@article{XIN2025, 
author = {Yalou XIN and Yunling JIAN and Hongfeng YIN and Hudie YUAN and Yun TANG and Xiaohu REN and Yuchi LIU and Guoqi LIU},
title = {Effect of Composition Design on Structure and Properties of Al2O3–Ti3Si(Al)C2–C Refractories},
year = {2025},
journal = {Journal of the Chinese Ceramic Society},
volume = {53},
number = {9},
pages = {2559-2567},
keywords = {composition design, alumina–titanium silicon aluminum carbon–carbon refractory, reactive melt infiltration method, mechanical properties, thermal shock resistance},
url = {https://www.sciopen.com/article/10.14062/j.issn.0454-5648.20240818},
doi = {10.14062/j.issn.0454-5648.20240818},
abstract = {IntroductionRecent development on low–carbon/ultra-low carbon refractories with superior properties for the rapid development of green low–carbon economy and high-quality clean steel is a research hotspot. The structure and properties of low–carbon refractories in a variety of ways are optimized to solve the problem of deterioration of high-temperature properties caused by simple reduction of graphite content. The introduction of carbon nanomaterials can significantly reduce the overall carbon content of the material. Also, the mechanical strength and thermal shock resistance of carbon-containing refractories are improved simultaneously because the nanostructures absorb and buffer the thermal stress generated by a large number of thermal shocks. In addition, reinforcement phases such as carbides, borides and nitrides are also applied to improve the organizational structure and properties of low–carbon refractories to solve the long-standing problem of carbon source oxidation. However, the poor dispersion of nanomaterials in the matrix is a significant technical problem, and the synthesis process of composite powders is complex and challenging. High production costs and the difficulty of achieving large-scale application restrict the industrial development of these materials. The structural degradation at high temperatures leads to a decline in the strength of refractories and even deterioration of comprehensive performance, which cannot guarantee the stability of long-term service of refractoriesMethodsThe MAX phase materials were expected to achieve the balance between low carbonization and service performance of carbon-containing refractories due to their graphite-like layered structure, high thermal conductivity, high damage tolerance and good oxidation resistance and thermal shock resistance. In this work, in-situ Ti3Si(Al)C2 reaction bonded low carbon Al2O3–C refractory was prepared by a reactive melt infiltration method based on the preparation process of ceramic matrix composite materials. The effects of the amount of TiC/graphite in the prefabricated material and the type of Si–Al alloy as the infiltration medium on the phase composition, microstructure, physical properties, mechanical properties and thermal shock resistance of the refractories were investigated.Results and discussionThe phase composition and performance (i.e., the apparent porosity, bulk density and flexural strength) are different at different compositions of the preforms. Corundum, Ti3Si(Al)C2 and TiC phases appear in all the samples, and trace amounts of SiC, TiAlxSiy and residual Al also occur. When the preform does not contain graphite, the content of Ti3Si(Al)C2 in the sample is higher, and the apparent porosity is much lower. The flexural strength of the sample increases from 9.0 MPa and 23.4 MPa to 79.4 MPa and 82.2 MPa, respectively, when the graphite removes from the raw material. Also, the bulk density of refractories is higher. This is due to the poor wettability of graphite and alloy, which prevents the infiltration of alloy melt into the preform. Graphite reacts with Si to form SiC phase and consumes Si element, which affects the growth of subsequent Ti3Si(Al)C2 phase. The content of titanium carbide in the raw material also affects the generation of Ti3Si(Al)C2, increasing the content of titanium carbide is beneficial to generating more Ti3Si(Al)C2, which causes a lower porosity and a higher bulk density of Al2O3–Ti3Si(Al)C2–C efractories. The overall apparent porosity of samples Al50Si50 and Al95Si5 is lower than that of sample Al5Si95, and the bulk density is relatively high. This is related to a fact that the presence of Al promotes the infiltration of alloy melt into the precast and is conducive to the formation of Ti3Si(Al)C2. The flexural strength of the sample T25@Al50Si50 using Al50Si50 alloy as a penetration medium increases from 75.5 MPa to 110.5 MPa after thermal shock. The rich toughening mechanism of Ti3Si(Al)C2 helps to improve the thermal shock resistance of the refractory, and the oxidation products generated after the oxidation of Ti3Si(Al)C2 can make the structure of the refractory more dense. The presence of whiskers in the refractory is also beneficial for better thermal shock resistance.ConclusionsLow carbon Al2O3–Ti3Si(Al)C2–C refractory could be prepared after the preform was infiltrated with Al50Si50 alloy. The presence of graphite in the preform obstructed the penetration of Si–Al alloy and ultimately affected the mechanical properties of the sample. The flexural strength of the preform without graphite was up to 82.2 MPa after the infiltration reaction at 1550 ℃. The content of Al in the infiltration medium had an effect on the production of Ti3Si(Al)C2 in the refractory. The presence of Al was conducive to the reduction of twinning grain boundary energy between TiC grains, effectively promoting the formation of TiCx twins. Ti3Si(Al)C2 phase was also easy to nucleate from the TiCx twin and grow in the Ti–Si–Al liquid phase. The Ti3Si(Al)C2 phase consumed energy through various deformation mechanisms, thus increasing the flexural strength of the refractory material at room temperature. Also, Ti3Si(Al)C2 could form a continuous and dense oxide layer during the thermal shock process, effectively preventing the Ti3Si(Al)C2 inside the sample from being further oxidized. The formation of the dense layer could restore or even strengthen the mechanical properties of the refractory after thermal shock. The flexural strength of sample T25@Al50Si50 increased from 75.5 MPa to 110.5 MPa after thermal shock.}
}