Prepare SiTiOC ceramic coatings by laser pyrolysis of titanium organosilicon compound

A SiTiOC ceramic coating with outstanding tribological performance was prepared by laser scanning the organosilicon coating with different laser power. The composition and structure of the obtained SiTiOC ceramic coatings were analyzed by scanning electron microscopy (SEM), infrared spectroscopy (FTIR), Raman spectra, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). The tribological performance of the coatings was studied using a multi-functional reciprocating friction and wear tester. The results showed that the chemical structure (chemical bonding) of the coatings prepared at 0 W, 350 W, and 500 W laser powers included Si-O-Si, Si-C, and TiO₂, while that prepared at 800 W was mainly composed of amorphous SiO₂, indicating that the coating had higher ceramization. The SiTiOC ceramic coatings prepared by the present process effectively reduced the friction coefficient and wear volume of the steel substrate, which indicated that they had good anti-friction and wear resistance properties.     

Jet pulse electrodeposition and characterization of Ni–AlN nanocoatings in presence of ultrasound

In current study, Ni–AlN nanocoatings were successfully prepared by adopting the jet pulse electrodeposition (JPE) technique with ultrasound. The scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Vickers microhardness test, electrochemical workstation and friction wear tests were utilized to investigate the microstructure, mechanical properties, corrosion degree and wear resistance of the coatings. The results indicated that the Ni–AlN nanocoatings deposited by using ultrasound demonstrated the minimum and most compact surface structure compared to the other coatings. The thicknesses of Ni coating and Ni–AlN nanocoatings were approximately 56 µm. The average atomic percent of Al and Ni elements in the Ni–AlN nano-coating prepared by using ultrasound, were approximately 21.4 at% and 47.5 at%, respectively. The maximum kinetic energy of the jet plating solution was 916 m²/s² during JPE-deposited Ni-AlN nanocoatings including ultrasound. The average micro-hardness value of the nano-coating prepared by using ultrasound equaled 767.9 HV. The Ni–AlN nanocoatings prepared using ultrasound had the minimum E_corr and I_corr values of ? 0.167 V and 6.363 × 10^?6 mA/cm², respectively. In this case, the demonstrated corrosion resistance was the most efficient. The Ni–AlN nanocoatings prepared using ultrasound sustained the minimum friction coefficients and the average friction coefficient was approximately 0.52. In contrast, the JPE-deposited Ni coating presented the maximum friction coefficient, while the average friction coefficient was approximately 1.43.     

Microstructure and deposition mechanism of CVD amorphous boron carbide coatings deposited on SiC substrates at low temperature

Amorphous boron carbide (α-B₄C) coatings were prepared on SiC substrates by chemical vapor deposition (CVD) from CH₄/BCl₃/H₂/Ar mixtures at low temperature (900–1050 °C) and reduced pressure (10 kPa). The deposited coatings were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-Raman spectroscopy, energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results showed that two kinds of α-B₄C coatings were deposited with different microstructures and phase compositions, and the effect of deposition temperature was significant. When deposited at 1000 °C and 1050 °C, the coatings exhibited a nodular morphology and had a relatively low content of boron. The free carbon was distributed in them inhomogeneously; in contrast, when deposited at 900 °C and 950 °C, the coatings presented a comparatively flat morphology and had a uniform internal structure and high boron content. They did not contain free carbon. At the last of this paper, the pertinent mechanisms resulting in differences in microstructure and phase composition were discussed.     

