Preparation of mullite fiber based porous ceramics via photocuring 3D printing

Li Xin, Cao Yueqi, Zhang Qiang, Guo Anran

2023, (6): 461-466. doi：10.3969/j.issn.1001-1935.2023.06.001

Abstract ( ) PDF (2081KB)( )

The traditional molding technology cannot meet the needs of high precision and complex structured mullite fiber based porous ceramics.Photocuring 3D printing technology can directly prepare ceramic materials with nearly net size,which is an ideal technology for preparing complex structured ceramics.The mullite fiber based porous ceramics were fabricated using mullite fibers (substrate) and nano SiO₂ powder (high temperature binder) as main raw materials via photocuring 3D printing technology.The effects of the SiO₂ addition (0,20%,27%,33%,and 38%,by mass) on the dispersion stability,rheological properties and photosensitive properties of the fiber slurries,and the microstructure and physical properties of the mullite fiber based ceramics were investigated.The results show that the introduction of nano SiO₂ significantly increases the viscosity of the slurry,which helps alleviate the fiber sedimentation and agglomeration,thus obtaining a uniform slurry;however,excessive SiO₂ leads to over-high slurry viscosity,which is unfavorable to the 3D printing;when the SiO₂ addition is 33%,the performance of the fiber slurry is suitable for 3D printing,with a settling rate less than 9.7% (within 1 h) and a viscosity of 3.95 Pa·s (shear rate of 30 s^-1);the corresponding mullite fiber based porous ceramics printed using the above slurry exhibit the best physical properties with the bulk density of 0.56 g·cm^-3,apparent porosity of 72%,and thermal conductivity at room temperature of 0.135 W·m^-1·K^-1.

Corrosion resistance of refractory materials for smelting reduction vessels in HIsmelt process

Che Lianfang, Shi Chenglong, Fu Wei, Cai Guoqing, Zhang Xiaoxu

2023, (6): 467-472. doi：10.3969/j.issn.1001-1935.2023.06.002

Abstract ( ) PDF (4126KB)( )

In order to promote the further development and application of the HIsmelt process,based on the characteristics of smelting reduction vessels (SRV) of the HIsmelt process,a static crucible method was used to compare the corrosion of iron slag from the SRV on chrome-corundum bricks,microporous corundum-mullite bricks,corundum-mullite bricks,and corundum-spinel bricks at 1 500 ℃.The results indicate that:(1)the chrome-corundum brick has the strongest resistance to SRV slag,because FeO reacts with Al₂O₃ and Cr₂O₃ in the brick to form a high melting point substance,which inhibits the penetration and corrosion of the slag;(2)the formed magnesium-aluminate spinel and gehlenite in microporous corundum-mullite bricks form a protective film in the corrosion layer to prevent the penetration and corrosion of SRV slag;among the three chrome-free materials,the microporous corundum-mullite brick shows the best corrosion resistance;(3)the formation of large amounts of anorthite in the corundum-mullite brick generates gaps,thus corrosion becomes severe for the continuous slag penetration;(4)the spinel grains with small particle sizes and high activity are in-situ generated in the corundum spinel brick,which effectively absorb iron ions in the slag to form magnesium-aluminum-iron composite spinel,blocking the corrosion of SRV slag.

Mullite-high silica glass composite materials prepared from kyanite tailings

Wang Zhifeng, Li Yawei, Ma Shulong, Ren Bo, Meng Linghan, Xu Yibiao, Sang Shaobai

2023, (6): 473-478. doi：10.3969/j.issn.1001-1935.2023.06.003

Abstract ( ) PDF (2967KB)( )

To efficiently utilize kyanite tailings,mullite-high silica glass composite materials were prepared using kyanite tailings as the raw material,adding corn starch and water,pressing into green bodies with dimensions of 50 mm×50 mm,and firing at 1 400,1 500,1 600 and 1 650 ℃ for 3 h.Afterwards,the alkali resistance of these fired specimens was examined by XRD and SEM.The results show that the composites obtained at 1 400 and 1 500 ℃ exhibit low glass phase contents,mainly open pores,and poor alkali attack resistance;in contrast to that,the composite materials treated at 1 600 and 1 650 ℃ display higher high-silica glass phase contents and predominantly closed pores;their alkali attack happens mainly on the surface,which is comparable to mullitized andalusite,showing excellent alkali resistance.

