Sol-gel Synthesis Research Articles

Research on Sol-Gel Synthesis of Low-Temperature Na2O-B2O3-SiO2 Vitrified Bonds and Preparation of High-Strength Stacked Abrasives Using the Molding and Crushing Method

Currently, the sol-gel technique is employed in the synthesis of high-performance vitrified bonds; however, its application in the fabrication of stacked abrasives has been minimally explored. Furthermore, the methods utilized in the production of abrasive particles for stacked abrasives are technically challenging and incur high costs, which hinders their actual industrial application. Consequently, this study utilizes the sol-gel approach to synthesize a Na2O-B2O3-SiO2 ternary system vitrified bond powder and employs a molding and crushing method, which offers a lower technological barrier and reduced preparation costs, for the production of abrasive particles subsequently fabricating corundum stacked abrasives. Upon setting the binder composition to a molar ratio of n(SiO2):n(B2O3):n(Na2O) = 65:23:12, it was observed that the crystallization within the glass matrix was minimized and the optimal sintering temperature for the synthesized laminate abrasive to be sustained at 820 °C. At the aforementioned temperature, the binder melt is capable of flowing uniformly amongst the abrasive granules, thereby ensuring a robust encapsulation of the particles. The average single particle compressive strength of the prepared corundum stacked abrasive with a grain size of forty mesh can reach the highest of all composition points at 28.56 N and the average single particle compressive strength of the prepared diamond stacked abrasive is 28.14 N.

From Gel to Crystal: Mechanism of HfO2 and ZrO2 Nanocrystal Synthesis in Benzyl Alcohol.

Nonaqueous sol-gel syntheses have been used to make many types of metal oxide nanocrystals. According to the current paradigm, nonaqueous syntheses have slow kinetics, thus favoring the thermodynamic (crystalline) product. Here we investigate the synthesis of hafnium (and zirconium) oxide nanocrystals from the metal chloride in benzyl alcohol. We follow the transition from precursor to nanocrystal through a combination of rheology, EXAFS, NMR, TEM, and X-ray total scattering (PDF analysis). Upon dissolving the metal chloride precursor, the exchange of chloride ligands for benzylalkoxide liberates HCl. The latter catalyzes the etherification of benzyl alcohol, eliminating water. During the temperature ramp to the reaction temperature (220 °C), sufficient water is produced to turn the reaction mixture into a macroscopic gel. Rheological analysis shows a network consisting of strong interactions with temperature-dependent restructuring. After a few minutes at the reaction temperature, crystalline particles emerge from the gel, and nucleation and growth are complete after 30 min. In contrast, 4 h are required to obtain the highest isolated yield, which we attribute to the slow in situ formation of water (the extraction solvent). We used our mechanistic insights to optimize the synthesis, achieving high isolated yields with a reduced reaction time. Our results oppose the idea that nonaqueous sol-gel syntheses necessarily form crystalline products in one step, without a transient, amorphous gel state.

Sol-gel synthesis of composite adsorbent coating from Prosopis juliflora–activated carbon for simultaneous adsorptive removal of Cd2+ and from wastewater

Abstract To overcome the challenges associated with powdered activated carbon (PAC) in wastewater treatment, the efficacy of composite adsorbent coating (CAC) prepared using a simple sol-gel method with Prosopis juliflora–activated carbon for the simultaneous reduction of Cd2+ and Cr2O72- was investigated. The synthesized CAC was characterized by Fourier-transform infrared spectroscopy (C–H, C = O, and O–H stretching), pH point of zero charge (6–6.6), scanning electron microscopy (porous-rough surface), and Brunauer–Emmett–Teller surface area (10.6 m2/g) techniques. The analysis of variance results showed that pH and contact time were significant (p < 0.0001) for both Cd2+ and Cr2O72- removal. Generally, Cd2+ removal was higher than that of Cr2O72- at various operating conditions owing to the former's superior ionic properties. At the optimized operating parameters (pH = 8.5, adsorbent dosage = 0.25 g, initial concentration = 5 mg/L, contact time = 105 min, and temperature = 23.73°), the predicted and experimental ion removal efficiencies were 86.86 and 83.98% for Cd2+ and 94.26 and 58.08% for Cr2O72-, respectively. The Langmuir adsorption isotherm was the best-suited model (R2 > 0.99), while the metal ions removal was regulated by the pseudo-second-order Kinetic model (R2 > 0.999). The − ΔG°, +ΔH°, and +ΔS° values revealed the endothermic character and spontaneity of the adsorption process. The findings demonstrate the high potential of using CAC as an adsorbent for removal of metal ions to circumvent the PAC challenges in wastewater treatment.

