Artykuły w czasopismach: „Crystallization onset time”

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Davoodi, E., M. Hasan, S. Rana i G. Kumar. "Effect of loading rate on crystallization of metallic glass supercooled liquids". American Journal of Physical Sciences and Applications 1, nr 3 (1.07.2020): 18–21. http://dx.doi.org/10.15864/ajps.1303.

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Metallic glasses exhibit unique thermoplastic processing capability, which is enabled by their metastable supercooled liquid state below the crystallization temperature. The thermoplastic processing critically depends on the crystallization time (processing time window), temperature (viscosity), applied load, and strain-rate. Among these parameters, the effects of crystallization time and processing temperature have been extensively studied. However, the effects of load and loading rate have not been thoroughly investigated. In this work, we performed a systematic study of load on the supercooled liquid state of three metallic glass formers: Pt-based, Zr-based, and Pd-based. The results show that the load-response of a metallic glass supercooled liquids is strongly composition dependent. The onset temperature of crystallization decreases with increasing load in Pt-based metallic glass whereas for Zr-based and Pd-based metallic glasses the onset temperature remains unchanged. The crystallization peak time is reduced for all three metallic glasses after thermoplastic forming. The results are discussed in terms of nucleation and growth of crystallites in metallic glasses.

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Tkatch, V. I., S. V. Vasiliev i K. A. Svyrydova. "Identification of the onset crystallization time in metallic glasses at isothermal conditions". Journal of Non-Crystalline Solids 463 (maj 2017): 102–7. http://dx.doi.org/10.1016/j.jnoncrysol.2017.03.008.

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Boudjemline, Attia, David T. Clarke, Neville J. Freeman, James M. Nicholson i Gareth R. Jones. "Early stages of protein crystallization as revealed by emerging optical waveguide technology". Journal of Applied Crystallography 41, nr 3 (8.04.2008): 523–30. http://dx.doi.org/10.1107/s0021889808005098.

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A highly sensitive method for studying the onset of protein crystallization in real time using an optical-waveguide-based technique is reported. Dual polarization interferometry uses light from sensing and reference waveguides to produce an interference pattern, which when the sensing waveguide is immersed in a protein solution supplies information on the thickness and density of any protein adlayer on the sensing waveguide's surface. This technique provides evidence that crystallization proceedsvialarge protein aggregates but, more strikingly, shows dramatic light loss from the sensing waveguide at a very early stage during crystallization. The technique proves relatively insensitive to the crystallization of small molecules or poorly formed protein crystals and affords a method of distinguishing crystal formation from the formation of other protein aggregates or salt crystals. The experimental setup currently necessitates crystallization using the batch method, and precipitant mixing at high supersaturation is known to introduce a greater variability compared with methods such as vapour diffusion or dialysis, but first results promise to bridge the paucity of real-time methods available to distinguish the onset of protein crystallization from other forms of aggregation.

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D´Eramo, F. J., J. J. Esteban, M. Demartis, E. Aragón, J. E. Coniglio i L. P. Pinotti. "Time lag between metamorphism and crystallization of anatectic granites (Córdoba, Argentina)". Geologica Acta 18 (2.11.2020): 1–14. http://dx.doi.org/10.1344/geologicaacta2020.18.17.

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SHRIMP and LA-ICP-MS analyses carried out on zircons from the Río de los Sauces granite revealed their metamorphic and igneous nature. The metamorphic zircons yielded an age of 537±4.8 (2σ)Ma that probably predates the onset of the anatexis during the Pampean orogeny. By contrast, the igneous zircons yielded a younger age of 529±6 (2σ)Ma and reflected its crystallization age. These data point to a short time lag of ca. 8Myr between the High Temperature (HT) metamorphic peak and the subsequent crystallization age of the granite. Concordia age of 534±3.8 (2σ)Ma, for both types of zircon populations, can be considered as the mean age of the Pampean HT metamorphism in the Sierras de Córdoba.

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Simmance, Kerry, Wouter van Beek i Gopinathan Sankar. "Time resolved in situ X-ray diffraction study of crystallisation processes of large pore nanoporous aluminophosphate materials". Faraday Discussions 177 (2015): 237–47. http://dx.doi.org/10.1039/c4fd00179f.

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Time resolved high-resolution X-ray powder diffraction was utilized to obtain detailed changes in the crystal structure parameters during the hydrothermal crystallization process of the nanoporous aluminophosphate AlPO-5 (AFI) structure. This in situ study offered not only the influence of metal ions on the onset of crystallization and estimation of the activation energy of the process, but also allowed us to determine in detail the changes in lattice parameters during this process. More importantly the time-resolved study clearly showed the lattice expansion in the divalent metal ions substituted system right from the on-set of crystallization process, compared to the one without any dopant ions, which suggest that an amorphous or poorly crystalline network is formed prior to crystallization that contains the large divalent ions (compared to Al(iii), the substituting element), which is in agreement with the combined XAS/XRD study reported earlier. A mechanism based on this and the earlier study is suggested.

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Misyura, S. Y., i V. S. Morozov. "Nonisothermal desorption of droplets of LiBr salt solution on a heated wall". MATEC Web of Conferences 194 (2018): 01040. http://dx.doi.org/10.1051/matecconf/201819401040.

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Nonisothermal desorption and crystallization of droplets of aqueous salts solution of H2O/LiBr were studied experimentally. A droplet was placed on a horizontal heated wall. The initial concentration of salt C0 varied within 0-53 %. The wall temperature Tw varied within 80 - 235 °C and ambient air pressure was 1 bar. It was shown that the desorption time t1 decreases sharply with increasing Tw and at Tw < 150-160 °C. The desorption time t1 is the time until the onset of crystallization. The desorption time t1 is quasi-constant at Tw > 160 °C and increases with growth in C0.

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Lednický, František, i Miroslava Muchová. "Revival of the Induction Time Concept in the Theory of Polymer Crystallization". Collection of Czechoslovak Chemical Communications 58, nr 10 (1993): 2444–50. http://dx.doi.org/10.1135/cccc19932444.

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To monitor early stages of spherulite growth, a microscopical method has been worked out based on the photometrical measurement of the intensity of depolarized light during isothermal crystallization. Application of the technique to polypropylene yields the evidence of existence of nucleation induction time which reflects the processes taking place prior to the onset of spherulite growth, viz. the formation of stable crystal nuclei. Using the method, it is possible to evaluate also systems with a dispersed phase, the interfacial relations being reflected in the induction time of the nucleation on the surface of the dispersed phase. Application to the model PP/carbon fibres system yields differing results for carbon fibres of various provenance and of various properties.

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Cai, Yan-Hua, i Yan-Hua Zhang. "The Crystallization, Melting Behavior, and Thermal Stability of Poly(L-lactic acid) Induced byN,N,N′-Tris(benzoyl) Trimesic Acid Hydrazide as an Organic Nucleating Agent". Advances in Materials Science and Engineering 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/843564.

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N,N,N′-Tris(benzoyl) trimesic acid hydrazide (TTAD), as a novel nucleating agent of poly(L-lactic acid) (PLLA), was synthesized and characterized by FT-IR and1H NMR. The crystallization, melting behavior, and thermal stability of PLLA induced by TTAD were investigated through DSC, TGA, depolarized-light intensity measurement, and so forth. The crystallization behavior indicated that the presence of TTAD accelerated the overall PLLA crystallization. Compared to neat PLLA, the crystallization onset temperature of PLLA/1%TTAD increased from 101.36°C to 125.26°C, the melt-crystallization peak temperature increased from 94.49°C to 117.56°C, crystallization enthalpy increased from 0.1023 J·g−1to 33.44 J·g−1at a cooling rate of 1°C/min from melt, and the crystallization half-time of PLLA/TTAD decreased from 2997.2 s to 108.9 s at 110°C. Moreover, the nonisothermal crystallization measurements also indicated that the crystallization peak became wider and shifted to a lower temperature with increasing cooling rate. With the presence of TTAD, the melting behavior of PLLA was affected significantly, and a double-melting peak occurred due to melting-recrystallization. Thermal stability research showed that there existed one degradation stage of PLLA and PLLA/TTAD samples, and the thermal degradation temperature of PLLA/TTAD decreased compared to neat PLLA.

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Hadinata, Chitiur, Claus Gabriel, Maximilian Ruellmann, Nhol Kao i Hans-Martin Laun. "Correlation between the gel time and quiescent/quasi-quiescent crystallization onset time of poly(butene-1) as determined from rheological methods". Rheologica Acta 45, nr 5 (29.11.2005): 631–39. http://dx.doi.org/10.1007/s00397-005-0017-7.

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Yan, Zhicheng, Yan Liu, Shaopeng Pan, Yihua Hu, Jing Pang i Weimin Wang. "The Structural Evolution of Al86Ni9La5 Glassy Ribbons during Milling at Room and Cryogenic Temperatures". Materials 11, nr 10 (12.10.2018): 1956. http://dx.doi.org/10.3390/ma11101956.

