Recrystallization Technique Research Articles

Radiation polymerized CsPbBr3-PMMA nanocomposite for alpha particle detection

Inorganic perovskite nanocrystals demonstrate tremendous optoelectronic properties and can be synthesized by various solution-processing techniques but they are largely overlooked for their alpha radiation scintillation applications. Synthesis of these perovskites from constituent solution and their efficient dispersion into matrix phase is still challenging. Here we demonstrate a simple, low-cost, in-situ strategy to fabricate CsPbBr3 – PMMA nanocomposite films through catalyst-free gamma irradiation and their room temperature alpha-scintillation response. Perovskite nanocrystals with average particle size of 43 nm were successfully prepared through the supersaturated recrystallization technique. Gamma-radiation-induced polymerization successfully yielded translucent yellow color nanocomposite films. Their optical properties were evaluated using UV–Vis absorbance and Photoluminescence (PL) spectroscopy. We report for the first time, facile development and preliminary alpha response of solution processable - γ radiation polymerized CsPbBr3 - PMMA based nanocomposite for plastic scintillation.

Investigation on crystallization phenomena with supercritical carbon dioxide (CO2) as the antisolvent

Abstract The supercritical antisolvent (SAS) recrystallization process is one of the most promising recrystallization techniques for the particle formation of pharmaceutical compounds. In this process, a solution of active pharmaceutical ingredient (API) is sprayed into the supercritical carbon dioxide (SC CO2) environment. The mass transport of both the solvent and the antisolvent results in supersaturation followed by the crystallization of the API. In this work, a model is developed to estimate the supersaturation profile of solute in a droplet falling in the SC CO2 environment. The droplet consists of paracetamol as a solute and ethanol as a solvent. It moves down in the antisolvent (supercritical CO2) environment. Interestingly, the present model predicts a rise in supersaturation followed by a fall for a while and then a sharp increase. The competing phenomena of nucleation and growth mechanisms are used to justify this variation in the supersaturation.

Production and optimization of sea salt quality on the coast of Tomini Bay

Tomini Bay is a water area with an area of 59,500 km2. Especially for Gorontalo Province, it has a length of about 436.52 Km. Based on this data, the province of Gorontalo, especially the coast of Tomini Bay, has the potential to be the source of raw material for salt production. Generally, the salt production process goes through various stages of the processes, namely the first evaporation process, the second evaporation process, the concentration process, and the crystallization process. The objective of this research is to obtain pure salt that meets the Standards of SNI. The salt production method used are evaporation and purification with re-crystallization techniques by physical means (using hot water) and chemical methods by the addition of chemicals Ca(OH)2, NaOH, and Na2CO3. The results of this study showed that the obtained salt has NaCl content of 97.04%, Ca 0.55%, and Mg 0.28%. The obtained saltdoes not meet the salt requirements for SNI standards because there is still a large amount of Ca (SNI=0.10) and Mg (SNI=0.06). However, it meets the type of salt group, namely in category 1 with the best quality that meets the requirements for industrial materials and for consumption.

Studies of molar refraction and polarizability constant of 6-(4-chlorophenyl)-1,2,3,4-tetrahydro-2, 4-dioxopyrimidine-5-carbonitrile in 60% DMSO in the temperature range 298 to 313 K

