• Korean Journal of Materials Research
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• v.22 no.5
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• pp.243-248
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• 2012

ZrN nanoparticles were prepared by an exothermic reduction of $ZrCl_4$ with $NaN_3$ in the presence of NaCl flux in a nitrogen atmosphere. Using a solid-state combustion approach, we have demonstrated that the zirconium nitride nanoparticles synthesis process can be completed in only several minutes compared with a few hours for previous synthesis approaches. The chemistry of the combustion process is not complex and is based on a metathesis reaction between $ZrCl_4$ and $NaN_3$. Because of the low melting and boiling points of the raw materials it was possible to synthesize the ZrN phase at low combustion temperatures. It was shown that the combustion temperature and the size of the particles can be readily controlled by tuning the concentration of the NaCl flux. The results show that an increase in the NaCl concentration (from 2 to 13 M) results in a temperature decrease from 1280 to $750^{\circ}C$. ZrN nanoparticles have a high surface area (50-70 $m^2/g$), narrow pore size distribution, and nano-particle size between 10 and 30 nm. The activation energy, which can be extracted from the experimental combustion temperature data, is: E = 20 kcal/mol. The method reported here is self-sustaining, rapid, and can be scaled up for a large scale production of a transition metal nitride nanoparticle system (TiN, TaN, HfN, etc.) with suitable halide salts and alkali metal azide.

• Korean Institute of Interior Design Journal
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• no.26
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• pp.57-63
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• 2001

The aim of this study is to measure sensitivity reaction of human being with a physical properties of color and average size of particle for building materials and predict the influence of color and average size of particle in evaluation of building materials. As a results, 1) In results of qualitative evaluation construction, all 16 adjectives were extracted by higher evaluation items and ,total 14 adjectives were extracted as evaluation adjectives except adjectives of a contrary concept in each other. 2) According to the result of factor analysis, all 4 group of $\ulcirner$potency$\lrcirner$, $\ulcirner$activity$\lrcirner$, $\ulcirner$evaluation$\lrcirner$, $\ulcirner$warmness$\lrcirner$ were extracted. In this time, $\ulcirner$potency$\lrcirner$ as the first factor indicates the most hign original value. Consequently, $\ulcirner$potency$\lrcirner$ factor have an hign influence in evaluation of building materials. 3) As a influence analysis of evaluation variable by evaluation item $\ulcirner$potency$\lrcirner$ factor have an high influence by influence of average size of a particle, $\ulcirner$activity$\lrcirner$ factor have influence hignly by influence of brightness, $\ulcirner$evaluation$\lrcirner$ factor have an hign influence by influence of average site of a particle and the hue, $\ulcirner$warmness$\lrcirner$ factor have an hign influence mainly by influence of the hue

• Journal of Powder Materials
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• v.20 no.1
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• pp.7-12
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• 2013

The effect of particle size distribution on green and sintered properties of Fe-Cr-Mo prealloy powder was investigated in this study. For the study, prealloyed Fe-Cr-Mo powders with different particle sizes were mixed as various ratios and cold compacted at various pressure and sintered at $1250^{\circ}C$ for 30 min, $90%N_2+10%H_2$ atmosphere in the continuous sintering furnace. The results shows that the powders with large particle size distribution have high compressibility and low ejection force. However the green strength are much less than those with small particle size distribution. Tensile prperties of the sintered specimes with large particles size also have high strength and elongation.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.6
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• pp.688-696
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• 2012

The particle depolarization ratios were retrieved from the observation with a multi-wavelength Raman lidar at Gwangju, Korea ($35.11^{\circ}N$, $126.54^{\circ}E$). The measurements were carried out on 24 February and 9 March 2004. Using the particle depolarization ratios, the non-dust aerosol particles were distinguished from the Asian dust plume, and the proportion of the non-dust particle to total dust plume was retrieved. The calculated proportion of the non-dust particle was used for the retrieval of backscatter coefficients at 355, 532, and 1064 nm and extinction coefficients at 355 and 532 nm of non-dust particles in the dust plume. Microphysical parameters of non-dust particles including single-scattering albedo at 532 nm were retrieved using retrieved optical values. The retrieved single-scattering albedo of non-dust particles was 0.92~0.95 below 1 km height and 0.82~0.91 above 1 km height on 24 February 2004 and $0.81{\pm}0.03$ on 9 March 2004.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.2
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• pp.130-140
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• 1993

Average particle deposition velocity toward a horizontal semiconductor wafer in vertical airflow is measured by a wafer surface scanner(PMS SAS-3600). Use of wafer surface scanner requires very short exposure time normally ranging from 10 to 30 minutes, and hence makes repetition of experiment much easier. Polystyrene latex (PSL) spheres of diameter between 0.2 and $1.0{\mu}m$ are used. The present range of particle sizes is very important in controlling particle deposition on a wafer surface in industrial applications. For the present experiment, convection, diffusion, and sedimentation comprise important agents for deposition mechanisms. To investigate confidence interval of experimental data, mean and standard deviation of average deposition velocities are obtained from more than ten data set for each PSL sphere size. It is found that the distribution of mean of average deposition velocities from the measurement agrees well with the predictions of Liu and Ahn(1987) and Emi et al.(1989).

