Search

Pathogenic microbes, such as bacteria and viruses, can spread quickly via contaminated surfaces. Most of these pathogenic microorganisms can survive on surfaces for a long time. Touching these surfaces can lead to the transmission of the microorganisms to the human body and cause serious illnesses. ZrN-Cu coatings containing different amounts of Cu were deposited using an industrial PVD system, and their ability to inhibit bacteria and inactivate the SARS-CoV-2 virus was tested. Microstructural studies showed the formation of two distinct ZrN and Cu phases when Cu content was sufficiently high. Hardness and elastic modulus were inversely proportional to the Cu content. The coatings showed outstanding bactericidal properties against Escherichia coli and Pseudomonas aeruginosa, especially when Cu content was more than 12 at.% and exposure time was longer than 40 min. The coatings, however, did not exhibit any significant virucidal properties. Good mechanical properties, along with excellent antibacterial effects, make these coatings suitable for use as self-sanitizing surfaces on objects that people regularly touch and that are prone to bacterial contamination. Their use would thus allow for only minimal transmission or multiplication of bacteria, and the treated surface would not serve as another source of infection.

Electrical resistivity (4.2–800 K), Seebeck coefficient (300–800 K), specific heat (2–110 K), Vickers hardness, elastic moduli (RT) were defined for single-phase nonstoichiometric compounds: Ti2.13Ni2Sn0.87, Zr2.025Ni2Sn0.975, and Hf2.055Ni2Sn0.945.

In this study mid-frequency pulsed-DC magnetron sputtering was used to deposit W-B-C coatings. The effect of coating composition and the deposition parameters on the structure, mechanical and tribological properties of the coatings was investigated. The broad diffraction peaks in the X-ray diffractogram indicated the amorphous to nanocrystalline nature of the coatings. The hardness of the coatings ranged from 22.6 to 26.2 GPa. The coatings prepared at the elevated temperature of 500 degrees C exhibited greater hardness compared to the coatings prepared at the ambient temperature. The amount of W in the coatings was the main parameter influencing the friction coefficient with a higher W content leading to a higher friction coefficient. The coatings prepared at 500 degrees C showed lower wear in tribological measurements due to their higher hardness compared to the coatings prepared at ambient temperature. The friction coefficient decreased as the testing temperature increased beyond 500 degrees C. XRD analyses after the high temperature tests have shown that this decrease was due to the formation of W-O Magneli phases, which acted as a solid-state lubricant.

Polyoxazoline thin coatings were deposited on glass substrates using atmospheric pressure plasma polymerization from 2-ethyl-2-oxazoline vapours. The plasma polymerization was performed in dielectric barrier discharge burning in nitrogen at atmospheric pressure. The thin films stable in aqueous environments were obtained at the deposition with increased substrate temperature, which was changed from 20◦ C to 150◦ C. The thin film deposited samples were highly active against both S. aureus and E. coli strains in general. The chemical composition of polyoxazoline films was studied by FTIR and XPS, the mechanical properties of films were studied by depth sensing indentation technique and by scratch tests. The film surface properties were studied by AFM and by surface energy measurement. After tuning the deposition parameters (i.e., monomer flow rate and substrate temperature), stable films, which resist bacterial biofilm formation and have cell-repellent properties, were achieved. Such antibiofouling polyoxazoline thin films can have many potential biomedical applications. © MDPI AG. All rights reserved., Czech Science FoundationGrant Agency of the Czech Republic [GACR 19-15240S]; Ministry of Defence of the Czech Republic

This research was devoted to studying the influence of the taper angle on the micro-compression of micro-pillars fabricated from near-amorphous and nanocrystalline Mo-B-C coatings. A series of micro-pillars with a taper angle between 4–14° was fabricated by focused ion beam technique. The deformation mechanism was found to be dependent on the taper and, also, on the crystallinity of the coating. In order to obtain correct values of yield strength and Young’s modulus, three empirical models of stress correction were experimentally tested, and the results were compared with nanoindentation measurements. It was shown that the average stress correction model provided comparable results with nanoindentation for the yield strength for taper angles up to ~10°. On the other hand, the average radius or area model gave the most precise results for Young’s modulus if the taper angle was

