Thematic area of your work (one of the thematic areas of International research and practice conference "Nanotechnology and nanomaterials")

Radio-absorbing composite ceramic materials
G.V. Lisachuk, R.V. Krivobok, O.M. Lapuzina, 
M.S.Maistat, B.A. Karputin 

Scientific and Research Part NTU "KhPI", National Technical University “Kharkiv Polytechnic Institute”. Frunze Street, 21, Kharkiv-61002, Ukraine. 
E-mail: krivobok@kpi.kharkov.ua

Currently, special ceramic materials for absorbing and transmitting electromagnetic radiation of the radio frequency range, which respectively have radio-absorbing and radio-transparent determinations. The most prospective direction of creating special ceramic materials are inorganic materials, which are characterized by uniformity of properties in a wide range of temperatures and the range of radio frequencies of electromagnetic radiation. By classification, the radio-absorbing materials can be magnetic and non-magnetic. Non-magnetic radio-absorbing materials in turn are divided into gradient, interference and combined ones. Gradient RAMs have a multilayer structure with a smooth change in the dielectric constant per material thickness ɛ1 > ɛ2 > ɛ3 > ɛn. The first layer of the RAM must be made of a radio-transparent material having low dielectric losses (ɛ1) for reconciling the air and material wave resistance. Other layers are made of solid dielectrics with high dielectric permeability (ferroelectrics, ferroelectronics and others).
In this work we will consider the direction of creating radio-absorbing materials in the compositional direction.  It should be noted that ceramics based on strontium titanate is a perspective for the creation of the second and subsequent layer of gradient composite radio-absorbing material due to relatively high and practically constant values of the dielectric constant and the tangent of the angle of dielectric losses in the broad frequency range of radio waves in comparison with other known crystalline phases and, according to various data, is ε = 155-255 at a frequency from 1 kHz to 10 GHz.
The technology of manufacturing composite ceramics based on strontium titanate was two-staged. The first stage of synthesis took place at a temperature of 1,300°C with an exposure at maximum temperature of 2 hours. The second stage was carried out at temperature of 1,330°C with an exposure of 1 hour.
It is established that compositions with a component ratio of slavonsonite and strontium titanate 20:80, 10: 90 wt. % correspondingly, has the best indicators: W water absorption – 0,8-0,5%, ρb apparent density – 4080-4130 kg/m3 and ε dielectric permittivity – 50-60. The generalization of the obtained data allows to draw a conclusion that the developed composition of the composite ceramic material on the basis of slavonsonite and strontium titanate is perspective for the creation of the second and subsequent layers of the gradient radio-absorbing material.