• Elastomers and Composites
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• v.56 no.2
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• pp.85-91
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• 2021

In this study, different types and shapes of various particles produced on the asphalt pavement road were analyzed. Road dust at a bus stop was collected and was separated as per their sizes by using a sieve shaker. Tire-road wear particles (TRWPs), asphalt pavement wear particles (APWPs), mineral particles, plant-related particles, glass beads, glass particles, road paint wear particles, plastic particles, and fibers were observed herein. The types and shapes of the particles varied depending on their sizes. TRWPs larger than 500 ㎛ were not observed. TRWPs with a size of 212-500 ㎛ were rarely present, but many TRWPs with a size smaller than 212 ㎛ were observed. APWPs were observed for whole-particle sizes of below 1,000 ㎛. A variety of particles on the road would lead to lower friction between the tires and the road, thereby increasing the braking distance of vehicles. Most of the particles include mineral particles, glass particles, and APWPs with rough surfaces. Therefore, the abrasion of the tire tread would accelerate owing to friction with the tough particles.

• Elastomers and Composites
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• v.57 no.3
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• pp.92-99
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• 2022

A large amount of particles on the roads is produced by friction between the vehicles and the road surface and by inflow from outside. The type of these particles affects the abrasion behavior of tire tread. In this study, road dust collected at a bus stop was separated by size, and the particles with sizes of 106-212 mm were analyzed. The particles were separated by density using NaI and NaBr aqueous solutions with densities in the range of 1.10-1.80 g/cm³ with the 0.10 g/cm³ interval. In the road dust sample, the following particle types were found: tire-road wear particles (TRWPs), asphalt pavement wear particles (APWPs), plant-related particles (PRPs), road paint wear particles (RPWPs), and plastic particles (PPs). The densities of TRWPs, APWPs, PRPs, and RPWPs were 1.20-1.80, >1.60, >1.10, and >1.40 g/cm³, respectively, while PPs were found in all density ranges. Additionally, many small mineral particles were observed on the particles. Order of the relative content of the particles was PRP > TRWP > APWP ~ RPWP > PP. APWPs that were stuck to TRWP could be removed by chloroform treatment. The shapes of the particles were characterized using their magnified images.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.579-584
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• 2001

Agglomerated and nonagglomerated SiO2 particles are synthesized in furnace by the electrohydrodynamic spraying method and the vapor feeding method for the test particle generator this study. These polydispersed particles are classified with DMA to extract equal mobility particles. Then these particles are introduced into CNC (Condensation Nuclei Counter) to see the pulse height using Multi-channel Analyzer. The response characteristics of these two kinds of particles in CNCs (TSI CNC 3022 and 3025A) have been studied as a function of particle size using mono disperse particles classified by DMA. The results show that the higher drag resistance particles, so called agglomerated particles have generated a lower CNC pulse height than the spherical particles for these two different CNCs, which means the nonagglomerated particles may start to grow larger than the agglomerated particles.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.7-8
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• 2006

Interest in "nanotechnology" has triggered the question whether new materials can be obtained blending nanosized particles with polymers. This contribution considers modification of polymer properties by nanoscale particles, stabilization of polymer properties by nanoscale particles, stabilization of nanoscale particles against Ostwald-ripening and agglomeration, synthesis of nanoscale particles assisted by polymers and effects of such particles on polymerization mechanisms.

• Particle and aerosol research
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• v.19 no.2
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• pp.31-42
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• 2023

The charge and magnetic characteristics of LM (Low-metallic) and NAO (Non-asbestos-organic) brake wear particles were analyzed. The ratio of charged particles from total particles is about 86% of the LM pad and about 92% of the NAO pad. Number of charge per particle from the NAO pad is also higher than that of the LM pad. The ratio of magnetic particles from total particles increases with the particle size. The ratio of magnetic particles from the LM pad is about 15% for the particles with the size of 1 ㎛, and about 74% for ones with 5 ㎛. The ratio from the NAO pad is about 5% for the particles with the size from 0.5 ㎛ to 2 ㎛, and about 80% for the particles with 5 ㎛. Through the analysis of the components of the two pads with SEM-EDS (Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopy), it was found that the LM pad was occupied with more iron fraction than the NAO pad and that PM_2.5-10 was occupied with more iron fraction than PM_2.5. The particles smaller than 10 ㎛ (i.e. PM₁₀) from the LM pad contained about 83% of charged particles, about 43% of magnetic particles, and about 93% of charged or magnetic particles. PM₁₀ from the NAO pad contained about 88% of charged particles, about 15% of magnetic particles, and about 89% of charged or magnetic particles.

