The Experts below are selected from a list of 105318 Experts worldwide ranked by ideXlab platform
J. Yon - One of the best experts on this subject based on the ideXlab platform.
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Specific surface area of combustion generated soot particles determined by TEM Image analysis: Effects of primary particle overlapping and necking
2020Co-Authors: Fengshan Liu, Joel Corbin, Coll I., Prem Lobo, G. J. Smallwood, Francois Xavier Ouf, Soleiman Bourrous, J. YonAbstract:The specific surface area of ultrafine particles is an important parameter affecting their physical and chemical properties. For example, the specific surface area of combustion-generated black carbon (BC) particles has been linked to their toxicity and identified to be a more relevant metric to assess their biological response than particle size or mass (Schmid and Stoeger, 2016). Several methods have been developed to measure or determine the specific surface area of aerosol particles, such as the Brunauer-Emmett-Teller (BET) method based on nitrogen adsorption, the diffusion charging (DC) method, scanning Mobility Particle Sizing (SMPS), and the laser-induced incandescence (LII). BET is used as a reference method; however, it is an off-line method and requires a large quantity of sample (several hundreds of milligrams). DC, SMPS, and LII are on-line and faster methods, however, they are indirect methods and rely on various assumptions. Although DC and LII hold a good potential for online determination of the specific surface area of irregular particles, they require further development and evaluation. Recently, it has been demonstrated that the specific surface area of combustion generated black carbon particles can also be determined based on transmission electron microscope (TEM) Image analysis; fairly good agreement between the results of BET and TEM was shown in several recent studies (Bau et al., 2010; Bourrous et al., 2018; Ouf et al., 2019). The fairly good agreement between the specific surface areas determined by BET and TEM Image analysis of various BC and carbon black (CB) aerosols is an indication that there are negligible internal voids in BC and CB particles. Although TEM Image analysis is an off-line method, its main advantage is that it requires only a small amount of sample to be collected on the grid for TEM analysis. Combustion generated BC particles appear as fractal aggregates formed by primary particles that display certain degrees of polydispersity, overlapping, and necking, which in general vary with fuel and flame conditions. Although the specific surface area of BC particles is mainly related to the mean primary particle diameter, other parameters, such as the aggregate size, fractal parameters (pre-factor and fractal dimension), the distribution of primary particles, and the degrees of primary particle overlapping and necking are also relevant. It is important to point out that whereas primary particle overlap reduces both the particle surface area and volume, primary particle necking reduces the particle surface area but increases the particle volume. Figure 1 shows two typical TEM Images of flame generated soot particles. Figure 1. Two typical TEM Images of flame generated soot particles showing primary particle overlapping, a, and primary particle necking, b (Yon et al., 2015). The effect of primary particle overlapping on the specific surface area of BC particles inferred from TEM Image analysis has been investigated recently by Bourrous et al. (2018) and Ouf et al. (2019). However, the potential importance of primary particle necking to BC particle specific surface area determined by TEM Image analysis has not been previously investigated. In this study, the TEM Images of BC particles produced in laboratory soot generators and from literature were analysed to obtain the primary particle size distribution, primary particle overlapping, and necking. Based on these parameters, the particle specific surface area was inferred, and the results are compared with those obtained from BET or reported previously in the literature. Bau, S., Witschger, O., Gensdarmes, F., Rastoix, O., and Thomas, D. (2010) Powder Technol. 200, 190-201. Bourrous, S., Ribeyre, Q., Lintis, L., Yon, Y., Bau, S., Thomas, D., Vallières, C., and Ouf, F.-X. (2018) J. Aerosol Sci. 126, 122-132. Ouf, F.-X., Bourrous, S., Vallières, C., Yon, J., and Lintis, L. (2019) J. Aerosol Sci. 137, 105436. Schmid, O., and Stoeger, T. (2016) J. Aerosol Sci. 99, 133-143. Yon, J., Bescond, A., Liu, F. (2015) J. Quantitative Spectroscopy & Radiative Transfer 162, 197-206.
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Automated determination of aggregate primary particle size distribution by TEM Image analysis Application to soot
Aerosol Science and Technology, 2014Co-Authors: A Bescond, J. Yon, Daniel Ferry, D Delhaye, D Gaffie, Alexis Coppalle, F.x. Ouf, Claude RozeAbstract:In many applications, nanoparticles appear to be in an aggregated form. Thus, a complete description of their morphology involves an analysis of their size at different scales, from the aggregate size to the primary particle size. In this study, we present an automated method for the determination of the primary particle size distribution. It is based on an Image-processing algorithm operating Euclidian distance mapping leading to a function that contains information about aggregates morphology. This algorithm is first applied to virtual aggregates with point contact between spheres, generated by diffusion limited cluster aggregation code. It shows that obtained functions can be used to retrieve the parameters of the primary particle diameter size distribution. However, it also demonstrates that overlapping or necking effects between primary spheres can have an impact on the shape of the function. The analysis is also performed on real soot Images generated by ethylene diffusion flame and civil aviation engine that are different from a physicochemical point of view. This leads to the definition of a calibrated morphological function that can be used for the determination of the parameters of the primary diameter distributions of real soot particles. Finally, the same method is applied to TEM Images of soot generated by a commercial soot generator miniCAST. Three operating conditions were investigated showing that generators can be used to produce soot particles with morphologies similar to those produced by jet engines.Copyright 2014 American Association for Aerosol Research © 2014 Copyright © American Association for Aerosol Research.
