Organization and Formation of the Crossed-Foliated Biomineral Microstructure of Limpet Shells.

To construct their shells, molluscs are able to produce a large array of calcified materials including granular, prismatic, lamellar, fibrous, foliated, and plywood-like microstructures. The latter includes an aragonitic (the crossed-lamellar) and a calcitic (the crossed-foliated) variety, whose modes of formation are particularly enigmatic. We studied the crossed-foliated calcitic layers secreted solely by members of the limpet family Patellidae using scanning and transmission electron microscopy and electron backscatter diffraction. From the exterior to the interior, the material becomes progressively organized into commarginal first-order lamellae, with second and third order lamellae dipping in opposite directions in alternating lamellae. At the same time, the crystallographic texture becomes stronger because each set of the first order lamellae develops a particular orientation for the c-axis, while both sets maintain common orientations for one {104} face (parallel to the growth surface) and one a-axis (perpendicular to the planes of the first order lamellae). Each first order lamella shows a progressive migration of its crystallographic axes with growth in order to adapt to the orientation of the set of first order lamellae to which it belongs. To explain the progressive organization of the material, we hypothesize that a secretional zebra pattern, mirrored by the first order lamellae on the shell growth surface, is developed on the shell-secreting mantle surface. Cells belonging to alternating stripes behave differently to determine the growth orientation of the laths composing the first order lamellae. In this way, we provide an explanation as to how plywood-like materials can be fabricated, which is based mainly on the activity of mantle cells.

Controlling crystallites orientation and facet exposure for enhanced electrochemical properties of polycrystalline MoO3 films.

This study focuses on the development and optimization of MoO3 films on commercially available FTO substrates using the pulsed laser deposition (PLD) technique. By carefully selecting deposition conditions and implementing post-treatment procedures, precise control over crystallite orientation relative to the substrate is achieved. Deposition at 450 °C in O2 atmosphere results in random crystallite arrangement, while introducing argon instead of oxygen to the PLD chamber during the initial stage of sputtering exposes the (102) and (011) facets. On the other hand, room temperature deposition leads to the formation of amorphous film, but after appropriate post-annealing treatment, the (00k) facets were exposed. The deposited films are studied using SEM and XRD techniques. Moreover, electrochemical properties of FTO/MoO3 electrodes immersed in 1 M AlCl3 aqueous solution are evaluated using cyclic voltammetry and electrochemical impedance spectroscopy. The results demonstrate that different electrochemical processes are promoted based on the orientation of crystallites. When the (102) and (011) facets are exposed, the Al3+ ions intercalation induced by polarization is facilitated, while the (00k) planes exposure leads to the diminished hydrogen evolution reaction overpotential.

Aerogels based on cationically modified chitosan and poly(vinyl alcohol) for efficient capturing of viruses.

In this study, we developed a new filtering bioaerogel based on linear polyvinyl alcohol (PVA) and the cationic derivative of chitosan (N-[(2-hydroxy-3-trimethylamine) propyl] chitosan chloride, HTCC) with a potential antiviral application. A strong intermolecular network architecture was formed thanks to the introduction of linear PVA chains, which can efficiently interpenetrate the glutaraldehyde(GA)-crosslinked HTCC chains. The morphology of the obtained structures was examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The aerogels and modified polymers' elemental composition (including the chemical environment) was determined using X-ray photoelectron spectroscopy (XPS). New aerogels with more than twice as much developed micro- and mesopore space and BET-specific surface area were obtained concerning the starting sample chitosan aerogel crosslinked by glutaraldehyde (Chit/GA). The results obtained from the XPS analysis showed the presence of cationic 3-trimethylammonium groups on the surface of the aerogel, which can interact with viral capsid proteins. No cytotoxic effect of HTCC/GA/PVA aerogel was also observed on fibroblast cells of the NIH3T3 line. Furthermore, the HTCC/GA/PVA aerogel has been shown that efficiently traps mouse hepatitis virus (MHV) from suspension. The presented concept of aerogel filters for virus capture based on modified chitosan and polyvinyl alcohol has a high application potential.

Synthesis of Manganese Zinc Ferrite Nanoparticles in Medical-Grade Silicone for MRI Applications.

