Microwave absorption and relaxation processes for some substituted benzotrifluorides in benzene solutions at different temperatures

1981 ◽  
Vol 77 (1) ◽  
pp. 169 ◽  
Author(s):  
M. L. Arrawatia ◽  
M. L. Sisodia ◽  
P. C. Gupta ◽  
S. C. Kabra
Keyword(s):  
Microwave Absorption ◽  
Relaxation Processes ◽  
Different Temperatures

Microwave wide band absorption by carbon from Corn cob-1

2016 ◽  
Vol 12 (2) ◽  
pp. 4204-4212 ◽  
Author(s):  
Maheshwar Sharon ◽  
Ritesh Vishwakarma ◽  
Abhijeet Rajendra Phatak ◽  
Golap Kalita ◽  
Nallin Sharma ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Agricultural Waste ◽  
Wide Band ◽  
Nickel Nitrate ◽  
Equivalent Amount ◽  
Frequency Range ◽  
Corn Cob ◽  
Different Temperatures ◽  
Band Absorption ◽  
5 Ghz

Corn cob, an agricultural waste, is paralyzed at different temperatures (700oC, 800oC and 900oC). Microwave absorption of carbon in the frequency range of 2 GHz to 8 GHz is reported. Carbon activated  with 5%  nickel nitrate showed more than 90% absorption of microwave in the frequency range from 6 GHz to 8 GHz, while carbon activated  with 10% Nickel nitrate treated corn cob showed 90% absorption  in the frequency range of 2.5 GHz to 5 GHz. Carbon showing the best absorption are characterized by XRD, Raman spectra and SEM . It is suggested that corn cob treatment   alone with KOH did not improve the microwave absorption, whereas treatment along with nickel nitrate improved the absorption property much better. It is proposed that treatment with nickel nitrate helps in creating suitable pores in carbon   which improved the absorption behavior because while treating carbon with 1N HCl helps to leach out nickel creating equivalent amount of pores in the carbon.

Relaxation Processes in the Deformation of Unloaded Rubbers and the Influence of the Degree of Vulcanization

1951 ◽  
Vol 24 (4) ◽  
pp. 810-819
Author(s):  
B. A. Dogadkin ◽  
M. M. Reznikovskii˘
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Elastic Deformation ◽  
Relaxation Processes ◽  
Spatial Network ◽  
Relaxation Properties ◽  
Constant Rate ◽  
Different Temperatures ◽  
Kinetics Of

Abstract 1. It is shown that the process of stress relaxation at different initial elongations as well as the process of deformation at constant rate for unloaded rubbers at different temperatures (20–70° C) can be represented quantitatively by equations suggested in earlier works. Likewise the possibility of expanding the theories proposed for the kinetics of high-elastic deformation of spatial polymers is substantiated. 2. It is shown that the relaxation properties of soft unloaded vulcanizates of natural rubber and many synthetic rubbers do not undergo essential changes during vulcanization. 3. The conjecture is expressed that the invariability of the relaxation properties during vulcanization continues until the bonds of the spatial network are distributed sufficiently widely not to influence the activity or heat movement of the chain segments between them.

The Impedance Spectroscopy Study of the Oxides Layer in Thermal Barrier Coatings

2018 ◽  
Vol 281 ◽  
pp. 510-515
Author(s):  
Zi Yuan Wang ◽  
Min Wang ◽  
Ya Jie Yuan ◽  
Wei Pan
Keyword(s):  
Impedance Spectroscopy ◽  
Thermal Barrier Coatings ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Relaxation Processes ◽  
Impedance Spectra ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Different Temperatures ◽  
Plasma Sprayed

Air-plasma-sprayed (APS) thermal barrier coatings (TBCs) were oxidized in air at different temperatures for 1000h and sequentially investigated by impedance spectroscopy (IS) and scanning electron microscopy (SEM). After oxidation at temperatures higher than 900°C, a thermally grown oxide (TGO) layer was formed at the bond coat/topcoat interface in TBCs. The impedance spectra of oxidized TBCs typically contains two relaxation processes that stem from the yttria-stabilized zirconia (YSZ) topcoat of TBCs and the TGO layer. The TGO resistivity that obtained by simulating the impedance spectra increased with the increasing of annealing temperature, demonstrating the growth and the densification of TGO layer.

scholarly journals Preparation of SiO2-MnFe2O4 Composites via One-Pot Hydrothermal Synthesis Method and Microwave Absorption Investigation in S-Band

Molecules ◽  
2019 ◽  
Vol 24 (14) ◽  
pp. 2605 ◽  
Author(s):  
Yin ◽  
Zhang ◽  
Wang ◽  
Feng ◽  
Zhao ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Microwave Absorption ◽  
Impedance Matching ◽  
Synthesis Method ◽  
Phase Identification ◽  
Relaxation Processes ◽  
Potential Candidate ◽  
One Pot ◽  
Debye Relaxation ◽  
Attenuation Characteristic

MnFe2O4 NPs are successfully decorated on the surface of SiO2 sheets to form the SiO2-MnFe2O4 composite via one-pot hydrothermal synthesis method. The phase identification, morphology, crystal structure, distribution of elements, and microwave absorbing properties in S-band (1.55~3.4 GHz) of the as-prepared composite were investigated by XRD, SEM, TEM, and Vector Network Analyzer (VNA) respectively. Compared with the pure MnFe2O4 NPs, the as-prepared SiO2-MnFe2O4 composite exhibits enhanced microwave absorption performance in this frequency band due to the strong eddy current loss, better impedance matching, excellent attenuation characteristic, and multiple Debye relaxation processes. The maximum reflection loss of −14.87 dB at 2.25 GHz with a broader −10 dB bandwidth over the frequency range of 1.67~2.9 GHz (1.23 GHz) can be obtained at the thickness of 4 mm. Most importantly, the preparation method used here is relatively simple, hence such composite can be served as a potential candidate for effective microwave absorption in S-band.

