Ternary Salt Research Articles

Ternary molten salt-assisted lignin pyrolysis for the co-production of monophenols and value-added carbon materials

In this paper, the ternary molten salt (Li2CO3-Na2CO3-K2CO3) was introduced into the lignin pyrolysis process for the co-production of monophenols and value-added carbon materials. The effect of lignin/molten salt ratios (i.e., 3:1, 1:1, and 1:3) on lignin pyrolysis behaviour was investigated herein. The pyrolytic products were characterized by gas chromatography–mass spectrometry, ultimate analyses, scanning electron microscopy, nitrogen adsorption analyses, and Raman analyses. Results showed that molten salt media can promote the conversion of bulky phenolic oligomers into mono-phenols by enhancing the cracking and deoxygenation reactions. P-type phenols (49.76 %) were produced when the lignin/molten salt mass ratio was 1:3. The porosity and aromaticity of biochar were regulated in-situ using molten salt. The possible catalytic effect of molten salt on lignin pyrolysis was proposed. This study provides a case reference for lignin waste resource utilization.

Preparation and thermal properties of LiNO3-NaNO3-NaCl/EG composite heat storage material

Nitrate phase change materials (PCM) have important applications in the field of thermal energy storage, but their latent heat value is relatively low. A novel LiNO3-NaNO3-NaCl ternary molten salt with high latent heat was prepared and studied. LiNO3-NaNO3-NaCl/expanded graphite (EG) composite phase change material (CPCM) was prepared by using high thermal conductivity EG as the carrier adsorption material. The performance of PCM and CPCM were tested and analyzed. Compared with LiNO3-NaNO3, the newly prepared ternary nitrate-chloride mixed molten salt has a lower phase change temperature, a higher latent heat value, and a higher thermal decomposition temperature. At the same time, the supercooling degree of LiNO3-NaNO3-NaCl is about half lower than that of LiNO3-NaNO3. There is no chemical reaction between different molten salts or between mixed molten salts and EG. The mixed molten salt is uniformly dispersed into the pore structure of EG, and no agglomeration occurs. Both LiNO3-NaNO3-NaCl and LiNO3-NaNO3-NaCl/EG have good cyclic thermal stability. The addition of EG greatly improves the thermal conductivity of LiNO3-NaNO3-NaCl. When the addition ratio of EG is 20%, the thermal conductivity of ternary molten salt increases from 1.378 to 5.453 W/m·K. The phase change materials added with EG still have high latent heat of phase change. The results show that LiNO3-NaNO3-NaCl/EG has broad application prospects in medium temperature heat storage.

Bottom-up Synthesis of Single-Crystalline Poly (Triazine Imide) Nanosheets for Photocatalytic Overall Water Splitting.

Poly (triazine imide) (PTI/Li+Cl-), one of the crystalline versions of polymeric carbon nitrides, holds great promise for photocatalytic overall water splitting. In principle, the photocatalytic activity of PTI/Li+Cl- is closely related to the morphology, which could be reasonably tailored by the modulation of the polycondensation process. Herein, we demonstrate that the hexagonal prisms of PTI/Li+Cl- could be converted to hexagonal nanosheets by adjusting the binary eutectic salts from LiCl/KCl or NaCl/LiCl to ternary LiCl/KCl/NaCl. Results reveal that the extension of in-plane conjugation is preferred, when the polymerisation was performed in the presence of ternary eutectic salts. The hexagonal nanosheets bears longer lifetimes of charge carriers than that of hexagonal prisms due to lower intensity of structure defects and shorter hopping distance of charge carriers along the stacking direction of triazine nanosheets. The optimized hexagonal nanosheets exhibits a record apparent quantum yield value of 25% (λ=365nm) for solar hydrogen production by one-step excitation overall water splitting.

