Results 1 - 10 of 15
Results 1 - 10 of 15. Search took: 0.017 seconds
|Sort by: date | relevance|
[en] Highlights: • Simple route for the preparation of nickel aluminate. • NiAl2O4 microwave absorbent was invented by a simple method. • High specific surface area was obtained at low temperature. • Evaluation of magnetic, optical and catalytic properties. - Abstract: Microwave combustion method (MCM) is a direct method to synthesize NiAl2O4 nanoparticles and for the first time we report the using of Sesame (Sesame indicum L.) plant extract in the present study. Solutions of metal nitrates and plant extract as a gelling agent are subsequently combusted using microwave. The structure and morphology of NiAl2O4 nanoparticles are investigated by X-ray diffraction (XRD), Fourier transforms infrared spectra (FT-IR), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), high resolution transmission electron microscopy (HR-TEM), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy, Brunauer–Emmett–Teller (BET) analysis and vibrating sample magnetometer (VSM). XRD pattern confirmed the formation of cubic phase NiAl2O4. The formation of NiAl2O4 is also confirmed by FT-IR. The formation of NiAl2O4 nanoparticles is confirmed by HR-SEM and HR-TEM. Furthermore, the microwave combustion leads to the formation of fine particles with uniform morphology. The magnetic properties of the synthesized NiAl2O4 nano and microstructures were investigated by vibrating sample magnetometer (VSM) and their hysteresis loops were obtained at room temperature. Further, NiAl2O4 prepared by MCM using Sesame (S. indicum L.) plant extract is tested for the catalytic activity toward the oxidation of benzyl alcohol
[en] Graphical abstract: A simple and rapid microwave-assisted combustion method was developed to synthesize MgO. The formation of novel MgO nanosheets structure was confirmed by HR-SEM and TEM. For the purpose of comparison, MgO was also prepared using conventional combustion route. The optical absorption and photoluminescence emissions were determined by DRS and PL spectra respectively. (a) SEM and (b) TEM images of MgO nanosheets. Highlights: → MgO nanosheets structure was synthesised by a simple microwave-assisted combustion method for the first time. → The as-synthesized MgO nanosheets and micro cubes were found to have good optical properties. → An attempt has been made to compare the lattice parameter and the PL intensity. - Abstract: Magnesium oxide (MgO) was synthesised by a simple microwave-assisted combustion route without using any template, catalyst or surfactant. For the purpose of comparison, it was also prepared using conventional method. The as-synthesized MgO was characterized by powder X-ray diffraction (XRD), Fourier Transform infrared spectra (FT-IR), high resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), Energy Dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS) and Photoluminescence (PL) spectroscopy. The XRD results confirmed the formation of cubic phase MgO. FT-IR was used to investigate the adsorption of water and CO2 on MgO surface and confirm the formation of Mg-O phase. The formation of MgO micro cubes structures was confirmed by HR-SEM. The formation of MgO nanosheets was confirmed by HR-SEM and TEM and their possible formation mechanisms were also proposed. The optical absorption and photoluminescence emissions were determined by DRS and PL spectra respectively. An attempt has been made to compare the lattice parameter and the PL intensity.
[en] In this study, the electronic structure of V-doped ZnO system is studied by means of density functional theory. Different concentrations of V and rising of Fermi level increase the relative occupation of majority/minority spin of 3d state and also induce strong spin-splitting. The existence of three different states of V spin moment has been confirmed and is found to be concentration dependent. We found that O p-orbitals are responsible for the origin of the magnetic moment. Ruderman–Kittel–Kasuya–Yosida mechanism and the atomic spin polarization of V are the key factors for the appearance of ferromagnetism in V-doped ZnO system. The synthesized nanoparticles exhibit hexagonal wurtzite crystal structure, where both crystallite size and lattice parameters vary with V content. Magnetic measurements at room temperature confirm the ferromagnetic behaviour of V-doped ZnO system.
