Decomposition of Na2CO3 by Interaction with SiO2 in Mold Flux of Steel Continuous Casting.

Abstract

The effect of SiO 2 addition on the decomposition of Na 2 CO 3 was investigated using the thermo-gravimetric and differential scanning calorimetric method (TG-DSC). Addition of SiO 2 greatly enhanced the decomposition of Na 2 CO 3 . The main decomposition reaction began to take place at a eutectic temperature of the Na 2 O-SiO 2 system (800°C). The initial decomposition product was identified as Na 2 SiO 3 , irrespective of the mixing ratio of Na 2 CO 3 to SiO 2 . The governing reaction of the decomposition was concluded to be Na 2 CO 3 ϩSiO 2 ϭNa 2 SiO 3 (s)ϩCO 2 (g). The decomposition rate was independent of the Na 2 CO 3 /SiO 2 mixing ratio until either one has completely been exhausted and hence was not available any more for the above reaction. If surplus Na 2 CO 3 exists after formation of Na 2 SiO 3 by reacting with all SiO 2 , the remaining Na 2 CO 3 decomposes partly by reacting with Na 2 SiO 3 to form Na 6 Si 2 O 7 and partly by thermal self-decomposition. A liquid layer that was formed at the carbonate/additive interface facilitated the decomposition of the carbonates. The melting behavior of a mold flux was greatly influenced by the lowest eutectic temperature that a mold flux system can exhibit. The apparent activation energy of the decomposition of Na 2 CO 3 in existence with SiO 2 was estimated to be 426 kJ · mol Ϫ1.

Decomposition of Li2CO3 by Interaction with SiO2 in Mold Flux of Steel Continuous Casting

“…Recently the present authors have studied, by employing a thermogravimetric and differential scanning calorimetric (TG-DSC) technique, the decomposition of Na 2 CO 3 on its own, with carbon and SiO 2 , and decomposition of Li 2 CO 3 on its own and with carbon. 4,5) They found thermal decomposition of Na 2 CO 3 being sluggish up to 1 200°C and formation of Na 2 O · SiO 2 both of which are in agreement with the report of Nakamura et al…”

Thermal behaviour of light lanthanide(III) complexes with 2,3-pyridinedicarboxylic acid

“…At 1023 K the whole amount of the substance forms Na 2 CO 3 , so the TG shows plateau. The melting point of formed disodium carbonate is visible at 1123 K (literature data 1124 K) [40,41]. Up to melting point, the weight loss of Na 2 CO 3 is extremely slow creating Na 2 O and CO 2 .…”

“…1) [40]. From the TG curves of complexes it is difficult to indicate the accurate mass loss connected with formation of oxocarbonates which starts at about 673 K and ends with oxide formation above 973 K. The anhydrous cerium(III) complex decomposes strictly to the cerium oxide CeO 2 .…”

Synthesis of Lithium Orthosilicate and Fabrication of Pebbles by the Solid-State Reaction Process

“…Kim et al [11] studied the decomposition of Li 2 CO 3 by interaction with SiO 2 in the molar ratio of 2:1. Donne et al [12] synthesised Li 4 SiO 4 by melting and fabricated pebbles by quenching droplets of liquid material to room temperature.…”

“…Li 4 SiO 4 is considered as an alternative or even better solid ceramic breeder as compared to Li 2 TiO 3 , especially for the high lithium density (0.54 g/cm 3 for Li 4 SiO 4 and 0.43 g/cm 3 for Li 2 TiO 3 ). Till date much work has been done on Li 4 SiO 4 synthesis, pebble fabrication, characterisation [5][6][7][8][9][10][11][12][13][14][15][16][17], tritium-release behaviour and its reprocessing [18]. Spray melting process is the process studied by many of the investigators for simultaneous synthesis and pebble fabrication [9][10][11][12][13][14].…”