Effects of rheology and mantle temperature structure on edge-driven convection: Implications for partial melting and dynamic topography

Kim, Dae-Hee,So, Byung-Dal Elsevier 2020 Physics of the earth and planetary interiors Vol.303 No.-

<P><B>Abstract</B></P> <P>Edge-driven convection, which affects partial melting, intraplate volcanism, and dynamic topography, is small-scale convection that occurs along a lithospheric keel with a sharp contrast in lithospheric thickness. Various factors, including Rayleigh number, lateral mantle temperature heterogeneity, and geometry of the keel, influence the edge-driven convection, and the correlation between edge-driven convection and surface expressions (dynamic topography and volcanism) is complicated. We performed a finite element study to quantify the effects of these factors on dynamic topography and partial melting. We found that the dynamic topography is more prominent when a strong edge-driven convection cell develops, which corresponds to homogeneous mantle temperatures and the absence of mantle wind. In contrast, the development of edge-driven convection cells and dynamic topography near the lithospheric keel are hindered when the mantle temperature is strongly heterogeneous (laterally varying ~280 K). This indicates that a large lateral contrast in mantle temperature results in a strong mantle wind that may prevent the development of edge-driven convection cells. An increase in the Rayleigh number results in more vigorous convection and enhances partial melting. Our study shows that the location of volcanic activity at craton edges and passive margins can be reproduced in models with weakly heterogeneous mantle temperature for given mantle viscosity. The existence of a strong mantle wind (e.g., related to subducting slabs or mantle plumes) may inhibit the formation of an edge-driven convection cell and its related partial melt near a lithospheric keel. However, mantle conditions with weak temperature heterogeneity (<~14 K) or high mantle viscosity (>17×10<SUP>19</SUP> Pa∙s), which corresponds to the Rayleigh number of 1.8×10<SUP>6</SUP>, do not induce partial melts despite the development of edge-driven convection cells. Our model parametrized the condition and location of edge-driven convection cells and partial melts, which can contribute to understanding anomalous intraplate volcanisms, such as in Jeju Island south of the Korean Peninsula and the Tanzania Craton near the East African Rift.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Small lateral thermal heterogeneity causes localized edge-driven convention. </LI> <LI> Topography increases and decreases due to upwelling and downwelling of EDC, respectively. </LI> <LI> Thermal heterogeneity has promoting and suppressing effects on partial melting at lithospheric edge. </LI> <LI> Strong mantle wind prevents the localization of mantle partial melting near lithospheric edge. </LI> <LI> Strict range of thermal heterogeneity is needed for partial melting at lithospheric edge. </LI> </UL> </P>

국부적 용융이 ${Si_3}{N_{4p}}$/2124 Al 복합재의 초소성 거동에 미치는 영향 (II)

정하국,김혜성,Jeong, Ha-Guk,Kim, Hye-Seong 한국재료학회 2001 한국재료학회지 Vol.11 No.7

많은 연구결과들은 국부적 용융체의 존재가 고온인장 변형 시 발생하는 내부공극의 발달을 억제할 수 있음을 보고하고 있다. 그러나 이러한 국부적 용융체가 존재한다고 해서 반드시 고변형속도 초소성 현상이 관찰될 수 있는 것은 아니다. 금속기지와 보강재간의 계면에 국부적 용융체의 양이 너무 많이 존재하면 두상간의 결합력이 떨어져 금속기지상으로부터 보강재가 분리되는 현상이 야기될 수 있기 때문이다. 그러므로, $Si_3$$N_{4p}$ 2124 Al 복합재의 초소성 유동 특성을 이해하기 위해 변형온도에 따른 미세구조 변화와 계면특성을 조사하였다. 본 연구를 룽해 $Si_3$$N_{4p}$ 2124 Al 복합재에서 Al-기지와 $Si_3$$N_{4p}$ 강화상간의 계면상의 국부적 용융이 시작되는 온도부근에서는 큰 초소성 특성이 얻어지지만, 국부적 용융이 시작되는 온도를 지난 인장온도범위에서는 오히려 초소성 특성이 현저하게 저하되는 현상이 관찰되었다. 위의 실험결과는 $Si_3$$N_{4p}$ 2124 Al복합재의 고변형속도 초소성 거동에 기여하는 최적의 액상량이 존재한다는 것을 의미한다. Many experimental results have revealed that the development of cavitaition during tensile deformation is limited by the Presence of liquid phases. However, the presence of liquid phases does not always lead to high-strain-rate superplasticity, because too much liquid causes intergranular decohesion at grain boundaries/interfaces in metal-matrix composites. Thus, it is important to examine the nature of interfaces of superplastic composites in order to understand the origin of superplastic flow related to liquid grain boundaries during high-strain-rate superplastic deformation. This study shows that a large elongation is obtained at the temperature, that is close to the onset temperature for partial melting in the superplastic composites, but the elongation significantly decreases at slightly higher temperatures, which are close to the end temperature fur partial melting. This indicates that there is an optimum amount of the liquid phase for obtaining high-strain-rate superplasticity in these materials.

