• Title/Summary/Keyword: Precipitate

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Separating nanocluster Si formation and Er activation in nanocluster-Si sensitized Er luminescence

  • Kim, In-Yong;Sin, Jung-Hun;Kim, Gyeong-Jung
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.109-109
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    • 2010
  • $Er^{3+}$ ion shows a stable and efficient luminescence at 1.54mm due to its $^4I_{13/2}\;{\rightarrow}\;^4I_{15/2}$ intra-4f transition. As this corresponds to the low-loss window of silica-based optical fibers, Er-based light sources have become a mainstay of the long-distance telecom. In most telecom applications, $Er^{3+}$ ions are excited via resonant optical pumping. However, if nanocluster-Si (nc-Si) are co-doped with $Er^{3+}$, $Er^{3+}$ can be excited via energy transfer from excited electrical carriers in the nc-Si as well. This combines the broad, strong absorption band of nc-Si with narrow, stable emission spectra of $Er^{3+}$ to allow top-pumping with off-resonant, low-cost broadband light sources as well as electrical pumping. A widely used method to achieve nc-Si sensitization of $Er^{3+}$ is high-temperature annealing of Er-doped, non-stoichiometric amorphous thin film with excess Si (e.g.,silicon-rich silicon oxide(SRSO)) to precipitate nc-Si and optically activate $Er^{3+}$ at the same time. Unfortunately, such precipitation and growth of nc-Si into Er-doped oxide matrix can lead to $Er^{3+}$ clustering away from nc-Si at anneal temperatures much lower than ${\sim}1000^{\circ}C$ that is necessary for full optical activation of $Er^{3+}$ in $SiO_2$. Recently, silicon-rich silicon nitride (SRSN) was reported to be a promising alternative to SRSO that can overcome this problem of Er clustering. But as nc-Si formation and optical activation $Er^{3+}$ remain linked in Er-doped SRSN, it is not clear which mechanism is responsible for the observed improvement. In this paper, we report on investigating the effect of separating the nc-Si formation and $Er^{3+}$ activation by using hetero-multilayers that consist of nm-thin SRSO or SRSN sensitizing layers with Er-doped $SiO_2$ or $Si_3N_4$ luminescing layers.

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In vitro and in vivo Antitumor Activity of the Fruit Body of Phellinus linteus (상황버섯 자실체의 in vitro 및 in vivo 항암활성)

  • Rhee, Young-Kyung;Han, Myung-Joo;Park, Soon-Young;Kim, Dong-Hyun
    • Korean Journal of Food Science and Technology
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    • v.32 no.2
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    • pp.477-480
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    • 2000
  • This study was undertaken to investigate immunochemotherapeutic activity against tumor growth and cytotoxic activity against tumor cell lines. Phellinus linteus (PL), which was artificially cultured in Morus alba, prolonged significantly the survival rate of mice intraperitoneally implanted with sarcoma 180 and inhibited solid tumor growth on mice subcutaneously implanted with sarcoma 180. The acetone precipitate of water extract of PL was better than its water extract. However, PL showed little cytotoxic activity against tumor cell lines.

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Effect of χ Phase on the Impact Toughness of 25Cr-7Ni-4Mo Super Duplex Stainless Steel (25Cr-7Ni-4Mo 수퍼 2상 스테인리스강의 충격인성에 미치는 χ의 영향)

  • Kang, C.Y.;Han, H.S.;Lee, S.H.;Han, T.S.
    • Journal of the Korean Society for Heat Treatment
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    • v.25 no.2
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    • pp.74-79
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    • 2012
  • This study has been carried out to investigate the precipitation behavior of ${\chi}$ phase and effect of ${\chi}$ phase precipitation on the impact toughness of 25%Cr-7%Ni-4%Mo super duplex stainless steel. It was proved that the ${\chi}$ phase was a intermetallic compound, which represented the higher chromium and molybdenum concentration than the matrix phases, and also showed the higher molybdenum concentration than the ${\sigma}$ phase. The ${\chi}$ phase was precipitated at the interface between ferrite and austenite or inside the ferrite matrix in the early stage of aging. The number of ${\chi}$ phase precipitates increased with increasing aging time, however, after showing the maximum value, the number was decreased due to the gradual transformation of ${\chi}$ phase into ${\sigma}$-phase. Aging ferrite phase was decomposed by the $r^2$ phase and ${\sigma}$-phase. Impact toughness rapidly decreased with time in the initial stage of aging at ${\chi}$ phase start to precipitate. Thus, the impact toughness was greatly influence for the precipitation of ${\chi}$ phase.