[en] Highlights: • Solid leather waste was used as a precursor for preparing HPCs—waste to energy storage. • The textural, structural and morphological properties show the hierarchical porous nature. • Porous carbon with surface area 716 m"2/g and pore volume 0.4030 cm"3/g has been produced. • HPCs based supercapacitor electrodes are fabricated with three electrode system in 1 M KCl. • Specific capacitance of 1960 F/g is achieved at scan rate of 1 mV/s in 1 M KCl. - Abstract: Utilization of crust leather waste (CLW) as precursors for the preparation of hierarchical porous carbons (HPC) were investigated. HPCs were prepared from CLW by pre-carbonization followed by chemical activation using KOH at relatively high temperatures. Textural properties of HPC’s showed an extent of micro-and mesoporosity with maximum BET surface area of 716 m"2/g. Inducements of graphitic planes in leather waste derived carbons were observed from X-ray diffraction and HR-TEM analysis. Microstructure, thermal behavior and surface functional groups were identified using FT-Raman, thermo gravimetric analysis and FT-IR techniques. HPCs were evaluated for electrochemical properties by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) by three electrode system. CLC9 sample showed a maximum capacitance of 1960 F/g in 1 M KCl electrolyte. Results achieved from rectangular curves of CV, GCD symmetric curves and Nyquist plots show that the leather waste carbon is suitable to fabricate supercapacitors as it possess high specific capacitance and electrochemical cycle stability. The present study proposes an effective method for solid waste management in leather industry by the way of converting toxic leather waste to new graphitic porous carbonaceous materials as a potential candidate for energy storage devices.
[en] Highlights: ► A modified sol–gel method for the preparation of nano CuAl2O4 spinel using ethylenediamine was studied. ► Role of ethylenediamine in enhancing the structural, electrical, optical and catalytic properties of copper aluminate is highlighted. ► Effect of preparation method on the activity and selectivity of the samples on the oxidation of benzyl alcohol by CuAl2O4 is studied. - Abstract: The effect of ethylenediamine addition in the sol–gel method for the preparation of nano CuAl2O4 spinel for the enhancement in their structural, electrical, optical and catalytic properties was investigated. The samples were prepared by two different methods: sol–gel and modified sol–gel technique using ethylenediamine. X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM), high resolution-transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), nitrogen adsorption/desorption isotherms, temperature dependent conductance measurements, thermoelectric power (TEP) measurements and UV–visible diffuse reflectance (UV–vis-DRS) spectra were used to characterize the samples prepared. CuAl2O4 prepared by modified sol–gel technique was found to possess a higher surface area, lower crystallite size, lower activation energy and high porosity than the one prepared by sol–gel method which in turn lead to the improved performance of it towards the selective oxidation of benzyl alcohol to benzaldehyde. Effect of solvent on the catalytic oxidation of benzyl alcohol by the nano CuAl2O4 prepared by modified sol–gel technique was also investigated.
[en] The objective of this investigation is to evaluate the electrical conductivity of activated carbon derived from rice husk (RHAC) by a two-stage process. dc conductivity measurements by two-probe method were determined for RHAC samples prepared at 700, 800 and 900 deg. C. The samples were compressed in the pressure range 75.9-578.2 kPa in a hollow glass cylinder using two metal plungers connected to a Keithley ammeter. The conductivity at room temperature was found to increase from 3.28 x 10-4 to 2.02 x 10-3 S cm-1 for increase in compression pressure. Dense packing of the material, collapse of pores and decrease in air gap between the carbon particles could be the factors for the increase in conductivity with compression pressures. The temperature-dependent conductivity of RHAC samples were determined by compressing the sample within the metal plungers, followed by heating in a tubular furnace. A K-type thermocouple whose hot junction was located in close proximity to the specimen, was used to monitor the temperature accurately. The specimen inside the furnace was heated by a microprocessor-controlled programmer up to 250 deg. C. The temperature-dependent conductivity study conducted for the samples activated at 700, 800 and 900 deg. C, revealed that the energy gap value of the samples were 0.1023, 0.0745 and 0.052 eV respectively, determined from the linear plot of ln I versus 1/T (K-1). The mesoporous RHAC samples were characterized using electron spin resonance, FT-IR spectroscopy and X-ray diffraction for quantitative evaluation of free electrons, functional groups and crystallites to support the mechanism of electrical conduction in mesoporous nonsinterable carbon samples
[en] Highlights: • We report the synthesis of CoFe2O4 nanoparticles using Okra plant gel as a reducing agent. • Simple green synthetic route based on “localized” microwave heating to synthesize nanoparticles. • High purity single phase CoFe2O4 nanoparticles are reported.
