Cation Diffusion Research Articles

Diffusion of multi-principal elements through stable Cr[formula omitted]O[formula omitted] and Al[formula omitted]O[formula omitted] scales

Understanding the oxidation mechanisms in multi-principal elements and high-entropy alloys (HEAs) is critical for their potential applications in high-temperature oxidative environmnts. In addition to the compositional complexity, the counter-diffusion of cations and anions through the oxide contributes to the growth of the oxide scales in these materials. We examine the cationic and anionic diffusion through the stable chromium and aluminum oxides that form in a model HEA using atomistic simulations. In accord with experiments, we find that the tracer cations diffuse faster than the native cations through the oxide scales at high temperature (1000 K to 2000 K) and the dynamics are directly correlated to the respective migration energies of the diffusion pathways. The oxide scale growth is strongly influenced by the presence of tracer/impurity elements in alumina forming alloys relative to those that predominantly form chromia. A geometric analysis of the vacancy-induced diffusion paths for the cation migration relative to the location of the oxygen atoms reveals the influence of the latter on the preferential diffusion pathway, resulting in anisotropy. The predictions offer insights on the diffusion characteristics in the oxide scales formed in HEAs and aid in our understanding of the oxide growth kinetics.

High-Performance Protonic Ceramic Electrochemical Cells

Protonic ceramic electrochemical cells (PCECs) have attracted considerable attention owing to their ability to reversibly convert chemical fuels into electricity at low temperatures below 600 °C. However, extreme sintering conditions during conventional convection-based heating induce critical problems for PCECs such as nonstoichiometric electrolytes and microstructural coarsening of the electrodes, leading to performance deterioration. Therefore, we fabricated PCECs via a microwave-assisted sintering process (MW-PCEC). Owing to the ultrafast ramping rate (∼50 °C/min) with bipolar rotation and the resistive heating nature of microwave-assisted sintering, undesirable cation diffusion and grain growth were effectively suppressed, thus producing PCECs with stoichiometric electrolytes and nanostructured fuel electrodes. The MW-PCEC achieved electrochemical performance in both in fuel cell (0.85 W cm–2) and in electrolysis cell (1.88 A cm–2) modes at 600 °C (70% and 254% higher than the conventionally sintered PCEC, respectively) demonstrating the effectiveness of using an ultrafast sintering technique to fabricate high-performance PCECs.

Thermally-induced drift of A-site cations at solid–solid interface in physically paired lead halide perovskites

The promise of hybrid organic–inorganic halide perovskite solar cells rests on their exceptional power conversion efficiency routinely exceeding 25% in laboratory scale devices. While the migration of halide ions in perovskite thin films has been extensively investigated, the understanding of cation diffusion remains elusive. In this study, a thermal migration of A‑site cations at the solid–solid interface, formed by two physically paired MAPbI3 and FAPbI3 perovskite thin films casted on FTO, is demonstrated through continuous annealing at comparably low temperature (100 °C). Diffusion of methylammonium (CH3NH3+, MA+) cations into the low‑symmetry yellow δ‑FAPbI3 phase triggers a transition from the yellow (δ) to black (α) phase evident in the distinctive color change and verified by shifts in absorption bands and X‑ray diffraction patterns. Intermixing of the A‑site cations MA+ and FA+ (CH(NH2)2+) occurred for both systems, α‑MAPbI3/δ‑FAPbI3 and α‑MAPbI3/α‑FAPbI3. The structural and compositional changes in both cases support a thermally activated ion drift unambiguously demonstrated through changes in the absorption and X-ray photoelectron spectra. Moreover, the physical contact annealing (PCA) leads to healing of defects and pinholes in α‑MAPbI3 thin films, which was correlated to longer recombination lifetimes in mixed MAxFA1−xPbI3 thin films obtained after PCA and probed by ultrafast transient absorption spectroscopy.

Visualizing the Nanoscale Oxygen and Cation Transport Mechanisms during the Early Stages of Oxidation of Fe–Cr–Ni Alloy Using In Situ Atom Probe Tomography

AbstractUnderstanding the early stages of interactions between oxygen and material surfaces—especially at very high spatial resolutions—is highly beneficial for fields ranging from materials degradation, corrosion, geological sciences, forensics, and catalysis. The ability of in situ atom probe tomography (APT) is demonstrated to track the diffusion of oxygen and metal ions at nanoscale spatial resolution during the early stages of oxidation of a model Fe–Cr–Ni alloy. Using 18O isotope tracers in these in situ APT experiments and complementary ex situ multimodal microscopy, spectroscopy, and computational simulations allows to precisely analyze the kinetics of oxidation and determine that outward cation diffusion to oxide/air interface is the primary mechanism for intragranular oxide growth in this alloy at 300 °C. This unique in situ isotopic tracer APT approach and the insights gained can be highly beneficial for studying early stages of gas–surface reactions in a broad array of materials.

