Magnesia-carbon refractories were prepared using fused magnesia,flake graphite and metal aluminum powder as starting materials,phenolic resin as the binder,heat-treating at 1 300-1 600 ℃ in a nitrogen atmosphere.The phase reconstruction and the microstructure evolution of the obtained magnesia-carbon refractories were analyzed.The formation mechanisms of magnesia crystals with different morphologies by chemical vapor deposition were revealed.The results show that at 1 300-1 500 ℃,the non-oxides within the samples are aluminum carbide (Al₄C₃),aluminum nitride (AlN) and magnesium aluminum nitride (Mg₃Al_nN_n+2,n=2 or 3);at 1 600 ℃,the diffraction characteristic peak intensity of Al₄C₃ and AlN decreases sharply,and sharp diffraction characteristic peaks of nitrogen aluminum carbide (Al₇C₃N₃) appear.Mg(g) is produced by the aluminothermic reduction and carbothermal reduction of magnesia.On the surface of the samples,Mg(g) reacts with oxygen to form MgO whiskers.Inside the samples,Mg(g) and O₂(g) undergo a CVD chemical deposition reaction to form cubic MgO crystals.There is a phase relationship between flake AlN and flake Mg₃Al_nN_n+2,and they are so associated with each other that the morphology is difficult to distinguish.

Viscose fiber templates (15 cm×15 cm×1 cm) were put into ZrOCl₂ solutions of different concentrations (1,2 and 3 mol·L^-1) and impregnated at 20,40 and 60 ℃ for 20 h,respectively.After washing,centrifugation and drying,ZrO₂ fiber precursors were obtained.ZrO₂ fibers were prepared by heat treatment of the precursors at 600,800,1 000 and 1 200 ℃ for 2 h.The effects of the impregnation temperature,the impregnation solution concentrations and the heat treatment temperature on the microstructure and the phase composition of the ZrO₂ fibers were studied.The results show that with the increase of the impregnation temperature from 20 ℃ to 60 ℃ and the impregnation solution concentration increases from 1 mol·L^-1 to 3 mol·L^-1,the microstructure of fiber cross section changes from flat to cylindrical,and the average fiber diameter increases,indicating that the increase of the impregnation solution concentration and the impregnation temperature is beneficial to increasing the adsorption capacity of Zr⁴⁺ on viscose fiber templates.After heat treatment,ZrO₂ fiber mainly exists in monoclinic ZrO₂ phase.With the increase of the heat treatment temperature,the grains in ZrO₂ fibers become larger and the crystallinity degree increases,meanwhile the fiber surface undergoes a transition from smooth to small grains and then to cracks.

In order to improve the anti-explosion performance of ρ-Al₂O₃ bonded corundum castables,H₂O₂ was added (0,0.025%,0.050%,0.075%,0.100% and 0.125%,by mass) as the explosion-proof agent.After mixing and casting,specimens were prepared.Some specimens were cured at room temperature for 12 h and demoulded for the anti-explosion performance test at different temperatures (450,500,550,600,650,700,750 and 800 ℃);the other specimens were cured,dried and fired,and tested in terms of the density,the cold mechanical properties,the air permeability and the pore size distribution.The results show that:(1)with the increase of the H₂O₂ addition,the anti-explosion performance of castables increases gradually,the average pore diameter increases gradually,and the density and the strength decrease gradually;(2)by comprehensive consideration,the appropriate addition of H₂O₂ shall be within 0.075%.

Ceramic slurry of 78 mass% solid loading was prepared using photosensitive acrylic resin and dispersant SP-710 as the liquid phase,Al₂O₃ powder (d₅₀=2.38 μm) and TiO₂ powder additive as the solid phase.Alumina ceramics were prepared by DLP,sintering for 4 h at 1 450,1 500,1 550 or 1 600 ℃,respectively.The effects of the TiO₂ addition (0,1%,2%,3% and 5%,by mass) on the properties of the ceramics were studied.The results show that the addition of TiO₂ can improve the sintering of Al₂O₃ ceramics,significantly improve the densification,and reduce the sintering temperature.With the optimum TiO₂ addition of 3 mass% and the optimum sintering temperature of 1 600 ℃,the obtained Al₂O₃ ceramics have shrinkage of 15.7%,15.8% and 23.8% at the x axis,the y axis,and the z axis,respectively,the porosity of 2.41%,the bulk density of 3.74 g·cm^-3 and the three-point bending strength of 251.1 MPa.Compared with the undoped alumina ceramics,the doped alumina ceramic has increased bulk density by 0.56 g·cm^-3,decreased apparent porosity from 20.19% to 2.41%,and the three-point bending strength increases by 2.5 times.Therefore,the density and strength of DLP prepared ceramics can be improved effectively by adding an appropriate addition of TiO₂,and the performance of the DLP prepared ceramics is close to that of the pressed samples.Thus,it is hopeful to apply DLP in refractories field.

