Crystallographic Modifications Research Articles

High-Entropy Fluorite Oxide-Modified CaO-Based Sorbent Pellets for Enhanced High-Temperature CO2 Capture.

The calcium looping technology employing CaO-based sorbents is pivotal for capturing CO2 from flue gas. However, the intrinsic low thermodynamic stability of CaO-based sorbents and the requisite molding step induce severe sintering issues, diminishing their cyclic stability. Herein, a high-entropy fluorite oxide (HEFO) inert stabilizer premised on entropy stabilization and synergistic effect strategies is introduced. HEFO-modified, CaO-based sorbent pellets are synthesized via a rapid cigarette butt-assisted combustion process (15 min) combined with the graphite molding method. Post-multiple cycles, their CO2 capture capacity reaches 0.373g g-1, which is 2.6-fold superior to that of pure CaO, demonstrating markedly enhanced anti-sintering properties. First, the subtle morphological and crystallographic modifications suggest that the inherent entropy stability of HEFO imparts robust thermal resistance. Concurrently, the disordered structure of single-phase HEFO exhibits a high affinity for CaO, resulting in an interface binding energy of -1.83eV, in sharp contrast to the -0.112eV of pure CaO, thereby restricting CaO migration. Additionally, the multi-element synergistic effect of HEFO reduces the energy barrier by 0.15eV, leading to a 40% and 140% increase in carbonation and calcination rates, respectively. This work presents highly efficient and rapidly synthesized CaO-based sorbent pellets, showcasing promising potential for industrial application.

Microstructure versus topography: the impact of crystallographic substrate modification during ultrashort pulsed direct laser interference patterning on the antibacterial properties of Cu

Introduction: Topographic surface patterning in the micro- and nanometer scale has evolved into a well applied approach in surface functionalization following biomimetic blueprints from nature. Depending on the production process an additional impact of process-related substrate modification has to be considered in functional surface optimization. This is especially true in case of antimicrobial applications of Cu surfaces where a modification of the substrate properties might impact bactericidal efficiency.Methods: In this regard, the effect of ultrashort pulsed direct laser interference patterning on the microstructure of pure Cu and resulting antimicrobial properties was investigated alongside line-like patterning in the scale of single bacterial cells.Results and Discussion: The process-induced microstructure modification was shown to play an important role in corrosion processes on Cu surfaces in saline environment, whereas the superficial microstructure impacts both corrosive interaction and ion emission. Surprisingly, antimicrobial efficiency is not predominantly following deviating trends in Cu ion release rates but rather depends on surface topography and wettability, which was shown to be impacted by the substrate microstructure state, as well. This highlights the need of an in-depth understanding on how different surface properties are simultaneously modulated during laser processing and how their interaction has to be designed to acquire an effective surface optimization e.g., to agitate active antimicrobial surface functionalization.

Study of the Composition and Properties of Bivalve Mollusk Shells as Promising Bio-Indifferent Materials for Photocatalytic Applications (Example of Practical Use)

This paper studies the composition and properties of shells of bivalve mollusks (Crenomytilus grayanus, Callista brevisiphonata, and Mizuhopecten yessoensis) from coastal discharges with a view to the possibility of their use in photocatalytic water treatment systems. The clam shells are considered in terms of application in the form of a powder material as a precursor for creating photocatalysts, and also as a carrier of photocatalytic coatings. It was shown that the main phase composing the shell material was calcium carbonate in two crystallographic modifications—calcite and aragonite. The presence of inorganic impurities in all studied clam shells did not exceed one mass percent. The main share was made up of elements included in the composition of calcium carbonate, which confirmed the high bio-indifference of the materials under study. Depending on the physiological and environmental features of the structure of clam shells, different contents of the organic component in their composition were observed. The granulometric characteristics of crushed clam shells (average diameter, specific surface area, and distribution modality) were studied. It was shown that the maximum values of bending strength of 5 MPa and compressive strength of 2 MPa are characterized by Mizuhopecten yessoensis shells with the lowest porosity of 2.91%. The features of sorption and photosorption processes of both whole and crushed shells in relation to four organic dyes at different temperatures and degrees of illumination were studied. Based on crushed shells of Mizuhopecten Yessoensis and titanium dioxide, functional materials (CaxTiyOz) were obtained, and their morphology and photocatalytic properties were studied. An example of the practical use of clam shells as a carrier of a photocatalytic coating is given.

