Objective:This study is aimed to measure the Bremsstrahlung spectrum produced by ^(204)Tl in barium compounds such as BaCl_(2),BaCO_(3),Ba(NO_(3))_(2),BaSO_(4) and BaTiO_(3).It is also aimed to study the attenuation o...Objective:This study is aimed to measure the Bremsstrahlung spectrum produced by ^(204)Tl in barium compounds such as BaCl_(2),BaCO_(3),Ba(NO_(3))_(2),BaSO_(4) and BaTiO_(3).It is also aimed to study the attenuation of bremsstrahlung in the given compounds.Materials and methods:Bremsstrahlung spectrum and yield ^(204)Tl in barium compounds such as BaCl_(2),BaCO_(3),Ba(NO_(3))_(2),BaSO_(4) and BaTiO_(3) have been measured using NaI(Tl)detector and multichannel analyzer(MCA).The beta stopper technique is employed to measure the bremsstrahlung spectrum.Liden-Starfelt procedure is used to unfold the measured raw spectrum.The unfolded spectra were compared with Tseng–Pratt theory.Results:The measured spectra agree with the theory at low energy end of spectrum and some deviation(less than 10%)at higher energy end of spectrum.Attenuation of the bremsstrahlung,excited by ^(204)Tl beta emitters in the same compounds,is also studied.The measured attenuation parameter is not constant with absorber thickness and it increases with increasing Zmod of the absorber.Conclusion:The discrepancy between measured spectrum and theory increases with Zmod of the target compound and photon energy.The attenuation of bremsstrahlung may be represented as a combination of a large number of exponential terms rather than single term.展开更多
W-type barium ferrites doped with Gd^3＋,Ba1-xGdx（Zn0.3Co0.7）2Fe16O27（x = 0,0.05,0.10,0.15,0.20）,were prepared by a sol-gel method.The effects of Gd^3＋ substitution on their microstructure,electromagnetic propert...W-type barium ferrites doped with Gd^3＋,Ba1-xGdx（Zn0.3Co0.7）2Fe16O27（x = 0,0.05,0.10,0.15,0.20）,were prepared by a sol-gel method.The effects of Gd^3＋ substitution on their microstructure,electromagnetic properties and microwave absorptive behavior were analyzed.The XRD patterns showed the single phase of W-type barium ferrite when x ≤ 0.15.Microwave electromagnetic properties of samples were studied at the frequency range from 2 GHz to 18 GHz using a network analyzer（Agilent 8722ET）.The complex permittivity ε（ε＇,ε＇＇） increased gradually when x ≤ 0.10,but it decreased as x = 0.15.The real permeability（μ＇） decreased with the increase of Gd^3＋ content,while the imaginary permeability（μ＇＇） increased when x ≤ 0.10.All these reasons were discussed using the electromagnetic theory.Furthermore,the ferrite-epoxy compound coating materials with 80 wt.% of Ba0.9Gd0.1（Zn0.3Co0.7）2Fe16O27 were prepared to measure the microwave absorbing properties.The maximum of reflection loss（RL） reached about-27 dB and RL was below-10 dB in the frequency range of 8-18 GHz when the thickness was 1.92 mm.展开更多
A new two-dimensional （2D） barium（AA） coordination polymer [Ba（3-NPA）]n （1） has been obtained by the hydro/solvothermal reaction of the corresponding metal salt with 3-nitrophthalic acid （3-NPAH2）. Compound ...A new two-dimensional （2D） barium（AA） coordination polymer [Ba（3-NPA）]n （1） has been obtained by the hydro/solvothermal reaction of the corresponding metal salt with 3-nitrophthalic acid （3-NPAH2）. Compound 1 was characterized by infrared spectrum, elemental analysis, powder X-ray diffraction （PXRD） and single-crystal X-ray diffraction analysis. Compound 1 crystallizes in triclinic, space group Pī with a = 4.9611（3）, b = 7.2599（4）, c = 12.9463（8） A, α = 89.0892（2）, β = 80.546（2）, γ = 73.211（2）°, V = 440.1（5） A3, Z = 2, C8H3BaNO6, Mr = 346.45, Dc = 2.614 g·cm^-3, μ = 4.526 mm^-1, S = 1.035, F（000） = 324, R = 0.0168 and wR = 0.0471 for 1712 observed reflections with I 〉 2σ（I）. （Aρ）max = 0.458, （Aρ）min = -0.565 e·A-3 and （A/σ）max = 0.001. In compound 1, each 3-NPA^2- ligand links six Ba（II） ions and each Ba（II） ion attaches to six 3-NPA^2- ligands to form an inorganic layer structure in the ab-plane. The phenyl groups of 3-NPA^2- ligands are grafted on the two sides of the inorganic layer, resulting in a two-dimensional （2D） layered structure. Furthermore, the thermal stability and luminescent properties of compound 1 have also been investigated in detail.展开更多
