Thermische Analyse eines chloridhaltigen basischen Cobaltcarbonates

Abstract

The thermal decomposition of a chloride and water-containing basic cobalt carbonate was studied. As a first step, crystal water is lost without change of structure. The following decomposition steps overlap and proceed in different ways, depending on the atmosphere over the sample: under nitrogen, chloride volatilizes as HCI and COCI2; in air, oxidation occurs. CoO and Co304, respectively, are the final solid products at 700--800 ~ .In der Literatur wird ~iber verschiedene basische Cobaltcarbonate berichtet, die durch die allgemeine Formel COCO3 9 xCo(OH)2 ~ YH20 (x = 1, 1.25, 1.5, 2; y = 0, 0.25, 0.5, 1.25, 1.5) beschrieben werden k6nnen [1][2][3][4][5][6][7]. R6ntgendaten dieser Verbindungen sind in der ASTM-Kartei nicht erfa~t, jedoch werden in zwei Publikationen von Feitknecht et al. [8,9]. Strichdiagramme von zwei verschiedenen basischen Cobaltcarbonaten mitgeteilt, deren Zusammensetzung aber nicht angegeben wird. Aus dem Context kann geschlul~folgert werden, daE es sich in dem einen Fall [9] um ein wasserfreies oder wasserhaltiges CoCO 3 ~ Co(OH) 2 handelt.Die thermische Zersetzung eines CoCO 3 ~ Co(OH) 2 ~ 0.5 H20 wurde yon Avramov und Betschev [ 10] untersucht.Im Rahmen unserer Arbeiten ~iber die Hydrolyse von Eisen(lll)-Salzen mittels Harnstoff in Gegenwart yon Fremdmetallionen sind wir auf ein kristallines basisches Cobaltcarbonat mit relativ hohem Chloridgehalt gestol~en, das wegen seiner exzellenten Nadelform f~r die Entwicklung magnetischer Pigmente auf Cobaltbasis interessant sein k6nnte. 0ber die Ergebnisse der thermischen Zersetzung dieser Verbindung, die mit denen einer deutlich weniger gut kristallisierten Substanz geringeren Chloridgehaltes verglichen werden, soil nachfolgend berichtet werden. ExperimentellesDas basische Cobaltcarbonat A wurde durch homogene F~llung mittels Harnstoffhydrolyse aus 0.3 molarer Cobalt(ll)-chloridl6sung bei 90 ~ hergestellt. Die Vergleichssubstanz B erhielten wir nach langsamer F~llung einer gleichkonzentrierten L6sung mit Sodal6sung und f~infst(indigem AItern bei 80 ~ Beide Verbindungen wurden je

Dimensional Control of Cobalt-hydroxide-carbonate Nanorods and Their Thermal Conversion to One-Dimensional Arrays of Co3O4 Nanoparticles

“…Except the cobalt-basic-carbonates, other possible precipitates, such as Co(OH) 2 , CoCO 3 , and Co(OH) x Cl 2 - x · n H 2 O, were not detected (verified by XRD analysis). The formation of chloride-containing basic-carbonates could also be ruled out, on the basis of our FTIR analysis (in Figure ).…”

“…Since the molar ratio of Co 2+ /OH - /CO 3 2- in our starting solutions is 1:1:0.5, which is identical to the stoichiometric requirement of this compound, it is not surprising that the compounds formed match the reported XRD pattern. Upon the addition of OH - and CO 3 2- anions into the CoCl 2 solution, the following reaction should take place: Due to its complexation ability with cobalt, however, Cl - anions present in the metal solution could also be incorporated into the precipitates to form basic chlorides [Co(OH) x Cl 2 - x · n H 2 O], , or chloride-containing basic carbonate compounds [Co(OH) x Cl y (CO 3 ) 0.5(2- x - y ) · n H 2 O] . The former compounds usually have a well-crystallized hexagonal structure, while the latter retain the same orthorhombic phase of cobalt-basic-carbonate.…”

A quarter of a century after its synthesis and with >200 papers based on its use, `Co(CO3)0.5(OH)·0.11H2O′ proves to be Co6(CO3)2(OH)8·H2O from synchrotron powder diffraction data

“…But they have to accommodate ten H atoms per cell, two of them forming the unique water molecule in the Co 6 (CO 3 ) 2 (OH) 8 ÁH 2 O formula (Z = 1), but they are difficult to locate since the site multiplicities of the O atoms are either 3 or 6. (CO 3 ) 0.35 Cl 0.20 (OH) 1.10 Á1.74H 2 O (Lorenz & Kempe, 1984), was observed to have a powder pattern very similar to that of the title compound, so that it can be concluded that both are very probably isostructural. It should be noted that for the Cl/ (OH)-based compound, the Co/(CO 3 ) ratio is close to 3, as expected now that CCH has been reformulated (it was originally 2).…”

Fabrication of morphology and crystal structure controlled nanorod and nanosheet cobalt hydroxide based on the difference of oxygen-solubility between water and methanol, and conversion into Co3O4

“…Meanwhile, the peak intensity ratios of the present films (a, c) are different from those of powders (b, d) and the reported pattern. 17 Here, the peaks marked (#) are relatively stronger, which indicates an occurrence of the preferential orientation of the films and is related to the orientation of the original CCCH or CNCH films on the substrate. Based on the TEM images (see Fig.…”