The current work aimed to characterize the morphology, chemical, and mechanical properties of Pt and PtTi thin films deposited via thermionic vacuum arc (TVA) method on glass and silicon substrates. The deposited thin films were characterized by means of a scanning electron microscope technique (SEM). The quantitative elemental microanalysis was done using energy-dispersive X-ray spectroscopy (EDS). The tribological properties were studied by a ball-on-disc tribometer, and the mechanical properties were measured using nanoindentation tests. The roughness, as well as the micro and nanoscale features, were characterized using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The wettability of the deposited Pt and PtTi thin films was investigated by the surface free energy evaluation (SFE) method. The purpose of our study was to prove the potential applications of Pt-based thin films in fields, such as nanoelectronics, fuel cells, medicine, and materials science.

The initial stage of graphene layer deposition on silicon oxide substrate by ethanol decomposition in dual-channel microwave plasma torch at atmospheric pressure was studied in dependence on precursor flow rate and delivered microwave power. Depending on ethanol flow rate and substrate temperature, horizontally or vertically aligned graphene nanosheets with various density could be prepared directly on dielectric substrate. In the regime with high microwave power, above 400 W, mixture of amorphous carbon particles and graphene sheets was deposited on the substrate. Prepared layers were analyzed by scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The microwave plasma diagnostics was carried out using optical emission spectroscopy (OES). The sample analysis showed increasing density of horizontally aligned carbon nanosheets with increasing ethanol flow rate and their delamination and transition into vertically aligned graphene sheets with increasing substrate temperature. The Raman spectroscopy analysis of layers showed presence of D (1345 cm(-1)), G (1585 cm(-1)) and 2D (2685 cm(-1)) peaks with 2D/G ratio of 1.59 and full width at half maximum (FWHM) of 2D peak was 42 cm(-1), corresponding to few layer graphene structure. In case of amorphous nanoparticles deposition, the D* peak at 1210 cm(-1) and D** at 1500 seem-1 was observed in Raman spectra with D/G ratio of 1.19 and Cls XPS spectra of carbon contained 20.4 at.% of spa carbon phase in comparison to 8.3 at.% in case of graphene nanosheets layer. High D/G ratio, up to 3.5, and low intensity 2D band was characteristic for vertically aligned graphene nanosheets layers. The possibility to influence density and size of graphene nanosheets on substrate represents promising alternative for future deposition of graphene on arbitrary substrate. Počáteční fáze nanášení grafenové vrstvy na substrát oxidu křemičitého rozkladem ethanolu v dvoukanálovém mikrovlnném plazmovém hořáku za atmosférického tlaku byl studován v závislosti na průtoku prekurzoru a dodávané mikrovlnné energii. V závislosti na průtoku ethanolu a teplotě substrátu lze přímo na dielektrickém substrátu připravit vodorovně nebo svisle uspořádané grafenové nanosheety s různou hustotou. V režimu s