最新刊期
卷 37 ， 期 9 ， 2016
- 摘要：The graphene quantum dots(GQDs) were prepared by pyrolyzing citric acid and dissolved with different organic solvents. The influence of solvent on luminescence properties is investigated. Transmission electron microscope(TEM), along with atomic force microscope(AFM) was employed for the morphology and structure analysis of the as-prepared samples. The results show that GQDs' diameters are distributed in the range of 2-12 nm(4.9 nm average diameter). Optical properties of the as-prepared samples were characterized by ultraviolet-visible spectra(UV-Vis) and fluorescence spectrophotometer. The photoluminescence spectra depict that the GQDs exhibited solvent-dependent behaviors. The position of the peak fluorescence of GQDs in polar solvent ethanol, acetone and ethylene glycol is dependent on excitation wavelength, emission wavelength is in a visible light area. The fluorescence of GQDs in a nonpolar solvent pentane is independent of excitation wavelength, the strong emission appeared in the near-UV region.关键词：graphene quantum dots (GQDs);photoluminescence;solvent dependence;excitation dependence131|252|3更新时间：2020-08-12
- 摘要：Ca2-xSnO4:xEu3+(x=0, 0.001, 0.005, 0.01, 0.015, 0.02) phosphors were prepared by solid-state reaction method in air and vacuum atmosphere, respectively. The influence of Eu3+-doped concentration and oxygen vacancies on the luminescence properties were investigated. With the increasing of Eu3+ concentration, the emission intensity increases and the two main emission peaks at 614 nm and 618 nm gradually become one at about 616 nm. In the excitation spectra of Ca2-xSnO4:xEu3+, the band between 200 nm and 295 nm is charge transfer band of Eu3+-O2-. The peak of charge transfer band moves from 271 nm to 286 nm with increasing Eu3+ concentration. In addition, under the same concentration of Eu3+, the luminescence intensity of samples sintered in vacuum is twice as much as that in air. Because the oxygen vacancies increase in the samples sintered in vacuum atmosphere, the conduction electron density rises, which leads to the higher emission intensity. Furthermore, the increase of electron trap leads to the improvement of afterglow properties of Ca2-xSnO4:xEu3+.关键词：doping concentration of Eu3+;luminescence;oxygen vacancies;afterglow97|43|3更新时间：2020-08-12
- 摘要：Ga2O3-B2O3-GeO2-SiO2 glasses doped with high Tb3+ concentration and co-doped with Tb3+ and Dy3+ were synthesized by high temperature melting method. The energy transfer between Tb3+ and Dy3+ was studied according to the excitation and emission spectra and decay time. The results show that the emission intensity and fluorescence lifetime decrease with the increasing of Tb3+ and Dy3+ content. Compared with the same content of Tb3+ single doped glass, the luminous intensity of Dy3+/Tb3+ co-doped glass first decreases slowly, and then decreases rapidly. It can be concluded that the energy transfer mechanism between Tb3+ and Dy3+includes nonradiative energy resonance transfer and 4F9/2+7F6→6H15/2+5D4 cross relaxation effect.关键词：energy transfer;Dy3+/Tb3+ co-doped;luminescence;dysprosium ion;terbium ion144|73|1更新时间：2020-08-12
- 摘要：In order to improve the efficiency of radiation flux color of phosphors converted light emitting diode (PC-LED), the phosphors with excitation source system were established and the relationship of phosphors and chip was investigated. The influence of a different excitation spectrum width on white light conversion efficiency of radiation flux was investigated with YAG phosphors as the objects of spectrum calculation method. The calculating result was confirmed by taking the measurements of the remote phosphors (YAG) with different spectrum width excitation light. The calculation and experimental results indicate that the conversion efficiency falls slowly with the increase of spectrum width when the spectral width is small, and the conversion efficiency sharply declines when the spectral width is larger than 18 nm. Each phosphor has its ideal excitation source spectral width. In this range, the efficiency of excitation radiation flux is higher and the impact of spectral width is weaker.关键词：white light source;excitation spectrum width;spectrum;radiation flux93|120|0更新时间：2020-08-12
