| 1. |
- Bazuev, Gennady V., et al.
(författare)
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The effect of manganese oxidation state on antiferromagnetic order in SrMn1-xSbxO3 (0 < x < 0.5) perovskite solid solutions
- 2019
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7526 .- 2050-7534. ; 7:7, s. 2085-2095
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Tidskriftsartikel (refereegranskat)abstract
- The mixed-valence manganese (Mn3+/Mn4+) solid solution, SrMn1-xSbxO3, was prepared for the first time. Two ranges of solid solutions were found: (1) SrMn1-xSbxO3 (0.025 x 0.09) with monoclinically distorted 6H-SrMnO3 polytype (sp. gr. C/2c) and (2) SrMn1-xSbxO3 (0.17 x 0.50) with a tetragonal unit cell (sp. gr. I4/mcm). Crystal structure refinement using X-ray and neutron powder diffraction data showed that the structure of the monoclinic solid solution consists of corner-sharing octahedra around sites occupied by manganese and antimony ions and face-sharing octahedra around sites occupied by manganese ions only, while the tetragonal solid solution has a random distribution of B-site cations. The presence of long-range antiferromagnetic order with a Neel temperature of about 148 K for SrMn0.80Sb0.20O3 and about 280 K for SrMn0.925Sb0.075O3 was found from the results of DC and AC susceptibility and neutron diffraction experiments at 5 K and 80 K.
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| 2. |
- Li, Zhuofeng, et al.
(författare)
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Inorganic/organic hybrid nanoparticles synthesized in a two-step radiation-driven process
- 2022
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 197, s. 110166-
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we have synthesized inorganic-organic hybrid nanoparticles via radiation synthesis of inorganic nanoparticles (Ag and CeO2) in aqueous dispersions containing radiation-synthesized poly(N-vinyl pyrrolidone) (PVP) nanogels (NG). The experiments show that there are strong interactions between the inorganic precursors (Ag+ and Ce3+) and the nanogel prior to irradiation. The two hybrid systems (Ag/NG and CeO2/NG) were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD confirms the formation of crystalline Ag and CeO2. TEM reveals that the inorganic nanoparticles are evenly distributed in/on the nanogel. Both XRD and TEM show that size of the inorganic particles is controlled by the nanogel.
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| 3. |
- Lousada, Cláudio M., et al.
(författare)
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Synthesis of copper hydride (CuH) from CuCO3·Cu(OH)2 – a path to electrically conductive thin films of Cu
- 2017
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 46:20, s. 6533-6543
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Tidskriftsartikel (refereegranskat)abstract
- The most common synthesis methods for copper hydride (CuH) employ hard ligands that lead to the formation of considerable amounts of metallic Cu as side-product. Here we explore a synthesis method for CuH(s) through the reaction of CuCO3 center dot Cu(OH)(2)(s) with hypophosphorous acid (H3PO2) in solution, via the formation of the intermediate Cu(H2PO2)(2)(aq) complex. The reaction products were characterized with XRD, FTIR and SEM at different reaction times, and the kinetics of the transformation of Cu(H2PO2)(2)(aq) to CuH(s) were followed with NMR and are discussed. We show that our synthesis method provides a simple way for obtaining large amounts of CuH(s) even when the synthesis is performed in air. Compared to the classic Wurtz method, where CuSO4 is used as an initial source of Cu2+, our synthesis produces CuH particles with less metallic Cu side-product. We attribute this to the fact that our reaction medium is free from the hard SO42- ligand that can disproportionate Cu(I). We discuss a mechanism for the reaction based on the known reactivity of the reagents and intermediates involved. We explored the possibility of using CuH(s) for making electrically conductive films. Tests that employed water-dispersed CuH particles show that this compound can be reduced with H3PO2 leading to electrically conductive thin films of Cu. These films were made on regular office paper and were found to be Ohmic conductors even after several weeks of exposure to ambient conditions. The fact that the synthesis reported here produces large amounts of CuH particles in aqueous media, with very little impurities, and the fact that these can then be converted to a stable electrically conductive film can open up new applications for CuH such as for printing electrically conductive films or manufacturing surface coatings.