Structural features of early fuel cycle taggant incorporation for intentional nuclear forensics

To develop strategies for incorporating transition metal taggants (Fe, Cr, and Ni) into oxide fuels and to understand how these taggant candidates persist through early fuel cycle processes, synthetic procedures are modified from established production routes to yield intentionally tagged early fuel cycle intermediates including uranyl nitrate hexahydrate (UNH, UO2(NO3)2·6H2O), uranyl peroxide tetrahydrate (studtite, UO2O2·4H2O), and uranyl peroxide dihydrate (metastudtite, UO2O2·2H2O). First, Fe, Cr, and Ni nitrate solutions are introduced to an aqueous solution of UNH followed by precipitation to produce tagged UNH. Then, studtite is precipitated from UNH followed by dehydration to metastudtite. Structural influences of taggant incorporation within all synthesized phases are investigated using powder X-ray diffraction (PXRD) and Raman spectroscopy to provide insight into crystallographic modifications resulting from the addition of tags to these early fuel cycle materials and elucidate the chemical form of taggants introduced at these stages. The possibility of segregation of taggant species into discrete phases within U matrices was examined using scanning electron microscopy with energy dispersive X-ray spectroscopy. Taggant concentrations in solid-phase materials were determined using inductively coupled plasma-optical emission spectroscopy. Observations from Raman spectroscopy and PXRD indicate that introducing transition metal tags during uranyl nitrate precipitation results in potential impurity phase segregation in UNH, but transition metal incorporation is suggested by results for tagged uranyl peroxide materials. Results from this study will inform strategies for optimizing taggant incorporation in UO2.

A comparison of silver nanoparticles made by green chemistry and femtosecond laser ablation and injected into a PVP/PVA/chitosan polymer blend

Due to their antibacterial effect, silver nanoparticles (AgNPs) are attracting more and more attention for various applications in biomedicine. The production of nanomaterials from organometallic precursors requires the use of a capping agent that acts as a stabilizer and provides colloidal stability while preventing agglomeration and excessive growth. In this research, we studied the optical properties and antibacterial activity of AgNPs loaded in a blend of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and chitosan, which were used as capping agents to control the shape and size of the nanoparticles and to impart stability to the synthesized Ag nanomaterials. Characterization studies showed that the blend provides a uniform and controlled distribution of AgNPs inside the polymeric matrix without the addition of any more stabilizers. The mean particle size for green and laser-ablated AgNPs was found to be ~ 50 nm according to transmission electron microscopy (TEM) studies. Fourier transform infrared (FTIR) studies showed the presence of characteristic main peaks corresponding to the vibrational groups which characterize the prepared samples. The interactions between the AgNPs and the blend were marked by changes in the intensity of vibrational peaks and spectral positions. X-ray diffraction (XRD) confirmed the crystallographic modification within the PVP/PVA/chitosan matrix because of AgNPs filling. The change in the absorbance has been studied with the help of measured ultraviolet–visible spectroscopy (UV–Vis.) and therefore the optical band gap was calculated. The filling of AgNPs in the blend shows a broad peak at 427 nm because of the phenomenon of surface plasmon resonance (SPR) and its intensity increases with increasing filler concentration. The blend and the Ag nanocomposite showed remarkable antibacterial activity and caused a significant decrease in microbial growth (Escherichia coli) in 24 h. These outcomes demonstrate the suitability and promise of the nanocomposites for various applications, including biomedical labels, sensors, and detectors.

