Hexagonal Plate-like Morphology Research Articles

Design of highly stable Co3O4/RGO/CoFe2O4 hybrid nanocomposites with multiple nanointerfaces for enhanced supercapacitor performance

In this study, we developed a novel hybrid electrode nanomaterial composed of Co3O4, CoFe2O4, and reduced graphene oxide (RGO) for electrochemical supercapacitor applications. The hybrid nanocomposite of Co3O4/RGO/CoFe2O4 was prepared using a modified chemical oxidation process and the phase formation of the composites was evidenced by X-ray diffraction (XRD). The grain size for Co3O4 and CoFe2O4 was estimated as 12 nm and 22 nm. For Co3O4/CoFe2O4 the reduced grain size of 19 nm for CoFe2O4 was observed and further it was reduced with RGO up to 15 nm. The bare Co3O4 exhibited a hexagonal plate-like morphology, whereas the bare CoFe2O4 showed mostly a spherical morphology. The reduced saturation magnetization for the hybrid electrode material due to the non-magnetic fraction of Co3O4 and RGO was observed to be 21 emu/g compared to the bare CoFe2O4 (77 emu/g). The Co3O4/RGO/CoFe2O4 electrode exhibited enriched electroactive sites and enhanced diffusion pathways, achieving a high specific capacity of 235C g − 1 at 5 A g − 1 with excellent durability.. This work highlights the significant charge storage potential of the Co3O4/RGO/CoFe2O4 hybrid, making it a promising candidate for advanced energy storage systems.

Microwave-assisted synthesis and functionalization of nanocrystalline Molybdenum trioxide for enhanced antimicrobial and photocatalytic activity

Molybdenum Trioxide nanoparticles (MoO3) were synthesized using ammonium heptamolybdate tetrahydrate [(NH4)6Mo7O24·4 H2O] as the primary precursor via the microwave-assisted method and subsequently functionalized with surfactants such as Cetyltrimethylammonium bromide (CTAB), Sodium n-dodecyl sulfate (SDS), and Thioglycolic acid (TGA). The characterization involved X-ray diffraction, field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and UV-Visible spectroscopy, revealing hexagonal plate-like morphology, UV absorbance at 202 – 216 nm with a band gap of 4.2 eV, and a crystalline structure with a 44 nm size calculated by the Scherrer’s equation. The synthesized pure (MoO3) and functionalized molybdenum trioxide nanoparticles (FMoO3) were tested for antibacterial activity against gram-positive Staphylococcus aureus and gram-negative Salmonella typhi. Furthermore, MoO3 and FMoO3 also demonstrated enhanced antifungal activity against the fungi Aspergillus niger (Accession No. MZ435922) and Aspergillus fumigatus (Accession No. MZ435863). Photocatalytic experiments demonstrated significant degradation of malachite green dye under UV light irradiation, notably with SDS functionalized MoO3 achieving 98.17% degradation rate within 20 minutes, with a linear rate constant of 0.20343 min-1. These findings highlight the potential of MoO3 and FMoO3 nanoparticles as effective antimicrobial agents and their suitability for water purification due to their low toxicity.

Zinc silicate phosphor: Insights of X-ray induced and temperature enabled luminescence.

The present investigation deals with the effect of calcination temperature on the structural and thermoluminescent (TL) properties of Zn2 SiO4 materials. For this study, Zn2 SiO4 was prepared via a simple hydrothermal route and calcinated at temperatures from 700°C to 1100°C in an air atmosphere. TL data of all Zn2 SiO4 samples showed two peaks at around 240°C and 330°C due to the formation of the luminescence centre during X-ray irradiation. More interestingly, the Zn2 SiO4 sample calcinated at 900°C exhibited a shift in the TL peak (282°C and 354°C) with an optimal TL intensity attributed to its good crystallinity with a well-defined hexagonal plate-like morphology. X-ray-irradiated Zn2 SiO4 samples calcinated at 900°C exhibited a high-temperature TL glow curve peak, suggesting that the present material could be used for high-temperature dosimetry applications.

