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催化学报 2015年第10期36卷 1656-1661页

作者： oleksiy v.khavryuchenko volodymyr D.khavryuchenko 苏党生计算化学集团乌克兰基辅UA-02091 中国科学院金属研究所沈阳材料科学国家(联合)实验室辽宁沈阳110016 马克斯普朗克协会弗里茨·哈伯研究所无机化学系德国柏林Faradayweg 4-6 D-14195

当初始态和过渡态之间存在能量差时,通常会考虑用催化的方法来增加反应速率,即经由能量更低过渡态的反应路径,或增加反应物初始态能量,如改变溶剂或在特殊表面吸附分子.然而,对于某些类型的反应,如H2和O2反应生成水,NO的氧化等,仅仅采... 详细信息

当初始态和过渡态之间存在能量差时,通常会考虑用催化的方法来增加反应速率,即经由能量更低过渡态的反应路径,或增加反应物初始态能量,如改变溶剂或在特殊表面吸附分子.然而,对于某些类型的反应,如H2和O2反应生成水,NO的氧化等,仅仅采用这些方法还不够,因为反应物和产物具有不同的自旋态,而自旋守恒定律一般会禁止该过程的发生.即使克服了能垒,该体系也不能转化成稳定的产物,且不改变其电子自旋多重态.但在特殊的非热力学条件下,该类反应仍可发生.这通常指自旋不守恒的过程.改变体系电子自旋最直接的方法是与原子核自旋有作用的电子自旋翻转.它可由自旋-轨道耦合来实现,因此,其实现的几率取决于元素的原子数.从3d金属开始,发生这种情况的可能性甚至更大.这是由于与d轨道耦合的效率更高所致,所以采用自旋交叉就能方便地解释自旋禁止反应发生的原因.然而,轻原子发生自旋翻转的可能性很低,因此,当面对无金属化学时,我们应该考虑自旋禁止反应发生的第二个方法—自旋催化.通过帮助克服自旋禁止的物质以促进化学反应,或通过顺磁催化剂诱导自旋解耦以降低活化能垒,这类现象就可定义为自旋催化.简而言之,为了得到想要的和热力学更有利的自旋态,一个反应粒子可以与自旋催化剂交换磁矩;该自旋催化剂需有拟自旋-简并基态或低激发态.因此,体系整个的自旋仍守恒,但可发生反应.值得强调的是,自旋"催化剂"指的是分子状态和固体状态,通常后者应用于工业中则方便得多.自旋催化是作为自旋化学的范例来研究的,或在外磁场中化学诱导动态核极化和反应,主要是指采用EPR光谱研究以液相为主的过程.本文简略介绍了自旋催化的理论.实际上,自旋催化与常规催化之间并不相互抵触—相同的材料既可作为自旋催化剂,也可用作常规催化剂,都起着降低反应能垒和提供自旋交换的自由基中心的作用.另外,许多现代材料包含着常规催化剂和自旋催化剂的特性.有些发生在多核磁性金属中心上的过程可能本身就包含着常规催化(活化底物)、自旋交叉(与d金属相互作用)和自旋催化(金属-氧簇合物中低能的铁磁-反铁磁转化)效应.气相自旋催化在实际应用中产生的主要问题是在稀释的体系中三粒子碰撞几率低,常规催化在这方面则有很多优势.我们首先列出固体成为自旋催化剂的条件:(1)活性中心中至少2个自旋态的能量差要小于反应温度下热运动的能量,这样无需额外的能量活化催化剂;(2)较大的比表面积以提供更多的自旋中心用于相互作用;(3)最好能够自旋导电,在此情况下反应无需三粒子碰撞即可发生.这是因为自由基可通过催化剂的电子系统交换自旋,使得自旋-自旋相互作用的几率迅速增加,从而有利于自旋催化反应的进行.另外,如果固体或载体具有自旋导电性,则无需外加电场或磁场,即有可能遥控催化中心的电荷和自旋态,从而避免使用外电场或磁场.实际上,许多反应过程本身就包含着自旋催化,它还可使反应过程的许多不足变成优势,如对于不需要的链式自由基反应;通过引入自旋捕获剂使得自旋禁止反应成为有用的自旋催化;磁性粒子的浓度以及外加磁场和电场均可导致自旋催化/禁止反应.由于均相自旋催化的研究较早,在此不再赘述.本文详细介绍了多相体系中的自旋催化的应用,如燃烧、温和氧化、环化、开环、非极性小分子的活化和不稳定自由基的耦合等.可能用作自旋催化剂的材料有:含有不同顺磁性的金属离子的磁性氧化物或多核磁性簇合物;嫁接在一些载体上的多核络合物或过渡金属(低温催化);带有非整数氧化价态的导电金属;各种具有半金属性和导电性的碳材料.研究自旋催化反应的一个突出问题就是这些过程大部分是自由基式的,趋于非线性区域,因而很难预测,也没有一个便利的工具用以描述,甚至预测自旋催化反应,但也许这些研究的特点就是不可预测性.自旋催化除了可调变反应的进行,我们还可从中获得一个独特的调节手段:通过外加磁场或电场触发基元过程,在非热力学上控制反应的进行.该手段在控制化学反应方面具有明显优势,因为现在大都是通过调节温度、压力和流量等参数来实现对化学反应的控制,且滞后严重.同时,通过添加外加磁场可立刻改变反应速率.另外,通过降温可精细控制基元反应,从而开辟了一种抑制副反应的方法,因而也使得反应的随机性降低.