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.1
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• pp.1-8
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• 2016

Optical particle sizer (OPS), optical particle counter (OPC), and aethalomter were deployed to measure the particle number concentrations from 0.3 to $10.0{\mu}m$ and black carbon (BC) concentrations. Comparisons of particle number concentrations measured by OPS and OPC were conducted to evaluate the performance of the each optical instrument at the Gwangju sampling site ($35.23^{\circ}N$, $126.84^{\circ}E$) for 14 days from Dec. 27 in 2014. Although a good correlation ($r^2=0.99$) between the OPS and OPC was observed for both the particle number and volume concentrations, different relationships by BC concentrations can be associated with the intensities by different light scattering angles. In addition, based on diurnal patterns of size distributions in 24 hr running correlation coefficient determination, BC concentrations were highly related to the particles less than $0.3{\mu}m$ observed in the morning traffic hour.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.4
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• pp.41-49
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• 2006

Since particle size distribution curves are useful to estimate permeability of soil, many formulae for permeability coefficient (k) have been published using the parameter from the curves and factors, such as grain size, particle shape and void ratio of soils. However, the parameters such as $C_c,\;C_u$ and $D_n$ derived from only some discrete points on the curve are insufficient to represent the whole gradation. In this paper fractal dimension which is quite new concept and known to be able to represent the entire curve of particle size distribution is employed for the parameters. An empirical formula of permeability coefficient has been developed with fractal dimension and percent of finer than 0.075 mm. The formula developed from this study has confirmed its effectiveness by a series of laboratory tests and comparison to other published formulae. It is found that permeability coefficient is proportional to fractal dimension and inversely proportional to percent of fines.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.22 no.2
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• pp.52-69
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• 1996

Nano-Sized TiO$_2$ particles with diameter between 2 and 5 nm are synthesized in Water/Triton X-100/n-Hexane microemulsion. Particles show the amorphous structure and partially hydroxide form. The optical absorbance of particles appears at 250nm and band edge at 340nm. Gold metal is deposited on the surface of TiO$_2$ particles by reduction reaction of Au(III) ion with sodium hypophosphite. The size of gold-deposited particles is 20nm, and the optical absorbance appears at 270nm and at 550nm. So particles show the red color. The dense precipitation is formed by aggregation in the TiO$_2$ nano-sized particles of about 5nm size. But the bulky precipitation is formed by agglomeration phenomena in the gold-deposited particles of 20nm size. And also gold-deposited particles is easily dispersed by being re-dispersed in PEG/Water solution. This study has compared those things measuring the SPF characteristics of the cosmetics made of the synthesized particles. If the particle size is controlled appropriately, then the SPF value will be higher, or more colorless cosmetics will be made.

• Particle and aerosol research
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• v.10 no.4
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• pp.163-167
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• 2014

Particle number portable emission measurement system (PN-PEMS) is an instrument for measuring number concentration of automobile exhaust. The principle of some pre-existing commercial PN-PEMS is to charge particles and display the number of particles by measuring current. However, this method has some problems for measuring exhaust. In this study, to solve these issues, we have developed a single particle counting PN-PEMS based condensation particle counter (CPC). The PN-PEMS based CPC does not affect driving conditions and it is convenient for mobile because the instrument is small and light in structure. We evaluated counting efficiency of PN-PEMS based CPC by using electrostatic method (electrometer and Faraday cup).

• Particle and aerosol research
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• v.9 no.2
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• pp.59-67
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• 2013

One of purposes in this study was to confirm the behavior of coughed particles under different ventilation conditions. Three types of ventilation systems were applied for this experiment and the properties of coughed particles were measured using computational fluid dynamics (CFD) in an intensive care unit. The changes of total airborne particles for each case showed different trends according to the ventilation type and time, but the deposited particles were similar in all conditions. Although the time taken for 50% of the particles to be deposited was the fastest in case 2, the portion of deposited particles after 300 seconds was only 5% in all conditions. In case 1, a relatively small number of particles were deposited on the wall, but the particle exhaust and deposition on the occupants were the highest. In case 3, the downward ventilation was applied as that recommended by the US Center for Disease Control and Prevention (CDC) and showed different exhaust efficiencies according to the particle size.