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automated determination of aggregate primary particle size distribution by TEM Image analysis application to soot
Aerosol Science and Technology, 2014Co-Authors: A Bescond, J. Yon, Daniel Ferry, D Delhaye, D Gaffie, Alexis Coppalle, F.x. Ouf, Claude RozeAbstract:In many applications, nanoparticles appear to be in an aggregated form. Thus, a complete description of their morphology involves an analysis of their size at different scales, from the aggregate size to the primary particle size. In this study, we present an automated method for the determination of the primary particle size distribution. It is based on an Image-processing algorithm operating Euclidian distance mapping leading to a function that contains information about aggregates morphology. This algorithm is first applied to virtual aggregates with point contact between spheres, generated by diffusion limited cluster aggregation code. It shows that obtained functions can be used to retrieve the parameters of the primary particle diameter size distribution. However, it also demonstrates that overlapping or necking effects between primary spheres can have an impact on the shape of the function. The analysis is also performed on real soot Images generated by ethylene diffusion flame and civil aviation e...
Hiroyuki Muramatsu - One of the best experts on this subject based on the ideXlab platform.
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compressive strength sensitivity of cement mortar using rice husk derived graphene with a high specific surface area
Construction and Building Materials, 2015Co-Authors: Inkyu Rhee, Gunok Shin, Hiroyuki MuramatsuAbstract:Abstract Herein, we demonstrate improvements to the compressive strength of cementitious mortar by incorporating rice husk-derived graphenes (GRHs). Several manufacturing trials were undertaken to synthesize optimized GRHs using different dosages of rice husk ash and potassium hydroxide as well as a range of activation TEMperatures. The incorporation of GRHs into mortar exhibits a generally enhanced reinforcing effect compared to graphene nanoplatelets (GNPs) and multi-walled carbon nanotubes (MWNTs) because of its high specific surface area. SEM/TEM Image analyses confirm that GRH has a corrugated graphene structure and clean edges at the atomic scale. GRH showed extremely high BET surface area (2274 m 2 /g) compared to those of multi-walled carbon nanotubes and GNPs (50–200 m 2 /g).
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TEM Image simulation study of small carbon nanotubes and carbon nanowire
Carbon, 2006Co-Authors: Takuya Hayashi, Hiroyuki Muramatsu, Yoong Ahm Kim, Hiroshi Kajitani, Shinji Imai, Hideyuki Kawakami, Masamitsu Kobayashi, Toshiharu Matoba, Morinobu Endo, Mildred S. DresselhausAbstract:Abstract Recent findings of extremely small diameter carbon nanotube and nanowire in the core of a multi-walled carbon nanotube (MWCNT) have attracted interests from broad range of researchers. Direct observation of carbon nanotube is usually done using a transmission electron microscope (TEM). When nanotubes become smaller, it becomes harder to correctly understand the TEM Images, not only because of the weak scattering, but also due to the artifact that starts to appear because of the interference effect and the inappropriate defocus condition. In this study, we have shown that the artifact such as ghost fringes due to inappropriate defocus conditions of the TEM appear in the core of an MWCNT, and can be misinterpreted as either carbon nanowire or small carbon nanotube. It is also shown that, in the TEM Image, it is hard to distinguish a single-walled nanotube bundle from a double-walled carbon nanotube bundle. Finally, we propose that the cross-sectional observation is necessary for the correct characterization of single- and double-walled carbon nanotube bundles.
Wen Jiang - One of the best experts on this subject based on the ideXlab platform.
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defocus and magnification dependent variation of TEM Image astigmatism
Scientific Reports, 2018Co-Authors: Rui Yan, Wen JiangAbstract:Daily alignment of the microscope is a prerequisite to reaching optimal lens conditions for high resolution imaging in cryo-EM. In this study, we have investigated how Image astigmatism varies with the imaging conditions (e.g. defocus, magnification). We have found that the large change of defocus/magnification between visual correction of astigmatism and subsequent data collection tasks, or during data collection, will inevitably result in undesirable astigmatism in the final Images. The dependence of astigmatism on the imaging conditions varies significantly from time to time, so that it cannot be reliably compensated by pre-calibration of the microscope. Based on these findings, we recommend that the same magnification and the median defocus of the intended defocus range for final data collection are used in the objective lens astigmatism correction task during microscope alignment and in the focus mode of the iterative low-dose imaging. It is also desirable to develop a fast, accurate method that can perform dynamic correction of the astigmatism for different intended defocuses during automated imaging. Our findings also suggest that the slope of astigmatism changes caused by varying defocuses can be used as a convenient measurement of objective lens rotation symmetry and potentially an acceptance test of new electron microscopes.