Highly refractory peridotites in Songshugou, Qinling orogen: Insights into partial melting and melt/fluid-rock reactions in forearc mantle

Cao, Y.,Song, S.,Su, L.,Jung, H.,Niu, Y. Universitetsforlaget ; Elsevier Science Ltd 2016 Lithos Vol.252 No.-

<P>The Songshugou ultramafic massif is located in the eastern segment of the Qinling orogenic belt, central China. It is a large spinel peridotite body dominated by coarse-grained, porphyroclastic, and fine-grained dunite with minor harzburgite, olivine clinopyroxenite, and banded/podiform chromitite. The compositions of the bulk rock dunite and harzburgite, and the constituent olivine and spinel, together with the textures and chemical characteristics of multiphase mineral inclusions, point to the highly refractory nature of these rocks with complex histories of high-temperature boninite melt generation and boninitic melt-rock reaction, probably in a young, warm, and volatile-rich forearc lithospheric mantle setting. Additionally, a subsequent low-temperature fluid rock reaction is also recorded by TiO2-rich spinel with Ti solubility/mobility enhanced by chloride- or fluoride rich subduction-zone fluids as advocated by Rapp et al. (2010). The olivine clinopyroxenite, on the other hand, was likely crystallized from a residual boninitic melt that had reacted with harzburgitic residues. The ubiquitous occurrences of hydrous minerals, such as anthophyllite, tremolite, Cr-chlorite, and serpentine (stable at lower PT crustal conditions) in the matrix, suggest that further low-temperature fluid-rock reaction (or retrograde metamorphism) has affected the original volatile-poor peridotites either in a mature and cool subduction zone, or in a continental crust during their exhumation into the Qinling collisional orogeny at early Paleozoic era, or both. The prolonged and intense ductile/brittle deformation can decrease the mineral grain size through dynamic recrystallization and fracturing, and thus aid the fluid-rock reaction or retrograde metamorphism and mineral chemical re-equilibration processes. Therefore, the Songshugou peridotites present a good example for understanding the petrogenesis and evolution of the mantle wedge, with the emphasis on the complex partial melting and melt/fluid-rock interactions in the forearc setting. (c) 2016 Elsevier B.V. All rights reserved.</P>

Steam explosion experiments using partially oxidized corium

J. H. Kim,B. T. Min,I. K. Park,H. D. Kim,S. W. Hong 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.11

Two steam explosion experiments were performed in the TROI (Test for Real cOrium Interaction with water) facility by using partially oxidized molten corium (core material), which is produced during a postulated core melt accident in a nuclear reactor. A triggered steam explosion occurred in one case, but none occurred in the other case. The dynamic pressure and the dynamic load measured in the former experiment show a stronger explosion than those performed previously with oxidic corium. Meanwhile, a steam explosion is prohibited when the melt temperature is low, because the melt is easily solidified to prevent a liquid-liquid interaction. The partially oxidized corium could enhance the strength of a steam explosion due to the thermal energy from an exothermic chemical reaction between the water and the uranium metal with a sufficient superheat extracted during melting. The melt composition effect on a steam explosion load, which was not included during the nuclear design, needs to be included in it.

