The “Three Exploitation” of Academician Zhong Xiangchong (1921.11.21—2015.02.11),who is the main founder and main pioneer of China’s refractories industry,was reviewed. The development of China’s refractories industry in different stages under his guidance,organization and participation was introduced.After receiving his doctor’s degree in Britain in 1949,Academician Zhong Xiangchong immediately returned to participate in the construction of P.R.China.From 1949 to 1969,he worked in the Ministry of Metallurgical Industry (Ministry of Heavy Industry) in Beijing,and planned the development of the China’s refractories industry.During this period,he established Luoyang Institute of Refractories Research (LIRR) and served as the director in 1963.From 1973 to 2000,he worked in Luoyang to develop LIRR.From 2000 to 2015 when he passed away,he established and developed High Temperature Ceramics Institute in Zhengzhou University.At the height of national and industrial development,he has always advocated the technical policy of “developing Chinese-style refractory materials based on China’s unique refractory resources”,and has made outstanding contributions to the development of China’s refractories industry in terms of production technology,talent training,academic exchange and higher education so he is regarded as the “Father of refractories”.The last two five-year plans in the 20 ^th century are of milestone significance in the development history of China’s refractories.During this period,the refractories industry undertook six major national science and technology projects.Through the implementation,drive,achievement transformation,popularization and application of these projects,the refractory industry has developed greatly,which laid an important foundation for the development in the 21^st century.The process technology and equipment development of iron and steel industry in different periods and its impact on the development of refractories industry,as well as the new progress and low-carbon transformation of refractories industry in the 21^st century were introduced.In the future,the refractories industry should continue to strive for the construction and formation of a green,low-carbon,circular and intelligent high-quality industrial system and an ecological industrial chain,achieving carbon neutrality before 2060,and constantly meeting the new requirements of the new development stage.

ased on the carbon emission peak and neutrality targets,the carbon reduction and green development situation of main high-temperature industries were introduced.The new technologies for pollution and carbon reduction in the iron and steel industry were emphasized.The challenges and opportunities for refractories industry under the double carbon targets were analyzed,and the main innovation directions of refractories were pointed out.

Bonding systems for Al₂O₃-C sliding plates were reviewed.The research on bonding performance improvement in China and overseas in recent years was outlined,mainly including phenolic resin bonding and ceramic bonding for Al₂O₃-C sliding plates.The possible development directions of bonding systems for Al₂O₃-C sliding plates were outlooked.

The application and research state of TiO₂ in Al₂O₃-SiO₂,MgO-Al₂O₃,and carbon containing systems as well as monolithic refractories were overviewed to provide references for the further application of TiO₂ in refractories.

Si₃N₄ porous ceramics were fabricated by foam-gelcasting combined catalytic nitridation using high-purity silicon powders as the starting material and Fe(NO₃)₃·9H₂O as the catalyst and CTAB as the foaming agent.The effects of the nitriding temperature (1 200,1 250,1 300 and 1 350 ℃) and the catalyst addition (0,1%,3% and 5%,by mass) on the phase composition,microstructure and physical properties of the Si₃N₄ porous ceramics were investigated.The results show that with 1% of Fe(NO₃)₃·9H₂O,the Si₃N₄ porous specimen nitridized at 1 300 ℃ has 29.7 MPa of compressive strength and 55.1% of apparent porosity.The relatively high strength of the porous ceramics can be attributed to the highly catalytic effect of Fe(NO₃)₃·9H₂O,which promotes the growth of Si₃N₄ whiskers inside the specimen and plays a positive role in the improvement of mechanical properties.

