Fine structure and phase composition of NiCrAlY sputtered coatings

Structure of sputtered high-temperature coatings of composition (wt %) 20–22 Ni, 11–13 Cr, 0.3–0.5 Al, and the balance Y was studied by transmission electron microscopy. The information obtained may be useful in an analysis of the deposition process and operating damages of such protective coatings.     

Effect of small concentrations of oxygen and nitrogen on the structure and mechanical properties of sputtered titanium films

The results of a study of small additions of oxygen and nitrogen on the structure and mechanical properties of nanocrystalline titanium films obtained by magnetron sputtering are presented.     

Reactive gas pulsing process: A method to extend the composition range in sputtered iron oxynitride films

Fe-O-N films were deposited on glass and silicon substrates using two reactive magnetron sputtering processes. In the first process called conventional process (CP), the oxygen flow rate was kept constant during the deposition duration. On the other hand, the oxygen flow rate was pulsed in the second process called reactive gas pulsing process (RGPP). To compare the ability of both processes for the deposition of Fe-O-N films, the same range of oxygen amounts was introduced in the deposition reactor by adjusting either the oxygen flow rate in the CP or the duration and the shape of the oxygen pulse in the RGPP. The deposition rate, the chemical composition and the optical transmittance of the films deposited using both processes were compared. The reactive gas pulsing process allowed the deposition of a wide range of film compositions with high deposition rate and tuneable optical properties.     

Effect of annealing temperature on the structure and optical properties of sputtered TiO2 films

TiO₂ thin films were deposited by DC reactive magnetron sputtering. Some TiO₂ thin films samples were annealed for 5 min at different temperatures from 300 to 900 °C. The structure and optical properties of the films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and ultraviolet-visible (UV-vis) spectrophotometry, respectively. The influence of the annealing temperature on the structure and optical properties of the films was investigated. The results show that the as-deposited TiO₂ thin films are mixtures of anatase and rutile phases, and possess the column-like crystallite texture. With the annealing temperature increasing, the refractive index and extinction coefficient increase. When the annealing temperature is lower than 900 °C, the anatase phase is the dominant crystalline phase; the weight fraction of the rutile phase does not increase significantly during annealing process. As the annealing temperature rises to 900 °C, the rutile phase with the large extinction coefficient becomes the dominant crystalline phase, and the columnar structure disappears. The films annealed at 300 °C have the best optical properties for the antireflection coatings, whose refractive index and extinction coefficient are 2.42 and 8 × 10⁻⁴ (at 550 nm), respectively.     

Effect of copper content and substrate bias on structure and mechanical properties of reactive sputtered CrCuN films

The CrCuN films with various Cu contents were deposited under different substrate bias by DC magnetron sputtering. The influence of Cu content and substrate bias was examined with regard to the microstructure, morphology, and mechanical properties of these films. The CrCuN films containing low Cu content (3.4 at.%) present distinctive columnar growth. Their preferred orientations change from (1 1 1) (?50 V bias) to (2 0 0) (?200 V bias) and surface morphology changes from porous to granular structure with increasing bias. However, when the copper content is increased to 15 at.%, CrCuN films remain (2 0 0) preferred growth independent of bias, while the film maximum hardness is reduced from 32 GPa to 20 GPa because of excess soft metal.     

Effects of deposition conditions on composition and thermal cycling life of lanthanum zirconate coatings

Lanthanum zirconate (La₂Zr₂O₇, LZ) coatings were prepared under four different deposition conditions by electron beam-physical vapor deposition (EB-PVD). The composition, crystal structure, surface and cross-sectional morphology, cyclic oxidation behavior of these coatings were studied. Elemental analysis indicates that the coating composition has partially deviated from the stoichiometry of pyrochlore, and the existence of excess La₂O₃ is also observed. The deviation could be reduced by properly controlling the electron beam current or by changing the ingot composition. Meanwhile, when the electron beam current was 500 - 600 mA, the thermal cycling life of the coating is superior to other coatings.     

Fabrication of porous lanthanum strontium manganite films by electrostatic spray deposition

In this work, electrostatic deposition was used to prepare porous lanthanum strontium manganite (LSM) films on a silicon substrate for cathode application in solid oxide fuel cells (SOFCs). The precursor solution was prepared by dissolving lanthanum nitrate hydrate, manganese nitrate hexahydrate and strontium chloride hexahydrate into a mixture of methanol and water. The morphology of the LSM film depended on process parameters such as substrate temperature, precursor flow rate, nozzle-substrate distance, and deposition time. The effect of heating temperature on the film’s crystal structure was investigated with X-ray diffraction in the heating temperature range of 700 °C to 900 °C. Porous LSM film was successfully prepared in the solution flow rate range of 2 l/min to 4.5 l/min, substrate temperatures of 127 °C to 330 °C, the nozzle-substrate distance range of 3 cm to 8 cm, and deposition times of 1 min to 16 min.     

