Acidic Melts Research Articles

A general Lewis acidic etching route for preparing MXenes with enhanced electrochemical performance in non-aqueous electrolyte.

Two-dimensional carbides and nitrides of transition metals, known as MXenes, are a fast-growing family of materials that have attracted attention as energy storage materials. MXenes are mainly prepared from Al-containing MAX phases (where A = Al) by Al dissolution in F-containing solution; most other MAX phases have not been explored. Here a redox-controlled A-site etching of MAX phases in Lewis acidic melts is proposed and validated by the synthesis of various MXenes from unconventional MAX-phase precursors with A elements Si, Zn and Ga. A negative electrode of Ti3C2 MXene material obtained through this molten salt synthesis method delivers a Li+ storage capacity of up to 738 C g-1 (205 mAh g-1) with high charge-discharge rate and a pseudocapacitive-like electrochemical signature in 1 M LiPF6 carbonate-based electrolyte. MXenes prepared via this molten salt synthesis route may prove suitable for use as high-rate negative-electrode materials for electrochemical energy storage applications.

Isotopic-Geochemical Features of the Generating of the Precious Metal Formations of the Jiamusi-Khanka Graphite-Bearing Province

Numerous occurrences of the precious metal mineralization located solely in the Jiamusi-Khanka province were detected within a single zone of the regional graphitization with ten kilometers submeridional strike towards the adjacent territories of the Primorsky krai (Russia) and the Heilongjian province (China), all the above said findings being obtained with the participation of the authors of the present scientific article. There are features of Dalnerechensk group (with Filinskoye being the largest of them), deposits of of Lesozavodsk group (Tamga, Turgenevo) and graphite-ore giant of Liumao Mashan group of the Heilongjian province in the Northern, central and Southern sides of this province respectively. The results of the isotopic-geochemical study of the graphite, the sulfides and the carbonates of these deposits, the formation of which has a common history with the one of the precious metal mineralization, indicate the participation of deep derivated recomposed fluids and the light isotopic-biogenic matter of the host rocks in the ore formation. Besides, the carbon and the oxygen from at least two more isotopic-contrast sources intruded into the ore-forming system. Some minerals were formed under the influence of the intrusive acidic melts on the carbonate rocks, other one were generated due to the involvement of the meteoric waters in the ore formation.

Sequence-selective dynamic covalent assembly of information-bearing oligomers

Relatively robust dynamic covalent interactions have been employed extensively to mediate molecular self-assembly reactions; however, these assembly processes often do not converge to a thermodynamic equilibrium, instead yielding mixtures of kinetically-trapped species. Here, we report a dynamic covalent self-assembly process that mitigates kinetic trapping such that multiple unique oligomers bearing covalently coreactive pendant groups are able to undergo simultaneous, sequence-selective hybridization with their complementary strands to afford biomimetic, in-registry molecular ladders with covalent rungs. Analogous to the thermal cycling commonly employed for nucleic acid melting and annealing, this is achieved by raising and lowering the concentration of a multi-role reagent to effect quantitative dissociation and subsequently catalyze covalent bond rearrangement, affording selective assembly of the oligomeric sequences. The hybridization specificity afforded by this process further enabled information encoded in oligomers to be retrieved through selective hybridization with complementary, mass-labeled sequences.

Dissolution of Pyrochlore and Microlite in Alkaline, Subaluminous, and Peraluminous Granitoid Melts

The represented experimental data on the Ta and Nb contents in acidic magmatic melts of different compositions, when dissolving pyrochlore and microlite at T = 650–850 °C and P = 100–400 MPa, make it possible to obtain quantitative characteristics to create physico-chemical models of the genesis of Ta–Nb deposits. At pyrochlore dissolution in granitoid melts at P = 100 MPa, the highest Nb content (0,7–1,9 wt.%) is obtained in alkaline melts, it decreases to 0,06–0,38 wt.% in sub-aluminous melts, and then slightly increases to 0,11–0,41 wt.% in high-alumina melts. An increase in temperature increases the dissolution of pyrochlore, and an increase in pressure decreases its. In high-alumina granite melts the pyrochlore is unstable. At the microlite dissolves with the increase in the alumina-rich melt, the Nb/Ta ratio in the melt increases approximately doubles.