Magnesium aluminate spinel hollow sphere heat insulation refractories were prepared by the foaming method using magnesium aluminate spinel hollow spheres (0.6-0.9 and 0.5-0.6 mm) and alumina micropowder (d₅₀=2.38 μm) as main starting materials,alumina sol as the binder,sodium lauryl sulfate as the foaming agent,sodium carboxymethyl cellulose and lauryl alcohol as the foam stabilizer.The effects of the particle size distribution of magnesium aluminate spinel hollow spheres and the alumina sol addition on the bulk density,the strength,the linear change after heating,the linear change on reheating,the thermal conductivity,the phase composition and the microstructure of the specimens were mainly studied.The results show that:(1)with the increasing addition of the 0.5-0.6 mm hollow spheres,the apparent porosity and the linear shrinkage after heating of the specimens gradually decrease,the bulk density,the linear change on reheating,the cold crushing strength and the thermal conductivity gradually increase;(2)when the 0.6-0.9 mm hollow spheres addition is 0,the 0.5-0.6 mm hollow spheres addition is 60 mass% and alumina sol addition is 13.972 7 g per 100 g of the main starting materials,the bulk density of the specimen is 1.13 g·cm^-3,the cold crushing strength is 19.3 MPa,and the linear change on reheating (1 600 ℃×3 h) is 0.22%,the thermal conductivity at 1 200 ℃ is 0.517 W·m^-1·K^-1;(3) with the increase of the alumina sol addition,the apparent porosity and the linear shrinkage after heating of the specimens gradually increase,and the bulk density,the linear change on reheating and the cold crushing strength gradually decrease;(4)when the 0.5-0.6 mm hollow spheres addition is 60 mass% and the alumina sol addition is 16.188 7 g per 100 g of the main starting materials,the apparent porosity is 69.7%,the cold crushing strength is 7.1 MPa,and the linear change on reheating (1 600 ℃×3 h) is 0.05%.

Lanthanum aluminate coating materials were prepared using Ca²⁺-Fe³⁺ doped lanthanum aluminate as the radiation powder matrix,aluminum dihydrogen phosphate,sodium silicate,silica sol and alumina sol as binders.The developed coating materials were spread on the surface of corundum bubble bricks,and the influences of different binders on the phase composition,the microstructure and the performance of the coating materials were explored.The results show that the coating material using alumina sol contains less impurities,which is the best binder choice.The Ca²⁺-Fe³⁺ doped lanthanum aluminate radiation agent with alumina sol as the binder performs excellent spalling resistance on the surface of the corundum bubble bricks.

CA₆ porous ceramics were synthesized by gel-casting using α-Al₂O₃ micropowder and CaCO₃ (analytical pure) as main raw materials,deionized water as the solvent,acrylamide as the monomer and N,N'-methylene bisacrylamide as the crosslinking agent.Effects of the (NaPO₃)₆ addition (0,0.2%,0.4%,0.6%,0.8%,and 1% of the powder mass,by mass),the pH value (7,8,9,10,11,12,and 13) and the solid loading (40%,42%,44%,46%,and 48%,by volume) on the rheological properties of the α-Al₂O₃-CaCO₃ composite slurries and the properties of CA₆ porous ceramics were studied for the best preparation process of CA₆ porous ceramics.The results show that with the increase of the (NaPO₃)₆ addition and the pH value of the α-Al₂O₃-CaCO₃ composite slurries,the viscosity firstly decreases and then increases;with the increase of the solid loading in the slurries,the viscosity increases gradually,the apparent porosity of CA₆ porous ceramics decreases,but the bulk density increases.The optimal conditions are the (NaPO₃)₆ addition of 0.4%,pH value of 11,and solid loading of 46%.The CA₆ ceramics prepared under these conditions have high mechanical strength and uniform microstructure.

