Journal articles: 'Metal oxide cation study'

1

Tsuji, Masamichi, and Yasuo Tanaka. "Spectroscopic study of a cryptomelane-type manganic acid exchanged by divalent transition-metal cations." Journal of Materials Research 16, no. 1 (January 2001): 108–14. http://dx.doi.org/10.1557/jmr.2001.0020.

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A cryptomelane-type manganic acid (CMA) exchanged by divalent transition-metal cations was studied by means of x-ray diffraction, electron microscopic observation, electron spin resonance, infrared spectra, and electron spectroscopy for chemical analysis. Especially the last three techniques were decisive for the chemical speciation of manganese oxide systems. The findings clearly eliminated a redox process as the principal process for cation uptake in the α–MnO2 phase. Transition-metal cations are stoichiometrically exchanged on this material on an equivalent basis similarly with alkali and alkaline-earth metal cations, except Fe2+. The last ion is oxidized to Fe3+ through a redox reaction with Mn3+ in the a–MnO2. The CMA is a mixed-valence compound represented by H2Mn2IIIMn6IVO16 2.3H2O. Two moles of tunnel protons are exchangeable to give 2.70 mequiv/g for the calculated ion-exchange capacity.

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Nowick, Arthur S. "Defects in Ceramic Oxides." MRS Bulletin 16, no. 11 (November 1991): 38–41. http://dx.doi.org/10.1557/s0883769400055500.

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The topic that I am attempting to cover easily requires a whole book to do it justice. To deal with it in a short article, I will focus on a few basic principles that dominate the behavior of defects in oxides and then present some examples taken from well-studied and relatively well-understood materials.The study of defects in oxides differs from the study of defects in metals and alloys or in semiconductors in several important ways. First, oxides generally have very high melting points so that intrinsic point defect concentrations at temperatures below ~1500°C are usually negligibly small. Second, an oxide does not always maintain the composition at which it was fabricated, as alloys do, but can exchange oxygen with the ambient atmosphere, according to the ambient partial pressure of oxygen, P(O2). Thus, the stoichiometry, and accordingly the defect concentration, can be controlled by annealing in a specific P(O2) atmosphere. Third, and most important, oxides have a high degree of ionicity so that most point defects possess an effective charge. The consequences of this fact are far reaching; some of them are as follows:1. In a binary oxide, e.g. a metal oxide (MO), there are two sublattices. The diffusion of cations and of anions proceeds each on its own sublattice, involving different point defects. Accordingly, cation and anion diffusion rates can be very different and, in fact, usually are.

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Zhou, Chen Liang, Bin Zheng Fang, Jian Wei Cao, Na Zhang, Jia Li Han, Hui Li, Xiao Long Gao, and Xi Dong Wang. "Effect of Doping Metal Ions on the Structure Transformation of Octahedral Layer Structure Manganese Oxide." Applied Mechanics and Materials 723 (January 2015): 670–73. http://dx.doi.org/10.4028/www.scientific.net/amm.723.670.

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The Octahedral layer structure manganese oxides (Buserite and Birnessite) have been synthesized and modified by aging a MnOx gel which was produced from the redox reactions between Mn2+ and MnO4- in the presence of other metal cations (Mg2+, Ni2+, Co2+ or Cu2+). The present study investigates the structure transformation between Buserite and Birnessite using X-ray powder diffraction conducted on cation doped manganese oxides at different stages of before and after hydration. The results indicate that introduction of Mg2+ into the interlayer can completely achieve the structure transformation between Birnessite and Buserite after hydrated at 24h, and Ni2+ can partially reverse.

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Afanas'ev, Valeri V. "Electron Band Alignment at Interfaces of Semiconductors with Insulating Oxides: An Internal Photoemission Study." Advances in Condensed Matter Physics 2014 (2014): 1–30. http://dx.doi.org/10.1155/2014/301302.

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Evolution of the electron energy band alignment at interfaces between different semiconductors and wide-gap oxide insulators is examined using the internal photoemission spectroscopy, which is based on observations of optically-induced electron (or hole) transitions across the semiconductor/insulator barrier. Interfaces of various semiconductors ranging from the conventional silicon to the high-mobility Ge-based (Ge,Si1-xGex,Ge1-xSnx) andAIIIBVgroup (GaAs,InxGa1-xAs, InAs, GaP, InP, GaSb, InSb) materials were studied revealing several general trends in the evolution of band offsets. It is found that in the oxides of metals with cation radii larger than≈0.7 Å, the oxide valence band top remains nearly at the same energy (±0.2 eV) irrespective of the cation sort. Using this result, it becomes possible to predict the interface band alignment between oxides and semiconductors as well as between dissimilar insulating oxides on the basis of the oxide bandgap width which are also affected by crystallization. By contrast, oxides of light elements, for example, Be, Mg, Al, Si, and Sc exhibit significant shifts of the valence band top. General trends in band lineup variations caused by a change in the composition of semiconductor photoemission material are also revealed.

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Gómez-Aguirre, Lilián Claudia, Jorge Otero-Canabal, Manuel Sánchez-Andújar, María Antonia Señarís-Rodríguez, Socorro Castro-García, and Breogán Pato-Doldán. "Thermal Decomposition of [AH][M(HCOO)3] Perovskite-Like Formates." Solids 2, no. 2 (May 2, 2021): 165–76. http://dx.doi.org/10.3390/solids2020011.

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A systematic study of the thermal decomposition of hybrid perovskites of formula [AH][M(HCOO)3] under inert atmosphere was performed by means of thermogravimetry and simultaneous infrared spectroscopy of the evolved gases. The influence of: (i) the metal ion of the [M(HCOO)3]- framework and (ii) the guest [AH]+ cation, in the composition of the final residue was evaluated. In this work, it has been demonstrated that these materials can be used as precursors of metal or metal-oxide compounds—obtained free of carbon—, and that the composition of the final residue is determined by the standard reduction potential of the metal cation of the framework.

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Sun, Dapeng, Xiang-Kui Gu, Runhai Ouyang, Hai-Yan Su, Qiang Fu, Xinhe Bao, and Wei-Xue Li. "Theoretical Study of the Role of a Metal–Cation Ensemble at the Oxide–Metal Boundary on CO Oxidation." Journal of Physical Chemistry C 116, no. 13 (March 23, 2012): 7491–98. http://dx.doi.org/10.1021/jp300924k.

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Roshchin, V. E., P. A. Gamov, A. V. Roshchin, and S. P. Salikhov. "ELECTRON THEORY OF METALS REDUCTION: THEORY AND METHODS OF METALS EXTRACTION FROM VARIOUS TYPES OF ORE." Izvestiya. Ferrous Metallurgy 62, no. 5 (June 19, 2019): 407–17. http://dx.doi.org/10.17073/0368-0797-2019-5-407-417.

