Mechanical,tribological and electrochemical behavior of Zr-based ceramic thin films for dental implants

To determine the possibility of using new thin films architectures as biocompatible materials, an experimental and computational study was performed to evaluate the mechanical, tribological, and corrosion properties in simulated physiological media (saliva and blood plasma) of Zr, ZrN, and ZrN/Zr coatings, deposited by PVD magnetron sputtering. The crystalline structure and chemical composition were well correlated with high resistance to plastic deformation, wear, and corrosion, making these materials excellent candidates for functionalizing and protecting dental prostheses. The predominant wear mechanism under consideration was abrasion, which was reduced when using ceramic ZrN coating as a base for the superficial Zr thin film. When exposed to simulated body fluids, these materials exhibited high corrosion resistance, which was demonstrated by potentiodynamic measurements. These results are consistent with those predicted by Density Functional Theory computational models, which showed that electron transfer associated with the wear mechanism is kinetically impeded, as a consequence of the large energy barriers for this process associated with the adsorption of the molecular species on the ZrN surface. Additionally, calculated adsorption energies indicated that urea (from the simulated saliva solution) interacts strongly with the surface. This interaction was associated to the formation of passivating protective layers, which is a key mechanism to protect against corrosion, acting in synergy with the kinetic barriers.     

High-temperature electrical properties of polymer-derived ceramic SiBCN thin films fabricated by direct writing

The in situ temperature monitoring of hot components in harsh environments remains a challenging task. In this study, SiBCN thin-film resistance grids with thicknesses of 1.8 μm were fabricated on alumina substrates via direct writing. Owing to their dense microscopic morphology and extremely high graphitisation level, the produced SiBCN films exhibited large high-temperature oxidation resistance and electrical conductivity. The resistance–temperature, stability, and repeatability characteristics of these films were examined in an aerobic environment at temperatures up to 800 °C. The obtained results revealed that the thermistor resistance decreased monotonously with increasing temperature from room temperature to 800 °C. The SiBCN film resistance variations observed during repeated temperature cycling in the regions of 505–620 °C and 610–720 °C were 0.09% and 1.7%, respectively. The high cyclability and stability of the SiBCN thin film thermistor suggested its potential applicability for the in situ temperature monitoring of hot components in harsh environments.     

Large-area fabrication of TiN thin films with photothermal effect via PECVD

Titanium nitride alloy has triggered extensive interests for the actual application in aeronautics and astronautics, especially in the biological window serving as cancer therapy and tumor detection due to broad band absorption. However, developing a facile and reliable method for the manufacture of TiN films is still a propelled and demanding challenge. Here we present a one-step approach to obtain cubic-TiN films using plasma-enhanced chemical vapor deposition (PECVD) for the first time. Large-scale TiN films can be deposited on sophisticated substrate (e.g. flattened and curled shape) with controllable size by our PECVD approach. The chemical composition and structural analysis were conducted by X-ray diffraction, scanning electron microscope, transmission electron microscopy, and X-ray photoelectron spectroscopy. Furthermore, the TiN powders extracted from our films for photothermal effect demonstrated an excellent photothermal conversion efficiency of 47.9% under 808 nm irradiation. Our study not only offers a facile PECVD route to realize the TiN films on sophisticated substrates, but also provides a promising candidate for photothermal therapy in the future.     

Mechanical spectroscopy of thin polystyrene films

Mechanical spectroscopy is applied to thin polystyrene films of 7.5-730 nm thickness spin coated on a thin silicon reed. Below a thickness of 100 nm, the α-relaxation peak (glass transition) broadens considerably and shifts to lower temperatures by a few degrees. These effects are attributed to a different polymer dynamics at the polymer/vacuum and the polymer/silicon interfaces.     

Mechanical properties and linear infrared dichroism of thin films of polyurethane nanocomposites

Morphological, mechanical, and Fourier transform infrared dichroic investigations were performed on neat polyurethane (PU) polymer matrix and PU+CaCO₃ nanocomposite thin films to determine how the nanofiller influenced the mechanical properties. The measurements were performed on strips that were cut from the prepared films in parallel and perpendicular directions with respect to the direction of film preparation. Optical microscopy of PU and the PU+CaCO₃ nanocomposite revealed the strain‐induced transition from a continuous spherulitic morphology to a fiberlike structure. The stress–strain behavior of the neat PU and PU+CaCO₃ nanocomposite films showed significant differences at large strain regimes. The experimental results suggest that the mechanical properties were strongly related to the orientational behavior of the separated phases. The orientation of the hard and soft segments was analyzed by the orientation function calculated from the IR absorbances. A correlation between the orientations of segments, tensile properties, and hardness of the investigated polymer films was established. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Analysis of the structure of thin ceramic films

Translated from Steklo i Keramika, No. 1, pp. 16–18, January, 1989.     

