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Direct 3D bioprinting of bioreactors containing microorganisms embedded inside hydrogel structures is a promising strategy for biotechnological applications. Nevertheless, microporous hydrogel networks hinder the supply of nutrients and oxygen to the cell and limit cell migration and proliferation. To overcome this drawback, we developed a feedstock for 3D bioprinting structures with hierarchical porosity. The feedstock is based on a highly particle-filled alumina/alginate nanocomposite gel with immobilized E. coli bacteria with the protein ovalbumin acting as foaming agent. The foamed nanocomposite is shaped into a porous mesh structure by 3D printing. The pore radius diameters inside the non-printed, non-foamed nanocomposite structure are below 10 µm, between 10 and 500 µm in the albumin-stabilized foam and with additional pores in the range of 0.5 and 1 mm in the printed mesh structure. The influence of albumin on the bubbles and hence pore formation was analyzed by means of interfacial shear rheology and porosity measurements with X-ray microtomography (µCT). Furthermore, averaged diffusion coefficients of water in printed and non-printed samples with different albumin concentrations were recorded using nuclear magnetic resonance (NMR) tomography to assess the water content in the porous structure. Moreover, the effective viability and accessibility of embedded E. coli cells were analyzed for various material compositions. Here, the addition of albumin induced bacterial growth and the porosity increased the effective viability of the embedded bacteria, most likely because of enhanced accessibility of the cells. The experimental results demonstrate the potential of this approach for producing macroscopic bioactive materials with complex 3D geometries as a platform for novel applications in bioprocessing.

Immobilizing microorganisms inside 3D printed semi-permeable substrates can be desirable for biotechnological processes since it simplifies product separation and purification, reducing costs, and processing time. To this end, we developed a strategy for synthesizing a feedstock suitable for 3D bioprinting of mechanically rigid and insoluble materials with embedded living bacteria. The processing route is based on a highly particle-filled alumina/chitosan nanocomposite gel which is reinforced by (a) electrostatic interactions with alginate and (b) covalent binding between the chitosan molecules with the mild gelation agent genipin. To analyze network formation and material properties, we characterized the rheological properties and printability of the feedstock gel. Stability measurements showed that the genipin-crosslinked chitosan/alginate/alumina gels did not dissolve in PBS, NaOH, or HCl after 60 days of incubation. Alginate-containing gels also showed less swelling in water than gels without alginate. Furthermore, E. coli bacteria were embedded in the nanocomposites and we analyzed the influence of the individual bioink components as well as of the printing process on bacterial viability. Here, the addition of alginate was necessary to maintain the effective viability of the embedded bacteria, while samples without alginate showed no bacterial viability. The experimental results demonstrate the potential of this approach for producing macroscopic bioactive materials with complex 3D geometries as a platform for novel applications in bioprocessing.

An assembled asymmetric alumina microfiltration membrane with high performance was prepared by combining freeze and tape casting techniques followed by two sintering steps. Freeze casting was used for manufacturing of the porous support layer with a highly interconnected pore network. Tape casting was applied on the top layer to form a pre-membrane with smaller pore size and controlled thickness, which was set on the sintered support. Morphology influences were investigated for different solid loadings, additives content and the assembled layer membrane structures. No delamination among the layers was observed. The assembled ceramic membrane had an average pore size between 30 and 50 μm together with a top surface layer around 0.35 μm, which is suitable to the microfiltration separation process. Porosity in the range of 26–50 % and water flux of 11–32 m3 m−2 h−1 bar−1 were reached for samples prepared with two sintering steps at 1600 and 1300 °C for 2 h.

