Mixed Nanopowders Research Articles

Scintillation properties of (Lu1-x Y x )3Al5O12:Ce3+ nanoscintillator solid solution garnet materials

In this study, the scintillation properties of the (Lu1-x Y x )3Al5O12: 0.1 at.%Ce3+ mixed nanopowder scintillators synthesized by the sol-gel method were investigated. The light yield, energy resolution and scintillation decay kinetics for different substitutions of Lu3+ by Y3+ ion, namely 0 at.%, 5 at.%, 10 at.%, 15 at.% and 20 at.% were evaluated. The relative light yields of all LuYAG mixed samples were determined by the comparison method and the LuAG:0.1 at.%Ce3+ single crystal grown by the Czochralski technique was used as a reference detector. The scintillation decay kinetics was measured at the photomultiplier tube anode output and a fast digital oscilloscope was used to digitize signals. All measurements were performed under α-particles excitation from 241Am (E = 5.48 MeV) source to avoid light scattering in powder materials. Results show that the scintillation light yield was affected by the insertion of Y3+ ions in the LuAG host matrix and tends to improve in the range 10–20 at.% of Y3+ content. Furthermore, it was found that the main contribution in the energy resolution originates from the nanoscintillator material. The scintillation decay curves were well-fitted to a sum of three exponential functions, and the decay time constants were determined. Additionally, pulse shape discrimination of the mixed LuYAG nanoscintillators was also checked, and good discrimination of the kinetics measured under α-particles and γ-quanta from 137Cs (E = 662 keV) was observed.

Flame synthesis of tungsten‐doped titanium‐dioxide nanoparticles using novel precursor combination of liquid titanium tetra‐isopropoxide and solid tungsten mesh

AbstractTungsten‐doped titanium‐dioxide (W‐TiO2) nanoparticles are successfully synthesized using a multiple‐diffusion‐flame burner with a separate center tube. Vaporized titanium tetra‐isopropoxide (TTIP) precursor issues from a center tube to produce TiO2 nanoparticles, while a tungsten mesh, suspended above the surrounding multiple over‐ventilated hydrogen diffusion flames, serves as the solid‐phase metal doping source. At a lower tungsten loading rate, W‐TiO2 nanoparticles are generated, as indicated by an obvious angle shift of 0.15° for the entire x‐ray diffraction spectrum. However, at a higher tungsten loading rate, homogenous nucleation of WOx occurs before or concurrently with TiO2 nucleation, producing mixed nanopowders, permitting fewer tungsten ions to be doped into TiO2. Ultraviolet–visible spectroscopic characterization reveals that the as‐synthesized W‐TiO2 nanoparticles possess augmented absorbing ability in the visible‐light wavelength range, where the band gap is reduced from 3.20 to 3.05 eV, compared with that for the nondoped TiO2 nanoparticles.

Synthesis of composite nanopowder through Mn doped ZnS-CdS systems and its structural, optical properties

• Mn 2+ ions doped ZnS/CdS nanopowder particles were synthesized by chemical precipitation method. • The properties of were investigated by XRD, TEM, SEM, PL, EPR, OPTICAL, FTIR. • Powder XRD pattern confirms the cubic phase of the prepared materials. • PL spectra exhibit strong UV-visible and visible regions. • Optical and EPR studies reveal site symmetry of Mn 2+ / ZnS/CdS nanopowders are distorted octahedral symmetry. The design of new functional materials is a driving force for the development of advanced materials chemistry. Out of many new-style substances, the fabrication of composite nanopowders possesses attracted considerable attention in industry and academia, as they often exhibit significant advancement in the effect of materials estimate to typical macro and micro combinations. The developed ZnS-CdS composite nanopowders with unique and tailored properties for various applications in the fields of surface-improved catalysis, photonic crystals, nano-electronic and LED appliances, etc. In practice, Mn 2+ ions doped ZnS-CdS mixed nanopowders are held in the lead 2–6 bulk solid-state mixture by the control bandwidth of 3.7 and 2.4 eV for ZnS and CdS at room temperature. The present research deals with the preparation, structural and spectral characterizations of transition metal ions doped ZnS-CdS composite nanopowders. X-ray diffraction patterns indexed to the cubic crystalline phase of both ZnS and CdS and the average crystallite size is evaluated using Scherer's formula is in the class of nanometer-range. Morphological images of Mn 2+ ions ZnS-CdS composite nanopowders are in unequal mode structure with agglomerated fragment with nano-size. The spectra of optical absorption and EPR reveal the distorted octahedral symmetry. By correlating optical and EPR data, the evaluated bonding parameters suggested that the bonding between the doped ions and ligands are partially covalent. The luminescent spectrum gives the emission bands in UV, blue, and green regions. The calculated CIE chromaticity coordinates from emission spectra give the color perception of the prepared nanocomposites. FTIR spectrum shows the essential oscillating function of ZnS, CdS plus additional active groups. Enhanced paramagnetic nature is observed at room temperature of the prepared material which is intrinsically caused by exchange coupling between the spin of the carriers and local magnetic moments. The emission process is attributed to the transition from lowest excited state to ground state, 4 T 1 → 6 A 1 , is arising from the octahedrally coordinated Mn 2+ sites. However, the PL spectrum of Mn 2+ doped ZnS-CdS composite nanopowder is recorded at room temperature under the excitation wavelength of 310 nm. It has exhibits four characteristic bands at UV, blue, green and red regions because of the variations in the local ligand field strength in the region of the Mn site. The sharp red emission band at 636 nm is due to the incorporation of Mn 2+ ions. Therefore, CIE chromaticity coordinates are also calculated from the corresponding PL spectrum as ( x = 0.3290, y = 0.3592) which represents orange- red emission. .

