Oxidation of carbon is the main problem or Al2O3 - C refractories. ZrO2 - nitrides composite powder was synthesized through carbothermal reduction and nitridation （CRN） of zircon. The effect of ZrO2 - nitrides compo...Oxidation of carbon is the main problem or Al2O3 - C refractories. ZrO2 - nitrides composite powder was synthesized through carbothermal reduction and nitridation （CRN） of zircon. The effect of ZrO2 - nitrides composite powder addition on oxidation resistance of the Al2O3 - C refractories was investigated by measuring the thickness of oxidation layer. Phase compositions of the Al2O3 - C refractories before and after oxidation were investigated by X-ray diffraction （ XRD ）. Results show that the oxidation resistance of the Al2O3 - C refractories can be obviously improved by adding the synthesized ZrO2 - nitrides composite powder. The formation of mullite and zircon in the oxidation layer results in the densification of oxidation layer, which prevents oxygen diffusion and bnproves the oxidation resistance of the Al2O3 - C refractories.展开更多
In order to improve oxidation resistance and ther- mal shock resistance of Al2O3-C refractories, two groups of specimens were prepared with phenolic resin as binder, adding 0, 2 wt% , 4 wt% and 6 wt% commercial SiC or...In order to improve oxidation resistance and ther- mal shock resistance of Al2O3-C refractories, two groups of specimens were prepared with phenolic resin as binder, adding 0, 2 wt% , 4 wt% and 6 wt% commercial SiC or ZrO2-SiC composite powder synthesized from zircon respectively to Al2O3- C refractories, pressing at 200 MPa, drying fully at 250℃, and then carbon embedded firing at 1400℃ for 2 h. Oxidation resistance and thermal shock resistance were researched, phase composition was analyzed by XRD. The results showed that the oxidation of SiC in additives could protect carbon in specimens effectively and thus decreased the mass loss ratio and oxidation area, and improved the oxidation resistance of the specimen. Thermal shock resistance was improved owing to the micro crack toughening of ZrO2 and grain toughening of SiC. In this experiment, the specimens with 6 wt% ZrO2 -SiC composite powder or 6 wt% SiC powder had the best oxidation resistance and thermal shock resistance.展开更多
ZrO2 sizing nozzles with a basic Jormulation were prepared using 45% （by mass, the same hereinafter ） （ Mg, Y） - PSZ aggregate, 55% （ Mg, Y） - PSZ fines and 5% PVA binder. Al2O3 - ZrO2 composite powders （ 3%, ...ZrO2 sizing nozzles with a basic Jormulation were prepared using 45% （by mass, the same hereinafter ） （ Mg, Y） - PSZ aggregate, 55% （ Mg, Y） - PSZ fines and 5% PVA binder. Al2O3 - ZrO2 composite powders （ 3%, 6%, 9% and 12% ） prepared by sol - gel method were added to replace the equal amount of （ Mg, Y） - PSZfines. Effects of Al2O3 - ZrO2 composite powders on physical properties, phase composition and microstructure of the ZrO2 sizing nozzles were studied. The results show that： the performances of the modified sizing nozzles with 3% Al2O3 - ZrO2 composite powder are better than those of the nobles without composite powder used in current production process, and the thermal shock resistance of the ,former nozzles is six times of that of the latter one.展开更多
Alumina-based composites containing 0-15wt% Ni metallic phase were produced by hot press-sintering Ni-coated alumina powders. The Ni-coated alumina powders were prepared by the aqueous heterogeneous precipitation of a...Alumina-based composites containing 0-15wt% Ni metallic phase were produced by hot press-sintering Ni-coated alumina powders. The Ni-coated alumina powders were prepared by the aqueous heterogeneous precipitation of alumina micro-powders and nickel sulfate salt followed by reduction process. The microstructural features and dispersion of Ni phase in Ni-coated alumina powders and the subsequent alumina-Ni cermets were investigated using scanning electron microscope （SEM）, X-ray diffractometer （XRD）, and transmission electron microscope （TEM）. The relative density of the hot press-sintered composites was measured with the Archimedes＇ method while the fracture strength and the fracture toughness were defined with the three-point bending method and the micro-indentation fracture method. In the formation of alumina-Ni cermets from sintered Ni-coated alumina powders, Ni phase to some extent limits the densification rate and stifles the coarsening and growing process of alumina grains. The Ni phase is found to be located at the interfaces and the triple-joint junctions of alumina grains which results into alteration of the fracture mode of alumina and its increased fracture strength and fracture toughness if compared with monolithic alumina.展开更多
A zirconia alumina powder with a near spherical shape and an average size of 0.1～0.2 μm was prepared by co precipitation. XRD analysis shows that α Al 2O 3 phase may be directly transformed from amorphous in calcin...A zirconia alumina powder with a near spherical shape and an average size of 0.1～0.2 μm was prepared by co precipitation. XRD analysis shows that α Al 2O 3 phase may be directly transformed from amorphous in calcining the hydroxide composite. The ZrO 2 Al 2O 3 composite ceramics manufactured from this powder has the maximum fracture toughness of 9 MPa·m -1/2 at 15% ZrO 2 and 740 MPa fracture strength at 5% ZrO 2. Zirconia grains about 1 μm in diameter are dispersed uniformly in the alumina ceramic matrix.展开更多
文摘Oxidation of carbon is the main problem or Al2O3 - C refractories. ZrO2 - nitrides composite powder was synthesized through carbothermal reduction and nitridation （CRN） of zircon. The effect of ZrO2 - nitrides composite powder addition on oxidation resistance of the Al2O3 - C refractories was investigated by measuring the thickness of oxidation layer. Phase compositions of the Al2O3 - C refractories before and after oxidation were investigated by X-ray diffraction （ XRD ）. Results show that the oxidation resistance of the Al2O3 - C refractories can be obviously improved by adding the synthesized ZrO2 - nitrides composite powder. The formation of mullite and zircon in the oxidation layer results in the densification of oxidation layer, which prevents oxygen diffusion and bnproves the oxidation resistance of the Al2O3 - C refractories.