Iron doped thin TiO2 films synthesized with the RF PECVD method

Iron doped titanium dioxide coatings were synthesized with the help of RF plasma enhanced CVD technique. As a source of titanium, titanium chloride (IV) TiCl₄ was used while iron pentacarbonyl (0) Fe(CO)₅ served as iron supply. The coatings were diagnosed using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Their elemental and chemical composition was studied with the help of X-ray energy dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy, respectively. For the determination of their optical properties, variable angle spectroscopic ellipsometry (VASE) and ultraviolet-visible (UV-Vis) spectroscopy techniques were used. Iron content in the range of 0.07–11.5 at% was found in the films. Apart from oxygen, titanium and iron, a presence of trace amounts of chlorine, very likely originating from the titanium precursor, was recorded. FTIR studies showed that iron was built-in in the structure of TiO₂ matrix. Surface roughness, assessed using SEM and AFM techniques, increases with an increasing content of this element. VASE measurements revealed an increase of the coatings refractive index with a growing iron concentration, with the extinction coefficient remaining low and independent of that parameter. Trace amounts of iron resulted in a lowering of an absorption threshold of the films as well as their optical gap, but the tendency was reversed for high concentrations of that element.     

Characterization on polymerized thin films for low-k insulator using PECVD

Plasma polymerized cyclohexane and TEOS hybrid thin films have been deposited on silicon substrates at room temperature with varying RF power by plasma-enhanced chemical vapor deposition (PECVD) method. As-grown thin films were annealed in vacuum. Cyclohexane monomer was utilized as organic precursor and TEOS monomer as inorganic precursor. Hydrogen and argon were used as bubbler and carrier gases, respectively. The as-grown plasma polymerized hybrid thin films were analyzed by FT-IR spectroscopy, hardness and modulus measurements, and electrical properties. Annealed hybrid thin films were also analyzed. The dielectric constant of thin films increases with increasing plasma power.     

Crystallization of amorphous silicon thin films deposited by PECVD on nickel-metalized porous silicon

ABSTRACT: Porous silicon layers were elaborated by electrochemical etching of heavily doped p-type silicon substrates. Metallization of porous silicon was carried out by immersion of substrates in diluted aqueous solution of nickel. Amorphous silicon thin films were deposited by plasma-enhanced chemical vapor deposition on metalized porous layers. Deposited amorphous thin films were crystallized under vacuum at 750 [DEGREE SIGN]C. Obtained results from structural, optical, and electrical characterizations show that thermal annealing of amorphous silicon deposited on Ni-metalized porous silicon leads to an enhancement in the crystalline quality and physical properties of the silicon thin films. The improvement in the quality of the film is due to the crystallization of the amorphous film during annealing. This simple and easy method can be used to produce silicon thin films with high quality suitable for thin film solar cell applications.     

Preparation and characterization of TiO2 thin films by PECVD on Si substrate

Titanium oxide thin films were prepared on p-Si(l00) substrate by plasma enhanced chemical vapor deposition using high purity titanium isopropoxide and oxygen. The deposition rate was little affected by oxygen flow rate, but significantly affected by RF power, substrate temperature, carrier gas flow rate, and chamber pressure. Morphology of the film became coarser with increasing deposition time and chamber pressure, and the film showed less uniformity at high deposition rates. It was also found that the overall deposition process is controlled by heterogeneous surface reaction below 200°C., but controlled by mass transfer of reactants at higher temperatures. TiO₂ films deposited at temperatures lower than 400°C was amorphous, but showed the anatase crystalline structure upon 400°C deposition. The dielectric constant was about 47 for the films post-treated by rapid-thermal annealing (RTA) at 800°C. The leakage current was about 2×10⁻⁵ A/cm² for the films deposited at 400°C and RTA-treated at 600°C. However, it was decreased to less than 3×10⁻⁷ A/cm² for the film RTA-treated at 800°C.     

