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1. Chemical durability of borosilicate pharmaceutical glasses: Mixed alkaline earth effect with varying [MgO]/[CaO] ratio

   https://doi.org/10.1111/jace.17850  

   Yang, Rui ; Liu, Hongshen ; Ding, Zhijie ; Zheng, Jinfeng ; Mauro, John C. ; Kim, Seong H. ; Zheng, Qiuju ( April 2021 , Journal of the American Ceramic Society)

   Glass for pharmaceutical packaging requires high chemical durability for the safe storage and distribution of newly developed medicines. In borosilicate pharmaceutical glasses which typically contain a mixture of different modifier ions (alkali or alkaline earth), the dependence of the chemical durability on alkaline earth oxide concentrations is not well understood. Here, we have designed a series of borosilicate glasses with systematic substitutions of CaO with MgO while keeping their total concentrations at 13 mol% and a fixed Na₂O concentration of 12.7 mol%. We used these glasses to investigate the influence ofR = [MgO]/([MgO] + [CaO]) on the resistance to aqueous corrosion at 80°C for 40 days. It was found that this type of borosilicate glass undergoes both leaching of modifier ions through an ion exchange process and etching of the glass network, leading to dissolution of the glass surface. Based on the concentration analysis of the Si and B species dissolved into the solution phase, the dissolved layer thickness was found to increase from ~100 to ~170 nm asRincreases from 0 to 1. The depth profiling analysis of the glasses retrieved from the solution showed that the concentration of modifier ions (Na⁺, Ca²⁺, and Mg²⁺) at the interface between the solution and the corroded glass surface decreased to around 40%–60% of the corresponding bulk concentrations, regardless ofRand the leaching of modifier cations resulted in a silica‐rich layer in the surface. The leaching of Ca²⁺and Mg²⁺ions occurred within ~50 and <25 nm, respectively, from the glass surface and this thickness was not a strong function ofR. The leaching of Na⁺ions varied monotonically; the thickness of the Na⁺depletion layer increased from ~100 nm atR = 0 to ~200 nm atR = 1. Vibrational spectroscopy analysis suggested that the partial depletion of the ions may have caused some degree of the network re‐arrangement or re‐polymerization in the corroded layer. Overall, these results suggested that for the borosilicate glass, replacing [CaO] with [MgO] deteriorates the chemical durability in aqueous solution.

    

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2. Literature mining for alternative cementitious precursors and dissolution rate modeling of glassy phases

   https://doi.org/10.1111/jace.17631  

   Uvegi, Hugo ; Jensen, Zach ; Hoang, Trong Nghia ; Traynor, Brian ; Aytaş, Tunahan ; Goodwin, Richard T. ; Olivetti, Elsa A. ( February 2021 , Journal of the American Ceramic Society)

   Efforts to reduce the carbon footprint associated with cement and concrete production have resulted in a number of promising lower‐emission alternatives. Still, research has emphasized a small subset of potentially useful precursor materials. With the goal of expanding the precursor pool, this work presents results of parallel literature mining and rate modeling activities. As a result of literature mining, materials with appropriate SiO₂, Al₂O₃, and CaO concentrations were assembled into a comprehensive, representative ternary diagram. 23 000+ materials were extracted from 7000 journal articles, and 7500 materials from 6000 articles with 80 ≤ SiO₂ + Al₂O₃ + CaO ≤105 wt% automatically classified. Both supervised and semi‐supervised models were used for dissolution rate prediction of glassy materials with all models pulling from a single data set (n = 802 reported dissolution rates from 105 different glasses). Supervised modeling utilized linear and decision tree regressions to determine features most predictive of dissolution rate, resulting in log‐linear relationships between rate and pH, inverse temperature (1/K), and non‐bridging oxygen per tetrahedron (NBO/T). Semi‐supervised modeling was observed to be more robust to broader feature inclusion, providing similar predictive ability with a relatively larger set of descriptive features. Most importantly, results indicated that models trained on data from disparate scientific communities were adequately predictive (RMSE ≈ 1), particularly under pH ≥7 conditions relevant to the cement and alkali activation communities.

    

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3. The effects of (di‐,tri‐valent)‐cation partitioning and intercalant anion‐type on the solubility of hydrotalcites

   https://doi.org/10.1111/jace.17324  

   Prentice, Dale P. ; Gomez‐Zamorano, Lauren ; Balonis, Magdalena ; Erdemli, Bartu ; Ellison, Kirk ; Neithalath, Narayanan ; Simonetti, Dante ; Sant, Gaurav ( July 2020 , Journal of the American Ceramic Society)