Bottom‐up Synthesis of Single‐Crystalline Poly (Triazine Imide) Nanosheets for Photocatalytic Overall Water Splitting

AbstractPoly (triazine imide) (PTI/Li+Cl−), one of the crystalline versions of polymeric carbon nitrides, holds great promise for photocatalytic overall water splitting. In principle, the photocatalytic activity of PTI/Li+Cl− is closely related to the morphology, which could be reasonably tailored by the modulation of the polycondensation process. Herein, we demonstrate that the hexagonal prisms of PTI/Li+Cl− could be converted to hexagonal nanosheets by adjusting the binary eutectic salts from LiCl/KCl or NaCl/LiCl to ternary LiCl/KCl/NaCl. Results reveal that the extension of in‐plane conjugation is preferred, when the polymerisation was performed in the presence of ternary eutectic salts. The hexagonal nanosheets bears longer lifetimes of charge carriers than that of hexagonal prisms due to lower intensity of structure defects and shorter hopping distance of charge carriers along the stacking direction of triazine nanosheets. The optimized hexagonal nanosheets exhibits a record apparent quantum yield value of 25 % (λ=365 nm) for solar hydrogen production by one‐step excitation overall water splitting.

Laser-texturing of stainless steel as a corrosion mitigation strategy for high-temperature molten salts applications under dynamic conditions

Molten salts are utilized in a wide range of applications including nuclear, fuel cells, Carnot batteries, and Concentrated Solar Power (CSP). In order to enhance the profitability of next-generation CSP plants, increasing their efficiency is imperative. Ternary carbonate salts are capable of elevating the maximum CSP operating temperature, which results in improved power generation efficiency. However, higher temperatures lead to accelerated corrosion and more severe conditions for structural materials. In this study, nanosecond laser micromachining is investigated as a potential corrosion mitigation technique for molten carbonate salts in dynamic conditions. SS310 samples with laser-induced surface textures are subjected to the flow of molten Li2CO3–K2CO3–Na2CO3 at 600 °C for a period of 600 h. Laser treatment significantly impedes corrosion in SS310, as untreated samples display pitting and scaling, while minimal surface changes are noted on treated samples. Cross-sectional analysis of the samples reveals considerable peeling in the untreated samples and a 45% increase in the corrosion rate compared to the treated samples. The concentrations of Cr and Mg in the salt (determined through ICP analysis) are found to be twofold and fourfold higher than those in treated samples. Laser treatment renders Cr and Mg less accessible to the salt ions, particularly Li, which results in improved corrosion resistance.

Effect of TiO2 nanoparticles on the thermal energy storage of HITEC salt for concentrated solar power applications

Thermal energy storage materials are substantial in concentrated solar power (CSP) plants as they absorb solar thermal energy and store it to be used for electricity production. Enhancing the thermophysical properties of these materials will positively affect the efficiency of the CSP plant system and lower electricity price. This research synthesized a novel composite of Titanium Dioxide (TiO2) nanoparticles and the ternary nitrate molten salt (HITEC) at different nanoparticle concentrations. The nano-enhanced molten salt (NEMS) samples were characterized for compatibility and nanostructure analysis. Also, the thermophysical properties and thermal cycling behaviour of the NEMS samples were evaluated. The results indicate that 0.1 wt% can enhance the specific heat capacity of HITEC by 5.5 %, latent heat by 78 %, and upper working temperature by 5 %. The morphological analysis of the 0.1 wt% NEMS sample revealed a good dispersion of nanoparticles in HITEC and the formation of nanostructures. The FT-IR analysis showed the chemical stability of the nanofluid with no presence of chemical reaction between its components. The thermal cycling test of the optimum sample showed the chemical stability of the nanocomposite and the thermal cycling stability of the enhanced thermophysical properties.

Study on preparation and application of NaCl-KCl-CsCl-Cs2ZrCl6 composite electrolyte

Preparing zirconium chloride composite salts such as Cs2ZrCl6 can replace highly volatile ZrCl4 for studying molten salt electrolytic refining zirconium. The NaCl-KCl-CsCl-Cs2ZrCl6 composite electrolyte was prepared using ternary molten salt with a molar ratio of NaCl: KCl: CsCl=30: 24.5: 45.5 and ZrCl4 as raw materials. According to thermodynamic analysis, ZrCl4 preferentially reacts with CsCl to form Cs2ZrCl6 with strong stability. X-ray diffraction analysis showed that the main phase of the product was Cs2ZrCl6. ICP-DSC analysis showed that the conversion rate of ZrCl4 to Cs2ZrCl6 reached 99.68%. To verify the properties of this electrolyte, it is applied to molten salt electrolytic refining sponge zirconium. Studies have shown that this electrolyte system obtains dendrite zirconium products with a maximum grain size of 6.29mm, a system with more application prospects.