Comparative investigation of antibacterial yet biocompatible Ag-doped multicomponent coatings obtained by pulsed electrospark deposition and its combination with ion implantation

The aim of this work is to obtain antibacterial yet biocompatible coatings using pulsed electrospark deposition (PED). For this purpose new composite electrodes were fabricated from reaction mixtures Ti–C–20%Fe-10%Ca₃(PO₄)₂–3.4%Mg–X%Ag with different amount of antibacterial component (X = 0, 0.5, 1.0, 1.5 and 2.0 at% of Ag) using self-propagating high-temperature synthesis method. The electrodes consisted of TiC grains surrounded by TiFe₂ and TiFeP intermetallic matrix, CaO and MgO inclusions, and Ag-based phase. The influence of Ag content on the electrode mass transfer kinetics was studied by comparing the total substrate weight gain and electrode mass loss during PED. The structure, elemental composition, and surface roughness of coatings were studied by means of X-ray diffraction, scanning electron microscopy, and optical profilometry. The coatings were characterized in terms of Ag⁺ ion release, mechanical and electrochemical properties, as well as biocompatibility. The antibacterial characteristics of Ag-doped PED coatings were compared with those obtained by PED using Ag-free electrode and then implanted with Ag⁺ ions. The results indicated that an increase in the Ag content in electrode leads to a decrease in electrode erosion and substrate weight gain, but the efficiency of the PED process increases. Doping with a small amount of Ag (≤ 1 at%) resulted in 100% antibacterial effect against both gram-positive S. aureus and gram-negative E. сoli bacteria. In addition, the dynamics of МС3Т3-Е1 cell proliferation on the surface of PED coatings with 0.6–0.7 at% of Ag was similar to that in control samples, hereby indicating their biocompatibility. The coating biological characteristics were discussed based on the results of Ag⁺ ion release and electrochemical tests.     

Surface modification of graphene and graphite by nitrogen plasma: Determination of chemical state alterations and assignments by quantitative X-ray photoelectron spectroscopy

Multilayer graphene (MLGR) and its bulk analog, highly oriented pyrolytic graphite (HOPG), were treated by radio frequency activated low pressure N₂ gas plasma (at negative bias 0–200 V, for 5–20 min). Surface composition and chemical-state alterations were delineated by X-ray photoelectron spectroscopy (XPS). Covalently bonded nitrogen of 5–15 at% incorporated into the surface. The higher N concentration in MLGR below 100 V is attributed to the larger number of defects. The equal N content at 200 V indicates intensive formation of reactive sites. In-depth distribution of N is restricted to 2–4 monolayers. Model calculation resulted in 23 at% N (at 100 V) in the top graphene layers of HOPG. Three different chemical states of nitrogen (pyridine-type at 398.3 eV, pyrrole- and triazine-type at 399.7 eV and N substituting C in graphite-like network at 400.9 eV) were determined from high-resolution N1s spectral region for all samples. Pyridine and pyrrole–triazine components increase preferentially with increasing bias. Alterations of the C1s and O1s spectra are discussed in a critical approach. The amount of reacted carbon was consistent with that required for the three different nitrogen and oxygen states, thus validating the proposed assignments.     

Alumina composite coatings with enhanced high-temperature electrical insulating properties on Ni-based superalloy substrates

Electrical insulation of nickel-based superalloy substrate, especially at high temperature range, is one of the major challenges for the reliability and stability of the integrated thin-film sensors. Here, we report a solution-processed approach to fabricating high-temperature, electrically insulating coatings on Ni-based superalloy substrates. NiCrAlY coatings were fabricated by DC magnetron sputtering and heat-treated, and then Al₂O₃ films were deposited by sol-gel method. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy were used to characterize the composition, phase, microstructure and morphology of these composite coatings. The electrical resistance of the composite coating was measured as a function of temperature up to 800 °C. Electrical resistance greater than 1 MΩ were consistently achieved from 600 °C to 800 °C. Moreover, this insulating coating survived thermal shock and thermal fatigue tests without cracking or delaminating. A type S thin-film thermocouple was prepared on the composite coating to verify its high-temperature electrical insulation performance.     

