Magnetic wood-based biomorphic Sr3Co2Fe24O41 Z-type hexaferrite ecoceramics made from cork templates

Abstract

Ecoceramics (environmentally conscious ceramics) are biomimetic/biomorphic ceramics, which use a naturally occurring and sustainable material as a template for their unique morphology and structure. Usually woods (or lignocellulosics) are used, due to the inherent cellular nature of their microstructures. The wood is pyrolised and the resulting carbon skeleton impregnated with a fluid, and this is then heated to combust the carbon template and convert the fluid precursor into a ceramic, while maintaining the structure of the original natural template. For the first time, ecoceramics have been made from cork, a totally sustainable wood that is harvested without harming the tree. Also for the first time, ecoceramics have been made of soft magnetic Z-type hexaferrites, in this case the room temperature multiferroic strontium Z ferrite Sr 3 Co 2 Fe 24 O 41 (SrZ). Cork powder was pyrolised at 1000°C, infiltrated with an aqueous sol-gel SrZ precursor, and then heated at 1200°C/2 h to produce the ecoceramic. The cellular structure of the cork was maintained, with a small reduction in the hexagonal cell dimension to 10 lm diameter, but the cell walls remained 1-2 lm thick, of a similar magnitude to the hexaferrite grain size. Both magnetic and XRD data agreed that there was a small portion of the SrW phase present in these ecoceramics as well, and the magnetic loop showed a magnetically soft ecoceramic with M s = 59.5 A m 2 kg À1 (at 3 T), and a low H c of 16 kA m À1 .

Biomimetic cork-based CeO2 ecoceramics for hydrogen generation using concentrated solar energy

“…SEM images showed that the cellular structure of the cork was maintained, with hexagonal cells around 20-30 μm in diameter, and cell walls <1 μm thick. Unlike the large grained hexaferrite ecoceramics made from cork reported previously by Pullar et al [26], the individual grains of these CeO2 ecoceramics were on the nanoscale size range, being no more than 100 nm in diameter. Another important feature was that, while the rectangular side walls were maintained to hold the cellular cork structure, the rear hexagonal walls were pierced, with these holes repeating through the structure.…”

“…The first biomorphic ceramics produced were of "SiC wood" [21] from charcoal, and since 1998 several types of pyrolised wood were used as templates to create SiC "ceramic wood" [22,23], as well as oxide ceramics such as CeO2 [24,25]. Many different soft and hard woods have been use as pyrolised templates for Ecoceramics, but cork was never used, despite its obvious suitability, until the pioneering work by Pullar et al [26], although this use was previously referred as a possible future trend [12]. Pullar et al created the first ever cork-based Ecoceramics, in the form of magnetic hexagonal ferrite ceramic foams, with the cellular structure of cork.…”

A Review of Solar Thermochemical CO2 Splitting Using Ceria-Based Ceramics With Designed Morphologies and Microstructures

“…Pullar et al have carried out innovative work to create biomorphic ecoceramics of ferrites and ceria from cork templates (Pullar et al, 2015, 2016; Pullar and Novais, 2017). Cork naturally has similar dimensions to the pine-derived ecoceramic above, yet with a more regular 3-DOM (three-dimensionally ordered macroporous) microstructure.…”

Efficient Pb2+ adsorption of biomorphic porous ZnO derived from legume straw

“…Adsorption is a well‐known equilibrium separation process and an effective method for water decontamination. A variety of adsorbents such as activated carbon , biomass , graphene oxide , natural mineral material , and waste materials have been used to deal with the wastewater. Among these adsorbents, activated carbon is the most commonly used adsorbent for the removal of heavy metals from wastewater.…”