Mobile Alkali Ions Research Articles

High-volume recycled glass cementitious and geopolymer composites incorporating graphene oxide

This study presents the development of high-volume recycled glass construction materials using recycled glass aggregate (RGA) as a 100 % sand replacement, recycled glass powder (RGP) as 40 wt% of the binder, and 0.1 wt% graphene oxide (GO) as nano-reinforcement. The research investigates the individual and their combined effects on the engineering performance, reaction kinetics (using calorimetry, X-ray diffraction-XRD, Fourier Transform Infrared-FTIR and Thermogravimetric analysis-TGA), and microstructure (Scanning Electron Microscopy/ Energy Dispersive X-ray Spectroscopy-SEM/EDS) for both cementitious and geopolymer systems. The results indicate that while RGA reduces strength and exacerbates alkali-silica reaction (ASR), the presence of 40 wt% RGP significantly mitigates ASR despite a lower strength gain in both systems. Geopolymers exhibit significantly lower ASR expansion compared to cementitious matrices owing to their superior alkali-binding capacity and denser microstructure, which restricts water and alkali ion mobility. 0.1 wt% GO was found to accelerate geopolymerisation, enhancing the strength of geopolymer mixes, but it decreased compressive strength in cement-based mixes due to self-desiccation-induced micro-cracking under ambient curing condition. The study also highlights that cement and metasilicate, as well as slag, are the main contributors to cost and CO2 emissions in cementitious and geopolymer systems, respectively. Overall, geopolymers exhibit a significantly lower global warming potential (< 180 kg CO2-eq/m3) compared to cement-based mixes (> 365 kg CO2-eq/m3) with a comparable cost (190–230 AUD/m3). The results indicate the potential for sustainable construction applications using high volumes of recycled glass, incorporating over 70 % of the mixture by weight.

Effect of silica fume on the efflorescence, strength, and micro-properties of one-part geopolymer incorporating sewage sludge ash

The application of sewage sludge ash (SSA) in alkali activated cementitious material, i.e., geopolymer, was one of the effective measures to dispose of and recycle the sewage sludge. However, the geopolymer efflorescence could be aggravated due to elevated alkali content, especially for one-part geopolymer, where the dissolution reaction of solid alkali activator was less sufficient. This study focused on the efflorescence of GGBS-SSA based one-part geopolymer, as compared to two-part geopolymer, and the effect of silica fume on the efflorescence, strength and micro-properties of the one-part geopolymer. The results showed that the extent of efflorescence crystallization and the concentration of leached Na+ ions in the one-part geopolymer were more severe than the two-part geopolymer, due to the lower degree of geopolymerization reaction and the heterogeneous dense microstructure of the one-part geopolymer. After adding silica fume to the one-part geopolymer, the extent of efflorescence crystallization and the concentration of leached Na+ ions reduced significantly, and the compressive strength increased from 41.6 MPa to 57 MPa when the silica fume content was 10 %, but then decreased slightly. Adding the silica fume reduced the release rate of reaction heat, which helped to increase the solubility of solid alkali activator and improve the geopolymerization reaction, thus significantly reducing the content of mobile alkali ions and enhancing the compressive strength. Moreover, the silica fume with tiny spherical particle had better ball effect and micro-aggregate filling effect, which refined the pore size and reduced the connectivity of pore network, significantly reducing the diffusion rate and leaching of mobile alkali ions.

(Invited) A Dive into the Complex Mechanisms That May or May Not Increase Li/Na Mobility in Solid State Conductors

The conductivity of Li and Na has achieved remarkably high values in some materials, higher than what has been achieved in liquid electrolytes. Because there is no mobile solvation shell in solid-state conductors, the maximum of conductivity is essentially unlimited. I will discuss our current understanding of the compositional and structural elements that contribute to very high alkali ion mobility. This will include a discussion, of activated complexes that create concerted motion, possible high-entropy effects, the effect of (poly)anions, and structural topology.

