Preparation and properties of foamed ceramics based on fly ash and lithium slag

Chang Xinglan, Chen Yaoji, Gu Yajie, Sun Shengrui, Sun Ke, Liao Dachen, Liu Yangqiao, Xi Shuang, Li Xiaohong

2024, (1): 1-7. doi：10.3969/j.issn.1001-1935.2024.01.001

In order to prepare low-cost foamed ceramics with high porosity and compressive strength,foamed ceramics samples were prepared at different temperatures (1 180,1 200,1 220 and 1 240 ℃) for different durations (10,20,40 and 60 min),using fly ash,lithium slag,feldspar,talcum and silicon carbide as raw materials.The effects of the lithium slag addition (0,10%,20% and 30%,by mass) on the phase composition,microstructure,porosity,and compressive strength of the samples were studied.The results show that:(1)with the increase of the lithium slag addition,the porosity of the samples increases;the bulk density decreases;the compressive strength fluctuates;(2)the calcium and sulfur components in lithium slag work as the fluxing agent and foaming agent,which reduces the sintering temperature,increases the porosity,improves the pore roundness and enhances the compressive strength;(3)when the lithium slag addition is 20%,for the sample obtained at 1 220 ℃ for 20-40 min,the bulk density is 0.32-0.40 g·cm^-3,the porosity is 84.4%-87.6% and the compressive strength is 1.51-2.35 MPa.

Mullite whisker-ceramic fiber reinforced cordierite thermal insulation materials

Qin Mengli, Luo Ying, Shen Zi-qiang, Liu Meng, Song Jieguang, Wang Ci, Liu Qiang

2024, (1): 8-12. doi：10.3969/j.issn.1001-1935.2024.01.002

Abstract ( ) PDF (2193KB)( )

Aiming at improving the low strength of cordierite insulation materials used in high-temperature industry,cordierite insulation materials were prepared using kyanite,clay,magnesia powder as raw materials,starch as the pore forming agent and curing agent,adding a suitable amount of aluminum silicate ceramic fiber and MoO₃.The prepared materials have a mullite whisker-ceramic fiber multi and interlocked structure by the in-situ formation of mullite whiskers on the surface of aluminum silicate fiber catalyzed by MoO₃.The effects of aluminum silicate ceramic fiber under the action of MoO₃ heat treated at different temperatures (1 200,1 250,1 300 and 1 350 ℃) on the microstructure,cold mechanical properties and thermal conductivity of the materials were studied.The results show that:under the action of MoO₃,mullite whiskers grow on the surface of aluminum silicate fiber,showing a vertical trend basically,and partially inserting in well-developed cordierite grains;with the heat treatment temperature increasing,the mullite whiskers on the surface of aluminum silicate ceramic fiber changes from short rods to slender needles,and the length to diameter ratio increases gradually;the cordierite material with the fiber-whisker multi and interlocked structure has improved mechanical properties while reduced thermal conductivity;the specimen heat treated at 1 350 ℃ has the optimal performance.

Corrosion behavior of slags with different basicities to corundum spinel castables

Yang Zongyuan, Wang Jing-ran, Wang Tong, Zhang Jinhua, Han Bingqiang, Ni Yue'e, Ke Changming

2024, (1): 13-18. doi：10.3969/j.issn.1001-1935.2024.01.003

Abstract ( ) PDF (3617KB)( )

The slag corrosion resistance of castables is closely related to the basicity of steel slag.Sintered corundum,defective spinel micropowder,active α-Al₂O₃ micropowder,fused magnesia fine powder,and calcium aluminate cement (Secar 71) were used as the main raw materials to prepare corundum spinel castables.The slag resistance test was conducted using the static crucible method at 1 600 ℃ for 3 h,and the amount and composition of the liquid phase were thermodynamically simulated.The slag corrosion resistance of the corundum spinel castables against the three slags with different basicities (1.6,2.3,and 7.6) was studied.The results show that the high basicity slag has limited solubility to corundum spinel castables;it is easy to form high melting point phases such as spinel solid solution and calcium hexaluminate at the interface between slag and castables,forming a dense layer to prevent slag penetration and corrosion;the solubility of corundum spinel castables is high in low basicity slag;spinel solid solution,calcium hexaluminate or other high temperature phases can't form until the slag and the castables reach a high reaction degree,thus an effective dense layer can't form to prevent the corrosion and penetration of slag into the castables.Therefore,corundum spinel castables have better slag corrosion resistance to high basicity slags than low basicity slags.

