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.

Calcium phosphate 결정 성장 최적화를 위한 Ti 표면의 BaTiO_3 박막 형성에 관한 연구

조진우,양홍서,박영준,황규석,송종은,이용렬 전남대학교 치과대학 2001 구강과학 Vol.13 No.2

This study was purposed to establish an optimized manufacturing process for a negatively charged ferroelectric thin flim on titanium substrate in order to develop a new implant system having the mechanical strength and bone forming ability. Ferroelectric materials show an alignment of positive and negative charges by poling treatment. Based on this property, this study was performed with the assumption that the Ca^2+ ions would be easily attracted on negatively charged surface and the attracted cation might behave as nuclei for bone-like crystal grownth in biological solutions. In order to have an osteoinducibility by the ferroelectric thin film coating, continuous and flawless crystalline thin film should be formed with ferroelectricity, and finally should be adequately poling treated. In this study, BaTiO_3 (BTO) was selected as a ferroelectric material. Before thin film coating process, most favorable poling condition was investiged with the evaluation of the difference in calcium phosphate (Ca-P) formation in simulated body fluid (SBF). Moreover, the parameters to form an optimum thin film were studied. Dense bulk BTO disks were fabricate using cold isostatic pressing(CIP) and sintered in air at 1300℃ for 2 hours. Sintered BTO disk was polished, and he crystallinity, microstructure, and ferroelectric characteristics were evaluated using an X-ray diffraction analysis (XRD), a field emission scanning electron microscope (FE-SEM), and an Impedance analyzer. To find the optimum poling condition for the calcium phosphate crystal formation, sintered bulk BTO specimens were treated with either of following poling conditions; 1) room temperature poling treatment [ polarizing field (Ep) = 25kV/cm, at 25℃ for 2 hours], 2) under Tc medium-temperaturepoling treatment (Ep=20kV/cm, from 85˚C to 25˚C for 2 hour), and 3) above Tc high-temperature poling were immesed in simulated body fluid (SBF) for 30 days, and the formation of calcium phosphate (Ca-P) layer n the surface was evaluated. The crystallinity, microstructure, and ferroelectric characteristic of BTO thin film were evaluated withthe variation of final heat treatment. It was performed after establishing the starting substance-solvent mixing ratio, coating times, and pre-heating temperature optimal to form continuous and flawless BTO thin film adequate for having ferroelectricity. Perparation of BTO thin film was made by dipping-pyrolysis technique using metal naphthenates as starting substances. BTO thin films was spin-coated on Ti substrate by dipping-pyrolysis technique using sol obtained by mixing Ba-naphthenate and Ti-naphthenate as starting substances. Pre-firing temperature of BTO thin film was performed at 450℃ because organic-solvent ws completely volatilized without any crystal growth, and the final heat treatment was performed at 600, 700 or 800℃, respectively. The results are as follows; 1. BTO disk sintered at 1300℃ for 2 hours showed average grain size of about 1㎛ and the relative dielectric constant at 1㎑ was abut 3000∼3500. 2. After immersing the sintered bulk BTO poled at respective conditions in SBF for 30 days, Ca-P layers were present on the negatively charged surfaces. In contrary, positively charged Bto surface did not show any noticeable charge of the surface microstructure after SBF immersion. 3. In he case of poling condition 1 and 2 treated with below Tc, Ca/P ratio showed a relatively low value of 1,.2∼1.5. While, in the case of poling condition 3 treated with above Tc, Ca/P ratio was 1.5∼1.67, which is similar to that of biological apatite. This phenomenon demonstrates that poling the BTO above the temperature of Tc is preferable for the Ca-P formation. 4. For thin film BTO coastin, the starting substance was prepared by an equimolar mixing of the Ba and Ti-naphthenate. Dilution of the starting substance with toluene was most appropriate at sol : toluene ratio of 5.2:4.8 Too thin sol produced porosity in film, and too thick sol resulted cracks in the film. By repeating the coating and pre-firing procedure 15 times, homogeneous film of 0.5㎛ thickness could be fabricated, and perfomed well during the poling treatment without breakdown. 5. The heat-treatmen of the BTO thin film at 700℃ produced a homogeneous crystalline structure without heterogeneous TiO2 formation. The BTO thin film heat-treated at 600℃ showed non-crystallinity and no ferroelectricity. Treatment at 800℃ produced heterogeneous TiO2 phase in the film, which is unfavorabe for having ferroelectricity by the distortion of the perovskite structure. The relative dielectic constant at 1 ㎑ was 152 and 112 by heat-treatment at 700 and 800℃, respectively. In summary, these results demonstrated that poling the ferroelectric B_aT_iO_3 surface negatively is effective for the formation of Ca-P layer in simulated body fluids. Poling condition at a temperature cooling from above Tc down to room temperature is most effective. By optimizing the method of BTO thin film coating on metal substrate for the formation of Ca-P layer, the data of this study might be applied for the manufacture of new bioactive implant system.

