Final Crystallization Products Research Articles

Feldspar crystallization and the behavior of fluorine in the Utagi trachyte, Oki-Dogo, Japan

Anti-rapakivi feldspar phenocrysts of ternary Or–Ab–An compositions in a sheet trachyte from Utagi Pass, Oki-Dogo Island (Sea of Japan), show characteristic lamellar–wavy textures, commonly also with patchy texture. These textures have scales ranging from micrometers to decamicrometers, show narrow variation in composition, and preserve very fine cryptoperthites with high-temperature structural states. Several types of fluorite alignment are developed in the lamellar–wavy–patchy textures. Small fluorite grains (mostly <100 nm in size) are not distributed homogeneously or randomly but are heterogeneously or locally dispersed/clustered. Complex microtextures and alignment of fluorites in groundmass feldspars are also observed. In addition to these occurrences of fluorite, interstitial fluorite is found in the groundmass. Feldspars were examined using an electron microprobe analyzer, a scanning electron microscope, a transmission electron microscope, cathodoluminescence imager spectrometers and a Fourier transform-infrared spectrometer. It is inferred from the obtained data that the feldspar microtextures are products of complex, kinetically controlled magmatic crystallization with predominantly diffusion-controlled resorption reactions under H2O-poor or near-anhydrous conditions, and they are developed in association with the crystallization of groundmass during magma ascent to final emplacement. In addition, fluorite alignments in the phenocrysts and groundmass feldspars are estimated to have formed by diffusion-controlled replacement through interaction with residual melt during magma ascent. The interstitial fluorite was the final crystallization product of the residual melt. These various occurrences of fluorite constitute a valuable record of the behavior of F in natural volcanic systems.

Lithium isotope behavior during magmatic differentiation and fluid exsolution in the Jiajika granite–pegmatite deposit, Sichuan, China

The Jiajika lithium (Li) deposit in Sichuan Province is the largest pegmatite-type Li deposit in China. The petrogenesis and metallogenesis of the Jiajika granitic pegmatites remain debatable. This study presents the Li isotopic compositions of two-mica granites, Li-rich and Li-poor pegmatites, and muscovites in Li-poor and Li-rich pegmatites to unravel the Li enrichment mechanism in the Jiajika deposit. The two-mica granites have a lower average δ7Li values than those of the Li-rich and Li-poor pegmatites. The Li contents of the two-mica granites are almost the same as those of the Li-poor pegmatites but are much lower than those of the Li-rich pegmatites. Muscovites in the Li-rich pegmatites have higher average Li contents and δ7Li values than those of the Li-poor pegmatites. All these results indicate the Jiajika granitic pegmatites were the final products of the extreme fractional crystallization of two-mica granitic magmas rather than direct anatectic melts, and that the Li-poor pegmatites derived from early differentiation of the two-mica granitic magmas before they evolved into Li-rich pegmatites during the late stage of magmatic differentiation. The lower average δ7Li values of the more evolved Li-rich pegmatites compared with the Li-poor pegmatites may have been caused by fluid exsolution and kinetic diffusive fractionation during melt-fluid separation. We discovered that fluid exsolution during melt-fluid separation can cause significant Li isotopic fractionation, with 7Li enriched in a H2O-poor silicate-rich melt system. Considering the crystallization ages of the two-mica granites and granitic pegmatites and other geochemical evidence (e.g., major- and trace-element compositions), the magmatic differentiation and fluid exsolution in the late stage of the granitic magma evolution together with the Li-rich surrounding strata led to the multistage enrichments in lithium, thus contributing to the formation of the Jiajika large Li deposit.

FİLLİPSİT, ERİONİT VƏ ANALSİM SEOLİTLƏRİNİN SİNTEZİ

On the basis of industrial aluminates solution and silica gel have been synthesized zeolites of phillipsite, analcime and erionite. By the method of X-Ray phase andX-Ray spectral analysis have been investigated the phase and chemical composition of the initial reaction masses, intermediate and final crystallization products. It has been studied the influence of the alkalinity of the reaction mass to the crystallization of zeolites.

