Microwave Route Research Articles

An effective, facile, and rapid synthesis of nanosized Mn3O4 using a microwave route

An effective, facile, and rapid synthesis of nanosized Mn3O4 using a microwave route

Microwave construction of the 3D porous interconnected structure of NiCoCr medium-entropy alloy with ultra-high specific capacity for supercapacitors and electrocatalysis

The effective design of bifunctional electrodes with unique morphology and remarkable electrochemical properties for energy conversion and storage devices is a promising but challenging endeavor. Herein, self-supporting NiCoCr medium-entropy alloy (MEA) with a hierarchical porous network structure was in situ synthesized on nickel foam (NiCoCr/NF) by a simple and rapid microwave route. The optimal NiCoCr/NF presented an ultra-high specific capacity of 3011.8 C g−1 (1 A g−1) and outstanding charge/discharge sustainability (83.4% retention at 10 A g−1 over 50,000 cycles) due to its multi-component synergistic effect and hierarchical porous structure. Meanwhile, subtle lattice distortions and electron density redistribution in the NiCoCr MEA tuned electronic structures, resulting in a low overpotential and Tafel slope. Aqueous and solid-state asymmetric supercapacitors were fabricated by using NiCoCr/NF as a cathode and Bi/NF as an anode. The aqueous supercapacitor displayed an exceptional energy density of 314.4 Wh kg−1 at a power density of 800 W kg−1 with 81.8% retention at 10 A g−1 over 20,000 cycles. This study provides a new strategy for the efficient synthesis of electrode materials with interconnected network structures and paves the way for the broader application based on medium-entropy and high-entropy materials as promising candidates for future energy storage devices.

A facile route to synthesize β‐Ga2O3 nanoparticles from γ‐polymorph through a rapid microwave route and their optical properties

AbstractDue to the wide bandgap, monoclinic structure and thermodynamic stability, β‐polymorph form of Ga2O3 nanomaterials is well‐received for various applications. However, as the γ‐Ga2O3 is difficult to synthesize, less attention has been paid towards it and its conversion to β‐polymorph. This paper reports the single‐step synthesis of γ‐Ga2O3 using a microwave‐assisted procedure. In this regard, γ‐Ga2O3 powders are synthesized in minutes using benzyl alcohol as the solvent using gallium acetylacetone as the precursor. The XRD of the as‐prepared powders indicates the formation of the γ‐Ga2O3 phase, the very broad peaks indicative of the small crystallite size as confirmed by TEM. The γ‐Ga2O3 powders were annealed at different temperatures and the complete phase conversion of γ‐Ga2O3 phase to β‐Ga2O3 phase happens at 700 °C. The TEM analysis shows the crystallite size to be ≈10 nm for the annealed β‐Ga2O3 phase. The as‐prepared nanopowders show very weak luminescence under excitation and in contrast, a blue‐green emission is observed in case of annealed powders. This confirms the presented strategy as having the potential to use β‐Ga2O3 nanopowders for different optoelectronic applications.

Exploring the effects of synthesis parameters on the properties and photoactivity of WO3–graphene oxide synthesized via a microwave route

Tungsten oxide (WO3) is a promising material for photocatalysis.

Solid-phase microwave synthesis of high-entropy graphene quantum dots as metal-free electrochemical catalysts

In this study, high-entropy graphene quantum dots (GQDs) are synthesized and utilized as metal-free electrocatalysts for the oxygen reduction reaction (ORR) in alkaline electrolyte. An efficient solid-state microwave route was used to synthesize the GQD catalysts. This synthesis method involves the pyrolysis of two carbon precursors and four dopant precursors under a pulse microwave irradiation at 180 °C. The synthesized efficient catalyst possesses an average particle size of about 5 nm. The synthesized GQDs catalyst contains six elements in the graphite-like lattices with numerous surface functionalities and dopants. Synthesized high-entropy GQD catalytic electrodes displayed ultra-high electrochemically active surface area and endurance for the ORR measurements. The GQD electrode shows a well-defined reduction peak at ca. −0.5 V and an onset potential at ca. −0.1 V vs. saturated calomel electrode in the diluted potassium hydroxide solution. The heteroatom doping into the GQD nanostructure greatly increased the ORR catalytic activity. The above synthesized non-metallic and inexpensive catalyst showed remarkable properties such as enhanced catalytic activity, selectivity, and superior durability. Therefore, synthesized GQD electrodes have great potential for energy applications, especially for fuel cells.

