Stable Solid Phase Research Articles

Atomic-scale investigation of the synergistic impact of Mo and Nb addition on enhancing the performance of laser cladding FeCoCrNi-based high entropy alloy coatings

Utilizing synchronous powder feeding laser cladding technology, two high entropy alloy coatings, FeCoCrNiMo and FeCoCrNiMoNb, were deposited on the surface of low-carbon steel. An in-depth investigation into the synergistic interplay of Mo and Nb on FeCoCrNi-based high entropy alloy coatings was conducted. The findings reveal that FeCoCrNiMo comprises an FCC stable solid solution, Mo3Co3C, and Ni3Mo3C. Conversely, FeCoCrNiMoNb exhibits a composition comprising an FCC stable solid solution phase, NbC, and (Mo, Nb)C. This is attributed to the robust interaction between Mo and Nb, wherein Mo infiltrates the NbC lattice, substituting for a portion of Nb atoms. Notably, the synergistic influence of Mo diminishes the formation energy of NbC, thereby lessening the energy barrier encountered during the nucleation of (Mo, Nb)C. Consequently, the incorporation of Mo facilitates the precipitation of Nb. The refined microstructure and solid solution strengthening effect of (Nb, Mo)C and NbC, coupled with their elevated Vickers hardness and hard elastic ratio, contribute significantly to the notable enhancement in surface hardness and wear resistance observed in the FeCoCrNiMoNb high entropy alloy coating.

Mild and friendly preparation of a high-surface porous organic polymers and its application for sensitive detections of endocrine disrupting chemicals

For sample pretreatment technique, the preparation of a stable, practical material with excellent enrichment performance is the core, and especially the preparation of an environmentally friendly adsorbent is desired. The preparation of most materials involves the use of organic solvents, which puts a strain on the environment to a certain extent, and the choice of aqueous solution as the reaction environment for the diazo-coupling reaction has attracted great attention, as a friendly strategy. We prepared the environmentally friendly porous organic polymer (POP) 2,4,6-tris(2,4,6-trihydroxyphenyl)-1,3,5-triazine-4,4′-diaminobiphenyl (CTT-BD) by diazo-coupling reaction, and further fabricated as stable solid phase microextraction (SPME) fiber. It achieved efficient extraction of derivatized bisphenol endocrine disrupting chemicals (EDCs) from water samples with enrichment factors ranging from 1306 to 2781. Under the optimum experimental conditions, the developed method by combining the CTT-BD coated fiber with gas chromatography mass spectrometry (GC–MS), demonstrated a wide linearity (10–10000 ng/L), low limits of detection (2.0–3.0 ng/L) and good reproducibility (relative standard deviations 3.1–8.1 %). Finally, the proposed method has been successfully used for the determinations of EDCs from water samples, and satisfactory recoveries (85.6–118.0 %) were achieved.

Phase diagrams of CoSO4-H2O and CoSO4-H2SO4-H2O systems for CoSO4·nH2O (n = 6,7) recovery by cooling and eutectic freeze crystallization

This paper reports the solid-liquid phase equilibria of the CoSO4-H2O and CoSO4-H2SO4-H2O systems at low temperatures. Binary and ternary phase diagrams, including the stable solid phases CoSO4·6H2O and CoSO4·7H2O were established using experimental data and thermodynamic modeling applying the mixed-solvent electrolyte (MSE) model. The results showed that the addition of H2SO4 shifts the eutectic temperature and concentration to lower values for cobalt sulfate and ice crystallization. The trends obtained from the experimental data and the modeling are consistent for the binary CoSO4-H2O system with good agreement, but the ternary CoSO4-H2SO4-H2O system shows some deviations. In general, the MSE model is shown to be reliable for inferring and establishing the phase diagram of the low-temperature system. The phase diagrams are helpful for designing the pathways of cooling crystallization and eutectic freeze crystallization and assessing the performance of the low-temperature crystallization process in the production of CoSO4 hydrates. In addition, some practical examples of cooling crystallization and eutectic freeze crystallization of CoSO4 solutions are provided.