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Melt-spun metallic Al86Ni9La5 glassy ribbons solidified at different circumferential speeds (Sc) were subjected to high-energy ball milling at room and cryogenic temperatures. Crystallization induced by milling was found in the Al86Ni9La5 solidified at lower circumferential speed (Sc = 14.7 m/s), while the Al86Ni9La5 with Sc = 36.6 m/s kept amorphous. Besides, a trend of structural rejuvenation during milling process was observed, as the onset temperatures (Tx1, Tx2) and the crystallization enthalpies (ΔH1, ΔH2) first decreased and then increased along with the milling time. We explored the structural origin of crystallization by ab initio molecular dynamic simulations and found that the tricapped trigonal prism (TTP) Ni-centered clusters with a higher frequency in samples solidified at a lower cooling rate, which tend to link into medium-range orders (MROs), may promote crystallization by initiating the shear bands during milling. Based on the deformation mechanism and crush of metallic glasses, we presented a qualitative model to explain the structural rejuvenation during milling.

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Lowndes, D. H., S. J. Pennycook, G. E. Jellison, S. P. Withrow i D. N. Mashburn. "Solidification of highly undercooled liquid silicon produced by pulsed laser melting of ion-implanted amorphous silicon: Time-resolved and microstructural studies". Journal of Materials Research 2, nr 5 (październik 1987): 648–80. http://dx.doi.org/10.1557/jmr.1987.0648.

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Nanosecond resolution time-resolved visible (632.8 nm) and infrared (1152 nm) reflectivity measurements, together with structural and Z-contrast transmission electron microscope (TEM) imaging, have been used to study pulsed laser melting and subsequent solidification of thick (190–410 nm) amorphous (a) Si layers produced by ion implantation. Melting was initiated using a KrF (248 nm) excimer laser of relatively long [45 ns full width half maximum (FWHM)] pulse duration; the microstructural and time-resolved measurements cover the entire energy density (E1) range from the onset of melting (at ∼ 0.12J/cm2) up to the onset of epitaxial regrowth (at ∼ 1.1 J/cm2). At low E1 the infrared reflectivity measurements were used to determine the time of formation, the velocity, and the final depth of “explosively” propagating buried liquid layers in 410 nm thick a-Si specimens that had been uniformly implanted with Si, Ge, or Cu over their upper ∼ 300 nm. Measured velocities lie in the 8–14 m/s range, with generally higher velocities obtained for the Ge- and Cu-implanted “a-Si alloys.” The velocity measurements result in an upper limit of 17 (± 3) K on the undercooling versus velocity relationship for an undercooled solidfying liquid-crystalline Si interface. The Z-contrast scanning TEM measurements of the final buried layer depth were in excellent agreement with the optical measurements. The TEM study also shows that the “fine-grained polycrystalline Si” region produced by explosive crystallization of a-Si actually contains large numbers of disk-shaped Si flakes that can be seen only in plan view. These Si flakes have highly amorphous centers and laterally increasing crystallinity; they apparently grow primarily in the lateral direction. Flakes having this structure were found both at the surface, at low laser E1, and also deep beneath the surface, throughout the “fine-grained poly-Si” region formed by explosive crystallization, at higher E1. Our conclusion that this region is partially amorphous (the centers of flakes) differs from earlier results. The combined structural and optical measurements suggest that Si flakes nucleate at the undercooled liquid-amorphous interface and are the crystallization events that initiate explosive crystallization. Time-resolved reflectivity measurements reveal that the surface melt duration of the 410 nm thick a-Si specimens increases rapidly for 0.3E1 <0.6 J/cm2, but then remains nearly constant for E1 up to ∼ 1.0 J/cm2. For 0.3 < E1 < 0.6 J/cm2 the reflectivity exhibits a slowly decaying behavior as the near-surface pool of liquid Si fills up with growing large grains of Si. For higher E1, a flat-topped reflectivity signal is obtained and the microstructural and optical studies together show that the principal process occurring is increasingly deep melting followed by more uniform regrowth of large grains back to the surface. However, cross-section TEM shows that a thin layer of fine-grained poly-Si still is formed deep beneath the surface for E1<0.9 J/cm2, implying that explosive crystallization occurs (probably early in the laser pulse) even at these high E1 values. The onset of epitaxial regrowth at E1 = 1.1 J/cm2 is marked by a slight decrease in surface melt duration.

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Jeong, H. G., i W. J. Kim. "Hardening by Crystallization During Superplastic Flow in a Powder-metallurgy-processed Zr65Al10Ni10Cu15 Glass Metallic Alloy". Journal of Materials Research 20, nr 6 (1.06.2005): 1447–55. http://dx.doi.org/10.1557/jmr.2005.0185.

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The superplastic behavior of the Zr65Al10Ni10Cu15 glass metallic alloy produced by the powder metallurgy method was examined in the supercooled liquid region. A tensile elongation as large as 750% was obtained at 6.3 × 10−3 s−1 at 697 K. Large strain hardening took place during the course of deformation and systematic trend was observed in the hardening behavior. Plots of stress versus strain and strain rate versus stress at 697 K showed that Newtonian viscous flow governed the plastic flow until the onset of strain hardening. Microstructure and differential scanning calorimetry analyses as well as flow stress versus testing time curves provided consistent evidence that the strain hardening was induced by crystallization. Crystallization was enhanced in the gauge region (deformed region) as compared to the grip region (undeformed region). Crystallization is expected to decrease tensile ductility by decreasing the strain-rate-sensitivity value and increasing the degree of brittleness. Hardening by crystallization, however, can contribute to neck stability if crystallization is enhanced in the neck region. The strain hardening and plastic stability parameters were measured as a function of strain for different strain rates at 696 K. The strain hardening parameter remained highly positive until failure. Because of this, the neck stability parameter (I) could be I < 0 in the entire hardening region. The contribution of hardening by crystallization to neck stability was found to be much more significant than that by grain growth in the superplastic metallic alloys. Reducing the specimen heating-and-holding time was suggested to promote superplasticity deformation without delaying initiation of crystallization. The largest tensile strain in the hardening region where crystallization may be obtained at the strain rates and temperatures where crystallization rate is controlled to be the lowest while maintaining I ≤ 0 throughout deformation.

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CAI, Yan-Hua, i Li-Sha ZHAO. "Heterogeneous Nucleation Effect of N, N'-Adipic Bis(4-phenylbutyric Acid) Dihydrazide on Crystallization Process of Poly(L-lactic Acid)". Materials Science 25, nr 4 (27.06.2019): 446–54. http://dx.doi.org/10.5755/j01.ms.25.4.20603.

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Enhancing crystallization ability is a fundamental challenges in Poly(L-lactic acid) (PLLA) industry, therefore, the goal of this work was to synthesis a new organic nucleating agent N, N'-adipic bis(4-phenylbutyric acid) dihydrazide (APAD), and investigate its effect on non-isothermal crystallization, isothermal crystallization, melting behavior, thermal stability, and optical property of PLLA. Non-isothermal melt crystallization results showed that APAD acted as more effective nucleating and accelerating agent for the crystallization of PLLA, as a result, upon cooling at 1 °C/min, PLLA/0.5 %APAD had the highest onset crystallization temperature 136.4 °C and the crystallization peak temperature 132.0 °C, as well as the largest non-isothermal crystallization enthalpy 48.1 J/g. However, with increasing of APAD concentration from 0.5 wt.% to 3 wt.%, the crystallization peak shifted to the lower temperature. In contrast, for the non-isothermal cold crystallization process, the effect of APAD concentration on the crystallization behavior of PLLA was negligible. Additionally, the non-isothermal crystallization process was also depended on the cooling rates and the final melting temperature. In isothermal crystallization section, to compare with the primary PLLA, the crystallization half-time of PLLA/APAD could decrease from 254.3 s to the minimum value 29.4 s, with 0.5 wt.% APAD contents at 125 °C. Melting behavior of PLLA/APAD samples under different conditions further confirmed the heterogeneous nucleation effect of APAD for PLLA, and the appearance of the double melting peaks was attributed to the melting-recrystallization. Finally, the addition of APAD decreased the thermal stability to some extent, although APAD could not change the thermal decomposition profile of PLLA. And a drop of PLLA/APAD samples in light transmittance resulted from the double influence of the enhancement of crystallization and the opaqueness of APAD.

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Lindberg, G. P., T. O’Loughlin, N. Gross, A. Reznik, S. Abbaszadeh, K. S. Karim, G. Belev, D. M. Hunter i B. A. Weinstein. "Raman and AFM mapping studies of photo-induced crystallization in a-Se films: substrate strain and thermal effects". Canadian Journal of Physics 92, nr 7/8 (lipiec 2014): 728–31. http://dx.doi.org/10.1139/cjp-2013-0586.

