Porous adsorbents with hierarchical structured macropores ranging from 1 to 100 μm are prepared using a combination of freeze casting and additional sacrificial templating of polyurethane foams, with a zeolite 13X powder serving as adsorbent. The pore system of the prepared monoliths features micropores assigned to the zeolite 13X particle framework, interparticular pores of ∼1-2 μm, lamellar pores derived from freeze casting of ∼10 μm, and an interconnected pore network obtained from the sacrificial templates ranging from around 100 to 200 μm with a total porosity of 71%. Gas permeation measurements show an increase in intrinsic permeability by a factor of 14 for monoliths prepared with an additional sacrificial templated foam compared to monoliths solely providing freeze casting pores. Cyclic CO2 adsorption and desorption tests where pressure swings between 8 and 140 kPa reveal constant working capacities over multiple cycles. Furthermore, the monoliths feature a high volumetric working capacity of ∼1.34 mmol/cm(3) which is competitive to packed beds made of commercially available zeolite 13X beads (∼1.28 mmol/cm(3)). Combined with the faster CO2 uptake showing an adsorption of 50% within 5-8 s (beads ∼10 s), the monoliths show great potential for pressure swing adsorption applications, where high volumetric working capacities, fast uptakes, and low pressure drops are needed for a high system performance.
The modification of titanium-based surfaces has been recently studied to accelerate the osseointegration process of endosseous implants. Indeed, bioabsorbable polymer veneers carrying antimicrobials or bone growth factors to the implant-bone interface could enhance such osseointegration process. The main aim of this work was to study the tribocorrosion behavior of veneering biodegradable poly(D,L-lactide) on titanium surfaces in an artificial saliva solution. Cylinders of Ti6Al4V were prepared by grit-blasting with 250-lm alumina particles followed by HF/HNO 3 etching technique to increase the roughness of the top surface. After surface modification and cleaning, the rough surface was covered with poly (D,L-lactic acid) (PDLLA) by spin-coating technique. Reciprocating sliding tests were performed against an alumina ball at a normal load of 0.5 N, a sliding frequency of 1 Hz, and linear displacement amplitude of 3 mm using a tribometer. The sliding tests associated to open-circuit potential (OCP) measurements were performed in artificial saliva solution to mimic the oral conditions for 60 min. After tribocorrosion tests, the worn surfaces were inspected by scanning electron microscopy. The results revealed a lower coefficient of friction (COF) on PDLLA than that recorded on Ti6Al4V. A protective effect of PDLLA against wear and corrosion of Ti6Al4V was noticed on the reciprocating sliding under OCP measurements for 60 min. Furthermore, a gradual degradation of PDLLA was detected, which could be useful in situ to release of therapeutic substances to be incorporated into the bioabsorbable polymer.
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