Influence of oxide additives and firing atmosphere on the recrystallization of chromium oxide

Degtyareva, É. V.; Kravchenko, V. I.; Alapin, B. G.; Krivoruchko, P. P.

doi:10.1007/bf01395849

Cited by 5 publications

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“…Sintering the specimens at 1450 o C does not lead to the expected enlargement of the crystals. However, significant recrystallization is observed above 1600°C, resulting in the mation of MgCr 2 O 4 spinel at the particle boundaries of the chrome oxide [7]. It was observed that open porosity was eliminated when magnesite-chromite bricks are sintered above 1750 o C [8].…”

Section: Introductionmentioning

confidence: 97%

“…Several studies have demonstrated that rapid recrystallization of refractory oxides occurs at the final stage of sintering, and the size of the crystals is affected by the pore [7]. It is possible to control recrystallization by making certain additions.…”

Section: Introductionmentioning

confidence: 98%

“…It is possible to control recrystallization by making certain additions. Additives entering into the magnesite-chromite composition contribute to the growth of Cr 2 O 3 grains [7]. Studies show that the addition of TiO 2 contributes to the recrystallization of Cr 2 O 3 [6,7].…”

Section: Introductionmentioning

confidence: 98%

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Investigation of TiO2-added refractory brick properties from calcined magnesite raw material

Kalpaklı

2008

Refract Ind Ceram

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This paper is the second part of a study on recycling magnesite and chromite ore (in the 0 -10 -3 m fraction) powder, which remains as a production process waste. In this work, 90% magnesite-10% chromite composition was used as a brick composition. Compaction pressure, sintering temperature, ratio of TiO 2 addition, and influence of bonding type on refractory properties were examined. In refractory brick production, one of the most important parameters that affects the properties of the product is the particle size distribution of the blend. Experiments show that using a magnesite particle size of -10 -3 m and a chromite particle size of -63´10 -6 m affects the properties of the product in a positive way. Experiment blends with the particle sizes selected above were used. Magnesite ore was used in experiments after calcination at 1200°C for four hours. In the experiments we mention, MgCl 2 and MgSO 4 solutions were used as a bonding agent, as a result of which a 6% bonding ratio of MgCl 2 and MgSO 4 solutions was determined as optimum. The effect of compacting pressure on the refractory properties was studied, and the optimum compacting pressure was determined as 180 MPa. For bricks prepared using calcined magnesite, the optimum sintering temperature was found to be 1750°C. The positive effect of TiO 2 addition on the magnesite chrome refractory brick structure has been reported in the literature. Thus, 1, 3, 5, and 7 wt.% TiO 2 ratios were used in the blend, and the refractory properties were positively affected by the 3% TiO 2 addition. Taking the result of the MgCl 2 and MgSO 4 bonding solution into consideration, it is clear that the refractory properties of brick can be improved by using a mixture of MgCl 2 and MgSO 4 bonding solutions. In light of the above concept, bonding mixtures with 1:3, 1:5, and 1:10 ratios were prepared, and these bonding mixtures were studies as a bonding material. The experimental results show that the cold crushing strength (CCS) and volume density of bricks increase, whereas the porosity decreases when a 1:5 ratio of MgCl 2 and MgSO 4 in the bonding mixture and 3% TiO 2 addition were used. Microstructural study of the produced bricks was done using scanning electron microscope (SEM). In addition to this, the phases forming the structure of brick were examined via x-ray diagrams of the material. In bricks where a mixture of a 1:5 MgCl 2 : MgSO 4 bonding solution was used as bonding agent and 3% TiO 2 was added, spinel (magnochromite (MgCr 2 O 4 )), magnesium orthotitanate (Mg 2 TiO 4 ), monticellite (CaMgSiO 4 ), and forsterite (Mg 2 SiO 4 ) phases were found. The perovskite phase was not observed during the experimental study.

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 98%