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361.
ZHANG Jian-Fu RUAN Xi-Chao HOU Long LI Xia BAO Jie ZHANG Guo-Guang HUANG Han-Xiong SONG Chao-Hong 《中国物理C(英文版)》2010,34(7)
The light output functions for protons of ST-401 and BC-408 plastic scintillators were measured using white neutron source produced by the 9Be(d,n)10B reaction at the HI-13 Tandem Accelerator at China Institute of Atomic Energy(CIAE).The LOFs of plastic scintillators for protons in the energy range of 0.516.5 MeV were obtained by the time-of-flight(TOF)technique and an iterative procedure.Two parameters(kB and C)were deduced by fitting the experimental data. 相似文献
362.
Y2O3:Er3+, Yb3+ nanocrystals have been obtained by ball milling and using a combustion synthesis procedure. In both cases the nanocrystals have been successfully coated with SiO2 following the Stöber method. The average size of the as-synthesized nanoparticles has been estimated from X-ray diffraction patterns and transmission electron microscopy images. The dependence of the optical properties of these samples on synthesis procedure or dopant concentration has been investigated. Emission, excitation and lifetime measurements have been carried out. Upconversion luminescence has been detected in all samples and an enhancement of the red to green emission ratio has been observed in all samples after infrared compared to visible excitation. The mechanisms responsible for the upconversion phenomena have been discussed. 相似文献
363.
ZnS and SiO2-ZnS nanophosphors, with or without different concentration of Mn2+ activator ions, were synthesized by using a sol-gel method. Dried gels were annealed at 600 °C for 2 h. Structure, morphology and particle sizes of the samples were determined by using X-ray diffraction (XRD), highresolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). The diffraction peaks associated with the zincblende and the wurtzite structures of ZnS were detected from as prepared ZnS powders and additional diffraction peaks associated with ZnO were detected from the annealed powders. The particle sizes of the ZnS powders were shown to increase from 3 to 50 nm when the powders were annealed at 600 °C. An UV-Vis spectrophotometer and a 325 nm He-Cd laser were used to investigate luminescent properties of the samples in air at room temperature. The bandgap of ZnS nanoparticles estimated from the UV-Vis data was 4.1 eV. Enhanced orange photoluminescence (PL) associated with 4T1→6A1 transitions of Mn2+ was observed from as prepared ZnS:Mn2+and SiO2-ZnS:Mn2+ powders at 600 nm when the concentration of Mn2+ was varied from 2-20 mol%. This emission was suppressed when the powders were annealed at 600 °C resulting in two emission peaks at 450 and 560 nm, which can be ascribed to defects emission in SiO2 and ZnO respectively. The mechanism of light emission from Mn2+, the effect of varying the concentration on the PL intensity, and the effect of annealing are discussed. 相似文献
364.
Spectroscopic concentration measurements of ammonia and ethylene were done with a pulsed, distributed feedback (DFB) quantum
cascade (QC) laser centered at 970 cm−1. An astigmatic Herriot cell with 150 m path length was employed, and we compare the results from experiments using inter-
and intrapulse techniques, respectively. The measurements include the detection of ammonia in breath with these methodologies.
In the interpulse technique, the laser was excited with short current pulses (5–10 ns), and the pulse amplitude was modulated
with an external current ramp resulting in a ∼0.3 cm−1 frequency scan. A standard amplitude demodulation technique was implemented for extracting the absorption line, thus avoiding
the need for a fast digitizer or a gated integrator. In the intrapulse technique, a linear frequency down-chirp is used for
sweeping across the absorption line. A 200 ns long current pulse was used for these measurements which resulted in a spectral
window of ∼1.74 cm−1 during the down-chirp. The use of a room temperature mercury-cadmium-telluride detector resulted in a completely cryogen
free spectrometer. We demonstrate detection limits of ∼3 ppb for ammonia and ∼5 ppb for ethylene with less than 10 s averaging
time with the intrapulse method and ∼4 ppb for ammonia and ∼7 ppb for ethylene with the interpulse technique with an integration
time of ∼5 s. 相似文献
365.