Objectives: The main purpose of this study is to investigate the impact of 6-(4-chlorophenyl)-1, 2, 3, 4-tetrahydro-2, 4-dioxopyrimidine-5-carbonitrile in binary solution at different concentrations and valuable information on electronic polarizability and molecular interactions in the solution. Methods: 6-(4-chlorophenyl)-1, 2, 3, 4-tetrahydro-2, 4-dioxopyrimidine-5-carbonitrile was synthesized and purified by recrystallization technique in laboratory(1). DMSO used is of analytical reagent grade (AR) of minimum assay of 99.9%. Stock solutions of 0.02 (mol L-1) of compound were prepared by dissolving calculated amounts in 60% dimethyl sulphoxide solution. Solutions in various concentration ranges from 0.002 to 0.010(mol L-1). The pycknometer was calibrated by measuring the densities of triple distilled water. The densities of distilled organic liquids like acetone, toluene and carbon tetrachloride were evaluated with respect to density of water. Refractive index were measured by Abbe’s Refractometer (AR-56, COSLAB) having range 1.3000 to 1.7100. The desired temperature was maintained by circulating water through refractometer. Findings: In the present work we found that density, refractive index, molar refraction and polarizability constant increases the increase in concentration due to decrease in angle of refraction or increase in angle of incidence. The decrease in density with increase in temperature is due to increase in molar volume of solvent. However, the decrease in refractive index is due to the fact that the solute-solute and solute-solvent interactions weaken with increase in temperature. This can be correlated that change in these properties changes the intermolecular attraction between solute and solvent. With increase in temperature the interaction between solute and solvent weakens and hence molar refraction and polarizability decreases. Novelty: The work incorporated with the study of molar refraction and molar polarizability of 6-(4-chlorophenyl)-1, 2, 3, 4-tetrahydro-2, 4-dioxopyrimidine-5-carbonitrilehas been not studied until now. So we wish to present the systematic measurement of refractive index of 6-(4-chlorophenyl)-1, 2, 3, 4-tetrahydro-2, 4-dioxopyrimidine-5-carbonitrile in 60% DMSO in the temperature range 298 to 313 K at different concentration. From refractive index we have calculated molar refraction and molar polarizability which has provided important information regarding interactions between solute and solvent. Keywords: 6-(4-chlorophenyl)-1; 2; 3; 4-tetrahydro-2; 4-dioxopyrimidine-5-carbonitrile; refractive index; molar refraction; molar polarizability

Formation of Heterostructure with Appearance of α-Al Phase in Hyper- and Eutectic Al-Si Alloys by Solidification at High Rate

Normally, the microstructure of eutectic and hypereutectic Al-Si alloys consists of Al-Si eutectic or Al-Si eutectic + SiI, that is why they have good wear-resistance properties, but their ductility decreases somewhat, which can be improved by the appearance of non-equilibrium α-aluminum grains. In present work, a recrystallization and partial melting (RAP) technique was applied in the preliminary research to investigate the solidification behavior of the eutectics at high cooling rate. The results show that numerous α-Al dendrites appeared instead of the eutectic structure. In the followed researches, the combination of some technological procedures, based on the competitive growth of dendrites and eutectics, such as heterogeneous nucleation and high cooling rate, were applied: A413.0 and A390.0 alloys were melted in resistant furnace and poured into a mold, made of copper at one side and of steel at another, which is connected to the temperature measuring device via four K-class thermocouples. The various pouring regimes: gravity, via 450 tilt cooling slope and injection with Argon gas for 2 min. before pouring, were applied at different temperatures of 680, 650, 6300 C. The results show that the hetero-structure of eutectic and hyper-eutectic Al-Si alloys, consists of non-equilibrium α-Al grains, primary silicon and eutectics was obtained. Grain size varies with cooling rate, with minimum value of 10 μm when the specimen thickness is 5 mm. Non-dendritic grains were achieved with semi-solid treatment (pouring via cooling slope). The elongation of alloy is expected to be enhanced due to the appearance of α-Al grains.

Enhanced photoluminescence and stability of ZnSe microspheres/Cs4PbBr6 microcrystals/CsPbBr3 nanocrystals composites

A ternary complex combining dual-phase perovskites - Cs4PbBr6/CsPbBr3 (DP-CPB) with ZnSe micropsheres (ZnSe-DP-CPB) was successfully prepared using supersaturated recrystallization technique at room temperature. It was showed that the DP-CPB composites were partially embedded in ZnSe microsphere composed with ZnSe NCs. The light absorption range of ZnSe-DP-CPB composites was extended from visible to near infrared light. Highly enhanced luminescence from ZnSe-DP-CPB composite was observed and the excitation power-dependent photoluminescence showed that the recombination involves excitons. The recombination lifetimes of the ternary composites increased compared with DP-CPB composite, indicating that the non-radiative combination was suppressed which may be possibly due to the decrease of both bulk and surface defects, owing to the passivation of ZnSe, as well as the suitable band alignments of these three components. The ternary complex also showed improved stability of photoluminescence (PL), which opens a new avenue for enhancing the stability of PL and optoelectronic applications for semiconductor-perovskite composites.