vysokým mikrovlnným výkonem nad 400 W byla na substrát nanesena směs amorfních uhlíkových částic a grafenových listů. Připravené vrstvy byly analyzovány skenovací elektronovou mikroskopií (SEM), Ramanovou spektroskopií a rentgenovou fotoelektronovou spektroskopií (XPS). Diagnostika mikrovlnné plazmy byla prováděna pomocí optické emisní spektroskopie (OES). Analýza vzorku ukázala rostoucí hustotu horizontálně uspořádaných uhlíkových nanosheet se zvyšující se průtokovou rychlostí ethanolu a jejich delaminaci a přechod na svisle zarovnané grafenové desky se zvyšující se teplotou substrátu. Ramanova spektroskopická analýza vrstev ukázala přítomnost píku D (1345 cm (-1)), G (1585 cm (-1)) a 2D (2685 cm (-1)) s poměrem 2D / G 1,59 a plnou šířkou při poloviční maximum (FWHM) 2D píku bylo 42 cm (-1), což odpovídá několika vrstvové grafenové struktuře. V případě ukládání amorfních nanočástic byl v Ramanově spektru pozorován D * pík při 1210 cm (-1) a D ** při 1500 zdán-1 s poměrem D / G 1,19 a Cls XPS spektra uhlíku obsahovala 20,4%. lázeňské uhlíkové fáze ve srovnání s 8,3 at.% v případě vrstvy nanočástic grafenu. Vysoký poměr D / G, až 3,5, a nízkointenzivní 2D pás byl charakteristický pro svisle zarovnané vrstvy nanočástic grafenu. Možnost ovlivnit hustotu a velikost grafenových nanosheetů na substrátu představuje slibnou alternativu pro budoucí depozici grafenu na libovolném substrátu. The initial stage of graphene layer deposition on silicon oxide substrate by ethanol decomposition in dual-channel microwave plasma torch at atmospheric pressure was studied in dependence on precursor flow rate and delivered microwave power. Depending on ethanol flow rate and substrate temperature, horizontally or vertically aligned graphene nanosheets with various density could be prepared directly on dielectric substrate. In the regime with high microwave power, above 400 W, mixture of amorphous carbon particles and graphene sheets was deposited on the substrate. Prepared layers were analyzed by scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The microwave plasma diagnostics was carried out using optical emission spectroscopy (OES). The sample analysis showed increasing density of horizontally aligned carbon nanosheets with increasing ethanol flow rate and their delamination and transition into vertically aligned graphene sheets with increasing substrate temperature. The Raman spectroscopy analysis of layers showed presence of D (1345 cm(-1)), G (1585 cm(-1)) and 2D (2685 cm(-1)) peaks with 2D/G ratio of 1.59 and full width at half maximum (FWHM) of 2D peak was 42 cm(-1), corresponding to few layer graphene structure. In case of amorphous nanoparticles deposition, the D* peak at 1210 cm(-1) and D** at 1500 seem-1 was observed in Raman spectra with D/G ratio of 1.19 and Cls XPS spectra of carbon contained 20.4 at.% of spa carbon phase in comparison to 8.3 at.% in case of graphene nanosheets layer. High D/G ratio, up to 3.5, and low intensity 2D band was characteristic for vertically aligned graphene nanosheets layers. The possibility to influence density and size of graphene nanosheets on substrate represents promising alternative for future deposition of graphene on arbitrary substrate.

