scholarly journals Electrochemical and microstructural characterization of platinum supported on glassy carbon

2007 ◽  
Vol 61 (3) ◽  
pp. 135-141
Author(s):  
Sanja Terzic ◽  
Vladislava Jovanovic ◽  
Dusan Tripkovic ◽  
Andrzej Kowal ◽  
Jerzy Stoch
Keyword(s):  
Methanol Oxidation ◽  
Glassy Carbon ◽  
Microstructural Characterization ◽  
Electrochemical Treatment ◽  
Organic Residues ◽  
Remarkable Effect ◽  
Platinum Particles ◽  
Order Of Magnitude

The effect of the electrochemical oxidation of glassy carbon on the deposition of platinum particles and the electrocatalytic activity of platinum supported on oxidized glassy carbon were studied for methanol oxidation in H2SO4 solution. Platinum was potentiostatically deposited from H2SO4 + 6mM H2PtCl6 solution. Glassy carbon was anodically polarized in 1 M NaOH at 1.41 V (SCE) for 35 and 95 s and in 0.5 M H2SO4 at 2V (SCE) for 35; 95 s and 2.25 V for 35 and 95 s. Electrochemical treatment of the GC support leads to a better distribution of platinum on the substrate and has remarkable effect on the activity. The activity of the Pt/GCox electrode for methanol oxidation is larger than that of polycrystalline Pt and by more than one order of magnitude larger than that of a Pt/GC electrode. This increase in activity indicates the pronounced role of the organic residues of the GC support on the properties of Pt particles deposited on glassy carbon.

scholarly journals Effect of glassy carbon properties on the electrochemical deposition of platinum nano-catalyst and its activity for methanol oxidation

2007 ◽  
Vol 72 (2) ◽  
pp. 165-181 ◽  
Author(s):  
Sanja Terzic ◽  
Dusan Tripkovic ◽  
Vladislava Jovanovic ◽  
Amalija Tripkovic ◽  
Andrzej Kowal
Keyword(s):  
Methanol Oxidation ◽  
Glassy Carbon ◽  
Specific Activity ◽  
Carbon Support ◽  
Pt Electrode ◽  
Nano Catalyst ◽  
Platinum Particles ◽  
Different Temperatures ◽  
Order Of Magnitude ◽  
Anodic Polarisation

The effects of the properties of glassy carbon on the deposition of platinum particles and the electrocatalytic activity of platinum supported on glassy carbon (GC/Pt) for methanol oxidation in alkaline and acidic solutions were studied. Platinum was potentiostatically deposited on two glassy carbon samples, thermally treated at different temperatures, which were either polished or anodicaly polarised in acid (GCOX-AC/Pt) and in alkali (GCOX-AL/Pt). Anodic polarisation of glassy carbon, either in alkaline or acidic solution, enhances the activity of both types of GC/Pt electrodes for methanol oxidation. The activity of the catalysts follows the change in the properties of the glassy carbon support upon anodic treatment. The specific activity of the GCOX-AL/Pt electrode for this reaction in alkali is increased only a few times in comparison with the activity of the GC/Pt one. On the other hand, the specific activity of the GCOX-AC/Pt electrode for methanol oxidation in acid is about one order of magnitude higher than that of the GC/Pt electrode. The role of the substrate on the properties of catalyst is discussed in detail. .

Microstructural Characterization of Porous Silicon SOI Structures

1987 ◽  
Vol 107 ◽  
Author(s):  
J.D. L'ecuyer ◽  
M.H. Loretto ◽  
J.P.G. Farr ◽  
J.M. Keen ◽  
J.G. Castledine ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Cross Section ◽  
Microstructural Characterization ◽  
Epitaxial Silicon ◽  
Order Of Magnitude ◽  
Oxidized Porous Silicon

AbstractSOI structures up to 60nm wide have been produced using oxidized porous silicon formed by selective n/n+ anodizing. The microstructures of the islands were investigated using TEM in both the planar and cross-section geometries. Typical island thickness is about 0.15nm and the buried oxidized porous silicon about 0.65μm. Retention of the island geometry is excellent. Few defects (essentially dislocations) are associated with either the anodizing or oxidation treatments. The interface sharpness between the epitaxial silicon/oxidized porous silicon is 10-20nm, an order of magnitude sharper than the back interface between the oxidized porous silicon and the substrate.

