β-Sialon has emerged as a promising material for enhancing the service life of Al2O3-C refractories due to its excellent physicochemical properties.The impact of varying concentrations of nanometer Al/Si alloy ...β-Sialon has emerged as a promising material for enhancing the service life of Al2O3-C refractories due to its excellent physicochemical properties.The impact of varying concentrations of nanometer Al/Si alloy on the in-situ synthesis of β-Sialon within Al2O3-C refractory materials,as well as its oxidation behavior,was investigated.The findings indicate that the presence of Al/Si alloy promotes the formation of AlN and SiC whiskers at 1300℃,which subsequently facilitate the production of plate-like β-Sialon at 1500℃.Density functional theory analysis reveals that the(020)crystal plane of β-Sialon exhibits the lowest adsorption energy for Al2O and AlO molecules under the influence of iron atoms,suggesting a solid-liquid-vapor growth mechanism for β-Sialon formation.The introduction of these ceramic phases significantly enhances the mechanical properties of Al2O3-C refractories.Specifically,the addition of 6 wt.%Al/Si alloy yielded specimens with the highest cold modulus of rupture and cold crushing strength at 1500℃,achieving values of 35.2 and 127.5 MPa,respectively--representing increases of 40.1%and 37.4%.Furthermore,during high-temperature oxidation,the formation of plate-like β-Sialon leads to the development of a dense protective layer on the surface.This impedes the diffusion pathways of oxygen and consequently enhances the oxidation resistance of the refractory.展开更多
Composite powders of nanocrystalline WC-10Co (15wt%),Y2O3 (8mol%) stabilized nanocrystalline ZrO2 (30wt%),industrial cobalt powder (4.5wt%) and submicron Al2O3 (55wt%) composite powders were fabricated by hi...Composite powders of nanocrystalline WC-10Co (15wt%),Y2O3 (8mol%) stabilized nanocrystalline ZrO2 (30wt%),industrial cobalt powder (4.5wt%) and submicron Al2O3 (55wt%) composite powders were fabricated by high-energy ball-milling process.The nanocomposite powders were consolidated by microwave sintering process at temperature ranged 1300℃-1550℃ for 15min,respectively.The optimum consolidation conditions,such as temperature,were researched during microwave sintering process.Vickers Hardness of the consolidated cermets was measured by using a Vickers indentation test,and density of specimens was also determined by Archimedes' principle.Microwave sintering process could not only increase the density of Al2O3-ZrO2-WC-Co cermets and reduce the porosity,but also inhibit abnormal grain growth.展开更多
Effects of particle size (A:d50 = 336. 9 μm, B:d50 =123.5μm, C: d50=19.5 μm, D: dso=2.21μm) and content (1 wt% , 3 wt% , 5 wt% , 7 wt% ) of silicon powder on cold crushing strength (CCS) , pore size dist...Effects of particle size (A:d50 = 336. 9 μm, B:d50 =123.5μm, C: d50=19.5 μm, D: dso=2.21μm) and content (1 wt% , 3 wt% , 5 wt% , 7 wt% ) of silicon powder on cold crushing strength (CCS) , pore size distribution and microstructure of Al2O3 - ZrO2 - C refractories coked at high temperature had been investigated by means of mercury porosimeter, SEM, EDS, tic. The results indicated that particle size and content of silicon powder affected the cold crushing strength of coked specimens. It increased with the addition of silicon powder and its finer particle size. However, it decreased greatly when using too fine silicon powder. The particle size and content of silicon powder also impacted the phase evolution and microstructure of coked specimens, much more β-SiC whiskers constituted network structure and well distributed in specimens with reduction of their slenderness ratios when finer silicon powder was added, corresponding to that, the specimens' pore size distribution range became narrower with smaller pore diameter, but β-SiC whiskers were distributed sparsely and the specific pore volume of small pores increased when much finer powder was added. It was worthly mentioned that some nitride could form in specimens with addition of appropriate particle size and content of silicon powder.展开更多
The aim of the present research is to provide a technique for preparing open-cell Al2O3-ZrO2 ceramic foams with uniform cell size.This technique used plant seeds to array templates and centrifugal slip casting to obta...The aim of the present research is to provide a technique for preparing open-cell Al2O3-ZrO2 ceramic foams with uniform cell size.This technique used plant seeds to array templates and centrifugal slip casting to obtain cell struts with high packing density.Aqueous Al2O3-ZrO2 slurries with up to 50 vol.% solid contents were prepared and the rheological characteristic of the slurries was investigated.Consolidation was performed at an acceleration of 2,860 g for 60 min.The effect of the characteristic of plant seeds on the drying behavior of Al2O3-ZrO2 green compact was analyzed.The effects of the solid contents of slurries on segregation phenomena of Al2O3 and ZrO2 particles and green compact uniformity were investigated.The compressive stress-strain curve and deformation behavior of Al2O3-ZrO2 ceramic foams prepared using plant seed template were analyzed.The results showed segregation phenomenon is negligible for highly stable slurry with 50 vol.% solid loading.The prepared cell struts of Al2O3-ZrO2 foams have high green density (61.9% TD), sintered density (99.1% TD) and homogeneous microstructure.When sintered at 1,550 ℃ for 2 h, the cell size of Al2O3-ZrO2 foam is approximately uniform and the diameter is about 1.1 mm.The porosity and compressive strength of sintered products is 66.2% and 5.86 MPa, respectively.展开更多
基金supported by the Natural Science Foundation of Henan Province(No.232300420329)Key Scientific Research Project of Colleges and Universities in Henan Province(Nos.23B430012,22A430028,and 25B430022)+2 种基金Henan Provincial Science and Technology Research Project(No.242102231064)National Natural Science Foundation of China(No.52202064)Luoyang Major Science and Technology Innovation Project(No.2301009A).
