Formation and Properties of Organic Long Persistent Luminescence Crystals Containing Benzidine Derivatives by Melt Crystallization

Organic molecules that exhibit long persistent luminescence (LPL) are rapidly gaining attention for a variety of applications. In this study, organic molecules with simple structures were selected and organic long persistent luminescence (OLPL) crystals were prepared. The crystal structure of the prepared OLPL crystal was elucidated and the guideline for the design of OLPL crystal was clarified. LPL was observed in OLPL crystals prepared with TMB as the guest molecule and 1,2-bis(diphenylphosphino)ethane as the host molecule. XRD measurements of the OLPL crystals suggest that the guest molecule is a solid solution substituted in the stable crystal structure of the host molecule in a lattice-shrinking direction.

CRYSTALLIZATION AND MELTING OF POLY(ETHYLENE OXIDE)CONFINED IN NANOSTRUCTURED PARTICLES WITH CROSS-LINKED SHELLS OF POLYBUTADIENE

Small fixed aggregates of a poly(ethylene oxide)-block-polybutadiene diblock copolymer(PEO-b-PB)in THFsolution were obtained by adding a selective solvent for PB blocks,followed by cross-linking the PB shells.Themorphologies of the nanostructured particles with a cross-linked shell were investigated by atomic force microscopy andtransmission electron microscopy.The average behaviors of the PEO crystallization and melting confined within thenanostructured particles were studied by using differential scanning calorimetry experiments.For the deeply cross-linkedsample(SCL-1),the crystallization of the PEO blocks was fully confined.The individual nanoparticles only crystallized atvery low crystallization temperatures(T_cs),wherein the homogenous primary nucleation determined the overallcrystallization rate.For the lightly cross-linked sample(SCL-2),the confinement effect was T_c dependent.At T_c(?)42℃,thecrystallization and melting behaviors of SCL-2 were similar to those of the pure PEO-b-PB diblock copolymer.At T_c>42℃,SCL-2 could form PEO lamellae thicker than those of the pure PEO-b-PB crystallized at the same T_c.

Optimization of Parameters for Melt Crystallization of p-Cresol

Laboratory-scale experiments were carried out to evaluate the influences of operational parameters on the melt crystallization efficiency for p-cresol purification.The optimal crystallization conditions were determined:dynamic pulsed aeration at 90 L·h-1 and the cooling rate of 0.6-0.8 ℃·min-1,followed by sweating at 0.2-0.3 ℃·min-1 for 40 min.Results also demonstrate that the melt crystallization efficiency is sensitive to feed concentration,which highlights this technology for separation and purification of high purity products.

Purification and separation of durene by static melt crystallization

The purification and separation of durene from the mixture containing durene isomers were studied.Since the boiling points of tetramethyl benzene isomers are very close but their melting points are of great differences,static melt crystallization was applied to separate and purify durene from its isomers.Crystallization experiments were carried out under various operating conditions.The effects of cooling rate,crystallization temperature,sweating temperature and sweating time on the yield and purity of crystal were investigated.Orthogonal experimental design method was adopted to analyze the factors that may affect the yield of durene.Under the optimal crystallization conditions,the purity of durene could reach as high as 99.06%with the yield of 75.3%through one crystallization process.By fitting purification data based on sweating time in isothermal operations,the purification rate coefficient was obtained.

Formation of anorthosite on the Moon through magma ocean fractional crystallization

