Primary Crystal Growth Research Articles

Synthesis, characterization, and performance evaluation of AA/AMPS copolymers with different molecular weights and explanation of the inhibition mechanism of calcium carbonate and calcium sulfate

Polymeric scale inhibitors are widely acknowledged for their eco-friendliness, strong compatibility, and versatile nature. However, the impact of molecular weight variation on their inhibitory efficacy remains a relatively understudied aspect. In this investigation, AA/AMPS copolymers with distinct molecular weights (1000, 2000, 3000, 4000, 5000, 6000) were synthesized and probed for their influence on mineral scale inhibition across diverse water quality parameters (e.g., calcium ion concentration, pH) and process conditions (e.g., temperature, duration). Concurrently, the crystalline and morphological alterations of AA/AMPS during mineral scale inhibition were delved. By integrating molecular dynamics simulations and quantum chemical calculations, the effects of varying molecular weights of AA/AMPS on mineral scale inhibition were scrutinized. Moreover, the inhibition mechanism was thoroughly explored. Our findings revealed that AA/AMPS with molecular weights of 2000 and 3000 exhibited superior inhibition efficacy against calcium carbonate and calcium sulfate. This phenomenon was attributed to the movement velocity and binding energy of AA/AMPS with corresponding molecular weights towards the primary crystal growth surface. Additionally, the carboxyl oxygen atoms on the polymers facilitated chelation with calcium ions, thereby impeding further crystal formation and growth. Consequently, achieving heightened efficiency in scale inhibition.

The capturing and decompression of melt inclusions in olivine and ilmenite megacrysts from the Monastery kimberlite, South Africa

Ilmenite and olivine megacrysts from the 89 Ma Monastery kimberlite (Kaapvaal Craton, South Africa) captured abundant and large melt inclusions containing quenched Si-Mg-rich melt, calcite, spinel, perovskite, phlogopite, and serpentine. Textural observations and 3D X-ray tomography of ilmenite and olivine megacrysts show melt inclusion shapes, sizes and distribution patterns indicative of melt capture during primary crystal growth near the base of the subcontinental lithospheric mantle (SCLM). Patterns supporting secondary melt injection along fractures or veins, such as planar arrays of melt inclusions, are absent. Melt inclusions in olivine, in some examples reaching the dimension of centimetres, likely were captured in skeletal voids forming in fast growing, up to decimetre-sized olivine megacrysts. These large melt inclusions commonly decrepitated, forming apophyses, radial fractures, and veins, along which residual volatile- and Si-Mg-rich melt was extracted. We attribute the decrepitation of melt inclusions in olivine to the rapidly increasing difference between the melt pressure in the inclusions, captured at mantle depth, and the decreasing confining stress to which the host olivines were exposed during magma ascent and after emplacement. In ilmenite, melt inclusions up to ∼ 6 mm in diameter remained commonly intact during the kimberlite ascent from its mantle source to the shallow crust. The quenched silicate melt in olivine- and ilmenite-hosted melt inclusions, in some places preserved as unaltered hydrous and CO3-bearing glass, shows systematic major element compositional variations that suggest that this melt formed by similar fractionation and depletion processes, irrespective of the hosting megacryst phase. Apparent modal variations in quenched silicate melt, calcite, and oxide contents suggest that the melt batches captured as inclusions in ilmenite and olivine either record different evolution stages in the megacryst magma, or document compositional heterogeneities in this magma at the time of megacryst growth.

An Approximate Model of the Process of Non-Dendritic Morphology Formation in Solidification of Binary Melt under Stirring

The primary crystal growth in a binary melt is modeled on the base of the phase field method with approximate consideration of melt stirring. Changes in the second component (solute) concentration near a solidification area during stirring are considered as a main reason of modification of dendritic morphology of crystals. An effect of stirring is approximately simulated as forced changes in the solute concentration by either resetting to initial concentration, or averaging concentration. Dendritic morphology is shown to change to rosette and then to globular one depending on space parameters of forced changes.