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The present work analyzes the existing mechanism of solid-phase metals reduction from oxides. It was shown that the existed mechanisms of reduction do not explain the diversity of the practical results leading to a generally accepted opinion that there is no single uniform reduction mechanism. This study presents the results of the solid-phase reduction of metals from lump magnetite, siderite, titanomagnetite and chromite types of ore by carbon from various deposits. The obtained results were compared with the results of reduction of chromium, silicon and aluminum by carbon from pure oxides. Change in the electrical characteristics and analysis of the processes of electron- and mass transfer under reducing conditions were performed to clarify the general theoretical concepts of reduction mechanism. It has been concluded that there is general process of transformation of the crystal lattice of oxide into the crystal lattice of metal for reduction of different metals. The positions of electron theory for solid-phase reduction of metals from crystal lattice of oxides were developed using the basic concepts of chemistry, solid state physics about imperfect crystals, quantum mechanics and character of electron distribution and transfer in metals and ionic semiconductors. The theory embraces all the known results of reduction with formation of metal on the surface of high-grade lump ore, nucleation of metal inside of the complex and low-grade types of ore and formation and sublimation of suboxides. Major ideas of the developing theory of electron reduction have been formulated on the basis of metals reduction as a result of the exchange of electrons between the reducing agent and metal cations in oxides by means of the charged anion vacancies formed on the surface and their scattering in the volume. The transformation of the cations’ ionic bond in oxides into metallic bond of the metal phase on the surface (or inside of the oxide lattice) occurs without the displacement of the cations over significant distances and thermodynamic difficulties for the formation of metallic nucleus when the charged anion vacancies merge (skipping the stage of formation of the atoms of metal). There might be no direct contact between the metal and the reducing agent in case of formation of the metal phase inside of the oxide volume. As a result, harmful impurities from the reducing agent, e.g. carbon and sulphur, do not penetrate into iron during reduction of complex and low-grade types of ore. Therefore, for the reduction of iron from such an ore, it is possible to utilize a low-quality reducing agent, e.g. steam coal. The selective solid-phase reduction of iron from lump complex ore makes it possible to obtain a metal-oxide composite material containing pure DRI and valuable oxides which are difficult for reduction, i.e. oxides of magnesium, titanium and vanadium.

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Mishra, Abhishek Kumar, Michael R. Marvel, Kenneth R. Poeppelmeier, and Umesh V. Waghmare. "Competing Cation–Anion Interactions and Noncentrosymmetry in Metal Oxide-Fluorides: A First-Principles Theoretical Study." Crystal Growth & Design 14, no. 1 (December 11, 2013): 131–39. http://dx.doi.org/10.1021/cg401296f.

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9

Cote, Linda J., Amyn S. Teja, Angus P. Wilkinson, and Z. John Zhang. "Continuous hydrothermal synthesis and crystallization of magnetic oxide nanoparticles." Journal of Materials Research 17, no. 9 (September 2002): 2410–16. http://dx.doi.org/10.1557/jmr.2002.0352.

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The continuous hydrothermal synthesis of nanoparticles of two metal oxides (α–Fe2O3 and Co3O4) is described. Two variations of the technique were investigated, involving the precipitation reaction between a metal salt solution and a hydroxide solution at ambient conditions and at elevated temperatures. Elevated temperatures resulted in more uniform particles of α–Fe2O3 and Co3O4, although the actual sizes of the particles were apparently unaffected by the temperature. This behavior was attributed to the species present in solution and the solubilities of the cation(s), both of which were calculated via a thermodynamic model for the systems under study.

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Nakao, Yoshihide, Kimihiko Hirao, and Tetsuya Taketsugu. "Theoretical study of first-row transition metal oxide cations." Journal of Chemical Physics 114, no. 18 (May 8, 2001): 7935–40. http://dx.doi.org/10.1063/1.1362323.

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11

Rahayu, Prapti, and Witri Wahyu Lestari. "STUDY OF SYNTHESIS AND CHARACTERIZATION OF METAL-ORGANIC FRAMEWORKS MOF-5 AS HYDROGEN STORAGE MATERIAL." ALCHEMY Jurnal Penelitian Kimia 12, no. 1 (August 17, 2016): 14. http://dx.doi.org/10.20961/alchemy.12.1.934.14-26.

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Metal-organic frameworks (MOFs) are porous coordination polymer containing bi-or polidentate organic linker coordinated with inorganic part, such as metal oxide cluster or metal cation as node which called as secondary building unit (SBU) to form infinite structure. Due to high porosity and surface area, good thermal stability as well as the availability of unsaturated metal center or the linker influence attracts the interaction with gases, thus MOFs have potential to be applied as hydrogen storage material. One type of MOFs that have been widely studied is [Zn4O(benzene-1,4-dicarboxylate)3], namely, MOF-5.Various synthesis method have been developed to obtain optimum results. Characterization of MOF-5 from various synthesis method such as crystallinity, capacity, stability, and quantum dot behavior of MOF-5 have been summarized in this review.

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Rahayu, Prapti, and Witri Wahyu Lestari. "STUDY OF SYNTHESIS AND CHARACTERIZATION OF METAL-ORGANIC FRAMEWORKS MOF-5 AS HYDROGEN STORAGE MATERIAL." ALCHEMY Jurnal Penelitian Kimia 12, no. 1 (August 17, 2016): 14. http://dx.doi.org/10.20961/alchemy.v12i1.934.

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Metal-organic frameworks (MOFs) are porous coordination polymer containing bi-or polidentate organic linker coordinated with inorganic part, such as metal oxide cluster or metal cation as node which called as secondary building unit (SBU) to form infinite structure. Due to high porosity and surface area, good thermal stability as well as the availability of unsaturated metal center or the linker influence attracts the interaction with gases, thus MOFs have potential to be applied as hydrogen storage material. One type of MOFs that have been widely studied is [Zn4O(benzene-1,4-dicarboxylate)3], namely, MOF-5.Various synthesis method have been developed to obtain optimum results. Characterization of MOF-5 from various synthesis method such as crystallinity, capacity, stability, and quantum dot behavior of MOF-5 have been summarized in this review.

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13

Yong, Raymond N., Rosa Galvez-Cloutier, and Yuwaree Phadungchewit. "Selective sequential extraction analysis of heavy-metal retention in soil." Canadian Geotechnical Journal 30, no. 5 (October 1, 1993): 834–47. http://dx.doi.org/10.1139/t93-074.

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The selective sequential extraction method of analysis is used in this study to determine the distribution of heavy metals in some clay soils, to assist in evaluation of the role of the various clay soil solids (clay minerals, organics, amorphous materials, and carbonates) in heavy-metal retention capability as a function of acidity of the leachate. The chemical speciation model MINTEQ (metal speciation equilibrium model for surface and groundwater) is used to calculate the probable percent distribution of different species of heavy metals present in the leachate used. The selective sequential extraction method is based on the fact that different forms of heavy metals that are retained in soil (e.g., as oxides, hydroxides, carbonates, bound with organic matter) can be extracted selectively by using appropriate reagents. The results show that heavy metals can be retained in the four clay soils studied by several soil phases or mechanisms such as exchangeable, carbonate, hydroxide, and organic phases. The retention of heavy metals in any phase depends on soil solution pH, soil constituents, and the type of heavy metal. At high soil solution pH values, retention of heavy metal by precipitation mechanisms prevails, whereas at low soil solution pH, retention by cation exchange mechanisms becomes dominant. The results from the selective sequential extraction analysis support the conclusion of the significance of soil buffer capacity with regard to heavy-metal retention. The capacity of the soils to retain high amounts of heavy metals as they receive increasing amounts of acid (i.e., as the pH is reduced) depends directly on the soil initial pH values and on their buffer capacities. Key words : selective sequential analysis, exchangeable cations, heavy metals, equilibrium models, oxides.

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Vegas, A., and R. Isea. "Distribution of the M-M Distances in the Rare Earth Oxides." Acta Crystallographica Section B Structural Science 54, no. 6 (December 1, 1998): 732–40. http://dx.doi.org/10.1107/s0108768198003759.

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A systematic study of the distribution of the M—M distances in all the binary, ternary and quaternary oxides of the rare earth elements (RE = Sc, Y, La–Lu), contained in the Inorganic Crystal Structure Database (ICSD) has been carried out. The results indicate that the RE—RE distances are not distributed uniformly, but present maxima which are close to the corresponding distances in the pure metals. In some of the histograms (Y, Ce, Pr, Sm, Tb, Dy, Ho, Lu) two maxima appear which correspond to the nearest-neighbor (b.c.c., h.c.p.) and second-nearest neighbor (b.c.c.) distances of the elemental phases. As examples of this behavior, the cation arrays of the binary oxides, hydroxides and ternary oxides of both the delafossite and \alpha-NaFeO2 type are analyzed. In all of them the cations form aggregates whose topologies and distances can be related to the structure of the parent metals. The size of the metal aggregates seems to decrease with increasing oxygen content.

