supercritical fluids separate into aqueous fluids and HMA melts at 92 km depth during ascent. The aqueous fluids are fluxed into the asthenospheric mantle to form arc basalts, which are locally associated with HMAs in hot subduction zones. The separated HMA melts retain their composition in limited equilibrium with the surrounding mantle. Alternatively, they equilibrate with the surrounding mantle and change the major element chemistry to basaltic composition. However, trace element signatures of sediment-derived supercritical fluids remain more in the melt-derived magma than in the fluid-induced magma, which inherits only fluid-mobile elements from the sediment-derived supercritical fluids. Separation of slab-derived supercritical fluids into melts and aqueous fluids can elucidate the two slab-derived components observed in subduction zone magma chemistry.

Separation of supercritical slab-fluids to form aqueous fluid and melt components in subduction zone magmatism

PubMed Central

Kawamoto, Tatsuhiko; Kanzaki, Masami; Mibe, Kenji; Ono, Shigeaki

2012-01-01

Subduction-zone magmatism is triggered by the addition of H2O-rich slab-derived components: aqueous fluid, hydrous partial melts, or supercritical fluids from the subducting slab. Geochemical analyses of island arc basalts suggest two slab-derived signatures of a melt and a fluid. These two liquids unite to a supercritical fluid under pressure and temperature conditions beyond a critical endpoint. We ascertain critical endpoints between aqueous fluids and sediment or high-Mg andesite (HMA) melts located, respectively, at 83-km and 92-km depths by using an in situ observation technique. These depths are within the mantle wedge underlying volcanic fronts, which are formed 90 to 200 km above subducting slabs. These data suggest that sediment-derived supercritical fluids, which are fed to the mantle wedge from the subducting slab, react with mantle peridotite to form HMA supercritical fluids. Such HMA supercritical fluids separate into aqueous fluids and HMA melts at 92 km depth during ascent. The aqueous fluids are fluxed into the asthenospheric mantle to form arc basalts, which are locally associated with HMAs in hot subduction zones. The separated HMA melts retain their composition in limited equilibrium with the surrounding mantle. Alternatively, they equilibrate with the surrounding mantle and change the major element chemistry to basaltic composition. However, trace element signatures of sediment-derived supercritical fluids remain more in the melt-derived magma than in the fluid-induced magma, which inherits only fluid-mobile elements from the sediment-derived supercritical fluids. Separation of slab-derived supercritical fluids into melts and aqueous fluids can elucidate the two slab-derived components observed in subduction zone magma chemistry. PMID:23112158

A numerical study of zone-melting process for the thermoelectric material of Bi2Te3

NASA Astrophysics Data System (ADS)

Chen, W. C.; Wu, Y. C.; Hwang, W. S.; Hsieh, H. L.; Huang, J. Y.; Huang, T. K.

2015-06-01

In this study, a numerical model has been established by employing a commercial software; ProCAST, to simulate the variation/distribution of temperature and the subsequent microstructure of Bi2Te3 fabricated by zone-melting technique. Then an experiment is conducted to measure the temperature variation/distribution during the zone-melting process to validate the numerical system. Also, the effects of processing parameters on crystallization microstructure such as moving speed and temperature of heater are numerically evaluated. In the experiment, the Bi2Te3 powder are filled into a 30mm diameter quartz cylinder and the heater is set to 800°C with a moving speed 12.5 mm/hr. A thermocouple is inserted in the Bi2Te3 powder to measure the temperature variation/distribution of the zone-melting process. The temperature variation/distribution measured by experiment is compared to the results of numerical simulation. The results show that our model and the experiment are well matched. Then the model is used to evaluate the crystal formation for Bi2Te3 with a 30mm diameter process. It's found that when the moving speed is slower than 17.5 mm/hr, columnar crystal is obtained. In the end, we use this model to predict the crystal formation of zone-melting process for Bi2Te3 with a 45 mm diameter. The results show that it is difficult to grow columnar crystal when the diameter comes to 45mm.

Ice Recrystallization in a Solution of a Cryoprotector and Its Inhibition by a Protein: Synchrotron X-Ray Diffraction Study.

PubMed

Zakharov, Boris; Fisyuk, Alexander; Fitch, Andy; Watier, Yves; Kostyuchenko, Anastasia; Varshney, Dushyant; Sztucki, Michael; Boldyreva, Elena; Shalaev, Evgenyi

2016-07-01

Ice formation and recrystallization is a key phenomenon in freezing and freeze-drying of pharmaceuticals and biopharmaceuticals. In this investigation, high-resolution synchrotron X-ray diffraction is used to quantify the extent of disorder of ice crystals in binary aqueous solutions of a cryoprotectant (sorbitol) and a protein, bovine serum albumin. Ice crystals in more dilute (10 wt%) solutions have lower level of microstrain and larger crystal domain size than these in more concentrated (40 wt%) solutions. Warming the sorbitol-water mixtures from 100 to 228 K resulted in partial ice melting, with simultaneous reduction in the microstrain and increase in crystallite size, that is, recrystallization. In contrast to sorbitol solutions, ice crystals in the BSA solutions preserved both the microstrain and smaller crystallite size on partial melting, demonstrating that BSA inhibits ice recrystallization. The results are consistent with BSA partitioning into quasi-liquid layer on ice crystals but not with a direct protein-ice interaction and protein sorption on ice surface. The study shows for the first time that a common (i.e., not-antifreeze) protein can have a major impact on ice recrystallization and also presents synchrotron X-ray diffraction as a unique tool for quantification of crystallinity and disorder in frozen aqueous systems. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Devitrification and recrystallization of nanoparticle-containing glycerol and PEG-600 solutions.

PubMed

Lv, Fukou; Liu, Baolin; Li, Weijie; Jaganathan, Ganesh K

2014-02-01

Nanoparticles in solution offer unique electrical, mechanical and thermal properties due to their physical presence and interaction with the state of dispersion. This work is aimed to study the effects of hydroxyapatite (HA) nanoparticles on the devitrification and recrystallization events of two important cryoprotective solutions used in cell and tissue preservation namely glycerol (60%w/w) and PEG-600 (50%w/w). HA nanoparticles (20, 40 or 60 nm) were incorporated into solutions at the content of 0.1% or 0.5%(w/w), and were studied by differential scanning calorimeter (DSC) and cryomicroscopy. The presence of nanoparticles does not change the glass transition temperatures and melting temperatures of quenched solutions, but significantly affects the behavior of devitrification and recrystallization upon warming. Cryomicroscopic investigation showed the complex interactions among solution type, nanoparticle size and nanoparticle content, which apparently influence ice crystal growth or recrystallization in the quenched dispersions. These findings have significant implications for biomaterial cryopreservation, cryosurgery, and food manufacturing. The complexity of ice crystal growth kinetics in nanoparticle-containing dispersions remains to be poorly understood at the moment. Copyright © 2013 Elsevier Inc. All rights reserved.

Growth of early continental crust by water-present eclogite melting in subduction zones

NASA Astrophysics Data System (ADS)

Laurie, A.; Stevens, G.

2011-12-01

The geochemistry of well preserved Paleo- to Meso-Archaean Tonalite-Trondhjemite-Granodiorite (TTG) suite rocks, such as the ca 3.45 Ga trondhjemites from the Barberton greenstone belt in South Africa, provides insight into the origins of Earth's early felsic continental crust. This is particularly well demonstrated by the high-Al2O3 variety of these magmas, such as the Barberton rocks, where the geochemistry requires that they are formed by high pressure (HP) melting of a garnet-rich metamafic source. This has been interpreted as evidence for the formation of these magmas by anatexis of the upper portions of slabs within Archaean subduction zones. Most of the experimental data relevant to Archaean TTG genesis has been generated by studies of fluid-absent melting of metabasaltic sources. However, water drives arc magmatism within Phanerozoic subduction zones and thus, understanding the behaviour of water in Archaean subduction zones, may have considerable value for understanding the genesis of these TTG magmas. Consequently, this study investigates the role of HP water-present melting of an eclogite-facies starting material, in the production of high-Al2O3 type TTG melts. Water-saturated partial melting experiments were conducted between 1.9 and 3.0GPa; and, 870°C and 900°C. The melting reaction is characterized by the breakdown of sodic Cpx, together with Qtz and H2O, to form melt in conjunction with a less sodic Cpx: Qtz + Cpx1 + Grt1 + H2O = Melt + Cpx2 + Grt2. In many of the experimental run products, melt segregated efficiently from residual crystals, allowing for the measurement of a full range of trace elements via Laser Ablation Inductively Coupled Plasma Mass Spectroscopy. The experimental glasses produced by this study have the compositions of peraluminous trondhjemites; and they are light rare earth element, Zr and Sr enriched; and heavy rare earth element, Y and Nb depleted. The compositions of the experimental glasses are similar to high-Al2O3 type

Slab melting versus slab dehydration in subduction-zone magmatism

PubMed Central

Mibe, Kenji; Kawamoto, Tatsuhiko; Matsukage, Kyoko N.; Fei, Yingwei; Ono, Shigeaki

2011-01-01

The second critical endpoint in the basalt-H2O system was directly determined by a high-pressure and high-temperature X-ray radiography technique. We found that the second critical endpoint occurs at around 3.4 GPa and 770 °C (corresponding to a depth of approximately 100 km in a subducting slab), which is much shallower than the previously estimated conditions. Our results indicate that the melting temperature of the subducting oceanic crust can no longer be defined beyond this critical condition and that the fluid released from subducting oceanic crust at depths greater than 100 km under volcanic arcs is supercritical fluid rather than aqueous fluid and/or hydrous melts. The position of the second critical endpoint explains why there is a limitation to the slab depth at which adakitic magmas are produced, as well as the origin of across-arc geochemical variations of trace elements in volcanic rocks in subduction zones. PMID:21536910

Deformation, recrystallization, strength, and fracture of press-forged ceramic crystals.

NASA Technical Reports Server (NTRS)

Rice, R. W.

1972-01-01

Sapphire and ruby were very difficult to press-forge because they deformed without cracking only in a limited temperature range before they melted. Spinel crystals were somewhat easier and MgO, CaO, and TiC crystals much easier to forge. The degree of recrystallization that occurred during forging (which was related to the ease and type of slip intersections) varied from essentially zero in Al2O3 to complete (i.e., random polycrystalline bodies were produced) in CaO. Forging of bi- and polycrystalline bodies produced incoherent bodies as a result of grain-boundary sliding. Strengths of the forged crystals were comparable to those of dense polycrystalline bodies of similar grain size. However, forged and recrystallized CaO crystals were ductile at lower temperatures than dense hot-pressed CaO. This behavior is attributed to reduced grain-boundary impurities and porosity. Fracture origins could be located, indicating that fracture in the CaO occurs internally as a result of surface work hardening caused by machining.-

Deformation and recrystallization behavior of super high-purity niobium for SRF cavity

NASA Astrophysics Data System (ADS)

Yamaguchi, Y.; Doryo, H.; Yuasa, M.; Miyamoto, H.; Yamanaka, M.

2017-05-01

Deformation and recyrstallization behavior of pure niobium was investigated in order to clarify the origin of its low hydro-formability despite of its high ductility comparable with pure iron. It was found that pure niobium exhibits lower strain hardening in cold rolling compared with pure iron. Furthermore, in post-deformation annealing, the hardness of niobium decreased monotonously with an increase of temperature, and the typical sharp drop by recrystallization was not evident. This softening behavior was contrasted with the high-purity iron. It is suggested that niobium exhibit the so-called in-situ recrystallization possibly because of low elastic modulus and low accumulative plastic strain energy in spite of high melting temperature. The low hydro-formability of pure niobium sheets or tubes is caused by its low strain hardening and its unique plastic anisotropy which is associated with this recovered residual rolled texture.

Resonant absorption induced fast melting studied with mid-IR QCLs.

PubMed

Lu, Jie; Lv, Yankun; Ji, Youxin; Tang, Xiaoliang; Qi, Zeming; Li, Liangbin

2017-02-01

We demonstrate the use of a pump-probe setup based on two mid-infrared quantum cascade lasers (QCLs) to investigate the melting and crystallization of materials through resonant absorption. A combination of pump and probe beams fulfills the two-color synchronous detection. Furthermore, narrow linewidth advances the accuracy of measurements and the character of broad tuning range of QCLs enables wide applications in various sample and multiple structures. 1-Eicosene was selected as a simple model system to verify the feasibility of this method. A pulsed QCL was tuned to the absorption peak of CH 2 bending vibration at 1467 cm -1 to resonantly heat the sample. The other QCL in continuous mode was tuned to 1643 cm -1 corresponding the C=C stretching vibration to follow the fast melting dynamics. By monitoring the transmission intensity variation of pump and probe beams during pump-probe experiments, the resonant absorption induced fast melting and re-crystallization of 1-Eicosene can be studied. Results show that the thermal effect and melting behaviors strongly depend on the pump wavelength (resonant or non-resonant) and energy, as well as the pump time. The realization and detection of melting and recrystallization can be performed in tens of milliseconds, which improves the time resolution of melting process study based on general mid-infrared spectrum by orders of magnitude. The availability of resonant heating and detections based on mid-infrared QCLs is expected to enable new applications in melting study.

Spatial distribution of quartz recrystallization microstructures across the Aar massif (Swiss Central Alps)

NASA Astrophysics Data System (ADS)

Peters, M.; Herwegh, M.

2012-04-01

In the Aar massif, main foliation and major deformation structures were developed during NW-SE compression associated with the Alpine orogeny (Steck 1968). To be precise, shearing at the brittle to ductile transition may have initiated at different stages between 22-20 Ma and 14-12 Ma, followed by purely brittle deformation at around 10 Ma (Rolland et al. 2009). In light of the onset of dynamic recrystallization in quartz, Bambauer et al. (2009) defined a quartz recrystallization isograd in the northern part of the Aar massif. To the south, the grain size of recrystallized grains increases due to an increase of metamorphic temperatures from N to S. The aim of the current project is to carry out quantitative analysis on changes of the dynamic and static recrystallization behavior of quartz. Across the Aar massif, two general types of microstructures have to be discriminated: (i) weakly to moderately deformed host rocks and (ii) intensely deformed mylonites to ultramylonites out of high strain shear zones. In (i), volume fraction and size of recrystallized quartz grains increase towards the S showing grain size changes from around 5 µm up to ca. 200 µm. Southern microstructures are characterized by complete recrystallization. In terms of recrystallization processes, a transition from bulging recrystallization in the N to subgrain rotation recrystallization in the S occurs. Such a change in dynamic recrystallization processes combined with a grain size increase points towards reduced differential stresses with increasing temperature. This temperature gradient is also corroborated by a switch in the active glide systems in quartz from basal to rhomb dominated glide. In contrast to the granitic host rocks, the mylonites and ultramylonites (ii) show smaller recrystallized grain sizes due to enhanced strain rates. However, they also reveal a general increase of recrystallized grain sizes from N to S. In the S, microstructures from (i) and (ii) show equidimensional

Relationship of Technological Properties with Dynamic Recrystallization of Quartz on the Example of Objects of the Karelian-Kola Region

NASA Astrophysics Data System (ADS)

Skamnitskaya, Lubov; Rakov, Leonid; Bubnova, Tatyana; Shchiptsov, Vladimir

2017-12-01

Despite the significant reserves of quartz raw materials, there is a deficit of high purity quartz. It is due to the strict technical requirements imposed by standards for this type of raw materials and technological properties of quartz, which are determined by the features of the crystal structure. The crystalline structure is of particular importance for the technological properties of quartz, since such important characteristics as the limit of raw material enrichment, dissolution rate in acid, melting point of quartz, etc., are determined. The formation of the crystal structure of quartz under natural conditions is associated with the successive dynamic recrystallization of the mineral. The degree of dynamic recrystallization of quartz reflects the distribution of dispersed impurities. If it is weakly manifested, the dispersed impurities are not displaced from one zone to another, and all quartz microblocks contain approximately the same concentration. In this case, more or less uniform dissolution of various regions of quartz is observed, and the pattern of distribution of submicroscopic inhomogeneities is monotonic. If intensive dynamic recrystallization of quartz takes place, then it causes a significant redistribution of the scattered impurities. Then the treatment in HF leads to the appearance of a contrast pattern of the distribution of submicroscopic inhomogeneities. The details of the crystal structure of quartz in this work were investigated by the electron paramagnetic resonance (EPR) method using the ER-420 “Bruker” spectrometer. In the selected samples of quartz, the concentrations of isomorphic impurities Al and Ti were measured, and the degree of crystallinity D of the mineral was estimated from the EPR spectra of each of them. Thus, the technological properties of quartz are determined by various geological processes. The results of the studies show that when evaluating the prospects of quartz raw materials, it is necessary to take into

The melting curve of Ni to 1 Mbar

NASA Astrophysics Data System (ADS)

Lord, Oliver T.; Wood, Ian G.; Dobson, David P.; Vočadlo, Lidunka; Wang, Weiwei; Thomson, Andrew R.; Wann, Elizabeth T. H.; Morard, Guillaume; Mezouar, Mohamed; Walter, Michael J.

2014-12-01

The melting curve of Ni has been determined to 125 GPa using laser-heated diamond anvil cell (LH-DAC) experiments in which two melting criteria were used: firstly, the appearance of liquid diffuse scattering (LDS) during in situ X-ray diffraction (XRD) and secondly, plateaux in temperature vs. laser power functions in both in situ and off-line experiments. Our new melting curve, defined by a Simon-Glatzel fit to the data where TM (K) = [ (PM/18.78 ± 10.20 + 1) ]1/2.42 ± 0.66 × 1726, is in good agreement with the majority of the theoretical studies on Ni melting and matches closely the available shock wave melting data. It is however dramatically steeper than the previous off-line LH-DAC studies in which determination of melting was based on the visual observation of motion aided by the laser speckle method. We estimate the melting point (TM) of Ni at the inner-core boundary (ICB) pressure of 330 GPa to be TM = 5800 ± 700 K (2 σ), within error of the value for Fe of TM = 6230 ± 500 K determined in a recent in situ LH-DAC study by similar methods to those employed here. This similarity suggests that the alloying of 5-10 wt.% Ni with the Fe-rich core alloy is unlikely to have any significant effect on the temperature of the ICB, though this is dependent on the details of the topology of the Fe-Ni binary phase diagram at core pressures. Our melting temperature for Ni at 330 GPa is ∼2500 K higher than that found in previous experimental studies employing the laser speckle method. We find that those earlier melting curves coincide with the onset of rapid sub-solidus recrystallization, suggesting that visual observations of motion may have misinterpreted dynamic recrystallization as convective motion of a melt. This finding has significant implications for our understanding of the high-pressure melting behaviour of a number of other transition metals.

Ultrasonic determination of recrystallization

NASA Technical Reports Server (NTRS)

Generazio, E. R.

1986-01-01

Ultrasonic attenuation was measured for cold worked Nickel 200 samples annealed at increasing temperatures. Localized dislocation density variations, crystalline order and colume percent of recrystallized phase were determined over the anneal temperature range using transmission electron microscopy, X-ray diffraction, and metallurgy. The exponent of the frequency dependence of the attenuation was found to be a key variable relating ultrasonic attenuation to the thermal kinetics of the recrystallization process. Identification of this key variable allows for the ultrasonic determination of onset, degree, and completion of recrystallization.

Secondary melting events in Semarkona chondrules revealed by compositional zoning in low-Ca pyroxene

NASA Astrophysics Data System (ADS)

Baecker, Bastian; Rubin, Alan E.; Wasson, John T.

2017-08-01

It is well established that many chondrules contain relict grains formed in previous generations of chondrules. We here describe evidence that chondrules experienced multiple mesostasis melting events while remaining closed systems. Spheroidal chondrule shapes resulted from surface-tension effects following a primary heating event that caused substantial melting (≳40%) of the precursor assemblages. In some high-FeO chondrules in LL3.00 Semarkona, low-Ca pyroxene phenocrysts show multiple overgrowth layers produced by secondary melting events. We characterized these layers with the electron microprobe in terms of Fe, Ca and Cr in two Semarkona chondrules. The first low-Ca pyroxene overgrowth that forms after a minor heating/melting event has low Ca and Fe; concentrations of these incompatibles gradually increase over the next 8 ± 4 μm until falling temperatures and slowing diffusion caused growth to stop. The next melting event remelts and mixes the local mesostasis; cooling causes growth of a normal igneously zoned layer. In the simplest cases, the Ca concentrations at the minima gradually increase towards the edge of the phenocryst. Heat deposition during heating events varied over a wide range; the weakest events produced recognizable changes in slopes (that we call "inflections" rather than minima). Large fractions of the individual phenocrysts were formed by the process that produced the overgrowth layers. It appears that overgrowth formation stopped when the Ca content of the mesostasis became high enough to make high-Ca pyroxene a liquidus phase. Both Semarkona chondrules include olivine phenocrysts similar in size and modal abundance to the low-Ca pyroxene phenocrysts. Olivine compositional profiles show symmetrical, apparently normal zoning except for asymmetries attributable to the presence of relict grains. Surface compositions of different olivine phenocrysts in the same chondrule are very similar to one another, consistent with growth from

Ultrasonic Determination Of Recrystallization

NASA Technical Reports Server (NTRS)

Generazio, Edward R.

1988-01-01

State of recrystallization identified. Measurement of ultrasonic attenuation shows promise as means of detecting recrystallization in metal. Technique applicable to real-time acoustic monitoring of thermomechanical treatments. Starting with work-hardened material, one ultrasonically determines effect of annealing, using correlation between ultrasonic attenuation and temperature.

Storage of fluids and melts at subduction zones detectable by seismic tomography

NASA Astrophysics Data System (ADS)

Luehr, B. G.; Koulakov, I.; Rabbel, W.; Brotopuspito, K. S.; Surono, S.

2015-12-01

During the last decades investigations at active continental margins discovered the link between the subduction of fluid saturated oceanic plates and the process of ascent of these fluids and partial melts forming a magmatic system that leads to volcanism at the earth surface. For this purpose the geophysical structure of the mantle and crustal range above the down going slap has been imaged. Information is required about the slap, the ascent paths, as well as the reservoires of fluids and partial melts in the mantle and the crust up to the volcanoes at the surface. Statistically the distance between the volcanoes of volcanic arcs down to their Wadati Benioff zone results of approximately 100 kilometers in mean value. Surprisingly, this depth range shows pronounced seismicity at most of all subduction zones. Additionally, mineralogical laboratory investigations have shown that dehydration of the diving plate has a maximum at temperature and pressure conditions we find at around 100 km depth. The ascent of the fluids and the appearance of partial melts as well as the distribution of these materials in the crust can be resolved by seismic tomographic methods using records of local natural seismicity. With these methods these areas are corresponding to lowered seismic velocities, high Vp/Vs ratios, as well as increased attenuation of seismic shear waves. The anomalies and their time dependence are controlled by the fluids. The seismic velocity anomalies detected so far are within a range of a few per cent to more than 30% reduction. But, to explore plate boundaries large and complex amphibious experiments are required, in which active and passive seismic investigations should be combined to achieve best results. The seismic station distribution should cover an area from before the trench up to far behind the volcanic chain, to provide under favorable conditions information down to 150 km depth. Findings of different subduction zones will be compared and discussed.

Fabric Development in a Late-Hercynian Magmatic Strike-Slip Shear Zone in Southern Corsica: Indications of Melt-Supported Large-Scale Deformation Localization

NASA Astrophysics Data System (ADS)

Kruhl, J. H.; Vernon, R. H.

2009-05-01

The calc-alcaline granitoids of the Hercynian Corsica Batholith show a large-scale magmatic flow pattern, outlined by the alignment of large (mm-cm) euhedral feldspar crystals. The trend of the steep magmatic foliation is generally N-S in the northern part of the island, swings to approximately E-W orientation in the central part of the Batholith and back again to approximately N-S orientation in the southern part. This pattern is intensified by large-scale magmatic layering, mainly kilometer long lenses and layers of mafic and intermediate intrusions into the granitoids. On the macro- to micro-scale, magma mingling and mixing are present, reflecting the complex intrusion history and the compositional variability of the Corsica Batholith on different scales. Around the Golf of Valinco, a steep, sinistral magmatic shear zone is represented by E-W trending magmatic layering in mingled dioritic, tonalitic, and granitic magmas - previously misleadingly interpreted as migmatites - and by a magmatic flow foliation formed by the alignment of platy feldspar crystals, as well as amphibole and biotite. Characteristic magmatic structures include multiple thin layering, boudinage, monoclinic folding, melt-injected micro shear zones, and fragmenting and back- veining of dioritic enclaves. The intensity of grain alignment roughly correlates with the thickness of layers. It is low in thick and short boudins and high in cm-thin and cm-m long layers. The monoclinic folds refold the magmatic layering. Flat faces of amphibole and biotite grains are aligned in the axial planes of the folds. The feldspar crystals are locally recrystallized to a few large polygonal grains (up to 1 mm across), and quartz commonly shows chessboard subgrain patterns. No further indications of solid-state deformation are present. Field observations, as well as pattern quantification on variably oriented rock surfaces, indicate variations of crystal alignment and fabric anisotropy in cm- to more than 100m

Fish antifreeze protein and the freezing and recrystallization of ice.

PubMed

Knight, C A; DeVries, A L; Oolman, L D

Antifreeze glycopeptide and peptides from the blood of polar fishes prevent the growth of ice crystals in water at temperatures down to approximately 1 degree C below freezing point, but do not appreciably influence the equilibrium freezing point. This freezing point hysteresis must be a disequilibrium effect, or it would violate Gibbs' phase rule, but the separate freezing and melting points are experimentally very definite: ice neither melts nor freezes perceptibly within the 'hysteresis gap', for periods of hours or days. We report here unusual crystal faces on ice crystals grown from solutions of very low concentrations of the anti-freeze glycopeptides and peptides. This is a clue to the mechanism of freezing inhibition, and it may be the basis of a simple, very sensitive test for antifreeze material. Very low concentrations of the antifreeze protein are also remarkably effective in preventing the recrystallization of ice.

Determination of calcium carbonate and sodium carbonate melting curves up to Earth's transition zone pressures with implications for the deep carbon cycle

NASA Astrophysics Data System (ADS)

Li, Zeyu; Li, Jie; Lange, Rebecca; Liu, Jiachao; Militzer, Burkhard

2017-01-01

Melting of carbonated eclogite or peridotite in the mantle influences the Earth's deep volatile cycles and bears on the long-term evolution of the atmosphere. Existing data on the melting curves of calcium carbonate (CaCO3) and sodium carbonate (Na2CO3) are limited to 7 GPa and therefore do not allow a full understanding of carbon storage and cycling in deep Earth. We determined the melting curves of CaCO3 and Na2CO3 to the pressures of Earth's transition zone using a multi-anvil apparatus. Melting was detected in situ by monitoring a steep and large increase in ionic conductivity, or inferred from sunken platinum markers in recovered samples. The melting point of CaCO3 rises from 1870 K at 3 GPa to ∼2000 K at 6 GPa and then stays within 50 K of 2000 K between 6 and 21 GPa. In contrast, the melting point of Na2CO3 increases continuously from ∼1123 K at 3 GPa to ∼1950 K at 17 GPa. A pre-melting peak in the alternating current through solid CaCO3 is attributed to the transition from aragonite to calcite V. Accordingly the calcite V-aragonite-liquid invariant point is placed at 13 ± 1 GPa and 1970 ± 40 K, with the Clapeyron slope of the calcite V to aragonite transition constrained at ∼70 K/GPa. The experiments on CaCO3 suggest a slight decrease in the melting temperature from 8 to 13 GPa, followed by a slight increase from 14 to 21 GPa. The negative melting slope is consistent with the prediction from our ab initio simulations that the liquid may be more compressible and become denser than calcite V at sufficiently high pressure. The positive melting slope at higher pressures is supported by the ab initio prediction that aragonite is denser than the liquid at pressures up to 30 GPa. At transition zone pressures the melting points of CaCO3 are comparable to that of Na2CO3 but nearly 400 K and 500 K lower than that of MgCO3. The fusible nature of compressed CaCO3 may be partially responsible for the majority of carbonatitic melts found on Earth's surface

Laser powder-bed fusion additive manufacturing: Physics of complex melt flow and formation mechanisms of pores, spatter, and denudation zones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khairallah, Saad A.; Anderson, Andrew T.; Rubenchik, Alexander

Our study demonstrates the significant effect of the recoil pressure and Marangoni convection in laser powder bed fusion (L-PBF) of 316L stainless steel. A three-dimensional high fidelity powder-scale model reveals how the strong dynamical melt flow generates pore defects, material spattering (sparking), and denudation zones. The melt track is divided into three sections: a topological depression, a transition and a tail region, each being the location of specific physical effects. The inclusion of laser ray-tracing energy deposition in the powder-scale model improves over traditional volumetric energy deposition. It enables partial particle melting, which impacts pore defects in the denudation zone.more » Different pore formation mechanisms are observed at the edge of a scan track, at the melt pool bottom (during collapse of the pool depression), and at the end of the melt track (during laser power ramp down). Finally, we discuss remedies to these undesirable pores are discussed. The results are validated against the experiments and the sensitivity to laser absorptivity.« less

Laser powder-bed fusion additive manufacturing: Physics of complex melt flow and formation mechanisms of pores, spatter, and denudation zones

DOE PAGES

Khairallah, Saad A.; Anderson, Andrew T.; Rubenchik, Alexander; ...

2016-02-23

Our study demonstrates the significant effect of the recoil pressure and Marangoni convection in laser powder bed fusion (L-PBF) of 316L stainless steel. A three-dimensional high fidelity powder-scale model reveals how the strong dynamical melt flow generates pore defects, material spattering (sparking), and denudation zones. The melt track is divided into three sections: a topological depression, a transition and a tail region, each being the location of specific physical effects. The inclusion of laser ray-tracing energy deposition in the powder-scale model improves over traditional volumetric energy deposition. It enables partial particle melting, which impacts pore defects in the denudation zone.more » Different pore formation mechanisms are observed at the edge of a scan track, at the melt pool bottom (during collapse of the pool depression), and at the end of the melt track (during laser power ramp down). Finally, we discuss remedies to these undesirable pores are discussed. The results are validated against the experiments and the sensitivity to laser absorptivity.« less

Hydrous partial melting in the sheeted dike complex at fast spreading ridges: experimental and natural observations

NASA Astrophysics Data System (ADS)

France, Lydéric; Koepke, Juergen; Ildefonse, Benoit; Cichy, Sarah B.; Deschamps, Fabien

2010-11-01

In ophiolites and in present-day oceanic crust formed at fast spreading ridges, oceanic plagiogranites are commonly observed at, or close to the base of the sheeted dike complex. They can be produced either by differentiation of mafic melts, or by hydrous partial melting of the hydrothermally altered sheeted dikes. In addition, the hydrothermally altered base of the sheeted dike complex, which is often infiltrated by plagiogranitic veins, is usually recrystallized into granoblastic dikes that are commonly interpreted as a result of prograde granulitic metamorphism. To test the anatectic origin of oceanic plagiogranites, we performed melting experiments on a natural hydrothermally altered dike, under conditions that match those prevailing at the base of the sheeted dike complex. All generated melts are water saturated, transitional between tholeiitic and calc-alkaline, and match the compositions of oceanic plagiogranites observed close to the base of the sheeted dike complex. Newly crystallized clinopyroxene and plagioclase have compositions that are characteristic of the same minerals in granoblastic dikes. Published silicic melt compositions obtained in classical MORB fractionation experiments also broadly match the compositions of oceanic plagiogranites; however, the compositions of the coexisting experimental minerals significantly deviate from those of the granoblastic dikes. Our results demonstrate that hydrous partial melting is a likely common process in the root zone of the sheeted dike complex, starting at temperatures exceeding 850°C. The newly formed melt can either crystallize to form oceanic plagiogranites or may be recycled within the melt lens resulting in hybridized and contaminated MORB melts. It represents the main MORB crustal contamination process. The residue after the partial melting event is represented by the granoblastic dikes. Our results support a model with a dynamic melt lens that has the potential to trigger hydrous partial melting

Copper isotope fractionation during partial melting and melt percolation in the upper mantle: Evidence from massif peridotites in Ivrea-Verbano Zone, Italian Alps

NASA Astrophysics Data System (ADS)

Huang, Jian; Huang, Fang; Wang, Zaicong; Zhang, Xingchao; Yu, Huimin

2017-08-01

To investigate the behavior of Cu isotopes during partial melting and melt percolation in the mantle, we have analyzed Cu isotopic compositions of a suite of well-characterized Paleozoic peridotites from the Balmuccia and Baldissero massifs in the Ivrea-Verbano Zone (IVZ, Northern Italy). Our results show that fresh lherzolites and harzburgites have a large variation of δ65Cu ranging from -0.133 to 0.379‰, which are negatively correlated with Al2O3 contents as well as incompatible platinum-group (e.g., Pd) and chalcophile element (e.g., Cu, S, Se, and Te) contents. The high δ65Cu can be explained by Cu isotope fractionation during partial melting of a sulfide-bearing peridotite source, with the light isotope (63Cu) preferentially entering the melts. The low δ65Cu can be attributed to precipitation of sulfides enriched in 63Cu during sulfur-saturated melt percolation. Replacive dunites from the Balmuccia massif display high δ65Cu from 0.544 to 0.610‰ with lower Re, Pd, S, Se, and Te contents and lower Pd/Ir ratios relative to lherzolites, which may result from dissolution of sulfides during interactions between S-undersaturated melts and lherzolites at high melt/rock ratios. Thus, our results suggest that partial melting and melt percolation largely account for the Cu isotopic heterogeneity of the upper mantle. The correlation between δ65Cu and Cu contents of the lherzolites and harzburgites was used to model Cu isotope fractionation during partial melting of a sulfide-bearing peridotite, because Cu is predominantly hosted in sulfide. The modelling results indicate an isotope fractionation factor of αmelt-peridotite = 0.99980-0.99965 (i.e., 103lnαmelt-peridotite = -0.20 to -0.35‰). In order to explain the Cu isotopic systematics of komatiites and mid-ocean ridge basalts reported previously, the estimated αmelt-peridotite was used to simulate Cu isotopic variations in melts generated by variable degrees of mantle melting. The results suggest that high

Activity of slip in amphibolite facies, fine-grained recrystallized quartz aggregates: high differential stress during high-T creep of quartz?

NASA Astrophysics Data System (ADS)

Viegas, G.; Menegon, L. M.; Archanjo, C. J.

2016-12-01

Quartz axis fabrics are a valuable tool to investigate strain partitioning/distribution in both naturally- and experimentally deformed quartz. Previous works have shown that slip dominates at high temperatures (> 600º C) and water-rich, commonly sub-magmatic conditions, typically associated with large grain sizes and grain boundary migration microstructures. In the Pernambuco shear zone, sheared quartz veins from a protomylonitic granitoid formed during the main amphibolite facies event constrained at mid-crustal conditions (550-600ºC, 5 kbar). The veins contain heterogeneously-deformed primary quartz grains, which typically form both flattened and elongated ribbons as well as more equant porphyroclasts surrounded by aggregates of fine-grained (ca. 20 µm) recrystallized aggregates. Recrystallized quartz with the same fine grain size may also occur in intracrystalline bands within the porphyroclasts. Chessboard extinction is widely observed in the porphyroclasts, and subgrain boundaries are either parallel or normal to the (0001) direction, suggesting slip on both basal and prismatic planes during recrystallization. Crystallographic preferred orientations (CPOs) of porphyroclasts (≥ 100 µm) show maxima of (0001) axes subparallel to Z and X, suggesting coeval glide along both basal and prism planes during shearing. In the recrystallized aggregates, fabric strength tends to become weaker, but still records glide along and directions. These preliminary results suggest that naturally deformed quartz veins record coeval activity of and slip during dynamic recrystallization under amphibolite facies conditions. The microstructure suggests that the CPO of the fine-grained aggregates is host-controlled and results from dominant subgrain rotation recrystallization. To our knowledge, activity of slip in fine-grained recrystallized aggregates has never been reported before. Thus, these preliminary results call into question the general view that slip is expected to be

Effects of V addition on recrystallization resistance of 7150 aluminum alloy after simulative hot deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, Jing; Shi, Cangji; Chen, X.-Grant, E-mail: xgrant_chen@uqac.ca

2014-10-15

The effects of different V contents (0.01 to 0.19 wt.%) on the recrystallization resistance of 7150 aluminum alloys during post-deformation heat treatment were investigated. The microstructural evolutions at as-cast, as-homogenized conditions and after post-deformation annealing were studied using optical, scanning electron and transmission electron microscopes and using the electron backscattered diffraction technique. The precipitation of Al{sub 21}V{sub 2} dispersoids was observed in alloys containing 0.11 to 0.19 wt.% V after homogenization. The dispersoids were mainly distributed in the dendrite cells, and the precipitate-free zones occurred in the interdendritic regions and near grain boundaries. V addition could significantly enhance the recrystallizationmore » resistance during post-deformation annealing, particularly in the presence of a great number of Al{sub 21}V{sub 2} dispersoids. Recrystallized grain growth was effectively restricted because of the dispersoid pinning effect. The alloy containing 0.15 wt.% V exhibited the highest recrystallization resistance amongst all V-containing alloys studied. - Highlights: • Investigated the effect of V level on microstructure and flow stress of 7150 alloys • Characterized microstructures using optical microscopy, SEM, TEM and EBSD • Described the precipitation behavior of V-dispersoids in the dendritic structure • Studied the V effect on recrystallization resistance during post heat treatment • V addition greatly enhanced the recrystallization resistance during annealing.« less

Deformation-related recrystallization processes

NASA Astrophysics Data System (ADS)

Drury, Martyn R.; Urai, Janos L.

1990-02-01

Recrystallization is a common microstructural transformation that occurs during deformation, metamorphism and diagenesis of rocks. Studies on minerals and rock analogues have demonstrated that a wide range of recrystallization mechanisms can occur. The range of mechanisms is related to the various ways in which two basic processes, grain boundary migration and new grain boundary formation combine to transform the microstructure. Two recent papers (Drury et al., 1985; Urai et al., 1986) have proposed different schemes for the description of recrystallization mechanisms. The purpose of this paper is to provide a unified framework for the description of mechanisms. Recrystallization mechanisms are divided into three main types; rotation mechanisms which principally involve the formation of new grain boundaries; migration mechanisms which principally involve grain boundary migration; and general mechanisms which involve both basic processes. A further distinction is made on the basis of the continuity of the microstructural transformation with respect to time. Each of the three main types of mechanism can be divided into a number of sub-types depending on whether the processes of grain boundary migration, new grain boundary formation and new grain formation occur in a discontinuous or continuous manner with respect to time. As the terms continuous and discontinuous have been used in the metallurgical literature to signify the spatial continuity of the microstructural transformation, the terms discontinuai and continual are used to refer to the temporal continuity of the transformation. It is recommended that the following aspects should be specified, if possible, in a general description of recrystallization mechanisms: (1) How do the basic processes combine to transform the microstructure. (2) If new grain development occurs, what is the development mechanism, and does new grain formation occur in a continual or discontinuai manner. (3) If grain boundary migration is

The Growth of Melt Inclusion- and Water-Rich Zones in Clinopyroxene Phenocrysts of the Powai Ankaramite Flow, Deccan Traps, India: Rapid Closed System Oscillatory Mineral Growth

NASA Astrophysics Data System (ADS)

Seaman, S. J.

2015-12-01

Water concentrations were measured and mapped using FTIR spectroscopy in clinopyroxene phenocrysts of the Powai ankaramite flow, located near Mumbai, west of the Western Ghats escarpment of the Deccan province, India. Samples were provided by Dr. Hetu Sheth of the Indian Institute of Technology, Mumbai. Chatterjee and Sheth (2015) showed that phenocrysts in the flow were part of a cumulate layer intruded by high-temperature basaltic melt at ~ 6 kb and ~1230oC. Cpx phenocrysts are euhedral and have concentric bands (100 to 200 microns thick) of fine (10-20 micron diameter) melt inclusions. Cpx bands that host melt inclusions have higher concentrations of water than inclusion-free bands. Water concentrations of cpx and ol were used to calculate water concentrations in the melt from which the crystals formed. Water concentrations in the parent magma were between 4.35 and 8.26 wt. % based on water concentrations in cpx, and between 8.24 and 9.41 wt. % based on those in ol. Both Mg and Fe are relatively depleted in the water- and melt inclusion-rich zones in cpx, and Ca is enriched in these zones. We suggest that oscillatory zoning in cpx is a result of repeated growth of cpx in water-richer and water-poorer boundary layers in which water lowered melt viscosity and enhanced diffusion and crystal growth rates. Water-enhanced growth rates may have resulted in preferential capture of melt inclusions preserved in water-rich cpx zones. Mg was preferentially incorporated into the cpx, causing Ca and water to build up in the boundary layer, and Mg and Fe to become relatively depleted in the boundary layer, as discussed for oscillatorially-zoned minerals by Wang and Merino (1993). Application of the equations for growth of oscillatory zones in crystals given by Wang and Merino (1993) to the growth of cpx crystals in the Powai ankaramite indicate that crystal growth occurred relatively quickly, on the order of days, although the width of the boundary zone, which is uncertain

Dynamic recrystallization and texture evolution of Mg–Y–Zn alloy during hot extrusion process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tong, L.B.; Li, X.; Guangzhou Research Institute of Non-ferrous Metals, Guangzhou 510651

2014-06-01

The microstructure and texture evolution of Mg{sub 98.5}Y{sub 1}Zn{sub 0.5} and Mg{sub 92.5}Y{sub 5}Zn{sub 2.5} (atomic percent) alloys during hot extrusion were systematically investigated. The coarse LPSO phases with higher volume fraction (∼ 57%) suppressed the twinning generation in the initial stage of extrusion, and accelerated the dynamic recrystallization through the particle deformation zones. Therefore, the volume fraction of DRXed grains in as-extruded Mg{sub 92.5}Y{sub 5}Zn{sub 2.5} alloy was much higher than that of Mg{sub 98.5}Y{sub 1}Zn{sub 0.5} alloy. The intensive recrystallization process resulted in the conventional basal texture weakening, although the texture evolution was mainly dominated by flow behavior.more » The dynamic recrystallization behavior in Mg{sub 92.5}Y{sub 5}Zn{sub 2.5} alloy restricted the formation of deformation texture, and thus the more random texture was observed during the whole extrusion process. - Highlights: • The densely coarse LPSO phases suppressed the twinning deformation. • Coarse LPSO phases induced the particle stimulated nucleation effect. • Dynamic recrystallization resulted in the basal texture weakening effect.« less

Critical porosity of melt segregation during crustal melting: Constraints from zonation of peritectic garnets in a dacite volcano

NASA Astrophysics Data System (ADS)

Yu, Xun; Lee, Cin-Ty A.

2016-09-01

The presence of leucogranitic dikes in orogenic belts suggests that partial melting may be an important process in the lower crust of active orogenies. Low seismic velocity and low electrical resistivity zones have been observed in the lower crust of active mountain belts and have been argued to reflect the presence of partial melt in the deep crust, but volcanoes are rare or absent above many of these inferred melt zones. Understanding whether these low velocity zones are melt-bearing, and if so, why they do not commonly erupt, is essential for understanding the thermal and rheologic structure of the crust and its dynamic evolution. Central to this problem is an understanding of how much melt can be stored before it can escape from the crust via compaction and eventually erupt. Experimental and theoretical studies predict trapped melt fractions anywhere from <5% to >30%. Here, we examine Mn growth-zoning in peritectic garnets in a Miocene dacite volcano from the ongoing Betic-Rif orogeny in southern Spain to estimate the melt fraction at the time of large-scale melt extraction that subsequently led to eruption. We show that the melt fraction at segregation, corresponding approximately to the critical melt porosity, was ∼30%, implying significant amounts of melt can be stored in the lower crust without draining or erupting. However, seismic velocities in the lower crust beneath active orogenic belts (southern Spain and Tibet) as well as beneath active magmatic zones (e.g., Yellowstone hotspot) correspond to average melt porosities of <10%, suggesting that melt porosities approaching critical values are short-lived or that high melt porosity regions are localized into heterogeneously distributed sills or dikes, which individually cannot be resolved by seismic studies.

Vitrification of waste with conitnuous filling and sequential melting

DOEpatents

Powell, James R.; Reich, Morris

2001-09-04

A method of filling a canister with vitrified waste starting with a waste, such as high-level radioactive waste, that is cooler than its melting point. Waste is added incrementally to a canister forming a column of waste capable of being separated into an upper zone and a lower zone. The minimum height of the column is defined such that the waste in the lower zone can be dried and melted while maintaining the waste in the upper zone below its melting point. The maximum height of the column is such that the upper zone remains porous enough to permit evolved gases from the lower zone to flow through the upper zone and out of the canister. Heat is applied to the waste in the lower zone to first dry then to raise and maintain its temperature to a target temperature above the melting point of the waste. Then the heat is applied to a new lower zone above the melted waste and the process of adding, drying and melting the waste continues upward in the canister until the entire canister is filled and the entire contents are melted and maintained at the target temperature for the desired period. Cooling of the melted waste takes place incrementally from the bottom of the canister to the top, or across the entire canister surface area, forming a vitrified product.

Use of olivine and plagioclase saturation surfaces for the petrogenetic modeling of recrystallized basic plutonic systems

NASA Technical Reports Server (NTRS)

Hanson, G. N.

1983-01-01

During petrogenetic studies of basic plutonic rocks, there are at least three major questions to be considered: (1) what were the relative proportions of cumulate crystals and intercumulus melt in a given sample? (2) what is the composition and variation in composition of the melts within the pluton? and (3) what is the original composition of the liquids, their source and evolution prior to the time of emplacement? Use of both saturation surfaces can place strong limits on the compositions of potential cumulate phases and intercumulus melts. Consideration of appropriate trace elements can indicate whether a sample is an orthocumulate, adcumulate or mesocumulate. Thus, when trace element and petrographic data are considered together with the saturation surfaces, it should be possible to begin to answer the three major questions given above, even for strongly recrystallized basic plutons.

Quantifying the Evolution of Melt Ponds in the Marginal Ice Zone Using High Resolution Optical Imagery and Neural Networks

NASA Astrophysics Data System (ADS)

Ortiz, M.; Pinales, J. C.; Graber, H. C.; Wilkinson, J.; Lund, B.

2016-02-01

Melt ponds on sea ice play a significant and complex role on the thermodynamics in the Marginal Ice Zone (MIZ). Ponding reduces the sea ice's ability to reflect sunlight, and in consequence, exacerbates the albedo positive feedback cycle. In order to understand how melt ponds work and their effect on the heat uptake of sea ice, we must quantify ponds through their seasonal evolution first. A semi-supervised neural network three-class learning scheme using a gradient descent with momentum and adaptive learning rate backpropagation function is applied to classify melt ponds/melt areas in the Beaufort Sea region. The network uses high resolution panchromatic satellite images from the MEDEA program, which are collocated with autonomous platform arrays from the Marginal Ice Zone Program, including ice mass-balance buoys, arctic weather stations and wave buoys. The goal of the study is to capture the spatial variation of melt onset and freeze-up of the ponds within the MIZ, and gather ponding statistics such as size and concentration. The innovation of this work comes from training the neural network as the melt ponds evolve over time; making the machine learning algorithm time-dependent, which has not been previously done. We will achieve this by analyzing the image histograms through quantification of the minima and maxima intensity changes as well as linking textural variation information of the imagery. We will compare the evolution of the melt ponds against several different array sites on the sea ice to explore if there are spatial differences among the separated platforms in the MIZ.

[Fine stereo structure for natural organic molecules, a preliminary study. II. Melting point influenced by structure factors].

PubMed

Lu, Y; Zheng, Q; Lu, D; Ma, P; Chen, Y

1995-06-01

Crystal structures of two compounds from Tripterygium wilfordii Hook f. have been determined by X-ray diffraction method. Structure factors influencing melting point of solid state have been analysed. Crystal class (or space group), recrystallization solvent, force between molecules and fine changes of molecular structures will all cause melting point changes of crystal substance.

Titanium concentration in quartz as a record of multiple deformation mechanisms in an extensional shear zone

NASA Astrophysics Data System (ADS)

Nachlas, William O.; Whitney, Donna L.; Teyssier, Christian; Bagley, Brian; Mulch, Andreas

2014-04-01

Results of high precision analysis of Ti concentration ([Ti]) in quartz representing different recrystallization microstructures in a suite of progressively deformed quartzite mylonites show the effect of recrystallization on distribution of Ti in quartz. Petrographic observations and ion microprobe analysis reveals three texturally and geochemically distinct quartz microstructures in mylonites: (1) cores of recrystallized quartz ribbons preserve the highest [Ti] and are interpreted to have recrystallized via grain boundary migration recrystallization, (2) recrystallized rims and grain margins preserve a lower and more variable [Ti] and are interpreted to reflect the combined influence of subgrain rotation and bulging recrystallization, and (3) neocrystallized quartz precipitated in dilatancy sites has low (˜1 ppm) [Ti], reflecting the Ti content of the syndeformational fluid. Muscovite in nonmylonitic quartzite (at the base of the sampling traverse) is compositionally zoned, whereas muscovite in mylonitic quartzite shows a progressive decreasing in zoning in higher strain samples. Three-dimensional phase distribution mapping using X-ray computed tomography analysis of rock hand samples reveals that Ti-bearing accessory phases are less abundant and more dispersed in higher strained mylonites compared to nonmylonitic quartzite. This study demonstrates the influence of dynamic recrystallization on Ti substitution in quartz and evaluates the Ti buffering capacity of aqueous fluids (meteoric versus metamorphic/magmatic) as well as the distribution and reactivity of Ti-bearing accessory phases in a deforming quartzite. Results of this study suggest that Ti-in-quartz thermobarometry of deformed quartz is a sensitive technique for resolving the multistage history of quartz deformation and recrystallization in crustal shear zones.

The effect of water on recrystallization behavior and grain boundary morphology in calcite observations of natural marble mylonites

NASA Astrophysics Data System (ADS)

Schenk, Oliver; Urai, Janos L.; Evans, Brian

2005-10-01

Fluids are inferred to play a major role in the deformation and recrystallization of many minerals (e.g. quartz, olivine, halite, feldspar). In this study, we sought to identify the effect of fluids on grain boundary morphology and recrystallization processes in marble mylonites during shear zone evolution. We compared the chemistry, microstructure and mesostructure of calcite marble mylonites from the Schneeberg Complex, Southern Tyrole, Italy, to that from the Naxos Metamorphic Core Complex, Greece. These two areas were selected for comparison because they have similar lithology and resemble each other in chemical composition. In addition, calcite-dolomite geothermometry indicates similar temperatures for shear zone formation: 279±25 °C (Schneeberg Complex) and 271±15 °C (Naxos high-grade core). However, the two settings are different in the nature of the fluids present during the shear zone evolution. In the Schneeberg mylonites, both the alteration of minerals during retrograde metamorphism in the neighboring micaschists and the existence of veins suggest that aqueous fluids were present during mylonitization. The absence of these features in the Naxos samples indicates that aqueous fluids were not as prevalent during deformation. This conclusion is also supported by the stable isotope signature. Observations of broken and planar surfaces using optical and scanning electron microscopes did not indicate major differences between the two mylonites: grain boundaries in both settings display pores with shapes controlled by crystallography, and have pore morphologies that are similar to observations from crack and grain-boundary healing experiments. Grain size reduction was predominantly the result of subgrain rotation recrystallization. However, the coarse grains inside the wet protomylonites (Schneeberg) are characterized by intracrystalline shear zones.

Hydration index--a better parameter for explaining small molecule hydration in inhibition of ice recrystallization.

PubMed

Tam, Roger Y; Ferreira, Sandra S; Czechura, Pawel; Chaytor, Jennifer L; Ben, Robert N

2008-12-24

Several simple mono- and disaccharides have been assessed for their ability to inhibit ice recrystallization. Two carbohydrates were found to be effective recrystallization inhibitors. D-galactose (1) was the best monosaccharide and D-melibiose (5) was the most active disaccharide. The ability of each carbohydrate to inhibit ice growth was correlated to its respective hydration number reported in the literature. A hydration number reflects the number of tightly bound water molecules to the carbohydrate and is a function of carbohydrate stereochemistry. It was discovered that using the absolute hydration number of a carbohydrate does not allow one to accurately predict its ability to inhibit ice recrystallization. Consequently, we have defined a hydration index in which the hydration number is divided by the molar volume of the carbohydrate. This new parameter not only takes into account the number of water molecules tightly bound to a carbohydrate but also the size or volume of a particular solute and ultimately the concentration of hydrated water molecules. The hydration index of both mono- and disaccharides correlates well with experimentally measured RI activity. C-Linked derivatives of the monosaccharides appear to have RI activity comparable to that of their O-linked saccharides but a more thorough investigation is required. The relationship between carbohydrate concentration and RI activity was shown to be noncolligative and a 0.022 M solution of D-galactose (1) and C-linked galactose derivative (10) inhibited recrystallization as well as a 3% DMSO solution. The carbohydrates examined in this study did not possess any thermal hysteresis activity (selective depression of freezing point relative to melting point) or dynamic ice shaping. As such, we propose that they are inhibiting recrystallization at the interface between bulk water and the quasi liquid layer (a semiordered interface between ice and bulk water) by disrupting the preordering of water.

Decoding a protracted zircon geochronological record in ultrahigh temperature granulite, and persistence of partial melting in the crust, Rogaland, Norway

NASA Astrophysics Data System (ADS)

Laurent, Antonin T.; Bingen, Bernard; Duchene, Stephanie; Whitehouse, Martin J.; Seydoux-Guillaume, Anne-magali; Bosse, Valerie

2018-04-01

This contribution evaluates the relation between protracted zircon geochronological signal and protracted crustal melting in the course of polyphase high to ultrahigh temperature (UHT; T > 900 °C) granulite facies metamorphism. New U-Pb, oxygen isotope, trace element, ion imaging and cathodoluminescence (CL) imaging data in zircon are reported from five samples from Rogaland, South Norway. The data reveal that the spread of apparent age captured by zircon, between 1040 and 930 Ma, results both from open-system growth and closed-system post-crystallization disturbance. Post-crystallization disturbance is evidenced by inverse age zoning induced by solid-state recrystallization of metamict cores that received an alpha dose above 35 × 1017 α g-1. Zircon neocrystallization is documented by CL-dark domains displaying O isotope open-system behaviour. In UHT samples, O isotopic ratios are homogenous (δ18O = 8.91 ± 0.08‰), pointing to high-temperature diffusion. Scanning ion imaging of these CL-dark domains did not reveal unsupported radiogenic Pb. The continuous geochronological signal retrieved from the CL-dark zircon in UHT samples is similar to that of monazite for the two recognized metamorphic phases (M1: 1040-990 Ma; M2: 940-930 Ma). A specific zircon-forming event is identified in the orthopyroxene and UHT zone with a probability peak at ca. 975 Ma, lasting until ca. 955 Ma. Coupling U-Pb geochronology and Ti-in-zircon thermometry provides firm evidence of protracted melting lasting up to 110 My (1040-930 Ma) in the UHT zone, 85 My (ca. 1040-955 Ma) in the orthopyroxene zone and some 40 My (ca. 1040-1000 Ma) in the regional basement. These results demonstrate the persistence of melt over long timescales in the crust, punctuated by two UHT incursions.

Silica-undersaturated reaction zones at a crust-mantle interface in the Highland Complex, Sri Lanka: Mass transfer and melt infiltration during high-temperature metasomatism

NASA Astrophysics Data System (ADS)

Fernando, G. W. A. R.; Dharmapriya, P. L.; Baumgartner, Lukas P.

2017-07-01

Sri Lanka is a crucial Gondwana fragment mostly composed of granulitic rocks in the Highland Complex surrounded by rocks with granulite to amphibolite grade in the Vijayan and Wanni Complex that were structurally juxtaposed during Pan-African orogeny. Fluids associated with granulite-facies metamorphism are thought to have controlled various lower crustal processes such as dehydration/hydration reactions, partial melting, and high-temperature metasomatism. Chemical disequilibrium in the hybrid contact zone between a near peak post-tectonic ultramafic enclave and siliceous granulitic gneiss at Rupaha within the Highland Complex produced metasomatic reaction zones under the presence of melt. Different reaction zones observed in the contact zone show the mineral assemblages phlogopite + spinel + sapphirine (zone A), spinel + sapphirine + corundum (zone B), corundum ( 30%) + biotite + plagioclase zone (zone C) and plagioclase + biotite + corundum ( 5%) zone (zone D). Chemical potential diagrams and mass balance reveal that the addition of Mg from ultramafic rocks and removal of Si from siliceous granulitic gneiss gave rise to residual enrichment of Al in the metasomatized mineral assemblages. We propose that contact metasomatism between the two units, promoted by melt influx, caused steady state diffusional transport across the profile. Corundum growth was promoted by the strong residual Al enrichment and Si depletion in reaction zone whereas sapphirine may have been formed under high Mg activity near the ultramafic rocks. Modelling also indicated that metasomatic alteration occurred at ca. 850 °C at 9 kbar, which is consistent with post-peak metamorphic conditions reached during the initial stage of exhumation in the lower crust and with temperature calculations based on conventional geothermometry.

Thermal Stability of Zone Melting p-Type (Bi, Sb)2Te3 Ingots and Comparison with the Corresponding Powder Metallurgy Samples

NASA Astrophysics Data System (ADS)

Jiang, Chengpeng; Fan, Xi'an; Hu, Jie; Feng, Bo; Xiang, Qiusheng; Li, Guangqiang; Li, Yawei; He, Zhu

2018-04-01

During the past few decades, Bi2Te3-based alloys have been investigated extensively because of their promising application in the area of low temperature waste heat thermoelectric power generation. However, their thermal stability must be evaluated to explore the appropriate service temperature. In this work, the thermal stability of zone melting p-type (Bi, Sb)2Te3-based ingots was investigated under different annealing treatment conditions. The effect of service temperature on the thermoelectric properties and hardness of the samples was also discussed in detail. The results showed that the grain size, density, dimension size and mass remained nearly unchanged when the service temperature was below 523 K, which suggested that the geometry size of zone melting p-type (Bi, Sb)2Te3-based materials was stable below 523 K. The power factor and Vickers hardness of the ingots also changed little and maintained good thermal stability. Unfortunately, the thermal conductivity increased with increasing annealing temperature, which resulted in an obvious decrease of the zT value. In addition, the thermal stabilities of the zone melting p-type (Bi, Sb)2Te3-based materials and the corresponding powder metallurgy samples were also compared. All evidence implied that the thermal stabilities of the zone-melted (ZMed) p-type (Bi, Sb)2Te3 ingots in terms of crystal structure, geometry size, power factor (PF) and hardness were better than those of the corresponding powder metallurgy samples. However, their thermal stabilities in terms of zT values were similar under different annealing temperatures.

Microstructure effects on the recrystallization of low-symmetry alpha-uranium

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCabe, Rodney James; Richards, Andrew Walter; Coughlin, Daniel Robert

2015-10-01

We employ electron backscatter diffraction (EBSD) to investigate microstructural evolution of uranium during recrystallization. To understand the relationship between microstructure and recrystallization, we use measures of intra-granular misorientation within grains and near grain boundaries in both deformed (non-recrystallized) uranium and recrystallizing uranium. The data show that the level of intra-granular misorientation depends on crystallographic orientation. However, contrary to expectation, this relationship does not significantly affect the recrystallization texture. Rather, the analysis suggests that recrystallization nucleation occurs along high angle grain boundaries in the deformed microstructure. Specifically, we show that the nucleation of recrystallized grains correlates well with the spatially heterogeneousmore » distribution of high angle boundaries. Due to the inhomogeneous distribution of high angle boundaries, the recrystallized microstructure after long times exhibits clustered distributions of small and large grains. Twin boundaries do not appear to act as recrystallization nucleation sites.« less

Solid dispersion of acetaminophen and poly(ethylene oxide) prepared by hot-melt mixing.

PubMed

Yang, Min; Wang, Peng; Huang, Chien-Yueh; Ku, M Sherry; Liu, Huiju; Gogos, Costas

2010-08-16

In this study, a model drug, acetaminophen (APAP), was melt mixed with poly(ethylene oxide) (PEO) using a Brabender mixer. APAP was found to recrystallize upon cooling to room temperature for all the drug loadings investigated. Higher drug loading leads to faster recrystallization rate. However, the morphology of the recrystallized drug crystals is identical in samples with different drug loadings and does not change with the storage time. To adjust the drug's dissolution rate, nanoclay Cloisite 15A and 30B were added into the binary mixture. The presence of either of the nanoclay dramatically accelerates the drug's recrystallization rate and slows down the drug's releasing rate. The drop of the releasing rate is mainly due to the decrease of wettability, as supported by the contact angle data. Data analysis of the dissolution results suggests that the addition of nanoclays changes the drug's release mechanism from erosion dominant to diffusion dominant. This study suggests that nanoclays may be utilized to tailor the drug's releasing rate and to improve the dosage form's stability by dramatically shortening the lengthy recrystallization process. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Molecular dynamics study of the melting of a supported 887-atom Pd decahedron.

PubMed

Schebarchov, D; Hendy, S C; Polak, W

2009-04-08

We employ classical molecular dynamics simulations to investigate the melting behaviour of a decahedral Pd(887) cluster on a single layer of graphite (graphene). The interaction between Pd atoms is modelled with an embedded-atom potential, while the adhesion of Pd atoms to the substrate is approximated with a Lennard-Jones potential. We find that the decahedral structure persists at temperatures close to the melting point, but that just below the melting transition, the cluster accommodates to the substrate by means of complete melting and then recrystallization into an fcc structure. These structural changes are in qualitative agreement with recently proposed models, and they verify the existence of an energy barrier preventing softly deposited clusters from 'wetting' the substrate at temperatures below the melting point.

Chlorite Stability in the Mantle Wedge and its Role in Subduction Zone Melting Processes

NASA Astrophysics Data System (ADS)

Grove, T. L.; Chatterjee, N.; Medard, E.; Parman, S. W.