Pilot test and cost-based feasibility study of solar-assisted evaporation for direct preparation of high-purity magnesium sulfate hydrates from metastable Na+,Mg2+//Cl−,SO42−-H2O salt-water system

To solve the longstanding problem of low purity that hampered the extraction of magnesium sulfate from the sea-type Na+,Mg2+//Cl−,SO42−–H2O system, solar collection was used to conduct pilot-scale evaporation and crystallisation at different temperatures, and brine was maintained in a metastable state to directly precipitate high-purity crystals of magnesium sulfate hexahydrate (MgSO4·6H2O). The precondition for preparing high-purity MgSO4·6H2O crystals was found to be an optimal ratio of 0.30–0.48 between the Jänecke indexes of SO42− and Mg2+. The purity of the directly precipitated MgSO4·6H2O crystals was >99.5%. Decreasing Cl− content in the feed brine was found to enhance the recovery ratio of Mg2+ and reduce the solar collector consumption. Solar-assisted evaporation technology can double the Mg2+ recovery and halve the water evaporation compared to high-purity salt production using the conventional natural evaporation and recrystallization technique. According to techno-economic analysis, the operating cost at a production scale higher than 20 t·d−1, brine evaporation temperature of 50 °C, and production from April to September can be adjusted to be as low as 41 USD·t−1. Compared to the market price of high-purity magnesium sulfate hydrates, the proposed solar-assisted evaporation/extraction method is economically feasible.

Stable Triple-Cation (Cs+-MA+-FA+) Perovskite Powder Formation under Ambient Conditions for Hysteresis-Free High-Efficiency Solar Cells.

Organometallic halide perovskite materials have promising photovoltaic properties and emerged as a cost-effective solar cell technology. However, a synthesis protocol to fabricate high-quality perovskite thin films under ambient conditions remains a critical issue and hinders commercialization of the technology. Therefore, this paper proposes efficient and stable fabrication of triple-cation perovskite photoactive solid-state thin film for solar cells using preformed perovskite powder under ambient conditions. Highly crystalline triple-cation perovskite powder was synthesized by a solution-processed antisolvent recrystallization technique, and films were prepared following a previously reported recipe for an efficient triple-cation perovskite. The synthesized perovskite powder was characterized using UV-visible absorption spectroscopy, X-ray diffraction, time-resolved photoluminescence, and field emission scanning electron microscopy. Fabricated solar cells were investigated for photovoltaic characteristics, including current density-voltage hysteresis, recombination losses, and thermal stability. The improved photovoltaic characteristics and thermal stability were attributed to the superior perovskite film quality and crystalline properties.

Solar-Light-Driven Efficient ZnO–Single-Walled Carbon Nanotube Photocatalyst for the Degradation of a Persistent Water Pollutant Organic Dye

An efficient photocatalyst, ZnO–single-walled carbon nanotube (ZnO–SWCNT) nanocomposite was successfully fabricated through a straightforward one-pot–two-chemical recrystallization technique followed by thermal decomposition. The photocatalytic efficiency of the prepared ZnO–SWCNT composite was investigated by assessing the degradation of a persistent water-pollutant dye (methylene blue, MB) under visible-light irradiation. We found that the synthesized photocatalyst is an effective and recyclable agent for the decomposition of an MB solution. Its photocatalytic performance was substantially better than that of pristine ZnO nanorods or pristine SWCNTs. The reusability of the photocatalyst was also examined, affirming that it could be used repeatedly for five cycles without conspicuous loss of morphology or catalytic performance.

