XRD characterization of highly dispersed metal catalysts on carbon support

1993 ◽  
Vol 8 (8) ◽  
pp. 1829-1835 ◽  
Author(s):  
Paolo Scardi ◽  
Pier Luigi Antonucci
Keyword(s):  
Particle Size ◽  
Supported Catalysts ◽  
Profile Analysis ◽  
Rietveld Method ◽  
Carbon Support ◽  
Lattice Parameter ◽  
Microstructural Parameters ◽  
Transmission Electron ◽  
Supported Pt Catalysts ◽  
Highly Dispersed

Carbon-supported Pt catalysts were prepared from H2PtCl6 or K2PtCl6 aqueous solutions. Particle size and structure after several thermal activation treatments were studied by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Cyclic Voltammetry (CV), and the results of the three techniques were compared. As the catalysts were highly dispersed on an amorphous support, a conventional XRD profile analysis for crystallite size determination could not be performed properly, because of the strong overlapping between the broad Pt peaks superposed to the halos of the amorphous phase. Thus, a new procedure of whole XRD pattern fitting, based on the Rietveld method, was used to have reliable data of Pt particle size (surface area) and lattice parameter. All structural and microstructural parameters were refined within the same procedure, also considering the transparency of the carbon supported catalysts and minimizing the effect of the amorphous background. The method can also take into account the presence of bimodal particle size distributions, which is difficult to study by CV or TEM.

Line profile analysis: pattern modellingversusprofile fitting

2006 ◽  
Vol 39 (1) ◽  
pp. 24-31 ◽  
Author(s):  
Paolo Scardi ◽  
Matteo Leoni
Keyword(s):  
Line Profile ◽  
Powder Diffraction ◽  
Profile Analysis ◽  
Domain Size ◽  
Systematic Errors ◽  
Powder Pattern ◽  
Line Profile Analysis ◽  
Microstructural Parameters ◽  
Profile Fitting ◽  
Transmission Electron

Powder diffraction data collected on a nanocrystalline ceria sample within a round robin conducted by the IUCr Commission on Powder Diffraction were analysed by two alternative approaches: (i) whole-powder-pattern modelling based upon a fundamental microstructural parameters approach, and (ii) a traditional whole-powder-pattern fitting followed by Williamson–Hall and Warren–Averbach analysis. While the former gives results in close agreement with those of transmission electron microscopy, the latter tends to overestimate the domain size effect, providing size values about 20% smaller. The origin of the discrepancy can be traced back to a substantial inadequacy of profile fitting with Voigt profiles, which leads to systematic errors in the following line profile analysis by traditional methods. However, independently of the model, those systematic errors seem to have little effect on the volume-weighted mean size.

Influence of La, Mn and Zn Substitution on the Structure, Magnetic and Absorption Properties of M-Type Barium Ferrites

2020 ◽  
Vol 855 ◽  
pp. 145-153
Author(s):  
Didin Sahidin Winatapura ◽  
Deswita ◽  
Ari Adi Wisnu ◽  
Setyo Purwanto ◽  
Y.F. Buys
Keyword(s):  
Electron Microscope ◽  
Rietveld Method ◽  
Structural Parameters ◽  
Lattice Parameter ◽  
Absorption Properties ◽  
Fine Grained ◽  
Zn Substitution ◽  
Transmission Electron ◽  
Barium Ferrites ◽  
Scherrer Formula