Magnetic graphene oxide functionalized dimercaptosuccinic acid/putrescine as a selective and stable solid-phase extraction adsorbent for preconcentration and speciation of arsenic (III) in water samples

ABSTRACT It is challenging for environmental scientists to identify the trace value of arsenite (As(III)) as an essential hazardous material in the presence of arsenate (As(V)) and other metal ions. This paper proposes a method of magnetic solid-phase extraction (MSPE) for the trace analysis of As(III) using magnetite graphene oxide (MGO) covalently functionalised with dimercaptosuccinic acid (DMSA) and putrescine (PUT). The hydrothermally synthesised MGO/DMSA-PUT adsorbent was carefully characterised by using energy-dispersive X-ray spectroscopy analysis, Fourier transform infrared, dynamic light scattering, scanning electron microscopy, zeta potential analyser, X-ray diffraction, and vibrating sample magnetometer techniques in detail. Maximum adsorption capacity of MGO/DMSA-PUT for As(III) was determined 144 mg g−1 which considerably improved vs. graphene oxide with the adsorption capacity of 54.8 mg g−1. Sample pH of 6 with a volume of 50 mL, contact time of 5 minutes, initial concentration of 50 μg L−1, adsorbent dosage of 0.1 g and volume of eluent 3 mL were obtained as the optimised parameters for the developed MSPE procedure. According to experimental data obtained with hydride generation atomic absorption spectroscopy, the linear range and detection limit of the proposed method for As(III) measurement was found to be 0.4–5000 µg L−1 and 9.914 ng L−1, respectively. According to experimental results, a preconcentration limit (PL) of 1.72 µg L−1 was achieved for As(III), corresponding to a preconcentration factor of 965. Statistical analysis of standard reference materials confirmed the accuracy of the method against systematic and constant errors (>95% recovery with <5% RSD). Because of the selectivity of MGO/DMSA-PUT towards the As(III), the developed MSPE procedure is capable for successful speciation and determination of As(III) in water samples with satisfactory analytical results.

Thermal and mechanical properties of PEG4000 and PUSSPCMs for thermoregulation of asphalt

The purpose of this study is to assess the effect of polyurethane solid-solid phase change materials (PUSSPCMs) and polyethylene glycol (PEG4000) on the thermoregulatory and rheological properties of asphalt, as well as their potential for regulating asphalt pavement temperature. The chemical and thermodynamic characteristics of PEG4000 and PUSSPCMs were investigated using infrared spectroscopy (FTIR), adsorption test, polarized light microscopy (POM), X-ray diffractometer (XRD), differential scanning calorimetry (DSC), thermogravimetric (TG), and atomic force microscopy (AFM). Meanwhile, the effects of PEG4000 and PUSSPCMs on asphalt road performance and micromorphology were determined by tests of thermoregulation, three major indexes, DSR segregation, and scanning electron microscopy (SEM). The results indicate that PUSSPCMs have no hydroxyl characteristic peaks of PEG4000 and isocyanate bonds after the complete reaction. PUSSPCMs exhibit better phase stability over PEG4000, the soft segment for thermal storage changes from crystalline to amorphous and is limited by the hard segment micro-region to maintain a stable solid phase. PUSSPCMs exhibit slightly weaker thermal storage properties than PEG4000, while the thermal stability and elastic modulus are stronger. PUSSPCMs-modified asphalt performs lower thermoregulation properties than PEG4000-modified asphalt, which improves with the increasing soft segments. Furthermore, the advantages of PUSSPCMs-modified asphalt are in terms of basic physical, rheological properties and storage stability. The micromorphology of PUSSPCMs-modified asphalt shows no visible cracks compared to PEG4000-modified asphalt and flattens with soft segment rises, which contributes to the thermoregulation and rheological properties of asphalt.