2006-12-01

New experimental constraints on the H2O-saturated melting behavior of mantle peridotite (Grove et al., 2006, EPSL 249: 74 - 89) show that chlorite is a stable phase on the vapor-saturated solidus of peridotite at a pressure of 2 GPa and higher. Hydrous melting in the presence of chlorite begins at 860 °C at 2 GPa and the solidus temperature decreases continuously to 800 °C at 3.2 GPa. The solidus phases include olivine, orthopyroxene, high-Ca clinopyroxene and spinel + chlorite over the pressure range of 2 to 2.4 GPa. Garnet + chlorite + ilmenite are present above 2.4 GPa. At 2.8 to 3.2 GPa, chlorite is stable on the vapor- saturated solidus, but it reacts out 20 to 40 °C above the solidus. The temperature-pressure range for chlorite stability and vapor-saturated melting behavior involving chlorite are similar to those inferred for the mantle wedge above the subducted slab by geodynamic thermal models. Thus, chlorite may be a stable phase within the mantle wedge and may play a role in the onset of hydrous mantle melting. The factors that lead to the initiation of melting in subduction zones have remained enigmatic. The occurrence of volcanic fronts above the mantle wedge-subducted slab interface near a depth of 100 km in most arcs has not been conclusively explained. Melting must somehow be linked to processes that involve the release of water from the slab into the overlying mantle wedge, but why does melting always begin at or below 100 km? A potential melt triggering mechanism is that H2O released from dehydration reactions in the subducted oceanic lithosphere at pressures > 2 GPa rises into the overlying mantle and reacts with peridotite to form chlorite. This chloritized peridotite is pulled down by mantle flow to pressures of 3 to 3.5 GPa. Increases in temperature in the mantle wedge above the subducted slab lead to chlorite breakdown and/or vapor-saturated melting initiation. When mantle peridotite is hydrated ~ 13 wt. % chlorite is produced for a bulk H2

Effect of cold deformation on the recrystallization behavior of FePd alloy at the ordering temperature using electron backscatter diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Hung-Pin; Chen, Yen-Chun; Chen, Delphic

2014-08-15

In this study, the evolution of the recrystallization texture and microstructure was investigated after annealing of 50% and 90% cold-rolled FePd alloy at 530 °C. The FePd alloy was produced by vacuum arc melting in an atmosphere of 97% Ar and 3% H{sub 2}. The specimens were cold rolled to achieve 50% and 90% reduction in thickness. Electron backscatter diffraction measurements were performed on the rolling direction–normal direction section. With increased deformation from 50% to 90%, recrystallized texture transition occurs. For the 50% cold-rolled alloy, the preferred orientation is (0 1 0) [11 0 1], which is close to themore » cubic orientation after 400 h of annealing. For the 90% cold-rolled alloy, the orientation changes to (0 5 4) [22–4 5] after 16 h of annealing. - Highlights: • Texture and microstructure in cold-rolled FePd alloy was investigated during annealing using EBSD. • The recrystallized texture of 50% cold-rolled FePd is (0 1 0) [11 0 1] at 530 °C for 400 hours. • The recrystallized texture of 90% cold-rolled FePd is changed to (0 5 4) [22–4 5] at 530 °C after 16 hours.« less

Preservation of Partial Melt Textures in Inclusions in Garnet Megacrysts of Pelitic Paragneiss, UHP Terrane, North-East Greenland Eclogite Province

NASA Astrophysics Data System (ADS)

Lang, H. M.; Gilotti, J. A.

2005-12-01

inclusions are commonly rimmed by a moat of plagioclase + K-feldspar, which extends into apophyses in garnet. These feldspar rims indicate that the most mobile and volatile-rich portion of the melt was able to penetrate garnets and travel along garnet-inclusion boundaries. Possible melt inclusions have been described in natural garnets from other UHP terranes (Stockert, et al., 2001, Geology; Hwang, et al., 2001, Earth and Planetary Science Letters) and have been produced experimentally (Perchuk, et al., 2005, Terra Nova). In the experiments and at least one of the natural occurrences, patchy microstructures (attributed to high Ca) were observed in BSE images of garnet surrounding the melt inclusions. Although we observe no garnet zoning in BSE images, patchy high-Ca zoning is apparent on X-ray maps of garnet surrounding the melt inclusions in our samples. Small, euhedral, high-Ca garnets are abundant in melt lenses in the matrix, so crystallization or recrystallization of high-Ca garnet surrounding the melt inclusions is not surprising.

Susceptibility of Goethite to Fe2+-Catalyzed Recrystallization over Time.

PubMed

Joshi, Prachi; Fantle, Matthew S; Larese-Casanova, Philip; Gorski, Christopher A

2017-10-17

Recent work has shown that iron oxides, such as goethite and hematite, may recrystallize in the presence of aqueous Fe 2+ under anoxic conditions. This process, referred to as Fe 2+ -catalyzed recrystallization, can influence water quality by causing the incorporation/release of environmental contaminants and biological nutrients. Accounting for the effects of Fe 2+ -catalyzed recrystallization on water quality requires knowing the time scale over which recrystallization occurs. Here, we tested the hypothesis that nanoparticulate goethite becomes less susceptible to Fe 2+ -catalyzed recrystallization over time. We set up two batches of reactors in which 55 Fe 2+ tracer was added at two different time points and tracked the 55 Fe partitioning in the aqueous and goethite phases over 60 days. Less 55 Fe uptake occurred between 30 and 60 days than between 0 and 30 days, suggesting goethite recrystallization slowed with time. Fitting the data with a box model indicated that 17% of the goethite recrystallized after 30 days of reaction, and an additional 2% recrystallized between 30 and 60 days. The decreasing susceptibility of goethite to recrystallize as it reacted with aqueous Fe 2+ suggested that recrystallization is likely only an important process over short time scales.

Modeling the Controlled Recrystallization of Particle-Containing Aluminum Alloys

NASA Astrophysics Data System (ADS)

Adam, Khaled; Root, Jameson M.; Long, Zhengdong; Field, David P.

2017-01-01

The recrystallized fraction for AA7050 during the solution heat treatment is highly dependent upon the history of deformation during thermomechanical processing. In this work, a state variable model was developed to predict the recrystallization volume fraction as a function of processing parameters. Particle stimulated nucleation (PSN) was observed as a dominant mechanism of recrystallization in AA7050. The mesoscale Monte Carlo Potts model was used to simulate the evolved microstructure during static recrystallization with the given recrystallization fraction determined already by the state variable model for AA7050 alloy. The spatial inhomogeneity of nucleation is obtained from the measurement of the actual second-phase particle distribution in the matrix identified using backscattered electron (BSE) imaging. The state variable model showed good fit with the experimental results, and the simulated microstructures were quantitatively comparable to the experimental results for the PSN recrystallized microstructure of 7050 aluminum alloy. It was also found that the volume fraction of recrystallization did not proceed as dictated by the Avrami equation in this alloy because of the presence of the growth inhibitors.

Melt extrusion vs. spray drying: The effect of processing methods on crystalline content of naproxen-povidone formulations.

PubMed

Haser, Abbe; Cao, Tu; Lubach, Joe; Listro, Tony; Acquarulo, Larry; Zhang, Feng

2017-05-01

Our hypothesis is that melt extrusion is a more suitable processing method than spray drying to prepare amorphous solid dispersions of drugs with a high crystallization tendency. Naproxen-povidone K25 was used as the model system in this study. Naproxen-povidone K25 solid dispersions at 30% and 60% drug loadings were characterized by modulated DSC, powder X-ray diffraction, FT-IR, and solid-state 13 C NMR to identify phase separation and drug recrystallization during processing and storage. At 30% drug loading, hydrogen bond (H-bond) sites of povidone K25 were not saturated and the glass transition (T g ) temperature of the formulation was higher. As a result, both melt-extruded and spray-dried materials were amorphous initially and remained so after storage at 40°C. At 60% drug loading, H-bond sites were saturated, and T g was low. We were not able to prepare amorphous materials. The initial crystallinity of the formulations was 0.4%±0.2% and 5.6%±0.6%, and increased to 2.7%±0.3% and 21.6%±1.0% for melt-extruded and spray-dried materials, respectively. Spray-dried material was more susceptible to re-crystallization during processing, due to the high diffusivity of naproxen molecules in the formulation matrix and lack of kinetic stabilization from polymer solution. A larger number of crystalline nucleation sites and high surface area made the spray-dried material more susceptible to recrystallization during storage. This study demonstrated the unique advantages of melt extrusion over spray drying for the preparation of amorphous solid dispersions of naproxen at high drug level. Copyright © 2017 Elsevier B.V. All rights reserved.

Reinforcement of the Cube texture during recrystallization of a 1050 aluminum alloy partially recrystallized and 10% cold-rolled

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Wei; Helbert, Anne-Laure, E-mail: anne-laure.helbert@u-psud.fr; Baudin, Thierry

In high purity Aluminum, very strong {l_brace}100{r_brace}<001> recrystallization texture is developed after 98% cold rolling and annealing at 500 Degree-Sign C. On the contrary, in Aluminum alloys of commercial purity, the Cube component hardly exceeds 30% after complete recrystallization. Parameters controlling Cube orientation development are mainly the solute dragging due to impurities in solid solution and the stored deformation energy. In the present study, besides the 85% cold rolling, two extra annealings and a slight cold rolling are introduced in the processing route to increase the Cube volume fraction. The Cube development was analyzed by X-ray diffraction and Electron BackScatteredmore » Diffraction (EBSD). The nucleation and growth mechanisms responsible for the large Cube growth were investigated using FEG/EBSD in-situ heating experiments. Continuous recrystallization was observed in Cube oriented grains and competed with SIBM (Strain Induced Boundary Migration) mechanism. This latter was favored by the stored energy gap introduced during the additional cold-rolling between the Cube grains and their neighbors. Finally, a Cube volume fraction of 65% was reached after final recrystallization. - Highlights: Black-Right-Pointing-Pointer EBSD in-situ heating experiments of aluminum alloy of commercial purity. Black-Right-Pointing-Pointer A 10% cold-rolling after a partial recrystallization improved Cube nucleation and growth. Black-Right-Pointing-Pointer Annealing before cold-rolling limited the solute drag effect and permitted a large Cube growth. Black-Right-Pointing-Pointer Cube development is enhanced by continuous recrystallization of Cube sub-grains. Black-Right-Pointing-Pointer The preferential Cube growth occurs by SIBM of small Cube grains.« less

A petrologic, thermodynamic and experimental study of brachinites: Partial melt residues of an R chondrite-like precursor

NASA Astrophysics Data System (ADS)

Gardner-Vandy, Kathryn G.; Lauretta, Dante S.; McCoy, Timothy J.

2013-12-01

The primitive achondrites provide a window into the initial melting of asteroids in the early solar system. The brachinites are olivine-dominated meteorites with a recrystallized texture that we and others interpret as evidence of partial melting and melt removal on the brachinite parent body. We present a petrologic, thermodynamic and experimental study of the brachinites to evaluate the conditions under which they formed and test our hypothesis that the precursor material to the brachinites was FeO-rich compared to the precursors of other primitive achondrites. Petrologic analysis of six brachinites (Brachina, Allan Hills (ALH) 84025, Hughes 026, Elephant Moraine (EET) 99402, Northwest Africa (NWA) 3151, and NWA 4969) and one brachinite-like achondrite (NWA 5400) shows that they are meteorites with recrystallized texture that are enriched in olivine (⩾80 vol.%) and depleted in other minerals with respect to a chondritic mineralogy. Silicates in the brachinites are FeO-rich (Fa32-36). Brachinite-like achondrite Northwest Africa 5400 is similar in mineralogy and texture to the brachinites but with a slightly lower FeO-content (Fa30). Thermodynamic calculations yield equilibration temperatures above the Fe,Ni-FeS cotectic temperature (∼950 °C) for all meteorites studied here and temperatures above the silicate eutectic (∼1050 °C) for all but two. Brachina formed at an fO2 of ∼IW, and the other brachinites and NWA 5400 formed at ∼IW - 1. All the meteorites show great evidence of formation by partial melting having approximately chondritic to depleted chondritic mineralogies, equilibrated mineral compositions, and recrystallized textures, and having reached temperatures above that required for melt generation. In an attempt to simulate the formation of the brachinite meteorites, we performed one-atmosphere, gas-mixing partial melting experiments of R4 chondrite LaPaz Ice Field 03639. Experiments at 1250 °C and an oxygen fugacity of IW - 1 produce residual

The Recrystallization Behavior of Unalloyed Mg and a Mg-Al Alloy

NASA Astrophysics Data System (ADS)

Murphy, Aeriel D.; Allison, John E.

2018-02-01

The static recrystallization behavior of pure Mg and Mg-4Al was characterized over a range of annealing temperatures. The electron backscatter diffraction grain orientation spread technique was used to quantify the level of recrystallization at various annealing times. Recrystallization kinetics were characterized using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) relationship and it was found that two sequential annealing stages exist. Stage 1 involves heterogeneous nucleation of recrystallization in regions with a high stored energy, including twins and grain boundaries, and can be represented by an Avrami exponent of n 1 ranging from 0.35 to 0.6. During Stage 2, recrystallization occurred predominately in the interior of deformed grains with incomplete recrystallization generally observed even at annealing times in excess of two weeks. The second recrystallization stage exhibited a much lower Avrami exponent, n 2, ranging from 0.02 to 0.2. Increasing the starting grain size in the pure Mg condition led to a significant delay in recrystallization. The addition of Al had a minimal effect on the recrystallization kinetics of Mg.

Surface melt effects on Cryosat-2 elevation retrievals in the ablation zone of the Greenland ice sheet

NASA Astrophysics Data System (ADS)

Slater, T.; McMillan, M.; Shepherd, A.; Leeson, A.; Cornford, S. L.; Hogg, A.; Gilbert, L.; Muir, A. S.; Briggs, K.

2017-12-01

Over the past two decades, there has been an acceleration in the rate of mass losses from the Greenland ice sheet. This acceleration is, in part, attributed to an increasingly negative surface mass balance (SMB), linked to increasing melt water runoff rates due to enhanced surface melting. Understanding the past, present and future evolution in surface melting is central to ongoing monitoring of ice sheet mass balance and, in turn, to building realistic future projections. Currently, regional climate models are commonly used for this purpose, because direct in-situ observations are spatially and temporally sparse due to the logistics and resources required to collect such data. In particular, modelled SMB is used to estimate the extent and magnitude of surface melting, which influences (1) many geodetic mass balance estimates, and (2) snowpack microwave scattering properties. The latter is poorly understood and introduces uncertainty into radar altimeter estimates of ice sheet evolution. Here, we investigate the changes in CryoSat-2 waveforms and elevation measurements caused by the onset of surface melt in the summer months over the ablation zone of the Greenland ice sheet. Specifically, we use CryoSat-2 SARIn mode data acquired between 2011 and 2016, to characterise the effect of high variability in surface melt during this period, and to assess the associated impact on estimates of ice mass balance.

Reconstructing Volatile Evolution at Lastarria Volcano (CVZ, Northern Chile) Using Melt Inclusions Analysis

NASA Astrophysics Data System (ADS)

Pizarro, M.; Cannatelli, C.; Morata, D.

2017-12-01

Melt inclusions Assemblages (MIAs) are considered the best tool available to provide insights into the pre-eruptive volatile contents in the magma and define the pattern of degassing at depth. Lastarria volcano is located in northern Chile, in the Central Volcanic Zone (CVZ). Lastarria's fumarolic activity is currently the most important source of gases of the CVZ and the volcano also exhibits constant deformation. The study of volatile contents in MIAs, allows us to determine the magmatic processes beneath Lastarria volcano, and there for, understand the current status of the volcanic system (deformation and fumarolic activity). We determined the pre-eruptive volatile content (H2O, CO2, F, S, Cl) in the magma by analyzing MIs hosted in feldspars and pyroxenes from 7 samples of lava and pyroclastic rocks, belonging to different eruptive periods of the volcano. All the samples are andesitic in composition. Lava samples contain phenocrysts of plagioclase and pyroxene (up to 45%) and a vitreous groundmass with microlites of plagioclase, pyroxenes, opaque minerals, and limited biotites. Pyroclastic samples contain phenocrysts of plagioclase and pyroxene (up to 30%), and a vitreous matrix with microlites of plagioclase and pyroxene. At least 3 MIAs have been described in feldspars from the lava samples: MIA1, completely homogenized, MIA2 composed of homogeneous glass and one bubble, and MIA3 composed of homogeneous glass and multiple bubbles. All MIAs display sizes between 3 and 200 um. In the pyroxenes, we have observed a wide range of MIAs, showing different sizes and various degrees of recrystallization, from completely homogenized to totally recrystallized. The petrographic study in the feldespars from the pyroclastic rocks shows two types of MIAs: MIA1, containing homogeneous glass associated with a single bubble, and MIA2, showing homogeneous glass with multiple bubbles. Few MIs appear to be slightly recrystallized. The size of this MIAs varies between 3 and 150

Solvent Selection for Recrystallization: An Undergraduate Organic Experiment.

ERIC Educational Resources Information Center

Baumann, Jacob B.

1979-01-01

This experiment develops the students' ability to carry out a simple recrystallization effectively, and demonstrates how a solvent may be selected or rejected for the recrystallization of a specific organic compound. (Author/BB)

Contactless heater floating zone refining and crystal growth

NASA Technical Reports Server (NTRS)

Lan, Chung-Wen (Inventor); Kou, Sindo (Inventor)

1993-01-01

Floating zone refining or crystal growth is carried out by providing rapid relative rotation of a feed rod and finish rod while providing heat to the junction between the two rods so that significant forced convection occurs in the melt zone between the two rods. The forced convection distributes heat in the melt zone to allow the rods to be melted through with a much shorter melt zone length than possible utilizing conventional floating zone processes. One of the rods can be rotated with respect to the other, or both rods can be counter-rotated, with typical relative rotational speeds of the rods ranging from 200 revolutions per minute (RPM) to 400 RPM or greater. Zone refining or crystal growth is carried out by traversing the melt zone through the feed rod.

A numerical treatment of melt/solid segregation - Size of the eucrite parent body and stability of the terrestrial low-velocity zone

NASA Technical Reports Server (NTRS)

Walker, D.; Stolper, E. M.; Hays, J. F.

1978-01-01

Crystal sinking to form cumulates and melt percolation toward segregation in magma pools can be treated with modifications of Stokes' and Darcy's laws, respectively. The velocity of crystals and melt depends, among other things, on the force of gravity (g) driving the separations and the cooling time of the environment. The increase of g promotes more efficient differentiation, whereas the increase of cooling rate limits the extent to which crystals and liquid can separate. The rate at which separation occurs is strongly dependent on the proportion of liquid that is present. The observation of cumulates and segregated melts among the eucrite meteorites is used as a basis for calculating the g (and planet size) required to perform these differentiations. The eucrite parent body was probably at least 10-100 km in radius. The earth's low velocity zone (LVZ) is shown to be unstable with respect to draining itself of excess melt if the melt forms an interconnecting network. A geologically persistent LVZ with a homogeneous distribution of melt can be maintained with melt fractions only on the order of 0.1% or less.

Along-strike variability of primitive magmas (major and volatile elements) inferred from olivine-hosted melt inclusions, southernmost Andean Southern Volcanic Zone, Chile

NASA Astrophysics Data System (ADS)

Weller, D. J.; Stern, C. R.

2018-01-01

Glass compositions of melt inclusions in olivine phenocrysts found in tephras derived from explosive eruptions of the four volcanoes along the volcanic front of the southernmost Andean Southern Volcanic Zone (SSVZ) are used to constrain primitive magma compositions and melt generation parameters. Primitive magmas from Hudson, Macá, and Melimoyu have similar compositions and are formed by low degrees (8-18%) of partial melting. Compared to these other three centers, primitive magmas from Mentolat have higher Al2O3 and lower MgO, TiO2 and other incompatible minor elements, and are generated by somewhat higher degrees (12-20%) of partial melting. The differences in the estimated primitive parental magma compositions between Mentolat and the other three volcanic centers are consistent with difference in the more evolved magmas erupted from these centers, Mentolat magmas having higher Al2O3 and lower MgO, TiO2 and other incompatible minor element contents, suggesting that these differences are controlled by melting processes in the mantle source region above the subducted oceanic plate. Parental magma S = 1430-594 and Cl = 777-125 (μg/g) contents of Hudson, Macá, and Melimoyu are similar to other volcanoes further north in the SVZ. However, Mentolat primitive magmas have notably higher concentrations of S = 2656-1227 and Cl = 1078-704 (μg/g). The observed along-arc changes in parental magma chemistry may be due to the close proximity below Mentolat of the subducted Guamblin Fracture Zone that could efficiently transport hydrous mineral phases, seawater, and sediment into the mantle, driving enhanced volatile fluxed melting beneath this center compared to the others. Table S2. Olivine-hosted melt inclusion compositions, host-olivine compositions, and the post-entrapment crystallization corrected melt inclusion compositions. Table S3. Olivine-hosted melt inclusion modeling information. Table S4. Major element compositions of the fractionation corrected melt inclusion

Frictional melting experiments investigate coseismic behaviour of pseudotachylyte-bearing faults in the Outer Hebrides Fault Zone, UK.

NASA Astrophysics Data System (ADS)

Campbell, L.; De Paola, N.; Nielsen, S. B.; Holdsworth, R.; Lloyd, G. E. E.; Phillips, R. J.; Walcott, R.

2015-12-01

Recent experimental studies, performed at seismic slip rates (≥ 1 m/s), suggest that the friction coefficient of seismic faults is significantly lower than at sub-seismic (< 1 mm/s) speeds. Microstructural observations, integrated with theoretical studies, suggest that the weakening of seismic faults could be due to a range of thermally-activated mechanisms (e.g. gel, nanopowder and melt lubrication, thermal pressurization, viscous flow), triggered by frictional heating in the slip zone. The presence of pseudotachylyte within both exhumed fault zones and experimental slip zones in crystalline rocks suggests that lubrication plays a key role in controlling dynamic weakening during rupture propagation. The Outer Hebrides Fault Zone (OHFZ), UK contains abundant pseudotachylyte along faults cutting varying gneissic lithologies. Our field observations suggest that the mineralogy of the protolith determines volume, composition and viscosity of the frictional melt, which then affects the coseismic weakening behaviour of the fault and has important implications for the magnitudes and distribution of stress drops during slip episodes. High velocity friction experiments at 18 MPa axial load, 1.3 ms-1 and up to 10 m slip were run on quartzo-feldspathic, metabasic and mylonitic samples, taken from the OHFZ in an attempt to replicate its coseismic frictional behaviour. These were configured in cores of a single lithology, or in mixed cores with two rock types juxtaposed. All lithologies produce a general trend of frictional evolution, where an initial peak followed by transient weakening precedes a second peak which then decays to a steady state. Metabasic and felsic single-lithology samples both produce sharper frictional peaks, at values of μ = 0.19 and μ= 0.37 respectively, than the broader and smaller (μ= 0.15) peak produced by a mixed basic-felsic sample. In addition, both single-lithology peaks occur within 0.2 m slip, whereas the combined-lithology sample displays a

The influence of partial melting and melt migration on the rheology of the continental crust

NASA Astrophysics Data System (ADS)

Cavalcante, Geane Carolina G.; Viegas, Gustavo; Archanjo, Carlos José; da Silva, Marcos Egydio

2016-11-01

The presence of melt during deformation produces a drastic change in the rheological behavior of the continental crust; rock strength is decreased even for melt fractions as low as ∼7%. At pressure/temperature conditions typical of the middle to lower crust, melt-bearing systems may play a critical role in the process of strain localization and in the overall strength of the continental lithosphere. In this contribution we focus on the role and dynamics of melt flow in two different mid-crustal settings formed during the Brasiliano orogeny: (i) a large-scale anatectic layer in an orthogonal collision belt, represented by the Carlos Chagas anatexite in southeastern Brazil, and (ii) a strike-slip setting, in which the Espinho Branco anatexite in the Patos shear zone (northeast Brazil) serves as an analogue. Both settings, located in eastern Brazil, are part of the Neoproterozoic tectonics that resulted in widespread partial melting, shear zone development and the exhumation of middle to lower crustal layers. These layers consist of compositionally heterogeneous anatexites, with variable former melt fractions and leucosome structures. The leucosomes usually form thick interconnected networks of magma that reflect a high melt content (>30%) during deformation. From a comparison of previous work based on detailed petrostructural and AMS studies of the anatexites exposed in these areas, we discuss the rheological implications caused by the accumulation of a large volume of melt ;trapped; in mid-crustal levels, and by the efficient melt extraction along steep shear zones. Our analyses suggest that rocks undergoing partial melting along shear settings exhibit layers with contrasting competence, implying successive periods of weakening and strengthening. In contrast, regions where a large amount of magma accumulates lack clear evidence of competence contrast between layers, indicating that they experienced only one major stage of dramatic strength drop. This comparative

New Insights on the Recrystallization and New Growth of Extensively Radiation-damaged Zircon

NASA Astrophysics Data System (ADS)

Hanchar, J. M.; Schmitz, M. D.; Wirth, R.

2012-12-01

Approximately 10 grams of cm-sized nearly metamict zircon crystals from the Saranac Prospect in the Bancroft District of Ontario were combined by breaking into small pieces and then ground under ethanol to a fine powder with an agate mortar and pestle in order to make enough homogeneously mixed material for multiple powder X-Ray and diffraction scans, high-resolution transmission electron microscopy (HR-TEM) measurements, and chemical abrasion isotope dilution thermal ionization mass spectrometry (CA-TIMS). While these large zircon crystals ground to a powder have a larger surface area and not in the same physical state (i.e., brown and metamict) as what is typically analyzed in single zircon CA-ID-TIMS U-Pb analysis (clear euhedral grains), the physical and chemical changes that occur during the heat treatment used in CA-TIMS are thought to be similar processes. Aliquots of the ground zircon powder were annealed in situ using a Pt furnace in a powder diffractometer during which time simultaneous powder diffraction patterns were acquired starting at 25°C, at elevated temperature (from 500°C to 1400°C) at selected time intervals, and then again at 25°C. The powder X-ray diffraction results indicate that below ~900°C the recrystallization of the zircon powder commences but is incomplete, even after 36 hours, with diffuse low intensity diffraction peaks. At 1150°C the zircon powder shows significant recrystallization. At 1150°C, the recrystallization is essentially complete in less than one hour. Before heating the zircon powder samples consisted of clear, transparent to brown, translucent, complexly zoned fragments. After heating at 900°C the zircon powder retained a smaller percentage of clear or brown complexly zoned fragments, while the majority of material had transformed to oscillatory or irregularly zoned, dominantly white opaque microcrystalline fragments. The clear fragments were hypothesized to be preexisting original crystalline zircon, the brown

Meteorite-asteroid spectral comparison - The effects of comminution, melting, and recrystallization

NASA Technical Reports Server (NTRS)

Clark, Beth E.; Fanale, Fraser P.; Salisbury, John W.

1992-01-01

The present laboratory simulation of possible spectral-alteration effects on the optical surface of ordinary chondrite parent bodies duplicated regolith processes through comminution of the samples to finer rain sizes. After reflectance spectra characterization, the comminuted samples were melted, crystallized, recomminuted, and again characterized. While individual spectral characteristics could be significantly changed by these processes, no combination of the alteration procedures appeared capable of affecting all relevant parameters in a way that improved the match between chondritic meteorites and S-class asteroids.

Generation of alkaline magmas in subduction zones by melting of mélange diapirs

NASA Astrophysics Data System (ADS)

Cruz-Uribe, A. M.; Marschall, H.; Gaetani, G. A.; Le Roux, V.

2016-12-01

and Na), and depletion in Nb and Ta. The presence of a light rare earth element (LREE)-bearing accessory phase results in trace element fractionation by a factor of 4.2 for Nd/Hf and 2.6 for Sr/Nd. Melting of mélange diapirs provides a simple, single-stage model for the origin of alkaline magmatism in the arc and backarc regions of subduction zones.

Geochemistry of speleothems affected by aragonite to calcite recrystallization - Potential inheritance from the precursor mineral

NASA Astrophysics Data System (ADS)

Domínguez-Villar, David; Krklec, Kristina; Pelicon, Primož; Fairchild, Ian J.; Cheng, Hai; Edwards, Lawrence R.

2017-03-01

Formerly aragonite speleothems recrystallized to calcite result from solutions subsaturated in aragonite and supersaturated in calcite that infiltrate into the speleothem through the interconnected porosity. In most cases, the crystal replacement takes place through a thin solution film. This diagenetic process can occur under open or semi-closed geochemical conditions. Thus, secondary calcite crystals record the composition of the fluid at the time of diagenesis affected by calcite partition coefficients and fractionation factors (open system) or partly inherit the composition of the primary aragonite (semi-closed system). So, whether or not recrystallized aragonite speleothems can record reliable geochemical signals from the time of speleothem primary deposition still is an open debate. We studied a stalagmite from Eagle Cave (Spain) predominantly composed of secondary calcite that replaced aragonite, although a core of primary aragonite extending 45 mm along the growth direction was preserved at the base of the sample. We obtained Mg and Sr compositional maps, paired U-Th dating and δ18O and δ13C profiles across the diagenetic front. Additionally, two parallel isotope records were obtained along the speleothem growth direction in the aragonite and calcite sectors. Our results support that recrystallization of this speleothem took place in open system conditions for δ18O, δ13C, Mg and Sr, but in semi-closed system conditions for U and Th. The recrystallization of this sample took place during one or several events, likely after the Younger Dryas as a result of climate change influencing drip water composition. Based on compositional zoned patterns, we suggest that the advance of diagenetic fronts in this speleothem had an average rate of 50 ± 45 μm/yr. Such recrystallization rate can transform any aragonite speleothem into calcite within a few centuries. We suggest that the volume of water interacting with the speleothem at the time of recrystallization is

Mesoscale model for fission-induced recrystallization in U-7Mo alloy

DOE PAGES

Liang, Linyun; Mei, Zhi -Gang; Kim, Yeon Soo; ...

2016-08-09

A mesoscale model is developed by integrating the rate theory and phase-field models and is used to study the fission-induced recrystallization in U-7Mo alloy. The rate theory model is used to predict the dislocation density and the recrystallization nuclei density due to irradiation. The predicted fission rate and temperature dependences of the dislocation density are in good agreement with experimental measurements. This information is used as input for the multiphase phase-field model to investigate the fission-induced recrystallization kinetics. The simulated recrystallization volume fraction and bubble induced swelling agree well with experimental data. The effects of the fission rate, initial grainmore » size, and grain morphology on the recrystallization kinetics are discussed based on an analysis of recrystallization growth rate using the modified Avrami equation. Here, we conclude that the initial microstructure of the U-Mo fuels, especially the grain size, can be used to effectively control the rate of fission-induced recrystallization and therefore swelling.« less

Dynamic recrystallization in friction surfaced austenitic stainless steel coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Puli, Ramesh, E-mail: rameshpuli2000@gmail.com; Janaki Ram, G.D.

2012-12-15

Friction surfacing involves complex thermo-mechanical phenomena. In this study, the nature of dynamic recrystallization in friction surfaced austenitic stainless steel AISI 316L coatings was investigated using electron backscattered diffraction and transmission electron microscopy. The results show that the alloy 316L undergoes discontinuous dynamic recrystallization under conditions of moderate Zener-Hollomon parameter during friction surfacing. - Highlights: Black-Right-Pointing-Pointer Dynamic recrystallization in alloy 316L friction surfaced coatings is examined. Black-Right-Pointing-Pointer Friction surfacing leads to discontinuous dynamic recrystallization in alloy 316L. Black-Right-Pointing-Pointer Strain rates in friction surfacing exceed 400 s{sup -1}. Black-Right-Pointing-Pointer Estimated grain size matches well with experimental observations in 316L coatings.

Laser Vacuum Furnace for Zone Refining

NASA Technical Reports Server (NTRS)

Griner, D. B.; Zurburg, F. W.; Penn, W. M.

1986-01-01

Laser beam scanned to produce moving melt zone. Experimental laser vacuum furnace scans crystalline wafer with high-power CO2-laser beam to generate precise melt zone with precise control of temperature gradients around zone. Intended for zone refining of silicon or other semiconductors in low gravity, apparatus used in normal gravity.

Origins of two types of serpentinites from the Qinling orogenic belt, central China and associated fluid/melt-rock interactions

NASA Astrophysics Data System (ADS)

Wu, Kai; Ding, Xing; Ling, Ming-Xing; Sun, Wei-dong; Zhang, Li-Peng; Hu, Yong-Bin; Huang, Rui-Fang

2018-03-01

Serpentinites are important volatile and fluid mobile element repositories in oceanic lithosphere and subduction zones, and thus provide significant constraints on global geochemical cycles and tectonic evolution at convergent margins. In this contribution, two types of serpentinites from the Mianlue suture zone in the Qinling orogenic belt, central China, are identified on the basis of detailed mineralogical and geochemical study. Serpentinites from the Jianchaling region (Group 1) are composed of lizardite/chrysotile + magnesite + magnetite. Most of these serpentinites (Group 1a), consist of pseudomorphic orthopyroxene and olivine, and are characterized by low Al2O3/SiO2, high MgO/SiO2 and Ir-type PGEs to Pt ratios, suggesting a residual mantle origin. Meanwhile, the U-shape REE pattern and positive Eu, Sr and Ba anomalies of these serpentinites indicate that serpentinization fluids have interacted with gabbroic cumulates at moderately high temperatures or associate with the chlorinity and redox conditions of the fluid. Considering the limited mobility of U in the hydrating fluids for the Group 1a serpentinites, hydrating fluids for these serpentinites are most likely derived from the dehydrated slab, and have been in equilibrium with subducting sediments. There are also some serpentinites with low-grade metamorphic recrystallization from the Jianchaling region (Group 1b), represented by recrystallized serpentine minerals (antigorite). The trace element compositions of these Group 1b serpentinites suggest that partial dehydration of serpentinites associated with the transformation from lizardite to antigorite in subduction zone is also likely to affect the geochemistry of serpentinites. Serpentinites from the Liangyazi region (Group 2) are composed of antigorite + dolomite + spinel + magnetite. The high Cr number (0.65-0.80) and low Ti concentrations of spinels in Group 2 serpentinites indicate a refractory mantle wedge origin. Fertile major element compositions

Inhibition of Ice Growth and Recrystallization by Zirconium Acetate and Zirconium Acetate Hydroxide

PubMed Central

Mizrahy, Ortal; Bar-Dolev, Maya; Guy, Shlomit; Braslavsky, Ido

2013-01-01

The control over ice crystal growth, melting, and shaping is important in a variety of fields, including cell and food preservation and ice templating for the production of composite materials. Control over ice growth remains a challenge in industry, and the demand for new cryoprotectants is high. Naturally occurring cryoprotectants, such as antifreeze proteins (AFPs), present one solution for modulating ice crystal growth; however, the production of AFPs is expensive and inefficient. These obstacles can be overcome by identifying synthetic substitutes with similar AFP properties. Zirconium acetate (ZRA) was recently found to induce the formation of hexagonal cavities in materials prepared by ice templating. Here, we continue this line of study and examine the effects of ZRA and a related compound, zirconium acetate hydroxide (ZRAH), on ice growth, shaping, and recrystallization. We found that the growth rate of ice crystals was significantly reduced in the presence of ZRA and ZRAH, and that solutions containing these compounds display a small degree of thermal hysteresis, depending on the solution pH. The compounds were found to inhibit recrystallization in a manner similar to that observed in the presence of AFPs. The favorable properties of ZRA and ZRAH suggest tremendous potential utility in industrial applications. PMID:23555701

Magma transport and olivine crystallization depths in Kīlauea's east rift zone inferred from experimentally rehomogenized melt inclusions

NASA Astrophysics Data System (ADS)

Tuohy, Robin M.; Wallace, Paul J.; Loewen, Matthew W.; Swanson, Donald A.; Kent, Adam J. R.

2016-07-01

Concentrations of H2O and CO2 in olivine-hosted melt inclusions can be used to estimate crystallization depths for the olivine host. However, the original dissolved CO2 concentration of melt inclusions at the time of trapping can be difficult to measure directly because in many cases substantial CO2 is transferred to shrinkage bubbles that form during post-entrapment cooling and crystallization. To investigate this problem, we heated olivine from the 1959 Kīlauea Iki and 1960 Kapoho (Hawai'i) eruptions in a 1-atm furnace to temperatures above the melt inclusion trapping temperature to redissolve the CO2 in shrinkage bubbles. The measured CO2 concentrations of the experimentally rehomogenized inclusions (⩽590 ppm for Kīlauea Iki [n = 10]; ⩽880 ppm for Kapoho, with one inclusion at 1863 ppm [n = 38]) overlap with values for naturally quenched inclusions from the same samples, but experimentally rehomogenized inclusions have higher within-sample median CO2 values than naturally quenched inclusions, indicating at least partial dissolution of CO2 from the vapor bubble during heating. Comparison of our data with predictions from modeling of vapor bubble formation and published Raman data on the density of CO2 in the vapor bubbles suggests that 55-85% of the dissolved CO2 in the melt inclusions at the time of trapping was lost to post-entrapment shrinkage bubbles. Our results combined with the Raman data demonstrate that olivine from the early part of the Kīlauea Iki eruption crystallized at <6 km depth, with the majority of olivine in the 1-3 km depth range. These depths are consistent with the interpretation that the Kīlauea Iki magma was supplied from Kīlauea's summit magma reservoir (∼2-5 km depth). In contrast, olivine from Kapoho, which was the rift zone extension of the Kīlauea Iki eruption, crystallized over a much wider range of depths (∼1-16 km). The wider depth range requires magma transport during the Kapoho eruption from deep beneath the summit

In situ deformation and mechanical properties of bismuth telluride prepared via zone melting

NASA Astrophysics Data System (ADS)

Lai, Tang-Yu; Hsiao, Yu-Jen; Fang, Te-Hua

2018-03-01

In this study, we prepared Bi2Te3 nanostructures via zone melting and characterized their mechanical properties by nanoindentation and in situ transmission electron microscopy (TEM). The nanoindentation results revealed that a significant ‘pop-in’ phenomenon occurs under high-loading conditions with multiple dislocations and phase transitions in the material structure. Young’s modulus of the nanostructures was found to be 42.7 ± 2.56 GPa from nanoindentation measurements and 12.3 ± 0.1 GPa from in situ TEM measurements. The results of this study may be useful for the future development of Bi2Te3 thermoelectric devices via printing processes.

The Melt Transition in Mature, Fluid-Saturated Gouge

NASA Astrophysics Data System (ADS)

Rempel, A. W.

2006-12-01

Mechanisms that link the evolution of fault strength and temperature during earthquakes have been studied extensively, with accumulating constraints from theoretical, field and laboratory investigations promoting increased confidence in our understanding of the dominant physical interactions. In mature fault zones that have accommodated many large earthquakes and are characterized by gouge layers that greatly exceed the thickness of the ~ mm-scale "principal slip surfaces" in which shear is localized, the thermal pressurization of pore fluids is expected to be particularly important for reducing the fault strength and limiting the extent of shear heating. Nevertheless, for sufficiently large slip distances and reasonable estimates of hydraulic transport properties and other controlling variables, the predicted temperature increases are sometimes able to reach the onset of melting, particularly at mid to lower seismogenic depths (e.g. 10km). Reported field observations of quenched glassy melt products, known as pseudotachylytes, are much more common on young faults, particularly where slip is initiated between coherent rock surfaces, rather than in exhumed mature fault zones, where thermal pressurization is likely to be more important and macroscopic melting appears to be rare. Those pseudotachylyte layers that are recovered from mature fault zones display a range of thicknesses and crystal contents, which indicate that significant shear heating continued long after the onset of melting, with work performed against the viscous resistance of a partially molten slurry. Models that describe the transition to melting in a finite shear zone that is initially saturated with pore fluids are presented with two main conceptual challenges: 1. the energy input for frictional heating is generally assumed to be proportional to the effective stress, which vanishes when macroscopic melt layers are produced and thermodynamic considerations require that the melt pressure balance the

Paramagnetic resonance of LaGaO3: Mn single crystals grown by floating zone melting

NASA Astrophysics Data System (ADS)

Vazhenin, V. A.; Potapov, A. P.; Artyomov, M. Yu.; Salosin, M. A.; Fokin, A. V.; Gil'mutdinov, I. F.; Mukhamedshin, I. R.

2016-02-01

The EPR spectrum of Mn-doped lanthanum gallate single crystals grown by floating zone melting with optical heating has been studied. In contrast to the crystals grown according to the Czochralski method, no manganese is found in these crystals even after high-temperature annealing in air. The spectral characteristics of Fe3+ and Gd3+ centers in crystals prepared by various methods have been compared in the rhombohedral phase, and the fourth-rank nondiagonal parameters of the Fe3+ trigonal centers have been determined, as well.

Numerical modelling of lithospheric flexure in front of subduction zones in Japan and its role to initiate melt extraction from the LVZ.

NASA Astrophysics Data System (ADS)

Bessat, A.; Pilet, S.; Duretz, T.; Schmalholz, S. M.

2017-12-01

Petit-spot volcanoes were found fifteen years ago by Japanese researchers at the top of the subducting plate in Japan (Hirano 2006). This discovery is of great significance as it highlights the importance of tectonic processes for the initiation of intraplate volcanism. The location of these small lava flows is unusual and seems to be related to the plate flexure, which may facilitate the extraction of low degree melts from the base of the lithosphere, a hypothesis previously suggested to explain changes in electric and seismic properties at 70-90 km depth, i.e. within the low velocity zone (LVS) (Sifré 2014). A critical question is related to the process associated with the extraction of this low degree melts from the LVZ. First models suggested that extension associated to plate bending allows large cracks to propagate across the lithosphere and could promote the extraction of low degree melts at the base of the lithosphere (Hirano 2006 & Yamamoto 2014). However, the study of petit-spot mantle xenoliths from Japan (Pilet 2016) has demonstrated that low degree melts are not directly extracted to the surface but percolate, interact and metasomatize the oceanic lithosphere. In order to understand the melt extraction process in the region of plate bending, we performed 2D thermo-mechanical simulations of Japanese-type subduction. The numerical model considers viscoelastoplastic deformation. This allows the quantification of state of the stress, strain rates, and viscosities which will control the percolation of melt initially stocked at the base of the lithosphere. Initial results show that plate flexure changes the distribution of the deformation mechanism in the flexure zone, between 40 km to 80 km depth. A change of the dominant deformation mechanism from diffusion creep to dislocation creep and from there to Peierls creep was observed about 200 to 300 km from the trench. These changes are linked to the augmentation of the stresses in the flexure zone. At the

Influence of Fe(2+)-catalysed iron oxide recrystallization on metal cycling.

PubMed

Latta, Drew E; Gorski, Christopher A; Scherer, Michelle M

2012-12-01

Recent work has indicated that iron (oxyhydr-)oxides are capable of structurally incorporating and releasing metals and nutrients as a result of Fe2+-induced iron oxide recrystallization. In the present paper, we briefly review the current literature examining the mechanisms by which iron oxides recrystallize and summarize how recrystallization affects metal incorporation and release. We also provide new experimental evidence for the Fe2+-induced release of structural manganese from manganese-doped goethite. Currently, the exact mechanism(s) for Fe2+-induced recrystallization remain elusive, although they are likely to be both oxide-and metal-dependent. We conclude by discussing some future research directions for Fe2+-catalysed iron oxide recrystallization.

A STATE-VARIABLE APPROACH FOR PREDICTING THE TIME REQUIRED FOR 50% RECRYSTALLIZATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

M. STOUT; ET AL

2000-08-01

It is important to be able to model the recrystallization kinetics in aluminum alloys during hot deformation. The industrial relevant process of hot rolling is an example of where the knowledge of whether or not a material recrystallizes is critical to making a product with the correct properties. Classically, the equations that describe the kinetics of recrystallization predict the time to 50% recrystallization. These equations are largely empirical; they are based on the free energy for recrystallization, a Zener-Holloman parameter, and have several adjustable exponents to fit the equation to engineering data. We have modified this form of classical theorymore » replacing the Zener-Hollomon parameter with a deformation energy increment, a free energy available to drive recrystallization. The advantage of this formulation is that the deformation energy increment is calculated based on the previously determined temperature and strain-rate sensitivity of the constitutive response. We modeled the constitutive response of the AA5182 aluminum using a state variable approach, the value of the state variable is a function of the temperature and strain-rate history of deformation. Thus, the recrystallization kinetics is a function of only the state variable and free energy for recrystallization. There are no adjustable exponents as in classical theory. Using this approach combined with engineering recrystallization data we have been able to predict the kinetics of recrystallization in AA5182 as a function of deformation strain rate and temperature.« less

Stable mineral recrystallization in low temperature aqueous systems: A critical review

NASA Astrophysics Data System (ADS)

Gorski, Christopher A.; Fantle, Matthew S.

2017-02-01

Minerals may undergo recrystallization reactions in low temperature (<100 °C) aqueous systems, during which they exchange isotopes and trace elements with the dissolved reservoir without undergoing overt structural, bulk compositional, or morphological changes. These interfacial reactions, which are often referred to in the literature as "atom exchange" and herein as "stable mineral recrystallization", have important implications for the use of isotopic and elemental proxies to interpret past temperatures, oxidation states, and aqueous chemistries on Earth. The reactions are also significant for modern environments, including engineered systems, as they imply that mineral lattices may be substantially more open to exchanging toxic elements and radionuclides with coexisting solutions than previously thought. To date, observations of stable mineral recrystallization are distributed among several disciplines, and no work has attempted to review their findings comprehensively. Accordingly, this review article presents laboratory evidence for stable mineral recrystallization, describes data collection and interpretation strategies, summarizes similar recrystallization systematics observed in multiple studies, explores the potential occurrence of stable mineral recrystallization in natural systems, and discusses possible mechanisms by which stable mineral recrystallization occurs. The review focuses primarily on carbonates, sulfates, and iron oxides because these minerals have been studied most extensively to date. The review concludes by presenting key questions that should be addressed in this field to further understand and account for stable mineral recrystallization in natural and engineered aqueous systems at low temperatures.

Full melting of a two-dimensional complex plasma crystal triggered by localized pulsed laser heating

NASA Astrophysics Data System (ADS)

Couëdel, L.; Nosenko, V.; Rubin-Zuzic, M.; Zhdanov, S.; Elskens, Y.; Hall, T.; Ivlev, A. V.

2018-04-01

The full melting of a two-dimensional plasma crystal was induced in a principally stable monolayer by localized laser stimulation. Two distinct behaviors of the crystal after laser stimulation were observed depending on the amount of injected energy: (i) below a well-defined threshold, the laser melted area recrystallized; (ii) above the threshold, it expanded outwards in a similar fashion to mode-coupling instability-induced melting, rapidly destroying the crystalline order of the whole complex plasma monolayer. The reported experimental observations are due to the fluid mode-coupling instability, which can pump energy into the particle monolayer at a rate surpassing the heat transport and damping rates in the energetic localized melted spot, resulting in its further growth. This behavior exhibits remarkable similarities with impulsive spot heating in ordinary reactive matter.

Contrasting accessory mineral behavior in minimum-temperature melts: Empirical constraints from the Himalayan metamorphic core

NASA Astrophysics Data System (ADS)

Cottle, John M.; Larson, Kyle P.; Yakymchuk, Chris

2018-07-01

Medium-grained leucogranite in the Tama Kosi region of the Nepalese Himalayan Metamorphic Core yields a relatively narrow range of monazite 208Pb/232Th dates with a dominant population at 21.0 Ma inferred to represent crystallization of an early plutonic phase. In contrast, the pegmatitic portion of the same intrusive complex, that cross-cuts the medium-grained leucogranite, contains zircon, monazite and xenotime that each display near-identical age spectra, recording semi-continuous (re-)crystallization from 27.5 Ma to 21.0 Ma, followed by a 2 m.y. hiatus then further (re-)crystallization between 19.4 and 18.6 Ma. The "gap" in pegmatite dates corresponds well to the crystallization age of the older leucogranite, whereas the end of accessory phase growth in the pegmatite coincides with the onset of regional-scale cooling. Detailed textural, trace element and thermochronologic data indicate that the range of zircon, monazite and xenotime dates recorded in the pegmatite reflect inherited components that underwent semi-continuous (re-)crystallization during metamorphism and/or anatexis in the source region(s), whereas dates younger than the hiatus indicate accessory phase recrystallization, related to both fluid influx and a concomitant increase in temperature. In contrast, the lack of an inherited component(s) in the medium-grained leucogranite phase is inferred to be a result of complete dissolution during partial melting. A model is proposed in which influx of heat and H2O-rich fluids associated with early leucogranite emplacement temporarily delayed zircon and monazite and xenotime crystallization, respectively. These data highlight the importance of measuring spatially resolved dates, trace elements and textural patterns from multiple accessory minerals combined with model constraints to better understand the often-complex crystallization history of anatectic melts in collisional orogens.

Subduction zone mantle enrichment by fluids and Zr-Hf-depleted crustal melts as indicated by backarc basalts of the Southern Volcanic Zone, Argentina

NASA Astrophysics Data System (ADS)

Holm, Paul M.; Søager, Nina; Alfastsen, Mads; Bertotto, Gustavo W.

2016-10-01

We aim to identify the components metasomatizing the mantle above the subducting Nazca plate under part of the Andean Southern Volcanic Zone (SVZ). We present new major and ICP-MS trace element and Sr, Nd and high-precision Pb isotope analyses of primitive olivine-phyric alkali basalts from the Northern Segment Volcanic Field, part of the Payenia province in the backarc of the Transitional SVZ. One new 40Ar-39Ar age determination confirms the Late Pleistocene age of this most northerly part of the province. All analysed rocks have typical subduction zone type incompatible element enrichment, and the rocks of the Northern Segment, together with the neighbouring Nevado Volcanic Field, have isotopic compositions intermediate between adjacent Transitional SVZ arc rocks and southern Payenia OIB-type basaltic rocks. Modelling the Ba-Th-Sm variation we demonstrate that fluids as well as 1-2% melts of upper continental crust (UCC) enriched their mantle sources, and La-Nb-Sm variations additionally indicate that the pre-metasomatic sources ranged from strongly depleted to undepleted mantle. Low Eu/Eu* and Sr/Nd also show evidence for a UCC component in the source. The contribution of Chile Trench sediments to the magmas seems insignificant. The Zr/Sm and Hf/Sm ratios are relatively low in many of the Northern Segment rocks, ranging down to 17 and 0.45, respectively, which, together with relatively high Th/U, is argued to indicate that the metasomatizing crustal melts were derived by partial melting of subducted UCC that had residual zircon, in contrast to the UCC melts added to Transitional SVZ arc magmas. Mixing between depleted and undepleted mantle, enriched by UCC and fluids, is suggested by Sr, Nd and Pb isotopes of the Northern Segment and Nevado magmas. The metasomatized undepleted mantle south of the Northern Segment is suggested to be part of upwelling OIB-type mantle, whereas the pre-metasomatically depleted mantle also can be found as a component in some arc

High temperature pseudotachylytes and ductile shear zones in dry rocks from the continental lower crust (Lofoten, Norway)

NASA Astrophysics Data System (ADS)

Menegon, Luca; Pennacchioni, Giorgio; Harris, Katherine; Wood, Elliot

2014-05-01

Understanding the mechanisms of initiation and growth of shear zones under lower crustal conditions is of fundamental importance when assessing lithosphere rheology and strength. In this study we investigate brittle-ductile shear zones developed under lower crustal conditions in anorthosites from Nusfjord, Lofoten (northern Norway). Steep ductile shear zones trend E-W to ESE-WSW and have a stretching lineation plunging steeply to the SSW or SSE. The shear sense is normal (south block down to the south) as indicated by SC and SC' fabrics and sigmoidal foliations. The shear zone show a mylonitic to ultramylonitic fabric, sharp boundaries to the host anorthosites, and abundant anastomosing dark fine-grained layers along the main foliation. The fine-grained layers localized much of the strain. Relatively lower strain domains within or adjacent to shear zones indicate that the fine dark bands of mylonites represent transposed pseudotachylyte which still locally preserve the pristine structures such as chilled margins, breccia textures with angular clasts of the host rock and injection veins; intersecting veins of pseudotachylyte record multiple stages of seismic slip. The orientation of injection veins and marker offset along the most preserved pseudotachylyte fault veins indicate approximately a sinistral strike slip kinematic during faulting event responsible for the friction-induced melting. These observations indicate that ductile shear zones exploited pre-existing brittle fault zones including a network of pseudotachylytes, and that the fine-grained "ultramylonites" derive from former fine-grained pseudotachylytes. The pseudotachylyte microstructure is dominated by plagioclase microlites dispersed in a groundmass of fine-grained clinopyroxene. Clinopyroxene recrystallizes in the damage zone flanking the pseudotachylytes, indicating high metamorphic grade during pseudotachylyte formation. Small idioblastic or cauliflower garnet are scattered through the matrix and

Incorporation of Eu(III) into Calcite under Recrystallization conditions.

PubMed

Hellebrandt, S E; Hofmann, S; Jordan, N; Barkleit, A; Schmidt, M

2016-09-13

The interaction of calcite with trivalent europium under recrystallization conditions was studied on the molecular level using site-selective time-resolved laser fluorescence spectroscopy (TRLFS). We conducted batch studies with a reaction time from seven days up to three years with three calcite powders, which differed in their specific surface area, recrystallization rates and impurities content. With increase of the recrystallization rate incorporation of Eu(3+) occurs faster and its speciation comes to be dominated by one species with its excitation maximum at 578.8 nm, so far not identified during previous investigations of this process under growth and phase transformation conditions. A long lifetime of 3750 μs demonstrates complete loss of hydration, consequently Eu must have been incorporated into the bulk crystal. The results show a strong dependence of the incorporation kinetics on the recrystallization rate of the different calcites. Furthermore the investigation of the effect of different background electrolytes (NaCl and KCl) demonstrate that the incorporation process under recrystallization conditions strongly depends on the availability of Na(+). These findings emphasize the different retention potential of calcite as a primary and secondary mineral e.g. in a nuclear waste disposal site.

Incorporation of Eu(III) into Calcite under Recrystallization conditions

PubMed Central

Hellebrandt, S. E.; Hofmann, S.; Jordan, N.; Barkleit, A.; Schmidt, M.

2016-01-01

The interaction of calcite with trivalent europium under recrystallization conditions was studied on the molecular level using site-selective time-resolved laser fluorescence spectroscopy (TRLFS). We conducted batch studies with a reaction time from seven days up to three years with three calcite powders, which differed in their specific surface area, recrystallization rates and impurities content. With increase of the recrystallization rate incorporation of Eu3+ occurs faster and its speciation comes to be dominated by one species with its excitation maximum at 578.8 nm, so far not identified during previous investigations of this process under growth and phase transformation conditions. A long lifetime of 3750 μs demonstrates complete loss of hydration, consequently Eu must have been incorporated into the bulk crystal. The results show a strong dependence of the incorporation kinetics on the recrystallization rate of the different calcites. Furthermore the investigation of the effect of different background electrolytes (NaCl and KCl) demonstrate that the incorporation process under recrystallization conditions strongly depends on the availability of Na+. These findings emphasize the different retention potential of calcite as a primary and secondary mineral e.g. in a nuclear waste disposal site. PMID:27618958

Frictional melting of clayey gouge during seismic fault slip: Experimental observation and implications

NASA Astrophysics Data System (ADS)

Han, Raehee; Hirose, Takehiro; Jeong, Gi Young; Ando, Jun-ichi; Mukoyoshi, Hideki

2014-08-01

Clayey gouges are common in fault slip zones at shallow depths. Thus, the fault zone processes and frictional behaviors of the gouges are critical to understanding seismic slip at these depths. We conducted rotary shear tests on clayey gouge (~41 wt % clay minerals) at a seismic slip rate of 1.3 m/s. Here we report that the gouge was melted at 5 MPa of normal stress and room humidity conditions. The initial local melting was followed by melt layer formation. Clay minerals (e.g., smectite and illite) and plagioclase were melted and quenched to glass with numerous vesicles. Both flash heating and bulk temperature increases appear to be responsible for the melting. This observation of clayey gouge melting is comparable to that of natural faults (e.g., Chelungpu fault, Taiwan). Due to heterogeneous fault zone properties (e.g., permeability), frictional melting may be one of the important processes in clayey slip zones at shallow depths.

Static Recrystallization Behavior of Z12CN13 Martensite Stainless Steel

NASA Astrophysics Data System (ADS)

Luo, Min; Zhou, Bing; Li, Rong-bin; Xu, Chun; Guo, Yan-hui

2017-09-01

In order to increase the hot workability and provide proper hot forming parameters of forging Z12CN13 martensite stainless steel for the simulation and production, the static recrystallization behavior has been studied by double-pass hot compression tests. The effects of deformation temperature, strain rate and inter-pass time on the static recrystallization fraction by the 2% offset method are extensively studied. The results indicate that increasing the inter-pass time and the deformation temperature as well as strain rate appropriately can increase the fraction of static recrystallization. At the temperature of 1050-1150 °C, inter-pass time of 30-100 s and strain rate of 0.1-5 s-1, the static recrystallization behavior is obvious. In addition, the kinetics of static recrystallization behavior of Z12CN13 steel has been established and the activation energy of static recrystallization is 173.030 kJ/mol. The substructure and precipitates have been studied by TEM. The results reveal that the nucleation mode is bulging at grain boundary. Undissolved precipitates such as MoNi3 and Fe3C have a retarding effect on the recrystallization kinetics. The effect is weaker than the accelerating effect of deformation temperature.

Recrystallization Behavior in SAC305 and SAC305 + 3.0POSS Solder Joints Under Thermal Shock

NASA Astrophysics Data System (ADS)

Han, Jing; Gu, Penghao; Ma, Limin; Guo, Fu; Liu, Jianping

2018-04-01

Sn-3.0Ag-0.5Cu (SAC305) and SAC305 + 3.0 polyhedral oligomeric silsesquioxanes (POSS) ball grid array (BGA) assemblies have been prepared, observed, and subjected to thermal shock. The microstructure and grain orientation evolution of the solder joints located at the same position of the package were characterized by scanning electron microscopy and electron backscattering diffraction, respectively. The results showed that the microstructure of the solder joints was refined by addition of POSS particles. In addition, compared with the single-grained or tricrystal joints normally observed in SAC305 BGA solder joints, the frequency of single-grained as-reflowed SAC305 + 3.0POSS BGA joints was greatly reduced, and the solder joints were typically composed of multicrystals with orientations separated by high-angle grain boundaries. These multicrystal joints appear to be obtained by dominant tricrystals or double tricrystals with deviation of the preferred [110] and [1\\bar{1}0] growth directions of Sn dendrites in Sn-Ag-based solder alloys during solidification from the melt. After 928 thermal shock cycles, the SAC305 solder joint had large-area recrystallization and cracks in contrast to the SAC305 + 3.0POSS solder joint located at the same position of the package, indicating that addition of POSS to SAC305 solder joints may contribute to postponement of recrystallization and subsequent crack initiation and propagation along recrystallized grain boundaries by pinning grain boundaries and movement of dislocations. This finding also confirms the double tricrystal solidification twinning nucleation behavior in Pb-free solder joints.

Thermogravimetric study of vapor pressure of TATP synthesized without recrystallization.

PubMed

Mbah, Jonathan; Knott, Debra; Steward, Scott

2014-11-01

This study aims at characterizing the vapor pressure signatures generated by triacetone triperoxide (TATP) that was synthesized without recrystallization by thermogravimmetric analysis (TGA) for exploitation by standoff detection technologies of explosive devices. The thermal behavior of the nonrecrystallized sample was compared with reported values. Any phase change, melting point and decomposition identification were studied by differential scanning calorimeter. Vapor pressures were estimated by the Langmuir method of evaporation from an open surface in a vacuum. Vapor pressures of TATP at different temperatures were calculated using the linear logarithmic relationship obtained from benzoic acid reference standard. Sublimation of TATP was found to follow apparent zero-order kinetics and sublimes at steady rates at 298 K and above. While the enthalpy of sublimation found, 71.7 kJ mol(-1), is in agreement with reported values the vapor pressures deviated significantly. The differences in the vapor pressures behavior are attributable to the synthesis pathway chosen in this study. Copyright © 2014 Elsevier B.V. All rights reserved.

Adaptive characterization of recrystallization kinetics in IF steel by electron backscatter diffraction.

PubMed

Kim, Dong-Kyu; Park, Won-Woong; Lee, Ho Won; Kang, Seong-Hoon; Im, Yong-Taek

2013-12-01

In this study, a rigorous methodology for quantifying recrystallization kinetics by electron backscatter diffraction is proposed in order to reduce errors associated with the operator's skill. An adaptive criterion to determine adjustable grain orientation spread depending on the recrystallization stage is proposed to better identify the recrystallized grains in the partially recrystallized microstructure. The proposed method was applied in characterizing the microstructure evolution during annealing of interstitial-free steel cold rolled to low and high true strain levels of 0.7 and 1.6, respectively. The recrystallization kinetics determined by the proposed method was found to be consistent with the standard method of Vickers microhardness. The application of the proposed method to the overall recrystallization stages showed that it can be used for the rigorous characterization of progressive microstructure evolution, especially for the severely deformed material. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

CO2 Solubility in Natural Rhyolitic Melts at High Pressures - Implications for Carbon Flux in Subduction Zones by Sediment Partial Melts

NASA Astrophysics Data System (ADS)

Duncan, M. S.; Dasgupta, R.

2011-12-01

Partial melts of subducting sediments is thought to be a critical agent in carrying trace elements and water to arc basalt source regions. For subduction zones that contain significant amount of carbonates in ocean-floor sediments, sediment melts likely also act as a carrier of CO2. However, the CO2 carrying capacity of natural rhyolitic melts at sub-arc depths remains unconstrained. We conducted experiments on a synthetic composition, similar to average, low-degree experimental partial melt of pelitic sediments. The composition was constructed with reagent grade oxides and carbonates, the source of excess CO2. Experiments were conducted between 1 and 3 GPa at 1200 °C in Au80Pd20 capsules using a piston cylinder apparatus with a half-inch BaCO3 assembly at Rice University. Quench products showed glasses with bubbles, the latter suggesting saturation of the melt with a CO2-rich vapor phase. Oxygen fugacity during the experiments was not strictly controlled but the presence of CO2 bubbles and absence of graphite indicates fO2 above the CCO buffer. Major element concentrations of glasses were measured using EPMA. The CO2 and H2O contents of experimental doubly polished (50-110 μm), bubble-free portions of the glass chips were determined using a Thermo Nicolet Fourier Transform Infrared Spectrometer. Spectra were recorded with a resolution of 4 cm-1, 512 scans, from 650 to 4000 cm-1, under a nitrogen purge to eliminate atmospheric gases. Dissolved volatile concentrations were quantified using the Beer-Lambert law and linear molar absorption coefficients from previous studies [1, 2]. Total dissolved carbon dioxide of experimental glasses was determined from the intensity of the ν3 antisymmetric stretch bands of CO32- at 1430 cm-1 and CO2mol at 2348 cm-1. Dissolved water content of experimental glasses was determined from the intensity of O-H stretching at 3520 cm-1. Estimated total CO2 concentrations at 3 GPa are in the range of 1-2 wt%, for melts with H2O contents

Mutual interaction between high and low stereo-regularity components for crystallization and melting behaviors of polypropylene blend fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawai, Kouya; Takarada, Wataru; Kikutani, Takeshi, E-mail: kikutani.t.aa@m.titech.ac.jp

Crystallization and melting behaviors of blend fibers of two types of polypropylene (PP), i.e. high stereo-regularity/high molecular weight PP (HPP) and low stereo-regularity/low molecular weight PP (LPP), was investigated. Blend fibers consisting of various HPP/LPP compositions were prepared through the melt spinning process. Differential scanning calorimetry (DSC), temperature modulated DSC (TMDSC) and wide-angle X-ray diffraction (WAXD) analysis were applied for clarifying the crystallization and melting behaviors of individual components. In the DSC measurement of blend fibers with high LPP composition, continuous endothermic heat was detected between the melting peaks of LPP at around 40 °C and that of HPP atmore » around 160 °C. Such endothermic heat was more distinct for the blend fibers with higher LPP composition indicating that the melting of LPP in the heating process was hindered because of the presence of HPP crystals. On the other hand, heat of crystallization was detected at around 90 °C in the case of blend fibers with LPP content of 30 to 70 wt%, indicating that the crystallization of HPP component was taking place during the heating of as-spun blend fibers in the DSC measurement. Through the TMDSC analysis, re-organization of the crystalline structure through the simultaneous melting and re-crystallization was detected in the cases of HPP and blend fibers, whereas re-crystallization was not detected during the melting of LPP fibers. In the WAXD analysis during the heating of fibers, amount of a-form crystal was almost constant up to the melting in the case of single component HPP fibers, whereas there was a distinct increase of the intensity of crystalline reflections from around 100 °C, right after the melting of LPP in the case of blend fibers. These results suggested that the crystallization of HPP in the spinning process as well as during the conditioning process after spinning was hindered by the presence of LPP.« less

The low magnetic field properties of superconducting bulk yttrium barium copper oxide - Sintered versus partially melted material

NASA Technical Reports Server (NTRS)

Hein, R. A.; Hojaji, H.; Barkatt, A.; Shafii, H.; Michael, K. A.; Thorpe, A. N.; Ware, M. F.; Alterescu, S.

