Radiation-Assisted Formation of Metal Nanoparticles in Molten Salts
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99 GENERAL AND MISCELLANEOUS↗
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Isotopic Constraints on the Nature of Primary Precipitates in Archean–Early Paleoproterozoic Iron Formations from Determinations of the Iron Phonon Density of States of Greenalite and 2L- and 6L-Ferrihydrite
Iron formations (IFs) are chemical sedimentary rocks that were widely deposited before the Great Oxidation Event (GOE) around 2.4- 2.2 Ga. It is generally thought that IFs precipitated as hydrated Fe 3+ oxides (HFOs) such as ferrihydrite following surface oxidation of Fe 2+ -rich, anoxic deep waters. This model often implicates biological oxidation and underpins reconstructions of marine nutrient concentrations. However, nanoscale petrography indicates that an Fe 2+ silicate, greenalite, is a common primary mineral in well-preserved IFs, motivating an alternative depositional model of anoxic ferrous silicate precipitation. It is unclear, however, if Fe 2+ -rich silicates can produce the Fe isotopic variations in IFs that are well explained by Fe 2+ oxidation. To address this question, we constrain the equilibrium Fe isotopic ( 56 Fe/ 54 Fe) fractionation of greenalite and ferrihydrite by determining the iron phonon densities of states for those minerals. Here, we use ab initio density functional theory (DFT + U) calculations and nuclear resonant inelastic X-ray scattering spectroscopy to show that ferrous greenalite should be isotopically lighter than ferrihydrite by similar to 1-1.2 parts per thousand at equilibrium, and fractionation should scale linearly with increasing Fe 3+ content in greenalite. By anchoring ferrihydrite-greenalite mineral pair fractionations to published experimental Fe isotopic fractionations between HFOs and aqueous Fe 2+ , we show that ferrous greenalite may produce all but the heaviest pre-GOE Fe isotopic compositions and mixed valence greenalites can produce the entire record. Our results suggest that heavy Fe isotope enrichments alone are not diagnostic of primary IF mineralogies, and ferrihydrite and partially oxidized or even purely ferrous greenalite are all viable primary IF mineralogies.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Electrochemical Conversion of CO 2 to Methyl Formate in a Flow Electrolyzer with Mixed Propylene Carbonate/Methanol Catholyte
Despite the promise of electrochemical carbon dioxide reduction as a technology for the production of clean fuels and decarbonization of the chemical industry, research has mostly focused on aqueous systems with a relatively limited set of products that have been achieved via electrosynthesis. Increasingly, CO 2 electroreduction in nonaqueous solvents is being pursued to develop new avenues for expanding the suite of products that can be made with high selectivity. CO 2 reduction in alcohols coupled with in situ esterification to produce esters is one such route that utilizes nonaqueous electrolyte. To be practical, such electrochemical syntheses need to be translated to a high-performance reactor such as a flow electrolyzer. However, many organic solvents, such as alcohols, wet and flood porous electrodes, thus impeding reactor performance. In this work, methanol was mixed with propylene carbonate as a catholyte for a gas-fed CO 2 flow electrolyzer that avoided cathode flooding. Simultaneously, a dual aqueous anolyte was used for water oxidation as a scalable and sustainable anodic half-reaction. The performance effect of methanol concentration, catholyte acidity, CO 2 flow rate, and dilute water in the catholyte were investigated. With 10 vol % methanol in 90 vol % propylene carbonate, 63% faradaic efficiency for methyl formate ester product was sustained without cathode flooding. However, improvements are still needed to lower the cell resistance and further increase the operating current density.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Formation of S0s in extreme environments Ⅲ: the role of environment in the formation pathways
It is well established that there are at least two main channels to form lenticular (or S0) galaxies. The first, which we name ‘faded spiral’ scenario, includes quenching events that led to consumption or removal of gas from a spiral progenitor. The second, which we call ‘merger’ scenario, includes merger-like events and interactions between galaxies. Each scenario leaves characteristic signatures in the newly formed lenticular galaxy. However, the conditions that trigger one mechanism over another are still unknown. This paper is the third of a series aimed at understanding the role of the environment in the formation of lenticular galaxies. In this study, we combine the kinematics, morphology, and properties of the stellar populations of 329 S0s from the SAMI and MaNGA surveys in order to highlight the role of the environment in the process. We divide the S0s into two classes (A and B) according to their global properties, that we can associate to the products of a faded spiral scenario (class A) or a merger scenario (class B). Here we then study how the various classes are distributed within different environments. Our study reveals that the ‘faded spiral’ pathway is the most efficient channel to produce S0s, and it becomes more efficient as the mass of the group or cluster or local density of galaxies increase. The merger pathway is also a viable channel, and its efficiency becomes higher with decreasing local density or environment mass.
