Refractories

Feasibility study on Ba₂ZrYO₅F crucible vacuum induction melting of Ti6Al4V alloy

Chen Guangyao, Guo Hang, Peng Kunjie, Dou Zhihe, Gao Pengyue, Feng Qisheng, Hou Xinmei, Li Chonghe

2026, (5): 369-375. doi：10.3969/j.issn.1001-1935.2026.05.001

Vacuum induction melting is an effective low-cost technical means for preparing titanium alloys.However,its application is limited by severe contamination of alloys caused by crucibles.In this study,vacuum induction melting of Ti6Al4V alloy was carried out using a Ba₂ZrYO₅F crucible with sponge Ti,Al ingots and AlV alloy.The interfacial reactions between the crucible and Ti6Al4V alloy melt as well as the oxygen content of the melted alloy were analyzed,and the microstructure and mechanical properties of as cast Ti6Al4V alloy were evaluated.The results show that the Ba₂ZrYO₅F crucible suffers physical dissolution by Ti6Al4V alloy melt,generating Y₂O₃ and Y₂O₃(ZrO₂) on the crucible wall,with the Ba₂ZrYO₅F matrix phase remaining.Owing to intense electromagnetic stirring,the Y₂O₃ formed on the crucible wall enters the melt and forms dispersively distributed inclusions with a size of approximately 2 μm.The oxygen content of the alloy after melting is about 0.18 mass%.The as cast alloy is composed of α and β phases,with a tensile strength of 1 108 MPa and an elongation of 1.8%,and the fracture surface presents a cleavage feature.This work preliminarily verifies the feasibility of preparing the alloy by Ba₂ZrYO₅F vacuum induction melting.

Effect of zircon on sintering behavior and alkali corrosion resistance of bauxite-based mullite homogeneous grogs

Zhao Fei, Li Ruoxi, Wang Yali, Mai Haixiang, Zuo Yudong, An Jiancheng, Lian Weikang

2026, (5): 376-382. doi：10.3969/j.issn.1001-1935.2026.05.002

Abstract ( ) PDF (2771KB)( )

To improve the alkali corrosion resistance of bauxite-based mullite homogeneous grogs,a series of ZrO₂-doped bauxite-based mullite homogeneous grogs were prepared by wet mixing,shaping and calcining at 1 350-1 650 ℃ for 4 h,using grade Ⅱ high-alumina bauxite as the main raw material and zircon as the modifying additive.The effects of varying zircon additions (0,2%,4%,and 6%,by mass) on the sintering behavior,phase composition,and cold physical properties of the grogs were investigated,and their alkali corrosion resistance was evaluated by the static crucible method.The results indicate that between 1 450 and 1 650 ℃,SiO₂ generated from zircon decomposition forms a SiO₂-rich liquid phase at the ZrO₂ interface,which accelerates the sintering shrinkage of the mullite homogeneous grogs.Concurrently,a portion of this SiO₂-rich liquid phase participates in the mullitization reaction during calcination and is consumed in situ.ZrO₂ decomposed from zircon is dispersively distributed in the glass phase and at mullite grain boundaries,increasing the viscosity of the glass phase.After calcination at 1 650 ℃,the apparent porosity of the homogeneous grogs decreases from 0.63% to 0.20% with the increase of zircon addition.Furthermore,the increased ZrO₂ addition inhibits the diffusion and penetration rate of K⁺ in alkaline corrosion environments,thereby improving the alkali corrosion resistance of the bauxite-based mullite homogeneous grogs.When the zircon addition is 4%,the sample calcined at 1 650 ℃ for 4 h exhibits high density,excellent cold mechanical properties and favorable alkali corrosion resistance.

