Salt Infiltration Research Articles

Creep rupture of smoothed and notched DD6 single crystal superalloy specimens subjected to high-temperature hot corrosion

This work studies the creep rupture behaviors of both smoothed and V-notched DD6 Ni-based single crystal superalloy specimens under both air and corrosion conditions, within a stress range of 300 to 700 MPa at 950 °C. The corrosive medium used consisted of a mixed salt containing 95 wt% Na2SO4 and 5 wt% NaCl. Experimental results revealed that notched specimens exhibited a creep rupture life extended by 6–16 times compared to smoothed specimens, with the extension becoming more pronounced as the stress concentration increased. High-temperature hot corrosion (HTHC) shortened the creep rupture time by up to 75 %. A significant HTHC-creep interactive effect was found through comparative creep experiments in air and corrosion conditions. The HTHC affected the fracture modes of the specimens, with factors such as the amount of salt infiltration into the superalloy, the corrosion duration, and specimen configurations playing critical roles. Microstructural analysis revealed that, compared with γ′ precipitates, γ matrix phase was more prone to creep damage and was more susceptible to corrosion.

Magnetized Saline Water Drip Irrigation Alters Soil Water-Salt Infiltration and Redistribution Characteristics

Magnetization constitutes an efficacious physical treatment technique applicable to saline water. The new spiral flow magnetizer, in conjunction with the cyclic magnetization process, has the effect of maximizing effective magnetization time and thereby achieving the optimal magnetization results. Based on this, saline water (0.27, 3, 6, and 10 g L−1) was treated with different levels of magnetization (0, 0.2, 0.4 and 0.6 T), and the effects of magnetized saline water (MSW) drip irrigation on loamy-sand soil moisture, soluble salt infiltration, and redistribution characteristics were studied through a vertical soil column simulation experiment. The results showed that the wetting front migration in MSW drip irrigation experiments exhibited minimal variation during soil water infiltration, and a notable change during redistribution with the experimental duration of 0.27 and 3g L−1 saline water treatments being significantly different (p < 0.05). Treating saline water with different mineralization levels with magnetization demonstrated water retention (0.27 g L−1 excluded) and salt drainage characteristics; calculated soil water storage increased by 1.58–14.19% and salt storage decreased by 0.22–7.66%. The optimal magnetization intensity for low-mineralization (0.27 and 3 g L−1) saline water was 0.2 T and for high-mineralization (6 and 10 g L−1) it was 0.6 T. The adsorption and exchange of cations (19.58–32.12%) by the optimum MSW treatments was greater than that of anions (9.46–14.15%); specifically, the relative exchange capacity of Ca2+ and Mg2+ in cations was more than K+ and Na+, while HCO3− and SO42− in anions was more than Cl−. This study provides theoretical and technical support for the irrigation of farmland with poor-quality water, as well as for the development of magnetized water irrigation technology.

Vacancy engineering-induced spin polarization in heterogeneous phosphides by simple iron salt infiltration for efficient overall water splitting

Optimizing electronic structure and facilitating electron transfer modulation in electrocatalyst is the key to enhancing overall water splitting (OWS) performance. In this work, the heterogeneous transition metal phosphide Fe-CoPv/Ni2P@NF, consisting of cobalt phosphide and nickel phosphide, is obtained by simple iron salt infiltration and high-temperature phosphatisation. Due to the doping of iron-atom and the formation of phosphorus vacancies, the activity of metal atoms with higher valence states and spins is induced, and then highly active Fe/Co-O-Ni channels are generated in the dynamic water-splitting process, thereby increasing the exposure of reaction center and total electron transfer rate. The catalytic mechanism is attributed to reducing the potential barrier of phase remodeling and optimizing the intermediate binding strength, thus thoroughly stimulating OER and HER activities. The Fe-CoPv/Ni2P@NF shows superior performance, requiring only total voltages of 1.626 V (OWS) to reach 100 mA·cm−2 and maintaining ultra-high stability for 500 h, suggesting promising industrial applications.

