| 1. |
- Emerging Risk Factors, Collaboration, et al.
(author)
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The Emerging Risk Factors Collaboration: analysis of individual data on lipid, inflammatory and other markers in over 1.1 million participants in 104 prospective studies of cardiovascular diseases
- 2007
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In: Eur J Epidemiol. - 0393-2990. ; 22:12, s. 839-69
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Journal article (peer-reviewed)abstract
- Many long-term prospective studies have reported on associations of cardiovascular diseases with circulating lipid markers and/or inflammatory markers. Studies have not, however, generally been designed to provide reliable estimates under different circumstances and to correct for within-person variability. The Emerging Risk Factors Collaboration has established a central database on over 1.1 million participants from 104 prospective population-based studies, in which subsets have information on lipid and inflammatory markers, other characteristics, as well as major cardiovascular morbidity and cause-specific mortality. Information on repeat measurements on relevant characteristics has been collected in approximately 340,000 participants to enable estimation of and correction for within-person variability. Re-analysis of individual data will yield up to approximately 69,000 incident fatal or nonfatal first ever major cardiovascular outcomes recorded during about 11.7 million person years at risk. The primary analyses will involve age-specific regression models in people without known baseline cardiovascular disease in relation to fatal or nonfatal first ever coronary heart disease outcomes. This initiative will characterize more precisely and in greater detail than has previously been possible the shape and strength of the age- and sex-specific associations of several lipid and inflammatory markers with incident coronary heart disease outcomes (and, secondarily, with other incident cardiovascular outcomes) under a wide range of circumstances. It will, therefore, help to determine to what extent such associations are independent from possible confounding factors and to what extent such markers (separately and in combination) provide incremental predictive value.
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| 2. |
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| 3. |
- Pietersz, R. N. I., et al.
(author)
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Prophylactic platelet transfusions
- 2012
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In: Vox Sanguinis. - : Wiley. - 0042-9007 .- 1423-0410. ; 103:2, s. 159-176
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Journal article (peer-reviewed)
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| 4. |
- Ruess, H., et al.
(author)
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HPPMS deposition from composite targets : Effect of two orders of magnitude target power density changes on the composition of sputtered Cr-Al-C thin films
- 2017
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In: Vacuum. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0042-207X .- 1879-2715. ; 145, s. 285-289
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Journal article (peer-reviewed)abstract
- The effect of target power density, substrate bias potential and substrate temperature on the thin film composition was studied. A Cr-Al-C composite target was sputtered utilizing direct current (DCMS: 2.3 W/cm(2)) and high power pulsed magnetron sputtering (HPPMS: 373 W/cm(2)) generators. At floating potential, all Cr-Al-C thin films showed similar compositions, independently of the applied target power density. However, as substrate bias potential was increased to -400 V, aluminum deficiencies by a factor of up to 1.6 for DCMS and 4.1 for HPPMS were obtained. Based on the measured ion currents at the substrate, preferential re-sputtering of Al is suggested to cause the dramatic Al depletion. As the substrate temperature was increased to 560 degrees C, the Al concentration was reduced by a factor of up to 1.9 compared to the room temperature deposition. This additional reduction may be rationalized by thermally induced desorption being active in addition to re-sputtering.
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| 5. |
- Aghda, Soheil Karimi, et al.
(author)
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Ion kinetic energy- and ion flux-dependent mechanical properties and thermal stability of (Ti,Al)N thin films
- 2023
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In: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 250
-
Journal article (peer-reviewed)abstract
- Ion-irradiation-induced changes in structure, elastic properties, and thermal stability of metastable c-(Ti,Al)N thin films synthesized by high-power pulsed magnetron sputtering (HPPMS) and cathodic arc deposition (CAD) are systematically investigated by experiments and density functional theory (DFT) simulations. While films deposited by HPPMS show a random orientation at ion kinetic energies (Ek)>105 eV, an evolution towards (111) orientation is observed in CAD films for Ek>144 eV. The measured ion energy flux at the growing film surface is 3.3 times larger for CAD compared to HPPMS. Hence, it is inferred that formation of the strong (111) texture in CAD films is caused by the ion flux-and ion energy-induced strain energy minimization in defective c-(Ti,Al)N. The ion energy-dependent elastic modulus can be rationalized by considering the ion energy-and orientation -dependent formation of point defects from DFT predictions: The balancing effects of bombardment-induced Frenkel defects formation and the concurrent evolution of compressive intrinsic stress result in the apparent independence of the elastic modulus from Ek for HPPMS films without preferential orientation. However, an ion energy-dependent elastic modulus reduction of similar to 18% for the CAD films can be understood by considering the 34% higher Frenkel pair concentration formed at Ek=182 eV upon irradiation of the experimentally observed (111)-oriented (Ti,Al)N in comparison to the (200)-configuration at similar Ek. Moreover, the effect of Frenkel pair concentration on the thermal stability of metastable c-(Ti,Al)N is investigated by differential scanning calorimetry: Ion-irradiation-induced increase in Frenkel pairs concentration retards the wurtzite formation temperature by up to 206 degrees C.
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| 6. |
- Greczynski, Grzegorz, et al.
(author)
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Extended metastable Al solubility in cubic VAlN by metal-ion bombardment during pulsed magnetron sputtering: film stress vs subplantation
- 2017
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In: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 122:2
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Journal article (peer-reviewed)abstract
- Dynamic ion-recoil mixing of near-film-surface atomic layers is commonly used to increase the metastable solubility limit x(max) in otherwise immiscible thin film systems during physical vapor deposition. Recently, Al subplantation achieved by irradiating the film growth surface with Al+ metal-ion flux was shown to result in an unprecedented x(max) for VAlN, far above values obtained with gas ion irradiation. However, it is reasonable to assume that ion irradiation necessary for subplantation also leads to a compressive stress sigma buildup. In order to separate the effects of Al+ bombardment on sigma and x(max), and realize low-stress high-x(max) nitride alloys, we grow metastable cubic V1-xAlxN (0.17 amp;lt;= x amp;lt;= 0.74) films using reactive magnetron sputtering under different ion irradiation conditions. Al and V targets are operated in Ar/N-2 discharges employing (i) conventional DC (Ar+, N-2(+)), (ii) hybrid High-power pulsed magnetron sputtering (HIPIMS)/DC processing with one type of metal ion present (Al+ or V+/V2+), and (iii) HIPIMS with concurrent Al+ and V+/V2+ fluxes. Comparison to the ab initio calculated Al solubility limit reveals that x(max) = 0.55 achieved with V+/V2+ irradiation is entirely accountable for by stress. In contrast, Al+ fluxes provide a substantial increase in x(max) to 0.63, which is 12% higher than that expected based on the stress-induced increase in metastable solubility. Correlative stress and atom probe tomography data confirm that the metastable Al solubility enhancement is enabled by Al+ subplantation. The here proposed processing strategy allows for growth of single-phase cubic nitride alloys with significantly increased Al concentrations embodying tremendous promise for substantial improvements in high temperature oxidation resistance and mitigates the risk of stress-induced adhesive or cohesive coating failure. Published by AIP Publishing.