Synthesis of Novel Zn3V2O8/Ag Nanocomposite for Efficient Photocatalytic Hydrogen Production

In this study, we fabricated Zn3V2O8 and a Ag-modified Zn3V2O8 composite (Zn3V2O8/Ag) by utilizing effective and benign approaches. Further characterization techniques such as powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) were explored to examine the phase and structural properties, respectively, of the synthesized Zn3V2O8/Ag and Zn3V2O8/Ag composite materials. The oxidation states and elemental composition of the synthesized Zn3V2O8/Ag and Zn3V2O8/Ag were characterized by adopting X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX). The optical band gaps of the synthesized Zn3V2O8/Ag and Zn3V2O8/Ag were examined by employing ultraviolet–visible (UV-vis) diffuse reflection spectroscopy. HRTEM images clearly show that ZnV@Ag NC has a hexagonal plate-like morphology. Subsequently, Zn3V2O8 and Zn3V2O8/Ag were used as photocatalysts for photocatalytic hydrogen (H2) production. It was observed that after Ag doping, the energy band gap of ZnV was reduced from 2.33 eV to 2.19 eV. EDX mapping images also show the presence of Ag, O, Zn, and V elements and confirm the formation of ZnV@Ag NC with good phase purity. Observations clearly showed the presence of excellent photocatalytic properties of the synthesized photocatalyst. The Zn3V2O8/Ag photocatalyst exhibited H2 generation of 37.52 µmolg−1h−1, which is higher compared to pristine Zn3V2O8. The Zn3V2O8/Ag photocatalyst also demonstrated excellent reusability, including decent stability. The reusability experiments suggested that ZnV@Ag NC has excellent cyclic stability for up to six cycles.

HRTEM Characterization of an Age-Hardened Mg–Ca Binary Alloy

A Mg–2.8 mass% Ca binary alloy was subjected to a homogenization treatment. The three-dimensional morphology and coherency of the Mg2Ca phase (with C14 structure), which precipitated in the primary α-Mg dendrite, were investigated for the specimens aged at 423 K. The Mg2Ca precipitate exhibited a hexagonal plate-like morphology, with a planar surface that is parallel to the (0001)α basal plane and sides that are parallel to the {-1010}α columnar plane of the α-Mg matrix. The coarsening Mg2Ca precipitate retained coherency with the α-Mg matrix for aging time of 3 h, which corresponded to the peak-aged condition. Furthermore, during the coarsening process, misfit dislocations were introduced on the planar surface of the precipitates, and the coherent interface became a semi-coherent interface for aging time of 100 h, which corresponded to the over-aged condition. The Mg2Ca precipitates evolved from a hexagonal plate-like morphology to a rectangular morphology and then to a polygonal morphology during aging treatment at 423 K.

Synthesis of Monophasic Al3BC3 Powder with Hexagonal Plate-like Morphology.

This paper describes the formation mechanism of monophasic Al3BC3 powder with hexagonal plate-like morphology using Al, B4C, and C powders in a stoichiometric ratio. For the synthesis of pure Al3BC3 by the conventional solid-state reaction method, it is important to avoid contamination from the starting powders. Thermogravimetry-differential thermal analysis curves and quantitative analysis by inductively coupled plasma-atomic emission spectroscopy revealed that there was no vaporization of the powder mixture during heating up to 1470 °C in a high-purity argon atmosphere. We found that the phases and Al3BC3 particle morphology after heating at 1800 °C strongly depended on the mixing conditions. In the case of a two-step process (remixing and reheating the sample), particles with random morphology were observed. On the other hand, well-faceted Al3BC3 particles were predominantly formed in a one-step process that involved heating after ball-milling for 24 h.

Expansion of orderly stacked metakaolinite layers and order destruction using a kaolinite-tetraphenylphosphonium chloride intercalation compound.