An Electrochemical Phase Field Model Applied to Molten Salt Dealloying Corrosion of Ni-Alloys

Metal alloys in contact with molten salts are known to corrode via a dealloying process, wherein the less-noble alloy elements (e.g. Cr) are selectively oxidized and dissolved, leaving behind a corroded structure that is enriched in the more-noble elements (e.g. Ni). In some cases, this can lead to molten salt infiltration into the alloy through discrete channels along specific microstructural features (e.g. grain boundaries). However, in other cases the dealloying process promotes a more full-scale attack of the alloy, generating a fine-scale ligament structure. This process can severely degrade the alloy’s structural integrity, which limits the practicality of these material systems in otherwise promising applications (e.g. molten salt-cooled power reactors).The thermokinetic conditions for dealloying corrosion depend on the salt chemistry and the metal microstructure, which together inform the reaction process occurring at their interface. The salt chemistry and oxidant content set the electrochemical potential for selective oxidation of the less-noble elements. The associated oxidation rate is expected to depend on the presence of an interfacial structure (e.g. double layer) and also on the transport rates of reactants towards the interface (e.g. species diffusion in the metal and oxidizer transport in the salt) and reaction products away from the interface (cation transport in the salt). The corrosion rate and morphology will also depend strongly on the rate of transport laterally along the metal-salt interface, since the reorganization of the more-noble species (Ni) towards ligament formation facilitates the attack of the alloy by the corrosive agent. It has been hypothesized that molten salts enhance this rate of solute diffusion along the metal interface.In this work, we propose an electrochemical phase field model to predict the microstructural evolution of model Ni-alloys undergoing dealloying corrosion in molten fluoride salts. The model incorporates metal oxidation and dissolution via experimentally determined redox potentials and activity coefficients for metal species in the molten salt. We show that the corrosion rate and development of pores is strongly dependent on solute transport rates within the metal and also along their solid-liquid interface. In particular, we reveal a mechanism in which grain boundaries couple with the solid-liquid corrosion front to promote rapid dealloying and molten salt attack. Oxidant content in the salt and double-layer formation at the interface are discussed for their roles in setting the electrochemical potential and reaction rate at the metal-salt interface. Finally, we discuss how the model leverages insights from atomistic modeling and highlight key knowledge gaps in the mesoscale modeling of electrochemical molten salt corrosion.

Superior molten FLiBe salt barrier properties of a mesophase-pitch-based carbon/carbon composite prepared via hot isostatic pressing

Carbon/carbon (C/C) composites are promising structural materials for molten salt reactors (MSRs) because of their exceptional high-temperature performance, resistance to fluoride salt corrosion, and low-neutron-absorption cross-section. However, fluoride salts can infiltrate the pores of C/C composites, potentially causing local hotspots and accelerating material degradation. In this study, a novel C/C composite was fabricated from mesophase-pitch-based carbon fibers and a pitch-based carbon matrix via hot isostatic pressing (HIP). To evaluate its performance under MSR conditions, the composite was exposed to molten FLiBe salt at 700 °C and 2–9 atm for a duration of 20 h. Weight gain, morphological characteristics, and crystallinity were characterized after the salt infiltration test. Compared with C/C composites fabricated via conventional chemical vapor infiltration (CVI), the HIP-C/C composite exhibited much better molten salt barrier properties owing to its compact structure and small pore diameter. The weight gain of the HIP-C/C composite was only 0.17 wt.% under 5 atm, significantly lower than the critical index proposed for carbon materials used in MSR. Morphological characterization revealed that FLiBe salt particles were rarely trapped in the small pores of the HIP-C/C composite. While the crystallinity of the salt-impregnated CVI-C/C composite increased, the HIP-C/C composite exhibited a slightly decreased degree of graphitization after salt infiltration. These findings provide insights into the design of high-performance C/C composites for applications in MSR systems.

Hydrochemical evolution and source mechanisms governing the unusual lithium and boron enrichment in salt lakes of northern Tibet