In order to improve the sintering densification of dolomite clinker and optimize its microstructure,dolomite clinkers were prepared by traditional sintering and induction sintering,respectively,using natural dolomite as the raw material and adding different amounts of Y₂O₃ (m(Y₂O₃)/(m(CaO+MgO):0,2.0%,2.5%,3.0% and 3.5%).The effects of the Y₂O₃ addition and the sintering method on the sintering properties and microstructure of dolomite were investigated.The results show that:(1)compared with the traditional sintering method,the induction sintering method improves the densification of the sintered dolomite clinker and increases the solid solution degree of Y₂O₃ in the main crystalline phase;(2)via the traditional sintering method,the Y₂O₃ doped sample has obviously increased CaO average grain size; while using the induction sintering method,the average grain size of CaO decreases and CaO and MgO distribute uniformly.

This work aims at solving the problems of difficult dispersion,easy oxidation and high cost of nano carbon during application.C/MgAl₂O₄ composite powders were synthesized using MgC₂O₄,MgO₂,Al₂O₃ powder,and Al powder as raw materials by combustion synthesis.The results indicate that the with the maximum MgC₂O₄ addition of 33.34 mass% the prepared powder contains 1.17 mass% of carbon and carbon distributes among spinel grains.The MgAl₂O₄ spinel shows both granular and rod-like morphologies.The granular MgAl₂O₄ is generated from the mutual diffusion between MgO and Al₂O₃;while the rod-like MgAl₂O₄ spinel is mainly formed by the vapor-solid growth mechanism from Mg vapor and Al₂O₃.

The evolution of the corrosion peak at the three-phase interface of acorundum based crucible was recorded using a self-made high-temperature visualization system,revealing the evolution law of the volcano-like corrosion peak morphology.The strain distribution nephogram of the side surface and the full field average strain-time curve of the block corundum specimen during slag corrosion were obtained by the high-temperature digital image correlation technology.The results show that the strain distribution nephogram of the side surface is highly correlated with the distribution regions of the corrosion and penetration caused by the slag in the refractories.The dynamic strain distribution nephogram can be used to reflect the dynamic development process of slag corrosion and penetration of refractories.

The stabilized magnesia dolomite sands were prepared using dolomite,magnesite and silica as the starting materials,digesting and two-step calcining.Sintered stabilized magnesia dolomite specimens with different calcia/silica mass ratios (2.6,2.8 and 3.0,respectively) were further prepared.Effects of the calcia/silica ratios on properties of the stabilized magnesia dolomite materials were investigated.The results show that with the increase of the calcia/silica ratio,the bulk density of the specimens gradually decreases,the thermal shock resistance gradually increases,the hydration mass gain rate slightly increases.Reducing the calcia/silica ratio affects the coating adhesion performance of magnesia-calcia materials,mainly due to the presence of a small amount of f-CaO in the specimen when the calcia/silica ratio is high,which can react with cement clinker and thus enhance the bonding strength.In order to satisfy the magnesia dolomite material with excellent high temperature performance and obviously enhanced hydration resistance,the optimal calcia/silica ratio of 2.8 is selected.

β-SiAlON bonded corundum composite was prepared using tabular corundum particles and fines,Al₂O₃ micropowder,Si and Al powders as starting materials,phenolic resin as the binder,firing at 1 450 ℃ for 72 h in flowing N₂.Effects of thermal shock and thermal shock cycles on oxidation behavior of the composite at different temperatures (900-1 300 ℃) were investigated.The results show that:the mass gain rate of the specimens oxidized at different temperatures with thermal shock is higher than without thermal shock,and the rate increases with the thermal shock cycle increasing,indicating that thermal shock can promote the oxidation.The reason of serious oxidation under thermal shock condition is as follows:without thermal shock,a dense oxidation protective layer is formed on the surface of the specimen after β-SiAlON oxidation,preventing oxygen diffusion into the inner.However,the oxidation protective layer is broken under thermal shock condition producing more microcracks,which provides passages for oxygen to enter the inner part of the specimen,thus accelerating the oxidation.

