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Degradation of Functional Materials in Temperature Gradients - Thermodiffusion and the Soret Effect
Janek, Jurgen,Sann, Joachim,Mogwitz, Boris,Rohnke, Marcus,Kleine-Boymann, Matthias The Korean Ceramic Society 2012 한국세라믹학회지 Vol.49 No.1
Functional materials are often exposed to high temperatures and inherent temperature gradients. These temperature gradients act as thermodynamic driving forces for the diffusion of mobile components. The detailed consequences of thermodiffusion depend on the boundary conditions of the non-isothermal sample: Once the boundaries of the sample are inert and closed for exchange of the mobile components, thermodiffusion leads to their pile-up in the stationary state (the so called Soret effect). Once the system is open for an exchange of the mobile component, chemical diffusion adds to the Soret effect, and stationary non-zero component fluxes are additionally observed in the stationary state. In this review, the essential aspects of thermodiffusion and Soret effect in inorganic functional materials are briefly summarized and our current practical knowledge is reviewed. Major examples include nonstoichiometric binary compounds (oxides and other chalcogenides) and ternary solid solutions. The potential influence of the Soret effect on the long term stability of high temperature thermoelectrics is briefly discussed. Typical Soret coefficients for nonstoichiometric compounds are found to be of the order of (d${\delta}$/dT) ${\approx}$ 1%/K.
Degradation of Functional Materials in Temperature Gradients -Thermodiffusion and the Soret Effect
Jürgen Janek,Joachim Sann,Boris Mogwitz,Marcus Rohnke,Matthias Kleine-Boymann 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.1
Functional materials are often exposed to high temperatures and inherent temperature gradients. These temperature gradients act as thermodynamic driving forces for the diffusion of mobile components. The detailed consequences of thermodiffusion depend on the boundary conditions of the non-isothermal sample: Once the boundaries of the sample are inert and closed for exchange of the mobile components, thermodiffusion leads to their pile-up in the stationary state (the so called Soret effect). Once the system is open for an exchange of the mobile component, chemical diffusion adds to the Soret effect, and stationary non-zero component fluxes are additionally observed in the stationary state. In this review, the essential aspects of thermodiffusion and Soret effect in inorganic functional materials are briefly summarized and our current practical knowledge is reviewed. Major examples include nonstoichiometric binary compounds (oxides and other chalcogenides) and ternary solid solutions. The potential influence of the Soret effect on the long term stability of high temperature thermoelectrics is briefly discussed. Typical Soret coefficients for nonstoichiometric compounds are found to be of the order of (dδ/dT) ≈ 1%/K.
Impulse Generation Mechanisms in a Laser-Driven In-Tube Accelerator
CHOI, Jeong-Yeol,KANG, Ki-Ha,SASOH, Akihiro,JEUNG, In-Seuck,URABE, Naohide,KLEINE, Harald 日本航空宇宙学会 2008 Transactions of the Japan Society for Aeronautical Vol.51 No.172
<P>To enhance laser-propulsion thrust performance, a unique Laser-driven In-Tube Accelerator (LITA) has been developed. This paper numerically analyzes the impulse generation mechanisms in LITA. For this purpose, a LITA performance experiment was conducted in atmospheric air with a projectile installed on a ballistic pendulum to calibrate the numerical approximations. We conducted experimental flow visualization by framing shadowgraph and computational fluid dynamics solving the axi-symmetric Euler equation applied to an ideal gas. The results show that a laser-driven blast wave is generated by a spherical hot gas core where the supplied laser energy is absorbed first. The effect of confinement by the tube or shroud wall is confirmed. The impulse production is established not only from the interaction between the incident blast wave and projectile, but also from the following repetitive pressure waves. Assuming that about 30% of the input laser energy is absorbed by the working air, both the impulse and peak pressure agrees quantitatively between the experiment and numerical simulation.</P>
Dirlam, Philip T.,Park, Jungjin,Simmonds, Adam G.,Domanik, Kenneth,Arrington, Clay B.,Schaefer, Jennifer L.,Oleshko, Vladimir P.,Kleine, Tristan S.,Char, Kookheon,Glass, Richard S.,Soles, Christopher American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.21