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Chandrappa, Gujjarahalli Thimmanna, Gangaiah Vijayakumar, and Jacques Livage. "Insertion study of alkali metal cations into layered vanadium oxide foam." Journal of Sol-Gel Science and Technology 73, no. 1 (October 2, 2014): 215–19. http://dx.doi.org/10.1007/s10971-014-3519-x.

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Auvray, Thomas, and Ellen M. Matson. "Polyoxometalate-based complexes as ligands for the study of actinide chemistry." Dalton Transactions 49, no. 40 (2020): 13917–27. http://dx.doi.org/10.1039/d0dt02755c.

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Complexation of actinide cations by polyoxometalates results in assemblies with exciting electronic properties and highly attractive potential as models for hetereogeneous systems based on actinides supported by metal oxide surfaces.

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Divya. "Graph Theoretical Representation, Analysis and Synthesis of Amorphous Metal Oxide Networks." MRS Advances 2, no. 48 (2017): 2639–44. http://dx.doi.org/10.1557/adv.2017.342.

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ABSTRACTWith the advent of amorphous oxide semiconductors (AOS) like amorphous indium gallium zinc oxide (a-IGZO), the analysis and prediction of amorphous structures has regained importance, more so, since first principles based studies are being increasingly employed to explain device behavior. Negative bias illumination stress in a-IGZO thin film transistors is one such example. However, the amorphous atomic structure is complex and defect or dopant studies require each site to be modeled independently and this leads to significant computational costs. Therefore, a simplification in the representation of the amorphous oxide network is effected so that it may lead to identifying similar atomic sites. The amorphous network is visualized as a network of polyhedra. The polyhedra has at its center a cation with the bonded oxygen atoms at the vertices and it comprises the short range interactions characterized by bond lengths and bond angles. Based on a first principles study of 10 a-IGZO models containing 36 cations each, it was found that the 360 polyhedra of the a-IGZO models can actually be described with only ten polyhedral motifs. These polyhedra are then connected to each other via a shared vertex or an edge; face-sharing was not observed in these models. Graph theory is used to map this network using either a graph of cationic polyhedra as the nodes or a bipartite graph (composed of cations and anions as individual nodes), each of which is described using the respective adjacency matrix. The second nearest interactions are characterized by the degree of each vertex and each atomic site is now characterized by a polyhedron and network metrics; and hence, can be compared with same-element sites. The changes in network itself, are quantified as the composition changes, when varying the ratio of In:Ga:Zn in a-IGZO. For example, the average vertex connectivity of a pair of indium sites reflects on the continuity of overlap between the In-5s orbitals which compose the conduction band minimum in a-IGZO, which, in turn, affects the transport properties of the semiconductor. Thus, the long range interactions of the physical amorphous network are described by the graph metrics. Moreover, evolutionary algorithm in conjunction with this graph theoretic representation can be used to generate new amorphous models. Two parent graph are chosen and then spliced and then bred. The new graph is then reverse-engineered to form an amorphous model which then undergoes ionic and volume relaxation in the framework of density functional theory. The resulting graph is the child and the new amorphous model, with the energy as the fitness criteria.

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Ketrot, D., A. Suddhiprakarn, I. Kheoruenromne, and B. Singh. "Interactive effects of iron oxides and organic matter on charge properties of red soils in Thailand." Soil Research 51, no. 3 (2013): 222. http://dx.doi.org/10.1071/sr13021.

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Iron (Fe) oxides and organic matter (OM) play important roles in maintaining the fertility of highly weathered soils. The main objective of this study was to investigate the interactive effects of variable surface charge minerals, particularly Fe oxide minerals, and OM on the charge properties of red soils from Thailand. We also evaluated the effect of the 5 m NaOH procedure, used to concentrate Fe oxides from soils, on the charge characteristics of Fe oxide concentrates. Fourteen clay fractions (untreated and OM-free clay fractions), and Fe oxide concentrates of these clays, were used in the study. Cation exchange capacity (CEC) and electrophoretic mobility (EM) were measured for the soil clays, artificial mixtures, and goethite adsorbed with humic acid (HA) and phosphate (P). Kaolinite and Fe oxides (predominantly a mixture of hematite and goethite) were the main minerals in the clay fraction. Results indicated that OM or metal–OM complexes may have blocked or neutralised negatively charged sites on clay minerals. After OM removal these sites became accessible, inducing an increase in CEC and shifting the EM values towards more negative values and the isoelectric point (IEP) towards lower pH for many samples. The CEC values of Fe oxide concentrates prepared by 5 m NaOH treatment were overestimated and their EM and IEP shifted towards more negative values. It is possible that the amorphous phase from clay dissolution was still present in the Fe oxide concentrates, or the adsorption of silicate ions modified the surfaces of Fe oxides concentrates. Humic acid and P adsorbed on Fe oxide surfaces caused the IEP to shift to lower values. In natural soil conditions, a variety of anions can be adsorbed on Fe oxide surfaces, which might lead to higher values of negative charge and lower IEP than observed for pure synthetic minerals.

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Xu, Lingqian, Nasreen Jeelani, Shubo Fang, Shuqing An, and Aixin Hou. "Assessing the hazards of trace metals in different land use types around a coastal wetland nature reserve in China." Marine and Freshwater Research 69, no. 5 (2018): 730. http://dx.doi.org/10.1071/mf17123.

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An understanding of trace metal pollution due to reclamation activities around Yancheng National Nature Reserve is important for the utilisation and management of the reserve and surrounding coastal and marine areas. In the present study, we evaluated the current state of Cu, Cd, Pb and Zn pollution (total concentrations and ecological risk), their potential hazard (availability index and desorption rate) and soil properties (cation exchange capacity, iron and manganese oxide content, soil organic matter, salinity and pH) in different land use types around this nature reserve. Although the current state of trace metal pollution was not severe, the potential hazards of these trace metals should not be ignored, especially for Cd because of its significantly higher availability index values in farmlands and aquaculture ponds than in natural habitats (by 33 and 32% of the total amount of Cd respectively). Thus, strict monitoring and environmentally responsible land reclamation management practices should be considered for these coastal areas.

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Ramamurthy, Sundar, Stuart McKernan, and C. Barry Carter. "Study of cobalt oxide films deposited on single-crystal yttria-stabilized zirconia by pulsed-laser ablation." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 1154–55. http://dx.doi.org/10.1017/s042482010015160x.

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One of the most common applications of pulsed-laser ablation (PLA) is the production of oxide films of almost any stoichiometry. In this work, thin films of cobalt oxide were grown onto single-crystal yttria-stabilized zirconia (YSZ) substrates of (100) orientation. Film morphology during the early stages of growth has been studied.Cobalt oxide films grown on suitable substrates have potential applications in electronic and magnetic devices. Like most transition metal oxides, cobalt oxide exists in more than one form, depending on the valence of the cations and their distribution . The transition from CoO to Co3O4 occurs at about 900°C in air, CoO being the high-temperature phase. However, by lowering the partial pressure of oxygen, the CoO stability region shifts down to much lower temperatures.The laser system used for the depositions was a Lambda Physik model 210i with KrF excimer laser (λ=248 nm) operating at an energy of 200 mJ per pulse. A Co3O4 pellet (96% dense) was fabricated as the target material.

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Theppitak, Chatphorn, and Kittipong Chainok. "Crystal structure of CdSO4(H2O): a redetermination." Acta Crystallographica Section E Crystallographic Communications 71, no. 10 (September 17, 2015): i8—i9. http://dx.doi.org/10.1107/s2056989015016904.

