Search Results (85)

The suitability of 347H stainless steel (SS347H) for chloride salt environments is critical in selecting materials for next-generation concentrated solar power (CSP) systems. This study investigated the corrosion behavior of SS347H in a ton-scale purification system with continuously flowing chloride salt under three conditions: exposure to NaCl-KCl-MgCl₂ molten salt vapor, immersion in molten salt, and at the molten salt surface interface. Results revealed that corrosion was most severe in the molten salt vapor, where HCl steam facilitated Cl⁻ reactions with Fe and Cr in the metal, causing dissolution and forming deep corrosion pits. At the interface, liquid Mg triggered displacement reactions with Fe²⁺/Cr²⁺ ions in the salt, depositing Fe and Cr onto the surface, which reduced corrosion intensity. Within the molten salt, Mg’s purification effect minimized impurity-induced corrosion, resulting in the least damage. In all cases, the primary corrosion mechanism involves the dissolution of Fe and Cr, with the formation of minor MgO. These insights provide valuable guidance for applying 347H stainless steel in chloride salt environments. Full article

In response to the growing impact of the climate crisis, many countries are accelerating efforts to develop sustainable and carbon-free energy solutions. This has led to increasing interest in advanced energy storage and conversion technologies, particularly the development of high-temperature molten salt energy systems. Among these, chloride salt-based molten salt systems, which offer excellent thermal properties such as high thermal conductivity, low melting points, and favorable chemical stability, are emerging as strong candidates for thermal energy storage and heat-transfer applications. This study focuses on deriving key thermophysical properties essential for selecting suitable molten salt heat-transfer fluids by examining their eutectic points and thermal stability with respect to various salt compositions. Three chloride mixtures—NaCl-MgCl₂, NaCl-KCl-MgCl₂, and NaCl-KCl-ZnCl₂—were evaluated for potential use in high-temperature molten salt energy systems. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were employed to measure the melting points and thermal stability of molten salts with various compositions near their eutectic regions. Experimental results were compared with predicted eutectic points to assess the thermal performance of each salt mixture. The findings indicate that the NaCl-KCl-MgCl₂ mixture exhibits the most promising characteristics, including a low melting point below 400 °C and superior thermal stability, making it highly suitable as a heat-transfer fluid in high-temperature molten salt energy systems. In contrast, NaCl-KCl-ZnCl₂ was found unsuitable for such applications due to its high hygroscopicity and poor thermal stability. This study provides essential data for selecting optimal molten salt compositions for the efficient and reliable operation of high-temperature molten salt energy systems. Full article

Presently, extensive research has been conducted on the electrochemical behavior of titanium ions in molten salt, especially in relation to titanium fluoride coordination. However, there is limited research on the coordination between titanium and oxygen. Consequently, this research delved into the influence of oxygen ions on the electrochemical behavior and coordination properties of titanium ions through the utilization of both electrochemical and spectroscopy techniques. The study involved the use of cyclic voltammetry (CV), square wave voltammetry (SWV), and the open-circuit potential (OCP) method to explore the electrochemical properties of titanium ions at different titanium-oxygen ratios. Furthermore, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were applied to assess the presence of titanium ions in molten salt and the coordination structure of titanium ions and anions in molten salts, respectively. The results demonstrate that with an increase in oxygen ion content, chloride ions are gradually replaced by oxygen ions, forming TiO_xCl_y^m− complexes. Full article

Rechargeable metal chloride batteries, with their high discharge voltage and specific capacity, are promising for next-generation sustainable energy storage. However, sluggish solid-to-gas conversion kinetics between solid metal chlorides and gaseous Cl₂ cause unsatisfactory rate capability and limited cycle life, hindering their further applications. Here we present a rechargeable aluminum-chlorine (Al-Cl₂) battery that relies on a confined chlorine conversion chemistry in a molten salt electrolyte, exhibiting ultrahigh rate capability and excellent cycling stability. Both experimental analysis and theoretical calculations reveal a reversible solution-to-gas conversion reaction between AlCl₄⁻ and Cl₂ in the cathode. The designed nitrogen-doped porous carbon cathode enhances Cl₂ adsorption, thereby improving the cycling lifespan and coulombic efficiency of the battery. The resulting Al-Cl₂ battery demonstrates a high discharge plateau of 1.95 V, remarkable rate capability without capacity decay at different rates from 5 to 50 A g⁻¹, and good cycling stability with over 1200 cycles at a rate of 10 A g⁻¹. Additionally, we implemented a carbon nanofiber membrane on the anode side to mitigate dendrite growth, which further extends the cycle life to 3000 cycles at an ultrahigh rate of 30 A g⁻¹. This work provides a new perspective on the advancement of high-rate metal chloride batteries. Full article

