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Emerging Materials for High-Performance Supercapacitors
Published in Anurag Gaur, A.L. Sharma, Anil Arya, Energy Storage and Conversion Devices, 2021
Historically, Ewald Georg von Kleist of Pomerania first observed double-layer charge storage in 1745 when he discovered charge storage by connecting a high-voltage electrostatic generator to the flow of liquid by connecting a wire in a glass jar. Since then, the double layer charge storage has progressed a great deal during which glass dielectrics have been replaced with aqueous, nonaqueous, gel, and solid electrolytes, and metal foils are replaced with carbons having high surface area. The new systems store an enormous amount of energy facilitated mostly by high electrode surface, and the high conductivity of materials can be broadly classified into electrochemical double-layer capacitive materials at which charge is stored only at the electrode–electrolyte interface without any transfer of charge and pseudocapacitive materials that perform charge storage through charging transmit and phase change at the electrode–electrolyte interface [Maldonado-Hódar et al. 2000; Zhang and Pan 2015]. Various carbon microstructures with a large effective surface have been used as electrode materials in EDLC. The most widely studied and exploited carbon forms are activated carbons or engineered carbon, carbon nanotubes, carbon nanofiber (CNF), graphene, etc., for the electrochemical capacitor application.
Ubiquitous Computing: A New Era of Computing
Published in Lavanya Sharma, Pradeep K Garg, From Visual Surveillance to Internet of Things, 2019
Shailja Gupta, Riya Sapra, Sugandhi Midha
Power Supply: In order to operate, electronic devices require a power supply. With improvements in chip technologies system size, power demands have been reduced and performance levels have improved. Still, establishing a constant power supply remains an issue of concern. For power supply, some devices operate on energy from the electric grid, while others, like wireless systems or mobile devices, depend on stored power sources. Therefore, power sources are required that provide long-term stability and excellent reliability. Moreover, improvements in power supply have allowed generating power without batteries. Some examples are photovoltaic generators (using solar cells, piezoelectric generators (mechanical to electrical energy), thermoelectric generators (heat to electrical energy), electromagnetic generators (based on dynamo principle), capacitive and electrostatic generator (uses electrostatic charges), and thermomechanical generators (mechanical to electric energy).
Renewable Energy Resources
Published in Julie Kerr, Introduction to Energy and Climate, 2017
By the seventeenth century, several electricity-related discoveries had been made, such as the invention of an early electrostatic generator, the differentiation between positive and negative currents, and the classification of materials as conductors or insulators. A conductor is a material through which an electrical current may pass; an insulator is a substance that does not readily conduct electricity. In the early 1600s English scientist, Thomas Browne, was conducting carefully planned “electricity” experiments. Then in 1752, Benjamin Franklin conducted his famous experiment with a kite, a key, and a storm. His experiment only proved that lightning and tiny electric sparks were the same thing. Following him, Italian physicist Alessandro Volta discovered that particular chemical reactions could produce electricity, and in 1800, he constructed the voltaic pile that produced a steady electric current, and so he was the first person to create a steady flow of electric charge. He was also the first to create a transmission of electricity by linking positively-charged and negatively-charged connectors and driving an electrical change or voltage through them.
