Nanolayer Coatings Research Articles

Tailoring Mechanical and Optical Properties of Sputtered SiNx/BN Coatings.

The swift evolution of contemporary electronics products, such as flexible screens and wearable electronic devices, highlights the significance of flexible protective coatings, which combine superior mechanical and optical properties. Even though the recently developed polymer protective coatings can satisfy requirements for flexibility and transparency, their intrinsic nature often results in a hardness below 1 GPa, rendering them susceptible to scratches. On the other hand, traditional inorganic coatings, known for their high hardness and transparency, fall short of meeting flexibility requirements. In the present study, a SiNx/BN periodical nanolayered coatings (PNCs) structure has been tailored to achieve high mechanical durability, transparency, and flexibility. In SiNx/BN PNCs, the optical and mechanical properties of the single-layer SiNx film are crucial to the overall performance of the PNCs. Therefore, pulse direct current (DC) magnetron sputtering was optimized first to enhance the ionization efficiency of Si and N, thereby promoting their reaction and diminishing the presence of elemental silicon in SiNx. The effects of the pulse frequency and duty cycle on SiNx were evaluated. Additionally, the influence of the thickness ratio and modulation periods on the overall performance of the SiNx/BN PNCs was investigated. As a result, a SiNx/BN coating with sapphire-grade hardness, almost no optical absorption in the visible-near-infrared (vis-NIR) range, high wear resistance, and exceptional flexibility was demonstrated.

Oxidation Performance of Nano-Layered (AlTiZrHfTa)Nx/SiNx Coatings Deposited by Reactive Magnetron Sputtering.

This work uses the direct current magnetron sputtering (DCMS) of equi-atomic (AlTiZrHfTa) and Si targets in dynamic sweep mode to deposit nano-layered (AlTiZrHfTa)Nx/SiNx refractory high-entropy coatings (RHECs). Transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) are used to investigate the effect of Si addition on the oxidation behavior of the nano-layered coatings. The Si-free nitride coating exhibits FCC structure and columnar morphology, while the Si-doped nitride coatings present a FCC (AlTiZrHfTa)N/amorphous-SiNx nano-layered architecture. The hardness decreases from 24.3 ± 1.0 GPa to 17.5 ± 1.0 GPa because of the nano-layered architecture, whilst Young's modulus reduces from 188.0 ± 1.0 GPa to roughly 162.4 ± 1.0 GPa. By increasing the thickness of the SiNx nano-layer, kp values decrease significantly from 3.36 × 10-8 g2 cm-4 h-1 to 6.06 × 10-9 g2 cm-4 h-1. The activation energy increases from 90.8 kJ·mol-1 for (AlTiZrHfTa)Nx nitride coating to 126.52 kJ·mol-1 for the (AlTiZrHfTa)Nx/SiNx nano-layered coating. The formation of a FCC (AlTiZrHfTa)-Nx/a-SiNx nano-layered architecture results in the improvement of the resistance to oxidation at high temperature.

Influence of the Ti-TiN-(Y,Ti,Al)N Nanolayer Coating Deposition Process Parameters on Cutting Tool Oxidative Wear during Steel Turning

Ti-TiN-(Y,Ti,Al)N coatings with a three-layer architecture (adhesive Ti layer, transition TiN layer, and wear-resistant (Y,Ti,Al)N layer) were studied. When depositing coatings, three arc current values of the yttrium cathode were used: 65, 85, and 105 A. The yttrium contents in the coatings were 30, 47, and 63 at. %, respectively. When turning 1045 steel, a coating with 30 at. % yttrium showed better wear resistance compared to a commercial (Ti,Cr,Al)N coating. The coating with 63 at. % yttrium did not show an increase in wear resistance compared to the uncoated sample. Nanolayers with a high yttrium content are oxidized more actively compared to nanolayers with a high titanium content. Phase analysis shows partial retention of the initial phases (Y,Ti,Al)N and (Ti,Y,Al)N during the formation of the Y2O3 oxide phase in the outer layers of the coating and the presence of only the initial phases in the deep layers. Coating nanolayers with high contents of aluminum and yttrium lose their original structure to a greater extent during oxidation compared to layers without aluminum.

