Microstructure,mechanical and tribological properties of Ti–B–C–N films prepared by reactive magnetron sputtering

Quaternary Ti–B–C–N thin films are deposited on high-speed steel substrates by the reactive magnetron sputtering (RMS) technique. The microstructure, mechanical and tribological properties of Ti–B–C–N films with different carbon contents (from 28.9 at.% to 54.2 at.%) are explored systematically. The microstructure of Ti–B–C–N films deposited by RMS is consisted mainly of Ti(C, N) nano-crystals embedded into an amorphous matrix of a-C/a-CN/a-BN/a-BC. As the carbon content increases, the crystalline size of the films diminishes, but the hardness linearly increases from 14 GPa to 26 GPa. The friction coefficient of the films sliding against steel GCr15 balls in air decreases with the increase of carbon content, which shows that Ti–B–C–N films with both higher hardness and lower friction coefficient can be obtained by means of increasing the carbon concentration in the films.     

Dielectric properties of composition spread SiO2–Al2O3 mixed phase thin films deposited at room temperature by off-axis RF magnetron sputtering

The dielectric properties of composition spread SiO₂–Al₂O₃ thin films deposited by off-axis radio-frequency magnetron sputtering at room temperature were explored to obtain optimized compositions, which have low dielectric constants and losses. The specific points (compositions) showing superior dielectric properties of low dielectric constants (8.13 and 9.12) and losses (tanδ ～0.02) at 1 MHz were found in area of the distance of 25.0 mm (Al₂Si₃O₈) and 42 mm (Al_2.4Si₃O₈) apart from SiO₂ target side in 75 mm × 25 mm sized Pt/Ti/SiO₂/Si(1 0 0) substrates, respectively. The specific thin films were amorphous phase and the compositions were Al₂Si₃O₈ (k ～8.13) and Al_2.4Si₃O₈ (k ～9.12).     

Structure and characteristics of amorphous (Ti,Si)–C:H films deposited by reactive magnetron sputtering

The hydrogenated amorphous carbon films doped with Ti and Si ((Ti,Si)–C:H) were deposited on silicon substrates using reactive magnetron sputtering Ti₈₀Si₂₀ composite target in an argon and methane gas mixture. The structures of the films were analyzed by X-ray photoelectron spectroscopy and Visible Raman spectroscopy. The morphologies were observed by atomic force microscope. The friction coefficients of the films were tested on the ball-on-disc tribometer. The results indicate that the sp³/sp² ratios in the films can be varied from 0.18 to 0.63 by changing Ti and Si contents at various CH₄ flow rates. The surface of the films becomes smoother and more compact as the CH₄ flow rate increases. The lowest friction coefficient is as low as 0.0139 for the film with Ti of 4.5 at.% and Si of 1.0 at.%. Especially, the film exhibits a superlow value (μ < 0.01) under ambient air with 40% relative humidity in friction process. The superlow friction coefficient in ambient air may be, attributable to synergistic effects of a combination of Ti and Si in the film.     

Demineralized whey–gelatin composite films: Effects of composition on film formation,mechanical, and physical properties

In this study, the objective was to prepare and characterize films with different concentrations of demineralized whey (3–10%) and gelatin (1–3%) containing glycerol (10–70%) as a plasticizer and chitosan or nanochitosan as an additive. Mechanical properties, thickness, grammage, opacity, moisture content, water, and ethanol solubilities of the obtained films were determined. The formation of films without glycerol and gelatin was not possible. A higher gelatin concentration led to more desirable mechanical properties. Thickness, grammage, opacity, and moisture content remained almost constant after increasing gelatin concentration. Heightening glycerol concentrations raised water and ethanol solubility. Despite presenting high water solubility, the films showed low ethanol solubility. The formulation containing whey (3%), glycerol (20%), gelatin (3%), and chitosan (0.1%) resulted in the highest performing film concerning physical and mechanical aspects. Through Fourier transform infrared spectroscopy analysis, it was possible to observe the displacement and the frequency reduction of the band near 3,300 cm⁻¹, revealing different protein interactions. It indicates that hydrogen bonds occur between the amino group and  OH of the protein molecules reducing film hydrophilicity. Contact angle measurements also showed a less hydrophilic character. The films present the potential to prolong the shelf life of food, such as dairy products.     