- 摘要：Mn2+/Fe3+ co-doped upconverting nanocrystals were prepared by hydrothermal method. The crystal phase, size and fluorescence intensity were modulated via changing the doping concentrations. The maximum intensity of upconversion luminescence (UCL) was observed in current work at the reaction time of 4 h when coating the silica shell of different thickness onto the NaYF4:Yb,Er,Fe nanocrystals through facilely altering the reaction time. The integrated overall intensity of upconversion luminescence was 3.7 and 4.5 times enhanced by co-doping Mn2+ and Fe3+, respectively. In particular, the red emission of NaYF4:Yb,Er,Fe nanocrystals was 7 times intensified selectively compared to the green band of Er3+. The intensified visible UCL especially the dominant red emission is mainly ascribed to the energy transfer from|2F7/2, 4T1g>(Yb3+-Mn2+/Fe3+ dimer) to 4F9/2(Er3+) states as well as the distortion of the crystalline field symmetry. The quenching of UCL as increasing dopants is stemming from the exchange interaction between 3d5 metal ions.关键词：upconversion luminescence;transition metal;core-shell nanostructures;energy transfer103|57|2更新时间：2020-08-12
- 摘要：In order to realize the application of mechanoluminescent materials in novel nondestructive examination sensors with high sensitivity, the ultrasound induced mechanoluminescent (ML) properties of SrAl2O4:Eu,Dy/Si rubber films were investigated. The ML particles were wrapped by Si rubberwith high elasticity. When the ultrasonic wave was applied on the film, the vibration induced the deformation of Si rubber easily. Then the particles wrapped by rubber deformed accordingly to produce strong ML. The experiment results indicate that the film thickness and ultrasonic frequency have strong effects on the ML intensity. The ML intensity enhances with the increasing of the film thickness, and reaches the strongest at 1 mm, then decreases with the increasing of the film thickness. The ML intensity enhances with the increasing of the ultrasonic frequency. Furthermore, even the ultrasonic frequency was as low as 500 Hz, the SrAl2O4:Eu,Dy/Si rubber films still can produce resolvable ML. These results indicate that SrAl2O4:Eu,Dy/Si rubber films possess great potential in the nondestructive examination sensors.关键词：SrAl2O4:Eu;Dy/Si rubber film;ultrasound induced mechanoluminescence;nondestructive examination sensors190|85|4更新时间：2020-08-12
- 摘要：In order to avoid the thermal effect of fiber-end in high power fiber laser, the fiber laser based on the multi-point cascaded was studied. First, the self-developed cascaded couplers were introduced. Then, the effect of the couplers insertion on the fiber laser was analyzed. Finally, the fiber laser and the master oscillator amplifier with the pumping distributed structure were built. Experimental results indicate that the research on the insertion loss of the coupler can promote the development of high power cascaded coupler. In the distributed fiber laser, the output power of 1 080 nm is 770 W with the pump power of 1.1 kW, and the optical to optical conversion efficiency is 77%. The output power of maser oscillator power amplifier structure is 635 W with the optical conversion efficiency is 78%. It can satisfy that the distributed pumping can solve the heat concentration in fiber laser, can achieve the kilowatt fiber lasers.关键词：fiber laser;laser oscillation;MOPA;cascaded couplers;high power112|62|8更新时间：2020-08-12
- 摘要：The spectral characteristics of different kinds of hexagon pattern with the same symmetry in evolutionary process were studied in dielectric barrier discharge by optical emission spectrum. It is found that the discharge undergoes hexagon superlattice pattern, hollow hexagon pattern and honeycomb pattern with the increasing of the applied voltage. The electronic density, electron excitation temperature and molecular vibration temperature of the three kinds of patterns were investigated by the broadening of spectral line 696.5 nm, the relative intensity ratio method of spectral lines of Ar Ⅰ 763.2 nm (2P6→1S5) and Ar Ⅰ 772.1 nm (2P2→1S3) and the emission spectra of nitrogen band of second positive system (C3Πu→B3Πg), respectively. The results show that the electronic density of the hexagon superlattice pattern, hollow hexagon pattern and honeycomb pattern gradually decreases, while the electron excitation temperature and molecular vibration temperature of the three kinds of patterns gradually increase with the applied voltage increasing. It is found that the change of the plasma state has effect on the self-organization of the pattern.关键词：dielectric barrier discharge;pattern;emission spectra;electronic density;electron excitation temperature;molecular vibration temperature99|313|1更新时间：2020-08-12