First-principles study on interfacial structure and strength of SiC/VC nano-layered hard coatings

The interfacial and strength properties of SiC/VC nanolayered hard coatings have been studied by using first-principles. Four SiC (0001)/VC (111) interface models are constructed for searching the stable interface configure of SiC/VC coatings. Due to C-C termination is much stronger than C-V, C-Si, Si-V terminations, the SiC1-VC2 interface has the largest adhesion work and the lowest interface energy than other models. Griffith work and fracture toughness analysis show that the mechanical failure of the coating begins at the interface between SiC and VC. The electronic structure of SiC/VC interface indicate that the interfacial bonding strength related to hardness is mainly determined by V-d, C2-p and Si-p orbitals.

Crack formation and oxidation wear in (Cr,Y,Al)N and (Mo,Y,Al)N nanolayer coatings with high content of yttrium

The article considers the processes of cracking and oxidation in the nanolayer coatings of (Cr,Y,Al)N and (Mo,Y,Al)N with a high (about 50 at%) content of yttrium (Y). The studies were carried out during the turning of steel with subsequent investigation of the wear area using scanning (SEM) and transmission (TEM) microscopes. Although the main parameters (elemental composition and structure) are identical and the values of hardness and elastic modulus are close, tools with the coatings under consideration demonstrated noticeable difference in wear resistance. The (Mo,Y,Al)N coated tool had a wear resistance 45% higher than the (Cr,Y,Al)N coated tool and 30% higher than the (Ti,Cr,Al)N reference coated tool. Active formation of cracks is detected in the (Cr,Y,Al)N coating, while oxidation wear dominated in the (Mo,Y,Al)N coating. Therefore, coatings containing layers of materials characterized by an increased tendency to oxidize, but at the same time providing a favorable compositional effect, can be effectively used. This is possible provided that the oxidation-resistant layers protect the oxidation-prone layers from active contact with oxygen.

Investigation of the structure and phase composition of the microdroplets formed during the deposition of PVD coatings

The paper deals with the features of the structure and phase composition typical for the microdroplets of various elemental composition, including Ti, Zr, Cr, and AlN, and the effect of microdroplets on the structure of nanolayer coatings of TiN-(Ti,Al)N, TiN-(Ti,Mo,Al)N, ZrN-(Zr,Mo,Al)N, and CrN-(Cr,Mo,Al)N. The studies were carried out using the methods of transmission electron microscopy, X-ray spectroscopy and scanning transmission electron microscopy. The experiments revealed the specific features of the deformation of the nanolayer structure of the coating under the impact of microdroplets hitting the coating surface. The study also determined the phases formed in the microdroplets of various compositions. The diffusion processes have been investigated, during which the metals, contained in the coating (in particular, molybdenum (Mo)), dissolve in the surface layers of the core of the main microdroplet element. According to the study, microdroplets can be formed both by pure metals and by their nitrides. The paper considers the possibility of a positive effect of a microdroplet on the cutting process due to the formation of an intermediate layer of a solid lubricant between the coating and the material being machined.

Comparative study of tribological properties of nanocomposite and nanolayer coatings containing low-friction MoSx and solid a-C(S,H) components

Reactive pulsed laser deposition was used to create solid lubricating coatings differing in the dimensions of MoSx and a-C(S,H) nanophases in the bulk of the coatings. For coating preparation, two deposition modes were used, including the co-deposition of Mo and C atomic fluxes in hydrogen sulfide and the successive deposition of Mo and C layers up to 12 nm thick in hydrogen sulfide. The two-phase composition of the coating formed by the co-deposition of Упрочняющие технологии и покрытия. 2022. Том 18, № 10 471 Strengthening technologies and coatings. 2022. Vol. 18, no. 10 УПРОЧНЯЮЩИЕ НАНОТЕХНОЛОГИИ atomic flows was recorded only by the method of micro-Raman spectroscopy. No fundamental difference in the tribological properties of these coatings was found during tests in humid and dry air, although some important differences in tribochemical processes on the surface of the coatings were revealed. The use of the technique of alternating deposition of thin layers of controlled thickness and composition opens more opportunities for controlling the nanostructure and phase composition of this type coatings than with the co-deposition of atomic flows. However, the successful implementation of the layer-by-layer deposition technique largely depends on the degree of adhesion between the nanolayers.