Lunar anorthosite is a major rock of the lunar highlands,which formed as a result of plagioclasefloatation in the lunar magma ocean（LMO）.Constraints on the sufficient conditions that resulted in the formation of a thick pure anorthosite（mode of plagioclase 〉95 vol.%） is a key to reveal the early magmatic evolution of the terrestrial planets.To form the pure lunar anorthosite,plagioclase should have separated from the magma ocean with low crystal fraction.Crystal networks of plagioclase and mafic minerals develop when the crystal fraction in the magma（φ） is higher than ca.40-60 vol.%,which inhibit the formation of pure anorthosite.In contrast,when φ is small,the magma ocean is highly turbulent,and plagioclase is likely to become entrained in the turbulent magma rather than separated from the melt.To determine the necessary conditions in which anorthosite forms from the LMO,this study adopted the energy criterion formulated by Solomatov.The composition of melt,temperature,and pressure when plagioclase crystallizes are constrained by using MELTS/pMELTS to calculate the density and viscosity of the melt.When plagioclase starts to crystallize,the Mg~# of melt becomes 0.59 at 1291 C.The density of the melt is smaller than that of plagioclase for P 〉 2.1 kbar（ca.50 km deep）,and the critical diameter of plagioclase to separate from the melt becomes larger than the typical crystal diameter of plagioclase（1.8-3 cm）.This suggests that plagioclase is likely entrained in the LMO just after the plagioclase starts to crystallize.When the Mg~# of melt becomes 0.54 at 1263 C,the density of melt becomes larger than that of plagioclase even for 0 kbar.When the Mg~# of melt decreases down to 0.46 at 1218 C,the critical diameter of plagioclase to separate from the melt becomes 1.5-2.5 cm,which is nearly equal to the typical plagioclase of the lunar anorthosite.This suggests that plagioclase could separate from the melt.One of the differences between the Earth and the Moon is the presence of water.If the terrestrial magma ocean was saturated with H_2O,plagioclase could not crystallize,and anorthosite could not form.

Optimization of heat shield for single silicon crystal growth by using numerical simulation

In integrated circuit-grade single silicon Czochralski growth, the position and material of heat shield are main parameters affecting the heat exchange and crystal growth condition. By optimizing the above parameters, we attempted to increase the growth rate and crystal quality. Numerical simulation proved to verify the results before and after optimization. Through analyses of the temperature and microdefect distribution, it is found that the optimized heat shield can further increase the pulling rate and decrease the melt/crystal interface deflection, increase the average velocity of argon flow from ~2 to ~5 m&middots-1, which is in favor of the transportation of SiO, and obtain the low defects concentration crystal and that the average temperature along the melt-free surface is 8 °C higher than before avoiding supercooled melt effectively. © The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2012.

INFLUENCE OF EXTERNAL MAGNETIC FIELD ON THE FLOW FIELD IN MOLTEN SEMICONDUCTOR OF CZOCHRALSKI CRYSTAL GROWTH——A NUMERICAL SIMULATION

Numerical results show that an external magnetic field may influence significantly the flow pattern in the molten semiconductor of Czochralski crystal growth. The melt flow could be pronouncedly damped by a magnet. ic field with the intensity of several thousands Gauss, while the temperature field is affected only in a less extent by the magnetic field.

Growth and Spectral Characterization of Nd^(3+):Sr_(0.7)Ca_(0.3)_3Y(BO_3)_3 Crystal

A Nd3＋：（Sr0.7Ca0.3）3Y（BO3）3 crystal with dimensions of Ф17×23 mm3 has been grown by the Czochralski method. The spectroscopic characterization of Nd3＋：（Sr0.7Cao.3）aY（BO3）3 crystal was investigated. The polarized absorption cross-sections of Nda＋：（Sr0.7Ca0.3）aY（BO3）3 crystal are 2.81×10-20 cm2 with full width at half maximum （FWHM） of 14 nrn at 808 nm for σ-polarization and 2.04×10-20 cm2 with FWHM of 19 nm at 807 nm for 7r-polarization, respectively. The polarized emission cross-sections of Nd3＋（Sr0.7Ca0.3）3Y（BO3）3 crystal are 12.2× 10.20 cm2 at 1062 nm for the π-polarization and 13.6×10-20 crn2 at 1061 nm for the a-polarization, respectively. After the Ca2＋ ion partly substitutes for Sr2＋ ion in the Sr3Y（BO3）3 crystal to form the （Sr0.7Ca0.3）3Y（BO3）3 solid solution, it can improve the quantum efficiency η of Nd3＋：（Sr0.7TCa0.3）3Y（BO3）3 crystal. The quantum efficiency is 31.7%. These results may be regarded Nd3＋：（Sr0.7Ca0.3）3Y（BO3）3 crystal as a potential solid-state laser material.