New composition perovskite-type compounds with formula Sr0.6Bi0.4FeO2.7,Sr1-xBixFeO3-y(x=0.1 to 0. 9 in interveral of 0.1),and Ba1.5Pt0.5Mn2O6 have been synthsized and structurally characterized.The crystal structure ...New composition perovskite-type compounds with formula Sr0.6Bi0.4FeO2.7,Sr1-xBixFeO3-y(x=0.1 to 0. 9 in interveral of 0.1),and Ba1.5Pt0.5Mn2O6 have been synthsized and structurally characterized.The crystal structure of Sr0.6Bi0.4FeO2.7has been determined by X-ray single crystal diffraction,and the data of neutron powder diffraction collected at both room temperature and elevated temperature(380℃).The compound Sr0.6Bi0.4FeO2.7 crystallizes in the cubic space group of Pm3m with Z=1,a=3.9330(6) at room temperature,a=3.9498(6)A at 380℃.The magnetic structure from the neutron powder diffraction data collected at room temperature is consistent with a simple G-type antiferromagnetism and has a magnetic moment of 4.98 μB per Fe atom.The structures of Sr1-xBixFeO3-y with x other than 0.4 were also refined from the X-ray powder diffraction data.The data were consistent with a tetragonal cell when x=0.1,a rhombohedral cell when x= 0.9,and a cubic cell for x=0.2～0.8.From single crystal X-ray diffraction data,Ba1.5Pt0.5Mn2O6 crystallizes in hexagonal space group of P63mc with a= 5.7722 (6),c=4.4504(9),V=128.42(2),Z=1.The Sr(1-x)BixFeO(3-y)are found to be a good electronic and ionic conductor.展开更多
In December of 1988, the authors successfully developed a high Jc Y-Ba-Cu-O superconductor tape on a nickel substrate by means of powder rolling. The tape is 0.94mm2 in cross-section and its critical current is 21.0A ...In December of 1988, the authors successfully developed a high Jc Y-Ba-Cu-O superconductor tape on a nickel substrate by means of powder rolling. The tape is 0.94mm2 in cross-section and its critical current is 21.0A at 77K and in zero applied field. The microstructures of the tapes with different Jc were analysed by TEM. The result shows that the tapes with different Jc have different microstructures. From the facts, it can be concluded that making the grain boundary 'clean' might have some effects on the weak-link problem and the twin zone might act as fluxing pinning centers. Therefore, to purify the grain boundary, to thin the twin and to homogenize the microstructure will be of benefit in increasing Jc.展开更多
A high-efficiency eye-safe Raman laser was demonstrated by use of the third Stokes radiation in a Ba（NO3）2 crystal pumped by a 1064-nm Nd：YAG laser. The output wavelength of the Raman laser was 1598.5 nm with a ful...A high-efficiency eye-safe Raman laser was demonstrated by use of the third Stokes radiation in a Ba（NO3）2 crystal pumped by a 1064-nm Nd：YAG laser. The output wavelength of the Raman laser was 1598.5 nm with a full-width at half-maximum （FWHM） of 1.5 nm. With an incident pump energy of 140 mJ, a maximum of 18-mJ Raman output energy was generated at a repetition rate of 30 Hz, corresponding to an optical-to-optical conversion efficiency of 12.9%. The Raman pulse duration was shortened to 2.9 ns compared with that of the pump pulse of 19.3 ns. The eye-safe solid-state Raman laser is expected to have wide applications in range-finding, telemetry, laser radar, and other aspects.展开更多