Application and damage mechanism of CA₆ refractories in transition zone of cement rotary kilns

Li Bin, Liu Jie, Zhu Bo, Guo Yutao, Ren Bo, Feng Jisheng, Chen Junhong

2023, (6): 479-483. doi：10.3969/j.issn.1001-1935.2023.06.004

Abstract ( ) PDF (2148KB)( )

In order to explore the application feasibility of CA₆ refractories in the transition zone of cement rotary kilns,CA₆ refractories with a porosity of 27.7% were prepared and then lined in the transition zone of a 5 000 ton/day rotary kiln.After two months operation,the residual thickness of the bricks was still 180-200 mm,exhibiting good corrosion resistance.Compared with magnesium aluminate spinel bricks,the cylinder temperature lined with CA₆ reduced by 40-80 ℃,performing a significant energy-saving and thermal insulation effect.As for the damage mechanism,it is believed that although alkali metals can react with CA₆ refractories to produce KAl₁₁O₁₇,the reaction is slow,so its impact on material damage is mild;in addition to the corrosion of cement clinker,a large amount of KCl sediment is the key factor for the structural deterioration of CA₆ refractories;CA₆ refractories can be used in the transition zone of rotary kilns,but better densification is required.

Crystallization behavior of fused silica with different particle sizes

Yang Shaowen, Wang Qinghu, Zhang Xiao-wei, Xu Yibiao, Liang Xiong, Li Yawei

2023, (6): 484-490. doi：10.3969/j.issn.1001-1935.2023.06.005

Abstract ( ) PDF (3396KB)( )

In order to systematically study the crystallization rules of fused silica ceramics,fused silica particles with three different particle sizes (d₅₀=660.82,42.12,and 5.58 μm) were used as raw materials to prepare fused silica ceramics at 1 250-1 400 ℃.The crystallization kinetics and crystallization processes were analyzed by the isothermal phase transition method and polarized light microscopy.The results show that with the decrease of the particle size,the crystallization activation energy of the fused silica ceramics gets lower,the crystallization onset temperature decreases continuously,and the crystallinity increases rapidly,generating more larger microcracks.The analysis shows that because of the different mass transfer efficiency in the solid phase sintering process,the Si—O bond rearrangement can fully occur between smaller fused silica particles thus crystallization is more likely to occur.In addition,fused silica crystallization exhibits the surface nucleation mechanism:crystallization starts from the surface of the fused silica particles and then gradually spreads inwards.

Preparation and performance lightweight mullite aggregates

Liu Pengcheng, Mao Zhongjun, Yu Long, Zhao Jialiang, Xie Zhipeng

2023, (6): 491-494. doi：10.3969/j.issn.1001-1935.2023.06.006

Abstract ( ) PDF (1496KB)( )

Lightweight mullite aggregates were prepared with cyanite fine powder as the main raw material,walnut shell powder as the pore forming agent,and silica sol as the binder.Effects of calcination temperatures (1 300,1 400,1 500,and 1 600 ℃ for 180 min) and holding times (1 500 ℃ for 60,120,and 180 min) on the bulk density,apparent porosity,linear change rate on heating,phase composition,and microstructure of lightweight mullite aggregates were investigated.The results show that the sample insulated at 1 500 ℃ for 60 min exhibits the optimum comprehensive properties,with bulk density of 1.18 g·cm^-3,apparent porosity of 59.8%,linear change rate on heating of 2.58%,and mullite content of 86 mass%.