Optimization of synthesis processes for nano zirconium carbide

Liu Jiageng, Wang Gang, Li Shipeng

2026, (5): 383-388. doi：10.3969/j.issn.1001-1935.2026.05.003

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To prepare finer nano zirconium carbide (ZrC) powder at low temperatures,zirconia powder and zirconium oxychloride were used as zirconium sources,nano carbon black as the carbon source,and absolute ethanol and deionized water as media.Two preparation routes were adopted,including the carbothermal reduction method and liquid precursor conversion method combined with carbothermal reduction.Different n(Zr)∶n(C) molar ratios (1∶2,1∶3,1∶3.3 and 1∶3.6) were designed,and the hot system was optimized by stepwise heat preservation at 1 200,1 400 and 1 600 ℃.Meanwhile,a reference sample with n(Zr)∶n(C)=1∶3 was prepared by direct heating to 1 600 ℃.The effects of the zirconium source,Zr/C molar ratio and hot treatment system on the phase composition and microstructure of ZrC powders were investigated.The results show that holding at 1 200 ℃ for 1 h with carbothermal reduction can completely convert m-ZrO₂ into high-activity c-ZrO₂,which significantly reduces the activation energy and energy consumption of the reaction.Pure-phase polygonal ZrC with grain size of 100-200 nm can be obtained by further heating to 1 600 ℃ and holding for 1 h.An additional heat preservation at 1 400 ℃ for 10 min promotes abundant nucleation and restricts grain growth,refining the grain size to 60-120 nm.Under the molar ratio of n(Zr)∶n(C)=1∶3,the adoption of zirconium oxychloride as the zirconium source realizes molecular-level mixing of reactants and further refines pure-phase ZrC grains to 60-90 nm.This crystal form regulation and stepwise sintering strategy provides a feasible route for preparing nano ZrC powders with low cost and low energy consumption.

Effects of nano-zirconia on microstructure and properties of mullite-corundum castables

Li Shien, Chen Ping’an, Qiao Mengke, Zhu Yingli, Chen Fu, Wu Jiang, Luo Gangtao, Li Xiangcheng

2026, (5): 389-396. doi：10.3969/j.issn.1001-1935.2026.05.004

Abstract ( ) PDF (3900KB)( )

To enhance their hot mechanical strength and satisfy their applicability and reliability in high-temperature industries,mullite-corundum castables were prepared using fused mullite as aggregates,corundum powder and α-Al₂O₃ powder as fine powders,ρ-Al₂O₃ powder and calcium aluminate cement as binders,and nano-ZrO₂ as the modifier.The effects of the nano-ZrO₂ additions (0,0.4%,0.8%,1.2%,1.5%,2.0%,and 3.0%,by mass) on the microstructure and properties of the castables were investigated.The results show that nano-ZrO₂ is dispersed in the matrix of the castables and promotes the nucleation and growth of calcium hexaluminate (CA₆) grains.With the increase of the nano-ZrO₂ addition,the amount of plate-like CA₆ increases,and CA₆ exhibits interlocking distribution in the matrix.Compared with the castable without nano-ZrO₂,the one with 2.0% nano-ZrO₂ demonstrates the optimal mechanical properties,while the one with 0.8% nano-ZrO₂ shows the best thermal shock resistance and slag corrosion resistance.

Effect of magnesia-zirconia powder on properties of corundum-spinel based castables

Lei Yutian, Nie Jianhua, Chen Ruifeng, Zhang Xiaoxu, Liang Yonghe

2026, (5): 397-401. doi：10.3969/j.issn.1001-1935.2026.05.005

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To develop high-performance chrome-free purging plugs,corundum-spinel castables were prepared using tabular corundum,sintered corundum,pure calcium aluminate cement,magnesia-zirconia powder,and premixed fine powders (spinel powder,tabular corundum,white corundum,alumina-rich spinel powder,and α-Al₂O₃ micropowder) as raw materials.The effects of magnesia-zirconia powder addition (0,0.5%,1.0%,1.5%,2.0%,2.5%,3.0%,and 3.5%,by mass) on the cold physical properties and thermal shock resistance of the corundum-spinel castables were investigated.The results show that after the heat treatment at 1 550 ℃,with the increasing magnesia-zirconia powder addition,ZrO₂ is uniformly distributed in the matrix;MgAl₂O₄ and CA₆ interlock with ZrO₂ in the matrix,making the structure denser;the permanent linear change decreases;and the strength of the samples increases.In addition,adding an appropriate amount of magnesia-zirconia powder significantly improves the thermal shock resistance of the samples.For the sample with 3.5% magnesia-zirconia powder,the retention ratio of the cold modulus of rupture reaches 63%,which is significantly higher than that of the sample without magnesia-zirconia powder.Considering overall performance and cost,the purging plug prepared with the castable formulation containing 3.5% magnesia-zirconia powder was trial-used in an LF refining ladle.Its service life was basically comparable to that of the chrome-containing purging plugs currently used in the steel plant,reaching 48-50 heats.