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| 7. |
- Greczynski, Grzegorz, et al.
(author)
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Unprecedented Al supersaturation in single-phase rock salt structure VAlN films by Al+ subplantation
- 2017
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In: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 121:17
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Journal article (peer-reviewed)abstract
- Modern applications of refractory ceramic thin films, predominantly as wear-protective coatings on cutting tools and on components utilized in automotive engines, require a combination of excellent mechanical properties, thermal stability, and oxidation resistance. Conventional design approaches for transition metal nitride coatings with improved thermal and chemical stability are based on alloying with Al. It is well known that the solubility of Al in NaCl-structure transition metal nitrides is limited. Hence, the great challenge is to increase the Al concentration substantially while avoiding precipitation of the thermodynamically favored wurtzite-AlN phase, which is detrimental to mechanical properties. Here, we use VAlN as a model system to illustrate a new concept for the synthesis of metastable single-phase NaCl-structure thin films with the Al content far beyond solubility limits obtained with conventional plasma processes. This supersaturation is achieved by separating the film-forming species in time and energy domains through synchronization of the 70-mu s-long pulsed substrate bias with intense periodic fluxes of energetic Al+ metal ions during reactive hybrid high power impulse magnetron sputtering of the Al target and direct current magnetron sputtering of the V target in the Ar/N-2 gas mixture. Hereby, Al is subplanted into the cubic VN grains formed by the continuous flux of low-energy V neutrals. We show that Al subplantation enables an unprecedented 42% increase in metastable Al solubility limit in V1-xAlxN, from x-0.52 obtained with the conventional method to 0.75. The elastic modulus is 325 +/- 5GPa, in excellent agreement with density functional theory calculations, and approximately 50% higher than for corresponding films grown by dc magnetron sputtering. The extension of the presented strategy to other Al-ion-assisted vapor deposition methods or materials systems is straightforward, which opens up the way for producing supersaturated single-phase functional ceramic alloy thin films combining excellent mechanical properties with high oxidation resistance. Published by AIP Publishing.
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| 8. |
- Holzapfel, Damian M., et al.
(author)
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Influence of ion irradiation-induced defects on phase formation and thermal stability of Ti0.27Al0.21N0.52 coatings
- 2022
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In: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 237
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Journal article (peer-reviewed)abstract
- The influence of changes induced by ion irradiation on structure and thermal stability of metastable cubic (Ti,Al)N coatings deposited by cathodic arc evaporation is systematically investigated by correlating experiments and theory. Decreasing the nitrogen deposition pressure from 5.0 to 0.5 Pa results in an ion flux-enhancement by a factor of three and an increase of the average ion energy from 15 to 30 eV, causing the stress-free lattice parameter to expand from 4.170 to 4.206 Å, while the chemical composition of Ti0.27Al0.21N0.52 remains unchanged. The 0.9% lattice parameter increase is a consequence of formation of Frenkel pairs induced by ion bombardment, as revealed by density functional theory (DFT) simulations. The influence of the presence of Frenkel pairs on the thermal stability of metastable Ti0.27Al0.21N0.52 is investigated by scanning transmission electron microscopy, differential scanning calorimetry, atom probe tomography and in-situ synchrotron X-ray powder diffraction. It is demonstrated that the ion flux and ion energy induced formation of Frenkel pairs increases the thermal stability as the Al diffusion enabled crystallization of the wurtzite solid solution is retarded. This can be rationalized by DFT predictions since the presence of Frenkel pairs increases the activation energy for Al diffusion by up to 142%. Hence, the thermal stability enhancement is caused by a hitherto unreported mechanism - the Frenkel pair impeded Al mobility and thereby retarded formation of wurtzite solid solution.
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| 9. |
- Kashani, Amir Hossein Navidi, et al.
(author)
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Morphology, mechanical properties, and oxidation behavior of stoichiometric Ti0.33-xAlxB0.67 coatings (x=0.04, 0.15, 0.21, and 0.28)
- 2024
-
In: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 270
-
Journal article (peer-reviewed)abstract
- Stoichiometric Ti0.33-xAlxB0.67 coatings with x = 0.04, 0.15, 0.21, and 0.28 were synthesized by magnetron sputtering and characterized regarding phase formation, mechanical properties, and oxidation behavior. By increasing the Al concentration from 4 to 28 at.%, the measured elastic modulus (496±19 GPa) and unit cell volume (25.646 Å3 ) decreased by 33 and 0.8 %, respectively. The Al concentration induced changes in measured elastic modulus and unit cell volume are in very good agreement with ab initio predictions, as the maximum deviations between experiment and theory, observed here, are 12 and 1.1 %, respectively. The corresponding hardness values decreased by 45 % from 22±1 to 12±1 GPa. The oxidation experiments were performed in ambient air at 700, 800, and 900 °C for 1, 4, and 8 h. Analysis by scanning transmission electron microscopy (STEM) revealed a bimodal, strongly Al concentration-dependent oxidation behavior where films containing ≤15 at.% of Al form a porous, non-passivating crystalline oxide scale containing Ti -rich as well as Al -rich oxide regions, while the formation of a passivating, dense, X-ray amorphous oxide scale was observed for films containing ≥ 21 at.% of Al. Coincident with the passive scale formation for Al concentrations ≥ 21 at.%, the elastic modulus decreases by ≥ 32.6 % compared to TiB2 and can be rationalized based on Al concentration induced bond weakening as revealed by the concomitant cohesive energy reduction of ≥ 22 %.
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| 10. |
- Kashani, Amir Hossein Navidi, et al.
