Refractories

Phase composition and microstructure of aluminium composite magnesia-carbon gas-supply elements after nitrogen heat treatment

Yan Mingwei, Chen Zijian, Sun Guangchao, Ye Shufeng, Liu Kaiqi

2025, (4): 277-282. doi：10.3969/j.issn.1001-1935.2025.04.001

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From the perspective of low-carbon economy,antioxidant aluminum powder was introduced as a raw material to explore its influence on the phase composition and microstructure of low-carbon magnesia-carbon materials in high temperature N₂,which aimed to prepare low-carbon gas-supply elements suitable for the bottom-blowing process of steel-making furnaces.The samples were prepared using fused magnesia,flake graphite and aluminum powder as raw materials and phenolic resin as the binder,with the aluminum powder addition of 5%,8% and 12%,by mass,respectively.The phase composition and microstructure of the samples were characterized and analyzed by XRD,SEM and EDS after nitrogen heat treatment at 1 300,1 400,1 500 and 1 600 ℃.The results show that with aluminum powder as the raw material,the magnesium-carbon samples exhibit a phase evolution different from the traditional ones,and the changes in the contents of aluminum and graphite make the modified phases on the surface of magnesia particles different.In the sample with 15% graphite and 5% aluminum powder,the modified phase is aluminum-doped cubic magnesia crystals.As the aluminum powder addition increases to 8% and above,Al₇C₃N₃ disappears,while Al₆O₃N₄ appears,whose formation temperature is higher than 1 400 ℃.In the sample with 5% graphite and 8%-12% aluminum,the modified phase is a magnesium aluminate spinel solid solution containing N element (MgAlON).

Effects of chopped glass fibers on properties of silica sol bonded corundum castables

Ding Yuhang, Liu Hui-yong, Wei Jianxiu, Xiong Jiquan, Xiang Bing, Xia Changyong

2025, (4): 283-288. doi：10.3969/j.issn.1001-1935.2025.04.002

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Improving the green body mechanical strength and thermal shock resistance of silica sol bonded corundum castables is of great significance for promoting their large-scale application.Silica sol bonded corundum castables were prepared with brown corundum,dense corundum powder,α-Al₂O₃ micropowder and SiO₂ micropowder as the main raw materials,and silica sol as the binder.The effects of different extra-additions of chopped glass fibers (0,0.2%,0.4%,0.6%,0.8% and 1%,by mass) on the properties of the castables were studied.The results show that with the increase of the fiber addition,the cold modulus of rupture,cold compressive strength and hot modulus of rupture of the samples first increase and then decrease.After drying at 110 ℃,the sample containing 0.4% fibers has the cold modulus of rupture of 9.1 MPa and cold compressive strength of 27.4 MPa,increasing by 80.4% and 41.2%,respectively,compared with the one without fibers.This is because the fibers combine with the silica sol gel interface to form a stressed skeleton,strengthening the bonding between the matrix and the aggregates.When subjected to external stress,the fibers can effectively share the load and prevent crack propagation,thus increasing the strength.In addition,the sample with 0.4% fibers has the highest cold modulus of rupture before and after thermal shock,and its strength retention ratio increases by 16.1% compared to the sample without fibers.Generally,the sample with 0.4% fibers exhibits the best comprehensive performance.

Thermal barrier coatings fabricated by atmospheric plasma spraying nano powder and their thermal shock resistance

Zhang Songting, Zhao Shixian, Li Hongyu, Li Hongxia, Si Yaochen, Li Lingfeng, Liu Guanghua

2025, (4): 289-296. doi：10.3969/j.issn.1001-1935.2025.04.003

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Based on the supersonic flame sprayed NiCoCrAlYTa bonding coating,8 mass% nano yttria-partially stabilized zirconia ceramic coatings were prepared by atmospheric plasma spraying to explore the regulation of agglomerated nano particles in the thermal barrier coating structure,and their influence on the coating performance.The structural regulation of the coatings was achieved by adjusting the spraying distance,substrate temperature and gun moving speed.The porosity and relative content of the unfused regions of the coatings were analyzed through Image J.The bonding strength and thermal shock resistance of the NiCoCrAlYTa+YSZ coatings were evaluated by the pairwise tensile method and water quenching method,respectively.The results show that the coating has high contents of unfused particle agglomerates and a suitable porosity when the powder delivery is 25 g·min^-1,the spraying distance is 115 mm,the gun moving speed is 500 mm·s^-1,and the substrate temperature is regulated at 200-300 ℃.Although the coating shows the lowest bonding strength by this process,about 26.8 MPa,it has the best resistance to thermal shock by water quenching,reaching 43 cycles at a surface failure area of 20%.

