Plate-like Particles Research Articles

2D-to-1D Conversion of a Layered Sodium Titanate via Rational Framework Splitting for Highly Efficient Cation Exchange.

Demand on high-performance ion exchangers is ever-increasing in energy and environment applications. Among many cation exchangers, layered alkali titanates generally show larger cation exchange capacity, but slower cation exchange rate due to their 2D micrometer-size particle morphologies, which limits their practical applications. Here, a rational conversion of a layered sodium titanate, Na2Ti3O7, is reported to the corresponding 1D ultra-narrow nanowires via hydrothermal treatment under basic conditions. The formation of nanowires is thought to involve the partial exfoliation of Na2Ti3O7 to form thin plate-like particles that subsequently split into nanowires along a crystallographically defined, chemically selective weakness in the Na2Ti3O7 crystals. This process is similar to a recently burgeoning materials design using atomic-level weakness in solids, such as zeolites and metal-organic frameworks. The proposed formation scheme is further supported by comparative experiments performed on another layered alkali titanate, K0.8Ti1.73Li0.27O4, which possesses randomly distributed defects at the Ti sites. Thanks to the shortening of diffusion path lengths of the interlayer cations, the resulting Na2Ti3O7 nanowires show an excellent cation exchange performance toward Cd2+ in aqueous solution, exceeding several existing cation exchangers such as zeolites and organic resins.

SEM-DIC characterization of the damage mechanism of an AlSi10Fe0.7 casting alloy on the microstructure scale

Various brittle phases are present in commercial cast aluminum alloys, which strongly influence their mechanical behavior. Among these, silicon precipitates are nearly omnipresent, as Si is a common alloying element. In secondary alloys, usually Fe-containing phases cannot be avoided, and they tend to degrade the mechanical properties. The interaction between the silicon phase and the failure-critical intermetallic phase in the Al-Si-Fe phase system (β-Al5FeSi) is studied in this paper in high resolution. A model alloy AlSi10Fe0.7 was defined, which is composed of a large grain Al-matrix, Si-precipitates and the plate-like β-Al5FeSi phase. The goal of the study was to identify “hot spots” in the microstructure from which cracks may initiate under mechanical loading. The main tool was a deformation analysis via digital image correlation in the SEM (SEM-DIC). This allows the identification and tracking of developing strain localizations at different potential crack initiation sites with a high resolution as well as capturing an overview over the whole specimen. An adapted frame averaging script minimized measurement errors induced by drift. The SEM-DIC results show that the deformation field is governed by the elastic incompatibility of the microstructural constituents. Crack initiation occurs because of the detachment of the Si + β-Al5FeSi phase boundary. Cracks then cross the phase boundary and propagate along twin boundaries in the β-Al5FeSi phase. Final failure is caused by linking fractured brittle plate-like particles.

Study of Intergranular Corrosion Behaviors of Mn-Increased 5083 Al Alloy with Controlled Precipitation States of Al6Mn Formed during Homogenization Annealing

In this study, as a vital part of the production of Mn-increased 5083 Al alloy, i.e., homogenization annealing before hot rolling, the target states of key Al6Mn precipitation, including the dispersed, initial coarsening and intensive coarsening states, were designed, and the corresponding precipitates formed via the control of the temperature and holding time in the annealing process. By means of metallographic corrosion and nitric acid mass loss tests (NAMLT) for assessing the intergranular corrosion (IGC) resistance, temperatures ranging from 175 °C to 225 °C were determined to induce a transition from sensitization to stabilization for this innovative 5083. At a temperature of 175 °C for a duration of up to 24 h (2 h, 4 h, 8 h, 16 h, 24 h), the results show that when the soak time is 24 h, the sample with initially coarsened Al6Mn phases has a lower degree of sensitization (DOS) compared to the samples with Al6Mn phases in both the dispersed and intensive coarsening states, and its NAMLT is reduced by 11% and 15%, respectively. Subsequently, transmission electron microscopy (TEM) analysis has investigated that for the sample with the best IGC resistance, i.e., that with initially coarsened Al6Mn phases, plate-like Al6Mn particles (200~500 nm) can act as heterogenous nucleation sites for β phases, driving their preferential precipitation on Al6Mn particles and resisting their precipitation along grain boundaries, ultimately improving the IGC resistance of 5083 Al alloy after homogenization annealing.

