• Journal of the Korean Society of Industry Convergence
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• v.23 no.1
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• pp.25-32
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• 2020

Generally, high-temperature, high-pressure, high-priced sintering equipment is used for diamond sintering, and conductivity is a problem for improving the surface modification of the sintered body. In this study, to improve the efficiency of diamond sintering, we identified a new process and material that can be sintered at low temperature, and attempted to develop a composite thin film that can be discharged by doping boron gas to improve the surface modification of the sintered body. Sintered bodies were sintered by mixing Si and two diamonds in different particle sizes based on CIP molding and HIP molding. In CVD deposition, CVD was performed using WC-Co cemented carbide using CH₄ and H₂ gas, and the specimen was made conductive using boron gas. According to the experimental results of the sintered body, as the Si content is increased, the Vickers hardness decreases drastically, and the values of tensile strength, Young's modulus and fracture toughness greatly increase. Conductive CVD deposited diamond was boron deposited and discharged. As the amount of boron added increased, the strength of diamond peaks decreased and crystallinity improved. In addition, considering the release processability, tool life and adhesion of the deposition surface according to the amount of boron added, the appropriate amount of boron can be confirmed. Therefore, by solving the method of low temperature sintering and conductivity problem, the possibility of solving the existing sintering and deposition problem is presented.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.1
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• pp.17-22
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• 2004

In the present study, newly developed spark plasma sintering(SPS) technique was introduced to refine the grain size of ${\gamma}$-based TiAl intermetallic compounds. Ti-46Al-1.5Mo and Ti-46Al-1.5Mo-0.2C(at%) prealloyed powders were produced by mechanical milling(MM) in high-energy attritor. The mechanically milled powders were characterized by XRD and SEM for the microstructural evolution as a function of milling time. And then, the MMed powders were sintered by both spark plasma sintering and hot pressing in vacuum (HP). After the sintering process, MM-SPSed specimens were heat-treated in a vacuum furnace (SPS-VHT) and in the SPS equipment(MM-SPS) for microstructural control. It was found from microstrutural observation that the microstructure consisting of equiaxed ${\gamma}$-TiAl with a few hundred nanometer in average size and ${\alpha}_2-Ti_3Al$ particles were formed after both sintering processes. It was also revealed from hardness test and three-point bending test that the effect of grain refinement on the hardness and bending strength is much higher than that of carbon addition. The fully lamellar microstructures, which is less than $80{\mu}m$ in average grain size was obtained by SPS-VHT process, and the fully lamellar microstructure which is less than $100{\mu}m$ in average grain size was obtained by MM-SPS for a relatively shorter heat-treatment time.

• Korean Journal of Materials Research
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• v.23 no.2
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• pp.135-142
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• 2013

The Ti-6Al-4V extra low interstitial (ELI) alloy has been widely used as an orthopedic implant material because of its excellent mechanical properties and biocompatibility. However, it still has many problems, including a high elastic modulus and toxicity of the Al and V elements. Therefore, non-toxic biomaterials with a low elastic modulus need to be developed. A high energy mechanical milling (HEMM) process is introduced to improve the effect of sintering. Rapid sintering of spark plasma sintering (SPS) under pressure was used to make an ultra fine grain of Ti-25 wt.%Nb-7 wt.%Zr-10 wt.%Mo-(10 wt.%CPP) composites with bio-attractive elements for increasing strength. These composites were fabricated by SPS at $1000^{\circ}C$ at 60 MPa using HEMM powders. During the sintering process, $CaTiO_3$, TixOy, and CaO were formed because of the reaction between Ti and CPP. The effects of CPP content on the physical and mechanical properties of the sintered Ti-Nb-Zr-Mo-CPP composites were investigated. The biocompatibility and corrosion resistance of the Ti-Nb-Zr-Mo alloys were improved by the addition of CPP.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.51-57
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• 2021

The quality of the ceramic sintered coating on a metal surface through laser surface treatment is affected by the laser irradiation pattern. Depending on the laser irradiation pattern, the amount of residual stress and heat applied or accumulated on the surface increases or decreases, affecting the thickness attained in the ceramic sintering area. When the heat energy accumulated in the sintering area is high, the ceramic and the metal alloy melt and sufficiently mix to form a homogeneous and thick bonding interface. In this study, the thermal energy accumulation in the region sintered with zirconia was controlled using four types of laser processing patterns. The thickness of the diffusion region is analyzed by laser-induced breakdown spectroscopy of Mg-ZrO2 generated by laser sintering zirconia powder on the magnesium alloy surface. On the basis of the analysis of the Mg and Zr present in the sintered region through LIBS, the effect of the irradiation pattern on the sintering quality is confirmed by comparing and analyzing the heat and mass transfer tendency of the diffusion layer and the degree of diffusion according to the irradiation pattern. The derived diffusion coefficients differed by up to 9.8 times for each laser scanning pattern.