To realize the effective utilization of ferrotitanium slag,TiCN containing composite material was synthesized by carbothermal reduction nitridation with ferrotitanium slag,coke,and SiO₂ as raw materials,and the effects of technological conditions on the reaction products were studied.The optimal synthesis condition of TiCN is 1 400 ℃ insulation for 4 h with flowing nitrogen,and the increase of the coke addition can promote the generation of TiCN.The non-isothermal kinetics of the reaction of TiCN prepared from ferrotitanium slag were studied by the methods of Kissinger,Ozawa,and Coats-Redfern.The most probable mechanism function of the reaction is G(α)=[-ln(1-α)]³,the reaction mechanism is random nucleation and subsequent growth,the reaction grade n is 3,the reaction activation energy E is 115.34 kJ·mol^-1,and the pre-exponential factor A is 6.76×10⁴⁷ min^-1.

The Al₂O₃-C materials with Mg powder addition were prepared using tabular corundum,α-Al₂O₃ micropowder,flake graphite and Mg powder as the starting materials,and phenolic resin as the binder.Effects of Mg powder on properties of unfired Al₂O₃-C materials carbon embedded treated at different temperatures (600-1 400 ℃) were investigated.The results show that metal Mg reacts with O₂,CO or CO₂ to form MgO ceramic phases at 600 ℃,avoiding the oxidation of phenolic resin and the in-situ formed MgO ceramic phases form a tight binding to enhance the medium and low temperature strength of unburned Al₂O₃-C materials;at 1 000-1 400 ℃,MgO reacts with Al₂O₃ to form MgAl₂O₄,and the amount and the crystal size of MgAl₂O₄ increase with the temperature rising,strengthening the material;however,the strength of the specimen greatly decreases after firing at 1 400 ℃ due to the micro-cracks resulting from the expansion caused by MgAl₂O₄ formation.

Effects of sintering aids and temperature (1 750 ℃,1 800 ℃,and 1 850 ℃) on densification,the mechanical properties and the microstructure of gas-pressure sintered Si₃N₄ ceramics were explored using Y₂O₃/Al₂O₃,Al₂O₃/MgO and Y₂O₃/Al₂O₃/MgO as composite sintering aids.The results show that the modulus of rupture,the hardness and the fracture toughness of the specimens prepared using Y₂O₃/Al₂O₃ as the sintering aid are better than those of the specimens using the other two aids,and the Y₂O₃/Al₂O₃ aid favors the formation of β-Si₃N₄ grains with high aspect ratio in the microstructures;when the sintering temperature is 1 800 ℃,the density and the mechanical properties of the specimens with Y₂O₃/Al₂O₃ as sintering aid are the best,the bulk density is 3.24 g·cm^-3,and the linear shrinkage rate is 20.73%,with the highest strength,hardness,fracture toughness of 821.9 MPa,14.25 GPa and 7.16 MPa·m^1/2,respectively.

Fine powder silicon carbide ceramics were prepared by reaction sintering using SiC powders(d₅₀=3.6 μm,SiC≥98 mass%) as the main raw material,added with carbon black,graphite,water reducing agent and dispersing medium,well mixed,slip cast,dried at 80 ℃ and reaction sintered at 1 720 ℃.Effects of the stirring time (1-5 h) and the carbon black addition (5.62%-6.93%,by mass) on properties of green bodies were researched,and the microstructure of the green bodies and the fired specimens was researched.The results show that the physical properties of the product added with graphite are improved obviously,the optimal addition of carbon black is 5.94%,the maximum bulk density of the sintered specimen is 3.02 g·cm^-3,and the bending strength can reach 580 MPa.

In view of the thermal protection requirements of the return-to-Earth process of the inflatable reentry deceleration system,on the basis of ceramic fiber cloth and high strength textile,the multilayer flexible thermal protection material was designed and developed using alumina fiber blanket,alumina composite silica fiber blanket,silica fiber blanket composite aerogel composite glass fiber.The performance of the material was verified by the thermal conductivity test,the static thermal shock test and the dynamic high enthalpy wind tunnel test.The results show that the developed multilayer flexible thermal protection material is intact in the dynamic high enthalpy wind tunnel test and has good heat insulation capacity,ensuring that the temperature of the internal bearing layer is within the allowable range.The insulation layer does not change significantly after the test and is still soft and folding.

Two silicon nitride bonded silicon carbide refractories with high silicon nitride content were prepared using high purity silicon carbide and silicon (the silicon addition of samples S1 and S2 is 25 mass% and 35 mass%,respectively) as raw materials,resin as the binder,and firing at 1 400 ℃ for 5 h in a nitrogen atmosphere.For comparison with commercial silicon nitride bonded silicon carbide sample S0 (added with 15 mass% of silicon),the phase composition,the modulus of rupture,the gas permeability,the abrasion resistance and the microstructure of the three samples were studied.The results show that samples S0,S1 and S2 all have excellent modulus of rupture and abrasion resistance.The sharpness of S0 is the strongest,followed by samples S1 and S2.Three samples have the same sequence in terms of the abrasion to the workpiece.Therefore,sample S2 is the most beneficial to the long term service of the workpiece.

