Degree Of Supersaturation Research Articles

Modulation of Oil/Polymer Nanocapsule Size via Phase Diagram-Guided Microfluidic Coprecipitation

Flow-based nanoprecipitation of different solutes via rapid mixing of two miscible liquids is a scalable strategy for manufacturing nanoparticles with various shapes and morphologies. Controlling the size of nanoparticles in flow-based nanoprecipitation, however, is often left to empirical variations in the flow rate ratios or the total flow rate of the two streams. In this work, we investigate the coprecipitations of oil and polymer to form nanocapsules via the Ouzo effect using glass capillary microfluidics across a range of mixing conditions. In the range of flow rates studied, the two streams mix convectively in micro-vortices formed at the junction of the two stream inlets. Using computational fluid dynamics simulations and glass capillary microfluidic nanoprecipitation, we establish a relationship between the precipitation conditions occurring experimentally in situ and the location on the ternary Ouzo phase diagram where precipitation is taking place. We find that a key variable in the resulting average diameter of the fabricated capsules is the degree of supersaturation experienced by both the oil and the polymer in the vortex zone of the device, showing a strong correlation between the two values. The control over the nanocapsule size by varying the extent of supersaturation of both precipitants is demonstrated by using two oils having distinct phase diagrams. This work provides a systematic approach to controlling the size of nanoparticles fabricated via continuous nanoprecipitation by linking the in situ flow conditions to ternary phase diagram behavior, enabling accurate control over nanocapsule size.

Crystal growth according to the law of proportionate effect

Abstract This paper summarizes an approach to crystal growth that was published in parts in various articles over the course of 25 years by the present author and his colleagues. Evidence for this approach, which is confirmed in detail by data in the cited publications and in the figures and equations in the supplementary material that accompanies this paper (see the Online Materials1), comes mainly from the shapes of crystal size distributions (CSDs). Such distributions reveal the growth histories of natural minerals and synthetic compounds, histories that can be used to make geological interpretations and to guide industrial syntheses. CSDs have three fundamental shapes: log-normal, asymptotic, and Ostwald. These shapes result from different degrees of supersaturation near the time of nucleation. The first two distribution shapes form according to the Law of Proportionate Effect (LPE) at moderate supersaturation, and the latter rare distribution forms by Ostwald ripening at large supersaturation. Initially, the first two distributions have mean diameters of up to tens of nanometers and grow by surface-limited growth kinetics. The slow step in this reaction is the incorporation of nanoparticles (bits of crystal or adparticles) onto the crystal surface. As the crystals become larger, their demand for nutrients, as calculated by the LPE, increases exponentially. Then the slow step in the reaction changes to the rate of transfer of nutrients to the crystal (supply- or transport-limited growth). Crystal diameters often grow the most during this latter stage, and the initial CSD shapes that originally formed during surface-limited growth are retained and scaled up proportionately. Proportionate growth during the supply-limited stage can be simulated approximately by multiplying the diameter of each crystal in a distribution by a constant. Crystals can also grow by a constant rate law in which a constant length is added to each crystal diameter in the distribution. This rare process causes the original CSD to narrow so that its initial shape is not preserved. The growth law that prevails, either proportionate or constant, is determined by the manner in which nutrients are supplied to the crystal. Supply is by advective flow during proportionate growth, with the nutrient solution moving with respect to the crystals. Constant growth relies on the random diffusion of nutrients through a quiescent solution. Proportionate growth is by far the most common growth law, and therefore, nutrient supply by diffusion alone during crystal growth is uncommon. Distributions formed by Oswald ripening and those formed by other rare processes are also discussed. During Ostwald ripening, nucleation caused by mixing reactants at large supersaturation forms crystals that are extremely fine and numerous. The larger crystals grow at the expense of the finer, less stable crystals, thereby forming, on completion, the universal steady-state CSD shape predicted by the Lifshitz-Slyozov-Wagner (LSW) theory. This unique CSD shape, as well as other rare shapes, then are scaled up to larger sizes by supply limited proportionate growth.

