scholarly journals Morphology and Raman spectra of aerodynamically-classified soot samples

2019 ◽  
Author(s):  
Alberto Baldelli ◽  
Steven Nicholas Rogak
Keyword(s):  
Particle Size ◽  
Primary Particle ◽  
Particle Diameter ◽  
Size Control ◽  
Aggregate Size ◽  
Aerodynamic Diameter ◽  
Carbon Nanostructure ◽  
Absorption Bands ◽  
Primary Particles ◽  
Combustion Processes

Abstract. Airborne soot is emitted from combustion processes as aggregates of primary particles. The size of the primary particles and the overall aggregate size control soot transport properties, and prior research shows that these parameters may be related to the soot nanostructure. In this work, a laminar, inverted non-premixed burner has been used as a source of soot that is almost completely elemental carbon. The inverted burner was connected to an Electrostatic Low-Pressure Impactor, which collected particles on stages according to the aerodynamic diameter, from 0.3 to 10 μm. The morphology was analyzed using a Transmission Electron Microscope followed by image processing to extract projected area and average primary particle size for each aggregate (approximately 1000 aggregates analyzed in total for the 9 impactor stages). Carbon nanostructure was analyzed using a Raman spectrometer, and 5 absorption bands (D4, D1, D3, G, and D2) were fitted to the spectra to obtain an estimate of the carbon disorder. The average primary particle diameter increases from 15 to 30 nm as the impactor stage aerodynamic diameter increases. The D1, D3, D2, and D4 bands decreased (relative to the G band) with the particle size, suggesting that the larger aggregates have larger graphitic domains.

scholarly journals Morphology and Raman spectra of aerodynamically classified soot samples

2019 ◽  
Vol 12 (8) ◽  
pp. 4339-4346 ◽  
Author(s):  
Alberto Baldelli ◽  
Steven Nicholas Rogak
Keyword(s):  
Particle Size ◽  
Primary Particle ◽  
Particle Diameter ◽  
Size Control ◽  
Aggregate Size ◽  
Aerodynamic Diameter ◽  
Carbon Nanostructure ◽  
Transmission Electron ◽  
Primary Particles ◽  
Combustion Processes

Abstract. Airborne soot is emitted from combustion processes as aggregates of primary particles. The size of the primary particles and the overall aggregate size control soot transport properties, and prior research shows that these parameters may be related to the soot nanostructure. In this work, a laminar, inverted nonpremixed burner has been used as a source of soot that is almost completely elemental carbon. The inverted burner was connected to an electrical low-pressure impactor, which collected particles on stages according to the aerodynamic diameter, from 0.03 to 10 µm. The morphology was analyzed using a transmission electron microscope followed by image processing to extract projected area and average primary particle size for each aggregate (approximately 1000 aggregates analyzed in total for the nine impactor stages). Carbon nanostructure was analyzed using a Raman spectrometer, and five vibrational bands (D4, D1, D3, G, and D2) were fitted to the spectra to obtain an estimate of the carbon disorder. The average primary particle diameter increases from 15 to 30 nm as the impactor stage aerodynamic diameter increases. The D1, D3, D2, and D4 bands decreased (relative to the G band) with the particle size, suggesting that the larger aggregates have larger graphitic domains.

Radiative Properties of Numerically Generated Fractal Soot Aggregates: The Importance of Configuration Averaging

2009 ◽  
Author(s):  
Fengshan Liu ◽  
Gregory J. Smallwood
Keyword(s):  
Primary Particle ◽  
Particle Diameter ◽  
Practical Interest ◽  
Aggregate Size ◽  
Small Variation ◽  
Radiative Properties ◽  
Fractal Aggregates ◽  
Cluster Aggregation ◽  
Fractal Parameters ◽  
Primary Particles

