Structure and properties of anorthite insulating refractories fabricated from solid-waste coal gangue

Guo Huishi, Gao Chaoyang, Li Wenfeng, Yang Jialin, Zhou Chaojie, Qin Xiaomei, Qin Xiaoyun, Hou Pei, Chen Fenghua, Gui Yanghai, Liu Yingfan

2025, (6): 461-465. doi：10.3969/j.issn.1001-1935.2025.06.001

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To utilize solid-waste coal gangue as a resource,a slurry was prepared by mixing coal gangue powder (d₅₀=75 μm),CaCO₃ powder (d₅₀=75 μm),and α-Al₂O₃ powder (d₅₀=5 μm) at a mass ratio of 6∶3∶1,with 35 mass% distilled water added.Then,2 mass% composite foaming agent NS-Ⅲ was added to the slurry to form a foamed slurry.The foamed slurry was poured into a 100 mm×100 mm×50 mm mold.The demolded green body was first dried at 100 ℃ for 24 h and then fired at different temperatures (1 200,1 250,1 300,and 1 350 ℃) for 3 h to fabricate anorthite insulating refractories.The effects of the heat treatment temperature on the phase evolution,microstructure and properties were investigated.The results show that (1) with the increasing heat treatment temperature,the diffraction peak intensity of anorthite and mullite gradually increases,the anorthite crystals increase and gradually develop from short columnar to lamellar;the bonding among crystals gradually densifies;the bulk density,linear shrinkage and thermal conductivity of the samples decrease firstly and then increase,while the apparent porosity shows an opposite trend,and the cold compressive strength gradually rises;(2)when the heat treatment temperature is 1 300 ℃,the sample exhibits the optimal overall performance,with the bulk density of 0.48 g·cm^-3,apparent porosity of 84.3%,cold compressive strength of 1.80 MPa,and thermal conductivity at 1 000 ℃ of 0.139 W·m^-1·K^-1,and the anorthite crystals in the sample show lamellar morphology and bond closely,which makes the sample suitable for long-term service at high temperatures.

Synthesis of SiAlON composite powders by carbothermal reduction and nitridation of coal gasification slag

Guo Shimeng, Yin Hongfeng, Jia Huan, Xin Yalou, Tang Yun, Yuan Hudie, Ren Xiaohu

2025, (6): 466-470. doi：10.3969/j.issn.1001-1935.2025.06.002

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Both coal gasification slag and iron tailings contain unreacted residual carbon and rich oxide components of silicon,aluminum,iron,and calcium,which can be used as secondary resources to prepare SiAlON ceramics,realizing high-value-added utilization of coal gasification slag.In this work,the carbothermal reduction and nitridation technology was adopted to synthesize SiAlON composite powders,with coal gasification slag as the raw material,iron tailings as the catalyst and carbon black as the reducing agent.The effects of the nitridation temperature (1 425,1 450,and 1 475 ℃),holding time (3,6 and 9 h) and iron tailings addition (10%,20%,30%,40%,50% and 60%,by mass) on the phase composition and microstructure of the nitridation products were studied.The results show that increasing the nitridation temperature or extending the holding time is conducive to the transformation from O’-SiAlON to β-SiAlON.When the nitridation temperature is 1 450 ℃ and the holding time is 6 h,with the increase of the iron tailings addition,β-SiAlON gradually develops from short rods to complete long columns.When the iron tailings addition exceeds 50%,flaky O’-SiAlON is obtained.The iron component forms a large amount of liquid phases at high temperatures and exerts a certain catalytic effect in the carbothermal reduction nitridation,which affects the phase composition and microstructure of SiAlON.

