Refractories

Preparation of MgB₂O₅ whiskers from reverse flotation magnesite tailings

Dong Zeming, Dong Zeguang, Wang Shuxing, Liu Zhaoyang

2025, (3): 185-191. doi：10.3969/j.issn.1001-1935.2025.03.001

Using reverse flotation magnesite tailings as a magnesium source,Mg₂B₂O₅ whiskers were synthesized via a molten salt method in order to improve the recycling utilization of magnesite tailings and find an environmental friendly magnesium source for MgB₂O₅ whiskers.The effects of the tailings activating treatment,reaction temperature (700,800 and 900 ℃),and mass ratio of boric acid to magnesite tailings (B/Mg mass ratio=0.62,1.24,1.86 or 2.48) on the phase composition and microstructure of the whiskers were investigated.The results indicate that the aspect ratio of Mg₂B₂O₅ whiskers initially increases and then decreases with the B/Mg mass ratio increasing,reaching the maximum value at a ratio of 1.86.Furthermore,800 ℃ is identified as the optimal temperature for the growth of Mg₂B₂O₅ whiskers; whisker formation is difficult below this temperature,while excessively high temperatures lead to whisker coarsening and a reduction in the aspect ratio.The ball milling and light burnt treatment of the magnesite tailings can disrupt pseudomorph after decomposition,and reduce the particle size,thereby enhancing the activity of the magnesium source and yielding uniform-sized Mg₂B₂O₅ whiskers with a high aspect ratio.

Effect of hydrothermal synthesis process on preparation and micromorphology of xonotlite fibers

Wang Dejing, Wang Wenwu, Ye Guotian, Cao Xiying, Wang Ziqiang, Zhou Yudong

2025, (3): 192-197. doi：10.3969/j.issn.1001-1935.2025.03.002

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To achieve high aspect ratios,xonotlite fibers were synthesized via the dynamic hydrothermal method using hydrated silica as the silicon source and Ca(OH)₂ as the calcium source.The effects of the insulating temperature (160,180,200,220 and 240 ℃),the stirring speed (50,100,150,200 and 300 r·min^-1),and the insulating time (2,6,12,24 and 36 h) on the phase composition and micromorphology of hydrothermal products were investigated through XRD and SEM.The results show that:with the increasing insulating temperature,the xonotlite content and fiber length increase;with the stirring speed increasing,the xonotlite content maintains constant,but the fiber length initially increases and then decreases;with the insulating time prolonging,the xonotlite content increases,while the fiber length significantly extends.Under the conditions of insulating at 220 ℃ for 24 h at the stirring speed of 100 r·min^-1,xonotlite fibers with a length of 14.7 μm and an aspect ratio of 47 can be obtained.

Property optimization of magnesium aluminate spinel based on orthogonal design

Cheng Qingnan, Qian Kun, Chen Bo, Wang Jianjun, Liu Kui

2025, (3): 198-202. doi：10.3969/j.issn.1001-1935.2025.03.003

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To investigate the influence of various factors on their properties and optimize the preparation process,magnesium aluminate spinel refractory materials were prepared with magnesium aluminate spinel particles,fine powder and micropowder as raw materials,methacrylamide as the monomer,N,N′-methylenebisacrylamide as the crosslinker,ammonium persulfate as the initiator,and N,N′-tetramethylethylenediamine as the catalyst through gel casting.The effects of the gel drying temperature (50,70 and 90 ℃),the initiator addition (0.5%,1.0% and 1.5%,by mass),the catalyst addition (0.3%,0.5% and 0.7%,by mass),and the monomer to crosslinker mass ratio (3∶1,5∶1 and 10∶1) on the properties and structure of the samples were investigated by an orthogonal test,with particular emphasis on their impact on the cold compressive strength.The results indicate that the influence of various factors on the cold compressive strength follows this order:initiator addition>drying temperature>monomer to crosslinker mass ratio>catalyst addition.Considering the apparent porosity of the samples,the optimal process parameters are determined:the drying temperature of 90 ℃,the initiator addition of 1.0%,the catalyst addition of 0.3% and the monomer to crosslinker mass ratio of 10∶1,and the obtained magnesium aluminate spinel material exhibits a bulk density of 2.80 g·cm^-3,an apparent porosity of 15.5%,a cold compressive strength of 5.29 MPa,and a linear shrinkage rate of 0.55%.

