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Journal articles on the topic 'Crystallization by controlled cooling'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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1

Bohlin, Martin, and Åke C. Rasmuson. "Application of controlled cooling and seeding in batch crystallization." Canadian Journal of Chemical Engineering 70, no. 1 (February 1992): 120–26. http://dx.doi.org/10.1002/cjce.5450700117.

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2

Yang, G., M. Louhi-Kultanen, Z. Sha, and J. Kallas. "Determination of Operating Conditions for Controlled Batch Cooling Crystallization." Chemical Engineering & Technology 29, no. 2 (February 2006): 200–205. http://dx.doi.org/10.1002/ceat.200500351.

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3

Seki, Hiroya, Noriyoshi Furuya, and Satoshi Hoshino. "Evaluation of controlled cooling for seeded batch crystallization incorporating dissolution." Chemical Engineering Science 77 (July 2012): 10–17. http://dx.doi.org/10.1016/j.ces.2012.01.057.

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4

Jasiurkowska-Delaporte, Małgorzata, Tomasz Rozwadowski, and Ewa Juszyńska-Gałązka. "Kinetics of Non-Isothermal and Isothermal Crystallization in a Liquid Crystal with Highly Ordered Smectic Phase as Reflected by Differential Scanning Calorimetry, Polarized Optical Microscopy and Broadband Dielectric Spectroscopy." Crystals 9, no. 4 (April 12, 2019): 205. http://dx.doi.org/10.3390/cryst9040205.

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The kinetics of the non-isothermal and isothermal crystallization of the crystalline smectic B phase (soft crystal B, SmBcr) in 4-n-butyloxybenzylidene-4′-n′-octylaniline (BBOA) was studied by a combination of differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and polarized optical microscopy (POM). On cooling, part of the SmBcr phase undergoes conversion to a crystalline phase and the remainder forms a glassy state; after the glass softens, crystallization is completed during subsequent heating. By analyzing the area of the crystal growing in the texture of SmBcr as a function of time, the evolution of degree of crystallinity, D(t), was estimated. It was demonstrated that upon heating, D(t) follows the same Avrami curve as the crystallization during cooling. Non-isothermal crystallization observed during slow cooling rates (3K/min ≤ ϕ ≤ 5K/min) is a thermodynamically-controlled process with the energy barrier Ea ≈ 175 kJ/mol; however, the crystallization occurring during fast cooling (5 K/min > ϕ ≥ 30K/min) is driven by a diffusion mechanism, and is characterized by Ea ≈ 305 kJ/mol. The isothermal crystallization taking place in the temperature range 274 K and 281 K is determined by nucleus formation.
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5

Yang, Xujing, Yazhuo Wu, Kai Wei, Wenjun Fang, and Haofei Sun. "Non-Isothermal Crystallization Kinetics of Short Glass Fiber Reinforced Poly (Ether Ether Ketone) Composites." Materials 11, no. 11 (October 25, 2018): 2094. http://dx.doi.org/10.3390/ma11112094.

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Due to its excellent chemical and temperature resistances, short glass fiber reinforced poly (ether ether ketone) composite (SGF/PEEK) is a promising material for application in automotive lightweight. Processing conditions, such as cooling rate, need to be well controlled to obtain the optimal crystallite morphology of PEEK composites. Thus, in this paper, the non-isothermal crystallization kinetics and melting behavior of SGF/PEEK were investigated by differential scanning calorimetry (DSC) at different cooling rates, and the crystallite sizes were evaluated by the X-ray diffraction technique (XRD). Crystallization kinetics models and effective activation energies were evaluated to determine the crystallization parameters of the composites. The results suggest that a lower cooling rate enlarges the size of crystallites and enhances the uniformity of size distribution. The addition of glass fibers improves the nucleation rate owing to heterogeneous nucleation while decreasing the growth rate due to retarded movement of the polymer chain. The combined Avrami-Ozawa equation was shown to describe accurately the non-isothermal crystallization. The absolute value of the crystallization activation energy for SGF/PEEK is lower than that of pure PEEK.
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6

SHI, BO, SHIYU LUAN, and PEIPENG JIN. "NANOSCALE DIMPLES AND PERIODIC CORRUGATIONS ON FRACTURE SURFACE OF Zr-BASED BULK METALLIC GLASS COMPOSITE." Surface Review and Letters 26, no. 08 (September 5, 2019): 1950037. http://dx.doi.org/10.1142/s0218625x19500379.

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Nanoscale dimples and periodic corrugations are observed on the fracture surface of Zr-based bulk metallic glass composite (BMGC). The nanoscale periodic corrugations display a curved shape, which is different from that observed in previous works. In addition, the crystallization behavior of [Formula: see text][Formula: see text][Formula: see text][Formula: see text] BMG was investigated. The second crystallization event of Zr-Cu-Ni-Al BMG can be controlled by annealing or tuning cooling rate. The in situ Zr-based BMGC was prepared via lowering cooling rate. The Zr-based BMGC displays completely brittleness.
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7

Fan, Helin, Dengfu Chen, Tao Liu, Huamei Duan, Yunwei Huang, Mujun Long, and Wenjie He. "Crystallization Behaviors of Anosovite and Silicate Crystals in High CaO and MgO Titanium Slag." Metals 8, no. 10 (September 24, 2018): 754. http://dx.doi.org/10.3390/met8100754.

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Electric-furnace smelting has become the dominant process for the production of the titanium slag from ilmenite in China. The crystallization behaviors of anosovite and silicate crystals in the high CaO and MgO titanium slag were studied to insure smooth operation of the smelting process and the efficient separation of titanium slag and metallic iron. The crystallization behaviors were studied by a mathematical model established in this work. Results show that the crystallization order of anosovite and silicate crystals in high CaO and MgO titanium slag during cooling is: Al2TiO5 > Ti3O5 > MgTi2O5 > MgSiO3 > CaSiO3 > FeTi2O5 > Mn2SiO4 > Fe2SiO4. Al2TiO5 and Ti3O5 have higher crystallization priority and should be responsible for the sharp increase in viscosity of titanium slag during cooling. The total crystallization rates of anosovite and silicate crystals are mainly controlled by Al2TiO5 and MgSiO3, respectively. The mass ratio of Ti2O3/ΣTiO2 has a prominent influence on the total crystallization rate of anosovite crystals while the mass ratio of MgO/FeO has a slight influence on the total crystallization rate of anosovite crystals.
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8

Vallasek, Stefan I., Zsolt Veres, András Roósz, János Szőke, Péter Szirovicza, and Pál Bárczy. "Production of Single Crystal Thermoelectric Bismuth Telluride Alloys." Materials Science Forum 659 (September 2010): 263–68. http://dx.doi.org/10.4028/www.scientific.net/msf.659.263.

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Thermoelectric (TE) semiconductor materials are widely used for miniaturized versatile cooling devices in a wide spectrum of equipments and energy generation in space vehicles. The bismuth telluride pseudobinary alloy family presents the best characteristics for room temperature TE cooling applications. Using appropriately oriented single crystals instead of the well known polycrystalline materials made by powder metallurgy methods, the efficiency of the TE device (Thermoelectric Cooler – TEC or Thermoelectric Generator – TEG) could be almost doubled. For having good quality TE material it is required to produce equally doped single crystals by the controlled crystallization process, namely with the Bridgman-Stockbarber method. Our experiments were made in the Universal Multizone Crystallizator Type UMC, developed by the ADMATIS Ltd., Miskolc, using a quartz tube under high vacuum conditions and automatically controlled thermal field parameters. The crystallographic analysis of the obtained samples was made by Scanning Electron Microscopy – (SEM), X Ray Diffraction – (XRD), and neutron diffraction (TOF spectrometry).
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9

Spicer, Patrick T., and Richard W. Hartel. "Crystal Comets: Dewetting During Emulsion Droplet Crystallization." Australian Journal of Chemistry 58, no. 9 (2005): 655. http://dx.doi.org/10.1071/ch05119.