Effects of recycled Al₂O₃-C composite slide gate material addition on properties of Al₂O₃-SiC-C castables

Chen Cong, Han Bingqiang, Wei Jiawei, Zhong Hutang, Zhao Haohao, Duan Junlong

2025, (6): 471-476. doi：10.3969/j.issn.1001-1935.2025.06.003

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The short service life of the currently used slide gates leads to significant waste of high-quality raw materials.Recycling spent slide gate materials into appropriate refractories can reduce costs and achieve comparable performance.In this work,Al₂O₃-SiC-C (ASC) castables were prepared using bauxite,the recycled alumina-carbon composite slide gate materials (abbreviated as “recycled material” hereinafter) and SiC as aggregates,and white corundum powder,SiO₂ micropowder,Si powder,α-Al₂O₃ micropowder,Secar 71 cement and spherical asphalt as fine powders.The performance of the recycled materials and the influence of the recycled materials addition to substitute for the bauxite (0,6%,12%,18%,and 24%,by mass) on the properties of the ASC castables were investigated.The results show that:(1)the recycled material has similar Al₂O₃ content to bauxite,containing graphite,Al,and Si,and slightly lower bulk density;(2)the introduction of the recycled material promotes the generation of SiC whiskers in the ASC castables,improving the cold strength and thermal shock resistance;(3)the recycled material exhibits higher reactivity,which can enhance the bonding with the matrix through reactive sintering,hinder further slag penetration and improve the slag corrosion resistance of the ASC castables;the ASC castables with 24% recycled material meet the performance requirements for the iron trough.

Effect of potassium feldspar addition on properties of ceramic proppant

Wang Chenzhe, Jin Endong, Ding Donghai, Xiao Guoqing, Zhu Xianfeng, Jia Xuhui

2025, (6): 477-481. doi：10.3969/j.issn.1001-1935.2025.06.004

Abstract ( ) PDF (1944KB)( )

To reduce the process cost and density of ceramic proppant,low-grade bauxite and coal gangue were adopted as raw materials,and potassium feldspar as sintering aid to prepare ceramic proppant.Green spherical pellets with particle sizes of 0.425-0.212 mm were obtained through granulation and sieving,then dried at 110 ℃ for 12 h and solid-phase-sintered at 1 220 ℃ for 2 h.The effects of the potassium feldspar addition (0,5%,10%,and 15%,by mass) on the density,breakage ratio,phase composition,and microstructure of the ceramic proppant were studied.The results show that (1)with the increase of the potassium feldspar addition,mullite and corundum crystals gradually grow and interlace with each other to form a reticulated structure,the liquid phase uniformly disperses and wraps the grains,enhancing the densification of the specimen;(2)during sintering,K₂O in potassium feldspar forms a liquid phase with SiO₂ and Al₂O₃,which fills the pores of the proppant and promotes the growth of corundum and mullite crystals,thereby reducing the breakage ratio and enhancing the mechanical strength;(3)when the potassium feldspar addition is 10%,the properties of the ceramic proppant are the optimal:bulk density of 1.41 g·cm^-3,breakage ratio of 10.7% under a closure pressure of 35 MPa and 17.5% under 52 MPa.

Preparation of MgO-Mg₂SiO₄ refractories from light burnt magnesia and their thermal shock resistance

Wang Cairan, Hou Qingdong, Yu Jiayao, Gao Huinan, Bian Zuomin, Luo Xudong, He Xinye, Li Yihan

2025, (6): 482-487. doi：10.3969/j.issn.1001-1935.2025.06.005

Abstract ( ) PDF (1774KB)( )

To solve the problems of wasting magnesite tailings resource and environmental pollution,medium burned magnesia prepared from magnesite tailings was selected as the raw material,adding SiO₂ and Ca(OH)₂ as additives to prepare MgO-Mg₂SiO₄ refractories at 1 450 ℃ for 3 h.The effects of SiO₂ and Ca(OH)₂ additions on the sintering and thermal shock resistance of the refractories were studied.The results show that the introduction of SiO₂ and Ca(OH)₂ jointly promotes the sintering of the material.When the additions of SiO₂ and Ca(OH)₂ are 1.96 mass% and 2.42 mass%,namely the molar ratio of Ca(OH)₂ to SiO₂ is 1,the sintering and thermal shock resistance of the sample are the optimal:the bulk density is 2.96 g·cm^-3,the apparent porosity is 16.7%,the retention ratios of the cold modulus of rupture and cold compressive strength after thermal shock are 80% and 53%,respectively.The introduction of SiO₂ and Ca(OH)₂ also promotes the solid solution reaction between monticellite and forsterite,thus forming microcracks at the grain boundaries of the material.The cracks propagate and undergo deflection under stress,which plays a role in crack deflection toughening,thereby improving the thermal shock resistance of MgO-Mg₂SiO₄ refractories.