Abstract The large-scale salt lakes widely distributed in the Tibetan Plateau provide unique and potential resources for lithium (Li) and boron (B). The concentration and characteristics of elements in these salt lakes resemble those found in geothermal water in northern Tibet, which highlights both as crucial sources of rare elements. This study presents comprehensive analyses of the hydrochemical composition and isotopes of B, strontium (Sr), hydrogen (H), and oxygen (O) in typical salt lakes, along with samples from surrounding springs and rivers in the Bangong-Nujiang suture zone of northern Tibet. The results reveal an extremely negative and anomalous distribution pattern of B isotopes in Zabuye Salt Lake that is closely associated with geothermal water. The enrichment of these elements in other salt lakes in the region is attributed to concentration of evaporation and sediment adsorption. Given the very high elevation of the recharge for geothermal water, the infiltration of salt lakes obviously cannot feed geothermal springs. On the contrary, we correlate the unusual enrichment of Li and B and other resources in salt lakes to geothermal spring discharge. The ultimate origin of these elements lies in magmatic sources, with later water-rock interaction leading to significant enrichment of incompatible elements such as Li, rubidium (Rb), cesium (Cs), and B in the geothermal system. The geothermal springs directly or indirectly fed the salt lakes, and with further evaporation, they became super-scale brine deposits.

Comparison of various drying methods on color, texture, nutritional components, and antioxidant activity of tumorous stem mustard

Exploring new dehydration technology can help to deal with the challenge of quality preservation and high salt waste brine problem in pickled mustard industry. In the current study, effects of vacuum freeze-drying (FD), heat pump drying (HPD), air-impingement jet drying (AIJD), and hot air drying (HD), on color, texture, nutritional component, and antioxidant capacity of tumorous stem mustard were determined. All drying methods significantly affected color and texture. The ascorbic acid (Vc), reducing sugar, protein, total phenolic content (TPC), ABTS, DPPH, and FRAP level of tumorous stem mustard were 123.20–768.74 mg/100 g, 2.49–17.90 g/100 g, 30.74–53.03 g/100 g, 1.98–4.13 mg gallic acid equivalent (GAE)/g, 1.42–8.28 mg Vc/g, 1.04–9.73 mg Vc/g, and 2.11–6.83 mg Vc/g, respectively. The content of individual phenolics were influenced by drying methods, and ferulic acid was determined as a major phenolic compound for all samples (8.15–65.43 μg/g). The content of total phenolic and monomeric polyphenols except for ferulic acid, positively correlated to their antioxidant activity. Furthermore, HD, FD, and AIJD were beneficial to promote the production of umami amino acids and reduce bitter amino acids, thus improving the flavor of tumorous stem mustard. The quality of tumorous stem mustard of FD was closest to that of fresh tumorous stem mustard. Overall, the drying technology is promising to replace the salt infiltration process to realize the dehydration of tumorous stem mustard in the manufacturing of pickled mustard.

Effects of Impurities and Additives on Interactions of Nuclear-Grade Graphite with Molten LiF-NaF-KF

It has been widely acknowledged that the presence of impurities in molten fluoride salt can alter the salt/material interactions. However, the effects of various impurities such as oxides, metal fluorides, reducing impurities, etc., on the behavior of nuclear-grade graphite in molten fluoride salts have not been reported. This study focuses on understanding the effects of various oxidizing and reducing impurities on the wetting and infiltration behavior of molten FLiNaK salt for nuclear-grade IG-110 graphite. Our results suggest that different impurities can cause different effects on nuclear graphite–molten salt interactions, with some impurities leading to significant degradation of the graphite. Our results demonstrate that certain impurities, such as Cr2O3 and CrF3, lead to a limited increase in wetting and infiltration of molten salt into nuclear graphite, while impurities such as Li2O lead to significantly increased wetting and infiltration throughout the cross section of the graphite specimen. Certain impurities, such as Li, can also lead to significant degradation of the graphite in the salt, with the extent of degradation increasing with the increase in the quantity of Li added. Our results also demonstrate that firing of IG-110 graphite at 900°C under a reducing atmosphere made the graphite surface resistant to wetting by molten FLiNaK salt, as compared to the nonfired sample.

Infiltration and Leaching Characteristics of Soils with Different Salinity under Fertilizer Irrigation

