Design, Properties, Damage and Lifetime of Refractory Ceramics

A special issue of Ceramics (ISSN 2571-6131).

Deadline for manuscript submissions: closed (30 November 2019) | Viewed by 42092

Special Issue Editor


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Guest Editor
Refractory Materials, design and corrosion, CEMHTI – CNRS, 1D, av de la Recherche Scientifique, 45071 Orléans cedex 2, France
Interests: refractory ceramics; the corrosion of refractory materials by gases, metals and liquid oxides at high temperature (the identification of the chemical reactions, modelling of the thermochemical mechanisms; transport of the liquid phases in the capillary network and impregnation modelling; relation between thermochemical and thermomechanical damage); Evolution of mineral phases and glasses at high temperature (microstructural observations; thermodynamic interpretation and kinetic modelling); development of better-adapted materials for specific applications

Special Issue Information

Dear Colleagues,

This Special Issue is dedicated to the latest research and development in refractory ceramics in the large fields of raw materials, design, properties, damage, and lifetime, in terms of thermochemical and thermomechanical behavior.

Refractories are subject to degradations in most applications. The industrial domains concerned are many and varied:

  • Traditional sectors involved in the high-temperature production of materials, such as the steel industry, non-ferrous metallurgy, cement works, glass, ceramic and raw materials industries, constantly looking to improve their manufacturing processes and energy efficiency;
  • Petrochemicals, electricity production from fossil fuels or emerging energy applications;
  • The environment, and more specifically the domains relating to waste treatment and recovery (thermal treatment of wastewater sludge, vitrification of asbestos, HWITR: Household waste incineration treatment residue and IWITR: Industrial waste incineration treatment residue, etc.);
  • Thermal and chemical sectors: Boilers, furnaces, evaporators, gasification reactors, treatment facilities, etc.;
  • The aeronautic, space, and arms industries, which use ceramic thermal barriers to confine heat and withstand the corrosive products generated by propulsion engines, but also to create the external coatings of spacecraft, which must withstand overheating when re-entering the Earth's atmosphere.

To assess the damage resistance of a refractory in a defined environment, the characteristics of the material must be known, and the effect of the properties on operational performance must be evaluated. This complex approach requires in-depth expertise.

Thorough understanding of damage mechanisms, as with refractory usage properties, requires knowledge of how these materials are manufactured, starting with their constituent raw materials.

The combination of different approaches, i.e., industrial appraisals associated with experimental laboratory methods and digital modeling, is very useful for taking a fresh look at the issue of refractory damage, giving rise to approaches which are completely different from traditional empirical ones.

Effective experimental techniques, combined with powerful digital tools, currently facilitate the acquisition of information which cannot be accessed directly (e.g., phase changes). The use of thermodynamic and thermomechanical simulation tools considers many parameters and the effect of the environment. The “Achilles’ heel” is without question the difficulty in accessing the data on the behavior of materials in relation to temperature. There is often a lack of data and kinetic coefficients.

Topics of interest (among others) include:

- Raw materials;
- Castables;
- Design of refractories (bricks, castables);
- Advanced laboratory experiments;
- Thermomechanical behavior;
- Corrosion;
- Recycling and environment aspects;
- Education.

Prof. Jacques Poirier
Guest Editor

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Keywords

  • Refractory ceramic
  • Raw materials
  • Design, lifetime, durability, mechanical behavior
  • Corrosion
  • Laboratory experiments
  • Modeling

Published Papers (12 papers)