Magnesium Magic: State-of-the-Art Nanocrystalline Materials Paving the Way for Hydrogen Storage.

Hydrogen has been regarded as a promising alternative to traditional fossil fuels, presenting itself as a viable and environmentally friendly energy choice. The design and fabrication of highly efficient hydrogen storage materials is crucial to the wide utilization of hydrogen-based technologies. Magnesium-based nanocrystalline materials have received significant interest in the field of hydrogen storage due to their remarkable hydrogen storage capabilities and release efficiency. This review emphasizes on the most useful techniques including vapor deposition, sol-gel synthesis, electrochemical deposition, magnetron sputtering, and template-assisted approaches used for the fabrication of Magnesium-based nanocrystalline hydrogen storage materials (Mg-NHSMs), stressing their advantages, limitations, and recent advancements. These cutting-edge techniques demonstrate their significance in offering useful insights into the performance of Mg-NHSMs. Further, this review describes various applications of Mg-NHSMs. In addition, this review highlights the conclusion and future perspectives on the improvement of magnesium based nanocrystalline materials for efficient hydrogen storage.

Sol-gel auto-combustion synthesis of bimetallic Pt-Co/Al2O3 catalysts for hydrogen production via acetic acid steam reforming

Green hydrogen production from renewable biomass via bio-oil catalytic steam reforming was a prospective technology. In order to accelerate the development of high-performance and long-term catalyst, we selected acetic acid as a typical bio-oil model compound to carry out the studies of steam reforming. Excellent bimetallic Pt-Co/Al2O3 catalysts were prepared using a sol-gel auto-combustion method. The effects of the molar ratio of ethylene glycol: citric acid: metal ions (EG/CA/M) on the catalyst structure and subsequent reforming performance were systematically investigated. It was found that the catalyst’s textural properties, reducibility, basic sites, and the dispersion of active metal could be carefully tuned by the EG/CA/M ratio. The catalyst prepared under EG/CA/M ratio of 6:3:1 performed the best reactivity in acetic acid steam reforming, showing a 97.6% acetic acid conversion and a 96.6% H2 yield at the reaction conditions of 650 °C, steam to carbon molar ratio of 5, and space velocity of 6957h–1. Furthermore, a bifunctional reaction mechanism of acetic acid catalytic steam reforming was proposed by in-situ diffuse reflective infrared Fourier transform spectroscopy analysis coupled with density functional theory calculations.

Template assisted sol-gel synthesis of BiFeO3 hollow tubes: Introducing kapok fiber as a bio-template.

Bismuth ferrite (BiFeO3) is a perovskite material well known for its multifunctional properties and related applications. The recent research on this material includes the synthesis of hollow-structured BiFeO3 using various methods and exploring their applications in photocatalysis and sensing. Here, we introduce a facile method for the synthesis of BiFeO3 hollow tubes using the sol-gel method, where kapok fiber collected from Ceiba Pentandra is used as a biotemplate for the first time. In the procedure, the annealing path was modified by introducing intermediate holding steps besides varying the final annealing temperature. The structural analysis was carried out using x-ray diffraction (XRD) and Raman analysis, whereas the formation of hollow tube morphology was confirmed with the help of FESEM analysis. The complete decomposition of the kapok fiber template during the annealing process was confirmed with the help of Fourier transform infrared spectroscopy. The XRD analysis indicated that monitoring both the annealing pathway and the final annealing temperature is pivotal in attaining the formation of phase pure BiFeO3. The proposed method eliminates the requirement for additional procedures for extracting the synthesized hollow tubes from the parent template, in addition to providing a less expensive strategy for the synthesis of BiFeO3 hollow tubes.

