• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.466-471
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• 2014

Hydrous zirconia particles were prepared from $ZrOCl_2$ aqueous solution using an electro-dialysis [ED] process. For the preparation of $(Zr,Y)(OH)_4$ precipitates, 3 mol% $YCl_3$ was added into $ZrOCl_2$ aqueous solution. During the hydrolysis of 0.5 mol/L $(Zr,Y)OCl_2$ solution at $90^{\circ}C$ a slurry solution was obtained. The ED process was used for the removal of chlorine from the slurry solution. Two kinds of slurry solution were sampled at the beginning and end of the ED process. The morphology of hydrous zirconia particles in the solution was observed using an inverted optical microscope and an FE-SEM. The hydrous zirconia particles were nano-crystalline, and easily coagulated with drying. Yttrium stabilized zirconia [YSZ] powder could be obtained by the calcination of $(Zr,Y)(OH)_4$ precipitates prepared from a $(Zr,Y)OCl_2$ solution by the ED process. The coagulated dry powders were shaped and sintered at $1500^{\circ}C$ for 2 h. The sintered body showed a dense microstructure with uniform grain morphology.

• Journal of Powder Materials
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• v.16 no.4
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• pp.275-279
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• 2009

The aging characteristics of gas atomized Mg-6 wt.% Al-1 wt.% Zn alloy were investigated and compared to those of cast Mg-6 wt.% Al alloy. The gas atomized Mg-6 wt.% Al-1wt.% Zn alloy powders had spherical morphology between 1 and 100 $\mu m$ in diameter. After compaction under the pressure of 700 MPa at $320^{\circ}C$ for 10 min, the Mg-6 wt.% Al-1 wt.% Zn alloy showed a grain size of approximately 40 $\mu m$ which is smaller than that of the cast Mg-6 wt.% Al alloy, and a relative compact density of approximately 93%. After ageing, the Mg-6 wt.% Al-1 wt.% Zn alloy showed much faster peak hardness than cast Mg-6 wt.% Al alloy. The Mg-6 wt.% Al-1 wt.% Zn alloy showed the new fine precipitations with ageing time, while the cast Mg-6 wt.% Al alloy was almost similar morphology.

• Journal of Powder Materials
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• v.23 no.2
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• pp.120-125
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• 2016

P-type ternary $Bi_{0.5}Sb_{1.5}Te_3$ alloys are fabricated via mechanical alloying (MA) and spark plasma sintering (SPS). Different ball sizes are used in the MA process, and their effect on the microstructure; hardness, and thermoelectric properties of the p-type BiSbTe alloys are investigated. The phases of milled powders and bulks are identified using an X-ray diffraction technique. The morphology of milled powders and fracture surface of compacted samples are examined using scanning electron microscopy. The morphology, phase, and grain structures of the samples are not altered by the use of different ball sizes in the MA process. Measurements of the thermoelectric (TE) transport properties including the electrical conductivity, Seebeck coefficient, and power factor are measured at temperatures of 300-400 K for samples treated by SPS. The TE properties do not depend on the ball size used in the MA process.

• Journal of the Korean Ceramic Society
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• v.55 no.4
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• pp.337-343
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• 2018

The influence of solid loading in the slurry composition on the morphology of 3Y-TZP granules fabricated by two-fluid spray drying was investigated for solid contents varying between 30 wt% and 50 wt%. The resulting 3Y-TZP granules showed a sphere-like shape with diameters of $40-70{\mu}m$. However, a donut-like shape and a few cracks were observed on the granule surfaces fabricated using the slurry with 50 wt% solid content. The green density after cold isostatic pressing at 200 MPa was $2.1-2.2g/cm^3$, and a homogeneous fracture surface was obtained by complete destruction of granules. After sintering at $1500^{\circ}C$ for 2 h, all specimens had relative densities of 96.2 - 98.3%. With increasing solid content, the relative density decreased from 98.3% to 96.2%, but the grain size increased from $0.3{\mu}m$ to $0.6{\mu}m$. Highly sinterable zirconia granule powder could be obtained by controlling the slurry composition.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1720-1723
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• 2000

Boron doped conducting diamond thin film were grown on Si substrate by microwave plasma chemical vapor deposition from a gaseous feed of hydrogen, acetone/methanol and solid boron. The doping level of boron was controlled from 0ppm to $10^4$ppm (B/C). The Si substrate was tilted ca. 10$^{\circ}$ to make Si substrate have different height and temperature. Experimental results show that same condition but different temperature of Si substrate by height made different crystalline of diamond thin film. There were appeared 3$\sim$4 step of different crystalline morphology of diamond. To characterize the boron-doped diamond thin film, Raman spectroscopy was used for identification of crystallinity. To survey surface morphology, microscope was used. Grain size was changed gradually by different temperature due to different height. The Raman spectrum of film exhibited a sharp peak at 1334$cm^{-1}$, which is characteristic of crystalline diamond. The lower position of diamond film position, the more non-diamond component peak appeared near 1550$cm^{-1}$.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.5
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• pp.303-308
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• 1999

Dielectric thin films of PLT(28) ($(Pb_{0.72}La_{0.28})Ti_{0.93}O_3$) have been deposited on $Pt/Ti/SiO_2/Si$ substrates in situ by a laser ablation. We have systematically changed the laser fluence from 0.4 J/$cm^2$ to 3 J/$cm^2$, and deposition temperature from $450^{\circ}C\; to\; 700^{\circ}C$. The surface morphology was changed from planar grain structure to columnar structure as the nucleation energy was increased. The PLT thin film with columnar structure showed good dielectric properties. The deposition temperature influenced on nucleation energy much stronger than the laser energy density did.

