Effect of AlN coating on hydrogen permeability and surface structure of VT6 alloy by vacuum arc ion plating

We study the absorption of hydrogen of metal by the permeability method. With the help of the gas reaction controller(GRC), the absorptive capacity of hydrogen, which is a function of time, temperature and pressure, can be recorded. The effect of the performance of the hydrogen permeability of AlN coating on the titanium alloy surface structure is studied.In the research, the AlN is selected to be added to the titanium alloy sample VT6, and the properties of the titanium alloy are investigated, and the hydrogen absorption rate of the coating is calculated by performing the hydrogen saturation of the test sample. The results show that under 600℃ the AlN film reduces the hydrogen absorption rate of titanium alloy and improves the surface properties of VT6 alloy.     

Hydrogen and Neutron Irradiation Induced Hardening in Vanadium Alloys

It is well known that vanadium alloy will face to strong neutron irradiation and hydrogen environments as a structural material in a fusion reactor. Some researches have reported that vanadium alloy took strongly hardening after an exposure to hydrogen environment and irradiation by neutron at a temperature lower than 400℃. The ductility of the alloy was lost largely, even entirely brittle fracture occurred sometimes in tension loading of the alloy. Therefore, it‘s to get the knowledge of the hardening mechanism and the fracture mechanical for the purpose to improve the performances of the alloy under the circumstances.     

Hydrogen absorption of LaFe11.5Si1.5 compound under low hydrogen gas pressure

Hydrogen absorptions of LaFe11.5Si1.5 compound in 1-atm hydrogen gas at different temperatures are investigated. The hydrogen content in the hydrogenated sample does not increase with the increase of temperature of hydrogen absorption but changes complicatedly. The characteristic of first-order transition in LaFe11.5Si1.5 compound is weakened after hydrogen absorption. It leads the peaks of magnetic entropy to become wider and the hysteresis loss to reduce significantly, but relative cooling power (RCP) is not changed considerably.     

Hydrogenation Properties of Zr Films Under Various Conditions of Hydrogen Plasma

The hydrogenation properties of Zr samples with and without an Ni overlayer under various plasma conditions were investigated by means of non-Rutherford backscattering and elastic recoil detection analysis.The theoretical maximum hydrogen capacity,66.7 at%,could be achieved at a hydrogen absolute pressure of-2Pa and a substrate temperature of-393K for a plasma irradiation of only 10min;this was significantly greater than that for gas hydrogenation under the same hydrogen pressure and substrate temperature.It was also found that the C and O contamination on the sample surface strongly influences the hydrogenation,and that the maximum equilibrium hydrogen content drops dramatically with the increasing total contamination.In addition,the influence of the Ni overlayer on the plasma hydrogenation is discussed.     

Gas leakage monitoring with scanned-wavelength direct absorption spectroscopy

<正>A natural gas leakage detector based on scanned-wavelength direct absorption spectroscopy is described. The sensor employs a multi-channel scanned-wavelength direct absorption strategy.It has the potential to simultaneously monitor methane and hydrogen sulfide in open path environment.Traditionally,scanned-wavelength direct absorption spectroscopy is the technique choice for natural gas leakage applications because of its simplicity,accuracy,and stability.We perform the gas sensor using direct-absorption wavelength scans with isolated features at 1-kHz repetition rate and the center wavelength is stabilized at the center of the 2v_3 band R(3) line of methane(1.65μm) and the(v_1+v_2+v_3) combination band of hydrogen sulfide(1.57μm),respectively.The influence of light intensity fluctuations can be eliminated by using scanned-wavelength direct absorption spectroscopy.Because of the fast wavelength scanning,the sensor has a response time of less than 0.1 s.The sensor can be configured to sense leakages in path-integrated concentrations of,for example,100-ppm·m hydrogen sulfide and 10-ppm·m methane.     