Effect of magnesium lactate and magnesium gluconate on hydration behavior of light-burnt magnesia

Zhou Jing, Wang Zhoufu, Liu Hao, Ma Yan, Xia Zhongfeng, Quan Zhenghuang, Deng Chengji

2025, (4): 297-301. doi：10.3969/j.issn.1001-1935.2025.04.004

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To optimize its hydration behavior,light-burnt magnesia was used as the raw material,with magnesium lactate and magnesium gluconate as retarders.The hydration degree,hydration heat,and ¹H-NMR of the light-burnt magnesia were characterized to study the effects of the two retarders on the setting time and the microscopic morphology of the hydration products of the light-burnt magnesia.The results show that,compared with magnesium lactate,magnesium gluconate has a more significant effect on the hydration,the hardening behavior,and the microscopic morphology of the hydration products of the light-burnt MgO.With 3 mass% magnesium lactate,the cumulative heat release after 50 h of hydration is approxi-mately 400 J·g^-1,the initial setting time is 15 min,and the hydration products exhibit lamellar petal-like crystal morphology.With 3 mass% magnesium gluconate,the cumulative heat release after 50 h of hydration is approximately 300 J·g^-1,the initial setting time extends to 45 min,and the hydration products show hexagonal plate-like or tetragonal bipyramidal crystal morphology.

Effect of Y₂O₃ addition on properties of low-carbon magnesia carbon refractories

Han Dongxu, She Yafeng, Zhang Zhicheng

2025, (4): 302-306. doi：10.3969/j.issn.1001-1935.2025.04.005

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To improve their cold performance,low-carbon magnesia carbon refractories were prepared with fused magnesia,flake graphite and aluminum powder as raw materials,Y₂O₃ as an additive,and phenolic resin as the binder by heat treatment in N₂ at 1 700 ℃ for 3 h.The effects of the Y₂O₃ addition (0,0.2%,0.5%,1%,1.2% and 1.5%,by mass) on the phase composition,microstructure and mechanical properties of the specimens were investigated.The results show that:(1) the introduced Y₂O₃ can react with the SiO₂ and Al₂O₃ in the matrix to form rare-earth compounds,and act as a bonding phase between grains or fill the gaps between particles during sintering,enhancing the density of the materials and thereby improving their mechanical properties;(2) the specimen with 0.2% Y₂O₃ exhibits the optimal comprehensive performance,with the bulk density of 2.83 g·cm^-3,apparent porosity of 10.1%,and cold modulus of rupture of 6.98 MPa,as well as good thermal shock resistance.

Crystal structure optimization and high-throughput intelligent calculation of Young’s modulus of Al₂O₃-Cr₂O₃ solid solution

Li Chuanhao, Cao Xiying, Yang Xiaoyu, Feng Haixia

2025, (4): 307-310. doi：10.3969/j.issn.1001-1935.2025.04.006

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To explore the application of high-throughput intelligent calculation in the field of refractory materials,targeting chrome corundum refractory raw materials,the Al₂O₃-Cr₂O₃ solid solution system as the research object was selected.By using high-throughput intelligent computing and machine learning methods,the effects of the Cr₂O₃ substitution concentration on the lattice constants and Young’s modulus of Al₂O₃-Cr₂O₃ solid solutions were investigated.The calculation results show that with the increase of the Cr₂O₃ substitution concentration,the Young’s modulus of Al₂O₃-Cr₂O₃ solid solutions shows an overall decreasing trend;however,at high Cr₂O₃ substitution concentrations of 70%-90%(x),the Young’s modulus of the solid solution is slightly lower than that of pure Cr₂O₃.In addition,the Young’s modulus of Al₂O₃-5%(x)Cr₂O₃ solid solution is directly calculated and compared with the predicted value of the machine learning model,and it was found that the two are not much different,which indicates the feasibility of obtaining the mapping relationship between material properties and components through the combination of high-throughput intelligent computing and data mining technology.

