Modelling of nanocrystalline iron nitriding process — influence of specific surface area

2011 ◽  
Vol 65 (2) ◽  
Author(s):  
Rafał Pelka ◽  
Walerian Arabczyk
Keyword(s):  
Specific Surface ◽  
Gaseous Phase ◽  
Tubular Reactor ◽  
Nitriding Process ◽  
Size Distributions ◽  
Surface Areas ◽  
Nanocrystalline Iron ◽  
Mean Size ◽  
The Mean ◽  
Nitriding Potential

AbstractSamples of iron catalysts of various specific surface areas for ammonia synthesis underwent nitriding with ammonia in a tubular reactor where continuous thermogravimetric measurement and measurements of hydrogen concentration in the gaseous phase were simultaneously performed. The nitriding process was performed under atmospheric pressure at 475°C. It was observed that, along with an increase in the mean size of iron nano-crystallites, the minimum nitriding potential (at which the iron nitriding reaction is initiated) of the gaseous phase also increased. The degree of nitriding of the catalyst samples increased with the increase in the mean size of iron crystallites. On the basis of the values of nitriding potential, nano-crystallite size distributions can be determined.

Size decrease of detonation nanodiamonds by air annealing investigated by AFM

MRS Advances ◽  
2016 ◽  
Vol 1 (16) ◽  
pp. 1067-1073 ◽  
Author(s):  
Stepan Stehlik ◽  
Daria Miliaieva ◽  
Marian Varga ◽  
Alexander Kromka ◽  
Bohuslav Rezek
Keyword(s):  
Size Distribution ◽  
Annealing Temperature ◽  
Detonation Nanodiamonds ◽  
Particle Analysis ◽  
Detonation Synthesis ◽  
Size Distributions ◽  
Force Microscopy ◽  
Atomic Force ◽  
Mean Size ◽  
The Mean

ABSTRACTNanodiamonds (NDs) represent a novel nanomaterial applicable from biomedicine to spintronics. Here we study ability of air annealing to further decrease the typical 5 nm NDs produced by detonation synthesis. We use atomic force microscopy (AFM) with sub-nm resolution to directly measure individual detonation nanodiamonds (DNDs) on a flat Si substrate. By means of particle analysis we obtain their accurate and statistically relevant size distributions. Using this approach, we characterize evolution of the size distribution as a function of time and annealing temperature: i) at constant time (25 min) with changing temperature (480, 490, 500°C) and ii) at constant temperature (490°C) with changing time (10, 25, 50 min). We show that the mean size of DNDs can be controllably reduced from 4.5 nm to 1.8 nm without noticeable particle loss and down to 1.3 nm with 36% yield. By air annealing the size distribution changes from Gaussian to lognormal with a steep edge around 1 nm, indicating instability of DNDs below 1 nm.

Experimental Characterization of Aerosol Production, Transport, Vaporization, and Atomization Systems. Part II: Factors Controlling Aerosol Size Distributions Produced

1985 ◽  
Vol 39 (6) ◽  
pp. 920-925 ◽  
Author(s):  
R. K. Skogerboe ◽  
S. J. Freeland
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Cross Flow ◽  
Size Distributions ◽  
Experimental Characterization ◽  
Gas Flow Rate ◽  
Mean Size ◽  
The Mean ◽  
Model Equations

The effects of nebulization conditions on the size characteristics of the aqueous aerosol produced have been investigated for a cross-flow nebulizer. It is shown that the nebulizer gas flow rate does not affect the upper limit mean sizes of the aqueous droplets transported from the nebulization chamber but that the mean size of the analyte-containing aerosol itself is affected. Model equations are presented descriptive of the effects of gas flow rate and analyte concentrations on analyte aerosol size characteristics.

scholarly journals Density and Size Distribution of the Sea Cucumber, Holothuria scabra (Jaeger, 1935), at Six Exploited Sites in Mahout Bay, Sultanate of Oman

2007 ◽  
Vol 12 ◽  
pp. 43 ◽  
Author(s):  
Khalfan M. Al-Rashdi ◽  
Michel R. Claereboudt ◽  
Saud S. Al-Busaidi
Keyword(s):  
Size Distribution ◽  
Sea Cucumber ◽  
Size Distributions ◽  
Sultanate Of Oman ◽  
Population Densities ◽  
Sea Cucumbers ◽  
Holothuria Scabra ◽  
Mean Size ◽  
Males And Females ◽  
The Mean

A rapid survey of the density and size distribution of recently exploited populations of Holothuria scabra in Mahout Bay (Ghubbat Hashish Bay) was carried out at six fishing sites. The results showed that population densities varied between 1170 and 4000 individuals ha-1 and biomass ranged between 393 and 2903 kg ha-1. The mean size of sea cucumbers and population densities were much lower in populations closer to human settlements, suggestive of overfishing. The sex ratio was estimated to be 1:1 and the size distributions of males and females did not differ significantly. The length-weight relationship for both sexes was calculated as W (g) = 0.033 Length (mm) 2.178. 

