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| 2. |
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| 3. |
- Böör, Katalin, et al.
(författare)
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On the growth kinetics, texture, microstructure, and mechanical properties of tungsten carbonitride deposited by chemical vapor deposition
- 2022
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Institute of Physics (AIP). - 0734-2101 .- 1520-8559. ; 40:5
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Tidskriftsartikel (refereegranskat)abstract
- Tungsten carbonitride [W(C,N)] was deposited on cemented carbide substrates by chemical vapor deposition (CVD) in a hot-wall reactor using tungsten hexafluoride (WF6), acetonitrile (CH3CN), and hydrogen (H-2) as precursors. Tungsten carbides and nitrides with a hexagonal 6-WC type structure are generally difficult to obtain by CVD. Here, it was found that the combination of WF6 and CH3CN precursors enabled the deposition of W(C,N) coatings with a delta-WC type structure and columnar grains. A process window as a function of the deposition temperature and precursor partial pressures was determined to establish the conditions for the deposition of such coatings. Scanning electron microscopy, x-ray diffraction, electron backscatter diffraction, and elastic recoil detection analysis were used for the investigation of the coating thickness, microstructure, texture, and composition. From the investigation of the kinetics, it was concluded that the growth was mainly controlled by surface kinetics with an apparent activation energy of 77 kJ/mol, yielding an excellent step coverage. The partial reaction orders of the reactants together with their influence on the microstructure and coating composition was further used to gain a deeper understanding of the growth mechanism. Within the process window, the microstructure and the texture of the W(C,N) coatings could be tailored by the process parameters, enabling microstructural engineering with tuning of the mechanical properties of the W(C,N) coatings. The nanoindentation hardness (36.6-45.7 GPa) and elastic modulus (564-761 GPa) were found to be closely related to the microstructure.
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| 4. |
- Fang, Hailiang, et al.
(författare)
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Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The low cost, rare earth free τ-phase of MnAl has high potential to partially replace bonded Nd2Fe14B rare earth permanent magnets. However, the τ-phase is metastable and it is experimentally difficult to obtain powders suitable for the permanent magnet alignment process, which requires the fine powders to have an appropriate microstructure and high τ-phase purity. In this work, a new method to make high purity τ-phase fne powders is presented. A high purity τ-phase Mn0.55Al0.45C0.02 alloy was synthesized by the drop synthesis method. The drop synthesized material was subjected to cryo milling and followed by a fash heating process. The crystal structure and microstructure of the drop synthesized, cryo milled and flash heated samples were studied by X-ray in situ powder diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy and electron backscatter diffraction. Magnetic properties and magnetic structure of the drop synthesized, cryo milled, flash heated samples were characterized by magnetometry and neutron powder diffraction, respectively. The results reveal that the 2 and 4hours cryo milled and flash heated samples both exhibit high τ-phase purity and micron-sized round particle shapes. Moreover, the fash heated samples display high saturation magnetization as well as increased coercivity.
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| 5. |
- Fondell, Mattis, 1984-, et al.
(författare)
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Phase control of iron oxides grown in nano-scale cauliflower structures: hematite, maghemite and magnetite
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We demonstrate that iron oxide in the form of hematite, suitable as absorber in photoelectrochemical cells, can be produced by pulsed chemical vapour deposition. By choosing carbon monoxide or nitrogen as carrier gases in the process the phase and granularity of the grown material can be controlled. The choice of carrier gas a ect the decomposition rate of iron pentacarbonyl used as iron precursor. The iron oxide phase is also dependent on the chosen substrate, here fluorine doped tin oxide and crystalline silicon have been used. Regardless of the substrate nitrogen yields hematite, whereas carbon monoxide gives magnetite on Si and maghemite on fluorine doped tin oxide. A combination of Raman spectroscopy, X-ray di raction, and hard X-ray photoelectron spectroscopy were used for characterization of the crystalline phase and chemical composition in the films. Scanning electron microscopy were used to visualise the deposited films’ nano-structure reminiscent of a cauliflower.
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| 6. |
- Fondell, Mattis, et al.