Transparent semiconductor zinc oxide thin films deposited on glass substrates by sol–gel process

Transparent semiconductor ZnO thin films were spin-coated onto alkali-free glass substrates by a sol–gel process. The influence of ZnO sols synthesized via different solvents (2-ME, EtOH or IPA) on the surface morphologies, microstructures, optical properties and resistivities of the obtained films were investigated. The as-coated films were annealed in ambient air at 500 °C for 1 h. X-ray diffraction results showed all polycrystalline ZnO thin films to have preferred orientation along the (0 0 2) plane. The surface morphologies, optical transmittances and resistivity values of the sol–gel derived ZnO thin films depended on the solvent used. The ZnO thin films synthesized with IPA as the solvent exhibited the highest average transmittance 92.2%, an RMS roughness of 4.52 nm and a resistivity of 1.5 × 10⁵ Ω cm.     

Effects of the pretreatment of a cemented carbide surface on its properties and on the properties of diamond coatings deposited by oxygen–acetylene flame CVD

The influence of the pretreatment of the WC (6% Co) surface on its properties (i.e. roughness, grain size and chemical composition) and on the properties of flame-deposited coatings have been studied. The surface treatments included the action of an oxidizing oxygen/acetylene flame at 1000 °C, scratching with diamond particles (14–20 μm), mixture with iron (<45 μm) in an ultrasound bath, and seeding with a nm-sized diamond suspension. An acid treatment was included in the pretreatment sequence. It is found that the oxidizing flame and the seeding decrease the surface roughness of the substrate as well as the diamond coatings, at the same time increasing the adhesion of the coating. Ultrasound scratching with the diamond/iron suspension increases the roughness of both the substrate and the diamond coating and decreases the adhesion of the coating. Scratching with diamond particles shows a similar but lesser effect. Except for scratching with diamond, all the surface pretreatment procedures lead to an increase in the density of diamond particles: this increase is greatest for seeding. Our results indicate that good adhesion and a small surface roughness are best obtained by the use of an oxidizing flame followed by acid treatment and seeding with nanoparticles.     

Corrosion protection by zirconia-based thin films deposited by a sol–gel spin coating method

This paper focuses on the structure and corrosion behavior of 316L stainless steel coated by inorganic ZrO₂, hybrid ZrO₂–PMMA, and combined inorganic–hybrid films. The coatings were deposited by a particulate sol–gel spin-coating route, using carboxymethyl cellulose as a nanoparticle dispersant. The electrochemical evaluations were conducted in a simulated body fluid, via potentiodynamic polarization and impedance spectroscopic experiments. According to the results, the hybrid coating presented a better corrosion protection compared to the inorganic coating, due to a lesser density of structural defects. However, the best corrosion resistance was found for a combined coating which consists of an inorganic bottom layer and a hybrid top layer, due to a desirable compromise of good adhesion and low defect density.     

Influence of transition metal doping on the structural,optical, and magnetic properties of TiO2 films deposited on Si substrates by a sol–gel process

Transition metal (TM)-doped TiO₂ films (TM = Co, Ni, and Fe) were deposited on Si(100) substrates by a sol–gel method. With the same dopant content, Co dopants catalyze the anatase-to-rutile transformation (ART) more obviously than Ni and Fe doping. This is attributed to the different strain energy induced by the different dopants. The optical properties of TM-doped TiO₂ films were studied with spectroscopic ellipsometry data. With increasing dopant content, the optical band gap (E_OBG) shifts to lower energy. With the same dopant content, the E_OBG of Co-doped TiO₂ film is the smallest and that of Fe-doped TiO₂ film is the largest. The results are related to electric disorder due to the ART. Ferromagnetic behaviors were clearly observed for TM-doped TiO₂ films except the undoped TiO₂ film which is weakly magnetic. Additionally, it is found that the magnetizations of the TM-doped TiO₂ films decrease with increasing dopant content.     

Electronic properties of nanocrystalline BN and AlN films deposited on Si and GaAs—a comparison

The dielectric and semiconducting properties of the systems formed by nanocrystalline AlN and BN layers on Si and GaAs substrates are compared. MIS structures and p–n heterojunctions with good and reproducible properties were obtained. The most interesting device appears to be the AlN–GaAs system.     

