Application of thermal analysis in nanotechnology

Journal of Thermal Analysis and Calorimetry, Aug 2010

The analysis of purification and carbonization process in argon with use of nc-TiC x /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 α(T) and r(α,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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Application of thermal analysis in nanotechnology

A. Biedunkiewicz 0 1 U. Gabriel 0 1 P. Figiel 0 1 D. Grzesiak 0 1 0 D. Grzesiak Institute of Mechanical Technology, West Pomeranian University of Technology , Szczecin, Av. Piastow 19, 70-310 Szczecin, Poland 1 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. - 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)


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A. Biedunkiewicz, U. Gabriel, P. Figiel, D. Grzesiak. Application of thermal analysis in nanotechnology, Journal of Thermal Analysis and Calorimetry, 2010, pp. 701-706, Volume 101, Issue 2, DOI: 10.1007/s10973-010-0919-1