Nm For Powders Research Articles

Optoelectronic properties of BiCuOSe p-type oxychalcogenides

BiCuOSe systems are proposed as candidates to develop transparent p-type semiconductors in the visible region. This work reports the characterization results obtained for the BiCuOSe powders, synthesized by the solid-state reaction (SSR) method through mechanical milling, and nanostructured thin films deposited from the same processed powders using the pulsed laser deposition (PLD) technique. Structural characterization through X-ray diffraction (XRD) showed that the material presents a tetragonal structure with an average crystallite size of 21 nm and a preferential orientation in the (1 0 2) plane. The morphological and particle size evolution of BiCuOSe powders is presented as a function of the milling time. Transmission and scanning electron microscopies confirmed the spherical geometry of the particles in the powders and nanosheets like structure for the films. Particle sizes were also estimated, ranging from 10 to 100 nm for powders and 60 to 70 nm for films. The bandgap values, EG, for BiCuOSe powders were estimated from diffuse reflectance spectra using the Kubelka–Munk method, yielding values close to 0.7 eV. For thin films, EG values were estimated using the Tauc method, obtaining values in the range of 0.8–3.5 eV, depending on the annealing treatment. Additionally, electrical properties were measured in all deposited thin films, confirming the p-type conductivity, a minimal resistivity of 0.0735 Ω cm, hole mobility on the order of 88 cm2/Vs, and carrier concentration of 9.7 × 1018 cm−3.

Green synthesis of Co3O4 nanoparticles using psyllium husk (Plantago Ovata) and application as electrocatalyst for oxygen evolution reaction

The continuous supply of hydrogen from renewable sources through water electrolysis technology is a key issue for the development of humanity. To meet this purpose, catalysts based on transition metals (Ni, Fe and Co) are promising candidates for the hydrogen and oxygen evolution reactions. Therefore, in this work, nanocrystalline Co3O4 with a spinel-like cubic structure was prepared by a proteic sol–gel synthesis using psyllium husk as a polymerizing agent, and later tested as an electrocatalyst for the oxygen evolution reaction (OER). The purity of the Co3O4 phase was confirmed by several characterization techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The size of crystallites and particles obtained from Rietveld refinement of X-ray diffraction patterns ranged from 16.5 nm to 25.3 nm for powders calcinated at 400 °C and 600 °C, respectively, confirming nanometric Co3O4 powders. Scanning electron microscopy shows nanostructures with predominantly spherical morphology. From the electrocatalytic point of view, it was observed that the larger particle size impairs the oxygen evolution reaction. The Co3O4 calcined at 400 °C showed superior electrocatalytic performance, with an overpotential of 328 mV at 10 mA cm−2, Tafel slope of 71 mV dec-1, CDL of 5.46 mF cm−2, ECSA of 91 cm2, specific activity of 4.73 mA cm−2 and mass activity of 718 A g−1.

Multifunctional behavior of a carbazole derivative: Red phosphorescent emission, aggregation-induced long-life exciton and light-emitting diode application

A D-π-A typed cyanyl-carboxylic derivative (named as CECZA) merely produced prompt fluorescence with lifetime at nanosceond scale in dilute solutions, whose solid-state luminescence exhibited 3.36 μs lifetime with 13.80 % quantum yield (QY, captured at 522 nm for powder at nanometer scale) at 298 K and 43.36 ms lifetime with 30.46 % QY (650 nm, 80 K, tiny crystals). Femtosecond transient absorption, Raman spectroscopy and quantum chemical calculation provided valid clues to reveal its excitonic transition mechanism. The results indicated that the restricted vibration of benzene ring on carbazole group and alkyl chain weakened the vibrational modes of CECZA molecule and strengthened inter-molecular interactions between adjacent molecules at low temperatures, which promoted the persistent phosphorescent emission. Due to strong UV–vis absorption, high quantum efficiency and excellent thermal stability, CECZA can be used as a potential candidate in light-emitting diode (LED) application. Combined with a commercial InGaN blue-emitting chip, CECZA-InGaN emitted daylight white light.

