We have studied the structural and atomic transport properties of liquid f-shell Yb in the temperature range 1123 K–1473 K. Pair interactions between atoms are derived using a local pseudopotential. The potential par...We have studied the structural and atomic transport properties of liquid f-shell Yb in the temperature range 1123 K–1473 K. Pair interactions between atoms are derived using a local pseudopotential. The potential parameters are fitted to the phonon dispersion curve at room temperature. The local pseudopotential used in the present study is computationally more efficient with only three parameters, and it is found to be transferable to the liquid phase without changing the parameters.Since the various computed properties agree with reported theoretical and experimental findings, the adopted fitting scheme is justified. As a significant outcome of the study, we find that(i) the melting in Yb is governed by the Lindemann's law,(ii)the mass transport mechanism obeys the Arrhenius law,(iii) the role of the three-particle correlation function in deriving the velocity autocorrelation function is small,(iv) the mean-square atomic displacement is more sensitive to the choice of interaction potential than the other bulk properties, and(v) liquid Yb does not show liquid–liquid phase transition within the studied temperature range. Further, due to the good description of the structural and mass transport properties, we propose that Yb remains divalent at reduced density.展开更多
In view of the difficulty in calculating the atomic structure parameters of high-Z elements,the Hartree–Fock with relativistic corrections(HFR)theory in combination with the ridge regression(RR)algorithm rather than ...In view of the difficulty in calculating the atomic structure parameters of high-Z elements,the Hartree–Fock with relativistic corrections(HFR)theory in combination with the ridge regression(RR)algorithm rather than the Cowan code’s least squares fitting(LSF)method is proposed and applied.By analyzing the energy level structure parameters of the HFR theory and using the fitting experimental energy level extrapolation method,some excited state energy levels of the Yb I(Z=70)atom including the 4f open shell are calculated.The advantages of the ridge regression algorithm are demonstrated by comparing it with Cowan code’s LSF results.In addition,the results obtained by the new method are compared with the experimental results and other theoretical results to demonstrate the reliability and accuracy of our approach.展开更多
Selective photoionization of ytterbium isotope is studied numerically based on a three-step photoionization scheme,4f^(14)6s^(21)S_0(0 cm^(-1))→4f~(14)6s6p~3P_1(17992.008 cm^(-1))→(4f~(13)6s~26p)(7/2,3/2)_2(35196.98...Selective photoionization of ytterbium isotope is studied numerically based on a three-step photoionization scheme,4f^(14)6s^(21)S_0(0 cm^(-1))→4f~(14)6s6p~3P_1(17992.008 cm^(-1))→(4f~(13)6s~26p)(7/2,3/2)_2(35196.98 cm^(-1))→auto-ionization state(52353 cm^(-1))→Yb^(+),by the density matrix theory with the consideration of atomic hyperfine structures and magnetic sublevels.To examine the physical model,the numerical isotopic abundance of ytterbium is compared with that from mass spectroscopy experiment,showing that they are in good agreement with each other.The excitation process and ionization process of ytterbium,especially for odd isotopes,are discussed and analyzed in detail on this basis.The effects of frequency detuning,power densities,spectral bandwidths,polarization of two excitation lasers,and atomic Doppler broadening on the total ionization yield and isotopic abundance are investigated numerically and the optimal excitation conditions for~(176)Yb enrichment are identified semi-quantitatively.展开更多
The based membrane extraction of Th 4+ and Yb 3+ was studied in HBTMPP heptane using a hollow fibber membrane. The separation method of Th 4+ and Yb 3+ was proposed by kinetics competition. The separation operation of...The based membrane extraction of Th 4+ and Yb 3+ was studied in HBTMPP heptane using a hollow fibber membrane. The separation method of Th 4+ and Yb 3+ was proposed by kinetics competition. The separation operation of Th 4+ and Yb 3+ mixture was carried out by two successive extraction and stripping simultaneously. The concentration ratio of Th 4+ to Yb 3+ is 16 74 in the stripping solution. The recovery and purity of Th 4+ are 71 6% and 95 74% respectively.展开更多