1989-01-01

A comparison of the low magnetic field properties of sintered (990 C) and partially melted samples (1050 C) has been performed. Changes in the microstructure produced by recrystallization from the melt result in a significant increase in flux pinning at 77 K. Low-frequency (10-100 Hz), low-ac magnetic-field (0.01-9.0 Oe) ac susceptibility data show that gross changes in the loss component accompany the observed changes in microstructure. The effects of applied dc magnetic fields (10-220 Oe) on the ac responses of these microstructures have also been probed.

Deformation Characteristics and Recrystallization Response of a 9310 Steel Alloy

NASA Astrophysics Data System (ADS)

Snyder, David; Chen, Edward Y.; Chen, Charlie C.; Tin, Sammy

2013-01-01

The flow behavior and recrystallization response of a 9310 steel alloy deformed in the ferrite temperature range were studied in this work. Samples were compressed under various conditions of strain (0.6, 0.8 and multi-axial), strain rate (10-4 seconds-1 to 10-1 seconds-1) and temperature [811 K to 1033 K (538 °C to 760 °C)] using a Gleeble thermo-mechanical simulator. Deformation was characterized by both qualitative and quantitative means, using standard microscopy, electron backscatter diffraction (EBSD) analysis and flow stress modeling. The results indicate that deformation is primarily accommodated through dynamic recovery in sub-grain formation. EBSD analysis shows a continuous increase in sub-grain boundary misorientation with increasing strain, ultimately producing recrystallized grains from the sub-grains at high strains. This suggests that a sub-grain rotation recrystallization mechanism predominates in this temperature range. Analyses of the results reveal a decreasing mean dynamically recrystallized grain size with increasing Zener-Hollomon parameter, and an increasing recrystallized fraction with increasing strain.

Microstructural Evolution during Mid-Crustal Shear Zone Thickening and Thinning, Mount Irene Detachment Zone, Fiordland, New Zealand

NASA Astrophysics Data System (ADS)

Negrini, M.; Smith, S. A. F.; Scott, J.; Rooney, J. S.; Demurtas, M.

2016-12-01

Recent work has shown that ductile shear zones experience cyclic variations in stress and strain rate due to, for example, elastic loading from earthquake slip on brittle faults or the presence of rigid particles and asperities within the shear zone. Such non-steady state flow conditions can promote microstructural changes including a decrease in grain sizes followed by a switch in the main deformation mechanisms. Understanding the microstructural changes that occur during non steady-state deformation is therefore critical in evaluating shear zone rheology. The Mount Irene shear zone formed during Cretaceous extension in the middle crust and was active at temperatures of 600°C and pressures of 6 kbar. The shear zone localized in a basal calcite marble layer typically 3-5 m thick containing hundreds of thin (mm-cm) calc-silicate bands that are now parallel to the shear zone boundaries. The lower boundary of the shear zone preserves meter-scale undulations that cause the shear zone to be squeezed in to regions that are <1.5 m thick. The calc-silicate bands act as "flow markers" and allow individual shear zone layers to be traced continuously through thick and thin regions, implying that the mylonites experienced cyclic variations in stress and strain rate. Calc-mylonite samples collected from the same layer close to the base of the shear zone reveal that layer thinning was accompanied by progressive microstructural changes including intense twinning, stretching and flattening of large calcite porphyroclasts as well as the development of interconnected networks of recrystallized calcite aggregates. EBSD analysis shows that the recrystallized aggregates contain polygonal calcite grains with microstructures (e.g. grain quadruple junctions) similar to those reported for neighbor-switching processes associated with grain boundary sliding and superplasticity. Ongoing and future work will utilize samples from across the full thickness of the shear zone to determine key

Temperature and Time Constraints on Dissolution, Fe-Mg Exchange and Zoning between Relict Forsterite and Chondrule Melt - Implications for Thermal History of Chondrules

NASA Astrophysics Data System (ADS)

Ustunisik, G. K.; Ebel, D. S. S.; Walker, D.

2016-12-01

The chemical and textural characteristics of different generations of relict olivine grains in chondrules record the fact that chondrules were re-melted. Mineral dissolution, Fe-Mg exchange, and zoning within the relict crystals constrain the T-t aspects of this re-melting process. Here, we performed isothermal and dynamic cooling experiments at LDEO of Columbia University. For each run, a cubic crystal of known dimensions of Mogok forsterite (Fo99) was placed in synthetic Type IIA chondrule mesostasis with 4.92 wt% FeO (TLiq 1315ºC). Pressed pellets of this mixture were hung on Pt-wire loops and inserted in vertical Deltech furnace where CO-CO2 gas mixtures kept fO2 IW-1. For isothermal experiments, each charge was heated to 1428ºC, 1350ºC, 1250ºC, and 1150ºC and was held there from 20 mins to several days (>3 days) before drop-quenching into cold water. The dynamic crystallization experiments were held at 1428ºC for 20 mins, cooled at rates of 75ºC, 722ºC, and 1444ºC/hr to 1000ºC and then water quenched. X-ray-CT and EMPA at AMNH were used to image the partially resorbed/zoned olivines in 3-D before and after each run to observe textural evolution of the crystal shapes and volumes and to determine chemical changes. The isothermal experiments at 1150 and 1250ºC for 20 mins, produced no bulk FeO diffusion into the Mogok forsterite. Very minor Fe-Mg exchange at the crystal rims gives slight MgO zoning within the nearby melt. With increasing duration (1 hr and 22 hrs), at 1250ºC, embayments of melt form into the rims of the crystal (amplified at 22 hrs) with significant Fe-Mg exchange. FeO content of Mogok increased with major MgO zonation within nearby melt. At 1150ºC, the same increase in FeO in Mogok and zonation in nearby glass could only be achieved in >3 days experiment. At high Ts (1428ºC) in 20 min run, 75 volume % of Mogok forsterite has been dissolved into the melt. Resorption erodes the Fe-Mg exchange at the rims of the crystal. At longer

Morphology Controls on Calcite Recrystallization.

PubMed

Heberling, Frank; Paulig, Leonie; Nie, Zhe; Schild, Dieter; Finck, Nicolas

2016-11-01

Environmental scientists and geoscientists working in different fields regard the reactivity of calcite and corresponding changes in its trace elemental- or isotopic composition from diametrically opposed points of view. As one extreme, calcite based environmental remediation strategies rely on the fast recrystallization of calcite and the concurrent uptake and immobilization of pollutants. Paleo-ecological investigations denote the other extreme, and rely on the invariability of calcite composition over geological periods of time. We use long-term radiotracer experiments to quantify recrystallization rates of seven types of calcite powder with diverse morphology and particle size distribution. On the one hand our results demonstrate the long-term metastability of calcite with equilibrated crystal surfaces even at isotopic dis-equilibrium. On the other hand, we document the extremely high reactivity and interfacial free energy of freshly ground, rough calcite. Our results indicate that bulk calcite recrystallization is an interfacial free energy driven Ostwald-ripening process, in which particle roughness effects dominate over the effect of crystal habitus and particle size. We confirm that the dynamic equilibrium exchange of crystal constituents between kink sites involves an activation barrier of about 25 kJ/mol. At room temperature the equilibrium exchange is limited to a near surface region and proceeds at a rate of (3.6 ± 1.4)·10 -13 mol/(m 2 ·s).

Changing Melt-Migration Geometries with Crustal Depth: an Example From the Eastern Transverse Ranges.

NASA Astrophysics Data System (ADS)

Brown, K. L.; Paterson, S. R.; Barth, A. P.

2006-12-01

Detailed studies of North American Cordilleran sheeted plutons (Miller and Paterson, 2001; Mahan et al., 2003; Manduca et al., 1993) reveal that some have predominantly sub-vertical geometries, indicating construction within fundamentally vertical boundary zones in mid-crustal terrains. In contrast, the Bighorn sheeted complex of the eastern Transverse Ranges in southern California preserves fabrics that indicate a gently to moderately dipping geometry. Preliminary barometry shows that the eastern Transverse Ranges constitutes a tilted cross- section of the Mesozoic arc to depths of about 24 km. Whereas the shallow part of the tilted section is dominated by comparatively homogeneous Mesozoic plutons that intrude Proterozoic basement, the deeper part is dominated by mid-crustal sheeted plutons of Jurassic and Late Cretaceous age. Volumetrically dominant components of the western sheeted plutonic complex are biotite hornblende tonalite, granodiorite, and two mica-garnet granite sheets interlayered at meter to decimeter scale. Field observations indicate a transition from discordant plutons with weak magmatic fabrics to the contemporaneous deeper sheeted plutons with intense magmatic fabrics, suggesting that fabric intensity is related to pluton geometry and depth. Microscope investigations reveal that magmatic textures and fabrics are dominant in sheeted igneous rocks. Magmatic textures are defined by euhedral to subhedral plagioclase, hornblende, and biotite that do not show significant internal crystal-plastic deformation. Magmatic fabrics observable at the outcrop scale are defined by shape preferred orientations of euhedral to subhedral plagioclase, hornblende, and biotite grains. Although magmatic textures and fabrics are observed in all compositions, intense magmatic fabrics are prominent in granodiorite and fine-grained tonalite. Solid-state textures are defined by recrystallization of interstitial quartz and microfracturing of feldspar. Although the sheeted

The melting curve of Ni to 125 GPa: implications for Earth's Fe rich core alloy

NASA Astrophysics Data System (ADS)

Lord, O. T.; Wood, I. G.; Dobson, D. P.; Vocadlo, L.; Thomson, A. R.; Wann, E.; Wang, W.; Edgington, A.; Morard, G.; Mezouar, N.; Walter, M. J.

2014-12-01

The melting curve of Ni has been determined to 125 GPa using laser-heated diamond anvil cell (LH-DAC) experiments and two melting criteria: the appearance of liquid diffuse scattering (LDS) during in situ X-ray diffraction (XRD) and simultaneous plateaux in temperature vs. laser power functions [1]. Our melting curve (Fig. 1) is in good agreement with most theoretical studies [e.g. 2] and the available shock wave data (Fig. 2). It is, however, dramatically steeper than the previous off-line LH-DAC studies in which the determination of melting was based on the visual observation of motion aided by the laser speckle method [e.g. 3]. We estimate the melting point of Ni at the inner-core boundary (ICB; 330 GPa) to be 5800±700 K (2σ), ~2500 K higher than the estimate based on the laser speckle method [3] and within error of Fe (6230±500 K) as determined in a similar in situ LH-DAC study [4]. We find that laser speckle based melting curves coincide with the onset of rapid sub-solidus recrystallization, suggesting that visual observations of motion may have misinterpreted dynamic recrystallization as melt convection. Our new melting curve suggests that the reduction in ICB temperature due to the alloying of Ni with Fe is likely to be significantly smaller than would be expected had the earlier experimental Ni melting studies been correct. We have applied our methodology to a range of other transition metals (Mo, Ti, V, Cu). In the case of Mo, Ti and V the melting curves are in good agreement with the shock compression and theoretical melting studies but hotter and steeper than those based on the laser speckle method, as with Ni. Cu is an exception in which all studies agree, including those employing the laser speckle method. These results go a long way toward resolving the the long-standing controversy over the phase diagrams of the transition metals as determined from static LH-DAC studies on the one hand, and theoretical and dynamic compression studies on the other

Periodic Viscous Shear Heating Instability in Fine-Grained Shear Zones: Mechanism for Intermediate Depth Earthquakes

NASA Astrophysics Data System (ADS)

Coon, E.; Kelemen, P.; Hirth, G.; Spiegelman, M.

2005-12-01

Kelemen and Hirth (Fall 2004 AGU) presented a model for periodic, viscous shear heating instabilities along pre-existing, fine grained shear zones. This provides an attractive alternative to dehydration embrittlement for explaining intermediate-depth earthquakes, especially those in a narrow thermal window within the mantle section of subducting oceanic plates (Hacker et al JGR03). Ductile shear zones with widths of cm to m are common in shallow mantle massifs and peridotite along oceanic fracture zones. Pseudotachylites in a mantle shear zone show that shear heating temperatures exceeded the mantle solidus (Obata & Karato Tectonophys95). Olivine grain growth in shear zones is pinned by closely spaced pyroxenes; thus, once formed, these features do not `heal' on geological time scales in the absence of melt or fluid (Warren & Hirth EPSL05). Grain-size sensitive creep will be localized within these shear zones, in preference to host rocks with olivine grain size from 1 to 10 mm. Inspired by the work of Whitehead & Gans (GJRAS74), we proposed that such pre-existing shear zones might undergo repeated shear heating instabilities. This is not a new concept; what is new is that viscous deformation is limited to a narrow shear zone, because grain boundary sliding, sensitive to both stress and grain size, may accommodate creep even at high stress and high temperature. These new ideas yield a new result: simple models for a periodic shear heating instability. Last year, we presented a 1D numerical model using olivine flow laws, assuming that viscous deformation remains localized in shear zones, surrounded by host rocks undergoing elastic deformation. Stress evolves due to elastic strain and drives viscous deformation in a shear zone of specified width. Shear heating and thermal diffusion control T. A maximum of 1400 C (substantial melting of peridotite ) was imposed. Grain size evolves due to recrystallization and diffusion. For strain rates of E-13 to E-14 per sec and

Ankaramite: A New Type of High-Magnesium and High-Calcium Primitive Melt in the Magnitogorsk Island-Arc Zone (Southern Urals)

NASA Astrophysics Data System (ADS)

Pushkarev, E. V.; Ryazancev, A. V.; Gottman, I. A.; Degtyarev, K. E.; Kamenetsky, V. S.

2018-04-01

This work describes the geological position, mineral and chemical composition of high-Mg effusive ankaramites occurring as dykes and lava flows. They were found in the mélange zone of the western margin of the Magnitogorsk island arc zone in the Southern Urals. Data on the liquidus association of phenocrysts and on the composition of the matrix of effusives are given. According to the data obtained, the conclusion was drawn that the ankaramites studied can be attributed to the primary island arc melts, which were not subject to essential differentiation. This type of effusives has not been distinguished previously among island arc volcanogenic formations of the Urals. It is shown that ankaramites can be considered to be primary melts parental for dunite-clinopyroxenites-gabbro complexes of Ural-Alaskan type. The occurrence of ankaramites in the Paleozoic island arc formations of the Urals indicates the wehrlite composition of the mantle as the reason for the extremely wide development of wehrlites and clinopyroxenites in different mafic-ultramafic complexes of the Urals.

Electrical conductivity during incipient melting in the oceanic low-velocity zone.

PubMed

Sifré, David; Gardés, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier-Majumder, Saswata; Gaillard, Fabrice

2014-05-01

The low-viscosity layer in the upper mantle, the asthenosphere, is a requirement for plate tectonics. The seismic low velocities and the high electrical conductivities of the asthenosphere are attributed either to subsolidus, water-related defects in olivine minerals or to a few volume per cent of partial melt, but these two interpretations have two shortcomings. First, the amount of water stored in olivine is not expected to be higher than 50 parts per million owing to partitioning with other mantle phases (including pargasite amphibole at moderate temperatures) and partial melting at high temperatures. Second, elevated melt volume fractions are impeded by the temperatures prevailing in the asthenosphere, which are too low, and by the melt mobility, which is high and can lead to gravitational segregation. Here we determine the electrical conductivity of carbon-dioxide-rich and water-rich melts, typically produced at the onset of mantle melting. Electrical conductivity increases modestly with moderate amounts of water and carbon dioxide, but it increases drastically once the carbon dioxide content exceeds six weight per cent in the melt. Incipient melts, long-expected to prevail in the asthenosphere, can therefore produce high electrical conductivities there. Taking into account variable degrees of depletion of the mantle in water and carbon dioxide, and their effect on the petrology of incipient melting, we calculated conductivity profiles across the asthenosphere for various tectonic plate ages. Several electrical discontinuities are predicted and match geophysical observations in a consistent petrological and geochemical framework. In moderately aged plates (more than five million years old), incipient melts probably trigger both the seismic low velocities and the high electrical conductivities in the upper part of the asthenosphere, whereas in young plates, where seamount volcanism occurs, a higher degree of melting is expected.

Ultrasonic attenuation measurements determine onset, degree, and completion of recrystallization

NASA Technical Reports Server (NTRS)

Generazio, E. R.

1988-01-01

Ultrasonic attenuation was measured for cold worked Nickel 200 samples annealed at increasing temperatures. Localized dislocation density variations, crystalline order and volume percent of recrystallized phase were determined over the anneal temperature range using transmission electron microscopy, X-ray diffraction, and metallurgy. The exponent of the frequency dependence of the attenuation was found to be a key variable relating ultrasonic attenuation to the thermal kinetics of the recrystallization process. Identification of this key variable allows for the ultrasonic determination of onset, degree, and completion of recrystallization.

Partially melted zone in aluminum welds

NASA Astrophysics Data System (ADS)

Huang, Chen-Che

The partially melted zone (PMZ) is a region immediately outside the weld metal where grain boundary (GB) liquation can occur and cause intergranular cracking. Aluminum alloys are known to be susceptible to liquation and liquation cracking. The PMZ of alloy 2219 (essentially Al-6.3Cu) was studied. Liquation is initiated eutectically. Solidification of the GB liquid was directional---upward and toward the weld as a result of the temperature gradients across the PMZ. The liquated material solidifies with severe segregation into a low-strength, low-ductility structure consisting of a solute-depleted ductile phase and a solute-rich brittle eutectic. In tensile testing the maximum load and displacement before failure were both far below those of the base metal. The GB eutectic fractured while the adjacent Cu-depleted a deformed readily under tension. The solidification mode of the grain boundary liquid was mostly planar. However, cellular solidification was also observed near the bottom of partial-penetration welds, where temperature gradients were lowest. The liquation mechanisms in wrought multicomponent aluminum alloys during welding were also studied. Three mechanisms were identified. They cover most, if not all, wrought aluminum alloys. Liquation cracking in the PMZ was investigated in full-penetration aluminum welds. Liquation cracking occurs because the solidifying PMZ is pulled by a solidifying and thus contracting weld metal that is stronger than the PMZ. Liquation cracking can occur if there is significant liquation in the PMZ, if there is no solidification cracking in the adjacent weld metal, and if the PMZ becomes lower in solid fraction (and hence strength) during its terminal solidification than the solidifying weld metal. Liquation cracking in the PMZ was also investigated in partial-penetration aluminum welds. The papillary (nipple) type penetration common in welding with spray transfer of the filler wire actually oscillates along the weld and promotes

Nanoparticle-induced unusual melting and solidification behaviours of metals

PubMed Central

Ma, Chao; Chen, Lianyi; Cao, Chezheng; Li, Xiaochun

2017-01-01

Effective control of melting and solidification behaviours of materials is significant for numerous applications. It has been a long-standing challenge to increase the melted zone (MZ) depth while shrinking the heat-affected zone (HAZ) size during local melting and solidification of materials. In this paper, nanoparticle-induced unusual melting and solidification behaviours of metals are reported that effectively solve this long-time dilemma. By introduction of Al2O3 nanoparticles, the MZ depth of Ni is increased by 68%, while the corresponding HAZ size is decreased by 67% in laser melting at a pulse energy of 0.18 mJ. The addition of SiC nanoparticles shows similar results. The discovery of the unusual melting and solidification of materials that contain nanoparticles will not only have impacts on existing melting and solidification manufacturing processes, such as laser welding and additive manufacturing, but also on other applications such as pharmaceutical processing and energy storage. PMID:28098147

Earth's interior. Dehydration melting at the top of the lower mantle.

PubMed

Schmandt, Brandon; Jacobsen, Steven D; Becker, Thorsten W; Liu, Zhenxian; Dueker, Kenneth G

2014-06-13

The high water storage capacity of minerals in Earth's mantle transition zone (410- to 660-kilometer depth) implies the possibility of a deep H2O reservoir, which could cause dehydration melting of vertically flowing mantle. We examined the effects of downwelling from the transition zone into the lower mantle with high-pressure laboratory experiments, numerical modeling, and seismic P-to-S conversions recorded by a dense seismic array in North America. In experiments, the transition of hydrous ringwoodite to perovskite and (Mg,Fe)O produces intergranular melt. Detections of abrupt decreases in seismic velocity where downwelling mantle is inferred are consistent with partial melt below 660 kilometers. These results suggest hydration of a large region of the transition zone and that dehydration melting may act to trap H2O in the transition zone. Copyright © 2014, American Association for the Advancement of Science.

Inhibiting ice recrystallization and optimization of cell viability after cryopreservation.

PubMed

Chaytor, Jennifer L; Tokarew, Jacqueline M; Wu, Luke K; Leclère, Mathieu; Tam, Roger Y; Capicciotti, Chantelle J; Guolla, Louise; von Moos, Elisabeth; Findlay, C Scott; Allan, David S; Ben, Robert N

2012-01-01

The ice recrystallization inhibition activity of various mono- and disaccharides has been correlated with their ability to cryopreserve human cell lines at various concentrations. Cell viabilities after cryopreservation were compared with control experiments where cells were cryopreserved with dimethylsulfoxide (DMSO). The most potent inhibitors of ice recrystallization were 220 mM solutions of disaccharides; however, the best cell viability was obtained when a 200 mM d-galactose solution was utilized. This solution was minimally cytotoxic at physiological temperature and effectively preserved cells during freeze-thaw. In fact, this carbohydrate was just as effective as a 5% DMSO solution. Further studies indicated that the cryoprotective benefit of d-galactose was a result of its internalization and its ability to mitigate osmotic stress, prevent intracellular ice formation and/or inhibit ice recrystallization. This study supports the hypothesis that the ability of a cryoprotectant to inhibit ice recrystallization is an important property to enhance cell viability post-freeze-thaw. This cryoprotective benefit is observed in three different human cell lines. Furthermore, we demonstrated that the ability of a potential cryoprotectant to inhibit ice recrystallation may be used as a predictor of its ability to preserve cells at subzero temperatures.

Correlation buildup during recrystallization in three-dimensional dusty plasma clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schella, André; Mulsow, Matthias; Melzer, André

2014-05-15

The recrystallization process of finite three-dimensional dust clouds after laser heating is studied experimentally. The time-dependent Coulomb coupling parameter is presented, showing that the recrystallization starts with an exponential cooling phase where cooling is slower than damping by the neutral gas friction. At later times, the coupling parameter oscillates into equilibrium. It is found that a large fraction of cluster states after recrystallization experiments is in metastable states. The temporal evolution of the correlation buildup shows that correlation occurs on even slower time scale than cooling.

Channelized Melting Drives Thinning Under a Rapidly Melting Antarctic Ice Shelf

NASA Astrophysics Data System (ADS)

Gourmelen, Noel; Goldberg, Dan N.; Snow, Kate; Henley, Sian F.; Bingham, Robert G.; Kimura, Satoshi; Hogg, Anna E.; Shepherd, Andrew; Mouginot, Jeremie; Lenaerts, Jan T. M.; Ligtenberg, Stefan R. M.; van de Berg, Willem Jan

2017-10-01

Ice shelves play a vital role in regulating loss of grounded ice and in supplying freshwater to coastal seas. However, melt variability within ice shelves is poorly constrained and may be instrumental in driving ice shelf imbalance and collapse. High-resolution altimetry measurements from 2010 to 2016 show that Dotson Ice Shelf (DIS), West Antarctica, thins in response to basal melting focused along a single 5 km-wide and 60 km-long channel extending from the ice shelf's grounding zone to its calving front. If focused thinning continues at present rates, the channel will melt through, and the ice shelf collapse, within 40-50 years, almost two centuries before collapse is projected from the average thinning rate. Our findings provide evidence of basal melt-driven sub-ice shelf channel formation and its potential for accelerating the weakening of ice shelves.

Magma transport and olivine crystallization depths in Kīlauea’s East Rift Zone inferred from experimentally rehomogenized melt inclusions

USGS Publications Warehouse

Tuohy, Robin M; Wallace, Paul J.; Loewen, Matthew W; Swanson, Don; Kent, Adam J R

2016-01-01

Concentrations of H2O and CO2 in olivine-hosted melt inclusions can be used to estimate crystallization depths for the olivine host. However, the original dissolved CO2concentration of melt inclusions at the time of trapping can be difficult to measure directly because in many cases substantial CO2 is transferred to shrinkage bubbles that form during post-entrapment cooling and crystallization. To investigate this problem, we heated olivine from the 1959 Kīlauea Iki and 1960 Kapoho (Hawai‘i) eruptions in a 1-atm furnace to temperatures above the melt inclusion trapping temperature to redissolve the CO2 in shrinkage bubbles. The measured CO2 concentrations of the experimentally rehomogenized inclusions (⩽590 ppm for Kīlauea Iki [n=10]; ⩽880 ppm for Kapoho, with one inclusion at 1863 ppm [n=38]) overlap with values for naturally quenched inclusions from the same samples, but experimentally rehomogenized inclusions have higher within-sample median CO2 values than naturally quenched inclusions, indicating at least partial dissolution of CO2 from the vapor bubble during heating. Comparison of our data with predictions from modeling of vapor bubble formation and published Raman data on the density of CO2 in the vapor bubbles suggests that 55-85% of the dissolved CO2 in the melt inclusions at the time of trapping was lost to post-entrapment shrinkage bubbles. Our results combined with the Raman data demonstrate that olivine from the early part of the Kīlauea Iki eruption crystallized at <6 km depth, with the majority of olivine in the 1-3 km depth range. These depths are consistent with the interpretation that the Kīlauea Iki magma was supplied from Kīlauea’s summit magma reservoir (∼2-5 km depth). In contrast, olivine from Kapoho, which was the rift zone extension of the Kīlauea Iki eruption, crystallized over a much wider range of depths (∼1-16 km). The wider depth range requires magma transport during the Kapoho eruption from deep beneath the

Negative Temperature Dependence of Recrystallized Grain Size: Formulation and Experimental Confirmation on Copper

PubMed Central

Elmasry, Mohamed; Liu, Fan; Jiang, Yao; Mao, Ze Ning; Liu, Ying; Wang, Jing Tao

2017-01-01

The catalyzing effect on nucleation of recrystallization from existing grains resulting from previous lower temperature deformation is analyzed, analogous to the size effect of foreign nucleus in heterogeneous nucleation. Analytical formulation of the effective nucleation site for recrystallization leads to a negative temperature dependence of recrystallized grain size of metals. Non-isochronal annealing—where annealing time is set just enough for the completion of recrystallization at different temperatures—is conducted on pure copper after severe plastic deformation. More homogeneous and smaller grains are obtained at higher annealing temperature. The good fit between analytical and experimental results unveils the intrinsic feature of this negative temperature dependence of recrystallized grain size. PMID:28772676

Effects of water, depth and temperature on partial melting of mantle-wedge fluxed by hydrous sediment-melt in subduction zones

NASA Astrophysics Data System (ADS)

Mallik, Ananya; Dasgupta, Rajdeep; Tsuno, Kyusei; Nelson, Jared

2016-12-01

This study investigates the partial melting of variable bulk H2O-bearing parcels of mantle-wedge hybridized by partial melt derived from subducted metapelites, at pressure-temperature (P-T) conditions applicable to the hotter core of the mantle beneath volcanic arcs. Experiments are performed on mixtures of 25% sediment-melt and 75% fertile peridotite, from 1200 to 1300 °C, at 2 and 3 GPa, with bulk H2O concentrations of 4 and 6 wt.%. Combining the results from these experiments with previous experiments containing 2 wt.% bulk H2O (Mallik et al., 2015), it is observed that all melt compositions, except those produced in the lowest bulk H2O experiments at 3 GPa, are saturated with olivine and orthopyroxene. Also, higher bulk H2O concentration increases melt fraction at the same P-T condition, and causes exhaustion of garnet, phlogopite and clinopyroxene at lower temperatures, for a given pressure. The activity coefficient of silica (ϒSiO2) for olivine-orthopyroxene saturated melt compositions (where the activity of silica, aSiO2 , is buffered by the reaction olivine + SiO2 = orthopyroxene) from this study and from mantle melting studies in the literature are calculated. In melt compositions generated at 2 GPa or shallower, with increasing H2O concentration, ϒSiO2 increases from <1 to ∼1, indicating a transition from non-ideal mixing as OH- in the melt (ϒSiO2 <1) to ideal mixing as molecular H2O (ϒSiO2 ∼1). At pressures >2 GPa, ϒSiO2 >1 at higher H2O concentrations in the melt, indicate requirement of excess energy to incorporate molecular H2O in the silicate melt structure, along with a preference for bridging species and polyhedral edge decorations. With vapor saturation in the presence of melt, ϒSiO2 decreases indicating approach towards ideal mixing of H2O in silicate melt. For similar H2O concentrations in the melt, ϒSiO2 for olivine-orthopyroxene saturated melts at 3 GPa is higher than melts at 2 GPa or shallower. This results in melts generated at

Mechanism of secondary recrystallization of Goss grains in grain-oriented electrical steel

NASA Astrophysics Data System (ADS)

Hayakawa, Yasuyuki

2017-12-01

Since its invention by Goss in 1934, grain-oriented (GO) electrical steel has been widely used as a core material in transformers. GO exhibits a grain size of over several millimeters attained by secondary recrystallization during high-temperature final batch annealing. In addition to the unusually large grain size, the crystal direction in the rolling direction is aligned with <001>, which is the easy magnetization axis of α-iron. Secondary recrystallization is the phenomenon in which a certain very small number of {110}<001> (Goss) grains grow selectively (about one in 106 primary grains) at the expense of many other primary recrystallized grains. The question of why the Goss orientation is exclusively selected during secondary recrystallization has long been a main research subject in this field. The general criterion for secondary recrystallization is a small and uniform primary grain size, which is achieved through the inhibition of normal grain growth by fine precipitates called inhibitors. This paper describes several conceivable mechanisms of secondary recrystallization of Goss grains mainly based on the selective growth model.

Mechanism of secondary recrystallization of Goss grains in grain-oriented electrical steel

PubMed Central

Hayakawa, Yasuyuki

2017-01-01

Abstract Since its invention by Goss in 1934, grain-oriented (GO) electrical steel has been widely used as a core material in transformers. GO exhibits a grain size of over several millimeters attained by secondary recrystallization during high-temperature final batch annealing. In addition to the unusually large grain size, the crystal direction in the rolling direction is aligned with <001>, which is the easy magnetization axis of α-iron. Secondary recrystallization is the phenomenon in which a certain very small number of {110}<001> (Goss) grains grow selectively (about one in 106 primary grains) at the expense of many other primary recrystallized grains. The question of why the Goss orientation is exclusively selected during secondary recrystallization has long been a main research subject in this field. The general criterion for secondary recrystallization is a small and uniform primary grain size, which is achieved through the inhibition of normal grain growth by fine precipitates called inhibitors. This paper describes several conceivable mechanisms of secondary recrystallization of Goss grains mainly based on the selective growth model. PMID:28804524

Mechanism of secondary recrystallization of Goss grains in grain-oriented electrical steel.

PubMed

Hayakawa, Yasuyuki

2017-01-01

Since its invention by Goss in 1934, grain-oriented (GO) electrical steel has been widely used as a core material in transformers. GO exhibits a grain size of over several millimeters attained by secondary recrystallization during high-temperature final batch annealing. In addition to the unusually large grain size, the crystal direction in the rolling direction is aligned with <001>, which is the easy magnetization axis of α-iron. Secondary recrystallization is the phenomenon in which a certain very small number of {110}<001> (Goss) grains grow selectively (about one in 10 6 primary grains) at the expense of many other primary recrystallized grains. The question of why the Goss orientation is exclusively selected during secondary recrystallization has long been a main research subject in this field. The general criterion for secondary recrystallization is a small and uniform primary grain size, which is achieved through the inhibition of normal grain growth by fine precipitates called inhibitors. This paper describes several conceivable mechanisms of secondary recrystallization of Goss grains mainly based on the selective growth model.

Monte Carlo modeling of recrystallization processes in α-uranium

DOE PAGES

Steiner, M. A.; McCabe, R. J.; Garlea, E.; ...

2017-08-01

In this study, starting with electron backscattered diffraction (EBSD) data obtained from a warm clock-rolled α-uranium deformation microstructure, a Potts Monte Carlo model was used to simulate static site-saturated recrystallization while testing a number of different conditions for the assignment of recrystallized nuclei within the microstructure. The simulations support observations that recrystallized nuclei within α-uranium form preferentially on non-twin high-angle grain boundary sites at 450 °C, and demonstrate that the most likely nucleation sites on these boundaries can be identified by the surrounding degree of Kernel Average Misorientation (KAM), which may be considered as a proxy for the local geometricallymore » necessary dislocation (GND) density.« less

Anisotropic Morphological Changes in Goethite during Fe(2+)-Catalyzed Recrystallization.

PubMed

Joshi, Prachi; Gorski, Christopher A

2016-07-19

When goethite is exposed to aqueous Fe(2+), rapid and extensive Fe atom exchange can occur between solid-phase Fe(3+) and aqueous Fe(2+) in a process referred to as Fe(2+)-catalyzed recrystallization. This process can lead to the structural incorporation or release of trace elements, which has important implications for contaminant remediation and nutrient biogeochemical cycling. Prior work found that the process did not cause major changes to the goethite structure or morphology. Here, we further investigated if and how goethite morphology and aggregation behavior changed temporally during Fe(2+)-catalyzed recrystallization. On the basis of existing literature, we hypothesized that Fe(2+)-catalyzed recrystallization of goethite would not result in changes to individual particle morphology or interparticle interactions. To test this, we reacted nanoparticulate goethite with aqueous Fe(2+) at pH 7.5 over 30 days and used transmission electron microscopy (TEM), cryogenic TEM, and (55)Fe as an isotope tracer to observe changes in particle dimensions, aggregation, and isotopic composition over time. Over the course of 30 days, the goethite particles substantially recrystallized, and the particle dimensions changed anisotropically, resulting in a preferential increase in the mean particle width. The temporal changes in goethite morphology could not be completely explained by a single mineral-transformation mechanism but rather indicated that multiple transformation mechanisms occurred concurrently. Collectively, these results demonstrate that the morphology of goethite nanoparticles does change during recrystallization, which is an important step toward identifying the driving force(s) of recrystallization.

Compositional zoning of the bishop tuff

USGS Publications Warehouse

Hildreth, W.; Wilson, C.J.N.

2007-01-01

Compositional data for >400 pumice clasts, organized according to eruptive sequence, crystal content, and texture, provide new perspectives on eruption and pre-eruptive evolution of the >4600 km3 of zoned rhyolitic magma ejected as the BishopTuff during formation of Long Valley caldera. Proportions and compositions of different pumice types are given for each ignimbrite package and for the intercalated plinian pumice-fall layers that erupted synchronously. Although withdrawal of the zoned magma was less systematic than previously realized, the overall sequence displays trends toward greater proportions of less evolved pumice, more crystals (0-5 24 wt %), and higher FeTi-oxide temperatures (714-818??C). No significant hiatus took place during the 6 day eruption of the BishopTuff, nearly all of which issued from an integrated, zoned, unitary reservoir. Shortly before eruption, however, the zoned melt-dominant portion of the chamber was invaded by batches of disparate lower-silica rhyolite magma, poorer in crystals than most of the resident magma but slightly hotter and richer in Ba, Sr, andTi. Interaction with resident magma at the deepest levels tapped promoted growth ofTi-rich rims on quartz, Ba-rich rims on sanidine, and entrapment of near-rim melt inclusions relatively enriched in Ba and CO2.Varied amounts of mingling, even in higher parts of the chamber, led to the dark gray and swirly crystal-poor pumices sparsely present in all ashflow packages. As shown by FeTi-oxide geothermometry, the zoned rhyolitic chamber was hottest where crystal-richest, rendering any model of solidification fronts at the walls or roof unlikely.The main compositional gradient (75-195 ppm Rb; 0.8-2.2 ppm Ta; 71-154 ppm Zr; 0.40-1.73% FeO*) existed in the melt, prior to crystallization of the phenocryst suite observed, which included zircon as much as 100 kyr older than the eruption.The compositions of crystals, though themselves largely unzoned, generally reflect magma temperature and

Microstructure formation in partially melted zone during gas tungsten arc welding of AZ91 Mg cast alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu Tianping; Chen, Zhan W.; Gao Wei

2008-11-15

During gas tungsten arc (GTA) welding of AZ91 Mg cast alloy, constitutional liquid forms locally in the original interdendritic regions in the partially melted zone (PMZ). The PMZ re-solidification behaviour has not been well understood. In this study, the gradual change of the re-solidification microstructure within PMZ from base metal side to weld metal side was characterised. High cooling rate experiments using Gleeble thermal simulator were also conducted to understand the morphological change of the {alpha}-Mg/{beta}-Mg{sub 17}Al{sub 12} phase interface formed during re-solidification after partial melting. It was found that the original partially divorced eutectic structure has become a moremore » regular eutectic phase in most of the PMZ, although close to the fusion boundary the re-solidified eutectic is again a divorced one. Proceeding the eutectic re-solidification, if the degree of partial melting is sufficiently high, {alpha}-Mg re-solidified with a cellular growth, resulting in a serrated interface between {alpha}-Mg and {alpha}-Mg/{beta}-Mg{sub 17}Al{sub 12} in the weld sample and between {alpha}-Mg and {beta}-Mg{sub 17}Al{sub 12} (fully divorced eutectic) in Gleeble samples. The morphological changes affected by the peak temperature and cooling rate are also explained.« less

Microstructure and critical strain of dynamic recrystallization of 6082 aluminum alloy in thermal deformation

NASA Astrophysics Data System (ADS)

Ren, W. W.; Xu, C. G.; Chen, X. L.; Qin, S. X.

2018-05-01

Using high temperature compression experiments, true stress true strain curve of 6082 aluminium alloy were obtained at the temperature 460°C-560°C and the strain rate 0.01 s-1-10 s-1. The effects of deformation temperature and strain rate on the microstructure are investigated; (‑∂lnθ/∂ε) ‑ ε curves are plotted based on σ-ε curve. Critical strains of dynamic recrystallization of 6082 aluminium alloy model were obtained. The results showed lower strain rates were beneficial to increase the volume fraction of recrystallization, the average recrystallized grain size was coarse; High strain rates are beneficial to refine average grain size, the volume fraction of dynamic recrystallized grain is less than that by using low strain rates. High temperature reduced the dislocation density and provided less driving force for recrystallization so that coarse grains remained. Dynamic recrystallization critical strain model and thermal experiment results can effectively predict recrystallization critical point of 6082 aluminium alloy during thermal deformation.

Effects of two-step homogenization on precipitation behavior of Al{sub 3}Zr dispersoids and recrystallization resistance in 7150 aluminum alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Zhanying; Key Laboratory for Anisotropy and Texture of Materials, Northeastern University, Shenyang 110819, China,; Zhao, Gang

2015-04-15

The effect of two-step homogenization treatments on the precipitation behavior of Al{sub 3}Zr dispersoids was investigated by transmission electron microscopy (TEM) in 7150 alloys. Two-step treatments with the first step in the temperature range of 300–400 °C followed by the second step at 470 °C were applied during homogenization. Compared with the conventional one-step homogenization, both a finer particle size and a higher number density of Al{sub 3}Zr dispersoids were obtained with two-step homogenization treatments. The most effective dispersoid distribution was attained using the first step held at 300 °C. In addition, the two-step homogenization minimized the precipitate free zonesmore » and greatly increased the number density of dispersoids near dendrite grain boundaries. The effect of two-step homogenization on recrystallization resistance of 7150 alloys with different Zr contents was quantitatively analyzed using the electron backscattered diffraction (EBSD) technique. It was found that the improved dispersoid distribution through the two-step treatment can effectively inhibit the recrystallization process during the post-deformation annealing for 7150 alloys containing 0.04–0.09 wt.% Zr, resulting in a remarkable reduction of the volume fraction and grain size of recrystallization grains. - Highlights: • Effect of two-step homogenization on Al{sub 3}Zr dispersoids was investigated by TEM. • Finer and higher number of dispersoids obtained with two-step homogenization • Minimized the precipitate free zones and improved the dispersoid distribution • Recrystallization resistance with varying Zr content was quantified by EBSD. • Effectively inhibit the recrystallization through two-step treatments in 7150 alloy.« less

High temperature microstructural stability and recrystallization mechanisms in 14YWT alloys

DOE PAGES

Aydogan, E.; El-Atwani, O.; Takajo, S.; ...

2018-02-09

In-situ neutron diffraction experiments were performed on room temperature compressed 14YWT nanostructured ferritic alloys at 1100°C and 1150°C to understand their thermally activated static recrystallization mechanisms. The existence of high density of Y-Ti-O rich nano-oxides (<5 nm) shift the recrystallization temperature up due to Zener pinning of the grain boundaries, making these materials attractive for high temperature applications. This study serves to quantify the texture evolution in-situ and understand the effect of particles on the recrystallization mechanisms in 14YWT alloys. We have shown, both experimentally and theoretically, that there is considerable recovery in the 20% compressed sample after 6.5 hmore » annealing at 1100°C while recrystallization occurs within an hour of annealing at 1100°C and 1150°C in the 60% compressed samples. Moreover, the 60% compressed samples show {112}<110> and {112}<111> texture components during annealing, in contrast to the conventional recrystallization textures in body centered cubic alloys. Furthermore, nano-oxide size, shape, density and distribution are considerably different in unrecrystallized and abnormally grown grains. Transmission electron microscopy analysis shows that oxide particles having a size between 5 and 30 nm play a critical role for recrystallization mechanisms in 14YWT nanostructured ferritic alloys.« less

High temperature microstructural stability and recrystallization mechanisms in 14YWT alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aydogan, E.; El-Atwani, O.; Takajo, S.

In-situ neutron diffraction experiments were performed on room temperature compressed 14YWT nanostructured ferritic alloys at 1100°C and 1150°C to understand their thermally activated static recrystallization mechanisms. The existence of high density of Y-Ti-O rich nano-oxides (<5 nm) shift the recrystallization temperature up due to Zener pinning of the grain boundaries, making these materials attractive for high temperature applications. This study serves to quantify the texture evolution in-situ and understand the effect of particles on the recrystallization mechanisms in 14YWT alloys. We have shown, both experimentally and theoretically, that there is considerable recovery in the 20% compressed sample after 6.5 hmore » annealing at 1100°C while recrystallization occurs within an hour of annealing at 1100°C and 1150°C in the 60% compressed samples. Moreover, the 60% compressed samples show {112}<110> and {112}<111> texture components during annealing, in contrast to the conventional recrystallization textures in body centered cubic alloys. Furthermore, nano-oxide size, shape, density and distribution are considerably different in unrecrystallized and abnormally grown grains. Transmission electron microscopy analysis shows that oxide particles having a size between 5 and 30 nm play a critical role for recrystallization mechanisms in 14YWT nanostructured ferritic alloys.« less

Dynamic moisture sorption characteristics of enzyme-resistant recrystallized cassava starch.

PubMed

Mutungi, Christopher; Schuldt, Stefan; Onyango, Calvin; Schneider, Yvonne; Jaros, Doris; Rohm, Harald

2011-03-14

The interaction of moisture with enzyme-resistant recrystallized starch, prepared by heat-moisture treatment of debranched acid-modified or debranched non-acid-modified cassava starch, was investigated in comparison with the native granules. Crystallinities of the powdered products were estimated by X-ray diffraction. Moisture sorption was determined using dynamic vapor sorption analyzer and data fitted to various models. Percent crystallinities of native starch (NS), non-acid-modified recrystallized starch (NAMRS), and acid-modified recrystallized starch (AMRS) were 39.7, 51.9, and 56.1%, respectively. In a(w) below 0.8, sorption decreased in the order NS > NAMRS > AMRS in line with increasing sample crystallinities but did not follow this crystallinity dependence at higher a(w) because of condensation and polymer dissolution effects. Adsorbed moisture became internally absorbed in NS but not in NAMRS and AMRS, which might explain the high resistance of the recrystallized starches to digestion because enzyme and starch cannot approach each other over fairly sufficient surface at the molecular level.

The thermal and deformational history of apollo 15418, A partly shock-melted lunar breccia

USGS Publications Warehouse

Nord, G.L.; Christie, J.M.; Lally, J.S.; Heuer, A.H.

1977-01-01

A thermal and mechanical history of lunar gabbroic anorthosite 15418 (1140g) has been deduced from petrographic examination of both exterior and interior thin sections and electron microprobe analysis and transmission electron microscopy of interior thin sections. We suggest that the rock underwent two major shock events - an early brecciation and annealing that produced a recrystallized breccia, followed by a second shock event that melted the surface of the rock, vitrified the interior plagioclase and heavily deformed the mafic phases. This latter shock even was also followed by annealing which crystallized the shock-produced glass and promoted recovery and recrystallization of the deformed crystalline phases. The complex mechanical and thermal history of 15418 compared with other ANT suite rocks at Spur Crater suggests that it had a different provenance. ?? 1977 D. Reidel Publishing Company, Dordrecht-Holland.

Facially Amphipathic Glycopolymers Inhibit Ice Recrystallization.

PubMed

Graham, Ben; Fayter, Alice E R; Houston, Judith E; Evans, Rachel C; Gibson, Matthew I

2018-05-02

Antifreeze glycoproteins (AFGPs) from polar fish are the most potent ice recrystallization (growth) inhibitors known, and synthetic mimics are required for low-temperature applications such as cell cryopreservation. Here we introduce facially amphipathic glycopolymers that mimic the three-dimensional structure of AFGPs. Glycopolymers featuring segregated hydrophilic and hydrophobic faces were prepared by ring-opening metathesis polymerization, and their rigid conformation was confirmed by small-angle neutron scattering. Ice recrystallization inhibition (IRI) activity was reduced when a hydrophilic oxo-ether was installed on the glycan-opposing face, but significant activity was restored by incorporating a hydrophobic dimethylfulvene residue. This biomimetic strategy demonstrates that segregated domains of distinct hydrophilicity/hydrophobicity are a crucial motif to introduce IRI activity, which increases our understanding of the complex ice crystal inhibition processes.

Low-Temperature Thermochronology for Unraveling Thermal Processes and Dating of Fault Zones

NASA Astrophysics Data System (ADS)

Tagami, T.

2016-12-01

Thermal signatures as well as timing of fault motions can be constrained by thermochronological analyses of fault-zone rocks (e.g., Tagami, 2012). Fault-zone materials suitable for such analyses are produced by tectocic and geochemical processes, such as (1) mechanical fragmentation of host rocks, grain-size reduction of fragments and recrystallization of grains to form mica and clay minerals, (2) secondary heating/melting of host rocks by frictional fault motions, and (3) mineral vein formation as a consequence of fluid advection associated with fault motions. The geothermal structure of fault zones are primarily controlled by the following three factors: (a) regional geothermal structure around the fault zone that reflect background thermo-tectonic history of studied province, (b) frictional heating of wall rocks by fault motions and resultant heat transfer into surrounding rocks, and (c) thermal influences by hot fluid advection in and around the fault zone. Thermochronological methods widely applied in fault zones are K-Ar (40Ar/39Ar), fission-track (FT), and U-Th methods. In addition, OSL, TL, ESR and (U-Th)/He methods are applied in some fault zones, in order to extract temporal imformation related to low temperature and/or very recent fault activities. Here I briefly review the thermal sensitivity of individual thermochronological systems, which basically controls the response of each method against faulting processes. Then, the thermal sensitivity of FTs is highlighted, with a particular focus on the thermal processes characteristic to fault zones, i.e., flash and hydrothermal heating. On these basis, representative examples as well as key issues, including sampling strategy, are presented to make thermochronologic analysis of fault-zone materials, such as fault gouges, pseudotachylytes and mylonites, along with geological, geomorphological and seismological implications. Finally, the thermochronologic analyses of the Nojima fault are overviewed, as an

The electrical conductivity during incipient melting in the oceanic low velocity zone

NASA Astrophysics Data System (ADS)

Gaillard, Fabrice; Sifre, David; Gardes, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier Majumder, Saswata

2014-05-01

A low viscosity layer at the Lithosphere-Asthenosphere Boundary (LAB) is certainly a requirement for plate tectonics but the nature of the rocks presents in this boundary remains controversial. The seismic low velocities and the high electrical conductivities of the LAB are attributed either to sub-solidus water-related defects in olivine minerals or to a few volume percents of partial melt but these two interpretations have shortcomings: (1) The amount of H2O stored in olivine is not expected to be high enough due to several mineralogical processes that have been sometimes ignored; (2) elevated melt volume fractions are impeded by the too cold temperatures prevailing in the LAB and by the high melt mobility that can lead to gravitational segregation. All this has in fact been partly settled 30 years ago, when a petrological LAB has been defined as a region of the upper mantle impregnated by incipient melts; that is small amounts of melt caused by small amount of CO2 and H2O. We show here that incipient melting is a melting regime that is allowed in the entire P-T-fO2 region of the LVZ. The top of the oceanic LVZ (LAB) is then best explained by a melt freezing layer due to a decarbonation reaction, whereas the bottom of the LVZ matches the depth at which redox melting defines the lower boundary of stability of incipient melts. Based on new laboratory measurements, we show here that incipient melts must be the cause of the high electrical conductivities in the oceanic LVZ. Considering relevant mantle abundances of H2O and CO2 and their effect on the petrology of incipient melting, we calculated conductivity profiles across the LAB for various ages. Several electrical discontinuities are predicted and match geophysical observations in a consistent petrological and geochemical framework. We conclude that incipient melts prevail in the LAB, what else?

Recrystallization characteristics of oxide dispersion strengthened nickel-base alloys

NASA Technical Reports Server (NTRS)

Hotzler, R. K.; Glasgow, T. K.

1980-01-01

Electron microscopy was employed to study the process of recrystallization in two oxide dispersion strengthened (ODS) mechanically alloyed nickel-base alloys, MA 754 and MA 6000E. MA 754 contained both fine, uniformly dispersed particles and coarser oxides aligned along the working direction. Hot rolled MA 754 had a grain size of 0.5 microns and high dislocation densities. After partial primary recrystallization, the fine grains transformed to large elongated grains via secondary (or abnormal) grain growth. Extruded and rolled MA 6000E contained equiaxed grains of 0.2 micron diameter. Primary recrystallization occurring during working eliminated virtually all dislocations. Conversion from fine to coarse grains was triggered by gamma prime dissolution; this was also a process of secondary or abnormal grain growth. Comparisons were made to conventional and oxide dispersion strengthened nickel-base alloys.

Melt migration modeling in partially molten upper mantle

NASA Astrophysics Data System (ADS)

Ghods, Abdolreza

The objective of this thesis is to investigate the importance of melt migration in shaping major characteristics of geological features associated with the partial melting of the upper mantle, such as sea-floor spreading, continental flood basalts and rifting. The partial melting produces permeable partially molten rocks and a buoyant low viscosity melt. Melt migrates through the partially molten rocks, and transfers mass and heat. Due to its much faster velocity and appreciable buoyancy, melt migration has the potential to modify dynamics of the upwelling partially molten plumes. I develop a 2-D, two-phase flow model and apply it to investigate effects of melt migration on the dynamics and melt generation of upwelling mantle plumes and focusing of melt migration beneath mid-ocean ridges. Melt migration changes distribution of the melt-retention buoyancy force and therefore affects the dynamics of the upwelling plume. This is investigated by modeling a plume with a constant initial melt of 10% where no further melting is considered. Melt migration polarizes melt-retention buoyancy force into high and low melt fraction regions at the top and bottom portions of the plume and therefore results in formation of a more slender and faster upwelling plume. Allowing the plume to melt as it ascends through the upper mantle also produces a slender and faster plume. It is shown that melt produced by decompressional melting of the plume migrates to the upper horizons of the plume, increases the upwelling velocity and thus, the volume of melt generated by the plume. Melt migration produces a plume which lacks the mushroom shape observed for the plume models without melt migration. Melt migration forms a high melt fraction layer beneath the sloping base of the impermeable oceanic lithosphere. Using realistic conditions of melting, freezing and melt extraction, I examine whether the high melt fraction layer is able to focus melt from a wide partial melting zone to a narrow region

Partial melting kinetics of plagioclase-diopside pairs

NASA Astrophysics Data System (ADS)

Tsuchiyama, Akira

1985-09-01

Partial melting experiments on plagioclase (An60) and diopside have been carried out using pairs of large crystals to investigate textures and kinetics of melting. The experiments were done at one atmosphere pressure as a function of temperature (1,190 1,307° C) and time (1.5 192 h). Melting took place mainly at the plagioclase-diopside contact planes. Reaction zones composed of fine mixtures of calcic plagioclase and melt were developed from the surface of the plagioclase crystal inward. There exists a critical temperature, below which only a few % melting can occur over the duration of the experiments. This sluggish melting is caused by slow NaSi-CaAl diffusion in plagioclase, because the plagioclase crystal must change its composition to produce albite-rich cotectic melts. Diffusion in the solid also affects the chemical composition of the melts. During initial melting, potassium is preferentially extracted from plagioclase because K-Na diffusion in plagioclase is faster than that of NaSi-CaAl. This also causes a shift in the cotectic compositions. Above the “critical temperature”, on the other hand, melting is promoted by a metastable reaction in which the plagioclase composition does not change, and which produces melts with compositional gradients along the original An60-diopside tie line. The critical temperature is determined by the intersection of the cotectic and the An60-diopside tie line. Interdiffusion coefficients of plagioclase-diopside components in the melt are estimated from melting rates above the critical temperature by using a simplified steady-state diffusion model (e.g., 10-8 cm2/sec at 1,300° C). Many examples of reaction zones due to partial melting have been described as spongy or fingerprint-like textures in xenoliths. Metastable melting above the critical temperature is considered to take place in natural melting where there is a high degree of melting. However, we cannot exclude the possibility of disequilibrium created by

A texture-component Avrami model for predicting recrystallization textures, kinetics and grain size

NASA Astrophysics Data System (ADS)

Raabe, Dierk

2007-03-01

The study presents an analytical model for predicting crystallographic textures and the final grain size during primary static recrystallization of metals using texture components. The kinetics is formulated as a matrix variant of the Johnson-Mehl-Avrami-Kolmogorov equation. The matrix form is required since the kinetic and crystallographic evolution of the microstructure is described in terms of a limited set of growing (recrystallizing) and swept (deformed) texture components. The number of components required (5-10) defines the order of the matrix since the kinetic coupling occurs between all recrystallizing and all deformed components. Each such couple is characterized by corresponding values for the nucleation energy and grain boundary mobility. The values of these parameters can be obtained by analytical or numerical coarse graining according to a renormalization scheme which replaces many individual grains which grow via recrystallization in a deformed texture component by a single equivalent recrystallization texture component or by fitting to experimental data. Each deformed component is further characterized by an average stored deformation energy. Each element of the kinetic matrix, reflecting one of the possible couplings between a deformed and a recrystallizing texture component, is then derived in each time step by a set of two differential equations. The first equation describes the thermally activated nucleation and growth processes for the expanded (free) volume for a particular couple of a deformed and a recrystallizing texture component and the second equation is used for calculating the constrained (real) volume for that couple which corrects the free volume for those portions of the deformation component which were already swept. The new method is particularly developed for the fast and physically based process simulation of recrystallization textures with respect to processing. The present paper introduces the method and applies it to the

Hydride reorientation and its impact on ambient temperature mechanical properties of high burn-up irradiated and unirradiated recrystallized Zircaloy-2 nuclear fuel cladding with an inner liner

NASA Astrophysics Data System (ADS)

Auzoux, Q.; Bouffioux, P.; Machiels, A.; Yagnik, S.; Bourdiliau, B.; Mallet, C.; Mozzani, N.; Colas, K.

2017-10-01

Precipitation of radial hydrides in zirconium-based alloy cladding concomitant with the cooling of spent nuclear fuel during dry storage can potentially compromise cladding integrity during its subsequent handling and transportation. This paper investigates hydride reorientation and its impact on ductility in unirradiated and irradiated recrystallized Zircaloy-2 cladding with an inner liner (cladding for boiling water reactors) subjected to hydride reorientation treatments. Cooling from 400 °C, hydride reorientation occurs in recrystallized Zircaloy-2 with liner at a lower effective stress in irradiated samples (below 40 MPa) than in unirradiated specimens (between 40 and 80 MPa). Despite significant hydride reorientation, unirradiated recrystallized Zircaloy-2 with liner cladding containing ∼200 wppm hydrogen shows a high diametral strain at fracture (>15%) during burst tests at ambient temperature. This ductile behavior is due to (1) the lower yield stress of the recrystallized cladding materials in comparison to hydride fracture strength (corrected by the compression stress arising from the precipitation) and (2) the hydride or hydrogen-depleted zone as a result of segregation of hydrogen into the liner layer. In irradiated Zircaloy-2 with liner cladding containing ∼340 wppm hydrogen, the conservation of some ductility during ring tensile tests at ambient temperature after reorientation treatment at 400 °C with cooling rates of ∼60 °C/h is also attributed to the existence of a hydride-depleted zone. Treatments at lower cooling rates (∼6 °C/h and 0.6 °C/h) promote greater levels of hydrogen segregation into the liner and allow for increased irradiation defect annealing, both of which result in a significant increase in ductility. Based on this investigation, given the very low cooling rates typical of dry storage systems, it can be concluded that the thermal transients associated with dry storage should not degrade, and more likely should actually

The electrical conductivity during incipient melting in the oceanic low velocity zone

PubMed Central

Sifré, David; Gardés, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier-Majumder, Saswata; Gaillard, Fabrice

2014-01-01

A low viscosity layer in the upper mantle, the Asthenosphere, is a requirement for plate tectonics1. The seismic low velocities and the high electrical conductivities of the Asthenosphere are attributed either to sub-solidus water-related defects in olivine minerals2-4 or to a few volume percents of partial melt5-8 but these two interpretations have shortcomings: (1) The amount of H2O stored in olivine is not expected to be higher than 50 ppm due to partitioning with other mantle phases9, including pargasite amphibole at moderate temperatures10, and partial melting at high temperatures9; (2) elevated melt volume fractions are impeded by the too cold temperatures prevailing in the Asthenosphere and by the high melt mobility that can lead to gravitational segregation11,12. Here we determined the electrical conductivity of CO2-H2O-rich melts, typically produced at the onset of mantle melting. Electrical conductivity modestly increases with moderate amounts of H2O and CO2 but it dramatically increases as CO2 content exceeds 6 wt% in the melt. Incipient melts, long-expected to prevail in the asthenosphere10,13-15, can therefore trigger its high electrical conductivities. Considering depleted and enriched mantle abundances in H2O and CO2 and their effect on the petrology of incipient melting, we calculated conductivity profiles across the Asthenosphere for various plate ages. Several electrical discontinuities are predicted and match geophysical observations in a consistent petrological and geochemical framework. In moderately aged plates (>5Ma), incipient melts most likely trigger both the seismic low velocities and the high electrical conductivities in the upper part of the asthenosphere, whereas for young plates4, where seamount volcanism occurs6, higher degree of melting is expected. PMID:24784219

Physicochemical properties of film-coated melt-extruded pellets.

PubMed

Young, Chistopher R; Crowley, Michael; Dietzsch, Caroline; McGinity, James W

2007-02-01

The purpose of this study was to investigate the physicochemical properties of poly(ethylene oxide) (PEO) and guaifenesin containing beads prepared by a melt-extrusion process and film-coated with a methacrylic acid copolymer. Solubility parameter calculations, thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), modulated differential scanning calorimetry (MDSC), X-ray powder diffraction (XRPD) and high performance liquid chromatography (HPLC) were used to determine drug/polymer miscibility and/or the thermal processibility of the systems. Powder blends of guaifenesin, PEO and functional excipients were processed using a melt-extrusion and spheronization technique and then film-coated in a fluidized bed apparatus. Solubility parameter calculations were used to predict miscibility between PEO and guaifenesin, and miscibility was confirmed by SEM and observation of a single melting point for extruded drug/polymer blends during MDSC investigations. The drug was stable following melt-extrusion as determined by TGA and HPLC; however, drug release rate from pellets decreased upon storage in sealed HDPE containers with silica desiccants at 40 degrees C/75% RH. The weight loss on drying, porosity and tortuosity determinations were not influenced by storage. Recrystallization of guaifenesin and PEO was confirmed by SEM and XRPD. Additionally, the pellets exhibited a change in adhesion behaviour during dissolution testing. The addition of ethylcellulose to the extruded powder blend decreased and stabilized the drug release rate from the thermally processed pellets. The current study also demonstrated film-coating to be an efficient process for providing melt-extruded beads with pH-dependent drug release properties that were stable upon storage at accelerated conditions.

The Influence of Grain Boundary Fluids on the Recrystallization Behavior in Calcite: A Comparison of "dry" and "wet" Marble Mylonites

NASA Astrophysics Data System (ADS)

Schenk, O.; Urai, J.; Evans, B.

2003-12-01

Carbonate rocks are able to accumulate large amounts of strain and deform crystal-plastically even at low p-T conditions and thus, marble sequences are often the site of strain localization in the upper crust during late-stage deformation in mountain building processes. In this study we sought to identify the effect of fluids on grain boundary morphology and recrystallization processes in marble mylonites during shear zone evolution, as fluids play a major role in the flow behavior of many rock materials during deformation (e.g. quartz, olivine, halite, feldspar). We compared calcite marble mylonites from two geological settings: (a) Schneeberg Complex, Southern Tyrole, Italy and (b) Naxos Metamorphic Core Complex, Greece. The shear zones of the selected areas are suitable for comparison, because they consist of similar lithology and the marble mylonites resemble each other in chemical composition. In addition, calcite-dolomite solvus geothermometry and TEM observations indicate similar p-T conditions for the shear zones formation. However, the two settings are different in the availability of fluids during the shear zone evolution: In the Schneeberg mylonites, both the alteration of minerals during retrograde metamorphism of neighboring micaschists and the existence of veins suggest that fluids were present during mylonitization. The absence of these features in the Naxos samples indicates that fluids were not present during deformation of these mylonites. This difference is also supported by the signature of stable isotopes. Microstructural investigations using optical and scanning electron microscopes on broken and planar surfaces did not indicate major differences between wet and dry mylonites: Grain boundaries of both types of samples display pores with shapes controlled by crystallography, and pore morphologies that are similar to observations from crack and grain-boundary healing experiments. Grain size reduction was predominantly the result of subgrain

Seismic evidence for silicate melt atop the 410-km mantle discontinuity

USGS Publications Warehouse

Revenaugh, Justin; Sipkin, S.A.