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Liquid oil emulsion droplets can violently dewet their own solid crystals during crystallization as a result of surfactant adsorption. The crystal shape formed is a function of the relative rates of dewetting and crystallization as controlled by surfactant adsorption, cooling rate, and lipid purity. For negligible dewetting rates, crystals nucleate and grow within the droplet. At similar crystallization and dewetting rates, the droplet is propelled around the continuous phase on a crystalline ‘comet tail’ much larger than the original droplet. Rapid dewetting causes the ejection of small discrete crystals across the droplet’s oil–water interface.
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10

Zeng, Qiang, Jianli Li, Yue Yu, and Hangyu Zhu. "Effect of Cooling Rate on Crystallization Behavior of CaO-SiO2-MgO-Cr2O3 Based Slag." High Temperature Materials and Processes 39, no. 1 (March 25, 2020): 74–80. http://dx.doi.org/10.1515/htmp-2020-0023.

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AbstractIn order to improve the recycling efficiency of stainless-steel slag resources, the effect of different cooling rates on the crystallization behavior of CaO-SiO2-MgO-Cr2O3 based system was studied by using FactSage 7.1, XRD, SEM and IPP 6.0. The results indicated that the spinel is a high-temperature precipitated phase and the cooling rate had less effect on the final grain size of spinel crystals, but had greater influences on the nucleation of spinel crystals and the crystallization of silicates such as α-C2S.When the cooling rate was 12∘C/min, the spinel crystals was the unique precipitation. However, the spinel crystals and α-C2S could produce during the slag cooling process as the cooling rate was1∘C/min. Chromium in silicate phase is inclinable to leaching with the dissolution of silicate phase, so the formation of silicate phase should be controlled. According to the influence of the cooling rate on the formation of spinel crystals and the erosion of spinel crystals by α-C2S, it is suggested that the cooling rate of the stainless-steel slag in industrial treatment should not be lower than 12∘C/min.
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11

Diepen, P. J., O. S. L. Bruinsma, and G. M. Van Rosmalen. "Melt crystallization by controlled evaporative cooling. The caprolactam–water system in batch operation." Chemical Engineering Science 55, no. 18 (September 2000): 3575–84. http://dx.doi.org/10.1016/s0009-2509(00)00044-0.

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12

Zhang, Teng, Botond Szilágyi, Junbo Gong, and Zoltan K. Nagy. "Thermodynamic Polymorph Selection in Enantiotropic Systems Using Supersaturation-Controlled Batch and Semibatch Cooling Crystallization." Crystal Growth & Design 19, no. 11 (October 17, 2019): 6715–26. http://dx.doi.org/10.1021/acs.cgd.9b01076.

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13

Nakata, Yoshitaka, Youko Kiyosawa, Kooji Kagara, and Masakuni Matsuoka. "Controlled Production of Polymorphic Mixtures of MPPO in Batch Cooling and Drowning-Out Crystallization." JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 43, no. 4 (2010): 374–80. http://dx.doi.org/10.1252/jcej.09we224.

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14

Chan, Y. C., S. H. Fan, and J. K. L. Lai. "The Effect of Cooling Rate on the Growth of Cu-Sn Intermetallics in Annealed PBGA Solder Joints." Journal of Electronic Packaging 125, no. 1 (March 1, 2003): 153–56. http://dx.doi.org/10.1115/1.1537070.

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In this study, the diffusion behavior and microstructural evolution of Cu-Sn intermetallics at eutectic Sn-Pb solder/copper substrate interface of PBGA solder joints was studied. The PBGA solder joints were formed by different profiles, which was devised to have the same “heating factor”—the integral of the measured temperature above the liquidus (183°C) with respect to dwell time in the reflow profile, but to have different conveyor speeds. Using the theory of heat transmission, it is shown that the solder joint cooling rate during solidification increases with increasing conveyor speed. As a result, the “crystallization degree” of the solder joint microstructure decreased with the increasing of cooling rate. The thickness of IMC layer increased with extension of aging time. The growth of IMC is a diffusion-controlled process, i.e., tin diffuses into copper, and the diffusion coefficient in the “disordered region” Db is much bigger than that in the “crystallization region” Dl, so the IMC growth rate of solder joint with faster cooling rate was larger. On the other hand, although Db>Dl at all temperatures, the difference increases as temperature decrease, consequently, the difference of IMC thickness growth among different cooling rate solder joints varied according to the aging temperature.
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15

Choi, Cheong Song, and Ik Soo Kim. "Controlled cooling crystallization of ammonium sulfate in the ternary system ammonium sulfate-ammonium nitrate-water." Industrial & Engineering Chemistry Research 30, no. 7 (July 1991): 1588–93. http://dx.doi.org/10.1021/ie00055a026.

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16

Matsuura, Shinji, Koichi Igarashi, Masayuki Azuma, and Hiroshi Ooshima. "Polymorphic Crystallization Design to Prevent the Degradation of the β-Lactam Structure of a Carbapenem." Crystals 11, no. 8 (August 11, 2021): 931. http://dx.doi.org/10.3390/cryst11080931.

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The cooling crystallization of carbapenem CS-023 was performed at 25 °C in an aqueous solution. Tetrahydrate crystals (form H) were obtained. Hydrate crystals are promising drugs, but there has been problems in manufacturing such crystals. During cooling crystallization, a dissolution process at a high temperature of 70 °C was utilized. The main problem in manufacturing was that the degradation rate of CS-023 at 70 °C was high, as expressed in the half-life period of 2.97 h. Poor solvent crystallization using ethanol was observed at 25 °C. Thus, a different polymorph (Form A) was obtained. Form A comprised CS-023, 5/2 ethanol, and 1/2 H2O. Form A, containing ethanol, is not suitable as a drug. Form A was then transformed to another polymorph of hydrate crystals or tetrahydrate Form H. Another hydrate polymorph, Form B, was obtained through the solid phase transformation of Form A and further transformed to the tetrahydrate Form H, at high humidity over 80% RH. This process, which proceeded at the low temperature of 25 °C, helped to prevent the degradation of CS-023, thereby avoiding wastage. Furthermore, the solid-phase transition could be controlled with vapor composition.
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17

Schawe, Jürgen E. K., and Claus Wrana. "Competition between Structural Relaxation and Crystallization in the Glass Transition Range of Random Copolymers." Polymers 12, no. 8 (August 8, 2020): 1778. http://dx.doi.org/10.3390/polym12081778.