Properties of sagger materials bonded by mullite-sol for cathode materials of lithium ion batteries

Ju Maoqi, Cheng Shuiming, Xia Changyong, Liang Yonghe, Cong Peiyuan, Nie Jianhua

2023, (6): 495-499. doi：10.3969/j.issn.1001-1935.2023.06.007

Abstract ( ) PDF (1893KB)( )

In order to further improve the properties of sagger materials for lithium ion batteries cathode materials,green samples with dimensions of 25 mm×25 mm×140 mm were prepared using mullite (3-1,and ≤1 mm),cordierite (≤1 mm),magnesium aluminate spinel (≤0.088 mm) and corundum (≤1 mm) as main raw materials,and mullite-sol as the binder,pressing under 150 MPa.Sagger samples for lithium cell cathode materials were prepared by drying the green samples at 110 ℃ for 24 h and then insulating at 1 400 ℃ for 3 h.Effects of mullite-sol additions (0,3%,4%,5%,and 6%,by mass) on the properties of the samples was researched.The results show that:(1)the mullite-sol shows a network structure after drying at 110 ℃ for 24 h,but it completely transforms into mullite phase after hot treatment at 1 000 ℃;(2)with 5% mullite-sol addition,the sagger shows good comprehensive properties with the bulk density of 2.83 g·cm^-3,apparent porosity of 14.6%,cold modulus of rupture of 8.4 MPa,cold strength retention ratio of 79.8% after 5 thermal shocks by water quenching.

Preparation of porous MgAl₂O₄ ceramics by dry pressing-solid phase reaction route

Piao Jiasi, Du Qing-yang, Bai Jiahai

2023, (6): 500-503. doi：10.3969/j.issn.1001-1935.2023.06.008

Abstract ( ) PDF (2043KB)( )

To solve the problem of property decline caused by the volume expansion during the preparation of porous MgAl₂O₄ ceramics by solid phase sintering method,porous MgAl₂O₄ ceramics were prepared via the dry pressing-solid phase reaction route using Al₂O₃ (d₅₀=1.1 μm) and MgO (d₅₀=1.5 μm) as the main raw materials and TiO₂ (d₅₀=1.5 μm) as the additive.Influences of hot treatment temperatures (1 300,1 350,1 400,1 450,and 1 500 ℃) and TiO₂ additions ( 0,0.5%,1.0%,1.5%,and 2.0%,by mass) on the linear change rate on heating,apparent porosity,bulk density,phase composition and microstructure of the porous MgAl₂O₄ ceramics were investigated.The experimental results show that:(1)as the hot treatment temperature increases,the densification of the porous ceramics increases,the bulk density increases but the apparent porosity decreases;(2)as the TiO₂ addition increases,the linear shrinkage rate on heating of the porous ceramics increases,the apparent porosity decreases remarkably,while the average grain size increases.

Configuration and application of refractories for titanium dioxide rotary kilns

Wang Minggang, Che Lianfang, Shi Chenglong, Yuan Hongwei, Liu Yongzhen

2023, (6): 504-507. doi：10.3969/j.issn.1001-1935.2023.06.009

Abstract ( ) PDF (960KB)( )

In view of the problems existing in refractories used in titanium dioxide rotary kilns,the configuration of refractories such as low thermal conductivity composite bricks,high strength acid-resistant bricks,spalling resistant fireclay bricks and mullite-andalusite bricks was put forward for energy saving and consumption reduction,lightweight,and long life and high efficiency,and their application effects were also introduced,which provided the basis for material selection and usage.

Effect of zircon addition on spalling resistance of low-carbon MgO-C bricks

Zheng Junguo, Zhao Wei, Huang Ao, Gu Huazhi, Sun Chunhui, Liu Jingxuan, Yan Hao, Zhao Xiantang

2023, (6): 508-513. doi：10.3969/j.issn.1001-1935.2023.06.010

Abstract ( ) PDF (2097KB)( )

In order to improve the spalling resistance of low-carbon MgO-C bricks for VOD ladles,the low-carbon MgO-C bricks were prepared using fused magnesia (5-3,3-1,＜1 and ＜0.088 mm),natural flaky graphite (<0.15 mm),metallic aluminum powder (<0.045 mm),and zircon powder (<0.05 mm) as main raw materials,thermosetting phenolic resin as the binder.Effects of zircon additions (0,1%,2%,and 5%,by mass) on the spalling resistance of low-carbon MgO-C bricks were studied.The results show that:(1)the hot modulus of rupture,thermal shock resistance,oxidation resistance and slag resistance of the sample with 1% zircon all reach the maximum,indicating that the addition of zircon helps to improve the spalling resistance of low-carbon MgO-C bricks;(2)AlON of needle-like and continuous flaky spatial structure and flaky Al₂O₃-ZrO₂ composite form in the matrix after being heated at 1 400 ℃ for 0.5 h in carbon embedded condition,which enhances the high temperature mechanical property and thermal shock resistance due to the effect of pinning toughening and particle toughening;(3)excessive zircon results in a substantial increase in zirconia,whose volume change at high temperatures leads to the aggregation of micro-cracks in the matrix,resulting in a significant decline in the anti-spalling property of low-carbon MgO-C bricks.