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Photo-induced crystallization (PC) is studied in amorphous selenium (a-Se) films deposited on glass with and without intermediate layers of indium tin oxide or polymer material. The spatial profile of PC domains is examined by co-localized scanning atomic force microscopy and Raman mapping. We also explore the thermal behavior of the onset and growth of PC in the a-Se films by Raman spectroscopy measurements at temperatures spanning the glass transition (Tg ∼ 313 K). In many films the onset time for PC shows a surprising discontinuity near Tg. Inserting a thin polyimide layer between the a-Se film and the substrate inhibits PC. Our results indicate that adhesion to a rigid substrate is important for promoting PC in a-Se films. We find that the discontinuities in the PC onset times, the shape of the mapping profiles, and the effects of having a soft polymer interface layer can be understood by a model that takes account of the substrate shear strain and its relaxation near Tg.

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Embi, Abraham A. "INTRODUCING CRYSTALLIZATION BACKWARD SUCTION TRAPPING LIPIDS AND DEBRIS AS PROPOSED ADDITIONAL FACTOR IN THE GENESIS OF CORONARY ARTERY DISEASE". International Journal of Research -GRANTHAALAYAH 8, nr 9 (1.10.2020): 215–33. http://dx.doi.org/10.29121/granthaalayah.v8.i9.2020.1174.

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Coronary artery disease progression involves a slow process of abnormal accumulation of lipid deposits to the inner walls of the arteries followed by an immune system response. It is known that an increase in lipid concentration could trigger cholesterol crystals deposition, thus starting a vicious cycle that could also progress into intra-arterial plaque formation, the hallmark of mature atheromas. The purpose of this manuscript is to introduce a proposed mechanism for the genesis of coronary artery disease; whereby the actual act of lipids crystallization starts a cycle demonstrated to induce additional crystallization via dehydration. Experiments demonstrate for the first time via images and video-recordings showing that when the onset crystallization occurs near the tissue (≅ 1 mm) a dehydration triggered backward hydrodynamic suction or vacuum ensues with enough force to withdraw lipid molecules from human tissue; these molecules are shown to adhere to the crystals.

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Hu, Man Hong, i Yong Hu. "Effect of Cold Rolling on Thermal Stability of Zr₅₅ Al₁₀Ni₅Cu₃₀ Bulk Metallic Glass". Advanced Materials Research 239-242 (maj 2011): 490–95. http://dx.doi.org/10.4028/www.scientific.net/amr.239-242.490.

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The effect of cold rolling on thermal stability of bulk Zr55Al10Ni5Cu30metallic glass at room temperature had been investigated by means of X-ray diffractometer, high-resolution transmission electron microscope and differential scanning calorimeter. A number of the cold rolling processes were carried out to obtain different thickness reduction in specimens with the same original size. The XRD patterns of cold rolled specimens with thickness reduction up to 95% showed no clear difference with that of completely amorphous specimens. The relationship of the deformation with the thermal parameters of cold rolled specimen indicates that with the increase of thickness reduction, the glass transition temperature decreases obviously and the crystallization onset temperature and peak temperature decreases slightly. At the same time, the enthalpy of crystallization peak keeps almost constant during rolling. These results have revealed that cold rolling deformation has an apparently effect on the glass transition process but slightly effect on the crystallization process of Zr55Al10Ni5Cu30BMG.

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Fan, G. J., M. X. Quan, Z. Q. Hu, W. Löser i J. Eckert. "Deformation-induced microstructural changes in Fe40Ni40P14B6 metallic glass". Journal of Materials Research 14, nr 9 (wrzesień 1999): 3765–74. http://dx.doi.org/10.1557/jmr.1999.0510.

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The effect of mechanical deformation via high-energy ball milling on the structure of the Fe40Ni40P14B6 metallic glass was studied by means of x-ray diffactometry, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). After 5 h of milling, TEM observations indicated that some nanocrystallites with a diameter of about 6 nm precipitated from surface layers of the amorphous ribbons, whereas the bulk remained amorphous. When milling time was increased to 11 h, bulk crystallization occurred. The amorphous Fe40Ni40P14B6 alloy crystallized into a mixture of γ–(Fe, Ni) and (Fe, Ni)3(P, B). To understand the microstructural changes occurring in the amorphous ribbons before the onset of bulk crystallization, the isothermal crystallization behavior of as-deformed amorphous ribbons was studied. Compared with as-quenched amorphous ribbons, the local value of the Avrami exponent, derived from isothermal DSC data, increased from 3.5 to 4.1 for bulk crystallization. The thermal crystallization mechanism of deformed amorphous Fe40Ni40P14B6 ribbons changed from an eutectic-type reaction with simultaneous precipitation of γ–(Fe, Ni) and (Fe, Ni)3(P,B) from the amorphous matrix to a primary-type reaction with precipitation of α–Fe(P,B) preceding the formation of γ–(Fe,Ni) and (Fe,Ni)3(P,B). Our results suggest that several hours of mechanical milling cause surface crystallization and some atomic rearrangements in the amorphous alloy. The latter effect may be responsible for the observed primary-type reaction for crystallization of the deformed amorphous alloy

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Nicula, R., M. Stir i E. Burkel. "Synchrotron Radiation Investigation of Thermal Stability and Grain-Growth in Pure and Metal-Doped Nanocrystalline TiO₂". Materials Science Forum 467-470 (październik 2004): 1307–12. http://dx.doi.org/10.4028/www.scientific.net/msf.467-470.1307.

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The crystallization and coarsening of pure and metal-doped (M: Ag, Fe, Co) TiO2 amorphous specimens were studied during in-situ synchrotron radiation diffraction experiments. The temperature and time dependence of the average grain-size of TiO2 anatase and rutile constituent phases was determined. Excess vacancies, secondary phases or solute elements cause the pinning of the grain-boundary motion, control the onset of the anataserutile transition and control the thermal stability of ultrafine microstructures in nanocrystalline TiO2 ceramics.

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Zalden, Peter, Florian Quirin, Mathias Schumacher, Jan Siegel, Shuai Wei, Azize Koc, Matthieu Nicoul i in. "Femtosecond x-ray diffraction reveals a liquid–liquid phase transition in phase-change materials". Science 364, nr 6445 (13.06.2019): 1062–67. http://dx.doi.org/10.1126/science.aaw1773.

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In phase-change memory devices, a material is cycled between glassy and crystalline states. The highly temperature-dependent kinetics of its crystallization process enables application in memory technology, but the transition has not been resolved on an atomic scale. Using femtosecond x-ray diffraction and ab initio computer simulations, we determined the time-dependent pair-correlation function of phase-change materials throughout the melt-quenching and crystallization process. We found a liquid–liquid phase transition in the phase-change materials Ag4In3Sb67Te26 and Ge15Sb85 at 660 and 610 kelvin, respectively. The transition is predominantly caused by the onset of Peierls distortions, the amplitude of which correlates with an increase of the apparent activation energy of diffusivity. This reveals a relationship between atomic structure and kinetics, enabling a systematic optimization of the memory-switching kinetics.

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Pal, Mrinal, Aiko Narazaki, Takeshi Sasaki i Naoto Koshizaki. "Parameter effect on the crystallization of Nd:yttrium aluminum garnet laser-ablated TiO2 thin film". Journal of Materials Research 16, nr 11 (listopad 2001): 3158–61. http://dx.doi.org/10.1557/jmr.2001.0435.

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Process parameter dependency on the phase transition from anatase to rutile phase of laser-ablated TiO2 films was investigated. Lower ambient argon pressure, longer deposition time, higher laser fluence, and smaller target–substrate separation give rutile phase from anatase phase at comparatively lower temperature. The relationship between thickness and onset temperature of anatase–rutile transformation can be comprehensively explained in terms of film thickness. Thinner films have higher phase transition temperature. The presence of helium gas during deposition favors the anatase–rutile transition at a temperature lower than that expected from the above relationship.

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Panine, P., V. Urban, P. Boesecke i T. Narayanan. "Combined small- and wide-angle X-ray scattering study of early stages of polymer crystallization". Journal of Applied Crystallography 36, nr 4 (19.07.2003): 991–94. http://dx.doi.org/10.1107/s0021889803008513.

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The early stage of melt crystallization in low-density polyethylene was investigated by simultaneous time-resolved small-angle and wide-angle X-ray scattering (SAXS/WAXS) techniques. The high detectivity of the two-dimensional detectors together with the large photon flux of an undulator source permitted the collection of SAXS and WAXS patterns with nearly single-photon sensitivity and sub-second time resolution. As a result, the crystalline fraction well below 0.001 can be reliably detected and the apparent induction time is considerably reduced (<10 s). The time evolution of both the SAXS invariant and the degree of crystallinity follow the well established Avrami-type growth law. Despite the orders of magnitude improvement in sensitivity, the difference in the onset time of SAXS and WAXS signals is not significant. The behaviour of the SAXS data in the very early stages is not consistent with spinodal decomposition mechanism as described by the linearized Cahn–Hilliard theory.

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Song, Se Ahn, Wei Zhang, Hong Sik Jeong, Jin Gyu Kim i Youn Joong Kim. "High-Resolution Dynamic Analysis of the Phase Transformation in Ge₂Sb₂Te₅ Alloy". Advanced Materials Research 26-28 (październik 2007): 1199–202. http://dx.doi.org/10.4028/www.scientific.net/amr.26-28.1199.

