In the present study, bond-coats for thermal barrier coatings were deposited via air plasma spraying(APS) techniques onto Inconel 800 and Hastelloy C-276 alloy substrates. Scanning electron microscopy(SEM), transm...In the present study, bond-coats for thermal barrier coatings were deposited via air plasma spraying(APS) techniques onto Inconel 800 and Hastelloy C-276 alloy substrates. Scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), and atomic force microscopy(AFM) were used to investigate the phases and microstructure of the as-sprayed, APS-deposited Co Ni Cr Al Y bond-coatings. The aim of this work was to study the suitability of the bond-coat materials for high temperature applications. Confirmation of nanoscale grains of the γ/γ′-phase was obtained by TEM, high-resolution TEM, and AFM. We concluded that these changes result from the plastic deformation of the bond-coat during the deposition, resulting in Co Ni Cr Al Y bond-coatings with excellent thermal cyclic resistance suitable for use in high-temperature applications. Cyclic oxidative stability was observed to also depend on the underlying metallic alloy substrate.展开更多
The paper deals with calculation of the centrally symmetric and vortex forces for the momentum of a particle in the distortion tensor field from the action minimum, by analogy with the calculation of forces for a char...The paper deals with calculation of the centrally symmetric and vortex forces for the momentum of a particle in the distortion tensor field from the action minimum, by analogy with the calculation of forces for a charge in an electromagnetic field. It is demonstrated that: 1) The compensating interaction tensor corresponds to the distortion tensor in a solid. 2) The centrally symmetric force of the distortion tensor acts on the momentum as a charge, and is analogous to the Coulomb force. In a gas, it results in change in the momentum value of the molecules exponentially to some extent. The action of this force explains the high-temperature plasma in the gas. 3) The vortex force of the distortion tensor is equivalent to the Peach-Koehler force in a solid. It acts on the momentum flow, similar to the Lorentz magnetic force, and explains the vortex motions in space, in the form of “black holes”, and in the atmosphere, in the form of cyclones and anticyclones.展开更多
To reveal the argon plasma characteristics within the entire region of an electron cyclotron resonance(ECR) ion source, the plasma parameters were diagnosed using a bended Langmuir probe with the filament axis perpe...To reveal the argon plasma characteristics within the entire region of an electron cyclotron resonance(ECR) ion source, the plasma parameters were diagnosed using a bended Langmuir probe with the filament axis perpendicular to the diagnosing plane. Experiments indicate that,with a gas volume flow rate and incident microwave power of 4 sccm and 8.8 W, respectively,the gas was ionized to form plasma with a luminous ring. When the incident microwave power was above 27 W, the luminous ring was converted to a bright column, the dark area near its axis was narrowed, and the microwave power absorbing efficiency was increased. This indicates that there was a mode transition phenomenon in this ECR ion source when the microwave power increased. The diagnosis shows that, at an incident microwave power of 17.4 W, the diagnosed electron temperature and ion density were below 8 eV and 3×10^17 m^-3, respectively, while at incident microwave power levels of 30 W and 40 W, the maximum electron temperature and ion density were above 11 eV and 6.8×10^17 m^-3, respectively. Confined by magnetic mirrors, the higher density plasma region had a bow shape, which coincided with the magnetic field lines but deviated from the ECR layer.展开更多
The plasma parameters of planar-type surface-wave plasmas (SWPs) are diagnosed based on the resonant excitation of surface plasmon polaritons (SPPs). The plasma parameter distributions are obtained by changing the...The plasma parameters of planar-type surface-wave plasmas (SWPs) are diagnosed based on the resonant excitation of surface plasmon polaritons (SPPs). The plasma parameter distributions are obtained by changing the discharge conditions of gas pressure and incident power. The measured experimental results show that the plasma near the heating layer is excited by surface waves of SPPs while the plasma located downstream originates from diffusion Moreover, the influence of high-frequency oscillations plays a significant role in producing the proposed SWPs with bi-Maxwellian electron energy distributions.展开更多
