Gelcasting Of Ceramic Radomes In The Si₃N₄-Al₂O₃-AlN-SiO₂System

Dense β-SiAlONs consolidated by a modified hydrolysis-assisted solidification route

“…A close CTE value of 4.1 × 10 −6 • C −1 between 25 and 1000 • C was also reported for ␤-Si 4 Al 2 O 2 N 6 consolidated by gelcasting. 10,11 Thus, the CTE values observed in the present study compare well with the reported results.…”

“…A similar BD of 3.02 g/cm 3 was also reported for the same ␤-Si 4 Al 2 O 2 N 6 composition consolidated by aqueous gelcasting. 10,11 Interestingly, both CDPP and HAS-5 samples exhibit values of BD >3.02 g/cm 3 and of AP and WA capacity <0.2 and <0.6%, respectively. The linear shrinkage values associated with the drying and sintering steps of HAS-5 sample obtained from a slurry with 48 vol.% solids loading were found to be ∼2 and ∼15%, respectively (total linear shrinkage of ∼17%).…”

Near‐Net Shape β‐Si4Al2O2N6 Parts by Hydrolysis Induced Aqueous Gelcasting Process

“…Due to this high and uniform stiffness, the consolidated part keeps its shape intact upon further drying and binder removal operations, which in turn minimizes the expensive postsintering machining operations. [6][7][8][9] However, in this process, a commercial AlN powder protected against hydrolysis with a coating layer of hydrophobic substance was used as a raw material. However, the thin wall ceramic components formed in this process often break due to their highly brittle nature.…”

“…15 Further, as the formation of green body is not affected by the externally applied pressure or water absorption by an absorptive mold, this process effectively utilizes various thermally activated chemical processes in situ. [6][7][8][9] Moreover, by following the reported processes shapes having different thicknesses at different places like nose and wall in the case of radome are rather difficult to fabricate as they normally crack due to differential shrinkage upon drying procedure involved. 15 Recently, an aqueous gelcasting (GC) process has been found to be one of the most effective processing routes for making near net-shape parts with relatively high green strength, which can be green machined.…”

Conductive graphene nanoribbon (GNR) thin film as anti-icing /de-icing heater

“…Besides, such film must be light-weight and low cost, with physical characteristics that allow it to cover large curved surface areas. Currently, most radome structures are constructed using a metal wire framework with supporting ceramic materials [1][2][3]. The metal wire framework serves as the conductive heat layer and the multi-layer ceramic sandwich is the RF transparent heat-transfer medium.…”