A Unique Mechanochemical Redox Reaction Yielding Nanostructured Double Perovskite Sr2_{2}FeMoO6_{6} With an Extraordinarily High Degree of Anti-Site Disorder

Strontium ferromolybdate, Sr(2)FeMoO(6), is an important member of the family of double perovskites with the possible technological applications in the field of spintronics and solid oxide fuel cells. Its preparation via a multi-step ceramic route or various wet chemistry-based routes is notoriously difficult. The present work demonstrates that Sr(2)FeMoO(6) can be mechanosynthesized at ambient temperature in air directly from its precursors (SrO, α-Fe, MoO(3)) in the form of nanostructured powders, without the need for solvents and/or calcination under controlled oxygen fugacity. The mechanically induced evolution of the Sr(2)FeMoO(6) phase and the far-from-equilibrium structural state of the reaction product are systematically monitored with XRD and a variety of spectroscopic techniques including Raman spectroscopy, (57)Fe Mössbauer spectroscopy, and X-ray photoelectron spectroscopy. The unique extensive oxidation of iron species (Fe(0) → Fe(3+)) with simultaneous reduction of Mo cations (Mo(6+) → Mo(5+)), occuring during the mechanosynthesis of Sr(2)FeMoO(6), is attributed to the mechanically triggered formation of tiny metallic iron nanoparticles in superparamagnetic state with a large reaction surface and a high oxidation affinity, whose steady presence in the reaction mixture of the milled educts initiates/promotes the swift redox reaction. High-resolution transmission electron microscopy observations reveal that the mechanosynthesized Sr(2)FeMoO(6), even after its moderate thermal treatment at 923 K for 30 min in air, exhibits the nanostructured nature with the average particle size of 21(4) nm. At the short-range scale, the nanostructure of the as-prepared Sr(2)FeMoO(6) is characterized by both, the strongly distorted geometry of the constituent FeO(6) octahedra and the extraordinarily high degree of anti-site disorder. The degree of anti-site disorder ASD = 0.5, derived independently from the present experimental XRD, Mössbauer, and SQUID magnetization data, corresponds to the completely random distribution of Fe(3+) and Mo(5+) cations over the sites of octahedral coordination provided by the double perovskite structure. Moreover, the fully anti-site disordered Sr(2)FeMoO(6) nanoparticles exhibit superparamagnetism with the blocking temperature T (B) = 240 K and the deteriorated effective magnetic moment μ = 0.055 μ (B) per formula unit

Characteristics of specialists treating hypothyroid patients:the “THESIS” collaborative

Introduction: Thyroid specialists influence how hypothyroid patients are treated, including patients managed in primary care. Given that physician characteristics influence patient care, this study aimed to explore thyroid specialist profiles and associations with geo-economic factors. Methods: Thyroid specialists from 28 countries were invited to respond to a questionnaire, Treatment of Hypothyroidism in Europe by Specialists: an International Survey (THESIS). Geographic regions were defined according to the United Nations Statistics Division. The national economic status was estimated using World Bank data on the gross national income per capita (GNI per capita). Results: 5,695 valid responses were received (response rate 33·0%). The mean age was 49 years, and 65·0% were female. The proportion of female respondents was lowest in Northern (45·6%) and highest in Eastern Europe (77·2%) (p &lt;0·001). Respondent work volume, university affiliation and private practice differed significantly between countries (p&lt;0·001). Age and GNI per capita were correlated inversely with the proportion of female respondents (p&lt;0·01). GNI per capita was inversely related to the proportion of respondents working exclusively in private practice (p&lt;0·011) and the proportion of respondents who treated &gt;100 patients annually (p&lt;0·01). Discussion: THESIS has demonstrated differences in characteristics of thyroid specialists at national and regional levels, strongly associated with GNI per capita. Hypothyroid patients in middle-income countries are more likely to encounter female thyroid specialists working in private practice, with a high workload, compared to high-income countries. Whether these differences influence the quality of care and patient satisfaction is unknown, but merits further study.</p

Effect of mechanical activation and thermal processing of Al/Ni mixtures on hydrodehalogenation of AOX dissolved in aqueous solution