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Phase transformation and crystal growth behavior of Ge2Sb2Te5 were investigated systematically by means of in situ heating (from room temperature to 500 oC) of amorphous Ge2Sb2Te5 alloy in a high voltage electron microscope with real-time monitoring. Large-scale crystallization occurred to amorphous Ge2Sb2Te5 around 200 oC. Large crystal growth developed on heating from 200 oC to 400 oC, and single crystalline grains grew up to 150 nm. Eventually the onset of partial melting of thin Ge2Sb2Te5 foil was at 500 oC and liquid Ge2Sb2Te5 was observed for the first time by high-resolution transmission electron microscopy. Hexagonal Ge2Sb2Te5 phase remains after a subsequent cooling.

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Lopez, Thomas, i Lorenzo Mangolini. "Crystallization Kinetics of Plasma-Produced Amorphous Silicon Nanoparticles". MRS Proceedings 1536 (2013): 213–18. http://dx.doi.org/10.1557/opl.2013.755.

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ABSTRACTThe use of a continuous flow non-thermal plasma reactor for the formation of silicon nanoparticles has attracted great interest because of the advantageous properties of the process [1]. Despite the short residence time in the plasma (around 10 milliseconds), a significant fraction of the precursor, silane, is converted and collected in the form of nanopowder. The structure of the produced powder can be tuned between amorphous and crystalline by adjusting the power of the radio-frequency excitation source, with higher power leading to the formation of crystalline particles. Numerical modeling suggests that higher excitation power results in a higher plasma density, which in turn increases the nanoparticle heating rate due to the interaction between ions, free radicals and the nanopowder suspended in the plasma [2]. While the experimental evidence suggests that plasma heating may be responsible for the formation of crystalline powder, an understanding of the mechanism that leads to the crystallization of the powder while in the plasma is lacking. In this work, we present an experimental investigation on the crystallization kinetic of plasma-produced amorphous powder. Silicon nanoparticles are nucleated and grown using a non-thermal plasma reactor similar to the one described in [1], but operated at low power to give amorphous nanoparticles in a 3-10 nm size range. The particles are then extracted from the reactor using an orifice and aerodynamically dragged into a low pressure reactor placed in a tube furnace capable of reaching temperatures up to 1000°C. Raman and TEM have been used to monitor the crystalline fraction of the material as a function of the residence time and temperature. It is expected that for a residence time in the annealing region of approximately ∼300 milliseconds, a temperature of at least 750 °C is needed to observe the onset of crystallization. A range of crystalline percentages can be observed from 750 °C to 830 °C. A discussion of particle growth and particle interaction, based on experimental evidence, will be presented with its relation to the overall effect on crystallization. Further data analysis allows extrapolating the crystallization rate for the case of this simple, purely thermal system. We conclude that thermal effects alone are not sufficient to explain the formation of crystalline powder in non-thermal plasma reactors.

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Qin, Frank G. F., Jian Chao Zhao, Andrew B. Russell, Xiao Dong Chen, John J. Chen i Lindsay Robertson. "Simulation and experiment of the unsteady heat transport in the onset time of nucleation and crystallization of ice from the subcooled solution". International Journal of Heat and Mass Transfer 46, nr 17 (sierpień 2003): 3221–31. http://dx.doi.org/10.1016/s0017-9310(03)00097-8.

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Ippolito, Fabio, Gunter Hübner, Tim Claypole i Patrick Gane. "Impact of Bimodal Particle Size Distribution Ratio of Functional Calcium Carbonate Filler on Thermal and Flowability Properties of Polyamide 12". Applied Sciences 11, nr 2 (11.01.2021): 641. http://dx.doi.org/10.3390/app11020641.

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In previous investigations, it was shown that the melting, as well as crystallization behavior of polyamide 12, could be manipulated by adjusting the particle size distribution of calcium carbonate as a functional filler. It was demonstrated that the melt properties of this compound show a significant dependency on the filler volume-based particle size. As finer and narrower the calcium carbonate particles in the polymer matrix become, the less influence the filler has on the melting properties, influencing the melt flow less significantly than the same surface amount of broad size distribution coarse calcium carbonate filler particles. However, due to increased nucleation, the crystallization behavior on cooling showed a markedly more rapid onset in the case of fine sub-micrometer filler particle size. To control further and optimize the thermal response properties of a filling compound for improved properties in additive manufacturing processing through selective laser sintering, the possibility to combine precisely defined particle size distributions has been studied, thereby combining the benefits of each particle size range within the chosen material size distribution contributes to the matrix. The melt flow at 190 °C, the melting speed, melting and crystallization point as well as crystallization time at 170 °C were analyzed. The thermal and flow properties of a polyamide 12 matrix can potentially be optimized with a combination of a precise amount of coarse and fine calcium carbonate filler. The improvements were exemplified using a twin-screw extruder for compounding, indicating the potential for optimizing functionally filled polymer in additive manufacturing.

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Ippolito, Fabio, Gunter Hübner, Tim Claypole i Patrick Gane. "Impact of Bimodal Particle Size Distribution Ratio of Functional Calcium Carbonate Filler on Thermal and Flowability Properties of Polyamide 12". Applied Sciences 11, nr 2 (11.01.2021): 641. http://dx.doi.org/10.3390/app11020641.

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In previous investigations, it was shown that the melting, as well as crystallization behavior of polyamide 12, could be manipulated by adjusting the particle size distribution of calcium carbonate as a functional filler. It was demonstrated that the melt properties of this compound show a significant dependency on the filler volume-based particle size. As finer and narrower the calcium carbonate particles in the polymer matrix become, the less influence the filler has on the melting properties, influencing the melt flow less significantly than the same surface amount of broad size distribution coarse calcium carbonate filler particles. However, due to increased nucleation, the crystallization behavior on cooling showed a markedly more rapid onset in the case of fine sub-micrometer filler particle size. To control further and optimize the thermal response properties of a filling compound for improved properties in additive manufacturing processing through selective laser sintering, the possibility to combine precisely defined particle size distributions has been studied, thereby combining the benefits of each particle size range within the chosen material size distribution contributes to the matrix. The melt flow at 190 °C, the melting speed, melting and crystallization point as well as crystallization time at 170 °C were analyzed. The thermal and flow properties of a polyamide 12 matrix can potentially be optimized with a combination of a precise amount of coarse and fine calcium carbonate filler. The improvements were exemplified using a twin-screw extruder for compounding, indicating the potential for optimizing functionally filled polymer in additive manufacturing.

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Okulov, Ilya, Ivan Soldatov, Ivan Kaban, Baran Sarac, Florian Spieckermann i Jürgen Eckert. "Fabrication of Metastable Crystalline Nanocomposites by Flash Annealing of Cu47.5Zr47.5Al5 Metallic Glass Using Joule Heating". Nanomaterials 10, nr 1 (1.01.2020): 84. http://dx.doi.org/10.3390/nano10010084.

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Flash Joule-heating was applied to the Cu47.5Zr47.5Al5 metallic glass for designing fully crystalline metastable nanocomposites consisting of the metastable B2 CuZr and low-temperature equilibrium Cu10Zr7 phases. The onset of crystallization was in situ controlled by monitoring resistivity changes in the samples. The effect of heating rate and annealing time on the volume fraction of the crystalline phases and mechanical properties of the nanocomposites was studied in detail. Particularly, an increase of the heating rate and a decrease of the annealing time lead to a lower number of equilibrium Cu10Zr7 precipitates and an increase of tensile ductility. Tailoring of these non-equilibrium microstructures and mechanical properties may not be possible unless one starts with a fully glassy material that opens new perspectives for designing metastable nanomaterials with unique physical properties.

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Wang, Tong Yang, Zhen Xi Sun, Lan Xiang Zhang i Yan Wang. "Glass Formation and Thermal Stability of Mechanically Alloyed Al₇₅Ni₁₀Ti₁₀Zr₅ Amorphous Composites with Graphene Addition". Materials Science Forum 849 (marzec 2016): 58–63. http://dx.doi.org/10.4028/www.scientific.net/msf.849.58.

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In this study, the influence of 0.5 wt.% graphene (Gr) addition on the glass formation and thermal stability of the Al75Ni10Ti10Zr5 alloy during mechanical alloying (MA) process has been investigated. The as-milled products consist of the amorphous phase and a small amount of the AlNi nanocrystals. The results showed that the 0.5 wt.% Gr addition could shorten the amorphization process, indicating the enhancement of the glass forming ability. Moreover, the onset crystallization temperature (Tx1) slightly decreased with prolonging milling time for the as-milled alloys. However, it is worth noting that the Gr addition effectively increased the Tx1 of the as-milled Al-based amorphous composites for the long duration of MA time. The Tx1 values of the as-milled AlNiTiZrGr amorphous composites were more than 1120 K, exhibiting the highly thermal stability.