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Structural relaxation in polymers occurs at temperatures in the glass transition range and below. At these temperatures, crystallization is controlled by diffusion and nucleation. A sequential occurrence of structural relaxation, nucleation, and crystallization was observed for several homopolymers during annealing in the range of the glass transition. It is known from the literature that all of these processes are strongly influenced by geometrical confinements. The focus of our work is copolymers, in which the confinements are caused by the random sequence of monomer units in the polymer chain. We characterize the influence of these confinements on structure formation and relaxation in the vicinity of the glass transition. The measurements were performed with a hydrogenated nitrile-butadiene copolymer (HNBR). The kinetics of the structural relaxation and the crystallization was measured using fast differential scanning calorimetry (FDSC). This technique was selected because of the high sensitivity, the fast cooling rates, and the high time resolution. Crystallization in HNBR causes a segregation of non-crystallizable segments in the macromolecule. This yields a reduction in mobility in the vicinity of the formed crystals and as a consequence an increased amount of so-called “rigid amorphous fraction” (RAF). The RAF can be interpreted as self-assembled confinements, which limit and control the crystallization. An analysis of the crystallization and the relaxation shows that the kinetic of both is identical. This means that the Kohlrausch exponent of relaxation and the Avrami exponent of crystallization are identical. Therefore, the crystallization is not controlled by nucleation but by diffusion and is terminated by the formation of RAF.
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18

Farhan, Muhammad, Marc Behl, Karl Kratz, and Andreas Lendlein. "Origami hand for soft robotics driven by thermally controlled polymeric fiber actuators." MRS Communications 11, no. 4 (June 28, 2021): 476–82. http://dx.doi.org/10.1557/s43579-021-00058-4.

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AbstractActive fibers can serve as artificial muscles in robotics or components of smart textiles. Here, we present an origami hand robot, where single fibers control the reversible movement of the fingers. A recovery/contracting force of 0.2 N with a work capacity of 0.175 kJ kg−1 was observed in crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) fibers, which could enable the bending movement of the fingers by contraction upon heating. The reversible opening of the fingers was attributed to a combination of elastic recovery force of the origami structure and crystallization-induced elongation of the fibers upon cooling. Graphic abstract
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19

Naffakh, Mohammed, Pablo Rica, Carmen Moya-Lopez, José Antonio Castro-Osma, Carlos Alonso-Moreno, and Diego A. Moreno. "The Effect of WS2 Nanosheets on the Non-Isothermal Cold- and Melt-Crystallization Kinetics of Poly(l-lactic acid) Nanocomposites." Polymers 13, no. 13 (July 5, 2021): 2214. http://dx.doi.org/10.3390/polym13132214.

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In the present work, hybrid nanocomposite materials were obtained by a solution blending of poly(l-lactic acid) (PLLA) and layered transition-metal dichalcogenides (TMDCs) based on tungsten disulfide nanosheets (2D-WS2) as a filler, varying its content between 0 and 1 wt%. The non-isothermal cold- and melt-crystallization and melting behavior of PLLA/2D-WS2 were investigated. The overall crystallization rate, final crystallinity, and subsequent melting behavior of PLLA were controlled by both the incorporation of 2D-WS2 and variation of the cooling/heating rates. In particular, the analysis of the cold-crystallization behavior of the PLLA matrix showed that the crystallization rate of PLLA was reduced after nanosheet incorporation. Unexpectedly for polymer nanocomposites, a drastic change from retardation to promotion of crystallization was observed with increasing the nanosheet content, while the melt-crystallization mechanism of PLLA remained unchanged. On the other hand, the double-melting peaks, mainly derived from melting–recrystallization–melting processes upon heating, and their dynamic behavior were coherent with the effect of 2D-WS2 involved in the crystallization of PLLA. Therefore, the results of the present study offer a new perspective for the potential of PLLA/hybrid nanocomposites in targeted applications.
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20

Naffakh, Mohammed. "Biopolymer Nanocomposite Materials Based on Poly(L-lactic Acid) and Inorganic Fullerene-like WS2 Nanoparticles." Polymers 13, no. 17 (August 31, 2021): 2947. http://dx.doi.org/10.3390/polym13172947.

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In the current study, inorganic fullerene (IF)-like tungsten disulphide (WS2) nanoparticles from layered transition metal dichalcogenides (TMDCs) were introduced into a poly(L-lactic acid) (PLLA) polymer matrix to generate novel bionanocomposite materials through an advantageous melt-processing route. The effectiveness of employing IF-WS2 on the morphology and property enhancement of the resulting hybrid nanocomposites was evaluated. The non-isothermal melt–crystallization and melting measurements revealed that the crystallization and melting temperature as well as the crystallinity of PLLA were controlled by the cooling rate and composition. The crystallization behaviour and kinetics were examined by using the Lui model. Moreover, the nucleating effect of IF-WS2 was investigated in terms of Gutzow and Dobreva approaches. It was discovered that the incorporation of increasing IF-WS2 contents led to a progressive acceleration of the crystallization rate of PLLA. The morphology and kinetic data demonstrate the high performance of these novel nanocomposites for industrial applications.
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21

Nguyen, Du, Tomoaki Morishita, Yusuke Soda, Akihiro Tamura, Biswajit Ghosh, Yumiko Harigane, Lydéric France, et al. "Occurrence of Felsic Rocks in Oceanic Gabbros from IODP Hole U1473A: Implications for Evolved Melt Migration in the Lower Oceanic Crust." Minerals 8, no. 12 (December 10, 2018): 583. http://dx.doi.org/10.3390/min8120583.

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Felsic rocks are minor in abundance but occur ubiquitously in International Ocean Discovery Program Hole U1473A, Southwest Indian Ridge. The trace element abundances of high-Ti brown amphibole, plagioclase, and zircon in veins, as well as the presence of myrmekitic texture in the studied felsic rocks support crystallization origin from highly-evolved melts, probably controlled by fractional crystallization. Based on geochemical criteria and texture of the mineral assemblage in felsic rocks and their relationship with host gabbros, they can be divided into three types: (1) Felsic rock with sharp boundaries is formed when felsic melt intrudes into fractures of host gabbros, resulting in minimal interaction between the melt and the wall minerals. (2) Replacive felsic rock, which is characterized by a pseudomorphic replacement of minerals in the host gabbro. This vein type is caused by the replacement of the host mineralogy by minerals in equilibrium with the felsic melts. (3) Felsic rock with diffused boundaries is formed either by infiltration of felsic melt into the solidifying gabbro body or crystallization of interstitial melts. Infiltration modes of felsic melts are likely controlled by the temperature condition of the cooling host gabbros.
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22

Vernède, Xavier, and Juan Carlos Fontecilla-Camps. "A method to stabilize reduced and/or gas-treated protein crystals by flash-cooling under a controlled atmosphere." Journal of Applied Crystallography 32, no. 3 (June 1, 1999): 505–9. http://dx.doi.org/10.1107/s0021889899002678.

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A customized glove box for protein crystallization under a controlled atmosphere is described along with a cryogenic technique adapted to freeze protein crystals inside the glove box and a very simple device for studying gas–protein complexes in the crystalline state at cryogenic temperatures. Using these techniques different redox states of oxygen-sensitive crystalline proteins have been stabilized and the interaction of hydrogenase with Xe, a model for the much lighter substrate molecular hydrogen, has been studied.
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23

Xiao, Zhuo Hao, and Jun Hui Liao. "Synthesis and Characterization of Transparent Glass-Ceramics in Na2O-CaO-SiO2 System." Advanced Materials Research 233-235 (May 2011): 1850–53. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.1850.