Předkládaná práce se zaobírá moţností aplikace mechanicky aktivovaných směsí neušlechtilého kovu (konkrétně hliníku) a hydrogenačního katalyzátoru (niklu) pro hydrodehalogenační odbourávání aromatických halogenovaných látek z vod. Mechanická aktivace představuje časově a ekonomicky nenáročný proces, při kterém dochází mletím k aktivaci kovů, hlavně vlivem zvětšování specifického povrchu i vznikem různých defektů v jejich krystalové struktuře. Termicky upravené aktivované směsi Al-Ni můţou několikanásobně sníţit celkové náklady na reduktivní dehalogenaci studovaných látek oproti doposud vyuţívané komerčně dostupné Raneyho slitině (50:50 wt.% Al-Ni).The presented thesis deals with the possibility of the application of mechanically activated metal mixtures (aluminum and nickel) for the removal of halogenated aromatic compounds from an aqueous environment. Mechanical activation is a process, in which the compounds are activated by milling, mainly due to an increase in a specific surface area and the formation of various defects in their crystal structure. Thermally treated activated Al-Ni mixtures may lead to a decrease in the total costs of reductive dehalogenation process for selected analytes in comparison with commercially available Raney type Al-Ni alloys; such as the 50:50 wt.% Al-Ni alloy.Fakulta chemicko-technologickáDokončená práce s úspěšnou obhajobo

Disorder of the dimeric TCNQ–TCNQ unit in the crystal structure of [Ni(bpy)3]2(TCNQ–TCNQ)(TCNQ)2·6H2O (TCNQ is 7,7,8,8-tetracyanoquinodimethane)

Crystallization from an aqueous methanol system composed of Ni(NO3)2, 2,2′-bipyridine (bpy) and LiTCNQ (TCNQ is 7,7,8,8-tetracyanoquinodimethane) in a 1:3:2 molar ratio yielded single crystals of bis[tris(2,2′-bipyridine-κ2N,N′)nickel(II)] bis(7,7,8,8-tetracyanoquinodimethane radical anion) bi[7,7,8,8-tetracyanoquinodimethanide] hexahydrate, [Ni(C10H8N2)3]2(C24H8N8)(C12H4N4)2·6H2O or [Ni(bpy)3]2(TCNQ–TCNQ)(TCNQ)2·6H2O. The crystal structure comprises [Ni(bpy)3]2+ complex cations, two centrosymmetric crystallographically independent TCNQ·− anion radicals with π-stacked exo groups, and an additional dimeric TCNQ–TCNQ unit which comprises 75.3 (9)% of a σ-dimerized (TCNQ–TCNQ)2− dianion and 24.7 (9)% of two TCNQ·− anion radicals with tightly π-stacked exo groups. The title complex represents the first example of an NiII complex containing a σ-dimerized (TCNQ–TCNQ)2− dianion. Disordered solvent water molecules present in the crystal structure participate in hydrogen-bonding interactions

Rychlá hydrodehalogenace chlorovaných benzoových kyselin s použitím mechano-termicky připravené Raneyovy slitiny zahrnující rychlejší průběh hydrodehalogenačního procesu

The present study reports on the degradation of chlorinated benzoic acids (CBAs), commonly present in the environment as pollutants, by a hydrodehalogenation reaction utilizing the Raney Al-Ni alloy (50:50 wt% Al:Ni). The hydrodehalogenation reaction using the Raney Al-Ni alloy has already been proven as an efficient tool for fast and efficient degradation of halogenated persistent organic pollutants (POPs). Herein, the nano-structured Raney Al-Ni alloy was prepared by an alternative mechano-thermal approach starting from pure elements in a form of powders. The prepared alloy was characterized by X-ray diffractometry, scanning electron microscopy, particle size distribution, and active surface area analyses. The properties of the material were compared with a commercial sample of the same alloy prepared by the atomization process. The activity of the synthesized alloy was evaluated as removal efficiency and a rate of dehalogenation of three different CBAs - 2-chlorobenzoic acid, 2,6-dichlorobenzoic acid, and 2,3,6-trichlorobenzoic acid (trysben); used in the past as an herbicide. Dehalogenation of all three tested CBAs yielded benzoic acid as the only product and followed the first-order reaction kinetics. Compared to the commercially available alloy, enhanced kinetics of CBAs removal was achieved, owing to the solid-state properties of the mechano-thermally prepared alloy.Práce srovnává účinek komerční Al-Ni slitiny s materiálem připraveným mechanotermickou cestou z výchozích práškových kovů. Připravený materiál bych charakterizován s pomocí XRD, velikosti částic a specifického povrchu a otestován

Mechanochemical Synthesis of Nickel Mono- and Diselenide: Characterization and Electrical and Optical Properties