Pulsed infrared stimulated luminescence measurements for defect pair model studies in feldspars

We present a time-resolved experimental study of feldspar infrared stimulated luminescence (IRSL) as part of a defect pair model investigation of the underlying mechanisms. Within our investigation we recorded ultraviolet emissions that covered a diverse range of alkali feldspars together with a limited selection of plagioclase feldspars. In analysing our measurements, we find that each IRSL pulse response is characterised by a combination of fast and slow components, the relative proportions of which vary across the range of feldspars we tested. We interpret the presence of the components as providing evidence as to the dual roles played by high mobility electrons and by the less mobile alkali ions that are released during the underlying physical processes. Consistent with earlier data, we find further that the luminescent sensitivities vary widely across the range of feldspars we tested.

Li diffusion and surface segregation in K0.5Na0.5NbO3 films grown by Pulsed Laser Deposition

Potassium Sodium Niobate has recently raised particular attention in the field of piezoelectric perovskites thanks to its remarkable piezoelectric properties and high Curie temperature. Previous works have shown that slight Lithium (Li) doping can improve the piezoelectric properties and reduce leakage of stoichiometric K0.5Na0.5NbO3 (KNN). In this paper, evidence is provided that this is not the case for thin films synthesized by Pulsed Laser Deposition, at growth temperature high enough to induce the (001) orientation on a Pt(111) /TiO2/SiO2/Si template. The high mobility of alkali ions leads to Li surface segregation and high non-uniformity of Li doping over the film thickness. This is accompanied by a degradation of KNN thin film electrical properties upon Li doping, with an increase in leakage currents by up to one order of magnitude which impedes a macroscopic piezoelectric characterization. On the other hand, local piezoelectric properties investigated by Piezoresponse Force Microscopy are unchanged upon doping. The results clearly point out the critical issues regarding the growth method to obtain a uniform doping of KNN with light elements such as Li. Due to the high mobility of this species, sizable migration phenomena can be thermally activated in physical vapor deposition processes with high thermal budget, ultimately hampering the envisaged benefits of Li on piezoelectric response.

Two-dimensional V-shaped PdI2: Auxetic semiconductor with ultralow lattice thermal conductivity and ultrafast alkali ion mobility

Using first-principles calculations, we predicted a multifunctional two-dimensional (2D) semiconductor PdI2 from its van der Walls layered bulk. Monolayer or multilayer PdI2 obtained by mechanical exfoliation exhibit high stability as freestanding 2D materials. Originating from its special corner-shared quasi-plane crystal structure, an amazing in-plane negative Poisson's ratio in monolayer PdI2 has been confirmed. The layer dependent electronic and thermal properties have also been discussed in detail. Encouragingly, it has been found that strong phonon scattering which is induced by low symmetry will further reduce the lattice thermal conductivity in monolayer PdI2 at room temperature. Besides, the monolayer PdI2 is seen as an excellent platform for alkali ions migration with ultralow diffusion barriers, benefiting from its distinctive V-shaped crystal structure. Considering these interesting findings, we believe the 2D PdI2 will be a promising candidate for future's low dimensional electron devices.

Electrostatic dust ejection from asteroid (3200) Phaethon with the aid of mobile alkali ions at perihelion

The asteroid (3200) Phaethon is known to be the parent body of the Geminids, although meteor showers are commonly associated with the activity of periodic comets. What is most peculiar to the asteroid is its comet-like activity in the ejection of micrometer-sized dust particles at every perihelion passage, while the activity of the asteroid has never been identified outside the near-perihelion zone at 0.14au from the Sun. From the theoretical point of view, we argue that the activity of the asteroid is well explained by the electrostatic lofting of micrometer-sized dust particles with the aid of mobile alkali ions at high temperatures. The mass-loss rates of micrometer-sized particles from the asteroid in our model is entirely consistent with the values inferred from visible observations of Phaethon’s dust tail. For millimeter-sized particles, we predict three orders of magnitudes higher mass-loss rates, which could also account for the total mass of the Geminid meteoroid stream by the electrostatic lofting mechanism.

