• Title/Summary/Keyword: Microstructure

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Development and Evaluation of Natural Hydroxyapatite Ceramics Produced by the Heat Treatment of Pig Bones

  • Lim, Ki-Taek;Kim, Jin-Woo;Kim, Jangho;Chung, Jong Hoon
    • Journal of Biosystems Engineering
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    • v.39 no.3
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    • pp.227-234
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    • 2014
  • Purpose: The aim of this research was to develop and evaluate natural hydroxyapatite (HA) ceramics produced from the heat treatment of pig bones. Methods: The properties of natural HA ceramics produced from pig bones were assessed in two parts. Firstly, the raw materials were characterized. A temperature of $1,200^{\circ}C$ was chosen as the calcination temperature. Fine bone powders (BPs) were produced via calcinations and a milling process. Sintered BPs were then characterized using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, and a 2-year in vitro degradability test. Secondly, an indirect cytotoxicity test was conducted on human osteoblast-like cells, MG63, treated with the BPs. Results: The average particle size of the BPs was $20{\pm}5{\mu}m$. FE-SEM showed a non-uniform distribution of the particle size. The phase obtained from XRD analysis confirmed the structure of HA. Elemental analysis using XRF detected phosphorus (P) and calcium (Ca) with the Ca/P ratio of 1.6. Functional groups examined by FTIR detected phosphate ($PO{_4}^{3-}$), hydroxyl ($OH^-$), and carbonate ($CO{_3}^{2-}$). The EDX, XRF, and FTIR analysis of BPs indicated the absence of organic compounds, which were completely removed after annealing at $1,200^{\circ}C$. The BPs were mostly stable in a simulated body fluid (SBF) solution for 2 years. An indirect cytotoxicity test on natural HA ceramics showed no threat to the cells. Conclusions: In conclusion, the sintering temperature of $1,200^{\circ}C$ affected the microstructure, phase, and biological characteristics of natural HA ceramics consisting of calcium phosphate. The Ca-P-based natural ceramics are bioactive materials with good biocompatibility; our results indicate that the prepared HA ceramics have great potential for agricultural and biological applications.

Determination of Hydroxyapatite Precipitation Condition from the $Ca-PO_4-H_2O$ System ($Ca-PO_4-H_2O$계로부터 수산화아파타이트의 침전조건 결정)

  • Oh, Young-Jei
    • Analytical Science and Technology
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    • v.13 no.2
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    • pp.208-214
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    • 2000
  • The formation and dissolution of hydroxides, carbonates and hydroxyapatite (HAp), which depend on the pH of solution, are important factor for the preparation of homogeneous and fine HAp, $Ca_{10-x}(HPO_4)_x(PO_4)_{6-x}(OH)_{2-x}(x=0)$, ceramic powder from the $Ca-PO_4-H_2O$ system. Since the solubility of each complex ion is a linear function of pH, the solubility diagram can be obtained by plotting the logarithmic molar concentrations calculated from the values of the equilibrium constants and solubility products for hydroxides, carbonates, and hydroxyapatite. The optimum pH condition for the formation of single phase $Ca_{10-x}(HPO_4)_x(PO_4)_{6-x}(OH)_{2-x}(x=0)$ powder in $Ca-PO_4-H_2O$ system at $25^{\circ}C$ was estimated as $10.5{\pm}0.5$ through the theoretical consideration. The HAp powder dried at $80^{\circ}C$ showed a fine agglomerated particles with a size of 75 nm. The HAp powder calcined at $1,000^{\circ}C$ consisted of nearly homogeneous particles with a size of 450 nm. Even though the dried HAp particles consisted of agglomeration, mechanical properties were superior due to fine microstructure after sintering.

