Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Design and Performance of SiOC Foam-Silica Aerogel Composites for Hot and Cold Thermal Management Applications(Elsevier Ltd, 2025) Icin, Oyku; Vakifahmetoglu, CekdarThis study focuses on the fabrication of monolithic preceramic polymer-derived ceramic (SiOC) foam-silica aerogel composites by filling the open cells of ceramic foam with a silica aerogel solution using the sol-gel technique. The effects of different drying techniques (ambient pressure vs CO2 supercritical drying) and surface modification agents, including trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDZ), are comprehensively investigated. These factors are analyzed for their influence on the composites' morphology, porosity, chemical structure, and thermal insulation performance. The drying technique and surface modification agents are found to play a critical role in achieving a high filling ratio of silica aerogel within the composites. Pure silica aerogels exhibit specific surface areas (SSAs) reaching similar to 1120 m(2).g(-1), while the SiOC foam-silica aerogel composites demonstrate SSAs of 385-440 m(2).g(-1). Nearly all samples achieve a total porosity of similar to 93 vol%. Surface modification effectively tailors the surface properties, imparting hydrophobicity with a water contact angle of 133 degrees. Thermal conductivity at room temperature ranges between 38 and 43 mW<middle dot>m(-1)<middle dot>K-1. The potential applications of these SiOC foam-silica aerogel composites as thermal insulators are assessed under extreme thermal conditions. For instance, a 14 mm thick composite has a temperature of -27 degrees C when subjected to a cold source at -78 degrees C. Instead, when exposed directly to a butane flame (similar to 1200 degrees C), the backside of the composite recorded only similar to 57 degrees C.Article Citation - WoS: 5Citation - Scopus: 5Sioc Foam-Aerogel Composites: Optimal Balance of Lightness and Excellent Thermal Insulation(Wiley, 2024) Icin, Oyku; Abebe, Adane Muche; Soraru, Gian Domenico; Vakifahmetoglu, CekdarFoam-aerogel composites are synthesized in polymeric, hybrid, and ceramic states by completing the open cells of the foam with a solution forming a wet gel, carbon dioxide (CO2) supercritically dried, and pyrolyzed. Thermal diffusivity measurements are conducted using the laser flash, and for mechanical performance, cold crushing tests are done to obtain compressive strengths. Samples possess a range of specific surface area (SSA) values up to similar to 650 m2/g contingent upon the material state, that is, polymeric, hybrid, or ceramic. While SSA values can be deliberately altered, almost all samples demonstrated a total porosity of similar to 90 vol%, with superb specific compressive strength reaching around 2 MPa. In addition to adjustable surface characteristics granting hydrophobic and hydrophilic features, the study revealed the potential use of these foam-aerogel composites as thermal insulators with low thermal conductivities of 0.02 W<middle dot>m-1<middle dot>K-1 at RT and 0.05 W<middle dot>m-1<middle dot>K-1 at 500 degrees C. When exposed directly to a butane flame gun with a flame temperature reaching similar to 1200 degrees C, from the backside of a 5 mm-thick foam-aerogel composite, only similar to 200 degrees C is recorded, which is lower than a comparable commercial insulator panel tested under the same conditions.