Green synthesis of CoFe2O4 nanoparticles assisted with bio-waste (Gomutram): Sintering effect on the properties of structural, microstructural and vibrational bands

Synthesis of CoFe2O4 nanoparticles has been effectively accomplished by the cow-urine (Gomutram) as a chelating agent. The liberation of hazardous gases during the sol-gel synthesis process are minimized using cow-urine (Gomutram) as a chelating agent. The Energy Dispersive X-ray Spectrum offers insights on the current composition of ferrite by providing information on the stoichiometric ratio of its constituent elements. The X-ray diffraction patterns provide substantiation for the formation of the spinel phase of present ferrite system. The ferrite systems that underwent sintering at lower temperatures exhibited a more conspicuous amorphous morphology. The experimental lattice parameter (a) and average crystallite size (D) were found to be within the range of 8.0688–8.3779 Å and 3.7–9.4 nm respectively. Both a and D demonstrate an augmentation in magnitude due to the heat treatment procedure. The function of activation energy in the ripening of crystalline size during the sintering process is significant particularly in relation to grain boundary energy. The aggregation of nanoparticles into large clusters can be attributed to the strong magnetic interactions present among them. The inherent characteristics of scanning electron micrographs unambiguously demonstrate. The vibrational frequencies (υ1 and υ2) observed from Fourier Transform Infrared spectra confirm the spinel phase of the present ferrite system. The changes seen in vibrational frequencies do not offer empirical support for the association between annealing and the expansion of the lattice constant. But, offers an empirical support for the hypothetical redistribution of cations in the spinel structure.

CO2 capture and methanation using Ru/Na2O/Al2O3 dual-function materials: Effect of support synthesis method and Ru load

Ru/Na2O/Al2O3 dual-function materials were prepared by varying the support synthesis method and Ru load. Different sol-gel-type and precipitation/ hydrothermal preparation methods were employed in order to synthesize materials with variable nanostructure, surface chemistry and textural properties, thereby effectively tuning the material activity for the methanation of pre-adsorbed CO2. The materials were thoroughly characterized and evaluated during the integrated CO2 capture and methanation process. It was found that the Pechini sol-gel synthesis method led to the structure with the highest porosity, basic site population and high dispersion of methanation and adsorption active Ru0 and Al-O--Na+ sites. The corresponding material displayed the highest CH4 yield (0.47mmol/g) and fastest CH4 production kinetics, while stable performance was achieved under successive adsorption-hydrogenation cycles and under the co-presence of O2 and H2O during CO2 adsorption. Lastly, the increase in Ru load (0.25wt% - 4wt% range) could incrementally improve the CH4 production kinetics during hydrogenation.

Sol-Gel Spin Coated Transparent Single-TiO2 and SiO2 Thin Film on Glass for Opto-electronic Applications

Great attention has been given on the sol-gel synthesis and spin-coating deposition techniques for the fabrication of various thin films. Because of its simple technique to fabricate dielectric (metal oxide) films using tetraethyl orthosilicate and titanium isopropoxide precursors. In this work, transparent single layer of SiO2 and TiO2 thin film was deposited on a glass substrate and characterized by  FTIR, UV-visible spectroscopy, fluorescence and scanning electron microscopy techniques. The single layer thin film was mechanically  stable and strong by adhering to glass substrates. The FTIR transmittance spectrum evidenced the existence of Si-O-Si and Ti-O-Ti at  ~1100 and 1400 cm-1. The UV-visible absorbance spectra of single layer of SiO2 and TiO2 thin films showed strong absorption at below  00 nm. The excitation wavelength at 380 nm, the fluorescence spectra of both thin films showed the highest emission spectrum  in between 733-798 nm. The SEM studies confirmed the smooth surface in both SiO2 and TiO2 layers. Further, it could be useful for  various applications such as back reflector in solar cells, anti-reflection coatings, hydrophobic and anti-fogging materials. 