A series of M-type barium ferrites with chemicals composition BaFe12O19 and Ba0.7La0.3Fe(12-2x)(MnZn)xO19 (with x = 0.0, 0.2, 0.5) were synthesized using a chemical coprecipitation based technique. The sample was then called as BFO and BLF, BLFMZ-02 and BLFMZ-05, respectively. The structural parameters were measured by applying the full pattern fitting of Rietveld method using Fullprof program. The crystallite size was calculated using Scherrer formula and Williamson-Hall analysis method, and also confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM). The morphology of particle is composed of fine-grained aggregates with particle size distributions in the range of 70nm - 160nm. The lattice parameter (a = b and c), cell volume (Vcell) and density (ρ) of the samples were found to be changed with La, Mn and Zn substitution due to the dissimilar cationic radii of Ba2+ (1.49Å), La3+ (1.22Å), Fe3+ (0.64Å), Mn3+ (0.89Å) and Zn2+ (0.76Å) ions. The results of sample measurements with Vibrating Sample Magetometer (VSM) indicate that the magnetic behaviours showed that the saturation magnetization (Ms) increased gradually with the substitution of La3+, Mn3+ and Zn3+ ions, whereas the coercivity (Hc) was increase with addition of La3+ ions and then decrease significantly with the addition of Mn3+ and Zn2+ ions. The vector network analyzer (VNA) revealed that microwave absorption measured within 7 – 15 GHz frequency range indicated optimum reflection loss (RL) of-21.50dB at 10.5GHz for BLMZ-02 sample.

Study of Au-CeO2 Nano-particles using analytical Transmission Electron Microscopy

2007 ◽  
Vol 1 (1) ◽  
Author(s):  
P. Gu ◽  
G. Yang ◽  
R.F. Klie
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Particle Size ◽  
Rare Earth ◽  
Lattice Parameter ◽  
Nano Particles ◽  
Rare Earth Doping ◽  
Analytical Transmission Electron Microscopy ◽  
Transmission Electron ◽  
Shift Reaction

Cerium oxide doped with various rare earth metals is often used as a support for nano-sized gold particles, and demonstrates to be a promising catalyst for the water gas shift reaction at low temperatures. Many factors are hypothesized to affect the activity of this heterogeneous catalyst, including its loading with gold, the rare-earth dopant, the support and Au particle size, and leaching of the sample. In this study, we examined several Au/CeO2-based catalyst samples, including 2.4% Au/(Ce,Gd)O2, 1.8% Au/(Ce,La)O2 leached, 0.5% Au/(Ce,Gd)O2 leached, and 0.75% Au/CeO2 utilizing analytical transmission electron microscopy. The effects of Au and rare-earth doping on the ceria lattice parameter were investigated, and it was determined that there are no significant variations in the particle's structure or lattice-spacing. Furthermore, the particle sizes of each of the four samples were investigated concluding that although the 1.8% Au/(Ce,La)O2 leached sample has a slightly larger particle size, and the 2.4% Au/(Ce,Gd)O2 sample has a slightly smaller particle size, the differentiation is not adequate to be accountable for the radical distinction in catalytic activity.

Analysis of the Promoter-Catalyst interaction between Mn and Rh by Transmission Electron Microscopy

2014 ◽  
Vol 7 (1) ◽  
Author(s):  
B. Graham ◽  
R.F. Klie
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Particle Size ◽  
Average Particle Size ◽  
Lattice Parameter ◽  
Average Particle ◽  
Fischer Tropsch ◽  
Transmission Electron ◽  
Three Samples ◽  
Promoter Interaction

In the hope of optimizing the Fischer-Tropsch mechanism to produce cleaner ethanol, the catalyst- promoter interaction between rhodium and manganese was examined by transmission electron microscopy. Three samples were analyzed on a carbon nanotube (CNT) substrate with 3 wt% rhodium (3%Rh/CNT), 1% manganese with 3 wt% rhodium (1%Mn/3% Rh/CNT), and 2% manganese with 3 wt% rhodium (2% Mn/3% Rh/CNT). The average particle size were found to be (1.9 ± 0.6) nm, (2.1 ± 0.5) nm, and (3.2 ± 0.6) nm, respectively. An increase in particle size indicates that the rhodium and manganese are interacting. The lattice parameter for rhodium were also determined to be (4.1 ± 0.1) Å, (4.2 ± 0.1) Å, and (3.8 ± 0.1) Å, respectively. The decrease in lattice parameter in the 2%Mn/3%Rh/CNT sample was most likely due to a change in the crystal structure of the rhodium particles as a result of the interaction between the manganese and rhodium.

