• Title/Summary/Keyword: Elongated grain

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The Utilization of Yun Chun Andalusite as a Raw Material for High Alumina Refractories(III) -Effect of Impurities on the Mulltization- (고 알루미나질 내화물 원료로서 연천산 홍주석의 이용에 관한 연구(III) -홍주석의 물라이트화에 미치는 불순물의 영향-)

  • Ahn, Young-Pil;Choi, Long
    • Journal of the Korean Ceramic Society
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    • v.11 no.3
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    • pp.27-32
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    • 1974
  • The effect of impurities of andalusite on the morphology of the crystallization of mullite was investigated. The raw, concentrated and purified andalusite were fired at 145$0^{\circ}C$. and 150$0^{\circ}C$. Each of three grades of andalusite was examined in a scanning electron microscope, X-ray diffractometer and etc. The raw andalusite showed deeply etched textures and prismatic crystals which are estimated to be an average of 2.5u in width and 15u in length. Concentrated andalusite showed poorly formed and elongated prismatic crystals. Purified andalusite showed condensed needle-like crystals which are estimated to be an average of 0.4$\mu$ in width and 2.0$\mu$ in length, but at the boundary of the original andalusite grain, prismatic crystals were seen. It is supposed that the purified andalusite is able to utilize as a raw material for high alumina refractories with refractoriness S.K. 38.

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Electrical properties of S$SrBi_{2x}Ta_2O_9$ thin films with Bi content (Bi 함량에 따른 $SrBi_{2x}Ta_2O_9$ 박막의 전기적 특성)

  • 연대중;권용욱;박주동;오태성
    • Journal of the Korean Vacuum Society
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    • v.8 no.3A
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    • pp.224-230
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    • 1999
  • $SrBi_{2x}Ta_2O_9$ (SBT) thin films were prepared on platinized silicon substrates by MOD process, and their ferroelectric and leakage current characteristics were investigated. The grain size of the MOD derived SBT films increased with increasing the BI/Ta mole ration. Although the SBT films with x of 0.8~1.2 were composed of the equiaxed grains, the elongated grains were also observed for the SBT films with x of 1.4 and 1.6. The SBT film with x of 1.2 exhibited the optimum ferroelectric properties of 2PR : 9.79 $\muC/\textrm{cm}^2$ and Ec : 24.2kV/cm at applied voltage of 5V. The leakage current density of the SBT films increased with increasing the BI/Ta mole ratio. With post annealing process, 2Pr and $E_c$of the SBT film with x of 1.2 increases 11.3 $\muC/\textrm{cm}^2$ and 39.6kV/cm, respectively. decrement of the leakage current density by post annealing process increased remarkably with increasing the Bi/ta mole ratio, and the SBT film with x=1.6 exhibited the lowest leakage current density after post annealing process.

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Effects of Precipitates and Mn Solute Atoms on the Recrystallization Behavior of an Al-Mn Alloy

  • Lee, Yongchul;Kobayashi, Equo;Sato, Tatsuo
    • Korean Journal of Materials Research
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    • v.24 no.5
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    • pp.229-235
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    • 2014
  • In this paper, the effects of precipitates and Mn-solute atoms on the recrystallization behavior of an Al-Mn alloy was studied using micro-Vickers hardness, electrical conductivity measurements and optical microscopy. Various thermo-mechanical processes were designed to investigate the different morphologies, and the solute concentration, of Mn in the matrix. The results indicate that the recrystallization temperature, $T_R$ and time, $t_R$, are influenced by the amount of M-solute atoms in the matrix, and that the recrystallization microstructure is influenced by the amount of precipitates. Recrystallization in the Slow-Cooling specimen was rapid due to its low concentration of Mn-solute atoms, and the crystal-grain size was the smallest due to finely distributed precipitates. However, in the case of the No-Holding specimen, elongated grains were observed at the low annealing temperature and the largest recrystallized grains were observed at the high annealing temperatures (compared with Slow-Cooling and Base specimens) due to the high Mn-solute atoms in the matrix.