In this study,a single-doped phosphors yttrium aluminum garnet(Y_(3)Al_(5)O_(12),YAG):Ce^(3+),single-doped YAG:Sc^(3+),and double-doped phosphors YAG:Ce^(3+),Sc^(3+) were prepared by spark plasma sintering(SPS)(lower ...In this study,a single-doped phosphors yttrium aluminum garnet(Y_(3)Al_(5)O_(12),YAG):Ce^(3+),single-doped YAG:Sc^(3+),and double-doped phosphors YAG:Ce^(3+),Sc^(3+) were prepared by spark plasma sintering(SPS)(lower than 1 200℃).The characteristics of synthesized phosphors were determined using scanning electron microscopy(SEM),X-ray diffraction(XRD),and fluorescence spectroscopy.During SPS,the lattice structure of YAG was maintained by the added Ce^(3+) and Sc^(3+).The emission wavelength of YAG:Ce^(3+) prepared from SPS(425-700 nm) was wider compared to that of YAG:Ce^(3+) prepared from high-temperature solid-state reaction(HSSR)(500-700 nm).The incorporation of low-dose Sc^(3+) in YAG:Ce^(3+) moved the emission peak towards the short wavelength.展开更多
In order to prepare high quality Mo(Si,Al)2 feedstock characterized with C40 phase, higher Al doping amount andexcellent flowability, Mo(Si1-x,Alx)2 with different Al contents (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) were...In order to prepare high quality Mo(Si,Al)2 feedstock characterized with C40 phase, higher Al doping amount andexcellent flowability, Mo(Si1-x,Alx)2 with different Al contents (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized by self-propagatinghigh-temperature synthesis first and Mo(Si0.6,Al0.4)2 was confirmed as the suitable material through X-ray diffraction analysis. Aseries of tests with different parameters of induction plasma spheroidization were applied to improving the flowability of feedstock.Mo(Si,Al)2 feedstock with excellent flowability (26.2 s/50 g) was prepared through adding hydrogen into sheath gas and decreasingthe powder feeding rate. The composition segregation occurred in the spheroidized powder after Al consumption and oxidation. Theinhomogeneous structure of the same particle was caused by the asymmetric heating and cooling when particle passed through theplasma jet.展开更多
Through diagnosing the plasma density and calculating the intensity of microwave electric field,four 10 cm electron cyclotron resonance(ECR)ion sources with different magnetic field structures are studied to reveal th...Through diagnosing the plasma density and calculating the intensity of microwave electric field,four 10 cm electron cyclotron resonance(ECR)ion sources with different magnetic field structures are studied to reveal the inside interaction between the plasma,magnetic field and microwave electric field.From the diagnosing result it can be found that the plasma density distribution is controlled by the plasma generation and electron loss volumes associated with the magnetic field and microwave power level.Based on the cold plasma hypothesis and diagnosing result,the microwave electric field intensity distribution in the plasma is calculated.The result shows that the plasma will significantly change the distribution of the microwave electric field intensity to form a bow shape.From the boundary region of the shape to the center,the electric field intensity varies from higher to lower and the diagnosed density inversely changes.If the bow and its inside lower electric field intensity region are close to the screen grid,the performance of ion beam extracting will be better.The study can provide useful information for the creating of 10 cm ECR ion source and understanding its mechanism.展开更多
β-Si3N4 powders prepared by self-propagating high-temperature synthesis (SHS) with additions of Y2O3 and Al2O3 were sintered by spark plasma sintering (SPS). The densification, microstructure, and mechanical prop...β-Si3N4 powders prepared by self-propagating high-temperature synthesis (SHS) with additions of Y2O3 and Al2O3 were sintered by spark plasma sintering (SPS). The densification, microstructure, and mechanical properties of Si3N4 ceramics prepared using this method were compared with those obtained by hot pressing process. Well densified Si3N4 ceramics with finer and homogeneous microstructure and better mechanical properties were obtained in the case of the SPS technique at 200°C lower than that of hot pressing. The microhardness is 15.72 GPa, the bending strength is 716.46 MPa, and the fracture toughness is 7.03 MPa·m1/2.展开更多
An environmental barrier coating(EBC) consisting of a silicon bond coat and an Yb2-SiO5 top-coat was sprayed on a carbon fibers reinforced SiC ceramic matrix composite(CMC) by atmospheric plasma spray(APS). The micros...An environmental barrier coating(EBC) consisting of a silicon bond coat and an Yb2-SiO5 top-coat was sprayed on a carbon fibers reinforced SiC ceramic matrix composite(CMC) by atmospheric plasma spray(APS). The microstructure of the coating annealed at 1300 ℃ and its high-temperature oxidation behavior at 1350 ℃ were investigated. The significant mass loss of silica during the plasma spray process led to the formation of Yb2SiO5 and Yb2O3 binary phases in the top-coat. Eutectics of Yb2SiO5 and Yb2O3 were precipitated in the top-coat, and channel cracks were formed in the top-coat after 20 h annealing because of the mismatch between the coefficients of thermal expansion(CTEs) of Yb2SiO5 and the SiC substrate. The EBC effectively improved the oxidation resistance of the CMC substrate. The channel cracks in the Yb2SiO5 top-coat provided inward diffusion channels for oxygen and led to the formation of oxidation delamination cracks in the bond coat, finally resulting in spallation failure of the coating after 80 h oxidation.展开更多
