Submicron‐Scale Exclusion via Polymerizing an Aromatic Nylon in Molded Ceramic Monolith for Paving Interconnected Pore Channels

Abstract

A matrix with extensively interconnected channels is an important feature to pursue ceramic membrane technology. This work attempts an alternative pore‐forming strategy through utilizing in situ generated poly(p‐phenylene terephthalamide) (PPTA) nanorods as a pore former. Different from the conventional means, this approach relies on interstice exclusion of the PPTA rods throughout the green ceramic object. The spatial confinement restricts the polymerization extent of PPTA, resulting in a localized generation of nanocrystallite rods and an expansion of interparticle contacts simultaneously. Another feature of this PPTA is the high carbonization degree of PPTA which allows for space retention of the rods during the initial stage of calcination designed to sinter the object. The pore channels left behind in the sintered article possess the throat‐to‐void structural characteristic. Besides the marked improvement on fluid permeability and mechanical strength over the ones fabricated by using starch as pore former, such a pore structure claims an unusual capability to induce a shear thinning effect when a pressure‐driven dilute polymer solution passes through the channels.

Evolution of throttle-channel dual pores in YSZ ceramic monolith through in situ grown nano carbon wedges

“…These two discs shared an identical dimension before sintering, indicating that the YSZ particles are closer in the PVB-containing green body. It has been addressed in our previous study 16 that a more compact environment favors the growth of PPTA rods during polymerization.…”

“…16 The PPTA polymer generated in a green YSZ disc thus assumed a rod shape comprising of aligned aromatic chains (Fig. 3).…”

“…With reference to our previous study, 16 an equimolar mixture of terephthalic acid (TA, 98%, Sigma-Aldrich, St. Louis, MO, US) and p-phenylene diamine (p-PDA, Sigma-Aldrich) were introduced into 30 ml ethanol. The resulting suspension was stirred for 30 min before a control amount of YSZ powder (Y 0.08 Zr 0.92 O 2−δ , median particle diameter of 0.5-1.0 m, Stanford Material Corporation, Aliso Viejo, CA, USA) was added to allow for TA to dissolve in the solvent.…”

“…The pore size distribution and porosity of the sintered discs were measured by mercury porosimetry (Micrometrics AutoPore III, Norcross, GA, US). The air permeability of a sintered YSZ disc was measured using the module designed in our previous study 15,16 and the Darcy's permeability of the porous ceramic was calculated. Similarly, the edge of the pellet was sealed with aluminum sticker to prevent any leakage of air.…”

“…The adoption of more thermally stable polymer as porogen, such as poly(p-phenylene terephthamide) (PPTA) or Kevlar used in our previous work, 16 is a remedy to this problem. PPTA decomposes at a much higher temperature than traditional polymeric pore-formers such as starch and aliphatic polyethers.…”