Symposium CN
Refractories: Meeting Refractory Industry Needs of Today and It’s Future Challenges

Session CN-1 - Raw Materials Needs

CN-1:IL01  Fabrication and Characterization of Highly Porous Alumina using Platelets
SHINOBU HASHIMOTO, SAWAO HONDA, YUSUKE DAIKO, YUJI IWAMOTO, Nagoya Institute of Technology, Department of Life Science and Applied Chemistry, Nagoya, Japan

For steel-making refractories, porous alumina clinkers which also work as insulation materials are expected to reduce the energy costs. Alumina platelets were candidate materials for fabrication of porous alumina with a high porosity due to the formation of card-house structure. In this study, commercial alumina platelets which were produced by an autoclaved method were used. With use of the alumina platelets, novel two topics were noticed. First was fabrication of porous alumina bodies with anisotropic texture. Their properties such as mechanical strength and thermal conduction were different in direction. The maximum variation in the thermal conductivity of the same alumina body with changing direction was 11.6 W·m-1·K-1. Secondly, fabrication of highly porous alumina body using organic material (yeast fungi) as a pore forming agent with low thermal conductivity was performed. The thermal conductivity of the 72 % porosity derived from platelets was 0.50 W·m-1·K-1 at room temperature.


CN-1:IL02  Raw Material Needs for Modern Clean Steel Technology and Refractories Engineering
A. BUHR, Almatis GmbH, Frankfurt, Germany; R. BRUCKHAUS, Dillinger, Dillingen, Germany; R. FANDRICH, Stahlinstitut VDEh, Düsseldorf, Germany

The permanent development of steel producing technology is a main driver for the development of new and improved refractories, because of the high market share of steel refractories in the range of 60 to 70% and the harsh conditions for refractories in the steel making processes. A constant engineering of refractories is needed to cope with new and more demanding requirements in the steel making process. The first part of the paper briefly discusses trends in the steel making technology, and the second part describes examples how modern engineered refractories provide solutions for economical production of high quality steels. A special focus is given on secondary metallurgy and the steel ladle lining with synthetic alumina raw material based refractories.


CN-1:L04  Characterization of Porous Alumina Bodies Fabricated by High-temperature Evaporation of Boric Acid with Sodium Impurity
DAIMU MUTO, SHINOBU HASHIMOTO, SAWAO HONDA, YUSUKE DAIKO, YUJI IWAMOTO, Nagoya Institute of Technology, Department of Life Science and Applied Chemistry, Nagoya, Japan

For steel making refractories, a novel porous alumina bodies fabricated by evaporation of chemical impurities at highly temperatures has been studied. As the impurities, both boron hydroxide and sodium carbonate were added into a starting alumina hydroxide compact body. The starting aluminum hydroxide powder compacts with various ratios of both boron hydroxide and sodium carbonate were heated at various temperatures for 1 h to form porous alumina bodies. During heating, the formed borate compounds with sodium seemed to be liquid phase, so that each alumina particle could grow as platelet in shape. Although the sodium inside the compacts has been completely evaporated till 1400 °C, the liquid compound of boron remained over 1400 °C. Hence alumina platelets grown with a card house structure, resulted in keeping the highly porosity of the alumina body. After heating at 1600 °C for 1 h, the remaining boron oxide has been completely evaporated and sintering between the alumina particles began to start to decrease the porosity. Finally, the compressive strength and porosity of the porous alumina bodies after heating at 1700 °C for 1 h were 0.8 MPa and 64 %, respectively. The resultant porous alumina bodies are expected to be used as castable porous clinkers.

 
Session CN-2 - Product Testing and Quality Control

CN-2:IL01  Metastability, Energy Landscapes, and the Search for New Refractory Materials
A. NAVROTSKY, University of California, Davis, CA, USA

Many possible refractories, especially containing several anions (C,N,O) have been suggested theoretically but are difficult to access experimentally due to slow reaction rates, vaporization of components and other synthetic difficulties. Workarounds involving organometallic precursors have obtained materials such as polymer-derived ceramics (PDC) in the Si-C-O-N system. Calorimetric studies of their enthalpies of formation have shown many of them to be energetically stable with respect to crystalline binary components, suggesting that they should be accessible by other, simpler, means. PDC-like nanomaterials were produced by laser ablation of silica in an acetylene atmosphere. In refractory oxide systems such as pyrochlores, analogous complexity in structure and energetics has been found, with temperature, composition, grinding and radiation damage leading to different degrees of crystallinity and cation and anion ordering. Such different structures can persist even on heating. A general principle emerges, namely that structure at the nanoscale within refractory ceramics is more complex than previously imagined, and its variation leads to a rich structural and energy landscape of closely related phases which may provide new refractory materials with tailored properties.