EFFECT OF SOIL GELS ON HYSTERESIS PHENOMENA IN SOILS

Based on the analysis of the exist mechanisms of the hysteresis of soil water retention curve (WRC), as well as ideas about the nanostructural organization of soils, it is concluded that hysteresis can be caused either by stable (non-colloidal particles) or labile (gels) parts of the solid phase of soils. Due to the fact that until now the main attention has been paid to the study of the effect of stable solid phase of soils on the hysteresis of WRC, it was proposed to investigate the effect of soil gels on hysteresis. For this purpose, the effect of moisture content of soil samples prepared by drying and moistening on the initial viscosity of soil pastes was studied. It has been established that well-pronounced hysteresis is observed for samples of all studied soil types. To explain the hysteresis, two mechanisms based on changes in soil gels in the humidification-drying processes are proposed. One of them is based on the slowness of swelling and shrinkage of soil gels when they absorb and release water. The second is on the greater hydrophobicity of the surface of gels containing less water, and water slipping on hydrophobic areas of the surface with a decrease in the viscosity of pastes. Thus, the conducted studies have shown that hysteresis phenomena in soils are caused by soil gels and their changes during drying and moistening of soils.

An Upgraded Protocol for the Silanisation of the Solid Phase for the Synthesis of Molecularly Imprinted Polymers

The introduction of solid-phase imprinting has had a significant impact in the molecular imprinting field, mainly due to its advantage of orienting the template immobilisation, affinity separation of nanoMIPs and faster production time. To date, more than 600 documents on Google Scholar involve solid-phase synthesis, mostly relying on silanes mediating template immobilisation on the solid phase. Organosilanes are the most explored functionalisation compounds due to their straightforward use and ability to promote the binding of organic molecules to inorganic substrates. However, they also suffer from well-known issues, such as lack of control in the layer’s deposition and poor stability in water. Since the first introduction of solid-phase imprinting, few efforts have been made to overcome these limitations. The work presented in this research focuses on optimising the silane stability on glass beads (GBs) and iron oxide nanoparticles (IO-NPs), to subsequently function as solid phases for imprinting. The performance of three different aminosilanes were investigated; N-(6-aminohexyl) aminomethyltriethoxy silane (AHAMTES), 3-Aminopropyltriethoxysilane (APTES), and N-(2-aminoethyl)-3-aminopropyltriethoxysilane (AEAPTES), as well as studying the effect of dipodal silane bis(triethoxysilyl)ethane (BTSE). A stable solid phase was consequently achieved with 3% v/v AEAPTES and 2.4% BTSE, providing an upgraded protocol from Canfarotta et al. for the silanisation of the solid phase for molecular imprinting purposes.

Microstructure and wear resistance of CoCrFeNiMn coatings prepared by extreme-high-speed laser cladding

In this study, CoCrFeNiMn high-entropy alloy coatings with remarkable formability were deposited on a 316-steel substrate using conventional laser cladding (CLC) and extreme-high-speed laser cladding (EHLA) techniques. The microstructure, phase composition, element distribution, microhardness, and wear properties of the coatings prepared at various deposition speeds were analyzed. The results illustrated that the coatings comprised a stable FCC solid solution phase. The microstructure of the CLC-HEA coating was predominantly composed of columnar grains with an average size of 60.8 μm, whereas the grain size of the EHLA-HEA coating decreased to approximately 32.9 μm and 24.5 μm at deposition speeds of 20 m/min and 40 m/min, respectively. The quick cooling and heating properties of the EHLA-HEA coating finally led to a lowered dilution rate, changed grain growth orientation, and enhanced dislocation density. Furthermore, the surface hardness of the EHLA-HEA coating (251 HV) surpasses that of the CLC-HEA coating (173 HV), particularly at higher deposition speeds. The wear test analysis demonstrates a transition in wear mechanisms from abrasive to adhesive, fatigue, and oxidative wear as the load increases. Moreover, EHLA-HEA coating exhibited superior wear resistance, especially at low loads (5 N); the wear rate of EHLA-HEA coating (1.07 × 10−6 mm3N−1 m−1) deposited at 40 m/min is nearly an order of magnitude lower than for CLC-HEA coating (9.97 × 10−6 mm3N−1 m−1), which is owing to its fine sub-grain structure and its higher dislocation density.