Atomistic Simulations of Lithiation Induced Structural Changes in Layered-Spinel Nano-Architectured Li-Mn-O

Maximizing the potential of LIBs requires a firm and comprehensive understanding of the fundamental mechanisms during battery operation, including bulk phase transition of electrode materials, chemical variations at multiple interfaces between different battery components, changes in mechanical properties affecting the structural integrity, and so forth [1]. Atomistic modeling plays a vital role in advancement and understanding of microstructural evolution and mechanical properties of electrode materials. We present progress in the simulated synthesis of Li-Mn-O nanoporous electrode materials, from the atomic perspective using the amorphization and recrystallization technique [2]. The effect of lithiation on structural integrity and intercalation host capability of the LMO electrode are investigated under the NST ensemble. Evolution of a composite structured material is captured on the microstructures snapshots and XRD graphs, particularly co-existing formation of spinel and layered components. The nanoporous materials crystallize successfully although multiple grains are observed for Li1.75Mn2O4 (nanoporous with simulation lattice boxes of 67 Å and 75 Å) and subsequently yield a single crystals for Li2Mn2O4. However, this is not inherent on nanoporous 69 Å with the same concentration. Intercalation induced volume changes are observed during simulation of the discharge process, specifically when the lithium content in the system is increased above 75% (Li1.5Mn2O4). The nanoporous material contracts inwards and such accommodative nature may be attributed to flexing/relaxation into its pore/channel, unlike in the bulk structure, which suffers from drastic volume expansion.

Enhancement of hydrogen embrittlement resistance of Fe-Mn-C twinning-induced plasticity steel by partial recrystallization technique

We suggest that the partial recrystallization is a novel pathway to increase the hydrogen embrittlement resistance of Fe-Mn-C twinning-induced plasticity steels. The Fe-18Mn-0.6C (wt%) cold-rolled steel was annealed for from 3 min to 30 min at 650 °C. When the annealing time was shorter than 5 min, the specimen was partially recrystallized, while when the annealing time exceeded 10 min, the matrix was almost fully recrystallized. The partially recrystallized specimens exhibited the improved hydrogen embrittlement resistance because the inherited dislocation and mechanical twins in unrecrytallized grains acted as a trap site for diffusible hydrogen.

Atomistic Perspectives on Mechanical Properties of Nanoporous Li-Mn-O Cathode upon Li-Intercalation

Atomistic modeling plays a vital role in advancement and understanding of microstructural evolution and mechanical properties of electrode materials. We present progress in the simulated synthesis of Li-Mn-O nanoporous electrode materials, from an atomic perspective during which the amorphization and recrystallization technique has been employed. The effect of lithiation on structural integrity and intercalation host capability of the LMO electrode are investigated under the NST ensemble. Evolution of a composite structured material is captured on the microstructures snapshots and XRD graphs, particularly co-existing formation of spinel and layered components. The nanoporous materials crystallize successfully although multiple grains are observed for Li1.75Mn2O4 (nanoporous structure corresponding to cubic lattice boxes of side lengths 67 Å and 75 Å) and subsequently yield a single crystals for Li2Mn2O4. However, this is not inherent on nanoporous 69 Å with the same concentration. Intercalation induced volume changes are observed during simulation of the discharge process, specifically when the lithium content in the system is increased above 75% (Li1.5Mn2O4). The nanoporous material contracts inwardly and such accommodative nature may be attributed to flexing/relaxation into its pore/channel, unlike in the bulk structure, which suffers from drastic volume expansion. It is imperative to exclusively note the single crystallinity of the nanoporous (69 Å), that potentially contributes to the retention of yield strength unlike in the case of nanoporous (67 and 75 Å), where the simulations reveal that Li intercalation weakens the systems as the yield stresses (particularly for Li1.75Mn2O4), are reduced with gradual lithium intercalation into the lattice.

(E)-1-(2′,4′-Dimethyl)-(5-acetylthiazole)-(2,4″-difluorophenyl)-prop-2-en-1-one

Thiazole and chalcone motifs are of research interest to medicinal chemists due to their array of synthetic and biological utility. Hence, in the present study we intended to prepare (E)-1-(2′,4′-dimethyl)-(5-acetylthiazole)-(2,4″-difluorophenyl)-prop-2-en-1-one (3c) containing both these scaffolds. The compound 3c was synthesized by the acid-catalyzed condensation of 2,4-dimethyl-5-acetylthiazole with 2,4-difluorobenzaldehyde. Purification and characterization of the compound were carried out by recrystallization and spectral techniques including UV, IR, 1H-NMR, 13C-NMR, Mass spectrometry and X-ray powdered diffractometry. The molecule 3c was successfully synthesized, purified, and characterized.

