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1.
Nanotechnology ; 31(9): 095401, 2019 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-31711047

RESUMO

Despite many recent attempts to restrict it, the dissolution and diffusion of polysulfides, leading to inferior cycling performance, is still the main bottleneck hindering commercialization of the Li-S battery. Herein, a new strategy of using lithium polyacrylate (LiPAA) to clad multiwalled carbon nanotube/sulfur (MWNT/S) composites as the interface layer for an MWNT/S/LiPAA cathode was proposed, not only to suppress polysulfide migration through physical encapsulation and chemical adsorption, but also to facilitate Li+ diffusion during the charge/discharge process. Attributed to these functions of LiPAA, MWNT/S/LiPAA exhibited a rate capability and cycling performance superior to those of MWNT/S and MWNT/S/PAA. Moreover, thanks to the introduction of LiPAA, the MWNT/S/LiPAA was endowed with robust mechanical properties, making it suitable for a flexible cathode in a flexible Li-S battery with stable output under deformation. This work could open up a promising way to suppress polysulfide migration for high-performance flexible Li-S batteries.

2.
Rev Sci Instrum ; 90(5): 056103, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31153276

RESUMO

Transmission line pulse transformers have been widely used in pulsed power technology. Traditional transmission line pulse transformers often use separate structures, which always introduces larger spurious parameters, and have lower voltage levels. In order to solve these problems, this note proposes a coaxial transmission line pulse transformer. A circular symmetric structure is used in the input and output ports of the coaxial transmission line pulse transformer, and there are no spurious parameters theoretically. Furthermore, this structure is suitable for hundreds of kilovolts high voltage applications. The structure and working principle of the coaxial transmission line pulse transformer are introduced in this note, and the circuit simulation research is conducted. The factors that affect the pulse transformation are analyzed. Furthermore, experimental studies of the square wave impulse response are conducted on an actual device. The result shows that the proposed coaxial transmission line pulse transformer can achieve the purpose of increasing the voltage amplitude while keeping the pulse waveform undistorted.

3.
Macromol Rapid Commun ; 39(12): e1800195, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29770518

RESUMO

The main bottlenecks for the widespread application of radical polymers in organic radical batteries are poor cycling stability, due to the dissolution of radical polymers into the electrolyte, and the low efficiency of multi-step synthesis strategies. Herein, a kind of electrolyte-resistant radical polymer bearing multi-pendant groups (poly(ethylene-alt-TEMPO maleate) (PETM)) is designed and synthesized through a one-step esterification reaction to graft 4-hydroxy-2,2,6,6-teramethylpiperidinyl-1-oxy into the commercially available poly(ethylene-alt-maleic anhydride). Interestingly, PETM is hardly soluble in the ethylene carbonate/dimethyl carbonate/ethyl methyl carbonate-based electrolyte, showing an extremely low solubility of 0.59 mg mL-1 , but is easily soluble in tetrahydrofuran and N-Methyl pyrrolidone. The derived binder-free PETM cathode exhibits nearly 100% utilization of the grafted nitroxide radicals (88 mA h g-1 ) and excellent rate capability with almost invariant capacitance from 10 C to 40 C. Significantly, the PETM cathodes retain 94% of the initial capacity after 1000 cycles, outperforming most reported radical polymer-based cathodes.


Assuntos
Óxidos N-Cíclicos/química , Técnicas Eletroquímicas/métodos , Eletrólitos/química , Polímeros/química , Dioxolanos/química , Técnicas Eletroquímicas/instrumentação , Eletrodos , Formiatos/química , Furanos/química , Microscopia Eletrônica de Varredura , Polímeros/síntese química , Pirrolidinonas/química , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Marcadores de Spin
4.
Opt Express ; 25(19): 23312-23319, 2017 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-29041632

RESUMO

Vortex beams carrying orbital angular momentum (OAM) have been recently investigated intensely in optical communication systems, as using OAM mode multiplexing simultaneously with other conventional multiplexing techniques is the key to further expand data capacity. This article demonstrates a wavelength- and OAM-tunable vortex laser at 1.6 µm in an Er:YAG system. For the first time to the best of our knowledge, a reflective volume Bragg grating (VBG) was theoretically and experimentally proved to be an effective OAM-preserving wavelength selector inside the laser cavity. A z-shaped laser cavity employing a VBG as a folding mirror was constructed for the direct generation of vortex beams, and we finally obtained wavelength-tunable beams of five OAM states (0, ± h, and ± 2h) with a narrow bandwidth less than 0.04 nm. This laser supplies a new way for optical communication by combining the spatial degree of freedom for multiplexing information channels with the conventionally used wavelength domains in packable and robust resonant cavity.