(author)
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Synthesis and oxidation behavior of Ti0.35Al0.65By (y=1.7-2.4) coatings
- 2022
-
In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 442
-
Journal article (peer-reviewed)abstract
- The effect of B concentration on phase formation and oxidation resistance of (Ti0.35Al0.65)By coatings with y = 1.7, 2.0, 2.4 was investigated. Elemental B targets in radio frequency mode and a compound Ti0.4Al0.6 target in direct current mode were sputtered. The B concentration was varied systematically by adjusting the applied power to the respective magnetrons, while keeping the power supplied to the magnetron with the Ti0.4Al0.6 target constant. Measured lattice parameters and elastic properties are consistent with ab initio predictions. The oxidation resistance at 700 degrees C in air for up to 8 h was compared to a cathodic arc evaporated (Ti0.37Al0.63)0.49N0.51 coating with an Al/Ti ratio of 1.69 +/- 0.20 which is very similar to 1.84 +/- 0.40 for the boride coatings. Scanning transmission electron microscopy imaging revealed oxide scale thicknesses of 39 +/- 7 and 101 +/- 25 nm for (Ti0.35Al0.65)B2.0 and (Ti0.37Al0.63)0.49N0.51 after 8 h, respectively. Hence, the close to stoichiometric diboride outperforms the nitride coating. This behavior can be understood based on composition and structure analysis of the oxide scales: While the protective layer on the diboride is primarily composed of Al and O, the porous oxide layer on the nitride coating contains Ti, Al and O.
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| 11. |
- Sarakinos, Kostas, et al.
(author)
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On the phase formation of sputtered hafnium oxide and oxynitride films
- 2010
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In: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 108:1, s. 014904-
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Journal article (peer-reviewed)abstract
- Hafnium oxynitride films are deposited from a Hf target employing direct current magnetron sputtering in an Ar-O(2)-N(2) atmosphere. It is shown that the presence of N(2) allows for the stabilization of the transition zone between the metallic and the compound sputtering mode enabling deposition of films at well defined conditions of target coverage by varying the O(2) partial pressure. Plasma analysis reveals that this experimental strategy facilitates control over the flux of the O(-) ions which are generated on the oxidized target surface and accelerated by the negative target potential toward the growing film. An arrangement that enables film growth without O(-) ion bombardment is also implemented. Moreover, stabilization of the transition sputtering zone and control of the O(-) ion flux without N(2) addition is achieved employing high power pulsed magnetron sputtering. Structural characterization of the deposited films unambiguously proves that the phase formation of hafnium oxide and hafnium oxynitride films with the crystal structure of HfO(2) is independent from the O(-) bombardment conditions. Experimental and theoretical data indicate that the presence of vacancies and/or the substitution of O by N atoms in the nonmetal sublattice favor the formation of the cubic and/or the tetragonal HfO(2) crystal structure at the expense of the monoclinic HfO(2) one.
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| 12. |
- Achenbach, Jan-Ole, et al.
(author)
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Correlative Experimental and Theoretical Investigation of the Angle-Resolved Composition Evolution of Thin Films Sputtered from a Compound Mo2BC Targe
- 2019
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In: Coatings. - : MDPI AG. - 2079-6412. ; 9:3
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Journal article (peer-reviewed)abstract
- The angle-resolved composition evolution of Mo-B-C thin films deposited from a Mo2BC compound target was investigated experimentally and theoretically. Depositions were carried out by direct current magnetron sputtering (DCMS) in a pressure range from 0.09 to 0.98 Pa in Ar and Kr. The substrates were placed at specific angles α with respect to the target normal from 0 to ±67.5°. A model based on TRIDYN and SIMTRA was used to calculate the influence of the sputtering gas on the angular distribution function of the sputtered species at the target, their transport through the gas phase, and film composition. Experimental pressure- and sputtering gas-dependent thin film chemical composition data are in good agreement with simulated angle-resolved film composition data. In Ar, the pressure-induced film composition variations at a particular α are within the error of the EDX measurements. On the contrary, an order of magnitude increase in Kr pressure results in an increase of the Mo concentration measured at α = 0° from 36 at.% to 43 at.%. It is shown that the mass ratio between sputtering gas and sputtered species defines the scattering angle within the collision cascades in the target, as well as for the collisions in the gas phase, which in turn defines the angle- and pressure-dependent film compositions.
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| 13. |
- Azina, Clio, et al.
(author)
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Oxidation behaviour of V2AlC MAX phase coatings
- 2020
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In: Journal of the European Ceramic Society. - : ELSEVIER SCI LTD. - 0955-2219 .- 1873-619X. ; 40:13, s. 4436-4444
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Journal article (peer-reviewed)abstract
- We report on the oxidation behaviour of V2AlC coatings up to 800 degrees C, in air. The coatings were deposited at 580 degrees C using magnetron sputtering from a powder metallurgical composite V2AlC target and were subsequently oxidised for 5, 15 and 30 min. The microstructural evolution of the samples was investigated, and X-ray diffraction patterns were collected to track the formation of oxides. The first indications of oxidation appear after just 15 min at 500 degrees C, as V-based oxides grew on the surface of the coatings. Later, the presence of mostly V-based oxides and ternary (V, Al)-oxides was observed starting after 5 min at 600 degrees C. Further analyses confirmed outward diffusion of V and inward diffusion of O, while Al tends to sublimate. alpha-A12O3 was only indexed after 5 min at 800 degrees C. Ex-situ electrical resistivity measurements allowed tracking the oxidation progress of the V2AlC coating.
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| 14. |
- Bakhit, Babak, 1983-, et al.
(author)
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Dense Ti0.67Hf0.33B1.7 thin films grown by hybrid HfB2-HiPIMS/TiB2-DCMS co-sputtering without external heating
- 2021
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In: Vacuum. - : Elsevier. - 0042-207X .- 1879-2715. ; 186
-
Journal article (peer-reviewed)abstract
- There is a need for developing synthesis techniques that allow the growth of high-quality functional films at low substrate temperatures to minimize energy consumption and enable coating temperature-sensitive substrates. A typical shortcoming of conventional low-temperature growth strategies is insufficient atomic mobility, which leads to porous microstructures with impurity incorporation due to atmosphere exposure, and, in turn, poor mechanical properties. Here, we report the synthesis of dense Ti0.67Hf0.33B1.7 thin films with a hardness of ∼41.0 GPa grown without external heating (substrate temperature below ∼100 °C) by hybrid high-power impulse and dc magnetron co-sputtering (HfB2-HiPIMS/TiB2-DCMS) in pure Ar on Al2O3(0001) substrates. A substrate bias potential of −300 V is synchronized to the target-ion-rich portion of each HiPIMS pulse. The limited atomic mobility inherent to such desired low-temperature deposition is compensated for by heavy-mass ion (Hf+) irradiation promoting the growth of dense Ti0.67Hf0.33B1.7.
