scholarly journals Strategies to Hierarchical Porosity in Carbon Nanofiber Webs for Electrochemical Applications

Surfaces ◽  
2019 ◽  
Vol 2 (1) ◽  
pp. 159-176 ◽  
Author(s):  
Svitlana Yarova ◽  
Deborah Jones ◽  
Frédéric Jaouen ◽  
Sara Cavaliere
Keyword(s):  
Electrical Conductivity ◽  
Carbon Nanofiber ◽  
High Mass ◽  
Energy Storage And Conversion ◽  
High Porosity ◽  
Carbon Structure ◽  
Templating Method ◽  
Hierarchical Porosity ◽  
Fiber Porosity ◽  
Key Parameter

Morphology and porosity are crucial aspects for designing electrodes with facile transport of electrons, ions and matter, which is a key parameter for electrochemical energy storage and conversion. Carbon nanofibers (CNFs) prepared by electrospinning are attractive for their high aspect ratio, inter-fiber macroporosity and their use as self-standing electrodes. The present work compares several strategies to induce intra-fiber micro-mesoporosity in self-standing CNF webs prepared by electrospinning polyacrylonitrile (PAN). Two main strategies were investigated, namely i) a templating method based on the addition of a porogen (polymethyl methacrylate, polyvinylpyrrolidone, Nafion® or ZnCl2) in the electrospinning solution of PAN, or ii) the activation in ammonia of previously formed CNF webs. The key result of this study is that open intra-fiber porosity could be achieved only when the strategies i) and ii) were combined. When each approach was applied separately, only closed intra-fiber porosity or no intra-fiber porosity was observed. In contrast, when both strategies were used in combination all CNF webs showed high mass-specific areas in the range of 325 to 1083 m2·g−1. Selected webs were also characterized for their carbon structure and electrical conductivity. The best compromise between high porosity and high electrical conductivity was identified as the fibrous web electrospun from PAN and polyvinylpyrrolidone.

Mechanical Milling and its Influence on Microstructure and Electric Conductivity of High Mass Fraction TiC / Cu Composites

2013 ◽  
Vol 815 ◽  
pp. 790-795
Author(s):  
Jie Yan ◽  
Kai Yong Jiang
Keyword(s):  
Electrical Conductivity ◽  
Relative Density ◽  
Electric Conductivity ◽  
Ball Milling ◽  
Mechanical Milling ◽  
Mass Fraction ◽  
Milling Time ◽  
High Mass ◽  
Powder Metallurgy Method ◽  
X Ray Diffraction

The TiC-Cu composites with different mass fraction were prepared by powder metallurgy method. The effect of ball milling time and sintering temperature on the morphology, relative density and electrical conductivity of TiC/Cu composites has been investigated. As-milled sintered compacts were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and conductivity measurements. The results demonstrate that under laboratory conditions with the milling time increasing grains are remarkable refined. Mechanical milling can bring about changes of lattice parameters, the grain size first decrease and then increase as milling time increasing. Relative density showed strong dependency on the milling time. The effect of the grain being refined by ball milling is helpless to improve electrical conductivity of composites. For the composites with TiC content<50wt.%, as milling time prolonging the electric conductivity decreases while for the 50%TiC-Cu the conductivity are not be impacted.

Electrical Conductivity Measurements of Al-Doped ZnO Semiconductor in High Temperature

2018 ◽  
Vol 772 ◽  
pp. 105-109
Author(s):  
Syamsul Hadi ◽  
Husein Jaya Andika ◽  
Agus Kurniawan ◽  
Suyitno
Keyword(s):  
Electrical Conductivity ◽  
Temperature Effects ◽  
Sintering Temperature ◽  
High Porosity ◽  
Conductivity Measurements ◽  
Grain Sizes ◽  
Lower Porosity ◽  
Doped Zno ◽  
Zno Semiconductor ◽  
Zno Doping

Electrical conductivity plays an important role in the performance of thermoelectric semiconductor material. This study discusses the electrical conductivity measurements of Zinc Oxide (ZnO) doping Aluminium (Al) pellet as a material of thermoelectric using four-point probe method at high temperatures. Al-doped ZnO (2 wt%) pellet was sintered at the temperature of 1100°C, 1200°C, 1300°C, 1400°C, and 1500°C with the heating rate of 8°C/minute. SEM and XRD tests show that the higher sintering temperature effects to larger grain sizes, better crystallinity, and lower porosity. There is no electrical conductivity in the sintering sample at 1100°C due to the small grain sizes and high porosity. In the sintering sample at 1500°C, the phase of ZnAl2O4erupted. The highest electrical conductivity of 5923.48S/m of Al-doped ZnO pellet was obtained at the sintering temperature of 1400°C with measurement temperature of 500°C.

