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Monolithic barium aluminosilicate (Celsian), with good thermal shock resistance, high thermal stability, and strong versatility, is attractive material as a ceramic matrix for high‐temperature composites. However, Celsian cannot be precipitated directly during the synthesis process but can only be generated by crystallographic transformation of the metastable Hexacelsian at high temperatures, and this process is sluggish. In this study, mullite was chosen as the main raw material for the synthesis of Celsian with almost fully monoclinic through a simple one‐step solid‐state reaction process at a lower temperature and shorter time, which was investigated using differential thermal analysis, phase identification, microstructure observation, and FactSage thermodynamic calculations. The results showed that mullite is a favorable raw material for the synthesis of Celsian, effectively avoiding the appearance of BaAl2O4 in Hexacelsia, making it possible to synthesize Celsian with almost fully monoclinic with only 4.5 h of holding at 1300°C. This is a significant improvement compared to the higher temperatures and longer holding times required for the synthesis of Celsian from other raw materials, according to previous literature. [ABSTRACT FROM AUTHOR]

In order to realize efficient and comprehensive utilization of kyanite tailings (KT) mullite insulating firebrick (M‐IFB) with high strength and low thermal conductivity with spherical‐low connectivity porous were success fully prepared by using KT and alumina as the main raw material. Control of the porosity and properties of mullite insulating firebrick can be easily and accurately achieved by adjusting the heat treatment temperature and the amount of forming agent. The compressive strengths, bulk density, thermal conductivities, liner change, and porosities ranged from 25.86–53.26 MPa,.58–1.61 g/cm3,.236–.599 W/(m·K), −1.01 to −.426 % and 66.89 to 78.63 %, respectively. The creep rate of M‐IFB was compared with that of current insulating bricks after them used in the baking kiln of lithium ion battery cathode materials in the laboratory to simulate the environment. The results show that the M‐IFB corrosion resistance was obviously superior to the current insulation bricks. The high porosity high strength mullite insulating firebrick prepared by this method is expected to be used in thermal insulation system of kiln to realize the comprehensive utilization of solid waste. [ABSTRACT FROM AUTHOR]

The service condition of mullite thermal insulation materials is complicated, the effects of carbon deposition are always considered the primary cause of damage to mullite ceramic in carbon monoxide atmosphere. In the present study, mullite thermal insulation material was subjected to a carbon monoxide atmosphere at 1100°C–1400°C. The thermodynamics stability, phase composition, and microstructure of the mullite thermal insulation material were analyzed. Furthermore, the effects of carbon monoxide corrosion on thermal shock resistance and compressive creep behavior at high temperatures were evaluated. The carbon content in the mullite‐based insulation material is below 0.02% after treatment at 1100°C–1400°C. After treatment at 1400°C, most areas in the specimen comprised corundum and glass phase, and K, Na, Ca, Mg, and Fe were detected as impurities, leading to the improvement of cold crushing strength after 20 thermal shocks but a remarkable recession in high‐temperature compressive creep. [ABSTRACT FROM AUTHOR]

Thus far, studies on the damage to refractory materials under carbon monoxide atmospheres have mostly concentrated on the effects of carbon deposition, and the testing temperature was always set at approximately 500°C to promote the deposition of carbon. However, this testing temperature is far below the operating temperature of most refractories. In this study, mullite, a widely used high‐temperature structural material, was subjected to a carbon monoxide atmosphere at 1000°C‐1600°C to investigate its phase and microstructural evolutions. Changes to the grain boundaries were initially observed in mullite specimens treated at 1000°C and 1200°C. After treatment at 1400°C, the specimen surface comprised α‐Al2O3, a glass phase, and a small amount of mullite. However, treatment at 1600°C resulted in only α‐Al2O3 and a small amount of glass phase on the surface. Additionally, pores and voids were found in the glass phase on the surface and in the bulk of the specimens treated at 1400°C and 1600°C. This study demonstrated the stability of pure mullite in a carbon monoxide atmosphere and revealed that impurities accelerating generation of the liquid phase in Al2O3–SiO2 system significantly affect the stability of mullite in a carbon monoxide atmosphere. [ABSTRACT FROM AUTHOR]