Cocrystallization-Driven Double-Optimized Stratagem toward Directional Self-Assembly for the First Ternary Salt Cocrystal of Cardiotonic Drug Milrinone with Different Phenolic Acids Exhibits Optimal In Vitro/Vivo Biopharmaceutical Peculiarities.

The current research leverages the structural features and property superiorities along with benefits in protecting cardiovascular system of gallic acid (GLC) and gentisic acid (HGA) to optimize in vitro/vivo peculiarities of cardiotonic drug milrinone (MIL) through developing a stratagem of cocrystallization-driven double-optimized ternary salt cocrystal. This strategy assembles MIL ternary salt cocrystal by shaping a cocrystallization moiety relying on noncovalent interplays with GLC to obtain permeability advancement and molding a salt segment via the salification of proton transfer between HGA and MIL molecules to facilitate solubility enhancement. While the ameliorative in vitro properties further modulate the in vivo pharmacokinetic behaviors, thus fulfilling a dual optimization of MIL's biopharmaceutical characteristics on both in vitro and in vivo aspects. Along this line, the first MIL ternary salt cocrystal, viz., [HMIL+-GA-]-MIL-GLC-H2O (denoted as MTSC hereinafter), has been satisfactorily constructed and precisely structurally identified by diversified techniques. The single-crystal X-ray diffraction experiment validates that a molecular salt [HMIL+-GA-] species cocrystallizes with one neutral MIL, two GLC, and five solvent water molecules, among which the organic constituents compose laminated hydrogen bond networks, and then are self-assembled by water molecules to a 3D supramolecular structure. The unique structural feature and stacking pattern of MTSC make both the permeability and solubility be respectively enhanced by 9.69 times and 5.17- to 6.03-fold compared with the parent drug per se. The experimental outcomes are powerfully supported by associated calculations based on density functional theory. Intriguingly, these optimal in vitro physicochemical natures of MTSC have been potently converted into strengths of in vivo pharmacokinetics, showcasing the elevated drug plasma concentration, elongated half-life, alongside advanced bioavailability. Consequently, this presentation not just contributes a brand-new crystalline form with utility values, but ushers in a new dimension of ternary salt cocrystals for improving in vitro/vivo limitations of poor drug bioavailability.

A study on vermiculite-based salt mixture composite materials for low-grade thermochemical adsorption heat storage

High-performance renewable energy technologies are desired to meet the enormous demand during the clean energy transition. Thermal energy storage can help balance the mismatch between renewable energy supplies and end-user's demands. Thermochemical adsorption heat storage (TAHS) has attracted widespread attention for its ability to efficiently utilise low-grade renewables and waste heat. Composite adsorbent materials have been gaining increased research interest, which combine hygroscopic salts and host matrix via impregnating salts in the matrix. This paper reviews recent progress in composite materials for TAHS and provides material characterisation analysis on different vermiculite-based composites. The composites use vermiculite as the host matrix with impregnation of different binary and ternary salt mixtures (i.e., MgSO4–CaCl2, MgCl2–LiNO3, MgSO4–LiCl and MgSO4–LiNO3–MgCl2). Vermiculite impregnated with a binary mixture of MgSO4–CaCl2 demonstrated a high energy storage density of 1213 kJ/kg, with fast desorption kinetics in the temperature range of low-grade heat. It shows good suitability for domestic TAHS applications, particularly for space heating, with stable cyclic performance over 20 charging-discharging cycles, maintaining approximately 91.3% of its initial energy storage density. The findings of this study contribute to the growing body of research on composite materials and demonstrate the potential of vermiculite-based composites impregnated with binary salt mixtures for low-grade TAHS.

High-Performance Li-CO2 Battery Based on Carbon-Free Porous Ru@QNFs Cathode.

