Hydrated Materials Research Articles

Felsic Tesserae on Venus Permitted by Lithospheric Deformation Models

AbstractVenus tessera terrain contains the oldest rocks preserved on the surface of the planet. The composition of the tesserae is unknown, but recent observations of near‐infrared emissivity from orbit suggest that they are silica rich. This contrasts with previous interpretation that silica‐rich rheologies are too weak to produce tessera folds. We examine the range of compositions consistent with the observed folds in the tessera. We map folds in Tellus Regio tessera using the highest resolution Magellan radar images (∼100 m) and stereo topography (∼1 km). We use fold spacings as input into a buckling analysis that simulates power law rheology using contemporary dry‐mineral flow laws and modeled igneous rock compositions, consistent with a predicted dry lithosphere for Venus in the recent era. The folds have dominant wavelengths of 6–19 km with amplitudes of 500–1,000 m, consistent with low strains (1%–12%). We confirm that observed folds require heat flows of ≥40 K/km and strain rates faster than 10−16s−1, higher than today. These low strain folds are unlikely to have significantly modified the preexisting tessera surface, thus older impact craters must have been removed by an earlier geologic process. We demonstrate that the folds can form in dry crust with a SiO2 content ranging from 48% to 72%. Dry felsic rheologies could explain low emissivity signatures of tesserae that are attributed to a low Fe2+. If felsic, tessera materials may have formed in a prior era via partial melting of hydrous materials derived from recycling of surface waters into the Venus mantle.

Recovery behaviors of acid-modified cement hydration material on phosphorous

Silicate cement hydration product is a promising phosphorus adsorption material. In view of the strong alkali characteristics of early hardening cement paste, this study adopted acid leaching method to modify and then investigated its phosphorus recovery performance. The results showed that acid modification could weaken the strong alkali property, nevertheless, it also lowered phosphorus removal efficiency. The decline of phosphorus recovery was closely related to the depletion of calcium source. By the fit calculation, it can be determined that the adsorption kinetics of modified material on phosphorus met the pseudo-second-order model. This was consistent with the behavior of unmodified material. Additionally, XRD analysis demonstrated that the phosphorus species enriched on the surface of modified material mainly consisted of hydroxyapatite and variscite, which was different from the brushite of unmodified material. Acid modification would provide much more aluminum sites on the adsorption of phosphorous.

Enzyme-Laden Bioactive Hydrogel for Biocatalytic Monitoring and Regulation.

Enzymes, a class of highly efficient and specific catalysts in Nature, dictate a myriad of reactions that constitute various cascades in biological systems. There is growing evidence that many cellular reactions within metabolic pathways are catalyzed by matrix-associated multienzyme complexes, not via the free enzymes, verifying the vital effects of microenvironmental organization, which would reveal implications for the high efficiency, specificity, and regulation of metabolic pathways. The extracellular matrix (ECM), as the noncellular component, is composed of various proteins such as collagens, laminins, proteoglycans, and remodeling enzymes, playing the key role in tissue architecture and homeostasis. Hydrogels are defined as highly hydrated polymer materials and maintain structural integrity by physical and chemical force, which are thought of as the most suitable materials for matching the chemical, physical, and mechanical properties with natural ECM. As one specific type of soft and wet materials, hydrogels are suitable three-dimensional carriers to locally confine bioactive guests, such as enzymes, for molecular-level biological interactions. The efficient cascade catalysis can be realized by enzyme-laden hydrogels, which can potentially interact with cells and tissues by material-to-biology communication. In this Account, we present recent progress on the preparation of enzymatic bioactive hydrogels, including in situ coassembly, in situ cross-linking strategy, and in situ enzymatic radical polymerization technology, further promoting their applications on biomedical tissue engineering, biocatalytic health monitoring, and therapeutic research. First, we provide a brief introduction of the basic concept related to an enzymatic strategy in living systems and the importance of bioinspired enzyme-laden bioactive hydrogel systems. We discuss the difficulties of the fabrication of a bioactive hydrogel with a high catalytic efficiency, thereby providing the novel molecular design and regulation based on a noncovalent coassembly and in situ self-immobilization strategy to obtain the compartmentalized enzyme-laden structure. Then the applications of an enzyme-laden bioactive hydrogel for biocatalytic applications are discussed in detail. The enzyme-laden bioactive hydrogel can maintain the favorable perception and regulation behavior of enzymes with optimal enzymatic efficacy between this confined hydrogel network and a surrounding environment. A highlight to the advances in the responsively biocatalytic monitoring and regulation of bioactive hydrogel, including the enzymatic biomedical tissue engineering and health monitoring, enzymatic regulation of tumor reactive oxygen species and therapeutic research are given. Finally, the outlook of open challenges and future developments of this rapidly evolving field is provided. This Account with highlights of diverse enzyme-laden bioactive hydrogel systems not only provides interesting insights to understand the cascade enzymatic strategy of life but also inspires to broaden and enhance the molecular-level material design and bioapplications of existing enzymatic materials in chemistry, materials science, and biology.

