scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Development of Activated Alumina and its Effect on the Properties of Cement Free Castables Refractories

01 Jan 2009-Transactions of The Indian Ceramic Society (Taylor & Francis)-Vol. 68, Iss: 1, pp 31-34
TL;DR: In this article, the authors used X-ray diffraction analysis to identify the phases formed while SEM studies have been used to get an idea about the microstructure of the castable matrix.
Abstract: Activated alumina is prepared by thermal dehydration (300°-600°C) of chemically pure aluminium hydroxide. The prepared materials have been characterized by residual water content, BET surface area and hydraulic activity. These aluminas are incorporated in cement free castable batch. Important properties like bulk density, apparent porosity, linear change, cold compressive strength, strength retainment after thermal shock have been studied. X-ray diffraction analysis has been performed to identify the phases formed while SEM studies have been used to get an idea about the microstructure of the castable matrix.
Citations
More filters
Journal ArticleDOI
TL;DR: In this article, a new fabrication process for high-quality activated alumina with aluminum hydroxide is introduced, and the effects of aging and drying condition during the fabrication process affected the loss of ignition, the sedimentation time of the alumina suspension, as well as the surface area of the activated alumina.
Abstract: Activated alumina was fabricated with aluminum hydroxide in this study. High-purity alumina gel and boehmite were prepared from aluminum hydroxide by a hydrothermal process and fired to activate alumina having a surface area of 380 ~ 480 ㎡/g with less loss of ignition. The aging and drying condition during the fabrication process affected the loss of ignition, the sedimentation time of the alumina suspension, as well as the surface area of the activated alumina. For pellet-type activated alumina, the pre-fired alumina gel and boehmite were press-formed and fired at 400℃ and 550℃ for 6 h, respectively. The fired pellets showed a low density of 2.0 ~ 2.2 g/㎥ with 20% firing shrinkage and sufficient handling strength. In this study, a new fabrication process for high-quality activated alumina with aluminum hydroxide is introduced. The effects of the processing parameters on the activated alumina properties are also examined.

1 citations


Additional excerpts

  • ...(1) 수산화알루미늄으로부터 수열합성법으로 제조된 알 루미나 겔은 숙성온도와 건조조건이 분말의 현탁액 안정 성과 강열감량에 영향을 미쳤으며, 400 o C에서 6시간 소성 후 486 m 2 /g의 높은 표면적을 보이는 활성 알루미나 제조 가 가능하였다....

    [...]

Journal ArticleDOI
TL;DR: In this article, white tabular alumina aggregate, calcium aluminate cement bond material, microsilica, microfine alumina and nanometric zirconia-mullite precursors are used in the formulation.
Abstract: Nanometric zirconia-mullite precursors are synthesized through sol-gel route. Incorporation of these precursors in low cement castable refractories improves the bulk density, compressive strength and thermal shock resistance through formation of integrated matrix of castable at high temperature. In the present investigation, white tabular alumina aggregate, calcium aluminate cement bond material, microsilica, microfine alumina and nanometric zirconia-mullite precursors are used in the formulation. The important properties like bulk density, apparent porosity, linear change, cold crushing strength before and after thermal spalling of castables are studied. Phases are identified by X-ray diffraction analysis. SEM study has been used to analyze the integrated matrix of the castables.

1 citations

References
More filters
Journal ArticleDOI
William E. Lee, W. Vieira, Shaowei Zhang, K.G. Ahari1, Hossein Sarpoolaky, C. Parr 
TL;DR: In this article, the development from conventional high cement materials, through low cement and ultra-low cement castables to the present materials which may be entirely free of CAC is discussed.
Abstract: Castable refractories containing calcium aluminate cement (CAC) are used ubiquitously in a range of furnace lining applications in the iron and steel, cement, glass, ceramic, and petrochemical industries. This review outlines their development from conventional high cement materials, through low cement and ultra-low cement castables to the present materials which may be entirely free of CAC. Castables are defined in terms of both CaO content and installation procedure. Production routes, compositions, and microstructural evolution on hydration, setting, dehydration, and firing are described for pure CACs and castable refractories. The development of the low cement systems is discussed in terms of particle packing, dispersion, and rheology highlighting the influence of colloidal matrix additions of silica and alumina. Recent developments including cement free, self-flowing, shotcreting, and basic castables are described and the potential for carbon-containing systems evaluated.

280 citations

Journal ArticleDOI
TL;DR: In this article, the drying behavior of a hydratable alumina-bonded (HAB) refractory castable was evaluated by thermogravimetric tests and compared with an ultra-low cement composition (CAC).
Abstract: The drying behavior of a hydratable alumina-bonded (HAB) refractory castable was evaluated by thermogravimetric tests and compared with an ultra-low cement composition (CAC). The key properties of monolithic refractory dry-out performance, such as fluid permeability and mechanical strength, were also determined. The results showed significant differences among the drying profiles ascribed to the distinct hydrated binding phases, which affect the castables’ physical properties to a differing extent. The consequences of these features on the explosive spalling tendencies of the compositions are discussed.

90 citations

Journal ArticleDOI
TL;DR: In this paper, the reactivities of four hydratable aluminas were investigated by isothermal calorimetry and the rates of heat liberation during hydration from 15° to 55°C were determined.
Abstract: The reactivities of four hydratable aluminas were investigated. Rates of heat liberation during hydration from 15° to 55°C were determined by isothermal calorimetry. Rates of heat evolution show two peaks. An initial mixing peak is due to wetting and initial dissolution reactions. A second, main heat peak is associated with the hydration step. The hydration product was bayerite in all cases. Although the specific surface areas for the aluminas studied were as high as about 260 m2/g, they did not react completely. The origin of incomplete reaction is related to the microstructure of the hydratable alumina grains. The particles are approximately 10 μm in size. High surface areas are not the result of small particle size, but are the result of high internal surface areas. The Bayerite formation appears to block the porosity in the grains, thereby inhibiting further reaction.

81 citations

Journal ArticleDOI
TL;DR: In this paper, the hydration behavior of hydratable alumina in the presence of several forms of magnesia used for production of refractory castables was investigated with an X-ray diffractometer and calculated from thermogravimetric analysis.

48 citations

Journal Article
TL;DR: Colloidal silica and hydratable alumina as a combined binding system can bring better advantages to the processing and properties of refractory castables as mentioned in this paper, which can be used to improve the efficiency of castable processing.
Abstract: Colloidal silica and hydratable alumina as a combined binding system can bring better advantages to the processing and properties of refractory castables.

48 citations