CN-2:IL02  New Approach of Corrosion Kinetics: High-temperature Time-resolved Raman and XRD Techniques and Applications
E. DE BILBAO¹, M. DOMBROWSKI¹, R. MICHEL¹, M. RAMZI AMMAR¹, A. CAZINARES¹, H. PILLIERE², P. SIMON¹, J. POIRIER¹, ¹CEMHTI CNRS Univ. Orleans, Orleans, France; ²Thermo Fisher Scientific Inel, France

The understanding of the ceramic powders reactivity at high temperature remains of outstanding importance. This is the case of refractory ceramics, operating at high temperature. Nevertheless, their understanding requires the development of new in situ experimental techniques well adapted to these extreme conditions. This talk will present high-temperature time-resolved Raman and XRD techniques used to study phase transformation in solid state reaction or in solid/liquid reaction. High-temperature X-ray diffraction was used to follow the formation of aluminates monomineral layer formation in the corrosion of alumina by Al2O3-CaO-SiO2 slag. Using a diffractometer equiped with a high temperature chamber and a curved position sensitive detector makes it possible to quantify the contents of CaAl2O4, CaAl4O7, and CaAl12O19 while Al2O3 powder reacts with CaO-Al2O3-SiO2 molten oxides at temperatures up to 1600°C. High-temperature Raman spectroscopy was used to investigate the solid state formation of Mg2SiO4 and MgSiO3 from MgO and SiO2 up to 1500°C. The spectra were recorded using a spectrometer based on a pulsed system to remove thermal emission. Both original studies shown that HT-RS and HT-XRD are powerful tools to investigate kinetics of phase transformation at high temperature.


CN-2:L03  Three Stage Creep Behavior of MgO Containing Ordinary Refractories in Tension and Compression 
S. SCHACHNER, S. JIN, H. HARMUTH, D. GRUBER, Montanuniversitaet, Leoben, Austria

Under thermo-mechanical loading, ordinary refractories may experience creep of primary stage and further proceed to the secondary or/and tertiary stages. To take into account this behavior, three stages refractory creep shall be investigated experimentally. Two advanced high temperature creep testing devices, a compressive one and a tensile one, were used to determine the three stages creep in a reasonable time. The Norton-Bailey creep equations and an inverse identification procedure were applied for characterization. A pure magnesia refractory was studied at elevated temperatures under sustainable loads, and its respective creep parameters of each stage at different temperatures were determined. A comparative study of creep parameters and creep rates was performed between the pure magnesia refractory and a magnesia chromite refractory. The results also demonstrate the significant asymmetrical creep behavior in tension and compression for both magnesia containing materials. This leads to an urgent requirement of a material constitutive model accounting for refractory creep asymmetry in thermomechanical modelling activities.


CN-2:L04  Laser Induced Thermal Cycling and Hot Thermal Shock on Refractories Using TOM_wave
H. FRIEDRICH, J. BABER, F. RAETHER, Fraunhofer Institute Silicate Research ISC, Fraunhofer-Center for High Temperature Materials and Design HTL, Bayreuth, Germany

Modern steel and ceramic production requires reliable and long lasting refractories. To minimize energy consumption the best available material has to be chosen. In order to get better and more representative high-temperature data the Fraunhofer Center HTL has been developing Thermo-Optical Measuring (TOM) devices for more than 20 years. The TOM method is based on a contact free measurement set-up with advanced sensor techniques which are applied in well-defined and controlled temperature fields and combined with specific software tools for data evaluation. Recent developments are driven by higher resolution, additional measurands and last but not least larger samples sizes with a volume of about 10 to 20 cm³, which is satisfactory to measure even heterogeneous refractory materials. In the present publication TOM_wave will be presented, which is focused on the measurement of thermal shock resistance, thermal diffusivity and other high temperature material properties by laser heating of samples in a furnace. Herby sample deterioration is monitored by microphones using acoustic emission analysis. In this contribution latest developments will be presented by current data on thermal cycling and hot thermal shock tests on refractories.