Abstract Mullite castables are widely used in hot metal pretreatment processing equipment. In this work, the effects of alumina bubble particle size on the microstructure and physical properties of mullite castables were studied. Grey relational analysis is a useful method for analyzing patterns in multivariate cases. In this paper, the grey relational analysis was used to estimate the relationship between the properties of samples and the structure of alumina bubbles. Using grey analysis, the specific surface area of alumina bubbles was determined to have the greatest influence on the properties of apparent porosity, cold mechanical properties and thermal shock resistance. The hollow radius of alumina bubbles has the greatest relationship to bulk density, hot modulus of rupture, flow values and coefficient of thermal expansion of samples. Finally, the mullite castables with a high modulus of rupture and thermal shock resistance was obtained by adding alumina bubbles with a particle size between 0.5 and 1 mm. The high modulus of rupture was shown to be caused by the alumina bubble spherical shape, hollow structure and the appropriate bonding at the alumina bubble/matrix interface. [ABSTRACT FROM AUTHOR]

The widespread use of ternary lithium-ion battery cathode Li(Ni x Co y Mn 1−x−y)O 2 (LNCM) materials in energy storage equipment has resulted in an increase in the demand for insulating refractory of roller kiln. However, the severe corrosion during LNCM calcination will result in desquamate and damage of the insulating refractory. In this study, the corrosion resistance of bubble alumina brick (bubble alumina), mullite and CA 6 (calcium hexaaluminate) insulating refractories was thoroughly investigated. This study combined the laboratory scale experiments on the interfacial reaction and after life cycle analysis on industrial insulating refractory to investigate the interactions between the insulating refractories and LNCM precursor mixture powders after the calcination temperature of 950 °C for 10 h and the corrosion behaviour of the LNCM precursor to different insulating fire bricks after the heat treatment temperature of 950 °C for 10 h every time and repeated 10 times according to the actual LNCM preparation system. The phase composition and microstructure of the three insulating refractories before and after corrosion were characterised to obtain a comprehensive understanding of the corrosion mechanism and behaviour. Results showed that the CA 6 has excellent corrosion resistance and has the potential to be used in the lithium battery industry. • CA6 insulating refractories were successfully prepared by industrial production process. • CA6 insulating refractories and commercially available insulating refractories were compared and evaluated. • The feasibility of applying CA6 insulating refractories to kiln lining materials for LNCM production was evaluated. • The prepared CA6 insulation refractory has a good prospect of industrial application. [ABSTRACT FROM AUTHOR]

In view of the increasing shortage of high quality alumina raw materials in China, the global distribution of kaolin resources and the resource characteristics of China were summarized. The application of coal series kaolin in refractories was mainly stated, such as preparation of Al2O3-SiO2 refractories, light/semi-light weight insulation refractory products and monolithic refractories. The development direction of coal series kaolin was indicated in order to provide reference for the research and comprehensive utilization of coal series kaolin in refractory industry. [ABSTRACT FROM AUTHOR]

In recent years, the rapid development of Li(Ni x Co y Mn 1-x-y)O 2 (LNCM) materials for application in ternary lithium-ion batteries has led to an increased demand for refractory kiln saggars in industries. However, saggars used for firing ternary Li-ion battery cathode materials are often subjected to severe corrosion and spalling. To investigate the damage mechanism of the saggar materials, non-contact corrosion experiments were designed to study the effects of the precursor additions, calcination temperature, and number of calcinations during the interaction between mullite saggar and LNCM materials. The phase composition and microstructure of the mullite saggar specimens before and after corrosion were characterized using X-ray diffraction and scanning electron microscopy, respectively, to obtain a comprehensive understanding of the causes of the deterioration of mullite saggar materials during corrosion. • The corrosion behavior of mullite-refractory saggars after different corrosion conditions were investigated. • Non-contact corrosion experiments were designed. • At 1100 °C, most of the mullite was completely corroded. • The new phase formed during the corrosion process was mainly LiAlO 2. [ABSTRACT FROM AUTHOR]

