Transmission Electron Microscopy Studies of Pd Encapsulation by Ceria-Zirconia Oxides

1998 ◽  
Vol 4 (S2) ◽  
pp. 724-725
Author(s):  
J. C. Jiang ◽  
X. Q. Pan ◽  
G. W. Graham ◽  
R. W. McCabe ◽  
J. Schwank
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Surface Area ◽  
High Speed ◽  
High Surface ◽  
Silicon Crystal ◽  
High Surface Area ◽  
Thermal Environments ◽  
Transmission Electron

High-temperature catalysts containing Pd supported on high-surface area ceria-zirconia are optimum materials for fuel economy when automotive engines operate under high speed or load conditions. A prerequisite for developing such thermally stable catalysts is to gain a good understanding of the thermal deactivation modes contributing to the aging and degradation of catalysts in harsh thermal environments. It was discovered by X-ray diffraction that upon hightemperature aging, Pd may sinter into large (about 10 nm diameter) particles and become encapsulated in the ceria-zirconia. To confirm this conclusion, a prototype high-temperature catalyst containing Pd supported on high-surface area ceria-zirconia, aged at temperature above 1100 °C is studied by transmission electron microscopy (TEM).The ceria-zirconia supported Pd (0.25 wt%) catalyst was aged at 1105 °C and calcined at 700 °C for 2 h. For TEM sample preparations, first of all, a large-size aggregate with diameter about 1 mm was selected and sandwiched between by two pieces of silicon crystal.

Characterization of an Inorganic Cryptomelane Nanomaterial Synthesized by a Novel Process Using Transmission Electron Microscopy and X-Ray Diffraction

2008 ◽  
Vol 14 (4) ◽  
pp. 328-334 ◽  
Author(s):  
Longzhou Ma ◽  
Thomas Hartmann ◽  
Marcos A. Cheney ◽  
Nancy R. Birkner ◽  
Pradip K. Bhowmik
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Surface ◽  
High Surface Area ◽  
Rietveld Analysis ◽  
X Ray ◽  
Transmission Electron ◽  
Potential Applications ◽  
Diffraction Patterns ◽  
Crystallographic Planes

Layer- and tunnel-structured manganese oxide nanomaterials are important because of their potential applications in industrial catalysis. A novel soft chemistry method was developed for the synthesis of inorganic cryptomelane nanomaterials with high surface area. Bright field transmission electron microscopy (BF-TEM) and high-resolution transmission electron microscopy (HRTEM) techniques were employed to characterize this nanomaterial. A nanosized material with fibrous texture comprised of 140–160 nm striations was identified by BF-TEM imaging. HRTEM images show multiple atomic morphologies such as “helix-type,” “doughnut-like,” and tunnel structures lying on different crystallographic planes. The crystallographic parameters of this material were analyzed and measured by X-ray powder diffraction (XRD) showing that the synthesized nanomaterial is single phased and corresponds to cryptomelane with major diffraction peaks (for 10° < 2θ < 60°) at d-spacing values of 6.99, 4.94, 3.13, 2.40, 2.16, 1.84, 1.65, and 1.54 Å. A “doughnut-like” crystal structure was confirmed based on the crystallographic data. Structure and lattice parameters refinement was performed by XRD/Rietveld analysis. Simple simulation of HRTEM images and selected area diffraction patterns were applied to interpret the HRTEM images as observed.

High Surface Area Silicon Carbide Doped with Zirconium for use as Heterogeneous Catalyst Support

1996 ◽  
Vol 454 ◽  
Author(s):  
Marc J. Ledoux ◽  
Cuong Pham-Huu ◽  
Christophe Bouchy ◽  
Pascal Del Gallo ◽  
Claude Estournes ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Surface Area ◽  
High Surface ◽  
Catalyst Support ◽  
High Surface Area ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Bet Method ◽  
Porosity Measurements

ABSTRACTHigh surface area (> 100 m2 · g−1) SiC doped with zirconium was prepared by the gas-solid reaction. The material was made up of three phases: β-SiC, covered by ZrO2 and an amorphous phase composed of Si, Zr and O. The characterization of the sample was performed by means of powder X-ray diffraction (XRD), surface area and porosity measurements by the BET method, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Preliminary catalytic tests, the standard n-C7 isomerization on supported MoOxCy showed that this new support was at least as effective as pure SiC.

scholarly journals Pd Nanoparticles Stabilized on the Cross-Linked Melamine-Based SBA-15 as a Catalyst for the Mizoroki–Heck Reaction

2021 ◽  
Author(s):  
Ayat Nuri ◽  
Abolfazl Bezaatpour ◽  
Mandana Amiri ◽  
Nemanja Vucetic ◽  
Jyri-Pekka Mikkola ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Inductively Coupled Plasma ◽  
High Surface ◽  
High Surface Area ◽  
Coupling Reaction ◽  
Pd Nanoparticles ◽  
Significant Activity ◽  
Inductively Coupled ◽  
Transmission Electron ◽  
Ft Ir

AbstractMesoporous SBA-15 silicate with a high surface area was prepared by a hydrothermal method, successively modified by organic melamine ligands and then used for deposition of Pd nanoparticles onto it. The synthesized materials were characterized with infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nitrogen physisorption, scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) and inductively coupled plasma (ICP-OES). The catalyst was effectively used in the Mizoroki–Heck coupling reaction of various reactants in the presence of an organic base giving the desired products in a short reaction time and with small catalysts loadings. The reaction parameters such as the base type, amounts of catalyst, solvents, and the temperature were optimized. The catalyst was easily recovered and reused at least seven times without significant activity losses. Graphic Abstract