Synchronous solid-state diffusion, dissolution-reprecipitation, and recrystallization leading to isotopic resetting: insights from chalcopyrite replacement by copper sulfides

Reactions among minerals occur via solid-state diffusion or fluid-induced, interface-coupled dissolution-reprecipitation (ICDR). Both mechanisms can coexist under conditions where the rates of both processes are similar, depending mainly on the nature of the mineral, temperature, and fluid composition. To clarify the synergies between these reaction mechanisms, we investigated the replacement and recrystallization reactions of chalcopyrite in the presence of a 65Cu-enriched aqueous fluid. The replacement of chalcopyrite by secondary copper sulfides follows a paragenetic sequence, whereby chalcopyrite is initially replaced by covellite, and then by digenite, with some of the digenite replacing covellite in longer duration experiments. The replacement reactions proceed via ICDR along with solid-state diffusion of 65Cu from the fluid into product minerals, with both mechanisms occurring at similar rates. Over time, chalcopyrite is completely replaced, and the secondary copper sulfides attain isotopic equilibrium with the fluid. Depending on temperature, thermal history, and fluid-mineral ratio, the reaction products may preserve kinetic or equilibrium signatures. We have identified a new geochemical process of ‘porosity-aided recrystallization’, which may result in a re-equilibration or perturbation of mineral isotopic/trace element compositions due to exchanges between the mineral and fluid facilitated by extensive micro- to nano-scale porosity created by ICDR reactions. Porosity-aided recrystallization will affect any mineral-fluid system where mass transfers via solid-state diffusion and ICDR operate at similar rates, causing rapid (days-weeks) ‘resetting’ of the original isotopic abundances and trace element contents of the affected minerals. In copper sulfides, porosity-aided recrystallization occurs at lower temperatures (<300 °C) due to fast cation diffusion rates (log10D ≈ –13.6, 300 °C), but also takes place across other mineral systems where diffusion rates are faster at high temperatures. The open-system isotopic and trace element exchanges associated with porosity-aided recrystallization could lead to erroneous petrological interpretations, especially where these markers are used as a proxy for reconstructing geological evolution.

Effect of Relaxations on the Conductivity of La1/2+1/2x Li1/2-1/2x Ti1-x Al x O3 Fast Ion Conductors.

Perovskite-type solid-state electrolytes, Li3xLa2/3–xTiO3 (LLTO), are considered among the most promising candidates for the development of all-solid-state batteries based on lithium metal. Their high bulk ionic conductivity can be modulated by substituting part of the atoms hosted in the A- or B-site of the LLTO structure. In this work, we investigate the crystal structure and the long-range charge migration processes characterizing a family of perovskites with the general formula La1/2+1/2xLi1/2–1/2xTi1–xAlxO3 (0 ≤ x ≤ 0.6), in which the charge balance and the nominal A-site vacancies (nA = 0) are preserved. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) investigations reveal the presence of a very complex nanostructure constituted by a mixture of two different ordered nanoregions of tetragonal P4/mmm and rhombohedral R3̅c symmetries. Broadband electrical spectroscopy studies confirm the presence of different crystalline domains and demonstrate that the structural fluctuations of the BO6 octahedra require to be intra- and intercell coupled, to enable the long-range diffusion of the lithium cation, in a similar way to the segmental mode that takes place in polymer-ion conductors. These hypotheses are corroborated by density functional theory (DFT) calculations and molecular dynamic simulations.

Co-gradient Li-rich cathode relieving the capacity decay in Lithium-ion batteries

Lithium-rich layered oxides (LLOs) are one of the promising cathode materials for next generation energy storage devices, but structural degradation and severe capacity decay during cycling have hindered applications. Here, we find cobalt effectively mitigate structural degradation and develop a simple and novel metal organic framework (MOF) treatment and surface reconstruction method to fabricate Co gradient layer on LLOs. In situ and ex situ microstructural studies show the capacity decay is mainly originated from the formation of microstructural defects such as voids and pores, continuous oxygen release and formation of spinel and rock-salt structure initiated from the surface. The reconstruction leads to the formation of an artificial layer of Co rich and Li poor spinel (Co3O4) and rock-salt (CoO) structure on surface, suppressing the diffusion of cations and O−1/O−2 anions toward the surface during cycling. The LLO-Co cathode exhibits enhanced cycling stability with a capacity retention of 94.4% at 0.2 C after 100 cycles and a high capacity of 183 mAh g−1 at 1 C, in comparison with those of untreated LLO (80.5% and 153 mAh g−1). This work sheds lights on better utilize rare Co resource in the development of high capacity and cyclability cathode materials for lithium-ion batteries.