8-Hydroxyquinolino cadmium chloride hydrate for generating nanosecond and picosecond pulses in erbium-doped fiber laser cavity

In this paper, we experimentally proposed and demonstrated the application of thin-film saturable absorber (SA) based on 8-Hydroxyquinolino cadmium chloride hydrate (8-HQCdCl2H2O) material as both Q-switcher and mode-locker in the cavity of erbium-doped fiber laser (EDFL). The 8-HQCdCl2H2O was embedded in polyvinyl alcohol (PVA) to fabricate the thin-film, which has then employed in the Q-switched and mode-locked EDFL cavity for passively generating nanosecond and picosecond pulses, respectively. At the maximum pump power of 167 mW, the Q-switched laser-produced pulse train with a pulse width of 726 ns, a repetition rate of 150 kHz, and a signal-to-noise ratio (SNR) of 72 dB. We also demonstrated the generation of mode-locked picosecond pulses by adding 200 m long single-mode fiber (SMF) into the ring EDFL cavity. The mode-locked laser-generated pulses have a pulse width of 1.83 ps, a repetition rate of 1 MHz, and the SNR of 77 dB for the electrical spectrum.

Characterization of an ettringite-based thermochemical energy storage material in an open-mode reactor

The mismatch between renewable energy supply and demand requires energy storage technologies to work out the dilemma. In the thermal energy field, ettringite-based energy storage seems to be a good solution thanks to its high energy density and low material cost. It can store excess solar energy to meet the heating and domestic hot water demand in buildings. Therefore, the current work experimentally examines the energetic performance of an ettringite-based material made of commercial cements. The TG-DSC analysis shows the energy storage capacity of the investigated material is as high as 282 kWh/m3 original hydrated materials. Besides, the laboratory reactor tests prove the charging temperature is as low as 55–65°C for ettringite. Under operating conditions, the average energy-releasing power during the full period is about 33.3 W/kg while the maximum power is about 915 W/kg original hydrated materials, which are significantly higher than most materials from the literature. The best volumetric energy-releasing density and the corresponding prototype storage density of the fixed-bed obtained are 176 kWh/m3 original hydrated materials and 104 kWh/m3, respectively.

