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XAS and XMCD studies of amorphous FeCo-based ribbons
Gautam, S.,Kane, S.N.,Park, B.-G.,Kim, J.-Y.,Varga, L.K.,Song, J.-H.,Chae, K.H. North-Holland 2011 Journal of non-crystalline solids Vol.357 No.11
This paper reports x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) studies at Fe L<SUB>3,2</SUB> and Co L<SUB>3,2</SUB>-edges to investigate the electronic structure of (Fe<SUB>100-x</SUB>Co<SUB>x</SUB>)<SUB>78</SUB>Si<SUB>9</SUB>Nb<SUB>3</SUB>B<SUB>9</SUB>Cu<SUB>1</SUB> (0<x<95) alloys. The influence of controlled Co addition on electronic structural and magnetic properties of (Fe<SUB>100-x</SUB>Co<SUB>x</SUB>)<SUB>78</SUB>Si<SUB>9</SUB>Nb<SUB>3</SUB>B<SUB>9</SUB>Cu<SUB>1</SUB> (x=0, 20, 40, and 60) alloys has been investigated and it has been observed that Co exists as Co<SUP>2+</SUP>/Co<SUP>3+</SUP>, while Fe exists as a mixture of Fe<SUP>0</SUP> (metallic) and Fe<SUP>2+</SUP>. The XMCD studies confirm these results and reveal that Co-ions are responsible for the room temperature ferromagnetism (RTFM) in the system, while at Fe L<SUB>3,2</SUB>-edge it shows a diamagnetic behavior.
Photoluminescence and photo-redox reactions of poly(2-methoxyaniline-5-sulfonic acid)
L.A.P. Kane-Maguire,Kane-Maguire,J. A. Causley,G. G. Wallace 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
The water-soluble fully sulfonated polyaniline, poly(2-methoxyaniline-5-sulfonic acid) has been found to photoluminesce in itsemeraldine oxidation state, ES(PMAS). Excitation of aqueous solutions at 450530 nm, near its characteristic absorption band at473 nm, led to emission at ca. 600 nm (2.1 eV). Calculations incorporating cyclic voltammetric data for ground state PMAS suggestthat the photo-generated ES.(PMAS) excited state should be both a very powerful oxidising agent and a strong reducing agent (ca.2.7 and 1.1 V of oxidising and reducing power, respectively). This prediction has been conrmed from photolysis studies ofES(PMAS) in the presence of the potentially reducible cobalt(III) cations CoCl(NH3)2þ5 , Co(H2O)(NH3)3þ5 and Co(en)3þ3 . In water,photo-oxidation of the ES(PMAS) to its fully oxidised pernigraniline base PB(PMAS) form was conrmed by UVvisible spec-troscopy. In the case ofK-Co(en)3þ3 as the acceptor, strong support for the concomitant reduction of the Co(III) complex to thecorresponding Co(II) species was obtained from its observed racemisation. Relatively low quantum eciencies (<3%) wereestablished for these novel, photo-initiated redox reactions. These photo-redox reactions were preceded by a photo-initiated con-formational change in the ES(PMAS) polymer from an ‘‘extended coil’’ to a ‘‘compact coil’’ conformation. The presence of addedNaþ and NHþ4 ions had a marked inuence on the nature of the photo-reactions, with Naþ ions retarding the photo-assistedelectron transfer, while NHþ4 ions prevented the initial conformational change in the ES(PMAS).
S. N. Kane,S. S. Khinchi,Zs. Gercsi,A. Gupta,L. K. Varga,F. Mazaleyrat,Y. H. Jeong 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6
The structural and the magnetic properties of Fe58Co25Nb7Cu1B9 (M83) and Fe60Co25Nb6Cu1B8 (M85) alloys have been studied using differential scanning calorimetery (DSC), X-ray diffraction (XRD), transmission Mossbauer spectroscopy, and magnetic measurements. Thefirst crystallization peak temperatures (TX1) of the as-cast alloys M83 and M85 are 443 and 426 ℃ respectively, showing that a slight variation in composition reduces the stability of the alloy against crystallization. Mossbauer and XRD measurements reveal that crystallization of the specimens starts after annealing at 370 ℃, exhibiting the coexistence of a bcc crystalline phase and a residual amorphous matrix. Nanocrystallization leads to the formation of a bcc Fe-Co nanocrystalline phase consisting of 10 % Co and average grain diameters ranging between 10 The structural and the magnetic properties of Fe58Co25Nb7Cu1B9 (M83) and Fe60Co25Nb6Cu1B8 (M85) alloys have been studied using differential scanning calorimetery (DSC), X-ray diffraction (XRD), transmission Mossbauer spectroscopy, and magnetic measurements. Thefirst crystallization peak temperatures (TX1) of the as-cast alloys M83 and M85 are 443 and 426 ℃ respectively, showing that a slight variation in composition reduces the stability of the alloy against crystallization. Mossbauer and XRD measurements reveal that crystallization of the specimens starts after annealing at 370 ℃, exhibiting the coexistence of a bcc crystalline phase and a residual amorphous matrix. Nanocrystallization leads to the formation of a bcc Fe-Co nanocrystalline phase consisting of 10 % Co and average grain diameters ranging between 10
S. N. Kane,Zs. Gercsi,F. Mazaleyrat,L. K. Varga,M. Coisson,,F. Vinai,F. Celegato,Y. H. Jeong 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6
