Ni Fe2O4 ceramics were prepared in different sintering atmospheres. The phase compositions, microstructures and mechanical properties were studied. The results show that the stoichiometric compound Ni Fe2O4 cannot be ...Ni Fe2O4 ceramics were prepared in different sintering atmospheres. The phase compositions, microstructures and mechanical properties were studied. The results show that the stoichiometric compound Ni Fe2O4 cannot be obtained in vacuum or atmospheres with oxygen contents of 2×10-5, 2×10-4 and 2×10-3, respectively. All the samples sintered in above-mentioned atmospheres contain phases of Ni Fe2O4 and Ni O. With increasing oxygen content, Ni Fe2O4 content in the ceramic increases, while Ni O content appears a contrary trend. In vacuum, Ni Fe2O4 ceramic has average grain size of 3.94 μm, and bending strength of85.12 MPa. The changes of the phase composition and mechanical properties of Ni Fe2O4 based cermets are mainly caused by the alteration of their properties of Ni Fe2O4 ceramic.展开更多
A comparative study on the corrosion resistance of NiFe_2O_4 ceramic inert anode for aluminum electrolysis prepared in the different sintering atmosphere was carried out in Na_3AlF_6-Al_2O_3 melt.The results show that...A comparative study on the corrosion resistance of NiFe_2O_4 ceramic inert anode for aluminum electrolysis prepared in the different sintering atmosphere was carried out in Na_3AlF_6-Al_2O_3 melt.The results show that the corrosion rates of NiFe_2O_4 ceramic inert anodes prepared in the vacuum and the atmosphere with oxygen content of 1×10^(-2) are 6.08 cm/a and 2.59 cm/a,respectively.A densification layer is formed at the surface of anode due to some reactions which produce aluminates.For the anode prepared in the atmosphere with oxygen content of 1×10^(-2),the thickness of the densification layer(about 50 μm) is thicker than that(about 20 μm) formed at the surface of anode prepared in the vacuum.The content of NiO and Fe(Ⅱ) in Ni(Ⅱ)x Fe(Ⅱ)1-x Fe(Ⅲ)_2O_4 increases with the decrease of the oxygen content of sintering atmosphere,which reduces the corrosion resistance of the material.展开更多
SrAl 2O 4∶Eu was adopted as main phase to prepare the ceramic pumping cavity material with ultraviolet(UV) converting function in order to match with laser absorption spectra. The relationship between SrAl 2O 4∶...SrAl 2O 4∶Eu was adopted as main phase to prepare the ceramic pumping cavity material with ultraviolet(UV) converting function in order to match with laser absorption spectra. The relationship between SrAl 2O 4∶Eu powder processing and fluorescence effect was studied. The glass material with lower refractive index was added to the SrAl 2O 4∶Eu based ceramics. The diffusive reflectivity and the influence of fluorescence effect on reflection spectra of the ceramics were investigated. Some experimental results can be used for evaluating technical feasibility of the SrAl 2O 4∶Eu based ceramics used for laser reflectors.展开更多
The effects of CuO and H3BO3 additions on the low-temperature sintering,microstructure,and microwave dielectric properties of Ba2Ti3Nb4O18 ceramics were investigated.The addition of less amount of CuO （ 〈1 wt%） con...The effects of CuO and H3BO3 additions on the low-temperature sintering,microstructure,and microwave dielectric properties of Ba2Ti3Nb4O18 ceramics were investigated.The addition of less amount of CuO （ 〈1 wt%） considerably facilitated the densification of Ba2Ti3Nb4O18 ceramics.Appropriate addition of H3BO3 （ 〈3.5 wt%） remarkably improved the microwave dielectric properties of ceramics.The addition of H3BO3 and CuO successfully reduced the sintering temperature of Ba2Ti3Nb4O18 ceramics from 1300 to 1050 ℃.Ba2Ti3Nb4O18 ceramics sintered at 1 050 ℃ for 4 h with the addition of 1.0 wt% CuO and 3.5 wt% H3BO3 exhibited good microwave dielectric properties：er=33.74,Q？f=13 812 GHz,and tf=-5.35 ppm/°C at about 5.0 GHz.展开更多
基金Project(2008AA030503)supported by the National High Technology Research and Development Program of ChinaProject(51474238)supported by the National Natural Science Foundation of China
文摘Ni Fe2O4 ceramics were prepared in different sintering atmospheres. The phase compositions, microstructures and mechanical properties were studied. The results show that the stoichiometric compound Ni Fe2O4 cannot be obtained in vacuum or atmospheres with oxygen contents of 2×10-5, 2×10-4 and 2×10-3, respectively. All the samples sintered in above-mentioned atmospheres contain phases of Ni Fe2O4 and Ni O. With increasing oxygen content, Ni Fe2O4 content in the ceramic increases, while Ni O content appears a contrary trend. In vacuum, Ni Fe2O4 ceramic has average grain size of 3.94 μm, and bending strength of85.12 MPa. The changes of the phase composition and mechanical properties of Ni Fe2O4 based cermets are mainly caused by the alteration of their properties of Ni Fe2O4 ceramic.
基金Projects(51474238,51334002)supported by the National Natural Science Foundation of China
文摘A comparative study on the corrosion resistance of NiFe_2O_4 ceramic inert anode for aluminum electrolysis prepared in the different sintering atmosphere was carried out in Na_3AlF_6-Al_2O_3 melt.The results show that the corrosion rates of NiFe_2O_4 ceramic inert anodes prepared in the vacuum and the atmosphere with oxygen content of 1×10^(-2) are 6.08 cm/a and 2.59 cm/a,respectively.A densification layer is formed at the surface of anode due to some reactions which produce aluminates.For the anode prepared in the atmosphere with oxygen content of 1×10^(-2),the thickness of the densification layer(about 50 μm) is thicker than that(about 20 μm) formed at the surface of anode prepared in the vacuum.The content of NiO and Fe(Ⅱ) in Ni(Ⅱ)x Fe(Ⅱ)1-x Fe(Ⅲ)_2O_4 increases with the decrease of the oxygen content of sintering atmosphere,which reduces the corrosion resistance of the material.
文摘SrAl 2O 4∶Eu was adopted as main phase to prepare the ceramic pumping cavity material with ultraviolet(UV) converting function in order to match with laser absorption spectra. The relationship between SrAl 2O 4∶Eu powder processing and fluorescence effect was studied. The glass material with lower refractive index was added to the SrAl 2O 4∶Eu based ceramics. The diffusive reflectivity and the influence of fluorescence effect on reflection spectra of the ceramics were investigated. Some experimental results can be used for evaluating technical feasibility of the SrAl 2O 4∶Eu based ceramics used for laser reflectors.
文摘The effects of CuO and H3BO3 additions on the low-temperature sintering,microstructure,and microwave dielectric properties of Ba2Ti3Nb4O18 ceramics were investigated.The addition of less amount of CuO （ 〈1 wt%） considerably facilitated the densification of Ba2Ti3Nb4O18 ceramics.Appropriate addition of H3BO3 （ 〈3.5 wt%） remarkably improved the microwave dielectric properties of ceramics.The addition of H3BO3 and CuO successfully reduced the sintering temperature of Ba2Ti3Nb4O18 ceramics from 1300 to 1050 ℃.Ba2Ti3Nb4O18 ceramics sintered at 1 050 ℃ for 4 h with the addition of 1.0 wt% CuO and 3.5 wt% H3BO3 exhibited good microwave dielectric properties：er=33.74,Q？f=13 812 GHz,and tf=-5.35 ppm/°C at about 5.0 GHz.
