Influence of Phase Composition in TiAlSiN Hard Coatings on the Evolution of Structure and Mechanical Properties

Jeong‑Han Lee,Ik‑Hyun Oh,Jun‑Ho Jang,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.3

The aim of this study is to investigate the structural evolution and mechanical properties of TiAlSiN coatings when processedby the arc ion plating method. To form a hard coating, Ti, Al, and Si powders were mechanically alloyed by planetary ballmilling; the powders were then densely compacted during a rapid sintering process into a ternary system coating, i.e. TiAlSi. The evolution of the structural phase from a powder to a compact material is dominated considerably by phase states suchas a supersaturated solid solution or intermetallic compounds. In the case of coating layers, the factors that determine thestructural evolution are associated with the phase stability of the nano-crystalline structure that in turn is associated withthe Ti/Al composition ratio. Motivated by this, we performed experiments to investigate the distribution of microstructures;the material’s binding energy, quantitative properties, transformation of crystal structure, and distribution of amorphous/crystalline were all recorded. In particular, the relationship between the physical and chemical properties during the coatingprocess is considered to be the dominant factor controlling the orientation and morphology of that zone (1, T, and 2). TheTiAlSiN coating layer was found to have hardness above 45 GPa and an adhesion above 100 N. In other words, understandingthe evolution and structure of TiAlSin helped us to produce a material with excellent properties that can be used as a hardcoating. Specifically, these properties were induced by a grain refinement of the nano-crystalline structure that correspondsto an increase in the silicon nitride contents.

Effect of Mechanical Alloying on the Microstructural Evolution of Al60Cr30Si10 Alloys Processed by Spark Plasma Sintering

Jeong‑Han Lee,Ik‑Hyun Oh,Jun‑Ho Jang,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5

In this study, Al, Cr and Si fine powders were alloyed by planetary ball milling to investigate their microstructural evolution,following their mechanical alloying behavior. The formation of Al(Cr) supersaturated solid solution by the Cr grainsembedded in Al-matrix, which contributed substitutional structure is discussed in relation to their structural evolution inaccordance with the distortion of a crystal lattice. The compacts of Al–Cr–Si alloys were prepared by rapid sintering withina short time by dense consolidation above the density of 99.9% as the formation of intermetallics, except in the case of thedistribution of single-phases induced by the Al-melting. The formation behavior of intermetallics was dominated by dependenceon the structures of the milled-powder and subsequent sintering temperature. To estimate the consolidated behaviorsof compacts, various approaches derived from TEM and XRD analysis were taken to obtain microstructural evidences ofthe inter-diffusion, following the presence of thermally stable intermetallics.

타타늄의 열처리 조건에 따른 동전위 양극분극특성 및 표면 미세구조 변화

주동현,이용렬,정영화,양홍서,박상원,이도재,송호준,박영준 大韓齒科器材學會 2002 대한치과재료학회지 Vol.29 No.2

The corrosion resistance of metallic implants is essential for successful implant osseointegration. Moreover, the implant surface should have appropriate surface roughness for the attachment of the osteoblast and collagen fibrils. When titanium is exposed to air a thermodynamically very stable oxide film is formed at once. This oxide is very thin and yet it protects the metal from corrosion instantaneously. However, the oxide would not be ideal, and it would be supposed that the state of oxide film would be various by the different conditions when it is formed. The objective of this study was to evaluate the electrochemical properties and surface microstructural changes of titanium after passivation treatment or exposure to high heat (in vacuum or in air). ASTM grade 2 commercially pure titanium (Ti) disks of 10㎜ diameter were wet ground and polished with 240 and 600 grit SiC, and then ultrasonically cleaned with distilled water and ethanol. Cleansed as-received samples (As-R group) were passivated with 30% nitric acid solution at 50℃ for 15 minutes to make the Pas group. The Std-V samples were made by treating the Ti disks in vacuum quartz tube (10^-8 Torr) at 530℃ for 40 min for stress relieving, followed by annealing at 700℃ for 90 min, and then slow cooling to room temperature. The Std-A samples undergo identical procedure as the Std-V group except that it is done in air. For 530℃-V samples, Ti disks were heated at 530℃ for 40 minutes and slow cooled to room temperature. The 1000℃-V samples were produced by heating Std-V specimens again at 1000℃ for 2 hr, followed by cooling to room temperature. 530℃-A and 1000℃-A samples were also prepared. Potentiodynamic anodic polarization measurement, SEM, AFM and XRD analysis were performed to evaluate the effects of the various treatments. The difference in the mean values of E_corr between groups showed statistically significant difference (P<0.05), but that of I_corr did not show significance (P>0.05). When Ti surface was passivated there was a shift of corrosion potential (E_corr) in the noble direction and a lower corrosion current density (I_corr) value. Std-A samples showed most noble E_corr value among the tested groups. 530℃-V samples showed more noble E-corr than other tested groups except Std-A group. 1000℃-V samples showed more noble E-corr than those of Std-V sample. In the case of Std-, 530℃- and 1000℃-groups, -A sub-groups showed better corrosion resistant characteristics than -V sub-groups in regard to E-corr and I_corr values. In the SEM observations, the surfaces of the As-R samples showed only scratch line on smooth surface. In Pas samples, thick oxide layer covered the surface under high magnification observation. 530℃-A samples were covered by oxide granules, and Std-A samples had 25~50 nm-thick acicular oxides. The 1000℃-A samples were covered by coarse oxide crystals with a granule diameter of 0.1~0.6 μm having a gross appearance of milky white color, which was identified by XRD as a rutile. On the other hand, 1000℃-V samples showed an Widmansta¨tten structrue of which the orientation of the lattice is formed along crystallographic planes of the parent crystals. On the AFM observation, 530℃-A samples showed RMS roughness of 79.38 nm which is 5 times rougher than those of the As-R samples. Std-A sample had a roughness of 330.47 nm which is about 20-times rougher than that of the As-R sample. 1000℃-A samples were covered by coarse granular oxides and the roughness were about 0.56 μm. Vacuum sub-group samples showed a more smooth surface than air sub-group samples, and the oxide film was more dense. Due to variability of the surface treatment and heat treatment conditions, the process of the oxide formation seems to be affected thereby making the corrosion properties and surface micro-morphology different. However, more various electrochemical analysis together with surface analysis, and an investigation for the effects of those on the osteoblast cell adhesion and calcium phosphate apposition are needed for the improvement of the osseointegration rates of the titanium implants.