Lithium-carbon dioxide (Li-CO2 ) batteries have attracted much attention due to their high theoretical energy density. However, due to the existance of lithium carbonate and amorphous carbon in the discharge products that are difficult to decompose, the battery shows low coulombic efficiency and poor cycle performance. Here, by adjusting the adsorption of carbon dioxide (CO2 )on ruthenium (Ru) catalysts surface, this work reports an ultralow charge overpotential and long cycle life Li-CO2 battery that consists of typical lithium metal, ternary molten salt electrolyte (TMSE), and Ru-based cathode. Experimental results show that the Ru catalysts deposited on quartz nanofiber (QF) can suppress the four-electron conversion of CO2 to lithium carbonate (Li2 CO3 ). As a result, the battery shows a long-cycle-life of over 457 cycles at 1.0 A g-1 with a limited capacity of 500 mAh g-1 Ru . Remarkably, a recorded low discharge potential of ≈3.0V has been achieved after 35 cycles at 0.5 A g-1 , with a charge potential retention of over 99%. Moreover, the battery can operate over 25 A g-1 and recover 96% potential. This battery technology paves the way for designing high-performance rechargeable Li-CO2 batteries with carbon neutrality.

Compressibility of Lithium Hexafluorophosphate Solutions in Two Carbonate Solvents.

Speed-of-sound measurements are performed to establish how the isentropic bulk modulus K s of the electrolyte system comprising lithium hexafluorophospate (LiPF6) in blends of propylene carbonate (PC) and ethyl methyl carbonate (EMC) varies with salt molality m, mass fraction of PC in the PC:EMC cosolvent f, and temperature T. Bulk moduli are calculated by combining acoustic time-of-flight data between parallel walls of a liquid-filled cuvette with densitometric data for a sequence of binary and ternary salt solutions. Correlations are presented to yield K s (m, f, T) accurately for nine compositions spanning the range m = 0-2 mol kg-1 and f = 0-1, at temperatures T ranging from 283.15 to 313.15 K. Electrolyte compressibility varies most with solvent ratio, followed by salt content and temperature, with K s ranging from 1 to 3 GPa. Composition-dependent acoustical properties elucidate the nature of speciation and solvation states in bulk electrolytes, and could be useful to identify the features of individual phases within solution-permeated porous electrodes.

Preparation and Application of a NaCl-KCl-CsCl-Cs2ZrCl6 Composite Electrolyte

Using ternary molten salt with a molar ratio of NaCl:KCl:CsCl = 30:24.5:45.5 and ZrCl4 as raw materials to prepare a NaCl-KCl-CsCl-Cs2ZrCl6 composite electrolyte. Characterizing by XRD, ICP-AES, optical microscopy and SEM-EDS, the results showed that when the molar ratio of CsCl:ZrCl4 ≥ 2:1, Cs2ZrCl6 was generated according to the stoichiometric reaction; when the molar ratio of CsCl:ZrCl4 < 2:1, CsCl in molten salt was almost completely converted to Cs2ZrCl6, and there was a ZrCl4 phase. When the molar ratio of CsCl:ZrCl4 = 2:1, with the increase of the reaction temperature and reaction time, the concentration of zirconium ions first increased and then decreased. The optimized preparation process conditions are: the 2:1 molar ratio of CsCl to ZrCl4 in NaCl-KCl-CsCl, 500 °C of reaction temperature of and 3 h of reaction time. Under this condition, 99.68% conversion rate from ZrCl4 to Cs2ZrCl6 was obtained. Taking the prepared NaCl-KCl-CsCl-Cs2ZrCl6 composite electrolyte as a raw material, a preliminary study of molten salt electrolytic refining zirconium was carried out, and a refined zirconium product with a dendrite of 10.61 mm was obtained under the conditions of a zirconium ions concentration of 5%, an electrolysis temperature of 750 °C, a current density of 0.1 A/cm2, and an electrolysis time of 9 h, indicating that the composite electrolyte can be used for the electrolytic refining of zirconium.

Solvent-Free and Long-Cycling Garnet-Based Lithium-Metal Batteries

Solid-state batteries using ceramic solid electrolytes promise to deliver enhanced energy density and intrinsic safety. However, the challenge of integrating solid electrolytes with electrode materials limits the electrochemical performance. Herein, we report a solvent-free ceramic-based lithium-metal battery with good cycling stability at a wide temperature range from 45 to 100 °C, enabled by an inorganic ternary salt of low eutectic point. By using a garnet electrolyte with molten salts at the electrolyte|cathode interface, the Li||LiFePO4 cells perform a long cycling with capacity retention of 81.4% after 1000 cycles at 1 C. High-voltage LiFe0.4Mn0.6PO4 cathodes also deliver good electrochemical performance. Specifically, commercial electrode pieces with high area capacities can be adopted directly in the quasi-solid-state lithium-metal batteries. These stable performances are ascribable to the low melting point, high ionic conductivity and good thermal/electrochemical stability of the ternary salt system. Our findings provide an effective method on fabrication of solid-state batteries for practical applications.

