Properties Of Nanopowders Research Articles

Influence of pH values on the surface and properties of BCZT nanopowders synthesized via sol-gel auto-combustion method

To investigate the preparation of lead-free nano-powder for piezoelectric thin film coating applications, in this work, barium calcium zirconate titanate (Ba0·85Ca0.15Zr0·1Ti0.9O3 or BCZT) was synthesized by the sol-gel auto-combustion method with controlled pH values. The change in pH value of 5, 7 and 9 was carried out by adjusting NH4OH content while the molar ratio of metal and citric acid was fixed at 1:1. The as-burnt powder was calcined at 900 °C for 2 h and was then characterized in terms of chemical bonding, crystal structure and morphology using Raman, FTIR spectroscopy, XRD and TEM techniques. Particle size and tetragonality of the powder increased with increasing pH value. Raman spectrum peaks of as-burnt powders showed an amorphous phase which was in agreement with XRD result. The calcined powders showed a broad peak at ~ 562 cm− 1 corresponding to the stretching vibration of TiO and ZrO bonds in perovskite structure. Crystallite size calculated using Scherrer's equation was in a range of 32–35 nm. SAED pattern showed that the calcined powders were polycrystalline with respective indices of perovskite unit cell. The pH 7 synthesis condition, which was found to be optimum for producing nano-sized powder with narrow size distribution, suggested that chemically neutral environment was an important factor for good reactivity with well-controlled nucleation and growth of BCZT particles.

Effect of Ag + Co doping on the antibacterial properties of ZnO nanopowders synthesized using combustion method

The present study reports the antibacterial activities of undoped and Ag (2 at.%) + Co (5 at.%) doped ZnO nanopowders synthesized using combustion method. The synthesized particles have been tested to find the effect of doping on the antibacterial activities against two different pathogens namely Shigella flexneri and Bacillus Cereus. Further structural, morphological, chemical, compositional and optical properties were studied using X ray diffractometer (XRD), Field emission scanning electron microscope (FESEM), Transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy and Photoluminescence spectroscopy, respectively. The results reveal that Ag + Co doped ZnO shows better antibacterial activity against both the tested bacterial strains when compared with bare ZnO. The possible mechanism for the antibacterial activity of Ag + Co doped ZnO is reported

Synthesis and properties of ferrite nanopowders for epoxy‐barium hexaferrite‐nanocarbon composites for microwave applications

The effect of the synthesis conditions (type of chemical reagents, temperature of treatment) on phase composition and morphology of ferrite nanopowders containing barium hexaferrite was investigated. X‐ray diffraction studies confirm the presence of two phases in synthesized powders – Fe2O3 and BaFe12O19 (BaM) – and ratio between these phases depends on the temperature of powder treatment at last stage of the synthesis. Electron microscopy studies showed that prepared ferrite powders consist of hexagonal particles having 20–50 nm thickness and 80–400 nm diameter, with exact values depending on the synthesis parameters. Measurements of magnetic susceptibility in the temperature range 300–850 K as well as the ferromagnetic resonance study confirm the presence of two phases in the prepared ferrite powders and correlate with the X‐ray diffraction data. It was found that the addition of conductive carbon nanotubes or graphite nanoplatelets into the hybrid epoxy‐barium hexaferrite composites allows to control the parts of absorbed and reflected microwave electromagnetic radiation in these composites.

Optical and structural properties of TiO2 nanopowders with Co/Ce doping at various temperature

In this study, preparation of 2 mol% Ce and 4 mol% Co doped TiO2 nanopowders via sol–gel process have been investigated. The effects of Co and Ce doping and calcination temperature (475–1000 °C) on the structural and optical properties of titania nanopowders studied by X-ray diffraction (XRD), scanning electron microscope, transmission electron microscope and UV–Vis absorption spectroscope. XRD results showed that, Titania rutile phase formation in ternary system (Ti–Co–Ce) was inhibited by Ce4+ and promoted by Co4+ co-doped TiO2 in high temperatures (500–700 °C) and 61 mol% anatase composition is retained even after calcination at 800 °C. The optical absorption spectrum indicates that the TiO2 nanoparticles have a direct band gap of 3.21 eV. But optical band gap of the doped TiO2 (2 mol% Ce and 4 mol% Co) was found to be 3.14–3.20 eV.

