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Conventional refractory materials used for calcining ternary lithium‐ion battery cathode materials, such as mullite, cordierite, and magnesia‐alumina spinel, are vulnerable to attack by Li(NixCoyMn1−x−y)O2 (LNCM) materials and therefore have a short service life. In order to improve the corrosion resistance of refractory materials to LNCM materials, mullite‐Al2TiO5 materials with different contents were synthesized in this paper by using calcined mullite powder, TiO2 powder, and La2O3 powder as raw materials, which were calcined at 1500–1600°C temperature, respectively. In this study, the potential of the materials for the preparation of LNCM materials was investigated in terms of its physical properties, resistance to the corrosion of LNCM materials, and resistance to thermal shock. The results showed that mullite‐Al2TiO5 composites can be successfully synthesized at 1500–1600°C, and the physical properties of the materials met the production requirements. The prepared mullite‐Al2TiO5 composites also exhibited better physical properties, good corrosion resistance, and proper thermal shock resistance compared with mullite refractories. [ABSTRACT FROM AUTHOR]

Fiberboard (FB) is extensively utilized in heat‐insulating refractory materials owing to its lightweight nature and excellent resistance to high temperatures. Nevertheless, the inadequate mechanical properties and limited dimensional stability of FB hinder its further application. The vacuum filtration was utilized in this study to manufacture inorganically modified insulation FB, incorporating plus fiber/1260 fiber and silica sol as the primary constituents and sepiolite powder (HS) as the modifier. The experimental results show that the fabricated samples exhibited extremely high porosity (75.3%–90.2%) and low thermal conductivity (.063–.15 W m−1 K−1, 200–800°C). The fibers were arranged in a three‐dimensional structure, overlapping with each other, and the silica sol adhered to the fibers, forming a spatial mesh structure through cross‐linking. Importantly, the incorporation of HS was effective in controlling the agglomeration of the silica sol, leading to a more uniform distribution within the fibers. Additionally, the study found that the mechanical properties (high hardness (64–72 HA)) and high‐temperature durability of the FBs were enhanced due to the flocculant modification. This study highlights promising prospects for industrial applications and offers a cost‐effective admixture for modifying and preparing high‐performance FBs, which is expected to see broad adoption in thermal insulation and energy conservation applications. [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 Application of waste foundry sand (WFS) obtained from investment casting in refractories is a promising alternative developed in recent years for reducing waste landfill while also producing high-value products. It is important to enlarge the applicable area in a refractory, especially with the increasing generation of WFS and growing tension in global mineral supply. Systematic studies on as-received WFS and its microstructure evolution after thermal treatment are rare; this imposes restrictions on using WFS in various applications. In this study, WFS is systematically analyzed, and the microstructure evolution of WFS specimens with thermal treatment at 1300–1550 °C is investigated. Quantitative analysis of the crystal phases indicates that WFS contains 46.2 wt% mullite, 28.1 wt% cristobalite , and 10.9 wt% zircon; the main oxidation states of Fe and Ti in WFS are Fe 3 O 4 and TiO 2. Leaching of WFS is hazardous; Thermal treatment below 1500 °C is harmless. The transformation of tetragonal ZrO 2 to monoclinic ZrO 2 in the specimens sintered at 1500 °C reduces the cold modulus of rupture, and Fe 2 O 3 decomposition at 1550 °C reduces the bulk density and modulus of elasticity. Phase changes significantly affect the true density and melting of cristobalite at 1550 °C causes a sharp decrease in density. Highlights • WFS contains 46.2 wt% mullite, 28.1 wt% cristobalite and 10.9 wt%. • The primary oxidation state of Fe and Ti in the WFS are Fe 3 O 4 and TiO 2. • The WFS is eco-friendly after thermal treatment below 1500 °C. • Fe 2 O 3 decomposition at 1550 °C decrease bulk density of sintered specimens. [ABSTRACT FROM AUTHOR]

