scholarly journals Estimation of the chemical specific surface area of catalytic nanoparticles by TEM images analysis

2018 ◽  
Vol 1 (87) ◽  
pp. 5-12 ◽  
Author(s):  
M. Pawlyta ◽  
B. Sobel ◽  
B. Liszka
Keyword(s):  
Fuel Cells ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Platinum Nanoparticles ◽  
Quantitative Methods ◽  
Particle Diameter ◽  
Spherical Particles ◽  
Platinum Particles ◽  
Materials Used

Purpose: The purpose of this article is the development of quantitative methods for assessing the quality of nanocomposite materials used in fuel cells. Design/methodology/approach: latinum is the most commonly used catalyst in fuel cells, commonly in the form of nanoparticles deposited on the surface of carbon black. Due to the nanometric size of platinum particles, transmission electron microscopy can be applied to evaluate the produced catalysts. TEM image also allow to determinate the approximate value of the chemical specific surface area) of platinum nanoparticles, but only in case of spherical particles. Findings: In present work, taking into account additional assumptions resulting directly from the analysis of microscopic images, the method of estimation of the particle diameter and the chemical specific surface area for nonsymmetrical (elongated) nanoparticles is present. Research limitations/implications: The presented work presents a method for determining the specific surface of platinum, when their shape is elongated. It is worth noting that the modified formulas for determining the particle diameter and the value of the chemically active specific surface of the platinum nanoparticles of the elongated shape are equivalent to the formulas previously given for spherical particles, if the particle length and its diameter are equal. In this case, patterns for symmetric particles and more general (modified) patterns can be used interchangeably. Practical implications: Development of new and more effective catalysts for fuel cells. Originality/value: The significance of the presented work results from the possibility of using the described method in the catalyst studies during real catalytic processes. It allows comparing catalytic activity after the process, also in unusual conditions and in an aggressive environment, using minimal amounts of material.

Influence of Surface Area on the Flowability Behaviour of Self-Flow Refractory Castables

2010 ◽  
Vol 636-637 ◽  
pp. 124-129 ◽  
Author(s):  
D.G. Pinto ◽  
Abílio P. Silva ◽  
A.M. Segadaes ◽  
T.C. Devezas
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Raw Materials ◽  
High Hardness ◽  
Size Composition ◽  
High Melting Point ◽  
Refractory Castables ◽  
Materials Used ◽  
The Relationship

Alumina, with high melting point (2050°C), high hardness and mechanical strength, and excellent abrasion resistance, is one of the most common raw materials used in self-flow refractory castables (SFRC) for monolithic linings and is commercially available in various fine to coarse size classes. However, the performance of the refractory lining depends not only on the properties of its ingredients but also on its easy installation (good flowability). The aim of this work was to evaluate the relationship between the flowability index (FI) of fresh castable and the specific surface area (SSA) of its particles, which is mostly determined by the finer particles content. The results obtained showed that, by controlling the proportion between matrix and aggregate, it is possible to control the SSA of the refractory castable and find a mathematical relationship between the specific surface area and the minimum flowability index required to obtain a self-flow refractory castable. It is, thus, possible to optimize the refractory castable size composition and obtain an estimate for FI as a function of SSA. Using a minimum 45 wt.% matrix content in the castable mixture, a SSA value above 2.215 m2/g is obtained, which leads to FI ≥ 80%, the recommended value for self-flow.

A simple approach for producing high aspect ratio fluorohectorite nanoplatelets utilizing a stirred media mill (ball mill)

Clay Minerals ◽  
2012 ◽  
Vol 47 (3) ◽  
pp. 341-353 ◽  
Author(s):  
M. Ziadeh ◽  
B. Chwalka ◽  
H. Kalo ◽  
M. R. Schütz ◽  
J. Breu
Keyword(s):  
Shear Stress ◽  
Aspect Ratio ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ball Mill ◽  
Particle Diameter ◽  
Batch Size ◽  
Full Potential ◽  
Stirred Media Mill

