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).

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.

Preparation and Microwave Permittivity of Nano-Sized Si/C/N Powder

2005 ◽  
Vol 475-479 ◽  
pp. 3571-3574 ◽  
Author(s):  
Xiao Kui Liu ◽  
Wan Cheng Zhou ◽  
Fa Luo ◽  
Dong Mei Zhu
Keyword(s):  
Nitrogen Content ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Dissipation Factor ◽  
Nano Powder ◽  
Heat Treated ◽  
Different Temperatures ◽  
Degree Of Crystallization ◽  
Microwave Permittivity ◽  
N Powder

Nano-sized Si/C/N powders are prepared from hexamethyldisilazane ((CH3)3Si)2NH) by chemical vapor deposition (CVD) at different pyrolysis temperatures from 900°C to 1200°C. The as-formed Si/C/N nano powder is amorphous, and after controlled heat-treatment, SiC crystals formed. The composition of the Si/C/N powders prepared at different conditions is analyzed and the result shows that the nitrogen content of the Si/C/N powder is related to the synthesizing temperature. Si/C/N powders heat-treated at different temperatures are mixed with paraffin wax and the microwave permittivity of the mixture is measured. The result shows that the e¢, e², and the dissipation factor tg d ( e²/ e¢) of the mixture are high at the frequency of 8.2~12.4GHz, and the nitrogen content and the degree of crystallization have influence on the microwave permittivity. We believe that the high value of e¢, e² ,and tg d are due to the dielectric relaxation as the result of nitrogen atoms doped in silicon carbide lattice.

scholarly journals Novel MNZ-type microwave sensor for testing magnetodielectric materials

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Abhishek Kumar Jha ◽  
Nicolò Delmonte ◽  
Adam Lamecki ◽  
Michal Mrozowski ◽  
Maurizio Bozzi
Keyword(s):  
Magnetic Properties ◽  
Relative Permittivity ◽  
Microstrip Line ◽  
Dielectric Materials ◽  
Metal Strip ◽  
Network Analyzer ◽  
Microwave Frequencies ◽  
Microwave Sensor ◽  
Iron Garnet ◽  
Good Agreement

Abstract A novel microwave sensor with the mu-near-zero (MNZ) property is proposed for testing magnetodielectric material at 4.5 GHz. The sensor has a double-layer design consisting of a microstrip line and a metal strip with vias on layers 1 and 2, respectively. The proposed sensor can detect a unit change in relative permittivity and relative permeability with a difference in the operating frequency of 45 MHz and 78 MHz, respectively. The MNZ sensor is fabricated and assembled on two layers of Taconic RF-35 substrate, with thicknesses of 0.51 mm and 1.52 mm, respectively, for the measurement of the sample under test using a vector network analyzer. The dielectric and magnetic properties of two standard dielectric materials (Taconic CER-10 and Rogers TMM13i) and of yttrium–gadolinium iron garnet are measured at microwave frequencies. The results are found to be in good agreement with the values available in the literature, which shows the applicability of the prototype for sensing of magnetodielectric materials.

scholarly journals Kinetics and mechanism of selenate and selenite removal in solution by green rust-sulfate

2019 ◽  
Vol 6 (4) ◽  
pp. 182147 ◽  
Author(s):  
Aina Onoguchi ◽  
Giuseppe Granata ◽  
Daisuke Haraguchi ◽  
Hiroshi Hayashi ◽  
Chiharu Tokoro
Keyword(s):  
Redox Reaction ◽  
Solid Phase ◽  
Heterogeneous Reaction ◽  
Reaction Model ◽  
Second Order ◽  
Green Rust ◽  
Solid Phase Reaction ◽  
Concentration Profiles ◽  
Phase Reaction ◽  
Adsorption Reduction

This work investigated the removal of selenite and selenate from water by green rust (GR) sulfate. Selenite was immobilized by simple adsorption onto GR at pH 8, and by adsorption–reduction at pH 9. Selenate was immobilized by adsorption–reduction to selenite and zero valent selenium (Se 0 ) at both pH 8 and 9. In the process, GR oxidized to a mixture of goethite (FeOOH) and magnetite (Fe 3 O 4 ). The kinetics of selenite and selenate sorption at the GR–water interface was described through a pseudo-second-order model. X-ray absorption spectroscopy data enabled to elucidate the concentration profiles of Se and Fe species in the solid phase and allowed to distinguish two removal mechanisms, namely adsorption and reduction. Selenite and selenate were reduced by GR through homogeneous solid-phase reaction upon adsorption and by heterogeneous reaction at the solid–liquid interface. The selenite reduced through heterogeneous reduction with GR was adsorbed onto GR but not reduced further. The redox reaction between GR and selenite/selenate was kinetically described through an irreversible second-order bimolecular reaction model based on XAFS concentration profiles. Although the redox reaction became faster at pH 9, simple adsorption was always the fastest removal mechanism.

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