Study of a Melt Crystallization Process for Seawater Desalination

The work aims to develop a process for freezing desalination of seawater on cold walls. The experiments were performed with water/NaCl solutions of different concentrations and with samples of seawater. The pilot crystallizer consists of a cooled tube immersed in a cylindrical double jacketed tank containing water to be treated. The complete process of desalination is conducted in two steps： the freezing step, leading to the crystallization of the ice layer and the sweating step, which consists of purifying the ice layer in depth by melting the impure zones. The systematic study of the influence of operating parameters has highlighted the important role of the cooling ramp and salinity of the solution on the purity of the ice produced. In the absence of stirring, the temperature of the double jacket also has a noticeable effect on the purity of the ice due to temperature gradients, and consequently, convection currents that may result in the solution. The results of this work show the feasibility of the technique and give a good indication of operating conditions that can be used to produce drinking water.

Organic Melt Crystallization as a Method for Synthesis of Supramolecular Complexes

The most simple method for solventless synthesis of supramolecular complex of CMCR·2BPY·BZP, [CMCR = C-methylcalix[4]resorcinarene, BPY = 4,4'-bipyridine, BZP = benzophenone], is proposed. Although CMCR by itself is high melting point compound (above 300°C), CMCR was found to be dissolved in melt mixture of BPY and BZPeven below 120°C. In the mixture of the three components, the reaction occurs to form CMCR·2BPY·BZP supramolecular complex.

Temperature of Prograde Metamorphism, Decompressional Partial Melting and Subsequent Melt Fractional Crystallization in the Weihai Migmatitic Gneisses,Sulu UHP Terrane:Constraints from Ti-in-Zircon Thermometer

In order to constrain temperature during subduction and subsequent exhumation of fel- sic continental crust, we carried out a Ti-in-zircon thermometer coupled with zircon internal structure and U-Pb age on migmatitic gneisses from the Weihai region in the Sulu ultra-high pres- sure （UHP） metamorphic terrane, eastern China. The Weihai migmatitic gneisses are composed of in- tercalated compositional layers of melanosome and plagioclase （Pl）-rich lencosome and K-feldspar （Kfs）-rich pegmatite veins. Four stages of zircon growth were recognized in the Weihai migmatitic gneisses. They successively recorded informations of protolith, prograde metamorphism, decompres- sional partial melting during early stage exhumation and subsequent fractional crystallization of pri- mary melt during later stage cooling exhumation. The inherited cores in zircon from the melanosome and the Pl-rich leucosome suggest that the pro- tolith of the migmatitic gneiss is Mid- Neoproterozoic （-780 Ma） magmatic rock. Metamorphic zircons with concordant ages ranging from 243 to 256 Ma occur as over- growth mantles on the protolith magmatic zir- con cores. The estimated growth temperatures （625-717 ＂C） of the metamorphic zircons have a negative correlation with their ages, indicating a progressive metamorphism in HP eciogite-facies condition during subduction. Zircon recrystal- lized rims （228-2 Ma） in the PI-rich ieucosome layers provide the lower limit of the decompress-sional partial melting time during exhumation. The ages from 228^-2 to 219~2 Ma recorded in the Pl-rich leucosome and the Kfs-rich pegmatite vein, respectively, suggest the duration of the fractional crystallization of primary melt during exhumation. The calculated growth temperatures of the zircon rims from the Pl-rich leucosome range from 858 to 739 , and the temperatures of new growth zircon grains （219±2 Ma） in Kfs-rich vein are between 769 and 529 . The estimated temperatures have a positive correlation with ages from the Pl-rich leucosome to the Kfs-rich pegmatite vein, strongly indi- cating that a process of fractional crystallization of the partial melt during exhumation.

Preparation of 2,6-diisopropylnaphthalene with recycled process of isomers

2,6-Diisopropylnaphthalene（2,6-DIPN）,as the precursor of important monomer 2,6-naphthalene dicarboxylic acid,was prepared by hydroisopropylation of refined naphthalene with propene over shape-selective catalyst.Naphthalene conversion of 92% and 2,6-DIPN selectivity of 64% were obtained.Static melt crystallization was applied to separate and purify 2,6-DIPN from its isomers,resulted in a product purity of≥99%.The other isomers were converted into monoisopropylnaphthalene,which also reacted with propene to form 2,6-DIPN.A recycled process including hydroisopropylation,separation and transalkylation was established,the yield of 2,6-DIPN based on naphthalene could be doubled by one cycle operation.