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Optimizing the Drying Conditions of Surimi Snacks Using a Response Surface Methodology (반응표면분석법을 이용한 생선연육 스낵의 건조조건 최적화)

  • Kim, Seonghui;Chae, Jiyeon;Choi, Gibeom;Kim, Jongmin;Lee, Jiho;Kim, Seon-Bong;Kim, Young-Mog;Kim, Jin-Soo;Lee, Jung-Suck;Cho, Suengmok
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.52 no.6
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    • pp.571-579
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    • 2019
  • Surimi has been widely investigated for developing fish snacks; however, few studies have examined the optimal drying conditions of surimi for fish snacks. This study used a response surface methodology to optimize the drying conditions for the overall acceptance of fish snacks. The drying temperature (X1, 51-65℃) and drying time (X2, 1.5-2.5 h) were chosen as independent variables. The dependent variables were overall acceptance (Y1, points), hardness (Y2, N), moisture content of the dried intermediate product (Y3, %), and volatile basic nitrogen of the fried final product (Y4, mg/100 g). The estimated optimal conditions for overall acceptance (Y1) were X1=64℃ and X2=2 h. The predicted values of the dependent variables at the optimal conditions were overall acceptance (Y1)=8.60 points, hardness (Y2)=10.07 N, and moisture content of the dried intermediate product (Y3)=10.00% and were similar to the experimental values. Scanning electron microscopy images revealed that the drying conditions affected the microstructure of the fish snacks. Our results could be used to increase the productivity of fish snacks made by small- and mid-sized seafood companies.

Physicochemical Characteristics of Fried-fish Snacks with Different Types of Starch (전분의 종류에 따른 생선연육 스낵의 물리화학적 품질 특성)

  • Chae, Jiyeon;Kim, Seonghui;Choi, Gibeom;Kim, Jongmin;Lee, Jiho;Kim, Seon-Bong;Kim, Young-Mog;Kim, Jin-Soo;Lee, Jung-Suck;Cho, Suengmok
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.52 no.6
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    • pp.580-586
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    • 2019
  • Fried-fish snacks containing surimi are a popular seafood product in Asia. To prepare fried-fish snacks, various ingredients are added to surimi. Among them, starch is important for producing snacks of desirable texture and taste. We investigated the physicochemical properties of fried-fish snacks containing arrowroot, potato, sweet potato, corn, and tapioca starches. The fried-fish snack with arrowroot starch showed the highest drying rate; after drying for 3 hours, the water content was unchanged. None of the starches affected the total volatile basic nitrogen values of the fried-fish snacks, which were approximately 1.5 mg/100 g, indicating freshness. The fried-fish snacks with corn and arrowroot starches had the highest brightness (L) values and the fried-fish snack with tapioca starch, the lowest L value. The hardness value of the fried-fish snack with tapioca starch was significantly higher than that of the other fried-fish snacks. In the sensory evaluation, the fried-fish snacks with arrowroot starch showed the best overall acceptance.

Fabrication of Single-Crystal Silicon Microstructure by Anodic Reaction in HF Solution (HF 양극반응을 이용한 단결정 실리콘 미세구조의 제조)

  • Cho, Chan-Seob;Sim, Jun-Hwan;Lee, Seok-Soo;Lee, Jong-Hyun
    • Journal of Sensor Science and Technology
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    • v.1 no.2
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    • pp.183-194
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    • 1992
  • Some silicon micromechanical structures useful in sensors and actuators have been fabricated by electropolishing or porous silicon formation technique by anodic reaction in HF solution. The microstructures were lightly doped single crystal silicon and the formation was isotropic independent of crystal directions. Porous silicon layer(PSL) was formed selectively in $n^{+}$ region of $n^{+}/n$ silicon structure by anodic reaction in concentrated HF(20-48%) solution. Characteristics of the formed PSL were investigated along with change of the reaction voltage, HF concentration and the reaction time. PSL was formed only in $n^{+}$ region. The porosity of the PSL was decreased with the increase of HF concentration and independent of reaction voltage. For the case of $n/n^{+}/n$ structures, the etched surface of silicon was fairly smooth and a cusp was not found. The thickness of the microstructures was the same as that of the epitaxial n-Si layer and good uniformity. We have fabricated acceleration sensors by anodic reaction in HF solution(5 wt%) and planar technology. The process was compatible with conventional It fabrication technique. Various micromechanical structures, such as rotors of motor, gears and linear actuator, were also fabricated by the technique and examined by SEM photographs.

