From Ti–Al- to Ti–Al–N-sputtered 2D materials (original) (raw)
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Structure, hardness and thermal stability of Ti(Al,N) coatings
Surface and Coatings Technology, 2006
In the past two decades, coatings of the Ti-Al-N ternary system have attracted considerable research and industrial interest. Nevertheless, the Ti-Al-N system still offers new interesting possibilities for coating developments such as the addition of low N contents to Ti-Al films in order to reach a good compromise between high hardness and a low friction coefficient. Ti-Al-N coatings with low nitrogen content were deposited by closed field unbalanced magnetron sputtering using two facing Ti targets inserted with Al rods. The Al/(Al + Ti) and N/(Al + Ti + N) atomic ratios were varied from 21 to 28 at.% and 0 to 33 at.%, respectively. Hexagonal close-packed (hcp) α-Ti with a preferential b001N orientation was the only phase detected by X-ray diffraction in the as-deposited films. A decrease in the α-Ti c lattice parameter was observed as aluminium was added to the films. Nitrogen addition increased the c lattice parameter and led to a progressive loss of crystallinity until quasi-amorphous films were obtained. A hardness of ≈13 GPa was obtained for the as-deposited films without nitrogen. A continuous increase in hardness was observed with increasing nitrogen content. The highest hardness values (up to 27 GPa) were obtained for the quasi-amorphous films. Annealing of the films with low aluminium content (Al/Al + Ti ≈ 21 at.%) did not significantly affect their structure as hcp Ti remains the only phase detected. On the contrary, annealing of the films deposited with higher aluminium contents (Al/(Al + Ti) ≈ 24 and ≈ 28 at.%) resulted in the formation of face centered cubic (fcc) Al or Ti 3 Al, showing that the thermal stability of the films decreased with aluminium incorporation.
Coatings and Thin-Film Technologies, 2019
For several decades, the increasing productivity in many industrial domains has led to a significant and ever-increased interest to protective and hard coatings. In this context, titanium-aluminum nitrides were developed and are now widely used in a large range of applications, due to their high hardness, good thermal stability, and oxidation resistance. This chapter reviews the thermodynamical characteristics of the Ti-Al-N system by reporting the progress made in the description of the Ti-Al-N phase diagram and the main mechanical and chemical properties of Ti 1Àx Al x N-based coatings. As a metastable phase, the existence of the fcc-Ti 1Àx Al x N depends on particular process parameters, allowing stabilizing this desirable solid solution. The influence of process parameters, with a particular interest for chemical vapor deposition (CVD) methods, on morphology and crystallographic structure is then described. The structure of Ti 1Àx Al x N thin films depends also on the aluminum content as well as on the annealing temperature, due to the spinodal nature of the Ti-Al-N system. These changes of crystallographic structure can induce an improvement of the hardness, oxidation resistance, and wear behavior of these coatings. The main mechanical and chemical properties of physical vapor deposition (PVD) and CVD Ti 1Àx Al x N-based coatings are also described.
Compositional and structural evolution of sputtered Ti-Al-N
Thin Solid Films, 2009
The compositional and structural evolution of Ti-Al-N thin films as a function of the total working gas pressure (p T ), the N 2 -to-total pressure ratio (p N2 /p T ), the substrate-to-target distance (ST), the substrate position, the magnetron power current (I m ), the externally applied magnetic field, and the energy and the ion-to-metal flux ratio of the ion bombardment during reactive sputtering of a Ti 0.5 Al 0.5 target is investigated in detail. Based on this variation we propose that the different poisoning states of the Ti and Al particles of the powder-metallurgically prepared Ti 0.5 Al 0.5 target in addition to scattering and angular losses of the sputter flux cause a significant modification in the Al/Ti ratio of the deposited thin films ranging from~1.05 to 2.15. The compositional variation induces a corresponding structural modification between single-phase cubic, mixed cubic-hexagonal and single-phase hexagonal. However, the maximum Al content for single-phase cubic Ti 1−x Al x N strongly depends on the deposition conditions and was obtained with x = 0.66, for the coating deposited at 500°C, p T = 0.4 Pa, ST = 85 mm, and p N2 /p T = 17%. Our results show, that in particular, the N 2 -to-total pressure ratio in combination with the sputtering power density of the Ti 0.5 Al 0.5 compound target has a pronounced effect on the Al/Ti ratio and the structure development of the coatings prepared.