Predicting conductivities of alkali borophosphate glasses based on site energy distributions derived from network former unit concentrations

Abstract For ion transport in network glasses, it is a great challenge to predict conductivities specifically based on structural properties. To this end it is necessary to gain an understanding of the energy landscape where the thermally activated hopping motion of the ions takes place. For alkali borophosphate glasses, a statistical mechanical approach was suggested to predict essential characteristics of the distribution of energies at the residence sites of the mobile alkali ions. The corresponding distribution of site energies was derived from the chemical units forming the glassy network. A hopping model based on the site energy landscape allowed to model the change of conductivity activation energies with the borate to phosphate mixing ratio. Here we refine and extend this general approach to cope with minimal local activation barriers and to calculate dc-conductivities without the need of performing extensive Monte-Carlo simulations. This calculation relies on the mapping of the many-body ion dynamics onto a network of local conductances derived from the elementary jump rates of the mobile ions. Application of the theoretical modelling to three series of alkali borophosphate glasses with the compositions 0.33Li2O–0.67[xB2O3–(1 − x)P2O5], 0.35Na2O–0.65[xB2O3–(1 − x)P2O5] and 0.4Na2O–0.6[xB2O3–(1 − x)P2O5] shows good agreement with experimental data.

Network-Forming Units, Energy Landscapes, and Conductivity Activation Energies in Alkali Borophosphate Glasses: Analytical Approaches

A major challenge in the modeling of ionically conducting glasses is to understand how the large variety of possible chemical compositions and specific structural properties influence ionic transport quantities. Here we revisit and extend a theoretical approach for alkali borophosphate glasses, where changes of conductivity activation energies with the borate to phosphate mixing ratio are related to modifications of the ionic site energy landscape. The landscape modifications are caused by varying amounts of different units forming the glassy network, which lead to spatial redistributions of the counter-charges of the mobile alkali ions. Theoretical approaches are presented to calculate variations of both network former unit concentrations and activation energies with the glass composition. Applications to several alkali borophosphate glasses show good agreement with experimental data.

On the disintegration of copper electrodes and the transport of Cu+ ions in a sodium potassium borosilicate glass

The disintegration of a copper electrode and the subsequent transport of Cu+ ions into a borosilicate glass has been qualitatively observed in a recent electron charge attachment induced transport (e-CAIT) experiment [SSI, 339 (2019) 114997]. This work reports the quantitative analysis of the transport coefficients of Cu+ and two native alkali ions in the glass. Electron attachment to the front side of the sample generates a negative surface potential inducing transport of mobile native alkali ions towards the front side. At the backside of the sample, in contact with a copper electrode, the electric field increases as a result of the alkali ion transport. Under these conditions, Cu+ ions become ejected from the electrode and enter into the glass. The concentration depth profiles of all mobile species in the glass have been quantitatively analyzed by means of the Nernst-Planck-Poisson theory. As the result of the analysis we arrive at a diffusion coefficient for Cu+ ions in the borosilicate glass at 160 °C of D(Cu+) = (5.2 ± 1) · 10−20 m2/s.to be published in Solid State Ionics.

Sodium-caesium electric field assisted ion exchange in a mixed-alkali (Na, K) lime silicate glass

In this study, sodium exchange for caesium in a mixed alkali lime silicate glass was carried out using electric field-assisted ion exchange (EF-IE). Na/Cs exchange was realised by applying electric fields up to 2000 V cm−1 for 5 min on glass tubes immersed in molten CsNO3 at 460 °C. The chemical concentration profiles measured near the glass surface showed a bilayer concentration profile which comprises caesium and potassium-rich layers, the formation of the potassium-rich layer being associated with the different mobility of alkali ions. Nanoindentation analysis outlined that surface layer produced by Na/Cs ion-exchange is characterised by poorer mechanical properties than Na/K ion-exchanged layer. Raman spectroscopy investigation revealed that the Na/Cs ion-exchanged layer has a denser structure with respect to raw glass, this being responsible for the different mechanical properties.