Effective bandgap tuning with non-trivial modulation in room temperature magnetic and electrical responses of low level Ba–Cr co-substituted BiFeO3 nanoparticles

This work reports the effects of low-level Ba(5%)-Cr(1–5%) co-incorporation on room temperature structural and functional properties of sol-gel synthesized bismuth ferrite (BiFeO3) nanoparticles. Within this co-substitution limit, structural stability of the main perovskite phase with rhombohedral (R3c) symmetry was enhanced by Ba substitution. The defect chemical and crystallographic modifications together brought about by the low level co-substitution considerably reduced the BiFeO3 nanoparticle's optical bandgap by ∼23% to 1.59 eV. An enhanced saturation magnetization (∼3.6 emu/g) observed in BiFeO3 was further raised by ∼ 100% through 5% Ba–Cr co-incorporation. This significant improvement in the magnetic property of the materials, recognized to be composed of single domain non-interacting nanoparticles was attributed to an enhanced super-exchange interaction phenomenon, and was further corroborated by the contributions from the deconvoluted magnetic components associated with different microstructural phases. The defect assisted variation in leakage current culminates in lossy dielectric type polarization-hysteresis responses. The origin of the leakage current was analyzed in terms ohmic, SCLC and Pool-Frankel emission mechanisms. Technically these observed developments in the functional responses of low level Ba–Cr co-substituted BiFeO3 nanoparticles, brought about by the structural and microstructural modifications open a potential window for photo-chemical/electric and magnetic applications.

Effect of processing temperature on structural, optical and frequency dependent electrical responses of solid-state sintered bismuth sodium titanate

A facile way to control the functional properties of pure Bi0.5Na0.5TiO3 (BNT) could be of great significance when it comes to manufacturing and application of Pb free dielectrics. Herein, a stark modulation in optical, dielectric and conductivity responses of pure BNT with morphological and crystallographic modifications brought about simply by changing the processing temperature (850 ≤ Tsint≤ 1150 °C) along with a detailed correlation between the functional and structural properties has been reported, which are yet to be addressed in detail for BNT in particular. Industrially, the solid state reaction (SSR) route being the most viable mass production technique was adopted in this study. A conspicuous change in crystallographic distortion along with microstructural development was rendered by increasing Tsint without generating any 2nd phase. A noticeable modulation in direct-mode optical transition energy enabled by morphology dependent size confinement effect with increase in Tsint makes BNT based compositions a potential candidate for photochemical application. An optimum Tsint corresponding to peak εr' for pure BNT was established and a technologically desired frequency-stable εr' plateau with low loss was observed to extend remarkably from over 1 MHz to below 0.1 kHz as Tsint reaches 1150 °C, in which both temperature dependent structure and morphology played a decisive role. Distinct frequency dependent conductivity zones were also identified for pure BNT under different measurement and processing temperatures, which were also in direct congruence with the dielectric responses.

First-Principles Calculations of Stable Geometric Configuration and Thermodynamic Parameters of Cadmium Sulfide Thin-Film Condensates

Thin-film CdS layers obtained by the open evaporation method in vacuum are considered and cluster models for calculation of crystal, band structure and thermodynamic parameters are proposed. The thermodynamic parameters of the formation energy ΔE, enthalpy of formation ΔH, Gibbs energy ΔG, entropy ΔS and specific heat capacities at constant pressure and volume for cubic and hexagonal crystallographic modifications are determined. The stable crystal structure for cadmium sulfide was determined from the analysis of Gibbs energy temperature dependences for the sphalerite and wurtzine phases.

Small grains as recombination hot spots in perovskite solar cells

Summary Non-radiative recombination in the perovskite bulk and at its interfaces prohibits the photovoltaic performance from reaching the Shockley-Queisser limit. While interfacial recombination has been widely discussed and demonstrated, bulk recombination and especially the influence of grain boundaries remain under debate. Most studies explore the role of grain boundaries on perovskite films rather than devices, making it difficult to link the film properties with those of the devices. Here, we systematically investigate the effects of grain boundaries on the performance of perovskite solar cells by two different methods. By combining experimental characterization with theoretical device simulations, we find that the recombination at grain boundaries is diffusion limited and hence is inversely proportional to the grain area to the power of 3/2. Consequently, the prevalence of small grains—which act as recombination hot spots—across the perovskite active layer dictates the photovoltaic performance of the perovskite solar cells.

Advances in Drug Delivery Nanosystems Using Graphene-Based Materials and Carbon Nanotubes.

