Browsing by Author "Lin, Ming-Hsien"

Now showing 1 - 4 of 4

A Holey Graphene Additive for Boosting Performance of Electric Double-Layer Supercapacitors
(2020-04-01)
Huang, Jun-Bin
;
Patra, Jagabandhu
;
Lin, Ming-Hsien
;
Ger, Ming-Der
;
Liu, Yih-Ming
We demonstrate a facile and effective method, which is low-cost and easy to scale up, to fabricate holey graphene nanosheets (HGNSs) via ultrafast heating during synthesis. Various heating temperatures are used to modify the material properties of HGNSs. First, we use HGNSs as the electrode active materials for electric double-layer capacitors (EDLCs). A synthesis temperature of 900 degrees C seems to be optimal, i.e., the conductivity and adhesion of HGNSs reach a compromise. The gravimetric capacitance of this HGNS sample (namely HGNS-900) is 56 Fg(-1). However, the volumetric capacitance is low, which hinders its practical application. Secondly, we incorporate activated carbon (AC) into HGNS-900 to make a composite EDLC material. The effect of the AC:HGNS-900 ratio on the capacitance, high-rate performance, and cycling stability are systematically investigated. With a proper amount of HGNS-900, both the electrode gravimetric and volumetric capacitances at high rate charging/discharging are clearly higher than those of plain AC electrodes. The AC/HGNS-900 composite is a promising electrode material for nonaqueous EDLC applications.
A Novel Moisture-Insensitive and Low-Corrosivity Ionic Liquid Electrolyte for Rechargeable Aluminum Batteries
(1970-01-01)
Li, Chi
;
Patra, Jagabandhu
;
Li, Ju
;
Rath, Purna Chandra
;
Lin, Ming-Hsien
Rechargeable aluminum batteries (RABs) are extensively developed due to their cost-effectiveness, eco-friendliness, and low flammability and the earth abundance of their electrode materials. However, the commonly used RAB ionic liquid (IL) electrolyte is highly moisture-sensitive and corrosive. To address these problems, a 4-ethylpyridine/AlCl3 IL is proposed. The effects of the AlCl3 to 4-ethylpyridine molar ratio on the electrode charge-discharge properties are systematically examined. A maximum graphite capacity of 95 mAh g(-1) is obtained at 25 mA g(-1). After 1000 charge-discharge cycles, approximate to 85% of the initial capacity can be retained. In situ synchrotron X-ray diffraction is employed to examine the electrode reaction mechanism. In addition, low corrosion rates of Al, Cu, Ni, and carbon-fiber paper electrodes are confirmed in the 4-ethylpyridine/AlCl3 IL. When opened to the ambient atmosphere, the measured capacity of the graphite cathode is only slightly lower than that found in a N-2-filled glove box; moreover, the capacity retention upon 100 cycles is as high as 75%. The results clearly indicate the great potential of this electrolyte for practical RAB applications.
A Right-Half-Plane Zero -Free Buck-Boost DC -DC Converter with 97.46% High Efficiency and Low Output Voltage Ripple
(2019-01-01)
Lin, Yen-An
;
Huang, Tzu-Ping
;
Ou-Yang, You-Zheng
;
Wu, Zheng-Ru
;
Chen, Ke-Horng
The right -half-plane (RIIP) zero can he eliminated in the proposed buck-boost (BB) converter to achieve fast transients for Internet-ofThing (IoT) applications. The pseudo-boost mode in the BB converter eliminates one power switch in the current path and ensures that the continuous inductor current is half of the conventional design value to achieve 97.46% peak efficiency. Besides, the output voltage ripple is reduced to 7mV. By inserting an additional phase, a smooth transition between the buck and pseudo -boost modes ensures a voltage drop less than 15mV. The slope-based transient enhancement (SBTE) circuit accelerates transient response in 9 S with a load variation of 400 mA.
Comparison of field emission performances and durability of three nanocarbon materials
(2020-07-01)
Youh, Meng-Jey
;
Lin, Chun-Shuan
;
Pu, Nen-Wen
;
Liu, Yih-Ming
;
Youh, Ru-Yi
The performances and operation lifetime of field emission (FE) cathodes made by spray-coating three different nanocarbon materials-carbon nanotubes (CNTs), graphene (GE), and carbon nanocoils (CNCs)-were compared. Though CNTs had the benefits of the lowest turn-on field, CNCs exhibited the most stable cycle-to-cycle repeatability and a significantly longer life than CNTs and GE under a continuous high-current-density operation. The microscopic morphology and Raman spectra of these nanocarbon emitters before and after the 50-h life tests were examined in order to understand the damage mechanism and the cause of their distinct performance decay behaviors. The results indicated that CNCs, whose diameters are significantly larger than those of CNTs and the thickness of GE, can withstand the thermal effects of high current density with the least degree of damage in the morphology and microstructure. According to our performance and life tests, CNTs are most suitable for low-voltage small-current FE applications because of their highest field enhancement factor and lowest turn-on field, while CNCs are a more favorable candidate for high-voltage long-term applications such as FE x-ray tubes.