Graphitization and particle size analysis of pyrolyzed cobalt phthalocyanine/carbon catalysts for oxygen reduction in fuel cells

1994 ◽  
Vol 9 (12) ◽  
pp. 3203-3209 ◽  
Author(s):  
L. Dignard-Bailey ◽  
M.L. Trudeau ◽  
A. Joly ◽  
R. Schulz ◽  
G. Lalande ◽  
...  
Keyword(s):  
Particle Size ◽  
Fuel Cells ◽  
Size Distribution ◽  
Amorphous Carbon ◽  
Pyrolysis Temperature ◽  
Carbon Support ◽  
Solid Polymer ◽  
Average Particle ◽  
Cobalt Phthalocyanine ◽  
X Ray

Cobalt phthalocyanine (CoPc) adsorbed on a carbon black support (Vulcan XC-72) and pyrolyzed at various temperatures is a potential catalyst for the reduction of oxygen in solid polymer electrolyte fuel cells. This paper reports the results of the microstructural characterization of β-Co particles that are formed after pyrolysis at temperatures of 700, 900, and 1050 °C. Transmission electron microscopy (TEM) indicated that (i) for a pyrolysis temperature of 700 °C, the size distribution of the Co particles is bell-shaped with an average value of 4 nm and mean deviation of 1 nm; (ii) for a pyrolysis temperature of 900 °C, the Co particle size distribution skews toward larger particle sizes. The most probable particle size is about 6 nm, and the average particle size is 13 nm. By comparison with the TEM results, the particle size estimated from a spectroscopic method like x-ray absorption is underestimated, while from x-ray diffraction is overestimated. The TEM images show that Co particles act as heterogeneous nucleation sites for the graphitization of amorphous carbon. It is shown that (i), at least for pyrolysis temperature of 900 °C and above, most of the β-Co particles are surrounded by a shell of graphitic carbon layers that appears to protect the particles from corrosion in acidic media; (ii) for pyrolysis temperature of 1050 °C, graphite strings also appear throughout the amorphous carbon support in areas where Co particles are not detected. This behavior was not observed after pyrolysis of as-received carbon support at 1050 °C. These results allow for a better understanding of the behavior of the pyrolyzed catalysts immersed in an acidic solution or in a solid polymer fuel cell.

Synchrotron X-Ray Scattering for the Structural Characterization of Catalysts

1986 ◽  
Vol 30 ◽  
pp. 389-394
Author(s):  
R. J. De Angelis ◽  
A. G. Dhere ◽  
M. A. Maginnis ◽  
P. J. Reucroft ◽  
G. E. Ice ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Profile Analysis ◽  
Average Particle Size ◽  
Initial Slope ◽  
Average Particle ◽  
Particle Size Range ◽  
Diffraction Profile ◽  
X Ray

Discussions exist in the literature concerning the application of single x-ray diffraction profile analysis to determine the average particle size, particle size distribution and root mean squared strain in catalytic systems. Nandi et al. have shown that the single order analysis can give erroneous strain results and is subject to error in the large particle size range. They further indicated that the initial slope of Stokes corrected Fourier coefficients gives more reliable average p article size than that which is calculated from single order peak shape analysis. There is apparent agreement that the average particle size and the particle size distribution measured by single order profile analysis, in small metal particle systems, are reliable.

scholarly journals Characterization of Magnetic Nanoparticles Coated with Chitosan: A Potential Approach for Enzyme Immobilization

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Azariel Díaz-Hernández ◽  
Jorge Gracida ◽  
Blanca E. García-Almendárez ◽  
Carlos Regalado ◽  
Rosario Núñez ◽  
...  
Keyword(s):  
Particle Size ◽  
Magnetic Nanoparticles ◽  
Size Distribution ◽  
Photoelectron Spectroscopy ◽  
Average Particle Size ◽  
Superparamagnetic Nanoparticles ◽  
Spherical Particles ◽  
Cross Linking ◽  
Average Particle ◽  
X Ray