<正>The influence of Yb_2O_3 and Pr_2O_3 doping on electrical and gas sensing properties of tin dioxide was studied.A doping content of 0.5wt%～5wt% was investigated by mechanical mixing.The significant improvem...<正>The influence of Yb_2O_3 and Pr_2O_3 doping on electrical and gas sensing properties of tin dioxide was studied.A doping content of 0.5wt%～5wt% was investigated by mechanical mixing.The significant improvement on sensitivity and selectivity to 200μg/g hydrogen sulphide gas has been achieved by 3wt% Pr_2O_3 and 5wt% Yb_2O_3 adding.The better response and revovery properties of Pr or Yb doped tin dioxide sensor for 200μg/g hydrogen sulphide gas were found.The maximum sensitivity to H_2S gas is observed at about 120℃.Pr has stronger catalysis than Yb for H_2S reaction on SnO_2 surface.S~ 2-) was oxidized to S~ 6+) on the SnO_2 surface according to XPS.展开更多
Light-emitting ytterbium-doped tantalum-oxide thin films were prepared using a simple co-sputtering method for the first time. Sharp photoluminescence peaks having a wavelength of around 980 nm were observed from film...Light-emitting ytterbium-doped tantalum-oxide thin films were prepared using a simple co-sputtering method for the first time. Sharp photoluminescence peaks having a wavelength of around 980 nm were observed from films annealed from 700°C to 1000°C for 10 to 40 min. The strongest intensity of the 980-nm peak was obtained from a film deposited using three ytterbium-oxide pellets and annealed at 800°C for 20 min. Such rare-earth doped tantalum-oxide sputtered films can be used as high-refractive-index materials of autocloned photonic crystals that can be applied to novel light-emitting devices, and they will also be used as both anti-reflection and down-conversion layers for realizing high-efficiency silicon solar cells.展开更多
The ytterbium complex of isonicotinoyl hydrazone was synthesized and the structure was determined by X ray diffraction analysis. The crystal and molecular structure of the title complex [Yb 2(L) 3](OH) 3 shows that th...The ytterbium complex of isonicotinoyl hydrazone was synthesized and the structure was determined by X ray diffraction analysis. The crystal and molecular structure of the title complex [Yb 2(L) 3](OH) 3 shows that the complex has two identical nine coordinated ytterbium ions with each surrounded by N 3O 6 donor set. Two ytterbium ions are bridged by three phenolate oxygen atoms. The geometry around each ytterbium ions can be considered as a three capped trigonal prism.展开更多
Rare earth doped orthovanadate crystal LuVO4∶Yb3+ shows high power laser applications because of the low quantum defect and the high thermal conductivity. Since electronic paramagnetic resonance (EPR) is a powerful t...Rare earth doped orthovanadate crystal LuVO4∶Yb3+ shows high power laser applications because of the low quantum defect and the high thermal conductivity. Since electronic paramagnetic resonance (EPR) is a powerful tool to analyze the electronic properties and the local structures of paramagnetic impurity centers in crystals, the EPR spectra of the Yb3+ centers in LuVO4 crystal were measured recently. However, the above experimental results have not been theoretically interpreted. In this work, The EPR g factors and the hyperfine structure constants of 171Yb3+ and 173Yb3+ isotopes in LuVO4 crystal were theoretically studied from the perturbation formulae of the spin Hamiltonian parameters for 4f13 ion in tetragonal symmetry. The needed crystal parameters were obtained from the superposition model and the local structure of the studied system. The calculated results were in reasonable agreement with the observed values.展开更多
The background absorption of Lu and Yb matrices was studied. The experimental results show that there is a significantly wavelength dependent. The effects of ashing temperature, heating mode, atomization temperature, ...The background absorption of Lu and Yb matrices was studied. The experimental results show that there is a significantly wavelength dependent. The effects of ashing temperature, heating mode, atomization temperature, recording time and matrix modifiers affecting the non specific absorption of Lu and Yb matrices were discussed.展开更多
The mass-transfer kinetics of ytterbium between aqueous solutions and heptane solutions of CA- 12 and CA-12-HEHEHP have been studied by using a constant interfacial area cell with laminar flow. The results have been i...The mass-transfer kinetics of ytterbium between aqueous solutions and heptane solutions of CA- 12 and CA-12-HEHEHP have been studied by using a constant interfacial area cell with laminar flow. The results have been interpreted according to a series of reversible interfacial reactions. In this work, it has been discovered that HEHEHP can increase the rate of ytterbium extraction by CA-12.展开更多
The complex [(ButC5H’4)2YbCl]2, crystallized in the triclinic system,space group P1, with a=8. 392(3), b=9. 402(3), c=12. 418(5) , a=68. 78(3),P= 77. 43(3), γ=86. 41 (3)°, V= 891. 4(5) , Z=1, Dc= 1. 68 g/cm3, M...The complex [(ButC5H’4)2YbCl]2, crystallized in the triclinic system,space group P1, with a=8. 392(3), b=9. 402(3), c=12. 418(5) , a=68. 78(3),P= 77. 43(3), γ=86. 41 (3)°, V= 891. 4(5) , Z=1, Dc= 1. 68 g/cm3, Mr=901. 79, λ=0. 71069, F(000) = 464, μ= 56. 49 cm-1. T= 298 K. Final R=0.073, Rw= 0.081 for 2214 reflections with I> 3σ(I0). The molecule has a dimerstructure with two asymmetrical chlorine bridges. Two Bu5C5H4 and two chlorineatoms around the central atom Yb form a distorted tetrahedral geometry.展开更多