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Research

12 pages, 6910 KiB  
Article
Experimental Investigation of the Tension and Compression Creep Behavior of Alumina-Spinel Refractories at High Temperatures
by Lucas Teixeira, Soheil Samadi, Jean Gillibert, Shengli Jin, Thomas Sayet, Dietmar Gruber and Eric Blond
Ceramics 2020, 3(3), 372-383; https://doi.org/10.3390/ceramics3030033 - 22 Sep 2020
Cited by 23 | Viewed by 4189
Abstract
Refractory materials are subjected to thermomechanical loads during their working life, and consequent creep strain and stress relaxation are often observed. In this work, the asymmetric high temperature primary and secondary creep behavior of a material used in the working lining of steel [...] Read more.
Refractory materials are subjected to thermomechanical loads during their working life, and consequent creep strain and stress relaxation are often observed. In this work, the asymmetric high temperature primary and secondary creep behavior of a material used in the working lining of steel ladles is characterized, using uniaxial tension and compression creep tests and an inverse identification procedure to calculate the parameters of a Norton-Bailey based law. The experimental creep curves are presented, as well as the curves resulting from the identified parameters, and a statistical analysis is made to evaluate the confidence of the results. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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12 pages, 4688 KiB  
Article
Differences in the Corrosive Spalling Behavior of Alumina-Rich Castables: Microstructural and Crystallographic Considerations of Alumina and Calcium Aluminate Matrices
by Lise Loison, Mouna Sassi, Thorsten Tonnesen, Emmanuel De Bilbao, Rainer Telle and Jacques Poirier
Ceramics 2020, 3(2), 223-234; https://doi.org/10.3390/ceramics3020020 - 11 May 2020
Cited by 1 | Viewed by 2616
Abstract
The energy transition from the incineration and gasification of fossil fuels to the incineration and gasification of biomass refractory linings is being held up by a severe corrosion issue, caused by high alkali contents and the wide variety of biomass sources. Incinerators optimized [...] Read more.
The energy transition from the incineration and gasification of fossil fuels to the incineration and gasification of biomass refractory linings is being held up by a severe corrosion issue, caused by high alkali contents and the wide variety of biomass sources. Incinerators optimized for fossil fuels are commonly lined with mullite, Al2O3-Cr or SiC-based refractory products; however, those materials are not always suitable for the use of organic fuels. Hibonite (CaO·6Al2O3)-based refractory products have shown promising performance because of their high resistance against alkali attacks. Indeed, previous works have shown that the reaction between calcium hexa-aluminate and an alkali does not lead to the strong volume expansion observed with other mineral phases, such as corundum or andalusite. The present work aims to describe the reactions kinetics occurring between hibonite-based raw materials and biomass ashes. Therefore, the three main oxides contained in an average biomass, namely, CaO, SiO2 and K2O, were selected to examine the high temperature reactions with a calcium hexa-aluminate matrix. The resulting phase composition and microstructure were compared with the performance of an alumina matrix through, respectively, X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The post-mortem observations show a higher extent of reaction for the alumina than for the calcium hexa-aluminate. Moreover, the microstructure of the alumina matrix suffered a strong chemical spalling, while the calcium hexa-aluminate microstructure remained undamaged after the corrosion. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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13 pages, 6799 KiB  
Article
Compressive Creep Measurements of Fired Magnesia Bricks at Elevated Temperatures Including Creep Law Parameter Identification and Evaluation by Finite Element Analysis
by Guenter Unterreiter, Daniel R. Kreuzer, Bernd Lorenzoni, Hans U. Marschall, Christoph Wagner, Robert Machhammer and Gernot Hackl
Ceramics 2020, 3(2), 210-222; https://doi.org/10.3390/ceramics3020019 - 22 Apr 2020
Cited by 3 | Viewed by 3220
Abstract
Creep behavior is very important for the selection of refractory materials. This paper presents a methodology to measure the compressive creep behavior of fired magnesia materials at elevated temperatures. The measurements were carried out at 1150–1500 °C and under compression loads from 1–8 [...] Read more.
