Abstract:In this work, the results of investigations of manufacturing ceramic materials on the basis of Ti, B, C and N containing systems are presented. The nanocrystalline ceramics were synthesized using a non-hydrolytic sol-gel method. The process was carried out in two stages. In the first low-temperature stage the precursor was obtained. The synthesis of ceramic phases, however, was conducted in the second high-temperature stage, in an argon atmosphere. Depending on the initial composition of the mixtures, the temperature and the time, the following products were obtained: TiC x , TiC x N 1−x , TiB 2 and B 4 C. The course of the process was investigated by thermogravimetric and differential scanning calorimetry methods (TG-DSC) coupled with mass spectrometry (MS). The solid state products were identified with use of X-ray diffraction (XRD). The size of the crystallites was estimated by the Scherrer method. The structure and morphology images of nanocrystalline powders were obtained using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
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 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.
The paper presents results of an analysis conducted over heating of nc-Ti-Si-C-N/C powder in argon atmosphere. TG-DSC-MS measurements were carried out under non-isothermal and isothermal conditions. The samples were heated up in series to 1573, 1673 and 1773 K. Four stages of the process were distinguished. In the first, endothermic stage, evolution of volatile products contained in raw samples took place. In the second, exothermic stage, oxidation of nc-Ti-Si-C-N/C contained in raw samples occured by the oxygen present in argon at a trace level. At the third stage pyrolysis of organic compounds, present in the samples, and carbonization of nc-Ti-Si-C-N/C, and in the fourth stage oxidation of purified composite by oxygen occurring in argon proceeded. Kinetic description of the process was presented at the example of series heated up to 1773 K. Coats-Redfern equation was applied. The kinetic models (forms of g(α) function) and Arrhenius parameters A and E were determined for the stages. An analysis of the process was performed using the obtained kinetic data.
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