• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.461-461
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• 2006

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.782-783
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• 2006

Titinium carbide $(TiC_x)$ was produced by self-propagating high temperature synthesis (SHS) method. The morphology and non-stoichiometric number of the SHS product were observed by scanning electron microscopy and neutron diffractometry, respectively. Tubular titanium carbide with hole inside was formed with different non-stoichiometric number (x), which value increased with combustion temperature.

• Korean Journal of Materials Research
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• v.12 no.9
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• pp.706-711
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• 2002

High-pure tantalum powder was fabricated through Na reduction process and has been produced by using $K_2$TaF$_{7}$, and KCI, KF for raw material and diluent, respectively. A raw material and diluent were charged at the hestalloy bomb by the weight rate of 1:2, 1:1, 1:0.5 and 1:0.25 each other, investigated properties of morphology, chemical composition and yield and particle size after reduced. Ta metal has been achieved by reduction of $K_2$$TaF_{7}$ 500g with 1% sodium in excess of stoichiometric amount in the charge at a reduction temperature of $850^{\circ}C$ for 3hours. According to amount of the diluent, a formation of the powder doesn't have an effect. The diluent prevented the temperature rising caused from the heat of reaction and it maintained the speed of reducing reaction. But in the mixture ratio of raw material and diluent in the 1 : 2 and 1 : 0.25, an oxide and partially not reacted K were detected. As the amount of diluent increased, the size of tantalum powder decreased. According as raw material and the mixture ratio of diluent change from 1:0.25 to 1:2, the size is decreased from 5$\mu\textrm{m}$ to 1$\mu\textrm{m}$, and a particle size distribution which is below 325 mesh in fined powder increases from 71% to 83%. In the case of average size of Tantalum powder which is the mixture ratio (1:0.5), we would get the Ta powder with grain size about 3$\mu\textrm{m}$, which come close to the average size (2~4$\mu\textrm{m}$) of tantalum powder which is used commonly in the present is Ta powder about 3$\mu\textrm{m}$.

• Journal of Powder Materials
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• v.20 no.1
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• pp.37-42
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• 2013

$YAG:Ce^{3+}$ phosphor powders were synthesized using a $Al_2O_3$ seed (average particle size: 5 ${\mu}m$) by the polymer solution route. PVA solution was added to the sol precursors consisting of the seed powder and metal nitrate salts for homogeneous mixing in atomic scale. All dried precursor gels were calcined at $500^{\circ}C$ and then heated at $1400^{\circ}C{\sim}1500^{\circ}C$ in $N_2/H_2$ atmosphere. The final powders were characterized by using XRD, SEM, PSA, PL and PKG test. All synthesized powders were crystallized to YAG phase without intermediate phases of YAM or YAP. The phosphor properties and morphologies of the synthesized powders were strongly dependent on the PVA content. Finally, the synthesized $YAG:Ce^{3+}$ phosphor powder heated at $1500^{\circ}C$, which is prepared from 12:1 PVA content and has an average particle size of 15 ${\mu}m$, showed similar phosphor properties to a commercial phosphor powder.

• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.36-39
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• 2022

Since the MgB₂ superconductor is simply composed of two constituents of Mg and B, its performance can be monitored easily with the change of one ingredient compared to the other. With the powder size of B less than 100 nm, two different sizes of Mg powders are used to investigate the reaction temperature dependence of MgB₂ bulk samples. In the range of 630-700℃ for the duration of 30 min., the un-reacted Mg is seen only at 630℃ with Mg powder size of <5 ㎛, whereas Mg traces are detected at all the temperature range with Mg powder size of <45 ㎛. The reaction temperature dependence of MgB₂ superconducting transition temperature, T_c, shows little difference whether Mg powder size is large or small in this range except for the 630℃. It is worthy of notice that the critical current densities of MgB₂ show higher performance with the small size of Mg compared to the large one at all field ranges. With the Mg powder size of <45 ㎛, flux pinning is enhanced with decreasing the reaction temperature, whereas flux pinning properties is quite similar in the Mg powder size of <5 ㎛ except for the 630℃, where Mg is left behind after the reaction.