The effect of Co addition and thermal treatments on the magnetic properties and the corresponding changes occurring in the nanostructure and magnetoimpedance in (Fe100−xCox)78Si9Nb3B9Cu1 with x = 0, 20, 40, 60, 70, 75, 80, 85, 90, 95 are reported. Results show that variation in the Co content affects the stability of the alloy against crystallization and that the specimen with x = 40 exhibits highest stability against crystallization. The volume fraction of the nanograins varies between 42 to 62 % and the corresponding grain diameter ranges between 9 to 13 nm. Obtained lattice parameter values suggest that the studied samples consist of bcc Co-Fe phase with Si impurities, with Co contents ranging between 50 to 74 % and Si contents ranging between 7 to 25 %. In the studied alloys, especially above x = 70, there is a tendency to form and to stabilize a Co70Fe30- like phase. The coercive force for as-cast specimens practically does not change with increasing Co content whereas the samples annealed with and without a magnetic field exhibit appreciable changes and display similar behaviours. The coercive field is systematically lower for field-annealed samples and the abrupt increase in the coercive field for alloys with x = 70 and above is attributed to the formation of a magnetically harder Co70Fe30-like phase (as compared to the Fe80Si20 phase), which were confirmed by a decrease in the lattice parameter. The maximum values of the obtained induced anisotropy constant and the anisotropy field are, respectively, 750 J/㎥ and ~ 1250 A/m. The magnetoimpedance maximum response of the studied samples remains almost constant as a function of Co concentration for the three kinds of samples (as-cast and annealed with and without a field). However, a threefold increase in the linear range is observed for the transverse-field-annealed samples, which should increase the dynamic range of field sensors based on these new materials. The effect of Co addition and thermal treatments on the magnetic properties and the corresponding changes occurring in the nanostructure and magnetoimpedance in (Fe100−xCox)78Si9Nb3B9Cu1 with x = 0, 20, 40, 60, 70, 75, 80, 85, 90, 95 are reported. Results show that variation in the Co content affects the stability of the alloy against crystallization and that the specimen with x = 40 exhibits highest stability against crystallization. The volume fraction of the nanograins varies between 42 to 62 % and the corresponding grain diameter ranges between 9 to 13 nm. Obtained lattice parameter values suggest that the studied samples consist of bcc Co-Fe phase with Si impurities, with Co contents ranging between 50 to 74 % and Si contents ranging between 7 to 25 %. In the studied alloys, especially above x = 70, there is a tendency to form and to stabilize a Co70Fe30- like phase. The coercive force for as-cast specimens practically does not change with increasing Co content whereas the samples annealed with and without a magnetic field exhibit appreciable changes and display similar behaviours. The coercive field is systematically lower for field-annealed samples and the abrupt increase in the coercive field for alloys with x = 70 and above is attributed to the formation of a magnetically harder Co70Fe30-like phase (as compared to the Fe80Si20 phase), which were confirmed by a decrease in the lattice parameter. The maximum values of the obtained induced anisotropy constant and the anisotropy field are, respectively, 750 J/㎥ and ~ 1250 A/m. The magnetoimpedance maximum response of the studied samples remains almost constant as a function of Co concentration for the three kinds of samples (as-cast and annealed with and without a field). However, a threefold increase in the linear range is observed for the transverse-field-annealed samples, which should increase the dynamic range of field sensors based on these new materials.
Additive Manufacturing of Metallic Materials: A Review
Zhang, Y.,Wu, L.,Guo, X.,Kane, S.,Deng, Y.,Jung, Y. G.,Lee, J. H.,Zhang, J. Springer Science + Business Media 2018 Journal of materials engineering and performance Vol.27 No.1
<P>In this review article, the latest developments of the four most common additive manufacturing methods for metallic materials are reviewed, including powder bed fusion, direct energy deposition, binder jetting, and sheet lamination. In addition to the process principles, the microstructures and mechanical properties of AM-fabricated parts are comprehensively compared and evaluated. Finally, several future research directions are suggested.</P>
Wallpaper fermions and the nonsymmorphic Dirac insulator
Wieder, Benjamin J.,Bradlyn, Barry,Wang, Zhijun,Cano, Jennifer,Kim, Youngkuk,Kim, Hyeong-Seok D.,Rappe, Andrew M.,Kane, C. L.,Bernevig, B. Andrei American Association for the Advancement of Scienc 2018 Science Vol.361 No.6399
<P>Materials whose gapless surface states are protected by crystal symmetries include mirror topological crystalline insulators and nonsymmorphic hourglass insulators. There exists only a very limited set of possible surface crystal symmetries, captured by the 17 'wallpaper groups.' Here we show that a consideration of symmetry-allowed band degeneracies in the wallpaper groups can be used to understand previously described topological crystalline insulators and to predict phenomenologically distinct examples. In particular, the two wallpaper groups with multiple glide lines, pgg and p4g, allow for a topological insulating phase whose surface spectrum consists of only a single, fourfolddegenerate, true Dirac fermion, representing an exception to a symmetry-enhanced fermion-doubling theorem. We theoretically predict the presence of this phase in Sr2Pb3 in space group 127 (P4/mbm).</P>