Structural and chemical analysis of amorphous B–N–C thin films deposited by RF sputtering

Ternary Boron–Nitrogen–Carbon (B–N–C) thin films were deposited, onto silicon substrates, by reactive radio frequency (RF) sputtering from a boron carbide (B₄C) target in a gas mixture of nitrogen and argon. The influence of the RF power (P_RF) on the structure and the chemical composition of these films are studied by Fourier transform Infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements. The two techniques reveal the presence of B, C and N atoms in the deposited films. The presence of nitrogen in the atmosphere of the deposition chamber produces ternary B–N–C films composed mainly with a mixture of B–N and CN bonds as revealed by these techniques. The boron content increases while carbon and nitrogen contents decrease with P_RF. The higher proportion of boron atoms produced a strong contribution of the boron nitride in the final compound B–N–C films.     

Preparation and dielectric properties of dense and amorphous alumina film by sol–gel technology

Dense and crack-free aluminum oxide films were fabricated by sol–gel spin-coating technology. Aluminum nitrate (Al(NO₃)₃.9H₂O) was used as the precursor material. X-ray diffraction shows that the fabricated films are amorphous. X-ray photoelectron spectroscopy confirms that the thin films are alumina (Al₂O₃). Field-emission scanning electron microscopy images of the films reveal that the films are compact with a dense cross section. Dielectric measurements were carried out on samples with a metal–insulator–metal structure. The electrical characteristics of the films were affected by the thermal sintering temperature of the films. The leakage current density of the films decreases with the increase in the sintering temperature and increases with the increase in the measuring temperature. The leakage current shows a linear dependence on the voltage in the low-electric field-regime. The current density ascends to higher values due to the effect of space charges in the high-electric-field regime. The ionization energy of the top-electrode metals (Au, Pt or Ti–Au) has a strong effect on the leakage current.     

Microstructure,mechanical and tribological properties of Mo–V–Cu–N coatings prepared by HIPIMS technique

A combination of high wear-resistance and low-friction is crucial for improving the wear performance of self-lubricating coatings, which is generally determined by an excellent lubricating effect and mechanical strength. In this study, the Mo–V–Cu–N coatings were prepared by HIPIMS technique with a spliced target of Mo–V–Cu at various charge voltages. The results revealed that Mo–V–Cu–N coatings presented a solid solution phase of B1–MoVN with (200) preferred orientation, and the preferred orientation was enhanced at high charge voltages. Whereas the Cu atoms formed an amorphous phase in Mo–V–Cu–N coatings due to a low Cu content of 2.3–3.6 at.%. As the charge voltage increased to 750 V, more charged metallic ions were accelerated and bombarded substrate surface efficiently, forming smooth and dense Mo–V–Cu–N coatings with a high hardness of 31.0 GPa. All the coatings presented a low friction coefficient of 0.34–0.39 due to the formation of MoO₂, VO₂ and CuO mixed oxides, and the wear mechanism was dominated by abrasive and tribo-oxidation wear at room temperature.     

Effect of annealing process on the growth and surface properties of Au–ZnO nanowire films grown by chemical routes

Au–ZnO nanowire films have been synthesized by chemical routes, electrochemical deposition (ECD) and chemical bath deposition (CBD) techniques, on zinc foil followed by annealing in air at 400 °C. X-ray diffraction patterns reveal formation of the ZnO wurtzite structure along with binary phases Au₃Zn and AuZn₃. Scanning electron microscopy shows the presence of ZnO nanowires having several micrometers in length and less than 120 nm in diameter synthesized by ECD and in the range of 70–400 nm using the CBD technique. During the annealing process, different surface morphologies originating from different catalytic effects of Au atoms/layers were observed. In addition, the effect of synthesis routes on crystalline quality and optical properties were studied by Raman and photoluminescence spectrometers indicating varying concentration of defects on the films. The Raman results indicate that Au–ZnO nanowire film prepared by chemical bath deposition route had better crystalline quality.     

