• Fisheries and Aquatic Sciences
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• 제9권1호
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• pp.1-6
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• 2006

Mature spermatozoa of dark chub Zacco temmincki (Temminck and Schlegel), were examined under a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The spermatozoa have a spherical, homogeneously electron-dense nucleus with an axial nuclear fossa containing two laterally oriented centrioles. The centrioles, which are arranged at about a $120^{\circ}$ angle to each other, have the 9+2 microtubule structure typical of flagella. The mature spermatozoon is of the primitive anacrosomal aquasperm type. The nuclear envelope is strongly undulated and contains nuclear vacuoles of different sizes and positions. The midpiece contains six or more mitochondria and encircles the basal body of the flagellum with an axoneme covered by the plasma membrane. Cytoplasmic vesicles lie between the axonemal doublets and the plasma membrane, and encircle the anterior part of the tail. The plasma membrane of the flagellum extends laterally and forms a pair of side fins. The species showed minor differences in number and structure of mitochondria, the angle between centrioles, and total length and occurrence of the fins. These characters, especially the side fins, appear to be apomorphic and useful for determining phylogenetic relationships at the genus or family level.

• 한국표면공학회지
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• 제37권1호
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• pp.5-12
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• 2004

The enhancement of adhesion for Cu film on polycarbonate (PC) surface with the $Ar/O_2$ gas plasma treatment and dc-bias sputtering was studied. The plasma treatment with this reactive mixture changes the chemical property of PC surface into hydrophllic one, which is shown by the variation of contact angle with surface modification. The micro surface roughness that also gives the high adhesive environment is increased by the $Ar/O_2$ gas plasma treatment. These results were observed distinctly from the atomic force microscopy (AFM). The negative substrate dc-bias effect for the Cu adhesion on PC was also investifated. Accelerated $Ar^{+}$ lons in sheath area of anode bombard the bare surface of PC during initial stage of dc bias sputtering. PC substrate. therefore, has severe roughen and hydrophilic surface due to the physical etching process with more activated functional group. As dc-bias sputtering process proceeds, morphology of Cu film shows better step coverage and dense layer. The results of peel test show the evidence of superiority of bias sputtering for the adhesion between metal Cu and PC.C.

• 한국표면공학회지
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• 제48권5호
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• pp.205-210
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• 2015

NbN coatings were prepared by ICP (inductively coupled plasma) assisted magnetron sputtering from a Nb metal target in $Ar+N_2$ atmosphere at various ICP powers. Effect of ICP on the microstructure, crystalline structure and mechanical properties of NbN coatings was investigated by field emission electron microscopy, X-ray diffraction, atomic force microscopy and nanoindentation measurements. The results show that ICP power has a significant influence on coating microstructure, structure and mechanical properties of NbN coatings. With the increasing of ICP power, coating microstructure evolves from the columnar structure of DC process to a highly dense one. Crystalline structure of NbN coatings were changed from cubic ${\delta}$-NbN to hexagonal ${\beta}-Nb_2N$ with increase of ICP power. The maximum nano hardness of 25.4 GPa with Ra roughness of 0.5 nm was obtained from the NbN coating sputtered at ICP power of 200 W.

• 한국표면공학회지
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• 제49권4호
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• pp.376-381
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• 2016

The effects of ICP (Inductively Coupled Plasma) power, ranging from 0 to 200 W, on the crystal structure, microstructure, surface roughness and mechanical properties of magnetron sputtered VN coatings were systematically investigated with FE-SEM, AFM, XRD and nanoindentation. The results show that ICP power has a significant influence on coating microstructure and mechanical properties of VN coatings. With the increasing of ICP power, coating microstructure evolves from a porous columnar structure to a highly dense one. Average crystal grain size of single phase cubic fcc VN coatings was decreased from 10.1 nm to 4.0 nm with increase of ICP power. The maximum hardness of 28.2 GPa was obtained for the coatings deposited at ICP power of 200 W. The smoothest surface morphology with Ra roughness of 1.7 nm was obtained from the VN coating sputtered at ICP power of 200 W.

• 한국표면공학회지
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• 제45권3호
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• pp.123-129
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• 2012

Nanocrystalline CrN coatings were fabricated by DC and ICP (inductively coupled plasma) assisted magnetron sputtering techniques. The effect of ICP power, ranging from 0 to 500 W, on coating microstructure, preferred orientation mechanical properties were systematically investigated with HR-XRD, SEM, AFM and nanoindentation. The results show that ICP power has an significant influence on coating microstructure and mechanical properties of CrN coatings. With the increasing of ICP power, coating microstructure evolves from the columnar structure of DC process to a highly dense one. Grain size of CrN coatings were decreased from 11.7 nm to 6.6 nm with increase of ICP power. The maximum nanohardness of 23.0 GPa was obtained for the coatings deposited at ICP power of 500 W. Preferred orientation in CrN coatings also vary with ICP power, exerting an effective influence on film nanohardness.