Microstructure and oxidation resistance of C-AlPO4–mullite coating prepared by hydrothermal electrophoretic deposition for SiC-C/C composites

Oxidation resistant C-AlPO₄–mullite coating for SiC pre-coated carbon/carbon composites (SiC-C/C) was prepared by a novel hydrothermal electrophoretic deposition process. The phase composition, surface and cross-section microstructure of the as-prepared multi-layer coatings were characterized by X-ray Diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The influence of deposition voltage on phase composition, microstructure and oxidation resistance of the as-prepared coatings was particularly investigated. Results show that the outer layer coating mainly composed of C-AlPO₄ and mullite phase can be achieved after the hydrothermal electrophoretic deposition. The thickness, density and anti-oxidation property of the C-AlPO₄–mullite coating was improved with the increase of deposition voltage from 160 V to 200 V. The multi-layer coating prepared at a voltage of 200 V exhibit excellent anti-oxidation property, which can effectively protect C/C composites from oxidation in air at 1773 K for 324 h with a weight loss of 1.01%. The failure of the multi-layer coatings is due to the generation of cross-holes in the coating, which cannot be self-cured by the metaphosphate and silicate glass layer after long time oxidation at 1773 K.     

Durable superhydrophobic Zn/ZnO/TiO2 surfaces on Ti6Al4V substrate with self-cleaning property and switchable wettability

Durable superhydrophobic (SHP) Zn/ZnO/TiO₂ surfaces with dendritic structures on Ti₆Al₄V substrate were obtained by chemical etching, electrodeposition and following annealing process. The resultant coatings electrodeposited at ?1.5 V for 10 min and annealed at 190 °C for 60 min showed fine superhydrophobicity with a water contact angle of 160° and a rolling angle less than 1°, showing excellent rolling-off and self-cleaning properties. The morphology, chemical components and growth mechanism of samples were investigated by scanning electron microscopy (SEM), X-ray diffraction pattern (XRD), Energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Surface tribological properties were characterized by a universal mechanical tester (UMT). The as-prepared Zn/ZnO/TiO₂ surface still kept excellent SHP stability after exposure to the air, buried in soil and cold storage at 5 °C in the fridge for one year, as well as excellent repellence to some daily-used liquids such as coke, coffee, red wine, milk and tea. The surface can be reversibly switched between superhydrophobicity and superhydrophilicity by alternating UV illumination and dark storage or heating, which offer possibilities to widen future applications.     

Synthesis,characterization and alcohol sensing property of Zn-doped SnO2 nanoparticles

The Zn-doped SnO₂ nanoparticles synthesized by the chemical co-precipitation route and having dopant concentration varying from 0 to 4 at%, were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) for structural and morphological studies. XRD analyses reveal that all the samples are polycrystalline SnO₂ having tetragonal rutile structure with nanocrystallites in the range 10–25 nm. The TEM images show agglomeration of grains (cluster of primary crystallites). A corresponding selected area electron diffraction pattern reveals the different Debye rings of SnO₂, as analyzed in XRD. Alcohol sensing properties of all the Zn-doped samples were investigated for various concentrations of methanol, ethanol and propan-2-ol in air at different operating temperatures. Among all the samples examined, the 4 at% Zn-doped sample exhibits the best response to different alcohol vapors at the operating temperature of 250 °C. For a concentration of 50 ppm, the 4 at% Zn-doped sample shows the maximum response 85.6% to methanol, 87.5% to ethanol and 94.5% to propan-2-ol respectively at the operating temperature of 250 °C. A possible reaction mechanism of alcohol sensing has been proposed.     

Composition,structure and mechanical properties of the titanium surface after induction heat treatment followed by modification with hydroxyapatite nanoparticles

Coatings of titania (TiO₂) and "titania–hydroxyapatite" were prepared by oxidation of commercially pure titanium VT1-00 using induction heat treatment (IHT), followed by modification with colloidal hydroxyapatite (HAp) nanoparticles. The IHT treatment was performed at temperatures within 600–1200 °C for 300 s. According to the results of scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray fluorescent analysis (EDX), nanoindentation and in vitro testing, titania coatings of high morphological heterogeneity, and high mechanical properties and biocompatibility were formed on the titanium surface after IHT. The coatings were found to consist of nano- and submicron crystals of oval, needle-like, plate and prismatic shapes. A subsequent modification with HAp nanoparticles of the coated titanium substrate leads to accelerated formation of mechanically strong oxidebioceramic composite coatings. It was established that the porous oxide coatings modified with nanoparticles of HAp that were formed at temperatures from 800 to 1000 °C and holding for at least 30 s had a high biocompatibility.     