Preparation of SiO₂-coated MgO composite powders by sol-gel method and their properties

Zhou Zhang-yan, Cao Jiyuan, Ma Beiyue, Li Guangming, Song Na, Ban Xia, Liu Yongli, Zhang Chengcheng, Zhao Guang-yi

2025, (6): 488-494. doi：10.3969/j.issn.1001-1935.2025.06.006

Abstract ( ) PDF (1447KB)( )

To address the challenges associated with the agglomeration of magnesia and its poor dispersion stability in sol systems,the effects of the sodium pyrophosphate additions (0-2.5 mass%),suspension pH (7.9-11.5),and ultrasonic dispersion time (0-20 min) on the dispersity and stability of the magnesia powder were investigated.Subsequently,SiO₂-coated magnesia powders were prepared using sodium silicate as the raw material through the sol-gel method.The influence of the coating time (1-9 h),coating temperature (55-95 ℃),suspension pH (7.5-11.3),and sodium silicate solution mass fraction (1%-5%) on the surface properties of the powders was studied.The results indicate that within certain ranges (the sodium pyrophosphate addition <1.5%,the pH <11.5,and the ultrasonic dispersion time <5 min),the dispersity of the magnesia powders improves with the above parameter values increasing;while at the sodium pyrophosphate addition >1.5% and ultrasonic dispersion time >5 min,the dispersity gradually deteriorates.After being coated with SiO₂,as the coating time prolongs,the coating temperature increases from 55-65 ℃,or the pH rises,the dispersity of the magnesia powders first increases and then decreases.Generally,under the following conditions:coating time of 7 h,coating temperature of 65 ℃,pH of 10.5,and sodium silicate solution mass fraction of 5%,the magnesia powder exhibits the optimal dispersity,with d₅₀=45.2 μm,d₉₀=70.5 μm,and the minimum specific surface area of 792 m²·kg^-1.

Effect of multi-scale gradation alumina on performance of alumina crucibles

Ouyang Li, Yang Shuang, Gu Huazhi

2025, (6): 495-499. doi：10.3969/j.issn.1001-1935.2025.06.007

Abstract ( ) PDF (2486KB)( )

To enhance their densification,mechanical properties and thermal shock resistance,alumina crucibles were prepared using alumina powders of different particle sizes (≤75 μm,≤4 μm,and ≤30 nm) as raw materials,based on a multi-scale composite gradation system designed by the Dinger-Funk gradation model.The effects of the multi-scale gradation on the microstructure,mechanical performance,and thermal shock resistance of the crucibles were systematically investigated.The results show that:(1)the multi-scale gradation optimizes the particle packing,and the crucible obtained has a bulk density of 3.82 g·cm^-3,an apparent porosity of 1.9%,and a linear shrinkage rate of 11.9%,featuring a homogeneous and dense microstructure with numerous intragranular closed pores;(2) the cold modulus of rupture (CMOR) and cold compressive strength (CCS) of the crucible are 225 and 434 MPa,respectively,lower than those of the crucible prepared from nano-alumina powder.However,compared with the MOR retention ratio of 33.9% for the crucible prepared from nano-alumina powder,that of the optimized crucible is 50.1%,demonstrating excellent thermal shock resistance.This is mainly attributed to the thermal stress absorption by the closed pores.