1994-01-01

LABORATORY results demonstrating that basic to ultrabasic melts become denser than olivine-rich mantle at pressures above 6 GPa (refs 1-3) have important implications for basalt petrogenesis, mantle differentiation and the storage of volatiles deep in the Earth. A density cross-over between melt and solid in the extensively molten Archaean mantle has been inferred from komatiitic volcanism and major-element mass balances, but present-day evidence of dense melt below the seismic low-velocity zone is lacking. Here we present mantle shear-wave impedance profiles obtained from multiple-ScS reverberation mapping for corridors connecting western Pacific subduction zone earthquakes with digital seismograph stations in eastern China, imaging a ~5.8% impedance decrease roughly 330 km beneath the Sea of Japan, Yellow Sea and easternmost Asia. We propose that this represents the upper surface of a layer of negatively buoyant melt lying on top of the olivine ??? ??- phase transition (the 410-km seismic discontinuity). Volatile-rich fluids expelled from the partial melt zone as it freezes may migrate upwards, acting as metasomatic agents and perhaps as the deep 'proto-source' of kimberlites. The remaining, dense, crystalline fraction would then concentrate above 410 km, producing a garnet-rich layer that may flush into the transition zone.

The risk of recrystallization: changes to the toxicity and morphology of pyrimethamine.

PubMed

Perold, Zak; Caira, Mino R; Brits, Marius

2014-01-01

Pyrimethamine, an anti-malarial agent known to exhibit solid state polymorphism, may be purified by means of recrystallization. Recrystallization may alter the solid state chemistry of pharmaceuticals, which may impact the toxicity and/or manufacturability thereof. We evaluated the risks associated with the recrystallization of pyrimethamine. Pyrimethamine was recrystallized using several organic solvents. X-ray diffraction, thermal analysis, infra-red spectroscopy, microscopy, flowability -, solubility and dissolution testing as well as computational work were employed to evaluate the recrystallized products. A toxic solvatomorph of pyrimethamine (Pyr-MeOH) was found to be the product from methanol recrystallization. The elucidation of - and the elaboration on the unique characteristics of Pyr-MeOH provides the pharmaceutical industry with several means to identify Pyr-MeOH and to distinguish it from the pharmaceutically preferred anhydrous form (Pyr). Thermal methods of analysis found that the toxicity of Pyr-MeOH may be reversed by overcoming a desolvation activation energy of 148 kJ/mol. In addition it was found that recrystallization altered the morphology of Pyr. Angle of repose and tapped density determinations identified that the different morphologies of Pyr displayed differences in powder flow and compressibility behaviour and In Silico calculations were successful in rendering morphologies resembling that found experimentally. We present a solvatomorph of pyrimethamine and provide several characteristic means to identify this unwanted toxic form and quantified the energy required to overcome its toxicity. In addition we describe that Pyr may present in different morphologies and show how it may impact the manufacturability thereof.

The petrology and chronology of NWA 8009 impact melt breccia: Implication for early thermal and impact histories of Vesta

NASA Astrophysics Data System (ADS)

Liao, Shiyong; Hsu, Weibiao

2017-05-01

Studies of petrology, mineralogy and geochronology of eucrites are keys to reconstruct the thermal and impact history of 4 Vesta, the proposed parent body for HED meteorites. Here we report the petrography, mineralogy and geochemistry of NWA 8009, a newly found eucritic impact-melt breccia, and present SIMS U-Pb ages of zircon and phosphates. NWA 8009 consists of coarse- and fine-grained lithic and mineral clasts set in fine-grained recrystallized matrix. It was derived from a protolith of monomict non-cumulate eucrite. Evidence for intense shock metamorphism observed in NWA 8009 includes mosaicism, deformed exsolution lamellae and partial melting of pyroxene, melting and incipient flow of plagioclase, planar fractures and granular textures of zircon. These shock effects indicate NWA 8009 was subjected to an impact metamorphism with peak pressure of ∼50-60 GPa and post-shock temperature of ∼1160-1200 °C. NWA 8009 is among the most intensely shocked HEDs reported yet. After the impact, the sample was buried near the surface in target rocks and experienced rapid cooling (∼23 °C/h) and annealing, resulting in recrystallization of the matrix and devitrification of plagioclase and silica glasses. U-Pb isotopic system of apatite within plagioclase groundmass of lithic clasts is completely reset and constrains the timing of impact at 4143 ± 61 Ma, providing a new robust impact age on Vesta. Combined with the presence of synchronous impact resetting events, especially those recorded by Lu-Hf, Sm-Nd, and Pb-Pb isotopic systems, we identified a period of high impacts flux at ca. 4.1-4.2 Ga on Vesta. This impact flux occurred coincident with the uptick at ca. 4.1-4.2 Ga in impact age spectra of the moon, probably reflects widespread intense bombardment throughout the inner solar system at ca. 4.1-4.2 Ga. Based on evidence from zircon chemical zoning, petrographic occurrences, as well as the distinctive Zr/Hf ratios, we suggested that zircons in NWA 8009 have had a

Effects of homogenization treatment on recrystallization behavior of 7150 aluminum sheet during post-rolling annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Zhanying; Department of Applied Science, University of Québec at Chicoutimi, Saguenay, QC G7H 2B1; Zhao, Gang

2016-04-15

The effects of two homogenization treatments applied to the direct chill (DC) cast billet on the recrystallization behavior in 7150 aluminum alloy during post-rolling annealing have been investigated using the electron backscatter diffraction (EBSD) technique. Following hot and cold rolling to the sheet, measured orientation maps, the recrystallization fraction and grain size, the misorientation angle and the subgrain size were used to characterize the recovery and recrystallization processes at different annealing temperatures. The results were compared between the conventional one-step homogenization and the new two-step homogenization, with the first step being pretreated at 250 °C. Al{sub 3}Zr dispersoids with highermore » densities and smaller sizes were obtained after the two-step homogenization, which strongly retarded subgrain/grain boundary mobility and inhibited recrystallization. Compared with the conventional one-step homogenized samples, a significantly lower recrystallized fraction and a smaller recrystallized grain size were obtained under all annealing conditions after cold rolling in the two-step homogenized samples. - Highlights: • Effects of two homogenization treatments on recrystallization in 7150 Al sheets • Quantitative study on the recrystallization evolution during post-rolling annealing • Al{sub 3}Zr dispersoids with higher densities and smaller sizes after two-step treatment • Higher recrystallization resistance of 7150 sheets with two-step homogenization.« less

Ion-specific ice recrystallization provides a facile approach for the fabrication of porous materials

NASA Astrophysics Data System (ADS)

Wu, Shuwang; Zhu, Chongqin; He, Zhiyuan; Xue, Han; Fan, Qingrui; Song, Yanlin; Francisco, Joseph S.; Zeng, Xiao Cheng; Wang, Jianjun

2017-05-01

Ice recrystallization is of great importance to both fundamental research and practical applications, however understanding and controlling ice recrystallization processes remains challenging. Here, we report the discovery of an ion-specific effect on ice recrystallization. By simply changing the initial type and concentration of ions in an aqueous solution, the size of ice grains after recrystallization can be tuned from 27.4+/-4.1 to 277.5+/-30.9 μm. Molecular dynamics simulations show that the ability of the ion to be incorporated into the ice phase plays a key role in the ultimate size of the ice grains after recrystallization. Moreover, by using recrystallized ice crystals as templates, 2D and 3D porous networks with tuneable pore sizes could be prepared from various materials, for example, NaBr, collagen, quantum dots, silver and polystyrene colloids. These porous materials are suitable for a wide range of applications, for example, in organic electronics, catalysis and bioengineering.

Ion-specific ice recrystallization provides a facile approach for the fabrication of porous materials

PubMed Central

Wu, Shuwang; Zhu, Chongqin; He, Zhiyuan; Xue, Han; Fan, Qingrui; Song, Yanlin; Francisco, Joseph S.; Zeng, Xiao Cheng; Wang, Jianjun

2017-01-01

Ice recrystallization is of great importance to both fundamental research and practical applications, however understanding and controlling ice recrystallization processes remains challenging. Here, we report the discovery of an ion-specific effect on ice recrystallization. By simply changing the initial type and concentration of ions in an aqueous solution, the size of ice grains after recrystallization can be tuned from 27.4±4.1 to 277.5±30.9 μm. Molecular dynamics simulations show that the ability of the ion to be incorporated into the ice phase plays a key role in the ultimate size of the ice grains after recrystallization. Moreover, by using recrystallized ice crystals as templates, 2D and 3D porous networks with tuneable pore sizes could be prepared from various materials, for example, NaBr, collagen, quantum dots, silver and polystyrene colloids. These porous materials are suitable for a wide range of applications, for example, in organic electronics, catalysis and bioengineering. PMID:28462937

Ion-specific ice recrystallization provides a facile approach for the fabrication of porous materials.

PubMed

Wu, Shuwang; Zhu, Chongqin; He, Zhiyuan; Xue, Han; Fan, Qingrui; Song, Yanlin; Francisco, Joseph S; Zeng, Xiao Cheng; Wang, Jianjun

2017-05-02

Ice recrystallization is of great importance to both fundamental research and practical applications, however understanding and controlling ice recrystallization processes remains challenging. Here, we report the discovery of an ion-specific effect on ice recrystallization. By simply changing the initial type and concentration of ions in an aqueous solution, the size of ice grains after recrystallization can be tuned from 27.4±4.1 to 277.5±30.9 μm. Molecular dynamics simulations show that the ability of the ion to be incorporated into the ice phase plays a key role in the ultimate size of the ice grains after recrystallization. Moreover, by using recrystallized ice crystals as templates, 2D and 3D porous networks with tuneable pore sizes could be prepared from various materials, for example, NaBr, collagen, quantum dots, silver and polystyrene colloids. These porous materials are suitable for a wide range of applications, for example, in organic electronics, catalysis and bioengineering.

Monazite behaviours during high-temperature metamorphism: a case study from Dinggye region, Tibetan Himalaya

NASA Astrophysics Data System (ADS)

Wang, Jia-Min; Wu, Fu-Yuan; Rubatto, Daniela; Liu, Shi-Ran; Zhang, Jin-Jiang

2017-04-01

Monazite is a key accessory mineral for metamorphic geochronology, but its growth mechanisms during melt-bearing high-temperature metamorphism is not well understood. Therefore, the petrology, pressure-temperature and timing of metamorphism have been investigated in pelitic and psammitic granulites from the Greater Himalayan Crystalline Complex (GHC) in Dinggye, southern Tibet. These rocks underwent an isothermal decompression process from pressure conditions of >10 kbar to <5 kbar with constant temperatures of 750-830°C, and recorded three metamorphic stages of kyanite-grade (M1), sillimanite-grade (M2) and cordierite-spinel grade (M3). Monazite and zircon crystals were analyzed for ages by microbeam techniques either in mounts or thin sections. Ages were linked to specific conditions of mineral growth by comprehensive studies on zoning patterns, trace element signatures, index mineral inclusions (melt inclusions, sillimanite and K-feldspar) in dated domains and textural correlations with coexisting minerals. The results show that inherited domains (500-400 Ma) are common in monazite even at granulite-facies conditions. Few monazites formed at the M1-stage ( 30-29 Ma) and recorded heterogeneous Th, Y, and HREE compositions, which formed by recrystallization related to muscovite dehydration melting reaction. These monazite grains were protected from dissolution or lateral overprinting mainly by the armour effect of matrix crystals (biotite and quartz). Most monazite grains formed at the M3-stage (21-19 Ma) through either dissolution-reprecipitation or recrystallization that was related to biotite dehydration melting reaction. These monazite grains record HREE and Y signatures in local equilibrium with different reactions involving either garnet breakdown or peritectic garnet growth. Another peak of monazite growth occurs during melt crystallization ( 15 Ma), and these monazites are unzoned and have homogeneous compositions. Our results documented the widespread

Primitive Melt Inclusions from Multiple Samples from the FAMOUS Zone: Insights into the Mantle Melting Column and the Fractionation Processes

NASA Astrophysics Data System (ADS)

Laubier, M.; Langmuir, C. H.

2008-12-01

On mid-ocean ridges, the influential work by Sobolev and Shimizu (Nature, 1993) and Sobolev (Petrology, 1996) has inferred fractional melting during polybaric upwelling by showing that olivine-hosted inclusions were formed over a range of pressures. However melt inclusion studies have often concerned single MORB samples and may be seen as anecdotal in the sense that they are neither repeated nor globally verified. Recent modeling and experimental results also suggest the importance of post-entrapment processes for major and trace elements. This study presents major and trace element data in 300 olivine-hosted melt inclusions from 11 samples from the FAMOUS segment on the Mid-Atlantic Ridge. Published data from Shimizu (Phys. Earth Planet. Int., 1998) and Kamenetsky (EPSL, 1996; spinel-hosted inclusions) are also reported. In parallel, major and trace element measurements were performed in 150 glasses of the segment in order to have consistent datasets. Melt inclusions, trapped in olivine phenocrysts Mg#85-92, display complex trends in major element plots and can be divided into three groups. Group 1, the largest, is characterized by high MgO (9.4-13.4 wt.%), intermediate SiO2 and Al2O3 contents. Group 2 displays distinctively high Al2O3 (up to 18.4 wt.%), low SiO2 (as low as 46.5 wt.%) and high MgO (10.5-12.8 wt.%) contents, along with low CaO and variable TiO2, K2O and incompatible element concentrations. Group 3 consists of the melt inclusions trapped in less primitive olivines (Mg#<88.5) and displays higher SiO2, CaO and trace element contents. In the lava population, two groups can be distinguished. A small subset, that shares many features with the group 2 melt inclusions, displays high MgO and Al2O3 and low SiO2 and incompatible element contents. This type of lava - high-Al, low-Si and high-Mg - has been previously reported for various mid-ocean ridges (e.g., le Roux et al., Contrib. Min. Petrol., 2002; Eason and Sinton, EPSL, 2008). The second group plots

The density, compressibility and seismic velocity of hydrous melts at crustal and upper mantle conditions

NASA Astrophysics Data System (ADS)

Ueki, K.; Iwamori, H.

2015-12-01

Various processes of subduction zone magmatism, such as upward migration of partial melts and fractional crystallization depend on the density of the hydrous silicate melt. The density and the compressibility of the hydrous melt are key factors for the thermodynamic calculation of phase relation of the hydrous melt, and the geophysical inversion to predict physicochemical conditions of the melting region based on the seismic velocity. This study presents a new model for the calculations of the density of the hydrous silicate melts as a function of T, P, H2O content and melt composition. The Birch-Murnaghan equation is used for the equation of state. We compile the experimentally determined densities of various hydrous melts, and optimize the partial molar volume, compressibility, thermal expansibility and its pressure derivative, and K' of the H2O component in the silicate melt. P-T ranges of the calibration database are 0.48-4.29 GPa and 1033-2073 K. As such, this model covers the P-T ranges of the entire melting region of the subduction zone. Parameter set provided by Lange and Carmichael [1990] is used for the partial molar volume and KT value of the anhydrous silicate melt. K' of anhydrous melt is newly parameterized as a function of SiO2 content. The new model accurately reproduces the experimentally determined density variations of various hydrous melts from basalt to rhyolite. Our result shows that the hydrous melt is more compressive and less dense than the anhydrous melt; with the 5 wt% of H2O in melt, density and KT decrease by ~10% and ~30% from those of the anhydrous melt, respectively. For the application of the model, we calculated the P-wave velocity of the hydrous melt. With the 5 wt% of H2O, P-wave velocity of the silicate melt decreases by >10%. Based on the melt P-wave velocity, we demonstrate the effect of the melt H2O content on the seismic velocity of the partially molten zone of the subduction zone.

Preparation and recrystallization behavior of spray-dried co-amorphous naproxen-indomethacin.

PubMed

Beyer, Andreas; Radi, Lydia; Grohganz, Holger; Löbmann, Korbinian; Rades, Thomas; Leopold, Claudia S

2016-07-01

To improve the dissolution properties and the physical stability of amorphous active pharmaceutical ingredients, small molecule stabilizing agents may be added to prepare co-amorphous systems. The objective of the study was to investigate if spray-drying allows the preparation of co-amorphous drug-drug systems such as naproxen-indomethacin and to examine the influence of the process conditions on the resulting initial sample crystallinity and the recrystallization behavior of the drug(s). For this purpose, the process parameters inlet temperature and pump feed rate were varied according to a 2(2) factorial design and the obtained samples were analyzed with X-ray powder diffractometry and Fourier-transformed infrared spectroscopy. Evaluation of the data revealed that the preparation of fully amorphous samples could be achieved depending on the process conditions. The resulting recrystallization behavior of the samples, such as the total recrystallization rate, the individual recrystallization rates of naproxen and indomethacin as well as the polymorphic form of indomethacin that was formed were influenced by these process conditions. For initially amorphous samples, it was found that naproxen and indomethacin recrystallized almost simultaneously, which supports the theory of formation of drug-drug heterodimers in the co-amorphous phase. Copyright © 2016 Elsevier B.V. All rights reserved.

Microstructure heterogeneity after the ECAP process and its influence on recrystallization in aluminium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wronski, S., E-mail: wronski@fis.agh.edu.pl; Tarasiuk, J., E-mail: tarasiuk@ftj.agh.edu.pl; Bacroix, B., E-mail: brigitte.bacroix@univ-paris13.fr

The main purpose of the present work is to describe the qualitative and quantitative behaviours of aluminium during high strain plastic deformation and the effect of deformation on the subsequent recrystallization process. An Electron Backscatter Diffraction analysis of aluminium after the Equal channel angular pressing (ECAP) and recrystallization process is presented. In order to do this, several topological maps are measured for samples processed by 4 and 8 passes and recrystallized. The processing was conducted with route C. For all samples, distributions of grain size, misorientation, image quality factor (IQ) and texture were preceded and then analysed in some detail.more » - Highlights: ► Describe the microstructure fragmentation in aluminum. ► High strain plastic deformation and effect of deformation on recrystallization. ► The microstructure fragmentation and its influence on recrystallization. ► Image quality factor and misorientation characteristics are examined using EBSD.« less

Timing of anatexis and melt crystallization in the Socorro-Guaxupé Nappe, SE Brazil: Insights from trace element composition of zircon, monazite and garnet coupled to Usbnd Pb geochronology

NASA Astrophysics Data System (ADS)

Rocha, B. C.; Moraes, R.; Möller, A.; Cioffi, C. R.; Jercinovic, M. J.

2017-04-01

The timing of partial melting and melt crystallization in granulite facies rocks of the Socorro-Guaxupé Nappe (SGN), Brazil is constrained using a combination of imaging techniques, LA-ICP-MS and EPMA dating, trace element geochemistry and thermobarometry. (Orthopyroxene)-garnet-bearing migmatite that records extensive biotite dehydration melting shows evidence for a clockwise P-T-t path. UHT peak conditions were attained at 1030 ± 110 °C, 11.7 ± 1.4 kbar, with post-peak cooling to 865 ± 38 °C, 8.9 ± 0.8 kbar. Cryogenian igneous inheritance of ca. 720-640 Ma is identified in oscillatory zoned zircon cores (n = 167) with steep HREE patterns. Resorbed, Y-rich monazite cores preserve a prograde growth stage at 631 ± 4 Ma prior to the partial melting event, providing an upper age limit for the granulite facies metamorphism in the SGN. REE-rich, Th-depleted monazite related to apatite records the initial stages of decompression at 628 ± 4 Ma. Multiple monazite growth episodes record melt crystallization events at 624 ± 3 Ma, 612 ± 5 Ma and 608 ± 6 Ma. Stubby, equant "soccer ball" zircon provide evidence for melt crystallization at 613 ± 2 Ma and 607 ± 4 Ma. The excess scatter in zircon and monazite age populations between 629 ± 4 and 601 ± 3 Ma is interpreted as discontinuous and episodic growth within this age range, characterizing a prolonged metamorphic event in the SGN lasting ca. 30 m.y. The development of Y + HREE-rich monazite rims at ca. 600 Ma documents retrograde garnet breakdown, extensive biotite growth and the final stages of melt crystallization. Th-rich, Y + HREE-poor monazite rims at ca. 590 Ma record monazite recrystallization.

Constraints on the dynamics of melt migration, flow and emplacement across the continental crust

NASA Astrophysics Data System (ADS)

Cavalcante, Carolina; Viegas, Gustavo

2015-04-01

The presence of partial melting during deformation produces a drastic change in the rheological behavior of the continental crust. The rock strength decreases with melt fractions as low as ~0.7 %. At pressure/temperature conditions typical of the middle crust, melt-bearing systems may play a critical role in the processes of strain localization and in the overall strength of the continental lithosphere. In eastern Brazil, Neoproterozoic tectonics are often associated with wide partial melting and shear zone development, that promote the exhumation of mid- to lower crustal layers where compositionally heterogeneous anatexites with variable melt fractions and leucosome structures are exposed. The leucosomes usually form interconnected networks of magma that reflect the high melt content present during deformation. In this contribution we address two case studies encompassing the dynamics of melt flow at magma chambers, represented by the Carlos Chagas anatexite, and the mechanisms of melt migration and channeling through shear zones, in which the Patos shear zone serves as an analogue. Through detailed petrostructural studies of anatexites exposed at these settings, we aim to demonstrate the way melt deforms and localizes strain, the different patterns of melt flow pathways across the crust, and the implications for the mechanical behaviour of the Earth's lithosphere during orogenic deformation.

Mechanism of drug release from polymethacrylate-based extrudates and milled strands prepared by hot-melt extrusion.

PubMed

Albers, Jessica; Alles, Rainer; Matthée, Karin; Knop, Klaus; Nahrup, Julia Schulze; Kleinebudde, Peter

2009-02-01

The aim of the study was the formulation of solid dispersions of the poorly water-soluble drug celecoxib and a polymethacrylate carrier by hot-melt extrusion. The objectives were to elucidate the mechanism of drug release from obtained extrudates and milled strands addicted to the solid-state properties of the solid dispersions and to examine and eliminate stability problems occurring under storage, exposure of mechanical stress, and in vitro dissolution. Transparent extrudates containing up to 60% drug could be prepared with a temperature setting below the melting point of celecoxib. XRPD and DSC measurements indicated the formation of a glassy solid solution, where the drug is molecularly dispersed in the carrier. The amorphous state of the glassy solid solution could be maintained during the exposure of mechanical stress in a milling process, and was stable under storage for at least 6 months. Solid-state properties and SEM images of extrudates after dissolution indicated a carrier-controlled dissolution, whereby the drug is molecularly dispersed within the concentrated carrier layer. The glassy solid solution showed a 58-fold supersaturation in 0.1 N HCl within the first 10 min, which was followed by a recrystallization process. Recrystallization could be inhibited by an external addition of HPMC.

An observational and thermodynamic investigation of carbonate partial melting

NASA Astrophysics Data System (ADS)

Floess, David; Baumgartner, Lukas P.; Vonlanthen, Pierre

2015-01-01

Melting experiments available in the literature show that carbonates and pelites melt at similar conditions in the crust. While partial melting of pelitic rocks is common and well-documented, reports of partial melting in carbonates are rare and ambiguous, mainly because of intensive recrystallization and the resulting lack of criteria for unequivocal identification of melting. Here we present microstructural, textural, and geochemical evidence for partial melting of calcareous dolomite marbles in the contact aureole of the Tertiary Adamello Batholith. Petrographic observations and X-ray micro-computed tomography (X-ray μCT) show that calcite crystallized either in cm- to dm-scale melt pockets, or as an interstitial phase forming an interconnected network between dolomite grains. Calcite-dolomite thermometry yields a temperature of at least 670 °C, which is well above the minimum melting temperature of ∼600 °C reported for the CaO-MgO-CO2-H2O system. Rare-earth element (REE) partition coefficients (KDcc/do) range between 9-35 for adjacent calcite-dolomite pairs. These KD values are 3-10 times higher than equilibrium values between dolomite and calcite reported in the literature. They suggest partitioning of incompatible elements into a melt phase. The δ18O and δ13C isotopic values of calcite and dolomite support this interpretation. Crystallographic orientations measured by electron backscattered diffraction (EBSD) show a clustering of c-axes for dolomite and interstitial calcite normal to the foliation plane, a typical feature for compressional deformation, whereas calcite crystallized in pockets shows a strong clustering of c-axes parallel to the pocket walls, suggesting that it crystallized after deformation had stopped. All this together suggests the formation of partial melts in these carbonates. A Schreinemaker analysis of the experimental data for a CO2-H2O fluid-saturated system indeed predicts formation of calcite-rich melt between 650-880 °C, in

Development and melt growth of novel scintillating halide crystals

NASA Astrophysics Data System (ADS)

Yoshikawa, Akira; Yokota, Yuui; Shoji, Yasuhiro; Kral, Robert; Kamada, Kei; Kurosawa, Shunsuke; Ohashi, Yuji; Arakawa, Mototaka; Chani, Valery I.; Kochurikhin, Vladimir V.; Yamaji, Akihiro; Andrey, Medvedev; Nikl, Martin

2017-12-01

Melt growth of scintillating halide crystals is reviewed. The vertical Bridgman growth technique is still considered as very popular method that enables production of relatively large and commercially attractive crystals. On the other hand, the micro-pulling-down method is preferable when fabrication of small samples, sufficient for preliminary characterization of their optical and/or scintillation performance, is required. Moreover, bulk crystal growth is also available using the micro-pulling-down furnace. The examples of growths of various halide crystals by industrially friendly melt growth techniques including Czochralski and edge-defined film-fed growth methods are also discussed. Finally, traveling molten zone growth that in some degree corresponds to horizontal zone melting is briefly overviewed.

Barite recrystallization in the presence of 226Ra and 133Ba

NASA Astrophysics Data System (ADS)

Heberling, Frank; Metz, Volker; Böttle, Melanie; Curti, Enzo; Geckeis, Horst

2018-07-01

Despite the long history of studies on (Ba,Ra)SO4, various recent investigations aimed at improving our understanding of its formation processes and thermodynamics. Accumulation of natural Ra isotopes (mainly 226Ra and 228Ra) in (Ba,Ra)SO4 plays an important role in many geotechnical applications and water desalination facilities. In the near field of a nuclear waste repository, barite formation may be expected e.g. as a consequence of contact of spent nuclear fuel or vitrified high level waste with sulfate containing ground water, and may control the potential release of Ra from waste forms upon leakage. Here, we present results of long term batch-type barite recrystallization experiments conducted in the simultaneous presence of 226Ra and 133Ba as a function of initial Ra2+ concentration and pH with the same type and charge of barite powder as used in previous studies (Curti et al., 2010; Klinkenberg et al., 2014; Brandt et al., 2015). Due to the simultaneous measurement of 133Ba and 226Ra our data allow for a direct relation of 226Ra uptake with barite recrystallization, which leads to more accurate partition coefficients compared to previous studies. During a reaction period of five years, barite is continuously recrystallizing. Within the investigated radium concentration range (Ba(1-X)RaXSO4 with X < 0.0006), we measure a partition coefficient of D = 2.1 ± 0.5. The partition coefficient is constant within uncertainty during almost five years (1793 days) of experimental duration. This value is in line with a description of (Ba,Ra)SO4 as an ideal solid solution based on the solubility products (KSP) of the endmembers barite (log10(KSP(barite)) = -9.97) and radium sulfate (log10(KSP(RaSO4)) = -10.26; dimensionless Guggenheim parameter, a0 = 0.0 ± 0.3). Apparent discrepancies to previous theoretical results (a0 = 1.0 ± 0.4) may be resolved when the uncertainties related to the solubility of RaSO4 are considered. Compared to results of previous publications

Disclination mediated dynamic recrystallization in metals at low temperature.

PubMed

Aramfard, Mohammad; Deng, Chuang

2015-09-16

Recrystallization is one of the most important physical phenomena in condensed matter that has been utilized for materials processing for thousands of years in human history. It is generally believed that recrystallization is thermally activated and a minimum temperature must be achieved for the necessary atomic mechanisms to occur. Here, using atomistic simulations, we report a new mechanism of dynamic recrystallization that can operate at temperature as low as T = 10 K in metals during deformation. In contrast to previously proposed dislocation-based models, this mechanism relies on the generation of disclination quadrupoles, which are special defects that form during deformation when the grain boundary migration is restricted by structural defects such as triple junctions, cracks or obstacles. This mechanism offers an alternative explanation for the grain refinement in metals during severe plastic deformation at cryogenic temperature and may suggest a new method to tailor the microstructure in general crystalline materials.

First in-situ monitoring of CO2 delivery to the mantle followed by compression melting, using synchrotron generated X-ray diffraction.

NASA Astrophysics Data System (ADS)

Hammouda, Tahar; Chantel, Julien; Manthilake, Geeth; Guignard, Jérémy; Crichton, Wilson; Gaillard, Fabrice

2014-05-01

Melting of peridotite + CO2 upon compression has been directly monitored in situ, for the first time. We have combined high pressure experiments in the multianvil apparatus with synchrotron-generated X-ray diffraction, in order to monitor sample decarbonation upon heating, followed by melting upon compression. Experiments were performed in the model system CaO-MgO-SiO2+CO2, using dolomite and silicates contained in graphite capsules as starting material. Save Al, starting composition was aimed at reproducing peridotitic system. The sample was first compressed at room temperature, then heated. Decarbonation was observed at 2.2 GPa and 1100°C. After further heating to 1300°C, pressure was increased. Melting was observed at 2.7 GPa, while temperature was kept at 1300°C. All transformations were followed using X-ray diffraction. Starting with silicate + carbonate mixtures, we were thus able to keep CO2 fluid in the experimental sample at high P and T, up to the solidus. Concerning carbon recycling at subduction zones, it is known that CO2 is a non-wetting fluid in silicate aggregates. Therefore, any CO2 resulting from carbonate breakdown likely remains trapped at grain corners either in the subducted lithosphere or in the mantle wedge before eventually being trapped in mantle minerals as fluid inclusions, due to dynamic recrystallization. In this way, CO2 released from the slab may be spread laterally due to mantle convection. Entrainment to further depths by deep subduction or in convection cells induces CO2 introduction to depth wherein the solidus can be crossed, due to pressure increase. The solidus corresponds to the so-called carbonate ledge, beyond which carbonatitic melts are produced. Therefore, compression melting of CO2-bearing lithologies is a way to produce carbonatitic melts at depths corresponding to about 80 km. This mechanism is a viable explanation for the observed geophysical anomalies, such as those revealed by electrical conductivity

Hot Deformation and Dynamic Recrystallization Behavior of the Cu-Cr-Zr-Y Alloy

NASA Astrophysics Data System (ADS)

Zhang, Yi; Huili, Sun; Volinsky, Alex A.; Tian, Baohong; Chai, Zhe; Liu, Ping; Liu, Yong

2016-03-01

To study the workability and to optimize the hot deformation processing parameters of the Cu-Cr-Zr-Y alloy, the strain hardening effect and dynamic softening behavior of the Cu-Cr-Zr-Y alloy were investigated. The flow stress increases with the strain rate and stress decreases with deformation temperature. The critical conditions, including the critical strain and stress for the occurrence of dynamic recrystallization, were determined based on the alloy strain hardening rate. The critical stress related to the onset of dynamic recrystallization decreases with temperature. The evolution of DRX microstructure strongly depends on the deformation temperature and the strain rate. Dynamic recrystallization appears at high temperatures and low strain rates. The addition of Y can refine the grain and effectively accelerate dynamic recrystallization. Dislocation generation and multiplication are the main hot deformation mechanisms for the alloy. The deformation temperature increase and the strain rate decrease can promote dynamic recrystallization of the alloy.

Microstructural and fabric characterization of brittle-ductile transitional deformation of middle crustal rocks along the Jinzhou detachment fault zone, Northeast China

NASA Astrophysics Data System (ADS)

Zhang, Juyi; Jiang, Hao; Liu, Junlai

2017-04-01

Detachment fault zones (DFZs) of metamorphic core complexes generally root into the middle crust. Exhumed DFZs therefore generally demonstrate structural, microstructural and fabric features characteristic of middle to upper crustal deformation. The Jinzhou detachment fault zone from the Liaonan metamorphic core complex is characterized by the occurrence of a sequence of fault rocks due to progressive shearing along the fault zone during exhumation of the lower plate. From the exhumed fabric zonation, cataclastic rocks formed in the upper crust occur near the Jinzhou master detachment fault, and toward the lower plate gradually changed to mylonites, mylonitic gneisses and migmatitic gneisses. Correspondingly, these fault rocks have various structural, microstructural and fabric characteristics that were formed by different deformation and recrystallization mechanisms from middle to upper crustal levels. At the meanwhile, various structural styles for strain localization were formed in the DFZ. As strain localization occurs, rapid changes in deformation mechanisms are attributed to increases in strain rates or involvement of fluid phases during the brittle-ductile shearing. Optical microscopic studies reveal that deformed quartz aggregates in the lower part of the detachment fault zone are characterized by generation of dynamically recrystallized grains via SGR and BLG recrystallization. Quartz rocks from the upper part of the DFZ have quartz porphyroclasts in a matrix of very fine recrystallized grains. The porphyroclasts have mantles of sub-grains and margins grain boundary bulges. Electron backscattered diffraction technique (EBSD) quartz c-axis fabric analysis suggests that quartz grain aggregates from different parts of the DFZ possess distinct fabric complexities. The c-axis fabrics of deformed quartz aggregates from mylonitic rocks in the lower part of the detachment fault zone preserve Y-maxima which are ascribed to intermediate temperature deformation (500

Low-Temperature Friction-Stir Welding of 2024 Aluminum

NASA Technical Reports Server (NTRS)

Benavides, S.; Li, Y.; Murr, L. E.; Brown, D.; McClure, J. C.

1998-01-01

Solid state friction-stir welding (FSW) has been demonstrated to involve dynamic recrystallization producing ultra-fine, equiaxed grain structures to facilitate superplastic deformation as the welding or joining mechanism. However, the average residual, equiaxed, grain size in the weld zone has ranged from roughly 0.5 micron to slightly more than 10 micron, and the larger weld zone grain sizes have been characterized as residual or static grain growth as a consequence of the temperatures in the weld zone (where center-line temperatures in the FSW of 6061 Al have been shown to be as high as 480C or -0.8 T(sub M) where T(sub M) is the absolute melting temperature)). In addition, the average residual weld zone grain size has been observed to increase near the top of the weld, and to decrease with distance on either side of the weld-zone centerline, an d this corresponds roughly to temperature variations within the weld zone. The residual grain size also generally decreases with decreasing FSW tool rotation speed. These observations are consistent with the general rules for recrystallization where the recrystallized grain size decreases with increasing strain (or deformation) at constant strain rate, or with increasing strain-rate, or with increasing strain rate at constant strain; especially at lower ambient temperatures, (or annealing temperatures). Since the recrystallization temperature also decreases with increasing strain rate, the FSW process is somewhat complicated because the ambient temperature, the frictional heating fraction, and the adiabatic heating fraction )proportional to the product of strain and strain-rate) will all influence both the recrystallization and growth within the FSW zone. Significantly reducing the ambient temperature of the base metal or work pieces to be welded would be expected to reduce the residual weld-zone grain size. The practical consequences of this temperature reduction would be the achievement of low temperature welding. This

Oceanic slab melting and mantle metasomatism.

PubMed

Scaillet, B; Prouteau, G

2001-01-01

Modern plate tectonic brings down oceanic crust along subduction zones where it either dehydrates or melts. Those hydrous fluids or melts migrate into the overlying mantle wedge trigerring its melting which produces arc magmas and thus additional continental crust. Nowadays, melting seems to be restricted to cases of young (< 50 Ma) subducted plates. Slab melts are silicic and strongly sodic (trondhjemitic). They are produced at low temperatures (< 1000 degrees C) and under water excess conditions. Their interaction with mantle peridotite produces hydrous metasomatic phases such as amphibole and phlogopite that can be more or less sodium rich. Upon interaction the slab melt becomes less silicic (dacitic to andesitic), and Mg, Ni and Cr richer. Virtually all exposed slab melts display geochemical evidence of ingestion of mantle material. Modern slab melts are thus unlike Archean Trondhjemite-Tonalite-Granodiorite rocks (TTG), which suggests that both types of magmas were generated via different petrogenetic pathways which may imply an Archean tectonic model of crust production different from that of the present-day, subduction-related, one.

Recrystallization and grain growth phenomena in a particle-reinforced aluminum composite

NASA Astrophysics Data System (ADS)

van Aken, D. C.; Krajewski, P. E.; Vyletel, G. M.; Allison, J. E.; Jones, J. W.

1995-06-01

Recrystallization and grain growth in a 2219/TiC/15p composite were investigated as functions of the amount of deformation and deformation temperature. Both cold and hot deformed samples were annealed at the normal solution treatment temperature of 535 °C. It was shown that large recrystallized grain diameters, relative to the interparticle spacing, could be produced in a narrow range of deformation for samples cold-worked and those hot-worked below 450 °C. For cold-worked samples, between 4 to 6 pct deformation, the recrystallized grain diameters varied from 530 to 66 μm as the amount of deformation increased. Subsequent grain growth was not observed in these recrystallized materials and noncompact grain shapes were observed. For deformations greater than 15 pct, recrystallized grain diameters less than the interparticle spacing were observed and subsequent grain growth produced a pinned grain diameter of 27 μm. The pinned grain diameter agreed well with an empirical model based on three dimensional (3-D) Monte Carlo simulations of grain growth and particle pinning in a two-phase material. Tensile properties were determined as a function of grain size, and it was shown that grain size had a weak influence on yield strength. A maximum in the yield strength was observed at a grain size larger than the normal grain growth and particle-pinned diameter.

Disclination mediated dynamic recrystallization in metals at low temperature

PubMed Central

Aramfard, Mohammad; Deng, Chuang

2015-01-01

Recrystallization is one of the most important physical phenomena in condensed matter that has been utilized for materials processing for thousands of years in human history. It is generally believed that recrystallization is thermally activated and a minimum temperature must be achieved for the necessary atomic mechanisms to occur. Here, using atomistic simulations, we report a new mechanism of dynamic recrystallization that can operate at temperature as low as T = 10 K in metals during deformation. In contrast to previously proposed dislocation-based models, this mechanism relies on the generation of disclination quadrupoles, which are special defects that form during deformation when the grain boundary migration is restricted by structural defects such as triple junctions, cracks or obstacles. This mechanism offers an alternative explanation for the grain refinement in metals during severe plastic deformation at cryogenic temperature and may suggest a new method to tailor the microstructure in general crystalline materials. PMID:26374603

Orogen-scale along-strike continuity in quartz recrystallization microstructures adjacent to the Main Central Thrust: implications for deformation temperatures, strain rates and flow stresses

NASA Astrophysics Data System (ADS)

Law, Richard

2015-04-01

Traced for ~ 1500 km along the foreland edge of the Himalaya from NW India to Bhutan published reports indicate a remarkable along-strike continuity of quartz recrystallization microstructures in the footwall and hanging wall to the Main Central Thrust (MCT). Recrystallization in Lesser Himalayan Series (LHS) rocks in the footwall to the MCT is dominated by grain boundary bulging (BLG) microstructures, while recrystallization in Greater Himalayan Series (GHS) rocks in the hanging wall is dominated by grain boundary migration microstructures that traced structurally upwards transition in to the anatectic core of the GHS. In foreland-positioned high-strain rocks adjacent to the MCT recrystallization is dominated by subgrain rotation (SGR) with transitional BLG-SGR and SGR-GBM microstructures being recorded at structural distances of up to a few hundred meters below and above the MCT, respectively. Correlation with available information on temperatures of metamorphism indicated by mineral phase equilibria and RSCM data suggests that recrystallization in the structural zones dominated by BLG, SGR and GBM occurred at temperatures of ~ 350-450, 450-550 and 550- > 650 °C, respectively. It should be kept in mind, however, that these temperatures are likely to be 'close-to-peak' temperatures of metamorphism, whereas penetrative shearing and recrystallization may have continued during cooling. The dominance of SGR along the more foreland-positioned exposures of the MCT intuitively suggests that shearing occurred under a relatively restricted range of deformation temperatures and strain rates. Plotting the 'close-to-peak' 450-500 °C temperatures of metamorphism indicated for SGR-dominated rocks located at up to a few hundred meters below/above the MCT on the quartz recrystallization map developed by Stipp et al. (2002) indicates 'ball-park' strain rates of ~ 10-13 to 10-10 sec-1. However, only strain rates slower than 10-12 sec-1 on the MCT are likely to be compatible with

Evaluating the Extent of C Cycling Through a Cold Subduction Zone: New Clues from Izu- Bonin Melt Inclusions

NASA Astrophysics Data System (ADS)

Shaw, A. M.; Hauri, E. H.; Fischer, T. P.; Hilton, D. R.

2006-05-01

Subduction zones provide our best window into C cycling processes between Earth's surface reservoirs and the mantle. The efficiency of this process can be constrained through volatile studies of melt inclusions, where measured pre-eruptive CO2 contents are combined with magma production rates to obtain an output CO2 flux. These outputs can then be compared to C inputs from the subducting slab (sedimentary, organic and altered oceanic crust) to evaluate budgets through a given arc system. Decarbonation of the various C components within a slab are strongly controlled by temperature, pressure and fluid availability. The Izu-Bonin subduction zone system is a cold subduction zone and modeled CO2 behaviour for low temperature geotherms suggest that little decarbonation would occur at subarc depths 1. However, fluids can effectively promote decarbonation. Trace element ratios of Izu arc rocks 2 predict that a significant amount of fluid is fluxed through the Izu-Bonin arc system. This study aims to evaluate the extent of C recycling through a cold, yet fluid-rich arc system. Here we report new CO2 melt inclusions abundance data from 4 volcanoes in the Izu-Bonin arc: Nijima, Oshima, Hachijojima and Aogashima. Concentrations of CO2, along with other volatiles (H2O, F, SO2, Cl), were determined using SIMS techniques at the Carnegie Institution of Washington. Various processes can modify intrinsic volatile contents such as degassing, fractional crystallization, crustal contamination and extent of melting, thereby masking true source values. CO2 contents of Izu-Bonin melt inclusions show positive trends with other volatiles (H2O and SO2) and with MgO contents (with the exception of Nijima). This indicates that differentiation and degassing have occurred simultaneously. In this case, we assume that the highest CO2 concentration samples (up to 1200 ppm CO2 from Nijima volcano) best represent pre-eruptive magma compositions. Comparing a total CO2 input of 10.35 Mmol/yr3 to our

Thermophysical Properties and Temperature of the Start of Titanium Recrystallization in Different Structural States

NASA Astrophysics Data System (ADS)

Pavlenko, D. V.; Tkach, D. V.; Danilova-Tret'yak, S. M.; Evseeva, L. E.

2017-05-01

The results of measurements of the thermal diffusivity, thermal conductivity, and heat capacity of VT1-0-grade titanium samples in as-cast, deformed submicrocrystalline, and sintered states are presented. It has been established that the decrease in the thermal conductivity and thermal diffusivity of titanium in the submicrocrystalline and sintered states is associated with the increase in the quantity of defects in the material volume, whereas the increase in the temperature of polymorphic transformation of titanium is connected with the dissolution of oxygen in its lattice. The results of investigation of the coefficient of thermal linear expansion of titanium in the macrocrystalline and submicrocrystalline states are presented. The decrease in the coefficient of thermal linear expansion of titanium of submicrocrystalline structure has been established, which may point to the decrease in its melting temperature. It is shown that annealing of samples in a submicrocrystalline state leads to the growth of the temperature coefficient of linear expansion, bringing its value closer to the temperature coefficient of linear expansion of titanium in the equilibrium state. Studies by the method of back reflection photography in a KROS chamber made it possible to estimate the temperature of the start of VT1-0-grade titanium recrystallization after intense plastic deformation by the twist extrusion method. The decrease in the temperature of the start of recrystallization for titanium in the deformed submicrocrystalline state has been established. Based on the trends revealed, optimum regimes of thermal treatment of VT1-0-grade titanium for removing internal stresses and preserving the submicrocrystalline structure have been established.

Improvement of seawater salt quality by hydro-extraction and re-crystallization methods

NASA Astrophysics Data System (ADS)

Sumada, K.; Dewati, R.; Suprihatin

2018-01-01

Indonesia is one of the salt producing countries that use sea water as a source of raw materials, the quality of salt produced is influenced by the quality of sea water. The resulting average salt quality contains 85-90% NaCl. The Indonesian National Standard (SNI) for human salt’s consumption sodium chloride content is 94.7 % (dry base) and for industrial salt 98,5 %. In this study developed the re-crystallization without chemical and hydro-extraction method. The objective of this research to choose the best methods based on efficiency. The results showed that re-crystallization method can produce salt with NaCl content 99,21%, while hydro-extraction method content 99,34 % NaCl. The salt produced through both methods can be used as a consumption and industrial salt, Hydro-extraction method is more efficient than re-crystallization method because re-crystallization method requires heat energy.

Modeling of Melt Growth During Carbothermal Processing of Lunar Regolith

NASA Technical Reports Server (NTRS)

Balasubramaniam, R.; Gokoglu S.; Hegde, U.

2012-01-01

The carbothermal processing of lunar regolith has been proposed as a means to produce carbon monoxide and ultimately oxygen to support human exploration of the moon. In this process, gaseous methane is pyrolyzed as it flows over the hot surface of a molten zone of lunar regolith and is converted to carbon and hydrogen. Carbon gets deposited on the surface of the melt, and mixes and reacts with the metal oxides in it to produce carbon monoxide that bubbles out of the melt. Carbon monoxide is further processed in other reactors downstream to ultimately produce oxygen. The amount of oxygen produced crucially depends on the amount of regolith that is molten. In this paper we develop a model of the heat transfer in carbothermal processing. Regolith in a suitable container is heated by a heat flux at its surface such as by continuously shining a beam of solar energy or a laser on it. The regolith on the surface absorbs the energy and its temperature rises until it attains the melting point. The energy from the heat flux is then used for the latent heat necessary to change phase from solid to liquid, after which the temperature continues to rise. Thus a small melt pool appears under the heated zone shortly after the heat flux is turned on. As time progresses, the pool absorbs more heat and supplies the energy required to melt more of the regolith, and the size of the molten zone increases. Ultimately, a steady-state is achieved when the heat flux absorbed by the melt is balanced by radiative losses from the surface. In this paper, we model the melting and the growth of the melt zone with time in a bed of regolith when a portion of its surface is subjected to a constant heat flux. The heat flux is assumed to impinge on a circular area. Our model is based on an axisymmetric three-dimensional variation of the temperature field in the domain. Heat transfer occurs only by conduction, and effects of convective heat transport are assumed negligible. Radiative heat loss from the

Contribution of slab melting to magmatism at the active rifts zone in the middle of the Izu-Bonin arc

NASA Astrophysics Data System (ADS)

Hirai, Y.; Okamura, S.; Sakamoto, I.; Shinjo, R.; Wada, K.; Yoshida, T.

2016-12-01

The active rifts zone lies just behind the Quaternary volcanic front in the middle of the Izu-Bonin arc. Volcanism at the active rifts zone has been active since ca. 2 Ma, and late Quaternary basaltic lavas (< 0.1 Ma) and hydrothermal activity occur along the central axis of the rifts (Taylor, 1992; Ishizuka et al., 2003). In this paper we present new Sr, Nd, and Hf isotope and trace element data for the basalts erupted in the active rifts zone, including the Aogashima, Myojin and Sumisu rifts. Two geochemical groups can be identified within the active rift basalts: High-Zr basalts (HZB) and Low-Zr basalts (LZB). In the case of the Sumisu rift, the HZB exhibits higher in K2O, Na2O, Y, Zr and Ni, and also has higher Ce/Yb and Zr/Y, lower Ba/Th than the LZB. Depletion of Zr-Hf in the N-MORB spidergram characterizes the LZB from the Aogashima, Myojin and Sumisu rifts. The 176Hf/177Hf ratios are slightly lower in the HZB than in the LZB, decoupling of 176Hf/177Hf ratios and 143Nd/144Nd ratios. Estimated primary magma compositions suggest that primary magma segregation for the HZB occurred at depths less than 70 km ( 2 GPa), whereas the LZB more than 70 km (2 3 GPa). ODP Leg126 site 788, 790, and 791 reached the basaltic basement of the Sumisu rift (Gill et al., 1992). The geochemical data and stratigraphic relations of the basement indicate that the HZB is younger than the LZB. Geochemical modelling demonstrates that slab-derived melt mixed with mantle wedge produces the observed isotopic and trace elemental characteristics. The LZB volcanism at the early stage of the back-arc rifting is best explained by a partial melting of subducted slab saturated with trace quantities of zircon under low-temperature conditions in the mantle wedge. On the other hand, the HZB requires a partial melt of subducted slab accompanied by full dissolution of zircon under high-temperature conditions in the mantle wedge, which could have been caused by hot asthenospheric injection during the

Seismic evidence for a possible deep crustal hot zone beneath Southwest Washington.

PubMed

Flinders, Ashton F; Shen, Yang

2017-08-07

Crustal pathways connecting deep sources of melt and the active volcanoes they supply are poorly understood. Beneath Mounts St. Helens, Adams, and Rainier these pathways connect subduction-induced ascending melts to shallow magma reservoirs. Petrogenetic modeling predicts that when these melts are emplaced as a succession of sills into the lower crust they generate deep crustal hot zones. While these zones are increasingly recognized as a primary site for silicic differentiation at a range of volcanic settings globally, imaging them remains challenging. Near Mount Rainier, ascending melt has previously been imaged ~28 km northwest of the volcano, while to the south, the volcano lies on the margin of a broad conductive region in the deep crust. Using 3D full-waveform tomography, we reveal an expansive low-velocity zone, which we interpret as a possible hot zone, linking ascending melts and shallow reservoirs. This hot zone may supply evolved magmas to Mounts St. Helens and Adams, and possibly Rainier, and could contain approximately twice the melt volume as the total eruptive products of all three volcanoes combined. Hot zones like this may be the primary reservoirs for arc volcanism, influencing compositional variations and spatial-segmentation along the entire 1100 km-long Cascades Arc.

Seismic evidence for a possible deep crustal hot zone beneath Southwest Washington

USGS Publications Warehouse

Flinders, Ashton; Shen, Yang

2017-01-01

Crustal pathways connecting deep sources of melt and the active volcanoes they supply are poorly understood. Beneath Mounts St. Helens, Adams, and Rainier these pathways connect subduction-induced ascending melts to shallow magma reservoirs. Petrogenetic modeling predicts that when these melts are emplaced as a succession of sills into the lower crust they generate deep crustal hot zones. While these zones are increasingly recognized as a primary site for silicic differentiation at a range of volcanic settings globally, imaging them remains challenging. Near Mount Rainier, ascending melt has previously been imaged ~28 km northwest of the volcano, while to the south, the volcano lies on the margin of a broad conductive region in the deep crust. Using 3D full-waveform tomography, we reveal an expansive low-velocity zone, which we interpret as a possible hot zone, linking ascending melts and shallow reservoirs. This hot zone may supply evolved magmas to Mounts St. Helens and Adams, and possibly Rainier, and could contain approximately twice the melt volume as the total eruptive products of all three volcanoes combined. Hot zones like this may be the primary reservoirs for arc volcanism, influencing compositional variations and spatial-segmentation along the entire 1100 km-long Cascades Arc.

Recrystallization characteristics and interfacial oxides on the compression bonding interface

NASA Astrophysics Data System (ADS)

Xie, Bijun; Sun, Mingyue; Xu, Bin; Li, Dianzhong

2018-05-01

Up to now, the mechanism of interface bonding is still not fully understood. This work presents interfacial characteristics of 316LN stainless steel bonding joint after cold compression bonding with subsequent annealing. EBSD analysis shows that fine recrystallization grains preferentially appear near the bonding interface and grow towards both sides of the interface. Transmission electron microscopy reveals that initial cold compression bonding disintegrates the native oxide scales and brings pristine metal from both sides of the interface come into intimate contact, while the broken oxide particles are remained at the original interface. The results indicate that partial bonding can be achieved by cold compression bonding with post-annealing treatment and recrystallization firstly occurs along the bonding interface. However, the interfacial oxides impede the recrystallization grains step over the interface and hinder the complete healing of the bonding interface.

Partial melting of carbonated pelite at 3-7 GPa and deep cycling of CO2 and H2O in subduction zones

NASA Astrophysics Data System (ADS)

Tsuno, K.; Dasgupta, R.; Danielson, L. R.; Righter, K.

2011-12-01

The exchange of water and carbon dioxide between the Earth's crustal rocks and the interior is important for understanding geochemical and geophysical evolution of the planet on geologic timescale. Subduction of pelitic sediments is a key mechanism for volatile introduction to the mantle but the high-pressure behavior of H2O+ CO2 bearing sediments is only constrained for alumina-rich, low-Mg# bulk compositions [1, 2]. However, the ocean-floor sediments for many subduction zones that contain both water and CO2 are alumina-poor and have higher Mg#. To constrain the melting behavior of a model alumina poor carbonated pelite, we performed new experiments. Piston cylinder (3 GPa) and multianvil (5 and 7 GPa) experiments were conducted between 800 and 1150 °C, using a model sediment composition containing 1 wt.% H2O and 5 wt.% CO2 (trace vapor-present at subsolidus conditions). The choice of the bulk composition was aimed to model the loss of siliceous hydrous fluid during the shallow part of subduction. We determined the solidus temperatures between 800 and 850 °C at 3 GPa, 900 and 950 °C at 5 GPa, and <1000 °C at 7 GPa. The subsolidus phases include cpx, garnet, coesite, rutile, phengite, and calcitess at 3 GPa, and kyanite comes in at 5 GPa. Hydrous rhyolitic silicate melt was observed at 3 GPa and up to 1150 °C. The near-solidus melt at 5-7 GPa was K-rich and calcio-carbonatitic, in contrast to the previous experimental results in alumina-rich and low Mg# bulk composition [1, 2], which showed the stability of Al-rich trachyitic silicate melt at near-solidus temperatures up to 5 GPa, and replaced by carbonate melt only at ≥5.5 GPa. Carbonate-silicate melt immiscibility was observed at 5 GPa, 1100 °C in our study. The phengite-out boundary is located between 850 and 900 °C at 3 GPa, between 1000 and 1100 °C at 5 GPa, and <1000 °C at 7 GPa. The crystalline carbonate-out boundary is between 950 and 1000 °C at 3 and 5 GPa, and <1000 °C at 7 GPa. Comparison of

Yttrium geothermometry: an approach to determine the oldest garnet growth recrystallization conditions from micaschists (Yunquera Unit, Betic Cordilleras, southern Spain

NASA Astrophysics Data System (ADS)

Esteban, J. J.; Cuevas, J.; Tubía, J. M.; Gil Ibarguchi, J. I.

2012-04-01

The garnet-xenotime geothermometry is nowadays been using as a tool to identify low-grade relic garnets and even to calculate garnet growth temperatures in metapelites that have undergone a polymetamorphic evolution (Pyle and Spear, 2000; Borghi et al., 2006). A prograde metamorphic evolution, under continuously increasing temperature, can induce garnet and accompanying phase's composition homogenization by intra-crystalline diffusion, leading to flat zoning profiles. Consequently, the application of conventional geothermobarometers on those mineral assemblages does establish minimum P-T conditions. Therefore, the less susceptible elements to diffusion processes, like trace elements, should be taken into account in order to reconstruct their metamorphic evolution. We studied a polymetamorphic micaschist recovered from the Yunquera Unit, one of the tectonic slices of the Internal Zone of the Betic Cordilleras (southern Spain) (Dürr, 1963). The Yunquera unit evidences three stages of recrystallization at different P-T conditions. According to conventional geothermobarometry (Esteban et al., 2005) the metamorphic peak, M2, is estimated at 1200-1300 MPa and 560-695 °C and the decompression path, M3, at 600 MPa and 700 °C. The lack of mineral paragenesis in apparent chemical equilibrium during M1, does not allow determining accurately its recrystallization conditions. Xenotime, identified by scanning electron microprobe, appears as matrix mineral and therefore the entire garnets are assumed to be in chemical equilibrium with it. Yttrium profiles of two garnets show a mean bell-shape compositional variation that differs significatively from the discontinuous profiles shown by Ca, Mg and Fe. This difference accounts for different diffusion rates for those elements and agree with the original Y-zoning preservation. A third Y-profile shows an oscillatory compositional variation. The internal part of garnets, bounded by sharp inclusion trails, are characterized by sawed

Effect of Sn Micro-alloying on Recrystallization Nucleation and Growth Processes of Ferritic Stainless Steels

NASA Astrophysics Data System (ADS)

He, Tong; Bai, Yang; Liu, Xiuting; Guo, Dan; Liu, Yandong

2018-04-01

We investigated the effect of Sn micro-alloying on recrystallization nucleation and growth processes of ferritic stainless steels. The as-received hot rolled sheets were cold rolled up to 80% reduction and then annealed at 740-880 °C for 5 min. The cold rolling and recrystallization microstructures and micro-textures of Sn-containing and Sn-free ferritic stainless steels were all determined by electron backscatter diffraction. Our Results show that Sn micro-alloying has important effects on recrystallization nucleation and growth processes of ferritic stainless steels. Sn micro-alloying conduces to grain fragmentation in the deformation band, more fragmented grains are existed in Sn-containing cold rolled sheets, which provides more sites for recrystallization nucleation. Sn micro-alloying also promotes recrystallization process and inhibits the growth of recrystallized grains. The recrystallization nucleation and growth mechanism of Sn-containing and Sn-free ferritic stainless steels are both characterized by orientation nucleation and selective growth, but Sn micro-alloying promotes the formation of γ-oriented grains. Furthermore, Sn micro-alloying contributes to the formation of Σ13b CSL boundaries and homogeneous γ-fiber texture. Combining the results of microstructure and micro-texture, the formability of Sn-containing ferritic stainless steels will be improved to some extent.

Ice patterns and hydrothermal plumes, Lake Baikal, Russia - Insights from Space Shuttle hand-held photography

NASA Technical Reports Server (NTRS)

Evans, Cynthia A.; Helfert, Michael R.; Helms, David R.

1992-01-01

Earth photography from the Space Shuttle is used to examine the ice cover on Lake Baikal and correlate the patterns of weakened and melting ice with known hydrothermal areas in the Siberian lake. Particular zones of melted and broken ice may be surface expressions of elevated heat flow in Lake Baikal. The possibility is explored that hydrothermal vents can introduce local convective upwelling and disrupt a stable water column to the extent that the melt zones which are observed in the lake's ice cover are produced. A heat flow map and photographs of the lake are overlaid to compare specific areas of thinned or broken ice with the hot spots. The regions of known hydrothermal activity and high heat flow correlate extremely well with circular regions of thinned ice, and zones of broken and recrystallized ice. Local and regional climate data and other sources of warm water, such as river inlets, are considered.

Numerical analysis of melt-solid interface shapes and growth rates of gallium antimonide in a single-zone vertical Bridgman furnace

NASA Astrophysics Data System (ADS)

Dutta, P. S.; Bhat, H. L.; Kumar, Vikram

1995-09-01

Numerical analysis has been carried out to determine the deviation of the growth rate from the ampoule lowering rate and the shape of the isotherms during the growth of gallium antimonide using the vertical Bridgman technique in a single-zone furnace. Electrical analogues have been used to model the thermal behaviour of the growth system. The standard circuit analysis technique has been used to calculate the temperature distribution in the growing crystal under various growth conditions. The effects of furnace temperature gradient near the melt-solid interface, the ampoule lowering rate, the ampoule geometry, the thermal conductivity of the melt, the mode of heat extraction from the tip of the ampoule and the extent of lateral heat loss from the side walls of the ampoule on the shape of isotherms in the crystal have been evaluated. The theoretical results presented here agree well with our previously obtained experimental results.

Matrix recrystallization for MALDI-MS imaging of maize lipids at high-spatial resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duenas, Maria Emilia; Carlucci, Laura; Lee, Young Jin

Matrix recrystallization is optimized and applied to improve lipid ion signals in maize embryos and leaves. A systematic study was performed varying solvent and incubation time. During this study, unexpected side reactions were found when methanol was used as a recrystallization solvent, resulting in the formation of a methyl ester of phosphatidic acid. Furthermore, using an optimum recrystallization condition with isopropanol, there is no apparent delocalization demonstrated with a transmission electron microscopy (TEM) pattern and maize leaf images obtained at 10 μm spatial resolution.

Matrix recrystallization for MALDI-MS imaging of maize lipids at high-spatial resolution

DOE PAGES

Duenas, Maria Emilia; Carlucci, Laura; Lee, Young Jin

2016-06-27

Matrix recrystallization is optimized and applied to improve lipid ion signals in maize embryos and leaves. A systematic study was performed varying solvent and incubation time. During this study, unexpected side reactions were found when methanol was used as a recrystallization solvent, resulting in the formation of a methyl ester of phosphatidic acid. Furthermore, using an optimum recrystallization condition with isopropanol, there is no apparent delocalization demonstrated with a transmission electron microscopy (TEM) pattern and maize leaf images obtained at 10 μm spatial resolution.

Matrix Recrystallization for MALDI-MS Imaging of Maize Lipids at High-Spatial Resolution

NASA Astrophysics Data System (ADS)

Dueñas, Maria Emilia; Carlucci, Laura; Lee, Young Jin

2016-09-01

Matrix recrystallization is optimized and applied to improve lipid ion signals in maize embryos and leaves. A systematic study was performed varying solvent and incubation time. During this study, unexpected side reactions were found when methanol was used as a recrystallization solvent, resulting in the formation of a methyl ester of phosphatidic acid. Using an optimum recrystallization condition with isopropanol, there is no apparent delocalization demonstrated with a transmission electron microscopy (TEM) pattern and maize leaf images obtained at 10 μm spatial resolution.

Through-thickness recrystallization characteristics of a laminated AA3xxx–AA6xxx aluminum alloy system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liao, L.H., E-mail: l2liao@uwaterloo.ca; Jin, H.; Gallerneault, M.