• Journal of Powder Materials
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• v.31 no.1
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• pp.43-49
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• 2024

In this study, a core-shell powder and sintered specimens using a mechanically alloyed (MAed) Ti-Mo powder fabricated through high-energy ball-milling are prepared. Analysis of sintering, microstructure, and mechanical properties confirms the applicability of the powder as a sputtering target material. To optimize the MAed Ti-Mo powder milling process, phase and elemental analyses of the powders are performed according to milling time. The results reveal that 20 h of milling time is the most suitable for the manufacturing process. Subsequently, the MAed Ti-Mo powder and MoO₃ powder are milled using a 3-D mixer and heat-treated for hydrogen reduction to manufacture the core-shell powder. The reduced core-shell powder is transformed to sintered specimens through molding and sintering at 1300 and 1400℃. The sintering properties are analyzed through X-ray diffraction and scanning electron microscopy for phase and porosity analyses. Moreover, the microstructure of the powder is investigated through optical microscopy and electron probe microstructure analysis. The Ti-Mo core-shell sintered specimen is found to possess high density, uniform microstructure, and excellent hardness properties. These results indicate that the Ti-Mo core-shell sintered specimen has excellent sintering properties and is suitable as a sputtering target material.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.185-190
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• 1999

An $Al_2O_3/Fe$ composite was synthesized through the double stage processes by a reaction sintering which requires simple process and equipments but provides near-net-shape, a reduction/oxidation process for 5 hrs at $650^{\circ}C$ was followed by sintering at $1200^{\circ}C$ to form an $Al_2O_3/Fe$ composite. The composite processed through the double stage sintering are mainly consists of $\alpha$-Fe and ${\alpha}Al_2O_3$ with minor amount of $FeAl_2O_4$, a spinnel structure which is known to prevent Fe from filling up the pores and good contact with $Al_2O_3/Fe$ particles.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.305-308
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• 2001

Powder injection molding (PIM) uses the shaping advantage of injection molding but is applicable to metals and ceramics. This process combines a small quantity of polymer with an inorganic powder to form a feedstock that can be molded. After shaping, the polymeric binder is extracted and the powder is sintered often to near-theoretical densities. Accordingly, PIM delivers structural materials in a shaping technology previously restricted to polymers. The process overcomes the shape limitations of traditional powder compaction, the costs of machining, the productivity limits of isostatic pressing and slip casting, and the defect and tolerance limitations of casting. The 17-4 PH stainless steel powders with average diameter of $10{\mu}m$ were injection-molded into flat tensile specimens. Sintering of the compacts was carried out at the various temperatures ranging from 900 to $1350^{\circ}C$. Sintering behavior of the compacts and tensile properties of sintered specimens were investigated.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.311-315
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• 1991

The formation and transition of 2212 and 2223 phase have been studied in BPSCCO system. The 2212 phase formed in early sintering state reacts on $Ca_2PbO_4,\;Ca_2CuO_3$ and CuO during sintering process and thus produces the 2223 phase. A long sintering period is need to fabricate the superconductor with large volume fraction of 2223 phase. Also, the thin plate-like grains composed of Bi, Sr, Ca and Cu contribute to 2223 phase formation. Though the sample has lower volume fraction of 2223 phase, the critical temperature is measured highly in case of the grain grown to plate-like shape. In this work, the critical temperature of the sample sintered for 264 hr in air was measured 108 K. Microstructure of the sample was varied with condition of heat treatment after sintering process and the sample annealed with $500^{\circ}C$ for 5 hr showed excellent charateristics of 2223 phase formation.

• Journal of Powder Materials
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• v.13 no.5 s.58
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• pp.351-359
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• 2006

Ni based($Ni_{57}Zr_{20}Ti_{18}Si_2Sn_3$) bulk metallic glass(BMG) powders were produced by a gas atomization process, and ductile Cu powders were mixed using a spray drying process. The Ni-based amorphous powder and Cu mixed Ni composite powders were compacted by a spark plasma sintering (SPS) processes into cylindrical shape. The relative density varied with the used SPS mold materials such as graphite, hardened steel and WC-Co hard metal. The relative density increased from 87% to 98% when the sintering temperature increased up to $460^{\circ}C$ in the WC-Co hard metal mold.

• Journal of Powder Materials
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• v.15 no.4
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• pp.302-307
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• 2008

$Gd_2O_3$-doped $CeO_2$(GDC) solid solutions have been considered as a promising materials for electrolytes in intermediate-temperature solid oxide fuel cells. In this study, the nano-sized GDC powder with average panicle size of 69nm was prepared by a high energy ball milling process and its sintering behavior was investigated. Heat-treatment at $1200^{\circ}C$ of nano-sized GDC powder mixture led to GDC solid-solution. The enhanced densification over 96% of relative density was obtained after sintering at $1300^{\circ}C$ for 2h. It was found that the sinterability of GDC powder could be significantly improved by the introduction of a high energy ball milling process.