To study the properties of sintered magnesia prepared from Xinjiang Jianshan magnesite,the sintered magnesia was prepared using the raw ore block,the raw ore powder and the concentrate after crushing and flotation purification respectively as raw materials and firing at 1 750 ℃ for 6 h by one-step calcination process.The physical properties and chemical composition of the sintered magnesia were tested,and its phase composition and microstructure were analyzed.The results show that:(1)the sintered magnesia directly calcined with raw ore block has 88.66% MgO,2.88% CaO and 5.13% SiO₂,and the sintered magnesia prepared from raw ore powder has 89.15% MgO,2.32% CaO,and 4.22% SiO₂,by mass,respectively,neither of which meets the requirements of grade MS88 sintered magnesia in GB/T 2273—2007;(2)the sintered magnesia prepared from concentrate has 94.18% MgO,1.43% CaO,1.21% SiO₂ and the bulk density of 3.25 g·cm^-3,which meets the requirements of grade MS94 sintered magnesia in GB/T 2273—2007.

To obtain Cr₂O₃ powder for additive manufacturing with good dispersion and uniform particle size,Cr₂O₃ powder was ground by a planetary ball mill.The influence of ball to powder mass ratio (1∶1.5,1∶1.3,1∶1.1,1.1∶1,1.3∶1 and 1.5∶1) and the different balls mass ratio (6 and 10 mm in diameter,1∶2,1∶1,2∶1,3∶1,4∶1 and 5∶1) on the grinding effect were studied.The results show that when the ball to powder mass ratio is 1.3∶1,the Cr₂O₃ powder has the particle size of d₁₀=0.694 μm,d₅₀=2.042 μm,and d₉₀=4.569 μm,which is the smallest;and when the different balls mass ratio is 5∶1,the Cr₂O₃ powder has the particle size of d₁₀=0.550 μm,d₅₀=1.843 μm,and d₉₀=4.516 μm,which is the optimal.

In order to reduce their bulk density and thermal conductivity,three kinds of high alumina castables were prepared with lightweight microporous mullite,porous high alumina clinker and alumina bubbles as aggregates,respectively,and their properties after drying and heat treatment at 1 250 ℃ were studied.The results show that:(1)the drying strength of the castables mainly depends on the strength of the lightweight aggregates used,and the strength after heat treatment at 1 250 ℃ is also related to the sintering degree of the castables;the thermal conductivity is mainly affected by the density of aggregates as well as the size and distribution of pores;(2)the castable prepared with the lightweight microporous mullite as the aggregates has higher cold strength and hot modulus of rupture,and lower thermal conductivity.

To improve the service life of wear-resistant bricks for the cooling zone of dry quenching coke ovens,a newly wear-resistant brick was developed by adjusting the aggregates particle size distribution and adding SiC powder and andalusite micropowder on the basis of grade B mullie brick.Its practical application in a 140 t·h^-1 dry quenching coke oven was introduced.The results show that the newly wear-resistant brick has the compressive strength of 160 MPa and the wear amount of only 1.92 cm³,which is better than the original grade B mullite brick.After 7 years of service in the cooling zone of a 140 t·h^-1 dry quenching coke oven,the lining still shows smooth surface with slight wear and is expected to serve for more than 10 years.

BN porous ceramics have great application potential in fields such as adsorption,heat insulation,environmental repairing,and electronic packaging owing to their high porosity,high specific surface area,low thermal conductivity,and excellent chemical stability.The recent progress on the preparation of BN porous ceramics was briefly summarized.The structure and performance of BN porous ceramics prepared by template and non-template methods as well as the advantages and disadvantages of these methods were sketched.The challenges and future development direction on the preparation and application of BN porous ceramics were proposed.

The rapid development of microelectronics technology puts forward higher and higher requirements for the performance of chip substrates and packaging materials.AlN ceramics are used as chip substrates and packaging materials due to their high thermal conductivity,high strength,linear expansion coefficient close to silicon,low dielectric constant,and excellent high temperature resistance and corrosion resistance.The research progress of AlN ceramics in term of the influence of sintering technologies and sintering aids on their properties was reviewed.The problems during the preparation and application of AlN ceramics were pointed out,and the development trend was prospected.