Influence of magnesium sources on properties of magnesium aluminate spinel prepared from secondary aluminum dross

Yue Wenjie, Tang Weipeng, Ma Chengliang, Tian Xiaoli, Liu Cheng, Feng Runtang, Gao Jinxing

2026, (5): 402-407. doi：10.3969/j.issn.1001-1935.2026.05.006

Abstract ( ) PDF (2497KB)( )

To investigate the effects of various magnesium sources on their preparation from secondary aluminum dross,magnesium aluminate spinel materials were synthesized using secondary aluminum dross as the aluminum source,high purity magnesia micropowder,Xizang microcrystalline magnesite,and calcined magnesite as the magnesium source,respectively,and phenolic resin as the binder,firing at 1 700 ℃ for 2 h.The effects of the magnesium sources and the molar ratios of Al₂O₃ to MgO (1∶1.05,1∶1.15,and 1∶1.25) on the phase composition,microstructure and properties of the synthesized magnesium aluminate spinel were studied.The results indicate that when the molar ratio of Al₂O₃ to MgO is 1∶1.25,all samples exhibit single-phase magnesium aluminate spinel.The sample with calcined magnesite as the magnesium source exhibits the optimal comprehensive properties: apparent porosity of 9.7%,bulk density of 2.84 g·cm^-3,the highest density,cold compressive strength of 136 MPa,and the maximum compressive strength after thermal shock of 92.4 MPa.

Application of fast-baking and explosive-spalling-resistant composite corundum-spinel castables for refining ladles

Hu Bo, Liu Guangping, Chen Junfeng, Song Yanan, Li Yuanyuan, Wang Yulong, Shen Mingke

2026, (5): 408-414. doi：10.3969/j.issn.1001-1935.2026.05.007

Abstract ( ) PDF (3925KB)( )

To further optimize the explosive spalling resistance and thermal shock resistance of corundum-spinel castables,a composite corundum-spinel castable was prepared using white fused corundum,composite sintered corundum,reactive alumina micropowder,90# alumina-rich spinel micropowder,70# spinel fine powder,and calcium aluminate cement as raw materials.A conventional corundum-spinel castable was also prepared for reference.The composition and microstructure of the spent fast-baking and explosive-spalling-resistant composite corundum-spinel castable were analyzed.The results show that during service,its degradation is mainly caused by the reactions with slag and molten steel,and the damage modes are predominantly slag corrosion,penetration,and structural spalling.By adjusting the matrix composition and microstructure and introducing composite sintered corundum,the strength of the cured castable was significantly improved,and its explosive spalling resistance and thermal shock resistance were enhanced.When applied in a domestic 300 t refining ladle,under relatively low ambient curing temperature conditions,it can meet the demands of short curing time and fast heating.Compared with the conventional corundum-spinel castable,its service life was increased by 60%.

Effect of carbon nanofiber/calcium aluminate composite powder on properties of ceramic composite resistors

Zhong Zhenxin, Yao Congwei, Wang Yunlong, Zhu Ruifeng, Wang Jiayi, Chong Xiaochuan, Xiao Guoqing, Ding Donghai

2026, (5): 415-421. doi：10.3969/j.issn.1001-1935.2026.05.008

Abstract ( ) PDF (2496KB)( )

