TJ958 : Fabrication of fused silica bodies through cold isostatic pressing and sintering and characterization of their physical and mechanical properties
Thesis > Central Library of Shahrood University > Mechanical Engineering > MSc > 2024
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Ceramic bodies made of fused silica and cordierites with low coefficient of thermal expansion are used to protect the radar in harsh environmental conditions in terms of temperature and abrasion. In this dissertation, forming of cordierite ceramic body through rubber isostatic pressing (RIP) process has been investigated. RIP method uses a hyperelastic solid medium for applying quasi static pressure and consolidating ceramic powder. Materials such as natural rubber, silicone and polyurethane with low compressibility (Poisson's ratio close to 0.5) and high elasticity are usually used in this method. Shear stress is not easily transferred in the medium of rubber under pressure. Also, it can be sealed well. The studied ceramic body is a cone-like shell with a height of 400 mm, a baxse diameter of 180 mm, and a thickness of 6 mm. Taking into account a 50% volumetric compaction of powder due to isostatic pressure, a 20% shrinkage caused by sintering and additional material for grinding the outer surface of the body, the RIP mold was designed. With the help of the finite element method, the process of forming the powder with rubber was simulated and the uniform pressure distribution and as a result the uniform compaction of the powder was ensured. To conduct the experimental study, a laboratory sample with a scale of one quarter of the real part was considered. Then, the RIP mold was designed and fabricated for this sample. The body of the mold was made of steel and rubber was made of silicone RTV25. The mixture of powders required for the synthesis of cordierite was granulated by adding polyvinyl alcohol binder. The shaping of the ceramic bodies using a hydraulic press with a force of 700 kN, and the use of a RIP mold was successful, and the part was free of any apparant defects and cracks. After shaping, the samples were fired at 1300°C. The results of the X-ray diffraction test on the sintered sample show that the cordierite phase has been successfully synthesized. The shrinkage of the samples after sintering was measured by 10%. Also, the bending strength of the samples was measured around 95 MPa.
Keywords:
#cold isostatic pressing #cordierite #sintering #finite element analysis. Keeping place: Central Library of Shahrood University
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