Simple Combustion Route Research Articles

Facile synthesis of boron doped NiCu2O4 for efficient methanol oxidation: Selective towards value-added formate formation

The design and development of low-cost non-noble metal electrocatalysts with superior activity towards methanol oxidation reaction are highly demanded. Herein, we demonstrate simple combustion route to synthesis NiCu2O4 electrocatalyst and the electronic structure of NiCu2O4 was deliberately tuned via doping boron heteroatom. The trace amounts of boron are atomically dispersed on the surface of the NiCu2O4 that helps in achieving highest current density of 73 mA/cm2, which is ∼2 fold higher than pristine catalyst. Unlike other noble metals, B/NiCu2O4 possess partial oxidation via indirect pathway and selective towards formate formation as demonstrated by NMR spectra and Nyquist plot. Interestingly, NiCu2O4 exhibits faradaic efficiency of 36% This work might be new insight for designing non-noble metals-based methanol oxidation via value added product.

Chemical activation of nanocrystalline LiNbO3 anode for improved storage capacity in lithium-ion batteries

It has become imperative to move forward towards developing and engineering highly active electrode materials with high electrochemical performance for rechargeable lithium-ion batteries. In this perspective, a highly efficient LiNbO3 (LNO) perovskite anode material has been successfully prepared from tartarate precursor via simple combustion route and chemically activated via acid treatment with 35% HClO4 acid for the first time. The synthesis process was systematically monitored by thermal gravimetric/differential thermal analyses (TGA/DTA) and X-ray diffraction (XRD). The chemical activation of the as-prepared LNO leads to a significant expansion in the lattice parameters and cell volumes as well as a noticeable reduction in the crystallite size as a result of Li-deficiency and O-vacancies creation. The surface characterization was sufficiently performed by field emission scanning electron microscope (FESEM) and X-ray photoelectron spectroscopy (XPS) techniques. XPS results for LNO-activated sample elucidated the presence of Nb4+/Nb5+ ions and revealed the existence of oxygen vacancies. The reduced band gap energy (Eg ∼ 3.95 eV) and low value of activation energy of conduction (Ea ∼ 0.35 eV) for LNO-activated sample confirmed the improved electronic connectivity for the bulk electrode material after chemical activation process. Galvanostatic cycling of LNO-activated anode material revealed an eminent enhancement in the initial specific discharge capacity of about 17.7% upon cycling at 100 mA.g−1 and high capacity retention of about 92 mAhg−1 after 200 cycles. The cyclic performance tests at different current densities 50, 150, 300 and 50 mAg−1 for the activated LNO anode showed excellent rate capability and high capacity retention of about 88.5% of the original capacity after returning to 50 mA.g−1 over 60 cycles. Electrochemical impedance spectroscopy (EIS) measurements confirmed the reduced charge transfer resistance and improved Li+ ions conductivity of the LNO anode after chemical activation.

Removal of Evans Blue dye from aqueous solution using magnetic spinel ZnFe2O4 nanomaterial: Adsorption isotherms and kinetics

Magnetic nano crystalline ZnFe2O4 was successfully synthesized by simple combustion route using oxalyldihydrazine as fuel and the material formed was characterized by powder X-ray diffraction, Fourier transform infra-red spectroscopy and scanning electron microscope. Surface area measurements (90.004 m2 g−1) were done using Brunauer–Emmett–Teller analysis. Magnetic measurements done using vibrating sample magnetometer shows that ZnFe2O4 nanoparticle is superparamagnetic. Adsorption capability of the as prepared nanospinel ZnFe2O4 was measured for the removal of Evans Blue, an anionic dye by batch adsorption process. Parameters like adsorbent loading, initial dye concentration and stirring effects were carried out at neutral pH and room temperature. Spinel ZnFe2O4 nanoparticles showed good adsorptive capacity and the maximum monolayer coverage (Q0) was determined as 46 mg/g of the adsorbent. The data were analyzed by three different kinetic models viz; Lagergren pseudo first order, pseudo second order and Intraparticle diffusion models and by various isotherm models like Langmuir, Freundlich and Temkin models to study the mechanism of adsorption process. Kinetic study shows that it follows pseudo second order with highest R 2=0.998 and the rate determining step was found to be intraparticle diffusion. Isotherm studies shows that the adsorption of EB is highly favorable and the value of Temkin constant, AT = 0.5445 and heat of adsorption, B = 14 J/mol indicates that the adsorption process is exothermic and physical in nature.