Effect of Synthesis Parameter on Properties of Heat-Sensitive Nanocapsules

2013 ◽  
Vol 675 ◽  
pp. 302-305
Author(s):  
Pu Ying An ◽  
Zhao Yun Yu ◽  
Hai Song Zhang ◽  
Xin Wu Ba
Keyword(s):  
Particle Size ◽  
Glass Transition ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Glass Transition Temperatures ◽  
Hyperbranched Poly ◽  
Crosslinker Content ◽  
Mean Size ◽  
The Mean ◽  
Triton X

The crosslinked poly(methylmethacrylate) (PMMA) heat-sensitive nanocapsules were prepared by emulsion polymerization, in which Triton X-100 was used as an emulsifier and unsaturated hyperbranched poly(amide-ester) (UHBP) as a crosslinker. The effects of three determinative process parameters on the particle size distributions, glass transition temperatures(Tgs) and heat sensitive color-developing properties of nanocapsules were investigated in detail. As a result, the mean size of nanocapsules became smaller and their particle size distribution became narrower with the increase in emulsifying rate. The Tg of nanocapsules was 123.8°C with the emulsifier content being 0.6%. The color-developing absorbency was the highest with the crosslinker content being 6.0 %.

Power generation in MFCs with architectures based on tubular cathodes or fully tubular reactors

2011 ◽  
Vol 64 (11) ◽  
pp. 2253-2258 ◽  
Author(s):  
Y. Zuo ◽  
B. E. Logan
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Power Density ◽  
Specific Surface Area ◽  
Microbial Fuel Cells ◽  
High Surface ◽  
Tubular Reactor ◽  
Total Surface Area ◽  
Carbon Cloth ◽  
Surface Areas

Tubular cathodes provide a method to obtain high surface areas for scaling up microbial fuel cells (MFCs), but the importance of the cathode shape is not known. We therefore examined power production using cathodes in various configurations (tubes or flat). The MFC with a single internal carbon cloth tube cathode (71 W/m3) produced more power than previously obtained with an ultrafiltration membrane (8 W/m3) due to the better performance of carbon material. This power density was slightly less than that of a flat carbon cloth cathode (81 W/m3; 88 m2/m3) due to the lower total surface area of the tube (68 m2/m3) and not as a result of the tubular cathode shape. Adding a second tube increased power (83 W/m3) in proportion to specific surface area (93 m2/m3). Wrapping the cathode completely around the anode formed a fully tubular MFC (external tubular reactor) with a higher surface area that produced 128 W/m3. Volumetric power density was highly correlated with cathode specific surface area (R2 = 0.93, p = 0.008) and did not depend on the cathode shape (tubes, completely tubular, or flat). Thus, future MFC designs should focus on increasing cathode specific surface area.

scholarly journals The connectivity of crystallite agglomerates in low-density firn at Kohnen station, Dronning Maud Land, Antarctica

2008 ◽  
Vol 49 ◽  
pp. 114-120 ◽  
Author(s):  
J. Freitag ◽  
S. Kipfstuhl ◽  
S.H. Faria
Keyword(s):  
Crystal Size ◽  
Three Dimensional ◽  
Grain Boundary Sliding ◽  
Size Distributions ◽  
Coordination Numbers ◽  
Dronning Maud Land ◽  
Mean Size ◽  
Surface Section ◽  
Boundary Sliding ◽  
The Mean