The effects of static magnetic field on microwave absorption of hydrogen plasma in carbon nanotubes: A numerical study

We theoretically investigate the microwave absorption properties of hydrogen plasma in iron-catalyzed highpressure disproportionation-grown carbon nanotubes under an external static magnetic field in the frequency range 0.3 GHz to 30 GHz, using the Maxwell equations in conjunction with a general expression for the effective complex permittivity of magnetized plasma known as the Appleton–Hartree formula. The effects of the external static magnetic field intensity and the incident microwave propagation direction on the microwave absorption of hydrogen plasma in CNTs are studied in detail. The numerical results indicate that the microwave absorption properties of hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes can be obviously improved when the external static magnetic field is applied to the material. It is found that the specified frequency microwave can be strongly absorbed by the hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes over a wide range of incidence angles by adjusting the external magnetic field intensity and the parameters of the hydrogen plasma.     

Modelling Neutral Hydrogen Discs of Spiral Galaxies

We present an analytical model of a neutral hydrogen disc in a spiral galaxy.The gas disc of the spiral galaxy is assumed to have an exponential surface density profile and to be ionized by the cosmic ultraviolet background.To compare with observations,we consider the disc position angle and inclination angle for a line of sight going through the galaxy disc,The HI column densities depend on the strength of ionizing field and disc position and inclination.The model was applied to NGC 3198 and the results were compared with observational data.The Hi disc profile at large disc radii can be tested by further HI observations using radio telescopes with a larger aperture than the present facilities.This HI disc model can be used to predict quasar absorption line systems by galaxy discs if quasar lines of sight go through the discs.     

Efficient up-conversion Yb~(3+), Er~(3+) co-doped Na_5Lu_9F_(32) single crystal for photovoltaic application under solar cell spectrum excitation

Yb~(3+)/Er~(3+)co-doped Na_5Lu_9F_(32) single crystals used as a spectral up-converter to improve the power conversion efficiency of perovskite solar cells are prepared via an improved Bridgman approach. Green and red up-conversion(UC) emissions under the excitation of near-infrared(NIR) bands of 900–1000 nm and1400–1600 nm can be observed. The effectiveness of the prepared materials as a spectral converter is verified by the enhancement of power conversion efficiency of perovskite solar cells. The sample with a UC layer is 15.5%more efficient in converting sunlight to electricity compared to the UC layer-free sample due to the absorption of sunlight in the NIR range. The results suggest the synthesized Yb~(3+)/Er~(3+)co-doped Na_5Lu_9F_(32) single crystals are suitable for enhancing the performance of perovskite solar cells.     

Mechanical and Magnetostrictive Properties of Fe—Doped Ni52Mn24Ga24 Single Crystals

To improve the magnetic and mechanical properties of a Heusler alloy of Ni52Mn24Ga24,iron was doped with some cotents,Single crystals of the pseudoquaternary Heusler alloy of Ni52Mn8Fe15Ga24 have been synthesized for mechanical and magnetostrictive measurements.The magnetostriction loops and stress-strain curves were measured under different coupled magnetic-mechanical loads.The experimental results show that the brittleness of the sample is clearly improved and Yong‘s modulus of 13.7GPa is obtained in the [001] direction due to the part substitution of Fe for Mn.Furthermore,the toughness and Vickers hardness of the sample are also given by use of the indentation technique.     

A preliminary study of a negative hydrogen PIG-type ion source for the compact cyclotron

A Penning ion gauge (PIG)-type ion source has been used for the generation of negative hydrogen ions (H^-) as the internal ion source of the compact cyclotron. The discharge characteristics of the ion source are systematically studied for hydrogen operation at different discharge currents and gas flow rates on the prototype cyclotron. The preliminary study results for the low DC voltage H^- extraction measurements are presented in this paper. The H^- beam current is measured by the order of magnitude from several tens to hundreds of microamperes at different parameter conditions. The discussion and analysis for the experimental results are good for improving the design and working stability of the ion source.     

Active Loss of Light Yield of PbWO4：Y Scintillation Crystals After Irradiation

PWO crystals doped with yttrium were grown with the Bridgman method in platinum crucible and by using an indigenously developed resistive heating furnace. After an exposure of γ-ray from a ^60Co source, with the dose rate of lS rad/h for 20h, the light output increases for about 15%, accompanied with vanishing of an optical absorption band at 420 nm. The excitation and emission spectra of PWO crystals were measured before and after irradiation with different dose rates. The optical absorption band at 420nm was also found in the PWO sample annealed in oxygen-rlch atmosphere. It is suggested that the absorption band at 42Onm is related to Pb^3 point defects existing in the PWO crystal. The unusual change of light output after irradiation probably results from the transformation of lead ions from Pb^3 to Pb^2 .     