(författare)
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Phase control of iron oxides grown in nano-scale structures on FTO and Si(100) : Hematite, maghemite and magnetite
- 2015
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Ingår i: Vacuum. - : Elsevier BV. - 0042-207X .- 1879-2715. ; 117, s. 85-90
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that iron oxide in the form of hematite, suitable as absorption material in photo-electrochemical cells, can be produced by pulsed chemical vapour deposition. By choosing carbon monoxide or nitrogen as carrier gases in the process the phase and granularity of the grown material can be controlled. The choice of carrier gas affect the decomposition rate of iron pentacarbonyl used as iron precursor. The iron oxide phase is also dependent on the chosen substrate, here fluorine doped tin oxide and crystalline silicon have been used. Regardless of the substrate nitrogen yields hematite, whereas carbon monoxide gives, magnetite on Si and maghemite on fluorine doped tin oxide. A combination of Raman spectroscopy, X-ray diffraction, and hard X-ray photoelectron spectroscopy were used for characterization of the crystalline phase and chemical composition in the films. Scanning electron microscopy were used to visualise the deposited films' nano-structure.
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| 7. |
- Fondell, Mattis, 1984-, et al.
(författare)
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Temperature Induced Diffusion of Sn and Si in Hematite and Implications for Photocatalytic Water Splitting Applications
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The performance of Hematite (α-Fe2O3) for the water oxidation step in solar hydrogen production is dependent upon annealing of the material. In this study, these effects are investigated in terms of temperature induced diffusion of Sn and Si from the substrate into thin films of hematite by using hard X-ray photoelectron spectroscopy (HAXPES). Here, HAXPES is used for the first time to characterize a buried interface between a conducting substrate and a nanostructured thin film overlayer by diffusion upon annealing. This process is prototypical for the large class of photoelectrochemical devices that uses indium and fluorine doped tin oxide as substrates where the device is subsequently annealed. Indeed, we observe that: diffusion of Sn and Si is significant, already at 550 °C; the photocatalytic efficiency of the hematite films increased, from low values to 0.23 mA/cm2; annealing in air preserves the hematite phase, while annealing in vacuum induces a phase transition into magnetite, which impairs the photocatalytic performance. The increase in efficiency is explained in terms of an improvement of the quantum efficiency of the oxygen evolution reaction accompanied by a slight improvement in charge carrier transport.
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| 8. |
- Fritze, Stefan, et al.
(författare)
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Hard and crack resistant carbon supersaturated refractory nanostructured multicomponent coatings
- 2018
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The combination of ceramic hardness with high crack resistance is a major challenge in the design of protective thin films. High entropy alloys have shown in earlier studies promising mechanical properties with a potential use as thin film materials. In this study, we show that small amounts of carbon in magnetron-sputtered multicomponent CrNbTaTiW films can lead to a significant increase in hardness. The film properties were strongly dependent on the metal composition and the most promising results were observed for TaW-rich films. They crystallised in a bcc structure with a strong (110) texture and coherent grain boundaries. It was possible to deposit films with 8 at.% C in a supersaturated solid-solution into the bcc structure without carbide formation. A major effect of carbon was a significant grain refinement, reducing the column diameter from approximately 35 to 10 nm. This resulted in an increase in hardness from 14.7 to 19.1 GPa while the reduced E-modulus stayed constant at 322 GPa. The carbon-containing films exhibited extremely little plastic deformation around the indent and no cracks were observed. These results show that supersaturation of carbon into high entropy films can be a promising concept to combine superior hardness with high crack resistance.
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| 9. |
- Fritze, Stefan, et al.
(författare)
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Influence of Deposition Temperature on the Phase Evolution of HfNbTiVZr High-Entropy Thin Films
- 2019
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Ingår i: Materials. - : MDPI. - 1996-1944. ; 12:4
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we show that the phase formation of HfNbTiVZr high-entropy thin films is strongly influenced by the substrate temperature. Films deposited at room temperature exhibit an amorphous microstructure and are 6.5 GPa hard. With increasing substrate temperature (room temperature to 275 degrees C), a transition from an amorphous to a single-phased body-centred cubic (bcc) solid solution occurs, resulting in a hardness increase to 7.9 GPa. A higher deposition temperature (450 degrees C) leads to the formation of C14 or C15 Laves phase precipitates in the bcc matrix and a further enhancement of mechanical properties with a peak hardness value of 9.2 GPa. These results also show that thin films follow different phase formation pathways compared to HfNbTiVZr bulk alloys.
