• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.953-954
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• 2006

Ti-Cu-Ni-Sn quaternary amorphous alloys of $Ti_{50}Cu_{32}Ni_{15}Sn_3$, $Ti_{50}Cu_{25}Ni_{20}Sn_5$, and $Ti_{50}Cu_{23}Ni_{20}Sn_7$ composition were prepared by mechanical alloying in a planetary high-energy ball-mill (AGO-2). The amorphization of all three alloys was found to set in after milling at 300rpm speed for 2h. A complete amorphization was observed for $Ti_{50}Cu_{32}Ni_{15}Sn_3$ and $Ti_{50}Cu_{25}Ni_{20}Sn_5$ after 30h and 20h of milling, respectively. Differential scanning calorimetry analyses revealed that the thermal stability increased in the order of $Ti_{50}Cu_{32}Ni_{15}Sn_3$, $Ti_{50}Cu_{25}Ni_{20}Sn_5$, and $Ti_{50}Cu_{23}Ni_{20}Sn_7$.

• 한국세라믹학회지
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• 제28권3호
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• pp.215-224
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• 1991

The synthesis of SrTiO3 powders having high purity and homogeneous submicron particle size was attempted by the oxalate method. The microstructure and dielectric properties of SrTiO3 based boundary layer capacitor (BLC) were investigated. Strontium titanyl oxalate[SrTiO(C2O4)2.4H2O] was prepared from the mixing solution of (Sr, Ti) using oxalic acid(H2C2O4) as a precipitating agent at 8$0^{\circ}C$. The crystalline SrTiO3 powder was obtained by thermal decomposition of the precipitate above $600^{\circ}C$. The crystalline SrTiO3 powder containing Nb2O5 as a dopant, TiO2 and SiO2 as additives was sintered at 1360~144$0^{\circ}C$ in the reducing atmosphere to get semiconductive SrTiO3. Insulating material containing PbO-Bi2O3-B2O3 frit was printed on the sintered semiconductive SrTiO3 and fired at 120$0^{\circ}C$ for 2h to get the grain boundary diffusion.

• 한국재료학회지
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• 제19권4호
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• pp.207-211
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• 2009

In this study, we attempted to develop a convenient aluminizing process, using Al-Ti mixed slurry as an aluminum source, to control the Al content of the aluminized layer as a result of a one-step process and can be widely adopted for coating complex-shaped components. The aluminizing process was carried out by the heat treatment on disc and rod shaped S45C steel substrates with Al-Ti mixed slurries that were composed of various mixed ratios (wt%) of Al and Ti powders. The surface of the resultant aluminized layer was relatively smooth with no obvious cracks. The aluminized layers mainly contain an Fe-Al compound as the bulk phase. However, the Al concentration and the thickness of the aluminized layer gradually decrease as the Ti proportion among Al-Ti mixed slurries increases. It has also been shown that the Al-Ti compound layer, which formed on the substrate during heat treatment, easily separates from the substrate. In addition, the incorporation of Ti into the substrate surface during heat treatment was not observed.

• 한국분말재료학회지
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• 제10권6호
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• pp.448-455
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• 2003

$TiO_2$ nanopowder has been synthesized by means of the flame method using a precursor of titanium tetraisopropoxide (TTIP, Ti$(OC_3H_7)_4)$. In order to clarify the effect of cooling rate of hot flame on the formation of $TiO_2$ crystalline phases, the flame was controlled by varying the mixing ratio and the flow rate of gases. Anatase phase was predominantly synthesized under the condition having the steep cooling gradient in flame, while a slow cooling gradient enabled to form almost rutile $TiO_2$ nanopowder of above 95%.

• 한국분말재료학회지
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• 제6권2호
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• pp.171-177
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• 1999

Ti-45.2at.%Ni-5at.%Cu and Ti-40.2at.%Ni-10atat.%Cu alloy powders were fabricated by gas atomization process. The microstructures, Shape, hardness and phase transformation behaviors of the powders were investigated by means of optical microscopy, scanning electron microscopy, micro-hardness measurement, x-ray diffraction analyses and differential scanning calorimetry. The hardness of the Ti-Ni-XCu alloy powders decreased as Cu-content increased. The x-ray diffraction analyses were carried out for powders without heat treatment, and those that treated at 85$0^{\circ}C$ for an hour in a vaccum state($10^5$ torr) and then quenched into ice water. The intensity of B$19^t$ phase increased with heat treating. The monoclinic B$19^t$ martensite was formed in the Ti-Ni-XCu alloy powders during cooling.