AbstractThe potential of platy nanofillers like clays in polymer nanocomposites is mostly determined by their aspect ratio. The degree of improvement that may be achieved in respect to reinforcement, gas-barrier properties and flame retardancy critically depends on the aspect ratio. Thus, increasing the aspect ratio is highly desirable in order to explore the full potential of the clay filler. Mechanical shear stress as generated in the grinding chamber of a stirred media mill (ball mill) induced an efficient exfoliation of highly hydrated and therefore ‘shear-labile’ synthetic Mg-fluorohectorite in aqueous dispersion. The attainable degree of exfoliation can be tuned and controlled through the shear forces applied by changing process parameters such as solid content and grinding media diameter. Characterization and evaluation of the exfoliation efficiency during milling was achieved by combining and cross-validating data obtained by powder X-ray diffraction (XRD), static light scattering (SLS), specific surface area measurements applying the Brunauer-Emmett-Teller (BET) equation, and scanning electron microscopy (SEM). This led to the identification of optimal processing parameters, allowing for control of the degree of exfoliation and, consequently, the aspect ratio of the nanoplatelets. Not surprisingly, besides exfoliation, increasing the magnitude of the shear stress also resulted in some reduction in platelet size.The clay platelets obtained showed a high average aspect ratio (>600), several times greater than that of original synthetic fluorohectorite. The increase of aspect ratio was reflected in a significant enhancement of both specific surface area and cation exchange capacity (CEC) of the external basal surfaces. This method has substantial advantages compared to microfluidizer processing with respect to feasibility, batch size and particle diameter size preservation. The exfoliated nanoplatelets obtained by milling have great potential to improve mechanical properties of polymer layered silicate nanocomposites (PLSN).

Enhancing the available specific surface area of carbon supports to boost the electroactivity of nanostructured Pt catalysts

2014 ◽  
Vol 16 (46) ◽  
pp. 25609-25620 ◽  
Author(s):  
Yaovi Holade ◽  
Claudia Morais ◽  
Karine Servat ◽  
Teko W. Napporn ◽  
K. Boniface Kokoh
Keyword(s):  
Catalytic Activity ◽  
Physicochemical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Platinum Nanoparticles ◽  
Pt Catalysts ◽  
Carbon Supports ◽  
Pre Treatment ◽  
Nanostructured Pt

We report a convenient and straightforward thermal pre-treatment to improve the physicochemical properties of carbon-based substrates to boost the catalytic activity of platinum nanoparticles.

scholarly journals High-quality mesoporous SiO2 nanospheres via a confined jet impingement continuous microchannel reactor

2021 ◽  
Author(s):  
Qiang Chen ◽  
Kai Chen ◽  
Feng Yu ◽  
Aixia Guo ◽  
Siqing Zou ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Particle Diameter ◽  
Jet Impingement ◽  
High Specific Surface Area ◽  
Lithium Silicate ◽  
Average Particle ◽  
Microchannel Reactor

Abstract High surface area mesoporous silica (SiO2) nanospheres has been considered an ideal material for the catalytic, adsorption and drug delivery. However, synthesis of ultra-high specific surface area mesoporous silica nanoparticles with well-defined sphere structure and small particle size (< 200 nm) is still challenging. Here, a two-stream confined jet impingement continuous microchannel reactor is proposed to produce novel mesoporous silica nanospheres (MSNs) with ultra-high specific surface area (SSA) and abundant worm-like meso-porosity. The as-obtained MSNs with worm-like mesoporous structure were produced with average particle diameter of 142 ~ 207 nm, high SSA of 1347 ~ 1854 m2/g, total pore volume of 0.86 ~ 1.23 cm3/g and pore diameter of 2.6 ~ 3.3nm. Moreover, the shear force field in the microchannel reactor on the mesoscopic structure of MSNs was simulated by mesoscopic kinetics. Additionally, MSNs was used as the silicon source to synthesize lithium silicate (Li4SiO4), which enhanced carbon dioxide (CO2) adsorption of 27.18 wt% at 650 ℃.

scholarly journals Carbonate-Based Lanthanum Strontium Cobalt Ferrite (LSCF)–Samarium-Doped Ceria (SDC) Composite Cathode for Low-Temperature Solid Oxide Fuel Cells

2020 ◽  
Vol 10 (11) ◽  
pp. 3761
Author(s):  
Muhammed Ali S.A. ◽  
Jarot Raharjo ◽  
Mustafa Anwar ◽  
Deni Shidqi Khaerudini ◽  
Andanastuti Muchtar ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Low Temperature ◽  
Solid Oxide Fuel Cells ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Composite Cathode ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Composite Electrolyte