Effect of polymer concentration,needle diameter and annealing temperature on TiO2-PVP composite nanofibers synthesized by electrospinning technique

In this study, TiO₂-PVP nanofibers were successfully synthesized on an aluminium collector by using cost-effective electrospinning technique. The nanofibers were prepared at different polymer concentrations, needle diameters and annealing temperatures and properties were studied by various characterizations. The structural properties were studied by X-ray diffraction (XRD) and Raman spectroscopy techniques. Surface morphology and elemental analysis of the samples were investigated by scanning electron microscopy (SEM) attached with energy dispersive spectroscopy (EDS). The optical properties were carried out by UV–Visible absorption spectroscopy (UV–Vis). By varying the polymer concentration and needle diameter, the effect of viscosity and surface tension on the formation of TiO₂-PVP nanofibers was clearly observed by SEM micro images. EDS spectrum shows effective composition of pure TiO₂ nanofibers. XRD peaks observed at temperatures 500 °C, 700 °C and 900 °C confirmed the anatase, mixed and rutile phases of TiO₂ nanofibers respectively. Raman studies also confirmed these phases of TiO₂ nanofibers. The optical band-gap values calculated using Kubelka-Munk function lies in the range of 3.02–3.22 eV.     

Multilayer organic–inorganic coating incorporating TiO2 nanocontainers loaded with inhibitors for corrosion protection of AA2024-T3

Organic–inorganic multilayer coating containing organically modified silicates, epoxy resins and TiO₂ nanocontainers loaded with 8-hydroxyquinoline were produced on AA2024-T3 substrates via dip coating method. The parameters of the curing temperature and time were optimized via variation in a widespread range in order to realize coatings with best anticorrosive properties. Curing temperature at 110 °C for 24 h presented the best anticorrosive behavior. The morphology of the coating was examined via scanning electron microscopy. The composition of the coatings was determined by energy dispersive X-ray analysis and Fourier transform infra-red spectroscopy. Furthermore, the coatings were exposed to corrosive environment and evaluated by electrochemical impedance spectroscopy. We demonstrate that the presence of loaded TiO₂ nanocontainers enhances the anticorrosive properties of the coatings; specifically, the total impedance values were increased about two orders of magnitude compare to the bare substrate after 400 h of exposure to aggressive environment.     

Nanostructure,mechanical and tribological properties of reactive magnetron sputtered TiCx coatings

This study describes the correlation between microstructure, mechanical and tribological properties of TiC_x coatings (with x being in the range of 0–1.4), deposited by reactive magnetron sputtering from a Ti target in Ar/C₂H₂ mixtures at ~ 200 °C. The mechanical and tribological properties were found to strongly depend on the chemical composition and the microstructure present. Very dense structures and high hardness, combined with low wear rates and friction coefficients, were observed for coatings with chemical composition close to TiC. X-ray diffraction and X-ray photoelectron spectroscopy analysis, used to evaluate coating microstructure, composition and relative phase fraction, showed that low carbon contents in the coatings lead to sub-stoichiometric nanocrystalline TiC_x coatings being deposited, whilst higher carbon contents gave rise to dual phase nanocomposite coatings consisting of stoichiometric TiC nanocrystallites and free amorphous carbon. Optimum performance was observed for nanocomposite TiC_1.1 coatings, comprised of nanocrystalline nc-TiC (with an average grain size of ~ 15 nm) separated by 2–3 monolayers of an amorphous a-DLC matrix phase.     