We demonstrate wavelength-selectable visible emissions from a miniature crystalline laser that combines the stimulated Raman scattering （SRS） effect in an Nd：YVO4 crystal with intracavity frequency mixing in an ang...We demonstrate wavelength-selectable visible emissions from a miniature crystalline laser that combines the stimulated Raman scattering （SRS） effect in an Nd：YVO4 crystal with intracavity frequency mixing in an angle-tuned beta barium borate （BBO） crystal. The presented laser is operating on demand at any one of three wavelengths in the green-yellow spectral region. Up to 600, 560, and 200 mW output powers at 559, 532, and 588 nm, respectively, are obtained from the continuous wave （CW） laser having a 18 mm long resonator and a 3.8 W laser diode end pumping. The pump threshold for each visible wavelength is less than 0.4 W.展开更多
Traditional pyrotechnic compositions formed by mechanically mixing flammable and oxidative agents face the problems of complex formulations,inaccurate chemical stoichiometry,and inefficient colour-producing reactions....Traditional pyrotechnic compositions formed by mechanically mixing flammable and oxidative agents face the problems of complex formulations,inaccurate chemical stoichiometry,and inefficient colour-producing reactions.Emerging molecular perovskite energetic materials with embedded ternary ions have evolved into a new platform for developing explosives,propellants,ignition materials,and energetic biocides,taking advantage of their easy preparation and high adjustability.However,their potential in pyrotechnic applications has not yet been investigated.Herein,by assembling barium(II)perchlorate with imidazolium(Him+)and quinuclidinium(Hqe^(+))ions,we obtained two new energetic compounds,(Him)(Ba)(ClO_(4))_(3)(IBP)with a cubic perovskite structure,and(Hqe)_(2)(Ba)(ClO_(4))_(4)(QBP)with a layered perovskite structure.Both IBP and QBP have decomposition peak temperatures exceeding 290℃ and much higher moisture stabilities than barium perchlorate.With a layered structure,QBP has significantly lower friction sensitivity(144 N)than IBP(5 N).Moreover,the tight stacking of barium(II),oxidative perchlorate ions,and carbon-rich fuel components at the molecular level allows QBP to exhibit high-efficiency and stable combustion,outputting a maximum combustion pressure of up to 550 kPa,a maximum pressure pulse rate of up to 10.48 MPa s^(-1),and a bright green flame.These findings demonstrate well that molecular perovskite energetic compounds integrating a luminescent component,oxidative anions,and organic cations are promising contenders for next-generation pyrotechnic materials.展开更多
A novel Tm^3＋/Yb^3＋ triply-doped glass ceramics containing BaF2 nano-crystals are successfully prepared. Fluoride nanocrystals BaF2 are successfully precipitated in glass matrix, which is affirmed by the X-ray diffr...A novel Tm^3＋/Yb^3＋ triply-doped glass ceramics containing BaF2 nano-crystals are successfully prepared. Fluoride nanocrystals BaF2 are successfully precipitated in glass matrix, which is affirmed by the X-ray diffraction results. The intense blue （476 nm）, green （543 nm）, and red （656 nm） emissions of the glass ceramics are simultaneously observed at room temperature under 980-am excitation, and the emission luminescence intensity increases significantly compared with the precursor glass, which is attributed to the low phonon energy of fluoride nanocrystals when rare-earth ions are incorporated into the precipitated BaF2 nanocrystals. Under 980-nm excitation at 400 mW, the international commission on illumination （CIE） chromaticity coordinate （X = 0.278, Y = 0.358） of the tridoped oxyfluoride glass ceramics＇ upconversion emissions is close to the standard white-light illumination （X = 0.333, Y= 0.333）. The results indicate that Tm^3＋/Yb^3＋ triply doped glass ceramics can act as suitable materials for potential three-dimensional displays applications.展开更多