Carbon is one of the most abundant elements on Earth. In addition to the well-known crystallographic modifications such as graphite and diamond, other allotropic carbon modifications such as graphene-based nanomaterials and carbon nanotubes have recently come to the fore. These carbon nanomaterials can be designed to help deliver or target drugs more efficiently and to innovate therapeutic approaches, especially for cancer treatment, but also for the development of new diagnostic agents for malignancies and are expected to help combine molecular imaging for diagnosis with therapies. This paper summarizes the latest designed drug delivery nanosystems based on graphene, graphene quantum dots, graphene oxide, reduced graphene oxide and carbon nanotubes, mainly for anticancer therapy.

Space weathering of iron sulfides in the lunar surface environment

Alteration of iron sulfides on the lunar surface by space weathering is poorly understood. We examined space weathering features of iron sulfides in lunar mature soil grains using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM observations reveal that iron sulfides have vesicular textures and iron whiskers on their surfaces. Iron sulfides observed using TEM are troilite and NC-pyrrhotite. The space-weathered rim on the iron sulfides is characterized by crystallographic misorientations and the disappearance of superstructure reflections of troilite in electron diffraction patterns. These crystallographic modifications are probably produced by solar wind irradiation. The rim contains opened vesicles that are aligned along the c-plane of the sulfides, as well as numerous tiny vesicles. The Fe/S ratio at the surface of the rim is higher than in non-altered regions, indicating selective sulfur loss from the surface. Iron whiskers protrude from the space weathered rim and consist of polycrystalline metallic iron. The sulfide rims and the iron whiskers are both coated with vapor-deposited materials rich in O and Si. The combined processes driven by the solar wind irradiation, heating during impact events, solar UV radiation, and the thermal cycling may cause vesicular textures, selective sulfur escape from the iron sulfides, and the formation of the iron whiskers. The rim textures support the notion that the enrichment of heavy sulfur isotopes in mature lunar soils is caused by space weathering of iron sulfides. The space weathered rims on lunar iron sulfides are similar to those observed in regolith samples from asteroid Itokawa. Therefore, alterations of sulfide surface might be common among airless bodies in the solar system.

Selective oxidation of 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furancarboxylic acid using silver oxide supported on calcium carbonate

This work revealed 5-hydroxymethylfurfural (HMF) oxidation towards 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) employed Ag2O supported on calcium carbonate as heterogeneous catalyst in conventional batch protocols and microwave-assisted batch conditions. Different reaction regimes were investigated, such as catalyst loading, reaction temperature, solvent types and oxidizing agent concentrations. 89 % HMF conversion, 85 % HMFCA yield as well as 95 % HMFCA selectivity achieved under optimum condition (125 mg 20 wt% Ag2O-CaCO3, 2 wt% aq. H2O2 with 0.1 mL min−1 flow rate in 50 min, oil bath 100 ºC). Microwave irradiation (30 W) afforded higher HMF conversion (95 %) as well as HMFCA yield (93 %) with HMFCA selectivity (97 %) under identical condition. Catalyst recycling showed deactivation (64 % HMF conversion and 50 % HMFCA yield in fourth time). Post-characterization was investigated to analyze catalyst deactivation. For instance, EDS and SEM mapping micrographs showed organic moieties deposited on the surface of catalyst. XRD exhibited no CaCO3 crystallographic modification happened after reaction, however, partial reduction of silver (I) to metallic silver (0) happened.

Nano-interface engineering in all-solid-state lithium metal batteries: Tailoring exposed crystal facets of epitaxially grown LiNi0.5Mn1.5O4 films