PMP에 따른 플라즈마 용사 Bi-2212/2223 초전도 피막 특성

조상흠 ( Sang Hum Cho ),이선홍 ( Seon Hong Lee ),박경채 ( Kyeong Chae Park ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 대한금속·재료학회지 Vol.44 No.7

Bi2Sr2CaCu2Ox(2212) and Bi2Sr2Ca2Cu2Oy(2223) high-Te superconductor (HTS) have been prepared by plasma spraying and PMP(Partial Melt Process). The 2212 HTS coating layer is synthesized through the peritectic reaction between Sr-Ca-Cu oxide coating layer and Bi-Cu oxide coating layer by partial melting process. The superconducting characteristics, it can be predicted from wetting secondary phase and mis-alignment of whisker, depends on the spray distance which was related to the spray particle melt. The 2212 HTS layer consists of the whisker grown in the diffusion direction. 2223 phase and secondary phase in 2212 layer were observed. The secondary phase is distributed uniformly over the whole surface which was caused to the mis-orientation of 2223. But it can be removed by oxygen pressure control. Spray coating layer shows superconducting with an onset Tr of about both 115 K and 77 K (Para-conductivity) in this study. There are two steps. step 1 at 115 K is due to the diamagnetism of the 2223 phase and step 2 at 78 K is due to the diamagnetism of the 2212 phase.

Synthesis and Superconductivity of Y₂Ba₁Cu₁O_(5) and Pt Added Nd₁Ba₂Cu₃O_(7-y) Bulk Superconductor

Song, Myoung Youp,Kim, Jong Jin,Hong, Gye Won,Lee, Hee Gyoun 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.5

Nd₁Ba₂Cu₃O_(7-y) (Nd123) bulk superconductor with T_(c) > 77 K was prepared by a melt process under 1 atm pure oxygen and reduced oxygen partial pressures. The addition of Y₂Ba₁Cu₁O_(5) (Y211) particles suppressed the generation of microcracks during oxygenation in resulting in the dispersion of Y211 fine particles. The addition of a small amount of Pt resulted in the reduction of the size of Y211 particles. The oxygen partial pressure (Po₂) of 0.01 atm was the optimum atmosphere for the synthesis of Nd123 in which Y211 particles were dispersed finely and homogeneously. The addition of Y211 and Pt enhanced the flux pinning force in a melt-processed Nd123 specimen because the presence of Y atoms in a melt phase suppressed, to some extent, the substitution of Nd on Ba site in an Nd123 crystal prepared by a melt process.

Li₂ZrO₃로 CO₂ 제거시 알칼리 첨가제 효과

박주원,강동환,조영도,유경선,이재구,김재호,한춘,Park, Joo-Won,Kang, Dong-Hwan,Jo, Young-Do,Yoo, Kyung-Seun,Lee, Jae-Goo,Kim, Jae-Ho,Han, Choon 한국화학공학회 2006 Korean Chemical Engineering Research(HWAHAK KONGHA Vol. No.