Preparation of a Large Quantity of CIS-9, trans-11 and trans-10, cis-12 Conjugated Linoleic Acid(CLA) Isomers from SYnthetic CLA

  • Kim, Seck-Jong;Park, Kyung-Ah;Park, Jung-H.Y.;Kim, Jeong-Ok;Ha, Yeong-Lae
    • Preventive Nutrition and Food Science
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    • v.5 no.2
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    • pp.86-92
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    • 2000
  • Conjugated linoleic acid(CLA) refers to a collective term of positional and geometric isomers of linoleic acid, which are different in their biological activities. The predominant isomer of CLA in animal tissues is cis-9, trans-11; smaller amounts of trans-10, cis-12 CLA isomers, CLA methyl ester (CLA-ME) was chemically syn-thesized from linoleic acid by the alkaline isomerization method. The synthetic CLA-ME, mainly composed of cis-9, trans-11 CLA and trans-10, cis-12 CLA, was dissolved in acetone, stored at 68$^{\circ}C$ for 1 day, and the supernatant(cis-9, trans-11 CLA-Me) was separated from the precipitate (trans-10, cis-12 CLA-Me). After the processes were repeated three times at -68$^{\circ}C$, the whole processes were repeated three times at -71$^{\circ}C$ in order to increase the purity of these two isomers. The cis-9, trans-11 CLA-Me and trans-10, cis-12 CLA isomers were further purified by the urea adduct. Purities of the cis-9, trans-11 CLA-Me and trans-10, cis-12 CLA-Me were 90.3 and 99.9%, respec-tively. This method could be employed for the preparation of a large quantity of highly purified cis-9, trans-11 CLA-Me or trans-10, cis-12 CLA-Me from synthetic CLA-Me.

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Evaluation of Soil Improvement by Carbonate Precipitation with Urease (요소분해효소에 의한 탄산칼슘 침전을 통한 지반 개량 평가)

  • Song, Jun Young;Sim, Youngjong;Jin, Kyu-Nam;Yun, Tae Sup
    • Journal of the Korean Geotechnical Society
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    • v.33 no.9
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    • pp.61-69
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    • 2017
  • This study presents the experimental results of $CaCO_3$ formation in sand by the Enzyme Induced Carbonate Precipitation (EICP) method. Concentration of $CaCO_3$ with elapsed reaction time is calibrated by standardized procedure by measuring $CO_2$ pressure, and it increases with time towards asymptotic value. Jumunjin sand saturated with EICP solution shows that both shear wave velocity and electrical conductivity sharply increase as the reaction starts to approach to the constant values after 50 hours of reaction time. Urease concentration of 0.5 g/L exhibits 224% higher final shear wave velocity than that of 0.1 g/L. The nucleation models hint that carbonate tends to precipitate not only at grain contacts but also at grain surfaces. Regardless of urease concentration, electrical conductivity and shear wave velocity follow the unique path. The scanning electron microscopic images and X-ray computed tomographic images validate the spatial configuration of produced $CaCO_3$ in soils.

Effect of an Excipient on the Formation of PLGA Particles Using Supercritical Fluid (초임계 유체를 이용한 PLGA 입자 제조에 첨가제가 미치는 영향)

  • Jung, In-Il;Haam, Seung-Joo;Lim, Gio-Bin;Ryu, Jong-Hoon
    • Polymer(Korea)
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    • v.36 no.1
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    • pp.1-8
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    • 2012
  • In this study, we employed hydroxypropyl-${\beta}$-cyclodextrin (HP-${\beta}$-CD) as an excipient to produce poly(lactic-$co$-glycolic acid) (PLGA) fine particles by a supercritical fluid process, called aerosol solvent extraction system (ASES), and investigated the effect of HP-${\beta}$-CD content on the morphology of the particles. The influence of HP-${\beta}$-CD on the drug release characteristics of paclitaxel-loaded PLGA particles was also evaluated. Fine particles were obtained when the HP-${\beta}$-CD content in PLGA/HP-${\beta}$-CD mixtures was greater than 40% and 30%, respectively, for PLGA(75:25) and PLGA(50:50), whereas a film-like precipitate was obtained for lower HP-${\beta}$-CD content. The release rate for paclitaxel loaded PLGA(75:25)/HP-${\beta}$-CD particles was found to increase with HP-${\beta}$-CD content.

A Study on Cementation Reaction Mechanism for Weathered Granite Soil and Microbial Mixtures (화강풍화토와 미생물 혼합물의 고결 반응 메카니즘)