• A novel reticulated prickly porous ceramics with mullite whiskers. • The mullite whiskers on the inside and outside surfaces of skeleton. • The number and length of mullite whiskers is highly controllable. • The potential of porous ceramics as catalyst supports was demonstrated. • A kind of raw materials of this work is waste. Porous materials are widely used in heat exchangers, sewage treatment, electromagnetic shielding, thermal insulation, gas adsorption, photocatalytic due to their high specific surface area. The specific surface area of materials plays a pivotal role in them. It can be enhanced by increasing the porosity of the material, but the cost of this improvement is reducing the strength of the material. In order to improve performance, it is necessary to increase its surface area without reducing the strength of the material. In this work, mullite porous ceramics with mullite whisker on the inside and outside surfaces structures, which known as prickly porous ceramics(PPCs). They were fabricated using polyurethane foam coated with slurries as the pore-forming agents, sintered after secondary impregnation with silica sol and ammonium fluoroaluminate. The the sintering temperature as well as slurry composition of secondary impregnation were tuned to tailor the strength and surface structures of the PPCs. In addition, the potential of PPCs as high-temperature catalyst supports was demonstrated. Overall, the PPCs demonstrated large surface areas and high mechanical strength. This study paved the way for the fabrication of high-performance porous ceramics. [ABSTRACT FROM AUTHOR]

A SiC whisker-bonded mullite foamed ceramic was prepared by using white clay, industrial alumina and silicon powder as raw materials without solid carbon sources. The XRD, SEM, EDS, and Factsage® software were used to investigate the effect of sintering temperature on the phase composition, microstructure, compressive strength, and Young's modulus of foamed ceramics. Additionally, the synthesis reaction of in-situ SiC whiskers and the effect of their formation on the properties of ceramics were studied. The results showed that the in-situ SiC whiskers with dendrite shapes were formed after firing above 1300 °C at the expense of Si/SiO vapors as well as CO vapor, though there were no solid carbon sources in raw materials, which provided a new idea for the synthesis of SiC whiskers. The formation of SiC whiskers was helpful for improving the compressive strength and Young's modulus of mullite foamed ceramics remarkably. Furthermore, the reinforcement mechanism has been investigated systematically. [ABSTRACT FROM AUTHOR]

Abstract Mullite-corundum foamed ceramics were prepared by direct-foaming method using white clay and industrial alumina as raw materials, and micro-pore-foaming agent (MPFA, the main composition was sodium dodecyl benzene sulfonate) as foaming agent. Effect of the MPFA addition on the phase compositions, microstructures and physical properties of the foamed ceramics were investigated by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), etc. The results showed that the specimens fired at 1500 °C mainly consisted of needle-like mullite, corundum, and a small amount of glass phase. The MPFA decreased the viscosities and then increased the volume expansion of foamed slurries. Meanwhile, the adding of the MPFA caused the increases of apparent porosities and average pore sizes, and the decrease of strengths of the fired specimens. The optimized product was a specimen with 1.0 wt% MPFA fired at 1500 °C which had a high porosity of 73.7%, a proper compressive strength of 3.05 MPa, a low thermal conductivity of 0.287 W/(mK) (1000 °C) and a positive reheating linear change. Based on the experimental dates, an emendatory GE model was presented, which could predict accurately the effective thermal conductivity at 1000 °C of the mullite-corundum foamed ceramics with different pore characteristics. Highlights • The mullite-corundum foam ceramics with low conductivity and sufficient strength were prepared. • The optimized product was a specimen with 1.0 wt% MPFA fired at 1500 °C. • A modified GE model, taking the conduction and radiation into account, was presented. [ABSTRACT FROM AUTHOR]

Abstract In this study, four mullite foam ceramics with porous struts and low thermal conductivities, were prepared by direct-foaming method from white clay and industrial alumina with the addition of sodium carboxymethyl cellulose (CMC) as foam stabilising agent. The effect of the CMC addition on the phase composition, pore characteristics, and strength was analysed through XRD, SEM and EDS, etc. The great part of struts for the foam ceramics was the needle-like mullite, the rest was the minor corundum and quartz. The addition of CMC decreased the apparent porosity of foam ceramics and pore area fractions of their struts, while the phase composition was nearly unaffected. Furthermore, the compressive strengths and the thermal conductivities of the foams ceramics increased. The optimized product contained 0.15 wt% CMC, which combined a high porosity of 81.3%, shown a low thermal conductivity of 0.095 W/(mK) (at 350 °C) and a minor positive reheating linear change. [ABSTRACT FROM AUTHOR]