Solid-liquid equilibria of Sorel phases and Mg (OH)2 in the system Na-Mg-Cl-OH-H2O. Part I: experimental determination of OH− and H+ equilibrium concentrations and solubility constants at 25°C, 40°C, and 60°C

Sorel phases are the binder phases of the magnesia building material (Sorel cement/concrete) and of special concern for the construction of long-term stable geotechnical barriers in repositories for radioactive waste in rock salt, as potentially occurring brines are expected to contain MgCl2. Sorel phases, in addition to Mg(OH)2, are equally important as pH buffers to minimize solubility and potential mobilization of radionuclides in brine systems. In order to obtain a detailed database of the relevant solid-liquid equilibria and the related pHm values of the equilibrium solutions, extensive experimental investigations were carried out. Solid phase formation was studied by suspending MgO and Mg(OH)2 in NaCl saturated MgCl2-solutions at 25°C. Mg(OH)2 and the 3-1-8 Sorel phase were identified as the stable solid phases, while the 5-1-8 Sorel phase is metastable. Equilibration at 40°C did not lead to any solid phase changes. Both OH− and H+ equilibrium concentrations were analyzed as a function of MgCl2 concentration at 25°C and 40°C. In addition to our already published solid-liquid equilibria for the ternary system Mg-Cl-OH-H2O (25°C–120°C), the equilibrium H+ concentrations (pHm) determined at 25°C, 40°C and 60°C are now reported. Analyzing these data together with known ion-interaction Pitzer coefficients, the solubility constants for Mg(OH)2 and the 3-1-8 phase at these three temperatures, for the metastable 5-1-8 phase at 25°C and for the 2-1-4 phase at 60°C have been consistently calculated.

Review article: Sol-gel method, ‘’synthesis and applications’’

The sol-gel method is one of the techniques discovered in the past, but its use began in the sixties of the last century with the increasing use of this technology because of its features that are not found in traditional methods. This technique is defined as the guided method for the formation of inorganic oxides, with gelatinous structures, which are converted into solid glass (amorphous structures) at low temperatures, and can be defined from a thermodynamic point of view as the formation of a relatively stable solid phase at a given temperature, starting from the liquid phase. Sol-gel process is used to produce ceramic nanoparticles

Thermodynamic assessment within the Zr–B–C–O quaternary system

AbstractThermodynamic modeling of Zr–B–C–O quaternary system is conducted within the CALPHAD framework by employing data obtained from first‐principle calculations and literature. The lower order binary B–O is assessed in this work by estimating the thermodynamic properties of stable solid phases of B2O3 and B6O and by estimating the gas and liquid phases. First‐principle calculations, in conjunction with special quasirandom structure were used to predict enthalpies of mixing for the ternary solid‐solution phase of FCC‐Zr(C, O). The calculated results were used to optimize the model parameters pertaining to the cubic phase, which is described by a two‐sublattice model. The modeled Zr–C–O ternary phase diagrams calculated at 1923 and 2273 K under ambient pressure and 4 Pa, respectively, are in agreement with experimental phase diagrams.