Rational material designs play a vital role in the gas diffusion layer (GDL) by increasing the oxygen diffusion rate and, consequently, facilitating a longer cycle life for metal-air batteries. In this work, a new porous conductive ceramic membrane has been developed as a cathodic GDL for zinc-air battery (ZAB). The bilayered structure with a thickness of 390 μm and an open porosity of 55% is derived from a preceramic precursor with the help of the freeze tape casting technique. The hydrophobic behaviour of the GDL is proved by the water contact angle of 137.5° after the coating of polytetrafluoroethylene (PTFE). The electrical conductivity of 5.59 * 10−3 S/cm is reached using graphite and MWCNT as filler materials. Tested in a ZAB system, the as-prepared GDL coated with commercial Pt-Ru/C catalyst shows an excellent cycle life over 200 cycles and complete discharge over 48 h by consuming oxygen from the atmosphere, which is comparable to commercial electrodes. The as-prepared electrode exhibits excellent ZAB performance due to the symmetric sponge-like structure, which facilitates the oxygen exchange rate and offers a short path for the oxygen ion/-electron kinetics. Thus, this work highlights the importance of a simple manufacturing process that significantly influences advanced ZAB enhancement.

Membranes showing monomodal pore size distributions with mean pore diameters of 23, 33, and 60 nm are chemically functionalized using silanes with varying chain length and functional groups like amino, alkyl, phenyl, sulfonate, and succinic anhydrides. Their influence on the morphology, pore structure, and gas flow is investigated. For this, single-gas permeation measurements at pressures around 0.1 MPa are performed at temperatures ranging from 273 to 353 K using He, Ne, Ar, N2, CO, CO2, CH4, C2H4, C2H6, and C3H8. Results show pore size and pore volume linearly depending on the length of functional molecules, as expected for monolayer deposition. However, the gas flow through functionalized membranes is disproportionally decreased up to a factor of around 10. Hence, the decreased pore size and pore volume cannot explain the large decrease in flow. Furthermore, there is no specific dependency between the decrease in flow and temperature or gas type other than the relation proposed by Knudsen (√RTM)-1. Considering the large variety of functional molecules used, it is very surprising that no correlations between the type of functional group and the flow have been found. The decrease in flow, however, is strongly dependent on the chain length of the silanes (factor of 10 at ∼2 nm length). This leads to the conclusion that the observed effect is not caused by sorption driven processes. It is proposed that steric interactions between functional groups and gas molecules lead to increased residence times on the surface and longer molecular trajectories, which, in turn, lead to a decrease in flow. In membrane design, any surface modification should, therefore, make use of functionalizing agents with chain length as short as possible.

In this study, porous zirconia membranes were developed by aqueous tape casting. The influence of poly (methyl methacrylate) (PMMA) as a pore former, and sintering temperatures (1300, 1400, and 1500 °C) on open porosity and pore size was investigated. The rheological behaviour of the suspensions was measured. The slurries showed pseudoplastic behavior, which is desirable for tape casting. Functionalization with an amino silane precursor (3-aminopropyl triethoxysilane, APTES) was carried out to increase the hydrophilic properties of the membranes. The functionalized samples were characterized by SEM-EDX to identify the moieties attached to the surface. Membranes with open porosity ranging from 27% to 51% and average pore sizes from 0.2 to 1.4 μm were obtained. Samples sintered at 1400 °C with added pore former yielded the highest water flux, 257 Lm−2h−1, which increased to 642 Lm−2h−1 after functionalization. Membranes with tailored porosity and pore size obtained in this study are indicated for applications involving separation processes, especially for microfiltration systems.