Materials science is an interdisciplinary field applying the properties of matter to various areas of science and engineering. This scientific field investigates the relationship between the structure of materials at ...Materials science is an interdisciplinary field applying the properties of matter to various areas of science and engineering. This scientific field investigates the relationship between the structure of materials at atomic or molecular scales and their macroscopic properties. It incorporates elements of applied physics and chemistry. With significant media attention focused on nanoscience and nanotechnology in recent years, materials science has been propelled to the forefront at many universities. Materials science encompasses various classes of materials, including electronic materials, functional ceramics, magnesium, material and processes for flat-panel displays, eco/environmental materials, sustainable energy materials, transportation materials, electronic packaging materials, etc.展开更多
文摘Objective:This study is aimed to measure the Bremsstrahlung spectrum produced by ^(204)Tl in barium compounds such as BaCl_(2),BaCO_(3),Ba(NO_(3))_(2),BaSO_(4) and BaTiO_(3).It is also aimed to study the attenuation of bremsstrahlung in the given compounds.Materials and methods:Bremsstrahlung spectrum and yield ^(204)Tl in barium compounds such as BaCl_(2),BaCO_(3),Ba(NO_(3))_(2),BaSO_(4) and BaTiO_(3) have been measured using NaI(Tl)detector and multichannel analyzer(MCA).The beta stopper technique is employed to measure the bremsstrahlung spectrum.Liden-Starfelt procedure is used to unfold the measured raw spectrum.The unfolded spectra were compared with Tseng–Pratt theory.Results:The measured spectra agree with the theory at low energy end of spectrum and some deviation(less than 10%)at higher energy end of spectrum.Attenuation of the bremsstrahlung,excited by ^(204)Tl beta emitters in the same compounds,is also studied.The measured attenuation parameter is not constant with absorber thickness and it increases with increasing Zmod of the absorber.Conclusion:The discrepancy between measured spectrum and theory increases with Zmod of the target compound and photon energy.The attenuation of bremsstrahlung may be represented as a combination of a large number of exponential terms rather than single term.
基金supported by the Pre-research Foundation of CPLA General Equipment Department (NO.9140A××××6401)
文摘W-type barium ferrites doped with Gd^3＋,Ba1-xGdx（Zn0.3Co0.7）2Fe16O27（x = 0,0.05,0.10,0.15,0.20）,were prepared by a sol-gel method.The effects of Gd^3＋ substitution on their microstructure,electromagnetic properties and microwave absorptive behavior were analyzed.The XRD patterns showed the single phase of W-type barium ferrite when x ≤ 0.15.Microwave electromagnetic properties of samples were studied at the frequency range from 2 GHz to 18 GHz using a network analyzer（Agilent 8722ET）.The complex permittivity ε（ε＇,ε＇＇） increased gradually when x ≤ 0.10,but it decreased as x = 0.15.The real permeability（μ＇） decreased with the increase of Gd^3＋ content,while the imaginary permeability（μ＇＇） increased when x ≤ 0.10.All these reasons were discussed using the electromagnetic theory.Furthermore,the ferrite-epoxy compound coating materials with 80 wt.% of Ba0.9Gd0.1（Zn0.3Co0.7）2Fe16O27 were prepared to measure the microwave absorbing properties.The maximum of reflection loss（RL） reached about-27 dB and RL was below-10 dB in the frequency range of 8-18 GHz when the thickness was 1.92 mm.
