Argemiro Soares da Silva Sobrinho

Silica-based Nano-coating on Zirconia Surfaces Using Reactive Magnetron Sputtering: Effect on Chemical Adhesion of Resin Cements

PURPOSE To compare the effect of silica (Si)-based nano-coating deposited by reactive magnetron sputtering (RMP) with that of conventional surface conditioning using metal/zirconia primer alone or after air-particle abrasion on the adhesion of resin cements to zirconia ceramic. MATERIALS AND METHODS Two hundred forty zirconia ceramic blocks (Cercon) were sintered, finished with 1200- grit SiC paper under water cooling, and cleaned ultrasonically in distilled water for 10 min. The blocks (4.5 mm x 3.5 mm x 4.5 mm) were randomly divided into 24 groups (n = 10) according to 3 testing parameters: a) resin cements (Multilink, Panavia F, RelyX U100), b) surface conditioning (no conditioning as control group; Metal/Zirconia Primer; air abrasion + Metal/Zirconia Primer; Si-based nanofilm + Monobond s); c) aging (no aging vs thermocycling at 5°C to 55°C, 6000 cycles). The nanofilm was deposited by direct current using argon/oxygen plasma (8:1 in flux) on the zirconia surface. Resin cements were bonded to zirconia surfaces using polyethylene molds. The shear bond strength (SBS) test was performed using a universal testing machine (1 mm/min), and after debonding, the substrate and adherent surfaces were analyzed using optical and scanning electron microscopes to categorize the failure types. The data were statistically evaluated using 3-way ANOVA and Tukeys test (5%). RESULTS Resin cement type (p < 0.05), surface conditioning method (p < 0.05), and aging condition (p < 0.05) had a significant effect on the bond strength results. Interactions were also significant (p < 0.05). In the nonaged condition, while control groups presented the lowest results with all cements (0 to 5.2 MPa), the airabraded group in combination with RelyX U100 resulted in the highest SBS (21.8 ± 6.7 MPa). After aging, the SBS results decreased in the air-abraded groups for all cements (4.54 to 9.44 MPa) and showed no statistical significance compared to the Si-based nanocoated groups (4.24 to 6.44 MPa). After air-abrasion and primer application, only Panavia F and RelyX U100 cements showed exclusively mixed failures, but after nanofilm coating and silanization, all cements showed exclusively mixed failures with and without aging. CONCLUSION Chemical adhesion of the resin cements tested to zirconia was similar after silica-based nanofilm deposition and air abrasion followed by primer application.

Evaluation of piezoresistivity properties of sputtered ZnO thin films

Zinc oxide (ZnO) thin films were deposited by RF reactive magnetron sputtering on silicon (100) substrates under different experimental conditions. ZnO films were studied before and after annealing treatment at 600 °C. The crystallinity, electrical resistivity, stoichiometry, thickness, and elastic modulus of the films were investigated. ZnO piezoresistors were produced using microelectronics processes, such as photolithography, lift-off, and reactive ion etching (RIE). Cantilever method was used to determine the gauge factor, and measurements of Temperature Coefficient of Resistance (TCR) were performed on a hotplate. The optimization of the deposition conditions produced ZnO thin films with controlled stoichiometry (ZnO), crystalline microstructure (phase wurzite, 002), high elastic modulus (156 GPa), and low electrical resistivity (0.072 ohm.cm), which are good properties for application as piezoresistive pressure microsensor. In addition, the ZnO piezoresistors had a GF of 2.6 on the deformation in the plane (100) and TCR of –1610 ppm/K up to 250 °C.

Characterization of SiC thin films deposited by HiPIMS

In this work thin films of silicon carbide (SiC) were deposited on silicon wafers by High Power Impulse Magnetron Sputtering (HiPIMS) technique varying the average power of the discharge on a stoichiometric SiC target. X-ray diffraction, Raman spectroscopy, scanning electron microscopy and profilometry were used to analyze the films. It was observed that high values of the average electric power favors the formation of C-C bonds, while low values of the power promote the formation of Si-C bonds. At high power, we have also observed higher deposition rates, but the samples present surface imperfections, causing increase in the roughness and decrease in the film uniformity.

Antimicrobial and anti-biofilm properties of polypropylene meshes coated with metal-containing DLC thin films

A promising strategy to reduce nosocomial infections related to prosthetic meshes is the prevention of microbial colonization. To this aim, prosthetic meshes coated with antimicrobial thin films are proposed. Commercial polypropylene meshes were coated with metal-containing diamond-like carbon (Me-DLC) thin films by the magnetron sputtering technique. Several dissimilar metals (silver, cobalt, indium, tungsten, tin, aluminum, chromium, zinc, manganese, tantalum, and titanium) were tested and compositional analyses of each Me-DLC were performed by Rutherford backscattering spectrometry. Antimicrobial activities of the films against five microbial species (Candida albicans, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis) were also investigated by a modified Kirby-Bauer test. Results showed that films containing silver and cobalt have inhibited the growth of all microbial species. Tungsten-DLC, tin-DLC, aluminum-DLC, zinc-DLC, manganese-DLC, and tantalum-DLC inhibited the growth of some strains, while chromium- and titanium-DLC weakly inhibited the growth of only one tested strain. In-DLC film showed no antimicrobial activity. The effects of tungsten-DLC and cobalt-DLC on Pseudomonas aeruginosa biofilm formation were also assessed. Tungsten-DLC was able to significantly reduce biofilm formation. Overall, the experimental results in the present study have shown new approaches to coating polymeric biomaterials aiming antimicrobial effect.Graphical Abstract