Effect of aggregate types on properties of Al₂O₃-SiC-C bricks for iron ladles

Gao Dongsheng, Nie Jianhua, Cai Manfei, Liang Yonghe, Zhang Xiaocun

2024, (1): 19-24. doi：10.3969/j.issn.1001-1935.2024.01.004

Abstract ( ) PDF (3836KB)( )

As an important part of refractory materials,aggregates determine the properties of materials.Al₂O₃-SiC-C bricks were prepared using bauxite,brown fused corundum or tabular corundum with particle sizes of 5-3,3-1 and ≤1 mm as aggregates,white fused corundum (≤0.045 mm),SiC (≤0.075 mm),active α-Al₂O₃ powder (≤0.045 mm) and flake graphite (≤0.15 mm) as matrix,and thermosetting phenolic resin as the binder.The effects of the three aggregates on the cold and hot mechanical properties as well as the slag resistance of Al₂O₃-SiC-C brick were studied.The results show that the Al₂O₃-SiC-C bricks has the best hot mechanical properties and slag resistance when using tabular corundum as aggregates due to its higher density and lower impurity phase contents;and when bauxite is used as aggregates,the hot mechanical properties and slag resistance of the brick are worst due to the high porosity and impurity contents of bauxite.

Dissolution behavior of waste high-alumina bricks in LF refining slag

Mu Xin, Jia Yi, Liu Chunyang, Chai Guangwei, Yu Wuming, Du Chuanming, Ma Beiyue

2024, (1): 25-29. doi：10.3969/j.issn.1001-1935.2024.01.005

Abstract ( ) PDF (2821KB)( )

The Al₂O₃ in LF slag usually originates from bauxite,and LF slag has similar composition with waste high-alumina bricks.Hence,it is possible to substitute for bauxite with waste high-alumina bricks.Waste high-alumina bricks were cut into cylindrical specimens (17.3 mm×12.0 mm) and put into the refining slag of 1 600 ℃ for different durations (5,10,15,and 25 min).The dissolution rate and microstructure of the waste high-alumina specimens as well as the composition of the refining slag after reaction were analyzed,and the dissolution mechanism of waste high-alumina bricks in the refining slag was explored.The results show that after dissolution,there is an obvious boundary layer between the high-alumina specimen and the refining slag,and MgO in the refining slag preferentially diffuses to the boundary layer to form Al₂O₃-MgO solid solution with the dissolved Al₂O₃ in the specimen;with the increasing reaction time,the Al₂O₃-MgO solid solution gradually increases,forming an Al₂O₃-MgO solid solution layer on the specimen surface at the later stage of reaction,which prevents the diffusion of dissolved calcium aluminate into the refining slag;after 25 min of reaction,the dissolution rate of the specimen reaches 35%;by comparing the slag reacted for 25 min with that reacted for 5 min,the Al₂O₃ content increases to 30.9 mass% from 27.1 mass%.

Hydration resistance of modified light-burned MgO fine powders

Xue Tianyu, Huang Zhong, Huang Ren, Zhang Haijun

2024, (1): 30-34. doi：10.3969/j.issn.1001-1935.2024.01.006

Abstract ( ) PDF (2463KB)( )

Regarding the easy-hydration of MgO,light-burned MgO fine powders were modified by mixing,grinding and heat-treatment using glycol and ISOBAM-104 as the modifiers.The effects of the ISOBAM-104 addition (0,1%,3%,5%,7% and 9% of the mass of MgO fine powder) and the heat treatment temperature (200,250 and 300 ℃ for 1 h) on the phase composition,microstructure and hydration resistance of the modified light-burned MgO (IM/EG-MgO) were investigated.The results show that the hydration mass gain rate of the light-burned MgO powder modified by ISOBAM-104 (7% of the mass of MgO fine powder) heat treated at 250 ℃ for 1 h is the lowest,which is 2.2%.The main reason for the improved hydration resistance of IM/EG-MgO is the generation of alcoholic magnesium compounds and hydrophobic imide groups on the surface.