基金supported by NNSFC(21101019)the Materials Key subject of Chizhou University(2011XK04)
文摘A new two-dimensional （2D） barium（AA） coordination polymer [Ba（3-NPA）]n （1） has been obtained by the hydro/solvothermal reaction of the corresponding metal salt with 3-nitrophthalic acid （3-NPAH2）. Compound 1 was characterized by infrared spectrum, elemental analysis, powder X-ray diffraction （PXRD） and single-crystal X-ray diffraction analysis. Compound 1 crystallizes in triclinic, space group Pī with a = 4.9611（3）, b = 7.2599（4）, c = 12.9463（8） A, α = 89.0892（2）, β = 80.546（2）, γ = 73.211（2）°, V = 440.1（5） A3, Z = 2, C8H3BaNO6, Mr = 346.45, Dc = 2.614 g·cm^-3, μ = 4.526 mm^-1, S = 1.035, F（000） = 324, R = 0.0168 and wR = 0.0471 for 1712 observed reflections with I 〉 2σ（I）. （Aρ）max = 0.458, （Aρ）min = -0.565 e·A-3 and （A/σ）max = 0.001. In compound 1, each 3-NPA^2- ligand links six Ba（II） ions and each Ba（II） ion attaches to six 3-NPA^2- ligands to form an inorganic layer structure in the ab-plane. The phenyl groups of 3-NPA^2- ligands are grafted on the two sides of the inorganic layer, resulting in a two-dimensional （2D） layered structure. Furthermore, the thermal stability and luminescent properties of compound 1 have also been investigated in detail.
文摘New composition perovskite-type compounds with formula Sr0.6Bi0.4FeO2.7,Sr1-xBixFeO3-y(x=0.1 to 0. 9 in interveral of 0.1),and Ba1.5Pt0.5Mn2O6 have been synthsized and structurally characterized.The crystal structure of Sr0.6Bi0.4FeO2.7has been determined by X-ray single crystal diffraction,and the data of neutron powder diffraction collected at both room temperature and elevated temperature(380℃).The compound Sr0.6Bi0.4FeO2.7 crystallizes in the cubic space group of Pm3m with Z=1,a=3.9330(6) at room temperature,a=3.9498(6)A at 380℃.The magnetic structure from the neutron powder diffraction data collected at room temperature is consistent with a simple G-type antiferromagnetism and has a magnetic moment of 4.98 μB per Fe atom.The structures of Sr1-xBixFeO3-y with x other than 0.4 were also refined from the X-ray powder diffraction data.The data were consistent with a tetragonal cell when x=0.1,a rhombohedral cell when x= 0.9,and a cubic cell for x=0.2～0.8.From single crystal X-ray diffraction data,Ba1.5Pt0.5Mn2O6 crystallizes in hexagonal space group of P63mc with a= 5.7722 (6),c=4.4504(9),V=128.42(2),Z=1.The Sr(1-x)BixFeO(3-y)are found to be a good electronic and ionic conductor.
文摘In December of 1988, the authors successfully developed a high Jc Y-Ba-Cu-O superconductor tape on a nickel substrate by means of powder rolling. The tape is 0.94mm2 in cross-section and its critical current is 21.0A at 77K and in zero applied field. The microstructures of the tapes with different Jc were analysed by TEM. The result shows that the tapes with different Jc have different microstructures. From the facts, it can be concluded that making the grain boundary 'clean' might have some effects on the weak-link problem and the twin zone might act as fluxing pinning centers. Therefore, to purify the grain boundary, to thin the twin and to homogenize the microstructure will be of benefit in increasing Jc.
基金This work was supported by the National High Technology Project (No. 2004AA846020) and the National Natural Science Foundation of China (No. 10334110).
文摘A high-efficiency eye-safe Raman laser was demonstrated by use of the third Stokes radiation in a Ba（NO3）2 crystal pumped by a 1064-nm Nd：YAG laser. The output wavelength of the Raman laser was 1598.5 nm with a full-width at half-maximum （FWHM） of 1.5 nm. With an incident pump energy of 140 mJ, a maximum of 18-mJ Raman output energy was generated at a repetition rate of 30 Hz, corresponding to an optical-to-optical conversion efficiency of 12.9%. The Raman pulse duration was shortened to 2.9 ns compared with that of the pump pulse of 19.3 ns. The eye-safe solid-state Raman laser is expected to have wide applications in range-finding, telemetry, laser radar, and other aspects.