79 ASTRONOMY AND ASTROPHYSICS↗
polyMOF Formation from Kinked Polymer Ligands via ortho -Substitution
Reticular chemistry is an important tool in the crystal engineering of metal-organic frameworks (MOFs). Isoreticular chemistry allows for the preparation of MOFs of the same topology from ligands with related geometries. Here in this work, reticular chemistry is used to explore the scope of polyMOFs, which are frameworks synthesized from polymer ligands. “Linked” ortho-substituted benzene dicarboxylate polymer ligands with varying length alkyl spacers were used to synthesize polyMOFs and elucidate the effects of polymer architecture on resulting crystal formation. It was found that these “kinked” polymer ligands were able to form polyIRMOF architectures, but did not readily form polyUiO-66 topologies.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Spatial and temporal variations of new particle formation in East Asia using an NPF-explicit WRF-chem model: North-south contrast in new particle formation frequency
The new particle formation (NPF)-explicit version of the WRF-chem model, which we developed recently, can calculate the growth and sink of nucleated clusters explicitly with 20 aerosol size bins from 1 nm to 10 μm. In this study, the model is used to understand spatial and temporal variations of the frequency of NPF events and the concentrations of aerosols (condensation nuclei, CN) and cloud condensation nuclei (CCN) within the boundary layer in East Asia in spring 2009. Model simulations show distinct north-south contrast in the frequency and mechanism of NPF in East Asia. NPF mostly occurred over limited periods and regions between 30° and 45°N, such as northeast China, Korea, and Japan, including regions around active volcanoes (Miyakejima and Sakurajima). At these latitudes, NPF was considerably suppressed by high concentrations of preexisting particles under stagnant air conditions associated with high-pressure systems, while nucleation occurred more extensively on most days during the simulation period. Conversely, neither nucleation nor NPF occurred frequently south of 30°N because of lower SO2 emissions and H2SO4 concentrations. The period-averaged NPF frequency was 3 times higher at latitudes of 30° - 45°N than at latitudes of 20° - 30°N. The north-south contrast of NPF frequency is validated by surface measurements in outflow regions in East Asia. The period- and domain-averaged contribution of secondary particles is estimated to be 44% for CN (> 10 nm) and 26% for CCN at a supersaturation of 1.0% in our simulation, though the contribution is highly sensitive to the magnitudes and size distributions of primary aerosol emissions and the coefficients in the nucleation parameterizations.
Matsui, H.↗
Triphenylene‐Derived Electron Acceptors and Donors on Ag(111): Formation of Intermolecular Charge‐Transfer Complexes with Common Unoccupied Molecular States
Abstract Over the past years, ultrathin films consisting of electron donating and accepting molecules have attracted increasing attention due to their potential usage in optoelectronic devices. Key parameters for understanding and tuning their performance are intermolecular and molecule–substrate interactions. Here, the formation of a monolayer thick blend of triphenylene‐based organic donor and acceptor molecules from 2,3,6,7,10,11‐hexamethoxytriphenylene (HAT) and 1,4,5,8,9,12‐hexaazatriphenylenehexacarbonitrile (HATCN), respectively, on a silver (111) surface is reported. Scanning tunneling microscopy and spectroscopy, valence and core level photoelectron spectroscopy, as well as low‐energy electron diffraction measurements are used, complemented by density functional theory calculations, to investigate both the electronic and structural properties of the homomolecular as well as the intermixed layers. The donor molecules are weakly interacting with the Ag(111) surface, while the acceptor molecules show a strong interaction with the substrate leading to charge transfer and substantial buckling of the top silver layer and of the adsorbates. Upon mixing acceptor and donor molecules, strong hybridization occurs between the two different molecules leading to the emergence of a common unoccupied molecular orbital located at both the donor and acceptor molecules. The donor acceptor blend studied here is, therefore, a compelling candidate for organic electronics based on self‐assembled charge‐transfer complexes.