NaNO3-KNO3-KCl/K2CO3 with the elevated working temperature for CSP application: Phase diagram calculation and machine learning

Mixed nitrates with relative low melting point have widely been used as thermal storage medium in the concentrated solar power stations. However, their maximum working temperatures aren’t high enough to integrate with more efficient power generation systems such as the supercritical CO2 cycle. In the present work, mixed nitrates with elevated working temperature were obtained by adding KCl/K2CO3. With the help of FactSage software and back-propagation (BP) algorithm combined with genetic algorithm (GA), the eutectic compositions and melting points of NaNO3-KNO3-KCl and NaNO3-KNO3-K2CO3 were predicted, and the validity of BP algorithm combined with GA was verified. Based on DSC and TG curves, the melting points of the as-prepared NaNO3-KNO3-KCl and NaNO3-KNO3-K2CO3 are 206.12 °C and 207.24 °C, respectively, which are in agreement with predicted values. Moreover, their decomposition temperatures were increased to more than 640 °C. In addition, the specific heat capacity of both mixed molten salts was measured, and it also was calculated by using FactSage software. This work provides two new ternary molten salts based on nitrates with higher working temperature and develops the prediction method on phase diagram calculation and machine learning.

Electrochemical behavior of iodide ions in molten fluoride salts

The electrochemical behavior of iodide ions has been studied in the ternary fluoride salt, LiF-NaF-KF and in the binary salts, LiF-CaF2 and LiF-ThF4. The electrochemical study demonstrated that iodide ions are oxidized to produce gaseous species in the three molten fluoride salts. However, the stability of iodide ions was observed to be influenced by the fluroacidity of the molten salt. The efficiency of the extraction of iodide ions was examined in LiF-NaF-KF and LiF-ThF4. UV-visible spectroscopy was used to quantify the amount of iodide ions oxidized after the execution of several coulometries at applied potential, these coulometries simulated the fluorination step in the reprocessing unit designed for the MSFR. The efficiency of extraction determined in LiF-ThF4 is higher than 95 % while it is close to 64 % in LiF-NaF-KF at 650°C.

First‐Principles Molecular Dynamics Study on Ionic Structure and Transport Properties of NaCl‐MgCl2‐CaCl2 Ternary Molten Salt System

AbstractThe carbochlorination in molten salt is an effective method for titanium extraction form low‐grade titanium slag with a high calcium and magnesium content. However, in industrial practice, the fluidity of molten salt will gradually decrease with the increase of CaCl2 content. It is important to elucidate the influencing mechanism of CaCl2 content on the microstructure and diffusion properties of molten salt for the rational selection of a molten salt system and clean utilization of titanium slag. In this study, the densities of molten salt systems with different CaCl2 contents are measured according to the Archimedes principle. Then, using the first‐principles molecular dynamics (FPMD) method, the ionic structure and transport properties of NaCl‐MgCl2‐CaCl2 ternary molten salt systems under different CaCl2 contents are qualitatively and quantitatively described by determining the partial radial distribution functions (PRDF), coordination number (CN), angular distribution functions (ADF), and diffusion coefficient (DC). The results show that with the addition of CaCl2, Ca2+ ion complexed with Cl− ion to form larger ionic clusters, which reduced the proportion of free Cl− ion and restricted the diffusion of Cl− ion.