It was first found that diisopropylamido bis(methycylclopentadienyl) ytterbium complex (MeCp)2YbN(i-Pr)2(THF) exhibits extremely high catalytic activity in the polymerization of methyl methacrylate. The reactions can ...It was first found that diisopropylamido bis(methycylclopentadienyl) ytterbium complex (MeCp)2YbN(i-Pr)2(THF) exhibits extremely high catalytic activity in the polymerization of methyl methacrylate. The reactions can be carried out over a quite broad range of polymerization temperatures from -78℃ to 40℃ The results of GPC (gel permeaion chromaography) indicate that the molecular weight distribution (Mw/Mn) becomes broad with the increase of temperature.展开更多
The Nd:YAG laser with a wavelength of 1.064 μm was used to generate plasmas on a high-purity solid ytterbium(70 Yb) target in a vacuum chamber. The soft x-ray time-and space-integration spectra from the Yb plasmas we...The Nd:YAG laser with a wavelength of 1.064 μm was used to generate plasmas on a high-purity solid ytterbium(70 Yb) target in a vacuum chamber. The soft x-ray time-and space-integration spectra from the Yb plasmas were measured in the wavelength range of 1.0–8.5 nm under different power densities. The atomic spectral data of the unresolved transition arrays from highly charged Yb ions were calculated based on Cowan's suite of codes, including configuration interaction. The calculated Gaussian envelope of the emission determined by the weighted spontaneous transition rates was compared with the experimental spectra, and a good agreement between them was obtained. The spatial-temporal evolutions of the plasmas under the experimental conditions are simulated based on the collisional-radiative model, enabling the understanding of the mechanism of the plasma conditions for optimal water window waveband emission output.展开更多
Due to its electron configuration (Xe) 4 f14 6 s2, Ytterbium (Yb) could form divalent oxide, YbO. In this study, the solid-state synthesis of metastable YbO was investigated by the oxidation of Yb metal at normal pres...Due to its electron configuration (Xe) 4 f14 6 s2, Ytterbium (Yb) could form divalent oxide, YbO. In this study, the solid-state synthesis of metastable YbO was investigated by the oxidation of Yb metal at normal pressure using two experimental conditions: 1) heat treatment of Yb metal under Ar gas atmosphere with metal carbonate as an oxygen source;and 2) heat treatment of Yb metal under the continuous gas flow condition using various gas atmospheres. Products were identified using the powder X-ray diffraction and scanning electron microscope. It was found that almost single phase YbO was obtained in the experimental condition 1) using the molar ratio of Ca-CO3/Yb = 0.4. Thermodynamic calculations suggested that the YbO formation be controlled not by thermodynamics but by kinetics, and further that the evaporation of Yb metal in the BN crucible played a key role for the formation of the meta-stable YbO.展开更多
With the rapid development of ytterbium-doped fiber lasers, some obtrusive limitations on power scaling appeared. In order to avoid these problems, a scheme called tandem pumping is introduced into the fiber laser fie...With the rapid development of ytterbium-doped fiber lasers, some obtrusive limitations on power scaling appeared. In order to avoid these problems, a scheme called tandem pumping is introduced into the fiber laser field. In this paper, the optical properties of an ytterbium-doped tandem-pumped fiber oscillator are presented. According to the oscillator profile, the proper gain fiber type and pump wavelength range are picked out, under the comprehensive consideration of laser conversion efficiency and beam quality. In addition, the photodarkening performances of tandem pumping lasers and conventional ones are compared based on practical application, with all possible impact parameters taken into account. Moreover, an all-fibered tandem-pumped oscillator centered at 1079.5 nm is built, in the way of clad pumping by a 1030-rim fiber laser. The laser power of the oscillator reaches 7 W, with an opto-optic efficiency of 82.4%.展开更多