Control of amyloidogenic protein aggregation by ultrasonic irradiation

Protein aggregation causes intractable diseases such as Alzheimer’s disease. In these diseases, crystal-like protein aggregates, so-called amyloid fibrils, form in vivo and induce severe malfunction of biological tissues. Amyloid fibril formation comprises primary nucleation from a supersaturated solution of protein monomers and subsequent fibril growth. Within them, primary nucleation possesses an extremely high energy barrier, resulting in a long induction time for nucleation, typically over a decade in vivo and several days even in a test tube. Our previous study (1) revealed that ultrasonic irradiation to supersaturated protein solution drastically accelerates amyloid formation because of the effects of ultrasonic cavitation, which is applicable to clinical diagnosis (2). However, the degree of acceleration has not been controlled yet. Furthermore, the reproducibility of the induction time for nucleation highly depends on ultrasonic-irradiation conditions and the degree of supersaturation of initial protein solutions. Herein, we systematically investigate the optimized condition to accurately control amyloid formation using an originally developed sonoreactor (3) and discuss the underlying mechanism governing ultrasonic induction of amyloid formation. (1) K. Nakajima et al., Ultrason. Sonochem. 36, 206-211 (2017). (2) K. Nakajima et al., Nat. Commun. 13, 5689 (2022). (3) K. Nakajima et al., Ultrason. Sonochem. 73 105508 (2022).

Evaluating environmental controls on the exoskeleton density of larval Dungeness crab via micro computed tomography

Dungeness crab (Metacarcinus magister) have significant socioeconomic value, but are threatened by ocean acidification (OA) and other environmental stressors that are driven by climate change. Despite evidence that adult harvests are sensitive to the abundance of larval populations, relatively little is known about how Dungeness megalopae will respond to these stressors. Here we evaluate the ability to use micro-computed tomography (μCT) to detect variations in megalope exoskeleton density and how these measurements reflect environmental variables and calcification mechanisms. We use a combination of field data, culture experiments, and model simulations to suggest resolvable differences in density are best explained by minimum pH at the time zoeae molt into megalopae. We suggest that this occurs because more energy must be expended on active ion pumping to reach a given degree of calcite supersaturation at lower pH. Energy availability may also be reduced due to its diversion to other coping mechanisms. Alternate models based on minimum temperature at the time of the zoea-megalope molt are nearly as strong and complicate the ability to conclusively disentangle pH and temperature influences. Despite this, our results suggest that carryover effects between life stages and short-lived extreme events may be particularly important controls on exoskeleton integrity. μCT-based estimates of exoskeleton density are a promising tool for evaluating the health of Dungeness crab populations that will likely provide more nuanced information than presence-absence observations, but future in situ field sampling and culture experiments are needed to refine and validate our results.

Phosphate Recovery from Aqueous Solutions via Vivianite Crystallization: Interference of FeII Oxidation at Different DO Concentrations and pHs.

Vivianite (Fe3(PO4)2·8H2O) crystallization has attracted increasing attention as a promising approach for removing and recovering P from wastewaters. However, FeII is susceptible to oxygen with its oxidation inevitably influencing the crystallization of vivianite. In this study, the profile of vivianite crystallization in the presence of dissolved oxygen (DO) was investigated at pHs 5-7 in a continuous stirred-tank reactor. It is found that the influence of DO on vivianite crystallization was highly pH-related. At pH 5, the low rate of FeII oxidation at all of the investigated DO of 0-5 mg/L and the low degree of vivianite supersaturation resulted in slow crystallization with the product being highly crystalline vivianite, but the P removal efficiency was only 30-40%. The removal of P from the solution was substantially more effective (to >90%) in the DO-removed reactors at pH 6 and 7, whereas the efficiencies of P removal and especially recovery decreased by 10-20% when FeII oxidation became more severe at DO concentrations >2.5 mg/L (except at pH 6 with 2.5 mg/L DO). The elevated degree of vivianite supersaturation and enhanced rate and extent of FeII oxidation at the higher pHs led to decreases in the size and homogeneity of the products. At the same pH, amorphous ferric oxyhydroxide (AFO)─the product of FeII oxidation and FeIII hydrolysis─interferes with vivianite crystallization with the induction of aggregation of crystal fines by AFO, leading to increases in the size of the obtained solids.