The effects of a static magnetic field on the microwave absorption of hydrogen plasma in carbon nanotubes： a numerical study

We theoretically investigate the microwave absorption properties of hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes under an external static magnetic field in the frequency range 0.3 GHz to 30 GHz, using the Maxwell equations in conjunction with a general expression for the effective complex permittivity of magnetized plasma known as the Appleton-Hartree formula. The effects of the external static magnetic field intensity and the incident microwave propagation direction on the microwave absorption of hydrogen plasma in CNTs are studied in detail. The numerical results indicate that the microwave absorption properties of hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes can be obviously improved when the exter- nal static magnetic field is applied to the material. It is found that the specified frequency microwave can be strongly absorbed by the hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes over a wide range of incidence angles by adjusting the external magnetic field intensity and the parameters of the hydrogen plasma.     

Practical absorption limits of MPP absorber

The construction and properties of microperforated panel (MPP) absorber are discussed. The absorption limit of the absorber had been shown that low values of the perforate constant k = d(f/10)1/2 and the orifice diameter d (in mm) are essential for MPP to have high absorption in wide frequency band. To find the exact limits, take 1 for k as a start, because both specific resistance and high absorption require k around one. And the orifice diameter d is chosen as 0.1 mm, so that the peak absorption coefficient (resonance absorption) is at 1000 Hz, and high sound frequency may be in the absorption region. Is it possible for a single layer of such an MPP to cover the whole absorption region required in practice? The half-absorption limit is not a good criterion, because low absorption comes in also in some cases. The 0.5 absorption coefficient limit is suggested for practical region, as a standard for comparison. Absorption curves were drawn for different load resistances, of absorption coefficients versus frequency. Ordinary MPP absorber absorbs in slightly over two octaves, and the new absorber with r = 1 (specific resistance equal to the characteristic impedance in air)is slightly better than these, 2.5 octaves. The new absorbers with r > 1, are much better than these, and some satisfies high absorption in broad frequency range. Realization of these will mean great progress of MPP absorbers.     

Enhanced absorption properties of ordered mesoporous carbon/Co-doped ordered mesoporous carbon double-layer absorbers

Ordered mesoporous carbon (OMC) and metal-doped (M-doped) OMC composites are prepared, and their electromagnetic (EM) parameters are measured. Using the measured EM parameters we calculate the EM wave absorption properties of a double-layer absorber, which is composed of OMC as an absorbing layer and M-doped OMC as the matching layer. The calculated results show that the EM wave absorption performance of OMC/OMC-Co (2.2mm/2.1mm) is improved remarkably. The obtained effective absorption bandwidth is up to 10.3 GHz and the minimum reflection loss reaches 47.6 dB at 14.3 GHz. The enhanced absorption property of OMC/OMC-Co can be attributed to the impedance match between the air and the absorber. Moreover, it can be found that for the absorber with a given matching layer, a larger value of -tanδε (= tan δε absorbing tan δε matching ) can induce better absorption performance, indicating that the difference in impedance between the absorbing layer and the matching layer plays an important role in improving the absorption property of double-layer absorbers.     

一台2.45GHz强流中子源

A 2.45GHz microwave-driven ion source is being used to provide 40mA of deuterium ion beam (peak current) for an RFQ accelerator as part of a neutron source system.We have also designed a 60kV electrostatic LEBT using computer simulations.In our experiment,we measured the hydrogen and deuterium ion beam currents as functions of discharge power,gas flow,and magnetic field strength.The required beam current was obtained using leas than 700W of net microwave power with a gas flow of less than 1.5sccm.From the rise time data,it was determined that in order to obtain a high percentage of atomic ions in the beam, the beam extraction should start after 1ms of switching on the microwave power.At steady state,the proton fraction was above 90%.     