Creep behavior is very important for the selection of refractory materials. This paper presents a methodology to measure the compressive creep behavior of fired magnesia materials at elevated temperatures. The measurements were carried out at 1150–1500 °C and under compression loads from 1–8 MPa. Creep strain was calculated from the measured total strain data. The obtained creep deformations of the experimental investigations were subjected to detailed analysis to identify the Norton-Bailey creep law parameters. The modulus of elasticity was determined in advance to simplify the inverse estimation process for finding the Norton-Bailey creep parameters. In the next step; an extended material model including creep was used in a finite element analysis (FEA) and the creep testing procedure was reproduced numerically. Within the investigated temperature and load range; the creep deformations calculated by FEA demonstrated a good agreement with the results of the experimental investigations. Finally; a finite element unit cell model of a quarter brick representing a section of the lining of a ferrochrome (FeCr) electric arc furnace (direct current) was used to assess the thermo-mechanical stresses and strains including creep during a heat-up procedure. The implementation of the creep behavior into the design process led to an improved prediction of strains and stresses. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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19 pages, 5632 KiB  
Article
Transient Thermo-Mechanical Analysis of Steel Ladle Refractory Linings Using Mechanical Homogenization Approach
by Mahmoud Ali, Thomas Sayet, Alain Gasser and Eric Blond
Ceramics 2020, 3(2), 171-189; https://doi.org/10.3390/ceramics3020016 - 2 Apr 2020
Cited by 21 | Viewed by 6593
Abstract
Mortarless refractory masonry structures are widely used in the steel industry for the linings of many high-temperature industrial applications including steel ladles. The design and optimization of these components require accurate numerical models that consider the presence of joints, as well as joint [...] Read more.
Mortarless refractory masonry structures are widely used in the steel industry for the linings of many high-temperature industrial applications including steel ladles. The design and optimization of these components require accurate numerical models that consider the presence of joints, as well as joint closure and opening due to cyclic heating and cooling. The present work reports on the formulation, numerical implementation, validation, and application of homogenized numerical models for the simulation of refractory masonry structures with dry joints. The validated constitutive model has been used to simulate a steel ladle and analyze its transient thermomechanical behavior during a typical thermal cycle of a steel ladle. A 3D solution domain and enhanced thermal and mechanical boundary conditions have been used. Parametric studies to investigate the impact of joint thickness on the thermomechanical response of the ladle have been carried out. The results clearly demonstrate that the thermomechanical behavior of mortarless masonry is orthotropic and nonlinear due to the gradual closure and reopening of the joints with the increase and decrease in temperature. In addition, resulting thermal stresses increase with the increase in temperature and decrease with the increase in joint thickness. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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16 pages, 3818 KiB  
Article
Corrosion Mechanism of A Density-Reduced Steel Ladle Lining Containing Porous Spinel-Calcium Aluminate Aggregates
by Christoph Wöhrmeyer, Jianying Gao, Christopher Parr, Magali Szepizdyn, Rose-Marie Mineau and Junhui Zhu
Ceramics 2020, 3(1), 155-170; https://doi.org/10.3390/ceramics3010015 - 23 Mar 2020
Cited by 6 | Viewed by 3084
Abstract
Refractory monolithics for steel ladle linings are typically products with low porosities and high bulk densities. They achieve high temperature, penetration, and corrosion resistance. Despite the high density of these products, which is due to the low porosity of the aggregates, their matrices [...] Read more.
Refractory monolithics for steel ladle linings are typically products with low porosities and high bulk densities. They achieve high temperature, penetration, and corrosion resistance. Despite the high density of these products, which is due to the low porosity of the aggregates, their matrices still exhibit a high amount of pores. Since calcium magnesium aluminate (CMA) has already proven its resistance to penetration and corrosion as a binder in the matrix, this paper investigated if alumina spinel refractories containing microporous calcium magnesium aluminate aggregates can withstand conditions that occur in a steel ladle wall. The objective was to reduce the castable density with the advantage of a lower material requirement for a ladle lining and reduced heat and energy losses. This was achieved by replacing dense alumina aggregates by up to 38% of porous CMA aggregates (grains with 30 vol% porosity), which resulted in a bulk density reduction from 3.1 g/cm3 for the dense alumina castable to 2.8 g/cm3 for the 38% CMA aggregates containing castable. However, the despite the higher porosity, penetration, and corrosion resistance and thermomechanical properties were not impacted negatively for a model alumina spinel castable. A postmortem investigation was conducted on a newly developed dry-gunning mix that was installed in a steel ladle wall on top of a slag penetrated castable and