CHARACTERISTICS OF SLAG ACTIVATED PHC-PILE WITH REDUCED CEMENT CONTENT

ABSTRACT Ground Granulated Blast-furnace Slag (GGBS) powders, the massive by-products produced in the process of manufacturing cast iron are actively used as a substitute for cement, one of the major causes of greenhouse gas emissions. The purpose of this study was to investigate the proper mixing ratio of the activator, and to reduce the usage of cement in the production of high-strength steam cured concrete using GGBS. The cured products of various ratio were analyzed by XRD and TG/DTA, and the best ratio of the cured product were applied to the Pre-stressed high-strength concrete (PHC) Pile, and the performance was then evaluated. The results showed that the fluidity was improved by mixing with GGBS, and when an appropriate amount of activator was used, it was possible to produce high-strength cured products. In the PHC-Pile test, the replacement rate of 40% GGBS and combined 4% anhydrite gypsum and 2% Ca(OH)2 as an activator was excellent. The compressive strength (2MPa more), shear strength (1.3MPa more), and Axial force strength (2.7Mpa more) were more improved than for the normal Portland cement PHC-Pile, and this GGBS pile can be manufactured more economically (the cost can be saved in the amount of 14.5%). This is caused by the activating agent destroying the glassy film of the GGBS, and actively inducing the pozzolanic reaction, so that the hydrate materials are generated, such as C–S–H. In addition, by positively utilizing the inexpensive industrial by-product, GGBS, it is possible to manufacture environmentally friendly concrete products, while reducing the amount of cement used.

Effect of curing humidity on performance of cemented paste backfill

Cemented paste backfill (CPB), a mixture of tailings, binder, and water, is widely and extensively used for the recovery of mineral resources, the prevention of ground subsidence, and the management of mine waste. When installed, the CPB is subjected to complex environmental conditions such as water content, temperature, and power, which have a significant impact on its efficiency. Thus, this study conducts a series of laboratory programs, including investigation of moisture, temperature, stress-strain relation, and microstructure to show the effect of curing humidity on the CPB behaviors. The results obtained indicate that ambient humidity can have a dramatic effect on CPB in terms of its macro performance of internal relative humidity, temperature and strength, as well as the micro expression. Typical examples of these effects on CPB include an increase in curing humidity, which favors binder hydration, and then an increase in hydration materials, temperature and peak stress in the CPB. The results obtained will lead to a better understanding of CPB’s responses to various environmental conditions.

Sierra Gorda 009: A new member of the metal‐rich G chondrites grouplet

AbstractWe investigated the metal‐rich chondrite Sierra Gorda (SG) 009, a member of the new G chondrite grouplet (also including NWA 5492, GRO 95551). G chondrites contain 23% metal, very reduced silicates, and rare oxidized mineral phases (Mg‐chromite, FeO‐rich pyroxene). G chondrites are not related to CH‐CB chondrites, based on bulk O, C, and N isotopic compositions, mineralogy, and geochemistry. G chondrites have no fine‐grained matrix or matrix lumps enclosing hydrated material typical for CH‐CB chondrites. G chondrites’ average metal compositions are similar to H chondrites. Siderophile and lithophile geochemistry indicates sulfidization and fractionation of the SG 009 metal and silicates, unlike NWA 5492 and GRO 95551. The G chondrites have average O isotopic compositions Δ17O>0‰ ranging between bulk enstatite (E) and ordinary (O) chondrites. An Al‐rich chondrule from SG 009 has Δ17O>0‰ indicating some heterogeneity in oxygen isotopic composition of G chondrite components. SG 009’s bulk carbon and nitrogen isotopic compositions correspond to E and O chondrites. Neon isotopic composition reflects a mixture of cosmogenic and solar components, and cosmic ray exposure age of SG 009 is typical for O, E, and R chondrites. G chondrites are closely related to O, E, and R chondrites and may represent a unique metal‐rich parent asteroid containing primitive and fractionated material from the inner solar system. Oxidizing and reducing conditions during SG 009 formation may be connected with a chemical microenvironment and possibly could indicate that G chondrites may have formed by a planetesimal collision resulting in the lack of matrix.