The molten salt reactor is a fourth-generation nuclear power plant considered a long-term eco-friendly energy source with high efficiency and the potential for green hydrogen production. The selection of alloys for such reactors, which can operate for more than 30 years, is a primary concern because of corrosion by high-temperature molten salt. In this study, three Fe- and Ni-based alloys were selected as structural material candidates. Corrosion immersion tests were conducted in NaCl–KCl molten salt for 48 h at 800 °C and 40% RH conditions in an air environment. In the absence of moisture and oxygen removal, ClNaK salt-induced damage was observed in the investigated alloys. The corrosion behavior of the alloys was characterized using various techniques, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. The results show that the corrosion process can be explained by salt-induced surface damage, internal ion migration, and depletion to the surface. The corrosion rate is high in SS316L (16Cr-Fe), N10003 (7Cr-Ni), and C-276 (16Cr-Ni), in decreasing order. Based on the corrosion penetration, ion elution, and interfacial diffusion results, C-276 and N10003 are good candidates for structural materials for MSRs. Therefore, Ni-based alloys with high Cr content minimize surface damage and ion depletion in unpurified molten salt environments. This indicates that Ni-based alloys with high Cr content exhibit highly corrosion resistance. Full article

The corrosion properties of 316L stainless steel (316L SS) alloy within molten NaCl-KCl salt were explored through a static immersion experiment carried out at 700 °C under Ar flow for 25, 50, 100, 200, and 400 h. The loss in weight of the corroded 316L SS alloy increased from 0.06 to 1.71 mg/cm², while the maximum corrosion depth increased from 1.71 to 14.09 μm. However, the corrosion rate initially increased from 27.54 μm/year to 93.45 μm/year and then decreased to 47.22 μm/year as the soaking time was increased from 25 to 400 h. The impurities in the molten salts produced corrosive Cl₂ and HCl, which corroded the 316L SS matrix. The accelerated selective Cr dissolution with small amounts of Fe and Ni resulted in intergranular corrosion as the time of corrosion was increased. The depletion depths for Ni, Cr, and Fe at 400 h were found to be 0.87 μm, 3.94 μm, and 1.47 μm, respectively. The formation of Cr and Fe oxides might potentially play a vital role. The grain boundary and outward diffusion of Mo may prevent the outward diffusion of Cr, thereby mitigating alloy corrosion. Therefore, molten chloride salt purification and the selection of stainless steel are crucial for developing future concentrated solar power technologies. The findings of this study provide guidelines for the use of 316L SS in NaCl-KCl salt at high temperatures. Full article

In the context of central solar receiver systems, the utilisation of S-CO₂ Brayton cycles as opposed to Rankine cycles confers a number of advantages, including enhanced efficiency, the requirement for less sophisticated turbomachinery, and a reduction in water consumption. A pivotal consideration in the design of such systems pertains to the thermal storage system. This work undertakes a comparative analysis of the performance of an S-CO₂ Brayton cycle utilising two distinct types of molten salts, namely solar salts and chloride salts (MgCl₂–KCl), as the heat transfer fluid on the thermal energy storage medium. The present study adopts an energetic and exergetic perspective with the objective of identifying areas of high irreversibility and proposing mechanisms to reduce them. The work is concluded with an analysis of the size of the different components. The overall energy efficiency is determined as 22.29 % and 23.76 % for solar and chloride salts, respectively. In the case of chloride salts, this efficiency is penalized by the higher losses in the solar receiver due to the higher operating temperature. The exergy analysis shows that using MgCl₂–KCl salts increases exergy destruction in the recuperators, lowering irreversibilities in other components. While the sizes of all components decrease when using chloride salts, the volume of the storage system increases. These results demonstrate that the incorporation of MgCl₂–KCl salts enhances the performance of S-CO₂ recompression cycles operating in conjunction with a central solar receiver. Full article

In the context of the global energy structure transformation, concentrated solar power (CSP) technology has gained significant attention. Its future trajectory is oriented towards the construction of ultra-high temperature (700–1000 °C) power plants, aiming to enhance thermoelectric conversion efficiency and economic competitiveness. Chloride molten salts, serving as a crucial heat transfer and storage medium in the third-generation CSP system, offer numerous advantages. However, they are highly corrosive to metal materials. This paper provides a comprehensive review of the corrosion behaviors of stainless steels and high-temperature alloys in molten salts. It analyzes the impacts of factors such as temperature and oxygen, and it summarizes various corrosion types, including intergranular corrosion and hot corrosion, along with their underlying mechanisms. Simultaneously, it presents an overview of the types, characteristics, impurity effects, and purification methods of molten salts used for high-temperature heat storage and heat transfer. Moreover, it explores novel technologies such as alternative molten salts, solid particles, gases, liquid metals, and the carbon dioxide Brayton cycle, as well as research directions for improving material performance, like the application of nanoparticles and surface coatings. At present, the corrosion of metal materials in high-temperature molten salts poses a significant bottleneck in the development of CSP. Future research should prioritize the development of commercial alloy materials resistant to chloride molten salt corrosion and conduct in-depth investigations into related influencing factors. This will provide essential support for the advancement of CSP technology. Full article