티타늄의 산화 조건에 따른 산화막의 특성 및 인산칼슘 생성에 미치는 영향

김인,양홍서,박연준,송호준,이용렬 전남대학교 치의학연구소 2003 구강과학 Vol.15 No.3

The objective of this study was to evaluate the changes of micro morphology, roughness and crystalline structure of titanium surface after various oxidation treatments. Moreover, the effect of titanium surface oxide characteristics on the formation of calcium phosphate in Eagle's MEM. Commercially pure Ti disks were treated at various thermal conditions of 530℃ (Ti-530), 600℃(Ti-600), 700℃(Ti-700), 800℃(Ti-800), 900℃(Ti-900), and 1000℃(Ti-1000), respectively, and as received cp Ti (AS-R) and passivated cp Ti (PAS) were used as comparison groups. Surface characteristics were investigated using FE-SEM, profilometer and XRD. After immersing each sample in MEM for 7days, calcium phosphate (Ca-P) formation was evaluated using FE-SEM and EDS. Crystallites of 10~30nm-size were observed on the surface of Ti-530 and Ti-600 samples. Needle-like crystals were formed on Ti-700 samples, and the crystal grain size was increased dramatically as the temperature increased higher than 800℃. The roughness of Ti-530 was higher comparing to AS-R and PAS, and the roughness decreased in the treatment range of 530-700 with dense crystalline oxide formation. However, at treatment temperatures higher than 800℃, the roughness increased and its degree was depended to the size of the crystals. The anatase structures were observed in Ti-530 and Ti-600, and anatase and rutile structures were co-existed in Ti-700 specimen. Only rutile TiO_(2) were observed in Ti-800, Ti-900 and Ti-1000 specimens. The Ca-P formation on AS-R and PAS specimens was low in MEM solution. However, the Ca-P formation was well observed on heat-treatedgroups, and its degree of formation and micro-morphology was different by the specimen groups. The crystalline and chemical structure, micro-morphology, and surface roughness of titanium were various by the conditions of heat treatments, and the grain size and crystal structure of titanium oxide affected on the degree of Ca-P formation on Ti samples in MEM solution

Monitoring of polycyclic aromatic hydrocarbons(PAHs) in soil and crops in Korea and their mobility from soil to crops

Hong-Ryeol Park,Jong-Soo Lim,Seong-Soo Kim,Dong-Sik Park,Chun-Keun Lim,Jang-Hyun Hur 한국농약과학회 2007 한국농약과학회 학술발표대회 논문집 Vol.- No.-

Stimuli‐Responsive Reversible Fluorescence Switching in a Crystalline Donor–Acceptor Mixture Film: Mixed Stack Charge‐Transfer Emission versus Segregated Stack Monomer Emission

Park, Sang Kyu,Cho, Illhun,Gierschner, Johannes,Kim, Jin Hong,Kim, Jong H.,Kwon, Ji Eon,Kwon, Oh Kyu,Whang, Dong Ryeol,Park, Jung‐,Hwa,An, Byeong‐,Kwan,Park, Soo Young WILEY‐VCH Verlag 2016 Angewandte Chemie Vol.55 No.1