Electrospun nanofibrous scaffolds of polycaprolactone containing binary ions of Pd/vanadate doped hydroxyapatite for biomedical applications

In this work, manipulation of scaffold compositions is executed, aiming to the enhancement of wound healing via the acceleration of the curing process and inhibition of bacterial growth. The study includes powder phase, palladium/vanadate hydroxyapatite (Pd/V-HAP), and fibrous phase (Pd/V-HAP@PCL) preparation in different Pd(II) ions contents. The structural inspection with palladium insertion is inspected for powder and nanofibrous compositions using XRD, while the morphological behavior was examined by the FESEM technique. The porous structure is detected clearly in the highest palladium composition in powder phase compositions, besides a significant reduction in fiber filament diameter from 4 μm to 1.5 μm. The roughness average of 0.8Pd/V-HAP@PCL shows detectable growing with palladium insertion reaching 23.6 and 103.7 nm for powder and fibrous phase, respectively. The narrowest contact angle is introduced by 0.8Pd/V-HAP@PCL scaffold with 88±3°, while it presented the highest cell viability with 95.1 ± 2%. Additionally, the 0.8Pd/V-HAP@PCL nanofibrous composite shows the maximum inhibition zones with 19.6 ± 0.8 and 18.7 ± 0.9 mm against E. coli and S. aureus microorganisms, respectively. It could be added that the cellular growth of fibroblasts cell line was observed via scanning microscope, where the spreading and the proliferation of cells increased upon the change of the compositions of nanofibers. The enlargement of the growing area of cells through the scaffold's surface might indicate the ability of these biomaterials for wound care potential applications.

Superfine-Nanocomposite Mo - Cu Powders Obtained by Using Planetary Ball Milling

Mo-10 at.% Cu nanocomposite powders were fabricated by using planetary ball-milling (PBM), a mechanical alloying technique for preparing nanocomposite alloy powders of metals with mutual insolubility, and the variations in the physical and the chemical characteristics with the process conditions were investigated. We observed that Mo-10 at.% Cu was an appropriate composition to ensure a good alloying grade and minimal welding between particles. The influences of the temperature and the milling conditions on the mechanical alloying process and the phase change of Mo-10 at.% Cu composite powders were investigated, and the particle and the grain sizes of the powders after mechanical alloying were confirmed. The Mo-10 at.% Cu powders showed homogeneous elemental distributions and no phase changes up to 1200 °C; their compositions were retained after the mechanical alloying process. The finest grain size obtained was about 5 nm for powders processed using optimum PBM processing conditions: ball-to-powder weight ratio of 5: 1, ambient air atmosphere, a milling time of 20 h, a rotation speed of 200 rpm, and a stearic acid content of 4 wt.% produced superfine-grained Mo-10 at.% Cu nanocomposite powders with an average grain size of 5 nm (which is smaller than that of other similar materials reported in the literature). The analytical results confirmed that the PBM technique presented here is a promising method for preparing superfine-grained Mo-10 at.% Cu powders with improved properties.

Preparation and photophysical properties of thienothiophene functionalized difluoroboron bis-β-diketonate complexes

A series of six new thienothiophene functionalized difluoroboron bis-β-diketonates were synthesized and characterized. Their photophysical properties were investigated by UV–vis absorption, fluorescence spectroscopy and the method of CIE chromaticity in solution and powders. The results showed that these difluoroboron complexes yielded a blue-green emission at 474–500 nm in DMF solution and emitted a green to yellow emission at 541–587 nm in powders. Especially, the complex 3c showed the stronger fluorescence intensity, much higher quantum yield (Φu = 0.89) in DMF solution and larger Stokes shifts (∆λstokes = 149 nm), longer lifetime value (τ = 3.54 ns) in powders as compared to other complexes. The CIE coordinate of the complex 3c was positioned in an ideal orange-yellow region of the chromaticity diagram. Meanwhile, their electrochemical properties were also studied by the cyclic voltammetry; the HOMO, LUMO energy levels and energy band gaps were determined from the onset oxidation and reduction potentials.