가연성 폐기물 가스화반응으로 생성되는 합성가스내의 $CO_2$ 제거반응에서 $Li_2ZrO_3$와 알칼리염 첨가제의 효과를 열중량 분석기를 이용하여 그 특성을 연구하였다. $Li_2ZrO_3$는 고체상태의 $ZrO_2$와 $Li_2CO_3$를 합성하여 제조하였고, 반응성향상을 위하여 $K_2CO_3$, $Na_2CO_3$, NaCl, LiCl 등의 알칼리염을 첨가한 후 열처리하여 사용하였다. 첨가한 알칼리염에 따른 반응성 향상은 $K_2CO_3>NaCl>LiCl>Na_2CO_3$ 순으로 나타났고 이는 $Li_2CO_3$의 partial melting에 기인한 것으로 사료된다. 반응 시료의 SEM 분석 결과 용융상태의 존재를 확인할 수 있었고, XRD를 통해 첨가된 알칼리염들의 화학적 성분 변화는 일어나지 않는 것으로 확인되었다. NaCl을 사용한 경우 반응 초기에 60분 정도의 유도시간이 발생하였으며, $Na_2CO_3$가 첨가된 경우 $700{\sim}750^{\circ}C$에서도 $Li_2ZrO_3$의 $CO_2$ 제거반응에 의해 생성된 $Li_2CO_3$의 분해가 유도되지 않아 반응성 감소현상이 나타나지 않았다. Effects of alkaline additives on the $CO_2$ removal reaction have been investigated by a thermogravimetric analyzer. $Li_2ZrO_3$ was synthesized by soild reaction of $ZrO_2$ with $Li_2CO_3$ and then alkali chemicals were added to the synthesized $Li_2ZrO_3$ and then heat treatment was carried out. Addition of alkali chemicals enhanced the reactivity of $Li_2ZrO_3$ with the following order; $K_2CO_3>NaCl>LiCl>Na_2CO_3$, which were resulted from the formation of partially melted $Li_2CO_3$. SEM photographs showed the presence of melted state and the XRD results showed that the chemical states of added salts were not changed. Addition of NaCl caused the induction time of about 60 min at the initial reaction stage and the addition of $Na_2CO_3$ inhibited the decomposition of $Li_2CO_3$ at about $700{\sim}750^{\circ}C$.

A Study on the Friction and Wear Properties of Tribaloy 800 Coating by HVOF Thermal Spraying

Tong Yul Cho,Jae Hong Yoon,Kil Su Kim,Suk Jo Youn,Ki Oh Song,Nam Ki Back,Hui Gon Chun,Soon Young Hwang 한국표면공학회 2006 한국표면공학회지 Vol.39 No.5

Tribaloy 800 (T800) powder is coated on the Inconel 718 substrate by the optimal High Velocity Oxy-Fuel (HVOF) thermal spray coating process developed by this laboratory. For the study of the possibility of replacing of the widely used classical chrome plating, friction, wear properties and sliding wear mechanism of coatings are investigated using reciprocating sliding tester both at room and at an elevated temperature of 1000°F (538°C). Both at room temperature and at 538°C, friction coefficients and wear debris of coatings are drastically reduced compared to those of non-coated surface of Inconel 718 substrate. Friction coefficients and wear traces of both coated and non-coated surfaces are drastically reduced at higher temperature of 538°C compared with those at room temperature. At high temperature, the brittle oxides such as CoO, Co₃O₄, MoO₂, MoO₃ are formed rapidly on the sliding surfaces, and the brittle oxide phases are easily attrited by reciprocating slides at high temperature through complicated mixed wear mechanisms. The sliding surfaces are worn by the mixed mechanisms such as oxidative wear, abrasion, slurry erosion. The brittle oxide particles and melts and partial-melts play roles as solid and liquid lubricant reducing friction coefficient and wear. These show that the coating is highly recommendable for the durability improvement coating on the surfaces vulnerable to frictional heat and wear.

열처리 조건에 따른 Bi-2212 초전도 튜브의 특성

박용민,장건익 한국전기전자재료학회 2001 전기전자재료학회논문지 Vol.14 No.7

Bi-2212 HTS tube was fabricated by centrifugal forming and partial melting processes. Bi-2212 bulk tube has been optimized to achieve smooth surface and uniform thickness. The slurry was prepared in the mixing ratio of 10:1 between Bi-2212 powder and binder and initially charged into the rotating mold under the speed of 300~450 rpm. Heat-treatment was performed at the temperature ranges of 860~89$0^{\circ}C$ in air for partial melting. the HTS tube fabricated by centrifugal forming process at 89$0^{\circ}C$ under the rotating speed of 450 rpm was highly densified and the plate-like grains with more than 20${\mu}{\textrm}{m}$ were well oriented along the rotating axis. The measured Tc and J$_{c}$ at 10K on specimen heat treated at 89$0^{\circ}C$ was around 85 K and 1,200 A/$\textrm{cm}^2$ respectively.y.

Selective Laser Melting을 이용한 코발트-크롬 가철성 국소의치의 수복 증례

임지훈(Ji-Hun Yim),신수연(Soo-Yeon Shin) 대한턱관절교합학회 2021 구강회복응용과학지 Vol.37 No.1