<div style="text-align:justify;"> Environmental barrier coatings (EBCs) play a critical role in mitigating the degradation of SiC<sub>f</sub>/SiC ceramic matrix composites (CMCs) in complex...<div style="text-align:justify;"> Environmental barrier coatings (EBCs) play a critical role in mitigating the degradation of SiC<sub>f</sub>/SiC ceramic matrix composites (CMCs) in complex combustion environment, and improve the service life of thermal engine components. In this paper, by adjusting the parameters of atmospheric plasma spraying (APS), the spraying process of ytterbium disilicate (Yb<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>) under a lower power has been optimized. A two-layer EBC system consisting of ytterbium disilicate and silicon is prepared on the SiC<sub>f</sub>/SiC composite substrate by using optimized technological parameters. The thermal resistance and water oxygen corrosion resistance of such two-layer EBC system are investigated. The results indicate that the current ytterbium disilicate/silicon EBC system exhibits good phase stability, excellent water vapor and oxygen corrosion resistance. However, the exposed silicon bonding layer tends to generate an excessive thermal growth oxide (TGO) layer known as SiO<sub>2</sub>, leading to an early spallation of the coating. </div>展开更多
The rare-earth metal, ytterbium (Yb), was deposited on graphene grown on Si-face SiC, kept at room temperature. Yb was not found to intercalate, destroy or dope the graphene layer before subsequent heating, unlike alk...The rare-earth metal, ytterbium (Yb), was deposited on graphene grown on Si-face SiC, kept at room temperature. Yb was not found to intercalate, destroy or dope the graphene layer before subsequent heating, unlike alkali metals such as Li and Na. Our photoemission results reveal that heating to 300oC promotes Yb intercalation into the graphene-substrate interface. Real-time low energy electron microscopy (LEEM) measurements indicated intercalation to start at a sample temperature of around 220oC. In the intercalation process, Yb penetrates through the graphene and buffer layer and forms bonds to the silicon in the topmost SiC substrate bilayer, as indicated by the shifted components observed in the C 1s, Si 2p, and Yb 4f spectra. The Yb intercalation decouples the buffer layer from the substrate and transforms it into another graphene layer as manifested by the absence of buffer layer spots in the μ-LEED pattern and the appearance of an additional π band in the ARPES spectra, respectively. Moreover, the observed shift of the Dirac point down from the Fermi level by 1.9 eV indicates electron doping of the graphene layer upon Yb intercalation. The Yb intercalated graphene sample was found to be thermodynamically stable up to temperatures around 700oC.展开更多
In this research, Amplified Spontaneous Emission (ASE) spectrum characteristics for a highly Yb3+ doped glass fiber with different pump powers and pump wavelengths are scrutinized. ASE spectral profile and wavelength ...In this research, Amplified Spontaneous Emission (ASE) spectrum characteristics for a highly Yb3+ doped glass fiber with different pump powers and pump wavelengths are scrutinized. ASE spectral profile and wavelength shift corresponding to different optical fiber lengths are measured. Highly-doped Yb3+ fiber lasers in a linear-cavity are both experimentally and analytically investigated. Rate equations are solved using quasi-numerical models. Numerical results are reported for wide range of operating conditions to enable design optimization. The model takes into account the scattering loss and the distributed laser loss power density in strongly pump condition. The effects of various parameters such as pump power, pump wavelength, signal wavelength and fiber length on the output power and laser threshold are studied. Theoretical results are shown to be in good agreement with the experimental data.展开更多
文摘We have studied the structural and atomic transport properties of liquid f-shell Yb in the temperature range 1123 K–1473 K. Pair interactions between atoms are derived using a local pseudopotential. The potential parameters are fitted to the phonon dispersion curve at room temperature. The local pseudopotential used in the present study is computationally more efficient with only three parameters, and it is found to be transferable to the liquid phase without changing the parameters.Since the various computed properties agree with reported theoretical and experimental findings, the adopted fitting scheme is justified. As a significant outcome of the study, we find that(i) the melting in Yb is governed by the Lindemann's law,(ii)the mass transport mechanism obeys the Arrhenius law,(iii) the role of the three-particle correlation function in deriving the velocity autocorrelation function is small,(iv) the mean-square atomic displacement is more sensitive to the choice of interaction potential than the other bulk properties, and(v) liquid Yb does not show liquid–liquid phase transition within the studied temperature range. Further, due to the good description of the structural and mass transport properties, we propose that Yb remains divalent at reduced density.