Modelling of the microstructure formation during solidification of binary alloy Al–Si under stirring

The growth of primary crystals from a supercooled binary melt is modeled on the basis of the phase-field method with an approximate consideration for melt stirring. Changes in the concentration of the solute in the melt near the solidification region due to stirring are considered as the main reason for modifying the dendritic morphology of the crystals. The stirring effect results in a partial removal of the melt with an increased solute concentration from the region near the interface, which is called washout in the work. This effect is approximately modeled as a forced periodic replacement of the current high solute concentration in this region either at the initial concentration or at the averaged concentration in the melt. In this paper, we propose a new algorithm for choosing such a correction region, which can be used for a small intensity of stirring. A value is introduced to describe the washout intensity-the washout parameter. It is shown that when washed away dendritic morphology passes into a rosette morphology, depending on the intensity of stirring. A numerical analysis of the growth of perturbations on the surface of the initial embryo of a circular crystal is carried out. The main differences in the development of such perturbations are shown, which leads to a non-dendritic morphology of the crystal. The growth of additional branches is demonstrated due to a decrease in the solute concentration near the center of the crystal. Calculations have been performed for the case of crystal growth with a decrease in washout intensity with growth time. For this case, the secondary arms grow on additional branches growing from the center of the crystal. It is shown that at a constant value of the washout intensity near the surface of a growing crystal, only two types of morphology are possible from a small round embryo, dendritic and rosette. At the same time, if the crystal already has a rosette morphology, it is retained and with its further growth with a decrease in the washout intensity.

Investigation of the processing conditions for the synthesis of rod-shaped LiCoO2

We investigate the processing conditions for the synthesis of rod-shaped LiCoO2 (LCO) by a solid-state calcination of a precursor material which was prepared by a hydrothermal method. The rod-like morphology appeared to be easily broken due to the growth of primary crystals recrystallized during the calcination process. Therefore, it is crucial to maintain the temperature under a certain limit. However, the temperature must be high enough to obtain proper crystallinity of the LCO, ideally above 800 °C. Thus, we determined the optimal calcination temperature condition from the common range of temperatures that satisfies both these limiting conditions. The precursor with average diameter of ~ 1 µm sustained the rod shape at calcination temperatures of up to 900 °C; therefore, the optimum calcination temperature could be determined between 800 and 900 °C. Whereas, a proper calcination temperature could not be found for the precursor with ~ 500 nm of diameter because the rod shape did not maintain even at 700 °C. Thus, the maximum temperature at which the rod shape is retained decreases with smaller diameter of the precursor rods, indicating adjusting the diameter above a limiting value is necessary to prepare LCO rod by conventional solid state calcination.

Two-Dimensional Raman Correlation Spectroscopy Study of Poly[(R)-3-hydroxybutyrate- co-(R)-3-hydroxyhexanoate] Copolymers.

Two-dimensional correlation analysis was applied to the time-dependent evolution of Raman spectra during the isothermal crystallization of bioplastic, poly[(R)-3-hydroxybutyrate- co-(R)-3-hydroxyhexanoate] or PHBHx copolymer. Simultaneous Raman measurement of both carbonyl stretching and low-frequency crystalline lattice mode regions made it possible to carry out the highly informative hetero-mode correlation analysis. The crystallization process of PHBHx involves: (1) the early nucleation stage; (2) the primary growth of well-ordered crystals of PHBHx; and (3) the secondary crystal growth phase. The latter stage probably occurs in the inter-lamellar region, with an accompanying reduction of the amorphous component, which occurs most dominantly during the primary crystal growth. The development of a fully formed lamellar structure comprising the 21 helices occurs after the primary growth of crystals. In the later stage, secondary inter lamellar space crystallization occurs after the full formation of packed helices comprising the lamellae.

Investigation on Viscosity and Nonisothermal Crystallization Behavior of P-Bearing Steelmaking Slags with Varying TiO2 Content

The viscous flow and crystallization behavior of CaO-SiO2-MgO-Al2O3-FetO-P2O5-TiO2 steelmaking slags have been investigated over a wide range of temperatures under Ar (High purity, >99.999 pct) atmosphere, and the relationship between viscosity and structure was determined. The results indicated that the viscosity of the slags slightly decreased with increasing TiO2 content. The constructed nonisothermal continuous cooling transformation (CCT) diagrams revealed that the addition of TiO2 lowered the crystallization temperature. This can mainly be ascribed to that addition of TiO2 promotes the formation of [TiO6]-octahedra units and, consequently, the formation of MgFe2O4-Mg2TiO4 solid solution. Moreover, the decreasing viscosity has a significant effect on enhancing the diffusion of ion units, such as Ca2+ and [TiO4]-tetrahedra, from bulk melts to the crystal–melt interface. The crystallization of CaTiO3 and CaSiTiO5 was consequently accelerated, which can improve the phosphorus content in P-enriched phase (n2CaO·SiO2-3CaO·P2O5). Finally, the nonisothermal crystallization kinetics was characterized and the activation energy for the primary crystal growth was derived such that the activation energy increases from −265.93 to −185.41 KJ·mol−1 with the addition of TiO2 content, suggesting that TiO2 lowered the tendency for the slags to crystallize.