Journal of colloid and interface science 611, 670 - 683 (2022). doi:10.1016/j.jcis.2021.12.113, Hypothesis: We test whether the wettability of nanoparticles (NPs) straddling at an air/water surface or oil/water interface can be extrapolated from sessile drop-derived macroscopic contact angles (mCAs) on planar substrates, assuming that both the nanoparticles and the macroscopic substrates are chemically equivalent and feature the same electrokinetic potential.Experiments: Pure silica (SiO$_2$) and amino-terminated silica (APTES-SiO$_2$) NPs are compared to macroscopic surfaces with extremely low roughness (root mean square [RMS] roughness ��� 2 nm) or a roughness determined by a close-packed layer of NPs (RMS roughness ��� 35 nm). Equivalence of the surface chemistry is assessed by comparing the electrokinetic potentials of the NPs via electrophoretic light scattering and of the macroscopic substrates via streaming current analysis. The wettability of the macroscopic substrates is obtained from advancing (ACAs) and receding contact angles (RCAs) and in situ synchrotron X-ray reflectivity (XRR) provided by the NP wettability at the liquid interfaces.Findings: Generally, the RCA on smooth surfaces provides a good estimate of NP wetting properties. However, mCAs alone cannot predict adsorption barriers that prevent NP segregation to the interface, as is the case with the pure SiO$_2$ nanoparticles. This strategy greatly facilitates assessing the wetting properties of NPs for applications such as emulsion formulation, flotation, or water remediation., Published by Elsevier, Amsterdam [u.a.]

This study presents a scalable method for designing magnetic Janus nanoparticles, which are capable of performing bacterial capture, while preventing agglomeration between bacterial cells. To this end, we prepared silica-coated magnetite Janus nanoparticles functionalized with a bacteria-specific antibody on one side and polyethylene glycol chains on the other, using the established wax-in-water emulsion strategy. These magnetic Janus nanoparticles specifically interact with one type of bacteria from a mixture of bacteria via specific antigen-antibody interactions. Contrarily to bacterial capture with isotropically functionalized particles, the bacterial suspensions remain free from cell-nanoparticle-cell agglomerates, owing to the passivation coating with polyethylene glycol chains attached to the half of the magnetic nanoparticles pointing away from the bacterial surface after capture. The selective magnetic capture of

During wound healing, a complex cascade of cellular and molecular events occurs, which is governed by topographical and biochemical cues. Therefore, optimal tissue repair requires scaffold materials with versatile structural and biochemical features. Nanoporous anodic aluminum oxide (AAO) membranes exhibit good biocompatibility along with customizable nanotopography and antimicrobial properties, which has brought them into the focus of wound treatment. However, despite their good permeability, such bioinert ceramic nanopores cannot actively promote cell growth as they lack biochemical cues to support specific ligand-receptor interactions. Therefore, we modified AAO nanopores with the biochemical features of collagen nanofibers or amino groups provided by silanization with (3-aminopropyl)triethoxysilane (APTES) to design a permeable scaffold material that can additionally promote cell adhesion. Viability assays revealed that the metabolic activity of both 3T3 fibroblasts and HaCaT keratinocytes on bare and silanized AAO pores was comparable to glass controls until 72 h. Interestingly, both cell types showed a reduced proliferation on AAO with collagen nanofibers. Nevertheless, scanning electron and fluorescence microscopy revealed that 3T3 fibroblasts exhibited a well-spread morphology with filopodia attached to the nanoporous surface of the underlying AAO membranes or nanofibrous collagen networks, thus indicating a close interaction with the composites. Keratinocytes, although growing in clusters on bare and APTES-modified AAO, also adhered well on collagen-modified AAO membranes. When in contact with

The development of porous ceramic screens with high chemical stability, low density, and thermal conductivity can lead to promising screen channel liquid acquisition devices (SC-LADs) for propellant management under microgravity conditions in the future. Therefore, SiOC screens with aligned pores were fabricated via freeze-casting and applied as a SC-LAD. The pore window sizes and open porosity varied from 6 µm to 43 µm and 65% or 79%, depending on the freezing temperature or the solid loading, respectively. The pore window size distributions and bubble point tests indicate crack-free screens. On the one hand, SC-LADs with an open porosity of 79% removed gas-free liquid up to a volumetric flow rate of 4 mL s−1. On the other hand, SC-LADs with an open porosity of 65% were limited to 2 mL s−1 as the pressure drop across these screens was relatively higher. SC-LADs with the same open porosity but smaller pore window sizes showed a higher pressure drop across the screen and bubble ingestion at higher values of effective screen area when increasing the applied removal volumetric flow rate. The removed liquid from the SC-LADs was particle-free, thus representing a potential for applications in a harsh chemical environment or broad-range temperatures.

