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1.
Nb3Al AND Nb3(Al,Ge) tapes with excellent superconducting properties have been fabricated using high energy density laser beam irradiation, irradiations were carried out continuously on Nb-25at%AI and Nb-20at%Al -5at%Ge tapes prepared by powder metallurgical processing. With the high power density and short irradiation time, the tape could be heated and cooled much faster than a tape heat treated by conventional methods. The results were fine structure and large critical current density Jc values at high magnetic fields. Jc at 23 Tesla was over 104 A/cm2. This value was much greater than that obtained from a commercial Nb3Sn superconductor. New continuous irradiation systems have been developed for scale-up development. Nb3Al tapes 10 m in length were successfully fabricated. There was some scatter in Jc along the tape length. Small coil tests in magnetic fields indicated that the tape had excellent stability against a flux jump and mechanical strain. 相似文献
2.
We report measurements of the energy transfer between Er3+ and Ce3+ in Y2O3. The transition between the Er3+ 4I11/2 and 4I13/2 excited states can be stimulated by energy transfer to Ce3+, augmenting the population in the 4I13/2 state at the expense of that in the 4I11/2 state. Experiments were performed on Y2O3 planar waveguides doped with 0.2 at.% erbium and 0–0.42 at.% cerium by ion implantation. From measurements of Er3+ decay rates as a function of cerium concentration we derive an energy transfer rate constant of 1.3×10−18 cm3/s. The efficiency of the energy transfer amounts to 0.47 at 0.42 at.% cerium. The energy transfer rate constant measured in Y2O3 is two times smaller for Er3+→Ce3+ than that for Er3+→Eu3+ in the same material. 相似文献
3.
This paper reports the preparation process and the long lasting phosphorescence of the Sr4Al14O25:Eu2+,Dy3+ thin films obtained by magnetron sputtering. Phosphorescence was achieved by annealing the films in reducing atmosphere. Sr4Al14O25 thin film was obtained when the films were treated at 1200 °C, while SrAl2O4 was generated as the intermediate phase during the annealing process. Sr4Al14O25:Eu2+,Dy3+ film generated an emission at 485 nm, and SrAl2O4:Eu2+,Dy3+ film showed an emission peaking at 515 nm. Afterglow characteristics were observed for both films, and Sr4Al14O25:Eu2+,Dy3+ film showed a better afterglow property than the SrAl2O4:Eu2+,Dy3+ film due to a deeper trap level and a higher trap concentration formed in the thin films. 相似文献
4.
We have measured Raman spectra of fluorine-doped SiO2 (SiOF) films and quartz glass. From a comparison between Raman spectra of the SiO2 film and quartz glass, it has been found that the SiO2 film is under compressive stress and that it has more threefold ring defects than quartz glass. Raman bands from threefold and fourfold ring defects in SiOF films become week as the fluorine/oxygen (F/O) ratio increases and as the stress decreases. The decrease of intensities of these Raman bands shows that ring defects in SiOF films decrease as the F/O ratio increases and as the stress decreases. The triply degenerated ω4 mode at 460 cm−1 becomes sharp as the F/O ratio increases and as the stress decreases. Furthermore, the peak-frequency of ω1 mode around 820 cm−1 decreases with a decrease of stresses whereas that of ω3 mode around 1065 cm−1 increases. These results can be well understood in terms of a decrease of O-Si-O bonding angle caused by relaxation of stresses. 相似文献
5.
Ta2O5 thin films were deposited onto monocrystalline silicon surfaces by magnetron reactive sputtering. When the Ta2O5 films are employed as antireflection coatings, the reflectance of the original silicon surface diminishes from about 30% to approximately 3%. At the same time, a very low absorption coefficient (less than 103 cm-1) for the Ta2O5 films below their fundamental absorption edge (hv < 4.2 eV) is obtained from reflectance and transmittance spectra of Ta2O5 deposited onto quartz substrates. Finally, the technique of reactive sputtering is considered from the point of view of preparing antireflection coatings for solar cells. 相似文献
6.
