Synthesis and Laser Spectroscopy of Monoclinic Eu3+: Y2O3 Nanocrystals

1996 ◽  
Vol 457 ◽  
Author(s):  
Bipin Bihari ◽  
Brian M. Tissue
Keyword(s):  
Gas Phase ◽  
Monoclinic Phase ◽  
Nanocrystalline Material ◽  
Secondary Phase ◽  
Nitrogen Atmosphere ◽  
Starting Material ◽  
Line Broadening ◽  
Transmission Electron ◽  
Laser Heated ◽  
Cation Sites

ABSTRACTGas-phase condensation of CO2 laser-heated EU3+:Y2O3 ceramics produces monoclinic-phase nanocrystalline material. Transmission electron microscopy shows particle diameters in the range 7–30 nm for particles quenched at 60 °C under 400 Torr of nitrogen atmosphere. The optical spectra of nanocrystals produced from 0.1% Eu3+:Y2O3 starting material have narrow lines, and the 5D0 lifetimes are 1.8, 1.2 and, 1.3 ms for the three Eu3+ cation sites. Nanocrystals obtained from 0.7 –5 % Eu3+:Y2O3 starting material show line broadening and the presence of Eu2O3 secondary phase.

Extraction and identification of fillers and pigments from pyrolyzed rubber and tire samples

1996 ◽  
Vol 54 ◽  
pp. 174-175
Author(s):  
P. Sadhukhan ◽  
J. B. Zimmerman
Keyword(s):  
Zinc Oxide ◽  
Electron Microscope ◽  
Carbon Black ◽  
Natural Rubber ◽  
Transmission Electron Microscope ◽  
Rolling Resistance ◽  
Synthetic Polymers ◽  
Nitrogen Atmosphere ◽  
Transmission Electron ◽  
Curing Agents

Rubber stocks, specially tires, are composed of natural rubber and synthetic polymers and also of several compounding ingredients, such as carbon black, silica, zinc oxide etc. These are generally mixed and vulcanized with additional curing agents, mainly organic in nature, to achieve certain “designing properties” including wear, traction, rolling resistance and handling of tires. Considerable importance is, therefore, attached both by the manufacturers and their competitors to be able to extract, identify and characterize various types of fillers and pigments. Several analytical procedures have been in use to extract, preferentially, these fillers and pigments and subsequently identify and characterize them under a transmission electron microscope.Rubber stocks and tire sections are subjected to heat under nitrogen atmosphere to 550°C for one hour and then cooled under nitrogen to remove polymers, leaving behind carbon black, silica and zinc oxide and 650°C to eliminate carbon blacks, leaving only silica and zinc oxide.

Observation of solid-state reaction between a thin yttria film and a (0001) α-alumina substrate

1994 ◽  
Vol 52 ◽  
pp. 644-645
Author(s):  
J. R. Heffelfinger ◽  
C. B. Carter
Keyword(s):  
Electron Microscopy ◽  
Solid State ◽  
Solid State Reaction ◽  
Yttrium Aluminum Garnet ◽  
Secondary Phase ◽  
Ceramic Composites ◽  
Alumina Substrate ◽  
Transmission Electron ◽  
Alumina Fibers ◽  
Optical Applications

Transmission-electron microscopy (TEM), scanning-electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) were used to investigate the solid-state reaction between a thin yttria film and a (0001) α-alumina substrate. Systems containing Y2O3 (yttria) and Al2O3 (alumina) are seen in many technologically relevant applications. For example, yttria is being explored as a coating material for alumina fibers for metal-ceramic composites. The coating serves as a diffusion barrier and protects the alumina fiber from reacting with the metal matrix. With sufficient time and temperature, yttria in contact with alumina will react to form one or a combination of phases shown by the phase diagram in Figure l. Of the reaction phases, yttrium aluminum garnet (YAG) is used as a material for lasers and other optical applications. In a different application, YAG is formed as a secondary phase in the sintering of AIN. Yttria is added to AIN as a sintering aid and acts as an oxygen getter by reacting with the alumina in AIN to form YAG.

scholarly journals In Situ Observation of Electron-Beam-Induced Formation of Nano-Structures in PbTe

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 163
Author(s):  
Iryna Zelenina ◽  
Igor Veremchuk ◽  
Yuri Grin ◽  
Paul Simon
Keyword(s):  
Electron Beam ◽  
Gas Phase ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Atomic Scale ◽  
In Situ Observation ◽  
Nano Structures ◽  
Transmission Electron ◽  
Initial Crystal

Nano-scaled thermoelectric materials attract significant interest due to their improved physical properties as compared to bulk materials. Well-shaped nanoparticles such as nano-bars and nano-cubes were observed in the known thermoelectric material PbTe. Their extended two-dimensional nano-layer arrangements form directly in situ through electron-beam treatment in the transmission electron microscope. The experiments show the atomistic depletion mechanism of the initial crystal and the recrystallization of PbTe nanoparticles out of the microparticles due to the local atomic-scale transport via the gas phase beyond a threshold current density of the beam.