2015-03-15

The through-thickness annealing behavior of a laminated AA3xxx–AA6xxx alloy system at 300 °C has been studied by scanning electron microscopy, electron backscatter diffraction analysis, electron probe micro-analysis, differential scanning calorimetry, and hardness measurement. Results show that the recrystallization process starts at the interface region between the AA3xxx (clad) and AA6xxx (core) layers. Subsequently, the recrystallization process front progresses into the core layer, while the clad layer is the last region to recrystallize. It is also found that precipitation precedes recrystallization in the entire laminate at the investigated temperature. The preferential onset of recrystallization at the interface region is attributed tomore » the net driving pressure being the highest in this region. The factors that lead to such enhanced net driving pressure are (a) deformation incompatibility between the two alloy layers, (b) lower solute content of the interface, which also leads to lower volume fraction of precipitates, and (c) an accelerated rate of precipitate coarsening due to the presence of a higher density of dislocations. The gradual progress of recrystallization from the interface towards the core layer is dictated by precipitate coarsening and the dependence of its rate on the density of deformation-induced dislocations. The lower driving pressure due to lower work hardening capacity, high solute drag pressure due to Mn, and additional Zener drag from precipitates that form due to solute redistribution during annealing explain the late initiation of recrystallization in the clad layer. - Highlights: • The through-thickness recrystallization of a laminated system is investigated. • The early onset of recrystallization at the interface is discussed. • The effects of precipitation and coarsening on recrystallization are analyzed.« less

Diffusive loss of argon in response to melt vein formation in polygenetic impact melt breccias

NASA Astrophysics Data System (ADS)

Mercer, Cameron M.; Hodges, Kip V.

2017-08-01

Many planetary surfaces in the solar system have experienced prolonged bombardment. With each impact, new rocks can be assembled that incorporate freshly generated impact melts with fragments of older rocks. Some breccias can become polygenetic, containing multiple generations of impact melt products, and can potentially provide important insights into the extensive bombardment history of a region. However, the amount of chronological information that can be extracted from such samples depends on how well the mineral isotopic systems of geochronometers can preserve the ages of individual melt generations without being disturbed by younger events. We model the thermal evolution of impact melt veins and the resulting loss of Ar from K-bearing phases common in impact melt breccias to assess the potential for preserving the 40Ar/39Ar ages of individual melt generations. Our model results demonstrate that millimeter-scale, clast-free melt veins cause significant heating of adjacent host rock minerals and can cause detectable Ar loss in contact zones that are generally thinner than, and at most about the same thickness as, the vein width. The incorporation of cold clasts in melt veins reduces the magnitudes of heating and Ar loss in the host rocks, and Ar loss can be virtually undetectable for sufficiently clast-rich veins. Quantitative evidence of the timing of impacts, as measured with the 40Ar/39Ar method, can be preserved in polygenetic impact melt breccias, particularly for those containing millimeter-scale bodies of clast-bearing melt products.

FEM study of recrystallized tungsten under ELM-like heat loads

NASA Astrophysics Data System (ADS)

Du, J.; Yuan, Y.; Wirtz, M.; Linke, J.; Liu, W.; Greuner, H.

2015-08-01

FEM thermal analysis has been performed on rolled tungsten plate loaded with heat load of 23 MW/m2 for 1.5 s. Gradient temperature field is generated due to the Gaussian shape beam profile. Recrystallization and grain growth of various scales were found at different areas of the sample depending on the localized thermal field. FEM thermal-mechanical analyses have been performed on the recrystallized tungsten exposed to ELMs-like heat loads. The analyzed load conditions were 0.38 and 1.14 GW/m2 with different base temperatures. Material deterioration due to recrystallization was implemented by adopting decreased yield stress, tangent modulus, strength coefficient and ductility coefficients. Life time predicted by adopting strain life criterion indicates grain growth from 5 μm to 100 μm causes the life decrease of 80%. This result is gained by pure mathematical calculation based on the empiric assumptions of material properties.

Predicting the Kinetics of Ice Recrystallization in Aqueous Sugar Solutions

PubMed Central

2018-01-01

The quality of stored frozen products such as foods and biomaterials generally degrades in time due to the growth of large ice crystals by recrystallization. While there is ample experimental evidence that recrystallization within such products (or model systems thereof) is often dominated by diffusion-limited Ostwald ripening, the application of Ostwald-ripening theories to predict measured recrystallization rates has only met with limited success. For a model system of polycrystalline ice within an aqueous solution of sugars, we here show recrystallization rates can be predicted on the basis of Ostwald ripening theory, provided (1) the theory accounts for the fact the solution can be nonideal, nondilute and of different density than the crystals, (2) the effect of ice-phase volume fraction on the diffusional flux of water between crystals is accurately described, and (3) all relevant material properties (involving binary Fick diffusion coefficients, the thermodynamic factor of the solution, and the surface energy of ice) are carefully estimated. To enable calculation of material properties, we derive an alternative formulation of Ostwald ripening in terms of the Maxwell–Stefan instead of the Fick approach to diffusion. First, this leads to a cancellation of the thermodynamic factor (a measure for the nonideality of a solution), which is a notoriously difficult property to obtain. Second, we show that Maxwell–Stefan diffusion coefficients can to a reasonable approximation be related to self-diffusion coefficients, which are relatively easy to measure or predict in comparison to Fick diffusion coefficients. Our approach is validated for a binary system of water and sucrose, for which we show predicted recrystallization rates of ice compare well to experimental results, with relative deviations of at most a factor of 2. PMID:29651228

Predicting the Kinetics of Ice Recrystallization in Aqueous Sugar Solutions.

PubMed

van Westen, Thijs; Groot, Robert D

2018-04-04

The quality of stored frozen products such as foods and biomaterials generally degrades in time due to the growth of large ice crystals by recrystallization. While there is ample experimental evidence that recrystallization within such products (or model systems thereof) is often dominated by diffusion-limited Ostwald ripening, the application of Ostwald-ripening theories to predict measured recrystallization rates has only met with limited success. For a model system of polycrystalline ice within an aqueous solution of sugars, we here show recrystallization rates can be predicted on the basis of Ostwald ripening theory, provided (1) the theory accounts for the fact the solution can be nonideal, nondilute and of different density than the crystals, (2) the effect of ice-phase volume fraction on the diffusional flux of water between crystals is accurately described, and (3) all relevant material properties (involving binary Fick diffusion coefficients, the thermodynamic factor of the solution, and the surface energy of ice) are carefully estimated. To enable calculation of material properties, we derive an alternative formulation of Ostwald ripening in terms of the Maxwell-Stefan instead of the Fick approach to diffusion. First, this leads to a cancellation of the thermodynamic factor (a measure for the nonideality of a solution), which is a notoriously difficult property to obtain. Second, we show that Maxwell-Stefan diffusion coefficients can to a reasonable approximation be related to self-diffusion coefficients, which are relatively easy to measure or predict in comparison to Fick diffusion coefficients. Our approach is validated for a binary system of water and sucrose, for which we show predicted recrystallization rates of ice compare well to experimental results, with relative deviations of at most a factor of 2.

Record of Fluctuating Magmatic Environments, Melt Fractionation, and Mixing of Crystals: Elemental Compositions of Zircon Zones, Spirit Mountain Batholith, Nevada

NASA Astrophysics Data System (ADS)

Miller, C. F.; Claiborne, L. L.; Wooden, J. L.; Mazdab, F. K.; Walker, B. A.

2006-12-01

Spirit Mountain batholith is a large, tilted, subvolcanic intrusion in southernmost Nevada (Walker et al., in press; Lowery Claiborne et al., in press). Field relations and elemental chemistry of rocks ranging from felsic cumulates to leucogranites demonstrate both fractionation and frequent recharging. SHRIMP U-Pb analysis of zircon reveals a 2 m.y. history (17.4-15.3 Ma) for the batholith; almost all of the samples record multiple age populations. Elemental concentrations and zoning patterns document the utility of zircon in tracking magmatic environments and crystal transfer processes and provide important insights into the complex and protracted history of the batholith. The data lend strong support to the Watson et al. (2006) Ti-in-zircon thermometer. At reasonable a(TiO2) between 0.5 and 0.9, all calculated T's are consistent with petrological constraints and granite phase equilibria; using a(TiO2) = 0.7, T ranges from 675-900 C. Over this apparent T interval, which reflects a range in Ti from 3.2-34 ppm, concentrations of Hf (6000-18000 ppm), U (20-5000 ppm), and Th (50-13,000 ppm), and REE patterns all vary dramatically and systematically. Hf, U, Th, and Ce/Ce* are negatively correlated with T; LREE/MREE, MREE/HREE, and Eu/Eu* are positively correlated with T. These variations indicate that zircon preferentially incorporated Zr over Hf (hence falling Zr/Hf); U and Th behaved as strongly incompatible elements in the crystallizing assemblage as a whole; compatibility of REE increased with decreasing atomic number (effect of LREE accessories?); Eu+2 was more compatible (feldspars) and Ce+4 less compatible than equivalent +3 REE. All of these trends are consistent with the observed crystallizing assemblage and with general trends in whole rocks. More striking, however, is intrasample and intragrain variability. Although leucogranite samples have a larger proportion of zircon with compositions indicating low T and growth from fractionated melt, all samples have

Matrix Recrystallization for MALDI-MS Imaging of Maize Lipids at High-Spatial Resolution.

PubMed

Dueñas, Maria Emilia; Carlucci, Laura; Lee, Young Jin

2016-09-01

Matrix recrystallization is optimized and applied to improve lipid ion signals in maize embryos and leaves. A systematic study was performed varying solvent and incubation time. During this study, unexpected side reactions were found when methanol was used as a recrystallization solvent, resulting in the formation of a methyl ester of phosphatidic acid. Using an optimum recrystallization condition with isopropanol, there is no apparent delocalization demonstrated with a transmission electron microscopy (TEM) pattern and maize leaf images obtained at 10 μm spatial resolution. Graphical Abstract ᅟ.

Inhibition of Recrystallization of Amorphous Lactose in Nanocomposites Formed by Spray-Drying.

PubMed

Hellrup, Joel; Alderborn, Göran; Mahlin, Denny

2015-11-01

This study aims at investigating the recrystallization of amorphous lactose in nanocomposites. In particular, the focus is on the influence of the nano- to micrometer length scale nanofiller arrangement on the amorphous to crystalline transition. Further, the relative significance of formulation composition and manufacturing process parameters for the properties of the nanocomposite was investigated. Nanocomposites of amorphous lactose and fumed silica were produced by co-spray-drying. Solid-state transformation of the lactose was studied at 43%, 84%, and 94% relative humidity using X-ray powder diffraction and microcalorimetry. Design of experiments was used to analyze spray-drying process parameters and nanocomposite composition as factors influencing the time to 50% recrystallization. The spray-drying process parameters showed no significant influence. However, the recrystallization of the lactose in the nanocomposites was affected by the composition (fraction silica). The recrystallization rate constant decreased as a function of silica content. The lowered recrystallization rate of the lactose in the nanocomposites could be explained by three mechanisms: (1) separation of the amorphous lactose into discrete compartments on a micrometer length scale (compartmentalization), (2) lowered molecular mobility caused by molecular interactions between the lactose molecules and the surface of the silica (rigidification), and/or (3) intraparticle confinement of the amorphous lactose. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

On the Coupling between Recrystallization and Precipitation Following Hot Deformation in a γ-γ' Nickel-Based Superalloy

NASA Astrophysics Data System (ADS)

Seret, Anthony; Moussa, Charbel; Bernacki, Marc; Bozzolo, Nathalie

2018-06-01

Postdynamic recrystallization and γ' precipitation during cooling from γ' supersolvus temperature after hot compression were studied in the AD730 (AD730 is a trademark of Aubert et Duval Company in Paris, France) γ-γ' nickel-based superalloy. Emphasis was on not only both phenomena as distinct mechanisms but also on their mutual influence in terms of physical mechanisms. The growth of γ' precipitates is hastened in the unrecrystallized grains compared to the recrystallized ones. This could possibly be attributed to the higher dislocation content acting as high-diffusivity paths. Postdynamic recrystallization is not prevented by Smith-Zener pinning of the recrystallization front by the γ' precipitates. Instead, the recrystallization front dissolves γ' precipitates, which then reprecipitate discontinuously or continuously and coherently with the surrounding γ matrix in the recrystallized grains.

QSAR Accelerated Discovery of Potent Ice Recrystallization Inhibitors

NASA Astrophysics Data System (ADS)

Briard, Jennie G.; Fernandez, Michael; de Luna, Phil; Woo, Tom. K.; Ben, Robert N.

2016-05-01

Ice recrystallization is the main contributor to cell damage and death during the cryopreservation of cells and tissues. Over the past five years, many small carbohydrate-based molecules were identified as ice recrystallization inhibitors and several were shown to reduce cryoinjury during the cryopreservation of red blood cells (RBCs) and hematopoietic stems cells (HSCs). Unfortunately, clear structure-activity relationships have not been identified impeding the rational design of future compounds possessing ice recrystallization inhibition (IRI) activity. A set of 124 previously synthesized compounds with known IRI activities were used to calibrate 3D-QSAR classification models using GRid INdependent Descriptors (GRIND) derived from DFT level quantum mechanical calculations. Partial least squares (PLS) model was calibrated with 70% of the data set which successfully identified 80% of the IRI active compounds with a precision of 0.8. This model exhibited good performance in screening the remaining 30% of the data set with 70% of active additives successfully recovered with a precision of ~0.7 and specificity of 0.8. The model was further applied to screen a new library of aryl-alditol molecules which were then experimentally synthesized and tested with a success rate of 82%. Presented is the first computer-aided high-throughput experimental screening for novel IRI active compounds.

QSAR Accelerated Discovery of Potent Ice Recrystallization Inhibitors

PubMed Central

Briard, Jennie G.; Fernandez, Michael; De Luna, Phil; Woo, Tom. K.; Ben, Robert N.

2016-01-01

Ice recrystallization is the main contributor to cell damage and death during the cryopreservation of cells and tissues. Over the past five years, many small carbohydrate-based molecules were identified as ice recrystallization inhibitors and several were shown to reduce cryoinjury during the cryopreservation of red blood cells (RBCs) and hematopoietic stems cells (HSCs). Unfortunately, clear structure-activity relationships have not been identified impeding the rational design of future compounds possessing ice recrystallization inhibition (IRI) activity. A set of 124 previously synthesized compounds with known IRI activities were used to calibrate 3D-QSAR classification models using GRid INdependent Descriptors (GRIND) derived from DFT level quantum mechanical calculations. Partial least squares (PLS) model was calibrated with 70% of the data set which successfully identified 80% of the IRI active compounds with a precision of 0.8. This model exhibited good performance in screening the remaining 30% of the data set with 70% of active additives successfully recovered with a precision of ~0.7 and specificity of 0.8. The model was further applied to screen a new library of aryl-alditol molecules which were then experimentally synthesized and tested with a success rate of 82%. Presented is the first computer-aided high-throughput experimental screening for novel IRI active compounds. PMID:27216585

QSAR Accelerated Discovery of Potent Ice Recrystallization Inhibitors.

PubMed

Briard, Jennie G; Fernandez, Michael; De Luna, Phil; Woo, Tom K; Ben, Robert N

2016-05-24

Ice recrystallization is the main contributor to cell damage and death during the cryopreservation of cells and tissues. Over the past five years, many small carbohydrate-based molecules were identified as ice recrystallization inhibitors and several were shown to reduce cryoinjury during the cryopreservation of red blood cells (RBCs) and hematopoietic stems cells (HSCs). Unfortunately, clear structure-activity relationships have not been identified impeding the rational design of future compounds possessing ice recrystallization inhibition (IRI) activity. A set of 124 previously synthesized compounds with known IRI activities were used to calibrate 3D-QSAR classification models using GRid INdependent Descriptors (GRIND) derived from DFT level quantum mechanical calculations. Partial least squares (PLS) model was calibrated with 70% of the data set which successfully identified 80% of the IRI active compounds with a precision of 0.8. This model exhibited good performance in screening the remaining 30% of the data set with 70% of active additives successfully recovered with a precision of ~0.7 and specificity of 0.8. The model was further applied to screen a new library of aryl-alditol molecules which were then experimentally synthesized and tested with a success rate of 82%. Presented is the first computer-aided high-throughput experimental screening for novel IRI active compounds.

Recrystallization and Grain Growth Kinetics in Binary Alpha Titanium-Aluminum Alloys

NASA Astrophysics Data System (ADS)

Trump, Anna Marie

Titanium alloys are used in a variety of important naval and aerospace applications and often undergo thermomechanical processing which leads to recrystallization and grain growth. Both of these processes have a significant impact on the mechanical properties of the material. Therefore, understanding the kinetics of these processes is crucial to being able to predict the final properties. Three alloys are studied with varying concentrations of aluminum which allows for the direct quantification of the effect of aluminum content on the kinetics of recrystallization and grain growth. Aluminum is the most common alpha stabilizing alloying element used in titanium alloys, however the effect of aluminum on these processes has not been previously studied. This work is also part of a larger Integrated Computational Materials Engineering (ICME) effort whose goal is to combine both computational and experimental efforts to develop computationally efficient models that predict materials microstructure and properties based on processing history. The static recrystallization kinetics are measured using an electron backscatter diffraction (EBSD) technique and a significant retardation in the kinetics is observed with increasing aluminum concentration. An analytical model is then used to capture these results and is able to successfully predict the effect of solute concentration on the time to 50% recrystallization. The model reveals that this solute effect is due to a combination of a decrease in grain boundary mobility and a decrease in driving force with increasing aluminum concentration. The effect of microstructural inhomogeneities is also experimentally quantified and the results are validated with a phase field model for recrystallization. These microstructural inhomogeneities explain the experimentally measured Avrami exponent, which is lower than the theoretical value calculated by the JMAK model. Similar to the effect seen in recrystallization, the addition of aluminum

Grain Boundary Evolution of Cold-Rolled FePd Alloy during Recrystallization at Disordering Temperature

PubMed Central

Lin, Hung-Pin; Chen, Delphic; Kuo, Jui-Chao

2015-01-01

In this study, the grain boundary character and texture of 50% and 90% cold-rolled FePd alloy was investigated during recrystallization at 700 °C. Electron backscatter diffraction (EBSD) measurements were performed on the rolling direction to normal direction section. Kernel average misorientation (KAM) calculated from EBSD measurements was employed to determine the recrystallization fraction. The Avrami exponent n of recrystallization is 1.9 and 4.9 for 50% and 90% cold rolling, respectively. The new formation of texture reveals random texture during the recrystallization process. As annealing time increased, the number of high angle boundary (HAGB) and coincidence site lattice (CSL) increased with consumption of low angle boundary (LAGB). In addition, possible transformations between different grain boundaries are observed here.

Bioinspired Materials for Controlling Ice Nucleation, Growth, and Recrystallization.

PubMed

He, Zhiyuan; Liu, Kai; Wang, Jianjun

2018-05-15

Ice formation, mainly consisting of ice nucleation, ice growth, and ice recrystallization, is ubiquitous and crucial in wide-ranging fields from cryobiology to atmospheric physics. Despite active research for more than a century, the mechanism of ice formation is still far from satisfactory. Meanwhile, nature has unique ways of controlling ice formation and can provide resourceful avenues to unravel the mechanism of ice formation. For instance, antifreeze proteins (AFPs) protect living organisms from freezing damage via controlling ice formation, for example, tuning ice nucleation, shaping ice crystals, and inhibiting ice growth and recrystallization. In addition, AFP mimics can have applications in cryopreservation of cells, tissues, and organs, food storage, and anti-icing materials. Therefore, continuous efforts have been made to understand the mechanism of AFPs and design AFP inspired materials. In this Account, we first review our recent research progress in understanding the mechanism of AFPs in controlling ice formation. A Janus effect of AFPs on ice nucleation was discovered, which was achieved via selectively tethering the ice-binding face (IBF) or the non-ice-binding face (NIBF) of AFPs to solid surfaces and investigating specifically the effect of the other face on ice nucleation. Through molecular dynamics (MD) simulation analysis, we observed ordered hexagonal ice-like water structure atop the IBF and disordered water structure atop the NIBF. Therefore, we conclude that the interfacial water plays a critical role in controlling ice formation. Next, we discuss the design and fabrication of AFP mimics with capabilities in tuning ice nucleation and controlling ice shape and growth, as well as inhibiting ice recrystallization. For example, we tuned ice nucleation via modifying solid surfaces with supercharged unfolded polypeptides (SUPs) and polyelectrolyte brushes (PBs) with different counterions. We found graphene oxide (GO) and oxidized quasi

Changes in DOM Character and Composition during Spring Snow Melt in the Jemez River Basin Critical Zone Observatory.

NASA Astrophysics Data System (ADS)

Thompson, M.; Olshansky, Y.; Chorover, J.

2017-12-01

Dynamics of dissolved organic matter (DOM) in stream waters are important indicators of internal processes in the critical zone, such as decomposition and mobilization of soil organic matter, hydrologic flow paths, potential for metal mobilization and nutrient redistribution. Previous studies indicate that DOM concentration was highest during peak snow melt in the La Jara catchment located in the Jemez River Basin Critical Zone Observatory (Perdrial et al., 2014). We postulate that the molecular composition and character of DOM changes with the advance of spring snow melt. Water samples were collected from two flumes located at the outlets of the La Jara Creek and from a zero order basin within this catchment through the spring snowmelt from March 1 to May 15 2017. DOM concentration increased with stream discharge. Quantification of molecular changes was conducted using Fourier transform infrared spectroscopy (FTIR), which showed the variation in carboxyl abundance (wavenumbers 1680, 1600 and 1410 cm-1) correlated with dissolved organic carbon concentration, indicating that this component is relatively a constant fraction of the organic carbon exported through the stream during spring snowmelt. In contrast, amide vibrations (3550, 1640 and 670 cm-1) were shown to decrease with the advance of spring snowmelt. This trend further corresponded to a decrease in the ratio of carboxylic acid (above) to aromatic (1622, 1490, 955 cm-1) moieties, suggesting either a flush of compounds accumulated prior to spring snow melt, or increased decomposition of plant derived material in the soil that was then transported to the stream. Aliphatic components (2965, 2925 and 2865 cm-1) decreased from the beginning to the middle of sampling period, then showed an increase toward the end of snowmelt. O-Alkyl peak (1150 and 1073 cm-1) varied without a clear trend during the spring snowmelt. These changes in O-Alkyl and aliphatic compounds may be related to microbial derived compounds and

Analysis of Particle-Stimulated Nucleation (PSN)-Dominated Recrystallization for Hot-Rolled 7050 Aluminum Alloy

NASA Astrophysics Data System (ADS)

Adam, Khaled F.; Long, Zhengdong; Field, David P.

2017-04-01

In 7xxx series aluminum alloys, the constituent large and small second-phase particles present during deformation process. The fraction and spatial distribution of these second-phase particles significantly influence the recrystallized structure, kinetics, and texture in the subsequent treatment. In the present work, the Monte Carlo Potts model was used to model particle-stimulated nucleation (PSN)-dominated recrystallization and grain growth in high-strength aluminum alloy 7050. The driving force for recrystallization is deformation-induced stored energy, which is also strongly affected by the coarse particle distribution. The actual microstructure and particle distribution of hot-rolled plate were used as an initial point for modeling of recrystallization during the subsequent solution heat treatment. Measurements from bright-field TEM images were performed to enhance qualitative interpretations of the developed microstructure. The influence of texture inhomogeneity has been demonstrated from a theoretical point of view using pole figures. Additionally, in situ annealing measurements in SEM were performed to track the orientational and microstructural changes and to provide experimental support for the recrystallization mechanism of PSN in AA7050.

Metadynamic and static recrystallization softening behavior of a bainite steel

NASA Astrophysics Data System (ADS)

Li, Lixin; Zheng, Liangyu; Ye, Ben; Tong, Zeqiong

2018-01-01

The metadynamic recrystallization (MDRX) and static recrystallization (SRX) softening behavior of a bainite steel was investigated by two-pass isothermal compression experiments at temperatures of 1173, 1273, 1373, and 1473 K and strain rates of 0.01, 0.1, 1, and 10 s-1 with inter-pass times of 1, 5, 10, and 30 s on a Gleeble-1500 thermo-mechanical simulator. Kinetic equations were developed to evaluate the softening fractions caused by MDRX and SRX. A comparison between the experimental and predicted softening fractions showed that the proposed kinetic equations can provide a precise estimation of the MDRX and SRX behavior of the studied steel. The results based on the kinetic equations indicated that the MDRX and SRX softening fraction increases with the increase in strain rate, deformation temperature, inter-pass time, and pre-strain; the activation energy of MDRX is much smaller than that of SRX; and the no-recrystallization temperature of the investigated steel is 1179.4 K.

Quarzt Fabric Insights Across a Low P-High T Shear Zone

NASA Astrophysics Data System (ADS)

Gomez Barreiro, J.; Martinez-Catalan, J. R.; Benitez Perez, J.; Wenk, H.; Vogel, S. C.; Alcock, J. E.

2013-12-01

The evolution of mylonitic fabric in quartzites across a Low-P / High-T gradient within the Lugo Dome Extensional system (NW Spain) is analyzed. Quantitative texture measurements with TOF neutron diffraction, Shape preferred orientation (SPO) and Crystal Size Distribution (CSD) analyses were correlated with tectonothermal data to constraint the prevalence of ductile deformative fabrics exposed to cycles of dynamic and static recrystallization. Results suggest two stages in the evolution of mylonites in close correlation to thermal gradient, 1) a pervasive ductile deformation affecting most of the shear zone volume, with the development of symmetric cross girdle c-axes fabric suggesting slip on {c,r,m} and dynamically recrystallized microstructures which resulted into the refinement of the grain-size. 2) An heterogeneous deformation stage where strain partition led to the formation of relatively active and passive domains. During this late stage, at deeper levels, High T detachments show [c]{m} slip system and dynamic recrystallization activation, with monoclinic texture patterns, meanwhile, passive domains followed an static recrystallization with abnormal grain growth and minor variation of early orthogonal texture patterns Neutron diffraction data (cross) and Rietveld model obtained with MAUD (solid line) of a mylonitic quartzite. Some important planes are indicated for the major phases.

Submarine melt rates under Greenland's ice tongues

NASA Astrophysics Data System (ADS)

Wilson, Nat; Straneo, Fiametta; Heimbach, Patrick; Cenedese, Claudia

2017-04-01

The few remaining ice tongues (ice-shelf like extensions) of Greenland's glaciers are undergoing rapid changes with potential implications for the stability of the ice sheet. Submarine melting is recognized as a major contributor to mass loss, yet the magnitude and spatial distribution of melt are poorly known or understood. Here, we use high resolution satellite imagery to infer the magnitude and spatial variability of melt rates under Greenland's largest remaining ice tongues: Ryder Glacier, Petermann Glacier and Nioghalvfjerdsbræ (79 North Glacier). We find that submarine plus aerial melt approximately balance the ice flux from the grounded ice sheet for the first two while at Nioghalvfjerdsbræ the total melt flux exceeds the inflow of ice indicating thinning of the ice tongue. We also show that melt rates under the ice tongues vary considerably, exceeding 60 m yr-1 near the grounding zone and decaying rapidly downstream. Channels, likely originating from upstream subglacial channels, give rise to large melt variations across the ice tongues. Using derived melt rates, we test simplified melt parameterizations appropriate for ice sheet models and find the best agreement with those that incorporate ice tongue geometry in the form of depth and slope.

Improvement of physicomechanical properties of carbamazepine by recrystallization at different pH values.

PubMed

Javadzadeh, Yousef; Mohammadi, Ameneh; Khoei, Nazaninossadat Seyed; Nokhodchi, Ali

2009-06-01

The morphology of crystals has an appreciable impact role on the physicochemical properties of drugs. Drug properties such as flowability, dissolution, hardness and bioavailability may be affected by crystallinity behaviours of drugs. The objective of this study was to achieve an improved physicomechanical property of carbamazepine powder through recrystallization from aqueous solutions at different pH values. For this purpose, carbamazapine was recrystallized from aqueous solutions at different pH values (1, 7, 11). The morphology of crystals was investigated using scanning electron microscopy; X-ray powder diffraction (XRPD) was used to identify polymorphism; thermodynamic properties were analyzed using differential scanning calorimetery (DSC). Dissolution rate was determined using USP dissolution apparatus. Mechanical behavior of recrystallized carbamazepine powders was investigated by making tablets under different compaction pressure and measuring their hardness. SEM studies showed that the carbamazepine crystallization in different media affected the morphology and size of carbamazepine crystals. The shape of carbamazepine crystals changed from flaky or thin plate-like to needle shape. XRPD and DSC results ruled out any crystallinity changes occurring due to the temperature during recrystallization procedure or pH of crystallization media. The crushing strength of tablets indicated that all of the recrystallized carbamazepine samples had better compactiblity than the original carbamazepine powder. In vitro dissolution studies of carbamazepine samples showed a higher dissolution rate for carbamazepine crystals obtained from media with pH 11 and 1. Carbamazepine particles recrystallized from aqueous solutions of different pH values (all media) appeared to have superior mechanical properties to those of the original carbamazepine sample.

Two-step recrystallization of water in concentrated aqueous solution of poly(ethylene glycol).

PubMed

Gemmei-Ide, Makoto; Motonaga, Tetsuya; Kasai, Ryosuke; Kitano, Hiromi

2013-02-21

Crystallization behavior of water in a concentrated aqueous solution of poly(ethylene glycol) (PEG) with a water content of 37.5 wt % was investigated by temperature variable mid-infrared (mid-IR) spectroscopy in a temperature range of 298-170 K. The mid-IR spectrum of water at 298 K showed that a large water cluster was not formed and that most of the water molecules were associated with the PEG chain. Ice formation, however, occurred as found in previous studies by differential scanning calorimetory. Ice formations were grouped into three types: crystallization at 231 K during cooling, that at 198 K during heating, and that at 210 K during heating. The latter two were just recrystallization. These ice formations were the direct transition from hydration species to ice without condensation regardless of crystallization or recrystallization. This means that the recrystallized water in the present system was not generated from low-density amorphous solid water. At a low cooling rate, nearly complete crystallization at 231 K during cooling and no recrystallization were observed. At a high cooling rate, no crystallization and two-step recrystallization at 198 and 210 K were observed. The former and latter recrystallizations were found to be generated from water associated with the PEG chains with ttg (the sequence -O-CH(2)-CH(2)-O- having a trans (t) conformation about the -C-O- bond and a gauche (g) conformation about the -C-C- bond) and random conformations, respectively. These results indicate that recrystallizable water does not have a single specific water structure.

Experiments on transient melting of tungsten by ELMs in ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Krieger, K.; Balden, M.; Coenen, J. W.; Laggner, F.; Matthews, G. F.; Nille, D.; Rohde, V.; Sieglin, B.; Giannone, L.; Göths, B.; Herrmann, A.; de Marne, P.; Pitts, R. A.; Potzel, S.; Vondracek, P.; ASDEX-Upgrade Team; EUROfusion MST1 Team

2018-02-01

Repetitive melting of tungsten by power transients originating from edge localized modes (ELMs) has been studied in ASDEX Upgrade. Tungsten samples were exposed to H-mode discharges at the outer divertor target plate using the divertor manipulator II (DIM-II) system (Herrmann et al 2015 Fusion Eng. Des. 98-9 1496-9). Designed as near replicas of the geometries used also in separate experiments on the JET tokamak (Coenen et al 2015 J. Nucl. Mater. 463 78-84 Coenen et al 2015 Nucl. Fusion 55 023010; Matthews et al 2016 Phys. Scr. T167 7), the samples featured a misaligned leading edge and a sloped ridge respectively. Both structures protrude above the default target plate surface thus receiving an increased fraction of the parallel power flux. Transient melting by ELMs was induced by moving the outer strike point to the sample location. The temporal evolution of the measured current flow from the samples to vessel potential confirmed transient melting. Current magnitude and dependency from surface temperature provided strong evidence for thermionic electron emission as main origin of the replacement current driving the melt motion. The different melt patterns observed after exposures at the two sample geometries support the thermionic electron emission model used in the MEMOS melt motion code, which assumes a strong decrease of the thermionic net current at shallow magnetic field to surface angles (Pitts et al 2017 Nucl. Mater. Energy 12 60-74). Post exposure ex situ analysis of the retrieved samples show recrystallization of tungsten at the exposed surface areas to a depth of up to several mm. The melt layer transport to less exposed surface areas leads to ratcheting pile up of re-solidified debris with zonal growth extending from the already enlarged grains at the surface.

Investigation of the Atypical Glass Transition and Recrystallization Behavior of Amorphous Prazosin Salts

PubMed Central

Kumar, Lokesh; Popat, Dharmesh; Bansal, Arvind K.

2011-01-01

This manuscript studied the effect of counterion on the glass transition and recrystallization behavior of amorphous salts of prazosin. Three amorphous salts of prazosin, namely, prazosin hydrochloride, prazosin mesylate and prazosin tosylate were prepared by spray drying, and characterized by optical-polarized microscopy, differential scanning calorimetry and powder X-ray diffraction. Modulated differential scanning calorimetry was used to determine the glass transition and recrystallization temperature of amorphous salts. Glass transition of amorphous salts followed the order: prazosin mesylate > prazosin tosylate ∼ prazosin hydrochloride. Amorphous prazosin mesylate and prazosin tosylate showed glass transition, followed by recrystallization. In contrast, amorphous prazosin hydrochloride showed glass transition and recrystallization simultaneously. Density Functional Theory, however, suggested the expected order of glass transition as prazosin hydrochloride > prazosin mesylate > prazosin tosylate. The counterintuitive observation of amorphous prazosin hydrochloride having lower glass transition was explained in terms of its lower activation energy (206.1 kJ/mol) for molecular mobility at Tg, compared to that for amorphous prazosin mesylate (448.5 kJ/mol) and prazosin tosylate (490.7 kJ/mol), and was further correlated to a difference in hydrogen bonding strength of the amorphous and the corresponding recrystallized salts. This study has implications in selection of an optimal amorphous salt form for pharmaceutical development. PMID:24310595

Investigation of the atypical glass transition and recrystallization behavior of amorphous prazosin salts.

PubMed

Kumar, Lokesh; Popat, Dharmesh; Bansal, Arvind K

2011-08-25

This manuscript studied the effect of counterion on the glass transition and recrystallization behavior of amorphous salts of prazosin. Three amorphous salts of prazosin, namely, prazosin hydrochloride, prazosin mesylate and prazosin tosylate were prepared by spray drying, and characterized by optical-polarized microscopy, differential scanning calorimetry and powder X-ray diffraction. Modulated differential scanning calorimetry was used to determine the glass transition and recrystallization temperature of amorphous salts. Glass transition of amorphous salts followed the order: prazosin mesylate > prazosin tosylate ~ prazosin hydrochloride. Amorphous prazosin mesylate and prazosin tosylate showed glass transition, followed by recrystallization. In contrast, amorphous prazosin hydrochloride showed glass transition and recrystallization simultaneously. Density Functional Theory, however, suggested the expected order of glass transition as prazosin hydrochloride > prazosin mesylate > prazosin tosylate. The counterintuitive observation of amorphous prazosin hydrochloride having lower glass transition was explained in terms of its lower activation energy (206.1 kJ/mol) for molecular mobility at Tg, compared to that for amorphous prazosin mesylate (448.5 kJ/mol) and prazosin tosylate (490.7 kJ/mol), and was further correlated to a difference in hydrogen bonding strength of the amorphous and the corresponding recrystallized salts. This study has implications in selection of an optimal amorphous salt form for pharmaceutical development.

The deformation record of olivine in mylonitic peridotites from the Finero Complex, Ivrea Zone: Separate deformation cycles during exhumation

NASA Astrophysics Data System (ADS)

Matysiak, Agnes K.; Trepmann, Claudia A.

2015-12-01

Mylonitic peridotites from the Finero complex are investigated to detect characteristic olivine microfabrics that can resolve separate deformation cycles at different metamorphic conditions. The heterogeneous olivine microstructures are characterized by deformed porphyroclasts surrounded by varying amounts of recrystallized grains. A well-developed but only locally preserved foam structure is present in recrystallized grain aggregates. This indicates an early stage of dynamic recrystallization and subsequent recovery and recrystallization at quasi-static stress conditions, where the strain energy was reduced such that a reduction in surface energy controlled grain boundary migration. Ultramylonites record a renewed stage of localized deformation and recrystallization by a second generation of recrystallized grains that do not show a foam structure. This second generation of recrystallized grains as well as sutured grain and kink band boundaries of porphyroclasts indicate that these microstructures developed during a stage of localized deformation after development of the foam structure. The heterogeneity of the microfabrics is interpreted to represent several (at least two) cycles of localized deformation separated by a marked hiatus with quasi-static recrystallization and recovery and eventually grain growth. The second deformation cycle did not only result in reactivation of preexisting shear zones but instead also locally affected the host rock that was not deformed in the first stage. Such stress cycles can result from sudden increases in differential stress imposed by seismic events, i.e., high stress-loading rates, during exhumation of the Finero complex.

Paradise Lost: Uncertainties in melting and melt extraction processes beneath oceanic spreading ridges

NASA Astrophysics Data System (ADS)

Kelemen, P. B.

2014-12-01

In many ways, decompression melting and focused melt transport beneath oceanic spreading ridges is the best understood igneous process on Earth. However, there are remaining - increasing - uncertainties in interpreting residual mantle peridotites. Indicators of degree of melting in residual peridotite are questionable. Yb concentration and spinel Cr# are affected by (a) small scale variations in reactive melt transport, (b) variable extents of melt extraction, and (c) "impregnation", i.e. partial crystallization of cooling melt in pore space. Roughly 75% of abyssal peridotites have undergone major element refertilization. Many may have undergone several melting events. The following three statements are inconsistent: (1) Peridotite melt productivity beyond cpx exhaustion is > 0.1%/GPa. (2) Crustal thickness is independent of spreading rate at rates > 2 cm/yr full rate (excluding ultra-slow spreading ridges). (3) Thermal models predict, and observations confirm, thick thermal boundary layers beneath slow spreading ridges. If (a) melt productivity is << 0.1%/GPa beyond cpx-out, and (b) cpx-out occurs > 15 km below the seafloor beneath most ridges, then the independence of crustal thickness with spreading rate can be understood. Most sampled peridotites from ridges melted beyond cpx-out. Cpx in these rocks formed via impregnation and/or exsolution during cooling. Most peridotites beneath ridges may undergo cpx exhaustion during decompression melting. This would entail an upward modification of potential temperature estimates. Alternatively, perhaps oceanic crustal thickness does vary with spreading rate but this is masked by complicated tectonics and serpentinization at slow-spreading ridges. Dissolution channels (dunites) are predicted to coalesce downstream, but numerical models of these have not shown why > 95% of oceanic crust forms in a zone < 5 km wide. There may be permeability barriers guiding deeper melt toward the ridge, but field studies have not identified

[Investigation of the recrystallization of trehalose as a good glass-former excipient].

PubMed

Katona, Gábor; Orsolya, Jójártné Laczkovich; Szabóné, Révész Piroska

2014-01-01

An amorphous form of trehalose is easy to prepare by using a solvent method. The recrystallization kinetics can be followed well, which is important because of the occurrence of polymorphic forms of trehalose. This is especially significant in the case of dry powder inhalers. Spray-drying was used as a preparation method this being one of the most efficient technologies with which to obtain an amorphous form. This method can result in the required particle size and a monodisperse distribution with excellent flowability and with moreover considerable amorphization. In our work, trehalose was applied as a technological auxiliary agent, and literature data relating to the spray-drying technology of trehalose were collected. Studies were made of the influence of the spraying process on the amorphization of trehalose and on the recrystallization of amorphous trehalose during storage. Amorphous samples were investigated under 3 different conditions during 3 months. The recrystallization process was followed by differential scanning calorimetry and X-ray powder diffraction. The results demonstrated the perfect amorphization of trehalose during the spray-drying process. The glass transition temperature was well measurable in the samples and proved to be the same as the literature data. Recrystallization under normal conditions was very slow but at high relative humidity the process was accelerated greatly. Amorphous trehalose gave rise to dihydrate forms (gamma- and h-trehaloses) during recrystallization, and beta-trehalose was also identified as an anhydrous form.

Recrystallization of freezable bound water in aqueous solutions of medium concentration

NASA Astrophysics Data System (ADS)

Lishan, Zhao; Liqing, Pan; Ailing, Ji; Zexian, Cao; Qiang, Wang

2016-07-01

For aqueous solutions with freezable bound water, vitrification and recrystallization are mingled, which brings difficulty to application and misleads the interpretation of relevant experiments. Here, we report a quantification scheme for the freezable bound water based on the water-content dependence of glass transition temperature, by which also the concentration range for the solutions that may undergo recrystallization finds a clear definition. Furthermore, we find that depending on the amount of the freezable bound water, different temperature protocols should be devised to achieve a complete recrystallization. Our results may be helpful for understanding the dynamics of supercooled aqueous solutions and for improving their manipulation in various industries. Project supported by the Knowledge Innovation Project of Chinese Academy of Sciences on Water Science Research (Grant No. KJZD-EW-M03) and the National Natural Science Foundation of China (Grant Nos. 11474325 and 11290161).

Lower continental crust formation through focused flow in km-scale melt conduits: The zoned ultramafic bodies of the Chilas Complex in the Kohistan island arc (NW Pakistan)

NASA Astrophysics Data System (ADS)

Jagoutz, O.; Müntener, O.; Burg, J.-P.; Ulmer, P.; Jagoutz, E.

2006-02-01

Whole-rock and Sm-Nd isotopic data of the main units of the Chilas zoned ultramafic bodies (Kohistan paleo-island arc, NW Pakistan) indicate that ultramafic rocks and gabbronorite sequences stem from a common magma. However, field observations rule out formation of both ultramafic and mafic sequences in terms of gravitational crystal settling in a large magma chamber. Contacts between ultramafic and gabbronorite sequences show emplacement of the dunitic bodies into a semi-consolidated gabbronoritic crystal-mush, which in turn has intruded and reacted with the ultramafic rocks to produce concentric zoning. Field and petrological observations indicate a replacive origin of the dunite. Bulk Mg#'s of dunitic rocks range from 0.87-0.81 indicating that the dunite-forming melt underwent substantial fractionation-differentiation and that percolative fractional crystallization probably generated the dunitic core. The REE chemistry of clinopyroxene in primitive dunite samples and the Nd isotopic composition of ultramafic rocks are in equilibrium with the surrounding gabbronorite. Accordingly, liquids that formed the dunitic rocks and later the mafic sequence derived from a similar depleted source ( ɛNd˜4.8). We propose a mechanism for the comagmatic emplacement, where km-scale ultramafic bodies represent continuous channels reaching down into the upper mantle. The melt-filled porosity in these melt channels diminishes the mean-depth-integrated density difference to the surrounding rocks. Due to buoyancy forces, melt channels raise into the overlying crustal sequence. In the light of such processes, the ultramafic bodies are interpreted as melt channels through which the Chilas gabbronorite sequence was fed. The estimated basaltic-andesitic, low Mg# (˜0.53) bulk composition of the Chilas gabbronorite sequence closely matches estimates of lower crustal compositions. Since the mafic sequence originated from a primary, high Mg# (> 0.7) basaltic arc magma, differentiation of

Oman Drilling Project GT3 site survey: dynamics at the roof of an oceanic magma chamber

NASA Astrophysics Data System (ADS)

France, L.; Nicollet, C.; Debret, B.; Lombard, M.; Berthod, C.; Ildefonse, B.; Koepke, J.

2017-12-01

Oman Drilling Project (OmanDP) aims at bringing new constraints on oceanic crust accretion and evolution by drilling Holes in the whole ophiolite section (mantle and crust). Among those, operations at GT3 in the Sumail massif drilled 400 m to sample the dike - gabbro transition that corresponds to the top (gabbros) and roof (dikes) of the axial magma chamber, an interface where hydrothermal and magmatic system interacts. Previous studies based on oceanic crust formed at present day fast-spreading ridges and preserved in ophiolites have highlighted that this interface is a dynamic horizon where the axial melt lens that top the main magma chamber can intrude, reheat, and partially assimilate previously hydrothermally altered roof rocks. Here we present the preliminary results obtained in GT3 area that have allowed the community to choose the drilling site. We provide a geological and structural map of the area, together with new petrographic and chemical constraints on the dynamics of the dike - gabbro transition. Our new results allow us to quantify the dynamic processes, and to propose that 1/ the intrusive contact of the varitextured gabbro within the dikes highlights the intrusion of the melt lens top in the dike rooting zone, 2/ both dikes and previously crystallized gabbros are reheated, and recrystallized by underlying melt lens dynamics (up to 1050°C, largely above the hydrous solidus temperature of altered dikes and gabbros), 3/ the reheating range can be > 200°C, 4/ the melt lens depth variations for a given ridge position is > 200m, 5/ the reheating stage and associated recrystallization within the dikes occurred under hydrous conditions, 6/ the reheating stage is recorded at the root zone of the sheeted dike complex by one of the highest stable conductive thermal gradient ever recorded on Earth ( 3°C/m), 7/ local chemical variations in recrystallized dikes and gabbros are highlighted and used to quantify crystallization and anatectic processes, and the

Slip Zone versus Damage Zone Micromechanics, Arima-Takasuki Tectonic Line, Japan

NASA Astrophysics Data System (ADS)

White, J. C.; Lin, A.

2017-12-01

The Arima-Takasuki Tectonic Line (ATTL) of southern Honshu, Japan is defined by historically active faults and multiple splays producing M7 earthquakes. The damage zone of the ATTL comprises a broad zone of crushed, comminuted and pulverized granite/rhyolite1,2containing cm-scale slip zones and highly comminuted injection veins. In this presentation, prior work on the ATTL fault rocks is extending to include microstructural characterization by transmission electron microscopy (TEM) from recent trenching of the primary slip zone, as well as secondary slip zones. This is necessary to adequately characterize the extremely fine-grained material (typically less than 1mm) in both damage and core zones. Damage zone material exhibits generally random textures3 whereas slip zones are macroscopically foliated, and compositionally layered, notwithstanding a fairly homogeneous protolith. The latter reflects fluid-rock interaction during both coseismic and interseismic periods. The slip zones are microstructurally heterogeneous at all scales, comprising not only cataclasites and phyllosilicate (clay)-rich gouge zones, but Fe/Mn pellets or clasts that are contained within gouge. These structures appear to have rolled and would suggest rapid recrystallization and/or growth. A central question related to earthquake recurrence along existing faults is the nature of the gouge. In both near-surface exposures and ongoing drilling at depth, "plastic" or "viscous" gouge zones comprise ultra-fine-grained clay-siliciclastic particles that would not necessarily respond in a simple frictional manner. Depending on whether the plastic nature of these slip zones develops during or after slip, subsequent focusing of slip within them could be complicated. 1 Mitchell, T.A., Ben-Zion, Y., Shimamoto, T., 2011. Ear. Planet. Sci. Lett. 308, 284-297. 2 Lin, A., Yamashita, K, Tanaka, M. J., 2013. Struc. Geol. 48, 3-13. 3 White, J.C., Lin, A. 2016. Proc. AGU Fall Mtg., T42-02 San Francisco.

New thermoresistant polymorph from CO2 recrystallization of minocycline hydrochloride.

PubMed

Rodrigues, Miguel A; Tiago, João M; Padrela, Luis; Matos, Henrique A; Nunes, Teresa G; Pinheiro, Lídia; Almeida, António J; de Azevedo, Edmundo Gomes

2014-11-01

To prepare and thoroughly characterize a new polymorph of the broad-spectrum antibiotic minocycline from its hydrochloride dehydrate salts. The new minocycline hydrochloride polymorph was prepared by means of the antisolvent effect caused by carbon dioxide. Minocycline recrystallized as a red crystalline hydrochloride salt, starting from solutions or suspensions containing CO2 and ethanol under defined conditions of temperature, pressure and composition. This novel polymorph (β-minocycline) revealed characteristic PXRD and FTIR patterns and a high melting point (of 247 ºC) compared to the initial minocycline hydrochloride hydrates (α-minocycline). Upon dissolution the new polymorph showed full anti-microbial activity. Solid-state NMR and DSC studies evidenced the higher chemical stability and crystalline homogeneity of β-minocycline compared to the commercial chlorohydrate powders. Molecular structures of both minocyclines present relevant differences as shown by multinuclear solid-state NMR. This work describes a new crystalline structure of minocycline and evidences the ability of ethanol-CO2 system in removing water molecules from the crystalline structure of this API, at modest pressure, temperature and relatively short time (2 h), while controlling the crystal habit. This process has therefore the potential to become a consistent alternative towards the control of the solid form of APIs.

ALHA 81011 -- an eucritic impact melt breccia formed 350 m.y. ago

NASA Astrophysics Data System (ADS)

Metzler, K.; Bobe, K. D.; Kunz, J.; Palme, H.; Spettel, B.; Stoeffler, D.

1994-07-01

The ALHA 81011 meteorite has been described as a eucritic breccia consisting of mineral and lithic clasts embedded in a vesicular, dark glassy matrix. Lithic clasts are equilibrated and dominated by subophitic and granulitic texture, frequently with gradual textural transitions in a given clast. Both mineral and lithic clasts were shocked in excess of approximately 30 GPa, transforming plagioclase into maskelynite, followed by thermally induced recrystallization. The observation that plagioclase fragments are 'swirled' into the dark matrix leaving pyroxene fragments unaffected, indicates that the plagioclase fragments were transformed into maskelynite prior to admixing as well. Scanning Electron Microscopy (SEM) investigations revealed that the dark matrix represents a quenched melt with eutectic fabric consisting of parallel intergrowths of pyroxene and plagioclase crystals, interspersed with small vesicles and larger subangular cavities up to 0.6 cm. One basalt clast with a partly granulitic texture and a portion of the dark crystallized matrix were separated and analyzed by Instrumental Neutron Activation Analysis (INAA). We performed age determinations on the separated lithologies by applying the Ar-40/AR-39 method. ALHA 81011 represents a clast-rich eucritic impact melt breccia not older than 350 Ma. It was either part of a rapidly cooled larger impact melt formation or represents a melt 'bomb' that originates from a suevitic ejecta blanket formed by a large-scale impact on the Howardite Eucritic and Diogenite (HED) parent body surface.

Evaporation-induced gas-phase flows at selective laser melting

NASA Astrophysics Data System (ADS)

Zhirnov, I.; Kotoban, D. V.; Gusarov, A. V.

2018-02-01

Selective laser melting is the method for 3D printing from metals. A solid part is built from powder layer-by-layer. A continuum-wave laser beam scans every powder layer to fuse powder. The process is studied with a high-speed CCD camera at the frame rate of 104 fps and the resolution up to 5 µm per pixel. Heat transfer and evaporation in the laser-interaction zone are numerically modeled. Droplets are ejected from the melt pool in the direction around the normal to the melt surface and the powder particles move in the horizontal plane toward the melt pool. A vapor jet is observed in the direction of the normal to the melt surface. The velocities of the droplets, the powder particles, and the jet flow and the mass loss due to evaporation are measured. The gas flow around the vapor jet is calculated by Landau's model of submerged jet. The measured velocities of vapor, droplets, and powder particles correlate with the calculated flow field. The obtained results show the importance of evaporation and the flow of the vapor and the ambient gas. These gas-dynamic phenomena can explain the formation of the denudated zones and the instability at high-energy input.

Effect of Prestraining of Recrystallization Temperature and Mechanical Properties of Commercial, Sintered, Wrought Molybdenum

NASA Technical Reports Server (NTRS)

Dike, Kenneth C; Long, Roger A

1953-01-01

Given three presumably identical lots of commercial, sintered, wrought molybdenum, the 1-hour recrystallization temperature of one lot remained above 2900 F by limiting the amount of effective restraining to 35 percent or less. Different recrystallization temperatures were obtained in various atmospheres, the highest in argon and the lowest in hydrogen. Metal thus fabricated and then stress-relieved possessed an ultimate tensile strength at room temperature within 10 percent of metal swaged 99 percent and also possessed equivalent ductility. At 1800 F, equivalent strength and ductility was obtained irrespective of the amount of swaging over the range of 10 to 99 percent. The amount of swaging greatly influenced the recrystallized grain size but the difference in grain size is not the major controlling factor which determines whether recrystallized molybdenum is ductile or brittle at room temperature.

CO2 solubility and speciation in rhyolitic sediment partial melts at 1.5-3.0 GPa - Implications for carbon flux in subduction zones

NASA Astrophysics Data System (ADS)

Duncan, Megan S.; Dasgupta, Rajdeep

2014-01-01

much as 2.6-5.5 wt.% CO2 to the sub-arc mantle source regions. At saturation, 1.6-3.3 wt.% sediment partial melt relative to the mantle wedge is therefore sufficient to bring up the carbon budget of the mantle wedge to produce primary arc basalts with 0.3 wt.% CO2. Sediment plumes in mantle wedge: Sediment plumes or diapirs may form from the downgoing slab because the sediment layer atop the slab is buoyant relative to the overlying, hanging wall mantle (Currie et al., 2007; Behn et al., 2011). Via this process, sediment layers with carbonates would carry CO2 to the arc source region. Owing to the higher temperature in the mantle wedge, carbonate can breakdown. Behn et al. (2011) suggested that sediment layers as thin as 100 m, appropriate for modern arcs, could form sediment diapirs. They predicted that diapirs would form from the slab in the sub-arc region for most subduction zones today without requiring hydrous melting. H2O-rich fluid driven carbonate breakdown: Hydrous fluid flushing of the slab owing to the breakdown of hydrous minerals could drive carbonate breakdown (Kerrick and Connolly, 2001b; Grove et al., 2002; Gorman et al., 2006). The addition of water would cause decarbonation creating an H2O-CO2-rich fluid that would then flux through the overlying sediment layer, lower the solidus temperature, and trigger melting. Recent geochemical (Cooper et al., 2012) and geodynamic (van Keken, 2003; Syracuse et al., 2010) constraints suggest that the sub-arc slab top temperatures are above the hydrous fluid-present sediment solidus, thus in the presence of excess fluid, both infiltration induced decarbonation and sediment melting may occur. Hot subduction: This is relevant for subduction zones such as Cascadia and Mexico, where slab-surface temperatures are estimated to be higher (Syracuse et al., 2010). A higher temperature could cause carbonate breakdown and sediment partial melting without requiring a hydrous fluid flux. In this case a relatively dry silicate

Molybdenum isotope systematics in subduction zones

NASA Astrophysics Data System (ADS)

König, Stephan; Wille, Martin; Voegelin, Andrea; Schoenberg, Ronny

2016-08-01

This study presents Mo isotope data for arc lavas from different subduction zones that range between δ 98 / 95 Mo = - 0.72 and + 0.07 ‰. Heaviest isotope values are observed for the most slab fluid dominated samples. Isotopically lighter signatures are related to increasing relevance of terrigenous sediment subduction and sediment melt components. Our observation complements previous conclusions that an isotopically heavy Mo fluid flux likely mirrors selective incorporation of isotopically light Mo in secondary minerals within the subducting slab. Analogue to this interpretation, low δ 98 / 95 Mo flux that coincides with terrigenous sediment subduction and sediment melting cannot be simply related to a recycled input signature. Instead, breakdown of the controlling secondary minerals during sediment melting may release the light component and lead to decreasing δ 98 / 95 Mo influx into subarc mantle sources. The natural range between slab dehydration and hydrous sediment melting may thus cause a large spread of δ 98 / 95 Mo in global subduction zone magmas.

Melting in super-earths.

PubMed

Stixrude, Lars

2014-04-28

We examine the possible extent of melting in rock-iron super-earths, focusing on those in the habitable zone. We consider the energetics of accretion and core formation, the timescale of cooling and its dependence on viscosity and partial melting, thermal regulation via the temperature dependence of viscosity, and the melting curves of rock and iron components at the ultra-high pressures characteristic of super-earths. We find that the efficiency of kinetic energy deposition during accretion increases with planetary mass; considering the likely role of giant impacts and core formation, we find that super-earths probably complete their accretionary phase in an entirely molten state. Considerations of thermal regulation lead us to propose model temperature profiles of super-earths that are controlled by silicate melting. We estimate melting curves of iron and rock components up to the extreme pressures characteristic of super-earth interiors based on existing experimental and ab initio results and scaling laws. We construct super-earth thermal models by solving the equations of mass conservation and hydrostatic equilibrium, together with equations of state of rock and iron components. We set the potential temperature at the core-mantle boundary and at the surface to the local silicate melting temperature. We find that ancient (∼4 Gyr) super-earths may be partially molten at the top and bottom of their mantles, and that mantle convection is sufficiently vigorous to sustain dynamo action over the whole range of super-earth masses.

Recrystallization-induced self-assembly for the growth of Cu₂O superstructures.

PubMed

Shang, Yang; Shao, Yi-Ming; Zhang, Dong-Feng; Guo, Lin

2014-10-20

The assembly of inorganic nanoparticles (NPs) into 3D superstructures with defined morphologies is of particular interest. A novel strategy that is based on recrystallization-induced self-assembly (RISA) for the construction of 3D Cu2O superstructures and employs Cu2O mesoporous spheres with diameters of approximately 300 nm as the building blocks has now been developed. Balancing the hydrolysis and recrystallization rates of the CuCl precursors through precisely adjusting the experimental parameters was key to success. Furthermore, the geometry of the superstructures can be tuned to obtain either cubes or tetrahedra and was shown to be dependent on the growth behavior of bulk CuCl. The overall strategy extends the applicability of recrystallization-based processes for the guided construction of assemblies and offers unique insights for assembling larger particles into complicated 3D superstructures. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermooptical properties of gold nanoparticles embedded in ice: characterization of heat generation and melting.

PubMed

Richardson, Hugh H; Hickman, Zackary N; Govorov, Alexander O; Thomas, Alyssa C; Zhang, Wei; Kordesch, Martin E

2006-04-01

We investigate the system of optically excited gold NPs in an ice matrix aiming to understand heat generation and melting processes at the nanoscale level. Along with the traditional fluorescence method, we introduce thermooptical spectroscopy based on phase transformation of a matrix. With this, we can not only measure optical response but also thermal response, that is, heat generation. After several recrystallization cycles, the nanoparticles are embedded into the ice film where the optical and thermal properties of the nanoparticles are probed. Spatial fluorescence mapping shows the locations of Au nanoparticles, whereas the time-resolved Raman signal of ice reveals the melting process. From the time-dependent Raman signals, we determine the critical light intensities at which the laser beam is able to melt ice around the nanoparticles. The melting intensity depends strongly on temperature and position. The position-dependence is especially strong and reflects a mesoscopic character of heat generation. We think that it comes from the fact that nanoparticles form small complexes of different geometry and each complex has a unique thermal response. Theoretical calculations and experimental data are combined to make a quantitative measure of the amount of heat generated by optically excited Au nanoparticles and agglomerates. The information obtained in this study can be used to design nanoscale heaters and actuators.

Thermal collapse and hierarchy of polymorphs in a faujasite-type zeolite and its analogous melt-quenched glass

NASA Astrophysics Data System (ADS)

Palenta, Theresia; Fuhrmann, Sindy; Greaves, G. Neville; Schwieger, Wilhelm; Wondraczek, Lothar

2015-02-01

We examine the route of structural collapse and re-crystallization of faujasite-type (Na,K)-LSX zeolite. As the first step, a rather stable amorphous high density phase HDAcollapse is generated through an order-disorder transition from the original zeolite via a low density phase LDAcollapse, at around 790 °C. We find that the overall amorphization is driven by an increase in the bond angle distribution within T-O-T and a change in ring statistics to 6-membered TO4 (T = Si4+, Al3+) rings at the expense of 4-membered rings. The HDAamorph transforms into crystalline nepheline, though, through an intermediate metastable carnegieite phase. In comparison, the melt-derived glass of similar composition, HDAMQ, crystallizes directly into the nepheline phase without the occurrence of intermediate carnegieite. This is attributed to the higher structural order of the faujasite-derived HDAcollapse which prefers the re-crystallization into the highly symmetric carnegieite phase before transformation into nepheline with lower symmetry.

Facile synthesis of hollow zeolite microspheres through dissolution–recrystallization procedure in the presence of organosilanes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, Haixiang; Ren, Jiawen; Liu, Xiaohui

2013-04-15

Hollow zeolite microspheres have been hydrothermally synthesized in the presence of organosilanes via a dissolution–recrystallization procedure. In the presence of organosilanes, zeolite particles with a core/shell structure formed at the first stage of hydrothermal treatment, then the core was consumed and recrystallized into zeolite framework to form the hollow structure during the second hydrothermal process. The influence of organosilanes was discussed, and a related dissolution–recrystallization mechanism was proposed. In addition, the hollow zeolite microspheres exhibited an obvious advantage in catalytic reactions compared to conventional ZSM-5 catalysts, such as in the alkylation of toluene with benzyl chloride. - Graphical abstract: Hollowmore » zeolite spheres with aggregated zeolite nanocrystals were synthesized via a dissolution–recrystallization procedure in the presence of organosiline. Highlights: ► Hollow zeolite spheres with aggregated zeolite nanocrystals were synthesized via a dissolution–recrystallization procedure. ► Organosilane influences both the morphology and hollow structure of zeolite spheres. ► Hollow zeolite spheres showed an excellent catalytic performance in alkylation of toluene with benzyl chloride.« less

Calcium phosphates recovery from digester supernatant by fast precipitation and recrystallization

NASA Astrophysics Data System (ADS)

Vasenko, Liubov; Qu, Haiyan

2018-01-01

Conditional solubility of dicalcium phosphate dihydrate (DCPD) and hydroxyapatite (HAp) in digester supernatant was determined as a function of pH and was compared to its conditional solubility in distilled water. Conditional solubility of both substances in digester supernatant at pH >5-6 was higher than their conditional solubility in pure water due to the presence of impurities, and this influence is more significant for HAp. Amorphous CaP was precipitated through a fast precipitation process from digester supernatant with initial total phosphate concentration 0.008 mol/L and 0.015 mol/L and Ca/P ratios 2 and 5. The amorphous CaP can be subsequently recrystallized into crystalline CaP. Obtained amorphous products have Ca/P ratio > 1, which allow performing the recrystallization process without further Ca dosing into the system. Batch recrystallization of the amorphous products resulted in crystallization of HAp, DCPD or their mixture depending on the conditions of the process. Maximum achieved P-recovery was 69.5%. The increase of phosphate concentration and the addition of seeding decreased the yield of the process but promoted crystallization of DCPD. The increase of Ca/P ratio had a positive effect on the total P-recovery. Compared with the direct batch crystallization of CaP from digester supernatant, the two-step process with fast precipitation and recrystallization significantly improved the color of the obtained products.