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| 15. |
- Bonninghoff, Niklas, et al.
(author)
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ZrCuAlNi thin film metallic glass grown by high power impulse and direct current magnetron sputtering
- 2021
-
In: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 412
-
Journal article (peer-reviewed)abstract
- High-power impulse magnetron sputtering (HiPIMS) is a thin film deposition technique that combines the advantages of energetic deposition methods with magnetron sputtering. HiPIMS has so far mostly been utilized for the growth of crystalline coatings. Here we offer a study devoted to metallic glasses, in which we compare Zr60Cu25Al10Ni5 (target composition) thin films deposited by conventional direct current magnetron sputtering (DC) and HiPIMS. Film microstructure is strongly dependent on the choice of the sputtering method. The DC layers show a columnar structure with intra-columnar porosity, which provides a pathway for oxygen diffusion into the film. In contrast, HiPIMS films are column-free and possess about 4% higher density, as revealed by X-ray reflectivity. Electron diffraction reveals a decrease in average atomic spacing for the latter film of about 12%. These differences in film properties and morphology can be attributed to an increase in ad-atom mobility during HiPIMS caused by an increase in ion energy and flux of the film-forming species enabling a more efficient energy and momentum transfer to the growing film surface. The relative contribution of metallic and hence film forming ions to the overall ion flux of the DC plasma compared to the HiPIMS plasma is 13% and 96%, respectively. Additionally, a substrate bias causes the ionized film forming species during HiPIMS to arrive close to the substrate normal reducing shadowing effects. Different microstructures have a direct effect on the average roughness values, which for DC and HiPIMS films are 1.4 nm and 0.2 nm, respectively. The indentation hardness H and Youngs modulus E are higher for the HiPIMS sample, at 9.2 +/- 0.3 GPa and 131.6 +/- 3.6 GPa, respectively. The increase in hardness for the HiPIMS sample as compared to the DC sample (similar to 35%) can be attributed to higher film density, compressive (HiPIMS) as opposed to tensile (DC) stress and the lack of a columnar structure.
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| 16. |
- Charalampopoulou, Evangelia, et al.
(author)
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Early stages of dissolution corrosion in 316L and DIN 1.4970 austenitic stainless steels with and without anticorrosion coatings in static liquid lead-bismuth eutectic (LBE) at 500 degrees C
- 2021
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In: Materials Characterization. - : ELSEVIER SCIENCE INC. - 1044-5803 .- 1873-4189. ; 178
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Journal article (peer-reviewed)abstract
- This work addresses the early stages (<= 1000 h) of the dissolution corrosion behavior of 316L and DIN 1.4970 austenitic stainless steels in contact with oxygen-poor (C-O < 10(-8) mass%), static liquid lead-bismuth eutectic (LBE) at 500 degrees C for 600-1000 h. The objective of this study was to determine the relative early-stage resistance of the uncoated steels to dissolution corrosion and to assess the protectiveness of select candidate coatings (Cr2AlC, Al2O3, V2AlxCy). The simultaneous exposure of steels with intended differences in microstructure and thermomechanical state showed the effects of steel grain size, density of annealing/deformation twins, and secondary precipitates on the steel dissolution corrosion behavior. The findings of this study provide recommendations on steel manufacturing with the aim of using the steels to construct Gen-IV lead-cooled fast reactors.
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| 17. |
- Chien, Yu-Ping, et al.
(author)
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Deviations between film and target compositions induced by backscattered Ar during sputtering from M-2-Al-C (M = Cr, Zr, and Hf) composite targets
- 2022
-
In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 446
-
Journal article (peer-reviewed)abstract
- M-Al-C (M = Cr, Zr, and Hf) thin films are deposited from stoichiometric M2AlC composite targets by direct current magnetron sputtering (DCMS) and high power pulsed magnetron sputtering (HPPMS) in an industrial coater. Using DCMS it is observed that the composition of the Cr-Al-C film is close to stoichiometric, while the Al concentration in the Zr-Al-C and Hf-Al-C films is significantly reduced compared to the Al concentration in the targets. It is evident that the magnitude of the difference in Al concentration between the target and the cor-responding film composition is strongly dependent on the atomic mass of the transition metal. Zr and Hf atoms are 1.8 and 3.4 times heavier than Cr. In HPPMS, the target potential is approximately 1.6 times larger than that in DCMS, which can result in the film compositions deviating even stronger from the target composition as compared to DCMS. The Zr-Al-C thin film deposited by HPPMS exhibits a larger Al-deficiency than the film deposited by DCMS. The energy distributions of backscattered Ar neutrals are simulated by utilizing a two-body collision model and the Transport of Ions in Matter (TRIM) code. Based on the simulation results the experimentally observed Al -deficient film compositions can be readily explained: As the mass of the transition metal in the target is increased, both, energy and flux of the (at the target) reflected Ar is increased causing preferential re-sputtering of Al in the films. As stoichiometric compositions are a prerequisite for the formation of single-phase compound thin films it is evident that composite targets with a transition metal mass-dependent Al-overstoichiometry are required to compensate the Al-loss induced by the energetic Ar neutrals.
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| 18. |
- Chiodin, G, et al.