Isotopic and textural analysis of giant unmelted micrometeorites – identification of new material from intensely altered 16O-poor water-rich asteroids

Bulk oxygen isotope data has the potential to match extraterrestrial samples to parent body sources based on distinctive δ18O and Δ17O ratios. We analysed 10 giant (>500 μm) micrometeorites using combined micro-Computer Tomography (μCT) and O-isotope analysis to pair internal textures to inferred parent body groups. We identify three ordinary chondrite particles (L and LL groups), four from CR chondrites and the first micrometeorite from the enstatite chondrite (EH4) group. In addition, two micrometeorites are from hydrated carbonaceous chondrite parent bodies with 16O-poor isotopic compositions and plot above the terrestrial fractionation line. They experienced intense aqueous alteration, contain pseudomorphic chondrules and are petrographically similar to the CM1/CR1 chondrites. These micrometeorites may be members of the newly established CY chondrites and/or derived from the enigmatic “Group 4” micrometeorite population, previously identified by Yada et al., 2005 [GCA, 69:5789-5804], Suavet et al., 2010 [EPSL, 293:313-320] (and others). One of our 16O-poor micrometeorite plots on the same isotopic trendline as the CO, CM and CY chondrites – “the CM mixing line” (with a slope of ∼0.7 and a δ17O intercept of -4.23‰), this implies a close relationship and potentially a genetic link to these hydrated chondrites. If position along the CM mixing line reflects the amount of 16O-poor (heavy) water-ice accreted onto the parent body at formation, then the CY chondrites and these 16O-poor micrometeorites must have accreted at least as much water-ice as CM chondrites but potentially more. In addition, thermal metamorphism could have played a role in further raising the bulk O-isotope compositions through the preferential loss of isotopically light water during phyllosilicate dehydration. The study of micrometeorites provides insights into asteroid belt diversity through the discovery of material not currently sampled by larger meteorites, perhaps as a result of atmospheric entry biases preventing the survival of large blocks of friable hydrated material.

Properties and characterization of alumina platelet reinforced geopolymer composites

AbstractGeopolymers are porous, amorphous, alkali‐aluminosilicate hydrate materials formed at room temperature via a solution process. Geopolymer based on metakaolin had a relatively homogeneous microstructure that offered consistent behavior but suffered from dehydration cracking and large densification shrinkages when heated. It was found that by reinforcing a metakaolin geopolymer of composition (K2O·Al2O3·4SiO2·11H2O) with 50 µm diameter alumina platelets, dehydration cracking could be prevented, and shrinkage could be reduced by an order of magnitude. Samples were reinforced with 30, 50, and 70 wt% of alumina platelets. Although the properties of the 30 and 50 wt% conditions were better than those of unreinforced geopolymer, those samples still showed warping, cracking, and strength losses on heating. The 70 wt% samples did not warp or crack when heated to temperatures of up to 1500°C. The room‐temperature 4‐point flexural strength of these samples remained at around 20 MPa regardless of heat treatments. The in situ measured flexural strength increased to almost 40 MPa at 600°C, and remained higher than 20 MPa until 1200°C. Samples subjected to propane‐torch thermal shock heating and subsequent quenching did not crack or fragment. Dilatometry, X‐ray diffraction, and scanning electron microscopy were used for additional characterization. Given these properties, this material showed promise as a castable refractory.

Interactions of Oxide Surfaces with Water Revealed with Solid-State NMR Spectroscopy

Hydrous materials are ubiquitous in the natural environment and efforts have previously been made to investigate the structures and dynamics of hydrated surfaces for their key roles in various chemical and physical applications, with the help of theoretical modeling and microscopy techniques. However, an overall atomic-scale understanding of the water-solid interface, including the effect of water on surface ions, is still lacking. Herein, we employ ceria nanorods with different amounts of water as an example and demonstrate a new approach to explore the water-surface interactions by using solid-state NMR in combination with density functional theory. NMR shifts and relaxation time analysis provide detailed information on the local structure of oxygen ions and the nature of water motion on the surface: the amount of molecularly adsorbed water decreases rapidly with increasing temperature (from room temperature to 150 °C), whereas hydroxyl groups are stable up to 150 °C, and dynamic water molecules are found to instantaneously coordinate to the surface oxygen ions. The applicability of dynamic nuclear polarization for selective detection of surface oxygen species is also compared to conventional NMR with surface selective isotopic-labeling: the optimal method depends on the feasibility of enrichment and the concentration of protons in the sample. These results provide new insight into the interfacial structure of hydrated oxide nanostructures, which is important to improve performance for various applications.