Synthesis,spheroidization and spray deposition of lanthanum zirconate using thermal plasma process

During the last decade, research efforts were devoted to the development and manufacturing of ceramic thermal barrier coatings (TBCs) on turbine parts because the traditional turbine materials have reached the limits of their temperature capabilities. TBCs have been widely used in hot-section metal components in gas turbines either to increase the inlet temperature with a consequent improvement of the efficiency or to reduce the requirements of the cooling air. There are several ceramics that have been evaluated as TBC materials, and lanthanum zirconate (LZ) is one of the most promising among them. The properties namely high-melting point, phase stability up to its melting point, low thermal conductivity, low sintering ability and oxygen-non transparent make the LZ a potential TBC material for high-temperature applications. However, the production methods used to synthesise LZ are highly time consuming and the powder is not commercially available. Hence, in this investigation an attempt was made to synthesise, spheroidize and spray deposit LZ material using thermal plasma process. This paper illustrates the effectiveness of thermal plasma as a major materials processing technique. Suitable characterization techniques have been used to study the material modifications after respective plasma processing exposures.     

Influence of process parameters on electrochemical and physical properties of sputtered iron-doped nickel oxide thin films

1Introduction A principal focus of modern research in electrocatalysis is to discover electrode materials that exhibit excellent electrochemical stability and show interesting activity towards typical electrochemical reaction[1?10].It is desirable that th…     

Effect of process factors and chemical composition of steels on the structure and properties of nickel-bearing diffusion coatings

The effect of the medium and regime of saturation and of the composition of the steel on the composition, structure, and properties of nickel, nickel-copper, and nickel-chromium diffusion coatings formed by selective transfer of the elements of the coating in a medium of low-melting liquid-metal solution is considered. The regular features of formation of nickel-bearing diffusion coatings on various steels are determined, which makes it possible to control the saturation process and form coatings with specified composition, structure, and properties. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 38–43, April, 2007.     

Effect of deposition conditions on the formation of silica-silicate thin films

The deposition kinetics of silica-silicate thin films on pure zinc from colloidal silica suspension (sol) was investigated by an in-situ mass gain method. With this method, the influence of sol ageing, temperature, zinc pretreatment and polarization of the zinc substrate on the silica-silicate deposition was described qualitatively. The oxidation/hydroxylation of the zinc surface was found to be important for the silica sol deposition process. Pretreatment of the zinc surface with alcohol solutions significantly increased the amount of deposited sol.     

Interface diffusion of sputtered CoZrNb films on silicon substrate

The amorphous CoZrNb films were deposited by DC magnetron sputtering.The depth distributions of the elements were analyzed by Rutherford backscattering spectrometry (RBS).The results indicate that when the deposition time is longer than 37 min, the film composition keeps constant along the depth.When the deposition time is longer than 45 min, the Co concentration at the interface of the silicon substrate is higher than the average value in the whole film.When the deposition time is longer than 52 min, the Co atoms diffuse into the substrate during the deposition.According to the Co composition profile in the substrate, which were determined from the RBS spectra, the Co diffusion coefficients in the substrate were calculated using the solution of Fick's second law corresponding to an infinite source with a constant diffusion coefficient.The calculated diffusion coefficients indicate an interstitial assisted diffusion mechanism.     

Aging process of photosensitive chalcogenide films deposited by electron beam deposition

Chalcogenide films attract broad interest due to their use as optical components like narrow band-pass filters, omnidirectional reflectors cladding, all-optical signal processing devices or optochemical sensors. Ge₁₅Sb₂₀S₆₅ and As₃₀Se₅₀Te₂₀ chalcogenide amorphous films were deposited by electron beam deposition (EBD) using their corresponding bulk glasses as targets. The structure of both bulk and thin film has been studied by far-IR and Raman spectroscopy. This study investigated an ordinary aging behavior of the chalcogenide films by exposing them to natural light under atmospheric conditions for a period of six months. Both films were found to be photosensitive as manifested by the shift of their optical band-gap to shorter or longer wavelength depending on chemical composition. Aging was found to induce also morphological changes, most notably the likely growth of arsenic trioxide micro-crystals on the surface of As₃₀Se₅₀Te₂₀ films. Such effects were discussed in terms of photo-oxidation and photo-hydrolysis phenomena, the extent of which was found to be relatively limited for Ge₂₅Sb₁₀S₆₅ films. The larger stability of the latter films against crystal growth at the surface was associated with the ability of germanium to bond to diffusing oxygen atoms in germanium-oxysulfide tetrahedral arrangements.     