Microstructure and corrosion properties of Ni-TiN nanocoatings prepared by jet pulse electrodeposition

Ni–TiN nanocoatings were successfully prefabricated by jet pulse electrodeposition. The effect of jet rate on cross-sectional composition, microstructure, microhardness, and corrosion properties of nanocoatings was examined by X-ray photoelectron spectroscopy, high-resolution transmission electron microscope, atomic force microscopy, microhardness tester and electrochemical workstation. Results illustrated that Ni–TiN nanocoatings deposited at jet rate of 3 m/s exhibited high concentration of Ni and Ti with average concentrations of Ni and Ti of 54.5 at% and 19.8 at%, respectively. Average diameters of Ni grains and TiN nanoparticles in Ni–TiN nanocoatings prepared at 3 m/s were 47.8 nm and 30.5 nm, respectively. Nanocoatings deposited at 1 m/s, 3 m/s and 5 m/s showed surface root-mean-square roughness value of 95.431, 30.091 and 58.454 nm, respectively, and presented maximum microhardness of 789.5, 876.2, and 849.9 HV, respectively. Ni–TiN nanocoating obtained at 3 m/s demonstrated minimum I_corr and E_corr values of 1.02 × 10⁻³ mA/cm² and − 0.551 V, respectively, signifying to offer the best corrosion resistance.     

Influence of deposition temperature on the properties of hydroxyapatite obtained by electrochemical assisted deposition

Surface functionalization of pure titanium (cp-Ti) with hydroxyapatite (HAp) was successfully achieved by means of electrochemical deposition (ED) in a solution containing calcium nitrate and ammonium dihydrogen phosphate. The aim of this study is to evaluate the influence of the deposition temperature on the elemental and phase composition, chemical bonds, morphology, and in vitro electrochemical behaviour in biological simulated media (simulated body fluid - SBF). The roughness and wettability of the developed coatings are also investigated. By increasing the deposition temperature from 50 °C to 75 °C, the HAp coatings present a well-crystalized structure, denser and a nobler behaviour in terms of electrochemical behaviour in SBF at 37 °C. Also, by increasing the deposition temperature from 50 °C to 75 °C, the contact angle has decreased from 76.1° to 27.4°, exhibiting a highly hydrophilic surface. Taking into consideration all the obtained data, electrodeposition of HAp at 75 °C was found preferable when compared to 50 °C. The characteristics of the HAp coatings can be easily adjusted by optimizing the electrochemical deposition parameters and/or controlling specific features like pH, temperature, or ionic concentration of electrolyte, etc.     

The effect of thermal annealing on Fe/TiO2 coatings deposited with the help of RF PECVD method. Part I. Chemical and phase composition

Results of the studies on chemical structure and phase composition of both non-annealed and thermally annealed iron doped TiO₂ coatings are presented. The coatings were synthesized with the help of radio frequency plasma enhanced chemical vapor deposition (RF PECVD) and characterized by iron content in the range of 0–4.76 at%. In these studies, an analysis of both elemental composition and chemical bonding was performed with the help of X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) was applied to determine phase composition and Fourier transform infrared spectroscopy (FTIR) was used as a supplementary source of information. The obtained elemental composition data show that, apart from titanium, oxygen and iron, traces of chlorine as well as substantial amounts of carbon are present in the coatings. While chlorine has originated from plasma decomposition of TiCl_4, used as a source of titanium, a presence of carbon is associated with a surface contamination resulting from photocatalytic reactions of TiO₂ with the adsorbed carbon dioxide. The results of XPS and FTIR indicate that thermal annealing not only modifies phase composition of these materials, but also affects chemical bonding. Finally, XRD analysis shows that iron content has an effect on the size of coherent diffraction domains present in the films.     

Ultrasonochemical coating and characterization of TiO2-coated zirconia fine particles

Zirconia fine particles were prepared by ultrasonic spray pyrolysis (USP) and employed as a substrate for titanium/titania coating by ultrasonochemistry. The effects of several process factors on the characteristics of the prepared particles were investigated and the particles were then characterized by various techniques. This substrate was coated with various titanium concentrations (0.025–0.1 M) for two ultrasonication time periods (30 min, 2 h) by sonochemistry, and finally calcined at 1100 °C. Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size analysis (PSA), Fourier transformation infrared spectroscopy (FT-IR) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) comprised the techniques used to characterize them. The particles were prepared in a monodispersed spherical form with no interior cavity; their average size was shown to be 0.62 μm before calcination and 2.57 μm after calcination. The titania surface coating acted to partially stabilize the particles to a tetragonal phase. Based on the analytical results, the optimum conditions for preparing the particles were shown to be 7.5 wt% of titania as an initial solution concentration and 0.5 h of coating time.     