Evidence for oxygenation of Fe-Mg oxides at mid-mantle conditions and the rise of deep oxygen.

As the reaction product of subducted water and the iron core, FeO2 with more oxygen than hematite (Fe2O3) has been recently recognized as an important component in the D” layer just above the Earth's core-mantle boundary. Here, we report a new oxygen-excess phase (Mg, Fe)2O3+δ (0 < δ < 1, denoted as ‘OE-phase’). It forms at pressures greater than 40 gigapascal when (Mg, Fe)-bearing hydrous materials are heated over 1500 kelvin. The OE-phase is fully recoverable to ambient conditions for ex situ investigation using transmission electron microscopy, which indicates that the OE-phase contains ferric iron (Fe3+) as in Fe2O3 but holds excess oxygen through interactions between oxygen atoms. The new OE-phase provides strong evidence that H2O has extraordinary oxidation power at high pressure. Unlike the formation of pyrite-type FeO2Hx which usually requires saturated water, the OE-phase can be formed with under-saturated water at mid-mantle conditions, and is expected to be more ubiquitous at depths greater than 1000 km in the Earth's mantle. The emergence of oxygen-excess reservoirs out of primordial or subducted (Mg, Fe)-bearing hydrous materials may revise our view on the deep-mantle redox chemistry.

Self-suspending proppant manufacturing method and its property evaluation

In recent years, a new technique involving the use of a self-suspending proppant has been a focus of research in relation to fracturing operations. The technique combines a proppant and sand-carrying fluid through the swelling and tackifying produced by the hydration material coating on the proppant surface. In this study, a self-suspending proppant was created using ceramic sand, polymer, guar gum, sucrose, and SiO2 nanoparticles. In laboratory evaluation experiments, this self-suspending proppant showed a good suspension effect in tap water, as well as a good temperature resistance. When each 100 g of proppant had 6.6 g of HAWP powder adhering to it, and the sand ratio was greater than 10%, the self-suspending proppant was found to be completely suspended in 120 s with no settlement occurring before 200 min. Furthermore, its core damage rate was low. In a field application, self-suspending proppant fracturing was used in the M block of the H Oilfield, which is located in the southern section of Qinshui Basin, China. For the two wells in the M block, well M13-X and well M13-Y, the volumes of fracturing fluid required for construction were reduced by 334 m3 and 351 m3, respectively, compared with untreated proppant fracturing. In addition, the fracturing construction times were reduced by 53.4 min and 88.2 min, and the CBM production values were increased by 286 m3 and 320 m3, respectively. The self-suspending proppant fracturing increased the construction efficiency and CBM production, and decreased the construction difficulty and risk of overpressure. These are important research findings and show its wide applicability.

The achievable resolution for X-ray imaging of cells and other soft biological material.