In order to investigate the effect of the ceramic particle reinforcement phase content on SiC-Al composites fabricated by selective laser melting (SLM),SiC-Al composites were prepared by SLM with SiC (d₅₀=30 μm) as the reinforcing phase and pure Al powder (d₅₀=33 μm) as the matrix material. Effects of SiC content (10%,15% and 20%,by mass) on the phase composition,the microstructure,the density,the microhardness,the wearing properties and the modulus of rupture of the SiC-Al composites were investigated.The results show that the amounts of the intermediate phases (Si and Al₄C₃) and defects (holes and cracks) in the SiC-Al composites increase with SiC content increasing,meanwhile,the density decreases gradually.The SiC-Al composite with 15% of SiC exhibits the highest modulus of rupture of 275 MPa.The developed material with 20% of SiC has the highest microhardness and the lowest wear rate of 1.3×10^-5 mm³·N^-1·m^-1 and 191.5 HV_0.1.

In order to improve the comprehensive utilization of refractory resources,the self-made stabilized magnesia dolomite composite material,fused magnesia,Al powder,Si powder,and flake graphite were used as raw materials to study the oxidation resistance of Al/Si composite low-carbon stabilized MgO-CaO materials,and to explore the relationship among the oxidation resistance,the phase composition and the microstructure.The results show that:(1)the oxidation mechanism of materials with Al/Si powder is obviously protective oxidation;(2)after oxidizing at 1 000 and 1 500 ℃ for 3 h respectively,the specimens without Al/Si powder are completely oxidized;the oxide layer thickness of the specimens with Al/Si powder reduces,and the oxidation resistance improves;the addition of Al powder can effectively improve the oxidation resistance of the material,the optimal Al powder addition is 4 mass%;the oxide layer thickness of the specimens with only Si powder does not change significantly.Comprehensive analysis shows that the optimal ratio is 4 mass% for Al powder or Si powder;(3)Al₂O₃ and SiO₂ are generated after oxidation of Al/Si powder,which react with periclase and calcium silicate in the material to form magnesium aluminate spinel,merwinite (magnesite pyroxene),monticellite,etc.,densifying the materials and enhancing the oxidation resistance.

To determine the transformation mechanism of CAH₁₀ to C₃AH₆ and AH₃ solid-state dehydration decomposition or dissolution-precipitation,the calcium aluminate slurry was cured at 10 ℃ for 1 and 3 d to form CAH₁₀,and then the slurry was cured at 60 ℃ in water and anhydrous conditions for 3 d,respectively,then the slurry hydration was terminated by vacuum freeze drying,and finally the phase composition and microstructure of the hydration products were studied by XRD and SEM.The results show that,with water,CAH₁₀ converts to C₃AH₆ and AH₃,without water,CAH₁₀ does not convert to C₃AH₆ and AH₃.This suggests that the transformation of CAH₁₀ to C₃AH₆ and AH₃ belongs to a dissolution-precipitation mechanism.

The effects of binders on the sintering performance,mechanical properties and microstructure of SiC-CA₆ composites were investigated using commercial SiC,CA₆ fine powder and activated α-Al₂O₃ as raw materials,water soluble resin and phenolic resin as the binder,and firing at 1 400,1 500,1 600 and 1 650 ℃ for 3 h,respectively.The results show that the properties changes of the two samples are similar,but the samples bonded with water soluble resin have better comprehensive properties.Firing at temperatures below 1 600 ℃ in carbon embedded atmosphere,SiC in the samples bonded with water soluble resin oxidizes to form SiO₂,andin turn reacts with CA₆ to generate low melting point phase,thus promoting thesintering.Firing at 1 650 ℃,SiC under goes activated oxidation and the SiO₂ content in liquid decreases allowing for substantial generation of well-developed flake CA₆ in the samples.As the temperature increases,the residual flakycarbon in the samples bonded with phenolic resin transforms to amorphous carbon,slowing the oxidation of SiC and reducing the liquid phase,which hinders the sintering and affects the performance of the samples to a certain extent.

