Fused Silica Ceramics and Composites for Radome Applications

Abstract

The processing methods, strengthening methods, water-proof coating procedures, and some ways to improve the transmission of microwaves have been reviewed in relation to fused silica ceramics and their composites for radome applications. Fused silica ceramics are characterized by a residual porosity (up to 18%), low dielectric constant (3.06-3.32), low loss tangent (0.00053-0.0065), excellent thermal properties, but low mechanical strength (37-65 MPa). To achieve higher mechanical strength and better transmission efficiency, new randome materials would be those engineered composites consisting, for instance, of a dense layer-porous core structure, a continuous fiber reinforcement, a multilayered structure, and/or frequency selective surface (FSS) layer (s)/metamaterials.

Slip-Cast Fused Silica Radomes for Hypervelocity Vehicles: Advantages, Challenges, and Fabrication Techniques

“…For high speed missile applications (Mach 6 to 8), only ceramics such as silica (SiO 2 ) (fused silica [8]), alumina (Al 2 O 3 ), magnesia (MgO), beryllia (BeO), boron nitride (BN), reaction-bonded silicon nitride (RBSN), hot-pressed silicon nitride (HPSN), silicon aluminum oxynitride (β-SiAlON), cordierite (2MgO.2Al 2 O 3 .5SiO 2 ) based glasses (Pyroceram-9606, Pyroceram-9608, AS-418, AS-370, which are known as Sitall glasses in Russia), a composite of barium aluminum silicate (termed as Celsian), a composite of silicon nitride, boron nitride and silica (Si 3 N 4 -BN-SiO 2 ) (termed as Nitroxyceram), etc., can be the candidate materials of choice (Tables 5 and 6). Figure 11a-c shows some examples of modern missile complexes equipped with radomes made of slip-cast fused-silica (SCFS) and Sitall radomes produced in Russia [1,2].…”

“…Thus, a radome is one of the most important parts of the modern radar-guided missile systems, which is also employed on high performance hypersonic airplanes, satellites, etc. [8][9][10]. In fact, among the various fairing accessories of a missile and aircraft, the radome occupies a highly important place.…”

Various types of ceramics used in radome: A review

“…Multilayer broadband designs, known as A-; B-, and C-sandwich structures, have been proposed to solve this problem [8]. As shown in Figure 3, the radome wall structure greatly determines the use of the de ned frequencies or broadband (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) wave transmission, and half-wave wall structure is used for the de ned frequency application [9]. The most commonly used and reported broadband radome wall structure consists of A-sandwich, C-sandwich, and multilayer.…”

“…In the years of 1945-50, radome manufacturers widely used fused silica or quartz glass, which enjoys properties such as low thermal conductivity (0.8 W/m.K), low thermal expansion coe cient (0.54-0.7*10 6 / C), low density, suitable mechanical strength, good resistance against thermal shock (no breakage after more than 20 thermal shock cycles between 25 C and 1000 C), and high electrical resistance [2,18,19]. Furthermore, the fabrication of radomes using this material is done through slip casting, which is a simple process.…”

“…Furthermore, the fabrication of radomes using this material is done through slip casting, which is a simple process. The properties of some of the fused silica ceramics and composites that are reported by di erent researchers are given in Table 6 [18]. Figure 4 shows the ow diagram for the production of radomes made of quartz ceramics [20].…”