  • Oh, Jongshin;Lee, Sungyeol;Kim, Jinyung;Kwon, Sungjin;Jung, Changsung;Lee, Jaesoo;Lee, Jeonghoon;Ko, Hwabin;Baek, Wonjin
    • Journal of The Korean Society of Agricultural Engineers
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    • v.61 no.6
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    • pp.103-110
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    • 2019
  • The purpose of this study is to investigate the reaction mechanism of soil and bacteria solution by various mixing ratios. For this purpose, in order to understand the reaction mechanisms of microorganisms and weathered granite soil, the tests were carried out under various mixing ratios additives such as soil, bacteria solution, $Ca(OH)_2$ and fixture. The test results from this study are summarized as follows. Firstly, the reaction between the bacteria solution and fixture produced a precipitate called vaterite, a type of silicate and calcium carbonate. Secondly, as a result of SEM analysis, the resulting precipitates generated from the test results using the specimens with various mixing ratios except SW condition and the irregular spherical microscopic shapes were formed in the size of $150{\mu}m$ to $20{\mu}m$. In addition, it can be seen that the bacteria solution and the fixture reacted between the granules to form an adsorbent material layer on the surface, and the microorganisms had a biological solidifying effect when the pores are combined into hard particles. Finally, The XRD analysis of the sediment resulting from the reaction between the microorganism and the deposit control agent confirmed the presence of a type of calcium carbonate ($CaCO_3$) vaterite, which affects soil strength formation, as well as silicate($SiO_2$).

Dental Co-Cr alloys fabricated by selective laser melting: A review article (선택적 레이저 용융 방법으로 제작한 치과용 코발트 크롬 합금에 대한 문헌고찰)

  • Kang, Hyeon-Goo
    • The Journal of Korean Academy of Prosthodontics
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    • v.59 no.2
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    • pp.248-260
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    • 2021
  • Cobalt-chromium alloys are used to fabricate various dental prostheses, and have advantages of low cost and excellent mechanical properties compared to other alloys. Recently, selective laser melting, which is an additive manufacturing method, has been used to overcome the disadvantages of the conventional fabrication method. A local rapid heating and cooling process of selective laser melting induces fine microstructures, grain refinement, and reduction of porosities of the alloys. Therefore, it can improve mechanical properties compared to the alloys fabricated by the conventional method. On the other hand, layering process and rapid heating and cooling cause accumulation of a large amount of residual stresses that can adversely affect the mechanical properties. A heat treatment for removing residual stresses through recovery and recrystallization process caused complicated changes in mechanical properties induced by phase transformation, precipitate and homogenization of the microstructures. The purpose of this review was to compare the manufacturing methods of Co-Cr alloys and to investigate the characteristics of Co-Cr alloys fabricated by selective laser melting.

Behavior of Macrosegregation and Precipitation Developed in Semi-continuously Cast Large Bloom (반연속주조된 대형 블룸에서 발생하는 거시편석 및 석출물 거동)

  • Kim, Hyeju;Lee, Hyoungrok;Kim, Kyeong-A;Lee, Joodong;Oh, Kyung-sik;Kwon, Sang-Hum;Kim, Donggyu
    • Journal of Korea Foundry Society
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    • v.39 no.1
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    • pp.7-13
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    • 2019
  • Few studies of large blooms over 700 mm thick among those used for the forging of raw materials have been reported. The cooling rate difference between the surface and the center of a large bloom is large, and the degradation of the mechanical properties is likely in cases involving excessively coarse precipitates resulted from the slow cooling rate of a large bloom after casting. Therefore, a schematic investigation of the growth behaviors of precipitates while varying their locations in blooms is necessary. The dissolution behaviors of precipitates were investigated by simulating a reheating process during which the bloom is heated to a high temperature. The segregation behavior of the as-cast large bloom was also investigated. Reheating specimens were obtained after an isothermal heat treatment at $1150^{\circ}C$ with various holding times to simulate the reheating process, with the samples undergoing a subsequent water quenching step. The precipitates were extracted using an electrolytic extractor and a particle size analysis was conducted with the aid of SEM, EDS, and TEM. In the present work, Al oxide, MnS and Nb carbide were mainly observed.

Mechanism of MnS Precipitation on Al2O3-SiO2 Inclusions in Non-oriented Silicon Steel

  • Li, Fangjie;Li, Huigai;Huang, Di;Zheng, Shaobo;You, Jinglin
    • Metals and materials international
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    • v.24 no.6
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    • pp.1394-1402
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    • 2018
  • This study investigates the mechanism of MnS precipitation on $Al_2O_3-SiO_2$ inclusions during the solidification of non-oriented silicon steel, especially the influence of the phase structures and sizes of the oxides on the MnS precipitation, by scanning electron microscopy and transmission electron microscopy coupled with energy dispersive spectrometry. The investigation results show that MnS tends to nucleate on submicron-sized $Al_2O_3-SiO_2$ inclusions formed by interdendritic segregation and that it covers the oxides completely. In addition, MnS can precipitate on micron-sized oxides and its precipitation behavior is governed by the phase structure of the oxides. The MnS embryo formed in a MnO-containing oxide can act as a substrate for MnS precipitation, thus permitting further growth via diffusion of solute atoms from the matrix. MnS also precipitates in a MnO-free oxide by the heterogeneous nucleation mechanism. Furthermore, MnS is less prone to precipitation in the $Al_2O_3$-rich regions of the $Al_2O_3-SiO_2$ inclusions; this can be explained by the high lattice disregistry between MnS and $Al_2O_3$.