For many current betavoltaics, beta sources and PN junction energy conversion units are separated. The air gap between the two parts could stop part of decay beta particles, which results in inefficient performance of...For many current betavoltaics, beta sources and PN junction energy conversion units are separated. The air gap between the two parts could stop part of decay beta particles, which results in inefficient performance of the betavoltaic. By employing 63Ni with an apparent emission activity density of 7.26×10~7 and 1.81×10~8 Bq cm^(-2), betavoltaic performance levels were calculated at a vacuum degree range of 1×10~5 to 1×10^(-1) Pa and measured at 1.0×10~5 and 1.0×10~4 Pa, respectively. Results show that betavoltaic performance levels improve significantly as the vacuum degree increases. The maximum output power (P_(max)) exhibits the largest change, followed by short-circuit current (I_(sc)), open-circuit voltage (V_(oc)), and fill factor. The vacuum degree effects on Isc, Voc,and Pmax of the betavoltaic with low apparent activity density 63Ni are more significant than those of the betavoltaic with high apparent activity density ^(63)Ni. Moreover, the improved efficiencies of the measured performances are larger than the calculated efficiencies because of the low ratio of Isc and reverse saturation current (I_0). The values of I0, ideality factor, and shunt resistance were estimated to modify the equivalent circuit model. The calculation results based on this model are closer to the measurement results. The results of this research can provide a theoretical foundation and experimental reference for the study of vacuum degree effects on betavoltaics of the same kind.展开更多
Sodium ions(Na+) and ether electrolyte coinserted graphite possesses a considerable volume expansion effect. However, the mechanism fails to clearly explain its stability. In response to this deficiency, the co-insert...Sodium ions(Na+) and ether electrolyte coinserted graphite possesses a considerable volume expansion effect. However, the mechanism fails to clearly explain its stability. In response to this deficiency, the co-inserted reaction is proposed, which is affected by the Lorentz force of the applied electric field under the high-current condition. The Na^(+) ions are separated out, while the ethylene glycol dimethyl ether molecules remain between the graphite layers. This insight provides a reasonable explanation for the extraordinary stability of this material. In situ X-ray diffraction and density functional theory calculations confirm the separation and release of Na+. On the basis of this result, unmodified commercial graphite was stably cycled 6400 times at a current density of up to 10 A g^(-1), and the capacity retention rate was as high as 97.2%. The full battery assembled in the laboratory has a maximum output power of 14,846 W kg^(-1)and an output energy density of 103 W h kg^(-1)(relative to the weight of anodic and cathodic active materials). The new mechanism provides innovative ideas for the design of large-scale energy storage devices.展开更多
A cymbal transducer is made up of a piezoceramic disk sandwiched between two dome-shaped metal endcaps.High circumferential stresses caused by flexural motion of the metal endcaps can induce the loss of mechanical inp...A cymbal transducer is made up of a piezoceramic disk sandwiched between two dome-shaped metal endcaps.High circumferential stresses caused by flexural motion of the metal endcaps can induce the loss of mechanical input energy.Finite element analysis shows that the radial slots fabricated in metal endcaps can release the circumferential stresses,and reduce the loss of mechanical input energy that could be converted into electrical energy.In this letter,the performance of a slotted-cymbal transducer in energy harvesting was tested.The results show that the output voltage and power of the cymbal are improved.A maximum output power of around 16 mW could be harvested from a cymbal with 18 cone radial slots across a 500 kΩ resistive load,which is approximately 0.6 times more than that of the original cymbal transducer.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 11505096 & 11675076)the National Defense Basic Scientific Research Project (Grant No. JCKY2016605C006)+5 种基金the Natural Science Foundation of Jiangsu Province (Grant No. BK20150735)the Shanghai Aerospace Science and Technology Innovation Fundthe Jiangsu Planned Projects for Postdoctoral Research Funds (Grant No. 1601139B)the Foundation of Graduate Innovation Center in NUAA (Grant No.kfjj20160609)the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Fundamental Research Funds for the Central Universities (Grant No. NJ20160031)
文摘For many current betavoltaics, beta sources and PN junction energy conversion units are separated. The air gap between the two parts could stop part of decay beta particles, which results in inefficient performance of the betavoltaic. By employing 63Ni with an apparent emission activity density of 7.26×10~7 and 1.81×10~8 Bq cm^(-2), betavoltaic performance levels were calculated at a vacuum degree range of 1×10~5 to 1×10^(-1) Pa and measured at 1.0×10~5 and 1.0×10~4 Pa, respectively. Results show that betavoltaic performance levels improve significantly as the vacuum degree increases. The maximum output power (P_(max)) exhibits the largest change, followed by short-circuit current (I_(sc)), open-circuit voltage (V_(oc)), and fill factor. The vacuum degree effects on Isc, Voc,and Pmax of the betavoltaic with low apparent activity density 63Ni are more significant than those of the betavoltaic with high apparent activity density ^(63)Ni. Moreover, the improved efficiencies of the measured performances are larger than the calculated efficiencies because of the low ratio of Isc and reverse saturation current (I_0). The values of I0, ideality factor, and shunt resistance were estimated to modify the equivalent circuit model. The calculation results based on this model are closer to the measurement results. The results of this research can provide a theoretical foundation and experimental reference for the study of vacuum degree effects on betavoltaics of the same kind.
基金supported by the National Natural Science Foundation of China (21978088, 91534202 and 51673063)sponsored by the Program of Shanghai Academic/Technology Research Leader (20XD1433600)+4 种基金the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutes of High Learningthe Basic Research Program of Shanghai (17JC1402300)the Social Development Program of Shanghai (17DZ1200900)the Shanghai City Board of education research and innovation projectthe Fundamental Research Funds for the Central Universities (222201718002)。
文摘Sodium ions(Na+) and ether electrolyte coinserted graphite possesses a considerable volume expansion effect. However, the mechanism fails to clearly explain its stability. In response to this deficiency, the co-inserted reaction is proposed, which is affected by the Lorentz force of the applied electric field under the high-current condition. The Na^(+) ions are separated out, while the ethylene glycol dimethyl ether molecules remain between the graphite layers. This insight provides a reasonable explanation for the extraordinary stability of this material. In situ X-ray diffraction and density functional theory calculations confirm the separation and release of Na+. On the basis of this result, unmodified commercial graphite was stably cycled 6400 times at a current density of up to 10 A g^(-1), and the capacity retention rate was as high as 97.2%. The full battery assembled in the laboratory has a maximum output power of 14,846 W kg^(-1)and an output energy density of 103 W h kg^(-1)(relative to the weight of anodic and cathodic active materials). The new mechanism provides innovative ideas for the design of large-scale energy storage devices.
基金supported by the National Natural Science Foundation of China (No.50875057)the Natural Scientific Research Innovation Foundation in Harbin Institute of Technology,China (No.HIT.NSRIF.2008.50)
文摘A cymbal transducer is made up of a piezoceramic disk sandwiched between two dome-shaped metal endcaps.High circumferential stresses caused by flexural motion of the metal endcaps can induce the loss of mechanical input energy.Finite element analysis shows that the radial slots fabricated in metal endcaps can release the circumferential stresses,and reduce the loss of mechanical input energy that could be converted into electrical energy.In this letter,the performance of a slotted-cymbal transducer in energy harvesting was tested.The results show that the output voltage and power of the cymbal are improved.A maximum output power of around 16 mW could be harvested from a cymbal with 18 cone radial slots across a 500 kΩ resistive load,which is approximately 0.6 times more than that of the original cymbal transducer.