Progress and prospects of two-dimensional materials for membrane-based osmotic power generation

The electrical energy that can be harnessed from the salinity difference across the sea water and river water interface can be one of the sustainable and clean energy resources of the future. This energy can be harnessed via the nanofluidic channels that selectively permeate ions. The selective diffusion of cations and anions can produce electricity through reverse electrodialysis. Two-dimensional (2D) materials are a class of nanomaterials that hold great promise in this field. Several breakthrough works have been previously published which demonstrate the high electrical power densities of 2D membranes. The ion transportation can be either through the nano-sized in-plane pores or interlayer spacings of 2D materials. This review article highlights the progress in 2D materials for salinity gradient power generation. Several types of 2D membranes with various nano-architectures are discussed in this review article. These include atom-thick 2D membranes with nanopores, 2D lamellar membranes, 2D lamellar membranes with nanopores, 2D/one-dimensional (1D), and 2D/2D hybrid membranes. The fabrication techniques, physical characteristics, ion transportation properties, and the osmotic power generation of these 2D membranes are elaborated in this review article. Finally, we overview the future research direction in this area. It is envisioned that the research on 2D materials can make practical salinity gradient power generation one step closer to reality.

Stability-Guided Strategies to Mitigate Dendritic Growth in Lithium-Metal Batteries

Dendritic growth is a leading cause of degradation and catastrophic failure of lithium-metal batteries. Deep understanding of this phenomenon would facilitate the design of strategies to reduce, or completely suppress, the instabilities characterizing electrodeposition on the lithium anode. We present a linear-stability analysis, which utilizes the Poisson-Nernst-Planck equations to describe Li-ion transport and, crucially, accounts for the lack of electroneutrality. This allows us to investigate the impact of electric-field gradients near the electrode surface on both ion diffusion and its anisotropy. Our analysis indicates that the use of anisotropic electrolytes (i.e., electrolytes with anisotropic diffusion coefficients of the Li ions) and the control of the local electric field can suppress dendritic growth of lithium metal. Specifically, changes in the local electric field can be used to enhance the longitudinal (perpendicular to the electrode) component of the cation diffusion coefficient tensor, which decreases the maximum growth rate of the dendrites. Electrolytes with electric field-dependent diffusion coefficients would reduce dendritic growth in small batteries, while anisotropic electrolytes (or separators with anisotropic pore structures or columnized membranes) are appropriate for batteries of any size.

Understanding the effect of tensile stress on erosion-corrosion of X70 pipeline steel

The pipelines in the oil and gas industry may simultaneously suffer damage from tensile stress and erosion at the internal surface, which could cause the pipeline failure easily. In this work, the combined effect of tensile stress and erosion on the corrosion of X70 pipeline steel was studied in a loop system coupled with a stress loading device. The general corrosion and localized corrosion under the combination of tensile stress and erosion was comprehensively investigated using finite element simulation analysis, potentiodynamic polarization curve, electrochemical impedance spectroscopy, scanning electron microscope as well as 3D ultra-depth microscope. The results show that both tensile stress and erosion can promote general corrosion independently. Furthermore, the combination of tensile stress and erosion can generate a synergistic effect on general corrosion of steels through reducing the compactness of corrosion products layer, accelerating the mass transfer process and improving the reaction activity of the steel, with a changed corrosion current density of 37.54 μA/cm2, even exceeding the influence of tensile stress (17.76 μA/cm2). For localized corrosion, erosion can enhance the inside-out diffusion of metal cations in the metastable pit and dilute the pit anolyte, while tensile stress may generate stress concentration on corrosion defects. Therefore, erosion shows a suppression on localized corrosion, but an enhancement effect from tensile stress.