关键词：催化自旋化学化学键均裂氧化过程自由基耦合

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基于前体聚合状态对碳材料进行分类以发展结构-性质关系(英文)

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催化学报 2014年第6期35卷 778-782页

作者： oleksiy v.khavryuchenko volodymyr D.khavryuchenko Chemistry Department Taras Shevchenko National University of KyivVolodymyrska str.64 Kyiv 01601 Ukraine CompChem Group Revutskogo str.13 Kyiv 02091 Ukraine

Modern carbon science lacks an efficient structure-related classification of materials. We present an approach based on dividing carbon materials by the aggregate state of the precursor. The common features in the structure of carbon particles that allow putting them into a group are discussed, with particular attention to the potential energy stored in the carbon structure from different rates of relaxation during the synthesis and prearrangement of structural motifs due to the effect of the precursor structure.

关键词：结构特性碳材料聚合状态分类前体结构相关耳鼻喉科聚集态

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Tribology of multilayer coatings for wear reduction: A review

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Friction 2017年第3期5卷 248-262页

作者： Mahdi KHADEM oleksiy v.PENKOv Hee-Kyung YANG Dae-Eun KIM Department of Mechanical Engineering Yonsei University Seoul 03722 Republic of KoreaCenter for Nano-Wear Yonsei University Seoul 03722 Republic of Korea Center for Nano-Wear Yonsei University Seoul 03722 Republic of Korea Department of Mechanical Engineering Yonsei University Seoul 03722 Republic of Korea

Friction and wear phenomena encountered in mechanical systems with moving components are directly related to efficiency,reliability and life of the ***,minimizing and controlling these phenomena to achieve the desired system performance is *** the numerous strategies developed for reducing friction and wear,coatings have been successfully utilized in various engineering applications to mitigate tribological *** of the benefits of coatings is that they may be fabricated using a variety of materials in several different forms and structures to satisfy the requirements of the operating *** many types,coatings that are comprised of a combination of materials in the form of a multilayer have been gaining much interest due to the added degree of freedom in tailoring the coating *** this paper,the properties and development status of multilayer coating systems for tribological applications were reviewed with the aim to gain a better understanding regarding their advantages and ***,focus was given to Ti-based and Cr-based coatings since Ti and Cr were identified as important elements in multilayer coating *** was given to materials,design concepts,mechanical properties,deposition method,and friction and wear characteristics of these types of coatings.

关键词： multilayer coating friction wear tribology

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Exhaust Cleaning with Dielectric Barrier Discharge

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Plasma Science and Technology 2010年第6期12卷 688-691页

作者： vadim Yu.PLAKSIN oleksiy v.PENKOv Min Kook KO Heon Ju LEE Department of Nuclear & Energy Engineering Jeju National University

To clean the exhaust emissions as one of the most important tasks in pollution control, a study on the treatment of engine emissions with discharge assistance was reported. A DBD plasma source shaped in grid and cylinder was examined in different engine operational modes to reduce the NOx content of diesel engine exhaust. The composition of the exhaust gases and chemical reactions initiated by the discharge were analyzed. The discharge frequency had a crucial impact on the device＇s performance and gas treatment. The voltages applied to the discharge gap could alter the chemical reactions occurring in the treated gases, which were indicated by the NO to NO2 ratio. The operation of the system was studied at frequencies ranging from 400 Hz to 16 kHz.

