Effect of WO3 on Hydration Resistance of CaO Aggregates Prepared by Thermal Decomposition

doi:10.19691/j.cnki.1004-4493.2020.03.006

China's Refractories ›› 2020, Vol. 29 ›› Issue (3): 32-37.DOI: 10.19691/j.cnki.1004-4493.2020.03.006

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Effect of WO₃ on Hydration Resistance of CaO Aggregates Prepared by Thermal Decomposition

Tao ZHANG, Yaowu WEI^*(), Nan LI, Bingrong LI, Jinhu WANG

The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China

Online:2020-09-15 Published:2020-09-15
Contact: Yaowu WEI
About author:Zhang Tao is a PhD candidate in School of Materials and Metallurgy, Wuhan University of Science and Technology. His research interests include smelting refractories for new technology and superalloy refining. He has published more than ten articles so far, five of which have been included by SCI.

Abstract

Abstract:

The application of CaO refractories was limited due to their poor hydration resistance. Introducing appropriate additive is an effective way to improve their hydration resistance. Additive WO₃ was introduced in the preparation of CaO aggregates using a calcination method in this study. The introduction of WO₃ decreased the apparent porosity of CaO aggregates and promoted the grain growth of CaO by the formation of liquid at high temperatures. The average grain size of the specimens with 0.4 mass% WO₃ and treated at 1 550 °C was increased to 51.6 μm comparing to 33.5 μm of those without WO₃ additive. As a result, the hydration resistance of CaO aggregates was significantly improved. Besides, WO₃ sublimated easily, therefore, less WO₃ remained after the heat treatment. The further increase of WO₃ addition had little effect on the hydration resistance of CaO specimens.

Key words: CaO, WO₃, calcination, hydration resistance

Tao ZHANG, Yaowu WEI, Nan LI, Bingrong LI, Jinhu WANG. Effect of WO₃ on Hydration Resistance of CaO Aggregates Prepared by Thermal Decomposition[J]. China's Refractories, 2020, 29(3): 32-37.

Figures/Tables 13

Table 1 Chemical composition of raw material /mass%

Raw material	SiO₂	Al₂O₃	Fe₂O₃	CaO	MgO	K₂O	TiO₂	IL
Active lime	0.55	0.27	0.09	97.43	0.51	0.06	0.007	0.92

Table 2 Batch composition of specimens /mass%

Specimen number	W0	W0.4	W0.7	W1.0
WO₃	0	0.4	0.7	1.0
Ca(OH)₂	100	99.6	99.3	99

Fig. 1 Linear shrinkage of specimens with different WO3 additions

Fig. 2 Bulk density and apparent porosity of specimens with different WO3 additions

Fig. 3 Pore diameter distribution of specimens

Fig. 4 Weight gain rates of the specimens

Fig. 5 XRD patterns of specimens with different WO3 additions or fired at different temperatures

Fig. 6 CaO-WO3 binary phase diagram

Fig. 7 SEM of specimens with different WO3 additions treated at 1 550 °C

Table 3 Typical results of EDS analysis at Fig. 7 /at%

	Ca	O	W	Mg
1	24.08	67.65	8.27	-
2	34.13	64.45	-	1.41

Table 4 Average grain size of specimens with different WO3 additions, 1 550 °C /μm

Specimens	W0	W0.4	W0.7	W1.0
Grain size	33.5	51.6	51.3	50.4

Fig. 8 SEM of specimens with 0.7 mass% WO3 fired at different temperatures

Table 5 The average grain size of specimens (W0.7) sintered at different temperatures

Temperature /℃	1 450	1 550	1 650
Grain size /μm	53.6	51.3	56.6

References 17

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Effect of WO₃ on Hydration Resistance of CaO Aggregates Prepared by Thermal Decomposition

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