Investigation on the incorporation of oxygen and thermal stability of HPPMS TiAlCrSiON nanolayer coatings

Abstract Ternary hard coatings like TiAlN and CrAlN are used to improve the tool lifetime during cutting. The addition of silicon leads to a nanocomposite coating architecture with advantageous properties, like a higher oxidation stability and higher indentation hardness. The coating system TiAlCrSiON is a combination of TiAlN and CrAlN with added oxygen: This coating is not sufficiently studied yet. However, it has a great potential to improve the cutting performance and tool lifetime. In the current study, three different TiAlCrSiON nanolayer coatings were deposited by direct current magnetron sputtering/high power pulsed magnetron sputtering hybrid processes on an industrial coating unit using three different gas flow ratios of oxygen to nitrogen. Bases on these coatings the influence of the incorporation of oxygen into the TiAlCrSiON coatings on the coating process and properties as well as on the thermal and oxidation stability is studied. The morphology of the coatings was investigated by scanning electron microscopy and transmission electron microscopy. It becomes increasingly columnar, when oxygen is incorporated into the coating. The phase composition was examined by X-ray diffraction. The results indicate an incorporation of oxygen into the cubic crystal lattice. The coatings show a nanocomposite and a nanolayer coating architecture. The oxygen is distributed inhomogeneously over the coating thickness and homogeneously within the nanolayers. Moreover, the coatings were investigated by nanoindentation. When the oxygen content increases, the indentation hardness decreases from HIT = (34 ± 2) GPa for the nitride Ti21Al17Cr5Si3N54 coating to HIT = (26 ± 2) GPa for the oxynitride Ti23Al13Cr5Si3O21N35 coating with a high oxygen content. The coatings show a high phase stability even at T = 1200 °C. The oxidation stability of the oxynitride coating with a high oxygen content is decreased T = 900 °C compared to the nitride coating.

Formation of Si-Rich Interfaces by Radiation-Induced Diffusion and Microsegregation in CrN/ZrN Nanolayer Coating.

A combination of coating deposition and consequent ion implantation could be beneficial in wear-resistant antifriction surface design and modification. In the present paper, the effects of low-energy 60 keV Si-ion implantation on multinanolayered CrN/ZrN grown on a stainless-steel substrate have been investigated. Complementary experimental (X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive spectroscopy, secondary ion mass spectrometry) and theoretical (first-principles) methods have been employed to investigate the structure, phase, and composition under a 1 × 10-17 cm-2 irradiation dose. This study has revealed a moderate radiation-tolerance of the CrN/ZrN system, with a 26 nm bilayer period, where the effective ion range after irradiation was below 110 nm. Within the ion range, a decrease in composition homogeneity and structure crystallinity has been found. Si negative ions have been distributed asymmetrically with peak concentrations (10 and 6%) occupying the interfaces between the CrN and ZrN layers. First-principles investigations of the CrN/ZrN(001) heterostructures were carried out to validate the experimental results, which showed that the alignment of Si-rich interfaces closer to chromium layers is a consequence of the lower substitution energy of CrN rather than ZrN. Thus, strong Si-Cr bindings and difference in displacement energies of ZrN and CrN have been attributed as the main factors in Si-rich interface formation. The pin-on-ball tribological test results have exposed the enhancement in wear resistance and the friction coefficient of nanoscale coating via amorphous Si particles descending from interfacial areas and acting as a third-body.