(author)
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High surface IgM levels associate with shorter response to ibrutinib and BTK bypass in patients with CLL
- 2022
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In: Blood advances. - : American Society of Hematology. - 2473-9537 .- 2473-9529. ; 6:18, s. 5494-5504
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Journal article (peer-reviewed)abstract
- Chronic lymphocytic leukemia (CLL) cells have variably low surface IgM (sIgM) levels/signaling capacity, influenced by chronic antigen engagement at tissue sites. Within these low levels, CLL with relatively high sIgM (CLLhigh) progresses more rapidly than CLL with low sIgM (CLLlow). During ibrutinib therapy, surviving CLL cells redistribute into the peripheral blood and can recover sIgM expression. Return of CLL cells to tissue may eventually recur, where cells with high sIgM could promote tumor growth. We analyzed time to new treatment (TTNT) following ibrutinib in 70 patients with CLL (median follow-up of 66 months) and correlated it with pretreatment sIgM levels and signaling characteristics. Pretreatment sIgM levels correlated with signaling capacity, as measured by intracellular Ca2+ mobilization (iCa2+), in vitro (r = 0.70; P < .0001). High sIgM levels/signaling strongly correlated with short TTNT (P < .05), and 36% of patients with CLLhigh vs 8% of patients with CLLlow progressed to require a new treatment. In vitro, capacity of ibrutinib to inhibit sIgM-mediated signaling inversely correlated with pretherapy sIgM levels (r = −0.68; P = .01) or iCa2+ (r = −0.71; P = .009). In patients, sIgM-mediated iCa2+ and ERK phosphorylation levels were reduced by ibrutinib therapy but not abolished. The residual signaling capacity downstream of BTK was associated with high expression of sIgM, whereas it was minimal when sIgM expression was low (P < .05). These results suggested that high sIgM levels facilitated CLL cell resistance to ibrutinib in patients. The CLL cells, surviving in the periphery with high sIgM expression, include a dangerous fraction that is able to migrate to tissue and receive proliferative stimuli, which may require targeting by combined approaches.
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| 19. |
- Eriksson, Anders, et al.
(author)
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Influence of Ar and N2 Pressure on Plasma Chemistry, Ion Energy, and Thin Film Composition during Filtered Arc Deposition from Ti3SiC2 Cathodes
- 2014
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In: IEEE Transactions on Plasma Science. - : IEEE Press. - 0093-3813 .- 1939-9375. ; 42:11, s. 3498-3507
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Journal article (peer-reviewed)abstract
- Arc plasma from Ti3SiC2 compound cathodes used in a filtered dc arc system has been characterized with respect to plasma chemistry and charge-state resolved ion energies. In vacuum, the plasma composition is dominated by Ti ions, with concentrations of 84.3, 9.3, and 6.4 at% for Ti, Si, and C ions, respectively. The reduced amount of Si and most notably C compared with the cathode composition is confirmed by analysis of film composition in corresponding growth experiments. The deposition of light-element deficient films is thus related to plasma generation or filter transport. The ion energy distributions in vacuum range up to 140, 90, and 70 eV for Ti, Si, and C, respectively. Corresponding average ion energies of 48, 36, and 27 eV are reduced upon introduction of gas, down to around 5 eV at 0.6 Pa Ar or 0.3 Pa N2 for all species. In vacuum, the charge state distributions of Si and C are shifted to higher values compared with corresponding elemental cathodes, likely caused by changed effective electron temperature of the plasma stemming from compound cathode material and/or by electron impact ionization in the filter. The average ion charge states are reduced upon addition of Ar, ranging between 1.97 and 1.48 for Ti, 1.91 and 1.46 for Si, and 1.25 and 1.02 for C. Similar effects are observed upon introduction of N2, though with more efficient charge state reduction with pressure. It is conceivable that the pressure-induced changes in ion energy and charge state are crucial for the film synthesis from a microstructure evolution point of view, as they affect the ion-surface interactions through supply of energy, especially when substrate biasing is employed during arc deposition from a compound cathode.
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| 20. |
- Greczynski, Grzegorz, et al.
(author)
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Control over the Phase Formation in Metastable Transition Metal Nitride Thin Films by Tuning the Al+ Subplantation Depth
- 2019
-
In: Coatings. - : MDPI. - 2079-6412. ; 9:1
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Journal article (peer-reviewed)abstract
- The performance of transition metal nitride based coatings deposited by magnetron sputtering, in a broad range of applications including wear-protective coatings on cutting tools and components in automotive engines, is determined by their phase content. The classical example is the precipitation of thermodynamically-favored wurtzite-AlN while alloying TiN with Al to obtain ternary single phase NaCl-structure films with improved high-temperature oxidation resistance. Here, we report on reactive high-power impulse and direct current magnetron co-sputtering (HiPIMS/DCMS) growth of Ti0.31Al0.69N and Zr0.48Al0.52N thin films. The Al concentrations are intentionally chosen to be higher than theoretically predicted solubility limits for the rock salt structure. The goal is to investigate the effect of the incident Al+ energy E-Al(+), controlled by varying the amplitude of the substrate bias applied synchronously with the Al+-rich portion of the ion flux from the Al-HiPIMS source, on the crystalline phase formation. For EAl+ amp;lt;= 60 eV, films contain predominantly the wurtzite phase. With increasing E-Al(+), and thus, the Al subplantation depth, the relative fraction of the NaCl structure increases and eventually for E-Al(+) amp;gt; 250 eV, Ti0.31Al0.69N and Zr0.48Al0.52N layers contain more than 95% of the rock salt phase. Thus, the separation of the film forming species in time and energy domains determines the phase formation of Ti0.31Al0.69N and Zr0.48Al0.52N layers and enables the growth of the cubic phase outside of the predicted Al concentration range. The new film growth concept can be applied to the entire family of multinary transition metal aluminum nitrides, where one of the metallic film constituents is available in the ionized form while the other arrives as neutral.
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| 21. |
- Greczynski, Grzegorz, et al.
(author)
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Metal-ion subplantation: A game changer for controlling nanostructure and phase formation during film growth by physical vapor deposition
- 2020
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In: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 127:18
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Journal article (peer-reviewed)abstract
- Up until recently, thin film growth by magnetron sputtering relied on enhancing adatom mobility in the surface region by gas-ion irradiation to obtain dense layers at low deposition temperatures. However, an inherently low degree of ionization in the sputtered material flux during direct-current magnetron sputtering (DCMS), owing to relatively low plasma densities involved, prevented systematic exploration of the effects of metal-ion irradiation on the film nanostructure, phase content, and physical properties. Employing only gas-ion bombardment results in an inefficient energy and momentum transfer to the growing film surface. Also, for enhanced substrate biasing, the higher concentration of implanted noble gas atoms at interstitial lattice positions causes elevated compressive stress levels. High-power impulse magnetron sputtering (HiPIMS), however, provides controllable metal-ion ionization and, more importantly, enables the minimization of adverse gas-ion irradiation effects. The latter can be realized by the use of pulsed substrate bias applied synchronously with the metal-ion-rich portion of each HiPIMS pulse (metal-ion-synchronized HiPIMS), based on the results of time-resolved ion mass spectrometry analyses performed at the substrate position. In this way, both the metal-ion energy and the momentum can be precisely controlled for one to exploit the benefits of irradiation by metal-ions, which are also the film-forming species. Systematic studies performed in recent years using binary and ternary transition metal-based nitrides as model systems revealed new phenomena with accompanying unique and attractive film growth pathways. This Perspective paper focuses on the effects of low-mass metal-ion irradiation and their role for the nanostructure and phase control. We review basic findings and present original results from ion mass spectrometry studies and materials characterization for the effect of metal-ion subplantation. Key correlations are highlighted, which, if properly engaged, enable unprecedented control over film nanostructure and phase formation and, hence, the resulting properties. We show generalization from the findings to present a new concept for thin film growth in a hybrid HiPIMS/DCMS configuration with metal-ion-synchronized bias. Based on the results obtained for TM-based nitrides, there are no evident physical limitations preventing the extension of this deposition process concept for other materials systems or other metal-ion-based thin film growth techniques. Further exciting findings could, thus, be anticipated for the future.
