alkali cations
Recently Published Documents


TOTAL DOCUMENTS

417
(FIVE YEARS 62)

H-INDEX

42
(FIVE YEARS 5)

2021 ◽  
Author(s):  
Hongyi Li ◽  
Masaki Murayama ◽  
Tetsu Ichitsubo

Alkali metals, such as lithium and sodium, have been expected to be used for rechargeable metal-anode batteries owing to their low electrode potentials and large capacities. However, the well-known fatal problem, “dendritic growth” causing a dangerous short circuit, is faced while charging the batteries. Here, through a comprehensive study with electrochemical experiments, Raman and soft X-ray emission spectroscopies, density-functional-theory calculation, and molecular dynamic simulations, we provide an advanced guideline for electrolyte design in which a mixture of alkaline earth (Mg, Ca, Ba) salts is used to inhibit dendrite growth of alkali metals (Li, Na) during electrodeposition. Especially, focusing on CaTFSA2, as a salient exemplary alkaline-earth-cation additive, we demonstrate that dendrite-free morphology upon alkali-metal electrodeposition can successfully be attained by modifying their solvation structures in the dual-cation electrolyte systems. Adding divalent Ca2+ promotes alkali cation (Li+ or Na+) to form the contact ion pairs (CIPs) with the counter anions, which replaces the solvent-separated ion pairs (SSIPs) commonly existing in single-cation electrolytes. Such CIPs related to alkali cations would separate Ca2+ ions distantly to shield the strong coulomb interaction among the divalent cations. The stronger binding of the CIPs would retard the desolvation kinetics of alkali cations and, consequently, realizes a severely constrained alkali-metal electrodeposition in a reaction-limited process that is required for the dendrite-free morphology. This work provides prospects to construct dual-cation electrolytes for dendrite-free alkali-metal-anode batteries utilizing the concerted interactions between monovalent and multivalent cations.


2021 ◽  
Vol 13 (22) ◽  
pp. 12833
Author(s):  
Ruoying Li ◽  
Hailong Ye

Vulnerability to atmospheric carbonation is one of the major durability concerns for limestone calcined clay cement (LC3) concrete due to its relatively low overall alkalinity. In this study, the natural carbonation behaviors of ternary ordinary Portland cement-metakaolin-limestone (OPC-MK-LS) blends containing various sulfate salts (i.e., anhydrous CaSO4, Na2SO4, and K2SO4) are studied, with the aim of revealing the influence of alkali cations (Na+, K+). Detailed analyses on the hydrated phase assemblage, composition, microstructure, and pore structure of LC3 pastes prior to and post indoor carbonation are conducted. The results show that the incorporation of sulfate salts accelerates the setting and strength gain of LC3 pastes, likely through enhancement of ettringite formation, but undermines its later age strength achievement due to the deleterious effect of alkali cations (Na+, K+) on late age OPC hydration. The carbonation resistance of LC3 systems is considerably undermined, particularly with the incorporation of Na2SO4 or K2SO4 salts, due to the simultaneous pore coarsening effect and reduced CO2-binding capacity. The carbonation-induced phase and microstructural alterations of LC3 pastes are discussed and compared with those of reference OPC pastes.


2021 ◽  
Author(s):  
◽  
Sean O'Connor

<p>Geopolymers are a class of cementitious aluminosilicate materials that are receiving an increasing amount of attention due to their potential applications in toxic waste remediation and as construction materials. They are composed of a network of crosslinked silicate and aluminate tetrahedra with charge-balancing alkali cations and are therefore similar in composition to alkali aluminosilicate zeolites. They are, however, x-ray amorphous.¹⁻⁴ They are formed by the dissolution of a solid aluminosilicate in a solution of alkali hydroxide or alkali silicate to form aluminosilicate ions which subsequently polymerise.  The effects of adding magnesium to metakaolin geopolymer systems was examined. Magnesium was added as soluble magnesium salts and as magnesium oxide and hydroxide. When added as a soluble salt, an amorphous magnesium (alumino)silicate with a lower degree of silicate polymerisation than a geopolymer is formed. When added as the oxide or hydroxide, hydrotalcite is formed. In both cases, the product is produced alongside a separate geopolymer phase. A magnesiumcontaining geopolymer phase was not found in either. When heated to 1200°C, geopolymers with magnesium oxide added bloated to form lightweight foams.  Lithium analogues of conventional metakaolin geopolymer systems with a range of lithium, aluminium, silicon and water contents were examined. Systems with molar ratios similar to those of commonly studied sodium and potassium metakaolin geopolymers produce self-pelletised lithium zeolites. The zeolite formed was Li-EDI, the lithium analogue of zeolite F. This is the first reported synthesis directly from metakaolin. True lithium geopolymers are found not to form in the systems examined. The zeolite bodies react to form β-eucryptite and β-spodumene at temperatures from 800 – 1350°C.  The use of aluminium hydroxide and amorphoud silica rather than aluminosilicates as raw materials for the formation of potassium geopolymers was found to produce geopolymers with embedded grains of unreacted silica and aluminium hydroxide.</p>


