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| 2. |
- Backholm, Jonas, et al.
(författare)
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Iridium-based oxides: Recent advances in coloration mechanism, structural and morphological characterization
- 2008
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 92:2, s. 91-96
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Tidskriftsartikel (refereegranskat)abstract
- Films of iridium-tantalum oxide and iridium oxide have been prepared by sputtering and studied regarding their structure and electrochemical properties. X-ray diffraction and transmission electron microscopy showed an average grain size of 3-4 nm for both films. Point energy dispersive X-ray spectrometry showed an inhomogeneous distribution of iridium and tantalum indicating that the iridium-tantalum oxide may be a mixture of small IrO2 and Ta2O5 grains, which is consistent with the determined composition IrTa1.4O5.6. X-ray photoelectron spectroscopy gave valuable information on the stabilization process of the as-deposited films involving an uptake of oxygen, and on a coloration mechanism only including protons.
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| 5. |
- Beste, Ulrik, et al.
(författare)
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Wear induced material modifications of cemented carbide rock drill buttons
- 2006
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Ingår i: International journal of refractory metals & hard materials. - : Elsevier BV. - 0263-4368. ; 24:1-2, s. 168-176
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Tidskriftsartikel (refereegranskat)abstract
- The drill crown of a rock drill is made of steel and equipped with WC/Co cemented carbide buttons (or inserts) of different geometries. These rock drill button are exposed to a large number of high load impacts into the rock. The complex and strongly shifting properties of rock minerals lead to a complex mixture of wear mechanisms. These wear mechanisms have recently been mapped by the present authors, and are divided into five classes of deterioration and five classes of material removal mechanisms. In this paper, two important deterioration mechanisms are studied in detail, namely the binder phase degradation and the rock intermixing.Transmission electron microscopy (TEM) has been employed for these high resolution studies. However, rock intermixture and huge internal stresses in the buttons lead to severe difficulties in preparing samples.Therefore, a focused ion beam-instrument (FIB) has been used to cut cross-section samples in the outermost surface on rock drill buttons. These have been investigated in the TEM by EDS, EFTEM, and STEM.Buttons from two rock drills of different history were selected for this investigation. One was used to drill 18 m in a hard rock type (quartzitic granite) and the other to drill 20 m in a much softer rock type (magnetite). Only selected regions of the outermost WC grain layers, which are in a steady state wear mode, were investigated.The crystallographic structure of the Co binder phase was investigated in both buttons, and it was represented mainly by the hcp-Co, but also small extent of fcc-Co. This is suggested to be a result of the mechanical fatigue, following one of two suggested Co-phase transformation series.The rock covers and intermixed zones formed were analysed in detail. The large part of the rock cover was found to be amorphous, containing rock and WC fragments. Adjacent to the WC grains, the rock cover was often found to have a porous structure, where the pores were surrounded by crystalline Co-particles adjacent to a carbon rich area. Apparently, the quartz rock locally melts and sticks very intimately to the WC grains and the porous structure forms during solidification. This feature was further analysed, and it was shown that the amorphous rock is seamlessly connected to WC on the atomic level. It was also stated that the rock cover and intermixed layers are very similar on both buttons, independent of rock type drilled.
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| 8. |
- Blom, Tobias, et al.
(författare)
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Fabrication and characterization of highly reproducible, high resistance nanogaps made by focused ion beam milling
- 2007
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 18:28, s. 285301-
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Tidskriftsartikel (refereegranskat)abstract
- Nanoelectrodes were fabricated combining photolithography, electron beam lithography and focused ion beam milling allowing for large scale integration and nanoengineering of the electrode properties. The structure determination by transmission and scanning electron microscopy showed a highly reproducible gap width. The atomic scale electrode structure was characterized using scanning and transmission electron microscopy. The nanogap resistances were found to be the highest hitherto reported for nanogaps, namely in the 300–1300 TΩ range. Gold nanoparticles were trapped by ac dielectrophoresis, and the electrodes were shown to be stable enough to endure empty gap voltages as high as 5 V as well as currents high enough to induce fusing of trapped nanoparticles.
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| 10. |
- Blomqvist, M., et al.
(författare)
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Structural and tribological properties of cluster-assembled CNx films
- 2007
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Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 87:4, s. 767-772
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Tidskriftsartikel (refereegranskat)abstract
- We report the structural and tribological characterization of nanostructured CNx thin films produced by the deposition of a supersonic carbon cluster beam assisted by nitrogen ion bombardment. The influence of the deposition parameters on the chemical composition and structure of the films has been systematically studied by X-ray photoelectron spectroscopy, elastic recoil detection analysis, transmission electron microscopy and atomic force microscopy. Depending on the deposition parameters, the films show a structure ranging from amorphous to disordered graphitic with interlinked planes. Nitrogen content depends on the nitrogen ion kinetic energy. The films have a very low density with a high surface roughness. Friction measurements at the nanoscale show a correlation between nitrogen content and mechanical properties of the system.
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