Solid phase microextraction of benzenes in river water by pomelo peel biochar

Pomelo peel, as a by-product of pomelo consumption, is rich in various fiber and functional compounds. The utilization of the valuable components found in pomelo peel may mitigate environmental concerns. In this study, pomelo peel rich in lignin and oxygen-containing functional groups was used to prepare pomelo peel biochar (PPB) via temperature-programmed pyrolysis at different temperatures (800 ℃ and 1000 ℃). Their structures were investigated by N2 adsorption-desorption isotherms and BJH pore size distribution. The results showed that PPB1000 (pomelo peel biochar prepared at 1000 ℃) had a higher specific surface area (749.9 m2/g), larger pore volume (0.42 cm3/g), more concentrated pore size distribution (2-3 nm), and better adsorption performance than commercial activated carbon. PPB1000 exhibited excellent capability to capture benzenes (BTEX, including benzene (B), toluene (T), ethylbenzene (E), and xylene (X)) through hydrogen bonds, π-π, and electrostatic interactions. Additionally, their honeycomb porous structure could provide additional adsorption sites and material transport paths. PPB1000 was coated on iron wire using the sol-gel method to prepare chemically and mechanically stable solid phase microextraction (SPME) fibers. By combining PPB1000-based SPME analysis with gas chromatography-flame ionization detection (GC-FID), an effective method was developed for the extraction and determination of BTEX. The optimized method had low LODs (0.004-0.032 μg/L), wide linear range (1-100 μg/L), and good linear relationship (determination coefficients, r2≥0.9919). The RSDs of the intra-batch (n=6) and inter-batch (n=5) precisions were 1.04%-6.56% and 1.03%-12.42%, respectively. The method validation results showed that PPB1000 had good stability. Compared with the commercial reagent polydimethylsiloxane (7 μm), PPB1000 had a higher extraction efficiency. When applied to the analysis of BTEX in natural water samples, trace levels of ethylbenzene (4.80 μg/L), o-xylene (3. 00 μg/L), and m-xylene and p-xylene (2.46 μg/L) were detected. Recovery tests were performed to validate the reliability of the method, and recoveries were between 75.7% and 117.6%. This effective pretreatment process combined with GC-FID could realize the rapid detection of BTEX and is promising for the analysis of BTEX in complex matrixes in the future.

Formation of Calcium Phosphate Apatite in System CaO-P2O5-H2O: Equilibrium at 298 K Under a Nitrogen Atmosphere

Aims: The formation of calcium phosphate apatite (hydroxyapatite, carbonate-containing hydroxyapatite, fluorapatite and carbonate-containing fluorapatite) in aqueous systems has been studied for over a century. Background: However, in the region of low concentrations of liquid phases, the question of the nature, composition and region of existence of apatite compounds remains controversial. Objective: The results of studying the phase equilibrium in the system CaO-P2O5-H2O at 298 K in the isotherm region from the invariant point of dicalcium phosphate and monocalcium phosphate monohydrate to the lowest concentrations of the liquid phase components are presented. Method: Chemical analysis, thermogravimetry, IR spectroscopy and optical microscopy were used for the analysis. Result: Long-term monitoring of the establishment of equilibrium (up to 20 months) resulted in the determination of regions of stable solid phases of calcium orthophosphates, calcium-deficient apatites, hydroxyapatite, and apatite with (Ca/P)at &gt;1.67. Two types of calcium-deficient apatite were identified that differ in the (Ca/P)at ratio: the first type is 1.33 &lt; (Ca/P)at ≤ 1.5; the second one is 1.5 ≤ (Ca/P)at &lt; 1.67. Conclusion: The invariant points of calcium orthophosphates and compounds with the apatite structure were determined. The diagram was constructed using the Miller-Kenrick method based on obtained experimental data, which confirms the established regions and invariant points of stable equilibrium solid phases of the studied ternary system. The data obtained can be useful for understanding the processes of formation and change of compounds with apatite structure.

Zinc Titanium Nitride Semiconductor toward Durable Photoelectrochemical Applications.

Photoelectrochemical fuel generation is a promising route to sustainable liquid fuels produced from water and captured carbon dioxide with sunlight as the energy input. Development of these technologies requires photoelectrode materials that are both photocatalytically active and operationally stable in harsh oxidative and/or reductive electrochemical environments. Such photocatalysts can be discovered based on co-design principles, wherein design for stability is based on the propensity for the photocatalyst to self-passivate under operating conditions and design for photoactivity is based on the ability to integrate the photocatalyst with established semiconductor substrates. Here, we report on the synthesis and characterization of zinc titanium nitride (ZnTiN2) that follows these design rules by having a wurtzite-derived crystal structure and showing self-passivating surface oxides created by electrochemical polarization. The sputtered ZnTiN2 thin films have optical absorption onsets below 2 eV and n-type electrical conduction of 3 S/cm. The band gap of this material is reduced from the 3.36 eV theoretical value by cation-site disorder, and the impact of cation antisites on the band structure of ZnTiN2 is explored using density functional theory. Under electrochemical polarization, the ZnTiN2 surfaces have TiO2- or ZnO-like character, consistent with Materials Project Pourbaix calculations predicting the formation of stable solid phases under near-neutral pH. These results show that ZnTiN2 is a promising candidate for photoelectrochemical liquid fuel generation and demonstrate a new materials design approach to other photoelectrodes with self-passivating native operational surface chemistry.