X-ray imaging of soft materials is often difficult because of the low contrast of the components. This particularly applies to frozen hydrated biological cells where the feature of interest can have a similar density to the surroundings. As a consequence, a high dose is often required to achieve the desired resolution. However, the maximum dose that a specimen can tolerate is limited by radiation damage. Results from 3D coherent diffraction imaging (CDI) of frozen hydrated specimens have given resolutions of ∼80 nm compared with the expected resolution of 10 nm predicted from theoretical considerations for identifying a protein embedded in water. Possible explanations for this include the inapplicability of the dose-fractionation theorem, the difficulty of phase determination, an overall object-size dependence on the required fluence and dose, a low contrast within the biological cell, insufficient exposure, and a variety of practical difficulties such as scattering from surrounding material. A recent article [Villaneuva-Perez et al. (2018), Optica, 5, 450-457] concluded that imaging by Compton scattering gave a large dose advantage compared with CDI because of the object-size dependence for CDI. An object-size dependence would severely limit the applicability of CDI and perhaps related coherence-based methods for structural studies. This article specifically includes the overall object size in the analysis of the fluence and dose requirements for coherent imaging in order to investigate whether there is a dependence on object size. The applicability of the dose-fractionation theorem is also discussed. The analysis is extended to absorption-based imaging and imaging by incoherent scattering (Compton) and fluorescence. This article includes analysis of the dose required for imaging specific low-contrast cellular organelles as well as for protein against water. This article concludes that for both absorption-based and coherent diffraction imaging, the dose-fractionation theorem applies and the required dose is independent of the overall size of the object. For incoherent-imaging methods such as Compton scattering, the required dose depends on the X-ray path length through the specimen. For all three types of imaging, the dependence of fluence and dose on a resolution d goes as 1/d 4 when imaging uniform-density voxels. The independence of CDI on object size means that there is no advantage for Compton scattering over coherent-based imaging methods. The most optimistic estimate of achievable resolution is 3 nm for imaging protein molecules in water/ice using lensless imaging methods in the water window. However, the attainable resolution depends on a variety of assumptions including the model for radiation damage as a function of resolution, the efficiency of any phase-retrieval process, the actual contrast of the feature of interest within the cell and the definition of resolution itself. There is insufficient observational information available regarding the most appropriate model for radiation damage in frozen hydrated biological material. It is advocated that, in order to compare theory with experiment, standard methods of reporting results covering parameters such as the feature examined (e.g. which cellular organelle), resolution, contrast, depth of the material (for 2D), estimate of noise and dose should be adopted.

The effect of size distribution of slag particles obtained in dry granulation on blast furnace slag cement strength

Water quenched blast furnace slag is an excellent hydrated material. However, dry granulation is a new treatment method for molten blast furnace slag that has numerous advantages compared to water quenching. This study investigated the size distribution of slag particles obtained from the dry granulation of molten slag. In addition, the effect of using the slag obtained from dry granulation in slag cement blends was analyzed. All the results showed that there was a wide size distribution range of blast furnace slag particles in ligament formation. The mean diameter of the solid particles decreased as the rotating speed increased. Meanwhile, the glass content in slag particles decreased for a fixed diameter of the metal collecting tray. The strength of slag cement concrete was low at a low rotating speed. In contrast, obtaining slag particles at a high rotating speed was beneficial for producing a compact structure in the slag cement blend.

Mantle Melting and Intraplate Volcanism Due to Self‐Buoyant Hydrous Upwellings From the Stagnant Slab That Are Conveyed by Small‐Scale Convection

AbstractThe mechanisms sustaining basaltic continental intraplate volcanism remain controversial. Continental intraplate volcanism is often geographically associated with slab stagnation in the mantle transition zone (MTZ), for example, in eastern Asia, central Europe, and western North America. Using 2‐D geodynamic models, we here explore the role of the stagnation of a slab and an associated hydrous layer in the MTZ on the formation and evolution of intraplate volcanism. Due to the intrinsic buoyancy of the hydrous layer atop the stagnant slab, upwellings develop within a few million years and rise to ~410‐km depth. At these depths, they partly lose their intrinsic buoyancy due to dehydration and stall intermittently. However, they are readily entrained by sublithospheric small‐scale convection to reach the base of lithosphere, sustaining mantle melting and intraplate volcanism. Water contents of &gt;0.3 wt.‐% in a ≥ 60‐km‐thick layer atop the slab are sufficient for an early (&lt;~20 Myr) onset of melting to account for volcanism, for example, in NE China. Thus, significant amounts of hydrous materials are not expected to remain stable in the MTZ for geological timescales, consistent with geophysical estimates. To explain the geochemical signatures of the Cenozoic basaltic volcanism in northern China, a mixed composition of the hydrous layer, including an enriched mantle‐type and a hybrid depleted mid‐ocean ridge basalts mantle/high μ‐type component, is required.

