Tetra-needle zinc oxide/silica composites: High-temperature dielectric properties at X-band

2013 ◽  
Vol 154 ◽  
pp. 64-68 ◽  
Author(s):  
Jie Yuan ◽  
Wei-Li Song ◽  
Xiao-Yong Fang ◽  
Xiao-Ling Shi ◽  
Zhi-Ling Hou ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
High Temperature ◽  
Dielectric Properties ◽  
X Band

scholarly journals SiC-Coated Carbon Nanotubes with Enhanced Oxidation Resistance and Stable Dielectric Properties

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2770
Author(s):  
Rong Li ◽  
Yuchang Qing ◽  
Juanjuan Zhao ◽  
Shiwen Huang
Keyword(s):  
Carbon Nanotubes ◽  
High Temperature ◽  
Dielectric Properties ◽  
Oxidation Resistance ◽  
Pyrolysis Temperature ◽  
X Band ◽  
Pristine Cnts ◽  
Long Time ◽  
Sic Composites ◽  
Coated Carbon

Carbon nanotubes (CNTs) coated with SiC coating was successfully prepared by pyrolysis of polycarbosilane (PCS) used as a precursor. The function of pyrolysis temperature on the oxidation resistance and the dielectric properties of CNTs/SiC were studied in X-band. The results demonstrate that the obtained dense SiC film can prevent the oxidation of CNTs when the pyrolysis temperature reaches 600 °C. Correspondingly, after heat treatment is at 400 °C for 200 h, the mass loss of P-600 is less than 1.86%, and the real and imaginary parts of the dielectric constant nearly keep constant (ε′ from 14.2 to 14, and ε″ from 5.7 to 5.5). SiC-coated CNTs have a better oxidation resistance than pristine CNTs. Therefore, this work, with a facile preparation process, enhances the oxidation resistance of CNTs at high temperature for a long time and maintains a stable dielectric property, which means CNTs/SiC composites can be good candidates for applications in the field of high-temperature absorbers.

scholarly journals Demonstration of Phase Change Thermal Energy Storage in Zinc Oxide Microencapsulated Sodium Nitrate

2021 ◽  
Vol 11 (13) ◽  
pp. 6234
Author(s):  
Ciprian Neagoe ◽  
Ioan Albert Tudor ◽  
Cristina Florentina Ciobota ◽  
Cristian Bogdanescu ◽  
Paul Stanciu ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Thermal Properties ◽  
High Temperature ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Sodium Nitrate ◽  
Thermal Energy Storage ◽  
Metal Corrosion ◽  
Scanning Calorimetry

Microencapsulation of sodium nitrate (NaNO3) as phase change material for high temperature thermal energy storage aims to reduce costs related to metal corrosion in storage tanks. The goal of this work was to test in a prototype thermal energy storage tank (16.7 L internal volume) the thermal properties of NaNO3 microencapsulated in zinc oxide shells, and estimate the potential of NaNO3–ZnO microcapsules for thermal storage applications. A fast and scalable microencapsulation procedure was developed, a flow calorimetry method was adapted, and a template document created to perform tank thermal transfer simulation by the finite element method (FEM) was set in Microsoft Excel. Differential scanning calorimetry (DSC) and transient plane source (TPS) methods were used to measure, in small samples, the temperature dependency of melting/solidification heat, specific heat, and thermal conductivity of the NaNO3–ZnO microcapsules. Scanning electron microscopy (SEM) and chemical analysis demonstrated the stability of microcapsules over multiple tank charge–discharge cycles. The energy stored as latent heat is available for a temperature interval from 303 to 285 °C, corresponding to onset–offset for NaNO3 solidification. Charge–self-discharge experiments on the pilot tank showed that the amount of thermal energy stored in this interval largely corresponds to the NaNO3 content of the microcapsules; the high temperature energy density of microcapsules is estimated in the range from 145 to 179 MJ/m3. Comparison between real tank experiments and FEM simulations demonstrated that DSC and TPS laboratory measurements on microcapsule thermal properties may reliably be used to design applications for thermal energy storage.