关键词： dielectric barrier discharge diesel engine emissions NOx atmospheric pressure

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Giant resonant light forces in microspherical photonics

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Light(Science & Applications) 2013年第1期2卷 176-183页

作者： Yangcheng Li oleksiy v Svitelskiy Alexey v Maslov David Carnegie Edik Rafailov vasily N Astratov Department of Physics and Optical Science Center for Optoelectronics and Optical CommunicationUniversity of North Carolina at CharlotteCharlotteNC 28223-0001USA Department of Radiophysics University of Nizhny NovgorodNizhny Novgorod 603950Russia Photonics and Nanoscience Group School of Electrical Engineering and PhysicsUniversity of DundeeNethergateDundee DD14HNUK Colgate University HamiltonNY 13346USA

Resonant light pressure effects can open new degrees of freedom in optical manipulation with microparticles,but they have been traditionally considered as relatively subtle *** a simplified two-dimensional model of surface electromagnetic waves evanescently coupled to whispering gallery modes(WGMs)in transparent circular cavities,we show that under resonant conditions the peaks of the optical forces can approach theoretical limits imposed by the momentum conservation law on totally absorbing ***,we proved the existence of strong peaks of the optical forces by studying the optical propulsion of dielectric microspheres along tapered *** observed giant optical propelling velocities,0.45 mm s21 for some of the 15-20 mm polystyrene microspheres in water for guided powers limited at,43 *** velocities exceed previous observations by more than an order of magnitude,thereby providing evidence for the strongly enhanced resonant optical *** analyzed the statistical properties of the velocity distribution function measured for slightly disordered(,1%size variations)ensembles of microspheres with mean diameters varying from 3 to 20 *** results demonstrate a principal possibility of optical sorting of microspheres with the positions of WGM resonances overlapped at the wavelength of the laser *** can be used as building blocks of the lossless coupled resonator optical waveguides and various integrated optoelectronics devices.

关键词： optical propulsion optical forces whispering gallery modes microspheres evanescent coupling

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Milliwatt terahertz harmonic generation from topological insulator metamaterials

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Light(Science & Applications) 2022年第11期11卷 2766-2773页

作者： Klaas-Jan Tielrooij Alessandro Principi David Saleta Reig Alexander Block Sebin varghese Steffen Schreyeck Karl Brunner Grzegorz Karczewski Igor Ilyakov oleksiy Ponomaryov Thales v.A.G.de Oliveira Min Chen Jan-Christoph Deinert Carmen Gomez Carbonell Sergio O.valenzuela Laurens W.Molenkamp Tobias Kiessling Georgy v.Astakhov Sergey Kovalev Catalan Institute of Nanoscience and Nanotechnology(ICN2) BIST and CSICCampus UABBellaterraBarcelona 08193Spain Department of Applied Physics TU EindhovenDen Dolech 25612 AZ EindhovenThe Netherlands School of Physics and Astronomy University of ManchesterM139PL ManchesterUK Physikalisches Institut(EP3) Universitat WurzburgAm Hubland97074 WurzburgGermany Institute of Physics Polish Academy of ScienceAl.Lotnikow 32/46PL-02668 WarsawPoland Helmholtz Zentrum Dresden-Rossendorf Bautzner Landstr.40001328 DresdenGermany ICREA Pg.Lluis Companys 2308010 BarcelonaSpain Institute for Topological Insulators Am HublandD-97074 WurzburgGermany

Achieving effcient,high-power harmonic generation in the terahertz spectral domain has technological applications,for example,in sixth generation(6G)communication *** Dirac fermions possess extremely large terahertz nonlinear susceptibilities and harmonic conversion ***,the observed maximum generated harmonic power is limited,because of saturation effects at increasing incident powers,as shown recently for ***,we demonstrate room-temperature terahertz harmonic generation in a Bi_(2)Se_(3) topological insulator and topological-insulator-grating metamaterial structures with surface-selective terahertz field *** obtain a third-harmonic power approaching the miliwatt range for an incident power of 75 mW-an improvement by two orders of magnitude compared to a benchmarked graphene *** establish a framework in which this exceptional performance is the result of thermodynamic harmonic generation by the massless topological surface states,benefiting from ultrafast dissipation of electronic heat via surface-bulk Coulomb *** results are an important step towards on-chip terahertz(opto)electronic applications.

关键词： harmonic insulator incident

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