The expansion of metakaolinite layers with stacking order and the order destruction were examined by the heat treatment of a kaolinite-tetraphenylphosphonium chloride intercalation compound (Kaol-TPhPCl) at 540 °C under a nitrogen atmosphere followed by the manual grinding of the product using a mortar and a pestle. Fourier-transform infrared spectroscopy and solid-state 27Al nuclear magnetic resonance spectroscopy with magic angle spinning revealed the kaolinite dehydroxylation. Moreover, the absence of kaolinite diffraction lines and the appearance of the 1.85 nm diffraction line in the X-ray diffraction pattern, together with the observation of the hexagonal plate-like morphology in the field-emission scanning electron microscopy, indicated the kaolinite amorphization with the orderly-stacked layers. These results, along with the disappearance of the 1.85 nm diffraction line upon the manual grinding of heat-treated Kaol-TPhPCl, clearly indicated the formation of expanded metakaolinite layers with stacking order and the subsequent order destruction by manual grinding.

Morphology control of aluminum nitride (AlN) for a novel high-temperature hydrogen sensor

Hydrogen is a promising renewable energy source for fossil-free transportation and electrical energy generation. However, leaking hydrogen in high-temperature production processes can cause an explosion, which endangers production workers and surrounding areas. To detect leaks early, we used a sensor material based on a wide bandgap aluminum nitride (AlN) that can withstand a high-temperature environment. Three unique AlN morphologies (rod-like, nest-like, and hexagonal plate-like) were synthesized by a direct nitridation method at 1400°C using γ-AlOOH as a precursor. The gas-sensing performance shows that a hexagonal plate-like morphology exhibited p-type sensing behavior and showed good repeatability as well as the highest response (S = 58.7) toward a 750 ppm leak of H2 gas at high temperature (500°C) compared with the rod-like and nest-like morphologies. Furthermore, the hexagonal plate-like morphology showed fast response and recovery times of 40 and 82 s, respectively. The surface facet of the hexagonal morphology of AlN might be energetically favorable for gas adsorption-desorption for enhanced hydrogen detection.

Preparation of composite powders containing TiB2 and ZrB2 particles through combustion synthesis of TiO2–ZrO2–B2O3–Mg system

Composite powders containing TiB2 and ZrB2 particles were successfully prepared through combustion synthesis of (2-x)TiO2–xZrO2–2B2O3–(10 + y)Mg system. Results showed increase in the x-value from 0 to 2 mol and y-value from 0 to 2.5 mol didn't have any considerable impact on reaction front velocity. In the case of TiO2–B2O3–Mg system with stoichiometric composition, agglomerates containing large TiB2 particles with hexagonal plate-like morphology embedded in a MgO matrix were remained after leaching. The addition of 25 wt% excess Mg (y = 2.5) to this mixture resulted in the dissolution of unwanted phases and the formation of pure submicron TiB2 particles. On the contrary, for the ZrO2–B2O3–Mg mixture (x = 2) unreacted ZrO2 remained and a ZrB2/ZrO2 composite powder was acquired. Both TiB2 and ZrB2 particles were only attained at x = 1.5 mol. The addition of 25 wt% excess Mg to this sample had an inverse effect and removed ZrB2 instead of ZrO2. Lastly, a TiB2/ZrO2 composite powder having submicron titanium boride particles was prepared after leaching process. Simultaneous thermal analyses results showed the combustion reaction sequence in the TiO2–ZrO2–B2O3–Mg system involves; dehydration of powders, melting of B2O3, reaction of molten B2O3 with solid Mg, solid-state reaction of TiO2 and Mg and the formation of Ti, partial reaction of ZrO2 with Mg and the formation of Zr and finally, development of TiB2 and ZrB2 through reaction of Ti and Zr with B element.