Petrologic and chemical changes in ductile shear zones as a function of depth in the continental crust

NASA Astrophysics Data System (ADS)

Yang, Xin-Yue

Petrologic and geochemical changes in ductile shear zones are important for understanding deformational and geochemical processes of the continental crust. This study examines three shear zones that formed under conditions varying from lower greenschist facies to upper amphibolite facies in order to document the petrologic and geochemical changes of deformed rocks at various metamorphic grades. The studied shear zones include two greenschist facies shear zones in the southern Appalachians and an upper amphibolite facies shear zone in southern Ontario. The mylonitic gneisses and mylonites in the Roses Mill shear zone of central Virginia are derived from a ferrodiorite protolith and characterized by a lower greenschist facies mineral assemblage. Both pressure solution and recrystallization were operative deformation mechanisms during mylonitization in this shear zone. Strain-driven dissolution and solution transfer played an important role in the mobilization of felsic components (Si, Al, K, Na, and Ca). During mylonitization, 17% to 32% bulk rock volume losses of mylonites are mainly attributed to removal of these mobile felsic components by a fluid phase. Mafic components (Fe, Mg, Ti, Mn and P) and trace elements, REE, Y, V and Sc, were immobile. At Rosman, North Carolina, the Brevard shear zone (BSZ) shows a deformational transition from the coarse-grained Henderson augen gneiss (HAG) to proto-mylonite, mylonite and ultra-mylonite. The mylonites contain a retrograde mineral assemblage as a product of fluid-assisted chemical breakdown of K-feldspar and biotite at higher greenschist facies conditions. Recrystallization and intra-crystalline plastic deformation are major deformation mechanisms in the BSZ. Fluid-assisted mylonitization in the BSZ led to 6% to 23% bulk volume losses in mylonites. During mylonitization, both major felsic and mafic elements and trace elements, Rb, Sr, Zr, V, Sc, and LREE were mobile; however, the HREEs were likely immobile. A shear zone

Factors controlling in vitro recrystallization of the Caulobacter crescentus paracrystalline S-layer.

PubMed Central

Nomellini, J F; Kupcu, S; Sleytr, U B; Smit, J

1997-01-01

The S-layer of Caulobacter is a two-dimensional paracrystalline array on the cell surface composed of a single protein, RsaA. We have established conditions for preparation of stable, soluble protein and then efficient in vitro recrystallization of the purified protein. Efficient recrystallization and long range order could not be obtained with pure protein only, though it was apparent that calcium was required for crystallization. Recrystallization was obtained when lipid vesicles were provided, but only when the vesicles contained the specific species of Caulobacter smooth lipopolysaccharide (SLPS) that previous studies implicated as a requirement for attaching the S-layer to the cell surface. The specific type of phospholipids did not appear critical; phospholipids rather different from those present in Caulobacter membranes or archaebacterial tetraether lipids worked equally well. The source of LPS was critical; rough and smooth variants of Salmonella typhimurium LPS as well as the rough form of Caulobacter LPS were ineffective. The requirement for calcium ions for recrystallization was further evaluated; strontium ions could substitute for calcium, and to a lesser extent, cobalt, barium, manganese and magnesium ions also stimulated crystallization. On the other hand, nickel and cadmium provided only weak crystallization stimulation, and zinc, copper, iron, aluminum ions, and the monovalent potassium, sodium, and lithium ions were ineffective. The recrystallization could also be reproduced with Langmuir-Blodgett lipid monolayers at an air-water interface. As with the vesicle experiments, this was only successful when SLPS was incorporated into the lipid mix. The best method for RsaA preparation, leading to apparently monomeric protein that was stable for many months, was an extraction with a low pH aqueous solution. We also achieved recrystallization, albeit at lower efficiency, using RsaA protein solubilized by 8 M urea, a method which allows retrieval of

Surface damage and structure evolution of recrystallized tungsten exposed to ELM-like transient loads

NASA Astrophysics Data System (ADS)

Yuan, Y.; Du, J.; Wirtz, M.; Luo, G.-N.; Lu, G.-H.; Liu, W.

2016-03-01

Surface damage and structure evolution of the full tungsten ITER divertor under transient heat loads is a key concern for component lifetime and plasma operations. Recrystallization caused by transients and steady-state heat loads can lead to degradation of the material properties and is therefore one of the most serious issues for tungsten armor. In order to investigate the thermal response of the recrystallized tungsten under edge localized mode-like transient thermal loads, fully recrystallized tungsten samples with different average grain sizes are exposed to cyclic thermal shocks in the electron beam facility JUDITH 1. The results indicate that not only does the microstructure change due to recrystallization, but that the surface residual stress induced by mechanical polishing strongly influences the surface cracking behavior. The stress-free surface prepared by electro-polishing is shown to be more resistant to cracking than the mechanically polished one. The resulting surface roughness depends largely on the loading conditions instead of the recrystallized-grain size. As the base temperature increases from room temperature to 400 °C, surface roughening mainly due to the shear bands in each grain becomes more pronounced, and sub-grains (up to 3 μm) are simultaneously formed in the sub-surface. The directions of the shear bands exhibit strong grain-orientation dependence, and they are generally aligned with the traces of {1 1 2} twin habit planes. The results suggest that twinning deformation and dynamic recrystallization represent the predominant mechanism for surface roughening and related microstructure evolution.

High-Temperature Flow Stress and Recrystallization Characteristics of Al-Bearing Microalloyed TWIP Steels

NASA Astrophysics Data System (ADS)

Somani, Mahesh Chandra; Porter, David A.; Hamada, Atef S.; Karjalainen, L. Pentti

2015-11-01

In this study, the effects of microalloying (Nb,V) and aluminum on the constitutive flow behavior and static recrystallization (SRX) characteristics of microalloyed TWIP steels (Fe-20Mn-0.6C-Al-(Nb,V)) have been investigated under hot deformation conditions. Compression tests in a Gleeble simulator, including the double-hit technique, enabled the acquisition of flow stress and recrystallization data. These were analyzed to determine the powers of strain and strain rate as well as the activation energies of deformation and recrystallization ( Q def and Q rex). Aluminum increased the flow stress and activation energy of deformation and delayed the onset of dynamic recrystallization of microalloyed TWIP steels. While microalloying with V up to 0.3 pct seems to have little or no effect on the SRX kinetics, microalloying with 0.026 pct Nb significantly slowed down the SRX rate, similarly as in the case of low C-Mn steels. Addition of high aluminum (4.9 pct) marginally retarded the SRX kinetics in comparison with the steels with low aluminum (1.5 pct), with or without microalloying with V.

Friction melt distribution in a multi-ring impact basin.

PubMed

Spray, J G; Thompson, L M

1995-01-12

It is generally accepted that multi-ring basins are the consequence of very large impacts, but the mechanism by which they form is still a matter of contention. Most of what is currently known about multi-ring basins is based on remote studies of the Moon and, to a lesser extent, Mars and Mercury. But at least two multi-ring impact basins have been recognized on Earth--the Sudbury (Canada) and Vredefort (South Africa) impact structures--providing an opportunity to study their properties directly. Here we describe the distribution of friction melt (pseudotachylyte) in the floor of the Sudbury impact basin. Although the veins and dykes of pseudotachylyte decrease in both thickness and frequency of occurrence towards the basin periphery, the greatest volumes of friction melt appear to define four rings around the central impact melt sheet. Field evidence indicates that the rings originated as zones of large displacement, which facilitated localized frictional melting of the basin floor during the modification (collapse) stage of the cratering process. By analogy, we argue that the rings of other multi-ring impact basins are also likely to be the remnants of such large-displacement fault zones.

Imaging Water in Deformed Quartzites: Examples from Caledonian and Himalayan Shear Zones

NASA Astrophysics Data System (ADS)

Kronenberg, Andreas; Ashley, Kyle; Hasnan, Hasnor; Holyoke, Caleb; Jezek, Lynna; Law, Richard; Thomas, Jay

2016-04-01

Infrared IR measurements of OH absorption bands due to water in deformed quartz grains have been collected from major shear zones of the Caledonian and Himalayan orogens. Mean intragranular water contents were determined from the magnitude of the broad OH absorption at 3400 cm-1 as a function of structural position, averaging over multiple grains, using an IR microscope coupled to a conventional FTIR spectrometer with apertures of 50-100 μm. Images of water content were generated by scanning areas of up to 4 mm2 of individual specimens with a 10 μm synchrotron-generated IR beam and contouring OH absorptions. Water contents vary with structural level relative to the central cores of shear zones and they vary at the grain scale corresponding to deformation and recrystallization microstructures. Gradients in quartz water content expressed over structural distances of 10 to 400 m from the centers of the Moine Thrust (Stack of Glencoul, NW Scotland), the Main Central Thrust (Sutlej valley of NW India), and the South Tibetan Detachment System (Rongbuk valley north of Mount Everest) indicate that these shear zones functioned as fluid conduits. However, the gradients differ substantially: in some cases, enhanced fluid fluxes appear to have increased quartz water contents, while in others, they served to decrease water contents. Water contents of Moine thrust quartzites appear to have been reduced during shear at greenschist facies by processes of regime II BLG/SGR dislocation creep. Intragranular water contents of the protolith 70 m below the central fault core are large (4078 ± 247 ppm, H/106 Si) while mylonites within 5 mm of the Moine hanging wall rocks have water contents of only 1570 (± 229) ppm. Water contents between these extremes vary systematically with structural level and correlate inversely with the extent of dynamic recrystallization (20 to 100%). Quartz intragranular water contents of Himalayan thrust and low-angle detachment zones sheared at upper

Residual Hydrochloride - Silicate Melt Associated With the Platinum-bearing Alaskan-type Galmoenan Intrusion (Koryak Highland, Russia)

NASA Astrophysics Data System (ADS)

Batanova, V.; Kamenetsky, D.; Pertsev, A.; Sobolev, A.

2005-12-01

Alaskan-type mafic-ultramafic complexes formed in subduction-related environments are considered to be a major source of platinum placer deposits [1]. A specific feature of these deposits is the dominant occurrence of Pt-Fe alloys (mainly isoferroplatinum) among PGE-bearing minerals [e.g. 2]. The PGE mineralization can be related to the high activity of chlorine in the parental magmas of Alaskan-type intrusions [3] and the potential of saline fluids to dissolve and transport Pt [4,5,6]. Fluxing of a refractory mantle wedge in a supra-subduction zone by chlorine-rich aqueous fluids was considered primarily responsible for the formation of PGE-enriched parental magmas [3]. Potential role of the saline magmatic fluids is further tackled by this study of melt/fluid inclusions in olivine from the Galmoenan pluton belonging to the Alaskan-type intrusive complex in the Kamchatka-Koryak province [7] and spatially associated with one of the most significant platinum placer deposits in Russia [8]. High-magnesian olivine (Fo 90.8) from the Galmoenan dunites hosts abundant hydrosaline chloride and hydrosaline chloride-silicate melt inclusions (5-30mkm). Inclusions trail fractures confined to individual olivine grains, and thus formed before re-crystallization completed. Heating stage experiments at 1 atm showed early melting within the inclusions at ~350C, however complete melting and homogenization was hampered by decrepitation at 650-750C. This suggests elevated pressures of trapping, at least 3-4 kb. The study of phase and chemical compositions of these inclusions by an electron probe, laser ablation ICP-MS and SIMS ion probe showed chlorides of Na, K, Ca, Fe and Ba, Fe-Cu-Ni sulfides and diopside among daughter phases; 2) high H2O abundances; 3) high abundances of alkali and alkali-earth elements (Na, K, Rb, Sr, Ba, Ca) and metals (Fe, Mn, Pb, Ni, Cu, Zn). Such compositions confirm the presence of metal-enriched hydrosaline melt at the latest stages of formation of the Pt

Recrystallization kinetics of warm-rolled tungsten in the temperature range 1150-1350 °C

NASA Astrophysics Data System (ADS)

Alfonso, A.; Juul Jensen, D.; Luo, G.-N.; Pantleon, W.

2014-12-01

Pure tungsten is a potential candidate material for the plasma-facing first wall and the divertor of fusion reactors. Both parts have to withstand high temperatures during service. This will alter the microstructure of the material by recovery, recrystallization and grain growth and will cause degradation in material properties as a loss in mechanical strength and embrittlement. The thermal stability of a pure tungsten plate warm-rolled to 67% thickness reduction was investigated by long-term isothermal annealing in the temperature range between 1150 °C and 1350 °C up to 2200 h. Changes in the mechanical properties during annealing are quantified by Vickers hardness measurements. They are described concisely by classical kinetic models for recovery and recrystallization. The observed time spans for recrystallization and the obtained value for the activation energy of the recrystallization process indicate a sufficient thermal stability of the tungsten plate during operation below 1075 °C.

Recrystallization Behavior in Mixed Solder Joints of BGA Components during Thermal Shock

NASA Astrophysics Data System (ADS)

Tan, Shihai; Han, Jing; Guo, Fu

2018-03-01

Sn-37Pb and Sn-3.0Ag-0.5Cu solder pastes printed onto a board were attached to ball grid array (BGA) samples using Sn-3.0Ag-0.5Cu solder balls. Before thermal shock, the initial grain orientations on the cross-section were obtained by scanning electron microscopy equipped with an electron backscattered diffraction system. Three mixed solder joints (two from the corner and another from the middle of the BGA component) and three lead-free solder joints (at the same positions) were selected to investigate the recrystallization behavior under thermal shock (TS) cycling conditions. All of the mixed and lead-free solder joints were initially single crystal. The results showed that recrystallization occurred in both the mixed and lead-free solder joints after 200 TS. For the mixed solder joints, more recrystallization was observed and the location of samples had a significant influence on their recrystallization behavior, while location was not as important for the lead-free samples after 200 TS in this study. Both the mixed and lead-free solder joints at the corner of BGA components showed the poorest reliability. According to misorientation distribution maps and subgrain rotation behaviors, the reliability of mixed solder joints was much poorer than that of lead-free solder joints.

Thick crystalline films on foreign substrates

DOEpatents

Smith, Henry I.; Atwater, Harry A.; Geis, Michael W.

1986-01-01

To achieve a uniform texture, large crystalline grains or, in some cases, a single crystalline orientation in a thick (>1 .mu.m) film on a foreign substrate, the film is formed so as to be thin (<1 .mu.m) in a certain section. Zone-melting recrystallization is initiated in the thin section and then extended into the thick section. The method may employ planar constriction patterns of orientation filter patterns.

Deducing Water Concentrations in the Parent Magma of Cumulate Clinopyroxene and Olivine: Implications for a Hydrous Parent Melt of a Primitive Deccan Lava

NASA Astrophysics Data System (ADS)

Seaman, S. J.

2017-12-01

Water concentrations of clinopyroxene megacrysts in the Powai ankaramite flow, located near Mumbai, Deccan province, India, indicate that the parent magma of the flow hosted at least 4.3 wt.% water, an unusually high water concentration for a continental flood basalt magma. The Powai flow hosts clinopyroxene and olivine phenocrysts. Chatterjee and Sheth (2015) showed that phenocrysts in the flow were part of a cumulate layer intruded by basaltic melt at 6 kb and 1230oC, so the phenocrysts record characteristics of the cumulate parent melt. Clinopyroxene phenocrysts are oscillatorily zoned in water, Mg, Fe, and Ca concentrations, and have concentric bands 100-200 microns thick of 10-20 micron diameter melt inclusions. Olivine phenocrysts host only larger isolated melt inclusions. Zones in the cpx phenocrysts where melt inclusion-rich concentric bands occur have higher concentrations of water than inclusion-free zones. Water concentrations of cpx were used to calculate water concentrations in the melt from which the crystals formed using partition coefficients of Hauri et al. (2004). Water concentrations in the parent magma were between 4.3 and 8.2 wt. % based on water concentrations in cpx. Both Mg and Fe are relatively depleted in the water- and melt inclusion-rich zones in cpx, and Ca is enriched in these zones. Oscillatory zoning in cpx may be a result of repeated growth of cpx in water- richer and water-poorer boundary layers where water lowered melt viscosity and enhanced diffusion and crystal growth rates. Water-enhanced growth rates may have resulted in capture of melt inclusions preserved in water-rich cpx zones. Melt inclusions in olivine phenocrysts preserve lower water concentrations ( 1.2 wt. %) than those indicated by water concentration in cpx phenocrysts. This disparity may be evidence of water loss from melt inclusions in olivine (Gaetani et al., 2009) or may indicate that cpx and ol crystals did not crystallize from the same parent at the same time.

The Gao-Guenie impact melt breccia—Sampling a rapidly cooled impact melt dike on an H chondrite asteroid?

NASA Astrophysics Data System (ADS)

Schmieder, Martin; Kring, David A.; Swindle, Timothy D.; Bond, Jade C.; Moore, Carleton B.

2016-06-01

The Gao-Guenie H5 chondrite that fell on Burkina Faso (March 1960) has portions that were impact-melted on an H chondrite asteroid at ~300 Ma and, through later impact events in space, sent into an Earth-crossing orbit. This article presents a petrographic and electron microprobe analysis of a representative sample of the Gao-Guenie impact melt breccia consisting of a chondritic clast domain, quenched melt in contact with chondritic clasts, and an igneous-textured impact melt domain. Olivine is predominantly Fo80-82. The clast domain contains low-Ca pyroxene. Impact melt-grown pyroxene is commonly zoned from low-Ca pyroxene in cores to pigeonite and augite in rims. Metal-troilite orbs in the impact melt domain measure up to ~2 mm across. The cores of metal orbs in the impact melt domain contain ~7.9 wt% of Ni and are typically surrounded by taenite and Ni-rich troilite. The metallography of metal-troilite droplets suggest a stage I cooling rate of order 10 °C s-1 for the superheated impact melt. The subsolidus stage II cooling rate for the impact melt breccia could not be determined directly, but was presumably fast. An analogy between the Ni rim gradients in metal of the Gao-Guenie impact melt breccia and the impact-melted H6 chondrite Orvinio suggests similar cooling rates, probably on the order of ~5000-40,000 °C yr-1. A simple model of conductive heat transfer shows that the Gao-Guenie impact melt breccia may have formed in a melt injection dike ~0.5-5 m in width, generated during a sizeable impact event on the H chondrite parent asteroid.

The initiation of segmented buoyancy-driven melting during continental breakup

PubMed Central

Gallacher, Ryan J.; Keir, Derek; Harmon, Nicholas; Stuart, Graham; Leroy, Sylvie; Hammond, James O. S.; Kendall, J-Michael; Ayele, Atalay; Goitom, Berhe; Ogubazghi, Ghebrebrhan; Ahmed, Abdulhakim

2016-01-01

Melting of the mantle during continental breakup leads to magmatic intrusion and volcanism, yet our understanding of the location and dominant mechanisms of melt generation in rifting environments is impeded by a paucity of direct observations of mantle melting. It is unclear when during the rifting process the segmented nature of magma supply typical of seafloor spreading initiates. Here, we use Rayleigh-wave tomography to construct a high-resolution absolute three-dimensional shear-wave velocity model of the upper 250 km beneath the Afar triple junction, imaging the mantle response during progressive continental breakup. Our model suggests melt production is highest and melting depths deepest early during continental breakup. Elevated melt production during continental rifting is likely due to localized thinning and melt focusing when the rift is narrow. In addition, we interpret segmented zones of melt supply beneath the rift, suggesting that buoyancy-driven active upwelling of the mantle initiates early during continental rifting. PMID:27752044

Dynamic recrystallization behavior of an as-cast TiAl alloy during hot compression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jianbo, E-mail: lijianbo1205@163.com; Liu, Yong, E-mail: yonliu@csu.edu.cn; Wang, Yan, E-mail: wangyan@csu.edu.cn

2014-11-15

High temperature compressive deformation behaviors of as-cast Ti–43Al–4Nb–1.4W–0.6B alloy were investigated at temperatures ranging from 1050 °C to 1200 °C, and strain rates from 0.001 s{sup −1} to 1 s{sup −1}. Electron back scattered diffraction technique, scanning electron microscopy and transmission electron microscopy were employed to investigate the microstructural evolutions and nucleation mechanisms of the dynamic recrystallization. The results indicated that the true stress–true strain curves show a dynamic flow softening behavior. The dependence of the peak stress on the deformation temperature and the strain rate can well be expressed by a hyperbolic-sine type equation. The activation energy decreases withmore » increasing the strain. The size of the dynamically recrystallized β grains decreases with increasing the value of the Zener–Hollomon parameter (Z). When the flow stress reaches a steady state, the size of β grains almost remains constant with increasing the deformation strain. The continuous dynamic recrystallization plays a dominant role in the deformation. In order to characterize the evolution of dynamic recrystallization volume fraction, the dynamic recrystallization kinetics was studied by Avrami-type equation. Besides, the role of β phase and the softening mechanism during the hot deformation was also discussed in details. - Highlights: • The size of DRXed β grains decreases with increasing the value of the Z. • The CDRX plays a dominant role in the deformation. • The broken TiB{sub 2} particles can promote the nucleation of DRX.« less

Characterization of thermoplastic polyimide NEW-TPI

NASA Technical Reports Server (NTRS)

Hou, T. H.; Reddy, R. M.

1991-01-01

Thermal and rheological properties of a commercial thermoplastic polyimide, NEW-TPI, were characterized. The as-received material possesses initially a transient crystallite form with a bimodal distribution in peak melting temperatures. After the meltings of the initial crystallite structures, the sample can be recrystallized by various thermal treatments. A bimodal or single-modal melting peak distribution is formed for annealing temperatures below or above 360 C, respectively. The recrystallized crystallinities are all transient in nature. The polymers are unable to be recrystallized after being subjected to elevated temperature annealing above 450 C. The recrystallization mechanism was postulated, and a simple kinetics model was found to describe the behavior satisfactorily under conditions of prolonged thermal annealing.

Influence of warm rolling temperature on ferrite recrystallization in low C and IF steels

NASA Astrophysics Data System (ADS)

Barnett, Matthew Robert

Experiments involving single pass laboratory rolling and isothermal salt bath annealing were carried out; three steels were studied: a titanium stabilized interstitial free grade and two low carbon grades, one of which contained a particularly low level of manganese (˜0.009wt.%). The two low carbon grades were produced such that any complication from AlN precipitation was avoided. X-ray, neutron diffraction, optical metallography and mechanical testing measurements were carried out on the samples before and after annealing. The main aim of this work was to further the understanding of the metallurgy of recrystallization after ferrite rolling at temperatures between room temperature and 700sp°C. Deformation textures, recrystallization kinetics, final grain sizes and recrystallization textures were quantified for all the samples and experimental conditions. A major conclusion based on these data is that the influence of rolling temperature is far greater in the low carbon samples than in the IF grade. Indeed, the IF results alter only marginally with increasing temperature. In the low carbon grades, however, the rolling texture sharpens, recrystallization slows, the final grain size coarsens, and the recrystallization texture changes when the rolling temperature is increased. This distinct difference between the two steel types is explained in terms of their contrasting deformation behaviors. Solute carbon and nitrogen in the low carbon grades interact with dislocations causing high stored energy levels after low temperature rolling (due to dynamic strain aging) and high strain rate sensitivities during high temperature rolling (due to the solute drag of dislocations in the transition region between DSA and DRC). Nucleation during subsequent recrystallization is strongly influenced by both the stored energy and the strain rate sensitivity. The latter affects the occurrence of the flow localisations that enhance nucleation.

Thermal-capillary analysis of small-scale floating zones Steady-state calculations

NASA Technical Reports Server (NTRS)

Duranceau, J. L.; Brown, R. A.

1986-01-01

Galerkin finite element analysis of a thermal-capillary model of the floating zone crystal growth process is used to predict the dependence of molten zone shape on operating conditions for the growth of small silicon boules. The model accounts for conduction-dominated heat transport in the melt, feed rod and growing crystal and for radiation between these phases, the ambient and a heater. Surface tension acting on the shape of the melt/gas meniscus counteracts gravity to set the shape of the molten zone. The maximum diameter of the growing crystal is set by the dewetting of the melt from the feed rod when the crystal radius is large. Calculations with small Bond number show the increased zone lengths possible for growth in a microgravity environment. The sensitivity of the method to the shape and intensity of the applied heating distribution is demonstrated. The calculations are compared with experimental observations.

Cellular monotectic model solidification

NASA Technical Reports Server (NTRS)

Kaukler, William F.

1987-01-01

Succinonitrile (sn) was purified to a superior level using a fractional recrystallization method. The melting point of the best twice recrystallized sn was not raised by following with double distillation. This was tested using differential scanning calorimetry. The peak shape on melting also proved that double distillation after double recrystallization did not improve the quality. Stability and phase diagrams for succinonitrile and glycerol are presented.

Feedbacks Between Deformation and Fluid Flow in Mantle Shear Zones from Zabargad, Red Sea

NASA Astrophysics Data System (ADS)

Tommasi, A.; Boudier, F. I.; Vauchez, A. R.; Zaderatzky, M.

2016-12-01

Peridotites in the Zabargad island, Red Sea, record different stages of lithospheric thinning and asthenospheric upwelling during rifting. Field mapping highlights a pervasive high-temperature NW-SE, subvertical foliation with lineations pluning 50°NW. This foliation is overprinted by a series of lower-temperature mylonitic zones with slightly oblique foliations and subhorizontal lineations, which record progressive strain localization under retrogressive conditions during the final exhumation of the peridotites (Nicolas and Boudier, JGR 1987). We performed a petrostructural study of ca. 50 samples collected by A. Nicolas and F. Boudier in the 80s from the different deformation facies. This study highlights: (1) a rather pervasive, but highly heterogeneous distribution of the LT deformation and (2) a feedback between deformation and fluid flow. The HT deformation is recorded in medium grained plagioclase- and spinel-peridotites by a homogeneous foliation and lineation marked by a shape-preferred orientation of plagioclase and olivine and a consistent CPO of all major-rock forming phases. The LT temperature deformation results in dynamic recrystallization of olivine leading to a marked grain size reduction by dynamic recrystallization of olivine, remobilization of orthopyroxene by dissolution-precipitation, and crystallization of amphibole. Increasing finite strain is recorded by the increase in the volume of the fine-grained material and of the amphibole proportion. The latter may attain in totally recrystallized cm-wide ultramylonite bands up to 30%. This together with the strong amphibole SPO and CPO corroborate fluid focusing and enhanced reaction rates into active shear zones. In the LT shear zones we also document: (1) changes in the olivine CPO, indicating changes in the dominant slip system and (2) unusual orthopyroxene CPO, which we interpret as due to oriented crystallization. Static replacement of pyroxenes by amphibole with no associated LT deformation

Recrystallization and grain growth behavior of rolled tungsten under VDE-like short pulse high heat flux loads

NASA Astrophysics Data System (ADS)

Yuan, Y.; Greuner, H.; Böswirth, B.; Krieger, K.; Luo, G.-N.; Xu, H. Y.; Fu, B. Q.; Li, M.; Liu, W.

2013-02-01

Short pulse heat loads expected for vertical displacement events (VDEs) in ITER were applied in the high heat flux (HHF) test facility GLADIS at IPP-Garching onto samples of rolled W. Pulsed neutral beams with the central heat flux of 23 MW/m2 were applied for 0.5, 1.0 and 1.5 s, respectively. Rapid recrystallization of the adiabatically loaded 3 mm thick samples was observed when the pulse duration was up to 1.0 s. Grains grew markedly following recrystallization with increasing pulse length. The recrystallization temperature and temperature dependence of the recrystallized grain size were also investigated. The results showed that the recrystallization temperature of the W grade was around 2480 °C under the applied heat loading condition, which was nearly 1150 °C higher than the conventional recrystallization temperature, and the grains were much finer. A linear relationship between the logarithm of average grain size (ln d) and the inverse of maximum surface temperature (1/Tmax) was found and accordingly the activation energy for grain growth in temperature evolution up to Tmax in 1.5 s of the short pulse HHF load was deduced to be 4.1 eV. This provided an effective clue to predict the structure evolution under short pulse HHF loads.

Experimental research of phase transitions in a melt of high-purity aluminum

NASA Astrophysics Data System (ADS)

Vorontsov, V. B.; Pershin, V. K.

2017-12-01

This scientific work is devoted to the studying of the genetic connection structures of solid and liquid phases. In this paper Fourier analysis of acoustic emission (AE) signals accompanying heating of high purity aluminum from the melting point up to 860 °C was performed. The experimental data allowed to follow the dynamics of disorder zones in the melt with increasing melt temperature up to their complete destruction. The presented results of spectral analysis of the signals were analyzed from the standpoint of the theory of cluster melting metals.

The Rheological Evolution of Brittle-Ductile Transition Rocks During the Earthquake Cycle: Evidence for a Ductile Precursor to Pseudotachylyte in an Extensional Fault System, South Mountains, Arizona

NASA Astrophysics Data System (ADS)

Stewart, Craig A.; Miranda, Elena A.

2017-12-01

We investigate how the rheological evolution of shear zone rocks from beneath the brittle-ductile transition (BDT) is affected by coeval ductile shear and pseudotachylyte development associated with seismicity during the earthquake cycle. We focus our study on footwall rocks of the South Mountains core complex, and we use electron backscatter diffraction (EBSD) analyses to examine how strain is localized in granodiorite mylonites both prior to and during pseudotachylyte development beneath the BDT. In mylonites that are host to pseudotachylytes, deformation is partitioned into quartz, where quartz exhibits crystallographic-preferred orientation patterns and microstructures indicative of dynamic recrystallization during dislocation creep. Grain size reduction during dynamic recrystallization led to the onset of grain boundary sliding (GBS) accommodated by fluid-assisted grain size-sensitive (GSS) creep, localizing strain in quartz-rich layers prior to pseudotachylyte development. The foliation-parallel zones of GBS in the host mylonites, and the presence of GBS traits in polycrystalline quartz survivor clasts indicate that GBS zones were the ductile precursors to in situ pseudotachylyte generation. During pseudotachylyte development, strain was partitioned into the melt phase, and GSS deformation in the survivor clasts continued until crystallization of melt impeded flow, inducing pseudotachylyte development in other GBS zones. We interpret the coeval pseudotachylytes with ductile precursors as evidence of seismic events near the BDT. Grain size piezometry yields high differential stresses in both host mylonites ( 160 MPa) and pseudotachylyte survivor clasts (> 200 MPa), consistent with high stresses during interseismic and coseismic phases of the earthquake cycle, respectively.

Experimental Phase Relations of Hydrous, Primitive Melts: Implications for variably depleted mantle melting in arcs and the generation of primitive high-SiO2 melts

NASA Astrophysics Data System (ADS)

Weaver, S.; Wallace, P. J.; Johnston, A.

2010-12-01

There has been considerable experimental and theoretical work on how the introduction of H2O-rich fluids into the mantle wedge affects partial melting in arcs and chemical evolution of mantle melts as they migrate through the mantle. Studies aimed at describing these processes have become largely quantitative, with an emphasis on creating models that suitably predict the production and evolution of melts and describe the thermal state of arcs worldwide. A complete experimental data set that explores the P-T conditions of melt generation and subsequent melt extraction is crucial to the development, calibration, and testing of these models. This work adds to that data set by constraining the P-T-H2O conditions of primary melt extraction from two end-member subduction zones, a continental arc (Mexico) and an intraoceanic arc (Aleutians). We present our data in context with primitive melts found worldwide and with other experimental studies of melts produced from fertile and variably depleted mantle sources. Additionally, we compare our experimental results to melt compositions predicted by empirical and thermodynamic models. We used a piston-cylinder apparatus and employed an inverse approach in our experiments, constraining the permissible mantle residues with which our melts could be in equilibrium. We confirmed our inverse approach with forced saturation experiments at the P-T-H2O conditions of melt-mantle equilibration. Our experimental results show that a primitive, basaltic andesite melt (JR-28) from monogenetic cinder cone Volcan Jorullo (Central Mexico) last equilibrated with a harzburgite mantle residue at 1.2-1.4 GPa and 1150-1175°C with H2O contents in the range of 5.5-7 wt% H2O prior to ascent and eruption. Phase relations of a tholeiitic high-MgO basaltic melt (ID-16) from the Central Aleutians (Okmok) show the conditions of last equilibration with a fertile lherzolite mantle residue at shallower (1.2 GPa) but hotter (1275°C) conditions with

The control of float zone interfaces by the use of selected boundary conditions

NASA Technical Reports Server (NTRS)

Foster, L. M.; Mcintosh, J.

1983-01-01

The main goal of the float zone crystal growth project of NASA's Materials Processing in Space Program is to thoroughly understand the molten zone/freezing crystal system and all the mechanisms that govern this system. The surface boundary conditions required to give flat float zone solid melt interfaces were studied and computed. The results provide float zone furnace designers with better methods for controlling solid melt interface shapes and for computing thermal profiles and gradients. Documentation and a user's guide were provided for the computer software.

Thick crystalline films on foreign substrates

DOEpatents

Smith, H.I.; Atwater, H.A.; Geis, M.W.

1986-03-18

To achieve a uniform texture, large crystalline grains or, in some cases, a single crystalline orientation in a thick (>1 [mu]m) film on a foreign substrate, the film is formed so as to be thin (<1 [mu]m) in a certain section. Zone-melting recrystallization is initiated in the thin section and then extended into the thick section. The method may employ planar constriction patterns of orientation filter patterns. 2 figs.

Evolution of Continental Lower Crust Recorded By an Exhumed Deep Crustal Intracontinental Shear Zone

NASA Astrophysics Data System (ADS)

Dumond, G.; Mahan, K. H.; Regan, S. P.; Williams, M. L.; Goncalves, P.; Wood, V. R.

2014-12-01

Exposures of deep crustal shear zones are fundamental records of strain localization and the temporal evolution of ductile to brittle behavior as these tectonites were exhumed to the surface. We present results from a decade of field-based research on a deeply exhumed (~35 km-paleodepths) strike-slip shear zone in the western Churchill province of the Canadian Shield. The Grease River shear zone is a >400 km-long and 7 km-thick structure that cuts the Athabasca granulite terrane, North America's largest exposure of continental lower crust (>20,000 km2). The shear zone is dominated by granulite- to amphibolite-grade L-S and L>S tectonites characterized by penetrative NE-striking steeply-dipping foliations with gently-plunging to sub-horizontal stretching and intersection lineations. These fabrics are locally overprinted by pseudotachylyte and narrow (<500 m-thick) greenschist-grade zones of cataclasite. Dextral kinematics are defined by deflected foliation trajectories, C' shear bands, and well-developed σ- and δ-type porphyroclasts of Kfs + Pl + Opx + Grt + Hb in felsic to intermediate granulite paragneisses and orthogneisses. Data collected along a well-exposed, nearly 150 km-long segment of the shear zone documents a >100 m.y. episodic record of transpressive to strike-slip intracontinental strain accumulation that coincided with two oppositely convergent orogenies: the east-vergent arc-continent collision of the 1.94-1.90 Ga Taltson orogen and the west-vergent continent-continent collision of the 1.9-1.8 Ga Trans-Hudson orogen. Deformation mechanisms evolved from distributed ductile dynamic recrystallization and grain-size reduction to localized pseudotachylyte development, cataclastic flow, and brittle faulting. Lower crustal behavior during strain localization was dynamic. Melt-weakened mono-cyclic crust was juxtaposed against strong isobarically-cooled poly-cyclic crust along the shear zone at 1.92-1.90 Ga. Brittle-ductile reactivation of the structure

Distribution of melt beneath Mount St Helens and Mount Adams inferred from magnetotelluric data

NASA Astrophysics Data System (ADS)

Hill, Graham J.; Caldwell, T. Grant; Heise, Wiebke; Chertkoff, Darren G.; Bibby, Hugh M.; Burgess, Matt K.; Cull, James P.; Cas, Ray A. F.

2009-11-01

Three prominent volcanoes that form part of the Cascade mountain range in Washington State (USA)-Mounts St Helens, Adams and Rainier-are located on the margins of a mid-crustal zone of high electrical conductivity. Interconnected melt can increase the bulk conductivity of the region containing the melt, which leads us to propose that the anomalous conductivity in this region is due to partial melt associated with the volcanism. Here we test this hypothesis by using magnetotelluric data recorded at a network of 85 locations in the area of the high-conductivity anomaly. Our data reveal that a localized zone of high conductivity beneath this volcano extends downwards to join the mid-crustal conductor. As our measurements were made during the recent period of lava extrusion at Mount St Helens, we infer that the conductivity anomaly associated with the localized zone, and by extension with the mid-crustal conductor, is caused by the presence of partial melt. Our interpretation is consistent with the crustal origin of silicic magmas erupting from Mount St Helens, and explains the distribution of seismicity observed at the time of the catastrophic eruption in 1980 (refs 9, 10).

Rheology linked with phase changes as recorded by development of shear bands in the South Armorican Shear Zone

NASA Astrophysics Data System (ADS)

Jeřábek, Petr; Bukovská, Zita

2015-04-01

The South Armorican Shear Zone in France represents a major right-lateral strike slip shear zone formed in the late stages of Variscan orogeny. The active deformation in this shear zone is associated with the development of S-C fabrics in granitoids where thin shear bands (C) overprint an earlier higher grade metamorphic foliation (S). In the studied samples covering low to high intensity of shear band overprint, we identified three stages of shear band evolution associated with distinct microstructures and deformation mechanisms. The initiation of shear bands stage I is associated with the formation of microcracks crosscutting the S fabric and detected namely in the recrystallized quartz aggregates. The microcracks of suitable orientation are filled by microcline, albite, muscovite and chlorite which is a typical assemblage also for the well developed shear bands. Phase equilibrium modeling in PERPLEX indicates that this assemblage formed at pressure-temperature range of 0.1-0.4 GPa and 300-340 °C. Stage II of shear band evolution is characterized by dynamic recrystallization and grain size reduction of quartz aggregates along the microcracks and replacement of quartz by microcline along grain boundaries. This process leads to disintegration of quartz aggregate fabric and phase mixing in the shear bands. The inferred deformation mechanism for this stage is solution-precipitation creep although recrystallization of quartz is still active at the contact between quartz aggregates and shear bands. The coarse grained microstructure of quartz aggregates with ca ~250 microns average grain size reduces to ~10 microns grain size when recrystallized along extremely thin shear bands/microcracks and to ~20 microns grain size when recrystallized along the thicker shear bands. By using the flow law of Patterson and Luan (1990) for dislocation creep in quartz and the quartz piezometer of Stipp and Tullis (2003) corrected after Holyoke and Kronenberg (2010), the quartz

Annealing effects in plated-wire memory elements. II - Recrystallization in Permalloy films.

NASA Technical Reports Server (NTRS)

Marquardt, S. J.; Kench, J. R.

1971-01-01

Results of grain-size measurements in Permalloy platings suggest that recrystallization is possible at temperatures as low as 200 C, but that it is an extremely heterogeneous process. No worthwhile correlation was found to exist between observed grain size and magnetic dispersion in samples aged in the temperature range from 180 to 230 C. It is suggested that the magnetic aging which occurs under these conditions may be due to some other diffusion-controlled process than recrystallization; a process such as chemical homogenization is tentatively preferred.

Deformation Mechanisms of Darreh Sary Metapelites, Sanandaj‒Sirjan Zone, Iran

NASA Astrophysics Data System (ADS)

Hemmati, O.; Tabatabaei Manesh, S. M.; Nadimi, A. R.

2018-03-01

The Darreh Sary metapelitic rocks are located in the northeast of Zagros orogenic belt and Sanandaj-Sirjan structural zone. The lithological composition of these rocks includes slate, phyllite, muscovitebiotite schist, garnet schist, staurolite-garnet schist and staurolite schist. The shale is the protolith of these metamorphic rocks, which was originated from the continental island arc tectonic setting and has been subjected to processes of Zagros orogeny. The deformation mechanisms in these rocks include bulging recrystallization (BLG), subgrain rotation recrystallization (SGR) and grain boundary migration recrystallization (GBM), which are considered as the key to estimate the deformation temperature of the rocks. The estimated ranges of deformation temperature and depth in these rocks show the temperatures of 275-375, 375-500, and >500°C and the depths of 10 to 17 km. The observed structures in these rocks such as faults, fractures and folds, often with the NW-SE direction coordinate with the structural trends of Zagros orogenic belt structures. The S-C mylonite fabrics is observed in these rocks with other microstructures such as mica fish, σ fabric and garnet deformation indicate the dextral shear deformation movements of study area. Based on the obtained results of this research, the stages of tectonic evolution of Darreh Sary area were developed.

Dynamic Recrystallization Behavior of Zr-1Sn-0.3Nb Alloy During Hot Rolling Process

NASA Astrophysics Data System (ADS)

Zhao, Siyu; Liu, Huiqun; Lin, Gaoyong; Jiang, Yilan; Xun, Jian

2017-11-01

Zirconium alloys are advanced materials with properties that are greatly affected by their crystalline structure. To investigate this, sheets of Zr-1Sn-0.3Nb alloy were hot rolled with different reductions (10%, 30%, 50%, and 60%) at 1023 K and 1073 K to investigate the alloy's dynamic recrystallization behavior. Recrystallization kinetics was observed via electron backscattering diffraction and transmission electron microscopy, and the results were compared with estimates based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. The values of the JMAK exponent n and k increased with the rolling temperature. The estimates and microstructural observations of dynamic recrystallization (DRX) kinetics were in good agreement.

Impact-melt origin for the Simondium, Pinnaroo, and Hainholz mesosiderites: implicatiions for impact processes beyond the Earth--Moon system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Floran, R J; Caulfield, J B.D.; Harlow, G E

The Simondium, Pinnaroo, and Hainholz mesosiderites are interpreted to be clast-laden impact melts that crystallized from immiscible silicate, metallic (Fe-FeS) liquids. The existence of silicate melts is shown by intergranular basaltic textures. Metallic melts are inferred on the basis of smooth boundaries between metal and troilite and the occurrence of troilite as anastomosing areas that radiate outward into the silicate fractions. These relations suggest that troilite crystallized after silicates, concentrating as a late-stage residuum. Evidence for impact melting includes: diversity and abundance of clast types (mineral, metal, lithic) in various stages of recrystallization and assimilation; differences in mineral chemistries betweenmore » clasts and igneous-textured matrix silicates; unusual metal plus silicate bulk composition. Silicate clasts consist primarily of orthopyroxene and minor olivine with a range of Fe/Fe + Mg ratios, anorthitic plagioclase, and rare orthopyroxenite (diogenite) fragments. Substantial amounts of Fe-Ni metal were melted during the impact events and minor amounts were incorporated into the melts as clasts. The clast populations suggest that at least four rock types were melted and mixed: (a) diogenite, (b) a plagioclase-rich source, possibly cumulate eucrite, (c) dunite, and (d) metal. Most orthopyroxene appears to have been derived from fragmentation of diogenites. Orthopyroxene (En/sub 82-61/) and olivine (Fo/sub 86-67/) clasts include much material unsampled as individual meteorites and probably represent a variety of source rocks.« less

Float-zone processing in a weightless environment

NASA Technical Reports Server (NTRS)

Fowle, A. A.; Haggerty, J. S.; Perron, R. R.; Strong, P. F.; Swanson, J. L.

1976-01-01

The results were reported of investigations to: (1) test the validity of analyses which set maximum practical diameters for Si crystals that can be processed by the float zone method in a near weightless environment, (2) determine the convective flow patterns induced in a typical float zone, Si melt under conditions perceived to be advantageous to the crystal growth process using flow visualization techniques applied to a dimensionally scaled model of the Si melt, (3) revise the estimates of the economic impact of space produced Si crystal by the float zone method on the U.S. electronics industry, and (4) devise a rational plan for future work related to crystal growth phenomena wherein low gravity conditions available in a space site can be used to maximum benefit to the U.S. electronics industry.

Polymineralic inclusions in mantle chromitites from the Oman ophiolite indicate a highly magnesian parental melt

NASA Astrophysics Data System (ADS)

Rollinson, Hugh; Mameri, Lucan; Barry, Tiffany

2018-06-01

Polymineralic inclusions interpreted as melt inclusions in chromite from the dunitic Moho Transition Zone in the Maqsad area of the Oman ophiolite have been analysed and compositions integrated using a rastering technique on the scanning electron microscope. The inclusions now comprise a range of inter-grown hydrous phases including pargasite, aspidolite, phlogopite and chlorite, indicating that the parental melts were hydrous. Average inclusion compositions for seven samples contain between 23.1 and 26.8 wt% MgO and 1.7-3.6 wt% FeO. Compositions were corrected to allow for the low FeO concentrations using coexisting olivine compositions. These suggest that the primary melt has between 20 and 22 wt% MgO and 7-9.7 wt% FeO and has an affinity with boninitic melts, although the melts have a higher Ti content than most boninites. Average rare earth element concentrations suggest that the melts were derived from a REE depleted mantle source although fluid-mobile trace elements indicate a more enriched source. Given the hydrous nature of the inclusions this enrichment could be fluid driven. An estimate of the melt temperature can be made from the results of homogenisation experiments on these inclusions and suggests 1300 °C, which implies for a harzburgite solidus, relatively shallow melting at depths of <50 km and is consistent with a boninitic origin. The current "basaltic" nature of the chromite host to highly magnesian melt inclusions suggests that the dunitic Moho Transition Zone operated as a reaction filter in which magnesian melts were transformed into basalts by the removal of high magnesian olivines, particularly in areas where the Moho Transition Zone is unusually thick. We propose therefore that podiform mantle chromitites, even those with an apparent MORB-like chemical signature, have crystallised from a highly magnesian parental melt. The data presented here strongly support the view that this took place in a subduction initiation setting.

Analysis of Picosecond Pulsed Laser Melted Graphite

DOE R&D Accomplishments Database

Steinbeck, J.; Braunstein, G.; Speck, J.; Dresselhaus, M. S.; Huang, C. Y.; Malvezzi, A. M.; Bloembergen, N.

1986-12-01

A Raman microprobe and high resolution TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582 cm{sup -1} and the disorder-induced mode at 1360 cm{sup -1}, the average graphite crystallite size in the resolidified region is determined as a function of position. By comparison with Rutherford backscattering spectra and Raman spectra from nanosecond pulsed laser melting experiments, the disorder depth for picosecond pulsed laser melted graphite is determined as a function of irradiating energy density. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence.

Evaluating flow laws for dynamically recrystallized quartz based on field data

NASA Astrophysics Data System (ADS)

Peters, Max; Herwegh, Marco

2013-04-01

The extrapolation of experimentally controlled deformation conditions, and the resulting relations between physical parameters acting during ductile deformation, to nature is considered controversial (see Herwegh et al., 2005 and references therein). Whereas the relationship between flow stress and recrystallized grain size can be empirically derived from lab experiments using paleopiezometers (e.g. Stipp & Tullis, 2003), the relation between recrystallized grain size, strain rate, differential stress, temperature and activation energy for dislocation creep requires further constraints. For these relations, various power law flow laws for dynamically recrystallized quartz were proposed over the past years (Paterson & Luan, 1990; Luan & Paterson, 1992; Gleason & Tullis, 1995; Hirth et al., 2001, Rutter & Brodie, 2004). The variations in the flow laws are mainly characterized by different starting materials, experimental conditions, the activation energy for dislocation creep and the stress exponent n. In this study we compare and evaluate experimentally derived flow laws regarding their reliability for the prediction of rheology of background deformation of naturally deformed crystalline samples from mylonites of the Aar massif (Swiss Central Alps). The majority of samples comprises highly deformed rocks (e.g. Central Aare granite), which exhibit severe grain size reduction. This reduction dominantly occurred by subgrain rotation (SGR), in the case of low temperature overprint by bulging recrystallization (BLG). Towards elevated temperatures, grain boundary migration (GBM) and SGR recrystallization were active. Along the metamorphic gradient (300 - 475°C) quartz microstructures and associated recrystallized grain size distributions indicate steady state mean grain sizes. The quantification of the metamorphic gradient (temperature, pressure, water fugacity) over the sampling area allowed the application of flow laws, yielding variations of 6 orders of magnitude in

Dehydration and melting experiments constrain the fate of subducted sediments

NASA Astrophysics Data System (ADS)

Johnson, Marie C.; Plank, Terry

1999-12-01

Geochemical tracers demonstrate that elements are cycled from subducted sediments into the arc melting regime at subduction zones, although the transfer mechanism is poorly understood. Are key elements (Th, Be, Rb) lost during sediment dehydration or is sediment melting required? To investigate this question, we conducted phase equilibria and trace element partitioning experiments on a pelagic red clay for conditions appropriate to the slab beneath arc volcanoes (2-4 GPa, 600°-1000°C). Using both piston cylinders and multianvils, we determined the solidus, phase stabilities, and major element compositions of coexisting phases. The solidus (H2O + Cl fluid-saturated) was located at 775 +/- 25°C at 2 GPa, 810 +/- 15°C at 3 GPa, and 1025 +/- 25°C at 4 GPa with noevidence for complete miscibility between melt and fluid. This sediment composition produces a profusion of phases both above and below the solidus: garnet, jadeitic pyroxene, alkali-rich amphibole, phengite, biotite, magnetite, coesite, kyanite, apatite, zircon, Cl-rich fluids, and peraluminous to peralkaline granitic melts. At 2 GPa the phengite dehydration solidus is at 800°-825°C, while biotite breaks down between 850° and 900°C. To explore trace element partitioning across the solidus at 2 GPa, we used diamonds to trap fluids and melts. Both the bulk sediment residues and diamond traps were analyzed postexperiment by inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) for 40 elements for which we calculated bulk partition coefficients (D = Csolid/Cfluid). Below the solidus, Rb, Sr, Ba, and Pb showed the greatest mobility (D ~ 0.5-1.0), while at the solidus, Th and Be became notably partitioned into the melt (D values changing from >2.0 to <1.0). K and Rb D values fall below 1.0 when the micas breakdown. Only at the solidus do Th and Rb attain similar partition coefficients, a condition required by arc data. Taken together, the

Dehydration and melting experiments constrain the fate of subducted sediments

NASA Astrophysics Data System (ADS)

Johnson, Marie C.; Plank, Terry

2000-12-01

Geochemical tracers demonstrate that elements are cycled from subducted sediments into the arc melting regime at subduction zones, although the transfer mechanism is poorly understood. Are key elements (Th, Be, Rb) lost during sediment dehydration or is sediment melting required? To investigate this question, we conducted phase equilibria and trace element partitioning experiments on a pelagic red clay for conditions appropriate to the slab beneath arc volcanoes (2-4 GPa, 600°-1000°C). Using both piston cylinders and multianvils, we determined the solidus, phase stabilities, and major element compositions of coexisting phases. The solidus (H2O + Cl fluid-saturated) was located at 775 ± 25°C at 2 GPa, 810 ± 15°C at 3 GPa, and 1025 ± 25°C at 4 GPa with noevidence for complete miscibility between melt and fluid. This sediment composition produces a profusion of phases both above and below the solidus: garnet, jadeitic pyroxene, alkali-rich amphibole, phengite, biotite, magnetite, coesite, kyanite, apatite, zircon, Cl-rich fluids, and peraluminous to peralkaline granitic melts. At 2 GPa the phengite dehydration solidus is at 800°-825°C, while biotite breaks down between 850° and 900°C. To explore trace element partitioning across the solidus at 2 GPa, we used diamonds to trap fluids and melts. Both the bulk sediment residues and diamond traps were analyzed postexperiment by inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) for 40 elements for which we calculated bulk partition coefficients (D = Csolid/Cfluid). Below the solidus, Rb, Sr, Ba, and Pb showed the greatest mobility (D ˜ 0.5-1.0), while at the solidus, Th and Be became notably partitioned into the melt (D values changing from >2.0 to <1.0). K and Rb D values fall below 1.0 when the micas breakdown. Only at the solidus do Th and Rb attain similar partition coefficients, a condition required by arc data. Taken together, the

Strain induced grain boundary migration effects on grain growth of an austenitic stainless steel during static and metadynamic recrystallization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paggi, A., E-mail: alpaggi@tenaris.com; Angella, G.; Donnini, R.

Static and metadynamic recrystallization of an AISI 304L austenitic stainless steel was investigated at 1100 °C and 10{sup −} {sup 2} s{sup −} {sup 1} strain rate. The kinetics of recrystallization was determined through double hit compression tests. Two strain levels were selected for the first compression hit: ε{sub f} = 0.15 for static recrystallization (SRX) and 0.25 for metadynamic recrystallization (MDRX). Both the as-deformed and the recrystallized microstructures were investigated through optical microscopy and electron back-scattered diffraction (EBSD) technique. During deformation, strain induced grain boundary migration appeared to be significant, producing a square-like grain boundary structure aligned along themore » directions of the maximum shear stresses in compression. EBSD analysis revealed to be as a fundamental technique that the dislocation density was distributed heterogeneously in the deformed grains. Grain growth driven by surface energy reduction was also investigated, finding that it was too slow to explain the experimental data. Based on microstructural results, it was concluded that saturation of the nucleation sites occurred in the first stages of recrystallization, while grain growth driven by strain induced grain boundary migration (SIGBM) dominated the subsequent stages. - Highlights: • Recrystallization behavior of a stainless steel was investigated at 1100 °C. • EBSD revealed that the dislocation density distribution was heterogeneous during deformation. • Saturation of nucleation sites occurred in the first stages of recrystallization. • Strain induced grain boundary migration (SIGBM) effects were significant. • Grain growth driven by SIGBM dominated the subsequent stages.« less

Constitutive relations for determining the critical conditions for dynamic recrystallization behavior

NASA Astrophysics Data System (ADS)

Choe, J. I.

2016-04-01

A series mathematical model has been developed for the prediction of flow stress and microstructure evolution during the hot deformation of metals such as copper or austenitic steels with low stacking fault energies, involving features of both diffusional flow and dislocation motion. As the strain rate increases, multiple peaks on the stress-strain curve decrease. At a high strain rate, the stress rises to a single peak, while dynamic recrystallization causes an oscillatory behavior. At a low strain rate (when there is sufficient time for the recrystallizing grains to grow before they become saturated with high dislocation density with an increase in strain rate), the difference in stored stress between recrystallizing and old grains diminishes, resulting in reduced driving force for grain growth and rendering smaller grains in the alloy. The final average grain size at the steady stage (large strain) increases with a decrease in the strain rate. During large strain deformation, grain size reduction accompanying dislocation creep might be balanced by the grain growth at the border delimiting the ranges of realization (field boundary) of the dislocation-creep and diffusion-creep mechanisms.

Glass-Transition Temperature of the β-Relaxation as the Major Predictive Parameter for Recrystallization of Neat Amorphous Drugs.

PubMed

Kissi, Eric Ofosu; Grohganz, Holger; Löbmann, Korbinian; Ruggiero, Michael T; Zeitler, J Axel; Rades, Thomas

2018-03-15

Recrystallization of amorphous drugs is currently limiting the simple approach to improve solubility and bioavailability of poorly water-soluble drugs by amorphization of a crystalline form of the drug. In view of this, molecular mobility, α-relaxation and β-relaxation processes with the associated transition temperatures T gα and T gβ , was investigated using dynamic mechanical analysis (DMA). The correlation between the transition temperatures and the onset of recrystallization for nine amorphous drugs, stored under dry conditions at a temperature of 296 K, was determined. From the results obtained, T gα does not correlate with the onset of recrystallization under the experimental storage conditions. However, a clear correlation between T gβ and the onset of recrystallization was observed. It is shown that at storage temperature below T gβ , amorphous nifedipine retains its amorphous form. On the basis of the correlation, an empirical correlation is proposed for predicting the onset of recrystallization for drugs stored at 0% RH and 296 K.

Combined Effect of Heating Rate and Microalloying Elements on Recrystallization During Annealing of Dual-Phase Steels

NASA Astrophysics Data System (ADS)

Bellavoine, Marion; Dumont, Myriam; Drillet, Josée; Hébert, Véronique; Maugis, Philippe

2018-05-01

Adjusting ferrite recrystallization kinetics during annealing is a way to control the final microstructure and thus the mechanical properties of advanced cold-rolled high-strength steels. Two strategies are commonly used for this purpose: adjusting heating rates and/or adding microalloying elements. The present work investigates the effect of heating rate and microalloying elements Ti, Nb, and Mo on recrystallization kinetics during annealing in various cold-rolled Dual-Phase steel grades. The use of combined experimental and modeling approaches allows a deeper understanding of the separate influence of heating rate and the addition of microalloying elements. The comparative effect of Ti, Nb, and Mo as solute elements and as precipitates on ferrite recrystallization is also clarified. It is shown that solute drag has the largest delaying effect on recrystallization in the present case and that the order of solute drag effectiveness of microalloying elements is Nb > Mo > Ti.

Combined Effect of Heating Rate and Microalloying Elements on Recrystallization During Annealing of Dual-Phase Steels

NASA Astrophysics Data System (ADS)

Bellavoine, Marion; Dumont, Myriam; Drillet, Josée; Hébert, Véronique; Maugis, Philippe

2018-07-01

Adjusting ferrite recrystallization kinetics during annealing is a way to control the final microstructure and thus the mechanical properties of advanced cold-rolled high-strength steels. Two strategies are commonly used for this purpose: adjusting heating rates and/or adding microalloying elements. The present work investigates the effect of heating rate and microalloying elements Ti, Nb, and Mo on recrystallization kinetics during annealing in various cold-rolled Dual-Phase steel grades. The use of combined experimental and modeling approaches allows a deeper understanding of the separate influence of heating rate and the addition of microalloying elements. The comparative effect of Ti, Nb, and Mo as solute elements and as precipitates on ferrite recrystallization is also clarified. It is shown that solute drag has the largest delaying effect on recrystallization in the present case and that the order of solute drag effectiveness of microalloying elements is Nb > Mo > Ti.

An electron microscopy examination of primary recrystallization in TD-nickel.

NASA Technical Reports Server (NTRS)

Petrovic, J. J.; Ebert, L. J.

1972-01-01

Primary recrystallization in TD-nickel 1 in. bar has previously been regarded as the process by which the initial fine grain structure is converted to a coarse grain size (increases in grain size by 500 times) under suitable deformation and annealing conditions. This process is dependent on deformation mode. While it occurs readily after rolling transverse to the bar axis and annealing (800 C), it is completely inhibited by longitudinal rolling and swaging deformations, even for very high (1320 C) annealing temperatures. A transmission electron microscopy examination of deformation and annealing substructures indicates that primary recrystallization in TD-nickel 1 in. bar actually occurs on the sub-light optical level, to produce a grain structure similar in size to the initial fine grained state.

Phase-pure eutectic CoFe2O4-Ba1-xSrxTiO3 composites prepared by floating zone melting

NASA Astrophysics Data System (ADS)

Breitenbach, Martin; Ebbinghaus, Stefan G.

2018-02-01

Composites consisting of ferrimagnetic CoFe2O4 and ferroelectric Ba1-xSrxTiO3 were grown by the floating zone technique. The influence of Sr substitution, growth rate and atmosphere during the floating zone process were investigated. The formation of the non-ferroelectric, hexagonal modification of BaTiO3 was avoided by a slight Sr substitution of 3 mol% and the formation of BaFe12O19 was suppressed using pure nitrogen as atmosphere during the floating zone melting. These synthesis parameters led to phase-pure, but electrically conductive CoFe2O4-Ba1-xSrxTiO3 composites. A thermal treatment at 973 K in air resulted in a strong increase of the electric resistivity accompanied by a decrease of the unit-cell parameters of both components indicating the healing of oxygen defects. SEM investigations revealed a variety of different geometric structures and crack-free interfaces between both phases. The low porosities observed in the micrographs correspond with densities above 90%. Magnetoelectric (ME) measurements confirmed a coupling between the ferroic orders of both phases with a hysteresis and maximum αME of 1.3 mV Oe-1 cm-1.

Effects of rolling conditions on recrystallization microstructure and texture in magnetostrictive Fe-Ga-Al rolled sheets

NASA Astrophysics Data System (ADS)

Li, Jiheng; Liu, Yangyang; Li, Xiaojuan; Mu, Xing; Bao, Xiaoqian; Gao, Xuexu

2018-07-01

The effects of different rolling conditions on the microstructure and texture of primary and secondary recrystallization in magnetostrictive Fe82Ga9Al9+0.1at%NbC alloy sheets were investigated. After the primary recrystallization annealing at 850 °C for 5 min, the as-rolled sheets prepared by warm-cold rolling with an intermediate annealing, can be fully recrystallized, and obtain the homogeneous matrix in which the fine dispersed NbC precipitate particles are distributed. The primary recrystallization textures of sheets with different rolling conditions consist mostly of strong {1 0 0} textures, γ-fiber textures, {4 1 1}〈1 4 8〉 texture and weak Goss texture. In the primary recrystallized sheets prepared by warm-cold rolling with an intermediate annealing, the high energy grain boundaries and ∑9 boundaries have the highest proportion. After high temperature annealing, the secondary recrystallizations of Goss grains in these sheets are more complete, and the size of abnormal grown Goss grain is up to several centimeters, which results in the strongest Goss texture. Correspondingly, the largest magnetostriction of 183 ppm is observed. The sample prepared by warm-cold rolling with an intermediate annealing, has homogeneous primary matrix, special texture components and grain boundary distribution, all of which provide a better surrounding for the abnormal growth of Goss grains. This work indicates that the control of rolling conditions of Fe-Ga-Al alloy sheets is necessary to achieve the strong Goss texture and obtain a possible high magnetostriction if other appropriate conditions (stress, domain structure) are achieved.

Slab melting beneath the Cascade Arc driven by dehydration of altered oceanic peridotite

NASA Astrophysics Data System (ADS)

Walowski, K. J.; Wallace, P. J.; Hauri, E. H.; Wada, I.; Clynne, M. A.

2015-05-01

Water is returned to Earth’s interior at subduction zones. However, the processes and pathways by which water leaves the subducting plate and causes melting beneath volcanic arcs are complex; the source of the water--subducting sediment, altered oceanic crust, or hydrated mantle in the downgoing plate--is debated; and the role of slab temperature is unclear. Here we analyse the hydrogen-isotope and trace-element signature of melt inclusions in ash samples from the Cascade Arc, where young, hot lithosphere subducts. Comparing these data with published analyses, we find that fluids in the Cascade magmas are sourced from deeper parts of the subducting slab--hydrated mantle peridotite in the slab interior--compared with fluids in magmas from the Marianas Arc, where older, colder lithosphere subducts. We use geodynamic modelling to show that, in the hotter subduction zone, the upper crust of the subducting slab rapidly dehydrates at shallow depths. With continued subduction, fluids released from the deeper plate interior migrate into the dehydrated parts, causing those to melt. These melts in turn migrate into the overlying mantle wedge, where they trigger further melting. Our results provide a physical model to explain melting of the subducted plate and mass transfer from the slab to the mantle beneath arcs where relatively young oceanic lithosphere is subducted.

Slab melting beneath the Cascades Arc driven by dehydration of altered oceanic peridotite

USGS Publications Warehouse

Walowski, Kristina J; Wallace, Paul J.; Hauri, E.H.; Wada, I.; Clynne, Michael A.

2015-01-01

Water is returned to Earth’s interior at subduction zones. However, the processes and pathways by which water leaves the subducting plate and causes melting beneath volcanic arcs are complex; the source of the water—subducting sediment, altered oceanic crust, or hydrated mantle in the downgoing plate—is debated; and the role of slab temperature is unclear. Here we analyse the hydrogen-isotope and trace-element signature of melt inclusions in ash samples from the Cascade Arc, where young, hot lithosphere subducts. Comparing these data with published analyses, we find that fluids in the Cascade magmas are sourced from deeper parts of the subducting slab—hydrated mantle peridotite in the slab interior—compared with fluids in magmas from the Marianas Arc, where older, colder lithosphere subducts. We use geodynamic modelling to show that, in the hotter subduction zone, the upper crust of the subducting slab rapidly dehydrates at shallow depths. With continued subduction, fluids released from the deeper plate interior migrate into the dehydrated parts, causing those to melt. These melts in turn migrate into the overlying mantle wedge, where they trigger further melting. Our results provide a physical model to explain melting of the subducted plate and mass transfer from the slab to the mantle beneath arcs where relatively young oceanic lithosphere is subducted.