Influence of Cooling Roll Roughness on Nucleation and Growth of Primary Crystals in Strip Cast NdFeB Alloy

Influence of Cooling Roll Roughness on Nucleation and Growth of Primary Crystals in Strip Cast NdFeB Alloy

Influence of Cooling Roll Roughness on Nucleation and Growth of Primary Crystals in Strip Cast NdFeB Alloy

Influence of Cooling Roll Roughness on Nucleation and Growth of Primary Crystals in Strip Cast NdFeB Alloy

Structural Design Parameters for Highly Birefringent Coordination Polymers.

A series of coordination polymer materials incorporating the highly anisotropic 2-(2-pyridyl)-1,10-phenanthroline (phenpy) building block have been synthesized and structurally characterized. M(phenpy)[Au(CN)2]2 (M = Cd, Mn) are isostructural and form a 1-D chain through bridging [Au(CN)2](-) units and extend into a 2-D sheet through aurophilic interactions. M(phenpy)(H2O)[Au(CN)2]2·2H2O (M = Cd, Mn, and Zn) are also isostructural but differ from the first set via the inclusion of a water molecule into the coordination sphere, resulting in a 1-D topology through aurophilic interactions. In(phenpy)(Cl)2[Au(CN)2]·0.5H2O forms a dimer through bridging chlorides and contains a free [Au(CN)2](-) unit. In the plane of the primary crystal growth direction, the birefringence values (Δn) of 0.37(2) (Cd(phenpy)[Au(CN)2]2), 0.50(3) (In(phenpy)(Cl)2[Au(CN)2]·0.5H2O), 0.56(3) and 0.59(6) (M(phenpy)(H2O)[Au(CN)2]2·2H2O M = Cd and Zn, respectively) were determined. β, a structural parameter defined by phenpy units rotated in the A-C plane relative to the light propagation (C) direction, was found to correlate to Δn magnitudes. The addition of a carbon-carbon double bond to terpy has increased the molecular polarizability anisotropy of the building block, and all structures have reduced deviation from planarity in comparison to terpy and terpy derivative structures, leading to these higher Δn values, which are among the highest reported for crystalline solids.

Supramolecular Assembly of Bis(benzimidazole)pyridine: An Extended Anisotropic Ligand For Highly Birefringent Materials

Four new bis(benzimidazole)pyridine (BBP)-containing compounds Zn(BBP)Cl[Au(CN)2], Mn(BBP)[Au(CN)2]2·H2O, Mn(BBP)Br2(MeOH) and Mn(BBP)Cl2(MeOH)·MeOH have been synthesized and structurally characterized and their birefringence values (Δn) determined. The structure of Zn(BBP)Cl[Au(CN)2] contains a hydrogen-bonded dimer of Zn(BBP)Cl[Au(CN)2] units which propagate into a 1D chain through Au-Au interactions, although the crystals are of poor optical quality. The supramolecular structure of Mn(BBP)[Au(CN)2]2·H2 O forms a 1D coordination polymer through chains of Mn(BBP)[Au(CN)2]2 units, each containing one bridging Au(CN)2 and one forming a 2D sheet through Au-Au interactions. The supramolecular structures of Mn(BBP)Br2(MeOH) and Mn(BBP)Cl2(MeOH)·MeOH are very similar, consisting of a complex hydrogen-bonded network between NH imidazole, methanol and halide groups to align BBP building blocks. In the plane of the primary crystal growth direction, the birefringence values of the three Mn-containing materials were Δn=0.08(1), 0.538(3) and 0.69(3), respectively. The latter two birefringence values are larger than in the related 2,2';6'2''-terpyridine systems, placing them among the most birefringent solids reported. These compounds illustrate the utility of extending the π-system of the building block and incorporating hydrogen-bonding sites as design elements for highly birefringent materials and also illustrates the effect on the measurable birefringence of the crystal quality, growth direction and structural alignment of the anisotropic BBP building blocks.