Cross-linking of magnetic nanoparticles with proteins plays a significant role in the preparation of new materials for biotechnological applications. The aim was the maximization of the magnetic mass attracted and protein loading of magnetic iron oxide nanoparticles coated with chitosan, synthesized in a single step by alkaline precipitation. Chitosan-coated magnetite particles (Fe3O4@Chitosan) were cross-linked to a xylanase and a cellulase (Fe3O4@Chitosan@Proteins), showing a 93% of the magnetic saturation of the magnetite. X-ray diffraction pattern in composites corresponds to magnetite. Thermogravimetry and differential scanning calorimetry showed that 162 mg of chitosan was coating one gram of composite and 12 mg of protein was cross-linked to each gram of magnetic support. Cross-linking between enzymes and Fe3O4@Chitosan was confirmed by infrared spectroscopy with Fourier transform, X-ray energy, and X-ray photoelectron spectroscopy dispersion analysis. From dynamic light scattering, transmission and electron microscopy the average particle size distribution was 230 nm and 430 nm for Fe3O4@Chitosan and Fe3O4@Chitosan@Proteins, showing agglomerates of individual spherical particles, with an average diameter of 8.5 nm and 10.8 nm, respectively. The preparation method plays a key role in determining the particle size and shape, size distribution, surface chemistry, and, therefore, the applications of the superparamagnetic nanoparticles.

scholarly journals Thermal, Structural, and Physical Properties of Freeze Dried Tropical Fruit Powder

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
K. A. Athmaselvi ◽  
C. Kumar ◽  
M. Balasubramanian ◽  
Ishita Roy
Keyword(s):  
Particle Size ◽  
Physical Properties ◽  
Average Particle Size ◽  
Average Particle ◽  
X Ray Diffraction ◽  
Tropical Fruit ◽  
X Ray ◽  
Freeze Dried ◽  
Fruit Powder ◽  
Lcr Meter

This study evaluates the physical properties of freeze dried tropical (guava, sapota, and papaya) fruit powders. Thermal stability and weight loss were evaluated using TGA-DSC and IR, which showed pectin as the main solid constituent. LCR meter measured electrical conductivity, dielectric constant, and dielectric loss factor. Functional groups assessed by FTIR showed presence of chlorides, and O–H and N–H bonds in guava, chloride and C–H bond in papaya, and chlorides, and C=O and C–H bonds in sapota. Particle size and type of starch were evaluated by X-ray diffraction and microstructure through scanning electronic microscopy. A semicrystalline profile and average particle size of the fruit powders were evidenced by X-ray diffraction and lamellar/spherical morphologies by SEM. Presence of A-type starch was observed in all three fruits. Dependence of electric and dielectric properties on frequency and temperature was observed.

Effects of Multiple Impacts and Size Distribution of Particles on Erosion Predictions Using CFD

2007 ◽  
Author(s):  
Yongli Zhang ◽  
Brenton S. McLaury ◽  
Siamack A. Shirzai
Keyword(s):  
Experimental Data ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Target Material ◽  
Average Particle ◽  
Multiple Impacts ◽  
Cfd Simulations ◽  
Erosion Damage ◽  
Wide Range