Enhanced Nonlinear Absorption and Optical Limiting Properties of Organic Material ZnTBP—CA—PhR in a DA—ET System

Nonlinear absorption of the organic material Zn-tetrabenzoporphin-cronicacid-phenonxy resin(ZnTBP-CA-PhR) in the donor-acceptor energy-transfer(DA-ET) system is investigated by the irradiation of Ar^ laser on its solid film.A reverse saturable absorption and an enhanced second reverse saturable absorption called the rereverse saturable absorption are observed in a visible wavelength range.The high performance of optical limiting of the sample possessing low input threshold and an over 95% linear transmission ratio are observed.The physical mechanism of rereverse satruable absorption is analysed by a five-level rate-equation simulating.According to the Huygens wave diffraction principle and the combination of Kerr effect,thermo-optic effect and optical absorption variation,a mathematical model for the optical limiting of ZnTBP-CA-PhR film limiter is established and the theoretical simulating gives a good agreement with the experimental results.     

Synthesis,Characterization of 9, 9＇-Bianthracene and Fabrication of 9, 9＇-Bianthracene Field-Effect Transistors

We synthesize and purify 9, 9＇-bianthracene with the purity up to 96.4%. The electronic and crystallographic structures of 9, 9＇-bianthracene are studied. The results of a joint experimental investigation based on a combination of x-ray diffraction （XRD） spectra, hydrogen nuclear magnetic （HNMR） spectra, infrared absorption （FT-IR） spectra, and mass spectra （MS） of 9, 9＇-bianthracene are obtained. The uniform compact film is observed by an atomic-force microscope （AFM）. Organic field effect transistors （OFETs） with an active layer based on the synthesized 9, 9＇-bianthracene are fabricated for the first time. Its field-effect mobility is as large as 0.067 cm^2 /（V·s） and the on/off ratio is above 5 ×10^4. The result demonstrates that the oligomerization of a small semiconductor molecule is an effective method to develop high-mobility organic semiconductors.     

Investigation of trace p-dichlorobenzene using laser mass spectrometry

The time-of-flight mass spectrum(TOFMS)relative to the resonant two-photon ionization of gas phase p- dichlorobenzene was obtained in the wavelength range of 240-250 nm by a home-made system.A special design was made to reduce the effect of memory on the inner wall of the sample inlet system suitable for the investigation of semi-volatile organic compound.In this wavelength range,p-dichlorobenzene molecules firstly absorbed one photon to be excited from the gTound state ~1A_g(S_0)to the first excited state 1B2u($1),then absorbed another photon to be ionized.The relationship between the signal intensity of p-dichlorobenzene molecular ion C_6H_4~(35)Cl_2~ at 248-nm wavelength and the laser power was given. The 1.52 power index of C_6H_4~(35)Cl_2~ was a typical identification of the 3/2 power law.The relationship between the ion signal intensity of C_6H_4~(35)Cl_2~ and the sample concentration was close to a linear one in the ppm(V/V)range,which led to a detection limit of 125 ppb(V/V)for p-dichlorobenzene.     

Shadow Effect and Its Revisal in Grid-Enhanced Plasma Source with Ion Implantation Method

The implanting voltage, gas pressure and the grid electrode radius are the key parameters influencing the surfacegrid shadow effect that has been observed in our grid-enhanced plasma source ion implantation experiment. To reduce the shadow effect and obtain a corresponding better implantation uniformity of sample surfaces, we needto use lower implanting voltage, higher gas pressure and smaller grid radius. Furthermore, we apply an axialmagnetic field to increase the plasma density inside the tube and to mix the plasma outside the grid, so that theshadow effect of sample surfaces can be weakened.     

Optical and magnetic properties of nitrogen ion implanted MgO single crystal

The microstructure,optical property and magnetism of nitrogen ion implanted single MgO crystals are studied. A parallel investigation is also performed in an iron ion implanted single MgO sample as a reference. Large structural,optical and magnetic differences are obtained between the nitrogen and iron implanted samples. Room temperature ferromagnetism with a fairly large coercivity field of 300 Oe (1Oe=79.5775 A/m),a remanence of 38% and a slightly changed optical absorption is obtained in the sample implanted using nitrogen with a dose of 1×1018 ions/cm2 . Tran- sition metal contamination and defects induced magnetism can be excluded when compared with those of the iron ion implanted sample,and the nitrogen doping is considered to be the main origin of ferromagnetism.