Fabrication and microstructural optimization of mullite-based porous ceramics

Jing Xuanhan, Dong Xianzhen, Ji Xiaojie, Liu Xingshuo, Zhou Wenying, Zhao Degang

2025, (6): 500-505. doi：10.3969/j.issn.1001-1935.2025.06.008

Abstract ( ) PDF (3933KB)( )

To broaden the design and development of high-performance porous ceramics,mullite porous ceramics were prepared by the direct foaming method,using industrial alumina and Guangxi white mud as raw materials,α-sodium olefin sulfonate as the foaming agent,modified polyethoxylated silicone (MPS) microemulsion as the foam stabiliser,and ammonium citrate as the dispersant.The effects of the MPS addition (0.2%,0.3% and 0.4%,by mass) and the stirring time (5,10 and 15 min) on the microstructure and properties of the ceramics were investigated.The results demonstrate that the main crystalline phase of the ceramics is mullite,with corundum as the secondary phase.With the increase in the MPS addition,the pore size distribution of the ceramics becomes more uniform while the median pore diameter decreases,and the cold compressive strength and bulk density increase.With the prolongation of the stirring time,the porosity and median pore diameter of the ceramics decrease first and then increase,while the cold compressive strength and bulk density show an opposite trend.With 0.3% MPS and a stirring time of 10 min,the mullite-based porous ceramics have the optimal performance.

Influence of raw material pretreatment on preparation of TiB₂ powder

Wang Xingguo, Xu Chen, Chang Shilun, Zhang Zhaolei, Li Xin, Chen Bin

2025, (6): 506-510. doi：10.3969/j.issn.1001-1935.2025.06.009

Abstract ( ) PDF (2316KB)( )

To explore the effect of raw material pretreatment on their preparation,TiB₂ powders were prepared with TiO₂,B₄C and carbon black as starting materials by the microwave-assisted boron/carbon thermal reduction method,firing at 1 450 ℃ for 20 min.The effects of three raw material pretreatment methods (no pretreatment,ball milling,and ball milling-pressing pellets) on the phase composition and microscopic morphology of the powders were investigated.The results show that after ball milling raw materials for 6 h and firing at 1 450 ℃ for 20 min,the TiB₂ powder obtained has an ideal hexagonal sheet-like structure with an average particle size about 0.52 μm as well as residual C and O contents of 0.254 mass% and 0.556 mass%.No other impurity phases are detected in the product.When using the unpretreated raw materials,there is residual TiC in the reaction products,mainly because the large particle size difference between the raw materials and slow diffusion rate lead to incomplete reaction.After pretreating the raw materials by ball milling-pressing pellets,there are TiBO₃ and Ti₂O₃ residues in the reaction products,mainly because the dense pellets inhibit the CO escape during the reaction,and then the forward progress of the reaction.Combined with the changes in the phase and morphology of the products,it is inferred that the unreacted TiC and TiBO₃ are formed by the reaction of TiO₂ and B₄C.

Effect of heat treatment temperature on properties of high-entropy spinel coatings

Sun Shuaimeng, Yang Shuang, Zhang Meijie, Fu Lyuping, Huang Ao, Gu Huazhi

2025, (6): 511-515. doi：10.3969/j.issn.1001-1935.2025.06.010

Abstract ( ) PDF (2402KB)( )

To expand the application of high-entropy spinel infrared radiation coatings in the field of energy saving and emission reduction,high-entropy spinel was prepared by heat treatment at 1 600 ℃ for 8 h with magnesia,alumina,cobalt oxide,nickel oxide,copper oxide and zinc oxide as raw materials,mixed in a stoichiometric ratio of 1∶5∶1∶1∶1∶1.Then it was sprayed on the surface of corundum-mullite small test blocks of 30 mm×30 mm×10 mm to form a high-entropy spinel infrared radiation coating.The effects of different heat treatment temperatures (1 300,1 400,1 500 and 1 600 ℃ for 2 h) on the infrared radiation performance and bonding strength of the coating were investigated.It is found that as the temperature increases from 1 300 to 1 600 ℃,the pores of the coating are gradually reduced,leading to a denser structure.The coating heat treated at 1 600 ℃ for 2 h has the infrared emissivity of 0.86 in the 0.2-2.5 μm band and 0.90 in the 2.5-15 μm band at room temperature.After the heat treatment at 1 500 ℃,the bonding strength between the coating and the substrate is the highest,6.16 MPa.