Understanding the solid electrolyte/cathode nano-interfacial kinetics is critical in designing advanced all-solid-state lithium metal batteries with improved performance and stability. However, the correlation between crystallographic features of cathodes and the solid nano-interface behaviour remains controversial due to the difficulty in eliminating the impact of other factors. Here, we systematically investigated the effect of exposed crystal facets of LiNi 0.5 Mn 1.5 O 4 on the solid nano-interface using the substrate orientation-dependent epitaxial growth of thin films as a model study. (100), (110), and (111)-oriented Pt/MgO substrates were used to make selective high-quality epitaxial LiNi 0.5 Mn 1.5 O 4 films with different {100}/{111}-exposed facet ratios. The atomic arrangement of the exposed facets was found to affect the electrochemical performance. Loosely packed {100} facets and densely packed {111} facets were beneficial for lithium ion diffusion and cycle stability, respectively. In particular, stable {111} facets effectively suppressed the dissolution and diffusion of transition metals at the solid nano-interface during charge-discharge, enabling a 99.6% retention after 100 cycles. In addition, this model study reveals that an amorphous cathode surface layer and a twin boundary inside the cathode are crystallographic origins that hinder the electrochemical performance of batteries. These findings suggest that crystallographic modifications of cathodes can be a key to improving the solid nano-interface. • Precise epitaxial growth creates different exposed crystal facets of LiNi 0.5 Mn 1.5 O 4. • Loosely packed {100} facets induces high capacity via fast lithium ion diffusion. • {111} facets blocks mutual diffusion across the nano-interface, enhancing stability. • Thin film model reveals crystallographic origins of the solid interface degradation.

Precisely Controlled Two-Dimensional Rhombic Copolymer Micelles for Sensitive Flexible Tunneling Devices

Nanoscale two-dimensional (2D) organic materials have attracted significant interest on account of their unique properties, which result from their ultrathin and flat morphology. Supramolecular 2D ...

Mo6Ga31 endohedral cluster superconductor

Endohedral cluster compounds are a rich source of new superconductors, where nontrivial properties are expected, including strong coupling regime and multigap superconductivity. Here, we report on the synthesis, crystal and electronic structure, and physical properties of the Mo6Ga31 endohedral cluster superconductor. The compound has two crystallographic modifications, monoclinic and triclinic, which are built by the Mo@Ga10 endohedral clusters. Both structures possess qualitatively the same electronic density of states showing a high peak at the Fermi level. Due to the proximity effect of the triclinic and monoclinic domains, which are in the strong contact with each other, bulk Mo6Ga31 exhibits single superconducting transition at the critical temperature of 8.2 K in zero magnetic field. The upper critical field, which is 7.8 T at zero temperature, shows clear enhancement with respect to the Werthamer-Helfand-Honenberg prediction. Accordingly, heat capacity measurements indicate strong electron-phonon coupling in the superconducting state with the large ratio of 2Δ(0)/(kBTc)=4.5, where 2Δ(0)=3.2 meV is the full superconducting gap at zero temperature.

Eco-designed iron aluminate (FeAl2O4) free-standing mesoporous films and supported ultrafiltration membranes for wastewater treatment

Abstract This paper reports a promising and facile strategy for the synthesis of iron aluminate films and ultrafiltration membranes by utilization of iron salt recovered from waste slag generated during TiO2 manufacturing process. The study includes crystallographic modification of alumina from γ to α phase for fabricating free-standing iron aluminate spinel film through a novel technique based on aqueous sol-gel method. Microstructural evolution prompted grain growth that ultimately resulted in porosity in the ultrafiltration range, enabling its application in the domain of ultrafiltration membranes. The membranes were characterized using Hagen-Poiseuille’s membrane model of parallel open pores. The surface characteristics with enhanced membrane permeability exhibited a rejection rate of about 90 % for BSA and Direct-red-75 dye. Furthermore, the retention behavior displayed the potential of using FeAl2O4 membranes for protein separation and treatment of textile wastewater. The eco-design concept is adopted to promote sustainable development, and waste management through fabrication of iron aluminate films and membranes.