Variation of Contents of Carbon, Nitrogen, and Oxygen upon Formation of Plasma Cermet Coatings with Steel Matrix Reinforced with Titanium Carbide

This article describes comparative studies of a coating made of high-speed steel and cermet powder on its basis with 50 vol % of TiC strengthening carbide phase. Coatings are formed by Ar–N2 plasma with local protection by powders with particle sizes from 25 to 55 μm. It is demonstrated that the TiC content in the coating is retained, but the lattice constant of this phase decreases from 0.43212 nm for powder to 0.43035 nm in the coating because of variation of contents of carbon, oxygen, and nitrogen. After plasma coating of 50 vol % TiC–R6M5 powder, the average carbon content in the coating decreases from 7.83 to 6.74 wt %. The oxygen content in the cermet coating increases to 2.8 wt % in comparison with 0.8 wt % in the initial powder. The nitrogen content also increases from 0.05 to 0.89 wt %. The microhardness of particles of initial powders of high-speed steel is 8.91 GPa, and that of 50 vol % TiC–R6M5 cermet is 9.5 GPa. The microhardness of the cermet coating, 11.0 GPa, corresponds to the calculated value obtained by the mixture rule at microhardness of the R6M5 steel coating equal to 6.64 GPa.

Synthesis and Characterization Red Emitting Iridium (III) Complex with 2-(4-cynophenyl)-4 Phenyl quinoline for PhOLEDs

A new red light emitting highly efficient Ir(III) complex Ir(CN-DPQ)2(acac), was synthesized for phosphorescent organic light-emitting diodes (PhOLEDs), and their photo physical, structural properties were investigated. The Ir(III) complex, including acetyl acetone (acac) as ancillary ligand, are comprised with 2-(4-cynophenyl)-4 Phenyl quinoline (CN-DPQ),main ligands. The synthesized iridium metal complex, Ir(CN-DPQ)2(acac), and ligand (CN-DPQ) were characterized by different techniques, e.g., Fourier transform infra-red spectroscopy (FTIR), the thermo gravimetric analysis (TGA) and the differential thermal analysis (DTA), UV-visible absorption and photoluminescence spectra. FTIR spectra confirms the presence of chemical groups such as C=O, NH, or OH in the synthesized complex and ligand and TGA/DTA curve revels that the synthesized complex is thermally stable up to 350 0 C .The synthesized 2-(4-cynophenyl)-4 Phenyl quinoline (CN-DPQ) phosphor when excited at 388 nm, demonstrate emission in blue region at 442 nm in formic acid with CIE co-ordinate X=0.1592 & Y=0.0786. A red emitting PL peaks at 626 nm in powder, 628 nm inTHF,631 nm in DCM and 638 nm in acetic acid solution was observed. It is proposed that the synthesized complex Ir(CN-DPQ)2(acac) may be efficiently used as the red emitter materials and CN-DPQ organic phosphor may be efficiently used as the blue emitter materials in Organic Light-Emitting Diodes (OLEDs). It is promising candidates for potential applications in organic light-emitting diodes (OLEDs), light-emitting electrochemical cells and solid-state organic lighting applications. The synthesized quinoline-based iridium complex are promising candidates for efficient red emitters in PhOLEDs

Synthesis, Structural Features, Cytotoxicity, and Magnetic Properties of Colloidal Ferrite Spinel Co1–xNixFe2O4(0.1 ≤ x ≤ 0.9) Nanoparticles

AbstractColloidal ferrite spinel nanoparticles (CoxNi1–xFe2O4) were prepared by a microwave‐stimulated Bradley technique under nonhydrolytic conditions. The effect of Ni2+doping on the structural properties was studied by powder XRD. The particle size, hydrodynamic size, and morphology were evaluated by transmission electron microscopy (TEM) and dynamic light scattering (DLS), which showed mean crystallite sizes of ca. 10 and 60 nm for powder and colloidal suspensions of CoxNi1–xFe2O4, respectively. The cytotoxicity of the nanoparticles was tested against murine macrophages J774.E, osteosarcoma D17 cells, and human red blood cells (RBCs). The adsorption of bovine serum albumin (BSA) was studied, and the BSA showed a high affinity for the surface of the nanoparticles. The CoxNi1–xFe2O4nanoparticles in colloidal suspension showed dose‐dependent cytotoxicity against all of the studied cell lines, and less harmful effects were observed against RBCs at concentrations of up to 0.1 mg/mL. The cytotoxicity towards the D17 and J774.E cells suggests that internalization by the living cells seems to be the key step to elicit the toxic response. Thus, the cytotoxicity of the particles under investigation seems to be cell‐type‐dependent and not uniform. The CoxNi1–xFe2O4colloids exhibited superparamagnetic behavior with blocking temperatures (TB) below 300 K. The magnetic characteristics are well preserved in colloidal form and are similar to those of the powdered ferrites.