Characterization and toxicity evaluation of chitosan/ZnO nanocompoite as promising nano-biopolymer for treatment of synthetic wastewater

Nanotechnology advances wastewater treatment through the application of Nano entities that optimize contaminant removal and enhance water purification efficacy. In this study, ZnO nanoparticles (ZnO NPs) were synthesized using Klebsiella pneumoniae, subsequently, a chitosan/ZnO nanocomposite (CS/ZnO NC) was prepared for removing reactive black 5 (RB-5) dye from synthetic wastewater. The biosynthesized nanomaterials were characterized using UV–VIS, FTIR, XRD, SEM and TEM techniques. The UV–Vis absorbance peaks at 370 nm and 350 nm corresponded to the characteristic surface plasmon resonance of ZnO NPs and the CS/ZnO NC, respectively. Additionally, FTIR analysis identified the various functional groups associated with ZnO NPs and the CS/ZnO NC. XRD analysis revealed their crystallinity to be approximately 22.44 and 25.76, respectively. The SEM images of ZnO NPs and the CS/ZnO NC show hexagonal plate-like particles with sizes of 33.66 nm and 38.64 nm, respectively. Four concentrations of ZnO NPs and CS/ZnO NC (0.25, 0.5, 1, and 2 mg/mL) were evaluated for RB-5 degradation at three different levels (25, 50, and 100 mg/L). Statistical analysis showed that chitosan/ZnO NC achieved 95 % dye degradation, compared to 81 % degradation with the same amount of ZnO nanoparticles. Furthermore, a pot experiment was carried out to evaluate the phytotoxicity effects of treated wastewater on wheat (Triticum aestivum L.). Both ZnO NPs and CS/ZnO NC did not significantly affect the viability of epithelial retinal cell lines at concentrations up to 100 µg/mL, suggesting a safe cytotoxic profile within this dosage range. Overall, CS/ZnO NC proved effective for treating industrial wastewater, making it suitable for recycling in agricultural applications

Growth orientation control in rapid solid-state crystal growth of (K,Na)NbO3 single crystals using plate-like NaNbO3 single crystal particles

The rolling-extended orientation technique and plate-like NaNbO3 (NN) single crystal particles prepared by a single-step molten salt synthesis, both of which have been developed to fabricate (K, Na)NbO3 (KNN) textured ceramics, were utilized to control the growth orientation of KNN single crystals synthesized by a rapid solid-stated crystal growth (RSSCG) method. As the seed crystals, two kinds of NN single crystal particles were synthesized using pure NaCl and KCl-NaCl mixed molten salts. Plate-like KNN single crystals of about 1 cm squares with the upper and lower faces almost parallel to the (100) (001) planes were obtained with a probability exceeding 50% when NN single crystal particles were synthesized from mixed salts and were subsequently thermal-treated again in Na2CO3-NaCl mixed molten salts under appropriate conditions to remove the Bi element, which is known as the suppression factor of the crystal growth. The average crystal growth rate was 0.6–1.2 mm h−1. Controlling the growth orientation of KNN single crystals produced by the SSCG method using seed crystals other than KTaO3 single crystals was successfully accomplished for the first time.

Effect of surfactant PEG on the property control of Bi2O3 and its photocatalytic activity

A detailed investigation into the effect of the poly(ethylene glycol) (PEG) addition mass on the bismuth (III) oxide (Bi2O3) photocatalyst is limited but necessary. Bismuth (III) oxide/PEG photocatalysts with different morphologies were prepared with different PEG mass via the solvothermal method and characterized for phase, morphology, optical absorption properties, elemental composition and specific surface area. The results indicated that all bismuth (III) oxide photocatalysts with different additions (Bi2O3/PEG-m x ) were pure β-bismuth (III) oxide phases, comprising larger platelike and smaller particle-like particles. Enhanced photocatalytic activity was attributed to increased larger specific surface area with PEG below 10 g. With 12 g of PEG, the formation of surface pores on plate-like bismuth (III) oxide impoved light penetration and utilization. Bi2O3/PEGm12 exhibited optimal photocatalytic activity, achieving over 90% bisphenol A(BPA) degradation after 180 min at 0.6 g·L−1 under visible light. Bismuth (III) oxide /PEG-ty prepared below 140°C showed poor activity, while above 160°C, high activity was observed. Bismuth (III) oxide/PEG effectively mineralize over 80% of bisphenol A into inorganic molecules and water under the co-oxidation of superoxide radicals (·O2 −) and holes (h+). This is the first detailed research on the regulation and modification of β-bismuth (III) oxide by PEG, which may provide new insights into the photocatalytic technology.