Effect of thermal treatment time on structure and properties of infrared radiation coating prepared by copper slag

Lyu Zihao, Gu Huazhi, Yang Shuang, Zhang Meijie, Fu Lyuping, Huang Ao

2024, (1): 35-39. doi：10.3969/j.issn.1001-1935.2024.01.007

Abstract ( ) PDF (3079KB)( )

Copper slag,as a solid waste generated during the copper smelting process,is often stacked,occupying land resources and polluting the environment.Its resource utilization is increasingly receiving widespread attention in China and overseas.To solve this problem,the infrared radiation coating was prepared at 1 200 ℃ with copper slag as the main raw material,terpineol as the film forming agent,ethyl cellulose as the thickening agent,and high alumina bricks as the substrate material of the infrared radiation coating.Effects of the heat treatment time (0.5,2, 4,and 8 h) on the microstructure and emissivity at room temperature and 400 ℃ were studied.The results show that the coating is well combined with the high alumina brick substrate,with heat treatment time prolonging, the coating gradually becomes dense;after heat treatment at 1 200 ℃ for 8 h,the near-infrared (0.8-2.5 μm) emissivity of the coating reaches the maximum (0.862);after heat treatment for 4 h,the emissivity increases and reaches the maximum (0.928) after heat treatment in the mid-infrared (2.5-25 μm) wave range;after heat treatment for different times,the emissivity of the coating fired at 400 ℃ in 1-22 μm wave range increases continually and is higher than 0.93.Combined with practical applications,the optimal heat treatment time is 4 h.

Effect of light burnt MgO powder on properties of porous MgAl₂O₄ ceramics by gel-casting route

Piao Jiasi, Du Qingyang, Tang Yudong, Bai Jiahai

2024, (1): 40-43. doi：10.3969/j.issn.1001-1935.2024.01.008

Abstract ( ) PDF (1486KB)( )

In order to reduce the raw materials cost,simplify the process,and improve the performance of porous MgAl₂O₄ ceramics,MgAl₂O₄ powders were synthesized using Al₂O₃ powder and MgO powder at 1 500 ℃ for 2 h,and then light burnt MgO powders (0.5%,1.0%,1.5% and 2.0%,by mass) were extrally added to prepare porous MgAl₂O₄ ceramics using the gel-casting route at 1 500 ℃ for 2 h.Effect of the light burnt MgO powder addition on the structure and performance of porous MgAl₂O₄ ceramics were investigated.The results show that:(1)the porous MgAl₂O₄ ceramics prepared using light burnt MgO powder as a hardener have small linear shrinkage and good volume stability,whose pore size is mainly in the range of 0.5-2.0 μm;(2)as the light burnt MgO powder addition increases,the apparent porosity and the gas flux increase,and the microstructure is uniform;(3)when the light burnt MgO powder addition is 2.0%,porous MgAl₂O₄ ceramics show the optimal comprehensive performance.

Effect of TiO₂ crystal forms on TiB₂ powder prepared by microwave heating

Chen Bin, Wang Xingguo, Li Xin, Wu Jiqing, Tang Jian, Yang Jianhong

2024, (1): 44-47. doi：10.3969/j.issn.1001-1935.2024.01.009

Abstract ( ) PDF (1974KB)( )

To explore the effect of TiO₂ crystal forms (anatase and rutile) on the microwave heating prepared TiB₂ powder,TiB₂ powder was rapidly prepared using anatase or rutile TiO₂ as the titanium source,B₄C as the boron source,and carbon black as the carbon source by the boro/carbothermal reduction method under the microwave heating condition.Effects of TiO₂ crystal forms on the phase composition,microstructure,and C and O impurity contents of the TiB₂ powder were investigated.The results show that by microwave heating,pure phase TiB₂ powder can be prepared from both forms of crystalline TiO₂ after reaction at 1 450 ℃ for 20 min.Among them,the TiB₂ powder prepared from rutile TiO₂ exhibits a regular hexagonal flake structure with perfect grain development.However,TiB₂ prepared from anatase TiO₂ has a nearly spherical structure.In comparison,rutile TiO₂ as boron source is more conducive to preparing TiB₂ powder with high purity and complete crystal form.