Enhancing saturation magnetization of Mg ferrite nanoparticles for better magnetic recoverable photocatalyst

Simple combustion route was implemented for the preparation of Mo-substituted magnesium ferrite nanoparticles; MgFe2−2xMoxO4 (x = 0.0, 0.1, 0.2 and 0.3). Samples, with x = 0.0, 0.1 and 0.2, revealed only the cubic spinel ferrite phase. Sample with x = 0.3 showed very small amount of FeMoO4, beside MgFe2O4. The lattice parameter diminished with increasing molybdenum contents to x = 0.1, then increased at x ≥ 0.2. The saturation magnetization (Ms) increased from 15.65 to 32.05 emu/g with low level of Mo6+ substitution (x = 0.1), then declined with x > 0.1. This is the first investigation to report Ms of Mg ferrite nanoparticles higher than its bulk value. The change in magnetic properties is correlated with cation distribution between tetrahedral sites (A) and octahedral sites (B). Mo6+ replaced the Fe3+ position in the tetrahedral A-sites for x = 0.1. In samples with x ≥ 0.2, Mo6+ occupied both A-sites and B-sites. Mo substitution decreased the crystallite size and increased the microstrain. Mo substitution in MgFe2O4 enhanced the photocatalytic action compared to bare MgFe2O4. The enhancement was due to the increase in structure defect that inhibits the electrons–holes recombination as well as the increase in surface area.

Narrowband ultraviolet B emitting Gd doped CaAl2O4 phosphors – An ESR and photoluminescence study

Phosphors with the composition Ca1-xGdxAl2O4 (x = 0.0025–0.09) were synthesized by a simple combustion route in a short time. The formation of the as-prepared combustion products was confirmed by the X-ray diffraction analysis, indicating the formation of a monoclinic phase. The PL spectroscopy assessment shows that with increasing Gd3+ concentration, the ultraviolet emission from Gd3+ at 314 nm (6P7/2→8S7/2) progressively enhanced. The Gd3+-doped CaAl2O4 displays electron spin resonance signals with the effective g values at g ≈ 1.95, 2.9, and 3.7. Additional lines were also observed at the approximate g values of ~2.2 and 5.3. Gd3+ ion located in the distorted surroundings and experiencing relatively strong crystal field, give rise to low field lines. Distorted surroundings in the present system may result from the nearness of the charge compensator oxygen vacancies.

Rapid visualization of fingerprints on various surfaces using ZnO superstructures prepared via simple combustion route

Abstract A simple solution combustion route has been used to prepare ZnO nanopowders (NPs) using different barbiturates (Barbituric acid, 1, 3-dimethyl barbiturates and 2-thiobarbiturates) as fuels. The obtained product was well characterized by powder X-ray diffraction (PXRD), scanning electron microscope (SEM), ultraviolet-visible Spectroscope (UV-Vis) and Photoluminescence (PL). The PXRD results confirm the hexagonal phase of the material. The detailed structural analysis is performed by Rietveld refinement method. The energy band gap of NPs is found to be in the range of 3.31 - 3.49 eV. The growth mechanism for the formation of 3D micro-architectures is discussed in detail. The PL emission spectrum shows a broad emission peak at 502 nm upon an 406 nm excitation wavelength. The ZnO NPs can be used for the visualization of latent finger prints (LFPs) under normal light on various porous and non-porous surfaces. In this case, the visualized LFPs are found to be excellent compared to the commercially available powders.

