Investigation on the thermal behaviour of Mg(NO3)2·6H2O I. The decomposition behaviour

Abstract

The decomposition mechanism of Mg(NO3) 2 . 6H20 was studied by means of simultaneous TG, DTG and DTA method combined with EGA technique under conventional and quasi isothermal~luasi isobaric conditions. It has been found that Mg(NO3) 2 9 6H20 melts at 89 ~ in a congruent way. The solution formed begins to boil at 147 ~ The water loss process of the salt hydrate and the decomposition process of the Mg(NO3)2 always overlap to some extent. Accordingly, Mg(NO3) 2 of stoichiometric composition cannot be prepared thermally, because the compound always contains some basic salt. The last part of water departs in the vicini;.y of 270 ~ with extreme rapidity. In contrast to expectations the compound decomposes in pure "self-generated" atmosphere at a temperature lower by about 80 ~ than in the presence of air which contains a small amount of the gaseous decomposition product.

Evolved gas analyses (TG/DTA–MS and TG–FTIR) on dehydration and pyrolysis of magnesium nitrate hexahydrate in air and nitrogen

“…The simultaneous TG/DTA measurements carried out in both air and nitrogen give TG and DTA curves corroborating very well with each other and with earlier measured curves in static air/self-generated [6,7] or in flowing argon [9] atmosphere. The salt, corresponding to its real [Mg(H 2 O) 6 ](NO 3 ) 2 structure melted congruently (and dissolved in its own water of crystallization) at around 99 8C.…”

“…Our evolved gas analysis study on [Mg(H 2 O) 6 ](NO 3 ) 2 , with simultaneous TG/DTA online coupled with mass spectrometry (TG/DTA-EGA-MS) and FTIR spectroscopic gas cell (TG-EGA-FTIR) was initiated by application of title compound 1 as sintering aid in Al 2 O 3 ceramics production, and dedicated to the blest memory of late Prof. Ferenc Paulik, who had formally studied this salt, as well [7]. During the sintering process, decomposition products (especially oxygen evolved) from magnesium nitrate may initialize the burning of organic type other additives used.…”

“…Thermogravimetric (TG) [1,2], differential thermal analysis (DTA) [3,4], differential scanning calorimetric (DSC) [5] studies were mainly focused on the temperature and heat of its congruent melting, possible intermediate hydrated forms and opportunities for formation of anhydrous salt. Simultaneous TG/DTA studies [6,7] show, that dehydration and pyrolysis processes are dependent on the sample size and heating rate, but cannot be separated at an anhydrous state. Under quasi-isothermal-quasi isobaric conditions [7] in self-generated atmosphere, the temperature of nitrate decomposition is significantly lower than expected, proven also by simultaneous thermogas-titrimetry (TGT) [7].…”

“…Simultaneous TG/DTA studies [6,7] show, that dehydration and pyrolysis processes are dependent on the sample size and heating rate, but cannot be separated at an anhydrous state. Under quasi-isothermal-quasi isobaric conditions [7] in self-generated atmosphere, the temperature of nitrate decomposition is significantly lower than expected, proven also by simultaneous thermogas-titrimetry (TGT) [7]. The decomposition products of 'anhydrous' compound in vacuum [8] contained small amounts of magnesium nitrite and nitrogen in addition to magnesium oxide, nitrogen dioxide and oxygen as the major products.…”

“…Magnesium nitrate hexahydrate, [Mg(H 2 O) 6 ](NO 3 ) 2 (1) a pyrotechnic material and widely used agent of burning organics to ash, had been studied several times by the means of thermal analysis [1][2][3][4][5][6][7][8][9]. Thermogravimetric (TG) [1,2], differential thermal analysis (DTA) [3,4], differential scanning calorimetric (DSC) [5] studies were mainly focused on the temperature and heat of its congruent melting, possible intermediate hydrated forms and opportunities for formation of anhydrous salt.…”