Abstract To improve the wear resistance of cutting tools made of high-speed steel, the Diamond-Like Carbon (DLC) coating appears as a promising alternative. There are several methods to assess wear, however, it is a challenge for manufacturing engineering to work with thin films, due to the uncertainty in the boundary of the substrate and the coating. Based on this concern, this study proposed the evaluation of the tribological behavior of the DLC coating deposited on AISI M35 steel, seeking to predict its behavior in machining conditions based on characterizations, nano-indentation, micro-abrasion and ball-on-disc test. Results showed that the DLC coating produced for this study consists mainly of sp2 hybridizations. The results of the nano-indentation showed that DLC coating may have a better wear resistance when compared to high-speed steel, and the nano-hardness and Young's modulus do not necessarily obey a positive correlation. Compared to high-speed steel, DLC provided reductions of 71% and 69% without micro-abrasive wear and without friction coefficient during sliding, respectively.

Abstract In this work we discuss the wettability, chemical composition, surface morphology and optical transmittance of polyvinyl chloride (PVC) samples treated by Plasma Immersion and by Plasma Immersion Ion Implantation. The total pressure of N2 or SF6 was 6.66 Pa, for treatments of 900 s, applied rf power of 25 and 100 W, and the substrate temperature was about 298 K. In PIII, high voltage pulses of -2400 V at a cycle time of 30 µs and a frequency of 300 Hz were used. The wettability of the samples was assessed via contact angle measurements, which indicated either hydrophilicity or hydrophobicity, depending on the plasma composition. X-ray Photoelectron Spectroscopic analysis confirmed strong fluorine attachment to the surface after treatments using SF6 plasmas, and the presence of oxygen after treatments using nitrogen plasmas. Atomic Force Microscopy images showed that the roughness Rrms, depends on the plasma conditions. Optical transmittance in the visible region, T (λ), was increased by plasma immersion. The greatest contact angle observed was 142º (PI cathode), while the highest roughness was 213.2 nm. The highest optical transmittance in the visible region was around to 90% (PI anode).

This study reports the structural properties of zinc oxide thin films co-doped with aluminum and nitrogen (ZnO:Al-N) grown by RF magnetron sputtering from an AZO (ZnO with 2 wt% Al2O3) target under nitrogen (N2) atmosphere at room temperature (RT). Nitrogen partial pressures of 0.00, 0.10, 0.25 and 1.00 mTorr were used. The film thickness was around 270 nm. Ultraviolet-Vis-NIR transmittance (T) spectra of the films revealed T values of 80 to 85% in the 400 to 700 nm wavelength range. XRD results indicated that the films had a hexagonal wurtzite structure and were preferentially oriented in the (002) plane. Analyses by EDS indicated that the N atoms tend to be incorporated into the ZnO matrix at the expense of oxygen atoms. The ideal [N]/[Al] was obtained at a N2 partial pressure of 0.25 mTorr, producing a p-type film. For a [N]/[Al] of 1.53, the film also exhibited p-type conduction with an electrical resistivity of 31.92 Ω cm, mobility of 18.65 cm2/V s and carrier density of 1.22 x 1016 cm-3. The low carrier density is attributed to the energetically favorable formation of inactive nitrogen phases instead of acceptor-receiver-acceptor complexes, even at the ideal [N]/[Al].

Aluminum zinc oxide (AZO) thin films were synthesized on glass substrates by radio frequency (rf) magnetron sputtering from a metallic Zn-Al (5 at. %) target at room temperature. The morphological, structural, electrical and optical properties of the films were studied as a function of the sputtering pressure, which was varied from 0.1 to 6.7 Pa. X-ray diffraction (XRD) analyses revealed that the films obtained were polycrystalline, having a hexagonal wurtzite structure with a preferential orientation in the (002) plane. In addition, the crystallite size increased as a function of sputtering pressure. Owing to the re-sputtering of the Zn atoms from the growing film, the aluminum concentration presented a maximum value of 13 at. %. At pressures close to 0.16 Pa, we obtained films with values of electrical resistivity and mobility of 2.8 10-3 Ω cm and 17 cm2/Vs, respectively. Finally, our results indicate that the structure zone diagram proposed by Thornton and later modified by Kluth does not fully predict the structural/morphological behavior of the AZO films, since plasma interactions must also be taken into account. With the methodology used, transparent conductive electrodes can be deposited on substrates at low temperatures.

Plasma Electrolytic Oxidation (PEO) is promising for the processing of biomaterials because it enables the production of surfaces with adjustable composition and structure. In this work, aimed at the improvement of the bioactivity of titanium, PEO has been used to grow calcium phosphide coatings on titanium substrates. The effects of the addition of magnesium acetate to the electrolytes on the composition of the coatings produced during 120 s on Ti disks using bipolar voltage pulses and solutions of calcium and magnesium acetates and sodium glycerophosphate as electrolytes have been studied. Scanning electron microscopy, X-ray energy dispersive spectroscopy, Rutherford backscattering spectroscopy, X-ray diffractometry with Rietveld refinement and profilometry were used to characterize the modified samples. Coatings composed of nearly 50 % of Mg-doped hydroxyapatite have been produced. In certain conditions up to 4% Mg can be incorporated into the coating without any observable significant structural modifications of the hydroxyapatite.