Genome-Wide Identification of Strawberry Metal Tolerance Proteins and Their Expression under Cadmium Toxicity

Metal tolerance proteins (MTPs) are divalent cation transporters, known to upkeep the mineral nutrition of plants and heavy metal transport at cell, tissue, or whole plant levels. However, information related to evolutionary relationships and biological functions of MTP genes in strawberry (Fragaria vesca L.) remain elusive. Herein, we identified 12 MTP genes from the strawberry genome and divided them into three main groups (i.e., Zn-MTP, Fe/Zn MTP, and Mn-MTP), which is similar to MTP grouping in Arabidopsis and rice. The strawberry MTPs (FvMTPs) are predicted to be localized in the vacuole, while open reading frame (ORF) length ranged from 1113 to 2589 bp with 370 to 862 amino acids, and possess 4 to 6 transmembrane domains (TMDs), except for FvMTP12 that possessed 16 TMDs. All the FvMTP genes had putative cation efflux and cation diffusion facilitator domains along with a zinc dimerization (ZT-dimer) domain in Mn-MTPs. The collinear analysis suggested their conservation between strawberry and Arabidopsis MTPs. Promoter analysis also demonstrated that some of them might possibly be regulated by hormones and abiotic stress factors. Moreover, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis proposed that FvMTP genes are involved in cation transport and homeostasis. The expression analysis showed that FvMTP1, FvMTP1.1, and FvMTP4 were significantly induced in leaf samples, while FvMTP1.1 and FvMTP4 were significantly regulated in roots of cadmium (Cd)-treated strawberry plants during progressive stress duration. The findings of Cd accumulation depicted that Cd contents were significantly higher in root tissues than that of leaf tissues of strawberry. These results are indicative of their response during the specific duration in Cd detoxification, while further functional studies can accurately verify their specific role.

Enhanced cyclic redox reactivity of Fe2O3/Al2O3 by Sr doping for Chemical-Looping combustion of solid fuels

Aiming at the problems of low redox activity and easy sintering deactivation of iron-based oxygen carriers (OCs), Sr was used to modify Fe2O3/Al2O3 in chemical looping combustion (CLC) of solid fuels. The Sr doped Fe2O3/Al2O3 possessed high fuel combustion reactivity with different solid fuels (coal, coal char and biomass). During consecutive cycles, high cycling durability and morphological preservation were observed for Sr doped Fe2O3/Al2O3, signifying that the addition of strontium effectively enhanced the anti-sintering ability and inhibited the phase segregation of Fe2O3/Al2O3 during cyclic reactions. By comparing the coal char combustion reactivity of Fe2O3/Al2O3 samples doped with different SrO content (1 wt%, 5 wt% and 10 wt%), the optimum additive amount of SrO was 5 wt%. In addition, the characterization analysis proved that the Sr dopant suppressed the outward diffusion of Fe cations and maintained the surface micro-morphology of Fe2O3/Al2O3 in the process of CLC. This study presented important guiding principle and strategy for the synthesis of iron-based OCs with high cyclic redox reactivity in the CLC of solid fuels.

Boosting Li-Ion Diffusion Kinetics of Na2Ti6-xMoxO13 via Coherent Dimensional Engineering and Lattice Tailoring: An Alternative High-Rate Anode.

Featured with an exposed active facet, favorable ion diffusion pathway, and tailorable interfacial properties, low-dimensional structures are extensively explored as alternative electroactive materials with game-changing redox properties. Through a stepwise "proton exchange-insertion-exfoliation" procedure, in this article, we develop Na2Ti6-xMoxO13 (NTMO) nanosheets with weakened out-of-plane bonding and in-plane Mo6+ doping of the tunnel structure. Real-time phase tracking of the laminated NTMO structures upon the lithiation/delithiation process suggests mitigated lattice variation; meanwhile, the kinetics simulation shows a mitigated Li-ion diffusion barrier along the [010] orientation. At an industrial-level areal capacity loading (2.5 mAh cm-2), the NTMO electrode maintains robust cycling endurance (91% capacity retention for 2000 cycles) even at 40 C, as well as the high energy/power densities in the as-constructed NTMO||LiFePO4 full cell prototype. The dimensional and lattice modifications presented in this study thus encourage further exploration of the tailored cation diffusion pathway for the construction of fast-charging batteries.