文摘We demonstrate wavelength-selectable visible emissions from a miniature crystalline laser that combines the stimulated Raman scattering （SRS） effect in an Nd：YVO4 crystal with intracavity frequency mixing in an angle-tuned beta barium borate （BBO） crystal. The presented laser is operating on demand at any one of three wavelengths in the green-yellow spectral region. Up to 600, 560, and 200 mW output powers at 559, 532, and 588 nm, respectively, are obtained from the continuous wave （CW） laser having a 18 mm long resonator and a 3.8 W laser diode end pumping. The pump threshold for each visible wavelength is less than 0.4 W.
基金supported by NSFC(U2341287 and 22488101)Guangzhou Science and Technology Programme(2024A04J6499)Fundamental Research Funds for the Central Universities,Sun Yat-Sen University(23lgzy001).
文摘Traditional pyrotechnic compositions formed by mechanically mixing flammable and oxidative agents face the problems of complex formulations,inaccurate chemical stoichiometry,and inefficient colour-producing reactions.Emerging molecular perovskite energetic materials with embedded ternary ions have evolved into a new platform for developing explosives,propellants,ignition materials,and energetic biocides,taking advantage of their easy preparation and high adjustability.However,their potential in pyrotechnic applications has not yet been investigated.Herein,by assembling barium(II)perchlorate with imidazolium(Him+)and quinuclidinium(Hqe^(+))ions,we obtained two new energetic compounds,(Him)(Ba)(ClO_(4))_(3)(IBP)with a cubic perovskite structure,and(Hqe)_(2)(Ba)(ClO_(4))_(4)(QBP)with a layered perovskite structure.Both IBP and QBP have decomposition peak temperatures exceeding 290℃ and much higher moisture stabilities than barium perchlorate.With a layered structure,QBP has significantly lower friction sensitivity(144 N)than IBP(5 N).Moreover,the tight stacking of barium(II),oxidative perchlorate ions,and carbon-rich fuel components at the molecular level allows QBP to exhibit high-efficiency and stable combustion,outputting a maximum combustion pressure of up to 550 kPa,a maximum pressure pulse rate of up to 10.48 MPa s^(-1),and a bright green flame.These findings demonstrate well that molecular perovskite energetic compounds integrating a luminescent component,oxidative anions,and organic cations are promising contenders for next-generation pyrotechnic materials.
基金supported by the National Natural Science Foundation of China(Nos.60508014 and 50772102)the Program for New Century Excellent Talents in University (No.NCET-07-0786)+1 种基金the Science Technology Project of Zhejiang Province(No.2008C21162)the Natural Science Foundation of Zhejiang Province(No. R406007)
文摘A novel Tm^3＋/Yb^3＋ triply-doped glass ceramics containing BaF2 nano-crystals are successfully prepared. Fluoride nanocrystals BaF2 are successfully precipitated in glass matrix, which is affirmed by the X-ray diffraction results. The intense blue （476 nm）, green （543 nm）, and red （656 nm） emissions of the glass ceramics are simultaneously observed at room temperature under 980-am excitation, and the emission luminescence intensity increases significantly compared with the precursor glass, which is attributed to the low phonon energy of fluoride nanocrystals when rare-earth ions are incorporated into the precipitated BaF2 nanocrystals. Under 980-nm excitation at 400 mW, the international commission on illumination （CIE） chromaticity coordinate （X = 0.278, Y = 0.358） of the tridoped oxyfluoride glass ceramics＇ upconversion emissions is close to the standard white-light illumination （X = 0.333, Y= 0.333）. The results indicate that Tm^3＋/Yb^3＋ triply doped glass ceramics can act as suitable materials for potential three-dimensional displays applications.
文摘Materials science is an interdisciplinary field applying the properties of matter to various areas of science and engineering. This scientific field investigates the relationship between the structure of materials at atomic or molecular scales and their macroscopic properties. It incorporates elements of applied physics and chemistry. With significant media attention focused on nanoscience and nanotechnology in recent years, materials science has been propelled to the forefront at many universities. Materials science encompasses various classes of materials, including electronic materials, functional ceramics, magnesium, material and processes for flat-panel displays, eco/environmental materials, sustainable energy materials, transportation materials, electronic packaging materials, etc.