Optimizing structural anisotropy and thermal properties of hexagonal boron nitride ceramics through bimodal particle size distribution

Hexagonal boron nitride (h-BN) ceramics exhibit exceptional thermal conductivity, yet integrating their anisotropic thermal properties into bulk ceramics remains challenging. This study investigates the impact of bimodal particle size distribution on the structure, thermal and mechanical properties of h-BN ceramics. Through DEM simulations and hot-pressing techniques, we demonstrate that incorporating large particles into fine ones significantly enhances the packing density, structural anisotropy and thermal properties of h-BN ceramics. The resulting high-purity h-BN ceramic prepared with 10 vol% large particles (10LBN) exhibits an Index of Orientation Preference (IOP) of −2780.57, surpassing that of ceramics without large particles (0LBN) at −1168.61. By regulating the structure, 10LBN h-BN ceramic show a notable increase of the in-plane thermal conductivity from 81.78 for 0LBN ceramics to 153.20 W/(m·K), along with a flexural strength of 58.21 MPa. Additionally, structural characterization and performance testing show that, compared to adding sintering additives, incorporating large plate-like h-BN particles offers greater benefits in optimizing the orientation structure and thermal conductivity of h-BN ceramics. These findings offer new insights for powder compaction using dual-sized plate-like particles and into the sintering of h-BN ceramics with tailored structural and thermal properties.

Structural analysis, relaxor-ferroelectric behavior and optical properties of Mn3+-doped CaBi3NdTi4O15 synthesized via hydrothermal technique

In this study, the synthesis of the Aurivillius Ca1-xBi3+xNdTi4-xMnxO15 (CBNTMx), where x is 0, 0.2, and 0.4, was carried out using the hydrothermal technique. The X-ray diffraction (XRD) data showed that the polar orthorhombic structure in space group of A21am was adopted by all powder samples. All samples possessed anisotropic plate-like particle shapes, and the particle size increased with increase in x value. The phase transition temperature (Tm) is decreased by the ionic substitution owing to the decrease in orthorhombic distortion reflected by the reduction of orthorhombicity. Relaxor-ferroelectric behavior was observed for CBNTM0.4 because of its strong frequency dispersion, while CBNTM0 and CBNTM0.2 only showed a diffused-phase transition (DPT) indicated by the broad dielectric constant at the transition temperature (Tm). The electrical conductivity exhibited an enhancement at higher x value since the ionic substitution with acceptor Mn3+ ions introduced the charge carrier in the lattice. Similarly, the reduction of optical band gap energy from 3.43 eV for the parent CBNTM0 to 2.75 eV and 2.71 eV for CBNTM0.2 and CBNTM0.4, respectively, was described as the contribution of the lower energy level of Mn 3d orbital than that of Ti 3d in the conduction band and also the less distorted structure.

A Layered Titanate Nanowire Helps Pt/TiO2 Photocatalyst for Solar Hydrogen Evolution from Water with High Quantum Efficiency

Abstract Research into TiO2 photocatalysts for solar H2 evolution from water is still growing for environmentally benign and economically valid H2 production. Herein, in contrast to many researches on the modification of TiO2 toward higher photocatalytic activities, we develop a photocatalytically inactive TiO2-based nanostructure and use it, like graphene, as a booster of a benchmark TiO2. A layered potassium titanate with two-dimensional plate-like particle morphology was converted to the corresponding one-dimensional nanowire form via a hydrothermal reaction, after which the layered potassium titanate nanowire was acid-treated to obtain a layered titanate nanowire. This nanowire was completely inactive toward H2 evolution from water containing methanol under solar simulator irradiation. However, when Pt nanoparticle-loaded P25 TiO2 (Pt/P25) was mixed with a considerably smaller amount of the layered titanate nanowire in water, a durable composite was obtained and the composite showed a good photocatalytic activity three times higher than Pt/P25. The apparent quantum efficiency of the reaction at wavelength of 350 nm was 56%, which was higher than or comparable to those of the state-of-the-art TiO2-based photocatalysts. The possible reason for the enhanced photocatalytic activity of the Pt/P25 and layered titanate nanowire composite involved the transfer of photogenerated holes from Pt/P25 to the nanowire to suppress charge recombination and/or disaggregation (improved dispersion) of Pt/P25 particles on the nanowire.