Nickel mono- (NiSe) and diselenide (NiSe2) were produced from stoichiometric mixtures of powdered Ni and Se precursors by the one-step, undemanding mechanochemical reactions. The process was carried out by high-energy milling for 30 and 120 min in a planetary ball mill. The kinetics of the reactions were documented, and the products were studied in terms of their crystal structure, morphology, electrical, and optical properties. X-ray powder diffraction confirmed that NiSe has hexagonal and NiSe2 cubic crystal structure with an average crystallite size of 10.5 nm for NiSe and 13.3 nm for NiSe2. Their physical properties were characterized by the specific surface area measurements and particle size distribution analysis. Transmission electron microscopy showed that the prepared materials contain nanoparticles of irregular shape, which are agglomerated into clusters of about 1&ndash;2 &mu;m in diameter. The first original values of electrical conductivity, resistivity, and sheet resistance of nickel selenides synthesized by milling were measured. The obtained bandgap energy values determined using UV&ndash;Vis spectroscopy confirmed their potential use in photovoltaics. Photoluminescence spectroscopy revealed weak luminescence activity of the materials. Such synthesis of nickel selenides can easily be carried out on a large scale by milling in an industrial mill, as was verified earlier for copper selenide synthesis

Temperature-dependent dimerization of TCNQ anion-radical in [Ni(bpy)3]2(TCNQ–TCNQ)(TCNQ)2·6H2O: Single-crystal structure, magnetic and quantum chemical study

The crystal structure of [Ni(bpy)3]2(TCNQ–TCNQ)(TCNQ)2·6H2O (1) was studied by X-ray single-crystal structure analysis at 145 K and 100 K. The crystal structures of 1 at these two temperatures are essentially the same as the crystal structure studied previously at 200 K: the structure is built up of [Ni(bpy)3]2+ complex cations, two centrosymmetric crystallographically independent TCNQ·- anion-radicals, disordered σ- and π-dimerized (TCNQ)2 units, and water molecules of crystallization. Lowering the temperature from 200 K, via 145 K–100 K has shown that at lower temperatures the proportions of σ- and π-dimerization in the disordered (TCNQ)2 unit are shifted in favor of σ-dimerization; moreover, variation of the weaker C–C σ-bond formed upon dimerization was observed. In addition, lowering the temperature led to a shortening of the distance between the two crystallographically independent anion-radicals which are stacked along the b-axis with overlapped exo groups. The σ- and π-dimerization in the disordered (TCNQ)2 unit was studied by quantum chemical calculations which showed smallest energy difference for σ and π-dimer at 200 K with respect to 145 K and 100 K in line with a lowest proportion of the dimerization observed experimentally. Temperature-dependent (1.8–270 K) magnetic study of 1 has shown the contribution of Ni(II) ions (S = 1) and the contribution of four S = 1/2 species carried by TCNQ radicals at higher temperatures, strongly coupled by antiferromagnetic (AFM) exchange interaction at 270 K while at low temperature a negligible contribution of TNCQ radical spins was observed.Financial support from Slovak Grant Agencies (APVV-18-0016, VEGA 1/0189/22), internal grants of P. J. Šafárik University in Košice (VVGS-PF-2021-1772 and VVGS-2020-1657) and by the Spanish Ministerio de Ciencia e Innovación (Grant PGC2018–093451-B-I00), the European Union Regional Development Fund, (FEDER), and the Diputación General de Aragón, Project M4, E11_20R.Peer reviewe

Syntheses, crystal structures and magnetic properties of complexes based on [Ni(L-L)3]2+ complex cations with dimethylderivatives of 2,2′-bipyridine and TCNQ