摘要β-Sialon has emerged as a promising material for enhancing the service life of Al2O3-C refractories due to its excellent physicochemical properties.The impact of varying concentrations of nanometer Al/Si alloy on the in-situ synthesis of β-Sialon within Al2O3-C refractory materials,as well as its oxidation behavior,was investigated.The findings indicate that the presence of Al/Si alloy promotes the formation of AlN and SiC whiskers at 1300℃,which subsequently facilitate the production of plate-like β-Sialon at 1500℃.Density functional theory analysis reveals that the(020)crystal plane of β-Sialon exhibits the lowest adsorption energy for Al2O and AlO molecules under the influence of iron atoms,suggesting a solid-liquid-vapor growth mechanism for β-Sialon formation.The introduction of these ceramic phases significantly enhances the mechanical properties of Al2O3-C refractories.Specifically,the addition of 6 wt.%Al/Si alloy yielded specimens with the highest cold modulus of rupture and cold crushing strength at 1500℃,achieving values of 35.2 and 127.5 MPa,respectively--representing increases of 40.1%and 37.4%.Furthermore,during high-temperature oxidation,the formation of plate-like β-Sialon leads to the development of a dense protective layer on the surface.This impedes the diffusion pathways of oxygen and consequently enhances the oxidation resistance of the refractory.
基金Funded by the Youth Science Plan for Light of the Morning Sun of Wuhan City (200750731270)
摘要Composite powders of nanocrystalline WC-10Co (15wt%),Y2O3 (8mol%) stabilized nanocrystalline ZrO2 (30wt%),industrial cobalt powder (4.5wt%) and submicron Al2O3 (55wt%) composite powders were fabricated by high-energy ball-milling process.The nanocomposite powders were consolidated by microwave sintering process at temperature ranged 1300℃-1550℃ for 15min,respectively.The optimum consolidation conditions,such as temperature,were researched during microwave sintering process.Vickers Hardness of the consolidated cermets was measured by using a Vickers indentation test,and density of specimens was also determined by Archimedes' principle.Microwave sintering process could not only increase the density of Al2O3-ZrO2-WC-Co cermets and reduce the porosity,but also inhibit abnormal grain growth.
摘要Effects of particle size (A:d50 = 336. 9 μm, B:d50 =123.5μm, C: d50=19.5 μm, D: dso=2.21μm) and content (1 wt% , 3 wt% , 5 wt% , 7 wt% ) of silicon powder on cold crushing strength (CCS) , pore size distribution and microstructure of Al2O3 - ZrO2 - C refractories coked at high temperature had been investigated by means of mercury porosimeter, SEM, EDS, tic. The results indicated that particle size and content of silicon powder affected the cold crushing strength of coked specimens. It increased with the addition of silicon powder and its finer particle size. However, it decreased greatly when using too fine silicon powder. The particle size and content of silicon powder also impacted the phase evolution and microstructure of coked specimens, much more β-SiC whiskers constituted network structure and well distributed in specimens with reduction of their slenderness ratios when finer silicon powder was added, corresponding to that, the specimens' pore size distribution range became narrower with smaller pore diameter, but β-SiC whiskers were distributed sparsely and the specific pore volume of small pores increased when much finer powder was added. It was worthly mentioned that some nitride could form in specimens with addition of appropriate particle size and content of silicon powder.
基金supported by the National Natural Science Foundation of China (50672014)Innovation Research Team Program of the Ministry of Education (IRT0713)
摘要The aim of the present research is to provide a technique for preparing open-cell Al2O3-ZrO2 ceramic foams with uniform cell size.This technique used plant seeds to array templates and centrifugal slip casting to obtain cell struts with high packing density.Aqueous Al2O3-ZrO2 slurries with up to 50 vol.% solid contents were prepared and the rheological characteristic of the slurries was investigated.Consolidation was performed at an acceleration of 2,860 g for 60 min.The effect of the characteristic of plant seeds on the drying behavior of Al2O3-ZrO2 green compact was analyzed.The effects of the solid contents of slurries on segregation phenomena of Al2O3 and ZrO2 particles and green compact uniformity were investigated.The compressive stress-strain curve and deformation behavior of Al2O3-ZrO2 ceramic foams prepared using plant seed template were analyzed.The results showed segregation phenomenon is negligible for highly stable slurry with 50 vol.% solid loading.The prepared cell struts of Al2O3-ZrO2 foams have high green density (61.9% TD), sintered density (99.1% TD) and homogeneous microstructure.When sintered at 1,550 ℃ for 2 h, the cell size of Al2O3-ZrO2 foam is approximately uniform and the diameter is about 1.1 mm.The porosity and compressive strength of sintered products is 66.2% and 5.86 MPa, respectively.