5.
Rev Sci Instrum ; 88(9): 096101, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28964179

RESUMO

A 10-GW high-energy-density Tesla-type pulse generator is developed with an improved insulating liquid based on a modified Tesla pulser-TPG700, of which the pulse forming line (PFL) is filled with novel insulating oil instead of transformer oil. Properties of insulating oil determining the stored energy density of the PFL are analyzed, and a criterion for appropriate oil is proposed. Midel 7131 is chosen as an application example. The results of insulating property experiment under tens-of-microsecond pulse charging demonstrate that the insulation capability of Midel 7131 is better than that of KI45X transformer oil. The application test in Tesla pulser TPG700 shows that the output power is increased to 10.5 GW with Midel 7131. The output energy density of TPG700 increases for about 60% with Midel 7131.

6.
Opt Express ; 25(3): 1815-1823, 2017 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-29519034

RESUMO

We report on stable passively harmonic mode-locking dissipative pulses with high repetition rate and narrow bandwidth in 2µm Tm: CaYAlO4 laser. At the large intracavity intensity, the laser generated 1st-order to 5th-order passively harmonic solitons with fundamental repetition rate of ~198 MHz and 5th-order repetition rate up to 0.98 GHz, which was mainly caused by the peak power clamp effect. The solitons yielded a tunable central wavelength from 1940nm to 1950 nm, and a narrow optical spectrum bandwidth of 60 pm without any active optical filter. At low intracavity intensity, the laser operated on the typical SESAM-guided mode-locking mode, with the scaled output average power up to 1.15 W. To our knowledge, this is the first observation of passively harmonic mode locking in 2µm solid laser system, and the first Watt-level output average power in Tm: CYA mode locking laser.

7.
Appl Opt ; 55(12): 3319-22, 2016 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-27140105

RESUMO

In this paper, we report on stable dual-wavelength operation of a thulium-doped compact all-fiber laser using a double-ring filter as the wavelength selective element. Simultaneously lasing at 2014.4 and 2018.4 nm has been obtained via tuning the polarization controllers to adjust the relative gain and loss of the laser cavity. The side mode suppression ratios are greater than 52 dB and the output power difference between the two lasing lines is less than 0.08 dB under 2.6 W of incident pump power.

8.
Opt Express ; 24(26): 30031-30037, 2016 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-28059388

RESUMO

Using a home-made black phosphorus plate (BPP) as handedness controller and Q-switch modulator synchronously, a ~1.6 µm pulsed vortex laser with well-determined handedness is demonstrated in this letter. Stable vortex pulses of LG0, + 1, LG0,-1, LG0, + 2 and LG0,-2 modes were respectively achieved from compact resonant cavities in this experiment. Such pulsed vortex laser should have promising applications in various fields based on its simple structure, controllable handedness, and carried orbital angular momentum.

9.
Rev Sci Instrum ; 85(2): 024708, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24593384

RESUMO

High voltage pulse generators are widely applied in many fields. In recent years, solid-state and operating at repetitive mode are the most important developing trends of high voltage pulse generators. A solid-state high voltage pulse generator based on saturable pulse transformer is proposed in this paper. The proposed generator is consisted of three parts. They are charging system, triggering system, and the major loop. Saturable pulse transformer is the key component of the whole generator, which acts as a step-up transformer and main switch during working process of this generator. The circuit and working principles of the proposed pulse generator are introduced first in this paper, and the saturable pulse transformer used in this generator is introduced in detail. Circuit of the major loop is simulated to verify the design of the system. Demonstration experiments are carried out, and the results show that when the primary energy storage capacitor is charged to a high voltage, such as 2.5 kV, a voltage with amplitude of 86 kV can be achieved on the secondary winding. The magnetic core of saturable pulse transformer is saturated deeply and the saturable inductance of the secondary windings is very small. The switch function of the saturable pulse transformer can be realized ideally. Therefore, a 71 kV output voltage pulse is formed on the load. Moreover, the magnetic core of the saturable pulse transformer can be reset automatically.

