X-ray determination of electron-density distributions in oxides, MgO, MnO, CoO, and NiO, and atomic scattering factors of their constituent atoms.

Sasaki, Satoshi; Fujino, Kiyoshi; Takéuchi, Yoshio

doi:10.2183/pjab.55.43

Cited by 358 publications

(194 citation statements)

References 2 publications

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“…For the calcined catalyst, nickel was coordinated by 6 oxygen atoms at 2.06 Å, and the second coordination shell was composed of 8.6 ± 0.9 nickel atoms at 2.96 Å. This local order was similar to NiO as expected; however, the number of nickel atoms at the second coordination shell was lower than that for NiO (12 nickel atoms 64 ), which indicates a small particle size of the NiO-like structure after calcination. The local chemical environment of the reduced catalyst was similar to a metallic nickel phase; nevertheless, the refined 9.2 ± 1.0 coordination number of the first shell showed that the reduced phase of the catalyst was structured as small particles.…”

Section: Xas Analysis Of Poisoned Catalystssupporting

confidence: 58%

Stability and resistance of nickel catalysts for hydrodeoxygenation: carbon deposition and effects of sulfur, potassium, and chlorine in the feed

Mortensen

Gardini

Carvalho

et al. 2014

Catal. Sci. Technol.

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aThe long term stability and resistance toward carbon deposition, sulfur, chlorine, and potassium of Ni/ZrO 2 as a catalyst for the hydrodeoxygenation (HDO) of guaiacol in 1-octanol (as a model compound system for bio-oil) has been investigated at 250°C and 100 bar in a trickle bed reactor setup. Without impurities in the feed good stability of the Ni/ZrO 2 catalyst could be achieved over more than 100 h of operation, particularly for a sample prepared with small Ni particles, which minimized carbon deposition.Exposing the catalyst to 0.05 wt% sulfur in the feed resulted in rapid deactivation with complete loss of activity due to the formation of nickel sulfide. Exposing Ni/ZrO 2 to chlorine-containing compounds (at a concentration of 0.05 wt% Cl) on-stream led to a steady decrease in activity over 40 h of exposure.Removal of the chlorine species from the feed led to the regaining of activity. Analysis of the spent catalyst revealed that the adsorption of chlorine on the catalyst was completely reversible, but chlorine had caused sintering of nickel particles. In two experiments, potassium, as either KCl or KNO 3 , was impregnated on the catalyst prior to testing. In both cases deactivation was persistent over more than 20 h of testing and severely decreased the deoxygenation activity while the hydrogenation of guaiacol was unaffected. Overall, sulfur was found to be the worst poison, followed by potassium and then chlorine. Thus, removal/limitation of these species from bio-oil is a requirement before long term operation can be achieved with this catalyst.

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Section: Xas Analysis Of Poisoned Catalystssupporting

confidence: 58%

Stability and resistance of nickel catalysts for hydrodeoxygenation: carbon deposition and effects of sulfur, potassium, and chlorine in the feed

Mortensen

Gardini

Carvalho

et al. 2014

Catal. Sci. Technol.

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“…The value of the cell parameter obtained for both S2 and S3 was 4.18(1) Å, very close to the reported value for bulk NiO (a bulk NiO = 4.178 Å). 59 On the other hand, a XRD was found to be 4.22(1) Å in the smallest NPs (S1). The lattice expansion experienced by the NPs of 2.5 nm and its effect on the interatomic distances will be further explored by means of EXAFS measurements.…”

Section: Resultsmentioning

confidence: 97%

Interplay between microstructure and magnetism in NiO nanoparticles: breakdown of the antiferromagnetic order

