Electronic and steric effects controlling efficiencies of photoaddition reactions of fullerene C₆₀ with N-α-trimethylsilyl-N-alkyl-N-benzylamines

Jeong, H.C.,Lim, S.H.,Sohn, Y.,Kim, Y.I.,Jang, H.,Cho, D.W.,Mariano, P.S. Pergamon Press ; Elsevier Science Ltd 2017 Tetrahedron letters: the international organ for t Vol.58 No.10

Single electron transfer (SET)-promoted photoaddition reactions between fullerene C<SUB>60</SUB> and both various alkyl (Me, Et, i-Pr, t-Bu)- and para-substituted (p-Me, p-OMe, p-F, p-CF<SUB>3</SUB>) arene ring containing, N-α-trimethylsilyl-N-alkyl-N-benzylamines were explored to gain information about photoproduct profiles and how the electronic and steric nature of the amine substrates influence reaction efficiencies. The results show that visible light (λ>540nm) irradiation of 10% EtOH-toluene solutions containing C<SUB>60</SUB> and N-α-trimethylsilyl-N-alkyl-N-benzylamines produce 1-aminomethyl-1,2-dihydrofullerenes as a sole photoproduct. In addition, SET-promoted photoaddition reactions of unsubstituted and para-electron donating group substituted arene ring containing N-α-trimethylsilyl-N-alkyl-N-benzylamines take place to give photoproducts more efficiently than those containing para-electron withdrawing group substituted arene rings. Moreover, although steric factors are less significant than the electronic nature of the amine substrates in governing reaction efficiencies, sterics do play a significant role in photoreactions of electron deficient amine substrates.

Si₃N₄/Ti와 Si₃N₄/TiAl합금의 계면반응 및 확산 거동

최광수,김선진,이지은,박준식,이종원,Choi, Kwang Su,Kim, Sun Jin,Lee, Ji Eun,Park, Joon Sik,Lee, Jong Won 한국재료학회 2017 한국재료학회지 Vol.27 No.11

$Si_3N_4$와 Ti 또는 TiAl 합금을 $900^{\circ}C$에서 확산쌍을 제조하여 분석하고, 확산층의 분석을 통하여 생성된 층마다의 조성을 분석하여 각 원소들의 확산 경로 및 속도를 비교 하였다. $Si_3N_4/Ti$의 확산 쌍의 확산 경로는 $Si_3N_4/Ti_5Si_3+TiN/TiN/Ti$로 나타났고, Ti 측면에서 TiN층이 생성 되었음으로 N의 확산 속도가 Si 보다 빠름을 알 수 있었다. $Si_3N_4/TiAl$ 합금의 확산쌍은 $Si_3N_4/Ti$ 사이의 확산쌍과는 다르게 Si, N, Ti, Al 의 각 원소 마다의 확산 속도 차이로 인하여 확산 경로는 $Si_3N_4/TiN(Al)/Ti_3Al/TiAl$ 상으로 나타났다. 상태도를 통하여 생성된 확산쌍의 확산경로를 파악한 결과, 확산경로의 요구사항을 모두 만족하였다. $Si_3N_4/Ti$ 확산에서 Ti를 이용한 적분확산 계수는 $Ti_5Si_3$, TiN에서 $2.18{\times}10^{-16}m^2/sec$, $2.19{\times}10^{-16}m^2/sec$, $Si_3N_4/TiAl$ 확산 쌍에서 Ti를 이용한 적분확산 계수는 각각 TiN(Al) 상에서 $2.88{\times}10^{-16}m^2/sec$, $Ti_3Al$ 상에서 $1.48{\times}10^{-15}m^2/sec$으로 나타났다. 본 연구는 $Si_3N_4$와 Ti 및 TiAl의 계면 반응을 분석한 결과로서 $Si_3N_4$ 상을 이용한 확산반응의 기초자료로 사용될 수 있을 것으로 사료된다. $Si_3N_4$ is a ceramic material attracting attention in many fields because of its excellent abrasion resistance. In addition, Ti and TiAl alloys are metals used in a variety of high temperature environments, and have attracted much attention because of their high strength and high melting points. Therefore, study of the interface reaction between $Si_3N_4/Ti$ and $Si_3N_4/TiAl$ can be a useful practice to identify phase selection and diffusion control. In this study, $Si_3N_4/Ti_5Si_3+TiN/TiN/Ti$ diffusing pairs were formed in the $Si_3N_4/Ti$ interfacial reaction and $Si_3N_4/TiN(Al)/Ti_3Al/TiAl$ diffusion pathway was identified in the $Si_3N_4/TiAl$ interfacial reaction. The diffusion layers of the interface reactions were identified and, to investigate the kinetics of the diffusion layer, the integrated diffusion coefficients were estimated.