Effects of silicon powder and graphite additions on properties of magnesia composites prepared from magnesite tailings

Yue Jingjing, Zhao Xin, You Jiegang, Zhang Ling, Zhang Xiaofang, Hou Qingdong, Feng Dong, Luo Shitong, Duan Mingjun, Zhang Yi

2025, (3): 203-207. doi：10.3969/j.issn.1001-1935.2025.03.004

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To improve the utilization rate and application value of magnesite tailings,magnesia composites were prepared using light burnt powder of magnesite tailings as the raw material,silicon powder and 95-graphite as additives and phenolic resin as the binder by the solid-state reaction pressureless sintering method.The effects of the Si powder and graphite powder additions on the cold modulus of rupture,density,linear change rate,thermal shock resistance,microstructure and phase composition of the composites were studied in the carbon embedded atmosphere.The results show that with the increasing additions of silicon powder and graphite powder,the contents of forsterite (M₂S) and SiC in the materials increase,finally forming an M₂S-SiC-C multiphase material with M₂S as the main crystal phase.The CO and SiO gases produced during reaction are not conducive to material sintering,leading to the decrease of the cold modulus of rupture,bulk density and linear shrinkage,and the increase of the porosity.After thermal shock,the strength retention ratio of the materials increases significantly compared with that of the sample without additives,because both the increased M₂S content and the generation of SiC whiskers in the materials are beneficial to improving the thermal shock resistance.

Effect of zirconia corundum addition on structure and properties of Al₂O₃-SiC-C materials

Du Juan, Li Wenfeng, Guo Huishi, Shen Tianzi, Shi Kai, Cao Jun

2025, (3): 208-212. doi：10.3969/j.issn.1001-1935.2025.03.005

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Al₂O₃-SiC-C materials were prepared using recycled corundum (1-3 and 3-5 mm),white fused corundum (≤1 mm),α-Al₂O₃ micropowder (≤10 μm),flake graphite (≤50 μm) and silicon carbide (≤1 mm) as main starting materials,silicon powder (≤74 μm) as the antioxidant,and thermosetting phenolic resin with a carbon residue of about 45 mass% as the binder.The effects of the zirconia corundum (AZ40,≤74 μm) addition (0,3%,6%,9% and 12%,by mass) on the structure and properties of the Al₂O₃-SiC-C materials were investigated.The fracture morphology of the samples after heat treatment was observed using a field emission scanning electron microscope,and the structure was analyzed.The results show that:(1)with the increase of the AZ40 addition,the bulk density,cold modulus of rupture,cold compressive strength,hot modulus of rupture,and the retention ratio of the cold modulus of rupture of the samples all increase first and then decrease,while the apparent porosity and oxidation index change in reverse;(2)with the AZ40 addition increasing to 12%,the sample performs lower mechanical and antioxidant properties than that without AZ40,indicating that an appropriate AZ40 addition is beneficial to improving the mechanical properties,thermal shock resistance and oxidation resistance of the Al₂O₃-SiC-C materials;(3)the sample with 3% AZ40 exhibits the best comprehensive performance.

Effect of Y₂O₃ extra-addition on properties of magnesia stabilized zirconia materials

Wang Dongdong, Yu Tongshu, Zhao Hongbo, Li Hongxia

2025, (3): 213-216. doi：10.3969/j.issn.1001-1935.2025.03.006

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In order to improve the comprehensive performance of high density zirconia metering nozzles for continuous casting of steel billets,dense zirconia materials were prepared using 60 mass% monoclinic zirconia powder and 40 mass% fused magnesia stabilized zirconia powder as raw materials,extra-adding 1.1 mass% magnesia micropowder and a certain amount of yttria micropowder as the stabilizers.The materials were formed into 125 mm×10 mm×10 mm specimens and standard nozzle cores,and fired at 1 730 ℃ for 8 h.The effects of yttria extra additions (0,0.325%,0.65%,0.975%,and 1.3%,by mass) on the properties,microstructure,and phase composition of zirconia materials were studied.The results show that with the increase of the yttria extra-addition,the netlike microcrack can be bridged,and the cold modulus of rupture and erosion resistance to molten steel of the material can be improved.However,the reduction in the proportion of monoclinic zirconia and the bridging of netlike microcrack are detrimental to the thermal shock resistance of the material.By controlling the yttria extra-addition,the thermal shock resistance and erosion resistance to molten steel of the material can meet different working conditions.