CN-2:L05  Analysis of the Fracture Behaviour of Magnesia-spinel Refractories by Digital Image Correlation
I. KHLIFI, M. HUGER, IRCER, Université de Limoges, UMR CNRS 7315, CEC, Limoges Cedex, France; O. POP, GEMH, Université de Limoges, Egletons Cedex, France; J.-C. DUPRÉ, P. DOUMALIN, Institut Pprime, Université de Poitiers, UPR CNRS 3346, Futuroscope Chasseneuil Cedex, France

Industrial refractory bricks destined to thermal shock applications often show more flexibility and an improved crack growth resistance due to an engineered microstructure design. In fact, the presence of a pre-fabricated network of microcracks within the microstructure decreases the elastic energy stored in the material during loading. Moreover, the crack propagation resistance is enhanced thanks to the presence of energy dissipating phenomena in the so-called process zone, which include crack bifurcation and crack branching among other mechanisms. Magnesia-spinel materials were investigated in order to highlight their complex fracture behaviour with regard to their microstructure. The Wedge Splitting Test (WST) has been chosen to promote stable crack propagation while a camera has been used to record the surface of the sample as loading occurs. Subsequently, images were analysed by a refined Digital Image Correlation process (2P-DIC), specifically developed to study the fracture behaviour of quasi-brittle materials. The coupling of the WST with 2P-DIC has proven to be an effective approach, which allows refined crack propagation monitoring while providing a better understanding of fracture mechanisms in magnesia-spinel materials.
 
 
Session CN-3 - Product Manufacturing and Installation

CN-3:IL01  Carbon-bonded Monolithic: Innovation and Perspectives
C. PAGLIOSA¹, V.C. PANDOLFELLI², ¹MAGNESITA S.A., Contagem, Brazil; ²Federal University of São Carlos (UFSCar), Brazil

MgO-C brick is the major refractory product for BOF converters and slag line of steel ladles. Through out campaign hot repair is usually carried out in order to extend these vessels working time. Most of repairing materials were based on dry or wet gunning products, using water as liquid. Thermal shock and hydration are observed in MgO-C bricks and the gunning material properties present a large scatter. Carbon bonded monolithic for hot repair material with phenolic resin was developed. A self flow shotcrete MgO-C castable was conceived to be delivered to the customer as a ready-to-use product and also to be compatible to MgO-C bricks. Recently due to restrictions on fume emissions and health and environment concerning in some customers, a new binder for carbon content monolithic was developed. This paper presents the evolution on carbon-bonded monolithic and the perspective for new generation of non pollutant binder for carbon monolithic.


CN-3:IL02  Applications of Microwave Heating to Refractory Materials
HATSUO TAIRA, Krosaki Harima Corporation, Kitakyusyu, Japan

A lot of studies on microwave heating in the ceramics field have been reported since the 1980's. In particular, it seemed that microwave technology would be an important technology in this field, such as synthesis of ceramic raw materials and microwave sintering On the other hand, since the 1970's, monolithic refractories have been installed and used in ladles in the steel industry in Japan. Monolithic refractories technology includes materials, mixing, installing by casting, curing, and drying. One of most important things is drying shortly without breakage. This paper reports on microwave drying mechanism of monolithic refractories and drying behavior of Al2O3- MgO precast blocks and developed a combination of drying method using microwaves and hot air. Heating by microwaves is internal heating, therefor, it is easier rapid heating until back of structure with appropriate microwave power applied. And we introduced microwave sintering results of refractories.

 
Session CN-4 - Modelling and Simulation of the Process Environment

CN-4:IL01  Application of Testing and Simulation for Fracture Mechanical Refractory Characterization
H. HARMUTH¹, Y. DAI², D. GRUBER¹, SHENGLI JIN¹, ¹Montanuniversitaet Leoben, Leoben, Austria; ²Wuhan University of Science and Technology, Wuhan, China

For ordinary ceramic refractory materials as they are widely applied in industrial furnaces deviations from pure linear elastic fracture mechanics (LEFM) are very relevant for their service behavior. This is mainly caused by two items: The development of a process zone where energy consuming processes occur apart from the crack tip also, and the fact that volumes loaded or unloaded under service conditions are in a similar order of magnitude as the process zone volume. Therefore material brittleness, properties related to it, their characterization, and possible brittleness reduction are major goals of research. Testing methods allowing for sufficiently large specimen size and nevertheless showing stable crack propagation have to be employed. While process zone was only indirectly observed in former times, digital image correlation and computed tomography enable direct visualization. This largely extends the options to observe, characterize and understand fracture process for materials of different brittleness. Refractories with reduced brittleness are desired for many applications. It can be shown that frequently brittleness reduction is achieved by a lower tensile strength, while deviations form LEFM increase at the same time and help to maintain the specific fracture energy.