Optical and Structure Properties of Nanocrystalline Titania Powders with Cu Dopant

TiO2 nanopowders doped by Cu were prepared by the sol–gel method. The effects of Cu doping on the structural, optical, and photo-catalytic properties of titania nanopowders have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Vis absorption spectroscopy. XRD results suggest that adding impurities has a significant effect on anatase phase stability, crystallinity, and particle size of TiO2. Titania rutile phase formation in the system (Ti–Cu) was promoted by Cu2+ doped TiO2. The photo-catalytic activity was evaluated by photo-catalytic degradation kinetics of aqueous methylene orange (MO) under visible radiation. The results show that the photo-catalytic activity of the 5 %Cu doped TiO2 nanopowders has a larger degradation efficiency than pure TiO 2 under visible light. Also, the minimum band gap was estimated to be ∼ 1.9–2 eV from UV–Vis spectra.

Influence of Fe-Doping on the Structural and Magnetic Properties of ZnO Nanopowders, Produced by the Method of Pulsed Electron Beam Evaporation

The nanopowders (NPs) ZnO-Zn-Fe and ZnO-Fe with the various concentrations of Fe (xFe) (0≤xFe≤0.619mass.%) were prepared by the pulsed electron beam evaporation method. The influence of doping Fe on structural and magnetic properties of NPs was investigated. X-ray diffraction showed that powders contain fine-crystalline and coarse-crystalline ZnO fractions with wurtzite structure and an amorphous component. Secondary phases were not found. The magnetic measurements made at room temperature, using the vibration magnetometer and Faraday’s scales, showed ferromagnetic behavior for all powders. Magnetization growth of NPs ZnO-Zn and ZnO-Zn-Fe was detected after their short-term annealing on air at temperatures of 300–500°C. The growth of magnetization is connected with the increase in the concentration of the phase ZnO with a defective structure as the result of oxidation nanoparticles (NPles) of Zn. The scanning transmission electron microscopy (STEM) showed a lack of Fe clusters and uniform distribution of atoms dopant in the initial powder ZnO-Zn-Fe. A lack of logical correlation between magnetization and concentration of a magnetic dopant of Fe in powders is shown.

Influence of some sol-gel synthesis parameters of mesoporous TiO2 on photocatalytic degradation of pollutants

The titanium dioxide (TiO2) nanopowders were produced by sol-gel technique from tetrabutyl titanate as a precursor by varying some parameters of the sol-gel synthesis like the temperature (500 and 550 ?C) and the duration of the calcination (1.5, 2, and 2.5 h). X-ray powder diffraction (XRPD) results have shown that all synthesized nanopowders are dominantly in anatase phase, with the presence of a small amount of rutile in samples calcined at 550 ?C. According to the results obtained by Williamson-Hall method, the anatase crystallite size was increased with the duration of the calcination (from 24 to 29 nm in samples calcined at lower, and from 30 to 35 nm in samples calcined at higher temperature). The analysis of the shift and linewidth of the most intensive anatase Eg Raman mode confirmed the XRPD results. The analysis of pore structure from nitrogen sorption experimental data described all samples as mesoporous, with mean pore diameters in the range of 5-8 nm. Nanopowder properties have been related to the photocatalytic activity, tested in degradation of the textile dye (C.I. Reactive Orange 16), carbofuran and phenol.

Effect of Cobalt Dopant on Structural and Optical Properties of Co-Precipitated TiO<sub>2</sub> Nanopowders

The effects of cobalt (Co) addition on structural and optical properties of TiO2 nanopowders have been investigated. A co-precipitation method was employed to synthesize TiO2 nanoparticles with various Co additives from 0-10 mol% using tetrabutyl titanate and Cobalt (II) nitrate hexahydrate as starting precursors for Ti and Co source, respectively. The crystallinity of Co-doped TiO2 nanopowders is heightened by calcination process. The crystal structure, phase formation and the corresponding functional groups of Co-doped TiO2 were analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The scanning electron microscope (SEM) was taken to observe their morphologies. The chemical compositions of Co additive into TiO2 matrix are confirmed by EDAX. Their optical properties were investigated by diffuse reflectance spectroscopy. Diffuse reflectance spectra of samples exhibit the increasing absorption in visible region with an increasing Co content. The overall characterization results indicated that the crystallinity and optical properties of TiO2 nanoparticles are significantly affected by Co dopant.

