scholarly journals Coupling of CH4 to C2 Hydrocarbons in a Packed Bed DBD Plasma Reactor: The Effect of Dielectric Constant and Porosity of the Packing

Energies ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 468 ◽  
Author(s):  
Mohammadreza Taheraslani ◽  
Han Gardeniers

The conversion of methane was investigated in a packed-bed dielectric barrier discharge (DBD) plasma reactor operated at ambient conditions. High dielectric BaTiO3 was utilized as packing in comparison with γ-alumina, α-alumina, and silica-SBA-15. Results show a considerably lower conversion of CH4 and C2 yield for the BaTiO3 packed reactor, which is even less than that obtained for the nonpacked reactor. In contrast, the low dielectric alumina (γ and α) packed reactor improved the conversion of CH4 and C2 yield. Additionally, the alumina packed reactor shifted the distribution of C2 compounds towards C2H4 higher than that obtained for the nonpacked reactor and resulted in a higher energy efficiency compared to the BaTiO3 packed reactor. This is attributed to the small pore size of BaTiO3 (10–200 nm) and its high dielectric constant, whereas the polarization inside small pores does not lead to the formation of an overall strong electric field.

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 774
Author(s):  
Mohammadreza Taheraslani ◽  
Han Gardeniers

Methane is activated at ambient conditions in a dielectric barrier discharge (DBD) plasma reactor packed with Pd/γ-alumina catalyst containing different loadings of Pd (0.5, 1, 5 wt%). Results indicate that the presence of Pd on γ-alumina substantially abates the formation of deposits, leads to a notable increase in the production of alkanes and olefins and additionally improves the energy efficiency compared to those obtained for the non-packed reactor and the bare γ-alumina packed reactor. A low amount of Pd (0.5 and 1 wt%) favors achieving a higher production of olefins (mainly C2H4 and C3H6) and a higher yield of H2. Increasing Pd loading to 5 wt% promotes the interaction of H2 and olefins, which consequently intensifies the successive hydrogenation of unsaturated compounds, thus incurring a higher production of alkanes (mainly C2H6 and C3H8). The substantial abatement of the deposits is ascribed to the role of Palladium in moderating the strength of the electric and shifting the reaction pathways, in the way that hydrogenation reactions of deposits’ precursors become faster than their deposition on the catalyst.


2018 ◽  
Vol 6 (9) ◽  
pp. 2370-2378 ◽  
Author(s):  
Yang Liu ◽  
Cheng Zhang ◽  
Benyuan Huang ◽  
Xu Wang ◽  
Yulong Li ◽  
...  

A novel skin–core structured fluorinated MWCNT nanofiller was prepared to fabricate epoxy composite with broadband high dielectric constant and low dielectric loss.


2021 ◽  
Vol 46 ◽  
pp. 101468
Author(s):  
Periyasamy Kaliyappan ◽  
Andreas Paulus ◽  
Jan D’Haen ◽  
Pieter Samyn ◽  
Yannick Uytdenhouwen ◽  
...  

RSC Advances ◽  
2017 ◽  
Vol 7 (38) ◽  
pp. 23309-23312 ◽  
Author(s):  
Ting Yang ◽  
Wenhui Xu ◽  
Xinwen Peng ◽  
Haoqing Hou

Crown ether-containing polyimides possess high dielectric constant and low dielectric loss, without sacrificing other properties.


2021 ◽  
Author(s):  
Shashwat Shukla ◽  
Gerald Wesley Patterson

<p>One of the unique candidates to explore the evolution of physical surface processes on the Moon is Tycho, a dark haloed impact crater representing well-preserved bright ray pattern and intact crater morphology. Sampling of the central peak in such complex crater formation proves significant in terms of unraveling intriguing science of the lunar interior. With the current state-of-the-art radar technology, it is possible to evaluate the response of the geologic features constrained in the near surface and subsurface regolith environments. This can be achieved by modelling the dielectric constant of media, which is a physical parameter crucial for furthering our knowledge about the distribution of materials within different stratigraphic layers at multiple depths. Here, we used the applicability of Mini-RF S-band data augmented with a deep learning based inversion model to retrieve the dielectric variations over the central peak of the Tycho crater. A striking observation is made in certain regions of the central peak, wherein we observe anomalously high dielectric constant, not at all differentiated in the hyperspectral image and first Stokes parameter image, which usually is a representation of retrieved backscatter of the target. The results are also supported by comparing the variations in the scattering mechanisms. We found those particular regions to be associated with high degree of depolarization, thereby attributing to the presence of cm- to m- scale scatterers buried within a low dielectric layer that are not big enough to produce even-bounce geometry for the radar wave. Moreover, we also observe high rock concentration in the central peak slopes from DIVINER data and NAC images, indicating the exposure of clasts ranging in size from 10 meter to 100s of meter. Furthermore, from surface temperature data, these distinctive outcrops sense warmer temperature at night than the surrounding, which suggests the existence of thermal skin depth in such vicinities. Interestingly, we are able to quantify the pessimistic dielectric constant limit of the large boulder in the middle of the central peak, observable at the Mini-RF radar wavelength, as 4.54 + j0.077. Compared to the expected dielectric constant of rocks, this value is lowered significantly. One probable reason could be the emergence of small radar shadows due to the rugged surface of the boulder on the radar illuminated portion. From our analysis, we showcase the anomalous dielectric variability of Tycho central peak, thereby providing new insights into the evolution of the impact cratering process that could be important for both science and necessary for framing human or robotic exploration strategies.  </p>