Optimum rolling ratio for obtaining {001}<110> recrystallization texture in Ti-Nb-Al biomedical shape memory alloy.

PubMed

Inamura, T; Shimizu, R; Kim, H Y; Miyazaki, S; Hosoda, H

2016-04-01

The rolling rate (r) dependence of textures was investigated in the Ti-26Nb-3Al (mol%) alloy to reveal the conditions required to form the {001}<110> recrystallization texture, which is a desirable orientation for the β-titanium shape memory alloy. {001}<110> was the dominant cold-rolling texture when r=90% and it was transferred to the recrystallization texture without forming {112}<110>, which is detrimental for the isotropic mechanical properties of the rolled sheet. A further increase in r resulted in the formation of {112}<110> in both rolling and recrystallization textures. Therefore, r should be controlled to form only the {001}<110> rolling texture, because the {112}<110> texture can overwhelm the {001}<110> texture during recrystallization. Copyright © 2016 Elsevier B.V. All rights reserved.

Modified floating-zone growth of organic single crystals

NASA Astrophysics Data System (ADS)

Kou, S.; Chen, C. P.

1994-04-01

For organic materials floating-zone crystal growth is superior to other melt growth processes in two significant respects: (1) the absence of crucible-induced mechanical damage and (2) minimum heating-induced chemical degradation. Due to the rather low surface tension of organic melts, however, floating-zone crystal growth under normal gravity has not been possible so far but microgravity is ideal for such a purpose. With the help of a modified floating-zone technique, organic single crystals of small cross-sections were test grown first under normal gravity. These small crystals were round and rectangular single crystals of benzil and salol, up to about 7 cm long and 6 mm in diameter or 9 mm × 3 mm in cross-section.

Investigation of primary static recrystallization in a NiTiFe shape memory alloy subjected to cold canning compression using the coupling crystal plasticity finite element method with cellular automaton

NASA Astrophysics Data System (ADS)

Zhang, Yanqiu; Jiang, Shuyong; Hu, Li; Zhao, Yanan; Sun, Dong

2017-10-01

The behavior of primary static recrystallization (SRX) in a NiTiFe shape memory alloy (SMA) subjected to cold canning compression was investigated using the coupling crystal plasticity finite element method (CPFEM) with the cellular automaton (CA) method, where the distribution of the dislocation density and the deformed grain topology quantified by CPFEM were used as the input for the subsequent SRX simulation performed using the CA method. The simulation results were confirmed by the experimental ones in terms of microstructures, average grain size and recrystallization fraction, which indicates that the proposed coupling method is well able to describe the SRX behavior of the NiTiFe SMA. The results show that the dislocation density exhibits an inhomogeneous distribution in the deformed sample and the recrystallization nuclei mainly concentrate on zones where the dislocation density is relatively higher. An increase in the compressive deformation degree leads to an increase in nucleation rate and a decrease in grain boundary spaces in the compression direction, which reduces the growth spaces for the SRX nuclei and impedes their further growth. In addition, both the mechanisms of local grain refinement in the incomplete SRX and the influence of compressive deformation degree on the grain size of SRX were vividly illustrated by the corresponding physical models.

Prediction of recrystallization behavior of troglitazone/polyvinylpyrrolidone solid dispersion by solid-state NMR.

PubMed

Ito, Atsutoshi; Watanabe, Tomoyuki; Yada, Shuichi; Hamaura, Takeshi; Nakagami, Hiroaki; Higashi, Kenjirou; Moribe, Kunikazu; Yamamoto, Keiji

2010-01-04

The purpose of this study was to elaborate the relationship between the (13)C CP/MAS NMR spectra and the recrystallization behavior during the storage of troglitazone solid dispersions. The solid dispersions were prepared by either the solvent method or by co-grinding. The recrystallization behavior under storage conditions at 40 degrees C/94% RH was evaluated by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. Solid dispersions prepared by the solvent method or by prolonged grinding brought about inhibition of the nucleation and the nuclei growth at the same time. No differences in the PXRD profiles were found in the samples prepared by the co-grinding and solvent methods, however, (13)C CP/MAS NMR showed significant differences in the spectra. The correlation coefficients using partial least square regression analysis between the PXRD profiles and the apparent nuclei-growth constant or induction period to nucleation were 0.1305 or 0.6350, respectively. In contrast, those between the (13)C CP/MAS NMR spectra and the constant or the period were 0.9916 or 0.9838, respectively. The (13)C CP/MAS NMR spectra had good correlation with the recrystallization kinetic parameters evaluated by the KJMA equation. Consequently, solid-state NMR was judged to be a useful tool for the prediction of the recrystallization behavior of solid dispersions.

Chlorine and fluorine partition coefficients and abundances in sub-arc mantle xenoliths (Kamchatka, Russia): Implications for melt generation and volatile recycling processes in subduction zones

NASA Astrophysics Data System (ADS)

Bénard, A.; Koga, K. T.; Shimizu, N.; Kendrick, M. A.; Ionov, D. A.; Nebel, O.; Arculus, R. J.

2017-02-01

We report chlorine (Cl) and fluorine (F) abundances in minerals, interstitial glasses, and melt inclusions in 12 andesite-hosted, spinel harzburgite xenoliths and crosscutting pyroxenite veins exhumed from the sub-arc lithospheric mantle beneath Avacha volcano in the Kamchatka Arc (NE Russia). The data are used to calculate equilibrium mineral-melt partition coefficients (D mineral / melt) for Cl and F relevant to subduction-zone processes and unravel the history of volatile depletion and enrichment mechanisms in an arc setting. Chlorine is ∼100 times more incompatible in pyroxenes (DClmineral/melt = 0.005-0.008 [±0.002-0.003]) than F (DFmineral/melt = 0.50-0.57 [±0.21-0.24]), which indicates that partial melting of mantle sources leads to strong depletions in Cl relative to F in the residues. The data set in this study suggests a strong control of melt composition on DCl,Fpyroxene/melt, in particular H2O contents and Al/(Al + Si), which is in line with recent experiments. Fluorine is compatible in Ca-amphibole in the 'wet' sub-arc mantle (DFamphibole/melt = 3.5-3.7 [±1.5]) but not Cl (DClamphibole/melt = 0.03-0.05 [±0.01-0.03]), indicating that amphibole may fractionate F from Cl in the mantle wedge. The inter-mineral partition coefficients for Cl and F in this study are consistent amongst different harzburgite samples, whether they contain glass or not. In particular, disseminated amphibole hosts much of the Cl and F bulk rock budgets of spinel harzburgites (DClamphibole/pyroxene up to 14 and DFamphibole/pyroxene up to 40). Chlorine and fluorine are variably enriched (up to 1500 ppm Cl and 750 ppm F) in the parental arc picrite and boninite melts of primitive pyroxenite veins (and related melt inclusions) crosscutting spinel harzburgites. Based on the data in this study, the main inferences on the behaviour of Cl and F during melting and metasomatic processes in the sub-arc mantle are as follow: (i) Melting models show that most depleted mantle protoliths

Magma evolution at Copahue volcano (Chile/Argentina border): insights from melt inclusions

NASA Astrophysics Data System (ADS)

Cannatelli, C.; Aracena, C.; Leisen, M.; Moncada, D.; Roulleau, E.; Vinet, N.; Petrelli, M.; Paolillo, A.; Barra, F.; Morata, D.

2016-12-01

Copahue volcano is an active stratovolcano in the Andean Southern Volcanic Zone (SVZ), straddling at the border between Central Chile and Argentina. The volcano's eruptive style during its history has changed from mainly effusive in the Pleistocene to explosive in the Holocene. The prehistoric eruptions can be divided into pre-glacial (PG), syn-glacial (SG) and post-glacial (PM) stages, with products ranging from basaltic andesites to andesites. In order to investigate the evolution of the magma source and volatiles through time, we have focused our study on the eruptive products from the SG to the 2014 eruption (SUM2014). Sampled rocks are glomero-porphyritic, with a paragenetic mineral sequence of feldspars, ortho- and clinopyroxene, and olivine in order of abundance. All samples present a variable number of vesicles, with SUM2014 samples containing the biggest amount. Feldspar composition varies from Na-rich (andesine) in SG to Ca-rich (labradorite) in SUM2014. Two pyroxene types are present in SG and PM samples (augite and enstatite), while SUM2014 presents augite, pigeonite and enstatite. Thermobarometric estimation, based on mineral chemistry, show a bimodal distribution for SG and SUM2014 (P=10-12 kbars and 5-8 kbars) and only one interval for PM (P=7-8 kbars). Melt Inclusions Assemblages (MIAs) are found in all mineral phases, mostly re-crystallized, with one or more bubbles and daughter oxide minerals. Compositions vary from trachy-andesitic to dacitic for SG, andesitic to trachydacitic for PM, and basaltic andesitic to trachydacitic for SUM2014. Major elements systematics show the existence of a bimodal distribution of pyroxene and feldspar hosted-MIA in SUM2014, which together with the co-presence of pigeonite (low-Ca pyroxene) and augite and the bimodal distribution of P, can be interpreted as evidence of mixing of two types of magmas, evolving at different depths. Trace elements systematics for MIA in SG, PM and SUM2014 show a negative anomaly for Nb

Deformation Mechanism and Recrystallization Relationships in Galfenol Single Crystals: On the Origin of Goss and Cube Orientations

NASA Astrophysics Data System (ADS)

Na, Suok-Min; Smith, Malcolm; Flatau, Alison B.

2018-06-01

In this work, deformation mechanism related to recrystallization behavior in single-crystal disks of Galfenol (Fe-Ga alloy) was investigated to gain insights into the influence of crystal orientations on structural changes and selective grain growth that take place during secondary recrystallization. We started with the three kinds of single-crystal samples with (011)[100], (001)[100], and (001)[110] orientations, which were rolled and annealed to promote the formation of different grain structures and texture evolutions. The initial Goss-oriented (011)[100] crystal mostly rotated into {111}<112> orientations with twofold symmetry and shear band structures by twinning resulted in the exposure of rolled surface along {001}<110> orientation during rolling. In contrast, the Cube-oriented (001)[100] single crystal had no change in texture during rolling with the thickness reduction up to 50 pct. The {123}<111> slip systems were preferentially activated in these single crystals during deformation as well as {112}<111> slip systems that are known to play a role in primary slip of body-centered cubic (BCC) materials such as α-iron and Fe-Si alloys. After annealing, the deformed Cube-oriented single crystal had a small fraction (<10 pct) of recrystallized Goss-oriented grains. The weak Goss component remained in the shear bands of the 50 pct rolled Goss-oriented single crystal, and it appeared to be associated with coalescence of subgrains inside shear band structures during primary recrystallization. Rolling of the (001)[110] single crystal led to the formation of a tilted (001)[100] component close to the <120> orientation, associated with {123}<111> slip systems as well. This was expected to provide potential sites of nucleation for secondary recrystallization; however, no Goss- and Cube-oriented components actually developed in this sample during secondary recrystallization. Those results illustrated how the recrystallization behavior can be influenced by deformed

Hydrous melt-rock reaction in the shallow mantle wedge

NASA Astrophysics Data System (ADS)

Mitchell, A.; Grove, T. L.

2017-12-01

In subduction zone magmatism, hotter, deeper hydrous mantle melts rise and interact with the shallower, cooler depleted mantle in the uppermost part of the mantle wedge. Here, we experimentally investigate these hydrous reactions using three different ratios of a 1.6 GPa mantle melt and an overlying 1.2 GPa harzburgite from 1060 to 1260 °C. At low ratios of melt/mantle (20:80 and 5:95), the crystallizing assemblages are dunites, harzburgites, and lherzolites (as a function of temperature). When the ratio of deeper melt to overlying mantle is 70:30, the crystallizing assemblage is a wehrlite. This shows that wehrlites, which are observed in ophiolites and mantle xenoliths, can be formed by large amounts of deeper melt fluxing though the mantle wedge during ascent. In all cases, orthopyroxene dissolves in the melt, and olivine crystallizes along with pyroxenes and spinel. The amount of reaction between deeper melts and overlying mantle, simulated here by the three starting compositions, imposes a strong influence on final melt compositions, particularly in terms of depletion. At the lowest melt/mantle ratios, the resulting melt is an extremely depleted Al-poor, high-Si andesite. As the fraction of melt to mantle increases, final melts resemble primitive basaltic andesites found in arcs globally. Wall rock temperature is a key variable; over a span of <80 °C, reaction with deeper melt creates the entire range of mantle lithologies from a depleted dunite to a harzburgite to a refertilized lherzolite. Together, the experimental phase equilibria, melt compositions, and calculated reaction coefficients provide a framework for understanding how melt-wall rock reaction occurs in the natural system during melt ascent in the mantle wedge.

Effect of Scandium on the Interaction of Concurrent Precipitation and Recrystallization in Commercial AA3003 Aluminum Alloy

NASA Astrophysics Data System (ADS)

Tu, Yiyou; Qian, Huan; Zhou, Xuefeng; Jiang, Jianqing

2014-04-01

In the current study, the effect of Sc addition on the interaction of concurrent precipitation and recrystallization in commercial AA3003 aluminum alloy was investigated using optical microscopy, scanning electron microscopy, and transmission electron microscopy. In case of AA3003 alloy, which was cold rolled to a true strain of 2.20 and heated at a heating rate of 150 K/s, the onset of precipitation and ending of recrystallization are signified by the critical temperature, T C ~740 K (467 °C). There is a change in the shape of the recrystallized grains from pancake-like to equiaxed shape, as the annealing temperature increases greater than T C. In case of AA3003 alloy microalloyed with 0.4 wt pct of Sc, the high no. density precipitation of coherent Al3Sc precipitates always occurs before recrystallization because of the small nucleation barrier and high rate of decomposition. This leads to extremely coarse pancake-like recrystallization grains with high fraction of low-angle grain boundaries in the entire annealing temperature range, even at a high brazing temperature of 883 K (610 °C).

Structure, Frictional Melting and Fault Weakening during the 2008 Mw 7.9 Wenchuan Earthquake Slip: Observation from the WFSD Drilling Core Samples

NASA Astrophysics Data System (ADS)

Li, H.; Wang, H.; Li, C.; Zhang, J.; Sun, Z.; Si, J.; Liu, D.; Chevalier, M. L.; Han, L.; Yun, K.; Zheng, Y.

2015-12-01

The 2008 Mw7.9 Wenchuan earthquake produced two co-seismic surface ruptures along Yingxiu-Beichuan fault (~270 km) and the Guanxian-Anxian fault (~80 km) simultaneously in the Longmen Shan thrust belt. Besides, two surface rupture zones were tracked in the southern segment of the Yingxiu-Beichuan rupture zone, one along the Yingxiu fault, the other along the Shenxigou-Longchi fault, which both converged into one rupture zone at the Bajiaomiao village, Hongkou town, where one distinct fault plane with two striation orientations was exposed. The Wenchuan earthquake Fault Scientific Drilling project (WFSD) was carried out right after the earthquake to investigate its faulting mechanisms and rupture process. Six boreholes were drilled along the rupture zones with depths ranging from 600 to 2400 m. WFSD-1 and WFSD-2 are located at the Bajiaomiao area, the southern segment of the Yingxiu-Beichuan rupture zone, while WFSD-4 and WFSD-4S are in the Nanba town area, in the northern part of the rupture zone. Detailed research showed that ~1 mm thick Principal Slip Zone (PSZ) of the Wenchuan earthquake is located at ~589 m-depth in the WFSD-1 cores. Graphite present in the PSZ indicates a low fault strength. Long-term temperature monitoring shows an extremely low fault friction coefficient during the earthquake. Recently, another possible PSZ was found in WFSD-1 cores at ~732 m-depth, with a ~2 mm thick melt layer in the fault gouge, where feldspar was melted but quartz was not, indicating that the frictional melting temperature was 1230°C < T < 1720°C. These two PSZs at depth may correspond to the two co-seismic surface rupture zones. Besides, the Wenchuan earthquake PSZ was also recognized in the WFSD-4S cores, at ~1084 m-depth. About 200-400 μm thick melt layer (fault vein, mainly feldspar), as well as melt injection veins, were observed in the slip zone, where oblique distinct striations were visible on the slip surface. Therefore, there are two PSZs in the shallow

Empirical Retrieval of Surface Melt Magnitude from Coupled MODIS Optical and Thermal Measurements over the Greenland Ice Sheet during the 2001 Ablation Season.

PubMed

Lampkin, Derrick; Peng, Rui

2008-08-22

Accelerated ice flow near the equilibrium line of west-central Greenland Ice Sheet (GIS) has been attributed to an increase in infiltrated surface melt water as a response to climate warming. The assessment of surface melting events must be more than the detection of melt onset or extent. Retrieval of surface melt magnitude is necessary to improve understanding of ice sheet flow and surface melt coupling. In this paper, we report on a new technique to quantify the magnitude of surface melt. Cloud-free dates of June 10, July 5, 7, 9, and 11, 2001 Moderate Resolution Imaging Spectroradiometer (MODIS) daily reflectance Band 5 (1.230-1.250μm) and surface temperature images rescaled to 1km over western Greenland were used in the retrieval algorithm. An optical-thermal feature space partitioned as a function of melt magnitude was derived using a one-dimensional thermal snowmelt model (SNTHERM89). SNTHERM89 was forced by hourly meteorological data from the Greenland Climate Network (GC-Net) at reference sites spanning dry snow, percolation, and wet snow zones in the Jakobshavn drainage basin in western GIS. Melt magnitude or effective melt (E-melt) was derived for satellite composite periods covering May, June, and July displaying low fractions (0-1%) at elevations greater than 2500m and fractions at or greater than 15% at elevations lower than 1000m assessed for only the upper 5 cm of the snow surface. Validation of E-melt involved comparison of intensity to dry and wet zones determined from QSCAT backscatter. Higher intensities (> 8%) were distributed in wet snow zones, while lower intensities were grouped in dry zones at a first order accuracy of ~ ±2%.

Distribution of melt beneath Mount St Helens and Mount Adams inferred from magnetotelluric data

USGS Publications Warehouse

Hill, G.J.; Caldwell, T.G.; Heise, W.; Chertkoff, D.G.; Bibby, H.M.; Burgess, M.K.; Cull, J.P.; Cas, Ray A.F.

2009-01-01

Three prominent volcanoes that form part of the Cascade mountain range in Washington State (USA)Mounts StHelens, Adams and Rainierare located on the margins of a mid-crustal zone of high electrical conductivity1,5. Interconnected melt can increase the bulk conductivity of the region containing the melt6,7, which leads us to propose that the anomalous conductivity in this region is due to partial melt associated with the volcanism. Here we test this hypothesis by using magnetotelluric data recorded at a network of 85 locations in the area of the high-conductivity anomaly. Our data reveal that a localized zone of high conductivity beneath thisvolcano extends downwards to join the mid-crustal conductor. As our measurements were made during the recent period of lava extrusion at Mount St Helens, we infer that the conductivity anomaly associated with the localized zone, and by extension with the mid-crustal conductor, is caused by the presence of partial melt. Our interpretation is consistent with the crustal origin of silicic magmas erupting from Mount St Helens8, and explains the distribution of seismicity observed at the time of the catastrophic eruption in 1980 (refs9, 10). ?? 2009 Macmillan Publishers Limited. All rights reserved.

CO2 Solubility in Rhyolitic Melts as a Function of P, T, and fO2 - Implications for Carbon Flux in Subduction Zones

NASA Astrophysics Data System (ADS)

Duncan, M. S.; Dasgupta, R.

2013-12-01

Understanding the balance between subduction inputs vs. arc output of carbon is critical for constraining the global carbon cycle. However, the agent of carbon transfer from slab to sub-arc mantle is not constrained [1]. Partial melt of ocean-floor sediments is thought to be a key agent of mass transfer in subduction zones, accounting for the trace element characteristics of arc magmas [2]. Yet the carbon carrying capacity of rhyolitic partial melts of sediments remains unknown at sub-arc depths. In our previous work [3], we constrained CO2 solubility of natural rhyolite from 1.5-3.0 GPa, 1300 °C and logfO2 at FMQ×1.0. However, the effects of T and fO2 on CO2 solubility remain unconstrained. In particular, for sediments with organic carbon, graphite stability is expected and the fO2 of C-dissolution can be lower, which may affect the solubility. Thus it is critical to constrain the CO2 solubility of sediment partial melts under graphite-saturated conditions. We determined CO2 solubility of a model rhyolite composition, similar to partial melt composition of natural metapelite [4], at graphite saturation, using Pt/Gr capsules and a piston cylinder device. Experiments were conducted at 1.5-3.0 GPa and 1100-1400 °C. FTIR was employed to measure the concentrations of CO2 and H2O in doubly polished experimental glasses. Raman and SIMS were used to determine the presence of reduced carbon species and total carbon, respectively. FTIR spectra reveal that CO2 is dissolved as both molecular CO2 (CO2mol.) and carbonates (CO32-). For graphite-saturated, hydrous melts with measured H2O ~2.0 wt.%, CO2tot. (CO2mol.+CO32-) values increase with increasing P from ~0.6 to 1.2 wt.% from 1.5 to 3.0 GPa at 1300 °C. These values are lower than more oxidized melts with the same water content, which were 0.85 to 1.99 wt.% CO2 as P increased. At 3 GPa, graphite-saturated experiments from 1100 to 1300 °C yield CO2tot. value of 1.18-1.20 wt.%, suggesting minor effect of temperature in

Copper phthalocyanine films deposited by liquid-liquid interface recrystallization technique (LLIRCT).

PubMed

Patil, K R; Sathaye, S D; Hawaldar, R; Sathe, B R; Mandale, A B; Mitra, A

2007-11-15

The simple recrystallization process is innovatively used to obtain the nanoparticles of copper phthalocyanine by a simple method. Liquid-liquid interface recrystallization technique (LLIRCT) has been employed successfully to produce small sized copper phthalocyanine nanoparticles with diameter between 3-5 nm. The TEM-SAED studies revealed the formation of 3-5 nm sized with beta-phase dominated mixture of alpha and beta copper phthalocyanine nanoparticles. The XRD, SEM, and the UV-vis studies were further carried out to confirm the formation of copper phthalocyanine thin films. The cyclic voltametry (CV) studies conclude that redox reaction is totally reversible one electron transfer process. The process is attributed to Cu(II)/Cu(I) redox reaction.

Rock Melt Borehole Sealing System, Final Technical Report for SBIR Phase I Grant No. DE-SC0011888

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osnes, John D.; Vining, Cody A.; Nopola, Jay R.

Purpose of Research Deep borehole disposal is one option that has received attention in recent years as a possible strategy for long-term disposal of the tens of thousands of tons of spent nuclear fuel. The feasibility of the deep borehole option relies upon designing and constructing an effective seal within the borehole to ensure that the waste package does not communicate with the shallow subsurface biosphere through the borehole itself. Some of the uncertainty associated with the long-term suitability of the deep borehole option is related to (1) the degradation of traditional sealing materials over time and (2) the inabilitymore » of traditional sealing methods to adequately seal a Disturbed Rock Zone surrounding the borehole. One possible system to address these concerns consists of encapsulating the waste in a melt generated from either the waste itself or a plug above the waste. This current project expanded on previous work to further advance the deep borehole disposal concept. Research Objectives & Findings The overarching objective of the study was to evaluate the feasibility of constructing a downhole heater that is capable of meeting the technical and logistical requirements to melt rock. This ultimate objective was accomplished by two primary approaches. The first approach was to define the heater requirements and conceptually design a system that is capable of melting rock. The second approach was to determine the feasibility of conducting an in situ, field-scale melting experiment to validate the suitability of the rock melt seal concept. The evaluation and conceptual design of the heater system resulted in the following primary findings: • Borehole wall temperatures capable of producing a partial melt are achievable under most expected thermal conductivities with a 12-kilowatt heater. • Commercially available components have been identified that meet the requirements of the heater system, including resistive elements that are capable of

Recrystallization as a controlling process in the wear of some f.c.c. metals

NASA Technical Reports Server (NTRS)

Bill, R. C.; Wisander, D.

1977-01-01

Detailed examination of copper specimens after sliding against 440 C steel in liquid methane at speeds up to 25 m/s and loads of up to 2 kg showed the metal comprising the wear surface to possess a fine cell recrystallized structure. Wear proceeded by the plastic shearing of metal in this near surface region without the occurrence of visible metal transfer. A dynamic balance between the intense shear process at the surface and the nucleation of recrystallized grains was proposed to account for the behavior of the metal at the wear surface. Sliding wear experiments were also conducted on Ag, Cu-10% Al, Cu-10% Sn, Ni and Al. It was found that low wear and the absence of heavy metal transfer were associated with those metals observed to undergo recrystallization nucleation without prior recovery.

Generating Melt During Exhumation of Continental Crust from Ultrahigh Pressure (UHP) Conditions

NASA Astrophysics Data System (ADS)

Brown, M.; Wang, S.; Wang, L.; Piccoli, P. M.; Johnson, T. E.

2017-12-01

Hydrate breakdown rather than fluid-present melting is commonly cited during exhumation of UHP continental crust, but may have been overemphasized in relation to petrographic evidence. In this study from the central Sulu belt, China, we posit that dm- to m-scale dikes of leucosome in stromatic migmatite, formerly UHP eclogite, crystallized from hydrous melt derived by evolution of supercritical fluid as it drained through exhuming crust and increased in solute content. Leucosomes comprise Qz + Ph + Ab + Aln/Ep + Grt. Overgrowths of Zrn on inherited cores and new grains crystallized at ca. 223-219 Ma, within the age range of HP eclogite facies recrystallization in the belt. Si-in-Ph/Ti-in-Zrn thermobarometry yields crystallization conditions of 3.0-2.5 GPa at 830-770 °C. Compositions are granitic with normalized TE patterns enriched in LREE relative to HREE and enriched in LILE relative to HFSE, features consistent with crystallization from crustally derived hydrous melt. The leucosomes have Sr-Nd isotope compositions intermediate between host eclogites and surrounding gneisses. At the metamorphic peak, the source rocks were likely fluid deficient or fluid absent. During exhumation from UHP conditions, structural water stored in nominally anhydrous minerals during the prograde evolution was exsolved to form a grain boundary supercritical fluid in eclogite and gneiss. By migrating from grain boundaries into channels and draining from the volumetrically dominant gneiss through eclogite, the fluid acquired a blended Sr-Nd isotope composition intermediate between end-members. Concomitantly, the ascending fluid evolved to a denser, more viscous and more polymerized hydrous melt by dissolution of the silicate matrix. Trapped around the transition from UHP to HP eclogite facies conditions, the melt crystallized by diffusive loss of water to the host eclogite. Aggregates of Pl + Bt around Ph and thin films and cuspate veinlets/patches of Kfs along grain boundaries in

Textural and Rb-Sr isotopic evidence for late Paleozoic mylonitization within the Honey Hill fault zone southeastern Connecticut

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Hara, K.D.; Gromet, L.P.

A petrographic and Rb-Sr isotopic study of rocks within and near the Honey Hill fault zone places important constraints on its history of movement. Rb-Sr apparent ages for micas and plagioclase from these rocks have been reset and range from Permian to Triassic, considerably younger than the minimum stratigraphic age (Ordovician) of the rocks studied or of Acadian (Devonian) regional metamorphism. Permian Rb-Sr ages of dynamically recrystallized muscovite date the development of mylonite fabric. An older age is precluded by the excellent preservation of unrecovered quartz, which indicates that these rocks did not experience temperatures high enough to anneal quartzmore » or thermally reset Rb-Sr isotopic systems in muscovite since the time of mylonitization. Metamorphic mineral assemblages and mineral apparent ages in rocks north of the fault zone indicate recrystallization under similar upper greenschist-lower amphibolite grade conditions during Permian to Triassic time. Collectively these results indicate that the Honey Hill fault zone was active during the Late Paleozoic and that ductile deformation and metamorphism associated with the Alleghanian orogeny extend well into southern Connecticut. An Alleghanian age for mylonitization within the Honey Hill fault zone suggests it should be considered as a possible site for the major Late Paleozoic strike-slip displacements inferred from paleomagnetic studies for parts of coastal New England and maritime Canada.« less

Interface structure and contact melting in AgCu eutectic. A molecular dynamics study

NASA Astrophysics Data System (ADS)

Bystrenko, O.; Kartuzov, V.

2017-12-01

Molecular dynamics simulations of the interface structure in binary AgCu eutectic were performed by using the realistic EAM potential. In simulations, we examined the time dependence of the total energy in the process of equilibration, the probability distributions, the composition profiles for the components, and the component diffusivities within the interface zone. It is shown that the relaxation to the equilibrium in the solid state is accompanied by the formation of the steady disordered diffusion zone at the boundary between the crystalline components. At higher temperatures, closer to the eutectic point, the increase in the width of the steady diffusion zone is observed. The particle diffusivities grow therewith to the numbers typical for the liquid metals. Above the eutectic point, the steady zone does not form, instead, the complete contact melting in the system occurs. The results of simulations indicate that during the temperature increase the phenomenon of contact melting is preceded by the similar process spatially localized in the vicinity of the interface.

Heterogeneous dissemination of projectile materials in the impact melts from Wabar crater, Saudi Arabia

NASA Astrophysics Data System (ADS)

Horz, F.; See, T. H.; Murali, A. V.; Blanchard, D. P.

The initial observations of Spencer (1933) that two distinct impact melts coexist at the 90-m-diameter Wabar crater, Saudi Arabia, is confirmed. A dark or 'black' melt contains on the order of 4 percent meteoritic contamination, while the transparent or 'white' melt contains less than 1 percent. The Fe/Ni ratios in both varieties exhibit considerable scatter on electron-microprobe scales, akin to those reported by others for metal spherules in the black melt. If the meteoritic component is subtracted, both melts are chemically very similar. Clasts engulfed by the Wabar melts were investigated also, as they represent the progenitor lithologies from which the melts formed. Bulk compositions for these clasts reveal subtle differences in modal feldspar content within the quartz-rich Wabar target. Both melts require that a minimum of two target lithologies be present in the Wabar melt zone.

Use of Traveling Magnetic Fields to Control Melt Convection

NASA Technical Reports Server (NTRS)

Ramachandran, Narayanan; Mazuruk, Konstantin; Volz, Martin P.

2000-01-01

An axially traveling magnetic wave induces a meridional base flow in an electrically conducting molten cylindrical zone. This flow can be beneficial for crystal growth applications. In particular, it can be effectively used to stir the melt in long cylindrical columns. It can also be tailored to modify the thermal and species concentration fields in the melt and to control the interface shape of the growing crystal. The basic theory of such an application is developed and data from a preliminary mercury column experiment are presented.

Formation of sinoite in EL chondrites by impact melting

NASA Astrophysics Data System (ADS)

Rubin, Alan E.

1997-03-01

Approximately 10-200-micron-sized sunhedral and euhedral grains of twinned, optically zoned sinoite associated with euhedral enstatite and graphite within impact-melted portions of QUE94368, the first EL4 chondrite, suggest that sinoite formed by crystallization from a melt, not by thermal metamorphism. The occurrence of olivine and enstatite with undulose extinction in QUE94368 indicates that the rock is shock stage S2, corresponding to an equilibration shock pressure of about 5 GPa, as in EL5 and EL6 chondrites.

Recrystallization and grain growth induced by ELMs-like transient heat loads in deformed tungsten samples

NASA Astrophysics Data System (ADS)

Suslova, A.; El-Atwani, O.; Sagapuram, D.; Harilal, S. S.; Hassanein, A.

2014-11-01

Tungsten has been chosen as the main candidate for plasma facing components (PFCs) due to its superior properties under extreme operating conditions in future nuclear fusion reactors such as ITER. One of the serious issues for PFCs is the high heat load during transient events such as ELMs and disruption in the reactor. Recrystallization and grain size growth in PFC materials caused by transients are undesirable changes in the material, since the isotropic microstructure developed after recrystallization exhibits a higher ductile-to-brittle transition temperature which increases with the grain size, a lower thermal shock fatigue resistance, a lower mechanical strength, and an increased surface roughening. The current work was focused on careful determination of the threshold parameters for surface recrystallization, grain growth rate, and thermal shock fatigue resistance under ELM-like transient heat events. Transient heat loads were simulated using long pulse laser beams for two different grades of ultrafine-grained tungsten. It was observed that cold rolled tungsten demonstrated better power handling capabilities and higher thermal stress fatigue resistance compared to severely deformed tungsten. Higher recrystallization threshold, slower grain growth, and lower degree of surface roughening were observed in the cold rolled tungsten.

Recrystallization and grain growth induced by ELMs-like transient heat loads in deformed tungsten samples

PubMed Central

Suslova, A.; El-Atwani, O.; Sagapuram, D.; Harilal, S. S.; Hassanein, A.

2014-01-01

Tungsten has been chosen as the main candidate for plasma facing components (PFCs) due to its superior properties under extreme operating conditions in future nuclear fusion reactors such as ITER. One of the serious issues for PFCs is the high heat load during transient events such as ELMs and disruption in the reactor. Recrystallization and grain size growth in PFC materials caused by transients are undesirable changes in the material, since the isotropic microstructure developed after recrystallization exhibits a higher ductile-to-brittle transition temperature which increases with the grain size, a lower thermal shock fatigue resistance, a lower mechanical strength, and an increased surface roughening. The current work was focused on careful determination of the threshold parameters for surface recrystallization, grain growth rate, and thermal shock fatigue resistance under ELM-like transient heat events. Transient heat loads were simulated using long pulse laser beams for two different grades of ultrafine-grained tungsten. It was observed that cold rolled tungsten demonstrated better power handling capabilities and higher thermal stress fatigue resistance compared to severely deformed tungsten. Higher recrystallization threshold, slower grain growth, and lower degree of surface roughening were observed in the cold rolled tungsten. PMID:25366885

Recrystallization and grain growth induced by ELMs-like transient heat loads in deformed tungsten samples.

PubMed

Suslova, A; El-Atwani, O; Sagapuram, D; Harilal, S S; Hassanein, A

2014-11-04

Tungsten has been chosen as the main candidate for plasma facing components (PFCs) due to its superior properties under extreme operating conditions in future nuclear fusion reactors such as ITER. One of the serious issues for PFCs is the high heat load during transient events such as ELMs and disruption in the reactor. Recrystallization and grain size growth in PFC materials caused by transients are undesirable changes in the material, since the isotropic microstructure developed after recrystallization exhibits a higher ductile-to-brittle transition temperature which increases with the grain size, a lower thermal shock fatigue resistance, a lower mechanical strength, and an increased surface roughening. The current work was focused on careful determination of the threshold parameters for surface recrystallization, grain growth rate, and thermal shock fatigue resistance under ELM-like transient heat events. Transient heat loads were simulated using long pulse laser beams for two different grades of ultrafine-grained tungsten. It was observed that cold rolled tungsten demonstrated better power handling capabilities and higher thermal stress fatigue resistance compared to severely deformed tungsten. Higher recrystallization threshold, slower grain growth, and lower degree of surface roughening were observed in the cold rolled tungsten.

Radial Anisotropy in the Mantle Transition Zone and Its Implications

NASA Astrophysics Data System (ADS)

Chang, S. J.; Ferreira, A. M.

2016-12-01

Seismic anisotropy is a useful tool to investigate mantle flow, mantle convection, and the presence of melts in mantle, since it provides information on the direction of mantle flow or the orientation of melts by combining it with laboratory results in mineral physics. Although the uppermost and lowermost mantle with strong anisotropy have been well studied, anisotropic properties of the mantle transition zone is still enigmatic. We use a recent global radially anisotropic model, SGLOBE-rani, to examine the patterns of radial anisotropy in the mantle transition zone. Strong faster SV velocity anomalies are found in the upper transition zone beneath subduction zones in the western Pacific, which decrease with depth, thereby nearly isotropic in the lower transition zone. This may imply that the origin for the anisotropy is the lattice-preferred orientation of wadsleyite, the dominant anisotropic mineral in the upper transition zone. The water content in the upper transition zone may be inferred from radial anisotropy because of the report that anisotropic intensity depends on the water content in wadsleyite.

Physical stability and recrystallization kinetics of amorphous ibipinabant drug product by fourier transform raman spectroscopy.

PubMed

Sinclair, Wayne; Leane, Michael; Clarke, Graham; Dennis, Andrew; Tobyn, Mike; Timmins, Peter

2011-11-01

The solid-state physical stability and recrystallization kinetics during storage stability are described for an amorphous solid dispersed drug substance, ibipinabant, at a low concentration (1.0%, w/w) in a solid oral dosage form (tablet). The recrystallization behavior of the amorphous ibipinabant-polyvinylpyrrolidone solid dispersion in the tablet product was characterized by Fourier transform (FT) Raman spectroscopy. A partial least-square analysis used for multivariate calibration based on Raman spectra was developed and validated to detect less than 5% (w/w) of the crystalline form (equivalent to less than 0.05% of the total mass of the tablet). The method provided reliable and highly accurate predictive crystallinity assessments after exposure to a variety of stability storage conditions. It was determined that exposure to moisture had a significant impact on the crystallinity of amorphous ibipinabant. The information provided by the method has potential utility for predictive physical stability assessments. Dissolution testing demonstrated that the predicted crystallinity had a direct correlation with this physical property of the drug product. Recrystallization kinetics was measured using FT Raman spectroscopy for the solid dispersion from the tablet product stored at controlled temperature and relative humidity. The measurements were evaluated by application of the Johnson-Mehl-Avrami (JMA) kinetic model to determine recrystallization rate constants and Avrami exponent (n = 2). The analysis showed that the JMA equation could describe the process very well, and indicated that the recrystallization kinetics observed was a two-step process with an induction period (nucleation) followed by rod-like crystal growth. Copyright © 2011 Wiley-Liss, Inc.

Intragranular Recrystallization and Lattice Reorientation of Calcite Grains in Experimentally Deformed Crinoids and Trilobites

NASA Astrophysics Data System (ADS)

Kim, N.; Takahashi, M.; Shigematsu, N.; Ree, J. H.; Jung, H.

2017-12-01

Intragranular recrystallization, including subgrain-rotation-recrystallization (SGR) and nucleation (and growth) of new grains along boundaries of deformation twins and bands, is an important process leading to grain-size reduction and causing rheological change depending on deformation condition. Despite of its importance, the detailed processes of intragranular recrystallization are still somewhat unclear. We deformed a limestone using triaxial testing machine at AIST of Japan at temperature of 500 700 °, strain rate of 10-4 10-5 s-1, confining pressure of 200 MPa and strain of up to 30%, to explore intragranular recrystallization processes of calcite. The limestone contains two abundant fossils, crinoid and trilobite. The crinoids are mono- or poly-crystalline. We focus on the monocrystalline crinoids with a coarser grain size ( 700 μm). The trilobites are polycrystalline and much finer-grained ( 7 μm) with initially a strong c-axis preferred orientation. At a lower temperature condition, subgrains develop both in twin and host domains of crinoids and evolve into new grains by SGR. At a higher temperature, recrystallized grains have irregular grain boundaries and bimodal grain-size distribution, implying grain-boundary migration (GBM) recrystallization. At a lower temperature, new grains nucleating and growing along twin boundaries inherit lattice orientation of twin domain, and with the nucleation site and usually a smaller grain size, they can be distinguished from new grains by SGR. At a higher temperature, however, the distinction is difficult at present due to extensive GBM. For the trilobites, there is only local GBM with no significant change in grain size, and flattening of grains reflects the bulk strain at a lower temperature. At a higher temperature, individual grains of the trilobites are equi-axed with weakened LPO, although the strain of trilobites is higher than bulk strain. These microfabrics suggest that the dominant deformation mechanism of

Constraints on Mantle Plume Melting Conditions in the Martian Mantle Based on Improved Melting Phase Relationships of Olivine-Phyric Shergottite Yamato 980459

NASA Technical Reports Server (NTRS)

Kiefer, Walter S.; Rapp, Jennifer F.; Usui, Tomohiro; Draper, David S.; Filiberto, Justin

2016-01-01

Martian meteorite Yamato 980459 (hereafter Y98) is an olivine-phyric shergottite that has been interpreted as closely approximating a martian mantle melt [1-4], making it an important constraint on adiabatic decompression melting models. It has long been recognized that low pressure melting of the Y98 composition occurs at extremely high temperatures relative to martian basalts (1430 degC at 1 bar), which caused great difficulties in a previous attempt to explain Y98 magma generation via a mantle plume model [2]. However, previous studies of the phase diagram were limited to pressures of 2 GPa and less [2, 5], whereas decompression melting in the present-day martian mantle occurs at pressures of 3-7 GPa, with the shallow boundary of the melt production zone occurring just below the base of the thermal lithosphere [6]. Recent experimental work has now extended our knowledge of the Y98 melting phase relationships to 8 GPa. In light of this improved petrological knowledge, we are therefore reassessing the constraints that Y98 imposes on melting conditions in martian mantle plumes. Two recently discovered olivine- phyric shergottites, Northwest Africa (NWA) 5789 and NWA 6234, may also be primary melts from the martian mantle [7, 8]. However, these latter meteorites have not been the subject of detailed experimental petrology studies, so we focus here on Y98.

In-situ observation of recrystallization in an AlMgScZr alloy using confocal laser scanning microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taendl, J., E-mail: johannes.taendl@tugraz.atl; Nambu, S.; Orthacker, A.

2015-10-15

In this work we present a novel in-situ approach to study the recrystallization behavior of age hardening alloys. We use confocal laser scanning microscopy (CLSM) at 400 °C to investigate the static recrystallization of an AlMg4Sc0.4Zr0.12 alloy in-situ. The results are combined with electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analyses. It was found that CLSM is a powerful tool to visualize both the local initiation and temporal sequence of recrystallization. After fast nucleation and initial growth, the grain growth rate decreases and the grain boundary migration stops after some minutes due to Zener pinning from Al{sub 3}(Sc,Zr)more » precipitates produced during the heat treatment. EBSD and TEM analyses confirm both the boundary movements and the particle-boundary interactions. - Highlights: • First time that CLSM is used to study recrystallization in-situ. • The start and end of recrystallization can be directly observed. • The procedure is easy to apply and requires only simple data interpretation. • In-situ observations on the surface correlate to modifications inside the bulk. • In-situ observations correlate to EBSD and EFTEM analyses.« less

Influence of Heating Rate on Ferrite Recrystallization and Austenite Formation in Cold-Rolled Microalloyed Dual-Phase Steels

NASA Astrophysics Data System (ADS)

Philippot, C.; Bellavoine, M.; Dumont, M.; Hoummada, K.; Drillet, J.; Hebert, V.; Maugis, P.

2018-01-01

Compared with other dual-phase (DP) steels, initial microstructures of cold-rolled martensite-ferrite have scarcely been investigated, even though they represent a promising industrial alternative to conventional ferrite-pearlite cold-rolled microstructures. In this study, the influence of the heating rate (over the range of 1 to 10 K/s) on the development of microstructures in a microalloyed DP steel is investigated; this includes the tempering of martensite, precipitation of microalloying elements, recrystallization, and austenite formation. This study points out the influence of the degree of ferrite recrystallization prior to the austenite formation, as well as the importance of the cementite distribution. A low heating rate giving a high degree of recrystallization, leads to the formation of coarse austenite grains that are homogenously distributed in the ferrite matrix. However, a high heating rate leading to a low recrystallization degree, results in a banded-like structure with small austenite grains surrounded by large ferrite grains. A combined approach, involving relevant multiscale microstructural characterization and modeling to rationalize the effect of the coupled processes, highlights the role of the cold-worked initial microstructure, here a martensite-ferrite mixture: recrystallization and austenite formation commence in the former martensite islands before extending in the rest of the material.

Empirical Retrieval of Surface Melt Magnitude from Coupled MODIS Optical and Thermal Measurements over the Greenland Ice Sheet during the 2001 Ablation Season

PubMed Central

Lampkin, Derrick; Peng, Rui

2008-01-01

Accelerated ice flow near the equilibrium line of west-central Greenland Ice Sheet (GIS) has been attributed to an increase in infiltrated surface melt water as a response to climate warming. The assessment of surface melting events must be more than the detection of melt onset or extent. Retrieval of surface melt magnitude is necessary to improve understanding of ice sheet flow and surface melt coupling. In this paper, we report on a new technique to quantify the magnitude of surface melt. Cloud-free dates of June 10, July 5, 7, 9, and 11, 2001 Moderate Resolution Imaging Spectroradiometer (MODIS) daily reflectance Band 5 (1.230-1.250μm) and surface temperature images rescaled to 1km over western Greenland were used in the retrieval algorithm. An optical-thermal feature space partitioned as a function of melt magnitude was derived using a one-dimensional thermal snowmelt model (SNTHERM89). SNTHERM89 was forced by hourly meteorological data from the Greenland Climate Network (GC-Net) at reference sites spanning dry snow, percolation, and wet snow zones in the Jakobshavn drainage basin in western GIS. Melt magnitude or effective melt (E-melt) was derived for satellite composite periods covering May, June, and July displaying low fractions (0-1%) at elevations greater than 2500m and fractions at or greater than 15% at elevations lower than 1000m assessed for only the upper 5 cm of the snow surface. Validation of E-melt involved comparison of intensity to dry and wet zones determined from QSCAT backscatter. Higher intensities (> 8%) were distributed in wet snow zones, while lower intensities were grouped in dry zones at a first order accuracy of ∼ ±2%. PMID:27873793

Cu refertilization of abyssal harzburgites by melt percolation

NASA Astrophysics Data System (ADS)

Ciazela, Jakub; Dick, Henry; Koepke, Juergen; Botcharnikov, Roman; Muszynski, Andrzej; Kuhn, Thomas

2015-04-01

Primitive mantle is depleted in many elements by partial melting processes, but it can be subsequently refertilized by impregnation with percolating melts. It is known that Cu can be enriched in primitive melts, depleting mantle residue, due to the former process (Patten et al. 2013). However, the behavior of Cu in the processes of mantle-melt interaction is poorly understood. The only comprehensive study is based on compositions of orogenic peridotites, representing the subcontinental mantle (Lorand et al. 1993; 2013), where a moderate enrichment of the mantle in Cu (up to ~50 ppm) has been observed. Here, we present the first results obtained for a suite of rocks from an oceanic core complex (OCC), the Kane Megamullion at 22°30'N at the Mid-Atlantic Ridge (Dick et al. 2008). OCC's provide large exposures of mantle and lower crustal rocks on the seafloor on detachment fault footwalls at slow and ultraslow spreading ridges. The mantle rocks are composed of spinel and plagioclase harzburgites. The spinel harzburgites represent depleted mantle, whereas the plagioclase harzburgites were formed by subsequent late-stage melt impregnation in the depleted mantle (Dick et al. 2010). We have determined Cu concentrations in 22 residual spinel harzburgites and 4 plagioclase harzburgites using total digestion ICP-MS. The average Cu concentration in spinel harzburgites is 35±11 ppm Cu (2σ). The average Cu concentration obtained for plagioclase harzburgites is 131±33 ppm Cu (2σ). Additionally, we have analyzed one 1.5 cm thick contact zone between an oxide gabbro vein and residual peridotite. The contact zone, which has been heavily impregnated by the melt, contains 284 ppm Cu. In contrast, the neighboring oxide gabbro vein and the hosting peridotite contain 147 and 68 ppm Cu, respectively. Furthermore, we have determined the concentration of Cu in a dunite (118 ppm), formed in a reaction between the mantle and melt ascending through the lithosphere (Dick et al. 2010

Recrystallization of Manganite (γ-MnOOH) and Implications for Trace Element Cycling.

PubMed

Hens, Tobias; Brugger, Joël; Cumberland, Susan A; Etschmann, Barbara; Frierdich, Andrew J

2018-02-06

The recrystallization of Mn(III,IV) oxides is catalyzed by aqueous Mn(II) (Mn(II) aq ) during (bio)geochemical Mn redox cycling. It is poorly understood how trace metals associated with Mn oxides (e.g., Ni) are cycled during such recrystallization. Here, we use X-ray absorption spectroscopy (XAS) to examine the speciation of Ni associated with Manganite (γ-Mn(III)OOH) suspensions in the presence or absence of Mn(II) aq under variable pH conditions (pH 5.5 and 7.5). In a second set of experiments, we used a 62 Ni isotope tracer to quantify the amount of dissolved Ni that exchanges with Ni incorporated in the Manganite crystal structure during reactions in 1 mM Mn(II) aq and in Mn(II)-free solutions. XAS spectra show that Ni is initially sorbed on the Manganite mineral surface and is progressively incorporated into the mineral structure over time (13% after 51 days) even in the absence of dissolved Mn(II). The amount of Ni incorporation significantly increases to about 40% over a period of 51 days when Mn(II) aq is present in solution. Similarly, Mn(II) aq promotes Ni exchange between Ni-substituted Manganite and dissolved Ni(II), with around 30% of Ni exchanged at pH 7.5 over the duration of the experiment. No new mineral phases are detected following recrystallization as determined by X-ray diffraction and XAS. Our results reveal that Mn(II)-catalyzed mineral recrystallization partitions Ni between Mn oxides and aqueous fluids and can therefore affect Ni speciation and mobility in the environment.

Recrystallization in Si upon ion irradiation at room temperature in Co/Si(111) thin film systems

NASA Astrophysics Data System (ADS)

Banu, Nasrin; Satpati, B.; Dev, B. N.

2018-04-01

After several decades of research it was concluded that for a constant flux recrystallization in Si upon ion irradiation is possible only at high temperature. At low temperature or at room temperature only amorphization can take place. However we have observed recrystallization in Si upon ion irradiation at room temperature in a Co/Si thin film system. The Co/Si sample was prepared by deposition of 25 nm Co on clean Si(111) substrate. An oxide layer (˜ 2nm) of cobalt at the top of the film due to air exposure. The ion irradiation was done at room temperature under high vacuum with 1MeV Si+ ion with low beam current < 400 nA. Earlier we have shown similar ion induced recrystallization in Si(100) substrate which had a sandwich Si/Ni/Si structure. This system had an epitaxial buffer Si layer on Si substrate. This study also shows that the phenomenon is independent of substrate orientation and buffer layer. We have used transmission electron microscopy (TEM) to study the recrystallization behavior.

An empirical method for calculating melt compositions produced beneath mid-ocean ridges: for axis and off-axis (seamounts) melting application

NASA Astrophysics Data System (ADS)

Batiza, Rodey

1991-12-01

We present a new method for calculating the major element compositions of primary melts parental to mid-ocean ridge basalt (MORB). This model is based on the experimental data of Jaques and Green (1980), Falloon et al. (1988), and Falloon and Green (1987, 1988) which are ideal for this purpose. Our method is empirical and employs solid-liquid partition coefficients (Di) from the experiments. We empirically determine Di=f(P,F) and use this to calculate melt compositions produced by decompression-induced melting along an adiabat (column melting). Results indicate that most MORBs can be generated by 10-20% partial melting at initial pressures (P0) of 12-21 kbar. Our primary MORB melts have MgO=10-12 wt %. We fractionate these at low pressure to an MgO content of 8.0 wt% in order to interpret natural MORB liquids. This model allows us to calculate Po, Pf, To, Tf, and F for natural MORB melts. We apply the model to interpret MORB compositions and mantle upwelling patterns beneath a fast ridge (East Pacific Rise (EPR) 8°N to 14°N), a slow ridge (mid-Atlantic Ridge (MAR) at 26°S), and seamounts near the EPR (Lamont seamount chain). We find mantle temperature differences of up to 50°-60°C over distances of 30-50 km both across axis and along axis at the EPR. We propose that these are due to upward mantle flow in a weakly conductive (versus adiabatic) temperature gradient. We suggest that the EPR is fed by a wide (~100 km) zone of upwelling due to plate separation but has a central core of faster buoyant flow. An along-axis thermal dome between the Siqueiros transform and the 11°45' Overlapping Spreading Center (OSC) may represent such an upwelling; however, in general there is a poor correlation between mantle temperature, topography, and the segmentation pattern at the EPR. For the Lamont seamounts we find regular across-axis changes in Po and F suggesting that the melt zone pinches out off axis. This observation supports the idea that the EPR is fed by a broad

An empirical method for calculating melt compositions produced beneath mid-ocean ridges: Application for axis and off-axis (seamounts) melting

NASA Astrophysics Data System (ADS)

Niu, Yaoling; Batiza, Rodey

1991-12-01

We present a new method for calculating the major element compositions of primary melts parental to mid-ocean ridge basalt (MORB). This model is based on the experimental data of Jaques and Green (1980), Falloon et al. (1988), and Falloon and Green (1987, 1988) which are ideal for this purpose. Our method is empirical and employs solid-liquid partition coefficients (Di) from the experiments. We empirically determine Di = ƒ(P,F) and use this to calculate melt compositions produced by decompression-induced melting along an adiabat (column melting). Results indicate that most MORBs can be generated by 10-20% partial melting at initial pressures (P0) of 12-21 kbar. Our primary MORB melts have MgO = 10-12 wt %. We fractionate these at low pressure to an MgO content of 8.0 wt % in order to interpret natural MORB liquids. This model allows us to calculate Po, Pƒ, To, Tƒ, and F for natural MORB melts. We apply the model to interpret MORB compositions and mantle upwelling patterns beneath a fast ridge (East Pacific Rise (EPR)8°N to 14°N), a slow ridge (mid-Atlantic Ridge (MAR) at 26°S), and seamounts near the EPR (Lament seamount chain). We find mantle temperature differences of up to 50°-60°C over distances of 30-50 km both across axis and along axis at the EPR. We propose that these are due to upward mantle flow in a weakly conductive (versus adiabatic) temperature gradient. We suggest that the EPR is fed by a wide (-100 km) zone of upwelling due to plate separation but has a central core of faster buoyant flow. An along-axis thermal dome between the Siqueiros transform and the 11°45' Overlapping Spreading center (OSC) may represent such an upwelling; however, in general there is a poor correlation between mantle temperature, topography, and the segmentation pattern at the EPR. For the Lament seamounts we find regular across-axis changes in Po and F suggesting that the melt zone pinches out off axis. This observation supports the idea that the EPR is fed by a

Hot Deformation Behavior and Dynamic Recrystallization of Medium Carbon LZ50 Steel

NASA Astrophysics Data System (ADS)

Du, Shiwen; Chen, Shuangmei; Song, Jianjun; Li, Yongtang

2017-03-01

Hot deformation and dynamic recrystallization behaviors of a medium carbon steel LZ50 were systematically investigated in the temperature range from 1143 K to 1443 K (870 °C to 1170 °C) at strain rates from 0.05 to 3s-1 using a Gleeble-3500 thermo-simulation machine. The flow stress constitutive equation for hot deformation of this steel was developed with the two-stage Laasraoui equation. The activation energy of the tested steel was 304.27 KJ/mol, which was in reasonable agreement with those reported previously. The flow stress of this steel in hot deformation was mainly controlled by dislocation climb during their intragranular motion. The effect of Zener-Hollomon parameter on the characteristic points of the flow curves was studied, and the dependence of critical strain on peak strain obeyed a linear equation. Dynamic recrystallization was the most important softening mechanism for the tested steel during hot deformation. Kinetic equation of this steel was also established based on the flow stress. The austenite grain size of complete dynamic recrystallization was a power law function of Zener-Hollomon parameter with an exponent of -0.2956. Moreover, the microstructures induced under different deformation conditions were analyzed.

The effect of precipitation on the evolution of recrystallization textures in an AA 8011 aluminum alloy sheet

NASA Astrophysics Data System (ADS)

Ryu, Jong-Ho; Lee, Yoon-Soo; Lee, Dong Nyung

2001-06-01

The texture of an AA 8011 aluminum alloy sheet cold rolled by 95% showed a typical β-fiber, which runs from the copper orientation [C={112}<111>] over S [{123}<634>] to brass [B={011}<112>]. The development of annealing textures depended on annealing temperatures due to the interaction between precipitation and recrystallization. Upon annealing at a low temperature of 275°C, precipitation took place before recrystallization. This led to a weak recrystallization texture consisting of {011}<122>, {001˜<100>, and {hk0}<001>, among which the {011}<122> orientation developed near large FeAl3 particles as the main orientation and the cube [{001}<100>] orientation originating from the matrix was relatively weak. After annealing at 350 and 500°C, a strong cube texture developed along with a weak {011}<122> orientation. When the cube orientation developed, the copper orientation disappeared most rapidly. These results were discussed based on the interaction between precipitation and recrystallization.

Crustal growth in subduction zones

NASA Astrophysics Data System (ADS)

Vogt, Katharina; Castro, Antonio; Gerya, Taras

2015-04-01

There is a broad interest in understanding the physical principles leading to arc magmatisim at active continental margins and different mechanisms have been proposed to account for the composition and evolution of the continental crust. It is widely accepted that water released from the subducting plate lowers the melting temperature of the overlying mantle allowing for "flux melting" of the hydrated mantle. However, relamination of subducted crustal material to the base of the continental crust has been recently suggested to account for the growth and composition of the continental crust. We use petrological-thermo-mechanical models of active subduction zones to demonstrate that subduction of crustal material to sublithospheric depth may result in the formation of a tectonic rock mélange composed of basalt, sediment and hydrated /serpentinized mantle. This rock mélange may evolve into a partially molten diapir at asthenospheric depth and rise through the mantle because of its intrinsic buoyancy prior to emplacement at crustal levels (relamination). This process can be episodic and long-lived, forming successive diapirs that represent multiple magma pulses. Recent laboratory experiments of Castro et al. (2013) have demonstrated that reactions between these crustal components (i.e. basalt and sediment) produce andesitic melt typical for rocks of the continental crust. However, melt derived from a composite diapir will inherit the geochemical characteristics of its source and show distinct temporal variations of radiogenic isotopes based on the proportions of basalt and sediment in the source (Vogt et al., 2013). Hence, partial melting of a composite diapir is expected to produce melt with a constant major element composition, but substantial changes in terms of radiogenic isotopes. However, crustal growth at active continental margins may also involve accretionary processes by which new material is added to the continental crust. Oceanic plateaus and other

Migmatites to mylonites - Crustal deformation mechanisms in the Western Gneiss Region, Norway

NASA Astrophysics Data System (ADS)

Lee, A. L.; Torvela, T.; Lloyd, G. E.; Walker, A.

2016-12-01

Strain and fluids localise into shear zones while crustal blocks remain comparatively dry, rigid and deform less. However when H2O is present in the crustal blocks they start to melt, deformation becomes more distributed and is no longer strongly localised into the weak shear zones. Using examples from the Western Gneiss Region (WGR), Norway, we show the deformation characteristics when mylonitic shear zones and migmatites coexist. The WGR is the lowest structural level of the Caledonian Orogeny, exposing Silurian to Devonian metamorphism and deformation of the Precambrian crust. WGR is predominantly composed of amphibolite-facies quartzofeldspathic gneiss that has undergone partial melting. This study focuses on the southwestern peninsula of the island of Gurskøy. Over a 1.2 kilometre section there is a diverse deformation sequence of migmatized gneiss, mylonitic shear zones, sillimanite bearing garnet-mica schists, augen gneiss and boudinaged amphibolite dykes resulting in a large competence differences between the lithologies over the area. The strongly deformed mylonitic shear zones extend from 5 to over 100 meters in width, but deformation is also high in the migmatitic layers as shown from S-C fabrics and isoclinal folding of leucratic and restitic layers. Microstructural evidence of dynamic recrystallization, symplectite textures and magmatic flow show deformation is widespread over the peninsula. Strain localisation, melting, and their interactions are shown by a combination of outcrop and quantitative modelling that uses field data, microstructural analysis, crystallographic preferred orientations and numerical Eshelby modelling. Detailed field mapping and microstructural analysis of samples from across the peninsula allows melt quantification and thus an understanding of strain mechanisms when melt is present. This area is important as it shows the heterogeneity of deformation within the partially melted lower crust on the sub-seismic scale.

ELECTROMAGNETIC STIRRING IN ZONE REFINING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braun, I.; Frank, F.C.; Marshall, S.

1958-02-01

The efficiency of the zone refining process can obviously be increased by stirring the molten zone to disperse the impurity-rich layer at the solid- liquid surface. Induction heating is sometimes preferred to radiant heat because it produces more convection, but no marked improvement has been reported. Pfann and Dorsi(1967) have described a method of stirring the melt by passing an electric current through the ingot and compressing a magnetic field across the molten zone. Preliminary results obtained by using a rotating magnetic field us the stirring agent during the purification of aluminum are described. (A.C.)

Macrosegregation During Re-melting and Holding of Directionally Solidified Al-7 wt.% Si Alloy in Microgravity

NASA Astrophysics Data System (ADS)

Lauer, M.; Ghods, M.; Angart, S. G.; Grugel, R. N.; Tewari, S. N.; Poirier, D. R.

2017-08-01

As-cast aluminum-7 wt.% ailicon alloy sample rods were re-melted and directionally solidified on Earth which resulted in uniform dendritically aligned arrays. These arrays were then partially back-melted through an imposed, and constant, temperature gradient in the microgravity environment aboard the International Space Station. The mushy zones that developed in the seed crystals were held for different periods prior to initiating directional solidification. Upon return, examination of the initial mushy-zone regions exhibited significant macrosegregation in terms of a solute-depleted zone that increased as a function of the holding time. The silicon (solute) content in these regions was measured on prepared longitudinal sections by electron microprobe analysis as well as by determining the fraction eutectic on several transverse sections. The silicon content was found to increase up the temperature gradient resulting in significant silicon concentration immediately ahead of the mushy-zone tips. The measured macrosegregation agrees well with calculations from a mathematical model developed to simulate the re-melting and holding process. The results, due to processing in a microgravity environment where buoyancy and thermosolutal convection are minimized, serve as benchmark solidification data.

High seismic attenuation at a mid-ocean ridge reveals the distribution of deep melt.

PubMed

Eilon, Zachary C; Abers, Geoffrey A

2017-05-01

At most mid-ocean ridges, a wide region of decompression melting must be reconciled with a narrow neovolcanic zone and the establishment of full oceanic crustal thickness close to the rift axis. Two competing paradigms have been proposed to explain melt focusing: narrow mantle upwelling due to dynamic effects related to in situ melt or wide mantle upwelling with lateral melt transport in inclined channels. Measurements of seismic attenuation provide a tool for identifying and characterizing the presence of melt and thermal heterogeneity in the upper mantle. We use a unique data set of teleseismic body waves recorded on the Cascadia Initiative's Amphibious Array to simultaneously measure seismic attenuation and velocity across an entire oceanic microplate. We observe maximal differential attenuation and the largest delays ([Formula: see text] s and δ T S ~ 2 s) in a narrow zone <50 km from the Juan de Fuca and Gorda ridge axes, with values that are not consistent with laboratory estimates of temperature or water effects. The implied seismic quality factor ( Q s ≤ 25) is among the lowest observed worldwide. Models harnessing experimentally derived anelastic scaling relationships require a 150-km-deep subridge region containing up to 2% in situ melt. The low viscosity and low density associated with this deep, narrow melt column provide the conditions for dynamic mantle upwelling, explaining a suite of geophysical observations at ridges, including electrical conductivity and shear velocity anomalies.