Biosphere Conversion of Substances and Energy in the Formation of Continents

The sedimentary stratum of the oceanic crust with a thickness of up to 3 kilometers and younger than the Jurassic age deposits of organic matter (OM) sediments, is saturated with O2 absorbed and dissolved in the ocean with binding energy in the range of 5–15 kJ/mol. During subduction of the oceanic crust into the mantle with T = 170–500°C, fluids of O2, H2O, CO2 are released and are subsequently filtered to the surface of the suprasubduction roof. The fluid O2 oxidizes the matters of the sedimentary cover, the mantle and the roof with O2 energy release of 14.97 kJ/kg. This results in the formation of a magma chamber. The melts of the chamber are divided with respect to density and composition into light-acidic enriched in SiO2 and compact—basic enriched in Са, Мg, K. The discharged acidic melts form a crust of a continental type. Energy saturation of the magma chamber is increased by exogenic energy of OM pyrolysis. At depths of subduction at T = 500–1200°C, OM undergoes deep metamorphism with the release of oil and gas fluids which form a planetary system of hydrocarbons. The continental crust and the hydrocarbon system are formed in many respects due to the biosphere conversion of solar energy, oxygen, and OM to the composition of the Earth’s outer shells.

MECHANISMS OF MAGMATIC MINGLING IN COMPOSITE DYKES: MODELS OF DISPERSION AND SHEAR DILATATION

This article is focused on the intrusion and formation of combined dykes. Two main groups of conventionally magmatic mingling are distinguished: (1) plutonic bodies, and (2) combined dykes. The first group is represented by small basite inclusions that are uniformly scattered in granitoid bodies, and includes elongated swarms and tails of small bodies. The second group includes composite dykes with the indicators of mechanical mingling of basic and acid melts. Despite the similarities in the structural and textural features and the indicators of mechanical mingling of melts, these two groups are characterized by clearly different proportions of the volumes of contrasting melts and differ in the duration of formation, place of melt mingling, and tectonic setting. None of the available models was able to explain the occurrence of magmatic mingling structures in individual dykes. In our study, the mingling mechanisms of contrasting melts are discussed using the data on the geological objects located in West Sangilen, an area of the Central Asian Orogenic Belt (CAOB). The general and specific parameters of combined dikes of the Saizyral and Tavyt‐ Dag sites are considered. The models of shear dilatation and dispersion are proposed for explaining the mechanisms of magmatic mingling in combined dykes.

Low-temperature acidic melts of Bazman volcano (Iran)

The inclusions of a silicate melt were investigated in quartz insets of the extrusive rhyolite collected at Bazman Cenozoic volcano (Iran) and associated with the process of recent subduction. Low temperatures of the silicate melt along with high concentrations of water in the melt are ascertained. The microelemental composition of the melt showed a similarity to acidic melts of island-arc formations.

The characteristic of acid melts which formed tephra of pleistocene-holocene eruptions of Ichinsky Volcano, Kamchatka (Results of melt inclusions study)

This paper presents the results of a study of melt inclusions in plagioclase, amphibole and pyroxene from Ichinsky volcano’s tephras of different age. Two types of melts have been identified, distinguished by different concentrations of potassium (K2O). Major and trace elements’ composition of these melts indicates that magma mixing was the dominating process in the Ichinsky magmatic system.

Low-Temperature Acidic Melts of Bazman Volcano (Iran)

The inclusions of a silicate melt were investigated in quartz insets of the extrusive rhyolite collected at Bazman Cenozoic volcano (Iran) and associated with the process of recent subduction. Low temperatures of the silicate melt along with high concentrations of water in the melt are ascertained. The microelemental composition of the melt showed a similarity to acidic melts of island–arc formations.

Bayan-Kol Gabbro–Granite Association (Western Sangilen, Southeastern Tuva): Composition, Age Boundaries, and Tectonic and Geodynamic Settings

Abstract —The Bayan-Kol gabbro–granite association has been recognized within the West Sangilen fragment of collision zone in the northwestern framing of the Tuva–Mongolian massif, and its composition, age, and tectonic and geodynamic settings have been studied. The association includes the Bayan-Kol pluton and composite (mingling) dikes, which formed in the late collision period (495 ± 5 Ma), during the transition from transpression to extension mode with left-lateral strike-slip kinematics. The Bayan-Kol gabbro–granite association is spatially confined to the penetrating tectonic zones of the West Sangilen shear system. The position of gabbroid and granite bodies is controlled by local zones of tectonic extension. Basic magmas have a similar petrogeochemical composition, which indicates their intrusion from a single chamber of basic composition and differentiation of ascending magma. The melting, transfer, and formation of crustal granitoids of the Bayan-Kol association are genetically related to the thermal effect of basic melt and a syntectonic drop in lithostatic pressure. The intrusion and formation of basic and acid melts of the Bayan-Kol association took place at the lower and middle crustal levels in the settings of the reactivation and subsequent fragmentation of the tectonic zone.