2021 ◽  
Author(s):  
◽  
Sean O'Connor

<p>Geopolymers are a class of cementitious aluminosilicate materials that are receiving an increasing amount of attention due to their potential applications in toxic waste remediation and as construction materials. They are composed of a network of crosslinked silicate and aluminate tetrahedra with charge-balancing alkali cations and are therefore similar in composition to alkali aluminosilicate zeolites. They are, however, x-ray amorphous.¹⁻⁴ They are formed by the dissolution of a solid aluminosilicate in a solution of alkali hydroxide or alkali silicate to form aluminosilicate ions which subsequently polymerise.  The effects of adding magnesium to metakaolin geopolymer systems was examined. Magnesium was added as soluble magnesium salts and as magnesium oxide and hydroxide. When added as a soluble salt, an amorphous magnesium (alumino)silicate with a lower degree of silicate polymerisation than a geopolymer is formed. When added as the oxide or hydroxide, hydrotalcite is formed. In both cases, the product is produced alongside a separate geopolymer phase. A magnesiumcontaining geopolymer phase was not found in either. When heated to 1200°C, geopolymers with magnesium oxide added bloated to form lightweight foams.  Lithium analogues of conventional metakaolin geopolymer systems with a range of lithium, aluminium, silicon and water contents were examined. Systems with molar ratios similar to those of commonly studied sodium and potassium metakaolin geopolymers produce self-pelletised lithium zeolites. The zeolite formed was Li-EDI, the lithium analogue of zeolite F. This is the first reported synthesis directly from metakaolin. True lithium geopolymers are found not to form in the systems examined. The zeolite bodies react to form β-eucryptite and β-spodumene at temperatures from 800 – 1350°C.  The use of aluminium hydroxide and amorphoud silica rather than aluminosilicates as raw materials for the formation of potassium geopolymers was found to produce geopolymers with embedded grains of unreacted silica and aluminium hydroxide.</p>


2021 ◽  
Vol 13 (36) ◽  
pp. 43573-43586
Author(s):  
Suresh Maniyarasu ◽  
J. Chun-Ren Ke ◽  
Ben F. Spencer ◽  
Alex S. Walton ◽  
Andrew G. Thomas ◽  
...  

Thermo ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 205-219
Author(s):  
Thomas Dumaire ◽  
Rudy J. M. Konings ◽  
Anna Louise Smith

Understanding the corrosion mechanisms and the effect of corrosion products on the basic properties of the salt (e.g., melting point, heat capacity) is fundamental for the safety assessment and durability of molten salt reactor technology. This work focused on the thermodynamic assessment of the CrF2−CrF3 system and the binary systems of chromium trifluoride CrF3 with alkali fluorides (LiF, NaF, KF) using the CALPHAD (computer coupling of phase diagrams and thermochemistry) method. In this work, the modified quasi-chemical model in the quadruplet approximation was used to develop new thermodynamic modelling assessments of the binary solutions, which are highly relevant in assessing the corrosion process in molten salt reactors. The agreement between these assessments and the phase equilibrium data available in the literature is generally good. The excess properties (mixing enthalpies, entropies and Gibbs energies) calculated in this work are consistent with the expected behaviour of decreasing enthalpy and Gibbs energy of mixing with the increasing ionic radius of the alkali cations.


Sign in / Sign up

Export Citation Format

Share Document