Line profile analysis of synchrotron X-ray diffraction data of iron powder with bimodal microstructural profile parameters

2021 ◽  
Vol 54 (2) ◽  
Author(s):  
Ashok Bhakar ◽  
Pooja Gupta ◽  
P. N. Rao ◽  
M. K. Swami ◽  
Pragya Tiwari ◽  
...  
Keyword(s):  
Diffraction Pattern ◽  
Line Profile ◽  
Profile Analysis ◽  
Rietveld Method ◽  
Domain Size ◽  
Microstructural Characterization ◽  
Line Profile Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microstructural Parameters

Room-temperature synchrotron X-ray diffraction and subsequent detailed line profile analysis of Fe powder were performed for microstructural characterization. The peak shapes of the diffraction pattern of Fe were found to be super-Lorentzian in nature and the peak widths were anisotropically broadened. These peak profile features of the diffraction pattern are related to the microstructural parameters of the material. In order to elucidate these features of the diffraction pattern, detailed line (peak) profile analyses were performed using the Rietveld method, modified Williamson–Hall plots and whole powder pattern modelling (WPPM), and related microstructural parameters were determined. Profile fitting using the Rietveld and WPPM methods with a single microstructural (unimodal) model shows systematic deviation from the experimentally observed diffraction pattern. On the basis of Rietveld analysis and microstructural modelling it is revealed that the microstructure of Fe consists of two components (bimodal profile). The microstructural parameters of crystallite/domain size distribution, dislocation density, nature of dislocations and phase fraction were evaluated for both components. The results obtained using different methods are compared, and it is shown that diffraction peak profile analysis is capable of modelling such inhomogeneous bimodal microstructures.

Examination by Electron Microscopy of Osmium Catalysts Supported on Thin Aluminium-Oxide Films

1982 ◽  
Vol 40 ◽  
pp. 658-659
Author(s):  
B. Tesche ◽  
E. Zeitler ◽  
E. A. Delgado ◽  
H. Knözinger
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Metal Atom ◽  
Supported Catalysts ◽  
Metal Particles ◽  
Transmission Electron ◽  
High Area ◽  
Instrumental Resolution ◽  
Electron Microscopes ◽  
Small Metal Particles

It is easy to obtain resolutions of atomic dimensions with current conventional transmission electron microscopes. Hence, in principle, the examination of small metal particles or metal atom ensembles (≤1 nra) in supported catalysts is not limited by the instrumental resolution. However, usually the metal is located on dispersed high-area supports such as silica or alumina and the characterization by electron microscopy of these systems down to the atomic dimension is not directly possible, since the contrast in the micrographs is an unknown combination of phase and amplitude contrast. This uncertainty can result in incorrect determinations of particle size, shape and distribution.

EFFECT OF HEAT TREATMENT ON THE STRUCTURE OF SiC−Si3N4 COMPOSITE ULTRAFINE POWDER

1996 ◽  
Vol 03 (01) ◽  
pp. 79-83 ◽  
Author(s):  
X. LI ◽  
Y. NAKATA ◽  
H. NAGAI ◽  
T. OKUTANI ◽  
M. SUZUKI
Keyword(s):  
Heat Treatment ◽  
Particle Size ◽  
Lattice Parameter ◽  
Ultrafine Powder ◽  
Phase Reaction ◽  
X Ray Diffraction ◽  
Xrd Pattern ◽  
Transmission Electron ◽  
Heat Treated ◽  
Original Powder

Effect of heat treatment on the structure of SiC−Si3N4 composite ultrafine powder was studied. SiC-Si3N4 composite ultrafine powder synthesized by laser-induced gas-phase reaction was heat-treated at various temperatures below 1773 K in 99% Ar +1% H2 gas mixture. The change of the structure was studied by chemical analysis, x-ray diffraction (XRD), and transmission electron microscope (TEM). The structure of the powder did not change significantly in lattice constant, particle size, and composition by the treatment up to 1573 K . The structure of the powder changed drastically by the treatment above 1673 K . The broad XRD pattern due to β- Si for the original powder changed to the four phases of β- SiC , Si and α, β- Si 3N4 by the treatment at 1773 K , accompanied by large increases in particle size and lattice parameter, and decreases in nitrogen content and specific surface area.