Highly visible-light-active sulfur and carbon co-doped TiO2 (SC-TiO2) heterogeneous photocatalysts prepared by underwater discharge plasma

To promptly and simply create highly crystalline S/C co-doped TiO2 (SC-TiO2) photocatalysts at room temperature and atmospheric pressure, we suggest a novel plasma-assisted sol-gel synthesis method. This method is a simultaneous synthetic process, in which an underwater plasma undergoes continuous reactions to generate high-energy atomic and molecular species that enable TiO2 to achieve crystallinity, a large surface area, and a heterogeneous structure within a few minutes. In particular, it was demonstrated that the heterogeneously structured TiO2 was formed by doping that sulfur and carbon replace O or Ti atoms in the TiO2 lattice depending on the composition of the synthesis solution during underwater plasma treatment. The resultant SC-TiO2 photocatalysts had narrowed bandgap energies and extended optical absorption scope into the visible range by inducing the intermediate states within bandgap due to generation of oxygen vacancies on the surface of TiO2 through synthesis, crystallization, and doping. Correspondingly, SC-TiO2 showed a significant degradation efficiency ([k] = 6.91 h−1) of tetracycline (TC, antibiotics) under solar light irradiation, up to approximately 4 times higher compared to commercial TiO2 ([k] = 1.68 h−1), resulting in great water purification. Therefore, we anticipate that this underwater discharge plasma system will prove to be an advantageous technique for producing heterostructural TiO2 photocatalysts with superior photocatalytic efficiency for environmental applications.

Synthesis, structural, optical, dielectric, magnetic and magneto-dielectric properties of CoFe2O4 and Graphene Quantum Dots (GQDs) decorated CoFe2O4 hybrid nanocomposite

A sol-gel synthesis method was used for the synthesis of pure CoFe2O4 (CFO) as well as Graphene Quantum Dots (GQDs) decorated CoFe2O4 Hybrid Nanocomposite (GCHN). From X-ray diffraction (XRD) data it was analyzed that both these samples have a cubic structure with Fd-3m space group. Using Debye-Scherer's equation, the average sizes were determined to be 24.48 and 13.74 nm, respectively. FTIR spectra revealed details about vibration bands and functional groups present. Raman spectra confirmed existence of GQDs in GCHN with an ID/IG ratio of ∼0.8. The results of Field emission scanning electron microscopy (FESEM) analysis exhibited microstructural morphological details having shapes of grains to be non-uniform in shape. UV–visible data was used to calculate band gap (Eg) energy by using Tauc plot method and found to be 2.52 eV and 2.99 eV respectively for CFO and GCHN. Urbach energy (EU) was found to be 1.03 and 1.19 eV for CFO and GCHN respectively. The dielectric properties of GCHN were analyzed for dependence on frequency and temperature and explained by Maxwell-Wagner-type polarization. The frequency-dependent ac conductivity (σac) followed Jonscher's power law and investigated dynamics of ion hopping. Impedance spectroscopy was used to further evaluate Nyquist plots with respect to temperature as well as magnetic fields to estimate grain and grain boundary contributions. This was further used to evaluate electrical characteristics such as relaxation time (τ). Activation energies (Ea) calculated using relaxation times were found to be 0.48 eV for CFO while 0.22 and 0.92 eV for GCHN respectively. At room temperature, CFO and GCHN exhibited a strong magneto-dielectric coupling (MD) and showed negative magneto-dielectric properties in low-frequency regions. At room temperature (RT), magnetization values of CFO and GCHN displayed were 38.48 and 7.52 emu/g respectively. The lower magnetization value was possibly due to shielding by GQDs in GCHN. These properties enable it to be used as a potential application in microelectronic systems, spintronics, optical and optoelectronic devices, magnetic resonance imaging (MRI) and memory devices.