AlO-C refractories were first fabricated in a coke bed at 1673 K (1400 °C) using tabular corundum, reactive alumina, carbon black, silicon, and microsilica as the starting materials and phenol resin as the binder. Then the alkali attack resistance of those materials was conducted in the powder mixture of carbon black and potassium carbonate (1:1 wt pct) in a graphite crucible at 1273 K (1000 °C) for 10 hours. The correlation between pore size, permeability of AlO-C refractories, and their alkali (KCO) attack was investigated by means of mercury intrusion porosimetry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results showed that the pore structure of AlO-C refractories was controlled by the addition of silicon, ultrafine reactive alumina, and microsilica to in-situ form SiC whiskers and mullite in the preparation process. The mean pore size of AlO-C refractories was strongly associated with permeability. With the decrease of the mean pore size, the permeability of the AlO-C refractories reduced constantly. The alkali attack test also verified that the AlO-C refractories with lower permeability had better alkali corrosion resistance, because the penetration of K vapor into the materials could be restricted effectively. The corrosion mechanism of AlO-C refractories supposes that (1) KCO was reduced to K vapor and penetrated into the specimen through the open pores and (2) K vapor reacted with SiC, SiO, and alumina to form KAlSiO and KAlSiO, which is in agreement with the thermodynamic prediction. [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 the ternary Li-ion battery cathode Li(Ni x Co y Mn z)O 2 (LNCM) materials industry has resulted in increased demand for refractory kiln furniture (saggars). To reduce the production cost of the saggars and improve their anti-corrosion performance, mullite-zirconia materials were synthesized from zircon-containing kyanite tailings. This study examines the potential of the materials as saggars in the preparation of the LNCM materials based on two aspects—the material's physical properties and its resistance to the corrosion of LNCM materials. The results show that mullite-zirconia composites can be successfully synthesized at 1500–1600 °C, and the physical properties of the materials meet the needs of production. Additionally, the mullite-zirconia material prepared at 1550 °C was more resistant to LCNM precursor corrosion than the ones prepared at 1500 and 1600 °C. [ABSTRACT FROM AUTHOR]

In this study, six gas-permeable mullite-corundum refractories with 45–95 wt% spherical porous mullite aggregates were prepared. The influence of the spherical porous aggregate content (SPAC) on the microstructure, gas permeability, and mechanical properties was analysed by XRD, SEM, EDS and image analysis method, etc. It's found that the SPAC affected the pore characteristics and mechanical properties through changing the packing and sintering behaviours of the aggregate and matrix in the refractories. When the SPAC was 45–65 wt%, the refractories had higher strengths as well as two gas-permeable channels in the aggregate and matrix respectively. Whereas, when the SPAC increased to 75–95 wt%, the refractories had lower strength as well as one gas-permeable channel in the matrix. The optimized product contained 65 wt% spherical porous aggregate and combined a high gas permeability of 4.9 × 10−12 m2, a high compressive strength of 18.5 MPa, a good thermal shock resistance and well-distributed gas-permeable channels. [ABSTRACT FROM AUTHOR]

A study of microstructural evolution, mechanical and thermo-mechanical properties of MgO–C refractories, based on graphite oxide nanosheets (GONs), carbon nanotubes (CNTs) and carbon black (CB), was carried out by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), three-point bending and thermal shock tests. Meanwhile, these results were compared to the conventional MgO–C refractory containing 10wt% flaky graphite prepared under the same conditions. The results showed that higher cold modulus of rupture was obtained for the composition containing GONs, and the composition containing CNTs exhibited larger displacement after coking at 1000°C and 1400°C. Also, the addition of nanocarbons led to an improvement of the thermal shock resistance; in particular, both compositions containing CNTs and CB had higher residual strength ratio, approaching the thermal shock resistance of the reference composition containing 10wt% flaky graphite, as it was associated with the presence of nanocarbons and in-situ formation of ceramic phases in the matrix. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanotubes (CNTs) are a promising reinforcement for fabricating Al2O3–C refractories. However, CNTs are prone to agglomerate or react with antioxidants or reactive gaseous phases such as Al (g), Si (g) and SiO (g), etc. at high temperatures. To overcome the problems above, polycarbosilane (PCS) and multi-walled carbon nanotubes (MWCNTs) were firstly mixed with micro-alumina powder in a liquid medium and then incorporated into Al2O3–C refractories. Then the microstructure and mechanical properties of Al2O3–C refractories fired in the temperature range from 800°C to 1400°C were investigated in this work. The results showed that the MWCNTs were well dispersed in the specimens with addition of PCS in contrast to the specimens without PCS due to the PCS adsorption on the surface of MWCNTs during the mixing process. And the mechanical properties, such as cold modulus of rupture (CMOR), flexural modulus (FM), forces and displacements of Al2O3–C refractories with PCS were much higher than those without PCS, which was attributed to more homogeneous dispersion of MWCNTs, more residual MWCNTs as well as different morphologies of ceramic whiskers. Meanwhile, the oxidation resistance of Al2O3–C refractories with PCS was improved greatly, which was supposed that the in situ formed SiC x O y coating prevented the oxidation of MWCNTs to some extent. [Copyright &y& Elsevier]

Abstract: MgO–C refractories containing expanded graphite particles (EGs) and Al, Si additives were prepared. The EGs were prepared firstly by exfoliating commercial expandable graphite. Then, the composite powder containing EGs was obtained by mixing EGs and magnesia powder and incorporated into MgO–C refractories. The microstructure and mechanical properties of all the MgO–C refractories obtained were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), three-point bending and thermal shock tests. The results showed that EGs affected the microstructural evolution of MgO–C refractories. Much more interlocking aluminum carbides and nitride phases formed in the matrix of the specimen containing EGs because of their higher activity compared to flaky graphite. Also, EGs had a positive influence on the mechanical properties of MgO–C refractories. MgO–C specimens containing EGs had much higher cold modulus of rupture and better toughness compared to the specimens containing only flaky graphite; furthermore, the thermal shock resistance of MgO–C refractories was improved with the addition of EGs. It was suggested that EGs and in-situ formed ceramic phases in the matrix had a strengthening and toughening effect on MgO–C refractories. [Copyright &y& Elsevier]