以Li2CO3与锐钛矿型TiO2为原料,六水合硝酸钇(Y(NO3)3·6H2O)为钇源,采用球磨辅助固相法合成了Li4Ti5-xYxO12(x=0,0.05,0.10,0.15,0.20)负极材料。通过X射线衍射分析(XRD)、扫描电镜(SEM)、能谱仪(EDS)与X射线光电子能谱(XPS)分别对材料的物相与形貌进行表征分析,并利用电化学工作站对材料的电化学性能与电荷输运特性进行测试。结果表明,Y3+掺杂没有影响尖晶石型Li4Ti5O12(LTO)材料的尖晶石结构,x=0.15时,Li4Ti4.85Y0.15O12样品的离子与电子电导率分别为2.68×10-7 S·cm-1和1.49×10-9 S·cm-1,比本征材料提升了1个数量级,表现出良好的电荷输运特性。电化学测试表明,Li4Ti4.85Y0.15O12样品在0.1 C倍率首次放电比容量可达171 mAh·g-1,且在10 C与20 C高倍率下仍然拥有102 mAh·g-1和79 mAh·g-1的较高比容量,循环200周次后容量保持率分别为92.6%和89.1%,表现出良好的倍率特性。 相似文献
7.
The kinetics of electrode reaction was investigated by cyclic voltammetry, and cyclic voltammograms show that the reversibility of the Fe(bpy)32+/Fe(bpy)33+ electrode reaction is better than that of the Zn/Zn2+ electrode reaction on the graphite disc. However, the Fe(bpy)32+ ion diffusion in electrolyte is subject to greater resistance than that of the Zn2+ ion one. The stability of the Fe(bpy)3Cl2 solution was investigated by UV–vis spectroscopy, and the performance of a mild redox flow battery employing ZnCl2 and Fe(bpy)3Cl2 in the NaCl aqueous solution with various membranes as the separator was also investigated. It was found that the Celgard 3501 membrane cannot effectively prevent Fe(bpy)32+ ions from leaking into anolyte, leading to the rapid failure of the flow battery. Although the Nafion 115 membrane can be polluted by Fe(bpy)32+ ions, it is not invalidated. The Nafion 115 membrane shows good selectivity, which can avoid Fe(bpy)32+ ions from leakage into anolyte. The ZnCl2/Fe(bpy)3Cl2 flow battery with the Nafion 115 membrane exhibits the capacity retention of 80% after 200 cycles. 相似文献
8.
Shimatsu T. Kondo T. Mitsuzuka K. Watanabe S. Aoi H. Muraoka H. Nakamura Y. 《IEEE transactions on magnetics》2007,43(6):2091-2093
The switching field distributions (SFD) of CoPtCr-SiO2 perpendicular media as a function of Pt content were characterized by subtracting the effect of thermal agitation, and discussed in relation to the microstructure. DC demagnetizing (DCD) magnetization curves and minor dc demagnetizing (M-DCD) magnetization curves were measured at applied field sweep rates of ~10 Oe/s and ~108 Oe/s. We estimated the width of SFD, DeltaSFD, from the difference between the DCD and M-DCD curves, and defined them as DeltaHr/Hr (at ~ 10 Oe/s) and DeltaHr P/Hr P (at ~108 Oe/s). The values of DeltaSFD characterized by subtracting the effect of thermal agitation, DeltaH 0/H0, were nearly half those of DeltaHr /Hr for 10-nm-thick media. DeltaH0/H0 was about 0.10 at 10 at%Pt content, and increased as the Pt content increased, reaching 0.17 at 30 at%Pt content. The increase in DeltaH0/H0 was probably caused by an increase in the stacking fault density and the formation of fcc layers in the hcp CoPtCr lattice. A simple calculation based on the coherent switching of magnetization revealed that the c-axis distribution results in DeltaH 0/H0 of about 0.08, independent of Pt content. These results suggest that the DeltaSFD due to the grain-to-grain anisotropy field variation was small, only 0.02-0.03 相似文献
9.