Preparation and characterization of graphitic carbon nitride through pyrolysis of melamine 总被引:1,自引:0,他引:1
Xuefei Li Jian Zhang Longhai Shen Yanmei Ma Weiwei Lei Qiliang Cui Guangtian Zou 《Applied Physics A: Materials Science & Processing》2009,94(2):387-392
Graphitic carbon nitride (g-C3N4) has been synthesized via a two-step pyrolysis of melamine (C3H6N6) at 800°C for 2 h under vacuum conditions. X-ray diffraction (XRD) patterns strongly indicate that the synthesized sample
is g-C3N4. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) morphologies indicate that the product is
mainly composed of graphitic carbon nitride. The stoichiometric ratio of C:N is determined to be 0.72 by elemental analysis
(EA). Chemical bonding of the sample has been investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform
infrared spectroscopy (FTIR). Electron energy loss spectroscopy (EELS) verifies the bonding state between carbon and nitrogen
atoms. Optical properties of the g-C3N4 were investigated by PL (photoluminescence) measurements and UV–Vis (ultraviolet–visible) absorption spectra. We suppose
its luminescent properties may have potential application as component of optical nanoscale devices. Thermogravimetric analysis
(TGA) and differential thermal analysis (DTA) were also performed. 相似文献
366.
Shu-Yi Liu Tao Chen Jing Wan Guo-Ping Ru Bing-Zong Li Xin-Ping Qu 《Applied Physics A: Materials Science & Processing》2009,94(4):775-780
Oriented ZnO nanorods were grown on ion-beam-sputtered ZnO seed layers through a hydrothermal approach without any metal catalyst.
The sputtered ZnO seed layers were pre-annealed at different temperatures before the growth of ZnO nanorods. The effects of
pre-annealing of the ZnO seed layers on the growth rate, crystallinity and optical properties of ZnO nanorods thereon were
studied. The obtained ZnO nanorods had a wurtzite structure and grew along the preferential [0001] orientation with a normal
direction to the substrates. Results show that the growth rate and density of the ZnO nanorods strongly depend on the pre-treatment
conditions of the ZnO seed layer. With higher pre-treatment temperature, the crystallinity and surface characteristics of
the ZnO seed layer were improved and thereafter the growth rate of ZnO nanorods thereon increased. Photoluminescence spectroscopy
results show that the UV emission also becomes stronger and sharper with increasing annealing temperature of the ZnO seed
layer. 相似文献
367.
368.
Some one-neutron halo nuclei can emit a proton in a β decay of the halo neutron. The branching ratio towards this rare decay mode is calculated within a two-body potential model of the initial core + neutron bound state and final core + proton scattering states. The decay probability per second is evaluated for the 11Be, 19C and 31Ne one-neutron halo nuclei. It is very sensitive to the neutron separation energy. 相似文献
369.
U.S. Taralkar 《Journal of Non》2007,353(2):194-199
The hydrothermal synthesis of Si-MCM-48 mesoporous molecular sieves was carried out using a ternary SiO2:CTAOH:H2O system wherein differently manufactured amorphous silica powders such as fumed silica (FMDS), spray dried precipitated silica (SDPS) and flash dried precipitated silica (FDPS) were used as silica source materials. The changes in structural/textural properties were evaluated using powder XRD, N2 adsorption-desorption and scanning electron microscopy techniques. Studies on the progressive development of MCM-48 mesophases revealed that, the reactivity of the silica source follow the trend: FMDS > SDPS > FDPS. MCM-48 synthesized using low cost FDPS has exhibited thicker pore walls but poorer orderness, while MCM-48 prepared from relatively expensive FMDS has thinner pore walls and more ordered structure. Moreover, the extent of contraction caused by calcinations, agglomerate size and structural stability were found to depend on the reactivity of the silica source used. 相似文献
370.
Uniform and large-scale Co-Ni-P alloy nanowire arrays have been fabricated by autocatalytic redox reaction in an anodic alumina membrane (AAM). The images of Co-Ni-P alloy nanowire arrays and single nanowires are obtained by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. Selected area electron diffraction (SAED), X-ray diffraction (XRD) and energy dispersive spectra (EDS) are employed to study the morphology and chemical composition of the nanowires. The results indicate that the Co-Ni-P nanowire arrays are amorphous in structure. The magnetic property of Co-Ni-P nanowire arrays is characterized using a vibrating sample magnetometer (VSM). The hysteresis loops show that the easily magnetized direction of Co-Ni-P nanowire arrays is parallel to the nanowire arrays and that it has obvious magnetic anisotropy as a result of the shape anisotropy. 相似文献