that achieved a service life of 31 heats versus only 18 heats for the reference mix that contained dense alumina and spinel aggregates. This new repair mix contained the newly designed porous CMA aggregates, which in this case partly replaced the dense alumina and spinel aggregates. These porous aggregates consisted of magnesium aluminate and calcium aluminate micro-crystals. The postmortem study revealed two important phenomena that can explain the improved performance: at the hot face in contact with steel and slag, a thin densified zone was observed that blocked the slag penetration into the porous matrix and the porous aggregates. Iron oxides were almost completely blocked from penetration, and only some manganese oxide was observed in the penetrated zone together with some silica and lime from the slag. Clusters of calcium aluminate (CA6) and magnesium aluminate (MA) spinel build the refractory back-bone on the hot side of the material and gussets filled with mostly glassy calcium aluminum silicates close to the hot face and gehlenite further inside the penetrated zone. Alumina grains had a reaction rim consisting of CA2 or CA6 and a very intimate connection to the surrounding matrix unlike the CMA-free mix that showed micro cracks around the alumina grains. At the colder side, the gunning mix with CMA aggregates showed a very good connection to the substrate, supported by a hercynite formation in the gunning mix resulting from a cross-reaction with remains of iron oxide on the CMA containing repair mix. Furthermore, macroscopic observations of a CMA aggregate containing alumina magnesia castable in the metal zone of a steel ladle revealed that macro cracks developed only very slowly, which resulted in a superior service life. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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11 pages, 6833 KiB  
Article
Qualitative and Quantitative Coating Tests: A Comparison in Magnesia–Spinel Refractory Bricks
by Graziella Pacheco, Geraldo Eduardo Gonçalves and Vanessa Lins
Ceramics 2020, 3(1), 144-154; https://doi.org/10.3390/ceramics3010014 - 21 Mar 2020
Cited by 3 | Viewed by 3510
Abstract
In cement processing, which involves the production of clinker in rotary kilns, the main refractories used in the transition and burning zones are magnesia–spinel bricks. These bricks present suitable chemical and thermomechanical properties, not to mention that they can be easily landfilled. Among [...] Read more.
In cement processing, which involves the production of clinker in rotary kilns, the main refractories used in the transition and burning zones are magnesia–spinel bricks. These bricks present suitable chemical and thermomechanical properties, not to mention that they can be easily landfilled. Among the main wear mechanisms of these bricks in the kiln, the infiltration of alkaline salts is noteworthy and occurs through the open pores of the refractory. In this way, the coating—a clinker layer adhered to the brick surface—appears as a protection mechanism of the lining against infiltration. Thus, the objective of this investigation is to run a qualitative coating test based on the contact method, and quantitative coating test based on the sandwich method to check the suitability of the methodologies and to evaluate the coating adherence on two different magnesia–spinel bricks. It was possible to distinguish the superior adherence ability of brick B in both coatings due to the higher porosity and the presence of nonreacted ZrO2. Despite the similarity between the test results, the quantitative sandwich-coating test is preferable because it does not depend on subjective analysis. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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17 pages, 3542 KiB  
Article
The Effect of Titanium Oxide Additions on the Phase Chemistry and Properties of Chromite-Magnesia Refractories
by Johan PR De Villiers, Delphin Mulange and Andrie Mariana Garbers-Craig
Ceramics 2020, 3(1), 127-143; https://doi.org/10.3390/ceramics3010013 - 20 Mar 2020
Cited by 3 | Viewed by 2760
Abstract
The microstructure of a direct-bonded chromite-magnesia refractory brick, typically used in copper and platinum converters, was modified by adding different amounts of nano-size TiO2 to the raw material mixture. Bricks with 0, 1, 3, 5, and 7 mass% TiO2 were produced [...] Read more.
The microstructure of a direct-bonded chromite-magnesia refractory brick, typically used in copper and platinum converters, was modified by adding different amounts of nano-size TiO2 to the raw material mixture. Bricks with 0, 1, 3, 5, and 7 mass% TiO2 were produced and compared in terms of spinel formation; the role of the tetravalent cation Ti4+ in the bonding phase; as well as changes in density, porosity, thermal expansion, and internal stress. This was done through a comprehensive XRD and SEM-EDS study. It was found that Ti is accommodated in the secondary spinel that has formed, where Mg in excess of unity in the tetrahedral site combines with an equal amount of Ti in the octahedral sites to maintain charge balance. The 1 mass% TiO2 brick had the lowest bulk density (but not significantly different from the original chromite-magnesia brick), the smallest difference in unit cell volumes between the primary and secondary spinels, and the lowest stress arising from the smallest difference in linear thermal expansion coefficients of the phases present. The calculated porosities correspond well with experimentally determined apparent porosity values, whereas the linear thermal expansion coefficients calculated at 1392K are similar to the values measured from 293 to 1273 K. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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13 pages, 6724 KiB  