Effect of Coupled Conditions of Thermal Cycle and Dump Environment on Conductivity of 5mol% Yttria Stabilized Zirconia

2013 ◽  
Vol 591 ◽  
pp. 245-248 ◽  
Author(s):  
Jin Feng Xia ◽  
Hong Qiang Nian ◽  
Tao Feng ◽  
Hai Fang Xu ◽  
Dan Yu Jiang
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Thermal Cycle ◽  
Oxygen Sensor ◽  
Yttria Stabilized Zirconia ◽  
Cyclic Change ◽  
Stabilized Zirconia ◽  
Transmission Electron

In some applications such as automotive oxygen sensor, 5mol% Y2O3stabilized zirconia (5YSZ) is generally used because it has both excellent ionic conductivity and mechanical properties. The automotive oxygen sensor would experience a cyclic change from high temperature (engine running) environment to the low temperature damp environment (in the tail pipe when vehicle stops). The conductivity change with coupled conditions of thermal cycle and dump environment in the 5mol%Y2O3ZrO2(5YSZ) system was examined by XRD,Impedance spectroscopy and transmission electron microscopy (SEM) in this paper.

Texture Evaluation of Sol-Gel Derived Mesoporous Bioactive Glass

2013 ◽  
Vol 284-287 ◽  
pp. 230-234
Author(s):  
Yu Jen Chou ◽  
Chi Jen Shih ◽  
Shao Ju Shih
Keyword(s):  
Surface Area ◽  
Calcination Temperature ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Nitrogen Adsorption ◽  
Bioactive Glasses ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Adsorption Desorption

Recent years mesoporous bioactive glasses (MBGs) have become important biomaterials because of their high surface area and the superior bioactivity. Various studies have reported that when MBGs implanted in a human body, hydroxyl apatite layers, constituting the main inorganic components of human bones, will form on the MBG surfaces to increase the bioactivity. Therefore, MBGs have been widely applied in the fields of tissue regeneration and drug delivery. The sol-gel process has replaced the conventional glasses process for MBG synthesis because of the advantages of low contamination, chemical flexibility and lower calcination temperature. In the sol-gel process, several types of surfactants were mixed with MBG precursor solutions to generate micelle structures. Afterwards, these micelles decompose to form porous structures after calcination. Although calcination is significant for contamination, crystalline and surface area in MBG, to the best of the authors’ knowledge, only few systematic studies related to calcination were reported. This study correlated the calcination parameters and the microstructure of MBGs. Microstructure evaluation was characterized by transmission electron microscopy and nitrogen adsorption/desorption. The experimental results show that the surface area and the pore size of MBGs decreased with the increasing of the calcination temperature, and decreased dramatically at 800°C due to the formation of crystalline phases.

In Situ High-Temperature Transmission Electron Microscopy Observations of the Formation of Nanocrystalline TiC from Nanocrystalline Anatase (TiO2)

1998 ◽  
Vol 4 (3) ◽  
pp. 269-277 ◽  
Author(s):  
A. Agrawal ◽  
J. Cizeron ◽  
V.L. Colvin
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Solid Phase ◽  
Anatase Phase ◽  
High Resolution Electron Microscopy ◽  
Rutile Phase ◽  
Transmission Electron ◽  
New Phase

In this work, the high-temperature behavior of nanocrystalline TiO2 is studied using in situ transmission electron microscopy (TEM). These nanoparticles are made using wet chemical techniques that generate the anatase phase of TiO2 with average grain sizes of 6 nm. X-ray diffraction studies of nanophase TiO2 indicate the material undergoes a solid-solid phase transformation to the stable rutile phase between 600° and 900°C. This phase transition is not observed in the TEM samples, which remain anatase up to temperatures as high as 1000°C. Above 1000°C, nanoparticles become mobile on the amorphous carbon grid and by 1300°C, all anatase diffraction is lost and larger (50 nm) single crystals of a new phase are present. This new phase is identified as TiC both from high-resolution electron microscopy after heat treatment and electron diffraction collected during in situ heating experiments. Video images of the particle motion in situ show the nanoparticles diffusing and interacting with the underlying grid material as the reaction from TiO2 to TiC proceeds.

Surface amorphization in diamond turning of silicon crystal investigated by transmission electron microscopy

2000 ◽  
Vol 272 (2-3) ◽  
pp. 174-178 ◽  
Author(s):  
Renato G Jasinevicius ◽  
Francisco J dos Santos ◽  
Paulo S Pizani ◽  
Jaime G Duduch ◽  
Arthur J.V Porto
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Silicon Crystal ◽  
Diamond Turning ◽  
Transmission Electron

Microstructure of LaB6-base thick film resistors

1992 ◽  
Vol 7 (8) ◽  
pp. 2225-2229 ◽  
Author(s):  
Z.G. Li ◽  
P.F. Carcia ◽  
P.C. Donohue
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Thick Film ◽  
Surface Area ◽  
Ion Milling ◽  
Cross Sectional ◽  
Electrically Conductive ◽  
Transmission Electron ◽  
High Temperature Processing ◽  
Thin Wedge

The microstructure of LaB6-base thick film resistors was investigated by cross-sectional transmission electron microscopy. The specimens were prepared by a technique that polished them to a thin wedge, thus avoiding ion-milling and permitting imaging over a distance of tens of microns. The resistor microstructure contained a finely divided electrically conductive phase of TaB2 and nonconducting crystals of CaTa4O11, formed during high temperature processing of glass and LaB6 ingredients of the thick film ink. Using higher surface area ingredients virtually suppressed the formation of CaTa4O11 crystals, and the microstructure became more uniform. Resistors made with higher surface area intermediates also had better voltage withstanding properties.

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