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The crystal structure of the title compound, cadmium sulfate monohydrate or poly[(μ2-aqua)(μ4-sulfato)cadmium], was redetermined based on modern CMOS (complementary metal oxide silicon) data. In comparison with the previous study [Bregeault & Herpin (1970).Bull. Soc. Fr. Mineral. Cristallogr.93, 37–42], all non-H atoms were refined with anisotropic displacement parameters and the hydrogen-bonding pattern unambiguously established due to location of the hydrogen atoms. In addition, a significant improvement in terms of precision and accuracy was achieved. In the crystal, the Cd2+cation is coordinated by four O atoms of four sulfate anions and two O atoms of water molecules, forming a distorted octahedraltrans-[CdO6] polyhedron. Each sulfate anion bridges four Cd2+cations and each water molecule bridges two Cd2+cations, leading to the formation of a three-dimensional framework, with Cd...Cd separations in the range 4.0757 (2)–6.4462 (3) Å. O—H...O hydrogen-bonding interactions of medium strength between the coordinating water molecules and sulfate anions consolidate the crystal packing.

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Tso, Chih-ping, Cheng-min Zhung, Yang-hsin Shih, Young-Ming Tseng, Shian-chee Wu, and Ruey-an Doong. "Stability of metal oxide nanoparticles in aqueous solutions." Water Science and Technology 61, no. 1 (January 1, 2010): 127–33. http://dx.doi.org/10.2166/wst.2010.787.

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The application of nanoparticles in the processes of making commercial products has increased in recent years due to their unique physical and chemical properties. With increasing amount of commercial nanoparticles released into nature, their fate and effects on the ecosystem and human health are of growing concern. This study investigated the stability and morphology of three metal oxide nanoparticles in aqueous solutions. The commercially available nanoparticles, TiO2, ZnO, SiO2, aggregated quickly into micrometer-size particles in aqueous solutions, which may not threaten human health. Their changes in morphology and characteristics were further examined by dynamic light scattering (DLS) method and transmission electron microscopy (TEM). Among the several dispersion approaches, ultrasonication was found to be the most effective for disaggregating nanoparticles in water. For these three selected nanoparticles, ZnO could not remain stable in suspensions, presumably due to the dissolution of particles to form high concentration of ions, resulting in enhanced aggregation of particles. In addition, the existence of dissolved organic matters stabilized nanoparticles in lake water and wastewater for several hours in spite of the high concentration of cations in these real-water samples. The fate of metal oxide nanoparticles in natural water bodies would be determined by the type and concentration of cations and organic matters. Results obtained in this study revealed that the stability of nanoparticles changed under different aqueous conditions and so did their fate in the environment.

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Zhang, G. H., and K. C. Chou. "Viscosity model for aluminosilicate melt." Journal of Mining and Metallurgy, Section B: Metallurgy 48, no. 3 (2012): 433–42. http://dx.doi.org/10.2298/jmmb120317054z.

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The structurally based viscosity model proposed in our previous study is extended to include more components, e.g. SiO2, Al2O3, FeO, MnO, MgO, CaO, Na2O and K2O. A simple method is proposed to calculate the numbers of different types of oxygen ions classified by the different cations they bonded with, which is used to characterize the influence of composition on viscosity. When dealing with the aluminosilicate melts containing several basic oxides, the priority order is established for different cations for charge compensating Al3+ ions, according to the coulombic force between cation and oxygen anion. It is indicated that basic oxides have two paradox influences on viscosity: basic oxide with a higher basicity decreases viscosity more greatly by forming weaker non-bridging oxygen bond; while it increases viscosity more greatly by forming stronger bridging oxygen bond in tetrahedron after charge compensating Al3+ ion. The present model can extrapolate its application range to the system without SiO2. Furthermore, it could also give a satisfy interpretation to the abnormal phenomenon that viscosity increases when adding K2O to CaO-Al2O3-SiO2 melt within a certain composition range.

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Baghaie, Amir Hossein. "Effect of Organic Nano-Materials on Heavy Metals Concentration of Wheat Plants Inoculated With Piriformospora indica Fungus and Irrigated With Wastewater of Plating Industry." Avicenna Journal of Environmental Health Engineering 7, no. 1 (June 29, 2020): 20–28. http://dx.doi.org/10.34172/ajehe.2020.04.

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Removal of heavy metals from industrial effluents is one of the most important in environmental research. This research was done to investigate the adsorption effect of multiwall carbon nanotubes (MWNTs) and nano Zn-oxide on decreasing chromium (Cr) and cadmium (Cd) concentration in wheat inoculated with Piriformospora indica (P.indica) that irrigated with wastewater of plating industry. Treatments were consist of applying MWCNs (0 and 0.5 % (W/W)) and nano Zn-oxide (0 and 1.5 % (W/W)) in the soil irrigated with the wastewater of plating industry under wheat inoculated with P.indica. This research was done as a factorial experiment in the layout of completely randomized block design in three replication After 90 days, plants were harvested and plant Cd and Cr were measured using atomic absorption spectroscopy. Using MWCNs had significant effect on increasing cation exchangeable capacity of soil. Applying 0.5 % (W/W) MWCNs in the soil irrigated with waste water significantly decreased the soil Cd concentration by 11.7%, while the plant biomass was increased by 13.4%. In addition, applying 1.5 % (W/W) nano Zn-oxide significantly decreased the negative effect of heavy metal toxicity that can be related to the role of nano Zn-oxide on increasing soil sorption properties. However, the interaction effect of Zn and Cd cannot be ignored. The results of this study showed that applying MWCNs and nano Zn-oxide has a significant effect on decreasing phytoremediation efficiency in soil irrigated with wastewater of plating industries. However, the type and the amount of heavy metals in wastewater cannot be ignored.

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Ferrari, V., and M. Weissmann. "Tuning the insulator-metal transition in oxide interfaces: An ab initio study exploring the role of oxygen vacancies and cation interdiffusion." physica status solidi (b) 251, no. 8 (July 2, 2014): 1601–7. http://dx.doi.org/10.1002/pssb.201451050.

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Bennett, Joseph W., Diamond T. Jones, Robert J. Hamers, and Sara E. Mason. "First-Principles and Thermodynamics Study of Compositionally Tuned Complex Metal Oxides: Cation Release from the (001) Surface of Mn-Rich Lithium Nickel Manganese Cobalt Oxide." Inorganic Chemistry 57, no. 21 (October 16, 2018): 13300–13311. http://dx.doi.org/10.1021/acs.inorgchem.8b01855.

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Ho, Mui Yen, Poi Sim Khiew, Dino Isa, and Wee Siong Chiu. "Electrochemical studies on nanometal oxide-activated carbon composite electrodes for aqueous supercapacitors." Functional Materials Letters 07, no. 06 (December 2014): 1440012. http://dx.doi.org/10.1142/s1793604714400128.

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In present study, the electrochemical performance of eco-friendly and cost-effective titanium oxide ( TiO 2)-based and zinc oxide-based nanocomposite electrodes were studied in neutral aqueous Na 2 SO 3 electrolyte, respectively. The electrochemical properties of these composite electrodes were studied using cyclic voltammetry (CV), galvanostatic charge–discharge (CD) and electrochemical impedance spectroscopy (EIS). The experimental results reveal that these two nanocomposite electrodes achieve the highest specific capacitance at fairly low oxide loading onto activated carbon (AC) electrodes, respectively. Considerable enhancement of the electrochemical properties of TiO 2/AC and ZnO /AC nanocomposite electrodes is achieved via synergistic effects contributed from the nanostructured metal oxides and the high surface area mesoporous AC. Cations and anions from metal oxides and aqueous electrolyte such as Ti 4+, Zn 2+, Na + and [Formula: see text] can occupy some pores within the high-surface-area AC electrodes, forming the electric double layer at the electrode–electrolyte interface. Additionally, both TiO 2 and ZnO nanoparticles can provide favourable surface adsorption sites for [Formula: see text] anions which subsequently facilitate the faradaic processes for pseudocapacitive effect. These two systems provide the low cost material electrodes and the low environmental impact electrolyte which offer the increased charge storage without compromising charge storage kinetics.