From the aqueous-methanolic systems Ni(NO3)2 – LiTCNQ – 5,5′-dmbpy and Ni(NO3)2 – LiTCNQ – 4,4′-dmbpy three novel complexes [Ni(5,5′-dmbpy)3](TCNQ)2 (1), [Ni(4,4′-dmbpy)3](TCNQ)2 (2) and [Ni(4,4′-dmbpy)3]2(TCNQ-TCNQ)(TCNQ)2∙0.60H2O (3), were isolated in single crystal form. The new compounds were identified using chemical analyses and IR spectroscopy. Single crystal studies of all samples corroborated their compositions and have shown that their ionic structures contain the complex cations [Ni(5,5′-dmbpy)]2+ (1) or [Ni(4,4′-dmbpy)]2+ (2 and 3). The anionic parts of the respective crystal structures 1–3 are formed by TCNQ⋅- anion-radicals and in 3 also by a σ-dimerized dianion (TCNQ-TCNQ)2- with a C-C distance of 1.663(5) Å. The supramolecular structures are governed by weak hydrogen bonding interactions. The variable-temperature (2–300 K) magnetic studies of 1 and 3 confirmed the presence of magnetically active Ni(II) atoms with S = 1 and TCNQ⋅- anion-radicals with S = 1/2 while the (TCNQ-TCNQ)2- dianion is magnetically silent. The magnetic behavior was described by a complex magnetic model assuming strong antiferromagnetic interactions between some TCNQ⋅- anion-radicals.Slovak grant agencies (APVV-14-0078, APVV-14-0073 and VEGA 1/0063/17) are acknowledged for the financial support of this work. The financial support from ERDF (European Regional Development Fund) under the contract Nos. ITMS26220120047 and ITMS26220220186 is acknowledged. Funding from the Spanish Ministry of Economy and Competitivity, Grant MAT2015-68200-C2-1-P with FEDER support, is acknowledged. We thank Dr. Beatriz Diosdado from the University of Zaragoza for X-ray data collection of complex 2. One of the authors (LV) thanks P. J. Šafárik University in Košice (Slovakia) for financial support of her post-doctoral position.Peer reviewe

Promoted crystallisation and cationic ordering in thermoelectric Cu 26 V 2 Sn 6 S 32 colusite by eccentric vibratory ball milling

International audienceA pristine colusite Cu26V2Sn6S32 was successfully synthesised on a 100 g scale via mechanochemical reaction in an industrial eccentric vibratory ball mill followed by spark plasma sintering (SPS) at 873 K. The milling of elemental precursors from 1 up to 12 hours was performed and the prepared samples were investigated in details by X-ray powder diffraction, Mössbauer spectroscopy, scanning electron microscopy, and thermoelectric property measurements. The results point to the formation of a high purity and high crystallinity non-exsoluted colusite phase after SPS process (4 # 3 , a = 10.7614(1) Å) in the case of a 12 h A c c e p t e d M a n u s c r i p t milled sample. In comparison, samples milled for 1-6 h displayed small quantities of binary Cu-S phases and vanadium core-shell inclusions, leading to a V-poor/Sn-rich colusite with higher degree of structural disorder. These samples exhibit lower electrical conductivity and Seebeck coefficient while an increase in the total thermal conductivity is observed. This phenomenon is explained by a higher reactivity and grain size reduction upon prolonged milling and by a weak evolution of the chemical composition from a partly disordered V-poor/Sn-rich colusite phase to a well-ordered stoichiometric Cu26V2Sn6S32 colusite, which leads to a decrease in carrier concentration. For all samples, the calculated PF values, around 0.7-0.8 mW m-1 K-2 at 700 K, are comparable to the values previously achieved for mechanochemically synthesised Cu26V2Sn6S32 in laboratory mills. This approach thus serves as an example of scaling-up possibility for sulphur-based TE materials and supports their future large-scale deployment

Promoted crystallisation and cationic ordering in thermoelectric Cu 26 V 2 Sn 6 S 32 colusite by eccentric vibratory ball milling

International audienceA pristine colusite Cu26V2Sn6S32 was successfully synthesised on a 100 g scale via mechanochemical reaction in an industrial eccentric vibratory ball mill followed by spark plasma sintering (SPS) at 873 K. The milling of elemental precursors from 1 up to 12 hours was performed and the prepared samples were investigated in details by X-ray powder diffraction, Mössbauer spectroscopy, scanning electron microscopy, and thermoelectric property measurements. The results point to the formation of a high purity and high crystallinity non-exsoluted colusite phase after SPS process (4 # 3 , a = 10.7614(1) Å) in the case of a 12 h A c c e p t e d M a n u s c r i p t milled sample. In comparison, samples milled for 1-6 h displayed small quantities of binary Cu-S phases and vanadium core-shell inclusions, leading to a V-poor/Sn-rich colusite with higher degree of structural disorder. These samples exhibit lower electrical conductivity and Seebeck coefficient while an increase in the total thermal conductivity is observed. This phenomenon is explained by a higher reactivity and grain size reduction upon prolonged milling and by a weak evolution of the chemical composition from a partly disordered V-poor/Sn-rich colusite phase to a well-ordered stoichiometric Cu26V2Sn6S32 colusite, which leads to a decrease in carrier concentration. For all samples, the calculated PF values, around 0.7-0.8 mW m-1 K-2 at 700 K, are comparable to the values previously achieved for mechanochemically synthesised Cu26V2Sn6S32 in laboratory mills. This approach thus serves as an example of scaling-up possibility for sulphur-based TE materials and supports their future large-scale deployment