Salt and nutrient transport and transformations during water infiltration directly influence saline soil improvement and the efficient use of water and fertilizer resources. The effects of soil initial salinity (18.3 g/kg, 25.5 g/kg, 42.2 g/kg, 79.94 g/kg, and 165 g/kg, respectively, labeled S1 to S5) on the infiltration and leaching characteristics of water, salt, and nitrogen were analyzed via a one-dimensional vertical fertilizer infiltration experiment. Meanwhile, the estimation models of cumulative infiltration and wetting front, including the effect of soil initial salinity, were established. The results showed that, with the increase in soil initial salinity, the cumulative infiltration within the same time decreased, and the migration time of wet front to 45 cm was longer. The time required for S5 to reach the preset cumulative infiltration was more than six times that of S1, and, for the wet front migration to 45 cm, the time requirement for S5 was about four times that of S1. In the established Kostiakov model and wetting front model, the coefficients all decreased with the increase in soil initial salinity, and the test index R2 values both reached 0.999. In the Kostiakov model, coefficient K had a linear relationship with the natural logarithm of initial soil salt content, while index a had a direct linear relationship with initial soil salt content. The cumulative leachate volume decreased with the increase in soil initial salinity, and the corresponding data of S3 and S5 were reduced by 37% and 57.3%, respectively, compared with S1. The electrical conductivity values of S1, S3, and S5 were 15.4, 209.8, and 205.6 ms/cm, respectively, being affected by the initial content in soil, soil moisture transport rate, and exogenous potassium nitrate (KNO3) addition. The NO3−-N concentrations in the leachates of S1, S3, and S5 at the end of leaching were 55.26, 16.17, and 3.2 mg/L, respectively. Based on the results of this study, for soil with high initial salinity, the conventional irrigation amount (2250 m3/ha) of the general soil in the study area could not meet the requirements of leaching salt. These results can provide a reference for the formulation of irrigation and fertilization strategies for soils with different salinity and contribute to the sustainable development of saline soil agriculture and the ecological environment.

Tracking the infiltration of molten salt into graphite using time-lapse X-ray micro-computed tomography

For the first time, X-ray Micro-Computed Tomography (µ-CT) has been used to track the infiltration of molten salt into a porous graphite sample. Quantitative analysis on the X-ray µ-CT virtual slices enabled the extent of the salt infiltration and its spatial distribution within the graphite to be determined. The evolution of the pore structure is elucidated by direct comparison of the XCT micrographs before and after salt infiltration.

Excellent oxyacetylene ablation performance of C/C-Me-Zr-Hf-C (Me=Ta, Si) composites prepared by a novel two-step molten salt infiltration

In this study, to overcome the difficulties associated with the preparation of PyC-ceramic interface and controllable deposition of the structure, we initially used a two-step molten salt infiltration method to prepare a C/C-Me-Zr-Hf (Me = Ta, Si) composite with excellent oxyacetylene ablation performance. The microstructure and the behavior of ablative were addressed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) as well as by X-ray diffraction（XRD）. The results reveals that C/C-ZrHfC-SiC composite prepared by two-step molten salt infiltration method have a controllable ultra-high temperature ceramic structure and better ablation resistance.

Effects of Salt Soaking Treatment on the Deodorization of Beef Liver and the Flavor Formation of Beef Liver Steak.

In this study, based on the evaluation of fishy value and sensory evaluation, this study determined that soaking in a 1% salt solution for 60 min had a significant impact on the deodorization of beef liver (p < 0.05). The results showed that salt infiltration promoted the release of fishy substances, improving the edible and processing performance of beef liver. The identification of flavor compounds in raw and roasted beef liver via GC-IMS implies that (E)-2-octenal-M, (E)-3-penten-2-one-M, ethyl acetate-M, ethyl acetate-D, and methanethiol are closely related to improving the flavor of beef liver; among them, (E)-2-octenal-M, (E)-3-penten-2-one-M, and methanethiol can cause beef liver odor, while nonanal-M, octanal-M, benzene acetaldehyde, n-hexanol-D, butyl propanoate-M, heptanal-D, heptanal-M, and 3-methylthiopropanal-M had significant effects on the flavor formation of beef liver steak. The determination of reducing sugars revealed that salt soaking had no significant effect on the reducing sugar content of beef liver, and the beef liver steak was significantly reduced (p < 0.05), proving that reducing sugars promoted the formation of beef liver steak flavor under roasting conditions. Fatty acid determination revealed that salt soaking significantly reduced the content of polyunsaturated fatty acids in beef liver (p < 0.05), promoting the process of fat degradation and volatile flavor production in the beef liver steak. Salt plays a prominent role in salting-out and osmosis during deodorization and flavor improvement. Through controlling important biochemical and enzymatic reactions, the release of flavor substances in a food matrix was increased, and a good deodorization effect was achieved, which lays a foundation for further research on the deodorization of beef liver and the flavor of beef liver steak.