Rapid Consolidation of WC‑ZrSiO4 Hard Materials by Spark Plasma Sintering: Microstructure, Densification, and Mechanical Properties

Jeong‑Han Lee,Ik‑Hyun Oh,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

Densely consolidated WC-based hard materials with 5–20 vol% ZrSiO4was fabricated by spark plasma sintering at 1400 ℃ ata constant heating rate of 70 ℃/min−1. To achieve mechanical alloying of WC-ZrSiO4, planetary ball milling was carried outfor 12 h, during which the brittle-brittle components (WC-ZrSiO4) became fragmented and their particles became refined. Itwas observed that certain, specific, non-isothermal sintering kinetics, such as apparent activation energy, sintering exponents,and densification strain, affected the densification behavior. The evolution of phase structure from powder to compact wasfound to be related the lattice distortion and micro-strain in the basal planes of WC. By examining the mechanical propertiesof the samples, it was that the added zircon content leads to enhanced fracture toughness (12.9 MPa m1/2) owing to thepresence of WC-ZrSiO4 in the cemented carbide. In fact, the microcrack propagation of the fracture passed through zirconfrom a transgranular to a ductile component (fcc) where the crack tips could be absorbed.

지지막을 이용하는 액막 추출기 내에서 아연 이온의 이동

주창식,이석희,이민규,홍성수,하홍두,정석기 한국환경과학회 2000 한국환경과학회지 Vol.9 No.2

For the purpose of development of a liquid membrane permeator which separates metal ions from aqueous solutions continuously and effectively, a continuous membrane permeator with the membrane solution trapped between extraction and stripping phases by two micro-porous hydrophilic films was manufactured. Experimental researches on the separation of zinc ion from aqueous solutions were performed in the liquid membrane permeator with 30 vol % D_2EHPA solution in kerosine as liquid membrane. As results, the liquid membrane permeator separates zinc ion from aqueous solutions continuously and effectively in the wide range of operating conditions. A simple mass transfer rate model using equilibrium constant of the extraction reaction for the system used were proposed, and the model was compared with experimental results of separation of zinc ion in the permeator. And the effects of operating factors, such as space time, pH of extraction solution, extraction temperature, on the separation rate of zinc ion in the permeator were experimentally examined.