- 摘要：In order to study the effect of doping graphene quantum dots (GQDs) on polymer solar cells, GQDs were prepared by solvothermal route. The polymer solar cells were prepared by doping GQDs in poly (3-hexylthiophene):6,6-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) as a photosensitive layer. Compared with P3HT:PCBM solar cells, the performance of polymer solar cells with different doping concentration of GQDs in P3HT:PCBM solution was improved. The optimized device was P3HT:PCBM:GQDs (0.15% mass fraction) with smooth and uniform thin films, and the fill factor (FF) was 17.42% higher than the solar cells without GQDs. To improve the performance of solar cells further, GQDs were reduced. The FF increased with the reductive time. At 45 min reductive time, the FF was improved from 31.57% to 40.80%, which was 29.24% higher than the solar cells without GQDs. The optimum polymer solar cell was obtained after annealing P3HT:PCBM:GQDs solar cell. The open voltage (Voc) was 0.54 V, FF was 55.56%, and the efficiency was 0.75%.关键词：graphene oxide;graphene quantum dots;doping;P3HT:PCBM;solar cells151|126|5更新时间：2020-08-12
- 摘要：P3HT/PMMA bilayer device was fabricated through layer by layer spin-coating method and the device performance was greatly enhanced comparing with P3HT and PMMA single layer device. SEM image was taken to study the cross-section morphology of the bilayer film. The current-voltage (I-V) and current-repeatable times (I-t) measurements were taken to investigate the performance of the devices. The bilayer one has a better ON/OFF ratio about 1×103 and the device is quite stable. The fitting of I-V curves was utilized to analyze the charge transport process with the help of the diagram of the energy bands. The results show that the charge trapping-detrapping theory can be used to explain the operating mechanism of the bilayer device.关键词：P3HT;PMMA;organic bistable devices;phase separation;charge trapping-detrapping theory114|206|1更新时间：2020-08-12
- 摘要：The cesium chloride (CsCl) methanol solution was introduced into the conventional organic polymer solar cells as cathode buffer layer to improve its properties. The charge accumulation between the Al cathode and PTB7/PC70BM was analyzed through capacitance-voltage (C-V) measurement and the change of work function of Al was investigated by ultraviolet photoelectron spectroscopy (UPS). The results show that the short-circuit current (Jsc), the open-circuit voltage (Voc), the fill factor and the power conversion efficiency (PCE) of the device with the CsCl methanol solution treatment have been improved. And the PCE reaches 6.36%, which has been improved 11% compared with the methanol treatment devices and 42.6% compared with the devices without any treatment. This one-step solution treatment can improve the device properties by reducing the charge accumulation and decreasing the work function of Al cathode which is benefit to electron collection.关键词：cesium chloride;methanol;polymer solar cells;charge accumulation;work function94|147|0更新时间：2020-08-12
- 摘要：Taking a medium power LED lamp as an example, the basic configuration of the plastic radiator was designed. The performance of the radiator was analyzed by numerical simulation, and the structure was improved and optimized according to the analytical results. The results show that the thermal dissipating capacity of the Al alloy radiator is better than the plastic radiator when they have the same configuration. Different from the traditional aluminum alloy radiator, the heat dissipating capacity of the radiator plastic tends to be stable when the fins are higher than 30 mm. Although the infrared emission rate of the conductive plastic is as high as 0.9, the thermal energy dissipated through thermal radiation is very small, which means the plastic radiator design should be prior to increasing the convective heat exchange area. The thermal dissipation capacity of the optimized plastic radiator is quite close to that of the Al alloy radiator, and its weight is reduced 30% of the aluminum alloy radiator, which verifies the superiority of the plastic radiator product.关键词：LED lamp;thermal conductive plastics;thermal radiator;design126|238|5更新时间：2020-08-12