Modification of CA₆ saggers for lithium-ion battery cathode materials

Yao Lijun, Wang Guanyu, Yin Zhiyuan, Wang Zhipeng, Wen Tianpeng

2025, (4): 311-316. doi：10.3969/j.issn.1001-1935.2025.04.007

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The saggers used for lithium-ion battery cathode materials are easily corroded by lithium-containing cathode materials,which leads to damage of the saggers and reduction of their service life.To improve the service performance,La₂O₃-doped modified CA₆ was proposed as the sagger material.The effects of La₂O₃ extra-additions (0,1.0%,2.0%,3.0%,and 4.0%,by mass,respectively) on properties of CA₆ materials such as bulk density and apparent porosity,as well as phase composition and microstructure evolution characteristics were studied.In addition,the corrosion behavior and mechanism of LiMn₂O₄ cathode material on the surface of CA₆ saggers were investigated.The results show that La³⁺ enters the lattice in the form of interstitial defects and forms oxygen vacancy defects simultaneously,which makes the crystal structure develop from lath-like to hexagonal columnar equiaxed state,and improves the densification degree and mechanical properties.When the extra-addition of La₂O₃ is 4.0%,the bulk density increases to 3.14 g·cm^-3 and the apparent porosity decreases to 12.0%.Due to the improved density of La₂O₃-modified CA₆,CA₆ sagger material can reduce the penetration of Li⁺,thus exhibiting good corrosion resistance.

Effect of magnesia raw materials on properties of MgO-MgAl₂O₄-ZrO₂ refractories

Wang Yujing, Bo Jun, Sun Honggang, Si Yaochen, Bai Wenxian, Cheng Yuan

2025, (4): 317-322. doi：10.3969/j.issn.1001-1935.2025.04.008

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To improve the performance of MgO-MgAl₂O₄-ZrO₂ refractories,the specimens were prepared by heat treatment at 1 650 ℃ for 3 h,using different magnesia raw materials as the aggregates and analytical pure MgO fine powder,α-Al₂O₃ micropowder,spinel fine powder and monoclinic zirconia micropowder as the matrix.The effects of different magnesia raw materials (97 sintered magnesia,97 fused magnesia,and 99 brine magnesia) on the mechanical properties,phase composition and microstructure of the specimens were studied.The results show that:(1)97 sintered magnesia and 97 fused magnesia contain high contents of impurities such as CaO and SiO₂,and generate liquid phases at 1 650 ℃,which promotes material sintering,resulting in high densification degree but reduced high-temperature performance;(2)compared with 97 fused magnesia,97 sintered magnesia has higher porosity,smaller grain size and higher activity,leading to excessive linear shrinkage of the material;99 brine magnesia has high purity,small grain size,high porosity,and large specific surface area and reactivity,which can react with the matrix to generate more in-situ spinel,reduce firing shrinkage,prevent crack propagation and improve the high-temperature mechanical properties of the material;(3)the specimen with 99 brine magnesia as the raw material has a bulk density of 3.04 g·cm^-3,an apparent porosity of 17.8%,a cold modulus of rupture of 7.4 MPa,a linear shrinkage of 0.73%,a hot modulus of rupture (held at 1 400 ℃ for 0.5 h) of 7.1 MPa,good thermal shock resistance,and the best comprehensive performance.