Role of Silver Doping in the Improvement of Electrical Properties of (Ba,Sr)TiO3 Thin Films

1999 ◽  
Vol 567 ◽  
Author(s):  
Anuranjan Srivastava ◽  
D. Kumar ◽  
Rajiv K. Singh ◽  
Harish Venkataraman ◽  
William R. Eisenstadt
Keyword(s):  
Electrical Properties ◽  
Oxygen Vacancies ◽  
Domain Walls ◽  
Silver Doping ◽  
Order Of Magnitude ◽  
Electrical And Dielectric Properties ◽  
Bst Films ◽  
Fabrication And Characterization

ABSTRACTIn this paper we report the fabrication and characterization of Ag/(Ba,Sr)TiO3 /LaNiO3/LaAlO3 capacitors. All the films, including the top (silver) and bottom (LaNiO3) electrodes, were deposited using a pulsed laser deposition technique. The electrical and dielectric properties of (Ba,Sr)TiO3 capacitors were found to improve significantly by means of silver doping. For example, the leakage current density of a Ag/Ag-doped-(Ba,Sr)TiO3 /LaNiO3/ capacitor was about an order of magnitude lower and dielectric constant was ∼40 % higher than that of a Ag/(Ba,Sr)TiO3 /LaNiO3/capacitor over a range of biases. The improvement in the electrical properties of (Ba,Sr)TiO3 films is believed to be caused by a double role of silver. The first one is associated with the reduced oxygen vacancies due to improved oxygenation of BST films in presence of silver and the second one is associated unpinning effect of domain walls again in presence of silver.

Local Dielectric Function Of Biogenic and Geological Polymorphs of CaCO3 Via Transmission Eels

1998 ◽  
Vol 4 (S2) ◽  
pp. 782-783
Author(s):  
Kalpana S Katti ◽  
Daniel Frech ◽  
Maoxu Qian ◽  
Mehmet Sarikaya
Keyword(s):  
Dielectric Function ◽  
Microstructural Characterization ◽  
Edge Length ◽  
Inorganic Materials ◽  
Transmission Electron ◽  
Columnar Organization ◽  
Inner Region ◽  
Electron Energy Loss

This paper focuses on the differences of physical properties, specifically local dielectric function, of biogenic and geological mineral CaCO3. The goal is to assess the role of organism in forming biogenic inorganic materials. Local dielectric functions of biogenic and geological minerals were determined by transmission electron energy loss spectroscopy using a previously developed strategy.Previous work on microstructural characterization of biological hard tissues, e.g., abalone shells, has shown variations in terms of defects, morphology, crystallography, and organization of nano- and microstructures in two biological polymorphs of calcium carbonate, calcite and aragonite, in the prismatic and nacreous regions, respectively. In the abalone, the outer (1-5 mm thick) region of the shell is composed of calcite crystallites (1-5 μm diameter) with columnar organization perpendicular to shell plane. On the inner region, 1-10 mm thick nacre is composed of aragonite crystallites (0.5 μm thick and 5 -10 μm edge-length) forming flat platelets, parallel to the shell plane.

Microstructural Characterization and Mathematical Modeling for Determination of Volume Fraction of Eutectoid Mixture of the Cu-8.5wt% Sn Alloy Obtained by Unidirectional Upward Solidification

2020 ◽  
Vol 1012 ◽  
pp. 302-307
Author(s):  
Ricardo Aparecido da Cruz ◽  
Givanildo Alves dos Santos ◽  
Mauricio Silva Nascimento ◽  
Carlos Frajuca ◽  
Francisco Yastami Nakamoto ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Solidification Time ◽  
Fourier Number ◽  
Proposed Model ◽  
Thermal Data ◽  
Order Of Magnitude

The Cu-8.5wt % Sn alloy presents an extensive microsegregation during its solidification. That microsegregation results in the formation of a eutectoid mixture, which is detrimental to subsequent forming processes. This study deals with the influence of solidification time and cooling rate on the microstructure of that alloy. The unidirectional solidification technique allowed the acquisition of thermal data. The optical microscopy enabled the microstructural characterization of the material, the measurement of dendrite arm spacings and the quantification of the volume fraction of the eutectoid mixture. A semi-analytical mathematical model was proposed to estimate the volume fraction of the eutectoid mixture. The model expresses the volume fraction as an implicit function of the Fourier number. The results showed that the microstructure is dendritic and that the characteristic spacings increase with the solidification time between the liquidus and the peritectic temperatures. The data also showed that for higher cooling rates the dendrite arm spacings are smaller and that there is a tendency for the volume fraction of eutectoid mixture in the columnar zone to increase with the Fourier number and to decrease with the cooling rate. The proposed model allowed obtaining values of volume fraction with the same order of magnitude of the experimental data, but with behavior tendency opposite to that observed.

Microstructural Characterization of Sol-Gel Derived Lead Titanate Deposited On Silica

1993 ◽  
Vol 310 ◽  
Author(s):  
Joseph M. Schwartz ◽  
Lorraine Falter Francis ◽  
Lanny D. Schmidt
Keyword(s):  
Lead Titanate ◽  
Sol Gel ◽  
Pyrochlore Phase ◽  
Microstructural Characterization ◽  
Barrier Materials ◽  
Support Materials ◽  
Treatment Conditions ◽  
Transmission Electron ◽  
Platinum Particles

AbstractThe microstructural evolution of lead titanate prepared by a sol-gel method was examined using transmission electron microscopy (TEM) following treatments in air at progressively higher temperatures. TEM specimens were prepared by spin coating a film or dispersing particles onto specimen grids coated with SiO2 or SiO2 with a barrier layer. The effects of different barrier materials, thermal treatment conditions, and the addition of platinum particles were examined. Lead titanate formed crystalline perovskite at ∼550-600°C on all support materials examined. On SiO2 supports, the pyrochlore phase formed at lower temperatures and converted partially to perovskite at higher temperatures. Barrier layers of TiO2, A12O3 and polyimide prevented pyrochlore formation.