Experimental Investigation of Graphene Nanoplatelets Enhanced Low Temperature Ternary Eutectic Salt Hydrate Phase Change Material

A sustainable approach to ensuring the thermal regulation of space is reliable with phase change materials (PCMs) operating at 15–25 °C. Henceforth, there is a need of a search of binary and ternary eutectic PCMs operating at desirable phase transition temperatures of 15–25 °C, high energy storage enthalpy (180–220 J/g), improved thermal conductivity and better absorptivity of solar energy. In this current research, we developed a ternary eutectic inorganic salt hydrate PCM intended for a low-temperature thermal regulation system. Based on the eutectic melting point theory, the phase transition temperature and proportion of sodium carbonate decahydrate (SCD), sodium phosphate dibasic dodecahydrate (SPDD) and sodium sulphate decahydrate (SSD) were determined. As per the calculated proportion, ternary eutectic PCM was experimentally prepared. Furthermore, to enhance the thermal property, graphene nanoplatelets (GNP) were dispersed at weight concentrations of 0.4%, 0.7% and 1.0%. The prepared nanoparticle-dispersed PCMs were characterized using an optical microscope, Fourier transform infrared (FT-IR) spectroscopy and a thermal conductivity meter, and a differential scanning calorimeter (DSC) was used to evaluate the morphology, chemical stability and thermal properties. The results showed increases in thermal conductivity and optical absorbance by 71.5% and 106.5%, respectively, with GNP at 1.0% weight concentration. Similarly, the degree of supercooling and transmissibility was reduced by 43.5% and 76.2% correspondingly. The prepared composite PCM is expected to contribute towards cooling, with an intention to contribute towards sustainable development.

Investigation of KNO2-KNO3-K2CO3 mixed molten salts with higher working temperature for supercritical CO2 concentrated solar power application

In the present work, the new eutectic composition of KNO2-KNO3-K2CO3 ternary salt for sCO2 solar thermal power generation is predicted by thermodynamic calculation, then the thermophysical properties of the eutectic salt are investigated by experiments combined with theoretical calculation, further studies are focused on its corrosivity. The results show that the predicted ternary molten salt is confirmed as 0.259KNO2–0.687KNO3–0.054K2CO3. Due to mixing a small amount of K2CO3, the upper limit of the operating temperature of the eutectic salt can reach 750.1 °C, and the melting point and the freezing point have a good thermal stability in the heating-cooling cycles. The calculated specific heat is lower than the measured one which can maintain at 1.407 J/(g·K) in the range of 400–450 °C. With the increase of temperature, the density decreases linearly and the thermal diffusivity tends to increase, thus there is a slight growing in thermal conductivity with an average value of 0.3 W/(m·K). The novel eutectic salt has an energy storage density of 865 MJ/m3. Although containing a low concentration of K2CO3, the eutectic salt shows low corrosion to 310S stainless steel. After the corrosion test of 240 h at 600 °C, the mass loss of stainless steel maintains a constant at 0.067 mg/cm2. The above results indicate that 0.259KNO2–0.687KNO3–0.054K2CO3 eutectic salt is a promising high-temperature thermal storage material for solar thermal power generation.

NiAs-derived cyanamide (carbodiimide) structures – a group-theoretical view

Abstract The cyanamide and carbodiimide anions are complex nitrogen-derived one-dimensional species of the type NCN2− (hence, resembling O2− but more covalently bonding) that form a huge number of salt-like phases with a variety of metal cations stemming from the whole Periodic Table. Depending on the coloring (binary, ternary and quaternary salts are known), the cationic size and charge as well as covalent contributions, different distortion (tilting in particular) and/or vacancy ordering variants of cyanamides/carbodiimides occur. Herein we summarize those cyanamide/carbodiimide structures that derive from the aristotype NiAs. The crystal chemistry is discussed on the basis of group-subgroup schemes (Bärnighausen trees).

High separation efficiency of ternary cathode materials from spent lithium-ion batteries by ternary molten Li-salt method

Recycling of spent lithium-ion batteries is an urgent task in view of the resource shortage and environmental concerns. Pretreatment as the first step in recycling of spent lithium-ion batteries has become urgent issue for efficient separation of spent cathode materials from aluminum foil. Herein, a facile ternary molten salts approach is presented for efficient separation of cathode material and aluminum foil synchronous implementation of regeneration of spent cathode material. The separation efficiency reaches 99.98% at molar ratio of LiNO3: LiOH·H2O: Li2CO3(LNOC) of 3:2:0.5 with mass ratio of spent cathode pieces to the ternary molten salts of 1:2 holding at 300 °C for 15 min. The regenerated materials show discharging capacity of 122.2 mAhg−1 at 1C with retention rate of 99.97% after 100 cycles. The ternary molten salts are also made available for separation of other spent cathode materials with achieving high separation efficiency.