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| 4. |
- Soroka, Inna L., et al.
(författare)
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Cuprous hydroxide in a solid form : does it exist?
- 2013
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Ingår i: Dalton Transactions. - : RSC Publishing. - 1477-9226 .- 1477-9234. ; 42:26, s. 9585-9594
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Tidskriftsartikel (refereegranskat)abstract
- Experimental studies have been performed to obtain the unknown cuprous hydroxide compound, which has recently been predicted theoretically (P. A. Korzhavyi et. al., Proc. Natl. Acad. Sci. U. S. A., 2012, 109, 686-689) to be metastable in a solid form. The reduction of Cu2+ with ferrous ethylenediamine tetraacetate (EDTA) results in the formation of a yellow powder precipitate whose composition corresponds to CuOH x H2O as probed by Fourier Transform Infrared Spectroscopy (FTIR) and cryogenic X-ray Photoelectron Spectroscopy (XPS). A similar compound has been found on the surface of Cu-CuH powder stored in water, as detected by XPS. The reduction of Cu2+ to Cu+ with free radicals in aqueous solutions results in a Cu2O precipitate as the final product, while the formation of the yellow cuprous hydroxide colloids may be an intermediate step. Our studies reveal that cuprous hydroxide does exist in a solid form and most likely has a hydrated form, CuOH x H2O.
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| 5. |
- Soroka, Inna L., et al.
(författare)
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Effect of synthesis temperature on the morphology and stability of copper(I) hydride nanoparticles
- 2013
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 15:42, s. 8450-8460
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Tidskriftsartikel (refereegranskat)abstract
- The effect of synthesis temperature on the morphology and stability of copper(I) hydride nanoparticles is studied. Monovalent copper hydride is obtained by reduction of Cu2+ sulfate with hypophosphorous acid at temperatures ranging from 45 degrees C to 75 degrees C. The CuH nanoparticles that formed have the shape of desert roses and are found to be very porous. The lattice parameter, size, and morphology of these nanoparticles depend on the synthesis temperature. CuH is a metastable compound. In air under ambient conditions, it first decomposes into copper metal and hydrogen gas and then the copper oxidizes. The copper particles that are left after the decomposition of copper(I) hydride in air have the same desert-rose morphology as the CuH nanoparticles. The copper particles with desert-rose shapes are observed for the first time. Copper(I) hydride decomposes slower in an aqueous environment than in air to form copper(I) oxide as the final product through formation of hydrated copper(I) hydroxide as an intermediate phase. The retarded decomposition of CuH in water may be explained by the formation of a protective CuOH center dot H2O layer on the surface of copper(I) hydride.
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| 6. |
- Soroka, Inna, et al.
(författare)
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Nonconvex Morphology of Metallic Copper Obtained via Nonclassical Crystallization of Copper Hydride
- 2019
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Ingår i: Crystal Growth & Design. - : AMER CHEMICAL SOC. - 1528-7483 .- 1528-7505. ; 19:9, s. 5275-5282
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Tidskriftsartikel (refereegranskat)abstract
- Copper particles with a desert rose morphology and high surface area were obtained via decomposition of a copper hydride whose particles possesses a similar shape. Copper hydride was synthesized by the reaction between copper sulfate and hypophosphorous acid at 50 degrees C. The different reaction steps of the copper hydride formation were monitored by two time-dependent techniques: in situ photon cross-correlation spectroscopy and ex -situ transmission electron microscopy. At the initial stage of the reaction, emulsion droplets of a particular size were formed, followed by the growth and agglomeration of copper hydride crystallites in the confinement of these droplets. The final structure consists of roselike shaped particles with an average size of about 217 +/- 53 nm arranged into chains. The surface area of these particles was estimated to be 41 +/- 8 m(2)/g. The nucleation and growth of the copper hydride occur via a nonclassical crystallization pathway.
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| 7. |
- Soroka, Inna, et al.