Partial Devitrification of Sintered Silicon Nitride During Static Fatigue Testing

1992 ◽  
Vol 287 ◽  
Author(s):  
W. Braue ◽  
G. D. Quinn
Keyword(s):  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Slow Crack Growth ◽  
Stress Rupture ◽  
Secondary Phase ◽  
Boundary Phase ◽  
Static Fatigue ◽  
Phase Assemblage ◽  
Transmission Electron ◽  
Stress States

ABSTRACTThe static fatigue behavior of sintered Y2O3/A12O3-fluxed Si3N4 in air is controlled by slow crack growth or creep fracture. Partial devitrification of the amorphous grain boundary phase at 1000°C and 1100°C improves the static fatigue resistance with specimens surviving up to 1500 hrs. during stress rupture experiments. In this study the early stages of partial devitrification during static fatigue testing at 1000°C are investigated by conventional and analytical transmission electron microscopy with emphasis on nucleation and growth of δ-Y2Si2O7 and X1-Y2SiO5 and possible constraints from different stress states. The results show that the stress state does not affect the nature of the secondary phase assemblage. However, the amount of crystallization is higher within the tensile region of the flexural specimens than in areas which experienced compressive stresses.

Transmission electron microscopy observation in a liquid-phase-sintered SiC with oxynitride glass

2001 ◽  
Vol 16 (8) ◽  
pp. 2189-2191 ◽  
Author(s):  
Guo-Dong Zhan ◽  
Mamoru Mitomo ◽  
Young-Wook Kim ◽  
Rong-Jun Xie ◽  
Amiya K Mukherjee
Keyword(s):  
Electron Microscopy ◽  
Liquid Phase ◽  
High Resolution Electron Microscopy ◽  
Nitrogen Atmosphere ◽  
X Ray Diffraction ◽  
Sintering Additive ◽  
Transmission Electron ◽  
High Annealing ◽  
Resolution Electron ◽  
Oxynitride Glass

Using a pure α–SiC starting powder and an oxynitride glass composition from the Y–Mg–Si–Al–O–N system as a sintering additive, a powder mixture was hot-pressed at 1850 °C for 1 h under a pressure of 20 MPa and further annealed at 2000 °C for 4 h in a nitrogen atmosphere of 0.1 MPa. High-resolution electron microscopy and x-ray diffraction studies confirmed that a small amount of β–SiC was observed in the liquid-phase-sintered α–SiC with this oxynitride glass, indicating stability of β–SiC even at high annealing temperature, due to the nitrogen-containing liquid phase.

Influence of ethanol on the chain-ordering of carbonised polyaniline

2013 ◽  
Vol 67 (8) ◽  
Author(s):  
Zuzana Morávková ◽  
Miroslava Trchová ◽  
Elena Tomšík ◽  
Jaroslav Stejskal
Keyword(s):  
Molecular Structure ◽  
Pure Water ◽  
Nitrogen Atmosphere ◽  
Ethanol Mixture ◽  
Electron Microscopies ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Pani Salt ◽  
Chain Ordering ◽  
Pani Base

AbstractPolyaniline (PANI) was prepared by the oxidation of aniline hydrochloride with ammonium peroxydisulphate in water or in a water-ethanol mixture. In the presence of ethanol, PANI nanotubes and nanorods were observed. Both products were carbonised in a nitrogen atmosphere at 650°C. Initial and carbonised products were characterised by scanning and transmission electron microscopies, thermogravimetric analysis and wide-angle X-ray scattering. Their molecular structure was studied by UV-VIS, infrared, and Raman spectroscopies. Carbonised sample obtained from the PANI salt prepared in the presence of ethanol exhibits Raman spectrum which corresponds to a more ordered carbon-like material than carbonised samples obtained from the PANI base and the PANI salt prepared in pure water. The influence of ethanol present in the reaction mixture on the molecular and supra-molecular structure of PANI and, consequently, on the enhancement of chainordering of carbonised PANI is discussed.

scholarly journals Ahmed Hassan Zewail. 26 February 1946—2 August 2016

2019 ◽  
Vol 68 ◽  
pp. 431-453
Author(s):  
John Meurig Thomas
Keyword(s):  
Electron Microscopy ◽  
Gas Phase ◽  
Ultrafast Lasers ◽  
Atomic Level ◽  
Women In Science ◽  
President Obama ◽  
Structure And Dynamics ◽  
Transmission Electron ◽  
The Individual ◽  
Gas Phase Electron Diffraction

Ahmed Zewail will forever be remembered for three main reasons: first, he was the individual who first demonstrated that the structure and dynamics of atoms in the transition state of chemical reactions could be determined through the judicious use of ultrafast lasers, in a field that he pioneered, for which he coined, called femtochemistry; second, he transformed both gas phase electron diffraction and transmission electron microscopy by improving their temporal resolution some 10 orders of magnitude, while simultaneously retaining the spatial resolution of electron microscopy at the atomic level; and third, he was the first US Science Envoy to the Middle East (appointed by President Obama). To all who knew him, he was a warm-hearted, life-enhancing person endowed with exceptional technical virtuosity as an experimentalist and a profound thinker, whose prodigality of output was also exceptional. He exhibited remarkable skills as an enterprising fundraiser in his determination to establish the Zewail City of Science and Technology on the outskirts of his beloved Cairo. He also influenced greatly the L'Oréal–UNESCO scheme for awarding prizes to women in science.

