• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.824-829
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• 2012

Zn wires have been electrically exploded in methanol or distilled water using the pulsed power technologies. The nanopowders produced by the explosions have been observed by using SEM and TEM, and analyzed its phase by using EDS and XRD. The nanopowders produced in distilled water showed ZnO phase only. On the other hands, the nanopowder produced in methanol showed mixed phases with Zn and ZnO. The HR-TEM images of the nanopowders produced in methanol showed that the some particles have been coated with carbon like materials. It is considered that the carbon coatings could be depended on the positions of the particles during the plasma state formed by explosion.

• Korean Journal of Materials Research
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• v.34 no.3
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• pp.138-143
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• 2024

Ni-CNT nanocomposites were synthesized via the electrical explosion of wire (EEW) in acetone and deionized (DI) water liquid conditions with different CNT compositions. The change in the shape and properties of the Ni-CNT nanopowders were determined based on the type of fluids and CNT compositions. In every case, the Ni nanopowder had a spherical shape and the CNT powder had a tube shape. However, the Ni-CNT nanopowders obtained in DI water exhibited irregular shapes due to the oxidation of Ni. Phase analysis also revealed the existence of nickel oxide when using DI water, as well as some unknown peaks with acetone, which may form due to the metastable phase of Ni. Magnetic properties were investigated using a Vibrating Sample Magnetometer (VSM) for all cases. Nanopowders prepared in DI water conditions had better magnetic properties than those in acetone, as evidenced by the simultaneous formation of super paramagnetic NiO peaks and ferromagnetic Ni peaks. The DI water (Ni:CNT = 1:0.3) sample revealed better magnetic results than the DI water (Ni-CNT = 1:0.5) because it had less CNT contents.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.9
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• pp.736-740
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• 2010

Nickel wires of 0.8 mm in diameter and 80 mm in length were electrically exploded in liquid media such as water, ethyl alcohol. The distribution of particle sizes was broad from a few micrometers to tens of nanometer. It was identified that the particles could be classified according to its sizes by using centrifugal separator. The powder prepared in distilled water showed mainly pure metallic Ni phase although a little oxide phase was observed. The powders prepared in ethyl alcohol showed complicated unknown phases, which is attributed to the compound of carbon in the organic liquid. This unknown phase was turned to pure metallic Ni phase after heat treatment.

• Journal of Powder Materials
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• v.11 no.2
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• pp.130-136
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• 2004

The passivation and oxidation process of tungsten and molybdenum narlopowders, produced by electrical explosion of wires was studied by means of FE-SEM, XPS. XRD, TEM, DIA-TGA and sire distribution analysis. In addition, the phase transformation of W and Mo nanopowders under oxidation in air was investigated. A chemical process is suggested for the oxidation of W and Mo nano-particles after a comprehensive testing of passivated and oxidized powders.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.7
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• pp.1272-1275
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• 2010

The Cu powder was prepared in distilled water. It has a wide range of size distribution. The submicron-sized particles in the Cu powder were removed by using continuous type centrifugal separator. The average particle size after classification was approximately 50nm. The XRD analysis showed that pure Cu phase and oxide phase ($Cu_2O$)weremixedinthepowderpreparedbythismethod.

• Fire Science and Engineering
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• v.19 no.1 s.57
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• pp.20-28
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• 2005

Major petrochemical companies in the USA and the EU map out the strategies step-by-step hazard evaluation for the efficient risk management. They adopted the risk screening methods, such as Dow fire & explosion index, as a preliminary phase to execute detailed evaluation such as QRA (Quantitative Risk Assessment). In this study, The FEDI (Fire & Explosion Damage Index), which a kind of risk screening method proposed by Khan and Abbasi, was applied to the BTX plant in Korea. We showed that the FEDI can be effectively used to classify the hazard potential by comparison of the result from the FEDI and the result from QRA. And we showed that the characteristics and the quantities of chemical are the factors which have a largest effect on fire and explosion by executing relative sensitivity analysis of the FEDI. In conclusion, if the FEDI was applied as a preliminary phase of HAZOP, more efficient hazard evaluation can be possible.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3027-3032
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• 2007

To understand the complex phenomena performed in steam explosion, the fast and global measurement of the steam distribution is imperative for this extremely rapid transient stimulation of the bubble breakup and coalescence due to turbulent eddies and shock waves. TROI, the experimental facility requests more robust sensor system to meet this requirement. In Europe, researchers are prefer a X-ray method but this method is very expensive and has limited measurement range. There is an alternative technology such as ECT. Because of TROI's geometry, however, we need axial tomography method. This paper reviews image reconstruction algorethms for axial tomography, including Tikhonov regularization and iterative Tikhonov regularization. Axial tomography method is examined by simulation and experiment for typical permittivity distributions. Future works in axial tomography technology is discussed.

• Journal of the Korean Society of Safety
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• v.18 no.1
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• pp.64-70
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• 2003

For the unconfined vapor cloud explosion(UVCE) accident by the continuous release of gas-liquid flow of various saturated liquids in a vessel at ground level, overpressures were estimated by TNT equivalency model with two estimation methods, such as UVCE I model based on a constant release time and UVCEII model based on a real travel time of vapor by dispersion and analyzed with various release conditions. As a simulation result the simple, easy, and correct method of evaluation of consequences of the UVCE accident was proposed by using consequences of UVCE I model and correlation equations for differences of overpressures between UVCE models, so that this evaluation method could be used easily in the small and medium size enterprises without using the dispersion model.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.509-516
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• 1995

The uncertainty analysis for the in-vessel steam explosion during severe accidents at a nuclear power plant is performed using a probabilistic approach. This approach consists of four steps; 1) screening, 2) quantification of uncertainty 3) propagation of uncertainty, and 4) output analysis. And the specific methods which satisfy the sub-objectives of each step are prepared and presented. Compared with existing ones, the unique feature of this approach is the improved estimation of uncertainties through quantification, which ensures the defensibility of the resultant failure probability distributions. Using the approach, the containment failure probability due to in-vessel steam explosion is calculated. The results of analysis show that 1) pour diameter is the most dominant factor and slug condensed phase fraction is the least and 2) fraction of core molten is the second most dominant factor, which is identified as distinct feature of this study as compared with previous studies.

• Journal of Powder Materials
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• v.19 no.1
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• pp.49-54
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• 2012

Tungsten nanopowders were produced by the method of wires electrical explosion in the different gases. The study of phase and dispersed composition of the powders was carried out. The influence of electrical parameters such as the value of energy input in wire and the arc stage of the explosion was discussed. The factors that make for decreasing the particles size are the lower pressure of surrounding gas and the use of addition of chemically reactive gas.