Effect of Sintering Atmosphere and Particle Size on the Ionic Conductivity of Gadolinia-Doped Ceria

Gadolinia-doped ceria has been intensively investigated over the last decades as a promising electrolyte and electrode material for intermediate-temperature solid oxide fuel cells [1]. The sintering behavior of this solid electrolyte in reducing atmosphere is different from that in air, because of the reduction of Ce4+ to Ce3+[2]. In this case, changes in the microstructure and in the related properties are expected to occur, due to variation in the oxygen-vacancy concentration. In this work, the effects of the sintering atmosphere and the particle size of powders on densification and ionic conductivity of Ce0.9Gd0.1O2-δ were systematically investigated. Ce0.9Gd0.1O2-δ commercial powders (>99.5%, Fuel Cell Materials) with specific surface area ranging from 7.4 to 210 m2.g-1were used as starting materials. Cylindrical pellets were prepared by uniaxial and isopressing following by sintering at 1250°C for 2 h under different atmospheres. The average initial particle size of the powders was evaluated by nitrogen adsorption (Quantachrome, NOVA 1200) using the BET method. Characterization of the sintered materials was carried out by density measurements, thermodilatometry (Anter-1161, Unitherm), electronic Raman spectroscopy (InVia Raman microscope, Renishaw), electron paramagnetic resonance (Bruker-EMS), field-emission scanning electron microscopy (FEI, Inspect F50) and impedance spectroscopy (HP4192A). The mean grain size was estimated by the linear intercept method. The sintered pellets reached relatively high densities (93 to 97% of the theoretical value) independent on the sintering atmosphere. The particle size determined by nitrogen adsorption of the starting powders was: 112, 23 and 4 nm for powders, hereafter named S1, S2 and S3, respectively. The linear shrinkage curves show that good densification of gadolinia-doped ceria is attained depending on the initial size of the powder particles. However, for isothermal treatments the densification is homogenized and all sintered pellets reached high values after 1250°C for 2 h.All investigated properties changed to some extent with the sintering atmosphere and the initial particle size of the starting powders. The grain conductivity, for example, of Ce0.9Gd0.1O2-δ pellets sintered in air and under inert atmospheres (argon and nitrogen) exhibit the same bulk conductivity not depending on the sintering atmosphere, in spite of the changes observed in the electron paramagnetic signal.

Photoluminescence Studies on Nanocrystalline Tin Oxide Powder for Optoelectronic Devices

Nanocrystalline tin oxide (SnO2) powders have been synthesized by a low temperature chemical precipitation method. As-prepared and heated powders were characterized by XRD, SEM and luminescence studies. Crystallographic parameters such as crystallite size, lattice parameters and dislocation density in SnO2 nanocrystalline powders were calcu- lated by Rietveld analysis. The average crystallite size of 9 - 43 nm was obtained for SnO2 powders through controlled heat treatment process. The washed powders morphology was almost spherical in shape and average agglomerate crystal size was between 0.2 - 0.4 μm. A Photoluminescence (PL) study was measured at an excitation wavelength of 265 nm for as-prepared and annealed powders; it showed a broad emission peak at 417 nm for all powders. The highest PL emission was attained for the powder annealed at 500℃. The synthesized nanocrystalline SnO2 oxide semiconductor material could be suitable for making optoelectronic and sensor devices.

Microstructure of Ba 1− xLa xTiO 3− δ ceramics sintered by Spark Plasma Sintering

Nano-sized Ba 1− x La x TiO 3 (0.00 ≤ x ≤ 0.14) powders were prepared by a coprecipitation method and calcined at 850 °C in air. The corresponding ceramics were obtained by Spark Plasma Sintering (SPS) at 1050 °C. These ceramics are oxygen deficient and are marked as Ba 1− x La x TiO 3− δ . Both powders and ceramics were characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The effect of lanthanum concentration on the densification behavior, on the structure and the microstructure of the oxides was investigated. Average grain sizes are comprised between 54 (3) nm and 27 (2) nm for powders, and 330 (11) nm and 36 (1) nm for ceramics according to the La-doping level. Powders crystallize in the cubic (or pseudo-cubic) perovskite phase. The structure of ceramics consists in a mixture of cubic (or pseudo-cubic) and tetragonal perovskite type phases. As the lanthanum content increases, the tetragonality of the samples decreases, as well as the grain size.