• 연구논문집
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• s.31
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• pp.113-125
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• 2001

Silicon addition in titanium alloys generally results in solid solution hardening by silicon itself and precipitation hardening by titanium silicides. The morphology and distribution of the titanium silicides depend upon the alloy chemistry or the heat treatment condition, and play an important role in improving the mechanical properties of the alloys. In this study, the morphology and crystallographic characteristics of the titanium silicides in the Ti-Fe-Si alloy system were studied. Three types of silicides were found in the alloys; (1) interconnected chain-like silicides at grain boundary, (2) coarse silicides over im, (3) fine silicides smaller than 0.2m. Ti3Si was dominant in cast + HIP condition while Ti5Si3 was dominant in as-cast state. It is recognized that $Ti_5Si_3$$\rightarrow$$Ti_3Si$ transition occurred by the peritectoid reaction and it may be promoted by the pressure during HIP. However, in the case of the fine silicides, $Ti_3Si$ and $Ti_5Si_3$ were found simultaneously even after HIP. Such a fine silicide was found to have a crystallographic orientation relationship with matrix.

• Journal of the Korean institute of surface engineering
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• v.52 no.2
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• pp.78-83
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• 2019

Chloride baths for electrodeposited Ni thin films were fabricated by dissolving metal Ni powders with the mixed solution consisting of HCl and de-ionized water. Current efficiency, residual stress, surface morphology and microstructure of Ni films with the change of metal ion ($Ni^{2+}$) concentrations in the plating solution were studied. Current efficiency was measured to be more than 90% with increasing $Ni^{2+}$ concentrations in the plating solution. Residual stress of Ni thin film was increased from about 400 to 780 MPa with increasing $Ni^{2+}$ concentration from 0.2 to 0.5 M. It is gradually decreased to 650 MPa at 0.9 M $Ni^{2+}$ concentration. Smooth surface morphologies were observed over 0.3 M $Ni^{2+}$ concentration, but nodule surface morphology at 0.2 M. Ni films consist of FCC(111), FCC(200), FCC(220) and FCC(311) peaks in XRD patterns. Preferred orientation of FCC(111) was observed and its intensity was slightly decreased with increasing $Ni^{2+}$ concentration. The average grain size was slightly increased at 0.3 M $Ni^{2+}$ concentration and then slightly decreased with increasing $Ni^{2+}$ concentration.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.1
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• pp.9-15
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• 2024

Nd-Fe-B permanent magnets have been utilized on various industrial fields such as electric vehicles, generator, robots with actuator, etc, due to their outstanding magnetic properties even 10 times better than conventional magnets. Recently, there are many researches that report magnetic properties improved by controlling microstructure through adjusting alloying elements or conducting various processing. Especially, post-sintering annealing (PSA) can significantly improve the coercivity by modifying the distribution and morphology of Nd-rich phase which formed at grain boundaries. In this study, Nd-Fe-B sintered magnets were subjected to primary heat treatment followed by secondary heat treatment at 460℃, 500℃, and 540℃ to investigate the changes in microstructure and magnetic properties with the secondary heat treatment temperature. EBSD analysis was conducted to compare anisotropic characteristics. Through the SEM and TEM observation for analyzing the morphology and distribution of Nd-rich phase, we investigated the relationship between microstructure and magnetic properties of sintered Nd-Fe-B magnets.

• Journal of the Korean Electrochemical Society
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• v.8 no.1
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• pp.32-36
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• 2005

[ $WO_3$ ] and $NiO-WO_3$ thin films were deposited on a Si (100) substrate by using high vacuum thermal evaporation. The effects of various film thicknesses on the surface morphology $WO_3$ and $NiO-WO_3$ thin films were investigated. X-ray diffraction (XRD), Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy(XPS) were employed to characterize the deposited films. The results suggest that as $WO_3$ thin films became thick, their grain grew up to a $0.6{\mu}m$. On the other hand, NiO-doping to $WO_3$ thin films inhibited the grain growth five times less than undoped $WO_3$ thin films. This results show that NiO doping inhibited the grain growing of $WO_3$ thin films. Also, the variation of NOx sensitivity $(R_{NOx}/R_{air})$ to the thickness of $WO_3$ and $NiO-WO_3$ thin films were measured according to the thickness change of thin films and the working temperature of sensor in 5ppm NOx gas. As a result, $NiO-WO_3$ thin films showed more excellent properties than $WO_3$ thin films for NOx sensitivity.