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3465-3474
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• 2014

Porous silica particles are the most prevailing raw material for stationary phases of liquid chromatography. During a long period of time, various methodologies for production of porous silica particles have been proposed, such as crashing and sieving of xerogel, traditional dry or wet process preparation of conventional spherical particles, preparation of hierarchical mesoporous particles by template-mediated pore formation, repeated formation of a thin layer of porous silica upon nonporous silica core (core-shell particles), and formation of specific silica monolith followed by grinding and calcination. Recent developments and applications of useful porous silica particles will be covered in this review. Discussion on sub-$3{\mu}m$ silica particles including nonporous silica particles, carbon or metal oxide clad silica particles, and molecularly imprinted silica particles, will also be included. Next, the individual preparation methods and their feasibilities will be collectively and critically compared and evaluated, being followed by conclusive remarks and future perspectives.

• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.989-994
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• 1994

This study aims at finding the closest packings of regular shape particles such as sphere, circle rod and hexagonal rod type. As the ratio of particle size to container lowered to less than 1/10, the wall effect decreased gradually. The tap density of spherical particles with almost orthorhombic arrangement was 59.5%, while those of circle rod and hexagonal rod type particles were 63.5% and 63.0% respectively. And it was decreased with increasing the aspect ratio of regular particles. The tap density of binary mixtures was larger than that corresponding to the monosized particles packing by about 15%. The tap density of ternary mixtures was larger than that of corresponding to the packing of binary mixtures by about 9%. This work employed the binary mixture of 60% coarse particles and 40% fine particles with size ratio of 1.0 to 1/10 and the ternary mixture of 60% coarse particles, 20% medium and 20% fine particles with size ratio of 1:1/10:1/400 respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.6
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• pp.478-481
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• 2013

Diameter controlled carbon nanotubes (CNTs) were grown using surface modified iron nano-particle catalysts with aminpropyltriethoxysilane (APS). Iron nano-particles were synthesized by thermal decomposition of iron pentacarbonyl-oleic acid complex. Subsequently, APS modification was done using the iron nano-particles synthesized. Agglomeration of the iron nano-particles during the CNT growth process was effectively prevented by the surface modification of nano-particles with the APS. APS plays as a linker material between Fe nano-particles and $SiO_2$ substrate resulting in blocking the migration of nano-particles. APS also formed siliceous material covering the iron nano-particles that prevented the agglomeration of iron nano-particles at the early stages of the CNT growth. Therefore we could obtain the diameter controlled CNTs by blocking agglomeration of the iron nano-particles.

• Korean Journal of Materials Research
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• v.13 no.5
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• pp.285-291
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• 2003

The nanosized silver and gold particles are prepared by ERC method in which metal vapors with high temperature is rapidly quenched by coolants such as liquid nitrogen or liquid argon. In order to monitor the crystal structural changes on the internal and the surface of the nanosized noble metal particles, lattice parameter, internal strain and Debye-Waller factor are investigated, and the calculation of X-ray diffraction scattering intensity is performed. The lattice parameters of silver and gold particles agree with those of bulk materials, and crystal internal strain of the metal particles is not changed by rapid cooling. The Debye-Waller factor of gold particles is increased with decreasing particle size because of the surface softening phenomenon of nanosized particles, but the crystal structural change on the surface of the particles is not detected from the comparison the calculated X-ray diffraction profile with the experimental profile on gold particles with the particle size of 4 nm.

• Journal of Korean Society on Water Environment
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• v.21 no.5
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• pp.500-504
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• 2005

Water samples were collected at 7 sites located along the River Nakdong on 30 occasions. Water qualities, size and fractal dimension ($d_F$) of suspended particles were measured. Laser light scattering method was used to obtain the size and $d_F$ of suspended particles. The average size of particles in this river ranged from $89{\mu}m$ and $169{\mu}m$, which appears to be relatively coarse compared with other rivers worldwide. The average $d_F$ of suspended particles in this study ranged from 1.8 to 1.9. The correlation analysis showed that DO, TN, $NO_3$ and chlorophyll-${\alpha}$ had significant positive relationships with particles size, whereas flow rates and TSS had negative relationships. Interestingly, the factors of which had positive relationships with particles size showed negative relationship with the fractal dimension ($d_F$) of suspended particles. Generally, as the size of particles increased, the fractal dimension of particles decreased which was indicating the shape of the larger particles became more irregular.