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Gao, Meng, Chengrong Cao i John H. Perepezko. "Analysis of Nucleation and Glass Formation by Chip Calorimetry". Applied Sciences 11, nr 16 (20.08.2021): 7652. http://dx.doi.org/10.3390/app11167652.

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The advent of chip calorimetry has enabled an unprecedented extension of the capability of differential scanning calorimetry to explore new domains of materials behavior. In this paper, we highlight some of our recent work: the application of heating and cooling rates above 104 K/s allows for the clear determination of the glass transition temperature, Tg, in systems where Tg and the onset temperature for crystallization, Tx, overlap; the evaluation of the delay time for crystal nucleation; the discovery of new polyamorphous materials; and the in-situ formation of glass in liquid crystals. From these application examples, it is evident that chip calorimetry has the potential to reveal new reaction and transformation behavior and to develop a new understanding.

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Васильев, С. В., В. И. Парфений, Е. А. Першина, А. С. Аронин, О. В. Коваленко i В. И. Ткач. "Эффективные коэффициенты диффузии и термическая устойчивость структуры металлического стекла Fe-=SUB=-48-=/SUB=-Co-=SUB=-32-=/SUB=-P-=SUB=-14-=/SUB=-B-=SUB=-6-=/SUB=-". Физика твердого тела 62, nr 12 (2020): 2012. http://dx.doi.org/10.21883/ftt.2020.12.50203.140.

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The values of linear growth velocities of the eutectic colonies in the temperature range of 679–717 K have been determined for the first time from the electron microscopic studies of the partially crystallized samples of Fe48Co32P14B6 metallic glass. Using these data, the values of the effective diffusion coefficients governing growth have been calculated. It has been established that the temperature dependence of the effective diffusivity in Fe48Co32P14B6 glass is well approximated by an Arrhenius law and their values in the temperature range of crystallization are about 2–3 orders of magnitude smaller than those in the Fe40Ni40P14B6 commercial glass. The values of the effective diffusion coefficients at the onset crystallization temperature have been determined, the correlation between pre-exponential factors and activation energies has been found. It has been shown that the parameters which characterize the effective diffusivity in the glass investigated are in good agreement with the published data for the eutectically crystallizing metallic glasses. It has been established that the physical reason of the enhanced thermal stability of the FeCo-based glass compared with that of Fe40Ni40P14B6 is the lower atomic mobility at the glass/crystal interface.

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Dimova, Margarita, i Yancho D. Devedjiev. "Protein crystal lattices are dynamic assemblies: the role of conformational entropy in the protein condensed phase". IUCrJ 5, nr 2 (10.01.2018): 130–40. http://dx.doi.org/10.1107/s2052252517017833.

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Until recently, the occurrence of conformational entropy in protein crystal contacts was considered to be a very unlikely event. A study based on the most accurately refined protein structures demonstrated that side-chain conformational entropy and static disorder might be common in protein crystal lattices. The present investigation uses structures refined using ensemble refinement to show that although paradoxical, conformational entropy is likely to be the major factor in the emergence and integrity of the protein condensed phase. This study reveals that the role of shape entropy and local entropic forces expands beyond the onset of crystallization. For the first time, the complete pattern of intermolecular interactions by protein atoms in crystal lattices is presented, which shows that van der Waals interactions dominate in crystal formation.

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Sabet, Maziyar, i Hassan Soleimani. "Broad studies of graphene and low-density polyethylene composites". Journal of Elastomers & Plastics 51, nr 6 (3.10.2018): 527–61. http://dx.doi.org/10.1177/0095244318802608.

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Graphene (Gr) distribution in low-density polyethylene (LDPE) considerably increased thermal stability, thermal conductivity, mechanical properties, and flexural properties of LDPE/Gr composites. Addition of Grs to LDPE postponed the time for making the polymer brittle. High specific surface area and superior properties of Gr improved thermal stability, conductivity, storage modulus, and mechanical properties of composites. The electrical conductivity of LDPE/Grs composites upgraded owing to the thermal stability of Grs in LDPE matrix. In terms of rheology, the addition of Grs augmented viscosity of the LDPE matrix. Addition of Grs to LDPE nucleates crystallization by reducing the activation energy along with rising crystallization onset temperature. Adding Gr facilitated decreasing aggregation, expanded crystallinity, improved the local lattice order of LDPE/Grs, and advanced Grs contact with LDPE. Thus, on a macroscopic scale, Gr constrains mobility of polymer chains, causing a growth in stiffness and strength of the composite. The distribution of Grs in LDPE at micron size scale was verified by atomic force microscopy and other microscopic testers. With further Grs inclusions to LDPE, the activation energy reduced, Grs proceeded as nucleating agents throughout the crystallization of composites, and increased the enhancement of relative crystallinity of LDPE/Gr compounds. The percolation phenomenon of LDPE/Gr composite occurred about 0.5 wt% of Gr loading. Due to further addition of Gr to LDPE, the impermeability of oxygen through the conduit raised somehow the LDPE/Gr sample with 0.5 wt% Gr content, generated a sharp improvement, and dropped fuel permeation with about 37% in comparison with pure LDPE.

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Roniger, Luis. "Connected histories, power and meaning: Transnational forces in the construction of collective identities". Journal of Classical Sociology 11, nr 3 (sierpień 2011): 251–68. http://dx.doi.org/10.1177/1468795x11406005.

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The construction of collective identities is central to Shmuel N.Eisenstadt’scomparative research program, as reflected in his studies of civilizations and multiple modernities. This article suggests the theoretical relevance of bridging comparative and transnational studies, calling attention to the impact of connected histories in processes of crystallization of collective identities. Focusing on Central America, this analysis shows that, following independence, the societies of this region found it hard to articulate distinct identities; they came to such issues belatedly, almost by default; and were unable to completely disengage from transnational forces that pulled them together time and again. It thus indicates how societies oftenlead a Janus-faced dynamics in constructing their visions of collective membership, which can only be followed by taking into account transnational undercurrents at worklong before the onset of recent cycles of globalization.

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Thomas, George H., Eliot D. Specht, John Z. Larese, Ziling B. Xue i David B. Beach. "Growth of epitaxial films of sodium potassium tantalate and niobate on single-crystal lanthanum aluminate [100] substrates". Journal of Materials Research 23, nr 12 (grudzień 2008): 3281–87. http://dx.doi.org/10.1557/jmr.2008.0393.

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Epitaxial films of sodium potassium tantalate (Na0.5K0.5TaO3, NKT) and sodium potassium niobate (Na0.5K0.5NbO3, NKN) were grown on single-crystal lanthanum aluminate (LAO) (100) (indexed as a pseudo-cubic unit cell) substrates via an all-alkoxide solution (methoxyethoxide complexes in 2-methoxyethanol) deposition route for the first time. X-ray diffraction studies indicated that the onset of crystallization in powders formed from hydrolyzed gel samples was 550 °C. 13C nuclear magnetic resonance studies of solutions of methoxyethoxide complexes indicated that mixed-metal species were formed, consistent with the low crystallization temperatures observed. Thermal gravimetric analysis with simultaneous mass spectrometry showed the facile loss of the ligand (methoxyethoxide) at temperatures below 400 °C. Crystalline films were obtained at temperatures as low as 650 °C when annealed in air. θ-2θ x-ray diffraction patterns revealed that the films possessed c-axis alignment in that only (h00) reflections were observed. Pole-figures about the NKT or NKN (220) reflection indicated a single in-plane, cube-on-cube epitaxy. The quality of the films was estimated via ω (out-of-plane) and φ (in-plane) scans and full-widths at half-maximum (FWHMs) were found to be reasonably narrow (∼1°), considering the lattice mismatch between the films and the substrate.

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Tomaszewska-Gras, Jolanta, Mahbuba Islam, Liliana Grzeca, Anna Kaczmarek i Emilia Fornal. "Comprehensive Thermal Characteristics of Different Cultivars of Flaxseed Oil (Linum usittatissimum L.)". Molecules 26, nr 7 (31.03.2021): 1958. http://dx.doi.org/10.3390/molecules26071958.

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The aim of this study was to describe the thermal properties of selected cultivars of flaxseed oil by the use of the differential scanning calorimetry (DSC) technique. The crystallization and melting profiles were analyzed depending on different scanning rates (1, 2, 5 °C/min) as well as oxidative induction time (OIT) isothermally at 120 °C and 140 °C, and oxidation onset temperatures (Ton) at 2 and 5 °C/min were measured. The crystallization was manifested as a single peak, differing for a cooling rate of 1 and 2 °C/min. The melting curves were more complex with differences among the cultivars for a heating rate of 1 and 2 °C/min, while for 5 °C/min, the profiles did not differ, which could be utilized in analytics for profiling in order to assess the authenticity of the flaxseed oil. Moreover, it was observed that flaxseed oil was highly susceptible to thermal oxidation, and its stability decreased with increasing temperature and decreasing heating rate. Significant negative linear correlations were found between unsaturated fatty acid content (C18:2, C18:3 n-3) and DSC parameters (OIT, Ton). Principal component analysis (PCA) also established a strong correlation between total oxidation value (TOTOX), peroxide value (PV) and all DSC parameters of thermo-oxidative stability.