Flow and rheology of suspensions of two-dimensional cylindrical or anisotropic particles with Navier slip

Through boundary integral simulations, we investigate, in the creeping flow limit and in the absence of Brownian noise, the effects of Navier slip on the orientational dynamics and effective shear viscosity of a semidilute suspension of two-dimensional particles with either circular or elongated (platelike) shape, interacting only via hydrodynamic and contact forces. We have recently shown that it is theoretically possible for a dilute system of slip platelike particles to display an effective shear viscosity smaller than the viscosity of the suspending fluid. This large viscosity reduction is primarily due to the suppression of the tumbling motion predicted for a no-slip particle and the attainment of a stable orientation. In this paper, we show that the effect of particle-particle interaction at semidilute concentrations is to cause the particles to fluctuate about the stable orientation and, above a threshold solid fraction ccrt, to tumble. As a consequence, a sharp increase in the effective shear viscosity with solid fraction c occurs for c>ccrt. Our results suggest that, for a given particle aspect ratio, there is a value of c that maximizes the reduction in the effective shear viscosity of the suspension. Published by the American Physical Society 2024

The Influence of CdS on the Structural and Optical Properties of Nano ZnWO4

We investigated the influence of CdS on the structural and optical properties of nano ZnWO4 for optical applications. (1−x)ZnWO4/xCdS (x; 0 to 0.25) heterojunctions were formed and the structure and microstructure of the ZnWO4 and CdS phases developed were investigated using Rietveld refinement analysis for synchrotron X-ray diffraction data. Phase analysis revealed the phase percentage of the CdS phase is always less than the nominated value (x), implying merging of some Cd and S into ZnWO4. Raman spectra showed CdS peaks, confirming the existence of CdS. Scanning electron microscopy showed two distinct morphologies: plate-like particles (ZnWO4 phase) and spherical shape (CdS phase). UV–vis diffuse measurements revealed enhancement of absorbance and reduction in reflectance and transmittance, in the range 300–56 nm, as the amount of CdS (x) increased in the (1−x)ZnWO4/xCdS system. Band gap of the ZnWO4 phase reduced from 4.0 eV for x = 0.0 to 3.9, 3.6, and 2.9 eV for x = 0.05, 0.1, and 0.25, respectively. The highest refractive index values were obtained as the amount of CdS reached 0.05. Impact of alloying on linear and nonlinear parameters and emitted photoluminescence spectra was studied. Upon loading ZnWO4 with CdS, the PL intensity is greatly quenched and the whole spectrum is red shifted, from 480 to 540 nm. CIE chromaticity diagrams show that ZnWO4 sample without any doping exhibits a blue color while the doped system reveals green-yellow colors.

Mass concentration of plastic particles from two-dimensional images

Imaging techniques play a crucial role in characterizing environmental plastics. However, most reported findings rely on two-dimensional projections of particles resting on flat surfaces. This limitation makes it challenging to accurately determine mass concentration, which is essential for deriving toxicologically relevant exposure data. The primary issue arises from the loss of information regarding particle height or thickness. This study aims to evaluate the assumptions necessary to compensate this loss of information. To achieve this, we used a set of environmental plastic particles, mesoplastics and microplastics, from marine campaigns, and precisely measured their three spatial dimensions and mass. Our study demonstrated the feasibility of estimating the mass of plastic particles through two-dimensional images. However, for enhanced accuracy, additional information derived from the dataset of particles under examination is necessary. Specifically, estimating the mass of platelike particles requires information about their height. Similarly, calculating the volume for elongated shapes as cylinders, should be limited to particles with the same width and height and for which their length can be precisely determined, even if the image depicts twisted forms. In conclusion, while obtaining mass concentration from single two-dimensional images enables reasonable estimations, achieving the precision needed for exposure data requires acquiring additional information from the sample and carefully considering the shape of each individual particle.