Phase Stability and Morphology of Gel Grown Crystals: The Case of CdCl2-bpp Polymeric System

A phenomenological study is carried out on a complex two-component diffusion-reacting system in gel, that is, the Cd-1,3-bis(4-pyridyl)propane (Cd-bpp) coordination polymer. The latter can exist in three solid forms, which exploit a 1:1 correspondence among the Cd/bpp ratio, the crystal structure and the crystal morphology (1/2: bipyramids; 2/3: needles; 1/3: plates). The aim was to clarify the role of key physicochemical variables (reactant concentrations, composition of the solvent and density of the transport medium) in determining the chemical nature and the morphology of the final crystallization products. The gel method was tested in a variety of different crystallization configurations, including single and double diffusion techniques. The density of the gel primarily affects the morphology of the synthesized crystals, with denser media favouring the needle-like 2/3 Cd-bpp species and diluted ones the 1/2 Cd-bpp bipyramidal one. However, higher densities of the gel are generally associated to strained crystals. The solvent composition is also important, as for example the 1/2 Cd-bpp bipyramids require at least a minimum amount of ethanol to appear. We demonstrated that in gel the strict “equality” stoichiometric criteria for metal-to-ligand ratios can be sometimes eluded, as non–equilibrium concentrations can be locally attained. In this respect, the crystallization geometry was proven to act as a key tool to influence the crystallization output, as it determines the direction and magnitude of the concentration gradients. Finally, the use of U tubes to perform one-pot screenings of a large part of the crystallization space is discussed.

Morphology-controlled synthesis of boehmite with enhanced efficiency for the removal of aqueous Cr(VI) and nitrates

Boehmite with different morphologies was synthesized using a simple hydrothermal method for the removal of Cr(VI) and nitrates from polluted water. When the pH of the hydrothermal system was changed, the final crystallization products had morphologies of one-dimensional rods or two-dimensional sheets with different sizes. The boehmites were characterized and used for the adsorption of aqueous Cr(VI) and nitrates. Their bulk structure and surface properties significantly changed with the corresponding morphology, which prominently affected their adsorption capacity. Boehmite with a 2D small sheet-like structure showed the highest adsorption capacity (64.7 mg g−1). Moreover, the small sheet-like boehmite showed a remarkable adsorption capacity towards nitrates (74.5–378.5 mg g−1) and maintained a high selectivity to Cr(VI) in the presence of competing anions such as NO3−, and Cl−. The isotherms for Cr(VI) sorption could be better explained using the Langmuir model, indicating a monolayer adsorption of the Cr species, while the isotherms for nitrate sorption followed the Freundlich model, suggesting a multilayer adsorption. The active adsorption sites of boehmite were found to be the Lewis acid sites and surface hydroxyl groups according to the outcomes of the analysis using a series of characterization methods such as IR, Raman and x-ray photoelectron spectra. The unique structure of boehmite is beneficial to adsorb anion containments while maintaining a high selectivity to Cr(VI) species. Because of the multiple Lewis or Brönsted acid sites in boehmite, the Cr(VI) was reduced to less toxic Cr(III) species and immobilized on the surface of boehmite. In consideration of the low-cost and good regeneration capacity, the small sheet-like boehmite would be useful for the removal of anions present in polluted water.

The Influence of Annealing on the Structural and Soft Magnetic Properties of (Fe0.4Co0.6)79Nb₃B18 Nanocrystalline Alloys.

The soft magnetic properties of Fe-based nanocrystalline alloys are determined by their grain size. In the present article, the (Fe0.4Co0.6)79Nb3B18 nanocrystalline alloys have been successfully prepared by isothermal annealing. The variation of soft magnetic properties as a function of annealing temperature and incubation time is investigated in detail. Two distinct crystallization behaviors were found for the (Fe0.4Co0.6)79Nb3B18 alloys. The initial nanocrystallization products comprise a mixture of α-Fe(Co), Fe2B, and Fe23B6-type crystalline metastable phases, and the final crystallization products are composed of α-Fe(Co), Fe2B, and Fe3B crystalline phases. The grain size decreases first and then increases with the increasing annealing temperature in the range of 764–1151 K, and a fine grain size with mean grain size of 12.7 nm can be achieved for alloys annealed at 880 K. As the annealing temperature increases from 764 K to 1151 K, the saturation magnetization increases first and then decreases without a significant increase of the coercivity. The alloys annealed at 880 K exhibit the optimized soft magnetic properties with high Ms of 145 emu g−1 and low Hc of 0.04 Oe.