Optical and magnetic properties of pure and Er, Yb-doped β-NaYF4 hexagonal plates for biomedical applications

The effects of Yb, Er on structural, optical, magnetic and biocompatibility of β-NaYF4 compounds were examined. The pure and Yb, Er-doped β-NaYF4 compounds were synthesized via simple hydrothermal method. X-ray diffraction analysis revealed the hexagonal crystal structure. The functional group present in the sample was identified by FT-IR analysis. The vibrational bands were analysed by Raman spectroscopy. Electron Microscope images exhibit the hexagonal plate-like morphology. The characteristic absorbance peaks of Yb, Er and host were obtained in UV–VIS–NIR absorbance spectra. The interesting green and enhanced red emission through Photoluminescence spectra of the prepared compounds might be useful for bio-imaging. Pure β-NaYF4 possessed diamagnetic property and Yb, Er-doped β-NaYF4 exhibited paramagnetic property at room temperature. Yb, Er-doped β-NaYF4 was incubated with HeLa cells and assessed cytotoxicity using MTT assay. Hence, Yb, Er-doped β-NaYF4 materials have promising application in cell imaging and bio-separation applications.

Preparation of hexagonal and amorphous chromium oxyhydroxides by facile hydrolysis of K CrO

Abstract The hydrolysis process and mechanisms of unique as-prepared KCrO2 and K3CrO4 were systematically investigated. The characterization results of XRD, IR and SEM show that the hydrolysis reaction can be realized at a low reaction temperature of 80 °C and a reaction time of 24 h. Moreover, the greyish-green α-CrOOH with a hexagonal plate-like morphology and a large size of 10 μm is formed via the hydrolysis of the single-phase hexagonal KCrO2, while the green sol−gel of amorphous Cr(OH)3 with a lumpy aggregate morphology is generated through the hydrolysis of a cubic K3CrO4. It is a facile and rapid method to synthesize pure-phase chromium oxyhydroxide via the above hydrolysis.

Photocatalytic La4Ti3O12 nanoparticles fabricated by liquid-feed flame spray pyrolysis

Hexagonal plate-like nanoparticles (NPs) of the layered perovskite La4Ti3O12 were fabricated using liquid-feed flame spray pyrolysis (LF-FSP) followed by subsequent heat-treatments. Their photocatalytic activity was evaluated using decolorization of methyl orange solutions under Uv irradiation. LF-FSP combusts metalloorganic precursor aerosols to produce mixtures of cubic simple perovskite (ABO3) phase and lanthanum oxycarbonate (La2O4·846C0.846) phase with very low agglomeration and average particle sizes (APSs) of 23 nm (as-produced NPs). Rietveld refinement of synchrotron XRD powder patterns verified that the simple perovskite in the as-produced NPs is LaTiO3 (originally cubic Pm-3m-type space group) and heat-treating gives NPs of the trigonal layered perovskite La4Ti3O12 (R-3-type space group). La4Ti3O12 NPs heat-treated at 1100 °C/3-6h/air exhibits hexagonal plate-like morphology and high crystallinity offering enhanced photocatalytic degradation of methyl orange solutions compared to the as-produced NPs. The LF-FSP approach to obtaining layered perovskite La4Ti3O12 NPs provides a simple route to photocatalytic materials in reasonable quantities.

Coupling in situ atomic force microscopy (AFM) and ultra-small-angle X-ray scattering (USAXS) to study the evolution of zinc morphology during electrodeposition within an imidazolium based ionic liquid electrolyte

