• Korean Journal of Materials Research
• /
• v.12 no.10
• /
• pp.803-808
• /
• 2002

Nickel powders were prepared from nickel chloride solution by wet reduction process, and the size control of the particles was investigated with reactant concentration, dispersant agent, and the addition of ethanol as an organic solvent in NiCl$_2$ aqueous solution. The size of the particle decreased with the increase of nickel chloride concentration. Their average particle size were 1.9$\mu\textrm{m}$, 1.6$\mu\textrm{m}$ and $1.5\mu\textrm{m}$ with 0.5M, 0.8M and 1.0M of nickel chloride concentration respectively. The spherical particle was easily controlled by the addition of ethanol as an organic solvent. Especially, in 30 vol% of ethanol, the average particle size and specific surface area were about 0.2$\mu\textrm{m}$ and 8.98m$^2$/g, respectively.

• Journal of Powder Materials
• /
• v.20 no.5
• /
• pp.338-344
• /
• 2013

Fe-TiC composite was fabricated from Fe and TiC powders by high-energy milling and subsequent spark-plasma sintering. The microstructure, particle size and phase of Fe-TiC composite powders were investigated by field emission scanning electron microscopy and X-ray diffraction to evaluate the effect of milling conditions on the size and distribution of TiC particles in Fe matrix. TiC particle size decreased with milling time. The average TiC particle size of 38 nm was obtained after 60 minutes of milling at 1000 rpm. Prepared Fe-TiC powder mixture was densified by spark-plasma sintering. Sintered Fe-TiC compacts showed a relative density of 91.7~96.2%. The average TiC particle size of 150 nm was observed from the FE-SEM image. The microstructure, densification behavior, Vickers hardness, and fracture toughness of Fe-TiC sintered compact were investigated.

• Journal of the Korean Ceramic Society
• /
• v.33 no.5
• /
• pp.547-555
• /
• 1996

Porous alumina ceramics were fabricated by pseudo-boehmite phydosol-gel process within/without commercial $\alpha$-alumina particles average 1 and 40 micron respectively. The pore characteristics of fired specimens were studied by the measurement of bulk density total porosity thyermal analysis pore volume pore distribution BET area XRD and SEM. with increasing of firing temperature pore volume and BET surface area were decreased and the average pore size was increased to approximately 146$\AA$ upto 80$0^{\circ}C$ by de-watering of [OH] and formation of $\alpha$-alumina. The fired relative density of the alumina-dispersed specimen with average 1 micron particle was increased with the amounts of dispersed particle by bimodal packing theory which is compared to the ones of specimen including of average 40 micron particle. It was confirmed that the percola-tion threshold in porous ceramics with coarser particle (40 micron) has formed between the transformed-alumina from hydrogel and dispersed-alumina of above 50 vol% particle and the total porosity was increased at the threshold point above.

• Resources Recycling
• /
• v.25 no.6
• /
• pp.41-49
• /
• 2016

The present study was intended to prepare cobalt oxide ($Co_3O_4$) powder of average particle size 50 nm or less by spray pyrolysis reaction using the raw cobalt chloride ($CoCl_2$) solution, in order to identify the change in the nature of the particles according to the change in the nozzle tip size. When the nozzle tip was 1 mm, it turned out that most of the droplets were spherical and the surface showed very tight structure. The average particle size of the finally formed particles was 20-30 nm. When the nozzle tip size was 2 mm, some of the droplets formed were spherical, but a considerable part of them showed severely disrupted form. particles formed showed an average particle size of 30 - 40 nm. For the nozzle tip size of 5 mm, spherical droplets were almost non-existent and most were in badly fragmented state. The tightness of surface structure of the droplets has greatly been reduced compared with other nozzle tip sizes. Average size of the formed particles was about 25 nm. As the nozzle tip size increased from 1 mm to 2 mm and 3 mm, the intensities of the XRD peaks have changed little, but significantly been reduced when the nozzle tip size increased to 5mm. As the nozzle tip size increased from 1 mm to 2 mm, the specific surface area of the particles decreased, but the nozzle tip size increased to 5mm, the specific surface area remarkably increased.