In this study, we present Janus nanoparticles that are designed for attaching to a eukaryotic cell surface with minimal cell uptake. This contrasts the rapid uptake via various endocytosis pathways that non-passivated isotropic particles usually encounter. Firmly attaching nanoparticles onto cell surfaces for extended periods of time can be a powerful new strategy to employ functional properties of nanoparticles for non-invasive interrogation and manipulation of biological systems. To this end, we synthesized rhodamine-doped silica (SiO2) nanoparticles functionalized with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE) on one hemisphere of the nanoparticle surface and high-molecular-weight long-chain poly(ethylene glycol) on the other one using the wax-Pickering emulsion technique. Nanoparticle localization was studied with NIH 3T3 rat fibroblasts in vitro. In these studies, the Janus nanoparticles adhered to the cell surface and, in contrast to isotropic control particles, only negligible uptake into the cells was observed, even after 24 h of incubation. In order to characterize the potential endocytosis pathway involved in the uptake of the Janus nanoparticles in more detail, fibroblasts and nanoparticles were incubated in the presence or absence of different endocytosis inhibitors. Our findings indicate that the Janus particles are not affected by caveolae- and receptor-mediated endocytosis and the prolonged attachment of the Janus nanoparticles is most likely the result of an incomplete macropinocytosis process. Consequently, by design, these Janus nanoparticles have the potential to firmly anchor onto cell surfaces for extended periods of time and might be utilized in various biotechnological and biomedical applications like cell surface tagging, magnetic manipulation of the cell membrane or non-invasive drug and gene delivery.

Porous SiOC monoliths were prepared by solution-based freeze casting of polysiloxane at constant freezing temperature or constant freezing front velocity. Dendritic and prismatic pore structures were obtained by using cyclohexane and tert-butyl alcohol as solvent, respectively. Gradients in freezing velocity lead to gradients in pore window size, whereas a constant freezing velocity (3.3–6.8 µm/s) generates homogeneous pore structures. The water permeability varies from 1.12 × 10−13 to 1.03 × 10−11 m2 and correlates with the pore window diameter (10–59 µm) and the porosity (51–82%). In wicking tests, the gradient in pore window size is clearly reflected by a pronounced decrease in the wicking speed. Contrary, a homogeneous pore structure results in wicking curves which are closer to the prediction according to the Lucas–Washburn equation. However, this theoretical approach based on the three parameters, pore window size, porosity and permeability, is insufficient to describe complex three-dimensional pore structures. Besides the porosity, the pore morphology was found to be a major influencing factor on the wicking. The filling of secondary dendrites slows down the wicking into the dendritic structure. Fastest wicking was observed for a prismatic pore structure at low freezing front velocity (6.6 µm/s) and high porosity (78%), whereas slowest wicking occurred into the dendritic structure with high porosity (76%) and constant freezing temperature (− 20 °C). The knowledge of the relationship between structural properties and the resulting wicking behavior can address a variety of pivotal applications in chemical engineering for capillary transport.

In order to investigate drying mechanisms at different stages, the distribution of water within the ceramic green bodies at different scales has been examined. The experimental measurements, using a simple weighing technique and Magnetic Resonance Imaging (MRI), show that during the first stage of drying involving shrinkage the material is constituted of uniquely solid and water with no gradient in water content within the sample. Then, during the second stage of drying, significant differences of water content as a function of position appear. As a complement, at the grain scale, observations using environmental scanning electron microscopy were made giving useful information on the solid–liquid–gas interfaces in the near surface part of the green body. Finally, the gradients in the water distribution were exploited to make a simple estimate of the diffusion coefficient of water with its dependence on the moisture content.