Facile Hydrogenolysis of Sugars to 1,2-Glycols by Ru@PPh3/OPPh3 Confined Large-Pore Mesoporous Silica.

Tandem hydrogenation vis-à-vis hydrogenolysis of xylose to 1,2-glycols remains a major challenge. Although one-pot conversion of xylose to 1,2-glycols requires stringent conditions, a sustainable approach would be quite noteworthy. We have developed a microwave route for the one-pot conversion of pentose (C5) and hexose (C6) sugars into glycol and hexitol, without pressurized hydrogen reactors. A pronounced hydrogenolysis of sugars to glycols is observed by Ru single atom (SA) on triphenylphosphine/phosphine oxide-modified silica (Ru@SiP), in contrast to Ru SA on pristine (Ru@SiC) and 3-aminopropyl-modified silica (Ru@SiN). A promising "ligand effect" was observed through phosphine modification of silica that presents a 70% overall yield of all reduced sugars (xylitol + glycols) from a 99% conversion of xylose with Ru@SiP. A theoretical study by DFT depicts an electronic effect on Ru-SA by triphenylphosphine that promotes the catalytic hydrogenolysis of sugars under mild conditions. Hence, this research represents an important step for glycols from biomass-derived sources.

Sliding wear study of WC-10Co4Cr clad on SS-316 using microwave energy

The current study comprises the changing surface morphology of austenitic stainless steel (SS-316) with WC-10Co4Cr powder using an affordable microwave route. The surface modification was achieved by utilizing a microwave apparatus (power: 1.2 kW; frequency: 2.45 GHz). The x-ray diffraction (XRD) study reveals the presence of various carbide phases in the deposited clad layer. The scanning electron microscope (SEM) examination reveals the unequally dispersed reinforced skeleton carbide in a metal-based matrix with an average porosity of less than 1%. The deposits exhibit significantly higher hardness than that of the SS-316. A pin-on-disc tribometer was utilized to assess the dry sliding wear performance of deposits. The results revealed that the deposits exhibited better wear resistance than the SS-316 substrate due to the presence of reinforced hard carbides in a tougher metal-based matrix. The improvement in microhardness also leads to enhancement in the wear resistance of the deposits. The loss of material from the deposit surfaces during sliding was primarily due to micro-cutting and rupturing of the unstable tribofilm layer.

On the structural and optical characterization of zinc aluminate nanoparticles synthesized via green microwave route

Zinc aluminate, a widely employed wide bandgap semiconductor, boasts exceptional mechanical and thermal properties, coupled with a high quantum yield. Its versatile applications include photocatalytic pollutant degradation, utilization in displays, and contributions to the medicinal field. However, challenges arise during synthesis processes, where high-temperature annealing reduces nanoparticle surface area, and cation contamination from precursors impacts material purity. In response to these challenges, green synthesis methods incorporating plant extracts as reductants have emerged to yield higher-quality phosphors. In this study, the focus is on microwave synthesis of Zinc Aluminate using Zinc Nitrate and Aluminum Nitrate in varying ratios as precursors. Comprehensive structural and optical characterizations, including X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Diffuse Reflectance Spectroscopy (DRS), and Photoluminescence Spectroscopy (PL), have been conducted to assess the influence of precursor molar ratios on the spinel growth and optimization of the synthesis process.