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| 22. |
- Greczynski, Grzegorz, et al.
(author)
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Native target chemistry during reactive dc magnetron sputtering studied by ex-situ x-ray photoelectron spectroscopy
- 2017
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In: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 111:2
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Journal article (peer-reviewed)abstract
- We report x-ray photoelectron spectroscopy (XPS) analysis of native Ti target surface chemistry during magnetron sputtering in an Ar/N-2 atmosphere. To avoid air exposure, the target is capped immediately after sputtering with a few-nm-thick Al overlayers; hence, information about the chemical state of target elements as a function of N-2 partial pressure p(N2) is preserved. Contrary to previous reports, which assume stoichiometric TiN formation, we present direct evidence, based on core-level XPS spectra and TRIDYN simulations, that the target surface is covered by TiNx with x varying in a wide range, from 0.27 to 1.18, depending on p(N2). This has far-reaching consequences both for modelling of the reactive sputtering process and for everyday thin film growth where detailed knowledge of the target state is crucial. Published by AIP Publishing.
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| 23. |
- Greczynski, Grzegorz, et al.
(author)
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Selectable phase formation in VAlN thin films by controlling Al+ subplantation depth
- 2017
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In: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 7
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Journal article (peer-reviewed)abstract
- We report on a thin film synthesis technique which allows for unprecedented control over the crystalline phase formation in metastable transition metal nitride based layers. For the model material system of V0.26Al0.74N, a complete transition from hexagonal to supersaturated cubic structure is achieved by tuning the incident energy, hence subplantation depth, of Al+ metal ions during reactive hybrid high power impulse magnetron sputtering of Al target and direct current magnetron sputtering of V target in Ar/N-2 gas mixture. These findings enable the phase selective synthesis of novel metastable materials that combine excellent mechanical properties, thermal stability, and oxidation resistance.
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| 24. |
- Greczynski, Grzegorz, et al.
(author)
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Substantial difference in target surface chemistry between reactive dc and high power impulse magnetron sputtering
- 2018
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In: Journal of Physics D. - : IOP PUBLISHING LTD. - 0022-3727 .- 1361-6463. ; 51:5
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Journal article (peer-reviewed)abstract
- The nitride layer formed in the target race track during the deposition of stoichiometric TiN thin films is a factor 2.5 thicker for high power impulse magnetron sputtering (HIPIMS), compared to conventional dc processing (DCMS). The phenomenon is explained using x-ray photoelectron spectroscopy analysis of the as-operated Ti target surface chemistry supported by sputter depth profiles, dynamic Monte Carlo simulations employing the TRIDYN code, and plasma chemical investigations by ion mass spectrometry. The target chemistry and the thickness of the nitride layer are found to be determined by the implantation of nitrogen ions, predominantly N+ and N-2(+) for HIPIMS and DCMS, respectively. Knowledge of this method-inherent difference enables robust processing of high quality functional coatings.
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| 25. |
- Greczynski, Grzegorz, et al.
(author)
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Unintentional carbide formation evidenced during high-vacuum magnetron sputtering of transition metal nitride thin films
- 2016
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In: Applied Surface Science. - : ELSEVIER SCIENCE BV. - 0169-4332 .- 1873-5584. ; 385, s. 356-359
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Journal article (peer-reviewed)abstract
- Carbide signatures are ubiquitous in the surface analyses of industrially sputter-deposited transition metal nitride thin films grown with carbon-less source materials in typical high-vacuum systems. We use high-energy-resolution photoelectron spectroscopy to reveal details of carbon temporal chemical state evolution, from carbide formed during film growth to adventitious carbon adsorbed upon contact with air. Using in-situ grown Al capping layers that protect the as-deposited transition metal nitride surfaces from oxidation, it is shown that the carbide forms during film growth rather than as a result of post deposition atmosphere exposure. The XPS signature of carbides is masked by the presence of adventitious carbon contamination, appearing as soon as samples are exposed to atmosphere, and eventually disappears after one week-long storage in lab atmosphere. The concentration of carbon assigned to carbide species varies from 0.28 at% for ZrN sample, to 0.25 and 0.11 at% for TiN and HfN, respectively. These findings are relevant for numerous applications, as unintentionally formed impurity phases may dramatically alter catalytic activity, charge transport and mechanical properties by offsetting the onset of thermally induced phase transitions. Therefore, the chemical state of C impurities in PVD-grown films should be carefully investigated. (C) 2016 Elsevier B.V. All rights reserved.
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| 26. |
- Greczynski, Grzegorz, et al.
(author)
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Venting temperature determines surface chemistry of magnetron sputtered TiN films
- 2016
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In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 108:4, s. 041603-1-041603-5
-
Journal article (peer-reviewed)abstract
- Surface properties of refractory ceramic transition metal nitride thin films grown by magnetron sputtering are essential for resistance towards oxidation necessary in all modern applications. Here, typically neglected factors, including exposure to residual process gases following the growth and the venting temperature T-v, each affecting the surface chemistry, are addressed. It is demonstrated for the TiN model materials system that T-v has a substantial effect on the composition and thickness-evolution of the reacted surface layer and should therefore be reported. The phenomena are also shown to have impact on the reliable surface characterization by x-ray photoelectron spectroscopy. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
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| 27. |
- Hu, Chun, et al.