Article
Correlation of Thermo-Elastic Material and Corrosion Behavior of Refractory Castables by In-Situ Measurements
by Wanja Reichert, Jonas Nießen, Peter Leto, Simon Etzold, Eva Kröll, Thorsten Tonnesen and Rainer Telle
Ceramics 2020, 3(1), 101-113; https://doi.org/10.3390/ceramics3010011 - 9 Mar 2020
Cited by 2 | Viewed by 2764
Abstract
Corrosion is one of the most common wear mechanisms of refractories. Corrosive attacks lead to chemical and microstructural changes. Hot corrosion compromises chemical and/or physical interactions. Thus, the process is complex and not yet fully understood. Currently, corrosion is investigated post mortem by [...] Read more.
Corrosion is one of the most common wear mechanisms of refractories. Corrosive attacks lead to chemical and microstructural changes. Hot corrosion compromises chemical and/or physical interactions. Thus, the process is complex and not yet fully understood. Currently, corrosion is investigated post mortem by means of X-ray diffraction or scanning electron microscopy. These methods have the drawback that some information is lost on cooling. In-situ measurements, however, take measurements within the process. In resonant frequency and damping analysis (RFDA), a sample is excited to vibrate by a mechanical impulse. The vibrating sample emits an acoustic signal. This is recorded with a microphone and evaluated by means of Fast Fourier Transformation (FFT). We measured the change of the frequency of a low cement castable during the corrosion process. Further simplified experiments with less complex materials were done to confirm the results. Distinctive points of the curves could be correlated to specific corrosion phenomena, like melting or infiltration. The applied methods include a first characterization of the material with open porosity, density and in-situ high-temperature (HT)-RFDA measurements as well as a study of the slag behavior. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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9 pages, 2012 KiB  
Article
Improvement in Slag Resistance of No-Cement Refractory Castables by Matrix Design
by Hong Peng, Jun Liu, Qinghu Wang and Yawei Li
Ceramics 2020, 3(1), 31-39; https://doi.org/10.3390/ceramics3010004 - 11 Jan 2020
Cited by 8 | Viewed by 3421
Abstract
The corrosion resistance of spinel containing cement bonded castables has been extensively investigated in the past. However, corrosion of no-cement refractory castables (NCC) has not been widely studied since the use of NCC has been relatively limited up till now. This paper focuses [...] Read more.
The corrosion resistance of spinel containing cement bonded castables has been extensively investigated in the past. However, corrosion of no-cement refractory castables (NCC) has not been widely studied since the use of NCC has been relatively limited up till now. This paper focuses on the slag resistance of NCCs, and the often-used spinel containing low cement castable (LCC) is used as the reference. Three different NCC binders were designed: (i) Al2O3 + MgO (alumina bond), in situ spinel formation; (ii) Al2O3 + SiO2 (microsilica-gel bond), mullite formation; and (iii) Al2O3 + MgO + SiO2 (MgO-SiO2 bond). Slag resistance tests were conducted using the static crucible method with ladle slag. The corrosion mechanisms were studied by means of Scanning Electron Microscopy (SEM/EDS), X-ray Diffraction (XRD), and thermodynamic simulations. The results confirmed that the mineral phases, microstructure, and liquid formation at a high temperature of the refractory materials had a strong impact on the corrosion resistance. The slag resistance was significantly improved when the cement was replaced by the cement-free binders. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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10 pages, 2469 KiB  
Article
Corrosion of MgO-C with Magnesium Aluminate Spinel Addition in A Steel Casting Simulator
by Steffen Dudczig, Gert Schmidt, Christos G. Aneziris, Christoph Wöhrmeyer, Christopher Parr and Patrick Gehre
Ceramics 2020, 3(1), 12-21; https://doi.org/10.3390/ceramics3010002 - 9 Jan 2020
Cited by 5 | Viewed by 2913
Abstract
For more than 20 years, the sidewalls and bottom of steel ladles have been lined with carbon-bonded magnesia (MgO-C) and magnesia-alumina bricks (MAC). The alumina raw materials react with magnesia forming a spinel, which decreases open porosity and slag infiltration. The amount, grain [...] Read more.