10.
Appl Opt ; 53(35): 8216-21, 2014 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-25608062

RESUMO

We numerically study the vector dynamics of dissipative solitons (DSs) in a 2 µm dispersion-managed fiber laser mode locked by a semiconductor saturable absorber mirror and operated in the normal dispersion regime. It is shown that the effective gain bandwidth is crucial for the DS generation. The steep spectral edges of DSs are the consequence of the interaction among the normal dispersion, fiber nonlinearity, gain and loss, and gain dispersion effect, etc. We numerically duplicate the experimental results and further explore the vector features of the generated DSs. Two DSs formed along the two orthogonal polarization directions which, incoherently coupled with each other, could propagate in the birefringent cavity with the same group velocity.

11.
Rev Sci Instrum ; 84(6): 064703, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23822362

RESUMO

LC generator is widely applied in the field of high voltage generation technology. A compact and all solid-state LC high voltage generator based on saturable pulse transformer is proposed in this paper. First, working principle of the generator is presented. Theoretical analysis and circuit simulation are used to verify the design of the generator. Experimental studies of the proposed LC generator with two-stage main energy storage capacitors are carried out. And the results show that the proposed LC generator operates as expected. When the isolation inductance is 27 µH, the output voltage is 1.9 times larger than the charging voltage on single capacitor. The multiplication of voltages is achieved. On the condition that the primary energy storage capacitor is charged to 857 V, the output voltage of the generator can reach to 59.5 kV. The step-up ratio is nearly 69. When self breakdown gas gap switch is used as main switch, the rise time of the voltage pulse on load resistor is 8.7 ns. It means that the series-wound inductance in the discharging circuit is very small in this system. This generator can be employed in two different applications.

12.
Rev Sci Instrum ; 83(12): 124703, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23278010

RESUMO

Magnetic switch has been widely used in the field of pulsed power system for its advantages of solid state, high repetition rate, and long lifetime. In this paper, the synchronization of ns-range multi-pulses based on magnetic switch is studied and two kinds of technical methods are proposed. One of which is based on magnetic switches on a communal magnetic core. It was proved that the synchronization accuracy of 3 pulses is about 2 ns. Another proposed method is ns-range multi-pulse synchronization based on saturable pulse transformer and the experimental result showed that the synchronization accuracy of 2 pulses could achieve 2.5 ns. In contrast to other multi-pulse synchronization methods controlled by high-voltage pulse trigger or laser trigger, the synchronization based on magnetic switch and saturable pulse transformer has the advantages of high synchronization accuracy, long lifetime, and exemption from external trigger signals.

13.
Rev Sci Instrum ; 82(10): 104701, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22047311

RESUMO

In this paper, the electromagnetic dispersion theory and the classic telegraph equations were combined to calculate the important parameters of the helical Blumlein pulse forming line (BPFL) of accelerator based on tape helix. In the work band of the BPFL at several hundred ns range, electromagnetic dispersion characteristics were almost determined by the zeroth harmonic. In order to testify the dispersion theory of BPFL in this paper, filling dielectrics, such as de-ionized water, transformer oil, and air were employed in the helical BPFL, respectively. Parameters such as capacitance, inductance, characteristic impedance, and pulse duration of the BPFL were calculated. Effects of dispersion on these parameters were analyzed. Circuit simulation and electromagnetic simulation were carried out to prove these parameters of BPFL filled with these three kinds of dielectrics, respectively. The accelerator system was set up, and experimental results also corresponded to the theoretical calculations. The average theoretical errors of impedances and pulse durations were 3.5% and 3.4%, respectively, which proved the electromagnetic dispersion analyses in this paper.

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