보툴리눔 독소 주사 효과의 정량적 분석을위한 복합근활동전위 측정

서정환,김상수,김남균,이주홍 大韓再活醫學會 1998 Annals of Rehabilitation Medicine Vol.22 No.6

보철물 절삭시 수종의 치과용 절삭기구와 냉각제의 효율성에 관한 연구

정은주,양홍서 전남대학교 치과대학 1996 전남치대논문집 Vol.8 No.1

The purpose of this study was to evaluate effects of dental cutting instruments and coolants to temperature changes of pulp chamber and to cutting weights. To evaluate effects of dental cutting instruments, the experimental groups were devided into 16. Four restorative materials (gold, base metal, resin, porcelain) were grinding with 4 cutting instruments(high speed diamond point, high speed fissure bur, low speed stone point, low speed rubber point). To evaluate effects of coolants, 16 groups were devided into 3 subgroups Group A : no use of coolant Group B : use of air coolant Group C : use of water-air spray coolant The results were as follows : 1. In kinds of coolants, temperature changes were shown in such order as group A, group B, group C. There was statistically significant difference between each group(p<0.05). Cutting weights were shown in such order as group C, group B, group A. There was statically significant difference between group C, B and A(p<0.05). 2. In kinds of cutting instruments, temperature change of diamond point as highest and temperature changes of high speed groups were higher than those of low speed groups. Cutting weights of fissure bur was highest and cutting weights of high speed groups were higher than those of low speed groups. 3. In kinds of materials of specimens, temperature change of base metal was highest and there were statistically significant difference between gold, base metal and resin, porcelain(p<0.05). Cutting weight of gold and base metal were higher than those of resin and porcelain. 4. The surface of specimen of group C, specially in use of high speed cutting instrument, showed less small particles than group A, B in SEM evaluation.

해양미생물로부터 카로테노이드 색소의 생산을 위한 최적조건

정영기,박정욱,주우홍,류병호,정명주,김태수 동의대학교 기초과학연구소 2000 基礎科學硏究論文集 Vol.10 No.1

The optimal medium composition for the production of carotenoid pigment from Haloarcular sp. EH-1 as a dietary for fishes were 1.0% sucrose, 1.0% yeast extract, 25% sodium chloride, 0.3% sodium citrate, 0.2% potassium chloride, 2.0% magnesium sulphate, 0.002% ferric sulphate(pH7.0). The incubation temperate, aeration rate and agitation speed were 40℃, 100ml medium/500ml vol. shaking flask, and 180 rpm/min. The carotenoid pigment production was highest after 5 days of incubation with the light.

악하선에서 분리된 NGF에 의해 유도되는 비만세포 활성화에 미치는 상백피의 억제효과

정홍주,백병주,김대범 大韓小兒齒科學會 1993 大韓小兒齒科學會誌 Vol.20 No.2

Cortex Mori(Norus alba L), the root bark of mulberry tree has been used as an antiphlogistic, diuretic, and expectorant in herbal medicine. Previous studies have demonstrated that Cortex Mori had inhibitory effects on the compound 48/80-induced degranulation and histamine release from rat peritoneal mast cells(RPMC). The purpose of this study is to determine whether Cortex Mori(CM) could inhibit the nerve growth factor(NGF)-induced activation of RPMC in vivo and in vitro. In vitro, various concentrations of NGF(0.1, 1, 10 and 100㎍/ml) were added into the RPMC suspension(??cells/ml) pretreated with lyso-PS at 37℃ for 10minutes. Cortex Mori pretreatment was performed before or after lyso-PS treatment at 37℃ for 10minutes. Histamine in the supernatants and calcium uptake of RPMC were measured by radioisotope enzymatic histamine assay and radioisotope calcium uptake method. In vivo experiment, to estimate the effect of Cortex Mori on NGF-induced cutaneous reaction, various doses of NGF with or without Co rtex Mori on NGF-induced cutaneous reaction, various doses of NGF with or without Cortex Mori were injected i.d. int the shaved flank of Sprague-Dawley rats, and the blue cutaneous staining induced by Evans’blue injection at the NGF alone Cortex Mori plus NGF injection sites were observed. Results were 1) the NGF-induced degranulation and histamine release of RPMC pretreated with Cortex Mori were significantly inhibited, compared to those of control without Cortex Mori pretreatment,2) Cortex Mori inhibited the NGF-induced cutaneous reaction remarkably. From the above results, it is suggested that Cortex Mori contains some substances with an activity to inhibit the NGF-induced activation of mast cell.

Electropulsing Treatment on Enhancement of Electrical Conductivity of Screen-Printed Ag Wire

Ju‑Won Park,Howook Choi,Hwangsun Kim,Simoon Sung,Hye‑Jin Jeong,Il Kim,Jaeseok Gong,Sung‑Tae Hong,Heung Nam Han 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5

The effect of high electric current density on the sintering of Ag wires manufactured by screen printing is evaluated throughelectrical resistivity analysis and microstructure observation. Different forms (continuous and pulsed) of electric currentwith different current densities are applied to the specimens. Conventional heat treatment is also performed as a controlgroup to examine the athermal effect of electropulsing treatment. Compared to the conventional heat treatment, the resistivityis reduced more under the electropulsing treatment with continuous current for the same temperature and treatment time.Also, the process time of electropulsing treatment can be reduced by applying a pulse form of high density current insteadof continuous current without losing the benefit of enhanced reduction of resistivity. The microstructural observationsobtained from high angle annular dark field scanning transmission electron microscope and a digital precession instrumentclearly show that necking connecting the crystals is formed more firmly under electric current. In addition, the temperaturechange of Ag wire and substrate is calculated according to the change of the resistivity when the electric current is appliedto confirm the reliability.