Low frequency plasmonic state and negative permittivity spectra of coagulated Cu granular composite materials in the percolation threshold

2013 ◽  
Vol 102 (18) ◽  
pp. 181904 ◽  
Author(s):  
Takanori Tsutaoka ◽  
Teruhiro Kasagi ◽  
Shinichiro Yamamoto ◽  
Kenichi Hatakeyama
2018 ◽  
Vol 9 (7) ◽  
pp. 476-480
Author(s):  
Takanori Tsutaoka ◽  
Herieta Massango ◽  
Teruhiro Kasagi

Author(s):  
Yuyan Li ◽  
Huan Ye ◽  
Yunpeng Qu ◽  
Zongxiang Wang ◽  
Kai Sun

Abstract Three-dimensional (3D) carbon networks composed of graphene (GR) and carbon nanotube (CNT) were constructed in copper calcium titanate (CCTO) in order to realize negative permittivity behavior. The results show that negative permittivity can be obtained at kHz frequencies above percolation threshold when 3D carbon networks are successfully constructed. Negative permittivity originates from the low-frequency plasmonic state which is explained by the Drude model. The magnitude of negative permittivity was tuned between 105 and 106 which significantly correlates with concentration of free carriers. Moreover, the reactance spectra clarify the inductive character of negative permittivity materials.


2017 ◽  
Vol 121 (10) ◽  
pp. 103902 ◽  
Author(s):  
Herieta Massango ◽  
Takanori Tsutaoka ◽  
Teruhiro Kasagi ◽  
Shinichiro Yamamoto ◽  
Kenichi Hatakeyama

2013 ◽  
Vol 103 (26) ◽  
pp. 261906 ◽  
Author(s):  
Takanori Tsutaoka ◽  
Koki Fukuyama ◽  
Hideaki Kinoshita ◽  
Teruhiro Kasagi ◽  
Shinichiro Yamamoto ◽  
...  

2021 ◽  
Author(s):  
Jiahong Tian ◽  
Runhua Fan ◽  
Zongxiang Wang ◽  
Jiahao Xin ◽  
Zhongyang Wang

Abstract Silver/polyaniline (Ag/PANI) composites were prepared by an in-situ synthesis method. Interestingly, the permittivity changed from positive to negative along with the formation of percolation network. The plasma oscillations of free electrons from the network made a dominant effect on the negative permittivity behavior. Further investigation based on equivalent circuit analysis revealed that the composites with negative permittivity presented inductive character. The epsilon-negative composites can be applied to electromagnetic shielding, absorbing and attenuation.


2021 ◽  
Author(s):  
Xiao-jian Wang ◽  
Liang-Bi Wang

Abstract The most common non-granular fillers are sheet and fiber. When they are distributed along the heat flux direction, the thermal conductivity of composite increases greatly. Meanwhile, the filler contact also has large effect on the thermal conductivity. However, the effect of filler contact on the thermal conductivity of composite with directional fillers has not been investigated. In this paper, the combined effects of filler contact, content and orientation are investigated. The results show that the effect of filler orientation on the thermal conductivity is greater than filler contact in low filler content, and exact opposite in high filler content. The effect of filler contact on fibrous and sheet fillers is far greater than cube and sphere fillers. This rule is affected by the filler contact. The filler content of 8% is the ideal percolation threshold of composite with fibrous and sheet filler. It is lower than cube filler and previous reports. The space for thermal conductivity growth of composite with directional filler is still very large. The effect of interfacial thermal resistance should be considered in predicting the thermal conductivity of composite under high Rc (>10-4).


2015 ◽  
Vol 383 ◽  
pp. 139-143 ◽  
Author(s):  
Takanori Tsutaoka ◽  
Teruhiro Kasagi ◽  
Shinichiro Yamamoto ◽  
Kenichi Hatakeyama

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Vladimir L. Shkuratnik ◽  
Petr V. Nikolenko

The article is devoted to the investigation of the spectral characteristics of acoustic emission signals that appear under various schemes of composite materials loading. The tests involved samples of composites reinforced with layers sheets of carbon fiber fabric and dispersed carbon fibers. Based on the results of laboratory tests, a comparison is made between the traditional parameters of acoustic emission and the complete spectrograms of the acoustic emission response developed with the use of a special algorithm. The relationship between the emission activity and the change in the spectral composition of emission hits is shown. For example, for some composites, the acoustic emission memory effect (Kaiser effect) manifests itself not only in the time domain but also in the spectral domain in a form of a sharp change in the amplitudes in the frequency range 130/150 kHz. Also, when the samples were loaded according to the Brazilian scheme, the presence of the so-called “inverse” Kaiser effect is observed, in which the memory carrier “remembers” the previously experienced level of tensile stresses and reproduces this information during subsequent unloading. Such effect manifests itself in the form of a sharp change in the amplitudes in the low-frequency region of the spectrum.


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