Calcium aluminate cement (CAC) bonded corundum based castables were prepared using tabular corundum and activated alumina as the starting materials,CAC as the binder,zinc hydroxide (Zn(OH)₂) and basic zinc carbonate (BZC) as the ZnO precursors.The effects of the two ZnO precursors on the phase composition and microstructure of the CAC bonded corundum based castable matrix were analyzed,and the reasons affecting the hot performance of the castables were studied.The results show that Zn(OH)₂ with a smaller particle size (d₅₀=1.26 μm) is prone to agglomerate during sample preparation and generates ZnAl₂O₄ spinel grains after firing,hindering the growth of CA₆,thus decreasing the mechanical strength of the castables.BZC with a larger particle size (d₅₀=2.91 μm),which shows a sound dispersity,in-situ generates nano-sized ZnO after firing,and ZnO or Zn²⁺ diffuses into calcium aluminates,promoting the sintering of CA₂ and CA₆,there by enhancing the hot properties of the CAC-bonded corundum based castables.

To explore the effect of the molten salt addition on their properties,calcium hexaaluminate (CA₆) porous materials were prepared using industrial CaCO₃ as the calcium source and α-Al₂O₃ as the aluminum source,adding molten salt of KCl and firing at 1 400,1 500,and 1 600 ℃ for 3 h.The results show that the KCl addition not only plays as a pore-forming agent,but also reduces the formation temperature of CA₆ and promotes the growth of CA₆ flake grains.With the firing temperature of 1 500 ℃ and the mass ratio of CaCO₃ and α-Al₂O₃ to KCl=4∶1,the prepared CA₆ porous material has the apparent porosity of 59.42%,the compressive strength of 46.15 MPa,the thermal conductivity of 1.02 W·(m·K)^-1 at 1 000 ℃,the main pore diameter distribution at 5-15 μm,the average pore size of 10 μm and the pore area ratio of 64%,showing relatively uniform distribution of internal pores and good comprehensive performance.

SiAlON bonded corundum materials were prepared using tabular corundum as the aggregatesand white fused corundum powder,Si powder,Al powder,and ultrafine alumina as the matrix,and nitridationfiring at 1 500 ℃ for 3 h.Three samples with the theoretical β-SiAlON generation amount of 10%,20% and 30%,by mass,respectively were designed,through adjusting the additions of Si and Al powders.The phase composition of the samples was analyzed by XRD.The density,the strength,the oxidation resistance,the thermal shock resistance,the slag corrosion resistance and the desulfurizer corrosion resistance of the samples were tested.The results show that:(1)the prepared materials are composed of corundum and β-SiAlON,and the β-SiAlON contentsare basically consistent with the designed ones;(2)with the increase of the β-SiAlON content,the apparent porosity of the as-prepared samples decreases,and the hot modulus of rupture,the oxidation resistance,the thermal shock resistance,the slag corrosion resistance and the desulfurizer corrosion resistance are significantly improved.

To develop alumina bubble castables with low density,high strength,easy molding and good thermal insulation,MgCO₃ micro-powder was introduced into their matrix.The alumina bubble castable samples were prepared using alumina bubbles with particle sizes of 5-3,3-1 and 1-0.2 mm,tabular corundum fine powder,alumina micro-powder and MgCO₃ micro-powder.The effects of the MgCO₃ micro-powder addition (0,1%,2%,3% and 4%,by mass) on the microstructure and the properties of the samples were studied.The results show that:(1)after firing at 1 500 ℃ for 3 h,the tabular crystal morphology of calcium hexaaluminate (CA₆) in the matrix is changed,a microcrystalline structure of smaller granular magnesium aluminate spinel (MA) coexisting with CA₆ microcrystalliteis formed,and the formed MA-CA₆ micro crystallite complex is uniformly distributed in the matrix pores;(2)after firing at 110 ℃ for 24 h,the bulk density of the castables decreases from 1.83 g·cm^-3 to 1.58 g·cm^-3,and the cold modulus of ruptureis over 5 MPa;after firing at 1 500 ℃ for 3 h,the sample slightly expands(0-0.5% of the permanent linear change),showing excellent volume stability;and the thermal conductivity at 400 ℃ decreases by nearly 30%.