Microwave Absorption in NaCl Crystals with Various Controlled Defect Conditions

1994 ◽  
Vol 347 ◽  
Author(s):  
Binshen Meng ◽  
John Booske ◽  
Reid Cooper ◽  
Sam Freeman
Keyword(s):  
Grain Boundaries ◽  
Microwave Absorption ◽  
Point Defects ◽  
High Speed ◽  
Microwave Sintering ◽  
Pure Point ◽  
Designed Experiments ◽  
Crystalline Defects ◽  
Different Temperatures ◽  
Initial Results

ABSTRACTA thorough understanding of fundamental microwave absorption mechanisms in ionic crystalline solids is important for microwave sintering of ceramics, as well as the design of high speed electronic packaging, advanced radomes, etc. Of particular importance to these applications are how the density and type of crystalline defects affect the dominant microwave absorption mechanisms. We have designed experiments to measure microwave absorption in NaCl samples with controlled variations in defect conditions(pure, point defects, dislocations and grain boundaries) at different temperatures (20–400 °C) and frequencies (2–20 GHz). Initial results are reported and discussed.

scholarly journals Characterization of Shape Memory Polymer Estane by Means of Dynamic Mechanical Thermal Analysis Technique

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Rasa Kazakevičiūtė-Makovska ◽  
Aycan Özlem Özarmut ◽  
Holger Steeb
Keyword(s):  
Thermal Analysis ◽  
Shape Memory ◽  
Dynamic Mechanical Thermal Analysis ◽  
Shape Memory Polymer ◽  
Relaxation Processes ◽  
Dynamic Mechanical ◽  
Analysis Technique ◽  
Storage And Loss Moduli ◽  
Different Temperatures ◽  
Linear Viscoelastic

Commercially available shape memory polymer (SMP) Estane (designation: ETE75DT3 NAT022) is investigated by means of dynamic mechanical thermal analysis (DMTA) technique in torsion mode using the Modular Compact Rheometer MCR-301 (Anton Paar GmbH). Amplitude sweep tests have been run below and above the glass transition temperature to establish the linear viscoelastic range (LVR) in glassy and rubbery phase of this SMP for the correct physical interpretation of DMTA data. Temperature sweep tests were performed at various frequencies to study the influence of this parameter on values of the storage and loss moduli and the storage and loss compliances as well as the viscosities. These tests have been carried out in heating mode with different rates and at different strain amplitudes. The short- and long-term behavior of SMP Estane have been studied by frequency sweep tests performed at different temperatures and data have been transformed into time-domain properties by applying time-temperature superposition principles. All these DMTA data provide the experimental basis for the study of relaxation processes, property-structure relationships, and the shape memory effect in this little-known SMP.

scholarly journals High Efficiency Microwave Absorption Performance of Cobalt Ferrite Microspheres/multi-walled Carbon Nanotube Composites

2021 ◽  
Author(s):  
Hongmei Liu ◽  
Min Zhang ◽  
Kang Hu ◽  
Xiangkai Kong ◽  
Qiang Li ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
High Efficiency ◽  
Magnetic Loss ◽  
Spinel Ferrite ◽  
Impedance Matching ◽  
Relaxation Processes ◽  
Nanotube Composites ◽  
Multi Walled Carbon Nanotubes ◽  
Absorption Performance ◽  
Microwave Absorption Performance

Abstract In this article, spinel ferrite CoFe2O4 and multi-walled carbon nanotubes (MWCNTs) composites are constructed by a facile one-step solvothermal method. The pure phase of CoFe2O4 particles is confirmed by X-ray diffraction patterns. Microstructure analysis demonstrates that monodisperse CoFe2O4 microspheres are wound by MWCNTs. By the introduction of CNTs, there is a significant enhancement in the imaginary part of permittivity (ε″) with the composites. The champion microwave absorption performance can be achieved in the composites by the balance of complex permittivity and permeability. When the mass fraction of CNTs is 3%, a minimum reflection loss (RLmin) of the composites is as high as -46.65 dB at 14.4 GHz at a thin thickness of 1.5 mm, and the corresponding effective absorption bandwidth below − 10 dB reaches 4.91 GHz ranging from 12.41 to 17.32 GHz which covers almost the whole Ku band (12.0–18.0 GHz). In other words, this as-synthesized composites show the most outstanding specific RLmin of -31.1 dB•mm− 1. Such superior microwave absorption behaviors of CoFe2O4/CNTs originate mainly from multiple dielectric relaxation processes, enhanced impedance matching and magnetic loss, as well as the considerable interface between mesoporous CoFe2O4 hollow microspheres and CNTs, and thereby promoting microwave reflection and scattering within the samples. Our results indicate that as-fabricated CoFe2O4/CNTs composites can be a promising microwave absorbent integrating with thin thickness, strong absorption ability, and broad bandwidth absorption.

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