• Journal of Korean Society of Water and Wastewater
• /
• v.20 no.6
• /
• pp.823-828
• /
• 2006

For this study, an online particle counter was installed before and after the activated carbon filtration process of D water treatment plant where has advanced water treatment processes, produces average 900,000ton/day of drinking water and supply the produced drinking water to Busan citizens. We collected and analyzed particle count data for about 1 year. We inspected particle breakthrough in three out of sixteen filter processes operated at same conditions, i.e. 5th filter, 6th filter and 7th filter. According to the monitoring results, 6th and 7th filters showed similar results while 5th filter showed different results. When compared seasonal effect, the particle count for dry season was below 10 particles/ml while the particle count for August when monthly average rainfall is over 200mm was much higher than for dry season. In January and August, there was a difference in breakthrough particle size. In January, small particles in 2~3um were mainly detected while in August 10um particles were mainly detected and the size distribution was 40% of total count.

• Korean Journal of Materials Research
• /
• v.15 no.7
• /
• pp.431-434
• /
• 2005

To investigate the dependences of the absorption spectrum and electronic structure properties on the ZnO nano-particle size, ZnO nanocrystals were synthesized by a sol-gel method. The absorption onset peak exhibits a systematic blue-shift with decreasing particle size due to the quantum confinement effect, as well as, with decreasing $Zn^{2+}$ concentration. The increase of particle size is mainly controlled by coarsening and aggregation step during the nucleation and growth of ZnO nano-particles. The onset absorption spectrum of ZnO colloids changes from 310 to 355 nm as $Zn^{2+}$ concentration increases from 0.01 to 0.1 mole. The average particle size as a function of aging- time can be determined from the absorption spectra. The freshly prepared nanocrystal size was about 2.8nm.

• Macromolecular Research
• /
• v.10 no.3
• /
• pp.140-144
• /
• 2002

Dispersion polymerization of acrylamide was carried out in the media of methyl alcohol/$H_2O$ mixtures using hydroxypropyl cellulose and ammonium persulfate as steric stabilizer and initiator, respectively. The effects of concentrations of initiator and steric stabilizer, amount of monomer, polymerization temperature, methyl alcohol/$H_2O$ ratio, and purification of monomer and nitrogen purge on the particle size of the latices and molecular weight of the polymers were investigated. The average particle diameter increased with increasing concentration of initiator, water content in methyl alcohol/$H_2O$ media, and polymerization temperature, but decreased with monomer and stabilizer concentrations. The viscosity average molecular weight increased with increasing concentrations of monomer, steric stabilizer, and water content in dispersion media, but decreased with initiator concentration and polymerization temperature. The PAM polymers prepared with the purified monomer and the nitrogen purging before the reaction showed the highest molecular weight.

• Journal of Powder Materials
• /
• v.28 no.1
• /
• pp.13-19
• /
• 2021

Bulk graphite is manufactured using graphite scrap as the filler and phenolic resin as the binder. Graphite scrap, which is the by-product of processing the final graphite product, is pulverized and sieved by particle size. The relationship between the density and porosity is analyzed by measuring the mechanical properties of bulk graphite. The filler materials are sieved into mean particle sizes of 10.62, 23.38, 54.09, 84.29, and 126.64 ㎛. The bulk graphite density using the filler powder with a particle size of 54.09 ㎛ is 1.38 g/㎤, which is the highest value in this study. The compressive strength tends to increase as the bulk graphite density increases. The highest compressive strength of 43.14 MPa is achieved with the 54.09 ㎛ powder. The highest flexural strength of 23.08 MPa is achieved using the 10.62 ㎛ powder, having the smallest average particle size. The compressive strength is affected by the density of bulk graphite, and the flexural strength is affected by the filler particle size of bulk graphite.

• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1997.10a
• /
• pp.87-89
• /
• 1997

The BaTiO$_3$ fine powder was prepared by hydrthermal method using titanium tetrahydoxide (Ti(OH)$_4$) and barium dihydroxide (Ba(OH)$_2$.8$H_2O$) as raw materials. The fine powder was obtained at temperatures as low as 160 to 185$^{\circ}C$. The properties of the BaTiO$_3$ powder were studied as a function of various parameters (reaction temperature, reaction time, Ba/Ti=ratio, etc). The average particle size of the BaTiO$_3$ increased with increasing reaction temperature. After hydrothermal treatment at 17$0^{\circ}C$ for 8 h, the average particle size of the BaTiO$_3$ powder was about 30 nm and the particle size distribution was narrow.

• Progress in Superconductivity and Cryogenics
• /
• v.7 no.1
• /
• pp.1-4
• /
• 2005

Nano- sized spherical $MgB_2$ Powders were synthesized by spray Pyrolysis method. The Influence of solution concentration and furnace reaction temperature on morphology and average particle size were investigated. For adequate preparation conditions, it has mostly spherical, solid and narrow particle size distribution. Average particle size$(X_{50})$ distribution was below 100 nm. The critical temperature for the synthesized $MgB_2$ was around 36K.