Combustion synthesis of crystalline nanomaterials

Andrzej Huczko 1Magdalena Kurcz 1Agnieszka M. Dąbrowska 1Ajaya Bhattarai 2

1. Warsaw University, Department of Chemistry, Pasteura 1, Warsaw 02-093, Poland
2. Departmenta of Chemistry M. M. A. M. C., Tribhuvan University, Biratnagar 00977, Nepal

Abstract

Combustion synthesis is a novel type of highly exothermic, self-sustained reaction between a strong reducer and a strong oxidant. After combustion initiation, the chemical reaction propagates through the reactants as a rapidly moving combustion wave. High temperature and pressure gradients within the combustion wave result in a growth of different nanomaterials [1], i.e., we demonstrated earlier the efficient formation of silicon carbide nanowires [2]. The present study is a continuation of that research aimed at more-in-depth study of the combustion mechanism. In a typical combustion synthesis, Si powder or Si-containing powdered compound (silicides, alloys) were thoroughly mixed with poly(tetrafluoroethylene) - PTFE, in a stoichiometric ratio to obtain a homogeneous mixture. The following silicon compounds were tested: CaSi2, Si2Ta, Mg2Si, NbSi2, Cu5Si, MoSi2, Si2Zr, CrSi2, Si2Sr, VSi2, FeSi2, Si2Ti, WSi2, Mn15Si26, HfSi2, Co0.5Ni0.5Si2, Ni0.5Fe0.5Si2, Co0.5Fe0.5Si2. Not all of them were reactive enough to instantly reduce PTFE so a small amount of a strong reductant (Mg powder) was added to commence such combustion. The reactants were transferred to a quartz crucible and then placed in a stainless steel high pressure reactor (Fig. 1) with a 350 cm3 volume. 

Fig. 1. High-pressure stainless steel reactor for combustion synthesis
After filling the reactor with either argon or carbon dioxide to a pressure of 1 MPa, the combustion process was commenced using an ohmic heating. A mechanism of the reaction can be presented in a following simplified form

MeSi + (CF2)n → MeF + SiC + C + SiF4

Fig. 2 presents registered sequence of combustion stages in Si/PTFE system.
The time of reaction is about 1.2 s. The oscillation of signal intensity may be noted. Fig. 2. Registered sequence of combustion stages in Si/PTFE system The product was collected for SEM, TEM, XRD, and chemical analyses. Electron microscopy observation showed a presence of one-dimensional (1-D) silicon carbide nanocrystallites (Fig. 3) and fluoride nanoparticles along with soot agglomerates.

Fig. 3. SEM image of reaction products (starting mixture: Si/PTFE) To accelerate the combustion, sodium azide (up to 85 wt%) was also added to the starting mixture. Branched and comb-like SiC nanocrystallites were found in products (SEM images in Fig. 4) .

Fig. 4. SEM image of reaction products (starting mixture: Si/PTFE/NaN3) After combustion initiation, the high temperature causes the pyrolysis of PTFE into CxFy radicals and melting of silicon. The reaction of radicals with Si generates gaseous species forming 1-D SiC nanocrystallites presumably via a well-known VLS growth.

Acknowledgement. This work was supported by NCN through grant No. UMO-2011/03/B/ST5/03256 and 2012/05/B/ST5/00709.

References:
[1] A. Huczko, M. Szala, A. Dąbrowska, “Combustion Synthesis of Nanostructured Materials”, Publ. Wydawnictwa UW, 2011, Warsaw.
[2] M. Soszyński, A. Dąbrowska, M. Bystrzejewski, A. Huczko, CrystalResearch and Technol., 45, 2010, 1241-1244.

Legal notice
  • Legal notice:

    Copyright (c) Pielaszek Research, all rights reserved.
    The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
    In every case, proper references including Author(s) name(s) and URL of this webpage: http://science24.com/paper/29078 must be provided.

 

Related papers
  1. Fast synthesis of TaC under high energy conditions
  2. Combustion synthesis of Si-related crystalline nanostructures
  3. In situ diagnostics of SiC nanostructures growth process
  4. Nanowłókna węglika krzemu SiC: produkcja, charakteryzacja, zastosowania
  5. Synthesis of single-walled carbon nanotubes from aliphatic alcohols by CCVD method
  6. Morphology and structure of collapsed carbon nanoparticles
  7. CCVD Growth of 1-D Crystalline Carbon Nanostructures
  8. Combustion Synthesis of Crystalline SiC Nanofibres: Process Characterization
  9. Carbon magnetic encapsulated nanoparticles for biomedical applications: thermal stability studies
  10. Arc plasma synthesis of carbon encapsulates containing Fe-Nd-B nanocrystallites

Presentation: Oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, General Session 8, by Andrzej Huczko
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-03-30 11:25
Revised:   2013-07-17 12:18
Google
 
Web science24.com
© 1998-2021 pielaszek research, all rights reserved Powered by the Conference Engine