以电纺TiO2纳米纤维为基体和反应物,通过一步水热法,将SrTiO3原位构筑在TiO2纳米纤维表面的同时将稀土Sm3+掺入SrTiO3中,合成了Sm3+-SrTiO3/TiO2复合纳米纤维光催化材料.利用XRD、XPS、FESEM和HRTEM等测试手段对样品进行了表征.以罗丹明B和对氯苯酚模拟有机污染物进行光催化降解.结果表明:稀土Sm3+掺杂进入SrTiO3晶格取代Sr2+,在SrTiO3禁带内形成杂质能级,拓宽了光谱响应范围;同时在SrTiO3晶格内引入了缺陷位,成为电子的捕获中心,降低了载流子的复合几率;而SrTiO3与TiO2复合形成异质结,进一步提高了光生电子-空穴的分离程度,Sm3+-SrTiO3/TiO2复合纳米纤维表现出良好的可见光催化活性。 相似文献
10.
L. Laversenne Y. Guyot C. Goutaudier M. Th. Cohen-Adad G. Boulon 《Optical Materials》2001,16(4):475-483
Absorption and emission spectra are given for Yb3+-doped Y2O3, Lu2O3 and Gd2O3 at room temperature. Y2O3 and Lu2O3 as close cubic matrices, show Yb3+ similar spectra different of Yb3+ in Gd2O3 monoclinic structure. Here, we use a new method to study and optimize the main spectroscopic properties with only one concentration gradient sample. Finally, assignments of Yb3+ Stark levels and Raman vibrations in Y2O3, Lu2O3 and Gd2O3 single crystal are given. 相似文献
11.
Lithium has been inserted into, and extracted from, the spinel Li1.0V2O4 both electrochemically and chemically. Electrochemical and structural data show that in the system Li1+xV2O4, for 0 < x ≤ 0.5, Li+ ions are inserted into the interstitial octahedral sites of the Atet[B2]octX4 spinel structure. At x ≈ 0.5, Li+ ions in the tetrahedral A-sites are displaced into the remaining octahedral sites to yield, at x = 1, a rocksalt phase Li2V2O4; the [B2]X4 framework is unperturbed by the lithiation process. This framework also remains intact when Li+ ions are removed from Li1.0V2O4 to a composition Li0.67V2O4. Further extraction of lithium from the structure is accompanied by migration of some vanadium ions from the B-sites to the interstitial octahedral sites of the spinel structure. This process reduces the crystal symmetry from cubic to trigonal symmetry. In Li0.27V2O4 the structure resembles that of Li0.22VO2, obtained by delithiation of layered LiVO2, in which the vanadium cations are distributed in a 2:1 ratio between alternate cubic-close-packed oxygen layers; in the LiV2O4 spinel this ratio is 3:1. 相似文献
12.
YxGd1−xVO4:Tm3+ (5 mol%) phosphors were prepared by in situ co-precipitation technology with the different content ratio of Y/Gd (x = 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, respectively). During the process, rare earth coordination polymers with o-hydroxylbenzoate were used as precursors, composing with polyethylene glycol (PEG) as dispersing media. After heat-treatment of the resulting multicomponent hybrid precursors at 900 °C, the samples were obtained. SEM indicated the particles present good crystalline state, whose crystalline grain sizes were about 0.2–2 μm. Under the excitation of 257 nm, all the materials show the characteristic emission of Tm3+ which is the strong blue emission centered at 475 nm originating from 1G4 → 3H6 of Tm3+. Besides this, concentration quenching appears in the system of YVO4:Tm3+ and GdVO4:Tm3+. And when x reaches 0.5, the system of YxGd1−xVO4:Tm3+ shows the strongest blue emission. 相似文献
13.
