Microwave Permittivity of Multi-Walled Carbon Nanotubes

2006 ◽  
Vol 11-12 ◽  
pp. 559-562 ◽  
Author(s):  
Xiao Lai Liu ◽  
Dong Lin Zhao
Keyword(s):  
Carbon Nanotubes ◽  
Dielectric Materials ◽  
Dissipation Factor ◽  
Paraffin Wax ◽  
Factor V ◽  
Frequency Range ◽  
Multi Walled Carbon Nanotubes ◽  
Absorbing Material ◽  
Walled Carbon Nanotubes ◽  
Microwave Permittivity

The microwave permittivity of multi-walled carbon nanotubes blended in paraffin wax has been studied in the frequency range from 2 to 18GHz. The dissipaton factors of the multi-walled carbon nanotubes are high at the microwave frequencies. The microwave permittivity of the multi-walled carbon nanotubes and paraffin wax (or other dielectric materials) composites can be tailored by the content of the carbon nanotubes. And ε′, ε″and tgδ of the composites increase with the volume filling factor (v) of the carbon nanotubes. The ε′ and ε″ of the multi-walled carbon nanotubes decrease with frequency in the frequency range from 2 to18 GHz. This property is very good for broadband radar absorbing materials. The classical effective medium functions can not effectively model the microwave permittivities of the composites containing multi-walled carbon nanotubes. The ε′ and ε″ can be effectively modeled using second-order polynomials (ε′, ε″=Av2+Bv+C). The high ε″ and dissipation factor tgδ (ε″/ε′) of multi-walled carbon nanotubes are due to the dielectric relaxation. The carbon nanotubes composites would be a good candidate for microwave absorbing material electromagnetic interface (EMI) shielding material.

scholarly journals Enhancing Microwave Absorbing Properties of Nickel-Zinc-Ferrite with Multi-walled Carbon Nanotubes (MWCNT) Loading at Higher Gigahertz Frequency

2021 ◽  
pp. 1-7
Author(s):  
Fadzidah Mohd Idris ◽  
Khamirul Amin Matori
Keyword(s):  
Carbon Nanotubes ◽  
Electromagnetic Radiation ◽  
Electromagnetic Interference ◽  
Zinc Ferrite ◽  
Dielectric Materials ◽  
Electronic Systems ◽  
Frequency Range ◽  
Nickel Zinc ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

The rapid growth of electronic systems and devices operating within the gigahertz (GHz) frequency range has increased electromagnetic interference. In order to eliminate or reduce the spurious electromagnetic radiation levels more closely in different applications, there is strong research interest in electromagnetic absorber technology. Moreover, there is still a lack of ability to absorb electromagnetic radiation in a broad frequency range using thin thickness. Thus, this study examined the effect of incorporating magnetic and dielectric materials into the polymer matrix for the processing of radar absorbing materials. The experiment evaluated the sample preparation with different weight percentages of multi-walled carbon nanotubes (MWCNT) mixed with Ni0.5Zn0.5Fe2O4 (Nickel-Zinc-Ferrite) loaded into epoxy (P) as a matrix. The prepared samples were analysed by examining the reflectivity measurements in the 8 – 18 GHz frequency range and conducting a morphological study using scanning electron microscopy analyses. The correlation of the results showed that different amounts of MWCNT influenced the performance of the microwave absorber. As the amount of MWCNTs increased, the reflection loss (RL) peak shifted towards a lower frequency range and the trend was similar for all thicknesses. The highest RL was achieved when the content of MWCNTs was 2 wt% with a thickness of 2 mm with an RL of – 14 dB at 16 GHz. The 2.5 GHz bandwidth corresponded to the RL below -10 dB (90% absorption) in the range of 14.5 – 17 GHz. This study showed that the proposed experimental route provided flexible absorbers with suitable absorption values by mixing only 2 wt% of MWCNTs.

