We investigated the influence of the growth temperature, O_(2) flow, molar ratio between Ga_(2)O_(3) powder and graphite powder on the structure and morphology of the films grown on the c-plane sapphire(0001) substrat...We investigated the influence of the growth temperature, O_(2) flow, molar ratio between Ga_(2)O_(3) powder and graphite powder on the structure and morphology of the films grown on the c-plane sapphire(0001) substrates by a carbothermal reduction method. Experimental results for the heteroepitaxial growth of β-Ga_(2)O_(3) illustrate that β-Ga_(2)O_(3) growth by the carbothermal reduction method can be controlled. The optimal result was obtained at a growth temperature of 1050 °C. The fastest growth rate of β-Ga_(2)O_(3) films was produced when the O_(2) flow was 20 sccm. To guarantee that β-Ga_(2)O_(3) films with both high-quality crystal and morphology properties, the ideal molar ratio between graphite powder and Ga_(2)O_(3) powder should be set at 10 : 1.展开更多
SiC-Al2O3 composite powder was prepared by sol-gel and carbothermal reduction method. The powder synthesized was characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM) to confirm the phase forma...SiC-Al2O3 composite powder was prepared by sol-gel and carbothermal reduction method. The powder synthesized was characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM) to confirm the phase formation, and the thermodynamic analysis was performed systematically. Moreover, the variation of its microwave permittivity with different atomic ratio of Al/Si was investigated in the frequency range of 8.2-12.4 GHz. The results show that, the powder obtained consists of spherical particles of 300-400 nm in diameter, which are composed of SiC and Al2O3 microcrystal with the grain size of approximately 45 nm. The results of XRD accord with those of the thermodynamic analysis. It is impossible for Al atoms to dissolve in the lattice of SiC during the carbothermal reduction process. Along with the increase of atomic ratio of Al/Si in the xerogel, the amount of Al2O3 in the powder synthesized increases, which reduces bothε', the real part of complex permittivity, and tgδ(ε'/ε'), the dissipation factor, whereε' is the imaginary part of complex permittivity.展开更多
A single phase of zirconium diboride(Zr B2)powder was successfully synthesized by sol-gel method in Zr-B-C-O system, using zirconium oxychloride(Zr OCl2·8H2O), nano-scale boron and sucrose(C12H22O11)as the starti...A single phase of zirconium diboride(Zr B2)powder was successfully synthesized by sol-gel method in Zr-B-C-O system, using zirconium oxychloride(Zr OCl2·8H2O), nano-scale boron and sucrose(C12H22O11)as the starting materials and propylene oxide(PO)as complexing agent at a low temperature. Simultaneously, the experimental and theoretical studies of Zr B2 synthesized by boro/carbothermal reduction from novel sol-gel technology were discussed. The results indicated that the pure rod-like Zr B2 powder without residual Zr O2 phase could be obtained with a B/Zr molar ratio of 3.5 at 1 400℃ in argon atmosphere. Besides, in this study, a kinetic model for the Zr-B-C-O system producing Zr B2 by boro/carbothermal reaction was established based on thermodynamic analysis. It was also observed that, with the increase of reaction temperature, the reaction which produced Zr B2 powders changed from the borothermal reaction to boro/carbothermal reaction in the Zr-B-C-O system.展开更多
Vanadium nitrides were prepared via one step method of carbothermal reduction and nitridation of vanadium trioxide. Thermalgravimetric analysis （TGA） and X-ray diffraction were used to determine the reaction paths o...Vanadium nitrides were prepared via one step method of carbothermal reduction and nitridation of vanadium trioxide. Thermalgravimetric analysis （TGA） and X-ray diffraction were used to determine the reaction paths of vanadium carbide, namely the following sequential reaction： V2O3→V8C7 in higher temperature stage, the rule of vanadium nitride synthesized was established, and defined conditions of temperature for the production of the carbides and nitrides were determined. Vanadium oxycarbide may consist in the front process of carbothermal reduction of vanadium trioxide. In one step method for vanadium nitride by carbothermal reduction and nitridation of vanadium trioxide, the nitridation process is simultaneous with the carbothermal reduction. A one-step mechanism of the carbothermal reduction with simultaneous nitridation leaded to a lower terminal temperature in nitridation process for vanadium nitride produced, compared with that of carbothermal reduction process without nitridation. The grain size and shape of vanadium nitride were uniform, and had the shape of a cube. The one step method combined vacuum carborization and nitridation （namely two step method） into one process. It simplified the technological process and decreased the costs.展开更多
基金supported by the National Natural Science Foundation of China under Grant 62104024, Grant 11875097, Grant 12075045, Grant 11975257, Grant 11961141014, and Grant 62074146the Fundamental Research Funds for the Central Universities under Grant DUT19RC (3)074the Natural Science Foundation of Liaoning Province under Grant 2021MS124, Grant 2022020474JH2/1013。
文摘We investigated the influence of the growth temperature, O_(2) flow, molar ratio between Ga_(2)O_(3) powder and graphite powder on the structure and morphology of the films grown on the c-plane sapphire(0001) substrates by a carbothermal reduction method. Experimental results for the heteroepitaxial growth of β-Ga_(2)O_(3) illustrate that β-Ga_(2)O_(3) growth by the carbothermal reduction method can be controlled. The optimal result was obtained at a growth temperature of 1050 °C. The fastest growth rate of β-Ga_(2)O_(3) films was produced when the O_(2) flow was 20 sccm. To guarantee that β-Ga_(2)O_(3) films with both high-quality crystal and morphology properties, the ideal molar ratio between graphite powder and Ga_(2)O_(3) powder should be set at 10 : 1.