<P><B>Abstract</B></P><P>We report on a molecularly tailored 1:1 donor–acceptor (D‐A) charge‐transfer (CT) cocrystal that manifests strongly red‐shifted CT luminescence characteristics, as well as noteworthy reconfigurable self‐assembling behaviors. A loosely packed molecular organization is obtained as a consequence of the noncentrosymmetric chemical structure of molecule <B>A1</B>, which gives rise to considerable free volume and weak intermolecular interactions. The stacking features of the CT complex result in an external stimuli‐responsive molecular stacking reorganization between the mixed and demixed phases of the D‐A pair. Accordingly, high‐contrast fluorescence switching (red↔blue) is realized on the basis of the strong alternation of the electronic properties between the mixed and demixed phases. A combination of structural, spectroscopic, and computational studies reveal the underlying mechanism of this stimuli‐responsive behavior.</P>

Over-expression of rice leucine-rich repeat protein results in activation of defense response, thereby enhancing resistance to bacterial soft rot in Chinese cabbage.

Park, Young Ho,Choi, Changhyun,Park, Eun Mi,Kim, Hyo Sun,Park, Hong Jae,Bae, Shin Cheol,Ahn, Ilpyung,Kim, Min Gab,Park, Sang Ryeol,Hwang, Duk-Ju Springer 2012 Plant cell reports Vol.31 No.10

<P>Pectobacterium carotovorum subsp. carotovorum causes soft rot disease in various plants, including Chinese cabbage. The simple extracellular leucine-rich repeat (eLRR) domain proteins have been implicated in disease resistance. Rice leucine-rich repeat protein (OsLRP), a rice simple eLRR domain protein, is induced by pathogens, phytohormones, and salt. To see whether OsLRP enhances disease resistance to bacterial soft rot, OsLRP was introduced into Chinese cabbage by Agrobacterium-mediated transformation. Two independent transgenic lines over-expressing OsLRP were generated and further analyzed. Transgenic lines over-expressing OsLRP showed enhanced disease resistance to bacterial soft rot compared to non-transgenic control. Bacterial growth was retarded in transgenic lines over-expressing OsLRP compared to non-transgenic controls. We propose that OsLRP confers enhanced resistance to bacterial soft rot. Monitoring expression of defense-associated genes in transgenic lines over-expressing OsLRP, two different glucanases and Brassica rapa polygalacturonase inhibiting protein 2, PDF1 were constitutively activated in transgenic lines compared to non-transgenic control. Taken together, heterologous expression of OsLRP results in the activation of defense response and enhanced resistance to bacterial soft rot.</P>

Synthesis and Biological Activities of N-Phosphinothioyl Carbofuran Derivatives

Hong-Ryeol Park,Kyung-Hyung Yang,Songmun Kim,Yong-Man Yu,Jang-Hyun Hur,Dae-Sung Han 한국농약과학회 2000 한국농약과학회 학술발표대회 논문집 Vol.- No.-

N-Phosphinothioyl carbofuran 유도체의 합성 및 살충 활성 검정

박홍열(Hong-Ryeol Park),김성문(Songmun Kim),허장현(Jang-Hyun Hur),한대성(Dae-Sung Han) 한국농약과학회 2000 농약과학회지 Vol.4 No.3

논문 : First Order Kinetic Model을 이용한 토양 중 Mecoprop-P의 반감기 산출

박홍열 ( Hong Ryeol Park ),김성수 ( Seong Soo Kim ),김종걸 ( Jong Geol Kim ),이경희 ( Kyung Hee Lee ),박동식 ( Dong Sik Park ),허장현 ( Jang Hyun Hur ) 강원대학교 농업과학연구소 2006 강원 농업생명환경연구 Vol.17 No.-

세탁기 급수소음 저감을 위한 저소음 유로 구조

박준홍(Jun hong Park),이건웅(Geon ung Lee),조황묵(Hwang mook Cho),서응렬(Eung ryeol Seo),박용종(Yong jong Park) 한국소음진동공학회 2017 한국소음진동공학회 학술대회논문집 Vol.2017 No.4