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Glass in Na2O-CaO-SiO2 was synthesized by conventional molten cooling method and then converted to glass-ceramics. Transparent glass-ceramics obtained by controlled crystallization process. DSC, SEM and XRD were used to determine the character temperature, microstructure and crystal type of the glass-ceramics, respectively. The results show the transition temperature of the matrix glass is 620°C and crystallization peak temperature is 730°C. Only Na2Ca2Si3O9 crystal phase was found in the glass-ceramics when the matrix glass was treated at 750°C for 1h. The crystal with size of 0.5um arranged regularly and formed a honeycomb-like structure in the glass-ceramics. UV-visible spectrum test indicate the transmittance of the glass-ceramic is as high as 75% in the visible region.
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24

Gumennik, Alexander, Etgar C. Levy, Benjamin Grena, Chong Hou, Michael Rein, Ayman F. Abouraddy, John D. Joannopoulos, and Yoel Fink. "Confined in-fiber solidification and structural control of silicon and silicon−germanium microparticles." Proceedings of the National Academy of Sciences 114, no. 28 (June 22, 2017): 7240–45. http://dx.doi.org/10.1073/pnas.1707778114.

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Crystallization of microdroplets of molten alloys could, in principle, present a number of possible morphological outcomes, depending on the symmetry of the propagating solidification front and its velocity, such as axial or spherically symmetric species segregation. However, because of thermal or constitutional supercooling, resulting droplets often only display dendritic morphologies. Here we report on the crystallization of alloyed droplets of controlled micrometer dimensions comprising silicon and germanium, leading to a number of surprising outcomes. We first produce an array of silicon−germanium particles embedded in silica, through capillary breakup of an alloy-core silica-cladding fiber. Heating and subsequent controlled cooling of individual particles with a two-wavelength laser setup allows us to realize two different morphologies, the first being a silicon−germanium compositionally segregated Janus particle oriented with respect to the illumination axis and the second being a sphere made of dendrites of germanium in silicon. Gigapascal-level compressive stresses are measured within pure silicon solidified in silica as a direct consequence of volume-constrained solidification of a material undergoing anomalous expansion. The ability to generate microspheres with controlled morphology and unusual stresses could pave the way toward advanced integrated in-fiber electronic or optoelectronic devices.
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25

Nývlt, Jaroslav, Věra Šnoblová, and Miloslav Karel. "Crystallization kinetics for the system CuSO4-ZnSO4-H2O forming solid solutions." Collection of Czechoslovak Chemical Communications 51, no. 11 (1986): 2473–80. http://dx.doi.org/10.1135/cccc19862473.

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The three-component system CuSO4-ZnSO4-H2O forms three types of solid solution. Metastable zone widths measured for selected solution compositions at two cooling rates were used to calculate the kinetic parameters of nucleation. The rate of crystal growth was measured by the fluidized bed method. The results show that the addition of Zn2+ to a solution of CuSO4 increases both the nucleation and crystal growth rates, whereas Cu2+ added to a solution of ZnSO4 retards the nucleation rate and slightly increases the rate of crystal growth. The nucleation rate (the metastable zone width) is substantially more sensitive to the addition of a second component than is the rate of crystal growth. The crystal growth rate is controlled by a diffusion mechanism.
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26

Quintana-Hernández, Pedro Alberto, Raúl Ocampo-Pérez, Salvador Tututi-Avila, and Salvador Hernández-Castro. "Nonlinear MIMO Control of a Continuous Cooling Crystallizer." Modelling and Simulation in Engineering 2012 (2012): 1–11. http://dx.doi.org/10.1155/2012/912071.

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In this work, a feedback control algorithm was developed based on geometric control theory. A nonisothermal seeded continuous crystallizer model was used to test the algorithm. The control objectives were the stabilization of the third moment of the crystal size distribution (μ3) and the crystallizer temperature (T); the manipulated variables were the stirring rate and the coolant flow rate. The nonlinear control (NLC) was tested at operating conditions established within the metastable zone. Step changes of magnitudes ±0.0015 and ±0.5°C were introduced into the set point values of the third moment and crystallizer temperature, respectively. In addition, a step change of ±1°C was introduced as a disturbance in the feeding temperature. Closed-loop stability was analyzed by calculating the eigenvalues of the internal dynamics. The system presented a stable dynamic behavior when the operation conditions maintain the crystallizer concentration within the metastable zone. Closed-loop simulations with the NLC were compared with simulations that used a classic PID controller. The PID controllers were tuned by minimizing the integral of the absolute value of the error (IAE) criterion. The results showed that the NLC provided a suitable option for continuous crystallization control. For all analyzed cases, the IAEs obtained with NLC were smaller than those obtained with the PID controller.
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27

Ştefănescu, Florin, Gigel Neagu, Alexandrina Mihai, and Iuliana Stan. "Controlled Temperature Distribution and Heat Transfer Process in the Unidirectional Solidification of Aluminium Alloys." Solid State Phenomena 188 (May 2012): 314–17. http://dx.doi.org/10.4028/www.scientific.net/ssp.188.314.

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Abstract. The paper presents some theoretical and experimental data regarding the directional solidification, revealing the main factors (especially those which are related to the heat transfer process) which have influence on the crystals size and morphology. The crystalline structure of alloys is determined by three important factors: chemical composition, thermal conditions, and characteristics of germination and growth from liquid of solid nuclei. The solidification structure can be influenced by acting on the mould properties or directly on the cast material, both of these actions being based upon the change of temperature distribution in the alloy-mould system. Experimental data demonstrated the major influence of the thermal regime on the crystallization-solidification process, on the transcrystallization zone and they pointed out the limits to direct the crystals formation (size and shape) by changing the cooling regime.
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28

Sun, Jing, Zhiwei Wang, Chenhui Zhu, Meiyao Wang, Zhekun Shi, Yuhan Wei, Xiaohui Fu, Xuesi Chen, and Ronald N. Zuckermann. "Hierarchical supramolecular assembly of a single peptoid polymer into a planar nanobrush with two distinct molecular packing motifs." Proceedings of the National Academy of Sciences 117, no. 50 (December 1, 2020): 31639–47. http://dx.doi.org/10.1073/pnas.2011816117.

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Hierarchical nanomaterials have received increasing interest for many applications. Here, we report a facile programmable strategy based on an embedded segmental crystallinity design to prepare unprecedented supramolecular planar nanobrush-like structures composed of two distinct molecular packing motifs, by the self-assembly of one particular diblock copolymer poly(ethylene glycol)-block-poly(N-octylglycine) in a one-pot preparation. We demonstrate that the superstructures result from the temperature-controlled hierarchical self-assembly of preformed spherical micelles by optimizing the crystallization−solvophobicity balance. Particularly remarkable is that these micelles first assemble into linear arrays at elevated temperatures, which, upon cooling, subsequently template further lateral, crystallization-driven assembly in a living manner. Addition of the diblock copolymer chains to the growing nanostructure occurs via a loosely organized micellar intermediate state, which undergoes an unfolding transition to the final crystalline state in the nanobrush. This assembly mechanism is distinct from previous crystallization-driven approaches which occur via unimer addition, and is more akin to protein crystallization. Interestingly, nanobrush formation is conserved over a variety of preparation pathways. The precise control ability over the superstructure, combined with the excellent biocompatibility of polypeptoids, offers great potential for nanomaterials inaccessible previously for a broad range of advanced applications.
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29

Farhan, Muhammad, Tobias Rudolph, Karl Kratz, and Andreas Lendlein. "Torsional Fiber Actuators from Shape-memory Polymer." MRS Advances 3, no. 63 (2018): 3861–68. http://dx.doi.org/10.1557/adv.2018.621.