Corrosion of MgO-C bricks in carbonization electric furnace

Huang Jiaxu, Qi Jianling, Lyu Xueming, Liu Yadong

2025, (6): 516-520. doi：10.3969/j.issn.1001-1935.2025.06.011

Abstract ( ) PDF (2104KB)( )

To clarify the dominant factors affecting the service life of MgO-C bricks in different parts of the carbonization electric furnace,the corrosion status of the MgO lining was studied through lining erosion measurement,microstructure analysis,and phase composition analysis.The results show that:MgO-C bricks above the slag line undergo an oxidation reaction,leading to the detachment of MgO particles under thermal stress;after reacting with the slag,the products of MgO-C bricks at the slag line dissolve into the slag,and simultaneously,MgO particles continuously spall off under slag erosion,accelerating the corrosion rate;for MgO-C bricks near the furnace bottom,influenced by the insulating effect of the residual slag,the temperature gradient between heats is smaller,the thermal stress is relatively reduced,and the corrosion rate is slower than that at the slag line.

Influence of dioctyl phthalate and phenolic resin on magnesium spinel sliding gate performance

Li Qiang, Zeng Qingyang, Liang Baoqing, Liu Xinhong, Zeng Xianxin, Wang Dajun

2025, (6): 521-524. doi：10.3969/j.issn.1001-1935.2025.06.012

Abstract ( ) PDF (1344KB)( )

Liquid thermosetting phenolic resin releases volatile organic compounds such as formaldehyde and free phenols during use,polluting the environment,and its viscosity increases during storage,affecting the stability of high manganese steel sliding gates.The magnesium spinel sliding gates were produced using tabular corundum and fused spinel as aggregates,introducing dioctyl phthalate as a reinforcing agent and 4 mass% thermoplastic phenolic resin powder as a binder.The effects of dioctyl phthalate additions (0,1%,1.2%,1.4%,and 1.6% by mass) on the structure and hot properties of the sliding gates were studied.The results show that the introduction of dioctyl phthalate increases the surface activity of the particles,improves the adhesion and toughness of the thermoplastic phenolic resin powder,and reduces the porosity of the sliding gates.When the addition of dioctyl phthalate is 1.2%,the sliding gate structure is dense,and the hot mechanical properties and erosion resistance against molten steel are significantly improved.The average service life of the sliding gates in a 150 t ladle continuous casting machine reached 2.8 heats,exceeding the average service life of 1.6 heats for the sliding gates before improvement.

Effect of microporous corundum aggregates on properties of corundum-spinel castables

Tan Xinyu, Wang Gang, Feng Haixia, Liu Jun, Li Chuanhao, Feng Zhiyuan

2025, (6): 525-529. doi：10.3969/j.issn.1001-1935.2025.06.013

Abstract ( ) PDF (2347KB)( )

To improve the thermal shock resistance of corundum-spinel castables,samples were prepared using white fused corundum aggregates (5-3,3-1,and ≤1 mm) and fine powder (≤0.074 mm),microporous corundum aggregates (5-3,3-1,≤1 mm),sintered spinel aggregates (≤1 mm) and fine powder (≤0.045 mm),BL-2 alumina micropowder,and Secar 71 calcium aluminate cement as raw materials.The effects of different heat treatment temperatures (1 000,1 200,1 400,1 500,and 1 600 ℃) and the equivalent replacement amount of white fused corundum with microporous corundum aggregates of the same particle size (0,13%,23%,33%,43%,and 54%,by mass) on the properties of the samples were investigated.The results show that:(1)as the heat treatment temperature increases,the strength of the samples increases accordingly;(2)with the microporous corundum aggregate addition increasing,the bulk density decreases,and the thermal shock resistance first decreases and then increases;(3)when the microporous corundum aggregates completely replace the white fused corundum aggregates,at the addition of 54% and heat treatment temperature of 1 600 ℃,the sample exhibits the optimal overall performance.

