• Title/Summary/Keyword: Grain Structure

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Relationship between Tensile Strength and Damping Capacity of Annealed Magnesium Alloys after Hot Rolling (열간 압연 후 어닐링처리한 Mg 합금의 인장강도와 감쇠능과의 관계)

  • Lee, Gyu-Hyun;Oh, Eun-Ji;Kim, Kwon-Hoo;Kim, Jae-Nam;Kang, Chang-Yong
    • Journal of the Korean Society for Heat Treatment
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    • v.27 no.6
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    • pp.295-301
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    • 2014
  • In this study, the relationship between strength and damping capacity of annealed magnesium alloys after hot rolling was investigated. The microstructure of hot rolled magnesium consisted of dendrite structure and $Mg_{17}Al_{12}$ compounds precipitated along the grain boundary. The dendrite structure was dissipated, $Mg_{17}Al_{12}$ compounds was decomposed by annealing, and then its dissolved in ${\alpha}$-Mg. With an increasing the annealing temperature and time, strength was slowly decreased and damping capacity was slowly increased by the growth of grain size and decreasing of defects induced by hot rolling. In annealing treatmented magnesium alloys after hot rolling, damping capacity was decreased rapidly with an increase of strength. There was on proportional relationship between tensile strength, and damping capacity.

Dielectric and Ferroelectric Properties of Nb Doped BNT-Based Relaxor Ferroelectrics

  • Maqbool, Adnan;Hussain, Ali;Malik, Rizwan Ahmed;Zaman, Arif;Song, Tae Kwon;Kim, Won-Jeong;Kim, Myong-Ho
    • Korean Journal of Materials Research
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    • v.25 no.7
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    • pp.317-321
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    • 2015
  • The effects of Nb doping on the crystal structure, microstructure, and dielectric ferroelectric and piezoelectric properties of $(Bi_{0.5}Na_{0.5})_{0.935}Ba_{0.065}Ti_{(1-x)}Nb_xO_3-0.01SrZrO_3$ (BNBTNb-SZ, with ${\chi}=0$, 0.01 and 0.02) ceramics have been investigated. X-ray diffraction patterns revealed that all ceramics have a pure perovskite structure with tetragonal symmetry. The grain size of the ceramics slightly decreased and a change in grain morphology from square to spherical shape was observed in the Nb-doped samples. The maximum dielectric constant temperature ($T_m$) increases with increasing amount of Nb; however, ferroelectric-relaxor transition temperature ($T_{F-R}$) and maximum dielectric constant (${\varepsilon}_m$) values decrease gradually. Nb addition disrupted the polarization hysteresis loops of the BNBT-SZ ceramics by leading a reduction in the remnant polarization coercive field and piezoelectric constant.

Effects of Chemical Vapor Deposition Parameters on The Hardness and the Structural Characteristics of TiN Film (TiN피막의 경도 및 구조적 특성에 미치는 화학증착 조건의 영향)

  • Shin, Jong-Hoon;Lee, Seong-Rae;Baek, Young-Hyun
    • Journal of Surface Science and Engineering
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    • v.20 no.3
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    • pp.106-117
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    • 1987
  • The microhardness and the structural characteristics of the chemically vapor deposited TiN film on the 430 stainless steel substrate have been investigated with various deposition parameters such as the deposition time, the total flow rate, the flow rate ratio $(H_2/N_2)$, and the deposition temperature. The most important factor to affect the microhardness of the TiN film in this study was the denseness of the structure in connection with the degree of the lattice strain. The relationship between the lattice parameter changes and the grain size variation under all deposition conditions generally followed the grain boundary relaxation model. The (111) preferred orientation prevailed in the early stage of the deposition conditions, however, the (200) preferred orientation was developed in the later stage. The surface morphology at optimum conditions displayed a dense diamond shaped structure and the microhardness of the films was high (1700-2400Hv) regardless of the type of the substrates used.

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Growth Characteristics of SnO2 Thin Film for Gas Sensor with Annealing Treatment (어닐링처리시킨 SnO2 가스센서의 박막성장특성)

  • Kang, Kae-Myung;Choi, Jong-Un
    • Journal of Surface Science and Engineering
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    • v.40 no.6
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    • pp.258-261
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    • 2007
  • Relationships between the electrical resistivity and the growth characteristic of $SnO_2$ thin films were investigated. $SnO_2$ thin films with thickness from 64 nm to 91 nm were made by controlling the RF deposition energy from 80 to 150 W. These $SnO_2$ thin films were annealed at $200^{\circ}C{\sim}700^{\circ}C$ temperature range of $100^{\circ}C$ interval in the $O_2$ gas condition. After annealing treatments, the microstructures of the $SnO_2$ thin films were changed mixed structure(amorphous & crystalline) to lamina columnar crystalline structure. Both the film thickness and the grain size were increased with increasing the local crystallization of $SnO_2$ microstructure of thin films by annealing treatment. Their electrical resistivity increased up to the annealing temperature of $400^{\circ}C$, and then slowly decreased.