• Journal of the Korean Ceramic Society
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• v.29 no.7
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• pp.525-532
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• 1992

TiO2 fine powder was synthesized in the gas phase by chemical vapor deposition using hydrolysis of TiCl4. Content of rutile phase in the powder was investigated. Powder characteristics such as size, crystallinity and morphology were also studied by means of TEM, SEM and XRD. Rutile phase in TiO2 powder started to be formed from 100$0^{\circ}C$ and the content increased with the reaction temperature and TiCl4 concentration. As the temperature increased from 80$0^{\circ}C$ to 140$0^{\circ}C$, the primary particle size increased while secondary particle size decreased. Spherical secondary particle with fine primary crystals agglomerated was produced at low temperature of 80$0^{\circ}C$ whereas the grown primary particle being final particle size was produced at higher temperature of 140$0^{\circ}C$. Other effects of TiCl4 and H2O partial pressures on particle size were also reported in this study.

• Journal of the Korean Ceramic Society
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• v.43 no.7 s.290
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• pp.445-450
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• 2006

The preparation of AlN powder by SHS in the system of $Al-AlN-NH_4Cl$ was investigated in this study. In the preparation of AlN powder, the effect of gas pressure and the composition such as Al, AlF, and additive in mixture on the reactivity were investigated. At 60 atm of the initial inert gas pressure in reactor, the optimum composition for the preparation of pure AlN was 35 wt%Al+5 wt% $NH_4Cl+60wt%$AlN. The AlN powder synthesized in this condition was a single phase AlN with a whisker morphology.

• Journal of Welding and Joining
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• v.14 no.6
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• pp.101-108
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• 1996

In this study, WC-l7wt% Co composite powder for thermal spray was fabricated by spray drying method. The agglomerated composite powder had spheroidal morphology and the particle size distribution was 20~60${\mu}{\textrm}{m}$. WC and Co were distributed homogeneously. However, the strength of the spray-dried agglomerate was low due to the pores within the agglomerate. Therefore, the spray-dried agglomerate was broken down during HVOF thermal spray and the microstructure was inhomogeneous with many pores within the coating layer. And the decomposition of WC to W and $W_{6}$ $C_{2.54}$ was accelerated. The strength and flowability of the agglomerate were greatly improved by sintering heat treatment(110$0^{\circ}C$, 1 hour, hi atmosphere), and then the coating layer showed dense and homogeneous microstructure with well-developed splats. The hardness of the coating layer was H $v_{300}$ = 1072.2.2.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2005.11a
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• pp.183-184
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• 2005

Four different coatings deposited using cold spray process were studied with two different powder agglomerating techniques (spray d교 and evaporated powder) and using $TiO_2$ nano-sized powders with and without a 10wt% addition of ZnO. Characterization was performed by SEM, XRD and roughness test. Also the photocatalytic effect of the coatings was evaluated. Although the change of powder preparation techniques and the addition of ZnO into $TiO_2$ did not show appreciable variations in the surface morphology and Anatase phase transformation, it did show influence on the surface roughness of the coating, the highest roughness being found in the coatings made by spray powder prepared method. Regarding the photocatalytic effect it was observed that the using the spray dry coating and the addition of ZnO are promoter of purification at higher rates.

• Journal of the Korean Society of Safety
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• v.21 no.1 s.73
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• pp.65-71
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• 2006

Flame retardancy and mechanical properties of polyolefinic mixed waste plastics/filler composites were investigated by using inorganic flame retardant(magnesium hydroxide) and PUB(polyurethane block) powder generated from cryogenic insulation process. All composites were obtained by extrusion and after compression molding. The effect of PUB powder on the properties of the composites was studied by tensile and izod impact test, morphology studies and flammability as LOI and UL94 vertical burning test and smoke density. The objective of this work is to obtain good mechanical properties from recycled PP composites with $Mg(OH)_{2}/PUB$ powder as fillers and optimum cost-performance balance, in addition to flame retardant characteristics.