基金the Fundamental Research Funds for the Central Universities(Grant No.10822041A2038).
文摘In view of the difficulty in calculating the atomic structure parameters of high-Z elements,the Hartree–Fock with relativistic corrections(HFR)theory in combination with the ridge regression(RR)algorithm rather than the Cowan code’s least squares fitting(LSF)method is proposed and applied.By analyzing the energy level structure parameters of the HFR theory and using the fitting experimental energy level extrapolation method,some excited state energy levels of the Yb I(Z=70)atom including the 4f open shell are calculated.The advantages of the ridge regression algorithm are demonstrated by comparing it with Cowan code’s LSF results.In addition,the results obtained by the new method are compared with the experimental results and other theoretical results to demonstrate the reliability and accuracy of our approach.
文摘Selective photoionization of ytterbium isotope is studied numerically based on a three-step photoionization scheme,4f^(14)6s^(21)S_0(0 cm^(-1))→4f~(14)6s6p~3P_1(17992.008 cm^(-1))→(4f~(13)6s~26p)(7/2,3/2)_2(35196.98 cm^(-1))→auto-ionization state(52353 cm^(-1))→Yb^(+),by the density matrix theory with the consideration of atomic hyperfine structures and magnetic sublevels.To examine the physical model,the numerical isotopic abundance of ytterbium is compared with that from mass spectroscopy experiment,showing that they are in good agreement with each other.The excitation process and ionization process of ytterbium,especially for odd isotopes,are discussed and analyzed in detail on this basis.The effects of frequency detuning,power densities,spectral bandwidths,polarization of two excitation lasers,and atomic Doppler broadening on the total ionization yield and isotopic abundance are investigated numerically and the optimal excitation conditions for~(176)Yb enrichment are identified semi-quantitatively.
文摘The based membrane extraction of Th 4+ and Yb 3+ was studied in HBTMPP heptane using a hollow fibber membrane. The separation method of Th 4+ and Yb 3+ was proposed by kinetics competition. The separation operation of Th 4+ and Yb 3+ mixture was carried out by two successive extraction and stripping simultaneously. The concentration ratio of Th 4+ to Yb 3+ is 16 74 in the stripping solution. The recovery and purity of Th 4+ are 71 6% and 95 74% respectively.
文摘<正>The influence of Yb_2O_3 and Pr_2O_3 doping on electrical and gas sensing properties of tin dioxide was studied.A doping content of 0.5wt%～5wt% was investigated by mechanical mixing.The significant improvement on sensitivity and selectivity to 200μg/g hydrogen sulphide gas has been achieved by 3wt% Pr_2O_3 and 5wt% Yb_2O_3 adding.The better response and revovery properties of Pr or Yb doped tin dioxide sensor for 200μg/g hydrogen sulphide gas were found.The maximum sensitivity to H_2S gas is observed at about 120℃.Pr has stronger catalysis than Yb for H_2S reaction on SnO_2 surface.S~ 2-) was oxidized to S~ 6+) on the SnO_2 surface according to XPS.
文摘Light-emitting ytterbium-doped tantalum-oxide thin films were prepared using a simple co-sputtering method for the first time. Sharp photoluminescence peaks having a wavelength of around 980 nm were observed from films annealed from 700°C to 1000°C for 10 to 40 min. The strongest intensity of the 980-nm peak was obtained from a film deposited using three ytterbium-oxide pellets and annealed at 800°C for 20 min. Such rare-earth doped tantalum-oxide sputtered films can be used as high-refractive-index materials of autocloned photonic crystals that can be applied to novel light-emitting devices, and they will also be used as both anti-reflection and down-conversion layers for realizing high-efficiency silicon solar cells.