Polyferrocenylsilane Block Copolymer Spherulites in Dilute Solution

Self-assembly of block copolymers (BCP) into uniform 3D structures in solution is an extremely rare phenomenon. Furthermore, the investigation of general prerequisites for fabricating a specific uniform 3D structure remains unknown and challenging. Here, through a simple one-pot direct self-assembly (heating and cooling) protocol, we show that uniform spherulite-like structures and their precursors can be prepared with various poly(ferrocenyldimethylsilane) (PFS) BCPs in a variety of polar and non-polar solvents. These structures all evolve from elongated lamellae into hedrites, sheaf-like micelles, and finally spherulites as the annealing temperature and supersaturation degree are increased. The key feature leading to this growth trajectory is the formation of secondary crystals by self-nucleation on the surface of early-elongated lamellae. We identified general prerequisites for fabricating PFS BCP spherulites in solution. These include corona/PFS core block ratios in the range of 1-5.5 that favor the formation of 2D structures as well as the development of secondary crystals on the basal faces of platelets at early stages of the self-assembly. The one-pot direct self-assembly provides a general protocol to form uniform spherulites and their precursors consisting of PFS BCPs that match these prerequisites. In addition, we show that manipulation of various steps in the direct self-assembly protocol can regulate the size and shape of the structures formed. These general concepts show promise for the fabrication and optimization of spherulites and their precursors from semicrystalline BCPs with interesting optical, electronic, or biomedical properties using the one-pot direct self-assembly protocol.

Change in evaporation flux due to homogeneous condensation of vapour near the interfacial surface

An approach that allows to estimate the necessity of homogeneous nucleation process accounting/not accounting for evaporation intensity and to predict the direction (increase or decrease) of mass flux density change of evaporating matter has been proposed. A dimensionless parameter making it possible to determine the areas of increase/decrease of evaporation intensity in the presence of a homogeneous nucleation process is proposed. It is shown that for some substances (methanol, ethanol) the direction of process significantly depends on the nature of heat exchange between the formed droplets and the surrounding vapor droplets. Keywords: homogeneous nucleation, evaporation, supersaturation degree.

Lateral variations in the Hosen 8‐2 vein in the Hishikari deposit, Japan: Implications for high Au‐grade zone

AbstractLateral sampling of each blasting interval (~ 2.6 m) along a 79 m strike length was conducted for the Hosen 8‐2 vein on the −5 ML (mining level, meters relative to sea level) of the Main ore zone in the Hishikari epithermal Au deposit, Kagoshima, Japan. The horizontal variation of mineral textures, bulk chemical compositions, and fluid inclusion temperatures and apparent salinity of ore fluids were determined. The major gangue minerals of the quartz veins studied include quartz and adularia with minor amounts of calcite and smectite. The major ore minerals include electrum, galena, and sphalerite with minor pyrite, petzite, and hessite. Electrum commonly occurs in a discrete band with microcrystalline quartz, granular adularia, and smectite. The electrum‐bearing band is followed by tabular adularia, and finally by granular or comb quartz. Mineral textures that indicate high degrees of supersaturation with respect to amorphous silica (presently quartz with microcrystalline/mosaic and feathery textures) and adularia (with tabular, rhombic, and granular textures) were common throughout the vein strike. Bulk chemical analyses indicate that Au grade is positively correlated with Ag, Bi, Pb, and Te contents. A bonanza zone with Au grades up to 10,800 ppm occurs in the central part of the Hosen 8‐2 vein on the −5 ML, and is associated with high adularia content, calculated as adularia / (quartz + adularia). The wide lateral variation in the geochemical composition contrasts with the consistent association of electrum with microcrystalline quartz, granular adularia, and smectite throughout the Hosen 8‐2 vein on the −5 ML. Fluid inclusion microthermometry of primary and pseudosecondary inclusions in quartz and adularia yielded histogram modes of homogenization temperature between 160 and 240°C; the most frequent mode is 200–210°C, with most data within ±10°C from this value. The maximum ice‐melting temperature of most samples excluding late comb quartz is −1.5°C, which is equivalent to an apparent salinity of 2.6 wt% NaCl eq. The wide variation in ice‐melting temperatures and apparent salinities (up to 5.2 wt% NaCl eq.) may be due to dissolved CO2 in the fluids, while the sharp decrease in apparent salinity with temperature decrease indicates CO2 loss due to fluid boiling during vein formation. The intimate association of electrum with microcrystalline quartz that recrystallized from amorphous silica indicate sharp boiling and vapor loss as the primary mechanism of Au deposition in the Hosen 8‐2 vein.