et al. 2014

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The possibility of tuning the magnetic behaviour of nanostructured 3d transition metal oxides has opened up the path for extensive research activity in the nanoscale world. In this work we report on how the antiferromagnetism of a bulk material can be broken when reducing its size under a given threshold. We combined X-ray diffraction, high-resolution transmission electron microscopy, extended X-ray absorption fine structure and magnetic measurements in order to describe the influence of the microstructure and morphology on the magnetic behaviour of NiO nanoparticles (NPs) with sizes ranging from 2.5 to 9 nm. The present findings reveal that size effects induce surface spin frustration which competes with the expected antiferromagnetic (AFM) order, typical of bulk NiO, giving rise to a threshold size for the AFM phase to nucleate. Ni 2+ magnetic moments in 2.5 nm NPs seem to be in a spin glass (SG) state, whereas larger NPs are formed by an uncompensated AFM core with a net magnetic moment surrounded by a SG shell. The coupling at the core-shell interface leads to an exchange bias effect manifested at low temperature as horizontal shifts of the hysteresis loop (∼1 kOe) and a coercivity enhancement (∼0.2 kOe). IntroductionThe steadily increasing interest in magnetic nanoparticles (NPs) over the past decade has been motivated by the unusual size-dependent magnetic behaviours and by their numerous applications in modern nano-electronics, magnetic separation or biomedical areas. [1][2][3][4][5][6][7] The growing research activity in this field has been propelled by the development of new chemical routes that allowed the synthesis of NPs with tuneable size distributions and being embedded in different insulating matrices. [8][9][10][11][12][13][14][15][16] It is worth noting that NPs of the same material and similar size but synthetized using different fabrication routes show a strong dependence of the magnetic properties on the morphology, microstructure or the nature of the matrix. 1,8,10,13 Moreover, 3d metal oxide NPs with different core-shell morphologies are also good candidates for a number of applications due to the possibility of tuning the magnetic response and/or the coating with a functional layer. 2,4,[13][14][15] Therefore, a comprehensive study combining advanced structural characterization techniques and meticulous magnetic measurements is needed to elucidate the microstructure-magnetism interplay at the nanoscale.Nickel oxide (NiO) has been under extensive research for decades due to its importance in numerous technological applications (i.e., catalysis, batteries, ceramics, etc.). Nowadays, nanosized NiO particles have generated a renewed interest because the combination of their unique properties (i.e., high surface area, short diffusional paths, exceptional magnetic properties, etc.) opens an avenue for their use in fields as diverse as catalysis, [17][18][19] anodic electrochromism, 20 capacitors, 21 smart windows, 22 fuel and solar cells 23,24 or biosensors. 25 Specially intense research effor...

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“…EXAFS curve fitting is performed using the IFEFFIT package 24,25) in k (wave number) space after the inverse Fourier transformation for the nearest Ni-O contribution (1.0-3.0 Å). The EXAFS spectra for the fcc NiO 26) calculated using the FEFF8 27) code are used as a theoretical standard. Experimental and fitted inverse Fourier-transformed EXAFS functions are displayed in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…We obtained the Ni-O bond length as 2.03 Å, and estimated the in-plane lattice constant of Ni-O as 0.406 nm. By taking into account that the lattice constant of BaTiO 3 (a = 0.398 nm) 28) is smaller than that of bulk NiO (a = 0.418 nm), 26) it is reasonably understood that the in-plane lattice constant of NiO shrinks to coordinate with that of BaTiO 3 , and the pseudomorphic growth of NiO is thus carried out.…”

Section: Resultsmentioning

confidence: 99%

Effect of interface NiO layer on magnetism in Fe/BaTiO₃ thin film

Sakamaki

Amemiya

2018

Jpn. J. Appl. Phys.

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The insertion effect of an interface NiO layer on magnetism in Fe/BaTiO 3 is investigated by X-ray absorption spectroscopy (XAS). From X-ray magnetic circular dichroism (XMCD) analysis, the enhancement of remanent magnetization in Fe is observed with increasing NiO thickness. We also find that the NiO layer is partially composed of metallic Ni, and its thickness is estimated to be >0.4 nm from the NiO-thickness dependence of the Ni XAS intensity by assuming that Ni is localized at the interface between Fe and NiO. Moreover, extended X-ray absorption fine structure data shows that the Ni-O distance of the interface NiO layer is shorter than that of bulk NiO, which leads to the pseudomorphic growth of NiO on BaTiO 3 . We thus suppose that the improved Fe growth promoted by the interface NiO layer enhances the magnetic moment in Fe.

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X-ray determination of electron-density distributions in oxides, MgO, MnO, CoO, and NiO, and atomic scattering factors of their constituent atoms.

Cited by 358 publications

References 2 publications

Stability and resistance of nickel catalysts for hydrodeoxygenation: carbon deposition and effects of sulfur, potassium, and chlorine in the feed

Stability and resistance of nickel catalysts for hydrodeoxygenation: carbon deposition and effects of sulfur, potassium, and chlorine in the feed

Interplay between microstructure and magnetism in NiO nanoparticles: breakdown of the antiferromagnetic order

Effect of interface NiO layer on magnetism in Fe/BaTiO₃ thin film

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X-ray determination of electron-density distributions in oxides, MgO, MnO, CoO, and NiO, and atomic scattering factors of their constituent atoms.

Cited by 358 publications

References 2 publications

Stability and resistance of nickel catalysts for hydrodeoxygenation: carbon deposition and effects of sulfur, potassium, and chlorine in the feed

Stability and resistance of nickel catalysts for hydrodeoxygenation: carbon deposition and effects of sulfur, potassium, and chlorine in the feed

Interplay between microstructure and magnetism in NiO nanoparticles: breakdown of the antiferromagnetic order

Effect of interface NiO layer on magnetism in Fe/BaTiO3 thin film

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Effect of interface NiO layer on magnetism in Fe/BaTiO₃ thin film