AbstractIn this study, the three-dimensional (3-D) microstructure of polar firn is investigated by means of X-ray microfocus computer tomography (mCT). Basic topological properties including the Euler and coordination numbers are derived from the reconstructed 3-D volume images. It is shown that sample volumes of about 4 cm3 are representative for polar firn in terms of their connectivity. The connectivity function defined as the change of Euler number with structure size is calculated via image-processing routines. It is used to split the ice phase at small bridges into single crystallite agglomerates. The bond-size distributions and the mean size of the agglomerates are estimated. All μCT measurements were carried out on the uppermost 9 m of a shallow firn core (B35) drilled during the 2005/06 field campaign at Kohnen station, Dronning Maud Land (DML), Antarctica. The results are compared with estimates from classical two-dimensional (2-D) surface section observations. The 3-D approach confirms the linear relationship between coordination number and density which hitherto has only been derived from 2-D observations. Layers of buried snow dunes show a stronger connectivity than layers of moderate crystal size and density. The formation of agglomerates made of crystallites is a common feature of polar firn in DML. It is proposed that the growth of agglomerates leads to reduced critical densities for the transition between the densification regime of grain boundary sliding and plastic deformation.

scholarly journals From Norway spruce bark to carbon foams: Characterization and applications

BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 3651-3666
Author(s):  
Toni Varila ◽  
Hanna Brännström ◽  
Petri Kilpeläinen ◽  
Jarkko Hellström ◽  
Henrik Romar ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Specific Surface ◽  
Total Pore Volume ◽  
Hot Water ◽  
Size Distributions ◽  
Surface Areas ◽  
Spruce Bark ◽  
Pore Size Distributions ◽  
Carbon Foams ◽  
Specific Surface Areas

Fresh bark from spruce Picea abies was milled and extracted with hot water. The extracts were purified in a number of steps in order to get tannin-extracts pure enough to prepare tannin-based carbon foams. The chemical composition of the extracts were analyzed. The foams were maturated and thermally treated to obtain desired properties, such as specific surface area, porosity, and compressive strength. It was possible to produce carbon foams even if they contained carbohydrate impurities. Differences in the properties of the carbon foams such as compressive strength, specific surface areas, and pore size distributions might be related to the compositions of the extracts. The foams were finally activated chemically and physically and were tested in adsorption of methylene blue. Results from the adsorption tests showed that adsorption was highly related to the total pore volume and the amount of mesopores created inside the foam structure during the thermal treatment.

Batch Precipitation of Lead Iodide

1994 ◽  
Vol 59 (6) ◽  
pp. 1301-1304
Author(s):  
Jaroslav Nývlt ◽  
Stanislav Žáček
Keyword(s):  
Aqueous Solution ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Crystal Size ◽  
Lead Nitrate ◽  
Lead Iodide ◽  
Constant Rate ◽  
Mean Size ◽  
The Mean

Lead iodide was precipitated by a procedure in which an aqueous solution of potassium iodide at a concentration of 0.03, 0.10 or 0.20 mol l-1 was stirred while an aqueous solution of lead nitrate at one-half concentration was added at a constant rate. The mean size of the PbI2 crystals was determined by evaluating the particle size distribution, which was measured sedimentometrically. The dependence of the mean crystal size on the duration of the experiment exhibited a minimum for any of the concentrations applied. The reason for this is discussed.

scholarly journals Effects of topical gel formulation of Ficus carica latex on cutaneous leishmaniasis induced by Leishmania major in BALB/c mice

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Ali Pouryousef ◽  
Erfan Eslami ◽  
Sepehr Shahriarirad ◽  
Sina Zoghi ◽  
Mehdi Emami ◽  
...  
Keyword(s):  
Cutaneous Leishmaniasis ◽  
Murine Model ◽  
Leishmania Major ◽  
Considerable Effect ◽  
Ficus Carica ◽  
Control Group ◽  
Topical Gel ◽  
The Third ◽  
Mean Size ◽  
The Mean

Abstract Objectives The current study aimed to evaluate the effects of Ficus carica latex on the treatment of cutaneous leishmaniasis (CL), induced by Leishmania major. A 5% topical gel with F. carica latex was prepared. BALB/c mice were infected by inoculation of amastigotes form of L. major. Thirty BALB/c mice were divided into five groups, where the first group was treated daily, the second group twice per day, and the third group every other day with the 5% topical gel, for 3 weeks. The sizes of the lesions were measured before and during the course of treatment. Results Although the mean size of lesions in the mice group treated with the 5% F. carica gel, especially in the group receiving daily treatment, was less than the mean size of the lesions in the control group, yet, the differences was not statistically significant (p > 0.05). The findings of the current study demonstrated that the 5% F. carica latex with a 3-week course of treatment had no considerable effect in recovery or control of CL induced by L. major in the murine model. Using higher concentration of F. carica latex and with longer treatment lengths may increase its efficacy in the treatment of CL.

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