Fabrication and properties of ultra highly porous silicon carbide by the gelation–freezing method

Silicon carbide (SiC) with ultra high porosity and unidirectionally oriented micrometer-sized cylindrical pores was prepared using a novel gelation–freezing (GF) method. Gelatin, water and silicon carbide powder were mixed and cooled at 7 °C. The obtained gels were frozen from ?10 to ?70 °C, dried using a vacuum freeze drier, degreased at 600 °C and then sintered at 1800 °C for 2 h. The gels could be easily formed into various shapes, such as cylinders, large pipes and honeycombs using molds. Scanning electron microscopy (SEM) observations of the sintered bodies showed a microstructure composed of ordered micrometer-sized cylindrical cells with unidirectional orientation. The cell size ranging from 34 to 147 μm could be modulated by changing the freezing temperatures. The numbers of cells for the samples frozen at ?10 and ?70 °C were 47 and 900 cells/mm², respectively, as determined from cross-sections of the sintered bodies. The resulting porous SiC with a total porosity of 86%, exhibited air permeability from 2.3 × 10^?11 to 1.0 × 10^?10 m², which was the same as the calculated ideal permeability, and high compressive strength of 16.6 MPa. The porosity, number of cells, air permeability and strength of the present porous SiC were significantly higher than that reported for other porous SiC ceramics.     

Microstructural,electrophysical and gas-sensing properties of CeO2–Y2O3 thin films obtained by the sol-gel process

Nanopowders and thin films of (СeO₂)_1-x(Y₂O₃)_x composition (x = 0.10, 0.15 and 0.20) were obtained by the sol-gel process, using hydrolytically active complexes of the metal alkoxoacetylacetonate class [M(C₅H₇O₂)_3-y(C₅H₁₁Oⁱ)_y] (M = Ce³⁺ and Y³⁺) as precursors. The impact of the chemical composition and crystallization conditions on the microstructure, electrophysical and chemosensory characteristics of the obtained planar-type solid electrolytes was studied. The prospects of the thin-film nanostructures obtained as receptor components of resistive oxygen sensors, as well as of electrolytes of planar-type intermediate-temperature solid oxide fuel cells (SOFC) have been shown. It has been found that (CeO₂)_0.90(Y₂O₃)_0.10 thin films demonstrate the maximum values of electrical conductivity (550 °C) and the highest sensory response when detecting oxygen (concentration range 1–20%, operating temperature range 300–450 °C).     

Surface properties and biological behaviour of Si-DLC coatings fabricated by a multi-target DC–RF magnetron sputtering method for medical applications

The Si-incorporated diamond-like carbon (DLC) coatings deposited on AISI 316 LVM medical steel using magnetron sputtering method are currently not widely described in the literature, especially in terms of their biological response. Therefore, in this study both the haemocompatibility and cytotoxicity, as well as the surface properties of the Si-DLC films prepared by multi-target DC–RF magnetron sputtering were assessed. According to the XPS analysis the content of Si in the obtained coatings varied from ~ 4 at.% up to ~ 16 at.%. SEM investigations showed that the surface of the Si-DLC coatings is uniform and homogenous without any local defects. The surface energy measurements and FTIR analysis demonstrated that hydrophilicity and polarity of the examined surfaces changes with the varying Si-concentration. The evaluation of biological response towards the deposited coatings revealed that the increasing concentration of Si suppresses the platelet adhesion and decreases their activation level. Moreover, the results of the live/dead test indicated that the examined Si-DLC coatings are not cytotoxic, regardless of the Si concentration. Only a slight decrease in the endothelial cells' proliferation was observed with the growing Si content. Hence, it was concluded that the Si-DLC layer with the Si concentration ~ 16 at.% would be the most bio- and haemocompatible.     

Process-dependent conductivity and film homogeneity of slot-die-coated PEDOT:PSS–PVA composite films

In this study, we investigate the impact of process parameters on homogeneity and electrical conductivity of slot-die-coated PEDOT:PSS–PVA composite films that are doped with DMSO. Due to a strong correlation between conductivity and morphology of PEDOT:PSS films and the latter’s dependency on the processing step itself, we apply slot die coating for maximized process control and systematically evaluate the impact of coating gap, speed, and film thickness. Since the entire coating and drying process is run in batch mode, the setup is optimized regarding steady-state conditions and high homogeneity of the films. Overall, for the films manufactured in batch mode, we obtain a reproducibility film thickness of 99% and a low deviation from the set film thickness (below 8%). In order to analyze the impact of the coating parameters, stable operating points derived from the viscocapillary model are chosen and either the dimensionless gap or the capillary number is varied. Coating gap and film thickness emerged as dominating parameters, leading to an increase in conductivity of 40% and 70%, respectively, or, when changing both simultaneously, of 157%. Only a minor impact of shear forces (increase of 10%) was found.     