The aim of this project is to fabricate hydrogen-rich silicone doped with magnetic nanoparticles for use as a temperature change indicator in magnetic resonance imaging-guided (MRIg) thermal ablations. To avoid clustering, the particles of mixed MnZn ferrite were synthesized directly in a medical-grade silicone polymer solution. The particles were characterized by transmission electron microscopy, powder X-ray diffraction, soft X-ray absorption spectroscopy, vibrating sample magnetometry, temperature-dependent nuclear magnetic resonance relaxometry (20 °C to 60 °C, at 3.0 T), and magnetic resonance imaging (at 3.0 T). Synthesized nanoparticles were the size of 4.4 nm ± 2.1 nm and exhibited superparamagnetic behavior. Bulk silicone material showed a good shape stability within the study's temperature range. Embedded nanoparticles did not influence spin-lattice relaxation, but they shorten the longer component of spin-spin nuclear relaxation times of silicone's protons. However, these protons exhibited an extremely high r2* relaxivity (above 1200 L s-1 mmol-1) due to the presence of particles, with a moderate decrease in the magnetization with temperature. With an increased temperature decrease of r2*, this ferro-silicone can be potentially used as a temperature indicator in high-temperature MRIg ablations (40 °C to 60 °C).

Half-Heusler phase TmNiSb under pressure: intrinsic phase separation, thermoelectric performance and structural transition.

Half-Heusler (HH) phase TmNiSb was obtained by arc-melting combined with high-pressure high-temperature sintering in conditions: p = 5.5 GPa, [Formula: see text] = 20, 250, 500, 750, and 1000 [Formula: see text]C. Within pressing temperatures 20-750 [Formula: see text]C the samples maintained HH structure, however, we observed intrinsic phase separation. The material divided into three phases: stoichiometric TmNiSb, nickel-deficient phase TmNi[Formula: see text]Sb, and thulium-rich phase Tm(NiSb)[Formula: see text]. For TmNiSb sample sintered at 1000 [Formula: see text]C, we report structural transition to LiGaGe-type structure (P[Formula: see text]mc, a = 4.367(3) Å, c = 7.138(7) Å). Interpretation of the transition is supported by X-ray powder diffraction, electron back-scattered diffraction, ab-initio calculations of Gibbs energy and phonon dispersion relations. Electrical resistivity measured for HH samples with phase separation shown non-degenerate behavior. Obtained energy gaps for HH samples were narrow ([Formula: see text] 260 meV), while the average hole effective masses in range 0.8-2.5[Formula: see text]. TmNiSb sample pressed at 750 [Formula: see text]C achieved the biggest power factor among the series, 13 [Formula: see text]WK[Formula: see text]cm[Formula: see text], which proves that the intrinsic phase separation is not detrimental for the electronic transport.

Synthesis and Properties of the Gallium-Containing Ruddlesden-Popper Oxides with High-Entropy B-Site Arrangement.

For the first time, the possibility of obtaining B-site disordered, Ruddlesden-Popper type, high-entropy oxides has been proven, using as an example the LnSr(Co,Fe,Ga,Mn,Ni)O4 series (Ln = La, Pr, Nd, Sm, or Gd). The materials were synthesized using the Pechini method, followed by sintering at a temperature of 1200 °C. The XRD analysis indicated the single-phase, I4/mmm structure of the Pr-, Nd-, and Sm-based materials, with a minor content of secondary phase precipitates in La- and Gd-based materials. The SEM + EDX analysis confirms the homogeneity of the studied samples. Based on the oxygen non-stoichiometry measurements, the general formula of LnSr(Co,Fe,Ga,Mn,Ni)O4+δ, is established, with the content of oxygen interstitials being surprisingly similar across the series. The temperature dependence of the total conductivity is similar for all materials, with the highest conductivity value of 4.28 S/cm being reported for the Sm-based composition. The thermal expansion coefficient is, again, almost identical across the series, with the values varying between 14.6 and 15.2 × 10-6 K-1. The temperature stability of the selected materials is verified using the in situ high-temperature XRD. The results indicate a smaller impact of the lanthanide cation type on the properties than has typically been reported for conventional Ruddlesden-Popper type oxides, which may result from the high-entropy arrangement of the B-site cations.