Effect of Cadmium on Structure and Optical Properties of ZnO Nanopowders by Sol-Gel Method

Zn1-xCdxO (x=0, 0.04, 0.06, 0.08) ternary alloys were successfully synthesized by Sol–gel method. The prepared powders were sintered at 800°C for 4hrs. The compositional, structural and optical studies were investigated by SEM equipped with EDS, XRD and UV-Visible Spectroscopy. XRD results were compared with JCPDS data and confirmed the formation of Cd doped ZnO nanoparticles with polycrystalline single phase hexagonal wurtzite structure. The crystallite size was found to decrease from 21 to 17 nm with increase in the concentration of Cd. EDS analysis revealed the existence of Cd content in ternary alloys. From Ultraviolet-visible spectral studies optical band gap vary from 3.21 eV to 3.12 eV with Cd concentration.© 2016 Elsevier Ltd. All rights reserved.Selection and Peer-review under responsibility of International conference on materials research and applications-2016.

The influence of different Ni contents on the radar absorbing properties of FeNi nano powders

Absorbing property of Fe20Ni80 nanopowder was better than that of other Fe100−xNix powder fabricated by liquid phase reduction method. Absorbing band could be effectively broadened and absorbing property improved through optimal structural designs.

FUNDAMENTAL INVESTIGATIONS AS THE BASIS OF CREATION OF NEW MATERIALS AND TECHNOLOGIES IN METALLURGY. PART 2. POWDER NANOMATERIALS

The paper presents a review of the investigation results in the field of nanopowder and consolidated powder nanomaterials. The features of the various powder fabrication methods are described and analyzed, as well as the produced nanopowders properties. The different methods of nanopowder consolidation (consolidation, sintering, sintering under pressure) are considered. The properties of such consolidated nanomaterials are listed and some perspective directions of their usage (as the engineering, functional and high-energetic materials) are pointed out.

Electrochemical properties of Sn-based nanopowders synthesized by a pulsed wire evaporation method and effect of binder coating

Sn-based nanoparticles are prepared with the O2 concentrations in chamber of Ar atmosphere (by v/v) by using the pulsed wire evaporation (PWE) method. The prepared electrodes are only Sn-based powder electrode, its binder coating electrode and Sn-based powder/graphene nanocomposite electrode. Morphology and structure of the synthesized powders and electrodes are investigated with a field emission scanning electron microscope (FE-SEM) and an X-ray diffraction (XRD) analysis. The electrochemical measurements were performed with galvanostatic cycling experiments using a coin type cell of CR2032 (Ø20, T3.2mm). The binder coating electrode is superior to others and maintains delithiation capacity nearly of 501mAhg−1 as 58.3% of first delithiation capacity at 0.2 C-rate up to 100 cycles.

Temperature Stability and Photocatalytic Activity of Nanocrystalline Cristobalite Powders with Cu Dopant

The SiO2 nanoparticles doped by 10 % mol Cu were prepared via a sol-gel method under process control. The effects of doping and calcination temperature on the structural and photo-catalytic properties of SiO2 nanopowders have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis absorption spectroscopy. Cristobalite and tridymite crystalline phases were found at a calcinations temperature range of 900∼1200 °C and amorphous phase was formed at a temperature of 800 °C for doped SiO2. The photocatalyst activity was evaluated by photocatalytic degradation kinetics of aqueous methyl orange (MO) under visible radiation. The results show that the photocatalytic activity of the 10 % mol Cu doped SiO2 nanopowders have a larger degradation efficiency than pure SiO2 under visible light at 900 °C temperature.

Synthesis and Pressure Sensing Properties of the Pristine Cobalt Oxide Nanopowder

Synthesis and Pressure Sensing Properties of the Pristine Cobalt Oxide Nanopowder

Microstructure and Optical Properties of Yttrium-doped Zinc Oxide (YZO) Nanobolts Synthesized by Hydrothermal Method

In this work, yttrium-doped zinc oxide (YZO) nanopowder was synthesized via hydrothermal precipitation-method. The microstructure and optical properties of yttrium-doped zinc oxide nanopowder were characterized, which confirmed the well-crystalline wurtzite hexagonal phase of ZnO. The yttrium-doped zinc oxide nanopowder grains formed the nanobolts of ~400 nm in length and ~900 nm in width. High resolution-transmission electron microscopy (HR-TEM) of the nanobolts revealed uniform lattice fringes and no visible faults and/or distortions. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of yttrium in the zinc oxide lattice, proving the contribution of yttrium on the microstructural and optical properties of the material. A strong ultra violet (UV) emission peak of the YZO exhibited a red shift compared to pure zinc oxide, which was ascribed to the defects and the formation of a shallow energy level caused by the incorporation of yttrium.