A CaO/zeolite-based catalyst obtained from waste chicken eggshell and coal fly ash for biodiesel production

The present paper is focused on the development of a new environment-friendly methanolysis catalyst completely based on waste materials: lignite coal fly ash and chicken eggshells. A novel catalyst based on CaO supported on a fly ash-based zeolitic material (CaO/FA-ZM) was obtained from a cancrinite-sodalite group zeolite-like material (vishnevite type) and active CaO by alkali activation in a new miniature autoclave reactor system and hydration-dehydration. Agitation by rotation of the entire reaction mixture led to a more homogeneous zeolitic product and saved both time and energy. The obtained catalyst structure corresponds to gismondine and the crystallographic modification of calcium silicate (α’-dicalcium silicate) with deposited CaO. The characteristics of the synthesized catalyst were determined using ED-XRF, XRD, FT-IR, SEM, Hg-porosimetry, N2-physisorption, LDPSA, and Hammett indicators. The CaO/FA-ZM catalyst exhibited a high activity (97.8% of FAME for only 30 min) and stability (a negligible drop in activity in five consecutive cycles) in the methanolysis reaction under the optimal reaction conditions (temperature of 60 °C, methanol/oil molar ratio of 6:1, and catalyst concentration of 6 wt%). A kinetic study was performed using two different mechanisms: the irreversible pseudo-first-order reaction mechanism in two regimes (heterogeneous and homogeneous) and the changing mechanism combined with the triacylglycerol mass transfer limitation. Both models showed a satisfactory agreement between the experimental and predicted values of conversion degree (R2 > 0.93), confirming their validity for the CaO-based heterogeneously catalyzed methanolysis. The values of the activation energy calculated for both mechanisms were 67.17 and 58.03 kJ mol−1, respectively.

Thermodynamic assessment of the CaO–P2O5–SiO2–ZnO system with special emphasis on the addition of ZnO to the Ca2SiO4–Ca3P2O8 phase

The CaO–P2O5–SiO2–ZnO system including all binary and ternary sub-systems has been thermodynamically assessed using all available experimental data. Particular attention was given to the phase C2S–C3P which forms a complete solid solution with end-members α-Ca2SiO4 and α′-Ca3P2O8. In addition, the present modelling of the phase C2S–C3P allows the inclusion of experimentally determined solubility values of zinc oxide in both end-members of the phase C2S–C3P. The mutual solubility between different crystallographic modifications of calcium and zinc phosphates is also described in this work using available experimental data. 24 phospates as stoichiometric phases have also been included in the database.

Growth of 12-inch uniform monolayer graphene film on molten glass and its application in PbI2-based photodetector

Direct growth of large area uniform graphene on functional insulating materials is essential for engineering versatile applications of graphene. However, the existing synthesis approaches can hardly avoid the generation of non-uniform multilayer graphene along the gas flow direction, affording huge challenges for further scaling up. Herein, by exploiting the molten state of soda-lime glass, we have accomplished the direct growth of large area uniform (up to 30 cm × 6 cm) graphene via a facile chemical vapor deposition route on low cost soda-lime glass. The use of molten glass eliminates the chemically active sites (surface corrugations, scratches, defects), and improves the mobility of carbon precursors, affording uniform nucleation and growth of monolayer graphene. Intriguingly, thus-obtained graphene acts as an ideal coating layer for the surface crystallographic modification of soda-lime glass, making it epitaxy substrates for synthesizing high-quality PbI2 nanoplates and continues films. Accordingly, a prototype photodetector was fabricated to present excellent photoelectrical properties of high responsivity (∼ 600 on/off current ratio) and fast response speed (18 µs). This work hereby paves ways for the batch production and the direct applications of graphene glass as platforms for constructing high performance electronic and optoelectronic devices.

Experimental molecular adsorption: electronic buffer effect of germanene on Al(1 1 1)

The interaction of organic C60 molecules with germanene grown on Al(1 1 1) is investigated by experimental tools and calculations. By mean of scanning tunneling microscopy, we show that a single but disordered C60 layer is formed upon deposition in the monolayer range. Density functional theory calculations indicate that van der Waals and electrostatic interactions are present between the C60 layer and the germanene, without formation of covalent bond. Moreover, the C60 molecules are adsorbed without major crystallographic and charge modifications at the interface between germanene and the Al(1 1 1) substrate. The predicted charge transfer from the Al(1 1 1) substrate to the C60 molecules is very small, which means that the germanene layer acts as an electronic buffer between the highly electron attractor C60 molecules and the large electron reservoir Al(1 1 1). This leaves the C60 layer quite uncharged, and so preserves its electron attractor properties for further layers grown on it, in the design of new molecular sensors.