Thermodynamic and magnetic properties of Fe doped CaAl12O19 material prepared by combustion route and post-heat treatment

Fe-doped CaAl12O19 was prepared via a simple combustion route. The formation of the as-prepared and post-heated combustion products was confirmed using an XRD analysis. The EPR spectrum of this sample exhibited a number of resonance signals. The paramagnetic centers have been quantified at different g factors in the range of 19.3–1.14. These resonance signals are attributed to pairs of Fe3+ ions. The resonance signal at a g value of ~ 4.2 is attributed to the axial-symmetry tetrahedral site. The resonance signal at a g value of ~ 2.0 is attributed to the presence of Fe3+ ions in an axial-symmetry octahedral site. The EPR parameters of the post-heated CaAl12O19:Fe3+ sample at room temperature and 110 K were calculated and compared.

Luminescence and electron paramagnetic resonance investigation on ultraviolet emitting Gd doped MgAl2O4 phosphors

Phosphor powders of Gd doped MgAl2O4 have been prepared by a simple combustion route in a short time of 5min. Powder X-ray diffraction, scanning electron microscope and energy dispersive analysis of X-ray techniques were used to characterize the as-prepared combustion product. The luminescence of Gd3+ doped MgAl2O4 shows two emission bands centered at 306nm (6P5/2→8S7/2) and 312nm (6P7/2→8S7/2), under UV light excitation (273nm). Electron Paramagnetic Resonance (EPR) spectra reveal the U spectrum which is typical for Gd3+ ions disposed in tetrahedral, octahedral or cubic symmetry with moderate distortion. The number of spins, Gibbs energy, magnetic susceptibility, Curie constant and effective magnetic moment values are determined at 110 and 296K. The linewidth is found to increase with the decrease of temperature and this has been attributed to spin–spin interaction.

Synthesis and improved electrochemical performance of LiCo1‐xSnxO2 (x= 0 to 0.1) powders

AbstractLayered intercalation compounds LiCo1‐xSnxO2 (x= 0 to 0.1) have been prepared using a simple combustion route method. X‐ray diffraction patterns and Laser Raman spectrum suggest that the synthesized materials had the R‐3m structure. Scanning electron images show that particles are well‐crystallized with a size distribution in the range of 50‐100 nm. The room temperature electrical conductivity of the sample increased with Sn content. For LiCo1‐xSnxO2(x = 0, 0.01, 0.03, 0.05 and 0.1), the first discharge capacity increased with increase in Sn content. Among these samples, LiCo0.95Sn0.05O2had produced the best performance of all others with a stable reversible capacity of 186 mAhg‐1 after 30 cycles. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Preparation and photoluminescence characteristics of Eu 3+-doped MgAl 1.8Y 0.2O 4 nanocrystals

A simple combustion route was employed for the preparation of Eu 3+-doped MgAl 1.8Y 0.2− x O 4 nanocrystals using metal nitrates as precursors and urea as a fuel in a preheated furnace at 500 °C. The powders thus obtained were then fired at 1000 °C for 3 h to get better luminescent properties. The incorporation of Eu 3+ activator in these nanocrystals was checked by luminescence characteristics. These nanocrystals displayed bright red color on excitation under 254 nm UV source. The main emission peak was assigned to the transition [ 5D 0→ 7F 2] at 615 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies were carried out to understand surface morphological features and the particle size. Crystal structures of the nanocrystals were investigated by the X-ray diffraction (XRD) technique. The crystallite size of the as-prepared nanocrystals was around 29 nm, which was evaluated from the broad XRD peaks. The crystallite size increased to ∼45 nm on further heat treatment at 1000 °C.

A novel and simple combustion route towards long legs nanotetrapod ZnO

The long legs nanotetrapod ZnO was synthesized by a novel combustion oxidization method without any catalyst or carrier gas at high temperature, different completely from any other thermal evaporation method. SEM and transmission electron microscopy (TEM) investigations show that the long legs nanotetrapod ZnO is high-quality single crystal. The as-synthesized product is high yield with the legs length of about 30–50 μm. Interestingly, these long legs of different nanotetrapod could be connected to each other via self-assembly under proper condition. The possible growth mechanism is discussed in detail.