Structural studies of molybdo-phosphate glasses doped with Zn2+ and Cl- ions

Molybdo – Phosphate glasses with a chemical formula xMoO3-15ZnO-2 PbCl2-(83-x) NaPO3 doped with Zn2+ and Cl- ions has been synthesized by microwave route. The vitreous system is studied for the structural evolution using Infra-Red Spectra. The modulated DSC of the investigated samples shows strong composition dependent trends. Glass transition temperatures (Tg) extracted from DSC lies between 593 K and 647 K and it increases with MoO3 content. Addition of MoO3 replaces weaker linkages like P-O-P by stronger Mo-O-P and Mo-O-Mo linkages. The variation of Tg can be understood in terms of the structural groupings, cross- link density and bond strength of the glass network forming units. To verify the variation to the presence of Na2O creates several structural units. Density of the glass samples increases with the concentration of MoO3. Tg, density and molar volume of the glass samples were also observed. Analysis of the Structural investigations have been carried out using Infra-Red Spectra to study the network modification that reveals the structure of molybdo-phosphate glass network made of corner shared tetrahedral [POO3/2]0 and octahedral [MoO4/2]- units.

Rapid microwave fabrication of new nanocomposites based on Tb-Co-O nanostructures and their application as photocatalysts under UV/Visible light for removal of organic pollutants in water

Herein, a novel and stable Tb-Co-O nanocomposite photocatalyst is fabricated through a one-pot microwave route for 2 min (600 W, 20 s On, 60 s Off), which is introduced as UV/Visible light active catalysts in wastewater treatment. Employing various combined parameters of Tb:Co ratio, pH adjustment agents, chemical and natural templates, the resulting nanostructures displayed the intrinsic structure nature, narrow size distribution, good optical properties, and excellent photocatalytic efficiency. The formation of Tb-Co-O nanostructures and their features were verified via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and ultraviolet–visible diffuse reflection spectroscopy (DRS) technologies. Detailed physic-chemical measurements exhibited that all as-prepared nano-photocatalysts possesses both cubic (TbO1.81) and orthorhombic (TbCoO3) crystal structures. Furthermore, optical characterization by DRS developed light-sensitive channelization with band-gap energies at approximately 2.95 and 3.20 eV for Tb-Co-O nanocomposites. Finally, the photocatalytic studies of the resulting nanocomposites were compared by determining the elimination of Erythrosine (EY), Acid Violet 7 (AV7), and Acid Black 1(AB1) under UV and Visble light illumination. As a results, the TbCoO3/TbO1.81 nanocomposties with molar ratio of 1:3 (Tb:Co), valerian distillate as natural directing agent and ethylenediamine (en) as alkaline template yielded the optimum degradation percentage of 88 % for EY dye under the reaction condition of 10 ppm dye concentration in the presence UV light toward other pathways. Also, we proposed a mechanistic insight of photodegradation based on the radical scavengers, which revealed that h+ did the important role, and OH• and •O2− represented an irrelevant role in the degradation of EY. The current study offer an effective way for development of a high-efficiency Tb-Co-O photocatalyst in eliminating dyes from contaminant water.

MICROWAVE IRRADIATION SYNTHESIS OF NITROGENDOPED Ag/MWCNT/ZnO NANOCOMPOSITE FOR PHOTOCATALYTIC APPLICATION

In this proposed research work, Zinc oxide is fabricated with carbon nanotubes, nitrogen, and silver. The conclusion of the distinctive hybrid of dopants on the ZnO/MWCNT nanocomposite was studied. Acidic and basic nature dyes are used to check the efficiency of the composite photocatalyst. The hydrothermal & microwave route was adapted for combining mesoporous nanocomposite samples. The XRD analysis confirmed the information to the nanoscale crystal with the hexagonal dimension of ZnO. The observation of UV-vis spectra validates its photocatalytic competency in the visible beam as an outcome of the reduction in the bandgap energy. The proficiency of the photocatalyst was additionally entrenched over the axing in electron-hole recombination activity referring to dwindling PL intensity. The BET inspection supports the mesoporous structures of the samples. The SEM micrograph revealed the existence of agglomeration in nanoparticles with MWCNT while the perusal of TEM images established the existence of a 16–24 nm diameter of the MWCNT. Furthermore, the EDX analysis confirmed the presence of the Zn, N, O, Ag, and C.