The Impact of Ar or N2 Atmosphere on the Structure of Bi-Fe-Carbon Xerogel Based Composites as Electrode Material for Detection of Pb2+ and H2O2

In this study, bismuth- and iron-embedded carbon xerogels (XG) were obtained using a modified resorcinol formaldehyde sol–gel synthesis method followed by additional enrichment with iron content. Pyrolysis treatment was performed at elevated temperatures under Ar or N2 atmosphere to obtain nanocomposites with different reduction yields (XGAr or XGN). The interest was focused on investigating the extent to which changes in the pyrolysis atmosphere of these nanocomposites impact the structure, morphology, and electrical properties of the material and consequently affect the electroanalytical performance. The structural and morphological particularities derived from X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) measurements revealed the formation of the nanocomposite phases, mostly metal/oxide components. The achieved performances for the two modified electrodes based on XG treated under Ar or N2 atmosphere clearly differ, as evidenced by the electroanalytical parameters determined from the detection of heavy metal cations (Pb2+) or the use of the square wave voltammetry (SWV) technique, biomarkers (H2O2), or amperometry. By correlating the differences obtained from electroanalytical measurements with those derived from morphological, structural, and surface data, a few utmost important aspects were identified. Pyrolysis under Ar atmosphere favors a significant increase in the α-Fe2O3 amount and H2O2 detection performance (sensitivity of 0.9 A/M and limit of detection of 0.17 μM) in comparison with pyrolysis under N2 (sensitivity of 0.5 A/M and limit of detection of 0.36 μM), while pyrolysis under N2 atmosphere leads to an increase in the metallic Bi amount and Pb2+ detection performance (sensitivity of 8.44 × 103 A/M and limit of detection of 33.05 pM) in comparison with pyrolysis under Ar (sensitivity of 6.47·103 A/M and limit of detection of 46.37 pM).

Determination of Optimal Conditions for Template Sol-Gel Synthesis for the Formation of Antibacterial Materials

Determination of Optimal Conditions for Template Sol-Gel Synthesis for the Formation of Antibacterial Materials

Ru-Ce0.7Zr0.3O2-δ as an Anode Catalyst for the Internal Reforming of Dimethyl Ether in Solid Oxide Fuel Cells.

The development of direct dimethyl ether (DME) solid oxide fuel cells (SOFCs) has several drawbacks, due to the low catalytic activity and carbon deposition of conventional Ni-zirconia-based anodes. In the present study, the insertion of 2.0 wt.% Ru-Ce0.7Zr0.3O2-δ (ruthenium-zirconium-doped ceria, Ru-CZO) as an anode catalyst layer (ACL) is proposed to be a promising solution. For this purpose, the CZO powder was prepared by the sol-gel synthesis method, and subsequently, nanoparticles of Ru (1.0-2.0 wt.%) were synthesized by the impregnation method and calcination. The catalyst powder was characterized by BET-specific surface area, X-ray diffraction (XRD), field emission scanning electron microscopy with an energy-dispersive spectroscopy detector (FESEM-EDS), and transmission electron microscopy (TEM) techniques. Afterward, the catalytic activity of Ru-CZO catalyst was studied using DME partial oxidation. Finally, button anode-supported SOFCs with Ru-CZO ACL were prepared, depositing Ru-CZO onto the anode support and using an annealing process. The effect of ACL on the electrochemical performance of cells was investigated under a DME and air mixture at 750 °C. The results showed a high dispersion of Ru in the CZO solid solution, which provided a complete DME conversion and high yields of H2 and CO at 750 °C. As a result, 2.0 wt.% Ru-CZO ACL enhanced the cell performance by more than 20% at 750 °C. The post-test analysis of cells with ACL proved a remarkable resistance of Ru-CZO ACL to carbon deposition compared to the reference cell, evidencing the potential application of Ru-CZO as a catalyst as well as an ACL for direct DME SOFCs.