Experimental investigation on the performance of composite electrostatic spraying milling using different inner/outer fluid combinations
Published in Machining Science and Technology, 2021
Yu Su, Wenhao Gao, Hai Jiang, Zhiqiang Liu
The atomization test platform was fabricated to observe the atomization morphology and evaluate the charging property and atomization stability. Figure 2 shows the atomization test platform of CES. It comprised CES system and microscope imaging system. The coaxial nozzle was composed of inner and outer metal nozzles, which was connected to the negative electrode of high-voltage electrostatic generator (DW-N603, Dongwen High Voltage Power Supply Ltd., China) through a wire. The inner nozzle and the outer nozzle were respectively connected to inner and outer fluid syringe pumps (LSP01-1A, Baoding Longer Precision Pump Ltd., China) through a silicone rubber tube. The titanium alloy workpiece was grounded and placed on the table. The milling cutter stood on the workpiece to simulate the relative position of cutting process. The spraying angle of 35° in relation to the milling cutter and spraying distance of 20 mm were used to effectively supply charged composite droplets to the cutting area. The charging property can be characterized by atomization current. The current transported by the CES was collected by the grounded picoammeter (Hest122, Beijing Huace Ltd., China) that was connected to the titanium alloy workpiece. The change of current indirectly reflected the atomization stability. The accurately measured 10 µL inner fluid and 10 µL outer fluid were simultaneously dropped through the coaxial nozzle on the surface of tempered glass film. The wetting angle of composite droplet was measured under different voltages using a microscope imaging system (WS-SZ7, Suzhou Lux Optoelectronics Technology Ltd., China), as shown in Figure 3.
Controlled release of resveratrol and xanthohumol via coaxial electrospinning fibers
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Xue Zhang, Libin Han, Qihao Sun, Wenlong Xia, Qifeng Zhou, ZhuanZhuan Zhang, Xiaofeng Song
The process of coaxial fibers is shown in Scheme 1. The PEO solution and PLGA solution were separately transferred to two syringes linked together through a coaxial needle, and were slightly pressurized to achieve stable electrospinning. 9.5 kV was applied between the cathode and anode by electrostatic generator (ES30P‐5w/DAM, Gamma high voltage, Ormond Beach, FL, USA) at a distance of 12 cm to produce the fibrous mesh. The spinning speeds were 0.2 ml/h and 0.4 ml/h, respectively. The collected mesh was placed in a vacuum oven to eliminate solvent residuals for 24 h.
Design and fabrication of injectable microcarriers composed of acellular cartilage matrix and chitosan
Published in Journal of Biomaterials Science, Polymer Edition, 2018
Farzane Sivandzade, Shohreh Mashayekhan
Various hybrid ECM/CS MCs were fabricated with the same diameter (400 ± 50 μm) using CS (medium molecular weight chitosan powder with Mw = 280 kDa (Sigma–Aldrich)) and ECM solution as presented in Table 1. ECM solution was prepared by enzymatic digestion according to our previous report [14]. In summary ECM powder was briefly digested in pepsin solution (1 mg/ml in 0.1 M HCl). In order to get a homogeneous solution, the suspension went under constant stirring for about 60 h at room temperature to complete the digestion process. CS solution (4% w/v acetic acid (Merck)) was prepared by dissolving CS in 2% (v/v) acetic acid and stirring overnight. Then, solubilized ECM and CS were mixed in certain quantities along with the carbodiimide solution containing 40 mM1-ethyl-3-[3 dimethylaminopropyl] carbodiimide (EDC) (Sigma–Aldrich), 20 mM (N-hydroxysuccinimide) (NHS) (Sigma–Aldrich), and 50 mM 2-[N-morpholine] ehanesulfonic acid (MES) (Sigma–Aldrich) followed by stirring for 20 h to reach a homogenous mixture. The homogeneous solution was dropped into a crosslinker solution containing 3% w/v sodium tripolyphosphate) TPP ((Sigma–Aldrich) through 16-gauge needle driven by a syringe pump under a high voltage electrostatic field to produce spherical shaped MCs. The needle was electrically connected to the positive electrode of a high voltage electrostatic generator, the negative electrode of which was electrically connected to an annular stainless steel plate fixed under the coagulation solution (Figure 1). The optimized potential between the needle and the stainless steel plate and the pumping rate was obtained between 7 and 11 kV and 300–700 μl/min, respectively. The fabricated MCs were frozen overnight at −20 °C, followed by lyophilisation for 24 h. Then, the MCs were immersed into 1 N NaOH solution for 30 min, rinsed by deionized water, and lyophilized again for 24 h.