Increased thermal stability of Ti–Al–N thin films by Ta alloying
Surface and Coatings Technology, 2012
To increase the thermal stability of protective coatings has always been a major topic for application oriented materials development. Here, we study the impact of Ta on the thermal stability of magnetron sputtered Ti 1−x Al x N thin films using a combined ab initio and experimental approach. With increasing Ta content in Ti 1−x−y Al x Ta y N, a decreasing energy of formation, as well as an increasing interaction of the transition metal d-states go along with an increase in cohesive energy, which point toward a higher stability of the quaternary system. The ab initio predicted increasing bonding strength of Ti 1−x−y Al x Ta y N with increasing Ta content was corroborated by structural and mechanical investigations of Ti 1−x−y Al x Ta y N thin films with y = 0, 0.03, 0.05, and 0.1, respectively. With increasing Ta content, a hardness increase of 25%, from 30 GPa to~40 GPa, can be observed after deposition. Annealing experiments in vacuum show that the decomposition process of the supersaturated solid solution towards their stable constituents c-Ti 1-z Ta z N (with z = y/(1− x)) and hexagonal (wurtzite structure, w) w-AlN, is effectively retarded from~900 to~1200°C with increasing Ta content. The involved decomposition into c-Ti-Ta-rich and c-Al-rich domains results in hardness maxima of~38 to~42 GPa for y =0 and 0.1, respectively. Oxidation experiments for 20 h at 850 and 950°C yielded fully oxidized Ta-free coatings, whereas the addition of only 3 at.% Ta to the metal sublattice results in the form of a layered oxide scale and remaining unoxidized nitride layer thicknesses of~95 and~87% (with respect to the as deposited films), respectively.
Ti-Al-N-Based Hard Coatings: Thermodynamical Background, CVD Deposition, and Properties. A Review
IntechOpen eBooks, 2019
For several decades, the increasing productivity in many industrial domains has led to a significant and ever-increased interest to protective and hard coatings. In this context, titanium-aluminum nitrides were developed and are now widely used in a large range of applications, due to their high hardness, good thermal stability, and oxidation resistance. This chapter reviews the thermodynamical characteristics of the Ti-Al-N system by reporting the progress made in the description of the Ti-Al-N phase diagram and the main mechanical and chemical properties of Ti 1Àx Al x N-based coatings. As a metastable phase, the existence of the fcc-Ti 1Àx Al x N depends on particular process parameters, allowing stabilizing this desirable solid solution. The influence of process parameters, with a particular interest for chemical vapor deposition (CVD) methods, on morphology and crystallographic structure is then described. The structure of Ti 1Àx Al x N thin films depends also on the aluminum content as well as on the annealing temperature, due to the spinodal nature of the Ti-Al-N system. These changes of crystallographic structure can induce an improvement of the hardness, oxidation resistance, and wear behavior of these coatings. The main mechanical and chemical properties of physical vapor deposition (PVD) and CVD Ti 1Àx Al x N-based coatings are also described.
Crystallization of amorphous phase in sputter-deposited Ti-Al alloy thin films
Metallurgical and Materials Transactions A, 1996
The formation of amorphous phases in metallic alloys by various nonequilibrium processing routes such as rapid solidification of molten alloys, vapor quenching, mechanical alloying, or solid state diffusion is well documented5 ~l These amorphous phases are usually referred to as metallic glasses. Thermodynamically, the amorphous phase in metallic glasses is in a state of metastable equilibrium. Therefore, unless prevented by kinetic considerations, it should be possible to transform the metastable amorphous phase into stable crystalline phases by suitable heat treatments, perhaps involving transitional metastable crystalline phases. The present study deals with the microstructural and phase characterization of as-deposited Ti-A1 alloy thin films and of the same thin films after annealing at 823 K. This is a relevant study because of the interest in efforts toward the synthesis of laminated thin film nano-and microcomposites based on intermetallic transition metal aluminides for structural coatings to be used in high-temperature aerospace ap-plications52] Amorphous Ti-A1 alloy thin films deposited by sputter deposition from dual targets of pure Ti and pure A1 have been found to exhibit extended periods of passivity in chloride-based solutions as compared to their crystalline counterparts, t3,4,51 Amorphous phases have also been found to form in mechanically alloyed Ti + AI powders c6---~41 and in irradiated Ti/AI multilayered thin films.US~ The as-deposited films as well as the annealed films have been characterized by transmission electron microscopy (TEM).