Perovskite-based composite cathodes, La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF)–Ce0.8Sm0.2O1.9-carbonate (SDCC), were investigated as cathode materials for low-temperature solid-oxide fuel cells. The LSCF was mixed with the SDC–carbonate (SDCC) composite electrolyte at different weight percentages (i.e., 30, 40, and 50 wt %) to prepare the LSCF–SDCC composite cathode. The effect of SDCC composite electrolyte content on the diffraction pattern, microstructure, specific surface area, and electrochemical performances of the LSCF–SDCC composite cathode were evaluated. The XRD pattern revealed that the SDCC phase diffraction peaks vary according to its increasing addition to the system. The introduction of SDCCs within the composite cathode did not change the LSCF phase structure and its specific surface area. However, the electrical performance of the realized cell drastically changed with the increase of the SDCC content in the LSCF microstructure. This drastic change can be ascribed to the poor in-plane electronic conduction at the surface of the LSCF cathode layer due to the presence of the insulating phase of SDC and molten carbonate. Among the cathodes investigated, LSCF–30SDCC showed the best cell performance, exhibiting a power density value of 60.3–75.4 mW/cm2 at 600 °C to 650 °C.

Study on the Preparing of Nanowhite Carbon Black by Silica Fume

2013 ◽  
Vol 423-426 ◽  
pp. 554-559 ◽  
Author(s):  
Xin Zhi ◽  
Zhan Cheng Guo
Keyword(s):  
Carbon Dioxide ◽  
Carbon Black ◽  
Specific Surface ◽  
Surface Area ◽  
Silica Fume ◽  
Specific Surface Area ◽  
Particle Diameter ◽  
Complete Response ◽  
High Specific Surface Area ◽  
Precipitated Silica

This research through the study on the properties of silicon dust, put forward in combination with lime kiln tail gas recycling carbon dioxide, preparation of precipitated silica (nanoWhite Carbon Black) of high value utilization technology, and studied and summarized process of the dissolution and precipitation by carbon dioxide. The silica fume is in amorphous form, and it has some special powder properties such as ultra fine grain size and high specific surface area and high chemical activity, these provide favorable foundation for low energy consumption process of recycling the powder. In the dissolution stage, the optimization reaction time is about 40 minutes, this time to complete the process of the reaction more than 90%. And the reaction is the fastest in the first 20 minutes, complete response 75% of the reaction. In the stage of carbonization, with increase of the concentration of the precursor, the particle diameter becomes larger, but the specific surface area of the powder will reduce, the porosity and the surface activity of it will reduce corresponding.

scholarly journals USE OF OPAL-CRYSTOBALITE-TRIDIMITE MICRO-FILLER IN DENSE AGGREGATE CONCRETE

2020 ◽  
pp. 8-17
Author(s):  
N. Lukutcova ◽  
A. Pykin ◽  
E. Chivikova
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Particle Diameter ◽  
Component Composition ◽  
Average Particle ◽  
Maximal Effect ◽  
Aggregate Concrete ◽  
Optimal Value ◽  
Cement System

Opal-cristobalite-tridimite micro-filler (OCTMF) as a component of dense aggregate concrete (DAC), obtained by grinding of sedimentary siliceous rock – abiomorphic silicite fractions of 0.315-0.63 mm was studied considered. The chemical-mineral composition and microstructure of the of OCTMF particles were determined. Comparative analysis of the relationship between particle size distribution, average particle diameter, specific surface area of OCTMF particle and grinding period in shock-abrasive and cavitation mills was carried out. The conductometric express method was applied to study the effect of the OCTMF specific surface area on hydration activity of cement system. The optimal value of OCTMF specific surface area was (880–900 m2/kg), achieved as a result of cavitation dispersion for 5–10 minutes, that provides increasing in t hydration activity of cement system by 52–54 %. The effect of the consumption of components on strength of the DAC after 28 days of hardening was determined using mathematical statistics method. That allows predicting this parameter by varying the component composition of the concrete mix. An assessment of the OCTMF efficiency was made. It was established, the maximal effect of the OCTMF is at concentration up to 5 % (by wt. of cement), that provides an increasing the design compressive strength of DAC up to 126 %.

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