(author)
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Influence of co-sputtering AlB2 to TaB2 on stoichiometry of non-reactively sputtered boride thin films
- 2024
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In: Materials Research Letters. - : TAYLOR & FRANCIS INC. - 2166-3831. ; 12:8, s. 561-570
-
Journal article (peer-reviewed)abstract
- Transition metal diboride thin films are promising functional materials for their outstanding mechanical properties and thermal stability. By combining experiment and simulations, we discuss angular distribution of the sputtered species, their scattering in the gas phase, re-sputtering and potential evaporation from the grown films for the complex evolution of film compositions, as well as energetic preference for vacancy formation and competing phases as factors for governing the phase constitution. By co-sputtering from two compound targets, we developed phase-pure crystalline (Ta,Al)B2 solid solution thin films and correlate the stoichiometry changes with the evolution of their microstructure, hardness, and elastic modulus. {GRAPHICAL ABSTRACT}
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| 28. |
- Karimi Aghda, Soheil, et al.
(author)
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Unravelling the ion-energy-dependent structure evolution and its implications for the elastic properties of (V,Al)N thin films
- 2021
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In: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 214
-
Journal article (peer-reviewed)abstract
- Ion irradiation-induced changes in the structure and mechanical properties of metastable cubic (V,Al)N deposited by reactive high power pulsed magnetron sputtering are systematically investigated by correlating experiments and theory in the ion kinetic energy (Ek) range from 4 to 154 eV. Increasing Ek results in film densification and the evolution from a columnar (111) oriented structure at Ek ≤ 24 eV to a fine-grained structure with (100) preferred orientation for Ek ≥ 104 eV. Furthermore, the compressive intrinsic stress increases by 336 % to -4.8 GPa as Ek is increased from 4 to 104 eV. Higher ion kinetic energy causes stress relaxation to -2.7 GPa at 154 eV. These ion irradiation-induced changes in the thin film stress state are in good agreement with density functional theory simulations. Furthermore, the measured elastic moduli of (V,Al)N thin films exhibit no significant dependence on Ek. The apparent independence of the elastic modulus on Ek can be rationalized by considering the concurrent and balancing effects of bombardment-induced formation of Frenkel pairs (causing a decrease in elastic modulus) and evolution of compressive intrinsic stress (causing an increase in elastic modulus). Hence, the evolution of the film stresses and mechanical properties can be understood based on the complex interplay of ion irradiation-induced defect generation and annihilation.
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| 29. |
- Liu, Sida, et al.
(author)
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Modeling of metastable phase formation for sputtered Ti1-xAlxN thin films
- 2019
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In: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 165, s. 615-625
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Journal article (peer-reviewed)abstract
- Metastable titanium aluminum nitride coatings are widely applied in cutting and forming applications. Although it is generally accepted that the phase formation of metastable TiAIN is governed by kinetic factors, modeling attempts today are based solely on energetics. In this work, the metastable phase formation of TiAIN is predicted based on one combinatorial magnetron sputtering experiment, the activation energy for surface diffusion, the critical diffusion distance, as well as thermodynamic calculations. The phase formation data obtained from further combinatorial growth experiments varying chemical composition, deposition temperature, and deposition rate are in good agreement with the model. Furthermore, it is demonstrated that a significant extension of the predicted critical solubility range is enabled by taking kinetic factors into account. Explicit consideration of kinetics extends the Al solubility limit to lower values, previously unobtainable by energetics, but accessible experimentally. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 30. |
- Liu, Sida, et al.
(author)
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Stress-dependent prediction of metastable phase formation for magnetron-sputtered V1-xAlxN and Ti1-xAlxN thin films
- 2020
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In: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 196, s. 313-324
-
Journal article (peer-reviewed)abstract
- Metastable transition metal aluminum nitride (TMAlN, TM = Ti, V) thin films are today deposited utilizing ionized vapor phase condensation techniques where variations in ion flux and ion energy cause compressive film stress, in turn affecting Al solubility. While the metastable phase formation of TiAlN has been modeled, the influence of film stresses on phase formation has so far been overlooked. Using combinatorial deposition via magnetron sputtering, thermodynamic modeling and density functional theory calculations, we investigated the phase formation of V1-xAlxN and Ti1-xAlxN thin films at various substrate temperatures and deposition rates. Ab initio calculations indicate that the maximum solid solubility of Al in face-centered cubic (fcc) V1-xAlxN or fcc-Ti1-xAlxN shows a linear trend as a function of the magnitude of compressive stress. Here, we consider the influence of film stresses on the metastable phase formation of fcc-V1-xAlxN and fcc-Ti1-xAlxN for the first time. Specifically, experimental data from a single combinatorial deposition is utilized to predict the stress-dependent formation of metastable phases based on thermodynamic and ab initio data. Explicit consideration of stress extends the Al solubility limit to higher values for both Ti1-xAlxN and V1-xAlxN thin films, previously unobtainable by energetics, but accessible experimentally. These predictions are experimentally verified and thus provide guidance for experimental efforts with the goal of increasing the Al concentration in fcc-TMAlN thin films. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 31. |
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| 32. |
- Nedfors, Nils, et al.
(author)
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Influence of the Al concentration in Ti-Al-B coatings on microstructure and mechanical properties using combinatorial sputtering from a segmented TiB2/AlB2 target
- 2019
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In: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 364, s. 89-98
-
Journal article (peer-reviewed)abstract
- A series of (TixAl1-x)B2 +y coatings with compositions in the range of x = 0.01-0.94 and y = 1.70-2.92 has been synthesized using magnetron sputtering from a segmented TiB2/AlB2 target. The coatings are amorphous at x amp;lt;= 0.05 while a (TixAl1-x)B2+y solid solution forms for x amp;gt; 0.05. As a consequence of the sputtering process, the B/(Ti + Al) atomic ratio varied with the metal content resulting in the formation of under-stoichiometric coatings at x amp;lt; 0.35 and over-stoichiometric coatings at x amp;gt; 0.35. Surplus Al segregates to grain boundaries of the under-stoichiometric coatings whereas the over-stoichiometric coatings have a tissue phase containing mainly B and some Al. The B-rich tissue phase restrains grain growth in the in-plane direction while an increase in Ti content promotes the growth of columnar structured coatings with a pronounced (001) texture up to x = 0.84. The combination of such preferred orientation and tissue phase results in the highest hardness of 39 GPa for the (Ti0.79Al0.21)B-2.70 coating. The Youngs modulus, on the other hand, increases continuously from 262 GPa for the most Al-rich coating to 478 GPa for the most Ti-rich coating. Comparing to calculated values of Youngs modulus, good agreement is observed for the close to stoichiometric coatings (x = 0.40-0.50). For the off-stoichiometric coatings, the experimental values are lower due to the existence of the tissue phase.