Erosion equations are usually obtained from experiments by impacting solid particles entrained in a gas or liquid on a target material. The erosion equations are utilized in CFD (Computational Fluid Dynamics) models to predict erosion damage caused by solid particle impingements. Many erosion equations are provided in terms of an erosion ratio. By definition, the erosion ratio is the mass loss of target material divided by the mass of impacting particles. The mass of impacting particles is the summation of (particle mass × number of impacts) of each particle. In erosion experiments conducted to determine erosion equations, some particles may impact the target wall many times and some other particles may not impact the target at all. Therefore, the experimental data may not reflect the actual erosion ratio because the mass of the sand that is used to run the experiments is assumed to be the mass of the impacting particles. CFD and particle trajectory simulations are applied in the present work to study effects of multiple impacts on developing erosion ratio equations. The erosion equation as well as the CFD-based erosion modeling procedure is validated against a variety of experimental data. The results show that the effect of multiple impacts is negligible in air cases. In water cases, however, this effect needs to be accounted for especially for small particles. This makes it impractical to develop erosion ratio equations from experimental data obtained for tests with sand in water or dense gases. Many factors affecting erosion damage are accounted for in various erosion equations. In addition to some well-studied parameters such as particle impacting speed and impacting angle, particle size also plays a significant role in the erosion process. An average particle size is usually used in analyzing experimental data or estimating erosion damage cases of practical interest. In petroleum production applications, however, the size of sand particles that are entrained in produced fluids can vary over a fairly broad range. CFD simulations are also performed to study the effect of particle size distribution. In CFD simulations, particle sizes are normally distributed with the mean equaling the average size of interest and the standard deviation varying over a wide range. Based on CFD simulations, an equation is developed and can be applied to account for the effect of the particle size distribution on erosion prediction for gases and liquids.

X-ray fluorescence spectrometry for rapid screening of particle size in soils

2021 ◽  
Author(s):  
Maame Croffie ◽  
Paul N. Williams ◽  
Owen Fenton ◽  
Anna Fenelon ◽  
Karen Daly
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Soil Texture ◽  
Particle Size Analysis ◽  
Parent Material ◽  
Fluorescence Spectrometry ◽  
Rapid Screening ◽  
Size Analysis ◽  
X Ray

<p>Soil texture is an essential factor for effective land management in agricultural production. Knowledge of soil texture and particle size at field scale can aid with on-going soil management decisions. Standard soil physical and gravimetric methods for particle size analysis are time-consuming and X-ray fluorescence spectrometry (XRF) provides a rapid and cost-effective alternative. The objective of this study was to explore the use of XRF as a predictor for particle size. An extensive archive of Irish soils with particle size and soil texture data was used to select samples for XRF analysis. Regression and correlation analyses on XRF determined results showed that the relationship between Rb and % clay varied with soil type and was dependent on the parent material. There was a strong relationship (R > 0.62, R<sup>2</sup>>0.30, p<0.05) between Rb and clay for soils originating from bedrock such as limestones and slate. Contrastingly, no significant relationship (R<0.03, R<sup>2</sup>=0.00, p>0.05) exists between Rb and % clay for soils originating from granite and gneiss. Furthermore, there was a significant negative correlation (p<0.05) between Rb and % sand. The XRF is a useful technique for rough screening of particle size distribution in soils originating from certain parent materials. Thus, this may contribute to the rapid prediction of soil texture based on knowledge of the particle size distribution.</p><p> </p>

scholarly journals Particle Size Distribution of E-Cigarette Aerosols and the Relationship to Cambridge Filter Pad Collection Efficiency

2015 ◽  
Vol 26 (4) ◽  
Author(s):  
Steven L. Alderman ◽  
Chen Song ◽  
Serban C. Moldoveanu ◽  
Stephen K. Cole
Keyword(s):  
Particle Size ◽  
Particulate Matter ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Propylene Glycol ◽  
Collection Efficiency ◽  
Transmission Measurement ◽  
Average Particle ◽  
Electrical Mobility ◽  
Total Particulate Matter

AbstractThe relatively volatile nature of the particulate matter fraction of e-cigarette aerosols presents an experimental challenge with regard to particle size distribution measure-ments. This is particularly true for instruments requiring a high degree of aerosol dilution. This was illustrated in a previous study, where average particle diameters in the 10-50 nm range were determined by a high-dilution, electrical mobility method. Total particulate matter (TPM) masses calculated based on those diameters were orders of magnitude smaller than gravimetrically determined TPM. This discrepancy was believed to result from almost complete particle evaporation at the dilution levels of the electrical mobility analysis. The same study described a spectral transmission measurement of e-cigarette particle size in an undiluted state, and reported particles from 210-380 nm count median diameter. Observed particle number concentrations were in the 10Described here is a study in which e-cigarette aerosols were collected on Cambridge filters with adsorbent traps placed downstream in an effort to capture any material passing through the filter. Amounts of glycerin, propylene glycol, nicotine, and water were quantified on the filter and downstream trap. Glycerin, propylene glycol, and nicotine were effciently captured (> 98%) by the upstream Cambridge filter, and a correlation was observed between filtration efficiency and the partial vapor pressure of each component. The present analysis was largely inconclusive with regard to filter efficiency and particle-vapor partitioning of water. [Beitr. Tabakforsch. Int. 26 (2014) 183-190]