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Hsiao, Yuan-Wen, Shi-Yu Wang, Cheng-Liang Huang, Ching-Chich Leu, and Chuan-Feng Shih. "Resistive Switching Property of Organic–Inorganic Tri-Cation Lead Iodide Perovskite Memory Device." Nanomaterials 10, no. 6 (June 12, 2020): 1155. http://dx.doi.org/10.3390/nano10061155.

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In this study, a glass/indium tin oxide (ITO)/formamidinium-methylammonium-cesium (FA-MA-Cs) tri-cation lead iodide perovskite/poly(methyl methacrylate (PMMA)/Al memory device with a controlled composition of (FA0.75MA0.25)1-xCsxPbI3 (x = 0–0.1) is demonstrated to exhibit bipolar resistive switching behavior. The tri-cation organic–inorganic metal halide perovskite film was prepared by a one-step solution process in which the amount of Cs was varied to modify the property of FA0.75MA0.25PbI3. It was found that the microstructure and defect properties of films are highly dependent on the contents of FA, MA, and Cs in the perovskite. The results found that 5% CsI doping is the optimized condition for improving the quality of FA0.75MA0.25PbI3, forming a high quality tri-cation perovskite film with a smooth, uniform, stable and robust crystalline grain structure. The resistive switching on/off ratio of the (FA0.75MA0.25)0.95Cs0.05PbI3 device is greater than 103 owing to the improved thin-film quality. Moreover, for the 5% CsI doped FA0.75MA0.25PbI3 films, the endurance and the stability of retention are better than the non-doped film. The improved microstructure and memory properties are attributed to the balance stress of FA/MA/Cs with different ionic size. It suggests the potential to achieve a desired resistive memory property of tri-cationic perovskite by carefully adjusting the cation ratios.

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29

Rupp, Jennifer L. M., Barbara Scherrer, Julia Martynczuk, and Ludwig J. Gauckler. "Self-Limited to Parabolic Grain Growth Kinetics in Metal Oxide Thin Films." Materials Science Forum 715-716 (April 2012): 333. http://dx.doi.org/10.4028/www.scientific.net/msf.715-716.333.

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Distinctive microstructure engineering of amorphous to nanocrystalline electroceramic thin films is of high relevance for integration in low to high temperature operating MEMS-devices. Up to now, kinetic rules of nucleation, crystallization and grain growth of precipitation-based ceramic thin films are unknown. In this study, general rules for the crystallization and grain growth kinetics of a pure single-phase metal oxide thin film with only one kind of cation, i.e. ceria, made by spray pyrolysis from a precursor with one single organic solvent is discussed [1,. The near-and long range disorder is studied via Raman, DSC investigation of crystallization enthalpy, XRD, SEM and TEM for amorphous to fully crystalline state. These 400 nm thick-thin films were dense, crack-free and amorphous directly after deposition on a sapphire substrate. Briefly, above deposition temperature crystallization sets in with respect to temperature and persists over a broad temperature range from 400 to 950°C. In this regime, biphasic amorphous-crystallien films exist and grain growth proceeds simultaneously to crystallization. Isothermal grain growth studies showed that after short dwell times of 10-20h stable microstructures established following self-limited grain growth law [. In this state, driving force for the crystallization is the reduction of free enthalpy for phase transformation and interface diffusion prevails. A transition to classical grain curvature-driven parabolic grain growth kinetics appeared once the material reached the fully crystalline state for average grain sizes larger than 140 nm and higher annealing temperatures. Volume diffusion was then activated in addition to the interface diffusion. It was found that once crystallized the material shows independent on processing route equal XRD density and microstrain, as well as Raman characteristics. However, dependent on processing conditions i.e. choice of organic and, according, deposition temperature of the film amorphous states vary and affect strongly crystallization and grain growth history for the biphasic films.

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30

Belles, Loukas, Constantinos Moularas, Szymon Smykała, and Yiannis Deligiannakis. "Flame Spray Pyrolysis Co3O4/CoO as Highly-Efficient Nanocatalyst for Oxygen Reduction Reaction." Nanomaterials 11, no. 4 (April 5, 2021): 925. http://dx.doi.org/10.3390/nano11040925.

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The oxygen reduction reaction (ORR) is the rate-limiting reaction in the cathode side of fuel cells. In the quest for alternatives to Pt-electrodes as cathodes in ORR, appropriate transition metal oxide-based electrocatalysts are needed. In the present work, we have synthesized Co3O4 and CoO/Co3O4 nanostructures using flame spray pyrolysis (FSP), as electrocatalysts for ORR in acidic and alkaline media. A detailed study of the effect of (Co-oxide)/Pt ratio on ORR efficiency shows that the present FSP-made Co-oxides are able to perform ORR at very low-Pt loading, 0.4% of total metal content. In acid medium, an electrode with (5.2% Pt + 4.8% Co3O4), achieved the highest ORR performance (Jmax = 8.31 mA/cm2, E1/2 = 0.66 V). In alkaline medium, superior performance and stability have been achieved by an electrode with (0.4%Pt + 9.6% (CoO/Co3O4)) with ORR activity (Jmax = 3.5 mA/cm2, E1/2 = 0.08 V). Using XRD, XPS, Raman and TEM data, we discuss the structural and electronic aspects of the FSP-made Co-oxide catalysts in relation to the ORR performance. Cyclic voltammetry data indicate that the ORR process involves active sites associated with Co3+ cations at the cobalt oxide surface. Technology-wise, the present work demonstrates that the developed FSP-protocols, constitutes a novel scalable process for production of co-oxides appropriate for oxygen reduction reaction electrodes.

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Pang, Xiaoying, Ying Liu, and Juanfang Wang. "Mixed Chlorometallate Ionic Liquids as C4 Alkylation Catalysts: A Quantitative Study of Acceptor Properties." Catalysts 8, no. 11 (October 26, 2018): 498. http://dx.doi.org/10.3390/catal8110498.

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The acceptor properties of mixed chlorometallate ionic liquids for isobutane-butene alkylation (C4 alkylation) reaction were studied. These ionic liquids were prepared by mixing metal chlorides with either triethylamine hydrochloride or 1-butyl-3-methylimidazolium chloride in various molar ratios. Using triethylphosphine oxide as a probe, Gutmann Acceptor Numbers (AN) of the catalysts were determined, and the Lewis acidity of mixed chlorometallate ionic liquids was quantitatively measured. Additionally, AN value was developed to determine the relationship between Lewis acidity and catalytic selectivity. The favorite AN value for the C4 alkylation reaction should be around 93.0. The [(C2H5)3NH]Cl–AlCl3−CuCl appears to be more Lewis acidity than that of [(C2H5)3NH]Cl–AlCl3. The correlation of the acceptor numbers to speciation of the mixed chlorometallate ionic liquids has also been investigated. [AlCl4]−, [Al2Cl7]−, and [MAlCl5]− (M = Cu, Ag) are the main anionic species of the mixed chlorometallate ILs. While the presence of [(C2H5)3N·M]+ cation always decreases the acidity of the [(C2H5)3NH]Cl−AlCl3−MCl ionic liquids.

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32

Kim, Young Ho, Han Sol Je, Eun Jee Kang, Su Gyung Lee, and Chu Sik Park. "Hydrogen Storage and Release by Redox Reaction of Iron Oxide Medium with Mo and Zr Additives." Advanced Materials Research 347-353 (October 2011): 3317–20. http://dx.doi.org/10.4028/www.scientific.net/amr.347-353.3317.