Fabrication and property characterization of self-toughened SiC-B₄C-ZrB₂ multiphase ceramics

Wang Wenlong, Liu Kai, Wang Hongjie, Chen Gang, Tian Zhaoyong, Tan Bo, Li Junying

2025, (3): 217-223. doi：10.3969/j.issn.1001-1935.2025.03.007

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To develop self-toughened SiC-B₄C-ZrB₂ multiphase ceramics with superior mechanical properties,specimens were fabricated via pressureless solid-state sintering at 2 200 ℃ for 2 h using SiC,B₄C,ZrO₂,and graphite micropowder as raw materials.The effects of ZrO₂ additions (0,5.60%,10.90%,15.93%,20.69%,and 25.25%,by mass) on the microstructure and mechanical properties of the ceramics were investigated.Key findings include:(1)the addition of ZrO₂ is conducive to sintering densification and the anisotropic growth of SiC grains,forming a unique multimodal grain interlocking microstructure,which significantly improves the damage tolerance of the material;(2)with the increase of ZrO₂ addition,the relative density,flexural strength and hardness of the samples show a trend of first increasing and then decreasing;when the ZrO₂ addition is 10.90%,the relative density is the highest,up to 98.23%,and the Vickers hardness and flexural strength reach the peaks,29.7 GPa and 443 MPa,respectively;in addition,when the ZrO₂ addition is 15.93%,the sample shows the highest fracture toughness of 6.43 MPa·m^1/2.

Research on SiC-Si₃N₄-C corrosion resistant materials for heat treatment furnaces used for extraction of valuable elements from spent lithium-ion batteries

Jiang Yuena, Ye Xinjian, Tao Tianyi, Yang Mengyao, Lin Fankai, Zheng Xiaohong, Sun Zhenhua, Wu Xiaowen, Huang Zhaohui

2025, (3): 224-228. doi：10.3969/j.issn.1001-1935.2025.03.008

Abstract ( ) PDF (1543KB)( )

The pyrometallurgy combined with hydrometallurgy process is commonly used for recovering valuable elements from spent lithium-ion batteries.To improve the corrosion resistance of heat treatment furnace lining materials in this process,SiC-Si₃N₄-C composite refractories were prepared by heat-treating at 800-1 400 ℃ for 3 h,using fine particles of used iron ladle bricks (1-0.5 and <0.5 mm),silicon carbide (2-1,1-0.5,and <0.5 mm) ,silicon nitride (<0.045 mm),and graphite as raw materials.The fine particles of used iron ladle bricks were used to replace silicon nitride with the same particle size.The effects of the used iron ladle brick fine particles additions (0,12.12%,26.25%,36.38%,and 48.5%,by mass) and the heat treatment temperature (800,1 000,1 200,and 1 400 ℃) on the properties of the composite refractories were studied.The results show that:(1)with the <1 mm used iron ladle brick fine particles addition increasing,the bulk density of the samples changes slightly,the apparent porosity gradually decreases,and the cold compressive strength (CCS) and cold modulus of rupture (CMOR) first decrease and then increase;(2)with the heat treatment temperature rising,the bulk density of the samples first increases and then decreases,the apparent porosity gradually decreases,and the CCS and the CMOR increase;(3)when the temperature is 1 400 ℃ and the used iron ladle brick fine particles completely replace the silicon nitride fine particles with the same particle size,the sample exhibits the best comprehensive performance,with the bulk density of 2.37 g·cm^-3,apparent porosity of 14.3%,CCS of 31.6 MPa,and CMOR of 9.0 MPa,and it has a good resistance to the corrosion of crushed spent lithium-ion battery crushing materials at 1 000 ℃.

Effect of sintering temperatures on properties of Mg-PSZ ceramics added with trace Al₂O₃ addition

Liu Yujia, Liu Tao, Han Lei

2025, (3): 229-233. doi：10.3969/j.issn.1001-1935.2025.03.009

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In order to study the effect of a trace Al₂O₃ addition on the properties of Mg-PSZ ceramics,MgO partially stabilized zirconia (Mg-PSZ) ceramic samples with trace Al₂O₃ were synthesized by solid-state sintering using ZrO₂,MgO,and Al₂O₃ as raw materials,and compared with Mg-PSZ samples without Al₂O₃.The effects of sintering temperatures (1 000-1 700 ℃ for 2 h with an interval of 100 ℃) on the phase composition,microstructure,properties of the samples were studied.The results show that:(1)with the sintering temperature rising,the total contents of c-ZrO₂ and t-ZrO₂ phases in the two samples both increase,the ionic conductivity increases;however,the bulk density of the sample without Al₂O₃ increases,while that of the samples with Al₂O₃ increases first and then decreases;(2)the comprehensive performance of the sample with Al₂O₃ is better than that without Al₂O₃;(3)the sample with Al₂O₃ has the best comprehensive performance after firing at 1 600 ℃.