Effects of Molecular Weight on the Crystallization and Melting Behaviors of Poly(L-lactide)

In this study, a series of monodispersed poly（L-lactide）（PLLA） were synthesized by the ring-opening polymerization with Schiff base aluminum catalyst, and the effects of the number-average molecular weight（Mn） on the crystallization and melting behaviors of PLLA were investigated by differential scanning calorimetry（DSC） and wide-angle X-ray diffraction（WAXD）. The total crystallization rate of PLLA was Mn-dependent, which reached the maximum value for PLLA with Mn of 18.6 kg/mol. In addition, when Mn of PLLA was 18.6 kg/mol, the melting enthalpy（ΔHm） showed a maximum value（87.1 J/g）, which was the highest reported value till now. The critical temperature for change of crystal formation from ？-form to ？-form crystals increased in the isothermal crystallization process with Mn increasing. In the reheating procedure, high-Mn PLLA demonstrated a small exothermal peak prior to the dominant melting peak, corresponding to crystal transition from ？- to ？-form, but low-Mn PLLA didn＇t show the peak of crystal transition. These different crystallization and melting behaviors were attributed to the different chain mobility of PLLA with different Mn.

块状晶体生长中的输运现象——从数值的非线性分析到工艺的改进

The quality of substrate crystals is critical to the performance of devices used in electronic and optoelectronic applications.These bulk crystals are mostly grown from the melt or solution,with a well controlled solidification or supersaturation,which is affected significantly by the heat and mass flows.Particularly,in the melt growth,the interface kinetics is so fast that the growth is mainly controlled by the transport processes.Hence,the intricate coupling of heat and mass transfer and melt flow strongly influences the grown crystal quality,but its analysis and control is not a trivial task.For most materials,such as semiconductors and oxides,a detailed analysis of the transport processes through experiments is extremely difficult due to the long growth period at high temperature.Therefore,numerical simulation is inevitable.For the past ten years,crystal growth modeling has become one of the most active research fields in materials processing.Indeed,as long as the melt crystal growth of semiconductors remains a mainstay of the microelectronics industry,its modeling continues to be important.In this talk,the role of transport phenomena in bulk crystal growth and their detailed nonlinear analysis are illustrated through our research work over the years.Particular interests will be paid to the zone melting and Bridgman crystal growth.The control of convection and interface shape through external forces,such as rotation,magnetic fields,and vibration will be discussed.Interface instability leading to“pit formation”and interface breakdown due to thermal and solutal flows will also be illustrated.

Purification of 2,6-Diisopropylnaphthalene by Static Melt Crystallization from a Mixture Containing Diisopropylnaphthalene Isomers

2,6-Diisopropylnaphthalene （2,6-DIPN）, as the precursor of important monomer 2,6-naphthalene dicarboxylic acid, could be produced by the shape-selective isopropylation of naphthalene with propene resulting in an isomeric mixture having different alkylation levels. Since the boiling points of DIPNs were very close and the differences of melting points in-between isomers were quite distinctive, the static melt crystallization was applied to separate and purify 2,6-DIPN from its isomers. 2,6-DIPN with purity ≥99% was produced through a process of three stages： crystallization→sweating→melting. The phase diagram of 2,6-DIPN-2,7-DIPN binary system was plotted to opti- mize the temperature control of crystallization. By repeated crystallization of melts with different concentration levels, the yield of pure 2,6-DIPN could be enhanced to 87%. No solvent was necessary. Keywords 2,6-diisopropylnaphthalene, static melt crystallization, crystallization rate, sweating rate, eutectic temperature

White light emission from Dy^(3+)-doped LiLuF_4 single crystal grown by Bridgman method