Measurement of isomeric yield ratios of ^{86<i>m</i>,<i>g</i>}Y and ^{87<i>m</i>,<i>g</i>}Y in the quasi-monoenergetic neutron induced reactions of ⁸⁹Y

Nadeem, Muhammad,Zaman, Muhammad,Naik, Haladhara,Kim, Kwangsoo,Kim, Guinyun Elsevier 2018 Nuclear physics. A Vol.970 No.-

<P><B>Abstract</B></P> <P>The isomeric yield ratios (IR) of <SUP>86<I>m</I>,<I>g</I> </SUP>Y and <SUP>87<I>m</I>,<I>g</I> </SUP>Y were measured in the 23 to 37 MeV quasi-monoenergetic neutron induced reaction of <SUP>89</SUP>Y by using an off-line <I>γ</I>-ray spectrometric technique. The IR values in the <SUP>89</SUP>Y( n , x n ) reactions were also calculated using the TALYS 1.8 code and found to be in good agreement for <SUP>87<I>m</I>,<I>g</I> </SUP>Y but slightly less for <SUP>86<I>m</I>,<I>g</I> </SUP>Y. The IR values of <SUP>86<I>m</I>,<I>g</I> </SUP>Y and <SUP>87<I>m</I>,<I>g</I> </SUP>Y from the present work in the <SUP>89</SUP>Y( n , x n ) reactions were compared with the literature data in the <SUP>89</SUP>Y( γ , x n ), <SUP>89</SUP>Y( p , x ) and <SUP>89</SUP>Y( α , x ) reactions. It was found that the IR values of <SUP>86<I>m</I>,<I>g</I> </SUP>Y and <SUP>87<I>m</I>,<I>g</I> </SUP>Y in all these reactions increase with excitation energy. At the same excitation energy, the IR values are higher in the alpha induced reaction than in the proton, neutron and photon induced reactions due to higher input angular momentum in the former than in the later. These two observations indicate the role of entrance parameters. However, it is surprising to see that at the same excitation energy, the IR values of <SUP>86<I>m</I>,<I>g</I> </SUP>Y and <SUP>87<I>m</I>,<I>g</I> </SUP>Y in the <SUP>89</SUP>Y( n , x n ) reaction are nearly constant and significantly higher than in the <SUP>89</SUP>Y( γ , x n ) reaction.</P>

Pt-Sn/θ-Al₂O₃촉매상에서 반응조건에 따른 n-부탄의 탈수소화 반응

조경호(Kyung Ho Cho),강성은(Seong-Eun Kang),박정현(Jung-Hyun Park),조준희(Jun Hee Cho),신채호(Chae-Ho Shin) 한국청정기술학회 2012 청정기술 Vol.18 No.2

Theoretical study on the hydrolysis mechanism of N,N-dimethyl-N′-(2-oxo-1, 2-dihydro-pyrimidinyl)formamidine: Water-assisted mechanism and cluster-continuum model

Wu, Yong,Jin, Lu,Xue, Ying,Xie, Dai Qian,Kim, Chan Kyung,Guo, Yong,Yan, Guo Sen Wiley Subscription Services, Inc., A Wiley Company 2008 Journal of computational chemistry Vol.29 No.8

<P>The hydrolysis reaction of N,N-dimethyl-N′-(2-oxo-1, 2-dihydro-pyrimidinyl)formamidine (DMPFA), a model compound of the antivirus drug amidine-3TC (3TC = 2′, 3′-dideoxy-3′-thiacytidine), is investigated by the hybrid density functional theory B3LYP/6-31+G (d,p) method. The hydrolysis reaction of the title compound is predicted to undergo via two pathways, each of which is a stepwise process. Path A is the addition of H<SUB>2</SUB>O to the C&n.dbond;N double bond in the amidine group to form a tetrahedral structure in its first step, and then the transfer of the H atom of hydroxyl leads to the corresponding products via four possible channels. Path B simultaneously involves the nucleophilic attack of H<SUB>2</SUB>O to the C atom of the C&n.dbond;N bond and the proton transfer to the N atom of amino group leading to the cleavage of the C&n.bond;N single bond in the amidine group. The results indicate that path A is more favorable than path B in the gas phase. Moreover, to simulate the title reaction in aqueous solution, water-assisted mechanism and the cluster-continuum model, based on the SCRF/CPCM model, are taken into account in our work. The results indicate that it is rational for two water molecules served as a bridge to assist in the first step of path A and that cytosine rather than the cytosine-substituted formamide should be released from the tetrahedral intermediate via s six-membered cycle transition state (channel 2). Our calculations exhibit that the process toward the tetrahedral intermediate is the rate-determining step both in the gas phase and in aqueous solution. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008</P> <B>Graphic Abstract</B> <P> <img src='wiley_img/01928651-2008-29-8-JCC20883-gra001.gif' alt='wiley_img/01928651-2008-29-8-JCC20883-gra001'> </P>