Investigation of multicomponent nanolayer coatings based on nitrides of Cr, Mo, Zr, Nb, and Al

This paper presents the results of the investigations of multicomponent nanolayer coatings of Cr,Mo-(Cr,Mo,Zr,Nb)N-(Cr,Mo,Zr,Nb,Al)N, Cr,Mo-(Cr,Mo)N-(Cr,Mo,Al)N, and Zr,Nb-(Zr,Nb)N-(Zr,Nb,Al)N. The data on the microstructures and nanostructures of the coatings, including the hardness, phase composition, and chemical composition by coating thickness are presented. The research considers the differences in the phase composition of the coatings and reveals the difference in the wear process on the contact pads of the carbide inserts between the studied coatings and the wear patterns on the coatings from cutting workpieces made of 1045 steel. The multicomponent Cr,Mo-(Cr,Mo)N-(Cr,Mo,Zr,Nb,Al)N coating contains two cubic phases of (Cr,Mo,Al)N and (Zr,Nb,Al)N with the space group Fm3¯m. The Cr,Mo-(Cr,Mo)N-(Cr,Mo,Zr,Nb,Al)N coating exhibited the maximum hardness among the studied coatings, and a tool with such a coating demonstrated the longest lifetime. The coating is also characterized by higher resistance to brittle fracture and cracking.

Design and validation of a high-efficiency planar solar thermophotovoltaic system using a spectrally selective emitter.

This paper presents a detailed-balance analysis required for the achievement of a high-efficiency spectral selective STPV system utilizing thermodynamic and optical modeling approaches. Key parameters affecting the design and optimization of spectrally selective surfaces that are essential for high-efficiency STPV applications are investigated. A complete GaSb-based planar STPV system utilizing a micro-textured absorber and a nanostructure multilayer metal-dielectric coated selective emitter was fabricated and evaluated. The micro-textured absorber features more than 90% absorbance at visible and near-infrared wavelengths. The selective emitter, consisting of two nanolayer coatings of silicon nitride (Si3N4) and a layer of W in between, exhibits high spectral emissivity at wavelengths matching the spectral response of the GaSb cells. The performance of the STPV system was evaluated using a high-power laser diode as a simulated source of concentrated incident radiation. When operated at 1670 K, an output power density of 1.75 W/cm2 and a system efficiency of 8.6% were recorded. This system efficiency is higher than those of previously reported experimental STPV systems. Optical and thermal losses that occurred at multiple stages of the energy transport process were modeled and quantified. Essential guidelines to mitigate these losses and further enhance the system performance are also provided.

Coating of Silica Nanolayers on Carbon Nanofibers via the Precursor Accumulation Method.

Surface modification of nanocarbons, for example, by coating with oxide nanolayers, is a research topic of significant interest because of the drastic changes in the physicochemical properties of the modified nanocarbons. One simple method of creating these oxide nanolayer coatings on nanocarbons is the precursor accumulation (PA) technique, which entails the following: (1) a precursor solution is added dropwise onto nanocarbon powder; (2) the solvent is dried, leaving the accumulated precursor on the nanocarbon surface; and (3) hydrolysis or decomposition of the precursor in air leads to the formation of oxide nanolayers on the nanocarbons. In this study, tetraethoxysilane (TEOS) was used as a precursor for coating silica nanolayers onto carbon nanofibers (CNFs). TEOS is so stable that it hardly undergoes hydrolysis on the surface of pristine CNFs. By treating CNFs with H2SO4/HNO3, acidic functional groups were introduced onto the CNF surfaces. Silica nanolayers were successfully synthesized on these acid-treated CNFs via PA coating because the acidic functional groups catalyzed the hydrolysis of TEOS accumulated on the CNF surfaces. Scanning transmission electron microscopy indicated that the thickness of silica layer is approximately several nanometers. Pore size distribution analysis for the silica nanolayer suggested the presence of nanopores with 3-5 nm. The TEOS molecules could have accessed the functional groups through the nanopore; therefore, the number of silica nanolayers formed increased with the number of PA coatings. Finally, we compared the PA coating with conventional sol-gel and atomic layer deposition techniques.