CN-4:IL02  Thermo-chemo-mechanical Modelling of Refractories at High Temperatures: Basics, Keypoints and New Numerical Developments
E. BLOND¹, A.K. NGUYEN^{1, 2}, T. SAYET¹, E. DE BILBAO³, A. BATAKIS², M.-D. DUONG⁴, ¹Université d’Orléans, LaMé, Polytech Orléans, Orléans, France; ²Université d’Orléans, MAPMO, UMR CNRS 6628, Orléans, France;  ³Université d’Orléans, CEMHTI, UPR CNRS 3079, Orléans, France; ⁴University of Science, Hochiminh city, Nguyen Van Cu, Vietnam

The lifespan of refractory results from a complex interaction between chemistry, thermal heat science and mechanics. The development of numerical models able to predict the results of such complex multi-physics couplings require an intensive use of the thermodynamic of irreversible processes framework. Today, the main barriers to reach fully predictive simulations are: the access to relevant data at high temperature (chemical kinetics, chemical expansion coefficient, etc.), the numerical complexity and the computational time. This talk will summarize the theoretical framework illustrated on refractory lining application following by a description of the case of the reactive impregnation of refractory by slag. Ensuring numerical convergence and results accuracy require small time step and fine space discretization craftily coupled that results which lead to a very long computational time. To overcome the numerical difficulties and to speed up the computation time, a new numerical method based on percolation theory is proposed. The basics of this method and the first numerical results in one dimension will be presented.


CN-4:L03  Numerical Modelling by Discrete Element Method of Nonlinear Mechanical Behaviour of Refractories: Influence of Damage Involved by CTE Mismatch
T.T. NGUYEN, D. ANDRE, N. TESSIER-DOYEN, M. HUGER, University of Limoges, UMR CNRS 7315 - IRCER, Centre Européen de la Céramique, Limoges, France

Refractories are highly used in steel-making and glass-making industries. Nowadays, empirical knowledge capitalized by the refractory-making industries is important in the optimization process of micro-structure designs of these very complex materials. However, the optimization of their lifetimes could further be improved by a better knowledge of the impact of the micro-structural designs on the physical behaviours. Generally, micro-structures of refractories are composed by a large amount of inclusions embedded in a brittle matrix. In some cases, these materials can advantageously exhibit complex nonlinear mechanical behaviours that results partially from the local thermal expansion mismatch. These phenomena involve a high amount of discontinuities and cannot be tackled easily with the Finite Element Method. The Discrete Element Method naturally accounts for discontinuities and is therefore a good alternative to the continuum approaches. The results given by the proposed approach are compared to experimental data obtained on simplified refractory materials. The numerical results show qualitatively and quantitatively a good agreement with the experimental observations and show the ability of the presented method to predict the behaviour of heterogeneous refractories.


CN-4:IL05  Thermodynamic Database for the Slag and Refractory System in the Coal Combustion Process
IN-HO JUNG, M.-A. VAN ENDE, Department of Materials Science and Technology, Seoul National University, Seoul, South Korea; DONG-GEUN KIM, E. MOOSAVI-KHOONSARI, Department of Mining and Materials Engineering, McGill University, Montreal, QC, Canada; Minami Tai, RCCM, Tokyo, Japan

The chemistry of slag and ash forming in the coal combustion process is very complex and highly depending on the coal chemistry and operation conditions. In order to understand the chemistry of liquid oxide containing sulphate in coal combustion process, complex thermodynamic reactions between gas, solid and liquid phases at high temperature should be analyzed.  The liquid oxide phase can also chemically corrode refractories in the chamber. To assist the analysis of such complex chemical reactions, thermodynamic calculations based on accurate thermodynamic databases are widely used recently. But no proper thermodynamic database dedicated for coal combustion process has been available so far. In the present study, the recent thermodynamic database for the CaO-MgO-Al2O3-SiO2-FeO-Fe2O3-Na2O-K2O-sulfide-sulphate system will be introduced. Thermodynamic database has been developed based on the critical evaluation/optimization of all available thermodynamic and phase diagram data in the literature. In the case that the system is a lack of the experimental data, key phase diagram experiments were performed to provide sufficient data for the thermodynamic optimization. The accuracy of new database and applications of the database for complex phase equilibration and refractory corrosion will be presented.  