Zinc (Zn) is a low-cost material that is widely used in plating and is under consideration as a reversible deposit for a range of energy storage applications. In recent years, researchers have demonstrated that the Zn morphology can be tuned by electrodepositing from an ionic liquid often leading to morphologies that improve cyclability. However, the underlying mechanisms that control deposition and morphology are not well understood. In this work, we evaluate the evolution of zinc morphology as a function of the deposition thickness using in situ atomic force microscopy (AFM), in situ ultra-small angle X-ray scattering (USAXS) and ex situ electron microscopy. Imaging reveals two dominant features: a hexagonal plate-like morphology associated with individual Zn crystals and larger domains in which the individual crystals appear co-aligned. Analysis of the key features observed by USAXS indicates that the growth of the domain size is non-linear with the charge passed and that at least some of this non-linearity can be attributed to increased coalescence of the individual plates as the deposit thickens. A more detailed analysis suggests that there is little change in the aspect ratio of the individual Zn crystals – this is consistent with a growth mechanism in which previously deposited plates grow in diameter as new plates nucleate on their surface and then coalesce into one crystal.

A Factorial Design Approach for Hydrothermal Synthesis of Phase‐Pure AgInO2: A Parametric Optimization Study

AbstractOwing to a wide range of industrial applications and fundamental importance, delafossite compounds have gathered tremendous interest in research community. In this study, the formation of hexagonal nanoplates of AgInO2 mainly dominated by (00l) facets with no metallic Ag impurity, reported using a facile hydrothermal route at 180 °C using KOH as mineralizer by adopting a factorial design approach. Rietveld analysis of the powder XRD pattern and SAED confirms the rhombohedral system of AgInO2. FE‐SEM image shows a uniform hexagonal plate‐like morphology with an average width of about 300 nm and thickness of 70 nm. XPS and EDX analysis confirm potassium ion free AgInO2. A specific surface area of about 48.5 m2 g−1 is arrived from N2 adsorption studies. Temperature‐dependent AC impedance measurements revealed an activation energy of 0.24 eV/f.u. Further, TG‐DTA studies found that the compound is stable in air up to 595 °C.

A Factorial Design Approach for Hydrothermal Synthesis of Phase-Pure AgInO2 : A Parametric Optimization Study.

Owing to a wide range of industrial applications and fundamental importance, delafossite compounds have gathered tremendous interest in research community. In this study, the formation of hexagonal nanoplates of AgInO2 mainly dominated by (00l) facets with no metallic Ag impurity, reported using a facile hydrothermal route at 180 °C using KOH as mineralizer by adopting a factorial design approach. Rietveld analysis of the powder XRD pattern and SAED confirms the rhombohedral system of AgInO2 . FE-SEM image shows a uniform hexagonal plate-like morphology with an average width of about 300 nm and thickness of 70 nm. XPS and EDX analysis confirm potassium ion free AgInO2 . A specific surface area of about 48.5 m2 g-1 is arrived from N2 adsorption studies. Temperature-dependent AC impedance measurements revealed an activation energy of 0.24 eV/f.u. Further, TG-DTA studies found that the compound is stable in air up to 595 °C.

Effects of in-situ synthesized TiB2 on crystallographic orientation, grain size and nanohardness of AA6061 alloy by laser surface alloying

TiB2 reinforced aluminum metal matrix composites (MMCs) were in-situ synthesized by laser surface alloying (LSA). SEM, XRD and EBSD were used to investigate the effect of TiB2 particles on the microstructure characteristics, phase constitution and crystallographic orientation. The results indicated that TiB2 particles mainly exhibited hexagonal plate-like morphology and distributed at high angle grain boundaries (HAGBs). The average grain size of the composites decreased with increasing TiB2 content, and the crystallographic orientation changed from (0 0 1) orientation to (1 1 1) and (1 0 1) orientations. The composites exhibited enhanced nanohardness of 2.74 ± 0.08 GPa, which was about 9.5 times of the matrix. Dislocation strengthening (ΔσCTE) and dispersion strengthening (ΔσOrowan) played dominating role in strengthening mechanism.