Surface conductivity of clays

SUMMARY Clay minerals are extensively used in a wide range of applications. In particular, clay-bearing formations are considered as suitable radioactive waste repository. Electrical resistivity tomography is an appropriate tool to monitor the properties of clay-bearing locations. However, an inherent drawback of a conventional resistivity survey is its ambiguity in distinguishing between the effects of groundwater salinity, clay content and porosity. A discrimination can be achieved on the basis of the induced polarization method that provides a complex conductivity. The main purpose of this study is the investigation of the complex conductivity of clay samples with a special focus on the contribution of surface conductivity produced by an excess of ions in the electrical double-layer coating the solid particles. Six clay mixtures were selected that include an almost pure kaolinite sample, a sample consisting of a mixture of kaolinite, illite and smectite, a crushed saponite breccia, a Ca-bentonite sample and two illite clay samples. Besides the enriched kaolinite, the other samples are natural geomaterials that contain more than 40 weight per cent clay minerals. The mineralogical compositions of the samples were determined by quantitative X-ray diffraction analysis. The clay powder was mixed with a varying volume of sodium chloride solution to get plastic state clay samples with varying water content. The samples were investigated by the spectral induced polarization method in a frequency range between 1 mHz and 1 kHz. The resulting complex conductivity spectra indicate a decrease of the real part of the electrical conductivity with rising water content for the illite, bentonite and saponite breccia samples. The overall conductivity of these clay samples is dominated by their surface conductivity. In contrast, the electrical conductivity of kaolinite and kaolinite–illite mixture does not show any significant changes with the water content. For all samples, the imaginary part of electrical conductivity increases at low water content. The real part of the surface conductivity indicates a linear dependence on the volumetric clay content. The slope of this linear relationship can be used to distinguish the types of clay. The ratio between imaginary conductivity and surface conductivity, which decreases with increasing clay content, proves to be a suitable parameter that characterizes the connectivity of clay aggregates in the sample. The surface conductivity of the pure kaolinite sample has been determined in an additional multisalinity experiment. The resulting surface conductivity is in good agreement with the experiment of varying water content. The multisalinity experiment has shown that the resulting petrophysical parameters depend on the procedure of sample packing, which may lead to anisotropy. The effect of anisotropy is attributed to the alignment of the plate-like kaolinite particles in the course of the packing and consolidation procedure.

Microstructural Analysis of K-TIG-Welded New Ni-Based Superalloy VDM Alloy 780

The fusion zone microstructures in K-TIG-welded and post-weld solution heat-treated new superalloy VDM Alloy 780 were examined. In addition, the kinetics of the base metal grain growth during solution heat treatments were analyzed. (S)TEM analyses show that major interdendritic microconstituents formed in the fusion zone due to elemental microsegregation are MC carbides and coarse irregularly shaped Laves phase. Additionally, minor secondary interdendritic phases are found to include γ′, γ″, and tiny plate-like Laves particles. To prevent any potential deterioration of mechanical properties caused by the irregular Laves phase, post-weld solution heat treatments (PWSHTs) at 954 °C to 1060 °C/1 hours were performed to remove the Laves phase. PWSHT at 954 °C only partially eliminates the Laves particles while forming an abundance of interdendritic δ/η phase. Laves phase is dissolved entirely without forming δ/η platelets after PWSHT at 1060 °C. It is proven that Laves eutectics in VDM Alloy 780’s fusion zone can be eliminated through PWSHT without significantly coarsening the base metal’s grain size in comparison to Alloy 718 as a result of substantial grain growth inhibition likely caused by solute segregation at grain boundaries.