The effects of X-doping (X = Mo, Ti, Ni) on the structure, stability, and electronic properties of B2-FeAl supercells, as well as the migration behavior of Cl atoms between interstitial sites and the corrosion behavior of FeAl coatings in molten chloride, were investigated by combining the first principles based on density functional theory (DFT) experiments. Our results confirmed that Mo and Ti atoms are more likely to replace Al atoms in B2-FeAl supercells, while Ni atoms preferentially replace Fe atoms. A single Cl atom is more inclined to be adsorbed at the tetrahedral (Tet) interstitial site of bulk B2-FeAl, and its formation energy $E_f=$− 2.504 eV, indicating that it can very easily invade FeAl alloys. (Mo, Ti, Ni) doping inhibited the diffusion of Cl atoms in the bulk B2-FeAl configuration and enhanced the corrosion resistance of the material to chlorinated molten salts, and Ti doping (overcoming the energy barrier by 0.326 eV) had the most obvious blocking effect. Based on the theoretical conclusions, this experimental study prepared an FeAl coating on 310S stainless steel with a Ni content of 20.22 wt.% at 800 °C for 15 h, which was then annealed at 900 °C for 25 h, and Ni was uniformly dissolved in the B2-FeAl phase. Subsequently, the annealed FeAl coating was corroded in molten chlorinated salts at 800 °C for 100 h, and an oxide layer with a thickness of 25–35 µm formed on the surface; the main components of this layer were Al₂O₃, NiFe₂O₄, and their solid solutions, which significantly improved the corrosion resistance of 310S stainless steel to chlorinated molten salt. Full article

This study presents a metallothermic reduction mechanism for fabricating Nd and Nd–Fe alloys at 850–1050 °C using anhydrous NdCl₃ and Ca, which have relatively low melting points. Our method decreased the process temperature while improving the recovery rate of Nd using the thermodynamic parameters of the CaCl₂–KCl–NaCl and Nd–Fe liquid solutions. To reduce the activity of the product (CaCl₂), the optimal composition of the CaCl₂–KCl–NaCl molten salt was $X_{{CaCl}_2}=0.4(X_{KCl}:X_{NaCl}=6:4)$. The molten metal bath (Nd or Nd–Fe) that formed at the bottom of the reaction zone during Nd and Nd–Fe alloy production absorbed metal particles generated in the molten salt during the reaction, thereby facilitating ingot formation. In Nd produced at 1050 °C using 1.2× the stoichiometric amount (by mass) of Ca, the Nd recovery rate was 97.0%. Moreover, in the Nd–Fe alloys produced at 1050 °C targeting eutectic compositions, the Nd recovery rate was 96.3%. Increased Fe contents in the Nd–Fe liquid solution reduced the Nd recovery rates, and the Nd–Fe alloy (Nd recovery rate: 89.8%) was produced at 850 °C, suggesting the possibility of increasing the energy efficiency of the Nd production process. The Nd–Fe alloy produced through this proposed process could be used as a raw material in the NdFeB strip casting process. Full article

A simple and cost-effective route based on a KOH-assisted molten salt method is designed here to synthesize LiNi_0.5Mn_1.5O₄ spinel. Pure-phase LiNi_0.5Mn_1.5O₄ can be successfully prepared using chlorides as raw materials and adding KOH at 700 °C. The structure, morphology, and performance are discussed in detail. The measurements reveal that using KOH-assisted synthesis can optimize the crystal structure of the obtained LiNi_0.5Mn_1.5O₄ samples, resulting in grain refinement while maintaining the predominantly octahedral structure that grows along the (111) crystal plane. This new synthesis pathway provides excellent performance in terms of cycle life. Electrochemical tests show that the KOH-assisted sample exhibits higher initial specific capacities (124.1 mAh·g⁻¹ at 0.2 C and 111.4 mAh·g⁻¹ at 3 C) and superior cycling performances (capacity retention of 85.0% after 200 cycles at 0.2 C and 95.70% after 100 cycles at 3 C). This provides a potential solution for the practical application of high-voltage LiNi_0.5Mn_1.5O₄ lithium-ion batteries. Full article

