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SiC-based materials produced by explosive compaction of powders without sintering
Krokhalev Aleksandr,Kharlamov Valentin,Kuz’min Sergey,Lysak Vladimir 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.5
The explosive compaction technique achieves a considerably higher pressure compared to conventional powder metallurgy. This study demonstrates the fundamental possibility of obtaining SiC-based materials by explosive compaction without sintering. It has been determined that an increase in the compacting pressure from 12 to 16.5 GPa and a decrease in the titanium binder content from 50 to 20 vol.% are accompanied by a decrease in the compacted residual porosity of the material from 7 to 2%. In this case, the best compaction is achieved at a lower metal binder content. Microstructure analysis of the obtained materials showed that explosive compaction allows titanium particles to retain their size and form isolated inclusions in a continuous silicon carbide matrix. The initially splinter-shaped particles of the matrix transform, which ensures tight contact between them. To form strong boundaries between powder mix components at the explosive compaction stage, the loading modes should provide heating of the material during shock wave compression to above 780 °C. As a result, the hardness of the material containing 20 vol.% titanium reached 1300 HV. To retain the initial phase composition of silicon carbide and titanium powder mixtures during explosive compaction, the upper temperature limit should be 840 °C. The loading modes accompanied by heating to a higher temperature initiate a chemical interaction between the powder mix components.
Volodymyr Fedorovych Kryvetskyi,Pavlo Serhiiovych Lysak,Svitlana Hryhorivna Kaminska,Bohdan Oleksiiovych Mitiuk 대한흉부외과학회 2021 Journal of Chest Surgery (J Chest Surg) Vol.54 No.6
This study examined a rarely seen benign heart tumor that was found incidentally on a chest X-ray. Radiological images were taken of a 42-year-old patient with no symptoms of a heart condition, showing a thick-walled left lung cavity that appeared after prior inflam- mation and concomitant enlargement of the cardiac shadow. A large subepicardial lipoma in combination with a chronic abscess on the left lung was revealed on chest computed tomography. The treatment consisted of simultaneous surgical removal of both the lung and heart lesions using video-assisted thoracoscopic surgery.
Mustary, M.H.,Ryu, B.D.,Han, M.,Yang, J.H.,Lysak, V.V.,Hong, C.H. Wissenschaftliche Verlagsgesellschaft m. b. H 2016 Optik Vol.127 No.4
<P>Light enhancement of GaN based light emitting diodes (LEDs) has been investigated by texturing the top p-GaN surface. Nano-textured LEDs have been fabricated using self-assembled Ni nano mask during dry etching process. Experimental result was further compared with simulation data. Three types of LEDs were fabricated: Conventional (planar LED), surface nano-porous (porous LED) and surface nano-cluster (cluster LED). Compared to planar LED there were about 100% and 54% enhancement of light output power for porous and cluster LED respectively at an injection current of 20 mA. Moreover, simulation result showed consistency with experimental result. The increased probability of light scattering at the nano-textured GaN-air interface is the major reason for increasing the light extraction efficiency. (C) 2015 Elsevier GmbH. All rights reserved.</P>
Mustary, Mumta Hena,Ryu, Beo Deul,Han, Min,Yang, Jong Han,Lysak, Volodymyr V.,Hong, Chang-Hee The Institute of Electronics and Information Engin 2015 Journal of semiconductor technology and science Vol.15 No.4
Light enhancement of GaN based light emitting diodes (LEDs) have been investigated by texturing the top p-GaN surface. Nano-textured LEDs have been fabricated using self-assembled Ni nano mask during dry etching process. Experimental results were further compared with simulation data. Three types of LEDs were fabricated: Conventional (planar LED), Surface nano-porous (porous LED) and Surface nano-cluster (cluster LED). Compared to planar LED there were about 100% and 54% enhancement of light output power for porous and cluster LED respectively at an injection current of 20 mA. Moreover, simulation result showed consistency with experimental result. The increased probability of light scattering at the nano-textured GaN-air interface is the major reason for increasing the light extraction efficiency.
Mumta Hena Mustary,유버들,한민,양종한,Volodymyr V. Lysak,홍창희 대한전자공학회 2015 Journal of semiconductor technology and science Vol.15 No.4
Light enhancement of GaN based light emitting diodes (LEDs) have been investigated by texturing the top p-GaN surface. Nano-textured LEDs have been fabricated using self-assembled Ni nano mask during dry etching process. Experimental results were further compared with simulation data. Three types of LEDs were fabricated: Conventional (planar LED), Surface nano-porous (porous LED) and Surface nano-cluster (cluster LED). Compared to planar LED there were about 100% and 54% enhancement of light output power for porous and cluster LED respectively at an injection current of 20 mA. Moreover, simulation result showed consistency with experimental result. The increased probability of light scattering at the nano-textured GaN-air interface is the major reason for increasing the light extraction efficiency.