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El-Eskandarany, M. Sherif, J. Saida i A. Inoue. "Mechanically induced devitrifications of ball-milled Zr70Pd20Ni10 glassy alloy powders". Journal of Materials Research 18, nr 2 (luty 2003): 250–53. http://dx.doi.org/10.1557/jmr.2003.0034.

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Mechanical alloying using a high-energy ball milling technique was used to fabricate a single glassy phase of Zr70Pd20Ni10 alloy powders after 100 h milling time. Annealing the glassy powders at a temperature just below the crystallization onset temperature led to thermally enhanced devitrification and the formation of a metastable big-cube phase with a lattice constant of 1.2289 nm. The same metastable phase was obtained upon subjecting the end product of the glassy powders to further ball milling time (150 h). This metastable big-cube phase could no longer withstand the shear and impact stresses generated by the milling media and transformed into a new metastable phase of face-centered cubic Zr70Pd20Ni10. The lattice constant of this metastable phase was calculated to be 0.56838 nm. These metastable phases are new and have never been, so far as we know, reported for the ternary Zr–Pd–Ni system or its binary phase relations.

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Blatchford, Hannah J., Keith A. Klepeis, Joshua J. Schwartz, Richard Jongens, Rose E. Turnbull, Elena A. Miranda, Matthew A. Coble i Andrew R. C. Kylander-Clark. "Interplay of Cretaceous transpressional deformation and continental arc magmatism in a long-lived crustal boundary, central Fiordland, New Zealand". Geosphere 16, nr 5 (31.08.2020): 1225–48. http://dx.doi.org/10.1130/ges02251.1.

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Abstract Recovering the time-evolving relationship between arc magmatism and deformation, and the influence of anisotropies (inherited foliations, crustal-scale features, and thermal gradients), is critical for interpreting the location, timing, and geometry of transpressional structures in continental arcs. We investigated these themes of magma-deformation interactions and preexisting anisotropies within a middle- and lower-crustal section of Cretaceous arc crust coinciding with a Paleozoic boundary in central Fiordland, New Zealand. We present new structural mapping and results of Zr-in-titanite thermometry and U-Pb zircon and titanite geochronology from an Early Cretaceous batholith and its host rock. The data reveal how the expression of transpression in the middle and lower crust of a continental magmatic arc evolved during emplacement and crystallization of the ∼2300 km2 lower-crustal Western Fiordland Orthogneiss (WFO) batholith. Two structures within Fiordland’s architecture of transpressional shear zones are identified. The gently dipping Misty shear zone records syn-magmatic oblique-sinistral thrust motion between ca. 123 and ca. 118 Ma, along the lower-crustal WFO Misty Pluton margin. The subhorizontal South Adams Burn thrust records mid-crustal arc-normal shortening between ca. 114 and ca. 111 Ma. Both structures are localized within and reactivate a recently described >10 km-wide Paleozoic crustal boundary, and show that deformation migrated upwards between ca. 118 and ca. 114 Ma. WFO emplacement and crystallization (mainly 118–115 Ma) coincided with elevated (>750 °C) middle- and lower-crustal Zr-in-titanite temperatures and the onset of mid-crustal cooling at 5.9 ± 2.0 °C Ma−1 between ca. 118 and ca. 95 Ma. We suggest that reduced strength contrasts across lower-crustal pluton margins during crystallization caused deformation to migrate upwards into thermally weakened rocks of the mid-crust. The migration was accompanied by partitioning of deformation into domains of arc-normal shortening in Paleozoic metasedimentary rocks and domains that combined shortening and strike-slip deformation in crustal-scale subvertical, transpressional shear zones previously documented in Fiordland. U-Pb titanite dates indicate Carboniferous–Cretaceous (re)crystallization, consistent with reactivation of the inherited boundary. Our results show that spatio-temporal patterns of transpression are influenced by magma emplacement and crystallization and by the thermal structure of a reactivated boundary.

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Dimesso, L., O. B. Hyun i I. Hirabayashi. "Preparation of LaBa2Cu3Oy thick films in the La–Ba–Cu–O system by partial melting techniques". Journal of Materials Research 10, nr 12 (grudzień 1995): 3016–25. http://dx.doi.org/10.1557/jmr.1995.3016.

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The preparation of thick films of the LaBa2Cu3Oy (La-123) phase by using the partial melting technique (PMT) of powders deposited on MgO substrates by drying alcoholic suspensions is reported. The effects of the starting composition, processing time (t), and temperature (T) on the superconducting properties of the La1+xBa2Cu3Oy (−0.25 ⋚ x ⋚ 0.5) system were investigated. The presence of the La4Ba2Cu2O10 (La 422) phase was detected in the samples quenched in liquid N2 after heating up to 1200 °C. The crucial step of the processing is the cooling rate down to the crystallization temperature, Tp, determined by DTA analysis, in order to favor the formation of the La-123 phase from the reaction between the La-422 solid phase and the liquid. The superconducting properties, tested by magnetization measurements, showed a diamagnetic onset temperature (Tc,diam) as high as 89 K.

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Moberg, Daniel R., Daniel Becker, Christoph W. Dierking, Florian Zurheide, Bernhard Bandow, Udo Buck, Arpa Hudait, Valeria Molinero, Francesco Paesani i Thomas Zeuch. "The end of ice I". Proceedings of the National Academy of Sciences 116, nr 49 (4.11.2019): 24413–19. http://dx.doi.org/10.1073/pnas.1914254116.

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The appearance of ice I in the smallest possible clusters and the nature of its phase coexistence with liquid water could not thus far be unraveled. The experimental and theoretical infrared spectroscopic and free-energy results of this work show the emergence of the characteristic hydrogen-bonding pattern of ice I in clusters containing only around 90 water molecules. The onset of crystallization is accompanied by an increase of surface oscillator intensity with decreasing surface-to-volume ratio, a spectral indicator of nanoscale crystallinity of water. In the size range from 90 to 150 water molecules, we observe mixtures of largely crystalline and purely amorphous clusters. Our analysis suggests that the liquid–ice I transition in clusters loses its sharp 1st-order character at the end of the crystalline-size regime and occurs over a range of temperatures through heterophasic oscillations in time, a process without analog in bulk water.

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Barberi, Baino, Fiume, Orlygsson, Nommeots-Nomm, Massera i Verné. "Robocasting of SiO2-Based Bioactive Glass Scaffolds with Porosity Gradient for Bone Regeneration and Potential Load-Bearing Applications". Materials 12, nr 17 (22.08.2019): 2691. http://dx.doi.org/10.3390/ma12172691.

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: Additive manufacturing of bioactive glasses has recently attracted high interest in the field of regenerative medicine as a versatile class of fabrication methods to process bone substitute materials. In this study, melt-derived glass particles from the SiO2-P2O5-CaO-MgO-Na2O-K2O system were used to fabricate bioactive scaffolds with graded porosity by robocasting. A printable ink made of glass powder and Pluronic F-127 (binder) was extruded into a grid-like three-dimensional structure with bimodal porosity, i.e., the inner part of the scaffold had macropores with smaller size compared to the periphery. The crystallization behavior of the glass powder was studied by hot-stage microscopy, differential thermal analysis, and X-ray diffraction; the scaffolds were sintered at a temperature below the onset of crystallization so that amorphous structures could be obtained. Scaffold architecture was investigated by scanning electron microscopy and microtomographic analysis that allowed quantifying the microstructural parameters. In vitro tests in Kokubo’s simulated body fluid (SBF) confirmed the apatite-forming ability (i.e., bioactivity) of the scaffolds. The compressive strength was found to slightly decrease during immersion in SBF up to 4 weeks but still remained comparable to that of human cancellous bone. The pH and concentration of released ions in SBF were also measured at each time point. Taken together, these results (favorable porosity, mechanical strength, and in vitro bioactivity) show great promise for the potential application of these robocast scaffolds in bone defect repair.

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Portale, Giuseppe, Dario Cavallo, Giovanni Carlo Alfonso, Daniel Hermida-Merino, Martin van Drongelen, Luigi Balzano, G. W. M. Peters, J. G. P. Goossens i Wim Bras. "Polymer crystallization studies under processing-relevant conditions at the SAXS/WAXS DUBBLE beamline at the ESRF". Journal of Applied Crystallography 46, nr 6 (15.11.2013): 1681–89. http://dx.doi.org/10.1107/s0021889813027076.