Particle Size Distribution of ZrO2:Pr3+ – Influences of pH, High Power Ultrasound, Surfactant and Dopant Quantity

2007 ◽  
Vol 128 ◽  
pp. 97-100 ◽  
Author(s):  
Stephanie Möller ◽  
Janusz D. Fidelus ◽  
Witold Łojkowski
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
High Power ◽  
Average Particle Size ◽  
Sodium Dodecyl ◽  
Average Particle ◽  
Power Ultrasound ◽  
High Power Ultrasound ◽  
Influence Of Ph

The aim of the work was to examine the influence of pH, high power ultrasound, surfactant and dopant quantity on the particle size distribution of ZrO2:Pr3+, with praseodymium content varying between 0.05 and 10 %. The nanopowders were obtained via a hydrothermal microwave driven process. To establish if the dopant was located on the surface of the zirconia nanoparticles, the particle size distribution, as a function of pH, was measured to obtain an estimate of the isoelectric point of the samples. All results indicated that the dopant was concentrated on the surface: the measurements of the particle size distribution show that the pH corresponding to maximum average particle size changes towards higher values when the Pr content increases. Measurements of the particle size distribution dependency on the application of high power ultrasound and the addition of the sodium dodecyl sulphate surfactant show that, under certain conditions, there is a better stabilisation of the nanopowders in a dispersion and undesirable agglomeration is hindered.

scholarly journals Preparation, Characterization and Performance Properties of Polydodecylmethylsilsesquioxane Nanoparticles

Coatings ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1045
Author(s):  
Fuquan Deng ◽  
Hua Jin ◽  
Wei Xu
Keyword(s):  
Thermal Stability ◽  
Particle Size ◽  
Electron Microscope ◽  
Contact Angles ◽  
Process Conditions ◽  
Average Particle ◽  
Gravimetric Analysis ◽  
Laser Scattering ◽  
Excellent Thermal Stability ◽  
X Ray

A series of polydodecylmethylsilsesquioxane (PDMSQ) nanocomposite latexes were prepared via emulsion polymerization of methyltriethoxysilane (MTES) and dodecyltrimethoxysilane (DTMS) and sodium hydroxide as the catalyst, and sodium dodecyl benzene sulfonate/Tween 80 as the mixed emulsifiers. Effects of the emulsifier doses, the reaction temperature, the catalyst concentration and the oil/water ratio on the particle size and distribution of the PDMSQ nanoparticles were discussed. Particle size and micromorphology, structure, thermal stability, crystallinity and hydrophobicity of PDMSQ nanoparticles (PDMSQ NPs) were investigated by dynamic laser scattering (DLS), Fourier transform infrared spectroscopy (FTIR), silicon-nuclear magnetic resonance (28Si-NMR), X-ray photoelectron spectroscope (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), atomic force microscope (AFM), thermo gravimetric analysis (TGA), X-ray diffraction (XRD) and contact angle tester. Results showed that a series of PDMSQ NPs could be obtained with an average particle size of less than 80 nm and narrow distribution as well as spherical structure under the optimal process conditions. PDMSQ NPs exhibited excellent thermal stability and were mainly amorphous but also contained some crystal structures. Importantly, the static water contact angles (WCAs) on its latex films were larger than 150° and the WCAs hysteresis were less than 10°, thus those PDMSQ nanocomposite latexes show potential in the field of superhydrophobic coatings.

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