(Invited) Morphology and Conductivity of Copper Hexacyanoferrate Films

Metal hexacyanometallates (MHCMs) form a large family of coordination network compounds [1]. They have variable and tunable physical and chemical properties due to the three-dimensional framework of alternating metal knots connected by a non-innocent small bridging ligand forming interconnected channels that can accommodate solvent molecules and counter ions. Therefore, these materials have been comprehensively studied in several different fields, including, functional materials for charge storage, electrocatalysis, electrochromic devices or light harvesting. For the mentioned applications, conductivity is critical, to which i) electronic conductivity by electrons or holes [2], ii) ionic conductivity by mobile alkali ions in the channels of the MHCMs [3], and iii) proton conductivity [4] may contribute. In larger scale for real application, the conductivity depends not only on intrinsic material properties but also on the morphology. Morphology (particularly grain boundaries) plays an important role in determining the pathway of charge carrier transport (electrons and holes) in the film. From first principles it is expected that continuous compact crystalline films will have better electrical conductivity.Here, we present results on copper hexacyanoferrate which demonstrate particularly well the variation of film morphology and its influence on conductivity as a key functional property. We succeeded in devising a simple method for preparation of metal hexacyanoferrates as a thin continuous film by a combination of sonication-assisted casting and vapor-assisted conversion, without the need for surface pre-treatment. This is especially helpful for coating substrates composed of different materials. Films obtained in this way show conductivities higher than that of powder pellets with equivalent crystal structure. Temperature-dependent and humidity-dependent measurements on powder pellets revealed the activation energies for charge transport as well as the role of zeolitic water in facilitating the charge transfer. 1. Paolella, A.; Faure, C.; Timoshevskii, V.; Marras, S.; Bertoni, G.; Guerfi, A.; Vijh, A.; Armand, M.; Zaghib, K. A Review on Hexacyanoferrate-based Materials for Energy Storage and Smart Windows: Challenges and Perspectives. Mater. Chem. A 2017, 5, 18919–18932.2. Behera, J. N.; D’Alessandro, D. M.; Soheilnia, N.; Long, J. R. Synthesis and Characterization of Ruthenium and Iron−Ruthenium Prussian Blue Analogues. Mater. 2009, 21, 1922–1926.3. Ishizaki, M.; Ando, H.; Yamada, N.; Tsumoto, K.; Ono, K.; Sutoh, H.; Nakamura, T.; Nakao, Y.; Kurihara, M. Redox-Coupled Alkali-Metal Ion Transport Mechanism in Binder-Free Films of Prussian Blue Nanoparticles. Mater. Chem. A 2019, 7, 4777–4787.4. Ohkoshi, S.-I.; Nakagawa, K.; Tomono, K.; Imoto, K.; Tsunobuchi, Y.; Tokoro, H. High Proton Conductivity in Prussian Blue Analogues and the Interference Effect by Magnetic Ordering. Am. Chem. Soc. 2010, 132, 6620–6621.

Polyoxovanadate-polymer hybrid electrolyte in solid state batteries

All-solid-state batteries are emerging as the new generation devices for safe and stable energy storage. However, insufficient ion conductivity of solid electrolyte impairs their practical applications. Herein, a series of fast alkali-ion conductor, polymer/polyoxovanadate hybrid nanowires were fabricated as solid electrolyte by a facile and scalable polyoxovanadate-induced self-assembly method. Combining abundant mobile alkali-ions and terminal oxygen atoms (Lewis base sites) of polyoxovanadates with the ion-migration favoured nanowire assemblage, ultrahigh ion conductivities of universal alkali-ions (25 ​°C, 3.30 ​× ​10−3, 2.00 ​× ​10−3, and 4.55 ​× ​10−3 ​S ​cm−1 for Li+, Na+ and K+ respectively) with low active energies are achieved. Remarkably, the hybrid solid-state electrolytes were applied in solid-state lithium and potassium batteries, exhibiting remarkable rate capability and comparable cycling stability. The chemical and structural design of polyoxometalate/polymer hybrid solid-state electrolyte shed light on the material design and chemical investigation of next-generation all-solid-state batteries.

Temperature dependence of the AC conductivity of illitic clay

Electrical conductivity measurement was used to characterize thermophysical processes occurring in illitic clay during firing. In this study, illitic clay was subjected to heating up to 1100 °C. The AC conductivity was measured at 10 different frequencies, ranging from 500 Hz up to 2 MHz. In the low-temperature interval (<250 °C) and during dehydroxylation (from 450 °C to 750 °C), H+ and OH– ions were the dominant charge carriers. Above 600 °C, the mobility of alkali ions was high enough to enable them to contribute to conductivity. Formation of glassy phase at high temperature rapidly increases conductivity. The conduction activation energies (EA) were calculated during a second firing. Above 350 °C, the values of EA lay in the interval between 0.79 eV (500 Hz) and 0.66 eV (2 MHz), which correspond to the conduction EA of alkali ions in an amorphous matrix. The responsible conduction mechanism was identified to be ion hopping.