Study on Deterioration Characteristics of a Composite Crossarm Mandrel in a 10 kV Distribution Network Based on Multi-Factor Aging.

This paper presents a study that conducted 5000 h of multi-factor aging tests on 10 kV composite crossarms, considering the natural environment in coastal areas and actual power line operations. Various aging conditions, such as voltage, rain, temperature, humidity, salt fog, ultraviolet light, and mechanical stress, were applied during the tests. The research initially analyzed the influence of multi-factor aging on the bending and tensile properties of the full-size composite crossarm. Subsequently, a detailed investigation was carried out to assess the impact of aging on the mechanical properties, electrical insulation properties, and microscopic characteristics of the composite crossarm core bar. Results indicated that the tensile strength and bending strength of the full-size composite crossarm mandrel experienced minimal changes after aging, remaining well within operational requirements. However, the silicone rubber outer sheath's hydrophobicity decreased, leading to the appearance of cracks and holes on the surface, which provided pathways for moisture and salt infiltration into the mandrel. As a consequence, the bending strength and shear strength of the mandrel material were reduced by 16.5% and 37.7%, respectively. Moreover, the electrical performance test demonstrated a slight change in the mandrel's leakage current, while the electrical breakdown strength decreased by 22.8%. Microscopic analysis using SEM, three-dimensional CT, and TGA revealed that a small amount of resin matrix decomposed and microcracks appeared on the surface. Additionally, the fiber-matrix interface experienced debonding and cracking, leading to an increased moisture absorption rate of the mandrel material.

Hot corrosion behavior of CYSZ thermal barrier coating with optimized laser surface modification

The current study aims to investigate the influence of laser surface modification on the hot corrosion, fracture toughness, and hardness resistance of atmospheric plasma sprayed Ceria-Yttria Stabilized Zirconia (CYSZ) thermal barrier coating. Throughout the laser surface modification process, a variety of laser processing parameters are used to obtain the finest surface properties and optimum laser parameters. In this study, the whole coating surface is modified using the optimal parameters. The results show that 52.9 W laser power at a 220 mm laser distance and a 60 mm/s scanning speed were found as the optimum laser glazing parameters. A hot corrosion test is performed in a box furnace for 20 h at 1050 °C. Scanning electron microscopy (SEM) images show denser surfaces in laser-glazed coatings when compared to air-spraying coatings. A dense microstructure combined with the top coat is created in the coating cross-section, and a smooth microstructure with a coaxial fracture network is produced on the surface. The laser-glazed layer has superior mechanical characteristics to the as-sprayed coating, including hardness and fracture toughness. This layer also restricts the damaging monoclinic-tetragonal phase change for CYSZ TBC, blocking the infiltration of molten salt. The hot corrosion behavior of TBCs is improved by the inclusion of a dense laser-glazed layer.

Hexamethylphosphoramide-Assisted Structure and Morphology Regulation of a PbI2 Film for Air-Processed Efficient Perovskite Solar Cells via a Two-Step Deposition Method

The two-step deposited method with the advantages of high reproducibility and controllability is widely used in fabricating highly efficient perovskite solar cells (PSCs). However, it is still a challenge to fabricate air-processed PSCs through this method due to the existing techniques with glove box circumstance that are not well extended to the ambient air-condition fabrication process. Here, hexamethylphosphoramide (HMPA) used as a solvent additive is incorporated into the first-step PbI2 precursor solution, which can effectively modify the morphology and crystallinity of the PbI2 layer, thereby creating more opportunities for the infiltration of the second-step organic salt. This two-step coating leads to the full conversion from PbI2 to the perovskite crystal and large grains, reduced defects, and enhanced uniformity for the final perovskite film. Consequently, a champion efficiency of 20.84% of the HMPA-based device fabricated using this procedure is achieved. The HMPA-based device shows long-term stability of the remaining 85.7% of the initial efficiency after 1000 h of storage in an ambient air environment. This method demonstrates the great potential toward air-processed efficient PSCs.

Molten salt infiltration–oxidation synergistic controlled lithium extraction from spent lithium iron phosphate batteries: an efficient, acid free, and closed-loop strategy

Based on a molten salt Li extraction from spent LiFePO4, which constitutes a one-step preparation with a LiFePO4 product, a closed-loop process was conducted to regenerate a spent LiFePO4 cathode.