Three-Dimensional Morphology of C15–Al<sub>2</sub>Ca Precipitates in a Mg–Al–Ca Alloy

The three-dimensional morphology and thickness of the C15–Al2Ca Laves phase, which precipitated within the primary α-Mg grains, were investigated for the Mg–5Al–1.5Ca alloy over-aged at 523 K for 100 h using the high-resolution transmission electron microscopy (HRTEM). The C15–Al2Ca phase precipitated with a hexagonal plate-like morphology along the (0001)α basal plane of the α-Mg matrix phase, where the sides of the hexagonal plates were parallel to the second columnar plane {1120}α of the α matrix. The typical coffee bean contrast was clearly visible around the precipitates, indicative of coherent precipitation of the C15–Al2Ca phase. The thickness of the C15–Al2Ca precipitates, which corresponds to the six layers of (111)C15 plane composed of Ca atoms, was evaluated to be approximately 1.5 nm.

Beam-induced oxidation of mixed-valent Fe (oxyhydr)oxides (green rust) monitored by STEM-EELS

Analytical transmission electron microscopy (TEM) is often used to investigate morphologies, crystal structures, chemical compositions and oxidation states of highly reactive mixed-valent mineral phases. Of prime interest, due to its potential role in toxic metal remediation, is green rust sulphate (GRSO4) an FeII-FeIII layered double hydroxide. In this study, we quantified the effects that TEM analysis has on GRSO4 in order to ensure the measured material properties are a result of synthesis and reaction kinetics, and not due to sample preparation and analysis technique. To do this, we compared two sample preparation techniques (anoxic drop-cast with drying, and frozen-hydrated cryogenic) and exposed samples to the electron beam for several minutes, acquiring fluence series between ca. 40 e− Å−2 and 10,000 e− Å−2. TEM imaging and electron diffraction showed that the hexagonal plate-like morphology and crystal structure of GRSO4 were largely unaffected by sample preparation and analysis technique. However, quantitative analysis of a series of monochromated Fe L3,2-edge electron energy loss spectra (EELS) showed that electron irradiation induces oxidation. We measured an Fe(II)/Fe(III) ratio of 1.94 (as expected for GRSO4) at 50 e− Å−2. However, above this fluence, the ratio logarithmically decreased and dropped to ca. 0.5 after 1000 e− Å−2. This trend was approximately the same for both sample preparation techniques implying that it is the beam alone which causes valence state changes, and not exposure to oxygen during transfer into the TEM or the vacuum of the TEM column. Ultimately this work demonstrates that GR valence can be quantified by EELS provided that the sample is not over exposed to electrons. This also opens the possibility of quantifying the effect of redox-sensitive toxic metals (e.g., As, Cr, Se) on Fe oxidation state in GR phases (relevant to the treatment of contaminated soils and water) with a higher spatial resolution than other techniques (e.g., Mössbauer spectroscopy).

Ce-Y co-substituted strontium nanohexaferrites: AC susceptibility and Mossbauer studies

Ce-Y co-substituted SrFe12O19, SrYxCexFe12–2xO19 (0.0 ≤ x ≤ 0.5), nanohexaferrites were synthesized via citrate sol-gel combustion route. X–ray diffractometry (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Energy dispersive spectroscope (EDXS) and Elemental mapping were used to study the structure, composition and morphology of the products. Examination through XRD confirms the formation of a pure M phase for all products. Hexagonal plate-like morphology was observed for all samples. EDX and elemental mapping analyses also validated the absence of impurity in the products. The variations in the values of line width, hyperfine magnetic field, quadrupole splitting and isomer shift on Ce and Y substitutions have been investigated through the data of 57Fe Mossbauer spectroscopy. The Mossbauer study indicated that Ce3+ and Y3+ ions are preferentially entering the 4f2 and 2b sites, respectively. The AC magnetic susceptibility experiments show dependency of the magnetic responses with applied frequency, revealing strongly magnetic interactions between the nano-sized particles. Moreover, it is explored that the magnetic interactions are strengthened in substituted nanohexaferrites. This is owed to the replacement of Fe3+ ions by both Ce3+ and Y3+ ions.

Anisotropic surface stability of TiB2: A theoretical explanation for the easy grain coarsening

Abstract