Effect of coating bath composition on the properties of electroless nickel-boron films

The effect of borohydride, thallium acetate, ethylenediamine and sodium hydroxide concentrations, and the coating bath temperature on both the coating rate and boron content of the electroless Ni-B films was investigated systematically. The Ni-B coating rate increased with the increase in thallium acetate and sodium hydroxide concentrations, but it was not very sensitive to the borohydride concentration. Below 90 g L^− 1 ethylenediamine concentration the coating efficiency was significantly low and above this value as the ethylenediamine concentration increased the coating rate decreased slightly. Below 85 °C the coating rate was very low and above this temperature it was insensitive to the bath temperature. The boron content of Ni-B film increased with the increase in the borohydride concentration and the bath temperature, and decreased with the increase in thallium acetate and ethylenediamine concentrations. Up to 50 g L^− 1 sodium hydroxide concentration, the boron content of the film increased and above this concentration it was insensitive to the sodium hydroxide concentration. As the boron content of Ni-B film increased, both the corrosion resistance and microhardness of Ni-B film increased. Heat treatment brought significant improvement in the microhardness but the corrosion resistance of Ni-B film was observed to decrease due to the disappearance of the amorphous characteristics of the as-deposited Ni-B film and the formation of the Ni-B compound phases.     

Stress and microstructure evolution in thick sputtered films

Materials synthesized by deposition techniques are often plagued by high levels of residual stress. While the origin and control of this stress in thin (sub-micron) films has been an active area of research, it is not clear how the results extrapolate with thickness. In the present work, in situ residual stress measurements are performed during the sputter deposition of beryllium, spanning the transition from thin to thick. Variables including sputtering gas pressure and substrate biasing are shown to strongly affect both the average and instantaneous stress levels measured during film growth. Detailed microstructural characterization is performed to assess the grain structure, surface morphology, and crystallographic growth texture of representative specimens. The microstructure is correlated with theoretical models of stress generation to interpret experimental measurements. A stress map is also constructed, generalizing the effects of processing and material parameters on stress state.     

Microstructural characterizations of magnetron sputtered Ti films on glass substrate

Magnetron sputtered Ti thin films deposited on glass substrates under varying deposition parameters were characterized by X-Ray Diffraction, Scanning Electron Microscopy and Atomic Force Microscopy. The textures of the Ti films characterized by X-ray diffraction revealed the initial (1 0 0) preferred orientation but it transformed in to (0 0 2) and (1 0 1) orientation with increase in sputtering power and substrate temperature, respectively. The preferred orientations of (0 0 2) and (1 0 1) were observed for the films deposited with the sputtering pressure of 5 mTorr and 20 mTorr, respectively. The average surface roughness of the Ti films showed an increasing trend with power, pressure, and temperature from the Atomic Force Microscopy analysis. The dense film morphology was observed in the Scanning Electron Microcopy images of Ti thin films deposited with higher substrate temperature (500 °C). X-ray diffraction analysis revealed that the grain size of the Ti thin films exhibits an increasing trend with varying deposition parameters.     

The mechanism of scale adhesion on sputtered microcrystallized CoCrAl films

The oxidation mechanisms of sputtered microcrystalline Co–30Cr–5Al coatings were investigated by an acoustic emission technique, scatch test, transmission electron microscope (TEM), which was compared with CoCrAlY alloy. The results indicated that the beneficial effects of microcrystallization on the scale adhesion of Co–30Cr–5Al alloy are as follows: (1) The sputtered CoCrAl coating possesses a columnar structure, and oxidation along the columnar grains may form many micropegs which can anchor the scale to the metallic substrate, enhancing bonding of the scale. (2) The grain size of the sputtered coating is several orders of magnitude smaller than that of the cast alloy, and the grain size of oxide scales formed on the former is finer than that of the latter. The finer oxide scale may relieve the growth stresses during isothermal oxidation and partial thermal stresses during cooling by plastic deformation through grain sliding. The microcrystalline coating is more plastic than the cast alloy, which may relieve a certain amount of thermal stresses of the oxide scales. On the basis of oxide adhesion and plasticity, microcrystallization is more beneficial than the addition of reactive elements.     

Oxidation process of lanthanum hexaboride ceramics

Oxidation process of lanthanum hexaboride (LAB6) ceramic powder was investigated. The LaB6 powder sampies were heated continually fTom room temperature to 1 473 K at a heating rate of 10 K/min by differential scanning calorimetry. The oxidation tests were conducted at different exposure temperatures. The phases and morphologies of the samples before and after exposure were analyzed by XRD and SEM. It was pointed out that before 1 273 K, LaB6 has high oxidation resistant ability, which was due to that the oxide layer hinders the oxygen diffusion fTom outer to the surface of LaB6 grains. The oxide layer was composed of the transition phases, which were composed of La203 and B2O3 formed fi‘om the initial oxidation; when the oxidation temperature exceeded 1 273 K, protective layer was destroyed due to the vaporization of liquid B2O3. Based on the results of X-ray diffraction analysis, oxidation process of LaB6 ceramicpowder can be described as follows: Before 1 273 K, lanthanum borate, La(BO2)3 was formed on the surface of samples,then lanthanum oxide (La2O3) and boron oxide (B2O3) were present on the surface of samples oxidized when the tempera-ture reached to 1 473 K.