Electrochemical behaviour and biocompatibility of claddings developed using microwave route

In recent years many different biomedical implants have been created for prolonged usage within the human body. The number of these implants has been steadily expanding. Mechanical characteristics of biomaterials, such as elastic modulus, hardness, tensile strength, and scratch resistance, are essential for implants. Biomechanical incompatibility is associated with implant fracture brought on by mechanical failure. The materials utilized to replace bone must have mechanical qualities comparable to those of bone. Metallic implants deteriorate due to wear, electrochemical breakdown, or a synergistic mix of the two. Biocompatible materials are used to repair or replace joints, fractured, or otherwise damaged bone. Corrosion is the main factor in hip implant failure. These characteristics also contain several other factors, such as solution factors, geometric factors, metallurgical factors, and mechanical factors. The mechanical properties of the implant materials were most important and had a considerable impact on the process of bone restoration. Metals have the highest tensile strength compared to other materials, followed by polymers and ceramics (except for zirconia). There are several issues with the metallic biomaterial that need to be fixed, including the release of harmful substances during metallic corrosion.

Development of Radiosterilized Porcine Skin Electrosprayed with Silver Nanoparticles Prevents Infections in Deep Burns.

Extensive burns represent a significant challenge in biomedicine due to the multiple systemic and localized complications resulting from the major skin barrier loss. The functionalization of xenografts with nanostructured antibacterial agents proposes a fast and accessible application to restore barrier function and prevent localized bacterial contamination. Based on this, the objective of this work was to functionalize a xenograft by electrospray deposition with silver nanoparticles (AgNPs) and to evaluate its antibiofilm and cytotoxic effects on human fibroblasts. Initially, AgNPs were synthesized by a green microwave route with sizes of 2.1, 6.8, and 12.2 nm and concentrations of 0.055, 0.167, and 0.500 M, respectively. The AgNPs showed a size relationship directly proportional to the concentration of AgNO3, with a spherical and homogeneous distribution determined by high-resolution transmission electron microscopy. The surface functionalization of radiosterilized porcine skin (RPS) via electrospray deposition with the three AgNP concentrations (0.055, 0.167, and 0.500 M) in the epidermis and the dermis showed a uniform distribution on both surfaces by energy-dispersive X-ray spectroscopy. The antibiofilm assays of clinical multidrug-resistant Pseudomonas aeruginosa showed significant effects at the concentrations of 0.167 and 0.500 M, with a log reduction of 1.3 and 2.6, respectively. Additionally, viability experiments with human dermal fibroblasts (HDF) exposed to AgNPs released from functionalized porcine skin showed favorable tolerance, with retention of viability more significant than 90% for concentrations of 0.05 and 0.167 M after 24 h exposure. Antibacterial activity combined with excellent biocompatibility makes this biomaterial a candidate for antibacterial protection by inhibiting bacterial biofilms in deep burns during early stages of development.

Highly efficient RuTe2/C electrocatalyst for oxygen reduction reaction in proton exchange membrane fuel cells

It is desirable but challenging for ruthenium (Ru)-based chalcogenides to achieve high activity and good durability toward oxygen reduction reaction (ORR) in fuel cell applications. In this work, a facile microwave route followed by heat treatment was utilized to synthesize carbon supported ruthenium tellurium (RuTe2/C) catalysts, and the effects of heat treatment temperature on crystal structure, microstructure, chemical state, electrocatalytic activity, and fuel cell performance were studied. The mixed phase of predominant orthorhombic RuTe2 and minor hexagonal Ru was identified as dual active sites for RuTe2/C catalysts. Density functional theory calculations demonstrated that orthorhombic RuTe2 exhibits enhanced intrinsic activity relative to pure Ru due to the weakened absorption energies of oxygen intermediates. Because of the smallest nanoparticle size and complete formation of an orthorhombic RuTe2 structure, the best ORR performance was achieved with the RuTe2/C catalyst heat treated at 400 °C, showing a maximum half-wave potential of 0.70 V and only a 70 mV drop (10.0% loss) after 6000 potential cycles. In a H2/O2 fuel cell test, the best-performed RuTe2/C catalyst delivered a maximum power density of 672 mW⋅cm−2 using a low cathode Ru loading of 0.18 mg·cm−2, which is the best performance ever achieved for the Ru-based catalysts. After 6000 cycles of rigorous accelerated degradation test, the cell performance decayed by 55.4% because of the migrations of Te and Ru from the cathode side to the anode side and the growth of the RuTe2/C nanoparticles.

