INORGANICANTISUBLIMATION MATERIAL FORTHERMOBATTERIES BRANCHES BASED ON SIGE ALLOYS

F.Basaria, G.Bokuchava, K.Barbakadze, G.Darsavelidze
(Georgia) 

Polycrystalline SiGe alloys are high-temperature thermoelectric materials and are widely used for production of p- and n-branches of thermoelectric batteries, with working temperature above 10000C. At these temperatures evaporation of germanium and dopant materials (boron and phosphorus) takes place from SiGe alloys. This process  might stipulate worsening thermoelectric characteristics of the thermoelectric converter and decreasing duration of its working resource. This highlights the need for the formation of antisublimation coatings on the surface of the thermoelements branches, compatible in their physical-chemical properties with their characteristics.

In practice, silicon nitride and high-temperature organic and inorganic materials are widely used to solve this problem. This is stipulated by the presence of relatively simple technological processes of their creation and practical application. These materials are characterized by high brittleness or become brittle during operation of the thermobatteries at high temperatures. In case of organic materials liquid hydrocarbons are additionally released, which form carbon at high temperatures. As a consequence, the electrical insulating characteristics of thermobatteries deteriorate, which often leads to a short circuit.  In the process of operation of thermobatteries, both planned and unplanned changes in temperature often take place. It can cause damage to the continuity of a thin layer of protective coating.

Hightemperatureelectroinsulatingantisublimation coatings based on vitreous enamels have been created by us for protecting p- and n-types branches of thermoelements based on SiGe. By varying the chemical composition of the glass frit, vitreous enamel has been obtained, that meets the requirements for the physical-chemical properties of antisublimation coatings at temperatures of 1000-1100°C.

The following chemical composition of glass frit: Na2O-K2O-ZnO-Cr2O3-Al2O3-SiO2 was developed based on liquid glass Na2O•n SiO2. Based on these materials, high-temperature antisublimation coatings of the highest quality are formed on the surface of p- and n-branches of SiGethermoelements. The proposed material can preserve the strength of the connection of the branches of thermoelements at the initial level, their electrical insulation and antisublimation properties in case of temperature change of the thermoelectric generator at a speed of 1000C C/min in the temperature interval of 1000-250C.






INTEGRATED (COMPREHENSIVE) UTILIZATION OF RENEWABLE ENERGY SOURCES AND ENERGY EFFICIENCY IN REMOTE MOUNTAINOUS AREAS

MERAB CHIRAKADZE

Georgian Technical University
Innovation Centre for renewable energy and energy efficiency
(Georgia)






HEAT  ACCUMULATOR

MERAB CHIRAKADZE

Georgian Technical University
Innovation Centre for renewable energy and energy efficiency
(Georgian)