(författare)
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Radiation-induced synthesis of nanoscale Co-and Ni-based electro-catalysts on carbon for the oxygen reduction reaction
- 2017
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Ingår i: Dalton Transactions. - London, Storbritannien : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 46:30, s. 9995-10002
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Tidskriftsartikel (refereegranskat)abstract
- A facile synthesis of 3d-metal based electro-catalysts directly incorporated into a carbon support was carried out by.-radiation. Transition metals of period 4, i.e. Ni and Co, were precipitated and reduced from their respective salt solutions. The obtained materials were characterized by XRD, SEM, SQUID and the BET methods. Thereafter, the electrodes for fuel cells were fabricated out of synthesized material and their electrochemical performance for the oxygen reduction reaction in 6 M KOH was measured. Although the concentrations of Co and Ni in the electrode material were low (3.4% Co and 0.4% Ni) after reduction by irradiation, both the Ni and Co-based gas diffusion electrodes showed high catalytic activity for oxygen reduction both at room temperature and at 60 degrees C.
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| 8. |
- Yang, Yi, et al.
(författare)
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Tuning Catalytic Activity of Ni-Co Nanoparticles Synthesized by Gamma-Radiolytic Reduction of Acetate Aqueous Solutions
- 2023
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Ingår i: Advanced Materials Interfaces. - : Wiley-Blackwell. - 2196-7350. ; 10:17
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Tidskriftsartikel (refereegranskat)abstract
- Transition metal-based catalysts show great potential to replace Pt-based material in energy conversion devices thanks to their low cost, reasonable intrinsic activity, thermodynamic stability, and corrosion resistance. The electrochemical performance of such catalysts is sensitive to their composition and structure. Here, it is demonstrated that homogeneous alloy nanoparticles with varying Ni-to-Co ratio and controlled structure can be synthesized from aqueous Ni(Co) acetate solutions using a facile gamma-radiolytic reduction method. The obtained samples are found to possess defects that are ordered to form polytypes structures. The concentration of these defects depends on the Ni-to-Co ratio, as supported by the results of ab initio calculations. It is found that structural defects may influence the activity of catalysts toward the oxygen evolution reaction, while this effect is less pronounced with respect to the oxygen reduction reaction. At the same time, the activity of Ni-Co catalysts in the hydrogen evolution reaction is affected by formation of Ni-OH bonds on the surface rather than by the presence of structural defects. This study demonstrates that the composition of Ni-Co nanoparticles is an essential factor affecting their structure, and both composition and structure can be tuned to optimize electrochemical performance with respect to various catalytic reactions.
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| 9. |
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| 10. |
- Zschiesche, Hannes, et al.
(författare)
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Non-classical crystallization of CeO2 by means of in situ electron microscopy
- 2023
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372.
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Tidskriftsartikel (refereegranskat)abstract
- During in situ liquid-phase electron microscopy (LP-EM) observations, the application of different irradiation dose rates may considerably alter the chemistry of the studied solution and influence pro-cesses, in particular growth pathways. While many processes have been studied using LP-EM in the last decade, the extent of the influence of the electron beam is not always understood and comparisons with corresponding bulk experiments are lacking. Here, we employ the radiolytic oxidation of Ce3+ in aqueous solution as a model reaction for the in situ LP-EM study of the formation of CeO2 particles. We compare our findings to the results from our previous study where a larger volume of Ce3+ precursor solution was subjected to ?-irradiation. We systematically analyze the effects of the applied irradiation dose rates and the induced diffusion of Ce ions on the growth mechanisms and the morphology of ceria particles. Our results show that an eight orders of magnitude higher dose rate applied during homogeneous electron-radiation in LP-EM compared to the dose rate using gamma-radiation does not affect the CeO2 particle growth pathway despite the significant higher Ce3+ to Ce4+ oxidation rate. Moreover, in both cases highly ordered structures (mesocrystals) are formed. This finding is explained by the stepwise formation of ceria particles via an intermediate phase, a signature of non-classical crystallization. Furthermore, when irradiation is applied locally using LP scanning transmission electron microscopy (LP-STEM), the higher conversion rate induces Ce-ion concentration gradients affecting the CeO2 growth. The appearance of branched morphologies is associated with the change to diffusion limited growth.
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