The First Discovery of Low-temperature Rhyolite Melts in Cenozoic Long-lived Bazman Volcano, East Iran; Some Problems and Discussion

The igneous rocks, some geological specifics, and also the very melt inclusions in Late Cenozoic rhyolites were studied in the long-lived Miocene (N1, ca. 20 Ma) - Late Quaternary (Q3?) Bazman volcano, eastern Iran. Unusual low temperature (ca. 690o C) silicate melt inclusions in quartz (Qtz) with a High/very High water content (from average 6.9 to 8.2 (up to 9.0 as a limit) wt% H2O) in the acid rocks were defined by independent methods for the first time. Whole-rock chemistry of the melts studied is similar to ones in subduction-related acid melts from different regions. Rhyolites studied sometimes have higher concentration of ore elements, similar to ones in even basites. Ore inheritance from economic porphyry – PCD (Cu-Au +- Mo) Paleogene (mainly Eocene - Pg2) mineralization and deposits in the region is proposed. Geological anomaly of the whole region is proposed by a complex analysis. This anomaly is maybe responsible for anomalous magmatism due to a known tomography data (since Paleocene (Pg1), as minimum), tectonics, metallogeny (including economic one), and maybe - hydrocarbons (HC, oil - gas) activity.

Calorimetric properties of 1,9‑Nonanedioic acid and its solubility in selected organic solvents

The solubility of a solid in a given solvent is decided jointly by its thermodynamic stability and the solute-solvent intermolecular forces. The melting point and enthalpy of melting of 1,9‑Nonanedioic acid as well as its heat capacities at solid and melt state were determined by DSC. The solubilities of 1,9‑Nonanedioic acid in ethanol, acetone, acetic acid and ethylene glycol were measured at temperatures from 276 to 337 K. The solubilities in the four solvents at constant temperature are in the order of ethanol > acetic acid > acetone > ethylene glycol while the temperature dependence is in the opposite order. The experimental solubility data were correlated with the van't Hoff, Wilson and the λh equations with the measured melting properties. The three models with optimized parameters are all able to reproduce the experimental data well, among which the λh equations has lowest average standard deviation and seems to be more consistent with the experimental data. Thermodynamic analysis of the obtained model parameters shows that the dissolution of 1,9‑Nonanedioic acid in the four solvents are all endothermic and mainly driven by the enthalpy change of the solution. The positive excess enthalpy of mixing the 1,9‑Nonanedioic acid melt and the solvent indicates the solute-solvent intermolecular interactions are dominated by repulsive forces.

Cellular target engagement: a new paradigm in drug discovery.

Cellular target engagement: a new paradigm in drug discovery.

Analysis of axisymmetric instability in polymer melt electrospinning jet

The linear stability analysis is carried out for the straight jet of a polymer melt in an electrospinning process. The stability of axisymmetric disturbances is examined in order to comprehend the onset of fiber morphology with diametric variations or bead formation along the fiber under non-isothermal electrospinning conditions. As the polymeric fluid (polylactic acid melt) is a low conductivity fluid with unentangled polymer molecules, the viscoelasticity is described using the non-linear rheological Giesekus constitutive model assuming very small axial conduction current. The non-periodic axisymmetric disturbances are imposed on the non-uniform radius jet, obtained as the solution of the 1-D slender filament governing equations and the eigenspectrum for the disturbance growth rate is constructed under the realistic melt electrospinning conditions. The growth rate corresponding to the leading mode in the eigenspectrum is found to increase with increasing surface tension forces and decrease with the enhanced external electric field. Thus, the leading growth rate behavior suggests that the classical Rayleigh–Plateau instability dominates over the conducting mode of instability for melt electrospinning. Further, the role of non-isothermal conditions in the stability behavior is examined. The convective heat transfer from electrified jet to the cooling ambiance leads to thicker fibers with greater stability to axisymmetric disturbances. The stabilizing effect of heat transfer is attributed mainly to the temperature sensitive fluid rheology. In particular, the enhancement in polymer viscosity in the jet propagation direction is responsible for the build up of stabilizing viscoelastic stress. The fluid elasticity, denoted by the flow Deborah number, also tends to stabilize the electrified jet as temperature drop along the flow increases the relaxation time of the polymer chains leading to high polymeric stress associated with the stretched chains. As crystallization of polymeric chains under non-isothermal condition is not considered, the analysis holds for either amorphous polymers or polymers with slow crystallization kinetics compared to the short residence time during the spinning flow.

