Scientists who are going to participate in the project:
- Georgy V. Lisachuk , Doctor of Sciences (since 2003), full Professor (since 2007), Head of Research department of National Technical University «Kharkiv Polytechnic Institute» (NTU «KhPI»). Specialist in material sciences of resource saving and energy-saving technologies, new structural ceramic materials and coatings. Author and co-author of more than 250 papers, 3 monographs, 83 author’s certificates and patents. Lecturer of major courses at the Department of Technology of ceramics, refractories, glass and enamels.
- Helen Y. Fedorenko, Doctor of Sciences (since 2013), full Professor (since 2014), Author and co-author of more than 125pers, 2 monographs, 25 author’s certificates and patents.
- Ruslan V. Kryvobok, Candidate of Technical Sciences (since 2007), Senior researcher (since 2010). Deputy Head of Scientific and Research Part NTU «KhPI». Specialist in material sciences of new special-purpose ceramic materials and coatings. Author and co-author of more than 24 papers, 6 patents.,
- Artem V. Zakharov, graduate studentSgraduate students, Author and co-author of more than 5 papers, 2 author’s certificates and patents.
- Keywords: ceramic, radiotransparent materials, electromagnetic wave, radio-frequency
- Abstract:
Ceramic radiotransparent materials are non-metallic materials which don’t substantially alter the amplitude and phase of the electromagnetic wave of radio-frequency range passing through them. Radiotransparency of ceramic materials is provided by low dielectric losses in the range of operating temperatures (tgδ 10-2…10-5, ε<10) and by low value of reflection coefficient of radio waves (S). Ceramic radiotransparent materials are mainly used for the manufacture of radomes protecting antennas against the environmental influence and so on. Besides the above mentioned requirements radio-ceramic materials must have: a high value of thermal resistance, low coefficient of linear expansion and at the same time should protect the equipment from external influences.
Nowadays a large number of materials in the world practice are used as radiotransparent silicate materials.
The main disadvantages of radiotransparent materials based on the vitroceramics and glass materials are their brittleness and the disadvantage of composite materials is their high cost of creation.
At the moment ceramic materials based on quartz, high-alumina and mullite ceramics, silicon nitride, boron and others are widely used for creation of radiotransparent materials. Table 1 shows the main advantages and disadvantages of the main ceramic radiotransparent materials.
Table 1 – Radiotransparent ceramic materials
| Name of material | Advantages | Disadvantages |
|
Quartz ceramics
|
High thermal stability, stability of dielectric properties over a wide temperature range | High melting temperature, low mechanical strength, the upper limit of operating temperature is 1000 ° C |
| High-alumina ceramics | High mechanical properties, resistance to corrosion | High temperature of sintering, low resistance to thermal shock — not higher than 200 ° C |
| Ceramics based on silicon nitride | High strength characteristics at high temperatures (1500 ° C), good resistance to oxidation and thermal stresses | High sintering temperature, complex technological process of production |
| Ceramics based on boron nitride | Has the best dielectric properties at temperatures up to 2000 ° C |
- Project Idea
The direction of creating of radiotransparent ceramic materials based on electrical ceramics was chosen on the basis of the literature review. Physicotechnical and chemical properties of crystals which form the basis of electrical materials are shown in the Table 2.
Table 2 — Electrical properties of the crystals which form the basis of radiotransparent ceramics
| Compound | Dielectric constant, ε | Dielectric loss tangent, 104 tgδ, 1 MHz |
| Anorthite SrO∙Al2O3∙2SiO2 | 6,2-6,8 | 11-50 |
| Anorthite СaO∙Al2O3∙2SiO2 | 6-7 | 2-3 |
| Wollastonite СaO∙SiO2 | 5 | 3 |
| Quartz β-SiO2 | 4,5 | 3 |
| Clinoenstatite MgO∙SiO2 | 7 | 3 |
| Corundum α-Al2O3 | 9,9-10,5 | 1-2 |
| Mullite 3Al2O3∙2SiO2 | 7 | 5-10 |
| Boron nitride BN | 4,2 | 2 |
| Silicon nitride Si3N4 | 8 | 2,4 |
| Spodumene Li2O∙Al2O3∙2SiO2 | 7,4 | 70-155 |
| Forsterite 2MgO∙SiO2 | 7 | 1-3 |
| Celsian BaO∙Al2O3∙2SiO2 | 6,5-7 | 1-2 |
| Spinel MgO∙Al2O3 | 8 | 3 |
Table 2 shows that all crystalline phases have low value of dielectric constant and dielectric loss tangent. Celsian (BaO∙Al2O3∙2SiO2) and Sr-anorthite (SrO∙Al2O3∙2SiO2) ceramics were selected for further investigation of the possibility of establishing of radiotransparent ceramic materials for missile radomes. These two ceramic materials are promising because of their almost constant values of the dielectric constant and dielectric loss tangent at high temperatures and high frequencies (35 GHz).
The crystalline phase of celsian and Sr- anorthite of monoclinic modification (symmetry), which in comparison with the hexagonal one has a higher melting point, low thermal expansion coefficient, low dielectric constant and dielectric loss tangent in a wide temperature and frequency range, is used for creation of radiotransparent ceramic materials.
We suggest to create radiotransparent ceramic materials on a basis Anorthite SrO∙Al2O3∙2SiO2 AND Celsian BaO∙Al2O3∙2SiO2.
Contacts:
Krivobok Ruslan, Deputy Head of Scientific and Research Part NTU «KhPI», National Technical University “Kharkiv Polytechnic Institute”, 21, Frunze str., 61002 Kharkiv, Ukraine, Kharkiv, Ukraine. Email: krivobok_ruslan@ukr.net
Phone: +380976068278.