A novel approach based on the ultrasonic-assisted microwave method for the efficient synthesis of Sc-MOF@SiO2 core/shell nanostructures for H2S gas adsorption: A controllable systematic study for a green future.

In this work, for the first time, novel Sc-MOF@SiO2 core/shell nanostructures have been synthesized under the optimal conditions of ultrasonic-assisted microwave routes. The final products showed small particle size distributions with homogeneous morphology (SEM results), high thermal stability (TG curve), high surface area (BET adsorption/desorption techniques), and significant porosity (BJH method). The final nanostructures of Sc-MOF@SiO2 core/shell with such distinct properties were used as a new compound for H2S adsorption. It was used with the systematic investigation based on a 2K−1 factorial design, which showed high-performance adsorption of about 5 mmol/g for these novel adsorbents; the optimal experimental conditions included pressure, 1.5 bar; contact time, 20 min; and temperature, 20°C. This study and its results promise a green future for the potential control of gas pollutants.

Effect of sintering routes on CIP/EIP – Al2O3 composite magnetic abrasive for chemo-mechanical magneto-rheological finishing of aluminium 6061

In magnetorheological fluid-based finishing processes, the lower gripping of abrasives in between ferromagnetic particle’s chain structure limits its finishing speed, resulting in a lower material removal rate and desired surface standard. In addition, tool ageing has significantly impacted these finishing processes at a higher speed. To improve the efficiency of finishing processes, composite magnetic abrasives are fabricated by using powder metallurgy techniques via both microwave and conventional processing (sintering) routes. Comparison studies were performed on these samples based on ferromagnetic materials (CIPs and EIPs) used and sintering at 950°C under fixed element composition. A newly advanced chemo-mechanical magneto-rheological finishing (CMMRF) process for aluminium alloy surface polishing was also proposed, combining mechanical abrasion and chemical action for the performance evaluation of composite magnetic abrasives. Most notably, the microwave processed composite magnetic abrasive outperformed conventionally processed samples in terms of magnetic and rheological properties. The composite magnetic abrasives significantly increased the rate of material removal from the metal surface while reducing the tool ageing effect. The surface profile and observation show that a nearly defect-free surface was produced at higher speeds using these composite magnetic abrasives compared to simply mixed abrasives based results.

Amorphous Iron Phosphate: Inorganic Sol-Gel Synthesis-Sodium and Potassium Insertion

Amorphous iron phosphate, FePO4.2H2O, was synthesized at ambient temperature using an inorganic sol-gel method coupled with a microwave route. The experimental conditions for the gelling of the Fe (III)-H3PO4 system are defined. Potentiometric Time Titration (PTT) and Potentiometric Mass Titration (PMT) methods were used to investigate the acid-base surface chemistry of obtained phosphate. Variations of surface charge with the contact time, Q = f(t), are examined for time contact ranged from 0 to 72 hours. The concentrations suspensions used for this purpose were 0.75, 1.25, and 2.5 g/L. The point of zero charges (PZC) and isoelectric point (IEP) were defined using the derivative method examining the variations , at lower contact time. A value of 5.4 was obtained for both PZC and IEP. Q in the function of the t method is performed for synthesized FePO4. 2H2O in NaCl and KCl electrolytes. The optimal surface charge of 40 C corresponding to insertion of 4.2x10-4 M of Na+ or K+, is achieved in explored conditions. The results suggest that the synthesized iron phosphate is amorphous.