文摘The ytterbium complex of isonicotinoyl hydrazone was synthesized and the structure was determined by X ray diffraction analysis. The crystal and molecular structure of the title complex [Yb 2(L) 3](OH) 3 shows that the complex has two identical nine coordinated ytterbium ions with each surrounded by N 3O 6 donor set. Two ytterbium ions are bridged by three phenolate oxygen atoms. The geometry around each ytterbium ions can be considered as a three capped trigonal prism.
基金the Science Foundations of CSTC (2007BB4385 , 2007BB4391)Education Committee of Chongqing (KJ060515 , KJ050502)
文摘Rare earth doped orthovanadate crystal LuVO4∶Yb3+ shows high power laser applications because of the low quantum defect and the high thermal conductivity. Since electronic paramagnetic resonance (EPR) is a powerful tool to analyze the electronic properties and the local structures of paramagnetic impurity centers in crystals, the EPR spectra of the Yb3+ centers in LuVO4 crystal were measured recently. However, the above experimental results have not been theoretically interpreted. In this work, The EPR g factors and the hyperfine structure constants of 171Yb3+ and 173Yb3+ isotopes in LuVO4 crystal were theoretically studied from the perturbation formulae of the spin Hamiltonian parameters for 4f13 ion in tetragonal symmetry. The needed crystal parameters were obtained from the superposition model and the local structure of the studied system. The calculated results were in reasonable agreement with the observed values.
文摘The background absorption of Lu and Yb matrices was studied. The experimental results show that there is a significantly wavelength dependent. The effects of ashing temperature, heating mode, atomization temperature, recording time and matrix modifiers affecting the non specific absorption of Lu and Yb matrices were discussed.
文摘The mass-transfer kinetics of ytterbium between aqueous solutions and heptane solutions of CA- 12 and CA-12-HEHEHP have been studied by using a constant interfacial area cell with laminar flow. The results have been interpreted according to a series of reversible interfacial reactions. In this work, it has been discovered that HEHEHP can increase the rate of ytterbium extraction by CA-12.
文摘The complex [(ButC5H’4)2YbCl]2, crystallized in the triclinic system,space group P1, with a=8. 392(3), b=9. 402(3), c=12. 418(5) , a=68. 78(3),P= 77. 43(3), γ=86. 41 (3)°, V= 891. 4(5) , Z=1, Dc= 1. 68 g/cm3, Mr=901. 79, λ=0. 71069, F(000) = 464, μ= 56. 49 cm-1. T= 298 K. Final R=0.073, Rw= 0.081 for 2214 reflections with I> 3σ(I0). The molecule has a dimerstructure with two asymmetrical chlorine bridges. Two Bu5C5H4 and two chlorineatoms around the central atom Yb form a distorted tetrahedral geometry.
文摘It was first found that diisopropylamido bis(methycylclopentadienyl) ytterbium complex (MeCp)2YbN(i-Pr)2(THF) exhibits extremely high catalytic activity in the polymerization of methyl methacrylate. The reactions can be carried out over a quite broad range of polymerization temperatures from -78℃ to 40℃ The results of GPC (gel permeaion chromaography) indicate that the molecular weight distribution (Mw/Mn) becomes broad with the increase of temperature.
基金support from Guangdong Major Project of Basic and Applied Basic Research (No. 2019B030302003)Hubei Key Laboratory of Optical Information and Pattern Recognition open fund (No. 201908)。
文摘The Nd:YAG laser with a wavelength of 1.064 μm was used to generate plasmas on a high-purity solid ytterbium(70 Yb) target in a vacuum chamber. The soft x-ray time-and space-integration spectra from the Yb plasmas were measured in the wavelength range of 1.0–8.5 nm under different power densities. The atomic spectral data of the unresolved transition arrays from highly charged Yb ions were calculated based on Cowan's suite of codes, including configuration interaction. The calculated Gaussian envelope of the emission determined by the weighted spontaneous transition rates was compared with the experimental spectra, and a good agreement between them was obtained. The spatial-temporal evolutions of the plasmas under the experimental conditions are simulated based on the collisional-radiative model, enabling the understanding of the mechanism of the plasma conditions for optimal water window waveband emission output.