Phenomena Occurring upon the Sintering of a Mixture of Yttria-Zirconia Nanometric Powder and Sub-Micrometric Pure Zirconia Powder.

Mixtures of powders essentially differing in their particle morphology and size were applied to prepare polycrystals in a Y2O3-ZrO2 system. An yttria-zirconia solid solution nanometric powder with a Y2O3 concentration of 3.5% was prepared by subjecting co-precipitated gels to hydrothermal treatment at 240 °C. The crystallization occurred in distilled water. The pure zirconia powders composed of elongated and sub-micrometer size particles were also manufactured through the hydrothermal treatment of pure zirconia gel, although in this case, the process took place in the NaOH solution. Mixtures of the two kinds of powder were prepared so as to produce a mean composition corresponding to an yttria concentration of 3 mol%. Compacts of this powder mixture were sintered, and changes in phase composition vs. temperature were studied using X-ray diffraction. The dilatometry measurements revealed the behavior of the powder compact during sintering. The polished surfaces revealed the microstructure of the resulting polycrystal. Additionally, the electron back scattering diffraction technique (EBSD) allowed us to identify symmetry between the observed grains. Hardness, fracture toughness, and mechanical strength measurements were also performed.

The Preparation of Dense Materials in the MgO-ZrO2 System by the Application of Nanometric Powders.

Crystallization under hydrothermal conditions allowed us to prepare nanometric powders in the MgO-ZrO2 system of different magnesia concentrations. Sintering runs of these powder compacts studied using dilatometry measurements during heating and cooling revealed essential differences in their behavior. The microstructure of the resulting polycrystal is strongly related to the magnesia content in the starting powder, which strongly influences the phase composition of the resulting material and its mechanical properties. It should be emphasized that the novel processing method of such materials differs from the usual applied technology and leads to magnesia-zirconia materials of a different microstructure than that of "classical" materials of this kind.

Formation of Solid Solutions and Physicochemical Properties of the High-Entropy Ln1-xSrx(Co,Cr,Fe,Mn,Ni)O3-δ (Ln = La, Pr, Nd, Sm or Gd) Perovskites.

Phase composition, crystal structure, and selected physicochemical properties of the high entropy Ln(Co,Cr,Fe,Mn,Ni)O3-δ (Ln = La, Pr, Gd, Nd, Sm) perovskites, as well as the possibility of Sr doping in Ln1-xSrx(Co,Cr,Fe,Mn,Ni)O3-δ series, are reported is this work. With the use of the Pechini method, all undoped compositions are successfully synthesized. The samples exhibit distorted, orthorhombic or rhombohedral crystal structure, and a linear correlation is observed between the ionic radius of Ln and the value of the quasi-cubic perovskite lattice constant. The oxides show moderate thermal expansion, with a lack of visible contribution from the chemical expansion effect. Temperature-dependent values of the total electrical conductivity are reported, and the observed behavior appears distinctive from that of non-high entropy transition metal-based perovskites, beyond the expectations based on the rule-of-mixtures. In terms of formation of solid solutions in Sr-doped Ln1-xSrx(Co,Cr,Fe,Mn,Ni)O3-δ materials, the results indicate a strong influence of the Ln radius, and while for La-based series the Sr solubility limit is at the level of xmax = 0.3, for the smaller Pr it is equal to just 0.1. In the case of Nd-, Sm- and Gd-based materials, even for the xSr = 0.1, the formation of secondary phases is observed on the SEM + EDS images.

Effect of Mo and Ta on the Mechanical and Superelastic Properties of Ti-Nb Alloys Prepared by Mechanical Alloying and Spark Plasma Sintering.