Bacterial cellulose as a carbon nano-fiber precursor: Enhancement of thermal stability and electrical conductivity

BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 3408-3426
Author(s):  
Fateme Rezaei ◽  
Rabi Behrooz ◽  
Shahram Arbab ◽  
Ehsanollah Nosratian Sabet
Keyword(s):  
Thermal Stability ◽  
Electrical Conductivity ◽  
Flame Retardant ◽  
Bacterial Cellulose ◽  
Heating Rate ◽  
Carbon Nanofiber ◽  
Diammonium Phosphate ◽  
Electrical Characteristics ◽  
Stabilization Process ◽  
Nanofiber Sheets

Bacterial cellulose was selected as a potential precursor for the production of carbon nanofiber because of its high purity and crystallinity. Diammonium phosphate ((NH4)2HPO4) as a flame retardant was used to impregnate the cellulosic nanofiber sheet precursor in order to increase its thermal stability during the thermal processing. Also, the effect of heating rate on the stabilization and carbonization processes of cellulosic nanofiber samples was investigated. The precursor and resulted carbon nanofiber sheets were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and electrical characteristics. The results showed that the simultaneous usage of flame retardant (diammonium phosphate) and low heating rate in the stabilization process (2 °C min-1) increases thermal stability of cellulosic nanofiber sheets and the carbon yield. The presence of a flame retardant acts like a low heating rate effect but does not significantly affect the high heating rate of the stabilization process. As carbonization temperature increased, electrical conductivity and crystallite size were increased for impregnated samples. The carbonization process at 1200 °C, with a heating rate of 2 °C min-1, makes bacterial cellulose precursor an appropriate candidate for producing carbon nanofiber sheets with proper electrical characteristics.

3D aquifer characterization of the Hermalle-sous-Argenteau test site using crosshole ground-penetrating radar amplitude analysis and full-waveform inversion

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. H133-H148
Author(s):  
Zhen Zhou ◽  
Anja Klotzsche ◽  
Thomas Hermans ◽  
Frédéric Nguyen ◽  
Jessica Schmäck ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Waveform Inversion ◽  
Test Site ◽  
Tracer Experiment ◽  
Transport Processes ◽  
High Porosity ◽  
Low Velocity ◽  
Amplitude Analysis ◽  
Ground Penetrating ◽  
Clay Lenses

To improve the understanding of flow and transport processes in the critical zone, high-resolution and accurate estimation of the small-scale heterogeneity is essential. Preferential flow paths related to high-porosity layers and clay lenses in gravel aquifers greatly affect flow and transport processes in the subsurface, and their high electrical contrast to their surrounding matrix and limited extent can act as low-velocity electromagnetic waveguides. In the past decade, time-domain full-waveform inversion (FWI) of crosshole ground-penetrating radar (GPR) data has shown to provide 2D decimeter-scale resolution images of relative permittivity and electrical conductivity of the subsurface, which can be related to porosity and soil texture. Most studies using crosshole GPR FWI resolved high-porosity zones that were identified by an amplitude analysis approach. But clay lenses or zones with higher electrical conductivity that act as low-velocity waveguides are hard to distinguish in the measured data and amplitude analysis because of the absence of characteristic wave-propagation features. We have investigated a set of nine crosshole GPR data sets from a test site in Hermalle-sous-Argenteau near the Meuse River in Belgium to characterize the aquifer within a decimeter-scale resolution and to improve the understanding of a previously performed heat tracer experiment. Thereby, we extend the amplitude analysis to identify two different types of low-velocity waveguides either caused by an increased porosity or a higher electrical conductivity (and higher porosity). Combining the GPR amplitude analysis for low-velocity waveguide zones with the standard FWI results provided information on waveguide zones, which modified the starting models and further improved the FWI results. Moreover, an updated effective source wavelet is estimated based on the updated permittivity starting models. In comparison with the traditional FWI results, the updated FWI results present smaller gradient of the medium properties and smaller root-mean-squared error values in the final inversion results. The nine crosshole sections are used to generate a 3D image of the aquifer and allowed a detailed analysis of the porosity distribution along the different sections. Consistent structures of the permittivity and electrical conductivity show the robustness of the updated FWI results. The aquifer structures obtained by the FWI results agree with those results of the heat tracer experiment.