Direct preparation of battery-grade lithium carbonate via a nucleation–crystallization isolating process intensified by a micro-liquid film reactor

With the lithium-ion battery industry booming, the demand for battery-grade lithium carbonate is sharply increasing. However, it is difficult to simultaneously meet the requirements for the particle size and the purity of battery-grade lithium carbonate. Herein, the nucleation–crystallization isolating process (NCIP) is applied to prepare battery-grade lithium carbonate without any post-treatment procedure. The nucleation process is intensified by a micro-liquid film reactor (MLFR), where the feedstock solution is subject to intensive shear force and centrifugal force. The feedstock solutions are mixed rapidly and a large number of nuclei form instantly in the MLFR. After nucleation, the crystallization process is achieved in another reactor. A few new nuclei form in the crystallization process. The nucleation intensification in the MLFR is verified by computational fluid dynamics (CFD) simulations and experimental results. The particle size distribution is narrower and the impurity residue in the products is far lower than that prepared by a traditional precipitation method. The effects of nucleation and crystallization on the particle size distribution and purity were investigated. In the optimized operation parameters, the particle size distribution of the Li₂CO₃ product is D₁₀ = 2.856 μm, D₅₀ = 5.976 μm, and D₉₀ = 11.197 μm, and the purity is 99.73%, both of which meet the requirements of battery-grade Li₂CO₃. Moreover, the lithium recovery rate is increased to 88.21% compared to that prepared by a traditional precipitation method (79.0%). This work provides an alternative way for the preparation of high-purity chemicals by process intensification.     

Comparison of a-C:H films deposited from methane–argon and acetylene–argon mixtures by electron cyclotron resonance–chemical vapor deposition discharges

Hydrogenated amorphous carbon (a-C:H) films are deposited from methane–argon and acetylene–argon gas mixtures in a microwave electron cyclotron resonance plasma reactor. The films deposited with the two different gas mixtures under similar input parameter conditions have substantially different properties, including deposition rate, mass density, optical absorption coefficient, refractive index, optical bandgap and hydrogen content. The deposition parameters varied include rf-induced dc substrate bias voltage (0 to −60 V), pressure (1–5 mTorr) and argon/hydrocarbon gas flow ratio (0–1.0). The discharge properties of the two different gas mixtures, including electron temperature, ion saturation current, and residual gas composition of the exit gas flow, are measured to help explain the different deposition results from the two different gas mixtures. The use of lower pressures is found to be critical for obtaining denser, lower hydrogen content films from acetylene. For the methane-deposited films the addition of argon to the discharge increased the film's mass density and lowered the hydrogen content. In both methane- and acetylene-based deposition processes the rf-induced bias is also a critical determining factor of film properties.     

Mechanical properties and thermal stability of ambient-cured thick polysiloxane coatings prepared by a sol–gel process of organoalkoxysilanes

Ambient-curable polysiloxane coatings were prepared by pre-hydrolysis/condensation of phenyltrimethoxysilane (PTMS) and dimethyldimethoxysilane (DMDMS) in the presence of ammonia solution and subsequently mixing with aminopropyltriethoxysilane (APS). The mechanical properties of coatings were thoroughly examined at both macro- and micro-level and the thermal stability of coatings was characterized by thermogravimetic analysis, both of which were correlated with coating composition and the hydrolysis/condensation degree of polysiloxane oligomer. It was found that pro-hydrolysis step is essential for fabrication of thick crack-free coatings (18–35 μm). Higher DMDMS molar ratio, more APS dosage and lower hydrolysis/condensation degree of polysiloxane oligomer favor enhancing the hardness. Excellent impact resistance (50 cm kg) of coatings was obtained at 5% and 10% APS dosage, despite of the type and structure of polysiloxane oligomer. Whatever, the best scratch resistance of coatings was attained using the polysiloxane oligomer, prepared at PTMS-to-DMDMS molar ratio of 2:8 and water-to-precursor molar ratio of 1:1, and 5% APS dosage. The polysiloxane coatings exhibit high thermal stability, however, which strongly depends on the coating composition.