Corrosion mechanism of TiC-containing slag to MgO-C bricks

Wang Dongsheng, Lyu Xueming, Liu Yadong

2024, (1): 48-52. doi：10.3969/j.issn.1001-1935.2024.01.010

Abstract ( ) PDF (1377KB)( )

To effectively recover titanium resources and meet the requirements of the high temperature carbonization-low temperature chlorination process to refractories,the corrosion mechanism of TiC-containing slag to MgO-C bricks during high-temperature carbonization process was analyzed through thermodynamic calculations,XRD and SEM.The thermodynamic calculation results show that:(1)the higher the temperature,the stronger the corrosion ability of the slag;below 1 560 ℃,the slag reacts with MgO-C bricks to generate high melting point phases such as MgAl₂O₄,Mg₂SiO₄,and MgTi₂O₄,which slow down the corrosion rate of MgO-C bricks;however,at above 1 560 ℃,the high melting point phases generated in the early stage gradually dissolve,thereby intensifying the corrosion to MgO-C bricks;(2)as the carbonization reaction progresses,the TiO₂ content in the slag decreases,while the TiC content gradually increases,and the corrosion of the slag to MgO-C bricks gradually weakens.According to the microstructure analysis of the used MgO-C bricks,the corrosion mechanism of MgO-C bricks is that O₂ in air reacts with graphite forming pores;TiO₂ and SiO₂ in the slag react with MgO and the matrix of the brick to form high-temperature intermediate phases first,and as the reaction progresses,low melting point phases form,leading to the gradual corrosion of MgO-C bricks.

Development and application of new generation calcium hexaaluminate castables

Xu Guotao, Wang Zhi-qiang, Qin Shimin, Liu Li, Zhang Honglei, Zhang Yanwen, Zhou Wangzhi

2024, (1): 53-56. doi：10.3969/j.issn.1001-1935.2024.01.011

Abstract ( ) PDF (1362KB)( )

In view of the characteristics of high thermal conductivity,great influence of temperature and limited thickness by volume of high alumina castables for the ladle permanent layer,calcium hexaaluminate castables for the ladle permanent layer were developed using calcium hexaluminate aggregates and fine powder,and Al₂O₃ micropowder as main raw materials,and calcium aluminate cement as the binder.The thermal conductivities of the castables at 500,800,and 1 000 ℃ are all about 0.63 W·m^-1·K^-1,less affected by temperature,which perform a good thermal insulation effect.For the permanent layer of a 200 t ladle using calcium hexaluminate castables and thermal insulation board,the average temperatures of the ladle shell were reduced by 30-50 ℃ compared with those of the permanent layer using high alumina castables.It is expected that the cost of calcium hexaluminate castables can be reduced by 20%-35% through suitable aggregate lightweight,consumption reducing and structure optimization.Meanwhile,through decreasing the temperature reduction of hot steel,the production cost of steel plants can be greatly reduced.

Research of used silica bricks for coke oven carbonization chambers

Liu Zhiyun, Jia Shuo, Lu Yiguo

2024, (1): 57-62. doi：10.3969/j.issn.1001-1935.2024.01.012

Abstract ( ) PDF (3641KB)( )

In order to understand the damage mechanism of silica bricks for coke oven carbonization chambers,the silica bricks from a JN43 side-spray coke oven carbonization chamber which have been used for more than 40 years were sampled.The appearance,physical properties and chemical composition,phase composition and microstructure of the samples were analyzed.The analysis finds that:(1)the silica bricks in the upper,middle and lower parts of the coke oven chamber form several layers with different colors and textures from the carbonization chamber to the combustion chamber;(2)the tar component in coal has a strong penetration effect on the furnace wall bricks,while the oxide components in coal have a slight penetration effect on the furnace wall bricks;(3)the furnace wall is sintered at high temperatures,and the volume generally shrinks;(4)the cristobalite and quartz phases in the bricks within about 1/3 of the furnace wall thickness on the combustion chamber side disappear;tridymite grains grow significantly,more open pores become closed pores,and the linear expansion rate decreases;(5)the quartz and cristobalite in the thickness of about 1/2 of the furnace wall near the carbonization chamber side partially turn into tridymite,resulting in a decrease in the linear expansion rate in this area.