High temperature dielectric loss of h-BN at X band and its dependence on the electron structure, defects and impurities

2010 ◽  
Vol 12 (9) ◽  
pp. 1599-1602 ◽  
Author(s):  
Ting Zhang ◽  
Mengqiang Wu ◽  
Shuren Zhang ◽  
Jinming Wang ◽  
Dahai Zhang ◽  
...  
Keyword(s):  
High Temperature ◽  
Dielectric Loss ◽  
Electron Structure ◽  
Structure Defects ◽  
X Band ◽  
Defects And Impurities

Uniformity and high temperature performance of X-band nitride power HEMTs fabricated from 2-inch epitaxy

1998 ◽  
Vol 42 (12) ◽  
pp. 2183-2185 ◽  
Author(s):  
R Hickman ◽  
J.M Van Hove ◽  
P.P Chow ◽  
J.J Klaassen ◽  
A.M Wowchack ◽  
...  
Keyword(s):  
High Temperature ◽  
Temperature Performance ◽  
X Band

scholarly journals Snow dielectric properties: from DC to microwave X-band

1994 ◽  
Vol 19 ◽  
pp. 92-96 ◽  
Author(s):  
TH. Achammer ◽  
A. Denoth
Keyword(s):  
Grain Size ◽  
Dielectric Properties ◽  
Water Content ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Frequency Range ◽  
Snow Density ◽  
Cold Room ◽  
X Band ◽  
Grain Size And Shape

Broadband measurements of dielectric properties of natural snow samples near or at 0°C are reported. Measurement quantities are: dielectric permittivity, loss factor and complex propagation factor for electromagnetic waves. X-band measurements were made in a cold room in the laboratory; measurements at low and intermediate frequencies were carried out both in the field (Stubai Alps, 3300 m; Hafelekar near Innsbruck, 2100 m) and in the cold room. Results show that in the different frequency ranges the relative effect on snow dielectric properties of the parameters: density, grain-size and shape, liquid water content, shape and distribution of liquid inclusions and content of impurities, varies significantly. In the low-frequency range the influence of grain-size and shape and snow density dominates; in the medium-frequency range liquid water content and density are the dominant parameters. In the microwave X-band the influence of the amount, shape and distribution of liquid inclusions and snow density is more important than that of the remaining parameters.

Dielectric properties of zinc oxide/low density polyethylene nanocomposites

2005 ◽  
Vol 59 (4) ◽  
pp. 473-476 ◽  
Author(s):  
J.I. Hong ◽  
P. Winberg ◽  
L.S. Schadler ◽  
R.W. Siegel
Keyword(s):  
Zinc Oxide ◽  
Dielectric Properties ◽  
Low Density Polyethylene ◽  
Low Density

scholarly journals Investigation on the Dielectric Properties of Pulverized Oil Palm Frond and Pineapple Leaf Fiber for X-Band Microwave Absorber Application

2014 ◽  
Vol 893 ◽  
pp. 488-491 ◽  
Author(s):  
Elfarizanis Baharudin ◽  
Alyani Ismail ◽  
Adam Reda Hasan Alhawari ◽  
Edi Syams Zainudin ◽  
Dayang L.A. Majid ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Oil Palm ◽  
Microwave Absorber ◽  
Band Frequency ◽  
Pineapple Leaf Fiber ◽  
X Band ◽  
Oil Palm Frond ◽  
Palm Frond ◽  
Leaf Fiber

This paper presents the results on dielectric properties of pulverized material based on agricultural waste namely oil palm frond and pineapple leaf fiber for microwave absorber application in the X-band frequency range. The investigation is started by identifying the pulverized materials permittivities and loss tangents using coaxial probe technique, followed by density measurement comprising the determination of bulk and solid densities. Then, by using dielectric mixture model, the solid particle dielectric properties were determined. It is observed that the air properties give quite an effect on the permittivity and loss tangent of the pulverized materials. It is also found that the lower the material density the higher material dielectric constant will be. Furthermore, the results show that, both oil palm frond and pineapple leaf fiber are potential to be X-band absorber with average dielectric constant of 4.40 and 3.38 respectively. The loss tangents for both materials were observed to be more than 0.1 which mark them as lossy materials.

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