The radiative properties of numerically generated fractal soot aggregates were studied using the numerically accurate generalized multi-sphere Mie-solution method. The fractal aggregates investigated in this study contain from 10 to 600 primary particles of 30 nm in diameter. These fractal aggregates were numerically generated using a combination of the particle-cluster and cluster-cluster aggregation algorithms with fractal parameters representing flame generated soot. Ten different realizations were obtained for a given aggregate size measured by the number of primary particles. The wavelength considered is 532 nm and the corresponding size parameter of primary particle is 0.177. Attention is paid to the effect of different realizations of a fractal aggregate with identical fractal dimension, prefactor, primary particle diameter, and the number of primary particles on its orientation-averaged radiative properties. Most properties of practical interest exhibit relatively small variation with aggregate realization. However, other scattering properties, especially the vertical-horizontal differential scattering cross section, are very sensitive to the variation in geometrical configuration of primary particles. Orientation-averaged radiative properties of a single aggregate realization are not always sufficient to represent the properties of random-oriented ensemble of fractal aggregates.

scholarly journals Radiative Properties of Numerically Generated Fractal Soot Aggregates: The Importance of Configuration Averaging

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Fengshan Liu ◽  
Gregory J. Smallwood
Keyword(s):  
Primary Particle ◽  
Particle Diameter ◽  
Practical Interest ◽  
Aggregate Size ◽  
Small Variation ◽  
Radiative Properties ◽  
Fractal Aggregates ◽  
Cluster Aggregation ◽  
Fractal Parameters ◽  
Primary Particles

The radiative properties of numerically generated fractal soot aggregates were studied using the numerically accurate generalized multisphere Mie-solution method. The fractal aggregates investigated in this study contain 10–600 primary particles of 30 nm in diameter. These fractal aggregates were numerically generated using a combination of the particle-cluster and cluster-cluster aggregation algorithms with fractal parameters representing flame-generated soot. Ten different realizations were obtained for a given aggregate size measured by the number of primary particles. The wavelength considered is 532 nm, and the corresponding size parameter of primary particle is 0.177. Attention is paid to the effect of different realizations of a fractal aggregate with identical fractal dimension, prefactor, primary particle diameter, and the number of primary particles on its orientation-averaged radiative properties. Most properties of practical interest exhibit relatively small variation with aggregate realization. However, other scattering properties, especially the vertical-horizontal differential scattering cross section, are very sensitive to the variation in geometrical configuration of primary particles. Orientation-averaged radiative properties of a single aggregate realization are not always sufficient to represent the properties of random-oriented ensemble of fractal aggregates.

Numerical Study of Temperature and Incandescence Intensity of Nanosecond Pulsed-Laser Heated Soot Particles at High Pressures

2005 ◽  
Author(s):  
Fengshan Liu ◽  
David R. Snelling ◽  
Gregory J. Smallwood
Keyword(s):  
Soot Particle ◽  
High Pressures ◽  
Particle Diameter ◽  
Aggregate Size ◽  
Primary Particle Diameter ◽  
Time Resolved ◽  
Soot Particles ◽  
Nanosecond Pulsed Laser ◽  
Primary Particles ◽  
Laser Heated

Histories of temperature and incandescence intensity of nanosecond pulsed-laser heated soot particles of polydispersed primary particles and aggregate sizes were calculated using an aggregate-based heat transfer model at pressures from 1 atm up to 50 atm. The local gas temperature, distributions of soot primary particle diameter and aggregate size assumed in the calculations were similar to those found in an atmospheric laminar diffusion flame. Relatively low laser fluences were considered to keep the peak particle temperatures below about 3400 K to ensure negligible soot particle sublimation. The shielding effect on the heat conduction between aggregated soot particles and the surrounding gas was accounted for based on results of direct simulation Monte Carlo calculations. After the laser pulse, the temperature of soot particles with larger primary particles or larger aggregates cools down slower than those with smaller primary particles or smaller aggregates due to smaller surface area-to-volume ratios. The effective temperature of soot particles in the laser probe volume was calculated based on the ratio of thermal radiation intensities of the soot particle ensemble at 400 and 780 nm. Due to the reduced mean free path of molecules with increasing pressure, the heat conduction between soot particles and the surrounding gas shifts from the free-molecular to the transition regime. Consequently, the rate of conduction heat loss from the soot particles increases significantly with pressure. The lifetime of laser-induced incandescence (LII) signal is significantly reduced as the pressure increases. At high pressures, the time resolved soot particle temperature is very sensitive to both the primary particle diameter and the aggregate size distributions, implying the time-resolved LII particle sizing techniques developed at atmospheric pressure lose their effectiveness at high pressures.

Ice nucleation by black carbon particles in the cirrus regime: dominated by pore condensation and freezing or deposition ice nucleation?