Measurement of (n,xnγ) Reactions of Interest for the New Nuclear Reactors

J. C. Thiry,C. Borcea,P. Dessagne,J. C. Drohe,E. Jericha,H. Karam,M. Kerveno,A. J. Koning,A. Negret,A. Pavlik,A. Plompen,C. Rouki,G. Rudolf,M. Stanoiu 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

The design of Generation IV nuclear reactors and the research of new fuel cycles require knowledge of the cross sections of different nuclear reactions. Our research is focused on cross section measurements of (n,xnγ) reactions occurring in these new reactors. The aim is to measure unknown cross sections and to reduce the uncertainty on present data relative to reactions and isotopes present in transmutation or regeneration processes. The current work consists of studying ^(232)Th(n,n'γ) and ^(235)U(n,xnγ) reactions in the fast neutron energy domain (up to 20 MeV). The experiments are performed at the GEel LINear Accelerator (GELINA) which delivers a pulsed, white neutron beam at IRMM, Belgium. The time characteristics of the beam enable us to measure neutron energies with the time of flight (TOF) technique. The neutron induced reactions (in this case inelastic scattering and (n,2n) reactions) are identified by online prompt γ spectroscopy with an experimental setup including 4 HPGe detectors. A double layered fission chamber is used to monitor the incident neutron flux. The experimental setup and analysis methods will be presented and a comparison between the obtained cross sections and the TALYS predictions will be discussed. This work is a first step in the preparation of the measurement of ^(233)U(n,xnγ) reactions, which are completely unknown at this stage although of very high importance in the ^(232)Th regeneration process.

Green synthesized N-doped graphitic carbon sheets coated carbon cloth as efficient metal free electrocatalyst for hydrogen evolution reaction

Jebakumar Immanuel Edison, Thomas Nesakumar,Atchudan, Raji,Karthik, Namachivayam,Lee, Yong Rok Elsevier 2017 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.42 No.21

<P><B>Abstract</B></P> <P>Heteroatom doped carbon structures received a great attention owing to its applications in catalysis, energy and optics. In this work, a simple hydrothermal approach for the synthesis of nitrogen doped graphitic carbon sheets (N-GCSs) is reported. <I>Rubus parvifolius</I> (<I>R. parvifolius</I>) fruit juice and aqueous ammonia are used as carbon precursor and nitrogen dopant, respectively. The synthesized N-GCSs are characterized using Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, high resolution transmission electron microscopy (HR-TEM) and field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectrum (EDS). The presence of hydroxyl and carbonyl functionalities in the synthesized N-GCSs are confirmed by the FT-IR analysis. The doping of nitrogen in N-GCSs is revealed through the XPS spectrum. The XRD and Raman studies imply that the synthesized N-GCSs are moderate graphitic nature. The FE-SEM and HR-TEM images of N-GCSs exposed its sheet like porous morphology. The electrocatalytic activity of N-GCSs coated carbon cloth (N-GCSs/CC) are examined towards hydrogen evolution reaction (HER) in 0.50 M H<SUB>2</SUB>SO<SUB>4</SUB> using linear sweep voltammetry (LSV), Tafel and electrochemical impedance spectroscopy (EIS) studies. The onset potential of synthesized N-GCSs/CC is about −0.25 V<SUB>RHE</SUB>, which is lower than that of bare carbon cloth (CC) −0.75 V<SUB>RHE</SUB>. The Tafel slope of N-GCSs/CC is smaller (198 mV dec<SUP>−1</SUP>) than that of bare CC (253 mV dec<SUP>−1</SUP>), suggested fast kinetics of N-GCSs. Moreover, the N-GCSs/CC is attained −10 mA cm<SUP>−2</SUP> of current density at very low over potential of −0.320 V<SUB>RHE</SUB>. The EIS studies also proved the excellent catalytic activity of N-GCSs/CC towards HER. Thus, the <I>R. parvifolius</I> derived N-GCSs is a better candidate for HER in acidic medium.</P> <P><B>Highlights</B></P> <P> <UL> <LI> N-doped graphitic carbon sheets (N-GCSs) were prepared by <I>Rubus parvifolius</I> fruit. </LI> <LI> N-GCSs coated carbon cloth (CC) shows good electrocatalytic activity towards HER. </LI> <LI> The onset potential of N-GCSs/CC is about −0.25 V<SUB>RHE</SUB>. </LI> <LI> Tafel slope of N-GCSs/CC is smaller (198 mV dec<SUP>−1</SUP>) than bare CC. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