Manipulating A2/B2 microstructure via adjusting Al/Ni ratio in cost-effective Fe-based AlNiFeCr alloys for controllable strength-plasticity combination

Cost-effective Fe-based Al-Cr-Fe-Ni alloys were prepared by arc melting process, and Al/Ni ratio in AlxNi(40-x)Fe40Cr20 (0 ≤ x ≤ 40, at.%) alloys was adjusted for superior mechanical properties. With increasing x, the initial FCC phase diminishes and A2/B2 phase is promoted. Two typical A2/B2 structures are observed, one consists of spherical/cuboidal B2 nanoparticles distributed in A2 matrix (denoted as AMBP), and the other consists of ellipsoidal and plate-like A2 particles distributed in B2 matrix (denoted as BMAP). The fraction of AMBP domains decreases while that of BMAP increases with increasing x, which is harder with lowered plasticity/toughness, accompanied with some micro-cracks propagating along the plate-like A2/B2 interfaces in BMAP domains. The alloy shows the best strength-plasticity combination at x = 15 with >95 vol% AMBP domains. This study suggests a cost-effective Al15Ni25Fe40Cr20 medium-entropy alloy with superior strength-plasticity combination. The Al15Ni25Fe40Cr20 alloy per metric ton is 13% and 18% cheaper than well-known equiatomic AlCrFeNi alloy and AlCrFe2Ni2 alloy, respectively.

Improving electrochemical performance of Ni-rich layered cathode material with combining Co-enriched compositional gradient and radial microstructure

Ni-rich complex layered oxides LiNixMnyCozO2 (x > 0.85) with a combined Ni/Co concentration gradient and radially oriented elongated plate-like primary particles were synthesized with hydrothermal microwave-assisted treatment of an as-prepared mixed hydroxide precursor with aqueous solution of Co source and urea followed by a high temperature annealing with a Li source. The radial distribution of plate-like primary crystallites in microwave-treated materials was achieved through Co-enrichment at the surface, which likely triggered the surface-to-bulk growth of plate-like particles rather than isotropic octahedral crystallites. The Co-modified cathode materials demonstrate greatly improved cycling stability (capacity fade per cycle of 0.04 ± 0.01%) compared to unmodified Ni-rich NMCs (capacity fade per cycle of 0.13 ± 0.02%) with similar Ni concentration, as well as good rate capability (215, 210, 199, 189, 178 and 160 mAh/g at C/10, C/5, C/2, 1C, 2C, and 5C rates at 2.7–4.3V vs Li/Li+). Enhanced electrochemical performance is linked to the improved mechanical integrity, which was achieved through radial microstructure organization of the agglomerates triggered by Co concentration gradient, suppressing the intragranular crack formation.

High-fidelity 3D simulation of dust-loading behavior and clogging process of coarse nonwoven filter media considering collision effect

The filter lifetime of fibrous media is important for the energy-saving application of air filters and efficient delivery of clean air. The clogging process significantly affects the dust-loading behavior of fibrous filter media. Therefore, an effective methodology for determining the deposition of dust particles inside filter structures is necessary. This study conducted numerical dust loading simulations on a three-dimensional (3D) X-ray tomographic structure of coarse nonwoven filter media. Spherical particles with a density of 1808 kg/m3 were used in the simulations instead of plate-like dust particles with a higher silica density. A high-fidelity simulation model was successfully developed by considering collision effects. Key factors were determined, including the Hamaker constant for the adhesion energy, restitution coefficient for the particle kinetic energy, and sliding motion. Remarkably, the deviation between the simulated and experimental dust holding capacity was less than 1 %. The developed simulation model enabled a quantitative evaluation of the clogging process and 3D in-situ evolution of particle deposition and pore structures. It was observed that 95.6 % of the maximum deposited dust mass within the fibrous structure was captured at the clogging point. Several computational methods yielded accurate pore size evaluations and clear 3D pore structure visualizations. The developed methodology for high-fidelity simulation and 3D analysis can be further applied to other two-phase filtration and separation fields, including aerosol filtration, coalescence filtration, membrane fouling, micro/nanoplastic capture, and oil/water separation.