Eco-friendly high entropy oxide rock-salt type structure for oxygen evolution reaction obtained by green synthesis

Global energy consumption increases year after year, causing the depletion of non-renewable sources. According to the International Energy Agency (IEA), global demand for electrical energy is expected to increase by 3.3 % in 2024. Therefore, developing new renewable sources is urgent, including new devices for energy storage and conversion, particularly those based on electrochemical reactions. Water splitting is a clean and sustainable technology capable of facing this issue by producing oxygen and hydrogen from water and electricity. However, an issue related to this technology is the slow kinetics of oxygen evolution reaction, making it necessary to develop new electrocatalysts with high electrochemical performance. To meet this requirement, this work deals, for the first time, with a high entropy oxide with a rock-salt structure synthesized by a green sol–gel synthesis using red seaweed (Rhodophyta) as a polymerizing agent. Sol-gel synthesis allows the large-scale production of nanomaterials with high uniformity and dispersion of the involved chemical elements. The literature, which discussed the synthesis of these oxides, reveals that agents harmful to the environment are employed, including sodium hydroxide, acetic acid, hexadecyltrimethylammonium bromide, urea, and ammonium hydroxide. The composition of the high entropy oxide is (Mg0.2Ni0.2Co0.2Cu0.2Zn0.2)O. As electrocatalyst for oxygen evolution reaction, it exhibits a low overpotential (336 mV vs. RHE at 10 mA cm−2), a Tafel slope of 68 mV dec-1, and excellent durability. The electrochemical performance of the high entropy oxide prepared in this work is superior to other electrocatalysts of the same class that were produced using transition metal-based precursors.

Sol-gel synthesis, physicochemical characteristics and in vitro pH-responsive metformin drug release of uniformly polydopamine coated mesoporous silica nanospheres

A recent attention has been paid to the repurposing potential of metformin drug for cancer chemotherapy. Herein, pH-responsive metformin drug delivery nanocarriers were achieved using sol-gel synthesized mesoporous silica nanospheres (MSN) uniformly coated with polydopamine (PDA) shell. The PDA coating shell around the MSN surface was in situ formed through oxidative self-polymerization of dopamine monomers in an alkaline solution at room temperature. The microstructure, structural and textural characteristics of PDA@MSN were examined and compared to uncoated MSN. Furthermore, PDA coated metformin (MET) drug-loaded MSN were used to study the pH-responsive MET drug release behaviour under neutral and acidic conditions. The in vitro release test showed that the PDA coating shell not only protects MET drug leakage under normal physiological conditions (pH 7.4) but also allows for its controlled/sustained release in acidic conditions (pH 4.5 and pH 5.5) which closely mimic the intracellular acidity (pH 4.5–5.5) of endosomes/lysosomes formed around drug-loaded nanocarriers after their endocytosis by cancer cells.

Cooperative sensitization upconversion of ex-situ sol-gel synthesized ZnO-SiO2: Nd3+/Yb3+ dense glass ceramic material under 980nm laser pumping

Herein, we use a modified ex-situ sol-gel synthesis route to prepare Zinc-Silicate (ZnO-SiO2:Nd3+/Yb3+) dense glass ceramic material. The Judd-Ofelt parameters were estimated from absorption spectra of the ZnO-SiO2:Nd3+/Yb3+ material. Upconversion luminescence (UCL) in the material was achieved due to the sensitization of Yb3+ ions through 980 nm diode laser excitation along with CIE 1931 chromaticity diagram to analyze the white light emission. PL confocal microscopy was used to confirm the spatially resolved PL of the material. Thus, the as-synthesized material demonstrates its viability by producing white luminescence across its surface when excited by a 980 nm diode laser, which could find potential applications in various photonic applications. TEM-EDS mapping of material was performed to visualize elemental doping of the material. The structural characterization of the material was studied with X-ray diffraction (XRD) analysis and FTIR spectroscopy to report invariance of ZnO-SiO2 host. The thorough removal of hydroxyl impurity (-OH) and the pyrolysis of zinc alkoxides were confirmed through thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis.