Continuous crystallization of α-form L-glutamic acid in an MSMPR-Tubular crystallizer system

Continuous crystallization of active pharmaceutical ingredients is of prime significance. A continuous mixed suspension mixed product removal (MSMPR)-tubular crystallizer geometry is designed and optimized to produce the metastable α-form crystals of L-glutamic acid with uniform mean size of 130 µm. The MSMPR is used to produce well-tuned seed crystals that undergo further growth in a series of tubular crystallizers. The effects of the initial supersaturation, stirring speed, nucleation temperature and residence time were optimized in the MSMPR crystallizer to tune the supply of continuous seeds by using the principal component analysis and in-situ particle tracking measurement. The continuous seeds of the desired metastable polymorphic form with specific size ranging from 5.0 to 15.0 µm and number density ranging from 500 to 1500 counts, were transferred to a series of three coiled tubular crystallizers for further growth. In addition, the cooling strategy in the tubular crystallizers was utilized to further optimize the quality of the final crystal product. The crystal size distribution (CSD) in the MSMPR-tubular crystallizer system was compared with a single MSMPR with the same residence time and found to be superior. Finally, a potential scale up strategy of the MSMPR-tubular crystallizer system was proposed for further study.

Crystallization behavior of Ce70−xAl10Cu20Cox (x = 0, 1, 3, 5 at.%) amorphous alloys

The effect of Co addition (substituting for Ce) on crystallization behavior of Ce70Al10Cu20 amorphous alloys has been investigated using X-ray diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM). The Co addition has an obvious effect on topological short-range ordering of Ce–Al–Cu–(Co) amorphous alloys. Moreover, the Co addition can slightly improve the thermal stability of Ce–Al–Cu based amorphous alloys. The 1 and 3 at.% Co additions do not obviously change the crystallization behavior of the Ce–Al–Cu–(Co) amorphous alloys, and the final crystallization products are FCC–CeAlCu(Co)O. However, the 5 at.% Co addition can alter the crystallization behavior of the Ce70Al10Cu20 amorphous alloys. Proper content of Co can effectively suppress the formation of oxide phases during annealing of the Ce–Al–Cu–(Co) amorphous alloys.

Powder X-ray diffraction method for the quantification of cocrystals in the crystallization mixture

Context: The solid state purity of cocrystals critically affects their performance. Thus, it is important to accurately quantify the purity of cocrystals in the final crystallization product.Objective: The aim of this study was to develop a powder X-ray diffraction (PXRD) quantification method for investigating the purity of cocrystals. The method developed was employed to study the formation of indomethacin-saccharin (IND-SAC) cocrystals by mechanochemical methods.Materials and methods: Pure IND-SAC cocrystals were geometrically mixed with 1:1 w/w mixture of indomethacin/saccharin in various proportions. An accurately measured amount (550 mg) of the mixture was used for the PXRD measurements. The most intense, non-overlapping, characteristic diffraction peak of IND-SAC was used to construct the calibration curve in the range 0–100% (w/w). This calibration model was validated and used to monitor the formation of IND-SAC cocrystals by liquid-assisted grinding (LAG).Results: The IND-SAC cocrystal calibration curve showed excellent linearity (R2 = 0.9996) over the entire concentration range, displaying limit of detection (LOD) and limit of quantification (LOQ) values of 1.23% (w/w) and 3.74% (w/w), respectively. Validation results showed excellent correlations between actual and predicted concentrations of IND-SAC cocrystals (R2 = 0.9981).Discussion: The accuracy and reliability of the PXRD quantification method depend on the methods of sample preparation and handling. The crystallinity of the IND-SAC cocrystals was higher when larger amounts of methanol were used in the LAG method.Conclusion: The PXRD quantification method is suitable and reliable for verifying the purity of cocrystals in the final crystallization product.