Microstructural Evolution of a Cold Roll-Bonded Multi-Layer Complex Aluminum Sheet with Annealing

  • Jo, Sang-Hyeon;Lee, Seong-Hee
    • Korean Journal of Materials Research
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    • v.32 no.2
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    • pp.72-79
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    • 2022
  • A cold roll-bonding process using AA1050, AA5052 and AA6061 alloy sheets is performed without lubrication. The roll-bonded specimen is a multi-layer complex aluminum alloy sheet in which the AA1050, AA5052 and AA6061 sheets are alternately stacked. The microstructural evolution with the increase of annealing temperature for the roll-bonded aluminum sheet is investigated in detail. The roll-bonded aluminum sheet shows a typical deformation structure in which the grains are elongated in the rolling direction over all regions. However, microstructural evolution of the annealed specimen is different depending on the type of material, resulting in a heterogeneous microstructure in the thickness direction of the layered aluminum sheet. Complete recrystallization occurs at 250 ℃ in the AA5052 region, which is lower by 100K than that of the AA1050 region. Variation of the misorientation angle distribution and texture development with increase of annealing temperature also differ depending on the type of material. Differences of microstructural evolution between aluminum alloys with increase of annealing temperature can be mainly explained in terms of amounts of impurities and initial grain size.

Effect of Sc Addition on Microstructure, Electrical Conductivity, Thermal Conductivity and Mechanical Properties of Al-2Zn-1Cu-0.3Mg Based Alloy (Al-2Zn-1Cu-0.3Mg합금의 Sc첨가에 따른 미세조직, 전기전도도, 열전도도 및 기계적 특성 변화)

  • Na, Sang-Su;Kim, Yong-Ho;Son, Hyeon-Taek;Lee, Seong-Hee
    • Korean Journal of Materials Research
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    • v.30 no.10
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    • pp.542-549
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    • 2020
  • Effects of Sc addition on microstructure, electrical conductivity, thermal conductivity and mechanical properties of the as-cast and as-extruded Al-2Zn-1Cu-0.3Mg-xSc (x = 0, 0.25, 0.5 wt%) alloys are investigated. The average grain size of the as-cast Al-2Zn-1Cu-0.3Mg alloy is 2,334 ㎛; however, this value drops to 914 and 529 ㎛ with addition of Sc element at 0.25 wt% and 0.5 wt%, respectively. This grain refinement is due to primary Al3Sc phase forming during solidification. The as-extruded Al-2Zn-1Cu-0.3Mg alloy has a recrystallization structure consisting of almost equiaxed grains. However, the as-extruded Sc-containing alloys consist of grains that are extremely elongated in the extrusion direction. In addition, it is found that the proportion of low-angle grain boundaries below 15 degree is dominant. This is because the addition of Sc results in the formation of coherent and nano-scale Al3Sc phases during hot extrusion, inhibiting the process of recrystallization and improving the strength by pinning of dislocations and the formation of subgrain boundaries. The maximum values of the yield and tensile strength are 126 MPa and 215 MPa for the as-extruded Al-2Zn-1Cu-0.3Mg-0.25Sc alloy, respectively. The increase in strength is probably due to the existence of nano-scale Al3Sc precipitates and dense Al2Cu phases. Thermal conductivity of the as-cast Al-2Zn-1Cu-0.3Mg-xSc alloy is reduced to 204, 187 and 183 W/MK by additions of elemental Sc of 0, 0.25 and 0.5 wt%, respectively. On the other hand, the thermal conductivity of the as-extruded Al-2Zn-1Cu-0.3Mg-xSc alloy is about 200 W/Mk regardless of the content of Sc. This is because of the formation of coherent Al3Sc phase, which decreases Sc content and causes extremely high electrical resistivity.