Thermophysics Simulation of Laser Recrystallization of High-Ge-Content SiGe on Si Substrate

The high-Ge-content SiGe material on the Si substrate can be applied not only to electronic devices but also to optical devices and is one of the focuses of research and development in the field. However, due to the 4.2% lattice mismatch between Si and Ge, the epitaxial growth of the high-Ge-content SiGe epitaxial layer directly on the Si substrate has a high defect density, which will seriously affect the subsequent device performance. Laser recrystallization technique is a fast and low-cost method to effectively reduce threading dislocation density (TDD) in epitaxial high-Ge-content SiGe films on Si. In this paper, by means of finite element numerical simulation, a 808 nm laser recrystallization thermal physics model of a high-Ge-content SiGe film (for example, Si0.2Ge0.8) on a Si substrate was established (temperature distribution physical model of Si0.2Ge0.8 epitaxial layer under different laser power, Si0.2Ge0.8 epitaxial layer thickness, and initial temperature). The results of this paper can provide important technical support for the preparation of high-quality high-Ge-content SiGe epilayers on Si substrates by laser recrystallization.

Study on structural conversion of dihydrochelerythrine in different solvents

Dihydrochelerythrine was isolated from the ethanol extract of Corydalis yanhusuo by chromatographic and recrystallization techniques. To our knowledge, this is the first report that dihydrochelerythrine was found to be unstable. The NMR, HPLC, and LC-MS were applied to monitor the structural conversion process of dihydrochelerythrine. The results showed that when dissolved in polar deuteration solvent (e.g., DMSO-d₆ & MeOD), dihydrochelerythrine is directly converted to chelerythrine gradually. However, if used non-polar reagent (e.g.,CD₂Cl₂), the sample of dihydrochelerythrine undergoes the formation of pseudobase, chelerythrine, and bimolecular ether then followed by oxidation to oxychelerythrine as the major final product. Which leads to this phenomenon maybe is that the C-6 in dihydrochelerythrine is highly reactive to nucleophiles, and is easily converted to different derivatives in different solvents attributed to the solvent effect. This finding will contribute to the extraction and isolation, bioactivity screening, and quality evaluation of medicinal materials containing dihydrochelerythrine and other similar derivatives.

Silicon on Dust Substrate: The Effect of Powder Size on Ribbon Production

The silicon on dust substrate process is a two‐step technique to produce multicrystalline silicon (mc‐Si) ribbons directly from gaseous feedstock. Silicon pre‐ribbons of very small grain size (ranging from nano to microcrystalline), with a porous structure and dimensions up to 25 × 100 mm2, are obtained using an inline optical chemical vapor deposition (CVD) system operating at atmospheric pressure and at low temperatures (<600 °C). Using silane as the gaseous precursor, nano or microcrystalline silicon layers can be grown, on top of silicon powder substrates, moving at constant speed, and crossing three hot deposition regions several times. The growth rates (GR) vary from 13.4 to 73.2 μm min−1, depending on the grain size of silicon powder. The last step is a floating zone (FZ) recrystallization technique, where the silicon pre‐ribbons obtained in the CVD step, become solid mc‐Si ribbons. The success of recrystallization depends on the grain size of silicon powder used as substrate on the CVD step, with lower grain sizes powders delivering better results. For the lower size powder substrates, multi‐crystalline areas of 5–20 mm2 were obtained, with an average crystal size in the (0.1; 1) mm range.

Anisotropic Thermoelectric Devices Made from Single-Crystal Semimetal Microwires in Glass Coating