• 대한금속재료학회지
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• 제49권1호
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• pp.40-45
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• 2011

Using the spark plasma sintering process (SPS process), the WC-6wt.%Co hard materials were densified using an ultra fine WC-Co powder. The WC-Co was almost completely dense with a relative density of up to 100% after the simultaneous application of a pressure of 60 MPa and the DC pulse current for 3 min without any significant change in the grain size. The average grain size of WC that was produced through this experiment was about $0.2{\sim}0.8{\mu}m$. The hardness and fracture toughness were about $1816kg/mm^2$ and $15.1MPa{\cdot}m^{1/2}$, respectively, for 60 MPa at $1200^{\circ}C$.

• 한국재료학회지
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• 제31권7호
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• pp.397-402
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• 2021

In this study, binderless-WC, WC-6 wt%Co, WC-6wt% 1 and 2.5 B₄C materials are fabricated by spark plasma sintering process (SPS process). Each fabricated WC material is almost completely dense, with a relative density up to 99.5 % after the simultaneous application of pressure of 60 MPa. The WC added Co and Co-B₄C materials resulted in crystalline growth. The WC with HCP crystal structure has respective interfacial energy (basal facet direction: 1.07 ~ 1.34 J·m^-2, prismatic direction: 1.43 ~ 3.02 J·m^-2) that depends on the grain growth direction. It is confirmed that the continuous grain growth, biased by the basal facet, which has relatively low energy, is promoted at the WC/Co interface. As abnormal grain growth takes place, the grain size increases more than twice from 0.37 to 0.8 um. It is found through analysis that the hardness property also greatly decreases from about 2661.4 to 1721.4 kg/mm², along with the grain growth.

• 한국건축시공학회지
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• 제21권6호
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• pp.539-550
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• 2021

일반 전기 아크에 의한 금속용사공법에 비해 시공속도와 효율성능이 우수한 플라즈마 아크 용사장비를 개발하여 이 플라즈마 용사장비에 의한 코팅의 부식특성 평가가 요구되었다. 본 연구에서는 일반 탄소강에 Zn 및 Zn-15Al을 플라즈마 아크 금속 용사법으로 코팅한 후 해수 환경과 유사한 3.5wt.% NaCl 용액에 침지하여 내식성을 평가하였다. SEM 및 XRD에 의한 표면 형상 분석 시험 결과, Zn 코팅이 다공성이고 침상 형태로 되어 있어 용액의 침투가 용이하여 부식 속도가 빠른 것을 알 수 있었다. 반면, Zn-15Al 코팅은 균일하고 조밀한 형태를 보여 부식을 억제하는 것으로 나타났다.

• Applied Microscopy
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• 제50권
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• pp.7.1-7.10
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• 2020

Tantalum nitride (TaN_x) thin films were grown utilizing an inductively coupled plasma (ICP) assisted direct current (DC) sputtering, and 20-100% improved microhardness values were obtained. The detailed microstructural changes of the TaN_x films were characterized utilizing transmission electron microscopy (TEM), as a function of nitrogen gas fraction and ICP power. As nitrogen gas fraction increases from 0.05 to 0.15, the TaN_x phase evolves from body-centered-cubic (b.c.c.) TaN_0.1, to face-centered-cubic (f.c.c.) δ-TaN, to hexagonal-close-packing (h.c.p.) ε-TaN phase. By increasing ICP power from 100 W to 400 W, the f.c.c. δ- TaN phase becomes the main phase in all nitrogen fractions investigated. The higher ICP power enhances the mobility of Ta and N ions, which stabilizes the δ-TaN phase like a high-temperature regime and removes the micro-voids between the columnar grains in the TaN_x film. The dense δ-TaN structure with reduced columnar grains and micro-voids increases the strength of the TaN_x film.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(2)
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• pp.216-221
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• 1998

A study on induction plasma deposition with ceramic materials, yttria-stabilized-zirconia ZrO$_2$-Y$_2$O$_3$ (m.p 264O $^{\circ}C$), was conducted with a view developing a new method for nuclear fuel fabrication Before making dense pellets more than 96％TD., the spraying condition was optimized through the process parameters, such as chamber pressure, plasma plate power powder spraying distance, sheath gas composition, probe position, particle size and powders different morphology. The results with a 5mm thick deposit on rectangular planar graphite substrates showed a 97.11％ theoretical density when the sheath gas flow rate was Ar/H$_2$120/20 l/min, probe position 8cm, particle size -75 ${\mu}{\textrm}{m}$ and spraying distance 22cm by AMDRY146 powder. The degree of influence of the main effects on density were powder morphology. particle size, sheath gas composition, plate power and spraying distance, in that order. Among the two parameter interactions, the sheath gas composition and chamber pressure affects density greatly. By using the multi-pellets mold wheel type, the pellet density did not exceed 94%T.D., owing to the spraying angle.