Commercial ceramic protective coatings usually exhibit high hardness, but low ductility impairs their performance and application-oriented properties. Accordingly, a state-of-the-art magnetron sputtered W-B-C coating can be a promising coating for the tooling industry due to its hard yet tough characteristics. In the present study, we have employed substrate biasing to enhance the delivered energy to the growing film and have investigated the effect of bias voltage on the structural and mechanical behavior of W-B-C coatings. The investigations revealed that increasing the substrate bias voltage enhanced the re-sputtering of B and C atoms and subsequently varied the chemical composition of the coatings and significantly decreased the growth rate. It also enhanced the crystallinity of the coatings. We demonstrate how the bias voltage led to an unusual transition from a featureless to a columnar microstructure. Furthermore, it was observed that as the substrate bias voltage increased from 0 V to −125 V, the compositional and structural changes resulted in a slight decrease of the hardness, while a further increase in the bias voltage to −200 V enhanced the hardness. This increase was attributed to the suppression of dislocation movement and grain boundary deformation processes by solute segregation and by lattice defects.

Polyoxazolines are a new promising class of polymers for biomedical applications. Antibiofouling polyoxazoline coatings can suppress bacterial colonization of medical devices, which can cause infections to patients. However, the creation of oxazoline-based films using conventional methods is difficult. This study presents a new way to produce plasma polymerized oxazoline-based films with antibiofouling properties and good biocompatibility. The films were created via plasma deposition from 2-methyl-2-oxazoline vapors in nitrogen atmospheric pressure dielectric barrier discharge. Diverse film properties were achieved by increasing the substrate temperature at the deposition. The physical and chemical properties of plasma polymerized polyoxazoline films were studied by SEM, EDX, FTIR, AFM, depth-sensing indentation technique, and surface energy measurement. After tuning of the deposition parameters, films with a capacity to resist bacterial biofilm formation were achieved. Deposited films also promote cell viability.

We combine theoretical and experimental tools to study elastic properties of Fe-Al-Ti superalloys. Focusing on samples with chemical composition Fe 71 Al 22 Ti 7 , we use transmission electron microscopy (TEM) to detect their two-phase superalloy nano-structure (consisting of cuboids embedded into a matrix). The chemical composition of both phases, Fe 66 . 2 Al 23 . 3 Ti 10 . 5 for cuboids and Fe 81 Al 19 (with about 1% or less of Ti) for the matrix, was determined from an Energy-Dispersive X-ray Spectroscopy (EDS) analysis. The phase of cuboids is found to be a rather strongly off-stoichiometric (Fe-rich and Ti-poor) variant of Heusler Fe 2 TiAl intermetallic compound with the L2 1 structure. The phase of the matrix is a solid solution of Al atoms in a ferromagnetic body-centered cubic (bcc) Fe. Quantum-mechanical calculations were employed to obtain an insight into elastic properties of the two phases. Three distributions of chemical species were simulated for the phase of cuboids (A2, B2 and L2 1 ) in order to determine a sublattice preference of the excess Fe atoms. The lowest formation energy was obtained when the excess Fe atoms form a solid solution with the Ti atoms at the Ti-sublattice within the Heusler L2 1 phase (L2 1 variant). Similarly, three configurations of Al atoms in the phase of the matrix with different level of order (A2, B2 and D0 3 ) were simulated. The computed formation energy is the lowest when all the 1st and 2nd nearest-neighbor Al-Al pairs are eliminated (the D0 3 variant). Next, the elastic tensors of all phases were calculated. The maximum Young&rsquo, s modulus is found to increase with increasing chemical order. Further we simulated an anti-phase boundary (APB) in the L2 1 phase of cuboids and observed an elastic softening (as another effect of the APB, we also predict a significant increase of the total magnetic moment by 140% when compared with the APB-free material). Finally, to validate these predicted trends, a nano-scale dynamical mechanical analysis (nanoDMA) was used to probe elasticity of phases. Consistent with the prediction, the cuboids were found stiffer.

Nanostructured C-Ag thin films of 200 nm thickness were successfully synthesized by the Thermionic Vacuum Arc (TVA) method. The influence of different substrates (glass, silicon wafers, and stainless steel) on the microstructure, morphology, and mechanical properties of nanostructured C-Ag thin films was characterized by High-Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and TI 950 (Hysitron) nanoindenter equipped with Berkovich indenter, respectively. The film’s hardness deposited on glass (HC-Ag/Gl = 1.8 GPa) was slightly lower than in the case of the C-Ag film deposited on a silicon substrate (HC-Ag/Si = 2.2 GPa). Also the apparent elastic modulus Eeff was lower for C-Ag/Gl sample (Eeff = 100 GPa) than for C-Ag/Si (Eeff = 170 GPa), while the values for average roughness are Ra=2.9 nm (C-Ag/Si) and Ra=10.6 (C-Ag/Gl). Using the modulus mapping mode, spontaneous and indentation-induced aggregation of the silver nanoparticles was observed for both C-Ag/Gl and C-Ag/Si samples. The nanocomposite C-Ag film exhibited not only higher hardness and effective elastic modulus, but also a higher fracture resistance toughness to the silicon substrate compared to the glass substrate.