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ABSTRACT:Humanoid robots, prosthetic limbs and exoskeletons require soft actuators to perform their primary function, which is controlled movement. In this work, we explored whether crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) fibers, with different vinyl acetate (VA) content can serve as torsional fiber actuators, exhibiting temperature controlled reversible rotational changes. Broad melting transitions ranging from 50 to 90 °C for cPEVA18-165 or from 40 to 80 °C for cPEVA28-165 fibers in combination with complete crystallization at temperatures around 10 °C make them suitable actuating materials with adjustable actuation temperature ranges between 10 and 70 °C during repetitive cooling and heating. The obtained fibers exhibited a circular cross section with diameters around 0.4±0.1 mm, while a length of 4 cm was employed for the investigation of reversible rotational actuation after programming by twist insertion using 30 complete rotations at a temperature above melting transition. Repetitive heating and cooling between 10 to 60 °C or 70 °C of one-end-tethered programmed fibers revealed reversible rotations and torsional force. During cooling 3±1 complete rotations (Δθr = + 1080±360°) in twisting direction were observed, while 4±1 turns in the opposite direction (Δθr = - 1440±360°) were found during heating. Such torsional fiber actuators, which are capable of approximately one rotation per cm fiber length, can serve as miniaturized rotary motors to provide rotational actuation in futuristic humanoid robots.
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30

Barka, E. Aït, and J. C. Audran. "Réponse des vignes champenoises aux températures negatives: effet d'un refroidissement contrôlé sur les réserves glucidiques du complexe gemmaire avant et au cours du débourrement." Canadian Journal of Botany 74, no. 3 (March 1, 1996): 492–505. http://dx.doi.org/10.1139/b96-060.

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Sugar concentrations were analyzed in grapevine (Vitis vinifera) buds at three different phenological stages (stage 1, dormant bud; stage 2, woolly bud; stage 5, green tip) and were submitted, under controlled conditions, to negative temperatures corresponding to the intracellular liquid crystallization points. In absence of any treatment, starch concentration diminished according to the phenological evolution, indicating its utilization during bud breaking. Starch and raffinose accumulated when controlled cooling was applied, except for stage 1 buds collected on March 6, 1993. Similarly, saccharose concentrations were reduced in bud complexes after temperature reductions. Fructose and glucose concentrations seemed to be less sensitive to thermal variations. The accumulation of starch observed at the end of a cold treatment could be partly explained by the inhibition of amylase activity under cold conditions. Keywords: bud, Vitis vinifera L., phenological stage, thermal stress, sugars. [Journal translation]
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31

Kudrna Prašek, Marko, Mattia Pistone, Don R. Baker, Nicola Sodini, Nicoletta Marinoni, Gabriele Lanzafame, and Lucia Mancini. "A compact and flexible induction furnace for in situ X-ray microradiograhy and computed microtomography at Elettra: design, characterization and first tests." Journal of Synchrotron Radiation 25, no. 4 (June 1, 2018): 1172–81. http://dx.doi.org/10.1107/s1600577518005970.

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A compact and versatile induction furnace for in situ high-resolution synchrotron and laboratory hard X-ray microradiography and computed microtomography is described. The furnace can operate from 773 to 1723 K. Its programmable controller enables the user to specify multiple heating and cooling ramp rates as well as variable dwell times at fixed temperatures allowing precise control of heating and cooling rates to within 5 K. The instrument can work under a controlled atmosphere. Thanks to the circular geometry of the induction coils, the heat is homogeneously distributed in the internal volume of the graphite cell (ca. 150 mm3) where the sample holder is located. The thermal gradient within the furnace is less than 5 K over a height of ca. 5 mm. This new furnace design is well suited to the study of melting and solidification processes in geomaterials, ceramics and several metallic alloys, allowing fast heating (tested up to 6.5 K s−1) and quenching (up to 21 K s−1) in order to freeze the sample microstructure and chemistry under high-temperature conditions. The sample can be held at high temperatures for several hours, which is essential to follow phenomena with relatively slow dynamics, such as crystallization processes in geomaterials. The utility of the furnace is demonstrated through a few examples of experimental applications performed at the Elettra synchrotron laboratory (Trieste, Italy).
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32

Gonik, Michael A., and Florin Baltaretu. "Problem of attaining constant impurity concentration over ingot height." Modern Electronic Materials 4, no. 2 (June 1, 2018): 41–51. http://dx.doi.org/10.3897/j.moem.4.2.38536.

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The possibility of growing crystals with homogeneous impurity distribution over crystal height has been demonstrated in a study of segregation during silicon and germanium growth from thin melt layers using the submerged heater method. Numeric simulation of 200 mm diam. antimony-doped germanium crystallization has shown that, beginning from a 40 mm melt layer thickness, the exact problem solution with convection allowance is identical to the unidimensional heat exchange problem solution in the central ingot part. The conditions under which convection can be ignored in mass transport calculation are more rigorous: the melt layer height must be within 20 mm. In this case Tiller’s ratio can be used for calculating the longitudinal impurity distribution for predominantly diffusion-controlled mass transport pattern. Analysis of the existing attempts to describe the experimental crystal growth results using the simplified formulae shows that they only yield acceptable results if the actual growth rate or change in melt layer thickness during crystallization are taken into account, e.g. as in the formula suggested by Marchenko et al. One can therefore analytically describe the longitudinal impurity distribution in the ingot, e.g. B and P distribution in silicon, and recommend the degree of additional doping of the melt zone under the heater so that to provide a constant impurity concentration over the ingot height. Homogeneous material can be obtained after residual layer solidification in the end portion of the ingot if the growth rate is controlled through varying the cooling rate.
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33

Kim, Seong-Jin, and T. E. Karis. "Glass formation from low molecular weight organic melts." Journal of Materials Research 10, no. 8 (August 1995): 2128–36. http://dx.doi.org/10.1557/jmr.1995.2128.

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Glass formation from the melt of organic monomers was studied for a variety of different organic molecular structures with Tg near ambient temperature. Crystallization is suppressed by one or more of the molecular properties, hydrogen bonding, interlocking, dipolar, and hydrogen bonding, combined with hindered rotational isomerism. Examples of materials in each category are presented for illustration. The viscosity of undercooled liquids was characterized by the Vogel-Tammon-Fulcher (VTF) equation, η = A cxp[DT0/(T - T0)], where A, D, and T0 are experimentally determined parameters. Our experimental D values are discussed in relation to the molecular structure and glass formation mechanism. The insight provided by our interpretation is intended to assist in the design of new molecular structures with controlled viscosity-temperature characteristics, as well as glass-forming ability by cooling from melts.
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34

Barlow, Sean T., Daniel J. Bailey, Adam J. Fisher, Martin C. Stennett, Claire L. Corkhill, and Neil C. Hyatt. "Synthesis of simulant ‘lava-like’ fuel containing materials (LFCM) from the Chernobyl reactor Unit 4 meltdown." MRS Advances 2, no. 11 (December 23, 2016): 609–14. http://dx.doi.org/10.1557/adv.2016.642.