Comparison of the mechanical properties and electrochemical behavior of TiN and CrN single-layer and CrN/TiN multi-layer coatings deposited by PVD method on a dental alloy

Metallic materials used in medicine and dentistry should have high corrosion resistance and high biocompability. In this study, the influence of TiN, CrN and TiN/CrN layers on the hardness, surface roughness, and the corrosion resistance of Ni–Cr ceramic dental alloys in an artificial saliva environment (pH = 8) were evaluated. Ni–Cr dental alloys were produced by lost-wax casting and the TiN, CrN and TiN/CrN nanolayer coatings were deposited by means of arc-physical vapor deposition method. The microstructural characterization of selected alloys was performed before and after electrochemical tests, using scanning electron microscopy, energy dispersion spectroscopy, and x-ray diffraction. The surface roughness of the alloys was investigated by Profilometer. Surface characterization of the passive layer formed on the coated and uncoated Ni–Cr dental alloys in artificial saliva was studied using impedance spectroscopy measurement. The results showed that hardness of the ceramic-coated materials is noticeably greater than that of the uncoated substrate. Also, polarization and impedance spectroscopy measurements revealed that CrN coating has an exceptionally high polarization resistance compared to Ni–Cr dental alloy and TiN and TiN/CrN coatings.

Selective TiO2 Nanolayer Coating by Polydopamine Modification for Highly Stable Ni-Rich Layered Oxides.

Ni-rich layered oxides are promising cathode materials for developing high-energy lithium-ion batteries. To overcome the major challenge of surface degradation, a TiO2 surface coating based on polydopamine (PDA) modification was investigated in this study. The PDA precoating layer had abundant OH catechol groups, which attracted Ti(OEt)4 molecules in ethanol solvent and contributed towards obtaining a uniform TiO2 nanolayer after calcination. Owing to the uniform coating of the TiO2 nanolayer, TiO2 -coated PDA-LiNi0.6 Co0.2 Mn0.2 O2 (TiO2 -PNCM) displayed an excellent electrochemical stability during cycling under high voltage (3.0-4.5 V vs. Li+ /Li), during which the cathode material undergoes a highly oxidative charge process. In addition, TiO2 -PNCM exhibited excellent cyclability at elevated temperature (60 °C) compared with the bare NCM. The surface degradation of the Ni-rich cathode material, which is accelerated under harsh cycling conditions, was effectively suppressed after the formation of an ultra-thin TiO2 coating layer.

Commentary on using H/E and H3/E2 as proxies for fracture toughness of hard coatings

While positive correlation between fracture toughness and H/E and H3/E2 has been reported for some ceramic coatings, we outline an argument that such correlation cannot be true in general, especially for nanolayer and nanocomposite coatings that present multiple interfaces to impede crack growth. Literature data are presented to support this argument.

Hard, Flexible, and Transparent Nanolayered SiNx/BN Periodical Coatings

In this study, SiN x/BN periodical nanolayered coatings (PNCs) are developed. PNCs were deposited at the room temperature on plastic and glass substrates. They demonstrate the excellent mechanical durability of inorganic materials and optical transparency and flexibility of organic ones. The 150 nm thick PNC shows optical transparency, sapphire-like hardness, high wear protection, and flexibility. Such a coating with a superior combination of optical and mechanical properties has not been reported previously.

Enhanced Corrosion Resistance and Interfacial Conductivity of TiC x/a-C Nanolayered Coatings via Synergy of Substrate Bias Voltage for Bipolar Plates Applications in PEMFCs.

Proton-exchange membrane fuel cells are one kind of renewable and clean energy conversion device, whose metallic bipolar plates are one of the key components. However, high interfacial contact resistance and poor corrosion resistance are still great challenges for the commercialization of metallic bipolar plates. In this study, we demonstrated a novel strategy for depositing TiC x/amorphous carbon (a-C) nanolayered coatings by synergy of 60 and 300 V bias voltage to enhance corrosion resistance and interfacial conductivity. The synergistic effects of bias voltage on the composition, microstructure, surface roughness, electrochemical corrosion behaviors, and interfacial conductivity of TiC x/a-C coatings were explored. The results revealed that the columnar structures in the inner layer were suppressed and the surface became rougher with the 300 V a-C layer outside. The composition analysis indicated that the sp2 content increased with an increase of 300 V sputtering time. Due to the synergy strategy of bias voltage, lower corrosion current densities were achieved both in potentiostatic polarization (1.6 V vs standard hydrogen electrode) and potentiodynamic polarization. With the increase of 300 V sputtering time, the interfacial conductivity was improved. The enhanced corrosion resistance and interfacial conductivity of the TiC x/a-C coatings would provide new opportunities for commercial bipolar plates.