A glycine–nitrate self-propagating high-temperature synthesis(SHS)was developed to produce composite MgO-Gd_(2)O_(3) nanopowders.The X-ray powder diffraction(XRD)analysis confirmed the SHS-product consists of cubic M...A glycine–nitrate self-propagating high-temperature synthesis(SHS)was developed to produce composite MgO-Gd_(2)O_(3) nanopowders.The X-ray powder diffraction(XRD)analysis confirmed the SHS-product consists of cubic MgO and Gd_(2)O_(3) phases with nanometer crystallite size and retains this structure after annealing at temperatures up to 1200℃.Near full dense high IR-transparent composite ceramics were fabricated by spark plasma sintering(SPS)at 1140℃and 60 MPa.The in-line transmittance of 1 mm thick MgO-Gd_(2)O_(3) ceramics exceeded 70%in the range of 4–5 mm and reached a maximum of 77%at a wavelength of 5.3 mm.The measured microhardness HV0.5 of the MgO-Gd2O3 ceramics is 9.5±0.4 GPa,while the fracture toughness(KIC)amounted to 2.0±0.5МPa·m1/2.These characteristics demonstrate that obtained composite MgO-Gd_(2)O_(3) ceramic is a promising material for protective infra-red(IR)windows.展开更多
We calculate the shear viscosity(η) and bulk viscosity(ζ) to entropy density(s) ratios η/s and ζ/s of a gluon plasma system in kinetic theory, including both the elastic gg←→gg forward scattering and the i...We calculate the shear viscosity(η) and bulk viscosity(ζ) to entropy density(s) ratios η/s and ζ/s of a gluon plasma system in kinetic theory, including both the elastic gg←→gg forward scattering and the inelastic soft gluon bremsstrahlung gg←→ggg processes. Due to the suppressed contribution to η and ζ in the gg←→gg forward scattering and the effective g←→gg gluon splitting, Arnold, Moore and Yaffe(AMY) and Arnold, Dogan and Moore(ADM) have got the leading order computations for η and ζ in high-temperature QCD matter. In this paper, we calculate the correction to η and ζ in the soft gluon bremsstrahlung gg←→ggg process with an analytic method.We find that the contribution of the collision term from the gg←→ggg soft gluon bremsstrahlung process is just a small perturbation to the gg←→gg scattering process and that the correction is at~ 5% level. Then, we obtain the bulk viscosity of the gluon plasma for the number-changing process. Furthermore, our leading-order result for bulk viscosity is the formula ζ∝(αs^2 T^3)/(lnαs^-1) in high-temperature gluon plasma.展开更多
基金provided by Technical Education Quality Improvement Programme-Ⅱ(TEQIP-Ⅱ)at MNNIT Allahabad
文摘In the present study, bond-coats for thermal barrier coatings were deposited via air plasma spraying(APS) techniques onto Inconel 800 and Hastelloy C-276 alloy substrates. Scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), and atomic force microscopy(AFM) were used to investigate the phases and microstructure of the as-sprayed, APS-deposited Co Ni Cr Al Y bond-coatings. The aim of this work was to study the suitability of the bond-coat materials for high temperature applications. Confirmation of nanoscale grains of the γ/γ′-phase was obtained by TEM, high-resolution TEM, and AFM. We concluded that these changes result from the plastic deformation of the bond-coat during the deposition, resulting in Co Ni Cr Al Y bond-coatings with excellent thermal cyclic resistance suitable for use in high-temperature applications. Cyclic oxidative stability was observed to also depend on the underlying metallic alloy substrate.
文摘The paper deals with calculation of the centrally symmetric and vortex forces for the momentum of a particle in the distortion tensor field from the action minimum, by analogy with the calculation of forces for a charge in an electromagnetic field. It is demonstrated that: 1) The compensating interaction tensor corresponds to the distortion tensor in a solid. 2) The centrally symmetric force of the distortion tensor acts on the momentum as a charge, and is analogous to the Coulomb force. In a gas, it results in change in the momentum value of the molecules exponentially to some extent. The action of this force explains the high-temperature plasma in the gas. 3) The vortex force of the distortion tensor is equivalent to the Peach-Koehler force in a solid. It acts on the momentum flow, similar to the Lorentz magnetic force, and explains the vortex motions in space, in the form of “black holes”, and in the atmosphere, in the form of cyclones and anticyclones.