Preparation of corundum-spinel castables using microporous corundum-spinel aggregates to replace corundum aggregates

Liu Xuexin, Zhang Jinhua, Chen Xinming, Wang Jingran, Yang Zongyuan, Han Bingqiang, Ke Changming

2023, (6): 514-517. doi：10.3969/j.issn.1001-1935.2023.06.011

Abstract ( ) PDF (1334KB)( )

To improve the thermal insulation properties of corundum-spinel castables for the steel ladle working lining,the castables were prepared using microporous corundum-spinel aggregates to partially or totally replace sintered corundum aggregates with the same grain size.Effects of the aggregates on the bulk density,porosity,mechanical strength,thermal conductivity and slag resistance were investigated.The results indicate that,when the sintered corundum aggregates were substituted by microporous corundum-spinel aggregates partially or totally with the same grain size,the bulk density and thermal conductivity decrease remarkably,and the slag resistance is similar.As the working lining,the developed castables are beneficial to reducing the ladle mass and improving ladle insulation performance.

Properties of new zirconia-based composites for glass kilns

Liang Xinxing, Gao Yuying, Ye Hang, Ma Cheng-liang, Liu Xiaogang, Fan Chongfang, Xu Enxia

2023, (6): 518-522. doi：10.3969/j.issn.1001-1935.2023.06.012

Abstract ( ) PDF (2139KB)( )

To provide a material with excellent comprehensive properties for the glass kiln melting pool,zirconia powder and alumina powder were fully mixed according to the ratio of m(ZrO2)∶ m(Al₂O₃)=4∶1 and fused in an arc furnace.The obtained fused zirconia-corundum eutectic material was processed into different particle sizes,batched according to a certain particle size distribution and mixed evenly.After pressure molding and sintering at 1 750 ℃,new zirconia-based composites were prepared.The phase composition and microstructure of the composites were analyzed.The molten glass corrosion resistance of the composites was compared with that of zirconia corundum bricks 33^# and 41^#.The results show that the new zirconia-based composites have a dense structure,high chemical purity without low melting point components,and good thermal shock resistance.Compared with zirconia corundum bricks 33^# and 41^#,after corroded by high temperature molten glass,the new composites have no corrosion cavities,no needle-like pores or defects or liquid phase infiltration and no reaction with molten glass,showing good corrosion resistance to molten glass.

Effect of aluminate cement on structure and properties of silica sol bonded corundum castables

Ding Yuhang, Liu Huiyong, Cong Peiyuan, Cai Wei, Xiang Bing, Xia Changyong

2023, (6): 523-527. doi：10.3969/j.issn.1001-1935.2023.06.013

Abstract ( ) PDF (2069KB)( )

Combining the advantages of aluminate cement and silica sol to improve the mechanical properties of castables is a cheap and simple optimization strategy.Corundum castables were prepared with brown corundum and dense corundum as the main raw materials,and silica sol and aluminate cement as the binders.The effect of the aluminate cement addition (0,1%,2%,3% and 4%,by mass,respectively) on the castables was studied.The results show that the hydration of aluminate cement promotes the coagulation and condensation reactions of silica sol,while Si—O—Ca and Si—O—Al chemical bonds are formed,which accelerates the formation of a stable three-dimensional network structure.With the increase of the aluminate cement addition,the cold strength of the samples after curing at 110 ℃ increases,that after heat treatment at 1 100 and 1 400 ℃ first increases and then decreases,the hot modulus of rupture after heat treatment at 1 400 ℃ decreases rapidly,the cold modulus of rupture after thermal shock first increases and then decreases slightly,and the strength retention ratio gradually increases.The silica sol bonded sample with 1% aluminate cement has the best comprehensive performance.