규소 고분자 복합체를 이용한 반응소결 질화규소

홍성진,안효창,김득중,Hong, Sung-Jin,Ahn, Hyo-Chang,Kim, Deug-Joong 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.6

Reaction-bonded $Si_3N_4$ has cost-reduction merit because inexpensive silicon powder was used as a start material. But its density was not so high enough to be used for structural materials. So the sintered reaction-bonded $Si_3N_4$techniques were developed to solve the low density problem. In this study the sintered reaction-bonded $Si_3N_4$ manufacturing method by using polymer precursor which recently attained significant interest owing to the good shaping and processing ability was proposed. The formations, properties of reaction-bonded $Si_3N_4$ from silicon and polysilazane mixture were investigated. High density reaction-bonded $Si_3N_4$ was manufactured from silicon and silicon-containing preceramic polymers and post-sintering technique. The mixtures of silicon powder and polysilazane were prepared and reaction sintered in $N_2$ atmosphere at $1350^{\circ}C$ and post-sintered at 1600~$1950^{\circ}C$. Density and phase were analyzed and correlated to the resulting material properties.

MMO 촉매 하에서 N₂O 분해에 대한 메탄 SCR 반응 및 CO 생성 효과의 비교 연구

박선주,박용성,Park, Sun Joo,Park, Yong Sung 한국공업화학회 2008 공업화학 Vol.19 No.6

Nitrous oxide ($N_2O$), known as one of the major greenhouse gases, is an important component of the earth's atmosphere, and gives rise to precursor of acid rain and photochemical smog. For the removal of $N_2O$ and other nitrogen oxides, the SCR reaction system with various reductants is widely used. This study is based on the results of experimental and theoretical examinations on the catalytic decomposition of sole nitrous oxide ($N_2O$) and selective catalytic reduction of $N_2O$ with $CH_4$ in the presence of oxygen using mixed metal oxide catalysts obtained from hydrolatcite-type precursors. When $CH_4$ is fed together with a reductant, it affects positively on the $N_2O$ decomposition activity. At an optimum ratio of $CH_4$ to $O_2$ mole ratio, the $N_2O$ conversion activity is enhanced on the SCR reaction with partial oxidation of methane. $N_2O$는 주요 온실가스 성분의 하나로서 광화학 스모그의 유발, 산성비의 전구체 등 온실효과에 상당한 기여를 하고 있는 물질이다. 이러한 $N_2O$ 및 질소산화물을 제거하기 위하여 환원제를 이용한 Selective Catalytic Reduction (SCR) 반응 공정이 널리 사용되고 있다. 본 연구에서는 Hydrotalcite 형태의 전구체로부터 Mixed Metal Oxide 촉매를 제조하고 그를 사용하여 $N_2O$ 분해를 위한 메탄 SCR 반응 및 CO의 생성효과를 비교 연구하였다. 실험결과 $CH_4$ 환원제의 첨가는 $N_2O$의 분해 반응에 긍정적인 영향을 미치며, 최적화된 $O_2/CH_4$ 비율의 조건에서 메탄의 부분산화에 의한 SCR 반응이 가장 높은 효율을 나타내는 것을 확인할 수 있었다.

총설 : 화력발전소용 V2O5/TiO2계 촉매상에서 NH3-SCR 탈질반응으로부터의 N2O 생성

김문현 ( Moon Hyeon Kim ) 한국화학공학회 2013 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.51 No.2

Selective catalytic reduction of NOx by NH3 (NH3-SCR) over V2O5/TiO2-based catalysts is recently reported to be an anthropogenic emitter of N2O that is a global warming gas with a global warming potential of 310. Therefore, this review will get a touch on significance of some parameters regarding N2O formation in the deNOxing reaction for fossil fuels-fired power plants applications. The N2O production in NH3-SCR reaction with such catalysts occurs via side reactions between NOx and NH3 in addition to NH3 oxidation, and the extent of these undesired reactions depends strongly on the loadings of V2O5 as a primary active component and the promoter as a secondary one (WO3 and MoO3) in the SCR catalysts, the feed and operating variables such as reaction temperature, NO2/NOx ratio, oxygen concentration, gas hourly space velocity, water content and thermal excursion, and the physical and chemical histories of the catalysts on site. Although all these parameters are associated with the N2O formation in deNOxing reaction, details of some of them have been discussed and a better way of suppressing the N2O production in commercial SCR plants has been proposed.