New insights into diffusive kinetic fractionation during liquid condensation under supersaturated environment: an alternative approach for isotope tagging of ground-level water vapour

ABSTRACT Stable water isotopes in ground-level vapour are key to estimating water exchange between geospheres. Their sampling, however, is limited to laser-absorption spectrometers and satellite observations, having inherent shortcomings. This study investigates diffusive kinetic fractionation during liquid condensation under supersaturated environment, providing a cost-effective, reliable way of sampling ground-level vapour isotopes (18O, 2H). Experiments were undertaken at three locations in India with ‘liquid’ samples collected from condensation of ambient air at 0°C. Simultaneously, pristine ‘vapour’ was sampled via cryogenic-trapping using liquid nitrogen–alcohol slush at –78°C. The ‘liquid’ condensed under supersaturation was progressively more depleted in 18O, and less enriched in 2H than expected under equilibrium fractionation, with an increasing degree of supersaturation expressed as saturation index (S i). This study revealed: (1) S i, molecular density, Rh, T together control the extent of isotopic kinetic fractionation. (2) The presence of diffusive concentration gradient inhibits the flow of heavier isotopes during liquid condensation. (3) The stochastic nature of the process cannot be explained using a physics-based model alone. The artificial neural network model is hence deployed to sample δ 18O (δ 2H) within –0.24 ± 1.79‰ (0.53 ± 11.23 ‰) of true value. (4) The approach can be extended to ground-validate isotope-enabled general circulation models and satellite observations.

Laser Directed Energy Deposition of an AlMgScZr-Alloy in High-Speed Process Regimes.

Aluminum-magnesium-scandium-zirconium (AlMgScZr) alloys need to be rapidly cooled from the liquid state to obtain a high degree of solute supersaturation that helps to exploit the precipitation hardening potential of the material. While AlMgScZr alloys have been successfully used in laser powder bed fusion (LPBF) processes, there has been little research in the field of laser directed energy deposition (DED) of the material. The limited previous studies have shown that the performance of AlMgScZr parts fabricated with DED only reached about 60% of that of the parts fabricated with LPBF. In view of breaking through the limitation associated with the process conditions of conventional DED, this work demonstrates the DED of AlMgScZr alloys in high-speed process regimes and elucidates the mechanism of enhancing the hardness and tensile strength of AlMgScZr alloys by increasing the cooling rate by one to two orders of magnitudes, as well as reducing the track overlapping and the porosity of the specimens during the process. A maximum average hardness of nearly 150 HV0.1 and a max. tensile strength of 407 MPa are obtained by using an energy per unit length of 5400 J/m and a powder feed rate per unit length of 0.25 g/m.

Improved stability of superelasticity and elastocaloric effect in Ti-Ni alloys by suppressing Lüders-like deformation under tensile load

Functional stability of superelasticity is crucial for practical applications of shape memory alloys. It is degraded by a Lüders-like deformation with elevated local stress concentration under tensile load. By increasing the degree of solute supersaturation and applying appropriate thermomechanical treatments, a Ti-Ni alloy with nanocrystallinity and dispersed nanoprecipitates is obtained. In contrast to conventional Ti-Ni alloys, the superelasticity in the target alloy is accompanied by homogeneous deformation due to the sluggish stress-induced martensitic transformation. The alloy thus shows a fully recoverable strain of 6% under tensile stress over 1 GPa and a large adiabatic temperature decrease of 13.1 K under tensile strain of 4.5% at room temperature. Moreover, both superelasticity and elastocaloric effect exhibit negligible degradation in response to applied strain of 4% during cycling. We attribute the improved functional stability to low dislocation activity resulting from the suppression of localized deformation and the combined strengthening effect of nanocrystalline structure and nanoprecipitates. Thus, the design of such a microstructure enabling homogeneous deformation provides a recipe for stable superelasticity and elastocaloric effect.