文摘In order to improve oxidation resistance and ther- mal shock resistance of Al2O3-C refractories, two groups of specimens were prepared with phenolic resin as binder, adding 0, 2 wt% , 4 wt% and 6 wt% commercial SiC or ZrO2-SiC composite powder synthesized from zircon respectively to Al2O3- C refractories, pressing at 200 MPa, drying fully at 250℃, and then carbon embedded firing at 1400℃ for 2 h. Oxidation resistance and thermal shock resistance were researched, phase composition was analyzed by XRD. The results showed that the oxidation of SiC in additives could protect carbon in specimens effectively and thus decreased the mass loss ratio and oxidation area, and improved the oxidation resistance of the specimen. Thermal shock resistance was improved owing to the micro crack toughening of ZrO2 and grain toughening of SiC. In this experiment, the specimens with 6 wt% ZrO2 -SiC composite powder or 6 wt% SiC powder had the best oxidation resistance and thermal shock resistance.
基金financially supported by National Natural Science Foundation of China(Grant No.51372193)Natural Science Basic Research Fund of Shaanxi Province(Grant No.2014JM6224)
文摘ZrO2 sizing nozzles with a basic Jormulation were prepared using 45% （by mass, the same hereinafter ） （ Mg, Y） - PSZ aggregate, 55% （ Mg, Y） - PSZ fines and 5% PVA binder. Al2O3 - ZrO2 composite powders （ 3%, 6%, 9% and 12% ） prepared by sol - gel method were added to replace the equal amount of （ Mg, Y） - PSZfines. Effects of Al2O3 - ZrO2 composite powders on physical properties, phase composition and microstructure of the ZrO2 sizing nozzles were studied. The results show that： the performances of the modified sizing nozzles with 3% Al2O3 - ZrO2 composite powder are better than those of the nobles without composite powder used in current production process, and the thermal shock resistance of the ,former nozzles is six times of that of the latter one.
基金Innovation Foundation of Jiangsu University(04CX01)
文摘Alumina-based composites containing 0-15wt% Ni metallic phase were produced by hot press-sintering Ni-coated alumina powders. The Ni-coated alumina powders were prepared by the aqueous heterogeneous precipitation of alumina micro-powders and nickel sulfate salt followed by reduction process. The microstructural features and dispersion of Ni phase in Ni-coated alumina powders and the subsequent alumina-Ni cermets were investigated using scanning electron microscope （SEM）, X-ray diffractometer （XRD）, and transmission electron microscope （TEM）. The relative density of the hot press-sintered composites was measured with the Archimedes＇ method while the fracture strength and the fracture toughness were defined with the three-point bending method and the micro-indentation fracture method. In the formation of alumina-Ni cermets from sintered Ni-coated alumina powders, Ni phase to some extent limits the densification rate and stifles the coarsening and growing process of alumina grains. The Ni phase is found to be located at the interfaces and the triple-joint junctions of alumina grains which results into alteration of the fracture mode of alumina and its increased fracture strength and fracture toughness if compared with monolithic alumina.
文摘A zirconia alumina powder with a near spherical shape and an average size of 0.1～0.2 μm was prepared by co precipitation. XRD analysis shows that α Al 2O 3 phase may be directly transformed from amorphous in calcining the hydroxide composite. The ZrO 2 Al 2O 3 composite ceramics manufactured from this powder has the maximum fracture toughness of 9 MPa·m -1/2 at 15% ZrO 2 and 740 MPa fracture strength at 5% ZrO 2. Zirconia grains about 1 μm in diameter are dispersed uniformly in the alumina ceramic matrix.