Stability of Studtite in Saline Solution: Identification of Uranyl–Peroxo–Halo Complex

Hydrogen peroxide is produced upon radiolysis of water and has been shown to be the main oxidant driving oxidative dissolution of UO2-based nuclear fuel under geological repository conditions. While the overall mechanism and speciation are well known for granitic groundwaters, considerably less is known for saline waters of relevance in rock salt or during emergency cooling of reactors using seawater. In this work, the ternary uranyl–peroxo–chloro and uranyl–peroxo–bromo complexes were identified using IR, Raman, and nuclear magnetic resonance (NMR) spectroscopy. Based on Raman spectra, the estimated stability constants for the identified uranyl–peroxo–chloro ((UO2)(O2)(Cl)(H2O)2–) and uranyl–peroxo–bromo ((UO2)(O2)(Br)(H2O)2–) complexes are 0.17 and 0.04, respectively, at ionic strength ≈5 mol/L. It was found that the uranyl–peroxo–chloro complex is more stable than the uranyl–peroxo–bromo complex, which transforms into studtite at high uranyl and H2O2 concentrations. Studtite is also found to be dissolved at a high ionic strength, implying that this may not be a stable solid phase under very saline conditions. The uranyl–peroxo–bromo complex was shown to facilitate H2O2 decomposition via a mechanism involving reactive intermediates.

An ab initio investigation of the temperature-dependent energetic barriers towards CrAlB and (Mo,Cr)AlB formation in a metastable synthesis scenario.

The orthorhombic CrAlB MAB phase has not been synthesized so far and was shown to be energetically unstable vs. the competing Cr2AlB2 phase in previous theoretical reports, which, however, did not explicitly investigate the magnitude of the energetic barrier towards CrAlB formation as a function of temperature. Temperature-dependent Gibbs energies of formation, obtained from density-functional-theory-based lattice dynamics simulations performed in this study, reveal that this barrier is very small (around 10 kJ mol-1 ≈ 0.008 eV per atom, on average) and may readily be overcome during high-energy synthesis scenarios, likely resulting in metastable phase formation. Furthermore, the electronic structures of MoAlB, a phase synthesized experimentally both in bulk and thin film form, and CrAlB are shown to be similar in direct comparison, with MoAlB exhibiting a higher electronic stability due to a local DOS minimum in proximity to the Fermi level, and quaternary compositions lying between the ternaries. Likewise, bonding characteristics are qualitatively very similar between both phases, with the transition metal-boron bonds being the dominant interaction in the entire unit cell, even though individual B-B bonds are stronger; quantitatively, all interactions are again stronger in MoAlB compared to CrAlB. It is reasonable to assume that, considering the successful synthesis of phase-pure MoAlB and known formation of metastable phases during physical vapor deposition, direct synthesis of metastable CrAlB thin films is possible due to the aforementioned small energy barrier. Furthermore, stability is enhanced upon alloying with Mo as this lowers the energy of formation, with a Mo/Cr ratio of approx. 0.33 sufficient to stabilize the Cr-rich (Mo,Cr)AlB solid solution vs. the primary competing phases, allowing for deposition of Mo-concentration-dependent stable and metastable (Mo,Cr)AlB solid solution phases.