Müller, Kathrin↗
Simultaneous Formation of Interphases on both Positive and Negative Electrodes in High-Voltage Aqueous Lithium-Ion Batteries
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Hou, Xu↗
Formation of secondary mineral coatings and the persistence of reduced metal-bearing phases in soils developing on historic coal mine spoil
Abstract not provided
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Formation of pyrophosphates across grain boundaries induces the formation of mismatched but oriented interfaces in silver phosphate polypods
The interfaces and their misfit defects determine the materials properties for a wide range of applications, such as electronic devices, photocatalysis, and mechanical engineering, etc. However, current understanding of atomic interfacial structures is limited. Here we discover a special interfacial structure, mismatched but oriented interface via two distinct facets. Transmission and scanning electron microscopy results suggest that, in Ag 3 PO 4 polypods structures, interfaces of {1 0 0} and {1 1 0}, ({1 0 0}/(1 1 0}), {1 0 0}/{1 1 1}, {1 1 0}/{1 1 1}, and {1 0 0}/{1 0 0}, etc., have a certain orientation relationship, corresponding to the energy minima and coincident site lattice of interfacial atoms as demonstrated by molecular dynamics simulations. Density functional theory demonstrates that the formation of pyrophosphate and/or phosphates rotation to bond across the interface compensate the lattice mismatch at the interfaces, as well as deformations of Ag-O bonds. Furthermore, our work opens up a new avenue for a much wider range of interfacial structures, allow for a higher diversity of structures, and shine light on tailoring crystal structures, morphologies, and the resulting properties.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Thermodynamics and reaction pathways of furfuryl alcohol oligomer formation
The acid-catalyzed transformation of furfuryl alcohol (FA) monomer to oligomers has been studied in the liquid phase to investigate the reaction mechanisms and intermediate species by using a combination of quantitative reaction product measurements and density functional theory calculations. FA monomer was converted into oligomers with a broad range of carbon number: C9–C10, C14–C15, C19–C29, NC29. Based on the calculations, terminal CH2OH dimer formation is both kinetically and thermodynamically favored, consistent with the experimental results. The order for dimer production in the C9–C10 range follows terminal CH2OH N ether bridged–methylene bridged dimer N OH-carbon bridge.
Density functional theory calculation↗
Membrane synthesis via in-situ pore formation in silica gels through dynamic miscibility with soybean oil
The dynamic immiscibility between vegetable oil and organic silica precursors during sol-gel synthesis was used to tailor the microstructure of gels made with tetraethoxysilane (TEOS) or tetraethoxysilane+methyltrimethoxysilane (MTMS). Vegetable oil was investigated as an environmentally friendly and cheaper alternative to many other porogens. Oil concentrations of 9.09 v/v% and 33.33 v/v% were studied. For both TEOS and TEOS+MTMS gels, the miscibility of the oil and precursor decreases as the silica gel network forms, leading to oil-rich regions within the silica matrix. Gels containing MTMS maintained partial miscibility with the oil during gel formation due to the non-hydrolysable methyl groups on the MTMS. The pore structure of MTMS gels appeared more interconnected compared to the isolated pores observed in gels made with only TEOS. To create membranes with hierarchical pore structures, solvent exchanges were performed on gels or dried gels (i.e., xerogels) were calcined. The effect of the methyl group was also observed in the results of the time sweep rheology, as the addition of oil to the TEOS+MTMS gels caused an increase in the time to form the spanning gel. The trend was the opposite for oil additions to TEOS gels, which only contained polar groups. Xerogel membranes made with TEOS+MTMS had higher specific surface areas (SSAs) than those made with TEOS. For oil concentrations of 33.33 v/v%, xerogels made from TEOS+MTMS had an average SSA of 1068 + 113 m2 g-1, an order of magnitude higher than the average SSA of 103 + 6 m2 g-1 for xerogels made with TEOS.
sol-gel, dynamic immiscibility, oil-alkoxide inter↗
Influence of Hydrogen Isotopes on Vacancy Formation and Antisite Defect Diffusion in Palladium and Vanadium Metals
Density functional theory calculations are performed to study the interaction between hydrogen isotopes, vacancy, and antisite defects in Pd and V. Various defect configurations and defect-defect distances are systematically explored. Binding energies and migration energy barriers are calculated and tabulated. The study provides atomistic data for subsequent mesoscale simulations of tritium, vacancy, and antisite diffusion. In Pd, a strong binding is found between a vacancy and tritium (0.16 eV). This tritium binding increases the thermal concentration of vacancies by a factor of ~10 at 500 ?C. The increase in vacancy concentration enhances V antisite diffusion in Pd by a factor of ~6 at 500 ?C. The influence of tritium is even stronger in V, with a tritium and vacancy binding energy of 0.38 eV. Such a strong binding increases the thermal concentration of vacancies by a factor of ~300 at 500 ?C. The increase in vacancy concentration enhances Pd antisite diffusion in V by a factor of ~640 at 500 ?C. Vanadium and Pd exhibit a strong driving force to intermix with a formation energy of -1.57 eV for V antisite in Pd and -1.05 eV for Pd antisite in V. The results suggest vanadium diffusion into Pd is energetically stronger than the reverse. Zero-point-energy corrections are taken into account and calculations for hydrogen and tritium are presented.
Setyawan, Wahyu↗
Formation and transformation of a short range ordered iron carbonate precursor
Abstract not provided
Dideriksen, Knud↗