Mechanism of Tacrine Transport across MBEC 4 Monolayers, an in vitro Model of the Blood Brain Barrier

JE Shin,CK Shim,MH Lee,SJ Chung 대한약학회 1999 大韓藥學會 總會 및 學術大會 Vol.2004 No.1

Microstructures and mechanical properties of TiO₂ dispersion strengthened nickel prepared using an alloying-carbonizing-oxidation-sintering process

Kim, Changjae,Yoon, Jeongmo,Lim, Jaewon,Park, Jeshin Elsevier 2019 Journal of alloys and compounds Vol.791 No.-

<P><B>Abstract</B></P> <P>Nickel particles containing TiO<SUB>2</SUB> grains were successfully fabricated using mechanical carbonization of Ni<SUB>3</SUB>Ti alloy powder, followed by selective oxidation of Ni-TiC to Ni-TiO<SUB>2</SUB>. For comparison, Ni-TiO<SUB>2</SUB> composites were prepared using a conventional mechanical alloying method. The two powders were sintered using a spark plasma sintering system at 850, 900, 950, and 1000 °C. Structural characterization was performed using X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The relative densities of all the sintered samples were up to 99.7% at all sintering temperatures. The average particle diameter, interparticle distance, and grain size of the matrix in the sintered Ni particle composites that contained TiO<SUB>2</SUB> grains were finer than others at all temperatures. These results imply that the alloying-carbonizing-oxidation-sintering (ACOS) process is a very promising method for refining oxide particles of oxide-dispersion-strengthened alloys. The enhanced mechanical properties such as compression yield strength and hardness of the sintered Ni-TiO<SUB>2</SUB> composite is a consequence of the refinement of oxide particles by the ACOS process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ACOS process enables the enhancement of the properties in ODS alloys. </LI> <LI> The particles and grains in ODS alloy refined through the ACOS process. </LI> <LI> The ODS alloy was strengthened due to the greater refinement, achieved through the use of the ACOS process. </LI> </UL> </P>

Efficiency of calcium vapor tunnels on non-contact deoxidation of irregular titanium powder

Hong, Chon-Il,Oh, Jung-Min,Park, Jeshin,Yoon, Jeong-Mo,Lim, Jae-Won Elsevier 2018 Advanced powder technology Vol.29 No.7

<P><B>Abstract</B></P> <P>This study developed a new process for the economical deoxidation of titanium powder in order to solve the problems associated with the previous deoxidation process. In the experiment, titanium powder with an irregular particle shape was used as the raw material with an oxygen concentration of 2100 ppm. The amount of Ca was reduced by 50% as compared to that used in a previous work and placed in an improved apparatus at a weight ratio of 2:1 (Ti:Ca). This modified deoxidation process decreased the oxygen concentration of the titanium powder to 805 ppm at 1273 K, leading to a ∼61.7% reduction of oxygen compared to the raw titanium powder. Low-oxygen irregular titanium powder can be produced at a low cost and high efficiency by applying a non-contact deoxidation process using Ca vapor.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new apparatus for an economical deoxidation of titanium powder was developed. </LI> <LI> The deoxidation process of titanium powder was performed by calcium vapor. </LI> <LI> The new apparatus can maximize the reaction of titanium oxide and calcium vapor. </LI> <LI> The cost effective deoxidation process of titanium powder was confirmed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

The effects of excess carbon on the surface area and crystallinity of TiO₂ powders prepared by oxidizing mechanically-synthesized TiC and their CO gas-sensing properties

Kim, Saehan,Yoon, Jeongmo,Park, Jeshin Elsevier 2017 Ceramics international Vol.43 No.17