Characterization of sol‐gel SiO2:Ce,Tb powder and pulsed laser deposited thin film phosphors

AbstractThin films of SiO2:Ce,Tb (Ce = Tb = 0.5 mol%) nanoparticulate phosphor (nanophosphor) were ablated on Si (100) substrates using either the conventional pulsed laser deposition (PLD) or pulsed reactive crossed beam laser ablation (PRCLA) technique. Morphology and surface topography of the films were analysed with scanning electron microscopy (SEM) and atomic force microscopy (AFM) respectively. The chemical composition and thicknesses of the films were determined by Rutherford backscattering spectroscopy (RBS). Luminescence properties of the films were studied with cathodoluminescence (CL) spectroscopy and a 325 nm HeCd laser. Enhanced green cathodoluminescence and photoluminescence (PL) associated with 5D4→7F4 transitions in Tb3+ was observed at ∼540 nm in powder and thin film samples, and is attributed to non‐radiative energy transfer from co‐doped Ce3+. Luminescence intensities of the films and that of the SiO2:Ce,Tb powder used to make the films are compared. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Sensor performance of nanostructured TiO 2 thin films derived from particulate sol–gel route and polymeric fugitive agents

High specific surface area (SSA) nanocrystalline powders and dip-coated TiO 2 thin films have been prepared by a particulate sol–gel route with added polymeric fugitive agents (PFAs), namely trehalose dihydrate (THD), polyethylene glycol (PEG6000) and hydroxypropyl cellulose (HPC). One of the highest SSA reported in the literature, obtained without PFA, was achieved (i.e., 181 m 2/g), a value that could be increased up to 304 m 2/g, 274 m 2/g and 200 m 2/g for PEG/TiO 2, HPC/TiO 2 and THD/TiO 2 powders, respectively. Furthermore, the crystallite size varied from 1 nm for as-produced powders up to 4 nm for powders heat-treated at 600 °C. Thin films produced under optimised conditions showed excellent microstructural properties for gas sensing applications. They exhibited a stable and reproducible response towards CO and NO 2 at a low operating temperature of 200 °C. Calibration curves revealed that all sensors followed the power law ( S = A[gas] B ) (where S is sensor response, and coefficients A and B are constants) for the two kinds of gases and they have good capability for the detection of low gas concentrations (25 ppm CO and 0.5 ppm NO 2). Amongst all sensors, HPC/TiO 2 sensor showed the highest response towards CO ≤ 100 ppm and NO 2 ≤ 2 ppm, whereas PEG/TiO 2 sensor had the highest response towards CO > 100 ppm and NO 2 > 2 ppm operated at 200 °C. The response of the sensors to both CO and NO 2 changed with operating temperature reaching a maximum at a specific temperature. Moreover, the sensor response decreased by increasing the film annealing temperature. The response magnitude and response time of the sensors obtained in this work are superior to those reported in previous studies. Furthermore, their low power consumption as a result of their low operating temperature manifests their good potential for industrial application.

Preparation of high surface area titania (TiO 2) films and powders using particulate sol–gel route aided by polymeric fugitive agents

High specific surface area (SSA) nanocrystalline powders and dip-coated TiO 2 films have been prepared by particulate sol–gel route aided with polymeric fugitive agents (PFA), namely trehalose dihydrate (THD), polyethylene glycol (PEG6000) and hydroxypropyl cellulose (HPC). Powders obtained without PFA, heat-treated at 160 °C show a SSA of 181 m 2/g, a value that could be increased up to 271 and 223 m 2/g for samples heat-treated at 300 °C when PEG6000 and HPC were used, respectively, whereas SSA of 201 m 2/g were achieved by using THD and subsequence heat-treating at 500 °C. Such surface area is one of the highest reported in the literature under these conditions. Crystallite sizes vary from 1 nm for as-produced powders up to 4 nm for powders heat-treated at 600 °C. It was found that crystallite size, microstructure, specific surface area and phase transformation are strongly dependent upon the PFA/TiO 2 ratio and annealing temperature. Films produced under optimised conditions showed excellent microstructural properties for gas sensing applications.