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Chemical hydrogen storage and release of iron-based oxide mediums were investigated by hydrogen reduction and water splitting oxidation (Fe3O4 + 4H2 ⇌ 3Fe + 4H2O). In this study, all metal oxide mediums were prepared by coprecipitation method using urea solution as precipitant. The redox reactions of the mediums were conducted using a fixed bed quartz reactor under atmospheric pressure. The theoretical amount of hydrogen storage that can be obtained from the redox reaction of iron oxide is calculated to be 4.8wt% on the basis of 1g-Fe. However, in case of using the iron oxide medium without additives, the medium was rapidly deactivated due to the agglomeration of Fe metals in the hydrogen reduction step of repeated redox cycles. In this study, therefore, Mo and Zr additives were added to iron oxide to improve the reactivity of the medium and to prevent the agglomeration of that. As a result, the reactivity for oxidation of the mediums was largely improved with the addition of Mo additive. It was concluded that change in the valence of Mo cations affected the redox behavior of the mediums.

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Lobacheva, Olga Leonidovna, and Natalia Vladimirovna Dzhevaga. "The Experimental Study of Innovative Methods Regarding the Removal of Sm(III)." Applied Sciences 11, no. 16 (August 22, 2021): 7726. http://dx.doi.org/10.3390/app11167726.

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The modern development of the construction materials sector determines the use of rare earth metals (REM) for various purposes. In particular, REM are added as basic alloying elements into magnesium alloys to increase alloy durability and strength. The complex systematic study of structural components and REM interaction are the basis for the phase state monitoring of multicomponent oxide polyfunctional materials. In addition, on the preparatory stage, layers with specified construction material coatings are formed. The paper presents experimental and theoretical results of studies of adsorptive bubble methods in the systems containing Samarium cations and surfactants, namely sodium dodecyl sulphate (NaDS). To identify the process mechanisms and prediction of optimal conditions of metal cations’ removal and separation by extraction, flotation, and ion flotation methods, one should know the pH of metal hydroxo-complexes and pH of the hydrate formation. The possibility of lanthanide ions’ removal (by the example of Samarium ions) by the solvent sublation method with NaDS as a collector and isooctyl alcohol as an extractant was studied. From the obtained experimental data, it was clear that the Sm3+ removal in acidic mediums is practically non-existent. The results obtained in this paper are topical in the production of electrode coating components, welding fluxes, sorbents for nuclear wastewater burial, wastewater treatment, highly porous heat-insulating and fire-resistant materials, cement, and concrete with improved frost resistance.

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34

Cai, Kui, Minjie Zhang, Yanqiu Yu, and Kangjoo Kim. "Pollution, Source, and Relationship of Trace Metal(loid)s in Soil-Wheat System in Hebei Plain, Northern China." Agronomy 9, no. 7 (July 17, 2019): 391. http://dx.doi.org/10.3390/agronomy9070391.

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To study the complex migration and transformation of trace metal(loid)s in a soil–wheat system, 225 pairs of surface soil and wheat samples were collected from the Taihang Mountains front plain, Hebei Province, northern China. The concentrations and pools (F1, water-soluble; F2, exchangeable; F3, carbonate-bound; F4, humic acid-bound; F5, Fe–Mn oxide-bound; F6, organic matter-bound; and F7, residual) of Cu, Pb, Zn, Cr, Ni, Cd, and Hg, and the soil properties of the samples were analyzed. The sum of the F1, F2, F3, and F4 proportions of Cd was higher than that of the other trace metal(loid)s, implying that Cd has greater mobility. We found a significant correlation (p < 0.01) between pools of trace metal(loid)s and the corresponding elements in wheat and a significant correlation (p < 0.01) between pools of trace metal(loid)s and pH, cation exchange capacity, clay, and total organic carbon. The results of principle component analysis (PCA)indicated that Cr, Ni and As mainly come from natural sources and Cu, Pb, Zn, and Cd from mixed groups related to farming and industry, Hg come from the coal burning. In addition, the total target hazard quotients showed the presence of harmful levels of trace metal(loid)s in wheat.

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35

Mobegi, Erick, Mildred Nawiri, and Dickson Andala. "Fabrication of metal oxide - biopolymer nanocomposite for water defluoridation." MRS Advances 3, no. 36 (2018): 2109–18. http://dx.doi.org/10.1557/adv.2018.251.

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ABSTRACTFluoride levels in drinking water exceeding 1.5 mg/L especially underground water can be detrimental to health. Various defluoridation technologies exist such as reverse osmosis, adsorption and ion exchange. However, adsorption has been preferred over the other due to its low cost and ease of operation. In this study, a novel adsorbent nanomaterial was prepared to remove fluoride from drinking water. The influence of different parameters such as pH, contact time, co-existing ions and dosage were investigated in order to understand the sorption behaviour of the adsorbent under varying conditions. The adsorption process best fitted with the Langmuir model with a maximum adsorption capacity of 62.5 mg/g. The adsorbent can be used under normal water pH=7. Anions and cations had no influence on the sorption capacity except for chlorides, carbonates and bicarbonates. The adsorbent reduced fluoride concentration from 10 ppm to approximately 1.5 ppm per 50 mg nanocomposite loading as recommended by World Health Organization. The synthesized nanocomposite can be used for defluoridation of water with high fluoride concentrations beyond recommended limit.

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36

Gudat, Axel, Sabine Haag, Rüdiger Kniep, and Albrecht Rabenau. "Ternäre Nitride des Lithiums mit den Elementen Cr, Mo und W / Ternary Lithium Nitrides with Elements Cr, Mo and W." Zeitschrift für Naturforschung B 45, no. 2 (February 1, 1990): 111–20. http://dx.doi.org/10.1515/znb-1990-0203.

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The ternary compounds were prepared by reaction of the transition metals with Li3N melt under nitrogen. The crystal structures of Li6MeN4 (P42/nmc, Z = 2; Me = Mo: a = 667.3(1) pm, c = 492.5(3) pm; Me = W: a = 667.9(1) pm, c = 492.7(1) pm) and Li15Cr2N9 (P4/ncc, Z = 4; a = 1023.3(5) pm, c = 938.9(7) pm) can be described as fluorite-type superstructures with the lithium and transition metal atoms in tetrahedral holes of the nearly fcc nitrogen arrangement and with an ordered distribution of defects within the cation substructure. In addition, the ternary system Li–Cr–N contains the compound Li6CrN4 with a crystal structure which is not quite clear at present, but which shows close relations to the structures of Li6MeN4 (Me = Mo, W). The previously reported compounds Li9MeN5 (Me = Cr, Mo, W) have not been observed during this study. The respective Cr compound in fact is a nitride-oxide (nitride-imide) of composition Li14Cr2N8(O,NH) with a crystal structure (P3̄, Z = 1, a = 579.9(1) pm, c = 826.3(6) pm) also showing a fluorite-type superstructure.

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Rudziński, Wladyslaw, Robert Charmas, and Wojciech Piasecki. "On the Nature of the Energetic Surface Heterogeneity in Ion Adsorption at an Electrolyte/Oxide Interface. Theoretical Studies of the Correlations between Binding-to-Surface Energies of Various Surface Complexes." Adsorption Science & Technology 14, no. 1 (February 1996): 25–38. http://dx.doi.org/10.1177/026361749601400103.

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When a metal oxide is brought into contact with an electrolyte, the outermost surface oxygens adsorb one or two protons, a cation or an aggregate composed of two protons and an anion. In this way, various surface complexes are formed. The actual surfaces are, as a rule, geometrically distorted. This causes a variation of the binding-to-surface energy from one surface oxygen to another for each of these complexes. This energetic heterogeneity of the actual oxide surfaces strongly affects the adsorption of ions within the electrical double layer formed at the oxide/electrolyte interface. The way in which the surface heterogeneity affects the adsorption of ions depends on the correlations between the binding-to-surface energies of the various surface complexes. To date, two extreme models have been considered by us; one assuming the existence of very high correlations, and the other one assuming a total lack of correlation between binding-to-surface energies in going from one surface oxygen to another. This paper presents a theoretical study of ion adsorption based on the assumption of a partial correlation between the binding-to-surface energies.