Session CN-5 - Refractory Failure Analysis

CN-5:IL01  Post-mortem Analysis of Refractory Wear in Metal Processing Caused by Slag and Temperature – The Importance of Understanding the Process and Requirements for the Slag
A.M. GARBERS-CRAIG, Centre for Pyrometallurgy, Department of Materials Science & Metallurgical Engineering, University of Pretoria, Pretoria, South Africa

Post-mortem analysis of refractory samples taken from high temperature units is the most common technique used to study and understand mechanisms through which refractories wear and degrade on an industrial scale. The main purpose of such an analysis is to find ways in which refractory life can be extended and new materials can be developed. This paper emphasizes the importance of understanding the thermodynamics of the reactions that take place in the industrial unit in which refractory wear is studied, specifically the role played by slag and temperature, and how it impacts on refractory wear. Slag that is produced in certain processes is simply a liquid in which the gangue is collected. In such instances slag design to achieve slag – refractory compatibility is relatively easy. However, in instances where the slag plays a major role in optimizing the recovery of components to the produced product and / or the refining of the produced product, slag design is more complex. Slag design for slag – refractory compatibility can therefore not be considered in isolation from the function required from the slag in the high temperature process. Examples of post-mortem studies on slag – refractory interactions, where different types of slags played different roles, are discussed.


CN-5:L02  Stability of Thermal Insulating Materials Used in Hall-Héroult Cells
R. LUNENG, T. GRANDE, Department of Materials Science and Engineering, NTNU, Norwegian University of Science and Technology, Trondheim, Norway; S.N. BERTEL, J. MIKKELSEN, Skamol A/S, Nykøbing Mors, Denmark; A.P. RATVIK, SINTEF Materials and Chemistry, Trondheim, Norway

The most common thermal insulating materials used in the cathode lining in aluminium electrolysis cells are Moler (diatomaceous earth), calcium silicate, or vermiculite based materials. The thermal insulation layer is critical for the overall thermal stability of the cell and is vulnerable to volatile species that may penetrate through the carbon and refractory layer above. Sodium vapour has been identified by autopsies of spent pot lining as the first volatile species that penetrate into the refractory layer. Here, we present an investigation of the chemical degradation of typical thermal insulating materials by two different laboratory tests. Changes in microstructure and chemical and mineralogical composition of the exposed materials are characterized by electronic microscopy and powder X-ray diffraction. The materials possess different reaction patterns, ranging from deformation by creep to formation of a glassy layer hindering further sodium penetration. The results from the laboratory tests were compared with chemical reactions with sodium based on computational thermodynamics, and discussed with respect to appropriate phase diagrams.


CN-5:L03  MgO Refractory Wear in the Ferrovanadium Production Process
M.C.J. VAN DER MERWE, R.D. CROMARTY, A.M. GARBERS-CRAIG, Centre for Pyrometallurgy, Department of Materials Science and Metallurgical Engineering, University of Pretoria, South Africa

Ferrovanadium (FeV) is produced from a titaniferous magnetite – containing ore in a crush-roast-leach-reduction process. Titaniferous magnetite can be rendered water soluble through a roasting process where both NaSO4 and NaCO3 are added. Ammonium vanadates are precipitated from the pregnant solution using ammonia, where after it is calcined in a reactor to form V2O3. FeV is then produced from V2O3 and Fe (scrap iron) through aluminothermic reduction in a DC arc furnace, while CaO is added to flux the slag. The use of MgO refractories in the DC arc furnace has several challenges due to the high operating temperature (1850˚C). A high refractory wear rate is evident in the process, resulting in the need to identify the mechanisms of wear. MgO was previously added to the slag, but due to the high amount of vanadium (V) losses that occurred, it is no longer done. This paper describes a post-mortem analysis of refractory bricks that were taken from a DC arc furnace in which FeV is produced. It describes the observed mechanisms of chemical wear and suggests how compatibility between the slag and MgO bricks can be achieved without increasing vanadium losses to the slag.


