Studium vlivu složení plniva kompozitního systému na jeho emisivitu – Ing. Milan Mauer

Anotace:

Byla studována možnost ovlivnit emisivní vlastnosti keramického kompozitu pouho změnou složení plniv. Cílem bylo najít takové složení plniv, které bude mít velmi vysokou emisivitu (> 0.90) a to i za teplot, ve kterých operují tepelná zařízení. Následně bylo nutné provést porovnávací testy mezi původní recepturou a nově vyvinutým emisivním materiálem (teplotní odolnost, tepelná vodivost, přilnavost a SEM analýzy vzorků vypalených při různých teplotách). …víceméně

Abstract:

The research work is focused on the possibility to influence the emissivity of an inorganic composite coating by changing the filler composition. These coatings can also be used in power-producing equipment and they can increase the efficiency of this type of equipment thanks to high emissivity. The intention of our project is to develop a system which will provide a very high normal spectral emissivity (0.75 - 0.99) within a short and medium wavelength range of infrared spectrum of electromagnetic radiation (1,5 ? 8,0 ?m) and at temperatures above 700 oC where most of the thermal energy is transfered. For example lining materials usually have the emissivity of 0.20 ? 0.40 in this spectral zone, steel has the emissivity of 0.60 ? 0.80. This provides sufficient space for the emissivity improvement by the developed emissivity coatings. The coatings have to be resistant to the given conditions which occure in the thermal equipments (very high temperature and different level of abrasion). BG HitCoat? is one of these protective coatings. Chromium Oxide is the active ingredient which is contained in the filler of its basic composition. Other active ingredients were also built into the matrix of the composite. Some of the active ingredients had high value of emissivity (Iron, Silicon Carbide), others had high value of melting temperature (Magnezite, Magnetite, Kaolin, Boron Carbide, Boron Nitride, Zirconium Oxide, etc.). Emissivity comparison of new samples then followed. Fourrier Transform Infra-Red (FTIR) Spectrometry was applied for measurement of normal spectral emissivity. Research required measurements carried out mainly at high temperatures. Radiation of researched materials was compared with radiation of the comparative high temperature coating based on Cr2O3 and with radiation of the black body. Influence of filler composition on the emissivity in monitored range of infrared spectrum was demonstrated. The least emissive active ingredient (Zirconium Oxide) had the values of 0.09 ? 0.60 in the range, the most emissive one (mixture of nitrides) had the values of 0,75 - 0,93. The material with the most emissive active ingredient was then subjected to comparison with the original formulation. All important parameters were compared (thermal resistance, thermal conductivity, adhesion, morphology) and the new material was comparable in all the tests. …víceméně