Formation Mechanism and Microwave Permittivity of Carbon Nanotubes Filled with Metallic Silver Nanowires

2007 ◽  
Vol 334-335 ◽  
pp. 685-688
Author(s):  
Dong Lin Zhao ◽  
Xia Li ◽  
Wei Dong Chi ◽  
Zeng Min Shen
Keyword(s):  
Carbon Nanotubes ◽  
Formation Mechanism ◽  
Silver Nanowires ◽  
Nitrate Solution ◽  
Silver Nitrate Solution ◽  
Metallic Silver ◽  
Transmission Electron ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes ◽  
Microwave Permittivity

The filling of multi-walled carbon nanotubes (MWNTs) with metallic silver nanowires via wet chemistry method was investigated. The carbon nanotubes were filled with long continuous silver nanowires. The carbon nanotubes were almost opened and cut after being treated with concentrated nitric acid. Silver nitrate solution filled carbon nanotubes by capillarity. Carbon nanotubes were filled with silver nanowires after calcinations by hydrogen. The diameters of silver nanowires were in the range of 20-40nm, and lengths of 100nm-10μm. We studied the micromorphology of the silver nanowires filled in carbon nanotubes by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Based on the experimental results, a formation mechanism of the Ag nanowire-filled carbon nanotubes was proposed. And the microwave permittivity of the carbon nanotubes filled with metallic silver nanowires was measured in the frequency range from 2 GHz to 18 GHz. The loss tangent of the carbon nanotubes filled with metallic silver nanowires is high. So the carbon nanotubes filled with metallic silver nanowires would be a good candidate for microwave absorbent.

Impedance characterization and microwave permittivity of multi-walled carbon nanotubes/BaTiO3/epoxy composites

2020 ◽  
Vol 126 (10) ◽  
Author(s):  
Ludmila L. Vovchenko ◽  
Oleg V. Lozitsky ◽  
Ludmila Y. Matzui ◽  
Viktor V. Oliynyk ◽  
Volodymyr V. Zagorodnii ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Epoxy Composites ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes ◽  
Impedance Characterization ◽  
Microwave Permittivity

scholarly journals Paraffin Wax [As a Phase Changing Material (PCM)] Based Composites Containing Multi-Walled Carbon Nanotubes for Thermal Energy Storage (TES) Development

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 951
Author(s):  
Norah Hamad Almousa ◽  
Maha R. Alotaibi ◽  
Mohammad Alsohybani ◽  
Dominik Radziszewski ◽  
Saeed M. AlNoman ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Paraffin Wax ◽  
Energy Storage Materials ◽  
Thermal Mass ◽  
Multi Walled Carbon Nanotubes ◽  
Nanocomposite Pcm ◽  
Walled Carbon Nanotubes

Thermal energy storage (TES) technologies are considered as enabling and supporting technologies for more sustainable and reliable energy generation methods such as solar thermal and concentrated solar power. A thorough investigation of the TES system using paraffin wax (PW) as a phase changing material (PCM) should be considered. One of the possible approaches for improving the overall performance of the TES system is to enhance the thermal properties of the energy storage materials of PW. The current study investigated some of the properties of PW doped with nano-additives, namely, multi-walled carbon nanotubes (MWCNs), forming a nanocomposite PCM. The paraffin/MWCNT composite PCMs were tailor-made for enhanced and efficient TES applications. The thermal storage efficiency of the current TES bed system was approximately 71%, which is significant. Scanning electron spectroscopy (SEM) with energy dispersive X-ray (EDX) characterization showed the physical incorporation of MWCNTs with PW, which was achieved by strong interfaces without microcracks. In addition, the FTIR (Fourier transform infrared) and TGA (thermogravimetric analysis) experimental results of this composite PCM showed good chemical compatibility and thermal stability. This was elucidated based on the observed similar thermal mass loss profiles as well as the identical chemical bond peaks for all of the tested samples (PW, CNT, and PW/CNT composites).

scholarly journals Electromagnetic Properties of Cold-Cure Silicone Mixtures Containing Multi-Walled Carbon Nanotubes

2020 ◽  
pp. 043-046
Author(s):  
A.G. Tkachev ◽  
◽  
N.R. Memetov ◽  
R.A. Stolyarov ◽  
N.A. Chapaksov ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Physical Properties ◽  
Electromagnetic Radiation ◽  
Nanocomposite Materials ◽  
Electromagnetic Properties ◽  
Frequency Range ◽  
Concentration Dependences ◽  
Multi Walled Carbon Nanotubes ◽  
Properties Of Materials ◽  
Walled Carbon Nanotubes