Heterostructure is an effective strategy to facilitate the charge carrier separation and promote the photocatalytic performance. In this paper, uniform SrTiO3 nanocubes were in-situ grown on TiO2 nanowires to construct heterojunctions. The composites were prepared by a facile alkaline hydrothermal method and an in-situ deposition method. The obtained SrTiO3/TiO2 exhibits much better photocatalytic activity than those of pure TiO2 nanowires and commercial TiO2 (P25) evaluated by photocatalytic water splitting and decomposition of Rhodamine B (RB). The hydrogen generation rate of SrTiO3/TiO2 nanowires could reach 111.26 mmol·g−1·h−1 at room temperature, much better than those of pure TiO2 nanowires (44.18 mmol·g−1·h−1) and P25 (35.77 mmol·g−1·h−1). The RB decomposition rate of SrTiO3/TiO2 is 7.2 times of P25 and 2.4 times of pure TiO2 nanowires. The photocatalytic activity increases initially and then decreases with the rising content of SrTiO3, suggesting an optimum SrTiO3/TiO2 ratio that can further enhance the catalytic activity. The improved photocatalytic activity of SrTiO3/TiO2 is principally attributed to the enhanced charge separation deriving from the SrTiO3/TiO2 heterojunction. 相似文献
14.
Bi2O3·B2O3 glasses doped with rare-earth oxides (RE2O3) (RE3+ = La3+, Pr3+, Sm3+, Gd3+, Er3+ and Yb3+) were prepared by the melting–quenching method. The relationships between composition and properties were demonstrated by IR, DSC, XRD and SEM analysis. The results show that the network structure resembles that of undoped Bi2O3·B2O3 glass, composing of [BO3], [BO4] and [BiO6] units. RE2O3 stabilizes the glass structure as a modifier. Transition temperature (Tg) increases linearly with cationic field strength (CFS) of RE3+. La2O3, Pr2O3, Sm2O3 and Gd2O3 are benefit to promote the formation of BiBO3 crystal. When Er2O3 and Yb2O3 are introduced, respectively, the main crystal phase changes to Bi6B10O24. Transparent surface crystallized samples are obtained by reheating at 460–540 °C for 5 h. In this case, needle like BiBO3 crystal or rare-earth-doped BiBO3 crystal (PrxBi1−xBO3 and GdxBi1−xBO3) are observed, which is promising for non-linear optical application. 相似文献
15.
The luminescence of nominally pure BaLn2(MoO4)4 (Ln = La,Gd) is reported. Below 300 K molybdate emission is observed. The following activators were investigated: Eu3+, Tb3+, Pb2+ and Bi3+. The two lanthanide ions show their characteristic emission, the two s2 configuration ions give an emission in which the host-lattice group as well as the activator is involved. The luminescence properties of these compositions are discussed and compared with those of related materials. 相似文献
16.
Ca5La5(SiO4)3(PO4)3O2 doped with Dy3+ were synthesized by sol–gel technology with hybrid precursor employed four different silicate sources, 3-aminopropyl-trimethoxysilane (APMS), 3-aminopropyl-triethoxysilane (APES), 3-aminopropyl-methyl-diethoxysilane (APMES) and tetraethoxysilane (TEOS), respectively. The SEM diagraphs show that there exist some novel unexpected morphological structures of microrod owing to the crosslinking reagents than TEOS as silicate source for their amphipathy template effect. X-ray pictures confirm that Ca5La5(SiO4)3(PO4)3O2:Dy3+ compound is formed by a pure apatitic phase. The Dy3+ ions could emit white light in Ca5La5(SiO4)3(PO4)3O2 compound, and the ratio of Y/B is 1.1, when the Dy3+ doped concentration is 1.0 mol%. 相似文献
17.
