Materials Science and Engineering / Malzeme Bilimi ve Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/4719

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  • Article
    Citation - WoS: 49
    Citation - Scopus: 54
    Closed Porosity Ceramics and Glasses
    (Wiley, 2020) Vakıfahmetoğlu, Çekdar; Semerci, Tuğçe; Soraru, Gian Domenico
    In the last three decades, considerable effort has been devoted to obtain both open and closed porosity ceramics & glasses in order to benefit from unique combination of properties such as mechanical strength, thermal and chemical stability at low-relative density. Most of these investigations were directed to the production and the analysis of the properties for open porosity materials, and regrettably quite a few compositions and manufacturing methods were documented for closed porosity ceramics & glasses in the scientific literature so far. This review focuses on the processing strategies, the properties and the applications of closed porosity ceramics & glasses with total porosity higher than 25%. The ones below such level are intentionally left out and the paper is set out to demonstrate the porous components with deliberately generated closed pores/cells. The processing strategies are categorized into five different groups, namely sacrificial templating, high-temperature bonding of hollow structures, casting, direct foaming, and emulsions. The principles underlying these methods are given, with particular emphasis on the critical issues that affect the pore characteristics, mechanical, thermal and electrical properties of the produced components.
  • Article
    Citation - WoS: 23
    Citation - Scopus: 23
    Hot Air Permeable Preceramic Polymer Derived Reticulated Ceramic Foams
    (American Chemical Society, 2020) de Mello Innocentini, Murilo Daniel; Marsola, Gabriel Antonio; Orlandi Lasso, Paulo Renato; Soraru, Gian Domenico; Semerci, Tuğçe; Vakıfahmetoğlu, Çekdar
    Open and partially closed cell polymer derived ceramic, specifically silicon oxycarbide, foams were produced from commercially available polyurethane (PU) foams through the replica technique combined with the preceramic polymer pyrolysis route. The focus was directed on the role of PU morphology (cell size and open/partially closed cells), synthesis parameters (cross-linking temperature and time), and type of the polysiloxane precursors for fine-tuning the microstructural features of the resulting ceramic foams and their eventual effect on the fluid dynamic/mechanical properties. Consequently, ceramic foams having dense/hollow struts with/without hierarchical porosity were able to be manufactured and characterized in detail. The average total porosity including all compositions was above 95%, the maximum surface area was found to be reaching 79 m(2).g(-1), and the room temperature permeability measurements indicated a wide range for k(1) (0.28 x 10(-9)-11.48 x 10(-9) m(2)) and k(2) (0.34 x 10(-5)-54.17 x 10(-5) m) according to the selected PU substrate. Hot air permeation tests showed that the foams were stable up to 700 degrees C without any loss of functionality. Accordingly, they are envisioned to be employed as reusable air filtration device parts for pollutants (viruses, bacteria, dust, etc.), catalytic supports, and filter components for reactions occurring in aggressive environments.
  • Article
    Citation - WoS: 39
    Citation - Scopus: 39
    Processing and Thermal Characterization of Polymer Derived Sicn(o) and Sioc Reticulated Foams
    (Elsevier, 2020) Santhosh, Balanand; Ionescu, Emanuel; Reitz, Emanuel; Albert, Barbara; Sorarù, Gian Domenico; Ahmetoğlu, Çekdar Vakıf
    Highly porous polymer-derived SiCN(O) and SiOC ceramics with low thermal conductivity were developed by replicating polyurethane (PU) foams. The PU templates were impregnated with polysilazane or polysiloxane precursor, followed by pyrolysis at different temperatures (1200 °C - 1500 °C) yielding SiCN(O) or SiOC ceramic foams, respectively. The swelling and cross-linking behavior of the used precursors had a significant impact on the morphology of the prepared foams. The samples had bulk densities ranging from 0.03 g.cm-3 to 0.56 g.cm-3 and a total porosity in the range from 75 to 98 vol%. Fourier transform infrared (FT-IR), Raman spectroscopy, X-ray diffraction (XRD) were employed to follow the structural evolution together with morphological characterization by scanning electron microscopy (SEM). The obtained ceramics were thermally stable up to 1400 °C, and the linear thermal expansion coefficient values of the porous SiCN(O) and SiOC components in the temperature range from 30 to 850 °C were found to be ~1.72 x 10-6.K-1 and ~1.93 x 10-6.K-1, respectively. Thermal conductivity (?) as low as 0.03 W.m-1 K-1 was measured for the SiCN(O) and SiOC foams at room temperature (RT). The ? of the ceramic struts were also assessed by using the Gibson-Ashby model and estimated to be 2.1 W.m-1 K-1 for SiCN(O), and 1.8 W.m-1 K-1 for SiOC. © 2019 Elsevier Ltd and Techna Group S.r.l.