The effect of ternary alloying elements (Mo and Ta) on the mechanical and superelastic properties of binary Ti-14Nb alloy fabricated by the mechanical alloying and spark plasma sintering was investigated. The materials were prepared in two ways: (i) by substituting Nb in base Ti-14Nb alloy by 2 at.% of the ternary addition, giving the following compositions: Ti-8Nb-2Mo and Ti-12Nb-2Ta and (ii) by adding 2 at.% of the ternary element to the base alloy. The microstructures of the materials consisted of the equiaxed ß-grains and fine precipitations of TiC. The substitution of Nb by both Mo and Ta did not significantly affect the mechanical properties of the base Ti-14Nb alloy, however, their addition resulted in a decrease of yield strength and increase of plasticity. This was associated with the occurrence of the {332} <113> twinning that was found during the in-situ observations. The elevated concentration of interstitial elements (oxygen and carbon) lead to the occurrence of stress-induced martensitic transformation and twinning mechanisms at lower concentration of ß-stabilizers in comparison to the conventionally fabricated materials. The substitution of Nb by Mo, and Ta caused the slight improvement of the superelastic properties of the base Ti-14Nb alloy, whereas their addition deteriorated the superelasticity.

Microstructure and Properties of Inconel 625 Fabricated Using Two Types of Laser Metal Deposition Methods.

The effect of using two different deposition systems on the microstructure and mechanical properties was studied in this paper. For this purpose, laser-engineered net shaping (LENS) and high-power CO2 laser deposition processes were applied to fabricate Inconel 625 samples. The microstructure of the Inconel 625 produced by both additive techniques was characterized using light microscopy (LM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The mechanical properties were characterized by tensile tests and microhardness measurements. High-power laser application resulted in a strong <100> build texture, while, at low powers, the {011} <100> Goss component increased. Both types of deposited materials showed dendritic microstructures with Ti-, Mo-, and Nb-rich zones at the cell boundaries, where numerous precipitates (Nb2C, NbC, titanium carbides, Nb3Ni, and NbNiCr) were also observed. It was also noted that both variants were characterized by the same slope with a proportional length, but the Inconel 625 fabricated via LENS showed a higher average yield strength (YS; 524 MPa vs. 472 MPa) and ultimate tensile strength (UTS; 944 MPa vs. 868 MPa) and lower elongation (35% vs. 42%) than samples obtained with the high-power CO2 laser deposition process.

The ability of seeds to float with water currents contributes to the invasion success of Impatiens balfourii and I. glandulifera.

Two alien species in Europe, Impatiens glandulifera and I. balfourii, are closely related, have similar growth rates and reproductive capacities, and are very attractive to pollinators. Nevertheless, only I. glandulifera is a highly invasive alien species in Europe, while I. balfourii is non-invasive. We assumed that the varying levels of invasiveness are driven by differences in the floating ability of their seeds, which may determine the invasion success of riparian alien plants, such as the Impatiens species. By mimicking two types of aquatic conditions, we determined seed floating ability for each species from younger and older populations. We also analyzed four seed traits: seed viability, surface, shape and coat structure. Seeds of the non-invasive I. balfourii float less well than seeds of the invasive I. glandulifera. We also found that the seeds of I. balfourii from the younger population have a higher floating ability in comparison with that of the seeds from the older population. The results for I. glandulifera were the opposite, with decreased floating ability in the younger population. These differences were associated with seed surface, shape and coat structure. These results indicate that the floating ability of I. balfourii seeds may increase over time following its introduction into a given area, while in the case of I. glandulifera, this ability may gradually decrease. Therefore, the former species, currently regarded as a poor disperser, has the potential to become invasive in the future, whereas the latter does not seem to benefit from further investments in the floating ability of its seeds.

Anisotropy of Mechanical Properties of Pinctada margaritifera Mollusk Shell.

The mechanical properties such as compressive strength and nanohardness were investigated for Pinctada margaritifera mollusk shells. The compressive strength was evaluated through a uniaxial static compression test performed along the load directions parallel and perpendicular to the shell axis, respectively, while the hardness and Young modulus were measured using nanoindentation. In order to observe the crack propagation, for the first time for such material, the in-situ X-ray microscopy (nano-XCT) imaging (together with 3D reconstruction based on the acquired images) during the indentation tests was performed. The results were compared with these obtained during the micro-indentation test done with the help of conventional Vickers indenter and subsequent scanning electron microscopy observations. The results revealed that the cracks formed during the indentation start to propagate in the calcite prism until they reach a ductile organic matrix where most of them are stopped. The obtained results confirm a strong anisotropy of both crack propagation and the mechanical strength caused by the formation of the prismatic structure in the outer layer of P. margaritifera shell.