Effects of waste high alumina sphere powder on performance of mullite-alumina-quartz multiphase materials

Lyu Zhenfei, Fan Mengke, Cao Yukun, Li Xihu, Ke Yanghui, Zhang Xuejia, Wang Xuekai, Shen Xiulin, Zhang Xiaoguang

2025, (4): 323-329. doi：10.3969/j.issn.1001-1935.2025.04.009

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To realize the comprehensive utilization of waste electric porcelain,mullite-alumina-quartz multiphase materials were prepared using waste electric porcelain with particle sizes of 1-0.3,0.3-0.125 and ≤0.074 mm as main raw materials,waste high alumina sphere powder and kaolin as the additives,and sodium silicate as the binder.The effects of heat treatment temperatures (1 200,1 250,1 300 and 1 350 ℃,holding for 3 h) and waste high alumina sphere powder additions (0,10%,20% and 30%,by mass,respectively) on the material properties were studied.The results show that:(1)with the heat treatment temperature rising,the bulk density,cold modulus of rupture (CMOR) and cold compressive strength (CCS) of the samples first increase and then decrease;(2)with the increase of the waste high alumina sphere powder addition,the bulk density gradually decreases,while the CMOR and CCS first increase and then decrease;(3)the samples with 20% waste high alumina sphere powder treated at 1 300 ℃ have relatively good comprehensive performance,with main phases of mullite and α-Al₂O₃,and the CMOR and CCS are 66.3 and 216 MPa,respectively.

Microstructure and thermal shock resistance of corundum-spinel castables containing nano-CaCO₃

Tan Dan, Wang Jingran, Zhang Jinhua, Ni Yue’e, Han Bingqiang

2025, (4): 330-336. doi：10.3969/j.issn.1001-1935.2025.04.010

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Corundum-spinel castables were prepared using sintered corundum,α-Al₂O₃ micropowder,90MA spinel micropowder,calcium aluminate cement,and fine fused magnesia powder as raw materials,then heat-treated at 1 100 and 1 600 ℃ for 3 h.The effects of nano-CaCO₃ extra-additions (0,0.5%,1.0%,1.5%,and 2.0%,by mass,respectively) on the microstructure,mechanical properties,and thermal shock resistance of the corundum-spinel castables were investigated.The results show that under the condition of maintaining the consistent flowability among all groups of castables,with the nano-CaCO₃ extra-addition increasing,the water consumption of castables gradually increases,the apparent porosity gradually rises,and the bulk density gradually decreases.After thermal decomposition,nano-CaCO₃ in situ reacts with Al₂O₃ in the matrix to form calcium aluminate phases such as CA₂ and CA₆,which can improve the cold modulus of rupture (CMOR) and the cold crushing strength (CCS) of the castables after heat treatment at 1 100 ℃,but the CMOR and the CCS of the castables after heat treatment at 1 600 ℃ gradually decrease.Nano-CaCO₃ can improve the thermal shock resistance of the castables,and the optimal nano-CaCO₃ extra-addition is 1.5%.

Preparation and properties of graphene coating for slide plate

Ruan Guozhi, Zhang Zhihui, Zhang Lanqin

2025, (4): 337-339. doi：10.3969/j.issn.1001-1935.2025.04.011

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To improve their viscosity,adhesion,and oxidation resistance of the slide plate coating thus increasing the continuous casting rate,graphene coatings for slide plate were prepared via a ball-milling process using graphene powder,sodium carboxymethyl cellulose (CMC),polyvinylpyrrolidone,emulsifier (OP-10),and boron carbide (B₄C) as the main raw materials.The effects of the ball-milling time (12,24,36,48,and 60 h) on the viscosity,brushing performance,air-drying speed,and oxidation resistance of the graphene coatings for slide plate were studied.The results show that with the increase of ball-milling time,the viscosity of the graphene coatings for slide plate gradually increases,while the brushing performance first improves and then decreases;and the coating exhibits the best brushing performance when the ball-milling time is 36 h.With the increase of ball-milling time,the oxidation resistance of the graphene coatings for slide plate first increases and then decreases,and the coating shows the best oxidation resistance when the ball-milling time is 36 h.Compared with the other two types of domestic slide plate coatings,the graphene coating has an obvious advantage in high-temperature oxidation resistance.