Influence of Deep Flooding on Rice Growth and Yield in Dry-seeded Paddy Field (벼 건답직파 재배시 심수관개가 생육과 수량에 미치는 영향)

  • 원종건;최충돈;이외현;김칠용;이상철
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.42 no.2
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    • pp.166-172
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    • 1997
  • This experiment was carried out to clarify the effect of the deep water irrigation on dry-seeded rice cultivation at the three different water managements-deep continuous flooding(DCF), water saving irrigation(WSI), ordinary irrigation(OI). The highest tillering numbers per $m^2$ of rice were 551, 466 and 455 in OI, WSI and DCF, respectively. The tillering number of rice plants were significantly reduced in DCF. Heading date was delayed and the total chlorophyll content in leaf after heading was higher in DCF than those in other irrigation methods. For the characteristics associated with lodging, the culm length in DCF was slightly elongated and the diameter of culm in DCF was thicker than that in WSI and OI. The breaking weight and bending moment in DCF also were higher than those in others. As the result, although the culm length in DCF was long, the lodging index was comparatively low. The panicle length in DCF was longer than in OI and WSI. The spikelet number per $m^2$ and 1,000-grain weight were the most in WSI, while panicle number, ripened grain ratio and grain weight were not significantly different. Longer panicle length and more spikelet number resulted in higher yielding capacity in DCF.

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Microstructure Development of Spark Plasma Sintered Silicon Carbide with Al-B-C (Al-B-C 첨가 탄화규소의 스파크 플라즈마 소결에 의한 미세구조 발달)

  • Cho, Kyeong-Sik;Lee, Kwang-Soon;Lee, Hyun-Kwuon;Lee, Sang-Jin;Choi, Heon-Jin
    • Journal of the Korean Ceramic Society
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    • v.42 no.8 s.279
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    • pp.567-574
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    • 2005
  • Densification of SiC powder with additives of total amount of2, 4, 8 $wt\%$ Al-B-C was carried out by Spark Plasma Sintering (SPS). The unique features of the process are the possibilities of a very fast heating rate and a short holding time to obtain fully dense materials. The heating rate and applied pressure were kept at $100^{\circ}C/min$ and 40 MPa, while the sintering temperature and holding time varied from 1700 - $1800^{\circ}C$ for 10 - 40 min, respectively. The SPS-sintered specimens with different amount of Al-B-C at $1800^{\circ}C$ reached near-theoretical density. The $3C{\rightarrow}6H,\;15R{\rightarrow}4H$ phase transformation of SiC was enhanced by increasing the additive amount. The microstructure of SiC sintered up to $1750^{\circ}C$ consisted of fine equiaxed grains. In contrast, the growth of large elongated grains in small matrix grains was shown in sintered bodies at $1800^{\circ}C$, and the plate-like grains interlocking microstructure had been developed by increasing the holding time at $1800^{\circ}C$. The grain growth rate decreases with increasing amount of Al-B-C in SiC starting powder, however, the both of volume fraction and aspect ratio of large grains in sintered body increased.

Morpho-Physiological Studies on Elongation of Mesocotyl and Seminal Root in Rice Plant I. Varietal Differences and Effects of Seed Maturity and Storage Condition on Mesocotyl Elongation (수도 중배축 및 종근 생장의 형태.생리학적 연구 I. 중배축 신장의 품종간 차이와 종자숙도 및 저장조건의 영향)

  • 김진호;정병관;이성춘
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.34 no.3
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    • pp.296-302
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    • 1989
  • The mesocotyl elongation, having much effect on emergence and stand establishment in the direct sowing culture of rice, was investingated and summarized as follows: As to origin of cultivars, the average lengths of mesocotyl were 9.6 mm in the Indica-Japonica hybrid cultivars, 4.4 mm in the native cultivars and 3.2mm in the Japonica type, respectively. The mesocotyl lengths were tjereh, aman, aus, boro and bulu in order, with the mesocotyl lengths of 29.3mm and 5.4 mm in tjereh and bulu, respectively. The mesocotyl lengths were great in Baekkyungjo, Dadajo & Hejo among the native cultivars, in Sangpungbyeo, Paltal & Gokyangdo of the Japonica type and in Weonpungbyeo, Gayabyeo, Milyang 30 & Sujeongbyeo in Indica- Japonica hybrid cultivars, respectively. The mesocotyl length was the greatest at the seeds sampled I week after flowering (39. 3mm in length), and became decreased with the longer grain-filling. The mesocotyl elongated worse with the longer duration of seed storage regardless of seed maturity, and became longer at the 5$^{\circ}C$ storage plot than at the 15 and 25$^{\circ}C$ plots.