Electrode processes in the production of microdispersed titanium powder by volumetric electrolytic reduction of its ions with sodium dissolved in the BaCl2–CaCl2–NaCl melt in the absence of titanium halides in the initial melt

The paper is devoted to a detailed study of cathodic processes, their influence on the anode process, and electrolysis performance. The polarization of a steel cathode in a CaCl2–BaCl2–NaCl melt at t = 610 °C was measured. The polarization curve clearly shows the potentials and current densities of the formation of a saturated sodium solution in the electrolyte (Esat = –2.97 V, ic = 0.04 A/cm2, lgic = –1,4), and the occurrence of sodium metal on the cathode (ENa = –3.22 V, iNa = 0.12 A/cm2, lgiNa = –0.92).The value of Esat was used to calculate the concentration of sodium in the electrolyte at t = 610 °С (1.3·10–4 mol. fr.). The values of Esat, ENa, and their difference (E = 0,25 В) were confirmed by long-term electrolysis. These fundamental characteristics are the basis for process control and management. During long-ter 3 regions close to rectilinear ones were revealed: the discharge of sodium ions from supersaturated solutions at E more negative than Esat (from ENa to Esat), from mixtures of supersaturated and saturated solutions (at a constant E equal to Esat), from diluted solutions (with E more positive than Esat). The activity coefficients of sodium in supersaturated solutions are close to 1, which ensures their increased reducing ability. Maximum degrees of supersaturation (>100) are created at formation and decomposition on the cathode of metallic sodium nuclei, which are sufficient to intensify and prolong electrolysis, to lower the lower temperature limit of its realization from 600 to 350 °С. The formation of metallic titanium in the near-anode layer is explained by the disproportionation of Ti2+ ions entering the near-anode electrolyte from the anode surface and from the near-cathode melt.

Effect of tool rotating rate and subsequent artificial aging on microstructure and mechanical properties of 7050-T7451 alloy

In this work, the effects of friction stir processing tool rotating rate and subsequent artificial aging on the microstructure and mechanical properties of 7050-T7451 alloy were investigated. The results show that the grain morphology and the evolution of precipitated phases were significantly affected by rotating rate and artificial aging treatment. Ultrafine equiaxed grains formed after FSP and the grain size tended to grow with the increase of rotating rate, however the growth rate decreased gradually. Nano-sized η' phases mainly dissolved back, accompanied by partial phases transformation at low rotating rate condition. With the rotating rate increased, η' phases were more fully dissolved and parts of η phases start to dissolve gradually too. The matrix supersaturation increased as the dissolution of η' & η phases, resulting improvement of the mechanical properties of the alloy via solid solution strengthening. Subsequent artificial aging treatment promoted the decomposition of solid solution, new GP zones and η' phases re-precipitated, and the density of precipitated phases were proportional to the degree of matrix supersaturation. And, the properties of the alloy were further improved by the precipitation strengthening effect of these new reprecipitated phase. • The grow rate of ultrafine equiaxed grains of FSPed 7050-T7451 alloy tend to decline with the increasing of FSP tool rotating rate. • The redissolution of nano-scale precipitates turn to be dominant in high FSP tool rotating rate. • New nano-scale precipitates re-precipitated during artificial aging resulting significant increasement of mechanical properties.

Mechanism of magnesium phosphate cement retardation by citric acid

Citric acid modulates the release of heat and the rates of reaction in magnesium phosphate cements, chemically-bonded ceramics employed in biomaterials, for the encapsulation of nuclear wastes and in civil engineering. To gain knowledge on the mechanism of action of citric acid and, therefore, help in the effective material design, the reaction was studied in-situ to address molecular issues. The results indicated that citric acid enhances dissolution of MgO by promoting surface ligand-exchange reaction which leads to a net acceleration of the first reaction step. The Mg2+ ions released in solution are complexed by citrates. The degree of supersaturation is therefore reduced, delaying the nucleation of phosphates. The growth of stable nuclei, the crystal growth, and the amorphous-to-crystalline transformation are hindered due to citrate adsorption. The formed surface complexes are prevalently inner-sphere complexes exhibiting the combined coordination of hydroxyl and carboxylate groups. The mutating chemical environment dictates the coordination modes of citrate, the competition with phosphates, and the stable forms of phosphate products.