Research progress on synthesis methods of CaZrO₃ powder

Zhao Xinxin, Xu Qing, Huang Xiaoyang, Peng Jinqi, Duan Hongjuan , Zhang Haijun, Li Shaoping

2025, (6): 530-535. doi：10.3969/j.issn.1001-1935.2025.06.014

Abstract ( ) PDF (1022KB)( )

CaZrO₃ is widely used in fields such as refractories,thermal barrier coatings,high mechanical strength ceramics,and biomedical materials owing to its high melting point,excellent thermal shock resistance,good mechanical properties,and low thermal conductivity.The recent research progress on the synthesis methods for CaZrO₃ powders was summarized,with a focus on analyzing the advantages and disadvantages of solid-state reaction,molten salt synthesis,and combustion synthesis methods.The CaZrO₃ powders obtained by different synthesis methods were compared.Future development direction of CaZrO₃ powders was prospected,including optimizing the precursor preparation process to lower the synthesis temperature and cost,deepening the theoretical research on synthesis mechanisms to improve the product quality and stability,enhancing the structural stability of zirconia crystals through raw material pretreatment,and expanding application fields via doping modification.

Research progress on interaction between high-temperature alloys and crucible refractory materials during vacuum induction melting

Liu Xingli, Xing Yidan, Huang Xiaoyang, Pang Baisheng, Huang Liang, Zhang Haijun

2025, (6): 536-541. doi：10.3969/j.issn.1001-1935.2025.06.015

Abstract ( ) PDF (1020KB)( )

High-temperature alloys are widely used in fields such as aerospace,nuclear industry,and chemical production.Vacuum induction melting (VIM),as one of the primary technical routes for refining high-temperature alloys,can effectively remove non-metallic elements like oxygen,nitrogen and hydrogen,thereby enhancing the cleanliness of the alloys.However,during the VIM process,the reactions between the high-temperature alloy melt and the crucible refractory material are inevitable,resulting in the formation of inclusions that affect the alloy performance.Consequently,it is essential to thoroughly analyze the mechanism of the interfacial interaction between the alloy and the refractory material and identify the key factors governing this reaction to optimize the crucible refractories.The recent research progress on the interactions between high-temperature alloys and various types of refractories were summarized.The outlook on future development directions in this field was provided.

Research progress on saggar refractories for lithium-ion battery cathodes

Peng Jinqi, Lei Huicong, Huang Xiao-yang, Huang Zhong, Zhang Haijun

2025, (6): 542-546. doi：10.3969/j.issn.1001-1935.2025.06.016

Abstract ( ) PDF (948KB)( )

Saggar refractories serve as a fundamental material for the high-temperature production of lithium-ion battery cathode materials.The corrosion mechanism between cathode materials and saggar refractories was analyzed,and the characteristics of saggar refractories for lithium-ion battery cathodes were summarized,including mullite,cordierite,and other systems.Finally,the main challenges in this research field were outlined,and the future development of saggar refractories was proposed.

Research progress on stability and rheology of SiC ceramic slurries

Xu Han, Gao Yuanyuan, Lei Zhifu, Ma Xin, Yan Senwang, Gu Qiang

2025, (6): 547-552. doi：10.3969/j.issn.1001-1935.2025.06.017

Abstract ( ) PDF (952KB)( )

SiC is a high-performance structural material.The key to prepare high-quality and low-cost SiC green bodies via the colloidal forming method is to obtain slurries with low viscosity and high solid content.The type,combination,and addition of dispersants directly determine the stability and rheological properties of the slurries.Therefore,the effects of single dispersant and mixed dispersant on the stability and rheology of SiC ceramic slurries were reviewed.The three stabilization mechanisms:electrostatic stabilization,steric stabilization,and electrosteric steric synergistic stabilization,were briefly described,aiming to provide a theoretical reference for subsequent research on optimizing the performance of SiC slurries.

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