Fabrication and Properties of $\alpha$-$Fe_{2}O_{3}$Thin Films Prepared by RF-magnetron sputtering method (RF-magnetron sputtering 법을 이용한 개스 센서용 $\alpha$-$Fe_{2}O_{3}$박막의 제조 및 특성)

  • 최진영;장건익
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.07a
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    • pp.499-502
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    • 2000
  • In this study, $\alpha$-Fe$_2$O$_3$thin films were deposited on $Al_2$O$_3$substrate by RF magnetron sputtering method from a $\alpha$-Fe$_2$O$_3$target(99.9%). The sputtering atmosphere was Ar and 80%Ar:20%O$_2$mixture in a total gas pressure of 1~3mTorr. As-deposited $\alpha$-Fe$_2$O$_3$thin films were heated to 300, 400, 500, $600^{\circ}C$ for 5hr in oxygen atmosphere. The structure and the morphology of $\alpha$-Fe$_2$O$_3$thin films were examined by scanning Electron microscopy(SEM) and the crystal structure was analyzed by X-Ray Diffractometer(XRD). The microstructure of the annealed $\alpha$-Fe$_2$O$_3$films exhibits rather gross particle and the grain size was less than 100nm. Since the grain size was very small, the gas sensitivity was expected to be improved.

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Microstructural investigation of the electroplating Cu thin films for ULSI application (ULSI용 Electroplating Cu 박막의 미세조직 연구)

  • 박윤창;송세안;윤중림;김영욱
    • Journal of the Korean Vacuum Society
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    • v.9 no.3
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    • pp.267-272
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    • 2000
  • Electroplating Cu was deposited on Si(100) wafer after seed Cu was deposited by sputtering first. TaN was deposited as a diffusion barrier before depositing the seed Cu. Electroplating Cu thin films show highly (111)-oriented microstructure for both before and after annealing at $450^{\circ}C$ for 30min and no copper silicide was detected in the same samples, which indicates that TaN barrier layer blocks well the Cu diffusion into silicon substrate. After annealing the electroplating Cu film up to $450^{\circ}C$, the Cu film became columnar from non-columnar, its grain size became larger about two times, and also defects density of stacking faults, twins and dislocations decreased greatly. Thus the heat treatment will improve significantly electromigration property caused by the grain boundary in the Cu thin films.

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Neutron imaging for metallurgical characteristics of iron products manufactured with ancient Korean iron making techniques

  • Cho, Sungmo;Kim, Jongyul;Kim, TaeJoo;Sato, Hirotaka;Huh, Ilkwon;Cho, Namchul
    • Nuclear Engineering and Technology
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    • v.53 no.5
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    • pp.1619-1625
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    • 2021
  • This paper demonstrates the possible nondestructive analysis of iron artifacts' metallurgical characteristics using neutron imaging. Ancient kingdoms of the Korean Peninsula used a direct smelting process for ore smelting and iron bloom production; however, the use of iron blooms was difficult because of their low strength and purity. For reinforcement, iron ingots were produced through refining and forge welding, which then underwent various processes to create different iron goods. To demonstrate the potential analysis using neutron imaging, while ensuring artifacts' safety, a sand iron ingot (SI-I) produced using ancient traditional iron making techniques and a sand iron knife (SI-K) made of SI-I were selected. SI-I was cut into 9 cm2, whereas the entirety of SI-K was preserved for analysis. SI-I was found to have an average grain size of 3 ㎛, with observed α-Fe (ferrite) and pearlite with a body-centered cubic (BCC) lattice structure. SI-K had a grain size of 1-3 ㎛, α-Ferrite on its backside, and martensite with a body-centered tetragonal (BCT) structure on its blade. Results show that the sample's metallurgical characteristics can be identified through neutron imaging only, without losing any part of the valuable artifacts, indicating applicability to cultural artifacts requiring complete preservation.