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The humidity effect of YBCO film by TFA-MOD process (TFA-MOD법으로 제조된 YBCO 박막의 습도분압 효과)

  • Jang, Seok-Hern;Lim, Jun-Hyung;Yoon, Kyung-Min;Lee, Seung-Yi;Kim, Kyu-Tae;Lee, Chang-Min;Joo, Jin-Ho;Nah, Wan-Soo;Lee, Hee-Gyoun;Hong, Gye-Won
    • Progress in Superconductivity
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    • v.8 no.1
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    • pp.65-70
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    • 2006
  • We fabricated $YBa_2Cu_33O_{7-x}$(YBCO) films on(00l) $LaAlO_3$ substrates prepared by metal organic deposition(MOD) method using trifluoroacetate(TFA) solution and evaluated the effects of the humidity on the microstructure, phase purity, and critical properties. The films calcined at $430^{\circ}C$ were fired at $775^{\circ}C$ at 0%, 4.2%, 12.1%, and 20.0% humidified As gas mixed with 0.1% $O_2$. We observed that the amount of $BaF_2$ phase was effectively reduced and that a sharp and strong biaxial texture formed under a humidified atmosphere, leading to increased critical properties. For the films fired at 0% humidity, the $T_c\;and\;I_c$ were undetectably small. When the humidity was increased to 4.2%, the corresponding $T_c$(onset) and $I_c$ were increased to 90.5 K and 8 A/cm-width, respectively. For the films at the humidity range of 12.1-20.0%, the $I_c$ was found to be 35 A/cm-width. According to the results of the XRD, pole-figure, and SEM, these improved critical properties are probably attributed to the formation of a purer YBCO phase, larger grain size, and stronger c-axis orientation.

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Optical properties and applications of $TiO_2$ films prepared by ion beam sputtering (이온빔 스퍼터링으로 증착한 $TiO_2$박막의 광학적 특성 및 응용)

  • 이정환;조준식;김동환;고석근
    • Journal of the Korean Vacuum Society
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    • v.11 no.3
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    • pp.176-182
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    • 2002
  • Amorphous $TiO_2$ thin films were deposited on glass substrates by ion beam sputtering in which the ratio of $O_2$/Ar gas used as discharged gas was varied from 0 to 2. After optical and microstructure properties and chemical composition of thin films was analyzed, antireflection coating layers were fabricated with $SiO_2$/$TiO_2$ multi-layers. Thin films deposition was performed at room temperature and ion beam voltage and ion current density for sputtering of target were fixed at 1.2 kV and 200 $\mu\textrm{A}/\textrm{cm}^2$, respectively. Refractive indexs of the deposited $TiO_2$films were 2.40-2.45 at a wavelength of 633 nm. $TiO_2$films had high transmission and stoichiometry when ratio of $O_2$/Ar was 1. Rms roughness of deposited $TiO_2$ film was below 7 $\AA$. In excessive $O_2$ environments, however Rms roughness increased over 50 $\AA$. Transmittance decreased by scattering of rough surface. Reflectance of $SiO_2$/$TiO_2$multi-layers was below 1% in visible light.

Joining properties and thermal cycling reliability of the Si die-attached joint with Zn-Sn-based high-temperature lead-free solders (Zn-Sn계 고온용 무연솔더를 이용한 Si다이접합부의 접합특성 및 열피로특성)