Phase Relations in MAFSH System up to 21 GPa: Implications for Water Cycles in Martian Interior

To elucidate the water cycles in iron-rich Mars, we investigated the phase relation of a water-undersaturated (2 wt.%) analog of Martian mantle in simplified MgO-Al2O3-FeO-SiO2-H2O (MAFSH) system between 15 and 21 GPa at 900–1500 °C using a multi-anvil apparatus. Results showed that phase E coexisting with wadsleyite or ringwoodite was at least stable at 15–16.5 GPa and below 1050 °C. Phase D coexisted with ringwoodite at pressures higher than 16.5 GPa and temperatures below 1100 °C. The transition pressure of the loop at the wadsleyite-ringwoodite boundary shifted towards lower pressure in an iron-rich system compared with a hydrous pyrolite model of the Earth. Some evidence indicates that water once existed on the Martian surface on ancient Mars. The water present in the hydrous crust might have been brought into the deep interior by the convecting mantle. Therefore, water might have been transported to the deep Martian interior by hydrous minerals, such as phase E and phase D, in cold subduction plates. Moreover, it might have been stored in wadsleyite or ringwoodite after those hydrous materials decomposed when the plates equilibrated thermally with the surrounding Martian mantle.

(Invited) Effect of Water and Carbon Dioxide on Anion-Exchange Membrane Fuel Cells

A decade of intensive research work on Anion Exchange Membrane Fuel Cells (AEMFCs) has finally yielded a high cell performance that is suitable for automotive applications. This achievement is mainly a result of the successful development of new anion-exchange membranes (AEMs) with high hydroxide conductivity (100 mS cm-1 and above). Thanks to these high-performance membranes, AEMFCs with power densities higher than 1 W cm-2 and limiting current densities above 4 A cm-2 have been reached [1-2], which seemed far from possible only a couple of years ago. In spite of this remarkable progress on cell performance, it is the low performance stability during cell operation what hampers further development and implementation of AEMFCs. As it has been recently reviewed, most of the AEMFC performance stability data are still limited to <1000 h [3]. One of the key reasons in the reduction of cell performance is the presence of CO2. If pure oxygen is fed to the cathode, OH– alone is present and carries the charge. If ambient air is used instead of pure oxygen, carbonation processes occur in which OH– as a counteranion reacts with CO2 present in air to produce (bi)carbonates. The main result of this carbonation process is a significant decrease in the effective anion conductivity in the AEM and, in turn, a reduction of the AEMFC power output [4-5]. While the carbonation process seems to be reversible [6-7], and so it could be mitigated, it may affect the chemical stability of the membrane, and in turn the cell performance stability. Furthermore, the hydroxide anions transported from the cathode to the anode may attack the positively charged functional groups of the polymeric membrane (and ionomer), neutralizing part of it and suppressing its anion-conducting capability. This process may actually cause irreversible performance losses during cell operation. To address this challenge, several new stable ionomeric materials have been proposed, and while they perform well in ex-situ chemical stability studies, their performance is still limited in real operating fuel cells. Although cation chemistry dictates the intrinsic chemical stability of the anion-conducting ionomeric materials, it was recently shown that the hydration level at which the fuel cell operates significantly affects the chemical degradation [8-9]. This relationship between local cell hydration and ionomeric material degradation has been analyzed in modelling studies, providing further insights about the critical role of water on the performance stability [10]. This talk will discuss the relationship between water, CO2, membrane/ionomer degradation, and their impact on the AEMFC performance stability. A unique recently developed model capable of predicting the performance stability of AEMFCs will be also presented. By using membranes with achievable targeted properties, the model predicts an AEMFC life-time higher than 8000 h [10], suitable for automotive applications. [1] T. J. Omasta, X. Peng, H. A. Miller, F. Vizza, L. Wang, J. R. Varcoe, D. R. Dekel, and W. E. Mustain; J. Electrochem. Soc. 165(15), J3039-J3044, 2018. [2] L. Q. Wang, E. Magliocca, E. L. Cunningham, W. E. Mustain, S. D. Poynton, R. Escudero-Cid, M. M. Nasef, J. Ponce-Gonzalez, R. Bance-Souahli, R. C. T. Slade, D. K. Whelligan, and J. R. Varcoe; Green Chem. 19, 831-843, 2017. [3] D. R. Dekel; J. Power Sources 375, 158-169, 2018. [4] N. Ziv, W. E. Mustain, and D. R. Dekel; ChemSusChem 11(7), 1136-1150, 2018. [5] U. Krewer, C. Weinzierl, N. Ziv, and D. R. Dekel; Electrochimica Acta 263, 433-446, 2018. [6] N. Ziv and D. R. Dekel; Electrochemistry Communications 88, 109-113, 2018 [7] S. Gottesfeld, D. R. Dekel, M. Page, C. Bae, Y. Yan, P. Zelenay, and Y.-S. Kim; J. Power Sources 375, 170-184, 2018. [8] C. E. Diesendruck and D. R. Dekel, Current Opinion in Electrochem. 9, 173–178, 2018. [9] D. R. Dekel, M. Amar, S. Willdorf, M. Kosa, S. Dhara, and C. Diesendruck; Chem. Mater. 29, 4425-4431, 2017. [10] D. R. Dekel, I. G. Rasin and S. Brandon; J. Power Sources, 420, 118-123, 2019.

