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.

Castable refractory concretes

Samples of red mud, by-products of alumina production from bauxite, are studied in the 120–1400°C interval. An extensive characterization was performed by thermal and X-ray diffraction analyses. The identification of gaseous species released upon heating was carried out by coupling the thermal analizer with a gas-chromatographic/mass spectrometer. Density evolution was also determined as a function of the heat treatment. Results indicate primary H2O release from aluminium hydroxides, followed by carbonate decomposition with CO2 evolution below 900°C. Alkaline oxides, mainly CaO and Na2O, lead to the formation of Ca3Al2O6 and NaAlSiO4 between 900 and 1100°C. At the highest temperatures, reduction of Fe3+ to Fe2+, involving O2 release, promotes the formation of Fe2TiO4, with the disappearance of the rutile-TiO2 phase. The various solid state reactions, ascertained at different stages of the heating process, and possible mass balances are discussed with reference to the state diagrams of principal red mud components.

Bauxite ‘red mud’ in the ceramic industry. Part 1: thermal behaviour

Spinel-containing alumina-based refractory castables

Some potential uses of red mud as a raw component in clay mixtures for ceramic bodies production are presented. The influence of increasing amounts of red mud on the forming procedure, sintering and final properties was analyzed. Samples were produced by uniaxial pressing and slip casting. Two different clays are used as basic materials, the former being currently employed for the production of bricks by extrusion, the second — almost pure Kaolin — for high quality ceramic manufacturing. In both cases the addition of red mud led to more deflocculated solid–water systems and an increase of the critical moisture content. Mixtures prepared with the first clay and red mud loads up to 50% were fired at 850°C. The red mud content did not influence the sample porosity while determining a strength decrease attributed to the inertness of red mud at the working temperature. Samples produced using the second clay and red mud (0 – 20%) were fired at 950 and 1050°C. The addition of red mud determined increases of density and flexural strength which can be accounted for by the formation of a larger amount of glassy phase at higher red mud contents. The results of this work indicate excellent perspectives for using ‘red mud’ as raw material in mixtures with clay for the production of ceramic bodies.

Bauxite ‘red mud’ in the ceramic industry. Part 2: production of clay-based ceramics

The adhesion of γ-alumina washcoats on cordierite honeycombs was investigated with the aim to correlate the adhesion properties to the characteristics of the deposited powders, and, determine the conditions that can ensure integrity and endurance of the substrate/washcoat system under the severe operating conditions of an automobile catalytic system. It is shown that adhesion depends primarily on the particle size of the deposited powder. Depending on the production method, some powders have the form of large agglomerates and, if deposited as such upon the honeycombs, exhibit very poor adhesion properties. Reduction of the agglomerates' size down to the order of a few (2–5) microns is necessary in order to ensure adhesion comparable to that of commercial catalysts. Particles of colloidal dimensions exhibit excellent adhesion to the support, provided that reduction of the agglomerates' size that they form during calcination, takes place before deposition.

The effect of powder characteristics on washcoat quality. Part I: Alumina washcoats

Introduction. History of Alumina Chemicals (L.D. Hart). World Production and Economics of Alumina Chemicals (L.H. Baumgardner). Fundamental Properties of Alumina Chemicals. Nomenclature, Preparation, and Properties of Aluminum Oxides, Oxide Hydroxides, and Trihydroxides (K. Wefers). Mechanical Properties of Alumina (R.C. Bradt and W.D. Scott). Colloidal Properties of Alumina (A. Bleier). Phase Equilibria of Alumina (L.P. Cook). Current Commercial Production Processes, Products, and Applications. Production Processes, Properties, and Applications for Aluminum-Containing Hydroxides (L.L. Musselman). Production Processes, Properties, and Applications for Activated and Catalytic Aluminas (K.P. Goodboy and J.C. Downing). Production Processes, Properties, and Applications for Calcined and High-Purity Aluminas (T.J. Carbone). Production Processes, Properties, and Applications for Tabular Alumina Refractory Aggregates (G. MacZura). Production Processes, Properties, and Applications for Calcium Aluminate Cements (J.E. Kopanda and G. MacZura). Gallium (A. Pearson and C.N. Cochran) Analytical Procedures for Alumina Chemicals -Editor's Note. State of the Art Assessments in Applications Utilizing Alumina Chemicals. Alumina Chemicals as Additives for Paper, Dentrifices, Paints, Coatings, Rubbers, and Plastics with Emphasis on Fire-Retardant Products (L.L. Musselman). Activated Alumina Desiccants (R.D. Woosley). Selective Adsorption Processes (H.L. Fleming and K.P. Goodboy). Water-Treatment Products and Processes (H.L. Fleming). Claus Catalysts and Alumina Catalyst Materials and Their Application (J.C. Downing and K.P. Goodboy). Monolithic Catalyst Systems (I.M. Lachman). Pelleted Catalyst Systems (W.S. Briggs). Electrical Properties of Alumina Ceramics (R.H. Insley). Electronic Ceramics (B. Schwartz). Alumina Usage in Electric Power Generation and Storage (W.T. Bakker). Alumina in Electrical Porcelain (R.H. Lester). Dinnerware Manufacture and Use in the United States (R.J. Beals). Advanced Ceramics Involving Alumina (J.B. Wachtman Jr. and R.A. Haber). Alumina as a Biomedical Material (J.W. Boretos). Alumina in Coatings (L.A. Ketron). Alumina as a Composite Material (G. Fisher). Alumina in Glasses and Glass-Ceramics (J.F. MacDowell). Alumina Powder Production by Aerosol Processes (T.T. Kodas and A. Sood). Refractory Ceramic Fiber (R.D. Smith). Fused Alumina-Pure and Alloyed-as an Abrasive and Refractory Material (P. Cichy). High-Alumina Refractories for Steelmaking in Europe (M. Koltermann). High-Alumina Refractories for Iron- and Steelmaking in Japan (N. Nameishi and T. Matsumura). Use of High-Alumina Refractories in the U.S. Steel Industry (D.H. Hubble). Petroleum and Petrochemical Applications for Refractories (M.S. Crowley and R.E. Fisher). Refractories Used for Aluminum Processing (G.E. Graddy Jr. and D.A. Weirauch Jr.). The Use of Alumina in Refractories for Melting Glass (E.A. Thomas). Refractories Used for Investment Casting of High-Temperature Alloys (M.Guerra Jr.). Alumina in Monolithic Refractories (L.P. Krietz and R.E. Fisher). Space Vehicle Thermal Protection (D.B. Leiser). Industrial Hygiene and Toxicology of Alumina Chemicals. The Aluminas and Health (B.D. Dinman). Long-Range Future Technology-The Role of Alumina Chemicals. The Future of Alumina Chemicals in Europe (P. Rothenbuehler, Y. Lazennec and L.D. Hart). Long Range Future Trends: The Role of Alumina Chemicals-The Japanese Viewpoint (H. Yanagida). The Future Role of Alumina in Ceramics Technology (M.J. Cima and H.K. Bowen). Long-Range Technology-The Role of Alumina Chemicals as Seen from the Japanese Viewpoint (S. Kazama). Present Situation and Future Technology of Alumina Chemicals in Japan (K. Yamada). A View of the Future for Alumina Chemicals (J.P. Starr). Glossary. A Glossary of Terms Most Frequently Used in Alumina Technology (S.C. Carniglia and B.J. Beadle).

L. D. Hart

Papers

Alumina chemicals : science and technology handbook