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| 10. |
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| 11. |
- Malinovskis, Paulius, et al.
(författare)
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Synthesis and characterization of multicomponent (CrNbTaTiW)C films for increased hardness and corrosion resistance
- 2018
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 149, s. 51-62
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Tidskriftsartikel (refereegranskat)abstract
- Multicomponent carbide thin films of (CrNbTaTiW)C (30–40 at.% C) with different metal contents were depos-ited at different temperatures using non-reactive DC magnetron sputtering. The lattice distortion for the metallattice was estimated to vary from about 3 to 5%. Most films crystallized in the cubic B1 structure but Ta/W-rich films deposited at 600 °C exhibited a tetra gonal distortion. X-ray diffraction results sh ow that near-equimolar films exhibited a strong (111) texture. In contrast, Ta/W-rich films exhibited a shift from (111) to(100) texture at 450 °C. The in-plane relationship was determined to MC(111)[-12-1]//Al2O3(001)[110] with alattice mismatch of about 11% along the Al2O3[110] direction. A segregation of Cr to the grain boundaries was ob-served in all films. The microstructure was found to be the most important factor for high hardness. Less denseNb-rich and near-equimolar films deposited at low tem peratures exhib ited the low est hardnes s (12 GPa),while very dense Ta/W-rich high temperature films were found to be the hardest (36 GPa). No correlation wasfound between the lattice distortion and the hardness. Corrosion studies revealed that the multicomponentfilms exhibited excellent corrosion resistance, superior to that of a reference hyper-duplex stainless steel, in1.0 M HCl.
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| 12. |
- von Fieandt, Linus, et al.
(författare)
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Chemical Interactions Between Cemented Carbide and Difficult-to-Machine Materials by Diffusion Couple Method and Simulations
- 2018
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Ingår i: Journal of phase equilibria and diffusion. - : SPRINGER. - 1863-7345 .- 1547-7037. ; 39:4, s. 369-376
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Tidskriftsartikel (refereegranskat)abstract
- A simple and efficient diffusion couple method is utilized to study the chemical interactions between cemented carbide cutting tools and difficult-to-machine materials (Ti, Ti-6Al-4V, Ni, Inconel 718, Fe, and AISI 316L). The experimental results and simulations probe different chemical interactions between the cemented carbide and work materials. In particular, the formation of a thick TiC layer is observed at the cemented carbide/Ti and Ti-6Al-4V interface while eta-phase is formed at the interface between the cemented carbide and work materials Inconel 718, Fe and AISI 316L. Pure titanium and Ti-6Al-4V both interact strongly with the tool causing formation of TiC and dissolution of WC-grains. Experiments and diffusion simulations confirm bcc-W formation and progressive diffusion of W into bcc-Ti. For both Ti and Fe work materials a dense band of carbides (WC + eta or WC + TiC) forms at the interface, effectively inhibiting further diffusion. Ni does not form any stable carbide and lowers the eta-phase limit in terms of carbon content, wherefore diffusion can occur freely. The diffusion couple method used in this work, corroborated by DICTRA simulations should serve as a useful tool in the detailed analysis of worn tools where chemical wear is dominant.
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| 13. |
- von Fieandt, Linus, et al.
(författare)
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Chemical vapor deposition of TiN on transition metal substrates
- 2018
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Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 334, s. 373-383
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Tidskriftsartikel (refereegranskat)abstract
- The growth of chemical vapor deposited TiN from a reaction gas mixture of TiCl 4 , N 2 and H 2 was investigated on three different transition metal substrates: Fe, Co and Ni at deposition temperatures ranging from 850 °C to 950 °C. The interactions between the substrate metals and the gas phase were investigated using thermodynamic calculations. The TiN coatings were characterized by scanning electron microscopy, scanning transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and transmission Kikuchi diffraction. Chemical vapor deposition (CVD) of TiN on Co substrates resulted in dense, columnar coatings of single phase TiN. The activation energy for TiN deposition on Co was determined to be 90 kJ/mol. CVD of TiN on Fe substrates caused severe substrate corrosion by the formation of gaseous FeCl x . Due to the substrate corrosion, the activation energy could not be determined. Furthermore, it was found that CVD of TiN on Ni substrates produced a phase mixture of TiN and Ni 3 Ti. Formation of Ni 3 Ti could be minimized by decreasing the H 2 partial pressure and increasing the N 2 partial pressure. Deposition on Ni yielded two different activation energies, 40 kJ/mol in the temperature interval 850 °C to 900 °C and 165 kJ/mol in the interval 900 °C to 950 °C. This is an indication of two different types of process control, which were identified as Ni diffusion into the growing film and a gas phase processes. The results of the present study showed that CVD of TiN on a cemented carbide using Fe and Ni in the binder phase, must be optimized in order to avoid corrosion or unwanted phases. Methods to achieve this are presented in this paper.