A study of the morphological effect of an α-Al2O3 layer on the creep life for nickel-based superalloys using microstructure-based geometrical models

A study on the role of the irregular geometry of the α-Al2O3 film during the creep rupture test was conducted on samples of DD6 Ni-based single-crystal superalloy at 980 °C/250 MPa. This study involved experimental and finite element analyses of creep-oxidation specimens. The experimental results showed that the creep rupture life of the 0.67 mm-thin samples was shorter than that of the 0.81 and 1.12 mm specimens. Microscopic examination of the oxidation-affected zones showed that the morphology of the inner α-Al2O3 layer of a 0.67 mm-thin sample was discontinuous and incomplete, and the sample (1.12 mm thick) included a continuous and complete α-Al2O3 film. Hence, the influence of different morphologies of the α-Al2O3 layer on the stress distribution was studied numerically using the ABAQUS software. The finite element modeling results showed that the maximum stress was concentrated in the blocks of a discontinuous α-Al2O3 layer, which increased the diffusion of ions and metal cations. As a result, excessive growth of the oxidation-affected zone of the thin samples and the formation of AlN particles in high density occurred. It also contributed to an increase in the surface crack growth rate in the thin wall sample, which reaches the critical value of crack length in a shorter time than thick ones. Microstructure-based modeling has provided further insight into the role of the α-Al2O3 layer morphology in the deterioration of the mechanical properties of thin creep specimens.

Diffusions in Aqueous Solutions with Multivalent Cations and Especially in Cationic First Hydration Shell.

Compared with univalent cationic diffusion, little is known about the diffusion behavior of multivalent cations let alone the diffusion of water in their first hydration shell. Here, we show that all published translational diffusion coefficients of multivalent cations and water measured at room temperature exhibit the same concentration dependence when plotted as a function of the mass fraction of free water or of hydrated solute. This behavior is held until only hydration and confined water remain in solutions, wherein their concentration dependences become cationic charge number-dependent. We also found that the iceberg model can well describe the diffusions of multivalent cations with decreasing water content until only hydration water is present. However, 1H-pulsed-field-gradient nuclear magnetic resonance measurements confirmed that 1H in the first hydration shell diffuses faster than Al3+ at room temperature and they have the same diffusion coefficient only with decreasing the temperature down to about 243 K. Therefore, iceberg model only equivalently describes the effect of strong ion-water interaction on multivalent cationic diffusion. These results will also help us reconceive our current understanding of the pathway for hydration water affecting the diffusion behavior of solutes with relatively weak solute-water interactions.

Organic Cation Diffusion-Induced Heterogeneous Viscoelasticity in Organic-Inorganic Hybrid Perovskite Polycrystalline Films.

Organic-inorganic hybrid perovskite (OIHP) polycrystalline films are the key light-absorbing layers of laminated-structure OIHP-based devices that have attracted increasing attention in photoelectronics and flexible electronics. Internal stresses induced by the mismatched responses of laminated layers to long-term and cyclic multiphysical fields generate time-dependent mechanical deformation in OIHP polycrystalline films, which makes the mechanical constitution relation of great significance. However, few studies focus on either the mechanical properties and behaviors of OIHP polycrystalline films or the underlying mechanism coupled with the grain structure and ion diffusion. Here, we uncovered the heterogeneous viscoelasticity of MAPbBr3 films strongly correlated with the grain structure. Combining experiments and modeling, we revealed that the organic cation diffusion from grain interiors to grain boundaries leads to heterogeneity in the chemical distribution and viscoelastic modulus. Our work provides the nanomechanical understanding of the OIHP polycrystalline films that are crucial for safety design and performance optimization in OIHP-based electronics.

Synergistic effects of Si and Y on corrosion behavior of cast cladding steels by pre-laying Y powder for nuclear applications in static liquid LBE

Ferritic/martensitic (F/M) steels with (9–12)wt.% Cr are potential candidates for structural applications in Lead-cooled Fast Reactors (LFR) due to their low solubility in liquid Lead-Bismuth Eutectic (LBE) coolant. How to improve corrosion resistance of 9-12Cr F/M steels has been a challenge. Here we cast three steels by pre-laying yttrium (Y) powder on the bottom of mold to obtained Y-bearing steels. Precursory work on this family of Y-bearing steels has previously highlighted them with the longer steady state creep stage and the lower minimum creep rate at 650 °C under 120 MPa, which has motivated their study under more extreme conditions, such as corrosion behavior in liquid LBE. We find a synergistic effect of Si and Y on both optimizing structure and reducing thickness of oxide scale at various oxygen concentrations, exposing temperatures and test times. The oxide scale changed from dual layers to single spinel layer, the thickness reduced from 36 μm to 4 μm, dissolution corrosion and PbBi penetration were inhibited. Low diffusion coefficient of ions in SiO2 and Y segregation on grain boundaries of steels hinder the outward diffusion of cations, and strong affinity between Y and O leads to the formation of Y2O3 preferentially, acting as nucleation sites of SiO2 and Cr2O3, accelerating a dense and continuous oxide scale. This work enables the development of structure steels with high corrosion resistance for various high temperature application, including boiler steel, gas turbine, and heat exchanger tubes.