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ABSTRACTA preliminary investigation of the synthesis and characterization of simulant ‘lava-like’ fuel containing materials (LFCM), as low activity analogues of LFCM produced by the melt down of Chernobyl Unit 4. Simulant materials were synthesized by melting batched reagents in a tube furnace at 1500 °C, under reducing atmosphere with controlled cooling to room temperature, to simulate conditions of lava formation. Characterization using XRD and SEM-EDX identified several crystalline phases including ZrO2, UOx and solid solutions with spherical metal particles encapsulated by a glassy matrix. The UOX and ZrO2 phase morphology was very diverse comprising of fused crystals to dendritic crystallites from the crystallization of uranium initially dissolved in the glass phase. This project aims to develop simulant LFCM to assess the durability of Chernobyl lavas and to determine the rate of dissolution, behavior and evolution of these materials under shelter conditions.
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35

Gruszka, Konrad, Marcin Nabialek, and Michal Szota. "Influence of Cu Substitution on the Structure and Magnetic Properties of Partially Crystallized Fe62-xCo10Y8MexB20 Alloys." Revista de Chimie 68, no. 2 (March 15, 2017): 408–10. http://dx.doi.org/10.37358/rc.17.2.5464.

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The paper presents results of structural and magnetic properties investigation of partially crystallized Fe62Co10Y8B20 and Fe61Co10Y8Cu1B20 alloys. Multicomponent bulk amorphous alloys exhibit a significant sensitivity to the composition changes. Even a small quantitative element substitution in composition of the initial alloy may lead to substantial changes in its various properties. Samples in form of thin plates were obtained by radial cooling method resulting in a complete amorphous structure material. Then, the one-step controlled heat treatment process led to partial crystallization of the sample causing the coexistence of amorphous matrix and embedded nanocrystalline phases. As shown in article, amorphous matrix has a noticeable influence on nano-sized grains resulting in a deformation of primary cell structure. Isothermal annealing process also had an impact on the magnetic properties of obtained samples, which was examined by the vibrating sample magnetometer (VSM).
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36

Ren, Qian, Yao, Gan, and Zhang. "Thermodynamic Evaluation of LiCl-H2O and LiBr-H2O Absorption Refrigeration Systems Based on a Novel Model and Algorithm." Energies 12, no. 15 (August 6, 2019): 3037. http://dx.doi.org/10.3390/en12153037.

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An absorption refrigeration system (ARS) is an alternative to the conventional mechanical compression system for cold production. This study developed a novel calculation model using the Matlab language for the thermodynamic analysis of ARS. It was found to be reliable in LiCl-H2O and LiBr-H2O ARS simulations and the parametric study was performed in detail. Moreover, two 50 kW water-cooled single effect absorption chillers were simply designed to analyze their off-design behaviors. The results indicate that LiCl-H2O ARS had a higher coefficient of performance (COP) and exergetic efficiency, particularly in the lower generator or higher condenser temperature conditions, but it operated more restrictively due to crystallization. The off-design analyses revealed that the preponderant performance of LiCl-H2O ARS was mainly due to its better solution properties because the temperature of each component was almost the same for both chillers in the operation. The optimum inlet temperature of hot water for LiCl-H2O (83 °C) was lower than that of LiBr-H2O (98 °C). The cooling water inlet temperature should be controlled within 41 °C, otherwise the performances are discounted heavily. The COP and cooling capacity could be improved by increasing the temperature of hot water or chilled water properly, contrary to the exergetic efficiency.
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37

Oh, Hyun Cheol, Jun Ho Ji, Jae Hee Jung, and Sang Soo Kim. "Synthesis of Titania Nanoparticles via Spark Discharge Method Using Air as a Carrier." Materials Science Forum 544-545 (May 2007): 143–46. http://dx.doi.org/10.4028/www.scientific.net/msf.544-545.143.

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A pulsed spark-discharge aerosol generator using air as a carrier gas was successfully applied to the titania nanoparticle production. The titanium vapor evaporated by spark discharge was subsequently supersaturated and condensed to titania nanoparticles by nucleation and condensation. The size and concentration of the particles can be controlled easily using air as a carrier gas by altering the repetition frequency, capacitance, gap distance, and flow rate of the spark-discharge system. TEM observation shows that the generated particles were aggregates, which primary particle sizes are a few nanometers. The element composition of the nanoparticles was titanium and the crystal phase was amorphous. XPS analysis shows that oxidation state of generated particles corresponded to TiO2. These XPS data indicates that some fraction of the evaporated titanium vapor could be oxidized in an air atmosphere by the oxidation with oxygen. However, enough time for crystallization was lacked because of raid cooling.
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38

Robert, Ch. "Hydrothermal alteration processes of the Tertiary lavas of Northern Ireland." Mineralogical Magazine 65, no. 4 (August 2001): 543–54. http://dx.doi.org/10.1180/002646101750377560.

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AbstractThe alteration mineralogy of two outcrops of basaltic lavas in northeast Ireland is studied with respect to the hydrothermal alteration history of basalts. Evidence for contact between basaltic flows and palaeorivers or palaeolakes is reported in both outcrops, which belong to two different formations: the Lower Basaltic Formation (LBF) and the Inter Basaltic Formation (Causeway Tholeiite Member, CTM). The secondary minerals consist of layer silicates (chlorite-smectite, C-S, di- and trioctahedral smectites), zeolites, calcite and silica minerals and there is a repetition of the sequence of alteration mineralogy in each formation. The mineralogy of phyllosilicates from the LBF (C-S) corresponds to hotter conditions of alteration than those of CTM (di/trioctahedral smectites), while the zeolite mineralogy is controlled by the fluid composition. In consequence, the mineralogy and the distribution of alteration minerals suggest that the crystallization of phyllosilicates and zeolites did not develop during burial of lavas a long time after the eruption, but reflects thermal gradients driven by lava heat flow and marked by local perturbation caused by regional water flow through the aquifer zone in the lava during the last cooling of each lava sequence.
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39

Sargent, David, Hsi-Wen Tung, Roel Pieters, and Bradley Nelson. "The RodBot approach to automated crystal harvesting." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1753. http://dx.doi.org/10.1107/s2053273314082461.

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Automated crystal harvesting is the main gap in the otherwise highly automated process of structure determination by X-ray crystallography. Many approaches have been presented, but few have proceeded beyond the initial, developmental stage. We recently introduced a rod-shaped microrobot1 (the "RodBot") to assist in the harvesting process. Driven by rotating magnetic fields to roll on a substrate, RodBots induce fluid flows that can lift crystals off the surface and trap them in a cylindrical vortex that travels with the RodBot. The gentle, fluidic force acting on the crystals is in the range of a few nanoNewtons to tens of nanoNewtons, and is spread over the whole surface of the crystal. Forces of this magnitude enable the RodBot to safely manipulate crystals ranging from a few microns to sub-millimeter size. With this technique individual crystals can be selected and brought to a loop positioned in the growth droplet to accept it. Harvesting and flash-cooling is then possible using a simple mechanical linkage. In this way the whole operation of crystal selection, harvesting and flash-cooling is remotely and gently carried out without the operator jitter or application of excessive strain that lead to high late-stage failure rates in crystal harvesting. Guidance is provided by the driving magnetic field, and can involve either manual input with a joystick or fully automated algorithms with feedback control. Because of this option of remote operation, RodBots can also be used for harvesting in hostile, sensitive or inconvenient environments such as anaerobic chambers, controlled humidity environments or cold rooms. The system is compatible with existing crystallization hardware and can be integrated readily into typical laboratory setups or high-throughput platforms.
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40

Tsybulenko, V. V., and S. V. Shutov. "Growing of heteroepitaxial layers on lattice mismatched substrates by the method of scanning liquid phase epitaxy." Технология и конструирование в электронной аппаратуре, no. 5-6 (2020): 33–39. http://dx.doi.org/10.15222/tkea2020.5-6.33.