Electric field-induced softening of alkali silicate glasses

Motivated by the advantages of two-electrode flash sintering over normal sintering, we have investigated the effect of an external electric field on the viscosity of glass. The results show remarkable electric field-induced softening (EFIS), as application of DC field significantly lowers the softening temperature of glass. To establish the origin of EFIS, the effect is compared for single vs. mixed-alkali silicate glasses with fixed mole percentage of the alkali ions such that the mobility of alkali ions is greatly reduced while the basic network structure does not change much. The sodium silicate and lithium-sodium mixed alkali silicate glasses were tested mechanically in situ under compression in external electric field ranging from 0 to 250 V/cm in specially designed equipment. A comparison of data for different compositions indicates a complex mechanical response, which is observed as field-induced viscous flow due to a combination of Joule heating, electrolysis and dielectric breakdown.

Sodium-Ion Diffusion in Alluaudite-Type Na2+ dFe2- d/2(SO4)3 Cathodes

Earth-abundance and low price of sodium led to intensive exploration for a range of layered transition metal oxides as cathode electrode materials. The cost advantage will, however only translate into commercially viable large-scale Na-based batteries if the concept of earth-abundant materials is consistently applied throughout their design. Hence, research on transition metal electrode materials for Na-based batteries should focus on the most abundant transition metal Fe. While iron oxides such as NaFeO2 and Nax[Fe0.5Mn0.5]O2 known to suffer from limited reversible capacity and low operating potential, the exploitation of the inductive effect of polyanion frameworks opened up the way to a range of iron phosphate cathodes with better capacity retention, in which the Fe3+/Fe2+ redox couple yields about 3V. Along the same line Barpanda et al.[1] realised the sulfate Na2+ dFe2- d /2(SO4)3and found that it combines an unusually high Fe redox potential of ~3.8 V versus Na (which corresponds to 4.1V vs. Li/Li+) with excellent rate capability. Here we analyze pathways for the mobile Na+ from literature structure and from our MD simulations using our bond valence pathway method.[2,3] This modelling of pathways for mobile alkali ions as regions of low site energy E(A) has been demonstrated to be a simple and reliable way of identifying transport pathways in local structure models, provided that the local structure model captures the essential structural features. Bond valence parameters are taken from our softBV database as published in [4]. In accordance to the suggestions in [1] the material is essentially a one-dimensional conductor with the lowest activation energy of ca 0.3 eV for transport in the ca. half-occupied Na(3) channels. The same empirical BV parameters bA-X , R0 (A-X) used in this pathway analysis are also used as force-field parameters for the generation of disordered local structure models by MD simulation of a 918 atoms 2x2x3 supercell of composition Na108Fe90(SO4)144, which corresponds to the fully discharged state factoring in the experimentally observed sodium excess and iron deficiency. The MD simulations yield a low activation energy of 0.26 eV for 1-dimensional transport along the c-direction in partially occupied Na(3) channels. With increasing temperature Na(1) can act as a source for an increased number of mobile ions in the Na(3) channels and Na(2) become mobile in separate partially occupied channels leading to a high temperature activation energy of 0.68 eV (see Fig. 1). For the favourable experimental performance of the material it is however important that the Fe-deficiency considerable lowers the activation energy for cross-linking in-between the fast-ion conducting channels to below 1 eV, which will be crucial to prevent the vulnerability to blocking of the one dimensional sodium transport channel by defects.

Volume changes in glass induced by an electron beam

Three glasses (float, borosilicate float and Schott D263 glasses) were irradiated by 50keV electron beams with doses within the range of 0.21–318.5kC/m2. Volume changes induced by electron bombarding were monitored by means of Atomic Force Microscopy. Incubation doses, related to mobility of alkali ions, were measured. Low doses showed compaction of all glasses while higher doses revealed volume inflation, except for borosilicate float glass. Both surfaces of float glass were irradiated and significant differences between them were found.