基金Project (50572090) supported by the National Natural Science Foundation of China
文摘SiC-Al2O3 composite powder was prepared by sol-gel and carbothermal reduction method. The powder synthesized was characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM) to confirm the phase formation, and the thermodynamic analysis was performed systematically. Moreover, the variation of its microwave permittivity with different atomic ratio of Al/Si was investigated in the frequency range of 8.2-12.4 GHz. The results show that, the powder obtained consists of spherical particles of 300-400 nm in diameter, which are composed of SiC and Al2O3 microcrystal with the grain size of approximately 45 nm. The results of XRD accord with those of the thermodynamic analysis. It is impossible for Al atoms to dissolve in the lattice of SiC during the carbothermal reduction process. Along with the increase of atomic ratio of Al/Si in the xerogel, the amount of Al2O3 in the powder synthesized increases, which reduces bothε', the real part of complex permittivity, and tgδ(ε'/ε'), the dissipation factor, whereε' is the imaginary part of complex permittivity.
基金Supported by the Fund for the Self-dependent Innovation of Tianjin University(2014)
文摘A single phase of zirconium diboride(Zr B2)powder was successfully synthesized by sol-gel method in Zr-B-C-O system, using zirconium oxychloride(Zr OCl2·8H2O), nano-scale boron and sucrose(C12H22O11)as the starting materials and propylene oxide(PO)as complexing agent at a low temperature. Simultaneously, the experimental and theoretical studies of Zr B2 synthesized by boro/carbothermal reduction from novel sol-gel technology were discussed. The results indicated that the pure rod-like Zr B2 powder without residual Zr O2 phase could be obtained with a B/Zr molar ratio of 3.5 at 1 400℃ in argon atmosphere. Besides, in this study, a kinetic model for the Zr-B-C-O system producing Zr B2 by boro/carbothermal reaction was established based on thermodynamic analysis. It was also observed that, with the increase of reaction temperature, the reaction which produced Zr B2 powders changed from the borothermal reaction to boro/carbothermal reaction in the Zr-B-C-O system.
文摘Vanadium nitrides were prepared via one step method of carbothermal reduction and nitridation of vanadium trioxide. Thermalgravimetric analysis （TGA） and X-ray diffraction were used to determine the reaction paths of vanadium carbide, namely the following sequential reaction： V2O3→V8C7 in higher temperature stage, the rule of vanadium nitride synthesized was established, and defined conditions of temperature for the production of the carbides and nitrides were determined. Vanadium oxycarbide may consist in the front process of carbothermal reduction of vanadium trioxide. In one step method for vanadium nitride by carbothermal reduction and nitridation of vanadium trioxide, the nitridation process is simultaneous with the carbothermal reduction. A one-step mechanism of the carbothermal reduction with simultaneous nitridation leaded to a lower terminal temperature in nitridation process for vanadium nitride produced, compared with that of carbothermal reduction process without nitridation. The grain size and shape of vanadium nitride were uniform, and had the shape of a cube. The one step method combined vacuum carborization and nitridation （namely two step method） into one process. It simplified the technological process and decreased the costs.
基金Project(u0837604)supported by the Natural Science Foundation of Yunnan Province,ChinaProject(51004058)supported by the National Natural Science Foundation of ChinaProject(20095314110003)supported by Specialized Research Fund for the Doctoral Program of Higher Education