Preparation of foam ceramics from waste glass and kaolin

Yuan Guodong, He Guichun, Jiang Zhangsong, Duan Yilong, Fu Hang, Zhang Yujie, Wu Jiahui

2025, (3): 234-238. doi：10.3969/j.issn.1001-1935.2025.03.010

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In order to prepare low-cost ceramic foams with low water absorption and high compressive strength,waste glass was used as the main raw material,kaolin as the auxiliary raw material,and SiC as the foaming agent to prepare foam ceramics through mixing,pressing and sintering.The effects of holding times (0,20,40,60 and 80 min),SiC extra-additions (0.1%,0.3%,0.5%,0.7% and 0.9%,by mass) and heat treatment temperatures (1 120,1 140,1 160,1 180 and 1 200 ℃) on the apparent morphology,bulk density,water absorption,and compressive strength of the foam ceramics were investigated.The results show that:(1)with the heat treatment temperature rising and the holding time prolonging,the average diameter and water absorption of the foam ceramics first increase and then decrease,while the bulk density and the compressive strength decrease first and then increase;(2)increasing the SiC extra-addition will increase the average diameter and water absorption of the sample,and decrease the bulk density and compressive strength;(3)when the heat treatment temperature is 1 140 ℃,the holding time is 40 min,and the SiC extra-addition is 0.5%,the sample exhibits the best comprehensive performance,with the bulk density of 0.86 g·cm^-3,water absorption of 0.5%,and compressive strength of 13.6 MPa.

Durability test of calcium hexaaluminate castables for reheating furnace in steel rolling

Ding Cuijiao, Bai Chunlei, Jiang Wenqing, Luo Wei, Yuan Wenjie

2025, (3): 239-243. doi：10.3969/j.issn.1001-1935.2025.03.011

Abstract ( ) PDF (2062KB)( )

Calcium hexaaluminate (CA₆) castables have broad application prospects in extreme working conditions of high-temperature industries due to their excellent mechanical properties,corrosion resistance,and low thermal conductivity.CA₆ castables with different pore-forming methods (particle packing,foaming method,and adding alumina hollow spheres) were placed in a steel rolling reheating furnace and operated for 10 months.The changes in bulk density,apparent porosity,strength,and microstructure were focused on for comparative analysis.The results show that after 10 months of service in the steel rolling reheating furnace,the bulk density of the CA₆ castables with different pore-forming methods has no obvious difference compared with that of castables after holding at 1 300 ℃ for 3 h in a test box furnace;the apparent porosity of all castables increases,among which the particle packing pore-forming specimen increases the most;the cold crushing strength of all castables increases,and the largest increase is in the group adding alumina hollow spheres (from 99.5 MPa to 137.3 MPa);the average pore size of the castables tends to increase,and the pore size distribution of the castable adding alumina hollow spheres changes the least.

Damage analysis of castables in hot blast stove mixing chamber

Ma Shichun, Han Junhua

2025, (3): 244-247. doi：10.3969/j.issn.1001-1935.2025.03.012

Abstract ( ) PDF (1602KB)( )

In response to the problem of abnormally high temperatures at multiple points in the outlet pipeline of the mixing chamber of a hot blast stove in a certain iron plant,samples were selected from the residual lining after dismantling the mixing chamber.The chemical composition,microstructure,phase composition,thermal expansion and thermal shock resistance of the lining material were analyzed.The results show that the lining material adopts corundum castables,which have high strength and good wear resistance,and can effectively resist hot air erosion and CO corrosion damage.However,it has poor thermal shock resistance,and exhibits significant thermal expansion at high temperatures,leading to large internal thermal stresses.These stresses cause cracks to form within the material,which in turn allow the high-temperature and high-pressure hot blast to leak,resulting in an increase in the steel shell temperature.The measures taken are as follows:changing the corundum castables to corundum-mullite castables;when the mixing chamber is constructed with layered casting,the upper layer of castables must be cast before the initial setting of the lower layer of castables to ensure better fusion between the two layers of castables;and the three-way junction part can be changed from combined bricks to integral corundum-mullite castables.After the improvement,the surface temperature of the tube shell has dropped to normal and remains stable,the repair effect is good,and the service life is extended by about 5 years.