Evaluation of thermophysical properties of shaped inorganic hydrated salt-based phase change materials for wall energy storage

In the present study, shaped inorganic hydrated salt-based phase change materials (PCMs) were prepared using a high-absorbent resin (acted as the support material) and a water retaining agent. The synthesized materials were added to a prefabricated wall, and measurement points were placed on the low-temperature side of the wall. The heat transfer performance of the wall was tested by a multi-point heat flow meter. The temperature and the heat flow rate at the low-temperature side of the wall were compared with the heat transfer performances of an ordinary wall and an amorphous phase-change wall. The obtained results revealed that the wall with PCMs manifested stable heat transfer performance with good heat storage capacity; thus it caused an improvement in indoor thermal comfort and achieved a good energy-saving effect. Results of the present study demonstrate the feasibility of PCMs in wall energy storage applications.

Exchange Capability of Cationic Silver 4,4'-Bipyrdine Materials for Potential Water Remediation: Structure, Stability, and Anion Exchange Properties.

An in-depth study of the class of cationic materials [Ag(4,4'-bipy)+][X-] (where X- = CH3CO2-, NO3-, BF4-, ClO4-, and MnO4-) has led to key insights on the relationship between anion hydration energy, material structure, solubility, and stability. Since these materials show promise for their potential as water remediation tools, understanding their properties in detail is of significant importance. The structure of the starting and ending materials is the main driving force behind the resultant stability and solubility and can be successfully used to predict the ion exchange capabilities. The solubility trend was determined to be, from most soluble to least soluble, X- = CH3CO2- > NO3- ∼ BF4- > ClO4- > MnO4-. Kinetics and thermal stability also follow predictable trends but involve additional factors. For instance, the kinetics of NO3- to MnO4- exchange was much slower than expected based on that seen for NO3- to ClO4-. Powder X-ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the materials. Solubility was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. Ion exchange was analyzed with ion chromatography (IC) and ultraviolet-visible spectroscopy (UV-vis), and thermal stability was determined with thermogravimetric analysis (TGA).