Films were deposited from aluminum acetylacetonate (Al(acac)3) using a methodology involving reactive sputtering and low energy ion bombardment. The plasma was generated by the application of radiofrequency power to the powder containing electrode and simultaneously, negative pulses were supplied to the electrode where the substrates were attached. It was investigated the effect of the duty cycle of the pulses (Δ) on the properties of the coatings. Association of ion bombardment to the deposition process increased film thickness, structure reticulation and organic content. Ions from the deposition environment were implanted at the film-air interface or underneath it. Morphology and topography were altered depending on Δ. Considering the enhancement of Δ, it affected the flux of ions reaching the depositing interface and then the deposition rate, H content, crosslinking degree and surface microstructure. Alumina groups were detected in the infrared spectra, whereas the precipitation of amorphous alumina was confirmed by X-ray diffraction.

Cellulose is a polymer widely available in nature, however its applications may be restrict due to its hydrophilic character. The creation of hierarchical structures on the surface is one of the required factors to obtain the hydrophobicity of this material. In order to compare the morphological and chemical effects caused by the action of different gases in the creation of nanostructures on the cellulose surface, samples were exposed to oxygen (O2) and sulfur hexafluoride (SF6) plasma treatments. The changes in morphology after treatment prove that both the gases were able to create similar nanostructures in the material. The analysis of elemental composition and identification of functional groups on the sample surface showed that chemical modifications occurred differently for each treatment. Contact angle measurements revealed that samples treated by O2 plasma remained hydrophilic, whereas low receptivity to polar (θ > 120º) and non-polar (θ > 100º) liquids was observed for samples exposed to SF6 plasma.

In this paper, we propose the production of ceramic protective thin films by plasma electrolytic oxidation using red mud-containing electrolytes. The treatments were performed through the application of pulsed voltage (600 V, 200 Hz) during 300 seconds to aluminum samples immersed in electrolytic solutions with 5 g of red mud per liter of distilled water. The coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and contact angle and surface energy measurements. The final current density during the experiments was 0.05 A/cm² and films as thick as 9.0 µm have been obtained. XRD patterns have clearly shown the incorporation of species from the red mud on the coating.

Alumina films were deposited from a new plasma method using aluminum acetylacetonate (AAA) powder as precursor. The AAA was sputtered in argon and oxygen plasma mixtures. It was investigated the effect of the oxygen proportion (O2%) on the properties of the coatings. Deposition rate was derived from the layer height measured by profilometry. The elemental composition and molecular structure of the films were determined by Rutherford backscattering and infrared spectroscopies, respectively. Grazing incidence X-ray diffraction was used to investigate the microstructure of the films while hardness was determined by nanoindentation technique. Inspections on the surface morphology and on the film composition were conducted associating scanning electron microscopy and energy dispersive spectroscopy. Incorporation of oxygen affects the plasma kinetics and consequently the properties of the coatings. As moderated concentrations of oxygen (< 25%) are added, the structure is predominantly organic containing stoichiometric amorphous alumina. On the other hand, as high O2% (> 25%) are incorporated, the structure become rich in metallic aluminum with carbon rising at low proportions. The deposited layer is not homogeneous in thickness once the chemical composition of the precursor is changed by the action of the reactive oxygen plasma. Oxygen ablation on the film surface also contributes to the lack of homogeneity of the structure, especially as high oxygen proportions are imposed. Hardness data (0.5-2.0 GPa) corroborated the idea of an amorphous structure. Based on the results presented here it was possible to identify the oxygen concentration in the plasma atmosphere which mostly removed organics while preserving the stoichiometric alumina precipitation, subject of great relevance as one considers the reduction in the energy necessary for the creation of fully oxide coatings.