Poly(butylene terephthalate)/montmorillonite nanocomposites: Effect of montmorillonite on the morphology, crystalline structure, isothermal crystallization kinetics and mechanical properties

Nanocomposites (PCNs), based on poly(butylene terephthalte) (PBT) and organoclay (Cloisite-15A) MMT were prepared by melt intercalation compounding process. The nanoscale dispersion and the microcrystal structure studied qualitatively using; X-ray diffraction (XRD) and electron microscopy (SEM, TEM and AFM). The XRD results indicated that the crystal size is highly dependent on the crystallization temperature. The isothermal crystallization kinetics of PBT in PCNs analysis indicated that the overall crystallization of PBT involved heterogeneous nucleated three-dimensional spherical primary crystallization growth process. The crystallization rate, however, is dependent on the PCN-composition, crystallization temperature and the dispersion state of clay in PCNs. Further analysis, based on Hoffman-Lauritzen theory revealed that the neat PBT and PBT in PCNs crystallization follow regime-II kinetics for temperature 195°C–205°C and enters the regime-III kinetics in lower Tc range, 185°C–195°C. The improvement in mechanical properties is highly dependent on the level of clay exfoliation in PBT matrix.

Solidification of Magnesium (AM50A) / vol%. SiCp composite

Magnesium matrix composite is one of the advanced lightweight materials with high potential to be used in automotive and aircraft industries due to its low density and high specific mechanical properties. The magnesium composites can be fabricated by adding the reinforcements of fibers or/and particles. In the previous literature, extensive studies have been performed on the development of matrix grain structure of aluminum-based metal matrix composites. However, there is limited information available on the development of grain structure during the solidification of particulate-reinforced magnesium. In this work, a 5 vol.% SiCp particulate-reinforced magnesium (AM50A) matrix composite (AM50A/SiCp) was prepared by stir casting. The solidification behavior of the cast AM50A/SiCp composite was investigated by computer-based thermal analysis. Optical and scanning electron microscopies (SEM) were employed to examine the occurrence of nucleation and grain refinement involved. The results indicate that the addition of SiCp particulates leads to a finer grain structure in the composite compared with the matrix alloy. The refinement of grain structure should be attributed to both the heterogeneous nucleation and the restricted primary crystal growth.

Crystallisation of iron containing glass–ceramics and the transformation of hematite to magnetite

Crystallisation of a glass with the composition 16Na2O·10CaO·49SiO2·25Fe2O3 led to the formation of hematite and magnetite crystals with various morphologies. Crystals containing both the hematite and the magnetite phases were detected and a strict orientation relationship between the phases is described. It is argued that hematite (Fe2O3) is the phase primarily crystallised and magnetite (Fe3O4) is the result of a phase transformation after the primary crystal growth. The main method of characterization was scanning electron microscopy (SEM) combined with electron backscatter diffraction (EBSD).

Highly Birefringent Cyanoaurate Coordination Polymers: The Effect of Polarizable C−X Bonds (X = Cl, Br)

Four new coordination polymers, Mn(Clterpy)[Au(CN)(2)](2) (Clterpy = 4'-chloro-2,2';6',2''-terpyridine), Mn(Brterpy)[Au(CN)(2)](2) (Brterpy = 4'-bromo-2,2';6',2''-terpyridine), Pb(Clterpy)[Au(CN)(2)](2), and Pb(Brterpy)(mu-OH(2))(0.5)[Au(CN)(2)](2) were synthesized and structurally characterized, and their birefringence values were measured. The supramolecular structures of the two Mn(II) polymers are the same: they form one-dimensional (1D) chains of Mn(Xterpy)[Au(CN)(2)](2) units (X = Cl, Br), each having one bridging and one terminal Au(CN)(2)(-). The Pb(II) analogues form 1D polymers containing chains of Pb(Xterpy)[Au(CN)(2)](+) linked via Au(CN)(2)(-) units. Pb(Brterpy)(mu-OH(2))(0.5)[Au(CN)(2)](2) also contains a bridging water unit. In the plane of the primary crystal growth direction, the birefringence values of the four coordination polymers were found to be 0.378(19), 0.50(3), 0.38(2), and 0.26(3), respectively. The birefringence values are related to the supramolecular structures in terms of maximizing the alignment of the terpyridine-based units and the maximum off-axis positioning of the C-X bonds. With the exception of that for the Pb(Brterpy)(mu-OH(2))(0.5)[Au(CN)(2)](2) polymer, the birefringence values are either as large as or significantly larger than in the related M(2,2';6',2''-terpyridine)[Au(CN)(2)](2) systems. These polymers illustrate the utility of adding polarizable carbon-halogen bonds as a design element in highly birefringent coordination polymers.