The molten salt chlorination method is one of the two main methods for producing titanium tetrachloride, an important intermediate product in the titanium industry. To effectively improve chlorination efficiency and reduce unnecessary waste salt generation, it is necessary to understand the mechanism of the molten salt chlorination reaction, and consequently this paper conducted studies on the carbon chlorination reaction mechanism in molten salts by combining ab initio molecular dynamics (AIMD) and deep potential molecular dynamics (DeePMD) methods. The use of DeePMD allowed for simulations on a larger spatial and longer time scale, overcoming the limitations of AIMD in fully observing complex reaction processes. The results comprehensively revealed the mechanism of titanium dioxide transforming into titanium tetrachloride. In addition, the presence form and conversion pathways of chlorine in the system were elucidated, and it was observed that chloride ions derived from NaCl can chlorinate titanium dioxide to yield titanium tetrachloride, which was validated through experimental studies. Self-diffusion coefficients of chloride ions in pure NaCl which were acquired by DeePMD showed good agreement with the experimental data. Full article

Concentrated solar power plant (CSP) technology holds significant application value in the renewable energy sector for converting solar radiation into thermal and electrical energy. As a heat storage medium for next-generation solar thermal power stations, chloride salts exhibit strong corrosive effects on structural components. To enhance corrosion resistance of the heated body in molten salt environments, Inconel 625 is modified by incorporating aluminum, which facilitates the formation of a protective oxide film. In this study, High-Aluminum Inconel 625, after cold rolling and solution treatment, was immersed in a NaCl-KCl-MgCl₂ eutectic chloride melt at 650 °C for 200 h. Post-corrosion analysis revealed the formation of an alumina layer on the surface, effectively mitigating corrosion. Increased aluminum content resulted in thicker alumina layers and the formation of oxidation products, such as Cr₂O₃, Fe₂O₃, MoO₂, and MgCr₂O₄ spinel structures, significantly enhancing the alloy’s corrosion resistance. The Inconel 625 cold-rolled plate with 5.31 wt% Al exhibited the best corrosion resistance (3510 μm/year), making it a promising candidate for use in next-generation CSP heat storage and exchange components. Full article

The electrochemical conversion of CO₂ into high value-added carbon materials by molten salt electrolysis offers a promising solution for reducing carbon dioxide emissions. This study focuses on investigating the influence of molten salt composition on the structure of CO₂ direct electroreduction carbon products in chloride molten salt systems. Using CaO as a CO₂ absorber, the adsorption principle of CO₂ in LiCl-CaCl₂, LiCl-CaCl₂-NaCl and LiCl-CaCl₂-KCl molten salts was discussed, and the reasons for the different morphologies and structures of carbon products were analyzed, and it was found that the electrolytic efficiency of the whole process exceeded 85%. Furthermore, cathode products are analyzed through Scanning Electron Microscope (SEM), X-Ray Diffractometer (XRD), Thermal Gravimetric Analyzer (TGA), Raman Spectra and Fourier Transform Infrared (FTIR) techniques with a focus on the content and morphology of carbon elements. It was observed that the carbon content in the carbon powder produced by molten salt electrochemical method exceeded 99%, with most carbon products obtained from electrolysis in the Li-Ca chloride molten salt system being in the form of carbon nanotubes. In contrast, the Li-Ca-K chloride system yielded carbon nanospheres, while a mixture was found in the Li-Ca-Na chloride system. Therefore, experimental results demonstrate that altering the composition of the system allows for obtaining the desired product size and morphology. This research presents a pathway to convert atmospheric CO₂ into high value-added carbon products. Full article

Ab initio methods based on DFT are utilized to study the formation energy, adsorption energy, and electronic properties of pure and X-doped (X = Mo, Ti, Ni) B2-FeAl (110) surface configurations. The effect of microalloying element doping on the corrosion resistance of B2-FeAl coating to molten chlorinated salts was evaluated by the CI-NEB method. Our results show that the Ni atom preferentially occupies the position of the Fe atom, while the Mo and Ti atoms preferentially replace the Al atom in the supercell. The Cl atom tends to be adsorbed at the SB-FeAl site on a pure B2-FeAl (110) surface. The adsorption energies of a single chlorine atom at stable adsorption sites of Ni-doped B2-FeAl (110) surface are small, which means that Ni doping reduces the possibility of corrosion. The PDOS diagrams confirm that for the chlorine adsorption model of Mo-doped B2-FeAl (110) surface, strong hybridization between Mo-d, Al-p, and Fe-d orbitals occur in the energy region of −4.5~−2 eV and 0.5~2.5 eV, while in the energy range of −7.0~4.8 eV, Cl-p interacts with Mo-d and Al-s, respectively, indicating that Cl bonds with Mo and Al atom, respectively. The addition of Mo and Ni hinders the diffusion of chlorine atoms on the surface, weakens the corrosion rate of B2-FeAl in chlorinated molten salt, and improves the corrosion resistance of B2-FeAl coating. However, Ti doping promotes the migration of chlorine atoms and increases the corrosion rate of B2-FeAl in chlorinated molten salt to a certain extent. The aim of this study is to reveal the corrosion resistance mechanism of FeAl coating from the atomic level and provide a theoretical basis for the application of chloride molten salt as an efficient heat storage medium in the field of photothermal. Full article