Дослідження параметрів структурно-фазових перетворень парафінів та їх сумішей з наночастинками металів оптичним методом

Анотація

STUDY OF PARAMETERS OF STRUCTURAL-PHASE TRANSFORMATIONS OF PARAFFINS AND THEIR MIXTURES WITH NANOPARTICLES OF METALS BY THE OPTICAL METHOD

I. Antypov, Yu. Nasieka

Introduction. The scarcity of traditional energy resources (gas, oil and solid fuel), steady increase in their prices and the negative impact of the products of combustion on the environment, indicate the need for more rational use, which can be achieved either through the use of modern energy saving equipment and establishment and practical application of battery power different types, that will not only improve the efficiency of heat and electricity, but also reduce its cost. We know that all types of existing designs accumulator of heat are the most promising phase of heat or chemical transformations accumulating material, which can provide high density of stored energy and a stable temperature at the outlet of the heat accumulator. However, such devices have certain drawbacks and points to the need for new research aimed at finding ways to improve the performance of accumulator of heat.

Analysis of recent researches and publications. Whereas the development of nanotechnology, involving the synthesis and dispersion of highly heat-conducting particles of micron and nanometer size and putting them in accumulating material mentioned problems, teploakumulyatorah fazoperehidnyh based materials can be solved. However, a number of issues concerning the dependence of thermal conductivity and thermal diffusivity of the concentration, type and size of nanoparticles introduced are currently not studied fully.

Formulation of the problem. To solve problems of optimization technology of domestic highly efficient heat accumulators based fazoperehidnyh materials (paraffin) should investigate the structure and thermodynamic behavior paraffins and mixtures of different chemical composition solid state nano- and microparticles; assess their impact on the effectiveness of these processes.

Methods. To establish the influence of temperature and additives on structural transformation heat accumulating substances experimentally applied method of spectroscopy Raman scattering (Raman or in foreign literature - Raman spectroscopy), which is non-contact and non-destructive method of mapping crystallization processes for the analysis of thermodynamic properties and interaction molecular chains of the samples. As source material used paraffin brand T3.

Results. To increase the thermal conductivity of paraffin test selected 3 types of carbon powders produced by the domestic industry. To correct systematically analyze the impact of these powders on the dynamics of phase transitions in a mixture of paraffin with a specific powder, was originally studied structural and vibrational properties of the initial powders.

Found that the spectra of Raman spectroscopy wax mixtures of powders observed oscillating band associated with fluctuations carbon atoms in graphite matrix. It should be noted that most of the powder is in the amount of the basic substance, and most evenly distributed when the present powder has the smallest fraction. A careful comparison of frequency bands provisions of the relevant vibrational spectra Raman spectroscopy output paraffin T3 and its mixtures with fillers, it was found that the addition of heat-conducting filler does not affect the frequency position of the main bands that characterize variations in paraffin. The latter indicates that the powder chemically react with the core matrix material.

In Raman spectroscopy spectra of mixtures of powders, which were fractions of 0.2 mm or more, a signal that indicates the presence of powder decreased with increasing temperature. That is, the particles settled to the bottom of the cell after melting paraffin. Therefore, this paper shows the results of experiments on powders, which had the effect of subsidence. Such effects are, in our view, is harmful, because after several thermal cycles the battery will occur accumulation of filler in places where the temperature of the working substance was reduced, or even at the bottom of heat accumulator.

As a result, improved heat-conducting properties of paraffin with fillers explained stimulated the formation of chemical processes between molecules z'yazkiv paraffinic matrix and filler that is, there is a decrease in thermal resistance at the interface of the filler particles and basic paraffin matrix.

Discussion. As a result of studies found that adding heat-conducting filler does not affect the frequency position of the main bands that characterize variations in paraffin and paraffin improves heat conducting properties of the excipients. In particular revealed the following:

1. The temperature dependence of Raman spectroscopy spectra and structural parameters for pure waxes and mixtures metallic heat conductive fillers. Analysis of these dependences made it possible to determine the temperature of the major phase transitions, both technically paraffins and reinforced heat conductive particles of different chemical composition submillimeter sizes.

2. Established and explained the difference in the dynamics of structural phase transitions net (source) paraffins and reinforced heat conductive fillers.

3. Investigated enhance thermal conductivity, more even distribution of thermal field and lowering the temperature of the main phase transitions in reinforced heat accumulating substances.