Effect of the Mechanical Treatment of Alumina on Thermal, Morphological and Dielectric Properties of LDPE/Al2O3 Composites

Composites of LDPE filled with different amounts of alumina Al 2 O 3 were prepared using co-mixing technique and melt-mixing. This technique, which is easy, non-toxic and inexpensive, has been successfully used in our laboratory for different polyolefins/metal oxides nanocomposites elaboration. Samples containing 0.5, 1 and 2 wt% of alumina, were prepared by melt-mixing at 190 °C without any chemical treatment or coupling agent. The effect of alumina treatment was studied. The Al 2 O 3 was first co-mixed with the stearic acid then added to the polymer. The stearic acid melts at 70 °C, thus ensuring the dispersion of the covered filler particles into the polymeric matrix, which leads to better experimental results. The morphological characterization was carried out by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal properties were investigated by thermogravimetric analysis (TGA). The electrical conductivity was also studied. The microstructure-properties relationships were also investigated. The composites prepared with the co-mixed Al 2 O 3 were compared to those prepared with the neat Al 2 O 3 . The thermogravimetric (TGA) results showed an enhancement of 55 °C in the thermal stability for the LDPE/Al 2 O 3 composition containing 1 wt% of treated Al 2 O 3 . The electrical conductivity results showed also an optimum value of 6.6.10–7 U –1 cm –1 for the same composition. Keywords: Composites, LDPE, Al 2 O 3 nanoparticles, stearic acid, co-mixing method

Development of Bigels Based on Stearic Acid–Rice Bran Oil Oleogels and Tamarind Gum Hydrogels for Controlled Delivery Applications

AbstractIn the last few decades, different types of gels have been widely studied as potential drug delivery carriers. In this paper, we propose the synthesis of an oleogel, a tamarind gum hydrogel, and bigels for applications as drug delivery matrices. The oleogel was prepared by mixing stearic acid and rice bran oil, whereas the hydrogel was prepared by mixing tamarind gum with a hydroethanolic solution. Hydrogel‐in‐oleogel and oleogel‐in‐hydrogel bigels were prepared by mixing the hydrogel and the oleogel. The suitability of the formulations for controlled drug release applications was thoroughly examined using microscopy, Fourier transform infrared (FTIR) spectroscopy, as well as mechanical, electrical, thermal, drug release, and antimicrobial studies. An alteration in the microarchitecture of the bigels is observed when the oleogel and the hydrogel are mixed in varying proportions. The associative interactions within the formulations increase with the increase in the hydrogel content. The bigels exhibit the presence of stearic acid melting endotherm (associated with the oleogel) and water evaporation endotherm (associated with the hydrogel). This study suggests that the hydrogel has lowest bulk resistance compared to the other formulations. The structural breakdown of the bigels is composition‐dependent, and the bulk electrical resistance is mainly governed by the oleogel phase. An increase in the diffusion of the moxifloxacin HCl from the formulations is observed with the increase of the hydrogel proportion, which in turn increases the rate of release of the drug. The proposed formulations also exhibit good antimicrobial efficacy. The analysis of these properties suggests that specific formulations can be tailored by need‐based applications of the drug release rate.

Catalyzed Oxidation of Chlorine and Bromine in Room Temperature Chloroaluminate and Bromoaluminate Melts

The use of haloaluminate room temperature molten salts has potential for interesting battery chemistries. This is particularly true for acidic (excess Lewis acid, e.g. AlCl3, over the organic chloride salts) compositions. In that case, Al is readily plated and stripped, as we discussed some time ago.1 A particularly interesting battery combination arises when the aluminum negative electrode is paired with the evolution of the halogen from the acidic melt. In that case, maximum redox active species concentration is achieved and maximum voltage can be obtained since the entire electrochemical window is utilized. However, several issues with chlorine evolution are known. First, in an acidic melt chlorination of imidazolium cations occurs. This can be partly mitigated by appropriate modification of the cation. A second problem is the somewhat sluggish catalysis of chlorine evolution observed on carbon surfaces. In this work, we report results of efforts to improve on the latter aspect. Specifically, we describe the catalysis of chlorine evolution by catalytically active surfaces. In particular, we show significant enhancements in onset potential for chlorine evolution using supported Ru catalysts. In Figure 1, we compare the chlorine evolution voltammetry in 1.5:1.0 AlCl3:EMIC on bare glassy carbon to that observed on the same electrode coated with a sample of 60 wt% Ru on multiwalled nanotubes (prepared in-house). The onset of chlorine evolution occurs on the order of 300 mV less positive with the supported Ru catalysts. We have deposited the Ru on various carbon structures to explore the applicability of this catalyst system for batteries and flow batteries. Studies of the same reaction on Pt electrodes show that the supported Ru nanoparticles have similar activity to that of Pt for this reaction. In addition, similar results were also obtained for bromine evolution. In that case, the lower volatility of the product allowed us to readily observe the bromine oxidation on the reverse scan. This reaction is substantially more reversible on these catalyzed surfaces. Figure 1: Voltammetry of 60%Ru on MWNT on glassy carbon compared to that of the bare glassy carbon electrode. Figure 1

Influence of Controlled Cooling in Bimodal Scaffold Fabrication Using Polymers with Different Melting Temperatures.

