Application of thermal analysis in nanotechnology
A. Biedunkiewicz
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U. Gabriel
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P. Figiel
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D. Grzesiak
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D. Grzesiak Institute of Mechanical Technology, West Pomeranian University of Technology
, Szczecin, Av. Piastow 19, 70-310 Szczecin,
Poland
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A. Biedunkiewicz (&) U. Gabriel P. Figiel Institute of Materials Science and Engineering, West Pomeranian University of Technology
, Szczecin, Av. Piastow 19, 70-310 Szczecin,
Poland
The analysis of purification and carbonization process in argon with use of nc-TiCx/C powder, obtained by sol-gel method, is presented. TG-DSC measurements were carried out under non-isothermal and isothermal conditions. The samples were heated up in series to 1473, 1573, 1673, and 1773 K. For this series description of process kinetics is presented. Four stages of the process have been distinguished. Kinetics was described using Coats-Redfern equation. The kinetic parameters were determined for particular stages. Using obtained kinetic data, the analysis of the process was performed. The a(T) and r(a,T) dependencies on heating rate and temperature were investigated. In order to obtain high carbonization degree and carbide particles of small size, an appropriate temperature and time of process duration have to be determined. Appropriate carbonization and particles size were obtained for series heated up to 1570 K. It has been demonstrated that the oxygen, present at trace level in argon, can react with components of the system in certain range of temperature, influencing the quality of obtained product. The particles have been depicted by TEM method, whereas characterization of structure and particles size was performed by XRD method. MS method was used to determine evolved gaseous products.
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Carbides, nitrides, and borides of transition metals belong
to the group of ceramic materials known as conventionally
hard materials. This results from the character of chemical
bound and crystallographic structure. Nanocrystalline
materials, playing the part of one of the phases of
nanocomposite, can contribute to the occurrence of
strengthening phenomena not existing in conventional materials of
micrometric size.
Appropriate selection of investigation methodology
enables understanding of process mechanisms, performing
quantitative analysis, and then correct determination of
synthesis conditions. The selection of investigation
methodology and the way of determination of nanomaterials
synthesis conditions were the purpose of this study.
Available analytical techniques were not sufficient to
bring the way of synthesis elaborated by the authoress to
manufacturing technology of unambiguously defined final
product. The internal randomness of the process, resulting
from the nature of nanomaterial, and the external
randomness resulting from limitations of analytical techniques
indicated necessity of statistical depiction. Complex
mechanism of solgel synthesis, increased chemical
activity of nanoparticles in oxidizing environments, even
occurring in trace amounts in high-purity gases, required
application of precise methods and performing
investigations for a wide range of parameters.
The original way of ceramic nanomaterials synthesis
based on non-hydrolytic solgel method was elaborated [1
8]. The method consists in mixing at molecular level
solution components which, thanks to the donoracceptor
interactions, get coordinated initializing spatial
cross-linking. Proceeding organicinorganic polymerization fixes the
system coordination at the gelling stage. Gels containing
carbon, along with donor groups, enable formation of
complex gels, in which one component forms organic
network enclosing inorganic clusters. This is the first stage
of elaborated method. The intermediate product, containing
low stoichiometric nanocrystalline carbides, like TiCx
(x B 0.7) in carbon matrix, is obtained. In second high
temperature stage carbonization and purification of raw
material takes place. The process is carried out in argon.
Obtaining the material of high carbonization degree,
remaining the right grains size and properties, is essential.
Selection of parameters meeting these requirements is
difficult. In this study kinetic investigations were applied.
Kinetic studies have major significance during
investigations of conversions proceeding with use of nanomaterials
[5, 8]. They allow to identify the intermediate and final
products, distinguish stages of the process, determine their
temperature ranges, and acquire the quantitative
description. The base of kinetic description of these processes is
usually thermogravimetric measurements TG-DSC.
The kinetic investigations were carried out by
thermoanalytical method using TG-DSC (SDT Q600, TA) coupled
with MS (Thermostar GDS 301 Pfeiffer Vacuum) for
gaseous products identification. Measurements were
performed in non-isothermal (b = 10, 20, and 50 K/min) and
isothermal (6 h) conditions. After parameters
determination the way of synthesis in larger scale was elaborated.
Performance parameters of ceram (...truncated)