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| 33. |
- Olsen, Jeanine L, et al.
(author)
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The genome of the seagrass Zostera marina reveals angiosperm adaptation to the sea.
- 2016
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In: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 530:7590, s. 331-5
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Journal article (peer-reviewed)abstract
- Seagrasses colonized the sea on at least three independent occasions to form the basis of one of the most productive and widespread coastal ecosystems on the planet. Here we report the genome of Zostera marina (L.), the first, to our knowledge, marine angiosperm to be fully sequenced. This reveals unique insights into the genomic losses and gains involved in achieving the structural and physiological adaptations required for its marine lifestyle, arguably the most severe habitat shift ever accomplished by flowering plants. Key angiosperm innovations that were lost include the entire repertoire of stomatal genes, genes involved in the synthesis of terpenoids and ethylene signalling, and genes for ultraviolet protection and phytochromes for far-red sensing. Seagrasses have also regained functions enabling them to adjust to full salinity. Their cell walls contain all of the polysaccharides typical of land plants, but also contain polyanionic, low-methylated pectins and sulfated galactans, a feature shared with the cell walls of all macroalgae and that is important for ion homoeostasis, nutrient uptake and O2/CO2 exchange through leaf epidermal cells. The Z. marina genome resource will markedly advance a wide range of functional ecological studies from adaptation of marine ecosystems under climate warming, to unravelling the mechanisms of osmoregulation under high salinities that may further inform our understanding of the evolution of salt tolerance in crop plants.
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| 34. |
- Patterer, Lena, et al.
(author)
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Effect of Si on the hydrogen-based direct reduction of Fe2O3 studied by XPS of sputter-deposited thin-film model systems
- 2023
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In: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 233
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Journal article (peer-reviewed)abstract
- Understanding the effect of gangue elements is of critical importance to optimize the efficiency of hydrogen -based direct reduction (HyDR) of iron ore, as one of the key steps towards climate-neutral steel production. Here, we demonstrate on the example of Si-doped Fe2O3, how thin films can be effectively utilized as a model system to facilitate systematic investigation of the solid-state reduction behavior. In-vacuo X-ray photoelectron spectroscopy (XPS) is used to probe the reduction kinetics by analyzing the chemical state of iron oxide thin films before and after annealing at 700 degrees C in an Ar+5%H2 atmosphere. It is demonstrated that even low Si concen-trations of 3.7 at.% inhibit the HyDR of Fe2O3 by the formation of a SiOx-enriched reduction barrier in the surface-near region.
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| 35. |
- Sarakinos, Kostas, et al.
(author)
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Exploring the potential of high power impulse magnetron sputtering for growth of diamond-like carbon films
- 2012
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In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 206:10, s. 2706-2710
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Journal article (peer-reviewed)abstract
- Amorphous carbon films are deposited employing high power impulse magnetron sputtering (HiPIMS) at pulsing frequencies of 250 Hz and 1 kHz. Films are also deposited by direct current magnetron sputtering (dcMS), for reference. In both HiPIMS and dcMS cases, unipolar pulsed negative bias voltages up to 150 V are applied to the substrate to tune the energy of the positively charged ions that bombard the growing film. Plasma analysis reveals that HiPIMS leads to generation of a larger number of ions with larger average energies, as compared to dcMS. At the same time, the plasma composition is not affected, with Ar+ ions being the dominant ionized species at all deposition conditions. Analysis of the film properties shows that HiPIMS allows for growth of amorphous carbon films with sp(3) bond fraction up to 45% and density up to 2.2 g cm(-3). The corresponding values achieved by dcMS are 30% and 2.05 g cm(-3), respectively. The larger fraction of sp(3) bonds and mass density found in films grown by HiPIMS are explained in light of the more intense ion irradiation provided by the HiPIMS discharge as compared to the dcMS one.
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| 36. |
- Thörnberg, Jimmy, et al.
(author)
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Oxidation resistance and mechanical properties of sputter-deposited Ti0.9Al0.1B2-y thin films
- 2022
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In: Surface & Coatings Technology. - : Elsevier Science SA. - 0257-8972 .- 1879-3347. ; 442
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Journal article (peer-reviewed)abstract
- Direct-current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS) were used to deposit understoichiometric Ti(1-x)Al(x)B(2-y )diboride coatings by sputtering from a segmented TiB2-AlB2 target using Ar and Kr as sputtering gas. For films with a fixed Al/(Ti + Al) ratio of x = 0.1 (Ti0.9Al0.1B2-y), the B content was varied with y & ISIN; (0.1, 0.6 and 0.7). For films with a fixed y = 0.7 (Ti1-xAlxB1.3), the Al content was varied with x & ISIN; (0.1, 0.4 and 0.7). Evaluation of the mechanical properties of the Ti1-xAlxB1.3 samples showed a reduction in both hardness and elastic modulus with increasing Al concentration, while the Ti0.9Al0.1B2-y samples showed a hardness increase with decreasing B content. Thus, Ti0.9Al0.1B1.3 films exhibited a superior hardness of 46.2 +/- 1.1 GPa and an elastic modulus of 523 & PLUSMN; 7 GPa, compared to the values for Ti0.9Al0.1B1.4 and Ti0.9Al0.1B1.9, showing a hardness of 44 +/- 1 GPa and 36 +/- 1 GPa, and an elastic modulus of 569 +/- 7 GPa and 493 +/- 6 GPa, respectively. The oxidation behavior of the mechanically most promising Ti0.9Al0.1B2-y sample series was investigated through air-annealing at 600 C for durations from 1 h to 10 h. All films formed a mixed non-conformal Al2O3-TiO2 oxide scale which acts as an inward and outward diffusion barrier, significantly reducing the oxidation rate compared to TiBz films, which form an oxide scale consisting of porous TiO2. The thinnest oxide scale after 10 h was found in the B-deficient samples, Ti0.9Al0.1B1.3 and Ti0.9Al0.1B1.4, at ~200 nm, which is significantly below that for Ti0.9Al0.1B1.9 at 320 nm. The enhanced oxidation resistance of highly understoichiometric films is due to the elimination of the B-rich tissue phase that is present at the grain boundaries for higher B content, where the latter has been shown to enhance the rate of oxidation in borides.
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