• 한국분말재료학회지
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• 제9권2호
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• pp.96-102
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• 2002

In the present study, equiatomic porous TiNi shape-memory alloys have been successfully prepared by self-propagating high-temperature synthesis (SHS) using elemental titanium and nickel powders. The porous TiNi alloys thus obtained have an open porous structure with about 64 vol.% porosity, and the pore size is about 1.8 mm. The effect of preheating temperature on the microstructure have been investigated. It is found that the pore size increases with increasing preheating temperature. Moreover, the preheating temperature was shown to have a significant effect on the microstructrue of the SHS-synthesized porous TiNi shape memory alloys.

• 한국분말재료학회지
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• 제2권3호
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• pp.216-222
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• 1995

$SiC/TiB_2$ composites of varying $TiB_2$ content from 0 to 52 vol.% were prepared by pressureless sintering. When these composites were sintered at $2150^{\circ}C$ the mechanical properties such as elastic modulus, strength and toughness increased with increasing $TiB_2$ content. On the other hand, at a sintering temperature of $2200^{\circ}C$, the mechanical properties reduced gradually with increasing $TiB_2$ content. The main reason was deduced from the onset of spontaneous microcracking and the critical particle size for microcracking was calculated approximately 5.6 $\mu\textrm{m}$.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.81-82
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• 2006

This paper presents the influence of the compositions of sintered Ti-Ni alloys on their thermo-mechanical properties. The Ti-Ni alloys having various compositions from 50at%Ni to 51at%Ni were sintered using elemental Ti and Ni powders by a pulse-current pressure sintering equipment. The deformation resistance in stress-strain curves increased with an increase in Ni content. In the case of Ti-50at%Ni, tensile strength and elongation were more than 500 MPa and 7%, respectively. The increase in Ni content also makes the transformation temperatures lower. The deformation resistance at a test temperature change from 293K and 353K in isothermal tensile test increased with elevating test temperature.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.107-108
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• 2006

The effect of WC or NbC addition on various properties of Ti(C0.7N0.3)-Ni cermets was investigated. The microstructure oj Ti(C0.7N0.3)-xWC-20Ni showed a typical core/rim structure, irrespective of the WC content, whereas the structure oj Ti(C0.7N0.3)-xNbC-20Ni was different and was dependent on the NbC content. The hardness (HV) and the fracture toughness (KIC) had a tendency to increase marginally, while the coercive force (HC) and the magnetic saturation $(4{\pi}{\sigma})$ decreased gradually with an increase in WC or NbC content in the systems studied. In addition, increasing WC content in Ti(C0.7N0.3)-xWC-20Ni system, decarburization was retarded, while denitrification was accelerated

• 환경위생공학
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• 제12권1호
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• pp.25-37
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• 1997

The synthesis of high purity and ultra-fine $BaTiO_{3}$ by precipitation with gaseous $NH_{3}$ as precipitator was investigated to find an alternative process to solve various problems of present wet methods. This study consisted of two parts ; synthesis of $BaTiO_{3}$ precipitation with gaseous $NH_{3}$ and test of electrical property for the $La_{2}O_{3}$ doped $BaTiO_{3}$. The proper condition for the synthesis of $BaTiO_{3}$ by precipitation with gaseous $NH_{3}$ is as follows. The pH was 9.0. $H_{2}O_{2}$ mole ratio to $TiCl_{4}$ was 10. $NH_{3}$ gas follow rate did not influence the synthesis of $BaTiO_{3}$. The calcination temperature of $BaTiO_{3}$ was $300^{\circ}C$. Also, the synthesis of $La_{2}O_{3}$-doped $BaTiO_{3}$ was tested through the wet process. Under these condition, the shape of prepared $BaTiO_{3}$ powder was spherical type and the size of that was about $0.2{\mu}m$. After the powder was pressed, this green body was sintered at the $1300^{\circ}C$. Under these conditions, the water absorptance and the density of the obtained sintered body were below 0.04 %, 5.2 g/$cm^{3}$, respectively. Also the grain size of that was about $10{\mu}m$ and it was similar to commercial product.