Towards the pseudo-2D modeling of frost growth between cold parallel plates

When a heat recovery ventilator is operating under winter conditions, the water vapor present in the exhaust airflow can lead to frost formation that depends on the outside air temperature, the heat exchanger plate temperature and their spacing, the exhaust air flow and its humidity. In this study, an available 1D frost formation model, based on frost growth and its densification, is improved and validated using experimental data available in the literature and measurements performed on a new test bench before extending the model on a 2D geometry. The objective of this study is to evaluate accurately the frost growth between cold parallel plates. The frost densification depends on the square root of time and the ratio of supercooling and supersaturation degrees. An energy balance equation for the heat conduction through the frost layer is solved and the heat and mass transfer from the moist air to the frost layer is used as a convergence criterion to predict the frost surface temperature. The proposed pseudo-2D model shows that the airflow from a 2.5 mm parallel plate spacing heat exchanger is reduced by 33% over a 25 min period due to frost growth. Using a 4.0 mm spacing, the airflow reduction gets only 5% over the same time period. It shows that larger plate spacing airflow are less affected by frost growth. After 25 min, the 2.5 mm spacing heat recovery efficiency decreases from 87% to 77% while for the 4.0 mm spacing, it decreases from 60% to 55%.

Supersaturation and crystallization behaviors of rare-earth based cuprate superconducting films grown by chemical solution deposition

Chemical solution deposition is widely used in the preparation of rare-earth-based cuprate superconducting thin films, namely RExBa2Cu3O7-y (RE = rare earth element). The crystallographic orientation of the films is strongly dependent on the degree of supersaturation during crystallization. In this paper, we systematically studied the crucial factors affecting supersaturation, such as the type and stoichiometry of the rare earth element and the sintering temperature. Furthermore, the relationship between c-axis orientation and supersaturation was established. The results demonstrate that a small RE ionic radius (e.g., RE = Yb) and reduced rE-stoichiometry, studied on the example of yttrium, are beneficial for the growth of c-axis-oriented films at lower temperatures. In addition, a Y-O/Ba-Cu-O stacked-layer structure was proposed to regulate the diffusion distance to the reaction site. Compared with a Y-Ba-Cu-O single-layer, a c-axis orientation percentage of more than 40 % is achieved in the Y-O/Ba-Cu-O stacked-layer at even lower sintering temperatures. The results suggest that a low supersaturation is favorable to promote the growth of c-axis-oriented nuclei and therefore suppresses the growth of random orientations. This paper provides a new strategy to realize orientation modulation of rare-earth-based cuprate superconducting thin films by controlled chemical solution method.

Controlled Synthesis of Tellurium Nanowires.

One-dimensional tellurium nanostructures can exhibit distinct electronic properties from those seen in bulk Te. The electronic properties of nanostructured Te are highly dependent on their morphology, and thus controlled synthesis processes are required. Here, highly crystalline tellurium nanowires were produced via physical vapour deposition. We used growth temperature, heating rate, flow of the carrier gas, and growth time to control the degree of supersaturation in the region where Te nanostructures are grown. The latter leads to a control in the nucleation and morphology of Te nanostructures. We observed that Te nanowires grow via the vapour-solid mechanism where a Te particle acts as a seed. Transmission electron microscopy (TEM) and electron diffraction studies revealed that Te nanowires have a trigonal crystal structure and grow along the (0001) direction. Their diameter can be tuned from 26 to 200 nm with lengths from 8.5 to 22 μm, where the highest aspect ratio of 327 was obtained for wires measuring 26 nm in diameter and 8.5 μm in length. We investigated the use of bismuth as an additive to reduce the formation of tellurium oxides, and we discuss the effect of other growth parameters.

Unraveling relative roles of bulk precipitation and surface growth in developing a scaling layer in membrane distillation

Scaling of sparingly soluble salts is a challenge standing in the way of enhancing water recovery of desalination via an approach based on membrane distillation (MD). Improvement of anti-scaling strategies is dependent on understanding various mechanisms accounting for evolution of the scaling layer. This study made efforts to address a fundamental concern as to how bulk precipitation is competing with surface growth to form a layer of crystalline particles in the process of MD. When concentrating a feed containing calcium sulfate, scaling was induced in a series of MD processes with a varied transmembrane temperature difference. In addition to the measurements of flux decline and electrical conductivity, optical coherence tomography (OCT) was explored to simultaneously monitor the formation of crystals in the feed bulk and resolve the scaling layer evolving on the membrane surface. Comparison of these characterization results revealed the key role of surface growth in initiating the scaling, while suggesting that the cake development could be gradually dominated by the deposition of crystals formed in the feed bulk. A further analysis of the local growth rates provided deeper insights into the mechanistic transition; effects of varying the degree of supersaturation were also discussed in the context of redistributing the size of deposits and inducing the crystal-membrane interactions. This study refines the picture of developing a scaling layer in MD, which would be of great value in advancing applications of MD-based desalination.