Dielectric properties of Mn doped Bismuth Barium Titanate based ceramic thin films prepared by PLD technique

In this article, the effect of Mn doping on the permittivity and dielectric loss in 0.67BiFeO₃-0.33BaTiO₃ (BF-BT) based film bulk acoustic resonator test structures has been investigated. BF-BT thin films were deposited on the fused silica substrates with Pt/TiO₂/Ti as bottom electrode. During the study of the BF-BT based parallel-plate structures, it has been revealed that BF-BT is in the ferroelectric state at room temperature. Higher permittivity (ԑ) is observed at a growth temperature of 600 °C and lower dielectric loss is achieved at 0.3 wt% Mn doping contents. These results show that the proposed BF-BT based FBAR test structure has a great potential for applications in tunable thin Film Bulk Acoustic Resonator (FBAR) devices. Comparison of the measured and simulation results has been made by utilizing the Mason equivalent circuit.     

Pyroelectric properties of PLT thin films

Pyroelectric properties of PLT thin films prepared by MOD method are characterized. Dynamic pyroelectric responses of the films measured with Chynoweth method are presented. Pyroelectric responses of point and quadruple pyroelectric detectors using PLT20 thin films are measured. One-dimensional heat conduction model is used to analyze the properties of the detectors. requirements to the PLT films used for pyroelectric detectors are proposed.     

Mechanical and field emission properties of CGed Si(C,N) films synthesized by PECVD from HMDS precursor

Compositionally graded (CGed) Si(C,N) films were prepared by Ar/H₂/N₂ plasma enhanced chemical vapor deposition from liquid injected hexamethyldisiloxane precursor. The films were characterized by scanning/transmission electron microscopy (SEM/TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Monolithic crystalline SiC and amorphous SiN_x films were produced from Ar/H₂ and Ar/H₂/N₂ thermal plasma, respectively. The CGed SiC–SiN_x film was obtained by changing N₂ flow rate from 2 L/min to zero in Ar/H₂/N₂ during the deposition process, and it was composed of an uppermost crystalline SiC layer, a thin intermediate layer containing nanocomposite c-SiC/a-SiN_x and an innermost layer of amorphous SiN_x. The CGed SiN_x–SiC film, in which SiN_x acts as a top layer with a SiC layer underneath, was fabricated by an inverse change of the plasma gas supply from initial Ar/H₂ to Ar/H₂/N₂. Microhardness increase and promising field emission properties were obtained from these CGed films in comparison with monolithic SiC and SiN_x films.     

Mechanical properties of UV-cured urethane films

A series of novel photosensitive urethane oligomers was synthesized in which methacryloyl group was contained in the hard segment. The hard segment was prepared by reacting 4,4′-diphenylmethane diisocyanate with glycerine mono methacrylate, which was successively reacted with three kinds of glycols involving 1,4-poly(butadiene glycol), poly(propylene glycol), and poly(caprolactone diol). The mechanical properties of synthesized urethane oligomers after irradiating with ultraviolet light were evaluated to elucidate the effect of the molecular structure and the content of the hard segment on the mechanical property.     

Mechanical properties of grafted casein films

Casein was grafted with mixtures of acrylonitrile (AN) and n-butyl methacrylate (n-BMA). The mole ratios of AN: n-BMA were 0.9:0.1 and 0.8:0.2. The mechanical properties of the grafted casein films were studied under uniaxial and biaxial stress conditions. A reduction in longitudinal stress and elongation at break was observed with the simultaneous application of lateral stress. Scanning electron micrographs of the stretched films (uniaxial and biaxial stress) are also presented.     

Mechanical properties of biomimetic ceramic with Bouligand architecture

Biomimetic Bouligand architecture is constructed in the ceramic to improve its toughness. Firstly, unidirectional carbon fiber-reinforced ZrB₂-SiC ceramic films are achieved through a vacuum-assisted filtration method using graphene oxide. Then, ceramic films are helically assembled at a fixed angle of 30° in the graphite die based on the fiber orientation. Finally, the spark plasma sintering method was utilized to densify helical assembly carbon fiber/ceramic films. By constructing Bouligand structure, high fracture toughness (7.4 MPa·m^0.5) and work of fracture (∼1055 J/m²) are achieved in ZrB₂-based ceramic. The toughening mechanisms mainly are crack deflection, twisting and branching, carbon fiber pulling out, and bridging.     