Effect of Al₂O₃-MgAl₂O₄ composite aggregate on slag resistance of corundum-spinel castables

Wang Zhi-qiang, Xu Guotao, Lei Zhongxing, Peng Xiaoqian, Zheng Jihong, Liu Li, Wang Xinyi, Liu Yi, Xu Yanming

2024, (1): 63-67. doi：10.3969/j.issn.1001-1935.2024.01.013

Abstract ( ) PDF (2439KB)( )

To study the effect of the Al₂O₃-MgAl₂O₄ composite aggregate on their slag resistance,corundum-spinel castables were prepared using the tabular corundum aggregate and Al₂O₃-MgAl₂O₄ composite aggregate,respectively,with or without spinel fine powder in the matrix.Firstly,the reaction thermodynamics between the tabular corundum aggregate or Al₂O₃-MgAl₂O₄ composite aggregate and slag at 1 600 ℃ was calculated using the FactSage reaction thermodynamics software,and the slag resistance of the two aggregates was studied using the soaking method.Secondly,the effect of the two aggregates on the slag resistance of the castables was studied by the static crucible method.The results show that compared with the tabular corundum aggregate,the Al₂O₃-MgAl₂O₄ composite aggregate has finer and fewer cracks in the corrosion layer,suggesting the resistance to peel off after slag corrosion.There are both CA₆ and spinel phases in the transition layer,and Fe and Mn elements solid dissolve in spinel,indicating that the aggregate not only blocks slag corrosion by forming a CA₆ layer,but also reduces the viscosity of the slag by absorbing substances such as FeO and MnO in the slag through spinel,thereby playing a role in resisting slag corrosion.Replacing the tabular corundum aggregate with the Al₂O₃-MgAl₂O₄ composite aggregate,the corroded and penetrated area percentages of the corundum-spinel castables decrease,especially,introducing spinel into both the matrix and aggregate can effectively improve the slag resistance of the castables.

Effect of microporous dolomite on properties of magnesia-calcia dry mix for tundishes

Meng Jiaze, Chen Ding, Gu Huazhi, Huang Ao, Fu Lyuping

2024, (1): 68-71. doi：10.3969/j.issn.1001-1935.2024.01.014

Abstract ( ) PDF (1017KB)( )

The dense magnesia-calcia sand prepared with dolomite as the raw material by the two-step calcination method is a common refractory starting material of magnesia-calcia dry mix for tundishes.However,the two-step calcination method is complex and resource-consuming,and the dense magnesia-calcia sand is not conducive to improving the thermal insulation performance of the dry mix for tundishes.Magnesia-calcia dry mix samples were prepared using microporous dolomite calcined by the one-step method (1 400 ℃ for 3 h) and fused magnesia as the main raw materials and heat treating at 1 100 and 1 550 ℃,respectively.The effects of the microporous dolomite addition (0,15%,30%,45%,and 60%,by mass,respectively) on the properties of the samples were studied.The results show that with the microporous dolomite addition increasing,for the samples heat treated at 1 100 ℃,the linear shrinkage and bulk density show decreasing trends and the cold compressive strength increases first and then decreases;for those heat treated at 1 550 ℃,the linear shrinkage decreases first and then significantly increases,the apparent porosity increases,the thermal conductivity significantly decreases,however,the cold compressive strength and slag resistance decrease.With 60% microporous dolomite,the sample heat treated at 1 550 ℃ has the thermal conductivity at 800 ℃ of 2.410 W·m^-1·K^-1,decreasing by 51.9% compared with the traditional magnesia dry mix,and the cold compressive strength of 26.0 MPa,which shows excellent thermal insulation performance when the mechanical property is slightly reduced.