Nickel Ferrite: Combustion Synthesis, Characterization and Magnetic Properties

2005 ◽  
Vol 498-499 ◽  
pp. 618-623 ◽  
Author(s):  
Ana Cristina Figueiredo de Melo Costa ◽  
Lucianna Gama ◽  
M.R. Morelli ◽  
Ruth Herta Goldsmith Aliaga Kiminami
Keyword(s):  
Magnetic Properties ◽  
Nickel Ferrite ◽  
High Speed ◽  
High Specific Surface Area ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Railway Systems ◽  
Transmission Electron ◽  
Dry Pressing

Nanosized spinel nickel ferrite particles have attracted considerable attention and efforts continue to investigate them for their technological importance to the microwave industries, high speed digital tap or disk recording, repulsive suspension for use in levitated railway systems, ferrofluids, catalysis and magnetic refrigeration systems. Nanosize nickel ferrite powders (NiFe2O4) have been prepared by combustion reaction using nitrates and urea as fuel. The resulting powders were characterized by X-ray diffraction (XRD), BET, and transmission electron microscopy (TEM). The results showed nanosize nickel ferrite powders with high specific surface area (55.21 m2/g). The powders showed extensive XRD line broadening and the crystallite size calculated from the XRD line broadening was 18.0 nm. The samples were uniaxially compacted by dry pressing, sintered at 1200°C/2h and characterized by bulk density, SEM and magnetic properties measurements. The samples showed uniform microstructures with grain size of 4.45 μm, maximum flux density of 0.18T, field coercive of the 488 A/m, and hysteresis loss of 47.58 W/kg.

Elemental, Thermal, and Structural Characterization of ZnO Doped 8 mol% Yttria-Stabilized Zirconia (8YSZ) Ceramics

2017 ◽  
Vol 888 ◽  
pp. 57-61 ◽  
Author(s):  
Johar Banjuraizah ◽  
Tinesha Selvaraj ◽  
Zainal Arifin Ahmad
Keyword(s):  
Structural Characterization ◽  
Tetragonal Phase ◽  
Monoclinic Phase ◽  
Ionic Conductivities ◽  
Secondary Phase ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Mixed Powder ◽  
Dominant Phase

8 mol% of Yttrium oxide doped Zirconia (8YSZ) is one of the most explored compositions which give high ionic conductivities and good power output at 1000 °C. Generally, dopant was added to improve the sinterability of 8YSZ ceramics. In this present study, granulated 8YSZ powders with multimodal size was mixed with ZnO (0,1,2,3 wt%) using mortar and pestle. The mixed powder was compacted and sintered at 1550°C for 2 hours. 2 distinct endothermic peaks were observed in DTA plot of all samples. However, samples contain high amount of ZnO had a broader endothermic peak which resulted from the melting of ZnO. Rietveld refinement results indicate that the tetragonal phase appeared as the dominant phase for all doped and undoped samples, while cubic and monoclinic phase as the secondary phase. The monoclinic phase decreased as the amount of ZnO increased.

Structural characterization of the n = 5 layered perovskite neodymium titanate using high-resolution transmission electron microscopy and image reconstruction

2003 ◽  
Vol 59 (4) ◽  
pp. 449-455 ◽  
Author(s):  
Maria Sayagués ◽  
Katherine Titmuss ◽  
Rudiger Meyer ◽  
Angus Kirkland ◽  
Jeremy Sloan ◽  
...  
Keyword(s):  
High Resolution ◽  
Plane Wave ◽  
Layered Perovskite ◽  
Exit Plane ◽  
Anion Sublattice ◽  
Oxygen Anion ◽  
Enhanced Resolution ◽  
Transmission Electron ◽  
Cation Sites

The structure of Nd5Ti5O17 has been refined from a reconstruction of the specimen exit-plane wave restored from a series of incrementally defocused high-resolution transmission electron microscope (HRTEM) images. The phase of the exit-plane wave shows contrast attributable to the oxygen anion sublattice and coupled with simulations provides confirmation of the composition of the cation sites as a function of sample thickness. The enhanced resolution in the exit-plane wave additionally allows a direct measurement of the `skewing' of the perovskite slabs.

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