<P><B>Abstract</B></P> <P>TiC-ec (with 20at% excess carbon), with TiC and TiN powders as comparative samples, were synthesized via ball milling. TiO<SUB>2</SUB>-ec and TiO<SUB>2</SUB>-n, TiO<SUB>2</SUB>-c sensing materials were prepared by oxidizing the synthesized TiC-ec, TiC, and TiN powders at 600°C. Structural characterization was performed via X-ray diffraction, field emission scattering electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The mean particle size of TiO<SUB>2</SUB>-ec was the smallest (40.8nm), and its SSA was the largest (14.3m<SUP>2</SUP>/g). The anatase crystallinity of the TiO<SUB>2</SUB>-ec powder was higher than those of the TiO<SUB>2</SUB>-n and TiO<SUB>2</SUB>-c samples, although the particle size was the smallest. The response of TiO<SUB>2</SUB>-ec to 1000ppm CO gas at a working temperature of 550°C was the highest (4.0) while the TiO<SUB>2</SUB>-c and TiO<SUB>2</SUB>-n samples showed a smaller response (1.2 and 1.4, respectively). The improved sensing properties of the TiO<SUB>2</SUB>-ec samples were due to a better crystallinity and larger surface area. Therefore, the enhanced surface area and crystallinity of the TiO<SUB>2</SUB>-ec are believed to be related to the presence of excess carbon.</P>

Sintered TiO₂ powder containing metallic Co binder prepared via mechanical carbonization, and its mechanical properties

Yim, Seungkyun,Park, Ilsong,Park, Jeshin Elsevier 2018 Ceramics international Vol.44 No.12

<P><B>Abstract</B></P> <P>A TiO<SUB>2</SUB>-Co-a composite powder was prepared via carbonizing and selective oxidation processing of a Ti-Co alloy. The conventionally mixed TiO<SUB>2</SUB>-Co-c composite powder and pure TiO<SUB>2</SUB> were sintered at 1100, 1200, 1300, 1400 °C, respectively. The structural characterization was performed using X-ray diffraction, field emission scattering electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The sintered samples were more densified, and melted bonding occurred at temperature higher than 1300 °C. The flexural strength and fracture toughness of the TiO<SUB>2</SUB>-Co-a sample were higher than those of the TiO<SUB>2</SUB> and TiO<SUB>2</SUB>-Co-c sintered at temperature higher than 1300 °C, while the Vickers hardness of TiO<SUB>2</SUB>-Co-a was the lowest at all sintering temperatures. The sintered TiO<SUB>2</SUB>-Co-a sample was more ductile and strengthened than the TiO<SUB>2</SUB>-Co-c sample with added metallic Co binder via mechanical mixing. The enhanced mechanical properties of the TiO<SUB>2</SUB>-Co-a sample were due to the fine dispersion of the metallic Co binder wetted with a TiO<SUB>2</SUB> matrix.</P>

Development of Detection Methods for Zinc Pyrithione in Polypropylene via Simple Extraction Methods for Quality Control

박찬영,문선희,백승훈,김민우,노지혁,Jeshin Sung,박태정 한국바이오칩학회 2020 BioChip Journal Vol.14 No.2

Zinc pyrithione (ZPT) is the antimicrobial substance and has been applied for various fields, including non-fouling coating paints and cosmetics. It also used for the tub part of the electronic machine with polypropylene (PP). Since the released ZPT can cause skeletal deformity or abnormality to coastal organisms, it is essential to quality check of ZPT in PP for environmental safety. However, as far as we knew, no previous reports about the analysis of ZPT in PP samples have been published; hence, we have developed a simple preparation method via extraction and precipitation. As assume that ZPT is just entrapped in the hydrocarbon chain of PP, ZPT was drawn out from the composites and homogeneously existed in the solution after untying the chain only precipitate PP with an organic solvent. This method could be applied for real manufactured samples with a low detection limit of 0.57 ppm within 10 min.

열 수소화법에 의해 제조된 TiO₂-Co 복합분말 SPS 소결체의 미세구조 및 기계적 성질

고명선,박일송,박제신,Ko, Myeongsun,Park, Ilsong,Park, Jeshin 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.4

$TiO_2$-particles containing Co grains are fabricated via thermal hydrogenation and selective oxidation of TiCo alloy. For comparison, $TiO_2$-Co composite powders are prepared by two kinds of methods which were the mechanical carbonization and oxidation process, and the conventional mixing process. The microstructural characteristics of the prepared composites are analyzed by X-ray diffraction, field-emission scattering electron microscopy, and transmission electron microscopy. In addition, the composite powders are sintered at $800^{\circ}C$ by spark plasma sintering. The flexural strength and fracture toughness of the sintered samples prepared by thermal hydrogenation and mechanical carbonization are found to be higher than those of the samples prepared by the conventional mixing process. Moreover, the microstructures of sintered samples prepared by thermal hydrogenation and mechanical carbonization processes are found to be similar. The difference in the mechanical properties of sintered samples prepared by thermal hydrogenation and mechanical carbonization processes is attributed to the different sizes of metallic Co particles in the samples.