2020 ◽  
Author(s):  
Cuiqi Zhang ◽  
Yue Zhang ◽  
Martin Wolf ◽  
Longfei Chen ◽  
Daniel Cziczo
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Black Carbon ◽  
Surface Area ◽  
Primary Particle ◽  
Ice Nucleation ◽  
Primary Particle Size ◽  
Ice Formation ◽  
Primary Particles

<p>Deposition ice nucleation (IN) is a heterogeneous pathway by which water vapor deposits directly onto a solid surface and forms ice. Deposition IN happens below water saturation. However, the pore condensation and freezing (PCF) mechanism offers another explanation to ice formation on porous particles at low ice supersaturation. A single black carbon (BC) aggregate consists of several primary particles, forming crevices between primary particles. Whether BC IN happens via deposition or PCF remains uncertain due to the fractal nature of BC particles.</p><p>We estimated aggregate surface area, morphology, and primary particle size distribution directly from scanning electron microscopy (SEM) images of size-selected (200 nm, 300 nm, and 400 nm) commercial BC particles. Correlations between surface area data obtained from SEM image estimation and traditional BET tests were explored. Several shape parameters were chosen to characterize particle morphology. The IN ability of aerosolized BC particles was determined with the Spectrometer for Ice Nuclei (SPIN) in the cirrus regime (-46 to -38°C). Particle number concentration and chemical composition were monitored online by a Condensation Particle Counter (CPC) and the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument, respectively.</p><p>Preliminary experimental results suggest that larger (400 nm) BC particles are more fractal and branching compared with smaller (200-300 nm) particles. Larger, more fractal BC particles are superior ice nucleating particles (INP) when compared with smaller, more spherical ones. The primary particle size distribution of all samples peaks around 30-45 nm. To understand the relevance of the PCF mechanism with our experimental IN results, we established Young-Laplace equations for the potential liquid-vapor interfaces within inter-primary particle crevices and pores and inter-aggregate pores. Solutions of the Young-Laplace equation on a saddle surface was deducted. Whether ice nucleation happens via PCF mechanism or deposition still requires further investigation, since particle surface chemistry can also affect both ice formation pathways.</p>

Application of Plakett-Burman Screening Design in Optimization of Process Parameters for Formulation of Canaglifozin Nanosuspension

2020 ◽  
Vol 13 (6) ◽  
pp. 5208-5216
Author(s):  
Nisha Patel ◽  
Hitesh A Patel
Keyword(s):  
Particle Size ◽  
Particle Diameter ◽  
Spherical Shape ◽  
Water Soluble ◽  
Pareto Chart ◽  
Independent Variables ◽  
Mean Particle Size ◽  
Screening Design ◽  
Stirring Time ◽  
Response Variables

In this study, we sought to improve the dissolution characteristics of a poorly water-soluble BCS class IV drug canaglifozin, by preparing nanosuspension using media milling method. A Plackett–Burman screening design was employed to screen the significant formulation and process variables. A total of 12 experiment were generated by design expert trial version 12 for screening 5 independent variables namely the amount of stabilizer in mg (X1), stirring time in hr (X2), amt of Zirconium oxide beads in gm (X3), amount of drug in mg (X4) and stirring speed in rpm (X5) while mean particle size in nm (Y1) and drug release in 10 min. were selected as the response variables. All the regression models yielded a good fit with high determination coefficient and F value. The Pareto chart depicted that all the independent variables except the amount of canaglifozin had a significant effect (p<0.001) on the response variables. The mathematical model for mean particle size generated from the regression analysis was given by mean particle size = +636.48889 -1.28267 amt of stabilizer(X1) -4.20417 stirring time (X2) -7.58333 amt of ZrO2 beads(X3) -0.105556 amt of drug(X4) -0.245167 stirring speed(X5) (R2=0.9484, F ratio=22.07, p<0.001). Prepared canaglifozin nanosuspension exemplified a significant improvement (p<0.05) in the release as compared to pure canaglifozin and marketed tablet with the optimum formulation releasing almost 80% drug within first 10min. Optimized nanosuspension showed spherical shape with surface oriented stabilizer molecules and a mean particle diameter of 120.5 nm. There was no change in crystalline nature after formulation and it was found to be chemically stable with high drug content.

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