Influence of Co + F doping on the physical and antibacterial properties of ZnO nanopowders prepared by a simple soft chemical method

Undoped, Co doped and Co + F doped ZnO nanopowders were synthesized using a simple soft chemical method and certain physical and antibacterial properties of the samples were studied and reported. The XRD patterns reveal that the samples has hexagonal wurtzite structure with preferential orientation along (101) plane. Reduction in grain size caused by Co and Co + F doping is observed from FESEM images. The observed photoluminescence peaks related to the defects confirmed the incorporation of Co, Co + F into the ZnO lattice. Co + F doped ZnO nanopowder exhibits higher antibacterial activity than undoped and Co doped ZnO nanopowders against all the four different bacteria tested in this study viz. B. subtilis, S. aureus, E. coli and P. aeruginosa. The enhanced antibacterial activity of doubly doped ZnO nanopowder is mainly due to the generation of hydroxyl radicals (OH−) in the system.

Influence of a novel triple doping (Ag+Mn+F) on the magnetic and antibacterial properties of ZnO nanopowders

In the present study, Ag+Mn and Ag+Mn+F doped ZnO nanopowders were synthesized using a combustion method and their magnetic, structural, surface morphological and antibacterial properties were studied. The magnetic studies reveal that the doped ZnO nanopowders exhibit superparamagnetic behavior. Surface morphological studies show that the grain size of the undoped ZnO is about 250nm and the size reduces by one order of magnitude (from 250nm to 23nm) after doping. The reason for this drastic decrease in the grain size and crystallite size is explained on the basis of Zener Pinning Effect. The antibacterial efficiency of the synthesized nanopowders is tested against two different bacteria viz. Escherichia Coli and Klebsiella Oxytoca and it is found that the antibacterial efficiency of ZnO nanopowder increases remarkably after multiple doping. All the doped and undoped nanopowders exhibit better efficiency against K. oxytoca than E. coli. The PL results confirm the presence of certain intrinsic and extrinsic defects in the crystalline structure.

Tuning the Microstructural and Magnetic Properties of ZnO Nanopowders through the Simultaneous Doping of Mn and Ni for Biomedical Applications

Undoped and Mn+Ni doped ZnO nanopowders were synthesized using a simple soft chemical route by varying the Ni doping level (1, 3, 5 and 7 at.%) and keeping the Mn doping level (10 at.%) constant. X-ray diffraction studies reveal that the incorporated Ni2+ ions form a secondary phase of cubic NiO beyond the Ni doping level of 3 at.%, which is also confirmed by Fourier transform infrared spectroscopy. The band gap of the nanopowders increases (from 3.32 to 3.44 eV) up to 3 at.% of Ni doping and decreases with further doping. ZnO:Mn:Ni nanopowders with 3 at.% of Ni concentration exhibit good antibacterial efficiency. The variation in the size of the nanoparticles, as observed from the TEM images and hydroxyl radicals as evidenced from the photoluminescence results, clearly substantiate the discussion on the antibacterial efficiency of the synthesized nanopowders. Magnetic properties of the synthesized nanopowders were studied using a vibrating sample magnetometer, and the results showed that the doping of Mn and Ni largely influences the magnetic properties of ZnO nanopowders.

Synthesis and characterization of nanostructured Ni-WO3 and NiWO4 for supercapacitor applications

Ni-WO3 and NiWO4 nanopowders have been prepared by microwave irradiation method. The prepared nanopowders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Vibrating sample magnetometer (VSM) techniques. The XRD pattern revealed the formation of orthorhombic and monoclinic phase for the as-synthesized and heat treated samples, respectively. The Ni-WO3 and NiWO4 samples show the nanoporous morphologies and it was confirmed by SEM. The VSM observation showed ferromagnetic properties of both as-prepared and heat-treated nanopowders. The electrochemical performance of the Ni-WO3 and Ni-WO4 coated electrodes has been investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and Galvanostatic charge–discharge (GCD) techniques. The maximum specific capacitance of 171.28 F/g was achieved for the Ni-WO3 nanopowder.

Structure and thermal properties of zeolites modified with Fe and Cu nanopowders

We have studied the thermal properties of copper and iron nanopowders supported on high-silica ZSM-5 zeolites. The results demonstrate that the attachment of metal nanoparticles to the zeolite surface improves the oxidation resistance of the metals. The oxidation onset temperature and the temperature range of the weight gain due to the oxidation of the metal nanopowders depend on the nature of the zeolite matrices and the metal.