CN-5:IL05  An European Innovative Training Network dedicated to Refractories: ATHOR
M. HUGER, University of Limoges, UMR CNRS 7315 - IRCER, Centre Européen de la Ceramique, Limoges, France

The international ATHOR network (www.etn-athor.eu) is firstly dedicated to train Early Stage Researchers (ESRs) in multi engineering fields for a better understanding of thermomechanical behaviour of refractory linings used in Ironmaking and Steelmaking. Through a multiscale approach, the project will cover all the main features of thermomechanical analysis of refractory linings including the influence of microstructures on material behaviour, the impact of corrosion on thermomechanical properties, the thermal shock resistance, the modelling of non-linear thermomechanical behaviours, the instrumentation of industrial vessels and the measurement of properties in operation conditions. With a total of 14 international partners, including 8 industrial companies and 6 universities, the young researchers will have the opportunity to collaborate with experts in various research groups and will take advantage of the most sophisticated numerical tools to model, design and predict the life of refractory lining configurations in critical operation conditions. Being trained in scientific, technical and soft skills, the 15 ESRs selected in the program will be the next generation of highly employable scientists and engineers in the refractory industry and related areas.


CN-5:L06  Autopsy of Refractory Lining in Anode Baking Furnaces with Open and Closed Design
T. BRANDVIK, T. GRANDE, NTNU Norwegian University of Science and Technology, Trondheim, Norway; A.P. RATVIK, SINTEF Materials and Chemistry, Trondheim, Norway
 
 Aluminosilicate refractory lining constitute a large part of the anode baking furnace and is exposed to harsh chemical conditions during operation. In this study, spent refractory lining from both an open and closed baking furnace is investigated in order to determine microstructural and mineralogical changes in the materials caused by the conditions during anode baking. The autopsy revealed significant variations in density and open porosity across the bricks and with respect to vertical position in the lining. The chemical and mineralogical composition of the samples were investigated by X-ray diffraction and scanning electron microscopy, with only minor variations in the mineralogical composition observed. Transport of silicon oxide over large distances within the furnace was observed, reflecting the variations in the reducing-oxidation conditions both locally in the lining and during an anode baking cycle. Significant densification of the material over time, being especially uneven across the lining wall, constitute the main degradation mechanism for the investigated lining. The observations and degradation mechanism are discussed and related to the main design differences of the two furnaces.


Session CN-6 -  Refractory Materials for Novel or Advanced Applications

CN-6:IL01  Innovative Sintered Mullite-zirconia Refractory Composite for Hazardous Waste Incinerators
A. VILLALBA WEINBERG^{1, 2, 5}, M.L. BOUCHETOU¹, E.S. FOTSO, O. JOUBERT⁴, C. VARONA⁵, D. GOEURIOT², J. POIRIER¹, ¹CNRS, CEMHTI UPR 3079, Univ. Orléans, Orléans, France; ² LGF CNRS UMR 5307, Mines Saint-Etienne, France; ³CARRD, Imerys, Villach, Austria; ⁴Imerys Refractory Minerals Clerac; ⁵Bony SA, Saint Etienne, France

Mullite-zirconia raw material is industrially produced through a fusion process by melting a mixture of zircon and alumina in an electric arc furnace. Zirconia crystal grains are dispersed in a mullite matrix. A glassy phase is present. The aim of this research is to propose an improved corrosion and thermal shock resistant sintered mullite-zirconia refractory. A new sintered mullite-zirconia material has been developed on basis of andalusite, alumina and zircon. Its microstructure consists of fine zirconia particles (5 µm) homogeneously distributed in a mullite matrix. The thermal shock resistance of the new composite, tested by heating the samples up to 1200°C and cooling to room temperature, increases with the first and second thermal cycling and stays constant afterward, whereas the thermal shock resistance of other materials like cordierite or alumina begin to decrease from the first thermal shock. The sintered mullite-zirconia grains were corroded by alumina-lime slag and soda-lime glass. Impregnation depth measurements show that the commercial fused zirconia mullite grains are completely impregnated while the new sintered zirconia mullite is only partially impregnated. Refractories were elaborated and tested in rotary furnaces used for the incineration of hazardous wastes.


CN-6:IL02  Enhanced Mechanical Properties of Al2O3-C Refractories with Silicon Hybridized Expanded Graphite
YAWEI LI, The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science & Technology, Wuhan, P.R. China