For more than 20 years, the sidewalls and bottom of steel ladles have been lined with carbon-bonded magnesia (MgO-C) and magnesia-alumina bricks (MAC). The alumina raw materials react with magnesia forming a spinel, which decreases open porosity and slag infiltration. The amount, grain size, and chemistry of the added spinel impact the properties of spinel-containing MgO-C. Corrosion tests have been performed in a steel casting simulator at 1580 °C using 18CrNiMo7-6 steel and Fe-rich slag as corrosion medium. Digital light microscopy and SEM/ EDS (scanning electron microscope with energy dispersive spectroscopy) were used to evaluate the corrosion mechanisms. The metal casting simulator test showed that the addition of CaO-MgO-Al2O3 aggregates results in the highest corrosion resistance against molten steel and synthetic basic slag compared to alumina-rich spinel aggregates. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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11 pages, 2434 KiB  
Article
Influence of Aluminium and Boron Orthophosphate on the Setting and the Resulting Structure of Alkali Silicate Binders for Refractory Application
by Vanessa Hopp, Ali Masoudi Alavi, Almuth Sax and Peter Quirmbach
Ceramics 2020, 3(1), 1-11; https://doi.org/10.3390/ceramics3010001 - 9 Jan 2020
Cited by 4 | Viewed by 2406
Abstract
Liquid alkali silicates (waterglasses) are used as chemical binders for a wide range of refractory applications, the setting of which can be initiated by the addition of phosphate hardeners. The duration of the setting process is of special interest for an economic lining [...] Read more.
Liquid alkali silicates (waterglasses) are used as chemical binders for a wide range of refractory applications, the setting of which can be initiated by the addition of phosphate hardeners. The duration of the setting process is of special interest for an economic lining with short aggregate downtimes. Therefore, in the present work, the influences of two different types of phosphate (aluminium orthophosphate and boron orthophosphate) on the hardening mechanisms of waterglasses are investigated. Time-dependent measurements by dynamic mechanical analysis (DMA) are carried out to observe the setting process. Structural information of the hardened amorphous samples is obtained by means of nuclear magnetic resonance (NMR) spectroscopy. It is shown that the use of different phosphates leads to differences in the setting rate, caused by different modes of network formation. The resultant silicate networks incorporate the aluminium or boron species but differ in the connectivity of those units. In addition, the distribution following the well-known Qn notation of the silicate units is directly influenced by the phosphate type. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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15 pages, 4854 KiB  
Article
Thermomechanical Characterisation of Mullite Zirconia Composites Sintered from Andalusite for High Temperature Applications
by Thierry Chotard, Lizeth Arbelaez Morales, Marie-Laure Bouchetou and Jacques Poirier
Ceramics 2019, 2(4), 587-601; https://doi.org/10.3390/ceramics2040046 - 6 Dec 2019
Cited by 7 | Viewed by 3037
Abstract
Mullite-Zirconia refractories are well known for their good resistance to corrosion and thermal shock. In this study, several mullite-zirconia composites were developed from andalusite, alumina and zircon sintered at 1600 °C for 10 hours. The samples were subjected to thermal shock carried out [...] Read more.
Mullite-Zirconia refractories are well known for their good resistance to corrosion and thermal shock. In this study, several mullite-zirconia composites were developed from andalusite, alumina and zircon sintered at 1600 °C for 10 hours. The samples were subjected to thermal shock carried out after heating at 1200 °C, in order to study the mechanical and thermomechanical behaviour as a function of the amount of zirconia dispersed in the mullite matrix. It appears that that the amorphous phase (SiO2), determined by X-ray diffraction, produced by the decomposition of andalusite, increases considerably with the amount of final zirconia in the composite and has a very important influence on the porosity. This amorphous phase seems also to have an important influence on the mechanical properties of the material. The characterisation of the thermomechanical behaviour (elastic properties and damage monitoring) was carried out thanks to ultrasonic techniques (US echography and Acoustic Emission). The “surprising” evolution (increase) of the Young’s modulus E of the material after being submitted to repeated thermal shocks is highlighted and explained. The acoustic emission technique carried out at high temperature and also coupled to 4-points bending tests (at room temperature) demonstrates its effectiveness for providing a better understanding of the chronology of the involved mechanisms involved at microstructural scale. Full article
(This article belongs to the Special Issue Design, Properties, Damage and Lifetime of Refractory Ceramics)
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