[en] Copper-strontium-aluminum mixed metal oxide composites prepared by sol-gel technique was investigated for humidity sensing properties. X-ray diffraction, scanning electron microscopy (SEM), FT-IR spectroscopy and nitrogen adsorption/desorption isotherm at 77 K was employed, respectively, to identify the structural phases, surface morphology, vibrational stretching frequencies and BET surface area of the composites. The composites were prepared with the mole ratios of Cu:Sr as (0.0:1.0, 0.2:0.8, 0.4:06, 0.6:0.4, 0.8:0.2 and 1.0:0.0) keeping the aluminium mole ratio as constant and were labeled as CuSA1, CuSA2, CuSA3, CuSA4, CuSA5 and CuSA6, respectively. The samples sintered at 900 deg. C for 5 h, were subjected to dc resistance measurements as a function of relative humidity (RH) in the range 5-98% and the results revealed that the sensitivity factor of CuSA5 possessed the highest humidity sensitivity of 42,000 while the pure composite copper aluminate (CuSA1) and strontium aluminate (CuSA6) possessed comparatively low sensitivities 10,000 and 20,000, respectively. The response and recovery characteristics of the composites CuSA1, CuSA5 and CuSA6 were studied
[en] Investigations were conducted in batch mode to study the adsorption behaviour of m-cresol on a porous carbon prepared from rice husk (RHAC) by varying the parameters such as agitation time, m-cresol concentration (50-300 mg/l), pH (2.5-10) and temperature (293-323 K). Studies showed that the adsorption decreased with increase in pH and temperature. The isotherm data were fitted to Langmuir, Freundlich, and Dubinin-Radushkevic (D-R) models. The kinetic models such as pseudo-first-order, pseudo-second-order and intraparticle diffusion models were selected to understand the reaction pathways and mechanism of adsorption process. The thermodynamic equilibrium coefficients obtained at different temperatures were used to evaluate the thermodynamic constants ΔGo, ΔHo and ΔSo. The sorption process was found to be exothermic in nature (ΔHo: -23.46 to -25.40 kJ/mol) with a decrease in entropy (ΔSo: -19.44 to -35.87 J/(mol K)). The negative value of Gibbs free energy, ΔGo indicates that the adsorption occurs via a spontaneous process. The decrease in the value of -ΔGo from 17.70 to 13.54 kJ/mol with increase in pH and temperature indicates that the adsorption of m-cresol onto activated carbon is less favourable at higher temperature and pH range. The influence of mesopore and a possible mechanism of adsorption is also suggested
[en] Strontium added NiAl2O4 composites prepared by sol-gel technique was utilized for the detection of methanol vapors. X-ray diffraction, scanning electron microscopy (SEM), FT-IR spectroscopy and nitrogen adsorption/desorption isotherm at 77 K was employed respectively to identify the structural phases, surface morphology, vibrational stretching frequencies and BET surface area of the composites. The composites were prepared with the molar ratios of Ni:Sr as (1.0:0.0, 0.8:0.2, 0.6:0.4, 0.4:0.6, 0.2:0.8, 0.0:1.0) keeping the aluminum molar ratio as constant for all the compositions and were labeled as NiSA1, NiSA2, NiSA3, NiSA4, NiSA5 and NiSA6, respectively. The samples sintered at 900 oC for 5 h were subjected to dc resistance measurements in the temperature range of 30-250 oC to study the methanol vapor detection characteristics. The results revealed that the sensitivity in detecting methanol vapor increased with increase in temperature up to 175 oC for the composites NiSA1 and NiSA6 while for the other composites up to 150 oC and thereafter decreased. The sensitivity increased with increase in methanol concentration from 100 to 5000 ppm at 150 oC. Among the different composites NiSA5 showed the best sensitivity to methanol detection at an operating temperature of 150 oC