The applicability of a new class of ceramic materials in Microbial Fuel Cells (MFCs) was investigated, targeting the development of cost-effective anode materials with long-term durability. In this work, silicon oxycarbide (SiOC)-based porous anodes were prepared by the polymer-derived ceramics (PDCs) route, using poly(methyl silsesquioxane) and poly(methyl phenyl silsesquioxane) as precursors while incorporating carbonaceous fillers (graphite and carbon black) and metal precursor (NiCl2). Tape casting was used in the manufacturing followed by pyrolysis at 1000 °C under nitrogen atmosphere. The interior structure and surface morphology were characterized with scanning electron microscopy (SEM), nitrogen adsorption, vapor adsorption, and contact angle measurements. The developed anodes were tested in MFC with aqueous cathode configuration using a low-cost clayware cylinder as the anodic chamber. The performance of MFC using PDC-based anodes was compared with MFC having carbon felt as anode material, which showed a two-fold increase in power density (211 and 111 mW m−2, respectively) and normalized energy recovery in former and also demonstrated chemical oxygen demand (COD) removal efficiency of about 85%. The improved performance of the PDC-based anodes is attributed to its porous structure, hydrophilic surface, and high specific surface area (39.89 m² g−1). The biocompatibility was confirmed by biofilm growth on the surfaces, while a sufficient electrical conductivity (0.10–0.18 S cm−1) makes it superior electrode material for application in MFCs.

In this study, we investigate the effect of membrane surface functionalization on the immobilization of the protease subtilisin A and its performance in the production of peptides from the model protein casein under flow. The surface of tubular ceramic membranes was silanized to yield carboxylated and aminated supports for enzyme immobilization via non-covalent and carbodiimide activated binding. The protease density correlated with electrostatic interactions between the positively charged enzyme and the supports, with the highest enzyme density reached on negatively charged, carboxylated membranes (0.019 molecules/nm², noncovalent approach). Enzyme leaching was reduced by covalent binding of protease to carboxylated supports (5% leached) and slightly improved by binding to aminated membranes (46%) over non-covalent binding to unfunctionalized reference capillaries (66%). Regarding carbodiimide activated immobilization, protease on unfunctionalized and aminated supports exhibited a significantly larger specific activity (0.99 μmol/min/mg) than enzymes on carboxylated surfaces (0.15 μmol/min/mg), which suggests preferred enzyme orientation. In protein hydrolysis, these differences in surface-enzyme interactions were reflected by variations in peptide composition and degree of hydrolysis. Accordingly, we demonstrate that surface functionalization critically determines the surface properties of protease support materials for the production of peptides under flow and allows tailoring the performance of proteolytic capillary membranes.

Polymethylsiloxane (MK) and aluminum diacetate have been stoichiometrically combined to synthesize a mullite-based powder (3Al2O3·2SiO2) at 850 °C (5 h) or 1200 °C (3 h). High-purity crystalline mullite (>99%) was obtained by heating the mixture in the air (thermal oxidation) at 1200 °C for 3 h, mainly due to the formation of highly reactive silica and alumina precursors. Afterward, the mullite-based powders were used to prepare planar asymmetric microfiltration membranes by phase-inversion tape casting. The green membranes were sintered at 1600, 1650 or 1700 °C during 2 h. The asymmetric morphology identified in the membranes by scanning electron microscopy analysis reveals a thin skin-layer (microfiltration layer

Damage analyses of a ceramic matrix composite during fatigue and quasi-static loads were performed by acoustic emission (A.E.) monitoring. The material studied was a 2.5D C/C-SiC composite produced by chemical vapor infiltration followed by liquid silicon infiltration. The analysis done during the first 200 cycles of a fatigue test showed that the number of A.E. hits is a good parameter for the quantification of damage. Furthermore, the A.E. hit energy was associated with the type of damage. In this sense, the damage developed during the fatigue loading was related to matrix crack initiation, propagation and re-opening, as well as fiber-matrix friction. Quasi-static tests on post-fatigue samples showed that the previous fatigue loadings increased the material`s damage threshold and hindered the development of new damage. Particular attention was given to the sample after 2,000,000 cycles as this sample showed distinct A.E. signals that could be related to fiber debonding.