Physics of aging of nanophase alloys: Mössbauer investigation of nanocrystalline iron-copper pseudoalloy

This communication considers structural features of nanocrystals synthesized at high pressure consolidated mixed nanopowders. This system presents a pseudoalloy of mutually insoluble elements Fe and Cu, and contains pores. The study aims to demonstrate quasi-stable state of nanocrystals and factors preventing the aging. Mossbauer and X-ray analyses show a strong dependence of phase composition of Fe-Cu nanocrystalline pseudo-alloy on pressure and on aging duration. It is found pressure to coarsen phase inhomogeneity which exists initially in an as-synthesized Fe-Cu pseudoalloy. Aging duration is shown to affect the nanophase state in the same manner. It is agued that aside with typical parameters as grain size, density, phase composition of nanocrystalline substances one should know a prehistory of every sample: synthesis duration, temperature and pressure, which have a marked influence on physical properties of nanophase compacts. The Fe disorder in the Cu lattice revealed by Mossbauer spectra substantially depends on applied pressure.

Scandia-stabilized zirconia doped with yttria: Synthesis, properties, and ageing behavior

Synthesis, ionic conductivity, and ageing behavior of [ x Y 2 O 3 –(10 − x ) Sc 2 O 3 ]–90 ZrO 2 ( x = 2, 3, 4, and 5 mol%) as well as 10–11 mol% Sc 2 O 3 –ZrO 2 electrolytes are presented. High dense homogeneous ceramic samples with fine microstructure were prepared from laser synthesized mixed nanopowders 10YSZ and 10ScSZ using low sintering temperatures of 1010–1300 °C. Stabilization of cubic fluorite-type phase has been achieved for Y-doped ScSZ composites at these temperatures. It is shown that the DC conductivity of the Y-doped ScSZs decreases proportionally to the yttria content throughout the temperature range studied, from 500 to 900 °C. Ageing behavior of the electrolytes was studied at 850 °C for 1200–2700 h. Low resistivity degradation of Y-doped ScSZ not exceeded 10% during extended annealing for 2700 h has been obtained for the samples sintered below 1100 °C. High and stable conductivity has been obtained for 10ScSZ and 11ScSZ. Any decrease in their conductivity during extended annealing was not detected. ► Highly conductive ScSZ-based electrolytes were obtained. ► Low temperature processing was used to prepare fine-structured high dense ceramics. ► Extended annealing of electrolytes was performed in air at 850 °C for 2700 h. ► Stable conductivity was obtained for Y-doped ScSZs sintered below 1100 °C.

Simultaneous synthesis and single-step sintering of lead magnesium niobate ceramic using mixed nanopowders

Abstract A high density single-phase lead magnesium niobate ceramic with the highest peak dielectric constant reported so far, has been synthesized and sintered simultaneously via a modified mixed oxide route, using mixed oxide nanopowder and single-step sintering. The mixed nanopowder was sintered at 1200 °C in air and PbO atmospheres. By comparison, samples sintered in air, gained pyrochlore structure, while those samples sintered in PbO atmosphere had pure perovskite structure. Pellets sintered for 2.5 h exhibited best dielectric properties with peak dielectric constant of 18,672 at the frequency of 1 kHz at −13 °C. The dielectric properties, compressibility, phase formation, densification, and microstructure of the samples were investigated.