• Korean Journal of Materials Research
• /
• v.9 no.5
• /
• pp.452-459
• /
• 1999

To develop advanced cladding materials, the effect of Nb addition on the microstructure and corrosion characteristics of Zr-0.8Sn-xNb alloys was investigated. As the Nb content increased, the grain size decreased and the volume fraction of precipitates increased. It was observed from the corrosion test at $360^{\circ}C$ that the corrosion resistance increased with decreasing Nb content. The best corrosion resistance was obtained in Zr-0.8Sn-0.2Nb alloy with high volume fraction of tetra-$ZrO_2$in the oxide. Therefore, it is suggested that Nb in theZr-0.85Sn-xNb system should be added within the solubility limit of Nb from the viewpoint of alloy design.

• Resources Recycling
• /
• v.14 no.4 s.66
• /
• pp.3-9
• /
• 2005

In this study, the utilization possibility of coal-preparation refuse emitted from Hwasun coal mine in Korea as a raw material for ceramic body was investigated. The firing shrinkage ratio of ceramic specimen made from the coal-preparation refuse was reduced with increasing the addition amounts of that, while the compressive strength was slightly decreased. The weight of ceramic body was also reduced because carbon contained in the coal-preparation refuse was burn by fring. The water adsorption ratio of the ceramic specimen was under 10 wt%, and the compressive strength of that was over 21 MPa at over $1,150^{\circ}C$ for 2 hr. Therefore, it was possible to make the 1st garde clay brick of KS L 4201 from the coal-preparation refuse.

• Fire Science and Engineering
• /
• v.29 no.6
• /
• pp.76-83
• /
• 2015

EPS sandwich panel contains flame retardants that slow down ignition during fires,reduce the amount of heat generated, and block the spread of combustion. However, if a sandwich panel does not satisfy standards for fire-retardant performance, it may increase damage to property and human life. It is difficult to test the fire-retardant performance of a finishing material with the naked eye, so it is necessary to develop convenient and fast evaluation methods that are convenient and fast. In this study, a fire safety evaluation method for EPS sandwich panel was analyzed using X-ray to detect specific components related to the fire-retardant performance X-ray fluorescence analysis (XRF) indicated that suitable panel products contained more aluminum in comparison to unsuitable products. Gibbsite was identified as the main crystalline material of flame retardant EPS through X-ray diffraction analysis (XRD) and was included in both suitable products and unsuitable products, but there was a difference in crystalline structure. This study was verifies the possibility of evaluating fire-retardant performance using ultimate analysis and crystal analysis through these X-ray methods.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.7 no.3
• /
• pp.1-7
• /
• 2003

In this research, it is intended to measure shape of the nozzle throat of the KL-3 engine, which is the main engine of the KSR-III rocket. For the purpose, an image-based method was invented to replace the 3D pointer, which is actually inaccessible to such large scale engines. As a result, our equipment showed satisfactory Performances. Analysing the results of experiments, we find that the pattern of ablation is determined by the spray pattern and that the process of thermal ablation phenomena can be categorized in three regimes - the first regime that the shape of nozzle throat is maintained and ablation is negligible, the second regime that saw-tooth form is developed and ablation is accelerated, and the third regime that the saw-tooth form is already established and the growth of ablation rate is reduced Also, we find that the ratio of area increase after 60 seconds combustion is +5.82% and conclude that the ratio is acceptable and satisfactory.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.18 no.4
• /
• pp.1-8
• /
• 2014

Overexpanded flow of an axisymmetric thruster nozzle is numerically simulated to investigate effects of nozzle pressure ratio (NPR) on the shock structure and thrust performance. The Reynolds-averaged Navier-Stokes equations with k-${\omega}$ SST turbulence model are solved utilizing FLUENT solver. As the NPR is raised, thrust performance monotonically increases with the shock structure and flow-separation point being pushed toward the nozzle exit. It is also discussed that the flow structure at nozzle-exit plane which is immediately affected by a position of nozzle-interior shocks and expansion waves, has strong influence upon the thrust performance of thruster nozzle.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.21 no.4
• /
• pp.52-62
• /
• 2017

