Pattanayak, J and Rao, V S and Maiti, Himadri Sekhar (1989) Preparation and thermal-stability of manganese oxides obtained by precipitation from aqueous manganese sulfate-solution. Thermochimica Acta, 153. pp. 193-204. ISSN 0040-6031

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Abstract

Precipitated products of hydrolysis of manganese sulphate with sodium hydroxide were obtained by adding manganese sulphate solution to boiling solutions of sodium hydroxide of varying pH. The products are Mn3O4 at pH 9, γ-Mn2O3 at pH 13, and possibly a mixture of Mn3O4 and γ-Mn2O3 at pH 10. DTA of Mn3O4 prepared at pH 9 shows two endothermic peaks, at 70 and 965° C, and two exothermic peaks, at around 180 and 655° C. TG analysis of the sample indicates continuous weight loss from 30 to 600° C, considerable weight gain beyond this, and then a further abrupt loss in weight above 960° C. On heating, Mn3O4 oxidizes to α-Mn2O3 above 600° C, possibly through an intermediate phase of γ-Mn2O3 , which on further heating reduces to Mn3O4 above 960 °C. Specimens prepared at pH 10 consist of a mixture of Mn3O4 and γ-Mn2O3, whose thermal transformations are nearly identical to those of Mn3O4. However, γ-Mn2O3 prepared at pH 13 goes through a quite different thermal transformation sequence. DTA of this sample shows a broad endotherm at around 70° C and an equally broad exotherm at around 320° C. The corresponding TG curve shows weight loss from 30 to 750° C through a number of distinct steps. On heating, γ-Mn2O3 loses moisture up to 450° C, and above this temperature it converts to Mn3O4.

Item Type:	Article
Subjects:	Electronics
Divisions:	UNSPECIFIED
Depositing User:	Bidhan Chaudhuri
Date Deposited:	05 Dec 2013 11:42
Last Modified:	19 Mar 2016 18:05
URI:	http://cgcri.csircentral.net/id/eprint/2425

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