Thermal and Tidal Evolution of Uranus with a Growing Frozen Core

Abstract The origin of the very low luminosity of Uranus is unknown, as is the source of the internal tidal dissipation required by the orbits of the Uranian moons. Models of the interior of Uranus often assume that it is inviscid throughout, but recent experiments show that this assumption may not be justified; most of the interior of Uranus lies below the freezing temperature of H2O. We find that the stable solid phase of H2O, which is superionic, has a large viscosity controlled by the crystalline oxygen sublattice. We examine the consequences of finite viscosity by combining ab initio determinations of the thermal conductivity and other material properties of superionic H2O with a thermal evolution model that accounts for heat trapped in the growing frozen core. The high viscosity provides a means of trapping heat in the deep interior while also providing a source of tidal dissipation. The frozen core grows with time because its outer boundary is governed by the freezing transition rather than compositional layering. We find that the presence of a growing frozen core explains the anomalously low heat flow of Uranus. Our thermal evolution model also predicts time-varying tidal dissipation that matches the requirements of the orbits of Miranda, Ariel, and Umbriel. We make predictions that are testable by future space missions, including the tidal Love number of Uranus and the current recessional rates of its moons.

Emergence of dynamical disorder and phase metastability in carbon nanobowls

The condensed phases of the carbon-based nanobowl corannulene are herein investigated in the temperature range 200–573 K, combining differential scanning calorimetry, synchrotron X-ray diffraction, and quasielastic neutron-scattering. For the first time, we identify the presence of a well-defined thermal event at 382 K, a figure well below a melting point of 540 K. Contrary to naïve expectation, detailed analysis of the neutron-scattering data below and above this pre-melting transition signals the emergence of correlated stochastic dynamics within both thermodynamically stable solid phases of the material. We find that these are progressively responsible for the suppression of molecular and supramolecular order over mesoscopic length scales, and are associated with the formation of high-symmetry rotor-like states exhibiting localized stochastic motions. Upon cooling from the melt, we have also discovered a robust hysteresis associated with the existence of hitherto-unknown metastable liquid (deep-supercooled) and disordered-solid phases. This behaviour is markedly different from that observed in the quintessential Buckminsterfullerene C60 or other chemically substituted fullerene adducts studied to date at this level of detail. These results evince new and yet-to-tapped opportunities for the use of the stable and metastable phases of carbon-based nanobowls in novel applications exploiting the emergence of dynamical disorder at the nanoscale.

Non-conventional CO2 sequestration via Vitamin C promoted green reaction: Yield evaluation

Carbon dioxide increase in the atmosphere is a relentless rise process. Many mitigation measures aimed at the reduction of carbon dioxide emissions coupled with capture in variously stable sequestration systems have been proposed over time.In a previous paper (Pastero, 2019), we proposed a new and green method to capture carbon dioxide avoiding the usage of hazardous reagents and the production of harmful compounds. The method involves the application of an aqueous solution of calcium ascorbate (vitamin C) as the only reagent and the precipitation of calcium oxalate as the main reaction product.The role of the chemical and physical process variables controlling the reaction has been investigated in order to increase significantly and stabilize the reaction yield in terms of CO2-sequestration capacity. In the present paper, we evaluated the performance of our method quantitatively, referring to two simple experimental setups: the maximum carbon dioxide yield exceeded 60 %, meaning that every 100 mol of carbon dioxide fed to the capturing system, 60 mol are removed and stored into a stable solid phase. This boost in the method’s performance was obtained optimizing the key-parameters of the reaction and increasing the exchange surface.

Electrolyte viscosity and solid phase formation during aluminium electrolysis

This paper presents experimental data on the dependence on alumina and calcium fluoride concentrations of the viscosity of the industrial electrolytes NaF-AlF3-CaF2-Al2O3 with cryolite ratios (CR) of 2.1, 2.3, 2.5 in the temperature range 1243–1293 K. The temperature dependence of the formation of a solid phase on the graphite crucible wall in cryolite-alumina electrolyte during aluminium electrolysis was studied in a laboratory-scale electrolytic cell. The viscosity of the industrial electrolytes was found to depend more on the temperature and cryolite ratio than on the alumina concentration in the melt. A long period of electrolysis with controlled solid phase formation on the cell wall was carried out, with a constant electrolyte composition (CR = 2.4), a calcium fluoride concentration of 5 wt% and an alumina content of 4.0 wt%. The formation of a stable solid phase layer on the graphite crucible wall was found to depend on the electrolysis temperature. A correlation was observed between the formation of a solid under the influence of temperature and the viscosity of the melt.