文摘Due to its electron configuration (Xe) 4 f14 6 s2, Ytterbium (Yb) could form divalent oxide, YbO. In this study, the solid-state synthesis of metastable YbO was investigated by the oxidation of Yb metal at normal pressure using two experimental conditions: 1) heat treatment of Yb metal under Ar gas atmosphere with metal carbonate as an oxygen source;and 2) heat treatment of Yb metal under the continuous gas flow condition using various gas atmospheres. Products were identified using the powder X-ray diffraction and scanning electron microscope. It was found that almost single phase YbO was obtained in the experimental condition 1) using the molar ratio of Ca-CO3/Yb = 0.4. Thermodynamic calculations suggested that the YbO formation be controlled not by thermodynamics but by kinetics, and further that the evaporation of Yb metal in the BN crucible played a key role for the formation of the meta-stable YbO.
文摘With the rapid development of ytterbium-doped fiber lasers, some obtrusive limitations on power scaling appeared. In order to avoid these problems, a scheme called tandem pumping is introduced into the fiber laser field. In this paper, the optical properties of an ytterbium-doped tandem-pumped fiber oscillator are presented. According to the oscillator profile, the proper gain fiber type and pump wavelength range are picked out, under the comprehensive consideration of laser conversion efficiency and beam quality. In addition, the photodarkening performances of tandem pumping lasers and conventional ones are compared based on practical application, with all possible impact parameters taken into account. Moreover, an all-fibered tandem-pumped oscillator centered at 1079.5 nm is built, in the way of clad pumping by a 1030-rim fiber laser. The laser power of the oscillator reaches 7 W, with an opto-optic efficiency of 82.4%.
文摘<div style="text-align:justify;"> Environmental barrier coatings (EBCs) play a critical role in mitigating the degradation of SiC<sub>f</sub>/SiC ceramic matrix composites (CMCs) in complex combustion environment, and improve the service life of thermal engine components. In this paper, by adjusting the parameters of atmospheric plasma spraying (APS), the spraying process of ytterbium disilicate (Yb<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>) under a lower power has been optimized. A two-layer EBC system consisting of ytterbium disilicate and silicon is prepared on the SiC<sub>f</sub>/SiC composite substrate by using optimized technological parameters. The thermal resistance and water oxygen corrosion resistance of such two-layer EBC system are investigated. The results indicate that the current ytterbium disilicate/silicon EBC system exhibits good phase stability, excellent water vapor and oxygen corrosion resistance. However, the exposed silicon bonding layer tends to generate an excessive thermal growth oxide (TGO) layer known as SiO<sub>2</sub>, leading to an early spallation of the coating. </div>
文摘The rare-earth metal, ytterbium (Yb), was deposited on graphene grown on Si-face SiC, kept at room temperature. Yb was not found to intercalate, destroy or dope the graphene layer before subsequent heating, unlike alkali metals such as Li and Na. Our photoemission results reveal that heating to 300oC promotes Yb intercalation into the graphene-substrate interface. Real-time low energy electron microscopy (LEEM) measurements indicated intercalation to start at a sample temperature of around 220oC. In the intercalation process, Yb penetrates through the graphene and buffer layer and forms bonds to the silicon in the topmost SiC substrate bilayer, as indicated by the shifted components observed in the C 1s, Si 2p, and Yb 4f spectra. The Yb intercalation decouples the buffer layer from the substrate and transforms it into another graphene layer as manifested by the absence of buffer layer spots in the μ-LEED pattern and the appearance of an additional π band in the ARPES spectra, respectively. Moreover, the observed shift of the Dirac point down from the Fermi level by 1.9 eV indicates electron doping of the graphene layer upon Yb intercalation. The Yb intercalated graphene sample was found to be thermodynamically stable up to temperatures around 700oC.
文摘In this research, Amplified Spontaneous Emission (ASE) spectrum characteristics for a highly Yb3+ doped glass fiber with different pump powers and pump wavelengths are scrutinized. ASE spectral profile and wavelength shift corresponding to different optical fiber lengths are measured. Highly-doped Yb3+ fiber lasers in a linear-cavity are both experimentally and analytically investigated. Rate equations are solved using quasi-numerical models. Numerical results are reported for wide range of operating conditions to enable design optimization. The model takes into account the scattering loss and the distributed laser loss power density in strongly pump condition. The effects of various parameters such as pump power, pump wavelength, signal wavelength and fiber length on the output power and laser threshold are studied. Theoretical results are shown to be in good agreement with the experimental data.