Primary crystal growth during spherical agglomeration in liquid: designing an ideal dry powder inhalation system

Spherical agglomerates of steroid KSR-592, consisting of fine primary drug crystals suitable for dry powder inhalation (DPI), were prepared by the spherical agglomeration method in liquid with a bridging liquid. It was found that the particle size of primary crystals increased until the dispersing medium was saturated with the bridging liquid introduced to the system, whereas the spherical agglomeration of primary crystals continued even after the saturation. The growth rates of primary crystals and agglomerates increased with an increase in the temperature and/or a reduction in the agitation speed of the system. The growth of primary crystals in the spherical agglomerates was explained by a crystallization and fusion mechanism proposed by us. The primary crystals were mechanically stronger than their agglomerates so that the agglomerates were disintegrated easily into the primary crystals, which retained their original size, under the shear force generated on being mixed with carrier particles for DPI.

Primary Solidification in Aluminum Alloys under Melt Overheating

We examined the effect of melt overheating on primary solidification in aluminum alloys of various systems. The alloys were poured from the temperature of overheating, and no special treatment of the melt was performed. We assessed the sizes of equiaxed and columnar grains or primary crystals and the size of dendritic cells. The experimental results show that the size of main primary crystals depends nonlinearly on the overheating temperature. One can observe the growth of primary crystals and their following refinement, the latter occurring at considerably high pouring temperatures depending on the alloy composition and the cooling rate. The observed results were interpreted in terms of the formation of solidification nuclei upon decomposition of a supersaturated during undercooling liquid solution (melt).

The effect of fluoride on the size and morphology of apatite crystals grown from physiologic solutions.

In adult human bone, fluoride uptake is accompanied by an increase in apatite crystal size. This increase, however, is not isotropic but is restricted primarily to growth in width and/or thickness, with no measurable change in length. In the present study, seeded growth experiments were conducted in vitro to determine whether this anisotropic effect is physicochemical in origin, i.e., a direct result of F- selectively enhancing lateral crystal growth, or is an indirect consequence of F--induced alterations in cellular function and matrix development. The growth reactions were maintained at 37 degrees C under physiologic-like solution conditions (1.33 mmol/liter Ca2+, 1.0 mmol/liter total phosphate, 0 or 26 mmol/liter carbonate, 270 mmol/kg osmolality, pH 7.4) using constant-composition methods. When new accretions accumulated to three times the initial seed mass, the solids were collected and net crystal growth was assessed by X-ray diffraction line broadening analysis. The X-ray results revealed that the carbonate constituent in our physiologic-like solutions promoted the proliferation of new crystals at the expense of further growth of the seed apatite. Solution F- concentrations of approximately 2 micromol/liter partially offset the repressive effect that carbonate had on primary crystal growth. Moreover, F- stimulated seed crystal growth in the same anisotropic manner as had been observed for adult human bone apatite, a finding that suggests that the latter growth in vivo was the consequence, in part, of direct F--mineral interactions.

On the effect of liquid mixing rate on primary crystal size during the gas-liquid precipitation of calcium carbonate

An analysis based on gas-liquid mass transfer with chemical reaction coupled with equations describing the dynamic population balance model of crystallization and precipitation kinetics is used to predict the effect of liquid mixing rate on the transient mean crystal size of calcium carbonate precipitated in a small flat-interface gas-liquid reaction cell via the gaseous carbonation of lime water. Experimentally, small discrete calcite crystals (<1μm) are formed initially in the vicinity of the gas-liquid interface during the early stages of batch precipitation followed by subsequent primary crystal growth reaching ∼6μm in the bulk. The mean crystal size increases with increasing agitation rate consistent with model predictions due to the effect of liquid agitation rate on gas-liquid mass transfer.

Precipitation kinetics; elementary processes

The paper contains the results of our previous investigations on the crystallization of ZnC 2O 4 · 2H 2O and a more detailed study of the behaviour of the solid phase based on the evolution of the crystal size distribution during the process. The overall supersaturation range (2.9 ⪕ S ⪕ 100) consists of three subranges which are characterized by different combinations of the elementary crystallization processes: (a) rapid growth of heterogeneous primary crystals accompanied by secondary processes (breaking and secondary nucleation) at low supersaturations ( S ⪕ 4 at pH = 2 and S ⪕ 20 at pH = 5); (b) molecular growth of primary crystals at medium supersaturations; (c) coagulation growth of homogeneous primary crystals followed by “pulsing” and formation of crystalline “coagulates” at high supersaturations ( S ⪖ 14 at pH = 2 and S ⪖ 75 at pH = 5).