Kinetics of thermal decomposition of siderite: effect of particle size

Jagtap, S.B.; Pande, Anita R.; Gokarn, A.N.

doi:10.1016/0301-7516(92)90068-8

Cited by 31 publications

(17 citation statements)

References 5 publications

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“…While the kinetics of the thermal decomposition of siderite and its solid-solutions have been extensively studied (Dhupe and Gokarn, 1990;Jagtap et al, 1992;Kubas and Szalkowicz, 1971;Zakharov and Adonyi, 1986) great care needs to be taken in interpreting the results of such studies since there are many discrepancies between datasets. The reasons appear to be two fold: first, reaction kinetics are sensitive to the physical parameters of the sample, e.g., degree of crystallinity, surface area, presence of impurities, particles size, and the degree of compaction or porosity.…”

Section: Kinetically Controlled Carbonate Decompositionbrearley (2003mentioning

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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Section: Kinetically Controlled Carbonate Decompositionbrearley (2003mentioning

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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“…Similar results were reported by previous researchers. 5,10) However, it was observed that the particle size effect is slight below the 67 mm molybenite particle size, as shown in the figure. The similar trends were also obtained at other temperatures considered in this research.…”

Section: 9)mentioning

confidence: 87%

Kinetics of the Oxidative Roasting of Low Grade Mongolian Molybdenite Concentrate

et al. 2009

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Molybdenite concentrate is the major mineral for the molybdenum industry. The industrial processing of molybdenite concentrate is first to convert to technical grade molybdenum trioxide by its oxidative roasting, followed by its purification by distillation or its ammonia leaching. In the present research, detailed experimental results for the oxidative roasting of low grade Mongolian molybdenite concentrate are presented. The experiments were carried out in the temperature range of 778 to 838 K under air atmosphere by using a thermogravimetric analysis technique. The particle size of the molybdenite concentrate was varied between 53 and 103 mm. As an example of the oxidative roasting of low grade Mongolian molybdenite concentrate, more than 95% of 53 mm particle size molybdenite was converted to molybdenum trioxide in 40 min at 823 K. The Jander equation was found to be useful in describing the rates of the oxidative roasting, which had an activation energy of 215.0 to 259.3 kJ/mol (51.4 to 62.0 kcal/mol) for various sizes, such as 53 mm, 67 mm and 103 mm.

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“…The mean particle size might have some effect; the possible effect of the spread of particle size in the sample appears, however, scarcely to have been considered [14]. Already, the effect of particle size on quantitative differential thermal analysis is generally considered in organic materials [8,9,26,27] and biomass sample, Pinus radiata [28]. Depending on various parameters such as particle size and density, surrounding temperature, oxygen concentration in the surrounding flow, the combustion of biomass particle may take place sequentially or simultaneously [29].…”

Section: Discussionmentioning

confidence: 97%

“…Previous studies have stated that the thermal decomposition and phase composition in thermal analysis are known to be influenced by particle size of the sample [8,9]. In the most popular thermoanalytical methods, such as TG, DTA, and DSC, powder samples are often the subject of investigation [10].…”

Section: Introductionmentioning

confidence: 99%

Thermal analysis of green algae for comparing relationship between particle size and heat evolved

Kang

Yoon

2014

Biomass Conv. Bioref.

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The thermal properties affected by particle size of microbial cell were investigated by the simultaneous thermogravimetry (TG) and differential thermal analysis (DTA). The particle size, which could affect the heat evolved, occurred from the combustion of the microbial cells. The model microorganism used in this study is Nostoc, a genus of flamentous, heterocystous, and cyanobacteria, known as a freshwater microalga, which can accumulate a large amount of lipid in the cell. As a result, the marked difference in heat energy between the different particle sizes of microbial sample was detected in the temperature range from 310 to 351°C. So, the two-step linear temperature program is used for resolving the overlapping exothermic peaks in the DTA curves in the temperature range from 310 to 315°C. The heat evolved from 45 μm-sized particle sample in this temperature range was 3.78±0.19 kJ/g which was 1.1-to 1.4-fold greater than those from the other particle size samples. The heat evolved occurred in 310-351°C was inversely proportional to the particle size of dried microbial cells. In conclusion, exothermic heat per dry sample mass (kJ/g) in the temperature range from 310 to 351°C is highly dependent on the particle size of dried microbial cell.

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Kinetics of thermal decomposition of siderite: effect of particle size

Cited by 31 publications

References 5 publications

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Kinetics of the Oxidative Roasting of Low Grade Mongolian Molybdenite Concentrate

Thermal analysis of green algae for comparing relationship between particle size and heat evolved

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