Selection of proton conducting membrane is currently a key factor that decides the performance of microbial fuel cell (MFC). Uniaxial pressed polysiloxane-derived ceramer and ceramic membrane with proton conducting fillers like montmorillonite and H3PMo12O40/SiO2 were applied for the first time as separator in MFC. Here, we present a series of polymer-derived ceramic membranes tailored based on pyrolysis temperature and filler addition, in which ion exchange capacity, cation transport number, and oxygen permeability are influenced through the hydrophilic and porous structural property. The maximum power density of MFC with polysiloxane-derived ceramer membrane modified with 20 wt% montmorillonite and 10 wt% H3PMo12O40/SiO2 reached a value of 5.66 W m−3, which was four times higher than that with non-modified polysiloxane-derived ceramer membrane. Furthermore, the specific power recovery per unit cost of the membrane was found to be 2-fold higher than MFC using polymeric Nafion membrane. In contrast, MFC with polysiloxane-derived ceramic membrane modified with 20 wt% montmorillonite delivers 1.2 times lower power density (4.20 W m−3) than that with non-modified macroporous polysiloxane-derived ceramic membrane. Hence, the findings demonstrated that tailoring the hydrophilic and porous structure of the ceramic membrane is a new and promising approach to enhance the performance of MFC.

In this work, we present a biocompatible one-pot processing route for ceramic/hydrogel nanocomposites in which we embed live bacteria. In our approach, we fabricate a highly stable alginate hydrogel with minimal shrinkage, highly increased structural and mechanical stability, as well as excellent biocompatibility. The hydrogel was produced by ionotropic gelation and reinforced with alumina nanoparticles to form a porous 3D network. In these composite gels, the bacteria Escherichia coli and Bacillus subtilis were embedded. The immobilized bacteria showed high viability and similar metabolic activity as non-embedded cells. Even after repeated glucose consumption cycles, the material maintained high structural stability with stable metabolic activity of the immobilized bacteria. Storing the bionanocomposite for up to 60 days resulted in only minor loss of activity. Accordingly, this approach shows great potential for producing macroscopic bioactive materials for biotechnological processes.

Hydrothermal fluids can contain trace elements such as arsenic (As), which are toxic to surrounding biota. In these kind of fluids, the bioavailability and biotransformation of As have been investigated but so far the ratio of total soluble As (

Nickel-containing hybrid ceramics were prepared by pyrolytic conversion from either methyl or methyl-phenyl polysiloxanes mixed with bistrimethoxysilylpropylamine (BisA) as a complexing agent and nickel salt. Materials with tailorable characteristics were generated by varying the pyrolysis temperature from 400 up to 600 °C in order to evaluate their applicability in the CO2 methanation. The materials were characterized by thermogravimetric analysis (TGA), N2 adsorption-desorption isotherms (BET-BJH), water and n-heptane adsorption, X-ray diffraction (XRD) and transmission electron microscopy (TEM). In-situ X-ray diffraction analysis (in-situ XRD) was used to evaluate the Ni particle structure and size during a simulated catalytic reaction. Porous hybrid ceramics (ceramers) with high specific surface areas (100–550 m2 g−1), hydrophobic or hydrophilic surfaces and different Ni particle sizes (4–7 nm) were obtained by varying the pyrolysis temperature and polysiloxane composition. The pyrolytic conversion of polysiloxanes combined with the complexing amino-siloxane BisA not only permitted a good dispersion of the Ni nanoparticles but also enabled the formation of hierarchical porosity with micro-, meso- and macropores. Regarding the catalytic performance, ceramers prepared from methyl polysiloxane exhibited a more hydrophobic surface and improved catalytic performance compared to the ones prepared from methyl-phenyl polysiloxane. A negative effect on the catalytic performance of ceramers was observed with increasing pyrolysis temperatures, which led to an increase in Ni particle size (from 4 to 7 nm), and lower levels of conversion and selectivity. The ceramers pyrolyzed at 400 °C exhibited the best catalytic performance, showing selectivity up to ∼77% and good stability over a 10 h test, during which the Ni particle size was preserved.