  • Kim, Seong-Jun;Kim, Keun-Soo;Suganuma, Katsuaki
    • Proceedings of the KWS Conference
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    • 2009.11a
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    • pp.72-72
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    • 2009
  • 전자부품의 내부접속 및 파워반도체의 다이본딩과 같은 1차실장에는 고온환경에서의 사용과 2차실장에서의 재용융방지를 위해 높은 액상선온도 및 고상선온도를 필요로 하여, Pb-5wt%Sn, Pb-2.5wt%Ag로 대표되는 납성분 85%이상의 고온솔더가 널리 사용되고 있다. 생태계와 인체에 대한 납의 유해성이 보고된 이래, 무연솔더에 대한 연구가 활발히 진행되어 왔으나, Sn-Ag-Cu계로 대표되는 Sn계 합금으로 대체 중인 중온용 솔더와는 달리, 고온용 솔더에 대해서는 대체합금에 대한 연구가 미흡한 실정이다. 대체재의 부재로 인해 기존의 납을 다량함유한 솔더로 1차실장이 지속됨으로서, 2차실장의 무연화에도 불구하고 전자부품 및 기기의 재활용에 큰 어려움을 겪고 있다. 지금까지 고온용 무연솔더로서는 융점에 근거해 Au-(Sn, Ge, Si)계, Bi-Ag계, Zn-(Al, Sn)계의 극히 제한된 합금계만이 보고되어 왔다. Au계 솔더는 현재 플럭스를 사용하지 않는 광학, 디스플레이 분야 등 고부가가치 공정에 사용되고 있으나, 합금가격이 매우 비싸며 가공성이 나빠 대체재료로서는 적합하지 않다. Bi-Ag계 솔더 또한 취성합금으로 와이어 및 박판으로 가공하는데 어려움이 크며, 솔더로서 중요한 특성중 하나인 전기전도도 및 열전도도가 나쁜 편이다. 이에 비해, Zn계 합금은 비교적 낮은 합금가격, 적절한 가공성과 뛰어난 인장강도, 우수한 전기전도도 및 열전도도를 지녀, 고온용솔더 대체재료의 유력한 후보로 생각된다.이전 연구에서, 필자의 연구그룹은 Zn-Sn계 합금을 고온용 무연솔더로서 제안한 바 있다. Zn-Sn계 합금은 충분히 높은 융점과 함께, 금속간화합물이 없는 미세조직, 우수한 기계적 특성, 높은 전기전도도 및 열전도도 등의 장점을 나타내었다. 본 연구에서는 기초합금특성상 고온솔더로서 다양한 장점을 지닌 Zn-30wt%Sn합금을 고온용 솔더의 대표적인 적용의 하나인 다이본딩에 적용하여, 접합부의 강도 및 미세조직, 열피로 신뢰성에 대해 분석을 함으로서 실제 공정에의 적용가능성에 대해 검토하였다. Zn-30wt%Sn을 이용해 Au/TiN(Titanium nitride) 코팅한 Si다이를 AlN-DBC(aluminum nitride-direct bonded copper)기판에 접합한 결과, 양측에 완전히 젖은 기공이 없는 양호한 다이접합부를 얻었으며, 솔더내부에는 금속간화합물을 형성하지 않았다. Si다이와의 계면에는 TiN만이 존재하였으며, Cu와의 계면에는 Cu로부터 $Cu_5Zn_8,\;CuZn_5$의 반응층을 형성하였다. 온도사이클시험을 통한 열피로특성평가에서, Zn-30wt%Sn를 이용한 다이접합부는 1500사이클 지점에서 Cu와 Cu-Zn금속간화합물의 사이에서 피로균열이 형성되며, 접합강도가 크게 감소하였다. 열피로특성 향상을 위해 Cu표면에 TiN코팅을 하여 Zn-30wt%Sn 솔더로 다이접합한 결과, Si다이와 기판 양측에 TiN만으로 구성된 계면을 형성하였으며, TEM관찰을 통해 Zn-30wt%Sn과 극히 미세한 접합계면이 형성하고 있음을 확인하였다. Zn-wt%30Sn솔더와 TiN층의 병용으로 2000사이클까지 미세조직의 변화 및 강도저하가 없는 극히 안정된 고신뢰성의 다이접합부를 얻을 수가 있었다.

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Study on microstructure and mechanical properties of friction stir welded 9% Ni steel (마찰교반접합된 9% Ni 강의 미세조직 및 기계적 특성에 관한 연구)