The Microstructural Characterization of Nanocrystalline CeO2 Ceramics Produced by the Sol-Gel Method

1994 ◽  
Vol 343 ◽  
Author(s):  
F. Czerwinski ◽  
J.A. Szpunar
Keyword(s):  
Sol Gel ◽  
Microstructural Characterization ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Structure Of Coatings ◽  
Heating Up

ABSTRACTCeO2 ceramics were manufactured in the form of surface coatings deposited onto various substrates by sol-gel technology. The size of the CeO2 crystallites, dried at room temperature, was about 5 nm and did not change significantly after heating, up to 680 K. Further increase of the temperature resulted in a rapid growth of crystallites. The process of growth depends also on the film thickness and nature of substrate. The results obtained using thermogravimetric analysis (TGA) and infrared spectroscopy (IR) demonstrated that the thermal decomposition of gel was completed at about 750 K. There was no evident texture in both the as-deposited state and after heat-treatment. X-ray diffraction (XRD), the atomic force microscopy (AFM), and transmission electron microscopy (TEM) were used to characterize the structure of coatings. The examples of application of CeO2 ceramics as coatings for high temperature corrosion protection are presented. The role of size of CeO2 particles in modification of grain boundary transport is discussed.

scholarly journals Biosensors Platform Based on Chitosan/AuNPs/Phthalocyanine Composite Films for the Electrochemical Detection of Catechol. The Role of the Surface Structure

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2152 ◽  
Author(s):  
Coral Salvo-Comino ◽  
Alfonso González-Gil ◽  
Javier Rodriguez-Valentin ◽  
Celia Garcia-Hernandez ◽  
Fernando Martin-Pedrosa ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Copper Phthalocyanine ◽  
Composite Films ◽  
Layer By Layer ◽  
Transfer Path ◽  
Layer Structures ◽  
Order Of Magnitude ◽  
Lbl Films

Biosensor platforms consisting of layer by layer films combining materials with different functionalities have been developed and used to obtain improved catechol biosensors. Tyrosinase (Tyr) or laccase (Lac) were deposited onto LbL films formed by layers of a cationic linker (chitosan, CHI) alternating with layers of anionic electrocatalytic materials (sulfonated copper phthalocyanine, CuPcS or gold nanoparticles, AuNP). Films with different layer structures were successfully formed. Characterization of surface roughness and porosity was carried out using AFM. Electrochemical responses towards catechol showed that the LbL composites efficiently improved the electron transfer path between Tyr or Lac and the electrode surface, producing an increase in the intensity over the response in the absence of the LbL platform. LbL structures with higher roughness and pore size facilitated the diffusion of catechol, resulting in lower LODs. The [(CHI)-(AuNP)-(CHI)-(CuPcS)]2-Tyr showed an LOD of 8.55∙10−4 μM, which was one order of magnitude lower than the 9.55·10−3 µM obtained with [(CHI)-(CuPcS)-(CHI)-(AuNP)]2-Tyr, and two orders of magnitude lower than the obtained with other nanostructured platforms. It can be concluded that the combination of adequate materials with complementary activity and the control of the structure of the platform is an excellent strategy to obtain biosensors with improved performances.

Microstructural characterization of CoPtCr/Cr thin film disks by cross-section TEM and elongated probe micro-diffraction

1991 ◽  
Vol 49 ◽  
pp. 762-763
Author(s):  
M.A. Parker ◽  
K.E. Johnson ◽  
C. Hwang ◽  
A. Bermea
Keyword(s):  
Magnetic Recording ◽  
Electron Probe ◽  
Microstructural Characterization ◽  
Crystallographic Structure ◽  
Recording Media ◽  
Layer By Layer ◽  
Cross Sectional ◽  
New Techniques ◽  
Polished Side

We have reported the dependence of the magnetic and recording properties of CoPtCr recording media on the thickness of the Cr underlayer. It was inferred from XRD data that grain-to-grain epitaxy of the Cr with the CoPtCr was responsible for the interaction observed between these layers. However, no cross-sectional TEM (XTEM) work was performed to confirm this inference. In this paper, we report the application of new techniques for preparing XTEM specimens from actual magnetic recording disks, and for layer-by-layer micro-diffraction with an electron probe elongated parallel to the surface of the deposited structure which elucidate the effect of the crystallographic structure of the Cr on that of the CoPtCr.XTEM specimens were prepared from magnetic recording disks by modifying a technique used to prepare semiconductor specimens. After 3mm disks were prepared per the standard XTEM procedure, these disks were then lapped using a tripod polishing device. A grid with a single 1mmx2mm hole was then glued with M-bond 610 to the polished side of the disk.

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