Effects of Melt Processing on Evolution of Structure in PEEK

NASA Technical Reports Server (NTRS)

Georgiev, Georgi; Dai, Patrick Shuanghua; Oyebode, Elizabeth; Cebe, Peggy; Capel, Malcolm

1999-01-01

We report on the effects of melt processing temperature on structure formation in Poly(ether-ether-ketone), PEEK. Real time Small Angle X-ray Scattering, SAXS, and thermal analysis are used to follow the melting behavior after various stages of processing. Assignment of peaks to structural entities within the material, the relative perfection of the crystals, and the possibility of their reorganization, are all influenced by the melt processing history. With the advent of high intensity synchrotron sources of X-radiation, polymer scientists gain a research tool which, when used along with thermal analysis, provides additional structural information about the crystals during growth and subsequent melting. PEEK is an engineering thermoplastic polymer with a very high glass transition temperature (145 C) and crystal melting point (337 C). PEEK has been the subject of recent studies by X-ray scattering in which melt and cold crystallization were followed in real-time. X-ray scattering and thermal studies have been used to address the formation of dual endothermic response which has been variously ascribed to lamellar insertion, dual crystal populations, or melting followed by re-crystallization. Another important issue is whether all of the amorphous phase is located in interlamellar regions, or alternatively whether some is located in "pockets" away from the crystalline lamellar stacks. The interpretation of scattering from lamellar stacks varies depending upon whether such amorphous pockets are formed. Some groups believe all of the amorphous phase is interlamellar. This leads to selection of a smaller thickness for the crystals. Other groups suggest that most amorphous phase is not interlamellar, and this leads to the suggestion that the crystal thickness is larger than the amorphous layer within the stacks. To investigate these ideas, we used SAXS and Differential Scanning Calorimetry to compare results of single and dual stage melt crystallization of PEEK using a

Modeling Deformation Flow Curves and Dynamic Recrystallization of BA-160 Steel During Hot Compression

NASA Astrophysics Data System (ADS)

Shahriari, Babak; Vafaei, Reza; Mohammad Sharifi, Ehsan; Farmanesh, Khosro

2018-03-01

The hot deformation behavior of a high strength low carbon steel was investigated using hot compression test at the temperature range of 850-1100 °C and under strain rates varying from 0.001 to 1 s-1. It was found that the flow curves of the steel were typical of dynamic recrystallization at the temperature of 950 °C and above; at tested strain rates lower than 1 s-1. A very good correlation between the flow stress and Zener-Hollomon parameter was obtained using a hyperbolic sine function. The activation energy of deformation was found to be around 390 kJ mol-1. The kinetics of dynamic recrystallization of the steel was studied by comparing it with a hypothetical dynamic recovery curve, and the dynamically fraction recrystallized was modeled by the Kolmogorov-Johnson-Mehl-Avrami relation. The Avrami exponent was approximately constant around 1.8, which suggested that the type of nucleation was one of site saturation on grain boundaries and edges.

Shock-induced fine-grained recrystallization of olivine - Evidence against subsolidus reduction of Fe/2+/

NASA Technical Reports Server (NTRS)

Ahrens, T. J.; Tsay, F.-D.; Live, D. H.

1976-01-01

Electron spin resonance (ESR) studies have been carried out on three single grains of terrestrial olivine (Fo90) shock loaded along the 010 line to peak pressures of 280, 330, and 440 kbar. The results indicate that neither metallic Fe similar to that observed in returned lunar soils nor paramagnetic Fe(3+) caused by oxidation of Fe(2+) has been produced in these shock experiments. Trace amounts of Mn (2+) have been detected in both shocked and unshocked olivine. The ESR signals of Mn(2+) show spectral features which are found to correlate with the degree of shock-induced recrystallization observed petrographically. The increasing mass fraction of recrystallized olivine correlates with increasing shock pressures. This phenomenon is modelled assuming it results from the progressive effect of the shock-induced transformation of the olivine to a yet unknown high-pressure phase and its subsequent reversion to the low-pressure olivine phase. The mass fraction of recrystallized material is predicted to be nearly linear with shock pressure.

Evidence for hydrous high-MgO melts in the Precambrian

NASA Astrophysics Data System (ADS)

Stone, William E.; Deloule, Etienne; Larson, Michelle S.; Lesher, C. Michael

1997-02-01

Prevailing petrogenetic models for Precambrian high-MgO melts such as komatiites invoke crystallization from nearly anhydrous melts (≪0.5% H2O) generated by partial melting of mantle peridotite at temperatures of (≤ 1900 °C and pressures of (18 GPa. However, ultramafic cumulate and gabbro zones of komatiitic and other high-MgO units in Precambrian greenstone belts contain vesicles and minor to major amounts (≤ 25%) of igneous amphibole. The textures (oikocrysts, rims on intercumulate pyroxene, and mineral inclusions within orthocumulate olivine) and the water-rich compositions (1.00% 2.50% H2O) of igneous amphiboles from the Archean Abitibi belt indicate crystallization in situ from significantly hydrous melts while the melt fraction was still as high as 40% 50%. Comparisons to experimental phase equilibria suggest that the residual melts from which the amphiboles crystallized contained 3% 4% H2O, and adjustments for fractional crystallization suggest that the initial melts may have contained as much as 2% H2O. H2O contents of this magnitude would require substantial revision of the nearly anhydrous models for Precambrian high-MgO melts, possibly permitting generation at lower temperatures and pressures, lowering their densities and viscosities, increasing their eruptibility, and enhancing the formation of spinifex textures.

Enrichments of the mantle sources beneath the Southern Volcanic Zone (Andes) by fluids and melts derived from abraded upper continental crust

NASA Astrophysics Data System (ADS)

Holm, Paul Martin; Søager, Nina; Dyhr, Charlotte Thorup; Nielsen, Mia Rohde

2014-05-01

Mafic basaltic-andesitic volcanic rocks from the Andean Southern Volcanic Zone (SVZ) exhibit a northward increase in crustal components in primitive arc magmas from the Central through the Transitional and Northern SVZ segments. New elemental and Sr-Nd-high-precision Pb isotope data from the Quaternary arc volcanic centres of Maipo (NSVZ) and Infernillo and Laguna del Maule (TSVZ) are argued to reflect mainly their mantle source and its melting. For the C-T-NSVZ, we identify two types of source enrichment: one, represented by Antuco in CSVZ, but also present northward along the arc, was dominated by fluids which enriched a pre-metasomatic South Atlantic depleted MORB mantle type asthenosphere. The second enrichment was by melts having the characteristics of upper continental crust (UCC), distinctly different from Chile trench sediments. We suggest that granitic rocks entered the source mantle by means of subduction erosion in response to the northward increasingly strong coupling of the converging plates. Both types of enrichment had the same Pb isotope composition in the TSVZ with no significant component derived from the subducting oceanic crust. Pb-Sr-Nd isotopes indicate a major crustal compositional change at the southern end of the NSVZ. Modelling suggests addition of around 2 % UCC for Infernillo and 5 % for Maipo.

Transient induced tungsten melting at the Joint European Torus (JET)

NASA Astrophysics Data System (ADS)

Coenen, J. W.; Matthews, G. F.; Krieger, K.; Iglesias, D.; Bunting, P.; Corre, Y.; Silburn, S.; Balboa, I.; Bazylev, B.; Conway, N.; Coffey, I.; Dejarnac, R.; Gauthier, E.; Gaspar, J.; Jachmich, S.; Jepu, I.; Makepeace, C.; Scannell, R.; Stamp, M.; Petersson, P.; Pitts, R. A.; Wiesen, S.; Widdowson, A.; Heinola, K.; Baron-Wiechec, A.; Contributors, JET

2017-12-01

Melting is one of the major risks associated with tungsten (W) plasma-facing components (PFCs) in tokamaks like JET or ITER. These components are designed such that leading edges and hence excessive plasma heat loads deposited at near normal incidence are avoided. Due to the high stored energies in ITER discharges, shallow surface melting can occur under insufficiently mitigated plasma disruption and so-called edge localised modes—power load transients. A dedicated program was carried out at the JET to study the physics and consequences of W transient melting. Following initial exposures in 2013 (ILW-1) of a W-lamella with leading edge, new experiments have been performed on a sloped surface (15{}\\circ slope) during the 2015/2016 (ILW-3) campaign. This new experiment allows significantly improved infrared thermography measurements and thus resolved important issue of power loading in the context of the previous leading edge exposures. The new lamella was monitored by local diagnostics: spectroscopy, thermography and high-resolution photography in between discharges. No impact on the main plasma was observed despite a strong increase of the local W source consistent with evaporation. In contrast to the earlier exposure, no droplet emission was observed from the sloped surface. Topological modifications resulting from the melting are clearly visible between discharges on the photographic images. Melt damage can be clearly linked to the infrared measurements: the emissivity drops in zones where melting occurs. In comparison with the previous leading edge experiment, no runaway melt motion is observed, consistent with the hypothesis that the escape of thermionic electrons emitted from the melt zone is largely suppressed in this geometry, where the magnetic field intersects the surface at lower angles than in the case of perpendicular impact on a leading edge. Utilising both exposures allows us to further test the model of the forces driving melt motion that

Development of high-temperature Kolsky compression bar techniques for recrystallization investigation

NASA Astrophysics Data System (ADS)

Song, B.; Antoun, B. R.; Boston, M.

2012-05-01

We modified the design originally developed by Kuokkala's group to develop an automated high-temperature Kolsky compression bar for characterizing high-rate properties of 304L stainless steel at elevated temperatures. Additional features have been implemented to this high-temperature Kolsky compression bar for recrystallization investigation. The new features ensure a single loading on the specimen and precise time and temperature control for quenching to the specimen after dynamic loading. Dynamic compressive stress-strain curves of 304L stainless steel were obtained at 21, 204, 427, 649, and 871 °C (or 70, 400, 800, 1200, and 1600 °F) at the same constant strain rate of 332 s-1. The specimen subjected to specific time and temperature control for quenching after a single dynamic loading was preserved for investigating microstructure recrystallization.

Scanning electron microscopy investigations of laboratory-grown gas clathrate hydrates formed from melting ice, and comparison to natural hydrates

USGS Publications Warehouse

Stern, L.A.; Kirby, S.H.; Circone, S.; Durham, W.B.

2004-01-01

Scanning electron microscopy (SEM) was used to investigate grain texture and pore structure development within various compositions of pure sI and sII gas hydrates synthesized in the laboratory, as well as in natural samples retrieved from marine (Gulf of Mexico) and permafrost (NW Canada) settings. Several samples of methane hydrate were also quenched after various extents of partial reaction for assessment of mid-synthesis textural progression. All laboratory-synthesized hydrates were grown under relatively high-temperature and high-pressure conditions from rounded ice grains with geometrically simple pore shapes, yet all resulting samples displayed extensive recrystallization with complex pore geometry. Growth fronts of mesoporous methane hydrate advancing into dense ice reactant were prevalent in those samples quenched after limited reaction below and at the ice point. As temperatures transgress the ice point, grain surfaces continue to develop a discrete "rind" of hydrate, typically 5 to 30 ??m thick. The cores then commonly melt, with rind microfracturing allowing migration of the melt to adjacent grain boundaries where it also forms hydrate. As the reaction continues under progressively warmer conditions, the hydrate product anneals to form dense and relatively pore-free regions of hydrate grains, in which grain size is typically several tens of micrometers. The prevalence of hollow, spheroidal shells of hydrate, coupled with extensive redistribution of reactant and product phases throughout reaction, implies that a diffusion-controlled shrinking-core model is an inappropriate description of sustained hydrate growth from melting ice. Completion of reaction at peak synthesis conditions then produces exceptional faceting and euhedral crystal growth along exposed pore walls. Further recrystallization or regrowth can then accompany even short-term exposure of synthetic hydrates to natural ocean-floor conditions, such that the final textures may closely mimic

Thermoplastic polyimide NEW-TPI (trademark)

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung; Reddy, Rakasi M.

1990-01-01

Thermal and rheological properties of a commercial thermoplastic polyimide, NEW-TPI (trademark), were characterized. The as-received material possesses initially a transient crystallite form with a bimodal distribution in peak melting temperatures. After the melting of the initial crystallite structure, the sample can be recrystallized by various thermal treatments. A bimodal or single modal melting peak distribution is formed for annealing temperatures below or above 360 C, respectively. The recrystallized crystallinities are all transient in nature. The polymers are unable to be recrystallized after being subjected to elevated temperature annealing above 450 C. The recrystallization mechanism was postulated, and a simple kinetics model was found to describe the behavior rather satisfactory under the conditions of prolonged thermal annealing. Rheological measurements made in the linear viscoelastic range support the evidence observed in the thermal analysis. Furthermore, the measurements sustain the manufacturer's recommended processing window of 400 to 420 C for this material.

Coseismic flow of frictional melts: insights from mini-AMS measurements on pseudotachylyte

NASA Astrophysics Data System (ADS)

Geissman, J. W.; Leibovitz, N.; Meado, A.; Campbell, L.; Ferre, E. C.

2017-12-01

Fault pseudotachylytes, widely regarded as earthquake fossils, are fascinating rocks that may hold important clues on the physics of seismic rupture and the lubrication of fault planes. Forceful injection of rapidly produced melts along a friction zone typically forms a complex network of veins along the slip zone and at a high angle to the generation plane. The flow patterns of these pseudotachylyte melts remain, however, poorly constrained except in rare cases when billow-like folds or other flow structures are preserved. Recent modifications to the anisotropy of magnetic susceptibility (AMS) method allow new directions of investigations of melt kinematics in pseudotachylyte veins, regardless of whether they are generation or injection veins. Here we present new mini-AMS results based on series of 3.5 mm cubes (≈200 times smaller than classic sample size) of pseudotachylyte veins from the Val Gilba (Italian Alps), the Cima di Gratera (Corsica) and Santa Rosa (California) classic localities. These preliminary analyses demonstrate the potential of this new mini-AMS method in tracking the complex coseismic movement of a low viscosity magma through dynamically deformed conduits. The lack of plastic deformation in pseudotachylyte clasts and along the pseudotachylyte margins supports the hypothesis that the coseismic melt flow pattern is frozen in situ without significant subsolidus deformation.

Primitive andesites from the Taupo Volcanic Zone formed by magma mixing

NASA Astrophysics Data System (ADS)

Beier, Christoph; Haase, Karsten M.; Brandl, Philipp A.; Krumm, Stefan H.

2017-05-01

Andesites with Mg# >45 erupted at subduction zones form either by partial melting of metasomatized mantle or by mixing and assimilation processes during melt ascent. Primitive whole rock basaltic andesites from the Pukeonake vent in the Tongariro Volcanic Centre in New Zealand's Taupo Volcanic Zone contain olivine, clino- and orthopyroxene, and plagioclase xeno- and antecrysts in a partly glassy matrix. Glass pools interstitial between minerals and glass inclusions in clinopyroxene, orthopyroxene and plagioclase as well as matrix glasses are rhyolitic to dacitic indicating that the melts were more evolved than their andesitic bulk host rock analyses indicate. Olivine xenocrysts have high Fo contents up to 94%, δ18O(SMOW) of +5.1‰, and contain Cr-spinel inclusions, all of which imply an origin in equilibrium with primitive mantle-derived melts. Mineral zoning in olivine, clinopyroxene and plagioclase suggest that fractional crystallization occurred. Elevated O isotope ratios in clinopyroxene and glass indicate that the lavas assimilated sedimentary rocks during stagnation in the crust. Thus, the Pukeonake andesites formed by a combination of fractional crystallization, assimilation of crustal rocks, and mixing of dacite liquid with mantle-derived minerals in a complex crustal magma system. The disequilibrium textures and O isotope compositions of the minerals indicate mixing processes on timescales of less than a year prior to eruption. Similar processes may occur in other subduction zones and require careful study of the lavas to determine the origin of andesite magmas in arc volcanoes situated on continental crust.

Shape Fixing via Salt Recrystallization: A Morphology-Controlled Approach To Convert Nanostructured Polymer to Carbon Nanomaterial as a Highly Active Catalyst for Oxygen Reduction Reaction.

PubMed

Ding, Wei; Li, Li; Xiong, Kun; Wang, Yao; Li, Wei; Nie, Yao; Chen, Siguo; Qi, Xueqiang; Wei, Zidong

2015-04-29

Herein, we report a "shape fixing via salt recrystallization" method to efficiently synthesize nitrogen-doped carbon material with a large number of active sites exposed to the three-phase zones, for use as an ORR catalyst. Self-assembled polyaniline with a 3D network structure was fixed and fully sealed inside NaCl via recrystallization of NaCl solution. During pyrolysis, the NaCl crystal functions as a fully sealed nanoreactor, which facilitates nitrogen incorporation and graphitization. The gasification in such a closed nanoreactor creates a large number of pores in the resultant samples. The 3D network structure, which is conducive to mass transport and high utilization of active sites, was found to have been accurately transferred to the final N-doped carbon materials, after dissolution of the NaCl. Use of the invented cathode catalyst in a proton exchange membrane fuel cell produces a peak power of 600 mW cm(-2), making this among the best nonprecious metal catalysts for the ORR reported so far. Furthermore, N-doped carbon materials with a nanotube or nanoshell morphology can be realized by the invented method.

Strong Surface Diffusion Mediated Glancing-Angle Deposition: Growth, Recrystallization and Reorientation of Tin Nanorods

NASA Astrophysics Data System (ADS)

Wang, Huan-Hua; Shi, Yi-Jian; William, Chu; Yigal, Blum

2008-01-01

Different from usual glancing-angle deposition where low surface diffusion is necessary to form nanorods, strong surface diffusion mediated glancing-angle deposition is exemplified by growing tin nanorod films on both silicon and glass substrates simultaneously via thermal evaporation. During growth, the nanorods were simultaneously baked by the high-temperature evaporator, and therefore re-crystallized into single crystals in consequence of strong surface diffusion. The monocrystalline tin nanorods have a preferred orientation perpendicular to the substrate surface, which is quite different from the usual uniformly oblique nanorods without recrystallization.

Content of toxic and essential metals in recrystallized and washed table salt in Shiraz, Iran

PubMed Central

2014-01-01

Background Table salt is the most commonly used food additive. Since most of the salt consumed in Iran comes from mines, contamination with heavy metals is a health concern. The commonest salt purification method in Iran is washing with water. But recently, some industries have turned to recrystallization method. The present study aimed to determine the level of essential and non-essential heavy metals in the table salt refined with recrystallization and washing methods. Methods Thirty eight pre-packed salt samples were directly collected from retail market in Shiraz (22 samples refined with recrystallization method and 16 with washing method). The level of lead, cadmium, copper, zinc, nickel and cobalt was determined using Voltammetric method. Daily intakes of lead and cadmium as well as their weekly intakes were calculated. Results The levels of lead, cadmium, copper, zinc, nickel and cobalt in recrystallized samples were 0. 30 ± 0.26, 0.02 ± 0.02, 0.11 ± 0.06, 0.34 ± 0.22, 0.15 ± 0.19 and 0.008 ± 0.007 μg/g, respectively, and also 0.37 ± 0.27, 0.017 ± 0.021, 0.19 ± 0.18, 0.37 ± 0.20, 0.13 ± 0.23 and 0.037 ± 0.06 μg/g in washed salt samples. The calculated weekly intake of lead and cadmium was 0.216 and 0.014 μg/kg, respectively for the recrystallized and 0.2653 and 0.0119 μg/kg for the washed salts. Conclusion All values for toxic metals were lower than the permitted maximum for human consumption as prescribed by Codex and Institute of Standards and Industrial Research of Iran. Only 0.8652-1.0612% of lead and 0.17-0.2% of cadmium PTWIs are received via salt consumption weekly. PMID:24398299

Modelling Subduction Zone Magmatism Due to Hydraulic Fracture

NASA Astrophysics Data System (ADS)

Lawton, R.; Davies, J. H.

2014-12-01

The aim of this project is to test the hypothesis that subduction zone magmatism involves hydraulic fractures propagating from the oceanic crust to the mantle wedge source region (Davies, 1999). We aim to test this hypothesis by developing a numerical model of the process, and then comparing model outputs with observations. The hypothesis proposes that the water interconnects in the slab following an earthquake. If sufficient pressure develops a hydrofracture occurs. The hydrofracture will expand in the direction of the least compressive stress and propagate in the direction of the most compressive stress, which is out into the wedge. Therefore we can calculate the hydrofracture path and end-point, given the start location on the slab and the propagation distance. We can therefore predict where water is added to the mantle wedge. To take this further we have developed a thermal model of a subduction zone. The model uses a finite difference, marker-in-cell method to solve the heat equation (Gerya, 2010). The velocity field was prescribed using the analytical expression of cornerflow (Batchelor, 1967). The markers contained within the fixed grid are used to track the different compositions and their properties. The subduction zone thermal model was benchmarked (Van Keken, 2008). We used the hydrous melting parameterization of Katz et.al., (2003) to calculate the degree of melting caused by the addition of water to the wedge. We investigate models where the hydrofractures, with properties constrained by estimated water fluxes, have random end points. The model predicts degree of melting, magma productivity, temperature of the melt and water content in the melt for different initial water fluxes. Future models will also include the buoyancy effect of the melt and residue. Batchelor, Cambridge UP, 1967. Davies, Nature, 398: 142-145, 1999. Gerya, Cambridge UP, 2010. Katz, Geochem. Geophys. Geosy, 4(9), 2003 Van Keken et.al. Phys. Earth. Planet. In., 171:187-197, 2008.

Using a Simulated Industrial Setting for the Development of an Improved Solvent System for the Recrystallization of Benzoic Acid: A Student-Centered Project

ERIC Educational Resources Information Center

Hightower, Timothy R.; Heeren, Jay D.

2006-01-01

Recrystallization of benzoic acid is an excellent way to remove insoluble impurities. In a traditional organic laboratory experiment, insoluble impurities are removed through the recrystallization of benzoic acid utilizing water as the recrystallization solvent. It was our goal to develop a peer-led, problem-solving organic laboratory exercise…

Mantle transition zone input to kimberlite magmatism near a subduction zone: Origin of anomalous Nd-Hf isotope systematics at Lac de Gras, Canada

NASA Astrophysics Data System (ADS)

Tappe, Sebastian; Graham Pearson, D.; Kjarsgaard, Bruce A.; Nowell, Geoff; Dowall, David

2013-06-01

Late Cretaceous-Eocene kimberlites from the Lac de Gras area, central Slave craton, show the most extreme Nd-Hf isotope decoupling observed for kimberlites worldwide. They are characterized by a narrow range of moderately enriched Nd isotope compositions (ɛNd(i)=-0.4 to -3.5) that contrasts strongly with their moderately depleted to highly enriched ɛHf(i) values (+3.9 to -9.9). Although digestion of cratonic mantle material in proto-kimberlite melt can theoretically produce steep arrays in Nd-Hf isotope space, the amount of contaminant required to explain the Lac de Gras data is unrealistic. Instead, it is more plausible that mixing of compositionally discrete melt components within an isotopically variable source region is responsible for the steep Nd-Hf isotope array. As development of strongly negative ΔɛHf requires isotopic aging of a precursor material with Sm/Nd≫Lu/Hf for billion-year timescales, a number of models have been proposed where ancient MORB crust trapped in the mantle transition zone is the ultimate source of the extreme Hf isotope signature. However, we provide a conceptual modification and demonstrate that OIB-type domains within ancient subducted oceanic lithosphere can produce much stronger negative ΔɛHf during long-term isolation. Provided that these OIB-type domains have lower melting points compared with associated MORB crust, they are among the first material to melt within the transition zone during thermal perturbations. The resulting hydrous alkali silicate melts react strongly with depleted peridotite at the top of the transition zone and transfer negative ΔɛHf signatures to less dense materials, which can be more easily entrained within upward flowing mantle. Once these entrained refertilized domains rise above 300 km depth, they may become involved in CO2- and H2O-fluxed redox melting of upper mantle peridotite beneath a thick cratonic lid. We argue that incorporation of ancient transition zone material, which includes

Impact of textural anisotropy on syn-kinematic partial melting of natural gneisses: an experimental approach.

NASA Astrophysics Data System (ADS)

Ganzhorn, Anne-Céline; Trap, Pierre; Arbaret, Laurent; Champallier, Rémi; Fauconnier, Julien; Labrousse, Loic; Prouteau, Gaëlle

2015-04-01

�C experiments NOP1 was previously hydrated at room pressure and temperature. According to melt fraction, deformation of partially molten gneiss induced different strain patterns. For low melt fraction, at 750°C, deformation within the initially isotropic gneiss NOP1 is localized along large scales shear-zones oriented at about 60° from main stress component σ1. In these zones quartz grains are broken and micas are sheared. Melt is present as thin film (≥20 µm) at muscovite-quartz grain boundaries and intrudes quartz aggregates as injections parallel to σ1. For higher melt fraction, at 850°C, deformation is homogeneously distributed. In the layered gneiss PX28, deformation is partitioned between mica-rich and quartz-rich layers. For low melt fraction, at 850°C, numerous conjugate shear-bands crosscut mica-rich layers. Melt is present around muscovite grains and intrudes quartz grains in the favor of fractures. For high melt fractions, at 900°C, melt assisted creep within mica-rich layers is responsible for boudinage of the quartz-feldspar rich layers. Melt-induced veining assists the transport of melt toward inter-boudin zones. Finite strain pattern and melt distribution after deformation of PX28 attest for appearance of strong pressure gradients leading to efficient melt flow. The subsequent melt redistribution strongly enhance strain partitioning and strength weakening, as shown by differential stress vs. strain graphs. Our experiments have successfully reproduced microstructures commonly observed in migmatitic gneisses like boudinage of less fertile layers. Comparison between non-layered and layered gneisses attest for strong influence of compositional anisotropies inherited from the protolith upon melt distribution and migmatite strength.

Ice Recrystallization Inhibiting Polymers Enable Glycerol-Free Cryopreservation of Micro-organisms.

PubMed

Hasan, Muhammad; Fayter, Alice E R; Gibson, Matthew I

2018-06-22

All modern molecular biology and microbiology is underpinned not only by the tools to handle and manipulate microorganisms, but also those to store, bank and transport them. Glycerol is the current gold-standard cryoprotectant but it is intrinsically toxic to most micro-organisms: only a fraction of cells survive freezing and the presence of glycerol can impact down-stream applications and assays. Extremophile organisms survive repeated freeze/thaw cycles by producing antifreeze proteins which are potent ice recrystallization inhibitors. Here we introduce a new concept for the storage/transport of micro-organisms by using ice recrystallization inhibiting poly(vinyl alcohol) in tandem with poly(ethylene glycol). This cryopreserving formulation is shown to result in a 4-fold increase in E. coli yield post-thaw, compared to glycerol, utilizing lower concentrations, with successful cryopreservation at just 1.1 weight percent of additive. The mechanism of protection is demonstrated to be linked to inhibiting ice recrystallization (by comparison to a recombinant antifreeze protein) but also to the significantly lower toxicity of the polymers compared to glycerol. Optimized formulations are presented and shown to be broadly applicable to the cryopreservation of a panel of Gram negative, Gram positive and Mycobacteria strains. This represents a step-change in how micro-organisms will be stored by the design of new macromolecular ice growth inhibitors; it should enable a transition from traditional solvent-based to macromolecular microbiology storage methods.

Application of melt extrusion in the development of a physically and chemically stable high-energy amorphous solid dispersion of a poorly water-soluble drug.

PubMed

Lakshman, Jay P; Cao, Yu; Kowalski, James; Serajuddin, Abu T M

2008-01-01

Formulation of active pharmaceutical ingredients (API) in high-energy amorphous forms is a common strategy to enhance solubility, dissolution rate and, consequently, oral bioavailability of poorly water-soluble drugs. Amorphous APIs are, however, susceptible to recrystallization and, therefore, there is a need to physically stabilize them as solid dispersions in polymeric carriers. Hot melt extrusion has in recent years gained wide acceptance as a method of choice for the preparation of solid dispersions. There is a potential that the API, the polymer or both may degrade if excessively high temperature is needed in the melt extrusion process, especially when the melting point of the API is high. This report details a novel method where the API was first converted to an amorphous form by solvent evaporation and then melt-extruded with a suitable polymer at a drug load of at least 20% w/w. By this means, melt extrusion could be performed much below the melting temperature of the drug substance. Since the glass transition temperature of the amorphous drug was lower than that of the polymer used, the drug substance itself served as the plasticizer for the polymer. The addition of surfactants in the matrix enhanced dispersion and subsequent dissolution of the drug in aqueous media. The amorphous melt extrusion formulations showed higher bioavailability than formulations containing the crystalline API. There was no conversion of amorphous solid to its crystalline form during accelerated stability testing of dosage forms.

Molecular Dynamics at the Interface between Ice and Poly(vinyl alcohol) and Ice Recrystallization Inhibition.

PubMed

Weng, Lindong; Stott, Shannon L; Toner, Mehmet

2018-05-01

Ice formation is a ubiquitous process that poses serious challenges for many areas. Nature has evolved a variety of different mechanisms to regulate ice formation. For example, many cold-adapted species produce antifreeze proteins (AFPs) and/or antifreeze glycoproteins (AFGPs) to inhibit ice recrystallization. Although several synthetic substitutes for AF(G)Ps have been developed, the fundamental principles of designing AF(G)P mimics are still missing. In this study, we explored the molecular dynamics of ice recrystallization inhibition (IRI) by poly(vinyl alcohol) (PVA), a well-recognized ice recrystallization inhibitor, to shed light on the otherwise hidden ice-binding mechanisms of chain polymers. Our molecular dynamics simulations revealed a stereoscopic, geometrical match between the hydroxyl groups of PVA and the water molecules of ice, and provided microscopic evidence of the adsorption of PVA to both the basal and prism faces of ice and the incorporation of short-chain PVA into the ice lattice. The length of PVA, i.e., the number of hydroxyl groups, seems to be a key factor dictating the performance of IRI, as the PVA molecule must be large enough to prevent the joining together of adjacent curvatures in the ice front. The findings in this study will help pave the path for addressing a pressing challenge in designing synthetic ice recrystallization inhibitors rationally, by enriching our mechanistic understanding of IRI process by macromolecules.

Plasticity-mediated collapse and recrystallization in hollow copper nanowires: a molecular dynamics simulation.

PubMed

Dutta, Amlan; Raychaudhuri, Arup Kumar; Saha-Dasgupta, Tanusri

2016-01-01

We study the thermal stability of hollow copper nanowires using molecular dynamics simulation. We find that the plasticity-mediated structural evolution leads to transformation of the initial hollow structure to a solid wire. The process involves three distinct stages, namely, collapse, recrystallization and slow recovery. We calculate the time scales associated with different stages of the evolution process. Our findings suggest a plasticity-mediated mechanism of collapse and recrystallization. This contradicts the prevailing notion of diffusion driven transport of vacancies from the interior to outer surface being responsible for collapse, which would involve much longer time scales as compared to the plasticity-based mechanism.

Plasticity-mediated collapse and recrystallization in hollow copper nanowires: a molecular dynamics simulation

PubMed Central

Raychaudhuri, Arup Kumar; Saha-Dasgupta, Tanusri

2016-01-01

Summary We study the thermal stability of hollow copper nanowires using molecular dynamics simulation. We find that the plasticity-mediated structural evolution leads to transformation of the initial hollow structure to a solid wire. The process involves three distinct stages, namely, collapse, recrystallization and slow recovery. We calculate the time scales associated with different stages of the evolution process. Our findings suggest a plasticity-mediated mechanism of collapse and recrystallization. This contradicts the prevailing notion of diffusion driven transport of vacancies from the interior to outer surface being responsible for collapse, which would involve much longer time scales as compared to the plasticity-based mechanism. PMID:26977380

High-pressure crystallization vs. recrystallization origin of garnet pyroxenite-eclogite within subduction related lithologies

NASA Astrophysics Data System (ADS)

Faryad, S. W.; Jedlicka, R.; Hauzenberger, C.; Racek, M.

2018-03-01

Mafic layers displaying transition between clinopyroxenite and eclogite within peridotite from felsic granulite in the Bohemian Massif (Lower Austria) have been investigated. The mafic-ultramafic bodies shared a common granulite facies metamorphism with its hosting felsic rocks, but they still preserve evidence of eclogite facies metamorphism. The selected mafic layer for this study is represented by garnet with omphacite in the core of coarse-grained clinopyroxene, while fine-grained clinopyroxene in the matrix is diopside. In addition, garnet contains inclusions of omphacite, alkali feldspars, hydrous and other phases with halogens and/or CO2. Textural relations along with compositional zoning in garnet from the clinopyroxenite-eclogite layers favour solid-state recrystallization of the precursor minerals in the inclusions and formation of garnet and omphacite during subduction. Textures and major and trace element distribution in garnet indicate two stages of garnet growth that record eclogite facies and subsequent granulite facies overprint. The possible model explaining the textural and compositional changes of minerals is that the granulite facies overprint occurred after formation and exhumation of the eclogite facies rocks.

Solid State Research.

DTIC Science & Technology

1984-02-15

Diode Lasers 10 - 3. MATERIALS RESEARCH 15 3.1 Role of Oxygen in Zone-Melting Recrystallization of Si Films on Si0 2 -Coated Si Substrates 15 3.2 Triple... Film that Has Been Etch-Delineated to Show Sub- ndaries. Upper Graphite Heater Was Scanned in Direction from top to Bottom of Micrograph. 15 3-2...Operation at 1060 nm with a 5-percent differential power efficiency has been obtained from a flashlamp-pumped laser rod of the sensitized garnet Nd:Cr:Gd 3Sc

Zircon Zoning, Trace Elements and U-Pb Dates Reveal Crustal Foundering Beneath the Pamir

NASA Astrophysics Data System (ADS)

Hacker, B. R.; Shaffer, M. E. F.; Ratschbacher, L.; Kylander-Clark, A. R.

2017-12-01

Xenoliths that erupted in the SE Pamir of Tajikistan at 11.2 Ma from 1000-1050°C and 90 km depth illuminate what happens when crust founders into the mantle. The xenoliths are a broad range of crustal rock types and contain abundant xenoliths whose U-Pb isotopic ratios and trace-element contents were examined by laser-ablation split stream inductively coupled plasma mass spectrometry. Cathodoluminescence imaging of the grains shows igneous cores with oscillatory zoning overprinted by substantial recrystallization. The bulk of the U-Pb dates are concordant and range from 160 Ma to 11 Ma. The range of dates suggest that the xenoliths were likely derived from the Jurassic-Cretaceous Andean-style magmatic arc and its Proterozoic-Mesozoic host rocks along the southern margin of Asia. The zircons show distinct changes in Eu anomaly, Lu/Gd ratio, and Ti concentrations that are interpreted to indicate garnet growth and minimal heating at 22-20 Ma, and then 200-300°C of heating, 25 km of burial, and alkali-carbonate melt injection at 14-11 Ma. These changes are interpreted to coincide with: i) heat input due to Indian slab breakoff at 22‒20 Ma; ii) rapid thickening and foundering of the Pamir lithosphere at 14‒11 Ma, prior to and synchronous with collision between deep Indian and Asian lithospheres beneath the Pamir.

Investigation and Characterization of Water-Recrystallized Croconic Acid

DTIC Science & Technology

2016-12-01

high- pressure synthesis. Thermal analysis, bomb calorimetry, X-ray diffraction, and Raman spectroscopy were performed on water- recrystallized...3.2.3 Raman Spectroscopy and X-ray Diffraction 12 3.2.4 Bomb Calorimetry 13 4. Conclusions 15 5. References 16 List of Symbols, Abbreviations, and...and is called the β-phase (the as-received [AR] material is also known as the α-phase). Bomb calorimeter testing of the β-CA indicated a heat of

Application of hot melt extrusion for poorly water-soluble drugs: limitations, advances and future prospects.

PubMed

Lu, Ming; Guo, Zhefei; Li, Yongcheng; Pang, Huishi; Lin, Ling; Liu, Xu; Pan, Xin; Wu, Chuanbin

2014-01-01

Hot melt extrusion (HME) is a powerful technology to enhance the solubility and bioavailability of poorly water-soluble drugs by producing amorphous solid dispersions. Although the number of articles and patents about HME increased dramatically in the past twenty years, there are very few commercial products by far. The three main obstacles limiting the commercial application of HME are summarized as thermal degradation of heat-sensitive drugs at high process temperature, recrystallization of amorphous drugs during storage and dissolving process, and difficulty to obtain products with reproducible physicochemical properties. Many efforts have been taken in recent years to understand the basic mechanism underlying these obstacles and then to overcome them. This article reviewed and summarized the limitations, recent advances, and future prospects of HME.

Chemical Characterization of Dimethylsulfoxide (DMSO) Munitions Recrystallization Process Samples.

DTIC Science & Technology

1984-10-01

position unless so designated by other aulthorized documents. Disposition Destroy this report when it is no longer needed. Do riot return it to the... DESTRIBUTION LIST ....... ........... ... ................................. -12 rABLES 1. HPLC Analyses of Munitions from DMS0 Recrystallization Process...characterization and identification of any trace organics present in addition to the nitramines. Portions of the two samples, designated as evaporator

Study on the dynamic recrystallization model and mechanism of nuclear grade 316LN austenitic stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Shenglong; Zhang, Mingxian; Wu, Huanchun

In this study, the dynamic recrystallization behaviors of a nuclear grade 316LN austenitic stainless steel were researched through hot compression experiment performed on a Gleeble-1500 simulator at temperatures of 900–1250 °C and strain rates of 0.01–1 s{sup −1}. By multiple linear regressions of the flow stress-strain data, the dynamic recrystallization mathematical models of this steel as functions of strain rate, strain and temperature were developed. Then these models were verified in a real experiment. Furthermore, the dynamic recrystallization mechanism of the steel was determined. The results indicated that the subgrains in this steel are formed through dislocations polygonization and thenmore » grow up through subgrain boundaries migration towards high density dislocation areas and subgrain coalescence mechanism. Dynamic recrystallization nucleation performs in grain boundary bulging mechanism and subgrain growth mechanism. The nuclei grow up through high angle grain boundaries migration. - Highlights: •Establish the DRX mathematical models of nuclear grade 316LN stainless steel •Determine the DRX mechanism of this steel •Subgrains are formed through dislocations polygonization. •Subgrains grow up through subgrain boundaries migration and coalescence mechanism. •DRX nucleation performs in grain boundary bulging mechanism and subgrain growth mechanism.« less

Pioneering In Situ Recrystallization during Bead Milling: A Top-down Approach to Prepare Zeolite A Nanocrystals.

PubMed

Anand, Chokkalingam; Yamaguchi, Yudai; Liu, Zhendong; Ibe, Sayoko; Elangovan, Shanmugam P; Ishii, Toshihiro; Ishikawa, Tsuyoshi; Endo, Akira; Okubo, Tatsuya; Wakihara, Toru

2016-07-05

Top-down approach has been viewed as an efficient and straightforward method to prepare nanosized zeolites. Yet, the mechanical breaking of zeolite causes amorphization, which usually requires a post-milling recrystallization to obtain fully crystalline nanoparticles. Herein we present a facile methodology to prepare zeolite nanocrystals, where milling and recrystallization can be performed in situ. A milling apparatus specially designed to work under conditions of high alkalinity and temperature enables the in situ recrystallization during milling. Taking zeolite A as an example, we demonstrate its size reduction from ~3 μm to 66 nm in 30 min, which is quite faster than previous methods reported. Three functions, viz., miniaturization, amorphization and recrystallization were found to take effect concurrently during this one-pot process. The dynamic balance between these three functions was achieved by adjusting the milling period and temperature, which lead to the tuning of zeolite A particle size. Particle size and crystallinity of the zeolite A nanocrystals were confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and water adsorption-desorption. This work presents a pioneering advancement in this field of nanosized zeolites, and will facilitate the mass production as well as boost the wide applications of nanosized zeolites.

Pioneering In Situ Recrystallization during Bead Milling: A Top-down Approach to Prepare Zeolite A Nanocrystals

PubMed Central

Anand, Chokkalingam; Yamaguchi, Yudai; Liu, Zhendong; Ibe, Sayoko; Elangovan, Shanmugam P.; Ishii, Toshihiro; Ishikawa, Tsuyoshi; Endo, Akira; Okubo, Tatsuya; Wakihara, Toru

2016-01-01

Top-down approach has been viewed as an efficient and straightforward method to prepare nanosized zeolites. Yet, the mechanical breaking of zeolite causes amorphization, which usually requires a post-milling recrystallization to obtain fully crystalline nanoparticles. Herein we present a facile methodology to prepare zeolite nanocrystals, where milling and recrystallization can be performed in situ. A milling apparatus specially designed to work under conditions of high alkalinity and temperature enables the in situ recrystallization during milling. Taking zeolite A as an example, we demonstrate its size reduction from ~3 μm to 66 nm in 30 min, which is quite faster than previous methods reported. Three functions, viz., miniaturization, amorphization and recrystallization were found to take effect concurrently during this one-pot process. The dynamic balance between these three functions was achieved by adjusting the milling period and temperature, which lead to the tuning of zeolite A particle size. Particle size and crystallinity of the zeolite A nanocrystals were confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and water adsorption-desorption. This work presents a pioneering advancement in this field of nanosized zeolites, and will facilitate the mass production as well as boost the wide applications of nanosized zeolites. PMID:27378145

Riparian zone flowpath dynamics during snowmelt in a small headwater catchment

NASA Astrophysics Data System (ADS)

McGlynn, B. L.; McDonnell, J. J.; Shanley, J. B.; Kendall, C.

1999-09-01

The hydrology of the near-stream riparian zone in upland humid catchments is poorly understood. We examined the spatial and temporal aspects of riparian flowpaths during snowmelt in a headwater catchment within the Sleepers River catchment in northern Vermont. A transect of 15 piezometers was sampled for Ca, Si, DOC, other major cations, and δ18O. Daily piezometric head values reflected variations in the stream hydrograph induced by melt and rainfall. The riparian zone exhibited strong upward discharge gradients. An impeding layer was identified between the till and surficial organic soil. Water solute concentrations increased toward the stream throughout the melt. Ca concentrations increased with depth and DOC concentrations decreased with depth. The concentrations of Ca in all piezometers were lower during active snowmelt than during post-melt low flow. Ca data suggest snowmelt infiltration to depth; however, only upslope piezometers exhibited snowmelt infiltration and consequent low δ18O values,(while δ18O values varied less than 0.5‰ in the deep riparian piezometers throughout the study period. Ca and δ18O values in upslope piezometers during low streamflow were comparable to Ca and δ18O in riparian piezometers during high streamflow. The upland water Ca and δ18O may explain the deep riparian Ca dilution and consistent δ18O composition. The temporal pattern in Ca and δ18O indicate that upland water moves to the stream via a lateral displacement mechanism that is enhanced by the presence of distinct soil/textural layers. Snowmelt thus initiates the flux of pre-melt, low Ca upland water to depth in the riparian zone, but itself does not appear at depth in the riparian zone during spring melt. This is despite the coincident response of upland groundwater and stream discharge.

Experimental constraints on mantle metasomatism caused by silicate and carbonate melts

NASA Astrophysics Data System (ADS)

Gervasoni, Fernanda; Klemme, Stephan; Rohrbach, Arno; Grützner, Tobias; Berndt, Jasper

2017-06-01

Metasomatic processes are responsible for many of the heterogeneities found in the upper mantle. To better understand the metasomatism in the lithospheric mantle and to illustrate the differences between metasomatism caused by hydrous silicate and carbonate-rich melts, we performed various interaction experiments: (1) Reactions between hydrous eclogite-derived melts and peridotite at 2.2-2.5 GPa and 900-1000 °C reproduce the metasomatism in the mantle wedge above subduction zones. (2) Reactions between carbonate-rich melts and peridotite at 2.5 GPa and 1050-1000 °C, and at 6 GPa and 1200-1250 °C simulate metasomatism of carbonatite and ultramafic silicate-carbonate melts in different regions of cratonic lithosphere. Our experimental results show that partial melting of hydrous eclogite produces hydrous Si- and Al-rich melts that react with peridotite and form bi-mineralic assemblages of Al-rich orthopyroxene and Mg-rich amphibole. We also found that carbonate-rich melts with different compositions react with peridotite and form new metasomatic wehrlitic mineral assemblages. Metasomatic reactions caused by Ca-rich carbonatite melt consume the primary peridotite and produce large amounts of metasomatic clinopyroxene; on the other hand, metasomatism caused by ultramafic silicate-carbonate melts produces less clinopyroxene. Furthermore, our experiments show that ultramafic silicate-carbonate melts react strongly with peridotite and cause crystallization of large amounts of metasomatic Fe-Ti oxides. The reactions of metasomatic melts with peridotite also change the melt composition. For instance, if the carbonatite melt is not entirely consumed during the metasomatic reactions, its melt composition may change dramatically, generating an alkali-rich carbonated silicate melt that is similar in composition to type I kimberlites.

The Effect of Dynamic Recrystallization on Monotonic and Cyclic Behaviour of Al-Cu-Mg Alloy.

PubMed

Tomczyk, Adam; Seweryn, Andrzej; Grądzka-Dahlke, Małgorzata

2018-05-23

The paper presents an investigation that was conducted to determine the possibility of the occurrence of the process of dynamic recrystallization in 2024 alloy during monotonic tensile and creep tests at the elevated temperatures of 100 °C, 200 °C, and 300 °C. As-extruded material was subjected to creep process with constant force at elevated temperatures, until two varying degrees of deformation were reached. After cooling at ambient temperature, the pre-deformed material was subjected to monotonic and fatigue tests as well as metallographic analysis. The process of dynamic recrystallization was determined in monotonic tests to occur at low strain rate (0.0015/s) only at the temperature of 300 °C. However, in the creep tests, this process occurred with varying efficiency, both during creep at 200 °C and 300 °C. Dynamic recrystallization was indicated to have a significant influence on the monotonic and cyclic properties of the material.

Effects of Static Recrystallization and Precipitation on Mechanical Properties of 00Cr12 Ferritic Stainless Steel

NASA Astrophysics Data System (ADS)

Shao, Yi; Liu, Chenxi; Yue, Tengxiao; Liu, Yongchang; Yan, Zesheng; Li, Huijun

2018-05-01

The 00Cr12 ferritic stainless steel samples were isothermally held at different temperatures in the range of 700 °C to 1000 °C to investigate the effect of static recrystallization and precipitation on mechanical properties, such as microhardness, tensile strength, and yield strength. The results show that the formation of the fine recrystallized grain, as well as precipitation, coarsening, and dissolution of the second-phase particles, influences the mechanical properties remarkably. The fine recrystallized grain can provide a positive grain boundary-strengthening effect in the sample under a relatively high holding temperature. Coarsening and dissolution of M23C6 result in partial depletion of precipitate hardening. In contrast, the size and number density of MX particles are almost constant, regardless of the holding temperature; therefore, it can provide a better precipitation-hardening effect.

Pairing Heterocyclic Cations with closo-Icosahedral Borane and Carborane Anions, II: Benchtop Alternative Synthetic Methodologies for Binary Triazolium and Tetrazolium Salts with Significant Water Solubility (POSTPRINT)

DTIC Science & Technology

2012-01-01

interesting property, eutectic melting-point depression. Recrystallization of ternary salts 12–14 was not attempted because of a concern that a cation... recrystallization solvent mixture for these powders, and while some individual successes resulted, a general efficient solvent system for all salt...product recrystallizations could not be found. So, rather than recrystallizing each individual adduct, spectroscopic examination of the amorphous solids was

Impact-induced frictional melting in ordinary chondrites: A mechanism for deformation, darkening, and vein formation

NASA Astrophysics Data System (ADS)

van der Bogert, C. H.; Schultz, P. H.; Spray, J. G.

2003-10-01

High speed friction experiments have been performed on the ordinary chondrites El Hammami (H5, S2) and Sahara 97001 (L6, S3) using an axial friction-welding apparatus. Each sample was subjected to a strain rate of 103 to 104 s-1, which generated 250 to 500 μm-deep darkened zones on each sample cube. Thin section analyses reveal that the darkened areas are composed of silicate glass and mineral fragments intermingled with dispersed submicron-size FeNi and FeS blebs. Fracturing of mineral grains and the formation of tiny metallic veins define the extent of deformation beyond the darkened shear zone. These features are not present in the original meteorites. The shear zones and tiny veins are quite similar to certain vein systems seen in naturally deformed ordinary chondrites. The experiments show that shock deformation is not required for the formation of melt veins and darkening in ordinary chondrites. Therefore, the presence of melt veins and darkening does not imply that an ordinary chondrite has undergone severe shock deformation. In fact, high strain rate deformation and frictional melting are especially important for the formation of veins at low shock pressures.

Atmospheric river impacts on Greenland Ice Sheet surface melt and mass balance

NASA Astrophysics Data System (ADS)

Mattingly, K.; Mote, T. L.

2017-12-01

Mass loss from the Greenland Ice Sheet (GrIS) has accelerated during the early part of the 21st Century. Several episodes of widespread GrIS melt in recent years have coincided with intense poleward moisture transport by atmospheric rivers (ARs), suggesting that variability in the frequency and intensity of these events may be an important driver of the surface mass balance (SMB) of the GrIS. ARs may contribute to GrIS surface melt through the greenhouse effect of water vapor, the radiative effects of clouds, condensational latent heating within poleward-advected air masses, and the energy provided by liquid precipitation. However, ARs may also provide significant positive contributions to GrIS SMB through enhanced snow accumulation. Prior research on the role of ARs in Arctic climate has consisted of case studies of ARs associated with major GrIS melt events or examined the effects of poleward moisture flux on Arctic sea ice. In this study, a long-term (1979-2016) record of intense moisture transport events affecting Greenland is compiled using a conventional AR identification algorithm as well as a self-organizing map (SOM) classification applied to integrated water vapor transport (IVT) data from several atmospheric reanalysis datasets. An analysis of AR effects on GrIS melt and SMB is then performed with GrIS surface melt data from passive microwave satellite observations and the Modèle Atmosphérique Régional (MAR) regional climate model. Results show that meltwater production is above normal during and after AR impact days throughout the GrIS during all seasons, with surface melt enhanced most by strong (> 85th percentile IVT) and extreme (> 95th percentile IVT) ARs. This relationship holds at the seasonal scale, as the total amount of water vapor transported to the GrIS by ARs is significantly greater during above-normal melt seasons. ARs exert a more complex influence on SMB. Normal (< 85th percentile IVT) ARs generally do not have a substantial impact on

Cube texture formation during the early stages of recrystallization of Al-1%wt.Mn and AA1050 aluminium alloys

NASA Astrophysics Data System (ADS)

Miszczyk, M. M.; Paul, H.

2015-08-01

The cube texture formation during primary recrystallization was analysed in plane strain deformed samples of a commercial AA1050 alloy and an Al-1%wt.Mn model alloy single crystal of the Goss{110}<001> orientation. The textures were measured with the use of X-ray diffraction and scanning electron microscopy equipped with an electron backscattered diffraction facility. After recrystallization of the Al-1%wt.Mn single crystal, the texture of the recrystallized grains was dominated by four variants of the S{123}<634> orientation. The cube grains were only sporadically detected by the SEM/EBSD system. Nevertheless, an increased density of <111> poles corresponding to the cube orientation was observed. The latter was connected with the superposition of four variants of the S{123}<634> orientation. This indicates that the cube texture after the recrystallization was a ‘compromise texture’. In the case of the recrystallized AA1050 alloy, the strong cube texture results from both the increased density of the particular <111> poles of the four variants of the S orientation and the ∼40°(∼< 111>)-type rotation. The first mechanism transforms the Sdef-oriented areas into Srex ones, whereas the second the near S-oriented, as-deformed areas into near cube-oriented grains.

Recrystallization of water in non-water-soluble (meth)acrylate polymers is not rare and is not devitrification.

PubMed

Gemmei-Ide, Makoto; Ohya, Atsushi; Kitano, Hiromi

2012-02-16

Change in the state of water sorbed into four kinds of non-water-soluble poly(meth)acrylates with low water content by temperature (T) perturbation was examined on the basis of T variable mid-infrared (MIR) spectroscopy. Many studies using differential scanning calorimetry suggested that there was no change in the state. T dependence of their MIR spectra, however, clearly demonstrated various changes in the state. Furthermore, recrystallization, which was crystallization during heating, was observed in all four polymers. The recrystallization observed in this study was not devitrification, which is the change in the state from glassy water to crystalline water, but vapor deposition during heating (vapor re-deposition). There were only two reports about recrystallization of water in a non-water-soluble polymer before this report; therefore, it might be considered to be a rare phenomenon. However, as demonstrated in this study, it is not a rare phenomenon. Recrystallization (vapor re-deposition) of water in the polymer matrices is related to a balance between flexibility and strength of the electrostatic interaction sites of polymer matrices but might not be related to the biocompatibility of polymers.

Chemical provinces and dynamic melting of the NE Atlantic mantle

NASA Astrophysics Data System (ADS)

Tronnes, R. G.

2009-12-01

Low-degree melting of fertile parts of the NE Atlantic mantle yields primitive alkaline basalts in the Icelandic off-rift zones and at Jan Mayen. Olivine tholeiites in the Icelandic rift zones and oceanic spreading ridges are formed by protracted decompressional melting. The V-shaped ridges SW and NE of Iceland indicate that rising, hot material is supplied by a pulsating plume and deflected laterally for distances of about 1000 km from Iceland (Jones et al. GGG 2002; Breivik et al. JGR 2006). Plume material deflected along the rift zones and spreading ridges undergoes mixing with the ambient asthenosphere and extensive melting at shallow level, whereas material deflected in other directions may flow laterally at deeper levels and remain largely unmelted and fertile. A recent investigation of a suite of primitive off-rift basalts from Iceland and Jan Mayen (Debaille et al., 2009, GCA) demonstrated an important source contribution from subcontinental lithospheric mantle (SCLM). Available data on the primitive off-rift basalts and tholeiitic basalts from Iceland and the NE Atlantic ridges indicates the existence of three main composite mantle components, characterized by the following relative isotope ratios (H: high, I: intermediate and L: low ratio) for 87/86Sr, 143/144Nd, 206/204Pb, 187/188Os and 3/4He, respectively: 1. Iceland plume with depleted lower mantle mixed with recycled oceanic crust: I, I, H, H, H 2. Strongly depleted and later re-enriched SCLM: H, L, I, L, L 3. Depleted asthenosphere: L, H, L, I, L The two first composite components contain enriched and depleted subcomponents with distinct isotope signatures. The isotope ratio variations between the fertile components are larger than between the refractory components. The 3/4He ratio, however, is much higher in the depleted plume component than in the depleted SCLM and asthenospheric components. The old SCLM material could in principle be recycled and embedded in the lower mantle and supplied to the

Investigation of nucleation processes during dynamic recrystallization of ice using cryo-EBSD.

PubMed

Chauve, T; Montagnat, M; Barou, F; Hidas, K; Tommasi, A; Mainprice, D

2017-02-13

Nucleation mechanisms occurring during dynamic recrystallization play a crucial role in the evolution of microstructures and textures during high temperature deformation. In polycrystalline ice, the strong viscoplastic anisotropy induces high strain heterogeneities between grains which control the recrystallization mechanisms. Here, we study the nucleation mechanisms occurring during creep tests performed on polycrystalline columnar ice at high temperature and stress (T=-5°C;σ=0.5 MPa) by post-mortem analyses of deformation microstructures using cryogenic electron backscatter diffraction. The columnar geometry of the samples enables discrimination of the nuclei from the initial grains. Various nucleation mechanisms are deduced from the analysis of the nuclei relations with the dislocation sub-structures within grains and at grain boundaries. Tilt sub-grain boundaries and kink bands are the main structures responsible for development of polygonization and mosaic sub-structures. Nucleation by bulging at serrated grain boundaries is also an efficient nucleation mechanism near the grain boundaries where strain incompatibilities are high. Observation of nuclei with orientations not related to the 'parent' ones suggests the possibility of 'spontaneous' nucleation driven by the relaxation of the dislocation-related internal stress field. The complexity of the nucleation mechanisms observed here emphasizes the impact of stress and strain heterogeneities on dynamic recrystallization mechanisms.This article is part of the themed issue 'Microdynamics of ice'. © 2016 The Author(s).

Investigation of nucleation processes during dynamic recrystallization of ice using cryo-EBSD

PubMed Central

Barou, F.; Hidas, K.; Tommasi, A.; Mainprice, D.

2017-01-01

Nucleation mechanisms occurring during dynamic recrystallization play a crucial role in the evolution of microstructures and textures during high temperature deformation. In polycrystalline ice, the strong viscoplastic anisotropy induces high strain heterogeneities between grains which control the recrystallization mechanisms. Here, we study the nucleation mechanisms occurring during creep tests performed on polycrystalline columnar ice at high temperature and stress (T=−5°C;σ=0.5 MPa) by post-mortem analyses of deformation microstructures using cryogenic electron backscatter diffraction. The columnar geometry of the samples enables discrimination of the nuclei from the initial grains. Various nucleation mechanisms are deduced from the analysis of the nuclei relations with the dislocation sub-structures within grains and at grain boundaries. Tilt sub-grain boundaries and kink bands are the main structures responsible for development of polygonization and mosaic sub-structures. Nucleation by bulging at serrated grain boundaries is also an efficient nucleation mechanism near the grain boundaries where strain incompatibilities are high. Observation of nuclei with orientations not related to the ‘parent’ ones suggests the possibility of ‘spontaneous’ nucleation driven by the relaxation of the dislocation-related internal stress field. The complexity of the nucleation mechanisms observed here emphasizes the impact of stress and strain heterogeneities on dynamic recrystallization mechanisms. This article is part of the themed issue ‘Microdynamics of ice’. PMID:28025294

Mantle melting and melt refertilization beneath the Southwest Indian Ridge: Mineral composition of abyssal peridotites

NASA Astrophysics Data System (ADS)

Chen, Ling; Zhu, Jihao; Chu, Fengyou; Dong, Yan-hui; Liu, Jiqiang; Li, Zhenggang; Zhu, Zhimin; Tang, Limei

2017-04-01

As one of the slowest spreading ridges of the global ocean ridge system, the Southwest Indian Ridge (SWIR) is characterized by discontinued magmatism. The 53°E segment between the Gallieni fracture zone (FZ) (52°20'E) and the Gazelle FZ (53°30'E) is a typical amagmatic segment (crustal thickness <2km) (Zhou and Dick, 2013) that opens a window to the mantle thus provides a chance to detect the mantle composition directly. We examine the mineral compositions of 17 peridotite samples from the 53°E amagmatic segment. The results show that the peridotites can be divided into two groups. The Group 1 peridotites are characterized by clinopyroxenes having LREE depleted patterns that is typical for the abyssal peridotite, thus are thought to be the residue of the mantle melting. The Group 2 peridotites show the lowest HREE content within the SWIR peridotites but are anomaly enriched in LREE, with flat or U-type REE patterns, thus cannot be the pure residue of mantle melting. Mineral compositions of the Group 2 peridotites are more depleted than that of peridotites sampled near the Bouvet hot spot (Johnson et al., 1990), implying that the depleted mantle beneath the 53°E segment may be the residue of ancient melting event. This hypothesis is supported by the the low Ol/Opx ratios, coarse grain sizes (>1cm) Opx, and Mg-rich mineral compositions akin to harzburgite xenoliths that sample old continental lithospheric mantle (Kelemen et al., 1998). Melt refertilization model shows that Group 2 peridotites were affected by an enriched low-degree partial melt from the garnet stability field. These results indicate that depleted mantle which experiences ancient melting event are more sensitive to melt refertilization, thus may reduce the melt flux, leading to extremely thin crust at 53°E segment. This research was granted by the National Basic Research Programme of China (973 programme) (grant No. 2013CB429705) and the Fundamental Research Funds of Second Institute of

User-independent EBSD parameters to study the progress of recovery and recrystallization in Cu-Zn alloy during in situ heating.

PubMed

Sharma, N K; Shekhar, S

2016-12-01

Microstructural evolution of cold-rolled Cu-5%Zn alloy during in situ heating inside field-emission scanning electron microscope was utilized to obtain user-independent parameters in order to trace the progress of static recovery and recrystallization. Electron back-scattered diffraction (EBSD)-based orientation imaging microscopy was used to obtain micrographs at various stages of in situ heating. It is shown that unlike the pre-existing methods, additional EBSD-based parameter can be used to trace the progress of recovery and recrystallization, which is not dependent on user input and hence less prone to error. True strain of 0.3 was imposed during cold rolling of alloy sample. Rolled sample was subjected to in situ heating from room temperature to 500°C (∼0.58 Tm) with soaking time of 10 min, at each of the intermediate temperatures viz. 100, 200, 300, 400 and 450°C. After reaching 500°C, the sample was kept at this temperature for a maximum duration of around 15 h. The sample showed clear signs of recovery for temperature up to 450°C, and at 500°C, recrystallization started to take place. Recrystallization kinetics was moderate, and full recrystallization was achieved in approximately 120 min. We found that EBSD parameter, namely, band contrast intensity can be used as an extra handle to map out the progress of recrystallization occurring in the sample. By contrast, mean angular deviation can be used to understand the evolution of recovery in samples. The parameters mentioned in the current study, unlike other pre-existing methods, can also be used for mapping local microstructural transformations due to recovery and recrystallization. We discuss the benefits and limitations in using these additional handles in understanding the changes taking place in the material during in situ heating. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

Analysis of ablation debris from natural and artificial iron meteorites

NASA Technical Reports Server (NTRS)

Blanchard, M. B.; Davis, A. S.

1977-01-01

Artificial ablation studies were performed on iron and nickel-iron samples using an arc-heated plasma of ionized air. Experiment conditions simulated a meteoroid traveling about 12 km/sec at an altitude of 70 km. The artificially produced fusion crusts and ablation debris show features very similar to natural fusion crusts of the iron meteorites Boguslavka, Norfork, and N'Kandhla and to magnetic spherules recovered from Mn nodules. X-ray diffraction, electron microprobe, optical, and scanning electron microscope analyses reveal that important mineralogical, elemental, and textural changes occur during ablation. Some metal is melted and ablated. The outer margin of the melted rind is oxidized and recrystallizes as a discontinuous crust of magnetite and wustite. Adjacent to the oxidized metallic ablation zone is an unoxidized metallic ablation zone in which structures such as Widmannstatten bands are obliterated as the metal is transformed to unequilibrated alpha 2 nickel-iron. Volatile elements are vaporized and less volatile elements undergo fractionation.

Is Myanmar jadeitite of Jurassic age? A result from incompletely recrystallized inherited zircon

NASA Astrophysics Data System (ADS)

Yui, Tzen-Fu; Fukoyama, Mayuko; Iizuka, Yoshiyuki; Wu, Chao-Ming; Wu, Tsai-Way; Liou, J. G.; Grove, Marty