Expanded graphite (EG) is a promising reinforcement for fabricating Al2O3-C refractories. In this work, two kinds of silicon hybridized EG were introduced into Al2O3-C refractories. They are β-SiC whiskers hybridized EG (named as EG/SiC) and SiOx spheres hybridized EG (named as EG/SiOx), respectively. Afterward, the microstructure and mechanical properties of Al2O3-C refractories coked at the temperatures ranging from 800 °C to 1400 °C were investigated in this work. The results showed that the interfacial characterization of EG/SiC and EG/SiOx hybrids were remarkably improved compared with original EG. Moreover, the EG/SiC and EG/SiOx hybrid remained relative intact structure at high temperature. In addition, the mechanical properties such as cold modulus of rupture (CMOR), force and displacement of Al2O3-C specimens containing hybrids were improved in comparison with the specimen containing original EG. Furthermore, with the addition of EG/SiC or EG/SiOx hybrid, the thermal shock resistance of Al2O3-C refractories was considerably promoted. The above enhanced mechanical properties could attribute to the hybridized β-SiC whiskers and SiOx spheres on EG, which were pulled out to consume the fracture energy when the Al2O3-C specimens were bearing loading.


CN-6:L03  Reactive Filter Collectors Based on Calcium Aluminates with Carbon for Clean Steel Approaches
E. STORTI, D. VERES, M. FARHANI, C.G. ANEZIRIS, Institute of Ceramic, Glass and Construction Materials, TU Freiberg, Freiberg, Germany; C. WÖHRMEYER, Kerneos GmbH, Oberhausen, Germany; C. PARR, Kerneos SA, Puteaux, France

To improve the purification performance of carbon-bonded alumina filters, calcium aluminate coatings containing carbon were applied. When such compositions come in contact with a steel melt, the following mechanisms may be expected: I) The calcium aluminates are reduced by the carbon, generating gaseous species at the interface with the metal melt. Next, a secondary calcium aluminate layer is generated thanks to the reaction of these suboxides with the oxygen of the steel melt. This layer between the decarburized zone and the steel melt will then contribute as an “active” collector for endogenous inclusions. II) The high vapor pressure of calcium with an associated bath stirring promotes collision and coalescence of the alumina fine inclusions in the melt. These nonbuoyant inclusions usually need to cluster on their own before they can separate from the melt. III) Depending on the applied composition of calcium aluminates, the softening point and/or the melting point of the coating can be adjusted in order to increase the roughness of the thin secondary layer (which copies the surface of the carbon-free calcium aluminate layer underneath). A higher roughness leads to higher wetting angle against the iron melt, which will promote a higher adhesion via collision of the inclusions.


CN-6:IL04  Flame Spraying Approaches for Advanced Refractory Applications
P. GEHRE, C.G. ANEZIRIS, TU Bergakademie Freiberg, Institute of Ceramic, Glass and Construction Materials, Freiberg, Saxony, Germany

Thermal spray is not only an environmentally friendly technology to deposit functional ceramic coatings on a substrate but also provides the opportunity to modify coating properties as well as characteristics of whole components. Thermal spray is a dynamic technology being developed continuously to meet upcoming challenges by the global market evolution. Next to enhancements in traditional application areas, thermal sprayed surfaces and coatings can fulfil rising demands on ceramic materials used in other industries like refractories and hence can contribute to their future development, too. The microstructure of flame sprayed ceramics is composed of overlaid platelets which results in different thermomechanical properties compared to common technical ceramics with same composition. Fracture toughness and potential R-curve behaviour of free standing flame sprayed alumina compounds have been evaluated. In addition, flame sprayed alumina based coatings with zirconia- and titania-addition with excellent thermal shock resistance will be presented. Furthermore, new developed low-wetting Al2O3-CaO-TiO2 coatings for application in aluminium foundry as well as proton conductive flame sprayed CaZrO3 oxides for water electrolysis in a system based on renewable energies were introduced.


CN-6:IL05  Refractory Filtering Materials for Clean Steel Technology
C.G. ANEZIRIS, P. GEHRE, A. SCHMIDT, E. STORTI, S. DUDCZIG, J. HUBALKOVA, Institute of Ceramic, Glass and Construction Materials, Technical University of Freiberg, Freiberg, Germany

Non-metallic inclusions in cast metal parts influence remarkably their performance during application. For the last three decades ceramic foam filters have been applied successfully in steel foundries for metal products with superior properties. Excellent operating filter systems fulfil two basic functions which are a) removing impurities on millimetre, micron as well as submicron scale and b) promoting a non-turbulent melt filling of the mould if they are applied correctly during operation especially for time depending on interactions according to the filter material contribution. At present, the formation mechanism as well as the kinetics of observed in-situ layers on filters in contact with steel melt and their influence on the deposition of inclusions from the steel melt is a main focus of the Collaborative Research Center 920 of the German Research Foundation in Freiberg. In terms of this presentation the contribution of different in situ formed layers as a function of their chemistry, porosity, time of interaction with the steel melt and the kind of treatment of the steel will be demonstrated and discussed in case of functional surface filter coatings as well as coatings on crucibles. Theoretical models are proposed which confirm the experimental results.