Stability of TaRhx as a potential diffusion barrier for Cu metallization: capacitance–voltage tests after bias temperature stress

Amorphous TaRhx was integrated in metal oxide semiconductor (MOS) capacitors with Cu gate metallization (Al/Si/25 nm SiO2/10 nm TaRhx/Cu). The stability of TaRhx diffusion barriers was investigated under bias temperature stress testing using capacitance–voltage (C–V) measurements. The stability of these capacitors was compared with similar capacitors with TaNx as the diffusion barrier layer or with capacitors with no diffusion barrier. The electrical measurements were compared with compositional information obtained by backside secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). Comparison of C–V measurements on capacitors with TaRhx/Cu and TaRhx/Al gate metallizations revealed that both mobile alkali ions and Cu+ contribute to the flatband voltage shift of the MOS capacitors. C–V measurements of capacitors with various barriers showed that the mobile ion concentration (Cu+) in the capacitors with TaRhx diffusion barriers is reduced to 32 % of the value for capacitors with no diffusion barrier. In contrast, capacitors with TaNx barriers showed the lowest mobile ion concentration among all the barrier types. Based on flatband voltage shift values, TaNx barriers outperform TaRhx barriers. However, if the percentage of deformed C–V curves is used as the reliability criterion, both barriers perform quite similarly. Compositional analysis data suggests that the concentrations of the diffused species are below the detection limits of SIMS and TEM. This work demonstrated the importance of employing electrical reliability tests for evaluation of potential diffusion barrier materials.

Towards in vivo biosensors for low‐cost protein sensing

In vivo biosensing requires stable transistor operation in high-salt concentration bodily fluids while exhibiting impermeability to mobile alkali ions that would otherwise render the metal-oxide-semiconductor (MOS) threshold voltage to drift. Metal oxide semiconductor capacitor structures using Al 2 O 3 as the gate dielectric were soaked in a sterile physiological buffer solution (PBS) up to 24 hours and for thicknesses from 100 to 10 nm. The triangular voltage sweep technique characterised alkali ion penetration, and measured no detectable alkali ions for the Al 2 O 3 capacitors. By contrast, the dose of alkali ions in silicon dioxide MOS capacitors steadily increased with increasing soak times in the PBS solution.

Evolution of Strategies for Modern Rechargeable Batteries

This Account provides perspective on the evolution of the rechargeable battery and summarizes innovations in the development of these devices. Initially, I describe the components of a conventional rechargeable battery along with the engineering parameters that define the figures of merit for a single cell. In 1967, researchers discovered fast Na(+) conduction at 300 K in Na β,β''-alumina. Since then battery technology has evolved from a strongly acidic or alkaline aqueous electrolyte with protons as the working ion to an organic liquid-carbonate electrolyte with Li(+) as the working ion in a Li-ion battery. The invention of the sodium-sulfur and Zebra batteries stimulated consideration of framework structures as crystalline hosts for mobile guest alkali ions, and the jump in oil prices in the early 1970s prompted researchers to consider alternative room-temperature batteries with aprotic liquid electrolytes. With the existence of Li primary cells and ongoing research on the chemistry of reversible Li intercalation into layered chalcogenides, industry invested in the production of a Li/TiS2 rechargeable cell. However, on repeated recharge, dendrites grew across the electrolyte from the anode to the cathode, leading to dangerous short-circuits in the cell in the presence of the flammable organic liquid electrolyte. Because lowering the voltage of the anode would prevent cells with layered-chalcogenide cathodes from competing with cells that had an aqueous electrolyte, researchers quickly abandoned this effort. However, once it was realized that an oxide cathode could offer a larger voltage versus lithium, researchers considered the extraction of Li from the layered LiMO2 oxides with M = Co or Ni. These oxide cathodes were fabricated in a discharged state, and battery manufacturers could not conceive of assembling a cell with a discharged cathode. Meanwhile, exploration of Li intercalation into graphite showed that reversible Li insertion into carbon occurred without dendrite formation. The SONY corporation used the LiCoO2/carbon battery to power their initial cellular telephone and launched the wireless revolution. As researchers developed 3D transition-metal hosts, manufacturers introduced spinel and olivine hosts in the Lix[Mn2]O4 and LiFe(PO4) cathodes. However, current Li-ion batteries fall short of the desired specifications for electric-powered automobiles and the storage of electrical energy generated by wind and solar power. These demands are stimulating new strategies for electrochemical cells that can safely and affordably meet those challenges.