The effect of thermal annealing on Fe/TiO2 coatings deposited with the help of RF PECVD method. Part II. Optical and photocatalytic properties

In this work, morphology, optical properties, photowetting effect, and bactericidal behavior of titanium dioxide coatings, both plain and iron doped within the range of 0.52 and 4.76 at%, are presented. The coatings were synthesized with the help of radio frequency plasma enhanced chemical vapor deposition technique followed by thermal annealing at 500 °C under normal atmospheric conditions. Atomic force microscopy examination of the film morphology reveal roughness differences depending on the concentration of iron. Measurements of optical properties, carried out with the UV–VIS absorption spectrometry, show high transmittance in the visible range. Optical gap values, determined with the help of the Tauc equation, exhibit a decreasing tendency with an increasing iron content, but only up to the concentration of 2.5 at%, with thermally annealed coatings characterized by higher E_g values than those of the non-annealed materials. Results of variable angle spectroscopic ellipsometry measurements indicate that both iron doping and thermal annealing have the effect of increasing refractive index of the films. An analysis of the coatings surface wettability, performed under conditions of an alternative exposure either to daylight or to the UV-B radiation, show the most important parameter to be the time of water contact angle return to its initial value under darkroom conditions. Finally, bactericidity studies of the UV-B irradiated samples, performed with the Escherichia coli DH5α bacteria, reveal the most extensive bactericidal effect observed for low iron concentrations, equally for both non-annealed and thermally annealed materials.     

Ceramic TiC/a:C protective nanocomposite coatings: Structure and composition versus mechanical properties and tribology

The relationship between the structure, elemental composition, mechanical and tribological properties of TiC/amorphous carbon (TiC/a:C) nanocomposite thin films was investigated. TiC/a:C thin film of different compositions were sputtered by DC magnetron sputtering at room temperature. In order to prepare the thin films with various morphology only the sputtering power of Ti source was modified besides constant power of C source. The elemental composition of the deposited films and structural investigations confirmed the inverse changes of the a:C and titanium carbide (TiC) phases. The thickness of the amorphous carbon matrix decreased from 10 nm to 1–2 nm simultaneously with the increasing Ti content from 6 at% to 47 at%. The highest hardness (H) of ~26 GPa and modulus of elasticity (E) of ~220 GPa with friction coefficient of 0.268 was observed in case of the film prepared at ~38 at% Ti content which consisted of 4–10 nm width TiC columns separated by 2–3 nm thin a:C layers. The H3/E2 ratio was ~0.4 GPa that predicts high resistance to plastic deformation of the TiC based nanocomposites beside excellent wear-resistant properties (H/E=0.12).     

Synthesis,spray granulation and plasma spray coating of lanthanum phosphate nanorods for thermal insulation coatings

Nanorods of lanthanum phosphate obtained by a wet chemical precipitation route were granulated to obtain sizes in the range of 10–15 µm by spray drying from aqueous slurry of 35 wt% solid loading and 2 wt% of PVA binder. The powders thus obtained displayed enhanced flowability and were plasma sprayed on to stainless steel substrates resulting in the formation of adherent coatings of 150–180 µm thickness. These coatings were characterized using electron microscopy, X-ray diffraction analysis and Raman spectroscopy. X-ray analysis indicated phase instability of LaPO₄ during plasma spraying resulting in the formation of oxy and polyphosphates of lanthanum (La₂P₄O₁₃ and La₃PO₇). However, post deposition heat treatment of coated samples at 1100 °C for 2 h resulted in the reversible formation of stoichiometric lanthanum orthophosphate (LaPO₄). Raman spectral analysis was used to confirm the phase structure of the coatings deposited at various plasma input powers. The coatings obtained were found to effectively lower the thermal conductivity of the substrates from ~24 W/mK to less than 19 W/mK (~10%) even at 200 °C.