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defocus and magnification dependent variation of TEM Image astigmatism
bioRxiv, 2017Co-Authors: Rui Yan, Wen JiangAbstract:Daily alignment of the microscope is a prerequisite to reaching optimal illumination lens and imaging lens conditions for high resolution imaging in cryo-EM. In contrast to the dramatic progress in automated Image acquisition and post-Image processing techniques, less attention has been paid to the improvement of microscope alignment before data collection. In this study, we have employed our recently published tool, s2stigmator, to study how Image astigmatism varies with the imaging conditions (e.g. defocus, magnification). We have found that the large change of defocus/magnification between visual correction of astigmatism and subsequent data collection tasks, or even during data collection will inevitably result in undesirable residual astigmatism in the final Images. Furthermore, the dependence of astigmatism on the imaging conditions varies significantly from time to time, so that it cannot be reliably compensated by pre-calibration of the microscope. These findings have essentially invalidated a basic assumption of current cryo-EM imaging strategies that assumes invariant astigmatism for different defocuses/magnifications used in the microscope alignment stage and the final data acquisition stage. Based on these findings, we recommend the same magnification and the median defocus of the intended defocus range for final data collection are used in the objective lens astigmatism correction task during microscope alignment and in the focus mode of the iterative low-dose imaging. It is also desirable to develop a fast, accurate method that can perform dynamic correction of the astigmatism for different intended defocuses during automated imaging.
Inkyu Rhee - One of the best experts on this subject based on the ideXlab platform.
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compressive strength sensitivity of cement mortar using rice husk derived graphene with a high specific surface area
Construction and Building Materials, 2015Co-Authors: Inkyu Rhee, Gunok Shin, Hiroyuki MuramatsuAbstract:Abstract Herein, we demonstrate improvements to the compressive strength of cementitious mortar by incorporating rice husk-derived graphenes (GRHs). Several manufacturing trials were undertaken to synthesize optimized GRHs using different dosages of rice husk ash and potassium hydroxide as well as a range of activation TEMperatures. The incorporation of GRHs into mortar exhibits a generally enhanced reinforcing effect compared to graphene nanoplatelets (GNPs) and multi-walled carbon nanotubes (MWNTs) because of its high specific surface area. SEM/TEM Image analyses confirm that GRH has a corrugated graphene structure and clean edges at the atomic scale. GRH showed extremely high BET surface area (2274 m 2 /g) compared to those of multi-walled carbon nanotubes and GNPs (50–200 m 2 /g).
Rui Yan - One of the best experts on this subject based on the ideXlab platform.
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defocus and magnification dependent variation of TEM Image astigmatism
Scientific Reports, 2018Co-Authors: Rui Yan, Wen JiangAbstract:Daily alignment of the microscope is a prerequisite to reaching optimal lens conditions for high resolution imaging in cryo-EM. In this study, we have investigated how Image astigmatism varies with the imaging conditions (e.g. defocus, magnification). We have found that the large change of defocus/magnification between visual correction of astigmatism and subsequent data collection tasks, or during data collection, will inevitably result in undesirable astigmatism in the final Images. The dependence of astigmatism on the imaging conditions varies significantly from time to time, so that it cannot be reliably compensated by pre-calibration of the microscope. Based on these findings, we recommend that the same magnification and the median defocus of the intended defocus range for final data collection are used in the objective lens astigmatism correction task during microscope alignment and in the focus mode of the iterative low-dose imaging. It is also desirable to develop a fast, accurate method that can perform dynamic correction of the astigmatism for different intended defocuses during automated imaging. Our findings also suggest that the slope of astigmatism changes caused by varying defocuses can be used as a convenient measurement of objective lens rotation symmetry and potentially an acceptance test of new electron microscopes.
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defocus and magnification dependent variation of TEM Image astigmatism
bioRxiv, 2017Co-Authors: Rui Yan, Wen JiangAbstract:Daily alignment of the microscope is a prerequisite to reaching optimal illumination lens and imaging lens conditions for high resolution imaging in cryo-EM. In contrast to the dramatic progress in automated Image acquisition and post-Image processing techniques, less attention has been paid to the improvement of microscope alignment before data collection. In this study, we have employed our recently published tool, s2stigmator, to study how Image astigmatism varies with the imaging conditions (e.g. defocus, magnification). We have found that the large change of defocus/magnification between visual correction of astigmatism and subsequent data collection tasks, or even during data collection will inevitably result in undesirable residual astigmatism in the final Images. Furthermore, the dependence of astigmatism on the imaging conditions varies significantly from time to time, so that it cannot be reliably compensated by pre-calibration of the microscope. These findings have essentially invalidated a basic assumption of current cryo-EM imaging strategies that assumes invariant astigmatism for different defocuses/magnifications used in the microscope alignment stage and the final data acquisition stage. Based on these findings, we recommend the same magnification and the median defocus of the intended defocus range for final data collection are used in the objective lens astigmatism correction task during microscope alignment and in the focus mode of the iterative low-dose imaging. It is also desirable to develop a fast, accurate method that can perform dynamic correction of the astigmatism for different intended defocuses during automated imaging.