CN-6:L06  Study of Innovative Refractory Solutions for Improving Efficiency of Industrial Furnaces
D. OLEVANO, U. MARTINI, P. MICELI, A. DI DONATO, RINA CONSULTING - Centro Sviluppo Materiali S.p.A., Rome, Italy

The use in industrial furnaces of new refractory solutions that guarantee an improvement of thermal insulation respect to the current situation will give undoubtedly benefits in terms of energy saving toward more environmental-friendly processes. Further improvements can be obtained by increasing material life in service, decreasing the use of raw materials and the energy required for material production. The choice of avant-garde solutions to produce refractory materials will allow to reach all these targets. Following this logic, different solutions have been explored. Compositionally Graded Refractory solutions can provide good thermal insulation maintaining at the same time good resistance to physicochemical degradation in the severe conditions of furnaces. Nanobonded refractories reduce production costs in respect to standard ones by lowering duration and temperature of refractory production. The reuse of industrial by-products in the production of new refractory with optimized performances is beneficial to reduce the amount of normally used raw materials for limiting their shortage. This work describes the experimented solutions for laboratory production of the innovative refractories and the related results obtained by laboratory tests.
Financed by H2020 - VULKANO project.


Session CN-7 - Future Refractory Education Needs

CN-7:IL01  Complex Engineering Systems; The Next Step for the Ceramic Refractory Area
V.C. PANDOLFELLI, Federal University of São Carlos - DEMa, São Carlos, SP, Brazil

The refractory field is an entangled network in which long-term trends are determined based on the interaction between different players such as raw material producers, refractory manufacturers, end users, research centers and universities. As it is a complex system, it is very difficult to forecast the next scientific development and what the future technologies and trends will be in the area. In order to recall the past, data mining and the graph theory were used to analyze publications from the major technical journals in the refractory area. Based on this study, a complete map of the international collaboration of the different leading countries in the refractory field was attained. A common factor of these countries is the active working interaction, which helps them to tackle challenging problems with a high degree of complexity. Technological trends were obtained from the analysis of selected keyword over the period considered showing a lack of a technological breakthrough in the past 10 years. Nevertheless, there is a clear path for high-temperature materials when artificial intelligence, big data, cloud computing are considered as tools to deal with the enormous amount of information required in such complex engineering system.


CN-7:IL02  The FIRE Compendium Series on Corrosion of Refractories to Match Educational Needs
M. RIGAUD, Ecole Polytechnique, University of Montreal, Montreal, Quebec, Canada

FIRE is committed to assist the education of young professionals and engineers of all horizons, to conceptualize, design, implement and organize efficient processes to manufacture the best refractoriy materials for all and specific users. FIRE education programs and the main accomplishments made since 2007 are at first briefly reviewed. In 2017, to enhance its educational mission FIRE members have undertaken the task to launch a second compendium series of books on the theme of Corrosion, to actualize the knowledge accumulated in the last three décades and to disseminate the main results for the benefit of the widest readership. The essential aspects of the 3 books to appear in 2018 are provided to illustrate the FIRE members' role in such an endeavour.


CN-7:IL03  How to Cover the Spectrum of Education Needs for the Refractory Industry
P. QUIRMBACH, ECREF European Centre for Refractories, Höhr-Grenzhausen, Germany

According to the principles of lifelong learning, the subject of education is split into (A) basic formal education and (B) continuing vocational education. There are two forms of basic education at academic institutions: (i) degrees which can only be acquired jointly with an industrial Enterprise, and (ii) those which are self-initiated without binding industrial participation. This is dependent on the candidate´s level of education and the type of school chosen for one specific education method. (A) School education In principle, this implies an embedding of the training centers in the field of ceramics, since a great variety of theoretical as well as practical aspects of education arise from this specialist field of ceramics. A subsequent focus on refractories is a specialization only after having acquired, to a large extent, the basic knowledge of ceramics. (B) Continuing vocational Training Seminars are preferably used for this specialization, the content of which should be aligned with the ideas and current needs of industrial companies. This role is ideally taken over by the respective industry association in order to coordinate the dialogue between tutors and interested participants. It´s necessary for both that comprehensive Information is provided to the public.