Structure–redox reactivity relationships in Co1−xZnxFe2O4: the role of stoichiometry

2019 ◽  
Vol 43 (7) ◽  
pp. 3038-3049 ◽  
Author(s):  
Tetiana Tatarchuk ◽  
Natalia Paliychuk ◽  
Michał Pacia ◽  
Wojciech Kaspera ◽  
Wojciech Macyk ◽  
...  
Keyword(s):  
Redox Reaction ◽  
Catalytic Properties ◽  
Ferrite Nanoparticles ◽  
Active Centers ◽  
Modeling Approach ◽  
Cationic Distribution ◽  
Zn Ferrite ◽  
Redox Reactivity ◽  
Strong Relation

The strong relation between the cationic distribution and catalytic properties of Co–Zn ferrite nanoparticles was studied and the new antistructure modeling approach has been proposed for identification of the active centers in the redox reaction.

Temperature and field dependences of transverse relaxivity of Co–Zn ferrite nanoparticles coated with silica: The role of magnetic properties and different regimes

2021 ◽  
Vol 260 ◽  
pp. 124178
Author(s):  
Pavel Veverka ◽  
Lenka Kubíčková ◽  
Zdeněk Jirák ◽  
Vít Herynek ◽  
Miroslav Veverka ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Ferrite Nanoparticles ◽  
Zn Ferrite

Polyol synthesis of non-stoichiometric Mn–Zn ferrite nanocrystals: structural /microstructural characterization and catalytic application

RSC Advances ◽  
2015 ◽  
Vol 5 (80) ◽  
pp. 65010-65022 ◽  
Author(s):  
Z. Beji ◽  
M. Sun ◽  
L. S. Smiri ◽  
F. Herbst ◽  
C. Mangeney ◽  
...  
Keyword(s):  
Dimethyl Ether ◽  
Oxidation Reaction ◽  
Catalytic Properties ◽  
Microstructural Characterization ◽  
Ferrite Nanoparticles ◽  
Polyol Synthesis ◽  
Catalytic Application ◽  
Zn Ferrite ◽  
Structure And Microstructure

The structure and microstructure of polyol-made non-stoichiometric Mn–Zn ferrite nanoparticles were successfully investigated and correlated to their catalytic properties toward dimethyl ether oxidation reaction.

Microstructure and reactivity of small metal particles: The role of Ce additives

1992 ◽  
Vol 50 (1) ◽  
pp. 318-319
Author(s):  
L.D. Schmidt ◽  
K. R. Krause ◽  
J. M. Schwartz ◽  
X. Chu
Keyword(s):  
Atmospheric Pressure ◽  
Noble Metals ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Chemical Shifts ◽  
Catalytic Converter ◽  
Structural Evolution ◽  
Single Particles ◽  
Small Metal Particles

The evolution of microstructures of 10- to 100-Å diameter particles of Rh and Pt on SiO2 and Al2O3 following treatment in reducing, oxidizing, and reacting conditions have been characterized by TEM. We are able to transfer particles repeatedly between microscope and a reactor furnace so that the structural evolution of single particles can be examined following treatments in gases at atmospheric pressure. We are especially interested in the role of Ce additives on noble metals such as Pt and Rh. These systems are crucial in the automotive catalytic converter, and rare earths can significantly modify catalytic properties in many reactions. In particular, we are concerned with the oxidation state of Ce and its role in formation of mixed oxides with metals or with the support. For this we employ EELS in TEM, a technique uniquely suited to detect chemical shifts with ∼30Å resolution.

Effect of grain size on the vapour phase hydration of monoclinic and triclinic modifications of tricalcium silicate; role of high temperature activation

1991 ◽  
Vol 56 (10) ◽  
pp. 1993-2008
Author(s):  
S. Hanafi ◽  
G. M. S. El-Shafei ◽  
B. Abd El-Hamid
Keyword(s):  
Particle Size ◽  
Vapour Phase ◽  
Tricalcium Silicate ◽  
Active Centers ◽  
Thermally Activated ◽  
Grain Sizes ◽  
Intermediate Size ◽  
Surface Active ◽  
Temperature Activation

The hydration of tricalcium silicate (C3S) with three grain sizes of monoclinic (M) and triclinic (T) modifications and on their thermally activated samples were investigated by exposure to water vapour at 80°C for 60 days. The products were investigated by XRD, TG and N2 adsorption. The smaller the particle size the greater was the hydration for both dried and activated samples from (M). In the activated samples a hydrate with 2θ values of 38.4°, 44.6° and 48.6° could be identified. Hydration increased with particle size for the unactivated (T) samples but after activation the intermediate size exhibited enhanced hydration. Thermal treatment at 950°C of (T) samples increased the surface active centers on the expense of those in the bulk. Changes produced in surface texture upon activation and/or hydration are discussed.

scholarly journals Microstructure and Electromagnetic Properties of Ni-Zn-Co Ferrite up to 20 GHz

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Charalampos Stergiou
Keyword(s):  
Wall Motion ◽  
Wave Attenuation ◽  
Domain Wall Motion ◽  
Electromagnetic Properties ◽  
Complex Permeability ◽  
Microwave Dielectric ◽  
Zn Ferrite ◽  
Spin Resonance ◽  
Production Stages

The present paper examines the relation between different developed microstructures and the microwave electromagnetic properties in Ni-Zn-Co ferrite. To this end, the Ni0.25Zn0.25Co0.5Fe2O4composition has been prepared with the conventional ceramic process with varied prefiringTP(750°C, 1000°C) and sinteringTStop temperatures (1200°C, 1250°C). When lower temperatures are applied in these production stages, incomplete microstructures with low density, higher porosity, or finer grains are achieved. On account of these features, the contributions of domain wall motion and spin rotation to the complex permeabilityμ⁎(f)move to higher frequencies, whereas microwave dielectric permittivityε⁎(f)is decreased. In particular in conjunction with the high Co content, the wall relaxation and spin resonance are interestingly forced to occur at 850 MHz and 8.05 GHz, respectively. Regarding the electromagnetic wave attenuation, the ferrite annealed at lower temperatures exhibits strong return loss peaks at higher frequencies, but without other performance improvement. We should notice that the variations in sintering temperatureTSyield the maximum changes in the recorded parameters, including the coercive field,μ⁎(f),andε⁎(f), indicating the inferior role of prefiringTPin Ni-Zn ferrite.

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