Ti_0.3Zr_0.2V_0.5 합금게터의 활성화 및 수소흡수특성

김원백,이동진,박제신,서창열,이재천,Kim Wonbaek,Lee Dongjin,Park Jeshin,Suh Changyul,Lee Jaechun 한국재료학회 2005 한국재료학회지 Vol.15 No.2

The lowest activation temperature of a commercial vacuum getter reported so far in literature was about $400^{\circ}C$. Recently, $Ti_{0.3}Zr_{0.2}V_{0.5}$ alloy has been reported to exhibit the activation temperature lower than $200^{\circ}C$ when they are prepared as thin film. In this study, the alloy was prepared as bulk form and its activation temperature and hydrogen sorption properties were investigated in compliance with a standard method. The alloy powder was prepared by arc melting and subsequent HDH(Hydride-DeHydride) process. The activation temperature of the alloy was estimated from the ultimate pressure-temperature curve and located between $150^{\circ}C\;and\;200^{\circ}C$. The hydrogen sorption speed measured by an orifice method was 0.895 liter/sec which is comparable to thin film of same composition.

Ti_0.3Zr_0.2V_0.5 합금의 수소흡수 특성에 미치는 수소화물의 영향

이동진,박제신,서창열,이재천,김원백,Lee Dongjin,Park Jeshin,Suh Changyoul,Lee Jaechun,Kim Wonbaek 한국재료학회 2005 한국재료학회지 Vol.15 No.5

The hydrogen sorption properties of $Ti_{0.3}Zr_{0.2}V_{0.5}$ NEC(non-evaporable getter) alloy and its hydrides were evaluated at room temperature. The alloy and hydride powders were prepared by the Hydride-DeHydride(HDH) method. The hydrogen sorption speed of $Ti_{0.3}Zr_{0.2}V_{0.5}$ alloy was measured to increase with the amounts of hydride phase in the getter. The hydrogen sorption speeds of $Ti_{0.3}Zr_{0.2}V_{0.5},\;(Ti_{0.3}Zr_{0.2}V_{0.5})H_{1.52},\;and\;(Ti_{0.3}Zr_{0.2}V_{0.5})H_{1.94}$ were 2.22, 3.14 and 5.08 liter/sec, respectively. The unexpected enhancement of hydrogen sorption speed with the presence of the hydride phase is considered to be due to the pre-saturation of hydrogen trap sites which can retard the diffusion of hydrogen in the alloy.

토양의 물리화학적 특성이 세슘 흡착에 미치는 영향

박상민,이제신,김영훈,이정선,백기태,Park, Sang-Min,Lee, Jeshin,Kim, Young-Hun,Lee, Jeung-Sun,Baek, Kitae 한국지하수토양환경학회 2017 지하수토양환경 Vol.22 No.1

Cesium (Cs) generated by nuclear accidents is one of the most hazardous radionuclides because of its gamma radiation and long half-life. Especially, when Cs is exposed on the soil environments, Cs is mainly adsorbed on the topsoil and is strongly combined with tiny soil particle including clay minerals. The adsorption of Cs onto soil can vary depending on various physicochemical properties of soil. In this study, the adsorption characteristics between soil and Cs were investigated according to various physicochemical properties of soil including organic matter contents, cation exchange capacity (CEC), soil particle size, and the types of clay minerals. Soil organic matter inhibited the adsorption of Cs onto the soil because organic matter was blocking the soil surface. In addition, it was estimated that the CEC of the soil influenced the adsorption of Cs onto the soil. Moreover, more Cs was adsorbed as the soil particles size decreased. It was estimated that Cs was mostly adsorbed onto the topsoil, this is related to the clay mineral. Therefore, soil organic matter, CEC, soil particle size, and clay minerals are considered the key factors that can influence the adsorption characteristics between soil and Cs.