In this work (Ti,Si,Al)N films were deposited using only rf or a combination of rf and d.c. reactive magnetron sputtering. Chemical composition, thickness, film structure and mechanical properties of the films were investigated by means of Rutherford backscattering (RBS), electron microprobe analysis (EPMA), ball-cratering, X-ray diffraction (XRD) and ultramicroindentation, respectively. All samples showed high hardness values, exceeding, in some cases, 50 GPa. XRD results revealed the formation of a mixture of two phases whose structure is similar to TiN. One phase is noted as being TiN bulk with a lattice parameter of 0.428 nm and develops only in conditions of high surface mobility. This behaviour can be associated with the segregation of the SiN phase, though the formation of an amorphous AlN phase cannot be excluded. Another phase, which is noted as Ti-Si-Al-N x (af0.420 nm), where Si and Al atoms substitute the Ti atoms on the TiN lattice, develops in situations of lower surface mobility. The thermal stability of these coatings was studied by thermal treatments in a vacuum atmosphere, where it was found that a small increase in hardness was obtained after 1 h heat treatment at 8008C. ᮊ
International Journal of Engineering Research and Technology (IJERT), 2012
https://www.ijert.org/titanium-aluminium-thin-films-preparation-by-oblique-angle-sputtering-and-their-characterization https://www.ijert.org/research/titanium-aluminium-thin-films-preparation-by-oblique-angle-sputtering-and-their-characterization-IJERTV1IS8631.pdf Intermetallic titanium (Ti) aluminium (Al) films (Al content ranging from ~48 to ~53 at.%) were prepared on different substrates at 500˚C by unbalanced reactive magnetron sputtering in an Argon atmosphere of varying pressure. The chemical composition, microstructure, stress and microhardness properties of these films were systematically investigated by means of energy dispersive spectrometry (EDS), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and microhardness measurements. Also heat treatment studies were carried out for the coated films. The XRD measurements reveal evolution of crystallite Ti-Al structure of the deposited films. The observed peak shows varying aluminium composition and their structures are in the form of Ti 1-x Al x In order to understand the microstructure evolution, the XRD spectra and corresponding calculations of the Ti-Al films without substrate heating during deposition are also analyzed. The surface roughness of Ti-Al films also exhibits a nonlinear variation, which is due to the variation of grain size and the competitive growth of different size particles. The influences of microhardness of the films with various substrates were analysed. All the intermetallic Ti-Al films show enhanced mechanical properties when compared with the composite TiN films deposited under the same condition. The best microhardness is obtained for the Ti-Al film with 52 at.% Al.
viXra, 2012
DC magnetron sputtering is a well-developed deposition technique for coatings and thin films used in industrial applications. The experiments were performed with unbalanced circular magnetron sputtering targets of aluminium (99.999%) and titanium (99.99%). Sputtering of aluminium (Al) and titanium (Ti) was carried out in pure argon (99.999%) atmosphere at base pressure of 4 × 10−6 torr and constant sputtering pressure of 5 × 10−3 torr. Substrate materials were mainly stainless steel (304) and aluminum plates. Characterization of TiAl films deposited onto different substrates was evaluated using XRD, SEM and EDS analysis techniques. The film surface and cross-section was examined using a scanning electron microscope (SEM). The TiAl phase was confirmed using XRD analysis. The composition of the TiAl film was determined using EDS technique. These characterizations revealed the growth of TiAl intermetallic thinfilm with a characteristic crystallite size of 123.9 A and a lattice strain o...
Thin Solid Films, 1996
In this paper, we report on the growth of titanium and titanium nitride thin films and of Ti/TiN nanometric multilayers. The elaboration of these films has been carried out by high-vacuum diode r.f. sputtering. The growth was monitored in-situ by kinetic ellipsometry. The film thickness ranged from 50 to 200 nm for the Ti and TiN single layers. For the multilayers, the thickness of each component was varied from 1 nm to 10 nm and alternately repeated in order to obtain a total thickness of 200 nm. After deposition, the films were characterised by means of X-ray diffraction, grazing incidence X-ray reflectometry, atomic force microscopy and transmission electron microscopy for structural determination. A comparison is made between the microstructural and the mechanical properties of Ti and TiN films on the one hand and the multilayers on the other hand (porosity, density and so on). We show that the wear properties are increased by multilayering.