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38

Sugurbekova, Gulnar, Yerzhigit Sugurbekov, Gulzat Demeuova, Oral Ualibek, Aliya Kurbanova, Olzat Toktarbaiuly, and Ozhet Mauit. "The Effect of Doping on the Structure of Zinc Oxide Obtained by Atomic Layer Deposition." Materials Science Forum 990 (May 2020): 330–36. http://dx.doi.org/10.4028/www.scientific.net/msf.990.330.

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Zinc oxide (ZnO) is an interesting inexpensive transparent conductive oxide for use as a transport layer in multilayer solar cells. We present the results of a study of the effect of aluminum doping on the structure of 50-65 nm thin films of zinc oxide obtained by atomic layer deposition (ALD) on different substrates (glass, sapphire with a-plane and c-plane orientations). Analysis of thin films by IR spectra and X-ray diffraction showed the effect of doping on the crystallographic texture of films grown by the ALD method by comparing substrates of simple glass, c-plane Al2O3 and a-plane Al2O3. We found that when doping zinc oxide, the orientation of the substrate plays a substantial role, which affects the mechanism of interaction of zinc oxide with a doping agent, leading to changes in the structure and properties of ZnO due to the interaction between ZnO molecules and water to form a Zn-O-H bond. Doping with aluminum leads to a strain stress, resulting in distortion of the structure and a decrease in the concentration of oxygen vacancies. This is turn facilitates the flow of water molecules into the interlayer space and an increase in the density of the positive charge on the metal cation, which leads to an increase in the coordination number, i.e. to an increase in the number of hydroxyl groups.

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39

Epifani, Mauro, Jordi Arbiol, Teresa Andreu, and Joan R. Morante. "Crystallization Pathways of Multicomponent Oxide Nanocrystals: Critical Role of the Metal Cations Distribution in the Case Study of Metal Ferrites." Crystal Growth & Design 10, no. 12 (December 2010): 5176–81. http://dx.doi.org/10.1021/cg100959j.

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Fan, Shou-kong. "A microscopic marker experiment study on high temperature oxidation of Ni-Al alloy." Proceedings, annual meeting, Electron Microscopy Society of America 44 (August 1986): 514–15. http://dx.doi.org/10.1017/s0424820100144085.

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Transmission and analytical electron microscopic studies of scale microstructures and microscopic marker experiments have been carried out in order to determine the transport mechanism in the oxidation of Ni-Al alloy. According to the classical theory, the oxidation of nickel takes place by transport of Ni cations across the scale forming new oxide at the scale/gas interface. Any markers deposited on the Ni surface are expected to remain at the scale/metal interface after oxidation. This investigation using TEM transverse section techniques and deposited microscopic markers shows a different result,which indicates that a considerable amount of oxygen was transported inward. This is the first time that such fine-scale markers have been coupled with high resolution characterization instruments such as TEM/STEM to provide detailed information about evolution of oxide scale microstructure.

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THOMAS, J. L. C., C. W. JUN BAUSCHLICHER, and M. B. HALL. "ChemInform Abstract: Binding of Nitric Oxide to First-Transition-Row Metal Cations: An ab initio Study." ChemInform 29, no. 2 (June 24, 2010): no. http://dx.doi.org/10.1002/chin.199802001.

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42

Marafatto, Francesco Femi, Matthew L. Strader, Julia Gonzalez-Holguera, Adam Schwartzberg, Benjamin Gilbert, and Jasquelin Peña. "Rate and mechanism of the photoreduction of birnessite (MnO2) nanosheets." Proceedings of the National Academy of Sciences 112, no. 15 (March 30, 2015): 4600–4605. http://dx.doi.org/10.1073/pnas.1421018112.

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The photoreductive dissolution of Mn(IV) oxide minerals in sunlit aquatic environments couples the Mn cycle to the oxidation of organic matter and fate of trace elements associated with Mn oxides, but the intrinsic rate and mechanism of mineral dissolution in the absence of organic electron donors is unknown. We investigated the photoreduction of δ-MnO2 nanosheets at pH 6.5 with Na or Ca as the interlayer cation under 400-nm light irradiation and quantified the yield and timescales of Mn(III) production. Our study of transient intermediate states using time-resolved optical and X-ray absorption spectroscopy showed key roles for chemically distinct Mn(III) species. The reaction pathway involves (i) formation of Jahn–Teller distorted Mn(III) sites in the octahedral sheet within 0.6 ps of photoexcitation; (ii) Mn(III) migration into the interlayer within 600 ps; and (iii) increased nanosheet stacking. We propose that irreversible Mn reduction is coupled to hole-scavenging by surface water molecules or hydroxyl groups, with associated radical formation. This work demonstrates the importance of direct MnO2 photoreduction in environmental processes and provides a framework to test new hypotheses regarding the role of organic molecules and metal species in photochemical reactions with Mn oxide phases. The timescales for the production and evolution of Mn(III) species and a catalytic role for interlayer Ca2+ identified here from spectroscopic measurements can also guide the design of efficient Mn-based catalysts for water oxidation.

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43

Maslen, E. N., V. A. Streltsov, and N. Ishizawa. "A synchrotron X-ray study of the electron density in C-type rare earth oxides." Acta Crystallographica Section B Structural Science 52, no. 3 (June 1, 1996): 414–22. http://dx.doi.org/10.1107/s0108768195013371.

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Structure factors for small synthetic crystals of the C-type rare earth (RE) sesquioxides Y2O3, Dy2O3 and Ho2O3 were measured with focused λ = 0.7000 (2) Å, synchrotron X-radiation, and for Ho2O3 were re-measured with an MoKα (λ = 0.71073 Å) source. Approximate symmetry in the deformation electron density (Δρ) around a RE atom with pseudo-octahedral O coordination matches the cation geometry. Interactions between heavy metal atoms have a pronounced effect on the Δρ map. The electron-density symmetry around a second RE atom is also perturbed significantly by cation–anion interactions. The compounds magnetic properties reflect this complexity. Space group Ia{\bar 3}, cubic, Z = 16, T = 293 K: Y2O3, Mr = 225.82, a = 10.5981 (7) Å, V = 1190.4 (2) Å3, Dx = 5.040 Mg m−3, μ 0.7 = 37.01 mm−1, F(000) = 1632, R = 0.067, wR = 0.067, S = 9.0 (2) for 1098 unique reflections; Dy2O3, Mr = 373.00, a = 10.6706 (7) Å, V = 1215.0 (2) Å3, Dx = 8.156 Mg m−3, μ 0.7 = 44.84 mm−1, F(000) = 2496, R = 0.056, wR = 0.051, S = 7.5 (2) for 1113 unique reflections; Ho2O3, Mr = 377.86, a = 10.606 (2) Å, V = 1193.0 (7) Å3, Dx = 8.415 Mg m−3, μ 0.7 = 48.51 mm−1 F(000) = 2528, R = 0.072, wR = 0.045, S = 9.2 (2) for 1098 unique reflections of the synchrotron data set.

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Georgescu, Vasile, Gabriel Vasilievici, Mihaela Bombos, and Casen Panaitescu. "Study of Co-Cr Mixed Oxides for Different Applications." Revista de Chimie 68, no. 9 (October 15, 2017): 2039–42. http://dx.doi.org/10.37358/rc.17.9.5817.