To address the problems that traditional carbon-based conductive fillers tend to agglomerate and distribute unevenly,resulting in the deterioration of mechanical and electrical properties of carbon-ceramic composite conductive materials,pre-synthesized carbon nanofiber/calcium aluminate composite powder (CNFs/CAC) was used as the conductive filler.It was dry ball milled and mixed with ceramic matrix materials including bauxite,kaolin,and potassium feldspar.After granulation and isostatic pressing,carbon nanofiber-reinforced carbon-ceramic composite resistor materials were fabricated by sintering in a carbon embedded reducing atmosphere.The effects of the composite powder addition (0.5%,1.0%,1.5%,and 2.0%,extra adding) on the phase composition,microstructure,physical properties and resistivity of the ceramic resistors were systematically investigated.The results show that with the increase of the composite powder addition,the density and cold compressive strength decrease,and the resistivity first increases and then decreases.The specimen with 1.5% composite powder exhibits the most uniform carbon distribution and the most complete conductive network,and possesses good resistance stability and mechanical properties meeting application requirements,which presents the optimal comprehensive performance.

Preparation and performance of flake alumina reinforced high-alumina electrical porcelain materials

Yue Yonggang, Tian Xiaoyun, Dang Dawei, Li Zhihui, Lei Taotao, Chong Xiaochuan, Ding Donghai, Xiao Guoqing

2026, (5): 422-429. doi：10.3969/j.issn.1001-1935.2026.05.009

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To improve the brittleness and enhance the mechanical properties of electrical porcelain materials,high-alumina porcelain insulators were prepared using spray-granulated powder for porcelain insulators as the raw material,introducing flake alumina (ρ-Al₂O₃) as a two-dimensional reinforcing phase,and pressureless sintering at 1 300 ℃ for 2 h.The effects of the particle size distribution of ρ-Al₂O₃ treated through different dispersion methods (mechanical grinding,vibratory milling,and dry ball milling),on the mechanical properties,phase composition,and microstructure of the insulators were investigated,and the toughening mechanism was analyzed.The results indicate that dry ball milling can most effectively refines ρ-Al₂O₃,reducing its d₅₀ to 3.73 μm while significantly promoting mullite formation and microstructural optimization during sintering.Compared to the sample containing mechanically-ground or vibratorily-milled ρ-Al₂O₃,the one with dry ball-milled ρ-Al₂O₃ exhibits the best overall performance,showing the lowest apparent porosity,flexural strength of 119 MPa,elastic modulus of 172 GPa,Vickers hardness of 30 GPa,and fracture toughness of 7.51 MPa·m^1/2.The fracture toughness significantly increases by 73.8% compared to the sample without ρ-Al₂O₃.This improvement primarily stems from the three-dimensional interlocking network structure constructed by the refined ρ-Al₂O₃ and in situ formed mullite whiskers,which effectively inhibits crack propagation through multiple toughening mechanisms,including crack deflection,branching,and bridging,thereby achieving the strengthening and toughening of high-alumina porcelain insulators.

Industrial air pollutant emission limits of refractories for different kiln temperatures

Sun Peng, Sun Hanghang, Deng Huaxiang, Xu Yuanqian, Yan Yali, Bai Ling, Cao Xia

2026, (5): 430-435. doi：10.3969/j.issn.1001-1935.2026.05.010

Abstract ( ) PDF (1150KB)( )

As a key process parameter for the firing of refractories,kiln temperature directly affects the generation and emission of air pollutants such as NO_x,SO₂,VOCs and particulate matter.This work aims to systematically analyze the variation characteristics of air pollutant concentrations in refractories industry kilns under different firing temperatures,so as to provide scientific references for the green upgrading and pollution emission reduction of the industry.Taking Henan Province as an example,the development status of the refractories industry and the generation-emission characteristics of major pollutants were firstly summarized,and then the stack emission limits of air pollutants under different kiln temperature conditions were determined.The results show that the emission limit of particulate matter for refractories industry is 10 mg·m^-3;and that of SO₂ is 50 mg·m^-3.There is a significant positive correlation between NO_x concentration and kiln temperature.The NO_x emission limit is 50 mg·m^-3 for kilns operating at 300-1 200 ℃,100 mg·m^-3 for 1 200-1 700 ℃,200 mg·m^-3 for kilns with temperatures above 1 700 ℃,and 300 mg·m^-3 for high-temperature electric smelting furnaces with temperatures exceeding 2 000 ℃.The emission limit of non-methane total hydrocarbons (NMHC) is 30 mg·m^-3.