   Synthetic hydrotalcites were produced by a co‐precipitation method. The hydrotalcites are represented by the general formula [M^II_(1‐x)M^III_(x)(OH)₂][Aⁿ⁻]_x/n·zH₂O, where M^IIis a divalent cation (eg, Mg²⁺or Ca²⁺), M^IIIis a trivalent cation (eg, Al³⁺) and Aⁿ⁻is the interlayer anion. Herein, M^II = Mg, and M^III = Al such that [Mg/Al] = [2, 3] (atomic units) and Aⁿ⁻, represents intercalant species including: OH⁻, SO₄²⁻and CO₃²⁻anions. The thermochemical data of each compound including their solubility constants (K_so), density and molar volume were quantified at T = 25 ± 0.5°C, andP = 1 bar. The solubilities of the synthetic hydrotalcites, irrespective of their divalent‐trivalent cation partitioning ratio, scaled as CO₃²⁻ < SO₄²⁻ < OH⁻; in order of decreasing solubility. The type of anion, very slightly, affected the solubility with less than ±1 log unit of variation for [Mg/Al] = 2, and ±2 log units of variation for [Mg/Al] = 3. The solubilities of these phases were strongly correlated with that of gibbsite (Al(OH)₃); such that activity of the [AlO₂⁻] species wassolubility determiningwith increasing pH. The tabulated thermodynamic data were used to construct solid‐solution models for phases encompassing both cation distribution ratios and to calculate stable phase equilibria relevant to alkali‐activated slag (AAS) systems for diverse activator compositions.

    

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4. Sorption-enhanced steam reforming of toluene using multifunctional perovskite phase transition sorbents in a chemical looping scheme

   https://doi.org/10.1088/2515-7655/acdbe9  

   Brody, Leo ; Rukh, Mahe ; Cai, Runxia ; Saberi Bosari, Azin ; Schomäcker, Reinhard ; Li, Fanxing ( June 2023 , Journal of Physics: Energy)

   Sorption-enhanced steam reforming (SESR) of toluene (SESRT) using catalytic CO₂sorbents is a promising route to convert the aromatic tar byproducts formed in lignocellulosic biomass gasification into hydrogen (H₂) or H₂-rich syngas. Commonly used sorbents such as CaO are effective in capturing CO₂initially but are prone to lose their sorption capacity over repeated cycles due to sintering at high temperatures. Herein, we present a demonstration of SESRT using A- and B-site doped Sr_1−xA’_xFe_1−yB’_yO_3−δ(A’ = Ba, Ca; B’ = Co) perovskites in a chemical looping scheme. We found that surface impregnation of 5–10 mol% Ni on the perovskite was effective in improving toluene conversion. However, upon cycling, the impregnated Ni tends to migrate into the bulk and lose activity. This prompted the adoption of a dual bed configuration using a pre-bed of NiO/γ–Al₂O₃catalyst upstream of the sorbent. A comparison is made between isothermal operation and a more traditional temperature-swing mode, where for the latter, an average sorption capacity of ∼38% was witnessed over five SESR cycles with H₂-rich product syngas evidenced by a ratio of H₂: CO_x> 4.0. XRD analysis of fresh and cycled samples of Sr_0.25Ba_0.75Fe_0.375Co_0.625O_3-δreveal that this material is an effective phase transition sorbent—capable of cyclically capturing and releasing CO₂without irreversible phase changes occurring.

    

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5. New insights into the mechanisms of carbon dioxide mineralization by portlandite

   https://doi.org/10.1002/aic.17160  

   Falzone, Gabriel ; Mehdipour, Iman ; Neithalath, Narayanan ; Bauchy, Mathieu ; Simonetti, Dante ; Sant, Gaurav ( January 2021 , AIChE Journal)

   Portlandite (Ca(OH)₂; also known as calcium hydroxide or hydrated lime), an archetypal alkaline solid, interacts with carbon dioxide (CO₂) via a classic acid–base “carbonation” reaction to produce a salt (calcium carbonate: CaCO₃) that functions as a low‐carbon cementation agent, and water. Herein, we revisit the effects of reaction temperature, relative humidity (RH), and CO₂concentration on the carbonation of portlandite in the form of finely divided particulates and compacted monoliths. Special focus is paid to uncover the influences of the moisture state (i.e., the presence of adsorbed and/or liquid water), moisture content and the surface area‐to‐volume ratio (s_a/v, mm⁻¹) of reactants on the extent of carbonation. In general, increasing RH more significantly impacts the rate and thermodynamics of carbonation reactions, leading to high(er) conversion regardless of prior exposure history. This mitigated the effects (if any) of allegedly denser, less porous carbonate surface layers formed at lower RH. In monolithic compacts, microstructural (i.e., mass‐transfer) constraints particularly hindered the progress of carbonation due to pore blocking by liquid water in compacts with limited surface area to volume ratios. These mechanistic insights into portlandite's carbonation inform processing routes for the production of cementation agents that seek to utilize CO₂borne in dilute (≤30 mol%) post‐combustion flue gas streams.

    

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