Electrical Conduction Mechanisms in Metal–Insulator–Metal (MIM) Structure with TiOxNy Thin Films Deposited with Different O/N Ratios

In this work, the current–voltage characteristics of titanium oxynitride thin films were measured and the charge carrier transport mechanisms established as a function of film composition. The films were deposited by magnetron sputtering, where the oxygen/nitrogen ratio was varied via a pulsing technique to enable the achievement of desired concentrations. Thus, the obtained films showed metallic titanium nitrate (TiN) or semiconductor titanium dioxide (TiO2) character and were used to fabricate metal–insulator–metal structures. An ohmic conduction mechanism was identified in the films with higher nitrogen incorporation or presenting TiN-rich phase. Decrease in the nitrogen content resulted in films with TiO2-rich phase. In this case, Poole–Frenkel and space-charge-limited current conduction mechanisms were observed. The dielectric constants were calculated from the high-frequency capacitance–voltage dependences, with a reduction from 10 to 3 being observed due to the stoichiometric changes and probable incorporation of defects into the film structure. Finally, the film composition and structural characteristics of the films were revealed by Rutherford backscattering and x-ray diffraction techniques, respectively.

Abutment Coating With Diamond-Like Carbon Films to Reduce Implant–Abutment Bacterial Leakage

BACKGROUND The influence of diamond-like carbon (DLC) films on bacterial leakage through the interface between abutments and dental implants of external hexagon (EH) and internal hexagon (IH) designs was evaluated. METHODS Film deposition was performed by plasma-enhanced chemical vapor deposition. Sets of implants and abutments (n = 30 per group, sets of 180 implants) were divided according to connection design and treatment of the abutment base: 1) no treatment (control); 2) DLC film deposition; and 3) Ag-DLC film deposition. Under sterile conditions, 1 μL Enterococcus faecalis was inoculated inside the implants, and abutments were tightened. The sets were tested for immediate external contamination, suspended in test tubes containing sterile culture broth, and followed for 5 days. Turbidity of the broth indicated bacterial leakage. At the end of the period, the abutments were removed and the internal content of the implants was collected with paper points and plated in Petri dishes. After 24-hour incubation, they were assessed for bacterial viability and colony-forming unit counting. Bacterial leakage was analyzed by χ(2) and Fisher exact tests (α = 5%). RESULTS The percentage of bacterial leakage was 16.09% for EH implants and 80.71% for IH implants (P <0.0001). The bacterial load was higher inside IH implants (P = 0.000). The type of implant significantly influenced the results (P = 0.000), whereas the films did not (P = 0.487). CONCLUSION IH implants show a higher frequency of bacterial leakage; and DLC and Ag-DLC films do not significantly reduce the frequency of bacterial leakage and bacteria load inside the implants.

Use of Cr Interlayer to Promote the Adhesion of SiC Films Deposited on Ti-6Al-4V by HiPIMS

In this paper, chrome (Cr) thin films were deposited and used as interlayer between SiC films and Ti-6Al-4V substrates. Films and interlayers were obtained by using HiPIMS (High Power Impulse Magnetron Sputtering) technique. Interlayers were growth for 5, 30, and 60 minutes. The films were analyzed with respect to morphology, stoichiometry, thickness, roughness, and adhesion. The results showed that the HiPIMS technique was efficient to produce dense thin films and that the adhesion increased with Cr thickness.

Characterization of Mo-AlNxOy Thin Films Deposited by RF MagnetronSputtering

Thin films of Mo-AlNxOy were grown on glass and silicon substrates by RF-reactive magnetron sputtering. The substrate deposition temperature was varied with the purpose of evaluating the composition variation, crystal structure, reflectance, absorptance and band gap of the films. The results showed that the most amorphous films presented the highest absorptance. The absorptance increase and the band gap reduction are due to the crystallinity and the molybdenum insertion. This change occurred due to the different behavior of band gap amorphous materials, the electron acceptors/donors increase and plasmon effect caused by molybdenum insertion.

Fabrication of dye-sensitized solar cells with N-doped TiO 2 thin films: Effect of the nitrogen doping on the photoexcitation processes and generation of electron acceptor states

Nowadays much efforts have been done with the aim to increase the global efficiency of the dye-sensitized solar cells so that the doping of the TiO2 structure have been suggested as one of the most interesting solutions. In this paper the effect of the nitrogen incorporation in the TiO2 structure and studies about the effect of the doped films on the general properties of the solar cells are conducted.