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| 14. |
- von Fieandt, Linus, et al.
(författare)
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Corrosion properties of CVD grown Ti(C,N) coatings in 3.5 wt-% NaCl environment
- 2018
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Ingår i: Corrosion Engineering, Science and Technology. - 1478-422X .- 1743-2782. ; 53:4, s. 316-320
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Tidskriftsartikel (refereegranskat)abstract
- The corrosion behaviour of Titanium carbonitride (Ti(C,N)) films grown by chemical vapour deposition was analysed in artificial sea water environment. From potentiodynamic polarisation curves, two passivation zones were detected, which originated from an initial oxidation of TiC and TiN to TiO2 followed by growth of the TiO2 layer upon increased polarisation. X-ray photoelectron spectroscopy analyses verified the mechanism by detecting a gradual decrease in Ti(C,N) peaks accompanied by a gradual increase of oxidised Ti (e.g. TiO2). It was likewise found that carbon in TiC mainly decomposes into carbonate species while the nitrogen in TiN remains elemental and likely escapes as nitrogen gas. Accordingly, Ti(C,N) behaves like a superposition of TiC and TiN with their individual oxidation behaviour, resulting in a highly corrosion resistant material.
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| 15. |
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| 16. |
- von Fieandt, Linus
(författare)
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Cutting Edge Titanium-based CVD Hard Coatings
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modern tools for metal cutting applications, such as turning or milling, are typically improved with a thin protective coating. Despite being only a few microns thick, the coating can increase the lifetime of the tool by more than 100 times compared to an uncoated tool. Two different types of techniques are normally used to deposit the coatings, i.e. chemical vapor deposition (CVD) or physical vapor deposition (PVD). A CVD coated tool often includes several different layers. TiN-Ti(C,N)-Al2O3-TiN is a common combination. The research in this thesis has focused on deposition, characterization, and optimization of TiN and Ti(C,N) layers. CVD has been used to deposit all coatings studied in this thesis. They were characterized with a variety of techniques such as: X-ray diffraction, electron microscopy and X-ray photoelectron spectroscopy.TiN was deposited on three different substrates, Co, Fe and Ni. It was found that the TiN coating was strongly affected by the substrate. TiN deposited on Fe substrates resulted in a porous interface caused by substrate etching by the reaction gas mixture. CVD of TiN on Ni substrates resulted in an unwanted intermetallic phase (Ni3Ti) in addition to TiN. Etching or corrosion of the Fe substrates could be reduced by lowering the deposition temperature. In addition, the formation of (Ni3Ti) could be significantly reduced by adjusting the partial pressure of the reactant gases. This shows that CVD of TiN on cutting tools with Fe or Ni as a binder phase needs to be optimized with respect to the process parameters.Thermodynamic calculations of the Ti(C,N) CVD process indicates that the major growth species using CH3CN, TiCl4 and H2 as precursors, was HCN and TiCl3. They were formed in the gas phase by homogeneous reactions. Furthermore, it was found that by adjusting the composition of the reaction gas mixture, the preferred orientation, morphology, and micro-structure of the Ti(C,N) coatings could be tailored. As a result, the tribological/mechanical properties of the Ti(C,N) coatings could be significantly improved. A hardness of 40 GPa, i.e. close to super hard could for instance be achieved. The origin of the mechanical improvements was attributed to a more ordered crystallographic orientation in the <111> direction as well as a high defect density close to the coating surface. In addition to the excellent mechanical properties, the Ti(C,N) coatings were also found to have a high corrosion resistance in sea water, thanks to a formation of a passivating surface layer (TiO2).