The iron storage protein ferritin is well known for its ability to mineralize iron oxides in its interior cavity. In this study, the authors investigated the mineralization behavior of H and L ferritin homopolymers assembled from individual subunits. The authors’ approach included molecular dynamics simulations, which suggested that ferritin subunits arrange themselves on silica surfaces with the active side facing away from the interface, although non covalent adsorption interactions might be weak. In experimental studies, the nucleation of iron oxide nuclei could be observed at ferritin homopolymers which were covalently immobilized through the EDC/NHS strategy at the surface of silica nanoparticles. Mineralization was initiated by the addition of ammonium iron (II) sulfate hexahydrate ((NH4)2Fe(SO4)2·6H2O) as the source of iron ions and trimethylamine N-oxide as the oxidant. The results demonstrate that immobilized H and L ferritin homopolymers on silica surfaces are able to induce the formation of a cohesive thin film of magnetic iron oxide crystals (magnetite and/or maghemite).

New metallic nickel/cobalt/iron silicide droplets at the tips of polymer-derived ceramic (PDC) nanowires have been identified as stable and efficient cathode catalysts for Zn-air batteries. The as-prepared catalyst having a unique one-dimensional (1D) PDC nanowire structure with the presence of metallic silicide tips of 1D-PDC plays a crucial role in facilitating oxygen reduction/evolution reaction kinetics. The Zn-air battery was designed using Ni/PDC, Co/PDC and Fe/PDC as air electrode catalysts. In electrochemical half-cell tests, it was observed that the catalysts have a good bifunctional electrocatalytic activity. The efficiency of the catalysts to function as a cathode catalyst in real-time primary and mechanically rechargeable Zn-air battery configurations was determined. The primary battery testing results revealed that Ni/PDC and Co/PDC exhibited a stable discharge voltage plateau up to 29 h. The Fe/PDC sample, on the other hand, performed up to 23 h with an operating potential of 1.20 V at the discharge current density of 5 mA cm

While structural ceramics usually display a brittle mechanical behavior, their composites may show non-linearities, mostly due to microcracking. In this work, we studied the evolution of the stiffness of a sandwich-like laminate consisting of an Al2O3-15%vol.ZrO2 matrix reinforced with Nextel™ 610 long fibers as a function of number of cycles N in uniaxial testing mode. We found that the stiffness of the composite degrades with increasing N, indicating increasing microcracking. However, synchrotron X-ray refraction radiography showed that the internal specific surface of inhomogeneities (mainly cracks and pores) decreases with N. A modeling strategy was developed, based on the combination of Voigt and Reus schemes for the calculation of equivalent stiffness of mixtures with the Bruno-Kachanov model for the calculation of equivalent stiffness in microcracked and porous materials. Through modeling we could estimate the initial microcrack density in the matrix (due to the simple thermal expansion mismatch between the two constituents) and the amount of microcracking increase upon cyclic load. We found that the stiffness in such a composite degrades dramatically already after as few as 20000 cycles, but then remains nearly constant. The combination of the mechanical testing, the quantitative imaging analysis, and the modeling provided insights into the damage mechanisms acting: microcrack propagation is far more active than microcrack initiation upon cyclic loading. This scenario corresponds to previous results obtained on porous and microcracked ceramics.