Hydrothermic reduction of rutile-ilmenite mineral producing an oxyhydride η-Ti<sub>2</sub>FeO<sub>0.2</sub>H<sub>2.8</sub>: Towards in-situ hydrogen production and storage

As an alternative to the physical storage of hydrogen as compressed gas or liquid hydrogen requiring high-pressure tanks and cryogenic temperatures, the material-based storage of hydrogen in solids involves hydrogen uptake and release from the surface of adsorbents or within interstitials of hydrides. We report a hydrothermic reduction of rutile-ilmenite mineral into hydrogen-rich fibrous products, η-Ti2FeO0.2H2.8, in an ethanol-water system at 120°C for 4 hrs. As part of a project to generate hydrogen from water-ethanol system using advanced catalysts containing graphene oxide (GO) as carbon source, a system of 62.5 μg graphene oxide per g of rutile-ilmenite mineral was employed in a concentration of 50 mg/mL of ethanol-water solution. As well as in the original mineral, XRD of thermal annealed mineral between 500 and 800°C showed no hydride or phase change in rutile-ilmenite. With hydrothermal treatment of GO/rutile-ilmenite (50 mg/mL) in ethanol-water (1:1 v/v) at 120°C, a hydrogen-rich ferrotitanium hydride phase was formed, and there was a change in morphology from plate-like and granular particles into fibrous structures. Like the release of hydrogen by its ‘carriers’ (e.g., CaH2, NH4BH4, NaBH4, NH3, formic acid), it is anticipated that hydrogen was generated from the ethanol-water system in-situ, which reduced the rutile-ilmenite mineral into a hydride. EDX results showed that the reduction affected specifically the oxides of Fe and aluminosilicates in the mineral. The study demonstrated a possibility of in-situ hydrogen generation and storage via low-temperature graphene oxide hydrothermic reduction of rutile-ilmenite mineral in an ethanol-water system.

Surfactant-assisted synthesis of plate-like CuS particles for high-performance symmetric capacitor

In this research, plate-like CuS particles were synthesized through a hydrothermal method using cetyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) as surfactants. The effects of surfactant type and content on the structural, microstructural, and electrochemical properties were explored by the various characterization techniques. Single-phase CuS powders with a space group of P63/mmc were crystallized by decomposition of the copper-thioacetamide complex during hydrothermal treatment. The spherical morphology transformed into plate-like particles by adding the CTAB surfactant, while the PVP surfactant led to an agglomeration of small spherical nanoparticles. With adding the CTAB surfactant, the specific capacitance increased from 630 to 1806 Fg−1 at a current density of 1 Ag−1, while it increased up to 1575 Fg−1 for the PVP surfactant. A symmetric capacitor was assembled on the base of spherical CuS nanoparticles as the negative electrode and the platelike CuS particles as the positive electrode. The CuS//CuS capacitor exhibited comparable electrochemical performance including an energy density of 25.62 Whkg−1 and a power density of 1488 Wkg−1, respectively.

Oleic acid-modified layered double hydroxide for Pickering emulsion: (II) Emulsification behavior

Layered double hydroxides (LDHs) are plate-like particles, being potential Pickering emulsifiers. Surfactant modification can regulate their surface properties, and thus can influence their emulsifying behavior. However, there is a lack of full understanding on the correlation between the surface modification of LDHs and their emulsification behavior. In the current work, one LDH and five oleic acid (OA)-modified LDH (LDH@OA) samples were chosen as emulsifiers, and emulsifying tests for pentadecane (oil)-water mixtures were performed at different oil/water volume ratios (1/9−9/1) and solid dosages (Cs, 1.00−10.0 g/L). The type, droplet size, and stability of emulsions were determined. The interfacial adsorption energy (ΔGad) and the coverage of solid particles for droplet surfaces (Rcov) were estimated, and the oil-water interfacial tension and viscoelastic moduli were determined. Results showed that LDH and LDH@OA particles can emulsify the oil-water mixture, forming coalescence-stable Pickering emulsions. The emulsion type is only determined by the solid wettability, independent of the oil/water ratio and Cs. The OA modification can change the wettability of LDH from hydrophilic to hydrophobic, thereby can regulate the type of emulsions from oil-in-water (O/W) to water-in-oil (W/O). Enhancing solid hydrophobicity decreases droplet sizes and increases interfacial viscoelasticity, thus improving the stability of emulsions. The droplet size decreases with an increase in Cs, while it increases with an increase in the volume fraction of dispersed liquid, both independent of the type of emulsions. The solid particles can irreversibly adsorb at the oil-water interface (with |ΔGad|/kT > 107), forming interfacial particle-layers with Rcov ∼0.4 and strong viscoelasticity, which endow the Pickering emulsions with extremely strong stability against coalescence.