Measurement of lattice parameter at the nanometer scale using convergent-beam microdiffraction from a thermal emission source

1993 ◽  
Vol 51 ◽  
pp. 690-691
Author(s):  
W. T. Pike
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Thermal Emission ◽  
Lattice Parameter ◽  
Scanning Transmission Electron Microscope ◽  
Emission Source ◽  
Device Structure ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Convergent Beam

With the advent of crystal growth techniques which enable device structure control at the atomic level has arrived a need to determine the crystal structure at a commensurate scale. In particular, in epitaxial lattice mismatched multilayers, it is of prime importance to know the lattice parameter, and hence strain, in individual layers in order to explain the novel electronic behavior of such structures. In this work higher order Laue zone (holz) lines in the convergent beam microdiffraction patterns from a thermal emission transmission electron microscope (TEM) have been used to measure lattice parameters to an accuracy of a few parts in a thousand from nanometer areas of material.Although the use of CBM to measure strain using a dedicated field emission scanning transmission electron microscope has already been demonstrated, the recording of the diffraction pattern at the required resolution involves specialized instrumentation. In this work, a Topcon 002B TEM with a thermal emission source with condenser-objective (CO) electron optics is used.

scholarly journals Towards High Efficacy of Pd-Au/C Catalyst for Tetrachloromethane Hydrodechlorination

Chemistry ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 338-359
Author(s):  
Magdalena Bonarowska ◽  
Zbigniew Kaszkur ◽  
Krzysztof Matus ◽  
Alicja Drelinkiewicz ◽  
Tomasz Szumełda ◽  
...  
Keyword(s):  
Microwave Irradiation ◽  
Gas Phase ◽  
Thermal Activation ◽  
Supported Catalysts ◽  
Carbon Support ◽  
Thermal Reduction ◽  
Microwave Oven ◽  
Optimal Conditions ◽  
Catalyst Activation ◽  
Critical Part

We present an efficient strategy for synthesising the PdAu catalysts with a homogeneous PdAu alloy phase for environmentally important hydrodechlorination of tetrachloromethane in the gas phase. The synthesis of carbon-supported catalysts involved two major steps: (i) incorporation of palladium and gold nanoparticles into carbon support and (ii) activation of the catalysts. The critical part of this work was to find the optimal conditions for both steps. Thus, the incorporation of the nanoparticles was carried out in two ways, by impregnation and direct redox reaction method using acetone solutions of metal precursor salts. The activation was performed either by a conventional thermal reduction in hydrogen or flash irradiation in a microwave oven. The homogeneity and structure of the PdAu alloy were found to depend on the catalyst activation method critically. In all cases, we observed better homogeneity for catalysts that were subject to microwave irradiation. Moreover, the flash microwave irradiation of prepared catalysts provided catalysts of better stability and selectivity towards the desired products (hydrocarbons) in the hydrodechlorination of tetrachloromethane as compared to the catalyst obtained by conventional thermal activation in hydrogen.

Microstructure Characterization of Ag Nanoparticles Prepared by Hydrothermal Method

2012 ◽  
Vol 476-478 ◽  
pp. 1138-1141
Author(s):  
Zhi Qiang Wei ◽  
Qiang Wei ◽  
Li Gang Liu ◽  
Hua Yang ◽  
Xiao Juan Wu
Keyword(s):  
Crystal Structure ◽  
Particle Size ◽  
Hydrothermal Method ◽  
Ag Nanoparticles ◽  
Average Particle Size ◽  
Average Particle ◽  
Face Centered Cubic ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Face Centered

Ag nanoparticles were successfully synthesized by hydrothermal method under the polyol system combined with traces of sodium chloride, Silver nitrate(AgNO3) and polyvinylpyrrolidone (PVP) acted as the silver source and dispersant respectively. The samples by this process were characterized via X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET) adsorption equation, transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED) to determine the chemical composition, particle size, crystal structure and morphology. The experiment results indicate that the crystal structure of the samples is face centered cubic (FCC) structure as same as the bulk materials, The specific surface area is 24 m2/g, the particle size distribution ranging from10 to 50 nm, with an average particle size about 26 nm obtained by TEM and confirmed by XRD and BET results.

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