A convenient route for the synthesis of complex metal oxides employing solid-solution precursors

Vidyasagar, K.; Gopalakrishnan, J.; Rao, C. N. R.

doi:10.1021/ic00177a008

Cited by 130 publications

(39 citation statements)

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“…Ca CoO transforms to the P3 structure. Vidyasagar et al have previously reported the preparation of Ca CoO by the decomposition of a carbonate precursor (29). The monoclinic unit cell of their product, however, was significantly larger than the one reported here, and it included several reflections not observed in our X-ray powder patterns.…”

Section: Ion Exchange Productscontrasting

confidence: 63%

Topotactic Routes to Layered Calcium Cobalt Oxides

Cushing

1998

Journal of Solid State Chemistry

100

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Section: Ion Exchange Productscontrasting

confidence: 63%

Topotactic Routes to Layered Calcium Cobalt Oxides

Cushing

1998

Journal of Solid State Chemistry

100

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“…Thermal decomposition of mixed cation (Mg,Ca,Mn)-siderites have been investigated under a wide variety of conditions, not only because of their geochemical importance, but also because they provide a convenient synthetic route to the preparation of complex metal oxides via the so-called 'solid-solution-precursor' method (Vidyasagar et al, 1984;Vidyasagar et al, 1985). The results of such studies are summarized in Table 6 and invariably demonstrate that thermal decomposition yields a mixed metal oxide phase as the product 17 .…”

Section: Prior Studiesmentioning

confidence: 99%

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Thomas‐Keprta

Clemett

McKay

et al. 2009

Geochimica et Cosmochimica Acta

108

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The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe 3 O 4 ) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterization of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the carbonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates.

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“…2) were synthesized according to the previously reported procedure. [21] In a 100 mL beaker, an aqueous solution of NaHCO 3 was made (4.2 g in 30 mL of water). The solution was maintained at 80 8C with constant stirring using a magnetic pellet.…”

Section: Experimental Section Materialsmentioning

confidence: 99%

Investigations of the Conversion of Inorganic Carbonates to Methane

2009

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Inorganic carbonates, which occur abundantly on earth, constitute an inexpensive natural source of carbon. Therefore, the direct conversion of these carbonates into methane is of considerable importance. Thermal decomposition of transition metal carbonates with the composition MCa(CO(3))(2) (where M=Co, Ni, or Fe, and M/Ca is 1:1) and M(1)M(2)Ca(CO(3))(3) (where M(1)M(2)=CoNi, NiFe, or FeCo, and M(1)/M(2)/Ca is 1:1:2) shows that the reduced transition metals in combination with metal oxide nanoparticles (e.g., Co/CoO/CaO) act as catalysts for the conversion of CO(2) (produced from the carbonates) into methane. The favorable decomposition conditions include heating at 550 degrees C in an H(2) atmosphere for 5-6 h. These catalysts are found to be excellent for the methanation of CaCO(3), exhibiting high efficiency in the utilization of H(2) with 100 % conversion and 100 % selectivity. The best catalyst for conversion of CaCO(3) into CH(4) is Co/CoO/CaO. There are also indications that similar catalysts based on Fe may yield higher hydrocarbons.

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A convenient route for the synthesis of complex metal oxides employing solid-solution precursors

Cited by 130 publications

References 1 publication

Topotactic Routes to Layered Calcium Cobalt Oxides

Topotactic Routes to Layered Calcium Cobalt Oxides

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Investigations of the Conversion of Inorganic Carbonates to Methane

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