10 research outputs found
SyntĂ©za a charakterizace Co5Cr2(P2O7)4 – NovĂ˝ pyrofosfát jako barvĂcĂ substance
A new pyrophosphate(V) of the formula Co5Cr2(P2O7)4 was obtained in the system Co2P2O7-Cr4(P2O7)3 as a result of solid-state reactions taking place between different reactants. The new compound crystallizes in the orthorhombic system and belongs to the family of pyrophosphates of the general formula M5(II+)M2(III+)(P2O7)4 and is probably isostructural with Fe5(II+)Fe2(III+)(P2O7)4. Powder diffraction pattern, infrared spectrum and SEM image of the new compound were presented. As a new potential inorganic pigment, Co5Cr2(P2O7)4 was tested for its thermal stability, particle size distribution and colour properties, which were studied both for powder and after introduction into organic matrix and leadless ceramic glaze. The colour of Co5Cr2(P2O7)4 powder was defined as deep grey with the colour coordinates L*/a*/b* = 60.63/-1.42/-3.41 and according to the hue angle (h degrees = 247.39°) it belongs to the blue region. Co5Cr2(P2O7)4, with its relatively high thermal stability (tm = 1230 +/- 10 °C) and appropriate colour properties, is a good candidate to be used as inorganic pigment for colouring of acrylic paints. In the case of leadless glaze, the obtained compound acts as a dye.NovĂ˝ pyrofosfát (V) chemickĂ©ho sloĹľenĂ Co5Cr2(P2O7)4 byl zĂskán v systĂ©mu Co2P2O7 – Cr4(P2O7)3 jako vĂ˝sledek reakcĂ v pevnĂ© fázi probĂhajĂcĂch mezi rĹŻznĂ˝mi reaktanty. Nová slouÄŤenina krystalizuje v ortorombickĂ©m systĂ©mu a patřà do rodiny pyrofosfátĹŻ s obecnĂ˝m vzorcem M5(II+)M2(III+)(P2O7)4 a je pravdÄ›podobnÄ› isostrukturálnĂ s Fe5(II+)Fe2(III+)(P2O7)4. Nová slouÄŤenina je pĹ™edstavena záznamem práškovĂ© difrakce, infraÄŤervenĂ˝m spektrem a SEM obrazem. Co5Cr2(P2O7)4 jako potencionálnĂ anorganickĂ˝ pigment, byl testován z pohledu jeho tepelnĂ© stability, distribuce velikosti částic a barevnĂ˝ch vlastnostĂ, kterĂ© byly studovány jak pro prášek, tak po zavedenĂ do organickĂ© matrice a bezolovnatĂ© keramickĂ© glazury. Barva prášku Co5Cr2(P2O7)4 byla definována jako tmavÄ› šedá s barevnĂ˝mi souĹ™adnicemi L*/a*/b* = 60,63 / -1,42 / -3,41 a podle Ăşhlu odstĂnu (h° = 247,39°) patřà do modrĂ© oblasti. Co5Cr2(P2O7)4, s jeho relativnÄ› vysokou tepelnou stabilitou (tm = 1230 ± 10 °C) a vhodnĂ˝mi barevnĂ˝mi vlastnostmi, je dobrĂ˝m kandidátem pro pouĹľitĂ jako anorganickĂ˝ pigment pro vybarvovánĂ akrylovĂ˝ch barev. V pĹ™ĂpadÄ› bezolovnatĂ© glazury pĹŻsobĂ zĂskaná slouÄŤenina jako barvivo
Magnetic frustration in lyonsite-type vanadates in FeVO
Six phases crystallizing in the lyonsite-type structure were synthesized by solid-state reaction between nFeVO4 and (1–n)Co3V2O8, where n = 0.73, 0.7143, 0.6667, 0.5843, 0.57, and 0.56. DC magnetic susceptibility in high-temperature range (T  > 100 K) was found to follow the Curie–Weiss law with negative and large value of the Curie–Weiss temperature. The effective magnetic moments were slightly bigger than for high-spin Co2+ and Fe3+ ions. Spin-glass-like features observed in magnetic FC/ZFC susceptibilities at low temperatures (T  < 15 K) could be the result of a huge magnetocrystalline anisotropy of randomly oriented crystallites or magnetic nanoclusters in the powder samples, or they could be due to magnetic frustration arising from competition of ferromagnetic (FM) and antiferromagnetic (AFM) exchange interactions. The presence of FM component with a large coercive field and strong magnetic remanence in samples with large Co content was evidenced at low temperature. Weak and very broad electron paramagnetic resonance (EPR) spectra were analyzed by decomposition on Lorentzian components and were attributed to magnetic spin clusters or metallic precipitates not involved in bulk magnetism registered in magnetization measurements. In addition, for n = 0.7143, 0.6667 samples, the much narrower line was due to the V4+ magnetic defects connected with oxygen vacancies
Složky systému Co3Cr4 (PO4)6-Cr(PO3)3 a sloučenina CoCr2(P2O7)2 jako nový keramický pigment
The compounds: Co3Cr4(PO4)6, Cr(PO3)3 and CoCr2(P2O7)2 were tested for possible application as ceramics and anticorrosive pigments. They were characterized by SEM analysis, determination of particle size distribution and thermal stability. All phosphates were thermally stable up to 1100 °C so they can be used for colouring of middle-temperature ceramic glazes. The gravimetrical determination of corrosive loss of steel sheets and other corrosion factors characterizing the resistance to corrosion in an aqueous environment of the phosphates were discussed. The colour properties of the compounds were studied for powders and pigments introduced into organic matrix and several single-firing ceramic glazes. It is shown that the investigated phosphates can be used as ceramic pigments only for leadless single-firing ceramic glaze. The optimum pigment concentration sufficient for colouring glaze was close to 2 wt %. Generally, the examined phosphates have interesting green, greenish-blue and cyan shades.SlouÄŤeniny: Co3Cr4(PO4)6, Cr(PO3)3 a CoCr2(P2O7)2 byly testovány pro moĹľnĂ© aplikaÄŤnà účely jako keramickĂ© a antikoroznĂ pigmenty. Byly charakterizovány analĂ˝zou SEM, stanovenĂm distribuce velikosti částic a termickĂ© stability. Všechny fosfáty byly termicky stabilnĂ aĹľ do 1100 °C, takĹľe je lze pouĹľĂt pro barvenĂ stĹ™ednÄ› teplotnĂch keramickĂ˝ch glazur. Diskutovány byly: gravimetrická stanovenĂ koroznĂch ĂşbytkĹŻ ocelovĂ˝ch plechĹŻ a dalšĂch koroznĂch faktorĹŻ charakterizujĂcĂch odolnost fosfátĹŻ proti korozi ve vodnĂ©m prostĹ™edĂ. BarevnĂ© vlastnosti slouÄŤenin byly studovány pro prášky a pigmenty dispergovanĂ© do organickĂ© matrice a nÄ›kolik jedno-vĂ˝palovĂ˝ch keramickĂ˝ch glazur. Ukázalo se, Ĺľe zkoumanĂ© fosfáty lze pouĹľĂt jako keramickĂ© pigmenty pouze pro bezolovnatou jedno-vĂ˝palovou keramickou glazuru. OptimálnĂ koncentrace pigmentu dostateÄŤná pro zbarvenĂ glazury byla tĂ©měř 2 hm. %. ZkoušenĂ© fosfáty majĂ obecnÄ› zajĂmavĂ© zelenĂ©, zelenkavÄ› modrĂ© a azurovĂ© odstĂny