- 摘要：By using sol-gel method, Zn and Cu co-doped TiO2:SnO2 gel was prepared and coated on glass substrates by spin coating method. Under the same experimental conditions, the effects of the different doped proportion of Zn and Cu and calcined temperature on the structure, morphology and property of Zn and Cu co-doped TiO2:SnO2 film were discussed. By using XRD, FTIR, FESEM, PL etc., Zn and Cu co-doped TiO2:SnO2 film was characterized and its photocatalytic degradation performance on methyl orange was researched. The results demonstrate that the particles of Zn and Cu co-doped TiO2:SnO2 film calcined at 600℃ have high crystallization and small size, and the surface is smooth and no obvious cracks. The absorbance of the film is very high in the visible and ultraviolet region. The degradation experiments under UV light illustrate that the photocatalysis degradation efficiency of the film on methyl orange increases greatly compare with pure TiO2 film, and the degradation rate reaches the highest with the molar ratio of n(Ti):n(Sn):n(Zn):n(Cu)=10:3:1:1.119|119|2更新时间：2020-08-12
- 摘要：SnS thin films were prepared on glass substrates by RF magnetron sputtering technique and then were rapidly annealed. The crystalline structure, phase composition, chemical composition, surface morphology and relevant optical properties of SnS thin films grown under various sputtering power (60-120 W) are investigated by X-ray diffraction (XRD), Raman spectroscopy (Raman), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM) and ultraviolet-visible-near infrared spectrophotometry (UV-Vis-NIR). The results show that all the rapidly annealed thin films are crystallized. The crystalline quality, degree of preferential orientation and stoichiometry of thin films are improved and the average particle sizes of thin films are enlarged by the increase of sputtering power. Under the condition of sputtering power of 100 W, the sample has high crystalline quality and degree of preferential orientation, the least strain, pure-phase SnS thin film, Sn/S mole ratio of 1:1.09, the absorption coefficient of 105 cm-1 and the direct band-gap of 1.54 eV.关键词：SnS thin film;RF magnetron sputtering;rapid thermal annealing;crystalline structure;optical properties127|71|2更新时间：2020-08-12
- 摘要：As polypyrrole and polythiophene (Ppy/PTh) had unique doping and dedoping characteristics, the new nano-materials redoped and doped Ppy/PTh composites with special anti-corrosive functional groups were successfully prepared by direct oxidation in zinc phosphate solution, respectively. The microcomic structure, morphology and anti-corrosive performance of the redoped Ppy/PTh were characterized by cyclic voltammetry(CV), scanning electron microscopy(SEM) and polarization curves(PC) and compared with a doped and undoped Ppy/PTh, and their anti-corrosion mechanism was investigated theoretically. The results show that the stainless steel surfaces covered with redoped and doped Ppy/PTh composites have good anti-corrosive performance, and the redoped Ppy/PTh composites is the best. The corrosion potential of the redoped Ppy/PTh composite increases by about 0.989 V and the corrosion current is reduced by about 2 orders of magnitude to pure Ppy.关键词：redoped;zinc phosphate;anti-corrosive performance;Ppy/PTh122|185|1更新时间：2020-08-12
- 摘要：A compatible stealth material against near/middle infrared as well as 1.06 μm and 1.54 μm lasers, based on the structure of one-dimensional photonic crystal (PC) was designed to achieve the compatible stealth of high temperature part of aircrafts against infrared and lasers. Based on the transfer matrix method (TMM) of thin-film optical theory and heterogeneous structure theory, the forbidden band can be broadened to cover the near/middle infrared wave band. Then, two defects were added to the periodical structure of the PC according to the doping theory. The results show that there are two defect modes that located in the wavelengths of 1.06 μm and 1.54 μm in the band gap of 1-5 μm, respectively, with the corresponding spectral reflectance of 1.21% and 1.79%. This PC with "hole-digging spectrum" can realize the compatible stealth against near/middle infrared as well as 1.06 μm and 1.54 μm lasers.关键词：photonic crystal;near/middle infrared;laser;compatible stealth134|44|12更新时间：2020-08-12