Effect of twist and porosity on the electrical conductivity of carbon nanofiber yarns

2013 ◽  
Vol 24 (25) ◽  
pp. 255708 ◽  
Author(s):  
S Chawla ◽  
M Naraghi ◽  
A Davoudi
Keyword(s):  
Electrical Conductivity ◽  
Carbon Nanofiber

Structure, Viscoelasticity and Electrical Conductivity of PMMA/HDPE/Carbon Nanofiber Composites

2013 ◽  
Vol 41 (3) ◽  
pp. 113-120 ◽  
Author(s):  
Masaoki Takahashi ◽  
Ryuji Ishikawa ◽  
Yukihiro Nishikawa
Keyword(s):  
Electrical Conductivity ◽  
Carbon Nanofiber

scholarly journals Effect Of The Gadolinium Oxide Addition On The Electrical Properties Of Tetragonal Zirconium Dioxide

2015 ◽  
Vol 60 (2) ◽  
pp. 993-998 ◽  
Author(s):  
J. Cyran ◽  
J. Wyrwa ◽  
E. Drożdż ◽  
M. Dziubaniuk ◽  
M. Rękas
Keyword(s):  
Electrical Conductivity ◽  
Solid Oxide Fuel Cells ◽  
Zirconium Dioxide ◽  
Tetragonal Zirconia ◽  
Solid Oxide ◽  
The Other ◽  
High Porosity ◽  
Oxide Fuel ◽  
Oxide Addition ◽  
Electrical Conductivities

Abstract The aim of this work was examination of gadolinium-doped 3YSZ electrical and structural properties. Such materials may be used as electrolytes in intermediate temperature solid oxide fuel cells (IT-SOFC). First step of the research was synthesis of 3YSZ with different contents of gadolinium (0.25; 0.5; 1.0 at %). Prepared materials were characterized by high porosity. No effect of gadolinium addition on grain size was observed. The experimentally determined values of grain interiors electrical conductivities for gadolinium doped samples are comparable to grain interior conductivities of gadolinium free tetragonal zirconia. On the other hand, a clear effect of gadolinium addition on electrical conductivity of grain boundaries was observed. It was found that 3YSZ containing 0.25 at. % Gd was the most promising from the investigated materials as a solid electrolyte for IT SOFC.

A 3D porous nitrogen-doped carbon-nanofiber-supported palladium composite as an efficient catalytic cathode for lithium–oxygen batteries

2017 ◽  
Vol 5 (4) ◽  
pp. 1462-1471 ◽  
Author(s):  
Jun Wang ◽  
Lili Liu ◽  
Shulei Chou ◽  
Huakun Liu ◽  
Jiazhao Wang
Keyword(s):  
Carbon Nanofiber ◽  
Synergistic Effects ◽  
Carbon Matrix ◽  
Bifunctional Catalyst ◽  
Full Potential ◽  
High Porosity ◽  
Supported Palladium ◽  
Nitrogen Doped Carbon ◽  
Lithium Oxygen Batteries ◽  
Supported Pd

A 3D porous N-doped carbon-nanofiber-supported Pd composite gives synergistic effects on electrocatalytic performance improvement. The carbon matrix with high porosity and conductivity could reach full potential of Pd particles as an excellent bifunctional catalyst cathode.

Cyclic Behavior of Electrical Resistance Type Low Stiffness, Large Strain Sensor by Using Carbon Nanofiber/Flexible Epoxy Composite

2011 ◽  
Vol 462-463 ◽  
pp. 1200-1205 ◽  
Author(s):  
Yoshinobu Shimamura ◽  
Kyohei Kageyama ◽  
Keiichiro Tohgo ◽  
Tomoyuki Fujii
Keyword(s):  
Electrical Conductivity ◽  
Electrical Resistance ◽  
Carbon Nanofiber ◽  
Epoxy Composite ◽  
Large Strain ◽  
Conductive Polymer ◽  
Cyclic Behavior ◽  
Resistance Change ◽  
Sensing Applications ◽  
Electrical Resistance Change

Carbon nanofiber (CNF) has good electrical conductivity. Addition of a few percentages of carbon nanofiber to polymer yields electrical conductivity but hardly affects the mechanical properties of polymer. This conductive polymer may be useful for sensing applications such as strain sensors and chem-resist sensors. Many researchers have reported on the electrical conductivity, but the electrical resistance change under strain of the carbon nanofiller composites is not fully investigated. In this study, the electrical resistance change under strain of CNF/flexible-epoxy composites was investigated experimentally. More than 100% of quasi-static strain can be measured by using CNF/flexible-epoxy composite with Young’s modulus of less than 1MPa. Cyclic and unloading behaviors were also measured and discussed. It was found that the cyclic behavior was strongly affected by viscoelasticity and damage.

Sign in / Sign up

Export Citation Format

Share Document