An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories.The effects of calcia-stabilized zirconia on the microst...An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories.The effects of calcia-stabilized zirconia on the microstructure evolution and properties of magnesia–spinel refractories were characterized by the high-temperature elastic modulus,thermal shock damage resistance parameters,retainment of elastic modulus after thermal shock,and scanning electron microscopy.The results indicated that the incorporation of calcia-stabilized zirconia improved the thermomechanical properties and thermal shock behavior of magnesia–spinel specimens.The hot modulus of rupture of magnesia–spinel specimens increased by 2.5-fold due to the incorporation of calcia-stabilized zirconia micro-powder.The presence of a martensitic phase transformation in partially unstable ZrO2 and thermal mismatches among various phases contributed to a controlled formation of microcracks.And the pinning effect caused by the calcia-stabilized zirconia particles surrounding the grain boundaries played a crucial role in preventing the propagation of microcracks.This phenomenon significantly bolstered the thermal shock stability of magnesia–spinel refractories,consequently prolonging their service life.展开更多
Si_(3)N_(4)–TiN–SiC composites were prepared by partial substitution of the Ti–Si–Fe alloy extracted from high-titanium blast furnace slag for Si under nitrogen atmosphere.The nitridation,microstructure and mechan...Si_(3)N_(4)–TiN–SiC composites were prepared by partial substitution of the Ti–Si–Fe alloy extracted from high-titanium blast furnace slag for Si under nitrogen atmosphere.The nitridation,microstructure and mechanical properties of the composites were investigated in detail.The results show that Ti–Si–Fe alloy facilitated the nitridation of Si and full nitridation of Si was achieved in the compacts with 3.6–5.4 wt.%Ti–Si–Fe alloy additive,and thus,densification and mechanical performances of the composites were improved obviously.Propagating of microcracks induced by the volume expansions accompanying with the conversion of Ti_(5)Si_(3)and TiSi_(2)to nitrides at 950–1050℃built new N_(2)(g)transport channels in the compacts.In the following up nitridation process,adequate N_(2)(g)was transported through these channels into the compacts to fundamentally enhance contact of N_(2)with Si,facilitate and ensure the complete nitridation of internal Si.Moreover,the Ti–Si–Fe–Mn–N eutectic liquid played an important role in the formation of bothα-andβ-Si_(3)N_(4),and the Fe in the Ti–Si–Fe alloy was of great importance for the formation of fibrous Si_(3)N_(4)by the reaction between SiO(g)and N_(2)(g).展开更多
High temperature industries are a critical focus for energy conservation and carbon reduction.As fundamental materials for these industries,refractories urgently require the development of high-performance,low thermal...High temperature industries are a critical focus for energy conservation and carbon reduction.As fundamental materials for these industries,refractories urgently require the development of high-performance,low thermal conductivity,and long service life materials to support green and low carbon development.To achieve refractories with both low thermal conductivity and excellent service performance,porous anorthite-spinel refractories were developed via in-situ decomposition pore-forming technology.The effects of spinel on microstructure evolution,strength,and thermal conductivity were investigated,supplemented by thermodynamic calculations.The results indicated that the porous anorthite-spinel refractory primarily consisted of anorthite and spinel,with minor corundum.Small-sized spinel particles were uniformly dispersed in the matrix,while the spinel reaction layers forming on the surfaces of large-sized crushed powder particles,wrapping around the remaining unreacted particles.The improvement of the degree of direct bonding between anorthite and spinel in the matrix and the small amount of diffusely distributed in situ spinel forced the deflection of the crack extension paths,which was conducive to the enhancement of the compressive strength of porous anorthite-spinel refractory.The optimized composition had 20 wt.%spinel and its apparent porosity and cold compressive strength were 43.6%and 37.8 MPa.Compared to porous anorthite refractories,the porous anorthite-spinel refractories exhibited a 21%reduction in thermal conductivity(500℃),and a 12%improvement in cold compressive strength.Valuable insights for the resource utilization of corundum dust and the design of energy efficient refractory insulation layers in high temperature industries are provided by this study.展开更多
基金supported by the Key Project of the National Natural Science Foundation of China(Grant No.U21A2058)the Hebei Guoliang New Materials Co.,Ltd.(Grant No.22150239J).