AA 2024 aluminum alloy is widely employed in aeronautic and automobilist industries. Its hardness and low density are attractive properties for such industrial areas. However, since it contains copper, it undergoes severe corrosion in aggressive media as saline or low Earth orbit environments. In this work, it was investigated the properties of films deposited by PECVD on AA 2024 aluminum alloy as well as the corrosion resistance of the film/substrate systems under different corrosive atmospheres. Films were prepared in a plasma atmosphere composed of 50% of oxygen and 50% of hexamethyldisiloxane resulting in a total gas pressure of 4.0 Pa. Plasma ignition was promoted by the application of radiofrequency signal (13.56 MHz) to the sample holder while grounding the topmost electrode. The plasma excitation power, P, was changed from 10 to 80 W in the six different set of experiments. Film thickness, measured by profilometer, increases by 5 times as P was elevated from 10 to 80 W. As demonstrated by the infrared spectra of the samples, films are essentially organosilicons with preservation of functional groups of the precursor molecule and with creation of different ones. The oxide proportion and the structure crosslinking degree are affected by the plasma excitation power. According to the results obtained by sessile drop technique, hydrophilic to moderately hydrophobic films are produced with changing P from 10 to 80 W. The corrosion resistance, evaluated by salt spray and electrochemical impedance spectroscopy, EIS, experiments, in general increases after film deposition. It is demonstrated that film deposition improves, in up to 36 times, the resistance of the alloy to salt spray attack. It is also shown an improvement of about 240 times in the alloy resistance under NaCl solution by the EIS data. Micrographs acquired by Scanning Electron Microscopy after the corrosion tests furnish further information on the importance of the layer physical stability on its barrier properties. Furthermore, films highly protect the alloy against the oxygen attack. Interpretations are proposed based on the modification of the plasma kinetics with P, altering film structure, composition and properties.

Bio-molecular computing, 'computations performed by bio-molecules', is already challenging traditional approaches to computation both theoretically and technologically. Often placed within the wider context of ´bio-inspired' or 'natural' or even 'unconventional' computing, the study of natural and artificial molecular computations is adding to our understanding of biology, physical sciences and computer science well beyond the framework of existing design and implementation paradigms. In this introduction, We wish to outline the current scope of the field and assemble some basic arguments that, bio-molecular computation is of central importance to computer science, physical sciences and biology using HOL - Higher Order Logic. HOL is used as the computational tool in our R&D work. DNA was analyzed as a chemical computing engine, in our effort to develop novel formalisms to understand the molecular scale bio-chemical computing behavior using HOL. In our view, our focus is one of the pioneering efforts in this promising domain of nano-bio scale chemical information processing dynamics.

During the extraction of aluminum from bauxite, a waste of oxides containing traces of heavy metals in a highly alkaline matrix, called Red Mud (RM), is produced. In this study RM is characterized and the feasibility of using it as a precursor for the production of thin films by Plasma Sputtering and by Plasma Immersion Ion Implantation and Deposition (PIIID) is demonstrated. The chemical structure and composition, surface morphology, topography, and wettability of the films prepared using such methodologies were investigated. The films consist mainly of the elements aluminum, silicon, iron and carbon. Infrared spectroscopic analyses reveal the presence of C=O, C-H2, Fe(OH), Al-O and Si-C functionalities. RF Sputtering produced films with smoother surfaces, whereas PIIID produced granular surface structures. Surface contact angle measurements showed that despite the presence of oxides and hydroxides, the films are hydrophobic, thus exhibiting an interesting link between the physical and thermodynamical properties.

In devices used in open-heart surgery and dialysis, blood must be continuously processed using extracorporeal circuits composed of peristaltic pumps and active components such as specific filters and oxygenators. Several procedures have been employed to avoid blood coagulation induced by contact with the artificial surfaces of such devices. Often heparin, a bioactive protein able to prevent clot formation, is employed. In this work, we have used heparin-containing gas plasmas to evaluate the possibility of depositing adherent anticoagulant films onto PVC and glass surfaces. The films were produced by radiofrequency plasma enhanced chemical vapor deposition from heparin/isopropanol and heparin/hexamethyldisiloxane solutions. In addition, the effects of exposure to SF6 plasmas on the compatibility of such surfaces have also been investigated. The blood compatibility was evaluated through the determination of the density of platelets and fibrinogen and activated partial thromboplastin (APTT) and prothrombin times (PT) of human blood freshly collected and after contact for 2.5 hours with different surfaces. The deposited films were also characterized by infrared spectroscopy, contact angle and surface energy measurements. The coagulation time of blood, placed in contact with glass substrates coated by PECVD films of heparin/isopropanol mixtures, and in contact with SF6 plasma-treated PVC, increased by about 60 and 20%, respectively, compared to the values measured with untreated samples.

In this work, thin polymer films were prepared from acetylene and argon radiofrequency (13.56 MHz, 80 W) glow discharges. Post-deposition treatment was performed by plasma immersion ion implantation in nitrogen or helium glow discharges (13.56 MHz, 70 W). In these cases, samples were biased with 25 kV negative pulses. Exposure time to the bombardment plasma, t, ranged from 900 to 7200 s. Chemical composition of the film surfaces was investigated by X-ray Photoelectron Spectroscopy and the resistance to oxidation by the etching process, in reactive oxygen plasmas. Oxygen and nitrogen were detected in all the samples. While the concentration of the former continuously changed with t, that of N kept practically constant in small proportions. The film is predominantly formed by sp² states, but the proportion of sp³ hybridization slightly increased with t. The etching rate dropped under certain conditions of nitrogen bombardment whereas helium implantation has not significantly improved it. These results are ascribed to the crosslinking degree of the polymeric chains, ruled by the total amount of energy delivered to the film.