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Recent developments on the experimental infrastructure and the acquisition of new detectors on the Dutch–Belgian beamline BM26B at the ESRF offer novel and promising possibilities for synchrotron X-ray experiments in the field of polymer crystallization under processing-relevant conditions. In this contribution, some of the most recent experiments mimicking conditions similar to those relevant for the plastics processing industry are discussed. Simultaneous thermal analysis and wide-angle X-ray scattering (WAXS) experiments, at the millisecond time-frame level, on β-nucleated isotactic polypropylene (i-PP) samples subjected to ballistic cooling up to 230 K s−1, show that the efficiency of the nucleating agent can be suppressed when quenched cooling rates higher than 130 K s−1are used.In situWAXS experiments using small-scale industrial equipment during a real film blowing process reveal the dependence of the onset of crystallinity (the so-called freeze line) and the crystal orientation as a function of different take-up and blow-up ratios.In situsmall-angle X-ray scattering (SAXS) experiments during high-flow fields reveal the formation of shish and kebab structures in i-PP as a function of the imposed stress. Quantitative analysis of i-PP flow-induced structures is presented. The beamline specifications required to obtain high quality and industrially relevant results are also briefly reported.

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Liang, Wang, Yin Xiaochun, He Guangjian, Feng Yanhong i Qu Jinping. "Ultrasound-assisted melt mixing for the preparation of UHMWPE/OMMT nanocomposites". Journal of Thermoplastic Composite Materials 31, nr 6 (21.07.2017): 784–802. http://dx.doi.org/10.1177/0892705717720972.

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Ultrahigh molecular weight polyethylene (UHMWPE)/organic montmorillonite (OMMT) nanocomposites were prepared via a self-made vane mixer which could supply a synergy of ultrasound and extensional deformation. Structure and working principle of this novel mixer were illustrated in detail. Effects of the OMMT content, mixing time, and ultrasound treat time on composites’ morphology, rheological properties, and thermal properties were reported in terms of transmission electron microscopy (TEM), wide-angle X-ray scattering, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). X-ray diffraction (XRD) and TEM showed that the OMMT lay spacing increased from 2.82 nm to 3.29 nm and OMMT dispersed evenly in the matrix using this novel melt mixing equipment. It certified that the melt mixing procedure synergized by ultrasound and extensional deformation was very effective in the exfoliation of silicate layers and also the filler distribution and dispersion. DSC measurements revealed that the crystallization temperature ( Tc) had no visible change with increasing the OMMT content and the melting temperature ( Tm) and melting enthalpy crystallinity ( Xc) increased with the proper OMMT content. The higher Tm and Xc showed with the proper ultrasound treatment time, however, the Tc had no visible change. TGA showed that the onset temperature at which 20% weight loss of the material increased markedly in the case of UHMWPE/OMMT-1 wt% nanocomposite. The onset temperature slightly decreased with the use of ultrasound. Rheological analyses showed that all the samples exhibited non-Newtonian and shear thinning characteristics. Both the storage modulus and complex viscosity increased with continuous addition of the OMMT layers. It also indicated that the introduction of ultrasound tended to decrease the storage modulus and complex viscosity. Universal tensile test indicated that superior tensile strength occurred in samples containing OMMT layers.

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Zhang, Feng-Qi, Hong-Xiang Wu, Yildirim Dilek, Wei Zhang, Kong-Yang Zhu i Han-Lin Chen. "Guadalupian (Permian) onset of subduction zone volcanism and geodynamic turnover from passive- to active-margin tectonics in southeast China". GSA Bulletin 132, nr 1-2 (14.05.2019): 130–48. http://dx.doi.org/10.1130/b32014.1.

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Abstract New stratigraphic, geochemical, and geochronological data from the late Paleozoic depositional record in Anhui Province, China, signal the onset of active-margin magmatism in East Asia. Chert-shale sequences of the Gufeng Formation are part of a Carboniferous–Permian carbonate platform that developed along the passive margin of the South China block. Thin tuffaceous interlayers in these sequences represent distal ash deposits, marking discrete volcanic events. Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon dating of the stratigraphically bottom and near-top tuffaceous interlayers has revealed crystallization ages of 270 Ma and 264 Ma, respectively, constraining the time span of subaerial eruptions to ∼6 m.y. during the Guadalupian Epoch. High SiO2 and Al2O3 contents, enrichments in large ion lithophile and light rare earth elements, and depletion patterns of high field strength and heavy rare earth elements indicate a calc-alkaline magma source in an arc setting for the origin of these volcanic tuff deposits. Detrital zircon geochronology of sandstones in the overlying Longtan Formation shows two prominent age populations of 290–250 Ma and 1910–1800 Ma. The former age cluster overlaps with the tightly constrained zircon ages obtained from the Gufeng Formation. The latter age group is compatible with the known magmatic-metamorphic ages from Cathaysia in the South China block, and it points to the existence of a NE-SW–trending topographic high as a major sediment source. We interpret this topographic high and silicic volcanism to represent an Andean-type active margin, developed above a north-dipping paleo-Pacific slab. Our tightly constrained Guadalupian eruption ages indicate the inception of magmatic arc construction and mark a major switch from passive- to active-margin tectonics along SE Asia.

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McCubbin, Francis M., i Jessica J. Barnes. "The chlorine-isotopic composition of lunar KREEP from magnesian-suite troctolite 76535". American Mineralogist 105, nr 8 (1.08.2020): 1270–74. http://dx.doi.org/10.2138/am-2020-7467.

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Abstract We conducted in situ Cl isotopic measurements of apatite within intercumulus regions and within a holocrystalline olivine-hosted melt inclusion in magnesian-suite troctolite 76535 from Apollo 17. These data were collected to place constraints on the Cl-isotopic composition of the last liquid to crystallize from the lunar magma ocean (i.e., urKREEP, named after its enrichments in incompatible lithophile trace elements like potassium, rare earth elements, and phosphorus). The apatite in the olivine-hosted melt inclusion and within the intercumulus regions of the sample yielded Cl-isotopic compositions of 28.3 ± 0.9‰ (2σ) and 30.3 ± 1.1‰ (2σ), respectively. The concordance of these values from both textural regimes we analyzed indicates that the Cl-isotopic composition of apatites in 76535 likely represents the Cl-isotopic composition of the KREEP-rich magnesian-suite magmas. Based on the age of 76535, these results imply that the KREEP reservoir attained a Cl-isotopic composition of 28–30‰ by at least 4.31 Ga, consistent with the onset of Cl-isotopic fractionation at the time of lunar magma ocean crystallization or shortly thereafter. Moreover, lunar samples that yield Cl-isotopic compositions higher than the value for KREEP are likely affected by secondary processes such as impacts and/or magmatic degassing. The presence of KREEP-rich olivine-hosted melt inclusions within one of the most pristine and ancient KREEP-rich rocks from the Moon provides a new opportunity to characterize the geochemistry of KREEP. In particular, a broader analysis of stable isotopic compositions of highly and moderately volatile elements could provide an unprecedented advancement in our characterization of the geochemical composition of the KREEP reservoir and of volatile-depletion processes during magma ocean crystallization, more broadly.

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JARRAR, G. "The youngest Neoproterozoic mafic dyke suite in the Arabian Shield: mildly alkaline dolerites from South Jordan – their geochemistry and petrogenesis". Geological Magazine 138, nr 3 (maj 2001): 309–23. http://dx.doi.org/10.1017/s0016756801005295.

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The Arabian–Nubian Shield evolved through a sequence of tectonomagmatic cycles, which took place during Neoproterozoic time (1000–540 Ma). Dyke emplacement constitutes one of the conspicuous features of the Arabian–Nubian Shield, with mafic dykes being the most abundant. The investigated dykes represent the youngest Neoproterozoic mafic dykes and have been dated in Jordan at 545 ± 13 Ma. Geochemically the studied dykes are mildly alkaline, are enriched in large ion lithophile elements (LILE) and high field strength cations (HFSC), show moderate enrichment of REE, and lack Nb anomaly. These features are consistent with a predominantly extensional continental tectonic setting. Crystallization temperatures of the suite fall between 1050 and 800 °C to as low as 650 °C as deduced from pyroxene thermometry. The investigated dykes were derived from a metasomatized lithospheric mantle by 5 % modal batch partial melting of phlogopite-bearing spinel lherzolite, according to geochemical modelling. The intra-suite geochemical features are explicable by 64 % fractional crystallization of olivine, pyroxene, plagioclase and titanomagnetite and possibly other accessories like apatite at a later stage. The cumulate produced from this fractionation of the investigated dyke suite contributed to the formation of the mafic lower crust of the Arabian–Nubian Shield. Elemental ratios and petrographic evidence indicate possible minor crustal contamination of the suite. The youngest mafic dykes show striking geochemical similarities to the same generation of dolerite dykes in the adjacent countries, to transitional young basalt suites of the Main East African Rift, and to Quaternary Jordanian basalts. The youngest mafic dyke suite, the rhyolites of the Aheimir suite, and St Katherina rhyolites of Sinai represent the last igneous activity in the Arabian–Nubian Shield before the onset of the Cambrian at about 545 Ma ago.

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Zöllmer, Volker, Klaus Raätzke i Franz Faupel. "Diffusion and isotope effect in bulk-metallic glass-forming Pd–Cu–Ni–P alloys from the glass to the equilibrium melt". Journal of Materials Research 18, nr 11 (listopad 2003): 2688–96. http://dx.doi.org/10.1557/jmr.2003.0375.