Sudhagar, P.,Devadoss, Anitha,Song, Taeseup,Lakshmipathiraj, P.,Han, Hyungkyu,Lysak, Volodymyr V.,Terashima, C.,Nakata, Kazuya,Fujishima, A.,Paik, Ungyu,Kang, Yong Soo The Royal Society of Chemistry 2014 Physical chemistry chemical physics Vol.16 No.33
<P>We demonstrate one-step gold nanoparticle (AuNP) coating and the surface nitridation of TiO<SUB>2</SUB> nanowires (TiO<SUB>2</SUB>-NWs) to amplify visible-light photon reflection. The surface nitridation of TiO<SUB>2</SUB>-NW arrays maximizes the anchoring of AuNPs, and the subsequent reduction of the band gap energy from 3.26 eV to 2.69 eV affords visible-light activity. The finite-difference time-domain (FDTD) simulation method clearly exhibits the enhancement in the strengths of localized electric fields between AuNPs and the nanowires, which significantly improves the photocatalytic (PC) performance. Both nitridation and AuNP decoration of TiO<SUB>2</SUB>-NWs result in beneficial effects of high (e<SUP>−</SUP>/h<SUP>+</SUP>) pair separation through healing of the oxygen vacancies. The combined effect of harvesting visible-light photons and reducing recombination in Au/N-doped TiO<SUB>2</SUB>-NWs promotes the photocatalytic activity towards degradation of methyl orange to an unprecedented level, ∼4 fold (1.1 × 10<SUP>−2</SUP> min) more than does TiO<SUB>2</SUB>-NWs (2.9 × 10<SUP>−3</SUP> min<SUP>−1</SUP>). The proposed AuNP decoration of nitridated TiO<SUB>2</SUB>-NW surfaces can be applied to a wide range of n-type metal oxides for photoanodes in photocatalytic applications.</P> <P>Graphic Abstract</P><P>Maximizing the Au nanoparticle decoration on TiO<SUB>2</SUB> nanowire through nitrogen doping for simultaneous enhancement in visible light scattering and electron–hole charge separation. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cp02009j'> </P>
Sudhagar, P.,Song, Taeseup,Devadoss, Anitha,Lee, Jung Woo,Haro, Marta,Terashima, Chiaki,Lysak, Volodymyr V.,Bisquert, Juan,Fujishima, Akira,Gimenez, Sixto,Paik, Ungyu The Royal Society of Chemistry 2015 Physical chemistry chemical physics Vol.17 No.29
<P>The interaction strength of Au nanoparticles with pristine and nitrogen doped TiO<SUB>2</SUB> nanowire surfaces was analysed using density functional theory and their significance in enhancing the solar driven photoelectrocatalytic properties was elucidated. In this article, we prepared 4-dimethylaminopyridine capped Au nanoparticle decorated TiO<SUB>2</SUB> nanowire systems. The density functional theory calculations show {101} facets of TiO<SUB>2</SUB> as the preferred phase for dimethylaminopyridine–Au nanoparticles anchoring with a binding energy of −8.282 kcal mol<SUP>−1</SUP>. Besides, the interaction strength of Au nanoparticles was enhanced nearly four-fold (−35.559 kcal mol<SUP>−1</SUP>) at {101} facets <I>via</I> nitrogen doping, which indeed amplified the Au nanoparticle density on nitrided TiO<SUB>2</SUB>. The Au coated nitrogen doped TiO<SUB>2</SUB> (N–TiO<SUB>2</SUB>–Au) hybrid electrodes show higher absorbance owing to the light scattering effect of Au nanoparticles. In addition, N–TiO<SUB>2</SUB>–Au hybrid electrodes block the charge leakage from the electrode to the electrolyte and thus reduce the charge recombination at the electrode/electrolyte interface. Despite the beneficial band narrowing effect of nitrogen in TiO<SUB>2</SUB> on the electrochemical and visible light activity in N–TiO<SUB>2</SUB>–Au hybrid electrodes, it results in low photocurrent generation at higher Au NP loading (3.4 × 10<SUP>−7</SUP> M) due to light blocking the N–TiO<SUB>2</SUB> surface. Strikingly, even with a ten-fold lower Au NP loading (0.34 × 10<SUP>−7</SUP> M), the synergistic effects of nitrogen doping and Au NPs on the N–TiO<SUB>2</SUB>–Au hybrid system yield high photocurrent compared to TiO<SUB>2</SUB> and TiO<SUB>2</SUB>–Au electrodes. As a result, the N–TiO<SUB>2</SUB>–Au electrode produces nearly 270 μmol h<SUP>−1</SUP> cm<SUP>−2</SUP> hydrogen, which is nearly two-fold higher than the pristine TiO<SUB>2</SUB> counterpart. The implications of these findings for the design of efficient hybrid photoelectrocatalytic electrodes are discussed.</P> <P>Graphic Abstract</P><P>The interaction strength of Au nanoparticles with pristine and nitrogen doped TiO<SUB>2</SUB> nanowire surfaces was analysed using density functional theory and their significance in enhancing the solar driven photoelectrocatalytic properties was elucidated. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5cp01175b'> </P>
Air-gap embedding GaN template for enhanced emission from light-emitting diodes
Y.S. Katharria,박영재,Jae Hyoung Ryu,Kang Bok Ko,유버들,V.V. Lysak,Chang-Hee Hong 한국물리학회 2013 Current Applied Physics Vol.13 No.9
Selective growth by metal-organic chemical vapor deposition (MOCVD), and electrochemical etching of aheavily Si-doped GaN (n+-GaN) interlayer were employed to obtain air-gaps embedded in a u-GaN layer. As confirmed by Raman spectroscopy, the introduction of an nþ-GaN, which was later etched to obtainair-gaps, also enhanced the strain-compliance of GaN epilayer on sapphire substrate. An enhancedelectroluminescence emission was observed from the light-emitting diodes (LEDs) fabricated on the airgapembedding template. Using theoretical LED simulation, it was discerned that the increase in opticalemission from the LED was caused predominantly by the redirection of photons at GaN/air-gap interface. Finite-difference time domain (FDTD) simulation method was employed to understand the mechanismof optical emission enhancement and its spatial variation over the LED surface.