Hydrophilic nanofibers in fog collectors for increased water harvesting efficiency.

The water crisis is a big social problem and one of the solutions are the Fog Water Collectors (FWCs) that are placed in areas, where the use of conventional methods to collect water is impossible or inadequate. The most common fog collecting medium in FWC is Raschel mesh, which in our study is modified with electrospun polyamide 6 (PA6) nanofibers. The hydrophilic PA6 nanofibers were directly deposited on Raschel meshes to create the hierarchical structure that increases the effective surface area which enhances the ability to catch water droplets from fog. The meshes and the wetting behavior were investigated using a scanning electron microscope (SEM) and environmental SEM (ESEM). We performed the fog water collection experiments on various configurations of Raschel meshes with hydrophilic PA6 nanofibers. The addition of hydrophilic nanofibers allowed us to obtain 3 times higher water collection rate of collecting water from fog. Within this study, we show the innovative and straightforward way to modify the existing technology that improves water collection by changing the mechanisms of droplet formation on the mesh.

Fiber-Based Composite Meshes with Controlled Mechanical and Wetting Properties for Water Harvesting.

Water is the basis of life in the world. Unfortunately, resources are shrinking at an alarming rate. The lack of access to water is still the biggest problem in the modern world. The key to solving it is to find new unconventional ways to obtain water from alternative sources. Fog collectors are becoming an increasingly important way of water harvesting as there are places in the world where fog is the only source of water. Our aim is to apply electrospun fiber technology, due to its high surface area, to increase fog collection efficiency. Therefore, composites consisting of hydrophobic and hydrophilic fibers were successfully fabricated using a two-nozzle electrospinning setup. This design enables the realization of optimal meshes for harvesting water from fog. In our studies we focused on combining hydrophobic polystyrene (PS) and hydrophilic polyamide 6 (PA6), surface properties in the produced meshes, without any chemical modifications, on the basis of new hierarchical composites for collecting water. This combination of hydrophobic and hydrophilic materials causes water to condense on the hydrophobic microfibers and to run down on the hydrophilic nanofibers. By adjusting the fraction of PA6 nanofibers, we were able to tune the mechanical properties of PS meshes and importantly increase the efficiency in collecting water. We combined a few characterization methods together with novel image processing protocols for the analysis of fiber fractions in the constructed meshes. The obtained results show a new single-step method to produce meshes with enhanced mechanical properties and water collecting abilities that can be applied in existing fog water collectors. This is a new promising design for fog collectors with nano- and macrofibers which are able to efficiently harvest water, showing great application in comparison to commercially available standard meshes.

Nanohydrogels Based on Self-Assembly of Cationic Pullulan and Anionic Dextran Derivatives for Efficient Delivery of Piroxicam.

A cationic derivative of pullulan was obtained by grafting reaction and used together with dextran sulfate to form polysaccharide-based nanohydrogel cross-linked via electrostatic interactions between polyions. Due to the polycation-polyanion interactions nanohydrogel particles were formed instantly and spontaneously in water. The nanoparticles were colloidally stable and their size and surface charge could be controlled by the polycation/polyanion ratio. The morphology of the obtained particles was visualized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The resulting structures were spherical, with hydrodynamic diameters in the range of 100-150 nm. The binding constant (Ka) of a model drug, piroxicam, to the cationic pullulan (C-PUL) was determined by spectrophotometric measurements. The value of Ka was calculated according to the Benesi-Hildebrand equation to be (3.6 ± 0.2) × 103 M-1. After binding to cationic pullulan, piroxicam was effectively entrapped inside the nanohydrogel particles and released in a controlled way. The obtained system was efficiently taken up by cells and was shown to be biocompatible.

The Effect of Calcination Temperature on the Structure and Performance of Nanocrystalline Mayenite Powders.