Lithium lutetium fluoride(LiLuF4) single crystals doped with different Dy3+ ion concentrations were grown by Bridgman method. The Judd-Ofelt(J-O) strength parameters(Ω2, Ω4, Ω6) of Dy3+ in LiLuF4 crystal are calculated according to the measured absorption spectra and the J-O theory, by which the asymmetry of the Dy3+:LiLuF4 single crystal and the possibility of attaining stimulated emission from 4F9/2 level are analyzed. The capability of the Dy3+:LiLuF4 crystal in generating white light by simultaneous blue and yellow emissions under excitation with ultraviolet light is produced. The effects of excitation wavelength and doping concentration on chromaticity coordinates and photoluminescence intensity are also investigated. Favorable CIE coordinates, x=0.319 3 and y=0.349 3, can be obtained for Dy3+ ion in 2.701% molar doping concentration under excitation of 350 nm.

Luminescence of Tb^(3+)/Eu^(3+) codoped LiYF_4 single crystals under UV excitation for white-light LEDs

The absorption spectra, excitation spectra, and emission spectra of Tb3＋/Eu3＋ ions in LiYF4 single crystals synthesized by an improved Bridgman method are measured. The emission spectra of several bands, mainly located at blue^487 nm （Tb：5D4→7F6）, yellowish green ~542 nm （Tb：SD4→ 7F5）, and red ~611 nm （Eu：SD0 → 7F2） wavelengths, are observed under excitation by UV light. An ideal white light emission as a result of simultaneous combination of these emissions can be obtained from 1.11 mol%Tb3＋ and 0.9 mol% Eu3＋ co-doped LiYF4 single crystals with chromaticity coordinates of x = 0.3242, y = 0.3389, color temperature Tc = 5878 K, color rendering index Ra = 77, and color quality scale Qa = 75 under excitation of 384 nm light. The chromaticity coordinate, color rendering index, and color quality scale can be modified by the change of the concentration of rare-earth dopants and the excitation wavelength.

The Effect of Self-nucleation on Isothermal Crystallization Kinetics of Poly(butylene succinate)(PBS) Investigated by Differential Fast Scanning Calorimetry

Differential fast scanning calorimetry（DFSC） was employed on the study of self-nucleation behavior of poly（butylene succinate）（PBS）.The ultra-fast cooling ability of DFSC allows investigating the effect of self-nucleation on the isothermal crystallization kinetics over a wide temperature range.Crystallization half-time,instead of crystallization peak temperature,was used to describe the self-nucleation behavior,and the self-nucleation domain for the samples crystallized at different temperatures was determined.Due to the competition between homogenous nucleation and self-nuclei,the effect of self-nucleation was less pronounced at high supercooling than that for the sample isothermally crystallized at higher temperature.An efficiency scale to judge the efficiency of nucleating agents from the crystallization half-time was also introduced in this work.

Permeability analysis and seepage process study on crystal layer in melt crystallization with fractal and porous media theory

In this paper a porous media seepage model was applied to analyze the permeability and study the seepage process of crystal pillar formed in the preparation of electronic grade phosphoric acid(EGPA).By inspecting the seeping process,the structure parameter of crystal pillar could be obtained.Two basic ideal models(perfectly separated model and perfectly connected model)were presented and a characterized factorφwas introduced to modify the model.A good simulation result was obtained which met the experiment result well.The relationship betweenφand permeability were also discussed.The characterized factorφshowed potential application on optimizing process.

Kinetic roughening transition and missing regime transition of melt crystallized polybutene-1 tetragonal phase: growth kinetics analysis

The morphology and lateral growth rate of isotactic polybutene-1(it-PB1)have been investigated for crystallization from the melt over a wide range of crystallization temperatures from 50 to 110℃.The morphology of it-PB1 crystals is a rounded shape at crystallization temperatures lower than 85℃,while lamellarsingle crystals possess faceted morphology at higher crystallization temperatures.The kinetic roughening transi-tion occurs around 85℃.The nucleation and growth mechanism for crystallization does not work below 85℃,since the growth face is rough.However,the growth rate shows the supercooling dependence derived from the nucleation and growth mechanism.The nucleation theory seems still to work even for rough surface growth.Possible mechanisms for the crystal growth of this polymer are discussed.