High pressure compacting of high speed steel powders: J. Asami, T. Aizawa (University of Tokyo, Tokyo, Japan)

Nd–Fe–B oxide powders with various pH were prepared using chloride and nitrate precursors including NdCl3·6H2O, FeCl3·6H2O, H3BO3, Nd2O3, Fe(NO3)3·9H2O, HNO3, citric acid (CA), ethylene glycol (EG) by Pechini type sol–gel method. The pH of chloride and nitrate base sols were 0 and 2.2, respectively. Mixed oxide powders were obtained by calcination and annealing the gels. These oxides by using a reduction-diffusion process under high vacuum and employing CaH2 as reducing agent at 800 °C were hated to prepare Nd2Fe14B nanoparticles. The role of pH on phase, morphologies, microstructure, and magnetic properties of the powders were investigated. The results show that with a decrease in pH, the average particle size and coercivity of Nd–Fe–B oxide powders were decreased and increased, respectively. Nd2Fe14B nanoparticles were formed successfully after reduction process. The average particle size of reduction treated products were 30 and 65 nm for powders which made of chloride and nitrate base metal salts, respectively. Final powders which made of chloride and nitrate base metal salts had a saturation magnetization of 127.7 emu/g and 122.8 emu/g while the coercivity of samples were 3.32 kOe and 1.82 kOe, respectively. The experimental results in the angular dependence of coercivity indicated that the normalized coercivity of the permanent magnets Hc(θ)/Hc(0) obeys the 1/cosθ law and intermediate between the 1/cosθ law and Stoner-Wohlfarth formula for different Nd2Fe14B magnets which made of nitrate and chloride base metal salts, respectively. Also, the results show that different Nd2Fe14B magnets which made of nitrate and chloride base metal salts had the maximum energy product of 5 and 16 MGOe, respectively. The Henkel plot showed that magnetic phases in synthesized NdFeB magnets which made of chloride and nitrate base metal salts were coupled by exchange and dipolar interactions, respectively. Different average particle size, morphology and microstructure were the reasons for variation of magnetic properties.

Principles and techniques of electron microscopy

Nd–Fe–B oxide powders with various pH were prepared using chloride and nitrate precursors including NdCl3·6H2O, FeCl3·6H2O, H3BO3, Nd2O3, Fe(NO3)3·9H2O, HNO3, citric acid (CA), ethylene glycol (EG) by Pechini type sol–gel method. The pH of chloride and nitrate base sols were 0 and 2.2, respectively. Mixed oxide powders were obtained by calcination and annealing the gels. These oxides by using a reduction-diffusion process under high vacuum and employing CaH2 as reducing agent at 800 °C were hated to prepare Nd2Fe14B nanoparticles. The role of pH on phase, morphologies, microstructure, and magnetic properties of the powders were investigated. The results show that with a decrease in pH, the average particle size and coercivity of Nd–Fe–B oxide powders were decreased and increased, respectively. Nd2Fe14B nanoparticles were formed successfully after reduction process. The average particle size of reduction treated products were 30 and 65 nm for powders which made of chloride and nitrate base metal salts, respectively. Final powders which made of chloride and nitrate base metal salts had a saturation magnetization of 127.7 emu/g and 122.8 emu/g while the coercivity of samples were 3.32 kOe and 1.82 kOe, respectively. The experimental results in the angular dependence of coercivity indicated that the normalized coercivity of the permanent magnets Hc(θ)/Hc(0) obeys the 1/cosθ law and intermediate between the 1/cosθ law and Stoner-Wohlfarth formula for different Nd2Fe14B magnets which made of nitrate and chloride base metal salts, respectively. Also, the results show that different Nd2Fe14B magnets which made of nitrate and chloride base metal salts had the maximum energy product of 5 and 16 MGOe, respectively. The Henkel plot showed that magnetic phases in synthesized NdFeB magnets which made of chloride and nitrate base metal salts were coupled by exchange and dipolar interactions, respectively. Different average particle size, morphology and microstructure were the reasons for variation of magnetic properties.