The influence mechanism of vanadic titanomagnetite solid-state reduction was studied in this paper.Optical microscopy(OM),scanning electron microscope(SEM),and X-ray diffraction(XRD)were used to characterize the struc...The influence mechanism of vanadic titanomagnetite solid-state reduction was studied in this paper.Optical microscopy(OM),scanning electron microscope(SEM),and X-ray diffraction(XRD)were used to characterize the structure and phases of the samples.The results show that the dense structure is not the reason that limits the reducibility of Panxi vanadic titanomagnetite.Metallization rate of 93%was achieved when it was reduced at 1100℃for 100 min.After pre-oxidation,Fe_(9)TiO_(15)and Fe_(2)O_(3)are the main phases of samples.Pre-oxidation could destroy the dense structure of vanadic titanomagnetite and increase the specific surface area of particles.However,reducibility of vanadic titanomagnetite is not improved obviously by pre-oxidation,with metallization rate increasing only 1%under the same reduction conditions,and the generated metallic iron grains are smaller.Phase transformation of vanadic titanomagnetite at different reduction temperatures shows that the presence of FeTi_(2)O_(5)is the main reason that limits the reducibility of Panxi vanadic titanomagnetite.展开更多
The influence of the certain specific vacuum pre-oxidation process on the phase transformation of thermally-grown oxides（TGO） was studied.The CoCrAlY high temperature corrosion resistance coatings were produced onto...The influence of the certain specific vacuum pre-oxidation process on the phase transformation of thermally-grown oxides（TGO） was studied.The CoCrAlY high temperature corrosion resistance coatings were produced onto the nickel-based superalloy substrate by high velocity oxygen fuel（HVOF）.It suggests that the TGO usually consists of a great number of chromium oxides,cobalt oxides and spinel oxides besides alumina during the initial period of the high temperature oxidation if the specimens are not subjected to the appropriate vacuum pre-oxidation process.Furthermore,the amount of alumina is strongly dependent on the partial pressure of oxygen;while the CoCr2O4 spinel oxides are usually formed under the conditions of higher partial pressure of oxygen during the initial period and the lower partial pressure of oxygen during the subsequent period of the isothermal oxidation.After the appropriate vacuum pre-oxidation process,the TGO is mainly composed of alumina that contains lower Y element,while alumina that contains higher Y element sporadically distributes,and the spinel oxides cannot be found.After a longer period of the isothermal oxidation,a small amount of porous CoCr2O4 and the chrome oxide sporadically distribute near the continuous alumina.Additionally,after the appropriate vacuum pre-oxidation process,the TGO growth rate is relatively slow.展开更多
基金the Program for New Century Excellent Talents in University(No.NCET-10-0834)。
文摘The influence mechanism of vanadic titanomagnetite solid-state reduction was studied in this paper.Optical microscopy(OM),scanning electron microscope(SEM),and X-ray diffraction(XRD)were used to characterize the structure and phases of the samples.The results show that the dense structure is not the reason that limits the reducibility of Panxi vanadic titanomagnetite.Metallization rate of 93%was achieved when it was reduced at 1100℃for 100 min.After pre-oxidation,Fe_(9)TiO_(15)and Fe_(2)O_(3)are the main phases of samples.Pre-oxidation could destroy the dense structure of vanadic titanomagnetite and increase the specific surface area of particles.However,reducibility of vanadic titanomagnetite is not improved obviously by pre-oxidation,with metallization rate increasing only 1%under the same reduction conditions,and the generated metallic iron grains are smaller.Phase transformation of vanadic titanomagnetite at different reduction temperatures shows that the presence of FeTi_(2)O_(5)is the main reason that limits the reducibility of Panxi vanadic titanomagnetite.
基金Project supported the by State Key Laboratory of Internal Combustion Engines of Tianjin University,ChinaProject(51507077)supported by the National Natural Science Foundation of China+1 种基金Project(15KJB470005)supported by the Natural Science Research of Higher Education Institutions of Jiangsu Province,ChinaProjects(YKJ201308,QKJB201401)supported by Nanjing Institute of Technology,China
文摘The influence of the certain specific vacuum pre-oxidation process on the phase transformation of thermally-grown oxides（TGO） was studied.The CoCrAlY high temperature corrosion resistance coatings were produced onto the nickel-based superalloy substrate by high velocity oxygen fuel（HVOF）.It suggests that the TGO usually consists of a great number of chromium oxides,cobalt oxides and spinel oxides besides alumina during the initial period of the high temperature oxidation if the specimens are not subjected to the appropriate vacuum pre-oxidation process.Furthermore,the amount of alumina is strongly dependent on the partial pressure of oxygen;while the CoCr2O4 spinel oxides are usually formed under the conditions of higher partial pressure of oxygen during the initial period and the lower partial pressure of oxygen during the subsequent period of the isothermal oxidation.After the appropriate vacuum pre-oxidation process,the TGO is mainly composed of alumina that contains lower Y element,while alumina that contains higher Y element sporadically distributes,and the spinel oxides cannot be found.After a longer period of the isothermal oxidation,a small amount of porous CoCr2O4 and the chrome oxide sporadically distribute near the continuous alumina.Additionally,after the appropriate vacuum pre-oxidation process,the TGO growth rate is relatively slow.