  • Choi, Don-Hyun;Ahn, Byung-Wook;Choi, Jung-Hyun;Lee, Chang-Yong;Yeon, Yun-Mo;Song, Keun;Lee, Jong-Seop;Jung, Seung-Boo
    • Proceedings of the KWS Conference
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    • 2009.11a
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    • pp.49-49
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    • 2009
  • 마찰교반접합법은 특정한 회전수로 회전하는 용접 툴을 이용하여 접합하고자 하는 피접합재의 맞댄면에 삽입시킨 후 툴을 이동시키거나 혹은 시편을 견고하게 고정시킨 장치(backing plate)가 움직여 고상 상태에서 접합이 이루어진다. 알루미늄, 마그네슘 등 비교적 융점이 낮은 저융점 재료의 재료에 처음 적용이 되어 많은 연구가 활발히 진행되었고 타 용접방법에 비해 우수한 접합특성을 나타내었다. 최근 이러한 마찰교반접합은 이러한 저융점 재료를 넘어서 스틸, 타이타늄, 니켈 등과 같은 고융점 재료 등에 대한 적용이 늘어나고 있다. 마찰교반접합을 이용하여 이러한 고융점 재료의 접합 경우 내마모성 및 내열성 등의 내구성이 갖추어진 툴과 이러한 툴을 냉각시킬 수 있는 냉각 장치 등이 필요로 하나 경제적 측면이나 접합부의 우수한 특성 등을 고려 할 때 그 적용 및 발전 가능성이 매우 높다고 볼 수 있다. 최근 무공해 연료로 각광받고 있는 액화천연가스 (LNG)의 수요가 급증함에 따라 LNG 저장탱크 소재로 널리 사용되고 있는 9% Ni강의 수요 또한 증가하고 있는 상황이다. 하지만 9% Ni 강은 극저온용 소재로 용접부의 저온인성 ($-196^{\circ}C$)이 가장 중요하기 때문에 저온인성을 확보하고자 Inconel 계나 Hastelloy계 등의 니켈 기 합금을 용접재료로 사용하고 있으나 이러한 용접재료는 가격이 매우 고가이며 또한 용접 후 용접부의 강도가 낮다는 문제가 제기되고 있다. 또한 LNG 탱크 제작시 사용되는 용접법은 GTAW, SAW 및 SMAW 이지만 국내에서는 주로 SMAW에 의존하고 있는 실정인 관계로 보다 더 경제적인 용접 프로세스의 적용 가능성이 검토되고 있는 상황이다. 본 연구에서는 마찰교반용접을 이용하여 두께 4mm의 9% Ni 강에 대해 맞대기 마찰교반접합을 실시하였다. 툴 회전 속도 및 접합 속도를 고정한 상태에서 접합을 실시 하였으며 접합 시 툴은 $Si_3N_4$로 제작된 툴을 사용하였다. 접합 후 외관상태 점검, 미세조직 관찰, 경도, 인장 강도 및 저은 충격 측정 등의 실험을 실시하였고, 이러한 결과를 이용하여 미세조직과 기계적 특성과의 관련성을 조사하였다.

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A Study on the High Frequency Ultrasonic Attenuation Characterization in Artificially Aging Degraded 2.25Cr-1Mo Steel (2.25Cr-1Mo 강 인공 열화재의 고주파수 초음파 감쇠특성에 관한 연구)

  • Park, Ik-Keun;Park, Un-Su;Kim, Chung-Seok;Kim, Hyun-Mook;Kwun, Sook-In;Byeon, Jai-Won
    • Journal of the Korean Society for Nondestructive Testing
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    • v.21 no.4
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    • pp.439-445
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    • 2001
  • The destructive method is reliable and widely used lot the estimation of material degradation but, it have time-consuming and a great difficulty in preparing specimens from in-service industrial facilities. Therefore, the estimation of degraded structural materials used at high temperature by nondestructive evaluation such as electric resistance method, replica method, Barkhausen noise method, electro-chemical method and ultrasonic method are strongly desired. Ultrasonic nondestructive evaluation technique has been reported good to attain efficiency of measurement, high sensitivity of measurement, and rapidity and reliability of result interpretation. In this study, it was verified experimentally the feasibility of the evaluation of degraded 2.25Cr-1Mo steel specimens which were prepared by the isothermal aging heat treatment at $630^{\circ}C$ by high frequency longitudinal wave method investigating the change of attenuation coefficient by FFT analysis and wavelet transform. Because of carbide precipitation increase and spheroidization near grain boundary of microstructure to aging degradation, attenuation coefficient had a tendency to increase as degradation proceeded. It was identified possibly to evaluate degradation using the characteristics of high-frequency ultrasonics. Frequency dependence of ultrasonic attenuation coefficient to aging degradation appeared large, which made sure that attenuation coefficient is an important parameter for evaluation of aging degradation.

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