Nanocomposite coatings consisting of nanocrystallites embedded in an amorphous matrix can be tailored to exhibit unusual combination of properties such as high hardness and modulus combined with low friction and wear. The properties of the coatings are governed by parameters of the deposition plasma, which are a nontrivial function of the deposition process parameters. Energy flux onto the growing films provided by ionized species is one of the key parameters influencing the properties of coatings. This study is focused on the influence of ion flux on the properties of the growing nc-TiC/a-C:H thin film in order to achieve enhanced mechanical properties. Two different magnetic field configurations were used. The saturated ion current on the substrate was found to be seven times higher in the strongly unbalanced magnetic configuration as compared to well-balanced configuration. The deposition temperature was constant at ~ 320 °C, which is higher than the usual temperature for similar depositions of nc-TiC/a-C(:H) coatings. The structure and mechanical properties of the coatings prepared at low or high ion flux were studied and compared. It is concluded that the level of the impinging ion flux in DC magnetron sputtering is not a significant factor influencing the mechanical properties of the coatings in the presented setup.

Titanium carbide/carbon nanocomposite hard coatings, which consist of TiC nanoparticles buried in amorphous carbon matrix, are prepared by a hybrid plasma process combining magnetron sputtering of a titanium target and plasma enhanced chemical vapor deposition using methane as a source for the growth of amorphous carbon. A particular attention was paid to the comparison of the surface and the bulk chemical compositions of the films determined by different analysis techniques: X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), wavelength dispersive X-ray spectroscopy (WDS) and energy dispersive X-ray spectroscopy (EDS). XPS and EDS show an underestimation in carbon concentration compared to RBS and WDS which provide similar values. This underestimation is more important in case of XPS and it is mainly attributed to the presence of oxygen contamination on the surface of the films strongly bonded to titanium. In case of EDS, the underestimation is related to the poor sensitivity of the used probe in regard to light elements such as carbon. Moreover, the structure of the coatings has been extensively probed by transmission electron microscopy, which has shown that the size of the TiC nanoparticles shrinks when increasing the carbon content within the films. We further demonstrate that this structural evolution has a direct impact on the hardness of the coatings which gets reduced when the grain size decreases.

Addition of lead into tin based solders represents a serious health risk and environmental problem. Lead-free solders represent one of the ways to remove pollution of lead into environment, nevertheless, new advanced joining methods have to be considered. Aggregation effect of nanoparticles studied in this work seems to be an interesting alternative. It was found experimentally that Ag nanopowder annealed at temperatures above silver oxide decomposition forms continuous Ag layer and yields a firm junction between copper plates. Oxide layer is observed at the Cu-Ag interface. The oxide interlayer thickness reflects the temperature and annealing time. Microstructure of prepared experimental joints, composition profiles and local mechanical properties were studied on cross-sectional samples by analytical electron microscopy and depth-sensing indentation technique. Práce se zabývá alternativou pájení za použití nanočástic stříbra, pozornost je věnována interakci s mědí, která je nejčastěji spojovaným materiálem v elektronice.

An atmospheric pressure dielectric barrier discharge burning in nitrogen with a small admixture of hexamethyldisiloxane (HMDSO) was used for the deposition of thin organosilicon films. The thin films were deposited on glass, silicon and polycarbonate substrates, and the substrate temperature during the deposition process was increased up to values within the range 25–150 °C in order to obtain hard SiO x -like thin films. The properties of the discharge were studied by means of optical emission spectroscopy and electrical measurements. The deposited films were characterized by the Rutherford backscattering and elastic recoil detection methods, x-ray photoelectron spectroscopy, infrared spectroscopy measurements, ellipsometry and the depth sensing indentation technique. It was found that the films' properties depend significantly on the substrate temperature at deposition. An increase in substrate temperature from 25 to 150 °C led to an increase in film hardness from 0.4 to 7 GPa and the film chemical composition changed from CH x Si y O z to SiO x H y . The films were transparent in the visible range.