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Heterostructures with lattice mismatched and compositionally different layers are widely used in modern electronic and optoelectronic device engineering. Generally such structures are manufactured by the methods of metal-organic vapor phase epitaxy, metal-organic chemical vapor deposition and molecular-beam epitaxy. However, the methods of deposition from a liquid phase are the most inexpensive and simple yet. Thus obtaining the above mentioned heterostructures from a liquid phase is still promising. In this work we demonstrated the possibility of using the method of scanning liquid phase epitaxy to grow continuous heteroepitaxial layers over the substrate surface highly mismatched by lattice constant and having different crystal-chemical properties. By controlling basic parameters of the method we created the conditions close to the solution-melt saturation limit. In other words, we created the conditions of ultra-fast solution-melt cooling and, respectively, high growth rate. We obtained the heterostructures of Ge layers grown on GaP substrates where the lattice mismatch made 3.7%. Gallium was used as the solvent for Germanium. The heterostructure was grown by the method of scanning liquid phase epitaxy in the conditions of ultra-fast initial cooling of the solution-melt. Overcooling at the crystallization front was controlled by an extra heater of the substrate back side. The growing time was 1 and 20 seconds for the two test samples. The layers thickness was determined by the spherical slice technique to be 1.2 and 1.5 μm for these two growing time values, accordingly. We showed that it was possible to obtain more perfect Ge layers on GaP substrate by lowering the growth rate in the final growth stage. This method can be used to grow heterostructures used in creating such modern electronic and optoelectronic devices as structures based on А3В5 compounds and their solid solutions, which cannot be obtained by other classical methods of liquid phase epitaxy due to significant differences in lattice constants and / or crystal-chemical properties.
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41

Chen, Liwen, Han Seung Lee, and Sangwoo Lee. "Close-packed block copolymer micelles induced by temperature quenching." Proceedings of the National Academy of Sciences 115, no. 28 (June 21, 2018): 7218–23. http://dx.doi.org/10.1073/pnas.1801682115.

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Close-packed structures of uniformly sized spheres are ubiquitous across diverse material systems including elements, micelles, and colloidal assemblies. However, the controlled access to a specific symmetry of self-assembled close-packed spherical particles has not been well established. We investigated the ordering of spherical block copolymer micelles in aqueous solutions that was induced by rapid temperature changes referred to as quenching. As a function of quench depth, the quenched self-assembled block copolymer micelles formed three different close-packed structures: face-centered cubic (fcc), random stacking of hexagonal-close-packed layers (rhcp), and hexagonal-close-packed (hcp). The induced hcp and rhcp structures were stable for at least a few weeks when maintained at their quench temperatures, but heating or cooling these hcp and rhcp structures transformed both structures to fcc crystallites with coarsening of the crystal grains, which suggests that these noncubic close-packed structures are intermediate states. Time-resolved scattering experiments prove that the micellar rhcp structures do not originate from the rapid growth of competing close-packed structures. We speculate that the long-lived metastable hcp and rhcp structures originate from the small size of crystal grains, which introduces a nonnegligible Laplace pressure to the crystal domains. The reported transitions from the less stable hcp to the more stable rhcp and fcc are experimental observations of Ostwald’s rule manifesting the transition order of the key close-packed structures in the crystallization of close-packed uniform spheres.
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42

Bortnikov, N. S., L. Ya Aranovich, S. G. Kryazhev, S. Z. Smirnov, V. G. Gonevchuk, B. I. Semanyak, E. O. Dubinina, N. V. Gorelikova, and E. N. Sokolova. "Badzhal tin magmatic-fluid system (Far east, Russia): the transition from the granite crystallization to the hydrothermal ore deposition." Геология рудных месторождений 61, no. 3 (June 19, 2019): 3–30. http://dx.doi.org/10.31857/s0016-77706133-30.

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With a view to reveal special characteristics of the transition stage from granite crystallization to rare-metal ore deposition it is studied Badzhal tin-bearing magmatic-fluid system of eponymously-named volcano-plutonic zone of the Middle Priamyrie. For that end the detail research of melt, fluid-melt and fluid inclusions and oxygen isotopes from minerals of granitoids from Verkne-Urmi massif from Badzhal volcano-plutonic zone and also minerals of Sn-W deposits Pravo-Urmi and Blizhnee have been carried out. The formation of greisens and hydrothermal veins were caused by the development of the integrated system associating with establishing of Verkne-Urmi granite massif which is one of a dome fold of Badzhal cryptobatholith. For the first time for tin deposits it has been followed up the transition from the magmatic phase of granite crystallization to the hydrothermal ore formation stage and the evolution of magmatic fluid from its separation from magmatic melt to Sn-W ore deposition. The direct evidence of tin-bearing fluid separation under melt crystallization is combined fluid-melt inclusions. Glass composition in inclusions shows that granites and granite-porphyry were crystallizing from acid and from limited to high-aluminous melts, that is value ASI changes from 0.95 to 1.33 and a content of alkalies varies from 6.02 up to 9.02 mass.%. Cl and F concentrations in glasses are according 0.03–0.14 and 0.14–0.44 mass.% and turned out to be higher of same in the total composition of rocks (0.02 and 0.05–0.13 mass.% in accordance). These differences indicate that Cl and F could be separated from granite melt under its crystallization and degasation. H2O content made from total deficiency electron microprobe analysis is 8–11 mass.%. This evaluation was made inclusive of a probable effect of “Na loss” (Nielsen, Sigurdson, 1981) under aqueous glass crystallization. Considering a high error of a such estimation (Devine et al., 1995), it should take to obtained values as a very approximate evaluation and consider that examined melts contained about 9,5–10,0 mass.% of H2O. The results of melt inclusion examination show that at any rate a part of melt forming magmatic rocks of Badzhal Ore Magmatic System are crystallizing at about T = 650 °C. These melts were acid, limited fluoride and meta- and high aluminous. The reason of low temperatures of its crystallization are likely a high pressure of aqua and also a increased content of F. Most likely that examined inclusions characterize the final stage of establishing of the massif, herewith at the system crystals, residual liquor and magmatic fluid phase coexist. The fluid from which greisens of Pravo-Urmi deposit formed is similar in properties to the supercritical fluid absorbing by magmatic minerals. The salinity of this fluid varying from ~9 to 12 mass.% equiv. NaCl, maximal T = 550 °C (with consideration for the temperature correction of T gom on a pressure ~1 кbar) are similar to such of magmatic fluid, which permit to connect its origin with pluton cooling. The formation of greisens and quartz-topaz veins of Pravo-Urmi deposit is related to fall of temperature of magmatic fluid from 550–450 up to 480–380 °C. The evolution of fluid deposited quartz-cassiterite veins of Blizhnee deposit, which based upon oxygen isotope composition (d18ОН2О ≈ 8.5‰) also separated from magma, was going at more subsurface conditions under much lesser pressure. That led to the gas separation of a fluid with salinity ~13 mass.% equa. NaCl under T = 420–340 °C on thin low salinity vapour and brine with concentration 33.5–37.4 mass.% equiv. NaCl. The research of oxygen isotope system testifies that oxygen isotope composition of ore-forming fluid controlled by equilibrium with granites at wide interval tempera­tures (from ~700 °С up to the beginning of greisen crystallization). Correspondence of measured and calculation data of the offered model indicates that the considerable volume of external fluid with other isotope characteristics which did not reach the isotope equilibrium with Verkhne-Urmi massif did not come into the magmatic isotope system. The discovered differences of physico-chemical conditions for two studied deposits are not “critical” and support an idea about their formation as the single magmatic-fluid system.
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43

Kim, Weon Ju, Seok Min Kang, and Ji Yeon Park. "Corrosion Behavior of Si3N4 Ceramics under High-Temperature and High-Pressure Water Condition." Advanced Materials Research 26-28 (October 2007): 259–62. http://dx.doi.org/10.4028/www.scientific.net/amr.26-28.259.