New materials for a transparent conducting oxide film are demonstrated. Highly transparent Zn2In2O5 films with a resistivity of 3.9 × 10−4 Ω cm were prepared on substrates at room temperature using a pseudobinary compound powder target composed of ZnO (50 mol.%) and In2O3 (50 mol.%) by r.f. magnetron sputtering. MgIn2O4---Zn2In2O5 films were prepared using MgIn2O4 targets with a ZnO content of 0–100 wt.%. The resistivity of the deposited films gradually decreased from 2 × 10−3 to 3.9 × 10−4 Ω cm as the Zn/(Mg + Zn) atomic ratio introduced into the films was increased. The greatest transparency was obtained in a MgIn2O4 film. The optical absorption edge of the films decreased as the Zn/(Mg + Zn) atomic ratio was increased, corresponding to the bandgap energy of their materials. It was found that the resistance of the undoped Zn2In2O5 films was more stable than either the undoped MgIn2O4, ZnO or In2O3 films in oxidizing environments at high temperatures. 相似文献
18.
The energy levels of neodymium in the Nd3+:Ca2Al2SiO7 (CAS) laser material with gehlenite structure are reported. As the Nd3+:Ca2Al2SiO7 compound presents a broad absorption around 806 nm, it is a good candidate for diode pumped laser. The 4F3/2→4I9/2 and 4F3/2→4I11/2 emission have been recorded and the fluorescence branching ratios calculated from the Judd-Ofelt analysis are 0.41 and 0.47 respectively. The emission cross section at 1.06 μm (4F3/2→4I11/2 transition) is 5 × 10-20 cm2. The decay profiles of the Nd3+ emission have been analyzed for several Nd3+ concentrations using the kinetic microparameters related to the cross relaxation (
and R0≈6 Å) and the energy migration probabilities (
). In the Nd:CAS laser material, the optimal concentration corresponding to the maximum of the fluorescence intensity is determined to be around 2.7 × 1020 Nd3+ ions cm-3. The Nd3+-Nd3+ interactions are not very strong in this material as the optical concentration value is two times higher than in the Nd:YAG laser material. 相似文献
19.
为研究增韧双马来酰亚胺方法及其对性能的影响,首先利用超临界乙醇处理纳米SiO2(SCE-SiO2),改善其表面活性;然后以4,4’-二氨基二苯甲烷双马来酰亚胺(MBMI)、3,3’-二烯丙基双酚A(BBA)、双酚A双烯丙基醚(BBE)为原料合成了MBMI-BBA-BBE(MBAE)复合材料基体,并利用原位聚合法和溶胶-凝胶法将SCESiO2和聚醚砜(PES)加入MBAE基体中制备了SCE-SiO2/PES-MBAE多相复合材料;最后采用SEM观察了SCESiO2/PES-MBAE复合材料断面形貌。SCE-SiO2的FTIR分析结果表明:在3 434cm-1处的Si—OH的吸收峰消失,出现了3 310cm-1处的乙醇分子间—OH的吸收峰、2 984cm-1处的甲基和亚甲基的吸收峰,证明纳米粒子可能以某种形式结合了乙醇分子,改善了表面性能。PES以"蜂窝"状分散相的形式存在于基体中,断裂方式由脆性断裂向韧性断裂转变,SCE-SiO2和PES对材料均有增韧作用,PES的增韧效果更明显,二者之间具有协同作用,当SCE-SiO2含量为2wt%、PES含量为4wt%时,多相复合材料的冲击强度和弯曲强度分别为15.02kJ/m2和130.47MPa,较MBAE树脂分别提高了57.3%和35.8%。介电性能测试表明:SCE-SiO2和PES的引入均会导致SCE-SiO2/PES-MBAE复合材料的介电常数和损耗略有上升,但二者之间的协同作用可以抑制PES组分所带来的负面影响。 相似文献
20.
The CO2 lasers, frequency stabilized on OsO4 transitions around 29 THz, are successfully used as secondary references for visible frequency synthesis and also for high-accuracy spectroscopy in the infrared domain. The BNM-LPTF CO2/OsO4 frequency standards exhibit high metrological performances: a long term reproducibility of ±10 Hz (1σ=2×10-13) and a stability σy=6.6×10-14/√τ with a Flicker plateau of 4×10-15 (Δν/ν=0.1) for 300 s to 103 s averaging times. These results and a preliminary study of the main effects which can induce frequency shifts are reported 相似文献