Abstract: MgOC refractories containing graphite oxide nanosheets (GONs) and Al, Si additives were prepared in this work. Firstly the MgOGONs composite powders were fabricated by common ball milling of expanded graphite and magnesia powders, and then incorporated into MgOC refractories. The phase composition, microstructure, mechanical and thermo-mechanical properties of MgOC refractories treated at the different temperatures were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), three-point bending method and thermal shock test. The results showed that the GONs of different sizes and thicknesses were well distributed in magnesia powders. Addition of GONs had a positive influence on the mechanical properties of MgOC refractories. After firing at 1400°C, much higher cold modulus of rupture (CMOR) and increased displacement were achieved for MgOC specimens with GONs added compared to that of the specimen contained only flaky graphite. Moreover, the thermal shock resistance of all the specimens containing GONs was better than that for the specimen containing no GONs. It was suggested that GONs and in-situ formed ceramic phases in the matrix strengthened and toughened MgOC refractories. [Copyright &y& Elsevier]

Abstract: Microstructure and mechanical properties of Al2O3–C refractories using Ni-catalyzed phenolic resin as binder coked in the temperature range from 800°C to 1400°C are investigated in the present work. The results showed that only amorphous carbon formed from as-received phenolic resin, while crystalline graphite carbons, particularly multi-walled carbon nanotubes (MWCNTs) were gradually obtained from Ni-catalyzed phenolic resin with increasing the pyrolysis temperature from 450°C to 1050°C. The morphology and quantity of in situ formed carbon nanotubes (CNTs) in Al2O3–C matrix specimens were closely associated with the coking temperature. The mechanical properties such as cold modulus of rupture (CMOR), flexural modulus (E), force and displacement of Al2O3–C refractory specimens with addition of Ni-catalyzed phenolic resin were greatly improved compared with those with as-received phenolic resin. The improvement was attributed to the in situ catalytic formation of CNTs and more ceramic whiskers in the specimens containing Ni-catalyzed phenolic resin. [Copyright &y& Elsevier]

Abstract: Microstructures and mechanical properties of Al2O3-C refractories with Al, Si and SiO2 as the additives fired in the temperature range from 800 to 1400°C are investigated when multi-walled carbon nanotubes (MWCNTs) were used as the carbon source to partially or totally replace graphite flake in the materials. The results showed that the mechanical properties such as cold modulus of rupture (CMOR), modulus of elasticity (E) of all the specimens increased in the firing temperature range from 800 to 1200°C, but decreased dramatically at 1400°C. Compared with specimens with only graphite flake, specimens containing 0.05wt% MWCNTs possessed better mechanical properties. However, they got deteriorated with the further increase of MWCNTs amount from 0.1 to 1wt%. The differences in mechanical properties were closely associated with the microstructures of Al2O3-C refractories. In comparison with specimens having only graphite flake, the improvement of mechanical properties of specimens containing MWCNTs was attributed to strengthening and toughening mechanism of MWCNTs as well as formation of larger amount of ceramic phases in the matrix at 800 and 1000°C, respectively. At 1200 and 1400°C, the improvement was mainly associated with the quantity and morphology of SiC whiskers induced from MWCNTs in the specimens. However, with the increase of MWCNTs amount, the mechanical properties of the materials got deteriorated because of agglomeration of MWCNTs and their influence on the morphology of ceramics phases. [Copyright &y& Elsevier]

Abstract: Silicon, microsilica and their combination were used as additive in carbon containing refractories, respectively. The effects of such additive on microstructures and mechanical properties of Al2O3–ZrO2–C refractories were investigated. The results show that in refractories of this kind, silicon is responsible for the formation of SiC whiskers; microsilica mainly dominates the formation of mullite; while their combination (silicon plus microsilica) brings high partial pressure of SiO(g) and leads to the co-existence of finer SiC whiskers and needle-like mullite. The various microstructures unquestionably cause differences in mechanical properties of Al2O3–ZrO2–C refractories. The use of silicon mainly results in an enhanced mechanical strength, while the addition of microsilica primarily triggers the improvement in toughness. When the combination of silicon and microsilica is used as additive, excellent strength and toughness can be obtained simultaneously in Al2O3–ZrO2–C refractories, which is mainly attributed to the synergistic effects of SiC whiskers formed from silicon additive and needle-like mullite formed from microsilica additive. [Copyright &y& Elsevier]