2016 ◽  
Vol 34 (2) ◽  
pp. 322-329 ◽  
Author(s):  
Wan Q. Cao ◽  
Ling F. Xu ◽  
Mukhlis M. Ismail ◽  
Li L. Huang

AbstractBaTiO3 ceramics doped with 0.40 mol% NaNbO3 were prepared using a traditional approach by sintering at temperature of 1250 °C to 1290 °C. The prepared ceramics was characterized by very good dielectric properties, such as high dielectric constant (1.5 × 105), low dielectric loss (0.1), and good dielectric temperature stability in the −40 °C to 100 °C range for the sample sintered below 1270 °C. The dielectric characteristics obtained with XPS confirmed that Ti4+ ions remain in the state without any change. The huge increase in dielectric constant in NaNbO3 doped BaTiO3 samples occurs when large amount of Ba2+ ions are excited to a high energy bound state of Ba2+ − e or Ba+ to create electron hopping conduction. For samples with the content of NaNbO3 higher than 0.40 mol%, or sintering temperature higher than 1280 °C, compensation effect is dominated by cation vacancies with sharply decreasing dielectric constant and increased dielectric loss. The polaron effect is used to explain the relevant mechanism of giant dielectric constant appearing in the ferroelectric phase.


1997 ◽  
Vol 476 ◽  
Author(s):  
C.T. Rosenmaver ◽  
J. W. Bartz ◽  
J. Hammes

AbstractPrevious work has demonstrated the potential of polytetrafluoroethylene (PTFE) thin films for ULSI applications. The films are deposited from PTFE nanoemulsions. They have an ultra-low dielectric constant of 1.7 to 2.0, a leakage current of less than 1.0 nA/cm2 @ 0.2 MV/cm and a dielectric strength of from 0.5 to 2.4 MV/cm. They are thermally stable (isothermal weight loss < 1.0 %/hr at 450 °C), uniform (thickness standard deviation < 2%), and have excellent gap-fill properties (viscosity of 1.55 cP and surface tension of 18 mN/m). The films are inert with respect to all known semiconductor process chemicals, yet they are easily etched in an oxygen plasma.This paper discusses the processing technology that has been developed to process PTFE films with these properties. Specifically, it addresses two recent discoveries: 1) Good adhesion of spin-coated PTFE to SiO2 surfaces; and 2) high dielectric strength of PTFE thin films spin-coat deposited onto rigid substrates. The adhesion-promoting and thermal treatments necessary to produce these properties are detailed. Stud pull test results and test results from metal-insulator-metal (MIM) capacitor structures are given.


2013 ◽  
Vol 1561 ◽  
Author(s):  
M.A Jithin ◽  
Lakshmi Ganapathi Kolla ◽  
Navakanta Bhat ◽  
S. Mohan ◽  
Yuichiro Morozumi ◽  
...  

ABSTRACTIn this study, synthesis and characterization of rutile-Titanium dioxide (TiO2) thin films using pulsed DC Magnetron Sputtering at room temperature, along with the fabrication and characterization of MIM capacitors have been discussed. XPS and RBS data show that the films are stoichiometric and have compositional uniformity. The influence of electrode materials on electrical characteristics of the fabricated MIM capacitors has been studied. The Al/TiO2/Al based capacitors show low capacitance density (9 fF/μm2) with low dielectric constant (K=25) and high EOT (3.67 nm) due to low dielectric constant TiO2 phase formation on Al/Si substrate. On the other hand, Ru/TiO2/Ru based capacitors show high capacitance density (49 fF/μm2) with high dielectric constant (K=130) and low EOT (0.7nm) values at high frequency (100 KHz) due to high dielectric constant phase (rutile) formation of TiO2, on Ru/Si substrate. Raman spectra confirm that the films deposited on Ru/Si substrate show the rutile phase.


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