- 摘要：The firmness model of agaricus bisporus pileus was established by using Raman spectroscopy combined with chemometric methods. With the help of PinPoniterTM portable Raman spectrometer, rapid and nondestructive for agaricus bisporus firmness prediction was studied. According to the average pileus diameter, the samples with pileus diameter of 2-3 cm were classified as class Ⅰ maturity, 3-5 cm as class Ⅱ. 65 samples of each type were used to collect spectrum and measure firmness. The data were pretreated by four methods of 1st derivatives, 2nd derivatives, standard normal variate and baseline, respectively. The model of partial least square was established. The best effect of both model was 1st derivative, but the correlation coefficient (Rp) and root mean square error of prediction (RMSEP) of Ⅰ were 0.887 and 0.444, respectively. Class Ⅱ's Rp and RMSEP were 0.896 and 0.435, respectively. The results show that the prediction of class Ⅱ mushroom firmness is more accurate than classⅠ. Under the same conditions, the more feasible storage measures can be implemented for class Ⅱ mushroom, so we shall try to capture the pileus diameter of 3-5 cm of agaricus bisporus for production, processing and daily sales.关键词：agaricus bisporus;portable Raman spectroscopy;firmness;PLS;non-destructive testing109|231|2更新时间：2020-08-12
- 摘要：In order to improve the detection rate of infrared small-target in complex environment, a infrared small-target detection algorithm based on the maximum of second-order directional derivative was proposed. Firstly, the properties of second-order directional derivative were analyzed, meanwhile, the flat component and edge of background were removed by threshold and flip operations of the maximum. Then, the background was predicted based on facet model and further enhanced the small-target by prediction error as weight. The above two steps can be achieved by four convolutions and the detection speed was accelerated. At last, the local contrast of candidate small-targets was calculated to reduce the false alarm rate. The experimental results show that the average signal to clutter ratio gain is 78.413 0 and the average background suppression factor is 35.079 6 in 6 kinds of complex background. The proposed detection algorithm has stronger robustness and higher detection rate.关键词：computer vision;facet model;directional derivative maximum (DDMax);infrared small-target99|133|1更新时间：2020-08-12
- 摘要：A prism surface plasmon resonance incentive model based on the porous silicon is proposed:prism base-metal-porous silicon layer-environmental media. The refractive index of the porous silicon will change with the sample absorbed on the porous silicon which causes the offset of surface plasmon resonance spectrum. Metal film and porous silicon layer compose the resonance film. According to the thin film optics and waveguide, the effect of resonance film on surface plasmons resonance spectrum is analyzed. With the method of finite element analysis, the resonance spectrum of the designed structure is obtained by numerical simulation. Through the comparison to the results, analysis and parameter optimization of the designed model are conducted. The results of analysis state the sensing performance of incentive model based on porous silicon is greatly improved compared by the common Kretschmann incentive model. The sensitivity of sensing structure is analyzed when the low concentration of ethylene glycol solution is as the sample. It can be obtained that the sensitivity is about 267.85(°)/RIU. That is about 2.13 times more than the sensitivity of the common Kretschmann incentive model. The resonance sensing of the designed structure provides theoretical reference for sample concentration detection, biological sensing and other aspects.关键词：surface plasmons resonance;optical sensor;resonance spectra;sensitivity88|115|4更新时间：2020-08-12
-
High Temperature Reliability of High-power LED Module Using Die Attach Material of Nano-silver Paste
摘要：A general procedure for accelerated degradation testing (ADT) was presented to predict the lifetime of three kinds of LED modules. The die attach materials of LED modules were nano-silver paste, Sn3Ag0.5Cu (Sn-based alloys), silver epoxy, respectively. The ambient temperature and forward current were controlled, and the light output at several time points was measured. The degradation mechanism of LEDs modules was analyzed. The lifetimes of LED modules under the condition of different die attach materials were predicted. The test results show that the nano-silver paste is a very promising die-attach material for the aging of multi-chip high power LED modules.关键词：high power LED module;die attach materials;nano-silver paste;accelerated degradation testing;lifetime241|64|0更新时间：2020-08-12
- Address：No.3888 Dong Nanhu Road, Changchun, Jilin, China Postal code：130033
- Tel：0431-86176862 Email：fgxbt@126.com
- Technical support is provided by Beijing Founder electronics co., LTD 吉ICP备11002662号-17
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0