Phase selection and transition in Hf-rich hafnia-titania nanolaminates

Hf-rich hafnia-titania nanolaminate films with five HfO2-TiO2 bilayer architectures (0.64 to 0.94 Hf atom fraction) were sputter deposited on unheated fused silica substrates, annealed post-deposition from 573 to 1273 K, and analyzed by x-ray diffraction to study phase selection and transition. Isochronal annealing for 1 h intervals from 573 to 1173 K produces weak crystallization into monoclinic (m) HfO2 doped with Ti, i.e., m-Hf1-xTixO2. The amount of Ti incorporated into m-HfO2 depends upon both architecture and overall stoichiometry, but in all but the coarsest architecture, exceeds the bulk solubility limit of x = 0.05. Initial annealing at 1273 K produces significant crystallization into a biphasic structure, m-Hf1-xTixO2 and orthorhombic (o) HfTiO4. From bulk phase equilibrium considerations, o-HfTiO4 is expected to crystallize under conditions of interfacial bilayer mixing. However, upon further annealing at 1273 K, o-HfTiO4 proves to be unstable. o-HfTiO4 demixing inevitably occurs independent of architecture and stoichiometry, resulting in final crystallization products after 96 h at 1273 K that are m-Hf1-xTixO2 with x ≈ 0.05 and TiO2 doped with Hf. We suggest that o-HfTiO4 instability arises from a driving force to form domains similar to those found in the low temperature in/commensurate structures of ZrTiO4. A detailed crystallographic group-subgroup analysis of the o (Pbcn) → m (P21/c) transition shows that these domains can be represented by an orientation twin in the latter structure and their creation can be achieved by a single step second-order phase transition.

Effect of polyacrylic acid and polyethylene glycol on the crystallization of calcium carbonates in the presence of magnesium ions

The effect of polyacrylic acid and polyethylene glycol on the crystallization of calcium carbonates in the presence of magnesium ions was studied. It was found that the presence of magnesium ions in solution and the treatment temperature (80°C) influence the formation of the final products of calcium carbonate crystallization. In binary mixtures, low-molecular-weight polyacrylic acid and polyethylene glycol affect synergistically, and such mixtures can be used for selectively influencing the formation of calcium carbonate polymorphs.

Oriented Aggregation: Formation and Transformation of Mesocrystal Intermediates Revealed

Oriented aggregation is a special case of aggregation in which nanocrystals self-assemble and form new secondary single crystals. This process has been suggested to proceed via an intermediate state known as the mesocrystal, in which the nanocrystals have parallel crystallographic alignment but are spatially separated. We present the first direct observations of mesocrystals with size and shape similar to product oriented aggregates by employing cryo-TEM to directly image the particles in aqueous suspension. The cryo-TEM images reveal that mesocrystals not only form but also transform to the final single crystal product while in the dispersed state. Further, high-resolution cryo-TEM images demonstrate that the mesocrystals are composed of spatially separated and crystallographically aligned nanocrystals.

Effects of 5%Ni addition on thermal stability and crystallization behavior of Mg 65Cu 25Tb 10 bulk metallic glass

The effects of 5%Ni addition on the glass forming ability, thermal stability and crystallization behavior of Mg 65Cu 25Tb 10 bulk metallic glass were investigated using X-ray diffractometry, differential scanning calorimetry and transmission electron microscopy. The small amount of Ni addition reduces the glass forming ability and thermal stability due to a significant decrease in the crystallization activation energy. Analyses of crystallization kinetics give evidence to the existence of quenched-in nuclei in amorphous Mg 65Cu 20Ni 5Tb 10. Final crystallization products are basically same for Mg 65Cu 25Tb 10 and Mg 65Cu 20Ni 5Tb 10.

Crystallization as a Purification Method for Jack Bean Urease: On the Suitability of Poly(Ethylene Glycol), Li2SO4, and NaCl as Precipitants

The purification of urease from jack bean meal by means of extraction and crystallization in the presence of different precipitants has been investigated. Purification with poly(ethylene glycol) proves to be a promising alternative to established methods. Although lower yields and purities were observed when compared to Sumner’s method, a suitable combination of process parameter changes has the potential to match or even exceed the product qualities previously obtained. Moreover, poly(ethylene glycol) shows promise as a washing liquid for the final crystal product. In contrast to extraction and crystallization of urease in the presence of acetone, the additive 2-mercaptoethanol has a detrimental effect upon product quality in the case presented here. The salts lithium sulfate and sodium chloride show no effective selective precipitation or crystallization of jack bean proteins.

