Gradient-Hierarchic-Aligned Porosity SiOC Ceramics

Abstract

This work describes a simple technique to produce porous ceramics with aligned porosity having very high permeability and specific surface area. SiOC-based compositions were processed from blends of three types of preceramic polymer and a catalyst, followed by curing and pyrolysis. The heating applied from the bottom of molds promoted the nucleation, expansion and rising of gas bubbles, and the creation of a ceramic matrix with axially oriented channels interconnected by small round pores. The samples were analyzed by SEM, tomography, BET, water immersion porosimetry and permeation to gas flow. The resulting bodies presented levels of open porosity (69.9–83.4%), average channel diameter (0.59–1.25 mm) and permeability (0.56–3.83 × 10−9 m2) comparable to those of ceramic foams and honeycomb monoliths, but with specific surface area (4.8–121.9 m2/g) typical adsorbents, enabling these lotus-type ceramics to be advantageously used as catalytic supports and adsorption components in several environmental control applications.

Polymer‐derived ceramic aerogels as sorbent materials for the removal of organic dyes from aqueous solutions

“…The polymer pyrolysis method offers another important advantage compared to the traditional powder processing of ceramic materials: a wide range of forming techniques are available to shape the components in the polymeric state which is then retained in the final ceramic state. Consequently, PDCs fibers, films, ceramic matrix composites, MEMS, and a variety of macro‐, meso‐, and micro‐porous ceramics (even with lotus‐type porosity) have been obtained via the PDC route and several comprehensive reviews are available on this topic . Concerning the processing of porous materials, the synthesis of PDC aerogels has been recently proposed by some of us and SiC, SiOC, and SiCN aerogels have been obtained and characterized …”

Polymer‐derived ceramic adsorbent for pollutant removal from water

“…The Barrett‐Joyner‐Halenda (BJH) used to obtain the pore size distribution (PSD). In a previous study, the SSA values were found ~120 m 2 /g for W and ~660 m 2 /g for W‐HF and PSD demonstrated that while sample W was mostly mesoporous, W‐HF had broad pore size distribution in both micro and mesopore range (see Figure ).…”

“…The samples were prepared following the procedure given in the literature . All the starting chemicals were used as received: Hydrotalcite, (LDH: Mg 6 Al 2 (CO 3 )(OH) 16 ·4H 2 O), vinyl‐terminated polydimethylsiloxane (PDMS, Gelest, USA, CAS# 68083‐19‐2) a cyclic 2,4,6,8‐tetramethyl‐2,4,6,8‐ tetravinlycyclotetrasiloxane (TMTVS 97%, Alfa Aesar, USA, CAS# 2554‐06‐5), and polymethylhydrosiloxane (PHMS, CAS# 63148‐57‐2, Gelest,USA), Platinum ‐ divinyltetramethyldisiloxane complex, ~Pt 2% in xylene (Sigma‐Aldrich, USA, CAS# 68478‐92‐2).…”

“…Considerable efforts are currently devoted to propose new adsorbents or improvement of the adsorption performance. In this context, preceramic polymers (PPs) offer several opportunities since their molecular composition/architecture can be altered easily and they can be processed to obtain in various forms following via plastic forming technique . Ceramics synthesized by the thermal decomposition of PPs, that is, polymer‐derived ceramics (PDCs), are novel class of nanostructured materials mostly composed of silicon, carbon, nitrogen, boron, and oxygen (depending on PP composition, heat‐treatment procedure: temperature, rate, dwell time, atmosphere, etc.…”

Closed porosity ceramics and glasses

“…Otherwise, initially formed microbeads can be infiltrated by the same chemical composition derivable PP. 4,211 | 2963 VAKIFAHMETOGLU ET AL.…”