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- Eriksson, Kristofer, et al.
(författare)
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Performance of a biomimetic oxidation catalyst immobilized on silica particles
- 2013
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 303, s. 16-21
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Tidskriftsartikel (refereegranskat)abstract
- A biomimetic oxidation catalyst, cobalt porphyrin with thiol linkers, was chemically conjugated to silica particles and utilized in the oxidation of hydroquinone to benzoquinone. The cobalt porphyrin/silica particle catalyst was characterized with Inductively Coupled Plasma (ICP) and X-ray Photoelectron Spectroscopy (XPS). The catalytic performance of the cobalt porphyrin molecules was compared to previous results for the same catalyst grafted to a gold surface and on silicon wafers. The measured catalytic activity, after background correction, was 100 times higher than that of its homogeneous counterpart, 10 times higher than that on a silicon wafer, and almost the same as that on a gold surface. The turnover frequency rates after 400 h are still comparable with initial rates reported for homogeneous porphyrins and salophens, whereas the use of particles as support increases the active surface area, which removes the limitations for scale-up associated with the previously used silicon wafers and gold surfaces.
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| 5. |
- Gothelid, M, et al.
(författare)
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Ge/(111)3x1:K/Sn; On the influence of tin substitution in a metal induced 3x1 reconstruction
- 1996
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 104, s. 113-117
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Tidskriftsartikel (refereegranskat)abstract
- Go-adsorption of tin and potassium is found to induce a 3x1 reconstruction on the Ge(lll) surface. A very small amount of tin influences the Ge 3d core level spectra substantially compared to the Ge(111)3x1:K reconstruction. This is interpreted as resulting from a relaxation of the strain in the rows Ge atoms running along the surface, as proposed for this structure.
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- Hirschauer, B, et al.
(författare)
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CeO2 on Si(111) 7 X 7 and Si(111)-H 1 X 1, an interface study by high-resolution photoelectron spectroscopy
- 1999
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 148:3-4, s. 164-170
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Tidskriftsartikel (refereegranskat)abstract
- The formation of the CeO2-Si(111) interface was studied by high-resolution photoelectron spectroscopy. It is shown that CeO2 and Si(111) forms a highly reactive: interface with a strong interdiffusion of Si into the CeO2. A passive silicon surface formed by saturating the Si dangling bonds with hydrogen is considerably less reactive. Defects on the surface, however, act as nucleations centres for reactions of a Si:Ce:O matrix. Oxygen leaves the surface at about 800 degrees C and at 1000 degrees C a surface reconstruction of Si(111)-Ce 2 X 2/root 3 X root 3 is formed. (C) 1999 Elsevier Science B.V. All rights reserved.
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| 7. |
- Janin, E, et al.
(författare)
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Hydrogen adsorption on the Pt(111)(root 3x root 5)R30 degrees-Sn surface alloy studied by high resolution core level photoelectron spectroscopy
- 1996
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 99:4, s. 371-378
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Tidskriftsartikel (refereegranskat)abstract
- Investigation of the clean and atomic hydrogen covered Pt(111)(root 3 x root 3)R30 degrees-Sn surface alloy has been carried out using high resolution core level photoelectron spectroscopy, The Pt 4(7/2) spectrum recorded from the clean surface alloy shows a single surface peak shifted - 0.25 eV relative to the bulk. Its interpretation by means of a thermodynamical model using Born-Haber cycles confirms the surface alloy model. Adsorption of H does not change the line shape of the Sn 4d core level while a new surface component shifted by 0.59 eV compared to the bulk peak appears in the Pt 4(7/2) spectrum. These results are discussed in the light of the thermodynamical calculations, H atoms are believed to bind only to Pt atoms, and their adsorption site seems to be influenced by the tin present in the surface layer.
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- Landälv, Ludvig, 1982-, et al.