Effect of Tungsten Nanolayer Coating on Si Electrode in Lithium-ion Battery

Tungsten (W) was coated onto a silicon (Si) anode at the nanoscale via the physical vaporization deposition method (PVD) to enhance its electrochemical properties. The characteristics of the electrode were identified by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis, and electron probe X-ray microanalysis. With the electrochemical property analysis, the first charge capacities of the W-coated and uncoated electrode cells were 2558 mAh g− 1 and 1912 mAh g− 1, respectively. By the 50th cycle, the capacity ratios were 61.1 and 25.5%, respectively. Morphology changes in the W-coated Si anode during cycling were observed using SEM and TEM, and electrochemical characteristics were examined through impedance analysis. Owing to its conductivity and mechanical properties from the atomic W layer coating through PVD, the electrode improved its cyclability and preserved its structure from volumetric demolition.

Borate crosslinking of polydopamine grafted carbon nanotubes membranes for protein separation

Poor dispersibility in aqueous media of polymer functionalized one-dimensional materials including carbon nanotubes (CNTs), inorganic nanoparticles and polymer nanofibers is an inherent challenge to their utilization in several applications. Herein, polydopamine grafted CNTs (PDA-CNTs) are rendered dispersible through chemical crosslinking via bioinspired borate chemistry. Nanolayer coatings of polydopamine are deposited on the side walls of CNTs forming aggregates that lead to highly dense and agglomerated PDA-CNTs sediments in aqueous media. Borate crosslinking facilitates the obtainment of a homogeneous dispersion of borate crosslinked PDA-CNTs (B-PDA-CNTs) by forming strong hydrogen bonds in solution and thus permitting the facile fabrication of B-PDA-CNTs membranes with an interconnected nanoporous structure on a macroporous support. The obtained membranes with a controllable thickness are stable and display good ultrafiltration performances of ferritin molecules (>90%) and high water permeability of more than 2.8 × 103 L m−2 h−1 bar−1. The borate chemical crosslinking highlights a versatile approach for the preparation of stable polydopamine coated nanomaterials for wide applications with bio-macromolecules and in nanocomposite materials.

Unexpected Bactericidal Activity of Poly(arginine)/Hyaluronan Nanolayered Coatings

The number of nosocomial infections related to implants and medical devices increase alarmingly worldwide. New strategies based on the design of antimicrobial coatings are required to prevent such infections. Polyelectrolyte “multilayer” films constitute a powerful tool for nanoscale surface functionalization which allows addressing this issue. By investigating films built up with poly(arginine) (PAR) of various chain lengths (10, 30, 100, and 200 residues) and hyaluronic acid (HA), we demonstrate that exclusively films constructed with poly(arginine) composed of 30 residues (PAR30) acquire a strong antimicrobial activity against Gram-positive and Gram-negative pathogenic bacteria associated with infections of medical devices. This chain-size effect is extremely striking and is the first example reported where the length of the polyelectrolytes played a key-role in the functionality of the films. Moreover, this unexpected functionality of nanolayered polypeptide/polysaccharide PAR30/HA films occurs without adding any specific antimicrobial agent, such as antibiotics or antimicrobial peptides. PAR30/HA film inhibits bacteria through a contact-killing mechanism due to the presence of mobile PAR30 chains. These chains are assumed to diffuse toward the interface, where they interact with the bacteria with the consequence of killing them. This new coating with unique properties based on the association of a homopolypeptide of 30 residues with a polysaccharide constitutes a simple system to prevent implant-related infections with a reasonable production cost.