The combination of different materials and capabilities to manufacture at several scales open new possibilities in scaffold design for bone regeneration. This work is focused on bimodal scaffolds that combine polylactic acid (PLA) melt extruded strands with polycaprolactone (PCL) electrospun fibers. This type of bimodal scaffold offers better mechanical properties, compared to the use of PCL for the extruded strands, and provides potential a means for controlled drug and/or growth factor delivery through the electrospun fibers. The technologies of fused deposition modeling (FDM) and electrospinning were combined to create 3D bimodal constructs. The system uses a controlled cooling system allowing the combination of polymers with different melting temperatures to generate integrated scaffold architecture. The thermoplastic polymers used in the FDM process enhance the mechanical properties of the bimodal scaffold and control the pore structure. Integrated layers of electrospun microfibers induce an increase of the surface area for cell culture purposes, as well as potential in situ controlled drug and/or growth factor delivery. The proposed bimodal scaffolds (PLA extruded strands and PCL electrospun fibers) show appropriate morphology and better mechanical properties when compared to the use of PCL extruded strands. On average, bimodal scaffolds with overall dimensions of 30 × 30 × 2.4 mm3 (strand diameter of 0.5 mm, strand stepover of 2.5 mm, pore size of 2 mm, and layer height of 0.3 mm) showed scaffold stiffness of 23.73 MPa and compression strength of 3.85 MPa. A cytotoxicity assay based human fibroblasts showed viability of the scaffold materials.

Metallogenic Dynamics Background of Ga’erqiong Cu-Au Deposit in Tibet, China

The Ga’erqiong Cu-Au deposit, which sits on the north side of the Coqên-Xainzamagmatite belt, is a large-scale skarn-type deposit, whose ore body has formed in the skarn zone in the contact part of quartz diorite and marble of Duoai formation or the cracks of quartz diorite. Its mineralization is closely related to quartz diorite. And granite porphyry-related molybdenum ore still exists in its deep part. Currently, there are disputes about the metallogenic dynamics background of this deposit. From previous studies, this paper carried out zircon LA-LCPMS U-Pb dating and petrogeochemistry study for quartz diorite of Ga’erqiong Cu-Au deposit. The testing result indicates: quartz diorite and granite porphyry were formed respectively in 88±2Ma and 83±1Ma, belonging to the magmatic activity of the early stage of Upper Cretaceous; quartz diorite and granite porphyry have geochemical characteristics similar to those of island arc rock of subduction zone and geochemical indexes similar to “adakite.” Combining with the regional tectonic evolution, we think that quartz diorite and granite porphyry were all formed in the extension environment after the collision of Lhasa block and Qiangtang block. Quartz diorite is the result of the migmatization of basic melt and acid melt evoked by asthenosphere material raise caused by lower crustal delamination; the formation of granite porphyry may be crust-mantle material’s partial melting results due to delaminated lower crustal. Therefore, Ga’erqiongskarn-type Cu-Au deposit belongs to the metallogenic response to the collisional orogeny in the closing process of Meso-Tethys.

Na2SO4-Deposit-Induced Corrosion of Mo-Containing Alloys

Disk alloys used in advanced gas turbine engines often contain significant amounts of Mo (2 wt% or greater), which is known to cause corrosion under Type I hot corrosion conditions (at temperatures around 900 °C) due to alloy-induced acidic fluxing. The corrosion resistance of several model and commercial Ni-based disk alloys with different amounts of Mo with and without Na2SO4 deposit was examined at 700 °C in air and in SO2-containing atmospheres. When coated with Na2SO4 those alloys with 2 wt% or more Mo showed degradation products similar to those observed previously in Mo-containing alloys, which undergo alloy-induced acidic fluxing Type I hot corrosion even though the temperatures used in the present study were in the Type II hot corrosion range. Extensive degradation was observed even after exposure in air. The reason for the observed degradation is the formation of sodium molybdate. Transient molybdenum oxide reacts with the sodium sulfate deposit to form sodium molybdate which is molten at the temperature of study, i.e., 700 °C, and results in a highly acidic melt at the salt alloy interface. This provides a negative solubility gradient for the oxides of the alloying elements, which results in continuous fluxing of otherwise protective oxides.