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| 17. |
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| 18. |
- von Fieandt, Linus, et al.
(författare)
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On the growth, orientation and hardness of chemical vapor deposited Ti(C,N)
- 2018
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 645, s. 19-26
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Tidskriftsartikel (refereegranskat)abstract
- Chemical vapor deposition (CVD) of Ti(C,N) from a reaction gas mixture of TiCl4, CH3CN, H2 and N2 was investigated with respect to gas phase composition and kinetics. The gas phase composition was modelled by thermodynamic calculations and the growth rate of the CVD process was measured when replacing H2 for N2 while the sum of partial pressures H2+N2 was kept constant. The N2/H2 molar ratio was varied from 0 to 19. Single crystal c-sapphire was used as substrates. It was found that low molar ratios (N2/H2 molar ratio below 0.6) lead to an increased Ti(C,N) growth rate with up to 22%, compared to deposition without added N2. The mechanism responsible for the increased growth rate was attributed to the formation and increased gas phase concentration of one major growth species, HCN, in the gas phase. The texture of the Ti(C,N) films were also studied. ⟨211⟩ textured layers were deposited at N2/H2 molar ratios below 9. At higher molar ratios, ⟨111⟩ oriented Ti(C,N) layers were deposited and the grain size increased considerably. The films deposited at a N2/H2 ratio above 9 exhibited superior hardness, reaching 37GPa. The increased hardness is attributed to an almost epitaxial orientation between the layer and the substrate. The absence of grain twinning in the ⟨111⟩ oriented layer also contributed to the increased hardness.The Ti(C,N) layers were characterized by elastic recoil detection analysis, X-ray photo electron spectroscopy, scanning electron microscopy, X-ray diffraction and nanoindentation.
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| 19. |
- von Fieandt, Linus, et al.
(författare)
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Texture formation in chemical vapor deposition of Ti(C,N)
- 2019
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 508, s. 90-95
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Tidskriftsartikel (refereegranskat)abstract
- The growth mechanism of Ti(C,N) coatings produced by chemical vapor deposition was investigated as a function of the TiCl4/CH3CN molar ratio in excess of H-2. The depositions were carried out at a total pressure of 8 kPa, using single crystalline (0 0 l) alpha-Al2O3 substrates. The Ti(C,N) coatings were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The investigated coatings were between 6 and 13 mu m thick. The reaction orders of TiCl4 CH3CN were determined to 0 and 1, respectively, showing that CH3CN is the rate-determining reactant. The preferred orientation of the deposited Ti(C,N) was investigated, showing that molar ratios TiCl4 /CH3CN higher than 2.5 lead to < 2 1 1 >/< 3 1 1 > oriented coatings. A formation mechanism for the < 2 1 1 >/< 3 1 1 > orientations is suggested. Such high ratios lead to the formation of Ti {1 1 1} twinning planes, which provide surface sites that can facilitate fast dissociation of the strong cyanide bond, and thereby cause faster growth in the < 2 1 1 >/< 3 1 1 > directions. Coatings deposited at lower molar ratios show a pronounced < 1 1 1 > out-of-plane orientation, characterized by a {1 1 1} rocking curve yielding values for full width at half maximum (FWHM) below 0.5 degrees.
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| 20. |
- von Fieandt, Linus, et al.
(författare)
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Tribological properties of highly oriented Ti(C,N) deposited by chemical vapor deposition
- 2018
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 119, s. 593-599
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Tidskriftsartikel (refereegranskat)abstract
- Two Ti(C,N) coatings were tested by means of micro abrasion and scratch testing. The coatings differed in grain size, orientation (<111> and <111>, <311> and <211> respectively) and hardness (36 GPa and 23 GPa respectively). The <111> oriented coating had a 20% higher wear resistance compared to the reference coating when abraded with 1 pm diamonds. When abraded with 6 pm diamonds the abrasion resistance of the reference coating was superior compared to the <111> oriented coating by 36%. Furthermore, it was found that the <111> oriented coating had 35% better adhesion compared to the reference. The improved mechanical properties of the <111> oriented coating was attributed to a high degree of orientation and the higher hardness.
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