The Effect of Molten Salt Infiltration on 2D SiCf/SiC Composite by Chemical Vapour Infiltration.

The SiCf/SiC composite manufactured by chemical vapour infiltration (CVI) is a kind of porous material. Liquid molten salt in a Molten Salt Reactor (MSR) may enter into the porous composites and affect their performance. Through the study of the internal pores in the material, the permeability behaviour of the material can be investigated, which is of great significance to the analysis of the properties of the material itself. However, there is less investigation on effects of molten salt infiltration on the internal pore structure of SiCf/SiC composites. In this paper, a molten salt infiltration experiment of 2D woven SiCf/SiC composites was implemented at 650 °C, 3 atm. SEM, CT and XRD were used to characterize it. The results indicated that the microstructure could be affected by partial molten salt infiltration and temperature change. The distribution of porosity of the composite showed an obvious transformation. The lattice spacing of SiC showed an increased tendancy of stress relaxation.

Temperature-Dependent Molten Chloride Salt Corrosion of Nickel Alloys

As next-generation clean and renewable energy technologies like concentrating solar power (CSP) systems and molten salt-cooled reactors (MSR) operate at ever higher temperatures (HT) to increase efficiency, their structural material and molten salt selection becomes increasingly important. To understand the corrosion behavior of candidate alloys to be used as materials for storage tanks, heat exchangers, and piping, seven alloys (Hastelloy N, Haynes 242, Haynes 214, Hastelloy C-276, Haynes 230, Haynes 224, Haynes 244) are immersed in purified 45.8 MgCl2- 38.5 KCl- 15.7 NaCl wt% chloride salt for 100 hours at 650°, 725°, and 800°C. After the exposure tests, the alloys are analyzed using SEM and EDS to determine the extent of salt infiltration and primary corrosion mechanisms. In addition, room-temperature XRD analysis provides quantitative information about the alloys’ corrosion products. These findings contribute important insight for molten salt energy system communities.

Using Microwave Irradiation for In-situ Infiltration of Electrodes in Solid Oxide Fuel Cells

ABSTRACT Infiltrating a thin porous scaffold on top of an electrolyte forms a high surface area catalyst that is finely distributed over a conductive matrix and could dramatically increase the performance. This research studied microwave irradiation in conjunction with salt infiltration for rapid catalyst synthesis inside the porous YSZ layer. A detailed comparison of crystal structure and electrochemical performance was made between microwave and traditional electric furnace heating. A maximum power density of 843 mW/cm2 at 800°C was achieved for the microwaved sample, more than a 20% improvement over its counterpart. The distribution function of relaxation of two cells was calculated and compared. Long-term stability for more than 96 hours of operation under load at 700°C was conducted. It was concluded that the enhancement of microwaved samples came from the enhanced morphology of the resulting particles.

Hot corrosion behavior of hybrid double-layered LZ/LZC + YSZ thermal barrier coatings made using powder and solution precursor feedstock

Lanthanum zirconate (La2Zr2O7; LZ) and cerium doped lanthanum zirconate (La2(Zr0.7Ce0.3)2O7; LZC) has gained immense attention as thermal barrier coating (TBC) materials because of their superior thermophysical properties, high-temperature phase stability and chemical inertness than yttria-stabilized zirconia (YSZ). In the present study, LZ and LZC double-layered TBCs are prepared by solution precursor plasma spray process (SPPS) as a top layer over the atmospheric plasma sprayed YSZ coatings, and their hot corrosion behavior is studied. The as-deposited SPPS coatings exhibited single phases, and the microstructural morphologies reveal a hierarchically structured surface with vertically cracked microstructure. Exposure to the high temperature corrosion process results in damage of the morphology and microstructure within the SPPS layer by forming lanthanum vanadate (LaVO4) and lanthanum cerium vanadate ((LaCe)VO4) in LZ and LZC coatings, respectively, while leaching out zirconia (ZrO2). In the case of conventional YSZ, the corrosive salts infiltrate entirely through the coating and result in complete densification and associated phase changes. While combining the above aspects, the hybrid double-layered architecture of LZ/YSZ and LZC/YSZ coatings can be beneficial to protect the underlying YSZ layer against the detrimental infiltration of molten corrosive salt.