Situation and countermeasures of pollution and carbon emission reduction of refractories industry in Henan Province

Qi Libin, Deng Huaxiang, Liu Jizhu, Cheng Sijia

2025, (3): 248-252. doi：10.3969/j.issn.1001-1935.2025.03.013

Abstract ( ) PDF (1159KB)( )

To actively explore a pollution and carbon emission reduction pathway tailored to Henan Province’s industrial characteristics and developmental needs,the current status of Henan’s refractories industry in terms of industrial layout,carbon emissions,and major air pollutant emissions was analyzed.Key challenges in achieving pollution and carbon emission reduction were identified.Targeted countermeasures were proposed,including resolving overcapacity and optimizing industrial layout,exploring the establishment of a product carbon footprint management system,advancing in-depth air pollution control,promoting technological development and innovation,strengthening policy mechanisms,aiming to provide a reference for the high-quality development of Henan’s refractories industry.

Crucible materials for melting superalloys and their performance optimization

Ouyang Li, Yang Shuang, Gu Huazhi

2025, (3): 253-258. doi：10.3969/j.issn.1001-1935.2025.03.014

Abstract ( ) PDF (1035KB)( )

Superalloys are widely used in aerospace,energy,automotive and other critical fields due to their excellent mechanical properties and corrosion resistance.However,the melting of superalloys imposes extremely high requirements on the performance of crucible materials,which need to possess excellent properties such as high thermal shock resistance and outstanding chemical stability.The main melting methods of superalloys and the performance requirements for crucible materials were described,various common oxide and non-oxide crucible materials were introduced,performance optimization strategies for crucibles were especially discussed,including material composition modification,microstructure adjustment,and surface coating introduction.It is expected to provide a reference for the design and development of new high-performance crucible materials.

Research progress on damage mechanism and performance of magnesia-carbon refractories

Wang Shengbo, Hou Qingdong, Tian Ji, Luo Xudong, Ma Beiyue, Li Jijia, Man Silin

2025, (3): 259-265. doi：10.3969/j.issn.1001-1935.2025.03.015

Abstract ( ) PDF (1007KB)( )

The damage mechanisms of magnesia-carbon refractories and research progress on the performance of low-carbon magnesia-carbon refractories in recent years were reviewed.The factors affecting the thermal shock resistance,oxidation resistance and slag corrosion resistance of low carbon magnesia-carbon refractories were summarized.The future development of low-carbon magnesia-carbon bricks was prospected.

Synthesis methods and applications of hexagonal boron nitride powders and nanosheets

Huang Yucan, Shen Jiajie, Guan Chengzhi, Long Dewu

2025, (3): 266-270. doi：10.3969/j.issn.1001-1935.2025.03.016

Abstract ( ) PDF (972KB)( )

Hexagonal boron nitride (h-BN) exhibits numerous excellent properties due to its unique hexagonal flake structure,and finds extensive application in various fields such as hydrogen storage materials,high-temperature materials,solid lubricating materials,catalytic carrier materials,optoelectronic materials,and thermal conductive materials.At present,there are many preparation methods for h-BN,but each method has its own advantages and disadvantages.Based on this,various preparation methods for h-BN powders and nanosheets were reviewed,and the application prospects of h-BN were expounded.

Research progress on reducing gas corrosion resistance of Al₂O₃-SiO₂ refractories

Liang Chengkai, Wang Zhanmin, Qin Hongbin, Chen Tianren

2025, (3): 271-276. doi：10.3969/j.issn.1001-1935.2025.03.017

Abstract ( ) PDF (990KB)( )

Under the goal of “double-carbon”,hydrogen metallurgy technology has become the focus of the industry.The hydrogen-based shaft furnace direct reduction method is a mainstream process,and its operating environment has extremely high requirements for the resistance of refractories to reducing gas corrosion.Al₂O₃-SiO₂ refractories are widely used in the working layer and insulation layer due to their excellent mechanical properties and corrosion resistance,and their applicability and corrosion mechanisms have garnered significant attention.The thermodynamic stability of Al₂O₃-SiO₂ refractories in the reducing atmosphere was summarized.Various factors affecting the reduction reaction were described.The evolution mechanism of Al₂O₃-SiO₂ refractories in the reducing atmosphere was analyzed and discussed.The future research direction for enhancing the resistance of Al₂O₃-SiO₂ refractories to reducing gas corrosion was prospected.