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Silicon nitride (Si3N4) ceramics have been considered for various components of nuclear power plants such as mechanical seal of reactor coolant pump (RCP), guide roller for control rod drive mechanism (CRDM), and seal support, etc. Corrosion behavior of Si3N4 ceramics in high-temperature and high-pressure water must be elucidated before they can be considered for components of nuclear power plants. In this study, the corrosion behaviors of Si3N4 ceramics at hydrothermal condition (300°C, 9.0 MPa) were investigated in pure water. The grain-boundary phase was preferentially corroded and the corrosion reaction was controlled by the diffusion of the reactive species and/or products through the corroded layer. Results of this study imply that the variation of sintering aids and/or the control (e.g., crystallization) of the grain-boundary phase are necessary to increase the corrosion resistance of Si3N4 ceramics in high-temperature water.
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44

Körber, Christoph. "Phenomena at the advancing ice–liquid interface: solutes, particles and biological cells." Quarterly Reviews of Biophysics 21, no. 2 (May 1988): 229–98. http://dx.doi.org/10.1017/s0033583500004303.

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SUMMARYIce formation in aqueous solutions and suspensions involves a number of significant changes and processes in the residual liquid. The resulting effects were described concerning the redistribution of dissolved salts, the behaviour of gaseous solutes and bubble formation, the rejection and entrapment of secondphase particles. This set of conditions is also experienced by biological cells subjected to freezing. The influences of ice formation in that respect and their relevance for cryopreservation were considered as well.A model of transient heat conduction and solute diffusion with a planar ice front, propagating through a system of finite length was found to be in good agreement with measured salt concentration profiles. The spacing of the subsequently developing columnar solidification pattern was of the same order of magnitude as the pertubation wavelengths predicted from the stability criterion. Non-planar solidification of binary salt solutions was described by a pure heat transfer model under the assumption of local thermodynamic equilibrium.The rejection of gaseous solutes and the resulting gas concentration profile ahead of a planar ice front has been estimated by means of a test bubble method, yielding a distribution coefficient of 0·05 for oxygen. The nucleation of gas bubbles has been observed to occur at slightly less than 20-fold supersaturation. The subsequent radial growth of the bubbles obeys a square-root time dependence as expected from a diffusion controlled model until the still expanding bubbles become engulfed by the advancing ice-liquid interface. The maximum bubble radii decrease for increasing ice front velocities.The transition between repulsion and entrapment of spherical latex particles by an advancing planar ice-front has been characterized by a critical value of the velocity of the solidification interface. The critical velocity is inversely proportional to the particle radius as suggested by models assuming an undisturbed ice front. The increase of the critical velocity for increasing thermal gradients shows good agreement with a theoretically predicted square-root type of dependence. Critical velocities have also been measured for yeast and red blood cells.The effect of freezing on biological cells has been analyzed for human lymphocytes and erythrocytes. The reduction of cell volume observed during non-planar freezing agrees reasonably well with shrinkage curves calculated from a water transport model. The probability of intracellular ice formation has been characterized by threshold cooling rates above which the amount of water remaining within the cell is sufficient for crystallization. The cooling rate dependence of viability exhibits largely different maxima for lymphocytes and erythrocytes at about 30 and 4700 K/min, respectively. The decrease of viability above these values has been attributed to the damaging effect of intracellular ice formation.
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45

Baldwin, J. R., P. G. Hill, A. A. Finch, O. von Knorring, and G. J. H. Oliver. "Microlite-manganotantalite exsolution lamellae: evidence from rare-metal pegmatite, Karibib, Namibia." Mineralogical Magazine 69, no. 6 (December 2005): 917–35. http://dx.doi.org/10.1180/0026461056960299.

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AbstractWe have analysed a rare occurrence of orange-brown manganotantalite lamellae (visible in hand specimen), intergrown with microlite [(Ca,Na)2(Ta,Nb)2(O,OH,F)7], aggregates of ferrotapiolite, bismuth minerals and apatite to understand more about the mechanisms of crystal growth and secondary modification in Ta-rich minerals. The intergrowth occurs within amblygonite/montebrasite nodules near the quartz core of the highly fractionated rare-metal Li/Be/Ta pegmatite at Rubicon, Karibib, Namibia. Electron microprobe analyses show that manganotantalite lamellae are variable in composition. Primary microlite (Ta2O5 82%, 1.97 Ta a.p.f.u.) forms the matrix mineral between the lamellae. Textural relations suggest an exsolution origin for the lamellae. Manganotantalite is represented by three generations: (1) primary late magmatic; (2) disequilibrium exsolution lamellae; and (3) subsolidus replacement. Crystallization commenced with primary microlite and likely simultaneous intergrowth between ferrotapiolite and a first generation of late-magmatic primary manganotantalite with low Ta (1.1—1.5 a.p.f.u.). On cooling this was followed by exsolution of manganotantalite lamellae, generation (2) with low—medium Ta (1.27—1.7 a.p.f.u.). The replacement of microlite by a highly fractionated late-stage melt rich in Mn2+, Ca2+ with low Na+ finally produces a third generation (3) of manganotantalite with high Ta (1.72—1.99 a.p.f.u.) at the contact with microlite. Native bismuth and bismutite cut across microlite and pseudomorph lamellae as a final hydrothermal replacement. Apatite is ubiquitous at the contact with amblygonite. The stability field of microlite may be extended by incorporation of CaTa2O6-rynersonite and Ca2Ta2O7 — idealized, components in solid solution. However, rynersonite-CaTa2O6 with distorted octahedra has some structural templates which are similar to the structure of pyrochlore (microlite). Hence, via the perovskite/pyrochlore analogy, hypothetical exsolution of manganotantalite-type structures may occur from a microlite (pyrochlore) host by solid-state diffusion via metastable rynersonite-type intermediates. Such a mechanism has the potential to explain the crystallographically controlled intergrowth textures and the compositional heterogeneity.
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46

Zarkadas, Dimitrios M., and Kamalesh K. Sirkar. "Solid Hollow Fiber Cooling Crystallization." Industrial & Engineering Chemistry Research 43, no. 22 (October 2004): 7163–80. http://dx.doi.org/10.1021/ie0401004.

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Ettouney, R. S., and M. A. El-Rifai. "Indirect Cooling Crystallization Process Analysis." Chemical Engineering Research and Design 85, no. 11 (January 2007): 1476–84. http://dx.doi.org/10.1205/cherd07052.

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48

Gros, Håkan, Teuvo Kilpiö, and Juha Nurmi. "Continuous cooling crystallization from solution." Powder Technology 121, no. 1 (November 2001): 106–15. http://dx.doi.org/10.1016/s0032-5910(01)00382-5.

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49

Liszi, Ilona, Tibor Blickle, and János Liszi. "Homogeneous nucleation in cooling crystallization." Crystal Research and Technology 20, no. 10 (October 1985): 1309–15. http://dx.doi.org/10.1002/crat.2170201004.

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Choong, K. L., and R. Smith. "Optimization of batch cooling crystallization." Chemical Engineering Science 59, no. 2 (January 2004): 313–27. http://dx.doi.org/10.1016/j.ces.2003.09.025.

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