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Mixture metal oxide system Co-Cr were prepared by decomposition of the precursor complexes obtained from a mixture Co-Cr nitrates with tartaric acid. The samples were subsequently submitted to chemical analysis, magnetic measurements, IR spectrometry, UV-Vis, thermal analysis, XRD, EXAFS and TPR. At 600oC was identificated a solid solution of CoCr2O4 with Co3O4. With Cu-CrK-edge EXAFS the local structure of samples calcinated of 420oC and 600oC was obtained. By theirs analysis was calculated: the lengths of M-O bounds, number of coordination (N), Debye-Waller factor (A1) and x metallic cations fraction in tetrahedral structures (spinelic centers). The TPR measurements were emphasized the existence of two reduction cycles.

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45

Solórzano, I. G., J. B. Vander Sande, K. K. Baek, and H. L. Tuller. "A high-resolution EM study of grain boundaries in Pr and Co-doped ZnO ceramics." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 1150–51. http://dx.doi.org/10.1017/s0424820100151581.

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Metal oxide varistors are multijunction materials whose nonlinear current-voltage characteristics derive from the electrical activity of their grain boundary regions. The high degree of nonlinear-ity in polycrystalline ZnO has been attributed to the synergistic action of two types of cations added in sufficient concentrations: transition metals, such as Co and Mn which have ionic radii similar to that of the ZnO matrix, and dopants with large ionic radii, such as Bi and Pr which segregate at grain boundaries and usually form intergranular phases. The present investigation was undertaken with the objective to clarify the role of dopants in an electrically active Pr and Co doped ZnO ceramic by studying the structure and chemistry of individual grain boundaries through high-resolution electron microscopy (HREM) and analytical electron microscopy (AEM).Bulk specimens containing 1 mol% Pr and 1 mol% Co were prepared by conventional sintering at 1400° C. Some samples followed an oxidative anneal at 650° C for 3 h to further enhance their electrical activity.

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46

da Silva, Mirele Costa, Hélio Lira Lucena, and Normanda Lino de Freitas. "Effect of Calcination Temperature in the Aluminum Oxide Synthesized by Pechini Method in the Citric Acid: Metal Cation Ratio of 2:1." Materials Science Forum 798-799 (June 2014): 139–44. http://dx.doi.org/10.4028/www.scientific.net/msf.798-799.139.

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Through the constant search by researchers to obtain materials with improved properties, literature has presented an annual increase in the number of articles that seek to optimize in the methodology used to prepare nanopowders. In this way, the aim of this work is to study how the calcined temperature (500, 600, 700, 800, 900, 1000, 1100 and 1200oC) changes the final properties of the alumina synthesized by Pechini method with citric acid: metallic cation ratio of 2:1. The alumina was characterized by thermal analysis, X-ray diffraction, particle size analysis and scanning electron microscopy. The results showed a total of mass loss of 61.6%. The alumina phase appear at 800°C of temperature, however the α-alumina only appear at 1100oC. The increase in the calcined temperature increases the crystallite size and the crystallinity of the alumina and the great value reached for the agglomerates diameter was 13μm for the alumina calcined at 1200oC. In relation to the morphology of the alumina, it was observed heterogeneous particles with different size and irregular geometry, with aspect of high density.

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Ponomarev, Ilia, and Peter Kroll. "Impact of Transition Metal Cations on the 29Si NMR Signal in Metal Oxide Glasses: A DFT Case Study of Hafnia Silica Glass." Journal of Physical Chemistry C 121, no. 43 (October 23, 2017): 24152–58. http://dx.doi.org/10.1021/acs.jpcc.7b06094.

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48

Abhyankar, Nandita, Amit Agrawal, Pragya Shrestha, Russell Maier, Robert D. McMichael, Jason Campbell, and Veronika Szalai. "Scalable microresonators for room-temperature detection of electron spin resonance from dilute, sub-nanoliter volume solids." Science Advances 6, no. 44 (October 2020): eabb0620. http://dx.doi.org/10.1126/sciadv.abb0620.

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We report a microresonator platform that allows room temperature detection of electron spins in volumes on the order of 100 pl, and demonstrate its utility to study low levels of dopants in perovskite oxides. We exploit the toroidal moment in a planar anapole, using a single unit of an anapole metamaterial architecture to produce a microwave resonance exhibiting a spatially confined magnetic field hotspot and simultaneously high quality-factor (Q-factor). To demonstrate the broad implementability of this design and its scalability to higher frequencies, we deploy the microresonators in a commercial electron paramagnetic resonance (EPR) spectrometer operating at 10 GHz and a NIST-built EPR spectrometer operating at 35 GHz. We report continuous-wave (CW) EPR spectra for various samples, including a dilute Mn2+-doped perovskite oxide, CaTiO3, and a transition metal complex, CuCl2.2H2O. The anapole microresonator presented here is expected to enable multifrequency EPR characterization of dopants and defects in perovskite oxide microcrystals and other volume-limited materials of technological importance.

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Chiromawa, Idris Muhammad, Amiruddin Shaari, Razif Razali, Summanuwa Timothy Ahams, and Mikailu Abdullahi. "Ab initio Investigation of the Structure and Electronic Properties of Normal Spinel Fe2SiO4." Malaysian Journal of Fundamental and Applied Sciences 17, no. 2 (April 29, 2021): 195–201. http://dx.doi.org/10.11113/mjfas.v17n2.2018.

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Transition metal spinel oxides have recently been predicted to create efficient transparent conducting oxides for optoelectronic devices. These compounds can be easily tuned by doping or defect to adapt their electronic or magnetic properties. However, their cation distribution is very complex and band structures are still subject to controversy. We propose a complete density functional theory investigation of fayalite (Fe2SiO4) spinel, using Generalized Gradient Approximation (GGA) and Local Density Approximation (LDA) in order to explain the electronic and structural properties of this material. A detailed study of their crystal structure and electronic structure is given and compared with experimental data. The lattice parameters calculated are in agreement with the lattice obtained experimentally. The band structure of Fe2SiO4 spinel without Coulomb parameter U shows that the bands close to Fermi energy appear to be a band metal, with four iron d-bands crossing the Fermi level, in spite of the fact that from the experiment it is found to be an insulator.

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Téllez, Helena, John Druce, John A. Kilner, and Tatsumi Ishihara. "Relating surface chemistry and oxygen surface exchange in LnBaCo2O5+δ air electrodes." Faraday Discussions 182 (2015): 145–57. http://dx.doi.org/10.1039/c5fd00027k.

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The surface and near-surface chemical composition of electroceramic materials often shows significant deviations from that of the bulk. In particular, layered materials, such as cation-ordered LnBaCo₂O_5+δ perovskites (Ln = lanthanide), undergo surface and sub-surface restructuring due to the segregation of the divalent alkaline-earth cation. These processes can take place during synthesis and processing steps (e.g. deposition, sintering or annealing), as well as at temperatures relevant for the operation of these materials as air electrodes in solid oxide fuel cells and electrolysers. Furthermore, the surface segregation in these double perovskites shows fast kinetics, starting at temperatures as low as 400 °C over short periods of time and leading to a decrease in the transition metal surface coverage exposed to the gas phase. In this work, we use a combination of stable isotope tracer labeling and surface-sensitive ion beam techniques to study the oxygen transport properties and their relationship with the surface chemistry in ordered LnBaCo₂O_5+δ perovskites. Time-of-Flight Secondary-Ion Mass Spectrometry (ToF-SIMS) combined with ¹⁸O isotope exchange was used to determine the oxygen tracer diffusion (D*) and surface exchange (k*) coefficients. Furthermore, Low Energy Ion Scattering (LEIS) was used for the analysis of the surface and near surface chemistry as it provides information from the first mono-atomic layer of the materials. In this way, we could relate the compositional modifications (e.g. cation segregation) taking place at the electrochemically-active surface during the exchange at high temperatures and the oxygen transport properties in double perovskite electrode materials to further our understanding of the mechanism of the surface exchange process.

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Journal articles on the topic 'Metal oxide cation study'

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