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Petrological Study on the Jecheon granite mass (제천(提川) 화강암체(花崗岩體)에 대(對)한 암석학적(岩石學的) 연구(硏究))

  • Kim, Yong Jun
    • Economic and Environmental Geology
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    • v.12 no.3
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    • pp.115-126
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    • 1979
  • The Jecheon granite mass has turtle-shape exposure of about $190km^2$ at vicinity of Jecheon-eup, and is elongated in the direction of NEE-SWW. It discordantly intrudes the Bakdalryong metamorphic rocks and the great limestone series(Samtaesan and Hungwolri formation) which belong to the pre-Cambrian and Ordovician, respectively. The mass is composed of five facies of different grain size; texture and charecteristic minerals. The five facies are (1) coarse grained biotite granodiorite, (2) fine grained hornblende biotite granodiorite, (3) coarse grained pink feldspar granodiorite (4) leucogranite, and (5) porphyritic biotite granite. The mutual relationship between each facies is intrusion in (1)-(2) and (2)-(3), but unknown in (3)-(4) and (4)-(5). 22 modal analyses and and 10 chemical analyses on more than a hundred of representative samples taken from the mass are listed as tables. Triangular plot of modal and normative Q-Kf-Pl of this mass show a continuous differentiation products from certain common magma by change of chemical composition and anorthite contents in plagioclase. The metamorphic facies of contact aureole in surrounding rocks adjacent to the granite body are corresponded to hornblende hornfels facies with mineral assemblages of wollastonite-diopside-calcite in calcareous rocks, and of quartz-biotite-muscovite-cordierite in argillaceous rocks. Variation of silica versus oxides of major elements shows that the mass is similar to the trend of Daly's average basalt-andesite-dacite-rhyolite which shows the trend of the fractional crystallization of magma, and is equivalent to the calc-alkali rock series by Peacock. AMF diagram shows that Jecheon granite mass is equivalent to normal diffentiation products such as skaergaard intrusion. The above evidences suggest that the Jecohon granite mass is normal differentiation products formed by fractional crystallization under relatively slow cooling condition.

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Properties and Manufacture of $\beta-SiC-ZrB_2$ Composites Densified by Liquid-Phase Sintering(II) (액상소결에 의한 $\beta-SiC-ZrB_2$ 복합체의 제조와 특성(II))

  • Yoon, Se-Won;Hwang, Chul;Ju, Jin-Young;Shin, Yong-Deok
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.49 no.2
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    • pp.92-97
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    • 2000
  • The mechanical and electrical properties of the hot-pressed and annealed $\beta$-SiC+39vol. %ZrB2 electroconductive ceramic composites were investigated by adding 1, 2, 3wt% Al2O3+Y2O3(6:4wt%) of the liquid forming additives. In this microstructures, no reactions were observed between $\beta-SiC$ and ZrB2. The relative density is over 90.8% of the theoretical density and the porosity decreased with increasing Al2O3+Y2O3 contents. Phase analysis of the composites by XRD revealed $\alpha-SiC(6H, 4H)$, ZrB2 and $\beta-SiC$(15R). Flexural srength showed the highest of 315.5MPa for composites added with 3wt% Al2O3+Y2O3 additives as room temperature. Owing to crack deflection and crack bridging of fracture toughness mechanism, the fracture toughness showed 5.5MPa.m1/2 and 5.3MPa.m1/2 for composites added with 2wt% and 3wt% Al2O3+Y2O3 additives respectively at room temperature. The area fraction of the elongated SiC grain in the etched surface of sample showed 65% and 65.1% for composite added with 2wt% and 3wt% Al2O3+Y2O3 additives respectively. The electrical resistivity at room temperature. The electrical resistivity of the composites wall all positive temperature coefficient(PTCR) against temperature up to $700^{\circ}C$.

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