Thermoelectric heat conversion based on the Seebeck and Peltier effects generated at the junction between two materials of type-n and type-p is well known. Here, we present a demonstration of an unconventional thermoelectric energy conversion that is based on a single element made of an anisotropic material. In such materials, a heat flow generates a transverse thermoelectric electric field lying across the heat flow. Potentially, in applications involving miniature devices, the anisotropic thermoelectric (AT) effect has the advantage over traditional thermoelectrics that it simplifies the thermoelectric generator architecture. This is because the generator can be made of a single thermoelectric material without the complexity of a series of contacts forming a pile. A feature of anisotropic thermoelectrics is that the thermoelectric voltage is proportional to the element length and inversely proportional to the effective thickness. The AT effect has been demonstrated with artificial anisotropic thin film consisting of layers of alternating thermoelectric type, but there has been no demonstration of this effect in a long single-crystal. Electronic transport measurements have shown that the semimetal bismuth is highly anisotropic. We have prepared an experimental sample consisting of a 10-m-long glass-insulated single-crystal tin-doped bismuth microwire (d = 4 μm). Crucial for this experiment is the ability to grow the microwire as a single-crystal using a technique of recrystallization with laser heating and under a strong electric field. The sample was wound as a spiral, bonded to a copper disk, and used in various experiments. The sensitivity of the sample to heat flow is as high as 10−2 V/W with a time constant τ of about 0.5 s.

Recrystallization techniques for the synthesis of ZnO nanorods: an in situ process for carbon doping and enhancing the dispersion concentration of ZnO nanorods.

Zinc acetate is recrystallized as lumber-shaped tetragonal rods by a novel recrystallization technique. Subsequently, the recrystallized zinc acetate is converted into ZnO nanorods in a glass vial by the simplest and cheapest method without utilizing any expensive instrumentation. Carbon is doped in ZnO nanorods during the preparation ZnO nanorods without any extra steps, chemicals, or effort. The carbon-doped ZnO nanorods can be dispersed in a solvent at very high concentrations and are also stable for a very long time, which are comparatively higher than those of the other existing ZnO nanoparticles. The higher dispersion concentration and higher stability of ZnO nanoparticles are explained by a scheme that demonstrates the suspending mechanism of the ZnO nanoparticles at higher concentrations with higher stabilities in a solvent through the anchoring groups of carbon. No materials are used for surface modification; no surface coatings, ionic materials, or pH controlling materials are used to increase the dispersion concentration and stability. This is the first observation of the doped carbon playing a significant role in the dispersion of ZnO nanoparticles at higher concentrations by withholding them in the solvent. Therefore, doped carbon at the surface of ZnO nanoparticles prevents the self-aggregation of ZnO nanoparticles in the solution phase by interfacial barrier layers among ZnO nanorods and interfacial interactive layer between ZnO nanorod and solvent.

Método preparativo para la obtención de ácido ursólico a partir de Clinopodium revolutum

En este trabajo se propuso un método para obtener ácido ursólico (AU) de manera fácil, rápida y económica teniendo como materia prima la planta medicinal Clinopodium revolutum endémica del Perú, conocida y comercializada con el nombre de flor de arena o té indio. La técnica de recristalización selectiva que se empleó resultó ser eficiente debido a que se obtuvo cristales de AU sin la necesidad de métodos cromatograficos de purificación ni el uso de solventes tóxicos. La pureza determinada por HPLC es mayor a 95%. Así, la flor de arena se convierte en una importante biofuente de este compuesto.

Valorization of spruce needle waste via supercritical extraction of waxes and facile isolation of nonacosan-10-ol

Supercritical carbon dioxide was utilized as a sustainable alternative to solvent extraction of waxes from the waste needles of two spruce species, namely Norwegian and Sitka spruce. These extracts were rich in nonacosan-10-ol, an organic compound with hydrophobic properties that lends its use in the preparation of superhydrophobic coatings. The highest crude yields were 1.7% w/w of needles obtained at 400 bar and 60 °C, while nonacosan-10-ol was selectively extracted at 200 bar and 60 °C (8070 ± 91.1 μg/g of needles). Purification of nonacosan-10-ol from the wax extracts was conducted using a simple rapid green recrystallization technique. This yielded a recovery of 44.6% ± 2% and 48.4% ± 2% of the total nonacosan-10-ol from the original crude Sitka (3600 μg/g of needles) and Norwegian wax (1920 μg/g of needles) respectively. Application of nonacosan-10-ol to a filter paper led to the formation of highly hydrophobic surfaces, with preliminary contact angles of up to 149°. This sustainable production method may develop opportunities to valorize forestry waste within a holistic biorefinery.