基金financial support of National Natural Science Foundation of China (Grant No.11475137)
文摘To reveal the argon plasma characteristics within the entire region of an electron cyclotron resonance(ECR) ion source, the plasma parameters were diagnosed using a bended Langmuir probe with the filament axis perpendicular to the diagnosing plane. Experiments indicate that,with a gas volume flow rate and incident microwave power of 4 sccm and 8.8 W, respectively,the gas was ionized to form plasma with a luminous ring. When the incident microwave power was above 27 W, the luminous ring was converted to a bright column, the dark area near its axis was narrowed, and the microwave power absorbing efficiency was increased. This indicates that there was a mode transition phenomenon in this ECR ion source when the microwave power increased. The diagnosis shows that, at an incident microwave power of 17.4 W, the diagnosed electron temperature and ion density were below 8 eV and 3×10^17 m^-3, respectively, while at incident microwave power levels of 30 W and 40 W, the maximum electron temperature and ion density were above 11 eV and 6.8×10^17 m^-3, respectively. Confined by magnetic mirrors, the higher density plasma region had a bow shape, which coincided with the magnetic field lines but deviated from the ECR layer.
基金supported by National Natural Science Foundation of China(No.11105002)Doctoral Scientific Research Fund of AUST(No.2010yb011)ITER Domestic Matching Item of China(No.GB105003)
文摘The plasma parameters of planar-type surface-wave plasmas (SWPs) are diagnosed based on the resonant excitation of surface plasmon polaritons (SPPs). The plasma parameter distributions are obtained by changing the discharge conditions of gas pressure and incident power. The measured experimental results show that the plasma near the heating layer is excited by surface waves of SPPs while the plasma located downstream originates from diffusion Moreover, the influence of high-frequency oscillations plays a significant role in producing the proposed SWPs with bi-Maxwellian electron energy distributions.
基金Funded by the Primary Research and Development Plan of Jiangsu Province(No.BE2016175)。
文摘In this study,a single-doped phosphors yttrium aluminum garnet(Y_(3)Al_(5)O_(12),YAG):Ce^(3+),single-doped YAG:Sc^(3+),and double-doped phosphors YAG:Ce^(3+),Sc^(3+) were prepared by spark plasma sintering(SPS)(lower than 1 200℃).The characteristics of synthesized phosphors were determined using scanning electron microscopy(SEM),X-ray diffraction(XRD),and fluorescence spectroscopy.During SPS,the lattice structure of YAG was maintained by the added Ce^(3+) and Sc^(3+).The emission wavelength of YAG:Ce^(3+) prepared from SPS(425-700 nm) was wider compared to that of YAG:Ce^(3+) prepared from high-temperature solid-state reaction(HSSR)(500-700 nm).The incorporation of low-dose Sc^(3+) in YAG:Ce^(3+) moved the emission peak towards the short wavelength.
基金Project (20101101120030) supported by International Graduate Exchange Program of Beijing Institute of Technologysupported by the Research Fund for the doctoral Program of Higher Education of China
文摘In order to prepare high quality Mo(Si,Al)2 feedstock characterized with C40 phase, higher Al doping amount andexcellent flowability, Mo(Si1-x,Alx)2 with different Al contents (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized by self-propagatinghigh-temperature synthesis first and Mo(Si0.6,Al0.4)2 was confirmed as the suitable material through X-ray diffraction analysis. Aseries of tests with different parameters of induction plasma spheroidization were applied to improving the flowability of feedstock.Mo(Si,Al)2 feedstock with excellent flowability (26.2 s/50 g) was prepared through adding hydrogen into sheath gas and decreasingthe powder feeding rate. The composition segregation occurred in the spheroidized powder after Al consumption and oxidation. Theinhomogeneous structure of the same particle was caused by the asymmetric heating and cooling when particle passed through theplasma jet.
基金the National Natural Science Foundation of China(Grant No.11875222)。
文摘Through diagnosing the plasma density and calculating the intensity of microwave electric field,four 10 cm electron cyclotron resonance(ECR)ion sources with different magnetic field structures are studied to reveal the inside interaction between the plasma,magnetic field and microwave electric field.From the diagnosing result it can be found that the plasma density distribution is controlled by the plasma generation and electron loss volumes associated with the magnetic field and microwave power level.Based on the cold plasma hypothesis and diagnosing result,the microwave electric field intensity distribution in the plasma is calculated.The result shows that the plasma will significantly change the distribution of the microwave electric field intensity to form a bow shape.From the boundary region of the shape to the center,the electric field intensity varies from higher to lower and the diagnosed density inversely changes.If the bow and its inside lower electric field intensity region are close to the screen grid,the performance of ion beam extracting will be better.The study can provide useful information for the creating of 10 cm ECR ion source and understanding its mechanism.