MWCNT@TiSiO4 nanocomposite for dispersive solid phase extraction of traces cadmium in food and environmental samples

Cadmium contamination presents substantial hazards to both human health and the environment due to its persistent presence in ecosystems and toxic characteristics. It accumulates in soil and water, causing chronic renal and respiratory issues, and carcinogenicity. Effective detection for monitoring the environmental and public health effects of Cd is required. This study addresses a new separation and enrichment method with a novel MWCNT@TiSiO4 nanocomposite synthesized via sol-gel and calcination synthesis techniques. A comprehensive characterization of the nanocomposite was conducted utilizing X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy, and Field Emission-Scanning Electron Microscopy (FE-SEM) techniques. The nano-sorbent was utilized in conjunction with dispersive solid phase extraction (DSPE) to separate and preconcentrate trace amounts of Cd(II) prior to its determination by using flame atomic absorption spectrometry (FAAS). The optimization of analytical parameters, including pH, sample and eluent volumes, sorbent quantities, and eluent composition, was studied. The effect of matrix components was investigated. The method showed a low limit of detection (LOD), limit of quantification (LOQ), and relative standard deviation (%RSD) of 0.053 ng mL−1, 0.176 ng mL−1, and 4.6%, respectively. The method was validated by analyzing certified reference materials. The developed methodology was applied to determine Cd(II) levels in water, tobacco, and food samples. The recovery values were quantitative (90–101%). The maximum and minimum concentrations of Cd in food samples were in shrimp (47.87 ng g−1) and lentil (11.25 ng g−1), respectively.

Enhancing dielectric properties of ZnO nanopowders with 2D hBN doping: production, structural, morphological and dielectric characterization

In this study, it was aimed to improve the dielectric properties of ZnO nanoparticles with the addition of hBN, which was not previously available in the literature, and thus to expand their usage areas. Sol–gel synthesis method was used in this study to create pure and hexagonal boron nitride (hBN) doped zinc oxide (ZnO) nanoparticles. Zinc acetate dihydrate Zn(CH3COO)22H2O), sodium hydroxide NaOH, and hexagonal boron nitride (hBN), all from Sigma Aldrich, were used as starting reagents. The reagents were dissolved during the sol–gel synthesis by being heated to 90 °C for 4 h in a magnetic stirrer. FT-IR, XRD, FE-SEM, EDX characterization techniques, and impedance analyzer were used to find functional groups, structural, morphological, and chemical composition, and dielectric properties of the nanoparticles, respectively. The produced un-doped and hBN-doped ZnO particles consist of nano-sized structures. Changes occurred in the intensities and locations of the XRD diffraction peaks and FT-IR peaks with the addition of hBN. Characteristic peaks of both ZnO and hBN were observed in the diffraction peaks of the doped nanoparticles. All nanoparticles were of high purity and were successfully produced by the sol–gel method. It was shown that as the hBN doping level increased, there were more hBN nanoplates in the ZnO matrix, and the EDX results also showed an increase in hBN addition. The frequency stability of the dielectric properties improved after hBN doping. While the dielectric constant at 1 kHz frequency at room temperature is 12.07 in pure ZnO nanoparticles, the increase up to 55.21 is observed in 10% hBN doped nanocomposites. This situation is considered as a great potential for technological applications of this novel nanocomposite material.

Synthesis and physico –chemical characteristics of complex ferriteCrNaFe2O5

The article discusses for the first time the synthesis, radiographic and electron microscopic examination of CrNaFe2O5, synthesized using the high – temperature Sol-gel method. The phase of complex ferrites was synthesized using Sol-Gel synthesis method at high temperature. Initially, the structure of CrNaFe2O5 composite ferrite was researched by X-ray phase analysis and SEM, the syngony type, elementary cell parameters, radiographic and pycnometric densities and elemental analysis were defined: CrNaFe2O5 -а=5.0289, в= 5.0289, с=13.6938 Å , ρx-ray.= 5.327 g/sm3 , ρpycn.=5.331 g/sm3. A comparative analysis of the connection between the parameters of the Crystal cell of the initial materials and of the obtained complex ferrites was carried out. Through a scanning electron microscope, microsystems were taken from different parts of CrNaFe2O5 type crystallite, the elemental composition of crystals was analyzed, and the general type of surface layer of complex ferrite was displayed. As a result, the fact that the compound consists of a single phase, the clarity of its construction was determined by the topography and chemical composition of the compound. Consequently, it was discovered that the newly synthesized complex ferrites correspond to the formula CrNaFe2O5. The particles of the formed compounds have a large size (between 200 µm, 20.0 µm and 5 µm). The results of the element analysis show that the compound is compatible.