Thermoelectric properties of FeVSb1-xTex half-heusler alloys fabricated via mechanical alloying process

  • Hasan, Rahidul;Ur, Soon-Chul
    • Journal of Ceramic Processing Research
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    • v.20 no.6
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    • pp.582-588
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    • 2019
  • FeVSb1-xTex (0.02 ≤ x ≤ 0.10) half-Heusler alloys were fabricated by mechanical alloying process and subsequent vacuum hot pressing. Near single half-Heusler phases are formed in vacuum hot pressed samples but a second phase of FeSb2 couldn't be avoided. After doping, the lattice thermal conductivity in the system was shown to decrease with increasing Te concentration and with increasing temperature. The lowest thermal conductivity was achieved for FeVSb0.94Te0.06 sample at about 657 K. This considerable reduction of thermal conductivities is attributed to the increased phonon scattering enhanced by defect structure, which is formed by doping of Te at Sb site. The phonon scattering might also increase at grain boundaries due to the formation of fine grain structure. The Seebeck coefficient increased considerably as well, consequently optimizing the thermoelectric figure of merit to a peak value of ~0.24 for FeVSb0.94Te0.06. Thermoelectric properties of various Te concentrations were investigated in the temperature range of around 300~973 K.

Magnetic Property Evolution of Co-22%Cr Alloy Thin Films with Self-Organized Nano Structure Formation (Co-22%Cr 합금박막의 자가정렬형 나노구조에 의한 자기적 물성)

  • Song, O-Seong;Lee, Yeong-Min
    • Korean Journal of Materials Research
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    • v.11 no.12
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    • pp.1042-1046
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    • 2001
  • Co-22%Cr alloy films are promising for high-density perpendicular magnetic recording media with their perpendicular anisotropy and large coercivity of 3000 Oe. We observed that a self organized nano structure(SONS) of fine ferromagnetic Co-enriched phase and paramagnetic Cr-enriched phase appears inside the grain of Co-Cr magnetic alloy thin films at the elevated substrate temperature after do-sputtering. We prepared 1000 $\AA$-thick Co-22%Cr films on 2000 $\AA$- SiO$_2$/Si(100) substrates at the deposition rate of 100 $\AA$/min with substrate temperatures of 3$0^{\circ}C$, 10$0^{\circ}C$, 15$0^{\circ}C$, 20$0^{\circ}C$, 30$0^{\circ}C$, and 40$0^{\circ}C$, respectively. We employed a vibrating sample magnetometer(VSM) to measure the B-H loops showing the saturation magnetifation, coercivity, remanence in in- plane and out- of- plane modes. In- plane coercivity, perpendicular coercivity, and perpendicular remanence increased as substrate temperature increased, how-ever they decreased after 30$0^{\circ}C$ slowly. Transmission electron microscope (TEM) characterization revealed that the self organized nano structure (SONS) appears at the elevated substrate temperature, which forms fine Co-enriched phases inside a grain, then it eventually affect the perpendicular magnetic property. Our results imply that we may tune the perpendicular magnetic properties with SONS obtained at appropriate substrate temperature.

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Chemo-Mechanical Analysis of Bifunctional linear DGEBF/Aromatic Amino Resin Casting Systems (DGEBF/방향족아민 경화계의 벤젠링 사이에 위치한 Methyl기와 Sulfone기가 유발하는 물성변화에 대한 연구)

  • Lee Jae-Rock;Myung In-Ho
    • Composites Research
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    • v.18 no.4
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    • pp.14-20
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    • 2005
  • To determine the effect of chemical structure of aromatic amino curing agents on thermal and mechanical properties, standard epoxy resin DGEBF (diglycidylether of bisphenol F) was cured with diaminodiphenyl methane (DDM) and diaminodiphenyl sulphone (DDS) in a stoichiometrically equivalent ratio. From this work the effect of aromatic amino curing agents on the thermal and mechanical properties is significantly influenced by the chemical structure of curing agents. In contrast, the results show that the DGEBF/DDS system having the sulfone structure between the benzene rings had higher values in the thermal stability, density, shrinkage ($\%$), thermal expansion coefficient, tensile modulus and strength, flexural modulus and strength than the DGEBF/DDM system having methylene structure between the benzene rings, whereas the DGEBF/DDS system presented low values in maximum exothermic temperature, conversion of epoxide, and grass transition temperature. These results are caused by the relative effects of sulfone group having strong electronegativity and methylene group having (+) repulsive property. The result of fractography shows that the grain distribution of DGEBF/DDS system is more irregular than that of the DGEBF/DDM system.