Synthesis of Sn and Zr‐Doped BiVO4 Nanocatalyst with Enhanced Photocatalytic and Photoelectrochemical Activity

AbstractHerein, a facile microwave route to synthesized of Tin (Sn) and Zirconium (Zr) doped BiVO4 with enhanced photocatalytic and photoelectrochemical performance are demonstrated. X‐ray diffraction (XRD) studies confirmed the monoclinic‐tetragonal structure of metal doped BiVO4. Field Emission Scanning Electron Microscopy (FE‐SEM) images confirmed the sphere like morphology while bare is in floral structure. The Raman (RS) and Fourier Transform Infra‐Red (FT‐IR) Spectroscopy indicate the functional group of composition. Photoluminance (PL) spectroscopy revealed that the doped BiVO4 showed better excitation then the bare BiVO4. The UV‐Visible diffused reflectance (UV‐vis‐DRS) spectroscopy exposed improved visible light driven by narrow band gap of metal doped BiVO4. Further Electrochemical impedance spectroscopy (EIS) and Linear Sweep voltammetry characterization (LSV) report that the metal doped BiVO4 established better photoelectrochemical activity in water splitting. The impact of metal doping in the crystallinity, optical properties, electrical properties and photocatalytic activity were evaluated using model pollutant of azo dyes and gaseous acetaldehyde under visible light irradiation. The Zr doped BiVO4 exhibit better performance for degradation of dyes, acetaldehyde decomposition and water splitting properties then the Sn doped BiVO4 and bare BiVO4. This work founds that the metal doping with semiconductor is effective in creating heterostructured nanomaterials, which result in reduce the recombination processes, leading to improved photocatalytic and photoelectrochemical performance.

Facile microwave route for the synthesis of CuS/CQDs/g-C3N4NS as a novel promising cathodic electrochemiluminescence detection of imidacloprid

Facile microwave route for the synthesis of CuS/CQDs/g-C3N4NS as a novel promising cathodic electrochemiluminescence detection of imidacloprid

Analysis of heating uniformity considering microwave transmission in stacked bulk of granular materials on a turntable in microwave ovens

Heating uniformity inside materials, as a concerned issue of microwave processing, influences essentially the energy utilization of microwave equipment and desired quality of the final product. For the microwave drying of granular materials like germinated brown rice (GBR) on a turntable in microwave ovens, the mode and route of microwave transmission considering sample rotation and the existence of pores inside GBR stacked bulk were investigated, and further to analyze the heating uniformity. The developed physics-based model and simulation strategy can describe microwave drying of GBR stacked bulk. The edge diffraction and uneven surface reflection for the stacked bulk of GBR dominates the transmission of microwaves. Under the fixed magnetron arrangement, same microwave input power and geometry shape of the sample, the absorption of microwave energy inside GBR stacked bulk mainly relies on the changes in dielectric properties of materials other than those of the electric field. The absorption of microwave energy in GBR stacked bulk greatly dominates the uniformity of temperature distribution. Rotation improves the uniformity of temperature distribution along with equatorial other than radial direction for GBR stacked bulk on a turntable under microwave drying. Sensitivity analysis indicated that increasing rotating speed of the sample has little effect on the heating uniformity as beyond a certain value of 5 circles per minute, and a low bed porosity for GBR stacked bulk relatively improve the heating uniformity, but temperature uniformity is relatively not sensitive to the capillary diffusivity. Research results may enhance understanding of the interaction between microwaves and the stacked bulk of granular materials like GBR with porosity. • Rotation improves uniformity of temperature distribution along equatorial other than radial direction for GBR stacked bulk. • The edge diffraction and uneven surface reflection for the stacked bulk of GBR dominate the transmission of microwaves. • The effects of rotation speed and porosity on heating uniformity in GBR stacked bulk were explored by sensitivity analysis.