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We report on radiotracer diffusion measurements in metallic bulk-glass-forming Pd-Cu-Ni-P alloys. The Pd-Cu-Ni-P system, with its high stability against crystallization, allows diffusion measurements from the glassy state to the equilibrium melt for the first time. Serial sectioning was performed by grinding and ion-beam sputtering. The time and temperature as well as mass dependence, expressed in terms of the isotope effect E, of codiffusion were investigated. In the glassy state as well as in the deeply supercooled state below the critical temperature Tc, where the mode-coupling theory predicts a freezing-in of liquidlike motion, the measured very small isotope effects indicated a highly collective hopping mechanism. Below Tc, the temperature dependence showed Arrhenius-type behavior. Above Tc, the onset of liquidlike motion was evidenced by a gradual drop of the effective activation energy, resulting from the decay of hopping barriers, and by the validity of the Stokes-Einstein equation, which was found to break down below Tc. This strongly supports the mode-coupling scenario. Isotope effect measurements, which have never been carried out near Tc in any material, showed atomic transport up to the equilibrium melt to be far away from the hydrodynamic regime of uncorrelated binary collisions. The latter appears to be a prerequisite of excellent glass-forming abilities.

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Chakoumakos, B. C., P. S. Ebey, B. C. Sales i Edward Sonder. "Characterization and superconducting properties of phases in the Bi–Sr–Cu–O system". Journal of Materials Research 4, nr 4 (sierpień 1989): 767–80. http://dx.doi.org/10.1557/jmr.1989.0767.

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Phase formation in the system Bi–Sr–Cu–O has been examined as a function of composition, temperature, ambient atmosphere, cooling history, and annealing time. Ceramic processing and melt crystallization techniques were used. For the ceramic materials (using Bi2O3, SrCO3, and CuO) processed at 700 °C in air the Bi2Sr2CuO6 composition (221) crystallizes to a mixture of CuO, SrCO3, and the rhombohedral Bi2O3 · xSrO solid solution. At 800–830 °C in air for short durations (5 min to 2 h) the reacted products consist principally of the ideal 221 phase with minor amounts of CuO. For longer reaction times (2–400 h) the reacted products consist of the ideal 221-type structure with c = 24.64 Å and a = 3.804 Å, a “collapsed” 221 structure with c = 23.6 Å, and CuO. With increasing reaction time the “collapsed” 221 phase grows gradually at the expense of the ideal 221 phase. The “collapsed” 221 phase is not an oxycarbonate and appears to be a distinct ternary compound near the 221 composition, with a layered structure having a 1 Å smaller stacking repeat. The ideal 221 phase is a solid solution with variable Sr content. With decreasing Sr in the starting mixture [2 to 1.25 atoms per formula unit (afu)] we observe the following: (1) the formation of the “collapsed” 221 structure is inhibited; (2) for the ideal 221 phase the c-cell dimension decreases significantly (0.2 Å) and the a-cell dimension increases slightly (0.02 Å); (3) the low temperature resistivity behavior changes from superconducting with Tc onset of 6 K for Sr>1.5 afu to semiconducting for Sr > 1.5 afu; (4) the positions of the superlattice peaks around the (001) reflections become more incommensurate with respect to the parent structure. Rapid quenching (<5 s) from temperatures near the melting point (900 °C) can raise the superconducting Tc onset to 9 K. Independent of the cell variation with Sr content, quenching causes the c-cell dimension to expand by 0.03 Å on average while the a-cell dimension remains invariant. A small number of oxygen vacancies are quenched in from high temperature, and presumably originate in the Bi2O2 layer. As grown from the melt, crystals of the ideal 221 phase exhibit semiconducting behavior at low temperature; but with an additional high-temperature anneal in oxygen, metallic resistivity is restored with a superconducting onset near 5 K. Ca doping does not increase Tc in the ideal 221 phase. La and Y substitution occurs for Sr in the ideal 221 phase and ruins superconductivity.

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Rwei, Syang-Peng, Palraj Ranganathan, Whe-Yi Chiang i Yi-Huan Lee. "Synthesis of Low Melting Temperature Aliphatic-Aromatic Copolyamides Derived from Novel Bio-Based Semi Aromatic Monomer". Polymers 10, nr 7 (19.07.2018): 793. http://dx.doi.org/10.3390/polym10070793.

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This work investigated the synthesis of a novel low melting temperature polyamide 6 (PA6) copolyamide (PA6-BABT/SA) with different aliphatic/aromatic units weight content using a melt poly-condensation process. The bio-based aromatic N1,N4-bis(4-aminobutyl) terephthalamide diamine (BABT) and long-chain aromatic polyamide salt (BABT/SA, salt of BABT, and sebacic acid), components used for the synthesis of copolyamides, were obtained from bio-based monomers. For the first time, the pertinent BABT/SA aromatic polyamide salt was isolated as a white solid and completely characterized. By varying the weight ratio of BABT/SA salt, a series of copolyamides with different molecular weights and physical properties were prepared. The aromatic BABT/SA salt disrupted crystallization of the final copolyamides and lowered the onset of melting. The Fourier transform infrared spectroscopy and X-ray diffraction results indicated a steady decrease in the degrees of crystallinity with increasing BABT/SA salt segment ratio. Furthermore, compared to neat PA6, the obtained PA6-BABT/SA copolymers possessed a similar thermal stability and high transparency, but lower glass transition temperature around human body temperature. The PA6-BABT/SA copolymers with number-average molecular weight ≥30,000 Da presented good mechanical properties, specifically showing excellent tensile strength and elongation at break up to 105.2 MPa and 218.3%, respectively.

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Hooper, P. R., B. A. Gillespie i M. E. Ross. "The Eckler Mountain basalts and associated flows, Columbia River Basalt Group". Canadian Journal of Earth Sciences 32, nr 4 (1.04.1995): 410–23. http://dx.doi.org/10.1139/e95-035.

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Recent mapping of flows of the Columbia River Basalt Group between Lewiston and Pomeroy, southeast Washington, places the chemically distinctive Shumaker Creek flow as a new member between the Frenchman Springs and Roza members of the Wanapum Basalt. This leaves the Eckler Mountain Formation composed of only the Robinette Mountain and Dodge chemical types, with the Lookingglass flow forming the base of the overlying Wanapum Basalt. One Robinette Mountain flow and five separate flows of Dodge composition are recognized and traced across the Blue Mountains Anticline of southeast Washington and northeast Oregon. The aerial distribution of the flows is used to constrain the onset of deformation in the Blue Mountains area between the Hite and Limekiln faults. A series of open east–west folds formed during late Wanapum and Saddle Mountains time, cut by northeast-trending faults with left-lateral strain. Chemical variations between Eckler Mountain, Grande Ronde, and Wanapum Basalt flows require different source components. But between the Eckler Mountain flows the variation of most chemical parameters is consistent with fractional crystallization in the crust and can be modeled for major and trace elements. An exception is the behaviour of Cr and Zr/Y between the Robinette Mountain and Dodge flows, which suggests variable partial melting or possibly olivine accumulation.

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Rätzke, Klaus, V. Zöllmer, A. Bartsch, Andreas Meyer i Franz Faupel. "Diffusion in Bulk Glass Forming Alloys– from the Glass to the Equilibrium Melt". Defect and Diffusion Forum 266 (wrzesień 2007): 109–18. http://dx.doi.org/10.4028/www.scientific.net/ddf.266.109.

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Since the discovery of bulk metallic glasses there has been considerable research effort on these systems, in particular with respect to mass transport. Now the undercooled melt between the melting temperature and the caloric glass transition temperature, which has not been accessible before due to the rapid onset of crystallization, can be investigated and theories can be tested. Here we report on radiotracer diffusion measurements in metallic bulk-glass-forming Pd-Cu-Ni-P alloys. Serial sectioning was performed by grinding and ion-beam sputtering. The time, temperature as well as the mass dependence, expressed in terms of the isotope effect E, of Co-diffusion were investigated. The Co isotope effect measurements, which have never been carried out near Tc in any material, show atomic transport up to the equilibrium melt to be far away from the hydrodynamic regime of uncorrelated binary collisions. In the glassy state as well as in the deeply supercooled state below the critical temperature Tc, where the mode coupling theory predicts a freezing-in of liquid-like motion, the experimentally determined very small isotope effects indicate a highly collective hopping mechanism involving some ten atoms. Below Tc the temperature dependence shows Arrhenius-type behavior with an effective activation enthalpy of 3.2 eV. Above Tc the onset of liquid-like motion is evidenced by a gradual drop of the effective activation energy and by the validity of the Stokes-Einstein equation, which is found to break down below Tc. Although having strong covalent bonding tendencies, Phosphorous diffusion is only slightly slower than Co diffusion, indicating that it does not determine the overall viscosity below Tc. The Stokes-Einstein equation is presently tested for other constituents of the alloy.

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