Carbon Nanotubes' and Silicon Carbide Whiskers' Growth on Metal Catalysts: Common Features of Formation Mechanisms

ABSTRACTThe formation mechanisms of carbon deposits and silicon carbide whiskers on metal surface catalysts have some common steps. The most important are: (1) the formation of metal particle alloys oversaturated with carbon or silicon and carbon atoms and (2) the nucleation of corresponding deposits on the metal catalyst surface. A thermodynamic analysis of the carbon and/or silicon carbide nucleation on the metal surface was performed. The master equations for the dependence of critical radius of carbon or SiC nucleus on reaction parameters, such as reaction temperature, supersaturation degree of catalyst particles with C (or Si and C), work of adhesion of metal to carbon (or metal to SiC), were obtained. These equations combined with the phase diagram approach can be used for the description of different scenarios of carbon and/or SiC deposits formation and for the development of the main principles of catalyst and promoters design.

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Thermodynamic Analysis of Carbon Nucleation on a Metal Surface

MRS Proceedings ◽

10.1557/proc-706-z6.22.1 ◽

2001 ◽

Vol 706 ◽

Cited By ~ 1

Author(s):

Vladimir L. Kuznetsov ◽

Anna N. Usoltseva ◽

Andrew L. Chuvilin ◽

Elena D. Obraztsova ◽

Jean-Marc Bonard

Keyword(s):

Metal Surface ◽

Thermodynamic Analysis ◽

Metal Particles ◽

Carbon Deposit ◽

Metal Catalyst ◽

Reaction Parameters ◽

Filamentous Carbon ◽

Catalytic Mechanisms ◽

Single Wall Nanotubes ◽

High Degree

AbstractA thermodynamic analysis of the carbon nucleation on the metal surface was performed. From the consideration of the catalytic mechanisms of carbon deposit formation on the metal surface we concluded that majority of these mechanisms include some common steps. The most important of them is the step of nucleation of carbon deposit on the metal surface. The master equation for the dependence of critical radius of the nucleus on reaction parameters was obtained. This equation demonstrates that a variation of the reaction parameters, such as the temperature, the nature of metal catalyst and the degree of supersaturation of the metal-carbon solution, can lead to the formation of different carbon deposits, such as filamentous carbon, multi-wall nanotubes (MWNT) or single-wall nanotubes (SWNT). The analysis performed allows us to conclude that for selective production of SWNT the nucleation must proceed at high temperature on the surface of liquid metal particles (Fe, Co, Ni). For solid metal particles (Mo) a high degree of supersaturation with carbon is also required.

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Synergy Effects in Electromagnetic Properties of Phosphate Ceramics with Silicon Carbide Whiskers and Carbon Nanotubes

Applied Sciences ◽

10.3390/app9204388 ◽

2019 ◽

Vol 9 (20) ◽

pp. 4388 ◽

Cited By ~ 2

Author(s):

Artyom Plyushch ◽

Jan Macutkevič ◽

Polina Kuzhir ◽

Aliaksei Sokal ◽

Konstantin Lapko ◽

...

Keyword(s):

Carbon Nanotubes ◽

Silicon Carbide ◽

Wide Frequency Range ◽

Electromagnetic Properties ◽

Aluminium Phosphate ◽

Silicon Carbide Whiskers ◽

Synergy Effects ◽

Multi Walled Carbon Nanotubes ◽

The Difference ◽

Walled Carbon Nanotubes

Hybrid composite materials based on an aluminium phosphate matrix with silicon carbide whiskers and multi-walled carbon nanotubes were studied in a wide frequency range (20 Hz to 36 GHz). It was demonstrated, that the addition of the silicon carbide whiskers enhances the dielectric permittivity and conductivity. This was explained by the difference in tunnelling parameters. Hybrid ceramics with nanotubes and whiskers also exhibits substantially improved electromagnetic shielding properties. The hybrid ceramics with 10 wt. % silicon carbide whiskers and a 1 mm thick 1.5 wt. % carbon nanotube layer, show higher than 50% absorption of electromagnetic radiation.

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Simultaneous effects of rice husk silica and silicon carbide whiskers on the mechanical properties and morphology of sodium geopolymer

Journal of Composite Materials ◽

10.1177/0021998320928579 ◽

2020 ◽

Vol 54 (29) ◽

pp. 4611-4620 ◽

Cited By ~ 2

Author(s):

Akm Samsur Rahman ◽

Chirag Shah ◽

Nikhil Gupta

Keyword(s):

Silicon Carbide ◽

Compressive Strength ◽

Flexural Strength ◽

Silica Nanoparticles ◽

Rice Husk ◽

Silicon Carbide Whiskers ◽

Short Beam ◽

Spherical Silica ◽

Beam Shear ◽

Strength Improvement

The current research is focused on developing a geopolymer binder using rice husk ash–derived silica nanoparticles. Four types of rice husks were collected directly from various rice fields of Bangladesh in order to evaluate the pozzolanic activity and compatibility of the derived rice husk ashes with precursors of sodium-based geopolymers. Silicon carbide whiskers were introduced into sodium-based geopolymers in order to evaluate the response of silicon carbide whiskers to the interfacial bonding and strength of sodium-based geopolymers along with rice husk ashes. Compression, flexural and short beam shear tests were performed to investigate the synergistic effect of rice husk ashes–derived silica and commercially available silicon carbide whiskers. Results show that rice husk ashes–derived spherical silica nanoparticles reduced nano-porosity of the geopolymers by ∼20% and doubled the compressive strength. The simultaneous additions of rice husk ashes and silicon carbide whiskers resulted in flexural strength improvement by ∼27% and ∼97%, respectively. The increase in compressive strength due to the inclusion of silica nanoparticles is related to the reduction in porosity. The increase in flexural strength due to simultaneous inclusion of silica and silicon carbide whiskers suggest that silica particles are compatible with the metakaolin-based geopolymers, which is effective in consolidation. Finally, microscopy suggest that silicon carbide whiskers are effective in increasing bridged network and crack resistance.

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