(författare)
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Structural evolution in reactive RF magnetron sputtered (Cr,Zr)2O3 coatings during annealing
- 2017
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Ingår i: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 131, s. 543-552
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Tidskriftsartikel (refereegranskat)abstract
- Reactive RF-magnetron sputtering is used to grow Cr0.28Zr0.10O0.61 coatings at 500 degrees C. Coatings are annealed at 750 degrees C, 810 degrees C, and 870 degrees C. The microstructure evolution of the pseudobinary oxide compound is characterized through high resolution state of the art HRSTEM and HREDX-maps, revealing the segregation of Cr and Zr on the nm scale. The as-deposited coating comprises cc-(Cr,Zr)(2)O-3 solid solution with a Zr-rich (Zr,Cr)O-x. amorphous phase. After annealing to 750 degrees C tetragonal ZrO2 nucleates and grows from the amorphous phase. The ZrO2 phase is stabilized in its tetragonal structure at these fairly low annealing temperatures, possibly due to the small grain size (below 30 nm). Correlated with the nucleation and growth of the tetragonal-ZrO2 phase is an increase in hardness, with a maximum hardness after annealing to 750 degrees C, followed by a decrease in hardness upon coarsening, bcc metallic Cr phase formation and loss of oxygen, during annealing to 870 degrees C. The observed phase segregation opens up future design routes for pseudobinary oxides with tunable microstructural and mechanical properties. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 9. |
- Le Lay, G., et al.
(författare)
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STM and synchrotron radiation studies of "prototypical" metal{plus 45 degree rule}semiconductor systems
- 1994
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Ingår i: Surface Science. - 0039-6028. ; 307-309:PART A, s. 280-294
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Tidskriftsartikel (refereegranskat)abstract
- Since the origin of surface science noble metal{plus 45 degree rule}elemental semiconductor couples have been considered as "prototypical" systems. After three decades of research their structural and electronic properties remain an intriguing maze despite recent advances made, especially thanks to the development of the near-field microscopies and the extensive use of synchrotron radiation in surface crystallography and in high-resolution photoelectron spectroscopy. In the last few years, lead, as a replacement inert metal, has nearly gained the pole position in the display of exotic behaviour. This paper gives a flavour of this mystery story and highlights some puzzling questions. © 1994.
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| 10. |
- LELAY, G, et al.
(författare)
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STM AND SYNCHROTRON-RADIATION STUDIES OF PROTOTYPICAL METAL-SEMICONDUCTOR SYSTEMS
- 1994
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 307, s. 280-294
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Tidskriftsartikel (refereegranskat)abstract
- Since the origin of surface science noble metal/elemental semiconductor couples have been considered as ''prototypical'' systems. After three decades of research their structural and electronic properties remain an intriguing maze despite recent advances made, especially thanks to the development of the near-field microscopies and the ''tensive use of synchrotron radiation in surface crystallography and in high-resolution photoelectron spectroscopy. In the last few years, lead, as a replacement inert metal, has nearly gained the pole position in the display of exotic behaviour. This paper gives a flavour of this mystery story and highlights some puzzling questions.
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| 11. |
- Zhirkov, Igor, 1980-, et al.
(författare)
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Effect of Si on DC arc plasma generation from Al-Cr and Al-Cr-Si cathodes used in oxygen
- 2017
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Ingår i: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 121:8
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Tidskriftsartikel (refereegranskat)abstract
- Al2O3 alloyed with Cr is an important material for the tooling industry. It can be synthesized from an arc discharge using Al-Cr cathodes in an oxygen atmosphere. Due to formation of Al-rich oxide islands on the cathode surface, the arc process stability is highly sensitive to oxygen pressure. For improved stability, the use of Al0.70Cr0.25Si0.05 cathodes has previously been suggested, where Si may reduce island formation. Here, we have investigated the effect of Si by comparing plasma generation and thin film deposition from Al0.7Cr0.3 and Al0.7Cr0.25Si0.05 cathodes. Plasma ion composition, ion energies, ion charge states, neutral species, droplet formation, and film composition have been characterized at different O-2 flow rates for arc currents of 60 and 90 A. Si and related compounds are detected in plasma ions and in plasma neutrals. Scanning electron microscopy and energy dispersive X-ray analysis show that the cathode composition and the film composition are the same, with Si present in droplets as well. The effect of Si on the process stability, ion energies, and ion charge states is found to be negligible compared to that of the arc current. The latter is identified as the most relevant parameter for tuning the properties of the reactive discharge. The present work increases the fundamental understanding of plasma generation in a reactive atmosphere, and provides input for the choice of cathode composition and process parameters in reactive DC arc synthesis.
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