<P>The practical implementation of Li-S technology has been hindered by short cycle life and poor rate capability owing to deleterious effects resulting from the varied solubilities of different Li polysulfide redox products. Here, we report the preparation and utilization of composites with a sulfur-rich matrix and molybdenum disulfide (MoS2) particulate inclusions as Li-S cathode materials with the capability to mitigate the dissolution of the Li polysulfide redox products via the MoS2 inclusions acting as 'polysulfide anchors'. In situ composite formation was completed via a facile, one-pot method with commercially available starting materials. The composites were afforded by first dispersing MoS2 directly in liquid elemental sulfur (S-8) with sequential polymerization of the sulfur phase via thermal ring opening polymerization or copolymerization via inverse vulcanization. For the practical utility of this system to be highlighted, it was demonstrated, that the composite formation methodology was amenable to larger scale processes with composites easily prepared in 100 g batches. Cathodes fabricated with the high sulfur content composites as the active material afforded Li-S cells that exhibited extended cycle lifetimes of up to 1000 cycles with low capacity decay (0.07% per cycle) and demonstrated exceptional rate capability with the delivery of reversible capacity up to 500 mAh/g at 5 C.</P>
Electronic Raman scattering in cuprate superconductors and parent insulating phases
Klein, M.V.,Salamon, D.,Blumberg, G.,Cooper, S.L.,Ginsberg, D.M.,Liu, R.,Reznik, D.,Lee, W.C. 숙명여자대학교 자연과학연구소 1994 자연과학논문집 Vol.- No.5
Raman scattering from charge and spin excitations in cuprates is reviewed. The two-magnon resonance Raman profile is used to determine the most probable energy for photon-assisted charge transfer leading to exchange between two spins. The difference between this energy and that for absorption is attributed to spin relaxation (spin polaron) effects. Two-magnon spectra in superconducting cuprates are presented. It is argued that their presence is evidence that the antiferromagnetic correlation length is equal to or greater than three lattice constants. The recently-discovered Raman-active excitons are described and possible assignments of them are discussed. It is pointed out that in highly correlated metals and insulators, the mechanisms for light scattering that are familiar for doped semiconductors or conventional metals are not necessarily the only ones that are operative.
Klein, Melanie 圓光大學校 醫科大學 神經精神科學敎室 1998 圓光精神醫學 Vol.14 No.2
앞서의 나의 논문들은, 어린이가 생후 1년동안 경험하는, 가학(sadism) 시기의 정점을 설명하였다. 태어나서 한달 동안, 어머니의 젖가슴뿐만 아니라, 어머니의 몸내부에 대해서도, 가학적인 충동을 갖는다 : 퍼내고, 먹어치우고, 가학증이 제시하는 모든 방법을 동원하여 파괴함. 유아의 발달은 함입(introjection)과 투사(projection)의 기전이 지배한다. 처음부터 자아는 대상들을 '좋은 것'과 '나쁜 것'으로 구분하는데, 모두 다 어머니의 젖가슴이 근본이다 - 젖가슴이 만족을 주면 좋은 것, 실망을 주면 나쁜 것이 된다. 어린이가 젖가슴을 '나쁜 것'으로 느끼는 것은, 젖가슴이 어린이의 욕구를 좌절시키기 때문만은 아니고, 어린이가 자신의 공격심을 젖가슴에 투사하기 때문이기도 하다: 어린이는 젖가슴을 실제로 위험한 가해자로 받아들이는데, 젖가슴이 자신을 먹어치우고, 자신의 몸 내부를 파내고, 모든 가학적인 수단을 동원하여 자신을 파괴시키려고 한다. 이러한 상들은 현실적인 대상들을 환상에서 왜곡시킨 것인데, 외부 세계뿐만 아니라, 함입에 의해, 자아에도 생기게 된다. 따라서 아주 어린 애들이 불안 상황을 경험하게 되는데 (방어기제를 사용하여 반응한다), 그 내용은 성인의 정신증의 상황과 비슷하다.
Klein, Michael J.,Goossens, Karel,Bielawski, Christopher W.,Manthiram, Arumugam The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.9
<P>The direct synthesis of Li2S2, a proposed solid intermediate in the discharge of lithium-sulfur (Li-S) batteries, was accomplished by treating elemental lithium with sulfur in liquid ammonia at -41 degrees C. The as-synthesized product was analyzed by X-ray photoelectron spectroscopy (XPS) as well as X-ray diffraction (XRD) and determined to be a mixture of crystalline Li2S, amorphous Li2S2, and higher-order polysulfides (Li2Sx, x > 2). Monitored filtration followed by a tailored electrochemical approach was used to successfully remove the higher-order polysulfides and yielded a powder, which was determined by XPS to be comprised of similar to 9 mol% insoluble polysulfide species (mainly Li2S2) and similar to 91 mol% Li2S. This material was discharged galvanostatically in an electrochemical cell and, despite the lack of soluble polysulfide species, was shown to exhibit a discharge plateau at similar to 2.1 V vs. Li/Li+. This result confirmed the electrochemical reducibility of electrolyte-insoluble polysulfides in Li-S batteries. Moreover, it was determined that the reduction of solid polysulfides was confined to areas where the sulfur-sulfur bonds were in intimate contact with the conductive current collector. Finally, it was observed that commercially available Li2S samples contain significant quantities of polysulfide-type impurities. (C) The Author(s) 2016. Published by ECS. All rights reserved.</P>