Properties comparison of reactive MgO and calcium aluminate cement bonded corundum-spinel castables

Zhao Zongqiang, Zhang Hongrui, Chen Liugang

2023, (6): 528-530. doi：10.3969/j.issn.1001-1935.2023.06.014

Abstract ( ) PDF (1373KB)( )

To improve their properties,corundum-spinel castables were prepared using tabular corundum,reactive alumina and sintered magnesia fines as the main starting materials,reactive magnesia (RM) and calcium aluminate cement (CAC) as the binder,respectively.The apparent porosity,permanent linear change on heating,cold modulus of rupture,cold crushing strength,and corrosion resistance to CaO-Al₂O₃-Fe₂O₃-SiO₂ (CAFS) slag of the two castables fired at 1 600 ℃ for 3 h were compared.The results show that,after heat treatment at 1 600 ℃,compared with the CAC-bonded castables,the RM-bonded castables perform lower cold modulus of rupture and cold crushing strength,but significantly improved volume stability and corrosion and penetration resistance to CAFS slag.

Research progress on strengthening and toughening of boron carbide composite ceramics

Yao Wankai, Fang Binxiang, Li Xiangcheng, Chen Ping’an, Zhu Yingli, Zhu Boquan

2023, (6): 531-537. doi：10.3969/j.issn.1001-1935.2023.06.015

Abstract ( ) PDF (957KB)( )

Boron carbide (B₄C) composite ceramics are widely used in armor and cutting tools due to their high strength.However,the poor sintering performance and low fracture toughness have limited their extended applications.The effects of oxides,carbides,borides and other reinforcement phases on the mechanical properties of B₄C composite ceramics were reviewed.The mechanisms and ways to reduce the sintering temperature and improve the strength and toughness of B₄C were explored.Among them,transition metal borides (such as TiB₂) could substantially improve the strength and toughness of B₄C composite ceramics through mechanisms such as particle toughening,crack deflection and bridging due to differences in the thermal expansion coefficient,and pullout of the reinforced phase,which is currently the most effective way for strengthening and toughening.

Research progress of lining refractories for hazardous waste treatment incinerators

Ding Jiahui, Zhang Li-xin, Deng Junjie, Liu Ping, Xu Enxia, Li Suping

2023, (6): 538-541. doi：10.3969/j.issn.1001-1935.2023.06.016

Abstract ( ) PDF (894KB)( )

The types of common lining refractories for hazardous waste incinerators were reviewed.It was pointed out that the lining refractories in different working environments mainly include corundum,SiC,mullite,fireclay,chrome-corundum,corundum-SiC,corundum-mullite and magnesia-alumina.The damage mechanism of lining refractories was summarized,including mechanical abrasion,thermal spalling and chemical corrosion.The development trend of lining refractories for hazardous waste incinerators was forecasted.

Research progress of waste refractories used as ferrous metallurgy flux

Yu Wuming, Mu Xin, Du Chuanming, Ma Beiyue, Yu Jingkun

2023, (6): 542-545. doi：10.3969/j.issn.1001-1935.2023.06.017

Abstract ( ) PDF (955KB)( )

The current exploitation situation of waste refractories was summarized.The resource utilization of waste refractories in foreign advanced steel enterprises was introduced,namely,waste MgO refractories as steelmaking flux instead of light burned dolomite refractories,and waste Al₂O₃ refractories as refining flux instead of bauxite refractories.Finally,the development and research direction of the resource utilization of waste refractories were prospected.

Research progress of preparing graphene by exfoliation method

Lyu Junyi, Li Yage, Cai Weijie, Li Tao, Xu Qing, Zhang Haijun

2023, (6): 546-552. doi：10.3969/j.issn.1001-1935.2023.06.019

Abstract ( ) PDF (938KB)( )

Graphene is widely used in the fields of optics,electricity,materials,biomedicine,etc.because of its advantages such as high carrier mobility,high thermal conductivity and large specific surface area.Currently,it is still a challenge to find a method of low-cost,high efficiency and large-scale for the industrial production of graphene.Based on the exfoliation mechanism,the research status of graphene prepared by mechanical exfoliation and liquid exfoliation was reviewed.The advantages and main problems of these two methods were summarized.The development direction of the exfoliation preparation technology of graphene was prospected.

Current Issue