Effect of Cationic/Anionic Diffusion Dominated Passive Film Growth on Tribocorrosion

Tribocorrosion behaviours of nickel (Ni) and niobium (Nb) in sodium sulfate (Na2SO4) solution under potentiodynamic and potentiostatic conditions were studied. Under the potentiodynamic condition, the passivation was early broken, accompanied by a sharp increase in frictional coefficient on Nb. The current was more fluctuant, and larger material loss appeared at the higher potential in the potentiostatic condition. However, these phenomena did not occur for Ni, and it even showed lower material loss at the higher potential in the potentiostatic tribocorrosion test. The differences in tribocorrosion behaviour had a close relationship to the passive film growth mechanism, which decided the passive film/metal interface structure. Nb with anionic diffusion dominated mechanism in passive growth would cause the accumulation of oxygen vacancies at the passive film/metal interface. This may weaken the adhesion between the metal and the passive film. However, with the cationic diffusion dominated passive film growth on Ni, cation vacancies concentrated at the passive film/tribo-film interface, and this did not affect the adhesion between metal and passive film. Ni or other passive elements with the cationic diffusion-dominated mechanism in passive film growth were recommended as the alloying element for improving the tribocorrosion resistance of alloys.

Effect of combined cations on chloride diffusion behavior in concrete

The effect of combined cations in diffusion source solutions on chloride diffusion behavior in concrete is unknown, and present research on the effect of combined cations on chloride diffusion behavior in concrete is insufficient. This paper uses natural diffusion experiment as research condition, and uses the concrete with water-binder ratio of 0.5 as research object to study the effect of chemical valence and combination relationship of cations in combined cations diffusion source solutions on chloride diffusion behavior in concrete. The results reveal that the higher the chemical valence of cations, the faster the chloride diffusion rate. When the combination relationship changes, cations with the same chemical valence have little effect on the chloride diffusion process; cations with different chemical valence have obvious effects on the chloride diffusion process. The higher the concentration of divalent cations in solutions, the lower the water-soluble chloride concentration, and the higher the acid-soluble chloride concentration. Divalent cation is favorable to the formation of Friedel's salt.

Chemical compatibility of hollow ceramic cenospheres as thermal insulation for high-temperature thermal energy storage applications with molten nitrate salt

An effective insulation material that is both thermally and chemically stable in molten salts could transform the design of molten-salt-based thermal energy storage (TES) tanks. Most current molten salt TES tanks hold the metallic tank structure in direct contact with hot salt inventory, a design which leads to thermal expansion of the tank and triggers stresses that can lead to thermomechanical failures. With an internal insulation to lower the temperature at the tank structure, the extent of thermal expansion can be reduced, thereby reducing expansion-induced stresses and allowing for consideration of lower-cost tank structure materials. Conventional insulation materials are either 1) too porous and allow molten salts to permeate into the matrix, which significantly increases the thermal conductivity or 2) too dense and have a thermal conductivity that cannot provide sufficient thermal insulation. This paper presents an alternative thermal insulation concept using cenospheres which have an alumino-silicate structure. The cost analysis suggests that the low-density cenospheres can be one of the cheapest materials to provide cost-effective thermal insulation. The chemical compatibility of cenospheres is investigated in molten 60 wt% NaNO 3 /40 wt% KNO 3 salt which is close to industrial-grade Solar Salt. This paper shows that diffusion of the sodium and potassium cations from the salt into the cenospheres occurs based on weight analysis, energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The cation diffusion breaks the bridging oxygen bonds and causes volume expansion of the microstructure which is responsible for the failure of the cenosphere particles. The chemical composition of the cenospheres is found to affect their compatibility with molten nitrate salt. A cenosphere product with low iron content showed the best compatibility with an average survival rate of 77.9% ± 9.8% after 7 days of immersion in the molten nitrate salt. While even the low-iron cenospheres appear to require protection from direct molten salt contact, their slow degradation rate, closed-cell porosity, and low cost hold potential for effective use as internal tank insulation. • Hollow cenospheres are investigated as insulation for molten nitrate salt storage. • Low level of impurities in cenospheres should improve chemical stability. • Cenospheres can provide cost-effective insulation. • Cenospheres can be fail-safer than conventional materials.