基金the National Natural Science Foundation of China (No.2001AA333080).
文摘β-Si3N4 powders prepared by self-propagating high-temperature synthesis (SHS) with additions of Y2O3 and Al2O3 were sintered by spark plasma sintering (SPS). The densification, microstructure, and mechanical properties of Si3N4 ceramics prepared using this method were compared with those obtained by hot pressing process. Well densified Si3N4 ceramics with finer and homogeneous microstructure and better mechanical properties were obtained in the case of the SPS technique at 200°C lower than that of hot pressing. The microhardness is 15.72 GPa, the bending strength is 716.46 MPa, and the fracture toughness is 7.03 MPa·m1/2.
基金sponsored by the National Natural Science Foundation of China (NSFC) under grant Nos. 51590894, 51425102, and 51231001
文摘An environmental barrier coating(EBC) consisting of a silicon bond coat and an Yb2-SiO5 top-coat was sprayed on a carbon fibers reinforced SiC ceramic matrix composite(CMC) by atmospheric plasma spray(APS). The microstructure of the coating annealed at 1300 ℃ and its high-temperature oxidation behavior at 1350 ℃ were investigated. The significant mass loss of silica during the plasma spray process led to the formation of Yb2SiO5 and Yb2O3 binary phases in the top-coat. Eutectics of Yb2SiO5 and Yb2O3 were precipitated in the top-coat, and channel cracks were formed in the top-coat after 20 h annealing because of the mismatch between the coefficients of thermal expansion(CTEs) of Yb2SiO5 and the SiC substrate. The EBC effectively improved the oxidation resistance of the CMC substrate. The channel cracks in the Yb2SiO5 top-coat provided inward diffusion channels for oxygen and led to the formation of oxidation delamination cracks in the bond coat, finally resulting in spallation failure of the coating after 80 h oxidation.
基金funded by the Russian Science Foundation(Research Project No.19-73-10127)。
文摘A glycine–nitrate self-propagating high-temperature synthesis(SHS)was developed to produce composite MgO-Gd_(2)O_(3) nanopowders.The X-ray powder diffraction(XRD)analysis confirmed the SHS-product consists of cubic MgO and Gd_(2)O_(3) phases with nanometer crystallite size and retains this structure after annealing at temperatures up to 1200℃.Near full dense high IR-transparent composite ceramics were fabricated by spark plasma sintering(SPS)at 1140℃and 60 MPa.The in-line transmittance of 1 mm thick MgO-Gd_(2)O_(3) ceramics exceeded 70%in the range of 4–5 mm and reached a maximum of 77%at a wavelength of 5.3 mm.The measured microhardness HV0.5 of the MgO-Gd2O3 ceramics is 9.5±0.4 GPa,while the fracture toughness(KIC)amounted to 2.0±0.5МPa·m1/2.These characteristics demonstrate that obtained composite MgO-Gd_(2)O_(3) ceramic is a promising material for protective infra-red(IR)windows.
基金Supported by Ministry of Science and Technology of China(MSTC)under the"973"Project(2015CB856904(4))National Natural Science Foundation of China(11735007,11521064)
文摘We calculate the shear viscosity(η) and bulk viscosity(ζ) to entropy density(s) ratios η/s and ζ/s of a gluon plasma system in kinetic theory, including both the elastic gg←→gg forward scattering and the inelastic soft gluon bremsstrahlung gg←→ggg processes. Due to the suppressed contribution to η and ζ in the gg←→gg forward scattering and the effective g←→gg gluon splitting, Arnold, Moore and Yaffe(AMY) and Arnold, Dogan and Moore(ADM) have got the leading order computations for η and ζ in high-temperature QCD matter. In this paper, we calculate the correction to η and ζ in the soft gluon bremsstrahlung gg←→ggg process with an analytic method.We find that the contribution of the collision term from the gg←→ggg soft gluon bremsstrahlung process is just a small perturbation to the gg←→gg scattering process and that the correction is at~ 5% level. Then, we obtain the bulk viscosity of the gluon plasma for the number-changing process. Furthermore, our leading-order result for bulk viscosity is the formula ζ∝(αs^2 T^3)/(lnαs^-1) in high-temperature gluon plasma.