The study for the performance characteristics of the nozzleless booster used in ramjet booster was carried out. Performances related to pressure and thrust for nozzleless booster are lower than classical motor those because of absence of convergent and divergent sections of nozzle. To solve this problem, it developed a high-performance propellant with maximum impulse density included Al as metal fuel. Using the nozzleless booster casted the propellant, ground test of it was carried out by varying the length-to-diameter ratio (L/D ratio) of the propellant. Specific impulse of nozzleless booster was limited to about 75 percents of its value compared with that of classical motor adapted nozzle in the same propellant and propellant length and will be estimated approximately 85 percents of its value compared with that of classical motor at same average pressure in terms of the curve fitting by our test results.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.6
• /
• pp.54-60
• /
• 2016

Multi-port HDPE and Paraffin firing tests are conducted for hybrid gas generator application of a ducted rocket in the low oxidizer mass flux range. A fuel rich gas of O/F ratio from 0.3 to 0.8, a typical O/F operating range of a ducted rocket gas generator, have been achieved with paraffin fuel implying that the hybrid system can be a potential candidate. It was also found that an almost constant O/F ratio regime exists under $35kg/m^2s$ of the oxidizer mass flux, opening a possibility for the paraffin fuel toward the VFDR gas generator application.

• Polymer(Korea)
• /
• v.31 no.5
• /
• pp.404-409
• /
• 2007

Polyurethane nanocomposites with inorganic nano fillers for the improvement thermal stability were prepared by the urethane reaction. Fire retardation properties of polyurethane nanocomposites were investigated by cone calorimeter and limited oxygen index (LOI). Maximum heat release rate of MMT-PU and $Bi_2O_3-PU$ polyurethane nanocomposites were decreased as 50% than polyurethane matrix and fire retardation properties of $MMT/Bi_2O_3-PU$ nanocomposte had the best improvement. The LOI of polyurethane nanocomposites also were improved as filling fillers in the nanocomposites over 20. The maximum heat release rates of MMT-PU, $Bi_2O_3-PU\;and\;MMT/Bi_2O_3-PU$ polyurethane nanocomposites were 764, 707, $635kW/m^2$, respectively and $MMT/Bi_2O_3-PU$ polyurethane nanocomposite exhibited the highest value of fire-retardant. We confirmed that polyurethane nanocomposites improved the fire retardation properties.

• Fire Science and Engineering
• /
• v.25 no.6
• /
• pp.146-155
• /
• 2011

In the study, test was carried out to compare the flame retardant performance for the specimen of MDF wood to which field flame retardant treatment (post processing flame retardant) is applied, which is coated with flame retardant film of 5 companies, locally distributed, and MDF wood (nontreated, flame retardant film non-coated) to which aqueous or oil-based fire-retardant paint is applied. As a result of combustion test of MDF wood which was coated with flame retardant film of 5 companies, 2 products showed suitable values in 4 criteria, but other 3 products showed 10~40 % disqualification rate. In regard of characteristics of fire-retardant paint, oil-based fire-retardant paint is better than aqueous fire-retardant paint in flame retardant performance criteria, but MDF wood to which oilbase fire-retardant paint was applied was shown to have higher toxicity index grade than MDF wood to which aqueous fire-retardant paint was applied relatively.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.25 no.4
• /
• pp.51-60
• /
• 2017

Bottom ash(BA) from coal-fired power plants is burnt and remaining ash at high temperature. Since the BA is baked at high temperature, it is considered to be the same function as the elvan. Nowadays, the demand for mortar with far infrared rays, antibacteria, antifungus, deodorization, aridity and humidity function is increasing as the materials such as Hwangtoh(yellow soil) and elvan rather than general mortar. As a result of comparing the functionality of eco-friendly bio BA mortar with that of general mortar, the far infrared ray emissivity is about $0.02{\times}10^2W/m^2$ more and the deodorization function is about 26% or more. Even in the case of humidity control, BA motors showed about 1.8 times higher than general mortar, and more than 10% higher than the "good" standards of moisture absorption and damp proofing construction materials established by the Ministry of Land, Transport and Maritime Affairs.