| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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