The effect of calcination temperature on the structural properties and phase formation of synthesized CaO-Al2O3 nanopowder was investigated and discussed. The calcination products were identified by differential thermal analysis (DTA) and the crystalline phase formation was analyzed by X-ray diffraction (XRD). The obtained results showed that the crystallization started at 460 °C. Finally, the microstructures of the nanoparticles were observed by scanning (SEM) and transmission electron (TEM) microscopes. The investigation showed that an increase in the calcination temperature led to the appreciable increase in the crystallite size and the crystallinity of the final product. The obtained data confirmed that the prepared materials were mayenite with different surface area in the range of 71.18 m2/g to 10.34 m2/g after annealing in the temperature range of 470 °C to 960 °C.

Guar Gum as an Eco-Friendly Corrosion Inhibitor for Pure Aluminium in 1-M HCl Solution.

Guar gum (GG) was investigated as a possible eco-friendly corrosion inhibitor for pure aluminium in a 1-M HCl solution at different temperatures and immersion times using gravimetric and electrochemical techniques. The results showed that GG was a good corrosion inhibitor for pure aluminium in the studied environment. The inhibition efficiency of GG increased with increasing inhibitor concentration and immersion time but decreased with increasing temperature. Polarisation measurements revealed that GG was a mixed type inhibitor with a higher influence on the cathodic reaction. The adsorption behaviour of the investigated inhibitor was found to obey the Temkin adsorption isotherm and the calculated values of the standard free adsorption energy indicate mixed-type adsorption, with the physical adsorption being more dominant. The associated activation energy (Ea) and the heat of adsorption (Qa) supported the physical adsorption nature of the inhibitor. Fourier-transform infrared spectroscopy (FTIR) and Raman/SERS were used to explain the adsorption interaction between the inhibitor with the surface of the metal. The results suggested that most inhibition action of GG is due to its adsorption of the metal surface via H-bond formation.

Crystallographic control on the substructure of nacre tablets.

Nacre tablets of mollusks develop two kinds of features when either the calcium carbonate or the organic portions are removed: (1) parallel lineations (vermiculations) formed by elongated carbonate rods, and (2) hourglass patterns, which appear in high relief when etched or in low relief if bleached. In untreated tablets, SEM and AFM data show that vermiculations correspond to aligned and fused aragonite nanogloblules, which are partly surrounded by thin organic pellicles. EBSD mapping of the surfaces of tablets indicates that the vermiculations are invariably parallel to the crystallographic a-axis of aragonite and that the triangles are aligned with the b-axis and correspond to the advance of the {010} faces during the growth of the tablet. According to our interpretation, the vermiculations appear because organic molecules during growth are expelled from the a-axis, where the Ca-CO3 bonds are the shortest. In this way, the subunits forming nacre merge uninterruptedly, forming chains parallel to the a-axis, whereas the organic molecules are expelled to the sides of these chains. Hourglass patterns would be produced by preferential adsorption of organic molecules along the {010}, as compared to the {100} faces. A model is presented for the nanostructure of nacre tablets. SEM and EBSD data also show the existence within the tablets of nanocrystalline units, which are twinned on {110} with the rest of the tablet. Our study shows that the growth dynamics of nacre tablets (and bioaragonite in general) results from the interaction at two different and mutually related levels: tablets and nanogranules.

Crystallographic orientation inhomogeneity and crystal splitting in biogenic calcite.

The calcitic prismatic units forming the outer shell of the bivalve Pinctada margaritifera have been analysed using scanning electron microscopy-electron back-scatter diffraction, transmission electron microscopy and atomic force microscopy. In the initial stages of growth, the individual prismatic units are single crystals. Their crystalline orientation is not consistent but rather changes gradually during growth. The gradients in crystallographic orientation occur mainly in a direction parallel to the long axis of the prism, i.e. perpendicular to the shell surface and do not show preferential tilting along any of the calcite lattice axes. At a certain growth stage, gradients begin to spread and diverge, implying that the prismatic units split into several crystalline domains. In this way, a branched crystal, in which the ends of the branches are independent crystalline domains, is formed. At the nanometre scale, the material is composed of slightly misoriented domains, which are separated by planes approximately perpendicular to the c-axis. Orientational gradients and splitting processes are described in biocrystals for the first time and are undoubtedly related to the high content of intracrystalline organic molecules, although the way in which these act to induce the observed crystalline patterns is a matter of future research.