文摘An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories.The effects of calcia-stabilized zirconia on the microstructure evolution and properties of magnesia–spinel refractories were characterized by the high-temperature elastic modulus,thermal shock damage resistance parameters,retainment of elastic modulus after thermal shock,and scanning electron microscopy.The results indicated that the incorporation of calcia-stabilized zirconia improved the thermomechanical properties and thermal shock behavior of magnesia–spinel specimens.The hot modulus of rupture of magnesia–spinel specimens increased by 2.5-fold due to the incorporation of calcia-stabilized zirconia micro-powder.The presence of a martensitic phase transformation in partially unstable ZrO2 and thermal mismatches among various phases contributed to a controlled formation of microcracks.And the pinning effect caused by the calcia-stabilized zirconia particles surrounding the grain boundaries played a crucial role in preventing the propagation of microcracks.This phenomenon significantly bolstered the thermal shock stability of magnesia–spinel refractories,consequently prolonging their service life.
基金This work was supported by the Open Foundation of the State Key Laboratory of Refractories and Metallurgy(Grant No.2018QN11)National Science and Technology Pillar Program during the Twelfth Five-Year Plan(Grant No.2011BAB05B05).
文摘Si_(3)N_(4)–TiN–SiC composites were prepared by partial substitution of the Ti–Si–Fe alloy extracted from high-titanium blast furnace slag for Si under nitrogen atmosphere.The nitridation,microstructure and mechanical properties of the composites were investigated in detail.The results show that Ti–Si–Fe alloy facilitated the nitridation of Si and full nitridation of Si was achieved in the compacts with 3.6–5.4 wt.%Ti–Si–Fe alloy additive,and thus,densification and mechanical performances of the composites were improved obviously.Propagating of microcracks induced by the volume expansions accompanying with the conversion of Ti_(5)Si_(3)and TiSi_(2)to nitrides at 950–1050℃built new N_(2)(g)transport channels in the compacts.In the following up nitridation process,adequate N_(2)(g)was transported through these channels into the compacts to fundamentally enhance contact of N_(2)with Si,facilitate and ensure the complete nitridation of internal Si.Moreover,the Ti–Si–Fe–Mn–N eutectic liquid played an important role in the formation of bothα-andβ-Si_(3)N_(4),and the Fe in the Ti–Si–Fe alloy was of great importance for the formation of fibrous Si_(3)N_(4)by the reaction between SiO(g)and N_(2)(g).
基金financially supported by the Key Projects of the National Natural Science Foundation of China(Grant No.U21A2058)Research Project of Hubei Provincial Department of Science and Technology(Grant No.2024CSA075)the Chiping Haoxin Industry Co.,Ltd.,Shandong,China.
文摘High temperature industries are a critical focus for energy conservation and carbon reduction.As fundamental materials for these industries,refractories urgently require the development of high-performance,low thermal conductivity,and long service life materials to support green and low carbon development.To achieve refractories with both low thermal conductivity and excellent service performance,porous anorthite-spinel refractories were developed via in-situ decomposition pore-forming technology.The effects of spinel on microstructure evolution,strength,and thermal conductivity were investigated,supplemented by thermodynamic calculations.The results indicated that the porous anorthite-spinel refractory primarily consisted of anorthite and spinel,with minor corundum.Small-sized spinel particles were uniformly dispersed in the matrix,while the spinel reaction layers forming on the surfaces of large-sized crushed powder particles,wrapping around the remaining unreacted particles.The improvement of the degree of direct bonding between anorthite and spinel in the matrix and the small amount of diffusely distributed in situ spinel forced the deflection of the crack extension paths,which was conducive to the enhancement of the compressive strength of porous anorthite-spinel refractory.The optimized composition had 20 wt.%spinel and its apparent porosity and cold compressive strength were 43.6%and 37.8 MPa.Compared to porous anorthite refractories,the porous anorthite-spinel refractories exhibited a 21%reduction in thermal conductivity(500℃),and a 12%improvement in cold compressive strength.Valuable insights for the resource utilization of corundum dust and the design of energy efficient refractory insulation layers in high temperature industries are provided by this study.