Performance research and process optimization of spinel-carbon stopper heads for continuous casting

Fang Wenji, Pan Lei, Gao Zhi, Wang Zuochuang, Yang Qin, Ma Beiyue

2025, (4): 340-344. doi：10.3969/j.issn.1001-1935.2025.04.012

Abstract ( ) PDF (1423KB)( )

Stoppers are an important flow-controlling component in continuous casting.Aluminum-carbon stopper heads are often damaged due to poor corrosion resistance,thermal shock resistance,and oxidation resistance during smelting high-oxygen and high-manganese steel,which leads to the flow-controlling failure of stoppers.Stopper head materials were prepared using fused magnesium aluminate spinel,flake graphite,Si powder,and SiC powder as main raw materials,powdered phenolic resin as the binder,and industrial alcohol as the solvent.The effects of resin additions (6%,7%,8%,and 9%,by mass) and SiC powder additions (1%,2%,3%,5%,and 8%,by mass) on the performance of the stopper heads were studied,and the head structure process was optimized.The result shows that when the resin addition is 7%,the material achieves the highest densification degree with a density of 2.65 g·cm^-3,and its cold and hot mechanical properties are optimal:the cold compressive strength of 41 MPa,the cold modulus of rupture of 14.3 MPa,and the hot modulus of rupture of 7.3 MPa.On this basis,adding 3% SiC powder can improve the thermal shock resistance and oxidation resistance of the head while ensuring its mechanical properties.In addition,optimizing the structural process to change the contact area between the head and the main body increases the fracture surface energy of the head,thus reduces the occurrence of head dropping,and improves the reliability of the stopper.

Thoughts and explorations on scientific and technological innovation of refractories

Gu Huazhi

2025, (4): 345-353. doi：10.3969/j.issn.1001-1935.2025.04.013

Abstract ( ) PDF (3135KB)( )

As core fundamental materials for high-temperature production processes in industries such as iron and steel,nonferrous metals,cement,glass,ceramics,chemical engineering,machinery,electric power,and national defense,refractories are directly related to the stability of production operations and the progress of technological innovation in these fields.However,the industry currently faces multiple challenges,including raw material resource constraints,process technology bottlenecks,and lag in intelligent transformation.To break through the development dilemma,from the perspective of scientific and technological innovation,this paper proposes to take diversified market demands as the orientation,deeply explore the advantages of raw material mineral characteristics,accelerate the integrated transformation of “artificial intelligence + refractories”,and strengthen the development of original innovation capabilities.Through a series of theoretical research and practical exploration,preliminary results have been achieved at the laboratory stage,providing a new path and reference for the high-quality development of the refractory industry.

Research progress on preparation of 1D/2D magnesium aluminate spinel

Hu Yanqiu, Xing Yidan, Zhong Qiao-fang, Qu Chao, Huang Liang, Zhang Haijun

2025, (4): 354-360. doi：10.3969/j.issn.1001-1935.2025.04.014

Abstract ( ) PDF (959KB)( )

Magnesium aluminate spinel features stable chemical properties,low thermal expansion coefficient,excellent corrosion resistance,good thermal shock resistance and slag resistance,thus boasting broad application prospects in fields like refractory materials,transparent ceramics and catalyst supports.The preparation methods of one-dimensional (1D) and two-dimensional (2D) magnesium aluminate spinel in China and abroad in recent years were reviewed,including high-temperature solid-phase template method,gas-liquid-solid method,gas-solid method,liquid-phase method,molten salt method and sol-gel method.The advantages and current main problems of the above methods were summarized.The development of preparation methods for 1D and 2D magnesium aluminate spinel was prospected.

Research progress on SiC ceramics preparation technology

Liu Yue, Ding Guoqiang, Liu Zeling, Cheng Shi-qi, Feng Dong, Ru Hongqiang, Luo Xudong, You Jiegang

2025, (4): 361-368. doi：10.3969/j.issn.1001-1935.2025.04.015

Abstract ( ) PDF (974KB)( )

Without sintering aids,SiC is difficult to densify even after high-temperature sintering.In this paper,the characteristics and current research progress of sintering processes for SiC ceramics were reviewed.The types of sintering aids for SiC ceramics and their sintering-aid mechanisms were discussed.The limitations in the preparation of high-performance SiC ceramics were pointed out.The future development directions were presented.