Development of a multiparticulate drug delivery system for in situ amorphisation

In the current study, the concept of multiparticulate drug delivery systems (MDDS) was applied to tablets intended for the amorphisation of supersaturated granular ASDs in situ, i.e. amorphisation within the final dosage form by microwave irradiation. The MDDS concept was hypothesised to ensure geometric and structural stability of the dosage form and to improve the in vitro disintegration and dissolution characteristics. Granules were prepared in two sizes (small and large) containing the crystalline drug celecoxib (CCX) and polyvinylpyrrolidone/vinyl acetate copolymer (PVP/VA) at a 50 % w/w drug load as well as sodium dihydrogen phosphate monohydrate as the microwave absorbing excipient. The granules were subsequently embedded in an extra-granular tablet phase composed of either the filler microcrystalline cellulose (MCC) or mannitol (MAN), as well as the disintegrant crospovidone and the lubricant magnesium stearate. The tensile strength and disintegration time were investigated prior to and after 10 min of microwave irradiation (800 and 1000 W) and the formed ASDs were characterised by X-ray powder diffraction and modulated differential scanning calorimetry. Additionally, the internal structure was elucidated by X-ray micro-Computed Tomography (XµCT) and, finally, the dissolution performance of selected tablets was investigated. The MDDS tablets displayed no geometrical changes after microwave irradiation, however, the tensile strength and disintegration time generally increased. Complete amorphisation of CCX was achieved only for the MCC-based tablets at a power input of 1000 W, while MAN-based tablets displayed partial amorphisation independent of power input. The complete amorphisation of CCX was associated with the fusion of individual ASD granules within the tablets, which negatively impacted the subsequent disintegration and dissolution performance. For these tablets, supersaturation was only observed after 60 min. On the other hand, the partially amorphised MDDS tablets displayed complete disintegration during the dissolution experiments, resulting in a fast onset of supersaturation within 5 min and an approx. 3.5-fold degree of supersaturation within the experimental timeframe (3 h). Overall, the MDDS concept was shown to potentially be a feasible dosage form for in situ amorphisation, however, there is still room for improvement to obtain a both fully amorphous and disintegrating system.

Управління структурою і властивостями ливарного алюмінієвого сплаву АМ4.5Кд (ВАЛ10) модифікуванням дрібнокристалічними лігатурами

To management the structure, mechanical and operational properties of the high-strength cast aluminum alloy АМ4.5Кд (ВАЛ10), the work uses a modification method based on the principle of structural inheritance, using rapidly cooled (Vcool. ≥ 10^5 °С/s) fine-crystal ligatures AlTi5 and AlZr10, and as well as ligatures of the chemical composition of the base alloy with nanoscale size of intermetallics and Alα crystals. Studies have shown that the introduction of fine-crystalline additives into the melt leads to a transition from a dendritic to a non-dendritic structure, a significant decrease in the size of the crystals of the Alα solid solution, and an increase in its degree of supersaturation. The microstructure becomes more uniform - the difference between the maximum and minimum size of the grains decreases. The most effective reduction of the grain size and the transition from dendritic to non-dendritic structure of the aluminum solid solution at increased cooling rates occurs when alloying with fine-crystal AlTi5 ligature introduced into the melt in terms of pure titanium 0.05-0.15 wt. %. We must think that the main factor of modification by rapidly cooled ligatures is the introduction of a large number of additional crystallization centers into the melt. After T6 heat treatment, the highest strength of AM4.5Kd alloy (VAL10) is achieved when modified with AlZr10 ligature, in particular, with a mass fraction of zirconium of 0.25%. Probably, this is mainly due to the expansion of the region of the solid solution of copper and zirconium in aluminum during high-speed cooling and its subsequent disintegration during heat treatment with the release of strengthening nano-sized CuAl2 and Al3Zr phases. Tribological studies of AM4.5Kd alloy (VAL10) were carried out. The alloy modified with fine crystal ligature of the base alloy composition in the amount of 12 wt.% has the highest wear resistance. Keywords: fine crystal ligatures, AM4.5Kd (VAL10), modification, microstructure, strength, wear resistance.