Composition optimization and performance enhancement of lightweight and high-strength mullite castables

Xia Yuting, Yang Wenbo, Rao Yutong, Nie Ruishan, Yao Yuan

2024, (1): 72-75. doi：10.3969/j.issn.1001-1935.2024.01.015

Abstract ( ) PDF (1057KB)( )

To actively respond to the dual-carbon policy and reduce industrial energy consumption,it is urgent to develop lightweight and high-strength refractories.Lightweight mullite castables were prepared using microporous mullite,mullite fine powder,alumina micropowder,alumina bubbles and silica micropowder as the raw materials and cement as the binder.The effects of the alumina bubbles addition (0,3%,6% and 9%,by mass,respectively) on the properties of the mullite castables were studied.The results show that alumina bubbles can increase the porosity of the samples and promote the formation of mullite from alumina micropowder and silica micropowder,which solves the problem that the mechanical properties of the samples decrease greatly due to the increase of the apparent porosity.With the increase of the alumina bubbles addition,the apparent porosity of the samples increases significantly,the bulk density decreases,the thermal conductivity decreases significantly,the thermal shock resistance improves,and the strength decreases slightly.When the alumina bubbles addition is 9%,the apparent porosity of the sample heat treated at 1 400 ℃ is high,the bulk density and thermal conductivity are low,but the cold strength is still high.

Performance analysis of bauxite-based mullite

Su Yuzhu, Luo Huaming, Wang Hanyu, Fan Mingming, Jin Yi, Zhan Huasheng

2024, (1): 76-79. doi：10.3969/j.issn.1001-1935.2024.01.016

Abstract ( ) PDF (2145KB)( )

To analyze the performance characteristics of bauxite-based mullite from typical production areas in China,eight kinds of bauxite-based mullite raw materials were obtained from Shanxi,Henan and Hunan,among which Shanxi A,Henan A,Shanxi B and Shanxi C were fired in tunnel kilns,Henan B,Shanxi D and Hunan A were fired in rotary kilns,and Hunan B was fired in electric arc furnaces.The apparent porosity,bulk density,water absorption,microstructure and phase composition of the raw materials were studied.The results show that:(1)the water absorption of mullite calcined in tunnel kilns is 2.5%-3.5%,and the mullite grains are fully developed as columnar,with large length-diameter ratios;(2)the water absorption of mullite calcined in rotary kilns is ≤2.0%,and the grain size of mullite is small;(3)fused mullite is the densest,with the water absorption <1.0% as well as completely developed sturdy crystals;(4)the main phase of all the bauxite-based mullite raw materials is mullite,and some of them contain a small amount of corundum and rutile;among them,fused mullite has a low glass phase content,and sintered mullite contains 8 mass%-14 mass% glass phases.

Application progress of mullite composite refractories

Zhang Wei, Wang Jingyang

2024, (1): 80-86. doi：10.3969/j.issn.1001-1935.2024.01.017

Abstract ( ) PDF (1027KB)( )

Mullite has a high melting point,high hardness,and good thermal shock resistance,corrosion resistance and hot mechanical properties.Mullite raw materials are mostly synthesized by the sintering method and electric melting method.The research and application progress of mullite composite refractories produced from mullite in the fields such as ceramics,metallurgy,aerospace,military industry,cement and glass were reviewed.The future developing of mullite in refractories was prospected.

Research status of toughening SiC composite ceramics

Wang Wenlong, Chen Gang, Wang Hongjie, Liu Kai

2024, (1): 87-92. doi：10.3969/j.issn.1001-1935.2024.01.018

Abstract ( ) PDF (924KB)( )

SiC ceramics have excellent properties and are widely used in various industries.However,the lack of toughness restricts their application as structural materials.Therefore,improving their toughness has become a research hotspot and focus.The research status of SiC composites toughened by different strengthening phases,such as particle phases,whiskers,fibers and low dimensional nano-materials (carbon nanotubes and graphene),was reviewed,expecting to provide a reference for toughening SiC ceramics in the future.

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