Nanocomposite materials based on a cold-cure silicone mixture containing multi-walled carbon nanotubes were obtained. The concentration dependences of the radio-physical properties of materials were investigated. An increase in the efficiency of shielding electromagnetic radiation in the radio frequency range of wavelengths with increasing concentrations of multi-walled carbon nanotubes up to 10 wt. % was verified.

scholarly journals Electrical properties of compacted carbon nanomaterials

2021 ◽  
Vol 340 ◽  
pp. 01047
Author(s):  
Nikita I. Lapekin ◽  
Artem A. Shestakov ◽  
Andrey E. Brester ◽  
Arina V. Ukhina ◽  
Alexander G. Bannov
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Properties ◽  
Carbon Nanofibers ◽  
Carbon Nanomaterials ◽  
Frequency Range ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes ◽  
Cylindrical Samples

In this paper, the electrical properties of various compacted carbon nanomaterials were investigated. Compacted carbon nanomaterials (carbon nanofibers, multi-walled carbon nanotubes) were compacted into cylindrical samples and the electrical properties were measured in a frequency range from 50 Hz to 1MHz.

scholarly journals Влияние методов формирования полимерных композитных материалов с углеродными нанотрубками на механизмы электропроводности

2021 ◽  
Vol 91 (3) ◽  
pp. 475
Author(s):  
Ф.Ф. Комаров ◽  
И.Д. Парфимович ◽  
А.Г. Ткачев ◽  
А.В. Щегольков ◽  
О.В. Мильчанин ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Composite Materials ◽  
Treatment Method ◽  
Filler Concentration ◽  
Electric Transport ◽  
Frequency Range ◽  
Nanostructured Polymer ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

The influence of the method of formation of nanostructured polymer composites filled with carbon nanotubes to their electrophysical properties was carried out. The influence of the «size effect» of multi-walled carbon nanotubes, functionalization method, and ultrasonic treatment method on the electrical conductivity of composite materials in the frequency range 50 Hz - 5 MHz and the temperature range 15 - 375 K has been established. The presence of various mechanisms of electric transport in composite materials that affect the final value of electrical conductivity is established. The best results of electrophysical parameters are observed with a combination of non-covalent functionalization of nanotubes and high-power ultrasonic exposure. This method allows us to achieve a conductivity value of composite materials of 0.01 S/cm in the studied frequency range at a filler concentration of 0.5 wt.%.

Microstructure and Effective Modeling of the Microwave Permittivity of Nano SiC(N) Composite Powder

2006 ◽  
Vol 11-12 ◽  
pp. 141-144 ◽  
Author(s):  
Dong Lin Zhao ◽  
Fa Luo ◽  
Wan Cheng Zhou
Keyword(s):  
Composite Powder ◽  
Filling Factor ◽  
Dielectric Materials ◽  
Second Order ◽  
Factor V ◽  
Phase Reaction ◽  
Microwave Frequencies ◽  
Nano Powder ◽  
Absorbing Material ◽  
Microwave Permittivity

The nano SiC(N) composite powder was synthesized from hexamethyldisilazane ((Me3Si)2NH) (Me:CH3) by a laser−induced gas-phase reaction. The microwave permittivity of the nano SiC(N) composite powder and paraffin wax (or other dielectric materials) composites can be tailored by the content of this nano powder. The dissipation factors (tgδ) of the nano SiC(N) composite powder are high at the microwave frequencies. And ε′, ε″ and tgδ of composites increase with the volume filling factor (v) of nano SiC(N) powder. The nano SiC(N) composite powder would be a good candidate for microwave absorbing material and electromagnetic interface (EMI) shielding material. The classical effective medium functions can not effectively model the microwave permittivities of the SiC(N) nanocomposites. We found that the microwave permittivities of the nanocomposites can be effectively modeled using second-order polynomials. These polynomials are dependent only on the filling factor and are purely mathematical models. The ε′ and ε″ of nanocomposites can be effectively modeled using second-order polynomials (ε′, ε″=Av2+Bv+C).

Multi-walled Carbon Nanotubes Penetrate into Plant Cells and Affect the Growth of Onobrychis arenaria Seedlings

Acta Naturae ◽  
2011 ◽  
Vol 3 (1) ◽  
pp. 99-106 ◽  
Author(s):  
E A Smirnova ◽  
A A Gusev ◽  
O N Zaitseva ◽  
E M Lazareva ◽  
G E Onishchenko ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Plant Cells ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes
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