Mechanical properties of graphene platelet-reinforced alumina ceramic composites

Alumina (Al₂O₃) ceramic composites reinforced with graphene platelets (GPLs) were prepared using Spark Plasma Sintering. The effects of GPLs on the microstructure and mechanical properties of the Al₂O₃ based ceramic composites were investigated. The results show that GPLs are well dispersed in the ceramic matrix. However, overlapping of GPLs and porosity within ceramics are observed. The flexural strength and fracture toughness of the GPL-reinforced Al₂O₃ ceramic composites are significantly higher than that of monolithic Al₂O₃ samples. A 30.75% increase in flexural strength and a 27.20% increase in fracture toughness for the Al₂O₃ceramic composites have been achieved by adding GPLs. The toughening mechanisms, such as pull-out and crack deflection induced by GPLs are observed and discussed.     

Optoelectronic properties of In-doped SnS thin films

Nanostructured un- and In-doped SnS thin films were deposited on fluorine-doped tin oxide (FTO) substrates via an electrochemical deposition technique. The deposited thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS), photoluminescence (PL) spectroscopy and UV–visible spectroscopy. The XRD patterns demonstrated that all deposited thin films are made of polycrystalline SnS particles. The AFM images illustrated a distinct change in the surface topography of the SnS thin films due to In-doping. The PL spectra showed two blue emission peaks and a green emission peak for all samples. Also, they highlighted a PL peak for the In-doped thin films. The incorporation of In-dopant leads to enhance in the optical absorption of SnS lattice. The optical energy band gap (E_g) of the deposited thin films was estimated using UV–vis spectroscopy, which indicated that In-doping decreases the E_g value of SnS thin films by creating defect levels. The photocurrent results demonstrated a higher photocurrent response and photocurrent amplitude for the In-doped SnS samples relative to the un-doped SnS thin film. The Mott–Schottky analysis revealed p-type conductivity for all samples. In addition, the carrier concentration of SnS was increased after In doping. The EIS spectra declared that In-doping improves the rate of charge transfer for SnS thin films. The charge transfer resistance of In-doped SnS decreased compared to the undoped SnS thin film. Finally, according to the J-V characteristics, the conversion efficiency of the In-doped SnS thin films was higher than that of the un-doped SnS sample. Therefore, the optical and electrical performance of SnS thin films were improved due to In-doping.     

Mechanical properties and characterisation of very thin CNx films synthesised by IBAD

Nanoindentation has been used to investigate the mechanical properties of very thin (<1 μm) CN_x films deposited by IBAD in order to understand the variation of properties with process parameters. The structural features of the films were characterised by EELS, XPS and ERDA. Examining the load–displacement (P–δ) curves in detail revealed a number of film responses such as pure elastic behaviour, densification and elastic-plastic deformation. The film-only hardness was calculated using a recently developed energy based model while the Hertzian contact analysis and laser-acoustic measurements were used to determine the Young's modulus. Generally, the film hardness and modulus exhibit two different regimes depending on the deposition parameters. Films deposited at high temperature contain less nitrogen and have lower hardness and Young's modulus than those deposited at room temperature. All films examined displayed P–δ curves exhibiting unusually large elastic recovery (80% or more) during unloading. Because of this, resultant indentation sizes always appear to be very small thus apparently producing very high hardnesses. However, our results clearly establish that the film behaviour is better viewed as that of a ‘super-hard rubber’ in which a large proportion of the contact load is supported elastically.     

Mechanical and transport properties of coextruded films

Two-layer films were produced by using the blown-film coextrusion apparatus constructed in our laboratory. For this study, we have produced films of the following combinations: (1) LDPE/CXA 3095; (2) LDPE/Plexar 3; (3) LDPE/EMA; (4) nylon 6/LDPE; (5) nylon 6/CXA 3095; (6) nylon 6/Plexar 3; (7) nylon 6/EMA. Tensile properties of the coextruded films were measured with an Instron testing machine, and correlated to processing variables, namely, takeup ratio and blowup ratio. From tensile property measurements, we have found that both the ultimate tensile strength and the tensile modulus of coextruded films follow the additivity rule with respect to the volume fraction of the individual components. With the films produced, we also conducted dynamic mechanical measurements with the aid of a Rheovibron Dynamic Viscoelastometer DDV-II, and attempted to test the Zorowski–Murayama theory to determine the adhesion characteristics of the coextruded films. Furthermore, permeability of the coextruded films to gases (namely, N₂, O₂, and CO₂) was measured by using a pressure differential apparatus constructed in our laboratory. We have found that the permeability of composite films follows the inverse additivity rule, i.e., the reciprocal of the permeability of composite film is given by the sum of the reciprocals of the permeabilities of the individual layers.