Research progress on applications and process optimization of fiber-reinforced SiC ceramic matrix composites

Gu Yinglei, Ma Chao, Bu Jinglong, Wu Yinlin, Shang Xiaoxian

2026, (5): 436-442. doi：10.3969/j.issn.1001-1935.2026.05.011

Abstract ( ) PDF (959KB)( )

Fiber-reinforced SiC matrix ceramic composites exhibit broad application prospects in aerospace,energy,automobile and other fields owing to their excellent properties such as high temperature resistance,oxidation resistance,high specific strength and high specific modulus.This paper reviewed the main structural systems of fiber-reinforced SiC matrix ceramic composites as well as domestic and international application progress.Meanwhile,it highlighted the latest advances in the optimization of their preparation processes,including chemical vapor infiltration (CVI),precursor infiltration and pyrolysis (PIP),reactive melt infiltration (RMI),3D printing,and the combined technologies of the above processes.Furthermore,the future development trends of preparation processes and applications were prospected.

Research status of yttria-based ceramic shell molds for precision casting of titanium alloys

Xu Yan, Liu Chencan, Chen Bowen, Xu Weitai, Wang Fei, He Bo

2026, (5): 443-448. doi：10.3969/j.issn.1001-1935.2026.05.012

Abstract ( ) PDF (956KB)( )

As a crucial forming technology for titanium alloys,precision casting lies in the selection and performance optimization of mold shell materials.Yttria has become the preferred material to suppress the interfacial reactions with molten titanium owing to its high melting point,excellent chemical stability and low thermal expansion coefficient.In this work,the research status of yttria mold shells for titanium alloy precision casting was reviewed,including advances in the aspects of binders,mineralizers,performance optimization,and preparation processes.The current challenges were analyzed and the future development trends were pointed out.

Research progress on high-value utilization of red mud:element extraction and functional material preparation

Yan Jie, Wang Jia, Ke Jun, Xia Hao

2026, (5): 449-453. doi：10.3969/j.issn.1001-1935.2026.05.013

Abstract ( ) PDF (979KB)( )

Red mud is a bulk solid waste generated in the alumina industry,posing a serious threat to the ecological environment.The chemical composition and physical properties of red mud solid waste as well as the correlation with its sources were analyzed.The research progress of red mud in the fields of valuable metal extraction,and the preparation of engineering materials,environmental functional materials and high-value products was systematically reviewed.Research ideas were put forward targeting the separation and purification of critical metal elements,development of low-energy activation technologies,and production of high value-added products,so as to ultimately achieve the multi-stage utilization goal of harmless disposal—resource recovery—high-value utilization of red mud.

Research progress of high temperature oxidation-resistant coatings for C/C composites

Hou Lichao, Tian Xuekun, Gu Qiang, Liu Xinhong

2026, (5): 454-460. doi：10.3969/j.issn.1001-1935.2026.05.014

Abstract ( ) PDF (963KB)( )

C/C composites are prone to oxidative failure under high-temperature oxygen-containing and severe ablation conditions,which seriously restricts their engineering service life.Constructing high-temperature oxidation-resistant ceramic coatings on their surfaces is an effective way to improve their high-temperature oxidation and ablation resistance.In this paper,the main failure mechanisms of C/C composites during high-temperature service and the protection mechanisms of oxidation-resistant coatings were systematically reviewed.The research progress of three typical ultra-high temperature ceramic coating systems was summarized,including ZrB₂-based,ZrC-based and ZrSiO₄-based coatings,in terms of structural design,preparation technology and high-temperature protective performance.Meanwhile,the functional mechanisms of novel protection systems such as multiphase doping,gradient composite structures and nano-reinforced coatings in inhibiting oxygen diffusion,relieving thermal stress and improving self-healing ability were emphatically analyzed.On this basis,the development directions of high-performance oxidation-resistant coatings were prospected in terms of material system design,green preparation process optimization and extreme environment adaptability evaluation,so as to provide a reference for the long-term and stable service of C/C composites in complex high-temperature environments.