Phase transformations in Zr–29.56 at.% Cu–19.85 at.% Ni melt-spun high-temperature shape memory alloy

The present paper focuses on the phase transformations during crystallization of the melt-spun Zr–29.56 at.% Cu–19.85 at.% Ni high-temperature shape memory alloy (HTSMA). This alloy exhibits a martensitic transformation in the bulk polycrystalline state at temperatures above crystallization of the metallic glass with the same composition. The crystallization kinetics were investigated by differential scanning calorimetry. The intermediate and final products of crystallization for this HTSMA were studied by means of transmission electron microscopy. The chain of the transformations starting from crystallization and ending at martensitic transformation will be described. Perspectives of the thin film production of Zr-based HTSMA will be discussed.

Structural evolution in the supercooled liquid of Zr36Ti24Be40 metallic glass

Local atomic structural changes associated with the exothermic heat flow in the supercooled liquid of Zr36Ti24Be40 metallic glass have been studied by using pair distribution function analysis. The exothermic heat flow that used to be interpreted as double glass transition is attributed to the evolution of short range ordering towards the final crystallization product in the supercooled liquid.

A study of the crystallization behavior of an amorphous Fe 77.5Si 13.5B 9 alloy

The crystallization behavior of an amorphous Fe 77.5Si 13.5B 9 alloy was studied by means of DSC, XRD, TEM, EDX and VSM techniques. Crystallization induced by heat treatment resulted in the formation of a Fe–Si phase with an unusual morphology: the branches of the dendrite were composed of closely spaced crystals, the spacing of such crystals was of the order of nanometer. Due to this dendritic morphology, the products of secondary crystallization grew not only among the dendritic branches but also within the dendrites at the interfaces of the closely spaced crystals. The products of secondary crystallization have a striped morphology and consist of the Fe–Si phase with B2 ordered structure and the Fe 3B phase. The final products of crystallization were the striped structure composed of the Fe–Si, Fe 2B and the Fe 3B phases. The Fe–Si phase was also found in the form of large crystals. The magnetization values showed little change as annealing time and temperatures were increased while the coercivity increased significantly due to the formation of the Fe 3B and Fe 2B phase.

Thermal dehydration of dipotassium tetraborate tetrahydrate and crystallization of amorphous dehydration product

As one of the typical examples of producing an amorphous dehydration product, the thermal dehydration process of K2B4O7·4H2O was subjected to thermoanalytical and morphological studies. An anhydrous glass was formed via three distinguished dehydration stages. The overall thermal dehydration process was characterized as a self-induced sol-gel process to form anhydrous glass. The as produced anhydrous glass exhibited glass transition at around 700 K and subsequently crystallized via two consecutive exothermic peaks at around 770 and 900 K. The final crystallization product, triclinic K2B4O7, melted at 1072 K.

Crystallization and structural relaxation of Fe78?xPtxB10Si12metallic glasses

Fe78−xPtxB10Si12 (x = 0, 5, 15, 25) metallic glasses were produced to investigate the effects of Pt on the thermally annealed microstructure and ensuing magnetic properties of the alloy. The Pt addition progressively lowered the glass stability and accelerated the onset of devitrification. Final crystallization products contained either Fe3Pt or FePt, depending on the Pt content together with Fe-borides. A maximum coercivity of 1140 Oe was obtained with the Fe63Pt15B10Si12 alloy annealed at 500 °C due to the precipitation of elongated FePt crystals. Measurements of the saturation magnetization of the annealed alloys gave an indication that the amorphous structure may have undergone structural relaxation prior to devitrification. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Structure and magnetic properties of thermally annealed Fe 73Pt 5B 10Si 12 amorphous metallic alloy

Fe 73Pt 5B 10Si 12 metallic glass was prepared to investigate the crystallization and ensuing changes in magnetic properties of the Fe-rich amorphous alloy. The Fe 73Pt 5B 10Si 12 alloy crystallized at 470 °C which was 50 °C below the crystallization temperature of the Pt-free Fe 78B 10Si 12. In addition, the Pt addition led to nucleation of Fe 3Pt compound in the final crystallization product of the amorphous alloy. Saturation magnetization of the Fe 73Pt 5B 10Si 12 alloy increased substantially when annealed below the crystallization temperature, which led us believe that the amorphous alloy underwent a structural change. The Pt addition had far reaching effects on the amorphous structure of the Fe-rich glass as well as on the magnetic properties of the annealed alloy.