Arsenic and sulfur mineralization is a natural phenomenon occurring in hydrothermal systems where parameters like temperature and organic matter (OM) can influence the mobilization of the toxic metalloid in marine environments. In the present study we analyze the influence of temperature and OM (particularly sulfur-containing additives) on As and S precipitation based on the recent discovery of As-rich nanoparticles in the hydrothermal system near the coast of the Greek island Milos. To this end, we experimentally recreate the formation of amorphous colloidal particles rich in As and S via acidification (pH 3–4) of aqueous precursors at various temperatures. At higher temperatures, we observe the formation of monodisperse particles within the first 24 h of the experiment, generating colloidal particles with diameters close to 160 nm. The S:As ratio and particle size of the synthetized particles closely correlates with values for AsxSy particles detected in the hydrothermal system off Milos. Furthermore, organic sulfur containing additives (cysteine and glutathione, GSH) are a key factor in the process of nucleation and growth of amorphous colloidal AsxSy particles and, together with the temperature gradient present in shallow hydrothermal vents, dictate the stabilization of As-bearing nanomaterials in the environment. Based on these findings, we present a simple model that summarizes our new insights into the formation and mobility of colloidal As in aquatic ecosystems. In this context, amorphous AsxSy particles can present harmful effects to micro- and macro-biota not foreseen in bulk As material.

In this study, we present hydrophobic yttria-stabilized zirconia capillary membranes conditioned for virus filtration. These macroporous ceramic filters (d50 = 150 nm) efficiently extract viruses regardless of their surface charge with high throughput rates. For hydrophobic functionalization of the ceramic membranes we used two different silanes, n-hexyltriethoxysilane (HTS, C6-chain) and n-octyltriethoxysilane (OTS, C8-chain), in three different molarities. The virus retention of the membranes is tested in dead-end mode by intracapillary virus feeding using two small bacteriophages as model species: MS2 and PhiX174. Virus retention increases most strongly for hydrophobic capillaries functionalized with 0.05 M OTS, showing a virtually complete retention with log-reduction values (LRVs) of ~ 9 for both bacteriophages compared to the non-functionalized membrane with LRVs of 0.3 ± 0.1 for MS2 and 3.4 ± 0.2 for PhiX174. The functionalized membranes allow a high membrane flux of ~ 150 L/(m2hbar), with throughput rates up to ~ 400 L/(m2 h) while maintaining high filtration efficiency. Even under varying feed conditions using only mono- or divalent salt ions or pH values ranging from 3 to 9, retention capacities of the capillary membranes are high. Accordingly, such hydrophobic ceramic membranes offer a versatile alternative to conventional polymeric membranes for virus removal with greatly improved membrane flux.

Cobalt/nickel-containing SiOC-based porous ceramic electrocatalysts were prepared by pyrolysis of poly(methyl silsesquioxane) and poly(methyl phenyl silsesquioxane) as preceramic precursors combined with graphite and Co/Ni metal salts at 1000 °C in an atmosphere of nitrogen. Subsequently, the Co/Ni–SiOC materials were N-doped using dicyandiamide (DCDA) as a nitrogen source and pyrolysed at 800 °C in an inert atmosphere. The structural properties and composition of the catalysts were characterised by scanning electron microscopy (SEM), X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and N2 adsorption analysis. The evaluation of the polymer-derived SiOC(N) ceramic electrocatalysts as a new class of catalysts for the oxygen reaction reduction (ORR) was carried out by the rotating disk electrode (RDE) method under acidic, neutral and alkaline conditions. The O2 reduction studies revealed that the N-doped materials exhibited enhanced ORR performance, confirming the positive influence of the nitrogen functionalities introduced into the catalysts. The Co-containing N-doped SiOC catalyst exhibited significantly higher ORR activity compared with the studied materials along with the highest electron transfer number in all the studied solutions. Long-term ORR performance testing indicated that the durability of this catalyst was superior as compared to that of commercial Pt/C. These observations suggest that the Co-containing N-doped SiOC catalyst is a promising cathode material for fuel cells (FCs) and microbial FC devices.